Electricity: electrical systems and devices – Electrolytic systems or devices – Double layer electrolytic capacitor
Reexamination Certificate
2001-05-23
2003-10-21
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Double layer electrolytic capacitor
C361S517000
Reexamination Certificate
active
06636417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric double layer capacitor and a battery. More specifically, the present invention relates to an electric double layer capacitor and a battery in which a cell is covered by an outer package in a decompression state.
2. Description of Related Art
Electric double layer capacitors have been conventionally used in practice and the structural characteristics thereof have recently been utilized to further decrease their sizes and increase their capacities. For instance, considerations have been made for new uses of electric double layer capacitors, such as a driving power source for a cell motor of a vehicle in combination with a lead battery or an auxiliary power source in combination with a solar battery.
Examples of the structure of electric double layer capacitors include the one shown in
FIGS. 7 and 8
.
The electric double layer capacitor shown in
FIG. 7
includes a basic cell
55
which is constituted by a separator
51
of porous sheet type, a pair of polarized electrodes
52
and
52
of plate shape, a pair of collectors
53
and
53
of sheet shape, and gaskets
54
of frame shape. The pair of polarized electrodes
52
is disposed so as to sandwich and make contact with the separator
51
from both sides. The pair of collectors
53
is disposed so as to sandwich the polarized electrodes
52
. That is, each of the pair of collectors
53
makes contact with the surface of the polarized electrodes
52
which is opposite the surface making contact with the separator
51
. The gaskets
54
are disposed between the pair of collectors
53
so as to make contact with end surfaces of the polarized electrodes
52
. The basic cell
55
contains an electrolyte sealed inside thereof.
In the electric double layer capacitor, a plurality of the above-mentioned basic cells
55
is laminated to form a multi-layered cell
56
shown in FIG.
8
. In
FIG. 8
, an electrode plate
57
to which a lead terminal is connected is closely attached to the collectors
53
located at the outermost side in the laminated direction of the multi-layered cell
56
, and the whole is covered by an outer package
58
in a decompression state (i.e., vacuum packed).
Since the electric double layer capacitor is covered by the outer package
58
in a decompression state, a compressive force is always applied to the capacitor from the outside due to atmospheric pressure. As a result, the degree of contact between the basic cells
55
and
55
, and between the basic cell
55
and the electrode plate
57
having the lead terminal is enhanced to decrease the equivalent series resistance (ESR). Accordingly, the performance of the capacitor may be further improved and stabilized.
The need for an electric double layer capacitor having an improved performance has recently been increasing and a further reduction of the ESR thereof is awaited. It has been discovered that if, for instance, a conductive film in which carbon is dispersed in an olefin resin is used for the collector
53
instead of a conventional conductive rubber in which carbon is dispersed in butyl rubber, the ESR of the collector
53
may be further reduced.
However, some of the above-mentioned conductive films have gas permeability coefficients higher than those of conventional ones, and electrolytes contained in the basic cells
55
may be gasified and leaked out from an interface
59
between the collectors
53
and the electrode plate
57
of the basic cells
55
which are located at the outermost side of the multi-layered cell
56
in some cases. If a gas were to leak out from the basic cell
55
, the decompression state in the outer package
58
would no longer be maintained and the degree of contact between the basic cells
55
and
55
, and between the basic cell
55
and the electrode plate
57
having a lead terminal would decrease. If the degree of contact were to decrease, the ESR thereof increases and the performance as a capacitor deteriorates and becomes unstable. This kind of problem is especially conspicuous under a high temperature atmosphere.
The present invention takes into consideration the above-mentioned circumstances, with an object of providing an electric double layer capacitor and a battery, which uses a material having high gas permeability constant for a collector in order to decrease the ESR, yet capable of preventing the increase of ESR due to a gas leak and, hence, electric performance thereof may be stabilized even under a high temperature atmosphere.
SUMMARY OF THE INVENTION
The present invention provides an electric double layer capacitor, including: at least one basic cell containing an electrolyte inside thereof, the basic cell may be laminated in its thickness direction to form a layered cell, including: a separator; a pair of polarized electrodes disposed so as to sandwich and make contact with the separator; a pair of collectors disposed so as to sandwich the polarized electrodes, each one of the pair of collectors making contact with the surface of one of the pair of polarized electrodes which opposes the surface making contact with the separator; and a gasket disposed between the pair of collectors so as to surround the pair of polarized electrodes; an electrode plate including an electrode body and a lead terminal extending from the electrode plate body, the electrode plate body being attached to the outer surface of each one of the collectors located at the outermost side in a laminated direction of the basic cell; an outer package which covers the basic cell and the electrode plate in a decompression state; and a sealing material having a higher gas barrier property than the collectors, the sealing material being disposed so as to seal an interface between each one of the collectors, which are located at the outermost side in a laminated direction of the basic cell, and the electrode plate body in the outer package.
According to the above electric double layer capacitor, since the sealing material having a higher gas barrier property than the collectors is disposed so as to seal an interface between each one of the collectors, which are located at the outermost side in a laminated direction of the basic cell, and the electrode plate body in the outer package, it becomes possible to prevent the electrolyte from being gasified and leaking out from the interface between the collector and the electrode plate body.
Accordingly, even if the collector were formed by using a material having a high gas permeability constant in order to lower the ESR thereof, the decompression state inside the outer package might be suitably maintained. Thus, it becomes possible to prevent an increase in the ESR due to a gas leak, and the electrical properties of the capacitor may be stabilized even if the capacitor were to be used under a high temperature atmosphere.
In accordance with another aspect of the invention, the gas permeability coefficient of each one of the collectors is at least 1×10
−12
[m
3
/(m
2
·s·Pa)].
According to the above electric double layer capacitor, since the gas permeability coefficient of a collector becomes 1×10
−12
[m
3
/(m
2
·s·Pa)] or greater, the amount of electrolyte which is gasified and leaked out from an interface between the collector and the electrode plate body to the inside of the outer package becomes too large to be ignored, the effect of preventing a gas leak due to the presence of the above-mentioned sealing material becomes significant.
In yet another aspect of the present invention, the electrode plate body extends in a circumferential direction thereof, and the sealing material is disposed between the extended portion of each one of the electrode bodies so as to surround the basic cell.
According to the above electric double layer capacitor, since the electrode plate body extends in a circumferential direction thereof and the sealing material is disposed between the extended portion of each one of the electrode bodies so as to surround the basic cell, the
Abe Satoshi
Mimura Kazuya
Nakazawa Yutaka
Sakata Koji
Dinkins Anthony
NEC Tokin Corporation
Sughrue & Mion, PLLC
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