JP2003188053A - Electric double-layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor having a high withstand voltage and enhanced reliability. <P>SOLUTION: In the electric double-layer capacitor that has a pair of polarization electrodes using a carbon material as a main constituent, and an electrolyte solution for forming an electric double layer in an interface with the polarization electrodes, salt such as (C<SB>2</SB>H<SB>5</SB>)<SB>3</SB>(CH<SB>3</SB>)NBF<SB>3</SB>(CF<SB>3</SB>) is set to be an electrolyte as the electrolyte solution, and a solution that dissolves into an organic solvent such as propylenecarbonate or sulfolane is used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor having an organic solvent type electrolytic solution, and particularly to an electric double layer capacitor having a high voltage and excellent reliability.

[0002]

2. Description of the Related Art An electric double layer capacitor contains a pair of polarizable electrodes, a separator between the polarizable electrodes, and an electrolytic solution in a case.

The electrolytic solution usually contains a solvent and an electrolyte, but is roughly classified into an aqueous electrolytic solution and an organic solvent-based electrolytic solution depending on the kind of the solvent. As the aqueous electrolyte, mineral acids such as sulfuric acid,
Examples thereof include alkali metal salts and alkalis. On the other hand, as an organic solvent-based electrolytic solution, Japanese Patent Application Laid-Open No. 49-6825
4 is propylene carbonate, γ-butyrolactone,
It has been proposed to use acetonitrile and dimethylformamide, and JP-A-62-237715 to use a sulfolane derivative.

Comparing the water-based electrolytic solution and the organic solvent-based electrolytic solution in terms of electrostatic energy of the electric double layer capacitor, since electrostatic energy is proportional to the square of withstand voltage, the withstand voltage of the aqueous electrolytic solution is 0.8V. On the other hand, the organic solvent electrolyte is 2.5
The organic solvent-based electrolytic solution is more advantageous because it is about 3.3 V.

However, the organic solvent-based electrolytic solution has a problem in that the presence of water in the electrolytic solution causes degradation of the capacitor performance due to hydrolysis of the electrolyte and the solvent. For example,
As the anion of the electrolyte of the electric double layer capacitor having the organic solvent-based electrolytic solution, electrochemically stable BF ₄ ⁻ ,
PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , AsF ₆ ⁻ , N (SO ₂ C
F ₃ ) ₂ ⁻ , ClO ₄ ^{− and the} like are known. Above all, B
It has been considered that F ₄ ⁻ is preferable because it is excellent in toxicity and safety and relatively excellent in hydrolysis resistance. However, even with BF ₄ ⁻ , when the amount of water in the electrolytic solution is 30 ppm or more, hydrolysis occurs and deterioration of the capacitor occurs, resulting in a decrease in capacity and an increase in internal resistance.

As a countermeasure against such deterioration, it has been attempted to remove water from constituent materials such as an organic solvent-based electrolytic solution and electrodes, but it is not possible to completely remove the water trapped in the activated carbon pores. Since it is difficult and it is also difficult to completely prevent the infiltration of water from the sealing portion, a sufficient solution has not been obtained yet.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electric double layer capacitor having an organic solvent-based electrolytic solution, which has a high withstand voltage, is less likely to cause deterioration of capacitor performance, and is highly reliable.

[0008]

An electric double layer capacitor of the present invention (hereinafter referred to as the present capacitor) comprises a pair of polarizable electrodes, and an electrolytic solution forming an electric double layer at the interface between the polarizable electrodes. In the electric double layer capacitor having, the electrolytic solution contains an organic solvent and an electrolyte, and the electrolyte is a cation and an anion represented by Formula 1 (where n is an integer of 0 to 3 and p is 0 to 4). The present invention provides an electric double layer capacitor, characterized in that n + p ≦ 4, m and k are each independently an integer of 1 to 4, where m ≠ k).

[0009]

[Chemical 3]

The anion of the electrolyte of the present capacitor is obtained by substituting a fluorine atom of BF ₄ ⁻ which is electrochemically stable with a fluoroalkyl group, which is electrochemically stable and defluorinated by fluoroalkylation. It is less likely to occur and has excellent hydrolysis resistance.

In the present invention, the anion includes
BF_Three(CF_Three)⁻, BF_Two(CF _Three)_Two ⁻, BF (C
F_Three)_Three ⁻, B (CF_Three)_Four ⁻, BF_Three(C
_TwoF₅)⁻, BF_Two(C_TwoF₅)_Two ⁻, BF (C
_TwoF₅)_Three ⁻, B (C_TwoF₅)_Four ⁻, BF_Three(C
_ThreeF₇)⁻, BF_Two(C_ThreeF₇)_Two ⁻, BF (C
_ThreeF₇)_Three ⁻, B (C_ThreeF₇)_Four ⁻, BF_Three(C
_FourF₉)⁻, BF_Two(C_FourF₉)_Two ⁻, BF (C
_FourF₉)_Three ⁻, B (C_FourF₉)_Four ⁻, BF_Two(CF_Three)
(C_TwoF₅)⁻, BF (CF_Three)_Two(C_TwoF₅)⁻, B
F (CF_Three) (C_TwoF₅)_Two ⁻, B (CF_Three)_Three(C_Two
F₅)⁻, B (CF_Three)_Two(C_TwoF₅)_Two ⁻, B (CF
_Three) (C_TwoF₅)_Three ⁻, BF _Two(CF_Three) (C_ThreeF₇)
⁻, BF (CF_Three)_Two(C_ThreeF₇)⁻, BF (CF_Three)
(C_ThreeF₇)_Two ⁻, B (CF_Three)_Three(C_ThreeF₇)⁻, B
(CF_Three)_Two(C_ThreeF ₇)_Two ⁻, B (CF_Three) (C_ThreeF
₇)_Three ⁻BF_Two(CF_Three) (C_FourF₉)⁻, BF (CF
_Three)_Two(C_FourF₉)⁻, BF (CF_Three) (C_FourF₉)_Two
⁻, B (CF_Three)_Three(C_FourF₉)⁻, B (CF_Three)
_Two(C_FourF₉)_Two ⁻, B (CF_Three) (C_FourF ₉)_Three ⁻,
BF_Two(C_TwoF₅) (C_ThreeF₇)⁻, BF (C_TwoF₅)
_Two(C_ThreeF₇)⁻, BF (C_TwoF₅) (C
_ThreeF₇)_Two ⁻, B (C_TwoF₅)_Three(C_ThreeF₇)⁻, B
(C_TwoF₅)_Two(C_ThreeF₇)_Two ⁻, B (C_TwoF₅) (C
_ThreeF₇)_Three ⁻, BF_Two(C_TwoF₅) (C_FourF₉)⁻, B
F (C_TwoF₅)_Two(C_FourF₉)⁻, BF (C_TwoF₅)
(C_FourF₉)_Two ⁻, B (C_TwoF₅)_Three(C_FourF₉)⁻,
B (C_TwoF₅)_Two(C_FourF₉)_Two ⁻, B (C_TwoF₅)
(C_FourF₉)_Three ⁻, BF_Two(C_ThreeF₇) (C
_FourF₉)⁻, BF (C_ThreeF₇)_Two(C_FourF₉)⁻, BF
(C_ThreeF₇) (C_FourF₉)_Two ⁻, B (C_ThreeF₇)_Three(C
_FourF₉)⁻, B (C_ThreeF₇)_Two(C_FourF₉)_Two ⁻, B
(C_ThreeF₇) (C_FourF₉)_Three ⁻Is mentioned.

Among them, an anion in which all four fluorine atoms of BF ₄ ⁻ are replaced with the same fluoroalkyl group (hereinafter, referred to as
An electrolyte having anions (hereinafter referred to as an anion having an asymmetric structure) that are different from those having an anion having a symmetrical structure has high solubility in an organic solvent of an electrolytic solution, and high conductivity can be obtained by increasing the concentration. preferable. Further, the carbon chain length of the perfluoroalkyl group bonded to the boron atom is preferably as short as possible.
This is because if the carbon chain is short, the ion size is small, so that the carbon chain can enter the activated carbon having a small pore size, and the amount of ions forming an electric double layer per unit volume increases.

From this point of view, the anion is BF ₃ (C
^{_{F 3) -, BF 2 (}} CF 3) 2 - and BF (CF _{3) 3} ^-
It is preferably at least one selected from the group consisting of

In the present capacitor, the cation of the electrolyte is preferably one represented by the formulas 2 to 7.

[0015]

[Chemical 4]

However, in the formula 2 or the formula 3, R ¹ , R ² ,
R ³ and R ⁴ are each independently an alkyl group having 1 to 3 carbon atoms. As the cation represented by formula 2 or formula 3, R is
¹ = R ² = R ³ = R ⁴ cations (hereinafter referred to as symmetrical cations) and other cations (hereinafter referred to as
There is a cation having an asymmetric structure), and either of them may be used. It is preferable that the cation represented by Formula 2 or Formula 3 is a cation having an asymmetric structure, since it has a higher solubility in a solvent than a cation having a symmetrical structure and high conductivity can be obtained by increasing the concentration.

As the cation having a symmetrical structure, (C_TwoH₅)
_FourN⁺, (C_ThreeH₇)_FourN⁺, (C _TwoH₅)_FourP⁺,
(C_ThreeH₇)_FourP⁺, Etc. are exemplified.

On the other hand, as the cation having an asymmetric structure,
Physically (C_TwoH₅)_Three(CH_Three) N⁺, (C_TwoH₅)
_Two(CH_Three)_TwoN⁺, (C_TwoH₅) (CH_Three)_ThreeN⁺,
(C _ThreeH₇)_Three(CH_Three) N⁺, (C_ThreeH₇)_Two(CH
_Three)_TwoN⁺, (C_ThreeH₇) (CH_Three)_ThreeN⁺, (C_ThreeH
₇)_Three(C_TwoH₅) N⁺, (C_ThreeH₇)_Two(C_TwoH₅)
_TwoN⁺, (C_ThreeH₇) (C_TwoH₅)_ThreeN⁺, (C
_TwoH₅)_Three(CH_Three) P⁺, (C_TwoH₅)_Two(CH_Three)
_TwoP⁺, (C_TwoH₅) (CH_Three)_ThreeP⁺Is mentioned.
Above all (C_TwoH₅)_Three(CH_Three) N⁺Or (C_TwoH
₅) (CH_Three)_ThreeN⁺Solubility in solvent
Highly preferred because of its high electrical conductivity and electrochemical stability
Yes.

The cations represented by the formulas 4 to 7 are compound cations.
It has a cyclic group. However, in formulas 4 to 6, R⁶Is
Hydrogen atom, fluorine atom, hydrocarbon group having 1 to 20 carbon atoms
(One or more hydrogen atoms are replaced by fluorine atoms or hydroxyl groups.
R), and R ⁵, R⁷, R⁸, R⁹Is
Independently hydrogen atom, fluorine atom or carbon number 1 to
10 hydrocarbon groups (one or more of which is a fluorine atom)
Or may be substituted with a monovalent organic group).

In formula 7, R¹⁰Is a hydrogen atom, a fluorine atom,
Hydrocarbon group having 1 to 20 carbon atoms (one or more hydrogen atoms are
Optionally substituted with a fluorine atom or a hydroxyl group)
R ¹¹, R¹², R^Thirteen, R¹⁴Each independently
Hydrocarbon group having 1 to 10 carbon atoms (one or more hydrogen atoms are
(It may be substituted with a fluorine atom or a monovalent organic group)
Is. Also, R¹¹, R¹², R^Thirteen, R¹⁴Is par
May be a fluoroalkyl group, in which case it is carbon
It is preferable that the number is 1 to 6.

Here, as the monovalent organic group, an amino group or a group
Ano group, aldehyde group,-(OA) _aRepresented by OR '
Group (A is an alkyl group having 1 to 4 carbon atoms which may contain a fluorine atom)
It is a xylene group and R'is a carbon which may contain a fluorine atom.
It is an alkyl group of the numbers 1 to 10, and a is an integer of 0 to 10.
There is) etc.

Among the cations having the heterocyclic groups represented by the formulas 4 to 6, in the formula 4, R ⁵ ═CH ₃ or C
₂ H ₅ , R ⁶ = H, R ⁷ = CH ₃ or C ₂ H ₅ , R ⁸
= H, R ⁹ = H, and an ethylmethylimidazolium ion is preferable in terms of solubility, electric conductivity of the solution, electrochemical stability, and the like.

In this capacitor, the cations of the electrolyte are (C ₂ H ₅ ) ₃ (CH ₃ ) N ⁺ , (C ₂ H ₅ ) (C
It is preferably at least one selected from the group consisting of H ₃ ) ₃ N ⁺ and ethylmethylimidazolium ion.

The electrolyte salt used in the present invention is
The solution when dissolved in a solvent has high electric conductivity, and the withstand voltage is further improved. Therefore, this capacitor has a high withstand voltage.

The organic solvent for the electrolytic solution of the present capacitor is not particularly limited, but examples thereof include cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate, and chain carbonates such as ethyl methyl carbonate, dimethyl carbonate and diethyl carbonate. , Lactones such as γ-butyrolactone and γ-valerolactone, nitriles such as acetonitrile and glutaronitrile, sulfolanes such as sulfolane and 3-methylsulfolane, dimethylformamide, 1,2-dimethoxyethane, nitromethane and trimethylphosphate. Is mentioned. These may be used alone or as a mixed solvent of two or more kinds. Of these, propylene carbonate is most preferable.

In the present invention, in order to increase the electric conductivity of the electrolytic solution, it is preferable that the concentration of the electrolyte is high, but if the concentration is too high, the viscosity becomes high and it becomes difficult to handle.
The concentration of the electrolyte is preferably 1.0 to 2.0 mol / L, and more preferably 1.2 to 1.8 mol / L. If the concentration of the electrolyte is less than 1.0 mol / L, the internal resistance may increase, while on the other hand, 2.0 mol / L
If it exceeds L, the electrolyte may precipitate during cold weather and the stability may decrease.

The organic solvent-based electrolytic solution containing the above-mentioned electrolyte and solvent is preferably such that the amount of metal impurities and water is small.
Usually, a water content of 10 ppm or less is preferably used.

In the present invention, as the polarizable electrode, one having a metal current collector (hereinafter simply referred to as a current collector) on which an electrode layer containing a carbon material such as activated carbon as a main component is formed is usually used. To do.

The capacitor can be suitably applied to any structure such as a coin structure, a cylindrical structure, and a rectangular structure depending on the form of the polarizable electrode. The coin-type structure is formed by disposing a separator between a pair of electrodes, accommodating it in a case together with an electrolytic solution, and sealing it with a metallic sealing lid and a gasket that insulates both.

In the cylindrical structure, a band-shaped positive electrode body having electrodes formed on both sides of a current collector and a band-shaped negative electrode body having the same structure are alternately laminated with a band-shaped separator interposed therebetween and wound. After accommodating the element body in a cylindrical case and impregnating it with an electrolytic solution, the current collecting leads drawn out from both electrode bodies are respectively connected to, for example, electrode terminals provided on an electrically insulating sealing lid. The sealing lid is fitted in the case.

The rectangular structure has a rectangular collector in which electrode layers are formed on both sides of a rectangular current collector, and a plurality of positive electrode bodies and negative electrode bodies are alternately laminated with separators in between to form a laminated element body. And the electrolytic solution is impregnated therein, and the sealing lid is fitted in a rectangular case.

The electrode used in the present capacitor preferably contains a carbon material as a main component. The carbon material has a specific surface area of 500 to 3000 m ² / g, and further 700 to 3
It is preferably 000 m ² / g, and specific examples thereof include activated carbon, carbon black, polyacene and the like. In particular, using highly conductive carbon black as a conductive material,
It is preferably used by mixing with activated carbon. In this case, it is preferable that the electrode contains 5 to 20% by mass of carbon black as a conductive material. If it is less than 5% by mass, the effect of reducing the resistance of the electrode is small, and usually, high conductivity carbon black cannot make the capacity of the electric double layer capacitor as large as activated carbon. Therefore, the content is preferably 20% by mass or less.

As the activated carbon, natural plant tissue such as coconut shell, synthetic resin such as phenol, coal, coke,
A fossil fuel-derived material such as pitch can be used as a raw material after activation treatment. The method for activating activated carbon varies depending on the raw material used, but is usually steam activation or KOH.
There is an alkali activation method such as an activation method. From the viewpoint of metal impurities, the steam activation method using a synthetic resin as a raw material is most suitable.

The electrode in the present invention can be obtained, for example, by kneading a mixture of a carbon material and polytetrafluoroethylene and then molding it into a sheet. The electrode sheet thus obtained is preferably thermocompression-bonded to both surfaces of the current collector, or adhered via a conductive adhesive or the like. Instead of kneading, a solvent containing the above binder (water, N-methyl-2-pyrrolidone, etc.) is mixed to form a slurry, which is applied to both surfaces of the current collector and dried to form electrodes. Good. Although the thickness of the electrode is not limited, it is preferably about 10 μm to 0.5 mm.

The current collector may be any metal that is electrochemically resistant to corrosion, and in the case of a coin type structure, a housing member such as a metal lid and a metal case often serves as the current collector. In the case of a cylindrical structure or a rectangular structure, a roughened foil of metal such as aluminum, stainless steel, nickel or tantalum, a net or the like is used, and among them, a foil of stainless steel and aluminum, a net or the like or an alloy thereof is preferable. It is more preferable that the aluminum foil has a purity of 99.9%, and further, a purity of 99.99%. The current collector made of metal foil preferably has a thickness of about 10 μm to 0.5 mm.

It is preferable to form a plurality of current collecting leads on the electrode body. The current collecting lead is formed by attaching conductive tab terminals, wires, tapes, ribbons, etc. to the portion of the current collector where the electrodes are not formed by welding or the like.

In the present invention, the separator is not particularly limited as long as it is a porous separator through which ions can pass, and it may be a microporous polyethylene film, a microporous polypropylene film, a polyethylene non-woven fabric, a polypropylene non-woven fabric, a polypropylene non-woven fabric or a glass. Fiber-blended non-woven fabric, glass mat filter, cellulose paper, kraft pulp, sisal hemp, Manila hemp and the like can be preferably used.

The thickness of the separator is preferably 20 to 200 μm, more preferably 30 to 100 μm. From the viewpoint of liquid absorbability to electrolyte, liquid retention, and internal resistance, the higher the porosity, the more preferable, but defects such as pinholes increase as the porosity increases, leading to poor self-discharge.
The range of 0% is preferable, and more preferably 60 to 85%.
Is the range.

[0039]

The present invention will be described in detail below with reference to Examples (Examples 1 to 5) and Comparative Examples (Examples 6 to 8).

Example 1 Steam Activated Specific Surface Area 200
Ethanol was added to a mixture consisting of 80% by weight of 0 m ² / g of phenolic resin-based activated carbon, 10% by weight of polytetrafluoroethylene and 10% by weight of carbon black, and kneaded to form a sheet, which was rolled into a thickness of 0.6 mm. Then, the obtained electrode sheet body was punched into a disk having a diameter of 12 mm.

The disc-shaped electrodes were bonded to the inside of the positive electrode side and the negative electrode side of a stainless steel case, which also serves as a collector and a housing member, by using a graphite-based conductive adhesive.
Next, this stainless steel case was heat-treated under reduced pressure to remove water and the like, and 1.5 mol / L of (C ₂ H ₅ ) ₃ (C
H ₃ ) NBF ₃ (CF ₃ ) is contained in the electrode and the electrolyte solution is impregnated in the electrode, polypropylene fiber nonwoven fabric separator paper is sandwiched between the electrodes, and the stainless case is an insulator gasket. Then, it was caulked and sealed to obtain a coin-type electric double layer capacitor having a diameter of 18.4 mm and a thickness of 2.0 mm.

Example 2 An electrolytic solution containing 1.5 mol / L of (C ₂ H ₅ ) ₃ (CH ₃ ) NBF ₂ (CF ₃ ) ₂ and containing 75% by volume of propylene carbonate and 25% by volume of methyl ethyl carbonate. A coin type electric double layer capacitor was obtained in the same manner as in Example 1 except that an electrolytic solution containing a mixed solvent as a solvent was used.

Example 3 Ethanol was added to a mixture consisting of 80% by mass of activated carbon of a phenol resin type having a specific surface area of 2000 m ² / g activated by molten KOH, 10% by mass of polytetrafluoroethylene and 10% by mass of carbon black and kneaded. Then, it was further rolled to obtain an electrode sheet body having a thickness of 0.1 mm.

The obtained electrode sheet body was attached to both sides of an aluminum foil whose surface was etched with a conductive adhesive. Next, heat treatment was performed under reduced pressure to remove water and the like, the glass fiber separator was sandwiched between positive and negative electrodes, and wound with a core having a diameter of 2 mm to obtain a cylindrical element having a diameter of 7 mm and a height of 20 mm.

An electrolytic solution of 1.5 mol / L was added to this.
(C_TwoH₅) (CH_Three)_ThreeNB (CF _Three)_FourContaining
Impregnate the electrolyte with ropylene carbonate as the solvent
Insert butyl rubber, seal it with a caulking machine, and
An electric double layer capacitor was obtained.

[Example 4] As Example 3 except that the electrolytic solution containing 1.5 mol / L of ethylmethylimidazolium trifluoromethyltrifluoroborate given by the formula 8 and containing propylene carbonate as a solvent was used. Similarly, a cylindrical electric double layer capacitor was obtained.

[0047]

[Chemical 5]

Example 5 Resol resin was used in a nitrogen atmosphere at 65
Specific surface area of 2000m activated by melting KOH by firing at 0 ° C
Ethanol is added to a mixture of 80% by mass of carbon material of ² / g, 10% by mass of polytetrafluoroethylene and 10% by mass of carbon black, and the mixture is kneaded and roll-rolled to form an electrode sheet body having a thickness of 0.6 mm and further having a diameter of 12m
I punched it into a disk of m.

The disk-shaped electrodes were bonded to the insides of the positive electrode side and the negative electrode side of a stainless steel case serving as a collector and a housing member, respectively, using a graphite-based conductive adhesive. Next, this stainless steel case was heat-treated under reduced pressure to remove water and the like, and 1.5 mol / L of (C ₂ H ₅ ) ₃
Sulfolane 80 containing (CH ₃ ) NBF ₃ (CF ₃ ).
The electrode is impregnated with an electrolytic solution containing a mixed solvent of 20% by volume of methyl ethyl carbonate and 20% by volume of methyl ethyl carbonate, and a polypropylene fiber nonwoven fabric separator is sandwiched between both electrodes.
The stainless steel case was caulked and sealed via a gasket which was an insulator to obtain a coin type electric double layer capacitor having a diameter of 18.4 mm and a thickness of 2.0 mm.

[Example 6] The same as Example 1 except that an electrolyte containing 1.5 mol / L of (C ₂ H ₅ ) ₃ (CH ₃ ) NBF ₄ and using propylene carbonate as a solvent was used as the electrolyte. A coin type electric double layer capacitor was obtained.

[Example 7] A mixed solvent of 80% by volume of propylene carbonate and 20% by volume of methylethyl carbonate was used as a solvent, which contained 1.5 mol / L of ethylmethylimidazolium tetrafluoroborate given by the formula 8 as an electrolytic solution. A cylindrical electric double layer capacitor was obtained in the same manner as in Example 3 except that the electrolytic solution was used.

[0052]

[Chemical 6]

[Example 8] A mixed solvent containing 80% by volume of sulfolane and 20% by volume of methyl ethyl carbonate as a solvent, containing 1.5 mol / L of (C ₂ H ₅ ) (CH ₃ ) ₃ NBF ₄ as an electrolytic solution. A coin type electric double layer capacitor was obtained in the same manner as in Example 5 except that the electrolytic solution was used.

[Evaluation] The voltages shown in Table 1 were applied to the electric double layer capacitors of Examples 1 to 8 to measure the initial capacitance and the initial internal resistance. In addition, the capacitance decrease rate after keeping for 1000 hours in a constant temperature and humidity chamber at 70 ° C and a humidity of 50% was measured,
The results are also shown in Table 1.

[0055]

[Table 1]

[0056]

According to the present invention, it is possible to provide an electric double layer capacitor having high withstand voltage and excellent reliability.

Continued front page    (72) Inventor Katsuji Ikeda             1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa             Asahi Glass Co., Ltd.

Claims (4)

[Claims] 1. An electric double layer capacitor having a pair of polarizable electrodes and an electrolytic solution forming an electric double layer at an interface between the polarizable electrodes, wherein the electrolytic solution contains an organic solvent and an electrolyte, And the electrolyte is a cation and an anion represented by the formula 1 (where n is an integer of 0 to 3, p is an integer of 0 to 4 and n + p ≦ 4, m and k are each independently an integer of 1 to 4, An electric double layer capacitor comprising a salt of m ≠ k). [Chemical 1] 2. The cation is represented by any one of formulas 2 to 7.
Cation (however, in the formula 2 or the formula 3, R¹, R^Two, R
^ThreeAnd R^FourAre independently alkyl having 1 to 3 carbon atoms
Basis. In formulas 4 to 6, R⁶Is hydrogen atom, fluorine atom, carbon number
1 to 20 hydrocarbon groups (one or more of the hydrogen atoms are fluorine atoms)
Child, or may be substituted with a hydroxyl group),
R ⁵, R⁷, R⁸And R⁹Are independent hydrogen
Child, a fluorine atom or a hydrocarbon group having 1 to 10 carbon atoms (water
One or more of the elementary atoms is replaced by a fluorine atom or a hydroxyl group
May be). In formula 7, R¹⁰Is a hydrogen atom, fluorine atom
Child, hydrocarbon group having 1 to 20 carbon atoms (one or more hydrogen atoms
May be substituted with a fluorine atom or a hydroxyl group)
Yes, R¹¹, R¹², R^Thirteen, R¹⁴Are independent
A hydrocarbon group having 1 to 10 carbon atoms (one or more of hydrogen atoms
May be substituted with a fluorine atom or a monovalent organic group
I). The electric double layer capacitor according to claim 1. [Chemical 2] 3. Anions of BF ₃ (CF ₃ ) ⁻ , BF ₂ (C
The electric double layer capacitor according to claim 1, which is at least one selected from the group consisting of F ₃ ) ₂ ⁻ and BF (CF ₃ ) ₃ ⁻ . 4. The cation is (C ₂ H ₅ ) ₃ (CH ₃ )
The electric double layer capacitor according to claim 1, 2 or 3, which is one or more selected from the group consisting of N ⁺ , (C ₂ H ₅ ) (CH ₃ ) ₃ N ⁺ and ethylmethylimidazolium ion.