JP2000173874A - Electrolytic solution for driving electric double-layered capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen an electrolytic solution in resistivity so a to reduce an electrolytic capacitor in resistance by a method wherein a non-proton low- viscosity solvent is added to an electrolytic solution. SOLUTION: A mixed solvent composed of propylene carbonate, ethylene carbonate, and non-proton low viscosity solvent is made to serve as the electrolytic solution of an electric double-layered capacitor. It is preferable that the a non-proton low-viscosity solvent to add amounts to 10 to 50 wt.%. An element selected out of diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methyl isopropyl carbonate, methyl formate, 1,2-dioxolane, acetonitrile, methoxy acetonitrile, 2-methyltetrahydrofuran, nitromethane, and nitroethane is made to serve as the non-proton low-viscosity solvent. Furthermore, trimethyl ethyl ammonium boron fluoride may be used as solute, or an optional mixture of tetraethyl ammonium boron fluoride and trimethyl ethyl ammonium boron fluoride may be used as solute.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte for driving an electric double layer capacitor (hereinafter referred to as an electrolyte).

[0002]

2. Description of the Related Art In general, carbon electrodes using carbon powder are widely used for both electrodes of an electric double layer capacitor. As the carbon electrode, polytetrafluoroethylene (PT
It is manufactured by applying an adhesive such as FE) or polyvinylidene fluoride on a metal foil serving as a current collecting electrode, followed by drying. These electrodes are opposed to each other via a separator made of a porous film or paper, and this separator is impregnated with an electrolytic solution and put to practical use. Usually, an aprotic high dielectric constant solvent such as propylene carbonate or ethylene carbonate has been used for the electrolytic solution.

[0003]

The aprotic high dielectric constant solvents such as propylene carbonate and ethylene carbonate that have been used in conventional electrolytes generally have a high viscosity and therefore have a high specific resistance of the electrolyte. However, there is a problem that the product resistance is increased.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention adds an aprotic low-viscosity solvent to an electrolytic solution to increase the ionic conduction rate, thereby lowering the specific resistance of the electrolytic solution and reducing the product resistance. Can be lowered. That is, the electrolytic solution of the electric double layer capacitor is characterized in that the solvent of the electrolytic solution of the electric double layer capacitor comprises a mixed solvent of propylene carbonate, ethylene carbonate and an aprotic low-viscosity solvent.

Further, the above-mentioned aprotic low-viscosity solvent comprises:
Dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl isopropyl, methyl formate, methyl acetate, methyl propionate, 1,2-dimethoxyethane, 1,3-dioxolan, acetonitrile, methoxyacetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, nitromethane And at least one of nitroethane.

[0006] An electrolytic solution for an electric double layer capacitor in which the aprotic low viscosity solvent is added in an amount of 10 to 50 wt%.

Further, there is provided an electrolytic solution for driving an electric double layer capacitor, wherein tetraethylammonium fluoride and / or triethylmethylammonium fluoride is added to the above-mentioned mixed solvent.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is an electrolytic solution for an electric double layer capacitor using a mixed solvent comprising propylene carbonate, ethylene carbonate and an aprotic low viscosity solvent.

[0009]

EXAMPLE A slurry obtained by kneading PTFE, activated carbon, and carbon black was applied to a 20-μm-thick aluminum etching foil using a roll coater, dried, and then pressed by a 5-ton roll press to obtain a carbon electrode foil. . The carbon electrode foil was cut into a strip having a width of 28 mm, and a lead terminal was attached to the aluminum surface by a cold weld method. The capacitor element was produced by winding the sheet through a 25-μm-thick manila linen paper cut to a width of 30 mm with the carbon surfaces facing each other.

Examples and conventional examples are shown in Table 1 as a mixed solvent.
An electrolytic solution in which 1 mol / l of tetraethylammonium fluoride was dissolved was prepared. Then, the capacitor element is placed in a pressure cooker filled with an electrolytic solution, impregnated with the electrolytic solution at 100 ° C. and 2 atm, stored in a case, and sealed with a sealing plate.
100 electric double layer capacitors were produced for each.

When the capacitance and the equivalent series resistance of the product were measured, the results shown in Table 1 were obtained. It can be seen that the examples in which the aprotic low-viscosity solvent was added had lower equivalent series resistance than the conventional example, and improved electrical characteristics.

[0012]

[Table 1]

After mixing dimethyl carbonate as an aprotic low-viscosity solvent with a solvent in which propylene carbonate and ethylene carbonate are mixed by the same weight, 1 mol / l of tetraethylammonium fluoride is added, and the specific resistance is measured. Was obtained. The mixing amount of the aprotic low viscosity solvent is 10 w
If it is less than t%, there is no effect of lowering the specific resistance. Therefore,
The mixing amount of the aprotic low viscosity solvent is 10 to 50 wt%
Is preferred.

In the examples, diethyl carbonate, dimethyl carbonate and the like were used as the aprotic low viscosity solvent, but ethyl methyl carbonate, methyl isopropyl carbonate, methyl formate,
1,2-Dioxolan, acetonitrile, methoxyacetonitrile, 2-methyltetrahydrofuran, nitromethane, and nitroethane have the same effect. Further, FIG.
The same measurement was performed, and similar results were obtained (not shown).

Further, the solute may be triethylmethylammonium borofluoride, or tetraethylammonium borofluoride and triethylmethylammonium borofluoride may be appropriately mixed.

[0016]

As is apparent from the above results, the driving electrolyte for an electric double layer capacitor obtained by mixing the aprotic low-viscosity solvent with the aprotic high-dielectric-constant mixed solvent of propylene carbonate and ethylene carbonate of the present invention is as follows. By mixing an aprotic, low-viscosity solvent, the ionic conductivity in the electrolytic solution is increased, and the specific resistance of the electrolytic solution can be reduced, so that the product resistance can be reduced, and the high output of the current drawn from the product Since the density can be increased, its industrial and practical value is great.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of a mixed amount of dimethyl carbonate and a specific resistance.

Claims (4)

[Claims] 1. A driving electrolyte for an electric double layer capacitor, wherein the solvent for the driving electrolyte for the electric double layer capacitor comprises a mixed solvent of propylene carbonate, ethylene carbonate and an aprotic low viscosity solvent. . 2. The aprotic low-viscosity solvent according to claim 1, wherein the solvent is dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate,
Methyl isopropyl carbonate, methyl formate, methyl acetate, methyl propionate, 1,2-dimethoxyethane, 1,3
At least one of dioxolane, acetonitrile, methoxyacetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, nitromethane, nitroethane
An electrolytic solution for driving an electric double layer capacitor, which is a seed. 3. An electrolytic solution for driving an electric double layer capacitor, wherein the mixed amount of the aprotic low viscosity solvent according to claim 1 is 10 to 50 wt%. 4. An electrolytic solution for driving an electric double layer capacitor, wherein tetraethylammonium fluoride and / or triethylmethylammonium fluoride are added to the mixed solvent according to claim 1.