JP2013194112A - Agent for forming gel electrolyte, composition for forming gel electrolyte, gel electrolyte and power-accumulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an agent for forming a gel electrolyte, enabling the gel electrolyte to be produced, having an ion conductivity sufficient for exhibiting good charge-discharge characteristics, and exhibiting improved properties for retaining an electrolyte and a gel strength compared to conventional gel electrolytes.SOLUTION: An agent for forming gel electrolytes includes an acrylic polymer (A) and a vinylidene fluoride-based polymer (B), wherein the acrylic polymer (A) has a repeating unit (A1) derived from a (meth)acrylate having a cyclic ether structure.

Description

  The present invention relates to a gel electrolyte forming agent, a gel electrolyte forming composition containing the gel electrolyte forming agent, a gel electrolyte formed from the gel electrolyte forming composition, and an electricity storage device including the gel electrolyte.

  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 equipment. In such an electricity storage device, the electrolyte (ion conductor) is an indispensable element that greatly affects its performance. In general, a liquid substance has high ionic conductivity. Therefore, in a power storage device such as a lithium ion secondary battery or a lithium ion capacitor, a liquid electrolyte in which a lithium electrolyte salt is dissolved in a solvent mainly composed of propylene carbonate, ethylene carbonate, or the like is usually used.

  However, in an electricity storage device using such a liquid electrolyte, in addition to the risk of leakage of the electrolyte, there are safety problems such as temperature rise, internal pressure rise, rupture, and fire due to usage environment, misuse, accidents, etc. Has been pointed out. One of the causes is that a liquid is used for the electrolyte. Therefore, development of gel electrolytes (hereinafter also referred to as “gel electrolytes”) has been studied from the viewpoints of stability (nonvolatile), safety (non-explosive), and ease of production (thin film processing, etc.). (For example, see Patent Documents 1 to 3). As a technique for producing such a gel electrolyte, a physical gel electrolyte or a chemical gel electrolyte is generally known. The former is a solidification technique using non-covalent bonds such as hydrogen bonds and van der Waals forces, while the latter is a gelation method by a chemical reaction utilizing the formation of a polymer compound.

JP 2001-176555 A JP 2002-110245 A JP 2009-70605 A

  However, conventional physical gel electrolytes sometimes have insufficient electrolyte retention. If the electrolyte retention is insufficient, charge / discharge characteristics of the electricity storage device due to separation between the gel electrolyte and the electrolyte and deterioration of the electricity storage device due to leakage of the electrolyte separated from the gel electrolyte are sufficient. Could not be suppressed.

  On the other hand, in the conventional chemical gel electrolyte, the gel strength of the produced gel electrolyte may be insufficient. For example, when a chemical gel electrolyte is used for a laminate type battery (battery only covered with a film), there is a problem that it is difficult to maintain the shape.

  Therefore, some embodiments according to the present invention have sufficient ionic conductivity for expressing good charge / discharge characteristics by solving the above-described problems, and also have an electrolytic solution as compared with a conventional gel electrolyte. It is intended to provide a gel electrolyte forming agent capable of producing a gel electrolyte with improved liquid retention and gel strength.

  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 the following aspects or application examples.

[Application Example 1]
One aspect of the gel electrolyte forming agent according to the present invention is:
An acrylic polymer (A) and a vinylidene fluoride polymer (B),
The acrylic polymer (A) has a repeating unit (A1) derived from (meth) acrylate having a cyclic ether structure.

[Application Example 2]
In the gel electrolyte forming agent of Application Example 1,
The vinylidene fluoride polymer (B) can be contained in an amount of 5 parts by mass to 200 parts by mass with respect to 100 parts by mass of the acrylic polymer (A).

（式（１）中、Ｒ^１は水素原子またはメチル基を表し、Ｒ^２は２価の連結基を表し、Ｒ^３は水素原子または１価の有機基を表し、複数存在するＲ^４はそれぞれ独立に水素原子または１価の有機基を表す。ｍおよびｎは０以上の整数であり、ｍ＋ｎ＞１である。） [Application Example 3]
In the gel electrolyte forming agent of Application Example 1 or Application Example 2,
The (meth) acrylate having the cyclic ether structure may be a compound represented by the following general formula (1).

(In Formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent linking group, R ³ represents a hydrogen atom or a monovalent organic group, and a plurality of R ^{4 s} are present. Independently represents a hydrogen atom or a monovalent organic group, m and n are integers of 0 or more, and m + n> 1.)

[Application Example 4]
In the gel electrolyte forming agent of any one of Application Examples 1 to 3,
The acrylic polymer (A) may further have a repeating unit (A2) derived from (meth) acrylate having a chain ether structure.

（式（２）中、Ｒ^５は水素原子またはメチル基を表し、Ｒ^６は単結合または２価の有機基を表し、複数存在してもよいＲ^７はそれぞれ独立に２価の炭化水素基を表し、Ｒ^８は水素原子または１価の有機基を表す。ｘは１以上の整数である。） [Application Example 5]
In the gel electrolyte forming agent of Application Example 4,
The (meth) acrylate having the chain ether structure may be a compound represented by the following general formula (2).

(In formula (2), R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents a single bond or a divalent organic group, and a plurality of R ^{7 s} may be independently a divalent hydrocarbon group. R ⁸ represents a hydrogen atom or a monovalent organic group, and x is an integer of 1 or more.)

[Application Example 6]
In the gel electrolyte forming agent of Application Example 4 or Application Example 5,
When the total amount of the repeating unit (A1) and the repeating unit (A2) is 100 [mol%], the repeating unit (A2) with respect to the amount (M1 [mol%]) of the repeating unit (A1) The ratio (M2 / M1) of the amount of (M2 [mol%]) can be in the range of 1-10.

[Application Example 7]
In the gel electrolyte forming agent of Application Example 6,
The M1 [mol%] may be in the range of 10 mol% to 40 mol%.

[Application Example 8]
One aspect of the composition for forming a gel electrolyte according to the present invention is:
The gel electrolyte forming agent according to any one of Application Examples 1 to 7 and the liquid medium (C) are contained.

[Application Example 9]
One aspect of the gel electrolyte according to the present invention is:
It is produced by heating the gel electrolyte forming composition described in Application Example 8.

[Application Example 10]
One aspect of the electricity storage device according to the present invention is:
The gel electrolyte of Application Example 9 is provided.

  According to the gel electrolyte forming agent according to the present invention, a gel electrolyte having sufficient ionic conductivity for exhibiting good charge / discharge characteristics and having improved electrolyte retention and gel strength is obtained. Can do. According to this gel electrolyte, since it has good liquid retention and gel strength, separation of the gel electrolyte and the electrolytic solution can be suppressed, and as a result, deterioration of charge / discharge characteristics in the electricity storage device can be suppressed.

  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 the present specification, “(meth) acrylic” is a concept encompassing both “acrylic” and “methacrylic”. Further, “˜ (meth) acrylate” is a concept encompassing both “˜acrylate” and “˜methacrylate”.

1. Gel Electrolyte Forming Agent The gel electrolyte forming agent according to the present embodiment contains an acrylic polymer (A) and a vinylidene fluoride polymer (B), and the acrylic polymer (A) is cyclic. It has a repeating unit (A1) derived from (meth) acrylate having an ether structure.

  The gel electrolyte forming agent according to the present embodiment is to produce a gel electrolyte by heating a gel electrolyte forming composition obtained by mixing with a liquid medium (C) described later and other additives. Can do. This gel electrolyte is a gel rich in flexibility and gel strength, and has no thermoreversibility. Therefore, abnormal expansion of the battery due to heating or overcharging can be prevented, and workability such as thin film processing is improved. Among the components contained in the gel electrolyte forming agent according to the present embodiment, in particular, the acrylic polymer (A) can form a highly flexible chemical gel by heating. On the other hand, the vinylidene fluoride polymer (B) can form a physical gel for reinforcing the gel strength of the chemical gel formed from the acrylic polymer (A). A gel electrolyte having a double network of a chemical gel and a physical gel can be prepared by using two kinds of polymers having such different characteristics in combination. The gel electrolyte thus obtained becomes a gel electrolyte having good characteristics that complementarily complements the drawbacks of chemical gel and physical gel. Hereinafter, each component contained in the gel electrolyte forming agent according to the present embodiment will be described in detail.

1.1. Acrylic polymer (A)
The acrylic polymer (A) contained in the gel electrolyte forming agent according to the present embodiment has a repeating unit (A1) derived from (meth) acrylate having a cyclic ether structure. Furthermore, the acrylic polymer (A) preferably has a repeating unit (A2) derived from a (meth) acrylate having a chain ether structure.

1.1.1. Repeating unit (A1)
The acrylic polymer (A) has a repeating unit (A1) derived from (meth) acrylate having a cyclic ether structure. The repeating unit (A1) can be crosslinked by opening the cyclic ether structure when producing the gel electrolyte.

（式（１）中、Ｒ^１は水素原子またはメチル基を表し、Ｒ^２は２価の連結基を表し、Ｒ^３は水素原子または１価の有機基を表し、複数存在するＲ^４はそれぞれ独立に水素原子または１価の有機基を表す。ｍおよびｎは０以上の整数であり、ｍ＋ｎ＞１である。） The (meth) acrylate having a cyclic ether structure is not particularly limited as long as the cyclic ether structure can be opened and crosslinked, and is preferably a compound represented by the following general formula (1). .

(In Formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent linking group, R ³ represents a hydrogen atom or a monovalent organic group, and a plurality of R ^{4 s} are present. Independently represents a hydrogen atom or a monovalent organic group, m and n are integers of 0 or more, and m + n> 1.)

In the above formula (1), R ¹ is preferably a methyl group from the viewpoint of oxidation resistance of the acrylic polymer (A).

In the above formula (1), R ² represents a divalent linking group, for example, a divalent chain hydrocarbon group having 1 to 20 carbon atoms, a divalent cyclic saturated or unsaturated group having 3 to 20 carbon atoms. A hydrocarbon group or a divalent group obtained by combining these with an ether group, an ester group or a carbonyl group can be exemplified. The divalent linking group may have a substituent.

In the above formula (1), R ³ represents a hydrogen atom or a monovalent organic group, and the monovalent organic group is preferably a linear or branched alkyl group having 1 to 4 carbon atoms. Examples of the linear or branched alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, and a 1-methylpropyl group. Group, t-butyl group and the like. Among these, R ³ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms so that it can be easily crosslinked.

In the above formula (1), a plurality of R ⁴ each independently represent a hydrogen atom or a monovalent organic group, and the monovalent organic group is a linear or branched alkyl group having 1 to 4 carbon atoms. Preferably there is. Examples of the linear or branched alkyl group having 1 to 4 carbon atoms include those exemplified in the description of R ³ above. Among these, it is preferable that each R ⁴ is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms so that it can be easily crosslinked. Moreover, since it can react easily and stability of a polymer becomes favorable, it is preferable that m + n is 2 or more in said formula (1).

（式（１−１）中、Ｒ^１は水素原子またはメチル基を表し、Ｒ^９は単結合または２価の有機基を表し、Ｒ^３は水素原子または１価の有機基を表し、複数存在するＲ^４はそれぞれ独立に水素原子または１価の有機基を表す。） The (meth) acrylate having a cyclic ether structure is more preferably a compound represented by the following general formula (1-1). The repeating unit derived from the compound represented by the following general formula (1-1) can be easily ring-opened and crosslinked by lithium ions in a non-aqueous solvent. Therefore, for example, when a gel electrolyte is prepared using the gel electrolyte forming composition containing the gel electrolyte forming agent of the present invention, lithium ions are contained as the liquid medium (C) contained in the gel electrolyte forming composition. By using the electrolytic solution, the gel electrolyte forming agent can be easily cross-linked and a gel electrolyte excellent in electrical conductivity can be produced. In this case, the heat treatment of the gel electrolyte forming composition is not essential for producing the gel electrolyte, but from the viewpoint of producing a gel electrolyte with good gel strength, the heat treatment should be performed at a low temperature that does not deteriorate the active material. Is preferred.

(In Formula (1-1), R ¹ represents a hydrogen atom or a methyl group, R ⁹ represents a single bond or a divalent organic group, R ³ represents a hydrogen atom or a monovalent organic group, and a plurality of them exist. And each R ⁴ independently represents a hydrogen atom or a monovalent organic group.)

In the above formula (1-1), R ¹ , R ³ and R ⁴ have the same meaning as the above formula (1). In the above formula (1-1), R ⁹ represents a single bond or a divalent organic group, and examples of the divalent organic group include an alkylene group having 1 to 10 carbon atoms. Among these, R ⁹ is preferably a methylene group.

  The gel electrolyte produced by using the gel electrolyte-forming composition produced by mixing the gel electrolyte-forming agent according to the present embodiment and the liquid medium (C) described later is a cyclic unit of the repeating unit (A1). Since the ether structure is ring-opened and crosslinked, a strong polymer network structure can be constructed and a gel electrolyte having excellent gel strength can be obtained.

  Specific examples of the compound represented by the general formula (1) include tetrahydrofurfuryl (meth) acrylate, (3-oxetanyl) methyl (meth) acrylate, and (3-methyl-3-oxetanyl) methyl (meth) acrylate. , (3-ethyl-3-oxetanyl) methyl (meth) acrylate, (3-butyl-3-oxetanyl) methyl (meth) acrylate, (3-hexyl-3-oxetanyl) methyl (meth) acrylate, 3,4- An epoxy cyclohexyl methyl (meth) acrylate etc. are mentioned. These compounds may be used alone or in combination of two or more.

  The content of the repeating unit (A1) in the acrylic polymer (A) is such that the repeating unit (A1) is 10 to 40 mol% when the total amount of the repeating unit (A1) and other repeating units is 100 mol%. It is preferable that it is 15-35 mol%. Moreover, when an acrylic polymer (A) has a repeating unit (A1) and the repeating unit (A2) mentioned later, the content rate of the repeating unit (A1) in an acrylic polymer (A) is a repeating unit (A1). ) And the repeating unit (A2) are 100 mol%, the repeating unit (A1) is preferably 10 to 40 mol%, and more preferably 15 to 35 mol%. When the content ratio of the repeating unit (A1) in the acrylic polymer (A) is within the above range, a crosslinking reaction (cationic acid) can be easily carried out by heating using a metal ion such as lithium ion contained in the electrolytic solution as a catalyst. Polymerization) occurs, and a gel electrolyte can be prepared. Moreover, since it can also fully bridge | crosslink, the gel strength of a gel electrolyte can also be ensured.

  In general, it is necessary to add an additive such as a thermal acid generator or a photoacid generator for promoting gelation when producing the gel electrolyte. If this additive remains in the gel electrolyte, the charge / discharge characteristics may deteriorate over time in the electricity storage device. However, since the gel electrolyte forming agent according to the present embodiment does not require such an additive and can be gelled only by heating, it is possible to suppress the deterioration over time of the charge / discharge characteristics as described above. Is excellent.

（式（２）中、Ｒ^５は水素原子またはメチル基を表し、Ｒ^６は単結合または２価の有機基を表し、複数存在してもよいＲ^７はそれぞれ独立に２価の炭化水素基を表し、Ｒ^８は水素原子または１価の有機基を表す。ｘは１以上の整数である。） 1.1.2. Repeating unit (A2)
The acrylic polymer (A) preferably has a repeating unit (A2) derived from a (meth) acrylate having a chain ether structure. The (meth) acrylate having a chain ether structure is preferably a compound represented by the following general formula (2).

(In formula (2), R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents a single bond or a divalent organic group, and a plurality of R ^{7 s} may be independently a divalent hydrocarbon group. R ⁸ represents a hydrogen atom or a monovalent organic group, and x is an integer of 1 or more.)

In Formula (2), R ⁵ represents a hydrogen atom or a methyl group, and is preferably a hydrogen atom from the viewpoint of synthesizing a polymer with high yield. In formula (2), R ⁶ represents a single bond or a divalent organic group, and examples of the divalent organic group include an alkylene group having 1 to 10 carbon atoms.

In formula (2), a plurality of R ⁷ which may be present each independently represents a divalent hydrocarbon group, and the divalent hydrocarbon group includes a linear or branched alkylene having 1 to 10 carbon atoms. Groups. Among these, it is preferable that R ⁷ is independently a divalent hydrocarbon group having 1 to 3 carbon atoms because of high affinity with the electrolytic solution.

In Formula (2), R ⁸ represents a hydrogen atom or a monovalent organic group, and the monovalent organic group may be a linear or branched alkyl group having 1 to 4 carbon atoms or an aryl group. preferable. Examples of the linear or branched alkyl group having 1 to 4 carbon atoms include those exemplified in the description of R ³ above. Examples of the aryl group include a phenyl group and a naphthyl group. R ⁸ is preferably an alkyl group having 1 to 3 carbon atoms because of high affinity with the electrolytic solution.

（式（２−１）中、Ｒ^５は水素原子またはメチル基を表し、Ｒ^１０は単結合または２価の有機基を表し、複数存在するＲ^１１はそれぞれ独立に水素原子または１価の有機基を表し、Ｒ^８は水素原子または１価の有機基を表す。） The (meth) acrylate having a chain ether structure is more preferably a compound represented by the following general formula (2-1). The repeating unit derived from the compound represented by the following general formula (2-1) has a high affinity with a carbonate-based solvent or a lactone-based compound that is generally used in a non-aqueous electrolyte, and is crosslinked to form a polymer. Even when a strong network is formed, the nonaqueous electrolytic solution can be absorbed and sufficiently swelled, and movement of lithium ions between the nonaqueous electrolytic solution and the active material is not hindered. As a result, a gel electrolyte that exhibits good ionic conductivity can be produced.

(In the formula (2-1), R ⁵ represents a hydrogen atom or a methyl group, R ¹⁰ represents a single bond or a divalent organic group, and a plurality of R ¹¹ are each independently a hydrogen atom or a monovalent organic group. And R ⁸ represents a hydrogen atom or a monovalent organic group.)

In the above formula (2-1), R ⁵ represents a hydrogen atom or a methyl group, preferably a hydrogen atom from the viewpoint of synthesizing a high yield polymer. R ⁸ has the same meaning as ^{R 8} in the general formula (2). R ¹⁰ represents a single bond or a divalent organic group, and examples of the divalent organic group include an alkylene group having 1 to 10 carbon atoms. Among these, R ¹⁰ is preferably a single bond.

A plurality of R ¹¹ each independently represent a hydrogen atom or a monovalent organic group, and the monovalent organic group is preferably a linear or branched alkyl group having 1 to 4 carbon atoms. Examples of the linear or branched alkyl group having 1 to 4 carbon atoms include those exemplified in the description of R ³ above. Among these, it is preferable that each of R ¹¹ is a hydrogen atom because of its high affinity with the electrolytic solution.

  In general, if a (poly) ether type structural site is present, it degrades due to decomposition due to a change in oxidation-reduction potential associated with charging / discharging of the electricity storage device, making it difficult to develop good electricity storage device characteristics. It is. However, according to the acrylic polymer (A) having the repeating unit (A1) and the repeating unit (A2), deterioration due to a change in oxidation-reduction potential accompanying charging / discharging of the electricity storage device can be suppressed, and the electrolyte solution It is possible to prevent deterioration of the liquid retention.

  Specific examples of the compound represented by the general formula (2) include 2-methoxyethyl acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 2-ethylhexyl diglycol (meth) acrylate, methoxy Polyethylene glycol (meth) acrylate, 2-ethoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, ethoxy Dipropylene glycol (meth) acrylate, ethoxytripropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate Rate, phenoxy diethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate. These compounds may be used alone or in combination of two or more.

  The content of the repeating unit (A2) in the acrylic polymer (A) is such that the repeating unit (A2) is 60 to 90 mol when the total amount of the repeating unit (A1) and the repeating unit (A2) is 100 mol%. % Is preferable, and 65 to 85 mol% is more preferable. When the content ratio of the repeating unit (A2) in the acrylic polymer (A) is in the above range, a gel electrolyte having excellent oxidation-reduction resistance and excellent liquid retention can be produced.

1.1.3. Ratio of repeating unit (A1) and repeating unit (A2) When the acrylic polymer (A) contained in the gel electrolyte forming agent according to the present embodiment has the repeating unit (A1) and the repeating unit (A2), When the total amount of the repeating unit (A1) and the repeating unit (A2) is 100 mol%, the amount of the repeating unit (A2) relative to the amount of the repeating unit (A1) (M1 [mol%]) (M2 [mol %]) Ratio (M2 / M1) is in the range of 1 to 10, preferably in the range of 1.5 to 8, and more preferably in the range of 2 to 6. When the value of M2 / M1 is in the above range, it is possible to achieve both good electrolyte retention and sufficient gelling properties, as described above.

1.1.4. Manufacturing Method The acrylic polymer (A) contained in the gel electrolyte forming agent according to the present embodiment is a (meth) acrylate having the cyclic ether structure, and a (meth) acrylate having the chain ether structure as necessary. Can be easily produced by radical polymerization in a reaction solvent. When the acrylic polymer (A) thus obtained is a copolymer, the copolymer is any structure of a random copolymer, an alternating copolymer, a periodic copolymer, and a block copolymer. It may be.

  Although it does not restrict | limit especially as said reaction solvent, It is preferable that it is at least 1 sort (s) of the solvent which can be contained in the liquid medium (C) illustrated later, The solvent of the same kind as the solvent actually used for the composition for gel electrolyte formation It is more preferable that By performing radical polymerization using a solvent that can be contained in the liquid medium (C) as a reaction solvent, it is possible to produce a gel electrolyte that is superior in liquid retention of the liquid medium (C). In addition, since the affinity with the polymer obtained and a liquid medium (C) will become very favorable when the solvent of the same kind as the solvent actually used for the composition for gel electrolyte formation is used as a reaction solvent, gel electrolyte formation Preparation of the composition for use is facilitated, and liquid retention of the resulting gel electrolyte is very good.

  In the radical polymerization, a radical polymerization initiator is usually used. Examples of radical polymerization initiators include azo initiators such as N, N′-azobisisobutyronitrile and dimethyl N, N′-azobis (2-methylpropionate); benzoyl peroxide and lauroyl peroxide. And organic peroxide initiators such as The radical polymerization initiator may be added in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of all monomers.

  The acrylic polymer (A) is a monomer other than the (meth) acrylate having the cyclic ether structure and the (meth) acrylate having the chain ether structure (hereinafter referred to as “other monomer”). However, the content of other monomers in 100 mol% of all monomers is preferably less than 10 mol%, and more preferably 0 mol%.

  The number average molecular weight (Mn) of the acrylic polymer (A) obtained as described above is preferably 8,000 to 1,000,000, more preferably 100,000 to 700,000, and 200,000 to 500,000. It is particularly preferred that The number average molecular weight (Mn) of the acrylic polymer (A) can be determined by conversion from the relationship between the elution time and molecular weight of standard polystyrene measured by GPC (gel permeation chromatography) method. .

1.2. Vinylidene fluoride polymer (B)
The gel electrolyte forming agent according to the present embodiment contains a vinylidene fluoride polymer (B). By containing the vinylidene fluoride polymer (B), a physical gel for reinforcing the gel strength of the chemical gel formed from the acrylic polymer (A) can be formed. A gel electrolyte having a double network of a chemical gel and a physical gel can be produced by using two kinds of polymers having different properties in combination. The gel electrolyte thus obtained becomes a gel electrolyte having good characteristics that complementarily complements the drawbacks of chemical gel and physical gel.

  In the present invention, the vinylidene fluoride polymer (B) is a homopolymer of vinylidene fluoride, 80% by mass or more of vinylidene fluoride, and one or more types copolymerizable with vinylidene fluoride. And a copolymer of 20% by mass or less (preferably 0.3% by mass or more). By using such a copolymer, the gel strength of the obtained gel electrolyte can be improved.

  Examples of monomers copolymerizable with vinylidene fluoride include hydrocarbon monomers such as ethylene and propylene; vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, fluoro Fluorine-containing monomers such as alkyl vinyl ethers; or epoxy group-containing vinyl monomers such as allyl glycidyl ether and crotonic acid glycidyl ester. Moreover, in order to further improve the adhesion between the gel electrolyte and the electrode, a copolymer in which a polar group such as a carbonyl group or a carboxyl group is introduced by copolymerizing a monoester of unsaturated dibasic acid, vinylene carbonate or the like Are also preferably used. Furthermore, a silane coupling agent or titanate having both a reactive group and a hydrolyzable group in combination with a vinylidene fluoride polymer such as an amino group or a mercapto group in a solvent that dissolves or swells the vinylidene fluoride polymer. A modified vinylidene fluoride polymer obtained by treatment in a system coupling agent is also used.

  The vinylidene fluoride polymer (B) preferably has a weight average molecular weight (polystyrene converted weight average molecular weight by gel permeation chromatography) of 250,000 or more. When the weight average molecular weight is in the above range, the gel strength can be further improved when the gel electrolyte is formed.

  In order to stably inject the gel electrolyte forming composition into the housing of the electricity storage device without bubbles, the viscosity of the gel electrolyte forming composition is preferably 120,000 mPa · s or less. Therefore, the weight average molecular weight, the concentration of the vinylidene fluoride polymer in the gel electrolyte forming composition, and the weight average molecular weight are appropriately adjusted so that the viscosity of the gel electrolyte forming composition is 120,000 mPa · s or less. It is preferable.

  Specifically, the content ratio of the acrylic polymer (A) and the vinylidene fluoride polymer (B) contained in the gel electrolyte forming agent is 100% by mass with respect to 100 parts by mass of the acrylic polymer (A). The vinylidene chloride polymer (B) is preferably 5 to 200 parts by mass, more preferably 10 to 150 parts by mass, and 20 to 100 parts by mass. Particularly preferred.

2. Gel Electrolyte Forming Composition A gel electrolyte forming composition according to the present embodiment (hereinafter, also simply referred to as “composition”) contains the above-described gel electrolyte forming agent and a liquid medium (C). . By heating and cross-linking (cationic polymerization) the composition according to the present embodiment, a good gel electrolyte excellent in liquid retention and gel strength can be produced.

  When preparing the composition according to the present embodiment, the above-mentioned gel electrolyte forming agent and other additives are added to the liquid medium (C), and the mixture is sufficiently stirred while heating to about 40 to 60 ° C. Good. Thereby, the acrylic polymer (A) and the vinylidene fluoride polymer (B) contained in the gel electrolyte forming agent can be completely dissolved in the liquid medium (C). Note that if the heating temperature is raised to 70 to 100 ° C., a gel electrolyte is formed, so care must be taken.

  Note that the composition according to the present embodiment is stable near room temperature and does not gel. For this reason, since it can be set as a gel electrolyte by inject | pouring a liquid composition into the housing | casing of an electrical storage device, and heating after that, the storage stability and the freedom degree of an electrical storage device preparation process can be improved. Hereinafter, although each component contained in the composition which concerns on this Embodiment is demonstrated, since it is as having mentioned above about a gel electrolyte formation agent, description is abbreviate | omitted.

2.1. Liquid medium (C)
The liquid medium (C) contained in the composition according to the present embodiment further contains an electrolyte, a solvent for dissolving the electrolyte, and, if necessary, an additive.

Examples of the electrolyte, any conventionally known lithium salts can also be used, and specific examples _{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, a lower fatty acid Lithium etc. can be illustrated. These electrolytes may be used alone or in combination of two or more.

From the viewpoint of increasing the ionic conductivity of the liquid medium (C), it is possible to use an electrolyte other than Li. As such an electrolyte, for example, bis (fluorosulfonyl) imide _{(FSI) -, BF 4 -} , PF 6 -, SbF 6 -, NO 3 -, CF 3 SO 3 -, (CF 3 SO 2) 2 N _{-, TFSI -, (C 2} F 5 SO 2) 2 N -, (CF 3 SO 2) 3 C-, CF 3 CO 2 -, C 3 F 7 CO 2 -, CH 3 CO 2 -, (CN) _{2 A} salt composed of a combination of an anion such as N- and a cation.

  As the cation, a compound having any of N, P, S, O, C, Si or two or more elements in the structure and having a chain structure or a cyclic structure such as a 5-membered ring or a 6-membered ring in the skeleton Is mentioned. Examples of the chain compound include alkyl ammonium. Examples of cyclic compounds include: Ring compounds; and condensed heterocyclic compounds such as benzofuran, isobenzofuran, indole, isoindole, isodolidine, and carbazole.

Among the electrolytes exemplified above, particularly when LiPF ₆ or LiBF ₄ is used, since lithium ions act as a cationic polymerization initiator, it is not necessary to use another cationic polymerization initiator.

  Solvents for dissolving the electrolyte include ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), methyl ethyl carbonate (MEC), methyl propyl carbonate (PMC), butylene carbonate (BC), diethyl Carbonates such as carbonate (DEC); cyclic carboxylic acid esters such as γ-butyrolactone (GBL) and γ-valerolactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, methyl Cyclic ethers such as tetrahydrofuran and methyltetrahydrofuran; sulfolane and the like can be used. These solvents may be used alone or in combination of two or more.

  Such an electrolytic solution usually has an electrolyte concentration of 0.1 to 5 mol / L, particularly preferably 0.5 to 2 mol / L.

2.2. Additives Examples of the additives include additives that have been used in conventional electrolytes, and specifically use components for improving conductivity and forming a protective film on the electrode surface. be able to. For example, nitrogen-containing and sulfur-containing compounds such as azaindole, benzimidazole, benzodithiol, benzofuran, benzothiazole, 1-benzothiophene, 1H-benzotriazole, benzylcapton, 1-bromo-3-fluorobenzene; vinylene carbonate, Examples thereof include vinyl compounds such as vinyl acrylate and vinyl butyrate; sucrose fatty acid esters, and the addition amount is 10% by mass or less, preferably 3% by mass or less. Moreover, these additives may be used individually by 1 type, and may be used in combination of 2 or more types.

  The composition for forming a gel electrolyte according to the present embodiment can be further added with a cyclic ether compound from the viewpoint of improving the liquid retention of the resulting gel electrolyte and increasing the crosslinking density to improve the gel strength. . As such a cyclic ether compound, those having an alkyl group having 6 to 28 carbon atoms are preferable, an alkyl glycidyl ether having an alkyl group having 6 to 28 carbon atoms, and a fatty acid glycidyl ether having an alkyl group having 6 to 28 carbon atoms. Alkylphenol glycidyl ether having an alkyl group having 6 to 28 carbon atoms is more preferable. Among these, alkyl glycidyl ether having an alkyl group having 6 to 28 carbon atoms is particularly preferable. In addition, these cyclic ether compounds may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  In addition, the cyclic ether compound preferably has two or more cyclic ether groups in the molecule. By adding a cyclic ether compound having two or more cyclic ether groups in the molecule, the crosslinking density can be further increased, so that the gel strength of the gel electrolyte can be further improved. Examples of such cyclic ether compounds include vinylcyclohexene dioxide, dicyclopentadiene dioxide, alicyclic diepoxy-adipade, 1,6-bis (2,3-epoxypropoxy) naphthalene, and ethylene glycol diglycidyl ether. 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate, 1,2: 8,9-diepoxy limonene, and the like.

  When a cyclic ether compound is added to the gel electrolyte forming composition according to the present embodiment, the cyclic ether compound is different from the cyclic ether group contained in the repeating unit (A1) in the acrylic polymer (A). It preferably has a number of cyclic ether groups. For example, when the cyclic ether group contained in the repeating unit (A1) is an oxiranyl group, the cyclic ether compound to be added preferably has an oxetanyl group. On the other hand, when the cyclic ether group contained in the repeating unit (A1) is an oxetanyl group, the cyclic ether compound to be added preferably has an oxiranyl group. When the cyclic ether compound added in this way has a different number of cyclic ether groups from the cyclic ether group contained in the repeating unit (A1), it can be more effectively cross-linked, and the gel electrolyte can be produced. The heating temperature can be lowered. Thereby, deterioration of the electrolyte solution accompanying heating can be suppressed. Moreover, since a crosslinking density can be improved, the gel electrolyte excellent in gel strength can be produced.

  When adding a cyclic ether compound to the composition for gel electrolyte formation which concerns on this Embodiment, the content rate of a cyclic ether compound is the range of 0-50 mass parts with respect to 100 mass parts of acrylic polymers (A). It is preferable to contain.

3. Gel electrolyte The gel electrolyte which concerns on this Embodiment is produced by heating the above-mentioned composition for gel electrolyte formation. Since the gel electrolyte according to the present embodiment can be prepared simply by heating the above-described composition for forming a gel electrolyte, unlike a general gel electrolyte, a thermal acid generator or a light used for gel electrolyte preparation is used. An additive such as an acid generator may not be contained. For this reason, with the charge / discharge of the electricity storage device, it is possible to suppress the deterioration over time of the charge / discharge characteristics that may be caused by the decomposition of the thermal acid generator or the photoacid generator.

  Moreover, since the heating temperature at the time of gel electrolyte preparation can be 70-100 degreeC (preferably 75-95 degreeC, More preferably, 80-90 degreeC), it suppresses the deterioration of the active material layer of an electrical storage device. Can do. Further, since the ring-opening and crosslinking are performed, the change in the volume of the polymer is small, and damage to the structure of the electricity storage device such as peeling of the active material layer can be suppressed even if the polymer is gelled in a sealed state.

  The gel electrolyte according to the present embodiment is a gel rich in flexibility and gel strength, and has no thermoreversibility. Therefore, abnormal expansion of the battery due to heating or overcharging can be prevented, and workability such as thin film processing is improved.

4). Electric storage device The electric storage device according to the present embodiment may include a known configuration and material in addition to the gel electrolyte described above.

  The electrode material is not particularly limited as long as it can insert and desorb lithium ions. As the electrode, for example, an electrode in which a positive electrode / negative electrode active material layer is formed on the surface of a current collector can be used.

Examples of the positive electrode active material include metal oxides such as CuO, Cu ₂ O, MnO ₂ , V ₂ O ₅ , CrO ₃ , MoO ₃ , Fe ₂ O ₃ , Ni ₂ O ₃ , and CuO ₃ , and Li _x CO _2. , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , LiFePO ₄ and other complex oxides of lithium and transition metals, TiS ₂ , MoS ₂ , NbSe _{3 and} other metal chalcogenides, polyacene, polyparaphenylene, polypyrrole, Examples thereof include conductive compounds such as polyaniline. In particular, in the present invention, a composite oxide of lithium and one or more kinds selected from transition metals such as cobalt, nickel, manganese, and iron is preferable. Specific examples thereof include LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , and LiNi. _{x Co (1-x) O} 2, LiMn a Ni b Co c (a + b + c = 1), LiFePO 4 , and the like. These lithium composite oxides may be doped with a small amount of elements such as fluorine, boron, aluminum, chromium, zirconium, molybdenum, and iron.

Examples of the negative electrode active material include lithium storage metals such as lithium metal, Al, Mg, Pt, Sn, Si, Zn, and Bi; Al-based lithium alloys such as Al—Ni, Al—Ag, and Al—Mn; SbSn, Antimony type lithium alloys such as InSb, CoSb ₃ , Mi ₂ MnSb; Sn ₂ M (M = Fe, Co, Mn, V, Ti), Sn ₅ Cu ₆ , Sn ₃ V ₂ , Sn ₁₂ Ag ₁₃ , SnSb _0. Sn-based lithium alloys such as ₄ ; Sn oxides such as SnO ₂ , Sn ₂ P ₂ O ₇ , SNPBO ₆ , SnPO ₄ Cl; Si-based such as Si—C composite, Si—Ti composite, and Si—M thin film Lithium alloys; Nanocomposite materials such as Sn and Si; Amorphous alloy materials such as Sn, Co and Carbon; Sn-based plating alloys such as Sn-Ag and Sn-Cu; Si-based amorphous thin films Examples of carbon materials include amorphous carbon, mesocarbon microbeads, graphite, natural graphite, non-graphitizable carbon, and the like, and surface modified products of these carbon materials are preferable materials.

  A conductive agent may be further used for the electrode material. Any conductive material that does not adversely affect battery performance can be used as the conductive agent. Normally, carbon black such as acetylene black and kettin black is used, but carbon fibers such as natural graphite, artificial graphite, carbon whisker, vapor grown carbon, carbon nanotubes, fullerene, conductive ceramic materials, etc. may be used. Often, these can be included as a mixture of two or more.

  The current collector is not particularly limited as long as it is an electronic conductor that does not adversely affect the configured power storage device. For example, as a current collector for a positive electrode, in addition to aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass, etc., aluminum is used for the purpose of improving adhesiveness, conductivity, and oxidation resistance. Or a surface treated with carbon, nickel, titanium, silver or the like can be used. As a negative electrode current collector, in addition to copper, stainless steel, nickel, aluminum, titanium, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., the purpose of improving adhesion, conductivity, and oxidation resistance And what processed the surface, such as copper, with carbon, nickel, titanium, silver, etc. can be used. The surface of these current collector materials can be oxidized. As for these shapes, in addition to a foil shape, a film shape, a sheet shape, a net shape, a punched or expanded material, a vitreous body, a porous body, a foamed body and the like are also used.

As a binder for binding the positive electrode / negative electrode active material to the current collector, polyvinylidene fluoride (PVDF), hexafluoropropylene (HFP), perfluoromethyl vinyl ether (PFMV), and tetrafluoroethylene (TFE) are used together. PVDF copolymer resins such as polymers, fluorinated resins such as polytetrafluoroethylene (PTFE) and fluorine rubber, styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), styrene-acrylonitrile copolymers, etc. Examples of the polymer include polysaccharides such as carboxymethylcellulose (CMC) and thermoplastic resins such as polyimide resins, but are not limited thereto. Moreover, you may use these in mixture of 2 or more types. The amount added is preferably 0.2 to 30%, more preferably 0.5 to 10%, based on the amount of active material. As for the positive electrode active material whose surface is coated with carbon such as LiFePO ₄ , a carboxylic acid-modified PVDF or SBR aqueous binder can also be mentioned as a preferable material.

  As the separator, a porous film is used, and usually a porous polymer film or a nonwoven fabric is preferably used. In the present invention, those composed of a non-conductive porous material and electrically insulating particles are particularly suitable. The non-conductive porous material is selected from polyacrylonitrile, polyester (PET), polyimide, polyamide, polytetrafluoroethylene, polyolefin, glass, ceramic and the like. In particular, a nonwoven fabric having an electrically insulating inorganic film on a flat flexible substrate is suitable, and polyester (PET) and polyamide are particularly preferred.

  The insulating particles used in the separator include inorganic materials such as at least one kind of alumina, titania, silicon and / or zirconia, and organic materials such as fluororesin, polystyrene resin and acrylic resin. Particles are used.

  The separator may further have a shutdown mechanism by the presence of a very thin wax particle layer that melts at a desired blocking temperature or a blocking particle of a polymer particle layer in the separator. Advantageous materials for forming the blocking particles include natural or artificial waxes, low melting polymers such as polyolefins, which melt at the desired blocking temperature and close the pores of the separator. Further current during the abnormal operation of the battery can be suppressed.

  The electricity storage device according to this embodiment can be formed in a cylindrical shape, a coin shape, a square shape, or any other shape, and the basic configuration of the electricity storage device is the same regardless of the shape, and the design is changed according to the purpose. Can be implemented.

  As a specific manufacturing method of the electricity storage device according to the present embodiment, for example, a negative electrode formed by applying a negative electrode active material to a negative electrode current collector, and a positive electrode formed by applying a positive electrode active material to a positive electrode current collector Is obtained by storing a wound body wound through a separator in a casing, injecting the above-described composition for forming gel electrolyte, sealing with an insulating plate placed on the top and bottom, and heat-treating it. .

  When producing the electricity storage device according to the present embodiment, if the selected electrode active material generates a large amount of gas during the first charge and affects the cell performance, the above-mentioned gel electrolyte formation After injecting the composition into the pre-battery, a heat treatment may be performed after a charge or charge / discharge treatment as a pretreatment.

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. Example 1
5.1.1. Preparation of Gel Electrolyte Forming Agent In a well-dried container, 52 g of methoxyethyl acrylate (monomer content ratio; equivalent to 74% by mass, 80 mol%), 18 g of (3-ethyl-3-oxetanyl) methyl methacrylate (monomer content ratio) Equivalent to 26% by mass and 20 mol%), 211 g of ethylene carbonate (EC): diethyl carbonate (DEC) = 3: 7 (volume ratio) as a reaction solvent, and 0.1% of N, N′-azobisisobutyronitrile. 71 g (1 part by mass with respect to 100 parts by mass of monomer) was added, heated to 60 ° C. in a dry nitrogen atmosphere, reacted for 6 hours, and then cooled to room temperature. The cooled solution was put into hexane, and the resulting precipitate was collected by filtration. The recovered precipitate was dried under reduced pressure at 60 ° C. for 12 hours to synthesize an acrylic polymer A1 having a number average molecular weight of 200,000. A gel electrolyte forming agent was prepared by adding 3 g of “KF2801” manufactured by Arkema as a vinylidene fluoride polymer (B) to 3 g of the obtained acrylic polymer A1.

5.1.2. Preparation of Gel Electrolyte Forming Composition 6 g of the gel electrolyte forming agent prepared above was dissolved in 44 g of a liquid medium (C) containing 1 mol / L of LiPF ₆ and EC: DEC = 3: 7 (volume ratio), A gel electrolyte forming composition containing 12% by mass of the gel electrolyte forming agent prepared above was prepared.

5.1.3. Evaluation Test of Gel Electrolyte (1) Evaluation of Liquid Retention Property A gel electrolyte was prepared by filling 10 g of the prepared gel electrolyte forming composition into a 50 mL vial tube and leaving it at 80 ° C. for 30 minutes. The obtained gel electrolyte was allowed to stand at 25 ° C. for 1 day, and the appearance of the gel electrolyte was visually observed. The evaluation results are shown in Tables 2 to 3. In Tables 2 to 3, when the gel electrolyte and the electrolytic solution were not separated, it was judged as “good”, and when it was separated, it was judged as bad, and “x” was shown.

(2) Evaluation of ion conductivity The prepared composition for gel electrolyte formation was enclosed in an ion conductivity evaluation cell (manufactured by Solartron, model number “SR-CIR-C”), and heated in an oven at 80 ° C. for 30 minutes. Thus, a gel electrolyte was produced in the evaluation cell, and this was used as the measurement cell. After stabilizing the temperature of the measurement cell using a 25 ° C. thermostat, the measurement cell is connected to an electrochemical measurement device (Bio-Logic, model number “HJ-1001SM8A”), and the frequency is 0.2 MHz. Ion conductivity was measured based on the AC impedance method under the conditions of .about.0.1 Hz and amplitude width of 5 mV. The evaluation results are shown in Tables 2 to 3. If the ionic conductivity is 1.0 × 10 ⁻³ S / cm or more, it can be determined to be good, and if it is less than 1.0 × 10 ⁻³ S / cm, it can be determined to be defective.

(3) Gel strength 10 g of the prepared gel electrolyte forming composition was filled into a 50 mL vial tube and allowed to stand at 80 ° C. for 30 minutes to prepare a gel electrolyte. The obtained gel electrolyte was allowed to stand at 25 ° C. for 1 day, and the gel strength was evaluated by a method based on JIS6503 using a rheometer (product name “MCR301” manufactured by Anton Paar). By visual observation, when the crack did not occur in the gel, it was judged as good, and when the crack occurred, it was judged as bad and indicated as “x”.

5.2. Examples 2-16, Comparative Examples 1-2
Acrylic polymers A2 to A9 were synthesized in the same manner as in Example 1 except that the monomer composition, blending amount, and reaction solvent were changed to those shown in Table 1. The gel electrolyte forming agent was the same as in Example 1, except that the type of acrylic polymer (A), the amount of each component, and the liquid medium composition used were changed to those shown in Tables 2 to 3. And the composition for gel electrolyte formation was produced, and it carried out similarly to Example 1, and evaluated liquid retention property, ionic conductivity, and gel strength. The acrylic polymers A1 to A9 synthesized are shown in Table 1 below, and the composition of the gel electrolyte forming composition, the evaluation results of Examples and Comparative Examples are shown in Tables 2 to 3 below.

Abbreviations in Tables 1 to 3 represent the following compounds or product names, respectively.
OXMA: (3-ethyl-3-oxetanyl) methyl methacrylate MEA: methoxyethyl acrylate DEGA: ethoxydiethylene glycol acrylate AIBN: N, N′-azobisisobutyronitrile EC / DEC: ethylene carbonate Mixed solvent of diethyl carbonate in a volume ratio of 3: 7 • GBL: γ-butyrolactone • DG: diglyme (diethylene glycol dimethyl ether)
・ KF: Polyvinylidene fluoride resin (trade name “KF2801” manufactured by Arkema)
CEL: 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate (product name “Celoxide 2021P” manufactured by Daicel Chemical Industries, Ltd.)
EGDG: ethylene glycol diglycidyl ether PC: propylene carbonate

5.3. Evaluation Results According to the gel electrolytes of Examples 1 to 16, it was found that all had good ionic conductivity and excellent liquid retention and gel strength.

  On the other hand, since the gel electrolyte of Comparative Example 1 (conventional gel electrolyte) uses only polyvinylidene fluoride resin as the gel electrolyte forming agent, separation of the gel electrolyte from the liquid medium occurs, and the liquid retaining property is high. It turned out to be bad. Moreover, since the crack generate | occur | produced also in gel strength evaluation, it turned out that gel strength is unsatisfactory.

  The gel electrolyte of Comparative Example 2 uses only an acrylic polymer having a M2 / M1 value of 4.0 as a gel electrolyte forming agent, and has excellent liquid retention and good ionic conductivity. However, it turned out that it is inferior because gel strength is inferior.

  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 (10)

An acrylic polymer (A) and a vinylidene fluoride polymer (B),
A gel electrolyte forming agent, wherein the acrylic polymer (A) has a repeating unit (A1) derived from (meth) acrylate having a cyclic ether structure.   The gel electrolyte formation agent of Claim 1 which contains 5 to 200 mass parts vinylidene fluoride polymer (B) with respect to 100 mass parts of said acrylic polymers (A). The gel electrolyte formation agent of Claim 1 or Claim 2 whose (meth) acrylate which has the said cyclic ether structure is a compound represented by following General formula (1).

(In Formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent linking group, R ³ represents a hydrogen atom or a monovalent organic group, and a plurality of R ^{4 s} are present. Independently represents a hydrogen atom or a monovalent organic group, m and n are integers of 0 or more, and m + n> 1.)   The gel electrolyte formation according to any one of claims 1 to 3, wherein the acrylic polymer (A) further has a repeating unit (A2) derived from a (meth) acrylate having a chain ether structure. Agent. The gel electrolyte forming agent according to claim 4, wherein the (meth) acrylate having a chain ether structure is a compound represented by the following general formula (2).

(In formula (2), R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents a single bond or a divalent organic group, and a plurality of R ^{7 s} may be independently a divalent hydrocarbon group. R ⁸ represents a hydrogen atom or a monovalent organic group, and x is an integer of 1 or more.)   When the total amount of the repeating unit (A1) and the repeating unit (A2) is 100 [mol%], the repeating unit (A2) with respect to the amount (M1 [mol%]) of the repeating unit (A1) The gel electrolyte forming agent according to claim 4 or 5, wherein the ratio (M2 / M1) of the amount (M2 [mol%]) is in the range of 1 to 10.   The gel electrolyte forming agent according to claim 6, wherein the M1 [mol%] is in the range of 10 mol% to 40 mol%.   The composition for gel electrolyte formation containing the gel electrolyte formation agent as described in any one of Claims 1 thru | or 7, and a liquid medium (C).   The gel electrolyte produced by heating the composition for gel electrolyte formation of Claim 8.   An electricity storage device comprising the gel electrolyte according to claim 9.