KR20160008519A - 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 - Google Patents

Abstract

A water-soluble polymer, a polyether-modified silicone compound and water, wherein the water-soluble polymer contains 20 to 70% by weight of an acid group-containing monomer unit, and the amount of the polyether- 0.1 to 10 parts by weight based on 100 parts by weight of the binder component.

Description

FIELD OF THE INVENTION 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 method for manufacturing a binder composition for a lithium ion secondary battery. BATTERY, ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, LITHIUM ION SECONDARY BATTERY, AND METHOD FOR PRODUCING BINDER COMPOSITION FOR LITHIUM ION SECONDARY BATTERY}

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 method for producing a binder composition for a lithium ion secondary battery.

2. Description of the Related Art In recent years, portable terminals such as a notebook computer, a mobile phone, and a PDA (Personal Digital Assistant) have become popular. Lithium ion secondary batteries are widely used in secondary batteries used as power sources for these portable terminals. Portable terminals are required to have more comfortable portability, and miniaturization, thinning, light weight, and high performance are progressing rapidly, and as a result, portable terminals are used in various places. In addition, as for the secondary battery, the miniaturization, thinness, weight reduction, and high performance of the secondary battery have been demanded.

In order to improve the performance of the secondary battery, improvement of electrodes, electrolyte, and other battery members has been studied. The electrode is usually produced by mixing a liquid composition obtained by dispersing or dissolving a polymer as a binder in a solvent into an electrode active material to obtain a slurry composition, applying the slurry composition to a current collector, and drying the slurry composition. It has been attempted to realize high performance of a secondary battery by studying the composition of a slurry composition in an electrode manufactured by such a method.

Also, a technique similar to Patent Document 1 is known.

International Publication No. 2004/101103

In the lithium ion secondary battery, lithium metal may precipitate on the surface of the electrode in association with charge and discharge. This lithium metal may cause an increase in the internal resistance of the secondary battery. Therefore, in order to improve the performance such as high-temperature cycle characteristics and low-temperature output characteristics of the lithium ion secondary battery, it is desirable to suppress precipitation of the lithium metal.

Accordingly, it is an object of the present invention to provide a binder composition for a lithium ion secondary battery, a lithium ion secondary battery slurry composition for a lithium ion secondary battery capable of suppressing precipitation of lithium metal by charging and discharging, realizing a lithium ion secondary battery having excellent high temperature cycle characteristics and low- And an electrode for a lithium ion secondary battery; A lithium ion secondary battery capable of suppressing precipitation of lithium metal by charge and discharge and having excellent high-temperature cycle characteristics and low-temperature output characteristics; It is another object of the present invention to provide a method for producing a binder composition for a lithium ion secondary battery capable of suppressing precipitation of lithium metal by charge and discharge and realizing a lithium ion secondary battery having excellent high temperature cycle characteristics and low temperature output characteristics.

Means for Solving the Problems In order to solve the above problems, the present inventors have found that a water-soluble polymer comprising a particulate polymer, a water-soluble polymer, a polyether-modified silicone compound and water, The binder composition contained in a predetermined range with respect to the water-soluble polymer was examined. As a result, the use of this binder composition makes it possible to suppress precipitation of lithium metal and improve lithium ion conductivity in the lithium ion secondary battery, thereby improving the high-temperature cycle characteristics and low-temperature output characteristics of the lithium ion secondary battery And have accomplished the present invention.

That is, the present invention is as follows.

[1] A water-soluble polymer containing a particulate polymer, a water-soluble polymer, a polyether-modified silicone compound,

Wherein the water-soluble polymer contains 20 to 70% by weight of an acid group-containing monomer unit,

Wherein the amount of said polyether-modified silicone compound is 0.1 part by weight to 10 parts by weight based on 100 parts by weight of said water-soluble polymer.

[2] The binder composition for a lithium ion secondary cell according to [1], wherein the water-soluble polymer further contains 0.1% by weight to 30% by weight of a fluorine-containing monomer unit.

[3] The binder composition for a lithium ion secondary cell as described in [1] or [2], wherein the water-soluble polymer has a viscosity of 1% aqueous solution of 1 mPa · s to 1000 mPa · s.

[4] The binder composition for a lithium ion secondary cell 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.

[5] The lithium ion secondary battery binder 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 / Composition.

[6] The binder composition for a lithium ion secondary cell according to any one of [1] to [5], wherein the weight ratio of the particulate polymer and the water-soluble polymer is from particulate polymer / water-soluble polymer = 99/1 to 50/50.

[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 containing a thickener.

[9] The whole house,

An electrode for a lithium ion secondary battery comprising an electrode active material layer obtained by applying a slurry composition for a lithium ion secondary battery according to [7] or [8] on the current collector and drying the electrode active material layer.

[10] A lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte,

Wherein at least one of the positive electrode and the negative electrode is an electrode for a lithium ion secondary battery described in [9].

[11] A process for producing a polyether-modified silicone compound, which comprises mixing the particulate polymer, the polyether-

And then further mixing the water-soluble polymer. The method for producing a binder composition for a lithium ion secondary battery according to any one of [1] to [6]

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 according to the present invention can suppress precipitation of lithium metal by charging and discharging, and are excellent in lithium ion The secondary battery can be realized.

INDUSTRIAL APPLICABILITY The lithium ion secondary battery of the present invention is capable of suppressing precipitation of lithium metal by 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, it is possible to provide a lithium ion secondary battery capable of suppressing precipitation of lithium metal by charging and discharging and realizing a lithium ion secondary battery having excellent high temperature cycle characteristics and low- A binder composition can be prepared.

 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 arbitrarily changed without departing from the scope of the claims of the present invention and its equivalent scope.

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

In the following description, "water-soluble" means that the insoluble content is less than 0.5% by weight when dissolved in 100 g of water at 25 ° C. The term "water-insoluble" means that the 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 the polymer produced by copolymerizing a plurality of kinds of monomers, the ratio of the structural unit formed by polymerizing any monomer to the polymer is generally, unless otherwise specified, (Injection ratio) of the monomer in the monomer.

[One. Binder composition for lithium ion secondary battery]

The binder composition for a lithium ion secondary battery of the present invention (hereinafter occasionally referred to as "binder composition" as appropriate) contains a particulate polymer, a water-soluble polymer, a polyether-modified silicone compound and water.

[1.1. Particulate polymer]

Particulate polymers are particles of a polymer. By containing the particulate polymer, the binding property of the electrode active material layer is improved and the strength against the mechanical force applied to the electrode at the time of winding, transportation, and the like can be improved. In addition, since the electrode active material does not fall off from the electrode active material layer, the risk of short circuit due to foreign substances is reduced. In addition, 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. Further, by the particle standing, the particulate polymer can bind to the electrode active material at a point, not a surface. Therefore, since most of the surface of the electrode active material is not covered with the binder, it is possible to widen the area where ions are exchanged between the electrolyte solution and the electrode active material. Therefore, the internal resistance can be lowered and the output characteristics of the lithium ion secondary battery can be improved.

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 an acrylic polymer, a diene polymer, a fluorine-containing polymer, a polyimide, a polyamide, and a polyurethane polymer. Among them, a diene polymer and an acrylic polymer are preferable. These particulate polymers may have a crosslinked structure or may be obtained by introducing a functional group by modification. The particulate polymer may be used singly or in combination of two or more at any desired ratio.

The diene-based 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, Pentadienes having conjugated double bonds in the linear chain and substituents thereof; And hexadiene having a conjugated double bond in the side chain and substituents thereof. Of these, 1,3-butadiene is preferred. The aliphatic conjugated diene monomer and the aliphatic conjugated diene monomer unit may be used singly or two or more kinds may be used in combination at an arbitrary ratio.

The proportion of the aliphatic conjugated diene monomer unit in the diene polymer 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 preferably 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.

The aromatic vinyl monomers include, for example, styrene,? -Methylstyrene, vinyltoluene, and divinylbenzene. Among them, styrene is preferable. The diene polymer is preferably a polymer containing both an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit, and for example, a styrene-butadiene copolymer is preferable. The aromatic vinyl monomer and the aromatic vinyl monomer unit may be used singly or two or more of them may be used in combination at an arbitrary ratio.

When the aliphatic conjugated diene monomer and the aromatic vinyl monomer are used in combination in the production of the diene polymer, the resulting diene polymer may contain unreacted aliphatic conjugated diene monomer and unreacted aromatic vinyl monomer as the residual monomer . In this case, the amount of the unreacted aliphatic conjugated diene monomer contained in the diene-based 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, and more preferably 69% by weight or less.

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 contains a carboxyl group (-COOH group) and is a structural unit having high strength, it is preferable to increase the binding property of the electrode active material layer to the current collector, to improve the strength of the electrode active material layer can do. Therefore, the diene polymer contains an ethylenically unsaturated carboxylic acid monomer unit, whereby the 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 improved.

Examples of the ethylenically unsaturated carboxylic acid monomer include the same examples as those exemplified in the section of the water-soluble polymer. The ethylenic unsaturated carboxylic acid monomer and the ethylenic unsaturated carboxylic acid monomer unit may be used singly or in combination of two or more in any desired ratio.

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, and preferably 10% by weight % Or less, more preferably 8 wt% or less, particularly preferably 7 wt% or less.

The diene polymer may contain an arbitrary structural unit in addition to the above-mentioned structural units, unless the effect of the present invention is remarkably impaired. Examples of the monomer corresponding to any of the above structural units include a vinyl cyanide monomer, an unsaturated carboxylic acid alkyl ester monomer, an unsaturated monomer containing a hydroxyalkyl group, and an unsaturated carboxylic acid amide monomer. These may be used singly or in combination of two or more in an arbitrary ratio.

The vinyl cyanide monomer includes, for example, acrylonitrile, methacrylonitrile,? -Chlor acrylonitrile, and? -Ethyl acrylonitrile. Among them, acrylonitrile and methacrylonitrile are preferable.

Examples of the unsaturated carboxylic acid alkyl ester monomers include monomers such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate Dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, and 2-ethylhexyl acrylate. Among them, methyl methacrylate is preferable.

As the unsaturated monomer containing a hydroxyalkyl group, for example,? -Hydroxyethyl acrylate,? -Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate Hydroxypropylmethacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis 2-hydroxyethyl) maleate, and 2-hydroxyethyl methyl fumarate. Among them,? -Hydroxyethyl acrylate is preferable.

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

The diene polymer may contain a structural unit having a structure formed by polymerizing a monomer used in ordinary emulsion polymerization, such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, You can.

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. Among the (meth) acrylic acid ester monomers, those containing fluorine are distinguished from (meth) acrylic acid ester monomers as fluorine-containing (meth) acrylic acid ester monomers.

Examples of the (meth) acrylic acid ester monomer include the same examples as those exemplified in the examples of the water-soluble polymer. The (meth) acrylic acid ester monomer and the (meth) acrylic acid ester monomer unit may be used singly or in a combination of two or more.

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% , More preferably not more than 98 wt%, particularly preferably not more than 97 wt%.

The acrylic polymer is preferably a copolymer containing a combination of a (meth) acrylonitrile monomer unit and a (meth) acrylic acid ester monomer unit. (Meth) acrylonitrile monomer unit means a structural unit having a structure formed by polymerizing (meth) acrylonitrile. 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, and thus it is easy to obtain a high number of cells.

The acrylic polymer may contain, as the (meth) acrylonitrile monomer unit, only a structural unit having a structure formed by polymerization of acrylonitrile, or a structural unit having a structure formed by polymerization of methacrylonitrile Or both of structural units having a structure formed by polymerization of acrylonitrile and structural units having a structure formed by polymerization of methacrylonitrile may be contained in combination at an arbitrary ratio.

When the acrylic polymer contains the (meth) acrylonitrile monomer unit and the (meth) acrylic acid ester monomer unit in combination, the weight ratio of the (meth) acrylonitrile monomer unit to the (meth) acrylic acid ester monomer unit Quot; acrylonitrile monomer unit / (meth) acrylic acid ester monomer unit ") is preferably within a predetermined range. Specifically, the weight ratio is preferably 1/99 or more, more preferably 2/98 or more, still more preferably 30/70 or less, and still more preferably 25/75 or less. By making the weight ratio equal to or lower than the lower limit of the above range, the particulate polymer swells in the electrolytic solution, thereby preventing the resistance of the electrode from increasing and suppressing deterioration of the rate characteristic of the secondary battery.

The acrylic polymer may contain a crosslinkable monomer unit. The crosslinkable monomer unit is a structural unit having a structure formed by polymerizing a crosslinkable monomer. The crosslinkable monomer is a monomer capable of forming a crosslinked structure during polymerization or after polymerization by heating or irradiation of energy rays. Since the acrylic polymer contains a crosslinkable monomer unit, the particulate polymers can be crosslinked or the water-soluble polymer and the particulate polymer can be crosslinked.

Examples of the crosslinking monomer include the same examples as those exemplified in the section of the water-soluble polymer. The crosslinkable monomers may be used alone or in combination of two or more in an arbitrary ratio.

Further, the crosslinkable monomer unit may be introduced into the acrylic polymer by copolymerizing the crosslinkable monomer with the (meth) acrylic acid ester monomer unit. The crosslinkable monomer unit may be introduced into the acrylic polymer by introducing a crosslinkable group into the acrylic polymer by an ordinary modifying means using a compound having a crosslinkable group (crosslinking agent).

As the crosslinking agent, for example, an organic peroxide, a crosslinking agent exhibiting an effect by heat or light, or the like is used. The crosslinking agent may be used alone or in combination of two or more.

Of the crosslinking agents, organic peroxides and crosslinking agents capable of generating a crosslinking reaction by heat are preferable in that they contain heat-crosslinkable crosslinkable groups.

The proportion of the crosslinkable monomer units in the acrylic polymer is preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight or more, and most preferably 0.05 parts by weight or more, relative to 100 parts by weight of the total amount of (meth) acrylonitrile monomer units and (meth) Preferably not more than 5 parts by weight, more preferably not more than 4 parts by weight, particularly preferably not more than 3 parts by weight.

The acrylic polymer may contain an arbitrary structural unit in addition to the (meth) acrylonitrile monomer unit, the (meth) acrylic acid ester monomer unit and the crosslinkable group monomer unit described above. Examples of the monomers corresponding to these arbitrary structural units are styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, vinylbenzoate, vinylnaphthalene, chloromethylstyrene,? -Methylstyrene, divinylbenzene Styrene-based monomer; Olefins such as ethylene and propylene; Diene monomers such as butadiene and isoprene; Halogen-containing monomers such as vinyl chloride and vinylidene chloride; Vinyl esters such as vinyl acetate, vinyl propionate and 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; Heterocyclic-containing vinyl compounds such as N-vinylpyrrolidone, vinylpyridine and vinylimidazole; Amide monomers such as acrylamide, acrylamide-2-methylpropanesulfonic acid and the like. These may be used singly or in combination of two or more in an arbitrary ratio. However, from the viewpoint of remarkably exerting the advantage of containing the (meth) acrylonitrile monomer unit and the (meth) acrylic acid ester monomer unit as described above in combination, the amount of any structural unit is preferably small, It is particularly preferred that it does not contain any structural units.

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 further preferably 1,000,000 or less, and more preferably 500,000 or less. When the weight average molecular weight of the polymer constituting the particulate polymer is within 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 占 폚 or higher, more preferably -55 占 폚 or higher, particularly preferably -35 占 폚 or higher, further preferably 40 占 폚 or lower, more preferably 30 占 폚 More preferably not higher than 20 占 폚, particularly preferably not higher than 15 占 폚. When the glass transition temperature of the particulate polymer is in the above range, the flexibility and winding property of the electrode and the binding properties of the electrode active material layer and current collector are highly balanced and 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 further preferably 500 nm or less, and 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 is 50% in the particle diameter distribution measured by the laser diffraction method.

The method for producing the particulate polymer is not particularly limited, and for example, any of solution polymerization, suspension polymerization, emulsion polymerization and the like may be used. Among them, the emulsion polymerization method and the suspension polymerization method are preferred since they can be polymerized in water and can be used directly as a material for the binder composition. When a particulate polymer is produced, it is preferable to add a dispersant to the reaction system. The particulate polymer is usually formed by a polymer substantially constituting it, but it may contain an optional component such as an additive contained in the reaction system at the time of polymerization.

[1.2. Water-soluble polymer]

The water-soluble polymer usually has an action of uniformly dispersing the electrode active material in a slurry composition for a lithium ion secondary battery (hereinafter sometimes referred to as "slurry composition") containing the binder composition of the present invention. In addition, the water-soluble polymer can exhibit an action of binding the electrode active material and the current collector in the electrode active material layer, interposed between the electrode active materials, and between the electrode active material and the current collector. In addition, the water-soluble polymer can exhibit an action of suppressing the decomposition of the electrolytic solution by forming a stable layer covering the electrode active material, usually in the electrode active material layer.

(1.2.1. Acid-containing monomer unit)

The water-soluble polymer contains 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 shows acidity. Examples of the acid group include a carboxylic acid group such as a carboxyl group and an anhydrous carboxyl group, a sulfonic acid group, and a phosphoric acid group. Among them, a carboxylic acid group and a sulfonic acid group are preferable.

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

Examples of the ethylenically unsaturated carboxylic acid monomer include ethylenically unsaturated monocarboxylic acid monomers and derivatives thereof, ethylenically unsaturated dicarboxylic acid monomers and acid anhydrides and derivatives thereof. Examples of the ethylenically unsaturated monocarboxylic acid monomer include acrylic acid, methacrylic acid, and crotonic acid. Examples of the derivative of the ethylenically unsaturated monocarboxylic acid monomer include 2-ethyl acrylic acid, isocrotonic acid,? -Acetoxy acrylic acid,? -Trans-aryloxy acrylic acid,? -Chloro-? -E-methoxy acrylic acid, diaminoacrylic acid. Examples of the ethylenically unsaturated dicarboxylic acid monomer include maleic acid, fumaric acid, and itaconic acid. Examples of the acid anhydride of the ethylenically unsaturated dicarboxylic acid monomer include maleic anhydride, acrylic acid anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Examples of derivatives of the ethylenically unsaturated dicarboxylic acid monomer include substituted maleic acid such as methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, and fluoromaleic acid; And maleic acid esters such as maleic acid diphenyl, maleic anonil, maleic decyl, maleic acid dodecyl, maleic acid octadecyl, and maleic acid fluoroalkyl. Of these, ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid are preferable in that the water-soluble polymer obtained can be further improved in solubility in water.

Examples of the ethylenically unsaturated sulfonic acid monomer include a conjugated double bond of a diene compound such as isoprene and butadiene, a sulfonated monomer, a vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate, Acrylamide-2-methylpropanesulfonic acid (AMPS), 3-aryloxy-2-hydroxypropanesulfonic acid (HAPS), and salts thereof. Examples of the salt include a lithium salt, a sodium salt, a potassium salt, and the like. For example, a sodium salt of styrene sulfonic acid (p-styrenesulfonic acid or the like) (NaSS). Preferable examples of the ethylenic unsaturated sulfonic acid monomer include AMPS and NaSS. AMPS is particularly preferred.

Examples of the ethylenically unsaturated phosphoric acid monomer include a monomer having an ethylenic unsaturated group and having -OP (= O) (-OR ^a ) -OR ^b group, or a salt thereof. 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 compounds containing a phosphoric acid group and an aryloxy group, and phosphoric acid group-containing (meth) acrylic acid esters. Examples of the compound containing a phosphoric acid group and an aryloxy group include 3-aryloxy-2-hydroxypropane phosphoric acid. Examples of the phosphoric acid group-containing (meth) acrylic esters include dioctyl-2-methacryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, Methacryloyloxyethylphosphate, diethyl-2-methacryloyloxyethylphosphate, monoisopropyl-2-methacryloyloxyethylphosphate, dimethyl-2-methacryloyloxyethylphosphate, Butyl-2-methacryloyloxyethyl phosphate, di-n-butyl-2-methacryloyloxyethyl phosphate, mono-n-butyl-2-methacryloyloxyethyl phosphate, 2-methacryloyloxyethyl phosphate, dibutoxyethyl-2-methacryloyloxyethyl phosphate, mono (2-ethylhexyl) -2- methacryloyloxyethyl phosphate, di (2- Ethylhexyl) -2-methacryloyloxyethyl phosphate, and the like.

Of the above-mentioned examples, preferred are ethylenically unsaturated carboxylic acid monomers and ethylenically unsaturated sulfonic acid monomers. More preferred examples thereof include acrylic acid, methacrylic acid, itaconic acid, and 2-acrylamide-2- Sulfonic acid, and acrylic acid, methacrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid are more preferable.

The acid group-containing monomer and the acid group-containing monomer unit may be used singly or two or more thereof may be used in combination at an arbitrary ratio.

The proportion of acid group-containing monomer units 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% 65% by weight or less, and more preferably 60% by weight or less. By controlling the amount of the acid group-containing monomer units to be at least the lower limit of the above range, precipitation of lithium metal by charge and discharge in the lithium ion secondary battery can be suppressed. In addition, by setting the upper limit value to be less than or equal to the upper limit, the bondability between the electrode active material layer and the current collector can be enhanced.

(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.

Examples of the fluorine-containing monomer include fluorine-containing (meth) acrylic acid ester monomers. Examples of the fluorine-containing (meth) acrylic acid ester monomers include monomers represented by the following formula (I).

[Chemical Formula 1]

In the above formula (I), R ¹ represents a hydrogen atom or a methyl group.

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

Examples of the fluorine-containing (meth) acrylic acid ester monomer represented by the formula (I) include alkyl (meth) acrylate, aryl fluoride (meth) acrylate and aralkyl fluoride (meth) acrylate. Among them, alkyl (meth) acrylate is preferred. Specific examples of such monomers include 2,2,2-trifluoroethyl (meth) acrylate; ? - (perfluorooctyl) ethyl (meth) acrylate; 2,2,3,3-tetrafluoropropyl (meth) acrylate; 2,2,3,4,4,4-hexafluorobutyl (meth) acrylate; (Meth) acrylic acid 3 [4 [1-Trifluoromethyl-2,2-bis [bis (trifluoromethyl) fluoromethyl] ethynyl] benzooxy] 2-hydroxypropyl; Perfluorohexyl (meth) acrylate, perfluoro (meth) acrylate, perfluoro (meth) acrylate, 1H, Ethyl (meth) acrylate, and (meth) acrylic acid perfluoroalkyl esters such as (meth) acrylate trifluoromethyl.

The fluorine-containing monomer and the fluorine-containing monomer unit may be used singly or in combination of two or more at any ratio.

The proportion 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 30% More preferably 25% by weight or less, particularly preferably 20% by weight or less. By setting the ratio of the fluorine-containing monomer units to the lower limit value or more in the above range, the high-temperature cycle characteristics of the lithium ion secondary battery can be improved. In addition, by setting the upper limit value to be less than or equal to the upper limit value, precipitation of lithium metal by charge and discharge in the lithium ion secondary battery can be suppressed.

(1.2.3. Crosslinkable monomer unit)

The water-soluble polymer preferably contains a crosslinkable monomer unit. By containing the crosslinkable monomer unit, the water-soluble polymer can be crosslinked, so that the strength and stability of the electrode active material layer can be enhanced. Further, the swelling of the electrode active material layer against the electrolyte 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, there can be mentioned a monofunctional monomer having a thermally crosslinkable crosslinkable group and one olefinic double bond per molecule, and a polyfunctional monomer having at least two olefinic double bonds per molecule.

Examples of the heat-crosslinkable crosslinkable group contained in the monofunctional monomer include an epoxy group, an N-methylolamide group, an oxetanyl group, an oxazoline group, and a combination thereof. Of these, the epoxy group is more preferable because the crosslinking and the crosslinking density can be easily controlled.

Examples of the crosslinkable monomer having an epoxy group as the thermally crosslinkable crosslinkable group and having an olefinic double bond include vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenylglycidyl Unsaturated glycidyl ethers such as ethers; Butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene and 1,2-epoxy-5,9-cyclododecadien Monoepoxide of diene or polyene; Alkenyl epoxide such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene; And glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl Glycidyl esters of unsaturated carboxylic acids such as glycidyl esters of 3-cyclohexenecarboxylic acid and glycidyl esters of 4-methyl-3-cyclohexenecarboxylic acid, and the like, .

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

Examples of the crosslinkable monomer having an oxetanyl group as the thermally crosslinkable crosslinkable group and having an olefinic double bond include 3 - ((meth) acryloyloxymethyl) oxetane, 3 - ((meth) acryloyl (Meth) acryloyloxymethyl) oxetane, 2- ((meth) acryloyloxymethyl) oxetane, 2- ((Meth) acryloyloxymethyl) -4-trifluoromethyl oxetane, and the like.

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

Examples of the polyfunctional monomer having two or more olefinic double bonds include allyl (meth) acrylate, ethylenedi (meth) acrylate, diethyleneglycol di (meth) acrylate, triethyleneglycol di , Tetraethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diaryl ether, Trimethylolpropane-diallyl ether, allyl or vinyl ether of polyfunctional alcohols other than the above, triallylamine, methylenebisacrylamide, and divinylbenzene.

Among them, ethylene dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate are preferable as crosslinking monomers, and ethylene dimethacrylate and glycidyl methacrylate are more preferable.

The crosslinkable monomer and the crosslinkable monomer unit may be used singly or two or more may be used in combination at an arbitrary ratio.

The proportion of the crosslinkable monomer units in the water-soluble polymer is preferably 0.1% by weight or more, more preferably 0.15% by weight or more, particularly preferably 0.2% by weight or more, and preferably 2% More preferably not more than 1.5% by weight, particularly preferably not more than 1.0% by weight. By setting the ratio of the crosslinkable monomer units to the lower limit value or more in the above range, precipitation of lithium metal by charge and discharge in the lithium ion secondary battery can be suppressed. By setting the upper limit value to be less than or equal to the upper limit value, the high-temperature cycle characteristics of the lithium ion secondary battery can be enhanced.

(1.2.4. Reactive Surfactant Unit)

The water-soluble polymer may contain a reactive surfactant unit. The reactive surfactant unit is a structural unit having a structure formed by polymerizing a reactive surfactant. The reactive surfactant unit constitutes a part of the water-soluble polymer and can also function as a surfactant.

The reactive surfactant is a monomer having a polymerizable group capable of copolymerizing with another monomer, and also having a surfactant (a hydrophilic group and a hydrophobic group). Typically, the reactive surfactant has a polymerizable unsaturated group, and this group also functions as a hydrophobic group after polymerization. Examples of the polymerizable unsaturated group contained in the reactive surfactant include a vinyl group, an allyl group, a vinylidene group, a propenyl group, an isopropenyl group, and an isobutylidene group. These polymerizable unsaturated groups may be used singly or in combination of two or more at any ratio.

The reactive surfactant is a part which exhibits hydrophilicity, and usually has a hydrophilic group. The reactive surfactants are classified into anionic, cationic and nonionic surfactants depending on the type of the hydrophilic group.

Examples of anionic hydrophilic groups include -SO ₃ M, -COOM, and -PO (OH) ₂ . Wherein M represents a hydrogen atom or a cation. Examples of cationic ions include alkali metal ions such as lithium, sodium and potassium; Alkaline earth metal ions such as calcium and magnesium; Ammonium ion; Ammonium ions of alkylamines such as monomethylamine, dimethylamine, monoethylamine and triethylamine; 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. Wherein R ^X represents an alkyl group. Examples of R ^X include a methyl group, an ethyl group, a propyl group, and an isopropyl group.

An example of a nonionic system hydrophilic group is -OH.

Examples of the preferable reactive surfactant include compounds represented by the following formula (II).

(2)

In formula (II), R represents a divalent linking group. Examples of R include -Si-O- group, methylene group and phenylene group.

In the formula (II), R ³ represents a hydrophilic group. An example of R ³ is -SO ₃ NH ₄ .

In the formula (II), n represents an integer of 1 or more and 100 or less.

Another example of a preferable reactive surfactant includes a structural unit having a structure formed by polymerizing ethylene oxide and an alkenyl group having a structural unit having a structure formed by polymerization of butylene oxide and having a terminal double bond at the terminal, there may be mentioned a compound having a -SO ₃ NH _4. Specific examples of such a reactive surfactant include trade name "Latex PD-104" and "Latex PD-105" manufactured by Kao Corporation.

The reactive surfactant and the reactive surfactant unit may be used singly or in combination of two or more at any ratio.

The proportion of the reactive surfactant 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 5% More preferably 4% by weight or less, particularly preferably 2% by weight or less. By setting the ratio of the reactive surfactant unit to the lower limit value or more of the above range, the dispersibility of the slurry composition of the present invention can be improved. By setting the upper limit value to be less than or equal to the upper limit value, the durability of the electrode can be improved.

(1.2.5. Arbitrary structural units)

The water-soluble polymer may contain an arbitrary structural unit in addition to the above-mentioned acid group-containing monomer unit, fluorine-containing monomer unit, crosslinkable monomer unit and reactive surfactant unit.

For example, the water soluble polymer may contain (meth) acrylic acid ester monomer units.

Examples of the (meth) acrylic acid ester monomers include acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, Alkyl acrylate esters such as acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate and stearyl acrylate; And examples of the monomer include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, Methacrylic acid such as methacrylic acid, methacrylic acid such as methacrylic acid, methacrylic acid, methacrylic acid, etc., such as acrylate, methacrylate, Alkyl esters. The (meth) acrylic acid ester monomer and the (meth) acrylic acid ester monomer unit may be used singly or in a combination of two or more.

The proportion of the (meth) acrylic acid ester monomer unit in the water-soluble polymer is preferably 25% by weight or more, more preferably 30% by weight or more, particularly preferably 35% by weight or more, % Or less, more preferably 70 wt% or less, particularly preferably 65 wt% or less. By making the amount of the (meth) acrylic acid ester monomer unit equal to or more than the lower limit of the above range, the binding property of the electrode active material layer to the current collector can be enhanced. In addition, by setting the value to be not more than the upper limit value, the flexibility of the electrode can be increased.

Further examples of the optional 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, vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene,? -Methylstyrene and divinylbenzene; Amide-based monomers such as acrylamide; Alpha, beta -unsaturated nitrile compound monomers such as acrylonitrile and methacrylonitrile; Olefin monomers such as ethylene and propylene; Halogen-containing monomers such as vinyl chloride and vinylidene chloride; Vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; Vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; Vinyl ketone monomers such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; , And a structural unit having a structure formed by polymerizing at least one of heterocyclic-containing vinyl compound monomers such as N-vinylpyrrolidone, vinylpyridine, and vinylimidazole.

(1.2.6 Properties of Water-Soluble Polymer)

The viscosity of a 1% aqueous solution of a 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 further preferably 1,000 mPa · s or less, More preferably 500 mPa · s or less, and particularly preferably 100 mPa · s or less. Here, the 1% aqueous solution viscosity of the water-soluble polymer means the viscosity of the aqueous solution of the water-soluble polymer at a concentration of 1% by weight. By adjusting the viscosity of the aqueous solution of 1% aqueous solution of the water-soluble polymer to the lower limit value of the above range, the dispersibility of the slurry composition can be enhanced. In addition, by setting the upper limit value to be less than or equal to the upper limit, the bondability between the electrode active material layer and the current collector can be enhanced. The viscosity can be adjusted, for example, according to the molecular weight of the water-soluble polymer. Here, the viscosity is a value measured at 25 캜 and a rotation speed of 60 rpm 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 500000 or less, more preferably 450000 or less, particularly preferably 400000 or less to be. By setting the weight average molecular weight of the water-soluble polymer to a lower limit value or more of the above range, the strength of the water-soluble polymer can be increased and the durability of the electrode can be improved. In addition, by setting it to the upper limit value or less, the binding property between the current collector and the electrode active material layer can be enhanced. Here, the weight average molecular weight of the water-soluble polymer can be determined as a value in terms of polystyrene using a solution in which 0.85 g / ml of sodium nitrate is dissolved in a 10% by volume aqueous solution of dimethylformamide by GPC as a developing solvent.

(1.2.7. Amount of water-soluble polymer)

The weight ratio of the particulate polymer to the water-soluble polymer is preferably 50/50 or more, more preferably 60/40 or more, particularly preferably 70/30 or more, and more preferably 99 / 1 or less, more preferably 98/2 or less, particularly preferably 97/3 or less. By setting the weight ratio to a lower limit value or more of the above range, the high temperature cycle characteristics of the lithium ion secondary battery can be enhanced. In addition, by setting the upper limit value to be less than or equal to the upper limit, the bondability between the electrode active material layer and the current collector can be enhanced.

(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 proportion of each monomer in the monomer composition is generally the same as the proportion of the structural units in the water-soluble polymer.

The aqueous solvent is not particularly limited as long as it is capable of dispersing the water-soluble polymer. The boiling point at normal pressure is usually 80 ° C or higher, more preferably 100 ° C or higher, and preferably 350 ° C or lower, and more preferably 300 ° C or lower. Hereinafter, examples of the aqueous solvent will be given. In the following examples, the numeral in parentheses after the solvent name is the boiling point (unit C) at normal pressure, and the fractional part is the value rounded or truncated.

Examples of water-based solvents include water (100); Ketones such as diacetone alcohol (169) and? -Butyrolactone (204); Alcohols such as ethyl alcohol (78), isopropyl alcohol (82) and normal propyl alcohol (97); Propylene glycol monomethyl ether 120, methyl cellosolve 124, ethyl cellosolve 136, ethylene glycol tertiary butyl ether 152, butyl cellosolve 171, 3-methoxy-3- Glycol such as methyl-1-butanol (174), ethylene glycol monopropyl ether (150), diethylene glycol monobutyl ether (230), triethylene glycol monobutyl ether (271), dipropylene glycol monomethyl ether Ethers; And ethers such as 1,3-dioxolane (75), 1,4-dioxolane (101), and tetrahydrofuran (66). Among them, water is not particularly flammable and is particularly preferable from the viewpoint of easily obtaining a dispersion of a polymer. In addition, water may be used as the main solvent and an aqueous solvent other than the above-described water may be mixed in the range in which the dispersion state of the polymer can be ensured.

The polymerization method is not particularly limited and any of the solution polymerization method, suspension polymerization method, bulk polymerization method, emulsion polymerization method and the like can be used. As the polymerization method, any of ion polymerization, radical polymerization, living radical polymerization and the like can be used, for example. From the viewpoint of the production efficiency, it is preferable to use an emulsion polymerization method in which a high-molecular-weight polymer is easily obtained and a polymer is obtained in a state in which the polymer is dispersed in water as it is, The method is particularly preferred.

The emulsion polymerization is usually carried out by a conventional method. For example, the method described in " Experimental Chemistry Lecture " vol. 28, (published by Maruzen Co., Ltd., Japan Chemical Society). That is, water, an additive such as a dispersant, an emulsifying agent, a crosslinking agent, a polymerization initiator, and a monomer are added to a sealed container having a stirrer and a heating device so as to have a predetermined composition, the composition in the container is stirred, And the temperature is raised while stirring to initiate polymerization. Alternatively, the composition is emulsified and then placed in a sealed container to initiate the reaction in the same manner.

Examples of the polymerization initiator include organic peroxides such as lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate and 3,3,5-trimethylhexanoyl peroxide Peroxide; azo compounds such as?,? '- azobisisobutyronitrile; Ammonium persulfate; And potassium persulfate. The polymerization initiator may be used singly or in combination of two or more in an arbitrary ratio.

The emulsifier, the dispersant, the polymerization initiator and the like are generally used in these polymerization methods, and the amount of the emulsifier, the dispersant, and the polymerization initiator is generally used.

The polymerization temperature and the polymerization time may be arbitrarily selected depending on the polymerization method and the kind of the polymerization initiator. The polymerization temperature is usually about 30 ° C or higher, and the polymerization time is about 0.5 to 30 hours.

In addition, additives such as amines may be used as polymerization auxiliary agents.

By the polymerization, a reaction liquid containing a water-soluble polymer is usually obtained. The obtained reaction solution is usually acidic, and the water-soluble polymer is often dispersed in an aqueous solvent. The water-soluble polymer thus dispersed in the water-soluble solvent can be usually used in an aqueous solvent by adjusting the pH of the reaction solution to, for example, 7 to 13. The water-soluble polymer may be extracted from the reaction solution thus obtained. However, in general, water is used as an aqueous medium, and the binder composition of the present invention is prepared by using a water-soluble polymer dissolved in the water.

Examples of the method for alkalizing the reaction solution to pH 7 to pH 13 include an aqueous solution of an alkali metal such as an aqueous solution of lithium hydroxide, an aqueous solution of sodium hydroxide and an aqueous solution of potassium hydroxide; An aqueous solution of an alkaline earth metal such as an aqueous solution of calcium hydroxide and an aqueous solution of magnesium hydroxide; And an aqueous solution of an alkali such as an aqueous ammonia solution. The above-mentioned alkali aqueous solution may be used singly or in combination of two or more in an arbitrary ratio.

[1.3. Polyether-modified silicone compound]

The binder composition of the present invention contains a polyether-modified silicone compound. The polyether-modified silicone compound can suppress the precipitation of lithium metal by charging and discharging in the lithium ion secondary battery, so that the high temperature cycle characteristics can be improved. In addition, the polyether-modified silicone compound can increase the wettability of the electrode active material layer with the electrolytic solution, thereby increasing the lithium ion conductivity in the lithium ion secondary battery. Therefore, the internal resistance of the lithium ion secondary battery can be lowered, so that the low temperature output characteristic 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 substituted with a substituent having a polyoxyalkylene group.

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

(3)

The number of carbon atoms of the hydrocarbon group represented by R ⁴ and R ⁵ is preferably 1 to 6. Examples of the hydrocarbon group include alkyl groups such as methyl group, ethyl group and propyl group; And an aryl group such as a phenyl group. These hydrocarbon groups may be used alone, or two or more of them may be used in combination at an arbitrary ratio.

Examples of the organopolysiloxane include polydimethylsiloxane, methylethylsiloxane-dimethylsiloxane copolymer, methylphenylsiloxane-dimethylsiloxane copolymer, and the like. These may be used singly or in combination of two or more in an arbitrary ratio.

As the polyoxyalkylene group, a polyoxyalkylene group having a number average molecular weight of 100 to 2000 can be used. Examples of such polyoxyalkylene groups include polyoxyethylene groups, polyoxypropylene groups, and the like. These polyoxyalkylene groups may be used singly or two or more of them may be used in combination at an arbitrary ratio. 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 group such as a hydroxy (polyoxyalkylene) propylene group, a methoxy (polyoxyalkylene) propylene group, an ethoxy (polyoxyalkylene) propylene group, An oxyalkylene group, a methoxypolyoxyalkylene group, an ethoxypolyoxyalkylene group, and a polyoxyalkylene group. These may be used singly or in combination of two or more in an arbitrary ratio.

In the molecule of the polyether-modified silicone compound, the position of the substituent having a polyoxyalkylene group is optional. 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. Among them, the substituent having a polyoxyalkylene group is preferably located on the side chain of the siloxane skeleton.

When an aqueous solution containing a polyether-modified silicone compound at a concentration of 10% by weight is prepared, its surface tension is preferably included in 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 or less, particularly preferably 40 mN / m or less. By making the surface tension equal to or lower than the lower limit of the above range, deposition of lithium metal by charge and discharge in the lithium ion secondary battery can be suppressed. In addition, by making the upper limit value or less, the dispersibility of each component in the electrode active material layer can be enhanced.

The above surface tension can be measured by the following method. The polyether-modified silicone compound is dissolved in water to prepare a polyether-modified silicone compound aqueous solution having a concentration of 10% by weight. The surface tension of the 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 (Sanofco Corporation); 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 and L-77 (Nippon Unicasa). Among these, SN wet 123, SN 125, DAW-DC-67, SH-3771, SH3749, FZ2162 and L-7607N are preferable, SN wet 123, And SH-3749, more preferably SN wet 123, copper 125 and DAW-DC-67, particularly preferably SN wet 123 and copper 125. The polyether-modified silicone compound may be used singly or in combination of two or more at any ratio.

The amount of the polyether-modified silicone compound is usually at least 0.1 part by weight, preferably at least 0.15 part by weight, more preferably at least 0.2 part by weight, usually at most 10 parts by weight, Is not more than 8 parts by weight, more preferably not more than 5 parts by weight. By making the amount of the polyether-modified silicone compound equal to or lower than the lower limit of the above range, the binding property between the electrode active material layer and the current collector can be enhanced. In addition, by setting the upper limit value to be less than or equal to the upper limit value, precipitation of lithium metal by charge and discharge in the lithium ion secondary battery can be suppressed.

[1.4. water]

The binder composition of the present invention contains water. The water usually functions as a solvent or a dispersion medium, and the particulate polymer can be dispersed, or the water-soluble polymer and the polyether-modified silicone compound can be dissolved.

As the solvent, a solvent other than water may be used in combination with water. For example, when a liquid capable of dissolving a water-soluble polymer is combined with water, the water-soluble polymer is adsorbed on the surface of the electrode active material, thereby stabilizing the dispersion of the electrode active material.

The kind of liquid to be combined with water is preferably selected from the viewpoints of drying speed and environment. Preferable examples thereof include cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; Aromatic hydrocarbons such as toluene and xylene; Ketones such as ethyl methyl ketone and cyclohexanone; Esters such as ethyl acetate, butyl acetate,? -Butyrolactone and? -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; And amides such as N-methylpyrrolidone and N, N-dimethylformamide. Among them, N-methylpyrrolidone (NMP) is preferable. These may be used singly or in combination of two or more in an arbitrary ratio.

The amount of the solvent such as water can be appropriately adjusted so as to have a suitable concentration and viscosity for the preparation of the binder composition and the production of the slurry composition using the binder composition. Concretely, 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, To 60% by weight or less, more preferably 55% by weight or less, and particularly preferably 50% by weight or less. Here, the solid content of the binder composition refers to a substance remaining after drying of the binder composition.

[1.5. Any component]

The binder composition of the present invention may contain any component other than the above-described particulate polymer, water-soluble polymer, polyether-modified silicone compound and water, unless the effect of the present invention is remarkably impaired. The optional components may be used singly or in combination of two or more in an arbitrary ratio.

[1.6. Method for producing binder composition]

There is no limitation on the method for producing the binder composition of the present invention. For example, the binder composition of the present invention can be produced by mixing the above-mentioned particulate polymer, water-soluble polymer, polyether-modified silicone compound and water in an arbitrary order.

Particularly preferred manufacturing methods include the following manufacturing methods including the following steps (1) and (2).

Step (1); A step of mixing a particulate polymer, a polyether-modified silicone compound and water to obtain a mixture (1).

Step (2); After the step (1), a step of further mixing the mixture (1) with the water-soluble polymer.

By performing the mixing in this order, homogeneous mixing can be easily achieved, and high dispersibility can be obtained.

In the case where the particulate polymer is used in the form of an aqueous dispersion, or the polyether-modified silicone compound is used in the form of an aqueous solution or an aqueous dispersion, or the aqueous polymer is used in the form of an aqueous solution, water may be separately mixed with the aqueous solution and the aqueous dispersion And water may not be separately mixed with these aqueous solutions and water dispersions. Normally, water is mixed separately from these aqueous solutions and aqueous dispersions to adjust the solid content concentration of the binder composition to fall within a desired range.

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

Examples of the equipment for carrying out the mixing include a mixer such as a ball mill, a sand mill, a bead mill, a roll mill, a pigment disperser, a brain ball, an ultrasonic disperser, a homogenizer, a homomixer, a planetary mixer .

[2. Slurry composition for lithium ion secondary battery]

The slurry composition of the present invention is a slurry composition for a lithium ion secondary battery electrode, which contains the binder composition of the present invention and an electrode active material.

[2.1. Electrode active material]

(2.1.1. Positive electrode active material)

Among the electrode active materials, a material capable of inserting and desorbing lithium ions is usually used as the electrode active material for the positive electrode (hereinafter sometimes referred to as " positive electrode active material " Such a positive electrode active material is roughly classified into an inorganic compound and an organic compound.

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

Examples of transition metal oxides include MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ OP ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O _13, etc. Among them, MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ are preferable in terms of cycle stability and capacity.

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

The lithium-containing composite metal oxide includes, for example, 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.

A lithium-containing composite metal oxide having a layered structure, for example, lithium-containing cobalt oxide (LCO: LiCoO _2), lithium nickel oxide (LiNiO _2), lithium composite oxide of the Co-Ni-Mn (NMC: LiNi 0.8 _{Co 0.1 Mn 0.1 O 2, LiNi} 0.33 Co 0.33 Mn 0.33 O 2 , etc.), lithium composite oxide of Ni-Mn-Al lithium composite oxide, Ni-Co-Al of (NCA: Li [Ni-Co -Al] O 2 Etc.).

Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganese oxide (LMO: LiMn ₂ O ₄ ) or Li [Mn _3/2 M (LiMn ₂ O ₄ ) in which a part of Mn of lithium manganese oxide is replaced with another transition metal _1/2 ] O ₄ (where M is Cr, Fe, Co, Ni, Cu, etc.).

As the lithium-containing composite metal oxide having olivine structure, for example, Li _X MPO ₄ (where M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Ti, Al, Si, B and Mo, and X represents a number satisfying 0? X? 2. For example, olivine phosphoric acid represented by LFP: LiFePO ₄ or the like Lithium compounds.

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

Further, a positive electrode active material composed of a composite material in which an inorganic compound and an organic compound are combined may be used.

Further, for example, a composite material coated with a carbon material may be produced by reducing and firing an iron-based oxide in the presence of a carbon source material, and this composite material may be used as a positive electrode active material. The iron-based oxide tends to lack electrical conductivity, but by using the composite material as described above, it can be used as a high-performance positive electrode active material.

Further, the above-mentioned compound may be partially substituted with an element to use as a positive electrode active material.

A mixture of the inorganic compound and the organic compound may be used as the positive electrode active material.

The positive electrode active material may be used alone, or two or more types may be used in combination at an arbitrary 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 占 퐉 or more, more preferably 2 占 퐉 or more, further preferably 50 占 퐉 or less, and more preferably 30 占 퐉 or less. By setting the average particle diameter of the particles of the positive electrode active material within the above range, the amount of the binder in the positive electrode active material layer can be reduced, and the capacity of the lithium ion secondary battery can be suppressed from lowering. In addition, it is easy to adjust the viscosity of the slurry composition of the present invention to a suitable viscosity, which is easy to apply, and a uniform positive electrode can be obtained.

The amount of the positive electrode active material is 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 weight or less. By setting the amount of the positive electrode active material within the above range, the capacity of the lithium ion secondary battery can be increased, and flexibility of the positive electrode and binding performance of the current collector and the positive electrode active material layer can be improved.

(2.1.2. Negative active material)

Among the electrode active materials, an electrode active material for negative electrode (hereinafter sometimes referred to as " negative electrode active material " as appropriate) is a material that transports electrons in the negative electrode. As the negative electrode active material, usually, a material capable of absorbing and desorbing lithium ions is used.

The preferred negative electrode active material is, for example, carbon. Examples of the carbon include natural graphite, artificial graphite, carbon black and the like, among which natural graphite is preferably used.

As the negative electrode active material, it is preferable to use a negative electrode active material containing at least one kind selected from the group consisting of tin, silicon, germanium and lead. The negative electrode active material containing these elements has a small irreversible capacity. Among them, 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.

The negative electrode active material may be used singly or in combination of two or more in an arbitrary ratio. Therefore, two or more kinds of the above-mentioned negative electrode active materials may be used in combination. Among them, it is preferable to use a negative electrode active material containing one or both of carbon, metal silicon and silicon-based active material in combination. In the negative electrode active material containing one or both of carbon, metal silicon and silicon-based active material in combination, insertion and desorption of Li into one or both of the metal silicon and silicon-based active material occurs at a high electric potential, It is presumed that insertion and desorption of Li occurs. Therefore, the expansion and contraction are suppressed, so that the cycle characteristics of the lithium ion secondary battery can be improved.

Silicon-based active material, for example, SiO, SiO _2, and the like _{SiO x (0.01 ≤ x <2} ), SiC, SiOC, a SiO _x, SiC and SiOC is preferred. Among them, it is particularly preferable to use SiO _x as the silicon-based active material since expansion of the negative electrode active material itself is suppressed. SiO _x is a compound formed by using one or both of SiO and SiO ₂ and a metal silicon as raw materials. The SiO _x can be produced, for example, by cooling and precipitating silicon monoxide gas produced by heating a mixture of SiO ₂ and metal silicon.

When one or both of carbon and metal silicon and silicon-based active material is used in combination, it is preferable that one or both of the metal silicon and silicon-based active material are composite with conductive carbon. By compounding with the conductive carbon, expansion of the negative electrode active material itself can be suppressed.

As a method of the compounding, for example, a method of forming a composite by coating one or both of metal silicon and silicon-based active material with carbon; A method of composing a mixture containing conductive carbon and one or both of a metal silicon and a silicon-based active material by granulation.

Examples of the method of coating one or both of the metal silicon and the silicon-based active material with carbon include a method of heat treating one or both of the metal silicon and the silicon-based active material to make them non-uniform; A method of subjecting one or both of the metal silicon and silicon-based active materials to chemical treatment by heat treatment, and the like.

It is preferable that the negative electrode active material is formed into particles. When the particle shape is spherical, a more dense electrode active material layer can be obtained at the time of 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 balance with other constituent requirements of the lithium ion secondary battery, and is preferably 0.1 占 퐉 or more, more preferably 1 占 퐉 or more, further preferably 5 占 퐉 or more , Further preferably not more than 100 mu m, more preferably not more than 50 mu m, further preferably not more than 20 mu m.

The specific surface area of the negative electrode active material is preferably not less than 2 m 2 / g, more preferably not less than 3 m 2 / g, still more preferably not less than 5 m 2 / g, and preferably not less than 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, for example, by the BET method.

The amount of the negative electrode active material is preferably 85% by weight or more, more preferably 88% by weight or more, further preferably 99% by weight or less, more preferably 97% by weight or less, By weight or less. By setting the amount of the negative electrode active material within the above range, it is possible to realize a negative electrode which exhibits excellent flexibility and adhesion while showing a high capacity.

[2.2. Ratio of the binder composition in the slurry composition]

The proportion of the binder composition contained in the slurry composition of the present invention is preferably adjusted appropriately so that the performance of the resulting battery is satisfactorily expressed. 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, 10 parts by weight or less, more preferably 8 parts by weight or less, particularly preferably 5 parts by weight or less.

[2.3. Any component]

The slurry composition of the present invention may contain optional components in addition to the above-described electrode active material and binder composition.

For example, the slurry composition of the present invention may contain a thickener other than the water-soluble polymer. Examples of the thickening agent include water-soluble polymers such as water-soluble polysaccharides, sodium polyacrylate, polyethyleneimine, polyvinyl alcohol and polyvinylpyrrolidone. Among them, water-soluble polysaccharides are preferable, and carboxymethylcellulose 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 the slurry composition can be increased and the coating property can be improved. In addition, dispersion stability of the particles of the electrode active material or the like in the slurry composition can be enhanced. Further, the binding property between the electrode active material layer and the current collector can be enhanced.

The amount of the thickening agent is not constant depending on the type of the thickener and the like. For example, the amount of carboxymethylcellulose is preferably 0.1 parts by weight or more, more preferably 0.3 parts by weight or more, particularly preferably 100 parts by weight or more per 100 parts by weight of the electrode active material Is not less than 0.5 parts by weight, preferably not more than 5 parts by weight, more preferably not more than 4 parts by weight, particularly preferably not more than 3 parts by weight. By including the amount of the thickener in the above range, the dispersibility of the particles in the slurry composition is 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 suitable viscosity for application. Concretely, 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, further preferably 70% by weight or less, more preferably 65% Or less. Here, the solid content of the slurry composition refers to a material remaining as a constituent component of the electrode active material layer through drying of the slurry composition.

Also, for example, the slurry composition may contain a conductive material. The conductive material is a component that can improve the electrical contact between the electrode active materials. By containing the conductive material, the discharge rate characteristic of the lithium ion secondary battery can be improved.

Examples of the conductive material include conductive carbon such as furnace black, acetylene black, ketjen black, oil furnace black, carbon black, graphite, vapor grown carbon fiber, and carbon nanotube. Particularly, acetylene black, oil-based 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-span characteristics of the lithium ion secondary battery is good. The conductive material may be used alone, or two or more conductive materials may be used in combination at an arbitrary ratio.

The specific surface area of the conductive material is preferably at least 50 m 2 / g, more preferably at least 60 m 2 / g, particularly preferably at least 70 m 2 / g, further preferably at most 1,500 m 2 / g, Is not more than 1200 m 2 / g, particularly preferably not more than 1000 m 2 / g. By setting the specific surface area of the conductive material to a lower limit value or more of the above range, the low temperature output characteristics of the lithium ion secondary battery can be improved. In addition, by setting the upper limit value to be less than or equal to the upper limit, the bondability between the electrode active material layer and the current collector can be enhanced.

The amount of the conductive material is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, still more preferably 0.3 parts by weight or more, and preferably 10 parts by weight or less, based on 100 parts by weight of the electrode active material Preferably 8 parts by weight or less, 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. Further, by making the amount of the conductive material equal to or lower than the upper limit, the bondability between the electrode active material layer and the current collector can be enhanced.

Also, for example, the slurry composition may contain a reinforcing material. By using a reinforcing material, a strong 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 fillers such as spherical, plate, rod-like or fibrous fillers. The reinforcing materials may be used singly or in combination of two or more in an arbitrary ratio.

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

Further, for example, the slurry composition may contain an electrolyte additive. By using the electrolyte additive, for example, decomposition of the electrolyte can be suppressed. Examples of the electrolyte additive include vinylene carbonate and the like. As the electrolyte additive, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

The amount of the electrolyte additive is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the electrode active material. By setting the amount of the electrolyte additive within the above range, it is possible to realize a secondary battery excellent in cycle characteristics and high temperature characteristics.

Further, for example, the slurry composition may contain nanoparticles such as fumed silica and fumed alumina. In the case of containing nanoparticles, it is possible to adjust the plasticity of the slurry composition, and the leveling property of the electrode active material layer obtained thereby can be improved. The nanoparticles may be used singly or in combination of two or more in an arbitrary ratio.

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

[2.4. Method of 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 required. The specific order in this case is arbitrary. For example, when preparing a slurry composition containing an electrode active material, a binder composition, water, a thickener and a conductive material, a method of simultaneously adding and mixing an electrode active material, a binder composition, a thickener and a conductive material in water; A method in which an electrode active material, a conductive material and a thickening agent are added to water and mixed, and then a binder composition is added and mixed.

Examples of the equipment for carrying out the mixing include a mixer such as a ball mill, a sand mill, a bead mill, a roll mill, a pigment disperser, a brain ball, an ultrasonic disperser, a homogenizer, a homomixer, a planetary mixer .

[3. Electrode for Lithium Ion Secondary Battery]

An electrode for a lithium ion secondary battery of the present invention (hereinafter sometimes referred to as an &quot; electrode &quot; as appropriate) comprises a current collector and an electrode active material layer.

[3.1. Whole house]

The current collector may be made of a material having electrical conductivity and also electrochemically durable. Normally, a metal material is used as a material of the current collector. Examples thereof include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum and the like. Among them, aluminum is preferable as the current collector used for the positive electrode, and copper is preferable as the current collector used for the negative electrode. The above materials may be used singly or in combination of two or more in an arbitrary ratio.

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

It is preferable that the current collector is subjected to surface roughening treatment in order to increase the adhesion strength with the electrode active material layer. Examples of the roughening method include mechanical roughening, electrolytic roughening, and chemical roughening. In the mechanical polishing, for example, a wire brush having a polishing cloth fixed with abrasive particles, a grinding wheel, an emery buff, 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]

The electrode active material layer is a layer obtained by applying and drying the slurry composition of the present invention on a current collector. Therefore, since the electrode active material layer is a layer formed by the solid content of the slurry composition of the present invention, it contains an electrode active material, a particulate polymer, a water-soluble polymer and a polyether-modified silicone compound.

In producing the electrode active material layer, a slurry composition is applied on the current collector to form a film of the slurry composition. At this time, the slurry composition may be applied to one surface of the current collector or both surfaces thereof.

The coating method is not limited, and examples thereof include a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.

The thickness of the film of the slurry composition can be appropriately set in accordance with the thickness of the target electrode active material layer.

After the film of the slurry composition is formed, liquid such as water is removed from the film by drying. As a result, an electrode active material layer containing a solid content of the slurry composition is formed on the surface of the current collector to obtain an electrode.

Examples of the drying method include drying by wind, such as hot air, hot air, and low-humidity air; Vacuum drying; And a drying method by irradiation of energy rays such as infrared rays, far-infrared rays or electron rays. Among them, a drying method by far-infrared irradiation is preferable.

The drying temperature and the drying time are preferably a temperature and a time at which water can be removed from the film of the slurry composition. For a specific range, the drying time is usually 1 minute to 30 minutes, and the drying temperature is usually 40 ° C to 180 ° C.

After the membrane of the slurry composition is dried, it is preferable to apply pressure treatment to the electrode active material layer, for example, using a die press or a roll press, if necessary. The porosity of the electrode active material layer can be lowered by the pressure treatment. The porosity is preferably 5% or more, more preferably 7% or more, further preferably 30% or less, and more preferably 20% or less. By setting the porosity to be equal to or more than the lower limit of the above range, a high volume capacity is easily obtained and the electrode active material layer can be prevented from being peeled off from the current collector. In addition, by setting the amount below the upper limit value, a high charging efficiency and a high discharge efficiency can be obtained.

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 formation of the electrode active material layer.

The thickness of the electrode active material layer can be arbitrarily set according to the required cell performance.

For example, the thickness of the positive electrode active material layer is preferably not less than 5 占 퐉, more preferably not less than 10 占 퐉, and further preferably not more than 300 占 퐉, more preferably not more than 250 占 퐉. When the thickness of the positive electrode active material layer is in the above range, high characteristics in both the load characteristic and the energy density can be realized.

For example, the thickness of the negative electrode active material layer is preferably 5 占 퐉 or more, more preferably 20 占 퐉 or more, particularly preferably 30 占 퐉 or more, further preferably 1000 占 퐉 or less, Preferably 500 탆 or less, more preferably 300 탆 or less, particularly preferably 250 탆 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 the present invention comprises a positive electrode, a negative electrode, and an electrolytic solution. The lithium ion secondary battery of the present invention may include a separator. However, one or both of the negative electrode and the positive electrode are the electrodes of the present invention. By providing the electrode of the present invention, the lithium ion secondary battery of the present invention can prevent precipitation of lithium metal by charging and discharging, and ordinarily can increase the affinity between the electrode active material layer and the electrolytic solution, Characteristics and low-temperature output characteristics can be obtained.

[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 may be used. Lithium salts include, for _{example, 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, and (C ₂ F ₅ SO ₂ ) NLi. In particular, _{LiPF 6, LiClO 4, CF 3} SO 3 Li indicating a high degree of dissociation easily dissolved in a solvent is preferably used. These may be used singly or in combination of two or more in an arbitrary 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, and more preferably 20% by weight or less, as the concentration in the electrolytic solution. By including the amount of the supporting electrolyte within the above range, the ionic conductivity can be increased, so that the charging and discharging characteristics of the battery can be improved.

As the solvent used for the electrolytic solution, those capable of dissolving the supporting electrolyte can be used. Examples of such solvents include solvents such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylen carbonate (BC), methyl ethyl carbonate Alkyl carbonates; esters such as? -butyrolactone and methyl formate; Ethers such as 1,2-dimethoxyethane and tetrahydrofuran; Sulfur compounds such as sulfolane and dimethylsulfoxide, and the like are used. Particularly, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate and methyl ethyl carbonate are preferable because it is easy to obtain high ion conductivity and has a wide temperature range for use. One solvent may be used alone, or two or more solvents may be used in combination at an arbitrary ratio.

The electrolytic solution may contain additives as required. As the additive, for example, a carbonate-based compound such as vinylene carbonate (VC) is preferable. One kind of additives may be used alone, or two or more kinds of additives may be used in combination at an arbitrary ratio.

4.2. Separator]

As the separator, a porous substrate having pores is usually used. Examples of the separator include (a) a porous separator having pores, (b) a porous separator having a polymer coat layer formed on one side or both sides thereof, (c) a porous separator having a porous resin coat layer containing an inorganic ceramic powder, etc. . Examples thereof include solid polymers such as polypropylene-based, polyethylene-based, polyolefin-based or aramid-based porous separators, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride hexafluoropropylene copolymer Polymer films for electrolytes or gelated polymer electrolytes; A separator coated with a gelled polymer coat layer; And a separator coated with a porous film layer made of an inorganic filler and a dispersing agent for an inorganic filler.

[4.3. Manufacturing Method of Lithium Ion Secondary Battery]

The method for producing the lithium ion secondary battery of the present invention is not particularly limited. For example, the negative electrode and the positive electrode described above may be superimposed with a separator interposed therebetween, and the battery may be wound or folded according to the shape of the battery, and the electrolyte may be injected into the battery container to seal the battery container. Expanded metal as required; An overcurrent prevention element such as a fuse or a PTC element; A lead plate or the like may be inserted so as to prevent an increase in pressure inside the battery and overcharge discharge. The shape of the battery may be, for example, a laminate shape, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, or the like.

Example

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the embodiments described below, and can be arbitrarily changed without departing from the scope of the claims and the equivalent scope of the present invention.

In the following description, &quot;% &quot; and &quot; part &quot; representing amounts are based on weight unless otherwise specified. The operations described below were carried out at normal temperature and normal pressure unless otherwise noted.

[Assessment Methods]

(1) Method of measuring the precipitation amount of lithium metal

The lithium ion secondary batteries of the laminate type cells produced in the examples and the comparative examples were still stopped for 24 hours under an environment of 25 캜. Thereafter, the lithium ion secondary battery was charged at 4.35 V, 1 C, and 1 hour under an environment of -10 캜. Thereafter, the negative electrode was taken out from the lithium ion secondary battery in a glove box under a 100% argon atmosphere at room temperature. The negative electrode thus taken out was observed to measure the area S (cm &lt; 2 &gt;) where lithium metal precipitated.

The measured area is shown by the following evaluation criteria. The smaller the area where the lithium metal is precipitated, the smaller the precipitation of lithium metal by charge and discharge, and the negative electrode indicates that it is possible to smoothly accommodate lithium ions in the electrolytic solution.

(Criteria for evaluation of deposition amount of lithium metal)

A: 0? S <1 (cm 2)

B: 1? S <5 (cm 2)

C: 5? S <10 (cm2)

D: 10 < S &lt; 15 (cm &lt; 2 &

E: 15? S <20 (cm 2)

F: 20? S? 25 (cm2)

(2) Method of measuring the contact angle of the binder composition film with the electrolyte solvent

The binder compositions prepared in Examples and Comparative Examples were dried at room temperature for 7 days to prepare a binder composition film. Using a contact angle meter ("DM-701" manufactured by Kyowa Interface Science Co., Ltd.), 3 microliters of the electrolyte solvent was dropped on the film of the binder composition, and the contact angle W (°) after 10 seconds from the drop was measured. As the electrolyte solvent, a mixed solvent of ethylene carbonate, diethyl carbonate and vinylene carbonate (EC / DEC / VC = 68.5 / 30 / 1.5; volume ratio) was used. The smaller the value of the contact angle W obtained, the greater the wettability of the solid component and the electrolytic solution of the binder composition, and the greater the wettability of the electrode active material layer and the electrolytic solution. When the wettability between the electrode active material layer and the electrolyte solution is large, the internal resistance of the battery can be reduced. Thus, a lithium ion secondary battery having excellent battery characteristics such as low temperature output characteristics can be realized.

(3) Evaluation method of high temperature cycle characteristics

The lithium ion secondary batteries of the laminate type cells produced in the examples and the comparative examples were still stopped for 24 hours under an environment of 25 캜. Thereafter, the lithium ion secondary battery was charged and discharged at a temperature of 25 ° C to 4.35 V at 0.1 C, and discharged at a rate of 0.1 C to 2.75 V to measure an initial capacity C 0 . Charging and discharging were repeatedly performed on the lithium ion secondary battery under the same conditions under an environment of 45 占 폚, and the capacity C2 after 500 cycles was measured. The capacity retention rate? C = C2 / C0 占 100 (%) was calculated from the obtained initial capacity C0 and the capacity C2 after 500 cycles, and the high temperature cycle characteristic was evaluated by this capacity retention rate? C. The higher the value of the capacity retention rate? C, the better the high-temperature cycle characteristics of the lithium ion secondary battery and the longer life.

(4) Evaluation method of low temperature output characteristic

The lithium ion secondary batteries of the laminate type cells produced in the examples and the comparative examples were still stopped for 24 hours under an environment of 25 캜. Thereafter, the lithium ion secondary battery was charged at 0.1 C to 4.35 V over 5 hours under an environment of 25 캜, and the voltage V 0 at that time was measured. Thereafter, the lithium ion secondary battery was subjected to discharge operation at a discharge rate of 1 C under an environment of -10 占 폚 to measure a voltage V1 after 15 seconds from the start of discharge. The voltage drop? V = V0 - V1 was calculated from the obtained voltages V0 and V1, and the low temperature output characteristics were evaluated by this voltage drop? V. The smaller the value of the voltage drop? V, the better the low temperature output characteristic of the lithium ion secondary battery.

(5) Method of measuring surface tension of aqueous solution of polyether-modified silicone compound

The polyether-modified silicone compounds prepared in Examples and Comparative Examples were 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. Preparation 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) , 0.8 parts of ethylene dimethacrylate (crosslinkable monomer), 1.0 part of polyoxyalkylenealkenyl ether sulfuric acid ammonium (reactive surfactant), 0.6 part of t-dodecylmercaptan, 150 parts of ion exchanged water 150 And 1.0 part of potassium persulfate (polymerization initiator) were put in the flask and sufficiently stirred. Thereafter, the polymerization was started by heating to 60 占 폚. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the water-soluble polymer. 10% ammonia water 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. Preparation of particulate polymer)

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, And 0.5 part of potassium persulfate as a polymerization initiator were put in a flask, and the mixture was sufficiently stirred and then heated to 50 DEG C to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the particulate polymer (SBR). To the mixture containing the particulate polymer, a 5% aqueous solution of sodium hydroxide was added to adjust the pH to 8. Thereafter, unreacted monomers of the mixture containing the particulate polymer were removed by heating and vacuum distillation. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion liquid containing a desired particulate polymer.

(1-3 Preparation of Binder Composition)

In the vessel, 95 parts of the aqueous dispersion containing the particulate polymer prepared in the above step (1-2), corresponding to the solid content, and 95 parts of the polyether-modified silicone compound ("Noftex E-F070" Was mixed with 0.15 parts. Thereafter, 5 parts of the aqueous solution containing the water-soluble polymer prepared in the above step (1-1), corresponding to the solid content, was added to the vessel, and further water was mixed to adjust the solid content concentration to 25% .

A part of the binder composition for a secondary battery was used to prepare a binder composition film as described above, and the contact angle of the film with the electrolyte solvent was measured.

(1-4. Preparation of Slurry Composition for Negative Electrode)

100 parts of natural graphite (volume average particle diameter: 15.6 mu m) having a specific surface area of 5.5 m &lt; 2 &gt; / g as a negative electrode active material and 100 parts of a salt of carboxymethylcellulose ("MAC- 350HC &quot;) was added in an amount of 1.0 part based on the solids content, and ion-exchanged water was further added thereto to adjust the solid concentration to 60%, followed by mixing at 25 DEG C for 60 minutes. Next, ion exchanged water was added to the planetary mixer to adjust the solid content concentration to 52%, and further mixed at 25 DEG C for 15 minutes to obtain a mixed solution. To the mixed solution, 2.0 parts by weight of the binder composition prepared in the above step (1-3) was added in an amount corresponding to the solid content, and further ion-exchanged water was added to adjust the final solid content to 48% and mixed for 10 minutes. This was degassed under reduced pressure to obtain a negative electrode slurry composition having excellent flowability.

(1-5. Preparation of negative electrode)

The slurry composition for negative electrode obtained in the above step (1-4) was coated on a copper foil having a thickness of 20 mu m as a current collector with a comma coater so that the film thickness after drying was about 150 mu m and dried. This drying was carried out by conveying the copper foil in an oven at 60 캜 for 2 minutes at a speed of 0.5 m / min. Thereafter, it was heat-treated at 120 ° C for 2 minutes to obtain a negative electrode raw material before pressing. The negative electrode disk before the pressing was rolled by a roll press to obtain a pressed negative electrode having a thickness of the negative electrode active material layer of 80 mu m.

(1-6. Preparation of slurry composition for positive electrode)

100 parts of LiCoO ₂ having a volume average particle diameter of 12 탆 as a positive electrode active material, ₂ parts of acetylene black ("HS-100" manufactured by Denki Kagaku Kogyo K.K.) as a conductive material and 2 parts of polyvinylidene fluoride (# 7208, Was mixed with 2 parts by weight of the solid content, and further N-methylpyrrolidone was added thereto to adjust the total solid concentration to 70%. These were mixed by a planetary mixer to prepare a positive electrode slurry composition.

(1-7. Preparation of positive electrode)

The slurry composition for positive electrode obtained in the above step (1-6) was coated on an aluminum foil having a thickness of 20 mu m as a current collector with a comma coater so that the film thickness after drying was about 150 mu m and dried. This drying was carried out by conveying the aluminum foil in an oven at 60 ° C for 2 minutes at a rate of 0.5 m / min. Thereafter, it was heat-treated at 120 DEG C for 2 minutes to obtain a positive electrode plate before pressing. The raw disk of the positive electrode before the pressing was rolled by a roll press to obtain a pressed positive electrode having a thickness of the positive electrode active material layer of 100 mu m.

(1-8 Preparation of Separator)

A single-layered polypropylene separator (Celgard 2500, manufactured by Celgard Corporation) was cut into a square of 5 × 5 cm 2.

(1-9. Production of lithium ion secondary battery)

As an exterior of the battery, an aluminum-containing sheath was prepared. The positive electrode obtained in the above step (1-7) was cut into a square of 4.6 x 4.6 cm &lt; 2 &gt;, and the surface of the collector side was arranged so as to be in contact with the aluminum-covered sheath. On the surface of the positive electrode active material layer of the positive electrode, a 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 square of 5 x 5 cm 2, and this was placed on the separator so that the surface of the negative electrode active material layer faced the separator. Electrolyte (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 volume ratio, electrolyte: LiPF _{6 with a} concentration of 1 M) was injected without leaving air. Further, in order to seal the openings of the aluminum foil, a heat sealing at 150 DEG C was carried out to close the aluminum foil sheath, thereby manufacturing a lithium ion secondary battery.

Using this lithium ion secondary battery, measurement of deposition amount of lithium metal, measurement of capacity retention rate? C for evaluation of high temperature cycle characteristics, and measurement of voltage drop? V for evaluation of low temperature output characteristics were carried out Respectively.

[Example 2]

In the above step (1-3), the amount of the polyether-modified silicone compound was changed to 0.0075 parts in terms of solid content.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 3]

In the above step (1-3), the amount of the polyether-modified silicone compound was changed to 0.45 part in terms of the solid content.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 4]

In the above step (1-3), the kind of the polyether-modified silicone compound was changed to &quot; SN Wet 123 &quot;

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 5]

In the above step (1-3), the kind of the polyether-modified silicone compound was changed to "SH3746" manufactured by Toray-Dow Corning Incorporated.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 6]

In the above step (1-3), the kind of the polyether-modified silicone compound was changed to "L-7607N" manufactured by Nippon Unicar.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 7]

In the above step (1-3), the amount of the aqueous dispersion containing the particulate polymer was changed to 98 parts in terms of solid content, the amount of the polyether-modified silicone compound was changed to 0.06 part in terms of solid content, Was changed to 2 parts in terms of solid content.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 8]

In the above step (1-3), the amount of the aqueous dispersion containing the particulate polymer is changed to 85 parts by solid content, the amount of the polyether-modified silicone compound is changed to 0.45 part in terms of solid content, Was changed to 15 parts in terms of solid content.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 9]

In the above step (1-3), the amount of the aqueous dispersion containing the particulate polymer is changed to 75 parts in terms of solid content, the amount of the polyether-modified silicone compound is changed to 0.75 part in terms of solid content, Was changed to 25 parts in terms of solid content.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 10]

In the above step (1-3), the amount of the aqueous dispersion containing the particulate polymer is changed to 60 parts in terms of solid content, the amount of the polyether-modified silicone compound is changed to 1.2 parts in terms of solid content, Was changed to 40 parts in terms of solid content.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 11]

In the above 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 used in combination.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 12]

In the above 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 used in combination.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 13]

In the above 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.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 14]

In the above 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.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 15]

In the above step (1-1), perfluorooctyl acrylate was used instead of 2,2,2-trifluoroethyl methacrylate as the fluorine-containing monomer.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 16]

In the above step (1-1), perfluoroethyl acrylate was used instead of 2,2,2-trifluoroethyl methacrylate as the fluorine-containing monomer.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 17]

In the above step (1-1), the amount of 2,2,2-trifluoroethyl methacrylate was changed to 0.15 part, and the amount of ethyl acrylate was changed to 65.55 parts.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 18]

In the above 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.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 19]

In the above step (1-1), the amount of methacrylic acid was changed to 40 parts, and 2,2,2-trifluoroethyl methacrylate was not used.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Example 20]

(20-1. Preparation of particulate polymer)

In a 5 MPa pressure vessel equipped 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 0.5 part of potassium were added. After sufficiently stirring, the mixture was heated to 50 DEG C to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the particulate polymer (ACR). To the mixture containing the particulate polymer, a 5% aqueous solution of sodium hydroxide was added to adjust the pH to 8. Thereafter, unreacted monomers of the mixture containing the particulate polymer were removed by heating and vacuum distillation. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion liquid containing a desired particulate polymer.

(Preparation of Binder Composition)

In the vessel, 95 parts of the aqueous dispersion containing the particulate polymer prepared in the above step (20-1) in an amount corresponding to the solid content, and the polyether-modified silicone compound ("Noftex E-F070" 0.15 parts by weight. Thereafter, 5 parts of an aqueous solution containing the water-soluble polymer prepared in the step (1-1) of Example 1 corresponding to the solid content was added to this vessel, and further water was mixed to adjust the solid content concentration to 25% Thereby obtaining a binder composition for a battery.

A part of the binder composition for a secondary battery was used to prepare a binder composition film as described above, and the contact angle of the film with the electrolyte solvent was measured.

(20-3 Production of slurry composition for positive electrode)

100 parts of LiCoO ₂ having a volume average particle diameter of 12 탆 as a positive electrode active material, ₂ parts of acetylene black ("HS-100" manufactured by Denki Kagaku Kogyo K.K.) as a conductive material and 2 parts of carboxymethyl 1.0% of a 2% aqueous solution of a salt of cellulose ("MAC-350HC" manufactured by Nippon Paper Chemical Co., Ltd.) in an amount corresponding to the solid content was further added, ion-exchanged water was added thereto to adjust the solid concentration to 60% . Next, ion exchanged water was added to the planetary mixer to adjust the solid content concentration to 52%, and further mixed at 25 DEG C for 15 minutes to obtain a mixed solution. 2.0 parts of the binder composition prepared in the above step (20-2) was added to the mixed solution in an amount corresponding to the solid content, and further ion-exchanged water was added thereto to adjust the final solid concentration to 48%, followed by mixing for 10 minutes. This was degassed under reduced pressure to obtain a positive electrode slurry composition having good flowability.

(20-4 Production of positive electrode)

(1-7) of Example 1, except that the positive electrode slurry composition obtained in the above step (20-3) was used in place of the positive electrode slurry composition obtained in the above step (1-6) , A positive electrode after pressing having a thickness of 100 m of the positive electrode active material layer was obtained.

(Preparation of Slurry Composition for Negative Electrode)

Instead of using 2.0 parts by weight of the binder composition produced in the above step (1-3) as a solid component, the aqueous dispersion containing the particulate polymer prepared in the above step (1-2) , A negative electrode slurry composition having good flowability was obtained in the same manner as in the step (1-4) of Example 1. [

(20-6 Production of Negative Electrode)

(1-5) of Example 1, except that the negative electrode slurry composition obtained in the above step (20-5) was used as the negative electrode slurry composition in place of the negative electrode slurry composition obtained in the above step (1-4) , A negative electrode having a thickness of 80 탆 and a negative electrode active material layer after pressing was obtained.

(20-7. Preparation of lithium ion secondary battery)

(1-9) of the example 1, except that the positive electrode obtained in the above step (20-4) was used and the negative electrode was obtained in the above step (20-6) A battery was manufactured and evaluated.

[Comparative Example 1]

In the above step (1-4), an aqueous dispersion containing the particulate polymer prepared in the above step (1-2) was used in place of the binder composition prepared in the above step (1-3).

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Comparative Example 2]

In the step (1-3), an aqueous solution containing a water-soluble polymer was not used.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Comparative Example 3]

In the above step (1-1), the amount of ethyl acrylate was changed to 59 parts, and ethylene dimethacrylate was not used.

In the above step (1-3), the polyether-modified silicone compound was not used.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Comparative Example 4]

In the above step (1-3), 0.15 part of a silicone compound ("KS-530" manufactured by Shin-Etsu Silicone Co., Ltd.) was used in place of the polyether-modified silicone compound.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Comparative Example 5]

In the above step (1-3), 0.15 part of a polyether compound (&quot; SN Deformer 170 &quot; produced by Sanofuca) was used in place of the polyether-modified silicone compound.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Comparative Example 6]

In the above step (1-3), the amount of the polyether-modified silicone compound was changed to 0.6 parts in terms of solid content.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[Comparative Example 7]

In the above 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.

Production and evaluation of a lithium ion secondary battery were carried out in the same manner as in Example 1 except for the above.

[result]

The results of the above Examples and Comparative Examples are shown in the following table.

In the following table, the abbreviations have the following meanings.

SBR: Styrene-butadiene rubber

ACR: Acrylic rubber

Monomer I: Acid group-containing monomer

MAA: methacrylic acid

AMPS: 2-acrylamide-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: Polyoxyalkylene alkenyl ether ammonium sulfate

EA: Ethyl acrylate

Aqueous viscosity: Viscosity of a 1% aqueous solution of a water-soluble polymer

Weight ratio of polymer: weight ratio represented by "particulate polymer: water-soluble polymer"

Modified silicone compound: polyether-modified silicone compound

Amount: Amount of polyether-modified silicone compound relative to 100 parts of water-soluble polymer

Surface tension: Surface tension of a 10 wt% aqueous solution of a polyether-modified silicone compound

CMC salt: Carboxymethyl cellulose salt

[Review]

As shown in Tables 1 to 6, precipitation of lithium metal is small in Examples. In this respect, it has been confirmed that the precipitation of lithium metal by charge and discharge can be suppressed by the present invention.

As shown in Tables 1 to 6, in the examples, the contact angle of the binder composition film with the electrolyte is small. In this respect, it has been confirmed that the electrode related to the present invention is excellent in 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, the voltage drop in the low-temperature environment is small in the examples. In this respect, it has been confirmed that the present invention can realize a lithium ion secondary battery having excellent low-temperature output characteristics.

As shown in Tables 1 to 6, in the examples, the capacity retention rate when charging and discharging were repeated in a high temperature environment was high. In this respect, it has been confirmed that the present invention can realize a lithium ion secondary battery having excellent high temperature cycle characteristics.

Claims (11)

A particulate polymer, a water-soluble polymer, a polyether-modified silicone compound and water,
Wherein the water-soluble polymer contains 20 to 70% by weight of an acid group-containing monomer unit,
Wherein the amount of the polyether-modified silicone compound is 0.1 part by weight to 10 parts by weight based on 100 parts by weight of the water-soluble polymer. The method according to claim 1,
Wherein the water-soluble polymer further contains 0.1 to 30% by weight of a fluorine-containing monomer unit. 3. The method according to claim 1 or 2,
Wherein the viscosity of the aqueous polymer is 1% aqueous solution of 1 mPa · s to 1000 mPa · s. 4. The method according to any one of claims 1 to 3,
Wherein the water-soluble polymer further comprises 0.1 wt% to 2 wt% of a crosslinkable monomer unit. 5. The method according to any one of claims 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. 6. The method according to any one of claims 1 to 5,
Wherein the weight ratio of the particulate polymer and the water-soluble polymer is in a range of from 99/1 to 50/50 in the particulate polymer / water-soluble polymer. 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. 8. The method of claim 7,
A slurry composition for a lithium ion secondary battery, further comprising a thickener. The whole house,
An electrode active material layer obtained by applying the slurry composition for a lithium ion secondary battery according to claim 7 or 8 on the current collector and drying the electrode active material layer. A positive electrode, a negative electrode, and an electrolyte,
Wherein at least one of the positive electrode and the negative electrode is an electrode for a lithium ion secondary battery according to claim 9. A step of mixing a particulate polymer, a polyether-modified silicone compound and water,
And then further mixing the water-soluble polymer with the water-soluble polymer. The method for producing a binder composition for a lithium ion secondary battery according to any one of claims 1 to 6,