JPH01157511A - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To reduce the number of components and to improve strength and durability by a method wherein aluminum or stainless steel is used for a metal lid and a sheathing body which are used both as a collector body and a metal case and the water content of an electrolyte is limited. CONSTITUTION:Aluminum as a valve metal and stainless steel as rustproof steel are selected as metals for a metal lid 12 and a metal case 13. Polarizing electrodes 6 which have been brought into contact with both faces of a separator 9 are housed at the bottom of the metal case 13; the surface of the upper-face polarizing electrode 6 is covered with the metal lid 12; an insulating sealing substance 11 is laid between a peripheral edge of the metal lid 12 and an opening of the metal case 13; an edge of the opening of the metal case 13 is caulked onto the insulating sealing substance 11, and this assembly is united. Out of constituents, a carbon fiber cloth which has been transformed into activated carbon is used for the polarizing electrodes by a fine-pore and porous film of polypropylene or Manila paper with which a glass fiber has been mixed is used for the separator 9. An electrolyte 10 is used after its water content has been adjusted to be 50ppm or less.

Description

[Detailed description of the invention] The present invention relates to an electric double layer capacitor.

This electric double layer capacitor has a characteristic of high capacitance by utilizing an electric double layer formed at the interface between a polarizable electrode and an electrolyte (liquid). For example, a disc-shaped (
As shown in Fig. 1, a separator 3 impregnated with electrolyte 2 is interposed between carbon electrodes 1 made of graphite, activated carbon, carbon black, some binder, etc. The conductive resins 5 and 6 and the insulating ring 4, which served as both electric bodies and exterior materials, were sealed with adhesive. This method is advantageous in the case of electric double layer capacitors that use aqueous electrolyte because it does not dissolve the conductive resin, but since it is a synthetic resin, it is easy to receive external pressure and it is difficult to connect to the electric circuit. In the case of wire connection, it was necessary to arrange a metal plate on the entire surface of the conductive synthetic resins 5 and 6 and fix it under pressure. Therefore, the structure shown in FIG. 1 is only half-finished, and the number of parts increases as a finished product.

Therefore, it is possible to use a metal material instead of the conductive synthetic resins 5 and 6, but in order to make the separator 3 made of metal, select a metal that can withstand the electrolyte used for the separator 3 or an electrolyte that does not attack the metal. The disadvantage is that it requires force. In other words, synthetic resins are inert to aqueous electrolytes such as dilute sulfuric acid, and are easily soluble in organic solvents, but metals usually have the opposite properties.

Therefore, the purpose of this invention is to reduce the number of parts,
To provide an electric double layer capacitor which has a simple structure, has strength and durability, and can be mounted on a printed circuit board without any trouble.

This invention focuses on the greatly improved mechanical strength and high electrical conductivity of metal, and forms the metal lid 12 and metal case 13 in place of the conductive synthetic resin 5.6.

The metals selected were aluminum, which is a valve metal, and stainless steel, which is a stainless steel. Aluminum is 99.9%
It has been confirmed that 18-8 stainless steel and high chromium stainless steel with a high chromium ratio are desirable. However, separator 9
It has also been found that electrolyte 10 causes pitting corrosion on metals, especially if the water content is not sufficiently reduced. It was confirmed that it is necessary to reduce the water content to 150 ppm or less, preferably 50 ppm or less. The structure shown in FIG. 2 is the result of the above selection of materials. That is, the polarizable electrodes 8 are placed in contact with both sides of the separator 9 and placed in the bottom of the metal case 13, and the top surface of the polarizable electrodes 8 is covered with the metal lid 12, and the periphery of the metal lid 12 and the opening of the metal case 13 are placed. An insulating sealing body 11 is interposed between the metal case 13 and the opening edge of the metal case 13 is caulked onto the insulating sealing body 11 so as to be integrated. In the structure, activated carbonized carbon fiber cloth was used for the interpolar electrode 8. As the separator 9, a microporous polypropylene film or Manila paper mixed with glass fiber was used. The electrolytic solution 10 has the above-mentioned composition and water content of 50
It was adjusted to below ppm and used. Metal case 12.13 is 9
9.9% high purity aluminum or stainless steel (SU
S304) was used. The sealing body 11 was made of polypropylene, fluororubber, IIR rubber, EPT rubber, or the like.

An example will be described below. All product dimensions are 25φ (diameter) and thickness 1.5+nm.

Comparative Example 1 Conductive resins 5 and 6 are butyl rubber containing carbon black, electrolyte 2 is 30% sulfuric acid, separator 3 is 3
A 0 μm porous polypropylene film was used. As a result of actual measurements, the capacitance is 3F, the internal resistance is 0.5Ω, and the withstand voltage is 0.8V.

Comparative Example 2 The metal material of the metal case 13 and metal lid 12 has a thickness of 0
．． 35mm aluminum, electrolyte 10 is 30% sulfuric acid,
The separator 9 used was the same as in 1 above. As a result, the metal case 13 was melted and characteristics could not be measured.

Example 1 The metal materials (12, 13) are aluminum with a thickness of 0.35 mm, the electrolyte 10 is 2100 parts of gamma-butyrolact,
15 parts of tetraethylammonium barchlorate and separator 9 were the same as in 1 above. The result is a capacitance of 2F.
, the internal resistance is 1Ω, and the withstand voltage is 2V.

Example 2 The metal materials (12, 13) were 0.25+nm (thickness) stainless steel (SUS304), and the others were the same as in Example 1, and the characteristics were also almost the same.

Example 3 In Example 2, the water content of the electrolyte 10 was (1) 250
ppm, (2050ppm, (3) 50ppm.

(4) The initial value (before the test) was set to 10 ppm, and the changes after 2V application and 1000 hours at 70°C (after the test) were compared. The results are shown in the table below.

(Margins below) -〇- As described above, by regulating the water content of the electrolytic solution 10, it has become possible to use metal materials.

However, economical metal materials seem to be limited to high-purity aluminum, which forms a corrosion-resistant oxide film, and stainless steel, which is stainless steel. However, since a metal material can be used as the current collector and electrode plate, it is possible to make both polarizable electrodes face each other under pressure, and furthermore, it is possible to receive the connecting terminal in contact with only a local part of the plate. Terminals can be attached by welding, making it an independent electronic component. Also, when connecting in series to increase the withstand voltage, it is sufficient to simply tie them together in a loose stacked structure, which has a great effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional example, and FIG. 2 is a sectional view of an embodiment of the present invention. 9... Separator, 10... Electrolyte,
11... Sealing body, 12... Metal lid,
13...Metal case.

Claims (2)

[Claims] (1) A separator impregnated with an electrolytic solution, a polarizable electrode made of carbon fiber cloth or activated carbon fiber cloth, and a polarizable electrode made of carbon fiber cloth or activated carbonized carbon fiber cloth, which is placed in contact with both sides of the separator, and a combination thereof is housed, and the polarizable electrode is placed at the bottom of the separator. a metal case that is in electrical contact with one of the polarizable electrodes, a metal lid that is fitted into the metal case and that is in electrical contact with the other polarizable electrode, and a metal lid that is interposed between the peripheral edge of the metal lid and the opening edge of the metal case. An electric double layer capacitor comprising a sealing body which is mutually insulated and integrally caulked by an opening edge of the metal case. (2) The electric double layer capacitor according to claim (1), wherein the metal case and the metal lid are made of aluminum or stainless steel.