JPWO2013077211A1 - Gel electrolyte forming agent, composition for forming gel electrolyte, gel electrolyte, and electricity storage device - Google Patents

Abstract

  The gel electrolyte forming agent according to the present invention comprises a repeating unit (A1) derived from a (meth) acrylate having a cyclic ether structure and a repeating unit (A2) derived from a (meth) acrylate having a chain ether structure. And having the total amount of the repeating unit (A1) and the repeating unit (A2) as 100 [mol%], the repeating unit (M1 [mol%]) relative to the amount of the repeating unit (A1) (M1 [mol%]) The polymer (A) in which the ratio (M2 / M1) of the amount (M2 [mol%]) of A2) is in the range of 1 to 10 is contained.

Description

  The present invention relates to a gel electrolyte forming agent, a gel electrolyte forming composition containing the gel electrolyte forming agent and a liquid medium, a gel electrolyte formed from the gel electrolyte forming composition, and an electricity storage provided with the gel electrolyte Regarding devices.

  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 state 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, in Japanese Patent Laid-Open Nos. 2001-176555, 2009-70605 and 2002-110245, stability (non-volatile), safety (non-explosive), and ease of production (thin film processing, etc.) ), The development of a gel electrolyte (hereinafter also referred to as “gel electrolyte”) is being studied.

  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.

  However, conventional gel electrolytes sometimes have insufficient electrolyte retention. If the electrolyte retainability is insufficient, the charge / discharge characteristics of the electricity storage device may be deteriorated due to separation of the gel electrolyte matrix and the electrolyte solution, or the electricity storage device may be deteriorated due to leakage of the electrolyte separated from the gel electrolyte matrix. It was not able to suppress enough.

  In general, when the electrolyte is gelled, the ionic conductivity decreases. That is, in the gel electrolyte, the interface resistance between the active material surface and the electrolyte is inevitably increased as compared with a normal electrolytic solution. As a result, even a slight deterioration of the surface of the active material significantly increases the electrode resistance, which in turn may cause a significant deterioration of the charge / discharge characteristics of the electricity storage device. In addition, according to a conventional chemical gel electrolyte, a solution containing a gel electrolyte forming agent and an electrolyte is placed in a housing in which electrodes and separators are arranged, as in the conventional manufacturing process of a nonaqueous electrolyte type electricity storage device. By injecting and then gelling, a battery in which a gel electrolyte is easily arranged can be produced. However, heating the electrode or electrolyte at a high temperature during the gelation process may cause deterioration of the electrode, or it may be necessary to add an initiator for gelation, and components that hinder charging and discharging cannot be removed. For example, there is a problem that the charge / discharge characteristics of the power storage device to be manufactured deteriorate.

  On the other hand, the chemical gel electrolyte is usually produced by an irreversible chemical reaction by heating and / or irradiating light with a gel electrolyte forming agent containing a gel electrolyte prepolymer. However, since the reactivity of the gel electrolyte prepolymer is very high, gelation may have already progressed when an attempt was made to produce the gel electrolyte. Therefore, it has been an issue to suppress the reaction of the gel electrolyte prepolymer and ensure the storage stability of the gel electrolyte forming agent.

  Accordingly, some aspects of the present invention have sufficient ionic conductivity for expressing good charge / discharge characteristics by solving at least a part of the above-described problems, and are compared with conventional gel electrolytes. Thus, the present invention provides a gel electrolyte forming agent capable of producing a gel electrolyte with improved electrolyte retention.

  In addition to the above features, some embodiments according to the present invention provide a gel electrolyte forming agent that further improves storage stability.

  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:
A repeating unit (A1) derived from (meth) acrylate having a cyclic ether structure and a repeating unit (A2) derived from (meth) acrylate having a chain ether structure,
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%]) The polymer (A) which has the ratio (M2 / M1) of the quantity (M2 [mol%]) in the range of 1-10 is contained.

（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 2]
In the gel electrolyte forming agent of Application Example 1, 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.

（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 3]
In the gel electrolyte forming agent of Application Example 1 or Application Example 2, the (meth) acrylate having a 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 4]
In the gel electrolyte forming agent according to any one of Application Examples 1 to 3, the M1 [mol%] may be in the range of 10 to 40 mol%.

[Application Example 5]
In the gel electrolyte forming agent of any one of Application Examples 1 to 4, the number average molecular weight of the polymer (A) may be 1,000 or more and 100,000 or less.

[Application Example 6]
The gel electrolyte forming agent of any one of Application Examples 1 to 5 may further contain an ester compound (B) having at least one carbon-carbon unsaturated bond.

[Application Example 7]
In the gel electrolyte forming agent of Application Example 6, the component (B) may be at least one selected from the group consisting of cyclic carbonates and (meth) acrylates.

（式（３）中、Ｒ^１２およびＲ^１３はそれぞれ独立に、水素原子、ハロゲン原子、炭素数１〜６のアルキル基もしくはアルケニル基、またはフェニル基である。）[Application Example 8]
In the gel electrolyte forming agent of Application Example 7, the cyclic ester carbonate may be a compound represented by the following general formula (3).

(In Formula (3), R ¹² and R ¹³ are each independently a hydrogen atom, a halogen atom, an alkyl or alkenyl group having 1 to 6 carbon atoms, or a phenyl group.)

[Application Example 9]
In any one example of the gel electrolyte-forming agent applications 6 to Application Example 8, the M _A parts by mass content of the component (A), the content of the component (B) is taken as M _B parts by weight, ratio _(M a / M _B) can be in the range of 1 to 100.

[Application Example 10]
The gel electrolyte forming agent of any one of Application Examples 1 to 5 may further contain a compound (C) having a phenolic hydroxyl group.

（式（４）中、Ｒ^１４はそれぞれ置換もしくは非置換のアルキル基またはアルコキシ基を表す。ｎは０以上５以下の整数である。）[Application Example 11]
In the gel electrolyte forming agent of Application Example 10, the component (C) may be a compound represented by the following general formula (4).

(In formula (4), R ¹⁴ represents a substituted or unsubstituted alkyl group or alkoxy group. N is an integer of 0 or more and 5 or less.)

（式（５）中、Ｒ^１５はそれぞれ置換もしくは非置換のアルキル基またはアルコキシ基を表す。ｍは０以上３以下の整数である。）[Application Example 12]
In the gel electrolyte forming agent of Application Example 10, the component (C) may be a compound represented by the following general formula (5).

(In Formula (5), R ¹⁵ represents a substituted or unsubstituted alkyl group or alkoxy group. M is an integer of 0 or more and 3 or less.)

（式（６）中、Ｒ^１６およびＲ^１７は、それぞれ独立に、水素原子または炭素数１〜１０のアルキル基を表す。）[Application Example 13]
In the gel electrolyte forming agent of Application Example 10, the component (C) may be a compound having at least one group represented by the following general formula (6).

(In formula (6), R ¹⁶ and R ¹⁷ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.)

[Application Example 14]
In any one example of the gel electrolyte-forming agent applications 10 to application 13, the content of the component (A) M _A parts by weight, the amount of the component (C) is taken as M _C parts by weight, ratio _(M a / M _C) can be in the range of 10 to 1,000.

[Application Example 15]
One aspect of the composition for forming a gel electrolyte according to the present invention contains the gel electrolyte forming agent of any one of Application Examples 1 to 14, and the liquid medium (D).

[Application Example 16]
The gel electrolyte forming composition of Application Example 15 may further contain a cyclic ether compound.

[Application Example 17]
In the gel electrolyte forming composition of Application Example 16, the cyclic ether compound may have a cyclic ether group having a number of members different from that of the cyclic ether group contained in the (meth) acrylate having the cyclic ether structure.

[Application Example 18]
One aspect of the gel electrolyte according to the present invention is characterized by being produced by heating the gel electrolyte forming composition of any one of Application Examples 15 to 17.

[Application Example 19]
One aspect of the electricity storage device according to the present invention is characterized by including the gel electrolyte of Application Example 18.

  According to the gel electrolyte forming agent according to the present invention, a gel electrolyte having sufficient ionic conductivity for developing good charge / discharge characteristics and having improved liquid retention compared to a conventional gel electrolyte. Can be obtained. Moreover, according to the gel electrolyte formation agent which concerns on this invention, storage stability becomes very favorable further.

  According to the gel electrolyte according to the present invention, since it has good liquid retention, separation between the gel electrolyte matrix and the liquid medium can be suppressed. Further, since gelation can be performed under mild conditions, it is possible to suppress deterioration of the electrode and the gel electrolyte itself, and as a result, it is possible to suppress deterioration of charge / discharge characteristics of the electricity storage device. Furthermore, according to the electricity storage device including the gel electrolyte according to the present invention, the electricity storage device characteristics such as discharge rate characteristics, low temperature characteristics, DC-IR characteristics, and cycle characteristics are improved.

  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 includes a repeating unit (A1) derived from (meth) acrylate having a cyclic ether structure and a repeating unit derived from (meth) acrylate having a chain ether structure. (A2), and when the total amount of the repeating unit (A1) and the repeating unit (A2) is 100 [mol%], the amount of the repeating unit (A1) (M1 [mol%]) The polymer (A) having a ratio (M2 / M1) of the amount (M2 [mol%]) of the repeating unit (A2) to 1) in the range of 1 to 10 is contained.

  The gel electrolyte forming agent according to the present embodiment is obtained by heating a gel electrolyte forming composition obtained by mixing with a liquid medium (D) and other additives described below under mild conditions. Can be produced. In the present specification, “heating under mild conditions” means heating at a temperature of about 70 to 100 ° C. at which the electrode and the gel electrolyte do not deteriorate. The gel electrolyte is a highly flexible gel 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. Hereinafter, each component that may be included in the gel electrolyte forming agent according to the present embodiment will be described in detail.

1.1. Polymer (A)
The polymer (A) contained in the gel electrolyte forming agent according to the present embodiment includes a repeating unit (A1) derived from a (meth) acrylate having a cyclic ether structure and a (meth) acrylate having a chain ether structure. Derived repeating unit (A2).

1.1.1. Repeating unit (A1)
The repeating unit (A1) is derived from (meth) acrylate having a cyclic ether structure. The repeating unit (A1) can construct a crosslinked structure by opening the cyclic ether structure when producing a 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 represents a hydrogen atom or a methyl group, and is preferably a methyl group from the viewpoint of the oxidation resistance of the polymer (A).

In the above formula (1), R ² represents a divalent linking group, for example, a single bond, a divalent chain hydrocarbon group having 1 to 20 carbon atoms, a divalent cyclic saturated group having 3 to 20 carbon atoms, or An unsaturated hydrocarbon group, or a divalent group obtained by combining these with an ether group, an ester group, or a carbonyl group can be given. Such a divalent linking group may have a substituent. Is preferably a single bond or an alkylene group having 1 to 4 carbon atoms.

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 8 carbon atoms. Examples of the linear or branched alkyl group having 1 to 8 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 6 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 methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, and 1-methylpropyl group. , T-butyl group and the like. 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. M and n are integers of 0 or more, and m + n ≧ 1, but they can be easily reacted, and the stability of the polymer is good. Therefore, in the above formula (1), m + n is 2 or more. And m + n is more preferably 2.

（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 (D) contained in the gel electrolyte forming composition. By using such a liquid medium, the gel electrolyte forming agent can be easily cross-linked, and a gel electrolyte excellent in ion 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 (D) 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 (meth) acrylate having a cyclic ether structure include glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl (meth) acrylate, (3-oxetanyl) methyl (meth) acrylate, (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-ethyl-oxetane-3-yloxy) ethyl (meth) acrylate, (3-ethyl-oxetane-3-yloxy) butyl (meth) acrylate, 3,4-epoxycyclohexyl Methyl ) Acrylate and the like, can be preferably used (3-oxetanyl) methyl (meth) acrylate and (3-alkyl-3-oxetanyl) methyl (meth) acrylate. These compounds may be used alone or in combination of two or more.

  The content ratio of the repeating unit (A1) in the polymer (A) is such that when the total amount of the repeating unit (A1) and the repeating unit (A2) is 100 mol%, the repeating unit (A1) is 10 to 40 mol%. It is preferable that it is 15 to 35 mol%. When the content ratio of the repeating unit (A1) in the polymer (A) is in the above range, it is easy to heat under mild conditions using a metal ion such as lithium ion contained in the liquid medium (D) as a catalyst. A gel electrolyte can be produced without causing a deterioration of the coexisting electrode or liquid medium by causing a crosslinking reaction (cationic polymerization). Moreover, since it can also fully bridge | crosslink, the mechanical 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.

1.1.2. Repeating unit (A2)
The repeating unit (A2) is derived from (meth) acrylate having a chain ether structure. Since the repeating unit (A2) has a (poly) ether-type chain ether structure moiety, the affinity with the liquid medium used for the electricity storage device can be improved. Thereby, liquid retention property can be provided to a polymer (A).

  In general, the presence of a (poly) ether-type chain ether structure site degrades due to degradation due to a change in oxidation-reduction potential that accompanies charge / discharge of the electricity storage device. It is difficult to do. However, according to the polymer (A) having the repeating unit (A1) and the repeating unit (A2), it is possible to suppress deterioration due to a change in oxidation-reduction potential accompanying charging / discharging of the electricity storage device, and to maintain the gel electrolyte. Liquid deterioration can also be suppressed.

（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。）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 good yield. In formula (2), R ⁶ represents a single bond or a divalent organic group, and the divalent organic group is preferably an alkylene group having 1 to 10 carbon atoms.

In formula (2), a plurality of R ⁷ which may be present each independently represent a divalent hydrocarbon group, and the divalent hydrocarbon group may be a linear or branched 2 having 1 to 10 carbon atoms. Valent hydrocarbon group. Among these, since the affinity with the liquid medium becomes high, it is preferred that R ⁷ independently represents an alkylene group having 1 to 3 carbon atoms.

In formula (2), R ⁸ represents 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, or 6 to 12 carbon atoms. An aryl group is preferred. Examples of the linear or branched alkyl group having 1 to 4 carbon atoms include those exemplified in the description of R ⁴ 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 liquid medium. Moreover, in Formula (2), x is an integer greater than or equal to 1, It is preferable that it is 1-30, It is more preferable that it is 1-20, It is especially preferable that it is 1-10.

（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 polymer generally used in non-aqueous electrolytes, and is crosslinked to form a polymer. However, even when a strong network is formed, the nonaqueous electrolyte solution can be absorbed and sufficiently swelled, and movement of lithium ions between the nonaqueous electrolyte 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} has the same meaning as ^{R 5} in the general formula (2). 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 ⁴ above. Among these, each of R ¹¹ is preferably a hydrogen atom since affinity with the liquid medium (D) is increased. Moreover, in Formula (2-1), x is an integer greater than or equal to 1, It is preferable that it is 1-30, It is more preferable that it is 1-20, It is especially preferable that it is 1-10.

  Specific examples of the compound represented by the general formula (2) include 2-methoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, and 2-ethylhexyloxydiethylene glycol (meth). Acrylate, methoxypolyethylene glycol (meth) acrylate (repeating number of ethylene glycol units = 2-30), 2-ethoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, ethoxytriethylene glycol (meth) acrylate, methoxypropylene glycol (Meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxy Traethylene glycol (meth) acrylate, ethoxydipropylene glycol (meth) acrylate, ethoxytripropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate (ethylene glycol) And the number of unit repetitions = 2 to 30). These compounds may be used alone or in combination of two or more.

  The content ratio of the repeating unit (A2) in the polymer (A) is such that when the total amount of the repeating unit (A1) and the repeating unit (A2) is 100 mol%, the repeating unit (A2) is 60 to 90 mol%. It is preferable that it is 65 to 85 mol%. When the content ratio of the repeating unit (A2) in the 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) to Repeating Unit (A2) The polymer (A) contained in the gel electrolyte forming agent according to this embodiment has a total amount of 100 mol of the repeating unit (A1) and the repeating unit (A2). %, The ratio (M2 / M1) of the amount (M2 [mol%]) of the repeating unit (A2) to the amount (M1 [mol%]) of the repeating unit (A1) is in the range of 1-10. It is preferably within a range of 1.5 to 8, and more preferably within a range of 2 to 6. When the value of M2 / M1 is in the above range, it is possible to achieve both good liquid retention and sufficient gelling properties as described above.

1.1.4. Production Method Polymer (A) contained in the gel electrolyte forming agent according to the present embodiment starts radical polymerization of (meth) acrylate having a cyclic ether structure and (meth) acrylate having a chain ether structure. It can be easily prepared by radical (co) polymerization in a reaction solvent in the presence of an agent and optionally a molecular weight regulator. When the polymer (A) thus obtained is a copolymer, it may have any structure of a random copolymer, an alternating copolymer, a periodic copolymer, and a block copolymer.

Although it does not restrict | limit especially as said reaction solvent, For example, water, alcohol, ester, carbonate, ketone, lactone, ether, sulfoxide, amide etc. can be mentioned.
Examples of the alcohol include methanol, ethanol, isopropanol and the like;
Examples of the ester include ethyl acetate, methyl propionate, and butyl acetate;
Examples of the carbonate include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate;
Examples of the ketone include methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and diethyl ketone;
Examples of the lactone include γ-butyl lactone;
Examples of the ether include trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran and the like;
Examples of the sulfoxide include dimethyl sulfoxide and the like;
Examples of the amide include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like, and one or more selected from these can be used. Is preferred.

  The reaction solvent is preferably at least one solvent that can be contained in the liquid medium (D) exemplified later, and more preferably the same solvent as the solvent actually used in the gel electrolyte forming composition. . By using at least one solvent that can be contained in the liquid medium (D), the gel electrolyte-forming agent solution after polymerization can be directly used for the preparation of the gel electrolyte-forming composition, thus simplifying the process. be able to. In this case, it is possible to produce a gel electrolyte having better liquid retention by radical polymerization using a solvent that can be contained in the liquid medium (D) as a reaction solvent. If a solvent of the same type as the solvent actually used for the gel electrolyte forming composition is used as the reaction solvent, the affinity between the resulting polymer and the liquid medium (D) becomes very good. Preparation of the composition for use is facilitated, and liquid retention of the resulting gel electrolyte is very good.

  The liquid medium (D) will be described later. As the reaction solvent, it is preferable to use one or more selected from carbonates, lactones, ethers and sulfoxides. Among these, the liquid medium actually used or a mixture thereof is used. Most preferably it is used. Surprisingly, it has been revealed that the effect of improving the liquid retention is maintained even when the solvent is replaced after the polymerization in the reaction solvent.

  The ratio of the solvent used in producing the polymer (A) is preferably 100 to 1,000 parts by mass, and 200 to 500 parts by mass with respect to 100 parts by mass of the total amount of monomers. More preferred.

  In the radical (co) 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.

  Examples of the molecular weight regulator include halogenated hydrocarbons such as chloroform and carbon tetrachloride; mercaptan compounds such as n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dotezyl mercaptan, and thioglycolic acid; dimethyl Examples thereof include xanthogen compounds such as xanthogen disulfide and diisopropylxanthogen disulfide; and other molecular weight regulators such as terpinolene and α-methylstyrene dimer. The use ratio of the molecular weight regulator is preferably 5 parts by mass or less with respect to 100 parts by mass in total of the monomers.

  The polymer (A) is a radical (co) polymerization using a monomer other than the compound represented by the general formula (1) or (2) (hereinafter also 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 polymer (A) obtained as described above is preferably 1,000 to 1,000,000, more preferably 1,000 to 100,000, and 10,000 to 100,000. Is particularly preferred. When the number average molecular weight (Mn) of the polymer (A) is 100,000 or less, the impregnation property to the electrode plate is improved, so that the electrical characteristics (charge rate characteristics, DC-IR characteristics, cycle characteristics) of the obtained electricity storage device are obtained. ) Tend to be better. Furthermore, when the number average molecular weight (Mn) of the polymer (A) is 1000 or more and 100,000 or less, the cycle characteristics of the obtained electricity storage device tend to be particularly good. In addition, the number average molecular weight (Mn) of a polymer (A) can be calculated | required by converting from the relationship between the elution time of standard polystyrene measured by GPC (gel permeation chromatography) method, and molecular weight.

1.2. Ester compound (B) having at least one carbon-carbon unsaturated bond
The gel electrolyte forming agent according to the present embodiment may contain an ester compound (B) having at least one carbon-carbon unsaturated bond (hereinafter also referred to as “component (B)”). When the component (B) is contained in the gel electrolyte forming agent according to the present embodiment, the component (B) is also contained in the gel electrolyte produced using this gel electrolyte forming agent. In an electrode including a gel electrolyte containing such a component (B), it is considered that when a charge / discharge is started, the component (B) undergoes electropolymerization to form a protective film on the surface of the active material layer. Such a protective film is a stable film that does not crack during the charge / discharge cycle of the battery, and the active material surface is covered with the protective film, so that the liquid medium is decomposed and gas is generated by repeated charge / discharge. Therefore, it is considered that the charge / discharge characteristics of the electricity storage device can be improved. In particular, in an electricity storage device using metal ions such as lithium ions, dendrites due to metal ions are likely to occur on the electrode surface by repeated charge and discharge. Since such dendrites are usually precipitated as needle-like crystals, when the crystals grow, they are short-circuited with the counter electrode and lose the charge / discharge function. It can be presumed that the protective film described above also has an effect of suppressing the growth of dendrites on the electrode surface, and as a result, the charge / discharge characteristics of the electricity storage device can be improved.

The content of component (B) in the gel electrolyte-forming agent according to the present embodiment, M _A parts by weight and the content of the polymer (A), the content of the component (B) was M _B parts by weight when the ratio of _(M a / M _B) preferably in the range of 1 to 100. When the ratio (M _A / M _B ) is within the above range, the gelation is not inhibited when the gel electrolyte is produced from the gel electrolyte forming agent, and the surface of the active material layer is appropriately protected as described above. Since a film can be formed, deterioration of the active material layer surface can be suppressed. This improves the cycle characteristics of the electricity storage device. Furthermore, since the interface resistance between the gel electrolyte and the active material layer surface can be reduced by an appropriate protective film formed on the surface of the active material layer, an electricity storage device having good charge / discharge characteristics is manufactured. Can do.

  The component (B) is not limited as long as it is an ester having at least one carbon-carbon unsaturated bond, but is not soluble in the liquid medium (D) described later or phase separated from the polymer (A). From the viewpoint of producing a uniform gel electrolyte, it is preferably at least one selected from the group consisting of cyclic carbonates and (meth) acrylates. Hereinafter, the cyclic carbonate and (meth) acrylate will be described in this order.

1.2.1. Cyclic carbonate Examples of the cyclic carbonate include compounds represented by the following general formula (3).

In the above formula (3), R ¹² and R ¹³ are each independently a hydrogen atom, a halogen atom, an alkyl or alkenyl group having 1 to 6 carbon atoms, or a phenyl group. Note that when R ¹² or R ¹³ is an alkyl group, an alkenyl group, or a phenyl group, part of the hydrogen atoms may be substituted with a halogen atom (preferably a fluorine atom).

  Specific examples of the cyclic carbonate include vinylene carbonate (VC), 3-methyl vinylene carbonate, 3,4-dimethyl vinylene carbonate, 3-ethyl vinylene carbonate, 3,4-diethyl vinylene carbonate, 3-propyl vinylene carbonate, 3 , 4-dipropyl vinylene carbonate, 3-phenyl vinylene carbonate, 3,4-diphenyl vinylene carbonate, vinyl ethylene carbonate (VEC), divinyl ethylene carbonate (DVEC), fluorinated vinylene carbonate, and the like. These cyclic carbonates may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, and divinyl ethylene carbonate is preferable, and vinylene carbonate is particularly preferable from the viewpoint of efficiently forming a protective film on the surface of the active material layer.

  When using cyclic carbonate as a component (B), the content rate of the component (B) in a gel electrolyte formation agent has the density | concentration of the cyclic carbonate in the composition for gel electrolyte formation mentioned later 0.5-5. The content is preferably 0% by mass, more preferably 0.5 to 4.0% by mass, and particularly preferably 0.5 to 3.0% by mass. When the concentration of the component (B) in the gel electrolyte-forming composition is within the above range, the storage stability of the gel electrolyte-forming composition is improved, and the electricity storage provided with the gel electrolyte produced using the composition The device exhibits good charge / discharge characteristics.

1.2.2. Specific examples of (meth) acrylate (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl ( (Meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) Alkyl (meth) acrylates such as acrylate and decyl (meth) acrylate;
2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate Hydroxyl group-containing (meth) acrylates such as pentaerythritol hexa (meth) acrylate;
(Meth) acrylates having a chain ether structure such as methoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, ethoxytriethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate;
(3-ethyl-3-oxetanyl) methyl (meth) acrylate, (3-ethyl-3-oxetane-3-yloxy) ethyl (meth) acrylate, (3-ethyl-oxetane-3-yloxy) butyl acrylate, glycidyl ( (Meth) acrylates having a cyclic ether structure such as (meth) acrylate and tetrahydrofurfuryl (meth) acrylate;
Etc.

  When (meth) acrylate is used as the component (B), the content ratio of the component (B) in the gel electrolyte-forming agent is such that the concentration of (meth) acrylate in the gel electrolyte-forming composition described later is 0.01 to The content is preferably 5.0% by mass, more preferably 0.01 to 4.0% by mass, and particularly preferably 0.05 to 2.0% by mass. When the concentration of the component (B) in the gel electrolyte-forming composition is within the above range, the storage stability of the gel electrolyte-forming composition is improved, and the electricity storage provided with the gel electrolyte produced using the composition The device exhibits good charge / discharge characteristics.

  Since (meth) acrylates as exemplified above are likely to volatilize when heated, when preparing a gel electrolyte by heating a composition for forming a gel electrolyte containing (meth) acrylate, (meth) In some cases, the acrylate is vaporized to generate gas, and the housing of the electricity storage device is deformed. However, it is preferable that the concentration of (meth) acrylate is within the above-mentioned range because the generation of such gas can be effectively suppressed.

1.3. Compound having phenolic hydroxyl group (C)
The gel electrolyte forming agent according to the present embodiment may contain a compound (C) having a phenolic hydroxyl group (hereinafter also referred to as “component (C)”). In the present invention, the “phenolic hydroxyl group” means a hydroxyl group directly bonded to an aromatic ring such as a benzene ring, a condensed benzene ring, a non-benzene aromatic ring or a heteroaromatic ring.

  If a part of the polymerization initiator used for synthesizing the polymer (A) remains, the crosslinking reaction may proceed at a cyclic ether structure contained in the polymer (A) or a different site. . Thereby, it is thought that a part of gel electrolyte formation agent gelatinizes and the storage stability of a gel electrolyte formation agent falls. However, by adding the component (C) to the gel electrolyte forming agent, the storage stability is improved because the crosslinking reaction by the polymerization initiator of the gel electrolyte forming composition produced using the gel electrolyte forming agent can be suppressed. To do. Therefore, in an actual production line, since it can supply stably, without changing the characteristic of the composition for gel electrolyte formation, the gel electrolyte with stable quality can be supplied.

  In addition, although a part of component (C) remains in the gel electrolyte obtained, it has become clear that the remaining component (C) does not deteriorate the charge / discharge characteristics of the electricity storage device. The reason for this is not fully elucidated and is not preferred to be bound by theory, but in an electrode equipped with such a gel electrolyte, when charge / discharge is first performed, the component (C) undergoes electropolymerization, It is thought that a protective film is formed on the surface of the active material layer. By forming such a protective film, it is considered that decomposition of the liquid medium can be suppressed. Such a protective film is a stable film that does not crack during the charge / discharge cycle of the battery, and the surface of the active material layer is covered with the protective film, so that the liquid medium is decomposed or the gas is removed by repeated charge / discharge. Since generation | occurrence | production is suppressed, it is thought that the charging / discharging characteristic of an electrical storage device can be improved. In particular, in an electricity storage device using metal ions such as lithium ions, dendrites due to metal ions are likely to occur on the electrode surface by repeated charge and discharge. Since such dendrites are usually precipitated as needle-like crystals, when the crystals grow, they are short-circuited with the counter electrode and lose the charge / discharge function. It can be presumed that the protective film described above also has an effect of suppressing the growth of dendrites on the electrode surface, and as a result, the charge / discharge characteristics of the electricity storage device can be improved.

The content of component (C) in the gel electrolyte formers, M _A parts by weight and the content of the component (A), the content of the component (C) is taken as M _C parts by weight, the ratio (M _A / M _C ) is preferably in the range of 10 to 1000, and more preferably in the range of 75 to 250. When the content ratio of the component (C) is within the above range, not only can the storage stability of the gel electrolyte forming agent be ensured, but also the solubility in the liquid medium (D) described later, This is preferable in that a more uniform gel electrolyte can be produced without phase separation with the coalescence (A).

（式（４）中、Ｒ^１４はそれぞれ置換もしくは非置換のアルキル基またはアルコキシ基を表す。ｎは０以上５以下の整数である。）The component (C) is preferably a compound represented by the following general formula (4).

(In formula (4), R ¹⁴ represents a substituted or unsubstituted alkyl group or alkoxy group. N is an integer of 0 or more and 5 or less.)

In the above formula (4), a plurality of R ¹⁴ which may be present each represents a substituted or unsubstituted alkyl group or alkoxy group. As an alkyl group, it is preferable that it is a C1-C10 (preferably C1-C6) alkyl group. Such alkyl groups may be linear, branched or cyclic, such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, isobutyl. Group, amyl group, tertiary amyl group, cyclopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, isooctyl group, tertiary octyl group, 2-ethylhexyl group, nonyl group, decyl group and the like. When R ¹⁴ is an alkyl group, it is preferable that an alkyl group is substituted at the 2-position and / or the 6-position of the phenol group because the effect of improving the storage stability of the gel electrolyte forming agent is high. As an alkoxy group, a C1-C10 (preferably C1-C6) alkoxy group is preferable. Examples of such alkoxy groups include methoxy, ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptyloxy, octyloxy, isooctyloxy, nonyloxy, decyloxy, and the like. . When R ¹⁴ is an alkoxy group, it is preferable that an alkoxy group is substituted at the 4-position of the phenol group because the effect of improving the storage stability of the gel electrolyte forming agent is high.

（式（５）中、Ｒ^１５はそれぞれ置換もしくは非置換のアルキル基またはアルコキシ基を表す。ｍは０以上３以下の整数を表す。）As the component (C), among the compounds represented by the general formula (4), the compound represented by the following general formula (5) is more effective in improving the storage stability of the gel electrolyte forming agent. It is more preferable that

(In Formula (5), R ¹⁵ represents a substituted or unsubstituted alkyl group or alkoxy group. M represents an integer of 0 or more and 3 or less.)

In the above formula (5), a plurality of R ¹⁵ which may be present each represent a substituted or unsubstituted alkyl group or alkoxy group. The alkyl group preferably has 1 to 10 carbon atoms (preferably having 1 to 6 carbon atoms) alkyl group, may be exemplified the same alkyl group as R ¹⁴ in the formula (4). The alkoxy group preferably has 1 to 10 carbon atoms (preferably having 1 to 6 carbon atoms) alkoxy group, may be exemplified the same alkoxy group as R ¹⁴ in the formula (4).

  Specific examples of the compound represented by the general formula (4) include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,4 , 6-tri-t-butylphenol, 2,6-di-t-butyl-4-s-butylphenol, 2,6-di-t-butyl-4-methoxyphenol, 2,6-di-t-butyl- 4-hydroxymethylphenol, 2,6-di-tert-butyl-4- (methoxycarbonyl) phenol, 2,6-di-tert-butyl-4-nonylphenol, 4-methoxyphenol, 4-ethoxyphenol, 4- Examples include propoxyphenol, 4-isopropoxyphenol, 4-butoxyphenol, 4-t-butoxyphenol and the like.

Further, as the component (C), a compound having at least one group represented by the following general formula (6) (hydroxyphenylpropionate compound), hydroxybenzyl compound, thiobisphenol compound, thiomethylphenol compound An alkanediylphenol compound is also preferred.

In the above formula (6), R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, but an alkyl having 1 to 6 carbon atoms (more preferably 1 to 4 carbon atoms). It is preferably a group. The alkyl group may be any of linear, branched and cyclic, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, secondary butyl group, tertiary butyl group, isobutyl group, amyl Group, tertiary amyl group, cyclopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, isooctyl group, tertiary octyl group, 2-ethylhexyl group, nonyl group, decyl group and the like.

  Specific examples of hydroxyphenylpropionate compounds include 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethoxy. ] -2,4,8,10-terolaoxaspiro [5.5] undecane, pentaerythrityltetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol- Bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionate], 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tetrakis [methylene-3- (3,5′-di-tert-butyl-4′-hydroxyphenylpropionate)] methane, etc. Can be mentioned.

  Specific examples of hydroxybenzyl compounds include 1,3,5, -trimethyl-2,4,6, -tris (3 ′, 5′-di-t-butyl-4-hydroxybenzyl) benzene, 1,3. , 5-tris (4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, 1,3,5-tris (4-t-butyl-3) -Hydroxy-2,6-dimethylbenzyl) -isocyanurate and the like.

  Specific examples of the thiobisphenol compound include 4,4′-thiobis (6-t-butyl-3-methylphenol).

  Specific examples of the thiomethylphenol compound include 2,4-bis [(octylthio) methyl] -o-cresol.

  Specific examples of alkanediylphenol compounds include N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 2,2′-methylenebis (4-methyl). -6-tert-butylphenol), 4,4'-butylidene-bis (3-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) ) Butane and the like.

  In addition, it is preferable that the component (C) contained in the gel electrolyte formation agent which concerns on this Embodiment has a standard boiling point of 100-250 degreeC. When the standard boiling point is within the above range, vaporization of the component (C) can be suppressed in the step of heating when producing the gel electrolyte. That is, even if gelation is performed by heating in a state where the casing is sealed in the power storage device manufacturing process, deformation due to an increase in the casing internal pressure due to gas generation can be suppressed.

2. Composition for Gel Electrolyte Formation The composition for gel electrolyte formation according to the present embodiment (hereinafter also simply referred to as “composition”) contains the above-described gel electrolyte formation agent and the liquid medium (D). . By heating the composition according to the present embodiment under mild conditions for crosslinking (cationic polymerization), a good gel electrolyte having excellent liquid retention can be produced.

  When preparing the composition according to the present embodiment, the above-mentioned gel electrolyte forming agent and other additives as necessary are added to the liquid medium (D) and heated to about 40 to 60 ° C. It is sufficient to stir well. Thereby, the polymer (A) contained in the gel electrolyte forming agent can be completely dissolved in the liquid medium (D). Note that if the heating temperature is increased to 70 to 100 ° C., a gel electrolyte may be formed.

  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 (D)
The liquid medium (D) 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 gel electrolyte, it is possible to use an electrolyte other than Li. Examples of such an electrolyte include (FSO ₂ ) ₂ N ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , NO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , ( _{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 N - and the like anions And a salt composed of a combination of cation and cation.

  As the cation, any one of N, P, S, O, C, and Si or two or more kinds of elements are included in the structure, and a chain structure or a cyclic structure such as a 5-membered ring or a 6-membered ring is included in the skeleton. Compounds. Examples of the compound having a chain structure in the skeleton include alkyl ammonium. Examples of the compound having a cyclic structure in the skeleton include furan, thiophene, pyrrole, pyridine, oxazole, isoxazole, thiazol, isothiazole, furazane, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, pyrrolidine, Heterocyclic compounds such as piperidine; and condensed heterocyclic compounds such as benzofuran, isobenzofuran, indole, isoindole, isodridine, and carbazole.

Among the electrolytes exemplified above, when LiPF ₆ or LiBF ₄ is used, lithium ions act as a cationic polymerization initiator, which is preferable in that it is not necessary to use another cationic polymerization initiator. In addition, when LiPF ₆ is used, it is particularly preferable in that the discharge capacity retention rate at a low temperature of the obtained electricity storage device is good.

  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 a liquid medium (D) 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 conventionally used in electrolyte solutions, and specifically, components for improving ionic conductivity can be used. For example, nitrogen-containing or sulfur-containing compounds such as azaindole, benzimidazole, benzodithiol, benzofuran, benzothiazole, 1-benzothiophene, 1H-benzotriazole, benzylcapton, 1-bromo-3-fluorobenzene; sucrose fatty acid Examples of the ester include 10 mass% or less, preferably 3 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 may be further added with a cyclic ether compound from the viewpoint of improving the liquid retention of the resulting gel electrolyte and increasing the crosslink density to improve the mechanical strength. it can. 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 crosslink density can be further increased, so that the mechanical 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′-epoxycyclohexenecarboxylate, 1,2: 8,9-diepoxylimonene, 3-ethyl-3 {[(3-ethyloxetane-3-yl) Methoxy] methyl} oxetane, 3-ethyl-3-hydroxymethyloxetane, 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 has a different number of members from the cyclic ether group contained in the repeating unit (A1) in the polymer (A). It preferably has a cyclic ether group. 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 further reduced. Thereby, the deterioration of the electrode and gel electrolyte itself accompanying heating can be suppressed. Moreover, since a crosslinking density can be improved, the gel electrolyte excellent in mechanical 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 contains in the range of 0-50 mass parts with respect to 100 mass parts of polymers (A). It is preferred that

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 highly flexible gel 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 system, Si—Ti composite system, 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 electricity storage device. Examples of the positive electrode current collector include aluminum, titanium, stainless steel copper, nickel, baked carbon, conductive polymer, conductive glass, etc., and aluminum and copper for the purpose of improving adhesion, conductivity, and oxidation resistance. Or the like can be used which have been treated with carbon, nickel, titanium, silver or the like. Examples of the negative electrode current collector include copper, stainless steel, nickel, aluminum, titanium, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc. For the purpose, a surface of copper or the like treated with carbon, nickel, titanium, silver or the like 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 glass 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, a copolymer of polyvinylidene fluoride and hexafluoropropylene (HFP), perfluoromethyl vinyl ether (PFMV) or tetrafluoroethylene (TFE) Polyvinylidene fluoride copolymer resins such as polytetrafluoroethylene (PTFE), fluorine resins such as fluorine rubber; styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), styrene-acrylonitrile copolymer, etc. Examples of the polymer include polysaccharides such as carboxymethylcellulose (CMC) and thermoplastic resins such as polyimide resin, but are not limited thereto. Moreover, you may use these in mixture of 2 or more types. The addition amount is preferably 0.2 to 30 parts by mass, and more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the active material. As for the positive electrode active material whose surface is coated with carbon, such as LiFePO ₄ , a carboxylic acid-modified polyvinylidene fluoride or SBR aqueous binder can 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 for the separator include at least one kind of inorganic oxide such as alumina, titania, silicon and / or zirconia as the inorganic material, and polymers such as fluororesin, polystyrene resin and acrylic resin as the organic material. 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. Materials that are advantageous for forming the barrier particles include low melting polymers such as natural or artificial waxes and polyolefins, which melt at the desired barrier 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, a laminate shape, or any other shape, and the basic configuration of the electricity storage device is the same regardless of the shape, depending on the purpose. The design can be changed.

  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. .

  In the case of producing the electricity storage device according to the present embodiment, if the selected active material generates a large amount of gas during the first charge and affects the cell performance, the above-mentioned composition for gel electrolyte formation You may heat-process, after injecting | throwing-in an object to a pre-battery and performing the process of charge or charging / discharging as pre-processing.

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 collected precipitate was dried under reduced pressure at 60 ° C. for 12 hours to obtain a polymer P1 having a number average molecular weight of 200,000. This polymer P1 was used as a gel electrolyte forming agent.

5.1.2. Preparation of Gel Electrolyte Forming Composition 3 g of the obtained polymer P1 is weighed and dissolved in 47 g of a liquid medium (D) containing 1 mol / L of LiPF ₆ and EC: DEC = 3: 7 (volume ratio). A composition for forming a gel electrolyte containing 6% by mass of a gel electrolyte forming agent 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 obtained gel electrolyte forming composition into a 50 mL vial tube and heating in an oven 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. Table 3 shows the evaluation results. In Tables 3 to 10, if the gel electrolyte matrix and the liquid medium are not separated, it is judged that the liquid retaining property is good, and if it is separated, the liquid retaining property is judged to be poor. × ”.

(2) Evaluation of ion conductivity The composition for gel electrolyte formation obtained in the dry room is enclosed in an ion conductivity evaluation cell (manufactured by Solartron, model number "SR-CIR-C") at 80 ° C. A gel electrolyte was produced in an evaluation cell by heating in an oven for 30 minutes, and this was used as a 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. Table 3 shows the evaluation results. In Tables 3 to 10, when the ionic conductivity is 1.0 × 10 ⁻³ S / cm or more, it can be determined to be good, and when it is less than 1.0 × 10 ⁻³ S / cm, it is determined to be defective. it can.

(3) Storage stability of gel electrolyte forming agent 25 g of the obtained gel electrolyte forming agent was weighed and dissolved in 75 g of diethyl carbonate (DEC) to prepare a solution containing 25% by mass of the gel electrolyte forming agent. Next, the viscosity of the solution immediately after preparation and the viscosity after 6-month storage were measured at 25 ° C. using an E-type viscometer (manufactured by Toki Sangyo, model “RE-85L”). Viscosity change rate (%) represented by | (V ₀ −V ₆ ) / V ₀ | × 100, where V _{0 is} the viscosity of the solution immediately after preparation and V ₆ is the viscosity after storage for 6 months. did. In Tables 8 to 10, when the viscosity change rate was within 2%, the storage stability was judged to be good, and when the viscosity change rate was greater than 2%, it was judged as poor, and “x” was assigned.

(4) Production and evaluation of electricity storage device <Production of positive electrode>
Biaxial planetary mixer (product name "TK Hibismix 2P-03" manufactured by PRIMIX Corporation) and electrochemical device electrode binder (product name "KF polymer # 1120" manufactured by Kureha Co., Ltd.) 4.0 parts by mass (Solid content conversion), conductive assistant (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Denka Black 50% press product”) 3.0 parts by mass, LiCoO _{2 having a} particle diameter of 5 μm as a positive electrode active material (manufactured by Hayashi Kasei Co., Ltd.) ) 100 parts by mass (in terms of solid content) and 36 parts by mass of N-methylpyrrolidone (NMP) were added and stirred at 60 rpm for 2 hours. After adding NMP to the obtained paste to adjust the solid content to 65%, using a stirring defoaming machine (trade name “Awatori Netaro”, manufactured by Shinky Co., Ltd.), 2 minutes at 200 rpm, 1800 rpm The mixture was stirred and mixed for 5 minutes at 1,800 rpm for 1.5 minutes under vacuum to prepare a slurry for electrodes. The prepared electrode slurry was uniformly applied to the surface of a current collector made of an aluminum foil having a thickness of 30 μm by a doctor blade method so that the film thickness after drying was 80 μm, followed by drying at 120 ° C. for 20 minutes. Then, the positive electrode was obtained by pressing with a roll press so that the density of an electrode layer might be set to 3.0 g / cm < ³ >.

<Manufacture of negative electrode>
Thickener (trade name “CMC2200”, manufactured by Daicel Chemical Industries, Ltd.) in a biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.) 1 part by mass (solid content conversion) In addition, 100 parts by mass of graphite (manufactured by Hitachi Chemical Co., Ltd., product name “SMG-HE1”) and 68 parts by mass of water were added as the negative electrode active material, and stirred at 60 rpm for 1 hour. Thereafter, 2 parts by mass of the SBR binder composition (manufactured by JSR Corporation, trade name “TRD2001”) was added to the polymer, and the mixture was further stirred at 60 rpm for 1 hour to obtain a paste. After adding water to the obtained paste and adjusting the solid content to 50% by mass, the mixture was stirred at 200 rpm for 2 minutes at 200 rpm using a stirring defoamer (trade name “Awatori Nertaro” manufactured by Shinky Co., Ltd.). Then, a negative electrode slurry was prepared by stirring at 1,800 rpm for 5 minutes and further stirring at 1,800 rpm for 1.5 minutes under a reduced pressure of 25 kPa, followed by mixing. The negative electrode slurry prepared above was uniformly applied to the surface of a current collector made of copper foil having a thickness of 20 μm by a doctor blade method so that the film thickness after drying was 150 μm, and dried at 120 ° C. for 20 minutes. . Then, the negative electrode was obtained by pressing using a roll-press machine so that the density of a film | membrane may be 1.5 g / cm < ³ >.

<Assembly of lithium ion secondary battery cells>
In the glove box, a negative electrode terminal was attached to and mounted on the negative electrode cut out to 50 mm × 25 mm on a film-like exterior aluminum seal made of aluminum. Next, a separator made of a polypropylene porous film cut out to 54 mm × 27 mm (manufactured by Celgard, trade name “Celguard # 2400”, thickness 25 μm) was placed on the negative electrode, and then cut into 48 mm × 23 mm. A positive electrode terminal was attached to the positive electrode and placed on the separator. And the exterior aluminum seal similar to the said exterior aluminum seal was mounted on this positive electrode. Thus, the laminated body which consists of an exterior aluminum seal, a negative electrode, a separator, a positive electrode, and an exterior aluminum seal was obtained. Thereafter, the outer peripheral aluminum seals on the three sides of this laminate were sealed by bonding the outer peripheral edges of the two outer aluminum seals with a heating sealing device. Then, after injecting the gel electrolyte forming composition obtained above so that air does not enter between each layer and further degassing under reduced pressure, the negative electrode terminal and the positive electrode terminal are external to the outer aluminum seal under reduced pressure. The 4th side was sealed so that it might be exposed, and it sealed. The laminated cell thus sealed was heated in an oven at 80 ° C. for 30 minutes to produce a secondary battery (electrochemical device) composed of a bipolar single-layer laminated cell.

<Evaluation of discharge rate characteristics>
The secondary battery cell produced above was placed in a constant temperature bath at 25 ° C., charging was started at a constant current (0.2 C), and charging was continued until the voltage reached 4.2V. Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 0.2 C was measured.

  Next, the same cell was charged at 25 ° C. with a constant current (0.2 C), and charged until the voltage reached 4.2V. Next, discharge was started at a constant current (2C), and when the voltage reached 2.7 V, the discharge was completed (cutoff), and the discharge capacity at 2C was measured.

Using the above measured values, the discharge rate (%) was calculated by calculating the ratio (percent%) of the discharge capacity at 2C to the discharge capacity at 0.2C. The secondary battery cell produced using the above-mentioned gel electrolyte forming composition has a discharge rate of “A” and an electrolyte solution containing EC: DEC = 3: 7 (volume ratio) containing 1 mol / L of LiPF _6. When the discharge rate of the secondary battery cell produced by using is “B”, it can be evaluated that the discharge rate characteristic represented by the following formula (7) is 0.7 or more. .
Discharge rate characteristics = A / B (7)

  Table 3 shows the values of the obtained discharge rate characteristics. In the measurement conditions, “1C” indicates a current value at which discharge is completed in one hour after constant current discharge of a cell having a certain electric capacity. For example, “0.1 C” is a current value at which discharge is completed over 10 hours, and 10 C is a current value at which discharge is completed over 0.1 hours.

<Evaluation of low temperature characteristics>
The secondary battery cell produced above was placed in a constant temperature bath at 25 ° C., charging was started at a constant current (0.2 C), and charging was continued until the voltage reached 4.2V. Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 25 ° C. was measured.

  Next, the same cell was placed in a thermostatic chamber at 0 ° C., and charging was started at a constant current (0.2 C), and charging was continued until the voltage reached 4.2V. Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 0 ° C. was measured.

Using the measured values, the discharge capacity retention rate (percentage%) at 0 ° C. with respect to the discharge capacity at 25 ° C. was used as an index of low temperature characteristics. The secondary battery cell produced using the above-mentioned gel electrolyte forming composition has a discharge capacity retention at 0 ° C. of “C”, EC containing 1 mol / L of LiPF ₆ : DEC = 3: 7 (volume) When the discharge capacity retention rate at 0 ° C. of the secondary battery cell produced using the electrolyte solution of (R) is “D”, the low temperature characteristic represented by the following formula (8) is 0.8 or more. If it exists, it can be evaluated that it is favorable. Table 3 shows the obtained low temperature characteristic values.
Low temperature characteristics = C / D (8)

<Evaluation of internal DC resistance (DC-IR)>
The secondary battery cell produced above was placed in a thermostat set to 25 ° C., and charged to 50% DOD (3.8 V) at a constant current (0.2 C). After that, the voltage change when charging at a constant current (0.5C) for 10 seconds is read, and after a pause for 1 minute, the voltage change when discharging at a constant current (0.5C) for 10 seconds is further performed. I read. The voltage at the time of charging / discharging was read by the same method except having changed the electric current value from 0.5C to 1.0C, 2.0C, 3.0C, 5.0C. A graph was created with the applied current value (A) as the horizontal axis and the voltage value (V) as the vertical axis, and the slope value of the straight line connecting the plot points was calculated at each charge / discharge time. The gradient values were taken as internal DC resistance values (DC-IR) during charging and discharging, respectively. Electrolytic solution of EC: DEC = 3: 7 (volume ratio) containing DC-IR “E” and 1 mol / L of LiPF ₆ in the secondary battery cell produced using the above-described gel electrolyte forming composition When the DC-IR characteristic of the secondary battery cell produced using the battery is “F”, the DC-IR characteristic represented by the following formula (9) is 2.5 or less. be able to.
DC-IR characteristics = E / F (9)

  The obtained DC-IR characteristic values are shown in Table 3. In the measurement conditions, “DOD” indicates the ratio of the discharge capacity to the charge capacity. For example, “charge to 50% DOD” indicates that only 50% of the capacity is charged when the total capacity is 100%.

<Evaluation of cycle characteristics at 25 ° C.>
After the evaluation of <Internal DC Resistance Value (DC-IR)>, the same secondary battery cell is placed in a thermostat set at 25 ° C., and charging is started at a constant current (2.0 C). When the voltage became 4.2 V, the charging was continued at a constant voltage (4.2 V), and the charging was completed (cut off) when the current value reached 0.01C. Thereafter, discharging was started at a constant current (2.0 C), and the time when the voltage reached 3.0 V was regarded as the completion of discharging (cutoff), and the discharge capacity at the first cycle was calculated. Thus, charging / discharging was repeated 100 times, and the discharge capacity at the 50th cycle was calculated. A value obtained by dividing the discharge capacity at the 50th cycle thus measured by the discharge capacity at the first cycle was defined as the 50th cycle discharge retention rate (%). The secondary battery cell produced using the above gel electrolyte forming composition has a discharge capacity maintenance ratio of 50th cycle as “G” and EC: DEC = 3: 7 (volume) containing 1 mol / L of LiPF _6. The discharge rate characteristic represented by the following formula (10) is 0.7 or more when the discharge capacity maintenance rate at the 50th cycle of the secondary battery cell manufactured using the electrolyte solution of (R) is “H” If it is, it can be evaluated that it is favorable. Table 3 shows the obtained cycle characteristic values.
Cycle characteristics = G / H (10)

5.2. Examples 2-27, Comparative Examples 1-3
Polymers P2 to P20 were produced in the same manner as in Example 1 except that the monomer composition, the blending amount, and the reaction solvent were changed to those shown in Table 1 or Table 2. Moreover, each evaluation test was done like the said Example 1 except having changed the used composition for gel electrolyte formation into the thing of Tables 3-4. In addition, the content rate of the additive in Table 3-Table 4 represents content (mass part) of the additive with respect to 100 mass parts of gel electrolyte formation agents.

5.3. Examples 28-60, Comparative Examples 4-6
In Example 28, 6 parts by mass of the polymer P1 obtained above as a component (A) and 0.2 parts by mass of vinylene carbonate (VC) as a component (B) were weighed out, and no bubbles were mixed therein. Thus, a gel electrolyte forming agent was prepared by sufficiently stirring, mixing and homogenizing under reduced pressure. Each evaluation test was performed in the same manner as in Example 1 except that this gel electrolyte forming agent was used.

  Examples 29 to 60 and Comparative Examples 4 to 6 were the same as Example 1 except that gel electrolyte forming agents were prepared so as to have the compositions described in Tables 5 to 7 in the same manner as Example 28. Each evaluation test was conducted.

5.4. Examples 61-83, Comparative Examples 7-8
In Example 61, 6 parts by mass of the polymer P1 obtained above as the component (A) and 0.035 of 2,6-di-t-butyl-4-methylphenol (BHT) as the component (C). A gel electrolyte forming agent was prepared by weighing out a mass part and thoroughly agitating, mixing, and homogenizing the mixture under reduced pressure so that bubbles do not enter. Each evaluation test was performed in the same manner as in Example 1 except that this gel electrolyte forming agent was used.

  Examples 62 to 83 and Comparative Examples 7 to 8 were the same as Example 1 except that gel electrolyte forming agents were prepared so as to have the compositions shown in Tables 8 to 10 in the same manner as Example 61. Each evaluation test was conducted.

5.5. Evaluation results The monomer compositions, blending amounts and reaction solvents of the produced polymers P1 to P20 are shown in Tables 1 to 2, and the composition of the gel electrolyte forming composition used in each Example and each Comparative Example, and the evaluation results are shown. Tables 3 to 10 show.

Abbreviations in Tables 1 to 10 represent the following compounds or product names, respectively.
<(Meth) acrylate having cyclic ether structure>
OXMA: (3-ethyl-3-oxetanyl) methyl methacrylate OXEA: (3-ethyl-oxetane-3-yloxy) ethyl acrylate OXBA: (3-ethyl-oxetane-3-yloxy) butyl acrylate GMA: glycidyl Methacrylate / THFMA: Tetrahydrofurfuryl methacrylate / OXA: (3-Ethyl-3-oxetanyl) methyl acrylate OXEA is described in “Journal of Polymer Science: Part A: Polymer Chemistry, 2003, 41, 469-475”. And OXBA was synthesized in the same manner.

<(Meth) acrylate having a chain ether structure>
MEA: methoxyethyl acrylate TEGA: ethoxytriethylene glycol acrylate DEGMA: methoxydiethylene glycol methacrylate MTEGA: methoxytetraethylene glycol acrylate

<Polymerization initiator>
AIBN: N, N′-azobisisobutyronitrile

<(Polymerization) solvent>
EC / DEC: mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 3: 7 GBL: γ-butyrolactone DG: diglyme (diethylene glycol dimethyl ether)
・ DEC: Diethyl carbonate ・ MEK: Methyl ethyl ketone ・ PC: Propylene carbonate

<Ester compound having a carbon-carbon unsaturated bond>
・ VC: Vinylene carbonate ・ VEC: Vinyl ethylene carbonate ・ VA: Vinyl acetate

<Phenolic hydroxyl group-containing compound>
BHT: 2,6-di-t-butyl-4-methylphenol PTBHP: pentaerythrityltetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]
・ 4MP: 4-methoxyphenol

<Additive (cyclic ether compound)>
CEL: 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate (product name “Celoxide 2021P” manufactured by Daicel Chemical Industries, Ltd.)
EGDG: ethylene glycol diglycidyl ether DOX: 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane OXAL: 3-ethyl-3-hydroxymethyloxetane

<Others>
・ KF: Polyvinylidene fluoride resin (manufactured by Arkema, product name “Kyner Flex 2081”)
UA: Polyester diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name “NK Oligo UA-8651”)

  According to the gel electrolyte produced in Examples 1-83, it turned out that all have favorable ionic conductivity and are excellent in liquid retention. Furthermore, all of the lithium ion secondary batteries using these gel electrolytes had low internal DC resistance values and good discharge rate characteristics, low temperature characteristics, and cycle characteristics. Moreover, it turned out that the storage stability is very favorable for the gel electrolyte formation agent produced in Examples 61-83.

  On the other hand, in the gel electrolytes of Comparative Examples 1, 4, and 7 (conventional gel electrolytes), the use of polyvinylidene fluoride resin as the gel electrolyte forming agent caused separation of the gel electrolyte matrix and the liquid medium. It was found that the sex was poor.

  Since the gel electrolyte of Comparative Example 2 uses a gel electrolyte forming agent having an M2 / M1 value exceeding 10, gelation does not occur even when the gel electrolyte forming composition is heated. I could not.

  Since the gel electrolytes of Comparative Examples 3 and 5 use a gel electrolyte forming agent having an M2 / M1 value of less than 1, separation of the gel electrolyte matrix and the liquid medium occurs, and the liquid retention property is poor. I found out.

  In the gel electrolytes of Comparative Examples 6 and 8 (conventional gel electrolytes), the use of polyester diacrylate as the gel electrolyte forming agent causes separation of the gel electrolyte matrix and the liquid medium, resulting in poor liquid retention. I found out.

  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 (19)

A repeating unit (A1) derived from (meth) acrylate having a cyclic ether structure and a repeating unit (A2) derived from (meth) acrylate having a chain ether structure,
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%]) The gel electrolyte formation agent containing the polymer (A) which has the ratio (M2 / M1) of the quantity (M2 [mol%]) in the range of 1-10. The gel electrolyte formation agent of Claim 1 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 forming agent according to claim 1 or 2, 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.)   The gel electrolyte forming agent according to any one of claims 1 to 3, wherein the M1 [mol%] is in the range of 10 to 40 mol%.   The gel electrolyte forming agent according to any one of claims 1 to 4, wherein the number average molecular weight of the polymer (A) is 1,000 or more and 100,000 or less.   The gel electrolyte forming agent according to any one of claims 1 to 5, further comprising an ester compound (B) having at least one carbon-carbon unsaturated bond.   The gel electrolyte forming agent according to claim 6, wherein the component (B) is at least one selected from the group consisting of cyclic carbonates and (meth) acrylates. The gel electrolyte formation agent of Claim 7 whose said cyclic carbonate is a compound represented by following General formula (3).

(In Formula (3), R ¹² and R ¹³ are each independently a hydrogen atom, a halogen atom, an alkyl or alkenyl group having 1 to 6 carbon atoms, or a phenyl group.) _{M A} parts by mass and the content of the component (A), the content of the component (B) is taken as _{M B} parts by weight, the ratio _(M A / _{M B)} is within the range of 1 to 100, The gel electrolyte forming agent according to any one of claims 6 to 8.   Furthermore, the gel electrolyte formation agent as described in any one of Claims 1 thru | or 5 containing the compound (C) which has a phenolic hydroxyl group. The gel electrolyte formation agent of Claim 10 whose said component (C) is a compound represented by following General formula (4).

(In formula (4), R ¹⁴ represents a substituted or unsubstituted alkyl group or alkoxy group. N is an integer of 0 or more and 5 or less.) The gel electrolyte formation agent of Claim 10 whose said component (C) is a compound represented by following General formula (5).

(In Formula (5), R ¹⁵ represents a substituted or unsubstituted alkyl group or alkoxy group. M is an integer of 0 or more and 3 or less.) The gel electrolyte forming agent according to claim 10, wherein the component (C) is a compound having at least one group represented by the following general formula (6).

(In formula (6), R ¹⁶ and R ¹⁷ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.) _{M A} parts by mass and the content of the component (A), the content of the component (C) is taken as _{M C} parts by weight, the ratio _(M A / _{M C)} is within the range of 10 to 1,000, The gel electrolyte forming agent according to any one of claims 10 to 13.   The composition for gel electrolyte formation containing the gel electrolyte formation agent as described in any one of Claims 1 thru | or 14, and a liquid medium (D).   The composition for forming a gel electrolyte according to claim 15, further comprising a cyclic ether compound.   The composition for gel electrolyte formation according to claim 16, wherein the cyclic ether compound has a cyclic ether group having a number of members different from that of the cyclic ether group contained in the (meth) acrylate having the cyclic ether structure.   A gel electrolyte produced by heating the composition for forming a gel electrolyte according to any one of claims 15 to 17.   An electricity storage device comprising the gel electrolyte according to claim 18.