Binder composition for electrochemical element, electroconductor dispersant for electrochemical element, composite particles for electrochemical element electrode, electrode for electrochemical element, and electrochemical element

Abstract

The purpose of the present invention is to provide a binder composition for an electrochemical element, the binder composition being capable of causing an electrochemical element to exhibit excellent high-temperature storage properties. This binder composition for an electrochemical element is characterized by comprising at least one metal element selected from the group consisting of nickel, titanium, and chromium, and a polymer having a degree of swelling in an electrolyte solution of no greater than 2.5 times.

Description

Binder composition for electrochemical elements, conductive material dispersion for electrochemical elements, composite particles for electrodes of electrochemical elements, electrodes for electrochemical elements, and electrochemical elements

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

[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] Here, electrodes of electrochemical elements such as lithium ion secondary batteries typically include a current collector and an electrode mixture layer (positive electrode mixture layer, negative electrode mixture layer) formed on the current collector. Methods under consideration for forming the electrode mixture layer include a method of forming an electrode mixture layer by applying a slurry composition containing an electrode active material, a conductive material, a binder, and a solvent onto an electrode substrate and drying the slurry composition, and a method of forming an electrode mixture layer by spray-drying a slurry composition containing an electrode active material, a conductive material, a binder, and a solvent to obtain composite particles, and then pressure-molding the obtained composite particles onto the electrode substrate.

[0004] In recent years, attempts have been made to improve the binder compositions and slurry compositions used in forming the electrode mixture layer in order to achieve further improvements in the performance of electrochemical elements.

[0005] Specifically, for example, Patent Document 1 discloses a binder containing iron and at least one of ruthenium and rhodium, wherein the total content of the iron, ruthenium, and rhodium is 5×10 per 100 parts by mass of the first binder. －３ In Patent Document 1, the binder composition is used to improve the life characteristics of a secondary battery.

[0006] International Publication No. 2016 / 103730

[0007] However, the binder compositions of the above-mentioned prior art have room for improvement in terms of improving the high-temperature storage characteristics of electrochemical devices.

[0008] Therefore, an object of the present invention is to provide a binder composition for electrochemical elements that can provide excellent high-temperature storage properties for electrochemical elements. 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 provide excellent high-temperature storage properties for electrochemical elements. A further object of the present invention is to provide an electrode for electrochemical elements that can provide excellent high-temperature storage properties for electrochemical elements, and an electrochemical element that has excellent high-temperature storage properties.

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems, and have newly discovered that by using a binder composition for electrochemical elements containing a predetermined metal element and a polymer having a swelling degree in an electrolyte solution of a predetermined value or less, an electrochemical element including an electrode fabricated using the binder composition for electrochemical elements can exhibit excellent high-temperature storage properties, thereby completing the present invention.

[0010] That is, the present invention aims to advantageously solve the above-mentioned problems, and the present invention provides [1] a binder composition for electrochemical elements, comprising at least one metal element selected from the group consisting of nickel, titanium, and chromium, and a polymer having an electrolyte swelling ratio of 2.5 times or less. Thus, by using a binder composition for electrochemical elements containing a predetermined metal element and a polymer having an electrolyte swelling ratio of a predetermined value or less, an electrochemical element including an electrode fabricated using the binder composition can exhibit excellent high-temperature storage properties. In the present invention, the "electrolyte swelling ratio of the polymer" can be measured by the method described in the Examples.

[0011] [2] In the binder composition for electrochemical elements according to [1] above, the total concentration of the metal elements is preferably 0.5 ppm or more and 50 ppm or less. Thus, if the total concentration of the specified metal elements is within the above-mentioned range, the electrochemical element can exhibit even better high-temperature storage properties. In the present invention, the concentration of the metal elements can be measured by the method described in the Examples.

[0012] [3] In the binder composition for electrochemical elements according to the above [1], the total concentration of the metal elements is preferably 40 ppm or less. In this way, when the total concentration of the predetermined metal elements is within the above-mentioned range, the electrochemical element can exhibit even better high-temperature storage properties.

[0013] [4] In the binder composition for electrochemical elements according to the above item [1], the total concentration of the metal elements is preferably 30 ppm or less. In this way, when the total concentration of the predetermined metal elements is within the above-mentioned range, the electrochemical element can exhibit even better high-temperature storage properties.

[0014] [5] In the binder composition for electrochemical elements according to any one of [1] to [4] above, the metal element is preferably nickel. In this way, by including nickel as the metal element in the binder composition for electrochemical elements, the electrochemical element can exhibit even better high-temperature storage properties.

[0015] [6] In the binder composition for electrochemical elements according to any one of [1] to [5] above, the polymer preferably contains a block A consisting of a first repeating unit and a block B consisting of a second repeating unit. In this way, if the polymer contains two types of blocks A and B each consisting of a predetermined repeating unit, the electrochemical element can exhibit even better high-temperature storage properties.

[0016] [7] In the binder composition for electrochemical elements according to [6] above, the polymer preferably has a structure in which the block A is bonded to both ends of the block B. If the polymer has a structure in which the block A is bonded to both ends of the block B, the adhesive strength of the electrode can be improved and the electrochemical element can exhibit even better high-temperature storage properties.

[0017] [8] In the binder composition for electrochemical elements according to [6] or [7] above, the first repeating unit of the block A is preferably an aromatic vinyl monomer unit. If the block A is composed of an aromatic vinyl monomer unit, the electrochemical element can exhibit even better high-temperature storage properties.

[0018] [9] In the binder composition for an electrochemical element according to any one of the above [6] to [8], the second repeating unit of the block B is preferably at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit. Thus, when the block B is composed of at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit, the electrode resistivity can be reduced.

[0019]

[10] In the binder composition for an electrochemical element according to any one of [6] to [9] above, the weight-average molecular weight of the block A is preferably 5,000 or more and 200,000 or less. Thus, if the weight-average molecular weight of the block A is within the above range, the electrode resistivity can be reduced while the adhesive strength of the electrode can be improved. In the present invention, the weight-average molecular weight of the block A can be measured by the method described in the Examples.

[0020]

[11] In the binder composition for electrochemical elements according to any one of [6] to

[10] above, the weight-average molecular weight of the block B is preferably 5,000 or more and 300,000 or less. Thus, when the weight-average molecular weight of the block B is equal to or more than the above-mentioned lower limit, the electrode resistivity can be reduced while improving the adhesive strength of the electrode. Furthermore, when the weight-average molecular weight of the block B is equal to or less than the above-mentioned upper limit, an increase in the viscosity of the binder composition for electrochemical elements can be suppressed, thereby improving the productivity of the electrochemical element. In the present invention, the weight-average molecular weight of the block B can be measured by the method described in the Examples.

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

[12] a conductive material dispersion for electrochemical elements, comprising the binder composition for electrochemical elements according to any one of [1] to

[11] above, a conductive carbon material, and a solvent. In this way, by using a conductive material dispersion for electrochemical elements containing the binder composition for electrochemical elements, it is possible to make the electrochemical element exhibit excellent high-temperature storage properties.

[0022] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides composite particles for electrochemical element electrodes, comprising

[13] an electrode active material and any one of the binder compositions for electrochemical elements described above in [1] to

[11] . In this way, by using composite particles for electrochemical element electrodes, comprising an electrode active material and the binder composition for electrochemical elements, it is possible to form an electrode mixture layer that can enable an electrochemical element to exhibit excellent high-temperature storage properties.

[0023] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides an electrode for an electrochemical device, comprising an electrode mixture layer containing

[14] an electrode active material and any one of the binder compositions for electrochemical devices described above in [1] to

[11] . In this way, when an electrode has an electrode mixture layer containing the binder composition for an electrochemical device, the electrochemical device can exhibit excellent high-temperature storage properties.

[0024] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides

[15] an electrochemical element comprising the electrode for electrochemical elements according to the above

[14] . In this way, by using the electrode for electrochemical elements, an electrochemical element having excellent high-temperature storage properties can be obtained.

[0025] According to the present invention, it is possible to provide a binder composition for electrochemical elements that can provide excellent high-temperature storage properties to electrochemical elements. Also, according to the present invention, it is possible to provide a conductive material dispersion for electrochemical elements and composite particles for electrochemical element electrodes that can provide excellent high-temperature storage properties to electrochemical elements. Furthermore, according to the present invention, it is possible to provide an electrode for electrochemical elements that can provide excellent high-temperature storage properties to electrochemical elements, and an electrochemical element that has excellent high-temperature storage properties.

[0026] Hereinafter, embodiments of the present invention will be described in detail. Here, the binder composition for electrochemical elements of the present invention (hereinafter also simply referred to as "binder composition") 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.

[0027] (Binder Composition for Electrochemical Elements) The binder composition for electrochemical elements of the present invention is characterized by containing at least one metal element selected from the group consisting of nickel, titanium, and chromium, and a polymer having an electrolyte swelling ratio of 2.5 times or less. The binder composition of the present invention may further contain, as optional components, components used in the field of electrochemical elements in addition to the components described above. The binder composition of the present invention may contain a solvent, but is preferably substantially solvent-free. Here, "substantially solvent-free" means that the binder composition does not contain any solvent other than that inevitably mixed in during the preparation process of the binder composition. Furthermore, the binder composition of the present invention typically does not contain an electrode active material or a conductive material.

[0028] Furthermore, the binder composition of the present invention contains at least one metal element selected from the group consisting of nickel, titanium, and chromium (hereinafter simply referred to as the "predetermined metal element") and a polymer having an electrolyte swelling ratio of 2.5 times or less. This allows an electrochemical device equipped with an electrode having an electrode mixture layer formed using the binder composition to exhibit excellent high-temperature storage properties. While the mechanism is not entirely clear, it is presumed to be as follows. That is, the binder forms a coating in the electrode mixture layer of the electrode, and cracks or the like may occur in the formed binder coating, resulting in a deterioration of high-temperature storage properties. It is presumed that when a specific metal exhibiting catalytic activity is present in a polymer having an electrolyte swelling ratio of less than a predetermined value, it reacts with the electrolyte additive at defects such as cracks in the binder coating, which is thought to also function as a protective coating, to form a protective coating that fills the defects. In particular, the above-mentioned specified metal elements have a base oxidation-reduction potential, and are easily oxidized and ionized within the electrochemical element, and are coordinated to the double bonds of the electrolyte and electrolyte additives such as vinylene carbonate. This is thought to be highly effective in filling defects in the protective coating, resulting in improved high-temperature storage characteristics of the electrochemical element.

[0029] <Metal Element> The binder composition of the present invention is required to contain at least one metal element selected from the group consisting of nickel, titanium, and chromium. In particular, from the viewpoint of further improving the high-temperature storage characteristics of an electrochemical device, the binder composition of the present invention preferably contains nickel as the predetermined metal element, and more preferably contains only nickel. Note that the binder composition may contain metal elements other than the predetermined metal elements as long as the effects of the present invention are not impaired.

[0030] The predetermined metal element contained in the binder composition may be derived from a substance (e.g., a hydrogenation catalyst) used in preparing the polymer, or may be introduced by adding a compound containing the predetermined metal element, such as an organometallic complex, to the binder composition. The predetermined metal element is usually present in the binder composition in the form of a metal element alone or an ion complexed with a ligand.

[0031] The total concentration of the specified metal elements contained in the binder composition is preferably 0.5 ppm or more, more preferably 3 ppm or more, and even more preferably 5 ppm or more. It is also preferably 50 ppm or less, more preferably 40 ppm or less, even more preferably 30 ppm or less, even more preferably 28 ppm or less, even more preferably 20 ppm or less, and particularly preferably 19 ppm or less. If the total concentration of the specified metal elements is above the above-mentioned lower limit, the reaction with the electrolyte additives and the like is promoted in the defective portions of the binder protective coating, improving the effect of filling the defective portions, thereby further improving the high-temperature storage characteristics of the electrochemical element. Furthermore, if the total concentration of the specified metal elements is below the above-mentioned upper limit, the reaction with the electrolyte additives and the like in unnecessary portions is suppressed, thereby suppressing gas generation and other problems, thereby preventing deterioration of the high-temperature storage characteristics of the electrochemical element. The total concentration of the predetermined metal elements can be adjusted by changing the conditions for washing and / or precipitating the polymer during preparation of the polymer (the amount of solvent used for precipitation), the amount of hydrogenation catalyst containing the predetermined metal element used, and / or the amount of compound containing the predetermined metal element added to the binder composition.

[0032] <Polymer> The polymer contained in the binder composition is a component that can hold components contained in an electrode mixture layer so that they do not detach from the electrode mixture layer in an electrode having the electrode mixture layer produced using the binder composition (i.e., can function as a binder).

[0033] [Polymer Properties] The polymer contained in the binder composition must have an electrolyte swelling ratio of 2.5 times or less. If the electrolyte swelling ratio of the polymer exceeds 2.5 times, the polymer will swell excessively with the electrolyte, resulting in the obstruction of the conductive path in the electrode mixture layer and the deterioration of the high-temperature storage characteristics of the electrochemical element. Furthermore, if the electrolyte swelling ratio of the polymer exceeds 2.5 times, the polymer contains a large amount of electrolyte, so its function as a protective film is reduced, and the effect of filling partial defects due to the inclusion of the specified metal element is not fully achieved. From the viewpoint of further improving the high-temperature storage characteristics of the electrochemical element, the electrolyte swelling ratio of the polymer is preferably 1.75 times or less, more preferably 1.45 times or less, and even more preferably 1.3 times or less. Furthermore, from the viewpoint of suppressing an increase in the resistance of the electrode, the electrolyte swelling ratio of the polymer is preferably 1.1 times or more. The degree of swelling of the polymer in the electrolyte can be controlled, for example, by adjusting the composition of the polymer or, when the polymer is a hydrogenated polymer, by adjusting the hydrogenation rate.

[0034] The weight-average molecular weight of the polymer contained in the binder composition is preferably 10,000 or more, more preferably 15,000 or more, and preferably 700,000 or less, more preferably 600,000 or less. If the weight-average molecular weight of the polymer is equal to or greater than the lower limit, the adhesive strength of the electrode can be improved. If the weight-average molecular weight of the polymer is equal to or less than the upper limit, an excessive increase in the viscosity of the solution can be suppressed, and a stable dispersion can be provided. The weight-average molecular weight of the polymer can be measured by the method described in the Examples.

[0035] [Polymer Composition] The polymer is not particularly limited, but preferably contains an aromatic vinyl monomer unit and at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit, and may optionally further contain repeating units other than the aromatic vinyl monomer unit, the aliphatic conjugated diene monomer unit, and the alkylene structural unit (hereinafter simply referred to as "other repeating units"). Note that "containing a monomer unit" means that "a polymer obtained using that monomer contains a structural unit derived from the monomer."

[0036] [[Aromatic vinyl monomer unit]] Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include, but are not limited to, styrene, styrene sulfonic acid and its salts, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. These may be used alone or in combination of two or more in any ratio. Among these, styrene is preferred from the viewpoint of further improving the high-temperature storage characteristics of the electrochemical element.

[0037] The proportion of aromatic vinyl monomer units in the polymer is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 80% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 50% by mass or less, when the amount of all repeating units (monomer units and structural units) in the polymer is taken as 100% by mass. The content of aromatic vinyl monomer units within the above range can improve the adhesive strength of the electrode. When the polymer has a block A (described below) composed of aromatic vinyl monomer units, the proportion of the aromatic vinyl monomer units in the polymer typically coincides with the proportion of the block A in the polymer.

[0038] [[Aliphatic Conjugated Diene Monomer Unit]] Examples of aliphatic conjugated diene monomers that can form aliphatic conjugated diene monomer units include aliphatic 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. Of these, isoprene and 1,3-butadiene are preferred from the viewpoint of further improving the high-temperature storage characteristics of electrochemical elements.

[0039] [[Alkylene structural unit]] The alkylene structural unit is represented by the general formula: -C ｎ H ２ｎ- [where n is an integer of 2 or greater]. The alkylene structural unit may be linear or branched, but the alkylene structural unit is preferably linear, i.e., a linear alkylene structural unit. The alkylene structural unit preferably has 4 or more carbon atoms (i.e., n in the above general formula is an integer of 4 or greater).

[0040] Here, the method for introducing alkylene structural units into a polymer is not particularly limited, and examples thereof include the following methods (1) and (2): (1) a method in which a polymer is prepared from a monomer composition containing an aliphatic conjugated diene monomer and the polymer is hydrogenated to convert the aliphatic conjugated diene monomer units into alkylene structural units; (2) a method in which a polymer is prepared from a monomer composition containing a 1-olefin monomer (e.g., ethylene, propylene, 1-butene, 1-hexene, etc.). Among these, method (1) is preferred because it allows for easy production of the polymer.

[0041] Examples of the aliphatic conjugated diene monomer used in the above method (1) include conjugated diene compounds having 4 or more carbon atoms, such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, and 1,3-pentadiene. Among these, 1,3-butadiene and isoprene are preferred. That is, the alkylene structural unit is preferably a structural unit obtained by hydrogenating an aliphatic conjugated diene monomer unit (aliphatic conjugated diene hydride unit), and more preferably a structural unit obtained by hydrogenating a 1,3-butadiene unit (1,3-butadiene hydride unit) or a structural unit obtained by hydrogenating an isoprene unit (isoprene hydride unit).

[0042] The above-mentioned aliphatic conjugated diene monomers and 1-olefin monomers can be used alone or in combination of two or more kinds.

[0043] The total proportion of the aliphatic conjugated diene monomer and the alkylene structural unit in the polymer is preferably 20% by mass or more, more preferably 35% by mass or more, and even more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less, when the amount of all repeating units (structural units and monomer units) in the polymer is taken as 100% by mass. When the total proportion of the aliphatic conjugated diene monomer and the alkylene structural unit in the polymer is within the above range, the resistivity of the electrode can be reduced. When the polymer has a block B (described below) composed of aliphatic conjugated diene monomer units and alkylene structural units, the total proportion of the aliphatic conjugated diene monomer units and the alkylene structural unit in the polymer usually coincides with the proportion of the block B in the polymer.

[0044] [Other Repeating Units] Monomers that can form other repeating units (hereinafter also referred to as "other monomers") are not particularly limited, and examples include (meth)acrylic acid ester monomers and polymerizable monomers having a hydrophilic group. These monomers can be used alone or in combination of two or more. In the present invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0045] Here, examples of the (meth)acrylic acid ester monomer include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate; and alkyl methacrylates such as ethyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. Among these, preferred (meth)acrylic acid ester monomers are ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate, with n-butyl acrylate being more preferred.

[0046] Examples of polymerizable monomers having a hydrophilic group include monomers having a carboxylic acid group, monomers having a sulfonic acid group, monomers having a phosphoric acid group, and monomers having a hydroxyl group. From the viewpoint of increasing the binding strength of the polymer, the hydrophilic group is preferably a carboxylic acid group or a sulfonic acid group, and more preferably a carboxylic acid group.

[0047] Examples of monomers having a carboxylic acid group include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid esters such as methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleates. Examples of dicarboxylic acid anhydrides include maleic anhydride, acrylic anhydride, methylmaleic anhydride, and dimethylmaleic anhydride. Further, as the monomer having a carboxylic acid group, an acid anhydride that generates a carboxyl group upon hydrolysis can also be used.Other examples include monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate.

[0048] Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, etc. In the present invention, "(meth)allyl" means allyl and / or methallyl.

[0049] Examples of the monomer having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, ethyl-(meth)acryloyloxyethyl phosphate, etc. In the present invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0050] Examples of the monomer having a hydroxyl group include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-butene-1-ol, and 5-hexene-1-ol; alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconate; and compounds of the general formula: CH ２ =CR １ -COO-(C ｎ H ２ｎ O) ｍ -H (wherein m is an integer from 2 to 9, n is an integer from 2 to 4, R １represents hydrogen or a methyl group) and (meth)acrylic acid esters; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; alkyl ethers such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, and (meth)allyl-6-hydroxyhexyl ether; mono(meth)allyl ethers of ethylene glycol; polyoxyalkylene glycol mono(meth)allyl ethers such as diethylene glycol mono(meth)allyl ether and dipropylene glycol mono(meth)allyl ether; mono(meth)allyl ethers of halogen- and hydroxy-substituted (poly)alkylene glycols such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether and (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyhydric phenols such as eugenol and isoeugenol, and halogen-substituted products thereof; (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether; and the like.

[0051] The proportion of the other repeating units in the polymer is preferably 10% by mass or less, and more preferably 5% by mass or less, when the amount of all repeating units (structural units and monomer units) in the polymer is taken as 100% by mass. If the proportion of the other repeating units is not more than the above upper limit, the adhesive strength of the electrode can be improved.

[0052] [Hydrogenation Rate] When a polymer containing aromatic vinyl monomer units and alkylene structural units is produced using the method (1) above, the hydrogenation rate of aromatic carbon-carbon unsaturated bonds (i.e., the proportion of hydrogenated carbon-carbon unsaturated bonds in the aromatic rings of the aromatic vinyl monomer units, etc.) is preferably 50% or less, more preferably 30% or less, even more preferably 15% or less, even more preferably 3% or less, and particularly preferably 0%. When the hydrogenation rate of aromatic carbon-carbon unsaturated bonds of the aromatic vinyl monomer units is equal to or less than the upper limit described above, the electrode resistivity can be reduced. When the polymer is composed of a block A (described below) composed of aromatic vinyl monomer units and a block B (described below) composed of at least one of aliphatic conjugated diene monomer units and alkylene structural units, the hydrogenation rate of aromatic carbon-carbon unsaturated bonds usually matches the hydrogenation rate of aromatic carbon-carbon unsaturated bonds of block A.

[0053] Furthermore, when the above-described method (1) is used to produce a polymer containing alkylene structural units, the hydrogenation rate of non-aromatic carbon-carbon unsaturated bonds such as olefinic double bonds (i.e., the proportion of hydrogenated carbon-carbon unsaturated bonds in the main chain and side chain of the aliphatic conjugated diene monomer units, etc.) is preferably 50% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more. When the hydrogenation rate of non-aromatic carbon-carbon unsaturated bonds is equal to or greater than the above-described lower limit, the polymer has excellent oxidation resistance and the high-temperature storage characteristics of electrochemical devices can be further improved. Note that when the polymer is composed of a block A (described below) composed of aromatic vinyl monomer units and a block B (described below) composed of at least one of aliphatic conjugated diene monomer units and alkylene structural units, the hydrogenation rate of non-aromatic carbon-carbon unsaturated bonds usually matches the hydrogenation rate of non-aromatic carbon-carbon unsaturated bonds of block B.

[0054] The hydrogenation rate can be measured by the method described in the Examples. The hydrogenation rate can be adjusted, for example, by changing the type of hydrogenation catalyst and / or the conditions of the hydrogenation reaction.

[0055] [Polymer Structure] The polymer may be a homopolymer, a random copolymer, or a block copolymer. However, from the viewpoint of further improving the high-temperature storage characteristics of the electrochemical device, it is preferably a block copolymer containing one or more blocks A composed of a first repeating unit and one or more blocks B composed of a second repeating unit. Here, the number of blocks A in the block copolymer is usually three or less, preferably two. Furthermore, the number of blocks B in the copolymer is usually three or less, preferably one. The block copolymer may further contain a block or random region composed of the above-mentioned other repeating units.

[0056] The block configuration of the block copolymer is not particularly limited and may be a chain block or a radial block. However, a chain block is preferred, and a linear block is more preferred. The block copolymer preferably has, for example, a diblock structure having one of each of two types of blocks (e.g., a structure consisting of block A and block B) or a triblock structure consisting of three blocks. Among these, a structure in which block A is bonded to both ends of block B is more preferred. As such a structure in which block A is bonded to both ends of block B, a triblock structure represented by [A]-[B]-[A] or a pentablock structure represented by [A]-[B]-[A]-[B]-[A] is preferred, and a triblock structure represented by [A]-[B]-[A] is more preferred. From the same viewpoint, the first polymer preferably has a triblock structure, more preferably a triblock structure represented by [A]-[B]-[A]. The triblock structure or pentablock structure may be a symmetric or asymmetric block structure. For example, the triblock structure represented by the above [A]-[B]-[A] may be a symmetric triblock structure in which the two blocks A have the same degree of polymerization and / or the same type of repeating unit, or an asymmetric triblock structure in which the two blocks A have different degrees of polymerization and / or the same type of repeating unit.

[0057] The polymer may be a mixture of two or more types selected from the group consisting of a block copolymer having a pentablock structure, a block copolymer having a triblock structure, and a block copolymer having a diblock structure, but is preferably a block copolymer having a triblock structure.

[0058] -Block A- From the viewpoint of providing an electrochemical device with even better high-temperature storage properties, the first repeating unit constituting block A is preferably an aromatic vinyl monomer unit. That is, block A preferably consists of aromatic vinyl monomer units. Here, block A may be composed of only one type of aromatic vinyl monomer unit or may be composed of multiple types of aromatic vinyl monomer units, but is preferably composed of only one type of aromatic vinyl monomer unit. Furthermore, when the block copolymer has multiple blocks A, the types and proportions of the aromatic vinyl monomer units constituting these multiple blocks A may be the same or different, but are preferably the same.

[0059] The weight-average molecular weight of block A in the polymer is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 15,000 or more, and is preferably 200,000 or less, more preferably 120,000 or less, and even more preferably 40,000 or less. When the weight-average molecular weight of block A is within the above range, the adhesive strength of the electrode can be improved while suppressing an increase in the resistance of the electrode. Furthermore, when a polymer contains multiple blocks A, the weight-average molecular weights of the multiple blocks A may be the same or different, but are preferably the same. For example, when a polymer has a triblock structure represented by [A]-[B]-[A] in which blocks A are bonded to both ends of block B, the weight-average molecular weights of the two blocks A may be the same or different, but are preferably the same.

[0060] -Block B- From the viewpoint of providing an electrochemical device with even better high-temperature storage properties, the second repeating unit constituting block B is preferably at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit. That is, block B preferably comprises at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit. Here, block B may be composed of only one type of aliphatic conjugated diene monomer unit and / or alkylene structural unit, or may be composed of multiple types of aliphatic conjugated diene monomer units and / or alkylene structural units. However, block B is preferably composed of only one type of aliphatic conjugated diene monomer unit and / or alkylene structural unit. Furthermore, when the block copolymer has multiple blocks B, the types and proportions of the aliphatic conjugated diene monomer units and / or alkylene structural units constituting these multiple blocks B may be the same or different, but are preferably the same.

[0061] The weight-average molecular weight of block B in the polymer is preferably 5,000 or more, more preferably 65,000 or more, even more preferably 100,000 or more, particularly preferably 150,000 or more, and is preferably 300,000 or less, more preferably 200,000 or less. When the weight-average molecular weight of block B is equal to or greater than the above-mentioned lower limit, the electrode resistivity can be reduced while improving the adhesive strength of the electrode. When the weight-average molecular weight of block B is equal to or less than the above-mentioned upper limit, an increase in the viscosity of the binder composition for electrochemical elements can be suppressed, thereby improving the productivity of the electrochemical element. When the polymer contains multiple blocks B, the weight-average molecular weights of the multiple blocks B may be the same or different, but are preferably the same.

[0062] —Ratio of Blocks A and B— The ratio of block A in the block copolymer is preferably 10% by mass or more, more preferably 15% by mass or more, and is preferably 80% by mass or less, more preferably 65% ​​by mass or less. When the ratio of block A in the block copolymer is within the above range, the adhesive strength of the electrode can be improved.

[0063] The content of block B in the block copolymer is preferably 20% by mass or more, more preferably 35% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less. When the content of block B in the block copolymer is within the above range, the resistivity of the electrode can be reduced.

[0064] [Method for Preparing Polymer] The method for preparing the above-mentioned polymer is not particularly limited, and any method such as solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization can be used. Furthermore, as the polymerization method, addition polymerization such as ionic polymerization, radical polymerization, or living radical polymerization can be used. Furthermore, as the polymerization initiator, known polymerization initiators such as redox polymerization initiators containing iron-based compounds can be used.

[0065] When the polymer used in the present invention is a block copolymer, the block copolymer can be produced by a conventionally known method. Specifically, for example, a block copolymer can be prepared by adding a second monomer component different from the first monomer component to a solution obtained by polymerizing a first monomer component, polymerizing the second monomer component, and optionally further repeating the addition and polymerization of the monomer component.

[0066] Furthermore, when the above-described polymer is produced by the above-described method (1), the polymer can be hydrogenated using a known hydrogenation method such as an oil phase hydrogenation method or an aqueous phase hydrogenation method. Furthermore, the catalyst used for hydrogenation can be any known selective hydrogenation catalyst, and a palladium-based catalyst or a rhodium-based catalyst can be used without limitation. Furthermore, examples of hydrogenation catalysts used when the binder composition contains the above-described predetermined metal element derived from the hydrogenation catalyst include nickel(II) acetylacetonate, chromium(III) acetylacetonate, and titanyl(IV) acetylacetonate. Two or more of these hydrogenation catalysts may be used in combination.

[0067] After the hydrogenation reaction, a solvent such as isopropanol or cyclohexane is added to the reaction liquid to precipitate the polymer, which is then filtered, washed, and dried to recover the polymer.

[0068] <Other Components> In addition to the above components, the binder composition may contain components such as a reinforcing material, a leveling agent, a viscosity modifier, and an electrolyte additive. These are not particularly limited as long as they do not affect the electrochemical reaction, and known components, such as those described in WO 2012 / 115096, can be used. Furthermore, these components may be used alone or in combination of two or more types in any ratio.

[0069] <Preparation of binder composition> The binder composition is not particularly limited, and can be prepared, for example, by preparing a polymer according to the above-mentioned polymer preparation method and then removing the solvent used in preparing the polymer. When a compound containing the above-mentioned specified metal element or other components is to be blended, they may be mixed by a known method before or after removing the solvent.

[0070] (Conductive material dispersion for electrochemical elements) The conductive material dispersion for electrochemical elements of the present invention contains the binder composition 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. It should be noted 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 composition of the present invention, when an electrode is produced using the conductive material dispersion, an electrochemical element including the electrode can exhibit excellent high-temperature storage properties.

[0071] <Binder Composition for Electrochemical Elements> The binder composition for electrochemical elements may be any of those described above. The amount of the binder composition for electrochemical elements, calculated as solid content, is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, per 100 parts by mass of the conductive carbon material. When the amount of the binder composition is equal to or greater than the lower limit, the dispersion stability of the conductive carbon material can be further improved. When the amount of the binder composition is equal to or less than the upper limit, the electrode resistivity can be reduced.

[0072] <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 (CNT) and vapor-grown carbon fibers). Among these, from the viewpoints of conductivity and electrode resistivity, carbon black, carbon fiber (carbon nanofiber), graphite (graphene), and carbon nanotubes (CNT) are preferred, and carbon black and carbon nanotubes (CNT) are more preferred. Note that, from the viewpoints of processability such as dispersibility in addition to conductivity and electrode resistivity, carbon black is preferred. These materials can be used alone or in combination of two or more.

[0073] <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.

[0074] <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 composition of the present invention. These components may be used alone or in combination of two or more types in any ratio.

[0075] <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.

[0076] <Method for preparing conductive material dispersion> The conductive material dispersion can be prepared by mixing the above-mentioned components by a known mixing method. Among them, from the viewpoint of dispersing the conductive carbon material well, it is preferable to prepare the conductive material dispersion by adding the conductive carbon material and, optionally, an additional solvent to a mixture obtained by mixing a binder composition and a solvent, and mixing them. The mixing can be performed 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.

[0077] (Composite particles for electrochemical element electrodes) The composite particles for electrochemical element electrodes of the present invention comprise an electrode active material and the binder composition for electrochemical elements of the present invention described above, and may optionally further comprise a conductive carbon material, a solvent, 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 composition of the present invention, they can cause the electrochemical element to exhibit excellent high-temperature storage properties. 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.

[0078] <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.

[0079] 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.

[0080] 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.

[0081] <Binder Composition for Electrochemical Elements> The binder composition for electrochemical elements can be any of those described above. The amount of the binder composition, calculated as solid content, is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and preferably 5.0 parts by mass or less, and more preferably 4.0 parts by mass or less, per 100 parts by mass of the electrode active material. When the amount of the binder composition is equal to or greater than the lower limit, the dispersion stability of the electrode active material can be further improved, and an electrode mixture layer can be favorably formed. When the amount of the binder composition is equal to or less than the upper limit, the high-temperature storage characteristics of the electrochemical element can be further improved.

[0082] <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 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and preferably 5.0 parts by mass or less, and more preferably 4.0 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, a high-capacity electrochemical element can be provided without impairing the capacity per unit weight of the electrochemical element.

[0083] <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.

[0084] <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.

[0085] <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.

[0086] <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.

[0087] The production of composite particles by the stirring granulation method is not particularly limited, but the composite particles are preferably produced through a step of stirring an electrode active material (pre-stirring step), a step of adding a liquid containing the binder composition of the present invention, a solvent, and optionally further containing a conductive carbon material, preferably the above-mentioned conductive material dispersion liquid of the present invention, to the electrode active material while stirring the electrode active material to obtain a granulated product (granulation step), and a step of further stirring the granulated product and sizing it (sizing step). The production apparatus for composite particles by the stirring granulation method is not particularly limited, and known stirring granulators such as a batch-type stirring granulator or a continuous stirring granulator can be used.

[0088] (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 and the binder composition of the present invention. That is, the electrode mixture layer contains at least an electrode active material and a binder composition (a predetermined metal element and a polymer), and may optionally further contain a conductive carbon material, other components used in the field of electrochemical devices, a conductive material other than the conductive carbon material, etc.

[0089] Furthermore, since the electrode of the present invention contains the binder composition of the present invention, the use of this electrode makes it possible to obtain an electrochemical device with excellent high-temperature storage characteristics.

[0090] <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 electrical conductivity and voltage resistance.

[0091] <Electrode mixture layer> [Binder composition for electrochemical element] The binder composition for electrochemical element to be blended in the electrode mixture layer can be any of those described above. The blending amount of the binder composition is not particularly limited, and can be the blending amount described above in the section "Composite particles for electrochemical element electrode."

[0092] [Electrode active material] The electrode active material to be blended in the electrode mixture layer is not particularly limited, and may be the same as the electrode active material to be blended in the composite particle of the present invention. The blending amount of the electrode active material is not particularly limited, and may be the blending amount described above in the section "Composite particle for electrochemical element electrode."

[0093] [Conductive carbon material] The conductive carbon that can be arbitrarily blended in 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 electrodes."

[0094] [Other Components] Other components that can be optionally blended into the electrode mixture layer are not particularly limited, and include the same components as those that can be blended into the conductive material dispersion of the present invention.

[0095] [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.

[0096] 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.

[0097] <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. Specifically, for example, electrodes for lithium ion secondary batteries are manufactured by a method of forming the composite particles of the present invention described above into a sheet and then laminating them on a current collector, or by a method of directly pressurizing the composite particles on the current collector. Among these, a method of directly pressurizing the composite particles on the current collector is preferred. Examples of pressurizing methods include a roll pressurizing method using a roll pressurizing device equipped with a pair of rolls, in which the current collector is fed by the rolls while the composite particles are fed into the roll pressurizing 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 pressurizing method is preferred.

[0098] 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.

[0099] Alternatively, an electrode for a lithium ion secondary battery can be produced by a method including 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).

[0100] Here, the method for applying the slurry composition to the current collector and the method for drying the slurry composition on the current collector are not particularly limited, and for example, known methods described in JP 2022-041228 A can be used. The slurry composition can also be prepared by mixing the above components using a known mixing method. The slurry composition can also be prepared by, for example, preparing a liquid containing the binder composition of the present invention and a solvent, and optionally further containing a conductive carbon material, and adding an electrode active material to the liquid and mixing. When a conductive carbon material is included in the electrode mixture layer, the slurry composition can also be prepared by preparing a conductive material dispersion of the present invention in advance, adding the electrode active material to the conductive material dispersion, and mixing. In particular, from the viewpoint of dispersing the conductive carbon material well, it is preferable to prepare the slurry composition by adding the electrode active material and optional components (such as additional solvents, other components, other conductive materials, etc.) to the conductive material dispersion and mixing them. The amounts of the above components in the slurry composition are not particularly limited and can be the same as those described above in the section “Composite particles for electrochemical element electrodes.” Mixing can be carried out using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, or Filmix.

[0101] (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 has excellent high-temperature storage characteristics. 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.

[0102] <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.

[0103] <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.

[0104] 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. It is also preferable to add known additives, such as fluoroethylene carbonate and ethyl methyl sulfone, to the electrolytic solution. In the electrochemical element of the present invention, when an additive such as fluoroethylene carbonate is contained in the electrolytic solution, the high-temperature storage characteristics of the electrochemical element can be further improved.

[0105] <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.

[0106] 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.

[0107] 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, the terms "%" and "parts" used to represent 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 corresponds to 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, the concentration of metal elements in the binder composition, the degree of swelling of the polymer in an electrolyte solution, the weight-average molecular weight of the polymer and blocks in the polymer, the hydrogenation rate of the polymer, the adhesive strength of the electrode, the electrode resistivity, and the high-temperature storage characteristics were measured or evaluated using the following methods.

[0108] <Concentration of Predetermined Metal Elements> Approximately 1 g of binder composition was collected and incinerated in an electric furnace at 550°C for approximately 3 hours. Approximately 5 mL of concentrated sulfuric acid was then added to dissolve the binder composition, and approximately 5 mL of concentrated nitric acid was gradually added to perform wet decomposition. After decomposition, the acid was concentrated and the volume was adjusted to 10 mL with ultrapure water. The concentration of the predetermined metal elements in the binder composition was measured using an ICP-MS (Agilent, ICP-MS 7900). <Electrolyte Swelling Degree> Two parts of the polymer (binder composition) obtained in each of the Examples and Comparative Examples were dissolved in 18 parts of cyclohexane to prepare a binder solution with a solids concentration of 10 wt%. An appropriate amount of this solution was poured into a Petri dish and dried at 40°C for 3 hours, followed by further drying under reduced pressure at 40°C for 3 hours. The obtained polymer film was cut into a 1 cm x 1 cm sample, and the mass of the test piece (mass before immersion) was measured. Thereafter, the test piece was immersed in an electrolyte solution at a temperature of 60° C. for 72 hours. The immersed test piece was pulled out, the electrolyte solution was wiped off, and the mass (mass after immersion) was immediately measured. The value of (mass after immersion) / (mass before immersion) [times] was defined as the swelling degree. The electrolyte solution was LiPF 5 with a concentration of 1.0 M. ６ A solution (solvent: a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC)=3 / 7 (volume ratio), additive: containing 2% by volume of vinylene carbonate (solvent ratio)) was used. <Hydrogenation rate> The hydrogenation rate of the polymer was measured before and after the hydrogenation reaction. １H-NMR spectra were measured, and the weight-average molecular weight was calculated based on the decrease 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. <Weight-average molecular weight of polymer and polymer block> 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) The weight-average molecular weight of blocks A and B of the polymer was calculated according to the following formula using the weight-average molecular weight (M) of the polymer measured above, the mass (W1) of the monomers used in the polymerization of each block, and the total mass (W2) of all monomers used in the preparation of the polymer. Weight-average molecular weight of block = M × (W1 / W2) <Adhesion strength of electrode> The positive electrodes for lithium ion secondary batteries prepared in the examples and comparative examples were cut into test pieces 100 mm long and 10 mm wide. With the side having the electrode mixture layer facing down, cellophane tape (compliant with JIS Z1522) was attached to the electrode surface, and one end of the current collector was pulled vertically at a peeling rate of 50 mm / min to measure the stress when peeled off (note that the cellophane tape was fixed to the test table). Measurements were performed three times, and the average value was calculated as the binding strength. The binding strength was evaluated according to the following criteria. A higher binding strength indicates stronger adhesion of the positive electrode mixture layer to the current collector and superior electrode adhesive strength. A: Binding strength of 9 N / m or more B: Binding strength of 7 N / m or more but less than 9 N / m C: Binding strength of 5 N / m or more but less than 7 N / m D: Binding strength less than 5 N / m <Electrode Resistivity> For the positive electrodes for lithium ion secondary batteries produced in the Examples and Comparative Examples, the volume resistivity (Ω cm) of the positive electrode mixture layer was measured in an environment of 25°C using an electrode resistance system (manufactured by Hioki E.E. Corporation, "RM2610") and evaluated according to the following criteria. A lower volume resistivity of the positive electrode mixture layer indicates a lower electrode resistivity.A: 15.0 Ω cm or less B: More than 15.0 Ω cm and 17.5 Ω cm or less C: More than 17.5 Ω cm and 20.0 Ω cm or less D: More than 20.0 Ω cm <High-Temperature Storage Characteristics> After injecting the electrolyte, the lithium-ion secondary batteries prepared in the Examples and Comparative Examples were left standing at 25°C for 5 hours. Next, they were charged to a cell voltage of 3.65 V using a constant current method at 25°C and 0.2 C, and then aged for 12 hours at 60°C. Then, they were discharged to a cell voltage of 3.00 V using a constant current method at 25°C and 0.2 C. Thereafter, CC-CV charging (upper limit cell voltage 4.20 V) was performed using a constant current method at 0.2 C, and CC discharging was performed to 3.00 V using a constant current method at 0.2 C. This charge-discharge cycle at 0.2 C was repeated three times. The battery was then charged at 25°C until the charge rate reached 50% (i.e., until the charge capacity reached 500mAh for a 1000mAh cell), and the resistance was measured using the following procedure: (1) Determine the voltage change ΔV (0.2) when the battery was discharged for 30 seconds using a 0.2C constant current method (I0.2); (2) Charge the battery for 30 seconds using a 0.2C constant current method; and (3) Determine the voltage change ΔV (1.0) when the battery was discharged for 30 seconds using a 1.0C constant current method (I1.0). Resistance (Ω) = {ΔV (1.0) - ΔV (0.2)} / (I1.0 - I0.2). The lithium-ion secondary battery was then charged at 25°C using a 0.2C constant current method until the cell voltage reached 4.20V, and continued charging until the current value after the cell voltage reached 4.20V reached 0.02C. Next, the lithium ion secondary battery was removed from the charge / discharge control device and stored at 60°C for two weeks. After storage, it was cooled to 25°C and discharged to 3.0V using a 0.2C constant current method, and the resistance value was measured in the same manner as before storage. The ratio of the resistance value after storage to the resistance value before storage was calculated as the resistance increase rate. The smaller the resistance increase rate, the better the high-temperature storage characteristics. A: Resistance increase rate less than 150% B: Resistance increase rate 150% or more but less than 175% C: Resistance increase rate 175% or more but less than 200% D: Resistance increase rate 200% or more but less than 225% E: Resistance increase rate 225% or more.

[0109] Example 1 Preparation of Binder Composition 135 parts of dehydrated cyclohexane, 0.07 parts of dibutyl ether, and 6.8 parts of dehydrated styrene as an aromatic vinyl monomer were placed in a reactor equipped with a stirrer and thoroughly purged with nitrogen. 0.02 parts of n-butyllithium (15% cyclohexane solution) as a polymerization initiator was then added. The entire contents were then stirred at 60°C for 20 minutes. Gas chromatography of the reaction solution revealed a polymerization conversion of 99.5% at this point. Next, 31.5 parts of dehydrated isoprene as an aliphatic conjugated diene monomer were continuously added to the reaction solution over 30 minutes, and stirring was continued for 30 minutes after the addition was completed. The polymerization conversion at this point was 99.5%. Then, 6.8 parts of dehydrated styrene as an aromatic vinyl monomer was added and stirred for 20 minutes. The polymerization conversion at this point was approximately 99.7%. The reaction was then terminated by adding 0.1 parts of ethanol to the reaction solution. The resulting solution was then transferred to a pressure-resistant reactor equipped with a stirrer. 0.3 parts of nickel(II) acetylacetonate and 1.2 parts of triisobutylaluminum were added as hydrogenation catalysts, followed by the addition of 28 parts of dehydrated cyclohexane and mixing. The atmosphere inside the reactor was then purged with hydrogen gas. Hydrogen was then supplied to the solution while stirring, and the hydrogenation reaction was carried out for 6 hours at a temperature of 80°C and a pressure of 0.9 MPa. After the reaction was completed, 50 parts of the reaction solution was poured into 500 parts of isopropanol as a solvent for polymer precipitation (reprecipitation), resulting in the precipitation of a polymer. The polymer was filtered, washed, and then dried under reduced pressure at room temperature for 40 hours to obtain a binder composition containing a block copolymer having a triblock structure (a structure in which a block A composed of styrene units is bonded to both ends of a block B composed of aliphatic conjugated diene units and alkylene structural units). The concentration of selected metal elements in the binder composition, the electrolyte swelling degree of the polymer, the weight-average molecular weight of the polymer and block, and the hydrogenation rate of the polymer were measured or calculated. The results are shown in Table 1.

[0110] <Preparation of Conductive Material Dispersion> 2 parts of the binder composition obtained above was dissolved in 18 parts of cyclohexane as a solvent to prepare a binder solution with a solid content concentration of 10 mass %. Carbon black (BET specific surface area: 62 m) was used as a conductive carbon material.２ / g, bulk density 0.16 g / cm 3 ) and 2 parts of the binder solution (solid content equivalent), and cyclohexane was further added as a solvent to obtain a mixture of a conductive carbon material, a binder composition, and a solvent (solid content concentration 10%, total amount 1 kg). Next, the obtained 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, thereby preparing a conductive material dispersion containing a conductive carbon material, a binder composition, and a solvent.

[0111] <Production of Composite Particles> A composite particle production apparatus was prepared. The apparatus consisted of a cylindrical vessel with an inner diameter of 180 mm and a capacity of 2 L, and two agitating blades, one vertical and one horizontal, with the axis of the cylindrical vessel being the vertical direction (the main agitating blade was the vertical axis and the auxiliary agitating blade was the horizontal axis). 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 air to prevent raw materials from being mixed into their drive mechanisms. Using the composite particle production apparatus, composite particles were produced by performing (i) a preliminary agitation operation, (ii) a granulation operation, and (iii) a sizing operation in this order. Specifically, in (i) the preliminary agitation operation, 96 parts by mass (1,344 g) of NMC532 (average particle diameter 6 μm), a positive electrode active material for lithium-ion secondary batteries, was first added to the granulation vessel. Next, room-temperature air (hereinafter also referred to as "sealing air") for sealing the drive parts of the main and auxiliary stirring blades was circulated at 20 L / min (airflow rate 10 / min), and stirring was performed for 15 minutes under operating conditions of a main stirring blade peripheral speed of 5 m / s and a auxiliary stirring blade peripheral speed of 6 m / s. The solids concentration of the powder material after stirring was measured and found to be 99% by mass or more. Next, (ii) as a granulation operation, room-temperature sealing air was circulated at 20 L / min (airflow rate 10 / min), and the main stirring blade peripheral speed was 5 m / s and the auxiliary stirring blade peripheral speed was 6 m / s. 4 parts (560) g of the conductive material dispersion obtained above (solids concentration: 10% by mass, solvent: cyclohexane) was continuously added to the pre-stirred positive electrode active material over 15 minutes using a dropping funnel. Finally, (iii) as a particle size adjustment operation, room temperature sealing air was circulated at 20 L / min (airflow rate 10 / min), and the mixture was operated for 10 minutes under the conditions of a main stirring impeller peripheral speed of 2 m / s and a sub-stirring impeller peripheral speed of 2 m / s to produce composite particles. The maximum temperature in the system throughout steps (i) to (iii) was 38°C.

[0112] <Preparation of a positive electrode for a lithium-ion secondary battery> The composite particles prepared above were supplied to a press roll (roll temperature 100°C, press linear pressure 500 kN / m) of a roll press machine ("Oshikuri 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 attached to the aluminum foil as a current collector, followed by pressure molding at a molding speed of 1.5 m / min to obtain a positive electrode having a basis weight of 30 mg / cm. ２ This positive electrode raw sheet was rolled with a roll press to a density of 3.5 g / cm. ３ A sheet-shaped positive electrode for a lithium ion secondary battery was fabricated, which consisted of the positive electrode mixture layer and aluminum foil. The adhesive strength and resistivity of the resulting positive electrode for a lithium ion secondary battery were measured. The results are shown in Table 1.

[0113] <Preparation of Negative Electrode> 33 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 3.5 parts of itaconic acid as an acidic group-containing monomer, 63.5 parts of styrene as an aromatic vinyl monomer, 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, and after thorough stirring, the mixture was heated to 50 ° C to initiate polymerization. When the polymerization conversion rate reached 96%, the mixture was cooled to terminate the polymerization reaction, and a mixture containing a particulate binder (styrene-butadiene copolymer) was obtained. 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 binder for the negative electrode. 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 15 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 prepared, which consisted of negative electrode mixture layers (on both sides) of the above and copper foil.

[0114] <Preparation of Lithium-ion Secondary Battery> A single-layer laminate cell (discharge capacity equivalent to 250 mAh) was prepared using the positive and negative electrodes prepared above and a 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. ６A 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. The high-temperature storage characteristics were evaluated using this lithium ion secondary battery. The results are shown in Table 1.

[0115] Example 2 Except for changing isoprene as the aliphatic conjugated diene monomer to 1,3-butadiene in the preparation of the binder composition, a binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0116] (Example 3) In the preparation of the binder composition, except that isopropanol used for precipitating the polymer was changed to cyclohexane and the amount added was changed from 500 parts to 450 parts, a binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0117] (Example 4) In the preparation of the binder composition, except that isopropanol used for precipitating the polymer was changed to cyclohexane and the amount added was changed from 500 parts to 400 parts, a binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0118] (Example 5) In the preparation of the binder composition, except that isopropanol used for precipitating the polymer was changed to cyclohexane and the amount added was changed from 500 parts to 350 parts, a binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0119] (Example 6) In the preparation of the binder composition, except that isopropanol used for precipitating the polymer was changed to cyclohexane and the amount added was changed from 500 parts to 300 parts, a binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0120] Example 7 A binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, except that in the preparation of the binder composition, the polymer was produced according to the following procedure, and various measurements and evaluations were performed. The results are shown in Table 1. <Production of Polymer> A reactor equipped with a stirrer and whose interior had been thoroughly purged with nitrogen was charged with 135 parts of dehydrated cyclohexane, 0.04 parts of dibutyl ether, and 4.2 parts of dehydrated styrene as an aromatic vinyl monomer, and further added with 0.01 parts of n-butyllithium (15% cyclohexane solution) as a polymerization initiator. The entire contents were then stirred at 60°C for 20 minutes. The reaction solution was measured by gas chromatography, and the polymerization conversion rate at this point was 99.5%. Next, 13.4 parts of dehydrated isoprene as an aliphatic conjugated diene monomer was continuously added to the reaction solution over 30 minutes, and after the addition was completed, the entire contents were stirred for 30 minutes. The polymerization conversion rate at this point was 99.5%. Subsequently, 4.2 parts of dehydrated styrene as an aromatic vinyl monomer was added and stirred for 20 minutes. The polymerization conversion rate at this point was 99.7%. 0.05 parts of ethanol was added to the reaction solution to terminate the reaction. Next, the resulting solution was transferred to a pressure-resistant reactor equipped with a stirrer, and 0.3 parts of nickel (II) acetylacetonate and 1.2 parts of triisobutylaluminum were added as hydrogenation catalysts, followed by adding 28 parts of dehydrated cyclohexane and mixing. The inside of the reactor was purged with hydrogen gas, and hydrogen was further supplied while stirring the solution, and the hydrogenation reaction was carried out at a temperature of 80°C and a pressure of 0.9 MPa for 6 hours.

[0121] Example 8 A binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, except that in the preparation of the binder composition, the polymer was produced according to the following procedure, and various measurements and evaluations were performed. The results are shown in Table 1. <Production of Polymer> A reactor equipped with a stirrer and whose interior had been thoroughly purged with nitrogen was charged with 135 parts of dehydrated cyclohexane, 0.04 parts of dibutyl ether, and 1.9 parts of dehydrated styrene as an aromatic vinyl monomer, and further added with 0.01 parts of n-butyllithium (15% cyclohexane solution) as a polymerization initiator. The entire contents were then stirred at 60°C for 20 minutes. The reaction solution was measured by gas chromatography, and the polymerization conversion rate at this point was 99.5%. Next, 16.8 parts of dehydrated isoprene as an aliphatic conjugated diene monomer was continuously added to the reaction solution over 30 minutes, and after the addition was completed, the entire contents were stirred for 30 minutes. The polymerization conversion rate at this point was 99.5%. Subsequently, 1.9 parts of dehydrated styrene was added and stirred for 20 minutes. The polymerization conversion rate at this point was 99.7%. 0.05 parts of ethanol was added to the reaction solution to terminate the reaction. Next, the resulting solution was transferred to a pressure-resistant reactor equipped with a stirrer, and 0.3 parts of nickel (II) acetylacetonate and 1.2 parts of triisobutylaluminum were added as hydrogenation catalysts, followed by adding 28 parts of dehydrated cyclohexane and mixing. The inside of the reactor was purged with hydrogen gas, and hydrogen was further supplied while stirring the solution, and the hydrogenation reaction was carried out at a temperature of 80°C and a pressure of 0.9 MPa for 6 hours.

[0122] Example 9 A binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, except that in the preparation of the binder composition, the polymer having a triblock structure was replaced with a block copolymer having a diblock structure (a structure of a block A consisting of styrene units and a block B consisting of aliphatic conjugated diene units and alkylene structural units) prepared by the following procedure, and various measurements and evaluations were performed. The results are shown in Table 1. <Polymer Production> A reactor equipped with a stirrer and whose interior had been thoroughly purged with nitrogen was charged with 120 parts of dehydrated cyclohexane, 0.1 parts of dibutyl ether, and 12 parts of dehydrated styrene as an aromatic vinyl monomer, and further added with 0.03 parts of n-butyllithium (15% cyclohexane solution) as a polymerization initiator. The entire contents were then stirred at 50°C for 30 minutes. When the reaction solution was measured by gas chromatography, the polymerization conversion rate at this point was 99.5%. Next, 28 parts of dehydrated isoprene as an aliphatic conjugated diene monomer was continuously added to the reaction solution over 30 minutes, and after the addition was completed, the entire solution was stirred for 30 minutes. At this point, the polymerization conversion rate was nearly 100%. 0.3 parts of ethanol was added to the reaction solution to stop the reaction. Next, the polymer solution was transferred to a pressure-resistant reactor equipped with a stirrer, and 0.3 parts of nickel(II) acetylacetonate and 1.2 parts of triisobutylaluminum were added as hydrogenation catalysts, followed by the addition and mixing of 28 parts of dehydrated cyclohexane. 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 at a temperature of 80°C and a pressure of 0.9 MPa for 6 hours.

[0123] Example 10 In the preparation of the binder composition, the polymer having a triblock structure was replaced with a block copolymer having a diblock structure (a structure of block A consisting of styrene units and block B consisting of aliphatic conjugated diene units and alkylene structural units) prepared by the following procedure. A binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 1. <Polymer Preparation> 120 parts of dehydrated cyclohexane, 0.07 parts of dibutyl ether, and 28 parts of dehydrated styrene as an aromatic vinyl monomer were placed in a reactor equipped with a stirrer and the inside of which had been thoroughly purged with nitrogen. Furthermore, 0.02 parts of n-butyllithium (15% cyclohexane solution) as a polymerization initiator was added. The entire contents were then stirred at 50°C for 30 minutes. When the reaction solution was measured by gas chromatography, the polymerization conversion rate at this point was 99.5%. Next, 12 parts of dehydrated isoprene as an aliphatic conjugated diene monomer was continuously added to the reaction solution over 30 minutes, and after the addition was completed, the entire solution was stirred for 30 minutes. At this point, the polymerization conversion rate was nearly 100%. The reaction was stopped by adding 0.3 parts of ethanol to the reaction solution. The resulting solution was then transferred to a pressure-resistant reactor equipped with a stirrer, and 0.3 parts of nickel (II) acetylacetonate and 1.2 parts of triisobutylaluminum were added as hydrogenation catalysts, followed by the addition and mixing of 28 parts of dehydrated cyclohexane. 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 at a temperature of 80°C and a pressure of 0.9 MPa for 6 hours.

[0124] Comparative Example 1 A binder composition, a conductive material dispersion, composite particles, a positive electrode and a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared or manufactured in the same manner as in Example 1, except that the binder composition was prepared according to the following procedure, and various measurements and evaluations were performed. The results are shown in Table 1. <Preparation of Binder Composition> A reactor equipped with a stirrer and whose interior had been thoroughly purged with nitrogen was charged with 120 parts of dehydrated cyclohexane, 0.07 parts of dibutyl ether, and 30 parts of dehydrated styrene as an aromatic vinyl monomer, and further added with 0.02 parts of n-butyllithium (15% cyclohexane solution) as a polymerization initiator. The entire contents were then stirred at 50°C for 30 minutes. The reaction solution was measured by gas chromatography, and the polymerization conversion rate at this point was 99.5%. Next, 8.5 parts of dehydrated isoprene as an aliphatic conjugated diene monomer was continuously added to the reaction solution over 30 minutes, and after the addition was completed, the entire contents were stirred for 30 minutes. The polymerization conversion rate at this point was nearly 100%. The reaction was stopped by adding 0.3 parts of ethanol to the reaction solution. The resulting solution was then transferred to a pressure-resistant reactor equipped with a stirrer, and 0.3 parts of nickel (II) acetylacetonate and 1.2 parts of triisobutylaluminum were added as hydrogenation catalysts, 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 at a temperature of 80°C and a pressure of 0.6 MPa for 6 hours. After the reaction was completed, 50 parts of the reaction solution was poured into 250 parts of isopropanol to precipitate a polymer, which was then filtered, washed, and dried under reduced pressure at room temperature for 40 hours.

[0125] The results shown in Table 1 show that in Examples 1 to 10, which used binder compositions containing at least one metal element selected from the group consisting of nickel, titanium, and chromium and a polymer having an electrolyte swelling rate of 2.5 times or less, the electrochemical element can exhibit excellent high-temperature storage characteristics.

[0126] According to the present invention, it is possible to provide a binder composition for electrochemical elements that can provide excellent high-temperature storage properties to electrochemical elements. Also, according to the present invention, it is possible to provide a conductive material dispersion for electrochemical elements and composite particles for electrochemical element electrodes that can provide excellent high-temperature storage properties to electrochemical elements. Furthermore, according to the present invention, it is possible to provide an electrode for electrochemical elements that can provide excellent high-temperature storage properties to electrochemical elements, and an electrochemical element that has excellent high-temperature storage properties.

Claims

1. A binder composition for an electrochemical element, comprising: at least one metal element selected from the group consisting of nickel, titanium, and chromium; and a polymer having a swelling degree in an electrolyte of 2.5 times or less.

2. The binder composition for electrochemical elements according to claim 1, wherein the total concentration of the metal elements is 0.5 ppm or more and 50 ppm or less.

3. The binder composition for electrochemical elements according to claim 1, wherein the total concentration of said metal elements is 40 ppm or less.

4. The binder composition for electrochemical elements according to claim 1, wherein the total concentration of said metal elements is 30 ppm or less.

5. The binder composition for electrochemical elements according to claim 1, wherein the metal element is nickel.

6. The binder composition for an electrochemical element according to claim 1, wherein the polymer comprises a block A consisting of a first repeating unit and a block B consisting of a second repeating unit.

7. The binder composition for an electrochemical element according to claim 6, wherein the polymer has a structure in which the block A is bonded to both ends of the block B.

8. The binder composition for an electrochemical element according to claim 6, wherein the first repeating unit of the block A is an aromatic vinyl monomer unit.

9. The binder composition for an electrochemical element according to claim 6, wherein the second repeating unit of the block B is at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit.

10. The binder composition for an electrochemical element according to claim 6, wherein the weight average molecular weight of said block A is 5,000 or more and 200,000 or less.

11. The binder composition for an electrochemical element according to claim 6, wherein the weight average molecular weight of the block B is 5,000 or more and 300,000 or less.

12. A conductive material dispersion for an electrochemical element, comprising the binder composition for an electrochemical element according to any one of claims 1 to 11, a conductive carbon material, and a solvent.

13. Composite particles for an electrochemical element electrode, comprising an electrode active material and the binder composition for an electrochemical element according to any one of claims 1 to 11.

14. An electrode for an electrochemical element, comprising an electrode mixture layer containing an electrode active material and the binder composition for an electrochemical element according to any one of claims 1 to 11.

15. An electrochemical element comprising the electrode for an electrochemical element according to claim 14.

Images