Description:Background of the invention
The present invention relates to the general field of electric batteries intended for space applications, in particular those equipping extraterrestrial vehicles.
In the context of future extraterrestrial missions, for example on the Moon or on Mars, it is necessary to design space equipment that will need to operate under extremely restrictive environmental conditions (absence of air, absence of pressure, very high amplitude temperatures that can range from -170°C to +150°C, solar and cosmic radiation, etc.). This equipment includes vehicles in particular, but also electrical stations, residents, power tools, etc.
The use of lithium-ion batteries to operate such space equipment is known. Typically, such batteries are made up of several accumulators that are mechanically assembled and electrically connected together.
In their space applications, such batteries need to have the highest possible energy density in the smallest possible space. Moreover, the temperature of the battery must be uniform, despite the fact that a lithium-ion accumulator has an operating range of between -20°C and +60°C.
For obvious safety reasons, it is also very important to avoid any propagation of thermal runaway between the different accumulators. In addition, in the event of extreme thermal runaway of an accumulator, the ejection of the internal incandescent components of the damaged cell (also called ejecta) outside the accumulator must not damage the other accumulators of the battery, which must continue to function for the safety of the astronauts.
Due to these specific requirements, these space batteries are very expensive to design, with very long lead times, very low production quantities and non-standard packaging specific to each manufacturer.

Object and summary of the invention
The main aim of the present invention is therefore to overcome such disadvantages by providing a battery that meets all the requirements of the space industry while being of simple design.
According to the invention, this aim is achieved by means of a battery module for an extraterrestrial vehicle, comprising:
- a plurality of accumulator cells mechanically assembled together and electrically connected together, each accumulator cell comprising:
o a central body forming a support;
o a plurality of accumulators disposed in pairs on either side of the central body;
o two busbars mounted against the respective poles of the accumulators in order to connect them together electrically;
o two covers mounted against the busbars; and
o two lateral casings fitted against opposite lateral faces of the accumulators and fixed on the central body;
- a central mechanical support plate mounted against the covers of the accumulator cells on the side of a lateral assembly face of the battery module and comprising heating systems on the side opposite the covers; and
- an external thermal protection plate (6) mounted against the covers of the accumulator cells on the side opposite the lateral assembly face of the battery module, delimiting with these covers at least one internal ejecta containment volume which opens to the outside via particle filters.
The battery module according to the invention is characterised in particular in that it has an internal ejecta containment volume which makes it possible, in the event of extreme thermal runaway of an accumulator cell, to contain these ejecta to prevent them from spreading outside the module and damaging the other accumulator cells. This internal containment volume opens to the outside via a particle filter to release the internal pressure while containing the ejecta particles. Thus, even in the event of thermal runaway, the battery module can continue to operate correctly, limiting the loss of energy capacity.
In addition, the lateral casings enclose the accumulators in order to reinforce them mechanically and make their temperatures uniform. Thus, the battery module has a compact architecture with good thermal conduction in nominal operation.
In an embodiment, the external thermal protection plate comprises a first metal sheet mounted against the covers of the accumulator cells and having cut-outs around the accumulator poles, a second metal sheet mounted against the first metal sheet forming with the latter an internal ejecta containment volume which is common to all the accumulator cells, and at least one particle filter positioned at a lateral end of the external thermal protection plate and opening to the inside of the internal ejecta containment volume.
In this embodiment, the second metal sheet of each external thermal protection plate is advantageously coated on one internal face with a thermal protection sheet.
In another embodiment, wherein the central mechanical support plate comprises, on the side of the lateral assembly face of the battery module, a plurality of internal ejecta containment volumes which are independent from one another, each ejecta containment volume being associated with a same accumulator cell, comprising a plurality of pockets formed around the poles of said accumulator cell, and opening to the outside at each end via a manifold feeding a particle filter.
In this other embodiment, the external thermal protection plate may comprise, on the side opposite the lateral assembly face of the battery module, a plurality of internal ejecta containment volumes which are independent from one another, each ejecta containment volume being associated with a same accumulator cell, comprising a plurality of pockets formed around the poles of said accumulator cell, and opening to the outside at each end via a manifold feeding a particle filter.
In this case the pockets of the ejecta containment volumes are advantageously covered with a thermal protection material.
Whatever the embodiment, the heating systems of the central mechanical support plate can comprise electrical resistances each position facing an accumulator cell.
Moreover, the busbars of the accumulator cells are advantageously electrically connected to the poles of the accumulators by means of connecting wires welded onto the poles and covered with a layer of thermal insulation and with a layer of electrical insulation.
Furthermore, the external thermal protection plate can be coupled to a cooling system and the central mechanical support plate and the external thermal protection plate can be made of aluminium.
Another object of the invention is a battery for an extraterrestrial vehicle comprising at least two battery modules as described above, which are electrically coupled and mechanically assembled on one another at their respective lateral assembly face.

Brief description of the figures
Other features and advantages of the present invention will become apparent from the description given below, with reference to the appended drawings which illustrate exemplary embodiments that are in no way limiting. In the figures:
- figure 1 is an overview of a battery according to the invention;
- figure 2 is a longitudinal sectional view of the battery of figure 1;
- figure 3 is an exploded view showing an accumulator cell of a battery module according to the invention;
- figure 4 is a partial exploded view of a battery module according to a first embodiment of the invention;
- figure 5 is a magnification of figure 4;
- figure 6 is a longitudinal sectional view of a part of the module of figure 4 showing the ejecta manifolds;
- figures 7 and 8 are partially exploded views of a battery module according to a second embodiment of the invention; and
- figure 9 is a view showing the way in which the busbars of the accumulator cells are electricity connected to the accumulator poles.

Detailed description of the embodiments
The invention relates to a module for a lithium-ion battery for space applications, such as batteries equipping extraterrestrial vehicles.
In a known manner, an electric battery 2a, 2b for an extraterrestrial vehicle such as that shown in figures 1 and 2 is composed of a plurality of battery modules 4a, 4b which are coupled together electrically and mechanically assembled one on top of the other.
The battery modules 4a, 4b are sandwiched between two external thermal protection lateral plates 6a, 6b, which are made of a material with low thermal resistance but which can withstand the high temperatures of the ejecta, for example aluminium.
One or more thermal systems are mounted on each external thermal protection plate 6a, 6b, either for cooling using heat pipes 8 with variable or constant conductance (or thermal bridges with low thermal resistance), or for heating using electrical resistors (not shown in figures 1 and 2).
At one of its two end faces, the battery 2a, 2b further comprises a power connector 10 and fixing supports 12.
Each of the battery modules 4a, 4b consists of a plurality of accumulator cells 14 which are mechanically assembled and electrically connected together.
Figure 3 illustrates an example of the architecture of an accumulator cell 14 for producing a battery module according to the invention.
The accumulator cell 14 shown in this figure comprises a central body 16 forming a support on which a plurality of accumulators 18 is mounted. More specifically, the accumulators 18 are disposed in accumulator pairs disposed on either side of the central body 16. The central body 16 also acts as a thermal bridge in order to distribute the heat over the accumulators.
In the exemplary embodiment of figure 4, the accumulators 18 are cylindrical. Alternatively, they can have a prismatic shape.
Moreover, two busbars 20 (also called interconnection bars) are mounted against the respective poles 22 of the accumulators in order to connect them to one another electrically.
The busbars 20 are in the form of plates made of a conductive material having circular cut-outs 24 opposite the poles 22 of the accumulators and which are screwed at the each longitudinal end onto the central body 16.
As shown more precisely in figure 9, each busbar 20 is electrically connected to the accumulator poles 22 by means of connecting wires 26, the cross-section of which is calibrated to melt above a certain current amplitude.
The connecting wires 26 are welded (for example by ultrasound) to the poles and to the poles 22 of the accumulators, and are covered with several layers of thermal insulating material, electrical insulating material and fire insulating material.
In the example shown in figure 3, the connecting wires are covered with circular pellets 28 made of aerogel and glass fibres (for thermal and electrical protection), and circular mica pellets 30 (for fire protection).
The accumulator cell 14 also includes two covers 32 made from a material resistant to high temperatures of around 1200°C (for example G-10/FR-4, which is a thermosetting laminate consisting of a continuous filament glass fabric with an epoxy resin-based binder) and covering the busbars 20 and being fixed to them by a plurality of screws 33.
Moreover, two lateral casings 34 are fitted against opposite lateral faces of the accumulators and are fixed to the central body 16 of the accumulator cell 14 by means of a plurality of screws 36.
More specifically, the inside of the lateral casings 34 has a complementary shape to that of the accumulators so that they fit snugly against them. In this way, the accumulators of the cell are sandwiched between the lateral casings and the central body, providing mechanical support for the accumulators in order to resist vibrations and shocks.
A flexible element (not shown in the figures), for example a flexible electrically insulating and thermally conductive material, is advantageously inserted between the accumulators 18 and the lateral casings 34 and the central body 16, in order to obtain uniform contact on the accumulators.
A first embodiment of a battery 2a according to the invention will now be described in conjunction with figures 4 to 6.
In this example, the battery 2a comprises two battery modules 4a sandwiched between two external thermal protection plates 6a, each battery module 4a being formed by sixteen accumulator cells 14 as described above.
Of course, the number of accumulator cells per battery module could be different, as could the number of battery modules to form a battery.
The two battery modules 4a are assembled one against the other at one of their lateral faces (hereinafter referred to as the lateral assembly face), this lateral face being on the opposite side to the two external thermal protection plates 6a.
In this first embodiment, each battery module 4a further comprises a central mechanical support plate 38a which is mounted against the covers 32 of the accumulator cells on the side of the lateral assembly face of the module.
As shown in greater detail in figure 5, this central mechanical support plate 38a comprises, on the side facing the lateral assembly side of the corresponding battery module, a plurality of internal ejecta containment volumes 40 which are independent of one another.
More specifically, each of these ejecta containment volumes 40 is associated with and common to a same accumulator cell 14 and comprises a plurality of pockets 42 which are intended to be positioned around the poles of said accumulator.
At the two longitudinal ends of the accumulator cell, each ejecta containment volume 40 opens into a manifold 44 feeding a particle filter 46, which opens to the outside to discharge the filtered gases.
Similarly, the outer thermal protection plate 6a of the battery module 4a in this first embodiment comprises, on the side opposite the lateral assembly face of the module, a plurality of internal ejecta containment volumes 48 (see figure 6) which are independent of one another.
Each of these ejecta containment volumes 48 is common to and associated with a same accumulator cell and comprises a plurality of pockets 50 which are intended to be positioned around the poles of said accumulator.
As shown in figure 6, at the two longitudinal ends of the accumulator cell, the ejecta containment volumes 48 each open into a manifold 52 feeding a particle filter 54.
Typically, the particle filters 46, 54 contain stainless steel wool, glass fibre or wool, etc. in order to absorb all the kinetic energy of the ejecta while releasing the pressure.
In this way, in the event of extreme thermal runaway of one of the accumulator cells of the battery module, the ejecta spread within the corresponding ejecta containment volume 40, 48, which prevents the ejecta from propagating outside the module and damaging the other accumulator cells.
According to an advantageous arrangement, the respective pockets 42, 50 of these ejecta containment volumes 40, 48 are covered with a thermal protection material (for example glass fibre).
Still in this first embodiment, the central mechanical support plate 38a, which is mounted against the covers of the accumulator cells, comprises heating systems on the side opposite the covers.
These heating systems typically comprise electrical resistors 56 which are each positioned facing the accumulator cells 14 of the corresponding battery module.
A second embodiment of a battery 2b according to the invention will now be described in conjunction with figures 7 and 8.
In this second example, the battery 2b also comprises two battery modules 4b sandwiched between two external thermal protection plates 6b, each battery module 4b being formed by sixteen accumulator cells as described above.
Each battery module 4b further comprises a central mechanical support plate 38b which is mounted against the covers 32 of the accumulator cells on the side of the lateral assembly face of the module.
This central mechanical support plate 38b comprises heating systems on the side opposite the accumulator cell covers. These heating systems typically comprise electrical resistors 56 which are each positioned facing the accumulator cells of the corresponding battery module.
In this second embodiment, each external thermal protection plate 6b comprises, in particular, a first metal sheet 60 which is mounted against the covers 32 of the accumulator cells and which has cut-outs 62 around the respective accumulator poles.
The external thermal protection plate 6b further comprises a second metal sheet 64 which is mounted against the first metal sheet 60 forming with the latter an internal ejecta containment volume (not shown) which is common to all the accumulator cells.
Thus, in contrast to the first embodiment, the ejecta containment volume is not individualised for each accumulator cell, but is common here to all the accumulator cells in the same battery module.
At the two lateral ends of the outer thermal protection plate 6b, this ejecta containment volume opens to the outside via particle filters 68.
Thus, in the event of an extreme thermal runaway of one of the battery module accumulator cells, the ejecta spreads within the corresponding common ejecta containment volumes, thereby containing the ejecta and preventing it from propagating outside the battery module.
According to an advantageous provision, the second metal sheet 64 of each external thermal protection plate 6b is coated on an internal face with a thermal protection sheet (not shown in the figures), made for example of glass fibre, in order to ensure resistance to very high temperatures. , Claims:1. A battery module (4a; 4b) for an extraterrestrial vehicle, comprising:
- a plurality of accumulator cells (14) mechanically assembled together and electrically connected together, each accumulator cell comprising:
o a central body (16) forming a support;
o a plurality of accumulators (18) disposed in pairs on either side of the central body;
o two busbars (20) mounted against the respective poles (22) of the accumulators (18) in order to connect them together electrically;
o two covers (32) mounted against the busbars; and
o two lateral casings (34) fitted against opposite lateral faces of the accumulators and fixed on the central body;
- a central mechanical support plate (38a; 38b) mounted against the covers (32) of the accumulator cells (14) on the side of a lateral assembly face of the battery module and comprising heating systems (56) on the side opposite the covers; and
- an external thermal protection plate (6a; 6b) mounted against the covers of the accumulator cells on the side opposite the lateral assembly face of the battery module, and delimiting with these covers at least one internal ejecta containment volume (48) which opens to the outside via particle filters (54; 68).

2. The battery module (4b) according to claim 1, wherein the external thermal protection plate (6b) comprises:
- a first metal sheet (60) mounted against the covers of the accumulator cells and having cut-outs (62) around the accumulator poles,
- a second metal sheet (64) mounted against the first metal sheet (60) forming with the latter an internal ejecta containment volume which is common to all the accumulator cells, and
- at least one particle filter (68) positioned at a lateral end of the external thermal protection plate (6b) and opening to the inside of the internal ejecta containment volume.

3. The battery module (4b) according to claim 2, wherein the second metal sheet (64) of the external thermal protection plate (6b) is coated on an internal face with a thermal protection sheet.

4. The battery module (4a) according to claim 1, wherein the central mechanical support plate (38a) comprises, on the side of the lateral assembly face of the battery module, a plurality of internal ejecta containment volumes (40) which are independent from one another, each ejecta containment volume being associated with a same accumulator cell (14), comprising a plurality of pockets (42) formed around the poles (22) of said accumulator cell, and opening to the outside at each end via a manifold (44) feeding a particle filter (46).

5. The battery module (4a) according to claim 4, wherein the external thermal protection plate (6a) comprises, on the side opposite the lateral assembly face of the battery module, a plurality of internal ejecta containment volumes (48) which are independent from one another, each ejecta containment volume being associated with a same accumulator cell (14), comprising a plurality of pockets (50) formed around the poles (22) of said accumulator cell, and opening to the outside at each end via a manifold (52) feeding a particle filter (54).

6. The battery module (4a) according to claim 5, wherein the pockets (42, 50) of the ejecta containment volumes are covered with a thermal protection material.

7. The battery module (4a; 4b) according to any one of claims 1 to 6, wherein the heating systems of the central mechanical support plate comprise electrical resistances (56) each positioned facing an accumulator cell.

8. The battery module (4a; 4b) according to any one of claims 1 to 7, wherein the busbars (20) of the accumulator cells (18) are electricity connected to the poles (22) of the accumulators by means of connecting wires (28) welded onto the poles and covered with a layer of thermal insulation and with a layer of electrical insulation (28).

9. The battery module (4a; 4b) according to any one of claims 1 to 8, wherein the external thermal protection plate (6a; 6b) is coupled to a cooling system (8).

10. The battery module (4a; 4b) according to any one of claims 1 to 9, wherein the central mechanical support plate (38a; 38b) and the external thermal protection plate (6a; 6b) are made of aluminium.

11. A battery (2a; 2b) for an extraterrestrial vehicle comprising at least two battery modules (4a; 4b) according to any one of claims 1 to 10, which are electrically coupled and mechanically assembled on one another at their respective lateral assembly face.