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

This binder composition contains a particulate polymer having a graft portion and a stem portion formed of a block copolymer containing an aromatic vinyl monomer unit and an aliphatic conjugated diene monomer unit. The weight average molecular weight of an aromatic vinyl block region contained in the block copolymer is at least 15,000, the weight average molecular weight of the block copolymer is 150,000-500,000, and the ratio of the graft portion to 100% by mass of the block copolymer is 1.0-10.0% by mass.

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] An electrode for a secondary battery such as a lithium-ion secondary battery typically includes a current collector and an electrode mixture layer formed on the current collector. The electrode mixture layer is formed, for example, by applying a slurry composition, which is obtained by dispersing an electrode active material and a binder composition containing a binder in a dispersion medium (solvent), onto the current collector and then drying the slurry composition.

[0004] As a binder contained in a binder composition, a particulate polymer composed of a copolymer having an aromatic vinyl block region and a region containing an aliphatic conjugated diene monomer unit has conventionally been used. For example, Patent Document 1 discloses a binder composition for a non-aqueous secondary battery electrode, which comprises a particulate polymer A and a particulate polymer B, wherein the particulate polymer A is a copolymer having an aromatic vinyl block region and a region containing an aliphatic conjugated diene monomer unit, and the particulate polymer B is a random copolymer containing an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit. Furthermore, Patent Document 2 discloses a binder composition for a non-aqueous secondary battery, which comprises a particulate polymer composed of a polymer having an aromatic vinyl block region and a region containing an aliphatic conjugated diene monomer unit, and water, wherein the surface acidity of the particulate polymer is within a predetermined range. Furthermore, for example, Patent Document 3 discloses a binder composition for non-aqueous secondary battery electrodes, which contains a particulate polymer consisting of a graft polymer having hydrophilic graft chains, obtained by graft polymerization of a total of 1 part by mass to 40 parts by mass of hydrophilic monomers and / or macromonomers to 100 parts by mass of core particles containing a block copolymer having an aromatic vinyl block region and an isoprene block region, with the isoprene block region content being 70% by mass to 99% by mass, and a hindered phenol-based antioxidant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 168420 [Patent Document 2] International Publication No. 2019 / 107229 [Patent Document 3] International Publication No. 2019 / 172281 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, an electrode having an electrode mixture layer may be dried while being heated at a high temperature of, for example, 100°C (hereinafter, sometimes referred to as "heat drying") in order to thoroughly remove moisture before being used in assembling a secondary battery. The inventors have found that there is room for further improvement in the peel strength after heat drying of electrodes produced using the binder compositions of the above-mentioned conventional technology. Furthermore, in the manufacturing process of secondary batteries, formed electrodes are sometimes cut to a desired size. In this case, if the adhesiveness of the binder contained in the electrode is insufficient, particulate matter constituting the electrode may fall off from the electrode (hereinafter also referred to as "powder shedding"), which may cause a deterioration in battery performance under the operating environment of the battery. Therefore, battery components are required to be resistant to powder shedding, i.e., to have high resistance to powder shedding.

[0007] Therefore, an object of the present invention is to provide a binder composition for a non-aqueous secondary battery electrode that is highly resistant to powder shedding and that can form a non-aqueous secondary battery electrode that has excellent peel strength after heat drying. Another object of the present invention is to provide a slurry composition for a non-aqueous secondary battery electrode, which is capable of forming a non-aqueous secondary battery electrode that has high resistance to powder falling off and excellent peel strength after heat drying. Another object of the present invention is to provide an electrode for a non-aqueous secondary battery that has high resistance to powder falling off and excellent peel strength after heat drying. Another object of the present invention is to provide a non-aqueous secondary battery comprising the electrode for the non-aqueous secondary battery. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems, and have newly discovered that a non-aqueous secondary battery electrode binder composition containing a particulate polymer having a backbone portion composed of a block copolymer containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, and a graft portion, wherein the weight-average molecular weight of the aromatic vinyl block region constituting the block copolymer backbone, the weight-average molecular weight of the block copolymer itself, and the ratio of the graft portion to the block copolymer are all within predetermined ranges, thereby enabling the formation of a non-aqueous secondary battery electrode that is highly resistant to powder shedding and has excellent peel strength after heat drying, and have completed the present invention.

[0009] The present invention provides a binder composition for a non-aqueous secondary battery electrode, comprising a particulate polymer, the particulate polymer having a backbone portion composed of a block copolymer containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, and a graft portion, the block copolymer including an aromatic vinyl block region composed of the aromatic vinyl monomer units, the aromatic vinyl block region having a weight-average molecular weight of 15,000 or more, a weight-average molecular weight of 150,000 or more and 500,000 or less, and a proportion of the graft portion being 1.0% by mass or more and 10.0% by mass or less, based on 100% by mass of all repeating units constituting the block copolymer. The use of a binder composition containing such a specific particulate polymer allows the formation of a non-aqueous secondary battery electrode that has high resistance to powder shedding and excellent peel strength after heat drying. The term "monomer unit" of a polymer refers to "a repeating unit derived from that monomer contained in a polymer obtained using that monomer." The "weight average molecular weight" of a polymer can be measured by the method described in the Examples of this specification. The term "containing a block region consisting of a monomer unit" of a polymer means that the polymer contains a portion in which only that monomer unit is linked together. The "weight average molecular weight of the block region" or the "weight average molecular weight of the polymer" can be measured by the method described in the Examples of this specification. The proportion of the grafted portion can be measured by the method described in the Examples of this specification.

[0010] Here, in the binder composition for a non-aqueous secondary battery electrode of the present invention, it is preferable that the value obtained by the formula {G'(100)-G'(200)} / G'(200), where G'(100) is the storage modulus of the particulate polymer at 100°C and G'(200) is the storage modulus at 200°C, is 15.0 or less. If the particulate polymer satisfies the above-mentioned predetermined attribute values, the resulting non-aqueous secondary battery electrode can be further improved in terms of powder-fall resistance and peel strength after heat drying. The storage modulus of the particulate polymer at each temperature can be measured by the method described in the examples of this specification.

[0011] In addition, in the binder composition for a non-aqueous secondary battery electrode of the present invention, the proportion of the aromatic vinyl monomer units in the particulate polymer is preferably 20.0% by mass or more and 50.0% by mass or less, when the amount of all repeating units constituting the particulate polymer is taken as 100% by mass. If the proportion of the aromatic vinyl monomer units in the particulate polymer is within the above-mentioned range, the resulting non-aqueous secondary battery electrode can have further improved resistance to powder shedding and peel strength after heat drying. The ratio of the monomer units in the polymer is 1 It can be measured by H-NMR.

[0012] Furthermore, in the binder composition for a non-aqueous secondary battery electrode of the present invention, the graft moiety of the particulate polymer preferably contains a carboxylic acid group-containing monomer unit. If the graft moiety of the particulate polymer contains a carboxylic acid group-containing monomer unit, the stability of a slurry composition prepared using the binder composition can be improved.

[0013] The present invention also aims to advantageously solve the above-mentioned problems, and provides a slurry composition for a non-aqueous secondary battery electrode, characterized by comprising an electrode active material and any one of the binder compositions for a non-aqueous secondary battery electrode described above. Thus, a slurry composition comprising an electrode active material and any one of the binder compositions described above can form a non-aqueous secondary battery electrode that has high resistance to powder shedding and excellent peel strength after heat drying.

[0014] Furthermore, the present invention aims to advantageously solve the above-mentioned problems, and the electrode for a non-aqueous secondary battery of the present invention is characterized by including an electrode mixture layer formed using the above-mentioned slurry composition. The electrode including the electrode mixture layer formed using the above-mentioned slurry composition has high resistance to powder shedding and excellent peel strength after heat drying.

[0015] The present invention aims to advantageously solve the above-mentioned problems, and provides a nonaqueous secondary battery comprising the above-mentioned nonaqueous secondary battery electrode. The nonaqueous secondary battery of the present invention has excellent battery characteristics and high performance because it comprises the above-mentioned nonaqueous secondary battery electrode that has high resistance to powder falling and excellent peel strength after heat drying. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a binder composition for a non-aqueous secondary battery electrode that is capable of forming a non-aqueous secondary battery electrode that has high resistance to powder falling off and excellent peel strength after heat drying. 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 a non-aqueous secondary battery electrode that has high resistance to powder falling and excellent peel strength after heat drying. Furthermore, according to the present invention, it is possible to provide an electrode for a non-aqueous secondary battery that has high resistance to powder falling off and excellent peel strength after heat drying. Furthermore, according to the present invention, it is possible to provide a non-aqueous secondary battery including the electrode for a non-aqueous secondary battery. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a graph in which electrical conductivity is plotted against the cumulative amount of hydrochloric acid added in calculating the amount of surface acid on a particulate polymer. 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 is used in the manufacture of a non-aqueous secondary battery, and can be used, for example, 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 of the present invention can be used to form an electrode for a non-aqueous secondary battery, and is particularly suitable for use in forming a negative electrode of a non-aqueous secondary battery. The electrode for a non-aqueous secondary battery of the present invention is formed from the slurry composition for a non-aqueous secondary battery electrode of the present invention. The non-aqueous secondary battery of the present invention includes the electrode for a non-aqueous secondary battery of the present invention.

[0019] (Binder composition for non-aqueous secondary battery electrodes) The binder composition of the present invention contains a particulate polymer and, optionally, further contains other components that can be incorporated into secondary battery electrodes. The non-aqueous binder composition for secondary battery electrodes of the present invention can further contain a solvent such as water. The binder composition of the present invention is characterized by containing a particulate polymer having a backbone portion composed of a block copolymer containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, and a graft portion. More specifically, the particulate polymer is characterized by the aromatic vinyl block region contained in the block copolymer having a weight-average molecular weight of 15,000 or more, the weight-average molecular weight of the block copolymer being 150,000 or more and 500,000 or less, and the proportion of the graft portion relative to 100% by mass of the block copolymer being 1.0% by mass or more and 10.0% by mass or less.

[0020] Since the particulate polymer satisfying the above-mentioned predetermined conditions can exhibit high heat resistance, the particulate polymer can exhibit sufficiently high adhesive ability even after heat drying. Therefore, an electrode formed using a slurry composition containing the particulate polymer has excellent peel strength and powder shedding resistance even after heat drying.

[0021] In this specification, "heat drying" also includes heat drying performed in a vacuum state (under reduced pressure) (hereinafter, this may be referred to as "heat vacuum drying"). Electrodes formed using the binder composition of the present invention also have excellent peel strength after being vacuum dried while being heated at a high temperature of, for example, 100°C (i.e., peel strength after heat vacuum drying).

[0022] <Particulate polymer> The particulate 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 prevents components such as the electrode active material from detaching from the electrode mixture layer and enables adhesion between the electrode and the separator via the electrode mixture layer. Here, the particulate polymer is a water-insoluble particle. In the present invention, the particles being "water-insoluble" means that when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25°C, the insoluble content is 90 mass% or more.

[0023] <<Structure and composition>> The particulate polymer has a trunk portion consisting of a block copolymer containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, and a graft portion. More specifically, the particulate polymer is a graft copolymer having a structure in which a graft portion is bonded to a trunk portion consisting of a block copolymer having a block region consisting of aromatic vinyl monomer units (hereinafter sometimes abbreviated as "aromatic vinyl block region") and a block region consisting of aliphatic conjugated diene monomer units (hereinafter sometimes abbreviated as "aliphatic conjugated diene block region"). Here, the aromatic vinyl block region consists only of aromatic vinyl monomer units. The aliphatic conjugated diene block region preferably consists only of aliphatic conjugated diene monomer units, but may also contain alkylene structural units in addition to the aliphatic conjugated diene monomer units. The block copolymer, which is the trunk portion, may have other repeating units in addition to the aromatic vinyl monomer unit, the aliphatic conjugated diene monomer unit and the alkylene structural unit.

[0024] In the block copolymer serving as the trunk portion, the aromatic vinyl block region and the aliphatic conjugated diene block region are adjacent to each other. The copolymer serving as the trunk portion may have one or more aromatic vinyl block regions. Similarly, the block copolymer serving as the trunk portion may have one or more aliphatic conjugated diene block regions. Furthermore, the block copolymer serving as the trunk portion may have regions other than the aromatic vinyl block region and the aliphatic conjugated diene block region. Furthermore, a particulate polymer having a trunk portion composed of a block copolymer having an aromatic vinyl block region and an aliphatic conjugated diene block region has both rigidity and flexibility, and therefore can impart high resistance to powder shedding and excellent peel strength after heat drying to an electrode formed using the binder composition.

[0025] [Aromatic vinyl block region] As described above, the aromatic vinyl block region is a region that essentially contains 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 site (i.e., the aromatic vinyl monomer units constituting one aromatic vinyl block region may be connected via a coupling site). When the block copolymer serving as the trunk portion has a plurality of aromatic vinyl block regions, the types and proportions of the aromatic vinyl monomer units constituting the plurality of aromatic vinyl block regions may be the same or different, but are preferably the same.

[0026] Examples of aromatic vinyl monomers that can form the aromatic vinyl monomer units that constitute the aromatic vinyl block region of the block copolymer, which is the backbone portion, include styrene, styrene sulfonic acid and its salts, α-methylstyrene, pt-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. Among these, styrene is preferred. These can be used alone or in combination of two or more, but it is preferable to use one alone. Among these, styrene is preferred.

[0027] The proportion of aromatic vinyl monomer units in the particulate polymer is preferably 20.0% by mass or more, more preferably 25.0% by mass or more, and preferably 50.0% by mass or less, more preferably 40.0% by mass or less, and even more preferably 35.0% by mass or less, when the amount of all repeating units constituting the particulate polymer (the total of repeating units of the trunk portion and graft portion possessed by the particulate polymer) is taken as 100% by mass. The proportion of aromatic vinyl monomer units in the particulate polymer usually coincides with the proportion of aromatic vinyl block regions in the particulate polymer.

[0028] When the proportion of aromatic vinyl monomer units in the particulate polymer is within the above-mentioned specified range, the rigidity of the electrode mixture layer formed using the binder composition can be appropriately improved, and the peel strength of the electrode after heat drying can be further increased.

[0029] The weight-average molecular weight of the aromatic vinyl block region is preferably 15,000 or more, more preferably 25,000 or more, and even more preferably 27,000 or more, and is preferably 60,000 or less, and more preferably 40,000 or less. When the weight-average molecular weight of the aromatic vinyl block region is equal to or greater than the above-mentioned lower limit, the peel strength of an electrode formed using the binder composition after heat drying can be further increased. On the other hand, when the weight-average molecular weight of the aromatic vinyl block region is equal to or less than the above-mentioned upper limit, the rigidity of an electrode mixture layer formed using the binder composition can be appropriately improved, and the peel strength of an electrode formed using the binder composition after heat drying can be further increased.

[0030] [Aliphatic conjugated diene block region] As described above, the aliphatic conjugated diene block region is a region that essentially contains an aliphatic conjugated diene monomer unit as a repeating unit. Here, one aliphatic conjugated diene block region can be composed of one or more types of aliphatic conjugated diene monomer units. Furthermore, one aliphatic conjugated diene block region may contain a coupling site (i.e., the aliphatic conjugated diene monomer units constituting one aliphatic conjugated diene block region may be connected via a coupling site). When the block copolymer that is the trunk portion has a plurality of aliphatic conjugated diene block regions, the types and proportions of the aliphatic conjugated diene monomer units that constitute the plurality of aliphatic conjugated diene block regions may be the same or different.

[0031] Examples of the aliphatic conjugated diene monomer units constituting the aliphatic conjugated diene block region of the block copolymer, which is the trunk portion, 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. These can be used alone or in combination of two or more. Among these, 1,3-butadiene and isoprene are preferred, with 1,3-butadiene being particularly preferred, from the viewpoint of further increasing the peel strength of the electrode after heat drying.

[0032] Here, the aliphatic conjugated diene monomer units constituting the aliphatic conjugated diene block region of the block copolymer, which is the trunk portion, may be crosslinked. That is, the aliphatic conjugated diene monomer units constituting the aliphatic conjugated diene block region may contain structural units formed by crosslinking an aliphatic conjugated diene. If the aliphatic conjugated diene block region contains structural units formed by crosslinking an aliphatic conjugated diene, the electrolyte injectability of an electrode formed using the binder composition can be improved.

[0033] The structural unit formed by crosslinking the aliphatic conjugated diene monomer unit can be introduced by crosslinking the block copolymer that is the backbone portion. The crosslinking can be carried out using a radical initiator, such as a redox initiator comprising a combination of an oxidizing agent and a reducing agent, without any particular limitation. Examples of the oxidizing agent include organic peroxides such as diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, isobutyryl peroxide, and benzoyl peroxide. Examples of the reducing agent include compounds containing reduced metal ions, such as ferrous sulfate and cuprous naphthenate; sulfonic acid compounds, such as sodium methanesulfonate; and amine compounds, such as dimethylaniline. These organic peroxides and reducing agents can be used alone or in combination. Optionally, the crosslinking reaction can be carried out in the presence of a crosslinking ligand. Examples of the crosslinking ligand include, without any particular limitation, 3-mercapto-1,2-propanediol, for example. The crosslinking may be carried out in the presence of a crosslinking agent such as a polyvinyl compound such as divinylbenzene, a polyallyl compound such as diallyl phthalate, triallyl trimellitate, or diethylene glycol bisallyl carbonate, or various glycols such as ethylene glycol diacrylate. Alternatively, the crosslinking may be carried out by irradiation with active energy rays such as gamma rays.

[0034] The proportion of the aliphatic conjugated diene monomer units in the particulate polymer is preferably 50.0% by mass or more, more preferably 55.0% by mass or more, even more preferably 60.0% by mass or more, and preferably 80.0% by mass or less, and more preferably 75.0% by mass or less, when the amount of all repeating units in the particulate polymer (the sum of repeating units in the trunk portion and graft portion of the particulate polymer) is taken as 100% by mass. If the proportion of the aliphatic conjugated diene monomer units in the particulate polymer is within the above-mentioned predetermined range, the flexibility of the electrode mixture layer formed using the binder composition can be appropriately improved, and the peel strength of the electrode after heat drying can be further increased. Note that the "aliphatic conjugated diene monomer units" in the above also include structural units formed by crosslinking aliphatic conjugated dienes.

[0035] The aliphatic conjugated diene block region may also contain 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, and preferably has 4 or more carbon atoms (i.e., n in the above general formula is an integer of 4 or more).

[0036] The method for introducing alkylene structural units into the aliphatic conjugated diene block region is not particularly limited, and examples thereof include a method in which a polymer containing an aliphatic conjugated diene block region is hydrogenated to convert the aliphatic conjugated diene monomer units contained in the aliphatic conjugated diene block region into alkylene structural units.

[0037] [Weight average molecular weight of block copolymer] The weight-average molecular weight of the block copolymer that is the backbone portion must be 150,000 or more, preferably 180,000 or more, and must be 500,000 or less, preferably 400,000 or less, more preferably 300,000 or less, and even more preferably 250,000 or less. If the weight-average molecular weight of the block copolymer that is the backbone portion is within the above range, the resulting electrode can have improved resistance to powder shedding and peel strength after heat drying.

[0038] Furthermore, it is preferable that the weight average molecular weight of the block copolymer and the weight average molecular weight of the aromatic vinyl block region satisfy the following relationship: 0.140≦(weight average molecular weight of aromatic vinyl block region / weight average molecular weight of block copolymer)≦0.220 Furthermore, it is more preferable that the value of (weight average molecular weight of the aromatic vinyl block region / weight average molecular weight of the block copolymer) is 0.200 or less. When the weight-average molecular weight of the block copolymer and the weight-average molecular weight of the aromatic vinyl block region satisfy the above-described relationship, the resulting electrode for a nonaqueous secondary battery can have further improved resistance to powder falling and peel strength after heat drying.

[0039] [Graft part] The particulate polymer has a graft portion bonded to a trunk portion consisting of a block copolymer containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units. More specifically, the particulate polymer has a structure in which a polymer to be the graft portion is bonded to the aliphatic conjugated diene block region of the trunk portion consisting of the block copolymer having the above-mentioned aromatic vinyl block region and aliphatic conjugated diene block region. Examples of the repeating units contained in the graft portion of the particulate polymer include acidic group-containing monomer units, (meth)acrylic acid ester monomer units, and nitrile group-containing monomer units such as acrylonitrile units and methacrylonitrile units.

[0040] Examples of acidic group-containing monomers that can form acidic group-containing monomer units include monomers having an acidic group, such as monomers having a carboxylic acid group, monomers having a sulfonic acid group, and monomers having a phosphoric acid group. Examples of the monomer having a carboxylic acid group 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 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, and dimethyl maleic anhydride. As the monomer having a carboxylic acid group, an acid anhydride that generates a carboxylic acid group upon hydrolysis can also be used. Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid. Furthermore, examples of the monomer having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. In the present invention, "(meth)allyl" means allyl and / or methallyl, and "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0041] Examples of (meth)acrylic acid ester monomers that can form (meth)acrylic acid ester monomer units include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate. alkyl methacrylates; and alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate.

[0042] Here, the above-mentioned various monomers that can be used to form the repeating unit contained in the graft portion of the particulate polymer may be used alone or in combination of two or more.From the viewpoint of further improving the stability of the slurry composition prepared using the binder composition, it is preferable to use an acidic group-containing monomer as the monomer used to form the repeating unit contained in the graft portion of the particulate polymer, more preferably to use a carboxylic acid group-containing monomer, more preferably to use methacrylic acid, itaconic acid, and acrylic acid, and particularly preferably to use methacrylic acid.

[0043] The method for introducing the graft moiety into the block copolymer serving as the trunk portion is not particularly limited. For example, the above-mentioned predetermined block copolymer is prepared, and the block copolymer is used as the trunk portion, and the above-mentioned acidic group-containing monomer or the like is graft polymerized using a known method, thereby obtaining a graft copolymer having a structure in which the polymer of the graft moiety is bonded to the aliphatic conjugated diene monomer unit of the block copolymer serving as the trunk portion.

[0044] The proportion of the monomer units constituting the graft portion in the particulate polymer must be 1% by mass or more, preferably 1.5% by mass or more, and must be 10% by mass or less, preferably 5.0% by mass or less, when the amount of all repeating units constituting the trunk portion consisting of the block copolymer of the particulate polymer is taken as 100% by mass. If the proportion of the monomer units constituting the graft portion is within the above range, the powder shedding resistance and peel strength after heat drying of an electrode formed using the binder composition can be improved. In particular, if the proportion of the monomer units constituting the graft portion is equal to or greater than the above lower limit, the stability of a slurry composition containing the binder composition can be improved.

[0045] <<Volume average particle size>> The volume average particle diameter of the particulate polymer is preferably 0.10 μm or more, more preferably 0.18 μm or more, even more preferably 0.25 μm or more, and preferably 2.00 μm or less, more preferably 1.20 μm or less, and even more preferably 0.80 μm or less. By setting the volume average particle diameter of the particulate polymer to the above-mentioned lower limit or more, the electrolyte injectability of an electrode formed using a slurry composition containing the binder composition can be improved. Furthermore, by setting the volume average particle diameter of the particulate polymer to the above-mentioned upper limit or less, the specific surface area of ​​the particulate polymer is increased, improving the adhesive ability that can be achieved by the particulate polymer. As a result, the powder shedding resistance of an electrode formed using the binder composition and the peel strength after heat drying can be further improved.

[0046] <<Storage modulus of particulate polymers>> The particulate polymer preferably has storage modulus values ​​measured at 100°C and 200°C that satisfy the following relationship: {G'(100)-G'(200)} / G'(200)≦15.0 (Here, G'(100) is the storage modulus value of the particulate polymer at 100°C, and G'(200) is the storage modulus value at 200°C.)

[0047] Furthermore, the value of {G'(100)-G'(200)} / G'(200) is preferably 1.0 or more, more preferably 1.6 or more, more preferably 10.0 or less, and even more preferably 8.0 or less. When the storage modulus values ​​of the particulate polymer measured at 100°C and 200°C satisfy the above relationship, the resulting nonaqueous secondary battery electrode can have further improved resistance to powder falling and peel strength after heat drying.

[0048] The reason for this is not clear, but is presumed to be as follows. In polymers that have been used as conventional binder components, the storage modulus value has a tendency to decrease with increasing temperature. In this case, the higher the rate of decrease in storage modulus with increasing temperature, in other words, the lower the storage modulus value measured under higher temperature conditions is compared to the storage modulus value measured under lower temperature conditions, the lower the heat resistance of the polymer. Therefore, in the present invention, a particulate polymer whose composition and structure are designed so that the storage modulus values ​​measured at 100°C and 200°C satisfy the above-mentioned relationship is used, and it is believed that a new particulate polymer with significantly excellent heat resistance has been created.

[0049] The storage modulus of the particulate polymer can be controlled by appropriately designing the composition and structure of the particulate polymer. More specifically, in the particulate polymer, the weight-average molecular weight of the aromatic vinyl block region is made to be appropriately long, the weight-average molecular weight of the block copolymer is set to be within an appropriate range, and the ratio of the graft portion to the whole block copolymer is controlled to be within an appropriate range, so that the value of the storage modulus of the particulate polymer can be controlled within a suitable range.

[0050] Furthermore, the value of G'(200), which is the storage modulus of the particulate polymer at 200°C, is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and even more preferably 1.0 MPa or less. Furthermore, the value of G'(100), which is the storage modulus of the particulate polymer at 100°C, is preferably 0.4 MPa or more, more preferably 0.8 MPa or more, and even more preferably 1.0 MPa or less. If the storage modulus value satisfies the above range, the powder-fall resistance and peel strength after heat drying of the obtained nonaqueous secondary battery electrode can be further improved.

[0051] <<Method for preparing particulate polymer>> The above-mentioned particulate polymer can be prepared, for example, through the following steps: a step of block polymerizing monomers such as the above-mentioned aromatic vinyl monomer and aliphatic conjugated diene monomer in an organic solvent to obtain a solution of the block copolymer, which is the trunk portion (block copolymer solution preparation step); a step of adding water to the obtained block copolymer solution to emulsify the block copolymer, thereby forming the block copolymer into particles (emulsification step); and a step of graft polymerizing the particulate block copolymer to obtain an aqueous dispersion of the particulate polymer in which the graft portion is bonded to the block copolymer, which is the trunk portion (grafting step). In addition, in the preparation of the particulate polymer, the grafting step may be carried out before the emulsification step. That is, the particulate polymer may be prepared by carrying out a step (grafting step) of grafting the block copolymer contained in the obtained block copolymer solution after the block copolymer solution preparation step to obtain a solution of a polymer in which the graft moiety is bonded to the block copolymer as the trunk part, and then carrying out a step (emulsification step) of adding water to the polymer solution to emulsify the predetermined polymer to form particles and obtain an aqueous dispersion of the particulate polymer. The preparation of the particulate polymer may include other steps in addition to the above-mentioned block copolymer solution preparation step, emulsification step, and grafting step.

[0052] [Block copolymer solution preparation process] The method of block copolymerization 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, the block copolymer obtained by the block copolymerization as described above is preferably subjected to a coupling reaction using a coupling agent prior to the emulsification step described below. By carrying out the coupling reaction, for example, the ends of the diblock structures contained in the block copolymer can be bonded with the coupling agent to convert them into a triblock structure (i.e., the amount of the diblock structure can be reduced).

[0053] 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.

[0054] 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.

[0055] The block copolymer solution obtained after the above-described block polymerization and the optional coupling reaction may be subjected to the emulsification step described below as it is, or, if necessary, the block copolymer may be subjected to the above-described hydrogenation and then subjected to the emulsification step.

[0056] [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 include batch-type emulsifying dispersers such as "Homogenizer" (manufactured by IKA Corporation), "Polytron" (manufactured by Kinematica), 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 Mill" (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.), "Cavitron" (manufactured by Eurotech), and "Milder" (manufactured by Tokushu Kika Kogyo Co., Ltd.). Examples of suitable emulsifying and dispersing machines include continuous emulsifying and dispersing machines such as "Microfluidizer" (manufactured by Mizuho Kogyo Co., Ltd.), "Nanomizer" (manufactured by Nanomizer Co., Ltd.), "APV Gaulin" (manufactured by Gaulin Co., Ltd.), and "LAB1000" (manufactured by SPXFLOW Co., Ltd.), high-pressure emulsifying and dispersing machines such as "Microfluidizer" (manufactured by Reika Kogyo Co., Ltd.), membrane emulsifying and dispersing machines such as "Membrane Emulsifier" (manufactured by Reika Kogyo Co., Ltd.), vibration emulsifying and dispersing machines such as "Vibromixer" (manufactured by Reika Kogyo Co., Ltd.), and ultrasonic emulsifying and dispersing machines such as "Ultrasonic Homogenizer" (manufactured by Branson). The conditions for the emulsification operation using an 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 the phase inversion emulsification by a known method, thereby obtaining an aqueous dispersion of the particulate block copolymer.

[0057] [Grafting process] The method of graft polymerization in the grafting step is not particularly limited, but a preferred method is, for example, to simultaneously proceed with graft polymerization and crosslinking of the block copolymer using a radical initiator such as a redox initiator in the presence of a monomer to be graft polymerized. As the radical initiator, the redox initiators described above as radical initiators that can be used to introduce structural units formed by crosslinking aliphatic conjugated diene monomer units in the section "Structure and Composition" can be used. Here, the reaction conditions can be adjusted depending on the composition of the block copolymer, the desired amount of surface acid, and the like. In the grafting step, an aqueous dispersion of a particulate polymer having a trunk portion consisting of a block copolymer containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units and a graft portion can be obtained. Note that, when the grafting step is performed after the emulsification step, i.e., when graft polymerization is performed on the particulate block copolymer, the monomer units introduced by graft polymerization, such as the acidic group-containing monomer units, are present in greater amounts on the surface side than in the center of the particulate polymer, and are unevenly distributed in the surface layer portion.

[0058] [Other processes] The preparation of the particulate polymer may include steps other than the above-mentioned block copolymer solution preparation step, emulsification step, and grafting step. The preparation of the particulate polymer may further include a purification step of purifying the aqueous dispersion of the particulate polymer.

[0059] <Solvent> The binder composition of the present invention may further contain a solvent such as water. Examples of the solvent include water, an aqueous solution containing water, and a mixed solution of water and a small amount of an organic solvent. Among these, water is preferred as the solvent.

[0060] <Other ingredients> The binder composition of the present invention may contain components other than the above-mentioned components (other components). For example, the binder composition may contain a known particulate binder (e.g., styrene-butadiene random copolymer, acrylic polymer, etc.) other than the above-mentioned particulate polymer. The binder composition may further contain known additives. Examples of such known additives include antiaging agents, antioxidants, antifoaming agents, dispersants, etc. The antiaging agents are not particularly limited, and examples thereof include reaction products of p-cresol, cyclopentadiene, and isobutylene. The antioxidants are not particularly limited, and examples thereof include hindered phenol-based antioxidants such as 4-[[4,6-bis(octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-tert-butylphenol; phosphite-based antioxidants such as 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane; and the like. The other components may be used singly or in combination of two or more in any ratio.

[0061] <Method for preparing binder composition> The binder composition of the present invention is not particularly limited, and can be prepared by mixing the particulate polymer and other components that are optionally used in the presence of a solvent such as water. When the binder composition is prepared using a dispersion of the particulate polymer, the liquid contained in the dispersion may be used as it is as a solvent for the binder composition.

[0062] (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 includes the binder composition described above and further contains an electrode active material. That is, the slurry composition of the present invention contains the particulate polymer, electrode active material, and solvent described above, and optionally further contains other components. Furthermore, by using the slurry composition of the present invention, it is possible to form an electrode that has excellent resistance to powder shedding and peel strength after heat drying. Furthermore, by using an electrode that has excellent resistance to powder shedding and peel strength after heat drying in a secondary battery, the secondary battery can exhibit excellent battery characteristics.

[0063] <Binder composition> As the binder composition, the binder composition of the present invention containing the above-mentioned particulate polymer is used. The amount of the binder composition in the slurry composition is not particularly limited, and may be, for example, 0.5 to 15 parts by mass, in terms of solid content, per 100 parts by mass of the electrode active material.

[0064] <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.

[0065] [Cathode active material] The positive electrode active material to be blended in the positive electrode composite layer of the positive electrode of the lithium ion secondary battery can be, for example, a compound containing a transition metal, such as a transition metal oxide, a transition metal sulfide, or a composite metal oxide of lithium and a transition metal, etc. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo. Specifically, the cathode active material is not particularly limited, and includes lithium-containing cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium-containing nickel oxide (LiNiO2), 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), and lithium-excess spinel compounds represented by Li 1+x Mn 2-x O4 (0 < X < 2), 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 cathode active material may be used alone or in combination of two or more.

[0066] [Anode active material] Examples of the anode active material blended in the anode composite layer of the anode of the lithium-ion secondary battery include carbon-based anode active materials, metal-based anode active materials, and anode active materials combining these. Here, the carbon-based anode active material refers to an active material having carbon as the main skeleton into which lithium can be inserted (also referred to as "doped"). Specifically, examples of the carbon-based anode active material include carbonaceous materials such as coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, pyrolytic vapor-grown carbon fibers, phenolic resin fired bodies, polyacrylonitrile-based carbon fibers, isotropic carbon, furfuryl alcohol resin fired bodies (PFA), and hard carbon, as well as graphite 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.

[0067] <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.

[0068] <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 an aqueous medium. The solvent such as water used in preparing the slurry composition also includes the solvent contained in the binder composition. The mixing method is not particularly limited, and mixing can be performed using a commonly used stirrer or disperser.

[0069] (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 particulate polymer, and optionally 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 particulate polymer exists in particulate form in the slurry composition, but may be in particulate form or any other shape in the electrode mixture layer formed using the slurry composition. The nonaqueous secondary battery electrode of the present invention has an electrode mixture layer formed using the above-mentioned slurry composition for a nonaqueous secondary battery electrode, and therefore has excellent resistance to powder falling off and peel strength after heat drying. Furthermore, the nonaqueous secondary battery electrode of the present invention also has excellent peel strength after heat vacuum drying. By using an electrode with excellent resistance to powder falling off and peel strength after heat drying in a secondary battery, the secondary battery can exhibit excellent battery characteristics.

[0070] <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).

[0071] [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.

[0072] 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.

[0073] [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.

[0074] After the drying step, the electrode mixture layer may be subjected to a pressure treatment using a mold press or a roll press. 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. The density of the electrode mixture layer after the pressure treatment can be appropriately adjusted within a range in which the desired effects of the present invention can be obtained. 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.

[0075] (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, which has excellent powder-fall resistance and peel strength after heat drying, as at least one of the positive electrode and the negative electrode, and therefore can exhibit excellent battery 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.

[0076] <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.

[0077] <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.

[0078] 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.

[0079] <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.

[0080] 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 above-described nonaqueous secondary battery electrode may be dried (heat-dried) while heated at a high temperature, for example, 100°C, to thoroughly remove moisture before use in the production of a secondary battery. Furthermore, the nonaqueous secondary battery electrode may be vacuum-dried (heat-vacuum-dried) while heated at a high temperature, for example, 100°C, to further remove moisture before use in the production of a secondary battery. The nonaqueous secondary battery of the present invention may also be provided with a fuse, an overcurrent protection element such as a PTC element, an expanded metal, a lead plate, or the like, as needed, to prevent internal pressure buildup, overcharge / discharge, 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]

[0081] 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. In the examples and comparative examples, the various attributes were measured and evaluated according to the following methods.

[0082] <Proportion of each monomer unit> The binder compositions produced in each of the examples and comparative examples were solidified with methanol, and the solidified materials were then vacuum dried at 100°C for 5 hours to prepare measurement samples. 1 The intensity of the peak derived from each monomer unit contained in the measurement sample was calculated by H-NMR. Then, based on the ratio of the peak intensity derived from each monomer unit to the total peak intensity, the ratio of each monomer unit contained in the particulate polymer was calculated.

[0083] <Weight-average molecular weight of the aromatic vinyl block region> The molecular weight of the aromatic vinyl block region was calculated from the weight-average molecular weight of the diblock copolymer contained in the particulate polymer and the proportion of aromatic vinyl monomer units in the binder composition described above. The weight-average molecular weight of the copolymer contained in the particulate polymer was measured as a polystyrene-equivalent molecular weight using a high-performance liquid chromatography (apparatus: Tosoh Corporation, model number "HLC8220"). The particulate polymers produced in each Example and Comparative Example were used as measurement samples. The particulate polymers produced in each Example and Comparative Example were coagulated with methanol, and the obtained coagulated material was vacuum-dried at a temperature of 100°C for 5 hours. The tetrahydrofuran-soluble portion of this dried material was used as the high-performance liquid chromatography measurement sample. For the measurement, three connected columns (Showa Denko K.K., model number "Shodex KF-404HQ", column temperature: 40°C, carrier: tetrahydrofuran at a flow rate of 0.35 mL / min) and a differential refractometer and an ultraviolet detector were used as detectors. The molecular weight was calibrated using 12 standard polystyrenes (manufactured by Polymer Laboratory, standard molecular weight: 500 to 3,000,000). The weight-average molecular weight of the diblock structure was determined based on the peaks attributable to the diblock structure in the chart obtained by the high-performance liquid chromatography. Two very sharp peaks with a polydispersity close to 1 were detected in the chart obtained, and the molecular weight of the higher molecular weight side of the two detected peaks was approximately twice that of the lower molecular weight side. This confirmed that the measurement sample used contained a diblock structure (styrene-butadiene) and a triblock structure (styrene-butadiene-coupling moiety-butadiene-styrene). Furthermore, the following formula: [Weight average molecular weight of aromatic vinyl block region] = [Weight average molecular weight of diblock structure] × [Proportion (%) of aromatic vinyl monomer units in particulate polymer] ÷ 100 The weight average molecular weight of the aromatic vinyl block region was calculated using the formula: In the above formula, the "proportion (%) of aromatic vinyl monomer units in the particulate polymer" was the value obtained according to the method explained in the section <Proportion of each monomer unit>. If necessary, peak components are extracted and analyzed by a combination of mass spectrometry and infrared spectroscopy, etc., to qualitatively identify the peak components. 1 Analysis by H-NMR also enables the composition ratio of the peak components to be analyzed.

[0084] <Measurement of the surface acid content of particulate polymer by conductometric titration and conversion to the content ratio of grafted portion based on the backbone portion consisting of block copolymer> The binder compositions obtained in the Examples and Comparative Examples were diluted with ion-exchanged water to a solids concentration of 3%. The pH of the adjusted sample was then adjusted to 12.0 with a 3% aqueous sodium hydroxide solution. A 1.5 g (solids equivalent) aliquot of the pH-adjusted sample was placed in a 100 mL beaker, to which 3 g of a 0.2% diluted aqueous solution of Emulgen 120 (Kao Corporation) and 1 g of a 1% diluted aqueous solution of SM5512 (Dow Corning Toray Co., Ltd.) were added. While stirring uniformly with a stirrer, a 0.1 N aqueous solution of hydrochloric acid was added at a rate of 0.5 mL / 30 seconds, and electrical conductivity was measured every 30 seconds. The obtained electrical conductivity data was plotted on a graph with electrical conductivity as the vertical axis (Y-axis) and the cumulative amount of hydrochloric acid added as the horizontal axis (X-axis). This resulted in a hydrochloric acid amount-electrical conductivity curve with three inflection points, as shown in Figure 1. The X-coordinates of the three inflection points and at the end of hydrochloric acid addition were designated P1, P2, P3, and P4, respectively, in ascending order of value. Approximation lines L1, L2, L3, and L4 were calculated by the least squares method for the data in the four X-coordinate sections: from zero to P1, from P1 to P2, from P2 to P3, and from P3 to P4. The X-coordinate of the intersection of the approximated lines L1 and L2 was designated A1, the X-coordinate of the intersection of the approximated lines L2 and L3 was designated A2, and the X-coordinate of the intersection of the approximated lines L3 and L4 was designated A3. Then, the surface acid amount of the particulate polymer (acid amount per 1 g of solid content of the binder composition) was determined by conductometric titration using the following formula (a) as a hydrochloric acid equivalent value (mmol / g). (a) Amount of surface acid of particulate polymer = (A2 - A1) / 1.5g Then, the value obtained according to the above formula and the above 1 Based on the H-NMR measurement results, the proportion (mass%) of the grafted portion was calculated based on the total repeating units constituting the block copolymer backbone, which was taken as 100 mass%, and the results are shown in Table 1.

[0085] <Dynamic viscoelastic properties> The binder compositions obtained in the examples and comparative examples were cast into petri dishes and dried at room temperature (25°C) to obtain binder films. These binder films were then vacuum dried at room temperature for 12 hours to prepare measurement samples. Measurements were performed using a viscoelasticity measuring device (manufactured by Alpha Technology, "Production RPA") at a frequency of 1 Hz, strain of 10%, and while gradually increasing the temperature from 30°C to 200°C. By the above measurement, the storage modulus value of the particulate polymer at 100°C: G'(100) and the storage modulus value of the particulate polymer at 200°C: G'(200) were measured, and the value of {G'(100)-G'(200)} / G'(200) was calculated. The results are shown in Table 1.

[0086] <Stability of Slurry Composition> In the examples and comparative examples, when preparing the slurry composition, an aliquot of the solution before adding the binder composition was taken, and the viscosity M0 (mPa s) was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TV-25") at a measurement temperature of 25°C, measuring rotor No. 4, and a rotor rotation speed of 60 rpm. Furthermore, an aliquot of the slurry composition obtained by adding the binder composition was placed in a container with a diameter of 5.5 cm and a height of 8.0 cm and stirred at 3,000 rpm for 10 minutes using a TK Homodisper (manufactured by Primix Corporation, disper diameter: 40 mm). The viscosity M1 (mPa s) of the slurry composition after stirring was measured in the same manner as the viscosity M0 of the solution before the addition of the binder composition. The viscosity change rate ΔM (= {(M1-M0) / M0} × 100%) was then calculated and evaluated according to the following criteria. The smaller the viscosity change rate ΔM, the higher the viscosity stability of the slurry composition, indicating that the slurry composition is more stable. A: Viscosity change rate ΔM is less than 10% B: Viscosity change rate ΔM is 10% or more but less than 20% C: Viscosity change rate ΔM is 20% or more but less than 50% D: Viscosity change rate ΔM is 50% or more

[0087] <Peel strength of electrode after heating and vacuum drying> The negative electrodes prepared in the Examples and Comparative Examples were cut into rectangular specimens measuring 100 mm in length and 10 mm in width to prepare test specimens. These specimens were placed in a rectangular vacuum constant temperature dryer (manufactured by Yamato Scientific Co., Ltd., Model DP23) and vacuum-dried at 100°C for 10 hours. After the heat-vacuum drying, the test specimens were placed with the surface of the negative electrode composite layer facing downward, and cellophane tape was attached to the surface of the negative electrode composite layer. The cellophane tape used was cellophane tape specified in JIS Z1522. 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, and the stress when peeled was measured. This measurement was performed three times, and the average value was calculated. This average value was used as the peel strength of the electrode after heat-vacuum drying, and the peel strength was evaluated according to the following criteria. A:25N / m or more B: 20N / m or more and less than 25N / m C: 15N / m or more and less than 20N / m D: Less than 15N / m

[0088] <Powder shedding resistance> The negative electrodes prepared in the examples and comparative examples were cut into 10 cm x 10 cm squares to prepare samples. The mass (Y0) of each sample was measured. Five holes were then punched into the sample using a φ16 mm circular punching machine. Both the punched circular sample and the sample with the circular holes were airbrushed, and the total mass (Y1) of these was measured. The powder shedding ratio (the ratio of the mass after punching to the mass before punching) was calculated using the following formula. A larger value indicates less cracking and peeling at the edge of the negative electrode. Powder shedding ratio = (Y1 / Y0) x 100 (%) A: 99.98% or more B: 99.97% or more but less than 99.98% C: 99.96% or more and less than 99.97% D: Less than 99.96%

[0089] Example 1 <Preparation of particulate polymer> <<Preparation process of cyclohexane solution of block copolymer>> A pressure-resistant reactor was charged with 233.3 kg of cyclohexane, 31.03 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 at 40°C, 1034.5 mmol of n-butyllithium as a polymerization initiator was added, and polymerization was carried out for 1 hour while raising the temperature 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 1,3-butadiene as an aliphatic conjugated diene monomer was continuously added to the pressure-resistant reactor over 1 hour. After the addition of 1,3-butadiene was completed, the polymerization reaction was continued for another 1 hour. The polymerization conversion of 1,3-butadiene was 100%. Next, 460.3 mmol of dichlorodimethylsilane was added to the pressure reactor as a coupling agent, and the coupling reaction was carried out for 2 hours to form a styrene-butadiene coupled block copolymer. Then, 2069.0 mmol of methanol was added to the reaction solution to deactivate the active terminals and mixed thoroughly. 100 parts of this reaction solution (containing 30.0 parts of the polymer component) were mixed with 0.05 parts of 4-[[4,6-bis(octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-tert-butylphenol as a hindered phenol-based antioxidant and 0.09 parts of 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane as a phosphite-based antioxidant. The resulting mixed solution was gradually added dropwise to warm water at 85-95°C to volatilize the solvent, yielding a precipitate. The precipitate was then crushed 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 cyclohexane solution of the block copolymer with a block copolymer concentration of 10.0%. <<Emulsification process>> Sodium alkylbenzenesulfonate was dissolved in ion-exchanged water to prepare a 0.3% aqueous solution. Then, 1000 g of the obtained block copolymer solution and 1000 g of the obtained aqueous solution were charged into a tank and stirred to perform premixing to obtain a premix. Subsequently, the premix was transferred from the tank to a high-pressure emulsifying disperser "LAB1000" (manufactured by SPXFLOW) using a metering pump and circulated (number of passes: 5) to obtain an emulsion by phase inversion of the premix. Next, cyclohexane in the resulting emulsion was distilled off under reduced pressure using a rotary evaporator. Finally, the upper layer was filtered through a 100-mesh wire screen to obtain an aqueous dispersion containing the particulated block copolymer (block copolymer latex). <<Graft polymerization and crosslinking process>> The resulting block copolymer latex was diluted with distilled water to a ratio of 800 parts water per 100 parts of the granulated block copolymer (solids equivalent). 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, 10 parts of methacrylic acid (an acidic group-containing monomer) and 90 parts of distilled water were mixed to prepare a diluted methacrylic acid solution. This diluted methacrylic acid solution was added over 30 minutes to a polymerization reactor heated to 30°C, resulting in the addition of 10 parts methacrylic acid per 100 parts of the block copolymer. Subsequently, 1.0 part of 3-mercapto-1,2-propanediol (a crosslinking ligand) per 100 parts of the block copolymer (solids equivalent) was added. Furthermore, a solution containing 7 parts of distilled water and 0.01 parts of ferrous sulfate (manufactured by Chubu Cherest Co., Ltd., trade name "Frost Fe") as a reducing agent was prepared in a separate container. The resulting solution was added to a polymerization reaction vessel, and 0.5 parts of 1,1,3,3-tetramethylbutyl hydroperoxide (manufactured by NOF Corporation, trade name "Perocta H") as an oxidizing agent was added. The reaction was allowed to proceed at 30°C for 1 hour, followed by a further reaction at 70°C for 2 hours. This resulted in crosslinking of the block copolymer and graft polymerization of methacrylic acid onto the particulate block copolymer, yielding an aqueous dispersion of particulate polymer. The polymerization conversion rate was 99%. <<Preparation of binder composition>> A 5% aqueous solution of sodium hydroxide was added to the aqueous dispersion of the particulate polymer obtained as described above to adjust the pH to 8.0, and 0.5 parts of an antioxidant dispersion, which was a reaction product of p-cresol, cyclopentadiene, and isobutylene, was added per 100 parts (solid content equivalent) of the block copolymer.

[0090] <Preparation of Slurry Composition for Non-Aqueous Secondary Battery Negative Electrode> 97 parts of natural graphite (theoretical capacity: 360 mAh / g) as the negative electrode active material and 1 part (solid content equivalent) of carboxymethyl cellulose (CMC) as a thickener were added to a planetary mixer. The mixture was then diluted with ion-exchanged water to a solid content of 60% and then kneaded for 60 minutes at a rotation speed of 45 rpm. 1.5 parts (solid content equivalent) of the negative electrode binder composition obtained above was then added and kneaded for 40 minutes at a rotation speed of 40 rpm. Ion-exchanged water was then added to adjust the viscosity (measured using a Brookfield viscometer at 25°C and a rotor rotation speed of 60 rpm) to 3000±500 mPa·s to prepare a negative electrode slurry composition.

[0091] <Formation of the negative electrode> 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 2 Thereafter, 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 until the density of the negative electrode composite layer reached 1.60 g / cm 3 A negative electrode of 1000 .mu.m was obtained.

[0092] <Formation of the positive electrode> The planetary mixer uses a Co-Ni-Mn lithium composite oxide active material NMC532 (LiNi 5 / 10 Co 2 / 10 Mn 3 / 1097 parts of acetylene black (product name "HS-100" manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and 2 parts (solids equivalent) of polyvinylidene fluoride (product name "#7208" manufactured by Kureha Corporation) as a binder were added and mixed. Furthermore, 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 to obtain a positive electrode slurry composition with a viscosity of 3600 mPa s (measured using a Brookfield viscometer at a temperature of 25±3°C, a rotor M4, and a rotor rotation speed of 60 rpm). The obtained slurry composition for the positive electrode 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 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 having a positive electrode composite layer 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.

[0093] <Preparing the separator> As a separator made of a separator substrate, a single-layer polypropylene separator (manufactured by Celgard Co., Ltd., product name "Celgard 2500") was prepared.

[0094] <Fabrication of lithium-ion secondary batteries> 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 package 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 package was then heat-sealed at 150°C to seal the opening, completing the lithium-ion secondary battery.

[0095] The particulate polymer, binder composition, slurry composition, electrode (negative electrode), secondary battery, etc. obtained as described above were subjected to various measurements and evaluations according to the methods described above. The results are shown in Table 1.

[0096] (Examples 2 and 3) In preparing the particulate polymer, the amount of methacrylic acid added during graft polymerization was adjusted so that the ratio of the graft portion to 100% by mass of the block copolymer would be the value 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.

[0097] Example 4 When preparing the particulate polymer, the amount of TMEDA added was changed to 16.4 mmol, the amount of n-butyllithium added to 545.5 mmol, the amount of dichlorodimethylsilane added to 46.4 mmol, and the amount of methanol added to 1090.9 mmol, respectively. 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.

[0098] Example 5 In preparing the particulate polymer, the amounts of TMEDA, n-butyllithium, dichlorodimethylsilane, and methanol were changed to 36.0 mmol, 1200.0 mmol, 540.0 mmol, and 2400.0 mmol, respectively, and isoprene was used instead of 1,3-butadiene as the aliphatic conjugated diene monomer. 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.

[0099] (Comparative Example 1) A pressure-resistant reactor was charged with 233.3 kg of cyclohexane, 60.0 mmol of N,N,N',N'-tetramethylethylenediamine (hereinafter referred to as "TMEDA"), and 14.0 kg of styrene as an aromatic vinyl monomer. While stirring these at 40°C, 2000.0 mmol of n-butyllithium as a polymerization initiator was added, and polymerization was carried out for 1 hour while raising the temperature to 50°C. The polymerization conversion of styrene was 100%. Subsequently, while controlling the temperature to maintain 50-60°C, 86.0 kg of 1,3-butadiene as an aliphatic conjugated diene monomer was continuously added to the pressure-resistant reactor over 1 hour. After the addition of 1,3-butadiene was completed, the polymerization reaction was continued for another 1 hour. The polymerization conversion of 1,3-butadiene was 100%. Next, 820.0 mmol of dichlorodimethylsilane was added to the pressure reactor as a coupling agent, and a coupling reaction was carried out for 2 hours to form a styrene-butadiene coupled block copolymer. After that, 4000.0 mmol of methanol was added to the reaction solution and mixed well to deactivate the active terminals. The subsequent steps involved various operations, measurements, and evaluations in the same manner as in Example 1. The results are shown in Table 1.

[0100] (Comparative Example 2) A pressure-resistant reactor was charged with 233.3 kg of cyclohexane, 52.2 mmol of N,N,N',N'-tetramethylethylenediamine (hereinafter referred to as "TMEDA"), and 40.0 kg of styrene as an aromatic vinyl monomer. While stirring these at 40°C, 1739.1 mmol of n-butyllithium as a polymerization initiator was added, and polymerization was carried out for 1 hour while raising the temperature to 50°C. The polymerization conversion of styrene was 100%. Subsequently, while controlling the temperature to maintain 50-60°C, 60.0 kg of 1,3-butadiene as an aliphatic conjugated diene monomer was continuously added to the pressure-resistant reactor over 1 hour. After the addition of 1,3-butadiene was completed, the polymerization reaction was continued for another 1 hour. The polymerization conversion of 1,3-butadiene was 100%. Next, 695.7 mmol of dichlorodimethylsilane was added to the pressure reactor as a coupling agent and a coupling reaction was carried out for 2 hours to form a styrene-butadiene coupled block copolymer. After that, 3478.3 mmol of methanol was added to the reaction solution and mixed well to deactivate the active terminals. The subsequent steps involved various operations, measurements, and evaluations in the same manner as in Example 1. The results are shown in Table 1.

[0101] (Comparative Example 3) A pressure-resistant reactor was charged with 233.3 kg of cyclohexane, 46.9 mmol of N,N,N',N'-tetramethylethylenediamine (hereinafter referred to as "TMEDA"), and 25.0 kg of styrene as an aromatic vinyl monomer. While stirring these components at 40°C, 1562.5 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, 75.0 kg of isoprene as an aliphatic conjugated diene monomer was continuously added to the pressure-resistant reactor over 1 hour. After the addition of isoprene was completed, the polymerization reaction was continued for another 1 hour. The polymerization conversion of isoprene was 100%. Next, 585.9 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-isoprene coupled block copolymer. Thereafter, in order to deactivate the active terminals, 3125.0 mmol of methanol was added to the reaction solution and mixed well. The subsequent steps involved various operations, measurements, and evaluations in the same manner as in Example 1. The results are shown in Table 1.

[0102] (Comparative Examples 4 and 5) In preparing the particulate polymer, the amount of methacrylic acid added during graft polymerization was adjusted so that the ratio of the graft portion to 100% by mass of the block copolymer would be the value 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.

[0103] In Table 1, "ST" indicates a styrene unit, "BD" indicates a 1,3-butadiene unit; "IP" indicates an isoprene unit, "MAA" indicates a methacrylic acid unit.

[0104] [Table 1]

[0105] Table 1 shows that by using the binder compositions of Examples 1 to 5 containing particulate polymers in which the weight-average molecular weight of the aromatic vinyl block region was 15,000 or more, the weight-average molecular weight of the block copolymer was 150,000 or more and 500,000 or less, and the proportion of the graft portion relative to 100% by mass of the block copolymer was 1.0% by mass or more and 10.0% by mass or less, it was possible to form electrodes for nonaqueous secondary batteries that had high resistance to powder shedding and excellent peel strength after heat drying. On the other hand, in Comparative Example 1, in which a particulate polymer having an aromatic vinyl block region with a weight-average molecular weight of less than 15,000 was used instead of the above-mentioned particulate polymer, Comparative Examples 2 and 3, in which a particulate polymer having a block copolymer with a weight-average molecular weight of less than 150,000 was used, and Comparative Examples 4 and 5, in which a particulate polymer in which the ratio of the graft portion to 100% by mass of the block copolymer was less than 1.0% by mass, it was found that an electrode for a nonaqueous secondary battery having high resistance to powder falling and excellent peel strength after heat drying could not be formed. [Industrial Applicability]

[0106] According to the present invention, it is possible to provide a binder composition for a non-aqueous secondary battery electrode that is capable of forming a non-aqueous secondary battery electrode that has high resistance to powder falling off and excellent peel strength after heat drying. 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 a non-aqueous secondary battery electrode that has high resistance to powder falling and excellent peel strength after heat drying. Furthermore, according to the present invention, it is possible to provide an electrode for a non-aqueous secondary battery that has high resistance to powder falling off and excellent peel strength after heat drying. Furthermore, according to the present invention, it is possible to provide a non-aqueous secondary battery including the electrode for a non-aqueous secondary battery.

Claims

1. A binder composition for a non-aqueous secondary battery electrode, comprising a particulate polymer, the particulate polymer has a trunk portion composed of a block copolymer containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, and a graft portion; the block copolymer contains an aromatic vinyl block region composed of the aromatic vinyl monomer units, the weight average molecular weight of the aromatic vinyl block region is 15,000 or more; The weight average molecular weight of the block copolymer is 150,000 or more and 500,000 or less, and the proportion of the graft portion is 1.5% by mass or more and 5.0% by mass or less, when the amount of all repeating units constituting the block copolymer is 100% by mass, a proportion of the aromatic vinyl monomer units in the particulate polymer is 25.0% by mass or more, when the amount of all repeating units constituting the particulate polymer is taken as 100% by mass; the graft portion of the particulate polymer contains a carboxylic acid group-containing monomer unit; A binder composition for non-aqueous secondary battery electrodes.

2. the value of the storage modulus of the particulate polymer at 100°C is G'(100) and the value of the storage modulus at 200°C is G'(200), calculated by the formula: {G'(100)-G'(200)} / G'(200) is 15.0 or less; The binder composition for a non-aqueous secondary battery electrode according to claim 1 .

3. a proportion of the aromatic vinyl monomer units in the particulate polymer is 30.0% by mass or more and 50.0% by mass or less, when the amount of all repeating units constituting the particulate polymer is taken as 100% by mass; The binder composition for a non-aqueous secondary battery electrode according to claim 1 or 2.

4. 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 3.

5. 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 4.

6. A non-aqueous secondary battery comprising the electrode for a non-aqueous secondary battery according to claim 5 .

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