Assembly comprising an electrochemical element and an electrohydrodynamic pump, battery module, battery and associated method

Abstract

Assembly comprising an electrochemical element and an electrohydrodynamic pump, associated battery module, battery and method The assembly comprises an electrochemical element (22) comprising a container (50) containing at least one cathode, at least one anode and at least one internal separator interposed between each anode and each cathode. The container (50) has an external surface (26) intended to be immersed in a cooling fluid of the electrochemical element (22). The assembly comprises at least one flat electrohydrodynamic pump (24), attached to the external surface (26) of the container (50). The electrohydrodynamic pump (24) is configured to generate a local displacement of the cooling fluid in contact with the or each electrohydrodynamic pump (24) applied to the external surface (26) of the electrochemical element (22). Figure for abstract: Figure 1

Description

Title of the invention: Assembly comprising an electrochemical element and an electrohydrodynamic pump, battery module, battery and associated method

[0001] The present invention relates to an assembly, comprising an electrochemical element comprising a container containing at least one cathode, at least one anode and at least one internal separator interposed between each anode and each cathode, the container having an external surface intended to be immersed in a fluid for cooling the electrochemical element.

[0002] Such an assembly is intended to be included in a battery module used in particular in applications for supplying electrical power in the automotive, railway, aeronautical, space, and / or energy storage fields. The battery module including several electrochemical assemblies is particularly suitable for high electrical power applications.

[0003] The ecological transition requires having batteries in which the electrical powers involved are increasingly high, both when supplying current and voltage to a consumer system, or when recharging the battery module.

[0004] In this context, the battery module generally undergoes significant heating which requires efficient evacuation of the calories produced by the Joule effect.

[0005] To effectively cool the battery, it is known to at least partially immerse the battery elements of the module in a dielectric liquid which is circulated to pass around the battery elements and collect the heat they give off.

[0006] WO2020002254 describes a battery module of the aforementioned type, in which a fluid The cooling water is circulated by an electrohydrodynamic pump. The electrochemical elements are spaced apart and delimit large intermediate volumes. One or more electrohydrodynamic pumps in the form of grids are arranged in the intermediate volumes between the electrochemical elements, away from them.

[0007] Such a battery module is not entirely satisfactory. Indeed, the arrangement of a large intermediate volume between the electrochemical elements limits the volume available for storing electrical energy in the battery module. It is therefore not very compact.

[0008] Furthermore, the entrainment of the cooling fluid is significant at the level of the electrohydrodynamic pumps, but diminishes away from them, in particular at the surface of the electrochemical elements. Localized heating of the electrochemical elements is therefore always likely to occur, despite the presence and circulation of the cooling fluid.

[0009] An aim of the invention is therefore to provide an assembly which offers a particularly compact arrangement in a battery module, in order to increase the energy density stored by the battery module, while guaranteeing very efficient and low-energy cooling of the electrochemical elements present in the battery module.

[0010] To this end, the invention relates to an assembly of the aforementioned type, characterized in that it comprises at least one flat electrohydrodynamic pump, attached to the external surface of the container, the or each electrohydrodynamic pump being configured to generate a local displacement of the cooling fluid in contact with the or each electrohydrodynamic pump applied to the external surface of the electrochemical element.

[0011] The assembly according to the invention may comprise one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0012] - the electrohydrodynamic pump comprises at least one pair of electrodes of a first polarity defining between them an intermediate space along the external surface, the electrohydrodynamic pump comprising, for the or each pair of electrodes of first polarity, an electrode of a second polarity opposite to the first polarity, interposed in the intermediate space between the electrodes of first polarity;

[0013] - the electrodes of first polarity form parallel fingers, the electrode of second polarity forming an opposite finger arranged parallel and apart from the parallel fingers, the area of ​​each finger being different from the area of ​​the opposite finger;

[0014] - the electrohydrodynamic pump has a substrate carrying the electrodes of first and second polarities, the substrate being attached to the external surface;

[0015] - the substrate is a plate with an area greater than the area of ​​the first and second electrodes second polarities or the substrate is a flexible strip with an outline corresponding to the outline of the electrodes of first and second polarities;

[0016] - it comprises a separation system, the separation system defining at at least one coolant circulation channel having a coolant circulation axis;

[0017] - the separation system comprises a plurality of projecting wedges applied to the first and second polarity electrodes;

[0018] - the or each pair of electrodes of first polarity and the or each electrode of second polarity locally delimits the or each circulation channel in extending transversely to the fluid circulation axis;

[0019] - the separation system defines a plurality of parallel circulation channels of cooling fluid, the electrohydrodynamic pump comprising a plurality of successive first polarity electrodes and a plurality of successive second polarity electrodes interposed between the first polarity electrodes, the first polarity electrodes and the second polarity electrodes extending transversely to the parallel channels, at successive positions along the circulation axis;

[0020] - the container is a prismatic container, a cylindrical container or is a poached.

[0021] The invention also relates to a battery module comprising a housing and a plurality of electrochemical assemblies arranged in the housing, the plurality of electrochemical assemblies comprising at least a first assembly as defined above.

[0022] The battery module according to the invention may comprise one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0023] - the plurality of electrochemical assemblies forms a stack, at least one second set of the stack being placed adjacent and opposite the first set by defining an intermediate channel for circulating cooling fluid, the intermediate channel being delimited on one side at least in part by the electrohydrodynamic pump of the first set and being delimited on another side at least in part by an uncovered region of an external surface of the electrochemical element of the second set;

[0024] - the second set is as defined above, the external surface of the element electrochemical of the second assembly having on the side facing the first assembly, the uncovered region and on an opposite side, at least one electrohydrodynamic pump placed facing an uncovered region of an external surface of an electrochemical element of a third assembly of the stack;

[0025] - it comprises a transformer, electrically connected upstream to at least one electrochemical element of a set of the plurality of electrochemical assemblies and connected downstream to the or each electrohydrodynamic pump to electrically supply the or each electrohydrodynamic pump, advantageously with a voltage greater than 500 V, in particular between 500 V and 3000 V;

[0026] - it comprises a first row of terminals or connection tabs connected to the anodes of the electrochemical elements and a second row of terminals or connection tabs connected to the cathodes of the electrochemical elements, the transformer being arranged between the rows of terminals or connection tabs.

[0027] The invention also relates to a battery comprising at least one battery module as defined above and a cooling system, connected to the housing of the battery module.

[0028] The battery according to the invention may comprise the following characteristic:

[0029] - the cooling system comprises a cooling circuit, connected to the battery module housing, the cooling circuit comprising at least one heat exchanger, a coolant collection conduit to be cooled connecting the housing to the heat exchanger and a cooled coolant supply conduit connecting the heat exchanger to the housing.

[0030] The invention also relates to a method for cooling a battery module, comprising the following steps: - supply of cooling fluid, in particular a dielectric liquid, into the housing of a battery module as defined above; - bringing the cooling fluid into contact with the electrohydrodynamic pump of at least one assembly contained in the battery module; - power supply of the electrohydrodynamic pump; - circulation of the cooling fluid by the electrohydrodynamic pump along the electrohydrodynamic pump applied to the external surface of the electrochemical element of the assembly.

[0031] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings, in which:

[0032] - [Fig.l] [Fig.l] is a schematic view in partial section of a first battery comprising a battery module according to the invention;

[0033] - [Fig.2] [Fig.2] is a (a) front (b) side (c) rear view of an electric pump trophohydrodynamics applied to an external surface of an electrochemical element in an assembly according to the invention;

[0034] - [Fig.3] [Fig.3] is a schematic top view of a stack of assemblies electrochemicals according to the invention, in a battery module;

[0035] - [Fig.4] [Fig.4] is a schematic view describing the operating principle of an electrohydrodynamic pump on the external surface of a battery element in an assembly according to the invention;

[0036] - [Fig.5] [Fig.5] is an elevational view of a battery module comprising a stacking of several electrochemical assemblies and a transformer for electrically supplying the electrohydrodynamic pumps attached to electrochemical elements of the battery module;

[0037] - [Fig.6] [Fig.6] is a view of an overall variant according to the invention comprising a prismatic electrochemical element; and

[0038] - [Fig.7] [Fig.7] is a view of another overall variant according to the invention comprising a cylindrical electrochemical element.

[0039] A first battery 10 according to the invention is illustrated schematically in [Fig.l]. The battery 10 comprises at least one battery module 12, and a circuit 14 for circulating cooling fluid for cooling the battery module 12.

[0040] The battery module 12 comprises a housing 16, delimiting an interior volume 18. It further comprises a stack 20, received in the interior volume 18, comprising a plurality of electrochemical elements 22. At least a portion of the electrochemical elements 22, preferably all the electrochemical elements 22 are provided with an electrohydrodynamic pump 24 on their external surface 26 and thus form electrochemical elements according to the invention.

[0041] In this example, the battery module 12 further comprises a transformer 44 (see [Fig.5]) for powering each electrohydrodynamic pump 24 by the electrochemical elements 22.

[0042] Still with reference to [Fig. 5], the battery module 12 further comprises an electrical connection system 46 for the electrochemical elements 22 to connect them to electrical terminals (not shown) of the battery module 12, and advantageously, an electronic management system 48, interposed on the electrical connection system 46 between the electrochemical elements 22 and the terminals of the battery module 12.

[0043] In the example of [Fig.l], the housing 16 comprises a bottom 28, side walls 30, and a cover 32 which define between them the interior volume 18.

[0044] The housing 16 defines an inlet 34 for supplying a cooling fluid intended to be heated by heat exchange with the electrochemical elements 22, and an outlet 36 for discharging the heated cooling fluid. The cooling fluid is preferably a dielectric liquid.

[0045] The dielectric liquid advantageously has a resistivity greater than 50 GQ and a breakdown voltage greater than 40 kV for an air gap of 2.5 mm, preferably between 45 kV and 55 kV for an air gap of 2.5 mm.

[0046] The dielectric liquid further has a density advantageously less than 1, for example between 0.7 and 0.9 and a low viscosity, for example less than 3.3 mPa.s at 25°C, as measured by the ASTM D7042 standard.

[0047] In this example, the stack 20 extends along an axis AA' parallel to the bottom 28 of the interior volume 18 of the housing 16 when it is received in the interior volume 18. The axis A-A' is here horizontal.

[0048] The stack 20 comprises in particular more than two electrochemical assemblies, preferably between 2 and 20 stacked electrochemical assemblies. In this example, each assembly of the stack 20 comprises an electrochemical element 22 (sometimes referred to as an "electrochemical cell") and an electrohydrodynamic pump 24 on its external surface 26

[0049] As visible in [Fig. 3], the stack 20 further comprises a system 40 for separating the electrochemical elements 22 from adjacent electrochemical assemblies, defining channels 42 for circulating cooling fluid between each pair of adjacent electrochemical assemblies, and a system (not shown) for mechanically holding the stack 20, capable of keeping the electrochemical assemblies and the separation system 40 stacked in the form of a single block.

[0050] With reference to Figures 1 and 3, each electrochemical element 22 comprises a container 50, defining the external surface 26, and, in the internal volume defined by the container 50, an alternation of anodes, internal separators, and cathodes (not shown).

[0051] As visible in [Fig.5], the electrochemical element 22 further comprises at least one tab 52 for connecting the anodes, and at least one opposite tab 54 for connecting the cathodes.

[0052] In the example shown in Figures 1 to 5, the container 50 is formed by a pouch, advantageously deformable to the touch. In the variants of [Fig.6] and [Fig.7], which will be described later, the container 50 is of prismatic or cylindrical format respectively and is generally non-deformable to the touch.

[0053] The pocket is formed for example from two multilayer films welded together by their edges. Each multilayer film comprises a metal layer, generally made of aluminum, sandwiched between two layers of plastic material.

[0054] The container 50 thus constituted receives anodes and cathodes each separated by an internal separator, an electrolyte, and is closed in a sealed manner.

[0055] The electrochemical element 22 is for example of the lithium-ion type.

[0056] In the example shown in Figures 1 to 5, the container 50 has a shape generally prismatic. The external surface 26 thus has a front main face 56, on which the electrohydrodynamic pump 24 is mounted, and a rear main face 58 defining at least one uncovered region 60, intended to be swept by circulating cooling fluid. The main faces 56, 58 are connected laterally to each other at their peripheries.

[0057] Each tab 52, 54 projects out of the container 50, on either side of the container 50 relative to a median axial plane. Thus, all the tabs 52 connected to the anodes project from the same side of the container 50, and all the opposite tabs 54 connected to the cathodes project from another side of the container 50.

[0058] The tabs 52, 54 are connected to the electrical connection system 46, by example by welding.

[0059] According to the invention, at least a portion of the electrochemical elements 22 of the stack 20, preferably each electrochemical element 22 of the stack 20, is provided, on its front main face 56, with a planar electrohydrodynamic pump 24 applied to the main face 56 while being fixed thereto.

[0060] The electrohydrodynamic pump 24 is flat, in that it has a thickness less than the thickness of each electrochemical element 22, taken along the axis AA' between the front main face 56 and the rear main face 58.

[0061] The thickness of each electrohydrodynamic pump 24 is for example less than 2 mm.

[0062] In the example shown in [Fig. 2], the electrohydrodynamic pump 24 comprises a substrate 70, and an alternation of electrodes of a first polarity 72 and electrodes of a second polarity 74 formed on the substrate 70. Each electrode of second polarity 74 is interposed between a pair 76 of electrodes of first polarity 72.

[0063] The electrohydrodynamic pump 24 further comprises a common path 78 for supplying electricity to the electrodes of first polarity 72, and a common path 80 for supplying electricity to the electrodes of second polarity 74.

[0064] The substrate 70 here has a contour identical or homothetic to that of the main front face 56 on which it is fixed.

[0065] Its area is for example between 50% and 100% of the area of ​​the main front face 56, taken perpendicular to the axis A-A'.

[0066] In the example of [Fig.2], the substrate 70 further has an area greater than the area occupied by the electrodes 72, 74 and by the power supply paths 78, 80 on the substrate.

[0067] As a variant (not shown), the substrate 70 has a shape identical or homothetic to that of the electrodes 72, 74 and the power supply paths 78, 80.

[0068] The substrate 70 is for example formed from a plate made of electrically insulating material, in particular plastic material. The plate is for example formed from fluorinated polymer, in particular polytetrafluoroethylene, or even ceramic.

[0069] An electrically insulating material generally has a resistivity greater than 1015 ohm.m measured according to Standard NF EN 62631-1.

[0070] The substrate 70 generally has a low electrical permittivity, in particular less than 5, measured according to the IEC 62631-2-1:2018 Standard. This avoids electrical breakdown phenomena on the surface of the material.

[0071] In this case, the thickness of the substrate 70 is advantageously less than 2 mm.

[0072] Alternatively, the substrate 70 is made up of a strip that is deformable to the touch, in particular of the “Flex” type. It comprises a thin layer of a flexible polymer at touch, in particular a polyimide, such as Kapton®, on which the electrodes 72, 74 are deposited.

[0073] In this case, the thickness of the substrate 70 is advantageously less than 0.5 mm.

[0074] As illustrated by [Fig.2], the electrodes 72, 74, and the power supply paths 78, 80 are arranged on a first face 81A of the substrate 70, a second face 81B of the substrate 70 remaining devoid of electrodes 72, 74 and power supply paths 78, 80.

[0075] The second face 81B of the substrate is fixed on the front main face 56 of the electrochemical element 22.

[0076] Alternatively, the electrohydrodynamic pump 24 is substrate-free. The electrodes 72, 74 and the supply paths 78, 80 are applied directly to the external surface 26, which is then electrically insulating.

[0077] The electrodes 72, 74, and the supply paths 78, 80 are formed from a metal layer, for example containing copper or aluminum and / or alloys of these metals. The metal layer is generally less than 500 micrometers thick.

[0078] In the example shown in Figures 1 to 5, the electrodes of first polarity 72 extend perpendicularly to an elevation axis BB' of the substrate 70 and of the front main face 56 of the electrochemical element 22, along the width of the electrochemical element 22, substantially horizontally in [Fig.2].

[0079] The first polarity electrodes 72 are formed by fingers 82 projecting parallel to each other. Each finger 82 extends from the supply path 78 of the first polarity electrodes 72 towards the supply path 80 of the second polarity electrodes 74, up to a free end arranged opposite and away from the supply path 80 of the second polarity electrodes 74.

[0080] The adjacent parallel fingers 82 delimit between them an intermediate space 84 in which a second polarity electrode 74 is received.

[0081] Each second polarity electrode 74 also extends perpendicular to the elevation axis B-B', parallel to the first polarity electrodes 72.

[0082] The second polarity electrodes 74 are also formed by opposite fingers 86 projecting parallel to each other, each opposite finger 86 being interposed between two fingers 82 in the intermediate space 84.

[0083] Each opposing finger 86 extends from the supply path 80 of the second polarity electrodes 74 towards the supply path 78 of the first polarity electrodes 72, to a free end arranged opposite and away from the supply path 78 of the first polarity electrodes 72.

[0084] Along the elevation axis B-B', the height of the electrodes of first polarity 72 (corresponding here to the width of the fingers 82) is different from the height of the electrodes of second polarity 74 (corresponding to the width of the opposite fingers 86).

[0085] For example, the second polarity electrodes 74 have a height lower than that of the first polarity electrodes 72, in particular less than 50% of the height of the first polarity electrodes 72, the heights being taken parallel to the elevation axis B-B'.

[0086] The transverse extent of the electrodes 72, 74, taken perpendicular to the elevation axis BB' between the supply path 78, 80 from which they protrude and their free end is greater than 50%, in particular greater than 60% of the width of the substrate 70 and / or of the width of the front main face 56, taken perpendicular to the elevation axis B-B'.

[0087] The paths 78, 80 extend respectively along the lateral edges of the substrate 70, in the vicinity of the lateral edges of the front main face 56. They generally extend parallel to the elevation axis B-B'. They have a respective upper end 88, 90 for connection to a respective terminal of the transformer 44.

[0088] With reference to [Fig.4], under the effect of energizing the connection points 88, 90, in particular by applying an electric voltage greater than 500 V between these points 88, 90, an electric field is created between each electrode of first polarity 72, and the adjacent electrode of second polarity 74 along the axis B-B'. This electric field generates a phenomenon of dissociation of the molecules of the dielectric liquid into anions and cations.

[0089] Due to the different surface areas of the electrodes 72, 74 along the axis B-B', the anions and cations accumulate in different quantities on the respective electrodes 72, 74 and a flow F of liquid is generated along the elevation axis B-B' to compensate for the imbalance of the charges.

[0090] In an advantageous embodiment, shown in [Fig.5], each electrohydrodynamic pump 24 is electrically powered by one or more electrochemical elements 22 of the battery module 12.

[0091] In this case, the transformer 44 is connected upstream to the tabs 52, 54 of at least one electrochemical element 22, preferably of several electrochemical elements 22 of the battery module 12.

[0092] The transformer 44 is connected downstream to the connection points 88, 90 on each electrohydrodynamic pump 24.

[0093] The transformer 44 is configured to increase the electrical voltage received between the tabs 52, 54 of the electrochemical elements 22 and to provide an electrical voltage between the connection points 88, 90 which is greater than 500 V, and in particular between 500 V and 3000 V.

[0094] In the example illustrated in [Fig.5], the tabs 52 connected to the anodes are arranged on a first side of the electrochemical elements 22 of the stack 20, and the opposite tabs 54 connected to the cathodes are arranged on another side of the electrochemical elements 22 of the stack 20.

[0095] The tabs 52, 54 delimit between them an intermediate space 92 in which the transformer 44 is arranged. This optimizes the space available within the battery module 12.

[0096] With reference to [Fig. 3], the separation system 40 comprises a plurality of shims 100, applied to the electrohydrodynamic pump 24 of an assembly to be interposed between the electrodynamic pump 24 of the assembly and a rear main face 58 of an electrochemical element 22 of an assembly adjacent to the assembly carrying the electrohydrodynamic pump 24.

[0097] In the example shown in [Fig.3], each assembly is provided with a plurality of parallel shims 100, fixed to the electrohydrodynamic pump 24.

[0098] Each shim 100 is made of a rigid, non-compressible material, for example fluoropolymer, in particular polytetrafluoroethylene, or even ceramic.

[0099] Each shim 100 is made of an electrically insulating material which generally has a resistivity greater than 1015 ohm.m measured according to Standard NF EN 62631-1.

[0100] Each shim 100 generally has a low electrical permittivity, in particular less than 5, measured according to Standard IEC 62631-2-1:2018. This avoids electrical breakdown phenomena on the surface of the material.

[0101] Each shim 100 further has a compression rigidity allowing it to undergo a compression force within the stack 20 without significant deformation.

[0102] The Young's Modulus of the material forming each shim 100 is notably greater than 2000 MPa, as measured by Standard NF EN 12390-13.

[0103] The wedges 100 extend parallel to the elevation axis B-B', away from each other.

[0104] The spacing between two adjacent shims 100 is generally less than the width of a shim 100, taken perpendicular to the elevation axis B-B'. For example, the spacing between two shims 100 is less than 5 mm, in particular less than 3 mm.

[0105] The thickness of each shim 100, taken along the stacking axis AA', is generally less than or equal to the thickness of an electrochemical element 22. This thickness is generally less than 2 mm and is between 0.5 mm and 1 mm.

[0106] As illustrated by the enlargement shown on the right in [Fig.3], each pair of adjacent shims 100 defines between them a channel 42 for circulating cooling fluid.

[0107] The channel 42 is delimited laterally by the opposite lateral edges facing the two adjacent wedges 100. It is also delimited between on one side, the electrohydrodynamic pump 24 of the assembly, in particular in part by the electrodes 72, 74 of the electrodynamic pump 24, and on the other hand, an uncovered region 60 of the rear main face 58 of an electrochemical element 22 of an assembly adjacent to the assembly carrying the electrohydrodynamic pump 24.

[0108] As shown in [Fig.4], the electrodes 72, 74 extend successively perpendicular to the axis of the channel 42, with an alternation of electrodes of first polarity 72 and second polarity 74.

[0109] Thus, each channel 42 is delimited over its entire height along the axis BB' by a succession of electrodes of first polarity 72 and electrodes of second polarity 74.

[0110] The holding system (not shown) has for example one or more tie rods and end plates making it possible to hold the stack 20 of electrochemical assemblies stacked against each other in succession by means of the wedges 100.

[0111] Thus, in the stack 20 mechanically held by the holding system, each electrochemical element 22 of an assembly has, fixed on its front main face 56, an electrohydrodynamic pump 24, on which shims 100 are fixed, which are in contact with the rear main face 58 of an electrochemical element 22 of an adjacent assembly or of an end plate.

[0112] The electrochemical element 22 of the assembly receives, in support, on its rear main face 58, the shims 100 of an electrochemical element 22 of another adjacent assembly and / or of an end plate.

[0113] Each pair of facing electrochemical assemblies defines, between the shims 100, the electrohydrodynamic pump 24, and the uncovered region 60, a plurality of cooling fluid circulation channels 42 extending here parallel to the elevation axis B-B'.

[0114] With reference to [Fig.5], the electrical connection system 46 connects, on the one hand, the tabs 52 and, on the other hand, the tabs 54 to the electronic management system 48. The electronic management system 48 is itself connected to the terminals (not shown) of the battery module 12.

[0115] The electronic management system 48 comprises electronic components intended to control the voltage and / or the current delivered by each electrochemical element 22 of the battery module 12 during its discharge, and the voltage and / or the current received by each electrochemical element 22 of the battery module 12 during its recharge.

[0116] With reference to [Fig. 1], the cooling fluid circulation circuit 14 comprises a heat exchanger 110, arranged outside the housing 16 of the battery module 12, a collection conduit 112 for the cooling fluid to be cooled connecting the outlet 36 to an inlet of the heat exchanger 110, and a conduit 114 of supplying cooled coolant to the housing 16, connecting an outlet of the heat exchanger 110 to the inlet 34 of the housing 16.

[0117] The assembly of the battery module 12 will now be described.

[0118] Initially, each assembly is assembled by fixing, on an electrochemical element 22, an electrohydrodynamic pump 24 on the front main face 56 of the container 50 of the electrochemical element 22.

[0119] Then, the shims 100 of the separation system 40 are fixed on the electrohydrodynamic pump 24 by creating interstices intended for the formation of the channels 42.

[0120] Then, the electrochemical assemblies, each comprising an electrochemical element 22 and an electrohydrodynamic pump 24 assembled on the electrochemical element 22 are stacked on top of each other, with the interposition of the shims 100.

[0121] The cooling fluid circulation channels 42 are then closed on one side by the electrohydrodynamic pump 24 carried by an electrochemical element 22 of an assembly and on the other side by the uncovered region 60 of the rear main face 58 of an electrochemical element 22 of an adjacent assembly.

[0122] The holding system is then put in place to mechanically hold the stack 20 which can then be moved in one piece.

[0123] The stack 20 is then inserted into the internal volume 18 of the housing 16. It is then immersed in cooling fluid, in particular in dielectric liquid. The housing 16 is closed and is connected to the fluid circulation circuit 14.

[0124] The use of the battery 10 will now be described. During use, electrical power is delivered by the electrochemical elements 22 to the terminals of the or each battery module 12, during discharging, or is delivered to the electrochemical elements 22 through the terminals of the or each battery module 12 during charging.

[0125] During discharging or recharging, coolant is routed through the circulation circuit 14, in order to provide cooled coolant into the interior volume 18 through the supply inlet 34.

[0126] The cooling fluid is driven through the channels 42 located between the electrochemical elements 22.

[0127] For this purpose, each electrohydrodynamic pump 24 is activated. The connection points 88, 90 are powered by the transformer 44 to apply between these points an electrical voltage greater than 500 V.

[0128] This electrical voltage is applied between each electrode of first polarity 72 and each adjacent electrode of second polarity 74.

[0129] It causes a separation of molecules of the dielectric liquid into anions and cations. The cations accumulate on the electrodes of negative polarity, while the anions accumulate on the positive polarity electrodes.

[0130] Given the difference in area between the electrodes 72, 74, there is an imbalance between the charges accumulated on each electrode 72, 74, this imbalance causing fluid pumping.

[0131] Local turbulence is created in each channel 42 along the electrodynamic pump 24 along the elevation axis B-B'. This turbulence is created in the vicinity of a pair of electrodes 72, 74 where pumping occurs. The pumping locally generates turbulence in the flow which has the effect of improving heat transfers, in particular on the uncovered region 60 on each rear main face 58 delimiting a channel 42.

[0132] As a result, the heat exchange at the uncovered region 60 is improved, causing more efficient evacuation of the heat emitted in the electrochemical element 22, in particular by thermal convection between the uncovered region 60 and the cooling fluid present in the channel 42.

[0133] The heated cooling fluid from the channels 42 is then collected at the outlet 36 to be conveyed to the heat exchanger 110 via the collection pipe 112.

[0134] Thus, the use of flat electrohydrodynamic pumps 24 applied to the external surface 26 of the container 50 significantly increases the heat exchange between the cooling fluid and the electrochemical elements 22, providing very efficient cooling of these electrochemical elements 22. It also makes it possible either to eliminate or to minimize the need for an external pump on the circulation circuit 14.

[0135] This cooling efficiency is obtained by maintaining a very compact architecture of the battery module 12, since the electrochemical elements 22 are stacked on top of each other, the electrohydrodynamic pump 24 occupying minimal space in the interior volume 18 of the housing 16.

[0136] A beneficial effect is obtained by improved heat dissipation in the electrochemical elements 22, which makes it possible to bring them closer together in order to increase the energy density present in the battery 10 by limiting, or even eliminating, the risk of heating within the or each battery module 12.

[0137] Very low electrical consumption (for example less than 1 mW per electrohydrodynamic pump 24) is necessary to obtain this efficient cooling, since the electrohydrodynamic pumps 24 are low-power consumers.

[0138] The electrical power required for the operation of the electrohydrodynamic pumps 24 is advantageously supplied directly by the electrochemical elements 22 of the battery module 12, in particular by providing a transformer 44 which can be integrated compactly into the battery module 12.

[0139] Thus, the battery module 12 has better cooling performance, compared to air cooling.

[0140] The electrical consumption of the cooling system is low, in particular compared to an air cooling system and the noise emission is very reduced. The electrochemical elements 22 are better protected, since no oxidation of the external containers 50 occurs resulting from the circulation of an air flow.

[0141] Cooling is integrated into the battery module 12, which simplifies the circuitry and increases reliability. In addition, the use of electrohydrodynamic pumps 24 without moving components guarantees high reliability and reduced maintenance, while offering very high compactness.

[0142] In a variant (not shown), the separation system 40 is not formed by shims 100, but by another device defining at least one open channel for circulation of the dielectric liquid. The device is electrically insulating and has mechanical resistance to compression in the stack 20.

[0143] In another variant, shown schematically in [Fig.6], the electrochemical element 22 is a prismatic element. It comprises a container 50 which is rigid to the touch, on which the electrohydrodynamic pump 24 is fixed to form an assembly according to the invention.

[0144] In this example, the first polarity electrodes 72 and the second polarity electrodes 74 are mounted parallel to each other and parallel to the elevation axis B-B'.

[0145] On the contrary, the shims 100 are mounted perpendicular to the axis B-B'. The channels 42 thus extend perpendicular to the elevation axis B-B', horizontally on [Fig.6],

[0146] The operation of the battery module 12 comprising electrochemical assemblies such as represented in [Fig.6] is also analogous to that of the battery module 12 described previously in FIGS. 1 to 5.

[0147] In another variant, shown in [Fig.7], the electrochemical element 22 is cylindrical in shape. The electrodynamic pump 24 is wound around the cylindrical external surface 26 of the container 50 to form an assembly according to the invention.

[0148] The presence of the electrohydrodynamic pump 24 around the cylindrical electrochemical element 22 improves the heat exchange at the external surface 26, increasing the cooling provided by the cooling fluid.

Claims

Claims

1. Assembly, comprising an electrochemical element (22) comprising a container (50) containing at least one cathode, at least one anode and at least one internal separator interposed between each anode and each cathode, the container (50) having an external surface (26) intended to be immersed in a cooling fluid of the electrochemical element (22); characterized in that the assembly comprises at least one flat electrohydrodynamic pump (24), attached to the external surface (26) of the container (50), the or each electrohydrodynamic pump (24) being configured to generate a local displacement of the cooling fluid in contact with the or each electrohydrodynamic pump (24) applied to the external surface (26) of the electrochemical element (22).

2. An assembly according to claim 1, wherein the electrohydrodynamic pump (24) comprises at least one pair (76) of electrodes of a first polarity (72) defining between them an intermediate space (84) along the external surface (26), the electrohydrodynamic pump (24) comprising, for the or each pair (76) of electrodes of first polarity (72), an electrode of a second polarity (74) opposite to the first polarity, interposed in the intermediate space (84) between the electrodes of first polarity (72).

3. An assembly according to claim 2, wherein the first polarity electrodes (72) form parallel fingers (82), the second polarity electrode (74) forming an opposite finger (86) arranged parallel and spaced from the parallel fingers (82), the area of ​​each finger (82) being different from the area of ​​the opposite finger (86).

4. Assembly according to one of claims 2 or 3, in which the electrohydrodynamic pump (24) has a substrate (70) carrying the electrodes (72, 74) of first and second polarities, the substrate (70) being attached to the external surface (26).

5. An assembly according to claim 4, wherein the substrate (70) is a plate of greater area than the electrodes (72, 74) of first and second polarities or wherein the substrate (70) is a flexible strip of contour corresponding to the contour of the electrodes (72, 74) of first and second polarities.

6. An assembly according to any one of claims 2 to 5, comprising a separation system (40), the separation system (40) defining at least one cooling fluid circulation channel (42) having a cooling fluid circulation axis.

7. An assembly according to claim 6, wherein the separation system (40) comprises a plurality of projecting shims (100) applied to the electrodes (72, 74) of first and second polarities.

8. An assembly according to claim 6 or 7, wherein the or each pair of electrodes of first polarity (72) and the or each electrode of second polarity (74) locally delimit the or each circulation channel (42) by extending transversely relative to the fluid circulation axis.

9. An assembly according to any one of claims 6 to 8, wherein the separation system (40) defines a plurality of parallel channels (42) for circulating cooling fluid, the electrohydrodynamic pump (24) comprising a plurality of successive first polarity electrodes (72) and a plurality of successive second polarity electrodes (74) interposed between the first polarity electrodes (72), the first polarity electrodes (72) and the second polarity electrodes (74) extending transversely to the parallel channels (42), at successive positions along the circulation axis.

10. An assembly according to any preceding claim, wherein the container (50) is a prismatic container, a cylindrical container or is a pouch.

11. A battery module (12), comprising a housing (16) and a plurality of electrochemical assemblies disposed in the housing (16), the plurality of electrochemical assemblies comprising at least a first assembly according to any one of the preceding claims.

12. Battery module (12) according to claim 11, wherein the plurality of electrochemical assemblies form a stack (20), at least a second assembly of the stack (20) being placed adjacent and opposite the first assembly by defining an intermediate channel (42) for circulating cooling fluid, the intermediate channel (42) being delimited on one side at least in part by the electrohydrodynamic pump (24) of the first assembly and being delimited on another side at least in part by an uncovered region (60) of an external surface (26) of the electrochemical element (22) of the second assembly.

13. The battery module (12) of claim 12, wherein the second assembly is according to any one of claims 1 to 10, the external surface (26) of the electrochemical element (22) of the second assembly having on the side facing the first assembly, the uncovered region (60) and on an opposite side, at least one electrohydrodynamic pump (24) placed facing an uncovered region (60) of an external surface (26) of an electrochemical element (22) of a third assembly of the stack (20).

14. Battery module (12) according to any one of claims 12 to 13, comprising a transformer (44), electrically connected upstream to at least one electrochemical element (22) of a set of the plurality of electrochemical assemblies and connected downstream to the or each electrohydrodynamic pump (24) to electrically power the or each electrohydrodynamic pump (24), advantageously with a voltage greater than 500 V, in particular between 500 V and 3000 V.

15. Module according to claim 14, wherein the stack (20) comprises a first row of terminals or connection tabs (52) connected to the anodes of the electrochemical elements (22) and a second row of terminals or connection tabs (54) connected to the cathodes of the electrochemical elements (22), the transformer (44) being arranged between the rows of terminals or connection tabs (52, 54).

16. Battery (10) comprising at least one battery module (12) according to any one of claims 11 to 15 and a cooling system, connected to the housing (16) of the battery module (12).

17. Battery (10) according to claim 16, wherein the cooling system comprises a cooling circuit (14), connected to the housing (16) of the battery module (12), the cooling circuit (14) comprising at least one heat exchanger (110), a conduit (112) for collecting coolant to be cooled connecting the housing (16) to the heat exchanger (110) and a conduit (114) for supplying cooled coolant connecting the heat exchanger (110) to the housing (16).

18. Method for cooling a battery module (12), comprising the following steps: - supplying cooling fluid, in particular a dielectric liquid, into the housing (16) of a battery module (12) according to any one of claims 11 to 15; bringing the cooling fluid into contact with the electrohydrodynamic pump (24) of at least one assembly contained in the battery module (12); power supply of the electrohydrodynamic pump (24); circulating the cooling fluid by the electrohydrodynamic pump (24) along the electrohydrodynamic pump (24) applied to the external surface (26) of the electrochemical element (22) of the assembly.

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