Sealed cell having a multilayer case

The invention provides a sealed organic-electrolyte cell. A spiral-wound group of electrodes have at least one alternation of negative electrode, separator and positive electrode. The cell has an enclosure made up of a cover and an end wall interconnected in a sealed manner by a side case surrounding the group. Each cover and end wall has a respective current outlet terminal and a central core around which the electrode group is spiral-wound, with an end wall and the cover being fixed to the ends thereof. The case surrounding the group is made of a combined metal-and-plastics multilayer material of a thickness that is smaller than 0.5 mm. The invention also provides a module of such cells and a battery that has at least one such module. The battery is suitable for use as the battery of an electric vehicle.

The present invention relates to a sealed cell having a multilayer case. 
More particularly, the invention relates to such a cell having a 
spiral-wound electrode group. 
BACKGROUND OF THE INVENTION 
In a known embodiment, sealed cells have an electrochemical group including 
at least one alternation of negative electrode, separator, and positive 
electrode, together with an enclosure made up of a cover, an end wall, and 
a case, said case surrounding said group, and said cover and said end wall 
each having a respective current outlet terminal. 
Cells that operate with an organic electrolyte need to be housed in an 
enclosure that provides adequate sealing. The case must prevent external 
elements such as moisture or oxygen in the air, and in particular 
moisture, from penetrating into the inside of the cell and thus coming 
into contact with the electrochemical group. In addition, said enclosure 
must prevent electrolyte passing out from the cell. In order to avoid 
making the cell pointlessly heavy, the mass of the components constituting 
the enclosure must be as small as possible. For high-capacity cells, in 
order to avoid taking up too much volume compared with the working volume 
of the electrochemical group, the thickness of each of the components of 
the enclosure must be as small as possible. In order to be technically 
feasible, enclosures made of metal must be of considerable thickness, e.g. 
0.3 mm to 1 mm, and therefore of considerable weight. Enclosures made of 
plastics are lighter in weight but give rise to problems of sealing, in 
particular to-ingress of moisture into the cell. This requires them to be 
thicker, e.g. at least 1 cm thick. 
Japanese application JP-A-63.181.272 describes a sealed cell comprising a 
one-piece enclosure constituted by an outer film of light metal, e.g. 
aluminum, and an inner film of resin, e.g. polyethylene, with the hermetic 
seals for the electrodes being provided by epoxy resin. Such cells 
nevertheless suffer from a problem of insufficient mechanical strength. 
Thus the problem which is posed is that of providing a cell which is 
simultaneously sealed, both from the inside of the cell to the outside and 
from the outside of the cell to the inside, that possesses sufficient 
mechanical strength to provide said cell with a good lifetime, and whose 
enclosure is relatively lightweight and relatively thin. The cell of the 
invention solves the problem posed in that by combining two means, namely 
a case of multilayer material and a central supporting core, it makes it 
possible to provide sealing, mechanical strength, small volume occupied by 
the enclosure, and an overall assembly that is light in weight. 
OBJECTS AND SUMMARY OF THE INVENTION 
The present invention provides a sealed organic-electrolyte cell 
comprising: 
a spiral-wound group of electrodes comprising at least one alternation of 
negative electrode, separator, and positive electrode; 
said cell including: 
an enclosure made up of a cover and an end wall interconnected in sealed 
manner by a side case surrounding said group, each of said cover and said 
end wall having a respective current outlet terminal; and 
a central core around which the electrode group is spiral-wound, with the 
end wall and the cover being fixed to the ends thereof; 
and the case surrounding said group is made of a combined 
metal-and-plastics multilayer material of thickness that is smaller than 
0.5 mm. 
In an embodiment, said multilayer material is two-layer material. 
The thickness of the multilayer material preferably lies in the range 0.1 
mm to 0.5 mm. 
One of the advantages of having a central core present is that it enables 
the cell to be given good mechanical strength. In addition, the use of 
such a multilayer material for the case of the cell makes it possible to 
improve said cell both respect to cost and with respect to weight of the 
cell and volume occupied by its enclosure. 
Another advantage of using such multilayer material is the possibility of 
the case destroying itself automatically in the event of an operating 
anomaly, generally in the event of high temperature (e.g. higher than 
150.degree. C.) or in the event of an increase in internal pressure, 
thereby making it possible to provide greater safety for the user. 
Finally, an additional advantage of using such a multilayer material is the 
possibility of providing sealing between the case and the end wall (or the 
cover) by heat-sealing rather than by using epoxy resin adhesive only, 
thereby providing better effectiveness and better handling during the 
process of manufacturing such a cell. 
The invention also provides a module of the above-described cells, said 
module comprising a one-piece container having compartments each housing 
one such cell, said cells being interconnected in series and/or in 
parallel; the container typically having six compartments operating in a 
configuration of three in series by two in parallel or of two in series by 
three in parallel. Finally, the invention also provides a battery 
comprising at least one module as described above, and typically 
comprising thirty modules operating in series, and a vehicle having at 
least one propulsion means powered by a source of energy comprising at 
least one such battery. The invention thus applies in particular to using 
the above-described battery as a battery for an electric vehicle.

MORE DETAILED DESCRIPTION 
The cell 1 comprises an electrochemical group 12 made up of a positive 
electrode 11, a separator 15, a negative electrode 14, and a separator 19, 
said group being spiral-wound around a central core 10 of axis X. 
The cell 1 has a side case 2 together with a cover 3a and an end wall 3b 
with respective current outlet terminals 9a and 9b. Together, the case 2, 
the end wall 3b, and the cover 3a form the enclosure of the cell 1 and 
they are connected together in sealed manner. The cover 3a and the end 
wall 3b are fixed to the corresponding ends of the central core 10. 
The case 2 of the cell 1 is a body of revolution. It is substantially 
cylindrical. 
The case 2 is constituted by a film whose thickness is less than 0.5 mm, 
which film is made up of a multilayer material, two-layer in this case, 
and can be formed by co-laminating a metal sheet 5 and a plastics sheet 4. 
The metal 5 can be aluminum or stainless steel. The plastic 4 can be 
polypropylene or polyethylene. The thickness of the metal layer within 
said material can, for example, be no more than about 0.1 mm. 
The cover 3a is made of multilayer material, a two-layer material in this 
case, and can be formed by co-laminating a metal 6a and a plastic 7a. The 
metal 6a can be aluminum or stainless steel. The plastic 7a can be 
polypropylene or polyethylene. The thickness of the cover 3a generally 
lies in the range 0.5 mm to 3 mm. The thickness of the metal layer on its 
own in said material may for example be no more than about 0.1 mm. 
Identical considerations apply to the end wall 3b and to its metal and 
plastics sheets 6b and 7b. 
The case 2 is made by winding the multilayer sheet into a cylindrical 
structure with overlapping edges and then holding the resulting cylinder 
together by adhesive or preferably by heat-sealing along an axis parallel 
to the longitudinal axis. The case can also be made by winding the 
composite sheet around the cylindrical group and then holding together the 
resulting cylinder with overlapping edges. 
In the example shown in FIG. 1, the cover 3a is assembled to the case 2 by 
circular heat-sealing 8a so as to guarantee a sealed connection. The same 
applies to the end wall 3b and circular heat-sealing 8b. Said assembly can 
be performed by any means known to the person skilled in the art, e.g. 
using adhesive. So as to make heat-sealing easier, and thus facilitate the 
operation of manufacturing the cell, the cell of the invention as shown in 
FIG. 1 has its two-layer materials oriented as follows: the metal portion 
5 of the case 2 is situated on the outside of said cell and the metal 
portion 6a of the cover 3a is also situated on the outside of said cell, 
as is the metal portion 6b of the end wall 3b. However any combination is, 
a priori, possible in the context of a multilayer material for the case 
and for the cover or the end wall, with the inside of the cover, or of the 
end wall, or of the case being made of a metal material or of a plastics 
material. 
Outlet terminal 9a serves to collect current from the positive electrodes 
11 via a connection piece 21a interconnecting the outlet terminal and the 
electrodes. Similarly the outlet terminal 9b collects current from the 
negative terminals 14 via a connection piece 21b interconnecting the 
outlet terminal and the electrodes. Each of these end assemblies is sealed 
by a respective gasket 13a or 13b which bears against the core 10 and the 
cover 3a or the end wall 3b on the corresponding connection piece 21a or 
21b. A clamping cup 17a is applied on a gasket 23a and has a plastics 
washer 22a applied thereagainst. Similarly a clamping cup 17b is applied 
against a gasket 23b and has a plastics washer 22b applied thereagain. The 
entire assembly is held by a corresponding screw 24a or 24b held by a 
respective lock nut 18a or 18b. 
The cell shown in FIG. 1 was manufactured as follows: the electrochemical 
group 12 was wound on the core 10 and then the electrode connections 21a 
and 21b were put into place; the gasket 13b was installed on one end of 
the core; then the end wall 3b was installed over the gasket 13b; finally 
clamping was performed by installing the parts 24b, 23b, 17b, 22b, and 
18b. The group was then inserted into the case 2 with holding means (e.g. 
vacuum means) serving to spread apart the walls of the case 2 while the 
group 12 was being inserted therein. The end wall was then heat-sealed at 
8b to the case. Thereafter the cover was put into place by inserting the 
pieces 13a, 3a, 24a, 23a, 17a, 22a, and 18a. Finally heat-sealing was 
performed at 8a. 
FIG. 2 is a diagrammatic view showing the outside of a module made up of a 
one-piece container 16 of the invention having six compartments 20 each 
containing a respective cell 1 as shown in FIG. 1. The cell 1 as inserted 
in this way into a compartment of said container is thus supported 
mechanically by the walls of the compartment 20 containing it. The small 
bulk of the case 2 makes it possible for each compartment to have a large 
volume fraction thereof occupied by working volume of the electrochemical 
group. 
The case 2 shown in FIG. 1 is substantially cylindrical. It could also be 
prismatic. 
Another embodiment is such that the cover 3a, and also the end wall 3b, is 
made of a metal material of thickness lying in the range 0.5 mm to 3 mm 
(not shown). 
The cell of the invention operates, for example, with a liquid organic 
electrolyte, however the electrolyte could also be a solid polymer. The 
electrochemical couple involved is generally a rechargeable lithium-ion 
couple, however the invention can be extended to any primary or secondary 
cell using lithium metal.