Binder for electrochemical elements, conductive material dispersed liquid for electrochemical elements, composite particles for electrochemical element electrodes, electrode for electrochemical elements, and electrochemical element

Abstract

Disclosed is a block copolymer that includes a block region (A) which is composed of an aromatic vinyl monomer unit, and a block region (B) at least a part of which is composed of a hydrogenated aliphatic conjugated diene monomer unit, wherein the ratio of the unit derived from 1,4-addition polymerization of the aliphatic conjugated diene monomer in the block copolymer is 28% by mass to 75% by mass inclusive.

Description

Binder for electrochemical element, conductive material dispersion for electrochemical element, composite particle for electrochemical element electrode, electrode for electrochemical element, and electrochemical element

[0001] The present invention relates to a binder for an electrochemical device, a conductive material dispersion for an electrochemical device, composite particles for an electrode for an electrochemical device, an electrode for an electrochemical device, and an electrochemical device.

[0002] Electrochemical devices such as nonaqueous secondary batteries (e.g., lithium ion 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 electrochemical devices.

[0003] In order to improve the performance of electrochemical devices, various improvements have been made to the materials that form the electrodes for electrochemical devices. Electrodes for electrochemical devices have a structure in which an electrode mixture layer, which is mainly composed of an electrode active material and, as necessary, contains other components such as a conductive additive and a binder to impart specific functions such as conductivity, adhesion, and flexibility to the electrode, is disposed on an electrode substrate.

[0004] As methods for forming an electrode mixture layer, various methods have been investigated to date, including a method in which a slurry composition containing an electrode active material, a conductive carbon material, a binder, and a solvent is applied to an electrode substrate and dried to form an electrode mixture layer, and a method in which a slurry composition containing an electrode active material, a conductive carbon material, a binder, and a solvent is spray-dried to obtain composite particles, and the obtained composite particles are pressure-molded onto an electrode substrate to form an electrode mixture layer.

[0005] Various attempts have been made to improve the binders that can be used in the various ways described above in order to impart excellent performance to electrochemical elements.

[0006] Specifically, for example, Patent Document 1 discloses an electrode material using a binder that may contain at least one selected from the group consisting of styrene-ethylene / butylene-styrene block copolymer (SEBS) and styrene-ethylene / ethylene / propylene-styrene block copolymer (SEEPS), and that has a content of repeating units having an aromatic ring of 15% by mass or more. Furthermore, for example, Patent Document 2 discloses a binder composition for lithium-ion secondary battery electrodes that contains a rubber-based polymer (binder) that has a polymethylene-type saturated main chain and does not contain fluorine atoms, and a specified organic solvent, in which the gel content of the rubber-based polymer in the binder composition is less than 50%. Here, Patent Document 2 cites styrene-containing block ternary rubbers such as SEBM and SEPM as examples of rubber-based polymers that have a polymethylene-type saturated main chain and do not contain fluorine atoms.

[0007] International Publication No. 2022 / 249589 JP 10-188991 Publication

[0008] However, the binders of the above-mentioned prior art have room for improvement in terms of increasing the strength of the electrode mixture layer and suppressing the increase in resistance after cycling of the electrochemical device.

[0009] Therefore, an object of the present invention is to provide a binder for electrochemical elements that can provide electrochemical elements that can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling. Another object of the present invention is to provide a conductive material dispersion for electrochemical elements and composite particles for electrochemical element electrodes that can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling of the electrochemical element. A further object of the present invention is to provide an electrode for electrochemical elements that has a high-strength electrode mixture layer and is capable of suppressing an increase in resistance after cycling of the electrochemical element, and an electrochemical element in which an increase in resistance after cycling is suppressed.

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems, and have newly discovered that by using, as a binder, a block copolymer having a block region (A) composed of aromatic vinyl monomer units and a block region (B) at least a portion of which is composed of hydrogenated aliphatic conjugated diene monomer units, in which the proportion of units derived from 1,4-addition polymerization of the aliphatic conjugated diene monomer in the block copolymer is 28% by mass or more and 75% by mass or less, it is possible to increase the strength of an electrode mixture layer and suppress an increase in resistance after cycling of an electrochemical device, and have completed the present invention.

[0011] That is, the present invention has an object to advantageously solve the above-mentioned problems. The present invention provides [1] a binder for electrochemical elements, the binder being a block copolymer comprising at least a block region (A) and a block region (B), the block region (A) being a block region composed of aromatic vinyl monomer units, and the block region (B) being a block region composed at least in part of hydrogenated aliphatic conjugated diene monomer units, and the proportion of units derived from the 1,4-addition polymerization of the aliphatic conjugated diene monomer in the block copolymer being 28% by mass or more and 75% by mass or less. Thus, by using a predetermined block copolymer containing units derived from the 1,4-addition polymerization of the aliphatic conjugated diene monomer in a proportion of 28% by mass or more and 75% by mass or less as a binder, the strength of the electrode mixture layer can be increased and an increase in resistance after cycling of the electrochemical element can be suppressed. Note that, in this specification, the "proportion of units derived from the 1,4-addition polymerization of the aliphatic conjugated diene monomer" can be measured by the method described in the Examples.

[0012] [2] In the binder for electrochemical elements according to [1] above, the hydrogenation rate of the block region (A) is preferably 50% or less. If the hydrogenation rate of the block region (A) is 50% or less, the strength of the resulting electrode mixture layer can be further increased. The "hydrogenation rate" can be measured according to the method described in the Examples of this specification.

[0013] [3] In the binder for electrochemical elements according to the above [1] or [2], the hydrogenation rate of the block region (B) is preferably 50% or more. If the hydrogenation rate of the block region (B) is 50% or more, an increase in the initial resistance of the resulting electrochemical element and an increase in the resistance after cycling can be suppressed.

[0014] [4] In the binder for electrochemical elements according to any one of [1] to [3] above, the proportion of the block region (A) in the block copolymer is preferably 10% by mass or more and 50% by mass or less. Thus, if the proportion of the block region (A) in the block copolymer is 10% by mass or more and 50% by mass or less, the strength of the electrode mixture layer can be further increased and the increase in resistance after cycling of the electrochemical element can be more effectively suppressed. The proportion of the block region in the block copolymer is: １ It can be measured by H-NMR.

[0015] [5] In the binder for electrochemical elements according to any one of [1] to [4] above, the weight-average molecular weight of the block copolymer is preferably 50,000 or more and 500,000 or less. If the weight-average molecular weight of the block copolymer is 50,000 or more and 500,000 or less, the strength of the resulting electrode mixture layer can be further increased, and the increase in resistance of the resulting electrochemical element after cycling can be further suppressed. The weight-average molecular weight of the block copolymer can be measured by the method described in the Examples.

[0016] [6] In the binder for electrochemical elements according to any one of the above [1] to [5], the block copolymer is preferably a multiblock copolymer. If the block copolymer is a multiblock copolymer, the strength of the obtained electrode mixture layer can be further increased.

[0017] [7] In the binder for electrochemical elements according to any one of the above [1] to [6], the block copolymer is preferably a triblock copolymer. If the block copolymer is a triblock copolymer, the strength of the obtained electrode mixture layer can be further increased.

[0018] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides [8] a conductive material dispersion for electrochemical elements, comprising a conductive carbon material, a solvent, and the binder for electrochemical elements of any one of [1] to [7] above, a conductive carbon material, and a solvent. In this way, by using a conductive material dispersion for electrochemical elements containing the binder for electrochemical elements, it is possible to increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling of the electrochemical element.

[0019] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention relates to composite particles for an electrochemical element electrode, which include [9] an electrode active material, a conductive carbon material, and the binder for an electrochemical element according to any one of [1] to [7] above. Use of such composite particles can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling of the electrochemical element.

[0020] The present invention also aims to advantageously solve the above-mentioned problems, and provides an electrode for an electrochemical device, comprising:

[10] an electrode mixture layer containing an electrode active material, a conductive carbon material, and the binder for an electrochemical device according to any one of [1] to [7] above. In this way, when an electrode has an electrode mixture layer containing the binder for an electrochemical device, the electrode mixture layer has excellent strength and can further suppress an increase in resistance after cycling of the electrochemical device.

[0021] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides

[11] an electrochemical device comprising the electrode for electrochemical devices according to

[10] above. In this way, by using the electrode for electrochemical devices, an electrochemical device capable of suppressing an increase in resistance after cycling can be obtained.

[0022] According to the present invention, it is possible to provide a binder for electrochemical elements that can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling, and it is also possible to provide a conductive material dispersion for electrochemical elements and composite particles for electrochemical element electrodes that can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling of the electrochemical element. Furthermore, it is possible to provide an electrode for electrochemical elements that has a high-strength electrode mixture layer and that can suppress an increase in resistance after cycling of the electrochemical element, and an electrochemical element in which an increase in resistance after cycling is suppressed.

[0023] Hereinafter, embodiments of the present invention will be described in detail. Herein, the binder for electrochemical elements of the present invention (hereinafter also simply referred to as "binder") can be used, for example, when preparing a conductive material dispersion for electrochemical elements of the present invention (hereinafter also simply referred to as "conductive material dispersion") or a composite particle for electrochemical element electrodes of the present invention (hereinafter also simply referred to as "composite particles"). Furthermore, the conductive material dispersion of the present invention can be used as a material when preparing an electrode mixture layer of the composite particle of the present invention or the electrode for electrochemical elements of the present invention (hereinafter also simply referred to as "electrode"). Furthermore, the composite particle of the present invention can be used as a material when preparing an electrode mixture layer of the electrode of the present invention. And the electrochemical element of the present invention comprises the electrode of the present invention.

[0024] (Binder for Electrochemical Elements) The binder for electrochemical elements of the present invention is a block copolymer including at least a block region (A) and a block region (B). In this block copolymer, the block region (A) is a block region composed of aromatic vinyl monomer units, and the block region (B) is a block region composed at least in part of hydrogenated aliphatic conjugated diene monomer units. The block copolymer is further characterized in that the proportion of units derived from 1,4-addition polymerization of the aliphatic conjugated diene monomer in the block copolymer is 28% by mass or more and 75% by mass or less.

[0025] The binder of the present invention is a block copolymer including a block region (A) composed of aromatic vinyl monomer units and a block region (B) composed at least in part of hydrogenated aliphatic conjugated diene monomer units, and furthermore, the proportion of units derived from 1,4-addition polymerization of the aliphatic conjugated diene monomer in the block copolymer is 28% by mass or more and 75% by mass or less. This makes it possible to provide an electrochemical element that can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling. The reason for this is unclear, but is presumed to be as follows. First, the block region (A) composed of aromatic vinyl monomer units acts to increase the strength of the block copolymer. On the other hand, the presence of the block region (B) composed at least in part of hydrogenated aliphatic conjugated diene monomer units in the block copolymer suppresses oxidation-induced degradation of double bonds that occurs with repeated charge / discharge cycles, thereby suppressing an increase in resistance after cycling. Furthermore, by setting the proportion of units derived from the 1,4-addition polymerization of an aliphatic conjugated diene monomer to 28% by mass or more, the number of side chains in the block region (B) does not become excessively large, making it possible to suppress an increase in resistance after cycling due to oxidation of the side chains. Furthermore, by setting the proportion of units derived from the 1,4-addition polymerization of an aliphatic conjugated diene monomer to 75% by mass or less, the number of side chains in the block region (B) does not become excessively small, ensuring flexibility as a block copolymer and thereby increasing the strength of the resulting electrode mixture layer.

[0026] <Block Copolymer> The block copolymer serving as a binder is a component that can prevent components contained in an electrode mixture layer from being detached from the electrode mixture layer in an electrode having the electrode mixture layer produced using the block copolymer (i.e., can function as a binder).

[0027] <<Block Region (A)>> The block region (A) is a block region composed of aromatic vinyl monomer units. Hereinafter, a block region composed of aromatic vinyl monomer units may be referred to as the "aromatic vinyl block region (A)." The aromatic vinyl block region (A) is a region containing a portion in which only aromatic vinyl monomer units are linked together. The aromatic vinyl block region (A) is a region containing mainly aromatic vinyl monomer units as repeating units. In this specification, the term "mainly containing" an aromatic vinyl monomer unit means that, assuming that the total monomer units contained in a certain block region are 100% by mass, 80% by mass or more of the block region is occupied by aromatic vinyl monomer units. Herein, one aromatic vinyl block region (A) may be composed of only one type of aromatic vinyl monomer unit or multiple types of aromatic vinyl monomer units, but is preferably composed of only one type of aromatic vinyl monomer unit.

[0028] The aromatic vinyl monomer that can be used to form the aromatic vinyl monomer units that constitute the aromatic vinyl block region (A) is not particularly limited as long as it is an aromatic vinyl compound, but examples include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 4-bromostyrene, 2-methyl-4,6-dichlorostyrene, 2,4-dibromostyrene, vinylnaphthalene, and the like. Among these, styrene is preferred. These can be used alone or in combination of two or more, but it is preferable to use one type alone.

[0029] The use of styrene as the aromatic vinyl monomer further increases the strength of the resulting electrode mixture layer, presumably due to the synergistic effect of the high strength of the aromatic vinyl monomer unit itself and the pseudo-crosslinked state of the block copolymer resulting from π-π stacking between aromatic rings.

[0030] <<Hydrogenation Rate of Aromatic Vinyl Block Region (A)>> The hydrogenation rate of the aromatic vinyl block region (A) is preferably 50% or less, more preferably 30% or less, and even more preferably 5% or less. The lower limit of the hydrogenation rate is not particularly limited, and the block copolymer may be unhydrogenated, i.e., the hydrogenation rate may be 0%. If the hydrogenation rate is equal to or less than the upper limit, a certain amount of unhydrogenated aromatic rings remain, and the block copolymer is pseudo-crosslinked due to π-π stacking between the aromatic rings. This increases the strength of the resulting electrode mixture layer. Furthermore, the increased strength of the electrode mixture layer improves the cycle characteristics of the resulting electrochemical device and effectively suppresses an increase in resistance after cycling. Furthermore, a hydrogenation rate equal to or less than the upper limit reduces the elastic modulus of the aromatic vinyl block region (A), thereby improving the pressability of the resulting electrode mixture layer and reducing the initial resistance of the resulting secondary battery. The hydrogenation rate can be adjusted, for example, by changing the type of hydrogenation catalyst and / or the hydrogenation reaction conditions.

[0031] <<Proportion of Aromatic Vinyl Block Region (A)>> The proportion of the aromatic vinyl block region (A) in the block copolymer is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, when the amount of all repeating units (monomer units and structural units) in the copolymer is taken as 100% by mass. If the proportion of the aromatic vinyl block region (A) is equal to or greater than the above-mentioned lower limit, the strength of the resulting electrode mixture layer can be further increased. Furthermore, the aromatic vinyl block region (A) acts to effectively disperse solid components such as conductive materials when preparing a conductive material dispersion liquid or the like. Therefore, if the proportion of the aromatic vinyl block region (A) is equal to or greater than the above-mentioned lower limit, a uniform electrode mixture layer can be formed when the electrode mixture layer is formed, which can also contribute to increasing the strength of the electrode mixture layer. Furthermore, a uniform electrode mixture layer can also act to improve the output characteristics when an electrochemical device is formed. Furthermore, when the proportion of the aromatic vinyl block region (A) is equal to or less than the upper limit, the flexibility of the block copolymer is increased, thereby improving the pressability of the resulting electrode mixture layer. This can reduce the initial resistance of the resulting electrochemical device. Furthermore, the flexibility of the electrode mixture layer improves the cycle characteristics of the electrochemical device and effectively suppresses the increase in resistance after cycling.

[0032] <<Block Region (B)>> The block region (B) is a block region at least partially composed of hydrogenated aliphatic conjugated diene monomer units. Hereinafter, a block region at least partially composed of hydrogenated aliphatic conjugated diene monomer units may be referred to as a "hydrogenated aliphatic conjugated diene block region (B)" or simply as a "block region (B)." The hydrogenated aliphatic conjugated diene block region (B) is a region containing a portion in which only at least partially hydrogenated aliphatic conjugated diene monomer units are linked together. More specifically, the hydrogenated aliphatic conjugated diene block region (B) is a region mainly containing at least partially hydrogenated aliphatic conjugated diene monomer units. In this specification, the phrase "the hydrogenated aliphatic conjugated diene block region (B) mainly contains aliphatic conjugated diene monomer units" means that, when the total monomer units contained in a certain block region is 100% by mass, 80% by mass or more of the total monomer units contained in the certain block region is 100% by mass, the aliphatic conjugated diene monomer units account for 80% by mass or more of the total monomer units. Furthermore, "at least partially hydrogenated" means that at least some of the multiple aliphatic conjugated diene monomer units constituting the block region (B) are hydrogenated aliphatic conjugated diene monomer units. In particular, the proportion of repeating units of aliphatic conjugated diene monomer units in the block region (B) is preferably 95% by mass or more, more preferably 99% by mass or more, and even more preferably 100% by mass. That is, it is preferable that the block region (B) is a block region consisting only of repeating units of aliphatic conjugated diene monomer units, at least some of which are hydrogenated aliphatic conjugated diene monomer units. Here, the block (B) may be composed of one type of repeating unit or multiple types of repeating units.

[0033] -Aliphatic Conjugated Diene Monomer Unit- Examples of aliphatic conjugated diene monomers capable of forming the aliphatic conjugated diene monomer unit 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 may be used alone or in combination of two or more in any ratio. Among these, isoprene and 1,3-butadiene are preferred. When the aliphatic conjugated diene monomer unit contains a unit derived from at least one of isoprene and 1,3-butadiene, the phase consisting of the aromatic vinyl block region (A) and the phase consisting of the block region (B) are incompatible with each other, and therefore, the development of the pseudo-crosslinked structure described above can be promoted in the aromatic vinyl block region (A). Furthermore, by using at least one of isoprene and 1,3-butadiene, the ratio of linear and side chain structures can be controlled by the bonding mode, and the strength and flexibility of the resulting block copolymer can be controlled, resulting in a block copolymer that can optimize electrode strength. Of course, the block region (B) can also contain units derived from both isoprene and 1,3-butadiene.

[0034] When the block region (B) contains both a monomer unit derived from isoprene (hereinafter also referred to as an "isoprene monomer unit") and a monomer unit derived from 1,3-butadiene (hereinafter also referred to as a "butadiene monomer unit"), the proportion of the isoprene monomer unit is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 100% by mass, with the total content of these being 100% by mass. When the aromatic vinyl monomer block region (A), particularly the aromatic vinyl monomer block region (A), has a polystyrene structure, the solubility parameter (SP value) exhibited by the polystyrene structure is close to the SP value exhibited by the polyisoprene structure, and as a result, the polystyrene structure tends to be small, allowing the development of excellent mechanical properties.

[0035] When 1,3-butadiene is used to form the block region (B), butadiene monomer units that can constitute the repeating units of the resulting block region (B) include units derived from 1,2-addition polymerization and units derived from 1,4-addition polymerization. The units derived from 1,4-addition polymerization adopt a linear structure consisting of saturated carbon-carbon bonds upon hydrogenation, and this structure can act to increase the hardness of the block copolymer. A moderately high hardness of the block copolymer can increase the strength of the resulting electrode mixture layer. However, if the proportion of units derived from 1,4-addition polymerization of butadiene is excessively high, the hardness of the block copolymer may be excessively high. Therefore, when 1,3-butadiene is used to form the block region (B), it is necessary to more carefully control the bonding pattern during polymerization compared to when isoprene is used, thereby balancing the proportion of units derived from 1,4-addition polymerization and the proportion of units derived from 1,2-addition polymerization. The units derived from 1,2-addition polymerization have a vinyl bond in the side chain. If the proportion of such vinyl bonds is excessively high, it may adversely affect the dispersibility and oxidation resistance of the conductive carbon material when the binder is mixed with the conductive carbon material, etc. Therefore, it is necessary to control the proportion of units derived from 1,4-addition polymerization and the proportion of units derived from 1,2-addition polymerization in a well-balanced manner so that the proportion of units derived from 1,2-addition polymerization does not become excessively high.

[0036] On the other hand, when isoprene is used in forming the block region (B), the isoprene monomer units that can constitute the repeating units of the aliphatic conjugated diene monomer units may include units derived from 1,4-addition polymerization, units derived from 3,4-addition polymerization, and units derived from 1,2-addition polymerization.

[0037] <<Proportion of Units Derived from 1,4-Addition Polymerization in Block Copolymer>> The proportion of units derived from the 1,4-addition polymerization of an aliphatic conjugated diene monomer, based on the total mass of the block copolymer, must be 28% by mass or more and 75% by mass or less, preferably 35% by mass or more, more preferably 45% by mass or more, even more preferably 51% by mass or more, preferably 71% by mass or less, and more preferably 68% by mass or less. When the proportion of units derived from the 1,4-addition polymerization of an aliphatic conjugated diene monomer is equal to or greater than the above-mentioned lower limit, the number of side chains in the block region (B) is not excessively increased, and an increase in resistance after cycling due to oxidation of the side chains can be suppressed. When the proportion of units derived from the 1,4-addition polymerization of an aliphatic conjugated diene monomer is equal to or less than the above-mentioned upper limit, the number of side chains present in the block region (B) is not excessively decreased, ensuring the flexibility of the block copolymer and, as a result, increasing the strength of the obtained electrode mixture layer. Furthermore, when the proportion of the units derived from 1,4-addition polymerization is within the above range, the block copolymer can act to maintain the dispersibility of the conductive carbon material when mixed with the conductive carbon material, and can also impart excellent electrochemical stability to the resulting electrochemical device.

[0038] Here, the units derived from the 1,4-addition polymerization of an aliphatic conjugated diene monomer may exist in cis and trans forms. As a result of investigations by the present inventors, it was inferred that the occupancy rate of the units derived from the 1,4-addition polymerization has a stronger influence on the effects related to the flexibility and oxidation resistance of the block copolymer as described above than on whether the units derived from the 1,4-addition polymerization are cis or trans.

[0039] <<Proportion of Units Other than Units Derived from 1,4-Addition Polymerization in Block Region (B)>> Here, the proportion of units other than units derived from 1,4-addition polymerization in block region (B), in other words, the proportion of structural units derived from 1,2- and 3,4-addition polymerization, is preferably 5% by mass or more, more preferably 8% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less.

[0040] <<Hydrogenation Rate of Block Region (B)>> The hydrogenation rate of the block region (B) is preferably 50% or more, more preferably 75% or more, and even more preferably 95% or more. The upper limit of the hydrogenation rate is not particularly limited, and complete hydrogenation, i.e., a hydrogenation rate of 100%, may be achieved, or a hydrogenation rate of 99% or less may be achieved. A hydrogenation rate equal to or greater than the lower limit can prevent the residual carbon-carbon double bonds in the block copolymer from being oxidized during charge and discharge, thereby preventing the oxidation resistance of the block copolymer from deteriorating. If the residual carbon-carbon double bonds in the block copolymer are oxidized, reaction degradation products may form a coating on the surface of the electrode active material, potentially increasing the initial resistance of the electrochemical device. Furthermore, the residual carbon-carbon double bonds in the block copolymer may gradually deteriorate during charge and discharge cycles, potentially resulting in an increase in resistance after cycling. If the proportion of units derived from the 1,4-addition polymerization of an aliphatic conjugated diene monomer in the block region (B) is significantly high, and such units are completely hydrogenated (100% hydrogenation rate), the block region (B) may easily adopt a crystalline structure, resulting in a brittle block copolymer that is difficult to elongate, potentially resulting in reduced strength of the block copolymer. However, such problems can be avoided by setting the proportion of units derived from the 1,4-addition polymerization to the above-mentioned upper limit or less. A hydrogenation rate within the above range reduces the initial resistance of the resulting electrochemical device and suppresses block copolymer degradation during cycling, thereby suppressing an increase in resistance after cycling. Furthermore, a hydrogenation rate within the above range can impart mechanical strength to the copolymer. A hydrogenation rate within the above range is presumably due to the block copolymer's increased solubility in a solvent. This enhances the dispersibility of a conductive carbon material when dispersed in a binder solution, i.e., when a conductive material dispersion is prepared. The hydrogenation rate can be adjusted, for example, by changing the type of hydrogenation catalyst and / or the hydrogenation reaction conditions.

[0041] The hydrogenated aliphatic conjugated diene monomer units can form alkylene structural units. Therefore, the block region (B), "at least a portion of which is composed of hydrogenated aliphatic conjugated diene monomer units," can be said to be a block region that contains at least alkylene structural units as repeating units and may optionally contain aliphatic conjugated diene monomer units. The alkylene structural units are represented by the general formula: -C ｎ H ２ｎ - [where n is an integer of 2 or greater]. The alkylene structural unit may be linear or branched. The alkylene structural unit preferably has 4 or more carbon atoms (i.e., n in the above general formula is an integer of 4 or greater).

[0042] Specifically, when 1,3-butadiene is used as the aliphatic conjugated diene, the structural units derived from hydrogenated 1,2-addition polymerization can form polyethylene chains in the main chain of the block copolymer, and the structural units derived from hydrogenated 1,4-addition polymerization can form polybutylene chains. When isoprene is used as the aliphatic conjugated diene, the structural units derived from hydrogenated 1,4-addition polymerization can form a structure in which ethylene and propylene are alternately copolymerized in the main chain of the block copolymer. Note that the structural units derived from hydrogenated 3,4-addition polymerization and 1,2-addition polymerization can form a pentene structure.

[0043] <<Proportion of Block Region (B)>> The proportion of the block region (B) in the block copolymer is preferably 90% by mass or less, more preferably 80% by mass or less, preferably 50% by mass or more, and more preferably 60% by mass or more, based on 100% by mass of the total amount of repeating units (monomer units and structural units) in the copolymer. When the proportion of the block region (B) is equal to or less than the upper limit, the strength of the resulting electrode mixture layer can be further increased. Furthermore, when the proportion of the block region (B) is equal to or less than the upper limit, the dispersibility-improving effect of the aromatic vinyl block region (A) can be effectively exerted, and a uniform electrode mixture layer can be formed when the electrode mixture layer is formed. This can also contribute to increasing the strength of the electrode mixture layer. Furthermore, when the proportion of the block region (B) is equal to or greater than the lower limit, the flexibility of the block copolymer is increased, thereby improving the pressability of the resulting electrode mixture layer. This can reduce the initial resistance of the resulting electrochemical element. Furthermore, the flexibility of the electrode mixture layer improves the cycle characteristics of the electrochemical element and effectively suppresses the increase in resistance after cycling.

[0044] <<Other Repeating Units>> The block copolymer may contain other repeating units in addition to the aromatic vinyl block region (A) and block region (B). Monomers capable of forming the other repeating units (hereinafter also referred to as "other monomers") are not particularly limited, and examples thereof include (meth)acrylic acid ester monomers and monomers having a hydrophilic group. These monomers may be used alone or in combination of two or more. In the present invention, "(meth)acrylic" refers to acrylic and / or methacrylic. Furthermore, the block copolymer may be acid-modified using a monomer having a hydrophilic group.

[0045] For example, examples of the monomer having a hydrophilic group include a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and a monomer having a hydroxyl group.

[0046] The proportion of other repeating units and acid-modified units in the block copolymer is preferably 10% by mass or less, more preferably 5% by mass or less, when the amount of all repeating units (structural units and monomer units) in the block copolymer is taken as 100% by mass. Preferably, the block copolymer does not contain other repeating units and acid-modified units, i.e., 0% by mass. If the proportion of other repeating units and acid-modified units is not more than the above upper limit, the strength of the electrode mixture layer can be further increased and an increase in resistance after cycling of the electrochemical device can be further suppressed.

[0047] <<Structure of Block Copolymer>> The block copolymer preferably has, for example, a diblock structure having one of each of two types of blocks, or a multiblock structure consisting of three or more blocks. Being a block copolymer can improve the dispersibility of the conductive carbon material when mixed with the conductive carbon material. If the conductive carbon material is well dispersed in the electrode mixture layer, the electrode mixture layer has excellent strength, and furthermore, the output characteristics of an electrochemical device including the electrode mixture layer can be improved. If the block copolymer is a multiblock copolymer, the strength of the resulting electrode mixture layer can be further improved. Note that a multiblock structure of a triblock or higher may be a symmetric block structure or an asymmetric block structure.

[0048] The block copolymer that can constitute the binder of the present invention may contain one or more of a diblock copolymer and a multiblock copolymer having three or more blocks. Multiblock copolymers having three or more blocks may contain the respective asymmetric block copolymers. Among these, the block copolymer preferably contains at least one of a diblock copolymer and a triblock copolymer, and more preferably a triblock copolymer. If the block copolymer contains a triblock copolymer, the mechanical strength of the block copolymer itself is increased by the pseudo-crosslinking of the block region (A), which may also increase the strength of the resulting electrode mixture layer.

[0049] <<Weight-Average Molecular Weight of Block Copolymer>> The weight-average molecular weight of the block copolymer is preferably 50,000 or more, more preferably 80,000 or more, and even more preferably 120,000 or more, and is preferably 500,000 or less, and more preferably 400,000 or less. If the weight-average molecular weight is equal to or greater than the above-mentioned lower limit, when the block copolymer is mixed with a conductive carbon material, at least a portion of the block copolymer is adsorbed to the conductive carbon material, thereby forming steric hindrance, thereby improving the dispersibility of the conductive carbon material. Furthermore, if the weight-average molecular weight is equal to or less than the above-mentioned upper limit, when a binder solution in which the block copolymer is dissolved in a solvent is mixed with a conductive carbon material, appropriate viscosity can be imparted, thereby improving the dispersibility of the conductive carbon material in the solution.

[0050] <<Method for Preparing Block Copolymer>> The method for preparing the block copolymer is not particularly limited, and any method such as solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization can be used. Furthermore, addition polymerization such as ionic polymerization, radical polymerization, or living radical polymerization can be used as the polymerization method. Furthermore, known polymerization initiators such as redox polymerization initiators containing iron-based compounds can be used as the polymerization initiator.

[0051] More specifically, the block copolymer can be prepared, for example, by adding a second monomer component different from the first monomer component to a solution obtained by polymerizing a first monomer component, polymerizing the resulting mixture, and optionally further repeating the addition and polymerization of the monomer component.

[0052] The polymer can be hydrogenated using a known hydrogenation method such as oil phase hydrogenation or aqueous phase hydrogenation. The catalyst used for hydrogenation can be any known selective hydrogenation catalyst, including palladium catalysts, rhodium catalysts, and nickel (II) acetylacetonate. Two or more of these hydrogenation catalysts may be used in combination. A co-catalyst such as triisobutyl may also be used.

[0053] Then, if necessary, an aqueous solution containing a compound selected from the group consisting of an aminocarboxylic acid chelate compound, a phosphonic acid chelate compound, gluconic acid, citric acid, malic acid, and tartaric acid as a metal capture agent, and a surfactant, can be added to the reaction liquid after the hydrogenation reaction to remove metal components.

[0054] The reaction liquid obtained as described above is a binder solution in which the binder is dissolved in the solvent. If necessary, the binder may be precipitated and isolated from the reaction liquid by a known method, or the binder solution may be used as it is.

[0055] When the binder is used as a binder solution, the binder solution may contain, in addition to the above components, other components such as antioxidants such as phenolic antioxidants, reinforcing materials, leveling agents, viscosity modifiers, and electrolyte additives. These components are not particularly limited as long as they do not affect the electrochemical reaction, and known components, such as those described in International Publication No. 2012 / 115096, can be used. Furthermore, these components may be used alone or in combination of two or more types in any ratio.

[0056] (Conductive material dispersion for electrochemical elements) The conductive material dispersion for electrochemical elements of the present invention contains the binder for electrochemical elements of the present invention described above, a conductive carbon material, and a solvent, and may optionally further contain other components used in the field of electrochemical elements and conductive materials other than the conductive carbon material. Note that the conductive material dispersion of the present invention does not contain an electrode active material. Furthermore, since the conductive material dispersion of the present invention contains the binder of the present invention, it is possible to increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling of the electrochemical element.

[0057] <Binder for electrochemical element> The binder for electrochemical element may be any of those described above. The amount of the binder for electrochemical element, calculated as solid content, is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of the conductive carbon material. If the amount of the binder is equal to or greater than the lower limit, the strength of the resulting electrode mixture layer can be further increased. If the amount of the binder solution is equal to or less than the upper limit, the initial resistance can be effectively reduced.

[0058] <Conductive Carbon Material> Examples of conductive carbon materials that function as conductive materials that ensure electrical contact between electrode active materials in the electrode mixture layer include carbon black (e.g., acetylene black, Ketjen Black (registered trademark), furnace black, etc.), graphite (graphene), carbon fiber (carbon nanofiber), carbon flakes, and ultrashort carbon fibers (e.g., carbon nanotubes (CNTs) and vapor-grown carbon fibers). Among these, from the viewpoint of conductivity, carbon black, carbon fiber (carbon nanofiber), graphite (graphene), and carbon nanotubes (CNTs) are preferred, and carbon black is more preferred. These can be used alone or in combination of two or more.

[0059] <Solvent> Examples of the solvent that can be used include organic solvents such as cyclohexane, N-methylpyrrolidone (NMP), N,N-dimethylformamide, acetone, etc. Among these, cyclohexane is preferred from the viewpoint of dispersion stability of the conductive carbon material.

[0060] <Other Components> Other components that can be blended into the conductive material dispersion liquid are not particularly limited, and include the same components as the other components that can be blended into the binder solution described above. These components may be used alone or in combination of two or more at any ratio.

[0061] <Other Conductive Materials> Conductive materials other than conductive carbon materials (other conductive materials) are not particularly limited, and fibers, foils, etc. of various metals can be used.

[0062] <Method for preparing conductive material dispersion> The conductive material dispersion can be prepared by mixing the above-mentioned components by a known mixing method. The mixing can be carried out using a mixer such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, or a Filmix.

[0063] (Composite particles for electrochemical element electrodes) The composite particles for electrochemical element electrodes of the present invention comprise an electrode active material, a conductive carbon material, and the above-described binder for electrochemical elements of the present invention, and may optionally further comprise other components used in the field of electrochemical elements, conductive materials other than conductive carbon materials, etc. Furthermore, since the composite particles of the present invention contain the binder of the present invention, the strength of the electrode mixture layer can be increased and an increase in resistance after cycling of the electrochemical element can be suppressed. Note that, below, as an example, a case will be described in which the composite particles are composite particles for lithium ion secondary battery positive electrodes, but the present invention is not limited to the following example.

[0064] <Electrode active material> The electrode active material is a material that transfers electrons at the electrode of an electrochemical element. For example, as a positive electrode active material for a lithium ion secondary battery, a material that can absorb and release lithium is usually used. Hereinafter, a positive electrode active material for a lithium ion secondary battery will be described as an example, but the present invention is not limited to the following example.

[0065] The positive electrode active material for lithium ion secondary batteries can be 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, including Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

[0066] As the transition metal oxide, transition metal sulfide, and composite metal oxide of lithium and transition metal, for example, those described in JP-A-2020-198315 can be used.

[0067] <Binder for Electrochemical Element> The binder for electrochemical elements can be any of those described above. The amount of binder, calculated as solid content, is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the electrode active material. If the amount of binder is equal to or greater than the lower limit, the strength of the electrode mixture layer can be further increased. If the amount of binder is equal to or less than the upper limit, the increase in resistance after cycling can be further suppressed.

[0068] <Conductive Carbon Material> The conductive carbon material that can be optionally blended into the composite particles is not particularly limited, and examples thereof include the same conductive carbon materials that can be blended into the conductive material dispersion of the present invention. The blending amount of the conductive carbon material is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the electrode active material. When the blending amount of the conductive carbon material is equal to or greater than the above-mentioned lower limit, the output characteristics of the electrochemical element can be further improved. When the blending amount of the conductive carbon material is equal to or less than the above-mentioned upper limit, the dispersion stability of the conductive carbon material can be further improved.

[0069] <Solvent> The solvent that can be optionally blended into the composite particles is not particularly limited, and examples thereof include the same solvents that can be blended into the conductive material dispersion of the present invention.

[0070] <Other Components> Other components that can be added to the composite particles are not particularly limited, and include the same components as those that can be added to the conductive material dispersion of the present invention.

[0071] <Other Conductive Materials> Other conductive materials that can be blended into the composite particles are not particularly limited, and examples thereof include the same conductive materials as those that can be blended into the conductive material dispersion of the present invention.

[0072] <Method for producing composite particles> The method for producing composite particles is not particularly limited, but composite particles can be produced by methods such as spray drying granulation, tumbling bed granulation, compression granulation, stirring granulation, extrusion granulation, crushing granulation, fluidized bed granulation, fluidized bed multifunctional granulation, and melt granulation. Among these, stirring granulation is preferred from the viewpoint of increasing the strength of the composite particles.

[0073] In the production of composite particles by the stirring granulation method, it is preferable to carry out the following steps in this order in a granulation tank equipped with two or more stirring blades having different stirring shafts: (i) a step of stirring a powder material containing an electrode active material to create a stirred state; (ii) a step of adding a composition containing a binder, a conductive additive, and a solvent to the powder material in the stirred state to form composite particles. Optionally, following the operation (ii) above, a step of regulating the size of the composite particles by stirring them after the addition of the composition is complete may be carried out.

[0074] (Electrode for electrochemical device) The electrode for electrochemical device of the present invention comprises, for example, a current collector and an electrode mixture layer formed on the current collector, the electrode mixture layer comprising at least an electrode active material, a conductive carbon material, and the binder of the present invention. That is, the electrode mixture layer contains at least an electrode active material and a binder (predetermined block copolymer), and may further contain, as desired, other components used in the field of electrochemical devices, conductive materials other than conductive carbon materials, and the like.

[0075] Furthermore, since the electrode of the present invention contains the binder of the present invention, it has excellent strength and can suppress an increase in resistance after cycling of the electrochemical device.

[0076] <Current Collector> Examples of materials that can be used for the current collector include metals, carbon, and conductive polymers, with metals being preferred. Metals that are typically used include copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel, and other alloys. Among these, copper, aluminum, or aluminum alloys are preferred in terms of conductivity and voltage resistance.

[0077] <Electrode mixture layer> <<Binder for electrochemical element>> The binder for electrochemical element to be blended in the electrode mixture layer may be any of those described above. The blending amount of the binder is not particularly limited, and may be the blending amount described above in the section "Composite particles for electrochemical element electrode."

[0078] <<Electrode active material>> The electrode active material to be blended in the electrode mixture layer is not particularly limited, and examples thereof include the same electrode active material as that blended in the composite particle of the present invention. The blending amount of the electrode active material is not particularly limited, and can be the blending amount described above in the section "Composite particle for electrochemical element electrode."

[0079] <<Conductive Carbon Material>> The conductive carbon material for the electrode mixture layer is not particularly limited, and examples thereof include the same conductive carbon materials that can be blended in the conductive material dispersion of the present invention. The blending amount of the conductive carbon material is not particularly limited, and can be the blending amount described above in the section "Composite particles for electrochemical element electrode."

[0080] <<Other Components>> Other components that can be optionally blended into the electrode mixture layer are not particularly limited, and examples thereof include the same components as those that can be blended into the conductive material dispersion of the present invention.

[0081] <<Other Conductive Materials>> Other conductive materials that can be blended into the composite particles are not particularly limited, and examples thereof include the same conductive materials as those that can be blended into the conductive material dispersion of the present invention.

[0082] In the following, an example will be described in which the electrode of the present invention is an electrode for a lithium ion secondary battery, but the present invention is not limited to the following example.

[0083] <Method for Manufacturing Electrodes for Lithium-Ion Secondary Batteries> Electrodes for lithium-ion secondary batteries are manufactured, for example, by a method of forming an electrode mixture layer on a current collector using the composite particles of the present invention described above. Alternatively, electrodes for lithium-ion secondary batteries are manufactured by coating a current collector with a slurry composition containing the binder of the present invention, an electrode active material, a conductive carbon material, a solvent, and other optional components, and drying the coating. Among these, the former method is preferred. This is because, in manufacturing methods using composite particles, the electrode mixture layer, which is composed of a packed layer of composite particles, tends to become flexible due to differences in porosity. The flexible electrode mixture layer is more likely to increase in press density, and the increased density increases the strength of the electrode mixture layer. Furthermore, in manufacturing methods using composite particles, the binder coverage on the electrode active material surface is lower than in conventional manufacturing methods involving the application of a slurry composition, resulting in a lower initial resistance of the resulting electrochemical device.

[0084] When a manufacturing method using composite particles is used, for example, an electrode for a lithium ion secondary battery can be manufactured by a method in which the composite particles of the present invention described above are formed into a sheet and then laminated on a current collector, or by a method in which the composite particles are directly pressure-molded on the current collector. Among these, the method of directly pressure-molding the composite particles on the current collector is preferred. Examples of pressure-molding methods include a roll pressure molding method in which a roll pressure molding device equipped with a pair of rolls is used, and while the current collector is being fed by the rolls, the composite particles are fed into the roll pressure molding device with a feeder such as a vibration feeder or a screw feeder to form an electrode active material layer on the current collector; a method in which the composite particles are sprayed on a current collector, smoothed with a blade or the like to adjust the thickness, and then molded with a pressure device; and a method in which the composite particles are filled into a mold and pressurized to mold the mold. Among these, the roll pressure molding method is preferred.

[0085] Furthermore, to eliminate variations in thickness of the formed lithium-ion secondary battery electrode and increase the density of the electrode active material layer to achieve high capacity, post-pressing may be performed as needed. A preferred method of post-pressing is a roll pressing process. In the roll pressing process, two cylindrical rolls are arranged parallel to each other with a small gap between them, rotated in opposite directions, and pressed by clamping the electrode between them. In this process, the temperature of the rolls may be adjusted, for example, by heating or cooling.

[0086] The latter method using a slurry composition may include a step of applying a slurry composition containing the above-described components 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).

[0087] Here, the method for preparing the slurry composition, the method for applying the slurry composition onto the current collector, and the method for drying the slurry composition on the current collector are not particularly limited, and conventionally known methods can be used. The amount of each of the above components in the slurry composition is not particularly limited, and can be the same as the amount described above in the section "Composite particles for electrochemical element electrodes."

[0088] (Electrochemical element) The electrochemical element of the present invention includes, for example, a positive electrode, a negative electrode, an electrolyte, and a separator, and uses the electrode of the present invention as at least one of the positive electrode and the negative electrode, preferably as the positive electrode. Since the electrochemical element of the present invention includes the electrode of the present invention, it is possible to suppress an increase in resistance after cycling. Hereinafter, a description will be given of a case where the electrochemical element is a lithium ion secondary battery as an example, but the present invention is not limited to the following example.

[0089] <Electrode> Known electrodes can be used as electrodes other than the electrode of the present invention. Specifically, the electrode can be, for example, a negative electrode made of a thin plate of metallic lithium, or an electrode formed by forming an electrode mixture layer on a current collector. The current collector can be made of a metal material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum. The electrode mixture layer can be a layer containing an electrode active material and a binder. Furthermore, the binder is not particularly limited, and any known material can be used.

[0090] <Electrolyte> As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. As the supporting electrolyte, for example, a lithium salt is used. As the lithium salt, for example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Among them, LiPF is particularly preferred because it is easily soluble in solvents and shows a high degree of dissociation. ６ , LiClO ４ , C.F. ３ SO ３ Li is preferred, and LiPF ６ is particularly preferred. Note that one type of electrolyte may be used alone, or two or more types may be used in combination in 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.

[0091] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (EMC) are preferred. Other suitable solvents include 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 because of their high dielectric constant and wide stable potential range, and a mixture of ethylene carbonate and ethyl methyl carbonate is even more preferred. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. For example, it is preferably 0.5 to 15% by mass, more preferably 2 to 13% by mass, and even more preferably 5 to 10% by mass.

[0092] <Separator> The separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, a microporous film made of a polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it allows the thickness of the entire separator to be thin, thereby increasing the proportion of electrode active material in the electrochemical device and increasing the capacity per volume.

[0093] The electrochemical element is assembled by, for example, stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the stack as necessary according to the shape of the electrochemical element, placing the stack in a container, injecting an electrolyte into the container, and sealing the container. To prevent internal pressure buildup, overcharging and overdischarging, and the like, a fuse, an overcurrent protection element such as a PTC element, expanded metal, lead plates, and the like may be provided as necessary. The shape of the assembled electrochemical element may be any of, for example, a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, and the like.

[0094] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a polymer produced by copolymerizing multiple types of monomers, the proportion of a structural unit formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that certain monomer to all monomers used in the polymerization of the polymer, unless otherwise specified. In the examples and comparative examples, various measurements and evaluations were performed as follows.

[0095] <Calculation of the proportion of units derived from 1,2- and 3,4-addition polymerization in the block region (B) and the proportion of units derived from 1,4-addition polymerization in the entire block copolymer> Except for Comparative Example 1, the polymer before hydrogenation was measured. The proportion of structural units derived from 1,4-, 1,2-, and 3,4-addition polymerization among the structural units derived from the chain conjugated diene compound in the block region (B) (homopolymer in Comparative Example 2) was calculated by the following formula: １ From the H-NMR spectrum (in deuterated chloroform), it was found that the carbon-carbon unsaturated bond in the polymer main chain １ H bonded to the carbon of the carbon-carbon unsaturated bond in the polymer side chain １ The proportion of units derived from 1,4-addition polymerization in the block region (B) was converted into a value (% by mass) based on the entire block copolymer.

[0096] <Hydrogenation rate> The hydrogenation rate is calculated before and after the hydrogenation reaction. １ H-NMR spectra were measured, and the hydrogenation ratios were calculated based on the reduction in the integrated values ​​of the signals corresponding to the unsaturated bonds in the main chain and side chain portions and the unsaturated bonds in the aromatic ring before and after the hydrogenation reaction. The hydrogenation ratio of the block region (A) was calculated based on the reduction rate of the signal corresponding to the unsaturated bonds in the aromatic ring, and the hydrogenation ratio of the block region (B) was calculated based on the reduction rate of the signal corresponding to the unsaturated bonds in the main chain and side chain portions.

[0097] <Weight-average molecular weight of polymer> The weight-average molecular weight of the polymer was measured by gel permeation chromatography (GPC) under the following measurement conditions: Separation column: Shodex KD-806M (manufactured by Showa Denko K.K.) Detector: Differential refractometer detector RID-10A (manufactured by Shimadzu Corporation) Eluent flow rate: 0.3 mL / min Column temperature: 40°C Standard polymer: TSK standard polystyrene (manufactured by Tosoh Corporation)

[0098] <Pressability of Electrode> The pre-press electrodes prepared in the Examples and Comparative Examples were cut into 100 mm widths and roll pressed at a speed of 1 m / min, a gap of 80 μm, and a press pressure of 14 t. The electrode density 5 minutes after passing through the roll press was evaluated from the punched weight of the electrode and evaluated according to the following criteria. A: Electrode density is 3.5 g / cm or less. ３ B: Electrode density is 3.4 g / cm or more ３ 3.5g / cm or more ３ C: Electrode density is less than 3.3 g / cm ３ 3.4g / cm or more ３ D: Electrode density is less than 3.2 g / cm ３ 3.3g / cm or more ３ E: Electrode density is less than 3.2 g / cm ３ less than

[0099] <Electrode Composite Layer Strength> The pressed electrodes produced in the Examples and Comparative Examples were cut into 10 mm widths, and the composite layer was attached to a test plate using double-sided tape. The current collecting foil was then peeled off to prepare a test piece for measuring the composite layer strength. An 8 mm wide tape was adhered to the test piece, and the strength of the electrode composite layer was measured by measuring the strength when the tape was peeled off from the end in a 90 degree direction at a speed of 100 mm / min using a load cell. The higher the electrode composite layer strength, the stronger the adhesion between the materials contained in the composite layer. A: Composite layer strength of 10 N / m or more B: Composite layer strength of 9 N / m or more but less than 10 N / m C: Composite layer strength of 8 N / m or more but less than 9 N / m D: Composite layer strength of 2 N / m or more but less than 8 N / m E: Composite layer strength less than 2 N / m

[0100] <Initial Resistance> After injecting the electrolyte, the lithium ion secondary batteries used as electrochemical elements prepared in the Examples and Comparative Examples were left standing at 25°C for 5 hours. Next, the batteries were charged to a cell voltage of 3.65 V at 25°C using a constant current of 0.2 C, and then aged for 12 hours at 60°C. Then, the batteries were discharged to a cell voltage of 3.00 V using a constant current of 0.2 C at 25°C. Subsequently, CC-CV charging was performed at 0.2 C (upper limit cell voltage: 4.20 V), followed by CC discharging to 3.00 V using a constant current of 0.2 C. This 0.2 C charge-discharge cycle was repeated three times to obtain an evaluation cell. The evaluation cell was CC-CV charged at 0.2 C (upper limit cell voltage: 4.20 V) in an environment of 25°C, followed by CC discharging to 3.00 V using a constant current of 0.2 C, and the discharge capacity was designated R1. Thereafter, CC-CV charging was performed again at 0.2 C (upper limit cell voltage 4.20 V), and CC discharge was performed to 3.00 V by a 2 C constant current method, and the discharge capacity was taken as R2. Using the discharge capacity R1 and the discharge capacity R2, the initial resistance = (R2 / R1) x 100 (%) was calculated and evaluated according to the following criteria. A higher initial resistance value indicates that the lithium ion secondary battery, which is an electrochemical element, has better resistance characteristics. A: Initial resistance of 80% or more B: Initial resistance of 70% or more but less than 80% C: Initial resistance of 50% or more but less than 70% D: Initial resistance of 30% or more but less than 50% E: Initial resistance less than 30%

[0101] <Cycle Characteristics> The evaluation cell was subjected to 100 cycles of charge / discharge at a charge / discharge rate of 0.5C, at a cell voltage of 4.20-3.00V, in an environment at a temperature of 45°C. The discharge capacity at the first cycle was defined as X1, and the discharge capacity at the 100th cycle as X2. Using the discharge capacities X1 and X2, the capacity retention rate = (X2 / X1) x 100 (%) was calculated and evaluated according to the following criteria. A larger value of the capacity retention rate indicates that the lithium ion secondary battery, which is an electrochemical element, has better cycle characteristics. A: Capacity retention rate is 95% or more B: Capacity retention rate is 90% or more but less than 95% C: Capacity retention rate is 85% or more but less than 90% D: Capacity retention rate is 80% or more but less than 85% E: Capacity retention rate is less than 80%

[0102] <Resistance increase rate after cycling> When measuring the charge-discharge cycle retention rate, the resistance value was calculated from the voltage drop (ΔV) and current value (I) during 10 seconds of discharge, and the resistance value at the first charge-discharge cycle was defined as Y1, and the resistance value at the 100th charge-discharge cycle was defined as Y2. Using the resistance values ​​Y1 and Y2, the resistance increase rate = (Y2 / Y1) x 100 (%) was calculated and evaluated according to the following criteria. A smaller value of the resistance increase rate indicates that the lithium ion secondary battery, which is an electrochemical element, has excellent properties even after cycling. A: Resistance increase rate is less than 110% B: Resistance increase rate is 110% or more and less than 130% C: Resistance increase rate is 130% or more and less than 150% D: Resistance increase rate is 150% or more and less than 200% E: Resistance increase rate is 200% or more

[0103] Example 1 Polymerization Step to Hydrogenation Step A reactor equipped with a stirrer and thoroughly purged with nitrogen was charged with 135 parts of dehydrated cyclohexane, 0.07 parts of dibutyl ether, and 6.8 parts of dehydrated styrene, and further added with 0.02 parts of n-butyllithium (15% cyclohexane solution). The entire volume was then stirred at 60°C for 20 minutes. Measurement of the reaction solution by gas chromatography revealed that the polymerization conversion at this point was 99.5%. Next, 31.5 parts of dehydrated isoprene was continuously added to the reaction solution over 30 minutes, and after the addition was completed, the entire volume was stirred for 30 minutes. The polymerization conversion at this point was 99.5%. Subsequently, 6.8 parts of dehydrated styrene was added and stirred for 20 minutes. The polymerization conversion at this point was 99.7%. The reaction was terminated by adding 0.1 parts of ethanol to the reaction solution, yielding a polymer solution. Next, the polymer solution was transferred to a pressure-resistant reactor equipped with a stirrer, and 0.3 parts of nickel (II) acetylacetonate as a hydrogenation catalyst and 1.2 parts of triisobutylaluminum as a co-catalyst were added, followed by adding 28 parts of dehydrated cyclohexane and mixing. The atmosphere inside the reactor was replaced with hydrogen gas, and hydrogen was further supplied while stirring the solution, and the hydrogenation reaction was carried out for 6 hours at a temperature of 80°C and a pressure of 0.9 MPa. Next, in order to remove metal components derived from the catalyst used during hydrogenation, 1.1 parts of malic acid and 0.2 parts of a nonionic surfactant block copolymer of ethylene oxide and propylene oxide (manufactured by ADEKA Corporation, product name "L-64") were dissolved in 500 parts of ion-exchanged water in the polymer solution, and the mixture was then added to the reactor and stirred for 5 hours. Thereafter, 1 part of a xylene solution in which 0.1 parts of pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (manufactured by Koyo Chemical Laboratory, product name "Songnox 1010"), a phenolic antioxidant, was dissolved, was added and dissolved. Cyclohexane was further added to obtain a binder solution in which the binder was dissolved in the solvent at a predetermined concentration.

[0104] <Preparation of Conductive Material Dispersion for Electrochemical Elements> Two parts of acetylene black (manufactured by Denka, trade name "Li-400") as a conductive carbon material and one part of binder solution (solids equivalent) were mixed, and cyclohexane as a solvent was added to prepare a mixture of acetylene black, binder, and solvent with a solids concentration of 5% and a total amount of 1 kg. Next, the resulting mixture was dispersed for 1 hour using a bead mill (LMZ015, manufactured by Ashizawa Fine Tech) using zirconia beads with a diameter of 0.5 mm at a peripheral speed of 12 m / s to prepare a conductive material dispersion containing carbon, binder, and solvent. The resulting conductive material dispersion had a solids concentration of 5% by mass.

[0105] <Preparation of Composite Particles> A composite particle preparation device was prepared. The granulation vessel was a cylindrical vessel with an inner diameter of 180 mm and a capacity of 2 L. The axis of the cylindrical vessel was the vertical direction, and two agitating blades were attached to the vertical and horizontal axes (the vertical agitating blade was the main agitating blade, and the horizontal agitating blade was the auxiliary agitating blade). The main agitating blade was an inclined paddle with three main blades each 170 mm in diameter, and the auxiliary agitating blade had a V-shaped anchor blade with a diameter of 30 mm. The main and auxiliary agitating blades were sealed by ventilating to prevent raw materials from being mixed into their drive mechanisms. Composite particles were prepared using the composite particle preparation device. First, 97 parts by mass (1,358 g) of NMC532 (average particle diameter 6 μm), a positive electrode active material for lithium-ion batteries, was added to the granulation vessel. Next, room temperature sealing air was circulated at 20 L / min (airflow rate 10 / min), and 3 parts by mass (42 g) of a binder-containing carbon paste (solid content concentration: 5% by mass, viscosity index: 10 mPa s, solvent: cyclohexane) was added over 30 minutes under the operating conditions of a main stirring blade peripheral speed of 5 m / s and a sub-stirring blade peripheral speed of 6 m / s. In this way, composite particles were produced.

[0106] <Preparation of Positive Electrode for Lithium-Ion Secondary Battery> The prepared composite particles were supplied to a press roll (roll temperature 100°C, press linear pressure 500 kN / m) of a roll press machine ("Press-Cut Rough Surface Hot Roll" manufactured by Hirano Giken Kogyo Co., Ltd.) using a quantitative feeder ("Nikka Spray K-V" manufactured by Nikka Corporation). An aluminum foil having a thickness of 20 μm was inserted between the press rolls, and the composite particles supplied from the quantitative feeder were adhered to the aluminum foil and press-molded at a molding speed of 1.5 m / min to a basis weight of 20 mg / cm. 2 This pre-press electrode was rolled using a roll press to obtain a pre-press electrode for a lithium ion secondary battery having a positive electrode active material layer of 3.5 g / cm. ３ A sheet-shaped positive electrode (pressed electrode) consisting of the positive electrode mixture layer and aluminum foil was prepared. <Preparation of Negative Electrode> 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid as an acidic group-containing monomer, 63.5 parts of styrene, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.5 parts of potassium persulfate as a polymerization initiator were placed in a 5 MPa pressure vessel equipped with a stirrer, thoroughly stirred, and then heated to 50°C to initiate polymerization. When the polymerization conversion rate reached 96%, the mixture was cooled to terminate the polymerization reaction, yielding a mixture containing a particulate binder (styrene-butadiene copolymer). A 5% aqueous sodium hydroxide solution was added to this mixture to adjust the pH to 8, and unreacted monomer was removed by heated vacuum distillation. The mixture was then cooled to 30°C or below to obtain an aqueous dispersion containing a negative electrode binder. Next, 48.75 parts of artificial graphite as a negative electrode active material, 48.75 parts of natural graphite, and 1 part of carboxymethyl cellulose as a thickener were added to a planetary mixer. The mixture was then diluted with ion-exchanged water to a solids concentration of 60%, and then kneaded for 60 minutes at a rotation speed of 45 rpm. Then, 1.5 parts of the aqueous dispersion containing the negative electrode binder obtained as described above, equivalent to the solids content, was added, and the mixture was kneaded for 40 minutes at a rotation speed of 40 rpm. Then, ion-exchanged water was added to obtain a viscosity of 3000±500 mPa·s (measured with a Brookfield viscometer at 25°C and 60 rpm), thereby preparing a negative electrode composite layer slurry. Next, a 15 μm thick copper foil was prepared as a current collector. The negative electrode composite layer slurry was applied to the copper foil in a coating amount of 8 mg / cm after drying.２ The coating was dried at 60°C for 20 minutes and at 120°C for 20 minutes. Thereafter, the coating was heated at 150°C for 2 hours to obtain a negative electrode blank. This negative electrode blank was rolled using a roll press to a density of 1.6 g / cm. ３ A sheet-shaped negative electrode was fabricated consisting of the negative electrode composite layer (both sides) and copper foil. <Fabrication of Lithium-ion Secondary Battery> A single-layer laminate cell (discharge capacity equivalent to 50 mAh) was fabricated using the above positive electrode, negative electrode, and separator (made of polyethylene, thickness 12 μm) and placed in an aluminum package. Then, a 1.0 M LiPF 6 electrolyte was placed in the aluminum package. ６ A solution (solvent: a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), additive: containing 2 volume % vinylene carbonate (solvent ratio)) was filled. Furthermore, in order to seal the opening of the aluminum packaging, the aluminum packaging was closed by heat sealing at a temperature of 150°C, and a lithium ion secondary battery was produced. Various attributes were evaluated using this lithium ion secondary battery. The results are shown in Table 1.

[0107] (Example 2) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the <Polymerization step to Hydrogenation step>, 0.07 parts of dibutyl ether was replaced with 0.5 parts of ethylene glycol dibutyl ether so that the proportion of units derived from 1,4-addition polymerization of an aliphatic conjugated diene monomer in the block copolymer was as shown in Table 1. The results are shown in Table 1.

[0108] (Example 3) In the <Polymerization step to Hydrogenation step>, the amounts of dehydrated styrene, dehydrated isoprene, and dehydrated styrene were changed to 3.8 parts, 37.5 parts, and 3.8 parts, respectively, and dibutyl ether was changed to 0.05 parts, so that the proportions of units derived from 1,4-addition polymerization of an aliphatic conjugated diene monomer in the block copolymer and the proportions of block regions (A) and (B) in the block copolymer were as 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.

[0109] Example 4 In the <Polymerization step to Hydrogenation step>, the amounts of dehydrated styrene, dehydrated isoprene, and dehydrated styrene were changed to 11.3 parts, 22.5 parts, and 11.3 parts, respectively, so that the ratios of block regions (A) and (B) in the block copolymer and, accordingly, the ratios of units derived from 1,4-addition polymerization of an aliphatic conjugated diene monomer in the block copolymer were as 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.

[0110] (Example 5) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the <polymerization step to hydrogenation step>, butadiene was used instead of isoprene as the aliphatic conjugated diene monomer. The results are shown in Table 1.

[0111] (Example 6) In the <Polymerization step to Hydrogenation step>, a mixture of isoprene and butadiene was used as the aliphatic conjugated diene monomer. Specifically, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that a mixture of isoprene and butadiene in a mass ratio of 50:50 was used. The results are shown in Table 1.

[0112] (Example 7) In the <polymerization step to hydrogenation step>, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the temperature during the hydrogenation reaction was changed to 60°C and the time was changed to 3 hours so that the hydrogenation rate of the block region (B) would be as shown in Table 1. The results are shown in Table 1.

[0113] (Example 8) In the <polymerization step to hydrogenation step>, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that 7.0 parts of a diatomaceous earth-supported nickel catalyst (manufactured by JGC Catalysts and Chemicals, product name "E22U", nickel loading: 60%) was used as the hydrogenation catalyst instead of the hydrogenation catalyst and co-catalyst so that the hydrogenation rate of the block region (A) would be as shown in Table 1. The results are shown in Table 1.

[0114] (Example 9) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the <polymerization step to hydrogenation step>, the amount of n-butyllithium was changed to 0.01 part so that the weight average molecular weight of the block copolymer was as shown in Table 1. The results are shown in Table 1.

[0115] (Example 10) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the <Polymerization step to Hydrogenation step>, the amount of n-butyllithium was changed to 0.04 parts so that the weight average molecular weight of the block copolymer would be as shown in Table 1. The results are shown in Table 1.

[0116] (Example 11) In the <Polymerization Step>, the following changes were made so that the structure of the block copolymer would be a diblock structure. Except for this, various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. <Polymerization Step> A reactor equipped with a stirrer and thoroughly purged with nitrogen was charged with 120 parts of dehydrated cyclohexane, 0.07 parts of dibutyl ether, and 12.6 parts of dehydrated styrene, and 0.02 parts of n-butyllithium (15% cyclohexane solution). The entire volume was then stirred at 50°C for 30 minutes. Measurement of the reaction solution by gas chromatography revealed that the polymerization conversion at this point was 99.5%. Next, 31.5 parts of dehydrated isoprene was continuously added to the reaction solution over 30 minutes, and after the addition was completed, the entire volume was stirred for 30 minutes. The polymerization conversion at this point was nearly 100%. The reaction was then stopped by adding 0.3 parts of ethanol to the reaction solution, yielding a polymer solution in which the polymer was dissolved in the solvent.

[0117] (Example 12) Without producing composite particles, a binder solution prepared in the same manner as in Example 1 was used. First, 96 parts by mass (1,344 g) of NMC532 (average particle diameter: 6 μm) as a positive electrode active material for lithium ion batteries was added to a planetary mixer. With the main stirring blade operating at a peripheral speed of 5 m / s, 4 parts by mass (56 g) of a binder-containing carbon paste (solid content concentration: 5% by mass, viscosity index: 10 mPa s, solvent: cyclohexane) was added as solids to produce a slurry composition. The slurry composition was applied to aluminum foil with a thickness of 20 μm and dried to produce a slurry with a basis weight of 20 mg / cm. ２ A pre-press electrode for a lithium ion secondary battery having a positive electrode active material layer of 1000 μm was obtained. Except for these points, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0118] (Comparative Example 1) In the <Polymerization Step>, the following changes were made so that the resulting polymer would have a single structure without block regions. Except for these changes, various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. <Polymerization Step> A reactor equipped with a stirrer and the inside of which had been thoroughly purged with nitrogen was charged with 120 parts of dehydrated cyclohexane, 0.07 parts of dibutyl ether, and 45.1 parts of dehydrated styrene, and 0.02 parts of n-butyllithium (15% cyclohexane solution). The entire contents were then stirred at 50°C for 30 minutes. The polymerization conversion at this point was nearly 100%. Here, 0.3 parts of ethanol was added to the reaction solution to terminate the reaction, and a polymer solution in which the polymer was dissolved in the solvent was obtained.

[0119] (Comparative Example 2) In the <Polymerization Step>, the following changes were made so that the resulting polymer would have a single structure without block regions. Except for these changes, various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. <Polymerization Step> 120 parts of dehydrated cyclohexane, 0.07 parts of dibutyl ether, and 45.1 parts of dehydrated isoprene were placed in a reactor equipped with a stirrer and the inside of which had been thoroughly purged with nitrogen, and 0.02 parts of n-butyllithium (15% cyclohexane solution) was further added. The entire contents were then stirred at 50°C for 30 minutes. The polymerization conversion rate at this point was nearly 100%. Here, 0.3 parts of ethanol was added to the reaction solution to terminate the reaction, and a polymer solution in which the polymer was dissolved in the solvent was obtained.

[0120] (Comparative Example 3) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the <Polymerization step to Hydrogenation step>, 0.7 parts of ethylene glycol dibutyl ether was used instead of 0.07 parts of dibutyl ether so that the proportion of units derived from 1,4-addition polymerization of an aliphatic conjugated diene monomer in the block copolymer was as shown in Table 1. The results are shown in Table 1.

[0121] (Comparative Example 4) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the <Polymerization step to Hydrogenation step>, 0.03 parts of dibutyl ether was used instead of 0.07 parts, so that the proportion of units derived from 1,4-addition polymerization of an aliphatic conjugated diene monomer in the block copolymer was as shown in Table 1. The results are shown in Table 1.

[0122] (Comparative Example 5) Except for not carrying out the <hydrogenation step>, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0123]

[0124] The results shown in Table 1 indicate that Examples 1 to 12, which used a binder containing a block region (A) composed of aromatic vinyl monomer units and a block region (B) at least a portion of which was composed of hydrogenated aliphatic conjugated diene monomer units, and in which the proportion of units derived from the 1,4-addition polymerization of the aliphatic conjugated diene monomer in the block copolymer was 28% by mass or more and 75% by mass or less, were able to provide electrochemical elements that increased the strength of the electrode mixture layer and suppressed an increase in resistance after cycling. On the other hand, Comparative Examples 1 and 2, in which a polymer without a block structure was used as the binder instead of the block copolymer, Comparative Example 3, in which the proportion of units derived from the 1,4-addition polymerization of the aliphatic conjugated diene monomer was less than 28% by mass, Comparative Example 4, in which the proportion of units derived from the 1,4-addition polymerization of the aliphatic conjugated diene monomer was more than 75% by mass, and Comparative Example 5, in which the block region (B) was not hydrogenated, were unable to simultaneously increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling.

[0125] According to the present invention, it is possible to provide a binder for electrochemical elements that can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling, and it is also possible to provide a conductive material dispersion for electrochemical elements and composite particles for electrochemical element electrodes that can increase the strength of the electrode mixture layer and suppress an increase in resistance after cycling of the electrochemical element. Furthermore, it is possible to provide an electrode for electrochemical elements that has a high-strength electrode mixture layer and that can suppress an increase in resistance after cycling of the electrochemical element, and an electrochemical element in which an increase in resistance after cycling is suppressed.

Claims

1. A binder for electrochemical elements, the binder being a block copolymer comprising at least a block region (A) and a block region (B), the block region (A) being a block region made of aromatic vinyl monomer units, the block region (B) being a block region made at least in part of hydrogenated aliphatic conjugated diene monomer units, and the proportion of units derived from 1,4-addition polymerization of the aliphatic conjugated diene monomer in the block copolymer being 28% by mass or more and 75% by mass or less.

2. The binder for electrochemical elements according to claim 1, wherein the hydrogenation rate of the block region (A) is 50% or less.

3. The binder for electrochemical elements according to claim 1, wherein the hydrogenation rate of the block region (B) is 50% or more.

4. The binder for electrochemical elements according to claim 1, wherein the proportion of the block region (A) in the block copolymer is 10% by mass or more and 50% by mass or less.

5. The binder for electrochemical elements according to claim 1, wherein the weight average molecular weight of the block copolymer is 50,000 or more and 500,000 or less.

6. The binder for an electrochemical element according to claim 1, wherein the block copolymer is a multiblock copolymer.

7. The binder for an electrochemical element according to claim 6, wherein the block copolymer is a triblock copolymer.

8. A conductive material dispersion for electrochemical elements, comprising a conductive carbon material, a solvent, and the binder for electrochemical elements according to any one of claims 1 to 7.

9. Composite particles for an electrochemical element electrode, comprising an electrode active material, a conductive carbon material, and the binder for an electrochemical element according to any one of claims 1 to 7.

10. An electrode for an electrochemical element, comprising an electrode mixture layer containing an electrode active material, a conductive carbon material, and the binder for an electrochemical element according to any one of claims 1 to 7.

11. An electrochemical element comprising the electrode for an electrochemical element according to claim 10.

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