阅读说明：本技术 非水系电池电极用浆液、以及非水系电池电极和非水系电池的制造方法 (Slurry for nonaqueous battery electrode, and method for producing nonaqueous battery ) 是由 花崎充 彭骏 于 2019-01-31 设计创作，主要内容包括：本发明提供即使浆液涂布得厚、形成了较厚的电极活性物质层,也能够得到不容易产生裂纹的电极的非水系电池电极用浆液。本发明的非水系电池电极用浆液,其特征在于,含有非水系电池电极用活性物质(A)、粘合剂树脂(B)、裂纹防止剂(C)和水,所述裂纹防止剂(C)在1大气压下的沸点为120℃以上,20℃水中的溶解度为10g/100mL以上。(The invention provides a slurry for a non-aqueous battery electrode, which can obtain an electrode with less possibility of generating cracks even if the slurry is coated thickly and an electrode active material layer is formed thickly. The slurry for a non-aqueous battery electrode is characterized by comprising an active material (A) for a non-aqueous battery electrode, a binder resin (B), a crack inhibitor (C) and water, wherein the boiling point of the crack inhibitor (C) at 1 atmosphere is 120 ℃ or higher, and the solubility in water at 20 ℃ is 10g/100mL or higher.)

1. A slurry for a non-aqueous battery electrode, characterized by comprising an active material (A) for a non-aqueous battery electrode, a binder resin (B), a crack inhibitor (C) and water,

the crack inhibitor (C) has a boiling point of 120 ℃ or higher at 1 atmosphere and a solubility in water at 20 ℃ of 10g/100mL or higher.

2. The slurry for a non-aqueous battery electrode according to claim 1, wherein the crack inhibitor (C) is at least one selected from the group consisting of N-methylpyrrolidin-2-one, ethylene glycol, diethylene glycol, ethylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, N-dimethylformamide, and dimethylsulfoxide.

3. The slurry for a non-aqueous battery electrode according to claim 1, wherein the crack inhibitor (C) is an organic solvent having a boiling point of 150 ℃ or higher under 1 atmosphere.

4. The slurry for a non-aqueous battery electrode according to claim 1, wherein the crack inhibitor (C) is an organic solvent having a boiling point higher than 200 ℃ at 1 atmosphere.

5. The slurry for a non-aqueous battery electrode according to any one of claims 1 to 4, which contains 10 to 500 parts by mass of the crack inhibitor (C) per 100 parts by mass of the binder resin (B).

6. The slurry for a non-aqueous battery electrode according to any one of claims 1 to 5, further comprising a thickener (D).

7. The slurry for a non-aqueous battery electrode according to claim 6, wherein the thickener (D) is carboxymethyl cellulose (CMC).

8. The slurry for a non-aqueous battery electrode according to any one of claims 1 to 7, wherein the binder resin (B) is at least one selected from a copolymer (P1) of a styrene monomer and a diene monomer, and a copolymer (P2) of a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer.

9. The slurry for a non-aqueous battery electrode according to any one of claims 1 to 8, wherein the binder resin (B) contains a copolymer (P1) of a styrene monomer and a diene monomer, and the styrene monomer component is 5 to 70 mass% and the diene monomer component is 30 to 95 mass% of all the ethylenically unsaturated monomer components constituting the copolymer.

10. The slurry for a non-aqueous battery electrode according to any one of claims 1 to 9, wherein the binder resin (B) contains a copolymer (P2) of a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer.

11. The slurry for a non-aqueous battery electrode according to any one of claims 1 to 10, wherein the binder resin (B) contains a copolymer of a styrene-based monomer, an ethylenically unsaturated carboxylic acid ester monomer, and an ethylenically unsaturated carboxylic acid monomer.

12. The slurry for a non-aqueous battery electrode according to claim 11, wherein the amount of styrene used in the binder resin (B) is 10 to 70% by mass of the total ethylenically unsaturated monomer components forming the copolymer,

the amount of the ethylenically unsaturated carboxylic acid ester monomer used is 25 to 85 mass% of the total ethylenically unsaturated monomer components forming the copolymer,

the amount of the ethylenically unsaturated carboxylic acid monomer used is 0.01 to 10% by mass of the total ethylenically unsaturated monomer components forming the copolymer.

13. A method for producing a nonaqueous battery electrode, comprising the step of applying the slurry according to any one of claims 1 to 12 on a current collector and drying the applied slurry.

14. A method for producing a nonaqueous battery, comprising the method for producing a nonaqueous battery electrode according to claim 13.

Technical Field

The present invention relates to a slurry for a nonaqueous battery electrode, and a method for producing a nonaqueous battery.

This application claims priority based on patent application No. 2018-022334 filed in japan on day 9/2/2018, the contents of which are incorporated herein by reference.

Background

In recent years, lithium ion nonaqueous batteries have attracted attention because of demands for downsizing and weight reduction of electronic devices such as notebook personal computers, communication devices such as cellular phones, electric power tools, and the like.

The lithium ion nonaqueous battery includes a positive electrode containing a metal oxide such as lithium cobaltate as an active material, a negative electrode containing a carbon material such as graphite as an active material, and an electrolyte solvent mainly containing carbonates. A lithium ion nonaqueous battery performs battery charge and discharge by transferring lithium ions between a positive electrode and a negative electrode.

The positive electrode can be obtained by forming a positive electrode layer on the surface of a positive electrode current collector such as an aluminum foil from a composition containing a positive electrode active material such as a metal oxide and a binder. The negative electrode can be obtained by forming a negative electrode layer on the surface of a negative electrode current collector such as a copper foil from a composition containing a negative electrode active material such as graphite and a binder. Therefore, each binder has a function of binding the active material and the binder to each other and preventing aggregation breakdown of the positive electrode layer and the negative electrode layer.

As the binder, a poly 1, 1-difluoroethylene (PVDF) binder using N-methylpyrrolidin-2-one (NMP) as an organic solvent is known (see, for example, patent document 1). However, this binder has a disadvantage that the adhesion between the active materials and the current collector is low, and a large amount of binder is required for practical use, resulting in a decrease in the capacity of the nonaqueous battery. In addition, since NMP, which is an expensive organic solvent, is used as the binder, there are problems in terms of the price of the final product and the work environment protection in the production of the slurry or the current collector.

As a method for solving these problems, an aqueous dispersion adhesive has been developed in the past. As a thickener, a styrene-butadiene rubber (SBR) based aqueous dispersion used in combination with carboxymethyl cellulose (CMC) is known (see, for example, patent documents 2 to 4). Further, as an aqueous dispersion binder used for an electrode of a secondary battery, patent document 5 proposes a binder obtained by emulsion polymerization of an ethylenically unsaturated monomer containing styrene, an ethylenically unsaturated carboxylic acid ester monomer, an ethylenically unsaturated carboxylic acid monomer, and an internal crosslinking agent in the presence of a surfactant.

These are aqueous dispersions, and therefore, are inexpensive and advantageous from the viewpoint of protecting the working environment. Further, since the adhesion between the active materials and the current collector is good, the electrode can be produced in a smaller amount than the PVDF-based binder, and as a result, the nonaqueous battery has advantages of higher output and higher capacity.

In recent years, from the viewpoint of environmental protection, lithium ion nonaqueous batteries having high voltage, high capacity, and high energy density have been strongly demanded as nonaqueous batteries used for electric vehicles and hybrid vehicles.

As a solution, there is a method of applying a slurry thickly onto an electrode current collector to form a thick electrode active material layer.

However, if the coating is thick, the electrode is likely to crack, and the battery performance is not necessarily good.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a slurry for a nonaqueous battery electrode, which is an aqueous dispersion system, has good adhesion between active materials and between the active materials and a current collector, and is less likely to cause cracking and peel off the active materials from the surface of the current collector even when the slurry is applied thickly, and a nonaqueous battery electrode and a method for producing a nonaqueous battery using the slurry.

Means for solving the problems

The present inventors have made intensive studies to solve the above problems, and have paid attention to the fact that the occurrence of cracks can be prevented by adding a specific organic solvent as a crack inhibitor to an aqueous dispersion slurry, thereby solving the above problems.

That is, the present invention includes the following embodiments.

[1] A slurry for a non-aqueous battery electrode, characterized by comprising an active material (A) for a non-aqueous battery electrode, a binder resin (B), a crack inhibitor (C) and water,

the crack inhibitor (C) has a boiling point of 120 ℃ or higher at 1 atmosphere and a solubility in water at 20 ℃ of 10g/100mL or higher.

[2] The slurry for a non-aqueous battery electrode according to [1], wherein the crack inhibitor (C) is at least one selected from the group consisting of N-methylpyrrolidin-2-one, ethylene glycol, diethylene glycol, ethylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, N-dimethylformamide, and dimethylsulfoxide.

[3] The slurry for a non-aqueous battery electrode according to [1], wherein the crack inhibitor (C) is an organic solvent having a boiling point of 150 ℃ or higher under 1 atmosphere.

[4] The slurry for a non-aqueous battery electrode according to [1], wherein the crack inhibitor (C) is an organic solvent having a boiling point of more than 200 ℃ under 1 atmosphere.

[5] The slurry for a non-aqueous battery electrode according to any one of [1] to [4], comprising 10 to 500 parts by mass of the crack inhibitor (C) per 100 parts by mass of the binder resin (B).

[6] The slurry for a non-aqueous battery electrode according to any one of [1] to [5], further comprising a thickener (D).

[7] The slurry for a non-aqueous battery electrode according to [6], wherein the thickener (D) is carboxymethyl cellulose (CMC).

[8] The slurry for a non-aqueous battery electrode according to any one of [1] to [7], wherein the binder resin (B) is at least one selected from a copolymer (P1) of a styrene monomer and a diene monomer, and a copolymer (P2) of a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer.

[9] The slurry for a non-aqueous battery electrode according to any one of [1] to [8], wherein the binder resin (B) contains a copolymer (P1) of a styrene monomer and a diene monomer, and the styrene monomer component and the diene monomer component are 5 to 70% by mass and 30 to 95% by mass, respectively, of all the ethylenically unsaturated monomer components constituting the copolymer.

[10] The slurry for a non-aqueous battery electrode according to any one of [1] to [9], wherein the binder resin (B) contains a copolymer (P2) of a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer.

[11] The slurry for a non-aqueous battery electrode according to any one of [1] to [10], wherein the binder resin (B) contains a copolymer of a styrene-based monomer, an ethylenically unsaturated carboxylic acid ester monomer, and an ethylenically unsaturated carboxylic acid monomer.

[12] The slurry for a non-aqueous battery electrode according to [11], wherein the amount of styrene used in the binder resin (B) is 10 to 70% by mass of the total ethylenically unsaturated monomer components constituting the copolymer,

the amount of the ethylenically unsaturated carboxylic acid ester monomer used is 25 to 85 mass% of the total ethylenically unsaturated monomer components forming the copolymer,

the amount of the ethylenically unsaturated carboxylic acid monomer used is 0.01 to 10% by mass of the total ethylenically unsaturated monomer components forming the copolymer.

[13] A method for producing a nonaqueous battery electrode, comprising the step of applying the slurry according to any one of [1] to [12] to a current collector and drying the slurry.

[14] A method for producing a nonaqueous battery, comprising the method for producing a nonaqueous battery electrode according to [13].

Effects of the invention

By using the slurry for a nonaqueous battery electrode of the present invention, an electrode in which cracks are not easily generated can be obtained even when the slurry is applied thickly and an electrode active material layer is formed thickly.

Detailed Description

(slurry for nonaqueous Battery electrode)

The slurry for a non-aqueous battery electrode of the present invention contains an active material (A), a binder resin (B), a crack inhibitor (C) and water as components. The crack inhibitor (C) is characterized by having a boiling point of 120 ℃ or higher at 1 atmosphere and a solubility in water at 20 ℃ of 10g/100mL or higher. Further, it contains (D) a thickener.

In the present specification, "(meth) acrylic acid" is a general term for acrylic acid and methacrylic acid, and "(meth) acrylate" is a general term for acrylate and methacrylate.

[ active Material (A) ]

The slurry for a nonaqueous battery electrode of the present invention contains an active material (a) as an essential component. The active material used in the present invention may be a positive electrode active material or a negative electrode active material. In the slurry for a nonaqueous battery electrode according to one embodiment of the present invention, the active material (a) is a negative electrode active material. When a negative electrode active material is used as the active material (a), the effect is easily exhibited.

The shape of the active material is not particularly limited, and a spherical shape, a scale shape, or the like can be used. The average particle diameter (50% median diameter on a volume basis) of the active material is preferably 5 to 100 μm, more preferably 10 to 50 μm, and still more preferably 15 to 30 μm from the viewpoint of dispersibility of the active material. The 50% median diameter on a volume basis can be calculated by a laser diffraction method.

The BET specific surface area of the active material is preferably 0.1 to 100m from the viewpoint of dispersibility of the active material²A specific ratio of 0.5 to 50m²A specific ratio of 1.0 to 30m²(ii) in terms of/g. Further, the BET specific surface area can be obtained by measuring the specific surface area (according to JIS Z8830) by the BET nitrogen adsorption method.

Examples of the positive electrode active material include a metal composite oxide, for example, a metal composite oxide containing lithium and one or more metals selected from iron, cobalt, nickel, and manganese. Preferably, the compound contains Li_xM_y1O₂(wherein M represents 1 or more transition metals,preferably represents at least one of Co, Mn and Ni, 1.10 > x > 0.05, 1. gtoreq.y 1 > 0), Li_xM_y2O₄(wherein M represents 1 or more transition metals, preferably Mn or Ni, 1.10 > x > 0.05, 2. gtoreq. y2 > 0.) or Li_xM_y1PO₄(wherein M represents 1 or more transition metals, preferably at least one of Fe, Co, Mn and Ni, 1.10 > x > 0.05, 1. gtoreq.y 1 > 0). Specific examples thereof include LiCoO₂、LiNiO₂、Li_xNi_y3Mn_zCo_aO₂(wherein 1.10 > x > 0.05, 1 > y3 > 0, 1 > z > 0, 1 > a > 0.), and LiMn₂O₄、LiFePO₄And the like.

The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions (for example, lithium ions). Specific examples thereof include carbonaceous materials, metal complex oxides, and silicon compounds.

Examples of the carbonaceous material include graphite materials such as artificial graphite and natural graphite; and cokes such as petroleum coke, pitch coke, and coal coke. As the metal composite oxide, for example, lithium titanate or the like can be used. Silicon, silicon oxide, or the like can be used as the silicon compound. When these active substances are used, a very significant effect can be exhibited.

Among these active materials, carbonaceous materials, particularly graphite-based or coke-based among carbonaceous materials, are preferable from the viewpoint of improving the caking property. Among them, graphite-based materials such as artificial graphite and natural graphite are preferably used from the viewpoint of energy density per unit volume. In addition, in active materials other than carbonaceous materials, Li is present from the viewpoint of energy density per unit volume₄Ti₅O₁₂Lithium titanate, silicon and the like are also suitable.

These active substances may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The content of the active material in the nonvolatile matter in the slurry of the present invention is preferably 90.0 to 99.5 mass%, more preferably 95.0 to 99.0 mass%, and still more preferably 96.0 to 98.0 mass%. The nonvolatile content of the slurry was the residue of drying the slurry at 105 ℃ for 1 hour in the air. The "nonvolatile amount of the slurry" refers to the proportion of nonvolatile components contained in the slurry.

[ Binder resin (B) ]

The slurry for a nonaqueous battery electrode of the present invention contains a binder resin (B) as an essential component.

The content of the binder resin (B) in the nonvolatile matter in the slurry of the present invention is preferably 0.5 to 5.0 mass%, more preferably 0.5 to 2.0 mass%, and still more preferably 0.5 to 1.8 mass%.

The binder resin (B) used in the present invention is not particularly limited as long as it can uniformly disperse the active material (a), and is preferably a polymer of 1 or 2 or more ethylenically unsaturated monomers.

The binder resin (B) used in the present invention has a glass transition temperature of preferably 30 ℃ or lower, more preferably 20 ℃ or lower, and still more preferably 15 ℃ or lower, from the viewpoint that the electrode formed from the slurry of the present invention is not easily broken. From the viewpoint of handling properties, the glass transition temperature of the binder resin (B) is preferably-20 ℃ or higher.

The glass transition temperature of the binder resin (B), if the ethylenically unsaturated monomer M used in the polymerization of the binder resin (B)_iThe glass transition temperature of each homopolymer of (i ═ 1, 2., i) was Tg_i(i ═ 1, 2.. multidot.i), preparation of ethylenically unsaturated monomers M_iIs represented by X_i(I1, 2.. times.i), a theoretical value can be calculated according to the following formula (I).

1/Tg＝Σ(X_i/Tg_i) (I)

As the binder resin (B), a resin in a dispersed state in an aqueous Emulsion (EM) containing water as a dispersion medium is preferably used as a raw material for producing a slurry.

The aqueous Emulsion (EM) of the binder resin (B) can be prepared by the following method.

(1) The binder resin (B) was dispersed in water using an emulsifier and a homogenizer to prepare an aqueous Emulsion (EM).

(2) An aqueous Emulsion (EM) is prepared by emulsion polymerization using a polymerizable monomer capable of producing the binder resin (B) and an emulsifier.

The binder resin (B) preferably has an acid value of 100mgKOH/g or less, more preferably 75mgKOH/g or less, and still more preferably 50mgKOH/g or less.

The content of the binder resin (B) in the aqueous Emulsion (EM), that is, the nonvolatile amount of the aqueous Emulsion (EM), is preferably 1 to 60 mass%, and more preferably 1 to 55 mass%.

Examples of the binder resin (B) used in the present invention include a copolymer (P1) of a styrene monomer such as styrene-butadiene rubber and a diene monomer; a copolymer of a styrenic monomer and an ethylenically unsaturated carboxylic acid ester monomer (P2); ethylene-vinyl acetate copolymers, ethylene-C9-11 Versatic Acid (Versatic Acid) vinyl ester copolymers, ethylene-acrylic ester copolymers, and other ethylene-ethylenically unsaturated carboxylic Acid ester copolymers. Among them, a copolymer (P1) of a styrene monomer and a diene monomer and a copolymer (P2) of a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer are preferable in terms of good adhesion between the active material and the binder resin (B), excellent swelling resistance against an electrolyte solvent, and excellent charge-discharge cycle characteristics. Further, the copolymer (P1) of a styrene monomer and a diene monomer and the copolymer (P2) of a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer are excellent in adhesion to the current collector.

< copolymer of styrenic monomer and diene monomer (P1) >)

A copolymer (P1) of a styrene monomer and a diene monomer (hereinafter sometimes referred to simply as "copolymer (P1)") is a copolymer containing a structural unit derived from a styrene monomer such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, α -methylstyrene or the like, and a structural unit derived from a diene monomer such as butadiene, isoprene or the like.

The copolymer of a styrenic monomer and a diene monomer can be obtained, for example, by emulsion polymerization of a raw material composition containing styrene and butadiene in an aqueous solvent in the presence of an emulsifier.

In the copolymer (P1) of a styrene monomer and a diene monomer, the proportion of the structural unit derived from the diene monomer is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and still more preferably 50 to 70% by mass. That is, the proportion of the diene monomer contained in the raw material for producing the copolymer (P1) of a styrene monomer and a diene monomer is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and still more preferably 50 to 70% by mass.

The proportion of the structural unit derived from the styrene monomer in the copolymer (P1) of a styrene monomer and a diene monomer is preferably 5 to 70% by mass, more preferably 10 to 60% by mass. That is, the proportion of the styrene monomer contained in the raw material for producing the copolymer (P1) of styrene monomer and diene monomer is preferably 5 to 70% by mass, more preferably 10 to 60% by mass.

In addition, in order to obtain a copolymer (P1) of a styrene monomer and a diene monomer, the styrene monomer and the diene monomer may be copolymerized with another copolymerizable ethylenically unsaturated monomer such as an ethylenically unsaturated carboxylic acid monomer.

Examples of the other copolymerizable ethylenically unsaturated monomer include ethylenically unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; ethylenically unsaturated carboxylic acids such as (meth) acrylic acid; ethylenically unsaturated carboxylic acid esters such as methyl methacrylate; olefins such as ethylene and propylene; halogen atom-containing monomers such as vinyl chloride and 1, 1-dichloroethylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; vinyl compounds containing a heterocyclic ring such as N-vinylpyrrolidone, vinylpyridine and vinylimidazole.

< copolymer of styrenic monomer and ethylenically unsaturated carboxylic acid ester monomer (P2) >)

The copolymer (P2) of a styrene-based monomer and an ethylenically unsaturated carboxylic acid ester monomer (hereinafter sometimes referred to simply as "copolymer (P2)") has a structure derived from a styrene-based monomer and a structure derived from an ethylenically unsaturated carboxylic acid ester monomer. The copolymer (P2) can be obtained, for example, by emulsion polymerization of a raw material composition containing a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer in an aqueous solvent in the presence of an emulsifier.

The styrene monomer mainly has an effect of improving the adhesion between the active material and the resin and the adhesion between the electrode active material layer and the current collector. In particular, when artificial graphite is used as the active material, the effect can be further exhibited.

The amount of the styrene monomer used is preferably 10 to 75% by mass, more preferably 30 to 60% by mass, and still more preferably 35 to 55% by mass of the total ethylenically unsaturated monomer components constituting the copolymer (P2).

By setting the amount of styrene monomer used to 10% by mass or more, the adhesion between the active material and the resin and the adhesion between the electrode active material layer and the current collector can be improved. Further, by setting the amount of styrene used to 70% by mass or less, the electrode formed from the composition of the present invention can be made less prone to cracking (cracking is less prone to occur).

Examples of the styrene monomer include styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, and α -methylstyrene. Among them, styrene or vinyltoluene is preferable, and styrene is more preferable in terms of dispersibility of the active material.

The ethylenically unsaturated carboxylic acid ester monomer may or may not have a functional group.

Examples of the ethylenically unsaturated carboxylic acid ester monomer having no functional group include (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isononyl (meth) acrylate, isobornyl (meth) acrylate, and benzyl (meth) acrylate.

Examples of the ethylenically unsaturated carboxylic acid ester monomer having a functional group include ethylenically unsaturated carboxylic acid ester monomers having a hydroxyl group, a glycidyl group, and the like. Specific examples thereof include 2-hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, and glycidyl acrylate. Among them, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate are preferable from the viewpoint of ease of emulsion polymerization and durability.

The amount of the ethylenically unsaturated carboxylic acid ester monomer used is preferably 25 to 90% by mass, more preferably 30 to 65% by mass, and still more preferably 40 to 55% by mass of the total ethylenically unsaturated monomer components used for forming the copolymer (P2).

By setting the amount of the ethylenically unsaturated carboxylic acid ester monomer to 25% by mass or more, flexibility and heat resistance of the formed electrode can be improved, and by setting the amount to 90% by mass or less, adhesiveness between the active material and the resin and adhesiveness between the active material layer and the current collector can be improved.

As monomers for forming the above-mentioned copolymer (P2), ethylenically unsaturated carboxylic acid monomers can also be used.

Examples of the ethylenically unsaturated carboxylic acid monomer include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and half esters of these unsaturated dicarboxylic acids, and among these, acrylic acid and itaconic acid are preferable. These ethylenically unsaturated carboxylic acid monomers may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The amount of the ethylenically unsaturated carboxylic acid monomer used is preferably 0.01 to 10% by mass, more preferably 0.1 to 8% by mass, and still more preferably 0.1 to 7% by mass of the total ethylenically unsaturated monomer components constituting the copolymer (P2). When the content of the ethylenically unsaturated carboxylic acid monomer is 0.01% by mass or more, the emulsion polymerization stability and mechanical stability are improved. Further, if it is 10% by mass or less, the adhesiveness between the active material and the resin and the adhesiveness between the active material layer and the current collector become better.

Further, it is preferable in view of production stability to set the acid value of the copolymer (P2) within the aforementioned range.

As the monomer for forming the above-mentioned copolymer (P2), a monomer other than the above-mentioned monomer having at least one polymerizable ethylenically unsaturated group can also be used. Examples of such monomers include compounds other than ethylenically unsaturated carboxylic acid ester monomers having functional groups such as amide groups and nitrile groups, such as (meth) acrylamide, N-methylol (meth) acrylamide, (meth) acrylonitrile, vinyl acetate, and vinyl propionate, and sodium p-styrenesulfonate.

The raw material composition of the copolymer (P2) of a styrene monomer and an ethylenically unsaturated carboxylic acid ester monomer may further contain an internal crosslinking agent (internal crosslinkable monomer) in order to further improve the swelling resistance of the dried film against the electrolyte solvent.

As the internal crosslinking agent, a crosslinking agent having at least one ethylenically unsaturated group and having a reactive group reactive with the functional group of the monomer, or a crosslinking agent having 2 or more ethylenically unsaturated groups can be used.

Examples of such an internal crosslinking agent include crosslinkable polyfunctional monomers having 2 or more unsaturated groups such as divinylbenzene, ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate and triallyl cyanurate, and silane coupling agents having at least one ethylenically unsaturated group such as vinyltrimethoxysilane, vinyltriethoxysilane, gamma-methacryloxypropyltrimethoxysilane and gamma-methacryloxypropyltriethoxysilane, and among these, divinylbenzene, trimethylolpropane tri (meth) acrylate and gamma-methacryloxypropyltrimethoxysilane are preferable. These internal crosslinking agents may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The amount of the internal crosslinking agent to be used is preferably 0.01 to 5% by mass, more preferably 0.01 to 4% by mass, and still more preferably 0.01 to 3% by mass of the total ethylenically unsaturated monomer components constituting the copolymer (P2). When the amount of the internal crosslinking agent used is 0.01% by mass or more, the swelling resistance of the dried film to the electrolyte solution can be improved more easily, and when the amount is 5% by mass or less, the emulsion polymerization stability can be prevented from being lowered.

Further, as the monomer for forming the copolymer (P2), a reactive emulsifier described later can be used.

< emulsifier >

As the emulsifier used in the emulsion polymerization, a general anionic emulsifier or nonionic emulsifier can be used.

Examples of the anionic emulsifier include alkyl benzene sulfonate, alkyl sulfate, polyoxyethylene alkyl ether sulfate, and fatty acid salt. Examples of the nonionic emulsifier include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. These may be used alone in 1 kind, or in combination of 2 or more kinds.

Further, when a reactive emulsifier is used as the emulsifier, bleeding of the emulsifier can be prevented, and it is preferable from the viewpoint of improving mechanical stability of the electrode formed from the composition of the present invention. Examples of the reactive emulsifier include those represented by the following general formulae (1) to (5).

Wherein R represents an alkyl group, and m represents an integer of 10 to 40.

Wherein n represents an integer of 10 to 12, and m represents an integer of 10 to 40.

Wherein R represents an alkyl group, and M represents NH₄Or Na.

Wherein R represents an alkyl group.

Wherein A represents an alkyleneoxy group having 2 or 3 carbon atoms, and m represents an integer of 10 to 40.

The amount of the emulsifier used is preferably 0.1 to 3.0 parts by mass, more preferably 0.1 to 2.0 parts by mass, and still more preferably 0.2 to 1.0 part by mass, based on 100 parts by mass of all the ethylenically unsaturated monomer components constituting the copolymer, in the case of a non-reactive emulsifier. In the case of the reactive emulsifier, it is preferably 0.3 to 5.0% by mass, more preferably 0.5 to 4.0% by mass, and still more preferably 0.5 to 2.0% by mass of the total ethylenically unsaturated monomer components (including the reactive emulsifier) forming the copolymer. The non-reactive emulsifier and the reactive emulsifier may be used individually, but are preferably used in combination.

< initiator >

The radical polymerization initiator used in the emulsion polymerization may be any of those conventionally known and used, and examples thereof include ammonium persulfate, potassium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide. If necessary, these polymerization initiators may be used together with a reducing agent such as sodium hydrogen sulfite, rongalite (sodium formaldehyde sulfoxylate), ascorbic acid, or the like to perform redox polymerization.

In addition, in order to adjust the molecular weight of the above copolymer (P2), thiol, thioglycolic acid and esters thereof, β -mercaptopropionic acid and esters thereof, and the like may also be used at the time of polymerization.

< polymerization Process >

As the emulsion polymerization method, a polymerization method in which monomers constituting the binder resin (B) are added at once, a method in which polymerization is performed while continuously supplying each component, or the like can be used. The polymerization is usually carried out at a temperature of 30 to 90 ℃ under stirring. Further, the polymerization stability, mechanical stability and chemical stability at the time of emulsion polymerization can be improved by adding an alkaline substance to adjust the pH during or after the polymerization of the copolymer. As the basic substance used in this case, ammonia, triethylamine, ethanolamine, sodium hydroxide, or the like can be used. These may be used alone in 1 kind, or in combination of 2 or more kinds. The pH of the aqueous Emulsion (EM) prepared is preferably 2.5 to 8.0, and more preferably 5 to 7.

[ crack inhibitor (C) ]

The slurry of the present invention contains a crack inhibitor (C) having a boiling point of 120 ℃ or higher at 1 atmosphere and a solubility in water at 20 ℃ of 10g/100mL or higher. The crack inhibitor (C) is preferably an organic solvent, and its boiling point is preferably 150 ℃ or higher, and more preferably more than 200 ℃. The solubility in water at 20 ℃ is preferably 20g/100mL or more, more preferably 50g/100mL or more.

It is considered that when the boiling point of the crack inhibitor (C) is 120 ℃ or higher, the electrode active material layer can be formed while relaxing the stress that is likely to cause the crack generation at the time of drying the slurry.

It is considered that when the solubility in water at 20 ℃ is 10g/100mL or more, the solubility of the crack inhibitor (C) in water is high, the hydrophilicity is high, and the active material (A) constituting most of the slurry is not easily absorbed, so that the fluidity of the slurry can be maintained.

Further, it was found that, in the present invention, the higher the boiling point of the organic solvent, the better the adhesion of the active materials to each other and to the current collector becomes. The specific reason is not clear, but a high boiling point solvent having a large difference in boiling point from water does not easily entrain water when evaporated in the drying step. It is considered that since the positional change of the binder due to hydrogen bonds or the like caused by the entrainment of water does not easily occur, the binder can be dried while being uniformly adhered to the active material.

The crack inhibitor (C) is not particularly limited as long as it satisfies boiling point and solubility. Specific examples thereof include N-methylpyrrolidin-2-one (boiling point: 202 ℃ C., miscible with water), ethylene glycol (boiling point: 197 ℃ C., miscible with water), diethylene glycol (boiling point: 244 ℃ C., miscible with water), ethylene glycol monobutyl ether (boiling point: 171 ℃ C., miscible with water), 3-methoxy-3-methyl-1-butanol (boiling point: 174 ℃ C., miscible with water), N-dimethylformamide (boiling point: 153 ℃ C., miscible with water), and dimethylsulfoxide (boiling point: 189 ℃ C., solubility in water at 25 ℃ C., 25.3g/100 mL). Among them, N-methylpyrrolidin-2-one is particularly preferable because of its high water solubility and high boiling point.

The content of the crack inhibitor (C) is preferably 10 to 500 parts by mass, more preferably 20 to 400 parts by mass, still more preferably 30 to 300 parts by mass, and particularly preferably 100 to 200 parts by mass, based on 100 parts by mass of the binder resin (B).

The amount of the crack inhibitor (C) is preferably 0.1 to 20.0 parts by mass, more preferably 0.3 to 10.0 parts by mass, and still more preferably 0.5 to 5.0 parts by mass, based on 100 parts by mass of the nonvolatile components of the slurry.

The slurry of the present invention preferably contains 0.01 to 10% by mass of the crack inhibitor (C), more preferably 0.10 to 5.0% by mass, and still more preferably 0.20 to 3.00% by mass.

When an electrode is formed by the method described later, the amount of the crack inhibitor (C) contained in the slurry of the present invention is preferably as small as possible. The residual amount of the crack inhibitor (C) in the electrode is preferably 0.05 mass% or less, and more preferably 0.01 mass% or less.

[ thickener (D) ]

The slurry of the present invention may contain a thickener and the like as necessary. Examples of the thickener include carboxymethylcellulose (CMC), methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, polyacrylic acid, oxidized starch, phosphorylated starch, casein and salts thereof, gum arabic, xanthan gum, and arginine compounds. These may be used alone in 1 kind or in combination of 2 or more kinds.

The thickener is preferably 0.1 to 10.0% by mass, more preferably 0.5 to 5.0% by mass, and still more preferably 0.8 to 3.0% by mass, based on the whole nonvolatile components of the slurry.

[ slurry dispersing Medium ]

The slurry dispersion medium of the present invention is water. May be pure water or ion-exchanged water. The water may be used as it is as a dispersion medium in the production of the binder resin (B) by aqueous emulsion polymerization. The slurry may contain a dispersion medium other than water. However, the crack inhibitor (C) is not always contained in the dispersion medium. Examples of the other dispersion medium include alcohols such as methanol, ethanol, and isopropyl alcohol; ketones such as acetone. When another dispersion medium is used, the content of water is preferably 80% by mass or more of the entire dispersion medium.

[ other additives ]

The slurry of the present invention may contain a conductive aid. The conductive auxiliary agent may be any material having electrical conductivity between the active materials. Examples of the conductive assistant include carbon black such as acetylene black, polymer carbon, and carbon fiber.

(method for preparing slurry for nonaqueous Battery electrode)

As an embodiment of the method for preparing the slurry of the present invention, a method including the following steps can be mentioned.

(I) And (c) dispersing, dissolving or kneading the binder resin (B) in a solvent.

(II) a step of adding the active material (A) and an additive to be used as needed, and further dispersing, dissolving or kneading the mixture.

The crack inhibitor (C), the thickener (D), and other additives can be mixed in the step (I) or can be mixed in the step (II).

As another embodiment of the method for preparing a slurry according to the present invention, a method including the following steps can be mentioned.

(I) A step of emulsion-polymerizing 1 or 2 or more kinds of the ethylenically unsaturated monomers to obtain an aqueous Emulsion (EM) of the binder resin (B).

(II) a step of adding the active material (A) and an additive to be used as needed to the aqueous Emulsion (EM), and dispersing and dissolving the active material (A) in the aqueous Emulsion (EM).

The crack inhibitor (C), the thickener (D) and other additives may be mixed in the step (I) or may be mixed in the step (II).

(nonaqueous Battery electrode)

The nonaqueous battery electrode according to an embodiment of the present invention (hereinafter, also referred to as "electrode according to the present embodiment") has an electrode active material layer formed from the slurry for a nonaqueous battery electrode according to the present invention on a current collector.

The electrode according to an embodiment of the present invention can be used as a positive electrode or a negative electrode of a nonaqueous battery, and particularly, when used as a negative electrode, the electrode can exhibit an effect. Particularly, the lithium ion nonaqueous battery can exhibit the most advantageous effect when used as a negative electrode for a lithium ion nonaqueous battery electrode.

The current collector in the electrode of the present embodiment is not particularly limited as long as it is metallic, such as iron, copper, aluminum, nickel, and stainless steel. Among them, aluminum is preferable as the current collector for the positive electrode, and copper is preferable as the current collector for the negative electrode.

The shape of the current collector is not particularly limited, and a sheet having a thickness of 0.001 to 0.5mm is usually preferably used.

The electrode of the present embodiment includes a current collector and an electrode active material layer formed on the current collector, and the electrode active material layer contains a binder resin (B) and an active material (a). The electrode active material layer is formed by hardening (drying) a slurry for a nonaqueous battery electrode.

When the nonaqueous battery electrode according to one embodiment of the present invention is a negative electrode, the slurry for a nonaqueous battery electrode of the present invention containing the negative electrode active material can be used to form a negative electrode active material layer on a current collector. The amount of nonvolatile component of the slurry formed on one surface of the current collector (negative electrode active material layer)Basis weight of (1) is preferably 1 to 20mg/cm²And more preferably 5 to 20mg/cm²More preferably 10 to 15mg/cm²。

When the nonaqueous battery electrode according to an embodiment of the present invention is a positive electrode, a positive electrode active material layer is formed on a current collector by using the slurry for a nonaqueous battery electrode according to the present invention containing the positive electrode active material. The amount of nonvolatile components (the amount of the positive electrode active material layer) of the slurry formed on one surface of the current collector is preferably 10 to 40mg/cm on one surface²Further preferably 13 to 30mg/cm²More preferably 15 to 25mg/cm²。

In the electrode according to one embodiment of the present invention, the binder resin (B) provides good adhesion between the active materials, and can prevent aggregation breakdown of the electrode active material layer. In addition, the electrode of the present embodiment also has good adhesion between the electrode active material layer and the current collector. In particular, by using the slurry for a nonaqueous battery electrode of the present invention, an electrode in which cracks are not easily generated even if the slurry is applied thickly and the electrode active material layer is formed thickly can be obtained. This makes it possible to increase the energy density of the nonaqueous battery. This effect is particularly excellent when copper is used as the current collector.

[ nonaqueous Battery ]

The nonaqueous battery according to an embodiment of the present invention is a lithium ion nonaqueous battery (hereinafter, may be referred to as a "battery according to the present embodiment"). The battery of the present embodiment is obtained by using the nonaqueous battery electrode of the above-described embodiment of the present invention. That is, the nonaqueous battery electrode slurry of the present invention is used to form an electrode active material layer in a thick state and is a battery using an electrode in which cracks are not easily generated.

For example, the nonaqueous battery of the present embodiment preferably has a total thickness of 10 to 40mg/cm on both sides²The negative electrode active material layer of (1), more preferably 20 to 30mg/cm²。

The battery of the present embodiment can be manufactured by a known method using members such as a positive electrode, a negative electrode, an electrolytic solution, and a separator used as needed. The electrode of the present invention can be used as both the positive electrode and the negative electrode, and the electrode of the present embodiment may be used as one of the positive electrode and the negative electrode.

As the outer case of the battery, a metal outer case or an aluminum laminated outer case may be used. The shape of the battery may be any of coin, button, sheet, cylinder, square, flat, and the like. As the electrolyte in the electrolytic solution of the battery, any known lithium salt may be used, and may be selected according to the kind of the active material. Examples thereof include LiClO₄、LiBF₆、LiPF₆、LiCF₃SO₃、LiCF₃CO₂、LiAsF₆、LiSbF₆、LiB₁₀Cl₁₀、LiAlCl₄、LiCl、LiBr、LiB(C₂H₅)₄、CF₃SO₃Li、CH₃SO₃Li、LiCF₃SO₃、LiC₄F₉SO₃、Li(CF₃SO₂)₂N, lithium lower fatty acid carboxylate, and the like.

The solvent for dissolving the electrolyte is not particularly limited as long as it is a solvent generally used as a liquid for dissolving the electrolyte, and examples thereof include carbonate compounds such as Ethylene Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), Vinylene Carbonate (VC), and the like; lactone compounds such as γ -butyrolactone and γ -valerolactone; ether compounds such as trimethoxymethane, 1, 2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxide compounds such as dimethyl sulfoxide; oxolane compounds such as 1, 3-dioxolane and 4-methyl-1, 3-dioxolane; nitrogen-containing compounds such as acetonitrile, nitromethane, formamide, and dimethylformamide; organic acid ester compounds such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate; phosphotriester, diglyme compounds; a triglyme compound; sulfolane, methyl sulfolaneAnd sulfolane compounds; 3-methyl-2-Oxazolidinones and the likeAn oxazolidinone compound; sultone compounds such as 1, 3-propane sultone, 1, 4-butane sultone, and naphthalene sultone; and the like. These may be used alone in 1 kind, or in combination of 2 or more kinds.

The nonaqueous battery according to an embodiment of the present invention is a lithium ion nonaqueous battery.

(method for producing nonaqueous Battery electrode)

The method for manufacturing a nonaqueous battery electrode according to an embodiment of the present invention includes the following steps.

(III) a step of applying the slurry for a non-aqueous battery electrode obtained in the steps (I) and (II) to a current collector and drying the applied slurry to form an electrode active material layer.

The electrode of the present embodiment is obtained by, for example, applying the slurry for a non-aqueous battery electrode of the present invention described above on a current collector and drying the applied slurry.

The coating method may be a usual method, and examples thereof include a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain coating method, a gravure method, a bar method, a dipping method and an extrusion method. Among them, the doctor blade method, the knife method, or the extrusion method is preferable from the viewpoint that the surface state of the electrode active material layer can be made good by selecting a coating method so as to match the respective physical properties such as viscosity of the slurry of the present invention and the drying property. The drying temperature is 25 ℃ to 180 ℃ and can be selected according to the properties, drying properties and drying time of the resin contained in the slurry. From the viewpoint of work efficiency, it is preferably, for example, 50 to 150 ℃, and more preferably 60 to 120 ℃.

In addition, the electrode of the present embodiment may be pressed as necessary after the electrode active material layer is formed. As the method of pressing, a usual method can be used, but a die pressing method and calendar pressing (カレン) are particularly preferableダープレス) method. The pressure during pressing is not particularly limited, but is preferably 0.2 to 3t/cm²。