JP6579250B2 - Secondary battery binder composition, secondary battery electrode slurry composition, secondary battery electrode and secondary battery - Google Patents

Description

  The present invention relates to a binder composition for a secondary battery, a slurry composition for a secondary battery electrode, an electrode for a secondary battery, and a secondary battery.

  Secondary batteries such as lithium ion secondary batteries are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes has been studied for the purpose of further improving the performance of secondary batteries.

  Here, the electrode for secondary batteries, such as a lithium ion secondary battery, is normally provided with the electrical power collector and the electrode compound-material layer formed on the electrical power collector. The electrode mixture layer is formed, for example, by applying a slurry composition obtained by dispersing an electrode active material and a binder composition containing a binder in a dispersion medium on a current collector and drying it. Is done.

  Thus, in recent years, attempts have been made to improve the binder composition used for forming the electrode mixture layer in order to achieve further performance improvement of the secondary battery. Specifically, by devising the composition of the binder composition, the binding property between the components constituting the electrode mixture layer such as the electrode active material and the binding property between the electrode mixture layer and the current collector are improved. Or improving the electrical characteristics (for example, cycle characteristics, low-temperature output characteristics, etc.) of secondary batteries.

  More specifically, for example, in Patent Document 1, a water-soluble resin obtained by polymerizing a monomer group containing a polymerizable monomer of an unsaturated carboxylic acid, (meth) acrylamide, and organic particles. It has been proposed to use an acrylic aqueous dispersion containing a binder composition as a binder composition to improve the adhesion of the electrode plate and improve the cycle characteristics of the secondary battery.

JP 2012-151108 A

  However, from the viewpoint of further improving the performance of the secondary battery, the secondary battery electrode and the secondary battery are required to further improve various performances. Therefore, there is still room for improvement in terms of further improving the performance of the secondary battery electrode and the secondary battery.

Then, an object of this invention is to provide the binder composition for secondary batteries which can further improve the performance of the electrode for secondary batteries, and a secondary battery.
Moreover, an object of this invention is to provide the slurry composition for secondary battery electrodes which can further improve the performance of the electrode for secondary batteries, and a secondary battery.
Furthermore, an object of the present invention is to provide a secondary battery electrode that is excellent in performance such as peel strength and that can further improve the performance of the secondary battery.
And an object of this invention is to provide the secondary battery excellent in performance, such as an electrical property.

  The present inventors have intensively studied for the purpose of solving the above problems. Then, the present inventors added a small amount of a polyether-modified polydimethylsiloxane at a specific ratio to a binder composition containing a particulate polymer as a binder and a slurry composition for an electrode. The inventors have found that the peel strength of an electrode formed using a product and the electrical characteristics of a battery can be made excellent, and the present invention has been completed.

  That is, the present invention aims to advantageously solve the above problems, and the binder composition for a secondary battery of the present invention comprises a particulate polymer, a polyether-modified polydimethylsiloxane, water, The polyether-modified polydimethylsiloxane is contained in an amount of 0.01 to 0.19 parts by mass per 100 parts by mass of the particulate polymer. Thus, if the polyether-modified polydimethylsiloxane is added so that the ratio to the amount of the particulate polymer is within a specific range, a secondary battery electrode and a secondary battery are produced using the binder composition. As a result, a secondary battery electrode having excellent peel strength and a secondary battery having excellent electrical characteristics can be obtained.

  Here, the binder composition for secondary batteries of the present invention may further contain a crosslinking agent having a carbodiimide group. This is because the performance of the secondary battery electrode and the secondary battery can be further improved by further containing the crosslinking agent.

  Another object of the present invention is to advantageously solve the above-mentioned problems. The slurry composition for secondary battery electrodes of the present invention comprises an electrode active material, a particulate polymer, a polyether-modified polymer. It contains dimethylsiloxane and water, and is characterized by containing 0.01 to 0.19 parts by mass of the polyether-modified polydimethylsiloxane per 100 parts by mass of the particulate polymer. In this way, when the polyether-modified polydimethylsiloxane is added so that the ratio to the amount of the particulate polymer is within a specific range, a secondary battery electrode and a secondary battery are produced using the slurry composition. As a result, a secondary battery electrode having excellent peel strength and a secondary battery having excellent electrical characteristics can be obtained.

  Here, the slurry composition for secondary battery electrodes of the present invention may further contain a crosslinking agent having a carbodiimide group. This is because the performance of the secondary battery electrode and the secondary battery can be further improved by further containing the crosslinking agent.

  Moreover, this invention aims at solving the said subject advantageously, The electrode for secondary batteries of this invention is obtained using any of the slurry composition for secondary battery electrodes mentioned above. It has an electrode compound material layer. Thus, if an electrode compound-material layer is formed using the slurry composition for secondary battery electrodes mentioned above, the peel strength of an electrode can be made excellent. Moreover, if the electrode for secondary batteries provided with the said electrode compound material layer is used, the secondary battery which has the outstanding electrical property will be obtained.

  Furthermore, this invention aims at solving the said subject advantageously, The secondary battery of this invention is equipped with a positive electrode, a negative electrode, a separator, and electrolyte solution, and at least one of the said positive electrode and the said negative electrode is The electrode for a secondary battery described above. Thus, if at least one of a positive electrode and a negative electrode is comprised by the electrode for secondary batteries mentioned above, the secondary battery which has the outstanding electrical property will be obtained.

ADVANTAGE OF THE INVENTION According to this invention, the binder composition for secondary batteries which can further improve the performance of the electrode for secondary batteries and a secondary battery is obtained.
Moreover, according to this invention, the slurry composition for secondary battery electrodes which can further improve the performance of the electrode for secondary batteries and a secondary battery is obtained.
Furthermore, according to this invention, the electrode for secondary batteries which is excellent in performance, such as peel strength, and can further improve the performance of a secondary battery is obtained.
And according to this invention, the secondary battery excellent in performance, such as an electrical property, is obtained.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for secondary batteries of this invention can be used when preparing the slurry composition for secondary battery electrodes. And the slurry composition for secondary battery electrodes of this invention can be used when forming the electrode of a secondary battery. Furthermore, the secondary battery of the present invention is characterized by using the secondary battery electrode of the present invention. In addition, the binder composition for secondary batteries of this invention can be used also when preparing the slurry composition for porous films.

(Binder composition for secondary battery)
The binder composition for a secondary battery of the present invention is an aqueous binder composition using an aqueous medium as a dispersion medium, and includes a particulate polymer, a polyether-modified polydimethylsiloxane, and water. And the binder composition for secondary batteries of this invention is characterized by including 0.01 mass part or more and 0.19 mass part or less of polyether modified polydimethylsiloxane per 100 mass parts of particulate polymers.

<Particulate polymer>
The particulate polymer was prepared by forming an electrode mixture layer on a current collector using a slurry composition for a secondary battery electrode containing the binder composition for a secondary battery of the present invention and an electrode active material. In the secondary battery electrode, the component contained in the electrode mixture layer is a component that can be held so as not to be detached from the electrode mixture layer. Generally, when the particulate polymer in the electrode mixture layer is immersed in the electrolyte solution, the particulate polymer maintains the particulate shape while absorbing and swelling the electrolyte solution. And the current collector to prevent the electrode active material from falling off the current collector. The particulate polymer also binds particles other than the electrode active material contained in the electrode mixture layer, and also plays a role of maintaining the strength of the electrode mixture layer.

Here, as the particulate polymer, any polymer can be used as long as it has the above-described properties and exists in a particulate state in an aqueous medium as a dispersion medium. The particulate polymer is not particularly limited, and an acrylic polymer and a conjugated diene polymer can be suitably used.
The particulate polymer is obtained, for example, by polymerizing a monomer composition containing a monomer, an additive such as a polymerization initiator, and a polymerization solvent. In general, the particulate polymer has a structural unit derived from the monomer contained in the monomer composition at a ratio similar to the abundance ratio of each monomer in the monomer composition. Contains.

[Acrylic polymer]
Here, an acrylic polymer preferable as the particulate polymer will be described. An acrylic polymer is a polymer containing a structural unit derived from a (meth) acrylic acid ester monomer. The acrylic polymer is a monomer composition containing a (meth) acrylic acid ester monomer and, optionally, a carboxyl group-containing monomer, an α, β-unsaturated nitrile monomer, and other monomers. It is obtained by polymerizing the product.
In the present specification, (meth) acryl means acryl and / or methacryl.
Hereinafter, the (meth) acrylic acid ester monomer, the carboxyl group-containing monomer, the α, β-unsaturated nitrile monomer, and other monomers used for the preparation of the acrylic polymer will be described in detail.

-(Meth) acrylate monomer-
Examples of the (meth) acrylic acid ester monomer used for preparing the acrylic polymer include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, Acrylic acid alkyl esters such as heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, Alkyl methacrylates such as octyl methacrylate and 2-ethylhexyl methacrylate Ester and the like. These may be used alone or in combination of two or more. Among these, n-butyl acrylate and / or t-butyl acrylate are preferable.
The monomer contained in the monomer composition used for the preparation of the acrylic polymer preferably has a ratio of the above-mentioned (meth) acrylic acid ester monomer of 80% by mass or more, and 90% by mass. % Or more, more preferably 99.5% by mass or less, and even more preferably 98% by mass or less.

-Carboxyl group-containing monomer-
As carboxyl group-containing monomers used for the preparation of acrylic polymers, carboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid (2-ethylacrylic acid), itaconic acid, maleic acid, fumaric acid, citraconic acid, etc. Ethylenic unsaturation such as butenedioic acid monoalkyl ester monomers such as monomethyl maleate, monoethyl maleate, mono-n-butyl maleate, monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate; A carboxylic acid compound is mentioned. These may be used alone or in combination of two or more. Among these, methacrylic acid, acrylic acid, maleic acid, fumaric acid, or itaconic acid are preferable, and methacrylic acid is particularly preferable.
The monomer contained in the monomer composition used for the preparation of the acrylic polymer preferably has a ratio of the above-mentioned carboxyl group-containing monomer of 0.5% by mass or more, preferably 10% by mass. Or less, more preferably 5.0% by mass or less.

-Α, β-unsaturated nitrile monomer-
Examples of the α, β-unsaturated nitrile monomer used for preparing the acrylic polymer include acrylonitrile and methacrylonitrile. These may be used alone or in combination of two or more. Among these, acrylonitrile is preferable.
The monomer contained in the monomer composition used for the preparation of the acrylic polymer preferably has a ratio of the above-mentioned α, β-unsaturated nitrile monomer of 0.5% by mass or more. It is preferable that it is 10 mass% or less, and it is more preferable that it is 5.0 mass% or less.

-Other monomers-
Examples of other monomers include monomers copolymerizable with the above-described monomers. Specifically, as an optional monomer, a hydroxyl group-containing monomer such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate is used. Monomers; sulfate group-containing monomers such as acrylamide-2-methylpropanesulfonic acid; amide group-containing monomers such as acrylamide and methacrylamide; allyl glycidyl ether, allyl (meth) acrylate, N-methylol acrylamide, etc. Crosslinkable monomer (crosslinkable monomer): Styrene such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, α-methylstyrene, divinylbenzene Monomers; ethylene, propylene, etc. Fins; diene monomers such as butadiene and isoprene; halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; methyl vinyl ether; Vinyl ethers such as 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; Heterocycles such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole -Containing vinyl compounds; amino group-containing monomers such as aminoethyl vinyl ether and dimethylaminoethyl vinyl ether; These may be used alone or in combination of two or more.
And it is preferable that the ratio which the other monomer mentioned above occupies for the monomer which the monomer composition used for preparation of an acrylic polymer occupies is 0.5 mass% or more and 5 mass% or less.

  The method for producing the acrylic polymer is not particularly limited, and the monomer composition containing the above-described monomer can be obtained by a method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, or an emulsion polymerization method. Obtained by polymerization. As the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used. In addition, the additive and polymerization solvent contained in the monomer composition used for the preparation of the acrylic polymer are not particularly limited, and known ones can be used.

[Conjugated diene polymer]
Next, a preferred conjugated diene polymer as the particulate polymer will be described. The conjugated diene polymer is a polymer containing a structural unit derived from a conjugated diene monomer, and includes hydrogenated products thereof.
Specific examples of conjugated diene polymers include aliphatic conjugated diene polymers such as polybutadiene and polyisoprene; aromatic vinyl / aliphatic conjugated diene copolymers such as styrene-butadiene polymers (SBR); acrylonitrile-butadiene. Examples thereof include vinyl cyanide-conjugated diene copolymers such as a base polymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like. Among these, from the viewpoint of improving the adhesion between the electrode mixture layer formed using the binder composition of the present invention and the current collector, an aromatic vinyl / fatty material such as a styrene-butadiene polymer (SBR). A group conjugated diene copolymer is preferred. And, for example, an aromatic vinyl / aliphatic conjugated diene copolymer includes an aromatic vinyl monomer, an aliphatic conjugated diene monomer, and optionally a carboxyl group-containing monomer, a hydroxyl group-containing monomer, other It is obtained by polymerizing a monomer composition containing a monomer.
Hereinafter, aromatic vinyl monomer, aliphatic conjugated diene monomer, carboxyl group-containing monomer, hydroxyl group-containing monomer, and other used for the preparation of aromatic vinyl / aliphatic conjugated diene copolymer A monomer is explained in full detail.

-Aromatic vinyl monomer-
Examples of the aromatic vinyl monomer used for the preparation of the aromatic vinyl / aliphatic conjugated diene copolymer include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These may be used alone or in combination of two or more. Among these, styrene is preferable.
And the monomer which the monomer composition used for preparation of an aromatic vinyl-aliphatic conjugated diene copolymer contains 40% by mass or more of the above-mentioned ratio of the aromatic vinyl monomer. Preferably, it is 50 mass% or more, more preferably 80 mass% or less, and even more preferably 70 mass% or less.

-Aliphatic conjugated diene monomer-
Examples of the aliphatic conjugated diene monomer used for the preparation of the aromatic vinyl / aliphatic conjugated diene copolymer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1, Examples include 3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like. These may be used alone or in combination of two or more. Among these, 1,3-butadiene is preferable.
And the monomer which the monomer composition used for preparation of an aromatic vinyl-aliphatic conjugated diene copolymer contains 10% by mass or more of the above-mentioned aliphatic conjugated diene monomer. Is preferably 25% by mass or more, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

-Carboxyl group-containing monomer-
As the carboxyl group-containing monomer used for the preparation of the aromatic vinyl / aliphatic conjugated diene copolymer, the above-described ethylenically unsaturated carboxylic acid compound can be used in the same manner as the acrylic polymer. These may be used alone or in combination of two or more. Of these, itaconic acid is preferred.
The monomer composition used in the preparation of the aromatic vinyl / aliphatic conjugated diene copolymer has a ratio of the above-mentioned carboxyl group-containing monomer of 0.5% by mass or more. It is preferably 10% by mass or less, and more preferably 3.0% by mass or less.

-Hydroxyl group-containing monomer-
The hydroxyl group-containing monomers used for the preparation of the aromatic vinyl / aliphatic conjugated diene copolymer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxy Butyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2-hydroxyethyl methyl For example, fumarate. These may be used alone or in combination of two or more. Among these, 2-hydroxyethyl acrylate is preferable.
And the monomer which the monomer composition used for the preparation of the aromatic vinyl / aliphatic conjugated diene copolymer contains 0.1% by mass or more of the above-mentioned hydroxyl group-containing monomer. It is preferably 0.5% by mass or more, more preferably 10% by mass or less, and even more preferably 5.0% by mass or less.

-Other monomers-
Examples of other monomers include monomers copolymerizable with the above-described monomers. Specifically, as the other monomer, those listed as usable as the other monomer in the above-mentioned acrylic polymer, aromatic vinyl monomer, aliphatic conjugated diene monomer Body, those excluding those corresponding to hydroxyl group-containing monomers, and α, β-unsaturated nitrile monomers can be used. These other monomers may be used alone or in combination of two or more.
And the monomer which the monomer composition used for the preparation of the aromatic vinyl / aliphatic conjugated diene copolymer contains 0.5% by mass or more and 5% by mass of the other monomer described above. The following is preferable.

  The method for producing a conjugated diene polymer such as an aromatic vinyl / aliphatic conjugated diene copolymer is not particularly limited, and a monomer composition containing the above-described monomer is, for example, a solution polymerization method or a suspension. It is obtained by polymerizing by a polymerization method, a bulk polymerization method, an emulsion polymerization method or the like. As the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used. In addition, the additive and polymerization solvent contained in the monomer composition used for the preparation of the conjugated diene polymer are not particularly limited, and known ones can be used.

上記（１）式中、Ｒ^１は水素原子、アルキル基、カルボキシル基、ヒドロキシル基、またはエーテル基を示し、Ｒ^２は任意のポリエーテル基を示し、ｘおよびｙはそれぞれ任意の正の整数を示す。 <Polyether-modified polydimethylsiloxane>
The binder composition for a secondary battery of the present invention is obtained by adding a small amount of polyether-modified polydimethylsiloxane to a binder composition containing a particulate polymer, and using the binder composition, This is based on the new knowledge that, when a secondary battery is produced, a secondary battery electrode having excellent peel strength and a secondary battery having excellent electrical characteristics can be obtained.
Here, the polyether-modified polydimethylsiloxane is a kind of silicon compound and is a compound represented by the following general formula (1).

In the formula (1), R ¹ represents a hydrogen atom, an alkyl group, a carboxyl group, a hydroxyl group, or an ether group, R ² represents an arbitrary polyether group, and x and y each represents an arbitrary positive integer. Show.

The viscosity of the polyether-modified polydimethylsiloxane is preferably 0.1 mPa · s or more, more preferably 1 mPa · s or more, and preferably 10 mPa · s or less, preferably 5 mPa · s or less. More preferably, it is 2.5 mPa · s or less. This is because if the viscosity of the polyether-modified polydimethylsiloxane is within the above range, the peel strength and electrical characteristics can be further improved. Here, in this specification, “viscosity of polyether-modified polydimethylsiloxane” refers to the viscosity of a polyether-modified polydimethylsiloxane aqueous solution having a concentration of 2.0% by mass.
Further, the surface tension of the polyether-modified polydimethylsiloxane is preferably 10 mN / m or more, more preferably 15 mN / m or more, further preferably 20 mN / m or more, and 40 mN / m or less. Preferably, it is 30 mN / m or less, and more preferably 24 mN / m or less. This is because if the surface tension of the polyether-modified polydimethylsiloxane is within the above range, the peel strength and electrical characteristics can be further improved. Here, in this specification, “surface tension of polyether-modified polydimethylsiloxane” refers to surface tension of a polyether-modified polydimethylsiloxane aqueous solution having a concentration of 10.0% by mass.

  Here, specific examples of the polyether-modified polydimethylsiloxane as described above are not particularly limited, and examples include BYK-1770, BYK-1785, BYK-1610 (all manufactured by Big Chemie Japan Co., Ltd.) and the like. It is done.

  And in the binder composition of this invention, the compounding quantity of polyether modified polydimethylsiloxane needs to be 0.01 mass part or more per 100 mass parts of particulate polymers, and is 0.02 mass part or more. Preferably 0.03 parts by mass or more, more preferably 0.19 parts by mass or less, and preferably 0.1 parts by mass or less, and 0.08 parts by mass. It is more preferable that the amount is not more than part by mass. Unless the blending amount of the polyether-modified polydimethylsiloxane per 100 parts by mass of the particulate polymer is 0.19 parts by mass or less, the peel strength of the electrode and the electrical characteristics of the secondary battery cannot be improved. On the other hand, unless the blending amount of the polyether-modified polydimethylsiloxane per 100 parts by mass of the particulate polymer is 0.01 parts by mass or more, the effect of adding the polyether-modified polydimethylsiloxane cannot be sufficiently obtained.

<Crosslinking agent having carbodiimide group>
Here, the binder composition for secondary batteries of the present invention may further contain a crosslinking agent having a carbodiimide group. In particular, when a crosslinking agent having a carbodiimide group was added to a binder composition using a conjugated diene polymer as a particulate polymer, an electrode for a secondary battery and a secondary battery were produced using the binder composition. In this case, a secondary battery electrode having excellent peel strength and electrode drainage and a secondary battery having excellent electrical characteristics can be obtained.

  In addition, it is guessed that the crosslinking agent which has a carbodiimide group forms a crosslinked structure with the above-mentioned particulate polymer by heating. Specifically, it is speculated that the crosslinking agent having a carbodiimide group reacts with a functional group such as a carboxyl group or a hydroxyl group contained in the particulate polymer to form a crosslinked structure. The formation of this crosslinked structure is expected to improve the peel strength and electrode drainage of the electrode and the electrical characteristics of the secondary battery in the binder composition using the conjugated diene polymer as the particulate polymer. The

Here, as a crosslinking agent having a carbodiimide group, the molecule has a carbodiimide group represented by the general formula (2): -N = C = N -... (2), and between the particulate polymers. It is not particularly limited as long as it is a crosslinkable compound capable of forming a crosslinked structure. And as such a crosslinking agent having a carbodiimide group, for example, a compound having two or more carbodiimide groups, specifically, general formula (3): -N = C = N-R ³ (3) (In general formula (3), R ³ represents a divalent organic group.) Preferred examples include polycarbodiimide and / or modified polycarbodiimide having a repeating unit represented by formula (3). In addition, in this specification, a modified polycarbodiimide means resin obtained by making the reactive compound mentioned later react with polycarbodiimide.

The method for synthesizing the polycarbodiimide is not particularly limited. For example, the organic polyisocyanate is reacted in the presence of a catalyst for promoting the carbodiimidization reaction of the isocyanate group (hereinafter referred to as “carbodiimidization catalyst”). Thus, polycarbodiimide can be synthesized. Moreover, the polycarbodiimide which has a repeating unit represented by General formula (3) copolymerizes the oligomer (carbodiimide oligomer) obtained by making organic polyisocyanate react, and the monomer copolymerizable with the said oligomer. Can also be synthesized.
In addition, the modified polycarbodiimide is appropriately added with at least one reactive compound in at least one polycarbodiimide having a repeating unit represented by the general formula (3) in the presence or absence of an appropriate catalyst. It can be synthesized by reacting at a temperature (hereinafter referred to as “denaturation reaction”). In addition, as a reactive compound, the thing as described in Unexamined-Japanese-Patent No. 2005-49370 is mentioned, for example. Of these, trimellitic anhydride and nicotinic acid are preferable.

And it is preferable that the crosslinking agent which has a carbodiimide group as mentioned above is water-soluble. When the binder composition contains a water-soluble polymer as described later, the crosslinking agent having a carbodiimide group is between the water-soluble polymers and / or between the water-soluble polymer and the particulate polymer. A cross-linked structure can also be formed therebetween.
Specific examples of the crosslinking agent having such a carbodiimide group include, but are not limited to, SV-02 (manufactured by Nisshinbo Chemical Co., Ltd.) and the like.

  In the binder composition of the present invention, the amount of the crosslinking agent having a carbodiimide group is preferably 0.001 part by mass or more and 0.5 part by mass or more per 100 parts by mass of the particulate polymer. More preferably, it is more preferably 3 parts by mass or more, preferably 100 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 7 parts by mass or less. If the compounding quantity of the crosslinking agent which has a carbodiimide group is in the said range, a crosslinked structure can be formed with a moderate density and the performance of an electrode and a secondary battery can fully be improved.

<Water-soluble polymer>
Here, it is preferable that the binder composition for secondary batteries of this invention further contains a water-soluble polymer. And as a water-soluble polymer, it is preferable to use the compound which has at least one of a hydroxyl group and a carboxyl group in the molecular structure, and can be used as a water-soluble polymer. A slurry composition prepared using a binder composition containing a water-soluble polymer is excellent in storage stability and has good workability when applied on a current collector or the like.
Here, in the present invention, the polymer is “water-soluble” means that a mixture obtained by adding 1 part by mass of water-soluble polymer (corresponding to solid content) per 100 parts by mass of ion-exchanged water and stirring is set to a temperature of 20 ° C. Adjust to at least one of the conditions in the range of 70 ° C. or less and pH 3 or more and 12 or less (NaOH aqueous solution and / or HCl aqueous solution is used for pH adjustment). It means that the solid content of the residue remaining on the screen without passing through the screen does not exceed 50% by mass with respect to the solid content of the added polymer. In addition, even if the mixture of the polymer and water is in an emulsion state that separates into two phases when left standing, the polymer is water-soluble if the above definition is satisfied.

  Although it does not specifically limit as a water-soluble polymer, For example, carboxymethylcellulose, methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, polyvinyl alcohol, polycarboxylic acid, these salts etc. can be used. Examples of the polycarboxylic acid include polyacrylic acid, polymethacrylic acid, and alginic acid. One of these water-soluble polymers may be used alone, or two or more thereof may be used in combination at any ratio. Among these, from the viewpoint of further improving the workability when the slurry composition containing the binder composition is applied onto a current collector, the water-soluble polymer includes carboxymethyl cellulose, polyacrylic acid, or These salts are preferable, and carboxymethyl cellulose or a salt thereof (hereinafter sometimes abbreviated as “carboxymethyl cellulose (salt)”) is more preferable. By using carboxymethylcellulose (salt) as the water-soluble polymer, an electrode excellent in peel strength and electrode drainage can be obtained, and a secondary battery excellent in cycle characteristics can be obtained.

  In the slurry composition prepared using the binder composition of the present invention, the amount of the water-soluble polymer is preferably 0.1 parts by mass or more per 100 parts by mass of the electrode active material, and 0.2 parts by mass. More preferably, it is more preferably 0.5 parts by mass or more, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and 5 parts by mass or less. Further preferred. By making the blending amount of the water-soluble polymer within the above range, the viscosity at the time of the high step of the slurry composition is set to an appropriate size, and workability when the slurry composition is applied on a current collector or the like. Can be good.

<Other ingredients>
In addition to the above components, the binder composition of the present invention may contain components such as a conductive additive, a reinforcing material, a leveling agent, a viscosity modifier, and an electrolytic solution additive. These are not particularly limited as long as they do not affect the battery reaction, and known ones such as those described in International Publication No. 2012/115096 can be used. Moreover, these components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

<Preparation of secondary battery binder composition>
The binder composition of the present invention can be prepared by dispersing each of the above components in an aqueous medium as a dispersion medium. Specifically, the binder composition is prepared by mixing each of the above components and an aqueous medium using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, ultrasonic disperser, homogenizer, planetary mixer, or fill mix. Product can be prepared.
When the particulate polymer is prepared by polymerizing the monomer composition in an aqueous solvent, it can be mixed as it is in the state of an aqueous dispersion. Moreover, when mixing a particulate polymer in the state of an aqueous dispersion, you may use the water in an aqueous dispersion as said aqueous medium.

(Slurry composition for secondary battery electrode)
The slurry composition for secondary battery electrodes of the present invention includes an electrode active material, a particulate polymer, a polyether-modified polydimethylsiloxane, and water. And the slurry composition for secondary battery electrodes of this invention contains 0.01 mass part or more and 0.19 mass part or less of polyether modified polydimethylsiloxane per 100 mass parts of particulate polymers. .
Here, the particulate polymer, polyether-modified polydimethylsiloxane, and water contained in the slurry composition for secondary battery electrodes of the present invention are those contained in the above-described binder composition for secondary batteries of the present invention. The preferred abundance ratio of each component is the same as the preferred abundance ratio of each component in the binder composition. Therefore, the slurry composition for secondary battery electrodes of the present invention can be prepared using the binder composition for secondary batteries of the present invention.
And since the slurry composition for secondary battery electrodes of this invention uses the same component as the binder composition of this invention in the same compounding ratio, if an electrode compound-material layer is formed using this slurry composition, The peel strength of the electrode can be made excellent as described for the binder composition for secondary batteries. Moreover, if the electrode for secondary batteries provided with the said electrode compound-material layer is used, the secondary battery which has the outstanding electrical property will be obtained.

<Electrode active material>
The electrode active material is a substance that transfers electrons in the electrodes (positive electrode and negative electrode) of the secondary battery. Hereinafter, an electrode active material (positive electrode active material, negative electrode active material) used in an electrode of a lithium ion secondary battery will be described as an example.

[Positive electrode active material]
The positive electrode active material to be blended in the slurry composition of the present invention is not particularly limited, and a known positive electrode active material can be used.
Specifically, as the positive electrode active material, a compound containing a transition metal, for example, a transition metal oxide, a transition metal sulfide, a composite metal oxide of lithium and a transition metal, or the like can be used. In addition, as a transition metal, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo etc. are mentioned, for example.

Here, as the transition metal oxide, for example, MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , amorphous Examples include MoO ₃ , amorphous V ₂ O ₅ , and amorphous V ₆ O ₁₃ .
Examples of the transition metal sulfide include TiS ₂ , TiS ₃ , amorphous MoS ₂ , and FeS.
Examples of the composite metal oxide of lithium and transition metal include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure. It is done.

Examples of the lithium-containing composite metal oxide having a layered structure include lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), and Co—Ni—Mn lithium-containing composite oxide (Li (Co Mn Ni) O ₂ ), Ni—Mn—Al lithium-containing composite oxide, Ni—Co—Al lithium-containing composite oxide, solid solution of LiMaO ₂ and Li ₂ MbO _3, and the like. Note that the lithium-containing composite oxide of Co—Ni—Mn includes Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ , Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ etc. are mentioned. Examples of the solid solution of LiMaO ₂ and Li ₂ MbO ₃ include xLiMaO _2. (1-x) Li ₂ MbO ₃ . Here, x represents a number satisfying 0 <x <1, Ma represents one or more transition metals having an average oxidation state of 3+, and Mb represents one or more transition metals having an average oxidation state of 4+. To express. Examples of such a solid solution include Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ .
In this specification, the “average oxidation state” indicates an average oxidation state of the “one or more transition metals”, and is calculated from the molar amount and valence of the transition metal. For example, when “one or more transition metals” is composed of 50 mol% Ni ²⁺ and 50 mol% Mn ⁴⁺ , the average oxidation state of “one or more transition metals” is (0.5) X (2 +) + (0.5) * (4 +) = 3+.

Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganate (LiMn ₂ O ₄ ) and compounds in which a part of Mn of lithium manganate (LiMn ₂ O ₄ ) is substituted with another transition metal. Is mentioned. Specific examples _{include Li s [Mn 2 -tMc t]} O 4 , such as LiNi _{0.5 Mn} 1.5 _{O 4.} Here, Mc represents one or more transition metals having an average oxidation state of 4+. Specific examples of Mc include Ni, Co, Fe, Cu, and Cr. T represents a number satisfying 0 <t <1, and s represents a number satisfying 0 ≦ s ≦ 1. Note that as the positive electrode active material, a lithium-excess spinel compound represented by Li _{1 + x} Mn _2−x O ₄ (0 <X <2) can also be used.

Examples of the lithium-containing composite metal oxide having an olivine structure include olivine-type phosphorus represented by Li _y MdPO ₄ such as olivine-type lithium iron phosphate (LiFePO ₄ ) and olivine-type lithium manganese phosphate (LiMnPO ₄ ). An acid lithium compound is mentioned. Here, Md represents one or more transition metals having an average oxidation state of 3+, and examples thereof include Mn, Fe, and Co. Y represents a number satisfying 0 ≦ y ≦ 2. Furthermore, in the olivine-type lithium phosphate compound represented by Li _y MdPO ₄ , Md may be partially substituted with another metal. Examples of the metal that can be substituted include Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B, and Mo.

[Negative electrode active material]
In addition, examples of the negative electrode active material include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material obtained by combining these.

  Here, the carbon-based negative electrode active material refers to an active material having carbon as a main skeleton capable of inserting lithium (also referred to as “dope”). Examples of the carbon-based negative electrode active material include carbonaceous materials and graphite. Quality materials.

The carbonaceous material is a material having a low degree of graphitization (ie, low crystallinity) obtained by carbonizing a carbon precursor by heat treatment at 2000 ° C. or lower. In addition, although the minimum of the heat processing temperature at the time of carbonizing is not specifically limited, For example, it can be 500 degreeC or more.
Examples of the carbonaceous material include graphitizable carbon that easily changes the carbon structure depending on the heat treatment temperature, and non-graphitizable carbon having a structure close to an amorphous structure typified by glassy carbon. .
Here, as the graphitizable carbon, for example, a carbon material using tar pitch obtained from petroleum or coal as a raw material can be mentioned. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, pyrolytic vapor grown carbon fibers, and the like.
In addition, examples of the non-graphitizable carbon include a phenol resin fired body, polyacrylonitrile-based carbon fiber, pseudo-isotropic carbon, furfuryl alcohol resin fired body (PFA), and hard carbon.

The graphite material is a material having high crystallinity close to that of graphite obtained by heat-treating graphitizable carbon at 2000 ° C. or higher. In addition, although the upper limit of heat processing temperature is not specifically limited, For example, it can be 5000 degrees C or less.
Examples of the graphite material include natural graphite and artificial graphite.
Here, as the artificial graphite, for example, artificial graphite obtained by heat-treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB heat-treated at 2000 ° C. or higher, and mesophase pitch-based carbon fiber at 2000 ° C. Examples thereof include graphitized mesophase pitch-based carbon fibers that have been heat-treated.

  Further, the metal-based negative electrode active material is an active material containing a metal, and usually includes an element capable of inserting lithium in the structure, and the theoretical electric capacity per unit mass when lithium is inserted is 500 mAh / The active material which is more than g. Examples of the metal active material include lithium metal and a single metal capable of forming a lithium alloy (for example, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn). , Sr, Zn, Ti, etc.) and alloys thereof, and oxides, sulfides, nitrides, silicides, carbides, phosphides, and the like thereof. Among these, as the metal-based negative electrode active material, an active material containing silicon (silicon-based negative electrode active material) is preferable. This is because the capacity of the lithium ion secondary battery can be increased by using the silicon-based negative electrode active material.

Examples of the silicon-based negative electrode active material include silicon (Si), an alloy containing silicon, SiO, SiO _x , and a composite of a Si-containing material and a conductive carbon obtained by coating or combining a Si-containing material with a conductive carbon. Etc. In addition, these silicon type negative electrode active materials may be used individually by 1 type, and may be used in combination of 2 types.

  Examples of the alloy containing silicon include an alloy composition containing silicon, aluminum, and a transition metal such as iron, and further containing a rare earth element such as tin and yttrium.

SiO _x is a compound containing at least one of SiO and SiO ₂ and Si, and x is usually 0.01 or more and less than 2. Then, SiO _x, for example, can be formed by using a disproportionation reaction of silicon monoxide (SiO). Specifically, SiO _x is a SiO, heat treated in the presence of a polymer, such as any polyvinyl alcohol, by forming a silicon and silicon dioxide can be prepared. The heat treatment can be performed at a temperature of 900 ° C. or higher, preferably 1000 ° C. or higher, in an atmosphere containing an organic gas and / or steam after grinding and mixing SiO and optionally a polymer.

  As a composite of Si-containing material and conductive carbon, for example, a pulverized mixture of SiO, a polymer such as polyvinyl alcohol, and optionally a carbon material is heat-treated in an atmosphere containing, for example, an organic gas and / or steam. Can be mentioned. In addition, a method of coating the surface of the SiO particles by a chemical vapor deposition method using an organic gas, a method of forming composite particles (granulation) of the SiO particles and graphite or artificial graphite by a mechanochemical method, etc. It can also be obtained by a known method.

<Particulate polymer>
As a particulate polymer mix | blended with the slurry composition for secondary battery electrodes of this invention, the thing similar to the particulate polymer mix | blended with the binder composition for secondary batteries of this invention can be used.

  And in the slurry composition of this invention, it is preferable that the compounding quantity of a particulate polymer is 0.1 mass part or more per 100 mass parts of electrode active materials, and it is more preferable that it is 0.2 mass part or more. Preferably, it is 0.5 parts by mass or more, more preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and further preferably 2.5 parts by mass or less. By setting the blending amount of the particulate polymer to 0.1 parts by mass or more per 100 parts by mass of the electrode active material, the components constituting the electrode mixture layer and the electrode mixture layer and the current collector are bound well. It is because it can be made. In addition, by setting the blending amount of the particulate polymer to 10 parts by mass or less per 100 parts by mass of the electrode active material, ions of the ionic particles are obtained by the particulate polymer in the secondary battery electrode produced using the slurry composition of the present invention. This is because the movement is inhibited and the internal resistance of the secondary battery can be reduced.

<Polyether-modified polydimethylsiloxane>
As the polyether-modified polydimethylsiloxane blended in the slurry composition for secondary battery electrodes of the present invention, the same polyether-modified polydimethylsiloxane blended in the binder composition for secondary batteries of the present invention should be used. Can do.

  Also in the slurry composition of the present invention, the blending amount of the polyether-modified polydimethylsiloxane is 0.01 parts by mass or more per 100 parts by mass of the particulate polymer for the same reason as in the binder composition of the present invention. .19 parts by mass or less, preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, and preferably 0.1 parts by mass or less, More preferably, it is 0.08 parts by mass or less.

<Crosslinking agent having carbodiimide group>
Here, it is preferable that the slurry composition for secondary battery electrodes of the present invention further includes a crosslinking agent having a carbodiimide group. In particular, when a crosslinking agent having a carbodiimide group was added to a slurry composition using a conjugated diene polymer as a particulate polymer, an electrode for a secondary battery and a secondary battery were produced using the slurry composition. In this case, a secondary battery electrode having excellent peel strength and electrode drainage and a secondary battery having excellent electrical characteristics can be obtained.

  Here, the crosslinking agent having a carbodiimide group to be blended in the slurry composition for secondary battery electrodes of the present invention is the same as the crosslinking agent having a carbodiimide group that can be blended in the binder composition for secondary batteries of the present invention. Can be used.

  And also in the slurry composition of this invention, the compounding quantity of polyether modified polydimethylsiloxane is 0.001 mass part or more per 100 mass parts of particulate polymers for the same reason as the binder composition of this invention. Preferably, it is 0.5 parts by mass or more, more preferably 3 parts by mass or more, preferably 100 parts by mass or less, more preferably 10 parts by mass or less, More preferably, it is 7 parts by mass or less.

<Water-soluble polymer>
Moreover, it is preferable that the slurry composition for secondary battery electrodes of this invention further contains a water-soluble polymer.

  Here, as the water-soluble polymer blended in the slurry composition for secondary battery electrodes of the present invention, the same water-soluble polymer that can be blended in the binder composition for secondary batteries of the present invention is used. it can.

  The slurry composition of the present invention is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, particularly preferably 0.5 parts by mass of the water-soluble polymer per 100 parts by mass of the electrode active material. It contains above, Preferably it is 20 mass parts or less, More preferably, it is 10 mass parts or less, Most preferably, it contains 5 mass parts or less. By making the blending amount of the water-soluble polymer within the above range, the viscosity at the time of the high step of the slurry composition is set to an appropriate size, and workability when the slurry composition is applied on a current collector or the like. Can be good.

<Other ingredients>
Moreover, the slurry composition of this invention may contain components, such as a conductive support agent, a reinforcing material, a leveling agent, a viscosity modifier, an electrolyte solution additive, other than the said component. These are not particularly limited as long as they do not affect the battery reaction, and known ones such as those described in International Publication No. 2012/115096 can be used. Moreover, these components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

<Preparation of slurry composition for secondary battery electrode>
The slurry composition of the present invention may be prepared by dispersing each of the above components in an aqueous medium as a dispersion medium, or the binder composition of the present invention is prepared in advance in the presence of an aqueous medium. The binder composition, the electrode active material, and optionally, a crosslinking agent having a carbodiimide group, a water-soluble polymer, and other components may be mixed. In addition, the crosslinking agent which has a carbodiimide group, a water-soluble polymer, and another component can also be previously contained in a binder composition. It is easy to mix the crosslinking agent having a carbodiimide group at the time of preparing a binder composition having a relatively low viscosity, and the water-soluble polymer and other components at the preparation stage of a slurry composition having a relatively high viscosity. From the viewpoint of

  Here, the mixing can be performed using a mixer such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and a fill mix. And mixing can be normally performed in the range of room temperature to 80 degreeC for 10 minutes-several hours.

  As the aqueous medium, water is usually used, but an aqueous solution of an arbitrary compound or a mixed solution of a small amount of an organic medium and water may be used. In addition, when preparing a binder composition beforehand, the water which the binder composition contained in the water used as an aqueous medium may also be included.

(Electrode for secondary battery)
The slurry composition for secondary battery electrodes (slurry composition for negative electrode and slurry composition for positive electrode) of the present invention can be used for producing secondary battery electrodes (negative electrode and positive electrode).
Here, the electrode for a secondary battery of the present invention includes a current collector and an electrode mixture layer formed on the current collector, and the electrode mixture layer includes at least an electrode active material, as described above. A particulate polymer, polyether-modified polydimethylsiloxane, and water are included. In addition, each component contained in the electrode mixture layer is contained in the slurry composition for secondary battery electrodes, and a suitable abundance ratio of each component is in the slurry composition. It is the same as the preferred abundance ratio of each component.
And since the electrode for secondary batteries of this invention uses the slurry composition for secondary battery electrodes of this invention, it can make the peel strength of an electrode excellent. Moreover, if the electrode for secondary batteries of this invention is used, the secondary battery which has the outstanding electrical property will be obtained.

<Method for producing electrode for secondary battery>
The secondary battery electrode of the present invention includes, for example, a step of applying the above-described slurry composition for a secondary battery electrode on a current collector (application step), and a secondary battery applied on the current collector. The electrode slurry composition is dried to produce an electrode mixture layer on the current collector (drying step).

[Coating process]
A method for applying the slurry composition for a secondary battery electrode on the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used. At this time, the slurry composition may be applied to only one side of the current collector or may be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the electrode mixture layer obtained by drying.

  Here, as the current collector to which the slurry composition is applied, an electrically conductive and electrochemically durable material is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used. Especially, as a collector used for a negative electrode, copper foil is especially preferable. The current collector used for the positive electrode is particularly preferably an aluminum foil. In addition, the said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[Drying process]
A method for drying the slurry composition on the current collector is not particularly limited, and a known method can be used. For example, drying with warm air, hot air, low-humidity air, vacuum drying, irradiation with infrared rays, electron beams, or the like. A drying method is mentioned. Thus, by drying the slurry composition for electrodes on the current collector, an electrode mixture layer is formed on the current collector, and the electrode for a lithium ion secondary battery comprising the current collector and the electrode mixture layer Can be obtained.

Note that after the drying step, the electrode mixture layer may be subjected to pressure treatment using a die press or a roll press. The adhesion between the electrode mixture layer and the current collector can be improved by the pressure treatment.
Furthermore, when the electrode mixture layer includes a curable polymer, it is preferable to cure the polymer after the electrode mixture layer is formed.

(Secondary battery)
The secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolytic solution, and uses the secondary battery electrode of the present invention as at least one of the positive electrode and the negative electrode. And since the secondary battery of this invention is equipped with the electrode for secondary batteries of this invention, it has the outstanding electrical property.
In the following, a case where the secondary battery is a lithium ion secondary battery will be described as an example, but the present invention is not limited to the following example.

<Electrode>
As described above, the secondary battery electrode of the present invention is used as at least one of a positive electrode and a negative electrode. That is, the positive electrode of the lithium ion secondary battery may be an electrode of the present invention and the negative electrode may be another known negative electrode, and the negative electrode of the lithium ion secondary battery is an electrode of the present invention and the positive electrode is another known positive electrode. In addition, both the positive electrode and the negative electrode of the lithium ion secondary battery may be the electrode of the present invention.

<Separator>
As a separator, the thing of Unexamined-Japanese-Patent No. 2012-204303 can be used, for example. Among these, the thickness of the separator as a whole can be reduced, thereby increasing the ratio of the electrode active material in the lithium ion secondary battery and increasing the capacity per volume. A microporous film made of a series resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred.

<Electrolyte>
As the electrolytic solution, an electrolytic solution in which an electrolyte is dissolved in a solvent can be used.
Here, as the solvent, an organic solvent capable of dissolving the electrolyte can be used. Specifically, examples of the solvent include alkyl carbonate solvents such as ethylene carbonate, propylene carbonate, γ-butyrolactone, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl acetate, dimethoxyethane. , Dioxolane, methyl propionate, methyl formate and the like can be used.
A lithium salt can be used as the electrolyte. As lithium salt, the thing as described in Unexamined-Japanese-Patent No. 2012-204303 can be used, for example. Among these lithium salts, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable as the electrolyte from the viewpoint of being easily dissolved in an organic solvent and exhibiting a high degree of dissociation.

<Method for manufacturing secondary battery>
For example, a lithium ion secondary battery is formed by stacking a positive electrode and a negative electrode through a separator, and winding or folding the positive electrode and a negative electrode according to the shape of the battery as necessary. Can be prepared by injecting and sealing. In order to prevent the occurrence of pressure rise and overcharge / discharge inside the lithium ion secondary battery, an overcurrent prevention element such as a fuse or a PTC element, an expanded metal, a lead plate, etc. may be provided as necessary. . The shape of the lithium ion secondary battery may be any of, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “%” and “part” representing amounts are based on mass unless otherwise specified.
In the examples and comparative examples, the viscosity and surface tension of the polyether-modified polydimethylsiloxane, the peel strength and drainage of the electrode, the amount of lithium deposited on the electrode, and the low-temperature output characteristics and cycle characteristics of the secondary battery are as follows: Each was evaluated using the following method.

<Viscosity>
The viscosity of the polyether-modified polydimethylsiloxane was prepared by adding ion-exchanged water so that the polyether-modified polydimethylsiloxane had a solid content concentration of 2.0% by mass. (Toki Sangyo Co., Ltd. “RB-80L”) rotor No. 1 was measured at 60 rpm.

<Surface tension>
The surface tension of the polyether-modified polydimethylsiloxane was prepared by adding ion-exchanged water so that the polyether-modified polydimethylsiloxane had a solid content concentration of 10.0% by mass. Measurement was performed by a platinum plate method using a meter (“DY-300” manufactured by Kyowa Interface Science Co., Ltd.).

<Peel strength>
The produced negative electrode for a lithium ion secondary battery was cut into a rectangle having a length of 100 mm and a width of 10 mm to obtain a test piece, and a cellophane tape (specified in JIS Z1522) was formed on the surface of the negative electrode mixture layer with the surface having the negative electrode mixture layer facing down. The stress was measured when one end of the current collector was pulled in the vertical direction at a pulling speed of 50 mm / min and peeled off (the cellophane tape was fixed to the test stand). The measurement was performed 3 times, the average value was calculated | required, this was made into peel strength, and the following references | standards evaluated. It shows that it is excellent in the adhesiveness of a negative mix layer and an electrical power collector, so that the value of peel strength is large.
A: Peel strength is 20 N / m or more B: Peel strength is 15 N / m or more and less than 20 N / m C: Peel strength is 10 N / m or more and less than 15 N / m D: Peel strength is less than 10 N / m

<Electrode drainage>
The electrode mixture layer from which the current collector portion was removed from the prepared negative electrode for a lithium ion secondary battery was cut into a rectangle having a length of 70 mm and a width of 40 mm to obtain a sample, and the sample was put into a sample bottle for the Karl Fischer method, with a dew point The mixture was left for 12 hours in an environment at a temperature of −60 ° C. to −50 ° C., and then left for 12 hours in a vacuum environment at 60 ° C. Thereafter, the pressure was returned to normal pressure, the top of the sample bottle was covered, and the moisture content was measured by the Karl Fischer method in an environment of 200 ° C.

<Lithium deposition amount>
The prepared lithium ion secondary battery was allowed to stand for 24 hours in an environment of 25 ° C., and then charged with 4.2 V, 1 C, and 1 hour in an environment of −15 ° C. Thereafter, the negative electrode was taken out in an argon atmosphere at room temperature, and the ratio (%) of the area where lithium metal was deposited to the total area of the negative electrode was measured and evaluated according to the following criteria. The smaller the area where lithium metal is deposited, the better the low-temperature acceptance characteristics.
A: Area ratio is 0% or more and less than 10% B: Area ratio is 10% or more and less than 20% C: Area ratio is 20% or more and less than 30% D: Area ratio is 30% or more

<Low temperature output characteristics>
The prepared lithium ion secondary battery was allowed to stand for 24 hours in an environment at 25 ° C, and then charged at 4.2V, 0.1C for 5 hours in an environment at 25 ° C. V'0 was measured. Thereafter, a discharge operation was performed at a discharge rate of 2C in a -15 ° C environment, and the voltage V'1 20 seconds after the start of discharge was measured. The low-temperature characteristics were evaluated based on the following criteria based on a voltage change represented by ΔV ′ = V′0−V′1. It shows that it is excellent in low-temperature output characteristics, so that the value of voltage change is small.
A: ΔV ′ is less than 0.8V B: ΔV ′ is 0.8V or more and less than 0.9V C: ΔV ′ is 0.9V or more and less than 1.0V D: ΔV ′ is 1.0V or more

<Cycle characteristics>
The prepared lithium ion secondary battery was allowed to stand for 24 hours in an environment at 25 ° C., and then charged at 4.2 V, 0.1 C, and discharged at 3.0 V, 0.1 C at 25 ° C. The charge / discharge operation was performed, and the initial capacity C0 was measured. Furthermore, the charge / discharge operation was repeated in a 45 ° C. environment, and the capacity C2 after 100 cycles was measured. The high-temperature cycle characteristics were evaluated based on the following criteria at a capacity retention rate represented by ΔC = (C2 / C0) × 100 (%). It shows that it is excellent in cycling characteristics and life characteristics, so that the value of a capacity | capacitance maintenance factor is high.
A: ΔC is 90% or more B: ΔC is 80% or more and less than 90% C: ΔC is 70% or more and less than 80% D: ΔC is less than 70%

Example 1
<Preparation of particulate polymer>
In a 5 MPa pressure vessel with a stirrer, 33.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 1.0 part of itaconic acid as a carboxyl group-containing monomer, and styrene as an aromatic vinyl monomer 65.0 parts, 1.0 part of 2-hydroxyethyl acrylate as a hydroxyl group-containing monomer, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water and potassium persulfate as a polymerization initiator After adding 0.5 part and stirring sufficiently, it heated at 75 degreeC and superposition | polymerization was started. When the polymerization conversion rate reached 96%, the mixture was cooled and the reaction was stopped to obtain a mixture containing a particulate polymer (SBR). A 5% aqueous sodium hydroxide solution was added to the mixture containing the particulate polymer to adjust the pH to 8, and then unreacted monomers were removed by heating under reduced pressure. Then, it cooled to 30 degrees C or less, and obtained the water dispersion liquid containing a desired particulate polymer.

<Preparation of polyether-modified polydimethylsiloxane>
As the polyether-modified polydimethylsiloxane, “BYK-1770” manufactured by Big Chemie Japan Co., Ltd. was prepared. And the viscosity and surface tension of this polyether modified polydimethylsiloxane were measured. The results are shown in Table 1.

<Preparation of a crosslinking agent having a carbodiimide group>
“SV-02” manufactured by Nisshinbo Chemical Co., Ltd. was prepared as a crosslinking agent having a carbodiimide group.

<Preparation of water-soluble polymer>
As a water-soluble polymer, an aqueous solution (“MAC-350HC” manufactured by Nippon Paper Industries Co., Ltd.) containing 1.0 part of sodium salt of carboxymethyl cellulose (hereinafter sometimes abbreviated as “CMC-Na”) per 100 parts of the negative electrode active material. )).

<Preparation of secondary battery binder composition>
In a container, 100 parts of the above particulate polymer (SBR) corresponding to the solid content and 0.25 part of sodium dioctyl succinate were mixed, and then ion-exchanged water was mixed. Further, 5.0 parts of the crosslinking agent having the carbodiimide group and 0.05 parts of the polyether-modified polydimethylsiloxane were added to the mixture to obtain a binder composition for a secondary battery having a solid content concentration of 30%. .

<Preparation of slurry composition for negative electrode>
In a planetary mixer with a disper, 100 parts of natural graphite (volume average particle size: 15.6 μm) having a specific surface area of 5.5 m ² / g as a negative electrode active material, sodium carboxymethylcellulose as a water-soluble polymer (Nippon Paper Industries Co., Ltd.) 1.0 part of a 2% aqueous solution of “MAC-350HC” manufactured by the company was added in an amount equivalent to the solid content, adjusted to a solid content concentration of 60% with ion exchange water, and then mixed at 25 ° C. for 60 minutes. Next, after adjusting the solid content concentration to 52% with ion-exchanged water, the mixture was further mixed at 25 ° C. for 15 minutes to obtain a mixed solution. To the mixed solution, 2.0 parts of the secondary battery binder composition in an amount corresponding to the solid content and ion-exchanged water were added, adjusted to a final solid content concentration of 48%, and further mixed for 10 minutes. This was defoamed under reduced pressure to obtain a slurry composition for negative electrode having good fluidity.

<Preparation of negative electrode for secondary battery>
Using a comma coater (registered trademark), the negative electrode slurry composition is applied to a current collector copper foil having a thickness of 20 μm so that the film thickness after drying is about 150 μm, and is dried. It was. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode raw material before pressing. The negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode after pressing with a negative electrode mixture layer thickness of 80 μm.
And the peel strength and drainage property of the obtained negative electrode were evaluated. The results are shown in Table 1.

<Preparation of slurry composition for positive electrode>
100 parts of LiCoO ₂ having a volume average particle diameter of 12 μm as a positive electrode active material, ₂ parts of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and PVDF (manufactured by Kureha Corporation, polyvinylidene fluoride as a binder) , # 7208) was mixed with 2 parts corresponding to the solid content and N-methylpyrrolidone so that the total solid content concentration became 70%. These were mixed by a planetary mixer to prepare a positive electrode slurry composition.

<Preparation of positive electrode for secondary battery>
The positive electrode slurry composition was applied onto a 20 μm-thick aluminum foil as a current collector using a comma coater so that the film thickness after drying was about 150 μm and dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, it heat-processed for 2 minutes at 120 degreeC, and obtained the positive electrode.

<Production of lithium ion secondary battery>
A single-layer polypropylene separator (Celgard 2500, manufactured by Celgard) was cut into a 5 cm × 5 cm square. Moreover, the aluminum packaging material exterior was prepared as a battery exterior. The positive electrode for a secondary battery was cut out into a square of 4.6 cm × 4.6 cm and arranged so that the surface on the current collector side was in contact with the aluminum packaging material exterior. The square separator was disposed on the surface of the positive electrode mixture layer of the positive electrode. Furthermore, the negative electrode for secondary batteries was cut into a 5 cm × 5 cm square, and this was placed on the separator so that the surface on the negative electrode composite layer side faces the separator. An electrolyte solution (solvent: ethylene carbonate / dimethyl carbonate / vinylene carbonate = 68.5 / 30 / 1.5 (volume ratio), electrolyte: LiPF _{6 with a} concentration of 1M) was injected so that no air remained, In order to seal the opening of the material, heat sealing at 150 ° C. was performed to close the aluminum exterior, and a lithium ion secondary battery was produced.
And about the obtained lithium ion secondary battery, lithium precipitation amount, low temperature output characteristics, and cycling characteristics were evaluated. The results are shown in Table 1.

(Example 2)
A binder composition for a secondary battery, a slurry composition for a secondary battery negative electrode, as in Example 1, except that the amount of the polyether-modified polydimethylsiloxane added was 0.03 part per 100 parts of the particulate polymer. A slurry composition for a positive electrode of a secondary battery, a negative electrode for a secondary battery, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
A binder composition for a secondary battery, a slurry composition for a secondary battery negative electrode, in the same manner as in Example 1, except that the amount of the polyether-modified polydimethylsiloxane added was 0.08 part per 100 parts of the particulate polymer. A slurry composition for a positive electrode of a secondary battery, a negative electrode for a secondary battery, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Example 4
The binder composition for a secondary battery, the slurry composition for a secondary battery negative electrode, the slurry composition for a secondary battery positive electrode, and a secondary battery, as in Example 1, except that the crosslinking agent having a carbodiimide group was not added A negative electrode, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
A binder composition for a secondary battery, a slurry composition for a secondary battery negative electrode, in the same manner as in Example 1, except that the amount of the crosslinking agent having a carbodiimide group was 3.0 parts per 100 parts of the particulate polymer. A slurry composition for a positive electrode of a secondary battery, a negative electrode for a secondary battery, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 6)
A binder composition for a secondary battery, a slurry composition for a secondary battery negative electrode, in the same manner as in Example 1, except that the amount of the crosslinking agent having a carbodiimide group was 7.0 parts per 100 parts of the particulate polymer. A slurry composition for a positive electrode of a secondary battery, a negative electrode for a secondary battery, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 7)
As a water-soluble polymer, instead of carboxymethylcellulose sodium salt (MAC-350HC), an acid-containing copolymer (manufactured by Sigma-Aldrich, polyacrylic acid (weight average molecular weight = about 1.25 million, hereinafter may be abbreviated as PAA) .)) In the same manner as in Example 1 except that 1.0 part per 100 parts of the negative electrode active material was blended, a secondary battery binder composition, a secondary battery negative electrode slurry composition, and a secondary battery positive electrode slurry composition. A negative electrode for a secondary battery, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 8)
In a 5 MPa pressure vessel with a stirrer, 96.0 parts of butyl acrylate as a (meth) acrylic acid ester monomer, 2.0 parts of methacrylic acid as a carboxyl group-containing monomer, and (meth) acrylonitrile monomer Add 2.0 parts of acrylonitrile, 0.3 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.3 part of ammonium persulfate as a polymerization initiator. Uses 1.0 part of a solid polymer (acrylic polymer) polymerized in the same manner as SBR, except that the polymerization was started by heating, and was used as a polyether-modified polydimethylsiloxane as a big chemi japan stock. Similar to Example 1 except that 0.05 part of “BYK-1785” manufactured by the company was added per 100 parts of the particulate polymer. Binder composition for a secondary battery Te, secondary battery negative electrode slurry composition, a secondary battery positive electrode slurry composition, a negative electrode for a secondary battery was fabricated positive electrode, and a lithium ion secondary battery for a secondary battery. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Example 9
As a water-soluble polymer, instead of carboxymethylcellulose sodium salt (MAC-350HC), an acid-containing copolymer (manufactured by Sigma-Aldrich, polyacrylic acid (weight average molecular weight = about 1.25 million)) is used per 100 parts of negative electrode active material. Except for adding 0.0 part, the same as in Example 8, the secondary battery binder composition, the secondary battery negative electrode slurry composition, the secondary battery positive electrode slurry composition, the secondary battery negative electrode, and the secondary battery use. A positive electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 10)
A secondary battery binder composition, a secondary battery negative electrode slurry composition, a secondary battery positive electrode slurry composition, and a secondary battery use in the same manner as in Example 8 except that the carbodiimide group-containing crosslinking agent was not added. A negative electrode, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 11)
A secondary battery binder composition, a secondary battery negative electrode slurry composition, a secondary battery positive electrode slurry composition, and a secondary battery same as in Example 9 except that the crosslinking agent having a carbodiimide group was not added. A negative electrode, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Example 12
As a polyether-modified polydimethylsiloxane, a binder composition for a secondary battery was prepared in the same manner as in Example 1, except that 0.05 part of BYK-1610 manufactured by BYK Japan Japan Co., Ltd. was added per 100 parts of the particulate polymer. The slurry composition for secondary battery negative electrodes, the slurry composition for secondary battery positive electrodes, the negative electrode for secondary batteries, the positive electrode for secondary batteries, and the lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
A secondary battery binder composition, a secondary battery negative electrode slurry composition, a secondary battery positive electrode slurry composition, and a secondary battery use in the same manner as in Example 1 except that the polyether-modified polydimethylsiloxane was not added. A negative electrode, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
A binder composition for a secondary battery, a slurry composition for a secondary battery negative electrode, in the same manner as in Example 1, except that the amount of the polyether-modified polydimethylsiloxane added was 0.2 parts per 100 parts of the particulate polymer. A slurry composition for a positive electrode of a secondary battery, a negative electrode for a secondary battery, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
A binder composition for a secondary battery, a slurry composition for a secondary battery negative electrode, and a slurry for a secondary battery positive electrode in the same manner as in Example 1 except that the polyether-modified polydimethylsiloxane and the crosslinking agent having a carbodiimide group were not added. A composition, a negative electrode for a secondary battery, a positive electrode for a secondary battery, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, in Examples 1-12 to which a predetermined amount of polyether-modified polydimethylsiloxane was added, an electrode having excellent peel strength and water drainage properties was obtained, as well as excellent low-temperature output characteristics and cycle characteristics, and It turns out that the lithium ion secondary battery which can suppress the amount of lithium precipitation is obtained.
In particular, from Examples 1 and 4 to 6 in Table 1, when a conjugated diene polymer is used as the particulate polymer, a predetermined amount of a crosslinking agent having a carbodiimide group is added in addition to the polyether-modified polydimethylsiloxane. As a result, an electrode excellent in peel strength and water drainability can be obtained, and a lithium ion secondary battery excellent in low-temperature output characteristics and cycle characteristics and capable of further suppressing the amount of lithium deposited on the negative electrode can be obtained. I understand that.
On the other hand, from Table 1, in Comparative Example 2 in which the addition amount of the polyether-modified polydimethylsiloxane deviates from a predetermined range, and in Comparative Examples 1 and 3 in which no polyether-modified polydimethylsiloxane is added, the peel strength or drainage is improved. It can be seen that an excellent electrode cannot be obtained, and a lithium ion secondary battery that is excellent in low-temperature output characteristics and cycle characteristics and that can suppress the amount of lithium deposited on the negative electrode cannot be obtained.
Furthermore, from Examples 8 to 11 in Table 1, when an acrylic polymer is used as the particulate polymer, the cycle characteristics are better when a predetermined amount is not added when a crosslinking agent having a carbodiimide group is not added. It can be seen that a lithium ion secondary battery excellent in the above can be obtained.

ADVANTAGE OF THE INVENTION According to this invention, the binder composition for secondary batteries which can further improve the performance of the electrode for secondary batteries and a secondary battery is obtained.
Moreover, according to this invention, the slurry composition for secondary battery electrodes which can further improve the performance of the electrode for secondary batteries and a secondary battery is obtained.
Furthermore, according to the present invention, it is possible to obtain a secondary battery electrode that is excellent in performance such as peel strength and can further improve the performance of the secondary battery.
And according to this invention, the secondary battery excellent in performance, such as an electrical property, is obtained.

Claims (6)

Including a particulate polymer, a polyether-modified polydimethylsiloxane, and water;
The binder composition for secondary battery negative electrodes containing 0.01 mass part or more and 0.19 mass part or less of the said polyether modified polydimethylsiloxane per 100 mass parts of said particulate polymers. The binder composition for secondary battery negative electrodes of Claim 1 which further contains the crosslinking agent which has a carbodiimide group. Wherein a negative electrode active material, a particulate polymer, the polyether-modified polydimethylsiloxane, and water,
A slurry composition for secondary battery negative electrode, comprising 0.01 to 0.19 parts by mass of the polyether-modified polydimethylsiloxane per 100 parts by mass of the particulate polymer. The slurry composition for secondary battery negative electrodes of Claim 3 which further contains the crosslinking agent which has a carbodiimide group. A negative electrode mixture layer obtained by using the secondary battery negative electrode slurry composition according to claim 3 or 4, a negative electrode for a secondary battery. Comprising a positive electrode, a negative electrode, a separator and an electrolyte,
Before SL negative electrode, a negative electrode for secondary battery of claim 5, the secondary battery.