JP2006032372A - Electro-chemical capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electro-chemical capacitor which assures superior performance for storing electricity, by solving the problems about the stability, corrosion resistance, low-temperature characteristics, and cyclic performance (durability). <P>SOLUTION: The electro-chemical capacitor comprises a pair of conjugate aromatic group compound containing nitrogen atom, and an electrode layer containing an auxiliary conductive material and a film-electrode structure body provided with polymer electrolytic film held in between both electrode layers. The polymer electrolytic film is formed of an aromatic polymer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an electrochemistry having a membrane-electrode structure comprising a pair of electrode layers having a proton conductive compound and a membrane made of an aromatic polymer having a proton conductive substituent sandwiched between both electrode layers. More particularly, the present invention relates to an electrochemical capacitor using protons as charge carriers.

In recent years, large-capacity capacitor technology has attracted attention as an energy storage device. A large-capacity capacitor mainly uses an electric double layer capacitor that uses an electric double layer generated at the electrode / electrolyte interface for power storage, and a redox reaction (pseudo electric double layer capacitance) on the surface of a metal oxide or conductive polymer. It consists of redox capacitors to be used, and these are often collectively referred to as electrochemical capacitors.
An electrochemical capacitor using a proton-conducting conductive compound as an electrode is excellent in cycle characteristics and large current characteristics (Patent Document 1). On the other hand, an electrolyte such as a high-concentration sulfuric acid aqueous solution is used as an electrolyte. It is necessary to take measures against stability, leakage, and corrosion of electrolytes in the electrolyte, and to add freezing point depressant to prevent freezing of the electrolyte, which causes performance degradation at low temperatures. There is a problem that cannot be fully demonstrated.
In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on an electrochemical capacitor that uses a proton-conducting conductive compound as an electrode, instead of a capacitor that uses an electrolyte such as an aqueous sulfuric acid solution. An electrochemical capacitor using a membrane made of an aromatic polymer having a conductive substituent as an electrolyte layer in a water-containing state is excellent in stability and corrosivity, excellent in properties at low temperatures, and highly durable with little deterioration It was found to show.
JP 2000-54176 A

  The subject of this invention is providing the electrochemical capacitor provided with the outstanding electrical storage performance by solving the problems with respect to stability, corrosivity, low-temperature characteristics, and cycleability (durability) as described above.

The present invention relates to an electrochemical capacitor using a proton conductive type conductive compound as an electrode, wherein the membrane is made of an aromatic polymer having a proton conductive substituent as an electrolyte.
That is, the present invention is an electrochemical having a membrane-electrode structure comprising a pair of electrode layers containing a nitrogen atom-containing conjugated aromatic compound and a conductive auxiliary material, and a polymer electrolyte membrane sandwiched between both electrode layers. In the capacitor, the polymer electrolyte membrane is made of an aromatic polymer and provides an electrochemical capacitor.

  Since the electrochemical capacitor of the present invention uses an aromatic polymer as a polymer electrolyte, it has excellent durability.

Hereinafter, the electrochemical capacitor according to the present invention will be specifically described.
In the present invention, the aromatic polymer constituting the polymer electrolyte membrane includes aromatic polysulfone, polyethersulfone, polyetherether having proton conductive substituents such as sulfonic acid group, phosphoric acid group, and carboxylic acid group in the molecule. Sulfone, polyaryl ether sulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfoxide, polyparaphenylene, polyarylene, polyether ketone, polyether ether ketone, polyether ketone ketone, polybenzoxazole, polybenzothiazole, polybenzimidazole, polyimide It is preferable that the polymer is at least one aromatic polymer selected from polyamide and polyamideimide. These are polymers alone, two or more copolymers, or as required. Flip and may be used as a mixture of two or more thereof.
More preferably, the polymer segment (A) having a proton conductive substituent consisting of a sulfonic acid group, a phosphoric acid group, or a carboxylic acid group is covalently bonded to the polymer segment (B) having no proton conductive substituent. A block copolymer, more preferably a polyarylene having a structure in which an aromatic ring is covalently bonded with a linking group in the main chain skeleton, particularly preferably a structural unit represented by the following general formula (A) And a polyarylene having a sulfonic acid group containing a structural unit represented by the following general formula (B).

・・・（Ａ）
式（Ａ）中、Ｙは単結合、電子吸引基または電子供与基を示し、具体的には−ＣＯ−、−ＳＯ₂−、−ＳＯ−、−ＣＯＮＨ−、−ＣＯＯ−、−(ＣＦ₂)_p−（ここで、ｐは１〜１０の整数である）、−Ｃ(ＣＦ₃)₂−などの電子吸引基、−(ＣＨ₂)−、−Ｃ(ＣＨ₃)₂−、−Ｏ−、−Ｓ−などの電子供与基が挙げられる。
なお、電子吸引性基とは、ハメット（Hammett）置換基常数がフェニル基のｍ位の場合、０．０６以上、ｐ位の場合、０．０１以上の値となる基をいう。

... (A)
In formula (A), Y represents a single bond, an electron-withdrawing group or an electron-donating group, specifically, —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) _p- (wherein p is an integer of 1 to 10), an electron withdrawing group such as -C (CF ₃ ) ₂ -,-(CH ₂ )-, -C (CH ₃ ) _2- , -O Examples thereof include electron donating groups such as-and -S-.
The electron-withdrawing group refers to a group having a Hammett substituent constant of 0.06 or more when the phenyl group is in the m-position and 0.01 or more when it is in the p-position.

In the formula (A), Ar represents a mononuclear or polynuclear aromatic group, and specific examples include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group.
m represents an integer of 0 to 10, preferably 0 to 8, and more preferably 0 to 5. When m is 1 to 10, Ys may be the same as or different from each other.
In the formula (A), k represents an integer of 0 to 5, l represents an integer of 0 to 4, and k + l ≧ 1.

・・・（Ｂ）
式（Ｂ）中、Ｒ¹〜Ｒ⁸は互いに同一でも異なっていてもよく、水素原子、フッ素原子、アルキル基、フッ素置換アルキル基、アリル基およびアリール基からなる群より選ばれた少なくとも１種の原子または基を示す。
アルキル基としては、メチル基、エチル基、プロピル基、ブチル基、アミル基、ヘキシル基などが挙げられ、メチル基、エチル基などが好ましい。
フッ素置換アルキル基としては、トリフルオロメチル基、パーフルオロエチル基、パーフルオロプロピル基、パーフルオロブチル基、パーフルオロペンチル基、パーフルオロヘキシル基などが挙げられ、トリフルオロメチル基、ペンタフルオロエチル基などが好ましい。
アリル基としては、プロペニル基などが挙げられ、
アリール基としては、フェニル基、ペンタフルオロフェニル基などが挙げられる。

... (B)
In the formula (B), R ^{1 to} R ⁸ may be the same or different from each other, and are at least one selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, and an aryl group. An atom or group of
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable.
Examples of the fluorine-substituted alkyl group include trifluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, trifluoromethyl group, pentafluoroethyl group, and the like. Etc. are preferable.
Examples of allyl groups include propenyl groups,
Examples of the aryl group include a phenyl group and a pentafluorophenyl group.

W represents a single bond or a divalent electron withdrawing group, T represents a single bond, a divalent electron withdrawing group, a divalent electron donating group, represented by the following general formula (C-1) or (C-2) And at least one bond or group selected from the divalent groups represented.
Examples of the divalent electron withdrawing group include the same groups as the electron withdrawing group and the electron donating group represented by Y described above.

式（Ｃ−１）および（Ｃ−２）において、Ｒ⁹〜Ｒ²⁰は互いに同一でも異なっていてもよく、水素原子、フッ素原子、アルキル基、フッ素置換アルキル基、アリル基およびアリール基からなる群より選ばれた原子または基を示し、具体的には式（Ｂ）におけるＲ¹〜Ｒ⁸と同様の原子または基が挙げられる。
式（Ｃ−１）および（Ｃ−２）において、Ｑは単結合または２価の電子供与性基を示し、２価の電子供与性基としては例えば−Ｏ−、−Ｓ−、−ＣＨ＝ＣＨ−、−Ｃ≡Ｃ−などが挙げられる。
式（Ｃ−２）において、Ｊは単結合、アルキレン基、フッ素置換アルキレン基、アリール置換アルキレン基、アルケニレン基、アルキニレン基、アリーレン基、フルオレニリデン基、−Ｏ−、−Ｓ−、−ＣＯ−、−ＣＯＮＨ−、−ＣＯＯ−、−ＳＯ−および−ＳＯ₂−からなる群より選ばれた１種の原子または基を示す。

In the formulas (C-1) and (C-2), R ^{9 to} R ²⁰ may be the same as or different from each other, and are composed of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, and an aryl group. An atom or group selected from the group is shown, and specifically, the same atom or group as R ^{1 to} R ⁸ in formula (B) can be mentioned.
In formulas (C-1) and (C-2), Q represents a single bond or a divalent electron donating group, and examples of the divalent electron donating group include -O-, -S-, -CH =. CH—, —C≡C— and the like can be mentioned.
In the formula (C-2), J represents a single bond, an alkylene group, a fluorine-substituted alkylene group, an aryl-substituted alkylene group, an alkenylene group, an alkynylene group, an arylene group, a fluorenylidene group, -O-, -S-, -CO-, 1 atom or group selected from the group consisting of —CONH—, —COO—, —SO— and —SO ₂ —.

Specific examples of the alkylene group, fluorine-substituted alkylene group, aryl-substituted alkylene group, alkenylene group, alkynylene group, arylene group, and fluorenylidene group include -C (CH ₃ ) _2- , -CH = CH-, -CH = CH—CH ₂ —, —C≡C—, — (CF ₂ ) _p — (wherein p is an integer of 1 to 10), —C (CF ₃ ) ₂ —,

で表される基などが挙げられる。
式（Ｂ）において、ｎは２以上の整数であり、上限は通常１００、好ましくは１０〜８０である。ｎが２以下では、電気化学キャパシタの耐久性が得られないことがあり、実用上問題のない耐久性を保持させるためにはｎが１０以上であることが好ましい。一方、ｎが１００以上では、得られるスルホン化ポリアリーレン共重合体の粘度が高すぎ、電解質層を形成する際薄膜化が困難となる問題がある。

Group represented by these.
In the formula (B), n is an integer of 2 or more, and the upper limit is usually 100, preferably 10-80. When n is 2 or less, the durability of the electrochemical capacitor may not be obtained, and n is preferably 10 or more in order to maintain durability that does not cause a practical problem. On the other hand, when n is 100 or more, the resulting sulfonated polyarylene copolymer has a viscosity that is too high, which makes it difficult to reduce the thickness of the electrolyte layer.

  The polyarylene having a sulfonic acid group used in the present invention has a repeating structural unit represented by the formula (A) in a proportion of 0.05 to 99.95 mol%, preferably 10 to 99.5 mol%. The repeating structural unit represented by (B) is contained in a proportion of 99.95 to 0.05 mol%, preferably 90 to 0.5 mol%.

(Method for producing polyarylene having a sulfonic acid group)
The polyarylene having a sulfonic acid group includes a monomer having a sulfonic acid ester group that can be a structural unit represented by the general formula (A) and an oligomer that can be a structural unit represented by the general formula (B). It can be synthesized by polymerizing to produce a polyarylene having a sulfonic acid ester group, hydrolyzing the polyarylene having a sulfonic acid ester group, and converting the sulfonic acid ester group into a sulfonic acid group.
The polymer having a sulfonic acid group includes a structural unit having a skeleton represented by the general formula (A) and having no sulfonic acid group or sulfonic acid ester group, and a structural unit of the general formula (B). It can also be synthesized by previously synthesizing polyarylene having sulphonate and sulfonating the polymer.

  A monomer that can be a structural unit of the general formula (A) (for example, a monomer represented by the following general formula (D), also referred to as monomer (D)) and an oligomer that can be a structural unit of the general formula (B) (for example, In the case of synthesizing a polyarylene having a sulfonate group by copolymerizing with an oligomer represented by the following general formula (E) or oligomer (E), examples of the monomer (D) include: A sulfonic acid ester represented by the formula (D) is used.

・・・（Ｄ）
式（Ｄ）中、Ｘはフッ素を除くハロゲン原子（塩素、臭素、ヨウ素）、−ＯＳＯ₂Ｚ（ここで、Ｚはアルキル基、フッ素置換アルキル基またはアリール基を示す。）から選ばれる原子または基を示す。
式（Ｄ）中、Ｙ、Ａｒ、ｍ、ｋおよびｌは、それぞれ上記一般式（Ａ）中のＹ、Ａｒ、ｍ、ｋおよびｌと同義であり、ｍが１〜１０のときはＹは互いに同一でも異なっていてもよく、ｋ＋ｌ≧１である。

... (D)
In formula (D), X is an atom selected from halogen atoms other than fluorine (chlorine, bromine, iodine), —OSO ₂ Z (wherein Z represents an alkyl group, a fluorine-substituted alkyl group, or an aryl group) or Indicates a group.
In the formula (D), Y, Ar, m, k and l are respectively synonymous with Y, Ar, m, k and l in the general formula (A). When m is 1 to 10, Y is They may be the same as or different from each other, and k + l ≧ 1.

In the formula (D), R represents a hydrocarbon group having 4 to 20 carbon atoms, specifically, tert-butyl group, iso-butyl group, n-butyl group, sec-butyl group, neopentyl group, cyclopentyl. Group, hexyl group, cyclohexyl group, cyclopentylmethyl group, cyclohexylmethyl group, adamantyl group, adamantanemethyl group, 2-ethylhexyl group, bicyclo [2.2.1] heptyl group, bicyclo [2.2.1] heptylmethyl A linear hydrocarbon group such as a group, a branched hydrocarbon group, an alicyclic hydrocarbon group, or the like is used. Of these ester groups, bulky substituents such as branched and alicyclic structures derived from primary alcohols are preferred from the viewpoint of stability during the polymerization process.
Specific examples of the sulfonic acid ester represented by the formula (D) include the following compounds.

また、上記一般式（Ｄ）で表されるモノマー（Ｄ）と同様の骨格を有しスルホン酸基、スルホン酸エステル基を有しない化合物の具体例としては、下記の様な化合物が挙げられる。

Specific examples of the compound having the same skeleton as the monomer (D) represented by the general formula (D) and having no sulfonic acid group or sulfonic acid ester group include the following compounds.

オリゴマー（Ｅ）としては、例えば下記一般式（Ｅ）で表される化合物が用いられる。

As the oligomer (E), for example, a compound represented by the following general formula (E) is used.

・・・（Ｅ）
式（Ｅ）中、Ｒ'およびＲ''は互いに同一でも異なっていてもよく、フッ素原子を除くハロゲン原子または−ＯＳＯ₂Ｚ（ここで、Ｚはアルキル基、フッ素置換アルキル基またはアリール基を示す。）で表される基を示す。Ｚが示すアルキル基としてはメチル基、エチル基などが挙げられ、フッ素置換アルキル基としてはトリフルオロメチル基などが挙げられ、アリール基としてはフェニル基、ｐ−トリル基などが挙げられる。
式（Ｅ）中、Ｒ¹〜Ｒ⁸は互いに同一でも異なっていてもよく、上記一般式（Ｂ）におけるＲ¹〜Ｒ⁸と同様の原子または基原子または基を示し、ｎは２以上の整数であり、上限は通常１００、好ましくは１０〜８０である。
このような式（Ｅ）で表される化合物の例示としては、下記式で表される化合物などを挙げることができる。

... (E)
Wherein (E), R 'and R''may be the same or different, a halogen atom or -OSO ₂ Z other than fluorine atoms (where, Z is an alkyl group, a fluorine-substituted alkyl group or an aryl group The group represented by this is shown. Examples of the alkyl group represented by Z include a methyl group and an ethyl group, examples of the fluorine-substituted alkyl group include a trifluoromethyl group, and examples of the aryl group include a phenyl group and a p-tolyl group.
In formula (E), R ^{1 to} R ⁸ may be the same as or different from each other, and represent the same atom or group atom or group as R ^{1 to} R ⁸ in formula (B), and n is 2 or more. It is an integer, and the upper limit is usually 100, preferably 10-80.
Examples of such a compound represented by the formula (E) include a compound represented by the following formula.

上記のようなオリゴマー（Ｅ）は、例えば以下に示す方法で合成することができる。

The oligomer (E) as described above can be synthesized, for example, by the method shown below.

First, in order to convert bisphenol into an alkali metal salt, lithium, sodium, and sodium chloride in a polar solvent having a high dielectric constant such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, sulfolane, diphenylsulfone, and dimethylsulfoxide. Add alkali metals such as potassium, alkali metal hydrides, alkali metal hydroxides, alkali metal carbonates and the like.
Specific examples of bisphenol include 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-bis (4-hydroxyphenyl) ketone, 2, 2-bis (4-hydroxyphenyl) sulfone, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-phenylphenyl) fluorene, 9,9-bis (4-hydroxy) -3,5-diphenylphenyl) fluorene, 2-phenylphenol, 4,4'-bis (4-hydroxyphenyl) diphenylmethane, 4,4'-bis (4-hydroxy-3-phenylphenyl) diphenylmethane, 4,4 Examples include '-bis (4-hydroxy-3,5-diphenylphenyl) diphenylmethane, 2-phenylhydroquinone and the like.

Usually, the alkali metal is reacted in excess with respect to the hydroxyl group of phenol, and 1.1 to 2 times equivalent is used. Preferably, 1.2 to 1.5 times equivalent is used.
In this case, it is activated with an electron-withdrawing group in the presence of water and an azeotropic solvent such as benzene, toluene, xylene, hexane, cyclohexane, octane, chlorobenzene, dioxane, tetrahydrofuran, anisole, phenetole, fluorine, chlorine, etc. And an aromatic dihalide compound substituted with a halogen atom.
Bisphenol made into an alkali metal salt and a specific aromatic dihalide compound are reacted in the presence of a solvent azeotropic with water. The reaction between bisphenol and the aromatic dihalide compound is an aromatic nucleophilic substitution reaction.
Examples of the solvent azeotropic with water used in the present invention include benzene, toluene, xylene, hexane, cyclohexane, octane, chlorobenzene, dioxane, tetrahydrofuran, anisole, phenetole and the like. As the aromatic dihalide compound, an aromatic dihalide compound having an electron-withdrawing group and substituted with a halogen atom such as fluorine or chlorine is used.

Examples of the aromatic dihalide compound include 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, 4,4′-chlorofluorobenzophenone, bis (4-chlorophenyl) sulfone, and bis (4-fluorophenyl). Sulfone, 4-fluorophenyl-4′-chlorophenylsulfone, bis (3-nitro-4-chlorophenyl) sulfone, 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, hexafluorobenzene, decafluorobiphenyl, 2 , 5-difluorobenzophenone, 1,3-bis (4-chlorobenzoyl) benzene and the like.
In terms of reactivity, an aromatic dihalide compound of a fluorine compound is desirable, but in consideration of the synthesis of polyarylene by the following aromatic coupling reaction, an oligomer by an aromatic nucleophilic substitution reaction so that the terminal is a chlorine atom. It is necessary to assemble the synthesis of (E).
For example, an active aromatic halogen compound such as 4,4′-dichlorobenzophenone or bis (4-chlorophenyl) sulfone, or a substitution reaction using 4,4′-difluorobenzophenone and 4,4′-chlorofluorobenzophenone in combination. The desired compound is obtained.

For this reason, an aromatic dichloride compound such as 4,4′-dichlorobenzophenone or bis (4-chlorophenyl) sulfone is used, or an aromatic difluoride compound such as 4,4′-difluorobenzophenone and 4-chloro-4- When used in combination with chlorofluorobenzophenones such as fluorobenzophenone, a desired compound having a structure in which chlorobenzoyl groups are introduced at both ends can be obtained.
The usage-amount of an active aromatic dihalide can be changed according to the molecular weight of the target oligomer (E).
In the reaction for synthesizing the oligomer (E) as described above, bisphenol may be converted to an alkali metal salt in advance, but the above raw materials are charged into a reaction vessel at the same time and the bisphenol is converted to an alkali metal salt. An aromatic nucleophilic substitution reaction may be performed.
The reaction temperature is 60 ° C to 300 ° C, preferably 80 ° C to 250 ° C. The reaction time ranges from 15 minutes to 100 hours, preferably from 1 hour to 24 hours.

(Synthesis of polyarylene)
The polyarylene having a sulfonate group is synthesized by reacting the monomer (D) and the oligomer (E) in the presence of a catalyst. The catalyst used in this case is a catalyst system containing a transition metal compound.
Examples of the catalyst system include (1) transition metal salts (including copper salts) and compounds serving as ligands (hereinafter referred to as “ligand components”), or transition metal complexes in which ligands are coordinated. And (2) those containing a reducing agent as an essential component. Furthermore, in order to increase the polymerization rate, “salts” other than transition metal salts may be added.

Here, as the transition metal salt, nickel compounds such as nickel chloride, nickel bromide, nickel iodide and nickel acetylacetonate; palladium compounds such as palladium chloride, palladium bromide and palladium iodide; iron chloride and iron bromide And iron compounds such as iron iodide; cobalt compounds such as cobalt chloride, cobalt bromide, and cobalt iodide. Of these, nickel chloride, nickel bromide and the like are particularly preferable.
Examples of the ligand component include triphenylphosphine, 2,2′-bipyridine, 1,5-cyclooctadiene, 1,3-bis (diphenylphosphino) propane, and the like. Of these, triphenylphosphine and 2,2′-bipyridine are preferred. The said compound used as a ligand can be used individually by 1 type or in combination of 2 or more types.

Furthermore, as the transition metal complex in which the ligand is coordinated, for example, nickel chloride bis (triphenylphosphine), nickel bromide bis (triphenylphosphine), nickel iodide bis (triphenylphosphine), nickel nitrate bis (Triphenylphosphine), nickel chloride (2,2'-bipyridine), nickel bromide (2,2'-bipyridine), nickel iodide (2,2'-bipyridine), nickel nitrate (2,2'-bipyridine) ), Bis (1,5-cyclooctadiene) nickel, tetrakis (triphenylphosphine) nickel, tetrakis (triphenylphosphite) nickel, tetrakis (triphenylphosphine) palladium and the like. Of these, nickel chloride bis (triphenylphosphine) and nickel chloride (2,2′-bipyridine) are preferred.
Examples of the reducing agent that can be used in the catalyst system include iron (metal), zinc (metal), manganese (metal), aluminum (metal), magnesium (metal), sodium (metal), and calcium (metal). Etc. Of these, zinc, magnesium and manganese are preferred. These reducing agents can be used after being more activated by bringing them into contact with an acid such as an organic acid.

  Examples of the “salt” that can be used in the above catalyst system include sodium compounds such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide, sodium sulfate, potassium fluoride, potassium chloride, potassium bromide, Examples include potassium compounds such as potassium iodide and potassium sulfate; ammonium compounds such as tetraethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and tetraethylammonium sulfate. Of these, sodium bromide, sodium iodide, potassium bromide, tetraethylammonium bromide, and tetraethylammonium iodide are preferred.

  The proportion of each component used is usually 0.0001 to 10 moles, preferably 0.001 moles per mole of transition metal salt or transition metal complex ((D) + (E), hereinafter the same). 01-0.5 mol. If there are few transition metal salts or transition metal complexes, the polymerization reaction may not proceed sufficiently. On the other hand, even if there are many transition metal salts or transition metal complexes, the molecular weight of the resulting polymer may be reduced.

When a transition metal salt and a ligand component are used in the catalyst system, the ratio of the ligand component used is usually 0.1 to 100 mol, preferably 1 to 10 mol, per 1 mol of the transition metal salt. is there. If the ligand component is small, the catalytic activity may be insufficient. On the other hand, if the ligand component is large, the molecular weight of the resulting polymer may be reduced.
Moreover, the usage-amount of a reducing agent is 0.1-100 mol normally with respect to the total of 1 mol of the said monomer, Preferably it is 1-10 mol. If the amount of the reducing agent is small, the polymerization may not proceed sufficiently. If the amount of the reducing agent is too large, it may be difficult to purify the resulting polymer.
Furthermore, when using "salt", the usage-ratio is 0.001-100 mol normally with respect to the total of 1 mol of the said monomer, Preferably it is 0.01-1 mol. If the amount of “salt” is small, the effect of increasing the polymerization rate may be insufficient, and if the amount of “salt” is too large, purification of the resulting polymer may be difficult.

When reacting the monomer (D) and the oligomer (E), a polymerization solvent can be used as necessary. Examples of the polymerization solvent include tetrahydrofuran, cyclohexanone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, N, N′-dimethylimidazolidinone and the like. Can be mentioned. Of these, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and N, N′-dimethylimidazolidinone are preferable. These polymerization solvents are preferably used after sufficiently dried.
The total concentration of the monomers in the polymerization solution (solvent and monomer) is usually 1 to 90% by weight, preferably 5 to 40% by weight.
Moreover, the superposition | polymerization temperature at the time of superposing | polymerizing is 0-200 degreeC normally, Preferably it is 50-120 degreeC. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 40 hours.
The polyarylene having a sulfonic acid ester group obtained using the monomer (D) can be converted into a polyarylene having a sulfonic acid group by hydrolyzing the sulfonic acid ester group and converting it to a sulfonic acid group. .

Hydrolysis is
(1) A method in which polyarylene having the sulfonic acid ester group is added to an excess amount of water or alcohol containing a small amount of hydrochloric acid and stirred for 5 minutes or longer. (2) The sulfonic acid ester group is contained in trifluoroacetic acid. Method of reacting polyarylene for about 5 to 10 hours at a temperature of about 80 to 120 ° C. (3) 1 to 3 mol per mol of sulfonic acid ester group (—SO ₃ R) in polyarylene having a sulfonic acid ester group Examples include a method in which the polyarylene is reacted at a temperature of about 80 to 150 ° C. for about 3 to 10 hours in a solution containing double moles of lithium bromide, such as N-methylpyrrolidone, and then hydrochloric acid is added. Can do.

  The polyarylene having a sulfonic acid group is synthesized in advance using a monomer having a skeleton similar to the monomer (D) represented by the general formula (D) and having no sulfonic acid ester group. It can also be synthesized by sulfonating polyarylene. In this case, after producing a polyarylene by copolymerizing a monomer having no sulfonic acid group and an oligomer (E) by a method according to the above synthesis method, a polyarylene having no sulfonic acid group is prepared using a sulfonating agent. A polyarylene having a sulfonic acid group can be obtained by introducing a sulfonic acid group into.

As the reaction conditions for this sulfonation, polyarylene having no sulfonic acid group can be obtained by introducing a sulfonic acid group by a conventional method using a sulfonating agent in the absence of a solvent or in the presence of a solvent. .
As a method for introducing a sulfonic acid group, for example, the polyarylene having no sulfonic acid group is known by using a known sulfonating agent such as sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, sulfuric acid, sodium hydrogen sulfite and the like. [Polymer Preprints, Japan, Vol. 42, No. 3, p. 730 (1993); Polymer Preprints, Japan, Vol. 43, No. 3, p. 736 (1994); Polymer Preprints, Japan, Vol. 42, No. 7, p. 2490-2492 (1993)].
That is, as the reaction conditions for the sulfonation, the polyarylene having no sulfonic acid group is reacted with the sulfonating agent in the absence of a solvent or in the presence of a solvent. Examples of the solvent include hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, aprotic polar solvents such as dimethylacetamide, dimethylformamide, and dimethylsulfoxide, tetrachloroethane, dichloroethane, chloroform, and chloride. And halogenated hydrocarbons such as methylene. The reaction temperature is not particularly limited, but is usually −50 to 200 ° C., preferably −10 to 100 ° C. Moreover, reaction time is 0.5 to 1,000 hours normally, Preferably it is 1 to 200 hours.
In the polyarylene having a sulfonic acid group produced by the method as described above, the amount of the sulfonic acid group is usually 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g, more preferably 0.8 to 2.8 meq / g. If it is less than 0.3 meq / g, the proton conductivity is low and not practical. On the other hand, if it exceeds 5 meq / g, the water resistance may be significantly lowered, which is not preferable.
The amount of the sulfonic acid group can be adjusted, for example, by changing the type, usage ratio, and combination of the monomer (D) and the oligomer (E).

The molecular weight of the polyarylene having a sulfonic acid group thus obtained is 10,000 to 1,000,000, preferably 20,000 to 800,000 in terms of polystyrene-equivalent weight average molecular weight by gel permeation chromatography (GPC).
The polyarylene having a sulfonic acid group may contain an anti-aging agent, preferably a hindered phenol compound having a molecular weight of 500 or more, and the anti-aging agent can be used as an electrode electrolyte. Can be further improved.

As a hindered phenol compound having a molecular weight of 500 or more that can be used in the present invention, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) proonate] (trade name: IRGANOX 245) 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 259), 2,4-bis- (n- Octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -3,5-triazine (trade name: IRGANOX 565), pentaerythrityl-tetrakis [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 1010), 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate ] (Trade name: IRGANOX 1035), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) (trade name: IRGANOX 1076), N, N-hexamethylene bis (3.5 -Di-t-butyl-4-hydroxy-hydrocinnamamide) (IRGAONOX 1098) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4'- Hydroxybenzyl) benzene (trade name: IRGANOX 1330), tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate (trade name: IRGANOX 3114), 3,9-bis [2- [3- (3-tert-Butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane (product) Name: Sumilizer GA-80).
In the present invention, the hindered phenol compound having a molecular weight of 500 or more with respect to 100 parts by weight of the polyarylene having a sulfonic acid group is preferably used in an amount of 0.01 to 10 parts by weight.

(Electrochemical capacitor)
The electrochemical capacitor according to the present invention is:
A membrane-electrode structure comprising: a pair of nitrogen atom-containing conjugated aromatic compounds and an electrode layer containing a conductive auxiliary material; and a polymer electrolyte membrane sandwiched between both electrode layers. And polyarylene having a sulfonic acid group as described above.
Next, the electrode used for the membrane-electrode structure of the electrochemical capacitor according to the present invention will be specifically described.

(Electrode material)
An electrode material that can be used in the present invention is a proton-conducting conductive compound comprising a substituted or unsubstituted nitrogen atom-containing conjugated aromatic compound, and its oxidation-reduction reaction is caused by protons that are desorbed on nitrogen atoms. Containing.
Examples of the nitrogen atom-containing conjugated aromatic compound include anilines, indoles, quinoxalines, and derivatives thereof.
In order to ensure conductivity, a conductive auxiliary material is added to the electrode material as necessary. Examples of the conductive auxiliary material include conductive materials such as crystalline carbon, carbon black, and graphite.
In addition, a binder may be added as necessary in order to maintain the moldability of the electrode or to fix the proton conductive type conductive compound and the conductive auxiliary presence on the current collector and electrolyte membrane. As a binder, the aromatic polymer which has the said proton conductive substituent can also be used. By using a polymer binder having proton conductivity, the proton exchange reaction at the interface between the electrode and the electrolyte proceeds smoothly, and good power storage characteristics are obtained.

The mixing ratio of the constituent materials of the electrode is arbitrary as long as the desired characteristics can be obtained, but considering the efficiency per unit mass or unit capacity, the proton conductive type conductive compound is 20 to 98% by mass, and the conductive auxiliary material is 3%. The range of ˜60 mass% and the binder of 0 to 25 mass% is desirable.
The proton conductive compound according to the present invention may be doped by an electrochemical or chemical method. For example, sulfate ions, halide ions, perchlorate ions, trifluoroacetate ions, and the like, but are not limited to these as long as they are doped into a proton conductive compound and impart electrochemical activity.
The proton-conducting conductive compound thus doped causes an electrochemical reaction that accompanies adsorption / desorption of protons. That is, only the adsorption / desorption of protons is involved in the electron transfer accompanying the oxidation-reduction reaction of the proton conductive compound.

(Method for producing electrochemical capacitor)
Next, an electrochemical capacitor according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view showing a configuration example of a membrane-electrode structure used for an electrochemical capacitor.
The electrochemical capacitor includes, for example, a membrane-electrode structure having the configuration shown in FIG. In the membrane-electrode structure, the positive electrode layer 2 and the negative electrode layer 4 formed on the current collectors 1 and 6 are arranged opposite to each other with the polymer electrolyte membrane 3 interposed therebetween, and the polymer electrolyte membrane 3 is interposed therebetween. Gaskets 5 made of insulating rubber or the like are provided on both side surfaces of the laminate in which the positive electrode material layer 2 and the negative electrode material layer 4 are laminated.
The polymer electrolyte membrane 3 is composed of a membrane made of an aromatic polymer having the proton conductive substituent, and the electrode layer 2 and the negative electrode layer 4 have the proton conductive compound. . The current collectors 1 and 6 are made of carbon paper or metal foil, and a base layer is formed on the carbon paper or metal foil as necessary. The underlayer is provided in order to obtain good electrical bonding between the carbon paper or metal foil and the electrode layer.
In the membrane-electrode structure, the metal foil does not need to be corroded by an electrolytic solution such as an aqueous sulfuric acid solution, so there is no need to use a special and expensive metal such as titanium, and SUS, nickel, aluminum, etc. can be used. .

The electrode layer and the current collector are joined by directly applying an electrode paste having the above electrode material to the current collector, or by applying a paste on a polyester film and drying the electrode layer to the current collector. It is formed by pressing.
The electrode layer and the polymer electrolyte membrane can be joined by directly applying a polymer electrolyte solution to the electrode layer, or by forming the polymer electrolyte membrane on the electrode layer by hot pressing.
The polymer electrolyte membrane 3, the positive electrode layer 2, and the negative electrode layer 4 are each set in a sealing can which is an outer case in a state of being water-containing in water, and sealed to form an electrochemical capacitor.
As the material of the sealing can, SUS can be used because it is not necessary to consider corrosion due to an electrolytic solution such as an aqueous sulfuric acid solution.

By using a polymer electrolyte membrane instead of the electrolyte solution as described above, the reliability of the proton conductive compound is improved, the corrosion is improved by suppressing leakage, and the separator is removed. It has the advantages of being thin and suitable for flexible devices.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.
In the examples, the sulfonic acid equivalent, molecular weight, and proton conductivity were determined as follows.
1. Sulfonic acid equivalent The polymer having the sulfonic acid group was washed with water until the water was neutral, thoroughly washed with water except for free remaining acid, dried, weighed a predetermined amount, THF / Phenolphthalein dissolved in a mixed solvent of water was used as an indicator, titration was performed using a standard solution of NaOH, and the sulfonic acid equivalent was determined from the neutralization point.
2. Measurement of molecular weight The polyarylene weight average molecular weight having no sulfonic acid group was determined by GPC using tetrahydrofuran (THF) as a solvent, and the molecular weight in terms of polystyrene was obtained. The molecular weight of the polyarylene having a sulfonic acid group was determined by GPC using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as a solvent as an eluent.

[Synthesis Example 1]
2,2-bis (4-hydroxyphenyl) -1,1,1,3 was added to a 1 L three-necked flask equipped with a stirrer, thermometer, cooling tube, Dean-Stark tube, and three-way cock for introducing nitrogen. , 3,3-hexafluoropropane (bisphenol AF) 67.3 g (0.20 mol), 4,4′-dichlorobenzophenone (4,4′-DCBP) 60.3 g (0.24 mol), potassium carbonate 71 .9 g (0.52 mol), N, N-dimethylacetamide (DMAc) 300 mL, and toluene 150 mL were added, and the mixture was stirred and heated in a nitrogen atmosphere in an oil bath, and reacted at 130 ° C. with stirring. When water produced by the reaction was azeotroped with toluene and reacted while being removed from the system with a Dean-Stark tube, almost no water was produced in about 3 hours. Thereafter, most of the toluene was removed while gradually raising the reaction temperature from 130 ° C. to 150 ° C., and the reaction was continued at 150 ° C. for 10 hours. Then, 10.0 g (0.040 mol) of 4,4′-DCBP was added. The reaction was continued for another 5 hours. The resulting reaction solution was allowed to cool, and the precipitate of the inorganic compound produced as a by-product was removed by filtration, and the filtrate was poured into 4 L of methanol. The precipitated product was separated by filtration, collected, dried, and then dissolved in 300 mL of tetrahydrofuran. This was put into 4 L of methanol and reprecipitated to obtain 95 g (yield 85%) of the target compound.
The number average molecular weight (Mn) in terms of polystyrene determined by GPC (THF solvent) of the obtained compound was 11,200. Further, the obtained polymer was soluble in THF, NMP, DMAc, sulfolane and the like, Tg was 110 ° C., and thermal decomposition temperature was 498 ° C.
The obtained compound was an oligomer represented by the formula (I) (hereinafter referred to as “BCPAF oligomer”).

[Synthesis Example 2]
4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonic acid neo was added to a 1 L three-necked flask equipped with a stirrer, thermometer, condenser, Dean-Stark tube, and three-way cock for introducing nitrogen. -Pentyl (A-SO ₃ neo-Pe) 39.58 g (98.64 mmol), BCPAF oligomer obtained in Synthesis Example 1 (Mn = 11,200) 15.23 g (1.36 mmol), Ni (PPh _{3) 2} Cl ₂ 1.67g (2.55 mmol), PPh ₃ 10.49 g (40 mmol), NaI 0.45 g (3 mmol), zinc dust 15.69 g (240 mmol), under nitrogen dry NMP 390 mL Added in. The reaction system was heated with stirring (finally heated to 75 ° C.) and allowed to react for 3 hours. The polymerization reaction solution was diluted with 250 mL of THF, stirred for 30 minutes, filtered using Celite as a filter aid, and the filtrate was poured into a large excess of 1500 mL of methanol to coagulate. The coagulum was collected by filtration, air-dried, redissolved in THF / NMP (200/300 mL each), and coagulated with 1500 mL of a large excess of methanol. After air drying, 47.0 g (yield 99%) of a copolymer (PolyAB-SO ₃ neo-Pe) composed of a sulfonic acid derivative protected with a target yellow fibrous neopentyl group was obtained by heat drying. The molecular weight by GPC was 47,600 for Mn and 159,000 for Mw (weight average molecular weight).

[Synthesis Example 3]
5.1 g of PolyAB-SO ₃ neo-Pe obtained in Synthesis Example 2 was dissolved in 60 mL of NMP and heated to 90 ° C. A mixture of 50 mL of methanol and 8 mL of concentrated hydrochloric acid was added to the reaction system at one time. While in suspension, the reaction was allowed to proceed for 10 hours under mild reflux conditions. A distillation apparatus was installed, and excess methanol was distilled off to obtain a light green transparent solution. This solution was poured into a large amount of water / methanol (1: 1 weight ratio) to solidify the polymer, and then the polymer was washed with ion-exchanged water until the pH of the washing water became 6 or more. From the IR spectrum of the polymer thus obtained and the quantitative analysis of the ion exchange capacity, it was confirmed that the sulfonate group (—SO ₃ R ^a ) was quantitatively converted to the sulfonate group (—SO ₃ H). It was.
The obtained polyarylene copolymer having a sulfonic acid group had a molecular weight of GPC of Mn of 53,200, Mw of 185,000, and a sulfonic acid equivalent of 1.9 meq / g.

[Example 1]
A battery having the above-described structure shown in FIG. As the exterior material, a gasket 5 made of insulating rubber was provided, and the current collectors 1 and 6 made of conductive rubber were used. As the polymer electrolyte membrane, a dry film thickness of 40 μm prepared by casting the polyarylene having a sulfonic acid group synthesized in Synthesis Example 3 in N-methyl-2-pyrrolidone and using a casting method was used.
For the positive electrode layer 2, an indole-based trimer composed of a trimer of 6-nitroindole was used as a proton conductive conductive compound, and vapor-grown carbon fiber was used as a conductive auxiliary material.
For the negative electrode layer 4, polyphenylquinoxaline represented by the following formula was used as a proton conductive compound, and carbon black was used as a conductive auxiliary material. The mixing ratio of the proton conductive conductive compound and the conductive auxiliary material constituting the electrode was 75:25 (proton conductive conductive compound: conductive auxiliary material) in mass ratio for both the positive electrode and the negative electrode.
The polymer electrolyte membrane, the positive electrode layer, and the negative electrode layer are immersed in pure water at 80 ° C. for 30 minutes to contain water, and the structure shown in FIG. 1 is prepared and set in a SUS sealing can. The electrochemical capacitor of the present invention was formed.

A charge / discharge test was performed in order to evaluate the produced battery. The battery was charged at a constant current of up to 1.2 V at 10 mA / cm 2 and discharged at a constant current of 1 to 200 mA / cm 2. The discharge capacity was expressed based on the weight of the active material. Table 1 shows the capacity up to 0.9V.
Further, a cycle test was repeated in which charging to 1.2 V and discharging to 0.9 V (charging / discharging current was a constant current of 10 mA / cm 2) were repeated. Table 1 shows the number of capacity reduction cycles up to 20%.
Moreover, in order to investigate the temperature characteristic of a capacitor, the change of the discharge capacity in -20 degreeC was evaluated on the charge / discharge conditions similar to the above in a thermostat. Table 1 shows the amount of change when the 20 ° C. capacity is taken as 100.

[Comparative Example 1]
An electrochemical capacitor was constructed in the same manner as in Example 1 except that a film made of a perfluoroalkylenesulfonic acid polymer compound (Nafion (trademark) manufactured by DuPont) was used as the polymer electrolyte membrane, and the same evaluation was performed. It was.
[Comparative Example 2]
A battery similar to that of Example 1 was prepared except that a separator made of a porous film impregnated with an electrolytic solution was used as a separator instead of the polymer electrolyte membrane, and a 40% sulfuric acid aqueous solution was used as the electrolytic solution.

[Comparative Example 3]
In addition, in order to prevent corrosion of the outer case can due to sulfuric acid aqueous solution, a slurry obtained by adding ketjen black EC to SEBS toluene solution in advance so that SEBS / Ketjen black EC = 10/6 and sufficiently kneading is added to the outer case. An electrochemical capacitor was constructed in the same manner as in Comparative Example 2 except that a coated and dried product on the inner wall of the can was used as an outer case can, and the same evaluation as in Example 1 was performed.

Cross section of electrochemical capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current collector 2 Positive electrode layer 3 Polymer electrolyte membrane 4 Negative electrode layer 5 Insulator 6 Current collector

Claims (7)

In the electrochemical capacitor having a membrane-electrode structure comprising a pair of an electrode layer containing a nitrogen atom-containing conjugated aromatic compound and a conductive auxiliary material, and a polymer electrolyte membrane sandwiched between both electrode layers, the polymer An electrochemical capacitor, wherein the electrolyte membrane is made of an aromatic polymer. In the aromatic polymer, the polymer segment (A) having an ion conductive substituent composed of a sulfonic acid group, a phosphoric acid group, or a carboxylic acid group and the polymer segment (B) having no proton conductive substituent are shared. The electrochemical capacitor according to claim 1, wherein the electrochemical capacitor is a bonded block copolymer.   2. The electrochemical capacitor according to claim 1, wherein the aromatic polymer has a structure in which a main chain skeleton has a structure in which an aromatic ring is covalently bonded with a bonding group. The electrochemical capacitor, wherein the aromatic polymer is a polyarylene having a sulfonic acid group composed of a repeating unit represented by the following general formula (A) and a repeating unit represented by the following general formula (B) ;

... (A)
(In the formula (A), Y represents a single bond, an electron withdrawing group or an electron donating group, Ar represents a mononuclear or polynuclear aromatic group, m represents an integer of 0 to 10, and m represents 1 to 10. Y may be the same as or different from each other, k represents an integer of 0 to 5, l represents an integer of 0 to 4, and k + l ≧ 1.)

... (B)
(In Formula (B), R ^{1 to} R ⁸ may be the same as or different from each other, and at least one selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, and an aryl group) Indicates an atom or group of species.
W represents a divalent electron-withdrawing group or a single bond.
T is at least one selected from a single bond, a divalent electron-withdrawing group, a divalent electron-donating group, and a divalent group represented by the following general formula (C-1) or (C-2). N represents an integer of 2 or more. )

(In the formulas (C-1) and (C-2), R ^{9 to} R ²⁰ may be the same as or different from each other, and are selected from a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, and an aryl group. Q represents at least one atom or group selected from the group consisting of Q and Q represents a single bond or a divalent electron-donating group.
J represents a single bond, an alkylene group, a fluorine-substituted alkylene group, an aryl-substituted alkylene group, an alkenylene group, an alkynylene group, an arylene group, a fluorenylidene group, -O-, -S-, -CO-, -CONH-, -COO-, One atom or group selected from the group consisting of —SO— and —SO ₂ — is shown. ).   5. The electrochemical capacitor according to claim 4, wherein the polyarylene having a sulfonic acid group is a polyarylene containing a sulfonic acid group in a range of 0.3 to 5.0 meq / g.   2. The electrochemical capacitor according to claim 1, wherein the nitrogen atom-containing conjugated aromatic compound is an aniline, an indole or a quinoxaline. 2. The electrochemical capacitor according to claim 1, wherein the conductive auxiliary material is crystalline carbon, carbon black, or graphite.

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