KR20240014467A - Non-aqueous secondary battery electrode binder and non-aqueous secondary battery electrode - Google Patents

Abstract

Provided is a non-aqueous secondary battery electrode binder, a composition thereof, and a non-aqueous secondary battery electrode that can significantly improve the discharge capacity maintenance rate after charge and discharge cycles while improving the flexibility of the electrode active material layer formed on the current collector. The non-aqueous secondary battery electrode binder of the present invention contains a copolymer (P). The copolymer (P) is represented by the following general formula (1), a main chain containing bonds between carbon atoms, a substituent group having an amide bond bonded to the main chain, and a substituent group having a salt of a carboxyl group. It has a substituent (c). The amount of the amide bond contained per 1 g of copolymer (P) is 0.050 to 5.0 mmol/g, the amount of the substituent (b1) is 5.0 to 12.0 mmol/g, and the amount of the substituent (c) is 0.15×10 ^-2 to 8.0×10 ^-2 mmol/g.

Description

Non-aqueous secondary battery electrode binder and non-aqueous secondary battery electrode

The present invention relates to a binder for non-aqueous secondary battery electrodes, a composition thereof, a non-aqueous secondary battery electrode, and a non-aqueous secondary battery.

This application claims priority based on Patent Application No. 2021-090167 filed in Japan on May 28, 2021, and uses the content here.

Secondary batteries using non-aqueous electrolytes (non-aqueous secondary batteries) are superior to secondary batteries using aqueous electrolytes in terms of higher voltage, smaller size, and lighter weight. Therefore, non-aqueous secondary batteries are widely used as power sources for notebook-type personal computers, mobile phones, power tools, and electronic and communication devices. In addition, recently, non-aqueous batteries have been used for electric vehicles and hybrid vehicles from the viewpoint of environmental vehicle application, but there is a strong demand for higher output, higher capacity, and longer lifespan. A representative example of a non-aqueous secondary battery is a lithium ion secondary battery.

A non-aqueous secondary battery includes a positive electrode made of a metal oxide or the like as an active material, a negative electrode made of a carbon material such as graphite, and a non-aqueous electrolyte solution centered on carbonates or a flame-retardant ionic liquid. A non-aqueous secondary battery is a secondary battery in which the battery is charged and discharged by moving ions between a positive electrode and a negative electrode. In detail, the positive electrode is obtained by applying a slurry containing a metal oxide and a binder to the surface of a positive electrode current collector such as aluminum foil, drying it, and then cutting it into appropriate sizes. The negative electrode is obtained by applying a slurry containing a carbon material and a binder to the surface of a negative electrode current collector such as copper foil, drying it, and then cutting it into appropriate sizes. The binder has the role of binding the active materials to each other and the active material and the current collector in the positive electrode and the negative electrode, and preventing peeling of the active material from the current collector.

As a binder, a polyvinylidene fluoride (PVDF)-based binder using N-methyl-2-pyrrolidone (NMP), an organic solvent, as a solvent is well known. However, this binder has a low binding property between active materials and between the active material and the current collector, so a large amount of binder is required for actual use. Therefore, there is a drawback that the capacity of the non-aqueous secondary battery decreases. Additionally, since NMP, an expensive organic solvent, was used as the binder, it was difficult to suppress manufacturing costs.

As a way to solve these problems, the development of water-dispersible binders is in progress. As an aqueous dispersion-based binder, for example, it is known to use carboxymethyl cellulose (CMC) as a thickener and a (meth)acrylic acid ester-based or styrene-butadiene rubber (SBR)-based aqueous dispersion.

Patent Document 1 discloses a binder composition for lithium ion battery secondary battery electrodes containing a (meth)acrylic acid ester compound and a polyfunctional thiol compound. Additionally, Patent Document 2 discloses a binder composition for a lithium ion secondary battery silicon-based negative electrode containing acrylic acid, a tetrafunctional (meth)acrylate monomer, and acrylamide.

Patent Document 3 discloses a binder for non-aqueous battery electrodes containing a sodium acrylate-N-vinylacetamide copolymer (copolymerization ratio: sodium acrylate/N-vinylacetamide = 10/90 mass ratio).

Japanese Patent Publication No. 2014-116265 Japanese Patent Publication No. 2016-181422 International Publication No. 2017/150200

However, the binder using the polyfunctional thiol described in Patent Document 1 requires the combined use of carboxymethylcellulose as a thickener, making the slurry production process complicated. In addition, this binder did not have sufficient binding properties between the active materials and the active material and the current collector, so when an electrode was produced with a small amount of the binder, there was a problem in that part of the active material peeled off during the process of cutting the current collector.

In the binder using the tetrafunctional acrylate disclosed in Patent Document 2, as disclosed in Comparative Example 5 described later, the flexibility of the electrode could not be secured, and there was a problem in that cracks occurred when the electrode was wound.

The binder for non-aqueous battery electrodes disclosed in Patent Document 3 had the problem of low electrode flexibility and low discharge capacity retention after charge/discharge cycles, as disclosed in Comparative Example 3 described later.

Therefore, the present invention provides a non-aqueous secondary battery electrode binder and a non-aqueous secondary battery electrode binder composition that can significantly improve the discharge capacity maintenance rate after charge and discharge cycles while improving the flexibility of the electrode active material layer formed on the current collector. The purpose is to

Additionally, the present invention aims to provide a non-aqueous secondary battery electrode that is highly flexible and has a high discharge capacity retention rate after charge and discharge cycles.

Additionally, the present invention aims to provide a non-aqueous secondary battery equipped with an electrode that is highly flexible and has a high discharge capacity retention rate after charge and discharge cycles.

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

[1] A non-aqueous secondary battery electrode binder containing a copolymer (P),

The copolymer (P) is,

a main chain containing only bonds between carbon atoms,

A substituent having an amide bond,

A substituent having a salt of a carboxyl group,

Substituent (c) represented by the general formula (1) below:

With

The substituent having the amide bond, the substituent having the salt of the carboxyl group, and the substituent (c) are each bonded to the main chain,

The amount of amide bond contained per 1g of the copolymer (P) is 0.050 mmol/g or more and 5.0 mmol/g or less,

The amount of salt of the carboxyl group contained per 1g of the copolymer (P) is 5.0 mmol/g or more and 12.0 mmol/g or less,

The amount of the substituent (c) contained per 1g of the copolymer (P) is 0.15 × 10 ^-2 mmol/g or more and 8.0 × 10 ^-2 mmol/g or less.

A non-aqueous secondary battery electrode binder, characterized in that.

(In General Formula (1), R ³¹ is a hydrocarbon group, m and n each represent the number of the corresponding substituent directly bonded to R ³¹ , m is an integer of 0 or more, n is an integer of 1 or more, m +n≥2.)

[2] The non-aqueous secondary battery electrode binder according to [1], wherein the general formula (1) is, and R ³¹ contains a carbon atom and a hydrogen atom.

[3] In the general formula (1), R ³¹ has a plurality of carbon atoms, and all bonds between carbon atoms are single bonds. The non-aqueous secondary battery electrode binder according to [1] or [2].

[4] If the formula of the substituent (c) is Mc, the non-aqueous secondary battery electrode binder according to any of [1] to [3] where Mc/(m+n)≤400.

[5] The substituent (c) is a structure derived from the polyfunctional thiol compound (C), and the polyfunctional thiol compound (C) is any of [1] to [4] having two or more mercapto groups in one molecule. The non-aqueous secondary battery electrode binder described in

[6] The copolymer (P) further contains 0.50% by mass or more and 20.0% by mass or less of the structural unit (d) represented by the following general formula (2). The ratio described in any of [1] to [5] Aqueous secondary battery electrode binder.

(In General Formula (2), R ⁴¹ , R ⁴² , and R ⁴⁴ are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ⁴³ is an alkyl group having 1 to 6 carbon atoms, and has more carbon atoms than R ⁴² The number of is large. j and k each mean the number of the structures in the corresponding parentheses being combined in series. j is an integer greater than 1, k is an integer greater than 0, and j+k≥20.)

[7] The copolymer (P) further contains structural unit (e) represented by the following general formula (3) in an amount of 0.030 mmol/g or more and 1.75 mmol/g or less per 1 g of the copolymer (P). The non-aqueous secondary battery electrode binder according to any of [1] to [6].

(In General Formula (3), R ⁵¹ represents a hydrogen atom or a methyl group, and R ⁵² is a substituent having an aromatic ring.)

[8] In the copolymer (P), the non-aqueous polymer according to any of [1] to [7], in which at least a part of the amide bond is contained as a structural unit (a) represented by the following general formula (4) Secondary battery electrode binder.

(In General Formula (4), R ¹¹ and R ¹² each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

[9] In the copolymer (P), at least a part of the salt of the carboxyl group is a non-aqueous polymer according to any of [1] to [8], wherein at least a part of the salt of the carboxyl group is contained as a structural unit (b) represented by the following general formula (5) Secondary battery electrode binder.

(In General Formula (5), R ² represents a hydrogen atom or a methyl group, and X is a cation.)

[10] The non-aqueous secondary battery electrode binder according to any one of [1] to [9], wherein the weight average molecular weight of the copolymer (P) is 700,000 or more and 7.5 million or less.

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

[12] Equipped with a current collector and an electrode active material layer formed on the surface of the current collector,

The electrode active material layer is a non-aqueous secondary battery electrode containing the binder for a non-aqueous secondary battery electrode and an electrode active material according to any of [1] to [10].

[13] Contains a positive electrode, a negative electrode, and an electrolyte,

A non-aqueous secondary battery, wherein at least one of the positive electrode and the negative electrode is the non-aqueous secondary battery electrode described in [12].

[14] A non-aqueous secondary battery electrode binder comprising a polymerization step of radically polymerizing a monomer (M) having an ethylenically unsaturated bond in the presence of a polyfunctional thiol compound (C) having two or more mercapto groups in one molecule. This is a method of manufacturing,

The monomer (M) includes a monomer (A) having an amide bond and a monomer (B) having a salt of a carboxyl group,

When using the monomer (M), the polyfunctional thiol compound (C), a polymerization initiator, and a chain transfer agent, if the chain transfer agent is also considered a polymerization component,

The amount of the monomer (A) contained per 1g of the polymerization component is 0.050 mmol/g or more and 5.0 mmol/g or less,

The amount of the monomer (B) contained per 1g of the polymerization component is 5.0 mmol/g or more and 12.0 mmol/g or less,

The amount of the polyfunctional thiol compound (C) contained per 1 g of the polymerization component is 0.15 × 10 ^-2 mmol/g or more and 8.0 × 10 ^-2 mmol/g or less.

A method for producing a non-aqueous secondary battery electrode binder, characterized in that.

According to the present invention, it is possible to provide a non-aqueous secondary battery electrode binder and a composition thereof that can significantly improve the discharge capacity maintenance rate after charge and discharge cycles while improving the flexibility of the electrode active material layer formed on the current collector.

Additionally, according to the present invention, it is possible to provide a non-aqueous secondary battery electrode with high flexibility and a high discharge capacity retention rate after charge and discharge cycles.

Furthermore, according to the present invention, it is possible to provide a non-aqueous secondary battery equipped with an electrode that is highly flexible and has a high discharge capacity retention rate after charge and discharge cycles.

Hereinafter, embodiments of the present invention will be described in detail. In this embodiment, the battery is a secondary battery that involves the movement of ions between the positive electrode and the negative electrode during charging and discharging. The positive electrode has a positive electrode active material, and the negative electrode has a negative electrode active material. These electrode active materials are materials capable of intercalation and deintercalation of ions. A preferred example of a secondary battery with this structure is a lithium ion secondary battery.

“(meth)acrylic acid” refers to one or both of methacrylic acid and acrylic acid. “(Meth)acrylic acid monomer” refers to one or both of methacrylic acid monomer and acrylic acid monomer. “(meth)acrylate” refers to one or both of methacrylate and acrylate.

“Weight average molecular weight” is a pullulan conversion value calculated using gel permeation chromatography (GPC).

“Hydrocarbon group” means a structure containing only carbon atoms and hydrogen atoms. However, if there is a special explanation such as some hydrogen atoms being substituted, it is not limited to this.

In the following description, in the formula representing the structural unit, if there is no atom at the end of the line representing the bond, it means that that portion is bonded to another structural unit or terminal structure forming a polymer.

A salt of a functional group means a form in which an ion from which a part of the functional group is dissociated is combined with a counter ion other than a hydrogen ion and a hydroxide ion. For example, a salt of a carboxyl group means a combination of COO- and a cation other than a hydrogen ion. It means the form.

<1. Non-aqueous secondary battery electrode binder>

The non-aqueous secondary battery electrode binder (or non-aqueous secondary battery electrode binder; hereinafter sometimes referred to as “electrode binder”) according to the present embodiment contains the copolymer (P) described below. The electrode binder may contain other components, for example, polymers other than the copolymer (P), surfactants, etc.

Here, the electrode binder includes components that remain without volatilizing in a process involving heating in the battery manufacturing process described later. Specifically, the ingredients constituting the electrode binder are the ingredients remaining after weighing 1 g of the mixture containing the electrode binder on an aluminum dish with a diameter of 5 cm and drying it for 5 hours at 110°C while circulating air in a dryer at atmospheric pressure.

The content of the copolymer (P) in the electrode binder is preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 98% by mass or more. This is to increase the contribution of the copolymer (P) to the effect aimed at in the present invention.

〔1-1. Copolymer (P)]

The copolymer (P) has a main chain containing only bonds between carbon atoms, a substituent having an amide bond, a substituent having a salt of a carboxyl group, and a substituent (c) represented by the following general formula (1). It is preferable that the main chain contains only single bonds between carbon atoms.

The substituent having an amide bond, the substituent having a salt of a carboxyl group, and the substituent (c) are each bonded to the main chain. It is preferable that the substituent having an amide bond and the substituent having a salt of a carboxyl group are branched from the main chain. The substituent (c) is preferably bonded to the terminal of the main chain. Additionally, multiple main chains may be bonded to one substituent (c). That is, one molecule may have a structure in which multiple main chains including bonds between carbon atoms are bonded through the substituent (c).

The copolymer (P) preferably further has at least one of a structural unit (d) represented by the general formula (2) described later and a structural unit (e) represented by the general formula (3) described later, and both It is more desirable to have it. The copolymer (P) may have a structure other than the above structure, such as a molecular terminal structure.

The weight average molecular weight of the copolymer (P) is preferably 700,000 or more, more preferably 1 million or more, and even more preferably 1.5 million or more. Moreover, the weight average molecular weight of the copolymer (P) is preferably 7.5 million or less, more preferably 5 million or less, and still more preferably 4 million or less.

[1-1-1. amide bond]

The amount of amide bonds contained per 1 g of copolymer (P) is 0.050 mmol/g or more, preferably 0.085 mmol/g or more, and more preferably 0.40 mmol/g or more. This is because the dispersibility of electrode active materials, conductive additives, etc. when producing the electrode slurry described later is excellent, and an electrode slurry with good coatability can be produced. Additionally, this is because the electrolyte resistance of the negative electrode active material layer is improved by the copolymer (P).

The amount of amide bond contained per 1g of copolymer (P) is 5.0 mmol/g or less, preferably 3.0 mmol/g or less, more preferably 1.7 mmol/g or less, and still more preferably 0.90 mmol/g or less. . This is to make the copolymer (P) contain a different structure. In addition, this is because the occurrence of cracks in the electrode, which will be described later, is suppressed and the productivity of the electrode is improved.

Additionally, the amide bond may be included in all structural units having other functional groups, such as structural unit (e) described later.

In the copolymer (P), it is preferable that at least part of the amide bond is included as a structural unit (a) represented by the following general formula (4). This is because the amount of amide bonds relative to the mass of the structural unit (a) is large, and amide bonds can be efficiently incorporated into the copolymer (P). The proportion contained in the structural unit (a) among the amide bonds in the copolymer (P) is preferably 95 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more.

In General Formula (4), R ¹¹ and R ¹² each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

In general formula (4), it is more preferable that R ¹¹ and R ¹² are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably R ¹¹ and R ¹² are each independently a hydrogen atom or a methyl group. do.

A particularly preferred combination of R ¹¹ and R ¹² is R ¹¹ :H and R ¹² :H, or R ¹¹ :H and R ¹² :CH ₃ . This is because the amount of amide bonds relative to mass is large, so more amide bonds can be included in the copolymer (P).

[1-1-2. salt of carboxyl group]

The salt of the carboxyl group is preferably a salt of -COO- and a monovalent cation. The monovalent cation is more preferably an alkali metal ion or ammonium ion, more preferably an alkali metal ion, and particularly preferably a lithium ion or sodium ion.

The amount of salt of the carboxyl group contained per 1 g of copolymer (P) is 5.0 mmol/g or more, preferably 6.0 mmol/g or more, and more preferably 7.0 mmol/g or more. This is because an electrode active material layer with high peeling strength from the current collector can be obtained by using the copolymer (P).

The amount of salt of the carboxyl group contained per 1 g of copolymer (P) is 12.0 mmol/g or less, and is preferably 9.9 mmol/g or less. This is because the dispersibility of solid content such as electrode active materials and conductive additives during production of the electrode slurry described later is further improved.

In addition, the amount of salt of the carboxyl group is the amount of -COO- bonded to cations other than hydrogen ions. For example, when two COO- are bonded to one divalent cation, there are two salts of the carboxyl group.

In addition, the salt of the carboxyl group may be contained in all structural units having other functional groups, such as structural unit (e) described later.

In the copolymer (P), it is preferable that at least part of the salt of the carboxyl group is contained as a structural unit (b) represented by the following general formula (5). This is because the amount of salt of the carboxyl group relative to the mass is large, and the salt of the carboxyl group can be efficiently included in the copolymer (P). Among the salts of the carboxyl group in the copolymer (P), the proportion contained in the structural unit (b) is preferably 95 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more.

In General Formula (5), R ² represents a hydrogen atom or a methyl group, and X is a cation.

In General Formula (5), X is more preferably a monovalent cation, and more preferably at least one of lithium ion, sodium ion, potassium ion, and ammonium ion. Among these, it is particularly preferable to contain at least one of lithium ions and sodium ions.

As the structural unit (b), in the above general formula (5), two or more types of structures with different Xs may be contained in the copolymer (P). For example, the structural unit (b) may include two types of structures: a salt with lithium and a salt with sodium.

[1-1-3. substituent (c)]

The substituent (c) is expressed by the following general formula (1).

In General Formula (1), R ³¹ is a hydrocarbon group, and m and n each represent the number of corresponding substituents directly bonded to R ³¹ (the number of branches of the structure in parentheses corresponding to each of m and n). m is an integer of 0 or more, n is an integer of 1 or more, m+n≥2, and R ³² is a hydrogen atom or a methyl group.

The substituent (c) has the role of linking the main chains to extend the molecular chain, and if n≥3, a crosslinked structure can be formed in the copolymer (P).

In General Formula (1), it is preferable that m+n≥3, and it is more preferable that m+n≥4. This is because the peeling strength and toughness of the electrode active material layer containing the copolymer (P) against the current collector are improved, and this is because at least part of the substituent (c) forms a crosslinked structure in the copolymer (P) Because I think there is.

Moreover, although it is not specifically limited, it is preferable that m+n≤6, and it is more preferable that m+n≤5. It is more preferable that m+n≤4, and it is especially preferable that m+n=4. This is because the flexibility of the electrode active material layer containing the copolymer (P) is improved.

In General Formula (1), R ³¹ preferably contains a carbon atom and a hydrogen atom. It is more preferable that R ³¹ has a plurality of carbon atoms, and all bonds between carbon atoms are single bonds.

In General Formula (1), R ³¹ may be a straight-chain hydrocarbon group or a hydrocarbon group with a branched structure. The number of carbon atoms contained in R ³¹ is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. Additionally, it is preferable that R ³¹ is not directly bonded to the main chain. In R ³¹ , it is preferable that all bonds between carbon atoms are single bonds. This is to improve the flexibility of the electrode binder by improving the flexibility of the substituent (c).

In General Formula (1), R ³² is preferably a methyl group. This is because the peeling strength of the electrode active material layer containing the copolymer (P) is improved.

If the formula of substituent (c) is Mc, it is preferable that Mc/(m+n)≤400, more preferably Mc/(m+n)≤300, and Mc/(m+n)≤200. It is more desirable. This is because the effect of molecular chain extension and/or the crosslinking density of the copolymer (P) is improved by the substituent (c), and the peeling strength of the electrode active material layer from the current collector and the toughness of the electrode active material layer are improved.

The substituent (c) is a structural unit derived from the polyfunctional thiol compound (C), and the polyfunctional thiol compound (C) preferably has two or more mercapto groups in one molecule. Here, the polyfunctional thiol compound (C) more preferably has 3 or more mercapto groups per molecule, and even more preferably has 4 or more mercapto groups. Details of the polyfunctional thiol compound (C) are described later in the manufacturing method of the copolymer (P).

The amount of substituent (c) contained per 1 g of copolymer (P) is 0.15 × 10 ^-2 mmol/g or more, preferably 0.30 × 10 ^-2 mmol/g or more, and 0.65 × 10 ^-2 mmol/g or more. It is more preferable. This is because, in the electrode described later, the strength of the composite layer of the electrode is improved, and the discharge capacity maintenance rate after charge and discharge cycles is improved.

The amount of substituent (c) contained per 1g of copolymer (P) is 8.0×10 ^-2 mmol/g or less, preferably 5.5×10 ^-2 mmol/g or less, and 4.0×10 ^-2 mmol/g or less. It is more preferable, and it is even more preferable that it is 1.4×10 ^-2 mmol/g or less. This is because, in the electrode described later, the flexibility of the electrode is improved. In addition, in the non-aqueous secondary battery described later, this is because the cycle characteristics (discharge capacity maintenance rate) are improved.

[1-1-4. structural unit (d)]

The structural unit (d) is a structure expressed by the following general formula (2).

In General Formula (2), R ⁴¹ , R ⁴² , and R ⁴⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ⁴³ is an alkyl group having 1 to 6 carbon atoms, and has more carbon atoms than R ⁴² . In this formula, j and k each mean the number of the structures within the corresponding parentheses being combined in series. j is an integer greater than 1, k is an integer greater than 0, and j+k≥20.

In general formula (2), R ⁴¹ , R ⁴² , and R ⁴⁴ are each independently preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ⁴¹ , R ⁴² , and R ⁴⁴ are each independently a hydrogen atom or It is more preferable that it is a methyl group. R ⁴⁴ is more preferably a methyl group.

In General Formula (2), j is an integer of 1 or more, k is an integer of 0 or more, and j+k≥20. This is because when an electrode is manufactured using copolymer (P) as a binder for the electrode active material, the flexibility of the electrode is improved and the occurrence of cracks is suppressed. From this viewpoint, it is preferable that j+k≥30, and it is more preferable that j+k≥40. Additionally, it is preferable that j+k≤500, more preferably j+k≤200, and even more preferably j+k≤150. This is because the binding force of the electrode binder becomes higher.

Furthermore, in General Formula (2), it is limited that j structural units containing R ⁴² and k structural units containing R ⁴³ are included, but there is no limitation on the arrangement of these structural units. That is, in the case of k ≥ 1, in the polyoxyalkylene chain of general formula (2), all or part of each structural unit may have a continuous block structure, or a structure in which two structural units are arranged alternately, etc. It may be a structure arranged with periodic regularity, or it may be a structure in which two structural units are randomly arranged. A preferable form of the polyoxyalkylene chain of general formula (2) is a structure arranged with periodic regularity, or a structure arranged randomly. This is to suppress bias in the distribution of each structural unit within the molecular chain forming the general formula (2). A more preferable form of the copolymer of General Formula (2) is a randomly arranged structure. This is because polymerization is possible using a radical polymerization initiator without using a special catalyst, thereby reducing manufacturing costs.

In General Formula (2), examples of preferred combinations of R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ , j, and k include those shown in Table 1 below.

The content of structural unit (d) in the copolymer (P) is preferably 0.50 mass% or more, more preferably 0.70 mass% or more, and even more preferably 3.5 mass% or more. This is to suppress the occurrence of cracks in the electrodes described later.

The content of the structural unit (d) in the copolymer (P) is preferably 20.0% by mass or less, more preferably 14.0% by mass or less, and even more preferably 7.0% by mass or less. This is to improve the peeling strength of the electrode active material layer. Additionally, in the non-aqueous secondary battery described later, the purpose is to improve cycle characteristics (discharge capacity maintenance rate).

[1-1-5. structural unit (e)]

The structural unit (e) is a structure expressed by the following general formula (3).

In General Formula (3), R ⁵¹ represents a hydrogen atom or a methyl group, and R ⁵² is a substituent having an aromatic ring. It is preferable that there is only one aromatic ring contained in R ⁵² . R ⁵² preferably has neither an amide bond nor a salt of a carboxyl group. R ⁵² preferably has a benzene ring, and more preferably contains a carbon atom and a hydrogen atom.

The structural unit (e) is preferably expressed by the following general formula (6).

In General Formula (6), R ⁵¹ is a hydrogen atom or a methyl group. R ⁵³ is -CH ₂ - or -(CH ₂ CH ₂ O) _h - or -CH ₂ CH(OH)CH ₂ O-. Here, h is an integer between 1 and 5. R ⁵⁴ is a substituent having an aromatic ring. R ⁵³ is more preferably -CH ₂ - or -CH ₂ CH ₂ O-, and even more preferably -CH ₂ -. It is preferable that there is one aromatic ring contained in R ⁵⁴ . R ⁵⁴ preferably has a benzene ring, and more preferably contains a carbon atom and a hydrogen atom. R ⁵⁴ preferably has neither an amide bond nor a salt of a carboxyl group. It is particularly preferable that R ⁵⁴ is a phenyl group.

The amount of structural unit (e) contained per 1 g of copolymer (P) is preferably 0.030 mmol/g or more, more preferably 0.045 mmol/g or more, and even more preferably 0.30 mmol/g or more. This is because the occurrence of cracks in the electrode, which will be described later, is suppressed and the productivity of the electrode is improved.

The amount of structural unit (e) contained per 1 g of copolymer (P) is preferably 1.75 mmol/g or less, more preferably 1.50 mmol/g or less, and even more preferably 0.90 mmol/g or less. In the electrode described later, this is to improve the peeling strength of the electrode active material layer and to suppress expansion of the electrode active material layer. Additionally, in the non-aqueous secondary battery described later, the purpose is to improve cycle characteristics (discharge capacity maintenance rate).

[1-1-6. Other structures]

Other structures included in the copolymer (P) include structures at the terminals of the molecular chain and structures other than the above structures branched from the main chain.

Examples of the structure of the molecular chain terminal include a structure derived from a polymerization initiator, a structure derived from a chain transfer agent, etc. In addition, the substituent (c) does not have a structure at the terminal of the molecular chain even if n = 1 in General Formula (1), for example. The content of the terminal structure in the copolymer (P) is preferably 10% by mass or less, more preferably 2.0% by mass or less, and still more preferably 1.0% by mass or less. This is to further increase the effect of the above structure in the copolymer (P). Additionally, in the structure derived from one chain transfer agent, there is only one bonding site to the molecular chain of the copolymer (P).

Structures other than the above structures contained in the copolymer (P) include a carboxyl group. When the copolymer (P) has a carboxyl group, the amount of the carboxyl group contained per 1 g of the copolymer (P) is preferably 0.030 mmol/g or more, and more preferably 1.5 mmol/g or more. The amount of carboxyl groups contained per 1g of copolymer (P) is preferably 5.0 mmol/g or less, and more preferably 3.0 mmol/g or less.

Copolymer (P) includes any of the main chain containing bonds between carbon atoms, substituent (c), ester bond, amide bond, salt of carboxyl group, structural unit (d), structural unit (e), and carboxyl group. You may include structures that are not used. The content rate is preferably 0.50 mmol/g or less, more preferably 0.30 mmol/g or less, and even more preferably 0.10 mmol/g or less. This is to more strongly exhibit the effects of the functional groups and structures contained in the copolymer (P).

[1-1-7. Examples of suitable configurations of copolymer (P)]

An example of a suitable configuration of the copolymer (P) is the structural unit (a) represented by the general formula (4), the structural unit (b) represented by the general formula (5), and the substituent represented by the general formula (1) ( A copolymer having c) can be mentioned. In this copolymer, the molecular chain terminal may have a structure derived from an initiator, a structure derived from a chain transfer agent, etc. The content of each structural unit is determined depending on the amount of functional group and structure introduced into the copolymer (P). The amounts of functional groups and structures contained in the copolymer (P) are as described above. In this example, the total content of the structural unit (a), structural unit (b), and substituent (c) in the copolymer (P) is preferably 97.0% by mass or more, and more preferably 98.0% by mass or more, It is more preferable that it is 99.0 mass% or more.

Another example of a suitable configuration of the copolymer (P) is that, in addition to the structural unit (a), the structural unit (b) and the substituent (c), it has one or both of the structural units (d) and (e) above. A copolymer may be mentioned. In this copolymer, the molecular chain terminal may have a structure derived from an initiator, a structure derived from a chain transfer agent, etc. The content of each structural unit is determined depending on the amount of functional groups and structures introduced into the copolymer (P). The amounts of functional groups and structures contained in the copolymer (P) are as described above. In this example, the total content of the structural unit (a), structural unit (b), substituent (c), structural unit (d), and structural unit (e) in the copolymer (P) is 97.0% by mass or more. It is preferable, it is more preferable that it is 98.0 mass % or more, and it is still more preferable that it is 99.0 mass % or more.

〔1-2. [Method for producing copolymer (P)]

The method for producing the copolymer (P) is not particularly limited, but in the presence of a polyfunctional thiol compound (C) having two or more mercapto groups in one molecule, a monomer (M) having an ethylenically unsaturated bond is reacted with a radical. Polymerization is preferred. Polymerization is preferably carried out in an aqueous medium. As a polymerization procedure, for example, a method of polymerizing by adding all the monomers (M) used for polymerization at once, a method of polymerizing while continuously supplying the monomers (M) used for polymerization, etc. can be applied. The polymerization temperature is not particularly limited, but is preferably 30°C or higher and 90°C or lower.

As the monomer (M), it is preferable to use a monomer (A) having an amide bond or a monomer (B) having a salt of a carboxyl group to simplify the manufacturing process. When synthesizing the copolymer (P) containing the structural unit (d), it is preferable to use the monomer (D) represented by the general formula (10) described later to simplify the manufacturing process. When synthesizing the copolymer (P) containing the structural unit (e), it is preferable to use the monomer (E) represented by the general formula (11) described later to simplify the manufacturing process. In addition, without using these monomers, the necessary functional groups may be formed through a reaction after polymerization, etc.

[1-2-1. monomer (A)]

Monomer (A) has an ethylenically unsaturated bond and an amide bond. In addition, when monomer (A) has a salt of a carboxyl group, this monomer (A) also corresponds to monomer (B). The monomer (A) preferably has a (meth)acryloyloxy group. This is because the polymerization rate is improved and the productivity of the copolymer (P) is improved. It is more preferable that the monomer (A) has a structure represented by the following general formula (7).

In general formula (7), R ¹¹ and R ¹² have the same configuration as those in general formula (4). Particularly preferred embodiments of monomer (A) are N-vinylformamide (R ¹¹ :H or R ¹² :H) or N-vinylacetamide (R ¹¹ :H or R ¹² :CH ₃ ). This is because the amount of amide bonds relative to the mass of monomer (A) is large, so more amide bonds can be included in the copolymer (P).

[1-2-2. monomer (B)]

Monomer (B) has a salt of an ethylenically unsaturated bond and a carboxyl group. In addition, when monomer (B) has an amide bond, this monomer (B) also corresponds to monomer (A). The monomer (B) preferably has a (meth)acryloyloxy group. This is because the polymerization rate is improved and the productivity of the copolymer (P) is improved. It is more preferable that the monomer (B) has a structure represented by the following general formula (8).

R ² and X in General Formula (8) have the same configuration as those in General Formula (5). As the monomer (B), two or more types of compounds with different X in General Formula (8) may be used. For example, as the monomer (B), two types of compounds, lithium salt and sodium salt, may be used.

[1-2-3. Multifunctional thiol compound (C)]

The polyfunctional thiol compound (C) has two or more mercapto groups. The polyfunctional thiol compound (C) preferably has a structure represented by the following general formula (9). This is because it is inexpensive and readily available, the reaction rate is improved, and the productivity of the copolymer (P) is improved.

R ³² in general formula (9) has the same structure as in general formula (1). R ³³ is a hydrocarbon group. f represents the number of corresponding substituents directly bonded to R ³³ (number of branches of the structure in parentheses). f≥2.

It is preferable that f≥3, and it is more preferable that f≥4. This is because a crosslinked structure can be formed in the copolymer (P), and the peeling strength and toughness of the electrode active material layer containing the copolymer (P) against the current collector are improved. Also, although not particularly limited, it is preferable that f≤6, more preferably f≤5, even more preferably f≤4, and most preferably f=4. This is because the flexibility of the electrode active material layer containing the copolymer (P) is improved.

In General Formula (9), R ³³ may be a straight-chain hydrocarbon group or a hydrocarbon group with a branched structure. The number of carbon atoms contained in R ³³ is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. Additionally, R ³³ preferably does not have an ethylenically unsaturated bond. This is because it suppresses bias in the crosslinking density and excessive crosslinking density.

The thiol equivalent (molecular weight per mercapto group) of the polyfunctional thiol compound (C) is preferably 400 or less, more preferably 300 or less, and still more preferably 200 or less. This is because the polyfunctional thiol compound (C) improves the effect of molecular chain extension and/or the crosslinking density of the copolymer (P), and the peeling strength of the electrode active material layer from the current collector and the toughness of the electrode active material layer are improved. .

For the same reason, when the polyfunctional thiol compound (C) is a compound represented by formula (9), if the molecular weight of the polyfunctional thiol compound (C) is MC, it is preferable that MC/f≤400, and MC It is more preferable that /f≤300, and even more preferably MC/f≤200.

Examples of the polyfunctional thiol compound (C) include pentaerythritol = tetrakis (3-mercaptobutyrate), pentaerythritol = tetrakis (3-mercaptopropionate), trimethylolpropane = tris (3- mercaptobutyrate), trimethylolpropane=tris(3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, 1,4-bis(3-mer Captobutyryloxy)butane, tetraethylene glycol=bis(3-mercaptopropionate), dipentaerythritol=hexakis(3-mercaptopropionate), etc. Among these compounds, the monomer (C) is pentaerythritol = tetrakis (3-mercaptobutyrate), pentaerythritol = tetrakis (3-mercaptopropionate), and trimethylolpropane = tris (3-mercapto). butyrate), and 1,4-bis(3-mercaptobutyryloxy)butane.

[1-2-4. monomer (D)]

Monomer (D) is expressed by the following general formula (10).

In general formula (10), R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ , j and k have the same configuration as those in general formula (2).

In general formula (10), it is more preferable that k=0. Examples of the monomer (D) where k=0 include mono(meth)acrylate of polyethylene glycol, and more specifically, methoxypolyethylene glycol (meth)acrylate (e.g., monomer d1 in Table 1) , d2), etc. An example of methoxypolyethylene glycol methacrylate is VISIOMER (registered trademark) MPEG2005 MA W manufactured by EVONIK INDUSTRIES. In this product, R ⁴¹ =CH ₃ , R ⁴² =H, R ⁴⁴ =CH ₃ , j=45, k=0. Other examples of methoxypolyethylene glycol methacrylate include VISIOMER (registered trademark) MPEG5005 MA W manufactured by EVONIK INDUSTRIES, and in this product, R ⁴¹ =CH ₃ , R ⁴² =H, R ⁴⁴ =CH ₃ , j=113, k=0.

Other examples of the monomer (D) where k=0 include mono(meth)acrylate of polypropylene glycol, and more specifically, methoxypolypropylene glycol (meth)acrylate, etc.

[1-2-5. monomer (E)]

Monomer (E) is expressed by the following general formula (11).

R ⁵¹ and R ⁵² in general formula (11) have the same configuration as those in general formula (3).

The monomer (E) is preferably represented by the following general formula (12).

R ⁵¹ , R ⁵³ and R ⁵⁴ in general formula (12) are the same as those in general formula (6).

As monomer (E), for example, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth) Acrylate, ethoxylated-o-phenylphenol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, etc. are mentioned. Among these compounds, it is more preferable to use one or both of benzyl (meth)acrylate and phenoxyethyl (meth)acrylate as the monomer (E).

[1-2-7. polymerization initiator]

In the case of radical polymerization, examples of polymerization initiators include hydrogen peroxide, t-butylhydroperoxide, and azo compounds, but are not limited to these. Examples of the azo compound include 2,2'-azobis(2-methylpropionamidine) dihydrochloride. When polymerization is performed in water, it is preferable to use a water-soluble polymerization initiator. Additionally, if necessary, redox polymerization may be performed by using a radical polymerization initiator and a reducing agent together during polymerization. Examples of reducing agents include sodium bisulfite, rongalite, asrbic acid, and the like. Additionally, when using an azo compound as a polymerization initiator, components that assist in the generation of radicals from the azo compound, such as persulfate, may be added, but these components do not constitute the copolymer (P). Examples of persulfate include ammonium persulfate and potassium persulfate.

[1-2-8. aqueous medium]

It is preferable to use water as the aqueous medium, but as long as the polymerization stability of the resulting binder copolymer is not impaired, a hydrophilic solvent added to water may be used as the aqueous medium. Examples of hydrophilic solvents added to water include methanol, ethanol, and N-methylpyrrolidone.

[1-2-9. Chain transfer system]

During polymerization, a chain transfer agent may be used for the purpose of controlling the molecular weight of the copolymer (P). The chain transfer agent is not particularly limited, but examples include monofunctional thiols such as β-mercaptopropionic acid and octyl thioglycolate, alcohols such as isopropyl alcohol and ethanol, halogenated hydrocarbons such as carbon tetrabromide and carbon tetrachloride, and α- Methyl styrene dimer, etc. can be mentioned.

[1-2-10. [Content of each component in polymerization component]

If the compound that becomes part of the structure of the copolymer (P) through a polymerization reaction is referred to as a polymerization component, the polymerization component includes each monomer, a chain transfer agent, and a polymerization initiator. The composition of the polymerization component is determined depending on the amount of functional groups and structures introduced into the copolymer (P). In the case of radical polymerization, unless there is an operation to change a specific functional group, each monomer becomes a structural unit of the copolymer (P) without reacting in parts other than the ethylenically unsaturated bond. In addition, in the case of radical polymerization, all polyfunctional thiol compounds (C) become substituents (c) of the copolymer (P), unless there is an operation to change a specific functional group.

In the synthesis of copolymer (P), a form in which monomer (D) and monomer (E) are not used, and a form in which one or both of monomer (D) and monomer (E) are used.

Hereinafter, the appropriate usage amount of each monomer and polyfunctional thiol compound (C) used to obtain the copolymer (P) according to the present invention will be explained, but is not limited to this. Here, when the monomer, polyfunctional thiol compound (C), polymerization initiator, and chain transfer agent used in the synthesis of the copolymer (P) are used, the chain transfer agent is also collectively referred to as the polymerization component.

The amount of monomer (A) contained per 1 g of polymerization component is preferably 0.050 mmol/g or more, more preferably 0.085 mmol/g or more, and even more preferably 0.40 mmol/g or more. The amount of monomer (A) contained per 1 g of polymerization component is preferably 5.0 mmol/g or less, more preferably 3.0 mmol/g or less, further preferably 1.7 mmol/g or less, and especially 0.90 mmol/g or less. desirable.

The amount of monomer (B) contained per 1 g of polymerization component is preferably 5.0 mmol/g or more, more preferably 6.0 mmol/g or more, and even more preferably 7.0 mmol/g or more. The amount of monomer (B) contained per 1 g of polymerization component is preferably 12.0 mmol/g or less, and more preferably 9.9 mmol/g or less. In addition, when multiple carboxylic acid ions corresponding to the structure of monomer (B) are bonded to a divalent or higher cation, it is assumed that there are a number of monomers (B) bonded to the cation.

The amount of polyfunctional thiol compound (C) contained per 1 g of polymerization component is 0.15 × 10 ^-2 mmol/g or more, preferably 0.30 × 10 ^-2 mmol/g or more, and 0.65 × 10 ^-2 mmol/g or more. It is more preferable. The amount of polyfunctional thiol compound (C) contained per 1 g of polymerization component is 8.0 × 10 ^-2 mmol/g or less, preferably 5.5 × 10 ^-2 mmol/g or less, and 4.0 × 10 ^-2 mmol/g or less. It is more preferable, and it is even more preferable that it is 1.4×10 ^-2 mmol/g or less.

The content of monomer (D) in the polymerization component is preferably 0.50 mass% or more, more preferably 0.70 mass% or more, and even more preferably 3.5 mass% or more. The content of monomer (D) in the polymerization component is preferably 20.0% by mass or less, more preferably 14.0% by mass or less, and even more preferably 7.0% by mass or less.

The amount of monomer (E) contained per 1 g of polymerization component is preferably 0.030 mmol/g or more, more preferably 0.045 mmol/g or more, and even more preferably 0.30 mmol/g mass% or more. The amount of monomer (E) contained per 1 g of polymerization component is preferably 1.75 mmol/g or less, preferably 1.50 mmol/g mass % or less, and more preferably 0.90 mmol/g mass % or less.

The content of the chain transfer agent in the polymerization component is not particularly limited, but is preferably 0.10 mass% or more, more preferably 0.25 mass% or more, and even more preferably 0.35 mass% or more. The content of the chain transfer agent in the polymerization component is not particularly limited, but is preferably 10% by mass or less, more preferably 2.0% by mass or less, and even more preferably 0.70% by mass or less.

The amount of chain transfer agent contained per 1 g of polymerization component is preferably 1.0×10 ^-2 mmol/g or more, more preferably 2.0×10 ^-2 mmol/g or more, and even more preferably 3.0×10 ^-2 mmol/g or more. desirable. The amount of chain transfer agent contained per 1 g of polymerization component is preferably 20×10 ^-2 mmol/g or less, more preferably 10×10 ^-2 mmol/g or less, and even more preferably 7.0×10 ^-2 mmol/g or less. desirable.

The content of the polymerization initiator in the polymerization component is preferably 0.020 mass% or more, more preferably 0.10 mass% or more, and even more preferably 0.15 mass% or more. The content of the polymerization initiator in the polymerization component is preferably 1.0 mass% or less, more preferably 0.50 mass% or less, and even more preferably 0.35 mass% or less. Here, components that do not form the structure of copolymer (P), such as a reducing agent, and that assist the function of a polymerization initiator are not included.

The amount of polymerization initiator contained per 1 g of polymerization component is preferably 0.10×10 ^-2 mmol/g or more, more preferably 0.20×10 ^-2 mmol/g or more, and even more preferably 0.50×10 ^-2 mmol/g or more. desirable. The amount of polymerization initiator contained per 1 g of polymerization component is preferably 5.0×10 ^-2 mmol/g or less, more preferably 2.0×10 ^-2 mmol/g or less, and even more preferably 1.0×10 ^-2 mmol/g or less. desirable. Here, components that do not form the structure of copolymer (P), such as a reducing agent, and that assist the function of a polymerization initiator are not included.

As an example of a method for synthesizing copolymer (P), the total content of the monomer represented by formula (7) and the monomer represented by formula (8) in monomer (M) (all monomers) is 90% by mass or more, It is preferable that it is 95 mass % or more, and a structure where it is more preferable that it is 100 mass % is mentioned.

Another example is a configuration in which one or both of the monomer (D) and the monomer (E) are used. In this example, among monomers (M) (all monomers), there is a monomer represented by formula (7), a monomer represented by formula (8), a monomer represented by formula (10), and a monomer represented by formula (11). The total content of monomers is 90% by mass or more, preferably 95% by mass or more, and more preferably 100% by mass.

〔1-3. [Method for producing non-aqueous secondary battery electrode binder]

The method for producing a non-aqueous secondary battery electrode binder includes a polymerization step of radically polymerizing a monomer (M) having an ethylenically unsaturated bond in the presence of a polyfunctional thiol compound (C) having two or more mercapto groups in one molecule. do.

The manufacturing method of the non-aqueous secondary battery electrode binder may be the same as the manufacturing method of the copolymer (P), or additional steps may be added. The method for producing copolymer (P) is as described above. Additional processes include, for example, a purification process and an additive mixing process.

<2. Binder composition for non-aqueous secondary battery electrode>

The non-aqueous secondary battery electrode binder composition (hereinafter sometimes referred to as “electrode binder composition”) of this embodiment contains an electrode binder and an aqueous medium. Additionally, the electrode binder composition may contain other components, such as a pH adjuster and a surfactant, if necessary.

The aqueous medium included in the electrode binder composition includes water. The aqueous medium contained in the electrode binder composition may contain a hydrophilic solvent. Examples of hydrophilic solvents include methanol, ethanol, and N-methylpyrrolidone. The content of water in the aqueous medium contained in the electrode binder composition is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

The composition of the aqueous medium contained in the electrode binder composition may be the same as or different from the aqueous medium used for synthesis of the copolymer (P). In addition, in the electrode binder composition of this embodiment, the electrode binder may be dissolved or dispersed in the aqueous medium.

The content of the copolymer (P) in the electrode binder composition is preferably 30% by mass or less, and more preferably 20% by mass or less. This is to suppress an increase in the viscosity of the electrode binder composition and to efficiently disperse the electrode active material, etc. when producing an electrode slurry by mixing it with the electrode active material, etc., which will be described later.

The content of the copolymer (P) in the electrode binder composition is preferably 3.0 mass% or more, more preferably 5.0 mass% or more, and even more preferably 8.0 mass% or more. This is because electrode slurry and electrodes can be manufactured with less electrode binder composition.

The pH of the electrode binder composition is preferably 4.0 or higher, more preferably 5.0 or higher, and even more preferably 6.0 or higher. This is to efficiently disperse the electrode active material, etc., when producing an electrode slurry by mixing it with the electrode active material, etc., which will be described later. The pH of the electrode binder composition is preferably 11 or less, more preferably 10 or less, and even more preferably 9.0 or less. This is to efficiently disperse the electrode active material, etc., when producing an electrode slurry by mixing it with the electrode active material, etc., which will be described later. Here, pH is a value measured with a pH meter at a liquid temperature of 23°C.

<3. Non-aqueous secondary battery electrode slurry>

In the non-aqueous secondary battery electrode slurry (hereinafter sometimes referred to as “electrode slurry”) of this embodiment, the electrode binder and the electrode active material are dissolved or dispersed in an aqueous medium. The electrode slurry of this embodiment may contain a conductive additive, a thickener, etc. as needed, but in order to simplify the electrode slurry preparation process, it is preferable not to contain a thickener. The method of preparing the electrode slurry is not particularly limited, but includes, for example, a method of mixing the necessary components using a mixing device such as a stirring type, a rotating type, or a shaking type.

The nonvolatile content concentration of the electrode slurry is preferably 30% by mass or more, and more preferably 40% by mass or more. This is to form more electrode active material layers with a small amount of electrode slurry. The nonvolatile content concentration of the electrode slurry is preferably 70% by mass or less, and more preferably 60% by mass or less. The non-volatile matter concentration can be adjusted by the amount of aqueous medium.

Here, the non-volatile content concentration means that, unless otherwise specified, 1 g of the mixture is weighed on an aluminum plate with a diameter of 5 cm, dried at 130°C for 1 hour while circulating air in a dryer at atmospheric pressure, and the mass of the remaining components is calculated as the weight before drying. It is a ratio to mass.

〔3-1. [Content of copolymer (P) in electrode slurry]

The content of the copolymer (P) in the electrode slurry is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more, based on the total mass of the electrode active material (described later), the conductive additive (described later), and the electrode binder. And, it is more preferable that it is 2.0 mass% or more. This is because the copolymer (P) can ensure binding properties between electrode active materials and between the electrode active material and the current collector. The content of the copolymer (P) in the electrode slurry is preferably 10% by mass or less, more preferably 7.0% by mass or less, and even more preferably 4.0% by mass or less, based on the total mass of the electrode active material, conductive additive, and electrode binder. desirable. This is because the charge/discharge capacity of the electrode active material layer formed from the electrode slurry can be increased, and the internal resistance when used as a battery can also be lowered.

〔3-2. Electrode active material]

The non-aqueous secondary battery is not particularly limited, but in the case of a lithium ion secondary battery, examples of the negative electrode active material include conductive polymers, carbon materials, lithium titanate, silicon, and silicon compounds. Examples of the conductive polymer include polyacetylene, polypyrrole, and the like. As carbon materials, coke such as petroleum coke, pitch coke, and coal coke; carbides of organic compounds; Graphites such as artificial graphite and natural graphite can be mentioned. Examples of the silicon compound include SiO _x (0.1≤x≤2.0).

Additionally, as the electrode active material, a composite material containing Si and graphite (Si/graphite), etc. may be used. Among these active materials, it is preferable to use carbon materials, lithium titanate, silicon, and silicon compounds because they have a high energy density per volume. In addition, if it is a carbon material such as coke, carbide of an organic compound, or graphite, or a silicon-containing material such as _SiO The effect is remarkable. For example, a specific example of artificial graphite is SCMG (registered trademark) -XRs (manufactured by Showa Denko Co., Ltd.). Additionally, as a negative electrode active material, two or more types of materials mentioned here may be combined.

Examples of positive electrode active materials for lithium ion secondary batteries include lithium cobaltate (LiCoO ₂ ), lithium composite oxide containing nickel, spinel-type lithium manganate (LiMn ₂ O ₄ ), olivine-type lithium iron phosphate, TiS ₂ , and MnO ₂ , MoO ₃ , V ₂ O ₅ , and other chalcogen compounds. The positive electrode active material may contain any one of these compounds individually, or may contain multiple types. Additionally, oxides of other alkali metals can also be used. Examples of the lithium composite oxide containing nickel include Ni-Co-Mn-based lithium composite oxide, Ni-Mn-Al-based lithium composite oxide, and Ni-Co-Al-based lithium composite oxide. Specific examples of the positive electrode active material include LiNi _1/3 Mn _1/3 Co _1/3 O ₂ and LiNi _3/5 Mn _1/5 Co _1/5 .

〔3-3. Challenge supplement〕

The electrode slurry may contain carbon black, vapor-grown carbon fiber, etc. as a conductive additive. Specific examples of vapor-processed carbon fiber include VGCF (registered trademark)-H (Showa Denko Co., Ltd.).

〔3-4. Aqueous medium]

The aqueous medium of the electrode slurry includes water. The aqueous medium of the electrode slurry may contain a hydrophilic solvent. Examples of hydrophilic solvents include methanol, ethanol, and N-methylpyrrolidone. The water content in the aqueous medium is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The composition of the aqueous medium of the electrode slurry may be the same as or different from the aqueous medium contained in the electrode binder composition.

<4. Electrode>

The electrode of this embodiment has a current collector and an electrode active material layer formed on the surface of the current collector. The electrode active material layer contains the electrode active material and the electrode binder of this embodiment. The shape of the electrode includes, for example, a laminated body or a wound body, but is not particularly limited. The current collector is preferably a metal sheet with a thickness of 0.001 to 0.5 mm. Examples of metals of the current collector include iron, copper, aluminum, nickel, and stainless steel. When the non-aqueous secondary battery is a lithium ion secondary battery, aluminum is preferred as the positive electrode current collector, and copper is preferred as the negative electrode current collector, but is not particularly limited.

The electrode of this embodiment can be manufactured, for example, by applying an electrode slurry onto a current collector and drying it, but the method is not limited to this method.

Methods for applying the electrode slurry onto the current collector include, for example, the reverse roll method, direct roll method, doctor blade method, knife method, extrusion method, curtain method, gravure method, bar method, dipping method, and squeeze method. there is. Among these, the doctor blade method, knife method, or extrusion method is preferable, and application using a doctor blade is more preferable. This is because it is suitable for various physical properties such as the viscosity of the electrode slurry and drying properties, and a coating film with a good surface condition can be obtained.

The electrode slurry may be applied to only one side of the current collector or to both sides. When applying the electrode slurry to both sides of the current collector, it may be applied on one side at a time or on both sides simultaneously. In addition, the electrode slurry may be applied continuously to the surface of the current collector or may be applied intermittently. The application amount and application range of the electrode slurry can be appropriately determined depending on the size of the battery, etc. The weight per unit area of the electrode active material layer after drying is preferably 4 to 20 mg/cm2, and more preferably 6 to 16 mg/cm2.

An electrode sheet is obtained by drying the electrode slurry applied to the current collector. The drying method is not particularly limited, but for example, hot air, vacuum, (far) infrared rays, electron beams, microwaves, and low-temperature air can be used alone or in combination. The drying temperature is preferably 40°C or more and 180°C or less, and the drying time is preferably 1 minute or more and 30 minutes or less.

The electrode sheet may be used as an electrode as is, but may be cut to obtain an appropriate size or shape as an electrode. The cutting method of the electrode sheet is not particularly limited, but for example, slit, laser, wire cut, cutter, Thomson, etc. can be used.

Before or after cutting the electrode sheet, you may press it as needed. This allows the electrode active material to be firmly bound to the electrode and makes the electrode thinner, making it possible to compact the non-aqueous battery. As the press method, any general method can be used, and it is particularly preferable to use the mold press method or the roll press method. The press pressure is not particularly limited, but is preferably set to 0.5 to 5 t/cm2, which is a range that does not affect doping/undedoping of lithium ions or the like into the electrode active material by pressing.

<5. battery>

As a preferred example of the battery according to this embodiment, a lithium ion secondary battery will be described, but the configuration of the battery is not limited to the configuration described below. In the lithium ion secondary battery according to the example described here, components such as a positive electrode, a negative electrode, an electrolyte, and, if necessary, a separator are accommodated in an external body. At least one of the positive electrode and the negative electrode contains the electrode binder according to this embodiment.

<5-1. Electrolyte >

As the electrolyte solution, a non-aqueous liquid with ionic conductivity is used. Examples of the electrolyte solution include a solution in which an electrolyte is dissolved in an organic solvent, an ionic liquid, etc., but the former is preferable because the manufacturing cost is low and a battery with low internal resistance can be obtained.

As the electrolyte, an alkali metal salt can be used, and can be appropriately selected depending on the type of electrode active material, etc. Electrolytes include, for example, 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, etc. Additionally, other alkali metal salts can be used as the electrolyte.

The organic solvent that dissolves the electrolyte is not particularly limited, but examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and methyl ethyl carbonate (MEC). , carbonate ester compounds such as dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC), nitrile compounds such as acetonitrile, ethyl acetate, propyl acetate, methyl propionate, and propionic acid. and carboxylic acid esters such as ethyl and propyl propionate. These organic solvents may be used individually by one type, or may be used in combination of two or more types.

<5-2. External body>

As the exterior body, metal, aluminum laminate, etc. can be appropriately used. The shape of the battery may be any shape, such as coin shape, button shape, sheet shape, cylindrical shape, square shape, or flat shape.

Example

Below, the present invention will be described in more detail by showing examples and comparative examples for the negative electrode binder, negative electrode slurry, negative electrode, and lithium ion secondary battery. Additionally, the present invention is not limited to these examples.

<1. Negative bonding agent>

〔1-1. [Synthesis of copolymer]

The composition of each monomer, polyfunctional thiol compound (C), and chain transfer agent used in Examples 1 to 20 and Comparative Examples 1 to 5 are shown in Tables 2 to 4. Here, each monomer, polyfunctional thiol compound (C), chain transfer agent, and polymerization initiator shown in Tables 2 to 4 are referred to as polymerization components. Hereinafter, details of each raw material compound shown in Tables 2 to 4 are as follows. When used as a monomer solution, the amount of monomer used in the table represents the amount of the monomer itself without solvent.

Additionally, the polymerization initiator has some parts that are not introduced into the polymer, such as nitrogen that is desorbed. However, since the amount of polymerization initiator used is small, in Tables 2 to 4, the content rate (mass %) of each component in the polymerization component and the number of moles of each component per 1 g of the polymerization component are the structures corresponding to each component in the produced copolymer. It can be determined by the content rate of and the number of moles of the structure corresponding to each component per 1 g of copolymer.

Monomer (A-1): N-vinylacetamide (NVA)

Monomer (B-1): Sodium acrylate (AaNa) (28.5% by mass aqueous solution)

Monomer (B-2): Lithium acrylate (AaLi) (28.5% by mass aqueous solution),

Aa: Acrylic acid

Multifunctional thiol compound (C-1): pentaerythritol tetrakis (3-mercaptobutyrate)

Multifunctional thiol compound (C-2): Trimethylolpropanetris(3-mercaptobutyrate)

Polyfunctional thiol compound (C-3): 1,4-bis(3-mercaptobutyryloxy)butane

Multifunctional thiol compound (C-4): pentaerythritol tetrakis(3-mercaptopropionate)

Monomer (D-1): Methoxypolyethylene glycol methacrylate (manufactured by EVONIK INDUSTRIES; VISIOMER (registered trademark) MPEG2005 MA W) (R ⁴¹ =CH ₃ , R ⁴² =H, R ⁴⁴ =CH in general formula (10) 50.0% by mass aqueous solution of ₃ , j=45, k=0, j+k=45)

Monomer (E-1): Benzyl acrylate

MPA: β-mercaptopropionic acid

TMA: tetramethylolmethanetetraacrylate

Polymerization initiator: 2,2'-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd.; V-50) and ammonium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.)

In a separable flask equipped with a cooling tube, thermometer, stirrer, and dropping funnel, a total of 100 parts by mass of polymerization components of the composition (Tables 2 to 4) corresponding to each Example and Comparative Example and 0.050 parts by mass of ammonium persulfate were added. , 693 parts by mass of water were added at 30°C. This was heated to 80°C and polymerized for 4 hours to synthesize copolymers P1 to CP20 and copolymers CP1 to CP5, respectively.

〔1-2. Production of negative electrode binder composition]

To the reaction solution in which the copolymer was obtained, water was added so that the non-volatile matter concentration was 10.0% by mass (the amount of water added was adjusted considering the water contained in the monomer (B-1)), and negative electrode binder compositions Q1 to Q20 and CQ1 to CQ5 were prepared. was prepared. In the following description, when copolymers P1 to P20 are referred to without distinction, they may be referred to as copolymer (P), and when copolymers CP1 to CP5 are referred to without distinction, they may be referred to as copolymer (CP). When the negative electrode binder compositions Q1 to Q20 are referred to without distinction, they may be referred to as the negative electrode binder composition (Q), and when the negative electrode binder compositions CQ1 to CQ5 are referred to without distinction, they may be referred to as the negative electrode binder composition (CQ).

〔1-3. Weight average molecular weight of copolymer (P)]

The weight average molecular weight of the copolymer (P) and copolymer (CP) was measured under the following conditions using gel permeation chromatography (GPC), and the measurement results are shown in Table 4.

GPC device: GPC-101 (manufactured by Showa Denko Co., Ltd.)

Solvent: 0.1M NaNO ₃ aqueous solution

Sample Column: Shodex Column Ohpak SB-806 HQ (8.0mm I.D. x300mm)×2

Reference column: Shodex Column Ohpak SB-800 RL (8.0mm I.D. x300mm) × 2

Column temperature: 40℃

Sample concentration: 0.1 mass%

Detector: RI-71S (manufactured by Shimazu Seisakusho Co., Ltd.)

Pump: DU-H2000 (made by Shimazu Seisakusho Co., Ltd.)

Pressure: 1.3MPa

Flow rate: 1ml/min

Molecular weight standards: Pullulan (P-5, P-10, P-20, P-50, P-100, P-200, P-400, P-800, P-1300, P-2500 (Showa Denko ( subject))

<2. Negative electrode slurry>

〔2-1. Production of negative electrode slurry]

As graphite, 76.8 parts by mass of SCMG (registered trademark)-XRs (manufactured by Showa Denko Co., Ltd.), 19.2 parts by mass of silicon monoxide (SiO) (manufactured by Sigma-Aldrich), and VGCF (registered trademark)-H (manufactured by Showa Denko) 1.0 parts by mass of Denko Co., Ltd.), 30 parts by mass of binder composition (Q) (including 3.0 parts by mass of copolymer (P) and 27 parts by mass of water), and 20 parts by mass of water were mixed. Mixing was performed by kneading at 2000 revolutions/min for 4 minutes using a stirring mixing device (autorotating mixing mixer). An additional 53 parts by mass of water was added to the obtained mixture, and the mixture was further mixed at 2000 revolutions/min for 4 minutes in the above mixing device to prepare a negative electrode slurry.

〔2-2. Appearance evaluation of negative electrode slurry]

The appearance of the produced negative electrode slurry was visually confirmed, and the size of the aggregates was measured with a micrometer. The case where there was an aggregate of 1 mm or more in the longest dimension in 10 g of negative electrode slurry was designated as ×, and the case where there was no aggregate was designated as ○. The evaluation results are shown in Table 5.

<3. Negative pole>

〔3-1. Flexibility of negative electrode active material layer (winding test)]

The negative electrode slurry produced as described above was applied to both sides of a 10-μm-thick copper foil (current collector) using a doctor blade so that the weight per unit area after drying was 8 mg/cm2. The copper foil to which the negative electrode slurry was applied was dried at 60°C for 10 minutes and then dried again at 100°C for 5 minutes to produce a negative electrode sheet on which a negative electrode active material layer was formed. This negative electrode sheet was pressed at a press pressure of 1 t/cm2 using a mold press.

The negative electrode sheet pressed here was cut into a width of 50 mm and a length of 60 mm to prepare a test piece. This test piece was dried at 80°C for 12 hours. One side of the dried test piece in the width direction was fixed to a stainless steel bar with a diameter of 3 mm using a single-sided adhesive tape with a thickness of 50 μm (the width direction of the test piece and the longitudinal direction of the stainless steel bar were parallel). The other side of the test piece in the width direction was fixed to a glass plate. After the test piece was wound around this stainless steel bar, the test piece was visually observed to observe its appearance, and the number of cracks in the test piece was counted.

〔3-2. Peeling strength of negative electrode active material layer to current collector]

A pressed negative electrode sheet was produced in the same manner as the above evaluation of flexibility, except that the negative electrode slurry was applied to both sides of the copper foil so that the weight per unit area after drying was 8 mg/cm2.

Using the negative electrode sheet pressed here, the entire process was carried out in an atmosphere of 23°C and a relative humidity of 50% by mass. The tester used was Tensilon (registered trademark, A&D Co., Ltd.). The negative electrode sheet was cut to 25 mm in width and 70 mm in length to prepare a test piece. The negative electrode active material layer on the test piece and the SUS plate with a width of 50 mm and a length of 200 mm were joined using double-sided tape (NITTOTAPE (registered trademark) No5, manufactured by Nitto Denko Co., Ltd.) so that the center of the test piece coincides with the center of the SUS plate. did. Additionally, double-sided tape was bonded to cover the entire area of the test piece. Bonding was performed by reciprocating a 2 kg roller once over the entire test piece.

After leaving the test piece and the SUS plate together for 10 minutes, peel the copper foil from the negative electrode active material by 20 mm in the longitudinal direction from one end of the test piece, fold it 180°, and place the peeled portion of the copper foil in the chuck on the upper side of the testing machine. I grabbed it. Additionally, one end of the SUS plate on the side from which the copper foil was peeled was held by the lower chuck. In that state, the copper foil was peeled from the test piece at a rate of 100 ± 10 mm/min, and a graph of peeling length (mm) - peeling force (mN) was obtained. In the obtained graph, the average value (mN) of the peeling force in the peeling length of 10 to 45 mm is calculated, and the average value of the peeling force divided by the width of the test piece 25 mm is referred to as the peeling strength of the negative electrode active material layer (mN/mm). did. Additionally, in any 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 negative electrode active material layer did not occur during the test.

<4. Lithium ion secondary battery>

〔4-1. Manufacturing of batteries]

[Negative pole]

The pressed negative electrode sheet was cut into 22 mm x 22 mm, and a conductive tab was installed to produce a negative electrode.

[Positive pole]

90 parts by mass of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , 5 parts by mass of acetylene black, and 5 parts by mass of polyvinylidene fluoride were mixed, and then 100 parts by mass of N-methylpyrrolidone were mixed. A positive electrode slurry was prepared (the ratio of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ in the solid content was 0.90).

The prepared positive electrode slurry is spread on one side of a 20㎛ thick aluminum foil (current collector) using the doctor blade method so that the weight per unit area after drying is 22.5 mg/cm2 (22.5×10 ^-3 g/cm2). and applied it. The aluminum foil coated with the positive electrode slurry was dried at 120°C for 5 minutes and then pressed with a roll press to produce a positive electrode sheet with a positive electrode active material layer having a thickness of 100 μm. The obtained positive electrode sheet was cut into 20 mm x 20 mm (2.0 cm x 2.0 cm), and a conductive tab was installed to produce a positive electrode.

The theoretical capacity of the produced positive electrode is: weight per unit area after drying of the positive electrode slurry (22.5 × 10 ^-3 g/cm2) × application area of the positive electrode slurry ( _2.0 cm × _2.0 cm ₎ The capacity of _/3 O ₂ as a positive electrode active material (160 mAh/g) × the ratio of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ in the solid content (0.90) is calculated, and the calculated value is 13 mAh.

[Electrolyte]

In a mixed solvent of ethylene carbonate (EC), ethylmethyl carbonate (EMC), and fluoroethylene carbonate (FEC) in a volume ratio of 30:60:10, 1.0 mol/L of LiPF ₆ and vinylene were added. Carbonate (VC) was dissolved to a concentration of 1.0 mass% to prepare an electrolyte solution.

[Assembling the battery]

The positive electrode and the negative electrode were arranged so that each active material layer faced each other through a separator containing a polyolefin porous film, and were stored in an aluminum laminated exterior body (battery pack). An electrolyte solution was injected into this exterior body and packed with a vacuum heat sealer to obtain a laminated battery.

〔4-2. Evaluation of battery cycle characteristics (discharge capacity maintenance rate)]

The cycle characteristics of each battery produced in each Example and Comparative Example were evaluated. The evaluation method is as follows, and the evaluation results are as shown in Table 5.

Measurement of the discharge capacity maintenance rate of the battery (charge/discharge cycle test of the battery) was conducted under the conditions of 25°C and using the following procedures. First, it was charged with a current of 1C until the voltage reached 4.2V (CC charging), and then it was charged with a voltage of 4.2V until the current reached 0.05C (CV charging). After leaving for 30 minutes, it was discharged with a current of 1C until the voltage reached 2.75V (CC discharge). A series of operations of CC charging, CV charging, and CC discharging are performed as one cycle. The sum of the time integral values of the current in the nth cycle CC charging and CV charging is the nth cycle charge capacity (mAh), and the time integral value of the current in the nth cycle CC discharge is the nth cycle discharge. Capacity (mAh). The discharge capacity maintenance rate of the nth cycle of a battery is the ratio (%) of the discharge capacity of the nth cycle to the discharge capacity of the first cycle. In this example and comparative example, the discharge capacity maintenance rate at the 100th cycle was evaluated.

<5. Evaluation results>

As can be seen from Table 5, the negative electrode slurries produced in Examples 1 to 20 generate little aggregates. It can be seen that the negative electrodes produced in Examples 1 to 20 had few cracks generated in the winding test and the flexibility of the electrode active material layer was high. The negative electrodes produced in Examples 1 to 20 also had high peeling strength from the current collector of the negative electrode active material layer. It can be seen that the lithium ion secondary batteries produced in Examples 1 to 20 have a high discharge capacity maintenance rate accompanying use of the battery, that is, excellent cycle characteristics.

In Comparative Example 1, a negative electrode slurry was produced using copolymer CP1 without an amide bond. The negative electrode slurry produced in Comparative Example 1 contained aggregates. The negative electrode slurry produced in Comparative Example 1 could not be coated evenly on the current collector, and an evaluable negative electrode and battery could not be produced.

In Comparative Example 2, a negative electrode slurry, a negative electrode, and a lithium ion secondary battery were produced using copolymer CP2 containing excessive amide bonds. The electrode slurry produced in Comparative Example 2 contained aggregates. In the negative electrode produced in Comparative Example 2, the negative electrode active material layer slipped and fell during the winding test. Additionally, in Comparative Example 2, the peeling strength of the negative electrode active material layer from the current collector was low. The lithium ion secondary battery produced in Comparative Example 2 had a low discharge capacity maintenance rate.

In Comparative Example 3, a negative electrode slurry, a negative electrode, and a lithium ion secondary battery were produced using copolymer CP3 without the substituent (c). In the negative electrode produced in Comparative Example 3, many cracks occurred in the negative electrode active material layer after the winding test, and it was found that the flexibility of the negative electrode was low. Additionally, in Comparative Example 3, the peeling strength of the negative electrode active material layer from the current collector was low. The lithium ion secondary battery produced in Comparative Example 3 had a low discharge capacity maintenance rate.

In Comparative Example 4, an attempt was made to synthesize a copolymer CP4 containing an excessive amount of the substituent (c) by using a large amount of the polyfunctional thiol compound (C), but the product gelled and an evaluable negative electrode slurry could not be produced.

In Comparative Example 5, a negative electrode slurry, a negative electrode, and a lithium ion secondary battery were prepared using copolymer CP5, which does not contain a substituent (c) and contains a structural unit derived from tetrafunctional acrylate (tetramethylomethane tetraacrylate). produced. In the negative electrode produced in Comparative Example 5, many cracks occurred in the negative electrode active material layer after the winding test, and it was found that the flexibility of the negative electrode was low. Additionally, in Comparative Example 5, the peeling strength of the negative electrode active material layer from the current collector was low. The lithium ion secondary battery produced in Comparative Example 5 had a low discharge capacity maintenance rate.

Therefore, by using the binder copolymer according to this example as a binder for a non-aqueous battery negative electrode, sufficient binding property between the negative electrode active materials and between the negative electrode active material and the current collector in the non-aqueous battery negative electrode is ensured, and flexibility is maintained. It was found that this gave good charge/discharge cycle characteristics as a battery.

Additionally, these binders can also be used as binders for positive electrodes of non-aqueous batteries, and batteries with good charge/discharge cycle characteristics can be produced while ensuring sufficient binding properties between positive electrode active materials and between the positive electrode active materials and the current collector.

Claims (14)

It is a non-aqueous secondary battery electrode binder containing a copolymer (P),
The copolymer (P) is,
a main chain containing only bonds between carbon atoms,
A substituent having an amide bond,
A substituent having a salt of a carboxyl group,
Substituent (c) represented by the general formula (1) below:
With
The substituent having the amide bond, the substituent having the salt of the carboxyl group, and the substituent (c) are each bonded to the main chain,
The amount of amide bond contained per 1g of the copolymer (P) is 0.050 mmol/g or more and 5.0 mmol/g or less,
The amount of salt of the carboxyl group contained per 1g of the copolymer (P) is 5.0 mmol/g or more and 12.0 mmol/g or less,
The amount of the substituent (c) contained per 1g of the copolymer (P) is 0.15 × 10 ^-2 mmol/g or more and 8.0 × 10 ^-2 mmol/g or less.
A non-aqueous secondary battery electrode binder, characterized in that.

(In General Formula (1), R ³¹ is a hydrocarbon group, m and n each represent the number of the corresponding substituent directly bonded to R ³¹ , m is an integer of 0 or more, n is an integer of 1 or more, m +n≥2.) The non-aqueous secondary battery electrode binder according to claim 1, wherein in the general formula (1), R ³¹ contains a carbon atom and a hydrogen atom. The non-aqueous secondary battery electrode binder according to claim 1 or 2, wherein in the general formula (1), R ³¹ has a plurality of carbon atoms, and all bonds between carbon atoms are single bonds. The non-aqueous secondary battery electrode binder according to claim 1 or 2, wherein Mc/(m+n)≤400, assuming that the formula of the substituent (c) is Mc. The method according to claim 1 or 2, wherein the substituent (c) is a structure derived from a polyfunctional thiol compound (C), and the polyfunctional thiol compound (C) has two or more mercapto groups in one molecule. Aqueous secondary battery electrode binder. The non-aqueous secondary battery according to claim 1 or 2, wherein the copolymer (P) further contains 0.50% by mass or more and 20.0% by mass or less of the structural unit (d) represented by the following general formula (2). Electrode binder.

(In General Formula (2), R ⁴¹ , R ⁴² , and R ⁴⁴ are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ⁴³ is an alkyl group having 1 to 6 carbon atoms, and has more carbon atoms than R ⁴² The number of is large. j and k each mean the number of the structures in the corresponding parentheses being combined in series. j is an integer greater than 1, k is an integer greater than 0, and j+k≥20.) The method according to claim 1 or 2, wherein the copolymer (P) further contains a structural unit (e) represented by the following general formula (3) at 0.030 mmol/g per 1 g of the copolymer (P). A non-aqueous secondary battery electrode binder containing more than 1.75 mmol/g or less.

(In General Formula (3), R ⁵¹ represents a hydrogen atom or a methyl group, and R ⁵² is a substituent having an aromatic ring.) The non-aqueous secondary battery electrode according to claim 1 or 2, wherein in the copolymer (P), at least a part of the amide bond is contained as a structural unit (a) represented by the following general formula (4) Binding agent.

(In General Formula (4), R ¹¹ and R ¹² each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.) The non-aqueous secondary battery electrode according to claim 1 or 2, wherein in the copolymer (P), at least a part of the salt of the carboxyl group is contained as a structural unit (b) represented by the following general formula (5) Binding agent.

(In General Formula (5), R ² represents a hydrogen atom or a methyl group, and X is a cation.) The non-aqueous secondary battery electrode binder according to claim 1 or 2, wherein the weight average molecular weight of the copolymer (P) is 700,000 or more and 7.5 million or less. A non-aqueous secondary battery electrode binder composition comprising the non-aqueous secondary battery electrode binder according to claim 1 or 2 and an aqueous medium. Equipped with a current collector and an electrode active material layer formed on the surface of the current collector,
A non-aqueous secondary battery electrode in which the electrode active material layer contains the binder for a non-aqueous secondary battery electrode according to claim 1 or 2 and an electrode active material. Contains a positive electrode, a negative electrode, and an electrolyte,
A non-aqueous secondary battery, wherein at least one of the positive electrode and the negative electrode is the non-aqueous secondary battery electrode according to claim 12. Producing a non-aqueous secondary battery electrode binder comprising a polymerization step of radically polymerizing a monomer (M) having an ethylenically unsaturated bond in the presence of a polyfunctional thiol compound (C) having two or more mercapto groups in one molecule. It is a method,
The monomer (M) includes a monomer (A) having an amide bond and a monomer (B) having a salt of a carboxyl group,
When using the monomer (M), the polyfunctional thiol compound (C), a polymerization initiator, and a chain transfer agent, if the chain transfer agent is also considered a polymerization component,
The amount of the monomer (A) contained per 1g of the polymerization component is 0.050 mmol/g or more and 5.0 mmol/g or less,
The amount of the monomer (B) contained per 1g of the polymerization component is 5.0 mmol/g or more and 12.0 mmol/g or less,
The amount of the polyfunctional thiol compound (C) contained per 1 g of the polymerization component is 0.15 × 10 ^-2 mmol/g or more and 8.0 × 10 ^-2 mmol/g or less.
A method for producing a non-aqueous secondary battery electrode binder, characterized in that.