Battery comprising at least one stack of electrical cells and an associated elastic play recovery device

Abstract

This electrical energy storage battery (1) comprises at least one stack (7) of electrical cells (6) and a casing having a base (3) on which said stack (7) of battery cells (1) is fixed. The battery (1) comprises at least two compression plates (8) arranged on either side of the stack, means for fixing the compression plates (8) to the base (3), at least one tie rod (12) capable of compressing the compression plates (8) against the cells (6) of the stack (7), and at least one elastic device (15) for compensating for play in the stack in a direction of dimensional variation of the stack. Figure for the abbreviation: [Fig 3]

Description

Title of the invention: Battery comprising at least one stack of electrical cells and an associated elastic backlash compensation device. Technical field

[0001] The present invention relates to the storage of electrical energy, particularly in the field of aeronautics. It relates generally to the storage of electrical energy for applications in which mass is a significant factor, such as in aeronautics. Previous techniques

[0002] Classically, in the field of aeronautics, the storage of electrical energy is carried out by means of low voltage Lithium-Ion batteries, typically a voltage below 120V.

[0003] The term battery means a set of individual modules, each comprising power elements arranged in series and / or in parallel to achieve the desired electrical voltage and electrical capacity.

[0004] Modern aircraft have increasing electrical power requirements, which necessitates configuring batteries accordingly. Indeed, climate change is a major concern for many legislative and regulatory bodies worldwide. Various restrictions on carbon emissions have been, are being, or will be adopted by various states.

[0005] Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0006] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible, in order to reduce the environmental footprint of its activity.

[0007] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and finally aviation biofuels.

[0008] In order to supply the electrical power required in the aircraft network while minimizing the weight of the electrical equipment, it is advantageous to increase the voltage of the batteries, for example to 800 V.

[0009] Inside high-voltage batteries, the power elements or electrical cells of the battery are generally grouped into modules, each of which contains a certain number of cells, including mechanical fastening devices, electrical connection and possibly thermoregulation devices.

[0010] In order to improve the integration of the battery in terms of volume and mass, it is common to stack the cells within the battery module along a stacking axis.

[0011] However, depending on the chemistry of the cells, it is necessary to keep taking into account a possible significant variation in the thickness of the cells along the stacking axis during a charge and discharge cycle, otherwise there is a risk of damage to the structure of the cells, or even to the structure that holds them.

[0012] Conventionally, addressing this risk of dimensional variation involves inserting layers of foam between the cells, along the stacking axis, which allow for a certain degree of deformation. Thus, the foam layers accommodate the expansion and contraction of the cells while maintaining a pressure consistent with the cell structure.

[0013] However, the mechanical characteristics of foams sometimes lead to significant pressure increases, requiring an increased number of foam layers, which negatively affects the overall integration in terms of volume and mass. Furthermore, the mechanical characteristics of foams can change with age, potentially leading to permanent deformation of the foams. Description of the invention

[0014] The aim of the invention is therefore to provide an electrical energy storage battery, particularly for an aircraft, whose integration in terms of volume and mass is improved while taking into account the dimensional variation of the electrical cells during charge and discharge cycles. In particular, a battery module structure is sought that allows a certain variation in the thickness of the cells along their stacking axis without risking damage or loss of mechanical integrity of the cells.

[0015] The invention relates to an electrical energy storage battery comprising at least one stack of electrical cells and a housing having a base on which the battery stack is fixed.

[0016] The battery comprises at least two compression plates arranged on either side of said stack, and means for fixing said compression plates at the base, at least one tie rod capable of compressing the compression plates against the cells of the stack, and at least one elastic device for taking up play in the stack in a direction of dimensional variation of the stack.

[0017] Preferably, each elastic device comprises at least one spring compressed between a pair of support pieces substantially perpendicular to the direction of dimensional change of the stack. Such an elastic device makes it possible to absorb any dimensional change of the stack by a change in the length of the compressed spring.

[0018] Advantageously, each support piece comprises a first and a second flat, opposing face, the second face being provided with a reinforcement intended to house one end of at least one compressed spring. Such a reinforcement facilitates the installation and retention of springs on the second face while also increasing the rigidity of the support pieces.

[0019] Preferably, at least one elastic device comprises at least one flat-wire wave spring. Such a spring promotes the compactness of the elastic device.

[0020] Advantageously, at least one elastic device includes at least one spring having an axial direction oriented along the direction of dimensional variation of the stack.

[0021] For example, at least one elastic device comprises concentric springs around the direction of dimensional variation of the stack. Such a configuration facilitates obtaining the necessary stiffness of the elastic device.

[0022] Preferably, the support parts are made of an electrically insulating material. Such support parts promote the electrical safety of the battery environment, particularly with regard to leakage currents.

[0023] According to one feature, adjacent support pieces corresponding to adjacent stacks each comprise a first hook and a second hook, opposed to each other and aligned along a transverse direction, perpendicular to the longitudinal axes of the adjacent stacks, the hooks having complementary U shapes allowing the first hook of a first support piece to slide through the second hook of a second support piece adjacent to the first and allowing the passage of tie rods through said hooks without hindering the relative translation of the adjacent support pieces in the direction of dimensional variation of the stacks.

[0024] According to another feature, the number of tie rods is one more than the number of cell stacks. This configuration allows for a reduced number of tie rods and thus improves integration in terms of mass and volume.

[0025] According to another aspect, the invention relates to an aircraft comprising a battery as described above. Brief description of the drawings

[0026] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0027] [Fig-1] is a schematic perspective view of an energy storage battery electric according to an embodiment of the invention;

[0028] [Fig.2] is a perspective view of the battery of [Fig.1], in which the bell the casing has been removed;

[0029] [Fig.3] is a side view of the battery in [Fig.2]; and

[0030] [Fig.4] is a perspective view of a support piece according to an example of the invention. Detailed description of at least one embodiment

[0031] Figures 1 and 2 illustrate an example of an embodiment of an electrical energy storage battery according to the invention, designated by the general numerical reference 1.

[0032] The battery 1 includes a housing 2 having a base 3. Preferably, the housing 2 has a bell 4, covering the base 3. The housing 2 is intended to provide the mounting, connection and protection of the power elements of the battery 1, visible on [Fig.2] on which the bell has not been shown.

[0033] The housing 2 is equipped with mechanical means for fixing the bell to the base, made for example in the form of screws, bolts or any other suitable means of fixing for the intended use.

[0034] In the described embodiment, the battery 1 is intended to be installed on board an aircraft, for example in a turbomachine. The battery 1 serves, for example, to selectively deliver electrical energy for electric propulsion. It should be noted, however, that the invention also applies, in general, to other fields and environments in which mass management and integration issues arise (automotive, rail, etc.).

[0035] The base 3 is also equipped with several fastening elements 5 which allow its installation on board an aircraft. It should be noted, however, that the base 3 can alternatively consist of a structural aircraft support element designed for the integration of the battery.

[0036] As regards the bell 4, it covers all the elements located inside the housing 2 and represents a physical barrier which separates and protects the inside of the housing 2 and its external environment.

[0037] Where bell 4 is present, this bell is specifically intended to reduce the risk of gas leaks. Preferably, a sealing gasket is then installed between the base 3 and the bell 4 to contain the gases.

[0038] Furthermore, in the event of a thermal runaway event of the battery 1, the bell 4 ensures a function of protecting the external environment of the housing 2 by limiting the impact of this event on the external environment of the housing 2.

[0039] The power elements of the battery 1 comprise electrical cells 6. The cells 6 are preferably in a flexible packaging format, usually referred to by the Anglo-Saxon term "pouch". Alternatively, the electrical cells may be prismatic or cylindrical.

[0040] The electrical cells 6 are grouped in at least one stack 7. In other words, the cells of a stack are arranged side by side along a longitudinal axis X of the stack ([Fig. 3]). Preferably, the longitudinal axis X of the stack is parallel to the base 3. The longitudinal axis X is preferably parallel to the direction of dimensional variation of the stack.

[0041] The battery 1 comprises at least two opposing compression plates 8, arranged on either side of the stacks 7 of cells 6. The compression plates 8 are here placed in lateral positions, at the ends of at least one stack 7. Preferably, the number of compression plates is limited to two, i.e. one per side, but it remains possible to provide for a greater number of plates 8.

[0042] The compression plates 8 have a rigidity that allows compliance with maximum permissible deformation criteria along the longitudinal axis X of the stack, under the maximum pressure exerted by the cells 6. For example, the rigidity of the plates 8 is such that the maximum deformation is less than 0.1 mm.

[0043] In order to meet the maximum deformation criteria while reducing mass, the compression plates 8 include stiffeners 8a.

[0044] The compression plates 8 are preferably substantially flat and extend orthogonally to the longitudinal axis X of the cell stack.

[0045] The compression plates 8 are connected by their lower part 9 to the base 3 by means of fixing 10.

[0046] In the present example, the compression plates 8 are connected to each other by their upper part 11 by at least one tie rod, preferably by tie rods 12.

[0047] Preferably, the tie rods 12 are installed in a direction parallel to the longitudinal axes X of the stacks 7 and parallel to the base 3.

[0048] Advantageously, the number of tie rods 12 is reduced compared to conventional solutions in which tie rods are present both in the lower and upper parts of the compression plates. The tie rods 12 are Preferably, these tie rods are located only in the upper part 11 of the compression plates 8. Thus, a single stack of cells could be held together by only two tie rods. Alternatively, a single tie rod 12 could be located only in the upper part 11 of the compression plates 8 to further reduce the number of tie rods.

[0049] This results in a total number of tie rods 12 that is one more than the number of stacks 7. In the example shown in [Fig. 2], there are four tie rods 12 for three stacks 7, one more than the number of stacks. This reduction in the number of tie rods allows for better integration in terms of mass and volume.

[0050] The base 3 is capable of providing thermal management functionality and is associated for this purpose with thermal management means. The thermal management means may, in particular, include at least one heat exchanger 13, equipped with pipes through which a heat transfer fluid circulates. The heat transfer fluid is, for example, a coolant. The heat exchanger 13 may, for example, have a serpentine shape. The base 3 is advantageously made of a thermally conductive material, in particular a metallic material.

[0051] The heat exchanger 13 is, for example, integrated into the base 3, which optimizes the thermal path between the cells and the fluid, reducing thermal resistances related to the passages between components. Alternatively, the heat exchanger can be installed in a thermal exchange relationship with the base 3, preferably with an external face of the base 3, i.e., with the face opposite an internal face that houses the cells 6. The heat exchanger 13 is then, for example, bonded to a face of the base 3.

[0052] The base 3 is in thermal exchange relationship with the electrical cells 6 and can consequently bring and maintain the cells 6 at optimal operating temperatures.

[0053] The battery 1 preferably comprises at least one intermediate wall 14 fixed to the base 3, oriented parallel to the electrical cells 6 and arranged inside each stack 7. Figure 1 illustrates a single intermediate wall 14 arranged in a central area of ​​the base 3, corresponding approximately to the middle of the base 3. Alternatively, it is possible to provide several intermediate walls, arranged at regular intervals within each stack. Preferably, the intermediate walls 14 extend over most of the width of the base 3.

[0054] The presence of intermediate walls 14 contributes to stiffening the stacks 7 and has the effect of limiting deformations in a direction normal to the base 3. The presence of intermediate walls 14 contributes to good vibration resistance of battery 1. However, it is also possible to not provide any intermediate wall 14.

[0055] The battery 1 includes at least one elastic device 15 ([Fig. 3]) for compensating for the play in a stack 7 in a direction of dimensional change of the stack during the electrical charging or discharging of the cells 6 of the stack 7. Preferably, at least one elastic device 15 is associated with each stack 7 to ensure elastic support for each stack 7 in the direction of dimensional change of the stack. Generally, the direction of dimensional change of a stack is in the direction of the thickness of the cells 6 that form the stack, that is, parallel to the longitudinal axis X.

[0056] Thus, each elastic device 15 elastically supports the stack 7 to which it is associated. In other words, each elastic device 15 deforms elastically and provides an elastic compressive force to an associated stack, the compressive force preferably acting over the entire dimensional range of the stack. Being in an elastic range, no residual deformation of the elastic device is formed.

[0057] The same references correspond to the same elements from one figure to another.

[0058] In the example illustrated in [Fig. 3], battery 1 comprises two devices of elastic support 15 arranged inside the stack 7. It remains possible to adjust the position and number of devices 15, without going out of the scope of the invention. For example, when the battery 1 does not include an intermediate wall 14, the device 15 can be located in a central area of ​​the base 3, corresponding approximately to the middle of the base 3. It should be noted that a mid-position of the device 15 within a segment of a stack 7 whose ends are held fixed has the advantage of minimizing the maximum displacements of the internal components of the battery 1 induced by the electrical charging and discharging of the cells 6. The maximum value of the induced displacements can also be reduced by distributing several devices 15 along any segment of a stack 7 whose ends are held fixed. In an embodiment not shown, it is also possible to add foam layers between the cells 6 of a stack 7.These foam layers provide thermal insulation and exhibit elasticity capable of compensating for dimensional variations in the cells 6 during their operation, while reflecting a pressure compatible with the permissible limits of the cells 6.

[0059] The elastic device 15 comprises at least one compressed spring 16 between a pair of support pieces 17 substantially perpendicular to the direction of dimensional change of the stack. The support pieces 17 are sufficiently rigid to distribute the compressive force of the spring into a uniform pressure acting on the stacking cells. The support pieces can be reinforced to increase their rigidity while optimizing their mass.

[0060] As illustrated in [Fig. 4], each support piece 17 comprises a first flat face 18 and a second face 19, opposite in position. The second face 19 is provided with a reinforcement 20 for housing one end of at least one compressed spring 16. Preferably, the support pieces 17 are made of an electrically insulating material.

[0061] Preferably, the elastic device 15 comprises at least one flat-wire wave spring, so as to optimize the dimensions of the device 15. Alternatively, other spring systems may be used. For example, a stack of washers, such as a Belleville washer stack, may be used. Of course, it remains possible to use only helical springs with round wire.

[0062] Preferably, the springs 16 have an axial direction oriented along the direction of dimensional variation of the associated stacks, so as to optimize the support force.

[0063] In an example not shown, it is possible to use a plurality of concentric springs 16 around the direction of dimensional variation of the cell stacking, within the same elastic device 15, for example two concentric springs, in order to facilitate obtaining the necessary stiffness.

[0064] With reference to [Fig.3], each cell 6 comprises a first external surface SI and a second external surface S2 opposite to the first surface.

[0065] In the embodiment illustrated in [Fig.3], the first external SI surface of each cell 6 is in contact with a thermal drain 23. Alternatively, it remains possible that only some cells 6 of a given stack are in contact with a thermal drain, or even that the cells 6 are not in contact with any drain.

[0066] The thermal drain 23 preferably comprises at least one layer of graphite and at least one layer of adhesive. The graphite layer of the thermal drain 23 is placed in contact with the external SI surface of the associated cell 6 in order to maximize the heat transfer capacity between the drain and the associated cell.

[0067] In a particular embodiment, the thermal drain 23 comprises a metallic layer, for example made of aluminium or copper, associated with a layer of glue and a layer of graphite.

[0068] Each thermal drain 23 preferably comprises a main portion 23a and an end portion 23b. The main portion 23a is oriented in a direction perpendicular to a longitudinal axis X of the stack that is normal to the surfaces SI, S2 of the cells 6. In other words, the main portions 23a of the thermal drains 23 are parallel to the surfaces SI, S2. The main portion 23a is in contact with the surface SI of the associated cell 6 and the terminal part 23b is folded under the associated cell 6 so as to constitute a contact surface 23c of the drain 23 with the base 3.

[0069] The means for fastening the compression plates 8 10 preferably comprise first fastening elements 24 and second fastening elements 25. The first fastening elements 24 are fixed to the base 3. They are designed to pass through holes provided on a base 26 of each compression plate 8 and cooperate with the second fastening elements 25 to fix the compression plates 8 to the base 3. The first fastening elements 24 may, in particular, be studs, threaded rods, or bolts. The second fastening elements 25 may be nuts.

Claims

Demands

1. Electrical energy storage battery (1) comprising at least one stack (7) of electrical cells (6) and a housing (2) having a base (3) on which said stack (7) of the battery (1) is fixed, the battery being characterized in that it comprises at least two compression plates (8) disposed on either side of said stack, means for fixing said compression plates (8) to the base (3), at least one tie rod (12) capable of compressing the compression plates (8) against the cells (6) of said stack (7), and at least one elastic device (15) for taking up play of the stack in a direction of dimensional variation of said stack comprising at least one wave spring with flat wire.

2. Battery according to claim 1, wherein each elastic device (15) comprises at least one compressed spring (16) between a pair of support pieces (17) substantially perpendicular to said direction of dimensional variation of said stack.

3. Battery according to claim 2, wherein each support piece (17) comprises a first face (18) and a second face (19) that are flat and opposite, the second face (19) being provided with a reinforcement (20) intended to house one end of at least one compressed spring (16).

4. Battery according to any one of claims 1 to 3, wherein at least one elastic device (15) comprises at least one spring (16) having an axial direction oriented along said direction of dimensional variation of said stack.

5. Battery according to any one of claims 1 to 4, wherein at least one elastic device (15) comprises springs (16) concentric around the direction of dimensional variation of the stack.

6. Battery according to any one of the preceding claims 1 to 5, wherein the support parts (17) are made of an electrically insulating material.

7. Battery according to any one of the preceding claims 2 to 6, wherein adjacent support pieces (17) corresponding to adjacent stacks (7) each comprise a first

8.

9. hook (21) and a second hook (22), opposite each other and aligned along a transverse direction, perpendicular to the longitudinal axes (X) of the adjacent stacks (7), said hooks (21, 22) having complementary U shapes allowing the first hook (21) of a first support piece to slide through the second hook (22) of a second support piece adjacent to the first and allowing the passage of tie rods (12) through said hooks (21, 22) without hindering the relative translation of the adjacent support pieces in the direction of dimensional variation of said stacks. Battery according to any one of the preceding claims 1 to 7, wherein the number of tie rods (12) is one greater than the number of cell stacks (7). Aircraft comprising a battery according to any one of claims 1 to 8.

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