CN116745328A - Nonaqueous secondary battery electrode adhesive, nonaqueous secondary battery electrode adhesive composition, and nonaqueous secondary battery electrode - Google Patents

Abstract

Provided is a nonaqueous secondary battery electrode binder which can effectively improve the peel strength of an electrode active material layer to a current collector and can contribute to the reduction of the internal resistance of a battery and the improvement of cycle characteristics. The nonaqueous secondary battery electrode binder of the present invention comprises a copolymer (a) and a copolymer (B). The copolymer (A) has 11 th to 13 th structural units derived from monomers (a 1) and (a 2) having an ethylenically unsaturated bond and an internal crosslinking agent (a 3). The copolymer (B) has, among all the structural units, from the 21 st to 23 rd structural units represented by the following formulas (1) to (3), from 5.0 mol% to 98 mol%, from 0.30 mol% to 90 mol%, from 0.30 mol% to 10 mol%. (in formula (2), R ¹ To be branched can haveAlkyl groups having 1 to 6 carbon atoms. In formula (3), R ² Is a group having an ethylenically unsaturated bond. )

Description

Nonaqueous secondary battery electrode adhesive, nonaqueous secondary battery electrode adhesive composition, and nonaqueous secondary battery electrode

Technical Field

The present invention relates to a nonaqueous secondary battery electrode binder, a nonaqueous secondary battery electrode binder composition, and a nonaqueous secondary battery electrode.

The present application claims priority based on japanese patent application 2020-214882, which was invented in japan, 12/24/2020, the contents of which are incorporated herein.

Background

The nonaqueous secondary battery includes, for example, a positive electrode including a metal oxide or the like as a positive electrode active material, a negative electrode including a material such as graphite as a negative electrode active material, and an electrolyte. The nonaqueous secondary battery is a secondary battery in which ions serving as charge carriers move between a positive electrode and a negative electrode to charge and discharge the battery.

As a nonaqueous secondary battery, a lithium ion secondary battery is exemplified. Nonaqueous secondary batteries are used as power sources for notebook personal computers, mobile phones, electric tools, and electronic/communication devices in terms of downsizing and weight reduction. Further, recently, from the viewpoint of environmental protection vehicle applications, it is also used for electric vehicles, hybrid vehicles, and the like. Among them, nonaqueous secondary batteries are strongly demanded to have higher output, higher capacity, longer life, and the like.

The binder used for the positive electrode and the negative electrode has a function of binding the electrode active materials to each other and a function of binding the electrode active materials to the current collector. In order to improve the capacity of nonaqueous secondary batteries and protect the working environment, development of aqueous dispersion binders has been performed. For example, styrene-butadiene rubber (SBR) -based aqueous dispersions using carboxymethyl cellulose (CMC) as a thickener are known.

Patent document 1 describes a method of polymerizing ethylene oxide, an alkylene oxide other than ethylene oxide, an alkyl glycidyl ether, an allyl glycidyl ether, or a combination thereof. It is described that a composition containing a copolymer obtained by polymerization can be used as a binder material in a battery electrode containing electroactive particles.

Patent document 2 describes a secondary battery negative electrode including an electrode layer including: copolymers obtained from (meth) acrylic esters and vinyl monomers having an acid component; and at least one selected from polyoxyethylene alkyl ether derivatives, polyoxyethylene-polyoxypropylene condensates, and polyoxyethylene-polyoxypropylene alkyl ether derivatives.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2012-517519

Patent document 2: japanese patent laid-open publication No. 2014-239070

Disclosure of Invention

Problems to be solved by the invention

However, in the components described in patent documents 1 and 2, there is room for improvement in the peel strength of the electrode active material layer to the current collector and room for reduction in the internal resistance in the case of manufacturing the battery when the components are used as the electrode binder.

The purpose of the present invention is to provide a nonaqueous secondary battery electrode binder, a nonaqueous secondary battery electrode binder composition, and a nonaqueous secondary battery electrode, which can effectively improve the peel strength of an electrode active material layer from a current collector in a nonaqueous secondary battery and can contribute to the reduction of the internal resistance of the battery and the improvement of the cycle characteristics.

Means for solving the problems

In order to solve the above problems, the present invention is as described in the following [1] to [14 ].

[1] A nonaqueous secondary battery electrode binder characterized by comprising a copolymer (A) and a copolymer (B),

the copolymer (A) is a polymer of a compound having an ethylenically unsaturated bond,

the copolymer (A) has an 11 th structural unit derived from the monomer (a 1) and a 12 th structural unit derived from the monomer (a 2); alternatively, it has an 11 th structural unit derived from the monomer (a 1), a 12 th structural unit derived from the monomer (a 2), and a 13 th structural unit derived from the internal crosslinking agent (a 3),

the monomer (a 1) is a nonionic compound having an ethylenically unsaturated bond, neither a hydroxyl group nor a cyano group, and having a plurality of independent ethylenically unsaturated bonds,

the monomer (a 2) is a compound having an ethylenically unsaturated bond and an anionic functional group and having no independent plural ethylenically unsaturated bonds,

The internal crosslinking agent (a 3) is a compound having a plurality of independent ethylenically unsaturated bonds and capable of forming a crosslinked structure in radical polymerization of a monomer comprising the monomer (a 1) and the monomer (a 2),

in the copolymer (A), the content of the 12 th structural unit is 1.0 to 30 parts by mass based on 100 parts by mass of the 11 th structural unit,

in the copolymer (A), the content of the 13 th structural unit is 0 to 20 parts by mass based on 100 parts by mass of the 11 th structural unit,

the copolymer (B) has a 21 st structural unit represented by the following formula (1) of 5.0 mol% or more and 98 mol% or less in all structural units, a 22 nd structural unit represented by the following formula (2) of 0.30 mol% or more and 90 mol% or less in all structural units, and a 23 rd structural unit represented by the following formula (3) of 0.30 mol% or more and 10 mol% or less in all structural units,

the total content of the 21 st structural unit, the 22 nd structural unit, and the 23 rd structural unit in all the structural units of the copolymer (B) is 90 mass% or more,

the mass ratio of the content of the copolymer (A) to the content of the copolymer (B) is 50.0/50.0 or more and 99.0/1.0 or less.

(in formula (2), R ¹ An alkyl group having 1 to 6 carbon atoms which may have a branched chain. )

(in formula (3), R ² Is a group having an ethylenically unsaturated bond. )

[2] The nonaqueous secondary battery electrode binder according to [1], wherein the copolymer (B) comprises

5.0 to 50 mol% of the 21 st structural unit,

40 to 90 mol% of the 22 nd structural unit,

The 23 rd structural unit is 0.30 mol% or more and 10 mol% or less.

[3] The nonaqueous secondary battery electrode binder according to [1], wherein the copolymer (B) comprises

70 mol% or more and 98 mol% or less of the 21 st structural unit,

0.30 to 20 mol% of the 22 nd structural unit,

The 23 rd structural unit is 0.30 mol% or more and 10 mol% or less.

[4]According to [1]]～[3]The nonaqueous secondary battery electrode binder according to any one of the above formulas (3), wherein R ² Having a moiety selected from the group consisting of vinyloxy, allyloxy, (meth) acryl, (meth) acryloyloxy, and-OCH ₂ -CH ₂ -CH ₂ ＝CH ₂ At least any 1 of the above.

[5]According to [1]]～[4]The nonaqueous secondary battery electrode binder according to any one of the above formulas (3), wherein R ² Represented by the following formula (4).

-R ²¹ -R ²² (4)

(in formula (4), R ²¹ Is an alkylene group having 1 to 5 carbon atoms which may have a branched chain, R ²² Is 1 functional group selected from the group consisting of vinyloxy, allyloxy, (meth) acryl, and (meth) acryloyloxy. )

[6] The nonaqueous secondary battery electrode binder according to any one of [1] to [5], wherein the copolymer (B) is a block copolymer having a1 st block comprising a 21 st structural unit, a2 nd block comprising a 22 nd structural unit, and a 3 rd block comprising a 23 rd structural unit.

[7] The nonaqueous secondary battery electrode binder according to any one of [1] to [6], wherein the monomer (a 1) does not have a polar functional group.

[8] The nonaqueous secondary battery electrode binder according to any one of [1] to [7], wherein the monomer (a 2) is a compound having at least one of a carboxyl group and a sulfo group.

[9] The nonaqueous secondary battery electrode binder according to any one of [1] to [8], wherein the copolymer (A) contains the 11 th structural unit and the 12 th structural unit in a total amount of 80 mass% or more.

[10] The nonaqueous secondary battery electrode binder according to any one of [1] to [9], wherein the content of the 13 th structural unit in the copolymer (A) is 0.050 parts by mass or more based on 100 parts by mass of the 11 th structural unit.

[11] A nonaqueous secondary battery electrode binder composition comprising the nonaqueous secondary battery electrode binder of any one of [1] to [10], and an aqueous medium.

[12] A nonaqueous secondary battery electrode slurry comprising the nonaqueous secondary battery electrode binder of any one of [1] to [10], an electrode active material, and an aqueous medium,

the aqueous medium is 1 medium selected from the group consisting of water, hydrophilic solvents, and mixtures comprising water and hydrophilic solvents.

[13] A nonaqueous secondary battery electrode comprising the nonaqueous secondary battery electrode binder described in any one of [1] to [10 ].

[14] A nonaqueous secondary battery comprising the nonaqueous secondary battery electrode of [13 ].

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a nonaqueous secondary battery electrode binder, a nonaqueous secondary battery electrode binder composition, and a nonaqueous secondary battery electrode that can effectively improve the peel strength of an electrode active material layer to a current collector in a nonaqueous secondary battery and can contribute to reduction in internal resistance and improvement in cycle characteristics of the battery.

Detailed Description

Hereinafter, as embodiments of the present invention, a nonaqueous secondary battery electrode binder (also referred to as a nonaqueous secondary battery electrode binder), a nonaqueous secondary battery electrode binder composition (also referred to as a nonaqueous secondary battery electrode binder composition), a nonaqueous secondary battery electrode paste (also referred to as a nonaqueous secondary battery electrode paste), a nonaqueous secondary battery electrode, and a nonaqueous secondary battery will be described.

The term "(meth) acryl" refers to the general term of acryl and methacryl, and the term "(meth) acrylate" refers to the general term of acrylate and methacrylate.

The "nonvolatile component" was a component remaining after 1g of the composition was weighed in an aluminum dish having a diameter of 5cm, dried in a desiccator at 105℃for 1 hour while circulating air in the desiccator at 1 atmosphere (1013 hPa). The form of the composition may be, but not limited to, a solution, a dispersion or a slurry. The "nonvolatile content" is the ratio (mass%) of the mass of the nonvolatile component after drying under the above conditions to the mass (1 g) of the composition before drying.

The term "ethylenically unsaturated bond" means an ethylenically unsaturated bond having radical polymerization unless otherwise specified.

Among polymers of compounds having ethylenic unsaturation, those derived from certain compounds having ethylenic unsaturationA structural unit of a compound having an unsaturated bond, and a chemical structure of a portion of the compound other than the ethylenically unsaturated bond is the same as a chemical structure of a portion of the structural unit other than a portion corresponding to the ethylenically unsaturated bond in the polymer. For example, structural units derived from acrylic acid have-CH in the polymer ₂ CH (COOH) -structure.

In addition, regarding the compound having a plurality of independent ethylenically unsaturated bonds, the ethylenically unsaturated bonds may remain as a structural unit of the polymer. The plurality of independent ethylenically unsaturated bonds means a plurality of ethylenically unsaturated bonds which do not form conjugated dienes with each other. For example, the structural unit derived from divinylbenzene may have a structure having no ethylenic unsaturation (a structure in which all the portions corresponding to ethylenic unsaturation are incorporated into the chain of the polymer), or may have a structure having 1 ethylenic unsaturation (a structure in which only one portion corresponding to ethylenic unsaturation is incorporated into the chain of the polymer).

Further, when the chemical structure of the monomer does not correspond to the chemical structure of the polymer, such as by subjecting a portion other than the chain corresponding to the ethylenically unsaturated bond to a chemical reaction after the polymerization, the chemical structure after the polymerization is used as a reference. For example, in the case where vinyl acetate is polymerized and then saponified, it is considered that the structural unit is derived from vinyl alcohol instead of the structural unit derived from vinyl acetate based on the chemical structure of the polymer.

< 1. Nonaqueous secondary battery electrode adhesive >

The nonaqueous secondary battery electrode binder according to the present invention contains a copolymer (a) and a copolymer (B). Hereinafter, unless otherwise indicated, the electrode binder refers to the nonaqueous secondary battery electrode binder according to the present invention. The electrode binder may contain other components, for example, may contain polymers other than the copolymer (a) and the copolymer (B). The nonaqueous secondary battery electrode binder according to the present invention is preferably composed of the copolymer (a) and the copolymer (B).

Hereinafter, the copolymer (A) and the copolymer (B) are described in detail.

[ 1-1. Copolymer (A) ]

The copolymer (A) is a polymer of a compound having an ethylenically unsaturated bond. The copolymer (A) has an 11 th structural unit derived from the monomer (a 1) and a 12 th structural unit derived from the monomer (a 2). The copolymer (a) may further have a 13 th structural unit derived from the internal crosslinking agent (a 3). The copolymer (a) may contain structural units derived from other monomers (a 4) that do not conform to any of the monomers (a 1), the monomers (a 2), and the internal crosslinking agent (a 3). Details of the respective monomers and the internal crosslinking agent are described below.

[1-1-1. Monomer (a 1) ]

The monomer (a 1) is a nonionic (having neither an anionic functional group nor a cationic functional group) compound having an ethylenically unsaturated bond and having no independent plural ethylenically unsaturated bonds. The monomer (a 1) preferably does not have a polyoxyalkylene structure.

The monomer (a 1) has neither hydroxyl nor cyano groups. The monomer (a 1) preferably has no polar functional group. The monomer (a 1) may contain only 1 compound or may contain 2 or more compounds. The monomer (a 1) is preferably at least one of a (meth) acrylate having no polar functional group and an aromatic vinyl compound, and more preferably contains both. The (meth) acrylate having no polar functional group further preferably contains an alkyl (meth) acrylate. The total content of the alkyl (meth) acrylate and the aromatic vinyl compound in the monomer (a 1) is more preferably 80 mass% or more, still more preferably 90 mass% or more, and most preferably 100 mass%.

In addition, regarding the composition of the monomer (a 1), in order to adjust the glass transition temperature of the copolymer (a) or to adjust the polymerization rate according to the molecular design, it is preferable to appropriately adjust a preferable compound and the amount thereof within the range specified in the present invention.

Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like.

Here, the aromatic vinyl compound does not contain a (meth) acryl group. Examples of the aromatic vinyl compound include styrene, t-butylstyrene, α -methylstyrene, p-methylstyrene, and 1, 1-diphenylethylene. In the case where the monomer (a 1) contains an aromatic vinyl compound, the monomer (a 1) more preferably contains at least any one of styrene and α -methylstyrene, and further preferably contains styrene.

The monomer (a 1) may contain a plurality of ethylenically unsaturated bonds forming a conjugated diene with each other. Examples of the compound having a plurality of ethylenically unsaturated bonds forming a conjugated diene include 1, 3-butadiene and 1, 3-pentadiene.

[1-1-2. Monomer (a 2) ]

The monomer (a 2) is a compound having an ethylenically unsaturated bond and an anionic functional group. The monomer (a 2) does not have a plurality of independent ethylenically unsaturated bonds. The monomer (a 2) preferably does not have a polyoxyalkylene structure. Examples of the anionic functional group include a carboxyl group, a sulfo group, and a phosphate group. Furthermore, the anionic functional groups may form salts. The monomer (a 2) preferably contains a compound having at least any one of a carboxyl group and a sulfo group, more preferably contains a compound having a carboxyl group.

The monomer (a 2) may contain only 1 compound or may contain 2 or more compounds. The monomer (a 2) may contain a compound having a plurality of the same anionic functional groups in 1 molecule. That is, the copolymer (a) may contain a plurality of the same anionic functional groups in 1 structural unit. The monomer (a 2) may contain 1 molecule of a compound having 2 or more different anionic functional groups. That is, the copolymer (a) may contain 2 or more different anionic functional groups in 1 structural unit. In addition, the monomer (a 2) may contain 2 or more compounds containing different anionic functional groups. That is, the copolymer (a) may contain 2 or more structural units containing different anionic functional groups.

Examples of the monomer (a 2) include unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and the like; half esters of unsaturated dicarboxylic acids; p-styrenesulfonic acid, and the like. Among them, the monomer (a 2) preferably contains at least 1 of (meth) acrylic acid and itaconic acid.

At least a part of the structural unit derived from the monomer (a 2) may form a salt with an alkaline substance. Examples of the salt-forming monomer (a 2) include sodium (meth) acrylate and sodium p-styrenesulfonate.

The monomer (a 2) preferably contains at least any one of a sulfonic acid having an ethylenically unsaturated bond and a salt thereof, and more preferably contains a sulfonate having an ethylenically unsaturated bond. The sulfonic acid preferably contains an aromatic vinyl compound having a sulfo group, and more preferably contains p-styrenesulfonic acid. The sulfonate is preferably a salt of an aromatic vinyl compound having a sulfo group, more preferably a p-styrene sulfonate, and even more preferably sodium p-styrene sulfonate. This is because the generation of coarse particles can be suppressed in the electrode binder composition to be described later.

[1-1-3. Internal crosslinking agent (a 3) ]

The internal crosslinking agent (a 3) is a compound having a plurality of independent ethylenic unsaturated bonds and capable of forming a crosslinked structure in radical polymerization of a monomer including the monomers (a 1) and (a 2). Examples of such compounds include divinylbenzene, ethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, and 2-hydroxy-3-acryloxypropyl methacrylate.

[1-1-4. Other monomer (a 4) ]

The other monomer (a 4) does not correspond to any of the monomers (a 1) to (a 3). Examples of the other monomer (a 4) include, but are not limited to, a compound having an ethylenically unsaturated bond and a polar functional group, a surfactant having an ethylenically unsaturated bond (hereinafter, also referred to as "polymerizable surfactant"), a compound having an ethylenically unsaturated bond and functioning as a silane coupling agent, and the like.

The polar functional group preferably includes at least any one of a hydroxyl group and a cyano group. Examples of the monomer having an ethylenically unsaturated bond and a polar functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl acrylate, and (meth) acrylonitrile. The copolymer (a) preferably contains a structural unit derived from a compound containing an ethylenically unsaturated bond and a hydroxyl group, more preferably has a structural unit derived from a (meth) acrylate having a hydroxyl group, and still more preferably contains a structural unit derived from 2-hydroxyethyl (meth) acrylate.

The polymerizable surfactant is a compound having an ethylenically unsaturated bond and having a function as a surfactant, and examples thereof include compounds represented by the following chemical formulas (6) to (9).

In formula (6), R ³ Preferably alkyl, and p is preferably an integer of 10 to 40. R is R ³ More preferably 10 to 40, R ³ Further preferred is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.

In formula (7), R ⁴ Preferably alkyl, q is preferably an integer from 10 to 12. R is R ⁴ More preferably 10 to 40, R ⁴ Further preferred is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.

In formula (8), R ⁵ Preferably alkyl, M ¹ Preferably NH ₄ Or Na. R is R ⁵ More preferably 10 to 40, R ⁵ Further preferred is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.

In formula (9), R ⁶ Preferably alkyl, M ² Preferably NH ₄ Or Na. R is R ⁶ More preferably 10 to 40, R ⁶ Further preferred is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.

Examples of the compound having an ethylenically unsaturated bond and functioning as a silane coupling agent include vinyltrimethoxysilane, γ -methacryloxypropyl trimethoxysilane, vinyltriethoxysilane, γ -methacryloxypropyl triethoxysilane, and the like.

[ 1-1-5. Content of structural units in copolymer (A) ]

In the copolymer (a), the content of the 12 th structural unit derived from the monomer (a 2) is 1.0 part by mass or more, preferably 2.0 parts by mass or more, and more preferably 3.5 parts by mass or more, based on 100 parts by mass of the 11 th structural unit derived from the monomer (a 1). Because the mechanical stability of the electrode binder is improved. Further, the reason is that the peel strength of the electrode active material layer including the electrode binder according to the present invention is improved.

In the copolymer (a), the content of the 12 th structural unit derived from the monomer (a 2) is 30 parts by mass or less, preferably 15 parts by mass or less, and more preferably 7.5 parts by mass or less, per 100 parts by mass of the 11 th structural unit derived from the monomer (a 1). This is because gelation of the electrode binder is suppressed. In addition, the mechanical stability of the electrode binder is improved.

The total mass ratio of the 11 th structural unit and the 12 th structural unit in the copolymer (a) is preferably 80% by mass or more, more preferably 85% by mass or more, and still more preferably 90% by mass or more. The reason is that the effect obtained by the present invention is further increased by increasing the content of these structural units.

When the 13 th structural unit derived from the internal crosslinking agent (a 3) is contained in the copolymer (a), the content of the 13 th structural unit derived from the internal crosslinking agent (a 3) is 0 part by mass or more, preferably 0.050 part by mass or more, more preferably 0.075 part by mass or more, and still more preferably 0.50 part by mass or more, based on 100 parts by mass of the 11 th structural unit derived from the monomer (a 1). The reason is that deterioration of the electrode binder can be suppressed, and cycle characteristics (discharge capacity maintenance rate) of a battery using an electrode having an electrode active material layer including the electrode binder according to the present invention can be improved.

When the copolymer (a) contains a structural unit derived from the internal crosslinking agent (a 3), the content of the 13 th structural unit derived from the internal crosslinking agent (a 3) is 20 parts by mass or less, preferably 7.5 parts by mass or less, and more preferably 2.5 parts by mass or less, per 100 parts by mass of the 11 th structural unit derived from the monomer (a 1). This is because gelation of the electrode binder is suppressed.

[ glass transition temperature of copolymer (A) ]

The glass transition temperature Tg of the copolymer (a) is a peak top temperature of a DDSC graph obtained by performing DSC measurement at a temperature rising rate of 10 ℃/min under a nitrogen atmosphere using EXSTAR DSC/SS7020 manufactured by hitachi-tek corporation, and differentiating the temperature of the DSC.

The glass transition temperature Tg of the copolymer (A) is preferably-30℃or higher, more preferably-10℃or higher, and still more preferably 0℃or higher. The reason is that the cycle characteristics of the nonaqueous secondary battery including the electrode binder according to the present invention are improved.

The glass transition temperature Tg of the copolymer (A) is preferably 100℃or lower, more preferably 50℃or lower, and still more preferably 30℃or lower. The reason is that the adhesion of the electrode active material layer containing the electrode binder according to the present invention to the current collecting foil is improved.

[1-1-7. Synthesis method of copolymer (A) ]

The copolymer (a) is obtained by copolymerizing monomers comprising the monomers (a 1) and (a 2). The monomer may be copolymerized with the internal crosslinking agent (a 3) and other monomer (a 4) as required. The monomers used for synthesizing the copolymer (A) are sometimes referred to collectively as monomers (a). Examples of the polymerization method include emulsion polymerization of the monomer (a) in the aqueous medium (b). Examples of other components used for the synthesis of the copolymer (a) by emulsion polymerization include a surfactant (c) having no polymerizability, an alkaline substance (d), a radical polymerization initiator (e), a chain transfer agent (f), and the like. Hereinafter, these components and emulsion polymerization methods which are necessary for synthesizing the copolymer (a) or which may be used as needed are described, but the monomer (a) is described above and therefore not described below.

The aqueous medium (b) is water, a hydrophilic solvent, or a mixture thereof. Examples of the hydrophilic solvent include methanol, ethanol, isopropanol, and N-methylpyrrolidone. From the viewpoint of polymerization stability, the aqueous medium (b) is preferably water. In addition, as long as polymerization stability is not impaired, a substance in which a hydrophilic solvent is added to water may be used as the aqueous medium (b).

In the emulsion polymerization of the monomer (a), a surfactant (c) which is not polymerizable and does not correspond to the copolymer (B) described later may be used. The surfactant (c) can improve the dispersion stability of the dispersion (emulsion) during and/or after polymerization. As the surfactant (c), an anionic surfactant or a nonionic surfactant is preferably used.

Examples of the anionic surfactant include alkylbenzenesulfonate, alkyl sulfate, polyoxyethylene alkyl ether sulfate, and fatty acid salt.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester.

The surfactant may be used alone or in combination of at least 2 kinds.

In the case of emulsion polymerization of the monomer (a) in the aqueous medium (b), the alkaline substance (d) may be added. By adding the alkaline substance (d), the acidic component contained in the monomer (a) can be neutralized to adjust the pH. By adjusting the pH, the mechanical stability and chemical stability of the dispersion during and/or after emulsion polymerization can be improved.

The pH of the dispersion at 23 ℃ is not limited as long as it is appropriately adjusted according to the specification of the electrode, the conditions for producing a slurry to be described later, and the like, but is preferably 1.5 to 10, more preferably 6.0 to 9.0, and further preferably 5.0 to 9.0. This is because the sedimentation of the active material in the electrode slurry described later is suppressed.

Examples of the basic substance (d) include ammonia, triethylamine, sodium hydroxide, lithium hydroxide, and the like. These basic substances (d) may be used alone or in combination of 1 or more than 2.

The radical polymerization initiator (e) used in the emulsion polymerization is not particularly limited, and known ones can be used. Examples of the radical polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide; an azo compound; organic peroxides such as t-butyl hydroperoxide, t-butyl peroxybenzoate and cumene hydroperoxide. Among them, persulfates and organic peroxides are preferable. In this embodiment, the radical polymerization initiator may be used in combination with a reducing agent such as sodium bisulphite, rongalite (Rongalite), or ascorbic acid in emulsion polymerization to perform redox polymerization.

The amount of the radical polymerization initiator to be added is preferably 0.10 parts by mass or more, more preferably 0.80 parts by mass or more, based on 100 parts by mass of the monomer (a). This is because the conversion of the monomer (a) into the copolymer (A) during polymerization can be improved. The amount of the radical polymerization initiator to be added is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, based on 100 parts by mass of the monomer (a). This is because the molecular weight of the copolymer (a) can be increased and the swelling ratio of the electrode active material layer in the electrolyte can be reduced.

The chain transfer agent (f) is used in emulsion polymerization to adjust the molecular weight of the copolymer (A). Examples of the chain transfer agent (f) include n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, β -mercaptopropionic acid, methanol, n-propanol, isopropanol, t-butanol, and benzyl alcohol.

Examples of the emulsion polymerization method include a method of performing emulsion polymerization while continuously supplying each component used for emulsion polymerization. The temperature of the emulsion polymerization is not particularly limited, and is, for example, 30 to 90 ℃, preferably 50 to 85 ℃, and more preferably 55 to 80 ℃. The emulsion polymerization is preferably carried out with stirring. Further, the monomer (a) and the radical polymerization initiator are preferably continuously supplied in a uniform manner in the reaction vessel.

[ 1-2. Copolymers (B) ]

[1-2-1. Structural units contained in the copolymer (B) ]

The copolymer (B) has a 21 st structural unit represented by the following formula (1), a 22 nd structural unit represented by the following formula (2), and a 23 rd structural unit represented by the following formula (3). The copolymer (B) preferably has a plurality of ethylenically unsaturated bonds in 1 molecule. The copolymer (B) may contain a structural unit that does not conform to any of the 21 st structural unit, the 22 nd structural unit, and the 23 rd structural unit.

In addition, in the copolymer (B), the terminal structure is not considered unless otherwise specified in describing the constitution of the structural unit. For example, the content of a structural unit in the copolymer (B) is the content of the structural unit in a structure other than the terminal structure unless otherwise specified. In the case where the copolymer (B) is considered to be constituted of a certain structural unit, a terminal structure may be included in addition to the structural unit. The terminal structure in the copolymer (B) is a structure which is located on the molecular terminal side of the ether bond closest to the molecular terminal and is not included in any of the structures of the following formulas (1) to (3). The terminal structure does not include the structures represented by the following formulas (1) to (3).

In formula (2), R ¹ An alkyl group having 1 to 6 carbon atoms which may have a branched chain. R is R ¹ Preferably having 4 or less carbon atoms, more preferably having 2 or less carbon atoms, and still more preferably methyl.

In formula (3), R ² Is a group having an ethylenically unsaturated bond. R is R ² Preferably having a moiety selected from vinyloxy (-OCH) ₂ ＝CH ₂ ) Allyloxy (-OCH) ₂ -CH ₂ ＝CH ₂ ) (meth) acryl, (meth) acryloyloxy, and-OCH ₂ -CH ₂ -CH ₂ ＝CH ₂ More preferably at least any 1 of the groups (a) and (b) is selected from allyloxy, (meth) acryl, and (meth) acryloyloxy, and still more preferably allyloxy. The number of ethylenically unsaturated bonds contained in 1 23 rd structural unit is preferably 1.

R ² The structure of (2) is preferably represented by the following formula (4).

-R ²¹ -R ²² (4)

In formula (4), R ²¹ Is an alkylene group having 1 to 5 carbon atoms which may have a branched chain, R ²² Is vinyloxy, allyloxy, (meth) acryl, (meth) acryloyloxy, and-OCH ₂ -CH ₂ -CH ₂ ＝CH ₂ Any one of them.

In formula (4), R ²¹ An alkylene group having 1 or 2 carbon atoms is preferable, and a methylene group is more preferable. In formula (4), R ²² More preferably, any 1 of an allyloxy group, (meth) acryl group, and (meth) acryloyloxy group, and still more preferably, allyloxy group.

[1-2-2. Content of structural units contained in copolymer (B) ]

The hydrophilicity of the copolymer (B) can be controlled to an appropriate range by adjusting the content of the 21 st structural unit and the 22 nd structural unit in the copolymer (B). For example, if the content of the 21 st structural unit in the copolymer (B) is increased, the hydrophilicity of the copolymer (B) is increased, and if the content of the 21 st structural unit is decreased, the hydrophilicity of the copolymer (B) is decreased.

By adjusting the content of the 21 st structural unit and the 22 nd structural unit in the copolymer (B), the crystallinity of the copolymer (B) can be controlled to an appropriate range. For example, if the content of the 21 st structural unit in the copolymer (B) is increased, the crystallinity of the copolymer (B) is improved, and if the content of the 21 st structural unit is decreased, the crystallinity of the copolymer (B) is reduced.

The relationship between the content of these structural units contained in the copolymer (B) will be described below.

In the copolymer (B), the content of the 21 st structural unit in all the structural units is 5.0 mol% or more, preferably 18 mol% or more, and more preferably 25 mol% or more. In the copolymer (B), the content of the 21 st structural unit in all the structural units is 98 mol% or less, preferably 97 mol% or less.

In the copolymer (B), the content of the 22 nd structural unit in the total structural units is 0.30 mol% or more, preferably 0.50 mol% or more, and more preferably 0.70 mol% or more. In the copolymer (B), the content of the 22 nd structural unit in all the structural units is 90 mol% or less, preferably 80 mol% or less, and more preferably 75 mol% or less.

In the copolymer (B), the content of the 23 rd structural unit in the total structural units is 0.30 mol% or more, preferably 0.50 mol% or more, and more preferably 0.70 mol% or more. In the copolymer (B), the content of the 23 rd structural unit in the total structural units is 10 mol% or less, preferably 6.0 mol% or less, and more preferably 4.5 mol% or less.

The total content of the 21 st structural unit, the 22 nd structural unit, and the 23 rd structural unit in all the structural units of the copolymer (B) is 90 mass% or more, preferably 95 mass% or more, more preferably 98 mass% or more, and most preferably 100 mass%.

The structural unit constituting the copolymer (B) does not contain a terminal structure (definition is as described above). In this regard, the same applies to the copolymer (B1) according to the following embodiment 1 and the copolymer (B2) according to the following embodiment 2.

[ mode of 1-2-3. Copolymer (B) ]

The following 2 preferable modes of the copolymer (B) having different hydrophilicities are exemplified. The following modes will be described as the copolymer (B1) according to the mode 1 and the copolymer (B2) according to the mode 2. The copolymer (B2) according to the 2 nd aspect is more hydrophilic than the copolymer (B1) according to the 1 st aspect.

[1-2-4. Copolymer (B1) (mode 1) ]

In the copolymer (B1), the content of the 21 st structural unit in all structural units is preferably 5.0 mol% or more, more preferably 18 mol% or more, and still more preferably 25 mol% or more. In the copolymer (B1), the content of the 21 st structural unit in all the structural units is preferably 50 mol% or less, more preferably 40 mol% or less.

In the copolymer (B1), the content of the 22 nd structural unit in the total structural units is preferably 40 mol% or more, more preferably 50 mol% or more, and still more preferably 60 mol% or more. In the copolymer (B1), the content of the 22 nd structural unit in all the structural units is preferably 90 mol% or less, more preferably 80 mol% or less, and still more preferably 75 mol% or less.

In the copolymer (B1), the content of the 23 rd structural unit in the total structural units is preferably 0.30 mol% or more, more preferably 0.50 mol% or more, and still more preferably 0.70 mol% or more. In the copolymer (B1), the content of the 23 rd structural unit in the total structural units is preferably 10 mol% or less, more preferably 6.0 mol% or less, and still more preferably 4.5 mol% or less.

[1-2-5. Copolymer (B2) (mode 2) ]

In the copolymer (B2), the content of the 21 st structural unit in all the structural units is preferably 70 mol% or more, more preferably 80 mol% or more, and still more preferably 90 mol% or more. In the copolymer (B2), the content of the 21 st structural unit in all the structural units is preferably 98 mol% or less, more preferably 97 mol% or less.

In the copolymer (B2), the content of the 22 nd structural unit in the total structural units is preferably 0.30 mol% or more, more preferably 0.50 mol% or more, and still more preferably 0.70 mol% or more. In the copolymer (B2), the content of the 22 nd structural unit in the total structural units is preferably 20 mol% or less, more preferably 15 mol% or less, and still more preferably 10 mol% or less.

In the copolymer (B2), the content of the 23 rd structural unit in the total structural units is preferably 0.30 mol% or more, more preferably 0.50 mol% or more, and still more preferably 0.70 mol% or more. In the copolymer (B2), the content of the 23 rd structural unit in the total structural units is preferably 10 mol% or less, more preferably 6.0 mol% or less, and still more preferably 4.5 mol% or less.

[1-2-6. Structure of copolymer (B) ]

The copolymer (B) is preferably a block copolymer having a 1 st block comprising 21 st structural units, a 2 nd block comprising 22 nd structural units, and a 3 rd block comprising 23 rd structural units. The copolymer (B) is more preferably a 3-membered block copolymer composed of the 1 st block, the 2 nd block, and the 3 rd block (wherein, as defined above, a terminal structure may be contained). The copolymer (B) is further preferably a 3-membered block copolymer obtained by arranging the 1 st block, the 2 nd block, and the 3 rd block in this order (i.e., the 2 nd block is present between the 1 st block and the 3 rd block).

The preferable range of the weight average molecular weight of the copolymer (B) varies depending on the presence or absence of water solubility of the copolymer (B). In a state where the copolymer (B) can be dissolved in 0.1M NaNO ₃ When an aqueous solution containing 0.1% by mass of the copolymer (B) was prepared as an aqueous solution, the weight average molecular weight of the copolymer (B) was a pullulan equivalent measured by aqueous GPC under the conditions shown below.

(Water-based GPC)

GPC apparatus: GPC-101 (manufactured by Zhao Denko K.K.)

Solvent: 0.1M NaNO ₃ Aqueous solution

Sample column: shodex Column Ohpak SB-806HQ (8.0 mM I.D.x 300 mm). Times.2 reference column: shodex Column Ohpak SB-800RL (8.0 mM I.D.x 300 mm). Times.2 column temperature: 40 DEG C

Sample concentration: 0.1 mass%

A detector: RI-71S (Shimadzu corporation)

Flow rate: 1 ml/min

Molecular weight standard: pullulan polysaccharide (P-5, P-10, P-20, P-50, P-100, P-200, P-400, P-800, P-1300, P-2500 (manufactured by Showa Denko K.K.))

In this case, the weight average molecular weight M of the copolymer (B) _w The (pullulan equivalent) value is preferably 10000 or more, more preferably 30000 or more, and even more preferably 50000 or more. Because the strength of the electrode is improved. In this case, too, the weight-average molecular weight M of the copolymer (B) _w The (pullulan equivalent) value is preferably 300000 or less, more preferably 200000 or less, and even more preferably 120000 or less. This is because the dispersibility of the solid components in the electrode slurry described later is improved.

In the absence of dissolution of the copolymer (B) in 0.1M NaNO ₃ When an aqueous solution containing 0.1% by mass of the copolymer (B) was prepared as an aqueous solution, the weight average molecular weight of the copolymer (B) was a polystyrene equivalent measured by solvent-based GPC under the following conditions.

(solvent-based GPC)

GPC apparatus: waters GPC System e2695

Solvent: tetrahydrofuran (THF)

Column: SHODEX KF-806 LX 2, SHODEX KF-G (manufactured by SHOWAY electrical Co., ltd.)) column temperature: 40 DEG C

Column temperature: 40 DEG C

Sample concentration: 0.2 mass%

A detector: waters 2414RI

Flow rate: 0.65 mL/min

Molecular weight standard: polystyrene (Shodex Polystyrene STANDARD SL-105, SM-105 (manufactured by Showa Denko Co., ltd))

In this case, the weight average molecular weight M of the copolymer (B) _w The (polystyrene equivalent) value is preferably 10000 or more, more preferably 20000 or more, and even more preferably 30000 or more. Because the strength of the electrode is improved. Also in this case, the copolymer(B) Weight average molecular weight M of (2) _w The (polystyrene equivalent) value is preferably 200000 or less, more preferably 150000 or less, and still more preferably 80000 or less. This is because the dispersibility of the solid components in the electrode slurry described later is improved.

[1-2-7. Specific examples of copolymer (B) ]

The copolymer (B) is preferably a 3-membered block copolymer represented by the following formula (5), for example.

In formula (5), n is preferably: m: l=5.0 to 98:0.30 to 90:0.30 to 4.5, n: m: l=18 to 97:0.50 to 80:0.50 to 6.0, more preferably n: m: l=25 to 97:0.70 to 75:0.80 to 4.5. The preferred ranges for the weight average molecular weight are as described above.

Mode 1 of the copolymer represented by the above formula (5) is n: m: l=5.0 to 50: 40-90: 0.30 to 4.5, preferably n: m: l=18 to 40: 50-80: 0.50 to 6, more preferably n: m: l=25 to 40:60 to 75:0.80 to 4.5. In the absence of dissolution in 0.1M NaNO ₃ When an aqueous solution containing 0.1% by mass of the copolymer according to embodiment 1 is prepared from the aqueous solution, the weight average molecular weight is 10000 to 200000, preferably 20000 to 150000, more preferably 30000 to 80000 in terms of polystyrene.

As for embodiment 1, more specific examples of the copolymer include the copolymer represented by formula (5), n: m: l=30: 69:1.0, mw=50000, copolymer (B2-1).

The 2 nd mode of the copolymer represented by the above formula (5) is n: m: l=70 to 98:0.30 to 20:0.30 to 10, preferably n: m: l=80 to 97:0.50 to 15:0.50 to 6.0, more preferably n: m: l=90 to 97:0.70 to 10:0.80 to 4.5, mw=50000 to 80000. In a solvent capable of being dissolved in 0.1M NaNO ₃ When an aqueous solution containing 0.1% by mass of the copolymer according to embodiment 2 is prepared from the aqueous solution, the weight average molecular weight is 10000 to 300000, preferably 30000 to 200000, more preferably 50000 to 120000 in terms of pullulan.

As for embodiment 2, more specific polymers include those represented by formula (5), wherein n: m: l=93: 6.0:1.0, copolymer (B2-2) with mw=80,000, and n: m: l=96: 1.0:3.0, mw=80,000 (B2-3).

[1-2-8. Synthesis method of copolymer (B) ]

The method for synthesizing the copolymer (B) is not particularly limited, and it can be obtained, for example, by ring-opening polymerization of an epoxide using an acid catalyst. Further, as the catalyst, trialkylaluminum, hydroxide, alkali metal alkoxide, or the like can be used. When the copolymer (B) is a block copolymer, it is preferable to polymerize the monomers corresponding to the respective structural units one by one in sequence. In this case, the order of polymerization preferably corresponds to a desired arrangement. The polymerization is preferably carried out in an aqueous medium, and the aqueous medium that can be used is the same as the aqueous medium (b) described above, but may be different from the aqueous medium used for the synthesis of the copolymer (a).

[1-3 ratio by mass of copolymer (A) to copolymer (B) ]

In the electrode binder according to the present invention, the mass ratio of the copolymer (a) to the copolymer (B) (copolymer (a)/copolymer (B)) is 50.0/50.0 or more, preferably 53.0/47.0 or more, more preferably 64.0/36.0 or more, and still more preferably 77.0/23.0 or more. The reason is that the peeling strength of the electrode active material layer containing the electrode binder according to the present invention to the current collector is improved. Further, the electrode is provided with the electrode active material layer, and thus the cycle characteristics of the nonaqueous secondary battery are improved.

In the electrode binder according to the present invention, the mass ratio of the copolymer (a) to the copolymer (B) (copolymer (a)/copolymer (B)) is 99.0/1.0 or less, preferably 97.5/2.5 or less, more preferably 96.5/3.5 or less, and still more preferably 93.0/7.0 or less. The reason is that the internal resistance of the nonaqueous secondary battery having the electrode active material layer including the electrode binder according to the present invention is reduced and the cycle characteristics of the nonaqueous secondary battery are improved. In the case of further reducing the internal resistance of the nonaqueous secondary battery, the mass ratio is further preferably 88.0/12.0 or less.

< 2 > nonaqueous secondary battery electrode adhesive composition

The nonaqueous secondary battery electrode binder composition (hereinafter, sometimes referred to as binder composition) of the present embodiment contains an electrode binder comprising a copolymer (a) and a copolymer (B), and an aqueous medium (C). The nonaqueous secondary battery electrode binder composition of the present embodiment is the binder composition for a nonaqueous secondary battery electrode of the present embodiment. In the adhesive composition, the copolymer (A) is preferably dispersed in the aqueous medium (C). The copolymer (B) may be dispersed in the aqueous medium (C) or may be dissolved. The adhesive composition may contain, for example, components used for producing the electrode adhesive according to the present invention, adhesives other than the electrode adhesive according to the present invention, polymers which do not conform to the copolymer (a) or the copolymer (B), surfactants, and the like, in addition to these components.

The aqueous medium (C) may be the same as the aqueous medium (B) described above, but may be different from the aqueous medium used for the synthesis of the copolymer (a) or the aqueous medium used for the synthesis of the copolymer (B).

The content of the electrode binder according to the present invention in the nonvolatile component in the binder composition is preferably 80 mass% or more, more preferably 90 mass% or more, further preferably 95 mass% or more, and further preferably 98 mass% or more. Because of increasing contribution to the effect brought about by the electrode binder as an object of the present invention.

The nonvolatile content concentration of the adhesive composition is preferably 20 mass% or more, more preferably 25 mass% or more, and still more preferably 30 mass% or more. The reason is that the amount of the active ingredient contained in the adhesive composition is increased. The nonvolatile concentration of the adhesive composition can be adjusted by the amount of the aqueous medium (C).

The nonvolatile content concentration of the adhesive composition is preferably 80 mass% or less, more preferably 70 mass% or less, and further preferably 60 mass% or less. This is because the increase in viscosity of the adhesive composition is suppressed, and the slurry described later can be easily produced.

As an example of a method for producing the adhesive composition, a method of mixing a mixed solution containing the copolymer (a) with a mixed solution containing the copolymer (B) and adding other components as necessary can be given. As another example of the method for producing the adhesive composition, there is a method in which one of the copolymer (a) and the copolymer (B) is added as a mixed liquid, and the other is added as a solid such as powder, and other components are added as needed. As another example of the method for producing the adhesive composition, there is a method in which the copolymer (a) and the copolymer (B) are mixed as a solid and added to the aqueous medium (C), and other components are added as needed. The method for producing the adhesive composition is not limited to the examples given herein.

< 3 > nonaqueous secondary battery electrode slurry

Next, a nonaqueous secondary battery electrode slurry (hereinafter, also referred to as "electrode slurry") will be described in detail. The nonaqueous secondary battery electrode slurry is a nonaqueous secondary battery electrode slurry. The electrode slurry contains the electrode binder, the electrode active material, and the aqueous medium according to the present invention. In the electrode slurry, the copolymer (a) is preferably dispersed in an aqueous medium. The copolymer (B) may be dispersed in an aqueous medium or may be dissolved. The electrode paste may contain, in addition to these components, a thickener, a conductive aid, a component used for producing the electrode binder according to the present invention, a binder other than the electrode binder according to the present invention, a polymer which does not conform to either the copolymer (a) or the copolymer (B), a surfactant, and the like.

[ 3-1. Content of electrode Binder ]

The content of the electrode binder is preferably 0.50 parts by mass or more, more preferably 1.0 part by mass or more, based on 100 parts by mass of the electrode active material. This is because the effect by the electrode binder is sufficiently exhibited.

The content of the electrode binder is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less, based on 100 parts by mass of the electrode active material. The reason is that the content of the electrode active material is increased in the electrode active material layer produced using the electrode slurry.

[ 3-2. Electrode active Material ]

The electrode active material is a material capable of inserting (intercalation)/extracting (Deintercalation) ions which are ions to be charge carriers, such as lithium ions. The ion serving as the charge carrier is preferably an alkali metal ion, more preferably a lithium ion, a sodium ion, or a potassium ion, and still more preferably a lithium ion.

When the electrode is a negative electrode, the electrode active material, that is, the negative electrode active material preferably contains at least any one of a carbon material, a silicon-containing material, and a titanium-containing material. Examples of the carbon material used as the electrode active material include cokes such as petroleum cokes, pitch cokes, and coal cokes, carbides of organic polymers, graphite such as artificial graphite and natural graphite. Examples of the material containing silicon include a silicon compound such as elemental silicon and silicon oxide. Examples of the material containing titanium include lithium titanate and the like. These materials may be used alone or in combination.

The negative electrode active material preferably contains at least any one of a carbon material and a silicon-containing material, and more preferably contains a carbon material. The reason is that the effect of improving the adhesion between the electrode active materials and the current collector by the electrode binder is extremely large.

When the electrode is a positive electrode, a substance having a higher standard electrode potential than the negative electrode active material is used as the electrode active material, that is, the positive electrode active material. As the positive electrode active material, a positive electrode active material, examples thereof include Ni-Co-Mn-based lithium composite oxide, ni-Mn-Al-based lithium composite oxide nickel-containing lithium composite oxides such as Ni-Co-Al-based lithium composite oxides; lithium cobalt oxide (LiCoO) ₂ ) The method comprises the steps of carrying out a first treatment on the surface of the Spinel lithium manganate (LiMn) ₂ O ₄ ) The method comprises the steps of carrying out a first treatment on the surface of the Olivine-type lithium iron phosphate; tiS (TiS) ₂ 、MnO ₂ 、MoO ₃ 、V ₂ O ₅ And chalcogen compounds. As the positive electrode active material, 1 kind of these materials may be used, or 2 or more kinds may be used in combination.

[ 3-3. Thickeners ]

Examples of the thickener include cellulose such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose, and hydroxypropyl cellulose, ammonium salts of cellulose, alkali metal salts of cellulose, polyvinyl alcohol, and polyvinylpyrrolidone. The thickener preferably contains at least any one of carboxymethyl cellulose, an ammonium salt of carboxymethyl cellulose, and an alkali metal salt of carboxymethyl cellulose. This is because the electrode active material is easily dispersed in the electrode slurry.

The content of the thickener in the electrode slurry is preferably 0.50 parts by mass or more, more preferably 0.80 parts by mass or more, relative to 100 parts by mass of the electrode active material. The reason is that the adhesion between the electrode active materials and the current collector is improved in the electrode active material layer produced using the electrode slurry.

The content of the thickener in the electrode slurry is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, and further preferably 1.5 parts by mass or less, relative to 100 parts by mass of the electrode active material. This is because the coatability of the electrode paste is improved.

[ 3-4. Aqueous Medium ]

The aqueous medium is the same as the above-described aqueous medium (B), but may be different from the aqueous medium used for the synthesis of the copolymer (a) or the aqueous medium used for the synthesis of the copolymer (B).

[ 3-5. Conductive auxiliary ]

As the conductive auxiliary agent, carbon black, carbon fiber, or the like is preferably used. Examples of the carbon black include furnace black, acetylene black, tarn, and parts of the world, such as the world, and parts of the world, and the like. The carbon fibers include carbon nanotubes and carbon nanofibers, and as the carbon nanotubes, VGCF (registered trademark, manufactured by sho and electric company) is preferably used as vapor grown carbon fibers.

[ 3-6 Properties of electrode paste ]

The nonvolatile content concentration of the electrode slurry is preferably 20 mass% or more, more preferably 30 mass% or more, and still more preferably 40 mass% or more. The reason is that the concentration of the active ingredient in the electrode paste becomes high, and a sufficient amount of electrode active material layer can be formed with a small amount of electrode paste. The nonvolatile concentration of the electrode slurry may be adjusted by the amount of the aqueous medium in the electrode slurry.

The nonvolatile content concentration of the electrode slurry is preferably 85 mass% or less, more preferably 75 mass% or less, and further preferably 65 mass% or less. This is because the coatability of the electrode paste is well maintained.

The viscosity of the electrode paste is preferably 20000mpa·s or less, more preferably 10000mpa·s or less, and even more preferably 5000mpa·s or less. This is because the coating property of the electrode slurry on the current collector is improved, and the productivity of the electrode is improved. The viscosity of the electrode paste is greatly affected by the concentration of the nonvolatile components of the electrode paste and the kind and amount of the thickener.

The pH of the electrode slurry at 23 ℃ is not limited as long as it is appropriately adjusted according to the specification of the electrode, the production conditions, and the like, but is preferably 2.0 to 10, more preferably 4.0 to 9.0, and further preferably 6.0 to 9.0. This is because the durability of a battery manufactured using the electrode paste is improved.

[ 3-7. Method for producing electrode paste ]

Examples of the method for preparing the electrode slurry include, but are not limited to, a method in which a binder composition, an electrode active material, a thickener if necessary, an aqueous medium if necessary, a conductive additive if necessary, and other components if necessary are mixed. The order of adding the components is not particularly limited, as long as it is appropriately determined. Examples of the mixing method include a method using a mixing device of a stirring type, a rotary type, an oscillating type, or the like.

< 4. Nonaqueous secondary battery electrode >

The nonaqueous secondary battery electrode (hereinafter, also referred to as "electrode") according to the present embodiment includes a current collector and an electrode active material layer formed on the current collector. Examples of the shape of the electrode include a laminate, a wound body, and the like, but are not particularly limited. The electrode active material layer is not particularly limited in the range of formation on the current collector, and may be formed on the entire surface of the current collector or on a part of the surface of the current collector. In the case where the current collector has a plate, foil, or other shape, the electrode active material layer may be formed on both sides of the current collector or on only one side.

[ 4-1. Collector ]

The current collector is preferably a metal sheet having a thickness of 0.001mm or more and 0.5mm or less, and examples of the metal include iron, copper, aluminum, nickel, stainless steel, and the like. In the case where the nonaqueous secondary battery electrode is a negative electrode of a lithium ion secondary battery, the current collector is preferably copper foil.

[ 4-2. Electrode active Material layer ]

The electrode active material layer according to the present embodiment contains an electrode binder and an electrode active material. The electrode active material layer may contain a conductive auxiliary agent, a thickener, or the like. The components mentioned here are as described above.

[ 4-3. Method for manufacturing electrode ]

As a method for producing an electrode, for example, an electrode slurry is applied to a current collector, dried to form an electrode active material layer, and then cut into an appropriate size.

The method of applying the electrode slurry to the current collector is not particularly limited, and examples thereof include a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dipping method, and an extrusion method. Among them, in consideration of various physical properties such as viscosity and drying properties of the electrode paste, a doctor blade method, a knife method, or an extrusion method is preferably used. This is because an electrode active material layer having a smooth surface and small thickness variation can be obtained.

The electrode paste may be applied to only one surface of the current collector or to both surfaces. When the electrode slurry is applied to both surfaces of the current collector, the electrode slurry may be applied sequentially one by one or both surfaces may be applied simultaneously. The electrode paste may be applied continuously to the current collector or intermittently. The coating amount of the electrode paste may be appropriately determined according to the design capacity of the battery, the composition of the electrode paste, and the like. The coating amount of the electrode paste is similar to the properties of the electrode pasteIt is preferably 13mg/cm ² The following (coating amount per one side in the case of coating on both sides). This is because the occurrence of cracks on the electrode surface can be suppressed in the step of drying the electrode slurry.

The electrode slurry applied to the current collector is dried to form an electrode active material layer on the current collector. The method for drying the electrode paste is not particularly limited, and for example, hot air, reduced pressure or vacuum atmosphere, (far) infrared rays, and low-temperature wind may be used alone or in combination. The drying temperature and drying time of the electrode slurry may be appropriately adjusted according to the concentration of the nonvolatile components in the electrode slurry, the amount of the coating on the current collector, and the like. The drying temperature is preferably 40 ℃ to 350 ℃, more preferably 60 ℃ to 100 ℃ from the viewpoint of productivity. The drying time is preferably 1 minute to 30 minutes.

The electrode sheet having the electrode active material layer formed on the current collector may be cut to have an appropriate size and shape for forming an electrode. The method for cutting the electrode sheet is not particularly limited, and for example, slit, laser, wire cutting, cutting machine, thomson, and the like can be used.

The electrode sheet may be pressed as needed before or after cutting the electrode sheet. This firmly adheres the electrode active material to the current collector, and further, the nonaqueous battery can be miniaturized by making the electrode thin. As a method of pressing, a general method can be used, and a die pressing method or a roll pressing method is particularly preferably used. In the case of the die pressing method, the pressing pressure is not particularly limited, but is preferably 0.5t/cm ² Above and 5t/cm ² The following is given. In the case of the roll press method, the line pressure is not particularly limited, but is preferably 0.5t/cm or more and 5t/cm or less. This is because the above-described effects by pressing are obtained while suppressing the decrease in the capacity of intercalation and deintercalation of charge carriers such as lithium ions into the electrode active material.

< 5 > nonaqueous secondary battery

As a preferred example of the nonaqueous secondary battery according to the present embodiment, a lithium ion secondary battery is described, but the battery configuration is not limited to the description herein. The nonaqueous secondary battery according to the present embodiment includes a positive electrode, a negative electrode, an electrolyte, and, if necessary, a separator or other members in an exterior body, and one or both of the positive electrode and the negative electrode uses an electrode produced by the above method. In the nonaqueous secondary battery according to the present embodiment, at least one of the positive electrode and the negative electrode contains the electrode binder according to the present invention, but preferably at least the negative electrode contains the electrode binder according to the present invention.

[ 5-1. Electrolyte ]

As the electrolyte, a nonaqueous liquid having ion conductivity is used. The electrolyte may be a solution in which an electrolyte is dissolved in an organic solvent, an ionic liquid, or the like, but the former is preferable. The reason is that a nonaqueous battery having low internal resistance can be obtained at low manufacturing cost.

The electrolyte may be an alkali metal salt, and may be appropriately selected according to the type of the electrode active material. Examples of the electrolyte include LiClO ₄ 、LiBF ₆ 、LiPF ₆ 、LiCF ₃ SO ₃ 、LiCF ₃ CO ₂ 、LiAsF ₆ 、LiSbF ₆ 、LiB ₁₀ Cl ₁₀ 、LiAlCl ₄ 、LiCl、LiBr、LiB(C ₂ H ₅ ) ₄ 、CF ₃ SO ₃ Li、CH ₃ SO ₃ Li、LiCF ₃ SO ₃ 、LiC ₄ F ₉ SO ₃ 、Li(CF ₃ SO ₂ ) ₂ N, lithium aliphatic carboxylate, and the like. In addition, other alkali metal salts may be used as the electrolyte.

The organic solvent for dissolving the electrolyte is not particularly limited, and examples thereof include carbonate compounds such as Ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), methyl Ethyl Carbonate (MEC), dimethyl carbonate (DMC), fluoroethylene carbonate (Fluoroethylene carbonate) (FEC), and Vinylene Carbonate (VC); nitrile compounds such as acetonitrile

Carboxylic acid esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate. These organic solvents may be used alone or in combination of 1 or more than 2. Among them, a combination of linear carbonate solvents is preferably used. Examples of the linear carbonate solvent include diethyl carbonate, dimethyl carbonate and methylethyl carbonate.

[ 5-2. Outer cover ]

As the exterior body, for example, a laminate of aluminum foil and a resin film or the like can be suitably used, but is not limited thereto. The shape of the battery may be any of coin type, button type, sheet type, cylinder type, square type, flat type, and the like.

Examples

In the following examples, as an example of the constitution of the present invention, a negative electrode of a lithium ion secondary battery and a lithium ion secondary battery were produced, and the effects of the present invention were confirmed as compared with the negative electrode of a lithium ion secondary battery and a lithium ion secondary battery according to comparative examples. In addition, the present invention is not limited thereto. In addition, the water used in the following examples and comparative examples is ion-exchanged water unless otherwise specified.

< 1. Aqueous dispersion of copolymer (A) or Copolymer (CA) >)

[ 1-1. Preparation of aqueous dispersion of copolymer (A) or Copolymer (CA) ]

The monomer (a) having the composition (parts by mass) shown in Table 1 and Table 2 was subjected to radical polymerization to obtain aqueous dispersions of each of the copolymers (A-1) to (A-9) and the copolymers (CA-1) to (CA-3). Here, the copolymer (a) is described without distinguishing the copolymers (a-1) to (a-9), and the Copolymer (CA) is described without distinguishing the copolymers (CA-1) to (CA-3). The content of the copolymer (A) or the Copolymer (CA) in the aqueous dispersion was set to 40% by mass. In the polymerization, polyoxyethylene alkyl ether sulfate (a terminal 08E manufactured by first industrial pharmaceutical co.) was used as the surfactant. In the resulting aqueous dispersion, the surfactant was contained in an amount of 0.20 parts by mass based on 100 parts by mass of the copolymer (A) or the Copolymer (CA).

[ 1-2. Evaluation 1: determination of the glass transition temperatures of the copolymer (A) and the Copolymer (CA)

The measurement of the glass transition temperatures of the copolymer (A) and the Copolymer (CA) will be described. The resulting aqueous dispersion of the copolymer (A) and the Copolymer (CA) was cast on a polyethylene sheet, dried at 50℃for 5 hours, and then dried under vacuum at 50℃for 1 hour under 98kPa to obtain a film having a thickness of 0.5 mm.

The obtained film was cut into 2mm×2mm pieces, and the film was sealed in an aluminum pan, and DSC measurement was performed using an EXSTAR DSC/SS7020 manufactured by Hitachi-Tech, inc. at a temperature rise rate of 10 ℃/min under a nitrogen atmosphere. The peak top temperature of the DDSC graph obtained as the temperature differential of DSC was measured, and this temperature was set as the glass transition temperatures Tg (. Degree. C.) of the copolymer (P) and the Copolymer (CP). The measurement temperature range is set to be-40 ℃ to 200 ℃. The measured values of the glass transition temperatures are shown in table 1.

TABLE 2

1: the right column of the monomer (a) has a value of parts by mass of each monomer, based on 100 parts by mass of the total amount of the monomers (a 1)

<2 > preparation of aqueous solution or dispersion of copolymer (B)

3 aqueous dispersions and aqueous solutions containing 40 mass% of 3-membered block copolymers each comprising a block comprising the structural unit (10), a block comprising the structural unit (11) and a block comprising the structural unit (12) shown below were prepared in this order. The content of each structural unit contained in the 3-membered block copolymer of these aqueous dispersion and aqueous solution is different. The structures of these 3 copolymers (B-1) to (B-3) are shown in Table 3.

TABLE 3 Table 3

Copolymers (B)	Structural unit (10)	Structural unit (11)	Structural unit (12)	Weight average molecular weight Mw
					B-1	30mol％	69mol％	1.0mol％	50000 (polystyrene conversion)
B-2	93mol％	6.0mol％	1.0mol％	80000 (conversion of pullulan)
					B-3	96mol％	1.0mol％	3.0mol％	80000 (conversion of pullulan)

< 3 adhesive composition >

[ 3-1 preparation of adhesive composition ]

The dispersion of the copolymer (A) or the Copolymer (CA) and the dispersion or the aqueous solution of the copolymer (B) are mixed. The amounts of the copolymer (a) or the Copolymer (CA) and the copolymer (B) blended in each of the examples and comparative examples are mass ratios shown in tables 4 and 5 (for ease of comparison, examples 1 are shown in tables 4 and 5).

/>

The nonvolatile content concentrations (% by mass) of the adhesive compositions obtained in the examples and comparative examples were measured by the following methods. The measurement results are shown in tables 4 and 5.

[ 3-2. Evaluation 2: non-volatile concentration of adhesive composition

1g of the adhesive composition was weighed into an aluminum dish having a diameter of 5cm, dried at 105℃for 1 hour under 1 atmosphere (1013 hPa) while circulating air in a dryer, and then the mass of the remaining component was measured. The ratio (mass%) of the mass of the above-mentioned components remaining after drying to the mass (1 g) of the adhesive composition before drying was calculated as the nonvolatile component concentration.

< 4. Evaluation of electrode and cell Performance >

Negative electrodes and lithium ion secondary batteries were produced using the binder compositions produced in each of examples and comparative examples, and evaluated.

[ 4-1. Manufacture of batteries ]

[4-1-1. Preparation of Positive electrode ]

As a positive electrode active material, toLiNi is added to _0.6 Mn _0.2 Co _0.2 O ₂ 94 parts by mass, 3 parts by mass of acetylene black as a conductive additive and 3 parts by mass of poly (1, 1-difluoroethylene) as a binder were mixed, and 50 parts by mass of N-methylpyrrolidone was added thereto and mixed to prepare a positive electrode slurry.

The positive electrode slurry was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 15 μm by a direct roll method. The amount of the positive electrode slurry applied to the positive electrode current collector was adjusted so that the thickness of the positive electrode current collector after the roll press treatment became 125 μm on each surface.

The positive electrode slurry coated on the positive electrode current collector was dried at 120 ℃ for 5 minutes, and pressed by a roll press with a press load of 5t and a roll width of 7cm by taro company, to obtain a positive electrode sheet having a positive electrode active material layer formed. The positive electrode sheet was cut into 50mm×40mm pieces, and a conductive tab (tab) was attached thereto to prepare a positive electrode.

[4-1-2. Preparation of negative electrode ]

100 parts by mass of artificial graphite (G49, manufactured by jiang-sienna violet, ltd.) as a negative electrode active material, 3.9 parts by mass of the binder composition (1.5 parts by mass as a nonvolatile component) produced in each of examples and comparative examples, and 62 parts by mass of a 2% aqueous solution of CMC (carboxymethyl cellulose-sodium salt/japan kuwanken chemical company, ltd.) were mixed, and 28 parts by mass of water was further added to obtain a negative electrode slurry.

The negative electrode slurry was applied to both sides of a copper foil (negative electrode current collector) having a thickness of 10 μm by a direct roll method. The coating amount of the negative electrode slurry on the negative electrode current collector was adjusted so that the thickness of the negative electrode slurry after the roll press treatment became 170 μm on each surface.

The negative electrode slurry coated on the negative electrode current collector was dried at 90 ℃ for 10 minutes, and pressed by a roll press (press load 8t, roll width 7 cm) to obtain a negative electrode sheet having a negative electrode active material layer formed on the current collector. The obtained negative electrode sheet was cut into pieces of 52mm×42mm, and a conductive tab (tab) was attached thereto to prepare a negative electrode.

[4-1-3. Production of Battery ]

A separator (made of polyethylene, 25 μm) made of a polyolefin porous film was interposed between the positive electrode and the negative electrode, and was housed in an aluminum laminate casing (battery pack) so that the positive electrode active material layer and the negative electrode active material layer were opposed to each other. The electrolyte was injected into the exterior body and vacuum impregnation was performed, and the exterior body was packaged by a vacuum heat sealer, thereby producing a lithium ion secondary battery for evaluation. In the LiPF process ₆ An electrolyte was prepared by mixing 1 part by mass of ethylene carbonate with 99 parts by mass of a solution obtained by dissolving 1.0mol/L of a mixed solvent of Ethylene Carbonate (EC)/ethylmethyl carbonate (EMC)/diethyl carbonate (DEC) =30/50/20 (volume ratio).

[ 4-2. Evaluation of electrodes and cells ]

[4-2-1. Evaluation 3: peel strength (electrode performance) of negative electrode active material layer ]

The peel strength of the negative electrode active material layer to the current collector was measured as follows. The negative electrode sheet after the pressing in the negative electrode production step was cut into 25mm×100mm sizes, and test pieces were produced. The negative electrode active material layer on the test piece was bonded to a SUS plate having a width of 50mm and a length of 200mm using a double-sided tape (nitto ape (registered trademark) No.5, manufactured by ridong electric Co., ltd.) so that the center of the test piece was aligned with the center of the SUS plate. The double-sided tape was bonded so as to cover the entire range of the test piece.

After the test piece was left to stand in a state of being bonded to the SUS plate for 10 minutes, the negative electrode active material layer bonded to the SUS plate was peeled off 20mm in the longitudinal direction from one end of the test piece, the test piece on the copper foil side was folded back 180 °, and the portion (the copper foil side of the portion of the test piece from which the negative electrode active material layer was peeled off) was sandwiched by a chuck on the upper side of the tester. Further, one end of the SUS plate from which the negative electrode active material layer was peeled was sandwiched by a lower chuck. In this state, the copper foil was peeled off from the test piece at a speed of 100.+ -.10 mm/min, and a graph of peel length (mm) -peel force (mN) was obtained. The average value (mN) of the peel force at a peel length of 10 to 45mm was calculated in the obtained graph, and the value obtained by dividing the average value of the peel force by the width of the test piece of 25mm was set as the peel strength (mN/mm) of the negative electrode active material layer. In addition, in both of the examples and comparative examples, peeling between the double-sided tape and the SUS plate, and interfacial peeling between the double-sided tape and the anode active material layer did not occur in the test.

[4-2-2. Evaluation 4: internal resistance (DCR) of Battery

The measurement of the internal resistance (DCR (Ω)) of the battery was performed under the condition of 25 ℃. Constant current charging of 0.2C was performed from rest potential until 3.6V, so that the state of charge was 50% of the initial capacity (SOC 50%). Then, discharge was performed for 60 seconds at each current value of 0.2C, 0.5C, 1C, and 2C. The DCR (Ω) at SOC50% was determined from the relationship between these 4 current values (value at 1 second) and the voltage.

[4-2-3. Evaluation 5: cycle capacity maintenance Rate at high temperature (Battery Performance)

The cycle capacity retention rate of the battery at a high temperature was 45℃and the following steps (i) to (iv) were repeated. Here, the series of operations (i) to (iv) is set to 1 cycle for 1 time.

(i) Charging is performed with current 1C until the voltage becomes 4.2V (constant current (CC) charging).

(ii) Charging was performed at a voltage of 4.2V until the current became 0.05C (constant voltage (CV) charging).

(iii) Standing for 30 minutes.

(iv) Discharge with current 1C until voltage becomes 2.75V (constant current (CC) discharge).

The time-integrated value of the current in the steps (i) and (ii) is set as the charge capacity, and the time-integrated value of the current in the step (iv) is set as the discharge capacity. The discharge capacity at the 1 st cycle and the discharge capacity at the 100 th cycle were measured. The cycle capacity maintenance rate at high temperature of the battery was calculated as 100× (discharge capacity at 100 th cycle)/(discharge capacity at 1 st cycle) [% ], and is shown in tables 1 and 2.

< 5 evaluation results >)

When the evaluation results of the examples were observed, it was found that the peel strength of the negative electrode active material layer was high in any of the electrodes according to the examples. It is understood that the battery according to any of the examples has low internal resistance and high discharge capacity maintenance rate (excellent cycle characteristics) in the evaluation of the battery.

In comparative example 1, an electrode and a battery were fabricated using the binder composition not including the copolymer (B). However, the internal resistance of the battery cannot be sufficiently reduced, and furthermore, the discharge capacity maintenance rate is also insufficient.

In comparative example 2, an electrode and a battery were fabricated using an adhesive composition containing the copolymer (B) in excess. However, the peel strength of the anode active material layer in the electrode is low. In addition, the discharge capacity maintenance rate of the battery is also insufficient.

In comparative example 3, an adhesive composition was produced using a copolymer (CA-1) having no 12 th structural unit. In comparative example 4, an adhesive composition was produced using an excess of the copolymer (CA-2) having the 12 th structural unit. In comparative example 5, an adhesive composition was produced using an excess of the copolymer (CA-3) having the 13 th structural unit. However, the negative electrode active material layer in the electrode produced using these binder compositions has low peel strength. Further, the internal resistance of the battery cannot be sufficiently reduced, and the discharge capacity maintenance rate is also insufficient.

As described above, according to the nonaqueous secondary battery electrode binder of the present invention, the peeling strength of the electrode active material layer from the current collector is effectively improved in the nonaqueous secondary battery, and the reduction of the internal resistance and the improvement of the cycle characteristics of the battery can be facilitated.

Claims (14)

1. A nonaqueous secondary battery electrode binder characterized by comprising a copolymer (A) and a copolymer (B),

the copolymer (A) is a polymer of a compound having an ethylenically unsaturated bond,

the copolymer (A) has an 11 th structural unit derived from the monomer (a 1) and a 12 th structural unit derived from the monomer (a 2), or has an 11 th structural unit derived from the monomer (a 1), a 12 th structural unit derived from the monomer (a 2) and a 13 th structural unit derived from the internal crosslinking agent (a 3),

the monomer (a 1) is a nonionic compound having an ethylenically unsaturated bond, having neither a hydroxyl group nor a cyano group, and having no independent plural ethylenically unsaturated bonds,

the monomer (a 2) is a compound having an ethylenically unsaturated bond and an anionic functional group and having no independent plurality of ethylenically unsaturated bonds,

the internal crosslinking agent (a 3) is a compound having a plurality of independent ethylenic unsaturated bonds and capable of forming a crosslinked structure in radical polymerization of a monomer comprising the monomer (a 1) and the monomer (a 2),

In the copolymer (A), the content of the 12 th structural unit is 1.0 to 30 parts by mass based on 100 parts by mass of the 11 th structural unit,

in the copolymer (A), the content of the 13 th structural unit is 0 to 20 parts by mass based on 100 parts by mass of the 11 th structural unit,

the copolymer (B) has a 21 st structural unit represented by the following formula (1) of 5.0 mol% or more and 98 mol% or less in all structural units, a 22 nd structural unit represented by the following formula (2) of 0.30 mol% or more and 90 mol% or less in all structural units, and a 23 rd structural unit represented by the following formula (3) of 0.30 mol% or more and 10 mol% or less in all structural units,

the total content of the 21 st structural unit, the 22 nd structural unit, and the 23 rd structural unit in all structural units of the copolymer (B) is 90 mass% or more,

the mass ratio of the content of the copolymer (A) to the content of the copolymer (B) is 50.0/50.0 or more and 99.0/1.0 or less,

in formula (2), R ¹ An alkyl group having 1 to 6 carbon atoms which may have a branched chain;

in formula (3), R ² Is a group having an ethylenically unsaturated bond.

2. The nonaqueous secondary battery electrode binder according to claim 1, wherein the copolymer (B) comprises

5.0 to 50 mol% of the 21 st structural unit,

40 to 90 mol% of the 22 nd structural unit,

The 23 rd structural unit is 0.30 mol% or more and 10 mol% or less.

3. The nonaqueous secondary battery electrode binder according to claim 1, wherein the copolymer (B) comprises

70 mol% or more and 98 mol% or less of the 21 st structural unit,

0.30 to 20 mol% of the 22 nd structural unit,

The 23 rd structural unit is 0.30 mol% or more and 10 mol% or less.

4. The nonaqueous secondary battery electrode binder according to any one of claims 1 to 3, wherein in the formula (3), R ² Having a moiety selected from the group consisting of vinyloxy, allyloxy, (meth) acryl, (meth) acryloyloxy, and-OCH ₂ -CH ₂ -CH ₂ ＝CH ₂ At least any 1 of the above.

5. The nonaqueous secondary battery electrode binder according to any one of claims 1 to 4, wherein in the formula (3), R ² Represented by the following formula (4),

-R ²¹ -R ²² (4)

in formula (4), R ²¹ Is an alkylene group having 1 to 5 carbon atoms which may have a branched chain, R ²² Is selected from vinyloxy and allyl1 kind of functional group among an acyloxy group, (meth) acryl group, and (meth) acryloyloxy group.

6. The nonaqueous secondary battery electrode binder according to any one of claims 1 to 5, wherein the copolymer (B) is a block copolymer having a1 st block comprising a 21 st structural unit, a2 nd block comprising a 22 nd structural unit, and a 3 rd block comprising a 23 rd structural unit.

7. The nonaqueous secondary battery electrode binder according to any one of claims 1 to 6, wherein the monomer (a 1) has no polar functional group.

8. The nonaqueous secondary battery electrode binder according to any one of claims 1 to 7, wherein the monomer (a 2) is a compound having at least any one of a carboxyl group and a sulfo group.

9. The nonaqueous secondary battery electrode binder according to any one of claims 1 to 8, wherein the copolymer (a) contains the 11 th structural unit and the 12 th structural unit in a total of 80 mass% or more.

10. The nonaqueous secondary battery electrode binder according to any one of claims 1 to 9, wherein the content of the 13 th structural unit in the copolymer (a) is 0.050 parts by mass or more relative to 100 parts by mass of the 11 th structural unit.

11. A nonaqueous secondary battery electrode binder composition comprising the nonaqueous secondary battery electrode binder according to any one of claims 1 to 10, and an aqueous medium.

12. A nonaqueous secondary battery electrode slurry comprising the nonaqueous secondary battery electrode binder according to any one of claims 1 to 10, an electrode active material, and an aqueous medium,

the aqueous medium is 1 medium selected from the group consisting of water, hydrophilic solvents, and mixtures comprising water and hydrophilic solvents.

13. A nonaqueous secondary battery electrode comprising the nonaqueous secondary battery electrode binder according to any one of claims 1 to 10.

14. A nonaqueous secondary battery comprising the nonaqueous secondary battery electrode according to claim 13.