JP2019197695A - Composition for electric power storage device, slurry for electrode for electric power storage device, electrode for electric power storage device, and electric power storage device - Google Patents

Abstract

To provide a composition for an electrode for an electric power storage device having an excellent sealing performance and capable of manufacturing an electric power storage device indicating a preferable charging and discharging durability characteristic.SOLUTION: A composition for electric power storage device contains a polymer (A); a polymer (B); and a liquid medium (C). When a sum of a repetition unit contained in the polymer (A) is 100 pts.mass, the repetition unit derived from an unsaturated carboxylic ester in which the polymer (A) has a hydroxy group is contained 50 pts.mass or more. When the sum of the repetition unit contained in the polymer (B) is 100 pts.mass, the repetition unit derived from the unsaturated carboxylic ester in which the polymer (B) has the hydroxy group is 0 pts.mass or more and less than 50 pts.mass.SELECTED DRAWING: None

Description

  The present invention includes a power storage device composition, a power storage device electrode slurry containing the composition and an active material, a power storage device electrode formed by applying and drying the slurry on a current collector, and the electrode. The present invention relates to a storage device.

  In recent years, a power storage device having a high voltage and a high energy density has been required as a power source for driving electronic devices. As such an electricity storage device, a lithium ion battery, a lithium ion capacitor, and the like are expected.

  An electrode used for such an electricity storage device is usually produced by applying and drying a composition (electrode slurry) containing an active material and a polymer functioning as a binder on the surface of a current collector. The The properties required for the polymer used as the binder include the ability to bond between active materials and the adhesion between the active material and the current collector, the abrasion resistance in the process of winding the electrode, and subsequent cutting, etc. An example is powder resistance that prevents fine powders of the active material from falling off from the applied and dried composition coating (hereinafter also referred to as “active material layer”).

  In addition, it has been empirically clarified that the quality of the active materials is substantially proportional to the ability to bond the active materials to each other, the ability to adhere the active material to the current collector, and the powder-off resistance. Therefore, in the present specification, hereinafter, the term “adhesiveness” may be used in a comprehensive manner.

  Recently, studies have been made to use a material having a large lithium storage amount as an active material from the viewpoint of achieving the demand for higher output and higher energy density of power storage devices. For example, as disclosed in Patent Document 1, a method of utilizing a silicon material having a maximum lithium storage capacity of about 4,200 mAh / g as an active material is promising.

  However, an active material using such a material having a large amount of lithium storage is accompanied by a large volume change due to the storage and release of lithium. For this reason, when the conventionally used binder for electrodes is applied to such a material having a large lithium storage amount, the adhesive cannot be maintained, and the active material is peeled off. Capacity drop occurs.

  As a technique for improving the adhesiveness of the binder for an electrode, the above-mentioned technique using a technique for controlling the surface acid amount of particulate binder particles (see Patent Documents 2 and 3) or a binder having an epoxy group or a hydroxyl group is used. Techniques for improving characteristics (see Patent Documents 4 and 5) have been proposed. In addition, there has been proposed a technique (see Patent Document 6) that constrains the active material with a rigid molecular structure of polyimide and suppresses the volume change of the active material.

  On the other hand, lithium-containing phosphate compounds having an olivine structure (olivine-type lithium-containing phosphate compounds) have attracted attention as positively active positive electrode active materials. The olivine-type lithium-containing phosphate compound has high thermal stability because phosphorus and oxygen are covalently bonded, and does not release oxygen even at high temperatures.

  However, the olivine-type lithium-containing phosphate compound has a low output voltage because the Li ion storage / release voltage is around 3.4V. In order to compensate for the drawbacks, attempts have been made to improve the characteristics of peripheral materials such as electrode binders and electrolytes (see Patent Documents 7 to 9).

JP 2004-185810 A International Publication No. 2011/096463 International Publication No. 2013/191080 JP 2010-205722 A JP 2010-3703 A JP 2011-205942 A JP 2007-294323 A International Publication No. 2010/113940 JP 2012-216322 A

  However, electrode binders such as those disclosed in Patent Documents 1 to 6 have a large amount of lithium occlusion and practical use of a new active material typified by a silicon material that has a large volume change due to insertion and extraction of lithium. However, the adhesion was not sufficient. When such an electrode binder is used, the active material falls off due to repeated charge and discharge, and the electrode deteriorates, so that there is a problem that the durability required for practical use cannot be obtained sufficiently.

  Further, in the technology for improving the characteristics of the peripheral materials such as the electrode binder and the electrolytic solution as disclosed in the above Patent Documents 7 to 9, the electricity storage provided with the positive electrode using the olivine type lithium-containing phosphate compound as the positive electrode active material It has been difficult to sufficiently improve the charge / discharge durability characteristics of the device.

  Therefore, some embodiments according to the present invention provide a composition for an electricity storage device that can produce an electricity storage device electrode that has excellent adhesion and exhibits good charge / discharge durability characteristics. In addition, some embodiments according to the present invention provide a slurry for an electricity storage device electrode containing the composition. In addition, some embodiments according to the present invention provide an electricity storage device electrode that exhibits excellent adhesion and exhibits good charge / discharge durability characteristics. Furthermore, some embodiments according to the present invention provide an electricity storage device having excellent charge / discharge durability characteristics.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as any of the following aspects.

One aspect of the composition for an electricity storage device according to the present invention is:
Containing a polymer (A), a polymer (B), and a liquid medium (C),
When the total of repeating units contained in the polymer (A) is 100 parts by mass, the polymer (A) contains 50 parts by mass or more of repeating units derived from an unsaturated carboxylic acid ester having a hydroxyl group. ,
When the total of repeating units contained in the polymer (B) is 100 parts by mass, the polymer (B) contains 0 to 50 parts by mass of repeating units derived from an unsaturated carboxylic acid ester having a hydroxyl group. Contains less than part.

In one aspect of the composition for an electricity storage device,
When the polymer (A) is subjected to differential scanning calorimetry (DSC) in accordance with JIS K7121, an endothermic peak can be observed in the temperature range of −20 ° C. to 80 ° C.

In any embodiment of the composition for an electricity storage device,
The solubility of the polymer (A) in water at 25 ° C. and 1 atm can be 1 g or more with respect to 100 g of water.

In any embodiment of the composition for an electricity storage device,
The unsaturated carboxylic acid ester having a hydroxyl group may be at least one selected from the group consisting of hydroxyethyl (meth) acrylate and glycerin mono (meth) acrylate.

In any embodiment of the composition for an electricity storage device,
The polymer (A) may further contain 1 to 40 parts by mass of a repeating unit derived from (meth) acrylamide.

In any embodiment of the composition for an electricity storage device,
The polymer (B) may further contain 50 to 100 parts by mass of a repeating unit derived from an unsaturated carboxylic acid ester (excluding the unsaturated carboxylic acid ester having a hydroxyl group).

In any embodiment of the composition for an electricity storage device,
The polymer (B) may further contain 20 to 70 parts by mass of a repeating unit derived from a conjugated diene compound and 0.5 to 30 parts by mass of a repeating unit derived from an unsaturated carboxylic acid.

In any embodiment of the composition for an electricity storage device,
The polymer (B) may further contain 1 to 30 parts by mass of a repeating unit derived from a (meth) acrylamide compound.

In any embodiment of the composition for an electricity storage device,
When the content of the polymer (A) is Ma parts by mass and the content of the polymer (B) is Mb parts by mass, the value of Mb / Ma can be 0.5 to 5.0. .

In any embodiment of the composition for an electricity storage device,
The said polymer (B) is particle | grains, Comprising: The number average particle diameter can be 50 nm or more and 1000 nm or less.

In any embodiment of the composition for an electricity storage device,
The liquid medium (C) can be water.

One aspect of the slurry for the electricity storage device electrode according to the present invention is:
The power storage device composition according to any one of the above aspects and an active material are contained.

In one embodiment of the slurry for the electricity storage device electrode,
A silicon material can be contained as the active material.

In one embodiment of the slurry for the electricity storage device electrode,
The active material may contain at least one selected from the group consisting of an olivine-type lithium-containing phosphate compound, lithium cobaltate, lithium nickelate, lithium manganate, and ternary nickel cobalt lithium manganate.

One aspect of the electricity storage device electrode according to the present invention is:
A current collector, and an active material layer formed by applying and drying the slurry for an electricity storage device electrode according to any one of the above aspects on the surface of the current collector.

One aspect of the electricity storage device according to the present invention is:
The electrical storage device electrode of the said aspect is provided.

  According to the composition for an electricity storage device according to the present invention, since the adhesiveness is excellent, an electricity storage device electrode exhibiting good charge / discharge durability characteristics can be produced. The composition for an electricity storage device according to the present invention exhibits the above-described effect particularly when the electricity storage device electrode contains a material having a large lithium storage amount as an active material, for example, a carbon material such as graphite or a silicon material. In addition, the composition for an electricity storage device according to the present invention exhibits the above-described effect even when the electricity storage device electrode contains an olivine type lithium-containing phosphate compound as an active material.

  Hereinafter, preferred embodiments according to the present invention will be described in detail. It should be understood that the present invention is not limited only to the embodiments described below, and includes various modifications that are implemented within a scope that does not change the gist of the present invention. In this specification, “(meth) acrylic acid” is a concept encompassing both “acrylic acid” and “methacrylic acid”. Further, “˜ (meth) acrylate” is a concept encompassing both “˜acrylate” and “˜methacrylate”.

  In the present specification, a numerical range described using “to” means that numerical values described before and after “to” are included as a lower limit value and an upper limit value.

1. Composition for an electricity storage device The composition for an electricity storage device according to this embodiment contains a polymer (A), a polymer (B), and a liquid medium (C). The composition for an electricity storage device according to this embodiment is for producing an electricity storage device electrode (active material layer) with improved binding ability between active materials, adhesion ability between an active material and a current collector, and powder fall resistance. It can also be used as a material, and can also be used as a material for forming a protective film for suppressing a short circuit caused by dendrites generated in association with charge and discharge. Hereafter, each component contained in the composition for electrical storage devices which concerns on this embodiment is demonstrated in detail.

1.1. Polymer (A)
The polymer (A) contained in the composition for an electricity storage device according to the present embodiment may be in a latex form dispersed in the liquid medium (C), or may be dissolved in the liquid medium (C). Although it may be, it is preferable that it is the state melt | dissolved in the liquid medium (C). When the polymer (A) is in a state dissolved in the liquid medium (C), the stability of the slurry for an electricity storage device electrode (hereinafter, also simply referred to as “slurry”) produced by mixing with the active material is good. In addition, the coating property of the slurry to the current collector is favorable, which is preferable.

  In the polymer (A), the repeating unit (a1) derived from the unsaturated carboxylic acid ester having a hydroxyl group (hereinafter also referred to as “repeating unit (a1)”) is the total of the repeating units in the polymer (A). Is contained in an amount of 50 parts by mass or more. In addition to the repeating unit (a1), the polymer (A) may contain a repeating unit derived from another monomer copolymerizable therewith. Other monomers include, for example, (meth) acrylamide, unsaturated carboxylic acid, unsaturated carboxylic acid ester (excluding unsaturated carboxylic acid ester having a hydroxyl group), α, β-unsaturated nitrile compound, cationic monomer Examples thereof include a monomer, a conjugated diene compound, and an aromatic vinyl compound.

  Hereinafter, the repeating unit constituting the polymer (A), the characteristics of the polymer (A), and the synthesis method of the polymer (A) will be described in this order.

1.1.1. Repeating unit constituting polymer (A) <Repeating unit derived from unsaturated carboxylic acid ester having hydroxyl group>
The polymer (A) contains 50 parts by mass or more of repeating units derived from an unsaturated carboxylic acid ester having a hydroxyl group, where the total number of repeating units in the polymer (A) is 100 parts by mass. Is 51 parts by mass or more, more preferably 55 parts by mass or more, and particularly preferably 60 to 100 parts by mass. When the polymer (A) contains a repeating unit derived from an unsaturated carboxylic acid ester having a hydroxyl group within the above range, the dispersibility of the active material and filler becomes good, and a uniform active material layer or protective film can be produced. As a result, structural defects are eliminated and good charge / discharge characteristics are exhibited. Furthermore, by containing the repeating unit derived from the unsaturated carboxylic acid ester having a hydroxyl group within the above range, the surface of the active material is coated with the polymer (A), and the expansion of the active material during charging / discharging can be suppressed. Good charge / discharge durability characteristics are exhibited.

  Examples of the unsaturated carboxylic acid ester having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5 -Hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, glycerol mono (meth) acrylate, glycerol di (meth) acrylate and the like. Among these, 2-hydroxyethyl (meth) acrylate and glycerin monomethacrylate are preferable. In addition, these monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

<Repeating unit derived from (meth) acrylamide>
The polymer (A) preferably further contains a repeating unit derived from (meth) acrylamide. When the polymer (A) contains a repeating unit derived from (meth) acrylamide, the lower limit of the content ratio of the repeating unit derived from (meth) acrylamide is 100 as the total of repeating units in the polymer (A). When it is set as a mass part, Preferably it is 1 mass part, More preferably, it is 3 mass parts, Most preferably, it is 5 mass parts. As an upper limit of the content rate of the repeating unit derived from (meth) acrylamide, Preferably it is 40 mass parts, More preferably, it is 35 mass parts. When the content ratio of the repeating unit derived from (meth) acrylamide is within the above range, the glass transition temperature (Tg) of the resulting polymer (A) is suitable. As a result, it is possible to enhance the binding ability between active materials containing a carbon material such as graphite or a silicon material. Further, the obtained active material layer has better flexibility and adhesion ability to the current collector. Since Tg of a polymer (A) becomes suitable, the softness | flexibility of the active material layer obtained becomes moderate, and the adhesiveness of an electrical power collector and an active material layer becomes favorable.

  Examples of (meth) acrylamide include acrylamide, methacrylamide, N-isopropylacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide, N , N-dimethylaminopropyl acrylamide, N, N-dimethylaminopropyl methacrylamide, N-methylol methacrylamide, N-methylol acrylamide, diacetone acrylamide, maleic amide, acrylamide t-butyl sulfonic acid and the like. These (meth) acrylamides may be used alone or in combination of two or more.

<Other repeating units>
The polymer (A) may contain, in addition to the above repeating units, repeating units derived from other monomers copolymerizable therewith. Examples of such monomers include unsaturated carboxylic acids, unsaturated carboxylic acid esters (excluding the above unsaturated carboxylic acid esters having a hydroxyl group), α, β-unsaturated nitrile compounds, conjugated diene compounds, and aromatic vinyl compounds. And cationic monomers.

  Specific examples of the unsaturated carboxylic acid include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and one or more selected from these. Can be.

  As unsaturated carboxylic acid ester (except the unsaturated carboxylic acid ester which has the said hydroxyl group), (meth) acrylate is preferable. Specific examples of (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl ( (Meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) Acrylate, decyl (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, di Pentaerythritol hexa (meth) acrylate, allyl (meth) acrylate, and the like can be illustrated ethylene di (meth) acrylate, can be at least one selected from among these.

  Specific examples of the α, β-unsaturated nitrile compound include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide, and the like. be able to. Of these, at least one selected from acrylonitrile and methacrylonitrile is preferable, and acrylonitrile is particularly preferable.

  Specific examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and substituted linear chains. Examples thereof include conjugated pentadienes, substituted and side chain conjugated hexadienes, and can be one or more selected from these. Among these, 1,3-butadiene is particularly preferable.

  Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like. Can do. Among these, styrene is particularly preferable.

The cationic monomer is preferably at least one monomer selected from the group consisting of secondary amines (salts), tertiary amines (salts), and quaternary ammonium salts. Specific examples of these cationic monomers include (meth) acrylic acid 2- (dimethylamino) ethyl, dimethylaminoethyl (meth) acrylate methyl chloride quaternary salt, (meth) acrylic acid 2- (diethylamino) ethyl, (Meth) acrylic acid 3- (dimethylamino) propyl, (meth) acrylic acid 3- (diethylamino) propyl, (meth) acrylic acid 4- (dimethylamino) phenyl, (meth) acrylic acid 2-[(3,5 -Dimethylpyrazolyl) carbonylamino] ethyl, 2- (0- [1'-methylpropylideneamino] carboxyamino) ethyl (meth) acrylate, 2- (1-aziridinyl) ethyl (meth) acrylate,
Methacryloylcholine chloride, isocyanuric acid tris (2-acryloyloxyethyl), 2-vinylpyridine, quinaldine red, 1,2-di (2-pyridyl) ethylene, 4'-hydrazino-2-stilbazole dihydrochloride hydrate 4- (4-dimethylaminostyryl) quinoline, 1-vinylimidazole, diallylamine, diallylamine hydrochloride, triallylamine, diallyldimethylammonium chloride, dichlormide, N-allylbenzylamine, N-allylaniline, 2,4-diamino- 6-diallylamino-1,3,5-triazine, N-trans-cinnamyl-N-methyl- (1-naphthylmethyl) amine hydrochloride, trans-N- (6,6-dimethyl-2-heptene-4- Inyl) -N-methyl-1-naphthylmethylamine Examples include hydrochloride. These monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

1.1.2. Characteristics of polymer (A) <Solubility in water>
The polymer (A) is preferably a water-soluble polymer. When the polymer (A) is a water-soluble polymer, the surface of the active material is easily coated with the polymer (A). As a result, since the expansion of the active material during charging / discharging can be suppressed, it is easy to obtain an electricity storage device that exhibits good charge / discharge durability characteristics. The “water-soluble polymer” in the present invention refers to a polymer having a solubility in water of 1 g or more with respect to 100 g of water at 25 ° C. and 1 atm.

<Endothermic characteristics>
When the polymer (A) is subjected to differential scanning calorimetry (DSC) according to JIS K7121, it is preferable that an endothermic peak in a temperature range of −20 ° C. to 80 ° C. is observed. Since such a polymer (A) has a low glass transition temperature (Tg), it is possible to increase the bonding ability between active materials containing carbon materials such as graphite and silicon materials, and the active materials obtained The flexibility of the layer becomes appropriate, and the adhesion ability between the current collector and the active material layer becomes good.

<Weight average molecular weight (Mw)>
The polymer (A) preferably has a polystyrene equivalent weight average molecular weight (Mw) by a gel permeation chromatography (GPC) method of 1,000 or more, more preferably 10,000 or more, It is especially preferable that it is 000 or more. When the weight average molecular weight (Mw) of the polymer (A) is in the above range, the adhesion becomes good, and an electricity storage device excellent in charge / discharge characteristics is easily obtained.

1.1.3. Method for synthesizing polymer (A) The method for synthesizing polymer (A) is not particularly limited, but polymerization performed in the presence of a known chain transfer agent, polymerization initiator, etc. in a solvent containing water as a main component is preferable. . A particularly preferred polymerization form is aqueous solution polymerization. The chain transfer agent used in the synthesis of the polymer (A) is preferably a water-soluble chain transfer agent, and examples thereof include hypophosphites, phosphorous acids, thiols, secondary alcohols, amines and the like. In particular, thiols such as mercaptoacetic acid, 2-mercaptosuccinic acid, 3-mercaptopropionic acid, and 3-mercapto-1,2-propanediol are preferred. These water-soluble chain transfer agents may be used alone or in combination of two or more. The amount of the chain transfer agent used is preferably 5.0 parts by mass or less with respect to 100 parts by mass of the total mass of monomers to be polymerized.

  The polymerization initiator used in the synthesis of the polymer (A) is preferably a water-soluble radical initiator, and is a persulfate such as lithium persulfate, potassium persulfate, sodium persulfate, ammonium persulfate, or 4,4′-azobis (4 Water-soluble azo initiators such as -cyanovaleric acid) are particularly preferred. It is preferable that the usage-amount of a polymerization initiator is 0.1-5.0 mass parts with respect to 100 mass parts of total mass of the monomer to superpose | polymerize.

  The polymerization temperature during the synthesis of the polymer (A) is not particularly limited, but it should be synthesized in the range of 30 to 95 ° C. in consideration of the production time and the conversion rate (reaction rate) of the monomer to the copolymer. Is preferable, and 50-85 degreeC is more preferable. Further, at the time of polymerization, it is also possible to use a pH adjuster, EDTA which is a metal ion sealing agent or a salt thereof for the purpose of improving production stability.

  Further, before or after the polymerization, the pH may be adjusted with a general neutralizing agent such as ammonia, organic amine, potassium hydroxide, sodium hydroxide, or lithium hydroxide. It is preferable to adjust to the range. It is also possible to use EDTA which is a metal ion sealing agent or a salt thereof.

1.2. Polymer (B)
The polymer (B) contained in the composition for an electricity storage device according to the present embodiment may be in a latex form dispersed in the liquid medium (C), or may be dissolved in the liquid medium (C). However, it is preferably a latex in which the particles of the polymer (B) are dispersed in the liquid medium (C). When the polymer (B) is in the form of a latex dispersed in the liquid medium (C), the stability of the slurry prepared by mixing with the active material is improved, and the applicability of the slurry to the current collector is improved. Since it becomes favorable, it is preferable.

  The polymer (B) has a repeating unit (a1) derived from an unsaturated carboxylic acid ester having a hydroxyl group, and when the total number of repeating units in the polymer (B) is 100 parts by mass, it is 0 to 50 parts by mass. Contains less than part. Moreover, a polymer (B) may contain the repeating unit derived from another monomer. Examples of other monomers include unsaturated carboxylic acid esters (excluding unsaturated carboxylic acid esters having a hydroxyl group), conjugated diene compounds, unsaturated carboxylic acids, (meth) acrylamides, aromatic vinyl compounds, α, β -An unsaturated nitrile compound, other monomers, etc. are mentioned.

  Hereinafter, the repeating unit constituting the polymer (B), the characteristics of the polymer (B), and the synthesis method of the polymer (B) will be described in this order.

1.2.1. Repeating unit constituting polymer (B) <Repeating unit derived from unsaturated carboxylic acid ester having hydroxyl group>
When the polymer (B) is a repeating unit derived from an unsaturated carboxylic acid ester having a hydroxyl group and the total number of repeating units in the polymer (B) is 100 parts by mass, it is 0 to 50 parts by mass. contains. As a minimum of the content rate of the repeating unit originating in the unsaturated carboxylic acid ester which has a hydroxyl group, Preferably it is 1 mass part, More preferably, it is 3 mass parts. The upper limit of the content ratio of the repeating unit derived from the unsaturated carboxylic acid ester having a hydroxyl group is preferably 50 parts by mass, more preferably 40 parts by mass, and particularly preferably 30 parts by mass. When the polymer (B) contains a repeating unit derived from an unsaturated carboxylic acid ester having a hydroxyl group in the above range, the active material is excellent without agglomerating the active material when a slurry described later is prepared. A dispersed slurry can be made. As a result, the polymer (B) has a nearly uniform distribution in the active material layer produced by applying and drying the slurry, so that an electricity storage device electrode with very few binding defects can be produced. That is, the ability to bond active materials and the ability to adhere the active material layer and the current collector can be dramatically improved. In addition, about the illustration of unsaturated carboxylic acid ester which has a hydroxyl group, it is the same as that of a polymer (A).

<Repeating unit derived from unsaturated carboxylic acid ester>
When the polymer (B) has a repeating unit derived from an unsaturated carboxylic acid ester (excluding the above unsaturated carboxylic acid ester having a hydroxyl group), the affinity with the electrolytic solution is good, and the polymer (B) is heavy in the electricity storage device. While suppressing an increase in internal resistance due to the combined (B) becoming an electrical resistance component, it is possible to prevent a decrease in adhesion due to excessive absorption of the electrolytic solution.

  The content ratio of the repeating unit derived from the unsaturated carboxylic acid ester is preferably 0 part by mass as the lower limit when the total number of repeating units in the polymer (B) is 100 parts by mass. More preferably, it is a part. As an upper limit, it is preferable that it is 50 mass parts, It is more preferable that it is 45 mass parts, It is especially preferable that it is 40 mass parts. When the content ratio of the repeating unit derived from the unsaturated carboxylic acid ester is within the above range, the obtained polymer (B) has better affinity with the electrolytic solution, and the polymer (B) is contained in the electricity storage device. While suppressing an increase in internal resistance due to the electrical resistance component, it is possible to prevent a decrease in adhesion due to excessive absorption of the electrolyte. In addition, about illustration of unsaturated carboxylic acid ester, it is the same as that of a polymer (A).

<Repeating unit derived from conjugated diene compound>
When the polymer (B) has a repeating unit derived from a conjugated diene compound, it becomes easy to produce a polymer excellent in viscoelasticity and strength. That is, when the polymer (B) has a repeating unit derived from a conjugated diene compound, a strong binding force can be imparted to the resulting polymer. Since rubber elasticity derived from the conjugated diene compound is imparted to the polymer, it is possible to follow changes such as volume shrinkage and volume expansion of an active material containing a carbon material such as graphite or a silicon material. Thereby, it is considered that the adhesion can be further improved and the charge / discharge durability characteristics can be further improved over a long period of time.

  The content ratio of the repeating unit derived from the conjugated diene compound is preferably 20 parts by mass as a lower limit when the total number of repeating units in the polymer (B) is 100 parts by mass, and 25 parts by mass. More preferably, it is 30 parts by mass. As an upper limit, it is preferable that it is 70 mass parts, It is more preferable that it is 65 mass parts, It is especially preferable that it is 60 mass parts. When the content ratio of the repeating unit derived from the conjugated diene compound is in the above range, a polymer excellent in viscoelasticity and strength can be easily produced. In addition, about the illustration of a conjugated diene compound, it is the same as that of a polymer (A).

<Repeating unit derived from unsaturated carboxylic acid>
When the polymer (B) has a repeating unit derived from an unsaturated carboxylic acid, the adhesion of the polymer (B) can be improved. Specific examples of the unsaturated carboxylic acid include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and one or more selected from these. Can do. The polymer (B) preferably has two or more types of repeating units derived from the unsaturated carboxylic acids exemplified above, one or more of monocarboxylic acids such as acrylic acid and methacrylic acid, fumaric acid, and itacone. More preferably, one or more dicarboxylic acids such as acids are used in combination. The monocarboxylic acid can enhance the effect of improving the binding ability between the active materials containing the silicon material, and the dicarboxylic acid can enhance the effect of improving the adhesion ability between the active material layer and the current collector. Therefore, the adhesiveness of a polymer (B) can be improved greatly by using together monocarboxylic acid and dicarboxylic acid.

The content ratio of the repeating unit derived from the unsaturated carboxylic acid is preferably 0.5 parts by mass as a lower limit when the total number of repeating units in the polymer (B) is 100 parts by mass. More preferably, it is part by mass. As an upper limit, it is preferable that it is 30 mass parts, It is more preferable that it is 28 mass parts, It is especially preferable that it is 25 mass parts. When the content ratio of the repeating unit derived from the unsaturated carboxylic acid is in the above range, the polymer (B) has a binding ability between active materials having polar functional groups such as an active material containing a silicon material on the surface, And / or the adhesion | attachment capability of an active material layer and an electrical power collector becomes favorable. In addition, when the slurry is prepared, the dispersion stability of the active material is improved, so that agglomerates are hardly generated, and an increase in the slurry viscosity over time can be suppressed.

<Repeating unit derived from (meth) acrylamide>
The polymer (B) may have a repeating unit derived from (meth) acrylamide. When the polymer (B) has a repeating unit derived from (meth) acrylamide, the content ratio of the repeating unit derived from (meth) acrylamide is 100 parts by mass of the total repeating units in the polymer (B). In this case, the lower limit is preferably 0 part by mass, and more preferably 1 part by mass. As an upper limit, it is preferable that it is 30 mass parts, It is more preferable that it is 25 mass parts, It is especially preferable that it is 20 mass parts. When the content ratio of the repeating unit derived from (meth) acrylamide is in the above range, the polymer (B) has a binding ability between active materials having a polar functional group such as an active material containing a silicon material on the surface, In addition, both the adhesion capability between the active material layer and the current collector are improved. Moreover, since the dispersion stability of the active material is improved during slurry preparation, aggregates are hardly generated, and an increase in slurry viscosity over time can be suppressed. Accordingly, the active material layer can be formed uniformly, and the progress of deterioration of the active material layer can be suppressed by applying a potential uniformly to the active material layer.

<Repeating unit derived from aromatic vinyl compound>
When the polymer (B) has a repeating unit derived from an aromatic vinyl compound, since the glass transition temperature (Tg) of the polymer (B) is suitable, the flexibility of the obtained active material layer becomes appropriate. The adhesion ability between the current collector and the active material layer becomes good.

  The content ratio of the repeating unit derived from the aromatic vinyl compound is preferably 10 parts by mass as a lower limit when the total number of repeating units in the polymer (B) is 100 parts by mass, and 15 parts by mass. It is more preferable that it is, and it is especially preferable that it is 20 mass parts. As an upper limit, it is preferable that it is 60 mass parts, It is more preferable that it is 55 mass parts, It is especially preferable that it is 50 mass parts. When the content ratio of the repeating unit derived from the aromatic vinyl compound is in the above range, the Tg of the obtained polymer tends to be suitable. As a result, it is possible to enhance the binding ability between active materials containing a carbon material such as graphite or a silicon material. Further, the obtained active material layer has better flexibility and adhesion ability to the current collector. In addition, about the illustration of an aromatic vinyl compound, it is the same as that of a polymer (A).

<Repeating unit derived from α, β-unsaturated nitrile compound>
When the polymer (B) has a repeating unit derived from an α, β-unsaturated nitrile compound, the polymer (B) can be appropriately swollen by the electrolytic solution described later. That is, the presence of the nitrile group causes the electrolyte solution to enter the network structure composed of polymer chains, and the network interval is widened, so that solvated lithium ions can easily move through the network structure. As a result, it is considered that the diffusibility of lithium ions is improved. Thereby, since electrode resistance can be reduced, the more favorable charge / discharge characteristic of an electrode is implement | achieved.

  The content ratio of the repeating units derived from the α, β-unsaturated nitrile compound is preferably 0 parts by mass as a lower limit when the total number of repeating units in the polymer (B) is 100 parts by mass. The amount is more preferably 2 parts by mass, and particularly preferably 5 parts by mass. As an upper limit, it is preferable that it is 50 mass parts, It is more preferable that it is 45 mass parts, It is especially preferable that it is 40 mass parts. When the content ratio of the repeating unit derived from the α, β-unsaturated nitrile compound is in the above range, the affinity with the electrolyte used is superior, the adhesion and strength are superior, and the mechanical properties and electrical properties are excellent. The composition for electrical storage devices excellent in balance with characteristics can be produced. In addition, about the illustration of an (alpha), (beta)-unsaturated nitrile compound, it is the same as that of a polymer (A).

<Other repeating units>
The polymer (B) contained in the composition for an electricity storage device according to this embodiment can contain a repeating unit derived from a monomer copolymerizable therewith in addition to the above repeating unit.

  Specific examples of such a monomer include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, 1,1,2,2-tetrafluoro-1,2-bis [(trifluorovinyl) oxy]. Fluorine-containing compounds having an ethylenically unsaturated bond such as ethane; carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; acid anhydrides of ethylenically unsaturated dicarboxylic acids; aminoethylacrylamide, dimethylaminomethylmethacrylamide, methylamino Examples thereof include aminoalkylamides of ethylenically unsaturated carboxylic acids such as propylmethacrylamide, and can be one or more selected from these.

<Preferred embodiment of polymer (B)>
The polymer (B) is preferably any one of the following embodiments from the viewpoint of obtaining a binder composition having better adhesion.

(First aspect)
When the total number of repeating units in the polymer (B) is 100 parts by mass, the repeating unit derived from the unsaturated carboxylic acid ester having a hydroxyl group is 0 to 50 parts by mass, and the unsaturated carboxylic acid ester ( A polymer (B-1) containing 50 to 100 parts by mass of a repeating unit derived from an unsaturated carboxylic acid ester having a hydroxyl group).
The polymer (B-1) preferably further contains 0.5 to 5 parts by mass of a repeating unit derived from an unsaturated carboxylic acid. Further, the polymer (B-1) may further contain 1 to 30 parts by mass of a repeating unit derived from (meth) acrylamide. The polymer (B-1) may be composite particles obtained by combining a polymer having these repeating units and a fluorine-containing polymer.

(Second aspect)
When the total number of repeating units in the polymer (B) is 100 parts by mass, 0 to 50 parts by mass of the repeating unit derived from the unsaturated carboxylic acid ester having a hydroxyl group is derived from the conjugated diene compound. A polymer (B-2) containing 20 to 70 parts by mass of a repeating unit and 0.5 to 30 parts by mass of a repeating unit derived from an unsaturated carboxylic acid.
It is preferable that a polymer (B-2) contains 1-50 mass parts of repeating units derived from an aromatic vinyl compound further. The polymer (B-2) may further contain 1 to 30 parts by mass of a repeating unit derived from (meth) acrylamide.

1.2.2. Characteristics of polymer (B) <Solubility in water>
The polymer (B) is preferably a water-insoluble polymer. Since the polymer (B) is a water-insoluble polymer, the function of the polymer (B) as a binder (that is, the binding ability between the active materials and the adhesion ability between the active material layer and the current collector). This is preferable because it is easily exhibited. The “water-insoluble polymer” in the present invention refers to a polymer having a solubility in water at 25 ° C. and 1 atm of less than 1 g with respect to 100 g of water.

<Tetrahydrofuran (THF) insoluble matter>
The THF-insoluble content of the polymer (B) is preferably 75% by mass or more, and more preferably 80% by mass or more. It has been empirically confirmed that this THF insoluble matter is approximately proportional to the amount of insoluble matter with respect to the electrolyte used in the electricity storage device. For this reason, it is preferable to use the polymer (B) having a THF-insoluble content within the above-mentioned range because elution of the polymer (B) into the electrolytic solution can be suppressed even when charging and discharging are repeated for a long period of time.

The THF-insoluble content of the polymer (B) was obtained by immersing 1 g of the polymer (B) in 400 mL of tetrahydrofuran (THF) and shaking at 50 ° C. for 3 hours, and then filtering the THF phase through a 300-mesh wire mesh. From the value obtained by measuring the mass (Y (g)) of the residue obtained by evaporating and removing the dissolved THF after evaporating the insoluble matter, it can be calculated by the following formula (1).
THF insoluble matter (%) = ((1-Y) / 1) × 100 (1)

<Endothermic characteristics>
The polymer (B) preferably has only one endothermic peak in the temperature range of −40 ° C. to 30 ° C. when measured by differential scanning calorimetry (DSC) according to JIS K7121. The temperature of the endothermic peak (that is, the glass transition temperature (Tg)) is more preferably in the range of −30 ° C. to 25 ° C., and more preferably in the range of −25 ° C. to 20 ° C. When the polymer (B) has only one endothermic peak in the DSC analysis and the peak temperature is in the above range, the polymer (B) exhibits good adhesion and is active against the active material layer. Better flexibility and tackiness can be imparted, which is preferable.

<Number average particle diameter>
When the polymer (B) is in the form of a latex dispersed as particles in the liquid medium (C), the number average particle diameter of the polymer (B) is preferably in the range of 50 to 1,000 nm, 90 More preferably, it is in the range of ˜750 nm. When the number average particle diameter of the polymer (B) is in the above range, the polymer (B) is easily adsorbed on the surface of the active material, so that the polymer (B) follows the movement of the active material. Can move. As a result, it is possible to suppress only one of the both particles from migrating alone, so that deterioration of electrical characteristics can be reduced.

  The number average particle size of the polymer (B) is the cumulative frequency of the number of particles when the particle size distribution is measured using a particle size distribution measuring apparatus based on the light scattering method and the particles are accumulated from small particles. Is the value of the particle diameter (D50) at which 50%. Examples of such a particle size distribution measuring apparatus include Coulter LS230, LS100, LS13320 (above, manufactured by Beckman Coulter. Inc), FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.), and the like.

<Weight average molecular weight (Mw)>
The polymer (B) preferably has a polystyrene-equivalent weight average molecular weight (Mw) by a gel permeation chromatography (GPC) method of 10,000 or more, more preferably 100,000 or more, It is especially preferable that it is 000 or more. When the weight average molecular weight (Mw) of the polymer (A) is in the above range, the adhesion becomes good, and an electricity storage device excellent in charge / discharge characteristics is easily obtained.

1.2.3. Method for producing polymer (B) The method for synthesizing the polymer (B) is not particularly limited. For example, the emulsion polymerization method is carried out in the presence of a known emulsifier (surfactant), chain transfer agent, polymerization initiator and the like. Can be. Known emulsifiers, chain transfer agents, and polymerization initiators include compounds described in Japanese Patent No. 599399.

  The emulsion polymerization method for synthesizing the polymer (B) may be performed by one-stage polymerization or may be performed by two-stage or more multi-stage polymerization.

  When the synthesis of the polymer (B) is carried out by single-stage polymerization, the mixture of the above monomers is preferably present at 40 to 80 ° C. in the presence of a suitable emulsifier, chain transfer agent, polymerization initiator and the like. Can be by emulsion polymerization for 4-18 hours.

  When the synthesis of the polymer (B) is performed by two-stage polymerization, the polymerization at each stage is preferably set as follows.

  The proportion of the monomer used for the first stage polymerization is the total mass of the monomer (the sum of the mass of the monomer used for the first stage polymerization and the mass of the monomer used for the second stage polymerization). On the other hand, it is preferable to set it as the range of 40-95 mass%, and it is preferable to set it as the range of 45-90 mass%. By performing the first-stage polymerization with such an amount of monomer, it is possible to obtain particles of the polymer (B) which are excellent in dispersion stability and hardly generate aggregates, and over time of the composition for an electricity storage device. It is preferable because a significant increase in viscosity is suppressed.

  The type of monomer used in the first stage polymerization and its use ratio and the type of monomer used in the second stage polymerization and its use ratio may be the same or different. However, when a monomer having a high reactivity with a diene monomer such as an α, β-unsaturated nitrile compound is used as the monomer, the polymerization reaction proceeds rapidly, so that the reaction heat is increased at a time. May occur, making it difficult to control the polymerization temperature. For this reason, in order to further stabilize the temperature control of the polymerization, it is preferable to use 10 to 60% by mass, more preferably 15 to 50% by mass of these monomers for the second-stage polymerization.

  Moreover, it is preferable to use the monomer mixture containing unsaturated carboxylic acid ester which has unsaturated carboxylic acid, (meth) acrylamide, and a hydroxyl group for the monomer used for 2nd-stage polymerization. The content of unsaturated carboxylic acid, (meth) acrylamide, and unsaturated carboxylic acid ester having a hydroxyl group in the monomer mixture used in the second-stage polymerization is preferably 50% by mass or more, more preferably 75% by mass. As described above, the content is particularly preferably 100% by mass.

The polymerization conditions at each stage are preferably as follows from the viewpoint of the dispersibility of the resulting polymer.
First stage polymerization; preferably a temperature of 40 to 80 ° C .; preferably a polymerization time of 2 to 24 hours; preferably a polymerization conversion rate of 50% by mass or more, more preferably 60% by mass or more.
-Second stage polymerization; preferably at a temperature of 40-80 ° C; preferably a polymerization time of 2-6 hours.

  By setting the total solid content concentration in the emulsion polymerization to 50% by mass or less, the polymerization reaction can be allowed to proceed with good dispersion stability of the obtained polymer. This total solid content concentration is preferably 45% by mass or less, more preferably 40% by mass or less.

  Whether the synthesis of the polymer (B) is performed by one-stage polymerization or by the two-stage polymerization method, a neutralizing agent is added to the polymerization mixture after the emulsion polymerization is completed. The pH is preferably adjusted to about 3 to 6, preferably 3.5 to 5.5, more preferably 4 to 5. Although it does not specifically limit as a neutralizing agent used here, For example, metal hydroxides, such as sodium hydroxide and potassium hydroxide; Ammonia etc. can be mentioned. By setting the pH within the above range, the stability of the polymer (B) is improved. After carrying out the neutralization treatment, the concentration of the solid mixture can be increased while maintaining good stability of the polymer (B) by concentrating the polymerization mixture.

(B) When the polymer is a fluorine-containing polymer particle, as a specific aspect thereof, (1) polymer particles having a repeating unit derived from a monomer having a fluorine atom are synthesized by one-stage polymerization. Copolymer particles obtained; (2) composite particles having a polymer X having a repeating unit derived from a monomer having a fluorine atom and a polymer Y having a repeating unit derived from an unsaturated carboxylic acid; An embodiment is mentioned. Among these, from the viewpoint of excellent oxidation resistance, composite particles are preferable, and the composite particles are more preferably polymer alloy particles. As a method for producing such composite particles, for example, a method described in JP-A-2014-081996 and the like can be mentioned.

1.3. Liquid medium (C)
The composition for an electricity storage device according to this embodiment contains a liquid medium (C). The liquid medium (C) is preferably an aqueous medium containing water, and more preferably water. The aqueous medium can contain a non-aqueous medium other than water. Examples of the non-aqueous medium include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, and the like. Use one or more selected from these. Can do. By using an aqueous medium as the liquid medium (C), the composition for an electricity storage device according to the present embodiment has a low degree of adverse effects on the environment and is also safer for handling workers.

  The content ratio of the non-aqueous medium contained in the aqueous medium is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, particularly not substantially contained in 100 parts by mass of the aqueous medium. preferable. Here, “substantially does not contain” means that a non-aqueous medium is not intentionally added as a liquid medium, and is inevitably mixed when a composition for an electricity storage device is produced. May be included.

1.4. Other additive The composition for electrical storage devices which concerns on this embodiment can contain additives other than the component mentioned above as needed. Examples of such additives include polymers other than the polymer (A) and the polymer (B), preservatives, thickeners and the like. Examples of the preservative include compounds described in Japanese Patent No. 599399.

  When the composition for an electricity storage device according to the present embodiment contains a thickener, the applicability, the charge / discharge characteristics of the obtained electricity storage device, and the like may be further improved.

  Examples of such a thickener include cellulose compounds such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose; ammonium salts or alkali metal salts of the above cellulose compounds; polyvinyl alcohol, modified polyvinyl alcohol, and ethylene-vinyl alcohol copolymers. Examples include polyvinyl alcohol-based (co) polymers; water-soluble polymers such as saponified products of copolymers of unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and fumaric acid and vinyl esters. Among these, particularly preferred thickeners include alkali metal salts of carboxymethyl cellulose and alkali metal salts of poly (meth) acrylic acid.

  Examples of commercially available thickeners include alkali metal salts of carboxymethylcellulose such as CMC1120, CMC1150, CMC2200, CMC2280, and CMC2450 (manufactured by Daicel Corporation).

  When the composition for electrical storage devices according to the present embodiment contains a thickener, the content of the thickener is 5 parts by mass or less with respect to 100 parts by mass of the total solid content of the composition for electrical storage devices. Is preferable, and it is more preferable that it is 0.1-3 mass parts.

1.5. Physical properties of power storage device composition <content ratio of polymer (A) and polymer (B)>
In the composition for an electricity storage device according to this embodiment, when the content of the polymer (A) is Ma parts by mass and the content of the polymer (B) is Mb parts by mass, the value of Mb / Ma is It is preferably 0.5 to 5.0, more preferably 0.6 to 4.5, and particularly preferably 0.7 to 4.0. When the blending balance of the polymer (A) and the polymer (B) in the composition for an electricity storage device is within the above range, the surface of the active material of the polymer (A) is coated to suppress the expansion of the active material. Due to the synergistic effect of the effect and the adhesion ability between the active material and the current collector of the polymer (B) and the binding ability between the active materials, not only excellent adhesion but also very good charge / discharge durability characteristics are exhibited. An electricity storage device electrode is obtained.

<PH>
The pH of the composition for an electricity storage device according to this embodiment is preferably 3 to 8, more preferably 3.5 to 8, and particularly preferably 3.5 to 7.8. When the pH is within the above range, it is possible to suppress the occurrence of problems such as insufficient leveling and liquid dripping when applying the slurry, and an electric storage device electrode having both good electrical characteristics and adhesion can be obtained. It is easy to manufacture.

  “PH” in the present specification refers to physical properties measured as follows. It is a value measured according to JIS Z8802: 2011 with a pH meter using a glass electrode calibrated with a neutral phosphate standard solution and a borate standard solution as a pH standard solution at 25 ° C. Examples of such a pH meter include “HM-7J” manufactured by Toa DKK Corporation and “D-51” manufactured by Horiba, Ltd.

  In slurries made using a power storage device composition with a pH in the above range, the surface of the active material is corroded to such an extent that the charge / discharge characteristics are not deteriorated due to low pH, and contamination is caused by exposure to the atmosphere. The surface of the active material can be cleaned. As a result, it is considered that obstruction of occlusion and release of lithium ions can be suppressed between the active material and the electrolytic solution in the obtained active material layer, and good charge / discharge characteristics can be expressed.

  In addition, it is not denied that the pH of the composition for an electricity storage device is affected by the monomer composition constituting the polymer (A), but it is added that it is not determined only by the monomer composition. That is, it is generally known that the pH of the composition for an electricity storage device changes depending on polymerization conditions or the like even if the monomer composition is the same, and the examples of the present application show only one example.

  For example, even when the monomer composition is the same, when all of the unsaturated carboxylic acid is initially charged in the polymerization reaction solution and then other monomers are added in succession, a monomer other than the unsaturated carboxylic acid is added. Is added to the polymerization reaction solution, and finally the unsaturated carboxylic acid is added, the amount of the carboxyl group derived from the unsaturated carboxylic acid exposed on the surface of the resulting polymer is different. Thus, it is considered that the pH of the composition for an electricity storage device varies greatly only by changing the order in which the monomers are added by the polymerization method.

2. Power Storage Device Slurry The power storage device slurry according to the present embodiment contains the above-described power storage device composition. As described above, the composition for an electricity storage device according to the present embodiment can be used as a material for forming a protective film for suppressing a short circuit caused by dendrite that occurs in association with charge and discharge, It can also be used as a material for producing an electricity storage device electrode (active material layer) with improved bonding ability between active materials, adhesion ability between an active material and a current collector, and powder fall resistance. Therefore, a slurry for an electricity storage device for forming a protective film (hereinafter also referred to as “slurry for forming a protective film”) and a slurry for an electricity storage device for forming an active material layer of the electricity storage device electrode (hereinafter referred to as “electric storage device”). It is also referred to as “device electrode slurry”.

2.1. Protective film forming slurry In this specification, “slurry for forming a protective film” is applied to the surface of the electrode and / or separator and then dried to form a protective film on the surface of the electrode and / or separator. Refers to the dispersion used to form. The slurry for forming a protective film according to this embodiment may be composed only of the above-described composition for an electricity storage device, and may further contain an inorganic filler. Hereinafter, each component contained in the slurry for forming a protective film according to this embodiment will be described in detail. In addition, about the composition for electrical storage devices, since it is as above-mentioned, description is abbreviate | omitted.

2.1.1. Inorganic filler The slurry for protective film formation concerning this embodiment can improve the toughness of the protective film formed by containing an inorganic filler. As the inorganic filler, it is preferable to use at least one type of particles selected from the group consisting of silica, titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), and magnesium oxide (magnesia). 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 μm. In addition, it is preferable that the average particle diameter of an inorganic filler is larger than the average hole diameter of the separator which is a porous film. Thereby, damage to a separator can be reduced and it can prevent that an inorganic filler is clogged with the microporous of a separator.

  The slurry for forming a protective film according to this embodiment preferably contains 0.1 to 20 parts by mass of the above-described composition for an electricity storage device in terms of solid content with respect to 100 parts by mass of the inorganic filler. It is more preferable that 10 to 10 parts by mass is contained. When the content ratio of the composition for the electricity storage device is in the above range, the balance between the toughness of the protective film to be formed and the lithium ion permeability is improved, and as a result, the resistance increase rate of the obtained electricity storage device is further reduced. can do.

2.1.2. Liquid Medium For the protective film-forming slurry according to the present embodiment, materials described in “1.3. Liquid Medium (C)” of the above-described composition for an electricity storage device can be used as necessary. The addition amount of the liquid medium can be adjusted as necessary so that the optimum viscosity of the slurry can be obtained according to the coating method and the like.

2.1.3. Other Components In the slurry for forming a protective film according to the present embodiment, an appropriate amount of the materials described in “1.4. Other Additives” of the above-described composition for an electricity storage device can be used as necessary.

2.2. “Slurry for electricity storage device electrode” in the present specification is used to form an active material layer on the surface of the current collector after being applied to the surface of the current collector and then dried. Refers to a dispersion. The slurry for an electricity storage device electrode according to this embodiment contains the above-described composition for an electricity storage device and an active material. Hereinafter, the components contained in the slurry for an electricity storage device electrode according to this embodiment will be described. In addition, about the composition for electrical storage devices, since it is as above-mentioned, description is abbreviate | omitted.

2.2.1. Active Material Examples of the active material used in the power storage device electrode slurry according to the present embodiment include carbon materials, silicon materials, oxides containing lithium atoms, lead compounds, tin compounds, arsenic compounds, antimony compounds, aluminum compounds, and the like. Is mentioned.

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

Examples of the silicon material include silicon simple substance, silicon oxide, and silicon alloy. For example, SiC, SiO _x C _y (0 <x ≦ 3, 0 <y ≦ 5), Si ₃ N ₄ , Si oxide complex represented by Si ₂ N ₂ O, SiO _x (0 <x ≦ 2) (for example, materials described in JP-A Nos. 2004-185810 and 2005-259697), And the silicon material described in Unexamined-Japanese-Patent No. 2004-185810 can be used. The silicon oxide is preferably a silicon oxide represented by the composition formula SiO _x (0 <x <2, preferably 0.1 ≦ x ≦ 1). The silicon alloy is preferably an alloy of silicon and at least one transition metal selected from the group consisting of titanium, zirconium, nickel, copper, iron and molybdenum. These transition metal silicon alloys are preferably used because they have high electronic conductivity and high strength. Moreover, since the transition metal existing on the surface of the active material is oxidized and becomes an oxide having a hydroxyl group on the surface when the active material contains these transition metals, the binding force with the binder is also improved. preferable. As the silicon alloy, it is more preferable to use a silicon-nickel alloy or a silicon-titanium alloy, and it is particularly preferable to use a silicon-titanium alloy. The silicon content in the silicon alloy is preferably 10 mol% or more, and more preferably 20 to 70 mol%, based on all the metal elements in the alloy. Note that the silicon material may be single crystal, polycrystalline, or amorphous.

  Examples of the oxide containing a lithium atom include one or more selected from a lithium atom-containing oxide (olivine-type lithium-containing phosphate compound) represented by the following general formula (2) and having an olivine-type crystal structure: Is mentioned.

Li _1-x M _x (AO ₄ ) (2)
(In Formula (2), M is at least 1 selected from the group consisting of Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Ge, and Sn) (A) is at least one selected from the group consisting of Si, S, P, and V, and x is a number that satisfies the relationship 0 <x <1.
The value of x in the general formula (2) is selected according to the valences of M and A so that the overall valence of the general formula (2) becomes zero.

Examples of the olivine-type lithium-containing phosphate compound include lithium cobaltate, lithium nickelate, lithium manganate, ternary nickel cobalt lithium manganate, LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ , Li _0.90 Ti _0.05 Nb. _0.05 Fe _0.30 Co _0.30 Mn _0.30 PO _{4 and the} like. Among these, LiFePO ₄ (lithium iron phosphate) is particularly preferable because it is easy to obtain an iron compound as a raw material and is inexpensive.

  The average particle size of the olivine-type lithium-containing phosphate compound is preferably in the range of 1 to 30 μm, more preferably in the range of 1 to 25 μm, and particularly preferably in the range of 1 to 20 μm.

Further, the active material exemplified below may be included in the active material layer. For example, conductive polymer such as polyacene; A _X B _Y O _Z (where A is an alkali metal or transition metal, B is at least one selected from transition metals such as cobalt, nickel, aluminum, tin, manganese, O Represents an oxygen atom, and X, Y, and Z are numbers in the range of 1.10>X> 0.05, 4.00>Y> 0.85, and 5.00>Z> 1.5, respectively. And composite metal oxides represented by the above and other metal oxides.

  The slurry for an electricity storage device electrode according to this embodiment can be used when producing either an anode or an anode electricity storage device electrode, and is preferably used for both the positive electrode and the negative electrode.

When producing a positive electrode, it is preferable to use the oxide containing a lithium atom among the active materials illustrated above, an olivine type lithium-containing phosphate compound is more preferable, and lithium iron phosphate (LiFePO ₄ ) is particularly preferable. . Lithium iron phosphate is particularly preferable because it is easy to obtain an iron compound as a raw material and is inexpensive.

  By the way, when using lithium iron phosphate as a positive electrode active material, there existed a subject that charge / discharge characteristic was not enough and adhesiveness was inferior. Lithium iron phosphate has a fine primary particle size and is known to be a secondary aggregate thereof. Aggregation collapses in the active material layer when charging and discharging are repeated, and the active materials are separated from each other. It is considered that one of the factors is that peeling from the current collector and the conductive network inside the active material layer are easily broken.

  However, in the electricity storage device electrode produced using the electricity storage device electrode slurry according to the present embodiment, even when lithium iron phosphate is used, the above-described problems do not occur, and excellent electrical characteristics are exhibited. be able to. The reason for this is that the polymer (A) can firmly bind lithium iron phosphate, and at the same time can maintain the state in which lithium iron phosphate is firmly bound even during charge and discharge. It is thought that it is from.

  On the other hand, when producing a negative electrode, it is preferable that the active material illustrated above contains a silicon material. Since the silicon material has a large amount of lithium occlusion per unit weight compared to other active materials, by containing the silicon material as the negative electrode active material, it is possible to increase the storage capacity of the resulting electricity storage device, As a result, the output and energy density of the electricity storage device can be increased.

  The negative electrode active material is more preferably a mixture of a silicon material and a carbon material. Since the volume change due to charging and discharging is small, the use of a mixture of a silicon material and a carbon material as the negative electrode active material can alleviate the influence of the volume change of the silicon material. The adhesion ability with the electric body can be further improved. As such a mixture, a carbon-coated silicon material in which a carbon material film is formed on the surface of the silicon material can also be used. By using a carbon-coated silicon material, the effect of volume change associated with charging / discharging of the silicon material can be effectively mitigated by the carbon material existing on the surface, so that the active material layer and the current collector It becomes easy to improve the adhesion ability.

When silicon (Si) is used as an active material, silicon can occlude up to 22 lithium atoms per 5 atoms (5Si + 22Li → Li ₂₂ Si ₅ ). As a result, the theoretical silicon capacity reaches 4200 mAh / g. However, silicon causes a large volume change when occludes lithium. Specifically, the carbon material expands in volume up to about 1.2 times by occluding lithium, whereas the silicon material expands in volume up to about 4.4 times by occluding lithium. For this reason, the silicon material has the property that it is pulverized by repeated expansion and contraction, delamination from the current collector, and separation of the active materials, and the conductive network inside the active material layer is easily broken. As a result, the cycle characteristics are extremely deteriorated in a short time.

However, the electricity storage device electrode manufactured using the electricity storage device electrode slurry according to this embodiment may exhibit good electrical characteristics without causing the above-described problems even when a silicon material is used. it can. The reason for this is that the polymer (A) can firmly bind the silicon material, and at the same time, the polymer (A) expands and contracts even when the silicon material expands volume by occluding lithium. This is probably because the state in which the material is firmly bound can be maintained.

  The content ratio of the silicon material in 100 parts by mass of the active material is preferably 1 part by mass or more, more preferably 1 to 50 parts by mass, further preferably 5 to 45 parts by mass. It is especially preferable to set it as -40 mass parts. When the content ratio of the silicon material in 100 parts by mass of the active material is within the above range, an electricity storage device having an excellent balance between the output and energy density of the electricity storage device and charge / discharge durability characteristics can be obtained.

  When a silicon material and a carbon material are used in combination as the active material, the amount of the silicon material used is preferably 4 to 40 parts by mass when the total mass of the active material is 100 parts by mass, and 5 to 35 parts by mass. It is more preferable that it is 5-30 mass parts. Since the volume expansion of the carbon material relative to the volume expansion of the silicon material due to occlusion of lithium is small when the amount of silicon material used is within the above range, the volume change due to charge / discharge of the active material layer containing these active materials 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, and more preferably 1 to 20 μm.

  Here, the average particle diameter of the active material is a volume average particle diameter calculated from a particle size distribution measured by using a particle size distribution measuring apparatus based on a laser diffraction method. Examples of such a laser diffraction particle size distribution measuring apparatus include HORIBA LA-300 series, HORIBA LA-920 series (manufactured by Horiba, Ltd.) and the like. This particle size distribution measuring apparatus does not only evaluate primary particles of the active material, but also evaluates secondary particles formed by aggregation of the 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 the electricity storage device electrode. The average particle diameter of the active material can also be measured by centrifuging the slurry to settle the active material, removing the supernatant, and measuring the precipitated active material by the above method. .

  The use ratio of the active material is preferably such that the total content of the polymer (A) and the polymer (B) with respect to 100 parts by mass of the active material is 0.1 to 25 parts by mass, It is more preferable to use at a ratio of 0.5 to 15 parts by mass. By setting it as such a usage rate, it is possible to produce an electrode that is excellent in adhesiveness and has low electrode resistance and excellent charge / discharge characteristics.

2.2.2. Other Additives In addition to the components described above, other components may be added to the power storage device electrode slurry according to the present embodiment as necessary. Examples of such components include a conductivity-imparting agent, a thickener, a liquid medium (however, excluding a part brought in from the composition for an electricity storage device), a pH adjuster, a corrosion inhibitor, and the like.

<Conductivity imparting agent>
Specific examples of the conductivity-imparting agent include carbon in a lithium ion secondary battery. Examples of carbon include activated carbon, acetylene black, ketjen black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black and furnace black can be preferably used.
The use ratio of the conductivity-imparting agent is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, and particularly preferably 2 to 10 parts by mass with respect to 100 parts by mass of the active material. .

<Thickener>
From the viewpoint of improving the coatability of the slurry for the electricity storage device electrode, a thickener may be added. Specific examples of the thickener include the compounds described in “1.4. Other Additives”. The use ratio of the thickener is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the active material.

<Liquid medium>
Since the slurry for an electricity storage device electrode according to this embodiment contains the above-mentioned composition for an electricity storage device, it contains the liquid medium (C) contained in the composition for an electricity storage device. In addition to the liquid medium (C) brought from the composition for an electricity storage device, a slurry other than the liquid medium (C) may be added to the slurry for the electricity storage device electrode according to the present embodiment as necessary. Good.

  The liquid medium that can be added to the electricity storage device electrode slurry according to the present embodiment may be the same as or different from the liquid medium (C) contained in the electricity storage device composition, The liquid medium (C) in the composition for an electricity storage device is preferably selected from the liquid medium described above.

  The use ratio of the liquid medium (including the carry-in from the composition for the electricity storage device) in the slurry for the electricity storage device electrode according to this embodiment is the solid content concentration in the slurry (the total mass of components other than the liquid medium in the slurry). Is the ratio of 30 to 70% by mass, and more preferably 40 to 60% by mass.

<PH adjusters and corrosion inhibitors>
The slurry for an electricity storage device electrode according to the present embodiment can contain a pH adjusting agent or a corrosion inhibitor for the purpose of suppressing the corrosion of the current collector according to the type of the active material.

  Examples of the pH adjuster include hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, formic acid, ammonium phosphate, ammonium sulfate, ammonium acetate, ammonium formate, and ammonium chloride. Among these, sulfuric acid and ammonium sulfate are preferable.

  Corrosion inhibitors include ammonium metavanadate, sodium metavanadate, potassium metavanadate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, potassium paratungstate, and molybdic acid. Ammonium, sodium molybdate, potassium molybdate and the like can be mentioned, among which ammonium paratungstate, ammonium metavanadate, sodium metavanadate, potassium metavanadate and ammonium molybdate are preferable.

2.2.3. Method for Preparing Power Storage Device Electrode Slurry The power storage device electrode slurry according to the present embodiment was manufactured by any method as long as it contains the power storage device composition and the active material described above. However, it can be produced by a method described in, for example, Japanese Patent No. 599399.

3. An electricity storage device electrode according to this embodiment includes a current collector and an active material layer formed by applying and drying the above-mentioned slurry for an electricity storage device electrode on the surface of the current collector. It is. Such an electricity storage device electrode is formed by applying the above-mentioned slurry for an electricity storage device electrode on the surface of a current collector such as a metal foil to form a coating film, and then drying the coating film to form an active material layer. Can be manufactured. The electricity storage device electrode thus produced is an active material layer containing the above-described polymer (A), polymer (B), and active material on the current collector, and optional components added as necessary. Since it is formed by binding, it exhibits excellent adhesion and excellent charge / discharge durability characteristics.

  The current collector is not particularly limited as long as it is made of a conductive material, and examples thereof include current collectors described in Japanese Patent No. 599399.

  There is no restriction | limiting in particular also about the application | coating method to the electrical power collector of the slurry for electrical storage device electrodes, For example, it can apply | coat by the method described in patent 599399 grade | etc.,.

  In the electricity storage device electrode according to the present embodiment, when a silicon material is used as the active material, the content ratio of silicon element in 100 parts by mass of the active material layer is preferably 2 to 30 parts by mass, and 2 to 20 parts by mass. More preferably, it is 3 to 10 parts by mass. When the content of the silicon element in the active material layer is within the above range, an active material layer having a uniform silicon element distribution can be obtained in addition to improving the storage capacity of an electricity storage device manufactured using the active element layer. .

In the present invention, the content of silicon element in the active material layer can be measured by the following procedure. That is,
(1) Using a fluorescent X-ray analyzer (product name “Panalytic MagixPRO” manufactured by Spectris Co., Ltd.), a plurality of samples prepared in advance with a known silicon element content are measured, and a calibration curve is created.
(2) 3 g of the entire active material layer (not to collect only a part in the depth direction) is scraped from the power storage device electrode with a spatula or the like, and mixed with a mortar or the like so that the whole becomes uniform. Press into a disk-shaped plate. If the active material layer alone cannot be formed, an adhesive having a known elemental composition may be used as appropriate. As such an adhesive, for example, styrene / maleic acid resin, boric acid powder, cellulose powder and the like can be used. Further, even when the silicon content is high and the linearity of the calibration curve cannot be ensured, the sample can be diluted and measured using the adhesive. In addition, when using the said adhesive agent, in order to avoid the shift | offset | difference of the calibration curve by a matrix effect, it is preferable to similarly use an adhesive agent also for the calibration curve preparation sample.
(3) The obtained plate is set in a fluorescent X-ray analyzer and analyzed, and the silicon element content is calculated from the calibration curve. When the above adhesive is used, the silicon element content is calculated after subtracting the weight of the adhesive.

4). Power Storage Device The power storage device according to the present embodiment includes the above-described power storage device electrode, further contains an electrolytic solution, and can be manufactured according to a conventional method using components such as a separator. As a specific manufacturing method, for example, a negative electrode and a positive electrode are overlapped via a separator, and this is wound or folded according to the shape of the battery, and stored in a battery container, and an electrolytic solution is injected into the battery container. Can be mentioned. The shape of the battery can be an appropriate shape such as a coin shape, a cylindrical shape, a square shape, or a laminate shape.

The electrolyte solution may be liquid or gel, and an electrolyte that effectively expresses the function as a battery may be selected from the known electrolytes used for the electricity storage device according to the type of the active material. The electrolytic solution can be a solution in which an electrolyte is dissolved in a suitable solvent.

As the electrolyte, any conventionally known lithium salt can be used in the lithium ion secondary battery, and specific examples thereof include, for example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ CO ₂ , LiAsF _6. , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiCl, LiBr, LiB (C ₂ H ₅ ) ₄ , LiCF ₃ SO ₃ , LiCH ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, lower fatty acid lithium carboxylate and the like can be exemplified. In a nickel metal hydride secondary battery, for example, an aqueous potassium hydroxide solution having a conventionally known concentration of 5 mol / liter or more can be used.

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

5. EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. “Part” and “%” in Examples and Comparative Examples are based on mass unless otherwise specified.

5.1. Synthesis of Polymer (1) Synthesis of Polymers (A1) to (A-26) Polymer (A1) was obtained by polymerization as shown below. The interior of the 7 L separable flask was sufficiently purged with nitrogen, charged with 310 parts by mass of water, heated to an internal temperature of 80 ° C., and then charged with 0.5 parts by mass of sodium persulfate. Next, a mixed solution of 50 parts by mass of water and 100 parts by mass of 2-hydroxyethyl acrylate is dropped over 1 hour, reacted at 80 ° C. ± 3 ° C. for 2 hours, and further reacted at 90 ° C. ± 3 ° C. for 4 hours. went. Then, it cooled and adjusted to pH 7 with 2.5% sodium hydroxide aqueous solution, and the composition containing 20 wt% of polymers (A1) was obtained. The composition containing 20 wt% of the polymer (A1) thus obtained was designated as a power storage device composition A1.

  The polymers (A2) to (A26) were synthesized in the same manner as in the synthesis example of the polymer (A1) except that the types and content ratios of the monomers used were changed as shown in Tables 1 and 2. And composition A2-A26 for electrical storage devices was obtained.

Abbreviations of each component in Tables 1 and 2 represent the following compounds, respectively.
<Unsaturated carboxylic acid ester having a hydroxyl group>
-HEA: 2-hydroxyethyl acrylate-HEMA: 2-hydroxyethyl methacrylate <(meth) acrylamide>
AAM: acrylamide MAMA: methacrylamide <other monomers>
MMA: methyl methacrylate BA: n-butyl acrylate EA: ethyl acrylate

(2) Synthesis of polymers (B1) to (B13) A composition containing particles of the polymer (B1) was obtained by two-stage polymerization as shown below. In the first stage polymerization, 211 parts by weight of water, 79 parts by weight of a monomer mixture consisting of 33 parts by weight of 1,3-butadiene, 42 parts by weight of styrene, 2 parts by weight of methacrylic acid and 2 parts by weight of acrylic acid are added to the reactor. , 0.1 part by mass of t-dodecyl mercaptan as a chain transfer agent, 1 part by mass of sodium alkyldiphenyl ether disulfonate as an emulsifier, and 0.2 part by mass of potassium persulfate as a polymerization initiator were stirred at 60 ° C. Polymerization was carried out for 18 hours, and the reaction was terminated at a polymerization conversion of 96%. Subsequently, in the second stage polymerization, 189 parts by mass of water, 21 parts by mass of methacrylic acid, 0.05 parts by mass of potassium persulfate as a polymerization initiator, and 0.1 parts by mass of sodium carbonate were added to this reactor. After the addition and the polymerization reaction was continued at 80 ° C. for 2 hours, the reaction was terminated. The polymerization conversion rate at this time was 98%. Unreacted monomers are removed from the resulting latex of the polymer (B1) (particle dispersion of polymer (B1)), and after concentration, a 10% aqueous sodium hydroxide solution and water are added, and the polymer (B1 The solid content concentration and pH of the particle dispersion of () were adjusted to obtain a pH 4.4 power storage device composition B1 containing 20% of the polymer (B1) particles.

  Polymers (B2) to (B) are used in the same manner as in the synthesis example of the polymer (B1) except that the types, content ratios and synthesis methods used are changed as shown in Tables 3 to 4. B13) was synthesized to obtain power storage device compositions B2 to B13. The polymers (B5) to (B8) and (B10) to (B13) were synthesized by one-stage polymerization without performing the second-stage polymerization.

(3) Synthesis of polymers (B14) to (B18) The inside of an autoclave having an internal volume of 6 L equipped with an electromagnetic stirrer was sufficiently purged with nitrogen, and then deoxygenated 2.5 L of pure water and perfluorodecane as an emulsifier 25 g of ammonium acid was charged, and the temperature was raised to 60 ° C. while stirring at 350 rpm. Next, a mixed gas composed of 70% of vinylidene fluoride (VdDF) and 30% of propylene hexafluoride (HFP) as monomers was charged until the internal pressure reached 20 kg / cm ² . 25 g of Freon 113 solution containing 20% of diisopropyl peroxydicarbonate as a polymerization initiator was injected using nitrogen gas to initiate polymerization. During the polymerization, a mixed gas composed of 60% VdDF and 40% HFP was sequentially injected so that the internal pressure was maintained at 20 kg / cm ² to maintain the pressure at 20 kg / cm ² . Further, since the polymerization rate decreased as the polymerization progressed, the same amount of the same polymerization initiator solution as that described above was injected using nitrogen gas after 3 hours, and the reaction was continued for 3 hours. Thereafter, the reaction liquid was cooled and the stirring was stopped at the same time. After the unreacted monomer was released, the reaction was stopped to obtain an aqueous dispersion containing 40% of fluoropolymer particles. The obtained fluoropolymer was analyzed by ¹⁹ F-NMR. As a result, the mass composition ratio of each monomer was VdDF / HFP = 21/4.

After the inside of the 7-L separable flask was sufficiently purged with nitrogen, 25 parts by mass of an aqueous dispersion containing the fluoropolymer particles obtained in the above-mentioned step was converted into a fluoropolymer, and the emulsifier “Adekalia” Soap SR1025 "(trade name, manufactured by ADEKA Corporation) 0.5 parts by mass, cyclohexyl methacrylate (CHMA) 22.5 parts by mass, ethyl acrylate (EA) 48 parts by mass, allyl methacrylate (AMA) 0.5 parts by mass Part, 2 parts by weight of methacrylamide (AAM), 2 parts by weight of acrylic acid (AA) and 130 parts by weight of water were sequentially added and stirred at 70 ° C. for 3 hours to allow the fluoropolymer to absorb the monomer. Next, 20 mL of a tetrahydrofuran solution containing 0.5 part by mass of azobisisobutyronitrile, which is an oil-soluble polymerization initiator, is added, heated to 75 ° C. and reacted for 3 hours, and further reacted at 85 ° C. for 2 hours. went. Then, after cooling, the reaction was stopped, and the pH was adjusted to 6.8 with a 2.5N aqueous sodium hydroxide solution to obtain a power storage device composition B14 containing 40% of the polymer (B14).

  The polymers (B15) to (B18) were synthesized in the same manner as in the synthesis example of the polymer (B14) except that the types and content ratios of the monomers used were changed as shown in Table 4. Device compositions B15 to B18 were obtained.

Abbreviations of each component in Tables 3 to 4 represent the following compounds, respectively.
<Monomer having a fluorine atom>
VdDF: vinylidene fluoride HFP: propylene hexafluoride TFE: ethylene tetrafluoride 2VE: 1,1,2,2-tetrafluoro-1,2-bis [(trifluorovinyl) oxy] ethane <not Saturated carboxylic acid>
-AA: Acrylic acid-TA: Itaconic acid-MAA: Methacrylic acid <(Meth) acrylamide>
AAM: acrylamide MAMA: methacrylamide <conjugated diene compound>
BD: 1,3-butadiene <aromatic vinyl compound>
ST: Styrene <Unsaturated carboxylic acid ester having a hydroxyl group>
-HEA: 2-hydroxyethyl acrylate-HEMA: 2-hydroxyethyl methacrylate <unsaturated carboxylic acid ester>
MMA: methyl methacrylate CHMA: cyclohexyl methacrylate 2EHA: 2-ethylhexyl acrylate EA: ethyl acrylate BA: n-butyl acrylate AMA: methyl acrylate <α, β-unsaturated nitrile compound>
・ AN: Acrylonitrile

(4) Physical property evaluation <Solubility in water>
Whether or not 1 g of each of the polymers (A1) to (A26) obtained above was dissolved in 100 g of water was visually observed at 25 ° C. and 1 atm. The results are also shown in Table 1 and Table 2. The case where it was completely dissolved was indicated in the table as “◯”, and the case where there was an undissolved portion was indicated as “x”.

<Measurement of number average particle size>
Using a particle size distribution measuring apparatus (model “FPAR-1000” manufactured by Otsuka Electronics Co., Ltd.) having a dynamic light scattering method as a measurement principle, the particle size distribution of the polymers (B1) to (B18) obtained above is determined. The number average particle size was determined from the particle size distribution. The measurement conditions are as follows. The measurement results are also shown in Tables 3 and 4.
(Measurement condition)
-Dispersion medium: water-Measurement temperature: 25 ° C
・ Dilution factor: 0.1 wt%
-Scattering angle: 160 °
-Light source laser wavelength: 632.8 nm

<Measurement of pH>
About the electrical storage device composition B1-B18 obtained above, pH at 25 degreeC was measured using the pH meter (Horiba Ltd. make). The measurement results are also shown in Tables 1 to 4.

<Endothermic characteristics>
About composition A1-A26 and B1-B18 for electrical storage devices obtained above, JIS
When measured using a differential scanning calorimeter (made by NETZSCH, DSC204F1 Phoenix) based on K7121, one endothermic peak of the polymer was observed. The temperature at which the endothermic peak is observed can be regarded as the glass transition temperature (Tg). Tables 1 to 4 show the glass transition temperature (Tg) of each polymer.

5.2. Example 1
5.2.1. Preparation of composition for electricity storage device The composition A1 for electricity storage device and the composition B5 for electricity storage device obtained above were combined into 1.5 parts by mass of the polymer (A1) and 2.0 parts by mass of the polymer (B5). Only the corresponding amount was added, and the mixture was stirred at 60 rpm for 1 hour to obtain the composition for an electricity storage device used in Example 1.

5.2.2. Preparation and Evaluation of Storage Device Electrode Slurry (1) Synthesis of Silicon Material (Active Material) A mixture of pulverized silicon dioxide powder (average particle size 10 μm) and carbon powder (average particle size 35 μm) was heated to 1100-1600. Oxidation represented by the composition formula SiO _x (x = 0.5 to 1.1) by performing heat treatment for 10 hours in a nitrogen stream (0.5 NL / min) in an electric furnace adjusted to a range of ° C. A silicon powder (average particle size 8 μm) was obtained. 300 g of this silicon oxide powder was charged into a batch-type heating furnace, and the temperature was raised from room temperature (25 ° C.) to 1100 ° C. at a temperature raising rate of 300 ° C./h while maintaining a reduced pressure of 100 Pa absolute pressure with a vacuum pump. . Next, heat treatment (graphite coating treatment) was performed at 1100 ° C. for 5 hours while introducing methane gas at a flow rate of 0.5 NL / min while maintaining the pressure in the heating furnace at 2000 Pa. After the completion of the graphite coating treatment, the powder was cooled to room temperature at a temperature decrease rate of 50 ° C./h to obtain about 330 g of graphite-coated silicon oxide powder. This graphite-coated silicon oxide is a conductive powder (active material) in which the surface of silicon oxide is coated with graphite, and its average particle diameter is 10.5 μm. The ratio of the graphite film in the case of mass% was 2 mass%.

(2) Preparation of slurry for electricity storage device electrode A thickener (trade name “CMC2200”, manufactured by Daicel Corporation) is added to a biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation). 1 part by mass (added as an aqueous solution having a solid content conversion value and a concentration of 2% by mass), 94 parts by mass of artificial graphite (trade name “MAG”, manufactured by Hitachi Chemical Co., Ltd.) which is highly crystalline graphite as the negative electrode active material ( Solid content equivalent value), 6 parts by mass (solid content equivalent value) of the graphite-coated film silicon oxide powder obtained above, and 68 parts by mass of water were added and stirred at 60 rpm for 1 hour. Thereafter, the power storage device composition obtained above was added so that the polymer (A1) was 1.5 parts by mass and the polymer (B5) was 2 parts by mass with respect to 100 parts by mass of the active material. Stir for 1 hour to obtain a paste. Water is added to the obtained paste, and the solid content concentration is adjusted to 50% by mass. Then, using a stirring defoaming machine (trade name “Netaro Awatori” manufactured by Shinky Co., Ltd.) for 2 minutes at 200 rpm. By stirring and mixing at 1800 rpm for 5 minutes and further under reduced pressure (about 2.5 × 10 ⁴ Pa) at 1800 rpm for 1.5 minutes, a slurry for an electricity storage device electrode containing 5% by mass of Si in the negative electrode active material ( C / Si (5%)) was prepared.

In addition, a power storage device that does not contain Si in the negative electrode active material in the same manner as the slurry for power storage device electrodes (C / Si (5%)), except that the amount of artificial graphite and graphite coating film silicon oxide powder was adjusted. Device electrode slurry (C), power storage device electrode slurry (C / Si (10%)) containing 10% by mass of Si in the negative electrode active material, and power storage containing 20% by mass of Si in the negative electrode active material A device electrode slurry (C / Si (20%)) was prepared.

5.2.3. Production and evaluation of electricity storage device (1) Production of electricity storage device electrode (negative electrode) On the surface of a current collector made of copper foil having a thickness of 20 μm, the slurry for electricity storage device electrode obtained above (C / Si (5%)) Was applied uniformly by a doctor blade method so that the film thickness after drying was 80 μm, dried at 60 ° C. for 10 minutes, and then dried at 120 ° C. for 10 minutes. Then, the electrical storage device electrode (negative electrode) was obtained by pressing with a roll-press machine so that the density of an active material layer may be 1.5 g / cm < ³ >.

  In addition, the type of the slurry for the electricity storage device electrode to be applied is a slurry for the electricity storage device electrode (C), the slurry for the electricity storage device electrode (C / Si (10%)) that does not contain Si in the negative electrode active material obtained above, or An electricity storage device electrode (negative electrode) containing each active material in the active material layer in the same manner as in the method for producing an electricity storage device electrode, except that the slurry was changed to an electricity storage device electrode slurry (C / Si (20%)). Got.

(2) Manufacture of counter electrode (positive electrode) A biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) and an electrochemical device electrode binder (product name “KF” manufactured by Kureha Co., Ltd.) "Polymer # 1120", hereinafter abbreviated as "PVDF") 4.0 parts by weight (in terms of solid content), conductive aid (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name "Denka Black 50% Press") parts by, LiCoO ₂ (Hayashi Kasei Co., Ltd.) having an average particle diameter of 5μm as a positive electrode active material 100 parts by mass (in terms of solid content) and N- methylpyrrolidone (NMP) 36 parts by weight were charged, stirred for 2 hours at 60rpm Went. After adding NMP to the obtained paste and adjusting the solid content concentration to 65% by mass, the mixture was stirred at 200 rpm for 2 minutes at 200 rpm using a defoaming machine (product name “Netaro Awatori”). The positive electrode slurry was prepared by stirring and mixing at 1,800 rpm for 5 minutes and further under reduced pressure (about 2.5 × 10 ⁴ Pa) at 1,800 rpm for 1.5 minutes. The positive electrode slurry was uniformly applied to the surface of the current collector made of aluminum foil by a doctor blade method so that the film thickness after solvent removal was 80 μm, and the solvent was removed by heating at 120 ° C. for 20 minutes. . Then, the counter electrode (positive electrode) was obtained by pressing with a roll press so that the density of an active material layer might be 3.0 g / cm < ³ >.

(3) Assembly of lithium ion battery cell In a glove box substituted with Ar so that the dew point is −80 ° C. or lower, the negative electrode produced above was punched and molded to a diameter of 15.95 mm. It was mounted on a product name “HS flat cell” manufactured by Izumi Co., Ltd.). Next, a separator made of a polypropylene porous membrane punched to a diameter of 24 mm (product name “Celguard # 2400” manufactured by Celgard Co., Ltd.) was placed, and after injecting 500 μL of electrolyte so that air did not enter, The manufactured positive electrode was punched and molded to a diameter of 16.16 mm, and the outer body of the bipolar coin cell was sealed with a screw to assemble a lithium ion battery cell (storage device). The electrolytic solution used here is a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio).

(4) Evaluation of charge / discharge cycle characteristics About the electricity storage device manufactured above, charging was started at a constant current (1.0 C) in a thermostatic chamber adjusted to 25 ° C., and the voltage became 4.2V. Then, charging was continued at a constant voltage (4.2 V), and charging was completed (cut off) when the current value reached 0.01C. Thereafter, discharging was started at a constant current (1.0 C), and when the voltage reached 3.0 V, discharging was completed (cutoff), and the discharge capacity at the first cycle was calculated. Thus, charging / discharging was repeated 100 times, and the discharge capacity at the 100th cycle was calculated. A value obtained by dividing the discharge capacity at the 100th cycle thus measured by the discharge capacity at the 1st cycle was defined as a 100 cycle capacity retention rate (%). When the capacity retention ratio at the 100th cycle is 80% or more with respect to all the active materials, it can be determined that the deterioration of the electrode that occurs in the charge / discharge cycle is suppressed.

(5) Evaluation of electrode expansion coefficient The film thickness of the electricity storage device electrode (negative electrode) produced above was measured and used as the negative electrode film thickness (X0) before the cycle test. Next, charging of the electricity storage device manufactured above was started at a constant current (1.0 C) in a thermostatic chamber adjusted to 25 ° C., and when the voltage reached 4.2 V, the constant voltage ( Charging was continued at 4.2 V), and charging was completed (cut-off) when the current value reached 0.01C. Thereafter, discharge was started at a constant current (1.0 C), and the time when the voltage reached 3.0 V was defined as discharge completion (cutoff), and the first cycle. Thus, after repeating charging / discharging 10 times, the electrical storage device was disassembled and the negative electrode was taken out. The taken-out negative electrode was washed with dimethyl carbonate, dried at room temperature for 12 hours, and the film thickness was measured to obtain the negative electrode film thickness (X1) before the cycle test. The electrode expansion coefficient was a value defined by the following formula.
Electrode expansion rate (%) = (X1 / X0) × 100
The electrode expansion coefficient is 105% or less in the case of an electrode using the slurry (C) for an electricity storage device electrode not containing Si in the negative electrode active material, and the slurry for the electricity storage device electrode containing 20% by mass of Si in the negative electrode active material In the case of an electrode using (C / Si (20%)), if it is 130% or less, the expansion of the electrode occurring in the charge / discharge cycle is suppressed, and it can be determined that it is good.

5.3. Examples 2 to 21 and Comparative Examples 1 to 13
In “5.2.1. Preparation of composition for electricity storage device” in Example 1 above, the polymer (A) and the polymer (B) were changed so as to have the content ratios shown in Table 5 or Table 6. Except for the above, an electricity storage device composition was obtained in the same manner as in Example 1. Further, a slurry for an electricity storage device electrode was prepared in the same manner as in Example 1 except that the composition for an electricity storage device thus prepared was used, and an electricity storage device electrode and an electricity storage device were produced, respectively. Evaluation was performed in the same manner as in 1.

5.4. Evaluation results Tables 5 and 6 below summarize the compositions of the electricity storage device compositions used in Examples 1 to 21 and Comparative Examples 1 to 13 and the evaluation results.

5.5. Example 22
5.5.1. Preparation of composition for electricity storage device The composition A1 for electricity storage device and the composition B14 for electricity storage device obtained above were combined into 1.0 part by mass of the polymer (A1) and 2.0 parts by mass of the polymer (B14). Each of the corresponding amounts was added and stirred at 60 rpm for 1 hour to obtain a composition for an electricity storage device used in Example 22.

5.5.2. Production and evaluation of electricity storage device (1) Preparation of positive electrode slurry and production of electricity storage device positive electrode A biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) and a thickener (product) Name “CMC2200” (manufactured by Daicel Co., Ltd.) 1 part by mass (in terms of solid content), and a commercially available nickel / manganese / lithium cobaltate (nickel (Ni), cobalt (Co), manganese) having a particle size (D50 value) of 10 μm (Mn) ratio 1: 1: 1) 100 parts by mass of active material particles, 3 parts by mass of acetylene black, 1 part by mass of ammonium sulfate and 1 part by mass of water were added and stirred at 90 rpm for 1 hour. Thereafter, the composition for an electricity storage device obtained above was added so that the polymer (A1) was 1.0 part by mass and the polymer (B14) was 2.0 parts by mass with respect to 100 parts by mass of the active material. The mixture was further stirred for 1 hour to obtain a paste. After adding water to the obtained paste to adjust the solid content concentration to 65%, using a stirring defoamer (trade name “Awatori Nertaro” manufactured by Shinky Co., Ltd.) for 2 minutes at 200 rpm for 1 minute. The slurry for positive electrode was prepared by stirring and mixing at 800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes.

The positive electrode slurry was uniformly applied to the surface of the current collector made of aluminum foil by a doctor blade method so that the film thickness after solvent removal was 80 μm, and the solvent was removed by heating at 120 ° C. for 20 minutes. . Then, the positive electrode was obtained by pressing with a roll press so that the density of an active material layer might be set to 3.0 g / cm < ³ >.

(2) Production of Counter Electrode (Negative Electrode) Of the negative electrode produced in Example 1, produced using a slurry for an electricity storage device electrode (C / Si (10%)) containing 10% by mass of Si in the negative electrode active material. What was done was used.

(3) Assembly of lithium ion battery cell An electricity storage device was produced in the same manner as in Example 1 except that the electricity storage device electrode produced above was used, and evaluated in the same manner as in Example 1.

(4) Evaluation of crack rate of electrode plate The positive electrode plate obtained above was cut into a width of 2 cm and a length of 10 cm, and the positive electrode plate was repeatedly bent along a round bar with a diameter of 2 mm in the width direction at 100 times. A test was conducted. The crack size was measured by visually observing and measuring the size of the crack along the round bar. The crack rate was defined by the following formula (3).
Crack rate (%) = (Length with crack (mm) ÷ Total length of electrode plate (mm)) × 100 (3)
The crack rate was evaluated in 5% increments by rounding off to make it easier to clarify the difference. Here, the electrode plate excellent in flexibility and adhesion has a low crack rate. The crack rate is preferably 0%. However, when the electrode plate group is manufactured by winding the positive electrode plate and the negative electrode plate in a spiral shape through a separator, the crack rate is allowed to be up to 20%. However, when the crack rate is greater than 20%, the electrode plates are easily cut, making it impossible to manufacture the electrode plate group, and the productivity of the electrode plate group is lowered. From this, it was judged that the crack rate was up to 20%.

(5) Evaluation of charge / discharge cycle characteristics For the electricity storage device prepared above, 100 cycle capacity retention (%) was calculated in the same manner as in Example 1. In addition, charge and discharge were repeated up to 500 cycles, and the capacity retention rate (%) at 500 cycles was calculated. When the difference between the capacity retention rate at 100 cycles and the capacity retention rate at 500 cycles is 16% or less, it is possible to judge that the deterioration when charging and discharging are repeated is good.

5.6. Examples 23-29 and Examples 33-36
Except that the polymer (A) and the polymer (B) were changed so as to have the contents shown in Table 7 in “5.5.1. Preparation of composition for electricity storage device” in Example 22 above, A composition for an electricity storage device was obtained in the same manner as in Example 22. Furthermore, a slurry for an electricity storage device electrode was prepared in the same manner as in Example 22 except that the composition for an electricity storage device prepared above was used, and an electricity storage device electrode and an electricity storage device were produced, respectively. And evaluated in the same manner.

5.7. Example 30
5.7.1. Preparation of composition for electricity storage device The composition A11 for electricity storage device and the composition B18 for electricity storage device obtained above were mixed in 5.0 parts by mass of the polymer (A11) and 4.0 parts by mass of the polymer (B18). Each of the corresponding amounts was added and stirred at 60 rpm for 1 hour to obtain a composition for an electricity storage device used in Example 30.

5.7.2. Preparation of slurry for positive electrode and preparation of power storage device positive electrode A biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.) and a thickener (product name “CMC1120” manufactured by Daicel Corporation) ) 1 part by mass (in terms of solid content), 100 parts by mass of lithium iron phosphate (LiFePO ₄ ) manufactured by Hosen Co., Ltd., 5 parts by mass of acetylene black, and 68 parts by mass of water were added and stirred at 60 rpm for 1 hour. It was. The lithium iron phosphate is pulverized in an agate mortar and classified using a sieve to have an average particle diameter (D50 value) of 10 μm. The lithium iron phosphate is an example of a positive electrode active material. Thereafter, the composition for an electricity storage device obtained above was added so that the polymer (A11) was 5.0 parts by mass and the polymer (B18) was 4.0 parts by mass with respect to 100 parts by mass of the active material. The mixture was further stirred for 1 hour to obtain a paste.

Water was added to the obtained paste to adjust the solid content concentration to 50%, and then the mixture was stirred at 200 rpm for 2 minutes using a stirring defoamer (trade name “Awatori Nertaro” manufactured by Shinky Co., Ltd.). The slurry for positive electrode was prepared by stirring and mixing at 800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes. The positive electrode slurry was uniformly applied to the surface of the current collector made of aluminum foil by a doctor blade method so that the film thickness after solvent removal was 80 μm, and the solvent was removed by heating at 120 ° C. for 20 minutes. . Then, the positive electrode was obtained by pressing with a roll press so that the density of an active material layer might be 2.0 g / cm < ³ >.

  Thereafter, a negative electrode and an electricity storage device were produced in the same manner as in Example 22, and evaluated in the same manner as in Example 22.

5.8. Examples 31-32 and Comparative Example 14
Except that the polymer (A) and the polymer (B) were changed so as to have the contents shown in Table 7 in “5.7.1. Preparation of composition for electricity storage device” in Example 30 above, A composition for an electricity storage device was obtained in the same manner as in Example 30. Further, a slurry for an electricity storage device electrode was prepared in the same manner as in Example 30 except that the composition for an electricity storage device prepared above was used, and an electricity storage device electrode and an electricity storage device were produced, respectively. And evaluated in the same manner.

5.9. Evaluation Results Table 7 below summarizes the compositions of the electricity storage device compositions used in Examples 22 to 36 and Comparative Example 14 and the evaluation results.

Abbreviations of each component in Table 7 represent the following compounds, respectively.
<Active material>
NMC (111): nickel, manganese, lithium cobaltate (ratio of nickel (Ni), cobalt (Co), manganese (Mn) 1: 1: 1) active material particles NMC (532): nickel, manganese, cobalt Lithium oxide (nickel (Ni), cobalt (Co), manganese (Mn) ratio 5: 3: 2) active material particles NMC (622): nickel manganese manganese lithium cobaltate (nickel (Ni), cobalt (Co ), Manganese (Mn) ratio 6: 2: 2) active material particles • LCO: lithium cobaltate (LiCoO ₂ ), manufactured by Hayashi Kasei Co., Ltd. • LFP: lithium iron phosphate (LiFePO ₄ ), manufactured by Hosen Co., Ltd. <Conductive aid>
・ AB: Acetylene black

  As is apparent from Table 5, the electricity storage device including the negative electrode produced using the composition for electricity storage device according to the present invention shown in Examples 1 to 21 is 100 cycles regardless of which active material is used. The subsequent capacity retention was excellent, and the electrode expansion coefficient could be kept low. On the other hand, as is apparent from Table 6, in Comparative Examples 1 to 13, the capacity retention after 100 cycles tends to decrease as the content ratio of the silicon material in the active material increases, and the electrode expansion coefficient is observed. Could not be kept low.

  As is clear from Table 7, the electricity storage device including the positive electrode produced using the composition for electricity storage device according to the present invention shown in Examples 22 to 36 can suppress the crack rate to a low level, and is charged / discharged. It was found that the deterioration when the process was repeated was suppressed. On the other hand, in Comparative Example 14, it was found that the crack rate could not be kept low, and deteriorated early by repeated charge and discharge.

  The present invention is not limited to the above embodiment, and various modifications can be made. The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). The present invention also includes a configuration in which a non-essential part of the configuration described in the above embodiment is replaced with another configuration. Furthermore, the present invention includes a configuration that achieves the same effects as the configuration described in the above embodiment or a configuration that can achieve the same object. Furthermore, the present invention includes a configuration obtained by adding a known technique to the configuration described in the above embodiment.

Claims (16)

Containing a polymer (A), a polymer (B), and a liquid medium (C),
When the total of repeating units contained in the polymer (A) is 100 parts by mass, the polymer (A) contains 50 parts by mass or more of repeating units derived from an unsaturated carboxylic acid ester having a hydroxyl group. ,
When the total of repeating units contained in the polymer (B) is 100 parts by mass, the polymer (B) contains 0 to 50 parts by mass of repeating units derived from an unsaturated carboxylic acid ester having a hydroxyl group. The composition for electrical storage devices containing less than 1 part.   The endothermic peak is observed in the temperature range of -20 ° C to 80 ° C when differential scanning calorimetry (DSC) is performed on the polymer (A) according to JIS K7121. A composition for an electricity storage device.   The composition for an electricity storage device according to claim 1 or 2, wherein the solubility of the polymer (A) in water at 25 ° C and 1 atm is 1 g or more with respect to 100 g of water.   4. The unsaturated carboxylic acid ester having a hydroxyl group is at least one selected from the group consisting of hydroxyethyl (meth) acrylate and glycerin mono (meth) acrylate. 5. A composition for an electricity storage device.   The composition for an electrical storage device according to any one of claims 1 to 4, wherein the polymer (A) further contains 1 to 40 parts by mass of a repeating unit derived from (meth) acrylamide.   The polymer (B) further contains 50 to 100 parts by mass of a repeating unit derived from an unsaturated carboxylic acid ester (excluding the unsaturated carboxylic acid ester having a hydroxyl group). The composition for electrical storage devices as described in any one.   The polymer (B) further contains 20 to 70 parts by mass of a repeating unit derived from a conjugated diene compound and 0.5 to 30 parts by mass of a repeating unit derived from an unsaturated carboxylic acid. The composition for electrical storage devices as described in any one of Claims 5-6.   The composition for an electricity storage device according to any one of claims 1 to 7, wherein the polymer (B) further contains 1 to 30 parts by mass of a repeating unit derived from a (meth) acrylamide compound.   The value of Mb / Ma is 0.5 to 5.0, when the content of the polymer (A) is Ma parts by mass and the content of the polymer (B) is Mb parts by mass. The composition for electrical storage devices as described in any one of Claim 1 thru | or 8.   The composition for an electricity storage device according to any one of claims 1 to 9, wherein the polymer (B) is a particle, and the number average particle diameter thereof is 50 nm or more and 1000 nm or less.   The composition for electrical storage devices according to any one of claims 1 to 10, wherein the liquid medium (C) is water.   The slurry for electrical storage device electrodes containing the composition for electrical storage devices as described in any one of Claims 1 thru | or 11, and an active material.   The slurry for an electrical storage device electrode according to claim 12, comprising a silicon material as the active material.   The active material contains at least one selected from the group consisting of an olivine-type lithium-containing phosphate compound, lithium cobaltate, lithium nickelate, lithium manganate, and ternary nickel cobalt lithium manganate. The slurry for an electricity storage device electrode as described.   An electricity storage comprising: a current collector; and an active material layer formed by applying and drying the power device electrode slurry according to any one of claims 12 to 14 on a surface of the current collector. Device electrode.   An electricity storage device comprising the electricity storage device electrode according to claim 15.