JP2013062242A - Method of manufacturing thin film for thin film solid secondary battery, coating liquid used therefor, thin film, and thin film solid secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a thin film for a thin film solid secondary battery which contains each thin film of a positive/negative electrode collector layer, a positive/negative electrode active material layer, and a solid electrolyte layer, using a simple method called as a coating method to form each thin film, and to provide a coating liquid used therefor, a thin film obtained by the manufacturing method, and the thin film solid secondary battery of which reduction in thickness, size, and cost are promoted by using the thin film.SOLUTION: The present invention relates to a method of manufacturing at least one thin film among a positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer of the thin film solid secondary battery having a laminate structure comprising a positive electrode collector layer, positive electrode active material layer, solid electrolyte layer, negative electrode active material layer, and negative electrode collector layer being formed sequentially on a substrate or a laminate structure comprising a negative electrode collector layer, negative electrode active material layer, solid electrolyte layer, positive electrode active material layer, and positive electrode collector layer being formed on the substrate in the order opposite to the former. The thin film is made by a coating method which includes: a coating step for forming a coating film by applying a coating liquid that contains organic metal compound as a main component; a drying step for forming a dry coating film by drying the coating film; and an inorganic step for making the dry coating film inorganic whose main component is an organic metal compound formed in the drying step, to form an inorganic thin film whose main component is a metal oxide. The inorganic step is a step for forming an inorganic thin film (metal oxide fine particle film) containing fine particles whose main component is metal oxide by removing an organic component contained in the dry coating film by decomposing or oxidizing, otherwise, decomposing and oxidizing through at least any one process among a heating process, energy ray radiation process, and plasma radiation process in an oxygen-contained atmosphere.

Description

The present invention relates to a method for producing a thin film for a thin film solid secondary battery, a coating solution used therefor, a thin film produced by the production method, and a thin film solid secondary battery using the thin film.
More specifically, in a thin-film solid secondary battery having a current collector layer (positive electrode, negative electrode) and a thin film of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, the formation of each thin film is simply called a coating method. A thin film solid-state secondary battery that can be reduced in thickness, size, and cost by applying a thin film manufacturing method and a coating solution used therefor, and a thin film obtained by the manufacturing method. It is.

  Lithium ion secondary batteries have a large energy density and are excellent in charge / discharge cycle characteristics, and thus are widely used mainly in electronic devices such as portable devices.

A typical lithium ion secondary battery is composed of basic elements of a positive electrode, a negative electrode, an electrolytic solution, and a separator. The positive electrode and the negative electrode are immersed in the electrolytic solution with a separator that can hold an electrolyte between the electrodes. And covered with a container.
Further, the positive electrode and the negative electrode have a structure in which current collectors (metal foil, metal mesh, etc.) hold crystalline particles, conductive materials, binders, etc. of the respective active materials (positive electrode active material, negative electrode active material). Has been used.

A composite oxide containing lithium and a transition metal is used for the positive electrode active material. Specifically, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium-nickel-manganese-cobalt oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as layered materials. ), Lithium-manganese oxide (LiMn ₂ O ₄ ) as a spinel material, lithium iron phosphate (LiFePO ₄ ) as an olivine material, and the like are common.
As the negative electrode active material, graphite (graphite), lithium titanate (Li ₄ Ti ₅ O ₁₂ ) or the like is generally used.

However, in lithium ion secondary batteries using a liquid electrolyte as an electrolyte, there are limits to miniaturization and thinning, and polymer batteries using gel electrolytes and thin film solid secondary batteries using solid electrolytes have been developed. .
Among these, in a thin film solid secondary battery, the structure is a laminated structure in which a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer are sequentially formed on a substrate, or The laminated structure in which the above layers are formed in the reverse order on the substrate is adopted, and the thickness of the battery element portion excluding the substrate can be reduced to about 1 μm, thereby further reducing the thickness and size of the entire battery. It is.

  In particular, a thin-film solid-state secondary battery using a solid electrolyte has a high potential by applying a positive electrode active material (5 V system) having a high potential with respect to Li in addition to the advantage that it can be reduced in size and thickness, and has a wide potential window. In addition, it is possible to reduce the cost because it is easy to increase the voltage by serially stacking in one cell, and it is also expected to improve the safety due to the excellent heat resistance and flame resistance of the solid electrolyte .

Solid electrolytes used include oxide-based solid electrolytes and oxide-based solid electrolytes such as lithium phosphate (Li ₃ PO ₄ ) and Li ₃ PO ₄ N _X (referred to as LiPON) in which nitrogen is added to lithium phosphate. In contrast, sulfide-based solid electrolytes such as Li ₂ S—P ₂ S ₅ having higher conductivity are used.

  As a thin film solid secondary battery using such a solid electrolyte, a thin film of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer is formed using a physical film formation method (vapor phase growth method) such as a sputtering method. What was formed is proposed (refer patent documents 1-4).

Patent Document 1 discloses a solid electrolyte layer of a substance (LiPON) in which nitrogen is added to lithium phosphate (Li ₃ PO ₄ ) using a film formation method by an ion beam or an electron beam evaporation method, and a metal oxide containing lithium. A thin-film solid secondary battery in which a positive electrode active material layer of a product and a negative electrode active material layer of metallic lithium are formed is disclosed.

Patent Document 2 discloses a solid electrolyte layer of a lithium ion conductor (a composite oxide composed of Li, Ta, Nb, N, and O having high ionic conductivity), a metal containing lithium, using a film formation method by sputtering. A thin-film solid secondary battery in which a positive electrode active material layer made of an oxide (such as LiCoO ₂ or LiMn ₂ O ₄ ) and a negative electrode active material layer made of Si or Li ₄ Ti ₅ O ₁₂ is disclosed.

Patent Document 3 discloses a solid electrolyte layer of a substance (LiPON) in which nitrogen is added to lithium phosphate (Li ₃ PO ₄ ), a transition metal, and a metal oxide containing lithium using a film formation method by sputtering. A thin film solid secondary battery in which a negative electrode active material layer of any one of a positive electrode active material layer, a semiconductor, a metal, an alloy, or a metal oxide is formed is disclosed.

  Patent Document 4 discloses a lithium phosphate (LiPON) solid electrolyte layer to which nitrogen is added, a positive electrode active material layer of lithium-cobalt oxide, and a negative electrode active material layer of metallic lithium using a film formation method by sputtering. A thin-film solid secondary battery in which is formed is disclosed.

Further, in Patent Document 5, a solid electrolyte layer of lithium phosphate (Li ₃ PO ₄ ) or lithium phosphate (LiPON) to which nitrogen is added, lithium-manganese oxide, lithium using a film formation method by sputtering A positive electrode active material layer of one or more metal oxides of cobalt oxide, lithium-nickel oxide, lithium-manganese-cobalt oxide, lithium-titanium oxide, and negative electrode of lithium-titanium-niobium composite oxide A thin-film solid secondary battery in which an active material layer is formed is disclosed.

  As described above, in the conventional thin film solid secondary battery, each thin film of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is formed by ion / electron beam evaporation, direct current sputtering, RF magnetron sputtering. Such a physical film formation method (vapor phase growth method) is used.

JP 2004-183078 A JP 2004-179158 A Specification of WO2006 / 082846 US Pat. No. 7,959,769 JP 2008-159399 A

However, when the thin film of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer of the thin film solid secondary battery is formed by a physical film formation method (vapor phase growth method) such as a sputtering method, it is used. The film device is very expensive because it is based on a vacuum vessel, and the composition control of the film to be formed is not easy, and the film formation speed cannot be increased depending on the material to be formed. And there was a problem with mass productivity.
Therefore, a film forming method for forming each thin film of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer by a simpler method has been desired.

  The present invention provides a thin film solid secondary battery having a current collector layer (positive electrode, negative electrode) and a thin film of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. The object is to provide a method for forming a thin film, a coating solution used therefor, each thin film obtained by the method, and a thin film solid state secondary battery that is thinned, miniaturized and reduced in cost using each thin film. To do.

  In view of such a situation, the inventors obtained a coating solution for forming an active material layer or a coating solution for forming an electrolyte layer containing an organometallic compound as a main component (positive electrode, negative electrode) by applying, drying and mineralizing. As a result of extensive research on inorganic thin films mainly composed of metal oxides, at least one of heat treatment, energy ray irradiation treatment, and plasma irradiation treatment was performed in an oxygen-containing atmosphere during the mineralization process. For example, it has been found that mineralization is promoted, and an inorganic thin film mainly composed of a metal oxide suitable for each thin film of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer can be obtained.

  That is, the first invention of the present invention is a laminated structure comprising a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer sequentially formed on a substrate, or In a thin film solid secondary battery having a laminated structure comprising a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer formed on the substrate in the reverse order. A method for producing at least one thin film of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, wherein the thin film contains an organometallic compound as a main component, a coating liquid for forming a positive electrode active material layer, a solid A coating process for forming a coating film by applying any coating liquid selected from a coating liquid for forming an electrolyte layer and a coating liquid for forming a negative electrode active material layer, and a drying process for drying the coating film to form a dry coating film The main component is an organometallic compound formed in the drying process Formed by a coating method comprising each step of the mineralization step of mineralizing the dry coating film to form an inorganic thin film containing a metal oxide as a main component, and the mineralization step is a heat treatment in an oxygen-containing atmosphere. It consists of fine particles mainly composed of metal oxides by decomposing or oxidizing or removing organic components contained in the dried coating film by decomposition or oxidation by at least one of energy beam irradiation treatment and plasma irradiation treatment. This is a process for forming an inorganic thin film (metal oxide fine particle film).

  In the second invention of the present invention, the organometallic compound contained as a main component in the coating liquid for forming a positive electrode active material layer in the first invention is a transition of any one or more of manganese, cobalt, nickel, and iron. A metal organic metal compound and an organic lithium compound, and the metal oxide that is the main component of the formed inorganic thin film is a lithium composite oxide containing one or more transition metals of manganese, cobalt, nickel, and iron. There is a method for producing a thin film.

According to a third aspect of the present invention, the lithium composite oxide in the second aspect is LiMO ₂ , LiMPO ₄ , Li ₂ MSiO ₄ (M: one or more transition metals of manganese, cobalt, nickel, iron) ), LiMn ₂ O ₄ , and a method for producing a thin film.

  According to a fourth aspect of the present invention, the organometallic compound contained as a main component in the coating solution for forming a solid electrolyte layer according to the first aspect is an organophosphorus compound and an organolithium compound. The metal oxide as a component is a lithium composite oxide containing phosphorus.

In a fifth aspect of the present invention, the lithium composite oxide containing phosphorus in the fourth aspect is Li ₃ PO ₄ , Li ₂ O—Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ based oxide, Li _{2 O-Al 2 O 3 -GeO 2} -P 2 O 5 based _oxide, either _{Li 2 O-La 2 O 3} -TiO 2 based _{oxide, Li 2 O-La 2 O} 3 -ZrO 2 based oxide It is a manufacturing method of the thin film characterized by being 1 or more types.

  According to a sixth aspect of the present invention, the organic metal compound contained as a main component in the coating solution for forming a solid electrolyte layer according to the first aspect is an organic lanthanum compound and an organic lithium compound, The metal oxide as a component is a lithium composite oxide containing lanthanum, which is a method for producing a thin film.

In a seventh aspect of the present invention, the lithium composite oxide containing lanthanum according to the sixth aspect is Li ₂ O—La ₂ O ₃ —TiO ₂ oxide, Li ₂ O—La ₂ O ₃ —ZrO ₂ It is a manufacturing method of the thin film characterized by being 1 or more types of an oxide.

  According to an eighth aspect of the present invention, the organometallic compound contained as a main component in the coating liquid for forming a negative electrode active material layer according to the first aspect is an organic titanium compound and an organic lithium compound, or niobium, indium, tin, An organic metal compound of one or more metals of zinc and titanium, and the metal oxide that is the main component of the formed inorganic thin film is lithium-titanium oxide, niobium oxide, indium oxide, tin oxide, zinc oxide, It is a manufacturing method of a thin film characterized by being one or more of titanium oxides.

A ninth aspect of the present invention is a method for producing a thin film, characterized in that the lithium-titanium oxide in the eighth aspect is Li ₄ Ti ₅ O ₁₂ .

  A tenth invention of the present invention is a method for producing a thin film, characterized in that the energy beam irradiation in the first to ninth inventions is irradiation of ultraviolet rays containing at least a wavelength of 200 nm or less as one of main components. is there.

  In an eleventh aspect of the present invention, the irradiation of ultraviolet rays containing at least a wavelength of 200 nm or less as one of the main components in the tenth aspect is ultraviolet rays emitted from any one of a low-pressure mercury lamp, an amalgam lamp, and an excimer lamp. A thin film manufacturing method characterized by irradiation.

  According to a twelfth aspect of the present invention, there is provided a thin film characterized by controlling the packing density of an inorganic thin film mainly composed of a metal oxide by controlling the dew point temperature of the oxygen-containing atmosphere in the first to eleventh aspects. It is a manufacturing method.

  A thirteenth aspect of the present invention is a method for producing a thin film characterized in that the oxygen-containing atmosphere in the first to twelfth aspects is an air atmosphere.

  A fourteenth aspect of the present invention is a method for producing a thin film, wherein the substrate in the first aspect is a glass substrate, a ceramic substrate, or a heat-resistant plastic film.

  A fifteenth aspect of the present invention is a method for producing a thin film, characterized in that the positive electrode current collector layer and the negative electrode current collector layer in the first invention are a single metal or an alloy.

  In the sixteenth aspect of the present invention, a single positive electrode current collector layer or negative electrode current collector layer is used instead of the substrate on which the positive electrode current collector layer or the negative electrode current collector layer is formed. A thin film manufacturing method characterized by using a plate or foil made of a metal or an alloy.

According to a seventeenth aspect of the present invention, there is provided a coating solution for forming a positive electrode active material layer, a coating solution for forming a solid electrolyte layer, and a coating solution for forming a negative electrode active material layer, which are used in the method for producing a thin film according to the first to ninth aspects. The positive electrode active material layer forming coating solution is selected from the group consisting of an organic solvent and a main component dissolved in the organic solvent, of manganese, cobalt, nickel, and iron. An organic metal compound of any one or more transition metals and an organic lithium compound, and the coating solution for forming a solid electrolyte layer includes an organic solvent and an organic phosphorus compound as a main component dissolved in the organic solvent. An organic lithium compound, or an organic lanthanum compound and an organic lithium compound, and the coating liquid for forming a negative electrode active material layer is an organic solvent and an organic titanate as a main component dissolved in the organic solvent. Containing objects and organolithium compounds, organolithium compounds, lithium (I)-2,4-pentanedionate _{[Li (C 5 H 7 O} 2)], lithium (I) ethoxide [Li _(C 2 _{H 5} O)], lithium (I) -tert-butoxide [Li (C ₄ H ₉ O)], and the organic solvent is N-methyl-2-pyrrolidone, an amine having a boiling point of 150 ° C. or higher. It is a coating liquid characterized by being one or more of the system solvents.

  An eighteenth aspect of the present invention is a coating liquid characterized in that the amine solvent having a boiling point of 150 ° C. or higher in the seventeenth aspect is 3-amino-1-propanol.

  A nineteenth aspect of the present invention is a thin film for a thin film solid secondary battery obtained by the method for producing a thin film according to the first to sixteenth aspects.

  A twentieth aspect of the present invention is a thin film solid state secondary battery, wherein the thin film in the thin film solid state secondary battery having a thin film is a thin film for the thin film solid state secondary battery according to the nineteenth aspect.

  According to the method for producing a thin film for a thin film solid secondary battery of the present invention, coating using an active material layer forming coating solution or a solid electrolyte layer forming coating solution containing an organometallic compound as a main component (positive electrode, negative electrode). Since an inorganic thin film containing a metal oxide as a main component is easily formed by the method, a thin film such as an active material layer (positive electrode or negative electrode) or a solid electrolyte layer can be produced at low cost.

  The thin-film solid secondary battery according to the present invention employs an active material layer (positive electrode, negative electrode) or solid electrolyte layer that is extremely easily formed by a coating method, so that the cost is significantly reduced in addition to reduction in thickness and size. And can greatly contribute to application to IC cards, card-type electronic money, RFID tags, and the like.

It is a schematic diagram which shows an example of the structure of a thin film solid secondary battery. It is a schematic diagram which shows an example of the other structure of a thin film solid secondary battery. It is a schematic diagram of the thin film solid secondary battery which shows a structure different from the thin film solid secondary battery shown in FIGS. It is a figure which shows the relationship between saturated water vapor content (volume%) in air, and dew point temperature (degreeC). It is a schematic diagram which shows an example of the mineralization process using the heat processing and the energy ray (ultraviolet ray) irradiation process in the manufacturing method of the thin film by the coating method which concerns on this invention. It is a figure which shows the charging / discharging curve of the electrolyte-type coin cell which used the thin film for thin film solid secondary batteries which concerns on Example 6 as a positive electrode, and used lithium dope graphite for the negative electrode. It is a schematic diagram which shows an example of the mineralization process using the heat processing in the manufacturing method of the thin film by the coating method which concerns on this invention. It is a figure which shows the X-ray-diffraction chart, crystal structure, and crystallite size of the various thin films for thin film solid secondary batteries obtained by the heat processing of various temperatures which concern on Example 11. FIG. It is a figure which shows the charging / discharging curve of the electrolyte-type coin cell which used the thin film for thin film solid secondary batteries which concerns on Example 12 for the positive electrode, and used lithium dope graphite for the negative electrode. It is a schematic diagram which shows another example of the mineralization process using the heat processing in the manufacturing method of the thin film by the coating method which concerns on this invention. It is a figure which shows the X-ray-diffraction chart, crystal structure, and crystallite size of the various thin films for thin film solid state secondary batteries obtained by the heat processing of various temperatures which concern on Example 14. FIG. It is a figure which shows the X-ray-diffraction chart, crystal structure, and crystallite size of the various thin films for thin film solid secondary batteries obtained by the heat processing of various temperatures which concern on Example 16. FIG. It is a figure which shows the X-ray-diffraction chart, crystal structure, and crystallite size of the various thin films for thin film solid secondary batteries obtained by the heat processing of various temperatures which concern on Example 17. FIG. It is a figure which shows the charging / discharging curve of the thin film solid secondary battery (coin cell) which concerns on Example 19. FIG.

Hereinafter, embodiments of the present invention will be described in detail.
In the method for producing a thin film for a thin film solid secondary battery of the present invention, a positive electrode active material layer forming coating solution, a solid electrolyte layer forming coating solution, and a negative electrode active material layer forming coating solution containing an organometallic compound as a main component. In order to form an inorganic thin film mainly composed of a metal oxide by a coating method of coating, drying and mineralizing any coating liquid selected from: a positive electrode active material layer for a thin film solid secondary battery, a solid At least one or more thin films of the electrolyte layer and the negative electrode active material layer can be easily produced.

[Structure of thin-film solid secondary battery]
First, the structure of a thin film solid secondary battery to which the thin film of the present invention is applied will be described with reference to FIGS.
1 to 3 are schematic cross-sectional views showing a laminated structure in a thin film solid secondary battery having a different structure according to the present invention.
The thin film solid secondary battery shown in FIG. 1 has a structure in which a positive electrode current collector layer 2, a positive electrode active material layer 3, a solid electrolyte layer 4, a negative electrode active material layer 5, and a negative electrode current collector layer 6 are formed on a substrate 1 in this order. 2 or the thin film solid secondary battery shown in FIG. 2 has a laminated structure in which the above layers are formed on the substrate 1 in the reverse order of the thin film solid secondary battery shown in FIG.
In addition, since a thin film solid secondary battery deteriorates in performance due to moisture in the atmosphere, durability is improved by providing a protective film or a protective film 7.

Further, in FIG. 1, if the positive electrode current collector layer 2 is formed in a plate shape or a foil shape, the substrate 1 becomes unnecessary, and a substrate different from the thin film solid state secondary battery of FIGS. A thin-film solid secondary battery having a structure that is not required may be used.
Hereinafter, each element of the thin film solid secondary battery will be described in detail.

(A) Substrate The substrate to be used is preferably a heat-resistant substrate, and among them, a glass substrate such as soda lime glass, non-alkali glass or quartz glass, or a ceramic substrate such as alumina (Al ₂ O ₃ ) is preferable. In some cases, a heat-resistant resin substrate (plastic film) such as polyimide (PI) or polyamide can be used.

(B) Current collector layer (positive electrode current collector layer, negative electrode current collector layer)
Examples of materials for the positive electrode current collector layer 2 and the negative electrode current collector layer 6 include Cu, Mg, Ti, Fe, Co, Ni, V, Zn, Al, Ge, In, Au, Pt, Ag, Pd, and the like. , And an alloy containing any of these (for example, stainless steel) can be appropriately selected and used.
The above material may be used as a thin film formed on the substrate 1 using an existing film forming method such as a sputtering method, a vapor deposition method, a plating method, or a coating method, or like the thin film solid secondary battery of FIG. The material itself can be used in the form of a plate or foil.

(C) Positive electrode active material layer The material forming the positive electrode active material layer 3 may be any material as long as it can easily release and adsorb lithium ions and can release and occlude many lithium ions. (LiCoO ₂ [lithium cobaltate], LiCo ₂ O ₄ etc.) (referred to as LCO), lithium-nickel oxide (LiNiO ₂ [lithium nickelate], LiNi ₂ O ₄ etc.) (referred to as LNO), Lithium-manganese oxide (LiMnO ₂ [lithium manganate], LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ etc.) (called LMO), lithium-manganese-cobalt oxide (LiMnCoO ₄ , Li ₂ MnCoO ₄ etc.) ), Lithium-nickel-manganese-cobalt oxide (Li (Ni—Mn—Co) O ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ or the like) (referred to as NMC or NCM), lithium-nickel-cobalt-aluminum oxide (referred to as Li (Ni—Co—Al) O ₂ ) (referred to as NCA), lithium— Titanium oxide (Li ₄ Ti ₅ O ₁₂ , LiTi ₂ O _4, etc.) (referred to as LTO), lithium oxide containing other transition metals (Li ₂ CuO ₂ , LiCuO ₂ , LiVO ₂ , LiV ₂ O ₄ , LiCrO _{2, LiFeO 2, LiTiO 2,} LiScO 2, LiYO 2, LiMnCrO 4, LiNiVO 4, LiCoVO 4 , etc.), lithium phosphates including various transition metals (LiFePO ₄ [lithium iron _phosphate], LiCuPO _4, LiNiPO 4, _{LiCoPO 4, LiMnPO 4, Li 2} NiPO 4 F, Li 2 CoP _{4 F, Li 2 MnPO 4 F} , Li 2 FePO 4 F, LiVOPO 4, Li 3 V 2 (PO 4) 3 , etc.), lithium silicate including various transition metals _{(Li 2 MnSiO 4, Li 2} FeSiO 4, Li ₂ CoSiO ₄ , Li ₂ NiSiO _4, etc.), sulfides of various transition metals (TiS ₂ , MoS ₂ , FeS, FeS ₂ , CuS, Ni ₃ S ₂ ), oxides of various transition metals (Bi ₂ O ₃ , Bi ₂ Pb ₂ O ₅ , CuO, V ₂ O ₅ , V ₆ O ₁₃ , Nb ₂ O _5, etc.) can be used. Moreover, you may mix and use these.

Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, the charge / discharge potentials of the two types of compounds are compared, the positive potential is the positive electrode active material, and the base potential is the negative electrode active material. Can be used.
Among the many positive electrode active materials described above, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium-nickel-manganese-cobalt oxide (LiNi _1/3 Mn _1/3 Co) as layered materials _1/3 O ₂ ), lithium-manganese oxide (LiMn ₂ O ₄ ) as a spinel-based material, lithium iron phosphate (LiFePO ₄ ) as an olivine-based material are suitable and generally used .
The thickness of the positive electrode active material layer 3 is desirably as thin as possible from the viewpoint of reducing the thickness, but considering the securing of charge / discharge capacity, about 0.05 to 5 μm is appropriate.

(D) Negative electrode active material layer As described above, there is no clear distinction between the negative electrode active material and the positive electrode active material, and the material forming the negative electrode active material layer 5 easily adsorbs and desorbs lithium ions, and a large amount of lithium. Any substance that can occlude and desorb ions may be used. For example, lithium-titanium oxide (Li ₄ Ti ₅ O ₁₂ , LiTi ₂ O _4, etc.), lithium-titanium-niobium oxide (Li ₄ (T _i2 Nb ₃ ) O ₁₂ etc.), various metal oxides (Nb ₂ O ₅ , V ₂ O ₅ , NiO, In ₂ O ₃ , SnO ₂ , ZnO, TiO ₂ etc.), various simple elements (Si, Ge, Li) Mg, Al, etc.), various silicon alloys (Si-Mn, Si-Co, Si-Ni, etc.), magnesium-lithium alloys (Mg-Li), aluminum-lithium alloys (Al-Li system; AlLi, etc.), Indium - lithium alloy (an In-Li system; _In 2 Li ₃ etc.), graphite (natural graphite, artificial graphite, etc.) or the like can be used. Moreover, you may mix and use these.
Among the many negative electrode active materials, metallic lithium (Li), various lithium alloys (eg, AlLi, In ₂ Li _3, etc.), graphite, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), etc. are generally used. However, from the viewpoint of increasing the capacity, metallic lithium (Li) or various lithium alloys are preferable, and these can be applied to the negative electrode active material layer as a sheet or foil.
The thickness of the negative electrode active material layer 5 is desirably as thin as possible from the viewpoint of reducing the thickness, but considering the securing of charge / discharge capacity, about 0.05 to 5 μm is appropriate.

(E) Solid electrolyte layer The substance forming the solid electrolyte layer 4 needs to use a substance having high ion conductivity of lithium ions, and lithium phosphate (Li ₃ PO ₄ ) as an oxide solid electrolyte is used. Li ₃ PO ₄ N _X (referred to as LiPON) obtained by adding nitrogen to lithium phosphate, LiBO ₂ N _X , LiNbO ₃ , LiTaO ₃ , Li ₂ SiO ₃ , Li ₄ SiO ₄ —Li ₃ PO ₄ , Li _{4 SiO 4 -Li 3 VO 4, Li} 2 O-B 2 O 3 -P 2 O 5, Li 2 O-SiO 2, Li 2 O-B 2 O 3 -ZnO, Li 1 + X Al X Ti 2-X (PO _{. 4) 3} (called 0 ≦ X ≦ 1) (LATP or _{LTAP), Li 1 + X Al} X Ge 2-X (PO 4) 3 (0 ≦ X ≦ 1; Specifically, _{Li 1. .} Al called _{0.5 Ge 1.5 (PO 4) 3} ) (LAGP), LiTi 2 (PO 4) 3, Li 3X La 2 / 3X TiO 3 (0 ≦ X ≦ 2/3; specifically Li _0.33 La _0.56 TiO ₃ , Li _0.5 La _0.5 TiO _3, etc. (referred to as LLT or LLTO), Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ Li ₂ S—SiS ₂ as a sulfide-based solid electrolyte, such as O ₁₂ (referred to as LLZ or LLZO), Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li _3.6 Si _0.6 P _0.4 O _4, etc. _{, LiI-Li 2 S-SiS} 2, LiI-Li 2 S-P 2 S 5, LiI-Li 2 S-B 2 S 3, Li 3 PO 4 -Li 2 S-Si 2 S, Li 3 PO 4 - Li ₂ S-SiS ₂ LiPO ₄ —Li ₂ S—SiS, LiI—Li ₂ S—P ₂ O ₅ , LiI—Li ₃ PO ₄ —P ₂ S ₅ , Li ₂ S—P ₂ S ₅ , or LiI—LiI—Al ₂ O ₃ , Li ₃ N, Li ₃ N—LiI—LiOH, or the like can be used.

Furthermore, from the viewpoint of lithium ion conductivity, a sulfide-based solid electrolyte is preferable to an oxide-based solid electrolyte. On the other hand, a sulfide-based solid electrolyte reacts with moisture to generate toxic hydrogen sulfide gas. There is a problem.
Therefore, from the viewpoint of the workability of the manufacturing process of the lithium ion battery and the safety of the lithium ion battery as a product, the oxide solid electrolyte is preferable to the sulfide solid electrolyte.

Among the oxide-based solid electrolytes, the LATP, LLT, LLZ, and the like have relatively high lithium ion conductivity (LATP: 1 × 10 ⁴ S / cm [25 ° C.], LLT: 1 × 10 ⁴ S / cm [25 ° C.], LLZ: 4 × 10 ⁴ S / cm [25 ° C.]). However, when metal lithium or a lithium alloy is applied to the negative electrode active material, LATP or LLT containing titanium oxide (TiO ₂ ) as a constituent component is Ti ⁴⁺ is Ti ³⁺ at the interface between the metal lithium or lithium alloy and the solid electrolyte. It cannot be used because it is reduced to lithium ion conductivity and deteriorates significantly.
In addition, when metal lithium or a lithium alloy is used for the negative electrode active material, LLZ that does not cause the above-described deterioration is preferable.
The thickness of the solid electrolyte layer 4 is desirably as thin as possible from the viewpoint of reducing the thickness and moving the lithium ion, but if it is too thin, pinholes are easily generated in the solid electrolyte layer. From the viewpoint, about 0.05 to 1 μm is preferable.

[Structure of active material layer and solid electrolyte layer formed by coating method]
Next, the structure of the active material layer (positive electrode, negative electrode) and solid electrolyte layer, which are thin films formed using a coating method, will be described.
For example, when an active material layer (positive electrode, negative electrode) or solid electrolyte layer mainly composed of a metal oxide is formed using a vapor phase growth method such as a sputtering method, the crystal grains of the metal oxide usually have grain boundaries. A polycrystalline film structure (or a dense amorphous film structure), which is a film structure arranged through the film structure, is formed, and metal oxide fine particles are hardly observed in the film structure.
In addition, an active material layer (positive electrode, negative electrode) formed by a coating method in which an active material layer-forming coating solution or a solid electrolyte layer forming coating solution containing an organometallic compound as a main component (solid, positive electrode, negative electrode) is applied. ) And the solid electrolyte layer usually has a film structure in which metal oxide fine particles are bonded to each other. The particle size of the metal oxide fine particles and the size of the voids existing between the metal oxide fine particles are determined according to the mineralization conditions However, it is known that the active material layer (positive electrode, negative electrode) or solid electrolyte layer composed of metal oxide fine particles having open pores (open pores).

In the active material layer (positive electrode, negative electrode) or solid electrolyte layer in which the metal oxide fine particles formed by this coating method are bonded, the active material layer (positive electrode, negative electrode) or solid electrolyte layer is conductive (electron conduction). Or ionic conduction), the metal oxide fine particles come into contact with each other in a very small area because the conductive mechanism intervenes the contact portion (bonding portion) of the metal oxide fine particles, and the conductivity is expressed. it seems to do.
In addition, unlike a secondary battery using a normal liquid electrolyte layer, the solid secondary battery has a solid electrolyte layer component interposed between the active material components in the active material layer (positive electrode and negative electrode) and conducts ions (of lithium ions). Therefore, in addition to the conductivity between the metal oxide fine particles, the solid electrolyte layer component (lithium ion) ion conduction also exists between the metal oxide fine particles in the active material layer. It is necessary to appropriately control the size of the gap to be generated.

  In a thin-film active material layer (positive electrode, negative electrode) or solid electrolyte layer formed by using such a coating method, the filling state and packing density of the metal oxide fine particles in the active material layer are controlled, and an open gap (open) It is desirable to control the size and number of pores, and to control the state of contact between the metal oxide fine particles in the active material layer and the state of penetration (soaking) of the solid electrolyte component into the active material layer. It is desirable to apply an oxygen-containing atmosphere in which the water vapor content, that is, the dew point temperature is controlled, in the temperature raising process of the mineralization step in the method.

  The formation mechanism of the inorganic thin film mainly composed of such fine metal oxide fine particles has not been clarified yet and will be described in detail later (see paragraphs [0132] to [0133]). When water vapor is present in an oxygen-containing atmosphere, crystallization and crystal growth of metal oxides due to mineralization caused by pyrolysis and combustion of organometallic compounds, etc. are promoted by water vapor, and an inorganicization process in which pyrolysis and combustion are performed. It is presumed that the metal oxide fine particles adhere to each other at the initial stage and become immovable, so that the metal oxide fine particles are hardly densified.

  On the other hand, if an oxygen-containing atmosphere with a low water vapor content, that is, a low dew point temperature is applied in the mineralization step of the active material layer (positive electrode, negative electrode) or solid electrolyte layer by a coating method, the active material layer (positive electrode, negative electrode) Depending on the type and composition of the metal oxide of the solid electrolyte layer and the solid oxide layer, for example, the packing density of the metal oxide fine particles in the active material layer (positive electrode, negative electrode) or solid electrolyte layer may be changed depending on the true specific gravity of the metal oxide. In contrast, when an oxygen-containing atmosphere containing a large amount of water vapor is applied, it may remain at about 40 to 70% of the true specific gravity. In short, the dew point temperature of the oxygen-containing atmosphere in the mineralization step may be set to be optimal as appropriate according to the active material layer (positive electrode, negative electrode) or solid electrolyte layer to be applied.

[(Positive electrode, negative electrode) active material layer forming coating solution, solid electrolyte layer forming coating solution]
In the present invention, the active material layer (positive electrode, negative electrode) and the solid electrolyte layer are formed by using the (positive electrode, negative electrode) active material layer forming coating solution or the solid electrolyte layer forming coating solution. Will be described.

(A) Organometallic compound as main component of coating liquid (1) Coating liquid for forming positive electrode active material layer The coating liquid for forming a positive electrode active material layer used in the present invention will be described in detail.
In the present invention, using a coating liquid for forming a positive electrode active material layer containing, as a main component, an organic metal compound of one or more transition metals of manganese, cobalt, nickel, and iron, and an organic lithium compound, manganese, cobalt A positive electrode active material layer made of a fine particle film (inorganic thin film) mainly composed of a lithium composite oxide containing one or more transition metals of nickel, iron, and nickel is formed.

First, the organolithium compound used in the present invention will be described below.
The organic lithium compound becomes lithium oxide (Li ₂ O) by mineralization, and this lithium oxide constitutes the main component of the lithium composite oxide obtained by a coating method.
Examples of the organic lithium compound that can be used in the present invention include lithium acetylacetone (formal name: lithium (I) -2,4-pentanedionate [Li (C ₅ H ₇ O ₂ )], lithium formate (I). [Li (HCOO)], lithium (I) ethoxide as lithium alkoxide [Li (C ₂ H ₅ O)], lithium (I) -tert-butoxide [Li (C ₄ H ₉ O)], lithium (I) Isopropoxide [Li (C ₃ H ₇ O)] and the like can be mentioned. Basically, it is dissolved in a solvent and oxidized without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Of these, lithium acetylacetone is highly soluble in organic solvents, and decomposes and burns (oxidizes) to become an oxide. Fried preferred.

Next, the organometallic compounds of manganese, cobalt, nickel, and iron used in the present invention will be described below.
The organic manganese compound becomes manganese oxide (MnO, Mn ₂ O ₃ , MnO _2, etc.) by mineralization, and this manganese oxide constitutes the main component of the lithium composite oxide obtained by the coating method.
As an organic manganese compound that can be used in the present invention, for example, acetylacetone manganese {(formal name: manganese (II) -2,4-pentanedionate) [Mn (C ₅ H ₇ O ₂ )] as a manganese acetylacetone complex. ₂ ], (formal name: manganese (III) -2,4-pentanedionate) [Mn (C ₅ H ₇ O ₂ ) ₃ ]} and the like, and manganese acetate (II) [Mn (CH ₃ COO) ₂ ] and the like. Basically, it is an organic manganese compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. I just need it.

The organic iron compound becomes iron oxide (FeO, Fe ₂ O ₃ or the like) by mineralization, and this iron oxide constitutes the main component of the lithium composite oxide obtained by a coating method.
As an organic iron compound that can be used in the present invention, for example, acetylacetone iron (formal name: iron (III) -2,4-pentandionate) [Fe (C ₅ H ₇ O ₂ ) ₃ as an iron acetylacetone complex] ₃ , Etc., iron (III) ethoxide as an iron alkoxide [Fe (C ₂ H ₅ O) ₃ ], etc., iron acetate (III) as an organic acid iron [Fe (CH ₃ COO) ₃ ], etc. Basically, it may be an organic iron compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

The organic cobalt compound becomes cobalt oxide (CoO, Co ₂ O ₃ or the like) by mineralization, and this cobalt oxide constitutes the main component of the lithium composite oxide obtained by a coating method.
As an organic cobalt compound that can be used in the present invention, for example, acetylacetone cobalt as a cobalt acetylacetone complex {(formal name: cobalt (II) -2,4-pentanedionate) [Co (C ₅ H ₇ O ₂ )] ₂ ], (formal name: cobalt (III) -2,4-pentanedionate) [Co (C ₅ H ₇ O ₂ ) ₃ ]} and the like, and cobalt formate (II) as an organic acid cobalt [Co (COOH ) ₂ · 2H ₂ O], cobalt acetate (II) [Co (CH ₃ COO) ₂ ], etc., are basically dissolved in a solvent and chlorine gas, nitrogen oxide gas, etc. at the time of mineralization Any organic cobalt compound that decomposes into an oxide without generating any harmful gas may be used.

The organic nickel compound becomes nickel oxide (NiO, Ni ₂ O ₃ or the like) by mineralization, and this nickel oxide constitutes the main component of the lithium composite oxide obtained by a coating method.
Examples of the organic nickel compound that can be used in the present invention include acetylacetone nickel (formal name: nickel (II) -2,4-pentandionate) [Ni (C ₅ H ₇ O ₂ ) ₂ as a nickel acetylacetone complex. Etc., and nickel formate (II) [Ni (HCOO) ₂ · 2H ₂ O], nickel acetate (II) [Ni (CH ₃ COO) ₂ ], etc. as organic acid nickel, Any organic nickel compound can be used as long as it is dissolved in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

Here, in the case where the lithium composite oxide is LiMPO ₄ or Li ₂ MSiO ₄ (M: one or more transition metals of manganese, cobalt, nickel, and iron), an organometallic compound of phosphorus and silicon Since (organic phosphorus compound, organosilicon compound) are used, each will be described below.

The organic phosphorus compound becomes phosphorus oxide (P ₂ O ₅ or the like) by mineralization, and this phosphorus oxide is a transition of one or more of LiMPO ₄ (M: manganese, cobalt, nickel, iron) obtained by a coating method. The main component of (metal).
Examples of the organic phosphorus compound include triethyl phosphate [PO (C ₂ H ₅ O) ₃ ], tributyl phosphate [PO (C ₄ H ₉ O) ₃ ], and tripentyl phosphate (also known as triamyl phosphate). [PO (C ₅ H ₁₁ O) ₃ ], bis (2-ethylhexyl) phosphate [(C ₄ H ₉ CH (C ₂ H ₅ ) CH ₂ ) ₂ HPO ₄ ] and the like are basically mentioned. Any organic phosphorus compound that dissolves in a solvent and decomposes into an oxide without generating harmful gas such as chlorine gas or nitrogen oxide gas during mineralization may be used.
Among these, tripentyl phosphate and bis (2-ethylhexyl) phosphate are preferable because they have high solubility in organic solvents and low vapor pressure, so that component volatilization in the drying process can be suppressed.

The organosilicon compound becomes silicon oxide (SiO ₂ or the like) by mineralization, and this silicon oxide is Li ₂ MSiO ₄ (M: transition of any one or more of manganese, cobalt, nickel, and iron obtained by a coating method) The main component of (metal).
There are many types of organic silicon compounds. For example, silicon (IV) tetramethoxide [Si (CH ₃ O) ₄ ] or silicon (IV) tetraethoxide [Si ( _{C 2 H 5 O) 4]} , silicon (IV)-tert-butoxide _{[Si (C 4 H 9 O} ) 4], silicon (IV) tetra -n- butoxide _{[Si (C 4 H 9 O} ) 4], Silicon (IV) tetraisopropoxide [Si (C ₃ H ₇ O) ₄ ] and the like can be mentioned, but basically, it is dissolved in a solvent and harmful gases such as chlorine gas and nitrogen oxide gas at the time of mineralization Any organic silicon compound that can be decomposed into an oxide without generation of water may be used.

(2) Coating liquid for forming negative electrode active material layer Next, the coating liquid for forming negative electrode active material layer used in the present invention will be described in detail.
In the present invention, a coating liquid for forming a negative electrode active material layer containing, as a main component, an organotitanium compound and an organolithium compound, or an organometallic compound of one or more metals selected from niobium, indium, tin, zinc, and titanium A negative electrode active material layer comprising a fine particle film (inorganic thin film) containing as a main component any one or more of lithium-titanium oxide, niobium oxide, indium oxide, tin oxide, zinc oxide, and titanium oxide. Is forming.

The organolithium compound used in the present invention is the same as the organolithium compound used in the coating liquid for forming the positive electrode active material layer, and becomes lithium oxide (Li ₂ O) by mineralization. This lithium oxide is obtained by a coating method. It constitutes the main component of lithium-titanium oxide (Li ₄ Ti ₅ O ₁₂ ).

Next, each organometallic compound of titanium, niobium, indium, tin, and zinc used in the present invention will be described below.
The organic titanium compound becomes titanium oxide (TiO ₂ or the like) by mineralization, and this titanium oxide constitutes a main component of lithium-titanium oxide (Li ₄ Ti ₅ O ₁₂ ) obtained by a coating method, or alone. The main component of a negative electrode active material layer can be comprised.
As an organic titanium compound, for example, acetylacetone titanium (formal name: titanium (IV) di-n-butoxide bis (2,4-pentanedionate) [Ti (C ₄ H ₉ O) ₂ (C _{5 H 7 O 2) 2]} ), titanyl (IV) acetylacetonate _{[(C 5 H 7 O 2} ) 4 TiO], titanium (IV) diisopropoxide bis (2,4-pentanedionate) [Ti (C ₃ H ₇ O) ₂ (C ₅ H ₇ O ₂ ) ₂ ] and the like, titanium (IV) tetraethoxide [Ti (C ₂ H ₅ O) ₄ ] as titanium alkoxide, titanium (IV) -tert - butoxide _{[Ti (C 4 H 9 O} ) 4], titanium (IV) tetra -n- butoxide _{[Ti (C 4 H 9 O} ) 4], titanium (IV) tetra isopropoxide Kishido Although _{[Ti (C 3 H 7 O} ) 4] , and the like, basically, dissolved in a solvent, an oxide without generating harmful gas such as chlorine gas or nitrogen oxide gas at the time of mineralization Any of these may be used as long as it is an organic titanium compound that decomposes into acetylacetone, among which titanium acetylacetone, titanium (IV) tetra-n-butoxide, and titanium (IV) tetraisoproposide are preferable because they are inexpensive and readily available.

The organic niobium compound becomes niobium oxide (Nb ₂ O ₅ or the like) by mineralization, and niobium oxide obtained by this coating method constitutes the main component of the negative electrode active material layer.
Examples of the organic niobium compound include niobium (V) ethoxide [Nb (C ₂ H ₅ O) ₅ ], niobium (V) -n-butoxide [Nb (C ₄ H ₉ O) ₅ ] and the like as niobium alkoxide. Basically, any organic niobium compound that dissolves in a solvent and decomposes into an oxide without generating a harmful gas such as chlorine gas or nitrogen oxide gas at the time of mineralization may be used.

The organic indium compound becomes indium oxide (In ₂ O ₃ ) by mineralization, and indium oxide obtained by this coating method constitutes the main component of the negative electrode active material layer.
Examples of the organic indium compound include acetylacetone indium (formal name: tris (acetylacetonato) indium (III)) [In (C ₅ H ₇ O ₂ ) ₃ ], indium (III) 2-ethylhexanoate [In (C ₇ H ₁₅ COO ₂ ) ₃ ], indium formate (III) [In (HCOO) ₃ ], indium (III) acetate [In (CH ₃ COO) ₃ ], indium (III) methoxyethoxide as indium alkoxide [In (CH ₃ OC ₂ H ₄ O) ₃ ], etc., are basically used, but it is dissolved in a solvent, and in the mineralization, no harmful gas such as chlorine gas or nitrogen oxide gas is generated and the oxide is formed. Any organic indium compound that decomposes may be used. Among these, indium acetylacetone is preferable because it has high solubility in organic solvents and is easily decomposed and burned (oxidized) to become an oxide.

The organic tin compound becomes tin oxide (SnO ₂ ) by mineralization, and tin oxide obtained by this coating method constitutes the main component of the negative electrode active material layer.
The organic tin compound (the valence of tin in the compound is not limited to bivalent and tetravalent) is, for example, acetylacetone tin (formal name: di-n-butyl bis (2,4-pentanedionato) tin (IV) ) [Sn (C ₄ H ₉ ) ₂ (C ₅ H ₇ O ₂ ) ₂ ], tin (II) 2-ethylhexanoate (also known as tin (II) octylate) [Sn (C ₇ H ₁₅ COO ₂ ) _2], tin acetate _{(II) [Sn (CH 3} COO) 2], tin acetate _{(IV) [Sn (CH 3} COO) 4], di -n- butyl tin (IV) diacetate [Sn _(C 4 H ₉ ) ₂ (CH ₃ COO) ₂ ], tin (II) formate [Sn (HCOO) ₂ ], tin (IV) -tert-butoxide [Sn (C ₄ H ₉ O) ₄ ] as a tin alkoxide, and the like. Basically, however, it dissolves in the solvent and is added during mineralization. It may be a decomposed organic tin compound oxide without generating harmful gas such as chlorine gas or nitrogen oxide gas. Among these, acetylacetone tin is preferable because it is relatively inexpensive and easily available.

The organic zinc compound becomes zinc oxide (ZnO) by mineralization, and zinc oxide obtained by this coating method constitutes the main component of the negative electrode active material layer.
The organic zinc compound is, for example, acetylacetone zinc (formal name: zinc (II) -2,4-pentanedionate) [Zn (C ₅ H ₇ O ₂ ) ₂ ], zinc (II) -2 as a zinc acetylacetone complex. , 2,6,6-tetramethyl-3,5-heptanedionate _{[Zn (C 11 H 19 O} 2) 2], zinc as zinc alkoxide (II) methoxyethoxide _{[Zn (CH 3 OC 2 H} 4 O) ₂ ] and the like, but basically, an organic zinc compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. It ’s fine. Among these, zinc acetylacetone is preferable because it is inexpensive and easily available.

(3) Solid Electrolyte Layer Forming Coating Liquid The solid electrolyte layer forming coating liquid used in the present invention will be described in detail.
In the present invention, a coating solution for forming a solid electrolyte layer mainly composed of an organometallic compound of an organophosphorus compound and an organolithium compound, or a solid electrolyte layer formed mainly of an organometallic compound of an organic lanthanum compound and an organolithium compound A solid electrolyte layer made of a fine particle film (inorganic thin film) containing, as a main component, a lithium composite oxide containing phosphorus or a lithium composite oxide containing lanthanum is formed by using the coating liquid.

The organolithium compound used in the present invention is the same as the organolithium compound used in the coating liquid for forming the positive electrode active material layer, and becomes lithium oxide (Li ₂ O) by mineralization. This lithium oxide is obtained by a coating method. It constitutes a main component of a lithium composite oxide containing phosphorus or a lithium composite oxide containing lanthanum.

The organic phosphorus compound is also the same as the organic phosphorus compound used in the coating liquid for forming the positive electrode active material layer, and is converted to phosphorus oxide (P ₂ O ₅ ) by mineralization. Constitutes the main component of the lithium composite oxide containing.

Here, the lithium composite oxide containing phosphorus described above is Li ₂ O—Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ -based oxide (such as LATP) or Li ₂ O—Al ₂ O ₃ —GeO ₂ —. P ₂ O ₅ -based oxides (LAGP, etc.) and lithium composite oxides containing lanthanum are Li ₂ O—La ₂ O ₃ —TiO ₂ -based oxides (LLT, etc.) and Li ₂ O—La ₂ O _3. In the case of —ZrO ₂ -based oxides (LLZ, etc.), since each organometallic compound of titanium, aluminum, germanium, lanthanum, and zirconium is used, each will be described below.

The organic titanium compound used in the present invention is the same as the organic titanium compound used in the coating liquid for forming the negative electrode active material layer, and becomes titanium oxide (TiO ₂ or the like) by mineralization. This titanium oxide is obtained by a coating method. It constitutes the main component of Li ₂ O—Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ oxide or Li ₂ O—La ₂ O ₃ —TiO ₂ oxide.

The organoaluminum compound becomes aluminum oxide (Al ₂ O ₃ or the like) by mineralization, and this aluminum oxide is Li ₂ O—Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ oxide or Li oxide obtained by a coating method. _It constitutes the main component of ₂ O—Al ₂ O ₃ —GeO ₂ —P ₂ O ₅ oxide.
The organoaluminum compound includes acetylacetone aluminum (formal name: aluminum (III) -2,4-pentanedionate) [Al (C ₅ H ₇ O ₂ ) ₃ ] as aluminum acetylacetone complex, and aluminum (III) as aluminum alkoxide. ethoxide _{[Al (C 2 H 5 O} ) 3], aluminum (III)-n-butoxide _{[Al (C 4 H 9 O} ) 3], aluminum (III)-tert-butoxide _{[Al (C 4 H 9 O} ) ₃ ], aluminum (III) isopropoxide [Al (C ₃ H ₇ O) ₃ ], etc., are basically dissolved in a solvent, such as chlorine gas or nitrogen oxide gas during mineralization. Any organoaluminum compound that decomposes into an oxide without generating harmful gas may be used. Among these, acetylacetone aluminum and aluminum (III) -n-butoxide are preferable because they are relatively inexpensive and easily available.

The organic germanium compound becomes germanium oxide (GeO ₂ or the like) by mineralization, and this germanium oxide contains the main component of the Li ₂ O—Al ₂ O ₃ —GeO ₂ —P ₂ O ₅ oxide obtained by a coating method. Configure.
Examples of the organic germanium compound include germanium (IV) tetraethoxide [Ge (C ₂ H ₅ O) ₄ ] and germanium (IV) tetra-n-butoxide [Ge (C ₄ H ₉ O) ₄ ] as germanium alkoxides. , Germanium (IV) tetraisopropoxide [Ge (C ₃ H ₇ O) ₄ ] and the like, β-carboxyethyl germanium (IV) oxide [(GeCH ₂ CH ₂ COOH) ₂ O ₃ ], tetraethyl germanium (IV) [Ge (C ₂ H ₅ ) ₄ ], tetrabutyl germanium (IV) [Ge (C ₄ H ₉ ) ₄ ], tributyl germanium (IV) hydride [Ge (C ₄ H ₉ ) ₃ H] and the like. Basically, it dissolves in the solvent and generates harmful gases such as chlorine gas and nitrogen oxide gas during mineralization Any organic germanium compound that can be decomposed into an oxide without being used. Among these, germanium (IV) tetraethoxide, germanium (IV) tetra-n-butoxide, and germanium (IV) tetraisopropoxide are preferable because they are relatively inexpensive and easily available.

The organic lanthanum compound becomes lanthanum oxide (La ₂ O ₃ or the like) by mineralization, and this lanthanum oxide is Li ₂ O—La ₂ O ₃ —TiO ₂ oxide or Li ₂ O—La ₂ obtained by a coating method. It constitutes the main component of the O ₃ —ZrO ₂ -based oxide.
As an organic lanthanum compound, for example, acetylacetone lanthanum (formal name: lanthanum (III) -2,4-pentanedionate) [La (C ₅ H ₇ O ₂ ) ₃ ] as a lanthanum acetylacetone complex, Examples include lanthanum (III) isopropoxide [La (C ₃ H ₇ O) ₃ ] and the like, and lanthanum acetate (III) [La (CH ₃ COO) ₃ ] as an organic acid lanthanum. Any organic lanthanum compound that dissolves in a solvent and decomposes into an oxide without generating harmful gas such as chlorine gas or nitrogen oxide gas during mineralization may be used.

The organic zirconium compound becomes zirconium oxide (ZrO ₂ or the like) by mineralization, and this zirconium oxide constitutes the main component of Li ₂ O—La ₂ O ₃ —ZrO ₂ -based oxide obtained by a coating method.
Examples of the organic zirconium compound include zirconium (IV) di-n-butoxide bis (2,4-pentanedionate) [Zr (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) as a zirconium acetylacetone complex. _2], zirconium acetylacetonate (official name: zirconium _{(IV)-2,4-pentanedionate) [Zr (C 5 H 7} O 2) 4], zirconium as zirconium alkoxide (IV) ethoxide [Zr _(C 2 H ₅ O) ₄ ], zirconium (IV) -n-propoxide [Zr (C ₃ H ₇ O) ₄ ], zirconium (IV) isopropoxide [Zr (C ₃ H ₇ O) ₄ ], zirconium (IV) -n- butoxide _{[Zr (C 4 H 9 O} ) 4], zirconium (IV)-tert-butoxide [ _{r (C 4 H 9 O)} 4], zirconium (IV) -2-methyl-2-butoxide _{[Zr (C 5 H 11 O} ) 4], zirconium (IV) -2-methoxymethyl-2-propoxide [ Zr (CH ₃ OC ₄ H ₈ O) ₄ ] and the like are basically used, but the oxide is dissolved in a solvent and does not generate harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Any organic zirconium compound that can be decomposed into any form may be used. Among these, zirconium (IV) -n-propoxide and zirconium (IV) -n-butoxide are preferable because they are relatively inexpensive and easily available.

  In the above-described coating liquid for forming a positive electrode active material layer, coating liquid for forming a negative electrode active material layer, and coating liquid for forming a solid electrolyte layer, various organometallic compounds other than those described above may be blended as necessary. Various metal oxides formed by mineralization of the organometallic compound can be added to the metal oxides constituting the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer.

The various organometallic compounds to be blended as necessary include, for example, organic scandium compounds, organic vanadium compounds, organic chromium compounds, organic copper compounds, organic gallium compounds, organic yttrium compounds, organic molybdenum compounds, organic ruthenium compounds, and organic antimony compounds. Organic hafnium compounds, organic tantalum compounds, organic tungsten compounds, organic bismuth compounds, organic cerium compounds, organic neodymium compounds, organic samarium compounds, organic gadolinium compounds, organic magnesium compounds, organic calcium compounds, organic strontium compounds, organic barium compounds, etc. And various metal oxides formed by mineralization of these various organometallic compounds are scandium oxide, vanadium oxide, chromium oxide, copper oxide, gallium oxide, yttrium oxide, Molybdenum, ruthenium oxide, antimony oxide, hafnium oxide, tantalum oxide, tungsten oxide, bismuth oxide, cerium oxide, neodymium oxide, samarium oxide, gadolinium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide and the like.
Below, the said various organometallic compounds mix | blended as needed are demonstrated.

Examples of the organic scandium compound include acetylacetone scandium (formal name: scandium (III) -2,4-pentanedionate) [Sc (C ₅ H ₇ O ₂ ) ₃ ] as a scandium acetylacetone complex, Basically, it may be an organic scandium compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

Examples of the organic vanadium compound include vanadium (IV) oxide bis-2,4-pentanedionate [VO (C ₅ H ₇ O ₂ ) ₂ ] as a vanadium acetylacetone complex, acetylacetone vanadium (official name: vanadium (III)) -2,4-pentanedionate) [V (C ₅ H ₇ O ₂ ) ₃ ] and the like, but basically, it is dissolved in a solvent and used for chlorine gas or nitrogen oxide gas during mineralization. Any organic vanadium compound that decomposes into an oxide without generating harmful gas may be used.

As an organic chromium compound, for example, acetylacetone chromium (formal name: chromium (III) -2,4-pentanedionate) [Cr (C ₅ H ₇ O ₂ ) ₃ ] as a chromium acetylacetone complex, Chromium (III) isopropoxide [Cr (C ₃ H ₇ O) ₃ ] and the like, chromium (II) acetate [Cr (CH ₃ COO) ₂ ] as organic acid chromium, hydroxychromium (III) diacetate [Cr ( CH ₃ COO) ₂ (OH)], etc., are basically dissolved in a solvent and decomposed into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Any organic chromium compound may be used.

As an organic copper compound, for example, acetylacetone copper (formal name: copper (II) -2,4-pentanedionate) [Cu (C ₅ H ₇ O ₂ ) ₂ ] as a copper acetylacetone complex, Copper (II) ethoxide [Cu (C ₂ H ₅ O) ₂ ], etc., copper (II) formate as an organic acid copper [Cu (HCOO) ₂ ], copper (II) acetate [Cu (CH ₃ COO) ₂ ] Basically, any organic copper compound that dissolves in a solvent and decomposes into an oxide without generating harmful gas such as chlorine gas or nitrogen oxide gas at the time of mineralization may be used.

Examples of organic gallium compounds include acetylacetone gallium (official name: gallium (III) -2,4-pentanedionate) [Ga (C ₅ H ₇ O ₂ ) ₃ ] as gallium acetylacetone complex, and gallium (III ) Ethoxide [Ga (C ₂ H ₅ O) ₃ ] and the like are basically dissolved in a solvent and oxidized without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Any organic gallium compound that decomposes into a material may be used.

As an organic yttrium compound, for example, acetylacetone yttrium (formal name: yttrium (III) -2,4-pentanedionate) [Y (C ₅ H ₇ O ₂ ) ₃ ] as an yttrium acetylacetone complex, etc. Examples include yttrium (III) isopropoxide [Y (C ₃ H ₇ O) ₃ ], and yttrium acetate (III) [Y (CH ₃ COO) ₃ ] as an organic acid yttrium. Basically, Any organic yttrium compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization may be used.

Examples of the organic molybdenum compound include molybdenum (VI) oxide bis-2,4-pentanedionate [MoO ₂ (C ₅ H ₇ O ₂ ) ₂ ] as a molybdenum acetylacetone complex, and molybdenum (V) ethoxide as a molybdenum alkoxide. [Mo (C ₂ H ₅ O) ₅ ] and the like can be mentioned. Basically, it dissolves in a solvent and does not generate harmful gas such as chlorine gas or nitrogen oxide gas during mineralization, and it is converted into oxide. Any organic molybdenum compound that decomposes may be used.

Examples of the organic ruthenium compound include acetylacetone ruthenium (formal name: ruthenium (III) -2,4-pentandionate) [Ru (C ₅ H ₇ O ₂ ) ₃ ] as a ruthenium acetylacetone complex. The organic ruthenium compound may be any organic ruthenium compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

Examples of the organic antimony compound include antimony acetate (III) [Sb (CH ₃ COO) ₃ ], antimony (III) ethoxide as antimony alkoxide [Sb (C ₂ H ₅ O) ₃ ], and antimony (III) -n. -Butoxide [Sb (C ₄ H ₉ O) ₃ ] and the like can be mentioned. Basically, it dissolves in a solvent and oxidizes without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Any organic antimony compound that decomposes into a material may be used. Among these, antimony (III) -n-butoxide is preferable because it is relatively inexpensive and easily available.

As an organic hafnium compound, for example, hafnium (IV) di-n-butoxide bis (2,4-pentanedionate) [Hf (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) as a hafnium acetylacetone complex _2]), acetylacetone hafnium (official name: hafnium _{(IV)-2,4-pentanedionate) [Hf (C 5 H 7} O 2) 4], hafnium as hafnium alkoxide (IV) ethoxide [Hf _{(C 2} H _{5 O)} 4], hafnium (IV)-n-butoxide _{[Hf (C 4 H 9 O} ) 4], hafnium (IV)-tert-butoxide _{[Hf (C 4 H 9 O} ) 4], hafnium (IV ) Isopropoxide monoisopropylate [Hf (C ₃ H ₇ O) ₄ (C ₃ H ₇ OH)] and the like. Specifically, it may be an organic hafnium compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Among these, hafnium (IV) -n-butoxide is preferable because it is relatively inexpensive and easily available.

Examples of the organic tantalum compound include tantalum (V) tetraethoxide-pentanedionate [Ta (C ₅ H ₇ O ₂ ) (OC ₂ H ₅ ) ₄ ] as a tantalum acetylacetone complex, and tantalum (V) as a tantalum alkoxide. ) Methoxide [Ta (CH ₃ O) ₅ ], tantalum (V) ethoxide [Ta (C ₂ H ₅ O) ₅ ], tantalum (V) isopropoxide [Ta (C ₃ H ₇ O) ₅ ], tantalum ( V) -n-butoxide [Ta (C ₄ H ₉ O) ₅ ], tetraethoxyacetylacetonato tantalum (V) [Ta (C ₂ H ₅ O) ₄ (C ₅ H ₇ O ₂ )] and the like. However, it is basically an organic tantalum compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Just do it.

Examples of the organic tungsten compound include tungsten (V) ethoxide [W (C ₂ H ₅ O) ₅ ] and tungsten (VI) ethoxide [W (C ₂ H ₅ O) ₆ ] as tungsten alkoxide. Basically, any organic tungsten compound may be used as long as it is dissolved in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

Examples of the organic bismuth compound include acetylacetone bismuth (formal name: bismuth (III) -2,4-pentandionate) [Bi (C ₅ H ₇ O ₂ ) ₃ ] as a bismuth acetylacetone complex, and bismuth alkoxide. Bismuth (III) pentoxide [Bi (C ₅ H ₁₁ O) ₃ ] and the like are basically dissolved in a solvent, and harmful gases such as chlorine gas and nitrogen oxide gas are generated during mineralization. Any organic bismuth compound that can be decomposed into an oxide without being used.

Examples of the organic cerium compound include acetylacetone cerium (formal name: cerium (III) -2,4-pentandionate) [Ce (C ₅ H ₇ O ₂ ) ₃ ] as cerium acetylacetone complex, and cerium as cerium alkoxide. (IV) methoxide ethoxide _{[Ce (CH 3 OC 2 H} 5 O) 4], cerium (IV)-tert-butoxide _{[Ce (C 4 H 9 O} ) 4], cerium (IV) isopropoxide [Ce ( C ₃ H ₇ O) ₄ ], etc., are basically dissolved in a solvent, and are decomposed into oxides without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization. Any cerium compound may be used.

Examples of the organic neodymium compound include acetylacetone neodymium (formal name: neodymium (III) -2,4-pentanedionate) [Nd (C ₅ H ₇ O ₂ ) ₃ ] as a neodymium acetylacetone complex, Although neodymium (III) methoxyethoxide [Nd (CH ₃ OC ₂ H ₄ O) ₃ ] and the like, neodymium acetate (III) [Nd (CH ₃ COO) ₃ ] as the organic acid neodymium and the like can be basically mentioned. May be any organic neodymium compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

Examples of the organic samarium compound include acetylacetone samarium (formal name: samarium (III) -2,4-pentanedionate) [Sm (C ₅ H ₇ O ₂ ) ₃ ] as a samarium acetylacetone complex. Samarium (III) isopropoxide [Sm (C ₃ H ₇ O) ₃ ] and the like, and samarium acetate (III) as organic acid samarium [Sm (CH ₃ COO) ₃ ] and the like can be mentioned. Any organic samarium compound can be used as long as it dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

Examples of organic gadolinium compounds include acetylacetone gadolinium (formal name: gadolinium (III) -2,4-pentandionate) [Gd (C ₅ H ₇ O ₂ ) ₃ ]] as a gadolinium acetylacetone complex, and gadolinium organic acid. Gadolinium acetate (III) [Gd (CH ₃ COO) ₃ ] and the like are basically dissolved in a solvent, and harmful gases such as chlorine gas and nitrogen oxide gas are generated during mineralization. Any organic gadolinium compound that decomposes into an oxide without being decomposed may be used.

As an organic magnesium compound, for example, acetylacetone magnesium (formal name: magnesium (II) -2,4-pentanedionate) [Mg (C ₅ H ₇ O ₂ ) ₂ ] as a magnesium acetylacetone complex, or magnesium alkoxide Magnesium (II) ethoxide [Mg (C ₂ H ₅ O) ₂ ], magnesium (II) n-propoxide [Mg (C ₃ H ₇ O) ₂ ], and the like. Any organic magnesium compound that dissolves and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization may be used.

As an organic calcium compound, for example, acetylacetone calcium (formal name: calcium (II) -2,4-pentandionate) [Ca (C ₅ H ₇ O ₂ ) ₂ ] as a calcium acetylacetone complex, Examples include calcium (II) ethoxide [Ca (C ₂ H ₅ O) ₂ ] and the like, and calcium acetate (II) [Ca (CH ₃ COO) ₂ ] as an organic acid calcium. Any organic calcium compound that dissolves and decomposes into an oxide without generating harmful gases such as chlorine gas or nitrogen oxide gas during mineralization may be used.

Examples of the organic strontium compound include acetylacetone strontium (formal name: strontium (II) -2,4-pentandionate) [Sr (C ₅ H ₇ O ₂ ) ₂ ] as a strontium acetylacetone complex, Strontium (II) isopropoxide [Sr (C ₃ H ₇ O) ₂ ] and the like, and strontium acetate (II) [Sr (CH ₃ COO) ₂ ] as an organic acid strontium, etc. may be mentioned. Any organic strontium compound that dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization may be used.

As an organic barium compound, for example, acetylacetone barium (formal name: barium (II) -2,4-pentandionate) [Ba (C ₅ H ₇ O ₂ ) ₂ ] as a barium acetylacetone complex, barium (II) isopropoxide _{[Ba (C 3 H 7 O} ) 2] , etc., barium acetate _{(II) [Ba (CH 3} COO) 2] as an organic acid barium and others as mentioned, basically, Any organic barium compound may be used as long as it dissolves in a solvent and decomposes into an oxide without generating harmful gases such as chlorine gas and nitrogen oxide gas during mineralization.

(Positive electrode, negative electrode) The organic metal compound in the active material layer forming coating solution or solid electrolyte layer forming coating solution is the main compound raw material for forming an active material layer (positive electrode, negative electrode) or solid electrolyte layer by a coating method. The content is preferably in the range of 1 to 30% by mass, more preferably 5 to 20% by mass.
When the total content is less than 1% by mass, only a thin active material layer (positive electrode, negative electrode) or solid electrolyte layer can be obtained, so that a sufficient function as a thin film for a thin film solid secondary battery cannot be obtained. On the other hand, if it exceeds 30% by mass (positive electrode, negative electrode), the organometallic compound in the coating solution for forming the active material layer or the coating solution for forming the solid electrolyte layer is likely to precipitate, leading to a decrease in the stability of the coating solution. The resulting active material layer (positive electrode, negative electrode) or solid electrolyte layer may become too thick and cause cracks.

(B) Binder component of coating solution (Positive electrode, negative electrode) An organic binder may be added to the active material layer forming coating solution or the solid electrolyte layer forming coating solution as necessary.
By adding an organic binder, the wettability with respect to the substrate is improved, and at the same time, the viscosity of the coating solution can be adjusted. The organic binder to be added is preferably a material that burns or thermally decomposes at the time of mineralization, and as such a material, a cellulose derivative, an acrylic resin, or the like is effective.
Examples of cellulose derivatives used in organic binders include methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, carboxyethyl methyl cellulose, and nitrocellulose. Among these, hydroxypropyl cellulose (hereinafter sometimes referred to as “HPC”) is preferable.
In addition, many types of cellulose derivatives and acrylic resins having different molecular weights are commercially available. For example, HPC has a high molecular weight type, a medium molecular weight type, and a low molecular weight type depending on the molecular weight. The viscosity of the coating liquid for forming an active material layer or the coating liquid for forming a solid electrolyte layer blended as a binder (positive electrode, negative electrode) can be increased as the molecular weight increases. The selection of the molecular weight type and the determination of the blending amount are (positive electrode, negative electrode) coating material for forming the active material layer and coating liquid for forming the solid electrolyte layer, and (positive electrode, negative electrode) coating solution for forming the active material layer. Further, it is necessary to optimize at any time according to the coating method and coating thickness of the coating solution for forming the solid electrolyte layer.

If this HPC is used, sufficient wettability can be obtained with a content of 5% by mass or less, and at the same time, the viscosity can be greatly adjusted. The combustion start temperature of HPC is about 300 ° C., and the mineralization by heat treatment burns if performed at a heating temperature of 300 ° C. or higher, preferably 350 ° C. or higher. , Negative electrode) and a solid electrolyte layer can be produced.
When the content of HPC exceeds 5% by mass, it becomes a gel and tends to remain in the coating solution, and a very porous active material layer (positive electrode, negative electrode) or solid electrolyte layer is formed, resulting in remarkable film strength. It may be damaged.

Here, as the cellulose derivative, for example, when ethyl cellulose is used instead of HPC, the viscosity of the coating liquid can be set lower than that when HPC is usually used, but a high-viscosity coating liquid is suitable. Etc., the pattern printability is slightly lowered.
By the way, although nitrocellulose is excellent in thermal decomposability, harmful nitrogen oxide gas is generated during mineralization, which may cause problems in degradation of the mineralization furnace and exhaust gas treatment. As described above, the cellulose derivative to be used needs to be appropriately selected depending on the situation.

  The acrylic resin is preferably an acrylic resin that burns at a relatively low temperature.

(C) Solvent of coating solution (Positive electrode, negative electrode) As the solvent used for the coating solution for forming the active material layer and the coating solution for forming the solid electrolyte layer, various metal acetylacetone complex compounds and various metal alkoxide compounds can be dissolved at a high concentration, In addition, a high boiling point solvent capable of being heated and dissolved at 80 to 180 ° C. in the process of producing the coating liquid described later is suitable. Specifically, N-methyl-2-pyrrolidone (NMP) (boiling point 204). 1) -amino-2-propanol (boiling point: 159.9 ° C.), 2-aminoethanol (also known as monoethanolamine) (boiling point: 171 ° C.), Amino-1-propanol (bp 188 ° C.), 2- (2-aminoethylamino) ethanol (bp 238-240 ° C./752 mmHg), 3-amino-1,2-propanediene All (boiling point 264 to 265 ° C./739 mmHg) and diethanolamine (boiling point 269 ° C.) are preferable. In particular, N-methyl-2-pyrrolidone (NMP) and 3-amino-1-propanol are optimal.
Furthermore, as another preferable solvent, either or both of alkylphenol and alkenylphenol and dibasic acid ester, or either or both of alkylphenol and alkenylphenol and benzyl acetate, or a mixed solution thereof can be mentioned.

  Examples of the alkylphenol or alkenylphenol include cresols, xylenol, ethylphenol, p-tert-butylphenol, octylphenol, nonylphenol, cashew nut shell liquid [3 pentadecadeseal phenol], and dibasic acid esters (for example, dibasic acid esters). As the basic acid dimethyl, dibasic acid diethyl and the like, succinic acid ester, glutaric acid ester, adipic acid ester, malonic acid ester, phthalic acid ester and the like are used.

  Furthermore, when adjusting the coating liquid to a low viscosity, or in order to improve the coating properties (positive electrode, negative electrode), various organic metals may be used as the solvent to be mixed in the active material layer forming coating liquid or the solid electrolyte layer forming coating liquid. It only needs to be compatible with the solution in which the compound and the cellulose derivative or acrylic resin are dissolved. As a solvent other than the above, water, methanol (MA), ethanol (EA), 1-propanol (NPA), isopropanol (IPA), Alcohol solvents such as butanol, pentanol, benzyl alcohol and diacetone alcohol (DAA), ketone solvents such as acetone, methyl ethyl ketone (MEK), methyl propyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone, isophorone, ethyl acetate, Butyl acetate, isobutyl acetate, amyl formate, isoamyl acetate, pro Butyl onate, isopropyl butyrate, ethyl butyrate, butyl butyrate, methyl lactate, ethyl lactate, methyl oxyacetate, ethyl oxyacetate, butyl oxyacetate, methyl methoxyacetate, ethyl methoxyacetate, butyl methoxyacetate, methyl ethoxyacetate, ethyl ethoxyacetate , Methyl 3-oxypropionate, ethyl 3-oxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl 2-oxypropionate, Ethyl 2-oxypropionate, propyl 2-oxypropionate, methyl 2-methoxypropionate, ethyl 2-methoxypropionate, propyl 2-methoxypropionate, methyl 2-ethoxypropionate, 2-ethoxypropio Ethyl acetate, methyl 2-oxy-2-methylpropionate, ethyl 2-oxy-2-methylpropionate, methyl 2-methoxy-2-methylpropionate, ethyl 2-ethoxy-2-methylpropionate, methyl pyruvate , Ester solvents such as ethyl pyruvate, propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl 2-oxobutanoate, ethyl 2-oxobutanoate, ethylene glycol monomethyl ether (MCS), ethylene glycol monoethyl ether (ECS) , Ethylene glycol isopropyl ether (IPC), ethylene glycol monobutyl ether (BCS), ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol methyl ether (PGM), propylene glycol ethyl ether (PE), propylene glycol methyl ether acetate (PGM-AC), propylene glycol ethyl ether acetate (PE-AC), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl Ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol Glycol derivatives such as rumonobutyl ether, benzene derivatives such as toluene, xylene, mesitylene, dodecylbenzene, formamide (FA), N-methylformamide, dimethylformamide (DMF), dimethylacetamide, dimethylsulfoxide (DMSO), γ-butyrolactone , Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butylene glycol, pentamethylene glycol, 1,3-octylene glycol, tetrahydrofuran (THF), chloroform, mineral spirits, terpineol, etc., and these two types Although the above liquid mixture is mentioned, it is not limited to these.

  In view of the stability of the coating solution and film formability, the solvent used in combination is preferably methyl ethyl ketone (MEK), cyclohexanone, propylene glycol monomethyl ether (PGM), diethylene glycol monomethyl ether, γ-butyrolactone, or the like.

  The coating material for forming an active material layer (positive electrode, negative electrode) and the coating solution for forming a solid electrolyte layer used in the present invention are various organometallic compounds as the above-mentioned main component, various other organometallic compounds as necessary, If necessary, it is produced by heating and dissolving a mixture containing an organic binder in a solvent.

The heat dissolution is usually performed by setting the heating temperature to 80 to 180 ° C. and stirring for 0.5 to 6 hours.
If the heating temperature is lower than 80 ° C., the solution is not sufficiently dissolved. If the heating temperature is higher than 180 ° C., evaporation of the solvent becomes remarkable and the composition of the coating solution changes, which is not preferable.

  (Positive electrode, negative electrode) The viscosity of the coating material for forming the active material layer and the coating solution for forming the solid electrolyte layer can be adjusted by the molecular weight and content of the organic binder and the type of the solvent. Suitable for various application methods such as gravure printing method, offset printing method, flexographic printing method, dispenser printing method, slit coating method, die coating method, doctor blade coating method, wire bar coating method, spin coating method, spray coating method, etc. It can be adjusted by adjusting the viscosity.

  The coating liquid having a high viscosity (about 5000 to 50000 mPa · s) can be prepared by containing a high molecular weight organic binder in an amount of 5% by mass or less, preferably 2 to 4% by mass, and has a low viscosity (about 5 to 500 mPa · s). Can be prepared by containing a low molecular weight organic binder in an amount of 5% by mass or less, preferably 0.1 to 2% by mass, and diluting with a low viscosity diluting solvent. A medium viscosity (500 to 5000 mPa · s) coating solution can be prepared by mixing a high viscosity coating solution and a low viscosity coating solution.

[Thin Film Manufacturing Method]
The manufacturing method of the thin film for thin film solid secondary batteries of this invention is demonstrated in detail.
The thin film (positive electrode active material layer, solid electrolyte layer, negative electrode active material layer) of the present invention contains an organic metal compound as a main component (positive electrode, negative electrode) active material layer forming coating solution or solid electrolyte layer forming coating solution. A coating process for forming a coating film by coating, a drying process for drying the coating film to form a dry coating film, an inorganic thin film (metal oxide) containing the metal oxide as a main component by mineralizing the dry coating film It is formed through each step of the mineralization step for forming the fine particle film.

(A) Coating process (Positive electrode, negative electrode) Application of an active material layer forming coating solution or a solid electrolyte layer forming coating solution is performed by inkjet printing, screen printing, gravure printing, offset printing, flexographic printing, dispenser Various coating methods such as a printing method, a slit coating method, a die coating method, a doctor blade coating method, a wire bar coating method, a spin coating method, and a spray coating method are used.

  As shown in FIG. 1 or FIG. 2, the thin film solid secondary battery includes a positive electrode current collector layer 2, a positive electrode active material layer 3, a solid electrolyte layer 4, a negative electrode active material layer 5, and a negative electrode current collector on a substrate 1. Since the layer 6 has a laminated structure, the coating liquid for forming the positive electrode active material layer may be applied on the positive electrode current collector layer or the solid electrolyte layer, and the negative electrode active material layer The forming coating solution may be applied on the negative electrode current collector layer or the solid electrolyte layer. The coating solution for forming the solid electrolyte layer is applied on the active material layer (positive electrode, negative electrode).

  (Positive electrode, negative electrode) Application of the active material layer forming coating solution or the solid electrolyte layer forming coating solution is preferably performed in a clean atmosphere such as a clean room where the temperature and humidity are controlled. The temperature is generally room temperature (about 25 ° C.) and the humidity is generally 40 to 60% RH.

(B) Drying step In the next drying step, the substrate coated with the (positive electrode, negative electrode) active material layer forming coating solution or the solid electrolyte layer forming coating solution is usually dried in the atmosphere at a drying temperature of 80 to 200 ° C., preferably Is held at 100 to 180 ° C. and dried for 1 to 30 minutes, preferably 2 to 10 minutes, to dry the coating film to produce a dry coating film.
Generally, the solubility of various organometallic compounds (in the coating solution) contained in the (positive electrode, negative electrode) active material layer forming coating solution or solid electrolyte layer forming coating solution as a main component is high. It gets higher. Therefore, if the drying temperature is increased, the coating film in the drying process can form a solid dry coating film via a liquid in which the various organometallic compounds are dissolved at a higher concentration. This can be further increased and is preferable.

However, the upper limit of the drying temperature must be equal to or lower than the boiling point of the main high-boiling solvent contained in the coating solution for forming the positive electrode and the negative electrode active material layer and the coating solution for forming the solid electrolyte layer, for example, the main high-boiling point. If the solvent is N-methyl-2-pyrrolidone (NMP) [boiling point: 204 ° C.], the drying temperature is about 150 to 200 ° C. If the solvent is 3-amino-1-propanol [boiling point: 188 ° C.], 150 to 180. About ℃ is good.
The drying conditions such as the drying temperature and the drying time are not limited to the type of the high-boiling solvent used in the coating solution, the type of the substrate used, the coating solution for forming the positive electrode and the negative electrode active material layer, and the solid electrolyte layer. What is necessary is just to select suitably by application | coating thickness etc. of a coating liquid, and it is not necessarily limited to the said drying conditions. However, in consideration of productivity, it is desirable that the drying time is shortened to the minimum necessary so that the quality of the obtained dry coating film is not deteriorated.

  Also, the drying temperature needs to be lower than the heat resistance temperature of the substrate to be used. In addition, it is also possible to apply reduced-pressure drying (attainment pressure: usually 1 kPa or less) instead of drying in the air as necessary. In this drying under reduced pressure, the solvent in the applied (positive electrode, negative electrode) active material layer forming coating solution or solid electrolyte layer forming coating solution is forcibly removed under reduced pressure, and the drying proceeds. Compared to drying, drying at a lower temperature is possible.

  The produced dry coating film is obtained by volatilizing and removing the above organic solvent from the coating solution for forming the positive electrode and the negative electrode active material layer and the coating solution for forming the solid electrolyte layer. It is composed of organic components such as organic metal compounds (various organic metal compounds other than these, which are added in small amounts as necessary), organic binders and the like.

(C) Mineralization process In the next mineralization process, the dried coating film produced in the drying process is mineralized, and the organometallic compound as the main component in the dried coating film, or various organometallic compounds added in small amounts, and organic Organic components such as binders are mineralized by thermal decomposition and combustion (oxidation) by heat treatment, energy beam irradiation treatment, and plasma irradiation treatment in an oxygen-containing atmosphere, and metal oxides are the main components. An inorganic thin film (active material layer (positive electrode, negative electrode) or solid electrolyte layer as a metal oxide fine particle film filled with metal oxide fine particles) is formed.

  For example, in a mineralization process using heat treatment, if the heating temperature becomes higher during the temperature rising process, an organometallic compound as a main component in the dry coating film (including an organometallic compound added in a small amount). Are gradually pyrolyzed and burned (oxidized) to form a metal oxide in an amorphous state (herein, a crystallite size determined by X-ray diffraction: a state of very fine particles of less than 3 nm). Conversion, so-called mineralization occurs. Thereafter, when the heating temperature is further increased and usually exceeds 500 to 600 ° C., crystallization or crystal growth of the metal oxide occurs to produce metal oxide crystal fine particles, and an active material layer (positive electrode, negative electrode) or solid electrolyte layer. Becomes a crystalline thin film.

On the other hand, the organic binder is also thermally decomposed and burned (oxidized) gradually during the temperature rising process in the mineralization process using heat treatment, but it is mainly converted into carbon dioxide (CO ₂ ) and volatilized in the atmosphere. And disappears from the film (depending on the type of organic binder, but for HPC, for example, it disappears at about 300 to 350 ° C.), so that the active material layer (positive electrode, negative electrode) or solid electrolyte is finally obtained. Almost no residue in the layer. It should be noted that a large amount of organic binder remains until the initial stage of the mineralization process when heat treatment is used (at a stage where the temperature rises, for example, the stage where heating is performed from room temperature to reach 300 ° C.) An organic binder is uniformly present between the metal oxides, but when the heating temperature is further increased and inorganicization is advanced, the organic binder component gradually disappears and the crystallization of the metal oxide occurs. Conceivable.

Hereinafter, the mineralization process will be described in more detail.
In the mineralization process of the dry coating film of the present invention, carbon dioxide (CO ₂₎ concentration low oxygen-containing atmosphere (e.g., CO ₂ is removed by suction or the like due to zeolite from the atmosphere that contains typically 380ppm about CO ₂ It is desirable to apply an air atmosphere in which the CO ₂ concentration is less than 1 ppm. When the oxygen-containing atmosphere contains a large amount of carbon dioxide (CO ₂ ), lithium carbonate (Li ₂ CO ₃ ) is generated by reaction with lithium (Li), which is the main component of the inorganic thin film, during the formation of the inorganic thin film This is because an inorganic thin film having a desired composition may not be obtained.
In addition, dew point temperature, that is, an oxygen-containing atmosphere in which the water vapor content is controlled (for reference, FIG. 4 shows the relationship between the saturated water vapor content (volume%) in air and the dew point temperature (° C.)). Is desirable.
For example, when an oxygen-containing atmosphere having a low dew point temperature is applied to the mineralization process, as described above, the inorganic coating of the dry coating film at the initial stage of the mineralization process is suppressed, and the inorganic thin film is densely filled with metal oxide fine particles. The thin film structure can be obtained.

The mechanism by which the metal oxide fine particles are densely packed is not necessarily clear, but can be considered as follows, for example.
That is, at least in the mineralization process using heat treatment, in the temperature rising process in an air atmosphere with a low dew point temperature, a film structure in which an organic binder is uniformly interposed between the generated amorphous metal oxides is maintained. The film structure is flexible by the action of the organic binder, which is an organic substance, and the film can be contracted (densified) in the direction perpendicular to the substrate. It is presumed that the shrinkable film structure can be taken and the film is densified.

In addition, although the reason why demineralization of the dried coating film is suppressed in an air atmosphere having a low dew point temperature, that is, a low water vapor content is not clear, for example, water vapor in the air atmosphere is
(1) It has an action of promoting thermal decomposition and combustion (oxidation) of the organic binder component interposed between the metal oxides.
(2) has the effect of promoting mineralization of the metal oxide itself,
Etc. are considered.

Specifically, in the mineralization step using heat treatment, first, the oxygen-containing atmosphere gas having a dew point temperature of −80 ° C. to 30 ° C. is supplied, and the temperature is higher than the temperature at which mineralization crystallization of the metal oxide occurs (usually 300 to 330 ° C. The temperature is increased to the above) to perform mineralization, and the density of the thin film to be formed is controlled.
Active material layers (positive electrode, negative electrode) and solid electrolyte layer can be obtained by mineralization by simple heat treatment as described above, but energy beam irradiation treatment and plasma irradiation treatment described below are used alone or in combination with heat treatment. By performing the above treatment, it is possible to greatly promote the mineralization in the oxygen-containing atmosphere, particularly when the heating temperature is low. In other words, an inorganic thin film can be obtained by heat treatment at a low temperature (less than 300 ° C .; for example, about 150 ° C.).

In other words, the obtained dry coating film in the drying step, CO ₂ concentration is low, in an oxygen-containing atmosphere was controlled within the range of dew point -80 ° C. to 30 ° C., the inorganic process performing energy ray irradiation or plasma irradiation (If necessary, heat treatment is also used).
This method gradually decomposes and burns (oxidizes) the organic components of the dried coating film, advances the mineralization of the film, gradually decreases the thickness of the film, and the dew point temperature of the oxygen-containing atmosphere is low. Densification is further promoted. For example, a dry coating film having a thickness of 130 to 150 nm is finally made mineral by combining a low-temperature heat treatment of 150 to 200 ° C. with an energy ray irradiation treatment or a plasma irradiation treatment in an oxygen-containing atmosphere with a dew point temperature of about −50 ° C. In particular, it can be changed to an inorganic thin film having a thickness of about 60 to 70 nm.

In addition, the heating temperature in the case of using both energy beam irradiation treatment or plasma irradiation treatment and heat treatment is preferably less than 300 ° C, preferably 40 to 250 ° C, more preferably 100 to 200 ° C, and still more preferably 100 to 150. It is in the range of ° C. When the temperature is 300 ° C. or higher, the thermal decomposition of the dry coating film to which the energy beam irradiation or the plasma irradiation treatment is performed before the energy beam irradiation or the plasma irradiation treatment is started, so that densification of the film is hindered.
In addition, energy rays are usually emitted from a lamp for energy ray irradiation in addition to energy rays such as ultraviolet rays, and the substrate temperature rises by plasma energy even in the plasma irradiation treatment without using heat treatment. For example, in the energy ray irradiation treatment using ultraviolet rays, the substrate temperature rises to about 40 to 50 ° C., and therefore, it is not meaningful to use the heat treatment together when the heating temperature of the heat treatment is less than 40 ° C.

Hereinafter, the energy beam irradiation process will be described in detail.
The energy ray irradiation used for the energy ray irradiation treatment of the present invention is preferably ultraviolet ray irradiation containing at least a wavelength of 200 nm or less as one of main components, and more specifically, a low pressure mercury lamp, an amalgam lamp, an excimer. Irradiation with ultraviolet light emitted from any of the lamps is preferred. (Hereinafter, the energy ray irradiation treatment by ultraviolet irradiation with a wavelength of 200 nm or less may be referred to as “short wavelength UV irradiation treatment”.)
The irradiation amount of ultraviolet rays is the illuminance of light having a wavelength of 200 nm or less: ² mW / cm ² or more, preferably 4 mW / cm ² or more, and the irradiation time is 1 minute or more, preferably 2 minutes or more, more preferably 4 minutes or more. good. If the irradiation time is too short, the effect of energy beam irradiation (mineralization, densification) will be insufficient, and conversely if it is too long (for example, a long time exceeding 60 minutes), the productivity (treatment efficiency) will be remarkable. On the other hand, the effect (inorganicization and densification) of energy beam irradiation is not preferable because it is almost saturated in the middle.

  The irradiation amount of the ultraviolet rays can be appropriately adjusted by the distance between the substrate and the lamp (irradiation distance), the irradiation time, or the output of the lamp. In energy beam irradiation to the entire surface of the substrate using this lamp, for example, straight tube lamps may be arranged in parallel, or a surface light source of a grid type lamp may be used.

Here, the energy beam irradiation in the energy beam irradiation process may be performed on the entire surface of the dry coating film, or may be performed in a pattern shape only on a specific portion of the dry coating film. In this case, since the inorganicization of the above-described film proceeds only in the portion subjected to the energy beam irradiation, an inorganic thin film having a pattern shape can be formed.
In addition, when it is necessary to remove the dry coating film portion where the inorganic thin film has not been formed (the dry coating film portion where the energy beam has not been irradiated), the dry coating film can be dissolved because the portion is not mineralized. It can be removed by dissolving with an organic solvent, and in some cases with an alkaline aqueous solution. On the other hand, inorganicized inorganic thin film portions do not dissolve at all in organic solvents, and depending on the type of metal oxide and may not dissolve in alkaline aqueous solution, it is possible to leave only the inorganic thin film portions on the substrate. It becomes.

  Examples of the organic solvent excellent in solubility of the dry coating film used include methyl ethyl ketone (MEK), methyl propyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone, acetylacetone (2,4-pentanedione), dimethylformamide (DMF), Examples thereof include dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and γ-butyrolactone.

  Examples of the alkaline aqueous solution excellent in solubility of the dry coating film to be used include sodium carbonate, caustic soda, caustic potash, ammonia water, ethylamine, diethylamine, dimethylethanolamine, tetraethylammonium hydroxide, tetramethylammonium hydroxide (TMAH) and the like. Alkaline aqueous solution (concentration = 0.1 to 5 mass%) and the like.

  Hereinafter, the low-pressure mercury lamp and excimer lamp capable of emitting light with a wavelength of 200 nm or less will be described in detail. However, there are few restrictions on the use of energy beam irradiation, and the influence of heating on the lamp when used in combination with heat treatment will be described. It is more preferable to use a low-pressure mercury lamp that can be reduced.

Amalgam lamps generally contain argon gas and mercury in a quartz glass tube while low-pressure mercury lamps enclose an amalgam alloy that is an alloy of mercury and a special rare metal. The output can be increased by about 3 times, and the output wavelength characteristic is almost the same as that of the low-pressure mercury lamp, so that the detailed description is omitted. As a matter of course, an amalgam lamp is also preferable, as is the case with a low-pressure mercury lamp, because there are few restrictions on use in energy beam irradiation, and the influence of heating on the lamp can be reduced when used in combination with heat treatment.
However, it is also possible to use a special device that cools the lamp using nitrogen gas or the like that does not absorb ultraviolet rays as a cooling gas, and this is not the case.

The low-pressure mercury lamp emits ultraviolet rays having wavelengths of 185 nm and 254 nm. For example, in the air, 185 nm light decomposes oxygen to generate ozone as shown in the following reaction formulas (1) to (3). The ozone is decomposed by light of 254 nm at a speed of ms (milliseconds) to generate high energy active atomic oxygen O ( ¹ D). At the same time, 185 nm light (photon energy: 647 kJ / mol) and 254 nm light break the chemical bond of the organic substance, and ozone and active atomic oxygen act on the organic substance whose chemical bond is cut, and finally It is thought that organic substances are oxidized and volatilized into water and carbon dioxide gas. The effective irradiation distance is 0-20 mm (the critical irradiation distance is 200 mm), and a relatively long irradiation distance can be secured.

On the other hand, an excimer lamp (xenon excimer lamp) emits ultraviolet light having a wavelength of 172 nm. Unlike, for example, a low-pressure mercury lamp in air, high-energy active atomic oxygen O ( ¹ D shown in the following reaction formula (4) is used. ) Can be directly generated (the dissociation of the reaction formula (4) requires a wavelength of 175 nm or less, so this dissociation does not occur with light of 185 nm from a low-pressure mercury lamp). Further, ozone can be generated by the reaction formula (5), and active atomic oxygen can also be generated by the reaction formula (6) (the reaction formula (6) is a secondary reaction, and the main generation of active atomic oxygen is the reaction formula). (4).

Further, since the energy of photons is as large as 696 kJ / mol, there is an advantage that the ability to cut organic bonds is high (because it is higher than the molecular bond energy of most organic substances, the probability of breaking the molecular bonds increases). However, 172 nm light has an oxygen absorption coefficient about 100 times larger than that of 185 nm light from a low-pressure mercury lamp and is strongly absorbed by oxygen. Therefore, the ozone and high-energy active atomic oxygen are Oxidation reaction takes place only in the vicinity, and there is a drawback that the effective irradiation distance in the atmosphere is extremely shortened to 0 to 3 mm (critical irradiation distance is 8 mm).
As described above, an inorganic thin film filled with metal oxide fine particles can be obtained by densifying the organic component in the dry coating film while making it inorganic by thermal decomposition and combustion (oxidation).

Next, the plasma irradiation process will be described in detail.
As the plasma used for the plasma irradiation treatment of the present invention, microwave plasma or high frequency plasma (RF plasma) can be considered, but any plasma can be applied.

First, microwave plasma irradiation treatment using microwave plasma will be described. Microwave is an electromagnetic wave having an extremely short wavelength, and is a general term for radio waves having a wavelength of about 3 to 30 cm (frequency 1000 M to 10,000 MHz). 2450 MHz and 915 MHz are used, but 2450 MHz is common. The microwave plasma is generally stably formed under a reduced pressure atmosphere (pressure 2 to 200 Pa, preferably 3 to 20 Pa, more preferably ³ to 10 Pa), and a high-density plasma of 10 ¹¹ to 10 ¹² / cm ³ can be obtained. it can.
If the pressure is too high (over 200 Pa), microwave plasma formation becomes difficult, and at the same time, the existence lifetime of ions and active atoms in the plasma is shortened, and the ion concentration and active atom concentration are lowered. Since the effect of irradiation (mineralization, densification) becomes small, it cannot be said that it is preferable. Similarly, if the pressure is too low (less than 2 Pa), it is difficult to form microwave plasma, and at the same time, the ion concentration and active atom concentration in the plasma are lowered, which is not preferable.

Next, high-frequency plasma irradiation processing using high-frequency plasma will be described. High-frequency is an electromagnetic wave having a radio frequency (RF) wavelength, and is a general term for radio waves having a wavelength of about 1 m to 100 km (frequency 3 k to 300 MHz). Industrially, 13.56 MHz, 27.12 MHz, 40.68 MHz, and the like are used, but 13.56 MHz is common.
The high-frequency plasma can be formed relatively stably in a wider pressure range (pressure 2 Pa to 100 kPa (atmospheric pressure)) than the microwave plasma, and the plasma density is about 10 ⁹ to 10 ¹⁰ / cm ^3. Although somewhat lower than the above, for example, atmospheric pressure high-frequency plasma irradiation processing using an atmospheric pressure atmosphere has the advantage of simplifying the device structure and reducing the device cost.

  In plasma irradiation treatment, the substrate is heated because the electron temperature of plasma is high (electron temperature of microwave plasma: about 1 eV, high-frequency plasma: about several eV), and the heating temperature depends on the plasma irradiation treatment conditions (substrate and plasma). Depending on the distance of the generating part (irradiation distance), processing time, input energy (several hundred watts to several kilowatts, etc.), it varies greatly from 100 to several hundred degrees. Just do it. The setting of the heating temperature at the time of the heat treatment may be performed by the plasma irradiation treatment alone, or may be performed by using both the heat treatment (by the heating device) and the plasma irradiation treatment.

  Both the microwave and high-frequency plasma irradiation treatments have the effect of greatly promoting mineralization and densification in an oxygen-containing atmosphere, and the inorganic thin film is the same as the energy ray irradiation treatment such as ultraviolet rays described above. Can be used to form

By the way, after obtaining a dense thin film by mineralization in an oxygen-containing atmosphere having a low CO ₂ concentration and a low dew point temperature (−10 ° C. or lower; for example, −10 to −80 ° C.), Further, mineralization may be promoted by supplying an oxygen-containing atmosphere gas having a low CO ₂ concentration and a high dew point temperature (0 ° C. or higher; for example, 0 to 30 ° C.).
Furthermore, after obtaining an inorganic thin film as an active material layer (positive electrode, negative electrode) or a solid electrolyte layer by mineralization in an oxygen-containing atmosphere gas, if necessary, for example, for the purpose of improving electronic conductivity, In order to adjust the oxygen content of the film (the amount of oxygen deficiency, that is, the amount of oxygen vacancies), an inorganic treatment can be performed while supplying a neutral atmosphere or a reducing atmosphere gas.

The oxygen-containing atmosphere gas used in the present invention includes air, oxygen gas, or a mixed gas of oxygen gas and neutral atmosphere gas (nitrogen) / inert gas (argon, helium, etc.), but is available at a low price. Air that is easy to do, particularly air from which CO ₂ has been removed (CO ₂ concentration of less than 1 ppm) is preferred.

Here, the heating temperature (peak temperature) of the mineralization process using a simple heat treatment in an oxygen-containing atmosphere (that is, a heat treatment that is not combined with energy beam irradiation treatment or plasma irradiation treatment) is 300 ° C. or higher. More preferably, it is 350 degreeC or more, More preferably, it is 5-120 minutes at the heating temperature of 400 degreeC or more, More preferably, it is 15-60 minutes.
At a heating temperature lower than 300 ° C. (especially a heating temperature lower than 270 ° C.), the thermal decomposition or combustion of organic components (organic components contained in an organic metal compound organic binder, etc.) contained in the dried coating film is usually insufficient. These organic components remain in the active material layer (positive electrode, negative electrode) or solid electrolyte layer, resulting in insufficient mineralization, insufficient film densification, and active material layer (positive electrode, negative electrode) This is not preferable because it may not function as a solid electrolyte layer.

However, when the heat treatment time is increased to, for example, about 60 minutes or longer, or when the final active material layer (positive electrode, negative electrode) or solid electrolyte layer is as thin as about 50 nm or less, for example, even at about 270 ° C. In some cases, thermal decomposition or combustion of the organic component proceeds to achieve mineralization of the film.
Therefore, in mineralization using a simple heat treatment, a heating temperature of 300 ° C. or higher is generally preferable, but depending on the conditions (film thickness, mineralization time, etc.) of each process, a heating temperature of about 270 ° C. may be used. Applicable.

Moreover, although the upper limit of the heating temperature in the mineralization process using a simple heat treatment is not particularly limited, it is affected by the type of mineralizer used, the heat resistance of the substrate, and the like. For example, a soda-lime glass substrate that is inexpensive and most commonly used has a strain point of about 510 ° C., and therefore, it is preferable to mineralize at a temperature lower than this temperature. However, if the soda lime glass substrate is mineralized on a heat resistant base material having higher heat resistance, the distortion of the substrate can be relatively reduced, so that the mineralization at about 600 ° C. is also possible. Of course, when a glass substrate having higher heat resistance such as a quartz glass substrate, an alkali-free glass substrate, or a high strain point glass substrate is used, a higher heating temperature can be applied.
When a polyimide (PI) film, which is a heat resistant plastic, is used as the substrate, it can be inorganicized up to about 400 ° C., depending on the type of polyimide.

Examples of the mineralization apparatus used in the mineralization process using heat treatment include, but are not limited to, a hot plate, a hot-air circulating mineralization furnace, an electric furnace, and an infrared heating apparatus.
Among infrared heating devices, a rapid thermal annealing furnace (RTA furnace) enables heat treatment in a very short time by irradiating a sample with a strong infrared ray from a halogen lamp or a xenon flash lamp. Therefore, the efficiency of the mineralization process can be improved.
However, in order to carry out the present invention, it is preferable to use an oxygen-containing atmosphere that is low in carbon dioxide (CO ₂ ) and controlled in the range of dew point temperature of −80 ° C. to 30 ° C. The mineralization apparatus is required to be able to control the mineralization atmosphere.

There is no particular limitation on the rate of temperature increase up to a temperature at which crystallization of the metal oxide occurs in the temperature increase process of the mineralization step using heat treatment, but a range of 5 to 40 ° C./min is more general. Is 10 to 30 ° C./min.
If the heating rate is slower than 5 ° C./min, it takes too much time to raise the temperature and the efficiency is deteriorated. On the other hand, if it is attempted to realize a heating rate exceeding 40 ° C./min with the above mineralizer, In the case of a heater, the heater capacity becomes too large, which is not realistic. However, in the rapid heating apparatus (RTA furnace), rapid heating at 100 ° C./min or more is possible and can be used preferably.

  The neutral atmosphere used in the mineralization treatment while supplying the neutral atmosphere or reducing atmosphere gas is composed of one or more of nitrogen gas and inert gas (argon, helium, etc.). An atmosphere in which at least one or more of hydrogen or an organic solvent vapor (an organic gas such as methanol) is contained in the hydrogen gas or the neutral atmosphere is exemplified, but not limited thereto. A mixed gas of 1-2% hydrogen-99-98% nitrogen is a preferable reducing atmosphere because there is no risk of explosion even if it leaks into the atmosphere.

The treatment conditions for mineralization in a neutral or reducing atmosphere are a heating temperature of 250 ° C. or higher, more preferably a heating temperature of 350 ° C. or higher, for 5 to 120 minutes, more preferably 15 to 60 minutes.
Moreover, although the upper limit of this heating temperature is not specifically limited, The point affected by the kind of mineralization apparatus used at an inorganicization process and the heat resistance of a board | substrate is the same as that of mineralization in oxygen-containing atmosphere.

Note that, in the mineralization step using heat treatment, mineralization in an oxygen-containing atmosphere having various dew point temperatures with low CO ₂ concentration and mineralization in a neutral or reducing atmosphere can be performed continuously. it can. That is, in the mineralization of a substrate on which a dry coating film is formed, for example, after raising the temperature of the substrate to a heating temperature of 300 ° C. or higher, the dew point temperature with a low CO ₂ concentration is maintained while maintaining the temperature. May be switched to different oxygen-containing atmospheres, or neutral atmospheres or reducing atmospheres.

  Since the thin film for a thin film solid secondary battery according to the present invention can be formed by a very simple method called a coating method, it can be applied to the positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer of the thin film solid secondary battery. Thus, the present invention can greatly contribute to cost reduction of a thin film solid state secondary battery that can be reduced in thickness and size.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

[Preparation of coating liquid for forming positive electrode active material layer]
Lithium (I) -tert-butoxide (solid at room temperature) [Li (C ₄ H ₉ O)] (molecular weight = 80.05) 3.46 g, cobalt (II) formate (solid at room temperature) [Co (COOH) ₂ 2H ₂ O] (molecular weight = 185.0) 8.0 g, 3-amino-1-propanol 88.54 g mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve, then obtained To 10 g of the resulting solution, 9.996 g of propylene glycol monomethyl ether (PGM) and 0.004 g of a surfactant were mixed and stirred well until uniform, and lithium (I) -tert-butoxide and cobalt formate (II) were added. Coating liquid for forming positive electrode active material layer (lithium (I) -tert-butoxide: cobalt formate (II)) containing a total of 5.73% by mass (not containing hydroxypropyl cellulose) = 1: 1 [molar ratio]).

[Preparation of thin film]
The produced coating liquid for forming a positive electrode active material layer was formed on a non-alkali glass substrate (5 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) at 25 ° C. After spin coating (3000 rpm × 60 sec) on the entire surface, the coating was dried in air at 150 ° C. for 5 minutes to obtain a dry coating film (film thickness: about 120 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)) It was.
Next, as shown in the schematic diagram of mineralization process using heat treatment and energy ray irradiation step in the manufacturing method of a thin film by coating method of FIG. 5, a substrate 9 having the dry coating film 10, CO ₂ concentration 1ppm The temperature is raised to 150 ° C. in a low-humidity air having a dew point temperature of −55 ° C. (heating rate: 30 ° C./min), and the low-humidity air having a dew point temperature of −55 ° C. less than 1 ppm of CO ₂ is irradiated with the ultraviolet irradiation window 12 ( A synthetic quartz plate (thickness 2 mm) and a substrate 9 while being heated to 150 ° C. while being supplied between them, an energy ray irradiation treatment is performed in combination with a heat treatment for irradiating the low-pressure mercury lamp 11 for 30 minutes, and the dry coating film 10 Thin film solid according to Example 1 comprising a positive electrode active material layer mainly composed of a lithium composite oxide (LCO: LiCoO ₂ ) containing cobalt by promoting mineralization (decomposition or combustion of organic components) and densification two A thin film (film thickness: about 62 nm) for a secondary battery was produced.
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size (hereinafter also referred to as crystallite diameter) of the positive electrode active material layer formed by the coating method in the thin film produced Various characteristics were measured and the results are shown in Table 1.
From the result of X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method is an amorphous film. Further, when the cross section of the positive electrode active material layer of Example 1 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

The surface resistance of the positive electrode active material layer formed by the coating method was measured using a surface resistance meter Hiresta IP (MCP-HT260) manufactured by Mitsubishi Chemical Corporation. In addition, although it is thought that the measured surface resistance is combining both electron conduction and ion conduction, for example, the surface resistance is as low as about 10 ⁵ to 10 ⁶ Ω / □ (ohm per square). In the case of the value, the electron conduction is mainly, and in the case where the surface resistance is as high as 10 ⁸ to 10 ¹² Ω / □, the measurement is performed by applying a high voltage of 250 to 500 V to the measurement probe. The contribution is thought to have increased.
The film thickness was measured using an optical profiler (New View 6200 manufactured by Zygo).
The crystallite size was determined by the Scherrer method after X-ray diffraction measurement.

[Preparation of coating liquid for forming positive electrode active material layer]
Lithium (I) -tert-butoxide (solid at room temperature) [Li (C ₄ H ₉ O)] (molecular weight = 80.05) 9.07 g, nickel (II) formate (solid at room temperature) [Ni (HCOO) ₂ 2H ₂ O] (molecular weight = 184.77) 20.93 g and 3-amino-1-propanol 70 g are mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve, and then the resulting dissolution To 10 g of the liquid, 9.996 g of diethylene glycol monomethyl ether and 0.004 g of a surfactant were mixed and stirred well until uniform, and lithium (I) -tert-butoxide and nickel (II) formate totaled 10% by mass ( Coating liquid for forming positive electrode active material layer containing no hydroxypropyl cellulose) (lithium (I) -tert-butoxide: nickel formate (II) = 1: 1 [mol Ratio]).

[Preparation of thin film]
The produced coating liquid for forming a positive electrode active material layer was formed on a non-alkali glass substrate (5 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) at 25 ° C. After spin coating (3000 rpm × 60 sec) on the entire surface, the coating was dried in air at 150 ° C. for 5 minutes to obtain a dry coating film (film thickness: about 120 nm).
Next, as shown in the schematic diagram of the inorganic treatment process using the heat treatment and energy beam irradiation process in the thin film manufacturing method by the coating method of FIG. 5, the substrate 9 having this dry coating film 10 is made to have a CO ₂ concentration of 1 ppm. The temperature is raised to 150 ° C. in a low-humidity air with a dew point temperature of −30 ° C. (heating rate: 30 ° C./min), and the low humidity air with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −30 ° C. is applied to the ultraviolet irradiation window 12 ( A synthetic quartz plate (thickness 2 mm) and a substrate 9 while being heated to 150 ° C. while being supplied between them, an energy ray irradiation treatment is performed in combination with a heat treatment for irradiating the low-pressure mercury lamp 11 for 20 minutes. Thin film solid according to Example 2 comprising a positive electrode active material layer mainly composed of a lithium composite oxide containing nickel (LNO: LiNiO ₂ ) by promoting mineralization (decomposition or combustion of organic components) and densification two A thin film (film thickness: about 45 nm) for a secondary battery was produced.
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Further, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −30 ° C.) is approximately 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of the X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method is an amorphous film. Further, when the cross section of the positive electrode active material layer of Example 2 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating liquid for forming positive electrode active material layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] (molecular weight = 106.05) 1.31 g, manganese acetylacetone (solid at room temperature) [Mn (C ₅ H ₇ O ₂ ) ₃ ] (molecular weight = 352.26) 8.69 g, N-methyl-2-pyrrolidone (NMP) 39 g, hydroxypropylcellulose (HPC; low molecular weight type) 1 g are mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve. Next, 5 g of the resulting solution was mixed with 6 g of cyclohexanone, 3 g of propylene glycol monomethyl ether (PGM), 6 g of methyl ethyl ketone (MEK), and 0.004 g of a surfactant, and stirred well until uniform. And 5% by mass of acetylacetone manganese and 0.5% hydroxypropylcellulose % Positive electrode active material layer forming coating solution containing (acetylacetone lithium acetylacetone manganese = 1: 2 [molar ratio]) was prepared.

[Preparation of thin film]
The produced coating liquid for forming a positive electrode active material layer was formed on a non-alkali glass substrate (5 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) at 25 ° C. After spin coating on the entire surface (1500 rpm × 60 sec), drying in the atmosphere at 100 ° C. for 5 minutes yields a dry coating film (film thickness: about 105 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)) It was.
Next, as shown in the schematic diagram of the inorganic treatment process using the heat treatment and energy beam irradiation process in the thin film manufacturing method by the coating method of FIG. 5, the substrate 9 having this dry coating film 10 is made to have a CO ₂ concentration of 1 ppm. The temperature is raised to 150 ° C. in a low-humidity air having a dew point temperature of −55 ° C. (heating rate: 30 ° C./min), and the low-humidity air having a dew point temperature of −55 ° C. less than 1 ppm of CO ₂ is irradiated with the ultraviolet irradiation window 12 ( A synthetic quartz plate (thickness 2 mm) and a substrate 9 while being heated to 150 ° C. while being supplied between the substrate 9 and the low-pressure mercury lamp 11 for 10 minutes. Example 3 comprising a positive electrode active material layer mainly composed of a lithium composite oxide (LMO: LiMn ₂ O ₄ ) containing manganese by promoting mineralization (decomposition or combustion of organic components) and densification Thin film Thin film for a secondary battery: was produced (thickness: about 66 nm).
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² .
Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method is an amorphous film. Further, when the cross section of the positive electrode active material layer of Example 3 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.

  In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of thin film]
The coating liquid for forming the positive electrode active material layer of Example 3 was an alkali-free glass substrate at 25 ° C. (5 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%). After spin coating (2000 rpm × 60 sec) on the entire upper surface, it was dried in air at 100 ° C. for 5 minutes to dry coating film (film thickness: about 88 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)) Got.
Next, as shown in the schematic diagram of FIG. 5, the substrate 9 having the dry coating film 10 is heated in a low-humidity air having a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. without using heat treatment (heating). Low pressure mercury lamp while supplying low-humidity air having a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. between the ultraviolet irradiation window 12 (synthetic quartz plate; thickness 2 mm) and the substrate 9 (without using the apparatus 8) 11 is irradiated with energy rays for 10 minutes to promote mineralization (decomposition or combustion of organic components) and densification of the dried coating film 10 to promote lithium densification (LMO: LiMn ₂ O ₄ ) containing manganese. An inorganic thin film (thickness: about 47 nm) was obtained. The same film forming operation is repeated using a coating liquid for forming a positive electrode active material layer, and two layers of this inorganic thin film are laminated, and a positive electrode mainly composed of a lithium composite oxide containing manganese (LMO: LiMn ₂ O ₄ ). A thin film (film thickness: about 94 nm) for a thin film solid secondary battery according to Example 4 made of an active material layer was produced.
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.
In addition, in the energy ray irradiation treatment not using the above heat treatment, it was confirmed that the substrate temperature was raised to about 40 to 42 ° C. by the heat rays emitted from the low pressure mercury lamp 11.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method was an amorphous film. Further, when the cross section of the positive electrode active material layer of Example 4 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.

  In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating liquid for forming negative electrode active material layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] (molecular weight = 106.05) 1.78 g, titanium acetylacetone (liquid at room temperature) [Ti (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 392.32) 8.22 g, N-methyl-2-pyrrolidone (NMP) 39 g, and hydroxypropylcellulose (HPC; low molecular weight type) 1 g are mixed and heated to 120 ° C. The mixture is stirred for 120 minutes, and then mixed with 5 g of the obtained solution, 6 g of cyclohexanone, 3 g of propylene glycol monomethyl ether (PGM), 6 g of methyl ethyl ketone (MEK), and 0.004 g of a surfactant are mixed uniformly. Stir well until 5% by mass of lithium acetylacetone and titanium acetylacetone in total, hydroxypropylcellulose A coating liquid for forming a negative electrode active material layer (acetylacetone lithium: acetylacetone titanium = 4: 5 [molar ratio]) containing 0.5% by mass of sucrose was prepared.

[Preparation of thin film]
The prepared coating liquid for forming a negative electrode active material layer was placed on a non-alkali glass substrate (10 cm × 10 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) at 25 ° C. After spin coating (1000 rpm × 60 sec) on the entire surface, the coating was dried in air at 100 ° C. for 5 minutes to obtain a dry coating film (film thickness: about 100 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)) It was. As shown in the schematic diagram of FIG. 5, the substrate 9 having the dry coating film 10 is heated to 150 ° C. in a low-humidity air having a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. (heating rate: 30 ° C. / And heated at 150 ° C. while supplying low humidity air with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. between the ultraviolet irradiation window 12 (synthetic quartz plate; thickness 2 mm) and the substrate 9. An energy ray irradiation process combined with a heat treatment for irradiating the low-pressure mercury lamp 11 for 10 minutes is performed to promote mineralization (decomposition or combustion of the organic component) and densification of the dry coating film 10, and lithium-titanium oxide ( A thin film (thickness: about 58 nm) for a thin film solid secondary battery according to Example 5 consisting of a negative electrode active material layer mainly composed of LTO: Li ₄ Ti ₅ O ₁₂ ) was produced.
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the negative electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of the X-ray diffraction measurement, the negative electrode active material layer formed by the above coating method was an amorphous film. Further, when the cross section of the negative electrode active material layer of Example 5 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating liquid for forming negative electrode active material layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] (molecular weight = 106.05) 1.78 g, titanium acetylacetone (liquid at room temperature) [Ti (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 392.32) 8.22 g, N-methyl-2-pyrrolidone (NMP) 39 g, and hydroxypropylcellulose (HPC; low molecular weight type) 1 g are mixed and heated to 120 ° C. And then stirred for 120 minutes, and then mixed with 10 g of the resulting solution with 3.996 g of cyclohexanone, 2 g of propylene glycol monomethyl ether (PGM), 4 g of methyl ethyl ketone (MEK), and 0.004 g of a surfactant. Stir well until uniform, 10% by mass of acetylacetone lithium and acetylacetone titanium in total, A coating liquid for forming a negative electrode active material layer containing 1.0% by mass of propylcellulose (acetylacetone lithium: acetylacetone titanium = 4: 5 [molar ratio]) was prepared.

[Preparation of thin film]
The prepared negative electrode active material layer forming coating solution was spin-coated (1000 rpm × 60 sec) on the entire surface of a stainless steel substrate (diameter: 16 mm × 0.5 mm thickness; area: 2 cm ² , SUS304) at 25 ° C. Drying was carried out at 5 ° C. for 5 minutes to obtain a dried coating film (film thickness: about 250 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)). As shown in the schematic diagram of FIG. 5, the substrate 9 having the dry coating film 10 is heated to 150 ° C. in a low-humidity air having a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. (heating rate: 30 ° C. / And heated at 150 ° C. while supplying low humidity air with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. between the ultraviolet irradiation window 12 (synthetic quartz plate; thickness 2 mm) and the substrate 9. An energy ray irradiation process combined with a heat treatment for irradiating the low-pressure mercury lamp 11 for 10 minutes is performed to promote mineralization (decomposition or combustion of the organic component) and densification of the dry coating film 10, and lithium-titanium oxide ( An inorganic thin film (film thickness: about 70 nm) containing LTO: Li ₄ Ti ₅ O ₁₂ ) as a main component was obtained.

Using the coating liquid for forming the negative electrode active material layer, the same film formation operation is repeated, and four layers of this inorganic thin film are laminated to form a negative electrode mainly composed of lithium-titanium oxide (LTO: Li ₄ Ti ₅ O ₁₂ ). A thin film (thickness: about 280 nm, weight: 0.05 mg / cm ² ) for a thin film solid secondary battery according to Example 6 composed of the active material layer was produced.
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the negative electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show. The surface resistance could not be measured because highly conductive stainless steel was used as the substrate.
From the results of X-ray diffraction measurement, the negative electrode active material layer formed by the above coating method was an amorphous film. Further, when the cross section of the negative electrode active material layer of Example 6 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

Furthermore, a 2032 type coin cell incorporating the negative electrode active material layer as a positive electrode and lithium-doped graphite as a negative electrode was produced, and the charge / discharge characteristics of the negative electrode active material layer (applied as a positive electrode) were evaluated. The structure of the coin cell is that a stainless steel substrate (area 2 cm ² ) on which the negative electrode active material layer is formed is a commercially available graphite negative electrode sheet (active material: natural spherical graphite, base material sheet) through a polypropylene separator having a thickness of about 180 μm. : 20 μm thick copper foil, diameter 16 mm, area 2 cm ² , 1.6 mAh / cm ² ) and metallic lithium foil (about 2 mm × about 5 mm × thickness 100 μm) placed on the graphite sheet, negative electrode active material layer, graphite And lithium metal foil are sandwiched in an argon atmosphere so as to face each other and filled with an electrolytic solution (1M LiClO ₄ (EC: DEC = 1: 1 V / V%)).

Before the charge / discharge characteristics evaluation, the coin cell is left for one day after production and is subjected to lithium doping (lithium pre-doping) to the graphite via the electrolytic solution to sufficiently reduce the potential of the graphite negative electrode sheet (about 0.1 V in advance). vs Li). Therefore, the cell potential (V) in the charge / discharge characteristic evaluation is a potential with respect to lithium-doped graphite (about 0.1 V vs Li). In the above coin cell, charge / discharge at a charge / discharge current of 2 μA and a cut-off potential of 1.0-2.3 V was performed three times, and the obtained charge / discharge curve is shown in FIG.
As described above, since the negative electrode active material layer of Example 6 is an amorphous film, the plateau region (1.55 V vs Li) seen in the charge / discharge curve of normal crystalline LTO was not observed, but the average voltage was 1. The negative electrode capacity was estimated to be 140 to 155 mA / g from the total weight of 0.12 mg of the negative electrode active material layer (LTO thin film) (the actual negative electrode capacity of crystalline LTO: 160). ˜170 mA / g; the actual capacity is a capacity that is actually chargeable / dischargeable and smaller than the theoretical capacity calculated theoretically).

[Preparation of coating solution for forming a solid electrolyte layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] (molecular weight = 106.05) 2.54 g, tripentyl phosphate (also known as triamyl phosphate) [PO (C ₅ H ₁₁ O) ₃ ] triethyl phosphate (liquid at room temperature) [PO (C ₅ H ₁₁ O) ₃ ] (molecular weight = 308.39) 2.46 g, N-methyl-2-pyrrolidone (NMP) 69.46 g, hydroxypropylcellulose ( HPC; low molecular weight type) 0.5 g and 0.04 g of surfactant are mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve, and 6.67 mass in total of lithium acetylacetone and tripentyl phosphate %, A coating solution for forming a solid electrolyte layer containing 0.67% by mass of hydroxypropyl cellulose (lithium acetylacetone: Li pentyl phosphate = 3: 1 was prepared [molar ratio]).

[Preparation of thin film]
The prepared coating solution for forming a solid electrolyte layer was coated on a non-alkali glass substrate (10 cm × 10 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) at 25 ° C. After spin coating (1000 rpm × 60 sec), it was dried in air at 100 ° C. for 3 minutes to obtain a dry coating film (film thickness: about 90 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)). . As shown in the schematic diagram of FIG. 5, the substrate 9 having the dry coating film 10 is heated to 150 ° C. in a low-humidity air having a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. (heating rate: 30 ° C. / And heated at 150 ° C. while supplying low humidity air with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. between the ultraviolet irradiation window 12 (synthetic quartz plate; thickness 2 mm) and the substrate 9. Lithium composite oxide containing phosphorus by performing energy ray irradiation treatment combined with heat treatment for irradiating the low-pressure mercury lamp 11 for 10 minutes to promote mineralization (decomposition or combustion of organic components) and densification of the dried coating film 10 An inorganic thin film (thickness: about 22 nm) was obtained.

The same film formation operation is repeated using the coating liquid for forming the solid electrolyte layer, and two layers of this inorganic thin film are laminated, and the solid electrolyte layer mainly composed of lithium composite oxide (Li ₃ PO ₄ ) containing phosphorus is used. A thin film (thickness: about 44 nm) for a thin-film solid secondary battery according to Example 7 was prepared.
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the solid electrolyte layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. .
From the result of X-ray diffraction measurement, the solid electrolyte layer formed by the above coating method is an amorphous film. Further, when the cross section of the solid electrolyte layer of Example 7 was observed with a transmission electron microscope, it was mainly metal oxide of less than 3 nm. An inorganic thin film in which physical fine particles (amorphous microcrystals) are densely packed has been observed.

  In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating solution for forming a solid electrolyte layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] (molecular weight = 106.05) 0.79 g, lanthanum acetylacetone (formal name: lanthanum (III) -2,4-pentanedionate) (room temperature In solid) [La (C ₅ H ₇ O ₂ ) ₃ .H ₂ O] (molecular weight = 454.26) 3.38 g, titanium acetylacetone (liquid at room temperature) [Ti (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 392.32) 5.83 g, N-methyl-2-pyrrolidone (NMP) 39 g, and hydroxypropylcellulose (HPC; low molecular weight type) 1.0 g are mixed and heated to 120 ° C. The mixture was heated and stirred for 120 minutes to dissolve, and then 109.6 g of the resulting solution was added to 9.996 g of propylene glycol monomethyl ether (PGM), surfactant 0 004 g was mixed and stirred well until uniform, and a coating solution for forming a solid electrolyte layer (acetylacetone lithium: 10% by mass in total of acetylacetone lithium, acetylacetone lanthanum, and acetylacetone titanium and 1.0% by mass of hydroxypropylcellulose) Lanthanum acetylacetone: titanium acetylacetone = 1: 1: 2 [molar ratio]).

[Preparation of thin film]
The prepared coating solution for forming a solid electrolyte layer was coated on a non-alkali glass substrate (25 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) on the entire surface. After spin coating (2000 rpm × 60 sec), it was dried in air at 100 ° C. for 5 minutes to obtain a dry coating film (film thickness: about 230 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)). .
Next, as shown in the schematic diagram of the inorganic treatment process using the heat treatment and energy beam irradiation process in the thin film manufacturing method by the coating method of FIG. 5, the substrate 9 having this dry coating film 10 is made to have a CO ₂ concentration of 1 ppm. The temperature is raised to 150 ° C. in a low-humidity air having a dew point temperature of −55 ° C. (heating rate: 30 ° C./min), and the low-humidity air having a dew point temperature of −55 ° C. less than 1 ppm of CO ₂ is irradiated with the ultraviolet irradiation window 12 ( A synthetic quartz plate (thickness 2 mm) and a substrate 9 while being heated to 150 ° C. while being supplied between them, an energy ray irradiation treatment is performed in combination with a heat treatment for irradiating the low-pressure mercury lamp 11 for 20 minutes. It consists of a solid electrolyte layer mainly composed of lithium-lanthanum-titanium oxide (LLT: Li _0.5 La _0.5 TiO ₃ ) by promoting mineralization (decomposition or combustion of organic components) and densification Implementation Thin film for a thin film solid secondary battery according to 8: was produced (thickness: about 56 nm).
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the solid electrolyte layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. .
From the result of X-ray diffraction measurement, the solid electrolyte layer formed by the above coating method is an amorphous film. Further, when the cross section of the solid electrolyte layer of Example 8 was observed with a transmission electron microscope, it was mainly metal oxide of less than 3 nm. An inorganic thin film in which physical fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating solution for forming a solid electrolyte layer]
Lithium (I) -tert-butoxide (solid at room temperature) [Li (C ₄ H ₉ O)] (molecular weight = 80.05) 1.5 g was mixed with tetrahydrofuran (THF) 7.0 g, and dissolved by stirring. Then, niobium (V) -n-butoxide (liquid at room temperature) [Nb (C ₄ H ₉ O) ₅ ] (molecular weight = 458.12) 8.5 g, N-methyl-2-pyrrolidone (NMP) 11 .9 g, 21.25 g of propylene glycol monomethyl ether (PGM), 42.14 g of ethanol, 6.86 g of isopropyl alcohol (IPA), and 0.85 g of hydroxypropyl cellulose (HPC; low molecular weight type) are mixed and heated to 50 ° C. Then, the mixture was sonicated with stirring to uniformly dissolve, and lithium (I) -tert-butoxide and niobium (V) -n-butoxide were combined in a total of 1 A coating solution for forming a solid electrolyte layer (lithium (I) -tert-butoxide: niobium (V) -n-butoxide = 1: 1 [molar ratio]) containing 0% by mass and 0.85% by mass of hydroxypropylcellulose Produced.

[Preparation of thin film]
The prepared coating solution for forming a solid electrolyte layer was coated on a non-alkali glass substrate (10 cm × 10 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) at 25 ° C. After spin coating (500 rpm × 60 sec), it was dried in the atmosphere at 180 ° C. for 5 minutes to obtain a dried coating film (film thickness: about 410 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)). .
Next, as shown in the schematic diagram of the inorganic treatment process using the heat treatment and energy beam irradiation process in the thin film manufacturing method by the coating method of FIG. 5, the substrate 9 having this dry coating film 10 is made to have a CO ₂ concentration of 1 ppm. The temperature is raised to 200 ° C. in a low-humidity air with a dew point temperature of −55 ° C. (temperature increase rate: 30 ° C./min), and the low humidity air with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. is applied to the ultraviolet irradiation window 12 ( A synthetic quartz plate (thickness 2 mm) and a substrate 9 while being heated to 200 ° C. while being supplied between the substrate 9 and the low-pressure mercury lamp 11 for 20 minutes. Thin film solid secondary battery according to Example 9 comprising a solid electrolyte layer mainly composed of a lithium composite oxide (LiNbO ₃ ) containing niobium by promoting mineralization (decomposition or combustion of organic components) and densification For A thin film (film thickness: about 240 nm) was produced.
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the solid electrolyte layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. .
From the result of X-ray diffraction measurement, the solid electrolyte layer formed by the above coating method is an amorphous film. Further, when the cross section of the solid electrolyte layer of Example 9 was observed with a transmission electron microscope, it was mainly metal oxide of less than 3 nm. An inorganic thin film in which physical fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating solution for forming a solid electrolyte layer]
Lithium acetylacetone (solid at room temperature) [Li (C5H7O2)] molecular weight = 106.05) 0.827 g, acetylacetone aluminum (formal name: aluminum (III) -2,4-pentandionate) (solid at room temperature) [Al ( C ₅ H ₇ O ₂ ) ₃ ] 1.164 g, acetylacetone titanium (liquid at room temperature) [Ti (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 392.32) 2.979 g , bis (2-ethylhexyl) phosphate _{(C 4 H 9 CH (C} 2 H 5) CH 2) 2 HPO 4] ( liquid at room temperature) (molecular weight = 322.42) 5.03 g, N-methyl-2- Pyrrolidone (NMP) 13 g, p-tert-butylphenol 13 g, dibasic acid ester (manufactured by DuPont Japan; dimethyl succinate (boiling point: 1 6 ° C.), 13 g of dimethyl glutarate (boiling point: 210 to 215 ° C.), dimethyl adipate (boiling point: 215 to 225 ° C.)), 1 g of hydroxypropyl cellulose (HPC; low molecular weight type) and mixed to 120 ° C. The mixture was heated and stirred for 120 minutes to dissolve, and then 4 g of cyclohexanone, 2 g of propylene glycol monomethyl ether (PGM), 3.996 g of methyl ethyl ketone (MEK), and 0.004 g of a surfactant were added to 10 g of the resulting solution. Mix well and stir well until uniform, high viscosity solid containing 10% by mass total of acetylacetone lithium, acetylacetone aluminum, acetylacetone titanium, bis (2-ethylhexyl) phosphate and 1.0% by mass hydroxypropylcellulose Electrolyte layer forming coating solution (AS Le acetone lithium: aluminum acetylacetonate acetylacetone titanium: Bis (2-ethylhexyl) phosphate = 1.5: 0.69: 1.46: 3 [molar ratio]) was prepared.

[Preparation of thin film]
The prepared coating solution for forming a solid electrolyte layer was coated on a non-alkali glass substrate (25 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) on the entire surface. After spin coating (1500 rpm × 60 sec), it was dried in air at 100 ° C. for 5 minutes to obtain a dry coating film (film thickness: about 220 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)) .
Next, as shown in the schematic diagram of the inorganic treatment process using the heat treatment and energy beam irradiation process in the thin film manufacturing method by the coating method of FIG. 5, the substrate 9 having this dry coating film 10 is made to have a CO ₂ concentration of 1 ppm. The temperature is raised to 150 ° C. in a low-humidity air having a dew point temperature of −55 ° C. (heating rate: 30 ° C./min), and the low-humidity air having a dew point temperature of −55 ° C. less than 1 ppm of CO ₂ is irradiated with the ultraviolet irradiation window 12 A synthetic quartz plate (thickness 2 mm) and a substrate 9 while being heated to 150 ° C. while being supplied between them, an energy ray irradiation treatment is performed in combination with a heat treatment for irradiating the low-pressure mercury lamp 11 for 20 minutes. and the (decomposition or burning of organic components) mineralization and promotes densification, aluminum, titanium, lithium composite oxide containing phosphorus _{(LATP: Li 1.5 Al 0.69 Ti} 1.46 (PO 4) 3 The thin film for a thin film solid secondary cell according to example 10 consisting of a solid electrolyte layer composed mainly: was produced (thickness: about 65 nm).
The distance (irradiation distance) between the low-pressure mercury lamp 11 and the substrate 9 was 10.5 mm, the illuminance of 254 nm light: about 20 mW / cm ² , and the estimated illuminance of 185 nm light: about 5 mW / cm ² . Furthermore, the distance between the substrate 9 and the ultraviolet irradiation window 12 is 3.5 mm, and the average flow velocity of the atmospheric gas (CO ₂ concentration of less than 1 ppm and low-humidity air having a dew point temperature of −55 ° C.) is about 0.29 m / sec). there were.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the solid electrolyte layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. .
From the results of X-ray diffraction measurement, the solid electrolyte layer formed by the above coating method is an amorphous film. Further, when the cross section of the solid electrolyte layer of Example 10 was observed with a transmission electron microscope, it was mainly metal oxide of less than 3 nm. An inorganic thin film in which physical fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating liquid for forming positive electrode active material layer]
Lithium (I) -tert-butoxide (solid at room temperature) [Li (C ₄ H ₉ O)] (molecular weight = 80.05) 1.84 g, acetylacetone cobalt (solid at room temperature) {(formal name: cobalt (III) _{2,4-pentanedionate) [Co (C 5 H 7} O 2) 3]} ( molecular weight = 356.24) 8.16g, 3- amino-1-propanol 55 g, hydroxypropyl cellulose (HPC; high molecular weight Type) 1 g is mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve. Next, 33.98 g of propylene glycol monomethyl ether (PGM) and 0.02 g of surfactant are added to the resulting solution. Mix well and stir well until uniform, 10% by mass of lithium (I) -tert-butoxide and acetylacetone cobalt in total, hydroxypropyl The positive electrode active material layer forming coating solution containing the Le cellulose 1.0 wt% (lithium (I)-tert-butoxide acetylacetone cobalt = 1: 1 [molar ratio]) was prepared.

[Preparation of thin film]
The prepared coating liquid for forming a positive electrode active material layer is spin-coated (1000 rpm × 60 sec) on the entire surface of a transparent quartz glass substrate (5 cm × 5 cm × 2 mm thickness) at 25 ° C. and then dried at 180 ° C. for 5 minutes in the atmosphere. Thus, a dried coating film (film thickness: about 940 nm, surface resistance value:> 1 × 10 ¹³ Ω / □ (insulation)) was obtained. As shown in the schematic diagram of FIG. 7, the substrate 9 having the dry coating film 10 is placed in an electric furnace having a heating device (heater heater) 8, and has a low humidity with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. Under air (5 liters / min supply), heat treatment is performed at 500 ° C. for 60 minutes (temperature increase rate up to 500 ° C .: 20 ° C./min) to mineralize the dried coating film 10 (decomposition or combustion of organic components) ) And the densification, and the thin film (thickness: about 350 nm) for the thin film solid secondary battery according to Example 11 composed of the positive electrode active material layer mainly composed of lithium-cobalt oxide (LCO: LiCoO ₂ ). ) Was produced.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of the X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method is an amorphous film (amorphous film), and the cross section of the positive electrode active material layer of Example 11 was observed with a transmission electron microscope. Inorganic thin films in which metal oxide fine particles (amorphous microcrystals) of less than 3 nm are densely packed are observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

  Here, in order to investigate the relationship between the heating temperature and the crystal structure, the thin film obtained in Example 11 was subjected to additional heat treatment for 60 minutes at the respective temperatures of 600 ° C. and 700 ° C. in the same manner as described above. (Temperature increase rate up to each temperature of 600 ° C. and 700 ° C .: 20 ° C./min), the crystal structure by X-ray diffraction and the crystallite size were determined for each, and the results were obtained at 60 ° C. It shows in FIG. 8 with the result of the heat processing for a minute.

[Preparation of coating liquid for forming positive electrode active material layer]
Lithium (I) -tert-butoxide (solid at room temperature) [Li (C ₄ H ₉ O)] (molecular weight = 80.05) 1.73 g, cobalt (II) formate (solid at room temperature) [Co (COOH) ₂ · _H 2 O] (molecular weight = 185.0) 3.98 g, 3- amino-1-propanol 91.28G, hydroxypropylcellulose (HPC; high molecular weight type) 3 g, a surfactant 0.01g were mixed, 120 Warm to 120 ° C. and stir for 120 minutes to dissolve uniformly, and contains lithium (I) -tert-butoxide and cobalt formate (II) in a total of 5.71% by mass and hydroxypropyl cellulose in an amount of 3.0% by mass. A high-viscosity positive electrode active material layer forming coating solution (lithium (I) -tert-butoxide: cobalt formate (II) = 1: 1 [molar ratio]) was prepared.

[Preparation of thin film]
The prepared coating liquid for forming a positive electrode active material was coated on a stainless steel substrate (diameter 16 mm × 0.5 mm thickness; area 2 cm ² , SUS304) at 25 ° C. by doctor blade coating (gap between stainless steel substrate and doctor blade: 350 μm). Then, it was dried in the atmosphere at 180 ° C. for 5 minutes to obtain a dried coating film (film thickness: about 3 μm, surface resistance value:> 1 × 10 ¹³ Ω / □ (insulation)). As shown in the schematic diagram of FIG. 7, a substrate 9 having this dry coating film 10 is placed on a heating device (hot plate) 8 and low humidity air (3 liters) with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. / Min supply; average gas flow velocity on substrate: about 0.045 m / sec), heat treatment at 500 ° C. for 30 minutes (temperature rise rate up to 500 ° C .: 20 ° C./min), and dry coating film 10 promotes inorganicization (decomposition or combustion of organic components) and densification, and comprises a positive electrode active material layer mainly composed of lithium-cobalt oxide (LCO: LiCoO ₂ ). A thin film (film thickness: about 1.3 μm (1300 nm), weight: 0.30 mg / cm ² ) for a secondary battery was prepared.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show. The surface resistance could not be measured because highly conductive stainless steel was used as the substrate.
From the result of the X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method was an amorphous film. Further, when the cross section of the positive electrode active material layer of Example 12 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.

Furthermore, a 2032 type coin cell incorporating the positive electrode active material as a positive electrode and lithium-doped graphite as a negative electrode was produced, and the charge / discharge characteristics of the positive electrode active material layer were evaluated. The structure of the coin cell is that a stainless steel substrate (area 2 cm ² ) on which the positive electrode active material layer is formed is a commercially available graphite negative electrode sheet (active material: natural spherical graphite, base material sheet) through a polypropylene separator having a thickness of about 180 μm. : 20 μm thick copper foil, diameter 16 mm, area 2 cm ² , 1.6 mAh / cm ² ) and metallic lithium foil (about 2 mm × about 5 mm × thickness 100 μm) placed on the graphite sheet, positive electrode active material layer, graphite And metal lithium foil are sandwiched in an argon atmosphere so as to face each other and filled with an electrolytic solution (1M LiPF ₆ (EC: DEC = 1: 2 V / V%)).

Before the charge / discharge characteristics evaluation, the coin cell is left for one day after production and is subjected to lithium doping (lithium pre-doping) to the graphite via the electrolytic solution to sufficiently reduce the potential of the graphite negative electrode sheet (about 0.1 V in advance). vs Li). Therefore, the cell potential (V) in the charge / discharge characteristic evaluation is a potential with respect to lithium-doped graphite (about 0.1 V vs Li). In the coin cell, charging / discharging was performed twice at a charging current of 3 μA, a discharging current of 2 μA, and a cutoff potential of 2.1-4.3 V, and the obtained charging / discharging curve is shown in FIG.
As described above, the positive electrode active material layer of Example 12 is an amorphous film, and the plateau region (about 3.9 V vs Li) observed in the charge / discharge curve of crystalline LCO (LiCoO ₂ ) having a normal high-temperature stable phase is observed. Although not done, another plateau region (3.6 to 3.7 V vs Li) was observed, which was due to the low temperature stable phase formation of crystalline LCO because the heating temperature of Example 12 was as low as 500 ° C. It is expected to be. The positive electrode capacity was estimated to be about 70 mA / g from the total weight of the positive electrode active material (LiCoO ₂ ) of 0.60 mg (the actual capacity of the positive electrode of the crystalline LCO having a high-temperature stable phase: about 140 mA / g; It is smaller than the theoretical capacity that is theoretically calculated by the capacity that can be charged and discharged.)

[Preparation of thin film]
The coating liquid for forming the positive electrode active material layer of Example 11 was a non-alkali glass substrate at 25 ° C. (5 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%). After spin coating (1000 rpm × 60 sec) on the entire upper surface, it was dried in the air at 180 ° C. for 5 minutes to dry coating film (film thickness: about 940 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)) Got.
As shown in the schematic diagram of FIG. 10, the substrate 9 having the dry coating film 10 is placed in a rapid heating apparatus (RTA furnace) having a heating lamp (halogen lamp) 12, and the dew point temperature is less than 1 ppm in CO ₂ concentration. Rapid heating with a lamp for heating (average heating rate up to 500 ° C .: 100 ° C./min) under low humidity air at −55 ° C. (5 liter / min supply), followed by heating at 500 ° C. for 10 minutes Implementation of a positive electrode active material layer containing lithium-cobalt oxide (LCO: LiCoO ₂ ) as a main component by performing treatment to promote mineralization (decomposition or combustion of organic components) and densification of the dry coating film 10 A thin film (thickness: about 355 nm) for a thin film solid secondary battery according to Example 13 was produced.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of the X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method is an amorphous film (amorphous film), and the cross section of the positive electrode active material layer of Example 13 was observed with a transmission electron microscope. Inorganic thin films in which metal oxide fine particles (amorphous microcrystals) of less than 3 nm are densely packed are observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of coating liquid for forming positive electrode active material layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] molecular weight = 106.05) 1.31 g, manganese acetylacetone (solid at room temperature) [Mn (C ₅ H ₇ O ₂ ) ₃ ] (molecular weight = 352.26) 8.69 g, N-methyl-2-pyrrolidone (NMP) 39 g, and hydroxypropylcellulose (HPC; low molecular weight type) 1 g were mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve. Next, 10 g of the resulting solution was mixed with 4 g of cyclohexanone, 2 g of propylene glycol monomethyl ether (PGM), 3.996 g of methyl ethyl ketone (MEK), and 0.004 g of a surfactant, and stirred well until uniform. 10% by mass of lithium and acetylacetone manganese in total, hydroxypropylcellulose The positive electrode active material layer forming coating solution containing 1.0 wt% (acetylacetone lithium acetylacetone manganese = 1: 2 [molar ratio]) was prepared.

[Preparation of thin film]
The prepared coating solution for forming a positive electrode active material layer is spin-coated (500 rpm × 60 sec) on the entire surface of a transparent quartz glass substrate (5 cm × 5 cm × 2 mm thickness) at 25 ° C. and then dried at 180 ° C. for 5 minutes in the atmosphere. Thus, a dried coating film (film thickness: about 860 nm, surface resistance value:> 1 × 10 ¹³ Ω / □ (insulation)) was obtained.
In the same manner as in Example 13, the substrate 9 having the dry coating film 10 was supplied with low humidity air (5 liters / minute) with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. using a rapid heating apparatus (RTA furnace). ) Under heat treatment at 500 ° C. for 5 minutes to promote mineralization (decomposition or combustion of organic components) and densification of the dried coating film 10, and lithium-manganese oxide (LMO: LiMn ₂ O ₄ ) As a main component, an inorganic thin film (film thickness: about 130 nm) was obtained.

The same film formation operation was repeated using the coating liquid for forming the negative electrode active material layer layer, and after laminating two layers of this inorganic thin film, as shown in the schematic diagram of FIG. (Heating heater) Installed in an electric furnace having 8 and heated at 500 ° C. for 60 minutes under low humidity air (5 liters / minute supply) with a CO ₂ concentration of less than 1 ppm and dew point temperature of −55 ° C. (500 For a thin film solid secondary battery according to Example 14 comprising a positive electrode active material layer mainly composed of lithium-manganese oxide (LMO: LiMn ₂ O ₄ ). The thin film (film thickness: about 260 nm) was produced.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of the X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method is a microcrystalline film crystallized slightly, and further, the cross section of the positive electrode active material layer of Example 14 is observed with a transmission electron microscope. As a result, an inorganic thin film in which metal oxide fine particles (microcrystals) of about 3 nm are densely packed is observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).
Here, in order to investigate the relationship between the heating temperature and the crystal structure, the thin film obtained in Example 14 was subjected to a method using an electric furnace similar to the above (schematic diagram in FIG. 7) at 600 ° C. and 700 ° C. An additional heat treatment is performed at each temperature for 60 minutes (rate of temperature increase to each temperature of 600 ° C. and 700 ° C .: 20 ° C./min), and the crystal structure and crystallite size by X-ray diffraction are determined for each. The results obtained are shown in FIG. 11 together with the result of the heat treatment at 500 ° C. for 60 minutes.

[Preparation of coating liquid for forming positive electrode active material layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] molecular weight = 106.05) 1.36 g, manganese acetylacetone (solid at room temperature) [Mn (C ₅ H ₇ O ₂ ) ₃ ] (molecular weight = 352.26) 4.51 g, bis (2-ethylhexyl) phosphate (C ₄ H ₉ CH (C ₂ H ₅ ) CH ₂ ) ₂ HPO ₄ ] (liquid at room temperature) (molecular weight = 322.42) 4.13 g , 39 g of N-methyl-2-pyrrolidone (NMP) and 1 g of hydroxypropylcellulose (HPC; low molecular weight type) were mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve, and then the resulting dissolution The solution was mixed with 49.98 g of propylene glycol monomethyl ether (PGM) and 0.02 g of surfactant and stirred well until uniform, and acetylacetone was added. A coating solution for forming a positive electrode active material layer containing 10% by mass of thium, acetylacetone manganese and bis (2-ethylhexyl) phosphate and 1.0% by mass of hydroxypropylcellulose (acetylacetone lithium: acetylacetone manganese: bis (2- Ethylhexyl) phosphate = 1: 1: 1 [molar ratio]).

[Preparation of thin film]
The produced coating liquid for forming a positive electrode active material layer was formed on a non-alkali glass substrate (5 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) at 25 ° C. After spin coating (500 rpm × 30 sec) on the entire surface, the coating was dried in air at 100 ° C. for 5 minutes to obtain a dried coating film.
As shown in the schematic diagram of FIG. 7, a substrate 9 having this dry coating film 10 is placed on a heating device (hot plate) 8 and low humidity air (3 liters) with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. / Min supply; average gas flow velocity on substrate: about 0.045 m / sec), heat treatment at 500 ° C. for 30 minutes (temperature rise rate up to 500 ° C .: 20 ° C./min), and dry coating film The thin film according to Example 15 comprising a positive electrode active material layer mainly composed of lithium composite oxide (LiMnPO ₄ ) containing manganese and phosphorus by promoting 10 mineralization (decomposition or combustion of organic components) and densification A thin film (film thickness: about 140 nm) for a solid secondary battery was produced.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness) and crystallite size characteristics of the positive electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of the X-ray diffraction measurement, the positive electrode active material layer formed by the above coating method was an amorphous film. Further, when the cross section of the positive electrode active material layer of Example 15 was observed with a transmission electron microscope, it was mainly less than 3 nm. An inorganic thin film in which metal oxide fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Preparation of thin film]
The negative electrode active material layer forming coating solution of Example 6 was spin-coated (500 rpm × 60 sec) on the entire surface of a 25 ° C. transparent quartz glass substrate (5 cm × 5 cm × 2 mm thickness), and then 5 ° C. at 180 ° C. in the atmosphere. It was dried for a minute to obtain a dried coating film (film thickness: about 390 nm, surface resistance:> 1 × 10 ¹³ Ω / □ (insulation)).
In the same manner as in Example 13, the substrate 9 having the dry coating film 10 was supplied with low humidity air (5 liters / minute) with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. using a rapid heating apparatus (RTA furnace). ) Under heat treatment at 500 ° C. for 5 minutes to promote mineralization (decomposition or combustion of organic components) and densification of the dried coating film 10, and lithium-titanium oxide (LTO: Li ₄ Ti ₅ O). An inorganic thin film (film thickness: about 90 nm) having ₁₂ ) as a main component was obtained.

After repeating the same film formation operation using the coating liquid for forming the negative electrode active material layer layer and laminating three layers of this inorganic thin film, the substrate 9 having this multilayer film is heated as shown in the schematic diagram of FIG. Installed in an electric furnace having a device (heater heater) 8 and heated at 500 ° C. for 60 minutes under low-humidity air (5 liters / minute supply) with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. The temperature rise rate up to 500 ° C .: 20 ° C./min), and the thin-film solid 2 according to Example 16 consisting of a negative electrode active material layer mainly composed of lithium-titanium oxide (LTO: Li ₄ Ti ₅ O ₁₂ ) A thin film (film thickness: about 270 nm) for a secondary battery was produced.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the negative electrode active material layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. Show.
From the result of the X-ray diffraction measurement, the negative electrode active material layer formed by the above coating method was an amorphous film (amorphous film), and the cross section of the negative electrode active material layer of Example 16 was observed with a transmission electron microscope. Inorganic thin films in which metal oxide fine particles (amorphous microcrystals) of less than 3 nm are densely packed are observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).
Here, in order to investigate the relationship between the heating temperature and the crystal structure, the thin film obtained in Example 16 was subjected to a method using an electric furnace similar to the above (schematic diagram in FIG. 7) at 600 ° C. and 700 ° C. An additional heat treatment is performed at each temperature for 60 minutes (rate of temperature increase to each temperature of 600 ° C. and 700 ° C .: 20 ° C./min), and the crystal structure and crystallite size by X-ray diffraction are determined for each. The results obtained are shown in FIG. 12 together with the result of the heat treatment at 500 ° C. for 60 minutes.

[Preparation of coating solution for forming a solid electrolyte layer]
Lithium acetylacetone (solid at room temperature) [Li (C ₅ H ₇ O ₂ )] (molecular weight = 106.05) 0.79 g, lanthanum acetylacetone (formal name: lanthanum (III) -2,4-pentanedionate) (room temperature In solid) [La (C ₅ H ₇ O ₂ ) ₃ .H ₂ O] (molecular weight = 454.26) 3.38 g, titanium acetylacetone (liquid at room temperature) [Ti (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 392.32) 5.83 g, N-methyl-2-pyrrolidone (NMP) 51 g, p-tert-butylphenol 12 g, hydroxypropylcellulose (HPC; low molecular weight type) 0.5 g , 1.24 g of hydroxypropylcellulose (HPC; high molecular weight type) are mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve, In addition, 25.25 g of propylene glycol monomethyl ether (PGM) and 0.01 g of a surfactant were mixed in the obtained solution and stirred well until uniform, and a total of 10 acetylacetone lithium, acetylacetone lanthanum, and acetylacetone titanium were added. A coating solution for forming a solid electrolyte layer (acetylacetone lithium: acetylacetone lanthanum: acetylacetone titanium = 1: 1: 2 [molar ratio]) containing 1% by mass and 1.74% by mass of hydroxypropylcellulose was prepared.

[Preparation of thin film]
The prepared coating solution for forming a solid electrolyte layer is spin-coated (500 rpm × 60 sec) on the entire surface of a transparent quartz glass substrate (5 cm × 5 cm × 2 mm thickness) at 25 ° C. and then dried at 180 ° C. for 5 minutes in the atmosphere. Thus, a dried coating film (film thickness: about 900 nm, surface resistance value:> 1 × 10 ¹³ Ω / □ (insulation)) was obtained. In the same manner as in Example 13, the substrate 9 having the dry coating film 10 was supplied with low humidity air (5 liters / minute) with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. using a rapid heating apparatus (RTA furnace). )) At 500 ° C. for 5 minutes to promote mineralization (decomposition or combustion of organic components) and densification of the dried coating film 10, and lithium-lanthanum-titanium oxide (LLT: Li _0. An inorganic thin film (film thickness: about 210 nm) containing ₅ La _0.5 TiO ₃ as a main component was obtained.
The same film formation operation was repeated using the coating solution for forming the solid electrolyte layer, and after laminating four layers of this inorganic thin film, as shown in the schematic view of FIG. Heater) Installed in an electric furnace with 8 and heated at 500 ° C for 60 minutes under low-humidity air (5 liters / minute supply) with a CO ₂ concentration of less than 1 ppm and dew point of -55 ° C (up to 500 ° C) Temperature increase rate: 20 ° C./min), and a thin film according to Example 17 consisting of a solid electrolyte layer mainly composed of lithium-lanthanum-titanium oxide (LLT: Li _0.5 La _0.5 TiO ₃ ) A thin film (film thickness: about 840 nm) for a solid secondary battery was produced.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the solid electrolyte layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. .
From the result of the X-ray diffraction measurement, the solid electrolyte layer formed by the above coating method is an amorphous film (amorphous film). Further, when the cross section of the solid electrolyte layer of Example 17 was observed with a transmission electron microscope, In addition, an inorganic thin film in which metal oxide fine particles (amorphous microcrystals) of less than 3 nm are densely packed is observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).
Here, in order to investigate the relationship between the heating temperature and the crystal structure, the thin film obtained in Example 17 was subjected to a method using an electric furnace similar to the above (schematic diagram in FIG. 7) at 600 ° C., 700 ° C., Additional heat treatment for 60 minutes at each temperature of 800 ° C. (heating rate up to each temperature of 600 ° C., 700 ° C., and 800 ° C .: 20 ° C./min) is performed. And the crystallite size were determined, and the results are shown in FIG.

[Preparation of coating solution for forming a solid electrolyte layer]
Lithium acetylacetone (solid at room temperature) [Li (C5H7O2)] molecular weight = 106.05) 0.827 g, acetylacetone aluminum (formal name: aluminum (III) -2,4-pentandionate) (solid at room temperature) [Al ( C ₅ H ₇ O ₂ ) ₃ ] 1.164 g, acetylacetone titanium (liquid at room temperature) [Ti (C ₄ H ₉ O) ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 392.32) 2.979 g , bis (2-ethylhexyl) phosphate _{(C 4 H 9 CH (C} 2 H 5) CH 2) 2 HPO 4] ( liquid at room temperature) (molecular weight = 322.42) 5.03 g, N-methyl-2- Pyrrolidone (NMP) 29 g, p-tert-butylphenol 29 g, dibasic acid ester (manufactured by DuPont Japan; dimethyl succinate (boiling point: 1 6 ° C), dimethyl glutarate (boiling point: 210-215 ° C), 29 g of a mixture of dimethyl adipate (boiling point: 215-225 ° C)) and 3 g of hydroxypropylcellulose (HPC; high molecular weight type) were mixed to 120 ° C. Highly heated and stirred for 120 minutes to uniformly dissolve, containing 10% by mass of acetylacetone lithium, acetylacetone aluminum, acetylacetone titanium, bis (2-ethylhexyl) phosphate in total and 3.0% by mass of hydroxypropylcellulose A coating liquid for forming a solid electrolyte layer having a viscosity (acetylacetone lithium: acetylacetone aluminum: acetylacetone titanium: bis (2-ethylhexyl) phosphate = 1.5: 0.69: 1.46: 3 [molar ratio]) was prepared.

[Preparation of thin film]
The prepared coating solution for forming a solid electrolyte layer was coated on a non-alkali glass substrate (25 cm × 5 cm × 0.7 mm thickness; haze value = 0.26%, visible light transmittance = 91.2%) on the entire surface. After wire bar coating (# 12: wire diameter 0.3 mm), it was dried at 180 ° C. for 5 minutes in the air to obtain a dry coating film.
As shown in the schematic diagram of FIG. 7, a substrate 9 having this dry coating film 10 is placed on a heating device (hot plate) 8 and low humidity air (3 liters) with a CO ₂ concentration of less than 1 ppm and a dew point temperature of −55 ° C. / Min supply; average gas flow velocity on substrate: about 0.045 m / sec), heat treatment at 500 ° C. for 30 minutes (temperature rise rate up to 500 ° C .: 20 ° C./min), and dry coating film 10 mineralization (decomposition or combustion of organic components) and densification are promoted, and lithium composite oxide containing aluminum, titanium and phosphorus (LATP: Li _1.5 Al _0.69 Ti _1.46 (PO ₄ ) ₃ ) A thin film (thickness: about 165 nm) for a thin film solid secondary battery according to Example 18 composed of a solid electrolyte layer containing as a main component was prepared.

[Characteristic evaluation]
Next, the surface resistance, film thickness, specific resistance (= surface resistance × film thickness), and crystallite size characteristics of the solid electrolyte layer formed by the coating method on the prepared thin film were measured, and the results are shown in Table 1. .
From the result of X-ray diffraction measurement, the solid electrolyte layer formed by the above coating method is an amorphous film. Further, when the cross section of the positive electrode active material layer of Example 18 was observed with a transmission electron microscope, the metal was mainly less than 3 nm. An inorganic thin film in which oxide fine particles (amorphous microcrystals) are densely packed has been observed.
In addition, when the degree of mineralization of the thin film was evaluated by Fourier transform infrared spectroscopy (FTIR method), organic functional groups (C = O, etc.) and hydroxyl groups (-OH) were hardly observed from the thin film. It was confirmed that the glass substrate was inorganicized. (In the measurement by the FTIR method, there was a concern about the influence from the glass substrate. And a thin film is formed on the Al deposited film by the same method as described above and evaluated).

[Production of thin-film solid secondary batteries]
First, an inorganic thin film was formed on a mirror-polished smooth stainless steel substrate (diameter 16 mm × 0.5 mm thickness; area 2 cm ² , SUS304) by the same method as in Example 3 (150 ° C. heat treatment and energy ray irradiation). stacking twice, lithium composite oxide containing manganese: thin film made of a positive electrode active material layer mainly composed of (LMO LiMn ₂ O _4): was produced (thickness: about 130 nm).

Next, an inorganic thin film was laminated twice by the same method as in Example 10 (150 ° C. heat treatment and energy ray irradiation) on the thin film made of the positive electrode active material layer, and lithium containing aluminum, titanium, and phosphorus. A thin film (film thickness: about 300 nm) made of a solid electrolyte layer mainly composed of a complex oxide (LATP: Li _1.5 Al _0.69 Ti _1.46 (PO ₄ ) ₃ ) was produced.

On the thin film made of the solid electrolyte layer, an inorganic thin film was laminated twice by the same method (heating treatment at 150 ° C. and energy ray irradiation) as in Example 5, and lithium-titanium oxide (LTO: Li ₄ Ti) was formed. _A thin film (film thickness: about 120 nm) composed of a negative electrode active material layer containing ₅ O ₁₂ ) as a main component was produced.

  A 2032 type coin cell (stainless steel substrate / positive electrode active material layer / solid electrolyte layer / negative electrode active material layer) was used in an argon atmosphere using a substrate on which a deposited aluminum film was formed on a thin film made of the prepared negative electrode active material layer as a collecting electrode. / Aluminum vapor deposition film) was assembled to produce a thin film solid secondary battery according to Example 19.

In the coin cell, charging / discharging was performed at a charging current of 10 μA, a discharging current of 5 μA, and a cutoff potential of 0.7 V, and the obtained charging / discharging curve is shown in FIG.
Since the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer of Example 19 are all formed at a temperature of 150 ° C. or lower in the manufacturing process, all of these layers are amorphous films, and therefore Since the lithium ion conductivity of the solid electrolyte layer is small and current leakage due to electronic conduction is not negligible, only a capacity of about 3.5 μAh is obtained as shown in FIG. doing.

In Examples 1 to 10, the energy ray irradiation treatment is used in combination with the heat treatment in spite of the low maximum temperature of 100 to 150 ° C. in the production process of the inorganic thin film by the coating method (Example 4). It is confirmed that each thin film of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is made inorganic while being an amorphous film (amorphous film).
Furthermore, the negative electrode active material layer (LTO: Li ₄ Ti ₅ O ₁₂ ) of Example 6 was formed at a very low temperature of 150 ° C. when applied to the positive electrode of an electrolyte-based coin cell using lithium-doped graphite as the negative electrode. Although it is an amorphous film, it is confirmed that it has a relatively good negative electrode capacity of 140 to 155 mA / g (in the electrode configuration of the coin cell of Example 6, it should be referred to as “positive electrode capacity”. This is called “negative electrode capacity”.

In Examples 11 to 18, a heat treatment (hot plate, electric furnace, rapid temperature raising furnace (RTA)) of 500 ° C. or higher was used in the manufacturing process of the inorganic thin film by a coating method, and the obtained positive electrode active material layer, The thin films of the solid electrolyte layer and the negative electrode active material layer are all mineralized, and the temperature of the heat treatment is about 600 ° C. (for the LMO of Example 14 and the LLT of Example 17, about 500 ° C. and about 700 ° C., respectively) ) It is confirmed that crystallization has started.
In addition, the positive electrode active material layers (LCO: LiCoO ₂ ) of Examples 11 and 13 have a very low (electron conduction) specific resistance (11 Ω · cm) [reference: normal crystalline LiCoO ₂ , for no clear reason. Specific resistance = about 1000 Ω · cm], it is confirmed that it is useful as a positive electrode active material layer.
Further, the positive electrode active material layer (LCO: LiCoO ₂ ) of Example 12 is an amorphous film formed at a relatively low temperature of 500 ° C. when applied to the positive electrode of an electrolyte coin cell using lithium-doped graphite as a negative electrode. Nevertheless, it is confirmed that it has a positive electrode capacity of 70 mA / g.

  From each of Examples (Examples 1 to 18), the coating liquid of the present invention (active material layer forming coating liquid, solid electrolyte layer forming coating liquid) basically uses organometallic compounds having high solubility, and Since organic solvents with excellent solubility of organometallic compounds are optimally blended, the various constituent elements that make up the inorganic thin film are uniformly mixed at the molecular and ionic levels in the coating solution and dry coating film. Even if the inorganic thin film formed by a coating method using inorganic material is mineralized by heat treatment at a lower temperature, the target crystal structure can be easily obtained, and it is an amorphous film (amorphous film). It is also confirmed that the function (charge / discharge capacity) as an active material or a solid electrolyte is easily exhibited.

  From Example 19, the thin-film solid secondary battery using each thin film (positive electrode active material layer, solid electrolyte layer, negative electrode active material layer) formed by the coating method of the present invention has a small discharge capacity but a charge / discharge behavior. Since it was confirmed, it can be seen that the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer of the present invention can be applied to a thin film solid secondary battery individually or in combination.

  According to the method for producing a thin film for a thin film solid secondary battery according to the present invention, the coating using the coating liquid for forming an active material layer or the coating liquid for forming a solid electrolyte layer containing an organometallic compound as a main component (positive electrode, negative electrode). By using this method, thin films such as active material layers (positive and negative electrodes) and solid electrolyte layers can be easily and inexpensively manufactured. Thin-film solid-state secondary batteries using the thin films obtained can be made thinner and smaller. In addition, since significant cost reduction can be realized, application promotion to IC cards, card-type electronic money, RFID tags and the like can be expected.

1 Substrate (glass substrate, ceramic substrate, heat-resistant plastic film)
2 Positive electrode current collector layer 3 Positive electrode active material layer 4 Solid electrolyte layer 5 Negative electrode active material layer 6 Negative electrode current collector layer 7 Protective film or protective film 8 Heating device (hot plate, heater, etc.)
9 Substrate for applying coating solution 10 Dry coating film of coating solution formed by coating method 11 Energy beam irradiation lamp (ultraviolet irradiation lamp)
12 UV irradiation window (synthetic quartz plate, etc.)
13 Heating lamp (halogen lamp, xenon lamp, etc.)
14 Infrared irradiation window (fused quartz plate, etc.)

Claims (20)

A layered structure composed of a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer, which are sequentially formed on the substrate, or formed in the reverse order on the substrate. A positive electrode active material layer, a solid electrolyte layer, a negative electrode active layer in a thin film solid secondary battery having a laminated structure comprising a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer A method for producing at least one thin film of a material layer,
The thin film is coated with a coating solution selected from a coating solution for forming a positive electrode active material layer, a coating solution for forming a solid electrolyte layer, and a coating solution for forming a negative electrode active material layer, which contains an organometallic compound as a main component. A coating step for forming a coating film, a drying step for drying the coating film to form a dry coating film, a dry coating film mainly composed of the organometallic compound formed in the drying step is mineralized, and a metal oxide It is formed by the coating method consisting of each step of the mineralization step that forms an inorganic thin film mainly composed of an object,
In the mineralization step, an organic component contained in the dry coating film is removed by decomposition or oxidation, or decomposition and oxidation by at least one of heat treatment, energy ray irradiation treatment, and plasma irradiation treatment in an oxygen-containing atmosphere. A method for producing a thin film, comprising the step of forming an inorganic thin film (metal oxide fine particle film) composed of fine particles containing a metal oxide as a main component. The organometallic compound contained as a main component in the coating liquid for forming the positive electrode active material layer is an organometallic compound of one or more transition metals of manganese, cobalt, nickel, and iron, and an organolithium compound,
2. The thin film according to claim 1, wherein the metal oxide which is a main component of the inorganic thin film is a lithium composite oxide containing one or more transition metals of manganese, cobalt, nickel, and iron. Manufacturing method. The lithium composite oxide is any one or more of LiMO ₂ , LiMPO ₄ , Li ₂ MSiO ₄ (M: one or more transition metals of manganese, cobalt, nickel, iron) and LiMn ₂ O _4. The method for producing a thin film according to claim 2. The organometallic compound contained as a main component in the solid electrolyte layer forming coating solution is an organophosphorus compound and an organolithium compound,
The method for producing a thin film according to claim 1, wherein the metal oxide that is a main component of the inorganic thin film is a lithium composite oxide containing phosphorus. The lithium composite oxide containing phosphorus is Li ₃ PO ₄ , Li ₂ O—Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ based oxide, Li ₂ O—Al ₂ O ₃ —GeO ₂ —P ₂ O. _{5. The} oxide according to claim 4, wherein the oxide is any one or more of a ₅ oxide, a Li ₂ O—La ₂ O ₃ —TiO ₂ oxide, and a Li ₂ O—La ₂ O ₃ —ZrO ₂ oxide. The manufacturing method of the thin film of description. The organometallic compound contained as a main component in the coating solution for forming a solid electrolyte layer is an organic lanthanum compound and an organolithium compound,
The method for producing a thin film according to claim 1, wherein the metal oxide which is a main component of the inorganic thin film is a lithium composite oxide containing lanthanum. The lithium composite oxide containing lanthanum is at least one of Li ₂ O—La ₂ O ₃ —TiO ₂ oxide and Li ₂ O—La ₂ O ₃ —ZrO ₂ oxide. The method for producing a thin film according to claim 6. The organometallic compound contained as a main component in the coating liquid for forming the negative electrode active material layer is an organotitanium compound and an organolithium compound, or an organometallic compound of at least one of niobium, indium, tin, zinc, and titanium A compound,
The metal oxide that is a main component of the inorganic thin film is at least one of lithium-titanium oxide, niobium oxide, indium oxide, tin oxide, zinc oxide, and titanium oxide. A method for producing a thin film. The method for producing a thin film according to claim 8, wherein the lithium-titanium oxide is Li ₄ Ti ₅ O ₁₂ .   The method for producing a thin film according to any one of claims 1 to 9, wherein the energy ray irradiation is irradiation of ultraviolet rays including at least a wavelength of 200 nm or less as one of main components.   11. The ultraviolet irradiation including at least a wavelength of 200 nm or less as one of main components is irradiation of ultraviolet rays emitted from any one of a low-pressure mercury lamp, an amalgam lamp, and an excimer lamp. A method for producing a thin film.   The method for producing a thin film according to any one of claims 1 to 11, wherein the packing density of the inorganic thin film containing the metal oxide as a main component is controlled by controlling a dew point temperature of the oxygen-containing atmosphere. .   The method for producing a thin film according to any one of claims 1 to 12, wherein the oxygen-containing atmosphere is an air atmosphere.   The method for producing a thin film according to claim 1, wherein the substrate is a glass substrate, a ceramic substrate, or a heat-resistant plastic film.   The method for producing a thin film according to claim 1, wherein the positive electrode current collector layer and the negative electrode current collector layer are a single metal or an alloy.   A plate or foil made of a single metal or an alloy is used as the positive electrode current collector layer or the negative electrode current collector layer instead of the substrate on which the positive electrode current collector layer or the negative electrode current collector layer is formed. The method for producing a thin film according to claim 1. It is selected from the coating liquid for forming a positive electrode active material layer, the coating liquid for forming a solid electrolyte layer, and the coating liquid for forming a negative electrode active material layer used in the method for producing a thin film according to any one of claims 1 to 9. Any coating solution,
The positive electrode active material layer forming coating solution is an organic solvent, and an organic metal compound of a transition metal of at least one of manganese, cobalt, nickel, and iron as a main component dissolved in the organic solvent, And an organolithium compound,
The coating solution for forming a solid electrolyte layer contains an organic phosphorus compound and an organic lithium compound, or an organic lanthanum compound and an organic lithium compound as main components dissolved in an organic solvent and the organic solvent,
The coating liquid for forming the negative electrode active material layer contains an organic titanium compound and an organic lithium compound as main components dissolved in an organic solvent and the organic solvent,
The organolithium compound includes lithium (I) -2,4-pentanedionate [Li (C ₅ H ₇ O ₂ )], lithium (I) ethoxide [Li (C ₂ H ₅ O)], lithium (I) and a -tert- butoxide _{[Li (C 4 H 9 O} )] any one or more of,
The organic solvent is at least one of N-methyl-2-pyrrolidone and an amine solvent having a boiling point of 150 ° C. or higher.   The coating solution according to claim 17, wherein the amine solvent having a boiling point of 150 ° C or higher is 3-amino-1-propanol.   A thin film for a thin film solid secondary battery, which is obtained by the method for producing a thin film according to any one of claims 1 to 16.   The thin film in the thin film solid secondary battery which has a thin film is a thin film for thin film solid secondary batteries of Claim 19, The thin film solid secondary battery characterized by the above-mentioned.

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