JP6398995B2 - Binder composition for secondary battery electrode, slurry composition for secondary battery electrode, electrode for secondary battery, and secondary battery - Google Patents

Description

  The present invention relates to a binder composition for a secondary battery electrode, 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, a battery member such as an electrode (a positive electrode and a negative electrode) of a secondary battery has a binder (binding) between components contained in these battery members or between the component and a base material (for example, a current collector). It is formed by binding with an agent. Specifically, the electrode of the secondary battery usually includes a current collector and an electrode mixture layer (also referred to as an “electrode active material layer”) formed on the current collector. The electrode mixture layer is formed by, for example, applying a slurry composition for an electrode in which a binder, an electrode active material, and the like are dispersed in a dispersion medium on a current collector and drying to bind the electrode active material, etc. with the binder. It is formed by doing.
Therefore, in the electrode of a secondary battery, in order to improve the adhesiveness of an electrode compound-material layer and a collector, improvement of the binder composition for electrodes and the slurry composition for electrodes is tried.

  For example, Patent Document 1 includes functional group-containing resin fine particles obtained by emulsion polymerization of an ethylenically unsaturated monomer containing a keto group-containing ethylenically unsaturated monomer, and a polyfunctional hydrazide compound as a crosslinking agent. A binder composition for secondary battery electrodes has been proposed, and it has been reported that this binder composition is excellent in electrolytic solution resistance, adhesion to a current collector, and flexibility.

  Further, for example, in Patent Document 2, a binder for a non-aqueous secondary battery electrode including functional group-containing crosslinked resin fine particles obtained by copolymerizing a monomer containing an ethylenically unsaturated monomer having a specific functional group A composition has been proposed, and it has been reported that this binder composition is excellent in electrolytic solution resistance, adhesion to a current collector, and flexibility.

JP 2011-134618 A International Publication No. 2010/114119

  However, in the slurry composition comprising the conventional binder composition, the specific gravity of the binder (particulate polymer) made of a resin in a particulate form is small, and the particulate composition is insoluble in water. The viscosity of the slurry composition is low. Therefore, in the electrode using the conventional slurry composition, when the slurry composition applied on the current collector is dried, the particulate polymer rises in the slurry composition by heat convection, and after the drying is completed. Tends to be unevenly distributed (migration) on the surface of the electrode mixture layer. This migration has a problem that the amount of the particulate polymer existing on the surface in contact with the current collector in the electrode mixture layer is reduced, and the adhesion between the electrode mixture layer and the current collector is impaired. .

  In order to suppress the migration of the particulate polymer, for example, a method of increasing the viscosity of the slurry composition by using, for example, a thickener and suppressing the movement of the particulate polymer due to thermal convection can be considered. However, the high viscosity slurry composition has a problem that it is difficult to apply on the current collector.

  Therefore, from the viewpoint of suppressing the migration of the particulate polymer and ensuring the ease of application of the slurry composition on the current collector, the electrode slurry composition is applied to the current collector. In the case of (high shear), the viscosity is low, which makes it easy to apply. On the other hand, after application (under low shear), the property of high viscosity that can suppress the occurrence of migration (such viscosity behavior is “Thixo”). Called "sex").

Then, this invention provides the binder composition for secondary battery electrodes which can form the slurry composition which is excellent in thixotropy, and is excellent in adhesiveness with the electrical power collector at the time of setting it as an electrode compound-material layer. Objective.
Another object of the present invention is to provide a slurry composition for a secondary battery electrode that is capable of forming an electrode mixture layer that is excellent in thixotropy and adhesiveness to a current collector.
Furthermore, this invention aims at providing the electrode for secondary batteries which is excellent in the adhesiveness of an electrode compound-material layer and a collector.
In addition, an object of the present invention is to provide a secondary battery including a secondary battery electrode that is excellent in adhesion between the electrode mixture layer and the current collector.

  The inventor has intensively studied to achieve the above object. Then, the present inventor has excellent thixotropy when using a binder composition in which hydrophilic organic fibers are blended at a specific ratio with respect to the particulate polymer, and is applied onto a current collector and dried. When it became a compound material layer, it discovered newly that the slurry composition for water-system electrodes which can ensure the outstanding adhesiveness with a collector was discovered, and this invention was completed.

  That is, this invention aims at solving the said subject advantageously, The binder composition for secondary battery electrodes of this invention is a particulate polymer (A), hydrophilic organic fiber (B). And the hydrophilic organic fiber (B) is contained in an amount of 0.01 to 20 parts by mass per 100 parts by mass of the particulate polymer (A). Thus, according to the binder composition containing the particulate polymer (A) and the hydrophilic organic fiber (B) at a predetermined ratio, the current collector is excellent in thixotropy and used as an electrode mixture layer. It is possible to form a slurry composition that is excellent in adhesion.

  Here, as for the binder composition for secondary battery electrodes of this invention, it is preferable that the said hydrophilic organic fiber (B) has a hydroxyl group. If the hydrophilic organic fiber (B) has a hydroxyl group, the slurry composition obtained using the binder composition was excellent in thixotropy and adhesion to the current collector when used as an electrode mixture layer. Can be.

  Moreover, it is preferable that the average fiber diameter of the said hydrophilic organic fiber (B) is 1 nm or more and 1000 nm or less in the binder composition for secondary battery electrodes of this invention. If the average fiber diameter of the hydrophilic organic fiber (B) is within the above range, the storage stability of the binder composition and the slurry composition obtained using the binder composition, and the electrode mixture layer may be obtained. Adhesiveness with the current collector can be made excellent.

  Furthermore, the binder composition for secondary battery electrodes of the present invention further comprises a crosslinking agent (C), and the crosslinking agent (C) is at least one selected from the group consisting of a polyfunctional epoxy compound, an oxazoline compound and a carbodiimide compound. Preferably it is a seed. When such a crosslinking agent (C) is included, the adhesion between the electrode mixture layer formed from the slurry composition obtained using the binder composition and the current collector can be further improved.

  In addition, the binder composition for a secondary battery electrode of the present invention may contain 0.01 to 10 parts by mass of the crosslinking agent (C) per 100 parts by mass of the particulate polymer (A). preferable. When the cross-linking agent (C) is included within the above range, the storage stability of the binder composition and the slurry composition obtained using the binder composition, and the adhesion with the current collector when used as an electrode mixture layer The property can be further improved.

  And as for the binder composition for secondary battery electrodes of this invention, it is preferable that the surface acid amount of the said particulate polymer (A) is 0.01 mmol / g or more and 3.5 mmol / g or less. If the surface acid amount of the particulate polymer (A) is within the above range, the electrode material layer formed from the slurry composition obtained using the binder composition and the current collector having excellent adhesion can do.

  Moreover, this invention aims at solving the said subject advantageously, The slurry composition for secondary battery electrodes of this invention is a particulate polymer (A), hydrophilic organic fiber (B). In addition, the hydrophilic organic fiber (B) is contained in an amount of 0.01 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the particulate polymer (A). As described above, the slurry composition containing the particulate polymer (A) and the hydrophilic organic fiber (B) at a predetermined ratio is excellent in thixotropy, and the current collector when the electrode mixture layer is formed. Excellent adhesion.

  Here, the slurry composition for a secondary battery electrode of the present invention further includes a crosslinking agent (C), and the crosslinking agent (C) is at least selected from the group consisting of a polyfunctional epoxy compound, an oxazoline compound, and a carbodiimide compound. One type is preferable. When such a crosslinking agent (C) is included, the adhesion between the electrode mixture layer formed from the slurry composition and the current collector can be further improved.

  Moreover, it is preferable that the slurry composition for secondary battery electrodes of this invention further contains a water-soluble thickener (D). When the water-soluble thickener (D) is included, excellent storage stability of the slurry composition is obtained, and workability when the slurry composition is applied onto a current collector or the like is improved.

  Moreover, this invention aims at solving the said subject advantageously, The electrode for secondary batteries of this invention is obtained using one of the above-mentioned slurry compositions for secondary battery electrodes. It has an electrode compound material layer. An electrode using any one of the above-described slurry compositions for secondary battery electrodes for forming the electrode mixture layer is excellent in adhesion between the electrode mixture layer and the current collector.

  Moreover, this invention aims at solving the said subject advantageously, The secondary battery of this invention is equipped with a positive electrode, a negative electrode, electrolyte solution, and a separator, At least one of the said positive electrode and negative electrode is, It is an electrode for a secondary battery as described above. A secondary battery using the above-described electrode for a secondary battery is excellent in the adhesion between the electrode mixture layer and the current collector in the electrode.

According to the present invention, it is possible to provide a binder composition for a secondary battery electrode capable of forming a slurry composition that is excellent in thixotropy and has excellent adhesion to a current collector when an electrode mixture layer is formed. it can.
Moreover, according to this invention, the slurry composition for secondary battery electrodes which can form the electrode compound-material layer which is excellent in thixotropy and is excellent in adhesiveness with a collector can be provided.
Furthermore, according to this invention, the electrode for secondary batteries which is excellent in the adhesiveness of an electrode compound-material layer and a collector can be provided.
In addition, according to the present invention, it is possible to provide a secondary battery including an electrode having excellent adhesion between the electrode mixture layer and the current collector.

It is the graph which plotted electric conductivity (ms) with respect to the cumulative amount (mmol) of the added hydrochloric acid in calculation of the surface acid amount of a particulate polymer.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for secondary battery electrodes of this invention is used for preparation of the slurry composition for secondary battery electrodes. Moreover, the slurry composition for secondary battery electrodes of this invention is used for formation of the electrode of a secondary battery. And the electrode for secondary batteries of this invention can be manufactured using the slurry composition for secondary battery electrodes of this invention. Furthermore, the secondary battery of the present invention is characterized by using the secondary battery electrode of the present invention.

(Binder composition for secondary battery electrode)
The binder composition for secondary battery electrodes of the present invention contains a particulate polymer (A), a hydrophilic organic fiber (B), and water. And the binder composition for secondary battery electrodes of this invention contains a hydrophilic organic fiber (B) in the quantity of 0.01 to 20 mass parts per 100 mass parts of particulate polymers (A). To do. And according to the binder composition for secondary battery electrodes of this invention, the slurry composition which is excellent in thixotropy and is excellent in adhesiveness with the electrical power collector at the time of setting it as an electrode compound-material layer can be formed. .

Here, the reason why the thixotropy of the slurry composition is improved by using the secondary battery electrode binder composition of the present invention for the preparation of the slurry composition is not clear, but this thixotropy is improved by the aqueous slurry. In the composition, it is assumed that the cause is that the particulate polymer (A) and the hydrophilic organic fiber (B) interact with each other through hydrogen bonding or the like.
More specifically, the particulate polymer (A) and the hydrophilic organic fiber (B) interact with each other by hydrogen bonding, and these components form a network-like pseudo-bridge structure in the aqueous slurry composition. To do. And while this pseudo-bridge structure develops a certain degree of viscosity under low shear, the structure is not strong, so the pseudo-bridge structure cannot be maintained under high shear, and the network collapses It is assumed that the viscosity decreases, that is, thixotropy improves.

In addition, the reason for improving the adhesion with the current collector when the electrode composition layer is used by preparing the slurry composition for the secondary battery electrode binder composition of the present invention is not clear, i) Due to the improved thixotropy due to the above-mentioned pseudo-bridge structure, the migration (migration) of the particulate polymer due to thermal convection during drying (under low shear) of the slurry composition is suppressed by the development of high viscosity. In addition, (ii) when the slurry composition is dried, the hydrophilic organic fibers (B) may physically suppress the migration (migration) of the particulate polymer (A). That is, for the reason of (i) and / or (ii) above, the distribution of the particulate polymer (A) in the obtained electrode mixture layer becomes uniform, and the adhesion strength between the electrode active material layer and the current collector is increased. It is assumed that it will be excellent.
Hereafter, each component contained in the said binder composition for secondary battery electrodes is demonstrated.

<Particulate polymer (A)>
When the particulate polymer (A) is formed using the slurry composition containing the binder composition of the present invention, the component (for example, electrode active material) contained in the electrode is produced from the electrode. It is a component that can be held so as not to be detached. Here, when the electrode mixture layer is formed using the slurry composition, the particulate polymer in the electrode mixture layer generally absorbs the electrolyte when immersed in the electrolyte. While swelling, the particulate shape is maintained, the electrode active materials are bound together, and the electrode active material is prevented from falling off the current collector. Further, the particulate polymer also binds particles (for example, a conductive material) other than the electrode active material contained in the electrode mixture layer, and plays a role of maintaining the strength of the electrode mixture layer.
The “particulate polymer” is a polymer that can be dispersed in an aqueous medium such as water, and exists in a particulate form in the aqueous medium. In general, the particulate polymer has an insoluble content of 90% by mass or more when 0.5 g of the particulate polymer is dissolved in 100 g of water at 25 ° C. In the present invention, “particles” or “particulate” refers to those having an aspect ratio of 1 or more and less than 10 as measured with a scanning electron microscope.

[[Functional group capable of forming hydrogen bond]]
Here, the particulate polymer (A) preferably has a functional group capable of forming a hydrogen bond. Since the particulate polymer (A) has a functional group capable of forming a hydrogen bond, the interaction with the hydrophilic organic fiber (B) is enhanced, the thixotropy of the slurry composition is improved, and the electrode mixture layer And the current collector can be improved. Examples of the functional group capable of forming a hydrogen bond in the particulate polymer (A) include a carboxyl group, a hydroxyl group, a sulfonic acid group, and a thiol group. The particulate polymer (A) preferably has at least one selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a thiol group, and further has at least one of a carboxyl group and a hydroxyl group. preferable. In addition, when the binder composition contains a cross-linking agent (C) described later, the particulate polymer (A) has both a carboxyl group and a hydroxyl group from the viewpoint of adhesion between the electrode active material layer and the current collector. It is particularly preferred to have
Here, the carboxyl group, the hydroxyl group, and the thiol group have, for example, an ethylenically unsaturated carboxylic acid monomer, an unsaturated monomer having a hydroxyl group, and a thiol group in the preparation of the particulate polymer (A). By using a monomer, it can be introduced into the particulate polymer (A).
In addition, the sulfonic acid group is obtained by using, for example, potassium persulfate as an initiator in the preparation of the particulate polymer (A), or by using an unsaturated monomer having a sulfonic acid group. It can introduce | transduce into a polymer (A).
Hereinafter, the ethylenically unsaturated carboxylic acid monomer, the unsaturated monomer having a hydroxyl group, the unsaturated monomer having a sulfonic acid group, and the monomer having a thiol group will be described in detail.

Examples of the ethylenically unsaturated carboxylic acid monomer that can form the ethylenically unsaturated carboxylic acid monomer unit of the particulate polymer (A) include ethylenically unsaturated monocarboxylic acid and derivatives thereof, and ethylenically unsaturated dicarboxylic acid. Examples thereof include acids and acid anhydrides and derivatives thereof.
Examples of the ethylenically unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid and the like. Examples of ethylenically unsaturated monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E monomethoxyacrylic. Examples include acid and β-diaminoacrylic acid.
Examples of the ethylenically unsaturated dicarboxylic acid include maleic acid, fumaric acid, itaconic acid and the like. Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acids include maleic anhydride, diacrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, and the like. In addition, examples of ethylenically unsaturated dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate , Dodecyl maleate, octadecyl maleate, fluoroalkyl maleate and the like.
One of these may be used alone, or two or more of these may be used in combination at any ratio. Among these, from the viewpoint of the storage stability of the slurry composition using the binder composition containing the particulate polymer (A), ethylenically unsaturated dicarboxylic acid, its acid anhydride, and derivatives thereof are preferable. Acid is more preferred. That is, the particulate polymer (A) preferably contains an itaconic acid-derived monomer unit (ethylenically unsaturated carboxylic acid monomer unit).
In the present invention, “comprising a monomer unit” means “a monomer-derived structural unit is contained in a polymer obtained using the monomer”.

  In the particulate polymer (A), the content of the ethylenically unsaturated carboxylic acid monomer unit is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and preferably 30% by mass. Hereinafter, it is more preferably 10% by mass or less, and particularly preferably 5% by mass or less. When the content of the ethylenically unsaturated carboxylic acid monomer unit is 0.1% by mass or more, the storage stability of the slurry composition containing the binder composition is ensured, and the electrode mixture layer and the current collector Improved adhesion. On the other hand, when the content of the ethylenically unsaturated carboxylic acid monomer unit is 30% by mass or less, the adhesion between the electrode active material layer and the current collector formed using the slurry composition containing the binder composition Can be improved.

Examples of the unsaturated monomer having a hydroxyl group that can form an unsaturated monomer unit having a hydroxyl group of the particulate polymer (A) include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, Hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxy Ethyl) maleate, 2-hydroxyethyl methyl fumarate and the like.
One of these may be used alone, or two or more of these may be used in combination at any ratio. Among these, 2-hydroxyethyl acrylate is preferable from the viewpoint of storage stability of the slurry composition using the binder composition containing the particulate polymer (A). That is, the particulate polymer (A) preferably contains a monomer unit derived from 2-hydroxyethyl acrylate (an unsaturated monomer unit having a hydroxyl group).

  In the particulate polymer (A), the content ratio of the unsaturated monomer unit having a hydroxyl group is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and preferably 10% by mass or less. More preferably, it is 5 mass% or less. When the content ratio of the unsaturated monomer unit having a hydroxyl group is 0.1% by mass or more, the storage stability of the slurry composition using the binder composition containing the particulate polymer (A) is secured, By being 10 mass% or less, the adhesiveness of the electrode active material layer obtained using the binder composition containing a particulate polymer (A) and an electrical power collector is securable.

  Examples of the unsaturated monomer having a sulfonic acid group capable of forming an unsaturated monomer unit having a sulfonic acid group of the particulate polymer (A) include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) Examples include acrylic sulfonic acid, styrene sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, and 3-allyloxy-2-hydroxypropane sulfonic acid. One of these may be used alone, or two or more of these may be used in combination at any ratio. In the present specification, “(meth) acryl” means acryl and / or methacryl.

  In the particulate polymer (A), the content of the unsaturated monomer unit having a sulfonic acid group is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and preferably 10% by mass. % Or less, more preferably 5% by mass or less. The storage ratio of the slurry composition using the binder composition containing the particulate polymer (A) is ensured by the content ratio of the unsaturated monomer unit having a sulfonic acid group being 0.1% by mass or more. And the adhesiveness of the electrode active material layer and collector which are obtained using the binder composition containing a particulate polymer (A) can be ensured because it is 10 mass% or less.

  Examples of the monomer having a thiol group that can form a monomer unit having a thiol group of the particulate polymer (A) include pentaerythritol tetrakis (3-mercaptobutyrate), trimethylolpropane tris (3- Mercaptobutyrate), trimethylolethane tris (3-mercaptobutyrate), and the like. Among these, pentaerythritol tetrakis (3-mercaptobutyrate) is preferable. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  In the particulate polymer (A), the content ratio of the monomer unit having a thiol group is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and preferably 10% by mass or less. More preferably, it is 5 mass% or less. When the content ratio of the monomer unit having a thiol group is 0.1% by mass or more, the storage stability of the slurry composition using the binder composition containing the particulate polymer (A) is ensured. By being the mass% or less, it is possible to ensure the adhesion between the electrode active material layer obtained using the binder composition containing the particulate polymer (A) and the current collector.

[[Functional group capable of reacting with cross-linking agent (C)]]
Moreover, when the binder composition or slurry composition of this invention contains the crosslinking agent (C) mentioned later, it is preferable that a particulate polymer (A) has a functional group which can react with a crosslinking agent (C). When the particulate polymer (A) has a functional group capable of reacting with the crosslinking agent (C) to form a crosslinking bond, the crosslinking agent (C) is incorporated into the binder composition or slurry composition. In addition, the adhesion between the obtained electrode mixture layer and the current collector can be further improved. Examples of the functional group capable of reacting with the crosslinking agent (C) in the particulate polymer (A) include the above-mentioned carboxyl group, hydroxyl group, and thiol group. Besides these functional groups, a glycidyl ether group and the like are included. Can be mentioned.
Here, the glycidyl ether group can be introduced into the particulate polymer (A) by using, for example, an unsaturated monomer having a glycidyl ether group in the preparation of the particulate polymer (A). .

  Examples of the unsaturated monomer having a glycidyl ether group capable of forming an unsaturated monomer unit having a glycidyl ether group of the particulate polymer (A) include glycidyl acrylate and glycidyl methacrylate. It is done. Of these, glycidyl methacrylate is preferred. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

[Types of particulate polymer (A)]
The particulate polymer (A) includes, for example, a diene polymer, an acrylic polymer, regardless of the presence or absence of a functional group capable of forming a hydrogen bond and a functional group capable of reacting with the crosslinking agent (C). A polymer, a fluorine-based polymer, a silicon-based polymer, or the like can be used. As the particulate polymer (A), one type of polymer may be used alone, or two or more types of polymers may be used in combination at any ratio.

[[Particulate polymer for negative electrode (A)]]
Here, when the binder composition of the present invention is used for forming the negative electrode mixture layer, the particulate polymer (A) is preferably an acrylic polymer or a diene polymer. As the acrylic polymer, a copolymer containing a (meth) acrylic acid ester monomer unit and an α, β-unsaturated nitrile monomer unit (hereinafter referred to as “acrylic / unsaturated nitrile copolymer”). The diene polymer is preferably a copolymer containing an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit (hereinafter referred to as “conjugated diene / aromatic vinyl copolymer”). ) Is preferable, and it is particularly preferable to use a conjugated diene / aromatic vinyl copolymer.
An aliphatic conjugated diene monomer unit that is a low-rigidity and flexible repeating unit that can enhance the binding property, and the solubility of the polymer in the electrolytic solution is reduced to form particles in the electrolytic solution. Since the copolymer having an aromatic vinyl monomer unit capable of enhancing the stability of the polymer (A) can perform well as the particulate polymer (A) particularly in the negative electrode. is there.
Hereinafter, monomers that can be used for the preparation of the particulate polymer for negative electrode (A) will be described by taking conjugated diene / aromatic vinyl copolymer and acrylic / unsaturated nitrile copolymer as examples.

-Monomers used in the preparation of conjugated diene / aromatic vinyl copolymers-
When a conjugated diene / aromatic vinyl copolymer is used as the negative electrode particulate polymer (A), the aliphatic conjugated diene monomer capable of forming an aliphatic conjugated diene monomer unit is particularly limited. 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side Chain conjugated hexadienes and the like can be used, among which 1,3-butadiene is preferred. In addition, an aliphatic conjugated diene monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the negative electrode particulate polymer (A) which is a conjugated diene / aromatic vinyl copolymer, the content of the aliphatic conjugated diene monomer unit is preferably 10% by mass or more, more preferably 25% by mass or more. Yes, preferably 50% by mass or less, more preferably 40% by mass or less. When the content ratio of the aliphatic conjugated diene monomer unit is 10% by mass or more, the flexibility of the negative electrode can be increased, and when it is 50% by mass or less, the negative electrode mixture layer and the current collector In addition, it is possible to improve the electrolytic solution resistance of the negative electrode formed from the slurry composition containing the binder composition of the present invention.

  Further, the aromatic vinyl monomer that can form the aromatic vinyl monomer unit of the particulate polymer for negative electrode (A) that is a conjugated diene / aromatic vinyl copolymer is not particularly limited, Styrene, α-methyl styrene, vinyl toluene, divinyl benzene and the like can be mentioned, among which styrene is preferable. In addition, an aromatic vinyl monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the negative electrode particulate polymer (A) which is a conjugated diene / aromatic vinyl copolymer, the content of the aromatic vinyl monomer unit is preferably 40% by mass or more, more preferably 50% by mass or more. , Preferably it is 80 mass% or less, More preferably, it is 70 mass% or less. When the content ratio of the aromatic vinyl monomer unit is 40% by mass or more, the electrolytic solution resistance of the negative electrode formed from the slurry composition containing the binder composition of the present invention can be improved. % Or less makes it possible to improve the adhesion between the negative electrode mixture layer and the current collector.

  The negative electrode particulate polymer (A), which is a conjugated diene / aromatic vinyl copolymer, contains a 1,3-butadiene unit as an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit. It preferably contains a styrene unit (that is, a styrene-butadiene copolymer).

  Further, as described above, the negative electrode particulate polymer (A) which is a conjugated diene / aromatic vinyl copolymer contains at least one selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a thiol group. Preferably, the particulate polymer (A) has an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated monomer unit having a hydroxyl group, an unsaturated monomer unit having a sulfonic acid group, and a thiol group. It is preferable to include at least one selected from the group consisting of monomer units in the above-described content ratio. The particulate polymer (A) preferably contains at least one of an ethylenically unsaturated carboxylic acid monomer unit and an unsaturated monomer unit having a hydroxyl group. It is more preferable to include both a body unit and an unsaturated monomer unit having a hydroxyl group.

  Moreover, as mentioned above, when the binder composition or slurry composition of the present invention contains a crosslinking agent (C) described later, the particulate polymer for negative electrode (A) which is a conjugated diene / aromatic vinyl copolymer is It preferably has a functional group capable of reacting with the crosslinking agent (C) (the above-mentioned carboxyl group, hydroxyl group, thiol group, glycidyl ether group, etc.).

The negative electrode particulate polymer (A), which is a conjugated diene / aromatic vinyl copolymer, may contain any repeating unit other than those described above as long as the effects of the present invention are not significantly impaired.
In the particulate polymer (A), an aliphatic conjugated diene monomer unit, an aromatic vinyl monomer unit, an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated monomer unit having a hydroxyl group, a sulfonic acid group The content ratio of the other monomer units other than the unsaturated monomer unit having thiol and the monomer unit having thiol is not particularly limited, but the upper limit is preferably 6% by mass or less in total, and 4% by mass or less. Is more preferable, and 2% by mass or less is particularly preferable.

-Monomers used in the preparation of acrylic / unsaturated nitrile copolymers-
When an acrylic / unsaturated nitrile copolymer is used as the negative electrode particulate polymer (A), the (meth) acrylic acid ester monomer capable of forming a (meth) acrylic acid ester monomer unit is particularly limited. Without being methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl Acrylic acid alkyl esters such as acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate Methacryl such as isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate Examples include acid alkyl esters. Of these, butyl acrylate is preferred. In addition, a (meth) acrylic acid ester monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the negative electrode particulate polymer (A) which is an acrylic / unsaturated nitrile copolymer, the content ratio of the (meth) acrylic acid ester monomer unit is preferably 10% by mass or more, more preferably 20% by mass or more. Preferably, it is 99.5 mass% or less, More preferably, it is 98 mass% or less. When the content ratio of the (meth) acrylic acid ester monomer unit is 10% by mass or more, the internal resistance of the secondary battery can be reduced, and when it is 99.5% by mass or less, the negative electrode composite material The adhesion between the layer and the current collector can be improved.

  The α, β-unsaturated nitrile monomer that can form the α, β-unsaturated nitrile monomer unit of the particulate polymer for negative electrode (A), which is an acrylic / unsaturated nitrile copolymer, Without being particularly limited, acrylonitrile and methacrylonitrile can be mentioned. Of these, acrylonitrile is preferred.

  In the negative electrode particulate polymer (A) which is an acrylic / unsaturated nitrile copolymer, the content ratio of the α, β-unsaturated nitrile monomer unit is preferably 0.1% by mass or more, more preferably 0%. 0.5 mass% or more, preferably 10 mass% or less, more preferably 5 mass% or less. When the content ratio of the α, β-unsaturated nitrile monomer unit is 0.1% by mass or more, the mechanical strength and binding force of the particulate polymer (A) are increased, and the negative electrode mixture layer and the current collector The adhesiveness of the negative electrode can be improved, and when it is 10% by mass or less, the flexibility of the negative electrode is improved and cracking of the negative electrode is suppressed.

  Moreover, as mentioned above, the particulate polymer for negative electrode (A) which is an acrylic / unsaturated nitrile copolymer contains at least one selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a thiol group. The particulate polymer (A) is preferably an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated monomer unit having a hydroxyl group, an unsaturated monomer unit having a sulfonic acid group, or a single unit having a thiol group. It is preferable to include at least one selected from the group consisting of monomer units in the above-described content ratio. The particulate polymer (A) preferably contains at least one of an ethylenically unsaturated carboxylic acid monomer unit and an unsaturated monomer unit having a hydroxyl group, and at least an ethylenically unsaturated carboxylic acid unit. More preferably, it contains a monomer unit.

  Moreover, as mentioned above, when the binder composition or slurry composition of the present invention contains a crosslinking agent (C) described later, the particulate polymer for negative electrode (A) which is a conjugated diene / aromatic vinyl copolymer is It preferably has a functional group capable of reacting with the crosslinking agent (C) (the above-mentioned carboxyl group, hydroxyl group, thiol group, glycidyl ether group, etc.).

The negative electrode particulate polymer (A), which is an acrylic / unsaturated nitrile copolymer, may contain any repeating unit other than those described above as long as the effects of the present invention are not significantly impaired.
In the particulate polymer (A), a (meth) acrylate monomer unit, an α, β-unsaturated nitrile monomer unit, an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated monomer having a hydroxyl group The content ratio of other monomer units other than the body unit, the unsaturated monomer unit having a sulfonic acid group, and the monomer unit having a thiol is not particularly limited, but the upper limit is 6% by mass or less in total. Preferably, 4 mass% or less is more preferable, and 2 mass% or less is especially preferable.

[[Particulate polymer for positive electrode (A)]]
Here, when using the binder composition of this invention for formation of a positive mix layer, as a particulate polymer (A), an acrylic polymer is preferable and an acrylic / unsaturated nitrile copolymer is more preferable.
Hereinafter, the monomer that can be used for the preparation of the particulate polymer for positive electrode (A) will be described by taking an acrylic / unsaturated nitrile copolymer as an example.

-Monomers used in the preparation of acrylic / unsaturated nitrile copolymers-
When an acrylic / unsaturated nitrile copolymer is used as the positive electrode particulate polymer (A), the (meth) acrylic acid ester monomer that can form a (meth) acrylic acid ester monomer unit is particularly limited. Without mentioning, those described above in the section “Particulate polymer for negative electrode (A)” can be mentioned. Of these, 2-ethylhexyl acrylate is preferable. In addition, a (meth) acrylic acid ester monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the positive electrode particulate polymer (A) which is an acrylic / unsaturated nitrile copolymer, the content ratio of the (meth) acrylic acid ester monomer unit is preferably 50% by mass or more, more preferably 60% by mass or more. Preferably, it is 97 mass% or less, More preferably, it is 95 mass% or less. When the content ratio of the (meth) acrylic acid ester monomer unit is 50% by mass or more, the internal resistance of the secondary battery can be reduced. By being 97% by mass or less, the positive electrode mixture layer and The adhesion of the current collector can be improved.

  In addition, the α, β-unsaturated nitrile monomer that can form the α, β-unsaturated nitrile monomer unit of the particulate polymer for positive electrode (A) that is an acrylic / unsaturated nitrile copolymer, Without particular limitation, those described above in the section “Particulate polymer for negative electrode (A)” can be mentioned. Of these, acrylonitrile is preferred.

  In the positive electrode particulate polymer (A) which is an acrylic / unsaturated nitrile copolymer, the content ratio of the α, β-unsaturated nitrile monomer unit is preferably 3% by mass or more, more preferably 5% by mass. It is above, Preferably it is 40 mass% or less, More preferably, it is 30 mass% or less. When the content ratio of the α, β-unsaturated nitrile monomer unit is 3% by mass or more, the mechanical strength and binding force of the particulate polymer (A) are increased, and the positive electrode mixture layer and the current collector are in close contact with each other. Therefore, the flexibility of the positive electrode is improved and cracking of the positive electrode is suppressed.

  Further, as described above, the positive electrode particulate polymer (A) that is an acrylic / unsaturated nitrile copolymer contains at least one selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a thiol group. The particulate polymer (A) is preferably an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated monomer unit having a hydroxyl group, an unsaturated monomer unit having a sulfonic acid group, or a single unit having a thiol group. It is preferable to include at least one selected from the group consisting of monomer units in the above-described content ratio. The particulate polymer (A) preferably contains at least one of an ethylenically unsaturated carboxylic acid monomer unit and an unsaturated monomer unit having a hydroxyl group, and at least an ethylenically unsaturated carboxylic acid unit. More preferably, it contains a monomer unit.

  Further, as described above, when the binder composition or slurry composition of the present invention contains a crosslinking agent (C) described later, the particulate polymer for positive electrode (A) which is an acrylic / unsaturated nitrile copolymer is It preferably has a functional group (such as the above-described carboxyl group, hydroxyl group, thiol group, and glycidyl ether group) that can react with the crosslinking agent (C).

Here, the particulate polymer for positive electrode (A), which is an acrylic / unsaturated nitrile copolymer, may contain any repeating unit other than those described above as long as the effects of the present invention are not significantly impaired.
In the particulate polymer (A), a (meth) acrylate monomer unit, an α, β-unsaturated nitrile monomer unit, an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated monomer having a hydroxyl group The content ratio of other monomer units other than the body unit, the unsaturated monomer unit having a sulfonic acid group, and the monomer unit having a thiol is not particularly limited, but the upper limit is 6% by mass or less in total. Preferably, 4 mass% or less is more preferable, and 2 mass% or less is especially preferable.

[Production method of particulate polymer (A)]
And a particulate polymer (A) is manufactured by polymerizing the monomer composition containing the monomer mentioned above in an aqueous solvent, for example.
Here, in the present invention, the content ratio of each monomer in the monomer composition can be determined according to the content ratio of the monomer units (repeating units) in the particulate polymer.

  The aqueous solvent is not particularly limited as long as the particulate polymer (A) is dispersible in a particulate state, and usually has a boiling point at normal pressure of usually 80 ° C. or higher, preferably 100 ° C. or higher. It is selected from aqueous solvents at 350 ° C. or lower, preferably 300 ° C. or lower.

  Specifically, examples of the aqueous solvent include water; ketones such as diacetone alcohol and γ-butyrolactone; alcohols such as ethyl alcohol, isopropyl alcohol, and normal propyl alcohol; propylene glycol monomethyl ether, methyl cellosolve, and ethyl cellosolve. , Glycol ethers such as ethylene glycol tertiary butyl ether, butyl cellosolve, 3-methoxy-3methyl-1-butanol, ethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether; 1,3 -Ethers such as dioxolane, 1,4-dioxolane and tetrahydrofuran; Among these, water is particularly preferable from the viewpoint that it is not flammable and a dispersion of particles of the particulate polymer (A) can be easily obtained. In addition, using water as a main solvent, you may mix and use aqueous solvents other than said water in the range which can ensure the dispersion state of the particle | grains of a particulate polymer (A).

  The polymerization method is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. As the polymerization method, any method such as ionic polymerization, radical polymerization, and living radical polymerization can be used. In addition, it is easy to obtain a high molecular weight body, and since the polymer is obtained as it is dispersed in water, it does not require redispersion treatment, and can be used for production of the binder composition of the present invention as it is. From the viewpoint of production efficiency, the emulsion polymerization method is particularly preferable. The emulsion polymerization can be performed according to a conventional method.

  And generally used emulsifiers, dispersants, polymerization initiators, polymerization aids and the like used for the polymerization can be used, and the amount used is also generally used. In the polymerization, seed polymerization may be performed using seed particles. The polymerization conditions can also be arbitrarily selected depending on the polymerization method and the type of polymerization initiator.

Here, the aqueous dispersion of particles of the particulate polymer (A) obtained by the polymerization method described above is, for example, alkali metal (for example, Li, Na, K, Rb, Cs) hydroxide, ammonia, inorganic ammonium. Using a basic aqueous solution containing a compound (for example, NH ₄ Cl), an organic amine compound (for example, ethanolamine, diethylamine), etc., the pH is usually 5 or more, usually 10 or less, preferably 9 or less. You may adjust as follows. Of these, pH adjustment with an alkali metal hydroxide is preferable because it improves the adhesion between the current collector and the electrode mixture layer.

[Properties of particulate polymer (A)]
Hereinafter, the properties of the particulate polymer (A) used in the present invention will be described in detail.

[[Surface acid amount]]
In the present invention, the surface acid amount of the particulate polymer (A) refers to the surface acid amount per 1 g of the solid content of the particulate polymer (A). Here, the surface acid amount of the particulate polymer (A) can be calculated by the following method.

First, an aqueous dispersion (solid content concentration 2%) containing the particulate polymer (A) is prepared. In a glass container having a capacity of 150 ml washed with distilled water, 50 g of the aqueous dispersion containing the particulate polymer (A) is placed, and set in a solution conductivity meter and stirred. Stirring is continued until addition of hydrochloric acid described later is completed.
An aqueous 0.1N sodium hydroxide solution was added to the aqueous dispersion containing the particulate polymer so that the electrical conductivity of the aqueous dispersion containing the particulate polymer (A) was 2.5 to 3.0 mS. Added. Thereafter, after 5 minutes, the electrical conductivity is measured. This value is the electrical conductivity at the start of measurement.
Further, 0.5 ml of 0.1 N hydrochloric acid is added to the aqueous dispersion containing the particulate polymer (A), and the electrical conductivity is measured after 30 seconds. Thereafter, 0.5 ml of 0.1 N hydrochloric acid is added again, and the electrical conductivity is measured after 30 seconds. This operation is repeated at intervals of 30 seconds until the electrical conductivity of the aqueous dispersion containing the particulate polymer (A) becomes equal to or higher than the electrical conductivity at the start of measurement.
The obtained electric conductivity data is plotted on a graph with the electric conductivity (unit “mS”) on the vertical axis (Y coordinate axis) and the cumulative amount of added hydrochloric acid (unit “mmol”) on the horizontal axis (X coordinate axis). Plot. As a result, a hydrochloric acid amount-electric conductivity curve having three inflection points as shown in FIG. 1 is obtained. The X coordinate of the three inflection points and the X coordinate at the end of the addition of hydrochloric acid are P1, P2, P3, and P4 in order from the smallest value. X-coordinates are approximate straight lines by the least squares method for the data in the four sections, from zero to coordinate P1, from coordinate P1 to coordinate P2, from coordinate P2 to coordinate P3, and from coordinate P3 to coordinate P4. L1, L2, L3 and L4 are obtained. The X coordinate of the intersection of the approximate line L1 and the approximate line L2 is A1 (mmol), the X coordinate of the intersection of the approximate line L2 and the approximate line L3 is A2 (mmol), and the X point of the intersection of the approximate line L3 and the approximate line L4 The coordinates are A3 (mmol).
The surface acid amount per 1 g of the particulate polymer (A) is given as a value (mmol / g) in terms of hydrochloric acid from the following formula (a). The amount of acid in the aqueous phase per gram of the particulate polymer (A) (the amount of acid present in the aqueous phase in the aqueous dispersion containing the particulate polymer per gram of solid content of the particulate polymer) The acid amount of the polymer (also referred to as “the acid amount in the aqueous phase of the particulate polymer (A)”) is given as a value (mmol / g) converted to hydrochloric acid from the following formula (b). Further, the total acid amount per 1 g of the particulate polymer (A) dispersed in water is the sum of the formula (a) and the formula (b) as represented by the following formula (c).
(A) Particulate polymer (A) Surface acid amount per gram = A2-A1
(B) Particulate polymer (A) Acid amount in aqueous phase per gram = A3-A2
(C) Total amount of acid groups per 1 g of particulate polymer (A) dispersed in water = A3-A1

The surface acid amount of the particulate polymer (A) is preferably 0.01 mmol / g or more, more preferably 0.05 mmol / g or more, particularly preferably 0.1 mmol / g or more, preferably 1.0 mmol / g. g or less, more preferably 0.5 mmol / g or less, further preferably 0.38 mmol / g or less, even more preferably 0.3 mmol / g or less, and particularly preferably 0.2 mmol / g or less.
When the surface acid amount is 0.01 mmol / g or more, the wettability of the particulate polymer (A) with respect to water is improved, whereby the particulate polymer (A) is more suitably dispersed in water. Thus, the storage stability of the slurry composition is improved. In addition, the wettability of the particulate polymer (A) improves the applicability of the slurry composition and makes it possible to produce an electrode mixture layer with fewer defects, thus improving the low-temperature output characteristics of the secondary battery. be able to. In addition, when the surface acid amount of the particulate polymer (A) is 0.01 mmol / g or more, the surface tension of the aqueous dispersion containing the particulate polymer is lowered, and the aqueous dispersion containing the particulate polymer. The wettability with respect to the electrode active material and the current collector can be improved. For this reason, migration at the time of applying the slurry composition to the current collector is suppressed, the adhesion between the electrode mixture layer and the current collector can be enhanced, and the cycle characteristics of the secondary battery can be improved. it can.
On the other hand, when the surface acid amount of the particulate polymer (A) is 1.0 mmol / g or less, the adhesion between the electrode mixture layer and the current collector can be improved.

The surface acid amount of the particulate polymer (A) can be controlled, for example, by changing the type and ratio of the monomer units constituting the particulate polymer (A) and the polymerization method.
More specifically, for example, the amount of surface acid can be efficiently controlled by adjusting the type and ratio of the ethylenically unsaturated carboxylic acid monomer unit. Usually, among ethylenically unsaturated carboxylic acid monomers, the use of a monomer having a large number of carboxyl groups in one molecule (such as itaconic acid) tends to increase the surface acid amount.

[[Properties of other particulate polymer (A)]]
The metal component content (total of Na content and K content) of the particulate polymer (A) is preferably 10,000 ppm or less, more preferably 7000 ppm or less, and particularly preferably 5000 ppm or less. Since the content of the metal component in the particulate polymer (A) is 10000 ppm or less, in the secondary battery including the electrode using the particulate polymer (A), gas generation due to long-term storage is suppressed, The storage characteristics of the battery can be improved. Na and K are mixed by using a polymerization initiator containing them or using a base for adjusting the pH of the particulate polymer (A).
In addition, metal component content of a particulate polymer (A) can be measured using the measuring method as described in the Example of this specification.

  The number average particle diameter of the particulate polymer (A) is preferably 50 nm or more, more preferably 70 nm or more, preferably 500 nm or less, more preferably 400 nm or less. The standard deviation of the number average particle diameter is preferably 30 nm or less, more preferably 15 nm or less. When the number average particle diameter and the standard deviation are in the above ranges, the strength and flexibility of the obtained electrode can be improved. The number average particle diameter of the particulate polymer (A) can be easily measured by transmission electron microscopy. The particle size and its distribution can be controlled by the number of seed particles and their particle size.

<Hydrophilic organic fiber (B)>
The hydrophilic organic fiber (B) does not dissolve in the aqueous medium used as a dispersion medium in the binder composition or slurry composition of the present invention or the electrolyte solution of the secondary battery, and the shape thereof is also included in them. The fiber that is maintained. Further, since the hydrophilic organic fiber is electrochemically stable, it is stably present in the electrode mixture layer even during use of the secondary battery. In the present invention, “fiber” refers to a fiber having an aspect ratio of 10 or more measured with a scanning electron microscope. In the present invention, the hydrophilic organic fiber being “hydrophilic” means that the organic fiber has a functional group capable of forming a hydrogen bond. Examples of the functional group capable of forming a hydrogen bond in the hydrophilic organic fiber include a hydroxyl group, a carboxyl group, and an amino group.
And normally, when 25 g of the hydrophilic organic fiber (B) is dissolved in 100 g of water at 25 ° C., the insoluble content becomes 90% by mass or more.

  Specific hydrophilic organic fibers (B) include fibers composed of polysaccharides such as cellulose, chitin and chitosan, fibers composed of synthetic polymers having functional groups capable of forming hydrogen bonds (for example, polyester) Fiber, polyacrylonitrile fiber, polyaramid fiber, polyamideimide fiber, polyimide fiber, etc.). Cellulose contains at least a hydroxyl group as a functional group capable of forming a hydrogen bond, chitin contains at least a hydroxyl group as a functional group capable of forming a hydrogen bond, and chitosan has at least a hydroxyl group and an amino group as functional groups capable of forming a hydrogen bond. including. These may be used alone or in combination of two or more.

  From the viewpoint of improving the electrode mixture layer formed from the slurry composition, the slurry composition preferably has good thixotropy. For this reason, in the slurry composition, it is preferable that the hydrophilic organic fiber (B) forms a suitable pseudo-crosslinked structure with the particulate polymer (A). The hydrophilic organic fiber (B) is preferably an organic fiber having a hydroxyl group, and more preferably cellulose, in order to enhance the interaction with the particulate polymer (A).

The hydrophilic organic fiber (B) has an average fiber diameter of preferably 1 nm or more, more preferably 10 nm or more, particularly preferably 20 nm or more, preferably 1000 nm or less, more preferably 100 nm or less, and further preferably 70 nm. Hereinafter, it is particularly preferably 50 nm or less. When the average fiber diameter of the hydrophilic organic fibers (B) is 1 nm or more, the hydrophilic organic fibers (B) are less likely to aggregate, and the dispersibility of the fibers can be sufficiently secured, and the binder composition of the present invention. The storage stability of the slurry composition containing can be improved. On the other hand, even when the average fiber diameter of the hydrophilic organic fiber (B) is 1000 nm or less, the hydrophilic organic fiber (B) is not too thick, and the dispersibility of the fiber can be sufficiently secured, and the binder of the present invention. The storage stability of the slurry composition containing the composition can be improved. Furthermore, since the average fiber diameter of the hydrophilic organic fibers (B) is 1000 nm or less, the fibers are sufficiently loosened and excellent in dispersibility, so that the adhesion between the electrode mixture layer and the current collector can be improved. it can.
In the present invention, the “average fiber diameter” can be determined as an average value of the short diameters of 100 arbitrarily selected fibers measured using a scanning electron microscope.

The average fiber length of the hydrophilic organic fiber (B) is preferably 50 μm or more, more preferably 60 μm or more, particularly preferably 70 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, particularly preferably 200 μm or less. . When the average fiber length of the hydrophilic organic fiber (B) is 50 μm or more, the fiber has a sufficient length. Therefore, the particulate polymer (A) during drying of the slurry composition containing the binder composition of the present invention ) Can be suitably suppressed, and the adhesion between the electrode active material layer and the current collector can be improved. On the other hand, when the average fiber length of the hydrophilic organic fibers (B) is 1000 μm or less, the dispersibility of the fibers in the slurry composition containing the binder composition of the present invention is secured, and the storage stability of the slurry composition. Can be improved.
In the present invention, the “average fiber length” can be determined as an average value of the long diameters of 100 arbitrarily selected fibers measured using a scanning electron microscope.

  The aspect ratio (average fiber length / average fiber diameter) of the hydrophilic organic fiber (B) is preferably 100 or more, more preferably 500 or more, particularly preferably 1000 or more, preferably 10,000 or less, more preferably It is 7500 or less, particularly preferably 5000 or less. By setting the aspect ratio of the hydrophilic organic fiber (B) in the above-described range, the dispersibility of the fiber in the slurry composition is ensured, and the storage stability of the slurry composition can be improved.

  The binder composition of the present invention is required to contain 0.01 to 20 parts by mass of the hydrophilic organic fiber (B) per 100 parts by mass of the particulate polymer (A). 1 part by mass or more, more preferably 2 parts by mass or more, particularly preferably 5 parts by mass or more, preferably 15 parts by mass or less, more preferably 8 parts by mass or less, particularly preferably 7 parts by mass or less. In the binder composition, when the content of the hydrophilic organic fiber (B) is less than 0.01 parts by mass per 100 parts by mass of the particulate polymer (A), the slurry composition obtained using the binder composition Good thixotropy and the migration suppressing effect of the particulate polymer (A) cannot be obtained, and the adhesion between the electrode mixture layer and the current collector cannot be ensured. On the other hand, when the content of the hydrophilic organic fiber (B) exceeds 20 parts by mass per 100 parts by mass of the particulate polymer (A), the particulate polymer (A) aggregates together with the hydrophilic organic fiber (B). It becomes easy and the storage stability of a slurry composition cannot be ensured. Further, when the content of the hydrophilic organic fiber (B) exceeds 20 parts by mass per 100 parts by mass of the particulate polymer (A), the hydrophilic organic fiber (which has a lower binding force than the particle polymer (A)) ( As a result of the excessive amount of B), the adhesion strength between the electrode mixture layer and the current collector is lowered.

<Crosslinking agent (C)>
The binder composition of the present invention may contain a crosslinking agent (C) in order to improve the adhesion between the electrode mixture layer (particularly the negative electrode mixture layer) formed from the slurry composition containing the binder composition and the current collector. preferable. This is presumed to be because the particulate polymer (A) and the hydrophilic organic fiber (B) form a crosslinked structure by heating or the like by including the crosslinking agent (C).
That is, the slurry composition containing the binder composition of the present invention is subjected to a treatment such as heating for drying on a current collector, for example, so that the particulate polymer (A) contained in the slurry composition and The hydrophilic organic fiber (B) forms a crosslinked structure via the crosslinking agent (C). As a result, the elastic modulus, tensile rupture strength, stress due to cross-linking of the particulate polymer (A), the particulate polymer (A) and the hydrophilic organic fiber (B), and the hydrophilic organic fiber (B). A crosslinked structure having excellent mechanical properties such as relaxation, adhesiveness and low water solubility (that is, excellent water resistance) can be obtained. Therefore, if the slurry composition obtained by using the binder composition containing the crosslinking agent (C) is used for forming the electrode of the secondary battery, high adhesion between the electrode mixture layer and the current collector is ensured. It is inferred that

  Here, the cross-linking agent (C) is not particularly limited as long as it is a compound having a functional group that reacts with the particulate polymer (A) and the hydrophilic organic fiber (B), specifically the functional group contained therein. A compound having preferably 2 or more reactive functional groups in one molecule is preferable. Here, the reactive functional group in the crosslinking agent (C) is a functional group (hydroxyl group, carboxyl group, amino group, etc.) contained in the particulate polymer (A) and the hydrophilic organic fiber (B). It refers to a functional group that can react, and examples thereof include an epoxy group (including a glycidyl group and a glycidyl ether group), an oxazoline group, a carbodiimide group, and a hydroxyl group.

Specifically, as the crosslinking agent (C), for example, a polyfunctional epoxy compound having an epoxy group as a reactive functional group, an oxazoline compound having an oxazoline group as a reactive functional group, and a carbodiimide as a reactive functional group Examples thereof include carbodiimide compounds having a group.
Hereinafter, the polyfunctional epoxy compound, the oxazoline compound, and the carbodiimide compound will be described in detail.

[Polyfunctional epoxy compound]
The polyfunctional epoxy compound is a compound having two or more epoxy groups in one molecule. And as a polyfunctional epoxy compound, the compound which has the reactive functional group mentioned above preferably in less than 6, more preferably less than 4 in 1 molecule is preferred. The number of reactive functional groups in one molecule (the average value of the polyfunctional epoxy compound used as the crosslinking agent (C)) is within the above range, thereby preventing sedimentation due to aggregation of each component, The storage stability of the slurry composition can be ensured.
In addition, as a polyfunctional epoxy compound, polyfunctional glycidyl ether compounds, such as aliphatic polyglycidyl ether, aromatic polyglycidyl ether, diglycidyl ether, are preferable, for example. A polyfunctional glycidyl ether compound having two or more glycidyl ether groups in one molecule is particularly excellent in affinity with an electrolytic solution. Therefore, when used as a crosslinking agent (C), a secondary battery is produced. This is because the pouring property of the electrolyte is particularly improved.

[Oxazoline compound]
The oxazoline compound has an oxazoline group in its molecule, and is between the particulate polymer (A), between the particulate polymer (A) and the hydrophilic organic fiber (B), and hydrophilic organic. There is no particular limitation as long as it is a crosslinkable compound that can form a crosslinked structure between fibers (B). And as an oxazoline compound, the compound which has 2 or more of oxazoline groups in a molecule | numerator is preferable, for example. In addition, some or all of the hydrogen atoms of the oxazoline group may be substituted with other groups. Examples of the compound having two or more oxazoline groups in the molecule include, for example, a compound having two oxazoline groups in the molecule (a divalent oxazoline compound), a polymer containing an oxazoline group (an oxazoline group-containing polymer) ).

[[Divalent Oxazoline Compound]]
Examples of the divalent oxazoline compound include 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), and 2,2′-bis (4,4-dimethyl). -2-oxazoline), 2,2′-bis (4-ethyl-2-oxazoline), 2,2′-bis (4,4′-diethyl-2-oxazoline), 2,2′-bis (4- Propyl-2-oxazoline), 2,2′-bis (4-butyl-2-oxazoline), 2,2′-bis (4-hexyl-2-oxazoline), 2,2′-bis (4-phenyl-) 2-oxazoline), 2,2′-bis (4-cyclohexyl-2-oxazoline), 2,2′-bis (4-benzyl-2-oxazoline) and the like. Among these, 2,2′-bis (2-oxazoline) is preferable from the viewpoint of forming a more rigid cross-linked structure.

[[Oxazoline group-containing polymer]]
The oxazoline group-containing polymer is not particularly limited as long as it is a polymer containing an oxazoline group. In the present specification, the above-mentioned divalent oxazoline compound is not included in the oxazoline group-containing polymer.
The oxazoline group-containing polymer can be synthesized, for example, by copolymerizing an oxazoline group-containing monomer represented by the following formula (I) with another monomer.

[式中、Ｒ¹、Ｒ²、Ｒ³およびＲ⁴は、それぞれ独立して、水素原子、ハロゲン原子、アルキル基、置換基を有していてもよいアリール基、または、置換基を有していてもよいアラルキル基を示し、Ｒ⁵は、付加重合性不飽和結合を有する非環状有機基を示す]

[Wherein, R ¹ , R ² , R ³ and R ⁴ each independently have a hydrogen atom, a halogen atom, an alkyl group, an aryl group which may have a substituent, or a substituent. An aralkyl group that may be present, and R ⁵ represents an acyclic organic group having an addition polymerizable unsaturated bond]

  In the formula (I), examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom and a chlorine atom are preferable.

  In the formula (I), examples of the alkyl group include alkyl groups having 1 to 8 carbon atoms. Among these, an alkyl group having 1 to 4 carbon atoms is preferable.

  In the formula (I), examples of the aryl group which may have a substituent include an aryl group which may have a substituent such as a halogen atom. Examples of the aryl group include aryl groups having 6 to 18 carbon atoms such as phenyl group, tolyl group, xylyl group, biphenyl group, naphthyl group, anthryl group, and phenanthryl group. And as an aryl group which may have a substituent, a C6-C12 aryl group which may have a substituent is preferable.

  In the formula (I), examples of the aralkyl group which may have a substituent include an aralkyl group which may have a substituent such as a halogen atom. Examples of the aralkyl group include aralkyl groups having 7 to 18 carbon atoms such as a benzyl group, a phenylethyl group, a methylbenzyl group, and a naphthylmethyl group. And as an aralkyl group which may have a substituent, the C7-C12 aralkyl group which may have a substituent is preferable.

  In the formula (I), examples of the acyclic organic group having an addition polymerizable unsaturated bond include alkenyl groups having 2 to 8 carbon atoms such as vinyl group, allyl group, isopropenyl group, and the like. Of these, vinyl group, allyl group and isopropenyl group are preferable.

  Examples of the oxazoline group-containing monomer represented by the formula (I) include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline. 2-vinyl-4-propyl-2-oxazoline, 2-vinyl-4-butyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-5-ethyl-2-oxazoline, 2 -Vinyl-5-propyl-2-oxazoline, 2-vinyl-5-butyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl- 4-ethyl-2-oxazoline, 2-isopropenyl-4-propyl-2-oxazoline, 2-isopropenyl-4-butyl-2-oxazoline 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-5-propyl-2-oxazoline, 2-isopropenyl-5-butyl-2 -Oxazoline and the like. Among these, 2-isopropenyl-2-oxazoline is preferable because it can be easily obtained industrially. One of these oxazoline group-containing monomers may be used alone, or two or more thereof may be used in combination at any ratio.

  The other monomer that can be used for the synthesis of the oxazoline group-containing polymer is not particularly limited as long as it is a known copolymerizable monomer. For example, a (meth) acrylic acid monomer, (meta ) Acrylic acid ester monomers and aromatic monomers are preferred.

[Carbodiimide compound]
The carbodiimide compound has a carbodiimide group represented by the general formula (1): —N═C═N— (1) in the molecule, and the particulate polymer (A) It will not specifically limit if it is a crosslinkable compound which can form a crosslinked structure between A) and hydrophilic organic fiber (B), and between hydrophilic organic fibers (B). And as such a crosslinking agent (C) having a carbodiimide group, for example, a compound having two or more carbodiimide groups, specifically, general formula (2): -N = C = N-R ^1. (2) [In the general formula (2), R ¹ represents a divalent organic group. Suitable examples include polycarbodiimides and / or modified polycarbodiimides having a repeating unit represented by the formula: In addition, in this specification, a modified polycarbodiimide means resin obtained by making the reactive compound mentioned later react with polycarbodiimide.

[[Synthesis of 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”). Polycarbodiimide can be synthesized. The polycarbodiimide having a repeating unit represented by the general formula (2) is a copolymer of an oligomer obtained by reacting an organic polyisocyanate (carbodiimide oligomer) and a monomer copolymerizable with the oligomer. Can also be synthesized.
In addition, as organic polyisocyanate used for the synthesis | combination of this polycarbodiimide, organic diisocyanate is preferable.

  Examples of the organic diisocyanate used for the synthesis of polycarbodiimide include those described in JP-A-2005-49370. Among these, 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are particularly preferable from the viewpoint of the storage stability of the binder composition and the slurry composition containing polycarbodiimide as the crosslinking agent (C). An organic diisocyanate may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In addition to the above organic diisocyanates, organic polyisocyanates having three or more isocyanate groups (trifunctional or higher functional organic polyisocyanates), and stoichiometric excesses of trifunctional or higher organic polyisocyanates and difunctional or higher polyfunctionality. Terminal isocyanate prepolymer obtained by reaction with a reactive active hydrogen-containing compound (hereinafter, the trifunctional or higher functional organic polyisocyanate and the terminal isocyanate prepolymer are collectively referred to as “trifunctional or higher functional organic polyisocyanates”). May be used. Examples of such trifunctional or higher functional organic polyisocyanates include those described in JP-A-2005-49370. Trifunctional or higher functional organic polyisocyanates may be used alone or in combination of two or more at any ratio. The amount of the tri- or higher functional organic polyisocyanate used in the polycarbodiimide synthesis reaction is usually 40 parts by mass or less, preferably 20 parts by mass or less, per 100 parts by mass of the organic diisocyanate.

  Furthermore, in the synthesis of polycarbodiimide, an organic monoisocyanate can be added as necessary. By adding an organic monoisocyanate, when the organic polyisocyanate contains organic polyisocyanates having a functionality of 3 or more, the molecular weight of the resulting polycarbodiimide can be appropriately regulated, and the organic diisocyanate is used in combination with the organic monoisocyanate. By doing so, a polycarbodiimide having a relatively small molecular weight can be obtained. Examples of such organic monoisocyanates include those described in JP-A-2005-49370. An organic monoisocyanate may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The amount of the organic monoisocyanate used in the synthesis reaction of the polycarbodiimide depends on the molecular weight required for the polycarbodiimide to be obtained and the presence or absence of the use of trifunctional or higher functional organic polyisocyanates. It is usually 40 parts by mass or less, preferably 20 parts by mass or less per 100 parts by mass of the functional or higher organic polyisocyanate) component.

  Examples of the carbodiimidization catalyst include phospholene compounds, metal carbonyl complexes, metal acetylacetone complexes, and phosphate esters. Specific examples of these are disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-49370. A carbodiimidization catalyst may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The amount of the carbodiimidization catalyst is usually 0.001 part by mass or more, preferably 0.01 per 100 parts by mass of the total organic isocyanate (organic monoisocyanate, organic diisocyanate, and trifunctional or higher functional organic polyisocyanate) component. It is at least 30 parts by mass, preferably at most 10 parts by mass.

  The carbodiimidization reaction of the organic polyisocyanate can be carried out in the absence of a solvent or in a suitable solvent. The solvent for carrying out the synthesis reaction in the solvent is not particularly limited as long as it can dissolve the polycarbodiimide or carbodiimide oligomer generated by heating during the synthesis reaction, and is a halogenated hydrocarbon solvent, ether solvent. , Ketone solvents, aromatic hydrocarbon solvents, amide solvents, aprotic polar solvents, and acetate solvents. Specific examples of these are disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-49370. These solvents may be used alone or in combination of two or more at any ratio. The amount of the solvent used in the polycarbodiimide synthesis reaction is such that the concentration of the total organic isocyanate component is usually 0.5% by mass or more, preferably 5% by mass or more, and usually 60% by mass or less, preferably The amount is 50% by mass or less. If the concentration of the total organic isocyanate component in the solvent is too high, the polycarbodiimide or carbodiimide oligomer produced may gel during the synthesis reaction, and if the concentration of the total organic isocyanate component in the solvent is too low, the reaction will occur. The speed is slow and productivity is reduced.

  The temperature of the carbodiimidization reaction of the organic polyisocyanate is appropriately selected according to the type of the organic isocyanate component and the carbodiimidization catalyst, but is usually 20 ° C. or higher and 200 ° C. or lower. In the carbodiimidization reaction of the organic polyisocyanate, the organic isocyanate component may be added in the whole amount before the reaction, or a part or the whole thereof may be added continuously or stepwise during the reaction. Further, in the present invention, a compound capable of reacting with an isocyanate group is added at an appropriate reaction stage from the initial stage to the late stage of the carbodiimidization reaction of the organic polyisocyanate, and the terminal isocyanate group of the polycarbodiimide is sealed. The molecular weight of the polycarbodiimide can also be adjusted. Further, the molecular weight of the resulting polycarbodiimide can be regulated to a predetermined value by adding in the latter stage of the carbodiimidization reaction of the organic polyisocyanate. Examples of such a compound that can react with an isocyanate group include alcohols such as methanol, ethanol, i-propanol, and cyclohexanol; and amines such as dimethylamine, diethylamine, and benzylamine.

Moreover, as a monomer copolymerizable with a carbodiimide oligomer, an oligomer obtained by using a dihydric or higher alcohol, a dihydric or higher alcohol as a monomer, and an ester thereof, for example, 2 such as ethylene glycol and propylene glycol A hydric alcohol, polyalkylene oxide, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol monoacrylate, or polypropylene glycol monoacrylate is preferred.
For example, polycarbodiimide having a polycarbodiimide group and a monomer unit derived from a divalent alcohol is synthesized by copolymerizing a divalent alcohol having a hydroxyl group at both ends of the molecular chain with a carbodiimide oligomer by a known method. can do. Thus, when the polycarbodiimide as the crosslinking agent (C) has a divalent or higher alcohol-derived monomer unit, preferably a divalent alcohol-derived monomer unit, the binder composition containing the polycarbodiimide. The wettability with respect to the electrolyte solution of the electrode formed from the slurry composition using this can be improved, and the injection property of the electrolyte solution in the production of the secondary battery including the negative electrode can be improved. In addition, when the above-mentioned alcohol is copolymerized, the water solubility of the polycarbodiimide can be increased, and the polycarbodiimide is self-micelleized in water (the hydrophobic carbodiimide group is covered with a hydrophilic ethylene glycol chain). Therefore, chemical stability can be improved.

  The above-described polycarbodiimide is used for preparing the binder composition of the present invention as a solution or as a solid separated from the solution. As a method for separating polycarbodiimide from a solution, for example, a polycarbodiimide solution is added to a non-solvent inert to the polycarbodiimide, and the resulting precipitate or oil is separated and collected by filtration or decantation. A method of separating and collecting by spray drying; a method of separating and collecting by using a change in solubility with respect to the temperature of the solvent used in the synthesis of the obtained polycarbodiimide, that is, immediately after the synthesis, the solvent is dissolved in the solvent In the case where polycarbodiimide is precipitated by lowering the temperature of the system, a method of separating and collecting from the turbid liquid by filtration or the like can be exemplified, and further, these separation and collecting methods can be appropriately combined. The number average molecular weight in terms of polystyrene (hereinafter referred to as “Mn”) determined by gel permeation chromatography (GPC) of polycarbodiimide in the present invention is usually 400 or more, preferably 1,000 or more, particularly preferably 2, 000 or more, and usually 500,000 or less, preferably 200,000 or less, particularly preferably 100,000 or less.

[[Synthesis of modified polycarbodiimide]]
Next, a method for synthesizing the modified polycarbodiimide will be described. The modified polycarbodiimide is prepared by adding at least one reactive compound to at least one polycarbodiimide having a repeating unit represented by the general formula (2) at an appropriate temperature in the presence or absence of a suitable catalyst. It can be synthesized by reaction (hereinafter referred to as “denaturation reaction”).

  The reactive compound used for the synthesis of the modified polycarbodiimide has one group having reactivity with the polycarbodiimide (hereinafter, simply referred to as “reactive group”) in the molecule, and another functional group. The compound which has. This reactive compound can be an aromatic compound, an aliphatic compound or an alicyclic compound, and the ring structure in the aromatic compound and the alicyclic compound may be a carbocyclic ring or a heterocyclic ring. The reactive group in the reactive compound may be a group having active hydrogen, and examples thereof include a carboxyl group or a primary or secondary amino group. And a reactive compound has another functional group in addition to one reactive group in the molecule | numerator. Other functional groups possessed by the reactive compound include groups having an action of promoting the crosslinking reaction of polycarbodiimide and / or modified polycarbodiimide, and the second and subsequent groups in one molecule of the reactive compound (that is, as described above). In addition to reactive groups, the above-mentioned groups having active hydrogen are also included. For example, carboxyl groups and primary groups exemplified as groups having active hydrogen in addition to carboxylic anhydride groups and tertiary amino groups. Or a secondary amino group etc. can be mentioned. As these other functional groups, two or more identical or different groups may exist in one molecule of the reactive compound.

  Examples of the reactive compound include those described in JP-A-2005-49370. Of these, trimellitic anhydride and nicotinic acid are preferable. A reactive compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The amount of the reactive compound used in the modification reaction for synthesizing the modified polycarbodiimide is appropriately adjusted according to the type of polycarbodiimide and reactive compound, the physical properties required of the resulting modified polycarbodiimide, etc. The ratio of the reactive group in the reactive compound to 1 mol of the repeating unit represented by the general formula (2) is preferably 0.01 mol or more, more preferably 0.02 mol or more, preferably The amount is 1 mol or less, more preferably 0.8 mol or less. There exists a possibility that the storage stability of the slurry composition containing a modified polycarbodiimide may fall that the said ratio is less than 0.01 mol. On the other hand, when the ratio exceeds 1 mol, the original properties of polycarbodiimide may be impaired.

  In the modification reaction, the reaction between the reactive group in the reactive compound and the repeating unit represented by the general formula (2) of the polycarbodiimide proceeds quantitatively, and the functionality corresponding to the amount of the reactive compound used. Groups are introduced into the modified polycarbodiimide. The modification reaction can be carried out in the absence of a solvent, but is preferably carried out in a suitable solvent. Such a solvent is not particularly limited as long as it is inactive with respect to polycarbodiimide and a reactive compound and can dissolve them. Examples thereof are used for the synthesis of the above-mentioned polycarbodiimide. And ether solvents, amide solvents, ketone solvents, aromatic hydrocarbon solvents, aprotic polar solvents, and the like. These solvents may be used alone or in combination of two or more at any ratio. Moreover, when the solvent used at the time of the synthesis | combination of polycarbodiimide can be used for modification | denaturation reaction, the polycarbodiimide solution obtained by the synthesis | combination can also be used as it is. The amount of the solvent used in the modification reaction is usually 10 parts by mass or more, preferably 50 parts by mass or more, and usually 10,000 parts by mass or less, preferably 5,000 parts by mass, per 100 parts by mass of the reaction raw materials. It is as follows. The temperature of the modification reaction is appropriately selected according to the type of polycarbodiimide or reactive compound, but is usually -10 ° C or higher, usually 100 ° C or lower, preferably 80 ° C or lower. The Mn of the modified polycarbodiimide in the present invention is usually 500 or more, preferably 1,000 or more, more preferably 2,000 or more, and usually 1,000,000 or less, preferably 400,000 or less, more preferably. Is 200,000 or less.

[Properties of cross-linking agent (C), etc.]
Here, the crosslinking agent (C) is preferably water-soluble. The water-soluble cross-linking agent (C) prevents the cross-linking agent (C) from being unevenly distributed in the aqueous binder composition or slurry composition, and the resulting electrode mixture layer forms a suitable cross-linked structure. Can be. Therefore, it is possible to ensure the adhesion between the electrode mixture layer and the current collector in the obtained secondary battery, and to improve the water resistance and electrical characteristics (initial Coulomb efficiency, initial resistance, cycle characteristics, etc.) of the electrode. it can.

  Here, in the present specification, the term “water-soluble” means that the crosslinking agent (C) is a mixture obtained by adding 1 part by mass of a crosslinking agent (corresponding to solid content) per 100 parts by mass of ion-exchanged water and stirring. Is adjusted to at least one of the conditions within the range of temperature 20 ° C. or higher and 70 ° C. or lower and pH 3 or higher and 12 or lower (using NaOH aqueous solution and / or HCl aqueous solution for pH adjustment), 250 When passing through a mesh screen, the solid content of the residue remaining on the screen without passing through the screen does not exceed 50 mass% with respect to the solid content of the added crosslinking agent. In addition, even if the mixture of the said crosslinking agent and water is the emulsion state which isolate | separates into two phases, when left still, if the said definition is satisfy | filled, the crosslinking agent shall be water-soluble. The mixture of the crosslinking agent and water does not separate into two phases from the viewpoint of favorably proceeding the formation reaction of the crosslinked structure and improving the adhesion between the electrode mixture layer and the current collector (one phase More preferably, the crosslinking agent is water soluble in one phase.

Moreover, 80 mass% or more is preferable and 90 mass% or more is more preferable for the reason similar to the reason why it is preferable that the crosslinking agent is water-soluble as described above. The “water solubility” of the cross-linking agent (C) means that 1 part by mass of the cross-linking agent (corresponding to the solid content) is added per 100 parts by mass of ion-exchanged water, and the mixture obtained by stirring is adjusted to 25 ° C. and pH 7. When the ratio of the solid content of the residue remaining on the screen without passing through the screen to the mass of the solid content of the added crosslinking agent is X mass% It is defined by the formula of
Water solubility = (100−X) mass%

In the binder composition of the present invention, the crosslinking agent (C) is preferably at least one selected from the group consisting of polyfunctional epoxy compounds, oxazoline compounds, and carbodiimide compounds, more preferably carbodiimide compounds, and water-soluble carbodiimides. Compounds are particularly preferred. Since the carbodiimide compound is excellent in thermal stability as compared with the polyfunctional epoxy compound or oxazoline compound, the storage stability of the binder composition or slurry composition of the present invention can be improved by using the carbodiimide compound as the crosslinking agent (C). It can be excellent. In addition, the carbodiimide compound is less likely to be lost by reacting with water during the preparation of a binder composition or a slurry composition because of its excellent thermal stability, and the resulting electrode mixture layer and current collector It is possible to improve the adhesion.
In addition, by using the water-soluble carbodiimide compound, as described above, the water-soluble carbodiimide compound as the crosslinking agent (C) is prevented from being unevenly distributed in the water-based binder composition or slurry composition, and the electrode mixture layer And the current collector can be further improved.

  In the binder composition of the present invention, the crosslinking agent (C) is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and still more preferably 0.000 part by mass per 100 parts by mass of the particulate polymer (A). 5 parts by mass or more, particularly preferably 5 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, particularly preferably 10 parts by mass or less. In the binder composition, the content of the crosslinking agent (C) is 0.001 part by mass or more per part by mass of the particulate polymer (A), so that the electrode mixture formed from the slurry composition containing the binder composition The adhesion between the layer and the current collector can be improved, and when it is 20 parts by mass or less, the storage stability and thixotropy of the slurry composition can be ensured.

<Preparation of binder composition>
The binder composition of the present invention has, for example, the hydrophilic organic fiber (B), water, and the effect of the invention with respect to the aqueous dispersion of the particulate polymer (A) obtained by polymerizing the monomer composition. It can be prepared by adding any other component such as the above-mentioned cross-linking agent (C) within a range not to be damaged.

(Slurry composition for secondary battery electrode)
The slurry composition for secondary battery electrodes of the present invention contains a particulate polymer (A), a hydrophilic organic fiber (B), an electrode active material, and water. And the slurry composition for secondary battery electrodes of this invention contains 0.01 mass part or more and 20 mass parts or less of hydrophilic organic fiber (B) per 100 mass parts of particulate polymer (A). And the slurry composition for secondary battery electrodes of this invention is excellent in thixotropy, and according to this slurry composition, it suppresses the migration of a particulate polymer (A) and is excellent in adhesiveness with a collector. An electrode mixture layer can be formed.
Here, the particulate polymer (A), the hydrophilic organic fiber (B), and the optional cross-linking agent (C) contained in the slurry composition for a secondary battery electrode of the present invention are each of the above-mentioned two of the present invention. The thing similar to what was described in the term of the binder composition for secondary battery electrodes can be used in the same mixture ratio.

<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 .
The transition metal sulfide, TiS _2, TiS _3, such as an amorphous MoS _2, FeS, and the like.
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 examples of the lithium-containing composite oxide of Co—Ni—Mn include Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ and Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ . 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+. Represent. 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) × (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-t Mc} 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. 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 type 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.

Among these, from the viewpoint of increasing the capacity of the lithium ion secondary battery, LiMn ₂ O ₄ , LiNiO ₂ , Co—Ni—Mn lithium-containing composite oxide (Li (Co Mn Ni) O ₂ ), olivine type Lithium iron phosphate (LiFePO ₄ ), olivine-type lithium manganese phosphate (LiMnPO ₄ ), lithium-rich spinel compound, Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ , LiNi _0.5 Mn _1.5 O _4, etc. It is preferable to use it as a substance, olivine-type lithium iron phosphate (LiFePO ₄ ), Co—Ni—Mn lithium-containing composite oxide (Li (Co Mn Ni) O ₂ ), Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 It is more preferable to use O ₂ and a spinel compound containing excess lithium as the positive electrode active material. In addition, from the viewpoint of the output characteristics and high-temperature cycle characteristics of the lithium ion secondary battery, a lithium-containing composite oxide (Li (Co ₂ Mn Ni) O ₂ ) of Co—Ni—Mn is particularly preferable.

  Here, the compounding amount and particle size of the positive electrode active material are not particularly limited, and can be the same as those of conventionally used positive electrode active materials.

[Negative electrode active material]
As a negative electrode active material mix | blended with the slurry composition of this invention, a well-known negative electrode active material can be used, without being specifically limited. And as a negative electrode active material of a lithium ion secondary battery, the substance which can occlude and discharge | release lithium is used normally. Examples of the material that can occlude and release lithium 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 materials.

[[Carbon-based negative electrode active material]]
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-graphitic 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.

[[Metal negative electrode active material]]
The metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of inserting lithium in the structure, and the theoretical electric capacity per unit mass when lithium is inserted is 500 mAh / g or more. Is an active material. 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 metal-based negative electrode active materials, 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 silicon-based negative electrode active materials include silicon (Si), alloys containing silicon, SiO, SiO _x , and a composite of a Si-containing material obtained by coating or combining a Si-containing material with conductive carbon and 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 can be prepared by heat-treating SiO, optionally in the presence of a polymer such as polyvinyl alcohol, to produce silicon and silicon dioxide. 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.

  Here, the particle size and specific surface area of the negative electrode active material are not particularly limited, and can be the same as those of conventionally used negative electrode active materials.

  The slurry composition of the present invention is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, particularly preferably 1 part by mass of the particulate polymer (A) per 100 parts by mass of the electrode active material. The content is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, and particularly preferably 2 parts by mass or less. By setting the content of the particulate polymer (A) to 0.2 parts by mass or more per 100 parts by mass of the electrode active material, the binding properties with the electrode active material and the current collector can be enhanced. Moreover, when the electrode obtained by using the slurry composition of the present invention is applied to a secondary battery by adjusting the amount to 10 parts by mass or less, the charge carrier (lithium ion secondary battery of the lithium ion secondary battery) by the particulate polymer (A) is applied. In this case, inhibition of movement of lithium ions) can be suppressed, and the internal resistance of the secondary battery can be reduced.

<Water-soluble thickener (D)>
The slurry composition of the present invention preferably contains a water-soluble thickener (D). If the slurry composition contains a water-soluble thickener (D), excellent storage stability of the slurry composition can be obtained, and workability when applying the slurry composition on a current collector is good. Become.
Here, in the present invention, the thickener is “water-soluble” means that a mixture obtained by adding 1 part by weight (corresponding to solid content) of the water-soluble thickener (D) per 100 parts by weight of ion-exchanged water and stirring. Is adjusted to at least one of the conditions within a temperature range of 20 ° C. to 70 ° C. and within a range of pH 3 to 12 (pH adjustment uses NaOH aqueous solution and / or HCl aqueous solution), When passing through a 250-mesh screen, the solid content of the residue remaining on the screen without passing through the screen does not exceed 50 mass% with respect to the solid content of the added thickener. In addition, even if the mixture of the said thickener and water is an emulsion state which isolate | separates into two phases when it leaves still, if the said definition is satisfy | filled, the thickener shall be water-soluble.

  Although it does not specifically limit as water-soluble thickener (D), In order to make workability | operativity at the time of apply | coating a slurry composition on a collector etc. favorable, for example, carboxymethylcellulose, methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl Methyl cellulose, polyvinyl alcohol, polycarboxylic acid, salts thereof, and the like can be used. Examples of the polycarboxylic acid include polyacrylic acid, polymethacrylic acid, and alginic acid. One of these water-soluble thickeners (D) may be used alone, or two or more thereof may be used in combination at any ratio. Among these, carboxymethyl cellulose, polyacrylic acid, or a salt thereof is preferable in order to further improve workability when applied on the current collector of the slurry composition. Furthermore, in order to ensure adhesion between the electrode active material layer and the current collector, the slurry composition of the present invention contains carboxymethyl cellulose or a salt thereof (hereinafter sometimes abbreviated as “carboxymethyl cellulose (salt)”). Is preferred. In addition, the water-soluble thickener mentioned here has water solubility, and is clearly different from the hydrophilic organic fiber (B) which does not have water solubility.

  In the slurry composition of the present invention, the water-soluble thickener (D) is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, particularly preferably 0.5 parts per 100 parts by mass of the electrode active material. It is contained in an amount of at least part by mass, preferably at most 20 parts by mass, more preferably at most 10 parts by mass, particularly preferably at most 5 parts by mass. By setting the blending amount of the water-soluble thickener (D) within the above range, the slurry composition is applied on a current collector or the like with an appropriate viscosity at the high step of the slurry composition. The workability at the time can be improved.

  The slurry composition of the present invention is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and particularly preferably 50 parts by mass of the water-soluble thickener (D) per 100 parts by mass of the particulate polymer (A). It contains above, Preferably it is 200 mass parts or less, More preferably, it is 150 mass parts or less, Most preferably, it contains 100 mass parts or less. By setting the blending amount of the water-soluble thickener (D) within the above range, the slurry composition is applied on a current collector or the like with an appropriate viscosity at the high step of the slurry composition. The workability at the time can be improved.

<Other ingredients>
The slurry composition for a secondary battery electrode of the present invention may contain components such as a conductive material, a reinforcing material, a leveling agent, and an electrolytic solution additive in addition to the above components. In addition, when the slurry composition for secondary battery electrodes of this invention is a slurry composition for secondary battery positive electrodes, it is preferable that this slurry composition contains electrically conductive materials, such as acetylene black.
These other components are not particularly limited as long as they do not affect the battery reaction, and known ones such as those described in International Publication Nos. 2012/115096 and 2012-204303 may be used. it can. 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 arbitrarily premixing each of the above components and then dispersing it in an aqueous medium as a dispersion medium, or the particulate polymer (A) and hydrophilic After preparing a binder composition containing organic fiber (B) and water, in an aqueous medium using the binder composition, an electrode active material, and optionally a water-soluble thickener (D) as a dispersion medium It is also possible to prepare it by dispersing it in In order to facilitate production, the slurry composition of the present invention is prepared after preparing a binder composition containing a particulate polymer (A), a hydrophilic organic fiber (B), and water. You may prepare by disperse | distributing a binder composition, an electrode active material, etc. in the aqueous medium as a dispersion medium. Specifically, water dispersion of the particulate polymer (A) using a mixer such as a ball mill, a sand mill, a bead mill, a pigment disperser, a grinder, an ultrasonic disperser, a homogenizer, a planetary mixer, and a fill mix. After preparing a binder composition by mixing the liquid and the hydrophilic organic fiber (B), it is preferable to prepare a slurry composition by further adding and mixing an electrode active material and optionally an aqueous medium.
Here, water is usually used as the aqueous medium, 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. The solid content concentration of the slurry composition is a concentration at which each component can be uniformly dispersed, for example, 30% by mass to 90% by mass, and more preferably 40% by mass to 80% by mass. Can do. Furthermore, the mixing of each of the above components and the aqueous medium can usually be carried out in the range of room temperature to 80 ° C. for 10 minutes to several hours.

(Electrode for secondary battery)
The secondary battery electrode of the present invention can be produced using the secondary battery electrode slurry composition of the present invention.
And the electrode for secondary batteries of this invention is equipped with the electrical power collector and the electrode compound-material layer formed on the collector, and an electrode compound-material layer is a slurry composition for secondary battery electrodes of this invention. Obtained from. The electrode for a secondary battery of the present invention is excellent in the adhesion between the electrode mixture layer and the current collector.

  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. It is manufactured through a step of drying the electrode slurry composition to form an electrode mixture layer on the current collector (drying step) and, optionally, a step of further heating the electrode mixture layer (heating step). . When the slurry composition contains the crosslinking agent (C), for example, the crosslinking reaction via the crosslinking agent (C) proceeds by the heat applied in the drying process or the heat applied in the heating process. That is, a crosslinked structure in which the particulate polymer (A), the hydrophilic organic fiber (B), and any water-soluble thickener (D) are connected by the crosslinking agent (C) is formed in the electrode mixture layer. In addition, this cross-linked structure can improve the adhesion between the electrode mixture layer and the current collector. In addition, this cross-linked structure can improve the electrical characteristics of the secondary battery such as cycle characteristics.

[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. Among them, an aluminum foil (aluminum) is particularly preferable as the current collector used for the positive electrode, and a copper foil is particularly preferable as the current collector used for the negative electrode. 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. A drying method is mentioned. By drying the slurry composition on the current collector in this way, an electrode mixture layer is formed on the current collector, and a secondary battery electrode including the current collector and the electrode mixture layer can be obtained. it can. In addition, when a slurry composition contains a crosslinking agent (C), the crosslinking reaction through a crosslinking agent (C) advances with the heat | fever added at the time of drying of a slurry composition.

Note that after the drying step, the electrode mixture layer may be subjected to pressure treatment using a die press or a roll press. By the pressure treatment, the adhesion between the electrode mixture layer and the current collector can be improved.
Moreover, when a slurry composition contains a crosslinking agent (C), after formation of an electrode compound-material layer, it is preferable to implement a heating process and to advance a crosslinking reaction, and to make a crosslinked structure further sufficient. The heating step is preferably performed at 80 ° C. to 160 ° C. for about 1 hour to 20 hours.

(Secondary battery)
The secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and at least one of the positive electrode and the negative electrode is the electrode for the secondary battery of the present invention, and the electrode mixture layer and the current collector in the electrode Excellent adhesion. Moreover, since the secondary battery of this invention is equipped with the electrode for secondary batteries of this invention, it is excellent in electrical characteristics, such as a cycle characteristic.

<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 secondary battery of the present invention may be the electrode of the present invention and the negative electrode may be another known negative electrode, and the negative electrode of the secondary battery of the present invention is the electrode of the present invention and the positive electrode may be another known negative electrode. The positive electrode and the negative electrode of the secondary battery of the present invention may be both electrodes of the present invention.

<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, as the solvent, for example, when the secondary battery is a lithium ion secondary battery, an alkyl carbonate solvent such as ethylene carbonate, propylene carbonate, γ-butyrolactone, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, diethyl What added viscosity adjusting solvents, such as carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl acetate, dimethoxyethane, dioxolane, methyl propionate, methyl formate, can be used.
As the electrolyte, for example, when the secondary battery is a lithium ion secondary battery, a lithium salt can be used. 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 because they are easily dissolved in an organic solvent and exhibit a high degree of dissociation.

<Separator>
As the separator, for example, when the secondary battery is a lithium ion secondary battery, those described in JP 2012-204303 A can be used. 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.

<Method for producing secondary battery>
The secondary battery of the present invention includes, for example, a positive electrode and a negative electrode that are stacked with a separator interposed between them, wound as necessary according to the shape of the battery, folded into a battery container, and electrolyzed in the battery container. It can be manufactured by injecting and sealing the liquid. In order to prevent the occurrence of pressure increase and overcharge / discharge in the secondary battery, an overcurrent prevention element such as a fuse and a PTC element, an expanded metal, a lead plate, and the like may be provided as necessary. The shape of the secondary battery may be any of, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, and a flat shape.

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.
The surface acid amount of the particulate polymer was calculated and measured by the method described above. In the measurement of the amount of surface acid, a solution conductivity meter (manufactured by Kyoto Electronics Industry Co., Ltd .: CM-117, used cell type: K-121), 0.1 N sodium hydroxide and 0 As the 1N hydrochloric acid, Wako Pure Chemicals: Special grade reagent was used. Moreover, the average fiber diameter and average fiber length of the hydrophilic organic fiber, and the Na content and K content of the particulate polymer were measured by the following methods, respectively.
The storage stability of the slurry composition, the thixotropy of the slurry composition, and the adhesion strength between the negative electrode composite material layer and the current collector were evaluated using the following methods.

<Average fiber diameter and average fiber length of hydrophilic organic fiber>
The average fiber diameter and the average fiber length of the hydrophilic organic fibers were measured using a scanning electron microscope (S-2400, manufactured by Hitachi, Ltd.).
<Na content and K content of particulate polymer>
The particulate polymer was weighed into a platinum crucible, overheated and incinerated with a burner, and then heat incinerated with an electric furnace. The obtained ashed product was decomposed by heating with sulfuric acid and nitric acid and dissolved by heating with dilute nitric acid to obtain a constant volume. For this solution, the Na and K contents were measured by ICP emission spectroscopy, and the Na content (ppm) and K content (ppm) relative to the solid content of the particulate polymer were calculated. As an ICP emission spectroscopic analyzer, SPS4000 manufactured by SII Nanotechnology Inc. was used.
<Storage stability of slurry composition>
The prepared slurry composition was allowed to stand at room temperature, and then the initial viscosity (η0) was measured with a B-type viscometer (rotation speed: 60 rpm). And after initial viscosity measurement, it was left still at room temperature for 24 hours, and the viscosity ((eta) 1) after 24 hours passed was measured similarly.
The degree of viscosity change was calculated by (| η0−η1 |) / η1 × 100 (%) and evaluated according to the following criteria. It shows that it is excellent in storage stability, so that a viscosity change is small.
A: Viscosity change is less than 5.0% B: Viscosity change is 5.0% or more and less than 10.0% C: Viscosity change is 10.0% or more and less than 20.0% D: Viscosity change is 20.0% or more Less than 30.0% E: Viscosity change is 30.0% or more <Thixotropic properties of slurry composition>
About the prepared slurry composition, the viscosity ((eta) 6) in 6 rpm and the viscosity ((eta) 60) in 60 rpm were measured using the B-type viscosity meter under room temperature. The viscosity ratio (TI value) was calculated by η6 / η60 and evaluated according to the following criteria. It shows that it is excellent in thixotropy, so that TI value is large.
A: TI value is 3.0 or more B: TI value is less than 3.0 2.8 or more C: TI value is less than 2.8 2.6 or more D: TI value is less than 2.6 2.4 or more E: TI value is less than 2.4 <Adhesiveness between negative electrode composite material layer and current collector>
The produced negative electrode for a secondary battery was cut into a rectangular shape having a length of 100 mm and a width of 10 mm to obtain a test piece. The surface having the negative electrode mixture layer was face down, and a cellophane tape (specified in JIS Z1522) was formed on the surface of the negative electrode mixture layer. And a stress was measured when one end of the current collector was pulled in a 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 peeling peel strength, and the following references | standards evaluated. It shows that it is excellent in the adhesiveness of a negative mix layer and a collector, so that the value of peeling peel strength is large.
A: Peel peel strength is 5.0 N / m or more B: Peel peel strength is 4.5 N / m or more and less than 5.0 N / m C: Peel peel strength is 4.0 N / m or more and less than 4.5 N / m D: Peel peel strength is 3.0 N / m or more and less than 4.0 N / m E: Peel peel strength is less than 3.0 N / m

(Materials used)
In preparing the binder composition for secondary battery negative electrode and the slurry composition for secondary battery negative electrode in the following Examples and Comparative Examples, the following particulate polymer (A), hydrophilic organic fiber (B), and crosslinking agent are used. (C) and a water-soluble thickener (D) were used.
[Particulate polymer (A)]
As described below, the particulate polymer A1 and the particulate polymer A2 (both conjugated diene / aromatic vinyl copolymer having a carboxyl group + hydroxyl group) and the particulate polymer A3 (acrylic / non-acrylic having a carboxyl group) Saturated nitrile copolymer) was prepared.
(1) Particulate polymer A1:
In a 5 MPa pressure vessel with a stirrer, 65 parts of styrene (ST) as an aromatic vinyl monomer, 33 parts of 1,3-butadiene (BD) as an aliphatic conjugated diene monomer, and as an ethylenically unsaturated carboxylic acid monomer 1 part of itaconic acid (IA), 1 part of 2-hydroxyethyl acrylate (2-HEA) as an unsaturated monomer having a hydroxyl group, 0.3 part of t-dodecyl mercaptan as a molecular weight regulator, sodium dodecylbenzenesulfonate as an emulsifier 5 parts, 150 parts of ion-exchanged water as a solvent, and 1 part of potassium persulfate as a polymerization initiator were added and stirred sufficiently, and then heated to 55 ° C. to initiate polymerization.
When the monomer consumption reached 95.0%, the reaction was stopped by cooling. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. Then, the unreacted monomer was removed by heating under reduced pressure. Furthermore, it cooled to 30 degrees C or less after that, and obtained the aqueous dispersion liquid of particulate polymer A1. Particulate polymer A1 had a surface acid content of 0.1 mmol / g, an Na content of 1000 ppm, and a K content of 3000 ppm.
(2) Particulate polymer A2:
A particulate polymer, except that the amount of styrene (ST) as the aromatic vinyl monomer was changed to 62 parts and the amount of itaconic acid (IA) as the ethylenically unsaturated carboxylic acid monomer was changed to 4 parts. In the same manner as A1, an aqueous dispersion of the particulate polymer A2 was obtained.
Particulate polymer A2 had a surface acid content of 0.38 mmol / g, an Na content of 11000 ppm, and a K content of 3000 ppm. In addition, although Na content has risen compared with particulate polymer A1, this is because the required amount of 5% sodium hydroxide aqueous solution at the time of pH adjustment rose.
(3) Particulate polymer A3
In a reactor equipped with a stirrer, 96.0 parts of butyl acrylate (BA) as a (meth) acrylic acid ester monomer, 2.0 parts of methacrylic acid (MAA) as an ethylenically unsaturated carboxylic acid monomer, α, Add 2.0 parts of acrylonitrile as β-unsaturated nitrile monomer, 0.3 part of sodium dodecylbenzenesulfonate as emulsifier, 0.3 part of ammonium persulfate as polymerization initiator, and 300 parts of ion-exchanged water, and stir well. Then, the reaction was allowed to proceed to 70 ° C. for 3 hours, and further heated to 80 ° C. and aged for 3 hours to complete the reaction. Furthermore, it cooled to 30 degrees C or less after that, and obtained the aqueous dispersion of particulate polymer A3. Particulate polymer A3 had a surface acid content of 0.25 mmol / g, an Na content of 7000 ppm, and a K content of 1000 ppm.
[Hydrophilic organic fiber (B)]
(1) Hydrophilic organic fiber B1:
BiNFi-s (registered trademark) (manufactured by Sugino Machine), which is a cellulose fiber, was used. The average fiber diameter was 20 nm, the average fiber length was 67000 nm, and the aspect ratio was 3350.
(2) Hydrophilic organic fiber B2:
Celish (registered trademark) KY-100G (manufactured by Daicel), which is a cellulose fiber, was used. The average fiber diameter was 70 nm, the average fiber length was 100,000 nm, and the aspect ratio was 1430.
[Crosslinking agent (C)]
Crosslinking agent C1: Polycarbodiimide (manufactured by Nisshinbo Chemical Co., Ltd., product name: Carbodilite (registered trademark) SV-02, one-phase water-soluble)
Crosslinking agent C2: polyfunctional epoxy compound (manufactured by Nagase Chemtech, product name: EX-313, number of functional groups 3 molecules / 1 molecule (compound with 2 epoxy groups and 1 hydroxyl group per molecule and 3 epoxy groups) Mixture with water), water soluble in one phase)
Cross-linking agent C3: 2,2′-bis (2-oxazoline) (manufactured by Tokyo Chemical Industry Co., Ltd., one-phase water-soluble)
[Water-soluble thickener (D)]
CMC1: Sodium salt of carboxymethyl cellulose (manufactured by Nippon Paper Chemical Co., Ltd., product name: MAC350HC, etherification degree 0.8 1% aqueous solution viscosity 3500 mPa · s)
PAA1: Polyacrylic acid (Aldrich, weight average molecular weight 450,000)

Example 1
<Preparation of slurry composition for secondary battery negative electrode>
In a planetary mixer, the particulate polymer A1 as the particulate polymer (A) is 100 parts solid equivalent, and the hydrophilic organic fiber B1 as the hydrophilic organic fiber (B) is 5 parts solid equivalent. The cross-linking agent C1 as the agent (C) is charged with 5 parts (corresponding to the binder composition for a secondary battery negative electrode) corresponding to the solid content, and further, as a negative electrode active material, natural graphite (Nippon Carbon 7407 parts (product name: N98) manufactured by the company, and 74.1 parts (1 part per 100 parts by weight of the negative electrode active material) of a 1% aqueous solution of CMC1 as a water-soluble thickener (D) corresponding to the solid content were charged . And ion-exchange water is added and mixed so that solid content concentration may be 52%, The slurry for secondary battery negative electrodes containing particulate polymer A1, hydrophilic organic fiber B1, crosslinking agent C1, CMC1, and negative electrode active material A composition was prepared.
Using the prepared slurry composition for secondary battery negative electrode, the storage stability and thixotropy of the slurry composition were evaluated. The results are shown in Table 1.

<Manufacture of negative electrode>
Apply the above slurry composition for secondary battery negative electrode on a copper foil (current collector) having a thickness of 20 μm with a comma coater so that the coating amount is 8.8 mg / cm ^{2 to} 9.2 mg / cm ^2. It was applied to. By transporting the copper foil coated with the secondary battery negative electrode slurry composition at a rate of 0.3 m / min in an oven at 80 ° C. for 2 minutes and further in an oven at 120 ° C. over 2 minutes, The slurry composition on the copper foil was dried to obtain a negative electrode raw material.
And the resulting negative GokuHara anti mixture layer density was pressed so as to be 1.44g / cm ³ ~1.55g / cm ³ by a roll press machine, further, for the purpose of further promoting the removal of water and crosslinking Then, it was placed in an environment of 120 ° C. under vacuum conditions for 10 hours to obtain a negative electrode formed by forming a negative electrode mixture layer on the current collector.
Using the prepared negative electrode, the adhesion between the negative electrode mixture layer and the current collector was evaluated. The results are shown in Table 1.

<Production of positive electrode>
In a planetary mixer, 100 parts of LiCoO ₂ as a positive electrode active material, 2 parts of acetylene black as a conductive material (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.), PVDF (polyvinylidene fluoride, ( 2 parts of Kureha Chemical Co., Ltd. “KF-1100”) and N-methylpyrrolidone were added and mixed so that the total solids concentration was 67% to prepare a slurry composition for a secondary battery positive electrode.
The resulting secondary battery positive electrode slurry composition, a comma coater, coating with the amount on an aluminum foil having a thickness of 20μm was coated with a ^{17.5mg / cm 2 ~18.4mg / cm 2} , Dried. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material.
The obtained positive electrode raw pressed as mixture layer density after the pressing by a roll press machine is ^{3.40g / cm 3 ~3.50g / cm 3} , as further purpose of removing moisture, vacuum conditions A positive electrode obtained by forming a positive electrode mixture layer on a current collector was placed in a 120 ° C. environment for 3 hours.

<Manufacture of lithium ion secondary batteries>
A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm; manufactured by a dry method; porosity 55%) was prepared, and cut into a 5 cm × 5 cm square shape. Moreover, the aluminum packaging material exterior was prepared as a battery exterior.
The produced positive electrode was cut into a rectangular shape of 3.8 cm × 2.8 cm, and arranged so that the surface on the current collector side was in contact with the aluminum packaging exterior. Next, the above-described square separator was disposed on the surface of the positive electrode mixture layer of the positive electrode. Further, the produced negative electrode was cut into a 4.0 cm × 3.0 cm rectangular shape, and this was arranged on the separator so that the surface on the negative electrode mixture layer side faced the separator. Thereafter, a LiPF ₆ solution having a concentration of 1.0 M as an electrolytic solution (a solvent is a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3/7 (volume ratio)), and vinylene carbonate as an additive is 2% by volume (solvent. Ratio) containing). Furthermore, in order to seal the opening of the aluminum packaging material, heat sealing at 150 ° C. was performed to close the aluminum exterior, and a laminated cell type lithium ion secondary battery was manufactured.

(Examples 2 and 3)
A slurry composition for a negative electrode of a secondary battery, a negative electrode, a positive electrode, and a lithium ion secondary, as in Example 1, except that the blending amount of the hydrophilic organic fiber B1 is 1 part and 8 parts respectively corresponding to the solid content. A battery was manufactured. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

Example 4
A slurry composition for a secondary battery negative electrode, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the hydrophilic organic fiber B2 was used instead of the hydrophilic organic fiber B1. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Examples 5-7)
A slurry composition for a negative electrode of a secondary battery, a negative electrode, a positive electrode, lithium, and the same as in Example 1, except that the blending amount of the cross-linking agent C1 was 0 parts, 0.5 parts, and 10 parts corresponding to solid contents, respectively. An ion secondary battery was manufactured. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Examples 8 and 9)
A slurry composition for a negative electrode of a secondary battery, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the crosslinking agent C2 and the crosslinking agent C3 were used instead of the crosslinking agent C1, respectively. . And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Examples 10 and 12)
A slurry composition for a negative electrode for a secondary battery, a negative electrode, a positive electrode, and a lithium ion secondary battery were prepared in the same manner as in Example 1 except that the particulate polymers A2 and A3 were used instead of the particulate polymer A1. Manufactured. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Example 11)
A slurry composition for a negative electrode of a secondary battery, a negative electrode, a positive electrode, and a lithium ion secondary battery are manufactured in the same manner as in Example 1 except that PAA1 is used instead of CMC1 as the water-soluble thickener (D). did. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 1)
A slurry composition for a secondary battery negative electrode, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the hydrophilic organic fiber B1 and the crosslinking agent C1 were not used. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 2)
A slurry composition for a negative electrode of a secondary battery, a negative electrode, a positive electrode, and the like, except that the crosslinking agent C1 was not used and the blending amount of the hydrophilic organic fiber B1 was 50 parts corresponding to the solid content. A lithium ion secondary battery was manufactured. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 3)
A slurry composition for a negative electrode of a secondary battery, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the particulate polymer A1 and the crosslinking agent C1 were not used. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 4)
A slurry composition for a secondary battery negative electrode, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the hydrophilic organic fiber B1 was not used. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 5)
A slurry composition for a negative electrode of a secondary battery, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the blending amount of the hydrophilic organic fiber B1 was 25 parts corresponding to the solid content. . And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

From Table 1, Examples 1-12 which used particulate polymer (A) and hydrophilic organic fiber (B) by the specific ratio can ensure the excellent thixotropy of a slurry composition, and were excellent negative electrode It can be seen that adhesion between the composite layer and the current collector can be obtained.
On the other hand, Comparative Examples 1 and 4 in which the hydrophilic organic fiber (B) is not used, and Comparative Examples 2 and 5 in which the hydrophilic organic fiber (B) is used more than a predetermined amount are the thixotropy and negative electrode composite of the slurry composition. It can be seen that the adhesion between the layer and the current collector cannot be improved. In Comparative Example 3 in which the particulate polymer (A) is not used, the problem of migration of the particulate heavy body does not occur in the first place, but since there is no particulate polymer functioning as a binder, the negative electrode composite material layer and the current collector are not present. It can be seen that the adhesion of the body is extremely deteriorated.

In particular, from Examples 1 to 3 in Table 1, by changing the amount of the hydrophilic organic fiber (B), the storage stability of the slurry composition, the thixotropy of the slurry composition, the negative electrode mixture layer and the current collector It can be seen that the adhesion can be further improved.
In addition, from Examples 1 and 4 in Table 1, by changing the average fiber diameter of the hydrophilic organic fiber (B), the storage stability of the slurry composition and the adhesion between the negative electrode mixture layer and the current collector are further increased. It can be seen that it can be good.
And from Example 1, 5-7 of Table 1, the storage stability of a slurry composition, the thixotropy of a slurry composition, and a negative mix layer layer are changed by changing the presence or absence and the compounding quantity of a crosslinking agent (C). It can be seen that the adhesiveness of the current collector can be further improved.
Furthermore, from Examples 1, 8, and 9 in Table 1, by changing the type of the crosslinking agent (C), the storage stability of the slurry composition and the adhesion between the negative electrode mixture layer and the current collector are further improved. It can be understood that it can be assumed.
In addition, by changing the composition of the particulate polymer (A) or adjusting the surface acid amount of the particulate polymer (A) from Examples 1, 10, and 12 in Table 1, It can be seen that the adhesion between the material layer and the current collector can be further improved.

Further, the _secondary active materials of Examples 1 to 4 and 10 to 12 were changed except that the negative electrode active material was changed to LiCoO ₂ as the positive electrode active material, the crosslinking agent was not blended, and 2 parts of acetylene black as the conductive material was blended. In the same manner as the battery negative electrode slurry composition, an aqueous secondary battery positive electrode slurry composition was prepared. And also about these positive electrode slurry compositions, like the negative electrode slurry composition, the storage stability of the slurry composition, the thixotropy of the slurry composition, and the positive electrode mixture layer formed from the slurry composition, The adhesion strength of the current collector was evaluated. Evaluation of each positive electrode slurry composition was the same as the corresponding negative electrode slurry composition.

According to the present invention, it is possible to provide a binder composition for a secondary battery electrode capable of forming a slurry composition that is excellent in thixotropy and has excellent adhesion to a current collector when an electrode mixture layer is formed. it can.
Moreover, according to this invention, the slurry composition for secondary battery electrodes which can form the electrode compound-material layer which is excellent in thixotropy and is excellent in adhesiveness with a collector can be provided.
Furthermore, according to this invention, the electrode for secondary batteries which is excellent in the adhesiveness of an electrode compound-material layer and a collector can be provided.
In addition, according to the present invention, it is possible to provide a secondary battery including an electrode having excellent adhesion between the electrode mixture layer and the current collector.

Claims (11)

Including a particulate polymer (A), a hydrophilic organic fiber (B) and water,
The binder composition for secondary battery electrodes which contains 0.01 to 20 mass parts of said hydrophilic organic fibers (B) per 100 mass parts of said particulate polymers (A).   The binder composition for secondary battery electrodes according to claim 1, wherein the hydrophilic organic fiber (B) has a hydroxyl group.   The binder composition for secondary battery electrodes according to claim 1 or 2, wherein an average fiber diameter of the hydrophilic organic fibers (B) is 1 nm or more and 1000 nm or less.   The crosslinking agent (C) is further included, and the crosslinking agent (C) is at least one selected from the group consisting of a polyfunctional epoxy compound, an oxazoline compound, and a carbodiimide compound. The binder composition for secondary battery electrodes as described.   The binder composition for secondary battery electrodes according to claim 4, comprising 0.01 to 10 parts by mass of the crosslinking agent (C) per 100 parts by mass of the particulate polymer (A).   The binder composition for secondary battery electrodes according to any one of claims 1 to 5, wherein a surface acid amount of the particulate polymer (A) is 0.01 mmol / g or more and 3.5 mmol / g or less. Including a particulate polymer (A), a hydrophilic organic fiber (B), an electrode active material and water,
Per 100 parts by mass of the particulate polymer (A), the hydrophilic organic fiber (B) is contained in an amount of 0.01 to 20 parts by mass , and the solid content concentration is 30 to 90% by mass. A slurry composition for a secondary battery electrode.   The secondary battery electrode according to claim 7, further comprising a crosslinking agent (C), wherein the crosslinking agent (C) is at least one selected from the group consisting of a polyfunctional epoxy compound, an oxazoline compound, and a carbodiimide compound. Slurry composition.   The slurry composition for secondary battery electrodes according to claim 7 or 8, further comprising a water-soluble thickener (D).   The electrode for secondary batteries which has an electrode compound-material layer obtained using the slurry composition for secondary battery electrodes of any one of Claims 7-9. A positive electrode, a negative electrode, an electrolyte and a separator;
The secondary battery whose at least one of the said positive electrode and a negative electrode is the electrode for secondary batteries of Claim 10.

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