JP2016149195A - Binder resin composition for secondary battery electrode, dope for secondary battery electrode using the same, slurry for secondary battery electrode, secondary battery electrode and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a binder resin composition for a secondary battery electrode, good in binding properties with a current collector foil; a slurry for a secondary battery electrode, good in coating properties; a secondary battery electrode excellent in electrochemical performance; and a lithium ion secondary battery.SOLUTION: A binder resin composition for a secondary battery electrode is a mixture of a polymer (A) including a vinyl cyanide unit and a phosphate group-containing unit, as a constitutional unit, and a chelate agent (B).SELECTED DRAWING: None

Description

  The present invention relates to a secondary battery electrode binder resin composition, a secondary battery electrode dope, a secondary battery electrode slurry composition containing active material particles, and a secondary battery electrode manufactured using the slurry composition. And a secondary battery including the electrode.

In recent years, lithium ion secondary batteries are used in portable devices such as mobile phones, video cameras, and notebook computers, hybrid vehicles, and electric vehicles. An electrode for a lithium ion secondary battery is usually obtained by mixing a solvent in a mixture obtained by adding an appropriate amount of a binder to an electrode active material, applying it to a paste, applying it to a current collector, drying it and then pressing it. . As a binder, polyvinylidene fluoride (hereinafter abbreviated as “PVDF”) is used as a material satisfying solvent resistance to an organic solvent used in an electrolytic solution, oxidation resistance within a driving voltage, reduction resistance, and the like. Is used. However, PVDF has a problem of low adhesion to the current collector.
As a method for improving the low adhesion of PVDF, a proposal using a (meth) acrylonitrile polymer has been made. For example, in Patent Documents 1 and 2, an acrylonitrile polymer is used as a binder to improve the adhesion and adhesion to the current collector.
In Patent Document 3, a proposal is made to use an acrylic ester and a copolymer containing phosphoric acid or a phosphoric ester as a binder resin, and phosphoric acid or the phosphoric ester exhibits binding properties with the current collector foil. In addition, the dispersibility of the active material is improved, and an electrode excellent in battery performance can be obtained.

WO02 / 039518 JP2010-174058 WO2006 / 101182

However, in Patent Document 1, the amount of acrylonitrile in the total amount of the binder is small, and the good adhesion with the current collector of the (meth) acrylonitrile polymer cannot be fully exhibited.
Patent Document 2 proposes an electrode binder mainly composed of an acrylonitrile polymer. However, when the (meth) acrylonitrile polymer is the main component, the produced electrode is inferior in flexibility, and the mixture layer is cracked and cracked in the winding process in the production process, making it difficult to produce a battery. It was assumed that
Further, as described in Patent Document 3, the adhesion to the current collector foil is improved by polymerizing a unit containing phosphoric acid or phosphate in the binder resin, but the acrylic acid ester unit is the main component. For this reason, it is decomposed by the oxidation-reduction reaction in the battery, and there is a concern that the expected battery performance cannot be exhibited particularly in long-term use. In addition, when an electrode is made using a high-capacity active material containing nickel or manganese, the functional group on the active material surface and a unit containing phosphoric acid or phosphate form a bond, increasing the viscosity of the slurry. There is concern about causing gelation.

As a result of intensive investigations in view of the above-described problems and the consideration thereof, the present inventor has obtained a mixture of a polymer (A) and a chelating agent (B) containing a vinyl cyanide unit and a unit having a phosphate group as constituent units. By using as a binder resin composition for secondary battery electrodes, the unit having a phosphate group exhibits excellent adhesion to the current collector without forming a bond with an active material containing nickel or manganese, and cyanide It has been found that it is possible to obtain a battery that exhibits electrochemical stability in a battery having a vinyl unit.
The present invention relates to the following.
[1] A binder resin composition for a secondary battery electrode containing a mixture of a polymer (A) containing a vinyl cyanide unit and a unit containing a phosphate group as constituent units and a chelating agent (B).
[2] The binder resin composition for a secondary battery electrode according to [1], wherein the chelating agent (B) does not contain a metal atom.
[3] The binder resin composition for a secondary battery electrode according to [1], wherein the chelating agent (B) is composed of only carbon, hydrogen, and oxygen atoms.
[4] The binder resin composition for a secondary battery electrode according to any one of [1] to [3], wherein the chelating agent (B) is any one of diketone, oxycarboxylic acid, and polycarboxylic acid.
[5] A solution or dispersion for a secondary battery electrode in which the binder resin composition for a secondary battery electrode according to any one of [1] to [4] is dissolved or dispersed in a nonaqueous solvent.
[6] The secondary battery electrode solution or dispersion according to [5], wherein the non-aqueous solvent is N-methylpyrrolidone.
[7] A secondary battery electrode slurry comprising the secondary battery electrode solution or dispersion described in [5] or [6] above and a secondary battery electrode active material.
[8] The electrode slurry according to [7], wherein the active material for the secondary battery electrode contains nickel and / or manganese.
[9] A secondary battery electrode comprising a current collector and a mixture layer formed on the current collector and formed from the slurry for a secondary battery electrode according to the above [7] or [8] .
[10] A lithium ion secondary battery comprising the secondary battery electrode according to [9].

  According to the present invention, a binder resin composition for a secondary battery electrode having a good binding property to a current collector foil, an electrode slurry having a good coating property, and an electrode for a secondary battery having an excellent electrochemical performance, In addition, a lithium ion secondary battery can be provided.

Hereinafter, the present invention will be described in detail.
<Polymer (A)>
The polymer (A) in the present invention contains a vinyl cyanide unit and a unit containing a phosphate group as constituent units.
The vinyl cyanide monomer constituting the vinyl cyanide unit in the present invention is not particularly limited, but examples thereof include acrylic nitrile group-containing monomers such as acrylonitrile and methacrylonitrile, α-cyanoacrylate and dicyanovinylidene. Such a cyan nitrile group-containing monomer, a fumaric nitrile group-containing monomer such as fumaronitrile, and the like can be used. Among these, (meth) acrylonitrile is preferable from the viewpoint of easy polymerization and cost performance.
These vinyl cyanide monomers can be used alone or in combination of two or more.

  The content of the vinyl cyanide monomer is 50 mol% or more and 99.99 mol% or less, preferably 80 mol% or more and 99.95 mol% of all monomers forming the polymer (A). Hereinafter, it is more preferably 90 mol% or more and 99.9 mol% or less. When the content of the vinyl cyanide monomer is 50 mol% or more, it can be easily dissolved in a solvent when preparing a slurry, and the prepared polymer (A) is electrochemically maintained in the battery over a long period of time. Can exist stably.

As the monomer constituting the unit containing a phosphate group, a vinyl monomer having a phosphate group is preferable, and (meth) acrylates and allyl compounds having a phosphate group are more preferable.
Examples of the (meth) acrylate having a phosphoric acid group include 2- (meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxyethyl acid phosphate monoethanolamine salt, and diphenyl ((meth) acryloyloxyethyl). Phosphate, (meth) acryloyloxypropyl acid phosphate, 3-chloro-2-acid phosphooxypropyl (meth) acrylate, acid phosphooxypolyoxyethylene glycol mono (meth) acrylate, acid phosphooxypolyoxypropylene glycol ( And (meth) acrylate.
As an allyl compound which has a phosphoric acid group, allyl alcohol acid phosphate is mentioned, for example.
Among these phosphoric acid group-containing monomers, 2-methacryloyloxyethyl acid phosphate is preferable because of excellent adhesion to the current collector and handling properties during electrode production.
2-Methacryloyloxyethyl acid phosphate is industrially available as light ester P1-M (trade name, manufactured by Kyoeisha Chemical Co., Ltd.).
Phosphoric acid group-containing monomers can be used singly or in appropriate combination of two or more.
When the sum total of all the structural units which comprise a polymer (A) is 100 mol%, the content rate of the phosphoric acid group containing unit in a polymer is 0.01-10 mol%, Preferably it is 0.8. 1 to 5 mol%. If the content of the phosphoric acid group-containing unit is 0.01 mol% or more, adhesion to the current collector is increased, and if it is 10 mol% or less, it is easily dissolved in a solvent when preparing a slurry, Adhesion to the current collector is increased.

  The polymer (A) in the present invention can contain a monomer other than a vinyl cyanide monomer and a monomer having a phosphate group as a constituent unit. Other monomers are not particularly limited. For example, short-chain (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, etc. Body: Long-chain (meth) acrylate monomers such as stearyl (meth) acrylate and lauryl (meth) acrylate; Vinyl halide monomers such as vinyl chloride, vinyl bromide and vinylidene chloride; Maleic acid imide, phenyl Maleimides such as maleimide; aromatic vinyl monomers such as styrene and α-methylstyrene; (meth) acrylamide, vinyl acetate and the like.

<Weight average molecular weight of polymer (A)>
The weight average molecular weight of the polymer (A) of the present invention is from 50,000 to 2,000,000, preferably from 100,000 to 1,000,000, more preferably from 200,000 to 500,000. By making the weight average molecular weight of the polymer (A) 50,000 or more, the polymer (A) is prevented from being excessively dissolved in a solvent when the slurry is produced, and the polymer (A) is a slurry. It becomes possible to bind without covering the inner active material, and the flexibility of the electrode after application can be improved. In addition, when the weight average molecular weight is 2 million or less, the polymer (A) can be dissolved in a solvent when producing a slurry, and can exhibit excellent binding properties to the current collector foil. It becomes possible.

<Method for producing polymer (A)>
The polymerization method of the polymer (A) is not particularly limited, and solution polymerization, suspension polymerization, emulsion polymerization, etc. can be selected according to the type of monomer used and the solubility of the polymer to be formed. .
In the above suspension polymerization, emulsion polymerization, and solution polymerization, the method for charging the monomer is not particularly limited, and a method in which the entire amount of monomer is charged at once and polymerization is carried out dropwise. A method for polymerization can be selected.

<Polymerization initiator>
As a polymerization initiator used when carrying out suspension polymerization or emulsion polymerization, a water-soluble polymerization initiator is preferable because of excellent polymerization initiation efficiency.
Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; water-soluble peroxides such as hydrogen peroxide; 2,2′-azobis (2-methylpropionamidine) Water-soluble azo compounds such as dihydrochloride are exemplified.
An oxidizing agent such as persulfate is a redox initiator in combination with a reducing agent such as sodium hydrogen sulfite, ammonium hydrogen sulfite, sodium thiosulfate, hydrosulfite, and a polymerization accelerator such as sulfuric acid, iron sulfate, copper sulfate. Can also be used.
Of these, persulfates are preferred because the production of the copolymer is easy.

<Chain transfer agent>
When carrying out suspension polymerization or emulsion polymerization, a chain transfer agent can be used for the purpose of adjusting the molecular weight.
Examples of the chain transfer agent include mercaptan compounds, thioglycol, carbon tetrachloride, α-methylstyrene dimer, and sodium hypophosphite. Among these, α-methylstyrene dimer or sodium hypophosphite is preferable because it has little odor and is easy to handle.

<Solvent>
In the case of carrying out suspension polymerization, a solvent other than water can be added in order to adjust the particle size of the resulting copolymer.
Examples of solvents other than water include amides such as NMP, N, N-dimethylacetamide, and N, N-dimethylformamide; N, N-dimethylethyleneurea, N, N-dimethylpropyleneurea, tetramethylurea, and the like. Ureas; lactones such as γ-butyrolactone and γ-caprolactone; carbonates such as propylene carbonate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; methyl acetate, ethyl acetate, n-butyl acetate, butyl cellosolve acetate, Esters such as butyl carbitol acetate, ethyl cellosolve acetate and ethyl carbitol acetate; Grimes such as diglyme, triglyme and tetraglyme; Hydrocarbons such as toluene, xylene and cyclohexane; Examples thereof include sulfoxides such as til sulfoxide; sulfones such as sulfolane; and alcohols such as methanol, isopropanol and n-butanol.
These solvents may be used alone or in combination of two or more.

<Surfactant>
When the polymer is produced by emulsion polymerization, a surfactant can be used.
Examples of the surfactant include anionic surfactants such as dodecyl sulfate and dodecyl benzene sulfonate; nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene alkyl ester; alkyltrimethylammonium salt and alkyl Examples thereof include cationic surfactants such as amines. Surfactant may be used individually by 1 type and may use 2 or more types together.

<Chelating agent (B)>
The type of chelating agent (B) in the present invention is not limited as long as it is generally used as a chelating agent, but those containing no metal atoms are preferred. This is because the chelating agent containing a metal atom remains in the mixture layer in the drying process at the time of manufacturing the electrode, and may adversely affect the battery performance. By using the chelating agent (B) in the binder resin composition, a bond is preferentially formed with a functional group on the surface of the active material, and a bond is formed between the polymer (A) and the active material. It inhibits, prevents gelation of the electrode slurry using the binder resin composition, and keeps the viscosity suitable for coating.
Examples of the chelating agent (B) include β-diketones such as acetylacetone and 3,5-heptanedione; aminocarboxylic acids such as ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, and hydroxyethylethylenediaminetriacetic acid; pyruvic acid and acetoacetic acid , Levulinic acid, α-ketoglutaric acid, acetone dicarboxylic acid and other keto acids; glycolic acid, glyceric acid, xylonic acid, gluconic acid, lactic acid, tartronic acid, tartaric acid, xylaric acid, galactaric acid, malic acid, citric acid; Polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid; amino acids such as aspartic acid and glutamic acid; phytic acid, hydroxyethylidenediphosphoric acid, nitrilotrismethylenephosphoric acid, ethyl And polyphosphoric acid such as dimethyltetramethylene phosphoric acid; dioximes such as dimethylglyoxime, benzyl diglyoxime, and 1,2 cyclohexyl diglyoxime.

  Among these, a chelating agent composed only of carbon, hydrogen, and oxygen atoms is particularly excellent in solubility in N-methylpyrrolidone which is a solvent at the time of slurry preparation, and more easily binds to a functional group on the surface of the active material. Examples thereof include β-diketones such as acetylacetone and 3,5-heptanedione; keto acids such as pyruvic acid, acetoacetic acid, levulinic acid, α-ketoglutaric acid, and acetonedicarboxylic acid; glycolic acid, glyceric acid, and xylone Specific examples include hydroxy acids such as acid, gluconic acid, lactic acid, tartronic acid, tartaric acid, xylaric acid, galactaric acid, malic acid, and citric acid; and polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid Can be mentioned.

Of these, β-diketones, hydroxy acids, and polycarboxylic acids are particularly preferable.
Among these, as β-diketone, acetylacetone is preferably volatilized together with N-methylpyrrolidone during electrode drying and does not affect electrode performance, and is preferable from the viewpoint of availability.
In addition, as the hydroxy acid, tartaric acid, malic acid, citric acid, and gluconic acid preferentially form and hold a bond with the functional group on the active material surface, and a bond is formed between the polymer (A) and the active material. This is preferable from the viewpoint of inhibiting the treatment for a long period of time and the availability.
As the polycarboxylic acid, succinic acid, glutaric acid, and adipic acid preferentially form and hold a bond with the functional group on the active material surface, and a bond is formed between the polymer (A) and the active material. It is preferable from the viewpoint of inhibiting the treatment for a long time and the availability.

<Binder resin composition for secondary battery electrode>
The binder resin composition in the present invention contains a polymer (A) and a chelating agent (B). As a content ratio of the polymer (A) and the chelating agent (B) in the binder resin composition, when the polymer (A) is 100 parts by mass, the chelating agent (B) is 1 to 100 parts by mass. It is preferably 2 to 80 parts by mass, more preferably 5 to 70 parts by mass, and particularly preferably 5 to 50 parts by mass.
When the polymer (A) is 100 parts by mass, the presence of 1 part by mass or more of the chelating agent (B) makes the active material surface and the polymer (A) It is possible to inhibit the formation of a bond between them, and the coating property of the slurry is improved. Moreover, when the polymer (A) is 100 parts by mass, the excellent adhesion to the current collector foil possessed by the polymer (A) is inhibited by making the chelating agent (B) 100 parts by mass or less. Without doing so, it becomes possible to obtain a binder resin composition having excellent binding properties.

  The binder resin composition of the present invention may be combined with other "binders" that improve battery performance and additives such as "viscosity modifiers" that improve coatability within a range that does not impair the effects of the present invention.

  Examples of other binders include polymers such as styrene-butadiene rubber, poly (meth) acrylonitrile, and ethylene-vinyl alcohol copolymer; fluorine-based polymers such as polyvinylidene fluoride, tetrafluoroethylene, and pentafluoropropylene. .

Examples of the viscosity modifier include cellulose polymers such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, and ammonium salts thereof; poly (meth) acrylates such as sodium poly (meth) acrylate; polyvinyl alcohol, polyethylene oxide , Polyvinylpyrrolidone, acrylic acid or a copolymer of acrylic acid salt and vinyl alcohol, maleic anhydride, maleic acid or a copolymer of fumaric acid and vinyl alcohol, modified polyvinyl alcohol, modified polyacrylic acid, and polyethylene glycol.
The additive finally remaining on the electrode is preferably electrochemically stable.

  The binder resin composition for secondary battery electrodes may be used in any form of powder, a solution dissolved in a solvent, or an emulsion dispersed in an aqueous or oily medium.

<Use of binder resin composition>
Although the kind of battery which can use the binder resin for secondary battery electrodes of this invention is not specifically limited, The use to the positive electrode or negative electrode in a non-aqueous secondary battery, especially a lithium ion secondary battery is especially preferable.

<Slurry composition for secondary battery electrode>
The slurry composition for secondary battery electrodes includes at least the above-described binder resin composition, electrode active material, and solvent. Further, it may contain a conductive additive and other additives. Specifically, the binder resin composition for a secondary battery electrode and the electrode active material of the present invention can be obtained by dispersing or dissolving in a solvent together with a conductive additive and other additives.

  The composition of the secondary battery electrode slurry composition is 0.1 to 10 parts by mass of the binder resin composition for secondary battery electrodes of the present invention and 0.5% of the conductive auxiliary agent when the active material is 100 parts by mass. It is preferable to set it as -20 mass parts. Moreover, you may add 0-10 mass parts of other additives.

<Electrode for secondary battery>
The electrode for a secondary battery has a current collector and a mixture layer provided on at least one surface of the current collector. The binder resin composition of this invention is used as a material which comprises this mixture layer. Specifically, a solid phase obtained by blending an active material with the binder resin composition for a secondary battery electrode of the present invention and drying or dissolving the slurry composition dissolved or dispersed in a solvent becomes a mixture layer.

The active material used for the mixture layer may be any material in which the potential of the positive electrode material and the potential of the negative electrode material are different.
In the case of a lithium ion secondary battery, examples of the positive electrode active material used include a lithium-containing metal composite oxide containing lithium and at least one metal selected from iron, cobalt, nickel, and manganese. A positive electrode active material may be used individually by 1 type, and may use 2 or more types together. Among these, when producing a high capacity battery, it is preferable to use an active material containing nickel and / or manganese as the active material.
Examples of the negative electrode active material used include carbon materials such as graphite, amorphous carbon, carbon fiber, coke, and activated carbon; composites of the above carbon materials and metals such as silicon, tin, and silver, or oxides thereof. Products, titanium oxide, and the like. A negative electrode active material may be used individually by 1 type, and may use 2 or more types together.

In addition, you may use a positive electrode active material in combination with a conductive support agent.
Examples of the conductive assistant include graphite, carbon black, carbon nanotube, carbon nanofiber, acetylene black, ketjen black, and conductive polymer. These conductive auxiliary agents may be used individually by 1 type, and may use 2 or more types together.

The current collector may be any material having conductivity, and a metal can be used as the material. A metal that is difficult to alloy with lithium is desirable, and specific examples include aluminum, copper, nickel, iron, titanium, vanadium, chromium, manganese, and alloys thereof.
Examples of the shape of the current collector include a thin film shape, a net shape, and a fiber shape. Among these, a thin film is preferable. The thickness of the current collector is preferably 5 to 30 μm, more preferably 8 to 25 μm.

  The mixture layer is formed using a binder tree composition fat containing an electrode active material and the like. The mixture layer is obtained, for example, by preparing a slurry composition containing the binder resin composition, additive, solvent, and electrode active material, applying the slurry composition to a current collector, and drying and removing the solvent. It is done.

Solvents used for preparing the slurry composition are, for example, water, N-methylpyrrolidone, N-ethylpyrrolidone, N, N-dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethylsulfoxide, hexamethylsulfuramide, tetramethylurea, acetone , Methyl ethyl ketone, N-methylpyrrolidone and ester solvents (ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, etc.), N-methylpyrrolidone and glyme solvents (diglyme, triglyme, tetraglyme, etc.) A mixed solvent of the mixed solution may be used, and N-methylpyrrolidone is particularly preferable. These may be used alone or in combination of two or more.
Moreover, additives, such as a dispersing agent and a viscosity modifier, can be added to a slurry composition as needed. Specific examples include a rheology control agent that adjusts the viscosity of the slurry, a leveling agent that provides smoothness after application to the current collector, and a dispersant. Any of these can be used.

  As an example of a process for producing an electrode, the binder resin composition for a secondary battery electrode of the present invention, an electrode active material, and acetylene black are kneaded in the presence of a solvent such as N-methylpyrrolidone (NMP) to obtain a slurry. The slurry is applied to an electrode current collector, dried, and then pressed as necessary to obtain an electrode. The drying conditions are not particularly limited as long as the solvent can be sufficiently removed and the polymer (A) is not decomposed, but the heat treatment is performed at 40 to 160 ° C., preferably 60 to 140 ° C. for 1 minute to 10 hours. It is preferable to do. Within this range, the polymer (A) can impart adhesion between the active material and the current collector or the active material without being decomposed.

  The negative electrode structure and the positive electrode structure manufactured as described above are disposed with a liquid-permeable separator (for example, a polyethylene or polypropylene porous film) interposed therebetween, and non-aqueous electrolysis is provided therewith. A non-aqueous secondary battery is formed by impregnating the liquid. It also has a structure obtained by winding a negative electrode structure / separator with active layers formed on both sides / a positive electrode structure / separator with active layers formed on both sides into a roll (spiral shape). A cylindrical secondary battery is obtained by housing in the bottom metal casing, connecting the negative electrode to the negative electrode terminal, connecting the positive electrode to the positive electrode terminal, impregnating the electrolyte, and sealing the casing.

For example, in the case of a lithium ion secondary battery, an electrolytic solution in which a lithium salt as an electrolyte is dissolved in a non-aqueous organic solvent at a concentration of about 1M is used.
Examples of the lithium salt as the electrolyte solution, for _{example, LiClO 4, LiBF 4, LiI} , LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, LiCl, LiBr, LiB (C 2 _{H 5) 4, LiCH 3 SO} 3, LiC 4 F 9 SO 3, Li (CF 3 SO 2) 2 N, Li [(CO 2) 2] include ₂ B.

  Nonaqueous organic solvents include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as γ-butyrolactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl Ethers such as ether, 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; acetonitrile, nitromethane, NMP Nitrogens such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphoric acid triester; diglyme, triglyme, tetra Glymes such as lime; ketones such as acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone; sulfones such as sulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; 1,3-propane sultone, 4-butane sultone, Examples include sultone such as naphtha sultone. One type of electrolytic solution may be used alone, or two or more types may be used in combination.

<Secondary battery>
The battery can be manufactured using a known method. For example, in the case of a lithium ion secondary battery, first, two electrodes, a positive electrode and a negative electrode, are wound through a separator made of a polyethylene microporous film. . The obtained spiral wound group is inserted into a battery can, and a tab terminal previously welded to a negative electrode current collector is welded to the bottom of the battery can. Inject the electrolyte into the resulting battery can, weld the tab terminal that was previously welded to the positive electrode current collector to the battery lid, and place the lid on the top of the battery can via an insulating gasket A battery is obtained by caulking and sealing the part where the lid and the battery can are in contact.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, a following example does not limit the scope of the present invention.
In this example, the following active materials are used.
Active material: Nickel / manganese / cobalt composite oxide (nickel: manganese: cobalt = 1: 1: 1) (Nippon Chemical Industry Co., Ltd., product name: Cellseed NMC111)

<Synthesis of binder resin for secondary battery electrode>
(Production Example 1)
A 1-liter separable flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas introduction pipe was charged with 235 g of distilled water and a 1% by mass sulfuric acid aqueous solution, and nitrogen gas was bubbled for 15 minutes at an air flow rate of 100 mL / min. The temperature was raised to 60 ° C. while stirring, and the nitrogen gas aeration was switched to the flow.
Next, 0.27 g of ammonium persulfate, 0.81 g of 50% by mass ammonium hydrogen sulfite, 0.1875 g of 0.01% by mass iron sulfate and 15 g of distilled water were added as polymerization initiators.
A monomer in which 24.50 g of acrylonitrile and 0.49 g of light ester P1-M (manufactured by Kyoeisha Chemical Co., Ltd.) was mixed was bubbled into a separable flask for 30 minutes after bubbling nitrogen gas for 15 minutes. After completion of dropping, the polymerization was completed by maintaining at 60 ° C. for 3 hours. Acrylonitrile: light ester P1M = 99.5: 0.5 (molar ratio).

The stirring was stopped and the mixture was cooled, and the reaction solution was filtered with suction. After washing with warm water at 60 ° C., it was dried at 80 ° C. for 24 hours to obtain a polymer (A1).
The weight average molecular weight of the polymer (A1) by GPC measurement (solvent: DMF) was 470,000.

Example 1
<Confirmation of gelation suppression effect>
As active material, polymer (A1), and chelating agent (B), acetylacetone is mixed at a mass ratio of 100: 3: 0.25, N-methylpyrrolidone is used as a solvent, and the solid content is 60% by mass. It adjusted so that it might become. After the adjustment, kneading was carried out for 3 minutes using a rotation and revolution mixer (Awatori Nertaro ARV-200, manufactured by Shinky Corporation). About the slurry after kneading | mixing, the fluidity | liquidity immediately after kneading | mixing and one week after kneading | mixing (storage temperature 23 degreeC) was evaluated.

As an evaluation, ○: fluidity and appropriate viscosity that can be applied; Δ: fluidity but slightly higher than appropriate viscosity for coating; ×: lack of fluidity and application impossible It was carried out in three stages. The evaluation results are shown in Table 1.

(Examples 2 to 14, Comparative Example 1)
A slurry was prepared in the same manner as in Example 1 except that the type and addition amount of the chelating agent (B) were those described in Table 1, and the fluidity was evaluated. The results are shown in Table 1.

  In Comparative Example 1, a bond was formed between the active material and the binder resin composition, and the slurry was gelled by increasing the viscosity of the slurry, and fluidity was lost.

Table 1-1

Table 1-2

(Example 15)
<Preparation of slurry for battery electrode>
As an electrode composition, an active material, acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name: Denka Black), polymer (A1), and acetylacetone are mixed at a mass ratio of 100: 5: 3: 0.25, and used as a solvent. N-methylpyrrolidone was added and kneaded so as to be so-called kneading. For the kneading, an auto-revolving mixer (Awatori Nerita ARV-200, manufactured by Shinky Corporation) was used. Further, N-methylpyrrolidone was added and kneaded, and the solid content was lowered so that the viscosity could be applied. Thus, a final battery electrode slurry was obtained.

<Creation of electrode>
The slurry prepared above was applied to a current collector using a doctor blade. The set thickness of the doctor blade was 220 μm, and the current collector used was an aluminum foil (thickness 20 μm). The current collector coated with the slurry was dried at 80 ° C. for 30 minutes and then vacuum dried at 60 ° C. overnight to obtain an electrode having a weight of 21 mg / cm ² .

<Evaluation of electrode flexibility>
The electrode was cut into a width of 3 cm and a length of 5 cm to obtain a test piece. Measured by the method according to
Test piece 1 was obtained. Subsequently, a mandrel (diameters of 16 mm, 12 mm, 10 mm, 8 mm, and 6 mm, respectively) was applied to the copper foil surface of the test piece 1, and one side of the test piece 1 was fixed with tape. The condition of the mixture layer when the test piece 1 was bent so that the aluminum foil surface was on the inside was observed with a 100-fold microscope, and the flexibility of the electrode was evaluated. The evaluation was carried out in a dry chamber at a temperature of 23 ° C. and a humidity of less than 1%. The measurement was performed three times, and the results of matching o and x two times or more are described.
○: No change.
X: Cracks or peeling occurred.

<Evaluation of binding properties>
Cut out the positive electrode to 20 mm in width and 80 mm in length, and use the double-sided tape (Sekisui Chemical Co., Ltd., “# 570”) to cut the mixture layer surface of the cut piece into a polycarbonate sheet (width 25 mm, length 100 mm, thickness 1 mm) The test piece 2 was fixed.
The test piece 2 was set in a tensile strength test Tensilon tester (Orientec Co., “RTC-1210A”), the copper foil was peeled 180 ° at 10 mm / min, and the peel strength was measured. The test was performed 5 times and the average value was calculated. When performing the test, conditioning was performed for 30 minutes or more in a room at a temperature of 23 ° C. and a humidity of 50% or less.
The evaluation results are shown in Table 2.

(Examples 16 to 28, Comparative Example 2)
Except for changing the type and amount of the chelating agent (B) as shown in Table 2, an electrode was prepared in the same manner as in Example 15, and the flexibility (flexibility) and binding properties (peel strength) were improved. evaluated.

  In Comparative Example 2, a bond is formed between the active material and the binder resin composition, the viscosity of the slurry is increased, and the fluidity is lost and gelled. As a result, the slurry cannot be applied to produce an electrode. It became.

Table 2-1.

Table 2-2

Claims (10)

  A binder resin composition for a secondary battery electrode, comprising a mixture of a polymer (A) containing a vinyl cyanide unit and a unit containing a phosphate group as constituent units and a chelating agent (B).   The binder resin composition for a secondary battery electrode according to claim 1, wherein the chelating agent (B) does not contain a metal atom.   The binder resin composition for a secondary battery electrode according to claim 1, wherein the chelating agent (B) comprises only carbon, hydrogen, and oxygen atoms.   The binder resin composition for a secondary battery electrode according to any one of claims 1 to 3, wherein the chelating agent (B) is any one of diketone, oxycarboxylic acid, and polycarboxylic acid.   A solution or dispersion for a secondary battery electrode, wherein the binder resin composition for a secondary battery electrode according to any one of claims 1 to 4 is dissolved or dispersed in a non-aqueous solvent.   The secondary battery electrode solution or dispersion according to claim 5, wherein the non-aqueous solvent is N-methylpyrrolidone.   The slurry for secondary battery electrodes containing the solution or dispersion liquid for secondary battery electrodes of Claim 5 or 6, and the active material for secondary battery electrodes.   The electrode slurry according to claim 7, wherein the secondary battery electrode active material contains nickel and / or manganese.   An electrode for a secondary battery, comprising: a current collector; and a mixture layer formed from the slurry for a secondary battery electrode according to claim 7 or 8 provided on the current collector.   A lithium ion secondary battery comprising the secondary battery electrode according to claim 9.