Binder composition for non-aqueous secondary battery electrodes, slurry composition for non-aqueous secondary battery electrodes, electrodes for non-aqueous secondary batteries, and non-aqueous secondary batteries

Abstract

A binder composition for a non-aqueous secondary battery electrode including water and a polymer that contains an aromatic vinyl monomer unit, a conjugated diene monomer unit, and a hydrophilic monomer unit. The median diameter of the polymer is 50-800 nm (inclusive), and the content ratio of hydrophilic monomer units in the polymer is 4.0-20 mass% (inclusive). Furthermore, the value of the loss tangent tanδ of the polymer is at least 0.001 and less than 0.40, and the value of the loss modulus G" is 1600 kPa or less.

Description

[Technical Field]

[0001] The present invention relates to a binder composition for a non-aqueous secondary battery electrode, a slurry composition for a non-aqueous secondary battery electrode, an electrode for a non-aqueous secondary battery, and a non-aqueous secondary battery. [Background technology]

[0002] Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes simply referred to as "secondary batteries") are small, lightweight, have high energy density, and can be repeatedly charged and discharged, and are therefore used in a wide range of applications. Therefore, in recent years, improvements to battery components such as electrodes have been investigated with the aim of further improving the performance of non-aqueous secondary batteries.

[0003] Here, an electrode used in a secondary battery such as a lithium-ion secondary battery usually includes a current collector and an electrode mixture layer (positive electrode mixture layer or negative electrode mixture layer) formed on the current collector. This electrode mixture layer is formed, for example, by applying a slurry composition containing an electrode active material and a binder composition containing a binding agent onto the current collector and drying the applied slurry composition.

[0004] Therefore, in recent years, efforts have been made to improve the binder compositions used in forming electrode mixture layers in order to further improve the performance of secondary batteries. Specifically, Patent Document 1, for example, proposes an aqueous binder composition for battery electrodes, which contains a copolymer latex characterized by the following: (1) the dynamic viscoelasticity of the film, where Tp (°C) is the maximum peak temperature of the loss factor tan δ, Tp is in the range of −20 to 60°C, tan δ(Tp) is in the range of 4.0 × 10−1 to 1.0 × 100, and the temperature range of tan δ where tan δ(Tp) is 60% or more is 35°C or higher. The copolymer contained in this binder composition is obtained by emulsion polymerization of a monomer composition containing 12 to 50% by mass of an aliphatic conjugated diene monomer, 1.0 to 10% by mass of a carboxylic acid alkyl ester monomer, 0.1 to 10% by mass of an ethylenically unsaturated carboxylic acid monomer, and 30 to 86.9% by mass of a monomer copolymerizable with these monomers. Such a binder composition has a high binding ability even when used over a wide range of environmental temperatures, and furthermore, is capable of maintaining the electrode structure during charge and discharge. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-126456 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, from the viewpoint of improving the productivity of secondary batteries, it is necessary for the binder composition to have a polymer that is uniformly dispersed in the binder composition even after being stored for a certain period of time after preparation. Furthermore, it is necessary for the electrode formed using the binder composition to have a high binding strength between the composite layer that constitutes the electrode and the current collector, even when the temperature becomes high during the process of manufacturing the secondary battery. In other words, it is necessary for the binder composition to be capable of forming an electrode that exhibits high peel strength even when the manufactured electrode is exposed to high temperatures. Furthermore, it is preferable that the secondary battery equipped with an electrode formed using the binder composition has a low internal resistance.

[0007] However, the conventional binders described above have been unable to simultaneously achieve at a sufficiently high level the uniformity of the polymer in the binder composition after static storage (hereinafter, this may be referred to as "static stability"), the increase in the peel strength of the electrode after exposure to high temperatures, and the reduction in the internal resistance of the resulting secondary battery.

[0008] Therefore, an object of the present invention is to provide a binder composition for non-aqueous secondary battery electrodes that has excellent static stability and is capable of forming an electrode that has excellent peel strength after exposure to high temperatures and a non-aqueous secondary battery that has low internal resistance. Another object of the present invention is to provide a slurry composition for a non-aqueous secondary battery electrode, which is capable of forming an electrode having excellent peel strength after exposure to high temperatures and a non-aqueous secondary battery having low internal resistance. Another object of the present invention is to provide an electrode for a non-aqueous secondary battery that has excellent peel strength after exposure to high temperatures and is capable of forming a secondary battery with low internal resistance, and a non-aqueous secondary battery with low internal resistance. [Means for solving the problem]

[0009] The present inventors have conducted extensive research with the aim of solving the above-mentioned problems. As a result, the present inventors have found that a binder composition containing a polymer that satisfies predetermined composition and median diameter and has values ​​of loss tangent tanδ and loss modulus G″ measured by predetermined methods within predetermined ranges has excellent static stability, and that the use of such a binder composition makes it possible to obtain an electrode that has excellent peel strength after exposure to high temperatures and a secondary battery that has low internal resistance, and have completed the present invention.

[0010] The present invention has an object to advantageously solve the above-mentioned problems, and provides a binder composition for a non-aqueous secondary battery electrode, comprising a polymer containing aromatic vinyl monomer units, conjugated diene monomer units, and hydrophilic monomer units, and water, wherein the polymer has a median diameter of 50 nm or more and 800 nm or less, a content of the hydrophilic monomer units in the polymer of 4.0 mass % or more and 20 mass % or less, and the polymer has a loss tangent tanδ of 0.001 or more and less than 0.40, and a loss modulus G" of 1600 kPa or less. Thus, a binder composition containing a polymer that satisfies the specified composition and median diameter and whose loss tangent tanδ and loss modulus G" measured by a specified method are within the specified ranges has excellent static stability, and the use of such a binder composition allows for the production of an electrode that exhibits excellent peel strength after exposure to high temperatures, and a secondary battery that exhibits low internal resistance. In the present invention, the term "monomer unit" of a polymer means "a repeating unit derived from the monomer contained in a polymer obtained using the monomer." The "median diameter" of the polymer can be measured according to the method described in the Examples of this specification. Furthermore, the content ratio of each type of monomer unit in the polymer is: 1 It can be measured using H-NMR. The "value of loss tangent tan δ" and the "value of loss modulus G" of the polymer can be measured according to the method described in the examples of this specification.

[0011] In the binder composition for a non-aqueous secondary battery electrode of the present invention, the conjugated diene monomer units contained in the polymer are preferably units derived from a 1,3-butadiene monomer. When the conjugated diene monomer units contained in the polymer are units derived from a 1,3-butadiene monomer, the storage stability of a slurry composition for a non-aqueous secondary battery electrode obtained using the binder composition for a non-aqueous secondary battery electrode can be improved. Furthermore, a binder composition containing a polymer including units derived from a 1,3-butadiene monomer as conjugated diene monomer units can form an electrode with even better peel strength after exposure to high temperatures.

[0012] Furthermore, the binder composition for a non-aqueous secondary battery electrode of the present invention preferably has a gel content of 35% by mass or more and 60% by mass or less when the polymer is immersed in tetrahydrofuran and measured. If the gel content is 35% by mass or more and 60% by mass or less when the polymer is immersed in tetrahydrofuran and measured, it becomes possible to appropriately control the initial viscosity when a slurry composition is produced using the binder composition, and as a result, the battery characteristics of the resulting secondary battery can be further improved. The "gel content" of a polymer can be measured according to the method described in the Examples section of this specification.

[0013] In the binder composition for a non-aqueous secondary battery electrode of the present invention, the polymer preferably contains an aromatic vinyl block region composed of aromatic vinyl monomer units. When a binder composition contains a polymer containing an aromatic vinyl block region composed of aromatic vinyl monomer units, the use of such a binder composition can produce an electrode with even better peel strength after exposure to high temperatures and a secondary battery with even lower internal resistance. Here, in this specification, when a polymer "has a block region composed of a monomer unit," it means that "the polymer contains a portion in which only the monomer unit is linked together as a repeating unit."

[0014] The present invention also aims to advantageously solve the above-mentioned problems, and provides a slurry composition for a non-aqueous secondary battery electrode, which comprises an electrode active material and any one of the binder compositions for a non-aqueous secondary battery electrode described above. Thus, by incorporating the binder composition for a non-aqueous secondary battery electrode described above, it is possible to improve the peel strength of an electrode formed using the slurry composition after exposure to high temperatures (hereinafter, sometimes referred to as "high-temperature peel strength") and reduce the internal resistance of the secondary battery.

[0015] Furthermore, the present invention aims to advantageously solve the above-mentioned problems, and the non-aqueous secondary battery electrode of the present invention is characterized by comprising an electrode mixture layer formed using the above-mentioned non-aqueous secondary battery electrode slurry composition. In this way, by using the above-mentioned non-aqueous secondary battery electrode slurry composition, an electrode with excellent high-temperature peel strength can be obtained, which can form a secondary battery with low internal resistance.

[0016] The present invention has an object to advantageously solve the above-mentioned problems, and provides a nonaqueous secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is the above-mentioned electrode for a nonaqueous secondary battery. By using the above-mentioned electrode for a nonaqueous secondary battery, a nonaqueous secondary battery with low internal resistance can be obtained. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a binder composition for a non-aqueous secondary battery electrode that has excellent static stability and is capable of forming an electrode that has excellent peel strength after exposure to high temperatures and a non-aqueous secondary battery that has low internal resistance. Furthermore, according to the present invention, it is possible to provide a slurry composition for a non-aqueous secondary battery electrode, which is capable of forming an electrode that has excellent peel strength after exposure to high temperatures and a non-aqueous secondary battery that has low internal resistance. Furthermore, according to the present invention, it is possible to provide an electrode for a non-aqueous secondary battery that has excellent peel strength after exposure to high temperatures and is capable of forming a secondary battery with low internal resistance, as well as a non-aqueous secondary battery with low internal resistance. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail. Here, the binder composition for a non-aqueous secondary battery electrode of the present invention can be used to prepare a slurry composition for a non-aqueous secondary battery electrode of the present invention. The slurry composition for a non-aqueous secondary battery electrode prepared using the binder composition for a non-aqueous secondary battery electrode of the present invention can be used to manufacture electrodes for non-aqueous secondary batteries such as lithium-ion secondary batteries. Furthermore, the non-aqueous secondary battery of the present invention is characterized by using a non-aqueous secondary battery electrode of the present invention formed using the slurry composition for a non-aqueous secondary battery electrode of the present invention. The binder composition for a non-aqueous secondary battery electrode, the slurry composition for a non-aqueous secondary battery electrode, and the electrode for a non-aqueous secondary battery of the present invention are preferably for use in a negative electrode, and the non-aqueous secondary battery of the present invention preferably uses the electrode for a non-aqueous secondary battery of the present invention as a negative electrode.

[0019] (Binder composition for non-aqueous secondary battery electrodes) The binder composition for a non-aqueous secondary battery electrode of the present invention contains a polymer containing aromatic vinyl monomer units, conjugated diene monomer units, and hydrophilic monomer units, and water. The polymer is characterized in that it has a median diameter of 50 nm or more and 800 nm or less, and that the content of the hydrophilic monomer units in the polymer is 4.0 mass % or more and 20 mass % or less. The polymer is also characterized in that it has a loss tangent tanδ of 0.001 or more and less than 0.40, and a loss modulus G" of 1600 kPa or less, as measured according to the method described in the Examples below. Furthermore, the binder composition of the present invention has a polymer that satisfies predetermined composition and median diameter, and has values ​​of loss tangent tanδ and loss modulus G″ measured by predetermined methods that are within predetermined ranges. Therefore, the binder composition has excellent static stability, and by using such a binder composition, it is possible to form an electrode that has excellent peel strength after exposure to high temperatures, and a secondary battery that has low internal resistance.

[0020] <Polymer> The polymer is a component that functions as a binder, and in an electrode mixture layer formed using a slurry composition containing the binder composition, it holds components such as the electrode active material so that they do not detach from the electrode mixture layer. The polymer is a water-insoluble particle. In the present invention, the term "water-insoluble" refers to the fact that when 0.5 g of the polymer is dissolved in 100 g of water at 25°C, the insoluble content is 90 mass % or more.

[0021] <<Median diameter of polymer>> The median diameter of the polymer must be 50 nm or more and 800 nm or less. Furthermore, the median diameter of the polymer is preferably 100 nm or more, more preferably 200 nm or more, and preferably 500 nm or less. When the median diameter of the polymer is equal to or greater than the above-mentioned lower limit, the high-temperature peel strength of the resulting electrode can be improved and the internal resistance of the resulting secondary battery can be reduced. Furthermore, when the median diameter of the polymer is equal to or less than the above-mentioned upper limit, the static stability of the binder composition can be improved. The median diameter of the polymer is not particularly limited, and can be controlled by changing the conditions during polymer production, or by subjecting a polymer satisfying a desired particle size distribution to a classification process such as centrifugation and filtration. For example, the median diameter of the polymer can be controlled by subjecting core polymer particles to phase inversion emulsification and graft polymerization in a production method described below. Mutually The size can be increased by increasing the concentration of polymer particles during emulsification and by subjecting polymer particles with a large molecular weight to phase inversion emulsification.

[0022] <<Polymer loss tangent tanδ>> The loss tangent tanδ of the polymer must be 0.001 or more and less than 0.40, preferably 0.37 or less. If the loss tangent tanδ is within the above range, the high-temperature peel strength can be increased. The loss tangent tanδ of the polymer can be adjusted based on the polymer composition and production conditions of the polymer. For example, the loss tangent tanδ can be increased by increasing the content of aromatic vinyl monomer units in the polymer. The loss tangent tanδ can also be controlled by changing the additives added during the production of the polymer. From the viewpoint of improving the pressability of the obtained electrode, the value of the loss tangent tanδ of the polymer is preferably 0.001 or more and 0.80 or less. Specifically, good pressability of the electrode means that the amount of springback after pressing the electrode is small, the rate of density change is low, and the electrode mixture layer is less likely to peel off from the electrode base material after pressing the electrode, resulting in excellent adhesion.

[0023] <<Loss modulus G" of polymer>> The loss modulus G" of the polymer must be 1600 kPa or less, and preferably 1000 kPa or less. If the loss modulus G" is not more than the above upper limit, the peel strength of the electrode can be improved. Here, the peel strength of the electrode can include the peel strength after the manufactured electrode has been exposed to high temperatures (high-temperature peel strength) as described above, as well as the peel strength of the manufactured electrode before being exposed to high temperatures, in other words, the peel strength of the manufactured electrode as is (hereinafter sometimes referred to as "normal peel strength"). If the loss modulus G" of the polymer is not more than the above upper limit, both or either one of the high-temperature peel strength and the normal peel strength can be increased in consideration of other parameters such as the value of loss tangent tanδ. The value of the loss modulus G" is not particularly limited, but is usually 1 kPa or more. In addition, from the viewpoint of improving the pressability of the resulting electrode, the loss modulus G'' is preferably 1800 kPa or less. Here, the loss modulus G" of a polymer can be adjusted based on the composition of the polymer, the production conditions of the polymer, and the like. For example, the loss modulus G" can be reduced by reducing the content of aromatic vinyl monomer units in the polymer. In addition, the loss modulus G" can also be controlled by changing the additives added during the production of the polymer.

[0024] <<Gel content of polymer>> The gel content, measured by immersing the polymer in tetrahydrofuran, is preferably 35% by mass or more and 60% by mass or less. When the gel content of the polymer is within this range, the initial viscosity of the resulting slurry composition can be controlled within an appropriate range. Furthermore, when the gel content of the polymer is equal to or greater than the lower limit, the thermal stability of the polymer is enhanced, thereby increasing the high-temperature peel strength of the resulting electrode. The gel content of the polymer can be adjusted based on the polymer composition and the polymer production conditions. For example, the gel content of the polymer can be increased by increasing the reaction temperature in the graft polymerization reaction and by increasing the amount of initiator used.

[0025] <<Polymer composition>> The polymer must contain aromatic vinyl monomer units, conjugated diene monomer units, and hydrophilic monomer units, and may optionally contain other monomer units copolymerizable with these monomer units. Furthermore, from the viewpoints of enabling the formation of an electrode with even greater high-temperature peel strength and further reducing the internal resistance of the resulting secondary battery, the polymer preferably contains an aromatic vinyl block region composed of aromatic vinyl monomer units. In other words, the polymer is preferably a block copolymer containing a block region.

[0026] [Aromatic vinyl monomer unit] Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include aromatic monovinyl compounds such as styrene, styrene sulfonic acid and its salts, α-methylstyrene, pt-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. Among these, styrene and its derivatives are preferred. These can be used alone or in combination of two or more, but it is preferred to use one alone.

[0027] The aromatic vinyl monomer units of the polymer are preferably aromatic vinyl block regions composed of aromatic vinyl monomer units. The aromatic vinyl block region is a region containing only aromatic vinyl monomer units as repeating units. Here, one aromatic vinyl block region may be composed of only one type of aromatic vinyl monomer unit or may be composed of multiple types of aromatic vinyl monomer units, but is preferably composed of only one type of aromatic vinyl monomer unit. Furthermore, one aromatic vinyl block region may contain a coupling moiety (i.e., the aromatic vinyl monomer units constituting one aromatic vinyl block region may be connected via a coupling moiety). When a polymer has multiple aromatic vinyl block regions, the types and proportions of the aromatic vinyl monomer units constituting these multiple aromatic vinyl block regions may be the same or different, but are preferably the same.

[0028] The proportion of aromatic vinyl monomer units in the polymer is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 60% by mass or less, and more preferably 50% by mass or less, when the amount of all repeating units (monomer units and structural units) in the polymer is taken as 100% by mass. If the proportion of aromatic vinyl monomer units in the polymer is equal to or greater than the above-mentioned lower limit, the cycle characteristics of the secondary battery can be improved. On the other hand, if the proportion of aromatic vinyl monomer units in the polymer is equal to or less than the above-mentioned upper limit, the flexibility of the polymer can be ensured, and the peel strength of the electrode can be further improved. If the polymer is moderately flexible, both the high-temperature peel strength and the normal peel strength can be increased. When the aromatic vinyl monomer units contained in the polymer form an aromatic vinyl block region, the proportion of the aromatic vinyl monomer units in the polymer usually coincides with the proportion of the aromatic vinyl block region in the polymer.

[0029] [Conjugated diene monomer unit] Examples of conjugated diene monomers capable of forming conjugated diene monomer units include conjugated diene compounds having 4 or more carbon atoms, such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These can be used alone or in combination of two or more, but it is preferable to use one alone. This is because forming conjugated diene monomer units of a polymer using 1,3-butadiene can improve the dispersion stability and thermal stability of the resulting polymer.

[0030] The conjugated diene monomer units of the polymer are preferably conjugated diene block regions composed of conjugated diene monomer units. The conjugated diene block region is a region containing only conjugated diene monomer units as repeating units. Here, one conjugated diene block region may be composed of only one type of conjugated diene monomer unit or may be composed of multiple types of conjugated diene monomer units, but is preferably composed of only one type of conjugated diene monomer unit. Furthermore, one conjugated diene block region may contain a coupling site (i.e., the conjugated diene monomer units constituting one conjugated diene block region may be connected via a coupling site). When a polymer has multiple conjugated diene block regions, the types and proportions of the conjugated diene monomer units constituting these multiple conjugated diene block regions may be the same or different, but are preferably the same.

[0031] Here, the conjugated diene monomer unit is a repeating unit derived from a conjugated diene monomer, and may include both or either one of a unit made of a polymerized conjugated diene and a unit obtained by hydrogenating a unit made of a polymerized conjugated diene. The unit obtained by hydrogenating a unit made of a polymerized conjugated diene may be an alkylene structural unit. The alkylene structural unit is represented by the general formula: -C n H 2n - [where n is an integer of 2 or more]. Here, the alkylene structural unit may be linear or branched, but the alkylene structural unit is preferably linear, i.e., a linear alkylene structural unit. The alkylene structural unit preferably has 4 or more carbon atoms (i.e., n in the above general formula is an integer of 4 or more). The method for introducing the alkylene structural unit into the polymer is not particularly limited, and examples thereof include a method of hydrogenating the polymer. Hydrogenation of the polymer can be carried out using known methods such as oil phase hydrogenation and aqueous phase hydrogenation.

[0032] The proportion of the conjugated diene monomer units in the polymer is preferably 40% by mass or more, more preferably 50% by mass or more, and preferably 80% by mass or less, and more preferably 75% by mass or less, when the amount of all repeating units (monomer units and structural units) in the polymer is taken as 100% by mass. When the proportion of the conjugated diene monomer units in the polymer is equal to or greater than the above-mentioned lower limit, both the high-temperature peel strength and the normal peel strength of the electrode can be further improved. On the other hand, when the proportion of the conjugated diene monomer units in the polymer is equal to or less than the above-mentioned upper limit, the flexibility of the polymer can be ensured, and the cycle characteristics of the secondary battery can be further improved. Note that when the conjugated diene monomer units contained in the polymer form a conjugated diene block region, the proportion of the conjugated diene monomer units in the polymer usually coincides with the proportion of the conjugated diene block region in the polymer. In addition, when the polymer contains alkylene structural units, it is preferable that the total ratio of the alkylene structural units and the unhydrogenated conjugated diene monomer units satisfies the above-mentioned preferred range.

[0033] [Hydrophilic monomer unit] The hydrophilic monomer capable of forming the hydrophilic monomer unit is not particularly limited, and examples thereof include a carboxyl group-containing monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a hydroxyl group-containing monomer, and a reactive emulsifier.

[0034] Here, examples of the carboxyl group-containing monomer include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides and their derivatives. Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, and crotonic acid. Examples of the monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro-β-E-methoxyacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid monoesters such as butyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleates. Examples of the acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, and citraconic anhydride. Furthermore, as the carboxyl group-containing monomer, an acid anhydride that generates a carboxyl group upon hydrolysis can also be used. Furthermore, as the carboxyl group-containing monomer, ethylenically unsaturated polycarboxylic acids such as butenetricarboxylic acid, and partial esters of ethylenically unsaturated polycarboxylic acids such as monobutyl fumarate and mono-2-hydroxypropyl maleate can also be used.

[0035] Examples of sulfonic acid group-containing monomers include styrene sulfonic acid, vinyl sulfonic acid (ethylene sulfonic acid), methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, and 3-allyloxy-2-hydroxypropane sulfonic acid. In the present invention, "(meth)allyl" means allyl and / or methallyl.

[0036] Furthermore, examples of the phosphate group-containing monomer include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. In the present invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0037] Examples of the hydroxyl group-containing monomer include acrylic esters having a hydroxyl group in the molecule, such as 2-hydroxyethyl acrylate, and methacrylic esters having a hydroxyl group in the molecule, such as 2-hydroxyethyl methacrylate.

[0038] Examples of reactive emulsifiers include polyalkylene oxide emulsifiers having anionic functional groups and / or nonionic functional groups. Other examples that can be used include sodium styrene sulfonate, sodium allyl alkyl sulfonate, alkyl allyl sulfosuccinate, polyoxyethylene alkyl allyl glycerin ether sulfate, and polyoxyethylene alkyl phenol allyl glycerin ether sulfate.

[0039] Here, the above-mentioned hydrophilic monomers may be used singly or in combination of two or more. As the hydrophilic monomer, acidic group-containing monomers such as carboxyl group-containing monomers, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers are preferred, and from the viewpoint of further increasing the high-temperature peel strength, carboxyl group-containing monomers are more preferred, acrylic acid and methacrylic acid are further preferred, and methacrylic acid is particularly preferred.

[0040] Furthermore, it is preferable that at least a portion of the hydrophilic monomer units formed using the above-mentioned hydrophilic monomers are present in the polymer in the form of an alkali metal salt such as sodium or potassium or an ammonium salt. In particular, it is preferable that at least a portion of the hydrophilic monomer units are ammonium salts. If at least a portion of the hydrophilic monomer units are ammonium salts, the storage stability of the resulting slurry composition can be further improved.

[0041] The hydrophilic monomer units may be mixed with the aromatic vinyl monomer units and conjugated diene monomer units to form a random copolymer, or may be bonded as a graft chain to a core particle that is a block copolymer or a random copolymer composed of aromatic vinyl monomer units and conjugated diene monomer units. In particular, the polymer that is an essential component of the binder composition of the present invention is preferably a polymer in which a graft chain having a hydrophilic monomer unit as a repeating unit is bonded to a core particle that is a block copolymer composed of an aromatic vinyl block region and a conjugated diene block region. It is preferable that the block copolymer serving as the core particle has only an aromatic vinyl block region and a conjugated diene block region.

[0042] The proportion of hydrophilic monomer units in the polymer must be 4.0% by mass or more and 20% by mass or less, assuming that the amount of all repeating units (monomer units and structural units) in the polymer is 100% by mass. Furthermore, the proportion of hydrophilic monomer units in the polymer is preferably 5.0% by mass or more, more preferably 5.5% by mass or more, and preferably 16% by mass or less, and more preferably 10% by mass or less. When the proportion of hydrophilic monomer units in the polymer is equal to or greater than the lower limit, the stability of the prepared slurry composition can be improved, while the high-temperature peel strength and normal peel strength of the resulting electrode can be improved. On the other hand, when the proportion of hydrophilic monomer units in the block copolymer is equal to or less than the upper limit, the initial viscosity of the prepared slurry composition can be prevented from becoming excessively high, thereby improving the high-temperature peel strength and normal peel strength of the resulting electrode. From the viewpoint of improving the pressing properties of the resulting electrode, it is preferable that the proportion of hydrophilic monomer units in the polymer is 3.7% by mass or more and 20% by mass or less, when the amount of all repeating units (monomer units and structural units) in the polymer is taken as 100% by mass.

[0043] [Other monomer units] Monomers that can form other monomer units that can be optionally contained in the polymer are not particularly limited, and examples thereof include nitrile group-containing monomers such as acrylonitrile and methacrylonitrile; and amide group-containing monomers.

[0044] <<Polymer Preparation Method>> When the polymer as a whole or the core particles of the polymer are random polymers, the polymer can be polymerized according to known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. The polymerization reaction can be addition polymerization such as ionic polymerization, radical polymerization, or living radical polymerization. Commonly used emulsifiers, dispersants, polymerization initiators, polymerization aids, etc. can be used in the polymerization, and the amounts used can be the same as commonly used amounts.

[0045] When the polymer core particles are block copolymers, the core particles can be prepared, for example, through a step of block polymerizing the aromatic vinyl monomer and conjugated diene monomer in an organic solvent to obtain a solution of a block copolymer having an aromatic vinyl block region and a conjugated diene block region (block copolymer solution preparation step), and a step of adding water to the obtained block copolymer solution to emulsify the block copolymer into particles (emulsification step).

[0046] -Block copolymer solution preparation process- The method of block polymerization in the block copolymer solution preparation step is not particularly limited. For example, a block copolymer can be prepared by adding a second monomer component different from the first monomer component to a solution obtained by polymerizing a first monomer component, and then polymerizing the second monomer component. If necessary, the addition and polymerization of the monomer component can be further repeated. The organic solvent used as the reaction solvent is also not particularly limited and can be appropriately selected depending on the type of monomer, etc. Here, it is preferable that the block copolymer obtained by the block polymerization as described above is subjected to a coupling reaction using a coupling agent prior to the emulsification step described below.

[0047] The coupling agent that can be used in the above coupling reaction is not particularly limited, and examples thereof include bifunctional coupling agents, trifunctional coupling agents, tetrafunctional coupling agents, and pentafunctional or higher coupling agents. Examples of bifunctional coupling agents include bifunctional halogenated silanes such as dichlorosilane, monomethyldichlorosilane, and dichlorodimethylsilane; bifunctional halogenated alkanes such as dichloroethane, dibromoethane, methylene chloride, and dibromomethane; and bifunctional tin halides such as dichlorotin, monomethyldichlorotin, dimethyldichlorotin, monoethyldichlorotin, diethyldichlorotin, monobutyldichlorotin, and dibutyldichlorotin. Examples of trifunctional coupling agents include trifunctional halogenated alkanes such as trichloroethane and trichloropropane; trifunctional halogenated silanes such as methyltrichlorosilane and ethyltrichlorosilane; and trifunctional alkoxysilanes such as methyltrimethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane. Examples of tetrafunctional coupling agents include tetrafunctional halogenated alkanes such as carbon tetrachloride, carbon tetrabromide, and tetrachloroethane; tetrafunctional halogenated silanes such as tetrachlorosilane and tetrabromosilane; tetrafunctional alkoxysilanes such as tetramethoxysilane and tetraethoxysilane; and tetrafunctional tin halides such as tetrachlorotin and tetrabromotin. Examples of the pentafunctional or higher coupling agent include 1,1,1,2,2-pentachloroethane, perchloroethane, pentachlorobenzene, perchlorobenzene, octabromodiphenyl ether, and decabromodiphenyl ether. These may be used alone or in combination of two or more.

[0048] Among the above, dichlorodimethylsilane is preferred as the coupling agent. Note that, according to the coupling reaction using the coupling agent, a coupling moiety derived from the coupling agent is introduced into the polymer chain (e.g., triblock structure) constituting the block copolymer.

[0049] The block copolymer solution obtained after the above-described block polymerization and optional coupling reaction may be subjected to the emulsification step described below as is, or may be subjected to the emulsification step after adding an additive such as an antioxidant, if necessary. Alternatively, the block copolymer may be precipitated to obtain a dried product, and the dried product may be dissolved in a good solvent such as cyclohexane to obtain a block copolymer solution, which may then be subjected to the emulsification step.

[0050] -Emulsification process- The emulsification method in the emulsification step is not particularly limited, but a preferred method is, for example, a method of subjecting a preliminary mixture of the block copolymer solution obtained in the above-mentioned block copolymer solution preparation step and an aqueous solution of an emulsifier to phase inversion emulsification. Here, for example, known emulsifiers and emulsifying dispersers can be used for phase inversion emulsification. Specifically, the emulsifying disperser is not particularly limited, and examples thereof include batch-type emulsifying dispersers such as "Homogenizer" (manufactured by IKA Corporation), "Polytron" (manufactured by Kinematica Corporation), and "TK Auto Homo Mixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.); "TK Pipeline Homo Mixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.), "Colloid Mill" (manufactured by Kobe Steel Pantech Co., Ltd.), "Thrasher" (manufactured by Nippon Coke & Engineering Co., Ltd.), "Trigonal Wet Fine Mill" (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.), "Cavitron" (manufactured by Eurotech), "Milder" (manufactured by Pacific Machinery Co., Ltd.), and "Fine Fine Mill" (manufactured by Tokushu Kika Kogyo Co., Ltd.). Examples of suitable emulsifying and dispersing machines include a continuous emulsifying and dispersing machine such as "Lomil" (manufactured by Pacific Machinery Co., Ltd.); a high-pressure emulsifying and dispersing machine such as "Microfluidizer" (manufactured by Mizuho Industrial Co., Ltd.), "Nanomizer" (manufactured by Nanomizer Co., Ltd.), "APV Gaulin" or "LAB1000" (manufactured by SPXFLOW Corporation), "Starburst" (manufactured by Sugino Machine Co., Ltd.), or "Econizer" (manufactured by Mimaru Machinery Co., Ltd.); a membrane emulsifying and dispersing machine such as "Membrane Emulsifier" (manufactured by Reika Kogyo Co., Ltd.); a vibration emulsifying and dispersing machine such as "Vibromixer" (manufactured by Reika Kogyo Co., Ltd.); and an ultrasonic emulsifying and dispersing machine such as "Ultrasonic Homogenizer" (manufactured by Branson). The conditions for the emulsifying operation using the emulsifying and dispersing machine (e.g., processing temperature, processing time, etc.) are not particularly limited and may be appropriately selected to achieve the desired dispersion state. Then, if necessary, the organic solvent may be removed from the emulsion obtained after emulsification by a known method, thereby obtaining an aqueous dispersion of core particles containing the block copolymer.

[0051] Then, by bonding graft chains to the core particles (random polymers or block copolymers) obtained by these steps (grafting step), a graft polymer can be prepared in which graft chains having hydrophilic monomer units as repeating units are bonded to the core particles.

[0052] - Grafting process - The graft polymerization of the graft chains consisting of repeating units of hydrophilic monomer units can be carried out using any known graft polymerization method without any particular limitations. Specifically, the graft polymerization can be carried out using a radical initiator, such as a redox initiator comprising a combination of an oxidizing agent and a reducing agent. The oxidizing agent and reducing agent are not particularly limited, and known agents can be used. Furthermore, after terminating the graft polymerization, alkali metal salts such as sodium and potassium, or ammonium salts can be used as neutralizing agents. Among these, ammonium salts are preferred as neutralizing agents from the viewpoint of enhancing the storage stability of the resulting slurry composition. These neutralizing agents can be added, for example, as an aqueous solution to the graft polymerization reaction solution. When a block copolymer having an aromatic vinyl block region and a conjugated diene block region is graft polymerized onto core particles using a redox initiator, the conjugated diene units in the block copolymer may be crosslinked when introducing hydrophilic graft chains by graft polymerization. When preparing the graft polymer, crosslinking does not need to proceed simultaneously with graft polymerization, and only graft polymerization may be allowed to proceed by adjusting the type of radical initiator and reaction conditions.

[0053] Then, by subjecting the above-mentioned core particles to a graft polymerization reaction with a hydrophilic monomer, a polymer can be obtained as a graft polymer in which hydrophilic graft chains consisting of repeating hydrophilic monomer units are bonded to the core particles.

[0054] <Solvent> The binder composition of the present invention must contain water as a solvent, but may also contain a small amount of an organic solvent.

[0055] <Other ingredients> The binder composition of the present invention may contain components other than the above components (other components). For example, the binder composition may contain a known binder (such as a styrene-butadiene copolymer and / or an acrylic polymer) other than the above-mentioned polymers.

[0056] When the binder composition contains a binder in addition to the above-described polymer, the content of the above-described polymer is preferably 50% by mass or more of the total content of the polymer and the binder, more preferably 55% by mass or more, and even more preferably 60% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0057] The binder composition may also contain a water-soluble polymer. The water-soluble polymer is a component that can disperse the above-mentioned polymer and other blending components well in water. While not particularly limited, the water-soluble polymer is preferably a synthetic polymer, and more preferably an addition polymer produced via addition polymerization. The water-soluble polymer may also be in the form of a salt (a salt of a water-soluble polymer). In other words, in the present invention, the term "water-soluble polymer" also includes salts of the water-soluble polymer. In the present invention, a polymer is "water-soluble" when 0.5 g of the polymer is dissolved in 100 g of water at 25°C, resulting in an insoluble content of less than 1.0% by mass.

[0058] Furthermore, the binder composition may contain known additives, such as antioxidants such as 2,6-di-tert-butyl-p-cresol, antifoaming agents, and dispersants (excluding those corresponding to the water-soluble polymers described above).

[0059] The other components may be used singly or in combination of two or more in any ratio.

[0060] <Method for preparing binder composition> The binder composition of the present invention is not particularly limited, and can be prepared by mixing a polymer with other optional components in the presence of water. When the binder composition is prepared using a polymer dispersion, the liquid contained in the dispersion may be used as it is as a medium for the binder composition.

[0061] (Slurry composition for non-aqueous secondary battery electrodes) The slurry composition of the present invention is a composition used to form an electrode mixture layer of an electrode, and contains the binder composition described above and further contains an electrode active material. That is, the slurry composition of the present invention contains the polymer, electrode active material, and water described above, and may further contain other optional components. Furthermore, since the slurry composition of the present invention contains the binder composition described above, an electrode including an electrode mixture layer formed from the slurry composition has excellent peel strength after exposure to high temperatures. Furthermore, a secondary battery including the electrode has low internal resistance.

[0062] <Binder composition> As the binder composition, the above-described binder composition of the present invention containing a predetermined polymer and water is used. The amount of the binder composition in the slurry composition is not particularly limited, and may be, for example, an amount such that the amount of polymer is 0.5 parts by mass or more and 15 parts by mass or less in terms of solid content per 100 parts by mass of the electrode active material.

[0063] <Electrode active material> The electrode active material is not particularly limited, and known electrode active materials used in secondary batteries can be used. Specifically, for example, the electrode active material that can be used in the electrode mixture layer of a lithium ion secondary battery, which is an example of a secondary battery, is not particularly limited, and the following electrode active materials can be used.

[0064] [Cathode active material] As the positive electrode active material blended in the positive electrode mixture layer of the lithium ion secondary battery, for example, a compound containing a transition metal, such as a transition metal oxide, a transition metal sulfide, a composite metal oxide of lithium and a transition metal, etc. can be used. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, etc. Specifically, the positive electrode active material is not particularly limited, and includes lithium-containing cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium-containing nickel oxide (LiNiO2), LiNi 5 / 10 Co 2 / 10 Mn 3 / 10 O2 (NMC532) and other lithium-containing composite oxides of Co-Ni-Mn, lithium-containing composite oxides of Ni-Mn-Al, lithium-containing composite oxides of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO4), olivine-type lithium manganese phosphate (LiMnPO4), Li 1+x Mn 2-x O4 (0 < X < 2) and other lithium-excess spinel compounds represented by, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4, etc. In addition, the above-mentioned positive electrode active materials may be used alone or in combination of two or more.

[0065] [Negative electrode active material] As the negative electrode active material blended in the negative electrode mixture layer of the lithium ion secondary battery, for example, a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material combining these can be mentioned. Here, the carbon-based negative electrode active material refers to an active material having a carbon skeleton that can insert (also referred to as "doping") lithium. Specific examples of the carbon-based negative electrode active material include carbonaceous materials such as coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, pyrolytic vapor-grown carbon fiber, phenolic resin calcined body, polyacrylonitrile-based carbon fiber, pseudoisotropic carbon, furfuryl alcohol resin calcined body (PFA), and hard carbon, as well as graphitic materials such as natural graphite and artificial graphite. Metal-based negative electrode active materials are active materials containing metals, typically active materials containing an element capable of intercalating lithium and having a theoretical electrical capacity per unit mass of 500 mAh / g or more when lithium is intercalated. Examples of metal-based active materials include lithium metal, elemental metals capable of forming lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.), and oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. of these metals. Furthermore, oxides such as lithium titanate can also be used. The above-mentioned negative electrode active materials may be used singly or in combination of two or more.

[0066] <Other ingredients> Other components that can be blended into the slurry composition are not particularly limited and include conductive materials and the same components as those that can be blended into the binder composition of the present invention. Note that the other components may be used alone or in combination of two or more in any ratio.

[0067] <Preparation of Slurry Composition> The method for preparing the slurry composition is not particularly limited. For example, a slurry composition can be prepared by mixing the binder composition, the electrode active material, and other components used as needed in the presence of water. The medium used in preparing the slurry composition includes the medium contained in the binder composition. The mixing method is not particularly limited, but mixing can be performed using a commonly used stirrer or disperser.

[0068] (Electrode for non-aqueous secondary batteries) The non-aqueous secondary battery electrode of the present invention includes an electrode mixture layer formed using the above-described slurry composition for a non-aqueous secondary battery electrode. Therefore, the electrode mixture layer is composed of a dried product of the above-described slurry composition, and typically contains an electrode active material and a component derived from a polymer, and optionally further contains other components. The components contained in the electrode mixture layer are those contained in the above-described slurry composition for a non-aqueous secondary battery electrode, and the preferred ratios of the components are the same as the preferred ratios of the components in the slurry composition. Furthermore, the polymer is present in particulate form in the binder composition and the slurry composition, but may be in particulate form or any other shape in the electrode mixture layer formed using the slurry composition. The electrode for a non-aqueous secondary battery of the present invention has an electrode mixture layer formed using the above-mentioned slurry composition for a non-aqueous secondary battery electrode, and therefore has excellent peel strength after exposure to high temperatures. Furthermore, a secondary battery including the electrode has low internal resistance.

[0069] <Production of electrodes for non-aqueous secondary batteries> The electrode mixture layer of the electrode for a non-aqueous secondary battery of the present invention can be formed, for example, by the following method. 1) A method in which the slurry composition of the present invention is applied to the surface of a current collector and then dried; 2) a method of immersing a current collector in the slurry composition of the present invention and then drying the same; and 3) A method in which the slurry composition of the present invention is applied to a release substrate, and dried to produce an electrode mixture layer, and the resulting electrode mixture layer is transferred to the surface of a current collector. Among these, the method 1) is particularly preferred because it allows for easy control of the thickness of the electrode mixture layer. Specifically, the method 1) includes a step of applying a slurry composition onto a current collector (application step) and a step of drying the slurry composition applied onto the current collector to form an electrode mixture layer on the current collector (drying step).

[0070] [Coating process] The method for applying the slurry composition to the current collector is not particularly limited, and known methods can be used. Specifically, examples of the application method include a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. In this case, the slurry composition may be applied to only one side of the current collector, or may be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set depending on the thickness of the electrode mixture layer obtained by drying.

[0071] Here, the current collector to which the slurry composition is applied is made of a material that is electrically conductive and electrochemically durable. Specifically, the current collector may be made of, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. Note that one of the above materials may be used alone, or two or more may be used in combination in any ratio.

[0072] [Drying process] The method for drying the slurry composition on the current collector is not particularly limited and any known method can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams, etc. By drying the slurry composition on the current collector in this manner, an electrode mixture layer can be formed on the current collector, and a nonaqueous secondary battery electrode including the current collector and the electrode mixture layer can be obtained.

[0073] After the drying step, the electrode mixture layer may be subjected to a pressure treatment using a mold press, a roll press, or the like. The pressure treatment improves the adhesion between the electrode mixture layer and the current collector and further increases the density of the resulting electrode mixture layer. In addition, when the electrode mixture layer contains a curable polymer, it is preferable to cure the polymer after the electrode mixture layer is formed.

[0074] (Non-aqueous secondary battery) The nonaqueous secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolyte, and a separator, and uses the above-described nonaqueous secondary battery electrode as at least one of the positive electrode and the negative electrode. The nonaqueous secondary battery of the present invention is manufactured using the above-described nonaqueous secondary battery electrode as at least one of the positive electrode and the negative electrode, and therefore can exhibit excellent cycle characteristics. In the following, a case where the secondary battery is a lithium ion secondary battery will be described as an example, but the present invention is not limited to the following example.

[0075] <Electrode> Here, the electrodes other than the above-described nonaqueous secondary battery electrode of the present invention that can be used in the nonaqueous secondary battery of the present invention are not particularly limited, and known electrodes used in the manufacture of secondary batteries can be used. Specifically, the electrodes other than the above-described nonaqueous secondary battery electrode of the present invention can be electrodes formed by forming an electrode mixture layer on a current collector using a known manufacturing method.

[0076] <Electrolyte> As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. For example, a lithium salt is used as the supporting electrolyte of a lithium ion secondary battery. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, CF4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred because they are easily soluble in solvents and exhibit a high degree of dissociation. One type of electrolyte may be used alone, or two or more types may be used in combination at any ratio. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0077] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. Suitable examples include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. Mixtures of these solvents may also be used. Among these, carbonates are preferred due to their high dielectric constant and wide stable potential range. Generally, the lower the viscosity of the solvent used, the higher the lithium ion conductivity. Therefore, the lithium ion conductivity can be adjusted by the type of solvent. The concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate, and known additives can be added to the electrolytic solution.

[0078] <Separator> The separator is not particularly limited, and can be, for example, one described in JP 2012-204303 A. Among these, a microporous film made of a polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it can reduce the overall separator thickness, thereby increasing the proportion of electrode active material in the secondary battery and increasing capacity per volume.

[0079] The secondary battery of the present invention can be produced, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the stack as necessary according to the battery shape, placing the stack in a battery container, injecting an electrolyte into the battery container, and sealing the container. In the nonaqueous secondary battery of the present invention, the above-described nonaqueous secondary battery electrode is used as at least one of the positive electrode and negative electrode, preferably the negative electrode. The nonaqueous secondary battery of the present invention may be provided with a fuse, an overcurrent protection element such as a PTC element, an expanded metal, a lead plate, or the like, as necessary to prevent internal pressure buildup, overcharging and overdischarging, and the like within the secondary battery. The secondary battery may have any shape, such as a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, or a flat type. [Example]

[0080] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a polymer produced by polymerizing multiple types of monomers, the proportion of monomer units formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that certain monomer to all monomers used in the polymerization of the polymer, unless otherwise specified. In the examples and comparative examples, various attributes and evaluations were measured or carried out as follows.

[0081] <Content of Monomer Units in Polymer> The content ratio of the monomer units in the polymers prepared in the examples and comparative examples is: 1 Measurement was performed using H-NMR (manufactured by JEOL Ltd.) Specifically, the peak area assigned to each monomer was determined and divided by the number of protons contained in the peak to calculate the molar ratio of the monomer units, which was then converted into a weight ratio using the molecular weight of each monomer. <Median diameter of polymer> Measurement was performed using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, product name "SALD-2300") Specifically, an aqueous dispersion of the polymer was prepared, and the particle size distribution (volume basis) was measured using the above-mentioned analyzer. The particle size at which the cumulative volume calculated from the smallest diameter side reached 50% was determined as the median diameter (μm). <Gel content of polymer> The binder compositions prepared in the examples and comparative examples were dried at 50% humidity and room temperature (23°C to 25°C) to form films with a thickness of approximately 0.3 mm. The formed films were cut into 3 mm squares and precisely weighed. The mass of the film pieces obtained by cutting was designated w0. These film pieces were immersed in 100 g of tetrahydrofuran (THF) for 24 hours at 25°C. The film pieces were then removed from the THF and vacuum-dried at 105°C for 3 hours, and the mass of the insoluble matter, w1, was measured. The gel content (mass%) of the polymer was then calculated according to the following formula: Gel content (mass%) = (w1 / w0) × 100 <Polymer loss tangent tanδ and loss modulus G"> <<Preparation of polymer film>> The binder compositions prepared in the examples and comparative examples were weighed out onto a Teflon (registered trademark) petri dish so that the thickness after drying would be 50 μm. ,room The polymer film was obtained by vacuum drying at room temperature for 12 hours. <<Viscoelasticity measurement of polymer films>> Using the polymer film prepared above, measurements were performed using a viscoelasticity measuring device ("Production RPA" manufactured by Alpha Technology) under conditions of a frequency of 52 Hz and a strain of 10%, while gradually increasing the temperature from 30°C to 200°C. In the above measurements, the loss modulus G" and loss tangent tanδ were calculated based on the results at 30°C.

[0082] <Static Stability of Binder Composition> A 10 cm long test tube was prepared, and the binder composition prepared in each of the examples and comparative examples was poured into it to a height of 5 mm from the top of the tube. The tube was then capped and used as a test sample. After storing the tube at 25°C for one month, the tube was opened and 1 g of binder composition was sampled from the upper and lower layers of the liquid. Sampling was performed using a Pasteur pipette. The upper layer sample was taken at a depth of 1 cm from the liquid surface, and the lower layer sample was taken at a height of 1 cm from the bottom. Each sample was then dried on an aluminum plate, and the solids concentration was calculated from the change in weight before and after drying. The drying conditions were 130°C for 30 minutes, and the solids concentration was calculated based on the following formula: (Solid concentration)=(Weight after drying) / (Weight before drying)×100 A: The difference in solid content between the upper and lower layers is less than 1% B: The difference in solid content between the upper and lower layers is 1% or more but less than 2% C: The difference in solid content between the upper and lower layers is 2% or more but less than 3% D: The difference in solid content between the upper and lower layers is 3% or more. <Initial Viscosity of Slurry Composition> 97.5 parts of natural graphite (theoretical capacity: 360 mAh / g) as the negative electrode active material and 1 part of carboxymethyl cellulose as a thickener (solid content equivalent) were added to a planetary mixer. The mixture was then diluted with ion-exchanged water to a solid content concentration of 60%, and then kneaded for 60 minutes at a rotation speed of 45 rpm. 1.5 parts of the negative electrode binder composition obtained in the example (solid content equivalent) were then added, and kneaded for 40 minutes at a rotation speed of 40 rpm. The solid content was further adjusted to 48% with ion-exchanged water, and the viscosity was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVB-10", rotation speed: 60 rpm). A: Less than 3000 rpm B: 3000 rpm or more and less than 3500 rpm C: 3500 rpm or more and less than 4000 rpm D:4000rpm or more <Storage stability of slurry composition> The viscosity η0 of the resulting slurry composition was measured using a Brookfield viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVB-10", rotation speed: 60 rpm). Next, the slurry composition whose viscosity had been measured was stirred for 24 hours using a planetary mixer (rotation speed: 60 rpm), and the viscosity η1 of the slurry composition after stirring was measured using the same Brookfield viscometer (rotation speed: 60 rpm) as above. The viscosity retention rate of the slurry composition before and after stirring, Δη = (η0 - η1) / η0 × 100 (%), was then calculated, and the viscosity stability of the slurry composition was evaluated according to the following criteria. The temperature during viscosity measurement was 25°C. The closer the absolute value of the viscosity retention rate |Δη| is to 0, the better the viscosity stability of the slurry composition. A: The absolute value of viscosity retention rate |Δη| is 0% or more and less than 10% B: The absolute value of the viscosity retention rate |Δη| is 10% or more and less than 20% C: The absolute value of viscosity retention rate |Δη| is 20% or more and less than 30% D: Absolute value of viscosity retention rate |Δη| is 30% or more <Normal peel strength of electrode> The negative electrodes prepared in the Examples and Comparative Examples were cut directly into rectangular shapes measuring 100 mm in length and 10 mm in width to prepare test specimens. These test specimens were placed with the surface of the negative electrode composite layer facing downward, and cellophane tape was applied to the surface of the negative electrode composite layer. Cellophane tape specified in JIS Z1522 was used as the cellophane tape. The cellophane tape was fixed to a test table. One end of the current collector was then pulled vertically upward at a pulling rate of 50 mm / min to measure the stress when peeled off. This measurement was performed three times, and the average value was calculated and used as the peel strength. A higher peel strength indicates a stronger adhesive strength of the negative electrode composite layer to the current collector, i.e., a higher adhesion strength. A: Peel strength is 16N / m or more B: Peel strength is 14N / m or more and less than 16N / m C: Peel strength is 12N / m or more and less than 14N / m D: Peel strength is less than 12 N / m <High-temperature peel strength of electrodes> The negative electrodes prepared in the examples and comparative examples were vacuum-dried at 100°C for 10 hours and then cut into rectangular specimens measuring 100 mm in length and 10 mm in width to prepare test pieces. The test pieces were placed with the surface of the negative electrode composite layer facing down, and cellophane tape was attached to the surface of the negative electrode composite layer. Cellophane tape specified in JIS Z1522 was used as the cellophane tape. The cellophane tape was fixed to a test table. The stress was then measured when one end of the current collector was pulled vertically upward at a pulling rate of 50 mm / min to peel it off. This measurement was performed three times, and the average value was calculated and used as the peel strength. A higher peel strength measured in this way indicates a stronger adhesive strength of the negative electrode composite layer to the current collector after exposure to high temperatures, i.e., a higher adhesion strength after exposure to high temperatures. A: Peel strength is 22N / m or more B: Peel strength is 18N / m or more and less than 22N / m C: Peel strength is 14N / m or more and less than 18N / m D: Peel strength is less than 14 N / m <Internal resistance of secondary battery> The lithium-ion secondary batteries prepared in the Examples and Comparative Examples were used as test subjects for measuring IV resistance as follows. They were subjected to a conditioning treatment in which they were charged at a charge rate of 0.1 C at 25°C until the voltage reached 4.2 V, rested for 10 minutes, and then discharged three times at a discharge rate of 0.1 C to 3.0 V. Subsequently, they were charged to 3.75 V at 1 C (C is a value expressed as rated capacity (mA) / hour (h)) in a −10°C atmosphere, and then charged and discharged for 15 seconds from 3.75 V at 0.5 C, 1.0 C, 1.5 C, and 2.0 C. The battery voltage after 15 seconds on the charge side in each case was plotted against the current value, and the slope was calculated as the IV resistance (Ω) for charging. The resulting IV resistance values ​​(Ω) were evaluated according to the following criteria. A smaller IV resistance value indicates a lower internal resistance of the secondary battery and better low-temperature characteristics. A: IV resistance is 15Ω or less B: IV resistance is over 15Ω and 17Ω or less C: IV resistance is greater than 17 Ω <Adhesion of electrode mixture layer after pressing> The edge of each negative electrode prepared in the Examples and Comparative Examples was visually inspected to determine whether there was any separation between the negative electrode composite layer and the current collector at least 1 mm inward from the edge. If no such separation was observed, the electrode composite layer after pressing was deemed to be difficult to separate from the substrate and was evaluated as "good." <Density change rate of electrode after pressing> The negative electrodes prepared in the examples and comparative examples were stored in the same environment at 25±3°C for 24 hours, and then the density of the electrode mixture layer was measured again. 3 When the value was below this, the electrode was evaluated as "good" since it was deemed that springback was unlikely to occur.

[0083] Example 1 <Preparation of binder composition for non-aqueous secondary battery negative electrode> <<Polymer Preparation>> [Preparation of cyclohexane solution of block copolymer] A pressure-resistant reactor was charged with 233.3 kg of cyclohexane, 54.2 mmol of N,N,N',N'-tetramethylethylenediamine (hereinafter referred to as "TMEDA"), and 30.0 kg of styrene as an aromatic vinyl monomer. While stirring these mixtures at 40°C, 1806.5 mmol of n-butyllithium as a polymerization initiator was added, and polymerization was carried out for 1 hour while the temperature was raised to 50°C. The polymerization conversion of styrene was 100%. Subsequently, while controlling the temperature to maintain a temperature of 50-60°C, 70.0 kg of butadiene as an aliphatic conjugated diene monomer was continuously added to the pressure-resistant reactor over 1 hour. After the addition of butadiene was completed, the polymerization reaction was continued for another 1 hour. The polymerization conversion of butadiene was 100%. Next, 722.6 mmol of dichlorodimethylsilane as a coupling agent was added to the pressure-resistant reactor, and a coupling reaction was carried out for 2 hours to form a styrene-butadiene coupled block copolymer. Thereafter, 3612.9 mmol of methanol was added to the reaction solution to deactivate the active terminals and mixed thoroughly. Next, 0.3 parts of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to 100 parts of this reaction solution (containing 30.0 parts of the polymer component) and mixed. The resulting mixed solution was gradually added dropwise to warm water at 85 to 95°C to volatilize the solvent and obtain a precipitate. The precipitate was then pulverized and dried with hot air at 85°C to recover a dried product containing the block copolymer. The recovered dried product was then dissolved in cyclohexane to prepare a block copolymer solution with a block copolymer concentration of 15%. [Phase inversion emulsification] Sodium alkylbenzene sulfonate was dissolved in ion-exchange water to prepare a 5% aqueous solution. 5,000 g of the resulting block copolymer solution and 5,000 g of the resulting aqueous solution were then placed in a tank and premixed by stirring. The premix was then transferred from the tank to a continuous high-efficiency emulsifying disperser (manufactured by Pacific Machinery Works, product name "Cavitron") at a rate of 100 g / min using a metering pump, and the mixture was stirred at a rotation speed of 20,000 rpm to obtain an emulsion by phase inversion of the premix. Next, cyclohexane in the obtained emulsion was distilled off under reduced pressure using a rotary evaporator, and the distilled emulsion was then centrifuged at 7000 rpm for 10 minutes using a centrifuge (Hitachi Koki Co., Ltd., product name "Himac CR21N"), and the upper layer was removed for concentration. Finally, the upper layer was filtered through a 100-mesh wire screen to obtain an aqueous dispersion containing particulate block copolymers (block copolymer latex). [Graft polymerization and crosslinking] The obtained block copolymer latex was diluted with distilled water to a ratio of 850 parts water to 100 parts (solids equivalent) of the particulate block copolymer. This diluted block copolymer latex was placed in a nitrogen-substituted polymerization reactor equipped with a stirrer and heated to 30°C while stirring. In a separate vessel, 6 parts of methacrylic acid as a hydrophilic monomer and 15 parts of distilled water were mixed to prepare a diluted methacrylic acid solution. This diluted methacrylic acid solution was added over 30 minutes to the polymerization reactor heated to 30°C. Furthermore, a solution (g) containing 7 parts of distilled water and 0.6 parts of ascorbic acid as a reducing agent was prepared in a separate vessel. The resulting solution was added to a polymerization reactor, followed by the addition of 0.5 parts of cumene hydroperoxide (manufactured by NOF Corporation, trade name "CHP") as an oxidizing agent. The reaction was carried out at 30°C for 1 hour, and then at 70°C for a further 2 hours to obtain an aqueous dispersion of a particulate polymer. The polymerization conversion rate was 99%. The pH of the resulting aqueous dispersion was adjusted to 8 by adding 8% aqueous ammonia. <Preparation of Slurry Composition for Secondary Battery Positive Electrode> The planetary mixer uses Co-Ni-Mn lithium composite oxide active material NMC532, LiNi 5 / 10 Co 2 / 10 Mn 3 / 10A mixture of 97 parts of acetylene black (manufactured by Denki Kagaku Kogyo under the trade name "HS-100") as a conductive material, 1 part of the polymer obtained above (calculated as solids), and 1 part of PVdF (manufactured by Kureha Corporation under the trade name KF7208) was added and mixed. N-methyl-2-pyrrolidone (NMP) as an organic solvent was gradually added, and the mixture was stirred at a temperature of 25±3°C and a rotation speed of 25 rpm until the viscosity reached 3,600 mPa s [B-type viscometer, 60 rpm (rotor M4), 25±3°C]. <Production of positive electrodes> The positive electrode slurry composition obtained as described above was applied to a 20 μm thick aluminum foil current collector using a comma coater in an amount of 20±0.5 mg / cm 2 The coating was applied so that The aluminum foil was then transported at a speed of 200 mm / min through an oven at 120°C for 2 minutes and then through an oven at 130°C for 2 minutes to dry the slurry composition on the aluminum foil, thereby obtaining a positive electrode substrate in which a positive electrode composite layer was formed on the current collector. Thereafter, the positive electrode composite layer side of the prepared positive electrode blank was roll-pressed in an environment at a temperature of 25±3°C, and the density of the positive electrode composite layer was adjusted to 3.20 g / cm 3 A positive electrode of 1000 .mu.m was obtained. <Preparation of Slurry Composition for Negative Electrode> A planetary mixer was charged with 97.5 parts of natural graphite (theoretical capacity: 360 mAh / g) as the negative electrode active material and 1 part of carboxymethyl cellulose as a thickener (solids equivalent). The mixture was then diluted with ion-exchanged water to a solids concentration of 60% and then kneaded for 60 minutes at a rotation speed of 45 rpm. Next, 1.5 parts (solids equivalent) of the negative electrode binder composition obtained above was added and kneaded for 40 minutes at a rotation speed of 40 rpm. Ion-exchanged water was then added to the mixture to a viscosity of 3000±500 mPa·s (measured with a Brookfield viscometer at 25°C and 60 rpm), thereby preparing a negative electrode slurry composition. <Production of negative electrodes> The negative electrode slurry composition was applied to the surface of a 15 μm thick electrolytic copper foil current collector using a comma coater in an amount of 11±0.5 mg / cm 2Thereafter, the copper foil coated with the negative electrode slurry composition was transported at a speed of 400 mm / min through an oven at a temperature of 120°C for 2 minutes and then through an oven at a temperature of 130°C for 2 minutes, thereby drying the slurry composition on the copper foil and obtaining a negative electrode blank in which a negative electrode composite layer was formed on a current collector. Thereafter, the negative electrode composite layer side of the prepared negative electrode blank was roll-pressed in an environment at a temperature of 25±3°C, and the density of the negative electrode composite layer was adjusted to 1.60 g / cm 3 A negative electrode of 1000 .mu.m was obtained. <Preparation of secondary battery separator> A single-layer polypropylene separator (Celgard, "#2500") was used. <Preparation of non-aqueous secondary battery> A single-layer laminate cell (with an initial design discharge capacity of 30 mAh) was fabricated using the negative electrode, positive electrode, and separator described above. It was then placed in an aluminum foil bag and vacuum dried at 60°C for 10 hours. A 1.0 M LiPF solution (solvent: ethylene carbonate (EC) / diethyl carbonate (DEC) = 5 / 5 (volume ratio), additive: vinylene carbonate 2 vol% (solvent ratio)) was then filled as the electrolyte. The aluminum foil was then heat-sealed at 150°C to seal the opening, completing the lithium-ion secondary battery. The internal resistance of this lithium-ion secondary battery was evaluated as described above. The results are shown in Table 1.

[0084] Example 2 Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the blending amounts of styrene, 1,3-butadiene, and methacrylic acid were changed during polymer preparation so that the resulting polymer would have the composition shown in Table 1, and the concentration of the block copolymer added during phase inversion emulsification was changed so that the resulting polymer would have the particle size shown in Table 1. The results are shown in Table 1.

[0085] Examples 3 and 4 During the preparation of the polymer, the amounts of styrene and 1,3-butadiene added were changed so that the resulting polymer would have the composition shown in Table 1, and further, the concentration of the block copolymer added during phase inversion emulsification was changed so that a polymer with the particle size and film properties shown in Table 1 was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0086] Example 5 Various operations, measurements, and evaluations were carried out in the same manner as in Example 2, except that the concentration of the block copolymer added during phase inversion emulsification in the process of preparing the polymer was changed so as to obtain a polymer with the particle size and film properties shown in Table 1. The results are shown in Table 1.

[0087] Examples 6 to 8 In preparing the polymer, isoprene was used instead of 1,3-butadiene as the conjugated diene monomer. The amounts of styrene and isoprene added were changed so that the resulting polymer had the composition shown in Table 1. Furthermore, the concentration of the block copolymer added during phase inversion emulsification was changed so that a polymer with the particle size and film properties shown in Table 1 was obtained. Except for these changes, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0088] Example 9 During the preparation of the polymer, the amounts of styrene, 1,3-butadiene, and methacrylic acid were changed so that the resulting polymer had the composition shown in Table 1, and further, the concentration of the block copolymer added during phase inversion emulsification was changed so that a polymer having the particle size and film properties shown in Table 1 was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0089] Example 10 Various operations, measurements, and evaluations were carried out in the same manner as in Example 2, except that the concentration of the block copolymer added during phase inversion emulsification in the process of preparing the polymer was changed so as to obtain a polymer with the particle size and film properties shown in Table 1. The results are shown in Table 1.

[0090] Example 11 Except for using acrylic acid instead of methacrylic acid as the hydrophilic monomer during the preparation of the polymer, various operations, measurements, and evaluations were carried out in the same manner as in Example 2. The results are shown in Table 1.

[0091] Example 12 Various operations, measurements, and evaluations were performed in the same manner as in Example 1, except that a negative electrode slurry composition was prepared using a random copolymer prepared as follows as the polymer in addition to the block copolymer prepared in Example 1. The results are shown in Table 1. The mixing ratio of the block copolymer and the random copolymer when preparing the negative electrode slurry composition was 50:50 by mass. The copolymer composition, median diameter, and film properties shown in Table 1 are for the mixture of the block copolymer and the random copolymer. <Preparation of random copolymer> Addition of a mixture of 62 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 34 parts of styrene as an aromatic vinyl monomer, 4 parts of methacrylic acid as a hydrophilic monomer, 0.3 parts of tert-dodecyl mercaptan as a chain transfer agent, 0.3 parts of sodium lauryl sulfate as an emulsifier, and 150 parts of ion-exchanged water from vessel A to pressure vessel B was started, and at the same time, addition of 1 part of potassium persulfate as a polymerization initiator to pressure vessel B was started to initiate polymerization. The reaction temperature was maintained at 75°C. Five hours and 30 minutes after the start of polymerization, the mixture was further heated to 85°C and reacted for 6 hours. When the polymerization conversion rate reached 97%, the mixture was cooled to stop the reaction and obtain a mixture containing particulate random polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture containing particulate random polymer to adjust the pH to 8. Unreacted monomers were then removed by heating and vacuum distillation. The mixture was then cooled to obtain an aqueous dispersion (solid concentration: 40%) containing the random polymer.

[0092] Example 13 Except for using an aqueous sodium hydroxide solution for neutralization in the grafting step in preparing the polymer, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0093] Example 14 Except for preparing a negative electrode slurry composition using only the random polymer prepared in Example 12 as the polymer, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0094] (Comparative Example 1) During the preparation of the polymer, the amounts of styrene, 1,3-butadiene, and methacrylic acid were changed so that the resulting polymer would satisfy the composition, median diameter, and film properties shown in Table 1, and further, the concentration of the block copolymer added during phase inversion emulsification was changed so that the resulting polymer would have the particle diameter shown in Table 1. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0095] (Comparative Example 2) In preparing the polymer, itaconic acid was used instead of methacrylic acid as the hydrophilic monomer, the amounts of the various monomers were changed so that the resulting polymer would satisfy the composition, median diameter, and film properties shown in Table 1, and further, aqueous sodium hydroxide solution was used for neutralization in the grafting step in preparing the polymer. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0096] (Comparative Example 3) In preparing the polymer, acrylic acid was used instead of methacrylic acid as the hydrophilic monomer, the amounts of the various monomers were changed so that the resulting polymer would satisfy the composition, median diameter, and film properties shown in Table 1, and further, aqueous sodium hydroxide solution was used for neutralization in the grafting step in preparing the polymer. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0097] (Comparative Examples 4 to 5) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the blending ratio of the monomers blended during the preparation of the polymer was changed so that the resulting polymer satisfied the composition shown in Table 1. The results are shown in Table 1.

[0098] (Comparative Example 6) Various operations, measurements, and evaluations were carried out in the same manner as in Example 2, except that the concentration of the block copolymer added during phase inversion emulsification in the process of preparing the polymer was changed so as to obtain a polymer with the particle size and film properties shown in Table 1. The results are shown in Table 1.

[0099] In Table 1, "St" represents the styrene monomer unit, "BD" stands for 1,3-butadiene monomer unit, "MAA" stands for methacrylic acid monomer unit, "AA" stands for acrylic acid monomer unit, "IA" represents the itaconic acid monomer unit, "THF" stands for tetrahydrofuran, Each is shown.

[0100] [Table 1]

[0101] Table 1 shows that in Examples 1 to 14, binder compositions for non-aqueous secondary battery electrodes having excellent static stability were provided, which were capable of forming electrodes having excellent peel strength after exposure to high temperatures and non-aqueous secondary batteries having low internal resistance. Furthermore, Table 1 shows that in Comparative Examples 1 to 3, in which the values ​​of loss modulus G" and loss tangent tanδ were outside the ranges of the present invention, it was not possible to sufficiently increase the high-temperature peel strength of the resulting electrode and to sufficiently reduce the internal resistance of the resulting secondary battery. Furthermore, Table 1 shows that even in Comparative Examples 4 and 5, which used binder compositions containing polymers with hydrophilic monomer unit content ratios outside the range of the present invention, it was not possible to simultaneously sufficiently increase the high-temperature peel strength of the resulting electrode, sufficiently reduce the internal resistance of the resulting secondary battery, and increase the static stability of the binder composition itself. Furthermore, in Comparative Example 6, which used a binder composition containing a polymer with a median diameter exceeding the range of the present invention, the high-temperature peel strength of the resulting electrode could not be sufficiently increased, and the static stability of the binder composition itself was poor. In all Examples and Comparative Examples 2 and 3, the evaluation results for pressability were "good" for "adhesion of electrode mixture layer after pressing" and "rate of change in density of electrode after pressing." On the other hand, in Comparative Examples 1 and 4 to 6, the evaluation results for pressability were not good when evaluated according to the above criteria. That is, from these evaluation results, it is clear that a binder composition for a non-aqueous secondary battery electrode containing a polymer containing aromatic vinyl monomer units, conjugated diene monomer units, and hydrophilic monomer units, and water, wherein the median diameter of the polymer is 50 nm or more and 800 nm or less, the content of the hydrophilic monomer units in the polymer is 3.7 mass % or more and 20 mass % or less, and the polymer has a loss tangent tanδ value of 0.001 or more and 0.80 or less, and a loss modulus G" value of 1800 kPa or less, can be used to obtain a non-aqueous secondary battery electrode binder composition having excellent pressability. [Industrial Applicability]

[0102] According to the present invention, it is possible to provide a binder composition for a non-aqueous secondary battery electrode that has excellent static stability and is capable of forming an electrode that has excellent peel strength after exposure to high temperatures and a non-aqueous secondary battery that has low internal resistance. Furthermore, according to the present invention, it is possible to provide a slurry composition for a non-aqueous secondary battery electrode, which is capable of forming an electrode that has excellent peel strength after exposure to high temperatures and a non-aqueous secondary battery that has low internal resistance. Furthermore, according to the present invention, it is possible to provide an electrode for a non-aqueous secondary battery that has excellent peel strength after exposure to high temperatures and is capable of forming a secondary battery with low internal resistance, as well as a non-aqueous secondary battery with low internal resistance.

Claims

1. A binder composition for a non-aqueous secondary battery electrode, comprising: a polymer including an aromatic vinyl monomer unit, a conjugated diene monomer unit, and a hydrophilic monomer unit; and water, the polymer has a median diameter of 50 nm or more and 800 nm or less; The content of the hydrophilic monomer unit in the polymer is 4.0% by mass or more and 20% by mass or less, and The polymer has a loss tangent tanδ of 0.001 or more and less than 0.40, and a loss modulus G″ of 1600 kPa or less. A binder composition for non-aqueous secondary battery electrodes.

2. 2. The binder composition for a non-aqueous secondary battery electrode according to claim 1, wherein the conjugated diene monomer units contained in the polymer are units derived from a 1,3-butadiene monomer.

3. 3. The binder composition for a non-aqueous secondary battery electrode according to claim 1, wherein the polymer has a gel content of 35% by mass or more and 60% by mass or less when measured by immersing the polymer in tetrahydrofuran.

4. 4. The binder composition for a non-aqueous secondary battery electrode according to claim 1, wherein the polymer contains an aromatic vinyl block region composed of an aromatic vinyl monomer unit.

5. A slurry composition for a non-aqueous secondary battery electrode, comprising an electrode active material and the binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 4.

6. A non-aqueous secondary battery electrode comprising an electrode mixture layer formed using the slurry composition for a non-aqueous secondary battery electrode according to claim 5 .

7. A positive electrode, a negative electrode, a separator, and an electrolyte solution are included. A non-aqueous secondary battery, wherein at least one of the positive electrode and the negative electrode is the electrode for a non-aqueous secondary battery according to claim 6 .

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