Chemistry: electrical current producing apparatus – product – and – Plural concentric or single coiled electrode
Reexamination Certificate
1999-03-25
2001-02-20
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Plural concentric or single coiled electrode
C429S178000, C429S208000, C429S211000
Reexamination Certificate
active
06190794
ABSTRACT:
TECHNICAL FIELD
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 incorporates 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 has a high volumic power density, is lighter, a lower manufacturing cost than the prismatic batteries of the prior art as a result of a new concept of the jelly roll type of winding and which also allows safety of use to be increased.
The prismatic batteries of the prior art, schematically shown in
FIGS. 1 and 1A
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, which has then been impregnated by an electrolyte. It will be noted that, in order to obtain the highest possible power density, i.e. to be able to introduce into the container the greatest possible quantity of active materials, it is imperative that the electrolyte is added after winding
2
is put in place, because of the swelling phenomena. This winding, which is obtained from 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
, does not allow precise positioning of the electric connection zones of anode
2
a
and cathode
2
c
to be obtained. It is therefore necessary to provide intermediate connection means
5
,
6
between said connection zones and external contacts terminals
7
,
8
situated for example on a cover
4
hermetically sealed to container
1
. These intermediate connection means
5
,
6
have to be welded to the inside of the container, which means that it is difficult to control the quality thereof. Each additional weld represents a risk of malfunction, either because of mechanical shocks during use, or because of mechanical stress which will be exerted after assembly, in particular during charging/discharging cycles for a storage battery. This jelly roll is generally held compressed for example by means of two corrugated elastic plates
3
a
,
3
b
, arranged between the large walls of container
1
and said winding
2
. These elastic plates also allow small variations in volume of winding
2
during charging/discharging cycles to be absorbed. This type of prismatic battery, in particular in the case of a 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.
The jelly roll has advantages as regards the current density which is theoretically available, but requires a certain number of precautions to be taken, both as regards the manufacture thereof and the installation thereof in the metal container. Indeed, to have a maximum current density, it is important for the winding to have good cohesion at every point, i.e. for all the alternate layers of active materials and separators to be perfectly in contact with each other. This result is easily obtained for the rectilinear portion of the winding as a result of the compression means, for example by means of elastic plates
3
a
,
3
b
. For the curved portions at each end, the cohesion essentially depends upon the manufacturing method. In the current state of the art, a jelly roll is obtained first by effecting a winding on a cylindrical core which is then removed prior to exerting compression to give it an ellipsoidal shape suited to the opening of the container. In order to reduce dislocations observed in the curved portion of the jelly roll, U.S. Pat. No. 5,658,683 proposes using a substantially rhombic shaped core. In all cases, the winding obtained has to be manipulated with precaution to be introduced into the container at the same time as the elastic plates. In series manufacturing it is thus necessary to have improved automated equipment, which will have an influence on the unit price of the final product.
SUMMARY OF THE INVENTION
The object of the present invention is to overcome the aforementioned drawbacks by providing a prismatic battery in which a coiled winding of the jelly roll type provides, with a low manufacturing cost, high power density, increased reliability and longevity, and greater safety of use when the coiled winding is associated with a container of a particular shape.
The invention therefore concerns a prismatic battery including a metal container formed of at least two large walls, two small walls and a bottom delimiting a cavity within which is arranged a non circular spiral winding of at least one composite strip to form successive turns including an anode and a cathode separated by porous separators, the assembly being impregnated by an electrolyte, said container being sealed at its upper portion by a sealed cover carrying two contact terminals electrically connected to the anode and the cathode via connection means, characterised in that said spiral winding is formed around a rigid spool including an upper horizontal flange, having substantially the dimensions of the opening of the cavity, and a horizontal lower flange, having substantially the internal dimensions of the bottom, said flanges being joined by a vertical central neck and, on either side by two lateral necks, said necks delimiting two openings in the median plane of the spool and a free space at the periphery thereof to house the spiral winding.
A prismatic battery of the type which has just been described can be provided with usual connection means, such as a strip or a flexible conductive wire arranged, either at each end of the winding, or between the openings delimited by the necks. According to another aspect of the invention, said connection means are formed by two metal rods or tubes arranged between the openings, which are flattened in the portion situated between the two flanges and one of whose ends passes through the upper flange through orifices arranged therein.
According to another aspect of the invention the axial positioning of said rods or said tubes is also obtained as a result of orifices situated in the lower flange to accommodate the other end of each rod or tube.
According to another aspect of the invention, the upper and lower flanges are further provided with positioning orifices at right angles to the lateral necks and on either side of the median portion of the spool, said orifices being provided for setting in place positioning rods during coiling of the winding. Once the winding is obtained, the positioning rods are removed; which allows any mechanical stress on the weld points between the metal rods or tubes and the anode and cathode to be removed.
The invention also concerns a prismatic battery including in a metal container a coiled winding of the type which has just been described, said container having its large walls recessed by stamping after the spool has been set in place, so as to produce gripping of the lower flange. In such case, the lower flange has a greater width than that of the upper flange. S
Maples John S.
Pollock, Vande Sande & Amernick, R.L.L.P.
Renata AG
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