Binder composition for secondary batteries, electrode composition, electrode sheet and secondary battery, and method for manufacturing the same

Abstract

To provide a binder composition for secondary batteries, an electrode sheet and a secondary battery which can sufficiently enhance the cycle characteristics (to enable sufficiently long cycle life) of the resulting secondary battery even when an electrode active material exhibiting large volume changes during charging and discharging is used, and methods for manufacturing the electrode sheet and the secondary battery.SOLUTION: There are provided: a binder composition for secondary batteries including a water-soluble polymer (X), a water-soluble compound (Y), and polymer particles, the water-soluble polymer (X) being a polymer containing a structural component having a specific structure, the binder composition having a tensile modulus of 1500-9800 MPa and also satisfying the characteristic in which the difference in storage modulus measured under specific conditions at shear strains of 0.01% and 10% is 100-1000 Pa; an electrode sheet; a secondary battery; and methods for manufacturing the electrode sheet and the secondary battery.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a binder composition for a secondary battery, a composition for an electrode, an electrode sheet and a secondary battery, and methods for manufacturing these electrode sheets and secondary batteries. [Background technology]

[0002] Secondary batteries, such as lithium-ion secondary batteries, are used as power sources for portable electronic devices such as personal computers, video cameras, and mobile phones. Recently, against the backdrop of the global environmental challenge of reducing carbon dioxide emissions, they have become increasingly popular as power sources for transportation equipment such as automobiles, and for storing electricity such as nighttime power and electricity generated by natural energy sources.

[0003] The electrodes (positive and negative electrodes) of lithium-ion secondary batteries generally have electrode active material layers (positive and negative electrode active material layers), which contain electrode active material particles capable of absorbing and releasing lithium ions during charging and discharging, and also contain conductive additives, etc., as necessary. The electrode active material, conductive additives, etc. are so-called solid particles, and the electrical conductivity between the solid particles is easily impaired due to the expansion and contraction of the electrode active material particles accompanying the charging and discharging (intercalation and release of lithium ions) of the lithium-ion secondary battery. If the electrical conductivity is impaired, the internal resistance of the battery increases and the battery capacity decreases. To improve the cycle characteristics (extend the cycle life) of lithium-ion secondary batteries, it is important to be able to maintain adhesion between the solid particles even after repeated charging and discharging, and therefore the electrode active material layers usually contain a binder. For example, Patent Document 1 describes a binder composition for lithium ion secondary battery electrodes that includes a particulate polymer and a water-soluble polymer. Patent Document 1 also describes that the water-soluble polymer that constitutes this composition contains ethylenically unsaturated carboxylic acid monomer units, one or more carboxylic acid amide monomer units selected from (meth)acrylamide, N-2-dimethylaminoethyl(meth)acrylamide, and N-3-dimethylaminopropyl(meth)acrylamide, and crosslinkable monomer units other than the carboxylic acid amide monomer units, each in specific proportions; and that by combining this composition with an electrode active material and a carboxymethyl cellulose salt and applying it to form an electrode for a lithium ion secondary battery, gas generation in the resulting lithium ion secondary battery is suppressed and the cycle characteristics of the lithium ion secondary battery are improved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6361655 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the expansion of secondary battery applications has led to demands for higher energy density and improved cycle characteristics. To achieve even higher capacity in lithium-ion secondary batteries, the use of silicon-based active materials as negative electrode active materials has been actively investigated. Using silicon-based active materials in the negative electrode enables higher energy density. However, silicon-based active materials absorb a large amount of lithium ions and expand significantly during charging, which in turn leads to a correspondingly large contraction during discharging. Therefore, lithium-ion secondary batteries using silicon-based active materials as negative electrode active materials experience large volume changes during charging and discharging, which can lead to a loss of electrical conductivity (adhesion) between solid particles (electrode active materials, conductive additives, etc.). Loss of electrical conductivity due to repeated charging and discharging increases the battery's internal resistance, leading to a deterioration in battery performance. This means that improvements in cycle characteristics are limited. The present inventors have investigated the influence of conventional electrode binders, such as the binder described in Patent Document 1, on the cycle characteristics of secondary batteries using such silicon-based active materials as negative electrode active materials. As a result, it has become clear that conventional electrode binders are unable to adequately accommodate the dynamic volume changes of silicon-based active materials that occur during charge and discharge, making it difficult to achieve both the desired high level of adhesion of the electrode sheet and the cycle characteristics of the secondary battery.

[0006] An object of the present invention is to provide a binder composition for secondary batteries and a composition for electrodes that can sufficiently improve the adhesion of the resulting electrode sheet (adhesion between the negative electrode active material layer and the current collector) and can sufficiently improve the cycle characteristics of the resulting secondary battery (sufficiently extend the cycle life), even when an electrode active material that undergoes a large volume change during charge and discharge is used. Another object of the present invention is to provide an electrode sheet and a secondary battery using the above-mentioned binder composition for secondary batteries or electrode composition, and a method for manufacturing the above-mentioned electrode sheet and secondary battery. [Means for solving the problem]

[0007] In view of the above-mentioned problems, the present inventors have conducted extensive research into the chemical structure of the polymer constituting the binder, and the physical properties and shape of the binder. As a result, they have found that a binder composition comprising a water-soluble polymer (X) having a specific structure, a water-soluble compound (Y), polymer particles, and water, exhibits a specific tensile modulus, and when used as an electrode composition containing an electrode active material and a conductive additive, the binder composition has a specific relationship between the degree of shear strain and the storage modulus. This binder composition effectively contributes to excellent binding within or between layers of a secondary battery, thereby improving the adhesion of the electrode sheet and sufficiently extending the cycle life of the secondary battery. The present invention was completed through further research based on these findings.

[0008] That is, the above-mentioned problems of the present invention have been solved by the following means. <1> A binder composition for a secondary battery, comprising a water-soluble polymer (X), a water-soluble compound (Y), polymer particles, and water, The water-soluble polymer (X) is a polymer containing a component represented by the following general formula (B-2): The binder composition has a tensile modulus of 1500 to 9800 MPa, and A binder composition for a secondary battery, which satisfies the following <Storage modulus property 1>. <Storage modulus characteristics 1> Average particle size is 1 to 10 μm and specific surface area is 1 to 10 m 2 / g powdered carbon-coated silicon oxide with an average particle size of 15 to 25 μm and a specific surface area of ​​1 to 10 m 2 / g powdered graphite and graphite with an average particle size of 30-40 nm and a specific surface area of ​​65-75 m 2 In a slurry prepared by mixing powdered acetylene black having a mass of 10 ... A ' and storage modulus G at shear strain of 10% B The difference between ' and ' is 100 to 1000 Pa. -Quantity ratio- With respect to 100 parts by mass of the total solid content in the slurry, the content of the carbon-coated silicon oxide is 17.8 parts by mass, the content of the graphite is 71.2 parts by mass, the content of the acetylene black is 6 parts by mass, the content of the solid content in the binder composition for secondary batteries is 5 parts by mass, and the total solid content in the slurry is 52% by mass. TIFF2025168682000001.tif43166 In general formula (B-2), R 21 ~R 23 represents a hydrogen atom, a cyano group, or an alkyl group having 1 to 6 carbon atoms; R 24 represents a hydrogen atom, an acyl group, a hydroxy group, a phenyl group, or a carboxy group, and L 21 represents a single bond, an alkylene group having 1 to 16 carbon atoms, an arylene group having 6 to 12 carbon atoms, an oxygen atom, a sulfur atom, a carbonyl group, an imino group, or a linking group combining these. * represents a bonding site for incorporation into the main chain of the water-soluble polymer (X). <2> The content of the component represented by the general formula (B-2) in the water-soluble polymer (X) is 80 mass% or more. <1> The binder composition for a secondary battery according to claim 1. <3> The component represented by the general formula (B-2) contains a (meth)acrylamide component. <1> or <2> The binder composition for a secondary battery according to claim 1. <4> The water-soluble polymer (X) is a polymer further containing at least one of an acrylonitrile component, an N-vinyl-2-pyrrolidone component, and a styrene component. <1> ~ <3> 10. The binder composition for a secondary battery according to claim 1, <5> The water-soluble compound (Y) is a polysaccharide. <1> ~ <4> 10. The binder composition for a secondary battery according to claim 1, <6> The water-soluble compound (Y) contains at least one of carboxymethyl cellulose, cellulose nanofiber, hydroxyethyl cellulose, hydroxypropyl cellulose, and xanthan gum. <1> ~ <5> 10. The binder composition for a secondary battery according to claim 1, <7> The molecular weight distribution of the water-soluble polymer (X) is 5.0 or less. <1> ~ <6> 10. The binder composition for a secondary battery according to claim 1, <8> The tensile modulus of the water-soluble polymer (X) is 4000 MPa or more. <1> ~ <7> 10. The binder composition for a secondary battery according to claim 1, <9> the polymer constituting the polymer particles is a polymer containing at least one of a conjugated diene component, an ethylenically unsaturated carboxylic acid component, a cyano group-containing ethylenic monomer component, and an aromatic vinyl monomer component; <1> ~ <8> 10. The binder composition for a secondary battery according to claim 1, <10> The glass transition temperature of the polymer particles is −50 to 150° C. <1> ~ <9> 10. The binder composition for a secondary battery according to claim 1, <11> <1> 1. A composition for an electrode comprising the binder composition for a secondary battery according to claim 1, an active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table, and a conductive additive. <12> The active material includes a silicon-based active material. <11> The electrode composition according to claim 1. <13> <11> or <12> An electrode sheet having a layer formed using the electrode composition according to claim 1. <14> At least one of the positive electrode active material layer and the negative electrode active material layer is <11> or <12> A secondary battery, wherein the layer is formed using the electrode composition according to claim 1. <15> <11> or <12> and forming an electrode active material layer using the electrode composition according to claim 1. <16> <15> 10. A method for manufacturing a secondary battery, comprising incorporating an electrode sheet obtained by the manufacturing method described in claim 1 as an electrode of the secondary battery.

[0009] In the present invention, the term "water-soluble polymer" refers to a polymer having a solubility in water of 10 g / L-H2O or more at 20°C, i.e., a polymer that dissolves 10 g or more in 1 liter of water. The solubility of the "water-soluble polymer" is preferably 100 g / L-H2O or more. In the present invention, the term "water-soluble compound" refers to a compound having a solubility in water of 10 g / L-H2O or more at 20°C, i.e., a compound that dissolves 10 g or more in 1 liter of water. The solubility of the "water-soluble compound" is preferably 100 g / L-H2O or more. In the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present invention, the description of compounds, components, or substituents includes those in which the structure has been partially modified, as long as the effects of the present invention are achieved. Furthermore, in the present invention, compounds or components that are not specified as substituted or unsubstituted may have any substituent, as long as the effects of the present invention are achieved. This also applies to substituents (e.g., groups expressed as "alkyl group," "methyl group," "methyl," etc.) and linking groups (e.g., groups expressed as "alkylene group," "methylene group," "methylene," etc.). Among such optional substituents, preferred substituents in the present invention are those selected from the substituent group T described below. In the present invention, when there are a plurality of substituents or linking groups, etc. (hereinafter referred to as "substituents, etc.") represented by a specific symbol or formula, or when a plurality of substituents, etc. are simultaneously defined, the respective substituents, etc. may be the same or different from each other unless otherwise specified. This also applies to the constituent components of the polymer. In the present invention, one kind of each component may be contained, or two or more kinds thereof may be contained. In the present invention, (meth)acrylic means one or both of acrylic and methacrylic. The same applies to (meth)acrylate. In the present invention, the term "secondary battery" refers to a general device in which ions pass between positive and negative electrodes via an electrolyte upon charging and discharging, and energy is stored and released at the positive and negative electrodes. That is, the term "secondary battery" in the present invention encompasses both batteries and capacitors (e.g., lithium ion capacitors). From the viewpoint of energy storage capacity, the secondary battery of the present invention is preferably used for battery applications (not as a capacitor). Secondary batteries can be broadly classified into aqueous secondary batteries and nonaqueous secondary batteries depending on the electrolyte used, with nonaqueous secondary batteries being preferred. In the present invention, "aqueous secondary battery" refers to a secondary battery using an aqueous electrolyte solution as the electrolyte. In the present invention, "nonaqueous secondary battery" encompasses nonaqueous electrolyte secondary batteries and all-solid-state secondary batteries. In the present invention, "nonaqueous electrolyte secondary battery" refers to a secondary battery using a nonaqueous electrolyte solution as the electrolyte. In the present invention, "nonaqueous electrolyte solution" refers to an electrolyte solution that is substantially free of water. An electrolyte solution that is substantially free of water means that the "nonaqueous electrolyte solution" may contain a trace amount of water as long as it does not impair the effects of the present invention. In the present invention, the "nonaqueous electrolyte solution" has a water concentration of 200 ppm (by mass) or less, preferably 100 ppm or less, and more preferably 20 ppm or less. It is practically difficult to make a nonaqueous electrolyte solution completely anhydrous, and it usually contains 1 ppm or more of water. In the present invention, the term "all-solid-state secondary battery" refers to a secondary battery that does not use a liquid electrolyte, but uses a solid electrolyte such as an inorganic solid electrolyte or a solid polymer electrolyte. In the present invention, when the number of carbon atoms of a certain group is specified, this number of carbon atoms means the number of carbon atoms of the group itself unless otherwise specified in the present invention or this specification. In other words, when this group further has a substituent, the number of carbon atoms means the number of carbon atoms counted excluding the carbon atoms of the substituent. In the present invention, the term "solid content" used when describing the content or content ratio means components other than water and the liquid medium described below. [Effects of the Invention]

[0010] The binder composition for a secondary battery, the electrode composition, and the electrode sheet of the present invention can sufficiently extend the cycle life of the resulting secondary battery even when an electrode active material that undergoes a large volume change during charge and discharge is used. In addition, the electrode sheet of the present invention has excellent adhesion. The secondary battery of the present invention can achieve a sufficiently long cycle life even when an electrode active material that undergoes a large volume change during charging and discharging is used. The electrode sheet of the present invention can be obtained by the method for producing an electrode sheet of the present invention, and the secondary battery of the present invention can be obtained by the method for producing a secondary battery of the present invention. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a longitudinal sectional view showing a schematic basic layer structure of an embodiment of a secondary battery according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Binder composition for secondary batteries] The binder composition for secondary batteries of the present invention (hereinafter also referred to as "the binder composition of the present invention") contains a water-soluble polymer (X), a water-soluble compound (Y), polymer particles, and water. The binder composition of the present invention is suitable for use in forming members or constituent layers of preferably non-aqueous secondary batteries, more preferably non-aqueous electrolyte secondary batteries. The water contained in the binder composition of the present invention functions as a liquid medium. Typically, the binder composition of the present invention is suitable for use as an electrode composition containing the binder composition of the present invention, an electrode active material (a positive electrode active material or a negative electrode active material, collectively also simply referred to as "active material"), and a conductive additive, and is suitable for use in forming an electrode active material layer (a positive electrode active material layer or a negative electrode active material layer) in an electrode (a positive electrode or a negative electrode) of a secondary battery.

[0013] The water-soluble polymer (X) and polymer particles contained in the binder composition of the present invention are thought to function primarily as a binder that binds solid particles (electrode active material, conductive additive, etc.) together in a layer formed by mixing the binder composition of the present invention with solid particles. They may also function as a binder that binds the current collector and solid particles. The adsorption of the water-soluble polymer (X) and polymer particles to the solid particles and current collector includes not only physical adsorption but also chemical adsorption (adsorption by chemical bond formation, adsorption by electron exchange, etc.). On the other hand, the water-soluble compound (Y) contained in the binder composition of the present invention is thought to function mainly as a thickener (dispersant) in the binder composition of the present invention.

[0014] The binder composition of the present invention has a tensile modulus of 1500 to 9800 MPa. From the viewpoints of increasing adhesion to the current collector and effectively suppressing volumetric changes in the electrode active material layer to improve cycle characteristics, the tensile modulus of the binder composition is preferably 1600 to 8000 MPa, more preferably 1700 to 7000 MPa, and even more preferably 1800 to 6000 MPa. In the present invention, the tensile modulus is a value obtained by the method described in the examples below. The tensile modulus of the binder composition of the present invention can be adjusted within the above range by adjusting the types, contents, etc. of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles.

[0015] The binder composition of the present invention satisfies the following <Storage modulus property 1>. <Storage modulus characteristics 1> Average particle size is 1 to 10 μm and specific surface area is 1 to 10 m 2 / g powdered carbon-coated silicon oxide with an average particle size of 15 to 25 μm and a specific surface area of ​​1 to 10 m 2 / g powdered graphite and graphite with an average particle size of 30-40 nm and a specific surface area of ​​65-75 m 2In a slurry prepared by mixing powdered acetylene black having a mass of 10 ... A ' and storage modulus G at shear strain of 10% B The difference between ' and ' is 100 to 1000 Pa. -Quantity ratio- With respect to 100 parts by mass of the total solid content in the slurry, the content of the carbon-coated silicon oxide is 17.8 parts by mass, the content of the graphite is 71.2 parts by mass, the content of the acetylene black is 6 parts by mass, the content of the solid content of the binder composition for secondary batteries is 5 parts by mass, and the total solid content in the slurry is 52% by mass. In the present invention, the term "slurry" refers to a dispersion composition obtained by thoroughly and uniformly mixing the components, as in the mixing method in the Examples. In the present invention, "adjusting the total solid content of the slurry to 52% by mass" means that when the total solid content is adjusted from a state higher than 52% by mass to 52% by mass, the slurry is diluted with water, and when the total solid content is adjusted from a state lower than 52% by mass to 52% by mass, the slurry is concentrated by evaporating the solvent, for example. Evaporation of the solvent can be performed, for example, by vacuum drying or reduced pressure. In the present invention, the storage modulus G at a shear strain of 0.01% A ' and storage modulus G at shear strain of 10% B 'Difference' is the storage modulus G at a shear strain of 0.01% A Storage modulus G at shear strain of 10% B ' minus the value (G A '-G B '). Alternatively, the sufficiency of the above-mentioned <Storage modulus characteristic 1> can be determined by strain dispersion measurement using a rheometer. The detailed measurement conditions are as described in the Examples below. In addition, the average particle size (volume-based median diameter D50) of each of the carbon-coated silicon oxide, graphite, and acetylene black used in the above <Storage Elastic Modulus Characteristic 1> is in the range of 1 to 10 μm (preferably 2 to 7 μm) for the carbon-coated silicon oxide, 15 to 25 μm (preferably 17 to 22 μm) for graphite, and 30 to 40 nm (preferably 32 to 37 nm) for acetylene black. Also, the specific surface area of each of the carbon-coated silicon oxide, graphite, and acetylene black used in the above <Storage Elastic Modulus Characteristic 1> is 1 to 10 m 2 / g (preferably 2 to 7 m 2 / g) for the carbon-coated silicon oxide, 1 to 10 m 2 / g (preferably 2 to 7 m 2 / g) for graphite, and 65 to 75 m 2 / g (preferably 66 to 70 m 2 / g) for acetylene black. If it is within the range of these average particle sizes and specific surface areas, the values of the storage elastic modulus obtained are substantially the same. Also, the "powder form" of the carbon-coated silicon oxide, graphite, and acetylene black used in the above <Storage Elastic Modulus Characteristic 1> means that it is in the form of powder (powder containing primary particles and / or aggregates (secondary particles) formed by aggregation of primary particles), and for example, those obtained by pressing powder or granular ones are not included. In addition, the carbon-coated silicon oxide used in the above <Storage Elastic Modulus Characteristic 1> refers to a material in which a carbon material is supported on the surface of silicon oxide (SiO x (0 < x ≤ 1.5)), and the proportion of the carbon element content in the carbon-coated silicon oxide is in the range of 0.5 to 5 mass% (preferably 1 to 3 mass%). Note that the carbon-coated silicon oxide used in the above <Storage Elastic Modulus Characteristic 1> is not doped with metal elements (for example, it is not silicon oxide subjected to both carbon coating and metal element doping). As a commercially available product of carbon-coated silicon oxide, for example, carbon-coated silicon oxide powder manufactured by Osaka Titanium Technology Co., Ltd. (grade: SiO NC, average particle size: 5 μm, specific surface area: 2.6 m2 / g), and commercially available graphite products include, for example, massive artificial graphite powder (trade name: MAG-D, average particle size: 21 μm, specific surface area: 4 m) manufactured by Showa Denko Materials Co., Ltd. 2 / g), and commercially available acetylene black is, for example, acetylene black manufactured by Denka Corporation (trade name: Denka Black, grade: powder, average particle size: 35 nm, specific surface area: 68 m 2 / g) can be used.

[0016] The storage modulus G at the shear strain of 0.01% A ' and storage modulus G at shear strain of 10% B ' and the difference (G A '-G B The pressure is preferably 100 to 800 Pa, more preferably 100 to 600 Pa, further preferably 110 to 400 Pa, and particularly preferably 120 to 300 Pa. The difference in storage modulus (G A '-G B The storage modulus difference ′) can be adjusted to fall within the above range by adjusting the types and contents of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles. From the viewpoint of enhancing the dispersibility of the solid particles, it is preferable that the difference in storage modulus be large.

[0017] The storage modulus G of the binder composition of the present invention at a shear strain of 0.01% A ' is the difference (G A '-G B There are no particular limitations on the pressure, provided that it is 100 to 1000 Pa, but it is preferably 101 to 1500 Pa, more preferably 105 to 1300 Pa, and even more preferably 110 to 1200 Pa. The storage modulus G of the binder composition of the present invention at a shear strain of 10% B ' is the difference (G A '-G B There are no particular limitations on the pressure, provided that it is 100 to 1000 Pa, but it is preferably 1 to 500 Pa, more preferably 5 to 300 Pa, and even more preferably 10 to 200 Pa.

[0018] The binder composition of the present invention can be used, for example, to prepare an electrode composition containing an active material and a conductive additive, and then to prepare an electrode sheet. By applying this to the electrode of a secondary battery, the adhesion of the electrode sheet can be increased and the cycle characteristics of the secondary battery can be improved. Although the reason for this is unclear, it is thought to be as follows. The binder composition of the present invention, when mixed with an active material and a conductive additive, exhibits a specific relationship between the degree of shear strain and the storage modulus. This allows for more uniform dispersion of solid particles, such as the active material and conductive additive, when used in an electrode composition. This effectively contributes to the formation of a conductive network structure (suppressing localization of the conductive network structure), which is believed to be one of the reasons for the improved cycle performance. The uniform dispersion of solid molecules also contributes to increased peel strength from the current collector. Furthermore, the water-soluble polymer (X) interacts with the solid particles due to its specific structure, and the binder composition as a whole has a predetermined tensile modulus. These factors suppress the volumetric change of the electrode active material layer, allowing the polymer particles to adequately and smoothly utilize their adhesion and conformability to the solid particles. This is also believed to be another reason for the improved cycle performance.

[0019] The components contained in the binder composition of the present invention will be described below.

[0020] (Water-soluble polymer (X)) The water-soluble polymer (X) is a polymer containing a constituent component represented by the following general formula (B-2).

[0021] [ka]

[0022] In general formula (B-2), R 21 ~R 23represents a hydrogen atom, a cyano group, or an alkyl group having 1 to 6 carbon atoms. This alkyl group having 1 to 6 carbon atoms may be linear or branched. This alkyl group having 1 to 6 carbon atoms is preferably an alkyl group having 1 to 4 carbon atoms, more preferably methyl or ethyl, and even more preferably methyl. R 21 and R 22 is preferably a hydrogen atom. R 23 is preferably a hydrogen atom or methyl, more preferably a hydrogen atom. R 24 represents a hydrogen atom, an acyl group (an alkylcarbonyl group), a hydroxy group, a phenyl group, or a carboxy group. Examples of the alkyl group in the acyl group include the alkyl groups in the substituent group T described below, which may be linear or branched. Preferably, R 21 ~R 23 As the alkyl group, an alkyl group having 1 to 6 carbon atoms can be used. R 24 is preferably a hydrogen atom or a hydroxy group, more preferably a hydrogen atom. L 21 is a single bond, an alkylene group having 1 to 16 carbon atoms, an arylene group having 6 to 12 carbon atoms, an oxygen atom, a sulfur atom, a carbonyl group (>C=O), or an imino group (>NR N ), or a linking group combining these. 21 may have a substituent selected from the group T of substituents described below, and this substituent is preferably a hydroxy group. Above R N represents a hydrogen atom or an alkyl group. L 21 When L represents a linking group other than a single bond, 21 The chemical formula weight of L is preferably 14 to 2000, more preferably 14 to 500, and even more preferably 28 to 200. 21 The alkylene group having 1 to 16 carbon atoms may be linear or branched. The alkylene group preferably has 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms. L 21is preferably a single bond, methylene, ethylene, propylene, 2-hydroxypropylene or butylene, more preferably a single bond or ethylene, and even more preferably a single bond. * indicates a binding site for incorporation into the main chain of the polymer (water-soluble polymer (X)).

[0023] Specific examples of the component represented by the general formula (B-2) include a (meth)acrylamide component; and an N-(hydroxyalkyl)(meth)acrylamide component such as an N-(2-hydroxyethyl)(meth)acrylamide component, with a (meth)acrylamide component being preferred and an acrylamide component being more preferred. The constituent moiety represented by general formula (B-2) may be of one type or of two or more types.

[0024] From the viewpoint of effectively suppressing the volume change of the electrode active material layer and improving the cycle characteristics, the water-soluble polymer (X) preferably contains a (meth)acrylamide component, more preferably an acrylamide component.

[0025] The water-soluble polymer (X) used in the present invention may further contain components other than the component represented by the general formula (B-2) above (hereinafter referred to as "other components") within the range that does not impair the effects of the present invention. Examples of such components include the component represented by the following general formula (B-1), an acrylonitrile component, an N-vinyl-2-pyrrolidone component, and a styrene component. The other constituent components preferably include at least one of an acrylonitrile component, an N-vinyl-2-pyrrolidone component, and a styrene component, and more preferably include an acrylonitrile component.

[0026] [ka]

[0027] In general formula (B-1), R 11 ~R 13represents a hydrogen atom, a cyano group, or an alkyl group having 1 to 6 carbon atoms. This alkyl group having 1 to 6 carbon atoms may be linear or branched. This alkyl group having 1 to 6 carbon atoms is preferably an alkyl group having 1 to 4 carbon atoms, more preferably methyl or ethyl, and even more preferably methyl. R 11 and R 12 is preferably a hydrogen atom. R 13 is preferably a hydrogen atom or methyl, more preferably a hydrogen atom. R 14 represents a hydrogen atom, a hydroxy group, an alkoxy group (alkyloxy group) having 1 to 6 carbon atoms, a cyano group, a phenyl group, a carboxy group, a sulfo group (-S(=O)2(OH)), a phosphate group (-OP(=O)(OH)2), or a phosphonate group (-P(=O)(OH)2). The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear or branched. The alkoxy group having 1 to 6 carbon atoms is preferably an alkoxy group having 1 to 4 carbon atoms, and more preferably methoxy or ethoxy. R 14 is preferably a hydrogen atom, a hydroxy group, methoxy or ethoxy, more preferably a hydrogen atom. L 11 is a single bond, an alkylene group having 1 to 16 carbon atoms, an arylene group having 6 to 12 carbon atoms, an oxygen atom, a sulfur atom, a carbonyl group (>C=O), or an imino group (>NR N '), or a linking group combining these. 11 may have a substituent selected from the group T of substituents described below, and this substituent is preferably a hydroxy group. Above R N ' represents a hydrogen atom or an alkyl group. L 11 When L represents a linking group other than a single bond, 11 The chemical formula weight of L is preferably 14 to 2000, more preferably 14 to 500, and even more preferably 28 to 200. 11 The alkylene group having 1 to 16 carbon atoms may be linear or branched. The alkylene group preferably has 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms. L 11 As the alkyl group, a single bond, methylene, ethylene, propylene, 2-hydroxypropylene and butylene are preferred, and a single bond, ethylene or butylene is more preferred. * indicates a binding site for incorporation into the main chain of the polymer (water-soluble polymer (X)).

[0028] Specific examples of the constituent component represented by the general formula (B-1) above include a (meth)acrylic acid component; alkyl (meth)acrylate components such as a methyl (meth)acrylate component, an ethyl (meth)acrylate component, a propyl (meth)acrylate component, and a butyl (meth)acrylate component; hydroxyalkyl (meth)acrylate components such as a 2-hydroxyethyl (meth)acrylate component, a 4-hydroxybutyl (meth)acrylate component, and a 2,3-dihydroxypropyl (meth)acrylate component; and alkoxyalkyl (meth)acrylate components such as a methoxyethyl (meth)acrylate component and an ethoxyethyl (meth)acrylate component, with a (meth)acrylic acid component or a hydroxyalkyl (meth)acrylate component being preferred.

[0029] The number of types of constituent components contained in the water-soluble polymer (X) is not particularly limited, and is preferably 1 to 10 types, more preferably 1 to 5 types, even more preferably 1 to 3 types, and particularly preferably 1 or 2 types. Specific examples of the water-soluble polymer (X) described below include polymers having one, two, or three types of constituent components. In these specific examples, the polymer having one type of constituent component is polyacrylamide.

[0030] In the water-soluble polymer (X), the content of the component represented by the general formula (B-2) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and may be 100% by mass. When the water-soluble polymer (X) contains other constituent components, the content of the constituent component represented by the general formula (B-2) is preferably 65% ​​by mass or more, and more preferably 75% by mass or more. In the water-soluble polymer (X), the total content of the constituent component represented by the above general formula (B-1), the acrylonitrile component, the N-vinyl-2-pyrrolidone component, and the styrene component is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0031] The weight average molecular weight (Mw) of the water-soluble polymer (X) used in the present invention is not particularly limited, and is preferably from 100,000 to 900,000, more preferably from 200,000 to 500,000, from the viewpoint of improving cycle characteristics. The water-soluble polymer (X) preferably does not have a cross-linked structure, that is, it is preferably a chain polymer.

[0032] From the viewpoint of improving cycle characteristics, the molecular weight distribution of the water-soluble polymer (X) is preferably 5.0 or less, more preferably 3.0 or less, while a molecular weight distribution of 1.0 or more is practical. The molecular weight distribution of the water-soluble polymer (X) is also called dispersity and is calculated by [weight average molecular weight (Mw)] / [number average molecular weight (Mn)].

[0033] -Measurement of weight average molecular weight and number average molecular weight- In the present invention, the weight-average molecular weight and number-average molecular weight of a polymer are measured by gel permeation chromatography (GPC). The molecular weight refers to the weight-average molecular weight in terms of polyethylene oxide. The measurement method is basically the value measured under the method of measurement condition 1 below. However, depending on the type of polymer, an appropriate eluent may be selected and used. (Measurement condition 1) Measuring instrument: HLC-8220GPC (product name, manufactured by Tosoh Corporation) Columns: TOSOH TSKgel 5000PWXL (trade name, manufactured by Tosoh Corporation), TOSOH TSKgel G4000PWXL (trade name, manufactured by Tosoh Corporation), and TOSOH TSKgel G2500PWXL (trade name, manufactured by Tosoh Corporation) were connected together. Carrier: 200mM sodium nitrate aqueous solution Measurement temperature: 40℃ Carrier flow rate: 1.0 ml / min Sample concentration: 0.2% by mass Detector: RI (refractive index) detector If the molecular weight cannot be measured under the above measurement condition 1 due to crosslinking or other reasons, the molecular weight is measured by static light scattering under the following measurement condition 2. (Measurement condition 2) Measuring instrument: DLS-8000 (product name, manufactured by Otsuka Electronics Co., Ltd.) Measured concentration: 0.25, 0.50, 0.75, 1.00mg / mL Diluent: 0.1M NaCl aqueous solution Laser wavelength: 633nm Pinhole: PH1=Open, PH2=Slit Measurement angles: 60, 70, 80, 90, 100, 110, 120, 130 degrees Analysis method: The molecular weight is measured from the Zimm square root plot. The dn / dc required for analysis is measured using an Abbe refractometer.

[0034] The water-soluble polymer (X) used in the present invention preferably has a tensile modulus of 3500 MPa or more, more preferably 4000 MPa or more, even more preferably 5000 MPa or more, and particularly preferably 6000 MPa or more, from the viewpoint of effectively suppressing the volume change of the electrode active material layer and improving the cycle characteristics. On the other hand, a tensile modulus of 15000 MPa or less is practical. In the present invention, the tensile modulus is a value obtained by the same method as in the tensile modulus test of the binder composition of the present invention described in the Examples below, except that an aqueous solution of the water-soluble polymer (X) is used instead of the binder composition of the present invention.

[0035] The water-soluble polymer (X) may further have a substituent in each of the structures or partial structures described above, and examples of this substituent include those selected from the following group T of substituents.

[0036] - Substituent group T - alkyl groups (preferably alkyl groups having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), alkenyl groups (preferably alkenyl groups having 2 to 20 carbon atoms, for example, vinyl, allyl, oleyl, etc.), alkynyl groups (preferably alkynyl groups having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, phenylethynyl, etc.), cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms, for example , cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), aryl groups (preferably aryl groups having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, more preferably 5- or 6-membered heterocyclic groups having at least one of oxygen atom, sulfur atom, and nitrogen atom as a ring-constituting atom. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups. For example, tetrahydropyran a tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, etc.), an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), a heterocyclic oxy group (a group in which an -O- group is bonded to the above heterocyclic group ... Examples of the alkoxycarbonyl group include an alkoxycarbonyl group (preferably an alkoxycarbonyl group having 2 to 20 carbon atoms, such as ethoxycarbonyl or 2-ethylhexyloxycarbonyl), an aryloxycarbonyl group (preferably an aryloxycarbonyl group having 7 to 26 carbon atoms, such as phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl or 4-methoxyphenoxycarbonyl), an amino group (preferably an amino group having 0 to 20 carbon atoms, including an amino group substituted with a group selected from an alkyl group and an aryl group).For example, amino (-NH2), N,N-dimethylamino, N,N-diethylamino, N-ethylamino, anilino, etc.), sulfamoyl group (preferably a sulfamoyl group having 0 to 20 carbon atoms, including sulfamoyl groups substituted with a group selected from an alkyl group and an aryl group, for example, sulfamoyl (-SON2NH2), N,N-dimethylsulfamoyl, N-phenylsulfamoyl, etc.), acyl group (including an alkylcarbonyl group, an alkenylcarbonyl group, an alkynylcarbonyl group, an arylcarbonyl group, and a heterocyclic carbonyl group, preferably an acyl group having 1 to 20 carbon atoms, for example, formyl, acetyl, propionyl, butyryl, octanoyl, hexadecanoyl, acryloyl, methacryloyl, crotonoyl, benzoyl, naphthoyl, nicotinoyl, etc.), acyloxy group (alkylcarbonyloxy group, alkenyl Examples of the acyl group include an acylcarbonyloxy group, an alkynylcarbonyloxy group, an arylcarbonyloxy group, and a heterocyclic carbonyloxy group, and preferably an acyloxy group having 1 to 20 carbon atoms, such as formyloxy, acetyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonoyloxy, benzoyloxy, naphthoyloxy, and nicotinoyloxy; a carbamoyl group (preferably a carbamoyl group having 1 to 20 carbon atoms, and including a carbamoyl group substituted with a group selected from an alkyl group and an aryl group, such as N,N-dimethylcarbamoyl and N-phenylcarbamoyl); and an acylamino group (preferably an acylamino group having 1 to 20 carbon atoms, and preferred examples of the acyl group in the acylamino group include the above-mentioned acyl groups).For example, acetylamino, benzoylamino, etc.), alkylthio groups (preferably alkylthio groups having 1 to 20 carbon atoms, for example, methylthio, ethylthio, isopropylthio, benzylthio, etc.), arylthio groups (preferably arylthio groups having 6 to 26 carbon atoms, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc.), arylsilyl groups (preferably arylsilyl groups having 6 to 42 carbon atoms, for example, triphenylsilyl, etc.), heterocyclic thio groups (the above heterocyclic groups to which an -S- group is bonded), groups), alkylsulfonyl groups (preferably alkylsulfonyl groups having 1 to 20 carbon atoms, for example, methylsulfonyl, ethylsulfonyl, etc.), arylsulfonyl groups (preferably arylsulfonyl groups having 6 to 22 carbon atoms, for example, benzenesulfonyl, etc.), alkylsilyl groups (preferably alkylsilyl groups having 1 to 20 carbon atoms, for example, monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl, etc.), phosphite groups (preferably phosphite groups having 0 to 20 carbon atoms, for example, -OP(=O)(-OH)(R P )), a hypophosphite group (preferably a hypophosphite group having 0 to 20 carbon atoms, for example, —OP(═O)(R P )2), a phosphoryl group (preferably a phosphoryl group having 0 to 20 carbon atoms, for example, —P(═O)(R P )2), a phosphinyl group (preferably a phosphinyl group having 0 to 20 carbon atoms, for example, —P(R P ) 2), sulfo group, phosphate group, phosphonate group, carboxy group, hydroxy group, sulfanyl group, cyano group, halogen atom (e.g., fluorine atom, chlorine atom, bromine atom, iodine atom). P is a hydrogen atom or a substituent (preferably a group selected from the substituent group T). Furthermore, each of the groups listed in the substituent group T may further have each of the groups listed in the substituent group T above as a substituent.

[0037] The water-soluble polymer (X) used in the present invention can be obtained by a conventional polymer synthesis method. In the synthesis of the water-soluble polymer (X) used in the present invention, the method and conditions for chain polymerization etc. are not particularly limited, and conventional methods and conditions can be appropriately applied depending on the purpose. The "water solubility" of the water-soluble polymer (X) can be controlled, for example, by the type and content of the constituent components.

[0038] Preferred specific examples of the water-soluble polymer (X) used in the present invention are shown below, but the present invention is not limited to these. In the following specific examples, a, b, and c represent the proportions (mass%) of each component. a = 99 to 60, b = 1 to 40, and c = 1 to 40. However, a + b + c = 100, and b + c = 1 to 40.

[0039] [ka]

[0040] In the present invention, the water-soluble polymer (X) may be used alone or in combination of two or more.

[0041] (Water-soluble compound (Y)) In the present invention, the water-soluble compound (Y) is a water-soluble compound (monomer or polymer) having a structure different from that of the water-soluble polymer (X), and can be any of a wide variety of compounds that function as a thickener for the slurry for forming an electrode active material layer of a secondary battery. Examples of such thickeners include cellulose compounds and polysaccharides such as natural polysaccharides. Examples of cellulose compounds include methyl cellulose, ethyl cellulose, benzyl cellulose, triethyl cellulose, cyanoethyl cellulose, nitrocellulose, hydroxymethyl cellulose, hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), hydroxybutyl methyl cellulose, carboxymethyl cellulose (CMC), aminomethyl hydroxypropyl cellulose, aminoethyl hydroxypropyl cellulose, cellulose nanofiber (CNF), cellulose nanocrystal (CNC), etc. Furthermore, the cellulose compound may be in the form of a salt such as an ammonium salt, a sodium salt, or a lithium salt. Examples of natural polysaccharides include carrageenan, xanthan gum, guar gum, tamarind gum (tamarind seed gum), diutan gum, welan gum, gellan gum, locust bean gum, and tara gum. Among these, the water-soluble compound (Y) preferably contains at least one of carboxymethyl cellulose, cellulose nanofiber, hydroxyethyl cellulose, hydroxypropyl cellulose, and xanthan gum. In the present invention, the water-soluble compound (Y) may be used alone or in combination of two or more.

[0042] (polymer particles) The polymer particles used in the present invention are particulate polymers, and the "particulate" may be flat, amorphous, etc., and is preferably spherical or granular. The polymer particles are water-insoluble polymers, i.e., polymers whose solubility in water at 20°C is less than 10 g / L-H2O (10 g or more do not dissolve in 1 liter of water).

[0043] The tensile modulus of the polymer particles is not particularly limited, and is preferably 100 to 3,000 MPa, more preferably 100 to 1,000 MPa, from the viewpoint of increasing the adhesion between the solid particles or between the current collector and the solid particles, thereby improving the adhesion and cycle characteristics of the electrode sheet. In the present invention, the tensile modulus is a value obtained by the same method as in the tensile modulus test of the binder composition of the present invention described in the Examples below, except that polymer particles (latex polymer) are used instead of the binder composition of the present invention.

[0044] The glass transition temperature of the polymer particles is not particularly limited, and is preferably from -50 to 150°C, more preferably from -30 to 100°C, from the viewpoint of improving the adhesion and cycle characteristics of the electrode sheet. When the polymer particles have two or more glass transition temperatures, it is preferable that all of them fall within the above-mentioned preferred range.

[0045] - Glass transition temperature - When commercially available polymer particles are used, the glass transition temperature of the polymer particles is the value listed in the manufacturer's catalog. If glass transition temperature information from the manufacturer is unavailable or if synthetic polymer particles are used, the glass transition temperature in the table in Chapter 36 of POLYMER HANDBOOK 4th Edition is used. If the glass transition temperature is not listed in the literature, the glass transition temperature measured under the following measurement conditions is used.

[0046] The glass transition temperature (Tg) is calculated by measuring a dried sample of polymer particles using a differential scanning calorimeter: X-DSC7000 (trade name, manufactured by SII Nano Technology Co., Ltd.) under the following measurement conditions. The measurement is carried out twice on the same sample, and the result of the second measurement is used. (Measurement conditions) Atmosphere in the measurement chamber: Nitrogen gas (50 mL / min) Heating rate: 5℃ / min Measurement start temperature: -80℃ Measurement end temperature: 250℃ Sample pan: Aluminum pan Measurement sample mass: 5 mg Calculation of Tg: Tg is calculated by rounding off the decimal point of the midpoint between the start and end points of the decline in a DSC (differential scanning calorimetry) chart.

[0047] The average particle size (average primary particle size) of the polymer particles is not particularly limited, but is preferably from 50 to 300 nm, more preferably from 50 to 250 nm, and even more preferably from 50 to 200 nm. When commercially available polymer particles are used, the average particle size of the polymer particles is the value listed in the manufacturer's catalog. When information on the average particle size from the manufacturer is not available or when synthesized polymer particles are used, the average particle size of the polymer particles may be a value obtained by applying the measurement method for the average particle size (volume-based median diameter D50 in water) of the negative electrode active material described below.

[0048] The polymer particles may be either step-polymerized or chain-polymerized, with chain-polymerized particles being preferred. The chain-polymerized polymer particles may be either a homopolymer or a copolymer. The copolymer may be either random or block polymerized. Examples of the constituent components of the polymer particles (chain polymerization polymers) include a conjugated diene component, an aromatic vinyl monomer component, an ethylenically unsaturated carboxylic acid component, a cyano group-containing ethylenic monomer component, an ethylenically unsaturated carboxylic acid ester component, and a fluorinated vinyl monomer component, and it is preferable that the polymer particles contain at least one of the conjugated diene component, the ethylenically unsaturated carboxylic acid component, the cyano group-containing ethylenic monomer component, and the aromatic vinyl monomer component. Among the above constituent components, it is preferable that the polymer particles contain a conjugated diene component and an aromatic vinyl monomer component. In the above, the term "aromatic vinyl monomer component" refers to a component derived from a monomer having a carbon-carbon double bond (preferably one or two, more preferably one) and an aryl group (preferably one); the term "ethylenically unsaturated carboxylic acid component" refers to a component derived from a monomer having a carbon-carbon double bond (preferably one) and a carboxy group (preferably one or two); the term "cyano group-containing ethylenic monomer component" refers to a component derived from a monomer having a carbon-carbon double bond (preferably one) and a cyano group (preferably one or two, more preferably one); the term "ethylenically unsaturated carboxylic acid ester component" refers to a component derived from a monomer having a carbon-carbon double bond (preferably one) and a carboxylic acid ester moiety (esterified carboxy group) (preferably one); and the term "vinyl fluoride monomer component" refers to a component derived from ethylene having 1 to 4 (preferably 2) fluorine atoms. The above "carbon-carbon double bond" does not include a carbon-carbon double bond in an aromatic ring.

[0049] Examples of conjugated dienes that lead to the conjugated diene component include aliphatic conjugated dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene. Examples of aromatic vinyl monomers that lead to the aromatic vinyl monomer component include styrene, α-methylstyrene, 4-tert-butylstyrene, 4-tert-butoxystyrene, vinyltoluene (3-vinyltoluene, 4-vinyltoluene), and divinylbenzene (m-divinylbenzene, p-divinylbenzene). Examples of the ethylenically unsaturated carboxylic acid from which the ethylenically unsaturated carboxylic acid component is derived include (meth)acrylic acid, maleic acid, itaconic acid, and fumaric acid. Examples of cyano group-containing ethylenic monomers that lead to the cyano group-containing ethylenic monomer component include (meth)acrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and vinylidene cyanide. Examples of the ethylenically unsaturated carboxylic acid ester from which the ethylenically unsaturated carboxylic acid ester component is derived include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of vinyl fluoride monomers that lead to vinyl fluoride monomer components include vinylidene fluoride.

[0050] The polymer particles used in the present invention can be obtained by a conventional polymer synthesis method. In the synthesis of the polymer particles used in the present invention, the method and conditions for chain polymerization etc. are not particularly limited, and conventional methods and conditions can be appropriately applied depending on the purpose. The polymer particles may be particles obtained by subjecting the step-polymerized polymer particles and chain-polymerized polymer particles described above to a modification treatment such as carboxy modification. The method and conditions for the modification treatment are not particularly limited, and the modification treatment can be carried out by a conventional method. The water solubility, tensile modulus, glass transition temperature and average particle size of the polymer particles can be adjusted, for example, by the type and content of the constituent components in the polymer.

[0051] Specific examples of polymer particles include styrene / butadiene copolymers, acrylic polymers, and poly(vinylidene fluoride), with styrene / butadiene copolymers being preferred. The styrene / butadiene copolymer means a copolymer having the above aromatic vinyl monomer component and the above conjugated diene component, and may be a modified copolymer such as a carboxy-modified copolymer. In the present invention, the polymer particles may be used alone or in combination of two or more kinds.

[0052] The binder composition of the present invention may contain, in addition to the water-soluble polymer (X), the water-soluble compound (Y) and the polymer particles, other polymers that are commonly used as binders for batteries. The total proportion of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles in the total solid content of the binder composition of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Most preferably, the total solid content of the binder composition of the present invention is the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles. In the binder composition of the present invention, the mass ratio of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles (mass of the water-soluble polymer (X):mass of the water-soluble compound (Y):mass of the polymer particles) is not particularly limited, and is preferably 10-80 / 3-80 / 10-77, and more preferably 20-70 / 3-50 / 20-60.

[0053] The binder composition of the present invention contains water as the liquid medium. The water content in the binder composition of the present invention is not particularly limited and can be, for example, 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more. The binder composition of the present invention may contain 60% by mass or more of water, 70% by mass or more, or 80% by mass or more. On the other hand, it is practical for the water content in the binder composition of the present invention to be 99.5% by mass or less. The binder composition of the present invention may contain a liquid medium other than water. Examples of the liquid medium other than water include organic solvents that are miscible with water without phase separation when mixed with water (hereinafter referred to as water-soluble organic solvents), and preferred examples thereof include N-methylpyrrolidone, methanol, ethanol, acetone, and tetrahydrofuran.

[0054] In the binder composition of the present invention, the contents of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles may be appropriately set depending on the purpose. For example, the total content of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles in the binder composition may be 0.5 to 50% by mass, preferably 5 to 30% by mass, and more preferably 10 to 20% by mass. The binder composition of the present invention may contain other components in addition to the water-soluble polymer (X), the water-soluble compound (Y), the polymer particles, water, and a liquid medium other than water, depending on the purpose. Examples of other components include polyhydric alcohols (alcohols having two or more hydroxy groups). The binder composition of the present invention can also be prepared by, for example, diluting a synthesis liquid of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles. Therefore, the binder composition of the present invention may contain compounds used in the synthesis of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles, or by-products produced after the reaction thereof.

[0055] The binder composition of the present invention can be used for either a positive electrode or a negative electrode, but is preferably used for a negative electrode, and particularly preferably for a negative electrode composition having a silicon-based active material.

[0056] [Composition for electrode] The electrode composition of the present invention (hereinafter also referred to as "the electrode composition of the present invention") contains the binder composition of the present invention, an active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table (hereinafter also simply referred to as "active material"), and a conductive aid. That is, the electrode composition of the present invention is a composition containing a water-soluble polymer (X), a water-soluble compound (Y), polymer particles, water, an active material, and a conductive aid. The tensile modulus of the remainder obtained by removing the active material and the conductive assistant from the electrode composition of the present invention is preferably 1500 to 9800 MPa. The "remaining portion obtained by removing the active material and the conductive assistant from the electrode composition of the present invention" corresponds to the "binder composition of the present invention", and its composition is the same as that of the binder composition of the present invention. The "tensile modulus of the remainder obtained by removing the active material and the conductive assistant from the electrode composition of the present invention" corresponds to the "tensile modulus of the binder composition of the present invention", and its test method and preferred range are the same as those for the tensile modulus of the binder composition of the present invention.

[0057] The active material may be a positive electrode active material or a negative electrode active material. When the electrode composition of the present invention contains a positive electrode active material, the electrode composition of the present invention can be used as a slurry for forming a positive electrode active material layer of a secondary battery. When the electrode composition of the present invention contains a negative electrode active material, the electrode composition of the present invention can be used as a slurry for forming a negative electrode active material layer. The electrode composition of the present invention can be used for either a positive electrode or a negative electrode, but is preferably used as an electrode composition for a negative electrode, and is particularly preferably used as an electrode composition for a negative electrode containing a silicon-based active material. The electrode composition of the present invention may further contain other additives as required. The active material, conductive aid, and other additives are not particularly limited, and may be appropriately selected from those commonly used in secondary batteries according to the purpose.

[0058] The content of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles in the electrode composition of the present invention is not particularly limited, and is preferably 0.5 to 30 mass% in total, more preferably 1.0 to 20 mass%, even more preferably 1.5 to 15 mass%, and particularly preferably 2.5 to 10 mass%, based on the total solid content. In the electrode composition of the present invention, the mass ratio of the water-soluble polymer (X), the water-soluble compound (Y), and the polymer particles (mass of the water-soluble polymer (X):mass of the water-soluble compound (Y):mass of the polymer particles) is the same as the mass ratio thereof in the binder composition of the present invention. The content of water in the electrode composition of the present invention is preferably 30 to 70 mass%, more preferably 40 to 60 mass%, and even more preferably 45 to 55 mass%. When the electrode composition of the present invention contains the binder composition of the present invention, the electrode composition of the present invention contains water derived from the binder composition of the present invention and may further contain water added during the preparation of the electrode composition. The solid content of the composition for an electrode of the present invention is preferably 30 to 70 mass %, more preferably 40 to 60 mass %, and even more preferably 45 to 55 mass %. The total proportion of the water-soluble polymer (X), water-soluble compound (Y), polymer particles, active material, and conductive aid in the total solid content contained in the electrode composition of the present invention is preferably 70 mass % or more, more preferably 80 mass % or more, even more preferably 90 mass % or more, and particularly preferably 95 mass % or more. It is most preferable that the total solid content contained in the electrode composition of the present invention is the water-soluble polymer (X), water-soluble compound (Y), polymer particles, active material, and conductive aid.

[0059] The electrode composition of the present invention has a storage modulus G at a shear strain of 0.01% when used to form an electrode for a secondary battery. C ' and storage modulus G at shear strain of 10% D ' and the difference (G C '-G D It is preferable that the pressure drop σ′ is between 100 and 1000 Pa. This makes it easier for the electrode composition to enjoy the effects of the binder composition of the present invention, such as the uniform dispersion of solid particles and the improvement in the followability and binding properties of solid particles. As a result, it becomes possible to further improve the adhesion of an electrode sheet obtained using the electrode composition of the present invention, and further improve the cycle characteristics of a secondary battery. The storage modulus G at the shear strain of 0.01% C ' and storage modulus G at shear strain of 10% D "Storage modulus characteristic 1" can be measured using a rheometer. Specifically, the measurement can be performed under the same conditions as in the measurement for determining whether the above-mentioned "Storage modulus characteristic 1" is satisfied, except that the electrode composition of the present invention is used instead of the measurement slurry. The "storage modulus G at a shear strain of 0.01%" of the electrode composition of the present invention C ', 'Storage modulus G at shear strain of 10% D ', 'Storage modulus G at shear strain of 0.01% C ' and storage modulus G at shear strain of 10% D ' and the difference (G C '-G D ')" are the storage modulus G at a shear strain of 0.01% mentioned above, respectively. A', 'Storage modulus G at shear strain of 10% B ', 'Storage modulus G at shear strain of 0.01% A ' and storage modulus G at shear strain of 10% B ' and the difference (G A '-G B Preferred ranges for ")" can be applied.

[0060] (active material) The electrode composition of the present invention contains an active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table.

[0061] -Cathode active material- The positive electrode active material is an active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table, and among these, one capable of reversibly inserting and releasing lithium ions is preferred. The material is not particularly limited as long as it has the above properties, and may be 1) a transition metal oxide, 2) an organic substance, 3) an element capable of forming a complex with Li, such as sulfur, or 4) a complex of sulfur and a metal. Among these, it is preferable to use a transition metal oxide as the positive electrode active material, and a transition metal element M a A transition metal oxide containing at least one element selected from Co, Ni, Fe, Mn, Cu, and V is more preferred. b (Elements of Group 1 (Ia) of the periodic table other than lithium, elements of Group 2 (IIa) of the periodic table, Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, etc.) may be mixed. b The amount of the transition metal element M a The amount of the transition metal element M is preferably 0 to 30 mol % relative to 100 mol %. a The molar ratio of Li to a ) is more preferably 0.3 to 2.2. Specific examples of transition metal oxides include (MA) transition metal oxides having a layered rock salt structure, (MB) transition metal oxides having a spinel structure, (MC) lithium-containing transition metal phosphate compounds, (MD) lithium-containing transition metal halide phosphate compounds, and (ME) lithium-containing transition metal silicate compounds.

[0062] (MA) Specific examples of transition metal oxides with a layered rock salt structure include LiCoO2 (lithium cobalt oxide [LCO]), LiNi2O2 (lithium nickel oxide), and LiNi 0.85 Co 0.10 Al 0.05 O2 (nickel cobalt lithium aluminate [NCA]), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (lithium nickel manganese cobalt oxide [NMC]) and LiNi 0.5 Mn 0.5 O2 (lithium manganese nickel oxide). (MB) Specific examples of transition metal oxides having a spinel structure include LiMn2O4 (LMO), LiCoMnO4, Li2FeMn3O8, Li2CuMn3O8, Li2CrMn3O8, and Li2NiMn3O8. (MC) Examples of lithium-containing transition metal phosphate compounds include olivine-type iron phosphates such as LiFePO4 and Li3Fe2(PO4)3, iron pyrophosphates such as LiFeP2O7, cobalt phosphates such as LiCoPO4, and monoclinic Nasicon-type vanadium phosphates such as Li3V2(PO4)3 (lithium vanadium phosphate). (MD) Examples of lithium-containing transition metal halide phosphate compounds include iron fluorophosphates such as Li2FePO4F, manganese fluorophosphates such as Li2MnPO4F, and cobalt fluorophosphates such as Li2CoPO4F. (ME) Examples of lithium-containing transition metal silicate compounds include Li2FeSiO4, Li2MnSiO4, and Li2CoSiO4. In the present invention, transition metal oxides having a layered rock salt structure (MA) are preferred, and LCO or NMC are more preferred.

[0063] The shape of the positive electrode active material is not particularly limited, but a particulate form is preferred. The average particle size (volume-based median diameter D50) of the positive electrode active material is not particularly limited. For example, it can be 0.1 to 50 μm. The positive electrode active material can be adjusted to a predetermined particle size by a conventional method using a grinder or classifier. The method for adjusting the particle size of the negative electrode active material to a predetermined particle size, which will be described later, can also be applied. The positive electrode active material obtained by the firing method may be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, an organic solvent, or the like. When a commercially available positive electrode active material is used, the value described in the manufacturer's catalog is used as the average particle size of the positive electrode active material. When the information on the average particle size from the manufacturer is not available or when a synthesized positive electrode active material is used, the value measured and calculated by the method described below in the section on negative electrode active materials is used.

[0064] The chemical formula of the compound obtained by the above calcination method can be measured by inductively coupled plasma (ICP) emission spectroscopy, or simply calculated from the difference in mass of the powder before and after calcination.

[0065] The surface of the positive electrode active material may be coated with an oxide such as another metal oxide, a carbon-based material, etc. As the surface coating material, a surface coating material that can be used to coat the surface of a negative electrode active material, which will be described later, can be used.

[0066] The surface of the positive electrode active material may be treated with sulfur or phosphorus. Furthermore, the particle surfaces of the positive electrode active material may be subjected to a surface treatment with actinic rays or an active gas (plasma, etc.) before or after the above surface coating.

[0067] The positive electrode active materials may be used singly or in combination of two or more. When forming a positive electrode active material layer, the unit area (cm 2 The mass (mg) (weight per unit area) of the positive electrode active material is not particularly limited and can be determined appropriately depending on the designed battery capacity.

[0068] The content of the positive electrode active material in the electrode composition of the present invention is not particularly limited, and is preferably 10 to 99 mass % relative to the total solid content, more preferably 30 to 98 mass %, even more preferably 50 to 97 mass %, and particularly preferably 55 to 95 mass %.

[0069] -Negative electrode active material- The negative electrode active material is an active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table, and among these, those capable of reversibly inserting and releasing lithium ions are preferred. The material is not particularly limited as long as it has the above-mentioned properties, and examples thereof include carbonaceous materials, silicon-based materials (meaning materials containing silicon element), tin-based materials (meaning materials containing tin element), metal oxides, metal composite oxides, elemental lithium, and lithium alloys. Among these, carbonaceous materials and silicon-based materials are preferably used from the viewpoint of reliability.

[0070] The carbonaceous material used as the negative electrode active material is a material essentially composed of carbon. Examples include carbon black such as petroleum pitch and acetylene black, graphite (natural graphite such as flake graphite and block graphite, artificial graphite such as vapor-grown graphite and fibrous graphite, and expanded graphite obtained by specially processing flake graphite), activated carbon, carbon fiber, coke, soft carbon, hard carbon, and carbonaceous materials obtained by calcining various synthetic resins such as PAN (polyacrylonitrile)-based resins and furfuryl alcohol resins. Further examples include various carbon fibers such as PAN-based carbon fiber, cellulose-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, dehydrated PVA (polyvinyl alcohol)-based carbon fiber, lignin carbon fiber, glassy carbon fiber, and activated carbon fiber, mesophase microspheres, graphite whiskers, and tabular graphite.

[0071] Examples of tin-based materials (tin-based active materials) used as negative electrode active materials include Sn, SnO, SnO2, SnS, and SnS2.

[0072] The metal oxides and metal composite oxides used as the negative electrode active material are not particularly limited as long as they are oxides that can insert and release (preferably store and release) ions of a metal belonging to Group 1 or 2 of the periodic table (preferably lithium ions). Examples of metal oxides include oxides of metal elements (metal oxides) and oxides of metalloid elements (metalloid oxides). Examples of metal composite oxides include composite oxides of metal elements, composite oxides of metal elements and metalloid elements, and composite oxides of metalloid elements. These metal oxides and metal composite oxides are preferably amorphous oxides, and further preferred examples include chalcogenides, which are reaction products between metal elements and elements of Group 16 of the periodic table. The term "amorphous" as used herein means that the oxides have a broad scattering band with a peak in the 2θ range of 20° to 40° when measured by X-ray diffraction using CuKα radiation, and may also have crystalline diffraction lines. Among the compounds consisting of the amorphous oxides and chalcogenides, amorphous oxides or chalcogenides of metalloid elements are more preferred, and oxides or composite oxides or chalcogenides consisting of one or a combination of two or more elements selected from Groups 13 (IIIB) to 15 (VB) of the Periodic Table (e.g., Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi) are particularly preferred. Specific examples of amorphous oxides and chalcogenides include Ga2O3, GeO, PbO, PbO2, Pb2O3, Pb2O4, Pb3O4, Sb2O3, Sb2O4, Sb2O8Bi2O3, Sb2O8Si2O3, Sb2O5, Bi2O3, Bi2O4, GeS, PbS, PbS2, Sb2S3, and Sb2S5.

[0073] The metal (composite) oxides and the chalcogenides preferably contain at least one of titanium and lithium as a constituent component from the viewpoint of high current density charge / discharge characteristics. Examples of lithium-containing metal composite oxides (lithium composite metal oxides) include composite oxides of lithium oxide and the metal (composite) oxides or the chalcogenides, more specifically Li2SnO2.

[0074] The negative electrode active material preferably contains titanium element. More specifically, TiNb2O7 (niobium titanate oxide [NTO]), Li4Ti5O 12 (lithium titanate [LTO]) is preferable in that it has excellent rapid charge-discharge characteristics because of its small volume change during lithium ion intercalation and deintercalation, suppresses electrode deterioration, and enables improvement of the cycle characteristics of the lithium ion secondary battery.

[0075] The6]]The lithium alloy as the negative electrode active material is not particularly limited as long as it is an alloy commonly used as the negative electrode active material of a secondary battery. For example, a lithium aluminum alloy can be mentioned.

[0076] The silicon-based material (silicon-based active material) is a negative electrode active material containing silicon element. For example, silicon materials such as Si, SiOx (0 < x ≤ 1.5), and further, silicon-containing alloys containing titanium, vanadium, chromium, manganese, nickel, copper or lanthanum (for example, LaSi2, VSi2), or organized active materials (for example, LaSi2 / Si), and in addition, oxides or composite oxides containing silicon element in the description of the above metal oxides and metal composite oxides, active materials containing silicon element and tin element such as SnSiO3, SnSiS3, etc. can be mentioned. SiOx can be used as a negative electrode active material (semimetal oxide) itself, and can also be used as an active material (its precursor material) capable of forming an alloy with lithium because Si is generated by the operation of the battery.

[0077] In the above, the negative electrode active material has been described focusing on the components, but from the viewpoint of characteristics, the negative electrode active material is preferably a negative electrode active material capable of forming an alloy with lithium. <~ The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is a material commonly used as the negative electrode active material of a secondary battery. Examples of such an active material include the negative electrode active materials containing the above-mentioned silicon element and / or tin element, and various metals such as Al and In. A silicon-based active material is preferable in that it enables a higher battery capacity, and a silicon-based active material having a silicon element content of 40 mol% or more of all constituent elements is more preferable. Generally, negative electrodes containing these negative electrode active materials capable of forming an alloy with lithium (e.g., Si negative electrodes containing silicon-based active materials, Sn negative electrodes containing tin-based active materials) can store more Li ions than negative electrodes made solely of carbonaceous materials (e.g., graphite, carbon black, etc.). In other words, the amount of Li ions stored per unit mass increases. This allows for a larger battery capacity (energy density). As a result, there is the advantage that the battery operating time can be extended. Thus, negative electrode active materials capable of forming an alloy with lithium, such as negative electrode active materials containing silicon and / or tin, are also referred to as high-capacity active materials.

[0078] The surface of the negative electrode active material may be coated with an oxide such as another metal oxide, a carbon-based material, or the like (hereinafter, being surface-coated with a carbon-based material may be referred to as being "carbon-coated"). Examples of surface coating materials include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si, or Li. Specific examples include titanate spinel, tantalum-based oxides, niobium-based oxides, and lithium niobate-based compounds. More specifically, Li4Ti5O 12 , Li2Ti2O5, LiTaO3, LiNbO3, LiAlO2, Li2ZrO3, Li2WO4, Li2TiO3, Li2B4O7, Li3PO4, Li2MoO4, Li3BO3, LiBO2, Li2CO3, Li2SiO3, SiO2, TiO2, ZrO2, Al2O3, B2O3, etc. Carbon-based materials such as C, SiC, and carbon-added silicon oxides can also be used as surface coating materials.

[0079] The surface of the negative electrode active material may be treated with sulfur or phosphorus. Furthermore, the particle surfaces of the negative electrode active material may be subjected to a surface treatment with actinic rays or an active gas (plasma, etc.) before or after the above surface coating.

[0080] The negative electrode active material may be doped with a metal element, which is preferably at least one of Li, Ni, and Ti, and more preferably Li.

[0081] In the present invention, as the negative electrode active material, it is preferable to use a silicon-based active material, and it is more preferable to use silicon oxide (SiO x (0 < x ≤ 1.5)) or carbon-coated silicon oxide (carbon-coated SiOx (0 < x ≤ 1.5)), and it is even more preferable to use carbon-coated silicon oxide. The carbon-coated silicon oxide may be further doped with a metal element. The proportion of the content of the carbon element in the carbon-coated silicon oxide is not particularly limited. For example, 0.5 to 5% by mass is preferable, and 1 to 3% by mass is more preferable. Commercially available products may be used for the silicon oxide or the carbon-coated silicon oxide. In addition, the carbon-coated silicon oxide can also be prepared by carbon-coating silicon oxide, for example, referring to Japanese Patent Application Laid-Open No. 2019-204686. The content of the silicon oxide or the carbon-coated silicon oxide in the negative electrode active material is not particularly limited. For example, it can be 10 to 90% by mass, preferably 10 to 5% by mass, and more preferably 15 to 40% by mass. When the negative electrode active material is silicon oxide or carbon-coated silicon oxide, the average particle size is preferably 5 to 20 μm. In the present invention, as the negative electrode active material, it is also preferable to use a silicon-based material doped with a metal element, and a silicon-based material doped with at least one of Li, Ni, and Ti is more preferable, and a silicon-based material doped with Li is even more preferable. As the silicon-based material to be doped with the metal element, silicon oxide or carbon-coated silicon oxide is preferable. Commercially available products may be used as silicon oxide doped with a metal element and silicon oxide doped with both a carbon coating and a metal element. For example, see JP-A-2022-121582, WO 14 / 188851, and JP-A-2021-150077. Silicon oxide or carbon-coated silicon oxide may be doped with a metal element, or silicon oxide may be doped with a metal element and, if necessary, further coated with carbon. In the present invention, the phrase "both carbon coated and doped with a metal element" is used to mean both a material that has been doped with a metal element and then carbon coated, and a material that has been carbon coated and then doped with a metal element. In the present invention, it is also preferable to use, as the negative electrode active material, a silicon-based material that is both carbon-coated and doped with a metal element, more preferably silicon oxide that is both carbon-coated and doped with a metal element, and particularly preferably silicon oxide that is both carbon-coated and doped with lithium.

[0082] The shape of the negative electrode active material is not particularly limited, but a particulate form is preferred. The average particle size (volume-based median diameter D50) of the negative electrode active material is preferably 0.1 to 60 μm. To achieve a predetermined particle size, it can be prepared by a conventional method using a grinder or classifier. For example, a mortar, ball mill, sand mill, vibration ball mill, satellite ball mill, planetary ball mill, swirling airflow jet mill, or sieve is preferably used. Wet grinding in the presence of water or an organic solvent such as methanol can also be performed during grinding. Classification is preferably performed to achieve a desired particle size. The classification method is not particularly limited, and a sieve, air classifier, or the like can be used as desired. Classification can be performed using either a dry method or a wet method. When a commercially available negative electrode active material is used, the average particle size of the negative electrode active material is the value listed in the manufacturer's catalog. When information on the average particle size from the manufacturer is unavailable or when a synthesized negative electrode active material is used, the negative electrode active material is dispersed in water and measured using a laser diffraction / scattering particle size distribution analyzer (e.g., HORIBA Particle LA-960V2), and the average particle size (volume-based median diameter D50 in water) obtained is used.

[0083] The negative electrode active material may be used alone or in combination of two or more. Among them, a combination of a silicon-based active material and a carbonaceous material is preferred, a combination of a silicon-based active material and graphite is more preferred, and a combination of silicon oxide or carbon-coated silicon oxide and graphite is even more preferred. The silicon oxide and carbon-coated silicon oxide may be silicon oxide doped with the above-mentioned metal element and silicon oxide both carbon-coated and doped with the metal element, respectively. The doped metal element is preferably at least one of Li, Ni, and Ti, and more preferably Li, Ni, or Ti. When a silicon-based active material is combined with graphite, the mass ratio of the silicon-based active material to the graphite (silicon-based active material / graphite) is preferably 2 or less, more preferably 1 or less, and even more preferably 0.5 or less. There is no particular lower limit to the mass ratio of the silicon-based active material to the graphite, but a mass ratio of 0.05 or more is practical.

[0084] The specific surface area (BET specific surface area) of the negative electrode active material is 0.1 to 50 m 2 / g is preferred. When a commercially available negative electrode active material is used, the specific surface area of ​​the negative electrode active material is the value listed in the manufacturer's catalog. When the manufacturer's specific surface area information is unavailable or when a synthesized negative electrode active material is used, the negative electrode active material is packed into a sample tube and dried by flowing nitrogen, and the specific surface area (BET specific surface area) is calculated by the BET (single point) method using a nitrogen adsorption method using a specific surface area / pore distribution measuring device (e.g., Microtrack-Bel BELSORP MINI).

[0085] The content of the negative electrode active material in the electrode composition of the present invention is not particularly limited, and is preferably 10 to 99 mass % relative to the total solid content, more preferably 30 to 98 mass %, even more preferably 45 to 97 mass %, and particularly preferably 55 to 95 mass %.

[0086] In the present invention, when the negative electrode active material layer is formed by charging the battery, ions of a metal belonging to Group 1 or 2 of the periodic table that are generated in the secondary battery can be used instead of the above-mentioned negative electrode active material. The negative electrode active material layer can be formed by bonding these ions with electrons and depositing them as a metal.

[0087] (Conductive additive) The electrode composition of the present invention contains a conductive assistant. The conductive aid is not particularly limited, and can be any known conductive aid. For example, it can be an electron conductive material such as carbon blacks (acetylene black, ketjen black, furnace black, etc.), amorphous carbon (needle coke, etc.), carbon fibers (vapor-grown carbon fiber, carbon nanotube, etc.), carbonaceous materials (graphene, fullerene, etc.), metal powders (metal fibers) (e.g., copper, nickel, etc.), or conductive polymers (e.g., polyaniline, polypyrrole, polythiophene, polyacetylene, polyphenylene derivatives, etc.). Acetylene black is preferred as the conductive aid. In the present invention, among the above-mentioned conductive additives, those that do not insert or release ions of metals belonging to Group 1 or Group 2 of the periodic table (e.g., Li) when a battery is charged or discharged and do not function as an active material are defined as conductive additives. Therefore, among conductive additives, those that can function as an active material in the active material layer when a battery is charged or discharged are classified as active materials rather than conductive additives. Whether or not a conductive additive functions as an active material when a battery is charged or discharged is not uniquely determined, but is determined by its combination with the active material.

[0088] The conductive assistant may be used alone or in combination of two or more kinds. The content of the conductive auxiliary in the electrode composition of the present invention is preferably 0.5 to 60 mass% relative to the total solid content, more preferably 1.0 to 50 mass%, even more preferably 1.5 to 40 mass%, and particularly preferably 2.5 to 35 mass%. The content of the conductive auxiliary in the electrode composition of the present invention can be 2.5 to 25 mass%, 3.0 to 20 mass%, or 4.0 to 10 mass% relative to the total solid content.

[0089] The shape of the conductive additive is not particularly limited, but a particulate shape is preferred. The average particle size (volume-based median diameter D50) of the conductive assistant is not particularly limited, and is, for example, preferably 0.01 to 50 μm, more preferably 0.02 to 10.0 μm, and even more preferably 0.02 to 0.2 μm. When using a commercially available conductive additive, the average particle size of the conductive additive is the value listed in the manufacturer's catalog. When information on the average particle size from the manufacturer is not available or when a synthetic conductive additive is used, the average particle size of the conductive additive may be the value obtained by applying the above-mentioned method for measuring the average particle size of the negative electrode active material (volume-based median diameter D50 in water).

[0090] The specific surface area (BET specific surface area) of the conductive additive is 10 to 100 m 2 / g is preferred. When a commercially available conductive additive is used, the specific surface area of ​​the conductive additive is the value listed in the manufacturer's catalog. When the information on the specific surface area from the manufacturer is not available or when a synthetic conductive additive is used, the value obtained by applying the above-mentioned method for measuring the specific surface area (BET specific surface area) of the negative electrode active material (BET method using nitrogen adsorption) may be used.

[0091] (Other additives) The electrode composition of the present invention may contain, as desired, other components in addition to the above components, such as a lithium salt, an ionic liquid, a thickener, an antifoaming agent, a leveling agent, a dehydrating agent, and an antioxidant. For details of the active materials, conductive aids, and other additives, reference can be made to, for example, International Publication No. 2019 / 203334 and Japanese Patent Application Laid-Open No. 2015-46389.

[0092] [Method for preparing binder composition for secondary battery and electrode composition] The binder composition of the present invention can be prepared as a mixture, preferably as a slurry, by mixing the water-soluble polymer (X), the water-soluble compound (Y), polymer particles, water, and optionally any other components, for example, using any of various commonly used mixers. In the case of the electrode composition of the present invention, in addition to the above, an active material and a conductive aid are mixed with any other additives as appropriate to prepare a mixture, preferably a slurry. The mixing method is not particularly limited, and the components may be mixed all at once or sequentially. Furthermore, a mixture obtained by mixing multiple components may be mixed with other components. When preparing the electrode composition of the present invention, the binder composition of the present invention may be prepared first, followed by mixing with the active material, conductive additive, and other components. Alternatively, some of the components of the binder composition of the present invention may be mixed with the active material, conductive additive, and other components, and then the remaining components of the binder composition may be mixed. For example, the electrode composition of the present invention may be obtained by mixing the water-soluble polymer (X), the water-soluble compound (Y), the active material, the conductive additive, and water, followed by adding water and polymer particles and further mixing.

[0093] [Electrode sheet] The electrode sheet of the present invention has a layer (electrode active material layer, i.e., a negative electrode active material layer or a positive electrode active material layer) formed using the electrode composition of the present invention. The electrode sheet of the present invention may be an electrode sheet having an electrode active material layer formed using the electrode composition of the present invention, and may be a sheet in which the electrode active material layer is formed on a substrate such as a current collector, or a sheet in which there is no substrate and which is formed only of the electrode active material layer (a negative electrode active material layer or a positive electrode active material layer). This electrode sheet is usually a sheet configured by laminating the electrode active material layer on a current collector. The electrode sheet of the present invention may have other layers, for example, a protective layer such as a release sheet, or a coating layer. The electrode sheet of the present invention can be suitably used as a material constituting an anode active material layer or a cathode active material layer of a secondary battery, or as a laminate of an anode current collector and an anode active material layer (anode layer) or a laminate of a cathode current collector and a cathode active material layer (cathode layer).

[0094] When the electrode sheet of the present invention has a current collector, the current collector constituting the electrode sheet of the present invention is an electron carrier and is usually in the form of a film sheet. The current collector can be appropriately selected depending on the active material. Examples of materials for the positive electrode current collector include aluminum, aluminum alloys, stainless steel, nickel, and titanium, and aluminum or aluminum alloys are preferred. Examples of the positive electrode current collector include aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, or silver to form a coating layer (thin film). Examples of materials for the negative electrode current collector include aluminum, copper, copper alloys, stainless steel, nickel, and titanium, and aluminum, copper, copper alloys, and stainless steel are preferred. Examples of negative electrode current collectors include those in which the surface of aluminum, copper, copper alloys, or stainless steel is treated with carbon, nickel, titanium, or silver to form a coating layer (thin film).

[0095] There are no particular limitations on the thickness of the positive electrode active material layer that constitutes the electrode sheet of the present invention, and it can be, for example, 5 to 500 μm, and preferably 20 to 200 μm. The thickness of the positive electrode current collector constituting the electrode sheet of the present invention is not particularly limited, and can be, for example, 10 to 100 μm, preferably 10 to 50 μm.

[0096] There are no particular limitations on the thickness of the negative electrode active material layer that constitutes the electrode sheet of the present invention, and it can be, for example, 5 to 500 μm, preferably 20 to 200 μm. The thickness of the negative electrode current collector constituting the electrode sheet of the present invention is not particularly limited, and can be, for example, 10 to 100 μm, preferably 10 to 50 μm.

[0097] [Electrode sheet manufacturing method] The electrode sheet of the present invention can be obtained by forming an electrode active material layer using the electrode composition of the present invention. For example, the electrode sheet of the present invention can be manufactured by forming a film using the electrode composition of the present invention. Specifically, the electrode composition of the present invention is applied to a substrate such as a current collector (optionally via another layer) to form a coating film, which is then dried to obtain an electrode sheet having an active material layer (coated and dried layer) on the substrate. The secondary battery of the present invention can be obtained by incorporating the electrode sheet obtained by the above-described method for producing an electrode sheet into at least one of the electrodes (positive electrode and negative electrode) of the secondary battery.

[0098] [Secondary battery] In the secondary battery of the present invention, at least one of the positive electrode active material layer and the negative electrode active material layer is a layer formed using the electrode composition of the present invention. The secondary battery of the present invention will be described taking a non-aqueous electrolyte secondary battery as an example, but the secondary battery of the present invention is not limited to a non-aqueous electrolyte secondary battery and broadly includes secondary batteries in general.

[0099] A nonaqueous electrolyte secondary battery according to a preferred embodiment of the present invention includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. The positive electrode includes a positive electrode current collector and a positive electrode active material layer in contact with the positive electrode current collector, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer in contact with the negative electrode current collector. In the nonaqueous electrolyte secondary battery of the present invention, at least one of the positive electrode active material layer and the negative electrode active material layer is formed using the electrode composition of the present invention. The nonaqueous electrolyte secondary battery of the present invention also includes a nonaqueous electrolyte secondary battery having only one of a positive electrode active material layer and a negative electrode active material layer, the electrode active material layer being formed using the electrode composition of the present invention. The nonaqueous electrolyte secondary battery of the present invention functions as a secondary battery upon charge and discharge by filling the space between the positive electrode and the negative electrode with a nonaqueous electrolyte.

[0100] FIG. 1 is a cross-sectional view showing a schematic representation of the laminated structure of a typical nonaqueous electrolyte secondary battery 10, including the working electrodes when the battery is in operation. The nonaqueous electrolyte secondary battery 10 has a laminated structure, viewed from the negative electrode side, having a negative electrode current collector 1, a negative electrode active material layer 2, a separator 3, a positive electrode active material layer 4, and a positive electrode current collector 5, in this order. The space between the negative electrode active material layer and the positive electrode active material layer is filled with a nonaqueous electrolyte (not shown), and they are separated by the separator 3. The separator 3 has pores, and during normal battery use, it functions as a positive and negative electrode separator that insulates the positive and negative electrodes, allowing the electrolyte and ions to pass through these pores. With this structure, for example, in the case of a lithium-ion secondary battery, electrons (e - ) is supplied, and at the same time, lithium ions (Li + ) moves and accumulates in the negative electrode. On the other hand, during discharge, the lithium ions (Li + ) is returned to the positive electrode side through the electrolyte, and electrons are supplied to the operating part 6. In the example shown, a light bulb is used as the operating part 6, and it is lit by the discharge. In the present invention, the negative electrode current collector 1 and the negative electrode active material layer 2 are collectively referred to as the negative electrode, and the positive electrode active material layer 4 and the positive electrode current collector 5 are collectively referred to as the positive electrode.

[0101] The secondary battery of the present invention includes at least one of a positive electrode active material layer and a negative electrode active material layer formed using the electrode composition of the present invention. The electrolyte (aqueous electrolyte, non-aqueous electrolyte) or a solid electrolyte material, and other components such as a separator are not particularly limited. These materials and components can be appropriately applied to those used in conventional secondary batteries. Furthermore, for the method of manufacturing the secondary battery of the present invention, conventional methods can be appropriately adopted, except that at least one of a positive electrode active material layer and a negative electrode active material layer is formed using the electrode composition of the present invention. For details of components and manufacturing methods typically used in these secondary batteries, see, for example, JP 2016-201308 A, JP 2005-108835 A, JP 2012-185938 A, and WO 2020 / 067106 A. A preferred form of the non-aqueous electrolyte will now be described in more detail.

[0102] (electrolyte) The electrolyte used in the non-aqueous electrolyte is preferably a salt of a metal ion belonging to Group 1 or 2 of the periodic table. The salt of the metal ion used is appropriately selected depending on the intended use of the non-aqueous electrolyte. Examples include lithium salt, potassium salt, sodium salt, calcium salt, magnesium salt, etc., and when used in a secondary battery, etc., lithium salt is preferred from the viewpoint of output. When the non-aqueous electrolyte is used as an electrolyte for a lithium ion secondary battery, lithium salt may be selected as the salt of the metal ion. As the lithium salt, lithium salts commonly used in electrolytes for lithium ion secondary batteries are preferred, and examples thereof include the following lithium salts.

[0103] (L-1) Inorganic lithium salts: inorganic fluoride salts such as LiPF6, LiBF4, LiAsF6, and LiSbF6; perhalogenates such as LiClO4, LiBrO4, and LiIO4; inorganic chloride salts such as LiAlCl4;

[0104] (L-2) Fluorine-containing organic lithium salts: perfluoroalkanesulfonates such as LiCF3SO3, perfluoroalkanesulfonylimide salts such as LiN(CF3SO2)2, LiN(CF3CF2SO2)2, LiN(FSO2)2, LiN(CF3SO2)(C4F9SO2), perfluoroalkanesulfonylmethide salts such as LiC(CF3SO2)3, perfluoroalkyl fluorophosphates such as Li[PF5(CF2CF2CF3)], Li[PF4(CF2CF2CF3)2], Li[PF3(CF2CF2CF3)3], Li[PF5(CF2CF2CF2CF3)], Li[PF4(CF2CF2CF2CF3)2], Li[PF3(CF2CF2CF2CF3)3], etc.

[0105] (L-3) Oxalatoborate salts: lithium bis(oxalato)borate, lithium difluorooxalatoborate, etc.

[0106] Among these, LiPF6, LiBF4, LiAsF6, LiSbF6, LiClO4, Li(R f1 SO3), LiN(R f1 SO2)2, LiN(FSO2)2, or LiN(R f1 SO2)(R f2 SO2) are preferred, LiPF6, LiBF4, LiN(R f1 SO2)2, LiN(FSO2)2 or LiN(R f1 SO2)(R f2 SO2) is more preferred. f1 and R f2 represents a perfluoroalkyl group, preferably having 1 to 6 carbon atoms. The electrolytes used in the non-aqueous electrolytic solution may be used alone or in any combination of two or more.

[0107] The salt concentration of the electrolyte (preferably ions of a metal belonging to Group 1 or 2 of the periodic table or a metal salt thereof) in the non-aqueous electrolyte is appropriately selected depending on the intended use of the non-aqueous electrolyte, but is generally 10 to 50 mass % of the total mass of the non-aqueous electrolyte, and preferably 15 to 30 mass %. The molar concentration is preferably 0.5 to 1.5 M. When evaluating the ion concentration, it may be calculated in terms of a salt with the suitably applied metal.

[0108] (non-aqueous solvent) The non-aqueous electrolyte contains a non-aqueous solvent. The non-aqueous solvent is preferably an aprotic organic solvent, and more preferably an aprotic organic solvent having 2 to 10 carbon atoms. Examples of such non-aqueous solvents include linear or cyclic carbonate compounds, lactone compounds, linear or cyclic ether compounds, ester compounds, nitrile compounds, amide compounds, oxazolidinone compounds, nitro compounds, linear or cyclic sulfone or sulfoxide compounds, and phosphate ester compounds. Compounds having an ether bond, a carbonyl bond, an ester bond, or a carbonate bond are preferred. These compounds may have a substituent, for example, a substituent selected from the above-mentioned substituent group T.

[0109] Examples of non-aqueous solvents include ethylene carbonate, fluorinated ethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, Examples of the solvent include methyl acrylate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide, dimethyl sulfoxide phosphate, etc. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and γ-butyrolactone is preferred, and a combination of a high-viscosity (high-dielectric constant) solvent (e.g., relative dielectric constant ε≧30) such as ethylene carbonate or propylene carbonate with a low-viscosity solvent (e.g., viscosity≦1 mPa s) such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate is more preferred. By using a mixed solvent with such a combination, the dissociation of the electrolyte salt and the mobility of the ions are improved. However, the non-aqueous solvent used in the present invention is not limited to these.

[0110] The secondary battery of the present invention can be installed in electronic devices such as notebook computers, pen-input PCs, mobile PCs, electronic book players, mobile phones, cordless phone handsets, pagers, handheld terminals, portable fax machines, portable copiers, portable printers, headphone stereos, video camcorders, LCD televisions, handheld vacuum cleaners, portable CD players, mini-discs, electric shavers, transceivers, electronic organizers, calculators, portable tape recorders, radios, backup power supplies, and memory cards. It can also be installed in consumer products such as automobiles, electric vehicles, motors, lighting fixtures, toys, game devices, road conditioners, clocks, flash devices, cameras, and medical devices (pacemakers, hearing aids, shoulder massagers, etc.). It can also be used for various military applications and space applications. It can also be combined with solar cells. [Example]

[0111] The present invention will be described in more detail based on examples. It should be noted that the present invention is not limited to these examples except as specified herein. Room temperature refers to 27°C. Composition ratios, blend ratios, and contents are based on mass unless otherwise specified.

[0112] [Synthesis of water-soluble polymer (X)] The water-soluble polymers (X) used in preparing binder compositions 1 to 6 and c1 to c9 shown in Table 1 below were synthesized as follows.

[0113] (Water-soluble polymer (X) used in binder compositions 1 to 4, c3, c4, c8 and c9) Solution A was prepared by stirring and mixing 75.0 g of acrylamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 75.0 g of distilled water, and 0.53 g of VA-057 (trade name, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., a carboxyl group-containing water-soluble azo polymerization initiator) at room temperature. 337.5 g of distilled water was added to a 1 L three-neck flask equipped with a reflux condenser and a gas inlet valve. Nitrogen gas was introduced at a flow rate of 200 mL / min for 60 minutes, and then the temperature was raised to 75°C. Solution A prepared above was added dropwise to the distilled water in the 1 L three-neck flask over 1 hour. After completion of the addition, stirring was continued at 75°C for 3 hours. The solution was cooled to room temperature to obtain an aqueous solution of the water-soluble polymer (X) (PAAm) used in binder compositions 1 to 4, c3, c4, c8, and c9. The solids concentration was 14.0%, and the weight-average molecular weight was 347,000.

[0114] (Water-soluble polymer (X) used in preparation of binder composition 5) An aqueous solution of water-soluble polymer (X) (PAAm-HEAA-TBAAm) used in preparing binder composition 5 listed in Table 1 below was obtained in the same manner as in the synthesis of water-soluble polymer (X) (PAAm), except that acrylamide, N-(2-hydroxyethyl)acrylamide, and tert-butylacrylamide were used in place of acrylamide in a mass ratio of acrylamide / N-(2-hydroxyethyl)acrylamide / tert-butylacrylamide = 85 / 10 / 5. The solids concentration was 11.3 mass%, and the weight-average molecular weight was 724269.

[0115] (Water-soluble polymer (X) used in preparation of binder composition 6) An aqueous solution of water-soluble polymer (X) (PAAm-AN) used for preparing binder composition 6 listed in Table 1 below was obtained in the same manner as in the synthesis of water-soluble polymer (X) (PAAm), except that acrylamide and acrylonitrile were used in place of acrylamide in an acrylamide / acrylonitrile mass ratio of 80 / 20. The solids concentration was 13.3 mass%, and the weight-average molecular weight was 189,373.

[0116] (Water-soluble polymer used in preparation of binder composition c6) CLPA-C07 (trade name, cross-linked copolymer binder composed of acrylic acid and hydrophobic monomer, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the aqueous solution of water-soluble polymer used in preparing binder composition c6 shown in Table 1 below. The solid content concentration was adjusted to 10.0 mass %. CLPA-C07 is a polymer that does not contain the component represented by general formula (B-2).

[0117] (Water-soluble polymer used in preparation of binder composition c7) CLPA-W11 (trade name, cross-linked polyacrylic acid binder, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the aqueous solution of water-soluble polymer used to prepare binder composition c7 shown in Table 1 below. The solid content was adjusted to 10.3 mass %. CLPA-W11 is a polymer that does not contain the component represented by general formula (B-2). For convenience, these water-soluble polymers (CLPA-C07 and CLPA-W11) are shown in the "Water-soluble polymer (X)" column of Table 1 below.

[0118] All of the above water-soluble polymers exhibited a solubility of 100 g / L-H2O or more in water at 20°C.

[0119] [Preparation of binder composition] (Binder Composition 1) Binder composition 1 shown in Table 1 below was prepared as follows. Specifically, 1.68 g (solids content 0.08 g) of an aqueous solution of carboxymethyl cellulose (CMC) as the water-soluble compound (Y) and 0.41 g (solids content 0.20 g) of SR-151 (trade name, styrene butadiene rubber latex (SBR), hard type, glass transition temperatures: -27°C and 15°C, manufactured by Nippon A&L Co., Ltd.) as the polymer particles (Z) were added to 1.45 g (solids content 0.20 g) of the aqueous solution of the water-soluble polymer (X) (PAAm) obtained above, and the mixture was dispersed at 2000 rpm for 21 minutes using a THINKY Awatori Rentaro (trade name, manufactured by THINKY Co., Ltd.) to obtain binder composition 1. The solids concentration of binder composition 1 was 14% by mass.

[0120] (Binder compositions 2 to 6 and c1 to c9) Binder compositions 2 to 6 and c1 to c9 were prepared in the same manner as in the preparation of binder composition 1, except that the components and content ratios (mass ratios) shown in Table 1 below were used. Although the water glass used in binder composition c9 is not a polymer particle, it is shown in the "Polymer particle (Z)" column in Table 1 below for convenience.

[0121] For each binder composition, the mass ratio of the contents of the above three components (water-soluble polymer (X): water-soluble compound (Y): polymer particles (Z)) is shown in the "mass ratio of (X), (Y), and (Z)" column in Table 1. The mass ratio was calculated from the solid content of each component.

[0122] [Calculation of tensile modulus of binder composition] Each binder composition obtained above was applied to a peelable polyethylene terephthalate (PET) film and dried. The binder composition coating was peeled off from the PET film to obtain a test piece (5 cm long, 0.5 cm wide, 0.10 mm thick). The test piece was fixed to a jig at positions 1 cm from one end and 1 cm from the other end in the longitudinal direction, and a tensile test was performed using a tensile tester (product name: FGS-TV, manufactured by Nidec-Shimpo Corporation). This test was performed at 23°C and a tensile speed of 5 mm / min. The tensile modulus was calculated from the average value in the elastic region of the stress-strain curve obtained from the results of measuring the displacement against the load. The obtained tensile modulus is shown in Table 1 below.

[0123] [Preparation of electrode compositions E1 to E6 and cE1 to cE9] Electrode compositions were prepared containing the components of each binder composition described above and carbon-coated silicon oxide as a high-capacity active material. Each electrode composition thus obtained corresponds to the slurry used to assess <Storage Modulus Property 1>, containing specific amounts of carbon-coated silicon oxide with specific average particle size and specific surface area, graphite, and acetylene black. In Table 1 below, the components of each binder composition are listed in the "Binder Composition" column, and the components of electrode compositions E1 to E6 and cE1 to cE9 other than the binder composition components are listed in the "Electrode Slurry A" column. Although not listed in Table 1, electrode compositions E1 to E6 and cE1 to cE9 are electrode compositions containing the components of binder compositions 1 to 6 and c1 to c9, respectively.

[0124] (Electrode composition E1) In a 60 mL ointment container (Umano Chemical Co., Ltd.), SiOC (carbon-coated silicon oxide (carbon element content: 1.3 mass%), manufactured by Osaka Titanium Technologies Co., Ltd., grade: SiO NC 5 μm, average particle size: 5 μm, specific surface area: 2.6 m) was added as an active material. 2 / g) and graphite (product name: MAG-D, manufactured by Showa Denko Materials Co., Ltd., average particle size: 21 μm, specific surface area: 4 m 2 / g) 7.12 g, and acetylene black (trade name: Denka Black, manufactured by Denka Co., Ltd., powder, average particle size: 35 nm, specific surface area: 68 m) as a conductive additive. 20.60 g of cellulose acetate (1.45 g, solids content 0.20 g) was added to the aqueous solution of the water-soluble polymer (X) obtained above, 1.68 g of carboxymethyl cellulose (CMC) (solids content 0.08 g) as the water-soluble compound (Y), and 3.8 g of distilled water, and the mixture was dispersed at 2000 rpm for 6 minutes using a THINKY MIXER (trade name). An additional 1.8 g of distilled water was added to the dispersed solution, and the mixture was dispersed at 2000 rpm for 12 minutes using a THINKY MIXER (trade name). Furthermore, 0.41 g (solid content: 0.20 g) of polymer particles (SR-151, product name: styrene butadiene rubber latex (SBR), hard type, glass transition temperatures: -27°C and 15°C, manufactured by Nippon A&L Co., Ltd.) was added to the dispersion and dispersed at 2000 rpm for 3 minutes using a THINKY Mixer (product name: Awatori Rentaro) to obtain electrode composition E1 (slurry). This electrode composition E1 contained, per 100 parts by mass of total solids, 17.8 parts by mass of carbon-coated silicon oxide, 71.2 parts by mass of graphite, 6 parts by mass of acetylene black, and 5 parts by mass of binder components (water-soluble polymer (X), water-soluble compound (Y), and polymer particles (Z)) as solids, and the total solids content of the slurry was 52% by mass. The electrode composition E1 is prepared by adding the water-soluble polymer (X), the water-soluble compound (Y), the polymer molecules, and distilled water separately, but is equivalent to the binder composition 1 prepared by adding the active material and the conductive additive and controlling the moisture content to make the total solid content in the slurry 52% by mass. The binder components (water-soluble polymer (X), water-soluble compound (Y) and polymer particles (Z)) contained in electrode composition E1 are the same as those in binder composition 1 above in terms of type and mass ratio.

[0125] (Electrode compositions E2-E6 and cE1-cE9) Electrode compositions E2 to E6 and cE1 to cE9 were prepared in the same manner as electrode composition E1, except that in preparing electrode composition E1, the composition of the binder components (water-soluble polymer (X), water-soluble compound (Y), and polymer particles (Z)) was changed to be the same as each binder composition listed in Table 1 below.

[0126] [Measurement of strain dispersion of electrode composition and calculation of difference in storage modulus] Using 1 mL of each electrode composition (solid content 52% by mass) obtained above, the storage modulus was measured using a rheometer (Modular Compact Rheometer MCR102 (trade name), manufactured by Anton Paar) under conditions of 25°C, 10 rad / s, and rheometer jig PP50. The obtained storage modulus at a shear strain of 0.01% and the storage modulus at a shear strain of 10% were read, and the difference between them was calculated. The results are shown in Table 1 below.

[0127] [Preparation of electrode compositions E7 to E12 and cE10 to cE16] Each electrode composition containing the components of each binder composition described above and containing silicon oxide that was both carbon-coated and lithium-doped as a high-capacity active material was prepared as follows.

[0128] 1. Preparation of both carbon-coated and lithium-doped silicon oxide In the same manner as described in Example 1-1 of JP 2022-121582 A, silicon oxide having both carbon coating and lithium doping was produced. Specifically, the procedure was as follows. (i) Preparation of carbon-coated silicon oxide A mixture of silicon metal and silicon dioxide (vaporized starting material) was placed in a reactor. Vaporization occurred under a vacuum of 10 Pa. The material was deposited on an adsorption plate. After sufficient cooling, the deposit (silicon oxide) was removed and pulverized in a ball mill. After adjusting the particle size, a carbon coating was formed by thermal chemical vapor deposition (thermal CVD). For thermal CVD, the pulverized silicon oxide was placed in a silicon nitride tray and placed in a furnace capable of maintaining a constant atmosphere. Argon gas was then introduced to the furnace, and the atmosphere was replaced with argon. The furnace was then heated at a rate of 300°C / hr while a methane-argon gas mixture was introduced at 2 NL / min. The temperature was then maintained at 600–1,100°C for 3–10 hours, resulting in a carbon-coated silicon oxide (SiOC). After the temperature reached room temperature, the powder was collected. (ii) Lithium doping of carbon-coated silicon oxide Carbon-coated silicon oxide was modified by doping with lithium using a redox method. First, the carbon-coated silicon oxide was immersed in a solution (Solution A) prepared by dissolving lithium pieces and naphthalene in tetrahydrofuran (hereinafter referred to as THF). Specifically, Solution A was prepared by dissolving naphthalene in THF solvent at a concentration of 0.2 mol / L, and then adding 10% by mass of lithium pieces to the mixture of THF solvent and naphthalene. The temperature of Solution A during the immersion of the carbon-coated silicon oxide was 20°C, and the immersion time was 20 hours. The solid matter was then filtered off. The carbon-coated silicon oxide was doped with lithium through the above process. The resulting solid matter was heat-treated at 600°C for 24 hours in an argon atmosphere to stabilize the Li compound. In this way, the carbon-coated silicon oxide was modified to obtain silicon oxide (LiSiOC) that was both carbon-coated and lithium-doped. The carbon element content was 3 mass %, and the average particle size (volume-based median diameter D50) of the LiSiOC particles was 6.7 μm.

[0129] 2. Preparation of electrode composition Electrode compositions E7 to E12 and cE10 to cE16 were prepared in the same manner as electrode composition E1, except that in the preparation of electrode composition E1, the carbon-coated silicon oxide was changed to silicon oxide that was both carbon-coated and lithium-doped (LiSiOC), and the composition of the binder components (water-soluble polymer (X), water-soluble compound (Y), and polymer particles (Z)) was changed to be the same as the binder composition shown in Table 1 below. The corresponding binder compositions are shown in the column "Corresponding binder composition No." in Table 2 below.

[0130] [Measurement of strain dispersion of electrode composition and calculation of difference in storage modulus] Strain dispersion measurements were also performed on electrode compositions E7 to E12 and cE10 to cE16, reading the storage modulus at a shear strain of 0.01% and the storage modulus at a shear strain of 10%, and calculating the difference between them. The measurements were performed in the same manner as in the above [Strain dispersion measurements of electrode compositions and calculation of differences in storage modulus], except that electrode compositions E7 to E12 and cE10 to cE16 were used as the slurries. The results are shown in Table 2 below. Table 2 below also shows the measurement results for electrode compositions E1 to E6 and cE1 to cE9.

[0131] [Preparation of electrode compositions E13 to E24 and cE17 to cE30] Each electrode composition containing the components of each binder composition described above and including silicon oxide that was both carbon-coated and nickel-doped, or silicon oxide that was both carbon-coated and titanium-doped as a high-capacity active material, was prepared as follows.

[0132] 1. Preparation of both carbon-coated and nickel-doped silicon oxide, and both carbon-coated and titanium-doped silicon oxide In the same manner as in the preparation of the powder material for the negative electrode described in the examples of JP 2021-150077 A, silicon oxide (NiSiOC) to which both carbon coating and nickel doping were applied and silicon oxide (TiSiOC) to which both carbon coating and titanium doping were applied were prepared. Specifically, this was done as follows. (i) Preparation of Si alloy Each raw material was weighed to obtain the Si alloy composition shown in Table A below. The weighed raw materials were heated and melted using a high-frequency induction furnace to obtain a molten alloy. A powdered Si alloy was produced from the obtained molten alloy by gas atomization. An argon atmosphere was used during the preparation of the molten alloy and the gas atomization. During the gas atomization, high-pressure (4 MPa) argon gas was sprayed onto the molten alloy falling in a rod-like shape inside the atomization chamber. The obtained powder was sieved to a size of 25 μm or less and used as the Si alloy in the subsequent steps. (ii) Preparation for mechanical milling Si alloy and SiO2 powder as a metal oxide were placed in a stainless steel pot together with 30 metal balls (size: diameter 3 / 8 inch, material: SUJ2) in the mixing ratio shown in Table A below. For example, to prepare 10 g of the target product, 9.5 g of Si alloy and 0.5 g of SiO2 powder were placed. After the placement, the atmosphere inside the pot was replaced with Ar gas. (iii) Mechanical milling The pot was placed in a planetary ball mill (Fritsch, P-5 / 4) and milled at 300 rpm for 150 h. The resulting mixed powder was used as a metal-doped silicon-based material (nickel-doped silicon oxide (NiSiO) or titanium-doped silicon oxide (TiSiO)) in the subsequent steps. (iv) Carbon coating treatment on silicon-based materials doped with metal elements A carbon coating was formed on a metal-doped silicon-based material (NiSiO or TiSiO) by thermal CVD. For thermal CVD, the metal-doped silicon-based material after mechanical milling was placed in a silicon nitride tray and placed in a furnace capable of maintaining a constant atmosphere. Argon gas was then introduced into the furnace, and the atmosphere was replaced with argon. The furnace was then heated at a rate of 300°C / hr while a methane-argon gas mixture was introduced at 2 NL / min. The temperature was then maintained at 600–1,100°C for 3–10 hours, resulting in a carbon film. This produced silicon-based materials that were both carbon-coated and doped with a metal element (carbon-coated and nickel-doped silicon oxide (NiSiOC) and carbon-coated and titanium-doped silicon oxide (TiSiOC)). After the temperature reached room temperature, the powder was collected. The carbon element content was 3 mass %, and the average particle size (volume-based median diameter D50) of both the NiSiOC particles and the TiSiOC particles was 7 μm.

[0133] [Table A]

[0134] <Notes for Table A> NiSiO: Nickel-doped silicon oxide TiSiO: Titanium-doped silicon oxide Alloy composition: Indicates the percentage of each metal element in the Si alloy out of a total of 100 mass% of the Si alloy and SiO2 powder used to obtain the metal element-doped silicon-based material (NiSiO or TiSiO), and the unit is mass%, and the total alloy composition is 95 mass%. Mixing ratio: Indicates the ratio of each component (Si alloy or SiO2 powder) to the total amount of Si alloy and SiO2 powder added when obtaining a silicon-based material (NiSiO or TiSiO) doped with a metal element, expressed in mass%.

[0135] 2. Preparation of electrode composition Electrode compositions E13 to E18 and cE17 to cE23 were prepared in the same manner as electrode composition E1, except that in the preparation of electrode composition E1, the carbon-coated silicon oxide was changed to silicon oxide that was both carbon-coated and nickel-doped (NiSiOC), and the compositions of the binder components (water-soluble polymer (X), water-soluble compound (Y), and polymer particles (Z)) were changed to be the same as those of each binder composition listed in Table 1 below. The corresponding binder compositions are shown in the column "Corresponding binder composition No." in Table 3 below. Furthermore, electrode compositions E19 to E24 and cE24 to cE30 were prepared in the same manner as electrode composition E1, except that in the preparation of electrode composition E1, the carbon-coated silicon oxide was changed to silicon oxide that was both carbon-coated and titanium-doped (TiSiOC), and the compositions of the binder components (water-soluble polymer (X), water-soluble compound (Y), and polymer particles (Z)) were changed to be the same as those of each binder composition listed in Table 1 below. The corresponding binder compositions are shown in the "Corresponding binder composition No." column in Table 3 below.

[0136] [Measurement of strain dispersion of electrode composition and calculation of difference in storage modulus] Strain dispersion measurements were also performed on electrode compositions E13 to E24 and cE17 to cE30, reading the storage modulus at a shear strain of 0.01% and the storage modulus at a shear strain of 10%, and calculating the difference between them. The measurements were performed in the same manner as in the above [Strain dispersion measurements of electrode compositions and calculation of differences in storage modulus], except that electrode compositions E13 to E24 and cE17 to cE30 were used as the slurries. The results are shown in Table 3 below.

[0137] [Evaluation of electrode peel strength] 0.7 mL of each electrode composition prepared above was applied to a 20 μm-thick copper foil using an applicator and dried at 90°C for 1 hour. Further drying at 100°C in a vacuum for 10 hours yielded a negative electrode sheet (negative electrode active material layer + copper foil) for peel strength measurement. The thickness of the negative electrode active material layer was 65 μm. Three test pieces measuring 10 mm wide and 50 mm long were cut out from the obtained electrode sheet. Adhesive tape (10 mm wide, 50 mm long, product name: Nicetack Business Pack, manufactured by Nichiban Co., Ltd.) was applied to the negative electrode active material layer of each of the three cut test pieces, and the average stress when peeled off at a 90° angle at 100 mm / min was measured for each test piece. For the measurement, a small desktop testing machine (FGS-TV (product name), manufactured by Nidec-Shimpo Corporation) was used. The value (unit: N / m) obtained by dividing the sum of the obtained average stresses by 3 is shown in the "Peel Strength" column in Tables 2 and 3 below.

[0138] [Fabrication of non-aqueous electrolyte secondary battery (2032 type coin battery)] (Nonaqueous electrolyte secondary battery 101) A non-aqueous electrolyte secondary battery 101 was fabricated. Each electrode composition prepared above was applied to a 20 μm-thick copper foil (current collector) using an applicator and dried for 1 hour at 90° C. Thereafter, the composition was pressed using a press and then dried in a vacuum at 100° C. for 10 hours to obtain a negative electrode sheet (negative electrode active material layer + copper foil) with a negative electrode active material layer thickness of 25 μm. A disk having a diameter of 13.0 mm was cut out from the negative electrode sheet to obtain a disk-shaped negative electrode sheet. A lithium foil (50 μm thick, 14.5 mm diameter) and a polypropylene separator (25 μm thick, 16.0 mm diameter) were stacked in this order, and 200 μL of LiPF6 ethylene carbonate / ethyl methyl carbonate (volume ratio 1:2, concentration 1M) electrolyte was impregnated into the separator. Another 200 μL of the above electrolyte was impregnated on top of the separator, and a disk-shaped negative electrode sheet was placed on top of the separator with the negative electrode active material layer surface in contact with the separator. A 2032-type coin case was then crimped to produce a nonaqueous electrolyte secondary battery 101 (a battery having a laminate consisting of Li foil, separator, negative electrode active material layer, and copper foil).

[0139] (Nonaqueous electrolyte secondary batteries 102~124 and c101~c130) Non-aqueous electrolyte secondary batteries 102 to 124 and c101 to c130 were prepared in the same manner as non-aqueous electrolyte secondary battery 101, except that the electrode compositions shown in Tables 2 and 3 below were used.

[0140] [Evaluation of cycle characteristics] The discharge capacity retention rate of each coin battery was measured using a charge / discharge evaluation device: TOSCAT-3000 (trade name, manufactured by Toyo Systems Co., Ltd.). Charging was performed at a C rate of 0.2C (a rate at which the battery is fully charged in 5 hours) until the battery voltage reached 0.02V. Discharging was performed at a C rate of 0.2C until the battery voltage reached 1.5V. Each coin battery was initialized by repeating three charge / discharge cycles, with one charge and one discharge constituting one charge / discharge cycle. After initialization, the battery was charged at 0.5 C until it reached 0.02 V. Then, it was discharged at 0.5 C until it reached 1.5 V. This cycle of charging and discharging was counted as one charge / discharge cycle, and the cycle characteristics were evaluated by repeating the charge / discharge cycle 80 times. The discharge capacity retention rate after 80 charge / discharge cycles was calculated by taking the discharge capacity at the first cycle after initialization (initial discharge capacity) as 100% (100 × "discharge capacity after 80 charge / discharge cycles" / "initial discharge capacity"). The results are shown in the "Capacity retention rate 80 cycles" column in Tables 2 and 3 below. All charging and discharging was carried out at 25°C.

[0141] [Table 1]

[0142] <Notes for Table 1> "-": Indicates that the corresponding ingredient is not contained. PAAm: Polyacrylamide PAAm-HEAA-TBAAm: copolymer of acrylamide / N-(2-hydroxyethyl)acrylamide / tert-butylacrylamide = 85 / 10 / 5 (mass ratio) PAAm-AN: Acrylamide / acrylonitrile copolymer (mass ratio: 80 / 20) CLPA-C07: Product name, cross-linked copolymer binder made from acrylic acid and hydrophobic monomer, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. CLPA-W11: Product name, cross-linked polyacrylic acid binder, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. CMC: Carboxymethyl cellulose (etherification degree 0.66, product name: Cellogen WS-C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Cellenpia: Product name, cellulose nanofiber, manufactured by Nippon Paper Industries Co., Ltd. SR-151: Product name, hard type styrene butadiene rubber latex, manufactured by Nippon A&L Co., Ltd. SR-153: Product name, small particle size styrene butadiene rubber latex, manufactured by Nippon A&L * Both SR-151 and SR-153 exhibited a solubility of less than 10 g / L-H2O in water at 20°C. *SR-151 has two observed Tg points (-27°C and 15°C) (catalog values ​​from Nippon A&L Co., Ltd.). SR-153 has a Tg of 35°C. Water glass: sodium silicate aqueous solution, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. SiOC: Carbon-coated silicon oxide (Osaka Titanium Technologies Co., Ltd., grade: SiO NC 5 μm, average particle size: 5 μm, specific surface area: 2.6 m 2 / g, carbon element content 1.3% by mass Graphite: MAG-D (product name, manufactured by Showa Denko Materials Co., Ltd., average particle size: 21 μm, specific surface area: 4 m 2 / g) AB: Acetylene black (trade name: Denka Black, manufactured by Denka Co., Ltd., powder product, average particle size: 35 nm, specific surface area: 68 m 2 / g) Content: Indicates the proportion of each component (solid content) in the total of all components (solid content) contained in the electrode composition, expressed in mass %. G A ': Storage modulus at shear strain of 0.01% G B ': Storage modulus at 10% shear strain

[0143] [Table 2]

[0144] <Notes for Table 2> Secondary batteries 101-112 and c101-c116: Non-aqueous electrolyte secondary batteries 101-112 and c101-c116 Corresponding binder composition No.: Binder composition No. corresponding to the combination of binder components (water-soluble polymer (X), water-soluble compound (Y), and polymer particles (Z)) blended into the electrode composition. SiOC: Carbon-coated silicon oxide (Osaka Titanium Technologies Co., Ltd., grade: SiO NC 5 μm, average particle size: 5 μm, specific surface area: 2.6 m 2 / g, carbon element content 1.3% by mass LiSiOC: silicon oxide prepared as above that was both carbon-coated and lithium-doped (average particle size: 6.7 μm, carbon element content: 3% by mass) Graphite: MAG-D (product name, manufactured by Showa Denko Materials Co., Ltd., average particle size: 21 μm, specific surface area: 4 m 2 / g) AB: Acetylene black (trade name: Denka Black, manufactured by Denka Co., Ltd., powder product, average particle size: 35 nm, specific surface area: 68 m 2 / g) Content: Indicates the proportion of each component (solid content) in the total of all components (solid content) contained in the electrode composition, expressed in mass %. G C ': Storage modulus at shear strain of 0.01% G D ': Storage modulus at 10% shear strain

[0145] [Table 3]

[0146] <Notes for Table 3> Secondary batteries 113-124 and c117-c130: Non-aqueous electrolyte secondary batteries 113-124 and c117-c130 Corresponding binder composition No.: Binder composition No. corresponding to the combination of binder components (water-soluble polymer (X), water-soluble compound (Y), and polymer particles (Z)) blended into the electrode composition. NiSiOC: Silicon oxide prepared as above that was both carbon-coated and nickel-doped (average particle size: 7 μm, carbon element content: 3% by mass) TiSiOC: silicon oxide prepared as above that was both carbon-coated and titanium-doped (average particle size: 7 μm, carbon element content: 3 mass%) Graphite: MAG-D (product name, manufactured by Showa Denko Materials Co., Ltd., average particle size: 21 μm, specific surface area: 4 m 2 / g) AB: Acetylene black (trade name: Denka Black, manufactured by Denka Co., Ltd., powder product, average particle size: 35 nm, specific surface area: 68 m 2 / g) Content: Indicates the proportion of each component (solid content) in the total of all components (solid content) contained in the electrode composition, expressed in mass %. G C ': Storage modulus at shear strain of 0.01% G D ': Storage modulus at 10% shear strain

[0147] The following can be seen from Tables 1, 2 and 3. The composition contains a water-soluble polymer (X) containing a component represented by general formula (B-2), a water-soluble compound (Y), polymer particles, and water, and has a tensile modulus of 1500 to 9800 MPa and a storage modulus G at a shear strain of 0.01%. A ' and storage modulus G at shear strain of 10% B ' and the difference (G A '-GB Binder compositions c1 to c9 that do not satisfy at least one of the conditions that the surface tension (σ) is 100 to 1000 Pa exhibited a peel strength of 15.4 N / m or less and cycle characteristics below 90%, whether they were used in electrode compositions cE1 to cE9 employing carbon-coated silicon oxide as the high-capacity active material or in electrode compositions cE10 to cE30 employing silicon oxide that was both carbon-coated and doped with a metal element. In either case, it was not possible to increase adhesion and / or improve the cycle characteristics of the secondary battery. A binder composition comprising a water-soluble polymer (X) containing a component represented by general formula (B-2), a water-soluble compound (Y), polymer particles, and water, the binder composition having a tensile modulus of 1500 to 9800 MPa and a storage modulus G at a shear strain of 0.01%. A ' and storage modulus G at shear strain of 10% B ' and the difference (G A '-G B Binder compositions 1 to 6, which have a σ′ of 100 to 1000 Pa, were able to enhance adhesion and improve the cycle characteristics of secondary batteries when used in electrode compositions E1 to E6, which use carbon-coated silicon oxide as the high-capacity active material, and when used in electrode compositions E7 to E24, which use silicon oxide that is both carbon-coated and doped with a metal element. Despite the use of a silicon-based active material that is prone to volume change, the excellent cycle characteristics suggest that the electrode composition of the present invention suppresses destruction of the conductive network structure. It is clear that the electrode composition of the present invention can sufficiently increase the adhesion of the resulting negative electrode sheet and improve the cycle characteristics of the resulting secondary battery. It is clear that the binder composition of the present invention can be used to obtain the electrode composition of the present invention. It is also clear that the electrode sheet and secondary battery using the electrode composition of the present invention have high adhesion and excellent cycle characteristics. [Explanation of symbols]

[0148] 10 Nonaqueous electrolyte secondary battery 1 Negative electrode current collector 2 Negative electrode active material layer 3 Separator 4 Cathode active material layer 5 Positive electrode current collector 6. Working part (bulb)

Claims

1. A binder composition for a secondary battery, comprising a water-soluble polymer (X), a water-soluble compound (Y), polymer particles, and water, The water-soluble polymer (X) is a polymer containing a constituent component represented by the following general formula (B-2): The tensile modulus of the binder composition is 1500 to 9800 MPa, and A binder composition for a secondary battery, which satisfies the following <Storage modulus property 1>. <Storage modulus characteristics 1> Average particle size is 1 to 10 μm and specific surface area is 1 to 10 m ２ / g powdered carbon-coated silicon oxide, and a powder having an average particle size of 15 to 25 μm and a specific surface area of ​​1 to 10 m ２ / g of powdered graphite and a graphite powder having an average particle size of 30 to 40 nm and a specific surface area of ​​65 to 75 m ２ In a slurry prepared by mixing powdered acetylene black having a molecular weight of 1000 to 100000000 / g and the binder composition for a secondary battery in the following ratio, the storage modulus G of the slurry at a shear strain of 0.01% was Ａ ' and storage modulus G at shear strain of 10% Ｂ The difference between ' and ' is 100 to 1000 Pa. -Quantity ratio- With respect to 100 parts by mass of the total solid content in the slurry, the content of the carbon-coated silicon oxide is 17.8 parts by mass, the content of the graphite is 71.2 parts by mass, the content of the acetylene black is 6 parts by mass, the content of the solid content in the binder composition for secondary batteries is 5 parts by mass, and the total solid content in the slurry is 52% by mass. In general formula (B-2), R ２１ ~R ２３ represents a hydrogen atom, a cyano group, or an alkyl group having 1 to 6 carbon atoms; R ２４ represents a hydrogen atom, an acyl group, a hydroxy group, a phenyl group, or a carboxy group; L ２１ represents a single bond, an alkylene group having 1 to 16 carbon atoms, an arylene group having 6 to 12 carbon atoms, an oxygen atom, a sulfur atom, a carbonyl group, an imino group, or a linking group combining these. * represents a bonding site for incorporation into the main chain of the water-soluble polymer (X).

2. 2. The binder composition for a secondary battery according to claim 1, wherein the content of the component represented by general formula (B-2) in the water-soluble polymer (X) is 80 mass % or more.

3. 2. The binder composition for a secondary battery according to claim 1, wherein the constituent component represented by the general formula (B-2) includes a (meth)acrylamide component.

4. 2. The binder composition for a secondary battery according to claim 1, wherein the water-soluble polymer (X) is a polymer further containing at least one of an acrylonitrile component, an N-vinyl-2-pyrrolidone component, and a styrene component.

5. The binder composition for a secondary battery according to claim 1 , wherein the water-soluble compound (Y) is a polysaccharide.

6. 6. The binder composition for a secondary battery according to claim 5, wherein the water-soluble compound (Y) comprises at least one of carboxymethyl cellulose, cellulose nanofiber, hydroxyethyl cellulose, hydroxypropyl cellulose, and xanthan gum.

7. 2. The binder composition for a secondary battery according to claim 1, wherein the water-soluble polymer (X) has a molecular weight distribution of 5.0 or less.

8. 2. The binder composition for a secondary battery according to claim 1, wherein the water-soluble polymer (X) has a tensile modulus of elasticity of 4000 MPa or more.

9. 2. The binder composition for a secondary battery according to claim 1, wherein the polymer constituting the polymer particles is a polymer containing at least one of a conjugated diene component, an ethylenically unsaturated carboxylic acid component, a cyano group-containing ethylenic monomer component, and an aromatic vinyl monomer component.

10. 2. The binder composition for a secondary battery according to claim 1, wherein the polymer particles have a glass transition temperature of −50 to 150° C.

11. 10. A composition for an electrode comprising the binder composition for a secondary battery according to claim 1, an active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table, and a conductive additive.

12. The electrode composition according to claim 11 , wherein the active material comprises a silicon-based active material.

13. An electrode sheet having a layer formed using the electrode composition according to claim 11 or 12.

14. A secondary battery, wherein at least one of a positive electrode active material layer and a negative electrode active material layer is formed using the electrode composition according to claim 11 or 12.

15. A method for producing an electrode sheet, comprising forming an electrode active material layer using the electrode composition according to claim 11 or 12.

16. A method for producing a secondary battery, comprising incorporating an electrode sheet obtained by the method according to claim 15 as an electrode of the secondary battery.

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