JPWO2010074041A1 - Non-aqueous electrolyte secondary battery negative electrode mixture, non-aqueous electrolyte secondary battery negative electrode and non-aqueous electrolyte secondary battery - Google Patents

Abstract

An object of the present invention is to provide a negative electrode mixture for a nonaqueous electrolyte secondary battery, which is excellent in peel strength between the mixture layer and the current collector when a negative electrode for a nonaqueous electrolyte secondary battery is produced. The negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention contains a polar group-containing vinylidene fluoride polymer, a chlorine atom-containing vinylidene fluoride polymer, an electrode active material, and an organic solvent, and contains the chlorine atom The vinylidene fluoride polymer contains 0.3 to 5% by weight of chlorine atoms per 100% by weight of the polymer.

Description

  The present invention relates to a negative electrode mixture for a nonaqueous electrolyte secondary battery, a negative electrode for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery.

  In recent years, the development of electronic technology has been remarkable, and various devices have been reduced in size and weight. Along with the reduction in size and weight of the electronic device, there is a demand for reduction in size and weight of the battery serving as the power source. Non-aqueous electrolyte secondary batteries using lithium are mainly used as power sources for small electronic devices used in homes such as mobile phones, personal computers, and video camcorders as batteries that can obtain large energy with a small volume and weight. ing.

  For the electrodes (positive electrode and negative electrode) of such a non-aqueous electrolyte secondary battery, for example, a binder (binder) is mixed with a powdered electrode forming material such as an electrode active material and a conductive additive added as necessary. Then, an electrode mixture obtained by dissolving or dispersing in a suitable solvent is obtained by coating and drying on a current collector to form a mixture layer.

As the binder, for example, it is necessary to have durability against a non-aqueous electrolyte obtained by dissolving an electrolyte such as LiPF ₆ or LiClO _{4 in} a non-aqueous solvent such as ethylene carbonate or propylene carbonate, and the specific resistance is small. The thin film forming property is required to be good. As the binder, specifically, a vinylidene fluoride polymer is generally used.

  As the vinylidene fluoride polymer, for example, Patent Document 1 discloses a vinylidene fluoride copolymer obtained by copolymerizing vinylidene fluoride and an unsaturated dibasic acid monoester. Patent Document 1 aims to provide a vinylidene fluoride polymer that has good adhesion to a base material such as metal, is excellent in chemical resistance, and can be produced by aqueous polymerization. Although the electrode mixture used as a binder for manufacturing an electrode is described, the components contained in the electrode mixture other than the polymer are not particularly limited.

  By the way, when the peeling strength between the current collector constituting the electrode and the mixture layer is small, there is a problem that the electrode is cracked or peeled off in a process such as pressing, slitting or winding. Such a problem not only leads to a decrease in battery performance, but there is a risk that the peeling piece penetrates the separator and short-circuits, which is an important management item in manufacturing the electrode.

  Patent Document 2 discloses that an acid is added to a slurry applied to a current collector as a method for producing a battery electrode having excellent peel strength between the current collector and the mixture layer. Patent Document 2 describes that an organic acid is preferable as the acid, and a carboxylic acid is more preferable.

  However, the peel strength between the current collector and the mixture layer is not yet sufficient, and further improvement has been demanded.

Japanese Patent Laid-Open No. 6-172452 Japanese Patent Laid-Open No. 2-68855

  The present invention has been made in view of the above-described problems of the prior art, and has a non-aqueous electrolyte that is excellent in peel strength between a mixture layer and a current collector when a negative electrode for a non-aqueous electrolyte secondary battery is manufactured. An object is to provide a negative electrode mixture for a secondary battery, a negative electrode for a non-aqueous electrolyte secondary battery obtained by applying and drying the mixture to a current collector, and a non-aqueous electrolyte secondary battery having the negative electrode. To do.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have developed a non-aqueous electrolyte secondary battery containing a specific polymer containing a chlorine atom and a specific polymer containing a polar group. The negative electrode for non-aqueous electrolyte secondary batteries produced using the negative electrode mixture was found to have excellent peel strength between the mixture layer and the current collector, and the present invention was completed.

That is, the negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention contains a polar group-containing vinylidene fluoride polymer, a chlorine atom-containing vinylidene fluoride polymer, an electrode active material, and an organic solvent,
The chlorine atom-containing vinylidene fluoride polymer contains 0.3 to 5% by weight of chlorine atoms per 100% by weight of the polymer.

The polar group of the polar group-containing vinylidene fluoride polymer is preferably at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group. Further, when the polar group of the polar group-containing vinylidene fluoride polymer is at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group, the polar group-containing fluorine is contained. The absorbance ratio (I _R ) represented by the following formula (1) when the infrared absorption spectrum of the vinylidene fluoride polymer is measured is more preferably in the range of 0.10 to 1.5.

I _R = I ₁₇₅₀ / I ₃₀₂₅ (1)
(In the above formula (1), I ₁₇₅₀ is the absorbance of 1750 cm ^-1, I ₃₀₂₅ is the absorbance of 3025cm ^-1.)
The polar group-containing vinylidene fluoride polymer is obtained by copolymerizing 80 to 99.9 parts by weight of vinylidene fluoride and 0.1 to 20 parts by weight of a polar group-containing monomer ( However, the total of the vinylidene fluoride and the polar group-containing monomer is preferably 100 parts by weight). More preferably, the polar group-containing monomer is a monomer containing at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group.

  The chlorine atom-containing vinylidene fluoride polymer is a vinylidene fluoride copolymer obtained by copolymerizing 90 to 99 parts by weight of vinylidene fluoride and 1 to 10 parts by weight of a chlorine atom-containing monomer (however, the fluoride The total of vinylidene and chlorine atom-containing monomer is 100 parts by weight).

  The chlorine atom-containing monomer is preferably chlorotrifluoroethylene.

  The electrode active material is preferably a carbon material.

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

  The nonaqueous electrolyte secondary battery of the present invention has the above-described negative electrode for a nonaqueous electrolyte secondary battery.

  The negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention contains a polar group-containing vinylidene fluoride polymer and a chlorine atom-containing vinylidene fluoride polymer, and thus is manufactured using the mixture. The negative electrode for a water electrolyte secondary battery is excellent in the peel strength between the mixture layer and the current collector.

It is a figure which shows IR spectrum of the polar group containing vinylidene fluoride polymer- (1) used in the Example.

  Next, the present invention will be specifically described.

  The negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention contains a polar group-containing vinylidene fluoride polymer, a chlorine atom-containing vinylidene fluoride polymer, an electrode active material, and an organic solvent, and contains the chlorine atom The vinylidene fluoride polymer contains 0.3 to 5% by weight of chlorine atoms per 100% by weight of the polymer.

[Electrode active material]
The negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention contains an electrode active material. The electrode active material is not particularly limited, and conventionally known electrode active materials for negative electrodes can be used, and specific examples include carbon materials, metal / alloy materials, metal oxides, etc. Material is preferred.

  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.

[Polar group-containing vinylidene fluoride polymer]
The negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention contains a polar group-containing vinylidene fluoride polymer as a binder resin. In the present invention, the polar group-containing vinylidene fluoride polymer is a polymer containing a polar group in a polymer and obtained using at least vinylidene fluoride as a monomer. In addition, the polar group-containing vinylidene fluoride polymer is a polymer usually obtained using a monomer containing vinylidene fluoride and a polar group, and other monomers may be used. In the present invention, a monomer containing a polar group in the molecule is also referred to as a polar group-containing monomer.

  In the present invention, the polar group means an atomic group containing an atom having an electronegativity higher than that of carbon such as nitrogen, oxygen, sulfur, or phosphorus. That is, simple atoms such as fluorine and chlorine are not polar groups in the present invention.

  Examples of the polar group contained in the polar group-containing vinylidene fluoride polymer used in the present invention include a carboxyl group, an epoxy group, a hydroxy group, a sulfonic acid group, a carboxylic acid anhydride group, and an amino group. Carboxylic anhydride groups are preferred. The polar group-containing vinylidene fluoride polymer used in the present invention contains at least one of these polar groups, and may contain two or more. As the polar group-containing vinylidene fluoride polymer, a vinylidene fluoride polymer containing at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group is an adhesive performance and availability aspect. To preferred.

  The polar group-containing vinylidene fluoride polymer used in the present invention may be used alone or in combination of two or more.

  When the polar group-containing vinylidene fluoride polymer is at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group, the polar group-containing vinylidene fluoride polymer Is a polymer that usually has 80 or more, preferably 85 or more parts by weight of structural units derived from vinylidene fluoride per 100 parts by weight of the polymer.

  The polar group-containing vinylidene fluoride polymer used in the present invention is usually (1) a method of copolymerizing vinylidene fluoride and a polar group-containing monomer and, if necessary, other monomers (hereinafter referred to as the method of (1)). (2) Polymerization of vinylidene fluoride or copolymerization of vinylidene fluoride and other monomers, polymerization of vinylidene fluoride polymer and polar group-containing monomer, or polar group-containing monomer A method of grafting a polar group-containing polymer onto a vinylidene fluoride polymer using a polar group-containing polymer obtained by copolymerization of a monomer with another monomer (hereinafter also referred to as method (2)) ), (3) Polymerization of vinylidene fluoride or copolymerization of vinylidene fluoride and other monomers to obtain a vinylidene fluoride polymer, and then the vinylidene fluoride polymer is treated with maleic acid or anhydrous How to modified with polar group-containing monomers such as maleic acid is prepared by any method (hereinafter, (3) referred to as method).

  Since the polar group-containing vinylidene fluoride polymer used in the present invention has a polar group, adhesion to the current collector is improved as compared with polyvinylidene fluoride having no polar group. The polar group-containing vinylidene fluoride polymer has chemical resistance equivalent to that of polyvinylidene fluoride having no polar group.

  As a method for producing the polar group-containing vinylidene fluoride polymer, among the methods (1) to (3), it is preferable to produce the polymer by the method (1) from the viewpoint of the number of steps and production cost.

  The polar group-containing vinylidene fluoride polymer used in the present invention is usually 80 to 99.9 parts by weight of vinylidene fluoride and 0.1 to 20 parts by weight of a polar group-containing monomer (provided that the vinylidene fluoride and the polar group-containing monomer are Vinylidene fluoride copolymer obtained by copolymerization of 100 parts by weight in total. The polar group-containing vinylidene fluoride polymer may be a polymer obtained by copolymerizing another monomer in addition to the vinylidene fluoride and the polar group-containing monomer. In addition, when using another monomer, when the total of the said vinylidene fluoride and a polar group containing monomer shall be 100 weight part, 0.1-20 weight part of other monomers will be normally used.

  In the case of producing a vinylidene fluoride polymer containing at least one polar group selected from the group consisting of a carboxyl group and a carboxylic acid anhydride group, the polar group-containing monomer is usually a carboxyl group. And a monomer containing at least one polar group selected from the group consisting of carboxylic anhydride groups, and at least one selected from the group consisting of carboxyl group-containing monomers and carboxylic anhydride group-containing monomers It is preferable to use a monomer.

  When at least one monomer selected from the group consisting of a carboxyl group-containing monomer and a carboxylic acid anhydride group-containing monomer is used, the polar group-containing vinylidene fluoride polymer is 90 to 99.9 wt. 0.1 to 10 parts by weight of at least one monomer selected from the group consisting of a monomer, a carboxyl group-containing monomer, and a carboxylic acid anhydride group-containing monomer (however, vinylidene fluoride, a carboxyl group-containing monomer, and a carboxylic acid anhydride) A vinylidene fluoride copolymer obtained by copolymerizing a total of at least one monomer selected from the group consisting of physical group-containing monomers with 100 parts by weight, preferably vinylidene fluoride 95 ~ 99.9 parts by weight, a carboxyl group-containing monomer and a carboxylic acid anhydride group-containing module 0.1 to 5 parts by weight of at least one monomer selected from the group consisting of mer (however, at least one selected from the group consisting of vinylidene fluoride, a carboxyl group-containing monomer and a carboxylic anhydride group-containing monomer) It is more preferable to use a vinylidene fluoride copolymer obtained by copolymerizing a total of 100 parts by weight with the other monomers.

  As the carboxyl group-containing monomer, unsaturated monobasic acid, unsaturated dibasic acid, monoester of unsaturated dibasic acid and the like are preferable, and monoester of unsaturated dibasic acid and unsaturated dibasic acid are more preferable.

  Examples of the unsaturated monobasic acid include acrylic acid. Examples of the unsaturated dibasic acid include maleic acid and citraconic acid. The unsaturated dibasic acid monoester preferably has 5 to 8 carbon atoms, and examples thereof include maleic acid monomethyl ester, maleic acid monoethyl ester, citraconic acid monomethyl ester, and citraconic acid monoethyl ester. Can do.

  Among these, maleic acid, citraconic acid, maleic acid monomethyl ester, and citraconic acid monomethyl ester are preferable as the carboxyl group-containing monomer.

  Examples of the carboxylic acid anhydride group-containing monomer include unsaturated dibasic acid anhydrides, and examples of the unsaturated dibasic acid anhydride groups include maleic anhydride and citraconic anhydride.

  The polar group-containing vinylidene fluoride polymer of the present invention is a polymer having a polar group usually derived from a polar group-containing monomer. For example, when a carboxyl group-containing monomer is used as the polar group-containing monomer, a carboxyl group-containing vinylidene fluoride polymer is usually obtained as the polar group-containing vinylidene fluoride polymer. In addition, when a carboxylic acid anhydride group-containing monomer is used as the polar group-containing monomer, the polar group-containing vinylidene fluoride polymer has a carboxyl group obtained by hydrolysis of the carboxylic acid anhydride group. And may have a carboxylic anhydride group.

  The other monomer that can be used in the present invention means a monomer other than vinylidene fluoride and a polar group-containing monomer. Examples of the other monomer include a fluorine-based monomer copolymerizable with vinylidene fluoride or the like. Examples thereof include hydrocarbon monomers such as ethylene and propylene. Examples of the fluorine-based monomer copolymerizable with vinylidene fluoride include vinyl fluoride, trifluoroethylene, tetrafluoroethylene, and hexafluoropropylene.

  In addition, the said other monomer may be used individually by 1 type, and may use 2 or more types.

  As the method (1), methods such as suspension polymerization, emulsion polymerization, and solution polymerization can be employed. From the viewpoint of ease of post-treatment, aqueous suspension polymerization and emulsion polymerization are preferred, and aqueous suspension is preferred. Turbid 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 polar group-containing monomer, other monomer copolymerized as necessary) 0.005 to 1.0 part by weight, preferably 0.01 to 0.4 part by weight based on 100 parts by weight Add in the range of.

  As the polymerization initiator, diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, diisopropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, Di (perfluoroacyl) peroxide and the like can be used. The amount used is 0.1 to 5 parts by weight, assuming that 100 parts by weight of all monomers used for copolymerization (vinylidene fluoride and polar group-containing monomers, and other monomers copolymerized as necessary), Preferably it is 0.3-2 weight part.

  In addition, a polar 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 polymer. The amount used is usually 0.1 to 5 when 100 parts by weight of all monomers used for copolymerization (vinylidene fluoride and polar group-containing monomers and other monomers copolymerized as required) are used. Part by weight, preferably 0.5 to 3 parts by weight.

  The total amount of monomers used for copolymerization (vinylidene fluoride and polar group-containing monomers, and other monomers copolymerized as necessary) is 1: 1 to 1:10, preferably 1: 2 to 1: 5, the polymerization is at a temperature of 10 to 80 ° C., the polymerization time is 10 to 100 hours, and the pressure during the polymerization is usually performed under pressure, Preferably it is 2.0-8.0MPa-G.

  By performing aqueous suspension polymerization under the above conditions, it is possible to easily copolymerize vinylidene fluoride, polar group-containing monomers, and other monomers copolymerized as necessary. A group-containing vinylidene fluoride polymer can be obtained.

  Moreover, when manufacturing a polar group containing vinylidene fluoride polymer by the method of said (2), it can carry out with the following method, for example.

  When a polar group-containing vinylidene fluoride polymer is produced by the method (2), first, vinylidene fluoride is polymerized or vinylidene fluoride is copolymerized with another monomer to obtain a vinylidene fluoride polymer. Get. The polymerization or copolymerization is usually performed by suspension polymerization or emulsion polymerization. In addition to the vinylidene fluoride polymer, a polar group-containing polymer is obtained by polymerizing a polar group-containing monomer or copolymerizing a polar group-containing monomer and another monomer. The polar group-containing polymer is usually obtained by emulsion polymerization or suspension polymerization. Furthermore, the polar group-containing vinylidene fluoride polymer can be obtained by grafting the polar group-containing polymer onto the vinylidene fluoride-based polymer using the above-mentioned vinylidene fluoride-based polymer and the polar group-containing polymer. . The grafting may be carried out using a peroxide or using radiation. Preferably, a mixture of a vinylidene fluoride polymer and a polar group-containing polymer is heated in the presence of the peroxide. It is done by processing.

  The polar group-containing vinylidene fluoride polymer used in 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 -5.0 dl / g is preferable, and a value within the range of 1.1-4.0 dl / g is more preferable. If it is the viscosity within the said range, it can use suitably for the negative mix for nonaqueous electrolyte secondary batteries.

The inherent viscosity η _i is calculated by dissolving 80 mg of a polar group-containing vinylidene fluoride polymer in 20 ml of N, N-dimethylformamide and using an Ubbelote viscometer in a constant temperature bath at 30 ° C. Can do.

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.

  In addition, the polar group-containing vinylidene fluoride polymer usually has a weight average molecular weight measured by GPC (gel permeation chromatography) in the range of 50,000 to 1,500,000.

When the polar group-containing vinylidene fluoride polymer is a vinylidene fluoride polymer containing at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group, When the infrared absorption spectrum of the polymer is measured, the absorbance ratio (I _R ) represented by the following formula (1) is preferably in the range of 0.10 to 1.5. In addition, the measurement of the infrared absorption spectrum of this polymer is performed by measuring an infrared absorption spectrum about the film manufactured by hot-pressing this polymer.

I _R = I ₁₇₅₀ / I ₃₀₂₅ (1)
(In the above formula (1), I ₁₇₅₀ is the absorbance of 1750 cm ^-1, I ₃₀₂₅ is the absorbance of 3025cm ^-1.)
In the infrared absorption spectrum, the carbonyl group has an absorption band at 1650 to 1800 cm ⁻¹ .

Therefore, in the above formula (1), I ₁₇₅₀ is derived from a carbonyl group, and I ₃₀₂₅ is derived from a C—H structure. Therefore, I _R is the measure of the abundance of the carbonyl group of the polar group-containing vinylidene fluoride polymer.

[Chlorine atom-containing vinylidene fluoride polymer]
The negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention contains a chlorine atom-containing vinylidene fluoride polymer as a binder resin. In the present invention, the chlorine atom-containing vinylidene fluoride polymer is a polymer containing a chlorine atom in a polymer and obtained using at least vinylidene fluoride as a monomer. The chlorine atom-containing vinylidene fluoride polymer used in the present invention contains 0.3 to 5% by weight of chlorine atoms per 100% by weight of the polymer.

  The chlorine atom-containing vinylidene fluoride polymer is a polymer usually obtained using a monomer containing vinylidene fluoride and a chlorine atom, and other monomers may be used. In the present invention, a monomer containing a chlorine atom in the molecule is also referred to as a chlorine atom-containing monomer.

  The chlorine atom-containing vinylidene fluoride polymer used in the present invention may be used alone or in combination of two or more.

  Since the chlorine atom-containing vinylidene fluoride polymer used in the present invention has a chlorine atom, adhesion to the current collector is improved as compared with polyvinylidene fluoride having no chlorine atom. The chlorine atom-containing vinylidene fluoride polymer has chemical resistance equivalent to that of polyvinylidene fluoride having no chlorine atom.

  The polar group-containing vinylidene fluoride polymer used in the present invention is usually 90 to 99 parts by weight of vinylidene fluoride and 1 to 10 parts by weight of a chlorine atom-containing monomer (however, the total of vinylidene fluoride and chlorine atom-containing monomer is 100 weights). A vinylidene fluoride copolymer obtained by copolymerization. The chlorine atom-containing vinylidene fluoride polymer may be a polymer obtained by copolymerizing another monomer in addition to the vinylidene fluoride and the chlorine atom-containing monomer. In addition, when using another monomer, when the sum total of the said vinylidene fluoride and a chlorine atom containing monomer shall be 100 weight part, 0.1-20 weight part of another monomer will be normally used.

  As the chlorine atom-containing monomer, chlorotrifluoroethylene is usually used.

  The other monomer that can be used in the present invention means a monomer other than vinylidene fluoride and a polar group-containing monomer. Examples of the other monomer include a fluorine-based monomer copolymerizable with vinylidene fluoride or the like. Examples thereof include hydrocarbon monomers such as ethylene and propylene. Examples of the fluorine-based monomer copolymerizable with vinylidene fluoride include vinyl fluoride, trifluoroethylene, tetrafluoroethylene, and hexafluoropropylene.

  In addition, the said other monomer may be used individually by 1 type, and may use 2 or more types.

  The chlorine atom-containing vinylidene fluoride polymer used in the present invention is usually produced by a method of copolymerizing vinylidene fluoride and a chlorine atom-containing monomer and, if necessary, other monomers.

  As the copolymerization method, suspension polymerization, emulsion polymerization, solution polymerization and the like can be adopted, but aqueous suspension polymerization and emulsion polymerization are preferred from the viewpoint of ease of post-treatment, 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 chlorine atom-containing monomer, other monomer copolymerized as necessary) 0.005 to 1.0 part by weight, preferably 0.01 to 0.4 part by weight based on 100 parts by weight Add in the range of.

  As the polymerization initiator, diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, diisopropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, Di (perfluoroacyl) peroxide and the like can be used. The amount used is 0.1 to 5 parts by weight, assuming that 100 parts by weight of all monomers used for copolymerization (vinylidene fluoride and chlorine atom-containing monomers, and other monomers copolymerized as necessary), Preferably it is 0.3-2 weight part.

  In addition, a polar 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 polymer. The amount used is usually 0.1 to 5 when 100 parts by weight of all the monomers used for copolymerization (vinylidene fluoride, chlorine atom-containing monomers, and other monomers copolymerized as required) are used. Part by weight, preferably 0.5 to 3 parts by weight.

  The amount of all monomers used for copolymerization (vinylidene fluoride and chlorine atom-containing monomers, and other monomers copolymerized as necessary) is 1: 1 to 1:10, preferably 1: 2 to 1: 5, the polymerization is at a temperature of 10 to 80 ° C., the polymerization time is 10 to 100 hours, and the pressure during the polymerization is usually performed under pressure, Preferably it is 2.0-8.0MPa-G.

  By carrying out aqueous suspension polymerization under the above conditions, it is possible to easily copolymerize vinylidene fluoride, a chlorine atom-containing monomer, and other monomers copolymerized as necessary. An atom-containing vinylidene fluoride polymer can be obtained.

  As described above, the chlorine atom-containing vinylidene fluoride polymer used in the present invention contains 0.3 to 5% by weight, preferably 0.7 to 3% by weight of chlorine atoms per 100% by weight of the polymer. The chlorine atom content of the chlorine atom-containing vinylidene fluoride polymer was determined by ion chromatography using a test solution obtained by burning the chlorine atom-containing vinylidene fluoride polymer according to the flask combustion method (JIS K7229). Among the chromatograms obtained, the peak area of the chloride ion chromatogram can be obtained and obtained by the absolute calibration curve method.

  The chlorine atom-containing vinylidene fluoride polymer used in 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 -5.0 dl / g is preferable, and a value within the range of 1.1-4.0 dl / g is more preferable. If it is the viscosity within the said range, it can use suitably for the negative mix for nonaqueous electrolyte secondary batteries.

The inherent viscosity η _i is calculated by dissolving 80 mg of a chlorine atom-containing vinylidene fluoride polymer in 20 ml of N, N-dimethylformamide and using an Ubbelote viscometer in a constant temperature bath at 30 ° C. Can do.

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.

  Further, the chlorine atom-containing vinylidene fluoride polymer usually has a weight average molecular weight measured by GPC (gel permeation chromatography) in the range of 50,000 to 1,500,000.

  When a negative electrode for a nonaqueous electrolyte secondary battery is produced using the negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention, the negative electrode is excellent in peel strength between the mixture layer and the current collector. The reason why the peel strength is excellent is not clear, but some of the chlorine atoms contained in the chlorine atom-containing vinylidene fluoride polymer are eliminated, reacting with the surface of the current collector, and containing a polar group at the reaction point The present inventors estimated that the peel strength is excellent by reacting polar groups such as a carboxyl group and a carboxylic anhydride group of the vinylidene fluoride polymer.

  That is, in the negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention, it is necessary to use a chlorine atom-containing vinylidene fluoride polymer and a polar group-containing vinylidene fluoride polymer in combination. It is preferable to use chlorotrifluoroethylene as the chlorine atom-containing monomer because the negative electrode is particularly excellent in peel strength between the mixture layer and the current collector.

  By using the negative electrode mixture for nonaqueous electrolyte secondary batteries of the present invention, the peel strength between the mixture layer and the current collector can be improved in the negative electrode for nonaqueous electrolyte secondary batteries. Compared to a mixture, it is effective in solving problems of electrode cracking and peeling during electrode production.

〔Organic solvent〕
The negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention contains an organic solvent. As the organic solvent, those having an action of dissolving the polar group-containing vinylidene fluoride polymer and the chlorine atom-containing vinylidene fluoride polymer are used, and the solvent is preferably polar. Specific examples of the organic solvent include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide, hexamethylphosphoamide, dioxane, tetrahydrofuran, and tetramethylurea. , Triethyl phosphate, trimethyl phosphate and the like, and N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and N, N-dimethylsulfoxide are preferable. Moreover, the organic solvent may be used alone or in combination of two or more.

  The negative electrode mixture for nonaqueous electrolyte secondary batteries of the present invention contains the above-mentioned polar group-containing vinylidene fluoride polymer, chlorine atom-containing vinylidene fluoride polymer, electrode active material, and organic solvent.

  The content of each component of the negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention is usually based on 100 parts by weight of the electrode active material. The total of the combination is 1 to 25 parts by weight, the organic solvent is 20 to 300 parts by weight, and preferably the total of the polar group-containing vinylidene fluoride polymer and the chlorine atom-containing vinylidene fluoride polymer is 1 to 20 The organic solvent is 70 to 200 parts by weight. The weight ratio of the polar group-containing vinylidene fluoride polymer and the chlorine atom-containing vinylidene fluoride polymer is usually 5:95 to 95: 5, preferably 20:80 to 80:20. .

  When each component is contained within the above range, when a negative electrode for a nonaqueous electrolyte secondary battery is produced using the negative electrode mixture for a nonaqueous electrolyte secondary battery of the present invention, the electrode mixture layer and the current collector are collected. The peel strength from the body can be further improved, and when producing a negative electrode for a non-aqueous electrolyte secondary battery, the coating property when applying a negative electrode mixture for a non-aqueous electrolyte secondary battery to the current collector is improved. Also excellent.

  Further, the negative electrode mixture for a non-aqueous electrolyte secondary battery according to the present invention comprises other components other than the polar group-containing vinylidene fluoride polymer, chlorine atom-containing vinylidene fluoride polymer, electrode active material and organic solvent. You may contain. As other components, a conductive aid such as carbon black, a pigment dispersant such as polyvinylpyrrolidone, and the like may be included. As said other component, polymers other than a polar group containing vinylidene fluoride polymer and a chlorine atom containing vinylidene fluoride polymer may be included. Examples of the other polymer include fluorides such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-perfluoromethyl vinyl ether copolymer. Examples include vinylidene polymers. When the negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention contains other polymers, the total weight of the polar group-containing vinylidene fluoride polymer and the chlorine atom-containing vinylidene fluoride polymer is usually 100 weights. It is contained in an amount of 25 parts by weight or less based on parts.

The viscosity of the negative electrode mixture for a non-aqueous 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.

  The method for producing a negative electrode mixture for a non-aqueous electrolyte secondary battery according to the present invention comprises uniformly mixing the polar group-containing vinylidene fluoride polymer, the chlorine atom-containing vinylidene fluoride polymer, the electrode active material, and the organic solvent. What is necessary is just to mix so that it may become a slurry, The order at the time of mixing is not specifically limited, For example, the said polar group containing vinylidene fluoride polymer and a chlorine atom containing vinylidene fluoride polymer are made into a part of organic solvent. Dissolving, obtaining a binder solution, adding an electrode active material and the remaining organic solvent to the binder solution, stirring and mixing, and obtaining a negative electrode mixture for a non-aqueous electrolyte secondary battery, the polar group-containing vinylidene fluoride After dissolving the polymer and the chlorine atom-containing vinylidene fluoride polymer in a part of the organic solvent, the two binder solutions are blended, and the electrode active material and the binder solution are blended into the binder solution. And addition of the remaining organic solvent, stirring and mixing, a method may be mentioned of obtaining a non-aqueous electrolyte secondary battery negative electrode mixture.

[Negative electrode for non-aqueous electrolyte secondary battery]
The negative electrode for a non-aqueous electrolyte secondary battery of the present invention is obtained by applying and drying the negative electrode mixture for a non-aqueous electrolyte secondary battery on a current collector, and the current collector and the non-aqueous electrolyte secondary battery And a layer formed from the negative electrode mixture.

  In addition, in this invention, the layer formed by apply | coating and drying the negative mix for nonaqueous electrolyte secondary batteries to a collector is described as a mixture layer.

  Examples of the current collector used in the present invention include copper, and examples of the shape thereof include a metal foil and a metal net. As the current collector, a copper foil is preferable.

  The thickness of the current collector is usually 5 to 100 μm, preferably 5 to 20 μm.

  When producing the negative electrode for a nonaqueous electrolyte secondary battery of the present invention, the negative electrode mixture for a nonaqueous electrolyte secondary battery 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.

  By the above method, the negative electrode for nonaqueous electrolyte secondary batteries of this invention can be manufactured. In addition, as a layer structure of the negative electrode for non-aqueous electrolyte secondary batteries, when the negative electrode mixture for non-aqueous electrolyte secondary batteries is applied to one surface of the current collector, a two-layer structure of a mixture layer / current collector When the negative electrode mixture for a nonaqueous electrolyte secondary battery is applied to both sides of the current collector, it has a three-layer structure of a mixture layer / current collector / mixture layer.

  The negative electrode for a non-aqueous electrolyte secondary battery according to the present invention is excellent in the peel strength between the current collector and the mixture layer by using the negative 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 negative 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, the peel strength between the current collector and the mixture layer is According to JIS K6854, it is usually 0.5 to 20 gf / mm, preferably 1 to 10 gf / mm, when measured by a 180 ° peel test.

[Nonaqueous electrolyte secondary battery]
The nonaqueous electrolyte secondary battery of the present invention is characterized by having the negative electrode for a nonaqueous electrolyte secondary battery.

  The non-aqueous electrolyte secondary battery of the present invention is not particularly limited as long as it has the negative electrode for non-aqueous electrolyte secondary batteries, and a part other than the negative electrode, for example, a positive electrode, a separator, etc., use a conventionally known one. Can do.

  EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these.

[Production of Polar Group-Containing Vinylidene Fluoride Polymer (1)]
An autoclave with an internal volume of 2 liters was charged with 1036 g of ion-exchanged water, 0.8 g of methylcellulose, 1.8 g of diisopropyl peroxydicarbonate, 396 g of vinylidene fluoride and 4 g of maleic acid monomethyl ester, and subjected to suspension polymerization at 29 ° C. for 56 hours. went. The maximum pressure during this period reached 4.3 MPa. After the polymerization was completed, the polymer slurry was dehydrated, washed with water and dried at 80 ° C. for 20 hours to obtain a powdered polar group-containing vinylidene fluoride polymer- (1) containing a carboxyl group as a polar group.

  The polymerization yield was 85% by weight, and the inherent viscosity of the obtained polar group-containing vinylidene fluoride polymer- (1) was 2.1 dl / g.

[Production of chlorine atom-containing vinylidene fluoride polymer (1)]
An autoclave with an internal volume of 2 liters was charged with 1040 g of ion-exchanged water, 0.4 g of methyl cellulose, 1.6 g of diisopropyl peroxydicarbonate, 2 g of ethyl acetate, 372 g of vinylidene fluoride, and 28 g of chlorotrifluoroethylene, and the mixture was kept at 28 ° C. for 43 hours. Suspension polymerization was performed. The maximum pressure during this period reached 4.2 MPa. After the completion of the polymerization, the polymer slurry was dehydrated, washed with water and dried at 80 ° C. for 20 hours to obtain a powdery chlorine atom-containing vinylidene fluoride polymer- (1).

  The polymerization yield was 90% by weight, and the inherent viscosity of the obtained chlorine atom-containing vinylidene fluoride polymer- (1) was 2.0 dl / g.

[Production of polyvinylidene fluoride- (1)]
An autoclave with an internal volume of 2 liters is charged with 1100 g of ion-exchanged water, 0.2 g of methylcellulose, 2.2 g of diisopropyl peroxydicarbonate, 3.7 g of ethyl acetate, and 430 g of vinylidene fluoride, and suspension polymerization at 26 ° C. for 18.5 hours. Went. The maximum pressure during this period reached 4.1 MPa. After completion of the polymerization, the polymer slurry was dehydrated, washed with water and dried at 80 ° C. for 20 hours to obtain powdered polyvinylidene fluoride (1).

  The polymerization yield was 90% by weight, and the inherent viscosity of the obtained polyvinylidene fluoride- (1) was 2.0 dl / g.

[Production of vinylidene fluoride-hexafluoropropylene copolymer- (1)]
An autoclave having an internal volume of 2 liters was charged with 1075 g of ion-exchanged water, 0.2 g of methyl cellulose, 0.8 g of diisopropyl peroxydicarbonate, 3.2 g of ethyl acetate, 386 g of vinylidene fluoride, and 34 g of hexafluoropropylene. Time suspension polymerization was performed. The maximum pressure during this period reached 4.1 MPa. After completion of the polymerization, the polymer slurry was dehydrated, washed with water and dried at 80 ° C. for 20 hours to obtain a powdered vinylidene fluoride-hexafluoropropylene copolymer- (1).

  The polymerization yield was 90% by weight, and the inherent viscosity of the obtained vinylidene fluoride-hexafluoropropylene copolymer- (1) was 2.1 dl / g.

[Production of Vinylidene Fluoride-Trifluoroethylene Copolymer (1)]
An autoclave with an internal volume of 2 liters was charged with 1024 g of ion-exchanged water, 0.4 g of methylcellulose, 1.2 g of dinormal propyl peroxydicarbonate, 379.6 g of vinylidene fluoride, and 20.4 g of trifluoroethylene at 26 ° C. for 22 hours. Suspension polymerization was performed. The maximum pressure during this period reached 4.0 MPa. After completion of the polymerization, the polymer slurry was dehydrated, washed with water and dried at 80 ° C. for 20 hours to obtain a powdered vinylidene fluoride-trifluoroethylene copolymer- (1).

  The polymerization yield was 85% by weight, and the inherent viscosity of the obtained vinylidene fluoride-trifluoroethylene copolymer- (1) was 1.8 dl / g.

[Chlorine content]
The chlorine content of the chlorine atom-containing vinylidene fluoride polymer- (1) was measured by the following method.

  According to the flask combustion method (JIS K7229), the test liquid obtained by burning the chlorine atom-containing vinylidene fluoride polymer- (1) was analyzed by ion chromatography. The peak area of the ion chromatogram was determined, and the chlorine content of the chlorine atom-containing vinylidene fluoride polymer- (1) was determined by an absolute calibration curve method.

  The chlorine atom-containing vinylidene fluoride polymer (1) thus determined was 2.1% by weight per 100% by weight of the polymer.

  The chlorine atom content of the polar group-containing vinylidene fluoride polymer- (1) determined by the same method was 0% by weight per 100% by weight of the polymer.

  The chlorine atom content of polyvinylidene fluoride- (1) determined by the same method was 0% by weight per 100% by weight of the polymer.

  The chlorine atom content of vinylidene fluoride-hexafluoropropylene copolymer- (1) determined by the same method was 0% by weight per 100% by weight of the polymer.

  The chlorine atom content of vinylidene fluoride-trifluoroethylene copolymer- (1) determined by the same method was 0% by weight per 100% by weight of the polymer.

[Absorbance ratio (R)]
The IR spectrum of the polar group-containing vinylidene fluoride polymer- (1) was measured by the following method.

  Each of the powders of the polar group-containing vinylidene fluoride polymer- (1) was hot-pressed at 200 ° C. to prepare a press sheet 30 mm × 30 mm.

The IR spectrum of the press sheet using an infrared spectrophotometer FT-IR4100 (manufactured by JASCO Corporation) was measured in the range of 1500cm ^-1 ~4000cm ^-1.

The absorbance ratio (I _R ) represented by the following formula (1) was determined from the obtained IR spectrum.

I _R = I ₁₇₅₀ / I ₃₀₂₅ (1)
(In the above formula (1), I ₁₇₅₀ is the absorbance of 1750 cm ^-1, I ₃₀₂₅ is the absorbance of 3025cm ^-1.)
I ₁₇₅₀ and I ₃₀₂₅ can be obtained by subtracting the background absorbance from the apparent absorbance at the above wave number. That is, apparent absorbance at a wavenumber of 1750 cm ^-1 to I _20, when the I ₂₁ and background absorbance at a wave number of I _20, an I ₁₇₅₀ = I ₂₀ -I _21.

Further, when I ₁₀ is an apparent absorbance at a wave number of 3025 cm ⁻¹ and I ₁₁ is a background absorbance at a wave number of I ₁₀ , I ₃₀₂₅ = I ₁₀ −I ₁₁ .

The background absorbance indicates the absorbance when the bottom of the peak on the low wavenumber side is connected to the bottom of the high wavenumber side. That is, in I ₂₁ , a line connecting the low wave number side (1653 cm ^{−1 to} 1662 cm ⁻¹ ) and the high wave number side (1897 cm ^{−1 to} 1907 cm ⁻¹ ), which is an absorption skirt region, is used as a baseline. The absorbance at 1750 cm ⁻¹ is shown, and in I ₁₁ , the straight line connecting the low wave number side (2859 cm ^{−1 to} 2866 cm ⁻¹ ) and the high wave number side (3306 cm ^{−1 to} 3317 cm ⁻¹ ) is used as the baseline. , The absorbance at 3025 cm ⁻¹ .

  Specifically, for the polar group-containing vinylidene fluoride polymer- (1), the absorbance ratio (R) of the IR spectrum (FIG. 1) measured by the above method can be determined as follows.

From FIG. 1, I ₂₀ is the apparent absorbance at a wavenumber of 1750 cm ^-1 is 0.24, the absorbance at a wavenumber of 1750 cm ^-1 when I ₂₁ is connecting the skirt hem and 1900 cm ^-1 wave number 1660 cm ^-1 Is 0.06, and I ₁₇₅₀ is 0.18 from I ₂₀ and I ₂₁ . Further, the absorbance of the apparent I ₁₀ is wavenumber 3025cm ^-1 is 0.53, the absorbance at a wavenumber of 3025cm ^-1 when I ₁₁ is connecting the skirt hem and 3310cm ^-1 wavenumber 2863cm ^-1 is 0. 05, and I ₃₀₂₅ was 0.48 from I ₁₀ and I ₁₁ .

Therefore, the absorbance ratio (I _R ) of the polar group-containing vinylidene fluoride polymer- (1) is 0.38.

The absorbance ratio (I _R ) of the chlorine atom-containing vinylidene fluoride polymer- (1) was determined by the same method. The absorbance ratio (I _R ) of the chlorine atom-containing vinylidene fluoride polymer- (1) was 0.07.

The absorbance ratio (I _R ) of polyvinylidene fluoride- (1) was determined by the same method. The absorbance ratio (I _R ) of polyvinylidene fluoride- (1) was 0.05.

The absorbance ratio (I _R ) of vinylidene fluoride-hexafluoropropylene copolymer- (1) was determined in the same manner. The absorbance ratio (I _R ) of vinylidene fluoride-hexafluoropropylene copolymer- (1) was 0.06.

The absorbance ratio (I _R ) of vinylidene fluoride-trifluoroethylene copolymer- (1) was determined in the same manner. The absorbance ratio (I _R ) of vinylidene fluoride-trifluoroethylene copolymer- (1) was 0.06.

[Example 1]
A chlorine atom-containing vinylidene fluoride polymer- (1) 2.0 g and a polar group-containing vinylidene fluoride polymer- (1) 6.0 g were uniformly dissolved in 92 g of N-methyl-2-pyrrolidone, A solution was obtained.

  To 12.5 g of the obtained binder solution, 9.0 g of MAG (manufactured by Hitachi Chemical Co., Ltd., artificial graphite, average particle size 20 μm) and 3.5 g of N-methyl-2-pyrrolidone for dilution are added. The mixture was stirred and mixed using a product manufactured by Shinky Corporation to obtain a negative electrode mixture (A1) for a non-aqueous electrolyte secondary battery.

The negative electrode mixture (A1) for a non-aqueous electrolyte secondary battery is dried by using a bar coater on a rolled copper foil having a thickness of 10 μm as a current collector, and the weight of the mixture layer after drying is 150 g / m ² . The electrode (A1) having a bulk density of 1.7 g / cm ³ after pressing at 40 MPa after being uniformly applied, dried at 110 ° C. in a gear oven, and heat-treated at 130 ° C. Got.

[Comparative Example 1]
8.0 g of polar group-containing vinylidene fluoride polymer- (1) was uniformly dissolved in 92 g of N-methyl-2-pyrrolidone to obtain a binder solution.

  To 12.5 g of the obtained binder solution, 9.0 g of MAG (manufactured by Hitachi Chemical Co., Ltd., artificial graphite, average particle size 20 μm) and 3.5 g of N-methyl-2-pyrrolidone for dilution are added. A negative electrode mixture (B1) for a non-aqueous electrolyte secondary battery was obtained by stirring and mixing using a product manufactured by Shinky Corporation.

The negative electrode mixture (B1) for a non-aqueous electrolyte secondary battery is dried by using a bar coater on a rolled copper foil having a thickness of 10 μm as a current collector, and the weight of the mixture layer after drying is 150 g / m ² . After applying uniformly, drying at 110 ° C. in a gear oven, and heat-treating at 130 ° C., pressing is performed at 40 MPa, and the bulk density of the mixture layer is 1.7 g / cm ³ (B1) Got.

[Comparative Example 2]
Non-aqueous electrolyte secondary battery, except that 2.0 g of polyvinylidene fluoride- (1) was used instead of 2.0 g of the chlorine atom-containing vinylidene fluoride polymer- (1). Negative electrode mixture (B2) and electrode (B2) were obtained.

[Comparative Example 3]
Chlorine-atom-containing vinylidene fluoride polymer- Performed in the same manner as in Example 1 except that 2.0 g of vinylidene fluoride-hexafluoropropylene copolymer- (1) was used instead of 2.0 g. A negative electrode mixture (B3) and an electrode (B3) for a nonaqueous electrolyte secondary battery were obtained.

[Comparative Example 4]
Chlorine-atom-containing vinylidene fluoride polymer—Performed in the same manner as in Example 1 except that 2.0 g of vinylidene fluoride-trifluoroethylene copolymer- (1) was used instead of 2.0 g of (1). A negative electrode mixture (B4) and an electrode (B4) for a nonaqueous electrolyte secondary battery were obtained.

[Example 2]
A chlorine atom-containing vinylidene fluoride polymer- (1) 6.0 g and a polar group-containing vinylidene fluoride polymer- (1) 2.0 g are uniformly dissolved in N-methyl-2-pyrrolidone 92 g, and a binder is obtained. A solution was obtained.

  To 12.5 g of the obtained binder solution, 9.0 g of MAG (manufactured by Hitachi Chemical Co., Ltd., artificial graphite, average particle size 20 μm) and 3.5 g of N-methyl-2-pyrrolidone for dilution are added. The mixture was stirred and mixed using a product manufactured by Shinky Corporation to obtain a negative electrode mixture (A2) for a non-aqueous electrolyte secondary battery.

The negative electrode mixture for nonaqueous electrolyte secondary batteries (A2) is dried using a bar coater on a rolled copper foil having a thickness of 10 μm, and the weight of the mixture layer after drying is 150 g / m ² . The electrode (A2) has a bulk density of 1.7 g / cm ³ after being pressed at 40 MPa after being uniformly applied, dried at 110 ° C. in a gear oven, and heat-treated at 130 ° C. Got.

Example 3
4.0 g of chlorine atom-containing vinylidene fluoride polymer- (1) and 4.0 g of polar group-containing vinylidene fluoride polymer- (1) are uniformly dissolved in 92 g of N-methyl-2-pyrrolidone, and a binder is obtained. A solution was obtained.

  To 12.5 g of the obtained binder solution, 9.0 g of MAG (manufactured by Hitachi Chemical Co., Ltd., artificial graphite, average particle size 20 μm) and 3.5 g of N-methyl-2-pyrrolidone for dilution are added. A negative electrode mixture (A3) for a non-aqueous electrolyte secondary battery was obtained by stirring and mixing using a Shinky product.

The negative electrode mixture for nonaqueous electrolyte secondary batteries (A3) is dried using a bar coater on a rolled copper foil having a thickness of 10 μm, and the weight of the mixture layer after drying is 150 g / m ² . The electrode (A3) in which the bulk density of the mixture layer is 1.7 g / cm ³ is applied after being uniformly applied, dried at 110 ° C. in a gear oven, heat-treated at 130 ° C., and then pressed at 40 MPa. Got.

[Comparative Example 5]
8.0 g of chlorine atom-containing vinylidene fluoride polymer- (1) was uniformly dissolved in 92 g of N-methyl-2-pyrrolidone to obtain a binder solution.

  To 12.5 g of the obtained binder solution, 9.0 g of MAG (manufactured by Hitachi Chemical Co., Ltd., artificial graphite, average particle size 20 μm) and 3.5 g of N-methyl-2-pyrrolidone for dilution are added. The mixture was stirred and mixed using a product manufactured by Shinky Co., to obtain a negative electrode mixture (B5) for a non-aqueous electrolyte secondary battery.

The negative electrode mixture (B5) for a non-aqueous electrolyte secondary battery is dried by using a bar coater on a rolled copper foil having a thickness of 10 μm as a current collector, and the weight of the mixture layer after drying is 150 g / m ² . The electrode is uniformly applied, dried at 110 ° C. in a gear oven, heat-treated at 130 ° C., pressed at 40 MPa, and the mixture layer has a bulk density of 1.7 g / cm ³ (B5) Got.

[Comparative Example 6]
6.0 g of chlorine atom-containing vinylidene fluoride polymer- (1) and 2.0 g of polyvinylidene fluoride- (1) were uniformly dissolved in 92 g of N-methyl-2-pyrrolidone to obtain a binder solution.

  To 12.5 g of the obtained binder solution, 9.0 g of MAG (manufactured by Hitachi Chemical Co., Ltd., artificial graphite, average particle size 20 μm) and 3.5 g of N-methyl-2-pyrrolidone for dilution are added. The mixture was stirred and mixed using a product manufactured by Shinky Co. to obtain a negative electrode mixture (B6) for a non-aqueous electrolyte secondary battery.

Using the bar coater, the negative electrode mixture (B6) for non-aqueous electrolyte secondary batteries is rolled onto a rolled copper foil having a thickness of 10 μm, which is a current collector, so that the weight of the mixture layer after drying becomes 150 g / m ² . The electrode is uniformly applied, dried at 110 ° C. in a gear oven, heat-treated at 130 ° C., and then pressed at 40 MPa, and the bulk density of the mixture layer is 1.7 g / cm ³ (B6) Got.

[Peel strength]
The peel strength between the current collector and the mixture layer in the electrodes obtained in Examples and Comparative Examples was measured by a 180 ° peel test in accordance with JIS K6854. The results are shown in Tables 1 and 2.

  From Tables 1 and 2, it can be seen that the negative electrode produced using the negative electrode mixture for nonaqueous electrolyte secondary batteries of the present invention is excellent in the peel strength between the mixture layer and the current collector.

  Specifically, when Example 1 and Comparative Examples 1 to 4 are compared, the negative electrode mixture for a non-aqueous electrolyte secondary battery containing a chlorine atom-containing vinylidene fluoride polymer is a polar group-containing vinylidene fluoride polymer. As compared with the case of using only vinyl (Comparative Example 1) and the case of using a vinylidene fluoride polymer containing no chlorine atom instead of the chlorine atom-containing vinylidene fluoride polymer (Comparative Examples 2 to 4), Excellent peel strength. That is, the negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention includes a chlorine atom-containing vinylidene fluoride polymer as an essential component, so that the negative electrode produced using the mixture includes a mixture layer, Excellent peel strength from current collector.

  Further, when Examples 2 and 3 were compared with Comparative Examples 5 and 6, the negative electrode mixture for a non-aqueous electrolyte secondary battery containing a polar group-containing vinylidene fluoride polymer was a chlorine atom-containing vinylidene fluoride heavy polymer. Compared to the case of using only a coalescence (Comparative Example 5) and the case of using a vinylidene fluoride polymer not containing a polar group instead of a polar group-containing vinylidene fluoride polymer (Comparative Example 6), peeling Excellent strength. That is, the negative electrode mixture for a non-aqueous electrolyte secondary battery of the present invention contains a polar group-containing vinylidene fluoride polymer as an essential component, so that the negative electrode manufactured using the mixture includes a mixture layer, Excellent peel strength from current collector.

Claims (10)

Contains a polar group-containing vinylidene fluoride polymer, a chlorine atom-containing vinylidene fluoride polymer, an electrode active material, and an organic solvent,
The negative electrode mixture for a non-aqueous electrolyte secondary battery, wherein the chlorine atom-containing vinylidene fluoride polymer contains 0.3 to 5% by weight of chlorine atoms per 100% by weight of the polymer.   2. The polar group of the polar group-containing vinylidene fluoride polymer is at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group. A negative electrode mixture for non-aqueous electrolyte secondary batteries. The absorbance ratio (I _R ) represented by the following formula (1) when measuring the infrared absorption spectrum of the polar group-containing vinylidene fluoride polymer is in the range of 0.10 to 1.5. The negative electrode mixture for nonaqueous electrolyte secondary batteries according to claim 2.
I _R = I ₁₇₅₀ / I ₃₀₂₅ (1)
(In the above formula (1), I ₁₇₅₀ is the absorbance of 1750 cm ^-1, I ₃₀₂₅ is the absorbance of 3025cm ^-1.)   The polar group-containing vinylidene fluoride polymer is obtained by copolymerizing 80 to 99.9 parts by weight of vinylidene fluoride and 0.1 to 20 parts by weight of a polar group-containing monomer ( However, the total of the said vinylidene fluoride and a polar group containing monomer is 100 weight part), The negative mix for nonaqueous electrolyte secondary batteries of Claim 1 characterized by the above-mentioned.   The non-aqueous electrolyte secondary according to claim 4, wherein the polar group-containing monomer is a monomer containing at least one polar group selected from the group consisting of a carboxyl group and a carboxylic anhydride group. Negative electrode mixture for batteries.   The chlorine atom-containing vinylidene fluoride polymer is a vinylidene fluoride copolymer obtained by copolymerizing 90 to 99 parts by weight of vinylidene fluoride and 1 to 10 parts by weight of a chlorine atom-containing monomer (however, the fluoride 2. The negative electrode mixture for a non-aqueous electrolyte secondary battery according to claim 1, wherein the total of vinylidene and chlorine atom-containing monomer is 100 parts by weight.   The negative electrode mixture for a nonaqueous electrolyte secondary battery according to claim 6, wherein the chlorine atom-containing monomer is chlorotrifluoroethylene.   The negative electrode mixture for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the electrode active material is a carbon material.   A negative electrode for a non-aqueous electrolyte secondary battery obtained by applying and drying the negative electrode mixture for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 8 on a current collector. .   A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to claim 9.

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