阅读说明：本技术 非水系二次电池电极用粘结剂组合物及其制造方法、非水系二次电池电极用浆料组合物、非水系二次电池用电极以及非水系二次电池 (Binder composition for nonaqueous secondary battery electrode, method for producing same, slurry composition for nonaqueous secondary battery electrode, electrode for nonaqueous secondary battery, and) 是由 赤羽彻也 木所广人 堀田华纶 于 2019-03-05 设计创作，主要内容包括：本发明提供一种能够形成剥离强度优异的电极和循环特性优异的二次电池的非水系二次电池电极用粘结剂组合物。非水系二次电池电极用粘结剂组合物含有颗粒状聚合物和受阻酚系抗氧化剂,上述颗粒状聚合物包含具有亲水性接枝链的接枝聚合物,该具有亲水性接枝链的接枝聚合物是使合计为1质量份以上且40质量份以下的亲水性单体和/或大分子单体与100质量份的核颗粒进行接枝聚合反应形成的,该核颗粒包含嵌段共聚物,该嵌段共聚物含有由芳香族乙烯基单体单元形成的芳香族乙烯基嵌段区域和包含异戊二烯单元的异戊二烯嵌段区域,该异戊二烯嵌段区域的含有比例为70质量％以上且99质量％以下。(The invention provides a binder composition for a nonaqueous secondary battery electrode, which can form an electrode with excellent peeling strength and a secondary battery with excellent cycle characteristics. The binder composition for nonaqueous secondary battery electrodes contains a particulate polymer and a hindered phenol antioxidant, wherein the particulate polymer contains a graft polymer having a hydrophilic graft chain, the graft polymer having the hydrophilic graft chain is formed by graft polymerization of a hydrophilic monomer and/or a macromonomer, which is 1 to 40 parts by mass in total, and 100 parts by mass of a core particle, the core particle contains a block copolymer, the block copolymer contains an aromatic vinyl block region formed of an aromatic vinyl monomer unit and an isoprene block region containing an isoprene unit, and the content ratio of the isoprene block region is 70 to 99% by mass.)

1. A binder composition for a nonaqueous secondary battery electrode, comprising a particulate polymer and a hindered phenol antioxidant,

the particulate polymer comprises a graft polymer having hydrophilic graft chains,

the graft polymer having a hydrophilic graft chain is formed by graft-polymerizing a hydrophilic monomer and/or a macromonomer in a total amount of 1 to 40 parts by mass with 100 parts by mass of the core particle,

the core particle includes a block copolymer including an aromatic vinyl block region formed of an aromatic vinyl monomer unit and an isoprene block region including an isoprene unit, and the content ratio of the isoprene block region is 70 mass% or more and 99 mass% or less.

2. The binder composition for a non-aqueous secondary battery electrode according to claim 1, further comprising a phosphite-based antioxidant.

3. The binder composition for a non-aqueous secondary battery electrode according to claim 1 or 2, further comprising a metal-trapping agent.

4. The binder composition for a nonaqueous secondary battery electrode according to any one of claims 1 to 3, wherein the median diameter of the particulate polymer is 0.6 μm or more and 2.5 μm or less.

5. The binder composition for nonaqueous secondary battery electrodes according to any one of claims 1 to 4, wherein the hydrophilic graft chain has an acid group,

the particulate polymer has a surface acid amount of 0.02mmol/g to 1.0 mmol/g.

6. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 5, further comprising a particulate binder,

the particulate binder material comprises a styrene-butadiene copolymer and/or an acrylic polymer.

7. The binder composition for a non-aqueous secondary battery electrode according to claim 6, wherein the content of the particulate polymer is 50% by mass or more and 90% by mass or less of the total content of the particulate polymer and the particulate binder.

8. A slurry composition for a nonaqueous secondary battery electrode, comprising an electrode active material and the binder composition for a nonaqueous secondary battery electrode according to any one of claims 1 to 7.

9. An electrode for a nonaqueous secondary battery, comprising an electrode composite material layer formed using the slurry composition for a nonaqueous secondary battery electrode according to claim 8.

10. A nonaqueous secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolyte,

at least one of the positive electrode and the negative electrode is the electrode for a nonaqueous secondary battery according to claim 9.

11. A method for producing the binder composition for a nonaqueous secondary battery electrode according to any one of claims 1 to 7, comprising the steps of:

a step of emulsifying a mixture of a solution containing a block copolymer, a hindered phenol antioxidant and an aqueous medium, to obtain core particles, the block copolymer containing an aromatic vinyl block region composed of aromatic vinyl monomer units and an isoprene region containing isoprene units, the isoprene block region containing a proportion of 70 mass% or more and 99 mass% or less; and

and a step of forming hydrophilic graft chains on the core particles to obtain a particulate polymer containing a graft polymer.

12. The method for producing a binder composition for a non-aqueous secondary battery electrode according to claim 11, wherein the mixture further contains a phosphite antioxidant.

13. The method for producing a binder composition for a non-aqueous secondary battery electrode according to claim 11 or 12, wherein the mixture further contains a metal-trapping agent.

14. The method for producing a binder composition for a non-aqueous secondary battery electrode according to any one of claims 11 to 13, wherein the mixture further contains a coupling agent,

mixing a solution of the block copolymer, the hindered phenol antioxidant, the aqueous medium, and the coupling agent to obtain the mixture before the emulsification.

15. The method for producing a binder composition for a non-aqueous secondary battery electrode according to any one of claims 11 to 13, further comprising a step of adding a coupling agent to an emulsion containing the core particles between the step of obtaining the core particles and the step of obtaining the particulate polymer.

Technical Field

The present invention relates to a binder composition for a nonaqueous secondary battery electrode, a method for producing a binder composition for a nonaqueous secondary battery electrode, a slurry composition for a nonaqueous secondary battery electrode, an electrode for a nonaqueous secondary battery, and a nonaqueous secondary battery.

Background

Nonaqueous secondary batteries such as lithium ion secondary batteries (hereinafter, may be simply referred to as "secondary batteries") have characteristics of being small in size, light in weight, high in energy density, and capable of being repeatedly charged and discharged, and have been used in a wide range of applications. Therefore, in recent years, for the purpose of further improving the performance of nonaqueous secondary batteries, improvements in battery members such as electrodes have been studied.

Here, an electrode used for a secondary battery such as a lithium ion secondary battery generally has a current collector, and an electrode composite material layer (a positive electrode composite material layer or a negative electrode composite material layer) formed on the current collector. The electrode composite layer may be formed by, for example, applying a slurry composition containing a binder composition and the like on a current collector, and drying the applied slurry composition, wherein the binder composition contains an electrode active material and a binder.

Therefore, in recent years, in order to achieve further performance improvement of secondary batteries, improvement of a binder composition for forming an electrode composite layer has been attempted.

Specifically, for example, patent documents 1 and 2 propose techniques in which an antioxidant is added to a binder composition in order to improve the cycle characteristics of a secondary battery.

Disclosure of Invention

Problems to be solved by the invention

However, the above conventional binder composition for nonaqueous secondary battery electrodes containing an antioxidant has room for improvement in terms of improving the cycle characteristics of the secondary battery and further improving the peel strength of an electrode formed using the binder composition.

Accordingly, an object of the present invention is to provide a binder composition for a nonaqueous secondary battery electrode and a slurry composition for a nonaqueous secondary battery electrode, which can form an electrode having excellent peel strength and a secondary battery having excellent cycle characteristics.

Further, an object of the present invention is to provide an electrode for a nonaqueous secondary battery having excellent peel strength and capable of forming a secondary battery having excellent cycle characteristics, and a nonaqueous secondary battery having excellent cycle characteristics.

Means for solving the problems

The inventors have conducted intensive studies in order to solve the above problems. Then, the present inventors have found that, when a binder composition comprising a particulate polymer and a predetermined antioxidant is used, and the particulate polymer contains a predetermined polymer, an electrode having excellent peel strength and a secondary battery having excellent cycle characteristics can be obtained, and have completed the present invention.

That is, the present invention has been made to solve the above problems, and an object of the present invention is to provide a binder composition for a nonaqueous secondary battery electrode, which contains a particulate polymer and a hindered phenol antioxidant, wherein the particulate polymer contains a graft polymer having a hydrophilic graft chain, the graft polymer having the hydrophilic graft chain being formed by grafting a hydrophilic monomer and/or a macromonomer in a total amount of 1 part by mass or more and 40 parts by mass or less, and 100 parts by mass of a core particle, the core particle contains a block copolymer, the block copolymer contains an aromatic vinyl block region formed of an aromatic vinyl monomer unit and an isoprene block region containing an isoprene unit, and the content ratio of the isoprene block region is 70% by mass or more and 99% by mass or less. As described above, if the particulate polymer and the predetermined antioxidant are contained and the particulate polymer contains the predetermined polymer, the peel strength of the electrode formed using the binder composition and the cycle characteristics of the secondary battery can be improved.

In the present invention, the term "monomer unit" of a polymer means "a repeating unit derived from the monomer contained in a polymer obtained using the monomer".

In the present invention, the phrase "the polymer has a block region formed of a monomer unit" means "a portion linked and bonded as a repeating unit only by the monomer unit is present in the polymer".

In the present invention, the "content ratio of isoprene block region" can be used¹H-NMR was measured.

Here, the binder composition for a nonaqueous secondary battery electrode of the present invention preferably further contains a phosphite antioxidant. When the binder composition further contains a phosphite antioxidant, the peel strength of an electrode formed using the binder composition and the cycle characteristics of a secondary battery can be further improved.

In addition, the binder composition for a nonaqueous secondary battery electrode of the present invention preferably further contains a metal scavenger. When the metal-trapping agent is further contained, the peel strength of the electrode formed using the binder composition and the cycle characteristics of the secondary battery can be further improved.

Further, the binder composition for a nonaqueous secondary battery electrode of the present invention is preferably such that the median diameter of the particulate polymer is 0.6 μm or more and 2.5 μm or less. If the median diameter of the particulate polymer is within the above range, the peel strength of the electrode formed using the binder composition and the cycle characteristics of the secondary battery can be further improved.

In the present invention, the "median diameter of the particulate polymer" can be measured by the method described in the examples of the present specification.

In addition, in the binder composition for a nonaqueous secondary battery electrode of the present invention, it is preferable that the hydrophilic graft chain has an acid group, and the surface acid amount of the particulate polymer is 0.02mmol/g to 1.0 mmol/g. When the amount of the surface acid of the particulate polymer is within the above range, the peel strength of an electrode formed using the binder composition and the cycle characteristics of a secondary battery can be further improved.

In the present invention, the "surface acid amount" of the particulate polymer means the surface acid amount per 1g of the solid content of the particulate polymer, and can be measured by the measurement method described in the examples of the present specification.

Furthermore, the binder composition for a nonaqueous secondary battery electrode of the present invention preferably further comprises a particulate binder, and the particulate binder contains a styrene-butadiene copolymer and/or an acrylic polymer. When a particulate binder containing a styrene-butadiene copolymer and/or a particulate binder containing an acrylic polymer is further contained, the cycle characteristics of a secondary battery formed using the binder composition can be further improved.

In the binder composition for a nonaqueous secondary battery electrode of the present invention, the content of the particulate polymer is preferably 50 mass% or more and 90 mass% or less of the total content of the particulate polymer and the particulate binder. When the content of the particulate polymer is within the above range, the peel strength of an electrode formed using the binder composition and the cycle characteristics of a secondary battery can be further improved.

The present invention is also directed to solving the above-mentioned problems, and a slurry composition for a nonaqueous secondary battery electrode according to the present invention is characterized by containing any one of the above-mentioned binder compositions for a nonaqueous secondary battery electrode and an electrode active material. When the binder composition for a nonaqueous secondary battery electrode is contained in this manner, the peel strength of the electrode formed using the slurry composition and the cycle characteristics of the secondary battery can be improved.

Further, the present invention is directed to advantageously solve the above problems, and an electrode for a nonaqueous secondary battery according to the present invention is characterized by having an electrode composite layer formed using the slurry composition for a nonaqueous secondary battery electrode. Thus, if the slurry composition for a nonaqueous secondary battery electrode is used, an electrode having excellent peel strength, which can form a secondary battery having excellent cycle characteristics, can be obtained.

The present invention is also directed to a nonaqueous secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte solution, wherein at least one of the positive electrode and the negative electrode is the electrode for the nonaqueous secondary battery. When the electrode for a nonaqueous secondary battery is used, a nonaqueous secondary battery having excellent cycle characteristics can be obtained.

The present invention is also directed to a method for producing a binder composition for a nonaqueous secondary battery electrode, the method comprising the steps of: a step of emulsifying a mixture of a solution containing a block copolymer, a hindered phenol antioxidant and an aqueous medium to obtain core particles, the block copolymer containing an aromatic vinyl block region composed of aromatic vinyl monomer units and an isoprene block region containing isoprene units, the isoprene block region containing a proportion of 70 to 99 mass%; and a step of forming hydrophilic graft chains on the core particles to obtain a particulate polymer containing a graft copolymer. In this manner, if a mixture of a solution containing a block copolymer, a hindered phenol antioxidant, and an aqueous medium is emulsified to obtain core particles, and then hydrophilic graft chains are formed on the core particles to obtain a particulate polymer containing a graft copolymer, the binder composition for a non-aqueous secondary battery electrode can be easily obtained.

In the method for producing a binder composition for a nonaqueous secondary battery electrode according to the present invention, it is preferable that the mixture further contains a phosphite antioxidant. When the binder further contains a phosphite antioxidant, the adhesive composition can further improve the peel strength of the electrode and the cycle characteristics of the secondary battery.

In the method for producing a binder composition for a nonaqueous secondary battery electrode according to the present invention, it is preferable that the mixture further contains a metal-trapping agent. When the binder further contains a metal-capturing agent, a binder composition can be obtained which can further improve the peel strength of the electrode and the cycle characteristics of the secondary battery.

In the method for producing a binder composition for a nonaqueous secondary battery electrode according to the present invention, it is preferable that the mixture further contains a coupling agent, and the solution of the block copolymer, the hindered phenol antioxidant, the aqueous medium, and the coupling agent are mixed before the emulsification to obtain the mixture. If the emulsified mixture is made to contain a coupling agent, the particle stability of the particulate polymer comprising the graft polymer can be improved.

Further, in the method for producing a binder composition for a nonaqueous secondary battery electrode according to the present invention, it is preferable that a step of adding a coupling agent to an emulsion containing the core particles is further included between the step of obtaining the core particles and the step of obtaining the particulate polymer. If a coupling agent is added to the emulsion containing the core particle, the particle stability of the particulate polymer containing the graft polymer can be improved.

Effects of the invention

According to the binder composition for a nonaqueous secondary battery electrode and the slurry composition for a nonaqueous secondary battery electrode of the present invention, an electrode having excellent peel strength and a secondary battery having excellent cycle characteristics can be formed.

In addition, the nonaqueous secondary battery electrode of the present invention has excellent peel strength, and can form a secondary battery having excellent cycle characteristics.

Further, according to the present invention, a nonaqueous secondary battery having excellent cycle characteristics can be obtained.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

The binder composition for a nonaqueous secondary battery electrode of the present invention can be used for the preparation of the slurry composition for a nonaqueous secondary battery electrode of the present invention, and can be produced, for example, by using the method for producing a binder composition for a nonaqueous secondary battery electrode of the present invention. The slurry composition for a nonaqueous secondary battery electrode prepared using the binder composition for a nonaqueous secondary battery electrode of the present invention can be used for producing an electrode of a nonaqueous secondary battery such as a lithium ion secondary battery. Further, the nonaqueous secondary battery of the present invention is characterized by using the electrode for a nonaqueous secondary battery of the present invention, and the electrode for a nonaqueous secondary battery is formed using the slurry composition for an electrode of a nonaqueous secondary battery of the present invention.

The binder composition for a nonaqueous secondary battery electrode, the slurry composition for a nonaqueous secondary battery electrode, and the electrode for a nonaqueous secondary battery of the present invention are preferably for a negative electrode, and the nonaqueous secondary battery of the present invention preferably uses the electrode for a nonaqueous secondary battery of the present invention as a negative electrode.

(Binder composition for nonaqueous Secondary Battery electrode)

The binder composition for a nonaqueous secondary battery electrode of the present invention contains a particulate polymer and a hindered phenol-based antioxidant, and further optionally contains at least one selected from the group consisting of a phosphite-based antioxidant, a metal scavenger, and other components (for example, a particulate binder) that can be blended in the binder composition. The binder composition for a nonaqueous secondary battery electrode of the present invention usually further contains a dispersion medium such as water.

Further, the binder composition of the present invention contains a hindered phenol antioxidant, and the particulate polymer contains a graft polymer obtained by graft polymerizing 100 parts by mass of core particles with 1 part by mass or more and 40 parts by mass or less of a hydrophilic monomer and/or a macromonomer in total, the core particles containing a block copolymer containing an aromatic vinyl block region composed of aromatic vinyl monomer units and an isoprene block region composed of isoprene units, the content ratio of the isoprene block region being 70% by mass or more and 99% by mass or less, and therefore, it is possible to form an electrode having excellent peel strength and a secondary battery having excellent cycle characteristics.

< particulate Polymer >

The particulate polymer is a component that functions as a binder, and in the electrode composite material layer formed using the slurry composition containing the binder composition, the particulate polymer keeps components such as an electrode active material from being separated from the electrode composite material layer.

The particulate polymer is a water-insoluble particle formed of the specified graft polymer. In the present invention, the term "water-insoluble" as the polymer particles means that the insoluble content is 90% by mass or more when 0.5g of the polymer is dissolved in 100g of water at a temperature of 25 ℃.

[ graft Polymer ]

A graft polymer forming a particulate polymer is obtained by graft-polymerizing a hydrophilic monomer and/or a macromonomer in a total amount of 1 to 40 parts by mass with 100 parts by mass of a core particle comprising a block copolymer containing an aromatic vinyl block region composed of aromatic vinyl monomer units and an isoprene block region composed of isoprene units, wherein the content ratio of the isoprene block region is 70 to 99% by mass.

[ core particle ]

The block copolymer constituting the core particle contains an aromatic vinyl block region composed of an aromatic vinyl monomer unit and an isoprene block region including an isoprene unit, and further optionally contains a polymer chain portion (hereinafter, may be simply referred to as "other region") in which repeating units other than the aromatic vinyl monomer unit and the isoprene unit are linked. The content of the isoprene region in the block copolymer needs to be 70 mass% or more and 99 mass% or less. The core particle may contain at least one selected from the group consisting of a hindered phenol-based antioxidant, a phosphite-based antioxidant, and a metal scavenger, which will be described in detail later.

The block copolymer may have only 1 aromatic vinyl block region, or may have a plurality of blocks. Similarly, the block copolymer may have only 1 isoprene block region, or may have a plurality of isoprene block regions. Further, the block copolymer may have only 1 other region, or may have a plurality of regions. In addition, the block copolymer preferably has only an aromatic vinyl block region and an isoprene block region.

Aromatic vinyl block region

As described above, the aromatic vinyl block region is a region containing only an aromatic vinyl monomer unit as a repeating unit.

Here, the 1 aromatic vinyl block region may be composed of only 1 aromatic vinyl monomer unit, or may be composed of a plurality of aromatic vinyl monomer units, and is preferably composed of only 1 aromatic vinyl monomer unit.

In addition, in the 1 aromatic vinyl block region, a coupling site may be included (that is, the aromatic vinyl monomer units constituting the 1 aromatic vinyl block region may be linked via the coupling site).

In addition, when the polymer has a plurality of aromatic vinyl block regions, the kinds and proportions of the aromatic vinyl monomer units constituting the plurality of aromatic vinyl block regions may be the same or different, and preferably are the same.

Examples of the aromatic vinyl monomer capable of forming an aromatic vinyl monomer unit constituting the aromatic vinyl block region include aromatic monovinyl compounds such as styrene, styrene sulfonic acid and salts thereof, α -methylstyrene, p-tert-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. Among them, styrene is preferable. These can be used alone in 1 kind, or a combination of 2 or more, preferably used alone in 1 kind.

When the amount of all the repeating units (monomer units and structural units) in the block copolymer is 100% by mass, the proportion of the aromatic vinyl monomer units in the block copolymer is preferably 1% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, preferably 30% by mass or less, and more preferably 25% by mass or less. When the proportion of the aromatic vinyl monomer unit in the block copolymer is not less than the lower limit, the cycle characteristics of the secondary battery can be further improved. On the other hand, if the proportion of the aromatic vinyl monomer unit in the block copolymer is 30% by mass or less, the flexibility of the graft polymer obtained using the block copolymer can be ensured, and the peel strength of the electrode can be further improved.

In addition, the proportion of the aromatic vinyl monomer units in the block copolymer is generally the same as the proportion of the aromatic vinyl block regions in the block copolymer.

-isoprene block domains

The isoprene block region is a region containing an isoprene unit as a repeating unit.

In addition, in the isoprene region, a coupling site may be included (that is, isoprene units constituting 1 isoprene block region may be linked via the coupling site).

Further, the isoprene block region may have a crosslinked structure (that is, the isoprene block region may contain a structural unit obtained by crosslinking isoprene).

Further, the isoprene units contained in the isoprene block region may be hydrogenated (i.e., the isoprene block region may contain a structural unit (isoprene hydride unit) obtained by hydrogenating isoprene).

Further, by crosslinking the polymer including the aromatic vinyl block region and the isoprene block region, a structural unit obtained by crosslinking an isoprene unit can be introduced into the block copolymer.

Here, the crosslinking is not particularly limited, and can be performed using a radical initiator such as a redox initiator obtained by combining an oxidizing agent and a reducing agent. Examples of the oxidizing agent include organic peroxides such as dicumyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, 1,3, 3-tetramethylbutyl hydroperoxide, di-tert-butyl peroxide, isobutyryl peroxide, and benzoyl peroxide. As the reducing agent, a compound containing a metal ion in a reduced state such as ferrous sulfate or cuprous naphthenate; sulfonic acid compounds such as sodium methanesulfonate; amine compounds such as dimethylaniline, and the like. These organic peroxides and reducing agents may be used alone in 1 kind, or in combination in 2 or more kinds.

In addition, crosslinking can be performed with polyvinyl compounds such as divinylbenzene; polyallyl compounds such as diallyl phthalate, triallyl trimellitate, and diethylene glycol bis (allyl carbonate); in the presence of a crosslinking agent such as various esters including ethylene glycol diacrylate. The crosslinking can also be performed by irradiation with an active energy ray such as a gamma ray.

Further, a method for introducing an isoprene hydride unit into the block copolymer is not particularly limited. For example, a method of hydrogenating a polymer including an aromatic vinyl block region and an isoprene block region to convert an isoprene unit into an isoprene hydride unit and obtain a copolymer is preferable because the method facilitates production of a block copolymer.

When the amount of all the repeating units (monomer units and structural units) in the block copolymer is 100 mass%, the total amount of the isoprene units, the structural units formed by crosslinking the isoprene units, and the isoprene hydride units in the block copolymer needs to be 70 mass% or more and 99 mass% or less, preferably 75 mass% or more, preferably 90 mass% or less, and more preferably 85 mass% or less. When the total ratio of the isoprene unit, the structural unit formed by crosslinking the isoprene unit, and the isoprene hydride unit in the block copolymer is less than 70 mass%, the peel strength of the electrode is lowered. When the total ratio of the isoprene unit, the structural unit formed by crosslinking the isoprene unit, and the isoprene hydride unit in the block copolymer exceeds 99 mass%, the cycle characteristics of the secondary battery deteriorate.

The proportion of the isoprene unit, the structural unit formed by crosslinking the isoprene unit, and the isoprene hydride unit in the block copolymer is generally the same as the proportion of the isoprene block region in the block copolymer.

Other zones

As described above, the other region is a region containing only a repeating unit other than the aromatic vinyl monomer unit and the isoprene unit (hereinafter, may be simply referred to as "other repeating unit") as a repeating unit.

Here, the 1 other region may be composed of only 1 other repeating unit or may be composed of a plurality of other repeating units.

In addition, in 1 other region, may contain a coupling site (i.e., the 1 other region of the other repeating units can be connected through the coupling site).

In addition, when the polymer has a plurality of other regions, the kinds and proportions of the other repeating units constituting the plurality of other regions may be the same or different from each other.

The other repeating units are not particularly limited, and examples thereof include a nitrile group-containing monomer unit such as an acrylonitrile unit and a methacrylonitrile unit; (meth) acrylate monomer units such as alkyl acrylate units and alkyl methacrylate units; acid group-containing monomer units such as a carboxyl group-containing monomer unit, a sulfonic acid group-containing monomer unit, and a phosphoric acid group-containing monomer unit; and an aliphatic conjugated diene monomer unit other than isoprene, a structural unit obtained by crosslinking an aliphatic conjugated diene monomer unit other than isoprene, a structural unit obtained by hydrogenating an aliphatic conjugated diene monomer unit other than isoprene, and the like. Here, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid in the present invention.

[ method for producing core particles ]

The core particle comprising the above block copolymer can be prepared, for example, by the following steps: a step of obtaining a solution of a block copolymer having an aromatic vinyl block region and an isoprene block region by block polymerization of the aromatic vinyl monomer, isoprene or other monomer in an organic solvent (block copolymer solution preparation step); and a step (emulsification step) of adding water to the obtained block copolymer solution to emulsify the solution, thereby granulating the block copolymer.

Preparation procedure of the Block copolymer solution

The method of block polymerization in the block copolymer solution preparation step is not particularly limited. For example, a block copolymer can be prepared by adding a second monomer component different from the first monomer component to a solution in which the first monomer component is polymerized, and polymerizing the mixture, and if necessary, repeating the addition and polymerization of the monomer component. The organic solvent used as the reaction solvent is not particularly limited, and may be appropriately selected depending on the kind of the monomer.

Here, it is preferable that the block copolymer obtained by the block polymerization as described above is supplied to a coupling reaction using a coupling agent before the emulsification step described later. When the coupling reaction is carried out, the end of the diblock structures contained in the block copolymer can be bonded to each other by, for example, a coupling agent to convert the diblock structures into triblock structures (that is, the amount of diblock structure can be reduced).

The coupling agent that can be used in the coupling reaction is not particularly limited, and examples thereof include: a coupling agent with a functionality of 2, a coupling agent with a functionality of 3, a coupling agent with a functionality of 4, and a coupling agent with a functionality of 5 or more.

Examples of coupling agents with a functionality of 2 include: 2-functional halogenated silanes such as dichlorosilane, monomethyldichlorosilane, and dichlorodimethylsilane; 2-functional halogenated alkanes such as dichloroethane, dibromoethane, dichloromethane, and dibromomethane; and 2-functional tin halides such as tin dichloride, monomethyl tin dichloride, dimethyl tin dichloride, monoethyl tin dichloride, diethyl tin dichloride, monobutyl tin dichloride and dibutyl tin dichloride.

Examples of 3-functional coupling agents include: 3-functional halogenated alkanes such as trichloroethane and trichloropropane; 3-functional halogenated silanes such as methyltrichlorosilane and ethyltrichlorosilane; 3-functional alkoxysilanes such as methyltrimethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane.

Examples of 4-functional coupling agents include: 4-functional halogenated alkanes such as carbon tetrachloride, carbon tetrabromide, and tetrachloroethane; 4-functional halogenated silanes such as tetrachlorosilane and tetrabromosilane; 4-functional alkoxysilanes such as tetramethoxysilane and tetraethoxysilane; tin halide with 4-functionality such as tin tetrachloride and tin tetrabromide.

Examples of the coupling agent having a functionality of 5 or more include: 1,1,1,2, 2-pentachloroethane, perchloroethane, pentachlorobenzene, perchlorobenzene, octabromodiphenyl ether, decabromodiphenyl ether, and the like.

These can be used alone in 1 kind, or in combination of more than 2 kinds.

Among the above, dichlorodimethylsilane is preferable as the coupling agent. In addition, a coupling site derived from a coupling agent is introduced into a polymer chain (for example, a triblock structure) constituting the block copolymer by a coupling reaction using the coupling agent.

The solution of the block copolymer obtained after the block polymerization and the optional coupling reaction may be directly supplied to the emulsification step described later, or at least one selected from the group consisting of a hindered phenol-based antioxidant, a phosphite-based antioxidant and a metal scavenger may be added as needed, and preferably, the solution is supplied to the emulsification step after all of the hindered phenol-based antioxidant, the phosphite-based antioxidant and the metal scavenger are added.

-an emulsification procedure-

The method of emulsification in the emulsification step is not particularly limited, and for example, a method of emulsifying a mixture of the solution of the block copolymer obtained in the block copolymer solution preparation step and an aqueous medium is preferable, and a method of emulsifying a premix of the solution of the block copolymer and an aqueous solution of an emulsifier is preferable. Here, as described above, the solution of the block copolymer may contain at least one selected from the group consisting of a hindered phenol-based antioxidant, a phosphite-based antioxidant and a metal trapping agent, and preferably may contain all of them. As described later, the mixture may contain a coupling agent described later. Further, emulsification can use, for example, a known emulsifier and an emulsifying disperser. Specifically, the emulsifying and dispersing machine is not particularly limited, and a batch emulsifying and dispersing machine such as a product name "homogenizer" (IKA corporation), a product name "POLYTRON" (Kinematica corporation), a product name "TK AUTOHOMOMIXER" (Special Industrial products corporation) can be used; a continuous emulsification dispersion machine such as "TK PIPELINOMOMIXER" (manufactured by Special machines), "Colloid Mill" (manufactured by Shen Steel Pantec), "Thrasher" (manufactured by NIPPON COKE & ENGINEERING Co., manufactured by LTD.), and "Tri-party wet micro-crusher" (manufactured by Mitsui Sanchi chemical engineering Co., Ltd.), and "CAVITRON" (manufactured by Eurotec Co., Ltd.), and "Miller" (manufactured by Pacific machines Co., Ltd.), and "Fine flow Mill" (manufactured by Pacific machines Co., Ltd.); high-pressure emulsification dispersion machines such as "Microfluidizer" (manufactured by mizu inustral co., ltd.), "Nanomizer" (manufactured by nanomizerinc), and "APV Gaulin" (manufactured by Gaulin corporation); a membrane emulsification and dispersion machine such as a "membrane emulsifier" (manufactured by cooling industries, Ltd.); a vibration type emulsification and dispersion machine such as "VIBROMIXER" (manufactured by cooling industries, ltd.); an ultrasonic emulsification and dispersion machine such as a trade name "ultrasonic homogenizer" (manufactured by BRANSON). The conditions (for example, treatment temperature, treatment time, and the like) of the emulsification operation by the emulsification dispersion machine are not particularly limited, and may be appropriately selected so as to obtain a desired dispersion state.

If necessary, an aqueous dispersion of core particles containing a block copolymer can be obtained by removing an organic solvent and the like from the emulsion obtained after emulsification by a known method.

[ hydrophilic graft chain ]

The hydrophilic graft chain is not particularly limited, and a hydrophilic monomer or a macromonomer can be graft-polymerized to the block copolymer to be introduced into the block copolymer constituting the core particle.

The hydrophilic monomer is not particularly limited, and examples thereof include a carboxyl group-containing monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a hydroxyl group-containing monomer, and a reactive emulsifier. In addition, as the hydrophilic monomer, there may be mentioned other hydrophilic monomers other than the carboxyl group-containing monomer, the sulfonic acid group-containing monomer, the phosphoric acid group-containing monomer, the hydroxyl group-containing monomer and the reactive emulsifier.

Examples of the carboxyl group-containing monomer include monocarboxylic acid and its derivatives, dicarboxylic acid and its anhydride, and their derivatives.

Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid, and the like.

Examples of the monocarboxylic acid derivative include 2-ethacrylic acid, isocrotonic acid, α -acetoxyacrylic acid, β -trans-aryloxyacrylic acid, α -chloro- β -E-methoxyacrylic acid, and the like.

Examples of the dicarboxylic acid include maleic acid, fumaric acid, and itaconic acid.

Examples of the dicarboxylic acid derivative include maleic acid monoesters such as methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloro maleic acid, dichloro maleic acid, fluoro maleic acid, butyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate.

Examples of the acid anhydride of the dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, and citraconic anhydride.

Further, as the carboxyl group-containing monomer, an acid anhydride which generates a carboxyl group by hydrolysis can also be used.

Further, as the carboxyl group-containing monomer, a partial ester of an ethylenically unsaturated polycarboxylic acid such as butenetricarboxylic acid, monobutyl fumarate, mono-2-hydroxypropyl maleate, or the like can be used.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, vinylsulfonic acid (vinylsulfonic acid), methylvinylsulfonic acid, (meth) allylsulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid.

In the present invention, "(meth) allyl" means allyl and/or methallyl.

Further, examples of the phosphoric acid group-containing monomer include 2- (meth) acryloyloxyethyl phosphate, and ethyl- (meth) acryloyloxyethyl phosphate.

In the present invention, "(meth) acryloyl group" means an acryloyl group and/or a methacryloyl group.

Examples of the hydroxyl group-containing monomer include acrylates having a hydroxyl group in the molecule such as 2-hydroxyethyl acrylate and methacrylates having a hydroxyl group in the molecule such as 2-hydroxyethyl methacrylate.

Examples of the reactive emulsifier include a polyalkylene oxide emulsifier having an anionic functional group and/or a nonionic functional group. In addition, for example, sodium styrenesulfonate, sodium allylalkylsulfonate, alkylallylsulfosuccinate, polyoxyethylene alkylallylglycerol ether sulfate, polyoxyethylene alkylphenol allyllglycerol ether sulfate, and the like can also be used.

Examples of the other hydrophilic monomer include acrylamide, hydroxyethyl acrylamide, vinyl acetate, methoxy-polyethylene glycol polyacrylate, and tetrahydrofurfuryl acrylate.

Here, the hydrophilic monomer may be used alone in 1 kind, or may be used in combination in 2 or more kinds. The hydrophilic monomer is preferably an acidic group-containing monomer such as a carboxyl group-containing monomer, a sulfonic acid group-containing monomer, or a phosphoric acid group-containing monomer, more preferably vinylsulfonic acid, methacrylic acid, itaconic acid, or acrylic acid, still more preferably methacrylic acid or acrylic acid, and particularly preferably methacrylic acid.

The amount of the hydrophilic graft chain introduced by graft polymerization of the hydrophilic monomer is preferably 0.2 parts by mass or more, more preferably 0.8 parts by mass or more, further preferably 2.1 parts by mass or more, preferably 8.4 parts by mass or less, more preferably 7.4 parts by mass or less, and further preferably 6.1 parts by mass or less, based on 100 parts by mass of the particulate polymer.

Examples of the macromonomer include a macromonomer of a polycarboxylic acid polymer, a macromonomer of a polyvinyl alcohol (PVA) polymer, a macromonomer of a polyethylene oxide (PEO) polymer, and a macromonomer of a polyvinylpyrrolidone (PVP) polymer. Among these, the macromonomer of the polycarboxylic acid polymer is preferable.

The amount of the hydrophilic monomer and/or the macromonomer to be reacted with the block copolymer is required to be 1 part by mass or more and 40 parts by mass or less, preferably 2 parts by mass or more, more preferably 5 parts by mass or more, preferably 35 parts by mass or less, more preferably 25 parts by mass or less, per 100 parts by mass of the block copolymer. When the amount of graft polymerization reaction with the block copolymer is outside the above range, the peel strength of the electrode and the cycle characteristics of the secondary battery may be reduced.

[ method for producing graft Polymer ]

Here, the graft polymerization of the hydrophilic graft chain is not particularly limited, and can be performed by a known graft polymerization method. Specifically, the graft polymerization can be carried out using a radical initiator such as a redox initiator obtained by combining an oxidizing agent and a reducing agent. As the oxidizing agent and the reducing agent, as described above, the oxidizing agent and the reducing agent that can be used for crosslinking of the block copolymer including the block region formed of the aromatic vinyl monomer unit and the isoprene block region are exemplified, and the same oxidizing agent and the same reducing agent as those listed in this section can be used.

In addition, in the case where a block copolymer having an aromatic vinyl block region and an isoprene block region is graft-polymerized using a redox initiator, the isoprene unit in the block copolymer may be crosslinked when a hydrophilic graft chain is introduced by graft polymerization. In the preparation of graft polymerization, the graft polymerization may be carried out alone without simultaneously carrying out crosslinking and graft polymerization, or by adjusting the kind and reaction conditions of the radical initiator.

Further, the particulate polymer comprising a graft polymer can be obtained by graft polymerizing the hydrophilic monomer and/or the macromonomer with the core particle comprising the above block copolymer in the above ratio.

Here, the graft polymerization reaction is preferably carried out in the presence of a coupling agent. If the graft polymerization reaction is carried out in the presence of a coupling agent, the particle stability of the resulting particulate polymer can be improved. Further, the graft polymer obtained by graft polymerization in the presence of a coupling agent generally has a coupling site derived from the coupling agent in a hydrophilic graft chain.

The coupling agent that can be present in the reaction system during graft polymerization is not particularly limited, and examples thereof include silane-based coupling agents, titanate-based coupling agents, and aluminate-based coupling agents.

The silane coupling agent is not particularly limited, and examples thereof include alkoxysilanes having a vinyl group, such as vinyltriethoxysilane and vinyltris (2-methoxyethoxy) silane; alkoxysilanes having a methacryloyl group or an acryloyl group such as 3-acryloyloxypropyltrimethoxysilane and 3-methacryloyloxypropyltrimethoxysilane; alkoxysilanes having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane; alkoxysilanes having an amino group such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane; alkoxysilanes having a mercapto group such as 3-mercaptopropyltrimethoxysilane; alkoxysilanes having an isocyanate group such as 3-isocyanatopropyltriethoxysilane; and silazanes such as hexamethyldisilazane, tetramethyldisilazane, divinyltetramethyldisilazane, hexamethylcyclotrisilazane, octamethylcyclotetrasilazane, and the like.

The titanate-based coupling agent is not particularly limited, and examples thereof include isopropyl trioctyl titanate, isopropyl dimethacryloyl isostearyl titanate, isopropyl tristearyl titanate, isopropyl triisostearoyl titanate, isopropyl diacryloyl titanate, dicumylphenyloxyacetate titanate, diisostearoyl vinyl titanate, and bis (dioctylphosphato) oxyacetate titanate. Examples of commercially available titanate coupling agents include KRTTS, KR36B, KR55, KR41B, KR38S, KR138S, KR238S, 338X, KR44, and KR9SA (both of which are AjinomotoFine-Techno co., inc., product name "pleact (registered trademark)").

Further, examples of the aluminate coupling agent include an aluminum alkoxide such as trimethoxy aluminum, triethoxy aluminum, tripropoxy aluminum, triisopropoxyl aluminum, tributoxy aluminum, acetoxy aluminum diisopropoxide (commercially available as "plectant AL-M" manufactured by Ajinomoto Fine-Techno co., inc.).

Among them, a coupling agent having a carboxyl group, a coupling agent having a glycidyl group, or a coupling agent which generates a hydroxyl group by hydrolysis is preferable because the stability of the particles can be further improved.

The coupling agent may be present in the reaction system of graft polymerization by being mixed in the emulsified mixture in the emulsification step, or may be present in the reaction system of graft polymerization by being mixed in an emulsion containing core particles obtained by emulsifying the mixture in the emulsification step.

Here, in the case where the mixture contains the coupling agent, the coupling agent is preferably mixed with the solution of the block copolymer before the solution of the block copolymer and the aqueous medium are mixed, more preferably mixed with the solution of the block copolymer containing at least one selected from the group consisting of a hindered phenol-based antioxidant, a phosphite-based antioxidant and a metal trapping agent before the mixture is mixed with the aqueous medium, and further preferably mixed with the solution of the block copolymer containing all of the hindered phenol-based antioxidant, the phosphite-based antioxidant and the metal trapping agent.

The amount of the coupling agent to be added is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, further preferably 0.1 part by mass or more, preferably 1.0 part by mass or less, more preferably 0.5 part by mass or less, and further preferably 0.2 part by mass or less, based on 100 parts by mass of the block copolymer.

[ surface acid amount ]

In the case where the hydrophilic graft chain formed as described above has an acid group, that is, in the case where a hydrophilic graft chain is formed using an acid group-containing monomer or an acidic group-containing macromonomer, the surface acid amount of the particulate polymer is preferably 0.02mmol/g or more, more preferably 0.04mmol/g or more, still more preferably 0.10mmol/g or more, preferably 1.0mmol/g or less, more preferably 0.90mmol/g or less, and still more preferably 0.70mmol/g or less. If the amount of the surface acid of the particulate polymer is within the above range, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved.

[ median diameter ]

The median diameter of the particulate polymer is preferably 0.6 to 2.5 μm. If the median diameter of the particulate polymer is within the above range, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved.

< hindered phenol antioxidant >

The hindered phenol-based antioxidant contained in the adhesive composition is not particularly limited, and examples thereof include 4- [ [4, 6-bis (octylthio) -1,3, 5-triazin-2-yl ] amino ] -2, 6-di-tert-butylphenol, 2, 6-di-tert-butyl-p-cresol, stearyl 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], and 2,4, 6-tris (3 ', 5 ' -di-tert-butyl-4 ' -hydroxybenzyl) mesitylene. Among them, 4- [ [4, 6-bis (octylthio) -1,3, 5-triazin-2-yl ] amino ] -2, 6-di-t-butylphenol and 2, 6-di-t-butyl-p-cresol are preferable from the viewpoint of suppressing the expansion of the electrode with repetition of charge and discharge, and 4- [ [4, 6-bis (octylthio) -1,3, 5-triazin-2-yl ] amino ] -2, 6-di-t-butylphenol is more preferable from the viewpoint of suppressing the expansion of the electrode with repetition of charge and discharge and improving the peel strength of the electrode.

These hindered phenol antioxidants may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The amount of the hindered phenol antioxidant is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, further preferably 0.03 parts by mass or more, preferably 1.0 parts by mass or less, more preferably 0.50 parts by mass or less, and further preferably 0.30 parts by mass or less, based on 100 parts by mass of the particulate polymer and the particulate binder as an optional component in total. If the content of the hindered phenol antioxidant is not less than the lower limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved, and the expansion of the electrode due to repeated charge and discharge can be suppressed. Further, if the content of the hindered phenol antioxidant is not more than the above upper limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved.

< phosphite-based antioxidant >

The phosphite-based antioxidant that can be optionally contained in the binder composition is not particularly limited, and examples thereof include 3, 9-bis (octadecyloxy) -2,4,8, 10-tetraoxa-3, 9-disphosphite spiro [5.5] undecane, 3, 9-bis (2, 6-di-t-butyl-4-methylphenoxy) -2,4,8, 10-tetraoxa-3, 9-disphosphite spiro [5.5] undecane, 2-methylenebis (4, 6-di-t-butylphenyl) 2-ethylhexyl phosphite, tris (2, 4-di-t-butylphenyl) phosphite, and the like. Among them, 3, 9-bis (octadecyloxy) -2,4,8, 10-tetraoxa-3, 9-diphospho spiro [5.5] undecane and tris (2, 4-di-t-butylphenyl) phosphite are preferable from the viewpoint of suppressing the expansion of the electrode with repetition of charge and discharge, and 3, 9-bis (octadecyloxy) -2,4,8, 10-tetraoxa-3, 9-diphospho spiro [5.5] undecane is more preferable from the viewpoint of suppressing the expansion of the electrode with repetition of charge and discharge and improving the peel strength of the electrode.

These phosphite antioxidants may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The amount of the phosphite-based antioxidant is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, further preferably 0.08 part by mass or more, preferably 0.40 part by mass or less, more preferably 0.30 part by mass or less, and further preferably 0.20 part by mass or less, based on 100 parts by mass of the total of the particulate polymer and the particulate binder as an optional component. When the content of the phosphite antioxidant is not more than the lower limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved. Further, if the content of the phosphite-based antioxidant is not more than the above upper limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved, and the swelling of the electrode with repeated charge and discharge can be suppressed.

When the adhesive composition contains a phosphite antioxidant, the ratio of the content of the hindered phenol antioxidant to the content of the phosphite antioxidant (hindered phenol antioxidant/phosphite antioxidant) is preferably 0.05 or more, more preferably 0.2 or more, preferably 5 or less, and more preferably 3 or less. When the ratio of the hindered phenol-based antioxidant content to the phosphite-based antioxidant content is not less than the lower limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved, and the swelling of the electrode due to repeated charging and discharging can be suppressed. Further, if the ratio of the hindered phenol-based antioxidant content to the phosphite-based antioxidant content is not more than the above upper limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved.

< Metal trapping agent >

The metal-capturing agent that can be optionally contained in the binder composition is not particularly limited, and for example, a chelate compound can be used. The chelating compound is not particularly limited, and a compound selected from the group consisting of aminocarboxylic acid-based chelating compounds, sulfonic acid-based chelating compounds, gluconic acid, citric acid, malic acid, and tartaric acid can be preferably used. Among these, a chelate compound capable of selectively trapping transition metal ions without trapping ions involved in electrochemical reactions is particularly preferable, and an aminocarboxylic acid-based chelate compound and a sulfonic acid-based chelate compound are particularly preferable.

Examples of the aminocarboxylic acid-based chelating compound include ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), trans-1, 2-diaminocyclohexanetetraacetic acid (CyDTA), diethylene-triaminepentaacetic acid (DTPA), bis- (aminoethyl) glycolether-N, N '-tetraacetic acid (EGTA), N- (2-hydroxyethyl) ethylenediamine-N, N' -triacetic acid (HEDTA), and Dihydroxyethylglycine (DHEG).

Examples of the sulfonic acid chelating agent compound include 1-hydroxyethane-1, 1-disulfonic acid (HEDP).

Among the above, EDTA and CyDTA are preferable from the viewpoint of suppressing the electrode from expanding with repeated charge and discharge, and EDTA is more preferable from the viewpoint of suppressing the electrode from expanding with repeated charge and discharge and improving the peel strength of the electrode.

These chelating compounds can be used alone in 1, or can be combined with more than 2.

The amount of the metal scavenger is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, further preferably 0.03 parts by mass or more, preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, and further preferably 0.3 parts by mass or less, based on 100 parts by mass of the particulate polymer and the particulate binder as an optional component in total. If the content of the metal scavenger is not less than the lower limit value, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved, and the expansion of the electrode due to repeated charge and discharge can be suppressed. Further, if the content of the metal scavenger is not more than the above upper limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved.

In addition, when the adhesive composition contains the phosphite antioxidant and the metal scavenger, the ratio of the content of the metal scavenger to the total content of the hindered phenol antioxidant and the phosphite antioxidant (metal scavenger/hindered phenol antioxidant + phosphite antioxidant) is preferably 0.05 or more, more preferably 0.1 or more, preferably 1 or less, and more preferably 0.8 or less. When the ratio of the content of the metal trapping agent to the total content of the hindered phenol-based antioxidant and the phosphite-based antioxidant is not less than the lower limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved, and the expansion of the electrode due to repeated charge and discharge can be suppressed. Further, if the ratio of the content of the metal scavenger to the total content of the hindered phenol-based antioxidant and the phosphite-based antioxidant is not more than the above upper limit, the peel strength of the electrode and the cycle characteristics of the secondary battery can be further improved.

< aqueous Medium >

The aqueous medium contained in the binder composition of the present invention is not particularly limited as long as it contains water, and may be an aqueous solution or a mixed solution of water and a small amount of an organic solvent.

< other ingredients >

The binder composition of the present invention may contain components (other components) other than the above components. For example, the binder composition may contain a known particulate binder material (styrene-butadiene copolymer and/or acrylic polymer, etc.) other than the above-described particulate polymer.

The median diameter of the particulate binder is preferably 0.01 μm or more and 0.5 μm or less, more preferably 0.05 μm or more, still more preferably 0.1 μm or more, still more preferably 0.4 μm or less, and yet more preferably 0.3 μm or less. If the median diameter of the particulate binder is not less than the lower limit, the peel strength of the electrode can be further improved. Further, if the median diameter of the particulate binder is not more than the above upper limit, the cycle characteristics of the secondary battery can be improved. In the present invention, the "median diameter of the particulate binder" can be measured by the method described in the examples of the present specification.

When the binder composition contains the particulate binder, the content of the particulate polymer is preferably 50% by mass or more, more preferably 55% by mass or more, further preferably 60% by mass or more, preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less of the total content of the particulate polymer and the particulate binder. When the content of the particulate polymer is not less than the lower limit, the peel strength of the electrode produced using the binder composition can be further improved. Further, if the content of the particulate polymer is not more than the above upper limit, the cycle characteristics of the secondary battery formed using the binder composition can be further improved.

In addition, the binder composition may include a water-soluble polymer. The water-soluble polymer is a component capable of favorably dispersing the compounding component such as the particulate polymer in an aqueous medium, and is not particularly limited, but is preferably a synthetic polymer, and more preferably an addition polymer produced by addition polymerization. The water-soluble polymer may be in the form of a salt (salt of the water-soluble polymer). That is, in the present invention, the "water-soluble polymer" also includes a salt of the water-soluble polymer. In the present invention, the term "water-soluble" means that the insoluble content is less than 1.0% by mass when 0.5g of the polymer is dissolved in 100g of water at a temperature of 25 ℃.

In addition, the binder composition may contain known additives. Examples of such known additives include antioxidants such as 2, 6-di-t-butyl-p-cresol, defoaming agents, and dispersing agents (except for additives belonging to the above water-soluble polymer).

Further, 1 kind of the other component may be used alone, or 2 or more kinds may be used in combination at an arbitrary ratio.

< method for producing adhesive composition >

The binder composition of the present invention is not particularly limited, and can be prepared by mixing the particulate polymer, the hindered phenol antioxidant, and optionally other components in the presence of an aqueous medium.

Furthermore, the binder composition of the present invention can be prepared as follows: the method for producing the graft polymer comprises emulsifying a mixture comprising a solution of the block copolymer, a hindered phenol-based oxidizing agent and an aqueous medium, and optionally a phosphite-based antioxidant and/or a metal-capturing agent, optionally removing the organic solvent to obtain an aqueous dispersion of core particles, forming hydrophilic graft chains on the core particles to prepare an aqueous dispersion of a particulate polymer comprising a graft polymer, optionally adding other components to the aqueous dispersion, and mixing. Further, the adhesive composition of the present invention can be prepared as follows: the method for producing the graft polymer comprises emulsifying a mixture comprising a solution of the block copolymer, a hindered phenol-based oxidizing agent, an aqueous medium, a coupling agent, and optionally a phosphite-based antioxidant and/or a metal trapping agent, optionally removing the organic solvent to obtain an aqueous dispersion of core particles, forming hydrophilic graft chains on the core particles to prepare an aqueous dispersion of a particulate polymer comprising the graft polymer, optionally adding other components to the aqueous dispersion, and mixing. Further, the adhesive composition of the present invention can be prepared as follows: the method for producing the graft polymer comprises emulsifying a mixture comprising a solution of the block copolymer, a hindered phenol-based oxidizing agent and an aqueous medium, and optionally a phosphite-based antioxidant and/or a metal-capturing agent, optionally removing the organic solvent to obtain an aqueous dispersion (emulsion) of core particles, adding a coupling agent, forming hydrophilic graft chains on the core particles to obtain an aqueous dispersion of a particulate polymer comprising a graft polymer, optionally adding other components to the aqueous dispersion, and mixing. As described above, if the mixture is emulsified by adding a hindered phenol antioxidant or the like, a binder composition for a nonaqueous secondary battery electrode, which contains a hindered phenol antioxidant or the like favorably, can be easily obtained.

In the case of preparing the binder composition using a dispersion of the particulate polymer and/or an aqueous solution of the water-soluble polymer, the liquid component contained in the dispersion and/or the aqueous solution may be used as it is as an aqueous medium of the binder composition.

(slurry composition for nonaqueous Secondary Battery electrode)

The slurry composition of the present invention is a composition for use in forming an electrode composite material layer of an electrode, and includes the binder composition and further contains an electrode active material. That is, the slurry composition of the present invention contains the particulate polymer, the hindered phenol-based antioxidant, the electrode active material, and the aqueous medium, and further optionally contains at least one selected from the group consisting of a phosphite-based antioxidant, a metal scavenger, and other components. Further, since the slurry composition of the present invention contains the binder composition, an electrode having an electrode composite layer formed from the slurry composition has excellent peel strength. In addition, a secondary battery having the electrode can exhibit excellent cycle characteristics.

< Binder composition >

As the binder composition, the binder composition of the present invention described above, which comprises a particulate polymer comprising a predetermined graft polymer and a hindered phenol-based antioxidant, is used.

The amount of the binder composition to be blended in the slurry composition is not particularly limited. For example, the amount of the binder composition to be blended may be such that the amount of the particulate polymer is 0.5 parts by mass or more and 15 parts by mass or less in terms of solid content with respect to 100 parts by mass of the electrode active material.

< electrode active Material >

The electrode active material is not particularly limited, and known electrode active materials that can be used in secondary batteries can be used. Specifically, for example, the electrode active material particles that can be used in the electrode composite material layer of a lithium ion secondary battery, which is an example of a secondary battery, are not particularly limited, and the following electrode active materials can be used.

The tap density of the electrode active material is preferably 0.7g/cm³Above, more preferably 0.75g/cm³Above, more preferably 0.8g/cm³Above, preferably 1.1g/cm³Hereinafter, more preferably 1.05g/cm³Hereinafter, more preferably 1.03g/cm³. In the present invention, the "tap density" can be measured by the method described in the examples of the present specification.

[ Positive electrode active Material ]

As the positive electrode active material to be incorporated in the positive electrode composite material layer of the positive electrode of the lithium ion secondary battery, for example, a compound containing a transition metal, for example, a transition metal oxide, a transition metal sulfide, a composite metal oxide of lithium and a transition metal, or the like can be used. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

Specifically, the positive electrode active material is not particularly limited,examples thereof include: lithium-containing cobalt oxide (LiCoO)₂) Lithium manganate (LiMn)₂O₄) Lithium-containing nickel oxide (LiNiO)₂) Lithium-containing composite oxide of Co-Ni-Mn, lithium-containing composite oxide of Ni-Mn-Al, lithium-containing composite oxide of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO)₄) Olivine-type lithium manganese phosphate (LiMnPO)₄)、Li_1+xMn_2-xO₄(0<X<2) Spinel Compound with excess lithium, Li [ Ni ]_0.17Li_0.2Co_0.07Mn_0.56]O₂、LiNi_0.5Mn_1.5O₄And the like.

The positive electrode active material may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

[ negative electrode active Material ]

Examples of the negative electrode active material to be incorporated in the negative electrode composite material layer of the negative electrode of the lithium ion secondary battery include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material obtained by combining these materials.

Here, the carbon-based negative electrode active material is an active material having carbon as a main skeleton into which lithium can be inserted (also referred to as "doped"). Specific examples of the carbon-based negative electrode active material include carbonaceous materials such as coke, mesocarbon microbeads (MCMB), mesopitch-based carbon fibers, pyrolytic vapor-grown carbon fibers, phenol resin sintered bodies, polyacrylonitrile-based carbon fibers, quasi-isotropic carbon, furfuryl alcohol resin sintered bodies (PFA), and hard carbon, and graphitic materials such as natural graphite and artificial graphite.

The metal-based negative electrode active material is an active material containing a metal, and generally refers to an active material containing an element capable of inserting lithium in its structure, and having a theoretical capacity per unit mass of 500mAh/g or more when lithium is inserted. Further, examples of the metal-based active material include: lithium metal, elemental metals capable of forming lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.), and their oxides, sulfides, nitrides, silicides, carbides, phosphides, and the like. Further, oxides such as lithium titanate can be given.

The negative electrode active material may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

< other ingredients >

The other components that can be blended in the paste composition are not particularly limited, and examples thereof include a conductive material and the same components as the other components that can be blended in the binder composition of the present invention. Further, 1 kind of the other component may be used alone, or 2 or more kinds may be used in combination at an arbitrary ratio.

< production of slurry composition >

The method for preparing the slurry composition is not particularly limited.

For example, a slurry composition can be prepared by mixing the binder composition, the electrode active material, and other components used as needed in the presence of an aqueous medium.

The aqueous medium used for preparing the slurry composition also contains components contained in the binder composition. The mixing method is not particularly limited, and mixing can be performed using a commonly used stirrer or disperser.

(nonaqueous Secondary Battery electrode)

The electrode for a nonaqueous secondary battery of the present invention has an electrode composite layer formed using the slurry composition for a nonaqueous secondary battery electrode. Therefore, the electrode composite layer contains a dried product of the slurry composition, and usually contains an electrode active material, a component derived from the particulate polymer, and a hindered phenol-based antioxidant, and further optionally contains at least one selected from the group consisting of a phosphite-based antioxidant, a metal-capturing agent, and other components. The components contained in the electrode composite material layer are the components contained in the slurry composition for a nonaqueous secondary battery electrode, and the preferred presence ratio of these components is the same as the preferred presence ratio of the components in the slurry composition. The particulate polymer is present in the slurry composition in the form of particles, but the electrode composite layer formed using the slurry composition may be in the form of particles or may have any other form.

Further, the electrode for a nonaqueous secondary battery of the present invention has excellent peel strength because the electrode composite material layer is formed using the slurry composition for a nonaqueous secondary battery electrode. In addition, a secondary battery having the electrode can exhibit excellent cycle characteristics.

< production of electrode for nonaqueous Secondary Battery >

Here, the electrode composite material layer of the electrode for a nonaqueous secondary battery of the present invention can be formed by, for example, the following method.

1) A method of coating the slurry composition of the present invention on the surface of a current collector, followed by drying;

2) a method of immersing a current collector in the slurry composition of the present invention and then drying it; and

3) a method in which the slurry composition of the present invention is applied to a release substrate, dried to produce an electrode composite material layer, and the obtained electrode composite material layer is transferred to the surface of a current collector.

Among these, the method 1) is particularly preferable because the layer thickness of the electrode composite material layer can be easily controlled. The method of 1) above specifically includes a step of applying the slurry composition to the current collector (application step) and a step of drying the slurry composition applied to the current collector to form an electrode composite layer on the current collector (drying step).

[ coating Process ]

The method for applying the slurry composition to the current collector is not particularly limited, and a known method can be used. Specifically, as the coating method, a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure printing method, an extrusion method, a brush coating method, or the like can be used. In this case, the slurry composition may be applied to only one surface of the current collector, or may be applied to both surfaces. The thickness of the slurry film on the current collector after coating and before drying can be appropriately set according to the thickness of the electrode composite material layer obtained by drying.

Here, as the current collector to which the slurry composition is applied, a material having conductivity and electrochemical durability can be used. Specifically, as the current collector, for example, a current collector containing iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used. The above-mentioned materials may be used alone in 1 kind, or may be used in combination in 2 or more kinds at an arbitrary ratio.

[ drying Process ]

The method for drying the slurry composition on the current collector is not particularly limited, and known methods can be used, and for example, a drying method using warm air, hot air, or low-humidity air, a vacuum drying method, or a drying method using irradiation with infrared rays, electron beams, or the like can be used. By drying the slurry composition on the current collector in this manner, an electrode composite material layer can be formed on the current collector, and an electrode for a nonaqueous secondary battery having the current collector and the electrode composite material layer can be obtained.

After the drying step, the electrode composite material layer may be subjected to a pressing treatment using a metal press, a roll press, or the like. By the pressure treatment, the adhesion between the electrode composite material layer and the current collector can be improved, and the obtained electrode composite material layer can be further densified. In addition, when the electrode composite material layer contains a curable polymer, it is preferable to cure the polymer after the electrode composite material layer is formed.

(nonaqueous Secondary Battery)

The nonaqueous secondary battery of the present invention has a positive electrode, a negative electrode, an electrolytic solution, and a separator, and uses the electrode for a nonaqueous secondary battery as at least one of the positive electrode and the negative electrode. In addition, the nonaqueous secondary battery of the present invention is produced using the electrode for a nonaqueous secondary battery as at least one of a positive electrode and a negative electrode, and therefore can exhibit excellent cycle characteristics.

In addition, a case where the secondary battery is a lithium ion secondary battery will be described below as an example, but the present invention is not limited to the following example.

< electrode >

Here, the electrode other than the electrode for a nonaqueous secondary battery that can be used in the nonaqueous secondary battery of the present invention is not particularly limited, and a known electrode that can be used for manufacturing a secondary battery can be used. Specifically, as an electrode other than the electrode for a nonaqueous secondary battery of the present invention, an electrode in which an electrode composite material layer is formed on a current collector by a known production method, or the like can be used.

< electrolyte solution >

As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is generally used. As the supporting electrolyte of the lithium ion secondary battery, for example, a lithium salt can be used. Examples of the lithium salt include LiPF₆、LiAsF₆、LiBF₄、LiSbF₆、LiAlCl₄、LiClO₄、CF₃SO₃Li、C₄F₉SO₃Li、CF₃COOLi、(CF₃CO)₂NLi、(CF₃SO₂)₂NLi、(C₂F₅SO₂) NLi, etc. Among these, LiPF is preferable because LiPF is easily dissolved in a solvent and exhibits a high dissociation degree₆、LiClO₄、CF₃SO₃And Li. Further, 1 kind of electrolyte may be used alone, or 2 or more kinds may be used in combination at an arbitrary ratio. In general, since the lithium ion conductivity tends to be higher when a supporting electrolyte having a higher dissociation degree is used, the lithium ion conductivity can be adjusted by the type of the supporting electrolyte.

The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, and for example: carbonates such as dimethyl carbonate (DMC), Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC), Butylene Carbonate (BC), Ethyl Methyl Carbonate (EMC), and Vinylene Carbonate (VC); esters such as γ -butyrolactone and methyl formate; ethers such as 1, 2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide, and the like. Further, a mixed solution of these solvents may be used. Among them, carbonates are preferably used because of high dielectric constant and wide stable potential region. In general, the lithium ion conductivity tends to be higher as the viscosity of the solvent used is lower, and therefore, the lithium ion conductivity can be adjusted by the kind of the solvent.

In addition, the concentration of the electrolyte in the electrolytic solution can be appropriately adjusted. In addition, known additives can be added to the electrolytic solution.

< spacer >

The spacer is not particularly limited, and for example, the spacer described in japanese patent laid-open No. 2012-204303 can be used. Among these, a microporous membrane containing a polyolefin-based (polyethylene, polypropylene, polybutylene, polyvinyl chloride) resin is preferable because the film thickness of the entire separator can be reduced, the ratio of the electrode active material in the secondary battery can be increased, and the capacity per unit volume can be increased.

Also, the secondary battery of the present invention can be manufactured, for example, by: the positive electrode and the negative electrode are stacked with a separator interposed therebetween, and are wound, folded, and the like into a battery container according to the battery shape as necessary, and an electrolyte solution is injected into the battery container and sealed. In the nonaqueous secondary battery of the present invention, the nonaqueous secondary battery electrode is used for at least one of the positive electrode and the negative electrode, preferably the negative electrode. In the nonaqueous secondary battery of the present invention, an overcurrent prevention element such as a fuse or a PTC element, a porous metal mesh, a guide plate, or the like may be provided as necessary in order to prevent a pressure rise, overcharge, discharge, or the like from occurring in the secondary battery. The shape of the secondary battery may be any of coin type, button type, sheet type, cylindrical type, rectangular type, flat type, and the like, for example.