Cell

Details Cell Cell

1999-09-08

2002-08-27

Kalafut, Stephen (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S161000, C429S164000, C029S623100

Reexamination Certificate

active

06440604

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a cell having a wound type power generating element in which strip positive and negative electrodes are wound with a strip separator therebetween.
FIG. 9
shows a configuration example of a non-aqueous electrolyte secondary cell having a wound type power generating element
1
of an elliptic cylindrical shape. The power generating element
1
is configured by winding strip negative and positive electrodes
1
a
and
1
b
with a strip separator
1
c
therebetween into an elliptic cylindrical shape. The negative and positive electrodes
1
a
and
1
b
are wound with being slightly shifted in the vertical direction from each other, so that only upper edge portions of the negative electrode
1
a
protrude from the upper end of the power generating element
1
and only lower edge portions of the positive electrode
1
b
protrude from the lower end. In this case, the active material is not applied to the upper edge portions of the negative electrode
1
a
, and to the lower edge portions of the positive electrode
1
b
, thereby allowing metal foils of the negative and positive electrodes
1
a
and
1
b
to be respectively exposed in the upper and lower ends of the power generating element
1
. The wound separator
1
c
has a width at which the portion where the negative and positive electrodes
1
a
and
1
b
overlap with each other is surely covered and the upper and lower edge portions are not covered.
In such a non-aqueous electrolyte secondary cell, conventionally, a negative collector
2
such as shown in
FIG. 10
is disposed on the upper end portion of the power generating element
1
so as to perform current collection on the negative electrode
1
a
. The negative collector
2
consists of a copper plate and is configured so that a collector portion
2
a
is formed above one side with respect to the center of the upper end portion of the power generating element
1
. A flat platelike terminal connector
2
b
is drawn out from the collector portion
2
a
and placed above one semicircular area of the upper end portion of the power generating element
1
. In the collector portion
2
a
, the copper plate is repeatedly bent into a bellow-like shape so as to form press holds
2
c
which upward protrude, and press insertions
2
e
which downward protrude. In each of the press holds
2
c
, the copper plate is bent back at the apex so that two vertical copper plate portions are opposed via a small gap therebetween. In each of the press insertions
2
e
, the copper plate is bent back at the bottom so that the gap between two inclined copper plate portions is gradually increased to form a V-like section shape.
In the negative collector
2
, as shown in
FIG. 11
, plural edge portions of the negative electrode
1
a
protruding in the upper end of the power generating element
1
are pressingly held in bundle in each of the press holds
2
c
of the collector portion
2
a
and then connected and fixed by crimping and ultrasonic welding. In this case, the collector portion
2
a
is pressed down from the upper side to the upper end portion of the power generating element
1
, thereby pressingly inserting the downward-protruding tip ends of the press insertions
2
e
into gaps between the upper edge portions of the negative electrode
1
a
. As a result, the upper edge portions of the negative electrode
1
a
are distributed by the inclined faces on the both sides of the V-like section shape, and then guided into the gaps of the press holds
2
c.
A positive collector
3
such as shown in
FIG. 12
is disposed on the lower end portion of the power generating element
1
so as to perform current collection on the positive electrode
1
b
. The positive collector
3
is structured in the same manner as the negative collector
2
, and has a collector portion
3
a
. However, the positive collector consists of an aluminum plate in place of a copper plate. In the positive collector
3
, edge portions of the positive electrode
1
b
protruding in the lower end of the power generating element
1
are pressingly held in each of press holds
3
c
of the collector portion
3
a
and then connected and fixed by crimping and ultrasonic welding. In this case, similarly, the edge portions of the positive electrode
1
b
are distributedly guided by press insertions
3
e
into the gaps of the press holds
3
c
. In this example, however, a terminal connector
3
b
is drawn out above the upper end portion of the power generating element
1
. In the case where the positive terminal
5
is to protrude from a lower portion of the power generating element
1
, also the terminal connector
3
b
is disposed below the lower end portion of the power generating element
1
.
For the sake of simplicity, in the figures, the negative electrode
1
a
, the positive electrode
1
b
, and the like of the power generating element
1
are shown so as to be wound coarsely or with a reduced number of turns. In an actual case, they are wound very closely or with a large number of turns, so that many edge portions of the negative and positive electrodes
1
a
and
1
b
are pressingly held in the gaps of the press holds
2
c
and
3
c
of the collector portions
2
a
and
3
a
and then connected and fixed. In some case, the collector portions
2
a
and
3
a
of the negative and positive collectors
2
and
3
are disposed not only in one side with respect to the center of the power generating element
1
, but also above and below the both sides with respect to the center, thereby improving the current collecting efficiency.
In the negative and positive electrodes
1
a
and
1
b
of the power generating element
1
, however, very thin metal foils of copper, aluminum, or the like are exposed in the upper and lower edge portions. When the tip ends of the press insertions
2
e
and
3
e
of the collector portions
2
a
and
3
a
are actually pressingly inserted between the edge portions of the negative and positive electrodes
1
a
and
1
b
, therefore, the tip ends catch the inclined faces on the both sides of the V-like section shape, thereby producing a problem in that the edge portions cannot be smoothly guided into the gaps of the press holds
2
c
and
3
c.
Since the press insertions
2
e
and
3
e
are disposed in the collector portions
2
a
and
3
a
, the tip ends of the press insertions
2
e
and
3
e
are pushed into the power generating element
1
. Therefore, there arise further problems in that the tip ends may make contact with the positive or negative electrode
1
b
or
1
a
which is not subjected to current collection, to cause a short circuit, and that the application area of the active material is narrowed and hence the cell capacity is reduced. When the negative electrode
1
a
is to be connected and fixed to the press holds
2
c
of the collector portion
2
a
, for example, the upper end of the positive electrode
1
b
which is placed with being downward shifted approaches the tip ends of the press insertions
2
e
as shown in FIG.
13
. Therefore, there arises a possibility that the upper end makes contact with the tip end so as to cause a short circuit. In order to prevent such a short circuit from occurring, the amount of shift in each of the negative and positive electrodes
1
a
and
1
b
may be increased. However, this causes the area where the active material is not applied, to be widened. Consequently, the application area is reduced by an area corresponding to the widened area, thereby reducing the cell capacity.
The problem that the edge portions of the negative and positive electrodes
1
a
and
1
b
cannot be smoothly inserted into the gaps of the press holds
2
c
and
3
c
may be solved by employing the following configuration. Comb-like jigs which are made of a material of a low coefficient of friction and an excellent sliding property are prepared so as to have elongated V-like teeth in which the tip end is smaller in angle than the press insertions
2
e
and
3
e
. The jigs are pressed into the upper and lower end portions of the power generating ele

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