JP2021044182A - Selective extraction method for cathode active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for selectively extracting a positive electrode active material from a lithium ion battery by a simple operation. A lithium ion battery has a positive electrode having a positive electrode active material layer composed of a positive electrode resin current collector and a positive electrode composition containing a positive electrode active material formed on the positive electrode resin current collector, and a negative electrode active material layer. A power storage element composed of a negative electrode and a separator arranged between the positive electrode active material layer and the negative electrode active material layer is provided. In the selective extraction method of the positive electrode active material 15, the power storage element is taken out from the lithium ion battery, and the power storage element is brought into contact with a non-protic solvent having an SP value of 10 or less and a specific gravity smaller than that of water, and at the time of contact or after contact. A suspension preparation step of adding water 61 to obtain a suspension 90 containing water, a non-polar solvent and a positive positive active material, and an oil layer 70 containing a non-polar solvent after allowing the suspension to stand. It has a separation step of separating water and an aqueous layer 60 containing a positive electrode active material [selection diagram] FIG.

Description

The present invention relates to a method for selectively taking out a positive electrode active material.

Lithium-ion (secondary) batteries have been widely used in various applications in recent years as high-capacity, compact and lightweight secondary batteries. In a general lithium ion battery, a container in which a positive electrode active material layer containing a positive electrode active material and a non-aqueous electrolytic solution and a negative electrode active material layer containing a negative electrode active material and a non-aqueous electrolytic solution are sandwiched between separators. It is stored and configured in.

Nickel oxides and cobalt oxides are often used as the material for the positive electrode active material. Metals such as nickel and cobalt are expensive, and if they are discarded as they are, they impose an environmental burden, so it is desired to recycle them for use.

Patent Document 1 describes a technique relating to a method for recovering a positive electrode active material from a waste lithium ion battery or a waste electrode material.
In Patent Document 1, after separating and removing the separator from the crushed material obtained by crushing the waste lithium ion battery or the waste electrode material, the organic matter contained in the binder is removed by heating at 400 to 550 ° C. in the atmosphere. It is stated that it should be done.

Japanese Unexamined Patent Publication No. 2012-195073

However, the technique described in Patent Document 1 has a problem that it is necessary to go through a number of steps such as crushing, heating, separation, and purification before obtaining a new positive electrode active material from a waste lithium ion battery, and the recycling cost is high. there were.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for selectively extracting a positive electrode active material from a lithium ion battery by a simple operation.

The present inventors have arrived at the present invention as a result of diligent studies to solve the above problems.
That is, the present invention is a method for selectively extracting the positive electrode active material from the lithium ion battery, wherein the lithium ion battery is mounted on the positive electrode resin current collector and the positive electrode resin current collector. A negative electrode composed of a positive electrode having a positive electrode active material layer composed of a positive electrode active material containing the formed positive electrode active material, a negative electrode resin current collector, and a negative electrode composition containing a negative electrode active material formed on the negative electrode resin current collector. A power storage element including a negative electrode having an active material layer and a separator arranged between the positive electrode active material layer and the negative electrode active material layer is provided, and the power storage element is taken out from the lithium ion battery to obtain the power storage element. , SP value of 10 or less and contact with a non-polar solvent having a specific gravity smaller than that of water, and water was added at the time of the contact or after the contact to contain the water, the non-polar solvent and the positive electrode active material. A suspension preparation step for obtaining a suspension, and a separation step for separating the oil layer containing the non-polar solvent and the aqueous layer containing the water and the positive electrode active material after allowing the suspension to stand. The present invention relates to a method for selectively taking out a positive electrode active material, which comprises having.

The present invention can provide a method capable of selectively extracting a positive electrode active material from a lithium ion battery with a simple operation.

FIG. 1 is a cross-sectional view schematically showing an example of a lithium ion battery used in the method for selectively taking out a positive electrode active material of the present invention. FIG. 2 is a schematic view showing an example of a suspension preparation step constituting the method for selectively taking out the positive electrode active material of the present invention. FIG. 3 is a schematic view showing an example of a separation step constituting the method for selectively taking out the positive electrode active material of the present invention. FIG. 4 is a photograph showing the state of the suspension after the separation step according to Example 1.

Hereinafter, the present invention will be described in detail.
In the present specification, when the term lithium ion battery is used, the concept includes a lithium ion secondary battery.
Further, the lithium ion battery used in the method for selectively taking out the positive electrode active material of the present invention includes all the lithium ion batteries once manufactured, and it does not matter whether or not they are actually used. Therefore, in the method for selectively taking out the positive electrode active material of the present invention, a lithium ion battery determined to be defective by post-manufacturing inspection or an unused lithium ion battery that is generally distributed may be used.

[Selective extraction method of positive electrode active material]
The method for selectively taking out the positive electrode active material of the present invention is a method for selectively taking out the positive electrode active material from the lithium ion battery, wherein the lithium ion battery includes a positive electrode resin current collector and a positive electrode active material. A positive electrode having a positive electrode active material layer composed of a positive electrode composition containing a positive electrode active material formed on the positive electrode resin current collector, and a negative electrode active material formed on the negative electrode resin current collector and the negative electrode resin current collector. A storage element including a negative electrode having a negative electrode active material layer made of a negative electrode composition containing the above, and a separator arranged between the positive electrode active material layer and the negative electrode active material layer, and the storage element from the lithium ion battery to the power storage element Is taken out, and the power storage element is brought into contact with a non-polar solvent having an SP value of 10 or less and a specific gravity smaller than that of water, and water is added at the time of the contact or after the contact, and the water and the non-polar solvent are added. And a suspension preparation step of obtaining a suspension containing the positive electrode active material, an oil layer containing the non-polar solvent after allowing the suspension to stand, and an aqueous layer containing the water and the positive electrode active material. It is characterized by having a separation step for separating and.

In the present specification, selectively extracting the positive electrode active material from the lithium ion battery means that the positive electrode active material constituting the lithium ion battery is a component other than the positive electrode active material constituting the lithium ion battery (for example, conductive assistance). It means that it is separated from the lithium ion battery in a state where it does not contain other components constituting the positive electrode active material layer such as an agent or a binder and the negative electrode active material). The positive electrode active material to be taken out may contain water or may be deactivated.

[Lithium-ion battery]
FIG. 1 is a cross-sectional view schematically showing an example of a lithium ion battery used in the method for manufacturing a positive electrode for a lithium ion battery of the present invention.
The lithium ion battery 1 includes a positive electrode 10 including a positive electrode resin current collector 11 and a positive electrode active material layer 13 containing a positive electrode active material formed on the positive electrode resin current collector 11, and a negative electrode resin current collector 21 and a negative electrode resin. The negative electrode 20 including the negative electrode active material layer 23 containing the negative electrode active material formed on the current collector 21 has a power storage element 40 arranged so as to face each other with the separator 30 interposed therebetween. The outside of the battery is covered with the battery exterior body 50.

An insulating layer (not shown) is formed on the inner surface of the battery exterior body 50, and the positive electrode resin current collector 11 and the negative electrode resin current collector 21 are insulated from each other. Further, an external electrode (not shown) is connected to the positive electrode resin current collector 11 and the negative electrode resin current collector 21, and a part of the external electrode is pulled out to the outside of the battery exterior body 50.
The detailed configuration of the lithium ion battery will be described later.

[Suspension preparation process]
In the suspension preparation step, the power storage element taken out from the lithium ion battery is brought into contact with a non-protic solvent having an SP value of 10 or less and a specific gravity smaller than that of water, and water is added at the time of contact or after contact. A suspension containing water, a non-protic solvent and a positive electrode active material is obtained.
A mixture of water and a non-polar solvent is also referred to as a mixed solvent.

The positive electrode active material layer is formed by contacting the power storage element with a non-polar solvent to dissolve the positive electrode resin current collector in the non-polar solvent, or by swelling and softening the positive electrode resin current collector with the non-polar solvent. Will come into direct contact with the non-polar solvent and will be taken out of the power storage element.

As a method of adding water at the time of contact between the non-polar solvent and the power storage element, a method of contacting the power storage element with a mixed solvent of the non-polar solvent and water, or a method of contacting the power storage element with the non-polar solvent and water Can be mentioned at the same time.

When the positive electrode resin current collector and the separator are bonded with a sealing material containing an adhesive resin, the sealing material (positive positive seal) is used with a non-polar solvent or a mixed solvent instead of softening the positive resin current collector. A method of softening the material) can also be used.

An example of the suspension preparation step will be described with reference to FIG.
FIG. 2 is an example of a suspension preparation step in which water is added when the non-polar solvent comes into contact with the power storage element.
In the suspension preparation step, as shown in FIG. 2, the power storage element 40 taken out from the lithium ion battery is immersed in a mixed solvent 80 of water and a non-polar solvent having an SP value of 10 or less and a specific gravity smaller than that of water. Let me. By immersing the power storage element 40 in the mixed solvent 80, the positive electrode resin current collector 11 and the negative electrode resin current collector 21 are dissolved. When the positive electrode resin current collector 11 and the negative electrode resin current collector 21 are dissolved, the positive electrode active material layer 13 and the negative electrode active material layer 23 come into contact with the mixed solvent 80, and the positive electrode active material and the positive electrode active material forming the positive electrode active material layer 13 are conductively assisted. The agent and the negative electrode active material constituting the negative electrode active material layer 23 are dispersed in the mixed solvent 80 to obtain a suspension 90.

In the suspension preparation step shown in FIG. 2, since the same resin current collector is used for the positive electrode resin current collector 11 and the negative electrode resin current collector 21, the negative electrode resin current collector 21 is also in the mixed solvent 80. As the resin constituting the negative electrode resin current collector 21, a resin which is dissolved in the above-mentioned non-polar solvent may be selected. A resin that does not dissolve in a non-polar solvent does not dissolve in a mixed solvent.
When the resin constituting the negative electrode resin current collector 21 is a resin that does not dissolve in the non-polar solvent, the negative electrode resin current collector does not dissolve in the suspension preparation step and constitutes the negative electrode resin current collector. Conductive filler and negative electrode active material are not mixed in the suspension.
Further, in the suspension preparation step shown in FIG. 2, a mixed solvent may be used in which the separator is not dissolved in the mixed solvent, but the separator is dissolved.
When the positive electrode resin current collector and the separator are adhered to each other by the positive electrode sealing material, the positive electrode sealing material may be dissolved instead of dissolving the positive electrode resin current collector with the mixed solvent.

Non-polar solvents having an SP value of 10 or less and a specific gravity smaller than that of water include benzene (SP value: 9.2, specific gravity: 0.879), toluene (SP value: 8.8, specific gravity 0.867), and ethylbenzene. (SP value: 8.8, specific gravity 0.866), xylene (SP value: 8.8, specific gravity: 0.880), cyclohexane (SP value: 8.2, specific gravity: 0.779), hexane (SP value) : 7.3, specific gravity: 0.659), octane (SP value: 7.6, specific gravity: 0.703), pentane (SP value: 7.0, specific gravity: 0.630) and the like.
Of these, xylene is preferred.

The proportion of water in the mixed solvent is preferably 15 to 50% by volume.

In the suspension preparation step, it is preferable to heat the suspension to 50 to 100 ° C.

When the power storage element is brought into contact with a non-polar solvent or a mixed solvent, vibration, ultrasonic irradiation, or the like may be performed.

[Separation process]
In the separation step, after allowing the suspension obtained in the suspension preparation step to stand, the oil layer containing a non-polar solvent and the aqueous layer containing water and a positive electrode active material are separated.
Since the liquid components constituting the suspension are water and a non-polar solvent having an SP value of 10 or less, they are not mixed with each other and are separated into two layers. Therefore, it is easy to separate the oil layer and the aqueous layer by the separation step.

An example of the separation step will be described with reference to FIG.
FIG. 3 is a diagram schematically showing an example of the separation step.
As shown in FIG. 3, by allowing the suspension 90 to stand, it is separated into an aqueous layer 60 containing water 61 and an oil layer 70 containing a non-polar solvent having an SP value of 10 or less. Since the specific gravity of the non-polar solvent is smaller than that of water, the oil layer 70 is the upper layer, the water layer 60 is the lower layer, and the positive electrode active material 15 is precipitated at the bottom of the water layer 60.
The oil layer 70 contains a non-polar solvent having an SP value of 10 or less and a specific gravity smaller than that of water, a resin constituting a positive electrode resin current collector, a conductive filler forming a positive electrode resin current collector, a negative electrode active material, and a negative electrode resin collector. It contains a resin constituting an electric body and a conductive filler constituting a negative electrode resin current collector. When the positive electrode active material layer 13 contains a conductive auxiliary agent such as conductive carbon, the conductive auxiliary agent is also contained in the oil layer 70.
Therefore, the positive electrode active material constituting the lithium ion battery can be selectively taken out by separating the oil layer and the aqueous layer after allowing the suspension to stand.

From the above, in the method for selectively extracting the positive electrode active material of the present invention, the positive electrode active material can be selectively extracted from the lithium ion battery by a simple operation.
The use of the extracted positive electrode active material is not particularly limited, and examples thereof include use as a material for the positive electrode active material and use for extracting metal ions by acid extraction.
When the metal ions are extracted by acid extraction, it is preferable to further include an extraction step of extracting the metal ions from the positive electrode active material in the aqueous layer by adjusting the pH of the aqueous layer to 2 to 6 after the separation step.

Non-polar solvents have a lower specific gravity than water. When the specific gravity of the non-polar solvent is smaller than that of water, the upper layer (upper layer) becomes an oil layer and the lower layer (lower layer) becomes an aqueous layer, so that the positive electrode active material precipitated in the aqueous layer can be easily separated.

The suspension may contain a material constituting the negative electrode active material layer, for example, a negative electrode active material or a conductive auxiliary agent.
Since the negative electrode active material is usually composed of a carbon-based material, it is lipophilic like the conductive auxiliary agent and the conductive filler, and is present in the oil layer.
Therefore, even if the negative electrode active material or the conductive auxiliary agent is present in the suspension, the positive electrode active material can be selectively taken out.

Further, in the present specification, the SP value (cal / cm ³ ) ^0.5 is 25 ° C. calculated by the method described in Volumer engineering and science Vol. 14, pp. 151-154 by Robert F Fedors et al. Is the value in.

[Lithium-ion battery]
Hereinafter, the configuration of the lithium ion battery serving as the lithium ion battery will be described.
The lithium ion battery includes a positive electrode including a positive electrode resin current collector, a positive electrode active material layer containing a positive electrode active material formed on the positive electrode resin current collector, a negative electrode resin current collector, and a negative electrode resin current collector. It is provided with a negative electrode including a negative electrode active material layer containing the negative electrode active material formed in the above.

The positive electrode includes a positive electrode resin current collector and a positive electrode active material layer containing a positive electrode active material.
In addition to the positive electrode active material, the positive electrode active material layer may contain a conductive additive, a non-aqueous electrolytic solution, or the like.

The positive electrode resin current collector contains a matrix resin and a conductive filler.

The conductive filler is selected from materials having conductivity.
Specific examples thereof include carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.)].
These conductive fillers may be used alone or in combination of two or more.

The average particle size of the conductive filler is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm, and 0, from the viewpoint of the electrical characteristics of the battery. It is more preferably .03 to 1 μm. In addition, in this specification, "particle diameter" means the maximum distance L among the distances between arbitrary two points on the contour line of a particle. The value of the "average particle size" is the average value of the particle size of the particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

The shape (form) of the conductive filler is not limited to the particle form, and may be a form other than the particle form, and may be a form practically used as a so-called filler-based conductive resin composition such as carbon nanotubes. Good.

The conductive filler may be a conductive fiber whose shape is fibrous.
The conductive fibers include carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers in which highly conductive metals and graphite are uniformly dispersed in synthetic fibers, and the surface of organic fibers is conductive. Examples thereof include conductive fibers coated with a resin containing a substance. Among these conductive fibers, carbon fibers are preferable. Further, a polypropylene resin kneaded with graphene is also preferable.
When the conductive filler is a conductive fiber, its average fiber diameter is preferably 0.1 to 20 μm.

The weight ratio of the conductive filler in the positive electrode resin current collector is preferably 5 to 90% by weight, more preferably 20 to 80% by weight.
In particular, when the conductive filler is carbon, the weight ratio of the conductive filler is preferably 20 to 30% by weight.

Examples of the matrix resin constituting the positive electrode resin current collector include polyolefin resin and polyvinylidene fluoride, and polyolefin resin is preferable.
These resins are highly soluble in non-polar solvents with an SP value of 10 or less.

Examples of the polyolefin resin include polyethylene (PE), polypropylene (PP), polycycloolefin (PCO), polymethylpentene (PMP) and the like.
Among these, polyethylene (PE) and polypropylene (PP) are preferable.
As the polyolefin resin, for example, the following are available from the market.
PE: "Novatec LL UE320""Novatec LL UJ960" All made by Nippon Polyethylene Co., Ltd. PP: "SunAllomer PM854X""SunAllomerPC684S""SunAllomerPL500A""SunAllomerPC630S""SunAllomerPC630A""SunAllomerPB522M""Prime Polymer J-2000GP" manufactured by Prime Polymer Co., Ltd., "Wintech WFX4T" manufactured by Nippon Polypro Co., Ltd., "Sumitomo Noblen FL6737" manufactured by Sumitomo Chemical Co., Ltd .: "TPX" Mitsui Chemicals Co., Ltd. ) Made

The melt flow rate of the polyolefin resin is not particularly limited, but a polyolefin having a melt mass flow rate of 12 to 200 g / 10 min measured by the method described in JIS K7210: 1990 under the conditions of a temperature of 230 ° C. and a load of 2.16 kg is preferable. ..

The positive electrode resin current collector may contain other components (dispersant, cross-linking accelerator, cross-linking agent, colorant, ultraviolet absorber, plasticizer, etc.) in addition to the conductive filler and resin.

The thickness of the positive electrode resin current collector is not particularly limited, but is preferably 5 to 400 μm.

As the positive electrode active material, composite oxide of lithium and transition metal {composite oxide is a transition metal is one _{(LiCoO 2, LiNiO 2, LiAlMnO} 4, LiMnO 2 and LiMn ₂ O _4, etc.), transition metal elements Two types of composite oxides (eg 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 a composite oxide metal element is three or more [e.g. _{LiM a M 'b M''} c O 2 (M, M' and M '' is different from the transition metal elements, respectively , and the meet a + b + c = 1. for example _{LiNi 1/3 Mn 1/3 Co 1/3 O 2} ) , etc.] or the like}, lithium-containing transition metal phosphate (e.g. LiFePO _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 the like, and two or more of them may be used in combination.
The lithium-containing transition metal phosphate may be one in which a part of the transition metal site is replaced with another transition metal.

The volume average particle size of the positive electrode active material is preferably 0.01 to 100 μm, more preferably 0.1 to 35 μm, and even more preferably 2 to 30 μm from the viewpoint of the electrical characteristics of the battery. ..

In the present specification, the volume average particle size of the positive electrode active material means the particle size (Dv50) at an integrated value of 50% in the particle size distribution obtained by the microtrack method (laser diffraction / scattering method). The microtrack method is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light. A microtrack or the like manufactured by Nikkiso Co., Ltd. can be used for measuring the volume average particle size.

The conductive auxiliary agent is selected from materials having conductivity.
Specific examples thereof include carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.)].
These conductive auxiliaries may be used alone or in combination of two or more.

The average particle size of the conductive auxiliary agent is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm, and 0, from the viewpoint of the electrical characteristics of the battery. It is more preferably .03 to 1 μm. In the present specification, the “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the conductive auxiliary agent. The value of the "average particle size" is the average value of the particle size of the particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

The shape (form) of the conductive auxiliary agent is not limited to the particle form, and may be a form other than the particle form, and may be a form practically used as a so-called filler-based conductive resin composition such as carbon nanotubes. Good.

The conductive auxiliary agent may be a conductive fiber whose shape is fibrous.
The conductive fibers include carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers in which highly conductive metals and graphite are uniformly dispersed in synthetic fibers, and the surface of organic fibers is conductive. Examples thereof include conductive fibers coated with a resin containing a substance. Among these conductive fibers, carbon fibers are preferable. Further, a polypropylene resin kneaded with graphene is also preferable.
When the conductive auxiliary agent is a conductive fiber, its average fiber diameter is preferably 0.1 to 20 μm.

As the non-aqueous electrolyte solution, a known non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent, which is used in the production of a lithium ion battery, can be used.

As the electrolyte, those used in known non-aqueous electrolyte solutions can be used, for example, lithium salts of inorganic acids such as _{LiPF 6} , LiBF ₄ , LiSbF ₆ , _{LiAsF 6} and LiClO _{4 , LiN (FSO 2} ). _2. Lithium salts of organic acids such as LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) _{3 can be mentioned. Of these, LiPF 6} and LiN (FSO ₂ ) ₂ are preferable from the viewpoint of battery output and charge / discharge cycle characteristics.

As the non-aqueous solvent, those used in known non-aqueous electrolytic solutions can be used, and for example, a lactone compound, a cyclic or chain carbonate, a chain carboxylic acid ester, a cyclic or chain ether, or a phosphoric acid ester can be used. , A nitrile compound, an amide compound, a sulfone, a sulfolane and the like, and a mixture thereof can be used.

Examples of the lactone compound include a 5-membered ring (γ-butyrolactone, γ-valerolactone, etc.) and a 6-membered ring lactone compound (δ-valerolactone, etc.).

Examples of the cyclic carbonic acid ester include propylene carbonate, ethylene carbonate and butylene carbonate.
Examples of the chain carbonate ester include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate and the like.

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

Phosphate esters include 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 thereof include dioxaphosphoran-2-one and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one.
Examples of the nitrile compound include acetonitrile and the like. Examples of the amide compound include DMF and the like. Examples of the sulfone include dimethyl sulfone and diethyl sulfone.
One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

Among the non-aqueous solvents, lactone compounds, cyclic carbonates, chain carbonates and phosphate esters are preferable from the viewpoint of battery output and charge / discharge cycle characteristics, and lactone compounds, cyclic carbonates and chains are more preferable. A carbonic acid ester is particularly preferable, and a mixed solution of a cyclic carbonic acid ester and a chain carbonic acid ester is particularly preferable. The most preferable is a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC), or a mixed solution of ethylene carbonate (EC) and propylene carbonate (DEC).

The positive electrode active material layer may further contain a known solution-drying binder (carboxymethyl cellulose, SBR latex, polyvinylidene fluoride, etc.), an adhesive resin, or the like.
However, it is preferable that the non-binder does not contain a known binder (also referred to as a binder).
Further, it is desirable that the positive electrode active material layer contains an adhesive resin. When the electrode composition contains the above-mentioned solution-drying type known binder, it is necessary to integrate the electrode composition by performing a drying step after the electrode active material layer forming step, but it contains an adhesive resin. In this case, it is not necessary to be able to integrate the electrode composition with a slight pressure at room temperature without performing a drying step. When the drying step is not performed, the electrode composition does not shrink or crack due to heating, which is preferable.
Further, in the electrode composition containing the electrode active material, the non-aqueous electrolytic solution and the adhesive resin, the electrode active material layer is maintained as a non-bonded body even after undergoing the electrode active material layer forming step. .. When the electrode active material layer is a non-bonded body, the electrode active material layer can be made thicker, and a high-capacity battery can be obtained, which is preferable.

Examples of the adhesive resin include those prepared by mixing a small amount of an organic solvent with the non-aqueous secondary battery active material coating resin described in JP-A-2017-054703 and adjusting the glass transition temperature to room temperature or lower. Further, those described as an adhesive in JP-A No. 10-255805 can be preferably used.
Here, the non-bonded body means that the electrode active materials constituting the electrode composition are not bonded to each other, and means that the electrode active materials are fixed to each other irreversibly to the bond. To do.
The solution-drying type binder means a binder that dries and solidifies by volatilizing a solvent component to firmly bond and fix the active materials to each other. On the other hand, the adhesive resin is a resin having adhesiveness (property of adhering by applying a slight pressure without using water, solvent, heat, etc.) without solidifying even if the solvent component is volatilized and dried. Means.
Solution-drying binders and adhesive resins are different materials.

The positive electrode active material may be a coated positive electrode active material in which at least a part of the surface thereof is coated with a coating material containing a polymer compound.
When the periphery of the positive electrode active material is coated with a coating material, the volume change of the electrode is alleviated and the expansion of the electrode can be suppressed.

As the polymer compound constituting the coating material, those described as a resin for coating a non-aqueous secondary battery active material in Japanese Patent Application Laid-Open No. 2017-054703 can be preferably used.

The method for producing the coated positive electrode active material described above will be described.
The coated positive electrode active material may be produced, for example, by mixing a polymer compound, a positive electrode active material, and a conductive agent used if necessary, and when a conductive agent is used as the coating material, the polymer compound and the conductive agent are used. After preparing the coating material by mixing, the coating material may be produced by mixing the coating material with the electrode active material, or may be produced by mixing the polymer compound, the conductive agent and the electrode active material.
When the positive electrode active material, the polymer compound, and the conductive agent are mixed, the mixing order is not particularly limited, but after the positive electrode active material and the polymer compound are mixed, the conductive agent is further added and further mixed. Is preferable.
By the above method, at least a part of the surface of the positive electrode active material is coated with a coating material containing a polymer compound and a conductive agent used if necessary.

As the conductive agent which is an optional component of the coating material, the same conductive agent as the conductive auxiliary agent constituting the positive electrode active material layer can be preferably used.

The negative electrode includes a negative electrode resin current collector and a negative electrode active material layer containing a negative electrode active material.
In addition to the negative electrode active material, the negative electrode active material layer may contain a conductive auxiliary agent, a non-aqueous electrolytic solution, a binder, an adhesive resin, and the like, a conductive auxiliary agent, a non-aqueous electrolytic solution, a binder, and an adhesive resin. Can preferably be the same as that of the positive electrode.
Further, the negative electrode active material may be a coated negative electrode active material in which at least a part of the surface thereof is coated with a coating material containing a polymer compound. The coating material constituting the coated negative electrode active material is preferably the same as that of the coated positive electrode active material.

The negative electrode resin current collector contains a conductive filler and a resin.
As the conductive filler and resin, the same conductive filler and resin as those constituting the positive electrode resin current collector can be preferably used.
The weight ratio of the conductive filler in the negative electrode resin current collector is preferably 5 to 90% by weight, more preferably 20 to 80% by weight.
In particular, when the conductive filler is carbon, the weight ratio of the conductive filler is preferably 20 to 30% by weight.

Examples of the negative electrode active material include carbon-based materials [graphite, non-graphitizable carbon, amorphous carbon, calcined resin (for example, phenol resin, furan resin, etc. are calcined and carbonized), coke (for example, pitch coke, needle). Coke and petroleum coke, etc.) and carbon fiber, etc.], conductive polymers (eg, polyacetylene, polypyrrole, etc.), metals (tin, aluminum, zirconium, titanium, etc.) and the like.
As the carbon-based material, graphite, non-graphitizable carbon and amorphous carbon are preferable.
A part or all of the negative electrode active material may be pre-doped with lithium or lithium ions.

The volume average particle size of the negative electrode active material is preferably 0.01 to 100 μm, more preferably 0.1 to 20 μm, and even more preferably 2 to 10 μm from the viewpoint of the electrical characteristics of the battery.

As the separator, 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 (polyester fiber, aramid fiber, etc.) or glass fiber, and silica on the surface thereof. , Known separators for lithium-ion batteries, such as those to which ceramic fine particles such as alumina and titania are attached.

The number of separators is not particularly limited, but is preferably two or more.
When the number of separators is two or more, before the impregnation step, a positive electrode sheet composed of a positive electrode resin current collector, a positive electrode active material layer, and a separator (positive electrode side separator) in contact with the positive electrode active material, and a negative electrode resin. The negative electrode sheet composed of the current collector, the negative electrode active material layer, and the separator (negative electrode side separator) in contact with the negative electrode active material layer can be separated. If the positive electrode sheet and the negative electrode sheet are separated before the suspension preparation step, only the positive electrode sheet can be immersed in the mixed solvent, so that the negative electrode active material can be reliably prevented from being mixed in the mixed solvent.

The positive electrode resin current collector and the separator, and the negative electrode resin current collector and the separator may be adhered by a sealing material containing an adhesive resin.
The sealing material provided between the positive electrode resin current collector and the separator is also referred to as a positive electrode sealing material.
The sealing material provided between the negative electrode resin current collector and the separator is also referred to as a negative electrode sealing material.

It is preferable that the positive electrode resin current collector is adhered to the separator via the positive electrode sealing material at the outer peripheral edge portion where the positive electrode active material layer is not formed on the current collector.
It is preferable that the negative electrode resin current collector is adhered to the separator via the negative electrode sealing material at the outer peripheral edge portion where the negative electrode active material layer is not formed on the current collector.

Examples of the adhesive resin contained in the positive electrode sealing material and the negative electrode sealing material include polyamide, polyimide, polyvinylidene fluoride, polyester and polyolefin.
The adhesive resin contained in the positive electrode sealing material and the adhesive resin contained in the negative electrode sealing material may be the same or different.
Further, the adhesive resin contained in the positive electrode sealing material may be the same as the resin constituting the positive electrode resin current collector.

Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the Examples as long as the gist of the present invention is not deviated. Unless otherwise specified, parts mean parts by weight and% means% by weight.

[Manufacturing Example 1]
<Manufacturing of resin current collector>
With a twin-screw extruder, 50 parts of resin [Sumitomo Chemical Co., Ltd. Sumitomo Noblen FL6737 (random polypropylene)], 45 parts of conductive filler [Denka Black Li-400 manufactured by Denka Co., Ltd.] and 5 parts of dispersant are 190 parts. A material for a resin current collector was obtained by melt-kneading at ° C., 100 rpm, and a residence time of 5 minutes.
The obtained resin current collector material was extruded from a T-die and rolled with a cooling roll whose temperature was adjusted to 50 ° C. to obtain a resin current collector having a film thickness of 100 μm.

[Manufacturing Example 2]
[Preparation of coated positive electrode active material]
70.0 parts of DMF was placed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas introduction tube, and the temperature was raised to 75 ° C. Next, a monomer compounding solution containing 20.0 parts of butyl methacrylate, 55.0 parts of acrylate, 22.0 parts of methyl methacrylate, 3 parts of sodium allylsulfonate and 20 parts of DMF, and 2,2'-azobis (2). , 4-Dimethylvaleronitrile) 0.4 parts and 2,2'-azobis (2-methylbutyronitrile) 0.8 parts dissolved in 10.0 parts of DMF Initiator solution and nitrogen in a four-necked flask. Radical polymerization was carried out by continuously dropping the mixture with a dropping funnel over 2 hours while stirring. After completion of the dropping, the temperature was raised to 80 ° C. and the reaction was continued for 5 hours to obtain a copolymer solution having a resin concentration of 50% by weight. The obtained copolymer solution was transferred to a Teflon (registered trademark) vat and dried under reduced pressure at 120 ° C. and 0.01 MPa for 3 hours to distill off DMF to obtain a polymer compound for coating.
Subsequently, 100 parts of the positive electrode active material powder (LiNi _0.8 Co _0.15 Al _0.05 O ₂ powder, volume average particle diameter 4 μm) was placed in the universal mixer high-speed mixer FS25 [manufactured by Arstecnica Co., Ltd.]. In a state of stirring at room temperature and 720 rpm, 11.2 parts of the coating polymer compound solution obtained by dissolving the coating polymer compound in isopropanol at a concentration of 1.0% by weight was added dropwise over 2 minutes. , Stirred for another 5 minutes.
Then, in a stirred state, 6.2 parts of acetylene black [Denka Black (registered trademark) manufactured by Denka Co., Ltd.] was added as a conductive agent in 2 minutes while being divided, and stirring was continued for 30 minutes. Then, the pressure was reduced to 0.01 MPa while maintaining the stirring, then the temperature was raised to 140 ° C. while maintaining the stirring and the degree of pressure reduction, and the stirring, the degree of pressure reduction and the temperature were maintained for 8 hours to distill off the volatile components. .. The obtained powder was classified by a sieve having a mesh size of 212 μm to obtain a coated positive electrode active material.

[Manufacturing Example 3]
<Preparation of coated negative electrode active material>
100 parts of non-graphitizable carbon powder (volume average particle diameter 20 μm), which is a carbon-based material, was placed in a universal mixer high-speed mixer FS25 [manufactured by Arstecnica Co., Ltd.] and stirred at room temperature at 720 rpm. 9.2 parts of the polymer compound solution for coating obtained by dissolving the polymer compound for coating in isopropanol at a concentration of 19.8% by weight was added dropwise over 2 minutes, and the mixture was further stirred for 5 minutes.
Then, 11.3 parts of acetylene black [Denka Black (registered trademark) manufactured by Denka Co., Ltd.], which is a conductive agent, was added while being stirred in 2 minutes, and stirring was continued for 30 minutes. Then, the pressure was reduced to 0.01 MPa while maintaining the stirring, then the temperature was raised to 140 ° C. while maintaining the stirring and the degree of pressure reduction, and the stirring, the degree of pressure reduction and the temperature were maintained for 8 hours to distill off the volatile components. .. The obtained powder was classified by a sieve having a mesh size of 212 μm to obtain a coated negative electrode active material.

[Manufacturing Example 4]
<Cathode preparation>
42 parts of a non-aqueous electrolytic solution prepared by dissolving _{LiN (FSO 2} ) ₂ in a mixed solvent (volume ratio 1: 1) of ethylene carbonate (EC) and propylene carbonate (PC) at a ratio of 2 mol / L and carbon fibers [ Donna Carbo Mild S-243] manufactured by Osaka Gas Chemical Co., Ltd. was mixed with 4.2 parts at 2000 rpm for 7 minutes using a planetary stirring type mixing and kneading device {Awatori Kentarou [Shinky Co., Ltd.]}. After adding 30 parts of the non-aqueous electrolyte solution and 206 parts of the coated positive electrode active material, the mixture was further mixed by Rentaro Awatori at 2000 rpm for 1.5 minutes, and 20 parts of the non-aqueous electrolyte solution was further added and then Awatori. Stirring with Kentarou was performed at 2000 rpm for 1 minute, and after adding 2.3 parts of the non-aqueous electrolyte solution, stirring with Awatori Kentarou was mixed at 2000 rpm for 1.5 minutes to prepare a positive electrode active material slurry.
The obtained positive electrode active material slurry was applied to the surface of the resin current collector A and pressed at a pressure of 5 MPa for about 10 seconds to prepare a positive electrode (42 mm × 42 mm) for a lithium ion battery according to Example 1. In the positive electrode for a lithium ion battery according to the first embodiment, a positive electrode active material layer having a plan view dimension of 35 mm × 35 mm is arranged substantially in the center of the resin current collector A having a plan view dimension of 42 mm × 42 mm. ..

[Manufacturing Example 5]
<Manufacturing of negative electrode>
20 parts of a non-aqueous electrolytic solution prepared by dissolving _{LiN (FSO 2} ) ₂ in a mixed solvent (volume ratio 1: 1) of ethylene carbonate (EC) and propylene carbonate (PC) at a ratio of 2 mol / L and carbon fibers [ 2 parts of Donna Carbo Mild S-243 manufactured by Osaka Gas Chemical Co., Ltd.] were mixed at 2000 rpm for 7 minutes using a planetary stirring type mixing and kneading device {Awatori Kentarou [manufactured by Shinky Co., Ltd.]}, and then the above. After adding 50 parts of the non-aqueous electrolytic solution and 98 parts of the coated negative electrode active material, the mixture is further mixed with Awatori Rentaro at 2000 rpm for 1.5 minutes, and after further adding 25 parts of the non-aqueous electrolytic solution, Awatori Rentaro The stirring was performed at 2000 rpm for 1 minute, and after further 50 parts of the non-aqueous electrolytic solution was added, the stirring by Awatori Rentaro was mixed at 2000 rpm for 1.5 minutes to prepare a negative electrode active material slurry.
The obtained negative electrode active material slurry was applied to the surface of the resin current collector B and pressed at a pressure of 5 MPa for about 10 seconds to prepare a negative electrode 42 mm × 42 mm for a lithium ion battery according to Example 1.
In the negative electrode for a lithium ion battery according to the first embodiment, a negative electrode active material layer having a plan view dimension of 35 mm × 35 mm is arranged substantially in the center of the resin current collector B having a plan view dimension of 42 mm × 42 mm. ..

[Manufacturing Example 6]
<Manufacturing of lithium-ion batteries>
The positive electrode for the lithium ion battery and the negative electrode for the lithium ion battery are separated by a flat plate-shaped cell guard 3501 (made of PP, thickness 25 μm, plan view size 40 mm × 40 mm), and the positive electrode active material layer and the negative electrode active material. The layers are laminated so as to face each other, a sealing material (width 1 mm) is arranged between the outer peripheral portion of the resin current collector and the separator, and heat-bonded to obtain a power storage element, which is then sealed in an aluminum laminate film. The lithium ion battery according to Example 1 was obtained.
As the sealing material, Admer VE300 manufactured by Mitsui Chemicals, Inc. was used for both the positive electrode side and the negative electrode side.

[Example 1]
<Suspension preparation process>
After removing the aluminum laminate cell from the lithium ion battery according to Example 1, the aluminum laminate cell is immersed in a mixed solvent of xylene (SP value: 8.8) and water (volume ratio is xylene: water = 80:20) and mixed. When the solvent was stirred for 20 minutes while heating at 80 ° C., the positive electrode resin current collector, the negative electrode resin current collector, and the sealing material adhering each resin current collector and the separator were partially swollen and softened. Then, a suspension in which the positive electrode active material layer and the negative electrode active material layer were dispersed in the mixed solvent was obtained.

<Separation process>
When the obtained suspension was allowed to stand at room temperature for 30 minutes, it was separated into an aqueous layer (lower part) containing a precipitate and an oil layer (upper part) as shown in FIG. FIG. 4 is a photograph showing the state of the mixed solvent after the separation step according to Example 1.

<Analysis of the obtained positive electrode active material>
After separating the oil layer and the aqueous layer, the aqueous layer was filtered to collect the precipitate, and the composition of the precipitate was confirmed by TG-DTA analysis.
The TG-DTA analysis was carried out under the following conditions, and the content of the carbon-based material was determined from the weight loss rate before and after the decomposition temperature of the precipitate, and the separability was evaluated. The results are shown in Table 1.
Measurement temperature: 30 ° C → 900 ° C
Temperature rise rate: 10 ° C / min, held at 900 ° C for 15 min Data interval: 0.5s
Atmosphere: Air
Bread: The criteria for the platinum separability evaluation result are as follows.
〇: Ratio of carbon-based material ≤ 10% by weight
Δ: 10% by weight <ratio of carbon-based material ≤ 30% by weight
X: 30% by weight <Ratio of carbon-based material As a result of analysis, the ratio of carbon-based material contained in the precipitate was 10% by weight or less based on the weight of the precipitate.

<Example 2>
The separation step was carried out in the same procedure as in Example 1 except that the suspension preparation step in Example 1 was changed as follows, and the obtained positive electrode active material was analyzed. The results are shown in Table 1.
After removing the aluminum laminate cell from the lithium ion battery according to Example 1, it was immersed in xylene. When xylene was stirred for 1 hour while heating at 130 ° C., the positive electrode resin current collector and the negative electrode resin current collector were dissolved in xylene, and a dispersion liquid in which the positive electrode active material layer and the negative electrode active material layer were dispersed in xylene was prepared. did. Then, water was mixed so that xylene: water = 50:50 (weight ratio), and the suspension was obtained by heating at 80 ° C. for 10 minutes.
When the obtained suspension was allowed to stand at room temperature for 30 minutes, it was separated into an aqueous layer (lower part) containing a precipitate and an oil layer (upper part).

<Comparative Examples 1 to 4>
The suspension preparation step and the separation step were carried out in the same procedure as in Example 1 except that the composition of the current collector on the positive electrode side and the composition of the mixed solvent were changed as shown in Table 1. The results are shown in Table 1.
However, in Comparative Examples 1, 3 and 4, the current collector did not dissolve in the suspension preparation step, and the suspension could not be obtained. In the separability evaluation, these are set as "-".

From the results in Table 1, it was found that the positive electrode active material can be selectively extracted from the lithium ion battery by the present invention.

The method for selectively taking out the positive electrode active material of the present invention is useful as a method for reusing the positive electrode active material contained in the lithium ion battery.

1 Lithium ion battery 10 Positive electrode 11 Positive electrode current collector 13 Positive electrode active material layer 15 Positive electrode active material 20 Negative electrode 21 Negative electrode current collector 23 Negative electrode active material layer 30 Separator 40 Power storage element 50 Battery exterior 60 Water layer 61 Water 70 Oil layer 80 Mixing Electrode 90 suspension

Claims (6)

It is a selective extraction method of the positive electrode active material, which selectively extracts the positive electrode active material from the lithium ion battery.
The lithium ion battery includes a positive electrode having a positive electrode active material layer composed of a positive electrode resin current collector and a positive electrode composition containing a positive electrode active material formed on the positive electrode resin current collector, a negative electrode resin current collector, and the negative electrode. Storage of electricity including a negative electrode having a negative electrode active material layer made of a negative electrode composition containing a negative electrode active material formed on a resin current collector and a separator arranged between the positive electrode active material layer and the negative electrode active material layer. Equipped with elements
The power storage element is taken out from the lithium ion battery, and the power storage element is brought into contact with a non-polar solvent having an SP value of 10 or less and a specific gravity smaller than that of water, and water is added at the time of the contact or after the contact. , A suspension preparation step of obtaining a suspension containing the water, the non-polar solvent and the positive electrode active material.
Selection of a positive electrode active material, which comprises a separation step of separating the oil layer containing the non-polar solvent and the aqueous layer containing the water and the positive electrode active material after allowing the suspension to stand. Target extraction method. The positive electrode resin current collector is adhered to the separator via a positive electrode sealing material at an outer peripheral edge portion where the positive electrode active material layer is not formed on the current collector.
The positive electrode active material according to claim 1, wherein the negative electrode resin current collector is adhered to the separator via a negative electrode sealing material at an outer peripheral edge portion on which the negative electrode active material layer is not formed. Selective retrieval method. The method for selectively taking out a positive electrode active material according to claim 1 or 2, wherein the positive electrode active material layer is a non-binding body containing no binder. The method for selectively taking out a positive electrode active material according to any one of claims 1 to 3, wherein the positive electrode active material is a coated positive electrode active material in which at least a part of the surface thereof is coated with a coating material containing a polymer compound. The method for selectively taking out a positive electrode active material according to any one of claims 1 to 4, wherein the matrix resin constituting the positive electrode resin current collector is a polyolefin resin. The method for selectively taking out a positive electrode active material according to any one of claims 1 to 5, wherein the suspension is heated to 50 to 100 ° C. in the suspension preparation step.

Images