Binder composition for electrochemical elements, conductive material dispersion for electrochemical elements, slurry for electrochemical element electrodes, electrodes for electrochemical elements and electrochemical elements

Abstract

The present invention provides a binder composition that can be used to prepare a conductive material dispersion liquid having excellent dispersibility, and that can exhibit cycle characteristics excellent for an electrochemical element. A binder composition according to the present invention contains a first polymer, a second polymer, and an organic solvent. The first polymer includes a nitrile group-containing monomer unit and also includes an aliphatic conjugated diene monomer unit and / or an alkylene structural unit. The second polymer contains a structural unit of formula (I) at a proportion of 70-95 mass%. Note that in formula (I): R1 represents a hydrogen atom or a methyl group; R2 represents a hydrogen atom, a phenyl group, a 1-6C alkyl group, or a phenyl group having one to three 1-6C alkyl groups; and n is an integer of 3 or higher.

Description

[Technical Field]

[0001] The present invention relates to a binder composition for electrochemical elements, a conductive material dispersion for electrochemical elements, a slurry for electrochemical element electrodes, an electrode for an electrochemical element, and an electrochemical element. [Background technology]

[0002] Electrochemical elements such as lithium-ion secondary batteries, lithium-ion capacitors, and electric double-layer capacitors are small, lightweight, have high energy density, and can be repeatedly charged and discharged, making them suitable for a wide range of applications. Therefore, in recent years, improvements to battery components such as electrodes have been considered to further enhance the performance of electrochemical elements.

[0003] Here, the electrodes used in electrochemical elements typically comprise a current collector and an electrode composite layer formed on the current collector. This electrode composite layer is formed, for example, by applying an electrode slurry containing an electrode active material and a binder composition including a binder onto the current collector, and then drying the applied electrode slurry.

[0004] Therefore, in recent years, studies have been conducted to improve the performance of electrochemical elements by using polymers such as acrylonitrile butadiene rubber (NBR) and hydrogenated acrylonitrile butadiene rubber (H-NBR) as binders (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-234277 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Here, in order to impart sufficient conductivity to the electrode composite layer, as a material for forming the electrode composite layer, in addition to an electrode active material and a binder, fibrous conductive materials such as carbon nanotubes (hereinafter may be abbreviated as "CNT") may be used. However, fibrous conductive materials are prone to aggregation. Therefore, in order to sufficiently disperse the fibrous conductive material and exhibit excellent device characteristics in the electrochemical device, a method of pre-mixing the fibrous conductive material and the binder in a dispersion medium to form a conductive material dispersion liquid, and combining the obtained conductive material dispersion liquid with an electrode active material, etc. to prepare a slurry for an electrode is useful. However, even when preparing a conductive material dispersion liquid using the polymer in the above conventional technology, the fibrous conductive material cannot be well dispersed (that is, the dispersibility of the conductive material dispersion liquid cannot be ensured), and excellent cycle characteristics cannot be exhibited in the electrochemical device.

[0007] Therefore, an object of the present invention is to provide a binder composition for an electrochemical device that can prepare a conductive material dispersion liquid with excellent dispersibility and can exhibit excellent cycle characteristics in the electrochemical device. Another object of the present invention is to provide a conductive material dispersion liquid for an electrochemical device that has excellent dispersibility and can exhibit excellent cycle characteristics in the electrochemical device. And an object of the present invention is to provide a slurry for an electrode of an electrochemical device that can exhibit excellent cycle characteristics in the electrochemical device. In addition, an object of the present invention is to provide an electrochemical device with excellent cycle characteristics.

Means for Solving the Problems

[0008] The present inventor conducted intensive studies for the purpose of solving the above problems. And the present inventor found that by using a binder composition containing a first polymer and a second polymer each having a predetermined composition, it is possible to produce a conductive material dispersion liquid with excellent dispersibility and an electrochemical device with excellent cycle characteristics, and thus completed the present invention.

[0009] In other words, the present invention aims to advantageously solve the above problems, and according to the present invention, the following binder compositions for electrochemical elements [1] to

[10] , the conductive material dispersion for electrochemical elements

[11] , the slurry for electrochemical element electrodes

[12] to

[13] , the electrode for electrochemical elements

[14] , and the electrochemical element

[15] are provided. [1] A binder composition for an electrochemical element comprising a first polymer, a second polymer, and an organic solvent, wherein the first polymer contains nitrile group-containing monomer units and at least one of aliphatic conjugated diene monomer units and alkylene structural units, and the second polymer contains structural units represented by the following formula (I) in a proportion of 70% by mass or more and 95% by mass or less, with the total structural units in the second polymer being 100% by mass. [ka] [In formula (I), R 1 R represents a hydrogen atom or a methyl group. 2 [where n represents a hydrogen atom, a phenyl group, an alkyl group having 1 to 6 carbon atoms, or a phenyl group having 1 to 3 alkyl groups having 1 to 6 carbon atoms, and n represents an integer of 3 or more.] By using a binder composition containing both the first and second polymers described above, a conductive material dispersion with excellent dispersibility can be prepared, and electrodes formed using this binder composition can enable electrochemical elements to exhibit excellent cycle characteristics. In this invention, "monomer unit" means "a structural unit (repeating unit) derived from the monomer that is contained in a polymer obtained using the monomer." Furthermore, in this invention, "alkylene structural unit" means "general formula -C n H 2n -[where n is an integer greater than or equal to 2] This refers to a structural unit composed solely of alkylene structures. And the proportion of each structural unit contained in the polymer is, 1 H-NMR and 13It can be measured using nuclear magnetic resonance (NMR) methods such as 13C-NMR.

[0010] [2] The binder composition for electrochemical elements according to [1], wherein the second polymer further comprises aromatic monovinyl monomer units. If the second polymer includes aromatic monovinyl monomer units in addition to the structural unit shown in formula (I) above (hereinafter sometimes abbreviated as "structural unit (I)"), the dispersibility of the conductive material dispersion can be further improved.

[0011] [3] The binder composition for electrochemical elements according to [2] above, wherein the second polymer contains the aromatic monovinyl monomer units in a proportion of 5% by mass or more and 30% by mass or less, based on 100% by mass of all structural units in the second polymer. If the second polymer contains aromatic monovinyl monomer units in the proportions within the range described above, the dispersibility of the conductive material dispersion can be further improved while the electrochemical element exhibits sufficiently excellent cycle characteristics.

[0012] [4] The binder composition for electrochemical elements according to any one of [1] to [3] above, wherein the ratio of the mass of the second polymer to the total mass of the first polymer and the second polymer is 10% by mass or more and 40% by mass or less. If the ratio of the mass of the second polymer to the total mass of the first polymer is within the range described above, the dispersibility of the conductive material dispersion can be further improved, while the electrochemical element can exhibit even better cycle characteristics.

[0013] [5] A binder composition for electrochemical elements according to any one of [1] to [4] above, further comprising a nonionic surfactant. If the binder composition includes a nonionic surfactant in addition to the first and second polymers described above, the dispersibility of the conductive material dispersion can be further improved, and the electrochemical element can exhibit even better cycle characteristics. Furthermore, the resistance of the electrodes obtained using the binder composition can be reduced.

[0014] [6] The binder composition for electrochemical elements according to [5] above, wherein the nonionic surfactant is a fatty acid ester surfactant. If the binder composition includes a fatty acid ester-based surfactant as the nonionic surfactant described above, the dispersibility of the conductive material dispersion and the cycle characteristics of the electrochemical element can be further improved, while the resistance of the electrodes can be further reduced.

[0015] [7] The binder composition for electrochemical elements according to any one of [1] to [6] above, wherein the organic solvent is N-methyl-2-pyrrolidone. If the binder composition contains N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as "NMP") as an organic solvent, the dispersibility of the conductive material dispersion can be further improved, while the electrochemical element can exhibit even better cycling characteristics.

[0016] [8] A binder composition for electrochemical elements according to any of [1] to [7] above, wherein the contact angle with the polyethylene film is 30° or more and 60° or less when the solid content concentration is 15.0% by mass. Under conditions of a solid content concentration of 15.0% by mass, if the contact angle of the binder composition with respect to the polyethylene film is between 30° and 60°, the dispersibility of the conductive material dispersion can be further improved, while the electrochemical element can exhibit even better cycle characteristics. In addition, the electrode composite layer obtained using the binder composition can be firmly adhered to the current collector (i.e., the peel strength of the electrode can be improved), and the resistance of the electrode can be reduced. In this invention, the "contact angle with the polyethylene film when the solid content concentration of the binder composition is 15.0% by mass" can be measured using the method described in the examples.

[0017] [9] A binder composition for electrochemical elements according to any of [1] to [8] above, wherein the haze is 45% or less when the solid content concentration is 15.0% by mass. If the haze of the binder composition is 45% or less under conditions of a solid content concentration of 15.0% by mass, the dispersibility of the conductive material dispersion can be further improved, and the electrochemical element can exhibit even better cycle characteristics. Furthermore, the resistance of the electrodes obtained using the binder composition can be reduced. In this invention, the "haze when the solid content concentration of the binder composition is 15.0% by mass" can be measured using the method described in the examples.

[0018]

[10] The first polymer is a binder composition for electrochemical elements according to any one of [1] to [9] above, wherein the weight-average molecular weight is 20,000 or more and 250,000 or less. If the weight-average molecular weight of the first polymer is within the range described above, the dispersibility of the conductive material dispersion can be further improved, while the electrochemical element can exhibit even better cycle characteristics. In this invention, the "weight-average molecular weight" of the polymer can be measured using the method described in the examples.

[0019]

[11] A conductive material dispersion for an electrochemical element, comprising a binder composition for an electrochemical element described in any of [1] to

[10] above and a fibrous conductive material. A conductive material dispersion containing any of the above-mentioned binder compositions and a fibrous conductive material exhibits excellent dispersibility, and electrodes formed using this conductive material dispersion can enable electrochemical elements to exhibit excellent cycle characteristics. In this invention, "fibrous conductive material" means a conductive material whose aspect ratio, as measured using a transmission electron microscope (TEM), is 10 or greater.

[0020]

[12] A slurry for electrochemical element electrodes comprising the conductive material dispersion for electrochemical elements described in

[11] above and an electrode active material. By using the electrode slurry containing the conductive material dispersion described above and the electrode active material, electrodes capable of exhibiting excellent cycle characteristics in electrochemical elements can be fabricated.

[0021]

[13] The slurry for electrochemical element electrodes according to

[12] , further comprising a fluorine polymer. If the electrode slurry includes a fluorine-based polymer in addition to the conductive material dispersion and electrode active material described above, the peel strength of the electrode can be increased while further improving the cycle characteristics of the electrochemical element.

[0022]

[14] An electrode for an electrochemical element, comprising an electrode composite layer formed using the electrochemical element electrode slurry described in

[12] or

[13] above. An electrode comprising an electrode composite layer obtained using the electrode slurry described above can enable electrochemical elements to exhibit excellent cycle characteristics.

[0023]

[15] An electrochemical element comprising the electrodes for the electrochemical element described in

[14] above. The electrochemical element equipped with the electrodes described above exhibits excellent cycle characteristics. [Effects of the Invention]

[0024] According to the present invention, it is possible to prepare a conductive material dispersion with excellent dispersibility and to provide a binder composition for electrochemical elements that can enable electrochemical elements to exhibit excellent cycle characteristics. Furthermore, according to the present invention, it is possible to provide a conductive material dispersion for electrochemical elements that has excellent dispersibility and can enable the electrochemical element to exhibit excellent cycle characteristics. Furthermore, according to the present invention, it is possible to provide a slurry for electrochemical element electrodes that can enable the electrochemical element to exhibit excellent cycle characteristics. Furthermore, according to the present invention, an electrochemical element with excellent cycle characteristics can be provided. [Modes for carrying out the invention]

[0025] Embodiments of the present invention will be described in detail below. Here, the binder composition for electrochemical elements of the present invention can be used when preparing a slurry for electrochemical element electrodes. Furthermore, the binder composition for electrochemical elements of the present invention can be mixed with a fibrous conductive material such as CNTs to form a conductive material dispersion for electrochemical elements containing the binder composition and the fibrous conductive material, which can then be used to prepare a slurry for electrochemical element electrodes. The slurry for electrochemical element electrodes prepared using the conductive material dispersion can then be used to form electrodes for electrochemical elements such as lithium-ion secondary batteries. Moreover, the electrochemical element of the present invention is characterized by comprising electrodes for electrochemical elements formed using the slurry for electrochemical element electrodes.

[0026] (Binder composition for electrochemical elements) The binder composition of the present invention comprises a first polymer, a second polymer, and an organic solvent, and optionally further comprises a nonionic surfactant and components other than the first polymer, the second polymer, the organic solvent, and the nonionic surfactant (other components). In the binder composition of the present invention, The first polymer contains a nitrile group-containing monomer unit and also contains at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit, and The second polymer contains 70% to 95% by mass of structural units (I) having polyoxyethylene groups formed by a predetermined number or more oxyethylene structures (-CH2CH2O-), It is necessary.

[0027] Furthermore, by using the binder composition of the present invention, which contains both the first polymer and the second polymer described above, it is possible to produce a conductive material dispersion with excellent dispersibility and electrodes that can exhibit excellent cycle characteristics in electrochemical elements.

[0028] <First Polymerization> The first polymer is a component that can function as a binder in an electrode composite layer formed using the binder composition, holding the electrode active material and other components without detaching them from the current collector. The first polymer can also function as a dispersant in a conductive material dispersion prepared using the binder composition, capable of dispersing fibrous conductive materials.

[0029] <<Composition>> Here, the first polymer, as described above, comprises at least nitrile group-containing monomer units and aliphatic conjugated diene monomer units and / or alkylene structural units. The first polymer may also contain structural units other than nitrile group-containing monomer units, aliphatic conjugated diene monomer units, and alkylene structural units (other structural units).

[0030] [Nitrile group-containing monomer unit] Examples of nitrile group-containing monomers that can form nitrile group-containing monomer units include α,β-ethylenically unsaturated nitrile monomers. Specifically, the α,β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α,β-ethylenically unsaturated compound having a nitrile group, but examples include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. Note that one type of nitrile group-containing monomer may be used alone, or two or more types may be used in any ratio. Among these, acrylonitrile is preferred.

[0031] The content of nitrile group-containing monomer units in the first polymer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 36% by mass or more, preferably 55% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less. If the content of nitrile group-containing monomer units in the first polymer is within the above range, the solubility of the first polymer in organic solvents (especially NMP) is sufficiently ensured, and the dispersibility of the conductive material dispersion can be further improved. In addition, the peel strength of the electrode obtained using the binder composition can be improved.

[0032] [Aliphatic conjugated diene monomer units and alkylene structural units] Examples of aliphatic conjugated diene monomers that can form aliphatic conjugated diene monomer units include conjugated diene compounds having four 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. These may be used individually or in combination of two or more in any ratio. Among these, 1,3-butadiene is preferred.

[0033] Alkylene structural units may be linear or branched, but from the viewpoint of further improving the dispersibility of conductive material dispersions and the cycle characteristics of electrochemical elements, linear alkylene structural units are preferred. Furthermore, the number of carbon atoms in the alkylene structural unit is 4 or more (i.e., the general formula -C described above). n H 2n It is preferable that n is an integer greater than or equal to 4.

[0034] Here, the method for introducing alkylene structural units into the first polymer is not particularly limited, but for example, the following methods (1) and (2): (1) A method for converting aliphatic conjugated diene monomer units into alkylene structural units by preparing a polymer from a monomer composition containing an aliphatic conjugated diene monomer and hydrogenating the polymer. (2) Method for preparing a polymer from a monomer composition containing a 1-olefin monomer. These are some examples. Among these, method (1) is preferred because it facilitates the production of the first polymer.

[0035] In method (1), the aliphatic conjugated diene monomers that can be used are those described above as "aliphatic conjugated diene monomers that can form aliphatic conjugated diene monomer units". Among these, 1,3-butadiene is 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 monomer unit (1,3-butadiene hydride unit). Examples of 1-olefin monomers include ethylene, propylene, and 1-butene. Furthermore, when forming alkylene structural units, aliphatic conjugated diene monomers and 1-olefin monomers may be used individually, or two or more may be used in any ratio.

[0036] Here, the first polymer may contain at least one of aliphatic conjugated diene monomer units and alkylene structural units, as described above. That is, the first polymer may contain alkylene structural units but not aliphatic conjugated diene monomer units, or it may contain aliphatic conjugated diene monomer units but not alkylene structural units, or it may contain both aliphatic conjugated diene monomer units and alkylene structural units. However, from the viewpoint of further improving the dispersibility of the conductive material dispersion and the cycle characteristics of the electrochemical element, it is preferable that the first polymer contains at least alkylene structural units among aliphatic conjugated diene monomer units and alkylene structural units, and it is more preferable that it contains both aliphatic conjugated diene monomer units and alkylene structural units.

[0037] Furthermore, the total content of aliphatic conjugated diene monomer units and alkylene structural units in the first polymer is preferably 45% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, particularly preferably 60% by mass or more, preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 70% by mass or less. It is presumed that if the total content of aliphatic conjugated diene monomer units and alkylene structural units in the first polymer is within the above range, the affinity between the first polymer and fibrous conductive materials such as CNTs will increase, and the dispersibility of the conductive material dispersion can be further improved. In addition, since the first polymer coats fibrous conductive materials such as CNTs well, the cycle characteristics of the electrochemical element can be further improved.

[0038] [Other structural units] Other structural units are not particularly limited, but include, for example, (meth)acrylic acid ester monomer units, aromatic monovinyl monomer units, and hydrophilic group-containing monomer units. The first polymer may contain one other repeating unit, or two or more other repeating units. In this invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0039] Examples of (meth)acrylic acid ester monomers that can form (meth)acrylic acid ester monomer units include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, and other acrylates. Examples include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. Note that (meth)acrylic acid monomers may be used individually or in combination of two or more in any ratio.

[0040] Examples of aromatic monovinyl monomers that can form aromatic monovinyl monomer units include styrene, α-methylstyrene, pt-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. Aromatic monovinyl monomers may be used individually or in combination of two or more types in any ratio.

[0041] Examples of hydrophilic group-containing monomer units include carboxylic acid group-containing monomer units, sulfonic acid group-containing monomer units, phosphate group-containing monomer units, and hydroxyl group-containing monomer units. In other words, examples of hydrophilic group-containing monomers that can form hydrophilic group-containing monomer units include carboxylic acid group-containing monomers, sulfonic acid group-containing monomers, phosphate group-containing monomers, and hydroxyl group-containing monomers. Note that a single type of hydrophilic group-containing monomer may be used alone, or two or more types may be used in any ratio.

[0042] Examples of monomers containing carboxylic acid groups 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-ethyl acrylic 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 methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloro maleic acid, dichloro maleic acid, fluoromaleic acid, and maleic acid esters such as methyl allyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Examples of dicarboxylic acid acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Furthermore, as monomers having a carboxylic acid group, acid anhydrides that generate a carboxyl group by hydrolysis can also be used. In addition, mono-esters and di-esters of α,β-ethylenically unsaturated polyvalent carboxylic 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, dibutyl itaconate are also included.

[0043] Examples of the sulfonic acid group-containing monomer include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, 2-sulfoethyl (meth)acrylate, 2-acrylamido-2-methylpropane sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, and the like. In the present invention, “(meth)allyl” means allyl and / or methallyl.

[0044] Examples of the phosphate group-containing monomer include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, ethyl-(meth)acryloyloxyethyl phosphate, and the like. In the present invention, “(meth)acryloyl” means acryloyl and / or methacryloyl.

[0045] Examples of the hydroxyl group-containing monomer include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-buten-1-ol, 5-hexen-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, di-2-hydroxypropyl itaconate; general formula: CH2=CR A -COO-(C k H 2k O) m -H (where m is an integer from 2 to 9, k is an integer from 2 to 4, R APolyalkylene glycols represented by (where represents 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)acryloyl oxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyl oxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; alkyl groups 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 Examples include mono(meth)allyl ethers of alkylene glycols; 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 their halogen-substituted derivatives; and (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether.

[0046] Furthermore, if the first polymer contains other structural units, it is preferable that the content of these other structural units in the first polymer is 10% by mass or less, with the total amount of structural units in the first polymer being 100% by mass. This is because a content of 10% by mass or less of other structural units can further improve the dispersibility of the conductive material dispersion. Needless to say, the first polymer may not contain other structural units. That is, the content of other structural units in the first polymer may be 0% by mass.

[0047] <<Properties>> Here, the first polymer is not particularly limited, but preferably has the following properties.

[0048] [Iodine value] First, the first polymer preferably has an iodine value of 60 mg / 100 mg or less, more preferably 30 mg / 100 mg or less, even more preferably 20 mg / 100 mg or less, even more preferably 10 mg / mg or less, and particularly preferably 5 mg / mg or less. If the iodine value of the first polymer is 60 mg / 100 mg or less, the cycle characteristics of the electrochemical element can be further improved. The lower limit of the iodine value of the first polymer is not particularly limited, but for example, it is 1 mg / 100 mg or more. In this invention, the "iodine value" can be measured using the method described in the examples.

[0049] [Weight average molecular weight] Next, the weight-average molecular weight of the first polymer is preferably 20,000 or more, more preferably 25,000 or more, preferably 250,000 or less, more preferably 200,000 or less, even more preferably 150,000 or less, even more preferably 100,000 or less, and particularly preferably 50,000 or less. If the weight-average molecular weight of the first polymer is 20,000 or more, it is presumed that the elution of the first polymer into the electrolyte is suppressed, which can further improve the cycle characteristics of the electrochemical element. On the other hand, if the weight-average molecular weight of the first polymer is 250,000 or less, the dispersibility of the conductive material dispersion can be further improved.

[0050] <<Preparation method>> The method for preparing the first polymer is not particularly limited. The first polymer can be produced, for example, by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent and optionally performing hydrogenation (hydrogenation). The content ratio of each monomer in the monomer composition can be determined in accordance with the content ratio of each structural unit in the first polymer. Furthermore, there are no particular restrictions on the polymerization method; any method such as solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization can be used. Addition polymerization, such as ionic polymerization, radical polymerization, or living radical polymerization, can be used as the polymerization reaction. As for the polymerization initiator, known polymerization initiators, such as redox polymerization initiators containing iron-based compounds, can be used.

[0051] Here, the molecular weight (particularly the weight-average molecular weight) of the first polymer obtained during polymerization can be adjusted by using a molecular weight adjusting agent. Examples of such molecular weight adjusting agents include compounds having sulfur-containing groups such as mercapto groups. Examples of compounds having a mercapto group that can be used as molecular weight modifiers include compounds having 8 to 12 carbon atoms such as octyl mercaptan, 2,2,4,6,6-pentamethyl-4-heptanethiol, 2,4,4,6,6-pentamethyl-2-heptanethiol, 2,3,4,6,6-pentamethyl-2-heptanethiol, 2,3,4,6,6-pentamethyl-3-heptanethiol, t-dodecyl mercaptan, and n-dodecyl mercaptan; and compounds having a mercapto group such as 2,2,4,6,6-pentamethyl-4-octanthiol, 2,2,4,6,6,8,8-heptamethyl-4-nonanthiol, bis(2-mercaptoethyl) sulfide, methyl 3-mercaptopropionate, and 1-butanethiol.

[0052] Furthermore, when producing the first polymer by the method described in (1) above, it is preferable to use radical polymerization using a redox polymerization initiator containing an iron-based compound as the polymerization method for the hydrogenated polymer (i.e., a polymer containing nitrile group-containing monomer units and aliphatic conjugated diene monomer units). Here, the redox polymerization initiator containing an iron-based compound is not particularly limited, and for example, a combination of cumene hydroperoxide as a polymerization initiator and ferrous sulfate and / or monosodium iron ethylenediaminetetraacetate as an iron-based compound can be used. Furthermore, when producing the first polymer by the method described in (1) above, it is preferable to perform emulsion polymerization, then coagulate with a coagulant and recover the polymer, and then hydrogenate the recovered polymer (optionally after carrying out a "double decomposition reaction" described later). Furthermore, hydrogenation can be carried out using known hydrogenation methods such as oil-layer hydrogenation or aqueous-layer hydrogenation. In addition, any known selective hydrogenation catalyst can be used as the catalyst for hydrogenation, including palladium-based and rhodium-based catalysts. Two or more of these may be used in combination.

[0053] Furthermore, the hydrogenation of the polymer may be carried out using, for example, the method described in Japanese Patent No. 4509792. Specifically, the hydrogenation of the polymer may be carried out after a double decomposition reaction of the polymer in the presence of a catalyst and a co(co-)olefin. Here, known ruthenium-based catalysts can be used as catalysts for the double decomposition reaction. In particular, it is preferable to use Grubbs catalysts such as bis(tricyclohexylphosphine)benzylideneruthenium dichloride or 1,3-bis(2,4,6-trimethylphenyl)-2-(imidazolidinylidene)(dichlorophenylmethylene)(tricyclohexylphosphine)ruthenium as catalysts for the double decomposition reaction. As coolefins, olefins having 2 to 16 carbon atoms such as ethylene, isobutane, and 1-hexane can be used. Furthermore, as hydrogenation catalysts when hydrogenation is carried out after the double decomposition reaction, known homogeneous hydrogenation catalysts such as Wilkinson catalyst ((PPh3)3RhCl) can be used.

[0054] <Second Polymer> The second polymer, like the first polymer, is a component that functions as a binder and dispersant.

[0055] <<Composition>> The second polymer, as described above, contains structural unit (I) in a proportion of 70% to 95% by mass, and structural units other than structural unit (I) (other structural units) in a proportion of 5% to 30% by mass. Here, the second polymer contains structural unit (I) and therefore has a polyoxyethylene group as a side chain. It is presumed that this side chain contributes to the second polymer's ability to coat the electrode active material well, and by including the second polymer in the binder composition, good protection of the electrode active material by the polymer component is achieved, and as a result, the cycle characteristics of the electrochemical element can be improved.

[0056] [Structural Unit (I)] As described above, structural unit (I) has the structure of formula (I) below. [ka] In formula (I), R 1 R represents a hydrogen atom or a methyl group. 2 n represents a hydrogen atom, a phenyl group, an alkyl group having 1 to 6 carbon atoms, or a phenyl group having 1 to 3 alkyl groups having 1 to 6 carbon atoms, and n represents an integer of 3 or more.

[0057] Here, as mentioned above, n in structural unit (I) must be an integer of 3 or more, preferably an integer of 4 or more, more preferably an integer of 5 or more, preferably an integer of 25 or less, and more preferably an integer of 15 or less. If n is an integer less than 3 (i.e., 1 or 2), the cycle characteristics of the electrochemical element will decrease. In addition, the resistance of the electrode will increase and the peel strength will be impaired. On the other hand, if n is an integer of 25 or less, the amount of water introduced into the electrochemical element will decrease while ensuring the peel strength of the electrode, thereby improving the cycle characteristics of the electrochemical element. Furthermore, it will be possible to suppress an excessive increase in viscosity of the binder composition or conductive material dispersion due to the polyoxyethylene group becoming excessively long.

[0058] Furthermore, R in structural unit (I) 1 As mentioned above, this is either a hydrogen atom or a methyl group, and a hydrogen atom is preferred.

[0059] In addition, R in structural units (I) 2 As described above, this is a hydrogen atom, a phenyl group, an alkyl group having 1 to 6 carbon atoms, or a phenyl group having 1 to 3 alkyl groups having 1 to 6 carbon atoms. Here, R 2 The alkyl group having 1 to 6 carbon atoms that constitutes part or all of the alkyl group is not particularly limited, but examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, and sec-butyl group. And, R 2Preferably, the elements are a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom and a methyl group.

[0060] The first polymer may contain one type of structural unit (I), or it may contain two or more types of structural units (I).

[0061] And the monomers that can form structural unit (I) are given by the following equation (II): [ka] Examples include polyoxyethylene group-containing monomers represented by (hereinafter sometimes abbreviated as "monomer (II)"), where n, R 1 and R 2 These are the same as those in the corresponding formula (I), and their preferred ranges and preferred examples are also the same as those of the preferred ranges and preferred examples of formula (I). Examples of monomer (II) include polyoxyethylene group-containing (meth)acrylates such as the product names "AM-90G," "AM-130G," "M-90G," and "M-230G" (all manufactured by Shin-Nakamura Chemical Co., Ltd.), and the product name "Bremmer® PME-200" (manufactured by NOF Corporation). These may be used individually or in combination of two or more types in any ratio.

[0062] Here, the content of structural unit (I) in the second polymer must be 70% by mass or more and 95% by mass or less, with the total structural units in the second polymer being 100% by mass, as described above. It is preferably 72% by mass or more, more preferably 76% by mass or more, even more preferably 80% by mass or more, preferably 90% by mass or less, more preferably 87% by mass or less, and even more preferably 84% by mass or less. If the content of structural unit (I) is less than 70% by mass, the cycle characteristics of the electrochemical element will deteriorate, and if it exceeds 95% by mass, the dispersibility of the conductive material dispersion will be impaired.

[0063] [Other structural units] Other structural units are not particularly limited as long as they are derived from monomers copolymerizable with monomers (II) that can form the above-mentioned structural unit (I). For example, various structural units described above in the "First Polymer" section, or known crosslinkable monomer units (for example, those described in Japanese Patent Application Publication No. 2017-027856) can be used. Among these, aromatic monovinyl monomer units are preferred as other structural units to be included in the second polymer. It is presumed that aromatic monovinyl monomer units have excellent affinity for fibrous conductive materials such as CNTs. If the second polymer includes aromatic monovinyl monomer units in addition to the above-mentioned structural unit (I), the second polymer will be well adsorbed onto the fibrous conductive material in the conductive material dispersion, further improving the dispersibility of the conductive material dispersion.

[0064] Furthermore, aromatic monovinyl monomers that can form aromatic monovinyl monomer units are the same as those described above in the section on "First Polymer". The aromatic monovinyl monomer may be used alone or in combination of two or more types in any ratio. From the viewpoint of further improving the dispersibility of the conductive material dispersion, styrene is preferred as the aromatic monovinyl monomer.

[0065] Here, the content of aromatic monovinyl monomer units in the second polymer is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 13% by mass or more, even more preferably 16% by mass or more, particularly preferably 20% by mass or more, preferably 30% by mass or less, preferably 28% by mass or less, and more preferably 24% by mass or less. If the content of aromatic monovinyl monomer units is 5% by mass or more, the dispersibility of the conductive material dispersion is further improved, and if it is 30% by mass or less, the cycle characteristics of the electrochemical element can be sufficiently ensured.

[0066] <<Weight average molecular weight>> Here, the weight-average molecular weight of the second polymer is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, particularly preferably 25,000 or more, preferably 50,000 or less, more preferably 45,000 or less, and even more preferably 40,000 or less. It is presumed that if the weight-average molecular weight of the second polymer is within the above range, the affinity of the second polymer with the fibrous conductive material will increase, and the second polymer will be able to protect the electrode active material more effectively, thereby further improving the dispersibility of the conductive material dispersion and further improving the cycle characteristics of the electrochemical element.

[0067] <<Method for preparing the second polymer>> The method for preparing the second polymer is not particularly limited. The second polymer can be produced, for example, by polymerizing a monomer composition containing the monomers described above in an aqueous solvent. The content ratio of each monomer in the monomer composition can be determined in accordance with the content ratio of each structural unit in the second polymer.

[0068] Furthermore, there are no particular restrictions on the polymerization method; any method such as solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization can be used. In addition, addition polymerization methods such as ionic polymerization, radical polymerization, and living radical polymerization can be used as the polymerization reaction. Also, known polymerization initiators, molecular weight modifiers, and emulsifiers can all be used.

[0069] <<Mixing ratio of the first polymer and the second polymer>> In the binder composition of the present invention, the mixing ratio of the first polymer and the second polymer is not particularly limited, but the proportion of the mass of the second polymer in the total mass of the first polymer and the second polymer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, particularly preferably 30% by mass or more, preferably 40% by mass or less, more preferably 37% by mass or less, and even more preferably 33% by mass or less. If the proportion of the second polymer in the total mass of the first polymer and the second polymer is 10% by mass or more, the cycle characteristics of the electrochemical element can be further improved, and if it is 40% by mass or less, the dispersibility of the conductive material dispersion can be further improved.

[0070] <organic solvents> The organic solvent is not particularly limited as long as it can dissolve and / or disperse the first and second polymers described above. Examples include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and amyl alcohol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as diethyl ether, dioxane, and tetrahydrofuran; amide-based polar organic solvents such as N,N-dimethylformamide and NMP; and aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, and paradichlorobenzene. These may be used individually or in combination of two or more. Among these, NMP is preferred from the viewpoint of further improving the dispersibility of the conductive material dispersion while exhibiting even better cycle characteristics in the electrochemical element.

[0071] <Nonionic surfactants> The binder composition of the present invention preferably contains a nonionic surfactant. It is presumed that the inclusion of a nonionic surfactant in the binder composition of the present invention improves the affinity between the first polymer and the second polymer described above, thereby further enhancing the dispersibility of the conductive material dispersion, reducing electrode resistance, and further improving the electrochemical element cycle characteristics.

[0072] Examples of nonionic surfactants include polyoxyalkylene alkylaryl ether surfactants, fatty acid ester surfactants, silicone surfactants, acetylene alcohol surfactants, and fluorine-containing surfactants.

[0073] Examples of polyoxyalkylene alkylaryl ether surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene dodecylphenyl ether. Examples of polyoxyalkylene alkyl ether surfactants include polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl cetyl ether, and polyoxyethylene alkyl ether (with 12 to 14 carbon atoms in the alkyl portion). Examples of fatty acid ester surfactants include fatty acid ester surfactants having polyoxyalkylene groups, such as polyoxyethylene monolaurate, polyoxyethylene monostearate, and polyoxyethylene monooleate. Examples of silicone-based surfactants include dimethylpolysiloxane. Examples of fluorine-containing surfactants include fluorine alkyl esters.

[0074] Among these, fatty acid ester surfactants are preferred, fatty acid ester surfactants having polyoxyalkylene groups are more preferred, and polyoxyethylene monolaurate is even more preferred, from the viewpoint of further improving the dispersibility of the conductive material dispersion and the cycle characteristics of the electrochemical element while further reducing the resistance of the electrodes.

[0075] Here, the content of the nonionic surfactant in the binder composition of the present invention is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, based on 100 parts by mass of the total mass of the first polymer and the second polymer described above. If the amount of nonionic surfactant contained in the binder composition is 0.05 parts by mass or more per 100 parts by mass of the total mass of the first polymer and the second polymer, the resistance of the electrodes can be further reduced while further improving the dispersibility of the conductive material dispersion and the cycle characteristics of the electrochemical element. On the other hand, if the amount of nonionic surfactant contained in the binder composition is 10 parts by mass or less per 100 parts by mass of the total mass of the first polymer and the second polymer, the resistance can be sufficiently reduced while improving the peel strength of the electrodes.

[0076] <Other ingredients> Other components that may be included in the binder composition of the present invention, in addition to the first polymer, the second polymer, the organic solvent, and the nonionic surfactant, are not particularly limited, but include, for example, binders other than the first polymer and the second polymer (such as fluorine-based polymers described later), reinforcing agents, leveling agents, viscosity modifiers, and electrolyte additives. These are not particularly limited as long as they do not affect the battery reaction, and known ones, for example, those described in International Publication No. 2012 / 115096, can be used. These other components may be used individually or in combination of two or more components in any ratio.

[0077] <Properties of the binder composition> Herein, the binder composition of the present invention is not particularly limited, but it is preferable to have the following properties.

[0078] <<Contact angle with polyethylene film>> The binder composition of the present invention preferably has a contact angle of 30° or more with respect to the polyethylene film when the solid content concentration is 15.0% by mass, more preferably 35° or more, even more preferably 40° or more, particularly preferably 45° or more, preferably 60° or less, more preferably 55° or less, and even more preferably 50° or less. Here, according to the inventors' studies, the contact angle between the binder composition and the polyethylene film mainly composed of carbon atoms can be used as an indicator to estimate the affinity between the binder composition and the fibrous conductive material (particularly fibrous carbon material such as CNTs). Specifically, it is presumed that if the contact angle of the binder composition with respect to the polyethylene film is 30° or more under the condition of a solid content concentration of 15.0% by mass, it suppresses an excessive increase in affinity between the binder composition and the fibrous conductive material, and maintains a good dispersion state of the fibrous conductive material in the conductive material dispersion, thereby reducing the resistance of the electrodes. On the other hand, if the contact angle of the binder composition with respect to the polyethylene film is 60° or less under conditions of a solid content concentration of 15.0% by mass, sufficient affinity between the binder composition and the fibrous conductive material is ensured. This is presumably because it can suppress the bleeding of the fibrous conductive material when drying the electrode slurry containing the conductive material dispersion to produce electrodes, thereby improving the peel strength of the electrodes. Furthermore, it is possible to further improve the dispersibility of the conductive material dispersion while enabling the electrochemical element to exhibit even better cycle characteristics. Furthermore, the "contact angle with the polyethylene film when the solid content concentration of the binder composition is 15.0% by mass" can be controlled by changing the mixing ratio of the first polymer and the second polymer in the binder composition, the content of the nonionic surfactant, and the conditions during the preparation of the binder composition (such as the mixing temperature described later).

[0079] <<Hayes>> Furthermore, the binder composition of the present invention preferably has a haze of 45% or less, more preferably 40% or less, even more preferably 30% or less, even more preferably 20% or less, and particularly preferably 15% or less, when the solid content concentration is 15.0% by mass. If the haze of the binder composition under the condition of a solid content concentration of 15.0% by mass is 45% or less, the dispersibility of the conductive material dispersion can be further improved, and the electrochemical element can exhibit even better cycle characteristics. Moreover, the resistance of the electrodes can be reduced. Furthermore, the lower limit of the haze of the binder composition under the condition of a solid content concentration of 15.0% by mass is not particularly limited, but can be, for example, 1% or more, or 5% or more. Furthermore, the "haze when the solid content concentration of the binder composition is 15.0% by mass" can be controlled by changing the content of the nonionic surfactant in the binder composition and the conditions during the preparation of the binder composition (such as the mixing order described later).

[0080] Here, the sample to be measured for the contact angle and haze, i.e., the binder composition with a solid content concentration of 15.0% by mass, can be prepared as follows. First, for binder compositions with an unknown solid content concentration, the solid content concentration is measured. The solid content concentration of the binder composition can be measured in accordance with JIS K 6387-2:2011. If the solid content concentration of the binder composition is 15.0% by mass, the binder composition is used as the sample. Otherwise, the solid content concentration of the binder composition is adjusted using a known method that does not affect the solid content of the first polymer, second polymer, etc., with thermal denaturation or other effects, and then used as the sample. For example, if the solid content concentration of the binder composition is greater than 15.0% by mass, the solid content concentration is adjusted to 15.0% by mass by adding an organic solvent similar to the organic solvent contained in the binder composition (e.g., NMP) and then used as the sample.

[0081] <Method for preparing a binder composition> The method for preparing the binder composition of the present invention is not particularly limited, and can be obtained by mixing the above-mentioned components using a known mixing device such as a disper. Here, when mixing the above-mentioned components to obtain a binder composition, the mixing temperature is preferably 5°C or higher, more preferably 18°C ​​or higher, more preferably 50°C or lower, and more preferably 40°C or lower. If the mixing temperature is within the above range, the contact angle value of the obtained binder composition with the polyethylene film can be well controlled. As a result, the dispersibility of the conductive material dispersion can be further improved, and the electrochemical element can exhibit even better cycle characteristics. In addition, the peel strength of the electrode can be improved, and the resistance of the electrode can be reduced. Furthermore, when preparing a binder composition containing the nonionic surfactant described above, it is preferable to first mix the first polymer and the nonionic surfactant to form a premixture, and then mix the resulting premixture with the second polymer. By adopting this mixing order, the haze value of the resulting binder composition can be well controlled. As a result, the dispersibility of the conductive material dispersion can be further improved, and the electrochemical element can exhibit even better cycle characteristics. Moreover, the resistance of the electrode obtained using the binder composition can be reduced.

[0082] (Conductive material dispersion) The conductive material dispersion of the present invention is a composition comprising a fibrous conductive material and the binder composition described above. That is, the conductive material dispersion of the present invention contains a fibrous conductive material, the first polymer described above, the second polymer described above, and the organic solvent described above, and optionally contains a conductive material other than the fibrous conductive material (other conductive material), the nonionic surfactant described above, and / or other components. Furthermore, because the conductive material dispersion of the present invention contains the binder composition of the present invention, it has excellent dispersibility, and electrodes formed using the conductive material dispersion can exhibit excellent cycle characteristics in electrochemical elements. The conductive material dispersion of the present invention is an intermediate product for preparing the electrode slurry of the present invention, which will be described later, and does not usually contain electrode active material. Furthermore, the first polymer and the second polymer, as well as the optionally included nonionic surfactant, contained in the conductive material dispersion of the present invention are derived from the binder composition of the present invention, and their preferred ratios are the same as those of the binder composition of the present invention.

[0083] <Fibrous conductive material> Examples of fibrous conductive materials include fibrous carbon materials such as carbon nanotubes (single-walled CNTs, multi-walled CNTs), carbon nanohorns, carbon nanofibers, and milled carbon fibers. The fibrous conductive material may be used individually or in combination of two or more types in any ratio. Among these, carbon nanotubes are preferred from the viewpoint of further improving the cycle characteristics of the electrochemical element while reducing resistance.

[0084] <<Properties>> Here, the fibrous conductive material such as CNT is not particularly limited, but it is preferable to have the following properties.

[0085] [Surface base content] The fibrous conductive material preferably has a surface base content of 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, more preferably 0.10 mmol / g or less, and more preferably 0.08 mmol / g or less. If the surface base content of the fibrous conductive material is 0.01 mmol / g or more, there will be less residual acid component adhering to the surface of the fibrous conductive material, which can suppress a decrease in the dispersibility of the conductive material dispersion due to side reactions. On the other hand, if the surface base content of the fibrous conductive material is 0.10 mmol / g or less, it is presumed that the aggregation of the fibrous conductive material can be suppressed, and the resistance of the electrodes can be reduced. In this invention, the "surface base content" and "surface acid content" of the fibrous conductive material can be measured using the method described in the examples.

[0086] [Surface acid content / Surface base content] Furthermore, the fibrous conductive material preferably has a surface acid content ratio (surface acid content / surface base content) of 0.1 or more, more preferably 0.2 or more, preferably 1.0 or less, more preferably 0.8 or less, even more preferably 0.6 or less, and particularly preferably 0.5 or less. If the surface acid content / surface base content is 0.1 or more, sufficient adhesion of the electrode composite layer obtained using the conductive material dispersion can be ensured, and the peel strength of the electrode can be improved. On the other hand, if the surface acid content / surface base content is 1.0 or less, the dispersibility of the conductive material dispersion can be further improved.

[0087] [BET specific surface area] Furthermore, the fibrous conductive material has a BET specific surface area of ​​100 m². 2 It is preferable that it be 150m or more / g. 2 It is more preferable that it be 200m or more per gram. 2 It is even more preferable that it be 300m or more per gram. 2 It is preferable that the BET specific surface area is 100 m² or less. 2 If the value is above / g, the resistance of the electrode can be reduced, 300m 2 It is presumed that if the value is less than / g, the first polymer and / or the second polymer can bond well to the fibrous conductive material, and sufficient peel strength of the electrode can be ensured. In this invention, the "BET specific surface area" of the fibrous conductive material can be measured using the method described in the examples.

[0088] <<Preparation method>> The method for preparing the fibrous conductive material is not particularly limited. Below, we will describe the preparation method using CNTs as an example, where the surface base content and the surface acid content / surface base content values ​​are within the preferred range described above. CNTs in which the surface base content and the surface acid content / surface base content values ​​fall within the preferred range described above can be prepared by following three steps: an acid treatment step of raw material CNTs, a base treatment step of acid-treated raw material CNTs, and a washing step of base-treated raw material CNTs.

[0089] —Acid treatment process— In the acid treatment process, the raw material CNTs are subjected to acid treatment. The raw material CNTs are not particularly limited and can be appropriately selected from known CNTs according to the desired surface-treated CNT properties (number of layers, BET specific surface area, etc.).

[0090] The method of acid treatment is not particularly limited as long as it allows the raw material CNTs to come into contact with an acid, but a preferred method is to immerse the raw material CNTs in an acid treatment solution (an aqueous solution of acid). The acid contained in the acid treatment solution is not particularly limited, but examples include nitric acid, sulfuric acid, and hydrochloric acid. These can be used individually or in combination of two or more. Among these, nitric acid and sulfuric acid are preferred.

[0091] The immersion time for the raw material CNTs in the acid treatment solution is preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, particularly preferably 50 minutes or more, preferably 120 minutes or less, more preferably 100 minutes or less, and even more preferably 80 minutes or less. If the immersion time is 1 minute or more, the surface acid content of the surface-treated CNTs can be increased, and if it is 120 minutes or less, the surface acid content of the surface-treated CNTs will not become excessively high, and the production efficiency of the surface-treated CNTs will be sufficiently ensured.

[0092] Furthermore, the temperature at which the raw material CNTs are immersed in the acid treatment solution (immersion temperature) is preferably 20°C or higher, more preferably 40°C or higher, preferably 80°C or lower, and more preferably 70°C or lower. If the immersion temperature is within the above range, the surface acid content of the resulting surface-treated CNTs can be appropriately increased.

[0093] After the immersion described above, the acid-treated CNTs (CNTs that have undergone the acid treatment process) can be recovered from a mixture of the acid treatment solution by known methods such as filtration. The recovered acid-treated CNTs may be washed with water if necessary.

[0094] —Base treatment process— In the base treatment process, the acid-treated CNTs obtained through the acid treatment process described above are subjected to base treatment.

[0095] The method of base treatment is not particularly limited as long as it allows the acid-treated CNTs to come into contact with a base, but a preferred method is to immerse the acid-treated CNTs in a base treatment solution (an aqueous solution of a base). The bases included in the base treatment solution are not particularly limited, but examples include lithium hydroxide, ammonium chloride, sodium bicarbonate, and sodium hydroxide. These can be used individually or in combination of two or more. Among these, lithium hydroxide and ammonium chloride are preferred, with lithium hydroxide being more preferred.

[0096] The immersion time for acid-treated CNTs in the base treatment solution is preferably 10 minutes or more, more preferably 60 minutes or more, even more preferably 80 minutes or more, particularly preferably 90 minutes or more, preferably 240 minutes or less, more preferably 200 minutes or less, and even more preferably 150 minutes or less. If the immersion time is 10 minutes or more, the amount of surface base on the surface-treated CNTs can be increased, and if it is 240 minutes or less, the amount of surface base on the surface-treated CNTs will not increase excessively, and the production efficiency of surface-treated CNTs will be sufficiently ensured.

[0097] Furthermore, the temperature at which the acid-treated CNTs are immersed in the base treatment solution (immersion temperature) is preferably 10°C or higher, more preferably 20°C or higher, preferably 40°C or lower, and more preferably 27°C or lower. If the immersion temperature is within the above range, the amount of surface base in the resulting surface-treated CNTs can be appropriately increased.

[0098] —Cleaning process— In the washing process, the raw material CNTs (acid-base treated CNTs) obtained through the acid treatment and base treatment processes described above are washed. This washing removes excess acid and base components (especially base components) adhering to the surface of the acid-base treated CNTs, thereby obtaining surface-treated CNTs with predetermined properties.

[0099] Furthermore, while there are no particular limitations on the method for washing acid-base treated CNTs, washing with water is preferred. For example, the acid-base treated CNTs can be recovered from a mixture of acid-base treated CNTs and a base treatment solution by known methods such as filtration, and the acid-base treated CNTs can be washed with water. At this time, the extent to which acid and base components have been removed can be estimated by measuring the electrical conductivity of the water used to wash the acid-base treated CNTs (wash water). After the cleaning process described above, surface-treated CNTs can be obtained by removing any water adhering to the surface by drying, if necessary.

[0100] Furthermore, the surface acid content and surface base content of surface-treated CNTs can be adjusted by changing the conditions of the acid treatment process, base treatment process, and washing process described above. For example, the surface acid content and surface base content of surface-treated CNTs can be adjusted by changing the types of acids and bases contained in the acid treatment solution and base treatment solution used in the acid treatment process and base treatment process, respectively, as well as their concentrations. In addition, the surface acid content of surface-treated CNTs can be increased by increasing the immersion time in the acid treatment process, and the surface base content of surface-treated CNTs can be increased by increasing the immersion time in the base treatment process. Moreover, the surface acid content and surface base content (especially the surface base content) can be adjusted by changing the degree of washing in the washing process.

[0101] <Other conductive materials> Other conductive materials are not particularly limited as long as they have a shape other than fibrous form (e.g., particulate, plate-like), and include carbon black (e.g., acetylene black, Ketjenblack®, Farnest Black, etc.) and graphene. Note that these other conductive materials may be used individually or in combination of two or more types in any ratio.

[0102] <Binder composition> As the binder composition, the binder composition of the present invention is used, which contains the first polymer described above, the second polymer described above, and the organic solvent described above, and optionally contains a nonionic surfactant and / or other components.

[0103] Here, when mixing the fibrous conductive material and the binder composition to obtain a conductive material dispersion, the ratio of the fibrous conductive material to the binder composition is not particularly limited. For example, the fibrous conductive material and the binder composition may be mixed in such a ratio that the resulting conductive material dispersion contains, in total, 5 to 40 parts by mass, more preferably 10 to 30 parts by mass, of the first polymer and the second polymer per 100 parts by mass of the fibrous conductive material.

[0104] <Method for preparing conductive material dispersion> The method for preparing the conductive material dispersion is not particularly limited. The conductive material dispersion can be prepared by mixing a fibrous conductive material and a binder composition, for example, using a known mixing apparatus. When preparing the conductive material dispersion, other conductive materials may be mixed in addition to the fibrous conductive material and binder composition, and organic solvents such as NMP may also be added.

[0105] (Slurry for electrochemical element electrodes) The electrode slurry of the present invention is a composition comprising an electrode active material and the conductive material dispersion described above. That is, the electrode slurry of the present invention contains at least an electrode active material, the fibrous conductive material described above, the first polymer described above, the second polymer described above, and the organic solvent described above. Here, the electrode slurry of the present invention preferably contains a fluorine-based polymer from the viewpoint of increasing the peel strength of the electrode and further improving the cycle characteristics of the electrochemical element. Furthermore, since the electrode slurry of the present invention contains a conductive material dispersion of the present invention, electrodes formed using this electrode slurry can exhibit excellent cycle characteristics in electrochemical elements. The fibrous conductive material, the first polymer, the second polymer, and the optionally included nonionic surfactant contained in the electrode slurry of the present invention are derived from the binder composition and the conductive material dispersion liquid of the present invention, and their preferred abundance ratios are the same as those of the binder composition and the conductive material dispersion liquid of the present invention.

[0106] <Electrode active material> As the electrode active material (positive electrode active material, negative electrode active material) to be blended in the electrode slurry, known electrode active materials can be used without particular limitation.

[0107] For example, the positive electrode active material used in a lithium ion secondary battery is not particularly limited, but includes metal oxides containing lithium (Li). And as the positive electrode active material, in addition to lithium (Li), a positive electrode active material containing at least one selected from the group consisting of cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe) is preferred. Such positive electrode active materials include lithium-containing cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium-containing nickel oxide (LiNiO2), lithium-containing composite oxides of Co-Ni-Mn, lithium-containing composite oxides of Ni-Mn-Al, lithium-containing composite oxides of Ni-Co-Al, olivine-type lithium manganese phosphate (LiMnPO4), olivine-type lithium iron phosphate (LiFePO4), Li 1+x Mn 2-x O4 (0 <X <2) represented by lithium-excess spinel compounds, Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4 and the like. The positive electrode active material may be used alone or in combination of two or more in any ratio.

[0108] The particle size of the electrode active material is not particularly limited and can be the same as that of the electrode active materials conventionally used. Furthermore, the amount of electrode active material in the electrode slurry is not particularly limited and can be within the range of conventionally used materials.

[0109] <Conductive material dispersion> As the conductive material dispersion, the conductive material dispersion of the present invention is used, which contains at least the fibrous conductive material described above, the first polymer described above, the second polymer described above, and the organic solvent described above.

[0110] <Fluorine-based polymers> Examples of fluorinated polymers include polyvinylidene fluoride (PVdF) and polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymers. A single fluorinated polymer may be used, or two or more may be combined in any ratio. Among these, polyvinylidene fluoride is preferred from the viewpoint of further increasing the peel strength of the electrode while simultaneously improving the cycle characteristics of the electrochemical element.

[0111] Furthermore, from the viewpoint of further increasing the peel strength of the electrode and further improving the cycle characteristics of the electrochemical element, the content of the fluorine-based polymer in the electrode slurry is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, preferably 3 parts by mass or less, and more preferably 2 parts by mass or less per 100 parts by mass of electrode active material.

[0112] <Method for preparing electrode slurry> The method for preparing the electrode slurry is not particularly limited. The electrode slurry can be prepared by mixing the electrode active material, a conductive material dispersion, and an optional component such as a fluorinated polymer using, for example, a known mixing apparatus. Alternatively, the electrode slurry can be prepared without going through the conductive material dispersion; for example, it may be prepared by mixing the first polymer, the second polymer, an organic solvent, and the electrode active material all at once.

[0113] (Electrodes for electrochemical devices) The electrode of the present invention comprises an electrode composite layer obtained using the electrode slurry of the present invention described above. More specifically, the electrode of the present invention typically comprises the electrode composite layer on a current collector. Since the electrode composite layer of the electrode of the present invention is formed from the electrode slurry of the present invention described above, the electrochemical element can exhibit excellent cycle characteristics. Here, the electrode composite layer typically consists of the dried electrode slurry of the present invention described above. The electrode composite layer contains at least an electrode active material, a fibrous conductive material, a first polymer, and a second polymer. The components contained in the electrode composite layer are those contained in the electrode slurry of the present invention described above, and the preferred ratio of these components is the same as the preferred ratio of each component in the electrode slurry of the present invention.

[0114] <Current collector> The current collector is made of a material that is electrically conductive and electrochemically durable. The current collector is not particularly limited, and any known current collector can be used. For example, the current collector in the positive electrode of a lithium-ion secondary battery may be made of aluminum or an aluminum alloy. In this case, a combination of aluminum and an aluminum alloy may be used, or a combination of different types of aluminum alloys may be used. Aluminum and aluminum alloys are excellent current collector materials because they are heat-resistant and electrochemically stable.

[0115] <Method of manufacturing electrodes> The method for manufacturing the electrode of the present invention is not particularly limited. For example, the electrode of the present invention can be manufactured by applying the electrode slurry of the present invention described above to at least one surface of a current collector and drying it to form an electrode composite layer. More specifically, the manufacturing method includes the steps of applying the electrode slurry to at least one surface of a current collector (coating step) and drying the electrode slurry applied to at least one surface of the current collector to form an electrode composite layer on the current collector (drying step).

[0116] <<Coating process>> The method for applying the electrode slurry onto the current collector is not particularly limited, and known methods can be used. Specifically, application methods such as the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, and brush application method can be used. In this case, the electrode slurry may be applied to only one side of the current collector or to both sides. The thickness of the slurry film on the current collector before drying after application can be appropriately set according to the thickness of the electrode composite layer obtained after drying.

[0117] <<Drying process>> The method for drying the electrode slurry on the current collector is not particularly limited and known methods can be used, such as drying with hot air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. By drying the electrode slurry on the current collector in this way, an electrode composite layer is formed on the current collector, and an electrode comprising the current collector and the electrode composite layer can be obtained.

[0118] Furthermore, after the drying process, the electrode composite layer may be subjected to pressure treatment using a die press or roll press. This pressure treatment allows the electrode composite layer to adhere well to the current collector. Furthermore, if the electrode composite layer contains a curable polymer, the polymer may be cured after the formation of the electrode composite layer.

[0119] (Electrochemical element) The electrochemical element of the present invention comprises the electrodes of the present invention as described above. Furthermore, because the electrochemical element of the present invention is equipped with the electrodes of the present invention, it exhibits excellent element characteristics such as cycle characteristics. The electrochemical element of the present invention is, for example, a non-aqueous secondary battery, and preferably a lithium-ion secondary battery.

[0120] Hereinafter, the configuration of a lithium-ion secondary battery as an example of the electrochemical element of the present invention will be described. This lithium-ion secondary battery comprises a positive electrode, a negative electrode, an electrolyte, and a separator. At least one of the positive electrode and the negative electrode is the electrode of the present invention. That is, in this lithium-ion secondary battery, the positive electrode may be the electrode of the present invention and the negative electrode may be an electrode other than the electrode of the present invention, the positive electrode may be an electrode other than the electrode of the present invention and the negative electrode may be the electrode of the present invention, or both the positive electrode and the negative electrode may be the electrode of the present invention.

[0121] <Electrodes other than the electrode of the present invention> Electrodes that do not fall under the electrodes of the present invention are not particularly limited and any known electrodes can be used.

[0122] <Electrolyte> Typically, an organic electrolyte is used, which is obtained by dissolving a supporting electrolyte in an organic solvent. For example, lithium salts are used as supporting electrolytes. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred, with LiPF6 being particularly preferred, because they are easily soluble in the solvent and exhibit a high degree of dissociation. Note that one type of electrolyte may be used alone, or two or more types may be used 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.

[0123] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte, but suitable examples include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (EMC); 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. A mixture of these solvents may also be used. Among these, carbonates are preferred because they have a high dielectric constant and a 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 solution 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. In addition, known additives, such as fluoroethylene carbonate or ethyl methyl sulfone, may be added to the electrolyte solution.

[0124] <Separator> The separator is not particularly limited, and for example, those described in Japanese Patent Publication No. 2012-204303 can be used. Among these, a microporous membrane made of polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it allows for a thinner overall film thickness of the separator, thereby increasing the ratio of electrode active material in the lithium-ion secondary battery and thus increasing the capacity per unit volume.

[0125] <Manufacturing method for lithium-ion secondary batteries> A lithium-ion secondary battery according to the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed according to the battery shape, placing them in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent pressure rise inside the secondary battery, overcharge and discharge, etc., an overcurrent prevention element such as a fuse or PTC element, expanded metal, lead plates, etc. may be provided as needed. The shape of the secondary battery may be any of the following: coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc. [Examples]

[0126] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" used to express quantities refer to mass unless otherwise specified. Furthermore, in polymers produced by copolymerizing multiple types of monomers, the proportion of monomer units formed by polymerizing a certain monomer in the polymer is, unless otherwise specified, usually equal to the ratio of that particular monomer to the total monomers used in the polymerization of the polymer (starting ratio). Also, in the case of a hydrogenated polymer produced by hydrogenating a polymer containing aliphatic conjugated diene monomer units, the total content ratio of unhydrogenated aliphatic conjugated diene monomer units and alkylene structural units as hydrogenated aliphatic conjugated diene monomer units in the hydrogenated polymer is equal to the ratio of aliphatic conjugated diene monomers to the total monomers used in the polymerization of the polymer (starting ratio). In the examples and comparative examples, various measurements and evaluations were performed using the following methods.

[0127] <Weight average molecular weight> The weight-average molecular weight of the polymers (first polymer, second polymer) was measured by gel permeation chromatography (GPC). Specifically, the weight-average molecular weight was calculated as a standard substance equivalent by creating a calibration curve using polystyrene as the standard substance. The measurement conditions were as follows: <<Measurement Conditions>> Column: TSKgel α-M x 2 (Inner diameter 7.8mm x 30cm x 2, manufactured by Tosoh Corporation) Eluent: Dimethylformamide (50 mM lithium bromide, 10 mM phosphoric acid) Flow rate: 0.5mL / min Sample concentration: Approximately 0.5 g / L (solid content concentration) Injection volume: 200μL Column temperature: 40℃ Detector: Differential refractive index detector (RI) (Tosoh Corporation HLC-8320 GPC RI detector) Detector conditions: RI: Pol(+), Res(1.0s) Molecular weight marker: Tosoh Corporation standard polystyrene kit PStQuick K <Iodine value> The iodine value of the first polymer was measured in accordance with JIS K 6235. <Contact angle with polyethylene film> Using a contact angle meter (Kyowa Interface Chemical Co., Ltd., product name "DMs-400"), 3 microliters of a binder composition with a solid content concentration of 15.0% by mass were dropped onto the surface of a polyethylene film (polyethylene separator substrate, Asahi Kasei Corporation, product name "ND412", thickness: 12 μm), and the contact angle (angle between the tangent of the binder composition droplet and the polyethylene film surface) was measured 10 seconds after dropping. The measurement was performed under conditions of 25°C. <Hayes> A haze meter (product name "NDH7000SP", manufactured by Nippon Denshoku Industries Co., Ltd., conforming to JIS K 7136:2000) was used. Under 25°C conditions, NMP was placed in a glass cell for liquid measurement and then standard calibration was performed. After that, a binder composition with a solid content concentration of 15.0% by mass was placed in the glass cell and measured. <Surface acid amount> Approximately 1 g of CNTs to be measured was accurately weighed, and 0.01 mol dm³ was measured. -3Immerse it in 100 ml of a tetrabutyl hydride (also referred to as "tetrabutylammonium hydroxide", hereinafter abbreviated as "TBA OH") / 4-methyl-2-pentanone (MIBK) solution and stir with a stirrer for 1 hour. Then perform centrifugation and filter the supernatant with a filter. Quantitatively analyze the TBA OH remaining in 50 mL of the obtained filtrate by non-aqueous coulometric titration with a perchloric acid (HClO4) / MIBK solution, and specify the acid amount (mmol / g) per gram of CNT from the obtained value. For the analysis, an automatic coulometric titrator (manufactured by Kyoto Electronics Co., Ltd., product name "AT-700") was used. Also, the series of operations was carried out at room temperature under an argon stream. -3 Quantitatively analyze the remaining TBA OH in 50 mL of the obtained filtrate by non-aqueous coulometric titration with a perchloric acid (HClO4) / MIBK solution, and specify the acid amount (mmol / g) per gram of CNT from the obtained value. For the analysis, an automatic coulometric titrator (manufactured by Kyoto Electronics Co., Ltd., product name "AT-700") was used. Also, the series of operations was carried out at room temperature under an argon stream. <Surface base amount> Precisely weigh approximately 1 g of the CNT to be measured, immerse it in 100 ml of a 0.01 mol dm -3 HClO4 / MIBK solution, and stir with a stirrer for 1 hour. Then perform centrifugation and filter the supernatant with a filter. Quantitatively analyze the HClO4 remaining in 50 mL of the obtained filtrate by non-aqueous coulometric titration with a 0.01 mol dm -3 TBA OH / MIBK solution, and specify the base amount (mmol / g) per gram of CNT from the obtained value. For the analysis, an automatic coulometric titrator (manufactured by Kyoto Electronics Co., Ltd., product name "AT-700") was used. Also, the series of operations was carried out at room temperature under an argon stream. <BET specific surface area> The BET specific surface area of the CNT was measured using a Belsorp-mini (manufactured by Microtrac·BEL Co., Ltd., compliant with ASTM D3037-81). <Dispersibility> For the conductive material dispersion, measure the viscosity with a rheometer (MCR302 manufactured by Anton Paar) at a temperature of 25 °C and a shear rate of 0.1 s -1 . Using this viscosity, evaluate the dispersibility of the conductive material dispersion according to the following criteria. At the same solid content concentration (or solid content concentration with extremely close values), the lower the viscosity of the conductive material dispersion, the better the fibrous conductive materials such as CNTs are dispersed. A: Viscosity is less than 300 Pa·s B: Viscosity between 300 Pa·s and less than 500 Pa·s C: Viscosity between 500 Pa·s and less than 700 Pa·s D: Viscosity of 700 Pa·s or higher <Peel strength> A test specimen was prepared by cutting a lithium-ion secondary battery positive electrode into a rectangle measuring 100 mm in length and 10 mm in width. Cellophane tape (compliant with JIS Z1522) was attached to the surface of the positive electrode composite layer with the positive electrode composite layer facing downwards. The stress was measured when the tape was peeled off by pulling one end of the current collector vertically at a speed of 100 mm / min (the cellophane tape was fixed to the test stand). Three measurements were taken, and the average value was calculated as the peel strength, which was then evaluated according to the following criteria. A higher peel strength value indicates that the positive electrode composite layer is firmly adhered to the current collector made of aluminum foil. A: Peel strength of 25 N / m or more B: Peel strength is 20 N / m or more and less than 25 N / m C: Peel strength of 15 N / m or more and less than 20 N / m D: Peel strength less than 15 N / m <Resistance (Through-hole resistance)> A positive electrode for a lithium-ion secondary battery was punched out in a circular shape with a diameter of 12 mm, and the thickness d (μm) and the area S of the positive electrode composite layer of the punched-out test piece were measured. The test piece was clamped in a fixture of a tensile and compression testing machine (manufactured by Imada Seisakusho Co., Ltd., product name "SV-301NA") and pressurized to a pressure of 20 MPa. A two-terminal clip was connected to the fixture, and the measurement cable was connected to an automatic polarization system (manufactured by Hokuto Denko Co., Ltd., product name "HSV-110"). Using chronopotentiometry mode, a constant current I = 10 mA was passed through the fixture for 10 minutes, and the voltage V (V) at that time was measured. From Ohm's law, the resistance R (Ω) = V / I was calculated, and further, the volume resistivity ρ (Ω·cm) = R × S / d was calculated to obtain the volume resistivity ρ of the through-hole method. The volume resistivity ρ obtained in this way was evaluated according to the evaluation criteria below. A: Volume resistivity ρ is less than 15 Ω·cm B: Volume resistivity ρ is between 15 Ω·cm and less than 30 Ω·cm C: Volume resistivity ρ is between 30 Ω·cm and less than 45 Ω·cm D: Volume resistivity ρ is 45 Ω·cm or higher <Cycle Characteristics> After the electrolyte was injected into the lithium-ion secondary battery, it was left to stand at 25°C for 5 hours. Next, it was charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then aged at 60°C for 12 hours. Then, it was discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.20V) was performed using a constant current method at 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This charging and discharging at 0.2C was repeated three times. Subsequently, 100 charge-discharge cycles were performed in an environment of 25°C with a cell voltage of 4.20-3.00V and a charge-discharge rate of 1.0C. The discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 100th cycle as X2. Using these discharge capacities X1 and X2, the capacity retention rate, expressed as ΔC = (X2 / X1) × 100 (%), was calculated and evaluated according to the following criteria. A larger value of this capacity retention rate ΔC indicates superior cycle characteristics of the lithium-ion secondary battery. A: Capacity retention rate ΔC is 93% or more B: Capacity retention rate ΔC is 90% or more but less than 93% C: Capacity retention rate ΔC is between 87% and 90%. D: Capacity retention rate ΔC is less than 87%

[0128] (Example 1) <Preparation of the first polymer (polymer 1-1)> [Polymerization (Preparation of Polymer Intermediates)] In the reactor, 180 parts of deionized water, 25 parts of a 10% aqueous solution of sodium dodecylbenzenesulfonate (emulsifier), 36 parts of acrylonitrile as a nitrile group-containing monomer, and 0.8 parts of t-dodecyl mercaptan as a molecular weight modifier were charged in this order. After replacing the internal gas with nitrogen three times, 64 parts of 1,3-butadiene as an aliphatic conjugated diene monomer were charged. The reactor was then maintained at 10°C, and 0.1 parts of cumene hydroperoxide (polymerization initiator) and 0.1 parts of ferrous sulfate were charged, and the polymerization reaction was continued with stirring. When the polymerization conversion rate reached 85%, 0.1 parts of a 10% aqueous solution of hydroquinone (polymerization inhibitor) was added to stop the polymerization reaction. Next, residual monomers were removed at a water temperature of 80°C to obtain nitrile rubber latex. Then, a portion of the obtained latex was added to an aqueous solution of magnesium sulfate in an amount equal to 12% relative to the nitrile rubber content, and the mixture was stirred to solidify the latex. After that, it was filtered while being washed with water, and the resulting solidified material was vacuum-dried at a temperature of 60°C for 12 hours to obtain nitrile rubber, which is an intermediate (polymer intermediate) of the target polymer. [Double decomposition of polymer intermediates] Next, 9 parts of the obtained nitrile rubber were dissolved in 141 parts of monochlorobenzene and added to the reactor. After heating the reactor to 80°C, 2 L of monochlorobenzene solution containing bis(tricyclohexylphosphine)benzylideneruthenium dichloride as a Grubbs catalyst was added so that the amount of Grubbs catalyst was 0.25 parts per 100 parts of polymer. The reactor was then pressurized to 3.5 MPa with ethylene as a coolefin, and the double decomposition reaction of the nitrile rubber was carried out at a stirring speed of 600 rpm. During the reaction, the temperature was kept constant using a cooling coil connected to a temperature control device and a thermal sensor. [Hydrogenation of multiple decomposed polymer intermediates] Subsequently, the reactor was degassed three times with H2 at 0.7 MPa while continuing to stir. Then, the reactor temperature was raised to 130°C, and 1 L of monochlorobenzene solution containing Wilkinson catalyst and triphenylphosphine was added to the reactor. The amount of Wilkinson catalyst was 0.075 parts and the amount of triphenylphosphine was 1 part per 100 parts of the double-decomposed polymer intermediate. The temperature was then raised to 138°C, and the hydrogenation reaction of the polymer was carried out for 6 hours under a hydrogen pressure of 8.4 MPa to obtain the hydrogenated polymer. After the reaction was complete, 0.2 parts of activated carbon with an average diameter of 15 μm was added to the reactor and stirred for 30 minutes. Then, the solution was filtered through a pore size 5 μm filter to obtain the filtrate. [Preparation of NMP composition] Fifty parts (equivalent to three parts as solids) of the hydrogenated polymer obtained according to the above procedure were taken and mixed with 17 parts of NMP to obtain a mixture. Next, the monochlorobenzene contained in the obtained mixture was completely evaporated under reduced pressure to obtain a 15% solution of polymer 1-1 (NMP composition). The iodine value and weight-average molecular weight of polymer 1-1 were then measured. The results are shown in Table 1. <Preparation of the second polymer (polymer 2-1)> [polymerization] In a reactor equipped with a stirrer, 90 parts of deionized water and 0.5 parts of ammonium persulfate were supplied, the gas phase was replaced with nitrogen gas, and the temperature was raised to 80°C. Meanwhile, in another container, 40 parts of deionized water, 0.8 parts of sodium dodecylbenzenesulfonate as an emulsifier, and methoxypolyethylene glycol #400 acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., "AM-90G", R) were added as monomer (II). 1 is a hydrogen atom, R 2 ) corresponds to a methyl group and the compound of formula (II) with n=9. 24.0 parts of ) 6.0 parts of styrene as an aromatic monovinyl monomer and 0.8 parts of t-dodecyl mercaptan as a molecular weight modifier were mixed to obtain a monomer composition. This monomer composition was continuously added to the reactor over 4 hours to carry out polymerization. The reaction was carried out at 80°C during the addition. After the addition was completed, 0.5 parts of ammonium persulfate was added and the reaction was further stirred at 80°C for 3 hours to complete the reaction and produce an aqueous dispersion of polymer 2-1. [Preparation of NMP composition] Twenty parts (equivalent to 4.6 parts as solids) of the aqueous dispersion of polymer 2-1 obtained according to the above procedure were taken and mixed with 26.2 parts of NMP to obtain a mixture. Next, all the water contained in the obtained mixture was evaporated under reduced pressure to obtain a 15% solution of polymer 2-1 (NMP composition). The weight-average molecular weight of polymer 2-1 was then measured. The results are shown in Table 1. <Preparation of binder composition for positive electrode> 70 parts of the NMP composition of the first polymer (polymer 1-1) obtained according to the above (10.5 parts in terms of solid content of polymer 1-1) and 0.5 parts of polyoxyethylene monolaurate (trade name: "Nonionic L-4", manufactured by NOF Corporation) as a nonionic surfactant were mixed using a disperser at a rotation speed of 300 rpm for 30 minutes while maintaining the mixing temperature at 25°C. To the resulting premixture, 30 parts of the NMP composition of the second polymer (polymer 2-1) obtained according to the above (4.5 parts in terms of solid content of polymer 2-1) were added and mixed using a disperser at a rotation speed of 300 rpm for 30 minutes while maintaining the mixing temperature at 25°C to obtain a binder composition. The contact angle and haze with a polyethylene film were measured for the obtained binder composition when the solid content concentration was 15.0% by mass. The results are shown in Table 1. The content of nonionic surfactant in the binder composition was 3.33 parts, based on a total mass of 100 parts of the first and second polymers. The mixing ratio of polymer 1-1 to polymer 2-1 in the binder composition was polymer 1-1:polymer 2-1 = 70:30. <Preparation of surface-treated carbon nanotubes (CNTs)> 1g weighed multi-walled carbon nanotube (BET specific surface area: 250m²) 2The CNTs (CNTs) were added to a mixed solution of 40 mL of concentrated nitric acid and 40 mL of 2 M sulfuric acid, and stirred for 1 hour while maintaining the temperature at 60°C (acid treatment). Then, solid-liquid separation was performed by filtration using filter paper (Toyo Roshi Kaisha, Filter Paper No. 2, 125 mm). After washing the solids on the filter paper with 200 mL of purified water, the CNT solids (acid-treated CNTs) were recovered. Furthermore, these CNT solids were added to 200 mL of a 2.5 mol / liter lithium hydroxide aqueous solution, and stirred for 2 hours while maintaining the temperature at 25°C in a water bath (base treatment). Then, solid-liquid separation was performed by suction filtration using a membrane filter with a pore size of 10 μm. The CNT solids (acid-base treated CNTs) on the membrane filter were repeatedly washed with purified water. When the electrical conductivity of the washing water was 50 μs / m or less, the CNT solids were separated from the liquid using the same method as above. The obtained CNT solids were dried under reduced pressure at 50°C for 8 hours to prepare surface-treated CNTs. The surface acid content of this surface-treated CNT is 0.015 mmol / g, the surface base content is 0.05 mmol / g, and the BET specific surface area is 250 m². 2 The value was / g. The ratio of surface acid amount to surface base amount was 0.3. <Preparation of conductive material dispersion> A conductive material dispersion with a solid content of 3.6% was prepared by stirring 3.0 parts of the above-mentioned surface-treated CNTs as a fibrous conductive material, 0.6 parts of the above-mentioned binder composition (in terms of solid content), and 96.4 parts of NMP using a disperser (3000 rpm, 10 minutes), and then mixing for 1 hour at a peripheral speed of 8 m / s using a bead mill with 1 mm diameter zirconia beads. The dispersibility of this conductive material dispersion was evaluated. The results are shown in Table 1. <Preparation of cathode slurry> 0.04 parts of the conductive material dispersion obtained as described above (total solid content of the first polymer and the second polymer) and a ternary active material having a layered structure as a positive electrode active material (LiNi 0.5 Co 0.2 Mn 0.3A cathode slurry was prepared by stirring 100 parts of O2 (volume-average particle size: 10 μm), 0.96 parts of PVdF as a fluorine-based polymer, and NMP as an organic solvent in a planetary mixer (60 rpm, 30 minutes). The amount of NMP added was adjusted so that the viscosity of the resulting cathode slurry composition (measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803:1991; temperature: 25°C, rotation speed: 60 rpm) was within the range of 4000 to 5000 mPa·s. <Fabrication of the positive electrode> As a current collector, a 20 μm thick aluminum foil was prepared. The positive electrode slurry obtained as described above was coated onto one side of the aluminum foil using a comma coater, resulting in a basis weight of 20 mg / cm² after drying. 2 The material was applied in this manner, dried at 90°C for 20 minutes, then at 120°C for 20 minutes, and then heat-treated at 60°C for 10 hours to obtain a cathode base. This cathode base was rolled using a roll press to form a cathode composite layer (density: 3.2 g / cm³). 3 A sheet-like positive electrode was fabricated from aluminum foil and aluminum foil. The sheet-like positive electrode was then cut to a width of 48.0 mm and a length of 47 cm to be used as a positive electrode for a lithium-ion secondary battery. The peel strength and resistance of this positive electrode were evaluated. The results are shown in Table 1. <Fabrication of the negative electrode> A mixture of 90 parts of spherical artificial graphite (volume average particle size: 12 μm) and 10 parts of SiOx (volume average particle size: 10 μm) as negative electrode active material, 1 part of styrene-butadiene polymer as a negative electrode binder, 1 part of carboxymethylcellulose as a thickener, and an appropriate amount of water as a dispersion medium was mixed in a planetary mixer to prepare a negative electrode slurry. Next, a copper foil with a thickness of 15 μm was prepared as the current collector. The negative electrode slurry obtained as described above was applied to one side of the copper foil, with a dry coating amount of 10 mg / cm². 2 The material was applied and dried at 60°C for 20 minutes and then at 120°C for 20 minutes. After that, it was heat-treated at 150°C for 2 hours to obtain a negative electrode base. This negative electrode base was rolled in a roll press to obtain a density of 1.6 g / cm³. 3 A sheet-like negative electrode was fabricated consisting of a negative electrode composite layer and copper foil. The sheet-like negative electrode was then cut to a width of 50.0 mm and a length of 52 cm to be used as a negative electrode for a lithium-ion secondary battery. <Manufacturing of lithium-ion secondary batteries> The positive and negative electrodes prepared as described above were placed with their electrode composite layers facing each other, and a 15 μm thick separator (a microporous film made of polypropylene) was interposed between them. The electrodes were then wound around a 20 mm diameter core to obtain a wound body. The resulting wound body was then compressed from one direction at a speed of 10 mm / second until its thickness reached 4.5 mm. The compressed wound body was elliptical in plan view, and its ratio of major axis to minor axis (major axis / minor axis) was 7.7. In addition, an electrolyte solution (a 1.0 M LiPF6 solution (the solvent was a mixed solvent of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (mass ratio) to which 5% by mass of fluoroethylene carbonate was added, with 2% by volume of vinylene carbonate added as an additive)) was prepared. Subsequently, the compressed coil was placed in an aluminum laminate case along with 3.2 g of electrolyte. Nickel lead wires were then connected to the designated locations for the negative electrode of the lithium-ion secondary battery, and aluminum lead wires were connected to the designated locations for the positive electrode of the lithium-ion secondary battery. Finally, the opening of the case was sealed with heat to obtain a lithium-ion secondary battery. This lithium-ion secondary battery was a pouch type with a width of 35 mm, a height of 60 mm, and a thickness of 5 mm, and the nominal capacity of the battery was 700 mAh. The cycle characteristics of the obtained lithium-ion secondary batteries were evaluated. The results are shown in Table 1.

[0129] (Examples 2 and 3) In preparing the second polymer, the amounts of methoxypolyethylene glycol #400 acrylate (AM-90G) and styrene were changed as follows, respectively. Otherwise, the first polymer, the second polymer, the cathode binder composition, surface-treated CNTs, conductive material dispersion, cathode slurry, cathode, anode, and lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1. Example 2 (Polymer 2-2): 22.5 parts AM-90G, 7.5 parts styrene (75:25) Example 3 (Polymer 2-3): 25.5 parts AM-90G, 4.5 parts styrene (85:15)

[0130] (Examples 4, 5, 9, 10) In preparing the binder composition for the positive electrode, the first polymer, the second polymer, the binder composition for the positive electrode, surface-treated CNTs, conductive material dispersion, slurry for the positive electrode, the negative electrode, and a lithium-ion secondary battery were prepared in the same manner as in Example 1, except that the amount of each NMP composition added was changed to alter the equivalent solid content of polymer 1-1 and polymer 2-1 as follows. Various evaluations were then performed. The results are shown in Tables 1 and 2. Example 4: 12 parts of 1-1, 3 parts of 2-1 (80:20) Example 5: 9 parts of 1-1, 6 parts of 2-1 (60:40) Example 9: 1-1 was 14.25 parts, and 2-1 was 0.75 parts (95:5) Example 10: 7.5 parts of 1-1 and 7.5 parts of 2-1 (50:50)

[0131] (Examples 6, 7, 15) Except for changing the mixing temperature to 45°C (Example 6), 15°C (Example 7), and 70°C (Example 15) during the preparation of the positive electrode binder composition, the first polymer, the second polymer, the positive electrode binder composition, surface-treated CNTs, conductive material dispersion, positive electrode slurry, positive electrode, negative electrode, and lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Tables 1 and 2.

[0132] (Example 8) Except for using polymer 1-2, which was prepared as described below, as the first polymer, a second polymer, a binder composition for the positive electrode, surface-treated CNTs, a conductive material dispersion, a slurry for the positive electrode, a negative electrode, and a lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1. <Preparation of the first polymer (polymer 1-2)> Nitrile rubber, a polymer intermediate, was obtained in the same manner as in Example 1. Hydrogenation was carried out in the same procedure as in Example 1, except that double decomposition of the polymer intermediate was not performed, to obtain a 15% solution of polymer 1-2 (NMP composition).

[0133] (Example 11) Except for using the binder composition for the positive electrode obtained as described below, the first polymer, the second polymer, a conductive material dispersion, surface-treated CNTs, a slurry for the positive electrode, a positive electrode, a negative electrode, and a lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2. <Preparation of binder composition for positive electrode> A binder composition was obtained by mixing 70 parts of the NMP composition of the first polymer (polymer 1-1) (equivalent to 10.5 parts of the solid content of polymer 1-1), 0.5 parts of polyoxyethylene monolaurate (trade name: "Nonion L-4", manufactured by NOF Corporation) as a nonionic surfactant, and 30 parts of the NMP composition of the second polymer (polymer 2-1) (equivalent to 4.5 parts of the solid content of polymer 2-1) using a disperser at a rotation speed of 300 rpm for 30 minutes while maintaining the mixing temperature at 25°C.

[0134] (Example 12) Except for using the binder composition for the positive electrode obtained as described below, the first polymer, the second polymer, a conductive material dispersion, surface-treated CNTs, a slurry for the positive electrode, a positive electrode, a negative electrode, and a lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2. <Preparation of binder composition for positive electrode> 70 parts of the NMP composition of the first polymer (polymer 1-1) (equivalent to 10.5 parts of the solid content of polymer 1-1) and 30 parts of the NMP composition of the second polymer (polymer 2-1) (equivalent to 4.5 parts of the solid content of polymer 2-1) were mixed using a disperser at a rotation speed of 300 rpm for 30 minutes while maintaining the mixing temperature at 25°C. To the resulting premixture, 0.5 parts of polyoxyethylene monolaurate (trade name: "Nonionic L-4", manufactured by NOF Corporation) as a nonionic surfactant was added and mixed using a disperser at a rotation speed of 300 rpm for 30 minutes while maintaining the mixing temperature at 25°C to obtain a binder composition.

[0135] (Example 13) Except for using the binder composition for the positive electrode obtained as described below, the first polymer, the second polymer, a conductive material dispersion, surface-treated CNTs, a slurry for the positive electrode, a positive electrode, a negative electrode, and a lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2. <Preparation of binder composition for positive electrode> A binder composition was obtained by mixing 70 parts of the NMP composition of the first polymer (polymer 1-1) (equivalent to 10.5 parts of the solid content of polymer 1-1) and 30 parts of the NMP composition of the second polymer (polymer 2-1) (equivalent to 4.5 parts of the solid content of polymer 2-1) using a disperser at a rotation speed of 300 rpm for 30 minutes while maintaining the mixing temperature at 25°C.

[0136] (Example 14) Except for changing the amount of polyoxyethylene monolaurate as a nonionic surfactant to 8 parts in the preparation of the binder composition for the positive electrode, the first polymer, the second polymer, the binder composition for the positive electrode, a conductive material dispersion, surface-treated CNTs, a slurry for the positive electrode, a positive electrode, a negative electrode, and a lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2. Furthermore, the content of nonionic surfactant in the binder composition was 53.3 parts, with the total mass of the first polymer and the second polymer being 100 parts.

[0137] (Comparative Examples 1 and 2) In preparing the second polymer, the amounts of methoxypolyethylene glycol #400 acrylate (AM-90G) and styrene were changed as follows, respectively. Except for these changes, the first polymer, the second polymer, the cathode binder composition, surface-treated CNTs, conductive material dispersion, cathode slurry, cathode, anode, and lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2. Comparative Example 1 (Polymer 2-4): 15.0 parts AM-90G, 15.0 parts styrene (50:50) Comparative Example 2 (Polymer 2-5): 28.8 parts AM-90G, 1.2 parts styrene (96:4)

[0138] In addition, in Tables 1 and 2 shown below, "AN" stands for Acrylonitrile Unit. "Mw" stands for weight-average molecular weight. "AM-90G" refers to a structural unit derived from AM-90G (methoxypolyethylene glycol #400 acrylate). "St" stands for styrene unit. "L-4" stands for nonionic L-4 (polyoxyethylene monolaurate). "1→NS→2" refers to the procedure of mixing the first polymer with a nonionic surfactant, and then mixing the resulting premixture with the second polymer. "One-time mixing" refers to the procedure of mixing the first polymer, the nonionic surfactant, and the second polymer all at once. "1→2→NS" refers to the procedure of mixing the first polymer and the second polymer, and then mixing the resulting premixture with a nonionic surfactant. "1→2" indicates a procedure in which the first polymer and the second polymer are mixed without using a nonionic surfactant. "First:Second (mixing ratio)" refers to the mixing ratio (by mass) of the first polymer and the second polymer.

[0139] [Table 1]

[0140] [Table 2]

[0141] Tables 1 and 2 show that the binder compositions of Examples 1 to 15, which contain a predetermined first polymer and a predetermined second polymer, and an organic solvent, make it possible to produce a conductive material dispersion with excellent dispersibility and a positive electrode that can exhibit excellent cycle characteristics in an electrochemical element. [Industrial applicability]

[0142] According to the present invention, it is possible to prepare a conductive material dispersion with excellent dispersibility and to provide a binder composition for electrochemical elements that can enable electrochemical elements to exhibit excellent cycle characteristics. Furthermore, according to the present invention, it is possible to provide a conductive material dispersion for electrochemical elements that has excellent dispersibility and can enable the electrochemical element to exhibit excellent cycle characteristics. Furthermore, according to the present invention, it is possible to provide a slurry for electrochemical element electrodes that can enable the electrochemical element to exhibit excellent cycle characteristics. Furthermore, according to the present invention, an electrochemical element with excellent cycle characteristics can be provided.

Claims

1. A binder composition for an electrochemical element comprising a first polymer, a second polymer, a nonionic surfactant, and an organic solvent, The first polymer comprises a nitrile group-containing monomer unit and at least one of an aliphatic conjugated diene monomer unit and an alkylene structural unit. The second polymer contains structural units represented by the following formula (I) in a proportion of 70% by mass or more and 95% by mass or less, with the total structural units in the second polymer being 100% by mass. A binder composition for electrochemical elements, wherein the nonionic surfactant is one or more selected from the group consisting of polyoxyethylene monolaurate, polyoxyethylene monostearate, and polyoxyethylene monooleate. 【Chemistry 1】 [In formula (I), R １ R represents a hydrogen atom or a methyl group. ２ [where n represents a hydrogen atom, a phenyl group, an alkyl group having 1 to 6 carbon atoms, or a phenyl group having 1 to 3 alkyl groups having 1 to 6 carbon atoms, and n represents an integer of 3 or more.]

2. The binder composition for an electrochemical element according to claim 1, wherein the second polymer further comprises aromatic monovinyl monomer units.

3. The binder composition for an electrochemical element according to claim 2, wherein the second polymer contains the aromatic monovinyl monomer units in a proportion of 5% by mass or more and 30% by mass or less, based on 100% by mass of all structural units in the second polymer.

4. The binder composition for an electrochemical element according to claim 1, wherein the ratio of the mass of the second polymer to the total mass of the first polymer and the second polymer is 10% by mass or more and 40% by mass or less.

5. The binder composition for an electrochemical element according to claim 1, wherein the organic solvent is N-methyl-2-pyrrolidone.

6. The binder composition for an electrochemical element according to claim 1, wherein the contact angle with the polyethylene film is 30° or more and 60° or less when the solid content concentration is 15.0% by mass.

7. The binder composition for electrochemical elements according to claim 1, wherein the haze is 45% or less when the solid content concentration is 15.0% by mass.

8. The binder composition for an electrochemical element according to claim 1, wherein the first polymer has a weight-average molecular weight of 20,000 or more and 250,000 or less.

9. A conductive material dispersion for an electrochemical element, comprising the binder composition for an electrochemical element described in claim 1 and a fibrous conductive material.

10. A slurry for an electrochemical element electrode, comprising a conductive material dispersion for an electrochemical element according to claim 9 and an electrode active material.

11. The slurry for electrochemical element electrodes according to claim 10, further comprising a fluorine-based polymer.

12. An electrode for an electrochemical element, comprising an electrode composite layer formed using the electrochemical element electrode slurry described in claim 10 or 11.

13. An electrochemical element comprising an electrode for an electrochemical element as described in claim 12.

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