JPH04206919A - electric double layer capacitor - Google Patents

Abstract

PURPOSE:To contrive to reduce an internal resistance and make a capacity higher to improve a withstand voltage by constituting an apparatus of polarizable electrodes using an activated carbon block formed by carbonization and activation of a resin foam and of specific electrolytic solution coming in contact with the electrodes. CONSTITUTION:An activated carbon block is formed by carbonization and activation of a phenol formalin resin foam, substantially has an open-cell structure and has 0.1g/cm<3> or more bulk density and 500m<2>/g or more specific surface area. A pair of polarizable electrodes 1, 1 using the block and separator 3 arranged between are housed in a case 5 and impregnated with an electrolytic solution. This electrolytic solution is an organic electrolytic solution formed by dissolution of an electrolyte and ether compound represented by formula [I] in an organic solvent with 1.5cps [25 deg.C] or more viscosity. In the formula, R<1> and R<2> are straight chain or branched alkyl group with 1-4C and may be identical or different or may form a ring jointly.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an electric double layer capacitor using carbon-based electrodes.

Technical Background of the Invention In recent years, electric double layer capacitors, which have a long life and are capable of high-speed charging and discharging, have been used as backup power sources for electronic devices. An electric double layer capacitor is a type of capacitor that consists of a polarizable electrode and an electrolyte in contact with the polarizable electrode, and that charges are accumulated in the electric double layer where positive and negative electrodes are arranged and distributed facing each other at the interface between these electrodes. The capacity of the electric double layer increases according to the area of the electrode interface.

Activated carbon, which has a large specific surface area and excellent conductivity, has been attracting attention as a polarizable electrode used in such electric double layer capacitors.

Polarizable electrodes using activated carbon include, for example, electrodes in which activated carbon powder paste I is pressed onto a conductive rubber electrode, a metal collector electrode formed on one side of a bundle of activated carbon fibers or a cloth made of carbon fibers by thermal spraying. Electrodes, electrodes made of textiles made of activated carbon fibers and conductive wires, electrodes made by molding, carbonizing, and activating powdered phenolic resin that has thermal adhesive properties on a base made of fiber metal, etc. can be made. (Japanese Patent Publication No. 63-10574, Japanese Patent Publication No. 61-110416
Publication No. 14492, Special Publication No. 14492, Special Publication No. 14492, Special Publication No. 1983-
55205, JP-A-63-194319).

However, in a polarizable electrode in which activated carbon powder paste is pressed onto a conductive rubber electrode, the paste is prepared with activated carbon powder and a suitable binder, so the amount of activated carbon fiber cloth in one polarizable electrode is reduced. The advantages of activated carbon, such as excellent conductivity and large specific surface area, cannot be fully utilized, and the resulting electric double layer capacitor has the disadvantage of having a large internal resistance and a small capacity.

Polarizable electrodes made by thermally spraying metal onto activated carbon fibers or cloth using activated carbon fibers have a large contact resistance because the contact surface between the fibers is small, and this contact surface is deformed by external pressure applied during the manufacturing process. However, an electric double layer capacitor using this type has a disadvantage that the internal resistance becomes large and unstable.

In addition, when manufacturing large-capacity polarizable electrodes using activated carbon fiber cloth, the cloth must be laminated, which results in high resistance in addition to the contact resistance between the fibers and the high resistance between the cloths in surface contact. As a result, the electrical resistance becomes even more unstable.

A polarizable electrode made of a fabric of activated carbon fibers and conductive wires,
Polarizable electrodes are made by molding, carbonizing, and activating powdered phenolic resin with heat-adhesive properties onto a base made of metal fibers. Although these electrodes are effective in lowering internal resistance, the amount of activated carbon in the polarizable electrodes is low. Because of the small amount of metal, it is not suitable for increasing capacity, and the problem that it is difficult to process conductive metal into fibers cannot be ignored. As described above, each of the conventional polarizable electrodes has its own drawbacks.

On the other hand, the characteristics of an electric double layer capacitor are greatly influenced by the electrolyte; for example, the withstand voltage of an electric double layer capacitor is
In order to obtain an electric double layer capacitor with high withstand voltage, which is regulated by the decomposition voltage of the solvent used in the electrolytic solution, it is preferable to use an organic electrolytic solution using an organic solvent that is difficult to be electrolyzed. Furthermore, since the heat resistance of an electric double layer capacitor is regulated by the boiling point of the solvent, it is preferable to use an organic solvent with a high boiling point in order to obtain an electric double layer capacitor with high heat resistance.

However, organic solvents with a high boiling point have a high viscosity of 1.5 cps (centiboise) [25°C or more], so when such organic solvents are used, the result is an electrolytic solution with high viscosity and low electrical conductivity, which makes it difficult to use electric double layer capacitors. There was a problem in that it increased the internal resistance and internal impedance of the device.

Furthermore, the capacity of an electric double layer capacitor is affected by the relationship between the ion diameter of the electrolyte and the average pore diameter of the polarizable electrode, in addition to the properties of the electrolyte itself such as ion concentration. Optimal material combinations with solutions are required.

OBJECTS OF THE INVENTION The present invention aims to solve the problems associated with the prior art, and aims to provide an electric double layer capacitor that is easy to manufacture and has good characteristics.

Summary of the Invention An electric double layer capacitor according to the present invention includes a polarizable electrode using an activated carbon block formed by carbonizing and activating a resin foam, and an electrolyte in contact with the polarizable electrode. is an organic electrolytic solution in which an electrolyte and an ether compound represented by the following general formula [A] are dissolved in an organic solvent having a viscosity of 0.2 to 1.5 cps [25°C1].

R'-0-R2...[A] [In the above formula [A], R1 and R2 are linear or branched alkyl groups having 1 to 4 carbon atoms, and may be the same or different. or R1 and R2 may jointly form a ring] According to the electric double layer capacitor of the present invention, the electrical resistance of the activated carbon block constituting the polarizable electrode is small, and the bulk density is low. In addition to reducing internal resistance and increasing capacity due to the large specific surface area, an ether compound represented by the above formula [A] is added to the organic electrolyte to further improve electrical conductivity. An electric double layer capacitor with low resistance and internal impedance and high withstand voltage can be manufactured.

DETAILED DESCRIPTION OF THE INVENTION The electric double layer capacitor according to the present invention will be specifically described below.

The electric double layer capacitor according to the present invention uses an activated carbon block obtained by carbonizing and activating a resin foam as a polarizable electrode. The resin foam used in the present invention is a resin porous body having a cellular structure obtained by mixing a resin prepolymer with a foaming agent, a curing agent, etc., and foaming and curing the mixture.

Specifically, such resins include polyurethane,
Thermosetting resins such as phenol resin, furfural resin, epoxy resin, furan resin, polyisocyanurate resin, polyimide resin, and urea resin are mainly used.

Among these resin foams, phenolic resins, especially resol-type phenolic resins that use resol as a prepolymer, are preferred because they have uniform cell shapes, are easy to manufacture, and can be expected to have high yields when carbonized and activated. Preferably, foam is used.

Resoles can be obtained by reacting phenols and aldehydes in the presence of an alkali catalyst according to known methods.

Specific examples of such phenols include phenol, cresol, xylenol, and resorcinol, with phenol being particularly preferred.

Specific examples of the aldehydes include formaldehyde, trioxane, acetaldehyde, and furfural, with formaldehyde being particularly preferred.

In addition, as the alkali catalyst, specifically, LiOH
, KOH, NaOH, NH3, NH40H1, ethanolamine, ethylenediamine, triethylamine and the like.

As the blowing agent for obtaining the resin foam, conventionally known decomposition-type, reaction-type and evaporation-type blowing agents can be used, but among these, it is preferable to use an evaporation-type blowing agent that operates at relatively low temperatures. Specifically, butane, pentane, hexadi,
Examples include paraffinic hydrocarbons such as heptane, alcohols such as methanol, ethanol and butanol, halogenated hydrocarbons such as dichlorotrifluoroethane (Freon 123), ethers and mixtures thereof.

For foaming and curing, a curing agent is used together with a foaming agent. As this curing agent, a conventionally known curing agent is selected and used depending on the type of prepolymer. In the case of a prepolymer or resol type phenol-formalin resin, specifically, inorganic acids such as sulfuric acid, phosphoric acid, and hydrochloric acid, and organic acids such as paratoluenesulfonic acid and cresolsulfonic acid are used.

Resin foams can be obtained by mixing, for example, the above-mentioned resol-type phenolic resin prepolymer with a blowing agent, a curing agent, and if necessary, additives such as a foam stabilizer, filler, and stabilizer, either all at once or sequentially. The creamy material is heated and fed into a heated mold, wooden mold, or cardboard, or between a double belt conveyor, and foamed, hardened,
It can be obtained by trimming if necessary. Among these methods, the method of supplying a creamy substance into a mold and gradually foaming it at a slow speed is preferable in order to obtain a uniform foamed product. On the contrary, the cell structure of foams that are rapidly expanded and hardened on a conveyor belt, for example, tends to be non-uniform and the direction and location of the foaming is not uniform, leading to the problem of variations in internal resistance. Therefore, it is desirable to obtain a foam as uniform as possible.

Further, it is desirable that the bubbles have a large number of open cells in consideration of contact with the electrolytic solution and ion mobility.

The activated carbon block used in the present invention is produced by carbonizing and activating a molded resin foam as it is or cutting it into a desired shape such as a plate.

The carbonization treatment is performed by firing the resin foam in a non-oxidizing atmosphere. That is, the resin foam is prepared under reduced pressure or in Ar.
Among gases, He gas, N2 gas, C02 gas, halogen gas, ammonia gas, N2 gas, and mixed gases thereof, preferably 500 to 1200°C1, especially 600°C.
It is fired at a temperature of ~900°C (7). In this way, the foam is carbonized and a porous carbon body is obtained. Although there is no particular restriction on the rate of temperature increase during firing, it is preferable to increase the temperature gradually around 200 to 600°C, where decomposition of the resin generally begins.

The activation treatment is performed by heating the obtained porous carbon material in the presence of an oxidizing gas. Processing temperature is usually 800-1200°C
Do it with If the treatment temperature is too low, activation will not proceed sufficiently,
Only small specific surface areas can be obtained. On the other hand, if the treatment temperature is too high, cracks will easily form in the carbide foam.

The oxidizing gas in the present invention refers to an oxygen-containing gas such as water vapor, carbon dioxide, air, oxygen, etc. However, for ease of normal operation, these gases may be combined with an inert gas such as combustion gas, N2 gas, etc. Used as a mixed gas. The exposure time to the oxidizing gas depends on the concentration of the oxidizing gas and the treatment temperature, but as a guide, it should be within a range that does not damage the shape of the carbide foam.

Furthermore, the activation treatment may be a chemical activation method other than the above-mentioned gas activation method, or a combination of both methods. The chemical activation method is a method in which chemicals such as zinc chloride, phosphoric acid, potassium sulfide, etc. are added to the resin foam and then heated in an inert gas atmosphere to simultaneously carbonize and activate the foam.

The activated carbon porous material that can be used in the present invention has an entirely or substantially open cell structure, and has a bulk density of 0.1 g/cm.
” or more, preferably 0.15 g/cm3 to 0.7
0 g/cm3 and a specific surface area of 500 m2/g or more, preferably 700 n (7 g or more, more preferably 700 to 2000 rri'/g) to improve contact with the electrolyte and provide a capacitor with a large capacity. preferred above.

In the present invention, a substantially open cell structure means that the volume of the electrolytic solution impregnated into the activated carbon block under vacuum (10-'torr or less) is smaller than the theoretically calculated spatial volume of the activated carbon block. This refers to a case where the ratio is 60% or more, preferably 80% or more, and more preferably 90% or more.

In the present invention, the open cell ratio was determined as follows.

Examples of the types of electrolytes used during measurement include 3
0% by weight sulfuric acid (density 1.215g/cc (25°C))
Alternatively, an electrolytic solution (density 1.088 g/cc (25°C)) containing 10% by weight of tetraethylammonium tetrafluoroborate in propylene carbonate is used.

The theoretical space volume (V□) was measured using a pycnometer with a Gehrsack thermometer and toluene as an immersion liquid after pulverizing and drying the activated carbon block.

The volume (Vt, ) of the electrolytic solution impregnated into the activated carbon block is calculated from the impregnated surface weight (Wl) of the activated carbon block, the weight after impregnation (W2), and the density of the electrolytic solution (D+, ).

-15=V, , = (W2-W, )/DL Therefore, the open cell ratio is calculated as follows: VL/V, X 100 [:%:].

Since such an activated carbon block has a substantially open cell structure, it has a large specific surface area and is easily infiltrated with an electrolyte. In addition, this activated carbon block exhibits high strength because it has a continuous skeleton, and can manufacture self-supporting polarizable electrodes with a large specific surface area that are difficult to break.In addition, compared to electrodes using activated carbon fibers, this activated carbon block has a high strength and has a low electrical resistance. Small and stable. Furthermore, the activated carbon block can be trimmed to a desired thickness and shape to form polarizable electrodes of any shape, making it easy to manufacture electric double layer capacitors with a large planar size, thick thickness, and high capacity. In addition, the volume of the polarizable electrode can be reduced to reduce the size of the entire capacitor.

Since the activated carbon block used in the present invention has a suitable average pore diameter, ions can freely enter and exit the organic electrolyte, making it possible to obtain a polarizable electrode with a substantially large surface area. .

A current collector made of a conductive material is formed on one surface of the polarizable electrode made of such an activated carbon block. This current collector can be formed extremely easily by directly plasma spraying metal onto an activated carbon block, or by surface-contacting or bonding a conductive plate such as a metal plate, graphite plate, or conductive resin plate. It can be installed in

The electric double layer capacitor according to the present invention uses an organic electrolyte solution together with a polarizable electrode using such an activated carbon block.

As the electrolyte for such an organic electrolyte solution, in the present invention, a quaternary onium salt represented by the following general formula [I] is particularly preferably used.

In formula [I], A represents nitrogen or phosphorus.

Among the quaternary onium salts represented by the above general formula [I], quaternary ammonium salts represented by the following general formula [II] are more preferred.

However, in these formulas [1] and [II], n is 1
It is an integer of ~3.

Furthermore, R1, R2, Ril and R4 are either hydrogen, an alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and may be the same except that all of them are hydrogen. May be different.

Among these, a quaternary osmium salt in which at least one of R1, R2, R3 and R4 is a lower alkyl group having 1 to 4 carbon atoms; and at least one of R1, R2, R3 and R4;
A quaternary ammonium salt in which is an aryl group having 6 to 18 carbon atoms and one or two benzene nuclei is preferred.

The lower alkyl group having 1 to 4 carbon atoms may be linear or branched.

Moreover, Xn- is an anion having a valence corresponding to the above n, specifically, BF4-1PF6-1 (104\
ASF6-1SbF6-1AACβ4-1Rf SO3
-(Rf is a fluoroalkyl group having 1 to 8 carbon atoms)
,F-,Cl! -1B r -N 03-1HCO, -
Any of -valent anions such as 1HSO4-, divalent anions such as so4'-, and trivalent anions such as P○43- may be used.

In particular, Xn- is BF4-1PF6-1Cj20
A quaternary ammonium salt which is either 4- or RfSO3- is preferred. Even if electrolytes are used alone,
Two or more types may be used in combination.

Specifically, such ammonium salts include tetraedylammonium tetrafluoroborate (Et4N" B
F4-), tetrabutylammonium tetrafluoroborate (Bu<N″' BF4-), tetramethylammonium tetrafluoroborate (Me4N+BF4-), tetrafluoride-] 9- Ammonium borate, boron tetrafluoride 47 ammonium fluoroborate, such as benzyltrimethylammonium acid, 6
Tetraethylammonium fluoride phosphate (Et4N+P
F, -), tetrabutylammonium hexafluorophosphate (Bu4N' PF6-), tetramethylammonium hexafluorophosphate (Me4N"PF, -), ammonium hexafluorophosphate (NH4" PFg-), 6 Examples include ammonium hexafluoride phosphates such as benzyltrimethylammonium fluoride phosphate.

In the electrolytic solution used in the present invention, the electrolyte is preferably used in an amount of 0.1 to 2 equivalents, particularly 0.5 to 1.5 equivalents in the electrolytic solution.

In the present invention, such an electrolyte and an ether compound represented by the following general formula [A]], , 5 c p s [
25°C] or higher, preferably 1.13-3.0 cps[
An electrolytic solution is obtained in addition to an organic solvent with a viscosity of 25°C].

R'-0-R2...[A] The organic solvent has the above-mentioned viscosity and may be heated or used.

Specific examples of such organic solvents include propylene carbonate I, ethylene carbonate, γ-butyrolactone, sulfolane, dimethylformamide, dimethylsulfoxide, N-methylacetamide, N-methylformamide, and the like. I can do it.

In the ether compound represented by the above formula [A] (hereinafter also referred to as ether compound [A]), R' and R2 are linear or branched alkyl groups having 1 to 4 carbon atoms. Further, R1 and R2 may be the same or different (or may jointly form a ring).

Specifically, such ether compounds [A] include tetrahydrofuran, diethyl ether, dimethyl ether, 1,2-dimethoxyethane, 1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 1,
Examples include 4-dioxane and diethylene glycol dimethyl ether.

The ether compound [A] has a viscosity of 0.2 to 1.1 cp
s[25°C1, which is low, and therefore can reduce the viscosity of the electrolyte, and is electrically stable and can dissolve the electrolyte.

Such an ether compound [A] is an ether compound [
The viscosity of the mixture of A] and the solvent is 0.4 to 2.0 cp
s[25°C1, especially 0.7-1.5 c p s[2
It is preferable to use an amount that gives a temperature of 5°C1.

By using the ether compound [A] in such an amount, the movement of ions in the electrolyte becomes easy, the internal resistance and internal impedance are lowered, and the solvent is electrolyzed even when a high voltage is applied. Therefore, an electric double layer capacitor with excellent voltage resistance can be obtained.

The electrolytic solution used in the present invention may further contain additives such as trialkylphosphine and triarylphosphine, which are considered to have an effect as an electrolyte decomposition inhibitor.

Specific examples of substances that act as decomposition inhibitors include triphenylphosphine, triethylphosphine, and tributylphosphine.

Here, a specific structure of an electric double layer capacitor using polarizable electrodes and an organic electrolyte as described above will be explained with reference to the accompanying drawings.

The attached FIG. 1 shows an example of an electric double layer capacitor according to the present invention, and as shown in the figure, this electric double layer capacitor includes a pair of polarizable electrodes 1.1 and a conductor between them. The separator 3 to be disposed is housed in a case 5. In addition, in the figure, 6 is a lead wire.

The case 5 is made of plastic case halves 5a, 5.
b and an insulating packing 4 interposed therebetween.

To assemble an electric double layer capacitor equipped with such members, first, the polarizable electrodes 1, 1 and separator 3 are degassed and then impregnated with an electrolytic solution, and then a graphite plate or the like is placed between the separators 3 and 3. The polarizable electrodes are placed facing each other with a distance of ±1.1 between the polarizable electrodes with the current collector 2 on the outside. This is done by tightening with screws 7.

The electric double layer capacitor according to the present invention has no particular structural limitations other than the use of polarizable electrodes and an organic electrolyte as described in 1. It is also possible to adopt a structure that also serves as a current collector.

Effects of the Invention According to the electric double layer capacitor according to the present invention, the electrical resistance of the activated carbon block constituting the polarizable electrode is small;
Due to its large bulk density and specific surface area, it is possible to reduce internal resistance and increase capacity. Furthermore, since the organic electrolyte contains an ether compound shown by the above formula [A] that has a viscosity-lowering effect, electrolytic It is possible to provide an electric double layer capacitor that facilitates the movement of ions in the liquid, has low internal resistance and internal impedance, and has high voltage resistance.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

-241 Example 1 First, 100 parts by weight of resol (phenol-formalin resin prepolymer), 10 parts by weight of paratoluenesulfonic acid as a hardening agent, and 1.5 parts by weight of dichlorotrifluoroethane as a blowing agent were sufficiently mixed using a high-speed mixer. After stirring,
Pour this mixture into a mold, cover it, and leave it in an air oven at 80°C for 30 minutes.
cm, width 30cm, thickness 3cm, bulk density 0, 3g
/ crT! A plate-shaped phenolic resin foam was obtained.

This molded plate has a length of 20cm+, a width of 10cm, and a thickness of 1.0cm.
After cutting into pieces of 1.5 m long, they were placed in a Matsufuru furnace and heated under a nitrogen atmosphere at a heating rate of 60°C/hour to a temperature of 600°C, held at this temperature for 1 hour, cooled, and then heated vertically. 16c
m, width 8 cm, thickness 0.8 cm, bulk density 0.29 g
A plate-like porous carbon material of /crl was obtained.

Further, the temperature of this plate-shaped carbon porous body was raised to 950°C, steam was introduced into the combustion gas, and the temperature was maintained for 16 hours and then cooled.

The bulk density, strength, and specific surface area of the obtained activated carbon block were investigated.

The results are shown in Table 1.

Table 1 Tetraethylammonium fluoroborate (Et4N”
BF4- ) 27.1 g (0,1) was dissolved in a mixed solvent of propylene carbonate 1-/tetrahydrofuran-872 to prepare a 250 mN electrolytic solution.

The activated carbon block was cut into pieces 5 cm long, 2 cm wide, and 0.4 cm thick using a band saw to obtain two activated carbon plates.

This plate is degassed under reduced pressure and then impregnated with the electrolyte,
The electric double layer capacitor shown in Figure 1 was created by sandwiching a polypropylene nonwoven fabric between two plates as a separator, and then facing each other with a pair of polarizable electrodes made by applying a 1 mm thick graphite plate from the outside of both activated carbon plates. was created.

For the obtained capacitor, at a constant current of 30 mA, 3
The battery was charged and discharged until (2) and the capacity and internal resistance were measured.

The results are shown in Table 2.

Example 2 The same procedure as in Example I was carried out except that 0.125 mol of tetraethylammonium hexafluorophosphate was used instead of tetraethylammonium tetrafluoroborate in Example 1.

The results are shown in Table 2.

Example 3 The same procedure as in Example 1 was carried out except that 1,3-dioxolane was used instead of tetrahydrofuran.

The results are shown in Table 2.

Example 4 The same procedure as in Example 1 was conducted except that 1,2-dimethoxyethane was used instead of tetrahydrofuran.

The results are shown in Table 2.

Comparative Example 1 The same procedure as in Example I was carried out except that propylene carbonate was used in place of the mixed solvent propylene carbonate 1-/tetrahydrofuran-8/2 used in Example 1.

The results are shown in Table 2.

Comparative Example 2 The same procedure as in Example 2 was carried out except that propylene carbonate was used in place of the propylene carbonate/tetrahydrofuran-8/2 mixed solvent used in Example 2.

Table 2 PC: Propylene carbonate THF Tetrahydrofuran DMA: 1,2-dimethoxyethane

[Brief explanation of the drawing]

FIG. 1 attached herewith is a sectional view showing a preferred embodiment of the electric double layer capacitor according to the present invention. In the figure, 1 is a polarizable electrode, 2 is a current collector, 3 is a separator, 4 is an insulating packing, and 5 is a case.Patent applicant Mitsui Petrochemical Industries Co., Ltd. Representative Patent attorney Shun Suzuki 1st Department 1 figure b213

Claims (9)

[Claims] (1) It has a polarizable electrode using an activated carbon block made by carbonizing and activating a resin foam, and an electrolytic solution in contact with the polarizable electrode, and the electrolytic solution is an electrolyte and the following general formula [
The ether compound represented by A] has a viscosity of 1.5 cps [
An electric double layer capacitor characterized in that it is an organic electrolyte solution dissolved in an organic solvent at a temperature of 25° C.] or higher. R^1-O-R^2...[A] [In the above formula [A], R^1 and R^2 have 1 to 1 carbon atoms
4 straight-chain or branched alkyl groups, each of which may be the same or different, and R^1 and R^2 may jointly form a ring] (2) The electric double layer capacitor according to claim 1, wherein the activated carbon block has a bulk density of 0.1 g/cm^3 or more and a specific surface area of 500 m^2/g or more. (3) The activated carbon block is made by carbonizing and activating a phenol-formalin resin foam and has a substantially open cell structure. double capacitor. (4) The organic solvent is propylene carbonate, ethylene carbonate, γ-butyrolactone, sulfolane,
4. The electric double layer capacitor according to claim 1, wherein the electric double layer capacitor is made of at least one selected from dimethylformamide and dimethyl sulfoxide. (5) The ether compound represented by the above formula [A] is tetrahydrofuran, diethyl ether, dimethyl ether, 1,2-dimethoxyethane, 1,3-dioxolane,
5. The electric double layer capacitor according to claim 1, wherein the electric double layer capacitor is at least one selected from 3,3-dimethyl-1,3-dioxolane. (6) Claims 1 to 5, wherein the electrolyte is a quaternary onium salt represented by the following general formula [I].
The electric double layer capacitor described in . ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [I] [In the above formula [I], A is nitrogen or phosphorus, n is an integer from 1 to 3, R^1, R^2 , R^3 and R
^4 is hydrogen, an alkyl group having 1 to 18 carbon atoms, and 6 carbon atoms.
~18 aryl groups, each of which may be the same or different except that all are hydrogen, and X
^n^- is an anion with a valence corresponding to n above] (7) The electrolyte is a fourth compound represented by the following general formula [II].
7. The electric double layer capacitor according to claim 6, wherein the electric double layer capacitor is a class ammonium salt. ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [II] [In the above formula [II], n is an integer from 1 to 3, and R^1
, R^2, R^3 and R^4 are hydrogen, carbon number 1-1
8 alkyl group or an aryl group having 6 to 18 carbon atoms, which may be the same or different except that all are hydrogen, and X^n^- corresponds to n above. It is an anion with a valence.] (8) The quaternary ammonium salt is such that in the above formula [II], X^n^- is BF_4^-, PF_6^-, ClO
_4^-, AsF_6^-, SbF_6^-, AlCl
_4^-, RfSO_3^- (Rf is a fluoroalkyl group having 1 to 8 carbon atoms), F^-, Cl^-, Br^
-, NO_3^-, SO_4^2^- and PO_4^
8. The electric double layer capacitor according to claim 7, wherein the electric double layer capacitor is any one of 3^-. (9) The quaternary ammonium salt according to claim 8, wherein in the above formula [II], X^n^- is either BF_4^- or PF_6^-. Electric double layer capacitor.