Battery comprising at least one stack of electrical cells and associated mounting method

Abstract

The invention relates to an electrical energy storage battery (1) comprising at least one stack (7) of electrical cells (6), a casing having a base (3) on which said stack (7) of the battery (1) is fixed, and a bell covering the base (3). The battery (1) comprises at least two compression plates (8) disposed on either side of said stack (7), means for fixing said plates (8) to the base (3), and at least one tie rod (12) adapted to compress the compression plates against the cells of said stack (7). The base (3) comprises thermal management means (13) for the electrical cells (6). Figure 2

Description

Title of the invention: Battery comprising at least one stack of electrical cells and associated mounting method 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. 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 provide the required electrical power 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 possible to stack the cells.

[0011] Document FR 3 067 859 A1 describes in this regard a battery comprising a stack of a plurality of cells assembled by means of mechanical fastening devices including frames or shells into which the cells are inserted. This assembly multiplies the mechanical interfaces and does not allow for optimized integration in terms of volume and mass. Furthermore, the presence of frames or shells that are rather thermally insulating disrupts heat exchange within the battery, making thermal management of the battery more difficult.

[0012] There are also battery modules comprising stacked cell assemblies held in compression by means of four tie rods. The presence of such a large number of tie rods negatively affects the overall integration in terms of volume and mass. Furthermore, the thermal management of such assemblies is not considered. Description of the invention

[0013] The aim of the invention is therefore to propose an electrical energy storage battery, in particular for an aircraft, whose integration in terms of volume and mass is improved, and whose thermal management is facilitated.

[0014] The invention relates, according to a first aspect, to an electrical energy storage battery comprising at least one stack of electrical cells, a case comprising a base on which said stack of the battery is fixed and a bell covering the base.

[0015] The battery comprises at least two compression plates arranged on either side of said stack, means for fixing said plates to the base, and at least one tie rod capable of compressing the compression plates against the cells of said stack.

[0016] In addition, the base includes means for thermal management of the electrical cells.

[0017] The use of stacked electrical cells in such a battery improves integration in terms of volume and mass. Thermal management of the electrical cells is facilitated by heat exchange with the base. The use of compression plates on either side of the stack allows, in particular, for reduce the need to include other mechanical compression elements, such as additional tie rods.

[0018] Advantageously, the number of tie rods is exactly one greater than the number of stacks. According to a preferred feature of the invention, the tie rods are provided only in the upper part of the compression plates. This configuration reduces the number of tie rods and results in significant weight savings.

[0019] Thus, advantageously, a stack of cells can be held together by only two tie rods associated with the compression plates.

[0020] Preferably, each cell stack comprises at each of its ends an end foam layer, so that the compression plates are in contact with said end foam layers of the stacks.

[0021] For example, the battery includes at least one heat drain disposed on a first external surface of at least one cell of each stack and / or includes at least one intermediate layer of foam disposed on a second external surface of at least one cell of each stack, the second external surface being opposite the first.

[0022] According to one feature, the thermal drain comprises at least one layer of graphite and at least one layer of glue.

[0023] Preferably, the thermal drain is folded under the cell with which it is in contact, so as to constitute a contact surface of the drain with the base.

[0024] Such a configuration makes it possible to increase heat transfers between the base and the cells.

[0025] According to another feature, the battery includes a layer of glue covering the contact surface of the drain with the base.

[0026] For example, the fastening means include first and second fastening elements, said first elements being fixed to the base and intended to pass through holes provided on a base of each compression plate, and said second fastening elements cooperating with the first fastening elements to fix the compression plates to the base.

[0027] Preferably, the first fixing elements attached to the base include at least one stud.

[0028] Preferably, said stud passes through a hole provided at the level of the base of the compression plate, and oriented in the direction of the lateral movement of the compression plate.

[0029] Preferably, the second fastening elements include at least one nut.

[0030] Advantageously, the base includes adjustment means capable of imposing a lateral displacement on a compression plate so as to bring it closer or to move said compression plate away from the middle of the base, when said lateral displacement is respectively increased or decreased.

[0031] Such adjustment means allow perfect control of the relative distance between the compression plates.

[0032] Preferably, the adjustment means include at least one cam capable of cooperating with a base of the compression plate.

[0033] Advantageously, the battery includes a protective wall fixed to the compression walls and arranged between the cells and the bell, so as to protect the bell in case of thermal runaway of the cells.

[0034] For example, the battery includes at least one intermediate wall fixed to the base, oriented parallel to the electrical cells and arranged inside each stack.

[0035] According to another aspect, the invention relates to a method for mounting a battery as described above, comprising the following steps: - installation of a first compression plate, - placement of at least one stack of electrical cells against the first plate, - installation of a second compression plate opposite the first plate, and positioned in contact with the cell stacks, - applying pressure to the two compression plates against the stacks, - gradual convergence of the two compression plates, - following the bringing together of the plates, fixing the compression plates to the base and installing the tie rods, and - tensioning of the tie rods.

[0036] According to another aspect, the invention relates to an aircraft comprising at least one electrical energy storage battery comprising at least one stack of electrical cells, the battery being as defined above according to the first aspect. Brief description of the drawings

[0037] 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:

[0038] [Fig-1] is a schematic perspective view of an energy storage battery electric according to an embodiment of the invention;

[0039] [Fig.2] is a perspective view of the battery in [Fig.1], in which the bell housing has been removed;

[0040] [Fig.3] is a side view of the battery of [Fig.2];

[0041] [Fig.4] is a perspective view of a detail of the connection between a plate of compression and the battery base of the [Fig.2];

[0042] [Fig. 5] is a partial perspective view of a battery according to a mode of the invention; and

[0043] [Fig.6] is a flowchart of a method for assembling a battery according to a mode of the invention. Detailed description of at least one embodiment

[0044] 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.

[0045] The battery 1 includes a housing 2 comprising a base 3 and a bell 4. 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.

[0046] 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.

[0047] In the described embodiment, the battery 1 is intended to be carried on board an aircraft. 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.

[0048] 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.

[0049] 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.

[0050] The bell 4 is specifically designed to reduce the risk of gas leaks. Preferably, a sealing gasket is used between the base 3 and the bell 4 to contain the gases.

[0051] 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.

[0052] The power elements of the battery 1 comprise electrical cells 6. The cells 6 are preferably of prismatic format with flexible packaging, usually referred to by the Anglo-Saxon term "pouch".

[0053] 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.

[0054] 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.

[0055] 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.

[0056] In order to meet the maximum deformation criteria while reducing mass, the compression plates 8 include stiffeners 8a.

[0057] The compression plates 8 are preferably substantially flat and extend orthogonally to the longitudinal axis X of the cell stack.

[0058] The compression plates 8 are connected by their lower part 9 to the base 3 by means of fixing 10.

[0059] 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.

[0060] 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.

[0061] 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. Here, the tie rods 12 are preferably 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.

[0062] 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], four tie rods 12 are present 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.

[0063] The base 3 is capable of providing a thermal management function and is associated for this purpose with thermal management means. The thermal management means can Specifically, it includes 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.

[0064] 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.

[0065] 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.

[0066] 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 2 illustrates a single intermediate wall 14 located 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.

[0067] 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 the good resistance to vibrations of the battery 1.

[0068] With reference to [Fig.3], each stack 7 comprises at each of its ends 7a, 7b an end foam layer 15.

[0069] Each cell 6 comprises a first external surface S1 and a second external surface S2 opposite to the first.

[0070] In the embodiment illustrated in [Fig. 3], the first external surface SI of each cell 6 is in contact with a thermal drain 16, and the second external surface S2 is in contact with a foam layer 17, 15. Alternatively, it is possible that only some cells 6 of a given stack are in contact with a thermal drain and / or a foam layer 17, 15, or even that the cells 6 are in contact with neither a drain nor a foam layer 17. Here, the stack comprises two end foam layers 15 and a plurality of intermediate foam layers 17. The foam layers 15, 17 provide thermal insulation and have elasticity capable of compensating for variations dimensional changes in the cells 6 during their operation, while returning a pressure compatible with the permissible limits of the cells 6.

[0071] The foam layers 15, 17 may include, in particular, reinforcing fibers, an aerogel, a neoprene, and / or a thermoplastic.

[0072] The number of foam layers 17 required to compensate for the dimensional variation of the cells 6 depends on the type of cells used. Thus, depending on the chemistry of the cells 6, it is possible to drastically reduce the number of foam layers 17, or even eliminate them.

[0073] The thermal drain 16 comprises at least one layer of graphite and at least one layer of adhesive. The graphite layer of the thermal drain 16 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.

[0074] In a particular embodiment, the thermal drain 16 comprises a metallic layer, for example made of aluminium or copper, associated with a layer of glue and a layer of graphite.

[0075] Each thermal drain 16 comprises a main portion 16a and an end portion 16b. The main portion 16a is oriented in a direction perpendicular to a longitudinal axis X of the stack which is normal to the surfaces SI, S2 of the cells 6. In other words, the main portions 16a of the thermal drains 16 are parallel to the surfaces SI, S2. The main portion 16a is in contact with the surface SI of the associated cell 6 and the end portion 16b is folded under the associated cell 6 so as to form a contact surface 16c of the drain 16 with the base 3.

[0076] Preferably, a layer of glue covers the contact surface 16c of the drain 16 with the base 3, in order to reduce the risk of relative displacement between the drains and the base.

[0077] The means for fastening the compression plates 8 10 comprise first fastening elements 18 and second fastening elements 19. The first fastening elements 18 are fixed to the base 3. They are designed to pass through holes provided on a base 20 of each compression plate 8 and cooperate with the second fastening elements 19 to fix the compression plates 8 to the base 3. The first fastening elements 18 may, in particular, be studs, threaded rods, or bolts. The second fastening elements 19 may be nuts.

[0078] In the embodiment illustrated in [Fig. 4], the base 3 is equipped with adjustment means 21 capable of imposing a lateral displacement D on at least one compression plate 8. The lateral displacement is imposed here by a rotation R of a cam 22 whose profile is in contact with the plate 8 and which presses against it. The profile of the cam 22 can, for example, press against the edge of the base 20. The position of the plate 8 can be adjusted according to the rotation R of the cam, so as to move the compression plate 8 closer to or further from the middle of the base 3 when the lateral displacement D imposed by the rotation R is respectively increased or decreased.

[0079] In this embodiment, each first fixing element 18 passes through an oblong hole 23 provided on the base 20 and oriented in the direction of the lateral displacement D to allow this displacement.

[0080] The use of such adjustment means 22 makes it possible to guard against any negative consequences of manufacturing tolerances. It thus becomes possible to precisely adjust the longitudinal distance between the compression plates 8, and to allow better control of the pressure exerted on the stacks 7 of the cells 6.

[0081] Thus, thanks on the one hand to the presence of the two compression plates 8 on the sides, and thanks on the other hand to the precise mechanical fixing of the compression plates 8 on the base 3 using the fixing means 10 (including for example studs as described above), the base 3 participates in the compression of the cells 6 and in their retention in the stack 7.

[0082] With reference to [Fig.5], according to one possible variant, the battery is provided with a protective wall 24 fixed on the compression walls 8 and arranged between the electrical cells of the battery and the bell 4, so as to protect the bell 4 in case of thermal runaway of the cells.

[0083] The protective wall 24 is supported vertically by the base 3 and rests laterally on bosses 25 provided on the base 3.

[0084] The protective wall 24 can also be fixed to the intermediate walls 14.

[0085] Fig. 6 is a flowchart of a method for mounting a battery 1 according to a possible embodiment of the invention.

[0086] The process begins with a step 26 of setting up a first compression wall 8 at a first predetermined height.

[0087] In the following step 27, at least one stack 7 of electrical cells 6 is placed against the first plate 8. Each stack 7 is preferably installed at a second predetermined dimension, different from the first, so that the edge intended to be in contact with the base 3 is further from the center of the stack than the edge of the base 20 also intended to be in contact with the base 3. This difference between the first dimension and the second dimension is called "negative clearance". Alternatively, a flexible seal can be provided under each cell 6, also creating a negative clearance.

[0088] A second compression plate 8, opposite the first and positioned in contact with the stacks 7 of cells 6, is then put in place (step 28). The second compression plate is placed at the same first dimension as the first compression plate 8.

[0089] The process continues with a step 29 of pressurizing the two compression plates 8 against the cell stacks, using pressurization means. The pressurization means may, in particular, be hydraulic cylinders, preferably controllable by movement.

[0090] During the subsequent approach step 30, the two compression walls 8 are progressively brought together by controlling the pressurization means. This control is preferably carried out while moving the means to ensure perfect control of the relative position of the compression plates 8.

[0091] When the two compression plates 8 have been brought together, the process continues with a step 31 of fixing the compression plates to the base 3, followed by a step 32 of installing the tie rods 12. Alternatively, the step 32 of installing the tie rods 12 can be carried out before the step 31 of fixing the plates 8 to the base 3.

[0092] It should be noted that, during the assembly of the base 3 and the compression plates 8, the negative clearance between the stacks 7 and the compression plates 8 results in additional pressure between the stacks 7 and the base 3. This additional pressure improves the heat transfer coefficient between the stacks 7 and the base 3.

[0093] When the battery is equipped with thermal drains 16, the method may include an optional step of applying a layer of glue to the contact surfaces 16b of the thermal drains 16 with the base 3. The layer of glue and the additional pressure between the stacks 7 and the base 3 generated by the negative clearance described above contribute to maintaining contact between the thermal drains 16 and the base 3.

[0094] The process ends with the tensioning of the tie rods 12 (step 33). The tensioning of the tie rods can be achieved by removing or deactivating the pressure-generating means used during the preceding pressure-generating and tightening steps. Additionally, the tension of the tie rods 12 could be increased, for example, by means of active anchors. The tensile forces of the tie rods 12 are balanced by the compressive forces acting on the compression plates 8.

Claims

Demands

1. Electrical energy storage battery (1) comprising at least one stack (7) of electrical cells (6), a casing (2) having a base (3) on which said stack (7) of the battery (1) is fixed and a bell (4) covering the base (3), 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), and at least one tie rod (12) capable of compressing the compression plates (8) against the cells (6) of said stack (7), the base (3) comprising thermal management means for the electrical cells (6), the number of tie rods (12) being exactly one greater than the number of stacks (7).

2. Battery according to claim 1, wherein each stack (7) of cells comprises at each of its ends (7a, 7b) a layer (15) of end foam, such that the compression plates (8) are in contact with said layers (15) of end foam of the stacks.

3. Battery according to claim 1 or 2, comprising at least one thermal drain (16) disposed on a first external surface (SI) of at least one cell (6) of each stack (7) and / or comprising at least one intermediate layer (17) of foam disposed on a second external surface (S2) of at least one cell (6) of each stack (7), the second external surface (S2) being opposite the first (SI).

4. Battery according to claim 3, wherein said heat drain (16) comprises at least one layer of graphite and at least one layer of glue.

5. Battery according to claim 3 or 4, wherein said thermal drain (16) is folded under the cell (6) with which it is in contact, so as to constitute a contact surface (16c) of the drain (16) with the base (3).

6. Battery according to any one of claims 1 to 5, wherein the fastening means (10) comprise first (18) and second (19) fastening elements, said first elements being fixed to the base (3) and intended to pass through holes formed on a base plate (20) of each compression plate (8), said second (19) fixing elements cooperating with the first (18) fixing elements to fix the compression plates (8) to the base (3).

7. Battery according to claim 6, wherein the base (3) includes adjustment means (22) capable of imposing a lateral displacement (D) on at least one compression plate (8), so as to bring said compression plate (8) closer to or further from the middle of the base (3), when said lateral displacement (D) is respectively increased or decreased.

8. Battery according to any one of claims 1 to 7, comprising a protective wall (24) fixed to the compression plates (8) and disposed between the cells and the bell, so as to protect the bell in case of thermal runaway of the cells.

9. A method of mounting a battery according to any one of claims 1 to 8 comprising the following steps: - placing a first compression plate (8), - placing at least one stack (7) of electrical cells (6) against the first plate (8), - placing a second compression plate (8) opposite the first plate, and arranged in contact with the stacks (7) of cells (6), - pressurizing the two compression plates (8) against the stacks (7), - progressively bringing the two compression plates (8) together, - after the plates (8) have been brought together, fixing the compression plates (8) to the base (3) and installing the tie rods (12), and - tensioning the tie rods (12).

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