JP2012219125A - Vinylidene fluoride copolymer and use of the copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vinylidene fluoride copolymer excellent in adhesiveness with a base material such as metal, and to provide a binder for a battery electrode and a combined agent for a non-water electrolyte secondary battery containing the above copolymer, an electrode for a non-water electrolyte secondary battery obtained by using the above combined agent, and a non-water electrolyte secondary battery having the electrode.SOLUTION: The copolymer includes structural units expressed by general formulae a, b and c. In general formulae b and c, Rrepresents an organic group containing nitrogen and/or sulfur.

Description

  The present invention relates to a vinylidene fluoride-based copolymer and uses of the copolymer. Specifically, the present invention relates to a vinylidene fluoride copolymer, an electrode battery binder, a nonaqueous electrolyte secondary battery electrode mixture, a nonaqueous electrolyte secondary battery electrode, and a nonaqueous electrolyte secondary battery.

  Polyvinylidene fluoride (hereinafter also referred to as PVDF), which is a polymer of vinylidene fluoride (hereinafter also referred to as VDF), is excellent in chemical resistance, weather resistance, stain resistance, and the like. It is used as a material for manufacturing molded articles. PVDF is also used as a paint or a binder resin. However, PVDF has a low adhesive strength with a base material such as a metal, and thus it has been desired to improve the adhesive strength.

  Conventionally, various methods for improving the adhesion of PVDF have been proposed. Many of the conventionally proposed methods attempt to improve adhesion by introducing a carboxyl group into PVDF.

  As PVDF into which a carboxyl group is introduced, a carboxyl group-containing vinylidene fluoride copolymer obtained by copolymerizing VDF and maleic anhydride and hydrolyzing the acid anhydride (see, for example, Patent Document 1) In addition, a carboxyl group-containing vinylidene fluoride copolymer obtained by copolymerizing VDF and a monoester of an unsaturated dibasic acid such as maleic acid monomethyl ester (for example, see Patent Document 2) has been reported.

  However, even with these polymers, the adhesion to a substrate such as a metal has not been sufficient.

JP-A-2-604 Japanese Patent Laid-Open No. 6-172452

  The present invention has been made in view of the above-described problems of the prior art, and is a novel vinylidene fluoride that is more excellent in adhesion to a base material such as metal than PVDF having a conventionally known carboxyl group introduced. An object is to provide a copolymer.

  The present invention also includes a binder for a battery electrode and a mixture for a non-aqueous electrolyte secondary battery, the electrode for a non-aqueous electrolyte secondary battery obtained using the mixture, containing the vinylidene fluoride-based copolymer, It is another object of the present invention to provide a nonaqueous electrolyte secondary battery having the electrode.

  As a result of intensive research to achieve the above-mentioned problems, the present inventors have found that PVDF into which an organic group containing a heteroatom selected from nitrogen and sulfur is introduced has excellent adhesion to a substrate such as a metal. As a result, the present invention has been completed.

  That is, in the vinylidene fluoride copolymer of the present invention, the structural unit represented by the following general formula a is 80 to 99.95 mol%, the structural unit represented by the following general formula b is 0 to 19.99 mol%, and The structural unit represented by the general formula c is 0.01 to 20 mol% (provided that the total of the structural units represented by the general formulas a, b, and c is 100 mol%).

(In the general formula b, R _COOH is an organic group containing a carboxyl group, and R ¹ , R ² and R ³ are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or 5 alkyl groups,
In the general formula c, R _{N, S} is an organic group containing at least one heteroatom selected from nitrogen and sulfur, and R ⁴ , R ⁵ , R ⁶ are each independently a hydrogen atom, a halogen atom, It is a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms. )
In the general formula c, RN _{, S} is an organic group containing at least one group selected from amine, thioether, thiocarbonyl, and a heterocyclic ring, and the heterocyclic ring is at least selected from nitrogen and sulfur It is preferably a heterocycle containing a kind of heteroatom.

  The vinylidene fluoride copolymer of the present invention has a structural unit represented by the following general formula a of 80 to 99.95 mol%, and a structural unit represented by the following general formula b ′ of 0.05 to 20 mol% (provided that A carboxyl group-containing vinylidene fluoride copolymer (X) having a total of 100 mol% of the structural units represented by the general formulas a and b ′) and a carboxyl group or a derivative thereof to form a linking group It is preferably obtained by a linking group forming reaction with a compound having a group having at least one hetero atom selected from nitrogen and sulfur.

(In the general formula b ′, R _COOH is an organic group containing a carboxyl group,
In the general formula b ′, R ¹ , R ² and R ³ are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms. )
The vinylidene fluoride copolymer of the present invention preferably has an inherent viscosity of 0.5 to 5.0 dl / g.

The binder for battery electrodes of the present invention contains the vinylidene fluoride copolymer and a non-aqueous solvent.
The electrode mixture for a non-aqueous electrolyte secondary battery of the present invention contains the vinylidene fluoride copolymer, an electrode active material and a non-aqueous solvent, and the negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention is The vinylidene fluoride copolymer described above, a negative electrode active material, and a non-aqueous solvent are contained.

  The electrode for a nonaqueous electrolyte secondary battery of the present invention is obtained by applying and drying the electrode mixture for a nonaqueous electrolyte secondary battery described above on a current collector, and the nonaqueous electrolyte secondary battery of the present invention is obtained. The negative electrode for use is obtained by applying and drying the negative electrode mixture for a non-aqueous electrolyte secondary battery described above on a current collector.

  The non-aqueous electrolyte secondary battery of the present invention preferably includes the non-aqueous electrolyte secondary battery electrode and the non-aqueous electrolyte secondary battery negative electrode.

The vinylidene fluoride copolymer of the present invention is more excellent in adhesiveness to a substrate such as metal than PVDF having a carboxyl group introduced thereinto.
For this reason, the battery electrode binder and the nonaqueous electrolyte secondary battery electrode mixture of the present invention can produce the nonaqueous electrolyte secondary battery electrode and the nonaqueous electrolyte secondary battery with high productivity. And the electrode for nonaqueous electrolyte secondary batteries is excellent in the peeling strength of a mixture layer and a collector.

1 is a ¹ H NMR spectrum of a vinylidene fluoride copolymer (1) obtained in Example 1. 2 is a ¹ H NMR spectrum of a vinylidene fluoride copolymer (2) obtained in Example 2. 2 is a ¹ H NMR spectrum of a vinylidene fluoride copolymer (3) obtained in Example 3.

Next, the present invention will be specifically described.
[Vinylidene fluoride copolymer]
The vinylidene fluoride copolymer of the present invention has a structural unit represented by the following general formula a of 80 to 99.95 mol%, a structural unit represented by the following general formula b of 0 to 19.99 mol%, and the following general formula: The structural unit represented by c is 0.01 to 20 mol% (provided that the total of the structural units represented by the general formulas a, b and c is 100 mol%).

(In the general formula b, R _COOH is an organic group containing a carboxyl group, and R ¹ , R ² and R ³ are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or a carbon number of 1 to 5). An alkyl group of
In the general formula c, R _{N, S} is an organic group containing at least one heteroatom selected from nitrogen and sulfur, and R ⁴ , R ⁵ , R ⁶ are each independently a hydrogen atom, a halogen atom, It is a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms. )
The vinylidene fluoride copolymer of the present invention has a structural unit represented by the general formula a, that is, a structural unit derived from vinylidene fluoride and a structural unit represented by the general formula c. It is a polymer usually having a structural unit represented by b. Furthermore, you may have the structural unit derived from another monomer.

R _{COOH of the} structural unit represented by the general formula b is an organic group containing a carboxyl group, preferably a carboxyl group, a carboxyethyl ester group, a carboxypropyl ester group, a carboxymethyl group, a carboxyethyl group, a carboxypropyl group. More preferably a carboxyl group, a carboxyethyl ester group, or a carboxypropyl ester group. The R _COOH is preferably an organic group having a molecular weight of 500 or less.

R ¹ , R ² and R ³ of the structural unit represented by the general formula b are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms, Is a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, an ethyl group, a normal propyl group, a carboxyl group or a methyl ester group, more preferably a hydrogen atom, a fluorine atom, a chlorine atom or a methyl group.

  The structural unit represented by the general formula b is preferably a structural unit derived from a carboxyl group-containing monomer. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, monomethyl maleate, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, acryloyloxyethyl succinic acid, methacryloyloxyethyl succinic acid, and acryloyloxyethyl phthalic acid. Methacryloyloxyethyl phthalic acid, trifluoroacrylic acid, trifluoromethylacrylic acid and the like. In addition, as a carboxyl group-containing monomer, 1 type may be used individually, or 2 or more types may be used.

R _{N, S} included in the structural unit represented by the general formula c is an organic group containing at least one hetero atom selected from nitrogen and sulfur, preferably amine, thiol, thioether, thiocarbonyl, and hetero An organic group containing at least one group selected from a ring, more preferably an organic group containing at least one group selected from thioether, pyridine, thiophene, imidazole, and triazole. The _{RN, S} is preferably an organic group having a molecular weight of 500 or less.

The _{RN, S} is an organic group containing at least one heteroatom selected from nitrogen and sulfur. When the heteroatom is sterically protected by a bulky substituent, This is not preferable because the effects of the invention may not be obtained. Specifically, the cone angle of the substituent bonded to the hetero atom is preferably 180 degrees or less, and more preferably 160 degrees or less.

R ⁴ , R ⁵ and R ⁶ of the structural unit represented by the general formula c are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms, Is a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, an ethyl group, a normal propyl group, a carboxyl group or a methyl ester group, more preferably a hydrogen atom, a fluorine atom, a chlorine atom or a methyl group. In addition, when the vinylidene fluoride copolymer of the present invention is produced by the method 1 described later, R ⁴ , R ⁵ and R ⁶ which the structural unit represented by the general formula c has The same as R ¹ , R ² and R ^{3 of the} structural unit represented by the general formula b.

  The structural unit represented by the general formula c may be a structural unit derived from a monomer containing an organic group containing at least one heteroatom selected from nitrogen and sulfur. Compound having at least one heteroatom selected from nitrogen and sulfur, having a carboxyl group in a structural unit derived from a monomer and a group that forms a linking group by chemically reacting with the carboxyl group or a derivative thereof And are structural units obtained by a bonding group forming reaction. The bonding group forming reaction between the carboxyl group and the compound may be performed by a one-step reaction or a multi-step reaction. Examples of the linking group include ester (—COO—), carbonyl, alkyl, alkenyl, amide, ether and the like, and ester, carbonyl and amide are preferable, and ester is more preferable. Examples of the chemical reaction include esterification reaction, functional group substitution reaction, Wittig reaction, amidation reaction, and the like. Esterification reaction and amidation reaction are preferable, and esterification reaction is more preferable.

  The group that forms a bonding group by chemically reacting with the carboxyl group or derivative thereof is preferably a group that forms an ester by chemically reacting with the carboxyl group or derivative thereof, and is selected from a hydroxyl group, a chloro group, and a bromo group. And at least one kind of group is more preferred, and a hydroxyl group is particularly preferred.

  Specific examples of the compound having a group that forms a bonding group by chemically reacting with a carboxyl group or a derivative thereof and containing at least one heteroatom selected from nitrogen and sulfur include 3-hydroxypyridine, 2 -(2-thienyl) ethanol, 2- (methylthio) ethanol, 4-hydroxypyridine, allopurinol, 4-hydroxyindole, 4-hydroxyquinazoline, 2-hydroxybenzimidazole, hydroxyimidazole, etc., among others 3-hydroxypyridine 2- (2-thienyl) ethanol, 2- (methylthio) ethanol, 4-hydroxypyridine and hydroxyimidazole are preferred. These compounds are compounds having an ester group by chemically reacting with a carboxyl group or a derivative thereof, and containing at least one heteroatom selected from nitrogen and sulfur, and having a hydroxyl group. And a compound containing at least one heteroatom selected from nitrogen and sulfur.

As described above, the vinylidene fluoride copolymer of the present invention contains 80 to 99.95 mol% of the structural unit represented by the general formula a, 0 to 19.99 mol% of the structural unit represented by the general formula b, And 0.01 to 20 mol% of the structural unit represented by the general formula c (provided that the total of the structural units represented by the general formulas a, b and c is 100 mol%), preferably the general formula a The structural unit represented is 85 to 99.9 mol%, the structural unit represented by the general formula b is 0 to 14.99 mol%, and the structural unit represented by the general formula c is 0.01 to 15 mol%, and more Preferably, the structural unit represented by the general formula a is represented by 90 to 99.5 mol%, the structural unit represented by the general formula b is represented by 0 to 9.99 mol%, and the general formula c. A structural unit having 0.01~10mol%. It is preferable that the vinylidene fluoride copolymer of the present invention has each structural unit in the above-mentioned range because it can be provided with a functional group without impairing the excellent physical properties of polyvinylidene fluoride. The abundance of each structural unit can be determined by ¹ H NMR.

  Examples of the other monomer include a fluorine monomer copolymerizable with vinylidene fluoride or a hydrocarbon monomer such as ethylene and propylene, and a monomer copolymerizable with the carboxyl group-containing monomer. It is done. Examples of the monomer copolymerizable with the carboxyl group-containing monomer include methyl (meth) acrylate and alkyl (meth) acrylate represented by ethyl (meth) acrylate. In addition, the said other monomer may be used individually by 1 type, and may use 2 or more types.

  When the vinylidene fluoride copolymer of the present invention has a structural unit derived from the other monomer, if the structural unit derived from all monomers constituting the copolymer is 100 mol%, the other It is preferable to have 10 mol% or less of a structural unit derived from a monomer, and more preferable to have 0.01 to 10 mol%.

  The method for producing the vinylidene fluoride copolymer of the present invention is not particularly limited. For example, vinylidene fluoride, a carboxyl group-containing monomer that becomes a structural unit represented by the general formula b by polymerization, and necessary The carboxyl group-containing vinylidene fluoride copolymer (X) is produced by copolymerizing with the other monomer according to the above, and then the carboxyl group-containing vinylidene fluoride copolymer (X) and the carboxyl group Alternatively, by performing a bonding group forming reaction with a compound having a group that forms a bonding group by chemical reaction with a derivative thereof and containing at least one hetero atom selected from nitrogen and sulfur, A method for producing a vinylidene fluoride copolymer (Method 1), which is represented by the general formula c by polymerization with vinylidene fluoride. A monomer containing at least one heteroatom selected from nitrogen and sulfur as a constituent unit, a carboxyl group-containing monomer that becomes a constituent unit represented by the general formula b by polymerization, and, if necessary, A method of producing the vinylidene fluoride copolymer of the present invention by copolymerizing with the other monomer (Method 2), vinylidene fluoride, an epoxy group-containing monomer, and, if necessary, another monomer Is then used to produce an epoxy group-containing vinylidene fluoride copolymer, and then the epoxy group-containing vinylidene fluoride copolymer is chemically reacted with an epoxy group or a derivative thereof to form a bonding group. By modification with a compound having a group and containing at least one heteroatom selected from nitrogen and sulfur The method for producing a vinylidene fluoride copolymer of the present invention (Method 3) below.

Among these methods, the vinylidene fluoride copolymer of the present invention is preferably produced by Method 1 from the viewpoint of ease of synthesis.
The method 1 will be described in more detail. In the method 1, first, a vinylidene fluoride is copolymerized with a carboxyl group-containing monomer that becomes a structural unit represented by the general formula b by polymerization, and, if necessary, the other monomer to copolymerize the carboxyl group-containing fluorine. A vinylidene chloride copolymer (X) is produced. The carboxyl group-containing vinylidene fluoride copolymer (X) has a structural unit represented by the general formula a of 80 to 99.95 mol% and a structural unit represented by the following general formula b ′ of 0.05. ˜20 mol% (however, the total of the structural units represented by the general formulas a and b ′ is 100 mol%).

(In the general formula b ′, R _COOH is an organic group containing a carboxyl group,
In the general formula b ′, R ¹ , R ² and R ³ are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms. )
Incidentally, in the general formula b ', respectively ^{_{R COOH, R 1, R 2}} , R 3 are, in the formula b, is similar to ^{_{R COOH, R 1, R 2}} , R 3.

  As described above, the carboxyl group-containing vinylidene fluoride copolymer (X) contains 80 to 99.95 mol% of the structural unit represented by the general formula a and 0 of the structural unit represented by the general formula b ′. 0.05 to 20 mol% (provided that the total of structural units represented by general formulas a and b ′ is 100 mol%), preferably 85 to 99.9 mol% of structural units represented by general formula a, And the structural unit represented by the general formula b ′ is 0.01 to 15 mol%, more preferably the structural unit represented by the general formula a is 90 to 99.5 mol%, and the general formula b ′. It has 0.5-10 mol% of structural units. The carboxyl group-containing vinylidene fluoride copolymer (X) chemically reacts with the carboxyl group-containing vinylidene fluoride copolymer (X) and the carboxyl group or a derivative thereof when each structural unit is within the above range. A bonding group forming reaction with a compound having a group that forms a bonding group and containing at least one heteroatom selected from nitrogen and sulfur is made to be a suitable amount for exhibiting the effects of the present invention. Therefore, it is preferable.

  In addition, when the carboxyl group-containing vinylidene fluoride copolymer (X) is polymerized using the other monomer, the carboxyl group-containing vinylidene fluoride copolymer (X) is derived from the other monomer. A structural unit. When the constitutional unit derived from all monomers constituting the copolymer is 100 mol%, it is preferable to have 10 mol% or less of the constitutional unit derived from the other monomer, more preferably 0.01 to 10 mol%. preferable.

  A method for producing the carboxyl group-containing vinylidene fluoride copolymer (X) by copolymerization is not particularly limited, but is usually performed by a method such as suspension polymerization, emulsion polymerization, or solution polymerization. Aqueous suspension polymerization and emulsion polymerization are preferred from the standpoint of ease of post-treatment and the like, and aqueous suspension polymerization is particularly preferred.

  In suspension polymerization using water as a dispersion medium, all monomers used for the copolymerization of suspending agents such as methylcellulose, methoxylated methylcellulose, propoxylated methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, polyvinyl alcohol, polyethylene oxide, gelatin, etc. (Vinylidene fluoride and carboxyl group-containing monomer, other monomer copolymerized as necessary) 0.005 to 1.0 part by mass, preferably 0.01 to 0.4 part by mass with respect to 100 parts by mass Add in the range of.

  Polymerization initiators include diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, diisopropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, di (perfluoro) Acyl) peroxide, t-butyl peroxypivalate, and the like can be used. The amount used is 0.1 to 5 parts by mass, assuming that 100 parts by mass of all monomers used for copolymerization (vinylidene fluoride and carboxyl group-containing monomers, and other monomers copolymerized as necessary), Preferably it is 0.2-2 mass parts.

  In addition, a carboxyl group-containing vinylidene fluoride system obtained by adding a chain transfer agent such as ethyl acetate, methyl acetate, diethyl carbonate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate, carbon tetrachloride, etc. It is also possible to adjust the degree of polymerization of the copolymer (X). The amount used is usually 0.1 to 5 when 100 parts by mass of all monomers used for copolymerization (vinylidene fluoride and carboxyl group-containing monomers, and other monomers copolymerized as necessary) are used. Part by mass, preferably 0.5 to 3 parts by mass.

The total amount of monomers used for copolymerization (vinylidene fluoride and carboxyl group-containing monomers, and other monomers copolymerized as required) is usually the total monomer: water mass ratio. 1: 1 to 1:10, preferably 1: 2 to 1: 5. The polymerization temperature T is appropriately selected according to the 10-hour half-life temperature T ₁₀ of the polymerization initiator, and is usually selected in the range of T ₁₀ −25 ° C. ≦ T ≦ T ₁₀ + 25 ° C. For example, T ₁₀ for t-butyl peroxypivalate and diisopropyl peroxydicarbonate are 54.6 ° C. and 40.5 ° C., respectively. Therefore, in the polymerization using t-butylperoxypivalate and diisopropylperoxydicarbonate as polymerization initiators, the polymerization temperatures T are 29.6 ° C. ≦ T ≦ 79.6 ° C. and 15.5 ° C. ≦ T ≦ 65. It is appropriately selected within the range of 5 ° C. The polymerization time is not particularly limited, but is preferably 100 hours or less in consideration of productivity and the like. The pressure at the time of superposition | polymerization is normally performed under pressurization, Preferably it is 2.0-8.0 MPa-G.

  By performing aqueous suspension polymerization under the above conditions, it is possible to easily copolymerize vinylidene fluoride, a carboxyl group-containing monomer, and other monomers that are copolymerized as required. A vinylidene copolymer (X) can be obtained.

  The inherent viscosity of the resulting carboxyl group-containing vinylidene fluoride copolymer (X) is preferably 0.5 to 5.0 dl / g, more preferably 0.8 to 4.0 dl / g. The inherent viscosity of the carboxyl group-containing vinylidene fluoride copolymer (X) can be measured by the same method as the inherent viscosity of the vinylidene fluoride copolymer of the present invention.

  In the method 1, the carboxyl group-containing vinylidene fluoride copolymer (X) has a group that forms a bonding group by chemically reacting with the carboxyl group or a derivative thereof, and is selected from nitrogen and sulfur The vinylidene fluoride copolymer of the present invention is obtained by performing a bonding group forming reaction with a compound containing at least one heteroatom. The bonding group forming reaction may be performed by a one-step reaction or a multi-step reaction. Examples of the linking group forming reaction include esterification reaction, functional group substitution reaction, Wittig reaction, amidation reaction, and the like. Esterification reaction and amidation reaction are preferable, and esterification reaction is more preferable.

  When the vinylidene fluoride copolymer of the present invention is obtained by an esterification reaction, it has a group that forms a bonding group by chemically reacting with a carboxyl group or a derivative thereof, and at least selected from nitrogen and sulfur As a compound containing one kind of heteroatom, a compound having a group that forms an ester by chemically reacting with a carboxyl group or a derivative thereof, and containing at least one kind of heteroatom selected from nitrogen and sulfur, It is preferable to use a compound having a hydroxyl group and containing at least one heteroatom selected from nitrogen and sulfur.

  The esterification reaction may be performed by a one-stage reaction or a multi-stage reaction. In the esterification reaction, for example, the carboxyl group-containing vinylidene fluoride copolymer (X) is reacted with thionyl chloride in an organic solvent such as N-methylpyrrolidone, and at least a part of the carboxyl group is converted into an acid chloride group. This is carried out by obtaining a reaction product converted into the following, and then reacting the reaction product with a compound having a hydroxyl group and containing at least one heteroatom selected from nitrogen and sulfur.

  The organic solvent may be any solvent that dissolves the carboxyl group-containing vinylidene fluoride copolymer (X) and does not inhibit the desired esterification reaction. For example, N-methylpyrrolidone, N, N- Examples include dimethylformamide and dimethyl sulfoxide.

  In the method 1, at least a part of the carboxyl group of the carboxyl group-containing vinylidene fluoride copolymer (X) has a group that forms a bonding group by chemically reacting with the carboxyl group or a derivative thereof. And a compound containing at least one heteroatom selected from nitrogen and sulfur is bonded to form a structural unit represented by the general formula c.

  The amount of the compound having a group that forms a bonding group by chemically reacting with a carboxyl group or a derivative thereof used in the bonding group formation reaction and that contains at least one heteroatom selected from nitrogen and sulfur is obtained as follows. As described above, the vinylidene fluoride copolymer is 80 to 99.95 mol% of the structural unit represented by the general formula a, 0 to 19.99 mol% of the structural unit represented by the general formula b, and The amount is appropriately adjusted so that the structural unit represented by the general formula c is 0.01 to 20 mol% (provided that the total of the structural units represented by the general formulas a, b, and c is 100 mol%).

  Specific examples of the bonding group forming reaction in Method 1 other than the esterification reaction include an amidation reaction. In this case, a compound having a hydroxyl group and containing at least one heteroatom selected from nitrogen and sulfur is a compound having an amino group and containing at least one heteroatom selected from nitrogen and sulfur Except for changing to, it can be carried out in the same manner as in the esterification reaction.

  The method 2 will be described. 80 to 99.95 mol% of vinylidene fluoride, 0 to 19.99 mol% of a carboxyl group-containing monomer that becomes a structural unit represented by the general formula b by the polymerization, and the general formula c by the polymerization 0.01 to 20 mol% of a monomer containing at least one hetero atom selected from nitrogen and sulfur as a structural unit (provided that the total of the structural units represented by the general formulas a, b and c is 100 mol%) It is carried out by mixing and copolymerizing in the ratio of having. The copolymerization can be performed by the same method as that for the carboxyl group-containing vinylidene fluoride copolymer (X).

  The method 3 will be described. First, an epoxy group-containing vinylidene fluoride copolymer is produced in the same manner as the carboxyl group-containing vinylidene fluoride copolymer (X) of Method 1 except that the carboxyl group-containing monomer is changed to an epoxy group-containing monomer. Get. Then, an epoxy group-containing vinylidene fluoride copolymer and a compound having a group that forms a bonding group by chemically reacting with the epoxy group and containing at least one heteroatom selected from nitrogen and sulfur This is done by reacting. Examples of the group that forms a bonding group by chemically reacting with an epoxy group include a hydroxyl group.

  The vinylidene fluoride copolymer of the present invention has an inherent viscosity (logarithmic viscosity at 30 ° C. of a solution obtained by dissolving 4 g of resin in 1 liter of N, N-dimethylformamide. The same applies hereinafter). A value within the range of 0 dl / g is preferred, and a value within the range of 1.0 to 4.0 dl / g is more preferred. If it is a viscosity within the said range, it can be conveniently used for the electrode mixture for nonaqueous electrolyte secondary batteries.

The inherent viscosity η _i can be calculated by dissolving 80 mg of vinylidene fluoride copolymer in 20 ml of N, N-dimethylformamide and using an Ubbelote viscometer in a constant temperature bath at 30 ° C. .

η _i = (1 / C) · ln (η / η ₀ )
Here, η is the viscosity of the polymer solution, η ₀ is the viscosity of N, N-dimethylformamide alone as the solvent, and C is 0.4 g / dl.

[Binder for battery electrode]
The binder for battery electrodes of the present invention contains the vinylidene fluoride copolymer of the present invention and a nonaqueous solvent.

  The binder for battery electrodes of the present invention contains a vinylidene fluoride copolymer and a non-aqueous solvent as described above, and by adding an electrode active material to the binder, it is for a non-aqueous electrolyte secondary battery described later. An electrode mixture can be obtained. In addition, when an electrode active material is added to the binder, the electrode active material may be added to the binder as it is, or the electrode active material may be added to a non-aqueous solvent and mixed with stirring to the binder. Good.

(Non-aqueous solvent)
The binder for battery electrodes of the present invention contains a non-aqueous solvent. As the non-aqueous solvent, those having an action of dissolving the vinylidene fluoride copolymer are used, and preferably a solvent having polarity is used. Specific examples of the non-aqueous solvent include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoamide, dioxane, tetrahydrofuran, tetramethylurea, triethylphosphine. Examples thereof include fate and trimethyl phosphate, and N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, and dimethyl sulfoxide are preferable. Moreover, a non-aqueous solvent may be single 1 type, or may mix 2 or more types.

  In the battery electrode binder of the present invention, when the vinylidene fluoride copolymer is 100 parts by mass, the non-aqueous solvent is preferably 400 to 10000 parts by mass, and more preferably 600 to 5000 parts by mass. Within the above range, an appropriate solution viscosity is obtained and the handling property is excellent, which is preferable.

[Electrode mixture for non-aqueous electrolyte secondary battery]
The electrode mixture for nonaqueous electrolyte secondary batteries of the present invention contains the vinylidene fluoride copolymer of the present invention, an electrode active material, and a nonaqueous solvent. The negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention usually contains the vinylidene fluoride copolymer of the present invention, a negative electrode active material, and a non-aqueous solvent. Since the electrode mixture for a non-aqueous electrolyte secondary battery of the present invention contains the vinylidene fluoride copolymer, the electrode mixture for a non-aqueous electrolyte secondary battery obtained by applying and drying the mixture on a current collector The electrode is superior in adhesion between the current collector and the mixture layer.

  The electrode mixture for a non-aqueous electrolyte secondary battery of the present invention may be used as a negative electrode mixture, that is, a negative electrode mixture for a non-aqueous electrolyte secondary battery, by changing the type of the electrode active material, etc. You may use it as a mixture for positive electrodes, ie, a positive electrode mixture for nonaqueous electrolyte secondary batteries. In the vinylidene fluoride polymer, since the organic group having a hetero atom such as nitrogen or sulfur may be oxidized and deteriorated on the positive electrode, the electrode mixture for a non-aqueous electrolyte secondary battery of the present invention is a negative electrode. It is more preferable to use it as a combination material.

(Electrode active material)
The electrode active material included in the electrode mixture for a nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and conventionally known electrode active materials for negative electrodes (hereinafter also referred to as negative electrode active materials), active materials for positive electrodes. A substance (hereinafter also referred to as a positive electrode active material) can be used.

Examples of the negative electrode active material include carbon materials, metal / alloy materials, metal oxides, and the like. Among these, carbon materials are preferable.
As the carbon material, artificial graphite, natural graphite, non-graphitizable carbon, graphitizable carbon and the like are used. Moreover, the said carbon material may be used individually by 1 type, or may use 2 or more types.

When such a carbon material is used, the energy density of the battery can be increased.
The artificial graphite can be obtained, for example, by carbonizing an organic material, heat-treating it at a high temperature, pulverizing and classifying it. As the artificial graphite, MAG series (manufactured by Hitachi Chemical Co., Ltd.), MCMB (manufactured by Osaka Gas) and the like are used.

  The non-graphitizable carbon can be obtained, for example, by firing a material derived from petroleum pitch at 1000 to 1500 ° C. As the non-graphitizable carbon, Carbotron P (manufactured by Kureha) or the like is used.

The specific surface area of the negative active material is preferably 0.3~10m ² / g, more preferably 0.6~6m ² / g. If the specific surface area exceeds 10 m ² / g, the amount of decomposition of the electrolytic solution increases and the initial irreversible capacity increases, which is not preferable.

As the positive electrode active material, a lithium-based positive electrode active material containing at least lithium is preferable. The lithium-based positive active material for _{example, LiCoO 2, LiNi x Co 1} -x O 2 (0 ≦ x ≦ 1) Formula Limy ₂ (M such is, Co, Ni, Fe, Mn , Cr, V-like At least one kind of transition metal: Y is a chalcogen element such as O and S), a composite metal oxide having a spinel structure such as LiMn ₂ O ₄ , and an olivine-type lithium compound such as LiFePO ₄ It is done. In addition, you may use a commercial item as said positive electrode active material.

The specific surface area of the positive electrode active material is preferably 0.05~50m ² / g, more preferably 0.1~30m ² / g.
The specific surface area of the electrode active material can be determined by a nitrogen adsorption method.

(Non-aqueous solvent)
The electrode mixture for nonaqueous electrolyte secondary batteries of the present invention contains a nonaqueous solvent. As the non-aqueous solvent, those exemplified as the non-aqueous solvent contained in the battery electrode binder can be used. Moreover, a non-aqueous solvent may be single 1 type, or may mix 2 or more types.

The electrode mixture for a nonaqueous electrolyte secondary battery of the present invention contains the vinylidene fluoride copolymer, an electrode active material, and a nonaqueous solvent.
The electrode mixture for non-aqueous electrolyte secondary batteries of the present invention is 0.5 to 15 parts by mass of vinylidene fluoride copolymer per 100 parts by mass in total of the vinylidene fluoride copolymer and the electrode active material. It is preferable that it is 1-10 mass parts, and it is preferable that an active material is 85-99.5 mass parts, and it is more preferable that it is 90-99 mass parts. Further, when the total of the vinylidene fluoride copolymer and the electrode active material is 100 parts by mass, the non-aqueous solvent is preferably 20 to 300 parts by mass, and more preferably 50 to 200 parts by mass. .

  When each component is contained within the above range, it is possible to produce a non-aqueous electrolyte secondary battery electrode with high productivity using the non-aqueous electrolyte secondary battery electrode mixture of the present invention. When the secondary battery electrode is manufactured, the peel strength between the mixture layer and the current collector is excellent.

  Moreover, the electrode mixture for nonaqueous electrolyte secondary batteries of this invention may contain other components other than the said vinylidene fluoride type copolymer, an electrode active material, and a nonaqueous solvent. Other components may include a conductive aid such as carbon black, a pigment dispersant such as polyvinylpyrrolidone, an adhesion aid such as polyacrylic acid and polymethacrylic acid, and the like. As said other component, polymers other than the said vinylidene fluoride type copolymer may be included. Examples of the other polymer include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, and vinylidene fluoride. -Vinylidene fluoride polymers such as perfluoromethyl vinyl ether copolymer may be mentioned. When the non-aqueous electrolyte secondary battery electrode mixture of the present invention contains another polymer, it is usually contained in an amount of 25 parts by mass or less with respect to 100 parts by mass of the vinylidene fluoride copolymer. .

The viscosity of the electrode mixture for a nonaqueous electrolyte secondary battery of the present invention when measured at 25 ° C. and a shear rate of 2 s ⁻¹ using an E-type viscometer is usually 2000 to 50000 mPa · s, Preferably it is 5000-30000 mPa * s.

  As a method for producing the electrode mixture for a non-aqueous electrolyte secondary battery of the present invention, the vinylidene fluoride copolymer, the electrode active material, and the non-aqueous solvent may be mixed in a uniform slurry. The order in performing is not particularly limited. For example, the vinylidene fluoride copolymer is dissolved in a part of a non-aqueous solvent to obtain a binder solution, and the electrode active material and the remaining non-aqueous solvent are added to the binder solution. And stirring and mixing to obtain an electrode mixture for a non-aqueous electrolyte secondary battery.

[Electrode for non-aqueous electrolyte secondary battery]
The electrode for nonaqueous electrolyte secondary batteries of the present invention can be obtained by applying and drying the electrode mixture for nonaqueous electrolyte secondary batteries on a current collector. The electrode for nonaqueous electrolyte secondary batteries of the present invention has a current collector and a layer formed from an electrode mixture for nonaqueous electrolyte secondary batteries. When the non-aqueous electrolyte secondary battery negative electrode mixture is used as the non-aqueous electrolyte secondary battery negative electrode mixture, a non-aqueous electrolyte secondary battery negative electrode is obtained, and the non-aqueous electrolyte secondary electrode is obtained. When the positive electrode mixture for nonaqueous electrolyte secondary batteries is used as the electrode mixture for secondary batteries, a positive electrode for nonaqueous electrolyte secondary batteries is obtained. In the vinylidene fluoride polymer, an organic group having a heteroatom such as nitrogen or sulfur may be oxidized and deteriorated on the positive electrode. Therefore, the electrode for a nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary electrode. More preferably, it is used as a negative electrode for a secondary battery.

In addition, in this invention, the layer formed from the electrode mixture for nonaqueous electrolyte secondary batteries formed by apply | coating and drying the electrode mixture for nonaqueous electrolyte secondary batteries to a collector is used as a mixture. Marked as layer.
The current collector used in the present invention includes, for example, copper in order to obtain a negative electrode for a non-aqueous electrolyte secondary battery, and examples of the shape include a metal foil and a metal net. In order to obtain a negative electrode for a non-aqueous electrolyte secondary battery, it is preferable to use a copper foil as the current collector.

  The current collector used in the present invention includes, for example, aluminum in order to obtain a positive electrode for a non-aqueous electrolyte secondary battery, and examples of the shape thereof include a metal foil and a metal net. In order to obtain a positive electrode for a non-aqueous electrolyte secondary battery, it is preferable to use an aluminum foil as the current collector.

The thickness of the current collector is usually 5 to 100 μm, preferably 5 to 20 μm.
The thickness of the mixture layer is usually 20 to 250 μm, preferably 20 to 150 μm. Moreover, the fabric weight of a mixture layer is 20-700 g / m < ² > normally, Preferably it is 30-500 g / m < ² >.

  When manufacturing the electrode for nonaqueous electrolyte secondary batteries of the present invention, the electrode mixture for nonaqueous electrolyte secondary batteries is applied to at least one surface, preferably both surfaces of the current collector. The method for coating is not particularly limited, and examples thereof include a method using a bar coater, a die coater, or a comma coater.

  Moreover, as drying performed after apply | coating, it is normally performed for 1 to 300 minutes at the temperature of 50-150 degreeC. Moreover, the pressure at the time of drying is not particularly limited, but it is usually carried out under atmospheric pressure or reduced pressure.

  Further, heat treatment may be performed after drying. When performing heat processing, it is normally performed for 1 to 300 minutes at the temperature of 100-250 degreeC. In addition, although the temperature of heat processing overlaps with the said drying, these processes may be a separate process and the process performed continuously.

Further, press processing may be performed. When performing a press process, it is normally performed by 1-200MP-G. It is preferable to perform the press treatment because the electrode density can be improved.
By the above method, the electrode for nonaqueous electrolyte secondary batteries of this invention can be manufactured. In addition, as a layer configuration of the electrode for the nonaqueous electrolyte secondary battery, when the electrode mixture for the nonaqueous electrolyte secondary battery is applied to one surface of the current collector, the two-layer configuration of the mixture layer / current collector When the electrode mixture for non-aqueous electrolyte secondary batteries is applied to both sides of the current collector, it has a three-layer structure of mixture layer / current collector / mixture layer.

  The electrode for a non-aqueous electrolyte secondary battery of the present invention is excellent in peel strength between the current collector and the mixture layer by using the electrode mixture for a non-aqueous electrolyte secondary battery. It is preferable because the electrode is less likely to be cracked or peeled off in the process, etc., leading to improvement in productivity.

  The electrode for a non-aqueous electrolyte secondary battery of the present invention is excellent in the peel strength between the current collector and the mixture layer as described above. Specifically, instead of the vinylidene fluoride copolymer of the present invention, When compared with an electrode obtained using a conventionally known carboxyl group-containing vinylidene fluoride copolymer, the peel strength measured by a 180 degree peel test in accordance with JIS K6854 is usually It is 4.5 times or more, preferably 5 times or more, more preferably 5.5 times or more. Moreover, it is 30 times or less normally.

[Nonaqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention is characterized by having the non-aqueous electrolyte secondary battery electrode.

  The nonaqueous electrolyte secondary battery of the present invention is not particularly limited except that the nonaqueous electrolyte secondary battery has the electrode for nonaqueous electrolyte secondary batteries. As the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery electrode, preferably the non-aqueous electrolyte secondary battery negative electrode, members other than the non-aqueous electrolyte secondary battery electrode, for example, separators, etc. A conventionally well-known thing can be used.

EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these.
[Comparative Example 1]
(Production of carboxyl group-containing vinylidene fluoride copolymer (X1))
In an autoclave with an internal volume of 2 liters, 900 g of ion-exchanged water, 0.4 g of Metroze 90SH-100, 0.2 g of carboxyethyl acrylate (hereinafter also referred to as CEA), 50 wt% t-butyl peroxypivalate-Freon 2 g of a 225cb solution and 396 g of vinylidene fluoride were charged, and the temperature was raised to 50 ° C. over 2 hours.

Thereafter, the temperature was maintained at 50 ° C., and a 30 g / l CEA aqueous solution was gradually added at a rate at which the polymerization pressure became constant. CEA was added in a total amount of 5.92 g, including the amount added initially.
The polymerization was stopped simultaneously with the completion of the addition of the CEA aqueous solution, and was carried out for a total of 13.1 hours from the start of the temperature increase.

  After the polymerization, the polymer slurry was heat treated at 95 ° C. for 60 minutes, dehydrated, washed with water, and further dried at 80 ° C. for 20 hours to obtain a polymer powder (carboxyl group-containing vinylidene fluoride copolymer (X1)). Obtained. The polymerization rate was 25%, and the inherent viscosity of the obtained carboxyl group-containing vinylidene fluoride copolymer (X1) was 2.65 dl / g.

As a result of calculating the composition ratio of the carboxyl group-containing vinylidene fluoride copolymer (X1) from the ¹ H NMR spectrum, the molar ratio was VDF / CEA = 97.28 / 2.72.
The ¹ H NMR spectrum of the carboxyl group-containing vinylidene fluoride copolymer (X1) was determined under the following conditions.

Apparatus: Bruker AVANCE AC 400FT NMR spectrum meter Measurement conditions Frequency: 400 MHz
Measuring solvent: DMSO-d ₆
Measurement temperature: 25 ° C
The amount of structural units derived from the vinylidene fluoride of the polymer and the amount of structural units derived from carboxyethyl acrylate was determined mainly by the signal observed at 4.19 ppm mainly derived from carboxyethyl acrylate in the ¹ H NMR spectrum. Calculation was based on the integrated intensity of signals observed at 2.24 ppm and 2.87 ppm derived from vinylidene fluoride.

The melting point (Tm) of the carboxyl group-containing vinylidene fluoride copolymer (X1) was 163 ° C.
The melting point (Tm) of the carboxyl group-containing vinylidene fluoride copolymer (X1) was measured by differential scanning calorimetry (DSC). The DSC measurement sample was prepared by preheating the carboxyl group-containing vinylidene fluoride copolymer (X1) at 210 ° C. for 30 seconds using a press molding machine (AYSR-5, manufactured by Shinfuji Metal Industry Co., Ltd.), and then pressing pressure. A press sheet was prepared by holding at 0.5 MPa for 1 minute, and about 10 mg was cut out from the press sheet. DSC was measured under the following conditions, and Tm was determined from the endothermic peak temperature in the temperature rising process.

Device; DSC30 manufactured by METTTLER
Sample holder; Aluminum standard 40 μl
Measurement temperature range; 30-220 ° C
Temperature rising rate: 10 ° C / min
Nitrogen flow rate: 50 ml / min
(Measurement of peel strength)
94 parts by mass of artificial graphite (“MAG-D20” manufactured by Hitachi Chemical Co., Ltd.) and 6 parts by mass of the carboxyl group-containing vinylidene fluoride copolymer (X1) are combined with N-methylpyrrolidone (hereinafter also referred to as NMP). An electrode slurry having a solid content concentration of 41% by mass was prepared by dispersing in the solution.

The electrode slurry was applied onto a Cu foil having a thickness of 10 μm with a bar coater and dried at 110 ° C. for 30 minutes to produce a single-side coated electrode having a single-sided weight of 150 g / m ² .
The single-side coated electrode having a weight per side of 150 g / m ² was cut into a length of 50 mm and a width of 20 mm, and plane-pressed at room temperature and a press pressure of 0.8 t / cm ² to obtain a test piece.

  Gum tape is applied to the coated electrode surface of the test piece, Cu foil is used as a “flexible adherend”, and a tensile tester (“STA-1150 UNIVERSAL TESTING MACHINE” manufactured by ORIENTEC) is used according to JIS K-6854. Then, a 180 ° peel test was performed at a head speed of 200 mm / min, and the peel strength was measured.

[Example 1]
(Production of vinylidene fluoride copolymer (1))
To a 500 ml three-necked flask equipped with a Dimroth condenser, dropping funnel, and magnetic stirrer, 10.1 g of the carboxyl group-containing vinylidene fluoride copolymer (X1) prepared in Comparative Example 1 and 150 ml of N-methylpyrrolidone ( NMP) was added and dissolved.

To the resulting solution, 5.30 g (0.0445 mol) of thionyl chloride was added dropwise at room temperature, and after completion of the addition, the mixture was heated and stirred at 80 ° C. for 1.5 hours.
After completion of the heating and stirring, the mixture was allowed to cool to room temperature, 4.34 g (0.0456 mol) of 3-hydroxypyridine was added, and the mixture was further heated and stirred at 90 ° C. for 1.5 hours.

After completion of heating and stirring, the polymer was recovered by a reprecipitation operation using a water / methanol mixed solvent as a poor solvent.
The inherent viscosity of the obtained vinylidene fluoride copolymer (1) was 2.07 dl / g.

From the ¹ H NMR spectrum measured under the same conditions as in Comparative Example 1, 45 mol% of the carboxyl groups in the carboxyl group-containing vinylidene fluoride copolymer (X1) prepared in Comparative Example 1 was esterified. Confirmed that. The ¹ H NMR spectrum of the vinylidene fluoride copolymer (1) is shown in FIG. Confirmation of the esterification rate is confirmed by the integrated intensity of the peak derived from two hydrogen atoms of the pyridine ring observed at around 7.5 ppm and -C (O) O observed at around 4.2 ppm. It was calculated from the integrated intensity 1.66 of the peak derived from methylene having a —CH ₂ — structure.

Further, when the melting point (Tm) of the vinylidene fluoride copolymer (1) was measured by the same method as in Comparative Example 1, Tm was 164 ° C.
(Measurement of peel strength)
Peel strength was measured in the same manner as in Comparative Example 1 except that the carboxyl group-containing vinylidene fluoride copolymer (X1) was replaced with the vinylidene fluoride copolymer (1).

[Example 2]
(Production of vinylidene fluoride copolymer (2))
The compound was synthesized in the same manner as in Example 1 except that 3-hydroxypyridine in Example 1 was changed to 2- (2-thienyl) ethanol.

The inherent viscosity of the obtained vinylidene fluoride copolymer (2) was 2.11 dl / g.
From the ¹ H NMR spectrum measured under the same conditions as in Comparative Example 1, 74 mol% of the carboxyl groups in the carboxyl group-containing vinylidene fluoride copolymer (X1) prepared in Comparative Example 1 was esterified. Confirmed that. The ¹ H NMR spectrum of the vinylidene fluoride copolymer (2) is shown in FIG. Confirmation of the esterification rate is observed in the integrated intensity of 1.84 peak derived from three hydrogen atoms of the thiophene ring observed in the vicinity of 6.5 to 7.5 ppm and in the vicinity of 4.2 ppm. (O) It was calculated from the integrated intensity 2.89 of the peak derived from methylene having an O—CH ₂ — structure.

Moreover, when the melting point (Tm) of the vinylidene fluoride copolymer (2) was measured by the same method as in Comparative Example 1, Tm was 164 ° C.
(Measurement of peel strength)
Peel strength was measured in the same manner as in Comparative Example 1 except that the carboxyl group-containing vinylidene fluoride copolymer (X1) was replaced with the vinylidene fluoride copolymer (2).

Example 3
(Production of vinylidene fluoride copolymer (3))
The compound was synthesized in the same manner as in Example 1 except that 3-hydroxypyridine of Example 1 was changed to 2- (methylthio) ethanol.

The inherent viscosity of the obtained vinylidene fluoride copolymer (3) was 2.04 dl / g.
Further, from the ¹ H NMR spectrum measured under the same conditions as in Comparative Example 1, 79 mol% of the carboxyl groups in the carboxyl group-containing vinylidene fluoride copolymer (X1) prepared in Comparative Example 1 was esterified. Confirmed that. The ¹ H NMR spectrum of the vinylidene fluoride copolymer (3) is shown in FIG. The confirmation of the esterification rate is confirmed by the integrated intensity of 1.88 peak derived from the methyl group of the —S—CH ₃ structure observed near 2.1 ppm and the —C (O ) Calculated from the integrated intensity 2.84 of the peak derived from methylene having an O—CH ₂ — structure.

Further, when the melting point (Tm) of the vinylidene fluoride copolymer (3) was measured by the same method as in Comparative Example 1, Tm was 164 ° C.
(Measurement of peel strength)
Peel strength was measured in the same manner as in Comparative Example 1 except that the carboxyl group-containing vinylidene fluoride copolymer (X1) was replaced with the vinylidene fluoride copolymer (3).

[Comparative Example 2]
(Measurement of peel strength)
When preparing the electrode slurry, 3-hydroxypyridine in an amount of 45 mol% was further used when the carboxyl group contained in the carboxyl group-containing vinylidene fluoride copolymer (X1) was 100 mol%. Except for this, an electrode slurry was prepared in the same manner as in Comparative Example 1.

The peel strength was measured in the same manner as in Comparative Example 1 except that the electrode slurry was used.
[Comparative Example 3]
(Measurement of peel strength)
When preparing the electrode slurry, 2- (2-thienyl) ethanol in an amount of 74 mol% when the carboxyl group contained in the carboxyl group-containing vinylidene fluoride copolymer (X1) is 100 mol%. An electrode slurry was prepared in the same manner as in Comparative Example 1 except that was further used.

The peel strength was measured in the same manner as in Comparative Example 1 except that the electrode slurry was used.
[Comparative Example 4]
(Measurement of peel strength)
When preparing the electrode slurry, when the carboxyl group contained in the carboxyl group-containing vinylidene fluoride copolymer (X1) is 100 mol%, an amount of 2- (methylthio) ethanol of 79 mol% is further added. An electrode slurry was prepared in the same manner as in Comparative Example 1 except that it was used.

The peel strength was measured in the same manner as in Comparative Example 1 except that the electrode slurry was used.
Table 1 shows the peel strength measured in each example and comparative example.

  From Table 1 above, an electrode produced using a vinylidene fluoride copolymer having an organic group containing at least one heteroatom selected from nitrogen and sulfur of the present invention does not have the organic group. Compared to an electrode manufactured using a carboxyl group-containing vinylidene fluoride copolymer (Comparative Example 1), the peel strength is excellent.

  In addition, an electrode slurry was prepared under the condition that a compound having an organic group containing at least one hetero atom selected from nitrogen and sulfur was present in the system, and an electrode manufactured using the electrode slurry (Comparative Example) 2-4), the peel strength was comparable to that of Comparative Example 1.

  That is, an organic group containing at least one heteroatom selected from nitrogen and sulfur cannot improve the peel strength of the obtained electrode simply by being present in the system, and the vinylidene fluoride copolymer Must have the organic group.

Claims (11)

The structural unit represented by the following general formula a is 80 to 99.95 mol%, the structural unit represented by the following general formula b is 0 to 19.99 mol%, and the structural unit represented by the following general formula c is 0.01 to 20 mol% % (However, the total of the structural units represented by the general formulas a, b and c is 100 mol%).

(In the general formula b, R _COOH is an organic group containing a carboxyl group, and R ¹ , R ² and R ³ are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or 5 alkyl groups,
In the general formula c, R _{N, S} is an organic group containing at least one heteroatom selected from nitrogen and sulfur, and R ⁴ , R ⁵ , R ⁶ are each independently a hydrogen atom, a halogen atom, It is a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms. ) In the general formula c, R _{N, S} is an organic group containing at least one group selected from amines, thioethers, thiocarbonyls, and heterocyclic rings,
The vinylidene fluoride copolymer according to claim 1, wherein the heterocyclic ring is a heterocyclic ring containing at least one heteroatom selected from nitrogen and sulfur. The structural unit represented by the following general formula a is 80 to 99.95 mol%, and the structural unit represented by the following general formula b ′ is 0.05 to 20 mol% (however, the structural unit represented by the general formula a and b ′ Carboxyl group-containing vinylidene fluoride copolymer (X) having a total of 100 mol%),
2. A linking group-forming reaction with a compound having a group that forms a linking group by chemical reaction with a carboxyl group or a derivative thereof and containing at least one heteroatom selected from nitrogen and sulfur. Or a vinylidene fluoride copolymer according to 2.

(In the general formula b ′, R _COOH is an organic group containing a carboxyl group,
In the general formula b ′, R ¹ , R ² and R ³ are each independently a hydrogen atom, a halogen atom, a carboxyl group or a derivative thereof, or an alkyl group having 1 to 5 carbon atoms. )   The vinylidene fluoride copolymer according to any one of claims 1 to 3, wherein the inherent viscosity is 0.5 to 5.0 dl / g.   The binder for battery electrodes containing the vinylidene fluoride copolymer as described in any one of Claims 1-4, and a nonaqueous solvent.   The electrode mixture for nonaqueous electrolyte secondary batteries containing the vinylidene fluoride copolymer as described in any one of Claims 1-4, an electrode active material, and a nonaqueous solvent.   The negative electrode mixture for nonaqueous electrolyte secondary batteries containing the vinylidene fluoride copolymer as described in any one of Claims 1-4, a negative electrode active material, and a nonaqueous solvent.   The electrode for nonaqueous electrolyte secondary batteries obtained by apply | coating and drying the electrode mixture for nonaqueous electrolyte secondary batteries of Claim 6 to a collector.   The negative electrode for nonaqueous electrolyte secondary batteries obtained by apply | coating and drying the negative electrode mixture for nonaqueous electrolyte secondary batteries of Claim 7 to a collector.   The nonaqueous electrolyte secondary battery which has an electrode for nonaqueous electrolyte secondary batteries of Claim 8.   A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to claim 9.

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