KR20240070518A - Binder for electrodes, electrodes and storage devices - Google Patents

Abstract

A binder for electrodes with excellent cycle characteristics when used in power storage devices is provided. A structural unit (A) derived from a (meth)acrylic acid alkyl ester monomer and the following general formula (1) (wherein R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ² is an aromatic group which may have a substituent). ) and a structural unit (C) derived from a monomer having at least one selected from the group consisting of an epoxy group, a (block) isocyanate group, and a urethane group. Binder for electrodes.

Description

Binder for electrodes, electrodes and storage devices

The present invention relates to a binder for electrodes used in secondary batteries such as lithium ion secondary batteries and nickel hydride secondary batteries, power storage devices such as electrochemical capacitors, and especially non-aqueous electrolyte-based power storage devices using non-aqueous electrolytes such as organic solvents as electrolytes, and corresponding electrodes. It relates to an electrode containing a binder and a power storage device provided with the electrode.

Power storage devices such as lithium-ion secondary batteries and electrochemical capacitors are used in electronic devices such as mobile phones, laptop computers, and camcorders. In recent years, due to the growing awareness of environmental protection and the development of related laws, their application as storage batteries for vehicles such as electric vehicles and hybrid electric vehicles and for storing power for home use is also progressing.

In addition, as these applications progress, there is a demand for increased performance of power storage devices, and improvements in members such as electrodes are progressing. Electrodes used in such electrical storage devices are usually obtained by applying and drying an electrode material consisting of an active material, a conductive additive, a binder, and a solvent onto a current collector.

Therefore, recent attempts have been made to improve the binder used in electrodes. By improving the binder, the binding properties between active materials, the binding properties between active materials and conductive additives, and the binding properties between active materials and the current collector are improved, thereby improving electrical properties (e.g., cycle characteristics, output characteristics at low temperatures, and lower resistance). It is proposed to do so.

A binder is required to have excellent binding properties when used in an electrode and to be able to provide excellent electrical properties to a power storage device. For example, a new binder is proposed in Patent Document 1. However, recently, binders with particularly excellent binding properties have been required, necessitating additional review.

Therefore, the present applicant has been developing a binder having an aromatic group such as Patent Document 2 in order to develop a binder that has excellent binding properties and good characteristics when used in power storage devices, but additional examination is required.

Patent Document 1: International Publication No. 2013/180103 Patent Document 2: International Publication No. 2019/131771

The purpose of the present invention is to provide a binder for electrodes that has excellent cycle characteristics when used in an electrical storage device.

As a result of repeated studies to achieve the above problem, the present inventors have found that the structural units of the polymer contained in the binder for electrodes include a structural unit derived from a (meth)acrylic acid alkyl ester monomer and a structural unit derived from a monomer having an aromatic group. , an epoxy group, a (blocked) isocyanate group, and a urethane group.

That is, the present invention relates to the following.

Item 1. A structural unit (A) derived from a (meth)acrylic acid alkyl ester monomer,

A structural unit (B) derived from a monomer represented by the following general formula (1),

A binder for electrodes comprising a polymer containing a structural unit (C) derived from a monomer having at least one type selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group:

(In the formula, R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ² is an aromatic group that may have a substituent.)

Item 2. The binder for electrodes according to Item 1, wherein the structural unit (B) is a structural unit derived from a monomer represented by the following general formula (2):

(In the formula, R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² are each independently hydrogen, is any one of a hydroxyl group, an alkyl group having 1 to 3 carbon atoms, or an aromatic group which may have a substituent, R ¹³ is an alkylene group having 1 to 3 carbon atoms or a carbonyl group, R ¹⁴ is an aromatic group which may have a substituent, q , r are each independently an integer from 0 to 3, and s is an integer from 0 to 1.)

Item 3. The electrode binder according to Item 1 or 2, further comprising a polymer containing a structural unit (D) derived from a monomer having a hydroxyl group represented by the following general formula (3):

(In the formula, R ¹⁵ is a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, x is each independently an integer of 2 to 8, and n is an integer of 2 to 30.)

Item 4. The electrode binder according to any one of Items 1 to 3, further comprising a polymer containing a structural unit (E) derived from a pentafunctional or less polyfunctional (meth)acrylate monomer.

Item 5. The binder for electrodes according to item 4, wherein in the structural unit (E), the five-functional or less polyfunctional (meth)acrylate monomer is a compound represented by the following general formula (5):

(In the formula, R ¹⁶ is the same or different and is a hydrogen atom or a methyl group, R ¹⁷ is a pentavalent organic group having 2 to 100 carbon atoms, and m is an integer of 5 or less.)

Item 6. An electrode comprising the electrode binder according to any one of Items 1 to 5.

Item 7. An electrical storage device comprising the electrode according to item 6.

The binder of the present invention has constant dynamic viscoelastic properties in the swelling state of the solvent used in the electrolyte solution, and thus has excellent cycle characteristics when used in an electrical storage device. The reason for this is not clear, but when the active material of the electrode material in the electrode shrinks when using a power storage device, the toughness to follow the shrinkage is a monomer having an epoxy group, (block) isocyanate group, and urethane group in addition to the structural unit derived from the aromatic group. It is presumed that it was given by having a structural unit derived from . The power storage device of the present invention is useful for use in vehicles such as electric vehicles and hybrid electric vehicles, and for power storage devices such as storage batteries for home power storage.

In this specification, an electrical storage device includes a secondary battery (lithium ion secondary battery, nickel hydride secondary battery, etc.) and an electrochemical capacitor. Additionally, in this specification, “(meth)acrylate” means “acrylate or methacrylate” and the same applies to similar expressions.

<1. Binder for electrodes>

The binder for electrodes of the present invention includes a structural unit (A) derived from a (meth)acrylic acid alkyl ester monomer,

A structural unit (B) derived from a monomer represented by the following general formula (1),

A binder for electrodes containing a polymer containing a structural unit (C) derived from a monomer having at least one type selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group:

(In the formula, R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ² is an aromatic group that may have a substituent.)

Below, the structural units of the polymer of the present invention will be described in detail. Additionally, in the present invention, “(meth)acrylic” means “acrylic or methacrylic” and the same applies to similar expressions. Additionally, “(block) isocyanate group” means “isocyanate group or blocked isocyanate group.”

(Constitutive unit (A))

The structural unit (A) is a structural unit derived from a (meth)acrylic acid alkyl ester monomer.

The structural unit (A) is preferably a structural unit derived from a (meth)acrylic acid alkyl ester monomer having an alkyl group having 1 to 22 carbon atoms, and the structural unit is derived from a (meth)acrylic acid alkyl ester monomer having an alkyl group having 2 to 18 carbon atoms. It is more preferable that it is a unit, and it is especially preferable that it is a structural unit derived from a (meth)acrylic acid alkyl ester monomer having an alkyl group of 4 to 18 carbon atoms.

Specific examples of preferred structural units (A) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, ( (meth)acrylic acid n-pentyl, (meth)acrylic acid isopentyl, (meth)acrylic acid n-hexyl, (meth)acrylic acid isohexyl, (meth)acrylic acid n-heptyl, (meth)acrylic acid n-octyl, (meth)acrylic acid 2 -Constitutive units derived from (meth)acrylic acid alkyl esters such as ethylhexyl, lauryl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, and stearyl (meth)acrylate. can be exemplified. There may be one type of structural unit (A) contained in a polymer, and two or more types may be sufficient as it.

The lower limit of the ratio of the structural unit (A) of the polymer is preferably 30% by mass or more, more preferably 40% by mass or more, and the upper limit is preferably 65% by mass or less, more preferably 60% by mass or less, and 55% by mass. It is particularly preferable that it is % or less.

(Constitutive unit (B))

The structural unit (B) is a structural unit derived from general formula (1). There may be one type of structural unit (B) contained in the polymer, or two or more types may be used:

(In the formula, R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ² is an aromatic group that may have a substituent.)

In the structural unit derived from General Formula (1), R ¹ is hydrogen or an alkyl group with 1 to 4 carbon atoms, preferably hydrogen or an alkyl group with 1 to 2 carbon atoms, and particularly preferably hydrogen or a methyl group. R ² is an aromatic group that may have a substituent, and the substituents include alkyl groups such as methyl, ethyl and isopropyl groups, unsaturated hydrocarbon groups such as vinyl groups, halogeno groups such as fluoro groups, chloro groups, bromo groups and iodine groups, Amino group, nitro group, carboxyl group, etc. are mentioned. Additionally, you may have two or more aromatic rings.

The structural unit derived from general formula (1) is preferably a structural unit based on a monomer represented by the following general formula (2):

(In the formula, R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² are each independently hydrogen, is any one of a hydroxyl group, an alkyl group having 1 to 3 carbon atoms, or an aromatic group which may have a substituent, R ¹³ is an alkylene group or a carbonyl group having 1 to 3 carbon atoms, R ¹⁴ is an aromatic group which may have a substituent, q, r is each independently a number from 0 to 3, and s is a number from 0 to 1.)

In the structural unit derived from general formula (2), R ¹ is hydrogen or an alkyl group with 1 to 4 carbon atoms, preferably hydrogen or an alkyl group with 1 to 2 carbon atoms, and particularly preferably hydrogen or a methyl group. R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² may each independently have hydrogen, a hydroxyl group, an alkyl group having 1 to 3 carbon atoms, or a substituent. It is preferably any one of an aromatic group, a hydrogen group, a hydroxyl group, an alkyl group having 1 to 2 carbon atoms, or an aromatic group that may have a substituent. R ¹³ is an alkylene group or carbonyl group having 1 to 3 carbon atoms, and is preferably an alkylene group or carbonyl group having 1 to 2 carbon atoms. R ¹⁴ is an aromatic group that may have a substituent, and the aromatic group is preferably an aryl group, benzyl group, or phenoxy group. Substituents include alkyl groups such as methyl, ethyl, and isopropyl groups, unsaturated hydrocarbon groups such as vinyl groups, halogeno groups such as fluoro groups, chloro groups, bromo groups, and iodine groups, amino groups, nitro groups, and carboxyl groups. there is. Additionally, you may have two or more aromatic rings.

q and r are each independently numbers from 0 to 3, preferably from 0 to 2, and preferably satisfy q+r≥1. s is a number from 0 to 1.)

Specific examples of structural units derived from general formula (1) include benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, and 2-hyde (meth)acrylate. Structural units based on oxy-3-phenoxypropyl, (meth)acrylic acid phenoxydiethylene glycol, neopentyl glycol-(meth)acrylic acid-benzoic acid ester, and 2-(meth)acryloyloxyethyl-phthalic acid can be exemplified. there is. There may be one type or two or more types of structural units based on General Formula (1).

The lower limit of the proportion of the polymer structural unit (B) is preferably 20% by mass or more, more preferably 25% by mass or more, and especially preferably 30% by mass or more. Moreover, the upper limit of the proportion of the structural unit (B) of the polymer is preferably 60 mass% or less, more preferably 50 mass% or less, and especially preferably 45 mass% or less. This range is desirable because the affinity between the current collector foil and the active material is improved when used in an electrode.

It is preferable that the total of the structural units (A) and structural units (B) in the polymer is 70 mass% or more, more preferably 75 mass% or more, and especially preferably 80 mass% or more.

(Constitutive Unit (C))

The structural unit (C) is a structural unit derived from a monomer having at least one selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group (also referred to as a urethane bond). In the present invention, the polymer contained in the binder for electrodes preferably contains at least one selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group. That is, even after the monomer forming the structural unit (C) polymerizes with the monomer forming the structural unit (A) and the monomer forming the structural unit (B) to form a polymer, among the monomers forming the structural unit (C) It is preferable that at least a portion of at least one selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group remains. This is because the inclusion of these groups in the polymer can function as a crosslinking group in the electrode binder and contribute to improving the cycle characteristics of the electrical storage device. There may be one type of structural unit (C) contained in a polymer, and two or more types may be sufficient as it.

Among the monomers forming the structural unit (C), those having at least one type selected from the group consisting of an epoxy group, a (block) isocyanate group, and a urethane group are preferably those having a reactive double bond. In addition, there may be one type of this structural unit, or two or more types may be sufficient as it.

Specific examples of structural units derived from monomers having an epoxy group include allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, and 4-hydroxybutylacrylate glycidyl ether.

(Block) Specific examples of structural units derived from monomers having an isocyanate group include 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, and 2-[0-(1'-methylpropylidene amino) carboxyamino. ]Ethyl methacrylate, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, 2-(2-methacrylate Examples include structural units derived from 1oxyethyloxy)ethyl isocyanate, etc.

Specific examples of structural units derived from monomers having a urethane group include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, phenylglycidyl ether acrylate hexamethylene diisocyanate urethane prepolymer, and pentaerythritol triacrylate toluene diisocyanate urethane prepolymer. , pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, etc.

The lower limit of the proportion of the structural unit (C) in the polymer derived from a monomer having at least one selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group is preferably 0.5% by mass or more, and is preferably 1% by mass or more. It is more preferable, and it is especially preferable that it is 2 mass % or more. In addition, the upper limit of the proportion of the structural unit (C) in the polymer derived from a monomer having at least one selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group is preferably 10% by mass or less, and 8% by mass. It is more preferable that it is 6 mass % or less, and it is especially preferable that it is 6 mass % or less.

(Constitutive unit (D))

The structural unit (D) is a structural unit derived from a monomer having a hydroxyl group represented by the following general formula (3). In the binder for electrodes of the present invention, it is preferable that the polymer contains the structural unit (D) because ion conductivity is improved when the binder is used in an electrode:

(In the formula, R ¹⁵ is a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, each of the n x is independently an integer of 2 to 8, and n is an integer of 2 to 30.)

In general formula (3), R ¹⁵ preferably includes a hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, and isobutyl group. Preferably it is a hydrogen atom or a methyl group. That is, the monomer having a hydroxyl group in the structural unit (D) is preferably a (meth)acrylate monomer (where R ¹⁵ is a hydrogen atom or a methyl group).

In general formula (3), (C _x H _2x O) is a straight-chain or branched alkyl ether group, and each of the n Preferably it is an integer of 2 to 6.

In General Formula (3), n is an integer of 2 to 30, preferably an integer of 2 to 25, and more preferably an integer of 2 to 20.

The structural unit (D) is preferably derived from a monomer having a hydroxyl group represented by the following general formula (4):

In general formula (4), R ¹⁵ is a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, o is an integer from 0 to 30, p is an integer from 0 to 30, and o+p is an integer from 2 to 30. It's 30. Here, o and p only represent the composition ratio of the structural unit, and do not only mean a compound consisting of a block of (C ₂ H ₄ O) repeating units and a block of (C ₃ H ₆ O) repeating units, The repeating unit of (C ₂ H ₄ O) and the repeating unit of (C ₃ H ₆ O) may be arranged alternately or randomly, or may be a compound in which random portions and block portions are mixed.

In general formula (4), R ¹⁵ preferably includes a hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, and isobutyl group. Preferably it is a hydrogen atom or a methyl group. That is, the monomer having a hydroxyl group in the structural unit (D) is preferably a (meth)acrylate monomer (where R ¹⁵ is a hydrogen atom or a methyl group).

In general formula (4), o is an integer from 0 to 30, p is an integer from 0 to 30, o+p is an integer from 2 to 30, o is an integer from 0 to 25, and p is an integer from 0 to 25. It is an integer, and o+p is preferably an integer of 2 to 25, o is an integer of 0 to 20, p is an integer of 0 to 20, and o+p is particularly preferably an integer of 2 to 20.

Specific examples of monomers having a hydroxyl group represented by general formula (3) include diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, tetraethylene glycol mono(meth)acrylate, and polyethylene glycol mono(meth)acrylate. ) Acrylate, dipropylene glycol mono(meth)acrylate, tripropylene glycol mono(meth)acrylate, tetrapropylene glycol mono(meth)acrylate and polypropylene glycol mono(meth)acrylate, polyethylene glycol-propylene glycol- Mono(meth)acrylate, polyethylene glycol-tetramethylene glycol-mono(meth)acrylate, etc. can be mentioned. These can be used one type or two or more types together. Among these, tetraethylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, tetrapropylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate are preferable.

There may be one type of structural unit (D) arbitrarily contained in a polymer, and two or more types may be sufficient as it.

The lower limit of the proportion of the structural unit (D) based on a monomer having a hydroxyl group in the polymer is preferably 0.5 mass% or more, more preferably 1 mass% or more, and particularly preferably 1.5 mass% or more. The upper limit of the proportion of the structural unit (D) based on a monomer having a hydroxyl group in the polymer is preferably 15 mass% or less, more preferably 12 mass% or less, and especially preferably 10 mass% or less.

(Constitutive unit (E))

The structural unit (E) is a structural unit derived from a polyfunctional (meth)acrylate monomer of 5 or less functions. The polyfunctional (meth)acrylate monomer specifically means a (meth)acrylate monomer having two or more (meth)acryloyl groups. It is preferable that the polymer contains a structural unit (E) derived from a polyfunctional (meth)acrylate monomer of 5 or less functions in order to stabilize the binder particles. The structural unit (E) is preferably a structural unit derived from the following general formula (5):

In general formula (5), R ¹⁶ is the same or different and is a hydrogen atom or a methyl group, R ¹⁷ is a pentavalent organic group having 2 to 100 carbon atoms, and m is an integer of 5 or less.

In the general formula (5), m is preferably 2 to 5 (i.e., a structural unit in which the structural unit (D) is derived from a di- or penta-functional (meth)acrylate), and 3 to 5 (i.e., a structural unit derived from a di- or penta-functional (meth)acrylate). It is more preferable that the unit (E) is a structural unit derived from 3- to 5-functional (meth)acrylate), and 3 to 4 (i.e., the structural unit (E) is a structural unit derived from 3- to 4-functional (meth)acrylate). It is particularly preferable that it is a derived structural unit).

Specific examples of structural units based on monomers having two (meth)acryloyl groups in the structural unit (E) include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate. ) Acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, dioxane glycol di( Structural units derived from bifunctional (meth)acrylates such as meth)acrylate, bis(meth)acryloyloxyethyl phosphate, and neopentyl glycol di(meth)acrylate can be mentioned.

Specific examples of structural units based on monomers having three (meth)acryloyl groups in structural unit (E) include trimethylolpropane tri(meth)acrylate, trimethylolpropane EO addition tri(meth)acrylate, and trimethylolpropane. PO addition tri(meth)acrylate, pentaerythritol tri(meth)acrylate, 2,2,2-tris(meth)acryloyloxymethylethylsuccinic acid, ethoxylated isocyanuric acid tri(meth)acrylate, ε-caprolactone modified tris(2-(meth)acryloxyethyl)isocyanurate, glycerin EO added tri(meth)acrylate, glycerin PO added tri(meth)acrylate and tris(meth)acryloyloxyethyl. and structural units derived from trifunctional (meth)acrylates such as phosphate. Among these, structural units derived from trifunctional (meth)acrylates selected from trimethylolpropane tri(meth)acrylate, trimethylolpropane EO addition tri(meth)acrylate, and pentaerythritol tri(meth)acrylate are preferred. do.

Specific examples of structural units based on monomers having four (meth)acryloyl groups in structural unit (E) include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, and pentaerythritol EO. Structural units derived from tetrafunctional (meth)acrylates such as addition tetra(meth)acrylate can be mentioned.

Specific examples of structural units based on monomers having five (meth)acryloyl groups in the structural unit (E) include structural units derived from dipentaerythritol penta(meth)acrylate.

When the polymer contains the structural unit (E), the lower limit of the ratio is preferably 1 mass% or more, more preferably 3 mass% or more, may be 5 mass% or more, and may be 5.2 mass% or more. Moreover, the upper limit of the ratio of the structural unit (E) of the polymer is preferably 15 mass% or less, more preferably 12 mass% or less, and especially preferably 10 mass% or less. This range is preferable because binding properties improve when used in electrodes.

There may be one type of structural unit (E) arbitrarily contained in a polymer, and two or more types may be sufficient as it.

(Constitutive Unit (F))

The structural unit (F) is a structural unit derived from a (meth)acrylic acid monomer. It is preferable that the polymer contain a structural unit (F) derived from a (meth)acrylic acid monomer because it improves affinity with the active material when used in an electrode.

Examples of the structural unit (F) include structural units derived from compounds selected from acrylic acid and methacrylic acid. There may be one type, or two or more types, of structural units (F) arbitrarily contained in a polymer.

When the polymer contains a structural unit (F), the lower limit is preferably 3% by mass or more, more preferably 4% by mass or more, and especially preferably 5% by mass or more. The upper limit is preferably 15 mass% or less, more preferably 12 mass% or less, and particularly preferably 10 mass% or less.

The total ratio of the structural unit (A), structural unit (B), structural unit (C), structural unit (D), structural unit (E), and structural unit (F) in the polymer is preferably 85% by mass or more, and is preferably 90% by mass or more. It is more preferable that it is mass % or more, and it is especially preferable that it is 95 mass % or more, and it may be 97 mass % or more, and may be 100 mass %.

In addition to the above, the polymer includes structural units derived from other monomers such as fumaric acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, acrylonitrile, methacrylnitrile, α-chloroacrylonitrile, crotonnitrile, and α-chloroacrylonitrile. -It may have structural units derived from monomers selected from ethyl acrylonitrile, α-cyanoacrylate, vinylidene cyanide, and fumaronitrile. There may be one type, or two or more types, of these structural units arbitrarily contained in a polymer.

(Method for producing polymer)

As a method for obtaining the polymer, a general emulsion polymerization method, a soap-free emulsion polymerization method, etc. can be used. Specifically, in a closed container equipped with a stirrer and a heating device, a composition containing a monomer, an emulsifier, a polymerization initiator, water, and, if necessary, a dispersant, a chain transfer agent, a pH adjuster, etc., is stirred under an inert gas atmosphere at room temperature to dissolve the monomers, etc. in water. Emulsify. Emulsification methods can be applied by stirring, shearing, ultrasonic waves, etc., and stirring blades, homogenizers, etc. can be used. Subsequently, polymerization is initiated by raising the temperature while stirring to obtain a spherical polymer latex in which the polymer is dispersed in water. The monomer addition method during polymerization may include monomer instillation or preemulsion dripping in addition to bulk addition, and two or more of these methods may be used in combination. In addition, preemulsion dropwise refers to an addition method in which monomers, emulsifiers, water, etc. are first emulsified and then the emulsion is added dropwise.

The emulsifier used in the present invention is not particularly limited. Emulsifiers are surfactants, and these surfactants include reactive surfactants having reactive groups. Nonionic surfactants and anionic surfactants commonly used in emulsion polymerization can be used.

Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alcohol ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyalkylene alkyl ether, and sorbitol. Examples include bitan fatty acid ester, polyoxyethylene fatty acid ester, and polyoxyethylene sorbitan fatty acid ester, and examples of reactive nonionic surfactants include Lathemru PD-420, 430, 450 (manufactured by Kao Corporation) and Adecaria Soph ER ( (manufactured by Adeka Co., Ltd.), Aqualon RN (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Antox LMA (manufactured by Nippon New Kazai Co., Ltd.), and Antox EMH (manufactured by Nippon New Kazai Co., Ltd.).

Examples of anionic surfactants include sulfuric acid ester type, carboxylic acid type, or sulfonic acid type metal salt, ammonium salt, triethanol ammonium salt, and phosphoric acid ester type surfactant. Sulfuric acid ester type, sulfonic acid type, and phosphoric acid ester type are preferred, and sulfuric acid ester type is particularly preferred. Representative examples of sulfuric acid ester type anionic surfactants include alkyl sulfate metal salts such as dodecyl sulfate, ammonium or alkyl sulfate triethanolamine, polyoxyethylene dodecyl ether sulfuric acid, polyoxyethylene isodecyl ether sulfuric acid, and polyoxyethylene tridecyl ether. Examples include polyoxyethylene alkyl ether sulfate metal salts such as sulfuric acid, ammonium salts, or polyoxyethylene alkyl ether sulfate triethanolamine, etc. Specific examples of sulfuric acid ester type reactive anionic surfactants include Lathemru PD-104 and 105 (manufactured by Kao Corporation). ), Adecaria soap SR (manufactured by Adeka Corporation), Aqualon HS (manufactured by Daiichi Kogyo Seiyaku Corporation), and Aqualon KH (manufactured by Daiichi Kogyo Seiyaku Corporation). Preferred examples include sodium dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine dodecyl sulfate, sodium dodecylbenzenesulfonate, and Lathemru PD-104.

These nonionic surfactants and/or anionic surfactants may be used 1 type or 2 or more types.

The reactivity of a reactive surfactant means that it contains a reactive double bond and undergoes a polymerization reaction with a monomer during polymerization. In other words, the reactive surfactant acts as an emulsifier for monomers during polymerization to produce a polymer, and after polymerization, it is covalently bonded and introduced into a portion of the polymer. For this reason, emulsion polymerization and dispersion of the produced polymer are good, and the physical properties (flexibility and binding properties) as a binder for electrodes are excellent.

The amount of the structural unit of the emulsifier may be the amount generally used in emulsion polymerization. Specifically, it is in the range of 0.01 to 25% by mass, preferably 0.05 to 20% by mass, more preferably 0.1 to 20% by mass, relative to the amount of monomer charged (100% by mass).

The polymerization initiator used in the present invention is not particularly limited, and polymerization initiators commonly used in emulsion polymerization and suspension polymerization can be used. Preferably it is emulsion polymerization. In the emulsion polymerization method, a water-soluble polymerization initiator is used, and in the suspension polymerization method, an oil-soluble polymerization initiator is used.

Specific examples of the water-soluble polymerization initiator include water-soluble polymerization initiators represented by persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, and 2-2'-azobis[2-(2-imidazolin-2-yl). ) propane], or its hydrochloride or sulfate salt, 2,2'-azobis[2-methyl-n-(2-hydroxyethyl)triamide], 2,2'-azobis(2-methylpropanamidine) , or its hydrochloride or sulfate salt, 3,3'-[azobis[(2,2-dimethyl-1-iminoethane-2,1-diyl)imino]]bis(propanoic acid), 2'-[azo A polymerization initiator of a water-soluble azo compound such as [bis(dimethylmethylene)]bis(2-imidazoline) is preferred.

Oil-soluble polymerization initiators include organic peroxides such as cumene hydroperoxide, benzoyl peroxide, acetyl peroxide, and t-butyl hydroperoxide, azobisisobutyronitrile, and 1,1'-azobis(cyclohexanecarbonitrile). Polymerization initiators of oil-soluble azo compounds and redox-based initiators are preferred. These polymerization initiators may be used singly or in combination of two or more types.

The amount of polymerization initiator used may be the amount generally used in emulsion polymerization or suspension polymerization. Specifically, it is in the range of 0.01 to 10% by mass, preferably 0.01 to 5% by mass, more preferably 0.02 to 3% by mass, relative to the amount of monomer charged (100% by mass).

Chain transfer agents can be used as needed. Specific examples of chain transfer agents include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan; 2 , xanthine compounds such as 4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene, dimethylxanthine disulfide, diisopropylxanthine disulfide, terpinolene, Thiuram-based compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide, and phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol. Compounds, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, and α-benzyloxyacrylamide. , triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, etc., and these may be used alone or in combination of two or more. The amount of these chain transfer agents is not particularly limited, but is usually used in an amount of 0 to 5 parts by mass based on 100 parts by mass of the amount of monomer charged.

In the production of polymers, the polymerization temperature and polymerization time are not particularly limited. It can be appropriately selected depending on the type of polymerization initiator used, but generally the polymerization temperature is 20 to 100°C and the polymerization time is 0.5 to 100 hours.

The binder for electrodes of the present invention contains a polymer. Other substances such as moisture or emulsifiers may be contained inside the polymer or may adhere to the outside. The amount of the substance contained inside or attached to the outside is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, and especially preferably 3 parts by mass or less, based on 100 parts by mass of the polymer.

<Evaluation of dynamic viscoelasticity during swelling of binder>

Evaluation of the dynamic viscoelasticity of the electrode binder of the present invention when swollen in a solvent used in an electrolyte solution is performed by measuring the dynamic viscoelasticity of a film (swollen film with a thickness of 1.0 to 2.0 mm) obtained by swelling the electrode binder in a solvent used in an electrolyte solution. It consists of an elastic term (E') and a viscous term (E") measured using a device under the conditions of an indentation amount of 1㎛, a measurement temperature of 25℃, and a frequency of 1Hz.

As a method of producing a swollen film, a binder or a binder composition containing a binder and a solvent such as water is injected into a petri dish, dried at 60°C for 48 hours to obtain a 1 mm thick binder film, and dried at 25°C with a solvent used in the electrolyte solution. A method of immersing for 24 hours can be exemplified.

The elasticity term (E') and the viscosity term (E") of the swollen film as a measurement result are preferably those that satisfy either of the following requirements (1) and (2), and both (1) and (2) It is desirable to meet the requirements.

(1) Elasticity term (E') is ≥4.5×10 ⁶ (Pa)

(2) Viscosity term (E") ≥0.9×10 ⁶ (Pa)

The elastic term (E') of the swollen film is, for example, 4.5 × 10 ⁶ Pa or more, preferably 5.0 × 10 ⁶ Pa or more, particularly preferably 5.5 × 10 ⁶ Pa or more, and the upper limit is not particularly limited, but is 20 It is preferably 10 ⁶ Pa or less, more preferably 15×10 ⁶ Pa or less, and especially preferably 11×10 ⁶ Pa or less.

(1) The elasticity term (E') of the swollen film is satisfied and (2) the viscosity term (E") of the swollen film is not satisfied. However, in this case, (2) the viscosity term (E") of the swollen film is effective. ") is 0.2×10 ⁶ Pa or more, preferably 0.25×10 ⁶ Pa or more, particularly preferably 0.3×10 ⁶ Pa or more, and the upper limit is less than 0.9×10 ⁶ Pa.

The viscosity term (E") of the swollen film is 0.9×10 ⁶ Pa or more, preferably 0.95×10 ⁶ Pa or more, particularly preferably 1.0×10 ⁶ Pa or more, and the upper limit is not particularly limited, but is 4.0×10 ⁶ Pa. It is preferable that it is less than 3.0×10 ⁶ Pa, more preferably less than 3.0×10 6 Pa, and especially preferably less than 2.0×10 ⁶ Pa.

(2) The effect is shown even when the viscosity term (E") of the swollen film is satisfied and (1) the elasticity term (E') of the swollen film is not satisfied. However, in this case, (1) the elasticity term (E ') is 1.0×10 ⁶ Pa or more, preferably 1.5×10 ⁶ Pa or more, particularly preferably 2.0×10 ⁶ Pa or more, and the upper limit is less than 4.5×10 ⁶ Pa.

When both requirements (1) and (2) are satisfied, the elasticity term (E') of the swollen film is 4.5 × 10 ⁶ Pa or more, preferably 5.0 × 10 ⁶ Pa or more, and particularly preferably 5.5 × 10 ⁶ Pa or more. The upper limit is not particularly limited, but is preferably 20×10 ⁶ Pa or less, more preferably 15×10 ⁶ Pa or less, and especially preferably 11×10 ⁶ Pa or less.

The viscosity term (E") of the swollen film is 0.9×10 ⁶ Pa or more, preferably 0.95×10 ⁶ Pa or more, particularly preferably 1.0×10 ⁶ Pa or more, and the upper limit is not particularly limited, but is 4.0×10 ⁶ Pa. It is preferable that it is less than 3.0×10 ⁶ Pa, more preferably less than 3.0×10 6 Pa, and especially preferably less than 2.0×10 ⁶ Pa.

Solvents used in the electrolyte solution include aprotic organic solvents, specifically propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, 1,2-dimethoxyethane, and 1,2-diethoxyethane. , γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, dipropyl carbonate, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propylnitrile, anisole, acetic acid ester, propionic acid ester, diethyl Straight-chain ethers such as ether can be used, two or more types can be mixed, and examples include a mixed solvent in which propylene carbonate and diethyl carbonate are mixed at a volume ratio of 3:7.

The following can be exemplified as measurement conditions using a dynamic viscoelasticity measuring device for a swollen film. For samples with a diameter of 5 mm and a thickness of 1.0 to 2.0 mm, dynamic viscoelasticity was measured using a dynamic viscoelastic device Rheogel-E4000HP manufactured by BM Corporation under the conditions of compression mode, indentation amount of 1 μm, measurement temperature of 25°C, and frequency of 1 Hz. It is measured.

<2. Binder composition for electrode>

The binder composition of the present invention contains the binder of the present invention described in the above-mentioned section “1. Binder for electrodes” together with a solvent, and the binder may be dispersed in the solvent. The solvent can be water or an organic solvent. Organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, amyl alcohol, and acetone. , ketones such as methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as diethyl ether, dioxane, and tetrahydrofuran, n,n-dimethylformamide, and n-methyl-2. -Amide-based polar organic solvents such as pyrrolidone (NMP), and aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, and paradichlorobenzene can be used.

The binder composition for electrodes of the present invention is preferably an aqueous binder composition in which the binder is dispersed in water.

The binder composition for electrodes of the present invention may be an emulsion using an emulsion prepared when obtaining the binder.

The content of the binder in the binder composition for electrodes of the present invention is not particularly limited, but it is preferably contained so that the concentration of solids other than the solvent of the binder (hereinafter sometimes simply referred to as "solids") is 0.2 to 80% by mass, It is more preferable to contain it so that it may be 0.5-70 mass %, and it is especially preferable to contain it so that it may be 0.5-60 mass %.

The pH of the binder composition for electrodes of the present invention can be adjusted, if necessary, by using a base as a pH adjuster. Specific examples of bases include alkali metal (Li, Na, K, Rb, Cs) hydroxides, ammonia, inorganic ammonium compounds, and organic amine compounds. The pH range is pH 2 to 11, preferably pH 3 to 10, and more preferably pH 4 to 9.

The binder composition for electrodes of the present invention may contain polyacrylic acid or the like.

<3. Electrode>

The electrode of the present invention has an electrode material layer on a current collector.

For the electrode of the present invention, a known current collector can be used. Specifically, metals such as aluminum, nickel, stainless steel, gold, platinum, and titanium are used as the anode. As the cathode, metals such as copper, nickel, stainless steel, gold, platinum, titanium, and aluminum are used.

The electrode material layer contains at least an active material and the binder of the present invention described in the above-mentioned “1. Binder for electrode” column, and may further contain a conductive additive. For the production of the electrode material of the present invention, it is preferable to use the binder composition for electrodes of the present invention described in the section "2. Binder composition for electrodes" containing the binder for electrodes of the present invention together with a solvent. Specifically, in a lithium ion battery, the positive electrode material used in the positive electrode may contain the positive electrode active material and the electrode binder of the present invention and may also contain a conductive additive, and the negative electrode material used in the negative electrode may include the negative electrode active material and the electrode binder of the present invention. It may contain a binder and may also contain a conductive additive. In an electric double layer capacitor (electrochemical capacitor), the positive electrode material used for the anode may contain activated carbon as an active material and the binder for electrodes of the present invention and may also contain a conductive additive. , the negative electrode material used in the negative electrode may contain activated carbon and the binder for electrodes of the present invention as an active material, and may also contain a conductive additive.

The positive electrode active material used in lithium ion batteries is an alkali metal-containing complex oxide composed of any one of AMO ₂ , AM ₂ O ₄ , A ₂ Mo ₃ , and AMBO ₄ . A is an alkali metal, and M is made of a single or two or more types of transition metal, and a part of it may contain a non-transition metal. B is made of P, Si or a mixture thereof. Additionally, the positive electrode active material is preferably a powder, and its particle diameter is preferably 50 microns or less, more preferably 20 microns or less. These active materials have an electromotive force of 3V (vs. Li/Li+) or more.

Preferred specific examples of positive electrode active materials used in lithium ion batteries include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x CrO ₂ , Li _x FeO ₂ , Li _x Co _a Mn _1-a O ₂ , Li _x Co _a Ni _1-a O ₂ , Li _x Co _a Cr _1-a O ₂ , Li _x Co _a Fe _1-a O ₂ , Li _x Co _a Ti _1-a O ₂ , Li _x Mn _a Ni _1-a O ₂ , Li _{x Mna} Cr _1-a O ₂ , Li _x Mn _{a Fe 1-a} O ₂ , Li _{x Mn a} Ti _{1 -a} O _{2 , Li a} Fe _1-a O ₂ , Li _x Ni _a Ti _1-a O ₂ , Li _x Cr _a Fe _1-a O ₂ , Li _x Cr _a Ti _1-a O ₂ , Li _x Fe _a Ti _1-a O ₂ , Li _x Co _b Mn _c Ni _{1-bCO 2} , Li _x Ni _a Co _b Al _c O ₂ , Li _{x Cr b} Mn _{c Ni 1-bC O 2} , _{Li 2 , Li ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​-d} O ₄ , Li _x Mn _d Fe _2-d O ₄ , Li _x Mn _d Ti _2-d O ₄ , Li _y MnO ₃ , Li _y Mn _e Co _1-e O ₃ , Li _y Mn _e Ni _{1- e} O ₃ , Li _y Mn _e Fe _1-e O ₃ , Li _y Mn _e Ti _1-e O ₃ , Li _x CoPO ₄ , Li _x MnPO ₄ , Li _x NiPO ₄ , Li _x FePO ₄ , Li _x Co _f Mn _1-f PO ₄ , Li _x Co _f Ni _1-f PO ₄ , Li _x Co _f Fe _1-f PO ₄ , Li _x Mn _f Ni _1-f PO ₄ , Li _x Mn _f Fe _1-f PO _{4 , Li ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​g} SiO ₄ , Li _y Co _g Fe _1-g SiO ₄ , Li _y Mn _g Ni _1-g SiO ₄ , Li _y Mn _g Fe _1-g SiO ₄ , Li _y Ni _g Fe _1-g SiO ₄ , Li _y CoP _h Si _1-h O ₄ , Li _y MnP _h Si _1-h O ₄ , Li _y NiP _h Si _1-h O ₄ , Li _y FeP _h Si _1-h O ₄ , Li _y Co _g Mn _1-g P _h Si _1-h O ₄ , Li _y Co _g Ni _1-g P _h Si _1-h O ₄ , Li _y Co _g Fe _1-g P _h Si _1-h O ₄ , Li _y Mn _g Ni _1- Lithium-containing complex oxides such as _g P _h Si _1-h O ₄ , Li _y Mn _g Fe _1-g P _h Si _1-h O ₄ , Li _y Ni _g Fe _1-g P _h Si _1-h O ₄ (Here, x=0.01 to 1.2, y=0.01 to 2.2, a=0.01 to 0.99, b=0.01 to 0.98, c=0.01 to 0.98, but b+c=0.02 to 0.99, d=1.49 to 1.99, e=0.01 to 0.99, f=0.01 to 0.99, g=0.01 to 0.99, h=0.01 to 0.99.)

In addition, more preferred positive electrode active materials among the above preferred positive electrode active materials used in lithium ion batteries specifically include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x CrO ₂ , Li _x Co _a Ni _1-a O ₂ , Li _x Mn _a Ni _1-a O ₂ , _{Li x} Co _b Mn _{c Ni 1-bC} O ₂ , Li _x Ni _{a Co b} Al _{c O 2} , _{Li y} Mn _e Fe _1-e O ₃ , Li _y Mn _e Ti _1-e O ₃ , Li _x CoPO ₄ , Li _x MnPO ₄ , Li _x NiPO ₄ , Li _x FePO ₄ , Li _x Mn _f Fe _1-f PO ₄ (where x=0.01 to 1.2, y=0.01 to 2.2, a=0.01 to 0.99, b=0.01 to 0.98, c=0.01 to 0.98, but b+c=0.02 to 0.99, d=1.49 ~ 1.99, e = 0.01 ~ 0.99, f = 0.01 ~ 0.99. Additionally, the values of x and y increase and decrease by charging and discharging.

Negative active materials used in lithium ion batteries include carbon materials (natural graphite, artificial graphite, amorphous carbon, etc.) that have a structure (porous structure) that can occlude and release lithium ions, or lithium or aluminum-based compounds that can occlude and release lithium ions. It is a powder made of metal such as a tin-based compound, a silicon-based compound, and a titanium-based compound such as niobium titanium oxide. The particle diameter is preferably 10 nm or more and 100 μm or less, and more preferably 20 nm or more and 20 μm or less. Additionally, it may be used as a mixed active material of metal and carbon materials. Additionally, it is desirable to use a negative electrode active material with a porosity of about 70%.

Carbon materials include graphite, low-crystalline carbon (soft carbon, hard carbon), carbon black (Ketjen black, acetylene black, channel black, lamp black, oil furnace black, thermal black, etc.), fullerene, carbon nanotube, and carbon nanofiber. , carbon nanohorns, carbon fibrils, coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, phenolic resin sintered bodies, and polyacrylonitrile-based carbon fibers, and carbon materials such as graphite. It is desirable.

Silicon-based compounds include Si element, alloy with Si, oxide containing Si, carbide containing Si, etc., Si, SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _x (0 _< x2), _SnSiO

When using a combination of a carbon material and a silicon-based compound in an active material, it is preferable to contain them as follows.

The lower limit of the content of carbon material relative to the total amount of active material (100 mass%) is preferably 20 mass% or more, more preferably 40 mass% or more, especially preferably 60 mass% or more, and may be 70 mass% or more, and the upper limit is It is preferable that it is 99 mass% or less, more preferably 98 mass% or less, and especially preferably 96 mass% or less.

The lower limit of the content of the silicone compound relative to the total amount of the active material (100 mass%) is preferably 1 mass% or more, more preferably 2 mass% or more, particularly preferably 4 mass% or more, and the upper limit is preferably 80 mass% or less. It is more preferable that it is 60 mass% or less, especially preferably 40 mass% or less, and may be 30 mass% or less.

An example of an active material used in an electric double layer capacitor (electrochemical capacitor) is activated carbon. In general, activated carbon refers to activated carbide, and commercially available activated carbon may be used or activated carbon manufactured according to a known manufacturing method may be used. Activated carbon is produced by carbonizing raw materials such as wood, palm shells, pulp waste liquid, coal, heavy oil, and phenol resin, and activating the carbide obtained.

Activation may be any known activation method and can be performed by a gas activation method or a chemical activation method. In the gas activation method, carbides are activated by contacting them with gases such as water vapor, carbon dioxide, and oxygen under heating. In the chemical activation method, carbide is activated by heating while in contact with a known activating agent. Examples of the activating agent include zinc chloride, phosphoric acid, and/or alkaline compounds (metal hydroxides such as sodium hydroxide). It is preferable to use activated carbon activated with steam (herein referred to as steam-activated carbon) and/or alkali-activated activated carbon (herein referred to as alkali-activated activated carbon).

The content of the active material in the electrode material layer is not particularly limited and is, for example, 99.9 to 50% by mass, more preferably 99.5 to 70% by mass, and still more preferably 99 to 85% by mass, relative to the electrode material layer (100% by mass). can be mentioned. One type of active material may be used individually or two or more types may be used in combination.

The content of the binder of the present invention in the electrode material layer is not particularly limited and is, for example, 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and still more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of the active material. You can.

When using a conductive additive, known conductive additives can be used, and examples include conductive carbon black such as graphite, furnace black, acetylene black, and Ketjen black, carbon fiber such as carbon nanotubes (CNT), or metal powder. . You may use one type or two or more types of these conductive adjuvants.

When using a conductive additive, the content of the conductive additive is not particularly limited, but is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, with respect to 100 parts by mass of the active material. In addition, when a conductive additive is included in the positive electrode material, the lower limit of the content of the conductive additive is typically 0.05 parts by mass or more, 0.1 parts by mass or more, 0.2 parts by mass or more, 0.5 parts by mass or more, and 2 parts by mass or more.

The electrode material of the present invention may contain a thickener as needed. The type of thickener is not particularly limited, but preferably includes sodium salts, ammonium salts, polyvinyl alcohol, polyacrylic acid, and salts thereof of cellulose-based compounds.

Examples of the sodium or ammonium salts of cellulose-based compounds include sodium or ammonium salts of alkyl celluloses in which cellulose-based polymers are substituted with various derivative groups. Specific examples include sodium salt, ammonium salt, and triethanolammonium salt of methylcellulose, methylethylcellulose, ethylcellulose, and carboxymethylcellulose (CMC). The sodium or ammonium salts of carboxymethylcellulose are particularly preferred. These thickeners may be used individually, or two or more types may be used in combination at any ratio.

When using a thickener, the content of the thickener is not particularly limited, but is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the active material. In addition, when a thickener is included, the lower limit of the content of the thickener is typically 0.05 parts by mass or more, 0.1 parts by mass or more, 0.2 parts by mass or more, 0.5 parts by mass or more, and 1 part by mass or more.

The method of manufacturing the electrode is not particularly limited and general methods are used. This is done by uniformly applying the electrode material to an appropriate thickness on the surface of the current collector (metal electrode substrate) using a doctor blade method, applicator method, silk screen method, etc.

The electrode material of the present invention may contain water to form a slurry. The water is not particularly limited and commonly used water can be used. Specific examples include tap water, distilled water, ion-exchanged water, and ultrapure water. Among them, distilled water, ion-exchanged water, and ultrapure water are preferable.

When using the electrode material of the present invention in the form of a slurry, the solid content concentration of the slurry is preferably 10 to 90% by mass, more preferably 20 to 85% by mass, and especially preferably 20 to 80% by mass. .

When the electrode material of the present invention is used in the form of a slurry, the proportion of the polymer amount in the solid content of the slurry is preferably 0.1 to 15% by mass, more preferably 0.2 to 10% by mass, and 0.3 to 7% by mass. This is particularly desirable.

The method for preparing the electrode material is not particularly limited, and the positive or negative electrode active material, the binder for the electrode of the present invention, a conductive additive, water, etc. are dispersed using a conventional stirrer, disperser, kneader, planetary ball mill, homogenizer, etc. Just do it. To increase dispersion efficiency, heating may be performed within a range that does not affect the material. The binder for electrodes may be the binder composition for electrodes of the present invention described in the section "2. Binder composition for electrodes" containing the binder for electrodes of the present invention together with a solvent.

For example, in the doctor blade method, an electrode slurry is applied to a metal electrode substrate and then uniformized to an appropriate thickness using a blade with a predetermined slit width. After applying the active material, the electrode is dried under hot air at 100°C or under vacuum at 80°C to remove excess organic solvent and water. The dried electrode is press-molded using a press device to produce an electrode material. After pressing, heat treatment may be performed again to remove water, solvent, emulsifier, etc.

<4. Power storage device>

The electrical storage device of the present invention is characterized by being provided with the anode, cathode, and electrolyte solution described in the above-mentioned section “3. Electrodes.” That is, the electrode used in the electrical storage device of the present invention contains the electrode material of the present invention, that is, the binder for electrodes of the present invention. Details of the electrode of the present invention are as described above. In addition, for the electrical storage device of the present invention, an electrode using an electrode material containing the electrode binder of the present invention may be used for at least one of the anode and the cathode, and an electrode material containing the electrode binder of the present invention may not be used. As for the electrode, a known electrode can be used.

The electrolyte is not particularly limited and any known electrolyte can be used. Specific examples of the electrolyte solution include a solution containing an electrolyte and a solvent or room temperature molten salt. Electrolytes and solvents may be used individually or in combination of two or more types.

Examples of the electrolyte include lithium salt compounds, specifically LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN[CF ₃ SC(C ₂ F ₅ SO ₂ ) ₃ ] ₂ , etc. may be mentioned, but are not limited to these.

Electrolytes other than lithium salt compounds include tetraethylammonium tetrafluoroborate, triethylmonomethylammonium tetrafluoroborate, and tetraethylammonium hexafluorophosphate.

Examples of solvents used in the electrolyte solution include organic solvents.

Organic solvents include aprotic organic solvents, and specifically, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, and γ. -Butyrolactone, tetrahydrofuran, 1,3-dioxolane, dipropyl carbonate, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propylnitrile, anisole, acetic acid ester, propionic acid ester, diethyl ether, etc. Straight chain ethers can be used, and two or more types can be mixed.

Room temperature molten salt is also called an ionic liquid. It is a “salt” composed of only ions (anions and cations), and liquid compounds in particular are called ionic liquids.

In the present invention, room temperature molten salt refers to salt that is at least partially liquid at room temperature, and room temperature refers to the temperature range at which the battery is generally assumed to operate. The temperature range at which the battery is assumed to normally operate has an upper limit of approximately 120°C, in some cases approximately 80°C, and a lower limit of approximately -40°C, in some cases approximately -20°C.

As cationic species of molten salt at room temperature, pyridine-based, aliphatic amine-based, and alicyclic amine-based quaternary ammonium organic cations are known. Examples of quaternary ammonium organic cations include imidazolium ions such as dialkylimidazolium and trialkylimidazolium, tetraalkylammonium ions, alkylpyridinium ions, pyrazolium ions, pyrrolidinium ions, and piperidinium ions. You can. In particular, imidazolium ion is preferred.

In addition, tetraalkylammonium ions include, but are not limited to, trimethylethylammonium ion, trimethylethylammonium ion, trimethylpropylammonium ion, trimethylhexylammonium ion, tetrapentylammonium ion, and triethylmethylammonium ion.

Additionally, alkylpyridinium ions include N-methylpyridinium ion, N-ethylpyridinium ion, N-propylpyridinium ion, N-butylpyridinium ion, 1-ethyl-2 methylpyridinium ion, and 1-butyl-4. -Methylpyridinium ion, 1-butyl-2,4 dimethylpyridinium ion, etc. may be mentioned, but are not limited to these.

Examples of imidazolium ions include 1,3-dimethylimidazolium ion, 1-ethyl-3-methylimidazolium ion, 1-methyl-3-ethylimidazolium ion, and 1-methyl-3-butylimidazolium ion. , 1-butyl-3-methylimidazolium ion, 1,2,3-trimethylimidazolium ion, 1,2-dimethyl-3-ethylimidazolium ion, 1,2-dimethyl-3-propylimida Zolium ion, 1-butyl-2,3-dimethylimidazolium ion, etc. may be mentioned, but are not limited to these.

Anionic species in molten salt at room temperature include halide ions such as chloride ions, bromide ions, and iodide ions, perchlorate ions, thiocyanate ions, tetrafluoroborate ions, nitrate ions, and inorganic acid ions such as AsF ₆ ^- and PF ₆ ^- , organic acid ions such as stearylsulfonate ion, octylsulfonate ion, dodecylbenzenesulfonate ion, naphthalenesulfonate ion, dodecylnaphthalenesulfonate ion, 7,7,8,8-tetracyano-p-quinodimethane ion, etc. It is exemplified.

In addition, room temperature molten salt may be used individually or in combination of two or more types.

Various additives can be used in the electrolyte as needed. Additives include flame retardants, flame retardants, anode surface treatment agents, cathode surface treatment agents, overcharge prevention agents, etc. Examples of flame retardants and flame retardants include brominated epoxy compounds, phosphazene compounds, tetrabrominated bisphenol A, halides such as chlorinated paraffin, antimony trioxide, antimony pentoxide, aluminum hydroxide, magnesium hydroxide, phosphoric acid esters, polyphosphates, and zinc borate. there is. Examples of the anode surface treatment agent include inorganic compounds such as carbon and metal oxides (such as MgО and Zr0 ₂ ) and organic compounds such as ortho-terphenyl. Examples of the cathode surface treatment agent include vinylene carbonate, fluoroethylene carbonate, and polyethylene glycol dimethyl ether. Examples of overcharge prevention agents include biphenyl and 1-(p-tolyl)adamantane.

The manufacturing method of the electrical storage device of the present invention is not particularly limited, and is manufactured by a known method using an anode, a cathode, an electrolyte solution, and, if necessary, a separator. For example, in the case of the coin type, the anode, separator if necessary, and cathode are inserted into the external can. Add electrolyte to impregnate it. Thereafter, an electricity storage device is obtained by joining the sealing body and the sealing body using tab welding, etc. to enclose and fix the sealing body. The shape of the power storage device is not limited, but examples include coin shape, cylindrical shape, and sheet shape.

The separator prevents a short circuit within the battery due to direct contact between the positive and negative electrodes, and known materials can be used. Specific examples of the separator include porous polymer films such as polyolefin and paper. As porous polymer films, films such as polyethylene and polypropylene are preferable because they are less affected by the electrolyte solution.

Example

Specific modes for carrying out the present invention will be described below by way of examples. However, the present invention is not limited to the following examples as long as it does not deviate from the gist.

In this example, a binder film and a coin cell were produced, and the viscoelasticity test of the swollen film as an evaluation of the binder film and a cycle test as an evaluation of the coin battery were measured in the following experiments.

<Method for producing swollen film>

The swollen film was produced as follows. First, the binder composition was injected into the petri dish and dried at 60°C for 48 hours to produce a 1 mm thick binder film. A swollen film was produced by immersing the obtained film in a mixed solvent containing propylene carbonate and diethyl carbonate at a volume ratio of 3:7 at 25°C for 24 hours.

<Method for measuring viscoelasticity>

The viscoelasticity of the swollen film was measured under the following conditions.

(measuring device)

The viscoelasticity test of the swollen film was measured by dynamic viscoelasticity measurement using a dynamic viscoelasticity device Rheogel-E4000HP manufactured by BM Corporation under the conditions of compression mode, indentation amount of 1 μm, measurement temperature of 25°C, and frequency of 1 Hz. A swollen film with a diameter of 5 mm was used. The results are shown in Table 2.

<Measurement of average particle diameter>

The average particle diameter of the polymer was measured under the following conditions.

(measuring device)

Particle size distribution measurement device using dynamic light scattering: Zetasizer Nano (Spectress Kabushiki Kaisha)

(Measuring conditions)

1. Sample 50㎕ of the synthesized emulsion solution.

2. Dilute the sampled emulsion solution by adding 700㎕ of ion-exchanged water three times.

3. Extract 2100㎕ of liquid from the diluted solution.

4. Measure by adding and diluting 700㎕ of ion-exchanged water to the remaining 50㎕ of sample.

<Measurement of aggregates>

The polymer aggregates were measured as follows.

The polymerized emulsion solution is filtered using a 150 mesh stainless steel wire mesh (manufactured by Kansai Kanaami Co., Ltd.), and the aggregates adhering to the stirring blade and beaker are scraped off. Afterwards, the recovered aggregates are washed with ion-exchanged water, dried for 24 hours, and the mass of the aggregates is measured. The measured amount of aggregate is divided by the emulsion quantity to obtain the amount of aggregate (% by mass).

[Evaluation of characteristics of manufactured batteries]

To evaluate the characteristics of the produced coin battery, charge/discharge efficiency was measured.

<Measurement of charge/discharge efficiency>

(measuring device)

Charge/discharge evaluation device: TOSCAT-3100 (Toyo Systems Co., Ltd.)

(measurement method)

The produced coin battery was discharged to 0.2C by constant current-constant voltage discharge. The cessation current was equivalent to 0.04C. After discharging, the battery was stopped for 10 minutes. It was then charged to 1.2V by constant current charging at 0.2C. The above operation was regarded as 1 cycle, and 50 cycles of charge and discharge were performed. The discharge capacity at the 50th cycle was divided by the discharge capacity at the first time to obtain a percentage, resulting in a cycle capacity maintenance rate (%). The evaluation results are shown in Table 2.

[Implementary Synthesis Example 1]

In a beaker, 197.79 g of lauryl methacrylate, 136.63 g of benzyl methacrylate, 5.45 g of acrylic acid, 15.27 g of methacrylic acid, 14.51 g of polyethylene glycol monomethacrylate (made by Niche Oil: Brenmer PE-90), and trimethylolpropane trimethylene. 21.12 g of methacrylate (Kyoei Shaka Chemical: Light Ester TMP), 10.02 g of allyl glycidyl ether (Neo Allyl G, manufactured by Osaka Soda), 6.40 g of sodium dodecyl sulfate as an emulsifier, polyoxyethylene distyrenated phenyl ether Add 1.60 g of (Neugen EA-157 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 342 g of ion-exchanged water, and 0.87 g of t-butylhydroperoxide (Nichiyu Co., Ltd.: Perbutyl H-69) as a polymerization initiator, and then ultrasonic wave. The mixture was sufficiently stirred using a mozzenizer to obtain an emulsion. A reaction vessel equipped with a stirrer was heated to 58°C in a nitrogen atmosphere, and the emulsion was added over 220 minutes. After adding the emulsion, polymerization was continued for another hour and then cooled. After cooling, the pH of the polymerization solution was adjusted to 3.9 to 8.1 using a 28% ammonia aqueous solution, and binder composition C, which is an emulsion solution (polymerization conversion rate of 99% or more, solid content concentration of 40.0 wt%, aggregation amount: 0.0002 wt%) was obtained. The average particle diameter of the obtained polymer was 0.186 μm. The mass percent in the polymer is shown in Table 1. The thickness of the swollen film obtained by the method shown in <Method for producing a swollen film> was 1.1 mm.

[Implementary Synthesis Example 2]

In a beaker, 197.79 g of lauryl methacrylate, 136.63 g of benzyl methacrylate, 5.45 g of acrylic acid, 15.27 g of methacrylic acid, 14.51 g of polyethylene glycol monomethacrylate (made by Niche Oil: Brenmer PE-90), and trimethylolpropane trimethylene. Methacrylate (manufactured by Kyoeisha Chemical: Light Ester TMP) 21.12 g, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate (manufactured by Showa Denko: Karen's MOI-BP) 10.02 g, 6.40 g of sodium dodecyl sulfate as an emulsifier, 1.60 g of polyoxyethylene distyrenated phenyl ether (Neugen EA-157, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 349 g of ion-exchanged water, and t-butylhyde as a polymerization initiator. 0.87 g of loperoxide (Nichiyu product: Perbutyl H-69) was added and thoroughly stirred using an ultrasonic homogenizer to obtain an emulsion. A reaction vessel equipped with a stirrer was heated to 58°C in a nitrogen atmosphere, and the emulsion was added over 220 minutes. After adding the emulsion, polymerization was continued for another hour and then cooled. After cooling, the pH of the polymerization solution was adjusted to 4.4 to 8.0 using a 28% ammonia aqueous solution, and binder composition B, which was an emulsion solution (polymerization conversion rate of 99% or more, solid content concentration of 40.0 wt%, and aggregation amount: 0.0009 wt%) was obtained. The average particle diameter of the obtained polymer was 0.193 μm. The mass percent in the polymer is shown in Table 1. The thickness of the swollen film obtained by the method shown in <Method for producing a swollen film> was 1.3 mm.

[Implementary Synthesis Example 3]

In a beaker, 197.79 g of lauryl methacrylate, 136.63 g of benzyl methacrylate, 5.45 g of acrylic acid, 15.27 g of methacrylic acid, 14.51 g of polyethylene glycol monomethacrylate (made by Niche Oil: Brenmer PE-90), and trimethylolpropane trimethylene. Methacrylate (manufactured by Kyoeisha Chemical: Light Ester TMP) 21.12 g, 2-[0-(1'-methylpropylidene amino)carboxyamino]ethyl methacrylate (manufactured by Showa Denko: Karen's MOI-BM) 10.02 g, 6.40 g of sodium dodecyl sulfate as an emulsifier, 1.60 g of polyoxyethylene distyrenated phenyl ether (Neugen EA-157, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 349 g of ion-exchanged water, and t-butyl as a polymerization initiator. 0.87 g of hydroperoxide (Nichiyu product: Perbutyl H-69) was added and thoroughly stirred using an ultrasonic homogenizer to obtain an emulsion. A reaction vessel equipped with a stirrer was heated to 58°C in a nitrogen atmosphere, and the emulsion was added over 220 minutes. After adding the emulsion, polymerization was continued for another hour and then cooled. After cooling, the pH of the polymerization solution was adjusted to 3.0 to 8.1 using a 28% ammonia aqueous solution, and binder composition C, an emulsion solution (polymerization conversion rate of 99% or more, solid content concentration of 40.0 wt%, aggregation amount: 0.0006 wt%) was obtained. The average particle diameter of the obtained polymer was 0.203 μm. The mass percent in the polymer is shown in Table 1. The thickness of the swollen film obtained by the method shown in <Method for producing a swollen film> was 1.4 mm.

[Implementary Synthesis Example 4]

In a beaker, 204.09 g of lauryl methacrylate, 126.61 g of benzyl methacrylate, 5.45 g of acrylic acid, 15.27 g of methacrylic acid, 14.51 g of polyethylene glycol monomethacrylate (made by Niche Oil: Brenmer PE-90), and trimethylolpropane trimethylene. Methacrylate (Kyoei Shaka Chemical: Light Ester TMP) 14.83 g, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer (Kyoei Shaka Chemical: UA-306H) 20.04 g, sodium dodecyl sulfate 6.40 as an emulsifier. g, 1.60 g of polyoxyethylene distyrenated phenyl ether (Neugen EA-157, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 349 g of ion-exchanged water, and t-butylhydroperoxide as a polymerization initiator (made by Nichiyu Co., Ltd.: Perbutyl H) -69) 0.87 g was added and thoroughly stirred using an ultrasonic homogenizer to obtain an emulsion. A reaction vessel equipped with a stirrer was heated to 58°C in a nitrogen atmosphere, and the emulsion was added over 220 minutes. After adding the emulsion, polymerization was continued for another hour and then cooled. After cooling, the pH of the polymerization solution was adjusted to 3.0 to 8.1 using a 28% aqueous ammonia solution to obtain binder composition D, which is an emulsion solution (polymerization conversion rate of 99% or more, solid content concentration of 40.4 wt%, aggregation amount: 0.002 wt%). The average particle diameter of the obtained polymer was 0.183 μm. The mass percent in the polymer is shown in Table 1. The thickness of the swollen film obtained by the method shown in <Method for producing a swollen film> was 1.2 mm.

[Comparative Synthesis Example 1]

In a beaker, 197.79 g of n-butyl acrylate, 146.65 g of benzyl methacrylate, 5.45 g of acrylic acid, 15.27 g of methacrylic acid, 14.51 g of polyethylene glycol monomethacrylate (niche oil product: Brenmer PE-90), and trimethylolpropane trimethane. Crylate (light ester TMP, manufactured by Kyoeisha Chemical Co., Ltd.) 21.12 g, 3.20 g sodium dodecyl sulfate as an emulsifier, polyoxyethylene distyrenated phenyl ether (Neugen EA-157, manufactured by Daiichi Kogyo Chemical Co., Ltd.) 0.80 g, 352 g of ion-exchanged water and 0.58 g of ammonium persulfate as a polymerization initiator were added and stirred sufficiently using an ultrasonic homogenizer to obtain an emulsion. A reaction vessel equipped with a stirrer was heated to 58°C in a nitrogen atmosphere, and the emulsion was added over 220 minutes. After adding the emulsion, polymerization was continued for another hour and then cooled. After cooling, the pH of the polymerization solution was adjusted to 2.3 to 8.1 using a 28% ammonia aqueous solution to obtain binder composition E, which is an emulsion solution (polymerization conversion rate of 99% or more, solid content concentration of 39.5 wt%, aggregation amount: 0.0003 wt%). The average particle diameter of the obtained polymer was 0.279 μm. The mass percent in the polymer is shown in Table 1. The thickness of the swollen film obtained by the method shown in <Method for producing a swollen film> was 1.0 mm.

[Comparative Synthesis Example 2]

In a beaker, 197.79 g of lauryl methacrylate, 146.65 g of benzyl methacrylate, 5.45 g of acrylic acid, 15.27 g of methacrylic acid, 14.51 g of polyethylene glycol monomethacrylate (made by Niche Oil: Brenmer PE-90), and trimethylolpropane trimethylene. 21.12 g of methacrylate (Kyoei Chemical Co., Ltd.: Light Ester TMP), 6.40 g of sodium dodecyl sulfate as an emulsifier, polyoxyethylene distyrenated phenyl ether (Neugen EA-157, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1.60 g, 349 g of ion-exchanged water, and 0.87 g of t-butylhydroperoxide (Nichiyu Co., Ltd.: Perbutyl H-69) as a polymerization initiator were added and stirred sufficiently using an ultrasonic homogenizer to obtain an emulsion. A reaction vessel equipped with a stirrer was heated to 58°C in a nitrogen atmosphere, and the emulsion was added over 220 minutes. After adding the emulsion, polymerization was continued for another hour and then cooled. After cooling, the pH of the polymerization solution was adjusted to 3.0 to 8.2 using a 28% ammonia aqueous solution to obtain binder composition F, which is an emulsion solution (polymerization conversion rate of 99% or more, solid content concentration of 40.3 wt%, aggregation amount: 0.0005 wt%). The average particle diameter of the obtained polymer was 0.186 μm. The mass percent in the polymer is shown in Table 1. The thickness of the swollen film obtained by the method shown in <Method for producing a swollen film> was 1.0 mm.

In Table 1, n-butyl acrylate and lauryl methacrylate are monomers that form structural unit (A), and benzyl methacrylate is a monomer that forms structural unit (B). In addition, the monomer described in the item of reactive group is a monomer that forms the structural unit (C), and the epoxy group, (block) isocyanate group, and urethane group each become a reactive group in the polymer. Polyethylene glycol monomethacrylate corresponds to the monomer forming the structural unit (D), the crosslinking agent corresponds to the monomer forming the structural unit (E), and acrylic acid and methacrylic acid correspond to the monomers forming the structural unit (F).

<Manufacture example of electrode>

[Example 1 of electrode production]

85.4 parts by mass of graphite as the negative electrode active material, 10 parts by mass of SiO, 1 part by mass of acetylene black as a conductive additive, 0.1 part by mass of CNT (manufactured by Oxyral), 2 parts by mass of carboxymethyl cellulose sodium salt, the binder composition obtained in Synthesis Example 1. 1.5 parts by mass of the solid content of the binder composition A was added, and water was further added so that the solid content concentration of the slurry was 35% by mass, and thoroughly mixed using a planetary mill to obtain a slurry for a negative electrode. The obtained negative electrode slurry was applied on a copper current collector with a thickness of 10 ㎛ using a Baker-type applicator with a gap of 100 ㎛, dried in a vacuum at 110 ° C. for more than 10 hours, and then pressed with a roll press to obtain a thickness of 36 ㎛ and electrode density. A cathode of 1.6 g/cc was produced.

[Example 2 of electrode production]

85.4 parts by mass of graphite as a negative electrode active material, 10 parts by mass of SiO, 1 part by mass of acetylene black as a conductive additive, 0.1 part by mass of CNT (manufactured by Oxyral), 2 parts by mass of carboxymethyl cellulose sodium salt, in Synthesis Example 2 of the binder composition. The same as Example 1 of the electrode except that 1.5 parts by mass of the solid content of the obtained binder composition B was added, water was added so that the solid content concentration of the slurry was 35% by mass, and mixed sufficiently using a planetary mill to obtain a slurry for a negative electrode. The electrode was manufactured by doing so. The thickness of the obtained electrode was 36 μm, and the density of the electrode was 1.6 g/cc.

[Example 3 of electrode production]

85.4 parts by mass of graphite as the negative electrode active material, 10 parts by mass of SiO, 1 part by mass of acetylene black as a conductive additive, 0.1 part by mass of CNT (manufactured by Oxyral), 2 parts by mass of carboxymethyl cellulose sodium salt, obtained in Synthesis Example 3 of the binder composition. 1.5 parts by mass as the solid content of the binder composition C was added, water was added so that the solid content concentration of the slurry was 35% by mass, and the slurry for the negative electrode was obtained in the same manner as in Example 1 of the electrode except that the slurry for the negative electrode was obtained by thoroughly mixing using a planetary mill. Thus, electrodes were manufactured. The thickness of the obtained electrode was 38 μm, and the density of the electrode was 1.6 g/cc.

[Example 4 of electrode production]

In Synthesis Example 4 of a binder composition containing 85.4 parts by mass of graphite as a negative electrode active material, 10 parts by mass of SiO, 1 part by mass of acetylene black, 0.1 part by mass of CNT (manufactured by Oxyral), and 2 parts by mass of carboxymethyl cellulose sodium salt as a conductive additive. The same as Example 1 of the electrode except that 1.5 parts by mass of the solid content of the obtained binder composition D was added, water was added so that the solid content concentration of the slurry was 35% by mass, and mixed sufficiently using a planetary mill to obtain a slurry for a negative electrode. The electrode was manufactured by doing so. The thickness of the obtained electrode was 33㎛, and the density of the electrode was 1.6g/cc.

[Comparative manufacturing example 1 of electrodes]

In Comparative Synthesis Example 1 of a binder composition containing 85.4 parts by mass of graphite as a negative electrode active material, 10 parts by mass of SiO, 1 part by mass of acetylene black as a conductive additive, 0.1 part by mass of CNT (manufactured by Oxyral), and 2 parts by mass of carboxymethyl cellulose sodium salt. The same as Example 1 of the electrode except that 1.5 parts by mass of the solid content of the obtained binder composition E was added, water was added so that the solid content concentration of the slurry was 35% by mass, and mixed sufficiently using a planetary mill to obtain a slurry for a negative electrode. The electrode was manufactured by doing so. The thickness of the obtained electrode was 35㎛, and the density of the electrode was 1.6g/cc.

[Comparative manufacturing example 2 of electrodes]

In Comparative Synthesis Example 2 of a binder composition containing 85.4 parts by mass of graphite as a negative electrode active material, 10 parts by mass of SiO, 1 part by mass of acetylene black, 0.1 part by mass of CNT (manufactured by Oxyral), and 2 parts by mass of carboxymethyl cellulose sodium salt as a conductive additive. The same as Example 1 of the electrode except that 1.5 parts by mass of the solid content of the obtained binder composition F was added, water was added so that the solid content concentration of the slurry was 35% by mass, and mixed sufficiently using a planetary mill to obtain a slurry for a negative electrode. The electrode was manufactured by doing so. The thickness of the obtained electrode was 34㎛, and the density of the electrode was 1.6g/cc.

<Production example of battery>

[Implementary Manufacturing Example 1 of Coin Battery]

In a glove box replaced with argon gas, the cathode obtained in Example 1 of electrode production was bonded to a separator with a polypropylene/polyethylene/polypropylene porous film with a thickness of 18 μm, and a 500 μm thick metal lithium foil as a counter electrode. A 2032 type coin battery for testing was prepared by sufficiently impregnating and fixing a laminate with ethylene carbonate and diethyl carbonate (volume ratio 3:7) of lithium hexafluorophosphate at 1 mol/L with 0.5 wt% of fluoroethylene carbonate added as an electrolyte. manufactured. The evaluation results of the cycle test measurements are shown in Example 1 in Table 2.

[Implementation manufacturing of coin battery 2]

A coin battery was produced in the same manner as in Production Example 1 of the coin battery except that the negative electrode obtained in Production Example 2 of the electrode was used. The evaluation results of the cycle test measurements are shown in Example 2 in Table 2.

[Implementation manufacturing of coin battery 3]

A coin battery was produced in the same manner as in Production Example 1 of the coin battery except that the negative electrode obtained in Production Example 3 of the electrode was used. The evaluation results of the cycle test measurements are shown in Example 3 in Table 2.

[Implementation manufacturing of coin battery 4]

A coin battery was produced in the same manner as in Production Example 1 of the coin battery except that the negative electrode obtained in Production Example 4 of the electrode was used. The evaluation results of the cycle test measurements are shown in Example 4 in Table 2.

[Comparative manufacturing example 1 of coin battery]

A coin battery was produced in the same manner as in Production Example 1 of the coin battery except that the negative electrode obtained in Comparative Production Example 1 of the electrode was used. The evaluation results of the cycle test measurements are shown in Comparative Example 1 in Table 2.

[Comparative manufacturing example 2 of coin battery]

A coin battery was produced in the same manner as in Production Example 1 of the coin battery except that the negative electrode obtained in Comparative Production Example 2 of the electrode was used. The evaluation results of the cycle test measurements are shown in Comparative Example 2 in Table 2.

Table 2 shows the viscoelasticity and battery physical property evaluation results of the swollen binders of Examples and Comparative Examples.

Compared to Comparative Examples 1 to 2, Examples 1 to 4 of the present invention were found to have excellent dynamic viscoelastic properties in a swollen state in the solvent used in the electrolyte solution, thereby showing good cycle characteristics in a coin battery.

The binder for electrodes of the present invention has excellent binding properties and is useful when used in power storage devices, for example, for vehicle-mounted applications such as electric vehicles and hybrid electric vehicles, and in power storage devices such as storage batteries for household power storage.

Claims (7)

A structural unit (A) derived from a (meth)acrylic acid alkyl ester monomer,
A structural unit (B) derived from a monomer represented by the following general formula (1),
A binder for electrodes comprising a polymer containing a structural unit (C) derived from a monomer having at least one type selected from the group consisting of an epoxy group, (block) isocyanate group, and urethane group:
[Formula 1]

(In the formula, R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ² is an aromatic group that may have a substituent.) According to claim 1,
A binder for electrodes, wherein the structural unit (B) is a structural unit derived from a monomer represented by the following general formula (2):
[Formula 2]

(In the formula, R ¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² are each independently hydrogen, is any one of a hydroxyl group, an alkyl group having 1 to 3 carbon atoms, or an aromatic group which may have a substituent, R ¹³ is an alkylene group or a carbonyl group having 1 to 3 carbon atoms, R ¹⁴ is an aromatic group which may have a substituent, q, r is each independently an integer from 0 to 3, and s is an integer from 0 to 1.) The method of claim 1 or 2,
A binder for electrodes comprising a polymer further comprising a structural unit (D) derived from a monomer having a hydroxyl group represented by the following general formula (3):
[Formula 3]

(In the formula, R ¹⁵ is a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, x is each independently an integer of 2 to 8, and n is an integer of 2 to 30.) The method of claim 1 or 2,
A binder for electrodes comprising a polymer further comprising a structural unit (E) derived from a pentafunctional or less polyfunctional (meth)acrylate monomer. According to claim 4,
A binder for electrodes, wherein in the structural unit (E), the five-functional or less polyfunctional (meth)acrylate monomer is a compound represented by the following general formula (5):
[Formula 4]

(In the formula, R ¹⁶ is the same or different and is a hydrogen atom or a methyl group, R ¹⁷ is a pentavalent organic group having 2 to 100 carbon atoms, and m is an integer of 5 or less.) An electrode comprising the electrode binder according to claim 1 or 2. An electrical storage device comprising the electrode according to claim 6.