Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
1999-03-25
2001-05-15
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
C429S175000, C429S094000
Reexamination Certificate
active
06232015
ABSTRACT:
The present invention concerns a storage battery or prismatic cell, designated hereinafter by the generic term “battery”, whether the power source is rechargeable or not. The invention concerns more particularly such a battery in which the power source is formed of a winding of active materials of the jelly roll type.
BACKGROUND OF THE INVENTION
In portable equipment, such as mobile telephones, prismatic shaped batteries are generally preferred to rod shaped ones in particular to reduce the overall size of the equipment. This portable equipment, which must by definition be light, generally incorporate electronic circuits and components which are fragile and often demanding from the point of view of power consumption. It is thus desirable for the prismatic batteries used in such equipment to have high power density while being light and of the lowest manufacturing cost possible, for them to have sufficient longevity, in particular in the case of storage batteries, and for them to have during use all necessary guarantees from the safety point of view, as regards both the user and the contiguous electronic circuits.
An object of the present invention is to provide a prismatic battery which, for a determined current density, is lighter, has a lower manufacturing cost than the prismatic batteries of the prior art and whose design also allows safety of use to be increased.
The prismatic batteries of the prior art, schematically shown in
FIG. 1
are formed by a metal container
1
of parallelepiped shape, within which is placed a non circular spiral winding
2
, of the jelly roll type (visible in
FIGS. 1A
,
1
B), which is impregnated by an electrolyte after the winding is put in place. This winding is obtained from at least one composite strip including a layer of active material forming anode
2
a
, a porous separator
2
b
, a layer of active material forming cathode
2
c
and a second porous separator
2
b
. The anode and the cathode each include connection means
5
,
6
, generally arranged close to the inner wall of container
1
and at the center of winding
2
. This jelly roll is generally held compressed by means of two corrugated elastic plates
3
a
,
3
b
, arranged between the large walls
11
,
13
of container
1
and winding
2
. These elastic plates also allow the small variations in volume of winding
2
to be absorbed during the charging/discharging cycles. The unit thereby formed is hermetically sealed by a cover
4
carrying contact terminals
7
,
8
electrically connected to electrodes
2
a
,
2
c
by connection means
5
,
6
said electric connections being effected by welding. This type of prismatic battery, in particular in the case of an storage battery, generally also includes a safety vent schematically shown at
9
. This safety vent
9
is in fact necessary given the chemical reactions which take place and which can cause an increase in pressure and/or temperature. Because of the mechanical stress which are exerted on the case of the battery, the container was first chosen to be formed of steel sheet of equal thickness of the order f 0.5 mm (FIG. A). In order to make this battery lighter and less expensive, it was then proposed to replace the steel with aluminum or an aluminum alloy. In order to have the same resistance to deformation, it is then necessary to increase the thickness of the container wall, which has the drawback, either of increasing the size of the battery for a given power density, or reducing the quantity of active material and thus the power density if one wishes to keep the size of the battery within standard dimensions.
In order to avoid this drawback, U.S. Pat. No. 5,556,722 proposes reinforcing the angles
1
a
to
1
d
of the container, i.e. having a excess thickness locally, as shown in
FIG. 1
B. Although the manufacturing method for such a container is not described, it is obvious that such a configuration increases the cost of the final product given that one can no longer use a metal sheet of equal thickness as the starting material.
SUMMARY OF THE INVENTION
The object of the present invention is to overcome the aforementioned drawbacks by providing a prismatic jelly roll battery, having a low weight and manufacturing cost, while having available a power density at least equal to known prismatic batteries having the same external dimensions.
The invention therefore concerns a prismatic battery including a metal container of substantially identical thickness at any point, within which is arranged a non circular spiral winding formed by a composite strip including an anode, separators and a cathode impregnated by an electrolyte, the container being sealed at its upper portion by a sealed cover carrying two contacts terminals electrically connected to the anode and the cathode via connection means, characterized in that said container is formed by a rectangular base and, perpendicular to the latter, by two small walls attached to the base, two large walls attached on the one hand to the small walls via narrow strips of width I
1
, on the other hand to the base via narrow strips of width I
2
, the strips being inclined towards the external faces of the large walls and having between them junction lines from the four angles of the base.
The strips joining the large walls to the small walls form with respect to the plane of the large walls an angle &agr;
1
and the strips joining the large walls to the base an angle &agr;
2
. So that the junction lines between the strips are perfect at the angles, the variables &agr;
1
, &agr;
2
, I
1
and I
2
must satisfy by the relationship I
1
sin &agr;
1
=I2 sin &agr;
2
.
It is thus possible, by using the free space left in the angles by the spiral winding in a rational manner, and without thereby providing a particular profile for the tubular portion of the container, to give the large walls sufficient rigidity to resist the internal pressures of the prismatic battery. Indeed, a peripheral rib, which shortens the bending distance near the edges is thus formed. If aluminum or an aluminum alloy is used to manufacture the container, the thickness of the walls could be substantially the same as that of steel containers, i.e. of the order of 0.5 mm for batteries of the current type, and an advantage would thus be obtained as regards weight and cost.
If steel is still used, or a steel alloy, it would then be possible to reduce the thickness of the container walls for example from 0.5 mm to 0.35 mm while keeping the same mechanical properties, while still having an advantage as regards weight and cost.
According to another aspect of the invention the reduction in cost also results from the fact that it is no longer necessary to insert an elastic spacer between the large walls and the spiral winding to obtain good cohesion of the spiral winding, such cohesion being necessary to obtain the optimum yield from the active materials, and thus the best possible power density.
This result is obtained as a result of a method for manufacturing the container consisting in deforming a metal sheet by stamping so as to obtain a convex container having at its base junction strips corresponding to the values &agr;
1
, &agr;
2
,
1
1
, and
1
2
, then introducing the spiral winding and finally stamping the large walls to give them a concave shape.
It will be noted that the method according to the invention offers the advantage of having, prior to stamping the large walls, a cavity having a volume greater than the final volume, which allows the jelly roll to be put in place already impregnated by the electrolyte, despite the swelling that this has caused.
REFERENCES:
patent: 5434017 (1995-07-01), Berkowitz et al.
patent: 5439760 (1995-08-01), Howard et al.
patent: 5486215 (1996-01-01), Kelm et al.
patent: 5556722 (1996-09-01), Narukawa et al.
patent: 6033800 (2000-03-01), Ichiyanagi et al.
patent: 0 655 793 (1995-05-01), None
patent: 63-245851 (1988-10-01), None
patent: 6-342649 (1994-12-01), None
patent: 9-237613 (1997-09-01), None
Connolly Bove Lodge & Hutz
Maples John S.
Renata AG
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