阅读说明：本技术 蓄电设备用粘结剂组合物、蓄电设备电极用浆料、蓄电设备电极和蓄电设备 (Binder composition for electricity storage device, slurry for electricity storage device electrode, and electricity storage device ) 是由 大塚巧治 中山卓哉 本多达朗 西条飒一 于 2018-05-15 设计创作，主要内容包括：本发明提供粘结性优异的、且用于制作充放电特性(特别是高速放电特性)和耐久性优异的蓄电设备的蓄电设备用粘结剂组合物。本发明涉及的蓄电设备用粘结剂组合物的特征在于,含有聚合物(A)和液态介质(B),将上述聚合物(A)中含有的重复单元的合计设为100质量份时,上述聚合物(A)含有来自不饱和羧酸酯的重复单元(a1)23～70质量份和来自共轭二烯化合物的重复单元(a2)20～74质量份,上述重复单元(a1)和上述重复单元(a2)的合计量为76质量份以上。(The present invention provides a binder composition for an electricity storage device, which has excellent adhesion and is used for manufacturing an electricity storage device having excellent charge/discharge characteristics (particularly high-rate discharge characteristics) and durability. The adhesive composition for electricity storage devices is characterized by comprising a polymer (A) and a liquid medium (B), wherein the polymer (A) contains 23 to 70 parts by mass of a repeating unit (a1) derived from an unsaturated carboxylic acid ester and 20 to 74 parts by mass of a repeating unit (a2) derived from a conjugated diene compound, and the total amount of the repeating unit (a1) and the repeating unit (a2) is 76 parts by mass or more, when the total amount of repeating units contained in the polymer (A) is 100 parts by mass.)

1. A binder composition for an electricity storage device, comprising a polymer A and a liquid medium B,

the polymer A contains 23 to 70 parts by mass of a repeating unit a1 derived from an unsaturated carboxylic acid ester and 20 to 74 parts by mass of a repeating unit a2 derived from a conjugated diene compound, based on 100 parts by mass of the total of the repeating units contained in the polymer A,

the total amount of the repeating unit a1 and the repeating unit a2 is 76 parts by mass or more.

2. A binder composition for an electricity storage device, comprising a polymer A and a liquid medium B,

the polymer A contains 23 to 70 parts by mass of a repeating unit a1 derived from an unsaturated carboxylic acid ester, 20 to 74 parts by mass of a repeating unit a2 derived from a conjugated diene compound, and 3 to 50 parts by mass of a repeating unit a3 derived from a fluorine-containing vinyl monomer, wherein the total of the repeating units contained in the polymer A is 100 parts by mass,

the total amount of the repeating unit a1, the repeating unit a2 and the repeating unit a3 is 76 parts by mass or more.

3. The binder composition for power storage devices as claimed in claim 1 or 2, wherein the content ratio of the repeating unit a1 derived from an unsaturated carboxylic acid ester is 35 to 68 parts by mass.

4. The binder composition for power storage devices according to any one of claims 1 to 3, wherein the polymer A further contains 0.1 to 24 parts by mass of a repeating unit a4 derived from an unsaturated carboxylic acid.

5. The binder composition for power storage devices according to any one of claims 1 to 4, wherein the polymer A further contains 0.1 to 15 parts by mass of a repeating unit a5 derived from an α, β -unsaturated nitrile compound.

6. The binder composition for power storage devices according to any one of claims 1 to 5, wherein the polymer A further contains less than 15 parts by mass of a repeating unit a6 derived from an aromatic vinyl compound.

7. The binder composition for power storage devices according to any one of claims 1 to 6, wherein the polymer A is a particle.

8. The binder composition for power storage devices according to claim 7, wherein the number average particle diameter of the particles is 50nm to 5000 nm.

9. The binder composition for electric storage devices according to any one of claims 1 to 8, wherein the liquid medium B is water.

10. A slurry for an electrode of an electricity storage device, comprising an active material and the binder composition for an electricity storage device according to any one of claims 1 to 9.

11. The slurry for an electrode of a power storage device according to claim 10, wherein a silicon material is contained as the active material.

12. An electricity storage device electrode comprising a current collector and an active material layer formed by applying the slurry for an electricity storage device electrode according to claim 10 or 11 on the surface of the current collector and drying the slurry.

13. An electricity storage device comprising the electricity storage device electrode according to claim 12.

Technical Field

The invention relates to a binder composition for an electricity storage device, a slurry for an electricity storage device electrode, and an electricity storage device.

Background

In recent years, as a power source for driving electronic devices, a power storage device having a high voltage and a high energy density has been demanded. Lithium ion batteries and lithium ion capacitors are particularly expected as power storage devices having high voltage and high energy density.

An electrode used in such an electricity storage device is produced by applying a mixture of an active material and a binder for the electrode to a current collector and drying the applied mixture. Examples of the properties required for such an electrode binder include: the binding ability between active materials and the adhesion between the active materials and a current collector, and the resistance to powder falling (hereinafter, also referred to simply as "adhesion") of fine particles of the active materials from a coating film (hereinafter, also referred to simply as "active material layer") of a composition obtained by coating and drying are improved, and the internal resistance of a battery due to an electrode binder is reduced. For example, since the electrode binder has high adhesiveness, the electrode folding method, the winding radius, and the like can be easily designed, and the power storage device can be downsized. In addition, by reducing the internal resistance of the battery due to the electrode binder, good charge and discharge characteristics can be achieved. In recent years, there is a demand for an electric storage device that can perform high-speed discharge that can cope with rapid acceleration when mounted as a drive power source for an electric vehicle.

In view of the above, various proposals have been made in the prior art for adjusting the affinity of a binder material for an electrolyte solution in order to improve the adhesion, and the charge-discharge characteristics and durability of an electric storage device. For example, a technique of introducing a nitrile group into a polymer as a binder material (see patent document 1) has been proposed.

In addition, as a binder material having good adhesion and being less likely to cause coating defects on electrodes, a binder composition characterized by a combination of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer, and an ethylenically unsaturated monomer copolymerizable with these monomers has been proposed (see patent document 2). As a binder material having excellent adhesion and capable of forming an electrode coating layer having low surface resistivity, a binder composition characterized by a combination of an ethylenically unsaturated carboxylic acid monomer, a vinyl cyanide monomer, an ethylenically unsaturated carboxylic acid ester monomer, an aromatic vinyl monomer, and an aliphatic conjugated diene monomer has been proposed (see patent document 3).

In addition, in recent years, from the viewpoint of achieving a demand for higher output and higher energy density of an electric storage device, studies have been made to use a material having a large lithium occlusion amount. For example, it is considered that the use of graphite (graphite) having higher crystallinity as an active material can increase the lithium occlusion amount and realize a capacity close to the theoretical occlusion amount (about 370mAh/g) of a carbon material. On the other hand, a silicon material having a theoretical lithium occlusion amount of at most about 4200mAh/g is proposed as an active material (see patent document 4). In both cases, it is considered that the capacity of the power storage device can be greatly improved by using such an active material having a large lithium occlusion amount.

Disclosure of Invention

However, according to the above-described conventional techniques, a high-rate discharge characteristic of a level that can be mounted as a drive power source for an electric vehicle is not achieved. For example, the material described in patent document 1 is intended to realize high-rate discharge characteristics by improving the affinity of the binder material for the electrolyte, but since the swelling property of the material when it comes into contact with the electrolyte is very large, deterioration is remarkable particularly when the material is used at high temperature or when the material is stored in an electric storage device, and there is a problem in durability (for example, high-temperature cycle characteristics). The materials described in patent documents 2 and 3 have excellent durability, but the battery tends to have high resistance particularly at low temperatures, and the high-rate charge/discharge characteristics are insufficient. As described above, in the conventional art, durability and charge/discharge characteristics (particularly, high-rate discharge characteristics) of the electric storage device have a trade-off relationship, and there is a problem that these characteristics are desired to be obtained at a high level.

In addition, the binders for electrodes described in patent documents 1 to 3 cannot be said to have sufficient adhesion when an active material having a large lithium occlusion amount is put to practical use. When such a binder for an electrode is used, the electrode characteristics deteriorate due to, for example, the falling off of an active material caused by repeated charge and discharge, and therefore, there is a problem that durability required for practical use cannot be sufficiently obtained.

The present invention relates to several embodiments and provides a binder composition for an electric storage device, which has excellent adhesion and is used for manufacturing an electric storage device having excellent charge and discharge characteristics (particularly high-rate discharge characteristics), low-temperature resistance characteristics, and durability. In addition, several embodiments of the present invention provide a slurry for an electrode of an electric storage device containing the composition. Further, several aspects of the present invention provide an electric storage device electrode having excellent adhesion. Further, some aspects of the present invention provide an electric storage device having excellent charge/discharge characteristics (particularly high-rate discharge characteristics), low-temperature resistance characteristics, and durability.

The present invention has been made to solve at least some of the above problems, and can be implemented by the following modes or application examples.

[ application example 1]

One embodiment of the binder composition for an electricity storage device according to the present invention is characterized in that:

comprising a polymer (A) and a liquid medium (B),

the polymer (A) contains 23 to 70 parts by mass of a repeating unit (a1) derived from an unsaturated carboxylic acid ester and 20 to 74 parts by mass of a repeating unit (a2) derived from a conjugated diene compound, based on 100 parts by mass of the total of the repeating units contained in the polymer (A),

the total amount of the repeating unit (a1) and the repeating unit (a2) is 76 parts by mass or more.

[ application example 2]

One embodiment of the binder composition for an electricity storage device according to the present invention is characterized by containing a polymer (a) and a liquid medium (B),

the polymer (A) contains 23 to 70 parts by mass of a repeating unit (a1) derived from an unsaturated carboxylic acid ester, 20 to 74 parts by mass of a repeating unit (a2) derived from a conjugated diene compound, and 3 to 50 parts by mass of a repeating unit (a3) derived from a fluorine-containing vinyl monomer, based on 100 parts by mass of the total of the repeating units contained in the polymer (A),

the total amount of the repeating unit (a1), the repeating unit (a2), and the repeating unit (a3) is 76 parts by mass or more.

[ application example 3]

In the binder composition for electricity storage devices of the application example, the content ratio of the repeating unit (a1) derived from an unsaturated carboxylic acid ester may be 35 to 68 parts by mass.

[ application example 4]

In the binder composition for electricity storage devices of the application example, the polymer (a) may further contain 0.1 to 24 parts by mass of a repeating unit (a4) derived from an unsaturated carboxylic acid.

[ application example 5]

In the binder composition for electricity storage devices of the application example, the polymer (a) may further contain 0.1 to 15 parts by mass of a repeating unit (a5) derived from an α, β -unsaturated nitrile compound.

[ application example 6]

In the binder composition for electricity storage devices of the application example, the polymer (a) may further contain less than 15 parts by mass of a repeating unit (a6) derived from an aromatic vinyl compound.

[ application example 7]

In the binder composition for an electric storage device of the application example, the polymer (a) may be particles.

[ application example 8]

In the binder composition for an electric storage device of the application example, the number average particle diameter of the particles may be 50nm to 5000 nm.

[ application example 9]

In the binder composition for an electricity storage device of the application example, the liquid medium (B) may be water.

[ application example 10]

One embodiment of the slurry for an electric storage device electrode according to the present invention is characterized by containing the binder composition for an electric storage device and an active material.

[ application example 11]

The slurry for an electrode of an electric storage device according to the application example may contain a silicon material as the active material.

[ application example 12]

One embodiment of the power storage device electrode according to the present invention is characterized by having a current collector and an active material layer formed by applying the slurry for a power storage device electrode on a surface of the current collector and drying the applied slurry.

[ application example 13]

One aspect of the power storage device according to the present invention is characterized by including the power storage device electrode.

The binder composition for an electric storage device according to the present invention can be used to produce not only an electric storage device electrode having excellent adhesion but also an electric storage device having excellent charge/discharge characteristics (particularly high-rate discharge characteristics), low-temperature resistance characteristics, and durability.

Detailed Description

Hereinafter, preferred embodiments according to the present invention will be described in detail. The present invention is not limited to the embodiments described below, and it should be understood that the present invention also includes various modifications that can be implemented within a range not changing the gist of the present invention. In the present specification, "(meth) acrylic acid" is a concept including both "acrylic acid" and "methacrylic acid". Further, "- (meth) acrylate" is a concept including both of "-acrylate" and "-methacrylate".

1. Binder composition for electricity storage devices

The binder composition for an electricity storage device according to the present embodiment contains a polymer (a) and a liquid medium (B). The binder composition for an electricity storage device according to the present embodiment can be used as a material for forming a protective film for suppressing short-circuiting due to dendrites occurring during charge and discharge, and for producing an electricity storage device electrode (active material layer) for improving the binding ability between active materials, the adhesion ability between the active materials and a current collector, and the powder fall resistance. Hereinafter, each component contained in the binder composition for an electricity storage device according to the present embodiment will be described in detail.

1.1. Polymer (A)

The binder composition for an electricity storage device according to the present embodiment contains a polymer (a). In the present invention, the following 2 modes can be employed for the polymer (a).

The polymer (A) according to embodiment 1 has 23 to 70 parts by mass of a repeating unit (a1) derived from an unsaturated carboxylic acid ester and 20 to 74 parts by mass of a repeating unit (a2) derived from a conjugated diene compound, and the total amount of the repeating unit (a1) and the repeating unit (a2) is 76 parts by mass or more, when the total amount of the repeating units contained in the polymer (A) is 100 parts by mass.

The polymer (A) according to embodiment 2 has 23 to 70 parts by mass of a repeating unit (a1) derived from an unsaturated carboxylic acid ester, 20 to 74 parts by mass of a repeating unit (a2) derived from a conjugated diene compound, and 3 to 50 parts by mass of a repeating unit (a3) derived from a fluorine-containing vinyl monomer, and the total amount of the repeating unit (a1), the repeating unit (a2), and the repeating unit (a3) is 76 parts by mass or more, when the total of the repeating units contained in the polymer (A) is 100 parts by mass.

By using the polymer (a) according to aspects 1 and 2, it is possible to improve both low-temperature resistance characteristics and durability, and to produce an electric storage device having an excellent balance between charge-discharge characteristics and durability.

The polymer (a) may be dissolved in the liquid medium (B) or may be dispersed in the liquid medium (B) in a latex form, but is preferably a latex form in which particles of the polymer (a) are dispersed in the liquid medium (B). The binder composition for an electricity storage device according to the present embodiment is preferably in a latex form because the slurry for an electricity storage device electrode prepared by mixing the binder composition with an active material has good stability and good coatability.

Hereinafter, each repeating unit contained in the polymer (a) will be described.

1.1.1. Repeating Unit derived from unsaturated carboxylic acid ester (a1)

The polymer (A) in the 1 st and 2 nd embodiments contains 23 to 70 parts by mass of the repeating unit (a1) derived from the unsaturated carboxylic acid ester (excluding the repeating unit (a3) derived from the fluorine-containing vinyl monomer) when the total of the repeating units contained in the polymer (A) is 100 parts by mass. This improves the affinity of the polymer (a) for the electrolyte solution, suppresses an increase in internal resistance due to the binder serving as a resistance component in the power storage device, and prevents a decrease in adhesion due to excessive absorption of the electrolyte solution.

Among the unsaturated carboxylic acid esters, (meth) acrylic acid esters can be preferably used. Specific examples of the (meth) acrylic acid ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol hexa (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol hexa, Allyl (meth) acrylate, and the like, and 1 or more selected from these may be used. Of these, 1 or more selected from methyl (meth) acrylate, ethyl (meth) acrylate and 2-ethylhexyl (meth) acrylate is preferable, and methyl (meth) acrylate is particularly preferably contained. In the present invention, the alkyl amide of an ethylenically unsaturated carboxylic acid such as (meth) acrylamide or N-methylolacrylamide; the amino alkyl amides of ethylenically unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethylmethacrylamide, methylaminopropylmethacrylamide and the like are not included in the concept of unsaturated carboxylic acid esters.

The polymer (A) in the 1 st and 2 nd aspects contains 23 to 70 parts by mass of the repeating unit (a1) per 100 parts by mass of the total of the repeating units contained in the polymer (A), and the content ratio thereof is preferably 26 to 70 parts by mass, more preferably 35 to 68 parts by mass, and particularly preferably 41 to 65 parts by mass. If the content ratio of the repeating unit (a1) in the polymer (a) is within the above range, the low-temperature resistance characteristics of the power storage device can be further improved.

1.1.2. Repeating Unit derived from conjugated diene Compound (a2)

The polymer (A) in embodiments 1 and 2 contains 20 to 74 parts by mass of the repeating unit (a2) derived from the conjugated diene compound, based on 100 parts by mass of the total of the repeating units contained in the polymer (A). This can impart appropriate flexibility to the polymer (a) and improve the adhesion property, thereby improving the durability of the power storage device.

The conjugated diene compound is not particularly limited, and includes 1, 3-butadiene, 2-methyl-1, 3-butadiene, 2, 3-dimethyl-1, 3-butadiene, 2-chloro-1, 3-butadiene and the like, and may be 1 or more selected from these. Of these, 1, 3-butadiene is particularly preferable.

The polymer (A) in the 1 st and 2 nd embodiments contains 20 to 74 parts by mass of the repeating unit (a2) per 100 parts by mass of the total of the repeating units contained in the polymer (A), and the content ratio thereof is preferably 20 to 70 parts by mass, more preferably 30 to 68 parts by mass, and particularly preferably 40 to 65 parts by mass. If the content ratio of the repeating unit (a2) in the polymer (a) is within the above range, the adhesion is further improved, and the durability of the power storage device can be further improved.

1.1.3. Repeating units derived from a fluorine-containing vinyl monomer (a3)

The polymer (A) in embodiment 2 contains 3 to 50 parts by mass of the repeating unit (a3) derived from the fluorine-containing vinyl monomer, based on 100 parts by mass of the total of the repeating units contained in the polymer (A). This can further improve the low-temperature resistance characteristics of the power storage device.

The fluorine-containing vinyl monomer is not particularly limited, and examples thereof include olefin compounds having a fluorine atom, and (meth) acrylic acid esters having a fluorine atom. Examples of the olefin compound having a fluorine atom include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, 1,2, 2-tetrafluoro-1, 2-bis [ (trifluorovinyl) oxy ] ethane, and the like. Examples of the (meth) acrylate having a fluorine atom include 3[4[ 1-trifluoromethyl-2, 2-bis [ bis (trifluoromethyl) fluoromethyl ] ethynyloxy ] benzoyloxy ] 2-hydroxypropyl (meth) acrylate and the like.

The polymer (A) in the 2 nd embodiment contains 3 to 50 parts by mass of the repeating unit (a3) per 100 parts by mass of the total of the repeating units contained in the polymer (A), and the content ratio thereof is preferably 4 to 40 parts by mass, more preferably 5 to 30 parts by mass, and particularly preferably 5 to 25 parts by mass. If the content ratio of the repeating unit (a3) in the polymer (a) is within the above range, the balance between the low-temperature resistance characteristics and the durability of the power storage device can be further improved.

1.1.4. Repeating unit derived from unsaturated carboxylic acid (a4)

The polymer (a) in the embodiments 1 and 2 may contain the repeating unit (a4) derived from an unsaturated carboxylic acid. This can reduce the dissolution of the polymer (a) into the electrolyte solution, and can suppress the decrease in adhesiveness due to the electrolyte solution. In addition, it is possible to suppress an increase in internal resistance due to the polymer component dissolved in the electric storage device becoming a resistance component.

The unsaturated carboxylic acid is not particularly limited, and monocarboxylic acids and dicarboxylic acids (including anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid may be used, and 1 or more selected from these may be used. As the unsaturated carboxylic acid, 1 or more selected from acrylic acid, methacrylic acid, and itaconic acid is preferably used.

The polymer (A) in the 1 st and 2 nd embodiments preferably contains 0.1 to 24 parts by mass of the repeating unit (a4), more preferably 1 to 20 parts by mass, based on 100 parts by mass of the total of the repeating units contained in the polymer (A). If the content ratio of the repeating unit (a4) in the polymer (a) is within the above range, the electrolyte resistance can be further improved.

1.1.5. Repeating unit (a5) derived from an alpha, beta-unsaturated nitrile compound

The polymer (a) in the embodiments 1 and 2 may contain the repeating unit (a5) derived from the α, β -unsaturated nitrile compound. This can reduce the dissolution of the polymer (a) into the electrolyte solution, and can suppress the decrease in adhesiveness due to the electrolyte solution. In addition, it is possible to suppress an increase in internal resistance due to the polymer component dissolved in the electric storage device becoming a resistance component.

The α, β -unsaturated nitrile compound is not particularly limited, and acrylonitrile, methacrylonitrile, α -chloroacrylonitrile, α -ethylacrylonitrile, vinylidene cyanide and the like can be used, and 1 or more selected from these can be used. Of these, 1 or more species selected from acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is particularly preferable.

The polymer (A) in the 1 st and 2 nd embodiments preferably contains 1 to 20 parts by mass of the repeating unit (a5), more preferably 5 to 15 parts by mass, based on 100 parts by mass of the total of the repeating units contained in the polymer (A). If the content ratio of the repeating unit (a5) in the polymer (a) is within the above range, appropriate affinity for the electrolyte solution can be imparted to the polymer (a) and the low-temperature resistance characteristics of the power storage device can be further improved, but if the content ratio exceeds the above upper limit range, excessive affinity is imparted and the durability of the power storage device is reduced.

1.1.6. Repeating unit derived from aromatic vinyl Compound (a6)

The polymer (a) in embodiments 1 and 2 may contain a repeating unit (a6) derived from an aromatic vinyl compound. In the present specification, the term "aromatic vinyl compound" refers to an aromatic monofunctional vinyl compound and is a concept excluding an aromatic polyfunctional vinyl compound described later.

The aromatic vinyl compound is not particularly limited, and may include styrene, α -methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene and the like, and may be 1 or more selected from these.

The polymer (a) in the 1 st and 2 nd embodiments preferably contains less than 15 parts by mass of the repeating unit (a6), more preferably less than 10 parts by mass, even more preferably less than 5 parts by mass, and particularly preferably 0 part by mass, that is, it is substantially not contained, when the total of the repeating units contained in the polymer (a) is 100 parts by mass. If the content ratio of the repeating unit (a6) in the polymer (a) is in the above range, excessive swelling in the electrolyte solution is easily suppressed.

1.1.7. Repeating units derived from an aromatic polyfunctional vinyl compound (a7)

The polymer (a) in embodiments 1 and 2 may contain a repeating unit (a7) derived from an aromatic polyfunctional vinyl compound. This is preferable because excessive swelling of the polymer (a) in the electrolyte can be suppressed.

The aromatic polyfunctional vinyl compound is not particularly limited, and examples thereof include aromatic diene-based compounds such as divinylbenzene and diisopropenylbenzene, and 1 or more selected from these compounds may be used. Of these, divinylbenzene is preferable.

The polymer (a) in embodiments 1 and 2 preferably contains 0.1 part by mass or more and less than 5 parts by mass of the repeating unit (a7), more preferably 1 part by mass or more and less than 3 parts by mass of the repeating unit (a7), when the total of the repeating units contained in the polymer (a) is 100 parts by mass. If the content ratio of the repeating unit (a7) in the polymer (a) is within the above range, excessive swelling in the electrolyte can be suppressed, and the adhesiveness can be further improved.

1.1.8. Other repeating units

The polymer (a) in embodiments 1 and 2 may contain, in addition to the above-mentioned repeating units, repeating units derived from another unsaturated monomer copolymerizable with them.

Examples of such unsaturated monomers include vinyl carboxylates such as vinyl acetate and vinyl propionate; sulfonic acid group-containing compounds such as vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate, sulfobutyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid; alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylolacrylamide; and aminoalkylamides of ethylenically unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethylmethacrylamide, and methylaminopropylmethacrylamide, and the like, and 1 or more species selected from these may be used.

1.1.9. Total amount of repeating units

The total amount of the repeating unit (a1) derived from the unsaturated carboxylic acid ester and the repeating unit (a2) derived from the conjugated diene compound in the polymer (a) in the embodiment 1 is 76 parts by mass or more, and more preferably 80 parts by mass or more, when the total amount of the repeating units contained in the polymer (a) is 100 parts by mass. If the total amount of the repeating unit (a1) and the repeating unit (a2) is in the above range, the balance between the low-temperature resistance characteristics and the durability of the electric storage device is favorable, which is preferable.

The total amount of the repeating unit (a1) derived from an unsaturated carboxylic acid ester, the repeating unit (a2) derived from a conjugated diene compound, and the repeating unit (a3) derived from a fluorine-containing vinyl monomer is 76 parts by mass or more, and more preferably 80 parts by mass or more, based on 100 parts by mass of the total of the repeating units contained in the polymer (a). If the total amount of the repeating unit (a1), the repeating unit (a2), and the repeating unit (a3) is in the above range, the balance between the high-temperature cycle characteristics, the low-temperature resistance characteristics, and the durability of the electric storage device is favorable.

1.1.10. Characteristics of Polymer (A)

< toluene insolubles >

The polymer (A) is preferably 80% or more, more preferably 90% or more, and particularly preferably 98% or more, insoluble in toluene at 50 ℃ and substantially insoluble. The toluene insoluble matter is estimated to be approximately proportional to the amount of insoluble matter in the electrolyte solution used in the power storage device. Therefore, it is presumed that if the toluene insoluble matter is in the above range, the polymer (a) is favorably prevented from eluting into the electrolyte even when the electric storage device is produced and the charge and discharge are repeated for a long time. The toluene insolubles of the polymer (A) can be measured by the methods described in the examples described later.

< weight average molecular weight (Mw) >)

The weight average molecular weight (Mw) of the polymer (a) in terms of polystyrene obtained by Gel Permeation Chromatography (GPC) is preferably 10000 or more, more preferably 100000 or more, and particularly preferably 500000 or more. When the weight average molecular weight (Mw) of the polymer (a) is in the above range, the adhesion is better, and an electric storage device having excellent charge and discharge characteristics can be easily obtained.

< number average particle diameter >

When the polymer (A) is a particle, the lower limit of the number average particle diameter of the particle is preferably 50nm or more, more preferably 80nm or more, and particularly preferably 120nm or more. The upper limit of the number average particle diameter of the particles is preferably 5000nm or less, more preferably 1000nm or less, and particularly preferably 500nm or less. If the number average particle diameter of the particles is within the above range, the stability of the binder composition for an electric storage device is improved, and the strength of the composite layer (separator, protective film, etc.) constituting the electrode of an electric storage device can be maintained high.

The number average particle diameter of the (polymer) particles is a value of a particle diameter (D50) in which the cumulative frequency of the number of particles when particles are accumulated from small particles reaches 50% by measuring the particle size distribution using a particle size distribution measuring apparatus using a light scattering method as a measurement principle. Examples of such a particle size distribution measuring apparatus include Coulter LS230, LS100, LS 13320 (manufactured by BeckmanCoulter. Inc., above), FPAR-1000 (manufactured by Otsuka Denshi Co., Ltd.). These particle size distribution measuring apparatuses may be designed not to evaluate only primary particles of particles, but to evaluate secondary particles formed by aggregating primary particles. Therefore, the particle size distribution measured by these particle size distribution measuring apparatuses can be used as an index of the dispersion state of the (polymer) particles contained in the composition.

< endothermic characteristics >

When the polymer (A) is subjected to Differential Scanning Calorimetry (DSC) in accordance with JIS K7121, it is preferable that only 1 endothermic peak in a temperature range of-50 to +80 ℃ is observed. The endothermic behavior of the polymer (a) is presumed to be related to the shape stability of the (polymer) particles. Therefore, it is presumed that if the endothermic peak of the polymer (a) is in the above temperature range, the shape stability of the particles becomes good, and the formed active material layer and protective film have sufficient strength.

< insoluble substance in electrolyte >

The polymer (a) is preferably 80% or more, more preferably 90% or more, and particularly preferably 98% or more insoluble in electrolyte, that is, substantially insoluble. If the electrolyte-insoluble substance is in the above range, the polymer (a) can be inhibited from eluting into the electrolyte even when an electric storage device is manufactured and charging and discharging are repeated for a long time, and thus the durability is good.

< swelling ratio of electrolyte >

The swelling ratio of the electrolyte of the polymer (A) is preferably 100 to 420%, more preferably 120 to 400%, and particularly preferably 130 to 360%. If the electrolyte swelling ratio is within the above range, the polymer (a) can swell moderately in the electrolyte. As a result, the solvated lithium ions easily reach the active material, and the electrode resistance can be effectively reduced, thereby achieving more favorable charge and discharge characteristics. In addition, if the swelling ratio of the electrolyte is within the above range, a large volume change does not occur, and the adhesiveness is also excellent. The electrolyte swelling ratio of the polymer (a) can be measured by the method described in the examples described later.

1.1.11. Method for producing polymer (A)

The polymer (a) may be produced by single-stage polymerization, or may be produced by two-stage polymerization or multistage polymerization, and the polymerization may be carried out in the presence of a known polymerization initiator, a molecular weight regulator, an emulsifier (surfactant), or the like.

In the case of the polymer (a) of embodiment 2, the following two embodiments are mentioned as the polymer (a):

(1) copolymer particles obtained by synthesizing polymer particles having a repeating unit (a1) derived from an unsaturated carboxylic acid ester, a repeating unit (a2) derived from a conjugated diene compound, and a repeating unit (a3) derived from a fluorine-containing vinyl monomer by one-stage polymerization,

(2) a composite particle comprising a polymer X having a repeating unit (a3) derived from a fluorine-containing vinyl monomer and a polymer Y having a repeating unit (a1) derived from an unsaturated carboxylic acid ester and a repeating unit (a2) derived from a conjugated diene compound.

Of these, composite particles are preferable from the viewpoint of excellent oxidation resistance, and the composite particles are more preferably polymer alloy particles. The polymer alloy particles can be produced by the method described in japanese patent application laid-open No. 2014-081996 and the like.

Examples of the polymerization initiator include water-soluble polymerization initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate; oil-soluble polymerization initiators such as benzoyl peroxide, lauroyl peroxide, and 2, 2' -azobisisobutyronitrile; and redox polymerization initiators comprising a combination of a reducing agent such as sodium hydrogen sulfite, iron (II) salt or tertiary amine and an oxidizing agent such as persulfate or organic peroxide. These polymerization initiators may be used alone in 1 kind or in combination of 2 or more kinds. The proportion of the polymerization initiator used is preferably 0.3 to 3 parts by mass relative to 100 parts by mass of the total monomers used.

Examples of the molecular weight regulators include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, tert-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, and n-octadecyl mercaptan; xanthic acid compounds such as dimethyl xanthogen disulfide and diisopropyl xanthogen disulfide; thiuram compounds such as terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, and the like; phenol compounds such as 2, 6-di-tert-butyl-4-methylphenol and styrenated phenol; allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as methylene chloride, methylene bromide and carbon tetrabromide; vinyl ether compounds such as α -benzyloxystyrene, α -benzyloxyacrylonitrile and α -benzyloxyacrylamide, and the like, and further triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, α -methylstyrene dimer and the like can be mentioned, but not limited thereto. Of these, dodecyl mercaptan is preferred. The molecular weight regulators can be used alone in 1 kind, or can be combined with 2 or more kinds. The amount of the molecular weight modifier is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the total monomers used.

Examples of the emulsifier include anionic surfactants, nonionic surfactants, amphoteric surfactants, and fluorine-based surfactants, and known emulsifiers can be used. The emulsifier is preferably used in a proportion of 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, based on 100 parts by mass of the total monomers used.

The polymer (a) can be easily synthesized by, for example, a known emulsion polymerization process or by appropriately combining them. The emulsion polymerization is preferably carried out in an appropriate aqueous medium, more preferably in water. The total content of the monomers in the aqueous medium is preferably 10 to 50% by mass, and more preferably 20 to 40% by mass.

The conditions for the emulsion polymerization are preferably 40 to 85 ℃ for 2 to 24 hours, more preferably 50 to 80 ℃ for 3 to 20 hours.

1.2. Liquid medium (B)

The binder composition for an electricity storage device according to the present embodiment contains a liquid medium (B). The liquid medium (B) is preferably an aqueous medium containing water. The aqueous medium may contain a small amount of a nonaqueous medium in addition to water. Examples of such a nonaqueous medium include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, and the like, and 1 or more selected from these compounds can be used. The content of such a nonaqueous medium is preferably 10% by mass or less, more preferably 5% by mass or less, relative to the total amount of the aqueous medium. It is most preferable that the aqueous medium is composed of water alone without containing a nonaqueous medium.

The binder composition for an electric storage device according to the present embodiment uses an aqueous medium as the liquid medium (B), and preferably does not contain a non-aqueous medium other than water, thereby having a low degree of adverse effect on the environment and high safety for operators.

1.3. Other ingredients

1.3.1. Water-soluble polymers

The binder composition for an electric storage device according to the present embodiment can improve coatability and adhesion by containing a water-soluble polymer.

Examples of the water-soluble polymer include cellulose compounds such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl cellulose; ammonium salts or alkali metal salts of the above cellulose compounds; polycarboxylic acids such as poly (meth) acrylic acid and modified poly (meth) acrylic acid; alkali metal salts of the above polycarboxylic acids; polyvinyl alcohol (co) polymers such as polyvinyl alcohol, modified polyvinyl alcohol, and ethylene-vinyl alcohol copolymers; saponified copolymers of vinyl esters and unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, and fumaric acid; alternating copolymers of maleic anhydride and isobutylene; and water-soluble polymers such as ammonium salts or alkali metal salts of the alternating copolymers, polyacrylamides, and modified polyacrylamides. Among these, particularly preferred water-soluble polymers include alkali metal salts of carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, alkali metal salts of poly (meth) acrylic acid, alkali metal salts of alternating copolymers of maleic anhydride and isobutylene, polyacrylamide, modified polyacrylamide, and the like.

Examples of commercially available water-soluble polymers include alkali metal salts of carboxymethyl cellulose such as CMC1120, CMC1150, CMC2200, CMC2280, CMC2450 (available from DAICEL corporation), metholose SH type, and metholose SE type (available from shin-Etsu chemical Co., Ltd.). Further, examples of commercially available products of alternating copolymers of maleic anhydride and isobutylene include ISOBAM 06, ISOBAM 10, ISOBAM 18, and ISOBAM 110 (manufactured by KURARAY corporation).

When the binder composition for an electricity storage device according to the present embodiment contains a water-soluble polymer, the content ratio of the water-soluble polymer is preferably 5% by mass or less, and more preferably 0.1 to 3% by mass, relative to the total solid content of the binder composition for an electricity storage device.

1.3.2. Surface active agent

The binder composition for an electricity storage device according to the present embodiment may contain a surfactant from the viewpoint of improving dispersibility and dispersion stability. Examples of the surfactant include anionic surfactants, nonionic surfactants, amphoteric surfactants, and fluorine-based surfactants, and known surfactants can be used.

1.3.3. Preservative

The binder composition for an electricity storage device according to the present embodiment may contain a preservative from the viewpoint of long-term reliability. As the preservative, known preservatives can be used, and isothiazoline-based preservatives can be preferably used.

2. Slurry for electricity storage device

The slurry for an electricity storage device according to the present embodiment contains the binder composition for an electricity storage device. The binder composition for an electric storage device can be used as a material for forming a protective film for suppressing short-circuiting due to dendrites occurring during charge and discharge, and can also be used as a material for producing an electric storage device electrode (active material layer) for improving the binding ability between active materials, the adhesion ability between the active materials and a current collector, and the powder fall resistance. Therefore, a description will be given of a slurry for an electric storage device for forming a protective film (hereinafter also referred to as "slurry for forming a protective film") and a slurry for an electric storage device for forming an active material layer of an electric storage device electrode (hereinafter also referred to as "slurry for an electric storage device electrode").

2.1. Slurry for forming protective film

The "slurry for forming a protective film" in the present specification means a dispersion for forming a protective film on the surface of an electrode or a separator or on both surfaces thereof by applying the slurry to the surface of the electrode or the separator or on both surfaces thereof and then drying the slurry. The protective film forming slurry according to the present embodiment may be composed of only the binder composition for an electricity storage device, or may further contain an inorganic filler. Hereinafter, each component contained in the protective film forming slurry according to the present embodiment will be described in detail. The binder composition for an electric storage device is as described above, and therefore, the description thereof is omitted.

2.1.1. Inorganic filler

The protective film forming slurry according to the present embodiment can improve the toughness of the formed protective film by containing the inorganic filler. As the inorganic filler, at least 1 kind of particles selected from silica, titanium oxide (titania), alumina (alumina), zirconia (zirconia), and magnesia (magnesia) is preferably used. Among these, titanium oxide and aluminum oxide are preferable from the viewpoint of further improving the toughness of the protective film. Further, as the titanium oxide, rutile type titanium oxide is more preferable.

The average particle diameter of the inorganic filler is preferably 1 μm or less, and more preferably in the range of 0.1 to 0.8. mu.m. The average particle diameter of the inorganic filler is preferably larger than the average pore diameter of the separator, which is a porous film. This can reduce damage to the separator and prevent the inorganic filler from blocking the micropores of the separator.

The protective film-forming slurry according to the present embodiment preferably contains the binder composition for an electricity storage device in an amount of 0.1 to 20 parts by mass, more preferably 1 to 10 parts by mass, in terms of solid content, based on 100 parts by mass of the inorganic filler. When the content ratio of the binder composition for an electrical storage device is within the above range, the balance between the toughness of the formed protective film and the permeability of lithium ions can be improved, and as a result, the rate of increase in resistance of the resulting electrical storage device can be further reduced.

2.1.2. Liquid medium

The protective film-forming slurry according to the present embodiment may use the material described in "1.2. liquid medium (B)" of the above-described binder composition for an electric storage device, as needed. The amount of the liquid medium to be added may be adjusted as necessary so as to obtain an optimum slurry viscosity according to the coating method or the like.

2.1.3. Other ingredients

The protective film-forming slurry according to the present embodiment may contain, as necessary, an appropriate amount of the material described in "1.3. other component" of the binder composition for an electric storage device.

2.2. Slurry for electric storage device electrode

The "slurry for an electric storage device electrode" in the present specification refers to a dispersion for forming an active material layer on the surface of a current collector by applying the slurry to the surface of the current collector and then drying the applied slurry. The slurry for an electrode of an electricity storage device according to the present embodiment contains the binder composition for an electricity storage device and an active material. Hereinafter, the components contained in the slurry for an electrode of an electric storage device according to the present embodiment will be described in detail. The binder composition for an electric storage device, the liquid medium, and other components are as described above, and therefore, the description thereof is omitted.

2.2.1. Active substance

Examples of the active material include carbon materials, silicon materials, lithium atom-containing oxides, lead compounds, tin compounds, arsenic compounds, antimony compounds, aluminum compounds, and the like.

Examples of the carbon material include amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), pitch-based carbon fibers, and the like.

Examples of the silicon material include a silicon monomer, a silicon oxide, and a silicon alloy, and SiC and SiO may be used in addition to these materials_xC_y(0＜x≤3，0＜y≤5)、Si₃N₄、Si₂N₂O、SiO_x(0 < x.ltoreq.2) of a silicon oxide composite (e.g., Japanese patent application laid-open Nos. 2004-185810 and 2005-2005)The material described in-259697 publication), the silicon material described in jp 2004-185810 a. The silicon oxide is preferably represented by the formula SiO_x(0 < x < 2, preferably 0.1. ltoreq. x.ltoreq.1). As the silicon alloy, an alloy of silicon and at least 1 transition metal selected from titanium, zirconium, nickel, copper, iron, and molybdenum is preferable. Silicon alloys of these transition metals are preferably used because they have high electrical conductivity and high strength. Further, when the active material contains these transition metals, the transition metals present on the surface of the active material are oxidized to form oxides having hydroxyl groups on the surface, and therefore, the active material is also preferable from the viewpoint of further improving the adhesion to the binder. As the silicon alloy, a silicon-nickel alloy or a silicon-titanium alloy is more preferably used, and a silicon-titanium alloy is particularly preferably used. The content of silicon in the silicon alloy is preferably 10 mol% or more, and more preferably 20 to 70 mol% based on the total metal elements in the alloy. The silicon material may be any of single crystal, polycrystalline, and amorphous.

Examples of the lithium atom-containing oxide include lithium cobaltate, lithium nickelate, lithium manganate, ternary lithium nickel cobalt manganese oxide, and LiFePO₄、LiCoPO₄、LiMnPO₄、Li_0.90Ti_0.05Nb_0.05Fe_0.30Co_0.30Mn_0.30PO₄And the like.

The active material layer may contain an active material exemplified below. Examples of such active materials include conductive polymers such as polyacene; a. the_XB_YO_Z(wherein A represents an alkali metal or a transition metal, B represents at least 1 kind of transition metal selected from cobalt, nickel, aluminum, tin, manganese and the like, O represents an oxygen atom, and X, Y and Z are numbers in the ranges of 1.10 > X > 0.05, 4.00 > Y > 0.85, 5.00 > Z > 1.5, respectively), and other metal oxides.

The slurry for an electric storage device electrode according to the present embodiment can be used for producing any of a positive electrode and a negative electrode, and is particularly suitable for producing a negative electrode.

In the case of producing a positive electrode, an oxide containing a lithium atom is preferably used as the active material exemplified above.

In the case of producing a negative electrode, a material containing a carbon material and/or a silicon material is preferably used as the active material exemplified above. Since the silicon material has a larger amount of lithium absorbed per unit weight than other active materials, the storage capacity of the resulting power storage device can be increased by including the silicon material in the active material, and as a result, the output and energy density of the power storage device can be increased. The negative electrode active material is more preferably composed of a mixture of a carbon material and a silicon material. Since the carbon material has a small volume change accompanying charge and discharge, the use of a mixture of the carbon material and the silicon material as the negative electrode active material can alleviate the influence of the volume change of the silicon material, and can further improve the adhesion between the current collector and the active material layer. As the mixture, a carbon-coated silicon material in which a coating of a carbon material is formed on the surface of a silicon material may be used. By using the carbon-coated silicon material, the influence of the volume change accompanying the charge and discharge of the silicon material can be more effectively alleviated by the carbon material present on the surface, and therefore, the adhesion between the current collector and the active material layer can be easily improved.

When silicon (Si) is used as the active material, 22 lithium can be stored at most per 5 silicon atoms (5Si +22Li → Li)₂₂Si₅). As a result, the theoretical capacity of silicon reached 4200 mAh/g. However, silicon undergoes a large volume change when occluding lithium. Specifically, the carbon material is expanded by about 1.2 times to the maximum by lithium occlusion, and the silicon material is expanded by about 4.4 times to the maximum by lithium occlusion. Therefore, the silicon material is repeatedly expanded and contracted to be micronized, and the silicon material is peeled off from the current collector or the active materials are separated from each other, whereby the conductive network inside the active material layer is broken. And thus the cycle characteristics are extremely deteriorated in a short time.

However, by using the slurry for an electrode of an electric storage device according to the present embodiment, the above-described problems do not occur even when a silicon material is used, and favorable electric characteristics can be exhibited. This is considered to be because the polymer (a) can firmly bond the silicon material, and even if the silicon material expands in volume due to lithium occlusion, the polymer (a) can expand and contract to maintain the state where the silicon material is firmly bonded.

The content ratio of the silicon material to 100% by mass of the active material is preferably 1% by mass or more, more preferably 1 to 50% by mass, even more preferably 5 to 45% by mass, and particularly preferably 10 to 40% by mass.

When a silicon material and a carbon material are used together as an active material, the content of the silicon material is preferably 4 to 40 mass%, more preferably 5 to 35 mass%, and particularly preferably 5 to 30 mass% with respect to 100 mass% of the active material. If the amount of the silicon material used is within the above range, the volume expansion of the carbon material relative to the volume expansion of the silicon material caused by lithium occlusion is small, so that the volume change of the active material layer containing the active material due to charge and discharge can be reduced, and the adhesion between the current collector and the active material layer can be further improved.

The shape of the active material is preferably granular. The average particle diameter of the active material is preferably 0.1 to 100 μm, more preferably 1 to 20 μm.

Here, the average particle size of the active material is a volume average particle size calculated from a particle size distribution obtained by measuring the particle size distribution using a particle size distribution measuring apparatus based on the laser diffraction method. Examples of such a laser diffraction particle size distribution measuring apparatus include HORIBALA-300 series and HORIBALA-920 series (manufactured by horiba, Ltd.). This particle size distribution measuring apparatus is not intended to evaluate only primary particles of the active material, but also to evaluate secondary particles formed by aggregating primary particles. Therefore, the average particle diameter obtained by the particle size distribution measuring apparatus can be used as an index of the dispersion state of the active material contained in the slurry for an electrode of an electrical storage device. The average particle size of the active material may be measured by centrifuging the slurry to precipitate the active material, removing the supernatant, and measuring the precipitated active material by the above-described method.

The active material is preferably used in a proportion of 0.1 to 25 parts by mass, more preferably 0.5 to 15 parts by mass, based on 100 parts by mass of the active material in the polymer (A). By using such a ratio, an electrode having more excellent adhesion, small electrode resistance, and more excellent charge/discharge characteristics can be produced.

3. Electrode for electrical storage device

The power storage device electrode according to the present embodiment includes a current collector and a layer formed by applying the slurry for a power storage device electrode on a surface of the current collector and drying the applied slurry. The above-described slurry for an electric storage device electrode is applied to the surface of an appropriate current collector such as a metal foil to form a coating film, and then the coating film is dried to produce the electric storage device electrode. The thus-produced storage device electrode is formed by bonding an active material layer containing the polymer (a), an active material and, if necessary, an optional component, to a current collector.

The current collector is not particularly limited as long as it is made of a conductive material. In a lithium ion secondary battery, when a current collector made of metal such as iron, copper, aluminum, nickel, or stainless steel is used, particularly when aluminum is used for the positive electrode and copper is used for the negative electrode, the above-described effects of the slurry for an electrode of an electric storage device can be exhibited best. As the current collector in the nickel-hydrogen secondary battery, punched metal, expanded metal, metal mesh, metal foam, a mesh-like metal fiber sintered body, a metal-plated resin sheet, or the like is used. The shape and thickness of the current collector are not particularly limited, and the current collector is preferably formed into a sheet shape having a thickness of about 0.001 to 0.5 mm.

The method of applying the slurry for an electrode of an electricity storage device to the current collector is also not particularly limited. The coating can be carried out by an appropriate method such as a doctor blade method, an impregnation (dip) method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, or a brush coating method. The amount of the slurry for an electrode of an electricity storage device to be applied is also not particularly limited, but is preferably an amount such that the thickness of the active material layer formed after removing the liquid medium becomes 0.005mm to 5mm, and more preferably an amount such that the thickness becomes 0.01mm to 2 mm.

The method of drying the coating film after coating (method of removing water and optionally used nonaqueous medium) is also not particularly limited, and for example, drying by warm air, hot air, or low-humidity air; vacuum drying; drying by irradiation with (far) infrared rays, electron beams, or the like. The drying rate can be appropriately set so that the liquid medium can be removed quickly within a rate range that does not cause cracking of the active material layer due to stress concentration or peeling of the active material layer from the current collector.

Further, it is preferable to increase the density of the active material layer by pressurizing the dried active material layer. Examples of the pressing method include a press molding method and a roll pressing method. The density of the active material layer after pressurization is preferably 1.6 to 2.4g/cm³More preferably 1.7 to 2.2g/cm³。

4. Electrical storage device

The power storage device of the present embodiment includes the above-described power storage device electrode, further contains an electrolyte, and can be manufactured by a conventional method using a member such as a separator. Specific examples of the production method include a method in which the negative electrode and the positive electrode are stacked with a separator interposed therebetween, and the stack is wound or folded in accordance with the shape of the battery, and then the stack is stored in a battery container, and an electrolyte solution is injected into the battery container and sealed. The shape of the battery may be a coin shape, a cylinder shape, a square shape, a laminate shape, or other suitable shape.

The electrolyte may be in a liquid state or a gel state, and an electrolyte that effectively exhibits a function as a battery may be selected from known electrolytes used in power storage devices depending on the type of active material. The electrolyte solution may be a solution obtained by dissolving an electrolyte in an appropriate solvent.

As the electrolyte, any conventionally known lithium salt can be used in a lithium ion secondary battery, and specific examples thereof include LiClO₄、LiBF₄、LiPF₆、LiCF₃CO₂、LiAsF₆、LiSbF₆、LiB₁₀Cl₁₀、LiAlCl₄、LiCl、LiBr、LiB(C₂H₅)₄、LiCF₃SO₃、LiCH₃SO₃、LiC₄F₉SO₃、Li(CF₃SO₂)₂N, lithium lower fatty acid carboxylate, and the like. In nickel-hydrogen secondary electricityIn the cell, for example, a conventionally known potassium hydroxide aqueous solution having a concentration of 5 mol/liter or more can be used.

The solvent for dissolving the electrolyte is not particularly limited, and specific examples thereof include carbonate compounds such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactone compounds such as γ -butyrolactone; ether compounds such as trimethoxymethane, 1, 2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxide compounds such as dimethyl sulfoxide, and one or more selected from these compounds can be used. The concentration of the electrolyte in the electrolyte solution is preferably 0.5 to 3.0 mol/L, and more preferably 0.7 to 2.0 mol/L.

The above-described power storage device can be applied to a lithium ion secondary battery, an electric double layer capacitor, a lithium ion capacitor, and the like, which require discharge at a large current density. Among them, lithium ion secondary batteries are particularly preferable. In the electric storage device electrode and the electric storage device according to the present embodiment, known members for lithium ion secondary batteries, electric double layer capacitors, and lithium ion capacitors can be used as the members other than the binder composition for electric storage devices.