WO2024132861A1

WO2024132861A1 - Vehicle battery having an elastic return system

Info

Publication number: WO2024132861A1
Application number: PCT/EP2023/085895
Authority: WO
Inventors: Stéphane Ruby
Original assignee: Ampere S.A.S.
Priority date: 2022-12-19
Filing date: 2023-12-14
Publication date: 2024-06-27
Also published as: FR3143858A1

Abstract

The present invention relates to a battery (1) for a motor vehicle, comprising a plurality of electrochemical cells (2), a first plate (12) and a second plate (14), the electrochemical cells (2) being stacked on top of one another in a stacking direction between the first plate (12) and the second plate (14), the battery (1) comprising at least one elastic return system (18) that connects the first plate (12) and the second plate (14).

Description

DESCRIPTION

Title: Vehicle battery with elastic return system

The present invention relates to the field of electrical energy storage devices, and more particularly the means implemented to apply pressure forces to such devices, where appropriate to manage in parallel variations in volume of the cells which make up these devices.

It is known to equip electric or hybrid vehicles with electrical energy storage devices allowing an electrical supply to the various elements of the vehicle, for example those which participate in its propulsion. These electrical energy storage devices are generally composed of electrical or electrochemical cells positioned in a vehicle battery.

In a context of growing electrification of motor vehicles, it is known to have electrical energy storage devices which comprise a plurality of cells stacked in a housing, and the electrochemical technologies implemented for the production of these cells are evolving. so that each cell is always more efficient and compact.

In these new technologies, the electrochemical cells of certain batteries, for example and without these examples being limiting, solid electrolyte batteries known by the English name ASSB for "all solid state batteries", or even those whose chemistries include silicon and which are generally associated with liquid electrolytes, require pressurization so that each of the electrochemical layers of the cells is well pressed against the neighboring layer(s), in order to obtain optimal performance, whether in terms of efficiency, lifespan or even operational safety. This pressurization can result in very high pressures ranging from several bars to several tens of bars, which induces significant mechanical forces on the systems responsible for pressurization.

Electrochemical cells can also, over the course of their charge and discharge cycles or due to their aging, exhibit significant variations in volume, which must be taken into account when pressurizing. There are systems in the prior art capable of implementing, within the battery, pressurization of the electrochemical cells. Document FR3098353, for example, provides a frame containing springs and a movable plate which bears against a stack of cells, these springs exerting a pressure force on the movable plate to compress the cells. Such a system is, however, heavy and bulky, in particular due to the space required to accommodate the movable plate and the springs in the direction of stacking of the cells, and it therefore leads to a reduction in the efficiency of the battery. Such a system thus limits, at equal volume, the space dedicated to the electrochemical cells which dictate the performance of the battery.

The present invention fits into this context by proposing a battery equipped with a system making it possible to apply pressure on the electrochemical cells on the one hand and to manage their variations in volume on the other hand, while presenting advantages of compactness and lightness so as to guarantee optimal energy density of the battery.

The main object of the present invention is thus a battery for a motor vehicle, comprising a plurality of electrochemical cells, a first plate and a second plate, the electrochemical cells being superimposed on each other in a stacking direction between the first plate and the second plate, the battery comprising at least one elastic return system connecting the first plate and the second plate.

The battery according to the invention is intended to equip a vehicle, for example a hybrid or electric automobile vehicle, with a view to powering its electric motor. For this purpose, the battery includes electrochemical cells, which are units within which redox reactions take place allowing electrical energy to be obtained. These electrochemical cells are here arranged so as to be superimposed one above the other in a stacking direction which is substantially perpendicular to a plane in which they mainly extend. The electrochemical cells thus form a stack which is delimited at each end by a plate, with respectively a first plate and a second plate. Such plates are flat and are for example made of a metallic material.

The battery comprises an elastic return system which extends between the first plate on the one hand and the second plate on the other hand, this elastic return system being thus arranged along the stack of electrochemical cells. The elastic return system helps bring the first plate closer to the second plate, pressing on this occasion on the electrochemical cells which are superimposed between the plates. The result is that the elastic return system causes compression of the electrochemical cells, the elastic nature of the elastic return system also making it possible to adapt to a temporary or progressive increase in their volume, respectively during successive charges and discharges of the cells or due to their aging. The elastic return system is here passive in that it self-regulates the compression of the electrochemical cells.

According to an optional characteristic of the invention, the battery comprises a first elastic return system and a second elastic return system arranged on either side of the stack of electrochemical cells.

According to an optional characteristic of the invention, the electrochemical cells have a substantially rectangular shape, the first elastic return system being arranged along a first side of the electrochemical cells and the second elastic return system being arranged along a second side of the electrochemical cells opposite the first side.

Electrochemical cells are pocket-type cells, also known as “pouch cells”. Such cells have a substantially parallelepiped shape, and they comprise a flexible film which constitutes an envelope for a stack of electrochemical layers. The battery comprises two elastic return systems which are arranged along opposite sides in pairs of the stack of electrochemical cells. Such an arrangement of the elastic return systems makes it possible to distribute the pressure forces within the battery.

According to an optional characteristic of the invention, each of the first plate and the second plate has dimensions, measured in a longitudinal transverse plane perpendicular to the stacking direction, greater than the dimensions of an electrochemical cell so as to present a free peripheral portion, the elastic return system extending from the free peripheral portion.

The plates thus have dimensions greater than the electrochemical cells, so that they protrude on either side of the latter when the battery is seen in the stacking direction. In other words, the free peripheral portion corresponds to a portion of the plates which is not covered by the electrochemical cells.

According to an optional characteristic of the invention, the elastic return system comprises at least one arch.

According to an optional characteristic of the invention, the at least one arch comprises a head connecting a first arm and a second arm, the first arm being in contact with the first plate and the second arm being in contact with the second plate.

Each of the arms extends at least partially along one of the plates, with the first arm in contact with the first plate and the second arm in contact with the second plate. The positioning of the first arm and the second arm is here such that they are fixed in a corner of the plate which is respectively associated with them, with the first arm in contact with a corner of the first plate and the second arm in contact from a corner of the second plate. In other embodiments, the first and second arms can be further away from the corners of the plates, so as to apply a force closer to a central area of the plates. Deformation of the plates caused by this effort is thus reduced.

According to an optional characteristic of the invention, the elastic return system comprises a first arch and a second arch, the head of the first arch being arranged opposite the head of the second arch.

The elastic return system can be designed according to different embodiments, in some of which it takes the form of arches. These arches, including a first arch and a second arch which correspond to the at least one arch previously mentioned, have a shape similar to what has been described, with each arch which has a head of rounded shape which is extended by a first arm and a second arm. The arches are arranged opposite each other, such that the head of the first arch is closer to the head of the second arch than to the arms of the latter. Such opposition allows a homogeneous distribution of pressure on each electrochemical cell, particularly in the presence of two elastic return systems; the arms of each of the arches are thus in contact with the four corners of the plates, which makes it possible to distribute the forces over a surface of these plates. In certain embodiments, the elastic return system may comprise, in addition to the first arch and the second arch, two additional arches which induce a reduction in the forces on each arch.

According to an optional characteristic of the invention, the first arch and the second arch are connected by a connecting portion extending along the first plate and/or the second plate.

According to an optional characteristic of the invention, the first arch and the second arch are connected by a connecting portion extending substantially equidistant from the first plate and the second plate.

In certain embodiments of the elastic return system, the arches are made integral with each other by a connecting portion. Such a connecting portion can, according to variants, connect the arms of the arches by extending along each of the plates, or even connect the heads of these arches. When the connecting portion extends along the plates, it makes it possible to distribute the forces generated by the fixing between a plate the arms of the arches over a greater distance and thus makes it possible to reduce the forces which would otherwise be concentrated on a point of fixation. When placed between the heads of the arches, the connecting portion limits the lateral vibrations of these heads which are not fixed to the plates. The connecting portion then makes it possible to stiffen the elastic return system, by limiting the movement of the heads and thus their contact with the electrochemical cells.

According to an optional characteristic of the invention, the arch(s) are formed by a helical spring.

This is a particular embodiment of the arches, in which the head of the at least one arch corresponds to at least one turn of a helical spring while the arms of this arch are straight segments of the spring helical.

According to an optional characteristic of the invention, each of the first plate and the second plate respectively comprises a first pin and a second pin, the elastic return system comprising a first curved portion and a second curved portion each connected to one of the first pins by a first pivot connection and to one of the second pins by a second pivot link, the curved portions being joined to one another at their central portion. Each curved portion comprises a central portion and two end portions linked to the pins, the central portion being connected to the central portion of the other curved portion.

The pawns correspond to protruding parts of the plates, which extend mainly in a direction of elongation perpendicular to the direction of stacking. In this embodiment, the elastic return system takes a cross shape, each branch of this cross being connected to a pin of the first plate and to a pin of the second plate. The pivot connections make it possible to reduce the mechanical stress at the level of contact between the plates and the elastic return system.

According to an optional characteristic of the invention, the battery comprises a housing in which the electrochemical cells are arranged, at least one of the first or the second plate being formed by a wall of the housing.

The housing corresponds to a housing within which one or more stacks of electrochemical cells can be arranged. According to this alternative embodiment, either the first plate or the second plate is constituted by a wall of the housing; the stack of electrochemical cells is then directly in contact with the housing. For example, a bottom wall of this box can constitute the second plate. Such an alternative embodiment makes it possible to limit the number of parts used for the production of the battery, while constituting a gain in volume and mass. In other embodiments, the electrochemical cells can be integrated into the housing for reasons of protection or handling, without necessarily having a wall of this housing constitute one of the plates.

According to an optional characteristic of the invention, the elastic return system is made of a metallic material.

According to an alternative characteristic, the elastic return system is made of an elastomeric material.

These are two possible variants of materials constituting the elastic return system, such materials being chosen according to their degree of elasticity and their pressure capacity which respectively determine the deformation and compression capacities of the system. elastic reminder. An elastic recall system in one Elastomeric material is thus more elastic than an elastic return system made of a metallic material, which favors the regulation of volume variations within the battery. Conversely, the use of a metallic material allows the elastic return system to withstand high pressures. Among these metallic materials, steel makes the elastic return system more rigid than aluminum, for example.

The elastic return system can alternatively be made of a composite material, or even of carbon fibers.

According to an optional characteristic of the invention, the elastic return system is secured to the first plate by an irreversible fixing means and to the second plate by a reversible fixing means.

By “irreversible fixing means” is meant a means of securing the elastic return system to the first plate so that these elements form a single piece assembly, or one-piece assembly, which cannot be broken down without deterioration of the 'one of the elements. Conversely, the term “reversible fixing means” means a means of securing the elastic return system to the second plate so that this means can be removed without damaging one or the other of these parts. The elastic return system and the first plate can thus be assembled by welding or by gluing while the elastic return system and the second plate are associated by screwing. Such screwing makes it possible in particular to extend the elastic return system when it is secured to the second plate, for example by screwing the elastic return system while the second plate is maintained at a distance from the first plate which is greater than the maximum corresponding distance of the elastic return system at rest, so that this elastic return system is stressed in traction when the assembly is fixed and the elastic return effect tends to bring the plates closer to each other 'other and to compress the electrochemical cells arranged between these plates.

In certain alternative embodiments, the elastic return system is secured to the first plate by a first reversible fixing means and to the second plate by a second reversible fixing means.

The invention also relates to a motor vehicle comprising a battery as mentioned above. The invention further relates to a method of assembling a battery as mentioned above, comprising a step of securing the elastic return system to the first plate, a step of arranging the electrochemical cells on top of each other. according to the direction of stacking on the first plate, a step of covering the stack of electrochemical cells by the second plate and a step of securing the elastic return system to the second plate, during which the elastic return system is stretched.

The elastic return system is for example secured to the first plate by the irreversible fixing means. The electrochemical cells are then arranged on the first plate in the stacking direction, then they are covered by the second plate. It is notable that the height of the stack of cells, measured perpendicular to the plane in which the first plate extends, is then greater than the height of the elastic return system at rest. The second plate is then secured to the elastic return system by the reversible fixing means, and in particular by a screwing action of an arm of the elastic return system on the second plate. The screwing action generates traction on the elastic rest system, for example by holding the second plate in position when screwing. In other words, we ensure that the elastic return system stretches as the screwing progresses so that this elastic return system is stressed in traction and that the elastic return force tends to bring back the second plate towards the first plate and to compress the electrochemical cells interposed between these plates.

Other characteristics, details and advantages of the invention will emerge more clearly on reading the description which follows on the one hand, and examples of embodiment given for informational and non-limiting purposes with reference to the appended drawings on the other hand. , on which ones :

[Fig. 1] illustrates, schematically, a perspective view of a battery according to the invention, with an elastic return system according to a first embodiment;

[Fig. 2] illustrates, schematically, a side view of the battery of Figure 1;

[Fig. 3] illustrates, schematically, a side view of a battery similar to that of Figure 1 with an elastic return system according to a second embodiment;

[Fig. 4] illustrates, schematically, a side view of a battery similar to that of Figure 1 with an elastic return system according to a third embodiment; [Fig. 5] illustrates, schematically, a side view of a battery similar to that of Figure 1 with an elastic return system according to a fourth embodiment;

[Fig. 6] illustrates, schematically, a side view of a battery similar to that of Figure 1 with an elastic return system according to a fifth embodiment.

The characteristics, variants and different embodiments of the invention can be associated with each other, in various combinations, to the extent that they are not incompatible or exclusive with respect to each other. In particular, it will be possible to imagine variants of the invention comprising only a selection of characteristics described subsequently in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage and/or to differentiate the invention. compared to the prior art.

In the figures, elements common to several figures retain the same reference.

In the detailed description which follows, the designations “longitudinal”, “transverse” and “vertical” refer to the orientation of the battery according to the invention. A longitudinal direction corresponds to a main extension direction of an electrochemical cell of the battery, this longitudinal direction being parallel to a longitudinal axis L of a mark L, V, T illustrated in the figures. A vertical direction corresponds to a direction of stacking of the electrochemical cells, this vertical direction being parallel to a vertical axis V of the reference L, V, T and this vertical axis V being perpendicular to the longitudinal axis L. Finally, a transverse direction corresponds to a direction parallel to a transverse axis T of the reference L, V, T, this transverse axis T being perpendicular to the longitudinal axis L and to the vertical axis V, the electrochemical cells extending mainly in a longitudinal plane- transverse.

Figures 1 to 6 thus illustrate, schematically, a battery 1 according to the invention, this battery 1 being represented according to a first embodiment in Figures 1 and 2, according to a second embodiment in Figure 3, according to a third mode embodiment in Figure 4, according to a fourth embodiment in Figure 5 and according to a fifth embodiment in Figure 6. The characteristics which will be described in relation to one of these embodiments are intended to apply, mutatis mutandis, to all of the illustrated embodiments, as long as these characteristics are not incompatible. The battery 1 is intended to equip a vehicle, in particular a hybrid or electric vehicle, in order to power a thermal engine of this vehicle. The battery 1 thus comprises a plurality of electrochemical cells 2, which are pocket-type cells within which redox reactions necessary for the operation of the battery 1 take place. These electrochemical cells 2 comprise electrochemical layers, among which at least one electrolyte, an anode and a cathode, these electrochemical layers being contained in a flexible envelope which is an outer membrane of the electrochemical cells 2.

Within the battery 1, the electrochemical cells 2 are superimposed on each other in a stacking direction which corresponds to a vertical direction V, such stacking direction being substantially perpendicular to a longitudinaltransverse plane in which mainly extend electrochemical cells 2.

Each electrochemical cell 2 here has a generally rectangular shape, so that it extends between a first side 4 which is a first longitudinal end 4 and a second side 6 which is a second longitudinal end 6, these longitudinal ends 4, 6 being opposed to each other and connected together by a first transverse end 8 and a second transverse end 10, which form two other sides of the electrochemical cells 2.

The stack of electrochemical cells 2 is delimited, according to the stacking direction, by plates 12, 14 of the battery 1, which here are substantially flat rigid plates. The electrochemical cells 2 are more precisely superimposed between a first plate 12, which constitutes a base for the stack of the electrochemical cells 2, and a second plate 14, which forms a covering element for this stack. The plates 12, 14 are substantially flat rectangular pieces, one face of which is in contact with the electrochemical cells 2 and an opposite face is at a distance from them. These plates 12, 14 both have dimensions, measured in a longitudinal-transverse plane and which correspond to their respective lengths and widths, which are greater than the corresponding dimensions of the electrochemical cells 2. In this way, there is a free peripheral portion 16 for each of the plates 12, 14, this free peripheral portion 16 corresponding to a periphery of the plates 12, 14 not covered by the electrochemical cells 2. The battery 1 comprises a housing within which the electrochemical cells 2 are housed. In certain alternative embodiments, not shown here, at least one of the plates 12, 14 is formed by a wall of the housing. In other words, either the first plate 12 or the second plate 14 is formed by a wall of the housing.

According to the invention, the battery 1 comprises an elastic return system 18 intended to compress the stack of electrochemical cells 2 on the one hand and to manage variations in volume of these electrochemical cells 2 on the other hand. The battery 1 here has a first elastic return system 18 arranged along the first longitudinal end 4 of the electrochemical cells 2 and a second elastic return system 18 arranged along their second longitudinal end 6. It is thus understood that the first system elastic return system 18 and the second elastic return system 18 are arranged on opposite sides of the battery 1, so as to optimize a distribution of forces within the battery 1. We could also consider, without departing from the framework of the invention, an elastic return system 18 arranged in a central position of the battery 1.

One of these first and second elastic return systems 18 will now be described in detail, the following characteristics applying to each of the two elastic return systems 18.

The elastic return system 18 connects the first plate 12 to the second plate 14, that is to say it extends between these two plates 12, 14 while being secured to them. In the example illustrated in Figure 1, the elastic return system 18 extends between the free peripheral portion 16 of the first plate 12 and the free peripheral portion 16 of the second plate 14, from the faces of these plates 12 , 14 which are opposite the electrochemical cells 2.

As mentioned above, the elastic return system 18 is secured to both the first plate 12 and the second plate 14. More precisely, the elastic return system 18 is secured to the first plate 12 by an irreversible fixing means 101, for example by a welding or glue bead, while this elastic return system 18 is secured to the second plate 14 by a reversible fixing means 102, for example by screwing, these fixing means being represented schematically in Figures 1 and 2. Alternatively, the system of elastic return 18 and one of the first plate 12 and the second plate 14 can form a single-piece assembly, for example made by foundry or even cut from a block.

The elastic return system 18 is, depending on the embodiments, made of a metallic material, of a composite material, of carbon fibers, or of an elastomeric material, depending on the degrees of flexibility and compression desired for the return system elastic 18.

A morphology of the elastic return system 18 will now be detailed in relation to each of the embodiments. For each of the first, second, third and fourth embodiments, the elastic return system 18 comprises at least one arch. The elastic return system 18 comprises for example at least a first arch 20 and a second arch 22, which are both arranged along the stack of electrochemical cells 2, along one of the longitudinal ends 4, 6, that is to say on the same side of the battery 1. More specifically, the first arch 20 and the second arch 22 respectively comprise a head 24 of rounded shape, this head 24 connecting a first arm 26 and a second arm 28. These arms 26, 28 extend, at least partially, along the plates 12, 14; the first arm 26 is thus in contact with the first plate 12 while the second arm 28 is in contact with the second plate 14. The head 24 of a given arch 20, 22 is arranged, in the stacking direction, between its arms 26, 28, substantially equidistant from the first plate 12 and the second plate 14.

Within the battery 1, the arches 20, 22 are arranged in opposition, so that their respective heads 24 are facing each other while their arms 26, 28 of a given arch 20, 22 are oriented in a direction opposite to the head 24 of the other arch 20, 22. It is understood that the arms 26, 28 of the arches 20, 22 extend, from the heads 24, in the direction of the junctions between one of the longitudinal ends 4, 6 and one of the transverse ends 8, 10, that is to say the corners of the plates 10, 12, while their heads 24 are arranged at a central portion of the longitudinal ends 4, 6. We could also envisage, without departing from the scope of the invention and although this is not shown in the figures, embodiments in which conversely the heads 24 of the arches 20, 22 are arranged respectively at the level of opposite sides, while their arms 26, 28 are arranged at the level of the central portion of the longitudinal ends 4, 6.

As mentioned previously, the elastic return system is fixed irreversibly on the first plate 12 via the arms 26 and an irreversible fixing means 101 of the welding or gluing type. Conversely, the elastic return system is fixed, via the arms 28, reversibly on the second plate 14, with appropriate reversible fixing means 102, as shown schematically in Figures 1 and 2, it being understood that means Equivalent fixings can be implemented in the embodiments illustrated in the other figures. For example, the reversible fixing means 102 are formed by fixing screws which pass through a bore made in the second plate 12 and which engage in a threaded bore formed in the arms 28 of the arches 20, 22.

In certain embodiments, the first arch 20 and the second arch 22 are also joined by a connecting portion 30, which is a part of the elastic return system 18 which links this first arch 20 and this second arch 22 one to the other.

In the first embodiment, illustrated in Figures 1 and 2, the arches 20, 22 have a funnel shape, with a pinched portion between their head 24 and their arms 26, 28. The arches 20, 22 here have a dimension of section, measured in a vertical and transverse sectional plane, which in the example illustrated and without this being limiting to the invention, can be between 15 to 20 millimeters. The section dimension of the arches is a function of a desired compromise between flexibility of the elastic return system 18 and the compression force that it is capable of transmitting to compress the cells optimally. It should be noted that this section dimension value here is an example and that such a value may be different depending on the material used, the pressure to be applied, and/or the expected variations in cell volume.

In this first embodiment, the first arch 20 and the second arch 22 are not connected to each other; we understand that there is no connecting portion between this first arch 20 and this second arch 22.

In the second embodiment, shown in Figure 3, the elastic return system 18 comprises arches with simplified curvature, with a radius of curvature in the same direction from one arm to the other, but a number of arches more important than in the first embodiment. The elastic return system comprises, in addition to the first arch 20 and the second arch 22, a third arch 32 and a fourth arch 34. The first arch 20 is nested in the third arch 32 so that the head 24 of this first arch 20 is arranged between the arms 26, 28 of the third arch 32, and in the same way the second arch 22 is nested in the fourth arch 34 so that the head 24 of this second arch 22 is arranged between the arms 26 , 28 of the fourth arch 34. The first arch 20 and third arch 32 are thus oriented in the same direction of the longitudinal direction L, the second arch 22 and fourth arch 34 being oriented in an opposite direction of this longitudinal direction L. third arch 32 and the fourth arch 34 are also closer to each other than the first arch 20 and the second arch 22.

In this second embodiment, the first arch 20, the second arch 22, the third arch 32 and the fourth arch 34 are connected to each other by two connecting portions 30 extending respectively along the first plate 12 and of the second plate 14. These connecting portions 30 are strips of the elastic return system 18 which are substantially flat, forming an extra thickness along the plate 12, 14 which is respectively associated with them. As has been mentioned, the contact surface between the elastic return system and the plates is thus increased, which is here substantially equal to the total longitudinal dimension of the plates, which has the effect of distributing the forces which can be collected in the areas where the elastic return system is attached to the plates. For example, a middle part of the connecting portions 30 can be equipped with a fixing means, for example with threaded bores to receive fixing screws, while none of the arms are facing this part. median.

In the third embodiment, visible in Figure 4, the arches 20, 22 are U-shaped, in a curvature configuration substantially equivalent to that of the arches of the second embodiment. The number of arches is less than in this second embodiment but with section dimensions, in a vertical and transverse plane, which are greater than in this second embodiment. The first arch 20 and the second arch 22 are here connected by a connecting portion 30 which extends substantially equidistant from the first plate 12 and the second plate 14, this connecting portion 30 connecting more precisely the head 24 of the first arch 20 at the head 24 of the second arch 22, the elastic return system 18 then having a cross shape. We understand that we thus avoid the heads, which are arranged at a distance from the fixing zones on the rigid plates, from vibrating and moving laterally when the vehicle is rolling for example, by ensuring central rigidity of the elastic return system.

In the fourth embodiment, which is illustrated in Figure 5, the first arch 20 and the second arch 22 are each formed by a helical spring. The heads 24 of these arches 20, 22 are more particularly formed by one or more turns of these helical springs, the arms 26, 28 corresponding to straight segments which extend parallel to the first and second plates 12, 14. Due to the presence of turns, there is a transverse offset between the first arm 26 and the second arm 28, this transverse offset being more and more pronounced as the number of turns increases. In this fourth embodiment, the elastic return system 18 does not have a connecting portion.

In the sixth figure is shown a battery 1 with an elastic return system 18 according to a fifth embodiment. The elastic return system 18 here comprises two curved portions 36, 38, including a first curved portion 36 and a second curved portion 38. The first curved portion 36 is connected to the first plate and has a convex part which tends to approach of the second plate 14, while the second curved portion 38 is connected to the second plate 14 and has a convex part which tends to approach the first plate 12. These curved portions 36, 38 are joined to one another. another at the level of a central portion 39, which corresponds to a highest point of their concave shapes. The curved portions 36, 38 are associated with the plates 12, 14 via pins 40, 42 projecting from the plates 12, 14. Each of the first plate 12 and the second plate 14 more specifically comprises a first pin 40 and a second pin 42, which are respectively arranged in the vicinity of the junctions between the longitudinal end 4, 6 and the adjoining transverse ends 8, 10. The first curved portion 36 is connected to the first pin 40 and the second pin 42 of the first plate 12, while the second curved portion 38 is connected to the first pin 40 and the second pin 42 of the second plate 14. The curved portions 36 , 38 are more exactly connected to their respective pins 40, 42 via pivot connections, from the ends of the portions curved 36, 38 being wound around the pins 40, 42 so as to form these pivot connections.

A method of assembling the battery 1 according to the invention will now be described. Such an assembly method comprises a step of securing the elastic return system 18 to the first plate 12. Such a joining step is, in the case of the first to the fourth embodiment, a joining by an irreversible fixing means 101 , in particular by bonding or welding. The first plate 12 is for example a bottom wall of the battery case 1. On the contrary, in the case of the fifth embodiment, the connection corresponds to a winding of the elastic return system 18 around the pins 40, 42 of the first plate 12 so as to form pivot connections. The assembly process subsequently comprises a step of arranging the electrochemical cells 2 covering the first plate 12, according to the stacking direction. The electrochemical cells 2 can for this purpose be arranged one by one, or else a stack already formed of electrochemical cells 2 is deposited in a single operation on the first plate 12. It is understood that the electrochemical cells are deposited on the first plate 12 between the elastic return systems or around the elastic return system, depending on the number and arrangement of the elastic return systems on the first plate.

The assembly process continues with a covering step, during which the second plate 14 is placed on the stack of electrochemical cells 2. The plate can come to rest on the elastic return system, if the latter is already constrained in traction and has a length greater than its empty length, or else be kept at a distance from the arms of the elastic return system on which this plate must be fixed.

The assembly process then comprises a second joining step, which aims to join the elastic return system 18 and the second plate 14, whether by a reversible fixing means 102, for example by screwing as is the case from the first to the fourth embodiment, or by winding the ends of the second curved portion 38 around the pins 40, 42 of the second plate 14 as is the case in the fifth embodiment. During this second joining stage, the elastic return system 18 is stretched. It is understood in particular, for the first four embodiments, that the arms 26, 28 of a arch 20, 22 are deformed so as to be spaced apart from each other in the vertical direction V as the screwing progresses. The second joining step can be facilitated by the use of a press, which presses on the stack of electrochemical cells 2 so as to reduce their volume. Once the connection by the reversible fixing means has been carried out, the elastic return system 18 tends to return to its resting form, that is to say not separated, and on this occasion compresses the stack of electrochemical cells 2 by bringing it closer together. its arms 26, 28, which causes the first plate 12 and the second plate 14 to move towards each other. The present invention thus provides a battery presenting a system capable of applying compressive forces to the electrochemical cells, while presenting the flexibility necessary for managing their volume variations.

The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means and configuration as well as to any technically effective combination of such means.

Claims

1. Battery (1) for a motor vehicle, comprising a plurality of electrochemical cells (2), a first plate (12) and a second plate (14), the electrochemical cells (2) being superimposed on each other in a direction d stack between the first plate (12) and the second plate (14), the battery (1) comprising at least one elastic return system (18) connecting the first plate (12) and the second plate (14).

2. Battery (1) according to the preceding claim, comprising a first elastic return system (18) and a second elastic return system (18) arranged on either side of the stack of electrochemical cells (2).

3. Battery (1) according to any one of the preceding claims, in which each of the first plate (12) and the second plate (14) has dimensions, measured in a longitudinal-transverse plane perpendicular to the direction of stacking, greater than the dimensions of an electrochemical cell so as to present a free peripheral portion (16), the elastic return system (18) extending from the free peripheral portion (16).

4. Battery (1) according to any one of the preceding claims, in which the elastic return system (18) comprises at least one arch (20, 22).

5. Battery (1) according to the preceding claim, in which the at least one arch (20, 22) comprises a head (24) connecting a first arm (26) and a second arm (28), the first arm (26 ) being in contact with the first plate (12) and the second arm (28) being in contact with the second plate (14).

6. Battery (1) according to the preceding claim, in which the elastic return system (18) comprises a first arch (20) and a second arch (22), the head (24) of the first arch (20) being arranged opposite the head (24) of the second arch (22).

7. Battery (1) according to the preceding claim, in which the first arch (20) and the second arch (22) are connected by a connecting portion (30) extending along the first plate (12) and/ or the second plate (14).

8. Battery (1) according to claim 6, in which the first arch (20) and the second arch (22) are connected by a connecting portion (30) extending substantially equidistant from the first plate (12) and of the second plate (14).

9. Battery (1) according to any one of the preceding claims, in combination with claim 4, in which the at least one arch (20, 22) is formed by a helical spring.

10. Method for assembling a battery (1) according to any one of claims 1 to 9, comprising a step of securing the elastic return system (18) to the first plate (12), a step of arranging the electrochemical cells (2) on top of each other in the stacking direction on the first plate (12), a step of covering the stack of electrochemical cells (2) by the second plate (14) and a joining step from the elastic return system (18) to the second plate (14), during which the elastic return system (18) is stretched.