Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Tape or flexible-type cell including tape fuel cells or...
Reexamination Certificate
2001-09-26
2004-06-01
Bell, Bruce F. (Department: 1746)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Tape or flexible-type cell including tape fuel cells or...
C429S129000, C429S130000, C429S136000, C429S138000, C429S139000, C429S146000, C429S152000, C429S153000, C429S162000, C429S163000, C429S177000, C429S179000, C429S180000, C429S184000
Reexamination Certificate
active
06743546
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thin battery with a laminate casing, wherein the electricity generating elements are packaged in a casing which is formed by superposing two sheets of laminate and joining the periphery thereof.
BACKGROUND ART
Thin, lightweight non-aqueous electrolytic batteries with flexible laminate casing such as lithium polymer rechargeable battery are most suitable for use as the drive power sources of thin, portable electronic devices, and particularly of portable telephones that have become so popular in recent years.
FIG. 35
is a plan view showing a lithium polymer rechargeable battery as one example of a prior art battery with a laminate casing.
FIG. 36
is a cross-sectional view seen along the line XXXVI—XXXVI of FIG.
35
. As shown in
FIG. 36
, a plurality of electrode plate modules
3
are stacked up to form a stacked electrode assembly
2
, which is accommodated in a casing
1
made of a laminate sheet. Because of such flatness, the stacked electrode assembly
2
, being enveloped in a laminate sheet casing
1
, is advantageously used for constructing a flat and lightweight battery.
Referring to
FIG. 37
, the electrode plate module
3
includes a negative electrode plate
4
composed of a negative electrode current collector
7
and negative electrode mixture layers
8
formed on both sides thereof, a pair of positive electrode plates
9
composed of a positive electrode current collector
10
and positive electrode mixture layers
11
formed on both sides thereof. The positive electrode plates
9
are superposed on both sides of the negative electrode plates
4
with intervening separators
12
therebetween to form an integral unit of electrode plates. These electrode plate modules
3
are stacked upon one another to form the electrode assembly
2
shown in FIG.
36
and to attain a required voltage or battery capacity. Negative electrode terminals
7
a
extend from one end of each of the negative electrode current collectors
7
, and these negative electrode terminals
7
a
are bundled and welded together, with a negative electrode lead
13
welded to the weld joint. Similarly, positive electrode terminals
10
a
shown in
FIG. 37
which extend from one end of each of the positive electrode current collectors
10
are bundled together, and a positive electrode lead
14
shown in
FIG. 35
is welded to the weld joints of the positive electrode terminals.
The casing
1
consists of a laminate sheet, including a metal layer such as an aluminum foil for providing air-tight and liquid-tight properties, with a resin layer having a high melting point bonded to an outer side of the metal layer, and another resin layer of metamorphic polypropylene bonded to an inner side of the metal layer. The laminate sheet is folded in two as shown in
FIG. 38
, and formed into an envelope shape by heat-sealing the opposite edges P
1
, P
2
. The stacked electrode assembly
2
is inserted into the casing
1
through the open end, liquid electrolyte is injected thereinto, and the open end edge P
3
is heat-sealed such that the positive electrode lead
14
and the negative electrode lead
13
extend to the outside as shown in FIG.
35
.
Japanese Laid-open Patent Application No. 11-288698 proposes bonding of an additional resin seat or a sealing material
17
, by applying heat, to both sides of the positive electrode lead
14
and the negative electrode lead
13
where they pass through the open end edge P
3
, so that the portions of the open end edge P
3
where the positive electrode lead
14
and the negative electrode lead
13
pass through are reinforced with the additional resin sheet
17
to have enhanced leakage-proof property. For the resin sheet
17
, a copolymer of ionomer, ethylene and acrylic acid, polyethylene resin, polypropylene resin, polyamide resin, polyester resin or polyurethane resin are used.
Another conventional battery employs a casing
18
having a construction shown in FIG.
39
. The casing
18
made of a laminate sheet similar to the one mentioned above includes a base part
18
a
, which is one side of the folded laminate sheet, the other side thereof forming a cover
18
b
. The base part
18
a
has a recess
18
b
for accommodating the stacked electrode assembly
2
therein. One advantage of this casing
18
is that, as compared to the envelop-shaped casing
1
, the electrode assembly
2
can readily be inserted into the recess
18
b
of the base part
18
a
, with the cover
18
c
being widely opened.
The casing
18
has seal flanges
18
d
,
18
e
, and
18
f
, and when the stacked electrode assembly
2
is accommodated within the recess
18
b
, the positive electrode lead
14
and the negative electrode lead
13
sit on the seal flange
18
e
and extend to the outside of the base part
18
a
. The cover
18
c
is then closed, with its two opposite sides being heat-sealed with the seal flanges
18
d
,
18
f
, and liquid electrolyte is injected into the casing through the openings between the remaining seal flange
18
e
and one end edge of the cover
18
c
. Thereafter, the seal flange
18
e
and the end edge of the cover
18
c
is welded to seal the casing
18
.
Similarly to the envelop type casing
1
, a resin sheet
17
made of polypropylene film is joined to the positive electrode lead
14
and the negative electrode lead
13
from both sides where they pass through the seal flange
18
e
end, so that the sealing property at this end will not be deteriorated and reliable leakage-proof property is ensured. One side of the recess
18
b
, at which the positive electrode lead
14
and the negative electrode lead
13
extend to the outside, has an inclined surface
18
g
, so as to accommodate the negative electrode terminals
7
a
and positive electrode terminals
10
a
, which take a triangular shape as they are bundled together at a location near the seal flange
18
e.
In neither of the above-described batteries using either the casing
1
or
18
, the stacked electrode assembly
2
inside is not sufficiently retained in position, because it is accommodated within the casing made of a flexible laminate sheet with a certain gap provided in the direction parallel with the direction of the two extending leads
13
,
14
. As a result, continuous vibration transmitted from the portable electronic equipment in which the battery is installed may cause the stacked electrode assembly
2
to displace within the casing
1
or
18
, resulting in offsetting of the stacked electrode plate modules
3
.
Displacement of the stacked electrode assembly
2
or offsetting of the stacked electrode plates
3
give rise to various problems. For example, the joints between the negative and positive electrode leads
13
,
14
and their respective terminals
7
a
,
10
a
, and the joints between the leads and the casing
1
,
18
, which are mechanically weak, may be subjected to repeated bending, resulting in deformation or disconnection in these portions. The casing
1
,
18
is also constantly subjected to the risk of being damaged by pointed edges or burrs on the electrode assembly
2
. Also, the intermediate metal layer of the laminate sheet casing
1
,
18
may contact the electrode assembly
2
, whereby a local cell is formed due to the intervening electrolyte, resulting in development of gas, or short-circuiting across electrodes
9
,
4
or terminals
7
a
,
10
a
of opposite polarity. These troubles may lead to malfunctioning of battery output, electrolyte leakage, or corrosion of the metal layer in the laminate sheet casing caused by the electrolyte.
All of these troubles result from the structure wherein the electrode assembly
2
is not retained in position within the casing
1
,
18
. The electrode assembly
2
, in its widthwise direction which is orthogonal to the direction along the leads
13
,
14
, snugly fits in the casing
1
,
18
, because there are no leads in this direction. However, when welding the resin sheet
17
to the casing
1
,
18
with an automatic welder, welding points are spaced from the negative and positive electrod
Ichinose Hiroaki
Kaneda Masaaki
Matsumasa Yoshitaka
Suzuki Hitoshi
Tsuda Shingo
Bell Bruce F.
Jordan and Hamburg LLP
Matsushita Electric - Industrial Co., Ltd.
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