JP2016154068A - Binder resin for nonaqueous secondary battery electrode, binder resin composition for nonaqueous secondary battery electrode, slurry composition for nonaqueous secondary battery electrode, nonaqueous secondary battery electrode, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a water-soluble binder resin for a nonaqueous secondary battery electrode, which can be obtained by a simple and convenient manufacturing method, and which is superior in storing stability and electrode material binding property, a binder resin composition for a nonaqueous secondary battery electrode, which includes such a binder resin and others.SOLUTION: A binder resin for a nonaqueous secondary battery electrode consists of a polymer (II) obtained by the hydrolysis of a polymer (I) having a repeating structural unit expressed by the general formula (1) in the presence of a reductant. The amount of the reductant used is 0.1-10 pts.mass to 100 pts.mass of the polymer (I).SELECTED DRAWING: None

Description

  The present invention relates to a binder resin for a nonaqueous secondary battery electrode, a binder resin composition for a nonaqueous secondary battery electrode, a slurry composition for a nonaqueous secondary battery electrode, a nonaqueous secondary battery electrode, and a nonaqueous secondary battery It relates to batteries.

Secondary batteries are used for low-power consumer devices such as notebook computers and mobile phones, and as storage batteries for hybrid vehicles and electric vehicles. Among secondary batteries, lithium ion secondary batteries (hereinafter also referred to as “batteries”) are frequently used.
Generally, as an electrode for a lithium ion secondary battery, an electrode including a current collector and a mixture layer provided on the current collector is used, and an active material or the like is a binder layer. It is held by resin. Such an electrode is usually manufactured as follows.
That is, a binder resin, an active material, a solvent, and a conductive aid as necessary are kneaded to prepare a slurry composition for a non-aqueous secondary battery electrode (hereinafter also referred to as “electrode slurry”). This electrode slurry is applied to one or both sides of the current collector with a transfer roll or the like, the solvent is removed by drying to form a mixture layer, and then compression-molded with a roll press or the like as necessary. Get. As the solvent, a solvent in which an active material, a conductive aid or the like is dispersed and a binder resin is dissolved is used.

Conventionally, fluorine resin such as polyvinylidene fluoride (PVDF) has been used as a binder resin for electrodes, for example, for positive electrodes. However, when producing an electrode, a binder resin such as PVDF is dissolved in an organic solvent such as N-methyl-2-pyrrolidone (NMP). Problems such as high are becoming obvious.
Therefore, recently, there is a trend to replace the organic solvent with water. For example, a water-soluble binder resin such as styrene-butadiene rubber (SBR) latex or a thickener carboxymethyl cellulose (CMC) is used as the binder resin for the negative electrode. It has been.

On the other hand, since CMC is a water-soluble polymer, it can be used by dissolving in water at the time of electrode preparation. However, since CMC is derived from a natural product, the quality of each supply lot is difficult to stabilize, and as a result, the quality of the obtained electrode is difficult to stabilize.
Therefore, a non-natural and water-soluble binder resin that can be supplied with stable quality is desired.
In addition, the binder resin is also required to have performance capable of imparting high battery performance to the battery.

In order to solve these problems, a polymer having an N-vinylacetamide unit as a binder resin has been reported.
For example, Patent Document 1 discloses an electrode including a resin component containing poly N-vinylacetamide and a polymer of ethylene oxide (EO) and propylene oxide (PO) as a binder resin. According to Patent Document 1, by using this binder resin, the binding property, battery characteristics from low temperature to room temperature environment, and lithium ion conductivity are excellent.
However, since the binder resin described in Patent Document 1 has a molecular structure in which the EO chain or the PO chain is similar to the electrolyte composition, the polymer of EO and PO may elute into the electrolyte solution, which adversely affects battery performance. There was concern about the effects.

  Patent Document 2 discloses a positive paste for a non-aqueous battery containing poly N-vinylacetamide as a polymer containing a repeating structural unit having an amide structure. Poly N-vinylacetamide is said to be able to improve the required performance in secondary batteries (especially non-aqueous secondary batteries) such as paste stability, binding properties, and electrochemical stability. In addition, elution into the electrolyte is unlikely to occur.

  Patent Document 3 discloses a binder for a nonaqueous battery including a polymer obtained by partially hydrolyzing N-vinylformamide as a polymer including a repeating structural unit having an amide structure and a repeating structural unit having an amine structure. ing. The required performance of secondary batteries (especially non-aqueous secondary batteries) such as binding and electrode flexibility can be improved.

JP 2002-117860 A JP 2002-251999 A International Publication No. WO2013 / 081152 Pamphlet

  However, as described in Patent Document 2, poly N-vinylacetamide composed only of repeating structural units having an amide structure does not always satisfy the binding property sufficiently. Furthermore, when an electrode slurry is prepared using poly N-vinylacetamide, electrode materials (such as active materials and conductive assistants) may not be sufficiently dispersed in the electrode slurry. When an electrode is produced using an electrode slurry in which the electrode material is not sufficiently dispersed, the electrode material is likely to aggregate on the electrode surface (mixture layer surface), which causes a decrease in battery performance. Moreover, the polymer which partially hydrolyzed N-vinylformamide described in Patent Document 3 increased in viscosity during storage, and in some cases, the storage stability was poor. As a cause, it is considered that aldehydes generated by decomposition of the remaining monomer acted as a cross-linking agent to reduce the water solubility of the polymer.

  The present invention has been made in view of the above circumstances, and can be obtained by a simple production method, is excellent in storage stability, and has excellent binding properties for electrode materials. It aims at providing the binder resin composition for secondary battery electrodes, the slurry composition for non-aqueous secondary battery electrodes, the electrode for non-aqueous secondary batteries, and a non-aqueous secondary battery.

  As a result of intensive studies, the inventors of the present invention have obtained a polymer obtained by polymerizing an amide monomer, which is a source of amide structural units, in an aqueous solution and subsequently hydrolyzing a part of the substituent. The present inventors have found that it is water-soluble and has excellent binding properties, and has completed the present invention.

That is, this invention has the following aspects.
[1] Non-aqueous secondary battery, which is a polymer (II) obtained by hydrolyzing a polymer (I) having a repeating structural unit represented by the following general formula (1) in the presence of a reducing agent Binder resin for electrodes.

(In formula (1), R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms.)
[2] The binder resin for a nonaqueous secondary battery electrode according to [1], wherein the amount of the reducing agent used is 0.1 to 10 parts by mass with respect to 100 parts by mass of the polymer (I).
[3] An electrode slurry comprising a binder resin composition for a nonaqueous secondary battery electrode containing the binder resin for a nonaqueous secondary battery electrode according to [1] or [2], an active material, and a solvent.
[4] A current collector and a mixture layer provided on the current collector, wherein the mixture layer comprises the binder resin for a nonaqueous secondary battery electrode according to [1] or [2]. The electrode for non-aqueous secondary batteries containing the binder resin composition for non-aqueous secondary battery electrodes to contain.
[5] A non-aqueous secondary battery comprising the electrode for non-aqueous secondary battery according to [4].

  According to the present invention, a water-soluble binder resin for non-aqueous secondary battery electrodes, a binder resin composition for non-aqueous secondary battery electrodes, which can be obtained by a simple production method, has excellent storage stability and excellent binding properties, A slurry composition for a non-aqueous secondary battery electrode, an electrode for a non-aqueous secondary battery, and a non-aqueous secondary battery can be provided.

Hereinafter, the present invention will be described in detail.
In the present specification, “water-soluble” means that the binder resin is dissolved in water, and not only all of the binder resin is dissolved in water, but also when part of the binder resin is dissolved in water, Considered water soluble.
In the present specification, “(meth) acryl” is a general term for acrylic and methacrylic, “(meth) acrylate” is a general term for acrylate and methacrylate, and “(meth) allyl” means allyl and Generic name for methallyl.

[Binder resin for non-aqueous secondary battery electrode]
The binder resin for nonaqueous secondary battery electrodes of the present invention (hereinafter also referred to as “binder resin”) is obtained by hydrolyzing a polymer (I) having a repeating structural unit described later in the presence of a reducing agent. Contains the resulting polymer (II).

<Polymer (I)>
(Structural unit (A))
The structural unit (A) is a structural unit represented by the following general formula (1).

(In formula (1), R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms.)

Examples of the hydrocarbon group include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, t-butyl group, and pentyl group. The hydrocarbon group may be linear or branched.
From the viewpoint of increasing the water solubility of the resulting polymer (II), when R ¹ and R ² are hydrocarbon groups, it is preferable that the number of carbon atoms is smaller, and R ¹ and R ² are each independently a hydrogen atom. Or a C1-C3 alkyl group is preferable and a hydrogen atom or a methyl group is more preferable. In view of further increasing the water solubility of the polymer (II), it is particularly preferable that R ¹ and R ² are each a hydrogen atom.

  When the total of all the units constituting the polymer (II) is 100 mol%, the content of the structural unit (A) is 20 to 99.9 mol%, preferably 25 to 99 mol%, More preferably, it is -99 mol%. When the content of the structural unit (A) is within the above range, it exhibits high water solubility and is difficult to swell with respect to the electrolyte when used in an electrode, and can impart good cycle characteristics and the like to the battery. A binder resin is obtained.

  Examples of the monomer from which the structural unit (A) is derived (hereinafter referred to as “monomer (a)”) include N-vinylformamide, N-vinylacetamide, and the like. A monomer (a) may be used individually by 1 type, and may use 2 or more types together.

  The binder resin (polymer (II)) of the present invention can be obtained by hydrolyzing the polymer (I) having the repeating structural unit (A). In that case, the following structural unit (B) is generated as a repeating structural unit.

(Structural unit (B))
The structural unit (B) is a structural unit represented by the following general formula (2).

(In the formula (2), ^{R 1} is a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms.)

Examples of the hydrocarbon group include the hydrocarbon groups exemplified above in the description of the structural unit (A). The hydrocarbon group may be linear or branched.
From the viewpoint of increasing the water solubility of the resulting polymer (II), when R ¹ is a hydrocarbon group, it is preferred that the number of carbon atoms is small, and R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. , A hydrogen atom or a methyl group is more preferable. In view of further increasing the water solubility of the polymer (II), it is particularly preferable that R ¹ is a hydrogen atom.

  When the total of all the units constituting the polymer (II) is 100 mol%, the content of the structural unit (B) is preferably 0.1 to 80 mol%. If the content rate of a structural unit (B) is 0.1 mol% or more, binder resin excellent in binding property will be obtained. Therefore, an electrode having excellent adhesion between the mixture layer and the current collector can be obtained. On the other hand, if the content rate of a structural unit (B) is 80 mol% or less, battery performance can be maintained favorable.

  The polymer (II) is polymerized by allowing the monomer (a) and an optional monomer to coexist if necessary, and then the polymer (hereinafter referred to as “polymer (I)”). ) To produce the structural unit (B). According to this method, since the polymer (II) can be produced without using the monomer (b) which is the source of the structural unit (B), the boiling point of the monomer (b) is low. The use of the monomer (b) can be avoided when the handleability is poor or the toxicity is high.

Any known compound can be used as the anti-gelling agent in the present invention, but it is necessary to use a compound having reducibility, stable under hydrolysis conditions and having an aldehyde scavenging ability.
Specifically, under alkaline conditions, dithionite, sulfite, bisulfite, disulfite, Rongalite (sulfoxylate formaldehyde adduct), thiourea dioxide, sodium borohydride and the like are exemplified. The When the anti-gelling agent is a salt, the type of salt can be selected arbitrarily, such as alkali metal salts such as sodium, potassium and lithium, alkaline earth metal salts such as calcium, magnesium and zinc, and ammonium salts. Illustrated.
Under acidic conditions, hydroxylamine salt, aminoguanidine, phenylhydrazine and the like are exemplified.
Any one or more of these anti-gelling agents can be used as a mixture. In addition, for convenience, these gelation inhibitors may be appropriately selected from commercially available products.

  The addition amount of the reducing agent is usually 0.1 to 10 parts by mass, preferably 1 to 5 parts by mass with respect to 100 parts by mass of the polymer (I).

(Arbitrary unit)
The polymer (II) may contain units other than the structural unit (A) and the structural unit (B) (hereinafter referred to as “arbitrary unit”) as necessary.
The monomer that is a source of the arbitrary unit (hereinafter referred to as “optional monomer”) is not particularly limited as long as it can be copolymerized with the monomer (a). For example, methyl (meth) acrylate, (Meth) acrylates such as propyl (meth) acrylate, butyl (meth) acrylate and hexyl (meth) acrylate; (meth) acrylic acid and salts thereof; vinyl ketones such as methyl vinyl ketone and isopropyl methyl ketone; (meth) acrylamide Acrylamides such as N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide; acrylonitrile, methacrylonitrile, α-cyanoacrylate, dicyanovinylidene, fumaronitrile ethyl, etc. Vinyl cyanide monomer; vinyl chloride, bromide Halogenated vinyl monomers such as nyl and vinylidene chloride; carboxyl group-containing monomers such as itaconic acid and crotonic acid and salts thereof; aromatic vinyl monomers such as styrene and α-methylstyrene; maleimide and phenylmaleimide Maleimides; sulfonic acid group-containing vinyl monomers such as (meth) allylsulfonic acid, (meth) allyloxybenzenesulfonic acid, and styrenesulfonic acid; and salts thereof; phosphate-containing vinyl monomers and salts thereof; Examples include vinyl acetate and N-vinyl pyrrolidone.

Moreover, the structural unit represented by the following general formula (3) may be included.

(In Formula (3), R ⁴ is a monovalent substituent including a structure represented by — (R ⁶ O) —, R ⁵ is a hydrogen atom or a methyl group, and R ⁶ is a divalent substituent. Group.)

Examples of the divalent substituent include a linear or branched divalent hydrocarbon group, a divalent substituent obtained by removing two hydrogen atoms from any carbon atom of an aromatic ring or alicyclic ring, and the like. They may be single or bonded to other substituents, and may contain a hetero atom in the skeleton or substituent. Specifically, any of linear or branched divalent hydrocarbon groups such as ethylene group, propylene group and butylene group, aromatic rings such as benzene ring, naphthalene ring and thiophene ring, and alicyclic rings such as cyclohexane And divalent substituents obtained by removing two hydrogen atoms from a carbon atom.
The structure represented by — (R ⁶ O) — is preferably an alkylene oxide unit having 2 to 4 carbon atoms, specifically, an ethylene oxide unit or a propylene oxide unit is preferred, but an alkylene oxide having an arbitrary hydrocarbon group If it is a unit, it will not specifically limit. The terminal of R4 is a hydrogen atom or a monovalent substituent. Examples of the monovalent substituent include a linear or branched monovalent hydrocarbon group, a monovalent substituent obtained by removing one hydrogen from any carbon atom of an aromatic ring or alicyclic ring, and the like. They may be single or bonded to other substituents, and may contain a hetero atom in the skeleton or substituent. Specifically, any linear or branched monovalent hydrocarbon group such as an alkyl group having 1 to 20 carbon atoms, an aromatic ring such as a benzene ring, a naphthalene ring or a thiophene ring, or an alicyclic ring such as cyclohexane And monovalent substituents obtained by removing one hydrogen from a carbon atom.

As a monomer used as the origin of General formula (3), the compound represented, for example by following General formula (4) is mentioned.

(In the formula (4), R ⁵ is the same as R ⁵ in the general formula (3).)

R ⁷ is a hydrogen atom or a monovalent substituent. Examples of the monovalent substituent include a linear or branched monovalent hydrocarbon group, a monovalent substituent obtained by removing one hydrogen from any carbon atom of an aromatic ring or alicyclic ring, and the like. They may be single or bonded to other substituents, and may contain a hetero atom in the skeleton or substituent. Specifically, any linear or branched monovalent hydrocarbon group such as an alkyl group having 1 to 20 carbon atoms, an aromatic ring such as a benzene ring, a naphthalene ring or a thiophene ring, or an alicyclic ring such as cyclohexane And monovalent substituents obtained by removing one hydrogen from a carbon atom.

X ¹ is a divalent substituent containing a structure represented by — (R ⁶ O) —. Specifically, it is a divalent substituent containing at least one selected from the group consisting of a repeating unit of polyalkylene glycol, a repeating unit of polyester diol, and a repeating unit of polycarbonate diol. Among these, those having a repeating unit of polyalkylene glycol are preferable.
The form of X ¹ may be a repetition of a single structural unit or a repetition of two or more structural units. Further, if the form X ¹ is repeated two or more structural units, the arrangement of the structural units is not particularly limited, and the structural units may exist randomly, each structural unit is present in block Each structural unit may exist alternately.

Examples of the compound represented by the general formula (4) include those shown below.
R ⁵ is a methyl group, R ⁷ is a hydrogen atom, X ¹ is a repeating unit of ethylene glycol, Blenmer E (repeating units of ethylene glycol is 1), Blenmer PE series (e.g., repeating units of ethylene glycol is from about 2 to 8).
Blemmer P (repeat unit is 1), Blemmer PP series (for example, about 4 to 13 repeat units), wherein R ⁵ is a methyl group, R ⁷ is a hydrogen atom, and X ¹ is a propylene glycol repeat unit.
R ⁵ is a methyl group, ^{R 7} is a hydrogen atom, ^{X 1} is a repeating unit of ethylene glycol and propylene glycol, Blemmer 50PEP-300 (repeating units of ethylene glycol is about 3.5, the repeating units of propylene glycol is from about 2 .5), BLEMMER 70PEP-350B (ethylene glycol repeating unit of about 5, propylene glycol repeating unit of about 2).

BLEMMER 55PET-800, wherein R ⁵ is a methyl group, R ⁷ is a hydrogen atom, and X ¹ is a repeating unit of ethylene glycol and butylene glycol (the repeating unit of ethylene glycol is about 10, the repeating unit of butylene glycol is about 5).
Blemmer AE series wherein R ⁵ is a hydrogen atom, R ⁷ is a hydrogen atom, and X ¹ is a repeating unit of ethylene glycol (for example, ethylene glycol has a repeating unit of about 2 to 10).
BLEMMER AP series (for example, about 3 to 9 repeating units of propylene glycol), wherein R ⁵ is a hydrogen atom, R ⁷ is a hydrogen atom, and X ¹ is a repeating unit of propylene glycol.
BLEMMER PME series (for example, about 2 to 90 ethylene glycol repeating units) in which R ⁵ is a methyl group, R ⁷ is a methyl group, and X ¹ is an ethylene glycol repeating unit.
AM-130G (for example, about 13 repeating units of ethylene glycol), wherein R ⁵ is a hydrogen atom, R ⁷ is a methyl group, and X ¹ is an ethylene glycol repeating unit.

BLEMMER 50POEP-800B (ethylene glycol repeating unit is about 8), wherein R ⁵ is a methyl group, R ⁷ is CH ₂ CH (C ₂ H ₅ ) C ₄ H ₉ , and X ¹ is a repeating unit of ethylene glycol and propylene glycol. The repeating unit of propylene glycol is about 6).
BLEMMER PSE-1300 (ethylene glycol repeating unit is about 30), wherein R ⁵ is a methyl group, R ⁷ is an octadecyl group, and X ¹ is an ethylene glycol repeating unit.
BLEMMER PAE series (for example, ethylene glycol repeating unit 1 or 2), wherein R ⁵ is a methyl group, R ⁷ is a phenyl group, and X ¹ is an ethylene glycol repeating unit.
Blemmer ANP-300 in which R ⁵ is a hydrogen atom, R ⁷ is one in which one of the hydrogen atoms of the phenyl group is substituted with a nonyl group, and X ¹ is a propylene glycol repeating unit (the propylene glycol repeating unit is about 5) .

Blemmer AAE series wherein R ⁵ is a hydrogen atom, R ⁷ is a phenyl group, and X ¹ is an ethylene glycol repeating unit (for example, ethylene glycol repeating unit is about 1 to 5.5).
Methacryloyloxyethyl phosphate (ethylene glycol repeating unit is 1), wherein R ⁵ is a hydrogen atom, R ⁷ is a phosphoric acid group, and X ¹ is an ethylene glycol repeating unit.
These compounds may be used individually by 1 type, and may use 2 or more types together.
These arbitrary monomers may be used individually by 1 type, and may use 2 or more types together.

  When the total of all the units constituting the polymer (II) is 100 mol%, the content of arbitrary units is preferably 0 to 50 mol%, and more preferably 0 to 30 mol%. If the content of the arbitrary unit is within the above range, the battery performance can be maintained satisfactorily.

(Production method)
The polymer (I) can be obtained by subjecting the monomer (a) and optionally an optional monomer to aqueous solution polymerization. The polymerization method is not particularly limited, and solution polymerization, suspension polymerization, emulsion polymerization, adiabatic polymerization, and the like can be selected according to the type of monomer used and the solubility of polymer (I) to be generated.
For example, when the monomer to be used is soluble in water and the produced polymer (I) also has sufficient affinity for water, aqueous solution polymerization can be used. The aqueous solution polymerization is a method of obtaining a polymer (I) by dissolving a monomer as a raw material and a water-soluble polymerization initiator in water and heating.
Moreover, when the solubility of the monomer used in water is small, suspension polymerization, emulsion polymerization, or the like can be used. Emulsion polymerization is a method for obtaining a polymer (I) by adding a monomer as a raw material, an emulsifier, a water-soluble polymerization initiator and the like to water and heating with stirring.
After the polymerization, the polymer (I) in powder form is obtained by filtering, centrifuging, heat drying, drying under reduced pressure, and combining these to remove water.

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 [N- (2-carboxyethyl) ) -2-methylpropionamidine] and the like.
In carrying out the polymerization, a chain transfer agent may 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, hypophosphite and the like.

Subsequently, hydrolysis of the polymer (I) to obtain the polymer (II) includes hydrolysis with an acid, hydrolysis with an alkali, and hydrolysis by applying heat. Among these, hydrolysis with alkali is preferable.
Examples of the alkali (base) used for hydrolysis with an alkali include metal hydroxides of metals of the first and second main groups of the periodic table. Specific examples include sodium hydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide.
As the alkali, ammonia and alkyl derivatives of ammonia, for example, amines such as alkylamine and allylamine are also suitable. Examples of such amines include triethylamine, monoethanolamine, diethanolamine, triethanolamine, morpholine, aniline and the like.
Among these, as the alkali, sodium hydroxide, lithium hydroxide, and potassium hydroxide are preferable.

When the hydrolysis is performed, the timing of adding the reducing agent is not particularly limited. However, it is preferable to add the reducing agent before the hydrolysis reaction is started, for example, before heating by adding an acid or an alkali.
Use of a relatively stable antigelling agent among the antigelling agents used in the present invention is advantageous because it can be stored for a long period of time as a composition. This composition can be easily handled, and since the blending ratio of the anti-gelling agent to the (co) polymer is almost constant depending on the type, the composition should be dissolved in an alkaline aqueous solution and subjected to hydrolysis. Can do. Therefore, it is possible to obtain the desired polyvinylamine solution by hydrolyzing the composition in-situ according to where and when the polyvinylamine is used, thus avoiding problems such as transportation and storage of highly viscous hydrolyzed solutions. It is also advantageous from the viewpoint of handling and economy.

  When polymer (II) is produced by hydrolyzing polymer (I), the content of structural unit (A) and structural unit (B) in polymer (II) controls the degree of hydrolysis progress. You can adjust it. The degree of progress of hydrolysis can be controlled by the amount of alkali added as described above.

  When the polymer (I) is hydrolyzed using an acid or alkali, the pH of the resulting reaction solution becomes acidic or alkaline, but if necessary, the reaction solution can be neutralized to give a neutral aqueous solution. Good. The reaction solution obtained by hydrolysis can be used as an aqueous solution of the polymer (II) as it is, but a powder obtained by removing water from the reaction solution may be used as the polymer (II).

Further, the peak top molecular weight (Mp) of the polymer (II) is preferably 100,000 to 10,000,000, and more preferably 300,000 to 3,000,000. When the mass average molecular weight is at least the above lower limit value, the stability of the binder resin in the electrolyte solution with respect to elution and swelling is further enhanced, and when it is at most the above upper limit value, the water solubility becomes better.
The mass average molecular weight of the polymer (II) can be measured using gel permeation chromatography (GPC). For example, the calculated molecular weight can be obtained using a solvent such as tetrahydrofuran or water as an eluent and pullulan as an internal standard sample.

<Other ingredients>
The binder resin of the present invention may be composed only of the polymer (II), but may contain other polymers than the polymer (II) as long as the effects of the present invention are not impaired. .
Examples of other polymers include polyacrylic acid and salts thereof, polyvinyl alcohol, polyacrylamide, and the like. These may be used alone or in combination of two or more.
The content of the polymer (II) in 100% by mass of the binder resin is preferably 50 to 100% by mass or more, and the content of the other polymer is preferably 0 to 50% by mass.

<Form>
Examples of the form of the binder resin include a powder form and a dope form dissolved or dispersed in a solvent such as water.

<Effect>
The binder resin of this invention demonstrated above contains the polymer obtained by hydrolyzing in the presence of a reducing agent with respect to the polymer which has a structural unit (A) which is an amide structural unit. Since the reducing agent is allowed to coexist during hydrolysis, the obtained solution is excellent in storage stability. And since it has a structural unit (B), it is excellent in binding property.

  Therefore, the battery provided with the electrode manufactured using the slurry for an electrode containing the binder resin of the present invention is excellent in battery performance. Moreover, the binder resin solution provided is excellent in storage stability.

  The binder resin of the present invention may be used as it is in an electrode slurry or as a binder resin composition for non-aqueous secondary battery electrodes. Hereinafter, an example of the binder resin composition for nonaqueous secondary battery electrodes will be described.

"Binder resin composition for non-aqueous secondary battery electrode"
The binder resin composition for nonaqueous secondary battery electrodes of the present invention (hereinafter referred to as “binder resin composition”) contains the binder resin of the present invention described above.
Examples of the form of the binder resin composition include a powder form and a dope form dissolved or dispersed in a solvent such as water. From the viewpoint of stability during storage and distribution, economy, and ease of handling, powder is preferable during storage and distribution.

  The content of the binder resin of the present invention in the powdery binder resin composition is preferably 50% by mass or more, more preferably 80% by mass or more, and may be 100% by mass. If it is more than the said lower limit, the effect of this invention will be exhibited notably.

  As long as the amount of the binder resin composition does not affect the battery performance, a binder resin other than the binder resin of the present invention (another binder resin), a viscosity modifier, a binding improver, and a dispersion, as necessary. You may contain additives, such as an agent.

  Examples of other binder resins include vinyl acetate copolymer, styrene-butadiene block copolymer (SBR), acrylic acid-modified SBR resin (SBR latex), and acrylic rubber latex.

  The viscosity modifier improves the coatability of the binder resin. 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 acrylate and vinyl alcohol copolymer, maleic anhydride, maleic acid or fumaric acid and vinyl alcohol copolymer, modified polyvinyl alcohol, modified polyacrylic acid, polyethylene glycol, polycarboxylic acid Can be mentioned.

Since additives such as a viscosity modifier eventually remain on the electrode, it is desirable not to add them as much as possible, but when they are added, it is preferable to use an additive having electrochemical stability.
When the binder resin composition contains an additive such as a viscosity modifier, the content is preferably 50% by mass or less when the binder resin composition is 100% by mass. However, the content of the additive is preferably as small as possible from the viewpoint of further improving battery performance.

  The binder resin composition can be produced by a known method. For example, powdered binder resin of the present invention and powdered additive as required, or powdered binder resin of the present invention and powdered additive as necessary It can be obtained by dispersing in a solvent.

  Since the binder resin composition of the present invention described above contains the binder resin of the present invention, it is water-soluble, and an electrode slurry having excellent binding properties and good dispersibility of electrode materials can be obtained.

"Slurry composition for non-aqueous secondary battery electrode"
The slurry composition for non-aqueous secondary battery electrodes of the present invention (hereinafter also referred to as “electrode slurry”) includes the binder resin of the present invention or the binder resin composition of the present invention, an active material, a solvent, It contains.

  Although content of the binder resin of this invention in the slurry for electrodes is not specifically limited, 0.01-10 mass% is preferable in the total solid (all components except a solvent) of the slurry for electrodes, 7 mass% is more preferable. If it is 0.01 mass% or more, the adhesiveness (binding property) of the mixture layer formed using the electrode slurry and the current collector is further enhanced. If it is 10 mass% or less, since an active material, the conductive support agent added as needed, etc. can be contained enough, battery performance will improve.

The active material used for the electrode slurry of the present invention is not particularly limited, and known materials can be used depending on the type of non-aqueous secondary battery used for the electrode manufactured using the electrode slurry.
For example, in the case of a lithium ion secondary battery, as the positive electrode active material (positive electrode active material), a material having a higher potential than the negative electrode active material (negative electrode active material) and capable of absorbing and desorbing lithium ions during charge and discharge is used.
Specific examples of the positive electrode active material include a lithium-containing metal composite oxide containing at least one metal selected from iron, cobalt, nickel, and manganese and lithium. These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together.
Examples of the negative electrode active material include carbon materials such as graphite, amorphous carbon, carbon fiber, coke, and activated carbon; and composites of the carbon materials with metals such as silicon, tin, and silver, or oxides thereof. It is done. These negative electrode active materials 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 as the positive electrode active material and graphite as the negative electrode active material. By setting it as such a combination, the voltage of a lithium ion secondary battery can be raised, for example to 4V or more.

  The content of the active material in the electrode slurry of the present invention is not particularly limited, but is preferably 80 to 99.9% by mass, and 85 to 99% by mass in the total solid content (all components excluding the solvent) of the electrode slurry. % Is more preferable. If it is 80 mass% or more, the function as a mixture layer will fully be exhibited. If it is 99.9 mass% or less, the adhesiveness of a mixture layer and a collector is favorable.

The electrode slurry of the present invention may contain a conductive additive. In particular, when a positive electrode is produced using an electrode slurry, the electrode slurry preferably contains a conductive additive. By containing the conductive auxiliary agent, the electrical contact between the active materials and between the active material and the metal fine particles can be improved, and the battery performance such as the discharge rate characteristic of the non-aqueous secondary battery can be further improved.
Examples of the conductive assistant include graphite, carbon black, and acetylene black. These conductive assistants may be used alone or in combination of two or more.

  Although content of the conductive support agent in the slurry for electrodes of the present invention is not particularly limited, 0.01 to 10% by mass is preferable in the total solid content (all components excluding the solvent) of the slurry for electrodes. -7 mass% is more preferable. If it is 0.01 mass% or more, battery performance will be improved more. If it is 10 mass% or less, the adhesiveness of a mixture layer and a collector is favorable.

Examples of the solvent contained in the electrode slurry of the present invention include water, a mixed solvent of water and an organic solvent, and the like.
The organic solvent is not particularly limited as long as it is a solvent that can uniformly dissolve or disperse the binder resin of the present invention and the binder resin composition of the present invention. For example, NMP, NMP and ester solvents (ethyl acetate, n-butyl acetate) , Butyl cellosolve acetate, butyl carbitol acetate, etc.), NMP and glyme solvents (diglyme, triglyme, tetraglyme, etc.). These organic solvents may be used individually by 1 type, and may use 2 or more types together.
However, since an organic solvent has a high environmental load, it is preferable to use water alone as the solvent.
Since the binder resin and the binder resin composition of the present invention are water-soluble, they can be easily dissolved or dispersed in water.

  The content of the solvent in 100% by mass of the electrode slurry of the present invention may be a minimum necessary amount that can maintain the dissolved or dispersed state of the binder resin of the present invention or the binder resin composition of the present invention at room temperature. However, in the slurry preparation step described later, since the viscosity of the electrode slurry is usually adjusted while adding a solvent, it is preferable to use an arbitrary amount that is not excessively diluted. Specifically, 10 to 70% by mass is preferable, and 20 to 60% by mass is more preferable.

  The slurry composition for electrodes of the present invention may contain optional components such as an antioxidant and a thickener as necessary.

The slurry for electrodes of the present invention can be produced by kneading the binder resin of the present invention or the binder resin composition of the present invention, an active material, a solvent, and optionally a conductive additive and optional components. Kneading can be performed by a known method.
At the time of slurry preparation, the binder resin of the present invention may be used in the form of a powder as it is, and before being mixed with an electrode material such as an active material or a conductive aid, it is dissolved in a solvent in advance and used as a resin solution. May be.

  The electrode slurry of the present invention described above contains the binder resin of the present invention or the binder resin composition of the present invention, so that the dispersibility of the electrode material is good, the uneven distribution of the electrode material is small, and the uniformity is excellent. An agent layer can be formed. The mixture layer is also excellent in binding properties with the current collector.

"Nonaqueous secondary battery electrodes"
An electrode for a non-aqueous secondary battery of the present invention (hereinafter also referred to as “electrode”) includes a current collector and a mixture layer provided on the current collector, and the mixture layer includes the above-described mixture layer. The electrode slurry of the present invention is applied to a current collector and dried. That is, the mixture layer contains the binder resin of the present invention or the binder resin composition of the present invention and the active material.

The current collector may be any material having conductivity, and a metal can be used as the material. Specifically, aluminum, copper, nickel or the like can be used.
The shape of the current collector can be determined according to the shape of the target battery, and examples thereof 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 electrode of the present invention can be produced using a known method. For example, the electrode slurry of the present invention is prepared (slurry preparation step), and the electrode slurry is applied to a current collector (coating). Step) and then drying to remove the solvent (drying step), rolling as necessary (rolling step), and forming a mixture layer on the current collector surface.
In addition, you may cut | disconnect the obtained electrode to arbitrary dimensions.

In the slurry preparation step, the binder resin of the present invention or the binder resin composition of the present invention, the active material, and, if necessary, additives such as a conductive additive are dispersed in a solvent to prepare an electrode slurry.
In the coating process, the electrode slurry is applied to the current collector. The coating method is not particularly limited as long as the electrode slurry can be applied to the current collector with an arbitrary thickness. For example, a doctor blade or a comma coater can be used. The coating amount can be appropriately set according to the thickness of the mixture layer to be formed.
In the drying step, the solvent is removed. As the drying method, it is sufficient if the solvent can be removed. Examples thereof include drying with warm air, hot air, low-humidity air, vacuum drying, and drying method by irradiation with (far) infrared rays or electron beams.
In the rolling process, the formed mixture layer is rolled. As a rolling method, it is sufficient if the mixture layer can be rolled to an arbitrary thickness, and examples thereof include a die press and a roll press.

20-200 micrometers is preferable and, as for the thickness of a mixture layer, 30-120 micrometers is more preferable.
Since the positive electrode (positive electrode) has a smaller active material capacity than the negative electrode (negative electrode), the positive electrode mixture layer is preferably thicker than the negative electrode mixture layer.

  In the electrode of the present invention described above, since the mixture layer containing the binder resin of the present invention or the binder resin composition of the present invention is formed on the current collector, the binding property of the mixture layer to the current collector Is expensive. Further, the mixture layer is uniformly distributed with little uneven distribution of the electrode material, and is excellent in battery performance.

  The electrode of the present invention can be used for either a positive electrode or a negative electrode of a non-aqueous secondary battery, and is particularly suitable as an electrode for a lithium ion secondary battery.

"Non-aqueous secondary battery"
The nonaqueous secondary battery of the present invention comprises the above-described electrode of the present invention.
The “non-aqueous secondary battery” uses a non-aqueous electrolyte solution that does not contain water as the electrolyte solution, and examples thereof include a lithium ion secondary battery. A nonaqueous secondary battery usually includes electrodes (a positive electrode and a negative electrode), a nonaqueous electrolytic solution, and a separator. As a non-aqueous secondary battery, a positive electrode and a negative electrode are arranged with a permeable separator (for example, a porous film made of polyethylene or polypropylene) interposed therebetween, and this is impregnated with a non-aqueous electrolyte solution. Water secondary battery: A laminate of a negative electrode / separator / positive electrode with a mixture layer formed on both sides of a current collector and a positive electrode / separator with a mixture layer formed on both sides of the current collector The cylindrical non-aqueous secondary battery etc. with which the winding body wound by (1) was accommodated in the battery can (bottomed metal casing) with the non-aqueous electrolyte solution are mentioned.

The non-aqueous electrolytic solution is a solution in which an electrolyte is dissolved in an organic solvent.
Examples of the organic solvent 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 ether , Ethers such as 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 and the like Nitrogens such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphate 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, And sultone such as naphtha sultone. These organic solvents may be used individually by 1 type, and may use 2 or more types together.

As the electrolyte, 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] 2 B and the like.
As the non-aqueous electrolyte, a solution in which LiPF ₆ is dissolved in carbonates is preferable, and the solution is particularly suitable as an electrolyte for a lithium ion secondary battery.

In the nonaqueous secondary battery of the present invention, the electrode of the present invention is used for one or both of the positive electrode and the negative electrode.
When either one of the positive electrode and the negative electrode is the electrode of the present invention, a known one can be used as the other electrode.

  A well-known thing can be used as a separator. For example, a porous polymer film produced from a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer is used alone. Or by laminating them. In addition, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber or the like can be used, but is not limited thereto.

The non-aqueous secondary battery of this invention can be manufactured using a well-known method. Below, an example of the manufacturing method of a lithium ion secondary battery is demonstrated.
First, the positive electrode and the negative electrode are wound spirally through a separator to obtain a wound body. The obtained wound body is inserted into a battery can, and a tab terminal previously welded to the current collector of the negative electrode is welded to the bottom of the battery can.
Next, a non-aqueous electrolyte is injected into the battery can, and a tab terminal previously welded to the current collector of the positive electrode is welded to the battery lid, and the lid is attached to the upper portion of the battery can via an insulating gasket. The lithium ion secondary battery is obtained by caulking and sealing the part where the lid and the battery can are in contact.
The shape of the non-aqueous secondary battery may be any of a coin shape, a cylindrical shape, a square shape, a flat shape, and the like.

  Since the non-aqueous secondary battery of the present invention described above includes the electrode of the present invention, the battery performance is excellent. The battery performance is excellent because the electrode material has good dispersibility and the mixture layer contains the binder resin of the present invention or the binder resin composition of the present invention, so that the mixture layer is bound to the current collector. This is because high battery performance can be maintained because the binder resin is not easily eluted into the electrolyte solution.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to the following examples.

"Manufacture of binder resin"
<Production Example 1>
100 parts by mass of deionized water was placed in a separable flask equipped with a thermometer, and nitrogen aeration was performed at room temperature for 1 hour. Subsequently, after raising the temperature to 70 ° C., 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] (Wako Pure Chemical Industries, Ltd., “VA-057”) 750 ppm (vs. Was added as a 5% by weight aqueous solution. Further, 10.0 parts by mass of N-vinylformamide as the monomer (a) was subjected to nitrogen explosion for 20 minutes and then dropped over 1 hour. Then, after 3 hours, “VA-057”) 5000 ppm and after 2 hours “VA-057”) 1500 ppm were added as 5 mass% aqueous solutions, respectively, and the mixture was further heated and stirred for 2 hours.
After dissolving 0.1 parts by mass of sodium nitrite in water, it was added to the reaction solution. Further, the internal temperature was raised to 75 ° C., 23.6 parts by mass of a 10% by mass aqueous lithium hydroxide solution was added, water was added to the reaction solution to form a 3% by mass aqueous solution, and the mixture was heated for 5 hours to add water. A decomposition reaction was performed. The reaction solution after the hydrolysis reaction was cooled to obtain an aqueous solution containing a polymer. This was designated as binder resin aqueous solution 1.
About the obtained binder resin aqueous solution 1, the content rate of the structural unit in a polymer and the peak top molecular weight (Mp) were measured with the following method. The results are shown in Table 1.

(Measurement of structural unit content)
First, the content rate of the structural unit (B) was measured by the colloid titration method shown below.
The aqueous binder resin solution was precisely weighed and collected in a measuring flask, and demineralized water was added thereto. Demineralized water was added to the sample collected from the volumetric flask with a whole pipette, and the pH was adjusted to 2.5 with a 1N hydrochloric acid solution while confirming with a pH meter. This was used as a test solution.
Toluidine blue was added to the obtained test solution, and titrated with an N / 400-polyvinyl potassium sulfate solution (manufactured by Wako Pure Chemical Industries, Ltd., “PVSK”). The point at which the test solution turned from blue to purple was defined as the end point. From the titration result, the content ratio of the structural unit (B) was determined.

(Measurement of molecular weight)
Measured using GPC. NaCl (0.1 M) / phosphate buffer (10 mM, pH 6) was used as a carrier, and the flow rate was 0.5 mL / min. The detector used RID. Further, two SHODEX SB-807HQs were connected in series as GPC columns. Pullulan (Showa Denko) was used as an internal standard.

<Production Example 2>
The same operation as in Production Example 1 was carried out except that the amount of sodium nithionite used was 0.2 parts by mass to obtain an aqueous solution containing a polymer. This was designated as binder resin aqueous solution 2.
About the obtained binder resin aqueous solution 2, it carried out similarly to manufacture example 1, and measured the content rate of the structural unit in a polymer. The results are shown in Table 1.

<Production Example 3>
The same operation as in Production Example 1 was performed except that the amount of sodium nithionite used was 0.3 parts by mass to obtain an aqueous solution containing a polymer. This was designated as binder resin aqueous solution 3.
About the obtained binder resin aqueous solution 3, it carried out similarly to manufacture example 1, and measured the content rate of the structural unit in a polymer. The results are shown in Table 1.

<Production Example 4>
Except having changed the usage-amount of sodium nithionite into 0.5 mass part, operation similar to manufacture example 1 was performed and the aqueous solution containing a polymer was obtained. This was designated as binder resin aqueous solution 4.
About the obtained binder resin aqueous solution 4, it carried out similarly to manufacture example 1, and measured the content rate of the structural unit in a polymer. The results are shown in Table 1.

<Production Example 5>
The same operation as in Production Example 1 was carried out except that sodium nithionite was not used to obtain an aqueous solution containing a polymer. This was designated as binder resin aqueous solution 5.
About the obtained binder resin aqueous solution 5, it carried out similarly to manufacture example 1, and measured the content rate of the structural unit in a polymer. The results are shown in Table 1.

"Example 1"
<Preparation of slurry for electrode>
2.5 g of binder resin aqueous solution 1 and 5 g of a natural graphite-based negative electrode active material (Mitsubishi Chemical Co., Ltd., “MPGC16”) were used with a revolving mixer (Thinky Co., Ltd., “Awatori Netaro”), Kneading was performed under the condition of revolution 2000 rpm. Then, the slurry for electrodes was obtained by adjusting to the viscosity which can be applied with water.

<Preparation of negative electrode>
The obtained slurry for electrodes was uniformly coated on a current collector (copper foil, thickness 20 μm) by a doctor blade method and dried at room temperature for 1 hour. Furthermore, it dried under reduced pressure at 0.6 kPa and 60 degreeC with the vacuum dryer for 12 hours, and the negative electrode with which the mixture layer (negative electrode layer) was formed on the electrical power collector (copper foil) was obtained.
About the obtained negative electrode, binding property was evaluated with the following method.
The results are shown in Table 1.

<Evaluation>
(Evaluation of binding properties)
The negative electrode was cut out to have a width of 30 mm square and used as a test piece. For the test piece, using a 1 mm wide borazon cutting edge (rake angle 20 °, bald angle 10 °, blade angle 60 °), initial pressing load 0.5 N, balance load 0.3 → 0.2 N, horizontal speed 1 μm 3 points were recorded for the maximum stress value when the borazon cutting edge moved on the interface between the mixture layer and the copper foil under the conditions of / sec, vertical velocity of 0.2 μm / sec, and initial contact load of 0.08 to 1N. The average value of the maximum stress values was defined as the peel strength between the mixture layer and the current collector. The larger this value, the stronger the mixture layer is bound to the current collector.

(Viscosity measurement)
The obtained reaction solution (adjusted to a solution concentration of 3%) was measured with a B-type viscometer (manufactured by TOKI SANGYO CO. LTD) (measurement temperature 30 ° C.). Further, it was stored at a temperature of 25 ° C.

"Examples 2 to 4, Comparative Example 1"
Except having changed the binder resin aqueous solution into the thing shown in Table 1, the slurry for electrodes was prepared like Example 1, and the negative electrode was produced and evaluated. The results are shown in Table 1.

As shown in the results of Table 1, when sodium reducing agent, a reducing agent, was added, the increase in viscosity was suppressed even after storage for 20 days or more at room temperature. On the other hand, in the case of Comparative Example 1 in which no reducing agent was added, a marked increase in viscosity was confirmed, which was not suitable for use.
Although the adhesiveness gradually decreased as the amount of the reducing agent used increased, the peel strength of 0.1 N / cm or more was shown in each example, indicating that the binding property was excellent.

Claims (5)

Nonaqueous secondary battery electrode binder which is polymer (II) obtained by hydrolyzing polymer (I) having a repeating structural unit represented by the following general formula (1) in the presence of a reducing agent resin.

(In formula (1), R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms.)   The binder resin for nonaqueous secondary battery electrodes according to claim 1, wherein the amount of the reducing agent used is 0.1 to 10 parts by mass with respect to 100 parts by mass of the polymer (I).   The electrode slurry containing the binder resin composition for non-aqueous secondary battery electrodes containing the binder resin for non-aqueous secondary battery electrodes of Claim 1 or 2, an active material, and a solvent. A current collector, and a mixture layer provided on the current collector,
The said mixture layer is an electrode for nonaqueous secondary batteries containing the binder resin composition for nonaqueous secondary battery electrodes containing the binder resin for nonaqueous secondary battery electrodes of Claim 1 or 2.   A nonaqueous secondary battery comprising the electrode for a nonaqueous secondary battery according to claim 4.