JPS63181412A - Electric double-layer capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electric double layer capacitor that is highly airtight and free from stress cracks caused by electrolyte solution.

[Prior art]

FIG. 1 is a sectional view showing an example of an electric double layer capacitor. In this figure, each cavity 3.4 has a separation property (pole 5
．． A pair of gaskets 1.2 containing 6 are bonded together via a separator 7 having ion permeability and d-air insulation, and a conductive sheet 8.9 having #klL electrode is attached to the outside of the gasket 1.2. It is placed on the surface and adhered so as to close the space 3.4 that accommodates the polarizability 15.6.

FIG. 2 shows another example of the electric double layer capacitor in which a stainless steel protection plate 10.11 is attached to the surface of the conductive sheet 8.9.

Polarizability "Polarization 5.6" can be achieved by, for example, activated carbon powder, sulfuric acid,
It consists of a mixed paste with an electrolyte solution such as r-butyrolactone, acetonitrile, and propylene carbonate.

Therefore, the space 3.4 of the gasket 1.2 is filled with paste. (Unexamined Japanese Patent Publication No. 61-20701
No. 0) The gasket 1.2 is made of special polyethylene, and the conductive sheet 8.9 is made of carbon black-containing polyethylene or a high-density polyethylene sheet.

[Problems with conventional technology]

In conventional electric double layer capacitors, polyolefin resin with a relatively high melting point (124 to 165°C) is used as the conductive sheet 1"J material, so the thermal adhesive strength between the gasket 1.2 and the conductive sheet 8.9 is low. In some cases, electrolyte solution leaks out of the capacitor during use, rendering the capacitor unusable.In particular, capacitors with rigid protective plates 10 and 11 shown in Figure 2 are better protected. Leaks of electrolyte solution are more likely to occur than capacitors without plates.

This leakage of the electrolyte solution is caused by electrolysis occurring due to the presence of the electrolyte solution, especially when a voltage higher than the withstand voltage is applied to the electric double layer capacitor.As a result, gas is generated within the cavity of the gasket. The internal pressure increases due to the gas pressure in the plant, and as a result, the degree of adhesion between the gasket and the conductive sheet decreases, and eventually peels off, causing the conductive sheet to burst (12) (Figure 3), and the electrolyte solution leaks due to the gas pressure. Leak.

When a low-density polyethylene film containing carbon black powder is used as the material for the conductive sheet 8.9, it has excellent thermal adhesion with the gaskets 1 and 2, but low-density polyethylene film is not suitable for electrolyte solutions such as sulfuric acid or acetonitrile. Compared to high-density polyethylene, it has inferior leet resistance.
The bending strength is small, i.e. the tensile strength against internal gas pressure (
It has a drawback of low gas resistance (hereinafter referred to as "gas resistance").

When a mixture of high-density polyethylene and low-density polyethylene is used as the material resin, the conductive sheet exhibits only intermediate physical properties, as understood from Table 1 below.

Table 1 *Wall thickness: 80μ, carbon black content: 18wt%.

** Presence or absence of rupture of the sheet after storage at 85°C for 24 hours.

Splitting body Check for rupture of the conductive sheet at the thermally bonded part with the gasket.

[Specific measures to solve the problem]

In the present invention, the required performance of the electric double layer capacitor shown in Abstract 1 is improved by forming the conductive sheet into a laminated structure.

That is, the present invention provides a device in which a pair of polarized electrodes surrounded by an insulating member is arranged through a porosity separator having ion permeability, and a conductive sheet is bonded to the outer surface of the polarizable electrode. In an electric double layer capacitor in which the polarizability tW is made of solid carbon impregnated with an electrolyte solution, the conductive sheet has (4) a density of 0.8.
70-90% by weight of ethylene resin of 90-0.925t/- and 10-30% by weight of conductive carbon black powder
and a3) an electric double layer and/or a laminate sheet comprising at least a film base layer made of the following composition and/or a density of 0.89 t/c11. 70 to 90% by weight of the above propylene resin Φ) and 30 to 10% by weight of conductive carbon black powder.

In the present invention, the porous separator is composed of, for example, a nonwoven fabric made of polyolefin such as polyethylene or polypropylene, a stretched film, or cellulose for paper making such as kraft paper or manila paper.

Here the separator 7 is in contact with the polarizable electrode 5.6. A conductive foot 8 is provided on the outer surface of the gasket 1.2 and the polarizable electrode 5.6 so that the polarizable electrode 5.6 can be inserted therein.
．． 9 are joined.

The conductive sheet 8.9 is connected to the gasket 1.9 which is an insulating member.
An adhesive layer side (8a) is provided on the side to be bonded to 2. Of course, in the electric double layer capacitor shown in FIG. 2, adhesive layers 8a, 8a are provided on both sides of the base layer 8b as shown in FIG.
Using a three-layer conductive sheet provided with
Improves adhesion with 0.11.

Ethylene-based resins with a density of 0.890 to 0.925 f/cd used as the material resin for the adhesive layer (8a) of the conductive sheet (8) include low-density polyethylene with a melting point of 80 to 124°C; Metal salts of methacrylic acid copolymers (Na + zn, Ll l K), ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, linear linear polyethylene, etc. can be used, among which those that do not have polar groups Low-density polyethylene and linear cross-laminated polyethylene are preferred.

As the material resin for the base material layer (8b), homopropylene polymer, polypropylene such as ethylene-propylene copolymer, high-density polyethylene, etc. can be used.In terms of dispersibility of carbon black, high-density polyethylene alone is preferable. or,
From the viewpoint of gas resistance, a mixture of high density polyethylene and polypropylene (95:5 to 5:95 mixture) is preferred.

As the carbon black powder, acetylene black, Ketjen black, furnace black, channel black, etc. can be used, and the amount is 10 to 30% by weight in the layer composition.
used at a rate of If it is less than 10% by weight, the conductivity will not be sufficient, and if it exceeds 30% by weight, the film strength will decrease.
Gas resistance decreases. The content of carbon black is determined by Mfi5. It may be the same as or different from the base material layer.

The thickness of the thermal adhesive layer of the conductive sheet to the gasket surface is 5 to 50 microns, the thickness of the base material layer is 20 to 100ξcm, and the thickness ratio of the base material layer to the conductive sheet is 60 μm.
It is preferably 94%.

Such a conductive sheet with a laminated structure is produced by melt-kneading an adhesive layer composition and a base layer composition using separate extruders, supplying them to a single die, melting and laminating them within the die, and then forming them into a sheet. It is obtained by coextrusion and cooling.

The conductive sheet and the gasket are thermally bonded at a temperature that melts the adhesive layer.

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

Example 1 Thirty electric double layer capacitors shown in Fig. 2 were manufactured (diameter 13 ρ). Protective plate: stainless steel plate. (sus 304,
Thickness: 0.3 cm, diameter: 13 cm e) Polarizable electrode: A molded charcoal impregnated with 50% sulfuric acid.

Gasket: polyethylene ring. (Thickness 6■)
Porous separator: A stretched film made of a mixture of linear polyethylene, high-density polyethylene, and inorganic fine silk powder.

Conductive sheet: A three-layer sheet with a wall thickness of 80 microns manufactured by the following method.

High density polyethylene (density 0.95 Or/cIi)
A mixture of 12% by weight of Ketjenblack and 12% by weight of Ketjenblack was heated at 200°C for 80 r, using a Banbury mixer.
The mixture melt-kneaded for 10 minutes under the conditions of p, m, was used as a base layer composition, and this was melt-kneaded using an extruder with an L/D of 24 and a diameter of 65 m, and was fed to a co-extrusion die at 200 ° C. .

On the other hand, a mixture of 86% by weight of low-density polyethylene with a density of 0.920 f/- and 14% by weight of Ketjenblack was melt-kneaded at 170°C for 10 minutes using a Banbury mixer, and a mixture was used as the adhesive layer composition. This was melted and kneaded at 170°C using an extruder with an L/D of 24 and a diameter of 505W+, and then supplied to the co-extrusion die, melted and kneaded so that the adhesive layer was on both sides of the base material layer in the goo. After layering, 200
The laminated sheet was extruded at .degree. C. and then cooled to obtain conductive sheets each having an adhesive layer of 15 .mu.m and a base layer of 50 .mu.m.

When 30 of these electric double layer capacitors were stored in a constant temperature room at 85° C. for 24 hours, the state of corrosion of the stainless steel plates was examined, and no corrosion was observed.

Further, when the number of capacitors whose conductive sheet was damaged after being stored at 85° C. for 24 hours was investigated, it was found to be one.

Further, when the stainless steel plate and the conductive sheet were brought into contact with each other by coating a conductive paint (Dotite (trade name) manufactured by Fujikura Kasei) on the surface of the conductive sheet, the penetration resistance was 39 ohms.

Examples 2 to 6, Comparative Examples 1 to 3 A sheet with a three-layer structure shown in Table 1 (15
Electric double layer capacitors were obtained in the same manner except that 150 μm/152 m Examples 2 to 6) or a sheet with a single layer structure (80 μm wall thickness Comparative Examples 1 to 3) was used.

The performance is shown in the same table.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of an electric double layer capacitor, Figure 3 is a partial cross-sectional view showing damage to the capacitor during a gas resistance test, and Figure 4 is a cross-sectional view of a conductive sheet used in the implementation of the present invention. It is a diagram. Patent applicant: Mitsubishi Yuka Co., Ltd. Agent: Patent attorney: Masahisa Hase Patent attorney: Takaya Yamamoto Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] 1) A pair of polarized electrodes surrounded by an insulating member are arranged through a porous separator having ion permeability, and a conductive sheet is bonded to the outer surface of each polarized electrode. In an electric double layer capacitor in which the polarizable electrode is made of solid carbon impregnated with an electrolyte solution, the conductive sheet (A) has a density of 0.890 to 0.9;
A thermal adhesive layer to the gasket surface containing 25 g/cm^3 of 70 to 90% by weight of ethylene resin and 10 to 30% by weight of conductive carbon black powder, and (B) a film base material made of the following composition. An electric double layer capacitor (a) characterized in that it is a laminated sheet containing at least a layer, an ethylene resin having a density of 0.945 g/cm^3 or more and/or a propylene having a density of 0.89 g/cm^3 or more 2) Material resin of the base layer of the conductive sheet is 5-95% by weight of ethylene resin, 95-95% by weight of propylene resin (b), conductive carbon black powder 30-10% by weight. 5% by weight
Claim 1 characterized in that it is a mixture of
Electric double layer capacitor as described in section. 3) The electric double layer capacitor according to claim 1, wherein the electrolyte solution is sulfuric acid. 4) The conductive sheet has a thermal adhesive layer on the gasket surface with a thickness of 5 to 50 microns, and a base layer with a thickness of 20 to 100 microns.
2. The electric double layer capacitor according to claim 1, wherein the electric double layer capacitor is micron. 5) The thickness ratio of the base material layer in the conductive sheet is 60~
The electric double layer capacitor according to claim 4, wherein the electric double layer capacitor is 94%.