JP2024045918A - Electrolyte for hybrid capacitor and hybrid capacitor - Google Patents

Abstract

[Problem] To provide an electrolyte for hybrid capacitors that has high thermal stability and dielectric oxide film repair properties. Furthermore, by using the electrolyte for hybrid capacitors, to provide a hybrid capacitor that has excellent heat resistance while maintaining the electrostatic capacitance, dielectric dissipation factor (tan δ), equivalent series resistance (ESR), leakage current and voltage resistance properties. [Solution] An electrolyte for hybrid capacitors that contains as an electrolyte a phosphoric acid compound at least one of which is substituted with a phenyl group or a benzyl group. A hybrid capacitor characterized in that a solid electrolyte layer made of a conductive polymer is formed on a capacitor element formed by winding an anode electrode foil and a cathode electrode foil with a separator between them, and the capacitor electrolyte is filled into the voids in the capacitor element on which the solid electrolyte layer is formed. [Selected Figure] None

Description

The present invention relates to an electrolytic solution for a hybrid capacitor and a hybrid capacitor using the same, and more particularly, the present invention relates to an electrolytic solution for a hybrid capacitor and a hybrid capacitor using the same. This invention relates to a filled conductive polymer hybrid aluminum electrolytic capacitor.

Hybrid capacitors generally use an anode electrode made of an insulating oxide film formed as a dielectric on the surface of a valve metal such as aluminum by anodizing or other methods, a cathode electrode placed opposite the anode electrode, and a capacitor element wound with a separator between the anode electrode and the cathode electrode. A solid electrolyte layer containing a conductive polymer is formed on the capacitor element, which is then housed in a cylindrical exterior case with a bottom, and the voids in the capacitor element are filled with electrolyte to complete the hybrid capacitor.

Patent Document 1 discloses a hybrid capacitor that has good ESR characteristics at high temperatures by using a salt of a complex compound of an inorganic acid and an organic acid, such as borodisalicylate, as a solute in an electrolytic solution filled in a capacitor element. has been done. However, it is insufficient in other characteristics required of a hybrid capacitor, such as capacitance, dielectric loss tangent (tan δ), leakage current, and withstand voltage. Further, there is a problem that the resulting hybrid capacitor has insufficient heat resistance.

Regarding an electrolytic solution for an electrolytic capacitor, Patent Document 2 discloses an electrolytic solution that uses an electrolyte composed of an alkyl phosphate ester anion and a cation as an electrolytic solution that maintains high specific conductivity and has a high spark voltage. has been done. However, studies by the present inventors have revealed that the heat resistance is insufficient when applied to a hybrid capacitor.

JP 2019-145835 A Japanese Patent Application Publication No. 2008-135693

An object of the present invention is to provide a hybrid capacitor with excellent heat resistance and an electrolytic solution for a hybrid capacitor that contributes to the manufacture of such a hybrid capacitor.

The present inventors have a capacitor element in which a valve metal foil having a dielectric oxide film and a counter cathode foil are wound with a separator in between, and a solid electrolyte made of a conductive polymer is attached to the capacitor element. In a hybrid capacitor consisting of an exterior case that houses the capacitor element together with an electrolytic solution after forming a layer, the inventors have discovered that the above problems can be solved by a hybrid capacitor containing the following electrolytes as the electrolytic solution, and have completed the present invention. Ta.

That is, the present invention is as shown in (1) to (4) below.

(1): It is characterized by containing an electrolyte composed of a cation represented by the following general formula (1) and at least one anion selected from the group represented by the following general formulas (2) to (4). This is an electrolyte for hybrid capacitors.

In the above formula (1), R ₁ to R ₄ each represent hydrogen, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, and each of R ₁ to R 4 may be the same or different. R ₄ may be linked to form an alkylene group having 2 to 6 carbon atoms.

In the above formula (2), R ₅ and R ₆ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₅ and R ₆ is a phenyl group or a benzyl group.

In the above formula (3), R ₇ and R ₈ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₇ and R ₈ is a phenyl group or a benzyl group.

In the above formula (4), R ₉ and R ₁₀ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₉ and R ₁₀ is a phenyl group or a benzyl group.

(2): As described in (1) above, wherein the cation is one or more cations selected from the group consisting of ammonium cation, diethylamine cation, dimethylethylamine cation, diethylmethylamine cation, and triethylamine cation. This is an electrolyte for hybrid capacitors.

(3): The above anion is one or more anions selected from the group consisting of phenyl phosphate anion, diphenyl phosphate anion, benzyl phosphate anion, phenylbenzyl phosphate anion, and dibenzyl phosphate anion. The electrolytic solution for a hybrid capacitor as described in (1) above is characterized by:

(4): A solid electrolyte layer made of a conductive polymer is formed on a capacitor element in which an anode electrode foil and a cathode electrode foil are wound through a separator, and the solid electrolyte layer is formed inside the capacitor element. A hybrid capacitor characterized in that the void portion is filled with the electrolytic solution for a hybrid capacitor according to any one of (1) to (3) above.

The hybrid capacitor electrolyte of the present invention has high thermal stability and dielectric oxide film repair properties. Therefore, a hybrid capacitor using this hybrid capacitor electrolyte has excellent heat resistance while maintaining the capacitance, dielectric tangent (tan δ), equivalent series resistance (ESR), leakage current, and voltage resistance characteristics.

First, the electrolyte for hybrid capacitors of the present invention will be described below.

<Electrolyte>
The electrolyte contained in the electrolyte for a hybrid capacitor of the present invention is composed of a salt consisting of a cation and an anion, and may be used alone or in a mixture of two or more types.

<Cation>
The above cation is represented by the following general formula (1).

In the above formula (1), R ₁ to R ₄ each represent hydrogen, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, and each of R ₁ to R 4 may be the same or different. R ₄ may be linked to form an alkylene group having 2 to 6 carbon atoms.

Specific examples of the cation represented by the above formula (1) include quaternary ammonium cations such as ammonium cations, tetramethylammonium cation, tetraethylammonium cation, tetrapropylammonium cation, tetraisopropylammonium cation, tetrabutylammonium cation, trimethylethylammonium cation, triethylmethylammonium cation, dimethyldiethylammonium cation, dimethylethylmethoxyammonium cation, dimethylethylmethoxyammonium cation, dimethylethylethoxyammonium cation, trimethylpropylammonium cation, dimethylethylpropylammonium cation, triethylpropylammonium cation, spiro-(1,1')-bipyrrolidinium cation, piperidine-1-spiro-1'-pyrrolidinium cation, and spiro-(1,1')-bipiperidinium cation; trimethylamine cation, triethylamine cation, tripropylamine cation, triisopropylamine cation, tributylamine cation, and diethylmethylamine cation. Tertiary amine cations such as dimethylethylamine cation, diethylmethoxyamine cation, dimethylmethoxyamine cation, dimethylethoxyamine cation, diethylethoxyamine cation, methylethylmethoxyamine cation, N-methylpyrrolidine cation, N-ethylpyrrolidine cation, N-propylpyrrolidine cation, N-isopropylpyrrolidine cation, N-butylpyrrolidine cation, N-methylpiperidine cation, N-ethylpiperidine cation, N-propylpiperidine cation, N-isopropylpiperidine cation, and N-butylpiperidine cation; secondary amine cations such as dimethylamine cation, diethylamine cation, diisopropylamine cation, dipropylamine cation, dibutylamine cation, methylethylamine cation, methylpropylamine cation, methylisopropylamine cation, methylbutylamine cation, ethylisopropylamine cation, ethylpropylamine cation, ethylbutylamine cation, isopropylbutylamine cation, and pyrrolidine cation.

Among these, ammonium cation, diethylamine cation, dimethylethylamine cation, diethylmethylamine cation, and triethylamine cation are preferably used because of their excellent effect of improving heat resistance.

<Anion>
The anions mentioned above are those represented by the following general formulas (2) to (4).

In the above formula (2), R ₅ and R ₆ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₅ and R ₆ is a phenyl group or a benzyl group.

In the above formula (3), R ₇ and R ₈ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₇ and R ₈ is a phenyl group or a benzyl group.

In the above formula (4), R ₉ and R ₁₀ each represent hydrogen, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, which may be the same or different, and at least one of R ₉ and R ₁₀ One is a phenyl group or a benzyl group.

Specific examples of the anion represented by the above formula (2) include phenylphosphinic acid anion, methylphenylphosphinic acid anion, diphenylphosphinic acid anion, benzylphosphinic acid anion, methylbenzylphosphinic acid anion, phenylbenzylphosphinic acid anion, and diphenylphosphinic acid anion. Examples include benzylphosphinic acid anion.

Specific examples of the anion represented by the above formula (3) include phenylphosphonic acid hydrogen anion, methylphenylphosphonic acid anion, diphenylphosphonic acid anion, phenylbenzylphosphonic acid anion, benzylphosphonic acid anion, methylbenzylphosphonic acid anion, benzylphenylphosphonic acid anion, and dibenzylphosphonic acid anion.

Specific examples of the anion represented by the above formula (4) include phenyl phosphate anion, diphenyl phosphate anion, benzyl phosphate anion, phenylbenzyl phosphate anion, dibenzyl phosphate anion, and the like.

Among these, phenyl phosphate anion, diphenyl phosphate anion, benzyl phosphate anion, phenylbenzyl phosphate anion, and dibenzyl phosphate anion are preferably used because of their excellent effect of improving heat resistance.

<Organic solvent>
The electrolytic solution for a hybrid capacitor of the present invention may contain an organic solvent, and the organic solvent may be a protic polar solvent or an aprotic polar solvent, and may be used alone or in a mixture of two or more types. good.

Protic polar solvents include monohydric alcohols (methanol, ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols, and oxyalcohol compounds (ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.).

Aprotic polar solvents include γ-butyrolactone, γ-valerolactone, amides (N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphoric amide, etc.), sulfolanes (sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, etc.), chain sulfones (dimethylsulfone, ethylmethylsulfone, ethylisopropylsulfone, etc.), cyclic amines (dimethylsulfone, ethylmethylsulfone, ethylisopropylsulfone, etc.), and cyclic amines (dimethylsulfone, ethylmethylsulfone, ethylisopropylsulfone, etc.). These include amides (N-methyl-2-pyrrolidone, etc.), carbonates (ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitriles (acetonitrile, etc.), sulfoxides (dimethyl sulfoxide, etc.), and 2-imidazolidinones (1,3-dialkyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di(n-propyl)-2-imidazolidinone, 1,3,4-trialkyl-2-imidazolidinone, 1,3,4-trimethyl-2-imidazolidinone, etc.).

When used in hybrid capacitors, the main solvent is preferably γ-butyrolactone, ethylene glycol, or sulfolane. The amount of water contained in the hybrid capacitor electrolyte is not particularly limited, but is preferably 0.01 to 20% by mass, and more preferably 0.1 to 10% by mass. By adjusting the amount of water to this level, good heat resistance properties can be obtained.

The electrolytic solution for a hybrid capacitor of the present invention can be prepared by dissolving the electrolyte in the organic solvent. The amount of the electrolyte added is preferably 0.1 to 50% by mass, more preferably 1 to 15% by mass. Particularly preferred is 3 to 10% by mass. If it exceeds 50% by mass, heat resistance properties may deteriorate.

<Additives>
The electrolytic solution for a hybrid capacitor of the present invention may contain additives to the extent that the effects of the present invention are not impaired. As additives, phosphoric acid compounds such as dibutyl phosphate, tributyl phosphate, dibutyl phosphite, tributyl phosphite, ammonium phosphate, o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, Nitro compounds such as o-nitrophenol, m-nitrophenol, p-nitrophenol, polyethylene glycol, polyvinyl alcohol, boric acid, mannitol, boric acid and mannitol, complex compounds such as sorbitol, boric acid and ethylene glycol, glycerin Examples include boron compounds such as complex compounds with polyhydric alcohols, amine compounds, and triazoles.

<Hybrid capacitor>
Next, the hybrid capacitor of the present invention will be explained.
The hybrid capacitor of the present invention has a capacitor element in which an anode metal foil having a dielectric oxide film and a counter cathode foil are wound with a separator in between, and the capacitor element has a solid electrolyte containing a conductive polymer. The capacitor element is housed in an exterior case along with the hybrid capacitor electrolyte.

<Capacitor element>
A method for producing the hybrid capacitor will now be described.
The metal foil used for the anode may be an etched aluminum foil whose surface has been etched and roughened. The aluminum foil is anodized in a chemical conversion treatment solution such as an aqueous solution of diammonium adipate to form a dielectric oxide film layer on the anode surface, a lead terminal is attached to the anode, and a lead terminal is attached to an opposing cathode foil made of aluminum foil. The anode and cathode with the lead terminals are then opposed to each other via a separator and wound to produce a capacitor element.

<Solid electrolyte>
The hybrid capacitor of the present invention uses the above-mentioned capacitor element having a solid electrolyte layer made of a conductive polymer formed thereon.
The conductive polymer that forms the solid electrolyte can be a conductive polymer dispersion in which a conductive polymer is dispersed in a solvent, a conductive polymer solution in which a conductive polymer is dissolved, or a conductive polymer that is chemically oxidatively polymerized within the capacitor element using a conductive polymer monomer and an oxidizing agent.

<Conductive polymer dispersion>
As the conductive polymer dispersion described above, a conductive polymer dispersion containing at least a polythiophene derivative doped with a dopant component and a dispersion medium can be used.

The polythiophene derivative can be a polymer of a thiophene derivative monomer. Specific examples of the thiophene derivative monomer include 3,4-ethylenedioxythiophene, methyl-3,4-ethylenedioxythiophene, ethyl-3,4-ethylenedioxythiophene, propyl-3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, methyl-3,4-propylenedioxythiophene, ethyl-3,4-propylenedioxythiophene, propyl-3,4-propylenedioxythiophene, 3,4-ethylenedithiathiophene, methyl-3,4-ethylenedithiathiophene, ethyl-3,4-ethylenedithiathiophene, propyl-3,4-ethylenedithiathiophene, 3,4-propylenedithiathiophene, methyl-3,4-propylenedithiathiophene, ethyl-3,4-propylenedithiathiophene, and propyl-3,4-propylenedithiathiophene.

Among these, 3,4-ethylenedioxythiophene, methyl-3,4-ethylenedioxythiophene, ethyl- Particularly preferred is 3,4-ethylenedioxythiophene.

Specific examples of the dopant component include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyethyl acrylate sulfonic acid, polybutyl acrylate sulfonic acid, polyacryl sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamide-2-methyl sulfonic acid), polyisoprene sulfonic acid, polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacryl sulfonic acid, polymethacrylic carboxylic acid, poly(2-acrylamide-2-methyl carboxylic acid), polyisoprene carboxylic acid, paratoluene sulfonic acid, xylene sulfonic acid, methylnaphthalene sulfonic acid, butylnaphthalene sulfonic acid, etc. These may be used alone or in a mixture of two or more kinds.
Among these, polystyrene sulfonic acid is particularly preferred.

Particularly preferred examples of thiophene derivatives doped with a dopant component include poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid, poly(methyl-3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid, and poly(ethyl-3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

The dispersion medium may be water or an organic solvent.

<Chemical oxidation polymerization>
The conductive polymer obtained by chemical oxidative polymerization that can be used in the present invention can be obtained by chemically oxidatively polymerizing the aforementioned thiophene derivative monomer in the presence of an oxidizing agent and a dopant. As the oxidizing agent for chemical oxidative polymerization, a known oxidizing agent such as para-toluenesulfonic acid iron(III) salt can be used.

As the dopant, those having functional groups that can cause chemical oxidative doping to the conductive polymer can be used, for example, halogen ions such as iodine, bromine, and chlorine, halide ions such as hexafluorophosphorus, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, and perchloric acid, alkyl-substituted organic sulfonate ions such as methanesulfonic acid and dodecylsulfonic acid, cyclic sulfonate ions such as camphorsulfonic acid ions, and alkyl-substituted or unsubstituted benzene mono- or disulfonate ions such as benzenesulfonic acid, paratoluenesulfonic acid, dodecylbenzenesulfonic acid, polystyrenesulfonic acid, and benzenedisulfonic acid. , alkyl-substituted or unsubstituted ions of naphthalenesulfonic acid with 1 to 4 sulfonic acid groups such as 2-naphthalenesulfonic acid and 1,7-naphthalenedisulfonic acid, anthracenesulfonic acid ions, anthraquinonesulfonic acid ions, alkyl-substituted or unsubstituted biphenylsulfonic acid ions such as alkylbiphenylsulfonic acid and biphenyldisulfonic acid, polymeric sulfonic acid ions such as polystyrenesulfonic acid and naphthalenesulfonic acid-formaldehyde condensates, heteropolyacid ions such as molybdophosphoric acid, tungstophosphoric acid, and tungstomolybdophosphoric acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, and xylenesulfonic acid. Among these, at least one selected from polystyrenesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, polystyrenesulfonic acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, and xylenesulfonic acid is more preferably mentioned, and paratoluenesulfonic acid and polystyrenesulfonic acid are particularly preferably mentioned.

<Hybrid Capacitor>
The method for manufacturing the hybrid capacitor is described in detail below.

As described above, a capacitor element is manufactured by winding an anode metal foil on which a dielectric oxide film is formed and a counter cathode foil with a separator in between.
By bringing the conductive polymer dispersion into contact with the capacitor element and then drying it, a solid electrolyte layer made of the conductive polymer can be formed within the element. The contacting method may be any method, but a method of immersion is preferred. Next, the capacitor element with the solid electrolyte layer formed thereon is housed together with an electrolyte in a bottomed cylindrical metal case, and the open end is sealed, thereby producing a hybrid capacitor.

When using a conductive polymer produced by chemical oxidation polymerization, the conductive polymer produced by chemical oxidation polymerization can be formed by bringing a thiophene derivative monomer, an oxidizing agent, and a dopant solution into contact within the capacitor element. Next, the capacitor element with the solid electrolyte layer formed thereon is housed together with an electrolyte in a bottomed cylindrical metal case, and the open end is sealed, thereby producing a hybrid capacitor.

The present invention will be described below based on examples. Note that the present invention is not limited in any way by these examples.

<Preparation of Electrolyte Solution>
Example 1
14 parts by mass of triethylamine and 30 parts by mass of diphenylphosphinic acid were dissolved in 56 parts by mass of acetonitrile, and the mixture was heated at 80° C. for 3 hours, and then the solvent was distilled off in an evaporator at 80° C. under a reduced pressure of 15 Torr or less. The obtained electrolyte (triethylamine-diphenylphosphinic acid) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

Example 2
13 parts by mass of triethylamine and 33 parts by mass of benzylphenylphosphonic acid were dissolved in 54 parts by mass of acetonitrile, and the mixture was heated at 80° C. for 3 hours, and then the solvent was distilled off in an evaporator at 80° C. under a reduced pressure of 15 Torr or less. The obtained electrolyte (triethylamine-benzylphenylphosphinic acid) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

Example 3
15 parts by mass of triethylamine and 60 parts by mass of phenyl phosphate were dissolved in 60 parts by mass of acetonitrile, and the mixture was heated at 80° C. for 3 hours, and then the solvent was distilled off in an evaporator at 80° C. under a reduced pressure of 15 Torr or less. The obtained electrolyte (triethylamine-phenyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

(Example 4)
5 parts by mass of ammonium and 75 parts by mass of diphenyl phosphate were dissolved in 20 parts by mass of acetonitrile, heated at 80°C for 3 hours, and then the solvent was distilled off using an evaporator at 80°C under reduced pressure of 15 Torr or less. . The obtained electrolyte (diphenyl-ammonium phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

Example 5
12 parts by mass of diethylamine and 41 parts by mass of diphenyl phosphate were dissolved in 48 parts by mass of acetonitrile, and the mixture was heated at 80° C. for 3 hours, and then the solvent was distilled off in an evaporator at 80° C. under a reduced pressure of 15 Torr or less. The obtained electrolyte (diethylamine-diphenyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

Example 6
13 parts by mass of triethylamine and 33 parts by mass of diphenyl phosphate were dissolved in 54 parts by mass of acetonitrile, and the mixture was heated at 80° C. for 3 hours, and then the solvent was distilled off in an evaporator at 80° C. under a reduced pressure of 15 Torr or less. The obtained electrolyte (triethylamine-diphenyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

(Example 7)
15 parts by mass of tetraethylammonium hydroxide and 25 parts by mass of diphenyl phosphate were dissolved in 60 parts by mass of acetonitrile, and after heating at 80°C for 3 hours, the solvent was removed using an evaporator at 80°C under reduced pressure of 15 Torr or less. Distilled away. The obtained electrolyte (tetraethylammonium-diphenyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

(Example 8)
15 parts by mass of triethylamine and 25 parts by mass of benzyl phosphate were dissolved in 60 parts by mass of acetonitrile, and the mixture was heated at 80° C. for 3 hours, and then the solvent was distilled off in an evaporator at 80° C. under a reduced pressure of 15 Torr or less. The obtained electrolyte (triethylamine-benzyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

(Example 9)
13 parts by mass of triethylamine and 33 parts by mass of phenylbenzyl phosphate were dissolved in 54 parts by mass of acetonitrile, heated at 80°C for 3 hours, and then the solvent was distilled off using an evaporator at 80°C under reduced pressure of 15 Torr or less. did. The obtained electrolyte (triethylamine-phenylbenzyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

(Example 10)
13 parts by mass of triethylamine and 35 parts by mass of dibenzyl phosphate were dissolved in 52 parts by mass of acetonitrile and heated at 80° C. for 3 hours, and then the solvent was distilled off in an evaporator at 80° C. under a reduced pressure of 15 Torr or less. The obtained electrolyte (triethylamine-dibenzyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolyte solution.

(Comparative example 1)
1-ethyl-3-methylimidazolium bromide was ion-exchanged with an ion-exchange resin, and 78 parts by mass of the resulting 20% by mass 1-ethyl-3-methylimidazolium hydroxide aqueous solution and 22 parts by mass of diphenyl phosphate were added. After mixing and heating at 80° C. for 3 hours, the solvent was distilled off using an evaporator at 80° C. under reduced pressure of 15 Torr or less. The obtained electrolyte (1-ethyl-3-methylimidazolium-diphenyl phosphate) was dissolved in ethylene glycol to a concentration of 5% by mass to prepare an electrolytic solution.

(Comparative example 2)
To 95 parts by mass of ethylene glycol, 2 parts by mass of triethylamine and 3 parts by mass of dibutyl phosphate were added and heated at 80°C for 3 hours to obtain an ethylene glycol solution consisting of 5% by mass of electrolyte (triethylamine-dibutyl phosphate). Ta.

<Production of hybrid capacitor>
First, a capacitor element was produced by winding an anode foil and a cathode foil with a separator in between. An anode tab and a cathode tab are connected to the anode foil and the cathode foil, respectively. These anode tabs and cathode tabs are made of high-purity aluminum and consist of a flat part that connects to each foil and a continuous round bar part.The round bar part has an anode lead wire and a cathode lead wire, respectively. It is connected. Note that each foil and electrode tab are mechanically connected by stitching, ultrasonic welding, or the like.

The capacitor element thus constructed was impregnated with an aqueous dispersion of poly(3,4-ethylenedioxythiophene)-(polystyrenesulfonic acid) manufactured by ALDRICH, and then dried at 155° C. for 30 minutes to form a solid electrolyte layer.
The elements having the solid electrolyte layer formed thereon were impregnated with the electrolyte solutions obtained in Examples 1 to 10 and Comparative Examples 1 and 2, and then housed in a cylindrical aluminum exterior case with a bottom. A butyl rubber sealer having through holes for leading out lead wires was inserted into the open end of the exterior case, and the end of the exterior case was further crimped to seal it, thereby obtaining a hybrid capacitor.

<Evaluation of hybrid capacitors>
The hybrid capacitors obtained using the electrolytes of Examples 1 to 10 and Comparative Examples 1 and 2 were subjected to a heat resistance test at 135°C for 3000 hours using a Precision LCR meter E4980A manufactured by Agilent Technologies. The capacitance (μF) and dielectric loss tangent (tan δ) at 120 Hz were measured, and the equivalent series resistance (ESR) at 100 kHz was measured.

Table 1 shows the evaluation results below.

As described above, in the examples, a hybrid capacitor with excellent heat resistance characteristics could be obtained because it had excellent capacitance, dielectric loss tangent, and equivalent series resistance characteristics after the heat resistance test.

A hybrid capacitor using the hybrid capacitor electrolyte of the present invention has excellent heat resistance and can suppress deterioration of the characteristics of the hybrid capacitor over a long period of time, so it can be applied to high-frequency digital equipment, automobiles, etc.

Claims (4)

An electrolyte for a hybrid capacitor, comprising an electrolyte composed of a cation represented by the following general formula (1) and at least one anion selected from the group represented by the following general formulas (2) to (4):
(In the above formula (1), R ₁ to R ₄ may be the same or different and represent hydrogen, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, and R ₁ to R ₄ may be linked to form an alkylene group having 2 to 6 carbon atoms.)
(In the above formula (2), R ₅ and R ₆ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₅ and R ₆ is a phenyl group or a benzyl group.)

(In the above formula (3), R ₇ and R ₈ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₇ and R ₈ is a phenyl group or a benzyl group.)
(In the above formula (4), R ₉ and R ₁₀ may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group, and at least one of R ₉ and R ₁₀ is a phenyl group or a benzyl group.) The electrolyte for a hybrid capacitor according to claim 1, characterized in that the cation is one or more cations selected from the group consisting of ammonium cation, diethylamine cation, dimethylethylamine cation, diethylmethylamine cation, and triethylamine cation. The electrolyte for hybrid capacitors according to claim 1, characterized in that the anion is one or more anions selected from the group consisting of phenyl phosphate anion, diphenyl phosphate anion, benzyl phosphate anion, phenylbenzyl phosphate anion, and dibenzyl phosphate anion. A solid electrolyte layer made of a conductive polymer is formed on a capacitor element in which an anode electrode foil and a cathode electrode foil are wound with a separator in between. A hybrid capacitor filled with the electrolyte for a hybrid capacitor according to any one of claims 1 to 3.