JP2002231588A - Electric double-layered capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layered capacitor which can be increased in electrostatic capacity. SOLUTION: A polarizing electrode of the electric double-layered capacitor is formed by mixing and using at lest two kinds of powdery activated carbon having mutually different mean particle sizes. The activated carbon preferably has a 2- to 20-fold difference in a mean particle size between the kind having the largest mean particle size and the kind having the smallest mean particle size, and the powdery activated carbon having the largest particle size is mixed by 60 to 90 wt.pts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electric double layer capacitor, and more particularly to a polarizable electrode for driving the same.

[0002]

2. Description of the Related Art There are two types of electric double-layer capacitors: relatively small, small and large-capacity capacitors and relatively large and large-capacity capacitors.

[0003] A relatively small and small-capacity electric double layer capacitor is formed as an element by interposing a separator such as a polypropylene non-woven fabric between a pair of polarizable electrodes having a polarizable electrode layer mainly composed of activated carbon formed on a current collector. The element is impregnated with an electrolytic solution, accommodated in a metal container, and sealed in a metal container with a sealing plate and a gasket to form a coin-type structure.

On the other hand, a relatively large-capacity electric double-layer capacitor is formed by winding a laminated sheet having a separator interposed between a pair of sheet-shaped polarizable electrodes to form an element. It is housed in a container and has a wound structure in which the metal opening is sealed with a sealing member. These electric double layer capacitors are mainly used for backup of C memory and backup of actuators.

The polarizable electrodes constituting these electric double layer capacitors have conventionally been mainly made of activated carbon having a large surface area. In the wound type capacitor, activated carbon powder is kneaded with PTFE (polytetrafluoroethylene) as a binder to form a sheet, and in the coin type capacitor, the above-mentioned activated carbon or activated carbon fiber cloth is used. .

[0006]

However, the conventional electric double layer capacitor using the polarizable electrode has a problem that it is difficult to increase the capacitance because the carbon material in the polarizable electrode is small. .

[0007] Therefore, an object of the present invention is to provide an electric double layer capacitor capable of increasing the capacitance.

[0008]

The present invention relates to an electric double layer capacitor formed at an interface between a polarizable electrode and an electrolytic solution, wherein the polarizable electrode has at least two kinds of powders having different average particle diameters. Thus, an electric double layer capacitor characterized by being made by mixing and using activated carbon is obtained.

[0009] The powdered activated carbon may have a difference in average particle size between the type having the largest average particle size and the type having the smallest average particle size in the range of 2 to 20 times.

[0010] The powdered activated carbon may have a compounding ratio of the powdered activated carbon having the largest average particle diameter of 60 to 90 parts by weight.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a coin-type electric double layer capacitor according to a first embodiment of the present invention. As shown in FIG. 1, a metal case 10 made of stainless steel was used, a conductive adhesive 12 was applied on the inside thereof, and then a polarizable electrode 14 was fixed to the inner bottom. The polarizable electrode 14 was also fixed to the inner bottom of the metal lid 11 made of stainless steel in the same manner as described above. Although stainless steel is used for the metal case 10 and the metal lid 11, aluminum may be used.

The activated carbon powder used for the polarizable electrode 14 is as follows.
Activated carbon having an average particle size of 1 to 80 μm was used, and the mixing ratio of activated carbon having a large average particle size was 50 to 100 parts by weight. The average particle size and the mixing ratio of these particles are shown in Lot. 1-20
FIG. 2 shows the particle size distribution of the powdered activated carbon.

Next, the polarizable electrode 14 was manufactured by kneading and molding the carbon material such as the powdered activated carbon.

1 k of electrolytic solution is applied to the polarizable electrode 14 as an electrolytic solution.
mol / m ³ of a tetraethylammonium tetrafluoroborate-propylene carbonate solution, and the polarizable electrodes 14 are overlapped between them via a separator 13 such as a polypropylene non-woven fabric. The peripheral edge of 11 was integrally crimped via a gasket 15 and sealed.

According to the coin-type electric double layer capacitor shown in FIG. 1, the powdered activated carbon, which is the material of the polarizable electrode, is composed of a mixture of powdered activated carbons having two or more kinds of particle diameters. , More powdered activated carbon is filled in the polarizable electrode. As a result, the capacitance increases.

Table 1 shows the results of specific measurements of the capacitance.

[0018]

[Table 1]

A large capacitance can be generally obtained. 2, 3, 4, 5, 6, 9, 10, 11, 1
2, 13, 17, 18, and 19 have particularly high capacitance. That is, it can be seen that those satisfying the following conditions are more advantageous in increasing the limit of the capacitance.

The difference in average particle size between the type having the largest average particle size and the type having the smallest average particle size is 2-2.
It is within the range of 0 times.

The mixing ratio of the powdered activated carbon having the largest average particle size is 60 to 90 parts by weight.

FIG. 3 is a partially cutaway perspective view of a wound-type electric double layer capacitor according to a second embodiment of the present invention. In FIG. 3, powdery activated carbon or the like (excluding binder) is placed on a 30 μm-thick aluminum foil-shaped conductive current collector 22.
The paste in the form of slurry obtained by kneading
The polarizable electrode 21 was formed by coating to a thickness of μm. Again, two types of powdered activated carbons having different average particle sizes were used. The blending weight ratio of the two types of powdered activated carbon was calculated according to Lo in Table 2.
t. 21 to 40.

[0023]

[Table 2]

An aluminum electrode lead 20 mechanically connected to a conductive current collector by needle caulking is wound with a separator 23 and impregnated with an electrolytic solution. And sealed. As the electrolytic solution, a 1 kmol / m ³ tetraethylammonium tetrafluoroborate-propylene carbonate solution was used. Thus, a wound type electric double layer capacitor was obtained.

According to the wound electric double layer capacitor shown in FIG. 3, the powdered activated carbon, which is a material of the polarizable electrode, is composed of a mixture of powdered activated carbons having two or more kinds of particle diameters. The same volume of the polarizable electrode is filled with more powdered activated carbon. As a result, the capacitance increases.

Table 2 shows the results of specific measurements of the capacitance. A large capacitance can be generally obtained.
ot Lot 22, 23, 24, 25, 26, 29,
The elements 30, 30, 32, 33, 37, 38, 39 have particularly high capacitance.

The form of the electric double layer capacity to which the present invention can be applied is not limited to the above embodiment. Further, in the above-described embodiment, powdered activated carbon having two kinds of average particle diameters is used, but powdered activated carbon having three or more kinds of average particle diameters may be used. In this case, it is preferable to make the difference between the average particle diameters of the respective types twice or more. For example, in the case of three types, the average particle size of each powdery activated carbon used is 80 μm, 30 μm, 10 μm,
For the types, similarly, 80 μm, 30 μm, 10 μm,
4 μm.

[0028]

As described above, according to the electric double layer capacitor of the present invention, the polarizable electrode is more filled with the carbon material, so that the capacitance can be increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a coin-type electric double layer capacitor according to a first embodiment of the present invention.

FIG. 2 is a graph showing the particle size distribution of powdered activated carbon in the electric double layer capacity shown in FIG.

FIG. 3 is a partially cutaway perspective view showing a wound-type electric double layer capacitor according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal case 11 Metal cover 12 Conductive adhesive 13 Separator 14 Polarized electrode 15 Gasket 20 Aluminum electrode lead 21 Polarized electrode 22 Conductive current collector 23 Separator 24 Rubber cap 25 Aluminum exterior case

Claims (3)

[Claims] 1. An electric double layer capacitor formed at an interface between a polarizable electrode and an electrolytic solution, wherein the polarizable electrode comprises:
An electric double layer capacitor characterized by being made by mixing at least two types of powdered activated carbons having different average particle sizes. 2. The powdered activated carbon has a difference in average particle diameter between a type having the largest average particle size and a type having the smallest average particle size in a range of 2 to 20 times. 3. The electric double layer capacitor according to claim 1. 3. The electric double layer capacitor according to claim 1, wherein the powdered activated carbon has a compounding ratio of the powdered activated carbon having the largest average particle diameter of 60 to 90 parts by weight.