JP2018181802A - METHOD FOR MANUFACTURING ELECTRODE ACTIVE MATERIAL MOLDED BODY AND METHOD FOR MANUFACTURING LITHIUM ION BATTERY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a molded article of an electrode active material, which is capable of producing a molded article having a smooth surface state and high strength. The method includes a compression molding step of compression molding a mixture containing an aprotic solvent and an electrode active material and not containing a resin binder, and the melting point of the aprotic solvent is equal to or higher than an environmental temperature in the compression molding step. And the aprotic solvent is present as a solid in the mixture, the method for producing a molded electrode active material. [Selection diagram] None

Description

The present invention relates to a method of producing a molded electrode active material and a method of producing a lithium ion battery.

In recent years, reduction of carbon dioxide emissions is strongly desired for environmental protection. In the automobile industry, there are high hopes for reducing carbon dioxide emissions through the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs), and the development of motor-drive secondary batteries that hold the key to their practical application is keen It has been done. As secondary batteries, attention has been focused on lithium ion batteries which can achieve high energy density and high power density.

In Patent Document 1, as a method of manufacturing an electrode for a lithium ion battery, a slurry containing an electrode active material and an electrolytic solution is applied on a current collector to form a slurry layer, and a separator is disposed on the slurry layer. A method is described in which liquid is absorbed from the top side of the separator.

WO 2015/093411

When an electrode is manufactured by the method described in Patent Document 1, a molded body containing an electrode active material is produced on a current collector and becomes an electrode, but the surface state of the molded body may not be smooth on the separator side. . When a lithium ion battery is manufactured using an electrode whose surface state of the molded body is not smooth, it causes dispersion of electric characteristics and an increase in interfacial resistance with the current collector.
Here, if the flowability of the slurry is increased by increasing the amount of the electrolytic solution in the slurry in the method described in Patent Document 1, the strength of the molded body constituting the electrode decreases, so the electrolytic solution is removed. A process is required separately.

This invention is made in view of the said subject, and the surface state is smooth, And an object of this invention is to provide the manufacturing method of an electrode active material molded object which can manufacture a molded object with high intensity | strength. I assume.

The present inventors reached the present invention as a result of earnestly examining in order to solve the above-mentioned subject.
That is, the present invention has a compression molding step of compression molding a mixture containing an aprotic solvent and an electrode active material and containing no resin binder, and the melting point of the aprotic solvent is the environment in the compression molding step. A method for producing an electrode active material molded body characterized in that the temperature is equal to or higher and the aprotic solvent is present as a solid in the mixture, and an electrode produced by the method for producing an electrode active material molded body The present invention relates to a method for producing a lithium ion battery, including the step of impregnating the active material molded body with an electrolytic solution.

According to the method for producing an electrode active material molded body of the present invention, a molded body having a smooth surface and high strength can be produced.

Hereinafter, the present invention will be described in detail.
The method for producing an electrode active material molded body according to the present invention comprises a compression molding step of compression molding a mixture containing an aprotic solvent and an electrode active material and not containing a resin binder, and the melting point of the aprotic solvent Is above the environmental temperature in the compression molding step, and the above aprotic solvent is present as a solid in the above mixture.

First, each component contained in the mixture which is a material to be compression-molded in the compression molding step will be described.
The mixture contains at least an aprotic solvent and an electrode active material.
The electrode active material may be a positive electrode active material or a negative electrode active material.

The aprotic solvent is a solvent which does not have a hydrogen ion donating group (a group having a dissociative hydrogen atom such as an amino group, a hydroxyl group and a thio group), and can be preferably used as a solvent Lactone compounds, cyclic or chain carbonates, chain carboxylic acid esters, cyclic or chain ethers, phosphoric acid esters, nitrile compounds, amide compounds, sulfones and the like and mixtures thereof can be used, more preferably usually The non-aqueous solvent used for the non-aqueous electrolyte of can be used. In the compression molding step, the environmental temperature in the compression molding step is adjusted in accordance with the type of aprotic solvent, and the melting point of the aprotic solvent is used so as to be equal to or higher than the environmental temperature in the compression molding step.
Also, in the mixture, the aprotic solvent is not dissolved in the other liquid, that is, it is subjected to the compression molding step so as to be present as a solid.
The fact that the aprotic solvent is present as a solid in the mixture means that the state of the aprotic solvent (whether solid, liquid or gaseous) is solid and is dissolved in the other liquid. Means not being
The mixture of the electrode active material and the aprotic solvent as a whole is a solid (powdery mixture).

Examples of lactone compounds include 5-membered rings (such as γ-butyrolactone and γ-valerolactone) and 6-membered ring lactone compounds (such as δ-valerolactone).

Examples of cyclic carbonates include propylene carbonate, ethylene carbonate, butylene carbonate and vinylene carbonate.
Examples of chain carbonates include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate and di-n-propyl carbonate.

Examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate and methyl propionate.
Examples of cyclic ethers include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane and 1,4-dioxane.
Examples of the chain ether include dimethoxymethane and 1,2-dimethoxyethane.

As phosphoric acid esters, trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, Tri (trifluoroethyl) phosphate, tri (triperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphosphoran-2-one, 2-trifluoroethoxy-1,3,2- Examples include dioxaphospholan-2-one and 2-methoxyethoxy-1,3,2-dioxaphospholan-2-one.
Acetonitrile etc. are mentioned as a nitrile compound. Examples of the amide compound include N, N-dimethylformamide (hereinafter also referred to as DMF) and the like. Examples of sulfones include linear sulfones such as dimethylsulfone and diethylsulfone and cyclic sulfones such as sulfolane.
The aprotic solvent may be used alone or in combination of two or more.

Among these aprotic solvents, solvents having a melting point of 0 ° C. or higher are preferred.
In particular, it is preferable to use at least one solvent selected from the group consisting of ethylene carbonate (melting point 35 ° C.), dimethyl carbonate (melting point 3 ° C.) and vinylene carbonate (melting point 20 ° C.).
Among these solvents used as electrolytes, these solvents have relatively high melting points. Therefore, it is suitable for smoothing the surface state of a molded object by performing a compression molding process in the state in which an aprotic solvent exists as a solid.
In the present specification, the term "melting point of solvent" refers to the melting point measured under standard atmospheric pressure.

As a positive electrode active material as an electrode active material, a composite oxide of lithium and a transition metal {a composite oxide in which a transition metal is one kind (LiCoO ₂ , LiNiO ₂ , LiAlMnO ₄ , LiMnO _2, LiMn ₂ O ₄ etc.) a composite oxide transition metal element is two (e.g. _{LiFeMnO 4, LiNi 1-x Co} x O 2, LiMn 1-y Co y O 2, LiNi 1/3 Co 1/3 Al 1/3 O 2 and LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) and complex oxides containing three or more metal elements [eg LiMaM'bM''cO ₂ (M, M 'and M''are different transition metals, respectively] It is an element and satisfies a + b + c = 1. For example, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ etc., etc., etc.}, lithium-containing transition metal phosphate (eg LiFePO ₂ ) ₄ LiCoPO ₄ , LiMnPO ₄ and LiNiPO ₄ ), transition metal oxides (eg MnO ₂ and V ₂ O ₅ ), transition metal sulfides (eg MoS ₂ and TiS ₂ ) and conductive polymers (eg polyaniline, polypyrrole, Polythiophene, polyacetylene, poly-p-phenylene and polyvinylcarbazole) and the like may be mentioned, and two or more may be used in combination.
The lithium-containing transition metal phosphate may have a part of the transition metal site substituted with another transition metal.

Examples of negative electrode active materials as electrode active materials include carbon-based materials [eg, graphite, non-graphitizable carbon, amorphous carbon, resin fired bodies (eg, those obtained by firing and carbonizing phenol resins and furan resins, etc.), cokes (Eg pitch coke, needle coke and petroleum coke etc.), silicon carbide and carbon fiber etc.], conductive polymers (eg polyacetylene and polypyrrole etc.), metals (tin, silicon, aluminum, zirconium and titanium etc.), metal oxides (Titanium oxide, lithium titanium oxide, silicon oxide etc.) and metal alloys (eg lithium-tin alloy, lithium-silicon alloy, lithium-aluminum alloy, lithium-aluminum-manganese alloy etc.) etc. Mixtures with materials etc. may be mentioned.
About the thing which does not contain lithium or lithium ion inside among the said negative electrode active materials, you may perform the pre dope process which includes lithium or lithium ion in advance in part or all of an active material.

The electrode active material may be the electrode active material itself, and is a coated electrode active material coated with an electrode coating layer comprising a polymer compound which is a part or whole of the surface of the electrode active material as a coating resin. Although it may be present, a coated electrode active material is preferable.
When the surface of the electrode active material is covered with the electrode coating layer, it is easy to keep the distance between the electrode active materials constant, and it is easy to maintain the conductive path, which is preferable.

The electrode coating layer comprises a polymer compound which is a coating resin. Moreover, you may contain the conductive support agent mentioned later further as needed.
The coated electrode active material is one in which a part or the whole of the surface of the electrode active material is coated with an electrode coating layer containing a polymer compound. Even when the active materials are in contact with each other, the electrode coating layers are not irreversibly adhered to each other by the coating resin on the contact surface.

As a high molecular compound which comprises an electrode coating layer, a thermoplastic resin, a thermosetting resin, etc. are mentioned, For example, resin for lithium ion battery active material coating | cover as described in international publication 2015/005117 etc. is mentioned.

The electrode coating layer preferably further contains a conductive aid.
The conductive aid is selected from materials having conductivity, and specifically, carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.), PAN-based carbon Fibers and carbon fibers such as pitch carbon fibers, carbon nanofibers and carbon nanotubes, metals [nickel, aluminum, stainless steel (SUS), silver, copper, titanium and the like] can be used.
These conductive aids may be used alone or in combination of two or more. Also, these alloys or metal oxides may be used. From the viewpoint of electrical stability, it is preferably aluminum, stainless steel, carbon, silver, copper, titanium and a mixture thereof, more preferably silver, aluminum, stainless steel and carbon, and still more preferably carbon. Moreover, as these conductive support agents, conductive materials (of the above-described conductive materials, metals) may be coated by plating or the like around a particulate ceramic material or resin material. A polypropylene resin into which graphene is kneaded is also preferable as a conductive aid.

The average particle size of the conductive additive is not particularly limited, but is preferably 0.01 to 10 μm and 0.02 to 5 μm from the viewpoint of the electrical characteristics of the electrode for lithium ion batteries. More preferably, it is 0.03 to 1 μm. In the present specification, the particle diameter of the conductive additive means the largest distance L among the distance between any two points on the contour of the particle formed by the conductive additive. As the value of “average particle diameter of conductive aid”, particle diameter of particles observed in several to several tens of visual fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) A value calculated as an average value of

The shape (form) of the conductive aid is not limited to the particle form, and may be a form other than the particle form, and may be, for example, a fibrous conductive aid.
Examples of fibrous conductive assistants include conductive fibers obtained by uniformly dispersing metal and graphite having good conductivity in synthetic fibers, metal fibers obtained by fiberizing metals such as stainless steel, and organic fibers. Examples thereof include conductive fibers coated with metal and conductive fibers obtained by coating the surface of an organic substance with a resin containing a conductive substance.
The average fiber diameter of the fibrous conductive aid is preferably 0.1 to 20 μm.

When the electrode coating layer contains a conductive auxiliary agent, the weight of the conductive auxiliary agent contained in the electrode coating layer is 15 to 75% by weight based on the total weight of the polymer compound as a coating resin and the conductive auxiliary agent. Is preferred.
When the electrode coating layer of the coated electrode active material contains a conductive additive, the effect of the conductive additive contained in the electrode coating layer even if the SEI film is formed on the surface of the electrode active material after precharging. The conductive path between the active materials can be maintained by this, and the increase in resistance due to the formation of the SEI film can be suppressed. This is preferable, and when the ratio of the conductive additive is in this range, the resistance can be easily suppressed and is further preferable.

In the case of using a coated electrode active material as an electrode active material, for example, in a state where the electrode active material is placed in a universal mixer and stirred at 30 to 50 rpm, a polymer solution containing a polymer compound is taken over 1 to 90 minutes The mixture is added dropwise, and the conductive material is further mixed if necessary, and the temperature is raised to 50 to 200 ° C. with stirring, and the pressure is reduced to 0.007 to 0.04 MPa, and then the coated electrode is activated by holding for 10 to 150 minutes You can get the substance.

The mixture which is a material to be compression-molded in the compression molding step may contain a conductive material separately from the above-mentioned conductive aid contained in the electrode coating layer. The inclusion of a conductive material is preferable because it makes it easier to maintain the conductive path between the active materials.
As the conductive material, the same one as the above-mentioned conductive aid contained in the electrode coating layer can be used, and the preferable one is also the same.

The mixture which is a material to be compression-molded in the compression molding step does not contain a binder for a lithium ion battery electrode (hereinafter also referred to as a resin binder).
The resin binder in the present specification includes starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene and polypropylene.
Moreover, since the resin binder is not used, the process of solidifying the resin binder by heating etc. which is necessary when using the resin binder is unnecessary.

The compounding ratio of each component in the mixture is preferably 2 to 10% by weight of the aprotic solvent and 70 to 85% by weight of the electrode active material.
Furthermore, when it contains a conductive material, it is preferable to contain 0-5 weight% of a conductive material.
These weight ratios are ratios at the time of being subjected to the compression molding process.

In addition to the aprotic solvent (aprotic solvent present as a solid in the mixture subjected to the compression molding step), another type of solvent (a solvent having a low melting point and being a liquid at the time of preparation of the mixture) other than the aprotic solvent herein. To prepare a liquid mixture in which the aprotic solvent is dissolved in the solvent of the other type, and the liquid mixture and the electrode active material may be mixed to obtain a mixture precursor.
This has the advantage of facilitating uniform mixing of the aprotic solvent and the electrode active material.
Then, the mixture precursor may be dried by heating or the like to distill off the above-mentioned other type of solvent (which is distilled off earlier because the melting point is low).
In this way, the aprotic solvent remains as a solid in the mixture, and the mixture used in the method for producing an electrode active material molded body of the present invention is a solid in the form of a solid, and the aprotic solvent and the electrode active material are uniform. Obtained in the state of being mixed with

In the compression molding step, the above mixture is compression molded.
The compression molding can be performed using any pressing device such as a hydraulic pressing device and a pressing jig. For example, the mixture is placed in a cylindrical bottomed container, and a round bar-shaped pressing jig having a diameter slightly smaller than the inner diameter of the cylinder is inserted from above, and compressed by a pressing device to form a cylindrical shape The molded object shape | molded to is obtained.
By changing the shape of the pressing jig, it is possible to obtain a molded body of any shape.
It is preferable that the shape of the molded object to produce is 250-2000 micrometers in thickness.
Moreover, in the case of a cylindrical-shaped molded object, it is preferable that it is 10-70 mm in diameter.

In the compression molding step, the melting point of the aprotic solvent is made to be equal to or higher than the environmental temperature in the compression molding step. In other words, the environmental temperature in the compression molding process is lower than the melting point of the aprotic solvent.
In this way, since the aprotic solvent contained in the electrode active material molded body obtained through the compression molding step is solid, the shape of the electrode active material molded body after the compression molding step is stabilized without breaking. can get. In addition, an electrode active material compact having a smooth surface state can be obtained.

Moreover, it is preferable that the temperature of the pressing jig of the pressing apparatus is less than the melting point of the solvent.
Even if the room temperature of the room where the compression molding process is performed is higher than the melting point of the solvent, the environmental temperature in the compression molding process is set to the melting point of the aprotic solvent by lowering the temperature of the pressing jig of the pressure device. It can be less than.
As a method of lowering the temperature of the pressurizing jig of the pressurizing device, a method of arranging a cooling pipe in the pressurizing jig and circulating water or a frozen liquid cooled through the freezing apparatus to the cooling pipe is mentioned. Be

As compression conditions other than the environmental temperature in a compression molding process, it is preferable that the pressure concerning the said mixture is 100-3000 Mpa. Moreover, it is preferable that pressurization time is 1 to 300 second.

When pressure is applied to the mixture in the compression molding step, the melting point of the aprotic solvent in the mixture is lowered by the action of freezing point depression under pressure, and the aprotic solvent may be softened or melted. Although the details are not clear, the pressure in the compression molding process softens or melts the aprotic solvent, and then the aprotic solvent solidifies again when the pressure is returned to normal pressure. It is also conceivable that the function of binding between substances can be expressed. When the aprotic solvent in the mixture bonds the electrode active materials, the shape of the electrode active material compact after the compression molding step is further stabilized.
From the viewpoint of moldability and the like, the difference between the melting point of the solvent and the environmental temperature in the compression molding step (melting point of solvent-environmental temperature in the compression molding step) is preferably 10 ° C. or less.
As an example, when a solvent is ethylene carbonate (melting point 35 degreeC), it is preferable that the environmental temperature in a compression molding process is 25-30 degreeC.

The compression molding step may be performed on the current collector. By placing the mixture on the current collector and performing compression molding, an electrode active material compact can be obtained on the current collector.
The electrode active material molded body obtained on the current collector can be used as an electrode of a lithium ion battery together with the current collector.

As a material which comprises the positive electrode collector as a collector, copper, aluminum, titanium, stainless steel, nickel, baked carbon, a conductive polymer, conductive glass, etc. are mentioned. Alternatively, a resin current collector made of a conductive agent and a resin may be used as the positive electrode current collector.

As a material which comprises the negative electrode collector as a collector, metal materials, such as copper, aluminum, titanium, stainless steel, nickel, and these alloys, etc. are mentioned. Among them, copper is preferable from the viewpoint of weight reduction, corrosion resistance, and high conductivity. The negative electrode current collector may be a current collector made of calcined carbon, a conductive polymer, a conductive glass, or the like, or may be a resin current collector made of a conductive agent and a resin.

As for the positive electrode current collector and the negative electrode current collector, as the conductive agent constituting the resin current collector, the same conductive material as an optional component of the mixture can be suitably used.
Examples of the resin constituting the resin current collector include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyether nitrile (PEN), and polytetratetra Fluoroethylene (PTFE), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin or a mixture of these, etc. Can be mentioned.
From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferred, and more preferably polyethylene (PE), polypropylene (PP) and polymethylpentene (PMP).

An electrode active material molded body can be obtained by the above steps.
The electrode active material molded body obtained by the above-mentioned compression molding process does not use a resin binder and does not perform the process of solidifying the mixture by heating etc. Since they bind between the electrode active materials, their shape can be maintained.
Moreover, the obtained electrode active material molded body can be used for the manufacturing method of the lithium ion battery of this invention.
The method for producing a lithium ion battery of the present invention is characterized by including the step of impregnating the electrode active material molded body produced by the method for producing an electrode active material molded body of the present invention with an electrolytic solution.

In the case of manufacturing a lithium ion battery, it is preferable to accommodate the electrode active material compact with a separator in a cell container, inject the electrolytic solution, and impregnate the electrode active material compact with the electrolytic solution.
As an electrode active material molded body to be accommodated in a cell container, both of a positive electrode active material molded body and a negative electrode active material molded body manufactured by the method of manufacturing an electrode active material molded body of the present invention may be used. You may use.
When only one is used, a known counter electrode can be used as the opposite electrode.

The obtained electrode active material molded body is easy to handle because the electrode active materials are bonded with an aprotic solvent, and the electrode active material molded body is easily accommodated in the cell container. Furthermore, when the electrolytic solution is injected into the electrode active material molded body in the cell container and the electrolytic solution is impregnated in the electrode active material molded body, the aprotic solvent which has connected the electrode active materials is dissolved in the electrolytic solution. , Part of the electrolyte. By dissolving the aprotic solvent in the electrolyte solution inside the cell container, the electrode active material bonded and fixed to each other by the aprotic solvent is loosened, and the electrolyte solution penetrates between them, resulting in good ion conductivity. It is thought that it can be demonstrated.

As described above, when an electrode active material molded body is obtained on a current collector, it is possible to manufacture a lithium ion battery using the electrode active material molded body as an electrode in combination with the current collector. .

The separator may be a porous film made of polyethylene or polypropylene, a laminated film of a porous polyethylene film and a porous polypropylene, a non-woven fabric made of synthetic fibers (such as polyester fibers and aramid fibers) or glass fibers, and silica on their surfaces. And separators for known lithium ion batteries such as those to which ceramic fine particles such as alumina and titania are attached.

As the electrolytic solution, an electrolytic solution containing an electrolyte and a non-aqueous solvent, which is used for producing a lithium ion battery, can be used.

As the electrolyte, those used in common electrolytic solutions can be used, and preferred examples include lithium salt electrolytes of inorganic acids such as LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ and LiClO ₄ , Sulfonylimide electrolytes having a fluorine atom such as LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ , fluorine atoms such as LiC (CF ₃ SO ₂ ) ₃ Sulfonyl methide type electrolyte etc. are mentioned.

As a non-aqueous solvent used for the electrolyte solution to inject | pour, the solvent illustrated as an aprotic solvent which can be used in the manufacturing method of the electrode active material molded object of this invention can be used.
The non-aqueous solvent used for the electrolyte solution to be injected may be the same as or different from the aprotic solvent used in the method of producing the electrode active material molded body. Moreover, the mixed solvent which combined these solvent may be sufficient.
Among the aprotic solvents or mixed solvents thereof, solvents having a melting point of −20 ° C. or less are preferable, and more preferably −30 ° C. or less from the viewpoint of battery characteristics and the like at low temperatures.

The concentration of the electrolyte contained in the electrolytic solution is preferably 0.3 to 3 M in view of battery characteristics and the like at low temperatures.

EXAMPLES The present invention will now be specifically described by way of Examples, but the present invention is not limited to the Examples unless departing from the gist of the present invention. Unless otherwise stated, parts mean parts by weight and% mean% by weight.

Production Example 1: Production of Polymer Compound for Coating Layer and Solution Thereof
In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas inlet, 407.9 parts of DMF was charged and the temperature was raised to 75 ° C. Next, a monomer blend solution containing 242.8 parts of methacrylic acid, 97.1 parts of methyl methacrylate, 242.8 parts of 2-ethylhexyl methacrylate, and 116.5 parts of DMF, and 2,2′-azobis (2,4-dimethyldi) An initiator solution in which 1.7 parts of valeronitrile) and 4.7 parts of 2,2′-azobis (2-methylbutyronitrile) are dissolved in 58.3 parts of DMF is blown into a four-necked flask while nitrogen is blown: Under stirring, radical polymerization was performed by continuously dropping over 2 hours with a dropping funnel. After completion of the addition, the reaction was continued at 75 ° C. for 3 hours. Then, the temperature was raised to 80 ° C., and the reaction was continued for 3 hours to obtain a copolymer solution having a resin concentration of 50%. 789.8 parts of DMF was added to this, and the polymer compound solution for coating layers which is 30 weight% of resin solid content concentration was obtained.

Production Example 2 Production of Coated Positive Electrode Active Material Particles
100 parts of a positive electrode active material powder (LiNi _0.8 Co _0.15 Al _0.05 O ₂ powder, volume average particle diameter 4 μm) is placed in a universal mixer high speed mixer FS25 (manufactured by Earth Technica Co., Ltd.) at room temperature, While stirring at 720 rpm, 6.1 parts of the polymer compound solution for coating obtained in Production Example 1 was added dropwise over 2 minutes, and the mixture was further stirred for 5 minutes.
Next, in a stirred state, 6.1 parts of acetylene black (Denka Co., Ltd. Denka Black (registered trademark)), which is a conductive additive, was added in 2 minutes while being divided, and stirring was continued for 30 minutes. Thereafter, the pressure was reduced to 0.01 MPa while maintaining the stirring, and then the temperature was raised to 140 ° C. while maintaining the degree of stirring and the reduced pressure, and the volatile matter was distilled off while maintaining the degree of stirring, the reduced pressure and the temperature for 8 hours . The obtained powder was classified using a sieve with an aperture of 212 μm to obtain coated positive electrode active material particles.

Production Example 3: Production of Coated Negative Electrode Active Material Particles
100 parts of non-graphitizable carbon powder (average particle diameter 20 μm) was placed in a universal mixer high speed mixer FS25 (manufactured by Earth Technica Co., Ltd.) and stirred at 720 rpm at room temperature, the coating obtained in Production Example 1 6.1 parts of the layer polymer compound solution was added dropwise over 2 minutes, and the mixture was further stirred for 5 minutes.
Subsequently, 11.3 parts of acetylene black (Denka Co., Ltd. product Denka black (registered trademark)) which is a conductive support agent were dividedly added in 2 minutes while being stirred, and stirring was continued for 30 minutes. Thereafter, the pressure was reduced to 0.01 MPa while maintaining the stirring, and then the temperature was raised to 140 ° C. while maintaining the degree of stirring and the reduced pressure, and the volatile matter was distilled off while maintaining the degree of stirring, the reduced pressure and the temperature for 8 hours . The obtained powder was classified using a sieve with an aperture of 212 μm to obtain coated negative electrode active material particles.

(Example 1) Production of Cathode of Active Cathode Active Material: 5 g of coated cathode active material particles obtained in Production Example 2 and carbon fiber [Osaka Gas Chemical Co., Ltd. Dona Carbo Milled S-243: average fiber length 500 μm, average fiber diameter 13 μm: electric conductivity of 200 mS / cm] and 0.1 g were mixed for 3 minutes at 2000 rpm using a planetary stirring type mixing and kneading apparatus {Awatori Neritaro [product of Shinky Co., Ltd.]}.
Furthermore, 1.045 g of a mixed solution of ethylene carbonate and methyl ethyl carbonate (weight ratio 3: 7) was added, and mixed for 3 minutes at 2000 rpm.
Next, methyl ethyl carbonate is distilled off by drying under reduced pressure at 80 ° C. and −0.1 MPa, and the coated positive electrode active material, ethylene carbonate as an aprotic solvent in the solid state, and carbon fiber as a conductive material are included. A mixture was obtained.

0.636 g of the above mixture was weighed, and the mixture was placed in a cylindrical bottomed container and compressed by a pressing device to obtain a molded body formed into a cylindrical shape.
The pressing conditions were a pressing pressure of 150 MPa and a pressing time of 5 seconds, and the temperature of the pressing jig of the pressing apparatus was 20 ° C., equal to the room temperature at the time of pressing.

(Example 2) Production of negative electrode active material molded body 5 g of the coated negative electrode active material particles obtained in Production Example 3 and 3.248 g of a mixed solution of ethylene carbonate and methyl ethyl carbonate (3: 7 in weight ratio) were added and Mixed for 3 minutes.
Subsequently, methyl ethyl carbonate was distilled off by drying under reduced pressure at 80 ° C. and −0.1 MPa to obtain a mixture containing a coated negative electrode active material and ethylene carbonate as an aprotic solvent in the form of a solid.

0.292 g of the above mixture was weighed, and the mixture was placed in a cylindrical bottomed container and compressed by a pressure device to obtain a molded body formed into a cylindrical shape.
The pressing conditions were a pressing pressure of 150 MPa and a pressing time of 5 seconds, and the temperature of the pressing jig of the pressing apparatus was 20 ° C., equal to the room temperature at the time of pressing.

Example 3 Production of Molded Negative Electrode Active Material 5 g of the coated negative electrode active material particles obtained in Production Example 3 and 0.974 g of ethylene carbonate were mixed at 2000 rpm for 3 minutes in a 20 ° C. environment. 0.292 g of the obtained mixture was weighed, and the mixture was placed in a cylindrical bottomed container and compressed by a pressing device to obtain a molded body formed into a cylindrical shape.
The pressing conditions were a pressing pressure of 150 MPa and a pressing time of 5 seconds, and the temperature of the pressing jig of the pressing apparatus was 20 ° C., equal to the room temperature at the time of pressing.

(Comparative Example 1) Production of Comparative Cathode Active Material Molded Product Non-aqueous prepared by dissolving LiN (FSO ₂ ) ₂ at a ratio of 3 mol / L in a mixed solvent of ethylene carbonate and methyl ethyl carbonate (volume ratio 1: 1) Planetary stirring type mixing and kneading machine {20 parts of electrolytic solution and 2 parts of carbon fiber [Osaka Gas Chemical Co., Ltd. Dona Carbo Milled S-243: average fiber length 500 μm, average fiber diameter 13 μm: electric conductivity 200 mS / cm] { A mixed electrolyte was prepared by mixing for 7 minutes at 2000 rpm using Awatori Neritaro [made by Shinky Co., Ltd.]}.
Subsequently, 10 parts of the mixed electrolyte and 90 parts of the coated positive electrode active material particles manufactured in Production Example 2 are mixed, and further mixed by an air-washer Naritaro at 2000 rpm for 1.5 minutes to form a coated active material concentration of 90% by weight The positive electrode active material slurry of In the positive electrode active material slurry, ethylene carbonate is present in a state of being dissolved in methyl ethyl carbonate. Therefore, it can not be said that the aprotic solvent is present as a solid in the mixture to be subjected to the compression molding step.

0.636 g of the positive electrode active material slurry was weighed, and the mixture was placed in a cylindrical bottomed container and compressed by a pressurizing device to obtain a molded body formed into a cylindrical shape.
The pressure conditions were the same as in Example 1.

Comparative Example 2 Production of Comparative Anode Active Material Molded Product Non-aqueous prepared by dissolving LiN (FSO ₂ ) ₂ at a ratio of 3 mol / L in a mixed solvent of ethylene carbonate and methyl ethyl carbonate (volume ratio 1: 1) After mixing 10 parts of the electrolytic solution and 90 parts of the coated negative electrode active material particles produced in Production Example 3, using a planetary stirring type mixing and kneading apparatus {Awatori Neritaro [Shinky Co., Ltd.]}, 1.5 at 2000 rpm After mixing for a minute, a negative electrode active material slurry having a coated active material concentration of 90% by weight was produced. In the negative electrode active material slurry, ethylene carbonate is present in a state of being dissolved in methyl ethyl carbonate. Therefore, it can not be said that the aprotic solvent is present as a solid in the mixture to be subjected to the compression molding step.

0.292 g of the negative electrode active material slurry was weighed, and the mixture was placed in a cylindrical bottomed container and compressed by a pressurizing device to obtain a molded body formed into a cylindrical shape.
The pressure conditions were the same as in Example 2.

(Evaluation of shape maintenance)
Changes in shape were observed when the compacts produced in each of the examples and comparative examples were left in the air, or when the compact was placed on a mesh and immersed in the electrolyte.
As an electrolytic solution, a non-aqueous electrolytic solution prepared by dissolving LiN (FSO ₂ ) ₂ at a ratio of 3 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1: 1) used.
Evaluation criteria are shown in Table 1 as follows.
◎: The shape is maintained even after 10 minutes or more.
○: The shape was broken after 5 minutes and before 10 minutes.
X: The shape collapsed in less than 5 minutes immediately after standing in the air or after immersion in the electrolyte.

(Evaluation of surface smoothness)
A root mean square deviation: Sq was measured as an index of roughness in the height direction with a three-dimensional shape measuring instrument VR-3200 (manufactured by Keyence Corporation) for the molded articles produced in each of Examples and Comparative Examples.

The electrode active material molded body produced in each Example was able to maintain its shape for a long time in the air and in the electrolytic solution. Moreover, it was excellent in surface smoothness.

On the other hand, the electrode active material molded body produced in each comparative example can not maintain the shape for a long time in the electrolytic solution, and is inferior in surface smoothness.
In each comparative example, when released from the compression molding process, the active material may be adhered to the pressing jig, and it is presumed that the surface smoothness is deteriorated due to it.

The method for producing an electrode active material molded body according to the present invention is an electrode active material particularly used for producing bipolar secondary batteries and lithium ion secondary batteries used for mobile phones, personal computers, hybrid vehicles and electric vehicles. It is useful as a method of manufacturing a molded object.

Claims (5)

Having a compression molding step of compression molding a mixture containing an aprotic solvent and an electrode active material and not containing a resin binder,
The method for producing an electrode active material molded body, wherein the melting point of the aprotic solvent is equal to or higher than the environmental temperature in the compression molding step, and the aprotic solvent is present as a solid in the mixture. The method for producing an electrode active material compact according to claim 1, wherein the aprotic solvent is at least one selected from the group consisting of ethylene carbonate, dimethyl carbonate and vinylene carbonate. The method for producing an electrode active material compact according to claim 1, wherein the melting point of the aprotic solvent is 0 ° C. or higher. The method for producing an electrode active material compact according to any one of claims 1 to 3, wherein the mixture is disposed on a current collector, and compression molding is performed on the current collector. The manufacturing method of a lithium ion battery characterized by including the process of impregnating electrolyte solution in the electrode active material molded object manufactured with the manufacturing method of the electrode active material molded object in any one of Claims 1-4.