WO2014185381A1

WO2014185381A1 - Binder composition for lithium ion secondary battery, slurry composition for lithium ion secondary battery, electrode for lithium ion secondary battery, lithium ion secondary battery, and method for producing binder composition for lithium ion secondary battery

Info

Publication number: WO2014185381A1
Application number: PCT/JP2014/062607
Authority: WO
Inventors: 智一佐々木
Original assignee: 日本ゼオン株式会社
Priority date: 2013-05-14
Filing date: 2014-05-12
Publication date: 2014-11-20
Also published as: CN105122521B; CN105122521A; KR20160008519A; JPWO2014185381A1; JP6384476B2; KR102188318B1

Abstract

This binder composition for a lithium ion secondary battery includes: a particulate polymer; a water-soluble polymer; a polyether-modified silicone compound; and water. The water-soluble polymer includes 20-70 wt% of acid-group-containing monomer units. The content of the polyether-modified silicone compound is 0.1-10 parts by weight per 100 parts by weight of the water-soluble polymer.

Description

Lithium ion secondary battery binder composition, lithium ion secondary battery slurry composition, lithium ion secondary battery electrode, lithium ion secondary battery, and method for producing lithium ion secondary battery binder composition

The present invention relates to a binder composition for a lithium ion secondary battery, a slurry composition for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a binder composition for a lithium ion secondary battery. Regarding the method.

In recent years, portable terminals such as notebook personal computers, mobile phones, and PDAs (Personal Digital Assistants) have become widespread. Lithium ion secondary batteries are frequently used as secondary batteries used as power sources for these portable terminals. Mobile terminals are required to have more comfortable portability, and are rapidly becoming smaller, thinner, lighter, and higher performance. As a result, mobile terminals are used in various places. In addition, secondary batteries are also required to be smaller, thinner, lighter, and have higher performance, as with mobile terminals.

In order to improve the performance of secondary batteries, improvements to electrodes, electrolytes and other battery members are being studied. Of these, the electrode is usually obtained by mixing an electrode active material with a liquid composition in which a polymer as a binder is dispersed or dissolved in a solvent to obtain a slurry composition, and applying the slurry composition to a current collector. Manufactured by drying. In the electrode manufactured by such a method, it has been attempted in the past to improve the performance of the secondary battery by devising the composition of the slurry composition.

Also, a technique such as Patent Document 1 is known.

International Publication No. 2004/101103

In a lithium ion secondary battery, lithium metal may be deposited on the surface of the electrode during charging and discharging. This lithium metal can increase the internal resistance of the secondary battery. Therefore, in order to improve performance such as high temperature cycle characteristics and low temperature output characteristics of the lithium ion secondary battery, it is desirable to suppress the deposition of this lithium metal.
Therefore, the present invention can suppress the precipitation of lithium metal due to charge and discharge, and can realize a lithium ion secondary battery excellent in high-temperature cycle characteristics and low-temperature output characteristics, and a lithium ion secondary battery binder composition, for a lithium ion secondary battery Slurry composition and electrode for lithium ion secondary battery; Lithium ion secondary battery excellent in high temperature cycle characteristics and low temperature output characteristics that can suppress lithium metal precipitation due to charging and discharging; and Lithium metal deposition due to charging and discharging can be suppressed Another object of the present invention is to provide a method for producing a binder composition for a lithium ion secondary battery capable of realizing a lithium ion secondary battery excellent in high temperature cycle characteristics and low temperature output characteristics.

In order to solve the above problems, the present inventor includes a particulate polymer, a water-soluble polymer, a polyether-modified silicone compound, and water, and the water-soluble polymer includes a predetermined amount of acid group-containing monomer units, and The binder composition in which the amount of the polyether-modified silicone compound falls within a predetermined range with respect to the water-soluble polymer was examined. As a result, by using this binder composition, it becomes possible to suppress lithium metal deposition and improve lithium ion conductivity in the lithium ion secondary battery, so the high temperature cycle characteristics and low temperature output characteristics of the lithium ion secondary battery. The present invention has been completed.
That is, the present invention is as follows.

[1] A particulate polymer, a water-soluble polymer, a polyether-modified silicone compound and water,
The water-soluble polymer contains 20% by weight to 70% by weight of an acid group-containing monomer unit;
A binder composition for a lithium ion secondary battery, wherein the amount of the polyether-modified silicone compound is 0.1 to 10 parts by weight with respect to 100 parts by weight of the water-soluble polymer.
[2] The binder composition for a lithium ion secondary battery according to [1], wherein the water-soluble polymer further contains 0.1 to 30% by weight of a fluorine-containing monomer unit.
[3] The binder composition for a lithium ion secondary battery according to [1] or [2], wherein the 1% aqueous solution viscosity of the water-soluble polymer is 1 mPa · s to 1000 mPa · s.
[4] The lithium ion secondary battery according to any one of [1] to [3], wherein the water-soluble polymer further contains 0.1 to 2% by weight of a crosslinkable monomer unit. Binder composition.
[5] The lithium ion secondary solution according to any one of [1] to [4], wherein the aqueous solution containing the polyether-modified silicone compound at a concentration of 10% by weight has a surface tension of 20 mN / m to 50 mN / m. Secondary battery binder composition.
[6] The weight ratio of the particulate polymer to the water-soluble polymer is particulate polymer / water-soluble polymer = 99/1 to 50/50, any one of [1] to [5] The binder composition for a lithium ion secondary battery according to Item.
[7] A slurry composition for a lithium ion secondary battery, comprising the binder composition according to any one of [1] to [6] and an electrode active material.
[8] The slurry composition for a lithium ion secondary battery according to [7], further comprising a thickener.
[9] current collector;
The electrode for lithium ion secondary batteries provided with the electrode active material layer obtained by apply | coating the slurry composition for lithium ion secondary batteries as described in [7] or [8] on the said electrical power collector, and drying.
[10] A positive electrode, a negative electrode, and an electrolyte solution are provided.
A lithium ion secondary battery, wherein at least one of the positive electrode and the negative electrode is an electrode for a lithium ion secondary battery according to [9].
[11] a step of mixing the particulate polymer, the polyether-modified silicone compound and water;
The method for producing a binder composition for a lithium ion secondary battery according to any one of [1] to [6], further comprising a step of further mixing the water-soluble polymer.

According to the binder composition for a lithium ion secondary battery, the slurry composition for a lithium ion secondary battery, and the electrode for a lithium ion secondary battery of the present invention, lithium metal precipitation due to charge / discharge can be suppressed, and high temperature cycle characteristics and low temperature A lithium ion secondary battery having excellent output characteristics can be realized.
The lithium ion secondary battery of the present invention can suppress the precipitation of lithium metal due to charge and discharge, and is excellent in high temperature cycle characteristics and low temperature output characteristics.
According to the method for producing a binder composition for a lithium ion secondary battery of the present invention, lithium ion secondary battery that can suppress the deposition of lithium metal due to charge and discharge and that is excellent in high temperature cycle characteristics and low temperature output characteristics can be realized. A binder composition for a secondary battery can be produced.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

In the following description, (meth) acrylic acid includes both acrylic acid and methacrylic acid. Further, (meth) acrylate includes both acrylate and methacrylate. Furthermore, (meth) acrylonitrile includes both acrylonitrile and methacrylonitrile.

Furthermore, in the following description, a substance is water-soluble when an insoluble content is 0 wt% or more and less than 0.5 wt% when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C. Say something. Further, that a certain substance is water-insoluble means that an insoluble content is 90% by weight or more and 100% by weight or less when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C.

In addition, in a polymer produced by copolymerizing a plurality of types of monomers, the proportion of the structural unit formed by polymerizing a certain monomer in the polymer is usually that unless otherwise specified. This coincides with the ratio (preparation ratio) of the certain monomer in the total monomers used for polymerization of the polymer.

[1. Binder composition for lithium ion secondary battery]
The binder composition for a lithium ion secondary battery of the present invention (hereinafter sometimes referred to as “binder composition” as appropriate) includes a particulate polymer, a water-soluble polymer, a polyether-modified silicone compound, and water.

[1.1. (Particulate polymer)
The particulate polymer is a polymer particle. By including the particulate polymer, the binding property of the electrode active material layer can be improved, and the strength against mechanical force applied to the electrode during handling such as winding and transportation can be improved. In addition, since it becomes difficult for the electrode active material to fall off the electrode active material layer, the risk of a short circuit or the like due to foreign matter is reduced. Furthermore, since the electrode active material can be stably held in the electrode active material layer, durability such as cycle characteristics and high-temperature storage characteristics can be improved. Moreover, by being particulate, the particulate polymer can be bound to the electrode active material not by a surface but by a point. For this reason, most of the surface of the electrode active material is not covered with the binder, so that the field of exchange of ions between the electrolytic solution and the electrode active material can be widened. Therefore, the output resistance of the lithium ion secondary battery can be improved by reducing the internal resistance.

As the polymer constituting the particulate polymer, various polymers can be used, but usually a water-insoluble polymer is used. Examples of the polymer forming the particulate polymer include acrylic polymers, diene polymers, fluorine-containing polymers, polyimides, polyamides, polyurethane polymers, and the like. Of these, diene polymers and acrylic polymers are preferred. These particulate polymers may have a cross-linked structure or may have a functional group introduced by modification. Furthermore, one kind of particulate polymer may be used alone, or two or more kinds of particulate polymers may be used in combination at any ratio.

The diene polymer is a polymer containing an aliphatic conjugated diene monomer unit. The aliphatic conjugated diene monomer unit is a structural unit having a structure formed by polymerizing an aliphatic conjugated diene monomer.

Examples of the aliphatic conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene; And pentadiene having a conjugated double bond in a straight chain and a substituted product thereof; and hexadiene having a conjugated double bond in a side chain and a substituted product thereof. Of these, 1,3-butadiene is preferred. Moreover, an aliphatic conjugated diene monomer and an aliphatic conjugated diene monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

In the diene polymer, the proportion of the aliphatic conjugated diene monomer unit is preferably 20% by weight or more, more preferably 30% by weight or more, preferably 70% by weight or less, more preferably 60% by weight or less, Particularly preferred is 55% by weight or less.

The diene polymer preferably contains an aromatic vinyl monomer unit. The aromatic vinyl monomer unit is a structural unit having a structure formed by polymerizing an aromatic vinyl monomer.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyl toluene, and divinylbenzene. Of these, styrene is preferred. The diene polymer is preferably a polymer containing both an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit. For example, a styrene-butadiene copolymer is preferred. Moreover, an aromatic vinyl monomer and an aromatic vinyl monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

When using a combination of an aliphatic conjugated diene monomer and an aromatic vinyl monomer in the production of a diene polymer, the resulting diene polymer contains an unreacted aliphatic conjugated diene monomer as a residual monomer. And unreacted aromatic vinyl monomers. In that case, the amount of the unreacted aliphatic conjugated diene monomer contained in the diene polymer is preferably 50 ppm or less, more preferably 10 ppm or less, and ideally 0 ppm. The amount of the unreacted aromatic vinyl monomer contained in the diene polymer is preferably 1000 ppm or less, more preferably 200 ppm or less, and ideally 0 ppm.

The proportion of the aromatic vinyl monomer unit in the diene polymer is preferably 30% by weight or more, more preferably 35% by weight or more, preferably 79.5% by weight or less, more preferably 69% by weight or less. is there.

The diene polymer preferably contains an ethylenically unsaturated carboxylic acid monomer unit. The ethylenically unsaturated carboxylic acid monomer unit means a structural unit having a structure formed by polymerizing an ethylenically unsaturated carboxylic acid monomer. Since the ethylenically unsaturated carboxylic acid monomer unit is a structural unit that includes a carboxy group (—COOH group) and has high strength, it can increase the binding property of the electrode active material layer to the current collector, The strength of the layer can be improved. Therefore, when the diene polymer contains an ethylenically unsaturated carboxylic acid monomer unit, peeling of the electrode active material layer from the current collector can be stably prevented, and the mechanical strength of the electrode active material layer can be prevented. Can be improved.

Examples of the ethylenically unsaturated carboxylic acid monomer include the same examples as those exemplified in the section of the water-soluble polymer. Moreover, an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated carboxylic acid monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the ethylenically unsaturated carboxylic acid monomer unit in the diene polymer is preferably 0.5% by weight or more, more preferably 1% by weight or more, particularly preferably 2% by weight or more, preferably 10% by weight. % Or less, more preferably 8% by weight or less, and particularly preferably 7% by weight or less.

The diene polymer may contain any structural unit other than those described above as long as the effects of the present invention are not significantly impaired. Examples of monomers corresponding to the above arbitrary structural units include vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, unsaturated monomers containing hydroxyalkyl groups, and unsaturated carboxylic acids. Examples include acid amide monomers. One of these may be used alone, or two or more of these may be used in combination at any ratio.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-ethylacrylonitrile. Of these, acrylonitrile and methacrylonitrile are preferable.

Examples of unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, and dimethyl itaco. Nates, monomethyl fumarate, monoethyl fumarate, and 2-ethylhexyl acrylate. Of these, methyl methacrylate is preferable.

Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2- Examples include hydroxypropyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, and 2-hydroxyethyl methyl fumarate. Of these, β-hydroxyethyl acrylate is preferred.

Examples of the unsaturated carboxylic acid amide monomer include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, and N, N-dimethylacrylamide. Of these, acrylamide and methacrylamide are preferable.

Furthermore, the diene polymer has a structure formed by polymerizing monomers used in usual emulsion polymerization such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, etc. Units may be included.

The acrylic polymer is a polymer containing a (meth) acrylic acid ester monomer unit. The (meth) acrylic acid ester monomer unit is a structural unit having a structure formed by polymerizing a (meth) acrylic acid ester monomer. However, among the (meth) acrylate monomers, those containing fluorine are distinguished from (meth) acrylate monomers as fluorine-containing (meth) acrylate monomers.

Examples of the (meth) acrylic acid ester monomer include the same examples as those exemplified in the section of the water-soluble polymer. Moreover, a (meth) acrylic acid ester monomer and a (meth) acrylic acid ester monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the (meth) acrylic acid ester monomer unit in the acrylic polymer is preferably 50% by weight or more, more preferably 70% by weight or more, particularly preferably 90% by weight or more, and preferably 99% by weight or less. More preferably, it is 98 weight% or less, Most preferably, it is 97 weight% or less.

Also, the acrylic polymer is preferably a copolymer containing a combination of a (meth) acrylonitrile monomer unit and a (meth) acrylic acid ester monomer unit. The (meth) acrylonitrile monomer unit means a structural unit having a structure formed by polymerizing (meth) acrylonitrile. Since an acrylic polymer containing a combination of a (meth) acrylonitrile monomer unit and a (meth) acrylic acid ester monomer unit is stable to oxidation and reduction, it is easy to obtain a long-life battery.

The acrylic polymer may contain only a structural unit having a structure formed by polymerizing acrylonitrile as a (meth) acrylonitrile monomer unit, and has a structure formed by polymerizing methacrylonitrile. It may contain only structural units, and includes both a structural unit having a structure formed by polymerizing acrylonitrile and a structural unit having a structure formed by polymerizing methacrylonitrile in an arbitrary ratio. May be.

When the acrylic polymer contains a combination of a (meth) acrylonitrile monomer unit and a (meth) acrylate monomer unit, a (meth) acrylonitrile monomer unit relative to the (meth) acrylate monomer unit The weight ratio (weight ratio represented by “(meth) acrylonitrile monomer unit / (meth) acrylate monomer unit”) is preferably within a predetermined range. Specifically, the weight ratio is preferably 1/99 or more, more preferably 2/98 or more, 30/70 or less, and more preferably 25/75 or less. By setting the weight ratio to be equal to or higher than the lower limit of the range, it is possible to prevent the electrode polymer from being increased by swelling the particulate polymer in the electrolytic solution, and to suppress the deterioration of the rate characteristics of the secondary battery.

The acrylic polymer may contain a crosslinkable monomer unit. A crosslinkable monomer unit is a structural unit having a structure formed by polymerizing a crosslinkable monomer. A crosslinkable monomer is a monomer that can form a crosslinked structure during or after polymerization by heating or irradiation with energy rays. When the acrylic polymer contains a crosslinkable monomer unit, the particulate polymers can be crosslinked with each other, or the water-soluble polymer and the particulate polymer can be crosslinked.

Examples of the crosslinkable monomer include the same examples as mentioned in the section of the water-soluble polymer. Moreover, a crosslinking | crosslinked monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Furthermore, the crosslinkable monomer unit may be introduced into the acrylic polymer by copolymerizing the crosslinkable monomer with the (meth) acrylate monomer unit. Further, the crosslinkable monomer unit is introduced into the acrylic polymer by introducing the crosslinkable group into the acrylic polymer by a conventional modification means using a compound having a crosslinkable group (crosslinking agent). Also good.

As the crosslinking agent, for example, an organic peroxide, a crosslinking agent that exhibits an effect by heat or light, and the like are used. Moreover, a crosslinking agent may be used individually by 1 type, and may be used combining 2 or more types by arbitrary ratios.
Among the cross-linking agents, an organic peroxide and a cross-linking agent capable of causing a cross-linking reaction by heat are preferable because they contain a heat cross-linkable cross-linking group.

The proportion of the crosslinkable monomer unit in the acrylic polymer is preferably 0.01 with respect to 100 parts by weight of the total amount of the (meth) acrylonitrile monomer unit and the (meth) acrylic acid ester monomer unit. Part by weight or more, more preferably 0.05 part by weight or more, preferably 5 parts by weight or less, more preferably 4 parts by weight or less, and particularly preferably 3 parts by weight or less.

Further, the acrylic polymer may contain an arbitrary structural unit other than the above-mentioned (meth) acrylonitrile monomer unit, (meth) acrylic acid ester monomer unit and crosslinkable group monomer unit. Examples of monomers corresponding to these arbitrary structural units include styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, α-methyl. Styrene monomers such as styrene and divinylbenzene; Olefins such as ethylene and propylene; Diene monomers such as butadiene and isoprene; Monomers containing halogen atoms such as vinyl chloride and vinylidene chloride; Vinyl acetate and vinyl propionate Vinyl esters such as vinyl butyrate; 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; N- Nirupiroridon, vinylpyridine, heterocycle-containing vinyl compounds such as vinyl imidazole; acrylamide, amide monomers such as acrylamide-2-methylpropane sulfonic acid; and the like. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. However, the amount of any structural unit is small from the viewpoint of remarkably exhibiting the advantages of including the (meth) acrylonitrile monomer unit and the (meth) acrylic acid ester monomer unit in combination as described above. It is particularly preferable that it does not contain any structural unit.

The weight average molecular weight of the polymer constituting the particulate polymer is preferably 10,000 or more, more preferably 20,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less. It is. When the weight average molecular weight of the polymer constituting the particulate polymer is in the above range, the strength of the electrode and the dispersibility of the electrode active material are easily improved.
Here, the weight average molecular weight of the polymer constituting the particulate polymer can be determined by gel permeation chromatography (GPC) as a value in terms of polystyrene using tetrahydrofuran as a developing solvent.

The glass transition temperature of the particulate polymer is preferably −75 ° C. or higher, more preferably −55 ° C. or higher, particularly preferably −35 ° C. or higher, preferably 40 ° C. or lower, more preferably 30 ° C. or lower. More preferably, it is 20 degrees C or less, Most preferably, it is 15 degrees C or less. When the glass transition temperature of the particulate polymer is in the above range, characteristics such as flexibility and winding property of the electrode, and binding property between the electrode active material layer and the current collector are highly balanced, which is preferable. . The glass transition temperature of the particulate polymer can be adjusted by combining various monomers.

The volume average particle diameter D50 of the particulate polymer is preferably 50 nm or more, more preferably 70 nm or more, and preferably 500 nm or less, more preferably 400 nm or less. When the volume average particle diameter D50 of the particulate polymer is in the above range, the strength and flexibility of the obtained electrode can be improved. Here, the volume average particle diameter D50 is a particle diameter at which the cumulative volume calculated from the small diameter side becomes 50% in the particle diameter distribution measured by the laser diffraction method.

The production method of the particulate polymer is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method may be used. Among them, the emulsion polymerization method and the suspension polymerization method are preferable because they can be polymerized in water and used as they are as the material of the binder composition. Moreover, when manufacturing a particulate polymer, it is preferable to include a dispersing agent in the reaction system. The particulate polymer is usually formed of a polymer that substantially constitutes the particulate polymer, but may contain any component such as an additive that was included in the reaction system during the polymerization.

[1.2. Water-soluble polymer)
The water-soluble polymer usually disperses the electrode active material uniformly in a slurry composition for a lithium ion secondary battery (hereinafter sometimes referred to as “slurry composition” as appropriate) containing the binder composition of the present invention. Has an effect. In addition, the water-soluble polymer usually binds the electrode active material and the current collector by interposing between the electrode active materials and between the electrode active material and the current collector in the electrode active material layer. Can have an effect. Furthermore, the water-soluble polymer usually has an effect of suppressing the decomposition of the electrolytic solution by forming a stable layer covering the electrode active material in the electrode active material layer.

(1.2.1. Acid group-containing monomer unit)
The water-soluble polymer includes an acid group-containing monomer unit. The acid group-containing monomer unit is a structural unit having a structure formed by polymerizing an acid group-containing monomer.

An acid group refers to a group that exhibits acidity. Examples of acid groups include carboxylic acid groups such as carboxyl groups and carboxylic anhydride groups, sulfonic acid groups, and phosphoric acid groups. Of these, carboxylic acid groups and sulfonic acid groups are preferred.

Examples of the acid group-containing monomer include an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated sulfonic acid monomer, and an ethylenically unsaturated phosphoric acid monomer.

Examples of the ethylenically unsaturated carboxylic acid monomer include an ethylenically unsaturated monocarboxylic acid monomer and derivatives thereof, an ethylenically unsaturated dicarboxylic acid monomer and acid anhydrides thereof, and derivatives thereof. Examples of ethylenically unsaturated monocarboxylic acid monomers include acrylic acid, methacrylic acid, and crotonic acid. Examples of derivatives of ethylenically unsaturated monocarboxylic acid monomers include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxy Examples include acrylic acid and β-diaminoacrylic acid. Examples of ethylenically unsaturated dicarboxylic acid monomers include maleic acid, fumaric acid, and itaconic acid. Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acid monomers include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Examples of derivatives of ethylenically unsaturated dicarboxylic acid monomers include substituted maleic acids such as methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid; and diphenyl maleate, Examples include maleate esters such as nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Of these, ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid are preferred because the water-soluble polymer obtained can be more soluble in water.

Examples of ethylenically unsaturated sulfonic acid monomers include monomers sulfonated one of conjugated double bonds of diene compounds such as isoprene and butadiene, vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfone. Examples thereof include ethyl methacrylate, sulfopropyl methacrylate, sulfobutyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 3-allyloxy-2-hydroxypropanesulfonic acid (HAPS), and salts thereof. Examples of the salt include lithium salt, sodium salt, potassium salt and the like. For example, sodium salt (NaSS) of styrene sulfonic acid (p-styrene sulfonic acid etc.) can be mentioned. Preferred examples of the ethylenically unsaturated sulfonic acid monomer include AMPS and NaSS. AMPS is particularly preferable.

Examples of the ethylenically unsaturated phosphoric acid monomer include a monomer having an ethylenically unsaturated group and a —OP (═O) (— OR ^a ) —OR ^b group, or a salt thereof. Can be mentioned. Here, R ^a and R ^b are independently a hydrogen atom or any organic group. Specific examples of the organic group as R ^a and R ^b include an aliphatic group such as an octyl group and an aromatic group such as a phenyl group. Specific examples of the ethylenically unsaturated phosphoric acid monomer include a compound containing a phosphoric acid group and an allyloxy group, and a phosphoric acid group-containing (meth) acrylic acid ester. Examples of the compound containing a phosphoric acid group and an allyloxy group include 3-allyloxy-2-hydroxypropane phosphoric acid. Examples of phosphate group-containing (meth) acrylic acid esters include dioctyl-2-methacryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, monomethyl-2-methacryloyloxyethyl phosphate, dimethyl-2-methacrylate. Leuoxyethyl phosphate, monoethyl-2-methacryloyloxyethyl phosphate, diethyl-2-methacryloyloxyethyl phosphate, monoisopropyl-2-methacryloyloxyethyl phosphate, diisopropyl-2-methacryloyloxyethyl phosphate, mono n-butyl -2-Methacryloyloxyethyl phosphate, di-n-butyl-2-methacryloyloxyethyl phosphate, monobutoxyethyl-2-methacryloyloxyethyl phosphate , Dibutoxyethyl-2-methacryloyloxyethyl phosphate, mono (2-ethylhexyl) -2-methacryloyloxyethyl phosphate, and di (2-ethylhexyl) -2-methacryloyloxyethyl phosphate.

Among the above-mentioned examples, preferred are ethylenically unsaturated carboxylic acid monomers and ethylenically unsaturated sulfonic acid monomers, and more preferred are acrylic acid, methacrylic acid, itaconic acid and 2- Examples include acrylamido-2-methylpropanesulfonic acid, and acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid are more preferable.
As the acid group-containing monomer and the acid group-containing monomer unit, one type may be used alone, or two or more types may be used in combination at any ratio.

The ratio of the acid group-containing monomer unit in the water-soluble polymer is usually 20% by weight or more, preferably 25% by weight or more, more preferably 30% by weight or more, and usually 70% by weight or less, preferably 65%. % By weight or less, more preferably 60% by weight or less. By setting the amount of the acid group-containing monomer unit to be equal to or higher than the lower limit of the above range, it is possible to suppress the precipitation of lithium metal due to charge / discharge in the lithium ion secondary battery. Moreover, the binding property of an electrode active material layer and an electrical power collector can be improved by setting it as an upper limit or less.

(1.2.2. Fluorine-containing monomer unit)
The water-soluble polymer preferably contains a fluorine-containing monomer unit. The fluorine-containing monomer unit is a structural unit having a structure formed by polymerizing a fluorine-containing monomer.
As a fluorine-containing monomer, a fluorine-containing (meth) acrylic acid ester monomer is mentioned, for example. Examples of the fluorine-containing (meth) acrylic acid ester monomer include monomers represented by the following formula (I).

In the above formula (I), R ¹ represents a hydrogen atom or a methyl group.
In the formula (I) of the, R ² represents a hydrocarbon group containing a fluorine atom. The carbon number of the hydrocarbon group is usually 1 or more and usually 18 or less. Moreover, the number of fluorine atoms contained in R ² may be one or two or more.

Examples of fluorine-containing (meth) acrylic acid ester monomers represented by formula (I) include (meth) acrylic acid alkyl fluoride, (meth) acrylic acid fluoride aryl, and (meth) acrylic acid fluoride. Aralkyl is mentioned. Of these, alkyl fluoride (meth) acrylate is preferred. Specific examples of such monomers include 2,2,2-trifluoroethyl (meth) acrylate; β- (perfluorooctyl) ethyl (meth) acrylate; 2,2, (meth) acrylic acid 3,3-tetrafluoropropyl; (meth) acrylic acid 2,2,3,4,4,4-hexafluorobutyl; (meth) acrylic acid 3 [4 [1-trifluoromethyl-2,2-bis [ Bis (trifluoromethyl) fluoromethyl] ethynyloxy] benzooxy] 2-hydroxypropyl; (meth) acrylic acid 1H, 1H, 9H-perfluoro-1-nonyl, (meth) acrylic acid 1H, 1H, 11H-perfluoro (Medec) such as undecyl, perfluorooctyl (meth) acrylate, perfluoroethyl (meth) acrylate, trifluoromethyl (meth) acrylate, etc. ) Acrylic acid perfluoroalkyl ester.
A fluorine-containing monomer and a fluorine-containing monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The ratio of the fluorine-containing monomer unit in the water-soluble polymer is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, particularly preferably 0.5% by weight or more, and preferably It is 30% by weight or less, more preferably 25% by weight or less, and particularly preferably 20% by weight or less. By setting the ratio of the fluorine-containing monomer unit to be equal to or higher than the lower limit of the above range, the high temperature cycle characteristics of the lithium ion secondary battery can be enhanced. Moreover, precipitation to the lithium metal by charging / discharging can be suppressed in a lithium ion secondary battery by using below an upper limit.

(1.2.3. Crosslinkable monomer unit)
The water-soluble polymer preferably contains a crosslinkable monomer unit. By including a crosslinkable monomer unit, the water-soluble polymer can be crosslinked, so that the strength and stability of the electrode active material layer can be increased. Moreover, swelling of the electrode active material layer with respect to the electrolytic solution can be suppressed, and the low-temperature output characteristics of the lithium ion secondary battery can be improved.

As the crosslinkable monomer, a monomer capable of forming a crosslinked structure upon polymerization can be used. Examples of the crosslinkable monomer include monomers having two or more reactive groups per molecule. More specifically, a monofunctional monomer having a heat-crosslinkable crosslinkable group and one olefinic double bond per molecule, and a polyfunctional having two or more olefinic double bonds per molecule. Ionic monomers.

Examples of thermally crosslinkable groups contained in the monofunctional monomer include epoxy groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, and combinations thereof. Among these, an epoxy group is more preferable in terms of easy adjustment of crosslinking and crosslinking density.

Examples of the crosslinkable monomer having an epoxy group as a thermally crosslinkable group and having an olefinic double bond include vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl. Unsaturated glycidyl ethers such as ether; butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene Monoepoxides of dienes or polyenes such as; alkenyl epoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; and glycidyl acrylate, glycidyl methacrylate, Glycidyl crotonate, glycy Unsaturated carboxylic acids such as ru-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid Glycidyl esters of acids; and the like.

Examples of the crosslinkable monomer having an N-methylolamide group as a thermally crosslinkable group and having an olefinic double bond have a methylol group such as N-methylol (meth) acrylamide (meta ) Acrylamides.

Examples of the crosslinkable monomer having an oxetanyl group as a thermally crosslinkable group and having an olefinic double bond include 3-((meth) acryloyloxymethyl) oxetane, 3-((meth) Acryloyloxymethyl) -2-trifluoromethyloxetane, 3-((meth) acryloyloxymethyl) -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, and 2-((meth) acryloyloxymethyl) ) -4-trifluoromethyloxetane.

Examples of the crosslinkable monomer having an oxazoline group as a heat crosslinkable group and having an olefinic double bond include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2- Oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and And 2-isopropenyl-5-ethyl-2-oxazoline.

Examples of multifunctional monomers having two or more olefinic double bonds include allyl (meth) acrylate, ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Tetraethylene glycol di (meth) acrylate, trimethylolpropane-tri (meth) acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, trimethylolpropane-diallyl Examples include ethers, allyl or vinyl ethers of polyfunctional alcohols other than those described above, triallylamine, methylenebisacrylamide, and divinylbenzene.

Especially, as a crosslinkable monomer, ethylene dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate are preferable, and ethylene dimethacrylate and glycidyl methacrylate are more preferable.
Moreover, a crosslinking | crosslinked monomer and a crosslinking | crosslinked monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

In the water-soluble polymer, the proportion of the crosslinkable monomer unit is preferably 0.1% by weight or more, more preferably 0.15% by weight or more, and particularly preferably 0.2% by weight or more. Is 2% by weight or less, more preferably 1.5% by weight or less, and particularly preferably 1.0% by weight or less. By setting the ratio of the crosslinkable monomer unit to be equal to or higher than the lower limit of the above range, it is possible to suppress the precipitation of lithium metal due to charge / discharge in the lithium ion secondary battery. Moreover, the high temperature cycling characteristic of a lithium ion secondary battery can be improved by setting it as below an upper limit.

(1.2.4. Reactive surfactant unit)
The water-soluble polymer can contain reactive surfactant units. The reactive surfactant unit is a structural unit having a structure formed by polymerizing a reactive surfactant. The reactive surfactant unit forms part of the water-soluble polymer and can function as a surfactant.

The reactive surfactant is a monomer having a polymerizable group that can be copolymerized with another monomer and having a surfactant group (hydrophilic group and hydrophobic group). Usually, the reactive surfactant has a polymerizable unsaturated group, and this group also acts as a hydrophobic group after polymerization. Examples of the polymerizable unsaturated group that the reactive surfactant has include a vinyl group, an allyl group, a vinylidene group, a propenyl group, an isopropenyl group, and an isobutylidene group. One kind of the polymerizable unsaturated group may be used alone, or two or more kinds may be used in combination at any ratio.

The reactive surfactant usually has a hydrophilic group as a portion that exhibits hydrophilicity. Reactive surfactants are classified into anionic, cationic and nonionic surfactants depending on the type of hydrophilic group.

Examples of the anionic hydrophilic group include —SO ₃ M, —COOM, and —PO (OH) ₂ . Here, M represents a hydrogen atom or a cation. Examples of cations include alkali metal ions such as lithium, sodium and potassium; alkaline earth metal ions such as calcium and magnesium; ammonium ions; ammonium ions of alkylamines such as monomethylamine, dimethylamine, monoethylamine and triethylamine; and And ammonium ions of alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine.
Examples of the cationic hydrophilic group include —Cl, —Br, —I, and —SO ₃ OR ^X. Here, R ^X represents an alkyl group. Examples of R ^X is methyl group, an ethyl group, a propyl group, and isopropyl group.
An example of a nonionic hydrophilic group is —OH.

Examples of suitable reactive surfactants include compounds represented by the following formula (II).

In the formula (II), R represents a divalent linking group. Examples of R include —Si—O— group, methylene group and phenylene group.
In formula (II), ^{R 3} represents a hydrophilic group. An example of R ³ includes —SO ₃ NH ₄ .
In the formula (II), n represents an integer of 1 to 100.

Another example of a suitable reactive surfactant has a structural unit having a structure formed by polymerizing ethylene oxide and a structural unit having a structure formed by polymerizing butylene oxide. Mention may be made of compounds having an alkenyl group having a terminal double bond and —SO ₃ NH ₄ . Specific examples of such reactive surfactants include trade names “Latemul PD-104” and “Latemul PD-105” manufactured by Kao Corporation.
As the reactive surfactant and the reactive surfactant unit, one type may be used alone, or two or more types may be used in combination at any ratio.

In the water-soluble polymer, the proportion of the reactive surfactant unit is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, particularly preferably 0.5% by weight or more, and preferably Is 5% by weight or less, more preferably 4% by weight or less, and particularly preferably 2% by weight or less. The dispersibility of the slurry composition of this invention can be improved by making the ratio of a reactive surfactant unit more than the lower limit of the said range. Moreover, durability of an electrode can be improved by setting it as below an upper limit.

(1.2.5. Arbitrary structural unit)
The water-soluble polymer may contain an arbitrary structural unit in addition to the acid group-containing monomer unit, the fluorine-containing monomer unit, the crosslinkable monomer unit, and the reactive surfactant unit described above.
For example, the water-soluble polymer can contain (meth) acrylic acid ester monomer units.

Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, Acrylic acid alkyl esters such as 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; and methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t -Butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl Methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n- tetradecyl methacrylate, methacrylic acid alkyl esters such as stearyl methacrylate. Moreover, a (meth) acrylic acid ester monomer and a (meth) acrylic acid ester monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

In the water-soluble polymer, the proportion of the (meth) acrylic acid ester monomer unit is preferably 25% by weight or more, more preferably 30% by weight or more, particularly preferably 35% by weight or more, and preferably 75%. % By weight or less, more preferably 70% by weight or less, particularly preferably 65% by weight or less. By setting the amount of the (meth) acrylic acid ester monomer unit to be equal to or higher than the lower limit of the above range, the binding property of the electrode active material layer to the current collector can be increased. Moreover, the softness | flexibility of an electrode can be improved by making it into an upper limit or less.

Further examples of arbitrary structural units that the water-soluble polymer may have include structural units having a structure formed by polymerizing the following monomers. That is, aromatic vinyl monomers such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, α-methylstyrene, divinylbenzene, etc. Amide monomers such as acrylamide; α, β-unsaturated nitrile compound monomers such as acrylonitrile and methacrylonitrile; olefin monomers such as ethylene and propylene; halogen atoms such as vinyl chloride and vinylidene chloride Monomers; vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl ketone, Butyl vinyl Formed by polymerizing one or more of vinyl ketone monomers such as ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compound monomers such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole. Examples include structural units having a structure.

(1.2.6. Physical properties of water-soluble polymer)
The 1% aqueous solution viscosity of the water-soluble polymer is preferably 1 mPa · s or more, more preferably 2 mPa · s or more, particularly preferably 5 mPa · s or more, and preferably 1000 mPa · s or less, more preferably 500 mPa · s. s or less, particularly preferably 100 mPa · s or less. Here, the 1% aqueous solution viscosity of a water-soluble polymer refers to the viscosity of an aqueous solution of a water-soluble polymer having a concentration of 1% by weight. By setting the 1% aqueous solution viscosity of the water-soluble polymer to be equal to or higher than the lower limit of the above range, the dispersibility of the slurry composition can be enhanced. Moreover, the binding property of an electrode active material layer and an electrical power collector can be improved by setting it as an upper limit or less. The viscosity can be adjusted by, for example, the molecular weight of the water-soluble polymer. Here, the said viscosity is a value when it measures at 25 degreeC and rotation speed 60rpm using a B-type viscometer.

The weight average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 700 or more, particularly preferably 1000 or more, preferably 500,000 or less, more preferably 450,000 or less, and particularly preferably 400,000 or less. By setting the weight average molecular weight of the water-soluble polymer to be equal to or higher than the lower limit of the above range, the strength of the water-soluble polymer can be increased and the durability of the electrode can be improved. Moreover, the binding property of a collector and an electrode active material layer can be improved by setting it as an upper limit or less. Here, the weight average molecular weight of the water-soluble polymer can be determined by GPC as a value in terms of polystyrene using, as a developing solvent, a solution obtained by dissolving 0.85 g / ml sodium nitrate in a 10% by volume aqueous solution of dimethylformamide.

(1.2.7. Amount of water-soluble polymer)
The weight ratio of the particulate polymer to the water-soluble polymer is particulate polymer / water-soluble polymer, preferably 50/50 or more, more preferably 60/40 or more, and particularly preferably 70/30 or more. In addition, it is preferably 99/1 or less, more preferably 98/2 or less, and particularly preferably 97/3 or less. By setting the weight ratio to be equal to or higher than the lower limit of the above range, the high temperature cycle characteristics of the lithium ion secondary battery can be improved. Moreover, the binding property of an electrode active material layer and an electrical power collector can be improved by setting it as an upper limit or less.

(1.2.8. Method for producing water-soluble polymer)
The water-soluble polymer can be produced, for example, by polymerizing a monomer composition containing the above-described monomer in an aqueous solvent. At this time, the ratio of each monomer in the monomer composition is usually the same as the ratio of structural units in the water-soluble polymer.

The aqueous solvent is not particularly limited as long as the water-soluble polymer can be dispersed. Usually, the boiling point at normal pressure is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, preferably 350 ° C. or lower, more preferably 300 ° C. or lower. Examples of the aqueous solvent will be given below. In the following examples, the number in parentheses after the solvent name is the boiling point (unit: ° C) at normal pressure, and the value after the decimal point is a value rounded off or rounded down.
Examples of aqueous solvents include water (100); ketones such as diacetone alcohol (169) and γ-butyrolactone (204); ethyl alcohol (78), isopropyl alcohol (82), and normal propyl alcohol (97). Alcohols: propylene glycol monomethyl ether (120), methyl cellosolve (124), ethyl cellosolve (136), ethylene glycol tertiary butyl ether (152), butyl cellosolve (171), 3-methoxy-3-methyl-1-butanol (174) ), Ethylene glycol monopropyl ether (150), diethylene glycol monobutyl ether (230), triethylene glycol monobutyl ether (271), dipropylene glycol monomethyl ether (188) Glycol ethers; and 1,3-dioxolane (75), 1,4-dioxolane (101), ethers such as tetrahydrofuran (66) and the like. Among these, water is particularly preferable from the viewpoint that it is not flammable and a polymer dispersion can be easily obtained. Further, water may be used as the main solvent, and an aqueous solvent other than the above-described water may be mixed and used within a range in which the dispersion state of the polymer can be ensured.

The polymerization method is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. As the polymerization method, any method such as ion polymerization, radical polymerization, and living radical polymerization can be used. From the viewpoint of production efficiency, it is easy to obtain a high molecular weight product, and since the polymer is obtained in a state of being dispersed in water as it is, redispersion treatment is unnecessary and it can be used for production of a binder composition as it is. Of these, the emulsion polymerization method is particularly preferable.

The emulsion polymerization method is usually performed by a conventional method. For example, the method is described in “Experimental Chemistry Course” Vol. 28, (Publisher: Maruzen Co., Ltd., edited by The Chemical Society of Japan). That is, water, an additive such as a dispersant, an emulsifier, a crosslinking agent, a polymerization initiator, and a monomer are added to a sealed container equipped with a stirrer and a heating device so as to have a predetermined composition, and the composition in the container This is a method in which a product is stirred to emulsify monomers and the like in water, and the temperature is increased while stirring to initiate polymerization. Or after emulsifying the said composition, it is the method of putting into a sealed container and starting reaction similarly.

Examples of polymerization initiators include organic compounds such as lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Peroxides; azo compounds such as α, α′-azobisisobutyronitrile; ammonium persulfate; and potassium persulfate. A polymerization initiator may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Emulsifiers, dispersants, polymerization initiators, and the like are generally used in these polymerization methods, and the amount used is generally the amount generally used.

The polymerization temperature and polymerization time can be arbitrarily selected depending on the polymerization method and the type of polymerization initiator. Usually, the polymerization temperature is about 30 ° C. or more, and the polymerization time is about 0.5 to 30 hours.
Further, additives such as amines may be used as a polymerization aid.

By polymerization, a reaction liquid usually containing a water-soluble polymer is obtained. The obtained reaction solution is usually acidic, and the water-soluble polymer is often dispersed in an aqueous solvent. The water-soluble polymer dispersed in the water-soluble solvent as described above can usually be made soluble in an aqueous solvent by adjusting the pH of the reaction solution to, for example, 7 to 13. You may take out a water-soluble polymer from the reaction liquid obtained in this way. However, usually, water is used as an aqueous medium, and the binder composition of the present invention is produced using a water-soluble polymer dissolved in water.

Examples of the method for alkalizing the reaction solution to pH 7 to pH 13 include alkaline metal aqueous solutions such as lithium hydroxide aqueous solution, sodium hydroxide aqueous solution and potassium hydroxide aqueous solution; alkaline earth such as calcium hydroxide aqueous solution and magnesium hydroxide aqueous solution. Metal aqueous solution: A method of mixing an alkaline aqueous solution such as an aqueous ammonia solution. One kind of the alkaline aqueous solution may be used alone, or two or more kinds may be used in combination at any ratio.

[1.3. (Polyether-modified silicone compound)
The binder composition of the present invention contains a polyether-modified silicone compound. Since the polyether-modified silicone compound can suppress deposition of lithium metal due to charge / discharge in the lithium ion secondary battery, high temperature cycle characteristics can be improved. Moreover, since the wettability with the electrolyte solution of an electrode active material layer can be improved by a polyether modified silicone compound, lithium ion conductivity can be increased in a lithium ion secondary battery. Therefore, the internal resistance of the lithium ion secondary battery can be lowered, and the low temperature output characteristics can be improved.

The polyether-modified silicone compound is a compound having a structure in which a part of the hydrocarbon group of the organopolysiloxane is replaced with a substituent having a polyoxyalkylene group.

The organopolysiloxane usually contains a structural unit represented by the following formula (III). In this formula (III), R ⁴ and R ⁵ each independently represents a hydrocarbon group.

The number of carbon atoms of the hydrocarbon group represented by R ⁴ and R ⁵ is preferably 1-6. Examples of the hydrocarbon group include alkyl groups such as methyl group, ethyl group, and propyl group; and aryl groups such as phenyl group. Moreover, these hydrocarbon groups may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Examples of the organopolysiloxane include polydimethylsiloxane, methylethylsiloxane-dimethylsiloxane copolymer, and methylphenylsiloxane-dimethylsiloxane copolymer. One of these may be used alone, or two or more of these may be used in combination at any ratio.

As the polyoxyalkylene group, a polyoxyalkylene group having a number average molecular weight of 100 to 2000 can be used. Examples of such a polyoxyalkylene group include a polyoxyethylene group and a polyoxypropylene group. Moreover, these polyoxyalkylene groups may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. For example, a polyoxyethylene group and a polyoxypropylene group may be used in combination. In this case, the weight ratio of the polyoxyethylene group to the polyoxypropylene group is preferably 40:60 to 95: 5.

Examples of the substituent having a polyoxyalkylene group include a hydroxy (polyoxyalkylene) propylene group, a methoxy (polyoxyalkylene) propylene group, an ethoxy (polyoxyalkylene) propylene group, a hydroxy polyoxyalkylene group, and a methoxy polyoxyalkylene. Group, ethoxypolyoxyalkylene group, polyoxyalkylene group and the like. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

The position of the substituent having a polyoxyalkylene group in the molecule of the polyether-modified silicone compound is arbitrary. The substituent having a polyoxyalkylene group may be in the side chain of the siloxane skeleton, may be at the end of the siloxane skeleton, or may be in a position connecting the siloxane skeletons. Especially, it is preferable that the substituent which has a polyoxyalkylene group is located in the side chain of a siloxane skeleton.

When an aqueous solution containing a polyether-modified silicone compound at a concentration of 10% by weight is prepared, the surface tension is preferably within a predetermined range. Specifically, the surface tension is preferably 20 mN / m or more, more preferably 21 mN / m or more, particularly preferably 22 mN / m or more, and preferably 50 mN / m or less, more preferably 45 mN / m. m or less, particularly preferably 40 mN / m or less. By setting the surface tension to be equal to or higher than the lower limit of the above range, it is possible to suppress the precipitation of lithium metal due to charge / discharge in the lithium ion secondary battery. Moreover, the dispersibility of each component in an electrode active material layer can be improved by using below an upper limit.

The surface tension can be measured as follows. The polyether-modified silicone compound is dissolved in water to prepare an aqueous polyether-modified silicone compound solution having a concentration of 10% by weight. The surface tension of this polyether-modified silicone compound aqueous solution is measured by a platinum plate method using an automatic surface tension meter (“DY-300” manufactured by Kyowa Interface Science Co., Ltd.).

Examples of such polyether-modified silicone compounds include SN wet 123, 125 (San Nopco); DAW-DC-67 (Dow Corning Asia); SH-3771, SH-3771C, SH3746, SH3749 (Toray Dow Corning); and FZ-2162, FZ-2163, FZ-2104, L-7605, L-7607N, L-77 (H Hon-Unicar). Of these, SN wet 123, 125, DAW-DC-67, SH-3771, SH3749, FZ2162, and L-7607N are preferable, and SN wet 123, 125, DAW-DC-67, and SH-3749 are more preferable. More preferred are SN wet 123, 125 and DAW-DC-67, and particularly preferred are SN wet 123 and 125. Moreover, a polyether modified silicone compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The amount of the polyether-modified silicone compound is usually 0.1 parts by weight or more, preferably 0.15 parts by weight or more, more preferably 0.2 parts by weight or more, based on 100 parts by weight of the water-soluble polymer. It is 10 parts by weight or less, preferably 8 parts by weight or less, more preferably 5 parts by weight or less. By making the amount of the polyether-modified silicone compound at least the lower limit of the above range, the binding property between the electrode active material layer and the current collector can be enhanced. Moreover, precipitation to the lithium metal by charging / discharging can be suppressed in a lithium ion secondary battery by using below an upper limit.

[1.4. water〕
The binder composition of the present invention contains water. Water usually functions as a solvent or a dispersion medium, and can disperse the particulate polymer or dissolve the water-soluble polymer and the polyether-modified silicone compound.

As the solvent, a solvent other than water may be used in combination with water. For example, it is preferable to combine a liquid that can dissolve the water-soluble polymer with water, because the water-soluble polymer is adsorbed on the surface of the electrode active material, thereby stabilizing the dispersion of the electrode active material.

The type of liquid to be combined with water is preferably selected from the viewpoint of drying speed and environment. Preferred examples include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate, γ-butyrolactone, Esters such as ε-caprolactone; Nitriles such as acetonitrile and propionitrile; Ethers such as tetrahydrofuran and ethylene glycol diethyl ether; Alcohols such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; N-methyl Examples include pyrrolidone and amides such as N, N-dimethylformamide, among which N-methylpyrrolidone (NMP) is preferable. One of these may be used alone, or two or more of these may be used in combination at any ratio.

The amount of the solvent such as water can be appropriately adjusted so that the concentration and viscosity are suitable for the production of the binder composition and the slurry composition using the binder composition. Specifically, the concentration of the solid content in the total amount of the binder composition of the present invention is preferably 10% by weight or more, more preferably 15% by weight or more, particularly preferably 20% by weight or more, and preferably 60%. It can be set to an amount of not more than wt%, more preferably not more than 55 wt%, particularly preferably not more than 50 wt%. Here, solid content of a binder composition means the substance which remains after drying of a binder composition.

[1.5. (Optional ingredients)
Unless the effect of this invention is impaired remarkably, the binder composition of this invention can contain arbitrary components other than the particulate polymer mentioned above, a water-soluble polymer, a polyether modified silicone compound, and water. Moreover, arbitrary components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[1.6. Method for producing binder composition]
There is no restriction | limiting in the manufacturing method of the binder composition of this invention. For example, the binder composition of the present invention can be produced by mixing the above-described particulate polymer, water-soluble polymer, polyether-modified silicone compound and water in any order.

A particularly preferable production method includes a production method including the following step (1) and step (2).
Step (1): A step of mixing the particulate polymer, the polyether-modified silicone compound and water to obtain a mixture (1).
Step (2): A step of further mixing the mixture (1) and the water-soluble polymer after the step (1).
By mixing in such an order, homogeneous mixing can be easily achieved and high dispersibility can be obtained.

When the particulate polymer is used in the state of an aqueous dispersion, the polyether-modified silicone compound is used in the state of an aqueous solution or an aqueous dispersion, or the water-soluble polymer is used in the state of an aqueous solution, these Water may be mixed separately from the aqueous solution and the aqueous dispersion, or water may not be mixed separately from the aqueous solution and the aqueous dispersion. Usually, water is mixed separately from these aqueous solutions and aqueous dispersions, and adjustment is performed so that the solid content concentration of the binder composition falls within a desired range.

In addition, the particulate polymer, the water-soluble polymer, the polyether-modified silicone compound, and any component other than water can be mixed at any point in the production method described above.

Examples of equipment for mixing include, for example, mixing equipment such as a ball mill, a sand mill, a bead mill, a roll mill, a pigment disperser, a grinder, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer.

[2. Slurry composition for lithium ion secondary battery]
The slurry composition of this invention is a slurry composition for lithium ion secondary battery electrodes, Comprising: The binder composition and electrode active material of this invention are included.

[2.1. Electrode active material)
(2.1.1. Positive electrode active material)
Among the electrode active materials, as the electrode active material for the positive electrode (hereinafter sometimes referred to as “positive electrode active material” as appropriate), a material capable of inserting and desorbing lithium ions is usually used. Such positive electrode active materials are roughly classified into those made of inorganic compounds and those made of organic compounds.

Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, transition metal sulfides, lithium-containing composite metal oxides of lithium and transition metals, and the like. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

Examples of the transition metal oxide include MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O _{13 and the} like can be mentioned. Among them, MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ are preferable from the viewpoint of cycle stability and capacity.

Examples of the transition metal sulfide include TiS ₂ , TiS ₃ , amorphous MoS ₂ , FeS, and the like.

Examples of the lithium-containing composite metal oxide include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.

Examples of the lithium-containing composite metal oxide having a layered structure include lithium-containing cobalt oxide (LCO: LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), and Co—Ni—Mn lithium composite oxide (NMC: LiNi _0.8 Co _0.1 Mn _0.1 O _2, LiNi _0.33 Co _0.33 Mn _0.33 O _2, etc.), Ni—Mn—Al lithium composite oxide, Ni—Co—Al lithium Examples thereof include complex oxides (NCA: Li [Ni—Co—Al] O ₂ or the like).

Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganate (LMO: LiMn ₂ O ₄ ) or Li [Mn _{3 / 2} M _1/2 ] O ₄ (where M is Cr, Fe, Co, Ni, Cu, etc.).

Examples of the lithium-containing composite metal oxide having an olivine type structure include Li _X MPO ₄ (wherein M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti). Represents at least one selected from the group consisting of Al, Si, B and Mo, and X represents a number satisfying 0 ≦ X ≦ 2, for example, LFP: LiFePO ₄ etc.) Is mentioned.

Examples of the positive electrode active material made of an organic compound include conductive polymer compounds such as polyacetylene and poly-p-phenylene.

Moreover, you may use the positive electrode active material which consists of a composite material which combined the inorganic compound and the organic compound.
Alternatively, for example, a composite material covered with a carbon material may be produced by reducing and firing an iron-based oxide in the presence of a carbon source material, and the composite material may be used as a positive electrode active material. Iron-based oxides tend to have poor electrical conductivity, but can be used as a high-performance positive electrode active material by using a composite material as described above.

Furthermore, you may use as a positive electrode active material what carried out the element substitution of the said compound partially.
Moreover, you may use the mixture of said inorganic compound and organic compound as a positive electrode active material.
As the positive electrode active material, one type may be used alone, or two or more types may be used in combination at any ratio.

Particularly preferred examples of the positive electrode active material include LCO, LMO, NMC, and NCA.

The volume average particle diameter D50 of the particles of the positive electrode active material is preferably 1 μm or more, more preferably 2 μm or more, and preferably 50 μm or less, more preferably 30 μm or less. By setting the average particle diameter of the positive electrode active material particles in the above range, the amount of the binder in the positive electrode active material layer can be reduced, and the decrease in the capacity of the lithium ion secondary battery can be suppressed. Moreover, it becomes easy to adjust the viscosity of the slurry composition of the present invention to an appropriate viscosity that is easy to apply, and a uniform positive electrode can be obtained.

The amount of the positive electrode active material is a ratio of the positive electrode active material in the electrode active material layer, preferably 90% by weight or more, more preferably 95% by weight or more, and preferably 99.9% by weight or less, more preferably 99% by weight or less. By setting the amount of the positive electrode active material in the above range, the capacity of the lithium ion secondary battery can be increased, and the flexibility of the positive electrode and the binding property between the current collector and the positive electrode active material layer can be improved. .

(2.1.2. Negative electrode active material)
Among the electrode active materials, an electrode active material for a negative electrode (hereinafter also referred to as “negative electrode active material” as appropriate) is a substance that transfers electrons in the negative electrode. As the negative electrode active material, a material that can occlude and release lithium ions is usually used.
An example of a suitable negative electrode active material is carbon. Examples of carbon include natural graphite, artificial graphite, and carbon black. Among these, natural graphite is preferably used.

Further, as the negative electrode active material, it is preferable to use a negative electrode active material containing at least one selected from the group consisting of tin, silicon, germanium and lead. A negative electrode active material containing these elements has a small irreversible capacity. Among these, a negative electrode active material containing silicon is preferable. By using a negative electrode active material containing silicon, the electric capacity of the lithium ion secondary battery can be increased.

As the negative electrode active material, one type may be used alone, or two or more types may be used in combination at any ratio. Therefore, two or more kinds of the negative electrode active materials may be used in combination. Among these, it is preferable to use a negative electrode active material containing a combination of carbon and one or both of metallic silicon and a silicon-based active material. In a negative electrode active material containing a combination of carbon and one or both of metallic silicon and a silicon-based active material, Li insertion and desorption from one or both of metallic silicon and a silicon-based active material occurs at a high potential, It is presumed that Li insertion and desorption from carbon occur at low potential. For this reason, since expansion and contraction are suppressed, the cycle characteristics of the lithium ion secondary battery can be improved.

Examples of the silicon-based active material include SiO, SiO ₂ , SiO _x (0.01 ≦ x <2), SiC, SiOC, and the like, and SiO _x , SiC, and SiOC are preferable. Among these, it is particularly preferable to use SiO _x as the silicon-based active material from the viewpoint of suppressing the swelling of the negative electrode active material itself. SiO _x is a compound formed using one or both of SiO and SiO ₂ and metallic silicon as raw materials. This SiO _x can be produced, for example, by cooling and precipitating silicon monoxide gas generated by heating a mixture of SiO ₂ and metal silicon.

When carbon is used in combination with one or both of metallic silicon and a silicon-based active material, it is preferable that one or both of metallic silicon and the silicon-based active material is combined with conductive carbon. By combining with conductive carbon, swelling of the negative electrode active material itself can be suppressed.
Examples of the compounding method include a method of compounding one or both of metallic silicon and silicon-based active material with carbon; conductive carbon and one or both of metallic silicon and silicon-based active material The method of compounding by granulating a mixture; etc. are mentioned.

Examples of the method for coating one or both of metallic silicon and silicon-based active material with carbon include, for example, a method in which one or both of metallic silicon and silicon-based active material are subjected to heat treatment, and disproportionation; A method of performing chemical vapor deposition by subjecting one or both of the materials to a heat treatment; and the like.

The negative electrode active material is preferably sized in the form of particles. When the particle shape is spherical, a higher-density electrode active material layer can be obtained during the production of the electrode active material layer.
The volume average particle diameter D50 of the particles of the negative electrode active material is appropriately selected in consideration of other constituent requirements of the lithium ion secondary battery, preferably 0.1 μm or more, more preferably 1 μm or more, and further preferably 5 μm or more. In addition, it is preferably 100 μm or less, more preferably 50 μm or less, and further preferably 20 μm or less.

The specific surface area of the negative electrode active material, the output from the viewpoint of improving the density, preferably ^2m 2 / g or more, more preferably ^3m 2 / g or more, more preferably ^{5 m} 2 / g or more, and preferably ^{20 m} 2 / g or less, more preferably 15 m ² / g or less, and further preferably 10 m ² / g or less. The specific surface area of the negative electrode active material can be measured by, for example, the BET method.

The amount of the negative electrode active material is a ratio of the negative electrode active material in the electrode active material layer, and is preferably 85% by weight or more, more preferably 88% by weight or more, and preferably 99% by weight or less, more preferably 97% by weight. % Or less. By setting the amount of the negative electrode active material in the above range, it is possible to realize a negative electrode that exhibits excellent flexibility and binding properties while exhibiting high capacity.

[2.2. Ratio of binder composition in slurry composition]
The ratio of the binder composition contained in the slurry composition of the present invention is preferably adjusted as appropriate so that the performance of the obtained battery is satisfactorily exhibited. For example, the ratio of the solid content of the binder composition to 100 parts by weight of the electrode active material is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, particularly preferably 1 part by weight or more, and preferably It is 10 parts by weight or less, more preferably 8 parts by weight or less, and particularly preferably 5 parts by weight or less.

[2.3. (Optional ingredients)
The slurry composition of this invention can contain arbitrary components other than the electrode active material mentioned above and a binder composition.
For example, the slurry composition of the present invention may contain a thickener other than the water-soluble polymer. Examples of the thickener include water-soluble polymers such as water-soluble polysaccharides, sodium polyacrylate, polyethyleneimine, polyvinyl alcohol, and polyvinylpyrrolidone. Among them, water-soluble polysaccharides are preferable, and carboxymethyl cellulose is particularly preferable. The carboxymethyl cellulose may be used in the form of a salt such as a sodium salt or an ammonium salt. By using a thickener, the viscosity of a slurry composition can be raised and coating property can be made favorable. Moreover, the dispersion stability of particles, such as an electrode active material, in a slurry composition can be improved. Furthermore, the binding property between the electrode active material layer and the current collector can be enhanced.

The amount of the thickening agent is not uniform depending on the type of the thickening agent. For example, the amount of the carboxymethyl cellulose is preferably 0.1 parts by weight or more, more preferably 100 parts by weight of the electrode active material. Is 0.3 parts by weight or more, particularly preferably 0.5 parts by weight or more, preferably 5 parts by weight or less, more preferably 4 parts by weight or less, and particularly preferably 3 parts by weight or less. By keeping the amount of the thickener within the above range, the dispersibility of the particles in the slurry composition can be further improved, and the cycle characteristics of the lithium ion secondary battery can be effectively improved.

The slurry composition may further contain a solvent such as water in addition to the water contained in the binder composition. The amount of the solvent is preferably adjusted so that the viscosity of the slurry composition becomes a viscosity suitable for coating. Specifically, the concentration of the solid content of the slurry composition of the present invention is preferably 30% by weight or more, more preferably 35% by weight or more, and preferably 70% by weight or less, more preferably 65% by weight. It is used by adjusting to the following amount. Here, solid content of a slurry composition means the substance which remains as a structural component of an electrode active material layer through drying of a slurry composition.

For example, the slurry composition may include a conductive material. The conductive material is a component that can improve electrical contact between the electrode active materials. By including a conductive material, the discharge rate characteristics of the lithium ion secondary battery can be improved.
Examples of the conductive material include furnace black, acetylene black, ketjen black, oil furnace black, carbon black, graphite, vapor grown carbon fiber, and conductive carbon such as carbon nanotube. Among them, acetylene black, oil furnace black, and ketjen black are preferable, and acetylene black and ketjen black are particularly preferable because the balance between the low-temperature output characteristics and the life characteristics of the lithium ion secondary battery is good. Moreover, a conductive material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The specific surface area of the conductive material is preferably 50 m ² / g or more, more preferably 60 m ² / g or more, particularly preferably 70 m ² / g or more, and preferably 1500 m ² / g or less, more preferably 1200 m ^2. / G or less, particularly preferably 1000 m ² / g or less. By setting the specific surface area of the conductive material to be equal to or higher than the lower limit of the above range, the low temperature output characteristics of the lithium ion secondary battery can be improved. Moreover, the binding property of an electrode active material layer and an electrical power collector can be improved by setting it as an upper limit or less.

The amount of the conductive material is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and still more preferably 0.3 parts by weight or more with respect to 100 parts by weight of the electrode active material. Is 10 parts by weight or less, more preferably 8 parts by weight or less, and still more preferably 5 parts by weight or less. By setting the amount of the conductive material to the lower limit value or more, the low temperature output characteristics of the lithium ion secondary battery can be improved. Moreover, the binding property of an electrode active material layer and a collector can be improved by making the quantity of a electrically conductive material below the said upper limit.

For example, the slurry composition may contain a reinforcing material. By using the reinforcing material, a tough and flexible electrode can be obtained, and excellent long-term cycle characteristics can be obtained. Examples of the reinforcing material include various inorganic and organic spherical, plate-like, rod-like, or fibrous fillers. Moreover, a reinforcing agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The amount of the reinforcing agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, preferably 20 parts by weight or less, more preferably 10 parts by weight or less with respect to 100 parts by weight of the electrode active material. is there. By setting the amount of the reinforcing material in the above range, high capacity and high load characteristics can be obtained in the lithium ion secondary battery.

Also, for example, the slurry composition may contain an electrolyte solution additive. By using the electrolytic solution additive, for example, decomposition of the electrolytic solution can be suppressed. Examples of the electrolytic solution additive include vinylene carbonate. One electrolyte solution additive may be used alone, or two or more electrolyte solution additives may be used in combination at any ratio.

The amount of the electrolytic solution additive is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. By setting the amount of the electrolytic solution additive in the above range, a secondary battery excellent in cycle characteristics and high temperature characteristics can be realized.

Also, for example, the slurry composition may contain nanoparticles such as fumed silica and fumed alumina. When the nanoparticle is included, the thixotropy of the slurry composition can be adjusted, so that the leveling property of the electrode active material layer obtained thereby can be improved. One kind of nano fine particles may be used alone, or two or more kinds may be used in combination at any ratio.

The amount of the nanoparticles is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. When the nanoparticles are in the above range, the stability and productivity of the slurry composition can be improved and high battery characteristics can be realized.

[2.4. Method for producing slurry composition]
The slurry composition of the present invention can be produced, for example, by mixing an electrode active material, a binder composition, and optional components as necessary. The specific procedure at this time is arbitrary. For example, when manufacturing a slurry composition containing an electrode active material, a binder composition, water, a thickener and a conductive material, the electrode active material, the binder composition, the thickener and the conductive material are added to water at the same time. A method of mixing; a method of adding an electrode active material, a conductive material and a thickener to water and mixing, and then adding and mixing a binder composition; and the like.

[3. Electrode for lithium ion secondary battery]
The electrode for a lithium ion secondary battery of the present invention (hereinafter sometimes referred to as “electrode” as appropriate) includes a current collector and an electrode active material layer.

[3.1. Current collector]
The current collector may be made of a material having electrical conductivity and electrochemical durability. Usually, a metal material is used as the material of the current collector. Examples thereof include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum and the like. Among them, the current collector used for the positive electrode is preferably aluminum, and the current collector used for the negative electrode is preferably copper. Moreover, the said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The shape of the current collector is not particularly limited, but a sheet having a thickness of about 0.001 mm to 0.5 mm is preferable.

In order to increase the adhesion strength with the electrode active material layer, it is preferable that the current collector is used after the surface has been roughened. Examples of the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing method, for example, an abrasive cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like is used. In order to increase the adhesion strength and conductivity of the electrode active material layer, an intermediate layer may be formed on the surface of the current collector.

[3.2. Electrode active material layer
An electrode active material layer is a layer obtained by apply | coating the slurry composition of this invention on a collector, and drying. Therefore, since an electrode active material layer is a layer formed by solid content of the slurry composition of this invention, an electrode active material, a particulate polymer, a water-soluble polymer, and a polyether modified silicone compound are included.

When manufacturing an electrode active material layer, a slurry composition is apply | coated on a collector and the film | membrane of a slurry composition is formed. At this time, the slurry composition may be applied to one side of the current collector or may be applied to both sides.
There is no restriction | limiting in the coating method, For example, methods, such as a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, are mentioned.
Further, the thickness of the slurry composition film can be appropriately set according to the thickness of the target electrode active material layer.

After forming the slurry composition film, the liquid such as water is removed from the film by drying. Thereby, the electrode active material layer containing the solid content of the slurry composition is formed on the surface of the current collector, and an electrode is obtained.

Examples of the drying method include drying with warm air, hot air, low-humidity air or the like; vacuum drying; drying method by irradiation with energy rays such as infrared rays, far infrared rays, or electron beams. Among these, a drying method by irradiation with far infrared rays is preferable.
The drying temperature and drying time are preferably a temperature and a time at which water can be removed from the slurry composition film. Specifically, the drying time is usually from 1 minute to 30 minutes, and the drying temperature is usually from 40 ° C. to 180 ° C.

After drying the slurry composition film, the electrode active material layer is preferably subjected to pressure treatment using, for example, a die press or a roll press, if necessary. By the pressure treatment, the porosity of the electrode active material layer can be lowered. The porosity is preferably 5% or more, more preferably 7% or more, and preferably 30% or less, more preferably 20% or less. By setting the porosity to be equal to or higher than the lower limit of the above range, a high volume capacity can be easily obtained, and the electrode active material layer can be made difficult to peel from the current collector. Moreover, high charging efficiency and discharge efficiency are acquired by setting it as an upper limit or less.

Furthermore, when the electrode active material layer contains a polymer that can be cured by a curing reaction such as a crosslinking reaction, the polymer may be cured after the electrode active material layer is formed.

The thickness of the electrode active material layer can be arbitrarily set according to the required battery performance.
For example, the thickness of the positive electrode active material layer is preferably 5 μm or more, more preferably 10 μm or more, and preferably 300 μm or less, more preferably 250 μm or less. When the thickness of the positive electrode active material layer is in the above range, high characteristics can be realized in both load characteristics and energy density.
Further, for example, the thickness of the negative electrode active material layer is preferably 5 μm or more, more preferably 20 μm or more, particularly preferably 30 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, still more preferably 300 μm or less, Particularly preferably, it is 250 μm or less. When the thickness of the negative electrode active material layer is in the above range, load characteristics and cycle characteristics can be improved.

[4. Lithium ion secondary battery]
The lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, and electrolyte solution. Moreover, the lithium ion secondary battery of this invention can be equipped with a separator. However, one or both of the negative electrode and the positive electrode is an electrode of the present invention. By providing the electrode of the present invention, the lithium ion secondary battery of the present invention can prevent the deposition of lithium metal due to charge and discharge, and usually can increase the affinity between the electrode active material layer and the electrolyte solution, so that the high temperature The battery can be excellent in cycle characteristics and low-temperature output characteristics.

[4.1. Electrolyte)
As the electrolytic solution, for example, a solution obtained by dissolving a lithium salt as a supporting electrolyte in a non-aqueous solvent can be used. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. In particular, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferably used. One of these may be used alone, or two or more of these may be used in combination at any ratio.

The amount of the supporting electrolyte is preferably 1% by weight or more, more preferably 5% by weight or more, and preferably 30% by weight or less, more preferably 20% by weight or less, as the concentration in the electrolytic solution. By keeping the amount of the supporting electrolyte within the above range, the ionic conductivity can be increased, so that the charging characteristics and discharging characteristics of the battery can be improved.

As the solvent used in the electrolytic solution, a solvent capable of dissolving the supporting electrolyte can be used. Examples of such a solvent include alkyl carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC). Esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferred because high ion conductivity is easily obtained and the use temperature range is wide. A solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Moreover, the electrolytic solution may contain an additive as necessary. As the additive, for example, carbonate compounds such as vinylene carbonate (VC) are preferable. An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

[4.2. separator〕
As the separator, a porous substrate having a pore portion is usually used. Examples of separators include (a) a porous separator having pores, (b) a porous separator having a polymer coating layer formed on one or both sides, and (c) a porous resin coat containing inorganic ceramic powder. And a porous separator having a layer formed thereon. Examples of these include solid polymer electrolytes such as polypropylene, polyethylene, polyolefin, or aramid porous separators, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride hexafluoropropylene copolymers. Or a polymer film for a gel polymer electrolyte; a separator coated with a gelled polymer coat layer; a separator coated with a porous film layer composed of an inorganic filler and an inorganic filler dispersant; and the like.

[4.3. Method for producing lithium ion secondary battery]
The manufacturing method of the lithium ion secondary battery of the present invention is not particularly limited. For example, the above-described negative electrode and positive electrode may be overlapped via a separator, and this may be wound or folded in accordance with the shape of the battery and placed in the battery container, and the electrolyte may be injected into the battery container and sealed. Furthermore, if necessary, an expanded metal; an overcurrent prevention element such as a fuse or a PTC element; a lead plate or the like may be inserted to prevent an increase in pressure inside the battery or overcharge / discharge. The shape of the battery may be any of, for example, a laminate type, a coin type, a button type, a sheet type, a cylindrical type, a square type, and a flat type.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.
In the following description, “%” and “part” representing amounts are based on weight unless otherwise specified. In addition, the operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified.

[Evaluation methods]
(1) Method for Measuring Lithium Metal Deposition Amount The lithium ion secondary battery of the laminate type cell produced in Examples and Comparative Examples was allowed to stand in an environment of 25 ° C. for 24 hours. Thereafter, the lithium ion secondary battery was charged with 4.35 V, 1 C, and 1 hour in an environment of −10 ° C. Then, the negative electrode was taken out from the lithium ion secondary battery in a glove box under a 100% argon environment at room temperature. The taken-out negative electrode was observed, and the area S (cm ² ) where lithium metal was deposited was measured.
The measured area is shown by the following evaluation criteria. The smaller the area on which the lithium metal is deposited, the less lithium metal is deposited due to charge / discharge, indicating that the negative electrode can smoothly accept lithium ions in the electrolyte.

(Evaluation criteria for lithium metal deposition)
A: 0 ≦ S <1 (cm ² )
B: 1 ≦ S <5 (cm ² )
C: 5 ≦ S <10 (cm ² )
D: 10 ≦ S <15 (cm ² )
E: 15 ≦ S <20 (cm ² )
F: 20 ≦ S ≦ 25 (cm ² )

(2) Measuring method of contact angle of binder composition film with electrolyte solution solvent The binder composition produced in Examples and Comparative Examples was dried at room temperature for 7 days to prepare a binder composition film. Using a contact angle meter (“DM-701” manufactured by Kyowa Interface Chemical Co., Ltd.), 3 microliters of the electrolyte solution was dropped onto the binder composition film, and the contact angle W (°) 10 seconds after dropping was measured. did. Here, a mixed solvent of ethylene carbonate, diethyl carbonate and vinylene carbonate (EC / DEC / VC = 68.5 / 30 / 1.5; volume ratio) was used as the electrolyte solution solvent. It shows that the wettability of the solid content of a binder composition and electrolyte solution is so large that the value of the obtained contact angle W is small, and also shows that the wettability of an electrode active material layer and electrolyte solution is large. As described above, when the wettability between the electrode active material layer and the electrolytic solution is large, the internal resistance of the battery can usually be reduced, so that a lithium ion secondary battery excellent in battery characteristics such as low-temperature output characteristics can be realized.

(3) Evaluation method of high-temperature cycle characteristics The lithium ion secondary battery of the laminate type cell manufactured in the Example and the comparative example was left still for 24 hours in a 25 degreeC environment. Thereafter, the lithium ion secondary battery was charged and discharged at 0.1 C to 4.35 V and discharged at 0.1 C to 2.75 V in an environment of 25 ° C., and the initial capacity C 0 was set. It was measured. Further, the lithium ion secondary battery was repeatedly charged and discharged under the same conditions in a 45 ° C. environment, and the capacity C2 after 500 cycles was measured. The capacity retention ratio ΔC = C2 / C0 × 100 (%) was calculated from the obtained initial capacity C0 and the capacity C2 after 500 cycles, and the high temperature cycle characteristics were evaluated based on the capacity retention ratio ΔC. A higher value of the capacity retention ratio ΔC indicates that the lithium ion secondary battery has better high-temperature cycle characteristics and a longer life.

(4) Evaluation method of low-temperature output characteristic The lithium ion secondary battery of the laminate type cell manufactured in the Example and the comparative example was left still for 24 hours in a 25 degreeC environment. Then, the lithium ion secondary battery was charged over 5 hours at 0.1 C to 4.35 V in an environment of 25 ° C., and the voltage V0 at that time was measured. Thereafter, the lithium ion secondary battery was discharged at a discharge rate of 1 C in an environment of −10 ° C., and the voltage V1 15 seconds after the start of discharge was measured. The voltage drop ΔV = V0−V1 was calculated from the obtained voltages V0 and V1, and the low temperature output characteristics were evaluated based on the voltage drop ΔV. It shows that a lithium ion secondary battery is excellent in low temperature output characteristics, so that the value of this voltage drop (DELTA) V is small.

(5) Method for measuring surface tension of aqueous solution of polyether-modified silicone compound The polyether-modified silicone compound prepared in Examples and Comparative Examples was dissolved in water to obtain a polyether-modified silicone compound aqueous solution having a concentration of 10% by weight. . The surface tension of this polyether-modified silicone compound aqueous solution was measured by a platinum plate method using an automatic surface tension meter (“DY-300” manufactured by Kyowa Interface Science Co., Ltd.).

[Example 1]
(1-1. Production of water-soluble polymer)
In a 5 MPa pressure vessel equipped with a stirrer, 32.5 parts of methacrylic acid (acid group-containing monomer), 7.5 parts of 2,2,2-trifluoroethyl methacrylate (fluorine-containing (meth) acrylic acid ester monomer), Ethyl acrylate (optional monomer) 58.2 parts, ethylene dimethacrylate (crosslinkable monomer) 0.8 parts, polyoxyalkylene alkenyl ether ammonium sulfate (reactive surfactant) 1.0 part, t-dodecyl 0.6 parts of mercaptan, 150 parts of ion exchanged water, and 1.0 part of potassium persulfate (polymerization initiator) were added and sufficiently stirred. Then, it heated to 60 degreeC and superposition | polymerization was started. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a water-soluble polymer. 10% aqueous ammonia was added to the mixture containing the water-soluble polymer to adjust the pH to 8, and the water-soluble polymer was dissolved in water to obtain an aqueous solution containing the desired water-soluble polymer.

(1-2. Production of particulate polymer)
In a 5 MPa pressure vessel equipped with a stirrer, 33.0 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 62.5 parts of styrene, 1 part of 2-hydroxyethyl acrylate, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, After adding 150 parts of ion exchange water and 0.5 part of potassium persulfate as a polymerization initiator and stirring sufficiently, the mixture was heated to 50 ° C. to initiate polymerization. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a particulate polymer (SBR). A 5% aqueous sodium hydroxide solution was added to the mixture containing the particulate polymer to adjust the pH to 8. Thereafter, unreacted monomers were removed from the mixture containing the particulate polymer by heating under reduced pressure. Then, it cooled to 30 degrees C or less, and obtained the water dispersion liquid containing a desired particulate polymer.

(1-3. Production of binder composition)
In a container, 95 parts of the aqueous dispersion containing the particulate polymer prepared in the above step (1-2) corresponding to the solid content, and a polyether-modified silicone compound (“Noptex E-F070” manufactured by San Nopco) were added. 0.15 part of solid content was mixed. Thereafter, 5 parts of the aqueous solution containing the water-soluble polymer prepared in the above step (1-1) is put into this container in an amount corresponding to the solid content, and further mixed with water to adjust the solid content concentration to 25%. A binder composition was obtained.
Using a part of the binder composition for a secondary battery, a binder composition film was produced in the manner described above, and the contact angle of the film with the electrolytic solution solvent was measured.

(1-4. Production of slurry composition for negative electrode)
In a planetary mixer with a disper, 100 parts of natural graphite (volume average particle diameter: 15.6 μm) having a specific surface area of 5.5 m ² / g as a negative electrode active material, and a salt of carboxymethyl cellulose (Nippon Paper Chemicals) as a thickener 1.0 part of a 2% aqueous solution of “MAC-350HC” (manufactured by Kogyo Co., Ltd.) was added in an amount corresponding to the solid content, and ion exchange water was further added to adjust the solid content concentration to 60%, followed by mixing at 25 ° C. for 60 minutes. Next, ion exchange water was added to this planetary mixer to adjust the solid content concentration to 52%, and the mixture was further mixed at 25 ° C. for 15 minutes to obtain a mixed solution. To this mixed solution, 2.0 parts by weight of the binder composition produced in the above step (1-3) is added corresponding to the solid content, and ion-exchanged water is further added to adjust the final solid content concentration to 48%. Mix for 10 minutes. This was defoamed under reduced pressure to obtain a negative electrode slurry composition having good fluidity.

(1-5. Production of negative electrode)
The negative electrode slurry composition obtained in the above step (1-4) was applied onto a 20 μm thick copper foil as a current collector with a comma coater so that the film thickness after drying was about 150 μm. And dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode raw material before pressing. The negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode after pressing with a negative electrode active material layer having a thickness of 80 μm.

(1-6. Production of positive electrode slurry composition)
100 parts of LiCoO ₂ having a volume average particle diameter of 12 μm as a positive electrode active material, ₂ parts of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and polyvinylidene fluoride (manufactured by Kureha Co., # 7208) as a binder ) Was mixed in two parts corresponding to the solid content, and N-methylpyrrolidone was further added to adjust the total solid content concentration to 70%. These were mixed by a planetary mixer to prepare a positive electrode slurry composition.

(1-7. Production of positive electrode)
The positive electrode slurry composition obtained in the above step (1-6) was applied on a 20 μm thick aluminum foil as a current collector with a comma coater so that the film thickness after drying was about 150 μm. And dried. This drying was performed by conveying the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material before pressing. The positive electrode raw material before pressing was rolled with a roll press to obtain a positive electrode after pressing with a positive electrode active material layer thickness of 100 μm.

(1-8. Preparation of separator)
A single-layer polypropylene separator (Celgard 2500, manufactured by Celgard) was cut into a 5 × 5 cm ² square.

(1-9. Production of lithium ion secondary battery)
An aluminum packaging exterior was prepared as the battery exterior. The positive electrode obtained in the above step (1-7) was cut into a square of 4.6 × 4.6 cm ² and placed so that the surface on the current collector side was in contact with the aluminum packaging exterior. On the surface of the positive electrode active material layer of the positive electrode, the square separator obtained in the above step (1-8) was disposed. Further, the pressed negative electrode obtained in the above step (1-5) was cut into a 5 × 5 cm ² square, and this was placed on the separator so that the surface on the negative electrode active material layer side faces the separator. An electrolyte solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 volume ratio, electrolyte: LiPF ₆ having a concentration of 1 M) was injected so that no air remained. Further, in order to seal the opening of the aluminum packaging material, heat sealing at 150 ° C. was performed to close the exterior of the aluminum packaging material, and a lithium ion secondary battery was manufactured.
Using this lithium ion secondary battery, in the manner described above, measurement of lithium metal deposition amount, measurement of capacity retention ratio ΔC for evaluation of high temperature cycle characteristics, and voltage drop for evaluation of low temperature output characteristics ΔV was measured.

[Example 2]
In the step (1-3), the amount of the polyether-modified silicone compound was changed to 0.0075 part corresponding to the solid content.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 3]
In the step (1-3), the amount of the polyether-modified silicone compound was changed to 0.45 parts corresponding to the solid content.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 4]
In the step (1-3), the type of the polyether-modified silicone compound was changed to “SN Wet 123” manufactured by San Nopco.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 5]
In the step (1-3), the type of the polyether-modified silicone compound was changed to “SH3746” manufactured by Toray Dow Corning.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 6]
In the step (1-3), the type of the polyether-modified silicone compound was changed to “L-7607N” manufactured by Nihon Unicar.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 7]
In the step (1-3), the amount of the aqueous dispersion containing the particulate polymer was changed to 98 parts corresponding to the solid content, and the amount of the polyether-modified silicone compound was changed to 0.06 parts corresponding to the solid content. The amount of the aqueous solution containing the water-soluble polymer was changed to 2 parts corresponding to the solid content.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 8]
In the step (1-3), the amount of the aqueous dispersion containing the particulate polymer was changed to 85 parts corresponding to the solid content, and the amount of the polyether-modified silicone compound was changed to 0.45 parts corresponding to the solid content. The amount of the aqueous solution containing the water-soluble polymer was changed to 15 parts corresponding to the solid content.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 9]
In the step (1-3), the amount of the aqueous dispersion containing the particulate polymer was changed to 75 parts corresponding to the solid content, and the amount of the polyether-modified silicone compound was changed to 0.75 parts corresponding to the solid content. The amount of the aqueous solution containing the water-soluble polymer was changed to 25 parts corresponding to the solid content.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 10]
In the step (1-3), the amount of the aqueous dispersion containing the particulate polymer was changed to 60 parts corresponding to the solid content, and the amount of the polyether-modified silicone compound was changed to 1.2 parts corresponding to the solid content. The amount of the aqueous solution containing the water-soluble polymer was changed to 40 parts corresponding to the solid content.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 11]
In the step (1-1), instead of using 32.5 parts of methacrylic acid as the acid group-containing monomer, 30.0 parts of methacrylic acid and 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid were combined. Used.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 12]
In the step (1-1), instead of using 32.5 parts of methacrylic acid as the acid group-containing monomer, 30.0 parts of acrylic acid and 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid were combined. Used.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 13]
In the step (1-1), the amount of methacrylic acid was changed to 22 parts, and the amount of ethyl acrylate was changed to 68.7 parts.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 14]
In the step (1-1), the amount of methacrylic acid was changed to 68 parts, and the amount of ethyl acrylate was changed to 22.7 parts.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 15]
In the step (1-1), perfluorooctyl acrylate was used in place of 2,2,2-trifluoroethyl methacrylate as the fluorine-containing monomer.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 16]
In the step (1-1), perfluoroethyl acrylate was used in place of 2,2,2-trifluoroethyl methacrylate as the fluorine-containing monomer.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 17]
In the step (1-1), the amount of 2,2,2-trifluoroethyl methacrylate was changed to 0.15 parts, and the amount of ethyl acrylate was changed to 65.55 parts.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 18]
In the step (1-1), the amount of 2,2,2-trifluoroethyl methacrylate was changed to 28 parts, and the amount of ethyl acrylate was changed to 37.7 parts.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 19]
In the step (1-1), the amount of methacrylic acid was changed to 40 parts, and 2,2,2-trifluoroethyl methacrylate was not used.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Example 20]
(20-1. Production of particulate polymer)
In a 5 MPa pressure vessel with a stirrer, 96 parts of butyl acrylate, 2 parts of acrylonitrile, 2 parts of methacrylic acid, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and potassium persulfate as a polymerization initiator After 5 parts were added and sufficiently stirred, the polymerization was started by heating to 50 ° C. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a particulate polymer (ACR). A 5% aqueous sodium hydroxide solution was added to the mixture containing the particulate polymer to adjust the pH to 8. Thereafter, unreacted monomers were removed from the mixture containing the particulate polymer by heating under reduced pressure. Then, it cooled to 30 degrees C or less, and obtained the water dispersion liquid containing a desired particulate polymer.

(20-2. Production of binder composition)
In a container, 95 parts of the aqueous dispersion containing the particulate polymer prepared in the above step (20-1), corresponding to the solid content, and a polyether-modified silicone compound (“Noptex E-F070” manufactured by San Nopco) were added. 0.15 part of solid content was mixed. Thereafter, 5 parts of the aqueous solution containing the water-soluble polymer prepared in the step (1-1) of Example 1 is added to the solid content, and further mixed with water to adjust the solid content concentration to 25%. A binder composition for a secondary battery was obtained.
Using a part of the binder composition for a secondary battery, a binder composition film was produced in the manner described above, and the contact angle of the film with the electrolytic solution solvent was measured.

(20-3. Production of slurry composition for positive electrode)
In a planetary mixer with a disper, 100 parts of LiCoO ₂ having a volume average particle diameter of 12 μm as a positive electrode active material, ₂ parts of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and a thickener As a solid content, 1.0 part of a 2% aqueous solution of a carboxymethyl cellulose salt (“MAC-350HC” manufactured by Nippon Paper Chemical Co., Ltd.) was added, and ion-exchanged water was added to adjust the solid content concentration to 60%. Mix for 60 minutes at 25 ° C. Next, ion exchange water was added to this planetary mixer to adjust the solid content concentration to 52%, and the mixture was further mixed at 25 ° C. for 15 minutes to obtain a mixed solution. To this mixed solution, 2.0 parts of the binder composition produced in the above step (20-2) is added in an amount corresponding to the solid content, and further ion-exchanged water is added to adjust the final solid content concentration to 48%. Mix for 10 minutes. This was defoamed under reduced pressure to obtain a positive electrode slurry composition having good fluidity.

(20-4. Production of positive electrode)
The positive electrode slurry composition obtained in the step (20-3) was used in place of the positive electrode slurry composition obtained in the step (1-6) as the positive electrode slurry composition. In the same manner as in step (1-7) of Example 1, a pressed positive electrode having a positive electrode active material layer thickness of 100 μm was obtained.

(20-5. Production of slurry composition for negative electrode)
The negative electrode binder composition includes the particulate polymer produced in the above step (1-2) instead of using 2.0 parts by weight corresponding to the solid content of the binder composition produced in the above step (1-3). A slurry composition for negative electrode having good fluidity was obtained in the same manner as in Step (1-4) of Example 1 except that 1.0 part of the aqueous dispersion was used corresponding to the solid content.

(20-6. Production of negative electrode)
As the negative electrode slurry composition, the negative electrode slurry composition obtained in the step (20-5) was used in place of the negative electrode slurry composition obtained in the step (1-4). In the same manner as in Step (1-5) of Example 1, a negative electrode after pressing having a negative electrode active material layer thickness of 80 μm was obtained.

(20-7. Production of lithium ion secondary battery)
Step (1-9) of Example 1 except that the positive electrode obtained in the step (20-4) was used and the negative electrode obtained in the step (20-6) was used. The lithium ion secondary battery was manufactured and evaluated in the same manner as described above.

[Comparative Example 1]
In the step (1-4), an aqueous dispersion containing the particulate polymer produced in the step (1-2) was used instead of the binder composition produced in the step (1-3).
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Comparative Example 2]
In the step (1-3), an aqueous solution containing a water-soluble polymer was not used.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Comparative Example 3]
In the step (1-1), the amount of ethyl acrylate was changed to 59 parts, and ethylene dimethacrylate was not used.
In the step (1-3), the polyether-modified silicone compound was not used.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Comparative Example 4]
In the step (1-3), 0.15 parts of a silicone compound (“KS-530” manufactured by Shin-Etsu Silicone Co., Ltd.) was used instead of the polyether-modified silicone compound.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Comparative Example 5]
In the step (1-3), 0.15 parts of a polyether compound (“SN deformer 170” manufactured by San Nopco) was used in place of the polyether-modified silicone compound.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Comparative Example 6]
In the step (1-3), the amount of the polyether-modified silicone compound was changed to 0.6 parts corresponding to the solid content.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Comparative Example 7]
In the step (1-1), the amount of methacrylic acid was changed to 75 parts, and the amount of ethyl acrylate was changed to 24 parts without using 2,2,2-trifluoroethyl methacrylate.
Except for the above items, the lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1.

[result]
The results of the examples and comparative examples are shown in the table below.
In the following table, the meanings of the abbreviations are as follows.
SBR: Styrene-butadiene rubber ACR: Acrylic rubber Monomer I: Acid group-containing monomer MAA: Methacrylic acid AMPS: 2-Acrylamido-2-methylpropanesulfonic acid AA: Acrylic acid Monomer II: Fluorine-containing monomer TFEMA: 2,2,2-trifluoroethyl methacrylate PFOA: perfluorooctyl acrylate PFEA: perfluoroethyl acrylate monomer III: crosslinkable monomer EDMA: ethylene dimethacrylate monomer IV: reactive surfactant PD -104: Ammonium polyoxyalkylene alkenyl ether sulfate EA: Ethyl acrylate Aqueous solution viscosity: Viscosity of 1% aqueous solution of water-soluble polymer Weight ratio of polymer: Weight ratio represented by "particulate polymer: water-soluble polymer" Modification Silicone compound: Polyether-modified silicone Compound amount of compound: The amount the surface tension of the polyether-modified silicone compound to the water-soluble polymer 100 parts: surface tension CMC salt 10 wt% aqueous solution of the polyether-modified silicone compound: carboxymethyl cellulose salt

[Consideration]
As shown in Tables 1 to 6, in the examples, the precipitation of lithium metal is small. From this, it was confirmed by this invention that precipitation of lithium metal by charging / discharging can be suppressed.
Further, as shown in Tables 1 to 6, in Examples, the contact angle of the binder composition film with the electrolytic solution is small. From this, it was confirmed that the electrode according to the present invention is excellent in the wettability of the electrolytic solution, so that the internal resistance of the lithium ion secondary battery can be reduced.
Further, as shown in Tables 1 to 6, in the example, the voltage drop in the low temperature environment is small. From this, it was confirmed that the present invention can realize a lithium ion secondary battery having excellent low-temperature output characteristics.
Further, as shown in Tables 1 to 6, in the examples, the capacity retention rate is high when charging and discharging are repeated in a high temperature environment. From this, it was confirmed that the lithium ion secondary battery excellent in the high-temperature cycle characteristics can be realized by the present invention.

Claims

Including a particulate polymer, a water-soluble polymer, a polyether-modified silicone compound and water,
The water-soluble polymer contains 20% by weight to 70% by weight of an acid group-containing monomer unit;
A binder composition for a lithium ion secondary battery, wherein the amount of the polyether-modified silicone compound is 0.1 to 10 parts by weight with respect to 100 parts by weight of the water-soluble polymer.
The binder composition for a lithium ion secondary battery according to claim 1, wherein the water-soluble polymer further contains 0.1 to 30% by weight of a fluorine-containing monomer unit.
The binder composition for a lithium ion secondary battery according to claim 1 or 2, wherein the water-soluble polymer has a 1% aqueous solution viscosity of 1 mPa · s to 1000 mPa · s.
The binder composition for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the water-soluble polymer further contains 0.1 to 2% by weight of a crosslinkable monomer unit.
The binder composition for a lithium ion secondary battery according to any one of claims 1 to 4, wherein a surface tension of an aqueous solution containing the polyether-modified silicone compound at a concentration of 10% by weight is 20 mN / m to 50 mN / m. object.
The lithium according to any one of claims 1 to 5, wherein a weight ratio of the particulate polymer to the water-soluble polymer is particulate polymer / water-soluble polymer = 99/1 to 50/50. Binder composition for ion secondary battery.
A slurry composition for a lithium ion secondary battery, comprising the binder composition according to any one of claims 1 to 6 and an electrode active material.
Furthermore, the slurry composition for lithium ion secondary batteries of Claim 7 containing a thickener.
A current collector,
The electrode for lithium ion secondary batteries provided with the electrode active material layer obtained by apply | coating the slurry composition for lithium ion secondary batteries of Claim 7 or 8 on the said electrical power collector, and drying.
Comprising a positive electrode, a negative electrode and an electrolyte;
The lithium ion secondary battery whose at least one of the said positive electrode and the said negative electrode is an electrode for lithium ion secondary batteries of Claim 9.
Mixing the particulate polymer, the polyether-modified silicone compound and water;
The method for producing a binder composition for a lithium ion secondary battery according to any one of claims 1 to 6, further comprising a step of further mixing the water-soluble polymer.