Electricity: electrical systems and devices – Electrolytic systems or devices – Double layer electrolytic capacitor
Reexamination Certificate
2002-10-17
2004-06-15
Reichard, Dean A. (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Double layer electrolytic capacitor
C361S503000, C361S517000
Reexamination Certificate
active
06751084
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric double layer capacitor and a method for preparing the same.
2. Description of the Prior Art
Heretofore, electric double layer capacitors have been put to practical use as capacitors which enable obtaining high capacities of farad(F)-order without involving chemical reaction and which endure charge and discharge of heavy currents and charge-and-discharge cycles.
In recent years, with a view to making good use of electric double layer capacitors, studies on new applications thereof as an auxiliary power supply of an electronic appliance such as a cellular phone. Concomitantly therewith, further miniaturization and capacity increase of electric double layer capacitors have been attempted.
As shown in
FIG. 4
, a conventional electric double layer capacitor comprises a basic cell
10
including a porous separator
11
in the form of a sheet; a pair of current collectors in the form of a sheet disposed oppositely relative to the separator
11
; a pair of polarizable electrodes
13
,
13
having a plate-like form and disposed between the separator and the current collectors; and gasket
14
which is laterally contiguous to the separator
11
and the polarizable electrodes
13
,
13
and held between the current collectors
12
,
12
. The basic cell
10
is sealed with an electrolytic solution contained therein.
In most cases, the gasket
14
is prepared from two gasket elements
141
,
141
for manufactural reason.
In the next place, a method for preparing a conventional electric double layer capacitor will be described with reference to FIG.
4
.
FIGS.
4
(
a
) to
4
(
g
) are sectional views schematically showing a part of a method for preparing a conventional electric double layer capacitor.
As shown in FIG.
4
(
a
), a current collector
12
in the form of sheet is provided and, as shown in FIG.
4
(
b
), it is cut down to size.
As the current collector
12
, an electrically conductive film is generally employed which comprises an electrical insulating resin and electrically conductive particles. With respect to material and method for the production thereof, there maybe employed conventional techniques, for example, disclosed in Japanese Unexamined Patent Publication Nos.1998-4033 and 1998-4034 by Nagaki et al.
Further, as disclosed in U.S. Pat. No. 6,377,441 by Ohya et al., a laminate prepared by laminating a plurality of current collectors
12
may be employed.
Moreover, as materials suitable for the current collector, those disclosed in PCT/JP98/01021 and PCT/JP98/03073 may be employed.
Then, as shown in FIG.
4
(
c
), a gasket element
141
in the form of a frame, i.e., a gasket element
141
having an opening is disposed on the surface of the current collector
12
. Since the gasket element
141
is disposed on a peripheral portion of the surface of the current collector
12
, a portion of the surface of the current collector
12
within the opening remains uncovered.
Then, as shown in FIG.
4
(
d
), a polarizable electrode
13
is provided on the uncovered portion of the surface of the current collector
12
and, as shown in FIG.
4
(
e
), a separator
11
is so disposed on the gasket element
141
as to cover the opening of the gasket element
141
.
Thereafter, as shown in FIG.
4
(
f
), another product as shown in FIG.
4
(
d
) is disposed on the separator
11
in such a manner that inner portions of the gasket elements
141
,
141
of the two products as shown in FIG.
4
(
d
) oppositely abut on the separator
11
, and the gasket elements
141
,
141
are subjected to thermo-compression bonding from both sides via the current collectors
12
,
12
.
The gasket elements
141
,
141
are deformed so that outer portions of the gasket elements
141
,
141
vertically extend all around the separator
11
, and the gasket elements
141
,
141
are fusion-bonded together into a gasket
14
. As a result, the separator
11
is laterally covered with the gasket
14
all around to thereby obtain an electric double layer capacitor as shown in FIG.
4
(
g
).
In recent years, miniaturization of electronic parts has been advanced. In particular, the advents of small-sized electric double layer capacitors having high capacities and the like have strongly been desired as described above.
However, according to the conventional method for preparing an electric double layer capacitor, if it has been intended to prepare an electric double layer capacitor as a small-sized capacitor with a high capacitor, there have been limitations in size and in mechanical strength which are attributed to the preparation method.
Specifically, a current collector used in a conventional electric double layer capacitor has been a butyl rubber containing a carbon powder in most cases. With respect also to a gasket, a butyl rubber has been used because of its affinity with the current collector.
If a current collector and a gasket which are made of a butyl rubber or the like have been miniaturized in order to advance miniaturization of electric double layer capacitors, there has been a problem in poor mechanical strength in the fusion-bonding step or the like. This has created a limitation on miniaturization of electric double layer capacitors.
Further, if each of members including a current collector has been reduced to too thin a film with an intention to miniaturize electric double layer capacitors, transmission of electrolytic solution vaporized in the step of thermo-compression bonding has been liable to occur. As a result, there have been undesirable variations in equivalent series resistance (ESR). This leads to a lowered yield of electric double layer capacitors as products.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to solve the above-described problems caused concomitantly with miniaturization of an electric double layer capacitor and to provide an electric double layer capacitor, which is adaptable to miniaturization and which has a high capacity and stable characteristics such as ESR, and a method for preparing the same.
According to an embodiment of the present invention, an electric double layer capacitor has such a structure that current collectors as constituents of a basic cell laterally abut on a gasket. Accordingly, the current collectors do not undergo excess deformations by pressures which are exerted on the basic cell in the thickness direction thereof in the course of the preparation thereof, and hence leakage of the electrolytic solution is less likely to occur.
According to another embodiment of the present invention, an electric double layer capacitor is prepared by the preparation method including steps of forming a structure comprising a current collector and a gasket element which are applied on the same substrate. Accordingly, occurrence of defects in a step of fusion-bonding in the preparation of the electric double layer capacitor is suppressed even if the electric double layer capacitor is miniaturized, and hence high productivity of the electric double layer capacitor is realized.
REFERENCES:
patent: 5072335 (1991-12-01), Kurabayashi et al.
patent: 5786981 (1998-07-01), Aoki et al.
patent: 6324049 (2001-11-01), Inagawa et al.
patent: 6377441 (2002-04-01), Ohya et al.
patent: 10-004033 (1998-01-01), None
patent: 10-004034 (1998-01-01), None
patent: WO98/40435 (1998-09-01), None
patent: WO99/02585 (1999-01-01), None
Kasahara Ryuichi
Nakazawa Yutaka
Sakata Koji
NEC Tokin Corporation
Reichard Dean A.
Thomas Eric
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