Electrical double layer capacitor

Details Electrical double layer capacitor Electrical double layer capacitor

2000-09-07

2001-11-20

Dinkins, Anthony (Department: 2831)

Electricity: electrical systems and devices

Electrolytic systems or devices

Double layer electrolytic capacitor

C361S512000

Reexamination Certificate

active

06320741

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrical double layer capacitor, and in particular, relates to a large capacity electrical double layer capacitor using polarizing electrodes.
2. Description of the Related Art
A conventional electrical double layer capacitor will be explained referring to FIG.
12
. This electrical double layer capacitor is formed by one basic cell
55
or by two or more basic cells
55
, where the basic cells
55
comprises separators
51
, pairs of polarizing electrodes
52
and
52
that are disposed so as to contact respective separators
51
on both sides thereof, a pair of collectors
53
and
53
that are disposed so as to contact the surface of these polarizing electrodes
52
and
52
opposite to those of the respective separators
51
, and gaskets
54
disposed in proximity to the polarizing electrodes
52
and
52
(
FIG. 12
shows a two layer lamination).
The above separator
51
comprises a porous film that is non-electron conducting, and ion permeable.
The above polarizing electrodes
52
and
52
use a solid activated carbon having as a main component the activated carbon/polyacene material disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 4-288361.
The above collector
53
is a rubber or plastic that includes a conductive carbon, and during assembly, is crimped to the polarization electrode
52
.
The above pair of polarization electrodes
52
and
52
face each other across the separator
51
, and as a result, the collectors
53
and
53
are disposed respectively on both outside surfaces of the pair of polarizing electrodes
52
and
52
. In addition, the gasket
54
, which has a frame structure, is disposed so as to enclose the polarizing electrode
52
, the separator
51
, and the polarizing electrode
52
in a direction perpendicular to the direction of their arrangement, and thereby contact the collectors
53
and
53
on both sides so as to enclose an inner cell
56
that is filled by a hydrous (for example, sulfuric acid) or organic electrolyte solution
56
a.
The gasket
54
and the collectors
53
used here can utilize a structure wherein the sizes of their external dimensions are the same, like the electrical double layer capacitor disclosed, for example, in Japanese Unexamined Patent Application, First Publication, No. Hei 4-237109 and Japanese Unexamined Patent Application, First Publication, No. Hei 4-280517, or a structure wherein the sizes of the external dimensions of the gasket are larger than those of the external dimensions of the collectors, like the electrical double layer capacitor disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 8-78291.
Because the withstanding voltage of the two layered electric capacitor is limited by the electrolytic voltage of the electrolytic solution
56
a
, depending on the required withstanding voltage, the electrical double layer capacitor can be formed by layering in plurality the basic cells
55
and connecting them serially. Furthermore, in order to reduce the resistance to adhesion, pressure is applied between the terminal electrodes disposed on both sides of the layered basic cells
55
,
55
, . . . , and additionally, a pressure plate is applied to both sides of a terminal electrode, and thereby the basic cells
55
,
55
, . . . , are retained by a constant pressure.
Recently, new uses have been being discovered and tested for the above two layered electric capacitor due to increasing capacity and decreasing equalizing serial resistance (ESR) by using polarizing electrodes
52
. Examples are use in combination with a lead battery to form a starter motor drive power source for an automobile, and use in combination with a solar battery as a supplementary power source.
However, this type of electrical double layer capacitor has the problem that while pressure is applied in order to reduce the resistance to adhesion, at the same time, fractures occur in the collectors due to the force received from the polarizing electrodes and gaskets, and the inner cell is exposed to the outside via these fractures, and the electrolyte solution leaks to the outside.
In contrast, while the technological conception is different, in Japanese Unexamined Patent Application, First Publication, No. Hei 3-99422, a electrical double layer capacitor is disclosed in which a solid polarizing electrode is chamfered at the end facing the separator, and thus does not damage the separator.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a electrical double layer capacitor that can improve production yields and improve reliability by preventing the disadvantage wherein electrolyte solution is discharged to the outside due to fractures caused by the collectors.
In order to attain the above object, according to a first aspect of the invention, a electrical double layer capacitor provides one basic cell or two or more layers of basic cells, the basic cells providing separators, pairs of polarizing electrodes that are disposed so as to contact the respective separators on both sides thereof, a pair of collectors positioned so as to contact the surface of these polarizing electrodes opposite to those of the respective separators, and gaskets disposed in proximity to the polarizing electrodes, and wherein chamfered portions are formed on at least one among the corner that is a border between components adjacent to the surface of said polarizing electrodes that does not contact the separator or the collector, and the corner that is the border between the surface of the polarizing electrode that contacts the collector and the surface of the separator and the collector that is adjacent to the surface.
Thereby, because chamfered portions are formed on at least one of either the corner that is the border between the components adjacent to the surface of the polarizing electrode that do not contact the separator and the collector or the corner that is the border of the surface of the polarizing electrode that contacts the collector and the surface that does not contact the separator and collector adjacent to this surface, the stress focus on these corners, where a stress focus easily occurs at the contacting portions between the collector and the polarizing electrode, occurs with difficulty.
Therefore, because the occurrence of fractures in the collectors can be avoided, the defect of electrolyte solution leaking to the outside due to fractures occurring in the collector can be prevented, and both the yield during manufacture processing and the reliability can be improved.
According to a second aspect of the invention, in a electrical double layer capacitor according to the first aspect, chamfered portions are formed on the corners that are the border between components adjacent to the surface of the gasket that faces the polarizing electrodes.
Thereby, because chamfered portions are formed on the corners that are the border between components adjacent to the surface of the gasket facing the polarizing electrode, the stress focus at the corners, where a stress focus easily occurs between the contacting portions of the collector and the gasket, occurs with difficulty.
Therefore, because the occurrence of fractures in the collectors can be avoided, the defect of electrolyte solution leaking to the outside due to fractures occurring in the collector can be prevented, and both the yield during manufacture processing and the reliability can be improved.
According to a third aspect of the invention, in a electrical double layer capacitor according to the first and second aspects, projections that position the polarizing electrode with respect to the gasket are formed on at least one of the gasket and the polarizing electrode.
Thereby, since the polarizing electrodes are positioned by the projections that position the polarizing electrodes with respect to the gasket being formed on the gasket, as a result, in the case that the polarizing electrodes and the gasket are too close, stress

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