JP6618030B2 - Secondary battery electrode binder, secondary battery electrode slurry using the same, secondary battery electrode, and secondary battery - Google Patents

Description

The present invention is, for secondary battery electrode binder for secondary battery electrode slurry composition comprising a solvent the binder and the active material, the electrode for a secondary battery including該記binder, 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 the binder, polyvinylidene fluoride (hereinafter referred to as “PVDF”) is used as a material that satisfies the solvent resistance to the organic solvent used in the electrolytic solution, the oxidation resistance within the driving voltage, the 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.
Patent Document 3 proposes to use a copolymer containing an acrylate ester and a phosphate ester as a binder resin. The phosphate ester exhibits binding properties with the current collector foil, and the active material. It is said that an electrode having improved dispersibility and excellent 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
In addition, as described in Patent Document 3, the adhesion to the current collector foil is improved by polymerizing the acrylate ester unit in the binder resin, but since the acrylate ester unit is the main component, There is a concern that it is decomposed by the oxidation-reduction reaction, and that the expected battery performance cannot be exhibited particularly in long-term use.

As a result of intensive studies in view of the above problems and the consideration thereof, the present inventor includes 50 to 99.99 mol% of vinyl cyanide units as structural units, and 0.01 to 10 mol% of units having acidic groups, By using a secondary battery electrode binder that is a polymer having a mass average molecular weight of 200,000 to 2,000,000, the unit having an acidic group exhibits excellent adhesion to a current collector. The present inventors have found that it is possible to obtain a battery that exhibits electrochemical stability in a battery having a vinyl cyanide unit while improving the flexibility of the current collector foil with an appropriate molecular weight.

The present invention relates to the following.
[1] As a constituent unit, a polymer containing 50 to 99.99 mol% of vinyl cyanide units and 0.01 to 10 mol% of units having an acidic group and having a mass average molecular weight of 200,000 to 2,000,000 is included. Secondary battery electrode binder .
[2] The binder for a secondary battery electrode according to [1], wherein the acidic group is a phosphoric acid group .
[3] The binder for a secondary battery electrode according to [2], further including the polymer according to [1], wherein the acidic group is a carboxyl group .
[4] as a binder, wherein the vinyl cyanide units and polymers containing no units having an acidic group (B) wherein further comprising a (1) to (3) for secondary battery electrode binder according to any one .
[6] An electrode slurry containing the binder according to any one of [1] to [4], an active material, and a solvent.
[7] A current collector, and a mixture layer provided on the current collector,
The mixture layer contains a binder for secondary battery electrode according to any one of [1] to [4], the secondary battery electrode.
[8] A non-aqueous secondary battery comprising the secondary battery electrode according to [7].

According to the present invention is excellent in binding property to a current collector foil, whereby the secondary battery electrode binder to improve the flexibility of the electrode, it is possible to provide a secondary battery electrode slurry composition . Also it is possible to provide an excellent secondary battery electrode, and a nonaqueous secondary battery to the binder or al flexibility. Furthermore, it is possible to obtain a secondary battery and more electrode binder, electrochemical stability is high electrode for a secondary battery and a nonaqueous secondary battery of the present invention.

  Hereinafter, the present invention will be described in detail.

<Polymer (A)>
The binder used in the present invention includes 50 to 99.99 mol% of vinyl cyanide units as constituent units and 0.01 to 10 mol% of units having acidic groups, and has a mass average molecular weight of 200,000 to 2,000,000. The polymer (A) to be contained is contained.

<Vinyl cyanide unit>
Examples of the vinyl cyanide monomer constituting the vinyl cyanide unit include (meth) acrylonitriles such as acrylonitrile and methacrylonitrile; cyanine nitrile group-containing monomers such as α-cyanoacrylate and dicyanovinylidene; fumaronitrile and the like And a fumaric nitrile group-containing monomer. Among these, (meth) acrylonitrile is preferable from the viewpoint of ease of polymerization and cost performance.
These vinyl cyanide monomers may be used individually by 1 type, and may use 2 or more types together.

  The content of the vinyl cyanide unit is from 50 to 99.99 mol%, preferably from 80 to 99.95 mol%, more preferably from 90 to 99, based on all monomer units constituting the polymer (A). .9 mol%. When the content of the vinyl cyanide unit is 50 mol% or more, it can be easily dissolved in a solvent when preparing a slurry, and the prepared polymer (A) is electrochemically stable in the battery over a long period of time. Can exist.

<Units with acidic groups>
As an acidic group which the unit which has an acidic group has, a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group are mentioned, for example.
Examples of the monomer constituting the unit having an acidic group include aliphatic unsaturated carboxylic acids such as (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid and cinnamic acid. Carboxyl group-containing unsaturated carboxylic acid ester such as 2-carboxyethyl (meth) acrylate, 2-carboxyethyl crotonic acid, monomethyl maleate, monooctyl itaconate; carboxyl group-containing single amount such as vinyl 2-carboxypropionate Body; (meth) allylsulfonic acid, (meth) allyloxybenzenesulfonic acid, styrenesulfonic acid, sulfonic acid group-containing monomer such as 2-acrylamido-2-methylpropanesulfonic acid, or phosphoric acid group-containing monomer Of these acidic group-containing monomers; and mixtures thereof.
In these, a phosphate group containing monomer is preferable.
The phosphate group-containing monomer refers to a vinyl monomer having a phosphate group, and preferably a (meth) acrylate and an allyl compound having a phosphate group.

  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.).
A phosphate group containing monomer may be used individually by 1 type, and may use 2 or more types together.

  The content of the unit having an acidic group is 0.01 to 10 mol%, preferably 0.05 to 6 mol%, more preferably, of all monomer units constituting the polymer (A). It is 0.1-4 mol%, Most preferably, it is 0.3-2 mol%. If the content of the unit having an acidic group is 0.01 mol% or more, the 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 other monomer units other than vinyl cyanide units and units having acidic groups as constituent units.
Other monomers constituting other monomer units include, for example, short chains (meth) such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate and the like. Acrylic acid ester monomers; long chain (meth) acrylic acid ester monomers such as stearyl (meth) acrylate and lauryl (meth) acrylate; vinyl halide monomers such as vinyl chloride, vinyl bromide and vinylidene chloride; Maleimides such as maleic imide and phenylmaleimide; aromatic vinyl monomers such as styrene and α-methylstyrene; (meth) acrylamide and vinyl acetate.
The content of other monomer units is an amount that is 100 mol% in combination with the content (mol%) of vinyl cyanide units and units having acidic groups.

The polymer (A) of the present invention may be used in combination of a plurality of different ones. Preferred combinations include a polymer (a1) having a phosphate group and a polymer (a1 ′) different from a1 having a phosphate group, a polymer (a1) having a phosphate group and a polymer having a carboxylic acid group. (A2), a polymer (a1) having a phosphoric acid group and a polymer (a3) having a sulfonic acid group, among which a polymer (a1) having a phosphoric acid group and a polymer having a carboxylic acid group ( The combination of a2) is most preferred.
Examples of the monomer constituting the unit having a carboxylic acid group include carboxyl group-containing monomers such as (meth) acrylic acid, itaconic acid, crotonic acid, and salts thereof, and adhesion to the current collector and electrode production Methacrylic acid is preferred because it is excellent in handling at the time. A carboxylic acid group containing monomer may be used individually by 1 type, and may use 2 or more types together.

Polymers having a carboxylic acid group contained in the binder (a2) may be one kind or two or more kinds.
May include polymers having a carboxylic acid group in the binder with (a2), when all of the polymer contained in the binder to the total of (A) and 100 mass%, the proportion of the polymer having a phosphoric acid group (a1) is 5 to 99% by mass, more preferably 7 to 95% by mass, and particularly preferably 10 to 90% by mass. The ratio of the polymer (a2) having a carboxylic acid group is preferably 1 to 95% by mass, more preferably 5 to 93% by mass, and particularly preferably 10 to 90% by mass. If content of the polymer (a2) which has a carboxylic acid group is below the upper limit of the said range, the flexibility of the mixture layer formed by applying the slurry containing a resin composition will be more excellent. If content of the polymer (a2) which has a carboxylic acid group is more than the lower limit of the said range, the slurry using the binder of this invention will be excellent in coating stability.

<Mass average molecular weight of polymer (A)>
The polymer (A) of the present invention has a mass average molecular weight of 200,000 to 2,000,000, preferably 200,000 to 1,000,000, more preferably 200,000 to 750,000, most preferably 350,000 to 500,000. . By setting the mass average molecular weight of the polymer (A) to 200,000 or more, it is possible to prevent the polymer from being easily dissolved in a solvent at the time of preparing the slurry, and the polymer (A) is activated in the slurry. It becomes possible to bind without covering the substance, and the flexibility of the electrode after application can be improved. Moreover, when the mass 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 of 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.
In the case of using a chain transfer agent, the addition amount is preferably 0.001% by mass or more and 10% by mass or less as a monomer.
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-methylpyrrolidone), N, N-dimethylacetamide, and N, N-dimethylformamide; N, N-dimethylethyleneurea and N, N-dimethylpropyleneurea Ureas such as tetramethylurea; 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 acetate -Esters such as butyl, butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate and ethyl carbitol acetate; glymes such as diglyme, triglyme and tetraglyme; toluene, xylene, cyclohex Hydrocarbons such as sun; sulfoxides such as dimethyl sulfoxide; sulfones such as sulfolane; alcohols such as methanol, isopropanol, and n-butanol.
These solvents may be used alone or in combination of two or more.
When a solvent other than water is used, it is preferably added in the range of 0.01 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of water.

<Surfactant>
In the case of producing the polymer (A) 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.

<Polymer (B)>
Binder used in the present invention comprises a vinyl cyanide unit, and a polymer that does not contain a unit having an acidic group (B) may further contain a.
The vinyl cyanide unit contained in the polymer (B) is the same as the vinyl cyanide unit mentioned in the description of the polymer (A).
The vinyl cyanide unit contained in the polymer (B) may be one type or two or more types.
The polymer (B) is preferably a polymer mainly composed of vinyl cyanide units. When the vinyl cyanide unit is the main component, the solubility or dispersibility of the resin composition in the non-aqueous solvent is improved, and the adhesion of the mixture layer using the resin composition as a binder to the current collector is improved.
“Main component” means that the content of vinyl cyanide units is more than 50 mol% and 100 mol% or less when the total of all the structural units constituting the polymer (B) is 100 mol%. .
It is preferable that content of the vinyl cyanide unit in a polymer (B) is 90 to 100 mol% with respect to the sum total of all the structural units which comprise a polymer (B).
The mass average molecular weight of the polymer (B) is preferably in the range of 10,000 to 2,000,000, more preferably 30,000 to 1,000,000, and still more preferably 30,000 to 500,000. Particularly preferred is 50,000 to 500,000.
The mass average molecular weight of the polymer (B) can be measured by the same method as the mass average molecular weight of the polymer (A).

As the polymer (B), a commercially available product or a product produced by a known production method may be used.
The polymer (B) can be produced by a known polymerization method. For example, it can manufacture by the method similar to the manufacturing method quoted by description of the polymer (A) mentioned above except not using an acidic group containing monomer.
Polymer contained in the binder (B) may be one kind or two or more kinds.
If containing polymer in the binder of (B), when the total 100 mass% of the polymer (A) and the polymer contained in the binder (B), the proportion of the polymer (B), 1 to 90 weight %, More preferably 5 to 70% by mass, particularly preferably 10 to 50% by mass, and particularly preferably 10 to 35% by mass. If content of a polymer (B) is below the upper limit of the said range, the flexibility of the mixture layer formed by applying the slurry containing a resin composition will be more excellent. If content of a polymer (B) is more than the lower limit of the said range, the slurry using the binder of this invention will be excellent in coating stability.

The binder of the present invention contains other additives such as “binder” that improves battery performance, “viscosity modifier” that improves coating properties, and “plasticizer” that improves flexibility of the electrode. You may combine in the range which does not impair the expected effect.

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

  Examples of the viscosity modifier include cellulose polymers such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose and ammonium salts thereof; poly (meth) acrylates such as sodium poly (meth) acrylate; polyvinyl alcohol, polyethylene oxide , Polyvinylpyrrolidone, copolymer of acrylic acid or acrylate and vinyl alcohol, maleic anhydride, maleic acid or copolymer of fumaric acid and vinyl alcohol, modified polyvinyl alcohol, modified polyacrylic acid, polyethylene glycol, polycarboxylic acid Is mentioned.

Examples of the plasticizer include compounds having a hydroxyl group. Specific examples include glycols, glycerins, erythritols, and the like. Polyethylene glycol and polyglycerin that are polycondensates of polyhydric alcohols are preferable because they are difficult to elute into the electrolyte.
The additive finally remaining on the electrode is preferably electrochemically stable.

Binder for a secondary battery electrode, powdery, solution in a solvent may be used in any form of an emulsion dispersed in an aqueous or oily medium.

<Binder of applications>
Type of battery binders for a secondary battery of the present invention can be used is not particularly limited, the secondary battery of nonaqueous, among others, used to the positive electrode or the negative electrode in a lithium ion secondary battery is particularly preferable.

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

The composition of the slurry composition for a secondary battery electrode is 0.1 to 10 parts by mass of the binder for the secondary battery electrode of the present invention and 0.5 to 20 parts by mass of the conductive additive when the active material is 100 parts by mass. Part. 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 of this invention is used as a material which comprises this mixture layer. Specifically, an active material incorporated into the binder for secondary battery electrode of the present invention, the solid obtained phase becomes mixture layer and drying the slurry composition is dissolved or dispersed in a solvent.

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.
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. Things. A negative electrode active material may be used individually by 1 type, and may use 2 or more types together.

In the lithium ion secondary battery, it is preferable to use a lithium-containing metal composite oxide for the positive electrode and graphite for the negative electrode. By setting it as such a combination, the voltage of a lithium ion secondary battery will be about 4V.
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 slurry composition containing an electrode active material and the like. The mixture layer is obtained, for example, by preparing a slurry composition containing the binder , additive, solvent, and electrode active material, applying the slurry composition to a current collector, and drying and removing the solvent.

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 coating on the current collector, and a dispersant. Any of these can be used.

As an example of a process for producing an electrode, the secondary battery electrode binder 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 battery binder does not decompose, but heat treatment is performed at 40 to 160 ° C., preferably 60 to 140 ° C. for 1 minute to 10 hours. It is preferable. Within this range, the binder for the secondary battery can provide 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.

  Examples of non-aqueous 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 Ethers such as diethyl 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 Nitrogens such as NMP; methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphate triester; diglyme, triglyme Glymes such as tetraglyme; 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 And 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 that is a non-aqueous secondary battery, first, two electrodes, a positive electrode and a negative electrode, are made of a microporous polyethylene film. Wind through the separator. 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.

<Synthesis of binder resin for secondary battery electrode>
(Production Example 1)
A 1 liter separable flask equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas introduction tube 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 24.91 g of acrylonitrile and 0.10 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 the dropping, the polymerization was completed by maintaining at 60 ° C. for 3 hours.
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 mass average molecular weight of the binder resin 1 by GPC measurement (solvent: DMF) was 1,050,000.

(Production Example 2)
A polymer (A2) was obtained in the same manner as in Production Example 1 except that 24.50 g of acrylonitrile and 0.49 g of light ester P1-M were mixed as the monomer to be dropped.
The mass average molecular weight of the polymer (A2) by GPC measurement (solvent: DMF) was 470,000.

(Production Example 3)
A polymer (A3) was obtained in the same manner as in Production Example 1, except that 24.16 g of acrylonitrile and 0.97 g of light ester P1-M were mixed.
The mass average molecular weight of the polymer (A3) by GPC measurement (solvent: DMF) was 410,000.

(Production Example 4)
A 1-liter separable flask equipped with a stirrer, thermometer, cooling tube and nitrogen gas inlet tube was charged with 235 g of distilled water, 1% by mass sulfuric acid aqueous solution and 0.0125 g of sodium hypophosphite, and the nitrogen gas flow rate Bubbling at 100 mL / min for 15 minutes. 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 were mixed was bubbled into a separable flask for 30 minutes after bubbling nitrogen gas for 15 minutes. After completion of the dropping, the polymerization was completed by maintaining at 60 ° C. for 3 hours.
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 (A4).
The mass average molecular weight of the polymer (A4) by GPC measurement (solvent: DMF) was 450,000.

(Production Example 5)
A polymer (A5) was obtained in the same manner as in Production Example 4, except that 24.16 g of acrylonitrile and 0.97 g of light ester P1-M were mixed.
The mass average molecular weight of the polymer (A5) by GPC measurement (solvent: DMF) was 370,000.

(Production Example 6)
A polymer (A6) was obtained in the same manner as in Production Example 4 except that the amount of sodium diphosphite used was 0.25 g.
The mass average molecular weight of the polymer (A6) by GPC measurement (solvent: DMF) was 310,000.

(Production Example 7)
A polymer (A7) was obtained in the same manner as in Production Example 4 except that 22.46 g of acrylonitrile and 2.67 g of light ester P1-M were mixed as the monomer to be dropped.
The mass average molecular weight of the polymer (A7) by GPC measurement (solvent: DMF) was 440,000.

(Production Example 8)
A polymer (A8) was obtained in the same manner as in Production Example 4, except that 20.77 g of acrylonitrile and 4.33 g of light ester P1-M were mixed as the monomer to be dropped.
The mass average molecular weight of the polymer (A8) by GPC measurement (solvent: DMF) was 230,000.

(Production Example 9)
Polymer (A9) was prepared in the same manner as in Production Example 4 except that 20.77 g of acrylonitrile and 4.33 g of light ester P1-M were mixed as the monomer to be added, and 0.25 g of sodium hypophosphite was added. Obtained.
The mass average molecular weight of the polymer (A9) by GPC measurement (solvent: DMF) was 80,000.

(Production Example 10)
A polymer (A10) was obtained in the same manner as in Production Example 1 except that 12.56 g of acrylonitrile and 12.44 g of light ester P1-M were mixed as the monomer to be dropped.
The polymer (A10) was not dissolved in DMF, and the mass average molecular weight by GPC measurement could not be calculated.

(Production Example 11)
A 1 liter separable flask equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas introduction tube 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 mixed with 25.0 g of acrylonitrile was bubbled with nitrogen gas for 15 minutes and then added dropwise to a separable flask for 30 minutes. After completion of the dropping, the polymerization was completed by maintaining at 60 ° C. for 3 hours.
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 (B1).
The mass average molecular weight of the polymer (B1) by GPC measurement (solvent: DMF) was 310,000.

(Production Example 12)
A polymer (A11) was obtained in the same manner as in Production Example 1 except that 24.50 g of acrylonitrile and 0.50 g of methacrylic acid were mixed as the monomer to be dropped.
The mass average molecular weight of the polymer (A11) by GPC measurement (solvent: DMF) was 430,000.
Table 1 shows preparation molar ratios and mass average molecular weights of binder resin synthesis in Production Examples 1 to 12. In Table 1, the unit of the numerical value of the composition is mol%.

Example 1
Polymer prepared in Preparation Example 1 the electrode slurry composition using as a binder (A1) is prepared as follows, was subjected to the characteristic evaluation.

<Preparation of slurry for battery electrode>
As the slurry composition, lithium cobalt oxide (manufactured by Nippon Chemical Industry Co., Ltd., product name: Cellseed C-5H), acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name: Denka Black), polymer (A1), mass The mixture was mixed at a ratio of 100: 5: 3, and N-methylpyrrolidone was used as a solvent to add so-called kneading and knead. For the kneading, an auto-revolving mixer (Foam Remover Taro 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 50 minutes to obtain an electrode having a basis 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, and pressed with a press roll to adjust the electrode density to 3 g / cm ³ to obtain a test piece 1. Subsequently, a mandrel (diameters of 16 mm, 10 mm, 8 mm, 6 mm, and 5 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 state of the mixture layer when the test piece 1 was bent so that the aluminum foil surface was inside was visually observed, and the flexibility of the electrode was evaluated according to the following evaluation criteria.
○: No change.
X: Cracks or peeling occurred.

(Evaluation of binding properties)
The positive electrode was cut out to be 20 mm wide and 80 mm long, pressed with a press roll to adjust the electrode density to 3 g / cm ^3, and then the mixture layer surface of the cut piece was double-sided tape (Sekisui Chemical Co., Ltd., “ # 570 ") and fixed to a polycarbonate sheet (width 25 mm, length 100 mm, thickness 1 mm) to obtain test piece 2. 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 (N / cm) was measured. The test was performed 5 times and the average value was recorded.

(Examples 2 to 8) (Example 8: Reference example)
Except for using the polymer as a battery electrode binder a (A2) ~ (A8) is to prepare an electrode in the same manner as in Example 1 to evaluate flexibility and binding properties.

Example 9
Polymer (A2): Polymer (B1): Polyglycerin # 500 (trade name: Sakamoto Yakuhin Kogyo Co., Ltd. polyglycerin average molecular weight 500) as a battery electrode binder in a mass ratio of 45:45:10 A mixture was used.
As a slurry composition, lithium cobalt oxide (manufactured by Nippon Chemical Industry Co., Ltd., product name: Cellseed C-5H), acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name: Denka Black), binder , mass ratio 100: 5 : 3, and using N-methylpyrrolidone as a solvent, the mixture was kneaded so as to be so-called solidified. For the kneading, an auto-revolving mixer (Foam Remover Taro 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.

(Example 10)
Polymer as a binder (A2): the polymer (B1): except for using those polyglycerol # 500 mass ratio 63:27:10 was prepared in the same manner as the electrode as in Example 8, flexibility, cohesiveness Evaluated.

(Example 11)
Polymer as a binder (A5): The polymer (B1): except for using those polyglycerol # 500 mass ratio 63:27:10 was prepared in the same manner as the electrode as in Example 8, flexibility, cohesiveness Evaluated.

(Example 12)
Polymer as a binder (A5): The polymer (B1): except for using those polyglycerol # 500 mass ratio 56:24:20 was prepared in the same manner as the electrode as in Example 8, flexibility, cohesiveness Evaluated.

(Example 13)
Polymer as a binder (A2): except for using those of the polymer (A11) and the mass ratio of 50:50 was prepared in the same manner as the electrode of Example 9 was evaluated flexibility and binding properties.

(Example 14)
Polymer as a binder (A2): except for using those of the polymer (A11) and the mass ratio 25:75 were produced in the same manner as in the electrode of Example 9 was evaluated flexibility and binding properties.

Polymer (Example 15) binder (A2): except for using those of the polymer (A11) and the mass ratio 10:90 was prepared in the same manner as the electrode of Example 9, evaluation flexibility and binding properties did.
(Example 16)
Polymer as a binder (A2): the polymer (A11): except for using those polyglycerol # 500 mass ratio 9:81:10 was prepared in the same manner as the electrode of Example 9, flexibility, cohesiveness Evaluated.

(Example 17)
<Preparation of slurry for battery electrode>
As a slurry composition, lithium titanate (LTO), acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name: Denka Black), polymer (A2), and polymer (A11) were mixed at a mass ratio of 100: 5: 1. The mixture was mixed at 5: 1.5, and kneaded using N-methylpyrrolidone as a solvent so as to be so-called solidified. For the kneading, an auto-revolving mixer (Foam Remover Taro 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 current collector used was an aluminum foil (thickness 20 μm). The current collector coated with the slurry was dried at 80 ° C. for 50 minutes to obtain an electrode having a mass per unit area of 11.2 mg / cm ² .
The flexibility and binding properties of the electrodes were evaluated in the same manner as in Example 1 except that the thickness was about 70 μm and the electrode density was adjusted to 1.6 g / cm ³ by pressing with a press roll.

(Example 18)
An electrode was prepared in the same manner as in Example 17 except that a polymer (A2): polymer (A11) having a mass ratio of 25:75 was used as a binder to be mixed, and the flexibility and binding properties were evaluated.

(Example 19)
An electrode was produced in the same manner as in Example 17 except that a polymer (A2): polymer (A11) having a mass ratio of 10:90 was used as a binder to be mixed, and the flexibility and binding property were evaluated.

(Comparative Examples 1 and 2)
Polymer as a battery electrode binder (A9), except that (A10) were used respectively were produced in the same manner as in the electrode as in Example 1 to evaluate flexibility and binding properties.
The evaluation results of Examples 1 to 19 and Comparative Examples 1 and 2 are shown in Table 2. (Example 8 in Table 2 is a reference example.)

A polymer having 50 to 99.99 mol% of vinyl cyanide units and 0.01 to 10 mol% of units having an acidic group as a constitutional unit, and having a mass average molecular weight of 200,000 to 2,000,000. An electrode manufactured using a certain binder resin for secondary battery electrodes (Examples 1 to 19 all had high flexibility and high binder binding properties.
Moreover, when compared with the same active material, since Examples 13-16 further contain the polymer whose acidic group is a carboxyl group, compared with Examples 9-12, the high flexibility of the electrode is maintained. However, the binding property of the binder was particularly high.
Furthermore, if a binder further containing a polymer whose acidic group is a carboxyl group was used, it could be suitably used for other active materials as shown in Examples 17-19.
Since the binder resin described in Comparative Example 1 had a molecular weight of 80,000 and less than 200,000, the binder resin was excessively dissolved in the solvent N-methylpyrrolidone when the slurry was prepared, and the binder resin was in the slurry. As a result, the active material was covered and the flexibility of the mixture layer after electrode preparation was inhibited.
Since the binder resin described in Comparative Example 2 contained 20 mol% of a unit having a functional group containing a phosphorus atom, the solubility in N-methylpyrrolidone as a solvent was greatly reduced, and the binder resin was coated on the current collector foil. The electrode could not be obtained.

Claims (6)

As a constitutional unit, a polymer (a1) containing 50 to 99.99 mol% of vinyl cyanide units and 0.01 to 10 mol% of units having a phosphoric acid group, and having a mass average molecular weight of 310,000 to 2,000,000. Is a binder for secondary battery electrodes containing 9% by mass to 100% by mass . As a constitutional unit, a polymer (a2) containing 50 to 99.99 mol% of vinyl cyanide units and 0.01 to 10 mol% of units having a carboxyl group and having a mass average molecular weight of 200,000 to 2,000,000. further comprising, according to claim 1, wherein the secondary battery electrode binder. The binder for secondary battery electrodes according to claim 1 or 2, further comprising a polymer (B) containing a vinyl cyanide unit as a constituent unit and not containing a unit having an acidic group . Comprising a binder according to any one of claims 1 to 3, the active material and a solvent, the electrode slurry. A current collector, and a mixture layer provided on the current collector,
The mixture layer contains a binder for secondary battery electrode according to any one of claims 1 to 3, the secondary battery electrode.   A non-aqueous secondary battery comprising the secondary battery electrode according to claim 5.