Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed... – Blowout type
Reexamination Certificate
1999-11-10
2002-08-13
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
Blowout type
C429S053000, C429S094000, C429S120000
Reexamination Certificate
active
06432572
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery cell such as a nonaqueous electrolytic secondary cell in which a winding-type power-generating element is housed within a cell case, and a battery (multiple-cell set) using it.
2. Description of the Related Art
An explanation will be given of a conventional structure of a large-scale large-capacity elliptic-cylindrical nonaqueous secondary cell
1
. As seen from
FIG. 19
, a power generating element
2
of the nonaqueous secondary cell is composed of a belt-shaped electrolytic positive electrode
2
a
and a belt-shaped negative electrode
2
b
which are wound in an elliptic-cylinder through belt-shaped separators
2
c
. The positive electrode
2
a
has an area of a mixture
2
d
of an active material and binder for the positive electrode applied on the surface of an aluminum foil and another area on which the mixture
2
d
is not applied and to which the aluminum foil is exposed at the belt-shaped lower end of the foil. The negative electrode
2
b
has an area of a mixture
2
e
of an active material and binder for the negative electrode applied on the surface of a copper foil and another area on which the mixture
2
e
is not applied and to which the copper foil is exposed at the belt-shaped upper end of the foil. These positive electrode
2
a
and a negative electrode
2
b
are wound in a manner displaced horizontally little by little so that the lower end of the positive electrode
2
a
protrudes downward and the upper end of the negative electrode
2
b
protrudes upward.
As seen from
FIG. 20
, a negative electrode collector
9
is fixedly connected to the upper end of the negative electrode
2
b
of the power generating element
2
which protrudes upwards. The negative electrode collector
9
is made by stamping a copper alloy plate and folded to form slits. The copper foils exposed to the upper ends of the negative electrodes
2
b
are inserted in and fixedly connected to the respective slits by clamping or welding. A negative electrode terminal
5
of a copper alloy is fixedly connected to the negative electrode collector
9
by clamping or welding so that it protrudes upward. A positive electrode collector
8
is fixedly connected to the lower end of the positive electrode
2
a
of the power generating element
2
which protrudes downwards. The positive electrode collector
8
is made by stamping an aluminum alloy plate and folded to form slits. The aluminum foils exposed to the lower ends of the positive electrodes
2
a
are inserted in and fixedly connected to the respective slits by clamping or welding. The one end of the positive electrode collector
8
is extended to the negative electrode collector
9
along the power generating element
2
to reach the upper side thereof. A positive electrode terminal
4
of the aluminum alloy is fixedly connected to the positive electrode collector
8
by clamping or welding.
The power generating element
2
to which the positive electrode collector
8
and the negative electrode collector
9
are connected is housed within a cell case
3
as shown in FIG.
21
. The cell case
3
is made of an aluminum alloy plate or stainless steel plate, and is composed of an elliptic-cylindrical vessel-shaped case body
3
a
and an elliptic cover plate
3
b
fit in the upper opening thereof and sealed by welding on the periphery. The positive electrode terminal
4
and negative electrode terminal
5
which are fixedly connected to the power generating element
2
are caused to protrude upwards through the opening holes located at two positions of the cover plate
2
from the inside of the cell case
3
. These electrode terminals
4
and
5
are electrical insulating sealed by forming a glass hermetic seal in gaps between themselves and the opening holes. Incidentally, a metallic ring made of the same material as the cover plate
3
b
is electrical insulating secured to each of these positive electrode terminal
4
and negative electrode terminal
5
by a glass. hermetic seal or ceramic hermetic seal. These metallic rings are secured to seal the opening holes at two positions of the cover plate
3
b
. The cover plate
3
b
, thereafter, is fit in the case body
3
a
and sealed therein by welding.
The nonaqueous electrolytic secondary cell
1
is accompanied by the following danger. Namely, when the power generating element
2
is heated excessively while abnormality occurs, the electrolyte is decomposed to generate gas. Then, the inside pressure is boosted so that the cell case
3
may be broken. In order to overcome such an inconvenience, in the conventional art, safety valves
6
were formed on the bottom of the case body
3
a
and on the cover plate
3
b
. The safety valves
6
are constructed by the plate areas thinned by forming grooves in the aluminum alloy plate or stainless steel plate constituting the case body
3
a
and cover plate
3
b
. When the pressure within the cell case
3
is boosted abnormally, the grooved thin plate areas are broken so that the inside of the cell case is degassed.
Now, it should be noted that the gas generated in the power-generating element
2
can move only toward either the upper end or lower end along a winding axis direction because the positive electrode
2
a
and negative electrode
2
b
are closely wound. In order to avoid such an inconvenience, safety valves
6
are formed on the bottom of the case body
3
a
and on the cover plate
3
b
so that the gas moved out from the upper and lower ends in the winding axis direction can be smoothly discharged externally. However, where such an elliptic-cylindrical nonaqueous electrolytic secondary cell
1
is used as a single cell, when the internal pressure increases, the planar portion of the side wall of the case body
3
a
swells outwardly. Therefore, for example, the gas moved out from the lower end of the power-generating element
2
can be transferred to the upper end through the swelled side of the case body
3
a
. In this case, the safety valve
6
may be formed on only the cover plate
3
b
at the upper end. However, where a plurality of the nonaqueous electrolytic secondary cells
1
are closely arranged so that they can be used as a battery, the planar portions of the sides of the adjacent nonaqueous electrolytic secondary cells push each other so that each battery cannot swell by the internal pressure unlike the case of the single cell. Thus, the gas moved out from the lower end of the power generating element
2
cannot shift. In this case, the safety valve
6
must be also formed on the bottom of the case body
3
a.
Where the conventional nonaqueous electrolytic secondary cell
1
is used as a constituent of the battery, it cannot be used with the bottom of the cell where the safety valve
6
is formed being closed. For example, in the case of the battery for a special use such as aeronautics/space, as shown in
FIG. 22
, a cooling plate
7
of a material having a high thermal conductivity such as an aluminum alloy is arranged between the plurality of nonaqueous electrolytic secondary cells
1
and beneath the bottom of each nonaqueous secondary cell so that the battery can be cooled by a cooling means (not shown). In this case, the planar portion of the side of each nonaqueous secondary cell
1
is restrained by the cooling plate
7
and hence cannot swell. This requires for the safety valve to be formed on the bottom of the case body
3
a.
However, because the bottom of the case body
3
a
is also blocked by the cooling plate
7
, the safety valve
6
cannot operate normally.
Even where the nonaqueous electrolytic secondary cell
1
is used as a single cell, if the side wall of the case body
3
a
cannot swell because the cell is arranged with no gap within an installing space, the safety valve
6
must be formed on the bottom of the case body
3
a
. In this case also, the cell must be used with the bottom of the cell where the safety valve
6
is formed being not closed.
In the case of the cylindrical nonaqueous electrolytic secondary cell, th
Inoue Takefumi
Masuda Hideki
Yoshida Hiroaki
Japan Storage Battery Co., Ltd.
Maples John S.
Sughrue & Mion, PLLC
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