JPH0917698A - Electric double layer capacitor - Google Patents

Abstract

PURPOSE: To improve withstand voltage of a capacitor by using an electrolytic liquid having a solvent mainly composed of elythritan or its delivative. CONSTITUTION: An electrolytic liquid having a solvent mainly composed of elythritan or its delivative is used. As the delivative of elythritan, hydrogen atoms of one or two pieces of a hydroxyl radical of are replaced with an alkyl radical or an acetyl radical of a carbon number 1 to 4 are used. Further, an electrolytic liquid having a solvent mainly composed of maleic acid, carbonate or its ester is used. As a maleic acid carbonate ester, that in which hydrogen atoms of one or two pieces of carboxyl radicals of maleic acid carbonate are replaced with an alkyl radical having a carbon number 1 to 4, is used. Further, as an electrolyte, tetraalkyl ammonium salt or tetraalkyl phosphonium salt of acid to be selected from a radical consisting of perchloric acid, phosphoric acid hexafluorie, borofluoric acid and trifluoromethane sulphonium sulfonic acid.

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 capable of instantly charging and discharging a large amount of electricity.

[0002]

2. Description of the Related Art Conventionally, there are roughly two types of electric double layer capacitors using activated carbon powder or activated carbon fibers as a polarizable electrode. The first one has a structure shown in FIG. 1 and has a pair of polarized electrodes in which a layer 2 made of a mixture of activated carbon powder and polytetrafluoroethylene is coated on a collector net 1 made of aluminum. It is housed in the case 4 after being wound through. The opening of the case 4 is sealed with a rubber cap 5. 6 and 7 are positive and negative leads, respectively. The second structure has the structure shown in FIG. 2, in which one side of the activated carbon fiber 8 has an aluminum current collecting layer 9
It is basically composed of a pair of activated carbon fibers 8 provided with a separator 10, a separator 10 interposed between both electrodes, cases 11 and 12, and a gasket ring 13 that hermetically seals both cases. The cases 11 and 12 are in contact with the aluminum current collecting layer, and also serve as a positive electrode and a negative electrode.

The characteristics of the solvent used for the electrolytic solution of this type of electric double layer capacitor are as follows. (1) High electrolyte solubility. (2) The viscosity is low. (3)
High dielectric constant. (4) The potential window is wide. (5) Wide operating temperature range. (6) High safety. (7) The price is low. From these facts, the optimum system obtained to date is one in which propylene carbonate is used as a solvent and tetraethylammonium tetrafluoroborate is used as an electrolyte, and a working voltage of 2.5 V is obtained as a whole system. .

At present, a plurality of single cell capacitors as described above are combined in series for use where a working voltage of 2.5 V or higher is required. In this case, the capacitance value decreases in inverse proportion to the number of serially connected capacitors of the same volume, so that the size becomes large in order to obtain a high breakdown voltage and large capacity capacitor. Further, as a substitute for a button type battery, a capacitor having a withstand voltage of 3 V in a single cell is also required, and thus improvement of the withstand voltage of the capacitor has a great industrial value.

[0005]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an electric double layer capacitor excellent in withstand voltage.

[0006]

The present invention relates to an electric double layer capacitor utilizing an electric double layer formed at the interface between a polarizable electrode and an electrolytic solution, and an electrolytic solution containing erythritan or a derivative thereof as a solvent. Is used. Further, the present invention uses an electrolytic solution containing maleic acid carbonate or maleic acid carbonate ester as a solvent.

The solvent is propylene carbonate, butylene carbonate, γ-butyrolactone,
1,3-dioxolane, acetonitrile, propionitrile, butyronitrile, dimethylformamide, 1,2
-A mixed solvent containing at least one selected from the group consisting of dimethoxyethane and sulfolane is preferably used. Further, as the electrolyte, a tetraalkylammonium salt or a tetraalkylphosphonium salt of an acid selected from the group consisting of perchloric acid, hexafluorophosphoric acid, borofluoric acid and trifluoromethanesulfonic acid is preferably used.

As the derivative of erythritan, erythritan represented by the following formula (1) in which hydrogen atom of one or two hydroxyl groups is substituted with an alkyl group having 1 to 4 carbon atoms or an acetyl group, It has a low melting point and is preferred. Further, as the maleic acid carbonate ester, one obtained by substituting the hydrogen atom of one or two carboxyl groups of the maleic acid carbonate represented by the formula (2) with an alkyl group having 1 to 4 carbon atoms is preferable because of its low melting point.

[0009]

Embedded image

[0010]

[Function] By using erythritan or erythritan derivative, which has a dielectric constant similar to that of propylene carbonate and high electrolyte solubility, and maleic acid carbonate or maleic acid carbonate ester as a solvent, an electric double layer capacitor having high withstand voltage can be obtained. To be Erythritan or its derivative is more effective because it has a high dielectric constant and a high electrolyte solubility.

[0011]

EXAMPLES First, the results of measuring the decomposition potential, which is an index of the withstand voltage, of the electrolytic solution using various solvents will be described.
FIG. 3 shows a schematic configuration of the test apparatus used here. A test electrode chamber 21 and a counter electrode chamber 22 are separated from each other by a naphtho ion film 23.
The electrolytic solution to be tested is placed in each of the mold cells 20, and the test electrode chamber 21
Graphite electrode (surface area 0.0
7 cm ² ), an Ag / Ag ⁺ electrode as the reference electrode 25, and a Pt electrode as the counter electrode 26 on the counter electrode chamber 22 side, respectively, and fixed to complete the setting of the test apparatus. The solvents shown in Table 1 were used as the electrolytic solution, and No. 1 to
No. 6 is a tetraethylammonium salt of trifluoromethanesulfonic acid, No. 6 7 used tetraethylammonium salt of borofluoric acid. The concentration of solute is 0.65M in each case.

A predetermined electrolytic solution was put in the cell, and a test electrode, a reference electrode and a counter electrode were set in the cell, and then the potential was scanned at a speed of 5 mV / s, and a sharp rising point of the current was detected. It was set to the decomposition potential. Table 1 shows the results. Among the above-mentioned erythritan represented by the formula (1) or a derivative thereof, or maleic acid carbonate represented by the formula (2) or an ester thereof, ethyl carbonate maleate is mentioned and its properties are compared with propylene carbonate. While explaining. In Table 1, ethyl carbonate maleate,
The reductive decomposition potential, initial potential, and oxidative decomposition potential of propylene carbonate are shown. By the way, in the electric double layer capacitor of these two electrolytic solutions, the voltage that can be applied between the positive and negative electrodes is regulated as described below. That is, the voltage that can be applied is governed by the oxidative decomposition potential and the reduction decomposition potential of the electrolytic solution, as shown in Equation 1.

[0013]

[Equation 1]

The positive electrode potential and the negative electrode potential shift from the initial potential at the same rate, but since the potential window of propylene carbonate on the oxidation side is narrower than that on the reduction side, the positive electrode potential changes before the negative electrode potential reaches the reductive decomposition potential. The oxidative decomposition potential is reached. As a result, the voltage that can be applied is governed only by the oxidative decomposition potential of the electrolytic solution, as shown in Equation 2.

[0015]

[Equation 2]

Ethyl carbonate maleate also has a narrower potential window on the oxidation side than the reduction side, but since it is wider than the potential window on the oxidation side of propylene carbonate, ethyl carbonate carbonate functions as a long-term electrochemically stable solvent. It is expected.

[0017]

[Table 1]

Next, specific examples of the present invention will be described. Example 1 A pair of polarizable electrodes formed by applying a paste of a mixture of activated carbon powder, polytetrafluoroethylene and acetylene black on one side of an aluminum net having a size of 1 cm × 5 cm via a separator. It was wound to produce an electric double layer capacitor having a structure as shown in FIG. The electrolyte used was No. 1 in Table 1 of the present invention.

[Examples 2 to 6] N of Table 1 was used as an electrolytic solution.
o. Capacitors having the same configuration as that of the first embodiment except that the capacitors of Nos. 2 to 6 are used will be referred to as Embodiments 2 to 6, respectively. [Comparative Example 1] No. 1 in Table 1 was used as the electrolytic solution. A capacitor similar to that of Example 1 was manufactured except that the capacitor of No. 7 was used.

For each of the above capacitors, the initial capacity and impedance, and 3 V applied at 70 ° C. 10
Table 2 shows the capacity change rate (-ΔC) and impedance after 00 hours and 2000 hours.

[0021]

[Table 2]

[0022]

As described above, according to the present invention, it is possible to obtain a small electric double layer capacitor having a high oxidation resistance potential of the electrolytic solution, a high breakdown voltage and a high capacity.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an electric double layer capacitor according to an exemplary embodiment of the present invention with a main part cut away.

FIG. 2 is a vertical cross-sectional view showing the structure of an electric double layer capacitor of another embodiment.

FIG. 3 is a vertical cross-sectional view showing the configuration of an H-type cell used for evaluating an electrolytic solution in an example of the present invention.

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[Procedure amendment]

[Submission date] August 3, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art Conventionally, there are roughly two types of electric double layer capacitors using activated carbon powder or activated carbon fibers as a polarizable electrode. The first one has the structure shown in FIG. 1 and has a pair of polarizations obtained by coating aluminum current collecting nets 1 and 2 with layers 3 and 4 made of a mixture of activated carbon powder and polytetrafluoroethylene, respectively. The manufactured electrode is wound around the separator 5 and housed in the case 6 . The opening of the case 6 is sealed with a rubber cap 7 . Reference numerals 8 and 9 are positive and negative leads, respectively. The second configuration of things, those having a structure shown in FIG. 2, a pair of activated carbon fibers 1 4 where the aluminum collector layer 15 provided on one surface, the separator 10 is interposed between the electrodes, the case 11 and 12 , And a gasket ring 13 that hermetically seals between the two cases. The cases 11 and 12 are in contact with the aluminum current collecting layer, respectively, and serve as a positive electrode and a negative electrode .
Also serves as a terminal .

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

[Fig. 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Administration Tetsuo 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Akihiko Yoshida 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An electric double layer capacitor comprising a polarizable electrode and an electrolytic solution, wherein the solvent of the electrolytic solution is mainly erythritan or a derivative thereof. 2. An electric double layer capacitor comprising a polarizable electrode and an electrolytic solution, wherein a solvent of the electrolytic solution is mainly composed of maleic acid carbonate or maleic acid carbonate ester. 3. The solvent is propylene carbonate,
Butylene carbonate, γ-butyrolactone, 1,3-
The mixed solvent containing at least one selected from the group consisting of dioxolane, acetonitrile, propionitrile, butyronitrile, dimethylformamide, 1,2-dimethoxyethane and sulfolane.
The electric double layer capacitor described. 4. The electrolyte is perchloric acid, hexafluorophosphoric acid,
The electric double layer capacitor according to claim 3, which is a tetraalkylammonium salt or a tetraalkylphosphonium salt of an acid selected from the group consisting of borofluoric acid and trifluoromethanesulfonic acid.