CN117897833A - Binder for electrode, and power storage device - Google Patents

Binder for electrode, and power storage device Download PDF

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Publication number
CN117897833A
CN117897833A CN202280055557.8A CN202280055557A CN117897833A CN 117897833 A CN117897833 A CN 117897833A CN 202280055557 A CN202280055557 A CN 202280055557A CN 117897833 A CN117897833 A CN 117897833A
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China
Prior art keywords
group
electrode
mass
structural unit
binder
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CN202280055557.8A
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Chinese (zh)
Inventor
入江丽奈
横谷昌辉
宮本刚
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Osaka Soda Co Ltd
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Osaka Soda Co Ltd
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Publication of CN117897833A publication Critical patent/CN117897833A/en
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/26—Esters containing oxygen in addition to the carboxy oxygen
    • C08F220/30—Esters containing oxygen in addition to the carboxy oxygen containing aromatic rings in the alcohol moiety
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Abstract

The present invention provides a binder for an electrode, which has excellent cycle characteristics when used in an electric storage device. A binder for an electrode, which comprises a polymer comprising a structural unit (A) derived from an alkyl (meth) acrylate monomer and derived from the following general formula (1) (wherein R 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 2 Is an aromatic group which may have a substituent. ) Structural unit (B) of the monomer shown and derived from a monomer having a structural unit selected from the group consisting of epoxyA structural unit (C) of a monomer of at least one of a group, (blocked) isocyanate group and urethane group.

Description

Binder for electrode, and power storage device
Technical Field
The present invention relates to a binder for an electrode used in a secondary battery such as a lithium ion secondary battery and a nickel hydrogen secondary battery, and an electric storage device such as an electrochemical capacitor, and particularly to a binder for an electrode used in a nonaqueous electrolyte-based electric storage device in which a nonaqueous electrolyte such as an organic solvent is used as an electrolyte, an electrode containing the binder for an electrode, and an electric storage device including the electrode.
Background
Power storage devices such as lithium ion secondary batteries and electrochemical capacitors are used in electronic devices such as mobile phones, notebook computers, video cameras, and the like. Recently, due to the improvement of environmental awareness and the revision of related laws, batteries for vehicle-mounted applications such as electric vehicles and hybrid electric vehicles, and for household power storage have been used.
In addition, along with these applications, improvement of the power storage device in terms of performance and improvement of components such as electrodes have been demanded. The electrode used in such an electric storage device is generally obtained by applying an electrode material composed of an active material, a conductive additive, a binder, and a solvent to a current collector and drying the applied material.
Accordingly, attempts have been made in recent years to improve the binder used for the electrode. It has been proposed to improve the adhesion between active materials, the adhesion between active materials and a conductive auxiliary agent, and the adhesion between active materials and a current collector by improving the binder, and to improve electrical characteristics (for example, cycle characteristics, output characteristics at low temperatures, and low resistance).
The binder is required to have excellent adhesion when used for an electrode and to be capable of imparting excellent electrical characteristics to the power storage device, and for example, a new binder is proposed in patent document 1. However, in recent years, an adhesive having particularly excellent adhesion is demanded, and further investigation is required.
Accordingly, the applicant has developed an aromatic group-containing binder as in patent document 2 in order to develop a binder having more excellent adhesion and good characteristics when used in an electric storage device, but has demanded further investigation.
Prior art literature
Patent literature
Patent document 1: international publication No. 2013/180103
Patent document 2: international publication No. 2019/131771
Disclosure of Invention
Technical problem to be solved by the invention
The purpose of the present invention is to provide a binder for an electrode, which has excellent cycle characteristics when used in an electrical storage device.
Technical scheme for solving technical problems
The present inventors have conducted studies to achieve the above-described object and as a result, have found that the above-described object is achieved by a structural unit comprising a structural unit derived from an alkyl (meth) acrylate monomer, a structural unit derived from a monomer having an aromatic group, and a structural unit derived from a polymer contained in a binder for an electrode, the polymer having at least one monomer selected from the group consisting of an epoxy group, a (blocked) isocyanate group and a urethane group.
Namely, the present invention relates to the following.
The binder for an electrode of item 1, comprising a polymer comprising:
structural unit (A) derived from alkyl (meth) acrylate monomers,
a structural unit (B) derived from a monomer represented by the following general formula (1), and
[ chemical 1]
(wherein R is 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 2 Is an aryl group which may have a substituentA perfume group. )
A structural unit (C) derived from a monomer having at least one selected from the group consisting of an epoxy group, a (blocked) isocyanate group and a urethane group.
The binder for an electrode according to item 1, wherein the structural unit (B) is a structural unit derived from a monomer represented by the following general formula (2).
[ chemical 2]
(wherein R is 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 3 、R 4 、R 5 、R 6 、R 7 、R 8 、R 9 、R 10 、R 11 、R 12 Each independently represents any one of hydrogen, hydroxyl, alkyl having 1 to 3 carbon atoms, and aromatic group which may have a substituent, R 13 Is alkylene group having 1 to 3 carbon atoms or carbonyl group, R 14 Q and r are each independently an integer of 0 to 3, and s is an integer of 0 to 1. )
The binder for an electrode according to item 1 or 2, wherein the binder for an electrode comprises a polymer further having a structural unit (D) derived from a monomer having a hydroxyl group represented by the following general formula (3).
[ chemical 3]
(wherein R is 15 Is a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, x is an integer of 2 to 8, and n is an integer of 2 to 30. )
The binder for an electrode according to any one of items 1 to 3, wherein the binder for an electrode comprises a polymer further having a structural unit (E) derived from a polyfunctional (meth) acrylate monomer having 5 or less functions.
The binder for an electrode according to item 4, wherein in the structural unit (E), the polyfunctional (meth) acrylate monomer having 5 or less functions is a compound represented by the following general formula (5).
[ chemical 4]
(wherein R is 16 Each identical or different is a hydrogen atom or a methyl group, R 17 An organic group having 2 to 100 carbon atoms and having a valence of 5 or less, and m is an integer of 5 or less. )
An electrode according to item 6, which comprises the binder for an electrode according to any one of items 1 to 5.
An electric storage device according to item 7, which is provided with the electrode according to item 6.
Effects of the invention
The binder of the present invention has a certain dynamic viscoelastic property in a swollen state in a solvent used in an electrolyte, and is excellent in cycle characteristics when used in an electric storage device. The reason for this is not clear, but it is presumed that: when shrinkage of an active material of an electrode material in an electrode in use of the power storage device occurs, toughness for following the shrinkage is imparted by having a structural unit derived from a monomer having an epoxy group, (blocked) isocyanate group, or urethane group in addition to a structural unit derived from an aromatic group. The power storage device of the present invention is useful for power storage equipment such as a vehicle-mounted use such as an electric vehicle or a hybrid electric vehicle, and a battery for household power storage.
Detailed Description
In the present specification, the power storage device includes a secondary battery (a lithium ion secondary battery, a nickel hydrogen secondary battery, or the like) and an electrochemical capacitor. In the present specification, "(meth) acrylate" means "acrylate or methacrylate", and the similar expression is the same.
<1 > Binder for electrode >
The binder for an electrode of the present invention comprises a polymer comprising:
structural unit (A) derived from alkyl (meth) acrylate monomers,
a structural unit (B) derived from a monomer represented by the following general formula (1), and
[ chemical 5]
(wherein R is 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 2 Is an aromatic group which may have a substituent. )
A structural unit (C) derived from a monomer having at least one selected from the group consisting of an epoxy group, a (blocked) isocyanate group and a urethane group.
The structural units of the polymer of the present invention are described in detail below. In the present invention, "(meth) acrylic acid" means "acrylic acid or methacrylic acid", and the similar expressions are also the same. In addition, "(blocked) isocyanate group" means "isocyanate group or blocked isocyanate group".
(structural unit (A))
The structural unit (A) is a structural unit derived from an alkyl (meth) acrylate monomer.
The structural unit (a) is preferably a structural unit derived from an alkyl (meth) acrylate monomer having an alkyl group having 1 to 22 carbon atoms, more preferably a structural unit derived from an alkyl (meth) acrylate monomer having an alkyl group having 2 to 18 carbon atoms, and particularly preferably a structural unit derived from an alkyl (meth) acrylate monomer having an alkyl group having 4 to 18 carbon atoms.
Specific examples of the preferable structural unit (a) include: structural units derived from (meth) acrylic acid alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate. The number of structural units (a) contained in the polymer may be 1 or 2 or more.
The lower limit of the ratio of the structural unit (a) in the polymer is preferably 30 mass% or more, more preferably 40 mass% or more, and the upper limit is preferably 65 mass% or less, more preferably 60 mass% or less, particularly preferably 55 mass% or less.
(structural unit (B))
The structural unit (B) is a structural unit derived from the general formula (1). The number of structural units (B) contained in the polymer may be 1 or 2 or more.
[ chemical 6]
(wherein R is 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 2 Is an aromatic group which may have a substituent. )
In the structural unit derived from the general formula (1), R 1 The hydrogen or an alkyl group having 1 to 4 carbon atoms is preferable, and the hydrogen or an alkyl group having 1 to 2 carbon atoms is particularly preferable. R is R 2 Examples of the substituent include an unsaturated hydrocarbon group such as an alkyl group such as a methyl group, an ethyl group, or an isopropyl group, a halogen group such as a vinyl group, a fluoro group, a chloro group, a bromo group, or an iodo group, an amino group, a nitro group, or a carboxyl group. The number of aromatic rings may be 2 or more.
More specifically, the structural unit derived from the general formula (1) is preferably a structural unit based on a monomer represented by the following general formula (2).
[ chemical 7]
(wherein R is 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 3 、R 4 、R 5 、R 6 、R 7 、R 8 、R 9 、R 10 、R 11 、R 12 Each independently represents any one of hydrogen, hydroxyl, alkyl having 1 to 3 carbon atoms, and aromatic group which may have a substituent, R 13 Is alkylene group having 1 to 3 carbon atoms or carbonyl group, R 14 Q and r are each independently a number of 0 to 3, and s is a number of 0 to 1. )
In the structural unit derived from the general formula (2), R 1 The hydrogen or an alkyl group having 1 to 4 carbon atoms is preferable, and the hydrogen or an alkyl group having 1 to 2 carbon atoms is particularly preferable. R is R 3 、R 4 、R 5 、R 6 、R 7 、R 8 、R 9 、R 10 、R 11 、R 12 Each independently represents any one of hydrogen, a hydroxyl group, an alkyl group having 1 to 3 carbon atoms, and an aromatic group which may have a substituent, and preferably represents any one of hydrogen, a hydroxyl group, an alkyl group having 1 to 2 carbon atoms, and an aromatic group which may have a substituent. R is R 13 The alkylene group is preferably an alkylene group having 1 to 3 carbon atoms or a carbonyl group, more preferably an alkylene group having 1 to 2 carbon atoms or a carbonyl group. R is R 14 The aromatic group which may have a substituent is preferably an aryl group, a benzyl group or a phenoxy group. Examples of the substituent include an unsaturated hydrocarbon group such as an alkyl group such as a methyl group, an ethyl group, or an isopropyl group, a halogen group such as a fluoro group, a chloro group, a bromo group, or an iodo group, an amino group, a nitro group, or a carboxyl group. The number of aromatic rings may be 2 or more.
q and r are each independently a number of 0 to 3, preferably a number of 0 to 2, and preferably q+r is not less than 1.s is a number from 0 to 1.
Specific examples of the structural unit derived from the general formula (1) include structural units based on benzyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, neopentyl glycol- (meth) acrylic acid-benzoate, 2- (meth) acryloyloxyethyl-phthalic acid, and the like. The structural units based on the general formula (1) may be 1 or 2 or more.
The lower limit of the ratio of the structural unit (B) in the polymer is preferably 20 mass% or more, more preferably 25 mass% or more, and particularly preferably 30 mass% or more. The upper limit of the ratio of the structural unit (B) in the polymer is preferably 60 mass% or less, more preferably 50 mass% or less, and particularly preferably 45 mass% or less. When the amount is within the above range, the affinity between the collector foil and the active material is preferably improved when the electrode is used.
The total of the structural units (a) and (B) in the polymer is preferably 70% by mass or more, more preferably 75% by mass or more, and particularly preferably 80% by mass or more.
(structural 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, a (blocked) isocyanate group, and a urethane group (also referred to as a urethane bond). In the present invention, the polymer contained in the binder for an electrode preferably contains at least one selected from the group consisting of epoxy groups, (blocked) isocyanate groups and urethane groups. That is, it is preferable that at least a part of at least one selected from the group consisting of an epoxy group, (blocked) isocyanate group and a urethane group contained in the monomer forming the structural unit C is also remained after the polymerization of the monomer forming the structural unit C together with the monomer forming the structural unit (a) and the monomer forming the structural unit (B) to form a polymer. This is because the inclusion of these groups in the polymer functions as a crosslinking group in the electrode binder, and can contribute to improvement of cycle characteristics of the power storage device. The number of structural units (C) contained in the polymer may be 1 or 2 or more.
Among the monomers forming the structural unit (C), a reactive double bond is preferable as a monomer having at least one selected from the group consisting of an epoxy group, a (blocked) isocyanate group and a urethane group. The number of the structural units may be 1 or 2 or more.
Specific examples of the structural unit derived from a monomer having an epoxy group include allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, and the like.
Specific examples of the structural unit derived from a monomer having a (blocked) isocyanate group include structural units derived from 2-methacryloxyethyl isocyanate, 2-acryloxyethyl isocyanate, 2- [ O- (1' -methylpropyleneamino) carboxyamino ] ethyl methacrylate, 2- [ (3, 5-dimethylpyrazolyl) carbonylamino ] ethyl methacrylate, 1- (bisacryloxymethyl) ethyl isocyanate, 2- (2-methacryloxyethyl oxy) ethyl isocyanate, and the like.
Specific examples of the structural unit derived from a monomer having a urethane group include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, phenyl glycidyl ether acrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, and the like.
The lower limit of the ratio of the structural unit (C) derived from the monomer having at least one selected from the group consisting of an epoxy group, a (blocked) isocyanate group and a urethane group in the polymer is preferably 0.5 mass% or more, more preferably 1 mass% or more, and particularly preferably 2 mass% or more. The upper limit of the ratio of the structural unit (C) derived from the monomer having at least one selected from the group consisting of an epoxy group, a (blocked) isocyanate group and a urethane group in the polymer is preferably 10 mass% or less, more preferably 8 mass% or less, and particularly preferably 6 mass% or less.
(structural 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 an electrode of the present invention, the polymer preferably contains a structural unit (D) in terms of improvement in ion conductivity when the binder is used for an electrode.
[ chemical 8]
(wherein R is 15 Is a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, n x are each independently an integer of 2 to 8, and n is an integer of 2 to 30. )
In the general formula (3), R is 15 Preferred examples thereof include a hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, and isobutyl group. Preferably a hydrogen atom or a methyl group. That is, in the structural unit (D), the monomer having a hydroxyl group is preferably (R) 15 Is a hydrogen atom or a methyl) (methyl) acrylate monomer.
In the general formula (3), as (C) x H 2x O) is a linear or branched alkyl ether group, and n x are each independently an integer of 2 to 8, preferably an integer of 2 to 7, more preferably an integer of 2 to 6.
In the 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).
[ chemical 9]
In the 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 of 0 to 30, p is an integer of 0 to 30, and o+p is 2 to 30. Wherein o and p represent the constituent ratio of the structural unit only, and do not refer to the structural unit represented by (C 2 H 4 Blocks of repeating units of O) and (C) 3 H 6 The compound comprising a block of repeating units of O) may be (C) 2 H 4 Repeating units of O) and (C) 3 H 6 O) repeating units alternately arranged randomly or mixed with random and block unitsA compound present.
In the general formula (4), R is 15 Preferred examples thereof include a hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, and isobutyl group. Preferably a hydrogen atom or a methyl group. That is, in the structural unit (D), the monomer having a hydroxyl group is preferably (R) 15 Is a hydrogen atom or a methyl) (methyl) acrylate monomer.
In the general formula (4), o is an integer of 0 to 30, p is an integer of 0 to 30, o+p is an integer of 2 to 30, preferably o is an integer of 0 to 25, p is an integer of 0 to 25, o+p is an integer of 2 to 25, particularly preferably o is an integer of 0 to 20, p is an integer of 0 to 20, and o+p is 2 to 20.
Specific examples of the monomer having a hydroxyl group represented by the 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, 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, and the like. They may be used in combination of 1 or more than 2. Among them, tetraethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, tetrapropylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate are preferable.
The structural units (D) optionally contained in the polymer may be one kind or two or more kinds.
In the polymer, the lower limit of the ratio of the structural unit (D) based on the monomer having a hydroxyl group 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 ratio of the structural unit (D) based on the monomer having a hydroxyl group in the polymer is preferably 15 mass% or less, more preferably 12 mass% or less, and particularly preferably 10 mass% or less.
(structural unit (E))
The structural unit (E) is a structural unit derived from a polyfunctional (meth) acrylate monomer having 5 or less functions. The polyfunctional (meth) acrylate monomer specifically means a (meth) acrylate monomer having 2 or more (meth) acryloyl groups. In the polymer, in order to stabilize the binder particles, it is preferable to include a structural unit (E) derived from a polyfunctional (meth) acrylate monomer having 5 or less functions. The structural unit (E) is preferably a structural unit derived from the following general formula (5).
[ chemical 10]
In the general formula (5), R 16 Respectively the same or different, is a hydrogen atom or methyl, R 17 An organic group having 2 to 100 carbon atoms and having a valence of 5 or less, and m is an integer of 5 or less.
In the general formula (5), m is preferably 2 to 5 (i.e., the structural unit (D) is a structural unit derived from 2-5-functional (meth) acrylate), more preferably 3 to 5 (i.e., the structural unit (E) is a structural unit derived from 3-5-functional (meth) acrylate), and particularly preferably 3 to 4 (i.e., the structural unit (E) is a structural unit derived from 3-4-functional (meth) acrylate).
Specific examples of the structural unit (E) include structural units derived from 2 functional (meth) acrylates such as triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, dioxane glycol di (meth) acrylate, bis (meth) acryloyloxyethyl phosphate, neopentyl glycol di (meth) acrylate, and the like, based on a monomer having 2 (meth) acryloyl groups.
Specific examples of the structural unit (E) include structural units derived from 3 functional (meth) acrylates such as trimethylolpropane tri (meth) acrylate, trimethylolpropane EO-added tri (meth) acrylate, trimethylolpropane PO-added tri (meth) acrylate, pentaerythritol tri (meth) acrylate, 2-tris (meth) acryloyloxymethyl ethyl succinic acid, ethoxylated isocyanurate tri (meth) acrylate, epsilon-caprolactone-modified tri- (2- (meth) acryloyloxyethyl) isocyanurate, glycerol EO-added tri (meth) acrylate, glycerol PO-added tri (meth) acrylate, and tri (meth) acryloyloxyethyl phosphate. Among them, a structural unit derived from a 3-functional (meth) acrylate selected from trimethylolpropane tri (meth) acrylate, trimethylolpropane EO-added tri (meth) acrylate, pentaerythritol tri (meth) acrylate is preferable.
Specific examples of the structural unit (E) include structural units derived from 4 functional (meth) acrylates such as di (trimethylolpropane) tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, and pentaerythritol EO addition tetra (meth) acrylate, as structural units based on monomers having 4 (meth) acryloyl groups.
Specific examples of the structural unit (E) include structural units derived from dipentaerythritol penta (meth) acrylate, which are based on a monomer having 5 (meth) acryloyl groups.
When the polymer contains the structural unit (E), the lower limit of the ratio is preferably 1% by mass or more, more preferably 3% by mass or more, and may be 5% by mass or more, or may be 5.2% by mass or more. The upper limit of the ratio of the structural unit (E) in the polymer is preferably 15 mass% or less, more preferably 12 mass% or less, and particularly preferably 10 mass% or less. When the content is within this range, the adhesion is preferably improved when the electrode is used.
The structural units (E) optionally contained in the polymer may be one kind or two or more kinds.
(structural unit (F))
The structural unit (F) is a structural unit derived from a (meth) acrylic acid monomer. In the polymer, the structural unit (F) derived from a (meth) acrylic acid monomer is preferably contained in terms of improving affinity with an active material when used in an electrode.
The structural unit (F) may be exemplified by a structural unit derived from a compound selected from acrylic acid and methacrylic acid. The structural unit (F) optionally contained in the polymer may be one kind or two or more kinds.
When the polymer contains the structural unit (F), the lower limit is preferably 3% by mass or more, more preferably 4% by mass or more, and particularly 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 proportion of the structural units (a), the structural units (B), the structural units (C), the structural units (D), the structural units (E) and the structural units (F) in the polymer is preferably 85 mass% or more, more preferably 90 mass% or more, particularly preferably 95 mass% or more, and may be 97 mass% or more, or 100 mass% or more.
The polymer may have, in addition to the above-mentioned monomers, a structural unit derived from a monomer selected from fumaric acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, acrylonitrile, methacrylonitrile, α -chloroacrylonitrile, crotononitrile, α -ethylacrylonitrile, α -cyanoacrylate, vinylidene cyanide, and fumaric acid nitrile as a structural unit derived from another monomer. These structural units may be contained in any of the polymers, and may be one kind or two or more kinds.
(method for producing Polymer)
As a method for obtaining the polymer, a common emulsion polymerization method, a soap-free emulsion polymerization method, or the like can be used. Specifically, a composition containing a monomer, an emulsifier, a polymerization initiator, water, a dispersant, a chain transfer agent, a pH adjuster, and the like, which are added as needed, is stirred in a closed vessel equipped with a stirrer and a heating device at room temperature under an inert gas atmosphere, and the monomer and the like are emulsified in water. The emulsification method may be performed by stirring, shearing, ultrasonic wave, or the like, and stirring wings, homogenizers, or the like may be used. Then, the temperature is raised while stirring to initiate polymerization, thereby obtaining a latex of a spherical polymer in which the polymer is dispersed in water. The method of adding the monomer during polymerization may be, in addition to one-time addition, monomer dropwise addition, pre-emulsion dropwise addition, or the like, or 2 or more of these methods may be used in combination. The pre-emulsion dropwise addition means a method of adding a monomer, an emulsifier, water, and the like into an emulsion in advance and gradually dropwise adding the emulsion.
The emulsifier used in the present invention is not particularly limited. The emulsifier is a surfactant, and the surfactant contains a reactive surfactant having a reactive group. Generally used nonionic surfactants and anionic surfactants can be used in the emulsion polymerization method.
Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene diphenylated phenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene fatty acid ester, and polyoxyethylene sorbitan fatty acid ester, and examples of the reactive nonionic surfactant include latex PD-420, 430, and 450 (manufactured by queen corporation), adeka reasnap ER (manufactured by Adeka corporation), aqualon RN (manufactured by first industry pharmaceutical corporation), antox LMA (manufactured by japan emulsifier corporation), antox EMH (manufactured by japan emulsifier corporation), and the like.
Examples of the anionic surfactant include: a sulfate-type, carboxylic acid-type, or sulfonic acid-type metal salt, ammonium salt, triethanolamine salt, phosphate-type surfactant, or the like. The sulfate type, sulfonic acid type and phosphate type are preferable, and the sulfate type is particularly preferable. Typical examples of the sulfate type anionic surfactant include metal alkyl sulfate salts such as dodecyl sulfate, ammonium, triethanolamine alkyl sulfate, polyoxyethylene dodecyl sulfate, polyoxyethylene isodecyl sulfate, polyoxyethylene tridecyl sulfate, and other polyoxyethylene alkyl ether sulfate metal salts, ammonium salts, and polyoxyethylene alkyl ether sulfate triethanolamine; specific examples of the sulfate type reactive anionic surfactant include latex PD-104 and 105 (manufactured by king corporation), adeka Reasoap SR (manufactured by Adeka corporation), aqualon HS (manufactured by first industrial pharmaceutical corporation), and Aqualon KH (manufactured by first industrial pharmaceutical corporation). Sodium dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine dodecyl sulfate, sodium dodecyl benzene sulfonate, latex PD-104, and the like are preferable.
These nonionic and/or anionic surfactants may be used in an amount of 1 or 2 or more.
The reactivity of the reactive surfactant means that it contains a reactive double bond and undergoes polymerization reaction with the monomer at the time of polymerization. That is, the reactive surfactant functions as an emulsifier of a monomer at the time of polymerization of the polymer, and becomes a state of entering into a part of the polymer by covalent bond after the polymerization. Therefore, the emulsion polymerization and the dispersion of the produced polymer are good, and the physical properties (bendability, adhesiveness) as an electrode binder are excellent.
The amount of the constituent unit of the emulsifier may be any amount generally used in emulsion polymerization. Specifically, the amount of the monomer to be charged (100% by mass) is in the range of 0.01 to 25% by mass, preferably 0.05 to 20% by mass, and more preferably 0.1 to 20% by mass.
The polymerization initiator used in the present invention is not particularly limited, and a polymerization initiator generally used in emulsion polymerization and suspension polymerization can be used. Emulsion polymerization is preferred. 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 water-soluble azo compounds such as 2-2' -azobis [2- (2-imidazolin-2-yl) propane ], or hydrochloride or sulfate thereof, 2' -azobis [ 2-methyl-N- (2-hydroxyethyl) propionamide ], 2' -azobis (2-methylpropionamidine), or hydrochloride or sulfate thereof, 3' - [ azobis [ (2, 2-dimethyl-1-iminoethane-2, 1-diyl) imino ] ] bis (propionic acid), and 2,2' - [ azobis (dimethylmethylene) ] bis (2-imidazoline).
As the oil-soluble polymerization initiator, preferred are polymerization initiators of oil-soluble azo compounds such as cumene hydroperoxide, benzoyl peroxide, acetyl peroxide, t-butyl hydroperoxide and the like, azobisisobutyronitrile, 1' -azobis (cyclohexane carbonitrile) and the like, and redox initiators. These polymerization initiators may be used in an amount of 1 or 2 or more in combination.
The amount of the polymerization initiator to be used may be any amount generally used in emulsion polymerization or suspension polymerization. Specifically, the amount of the monomer to be charged (100% by mass) is in the range of 0.01 to 10% by mass, preferably 0.01 to 5% by mass, and more preferably 0.02 to 3% by mass.
Chain transfer agents may be used as desired. Specific examples of the chain transfer agent include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan; xanthate compounds such as 2, 4-diphenyl-4-methyl-1-pentene, 2, 4-diphenyl-4-methyl-2-pentene, dimethyl xanthate disulfide, diisopropyl xanthate disulfide and the like; terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide and other thiuram compounds; phenolic compounds such as 2, 6-di-t-butyl-4-methylphenol and styrenated phenol; allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as methylene chloride, dibromomethane and carbon tetrabromide, and vinyl ethers such as α -benzyloxystyrene, α -benzyloxyacrylonitrile and α -benzyloxyacrylamide; triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycollic acid, thiomalic acid, thioglycollic acid-2-ethylhexyl ester, etc., and 1 or 2 or more of them may be used. The amount of these chain transfer agents is not particularly limited, and is usually 0 to 5 parts by mass per 100 parts by mass of the amount of the monomer to be charged.
In the production of the polymer, the polymerization temperature and polymerization time are not particularly limited. The polymerization temperature is generally 20 to 100℃and the polymerization time is generally 0.5 to 100 hours, which may be appropriately selected depending on the kind of the polymerization initiator used.
The binder for an electrode of the present invention contains a polymer. Other substances such as moisture and an emulsifier may be contained in the polymer or may be externally attached. The amount of the substance contained in or attached to the outside is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less, per 100 parts by mass of the polymer.
< evaluation of dynamic viscoelasticity upon swelling of adhesive >
The dynamic viscoelasticity of the electrode binder of the present invention when swollen in a solvent used in an electrolyte is evaluated by using a dynamic viscoelasticity measuring device to measure the elastic term E' and the viscous term E″ of a film (a swollen film having a thickness of 1.0 to 2.0 mm) obtained by swelling the electrode binder in a solvent used in an electrolyte at a measurement temperature of 25℃and a frequency of 1 Hz.
As a method for producing the swelling film, the following method can be exemplified: the culture dish was filled with a binder or a binder composition containing a binder and a solvent such as water, and dried at 60℃for 48 hours to obtain a 1mm thick binder film, which was immersed in a solvent used in the electrolyte at 25℃for 24 hours.
The elastic term E' and the viscous term e″ of the swollen film as the measurement result preferably satisfy either one of the following conditions (1) and (2), and preferably satisfy both conditions (1) and (2).
(1) The elastic term E'. Gtoreq.4.5X10 6 (Pa)
(2) The sticky term E'. Gtoreq.0.9X10 6 (Pa)
The elastic term E' as a swelling film is, for example, 4.5X10 6 Pa or more, preferably 5.0X10 6 Pa or more, particularly preferably 5.5X10 6 Pa or more, and the upper limit is not particularly limited, and is preferably 20X 10 6 Pa or less, more preferably 15×10 6 Pa or less, particularly preferably 11×10 6 Pa or below.
Even in the case where the elastic term E' of the (1) (swollen) film is satisfied but the viscous term E "of the (2) swollen film is not satisfied, the viscous term E" of the (2) swollen film at this time is 0.2X10 6 Pa or more, preferably 0.25X10 6 Pa or more, particularly preferably 0.3X10 6 Pa or more, and an upper limit of less than 0.9X10 6 Pa。
Tack item E "as a swollen film"0.9X10 6 Pa or more, preferably 0.95X10 6 Pa or more, particularly preferably 1.0X10 6 Pa or more, and the upper limit is not particularly limited, and is preferably 4.0X10 6 Pa or less, more preferably 3.0X10 6 Pa or less, particularly preferably 2.0X10 6 Pa or below.
Even in the case where the adhesive term E "of the (2) swollen film is satisfied but the elastic term E 'of the (1) (swollen) film is not satisfied, the elastic term E' of the (1) (swollen) film at this time is 1.0X10 6 Pa or more, preferably 1.5X10 6 Pa or more, particularly preferably 2.0X10 6 Pa or more, and an upper limit of less than 4.5X10 6 Pa。
When the two conditions (1) and (2) are satisfied, the elastic term E' of the swollen film is 4.5X10 6 Pa or more, preferably 5.0X10 6 Pa or more, particularly preferably 5.5X10 6 Pa or more, and the upper limit is not particularly limited, and is preferably 20X 10 6 Pa or less, more preferably 15×10 6 Pa or less, particularly preferably 11×10 6 Pa or below.
The tack item E "as a swollen film was 0.9X10 6 Pa or more, preferably 0.95X10× 6 Pa or more, particularly preferably 1.0X10× 6 Pa or more, and the upper limit is not particularly limited, and is preferably 4.0X10 6 Pa or less, more preferably 3.0X10 6 Pa or less, particularly preferably 2.0X10 6 Pa or below.
The solvent used in the electrolyte may be an aprotic organic solvent, and specifically, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, γ -butyrolactone, tetrahydrofuran, 1, 3-dioxolane, dipropyl carbonate, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate, propionate, diethyl ether or other linear ethers may be used, or 2 or more linear ethers may be used in combination, and a mixed solvent in which propylene carbonate and diethyl carbonate are mixed at a volume ratio of 3:7 may be exemplified.
The following conditions can be exemplified as the measurement conditions of the dynamic viscoelasticity measurement device using the swelling film. For a sample having a diameter of 5mm and a thickness of 1.0 to 2.0mm, the measurement was performed by dynamic viscoelasticity measurement using a dynamic viscoelasticity device Rheogel-E4000HP manufactured by UBM Co., ltd.) under conditions of a compression mode, a press-in amount of 1 μm, a measurement temperature of 25℃and a frequency of 1 Hz.
<2 > Binder composition for electrode
The binder composition of the present invention contains both a solvent and the binder of the present invention described in the column "binder for electrode" described above, and the binder can be dispersed in the solvent. The solvent may be water or an organic solvent. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol (pentanol), hexanol, heptanol, octanol, nonanol, decanol, and amyl alcohol (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 polar organic solvents such as N, N-dimethylformamide and N-methyl-2-pyrrolidone (NMP); aromatic hydrocarbons such as toluene, xylene, chlorobenzene, o-dichlorobenzene, and p-dichlorobenzene.
The binder composition for an electrode of the present invention is preferably an aqueous binder composition in which a binder is dispersed in water.
The binder composition for an electrode of the present invention may be an emulsion using an emulsion produced when the binder is obtained.
The content of the binder in the binder composition for an electrode of the present invention is not particularly limited, but is preferably contained so that the concentration of a solid component (hereinafter, may be simply referred to as "solid component") other than the solvent of the binder is 0.2 to 80% by mass, more preferably 0.5 to 70% by mass, and particularly preferably 0.5 to 60% by mass.
The binder composition for an electrode of the present invention may be adjusted in pH by using a base as a pH adjuster as needed. Specific examples of the base include alkali metal (Li, na, K, rb, cs) hydroxide, ammonia, inorganic ammonium compound, and organic amine compound. The pH is in the range of 2 to 11, preferably 3 to 10, and more preferably 4 to 9.
The binder composition for an electrode of the present invention may contain polyacrylic acid or the like.
<3. Electrode >
The electrode of the present invention includes an electrode material layer on a current collector.
As for the electrode of the present invention, a known current collector can be used. Specifically, as the positive electrode, metals such as aluminum, nickel, stainless steel, gold, platinum, and titanium are used. As the negative electrode, metals such as copper, nickel, stainless steel, gold, platinum, titanium, and aluminum can be used.
The electrode material layer contains at least an active material and the binder of the present invention described in the column "binder for electrode" above, and may further contain a conductive auxiliary agent. In the production of the electrode material of the present invention, the electrode binder composition of the present invention described in the column "2. Electrode binder composition" containing both the solvent and the electrode binder of the present invention is preferably used. Specifically, in the lithium ion battery, the positive electrode material used as the positive electrode may further contain a conductive auxiliary agent, and the negative electrode material used as the negative electrode may further contain a negative electrode active material, a conductive auxiliary agent, and the electrode binder of the present invention; in an electric double layer capacitor (electrochemical capacitor), a positive electrode material used as a positive electrode may further contain a conductive auxiliary agent, and a negative electrode material used as a negative electrode may further contain an active carbon as an active material, a binder for an electrode of the present invention, and a conductive auxiliary agent.
The positive electrode active material used in the lithium ion battery comprises AMO 2 、AM 2 O 4 、A 2 MO 3 、AMBO 4 An alkali metal-containing composite oxide of any one of the compositions. A comprises an alkali metal, M comprises a single or more than 2 transition metals, and a part of the transition metals may also comprise non-transition metals. B comprises P, si or a mixture thereof. The positive electrode active material is preferably a powder, and the particle diameter thereof is preferably 50 μm or less, more preferably20 microns or less. These active materials have an electromotive force of 3V (vs. Li/li+) or more.
Preferred specific examples of the positive electrode active material used in the lithium ion battery include LixCoO 2 、LixNiO 2 、LixMnO 2 、LixCrO 2 、LixFeO 2 、LixCoaMn 1-a O 2 、LixCoaNi 1-a O 2 、LixCoaCr 1-a O 2 、LixCoaFe 1-a O 2 、LixCoaTi 1-a O 2 、LixMnaNi 1-a O 2 、LixMnaCr 1-a O 2 、LixMnaFe 1-a O 2 、LixMnaTi 1-a O 2 、LixNiaCr 1-a O 2 、LixNiaFe 1-a O 2 、LixNiaTi 1-a O 2 、LixCraFe 1-a O 2 、LixCraTi 1-a O 2 、LixFeaTi 1-a O 2 、LixCobMncNi 1-b-C O 2 、LixNiaCobAlcO 2 、LixCrbMncNi 1-b-C O 2 、LixFebMncNi 1-b-C O 2 、LixTibMncNi 1-b-C O 2 、LixMn 2 O 4 、LixMndCo 2-d O 4 、LixMndNi 2-d O 4 、LixMndCr 2-d O 4 、LixMndFe 2-d O 4 、LixMndTi 2-d O 4 、LiyMnO 3 、LiyMneCo 1-e O 3 、LiyMneNi 1-e O 3 、LiyMneFe 1-e O 3 、LiyMneTi 1-e O 3 、LixCoPO 4 、LixMnPO 4 、LixNiPO 4 、LixFePO 4 、LixCofMn 1-f PO 4 、LixCofNi 1-f PO 4 、LixCofFe 1-f PO 4 、LixMnfNi 1-f PO 4 、LixMnfFe 1-f PO 4 、LixNifFe 1-f PO 4 、LiyCoSiO 4 、LiyMnSiO 4 、LiyNiSiO 4 、LiyFeSiO 4 、LiyCogMn 1-g SiO 4 、LiyCogNi 1-g SiO 4 、LiyCogFe 1-g SiO 4 、LiyMngNi 1-g SiO 4 、LiyMngFe 1-g SiO 4 、LiyNigFe 1-g SiO 4 、LiyCoPhSi 1-h O 4 、LiyMnPhSi 1-h O 4 、LiyNiPhSi 1-h O 4 、LiyFePhSi 1-h O 4 、LiyCogMn 1-g PhSi 1-h O 4 、LiyCogNi 1-g PhSi 1-h O 4 、LiyCogFe 1-g PhSi 1-h O 4 、LiyMngNi 1-g PhSi 1-h O 4 、LiyMngFe 1-g PhSi 1-h O 4 、LiyNigFe 1-g PhSi 1-h O 4 And lithium-containing composite oxides. (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, wherein 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.)
Among the above-mentioned preferable positive electrode active materials used in lithium ion batteries, more preferable positive electrode active materials include LixCoO 2 、LixNiO 2 、LixMnO 2 、LixCrO 2 、LixCoaNi 1-a O 2 、LixMnaNi 1-a O 2 、LixCobMncNi 1-b-C O 2 、LixNiaCobAlcO 2 、LixMn 2 O 4 、LiyMnO 3 、LiyMneFe 1-e O 3 、LiyMneTi 1-e O 3 、LixCoPO 4 、LixMnPO 4 、LixNiPO 4 、LixFePO 4 、LixMnfFe 1-f PO 4 . ( Wherein 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, wherein 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. The values of x and y described above are increased or decreased by charge and discharge. )
As the negative electrode active material used in the lithium ion battery, a carbon material (natural graphite, artificial graphite, amorphous carbon, or the like) having a structure (porous structure) capable of occluding and releasing lithium ions, or a powder containing a metal such as lithium, an aluminum compound, a tin compound, a silicon compound, or a titanium compound such as a niobium-titanium oxide capable of occluding and releasing lithium ions is used. The particle diameter is preferably 10nm to 100 μm, more preferably 20nm to 20 μm. The active material may be used as a mixed active material of a metal and a carbon material. It is desirable to use a negative electrode active material having a porosity of about 70%.
Examples of the carbon material include graphite, low-crystalline carbon (soft carbon, hard carbon), carbon black (ketjen black, acetylene black, channel black, lamp black, oil furnace black, thermal black, and the like), fullerene, carbon nanotube, carbon nanofiber, carbon nanohorn, carbon fibril, coke, mesophase Carbon Microsphere (MCMB), mesophase pitch-based carbon fiber, phenolic resin fired body, and polyacrylonitrile-based carbon fiber, and graphite is preferable.
Examples of the silicon compound include Si element, an alloy with Si, an oxide containing Si, and a carbide containing Si, and Si and 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<x≤2)、SnSiO x LiSiO, preferably SiO x (0<x.ltoreq.2), silicon monoxide (SiO), and the like.
In the case where the carbon material and the silicon compound are used together, the active material is preferably contained in the following manner.
The lower limit of the content of the carbon material relative to the total amount of the active material (100 mass%) is preferably 20 mass% or more, more preferably 40 mass% or more, particularly preferably 60 mass% or more, and may be 70 mass% or more, and the upper limit is preferably 99 mass% or less, more preferably 98 mass% or less, particularly preferably 96 mass% or less.
The lower limit of the content of the silicon-based 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, more preferably 60 mass% or less, particularly preferably 40 mass% or less, and may be 30 mass% or less.
As an active material used in an electric double layer capacitor (electrochemical capacitor), activated carbon can be exemplified. The activated carbon is usually an activated carbide, and commercially available activated carbon may be used, or activated carbon produced by a known production method may be used. As a method for producing activated carbon, raw materials such as wood, coconut husk, pulp waste liquid, coal, heavy oil, and phenol resin are carbonized, and the obtained carbide is activated to obtain the activated carbon.
The activation may be performed by a known activation method, such as a gas activation method or a chemical activation method. In the gas activation method, carbide is activated by bringing it into contact with a gas such as steam, carbon dioxide gas, or oxygen gas under heating. In the chemical activation method, carbide is activated by heating in a state of being brought into contact with a known activation chemical. Examples of the activating chemical include zinc chloride, phosphoric acid, and/or an alkali compound (e.g., a metal hydroxide such as sodium hydroxide). Activated carbon activated with steam (referred to herein as steam activated carbon) and/or activated carbon activated with alkali (referred to herein as alkali activated carbon) are preferably used.
The content of the active material in the electrode material layer is not particularly limited, and examples thereof include 99.9 to 50 mass%, more preferably 99.5 to 70 mass%, and still more preferably 99 to 85 mass% with respect to the electrode material layer (100 mass%). The active material may be used alone or in combination of 1 or more than 2.
The content of the binder of the present invention in the electrode material layer is not particularly limited, and for example, it is 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, relative to 100 parts by mass of the active material.
In the case of using a conductive additive, a known conductive additive may be used, and examples thereof include conductive carbon black such as graphite, furnace black, acetylene black, ketjen black, carbon fibers such as Carbon Nanotubes (CNT), metal powder, and the like. These conductive assistants may be used in an amount of 1 or 2 or more.
In the case of using the conductive auxiliary, the content of the conductive auxiliary is not particularly limited, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, per 100 parts by mass of the active material. When the conductive auxiliary agent is included in the positive electrode material, the lower limit value of the content of the conductive auxiliary agent may be generally exemplified by 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 the thickener is not particularly limited, but sodium salt, ammonium salt, polyvinyl alcohol, polyacrylic acid, and salts thereof of the cellulose-based compound are preferable.
Examples of the sodium salt or ammonium salt of the cellulose-based compound include sodium salt or ammonium salt of alkyl cellulose obtained by substitution of a cellulose-based polymer with various derivative groups. Specific examples thereof include sodium salts, ammonium salts, and triethanolamine salts of methylcellulose, methylethylcellulose, ethylcellulose, and carboxymethylcellulose (CMC). Sodium or ammonium salts of carboxymethyl cellulose are particularly preferred. These thickeners may be used alone in 1 kind, or may be used in combination in an arbitrary ratio of 2 or more kinds.
In the case of using the thickener, the content of the thickener is not particularly limited, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, per 100 parts by mass of the active material. When the thickener is contained, the lower limit of the content of the thickener may be generally exemplified by 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 for producing the electrode is not particularly limited, and a usual method can be used. The electrode material is uniformly coated on the surface of the current collector (metal electrode substrate) to an appropriate thickness by a doctor blade method, a coater method, a screen method, or the like.
The electrode material of the present invention may also contain water to be made into a slurry. The water is not particularly limited, and commonly used water can be used. Specific examples thereof include tap water, distilled water, ion-exchanged water, ultrapure water, and the like. Among them, distilled water, ion-exchanged water and ultrapure water are preferable.
When the electrode material of the present invention is used 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 particularly 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 in the solid content of the slurry is preferably 0.1 to 15% by mass, more preferably 0.2 to 10% by mass, and particularly preferably 0.3 to 7% by mass.
The method for producing the electrode material is not particularly limited, and a common stirrer, a dispersing machine, a kneader, a planetary ball mill, a homogenizer, or the like may be used to disperse the positive electrode active material or the negative electrode active material, the binder for an electrode of the present invention, the conductive additive, water, or the like. In order to improve the dispersing efficiency, heating may be performed in a range that does not affect the material. The binder composition for electrode of the present invention described in column "2. Binder composition for electrode" containing a solvent and the binder for electrode of the present invention may also be used.
For example, in the doctor blade method, after the electrode slurry is applied to the metal electrode substrate, the electrode slurry is homogenized to an appropriate thickness by a doctor blade having a specific slit width. After the active material is applied, the electrode is dried, for example, in a hot air at 100℃and a vacuum at 80℃in order to remove excess organic solvent and water. The dried electrode is press-molded by a pressing device, thereby manufacturing an electrode material. After the pressing, the heat treatment may be performed again to remove water, solvents, emulsifiers, and the like.
<4 > electric storage device
The power storage device of the present invention is characterized by comprising the positive electrode, the negative electrode, and the electrolyte described in the column "3. Electrode". That is, the electrode used in the power storage device of the present invention includes the electrode material of the present invention, that is, the binder for an electrode of the present invention. The details of the electrode of the present invention are as described above. In the power storage device of the present invention, any electrode may be used as long as at least one of the positive electrode and the negative electrode is an electrode using an electrode material containing the electrode binder of the present invention, and any known electrode may be used as long as it does not use an electrode material containing the electrode binder of the present invention.
The electrolyte is not particularly limited, and a known electrolyte may be used. Specific examples of the electrolyte solution include a solution containing an electrolyte and a solvent, and a normal temperature molten salt. The electrolyte and the solvent may be used alone or in combination of 1 or more than 2 kinds.
The electrolyte may be a lithium salt compound, and specifically may be 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., but is not limited thereto.
Examples of the electrolyte other than the lithium salt compound include tetraethylammonium tetrafluoroborate, triethylmonomethyl ammonium tetrafluoroborate, and tetraethylammonium hexafluorophosphate.
As the solvent used in the electrolyte solution, an organic solvent can be exemplified.
The organic solvent includes aprotic organic solvents, and specifically, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, γ -butyrolactone, tetrahydrofuran, 1, 3-dioxolane, dipropyl carbonate, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate, propionate, diethyl ether and other linear ethers may be used, or 2 or more linear ethers may be used in combination.
The normal temperature molten salt is also called an ionic liquid, and is a "salt" composed of only ions (anions, cations), and particularly, a liquid compound is called an ionic liquid.
The normal temperature molten salt in the present invention means a salt that is at least partially in a liquid state at normal temperature, and normal temperature means a temperature range in which a battery is supposed to normally operate. The temperature range in which the battery normally operates is assumed to be about 120℃at the upper limit, and about 80℃at the lower limit, and about-40℃at the lower limit, and about-20 ℃.
As the cation type of the normal temperature molten salt, known are quaternary ammonium organic cations of pyridine-based, aliphatic-based, and alicyclic amine-based. Examples of the quaternary ammonium organic cation include imidazolium ions such as dialkylimidazolium and trialkylimidazolium, tetraalkylammonium ions, alkylpyridinium ions, pyrazolium ions, pyrrolidinium ions, and piperidinium ions. Imidazolium ions are particularly preferred.
Examples of the tetraalkylammonium ion include, but are not limited to, trimethylethylammonium ion, trimethylpropylammonium ion, trimethylhexylammonium ion, tetrapentylammonium ion, and triethylmethylammonium ion.
Examples of the alkylpyridinium ion include, but are not limited to, N-methylpyridinium ion, N-ethylpyridinium ion, N-propylpyridinium ion, N-butylpyridinium ion, 1-ethyl-2-methylpyridinium ion, 1-butyl-4-methylpyridinium ion, and 1-butyl-2, 4-dimethylpyridinium ion.
Examples of the imidazolium ion include 1, 3-dimethylimidazolium ion, 1-ethyl-3-methylimidazolium ion, 1-methyl-3-ethylimidazolium ion, 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-propylimidazolium ion, and 1-butyl-2, 3-dimethylimidazolium ion, but are not limited thereto.
Examples of the anion species of the normal temperature molten salt include halide ions such as chloride ions, bromide ions, and iodide ions; perchlorate ion, thiocyanate ion, tetrafluoroborate ion, nitrate ion, asF 6 - 、PF 6 - Such as inorganic acid radical ion, stearyl sulfonate ion, octyl sulfonate ion, dodecyl benzene sulfonate ion, naphthalene sulfonate ion, dodecyl naphthalene sulfonate ion, 7,organic acid ions such as 8, 8-tetracyano-p-quinone dimethane ion, etc.
The normal temperature molten salt may be used alone or in combination of 1 or more than 2 kinds.
Various additives may be used as needed in the electrolyte. Examples of the additive include flame retardants, incombustibles, positive electrode surface treatments, negative electrode surface treatments, and overcharge inhibitors. Examples of the flame retardant and the incombustible agent include halogenated compounds such as brominated epoxy compounds, phosphazene compounds, tetrabromobisphenol a, and chlorinated paraffin; antimony trioxide, antimony pentoxide, aluminum hydroxide, magnesium hydroxide, phosphate esters, polyphosphates, zinc borate, and the like. Examples of the positive electrode surface treatment agent include carbon and metal oxides (MgO, zrO 2 Etc.), an inorganic compound, an organic compound such as ortho-terphenyl, etc. Examples of the negative electrode surface treatment agent include vinylene carbonate, fluoroethylene carbonate, polyethylene glycol dimethyl ether, and the like. Examples of the overcharge inhibitor include biphenyl and 1- (p-tolyl) adamantane.
The method for manufacturing the power storage device of the present invention is not particularly limited, and the power storage device can be manufactured by a known method using a positive electrode, a negative electrode, an electrolyte, a separator if necessary, and the like. In the case of button type, for example, the positive electrode, and if necessary, the separator and the negative electrode are inserted into the outer can. To which an electrolytic solution is added for impregnation. Then, the battery is obtained by bonding the battery to the sealing member by tab welding or the like, sealing the sealing member, and caulking the sealing member. The shape of the power storage device is not limited, and examples thereof include button type, cylindrical type, sheet type, and the like.
The separator is a device that prevents a short circuit from occurring in the battery by direct contact between the positive electrode and the negative electrode, and a known material can be used. Specific examples of the separator include porous polymer films such as polyolefin and papers. The porous polymer film is preferably a film of polyethylene, polypropylene or the like, which is less affected by the electrolyte.
Examples
Specific modes for carrying out the present invention will be described below with reference to examples. However, the present invention is not limited to the following examples unless departing from the gist thereof.
In this example, an adhesive film and a button cell were produced, and the measurement of the viscoelasticity test of the swollen film as an evaluation of the adhesive film and the cyclic test as an evaluation of the button cell was performed by the following experiments.
< method for producing swollen film >
The swollen membrane was produced in the following manner. First, an adhesive composition was poured into a petri dish, and dried at 60℃for 48 hours to prepare an adhesive film 1mm thick. The obtained film was immersed in a mixed solvent in which propylene carbonate and diethyl carbonate were mixed at a volume ratio of 3:7 at 25℃for 24 hours, thereby producing a swollen film.
< method for measuring viscoelasticity >
The viscoelasticity of the swollen film was measured under the following conditions.
(measurement device)
The viscoelasticity test of the swollen film was carried out by dynamic viscoelasticity measurement using a dynamic viscoelasticity device Rheogel-E4000 HP manufactured by UBM Co., ltd. Under conditions of compression mode, 1 μm in pressure amount, measurement temperature 25℃and frequency 1 Hz. The swelling membrane used was a membrane having a diameter of 5 mm. 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.
(measurement device)
Particle size distribution determination apparatus using dynamic light scattering: zetasizer Nano (SPECTRIS Co., ltd.)
(measurement conditions)
1. The synthesized emulsion solution was sampled at 50. Mu.L.
2. To the sampled emulsion solution, 700. Mu.L of ion-exchanged water was added 3 times to dilute.
3. 2100. Mu.L of liquid was withdrawn from the dilution.
4. To the remaining 50. Mu.L of the sample, 700. Mu.L of ion-exchanged water was added for dilution and measurement.
< measurement of aggregate >
The polymer agglomerates were measured in the following manner.
The emulsion solution after polymerization was filtered using a 150 mesh stainless steel wire mesh (manufactured by Kagaku Kogyo Co., ltd.) to scrape the agglomerate adhering to the stirring blade and the beaker. Then, the recovered aggregate was washed with ion-exchanged water, dried for 24 hours, and the mass of the aggregate was measured. The amount of the agglomerate was divided by the amount of the emulsion to be obtained as the amount of the agglomerate (% by mass).
[ evaluation of characteristics of fabricated Battery ]
As a characteristic evaluation of the fabricated coin cell, a measurement of charge/discharge efficiency was performed.
< measurement of charging and discharging efficiency >
(measurement device)
Charge and discharge evaluation device: TOSCAT-3100 (Toyo System Co., ltd.)
(measurement method)
The fabricated coin cell was discharged at 0.2C by constant current-constant voltage discharge. The termination current corresponds to 0.04C. After discharging, the cell was allowed to rest for 10 minutes. Then, the charge was carried out to 1.2V by constant current charging at 0.2C. The charge and discharge operations were performed for 50 cycles with the above operation as 1 cycle. The discharge capacity at the 50 th cycle was divided by the discharge capacity at the 1 st cycle to obtain a percentage as a cycle capacity maintenance rate (%). The evaluation results are shown in table 2.
Synthesis example 1
Into a beaker were placed 197.79G of lauryl methacrylate, 136.63G of benzyl methacrylate, 5.45G of acrylic acid, 15.27G of methacrylic acid, 14.51G of polyethylene glycol monomethacrylate (manufactured by Nippon Co., ltd.: BLEMER PE-90), 21.12G of trimethylolpropane trimethacrylate (manufactured by Zoongsha Chemie: LIGHT ESTER TMP), 10.02G of allyl glycidyl ether (manufactured by Osaka Caesalpinia: NEOALLYL G), 6.40G of sodium dodecyl sulfate as an emulsifier, 1.60G of polyoxyethylene diphenylether (manufactured by Nippon Co., ltd., NOIGEN EA-157) as an emulsifier, 342G of ion-exchanged water and 0.87G of t-butyl hydroperoxide (manufactured by Nippon Co., ltd.: PERBUTYL H-69) as a polymerization initiator, and the mixture was sufficiently stirred by an ultrasonic homogenizer to prepare an emulsion. The reaction vessel with stirrer was heated to 58 ℃ under nitrogen atmosphere and the emulsion was added over 220 minutes. After the addition of the emulsion, polymerization was further continued for 1 hour and then cooled. After cooling, the pH of the polymerization solution was adjusted from 3.9 to 8.1 using a 28% aqueous ammonia solution to obtain an emulsion-type adhesive composition C (polymerization conversion: 99% or more, solid content concentration: 40.0% by weight, and aggregation: 0.0002% by weight). The average particle diameter of the obtained polymer was 0.186. Mu.m. The mass% in the polymer is shown in table 1. The thickness of the swollen film obtained by the method shown in < method of producing swollen film > was 1.1mm.
Synthesis example 2
Into a beaker were placed 197.79g of lauryl methacrylate, 136.63g of benzyl methacrylate, 5.45g of acrylic acid, 15.27g of methacrylic acid, 14.51g of polyethylene glycol monomethacrylate (manufactured by Nippon Co., ltd.: BLEMER PE-90), 21.12g of trimethylolpropane trimethacrylate (manufactured by ZRONGS Chemie: LIGHT ESTER TMP), 10.02g of 2- [ (3, 5-dimethylpyrazolyl) carbonylamino ] ethyl methacrylate (manufactured by Showa electric company: KARENZ MOI-BP), 6.40g of sodium dodecyl sulfate as an emulsifier, 1.60g of polyoxyethylene diphenylether (manufactured by Nippon Co., ltd., NOIGEN EA-157), 349g of ion-exchanged water and 0.87g of t-butyl hydroperoxide (manufactured by Nippon Co., ltd.: PERBUTYL H-69) as a polymerization initiator, and the mixture was thoroughly stirred by an ultrasonic homogenizer to prepare an emulsion. The reaction vessel with stirrer was heated to 58 ℃ under nitrogen atmosphere and the emulsion was added over 220 minutes. After the addition of the emulsion, polymerization was further continued for 1 hour and then cooled. After cooling, the pH of the polymerization solution was adjusted from 4.4 to 8.0 using a 28% aqueous ammonia solution to obtain an emulsion-type adhesive composition B (polymerization conversion: 99% or more, solid content concentration: 40.0% by weight, and aggregation: 0.0009% by weight). The average particle diameter of the obtained polymer was 0.193. Mu.m. The mass% in the polymer is shown in table 1. The thickness of the swollen film obtained by the method shown in < method of producing swollen film > was 1.3mm.
Synthesis example 3
Into a beaker were placed 197.79g of lauryl methacrylate, 136.63g of benzyl methacrylate, 5.45g of acrylic acid, 15.27g of methacrylic acid, 14.51g of polyethylene glycol monomethacrylate (manufactured by Nippon Co., ltd.: BLEMER PE-90), 21.12g of trimethylolpropane trimethacrylate (manufactured by Zosterol Co., ltd.: LIGHT ESTER TMP), 10.02g of 2- [ O- (1' -methylpropyleneamino) carboxyamino ] ethyl methacrylate (manufactured by Showa electric company: KARENZ MOI-BM), 6.40g of sodium dodecyl sulfate as an emulsifier, 1.60g of polyoxyethylene diphenylether (manufactured by Nippon Co., ltd., NOIGEN EA-157), 349g of ion-exchanged water and 0.87g of t-butyl hydroperoxide (manufactured by Nippon Co., ltd.: PERBUTYL H-69) as a polymerization initiator, and the mixture was thoroughly stirred by an ultrasonic homogenizer to prepare an emulsion. The reaction vessel with stirrer was heated to 58 ℃ under nitrogen atmosphere and the emulsion was added over 220 minutes. After the addition of the emulsion, polymerization was further continued for 1 hour and then cooled. After cooling, the pH of the polymerization solution was adjusted from 3.0 to 8.1 using a 28% aqueous ammonia solution to obtain an emulsion-type adhesive composition C (polymerization conversion: 99% or more, solid content concentration: 40.0% by weight, and aggregation: 0.0006% by weight). The average particle diameter of the obtained polymer was 0.203. Mu.m. The mass% in the polymer is shown in table 1. The thickness of the swollen film obtained by the method shown in < method of producing swollen film > was 1.4mm.
Synthesis example 4
Into a beaker were added 204.09g of lauryl methacrylate, 126.61g of benzyl methacrylate, 5.45g of acrylic acid, 15.27g of methacrylic acid, 14.51g of polyethylene glycol monomethacrylate (manufactured by Nippon oil Co., ltd.: BLEMER PE-90), 14.83g of trimethylolpropane trimethacrylate (manufactured by ZRONGS Chemie Co., ltd.: LIGHT ESTER TMP), 20.04g of pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer (manufactured by ZROS Chemie Co., ltd.: UA 306H), 6.40g of sodium dodecyl sulfate as an emulsifier, 1.60g of polyoxyethylene diphenylether (manufactured by Nippon Co., ltd., NOIGEA-157), 349g of ion-exchanged water and 0.87g of t-butyl hydroperoxide (manufactured by Nippon oil Co., ltd.: PERTTYL H-69) as a polymerization initiator, and the mixture was thoroughly stirred by an ultrasonic homogenizer to prepare an emulsion. The reaction vessel with stirrer was heated to 58 ℃ under nitrogen atmosphere and the emulsion was added over 220 minutes. After the addition of the emulsion, polymerization was further continued for 1 hour and then cooled. After cooling, the pH of the polymerization solution was adjusted from 3.0 to 8.1 using a 28% aqueous ammonia solution to obtain a binder composition D (polymerization conversion: 99% or more, solid content concentration: 40.4% by weight, coagulation amount: 0.002% by weight) as an emulsion solution. The average particle diameter of the obtained polymer was 0.183. Mu.m. The mass% in the polymer is shown in table 1. The thickness of the swollen film obtained by the method shown in < method of producing swollen film > was 1.2mm.
Comparative Synthesis example 1
Into a beaker were added 197.79g of n-butyl acrylate, 146.65g of benzyl methacrylate, 5.45g of acrylic acid, 15.27g of methacrylic acid, 14.51g of polyethylene glycol monomethacrylate (manufactured by Nippon oil Co., ltd.: LIGHT ESTER TMP), 21.12g of trimethylolpropane trimethacrylate (manufactured by Kyowa Co., ltd.: LIGHT ESTER TMP), 3.20g of sodium dodecyl sulfate as an emulsifier, 0.80g of polyoxyethylene diphenylether (NOIGEN EA-157 manufactured by first Industrial pharmaceutical Co., ltd.), 352g of ion-exchanged water and 0.58g of ammonium persulfate as a polymerization initiator, and the mixture was thoroughly stirred using an ultrasonic homogenizer to prepare an emulsion. The reaction vessel with stirrer was heated to 58 ℃ under nitrogen atmosphere and the emulsion was added over 220 minutes. After the addition of the emulsion, polymerization was further continued for 1 hour and then cooled. After cooling, the pH of the polymerization solution was adjusted from 2.3 to 8.1 using a 28% aqueous ammonia solution to obtain an adhesive composition E (polymerization conversion: 99% or more, solid content concentration: 39.5% by weight, coagulation amount: 0.0003% by weight) as an emulsion solution. The average particle diameter of the obtained polymer was 0.279. Mu.m. The mass% in the polymer is shown in table 1. The thickness of the swollen film obtained by the method shown in < method of producing swollen film > was 1.0mm.
Comparative Synthesis example 2
Into a beaker were placed 197.79g of lauryl methacrylate, 146.65g of benzyl methacrylate, 5.45g of acrylic acid, 15.27g of methacrylic acid, 14.51g of polyethylene glycol monomethacrylate (manufactured by daily oil: BLEMER PE-90), 21.12g of trimethylolpropane trimethacrylate (manufactured by Kyowa Co., ltd.: LIGHT ESTER TMP), 6.40g of sodium dodecyl sulfate as an emulsifier, 1.60g of polyoxyethylene diphenylether (manufactured by NOIGEN EA-157, manufactured by first Industrial pharmaceutical Co., ltd.), 349g of ion-exchanged water and 0.87g of t-butyl hydroperoxide (manufactured by daily oil: PERBUTYL H-69) as a polymerization initiator, and the mixture was thoroughly stirred by an ultrasonic homogenizer to prepare an emulsion. The reaction vessel with stirrer was heated to 58 ℃ under nitrogen atmosphere and the emulsion was added over 220 minutes. After the addition of the emulsion, polymerization was further continued for 1 hour and then cooled. After cooling, the pH of the polymerization solution was adjusted from 3.0 to 8.2 using a 28% aqueous ammonia solution to obtain an emulsion-type adhesive composition F (polymerization conversion: 99% or more, solid content concentration: 40.3% by weight, and aggregation: 0.0005% by weight). The average particle diameter of the obtained polymer was 0.186. Mu.m. The mass% in the polymer is shown in table 1. The thickness of the swollen film obtained by the method shown in < method of producing swollen film > was 1.0mm.
TABLE 1
In Table 1, n-butyl acrylate and lauryl methacrylate are monomers forming the structural unit (A), and benzyl methacrylate is a monomer forming the structural unit (B). The monomer described in the item of the reactive group is a monomer forming the structural unit (C), and the epoxy group, the (blocked) isocyanate group, and the urethane group are reactive groups in the polymer, respectively. 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 monomer forming the structural unit (F).
< example of electrode production >
Example of electrode production example 1
To 85.4 parts by mass of graphite and 10 parts by mass of SiO as a negative electrode active material, 1 part by mass of acetylene black, 0.1 part by mass of CNT (manufactured by OCSiAL corporation), 2 parts by mass of carboxymethyl cellulose sodium salt, and 1.5 parts by mass of the solid content of the binder composition a obtained in example 1 of the binder composition were added, and water was further added so that the solid content concentration of the slurry became 35% by mass, and the mixture was thoroughly mixed by using a planetary mill, thereby obtaining a slurry for a negative electrode. The obtained slurry for negative electrode was applied to a copper current collector having a thickness of 10 μm using a beck coater (Baker type applicator) having a gap of 100 μm, dried at 110 ℃ under vacuum for 10 hours or more, and then pressed by a roll press to prepare a negative electrode having a thickness of 36 μm and an electrode density of 1.6 g/cc.
Example of electrode production example 2
An electrode was produced in the same manner as in example 1 of an electrode, except that 85.4 parts by mass of graphite as a negative electrode active material, 1 part by mass of acetylene black as a conductive additive, 0.1 part by mass of CNT (manufactured by OCSiAL corporation), 2 parts by mass of carboxymethyl cellulose sodium salt, and 1.5 parts by mass of the solid content of the binder composition B obtained in example 2 of a binder composition were added to 10 parts by mass of SiO 10 parts by mass of graphite as a negative electrode active material, and water was further added so that the solid content concentration of the slurry was 35% by mass, and the mixture was thoroughly mixed by a planetary mill to obtain a negative electrode slurry. The thickness of the obtained electrode was 36. Mu.m, and the density of the electrode was 1.6g/cc.
Example of electrode production example 3
An electrode was produced in the same manner as in example 1 of an electrode, except that 85.4 parts by mass of graphite as a negative electrode active material, 1 part by mass of acetylene black as a conductive additive, 0.1 part by mass of CNT (manufactured by OCSiAL corporation), 2 parts by mass of carboxymethyl cellulose sodium salt, and 1.5 parts by mass of the solid content of the binder composition C obtained in example 3 of the binder composition were added to 10 parts by mass of SiO 10 parts by mass of graphite as a negative electrode active material, and water was further added so that the solid content concentration of the slurry was 35% by mass, and the mixture was thoroughly mixed by a planetary mill to obtain a negative electrode slurry. The thickness of the obtained electrode was 38. Mu.m, and the density of the electrode was 1.6g/cc.
Example of electrode production example 4
An electrode was produced in the same manner as in example 1 of an electrode, except that 85.4 parts by mass of graphite as a negative electrode active material, 1 part by mass of acetylene black as a conductive additive, 0.1 part by mass of CNT (manufactured by OCSiAL corporation), 2 parts by mass of carboxymethyl cellulose sodium salt, and 1.5 parts by mass of the solid content of the binder composition D obtained in example 4 of a binder composition were added to 10 parts by mass of SiO 10 parts by mass of graphite as a negative electrode active material, and water was further added so that the solid content concentration of the slurry was 35% by mass, and the mixture was thoroughly mixed by a planetary mill to obtain a negative electrode slurry. The thickness of the obtained electrode was 33. Mu.m, and the density of the electrode was 1.6g/cc.
Comparative production example 1 of electrode
An electrode was produced in the same manner as in example 1 of an electrode, except that 1 part by mass of acetylene black, 0.1 part by mass of CNT (manufactured by OCSiAL corporation), 2 parts by mass of carboxymethyl cellulose sodium salt, and 1.5 parts by mass of the solid content of the binder composition E obtained in comparative synthesis example 1 of the binder composition were added to 85.4 parts by mass of graphite and 10 parts by mass of SiO as negative electrode active materials, and water was further added so that the solid content concentration of the slurry was 35% by mass, and the mixture was thoroughly mixed using a planetary mill, thereby obtaining a negative electrode slurry. The thickness of the obtained electrode was 35. Mu.m, and the density of the electrode was 1.6g/cc.
Comparative production example 2 of electrode
An electrode was produced in the same manner as in example 1 of an electrode, except that 1 part by mass of acetylene black, 0.1 part by mass of CNT (manufactured by OCSiAL corporation), 2 parts by mass of carboxymethyl cellulose sodium salt, and 1.5 parts by mass of the solid content of the binder composition F obtained in comparative synthesis example 2 of the binder composition were added to 85.4 parts by mass of graphite and 10 parts by mass of SiO as negative electrode active materials, and water was further added so that the solid content concentration of the slurry was 35% by mass, and the mixture was thoroughly mixed using a planetary mill, to obtain a slurry for a negative electrode. The thickness of the obtained electrode was 34. Mu.m, and the density of the electrode was 1.6g/cc.
< example of producing Battery >
Example of button cell production example 1
In a glove box replaced with argon gas, a laminate of a negative electrode obtained in example 1 of an electrode, a polypropylene/polyethylene/polypropylene porous film 1 sheet having a thickness of 18 μm as a separator, and a metal lithium foil having a thickness of 500 μm as a counter electrode was laminated, and ethylene carbonate and diethyl carbonate (volume ratio 3:7) of lithium hexafluorophosphate of 1mol/L, to which 0.5wt% of fluoroethylene carbonate was added as an electrolyte solution, were sufficiently impregnated, and then subjected to caulking, to produce a 2032 type coin cell for test. The evaluation results of the measurement in the cycle test are shown in example 1 of table 2.
[ manufacturing of button cell 2]
A button cell was produced in the same manner as in example 1 of button cell except that the negative electrode obtained in example 2 of the electrode was used. The evaluation results of the measurement in the cycle test are shown in example 2 of table 2.
[ manufacturing of button cell 3]
A button cell was produced in the same manner as in example 1 of button cell except that the negative electrode obtained in example 3 of the electrode was used. The evaluation results of the measurement in the cycle test are shown in example 3 of table 2.
[ manufacturing of button cell 4]
A button cell was produced in the same manner as in example 1 of button cell except that the negative electrode obtained in example 4 of the electrode was used. The evaluation results of the measurement in the cycle test are shown in example 4 of table 2.
Comparative production example 1 of button cell
A button cell was produced in the same manner as in example 1 of the button cell except that the negative electrode obtained in comparative production example 1 of the electrode was used. The evaluation results of the measurement in the cycle test are shown in comparative example 1 of table 2.
Comparative production example 2 of button cell
A button cell was produced in the same manner as in example 1 of the button cell except that the negative electrode obtained in comparative production example 2 of the electrode was used. The evaluation results of the measurement in the cycle test are shown in comparative example 2 of table 2.
Table 2 shows the results of evaluation of the viscoelasticity and battery physical properties of the swelling binders of examples and comparative examples.
TABLE 2
Examples 1 to 4 of the present invention showed good cycle characteristics in button cells because they had excellent dynamic viscoelastic characteristics in the swollen state in the solvent used in the electrolyte, compared with comparative examples 1 to 2.
Industrial applicability
The electrode adhesive of the present invention has excellent adhesion, and can be used in power storage devices, for example, in vehicle-mounted applications such as electric vehicles and hybrid electric vehicles, and power storage devices such as batteries for household power storage.

Claims (7)

1. A binder for an electrode, comprising a polymer having the following structural units:
structural unit (A) derived from alkyl (meth) acrylate monomers,
a structural unit (B) derived from a monomer represented by the following general formula (1), and
a structural unit (C) derived from a monomer having at least one selected from the group consisting of an epoxy group, a (blocked) isocyanate group and a urethane group,
in the formula (1), R 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 2 Is an aromatic group with or without substituents.
2. The binder for electrodes according to claim 1, wherein the structural unit (B) is a structural unit derived from a monomer represented by the following general formula (2),
In the formula (2), R 1 Is hydrogen or alkyl with 1-4 carbon atoms, R 3 、R 4 、R 5 、R 6 、R 7 、R 8 、R 9 、R 10 、R 11 、R 12 Each independently is hydrogen, hydroxyA group, an alkyl group having 1 to 3 carbon atoms, or an aromatic group having or not having a substituent, R 13 Is alkylene group having 1 to 3 carbon atoms or carbonyl group, R 14 Q and r are each independently an integer of 0 to 3, and s is an integer of 0 to 1.
3. The binder for an electrode according to claim 1 or 2, wherein the binder for an electrode comprises a polymer further having a structural unit (D) derived from a monomer having a hydroxyl group represented by the following general formula (3),
in the formula (3), R 15 Is a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, x is an integer of 2 to 8, and n is an integer of 2 to 30.
4. The binder for an electrode according to claim 1 or 2, wherein the binder for an electrode comprises a polymer further having a structural unit (E) derived from a polyfunctional (meth) acrylate monomer having 5 or less functions.
5. The binder for electrodes according to claim 4, wherein the constituent unit (E) is a compound represented by the following general formula (5) as the polyfunctional (meth) acrylate monomer having 5 or less functions,
In the formula (5), R 16 Each identical or different is a hydrogen atom or a methyl group; r is R 17 An organic group having 2 to 100 carbon atoms and having a valence of 5 or less; m is an integer of 5 or less.
6. An electrode comprising the binder for an electrode according to claim 1 or 2.
7. An electric storage device comprising the electrode according to claim 6.
CN202280055557.8A 2021-09-30 2022-09-06 Binder for electrode, and power storage device Pending CN117897833A (en)

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