ELECTRIC MODULE COMPRISING A PLURALITY OF BATTERY CELLS IMMERSED IN A DIELECTRIC LIQUID

Abstract

Electric module comprising a plurality of battery cells immersed in a dielectric liquid The invention relates to an electric battery module (10) comprising a housing (2, 12) in which a plurality of cells (1, 70) are arranged in heat exchange with a cooling liquid circulating between interstices formed between said adjacent cells (1, 29, 70), characterized in that said housing (2, 12) has an intermediate volume (150) in which said adjacent cells (1, 9, 70) are arranged vertically and between which said cooling liquid (5) flows, a lower volume (130) supplied by said at least one inlet port (3) for cooling liquid (5), an upper volume (140), and opening towards the outside of said housing by said at least one outlet port (4) for cooling liquid (5).A pressure drop device (6) is arranged between said lower volume (130) and said intermediate volume (150), and configured to locally modulate the flow resistance between the zone(s) closest to said at least one inlet port (3) of coolant (5), and the opposite zone(s) of said lower volume (130). The invention also relates to an electric battery comprising a plurality of such sealed modules (10) whose valves are connected to the frame of said battery. Abstract figure: 1.

Description

Title of the invention: ELECTRICAL MODULE COMPRISING A PLURALITY OF BATTERY CELLS IMMERSED IN A DIELECTRIC LIQUID Field of the invention

[0001] The present invention relates to a battery pack having an optimized thermal management system in which a temperature-controlled liquid comes into direct contact with the battery cells. It applies in particular, but not exclusively, to the field of mobility. It applies, for example, to traction batteries of electric vehicles (EV) and hybrid electric vehicles (HEV) as well as to batteries of airplanes, vertical take-off aircraft, rockets and satellites.

[0002] A lithium-ion (Li-ion) electrochemical cell battery module regularly undergoes charging and discharging phases, resulting in heating which can be significant. This electrochemistry also has a reduced operating temperature range, typically between 0 and 55°C for charging and -20°C and 75°C for discharging. Accelerated cell aging increases when the cell temperature deviates from an ideal operating temperature, typically 25°C.

[0003] It is therefore necessary to cool it efficiently in order, on the one hand, to maintain its performance level, and on the other hand to limit its accelerated aging. The power density of these batteries tends to increase in order to meet the needs in terms of autonomy and rapid charging. Liquid cooling, generally glycolated water, makes it possible to meet these needs. The water conventionally circulates in one or more plates, itself placed in contact with the electrochemical cells. The contact between the cells and the water is therefore indirect and local, reducing the efficiency of the system. The water can sometimes be replaced by dielectric thermal liquids to limit the risk of short circuit in the event of a leak. State of the art

[0004] Known in the state of the art is patent application EP3726613 describing a liquid-cooled battery system which comprises rows of battery cells, an outer casing and a cell fixing system whose body extends in a vertical direction.

[0005] The battery cells of each row are offset with the battery cells of an adjacent row. The outer housing defines a housing space for housing the battery cells, and has a first port unit and a second port unit that are configured to allow a coolant to flow through the housing space from port units to each other so as to allow the battery cells to be cooled by the coolant. The cell fastener includes a retaining strip that is fitted within the housing space, and that is formed with a plurality of rows of retaining holes. The retaining holes of each row are offset with the retaining holes of an adjacent row, and are configured to retain the cell bodies of a respective row of the battery cells so as to allow the battery cells to be held in the housing space by the holder, thereby keeping the battery cells in a stable position against unwanted vibrations.

[0006] A similar solution is described in patent application US2010047682 proposing a method for managing the temperature of cells within a battery module consisting of directing a gaseous fluid (air) in front of a device configured to modify the temperature of the fluid.

[0007] The fluid is directed into an inlet of the battery module such that the fluid flows proximate the plurality of cells to change the temperature of the cells. The device is configured such that the fluid enters the inlet at a first temperature for a first period and at a second temperature for a second period, the first temperature being different from the second temperature. The temperature difference between a first group of cells closest to the inlet and a second group of cells farthest from the inlet is less than it would be if the fluid were supplied into the battery module at a constant temperature.

[0008] Also known is patent application DE102014106852 describing a battery module having a battery housing comprising an inlet for introducing a refrigerant into a cooling space which is partially delimited by the battery housing and an outlet for discharging the refrigerant from the cooling space. Battery cells for storing electrical energy are inserted into the battery housing and are arranged to a large extent in the cooling space. An insulating layer is provided for liquid-tight closure of the cooling space. At least one electrical pole of the battery cell protrudes out of the cooling space through the insulating layer. The insulating layer is formed from a cured sealing compound.

[0009] The cooling space formed in the battery housing can be sufficiently sealed by the insulating layer so that the cooling space can be supplied with an electrically conductive coolant, for example water, without the coolant reaching the electrical pole of the battery cell which is guided through the insulating layer.

[0010] Patent application DE102009006216 also describes a battery comprising a housing in which the cells are arranged and are in heat exchange with an inert liquid which evaporates in the housing and condenses on a cooler. Interstices provided between the cells containing the inert liquid are made of a granular bulk material or a lattice-like structure or the like in order to minimize the required quantity of inert liquid. Disadvantage of the prior art

[0011] The solutions of the prior art have the disadvantage of a relatively long coolant circulation circuit, especially when the battery comprises a large number of cells and the forced circulation between the cells presents significant variations between those which are closest to the coolant inlets, and those which are furthest from them. The thermal control of the cells is then very inhomogeneous, some being more cooled than others, leading to different operating temperatures and heterogeneous electrical characteristics, partly dependent on the temperature of the cell. This results in electrical operating anomalies of the cells connected in series or in parallel, directly or via an electrical management module. Solution provided by the invention

[0012] The solutions implemented in the invention consist of circulating the coolant from bottom to top, which allows both automatic purging of air through the outlet port and possible emptying of liquid through the inlet port. In addition, section restrictions are created to standardize the distribution of liquid in order to serve all the cells with a liquid at substantially the same temperature and at the same flow rate, which allows for homogeneous performance and aging of the battery. Finally, these section restrictions are practiced only on the bottom of the cells, which promotes natural circulation, in particular during thermal runaway of a cell. This natural circulation adds to or even supplements the flow rate imposed by the pump to avoid the propagation of thermal runaway. In the case of prismatic cells, these restrictions are carried by spacers inserted between the cells.These spacers also have means of distributing the compression force to control the internal mechanical constraints of the cells to avoid premature aging.

[0013] The solutions implemented in the invention also consist of including all of the peripheral components to the battery cells inside the sealed enclosure, by immersing them in a dielectric liquid. Thus, the electronic circuits, contactors, fuses, current and voltage sensors, precharge resistors, bus bars and connectors are cooled. In addition, the number of interfaces with the outside of the enclosure is considerably reduced, which facilitates the implementation of the enclosure's waterproofing.

[0014] Furthermore, to reduce the size and weight, the proposed solution consists of integrating the expansion tank into other components, such as the junction box, a component which contains all or part of the electrical safety features of the battery: fuse, contactors, pre-charge resistor, current sensor, insulation board, voltage, temperature and current monitoring board of the battery. Alternatively, the sealed enclosure applied to each of the modules is extended to the entire battery, which relieves the modules of this function: they are then more compact and lighter. The enclosure then also takes on the function of the expansion tank. Purpose of the invention

[0015] The present invention relates to, in its most general sense, an electric battery module comprising a housing in which a plurality of cells are arranged in direct heat exchange with a dielectric cooling liquid circulating between interstices formed between said adjacent cells, characterized in that said housing has: • an intermediate volume in which said adjacent cells are arranged and between which said dielectric liquid flows, • a lower volume located below said intermediate volume, and supplied by at least one dielectric liquid inlet port, • an upper volume, located above said intermediate volume, and opening towards the outside of said housing via at least one dielectric liquid outlet port, • and in that a pressure drop device is arranged between said lower volume and said intermediate volume, said pressure drop device being configured to locally modulate the flow resistance between the zone(s) closest to said at least one dielectric liquid inlet port (3), and the opposite zone(s) of said lower volume.

[0016] Preferably, the pressure drop between said intermediate volume and said upper volume is substantially lower than between said lower volume and said intermediate volume so as to promote natural convection in the event of an absence of dielectric liquid supply through said at least one inlet port.

[0017] Preferably, said pressure loss device consists of orifices between 0.3mm2 and 2.3mm2 in section each.

[0018] According to a first variant, said cells are of the prismatic or sachet type, and are arranged vertically in said intermediate volume.

[0019] Preferably, spacers are interposed between two adjacent cells.

[0020] Advantageously, said spacers form a lattice for absorbing the compression force applied to the set of cells on the large faces thereof.

[0021] Preferably, said spacers have a flexibility in their thickness greater than 1 mm per MPa.

[0022] Preferably, said spacers have meshes less than 30% of the length of said cells.

[0023] According to a particular embodiment, said spacers: • are formed by an electrically insulating frame cut with a thickness between 7 and 15% of the thickness of the cells, • have lower slots allowing pressure loss, • have upper slots that are significantly wider than said slots inferior, • have reinforcements configured to avoid direct thermal contact between cells, • are made of compressible material with a flexibility greater than 1mm per MPa, • and have a window for the circulation of liquid from a lower volume to a higher volume.

[0024] Advantageously, said spacers are grids obtained by folding-cutting according to a pattern with offset notches, from a metal sheet with a thickness of less than 0.2 mm.

[0025] According to another variant, said spacers: • are formed by a grid with a thickness between 7 and 15% of the thickness of the cells, • have a contact surface with the cells greater than 30% of the surface of the large face of said cells, • allow the circulation of liquid from a lower volume to a higher volume.

[0026] Preferably, said spacers: • have a contact surface with the cells greater than 50% of the surface of the large face of said cells, • have a 'dovetail' folding pattern giving the grid compressibility to conform to the swelling of said cells, • are formed from a stainless steel sheet with a thickness of less than 0.1mm.

[0027] Advantageously, said cells are cylindrical in shape and are arranged vertically in said intermediate volume.

[0028] According to a particular embodiment, said pressure loss device consists of orifices distributed around the periphery of each of said cylindrical cells, in each of the two shells of the cell support and represents between 1mm2 and 12mm2 around each of said cylindrical cells.

[0029] According to another variant, an internal bucket-shaped hydraulic conduit collects the dielectric liquid from the upper volume near the upper internal face of the enclosure to guide it towards the outlet port.

[0030] Advantageously, an internal tub-shaped conduit collects the gases emitted in the event of thermal runaway in the upper volume near the upper internal face of the enclosure to guide them towards the safety valve, so as to define a dielectric liquid level in the upper volume as high as possible in the module when said valve is open.

[0031] The invention also relates to an electric battery characterized in that it comprises a plurality of battery modules having the characteristics of the aforementioned module and in that they are sealed, said modules each having a safety valve connected to a hollow tube of the chassis so that the gases emitted during thermal runaway are directed inside said chassis and expelled from said battery without propagating therein.

[0032] Detailed description of a non-limiting example of the invention

[0033] The present invention will be better understood upon reading the detailed description of a non-limiting example of the invention which follows, referring to the appended drawings where:

[0034] - [Fig.l] [Fig.l] represents a schematic view of the circulation of the liquid in an immersion-cooled battery module

[0035] - [Fig.2] [Fig.2] represents a state-of-the-art diagram of a modular battery immersion cooled

[0036] - [Fig.3] [Fig.3] represents a diagram of a modular battery cooled by immersion with a submerged junction box acting as an expansion tank

[0037] - [Fig.4] [Fig.4] represents a diagram of a cooled mono-structural battery by immersion

[0038] - [Fig.5]

[0039] - [Fig.6] Figures 5 and 6 represent a cell battery module (10) taken matics

[0040] - [Fig.7] [Fig.7] represents an exploded view of the cell battery module (10) prismatic

[0041] - [Fig.8] [Fig.8] represents an exploded view of the assembly (20) of cells taken matics

[0042] - [Fig.9] [Fig.9] represents a detail of the assembly (20) of prismatic cells representing the inter-cell

[0043] - [Fig. 10] [Fig. 10] represents the flow of liquid in the module (10) at prismatic cells

[0044] - [Fig. 11] [Fig. 11] shows spacer variants (71)

[0045] - [Fig. 12] [Fig. 12] represents the mechanical fixing system of the assembly (20) prismatic cells

[0046] -[Fig. 13]

[0047] - [Fig. 14] Figures 13 and 14 show a cy-cell battery module (10) lindriques

[0048] - [Fig. 15] [Fig. 15] shows an exploded view of the cell battery module (10) cylindrical

[0049] - [Fig. 16] [Fig. 16] represents an exploded view of the assembly (20) of cy cells lindriques

[0050] - [Fig. 17] [Fig. 17] represents the flow of liquid in the module (10) at cylindrical cells

[0051] - [Fig. 18] [Fig. 18] represents a detail of the assembly (20) of cy cells lindriques

[0052] - [Fig. 19] [Fig. 19] represents an immersion-cooled modular battery

[0053] - [Fig.20] [Fig.20] represents a bag cell battery module

[0054] - [Fig.21] [Fig.21] shows an exploded view of the battery module with cells in bag

[0055] - [Fig.22] [Fig.22] represents an exploded view of the cell assembly in bag

[0056] - [Fig.23] [Fig.23] represents a possible embodiment of the loss of charges

[0057] - [Fig.24] [Fig.24] represents a possible embodiment of a spacer

[0058] - [Fig.25] [Fig.25] represents the flow of liquid in the cell module in bag

[0059] - [Fig.26] [Fig.26] shows two sectional views of the sachet cell module

[0060] General architecture and operating principle

[0061] The module (10) described in [Fig.l] consists of an enclosure (2) inside which battery cells (1) are arranged. The module (10) has hydraulic inlet (3) and outlet (4) ports allowing the circulation of a heat-transfer dielectric liquid (5). The liquid (5) comes into direct contact with the live parts, according to the principle of immersion cooling.

[0062] In operation, the battery cells (1) heat up by the Joule effect. Indeed, when subjected to a current, their internal resistance in particular produces heat, the power of which is equal to the internal resistance multiplied by the intensity squared. As a result, the liquid (5) inside the module (10) heats up, cooling the cells (1). Then it transports this heat out of the module (10). The liquid (5) escapes from the module (10) through the outlet ports (4).

[0063] The module is divided into several internal volumes: • an intermediate volume (150) in which battery cells (1) are arranged vertically and between which the liquid (5) flows, • a lower volume (130) located below the intermediate volume (150), and supplied by at least one inlet port (3) for liquid (5), • an upper volume (140), located above the intermediate volume (150), and opening towards the outside of the housing via at least one outlet port (4) for liquid (5).

[0064] The liquid is distributed under the cell assembly (1) in the lower volume (130) then passes through a device (6) creating a pressure drop substantially greater than the other pressure drops experienced by the liquid when passing through the module (10). This pressure drop device (6) allows a substantially equal distribution of the liquid over all the cells (1) of the module (10).

[0065] This pressure drop device (6) may be a perforated wall or be composed of an assembly of parts which are substantially sealed against each other and have calibrated orifices or slots which allow the cooling liquid to pass through, creating locally a dissipation, by friction, of the mechanical energy of the cooling liquid passing through the device, and a pressure drop which varies according to the distance from the inlet port (3) of the cooling liquid.

[0066] This results in better temperature uniformity of the cells (1) which induces homogeneous electrical behavior and homogeneous aging of the cells (1). In addition, this arrangement allows better natural circulation of the liquid, by thermosiphon, in the event of failure of the pump during normal operation and in the event of thermal runaway of a cell (1). This natural circulation then makes it possible to avoid the propagation of thermal runaway to adjacent cells by efficiently redistributing the heat from the combustion of the faulty cell over the entire mass of the module (10). Thus, the adjacent cell(s) receive less heat and do not exceed the limit temperature above which thermal runaway is initiated.

[0067] The dielectric liquid (5) has the following characteristics:

[0068] - Kinematic viscosity at 40°C preferably less than 30 mm2 / s and ideally less than 5mm2 / s

[0069] - Flash point above 93.5°C, ideally above 130°C

[0070] - breakdown voltage preferably greater than 1 kV / mm in liquid phase and gaseous,

[0071] - electrical resistivity at 40°C preferably greater than 0.2 GOhm.m

[0072] - Volumetric heat capacity preferably greater than 1.5 MJ / m3 / K,

[0073] - Liquid thermal conductivity preferably greater than 0.125 W / m / K

[0074] - Kinematic viscosity at -20°C preferably less than 200 mm2 / s

[0075] - Saturation pressure at 70°C preferably less than 1.5 barA

[0076] - Density gradient between 20°C and 200°C preferably greater than 0.65 kg / m3 / K

[0077] Here is a non-limiting example of the liquid used: a formulated or unformulated dielectric oil, the base oil of which may be of the PAO (polyalphaolefin) type or of the ester type.

[0078] The performance of a cooling system depends on the product of the heat exchange coefficient, specific to the liquid and the architecture used, by the cooled surface. The different immersion cooling systems presented in this patent prioritize the quantity of cooled surface to increase the cooling performance. This makes it possible to work with liquids that are simpler to implement and less expensive, and to cool the hot spots of the battery. The cooled surfaces vary between 20 and 98% of the surface area of ​​the cells (1) and the exchange coefficients obtained vary between 100 and 300 W / m2 / K.

[0079] Detailed description of a state-of-the-art modular immersion battery (100)

[0080] [Fig.2] illustrates a possible diagram of a modular battery cooled by immersion. The battery (100) is divided into modules (10) in which a liquid (5) circulates. These modules (10) are sealed against the liquid (5). They have hydraulic inlet and outlet ports.

[0081] The modules (10) are electrically connected to each other, for example in series, by a bus bar (101). This bus bar passes through a junction box (102) which contains electrical control and protection elements (fuses, contactors, relays and precharge resistor, current and voltage sensor, electronic insulation measurement card, electronic battery management card) before joining a connector (103) of the battery (100). Other cables not shown in the figure, such as electrical communication harnesses, also run from module to module to the junction box.

[0082] The liquid (5) is distributed between each of the modules (10), for example in parallel, by a pipe (113). A pump (109) creates a pressure making it possible to push the liquid through the modules.

[0083] The hydraulic circuit is provided with one or more desiccant and particulate filters (108) which can be placed before the pump or before the battery to protect them.

[0084] The hydraulic circuit comprises an exchanger (110) which allows the cooling or heating of the liquid (5). This exchanger transfers the heat to a fluid (111) which may be air, glycolated water, a refrigerant fluid, or even a cryogenic fluid for space applications, or a mixture of these different fluids in different circuits. This exchanger (110) can be placed at different locations on the circuit: after the pump and before the modules (10) preferably in order to reduce the hydraulic pressure in the modules (10).

[0085] The hydraulic circuit also contains an expansion tank (112). This tank allows thermal expansion of the liquid because it comprises either a gaseous fluid or a deformable membrane.

[0086] The hydraulic circuit also includes a safety valve (105) to prevent pressure build-up in the circuit in the event of a failure: gas emission from the cells, blockage of the circuit, etc.

[0087] This or these valves can be placed in different locations, on the vase (112), on the modules (10) or on the pipes (113) containing the liquid (5).

[0088] A filling device (114) and a purging device (115) complete this hydraulic circuit.

[0089] Detailed description of a junction box acting as an expansion tank

[0090] In order to reduce the size of the batteries, it is interesting to share functions on components. Thus, in order to cool the junction box (102), it may be relevant to cool it by immersion like the modules (10). For greater compactness, [Fig.3] shows a component (116) which merges the junction box (102) and the expansion tank (112). This new component (116) also carries a safety valve (105), a desiccant filter (108), as well as a filling device (114).

[0091] Detailed description of an immersion-cooled mono-structural battery

[0092] [Fig.4] illustrates an immersion-cooled mono-structural battery (100) to further reduce weight and size. This battery (100) is contained in a single sealed enclosure (104). The battery is divided into cell assemblies (20) which are not sealed, as opposed to modules (10).

[0093] The cell assemblies (20) are electrically connected to each other, for example in series, by a bus bar (101). This bus bar passes through a junction box (102) which contains electrical control and protection elements (fuses, contactors, relays and precharge resistor, current and voltage sensor, electronic insulation measurement card, electronic battery management card) before joining a connector (103) of the battery (100). Other cables not shown in the figure, such as electrical communication harnesses, also run from cell assembly to cell assembly up to the junction box. The connector (103) is sealed against the liquid (5) contained in the enclosure (104). The junction box (102) is immersed in the liquid (5).

[0094] The liquid (5) is distributed between each of the modules (10), for example in parallel, by a pipe (113). A pump (109) creates a pressure making it possible to push the liquid through the modules.

[0095] The hydraulic circuit is provided with one or more desiccant and particulate filters (108) which can be placed before the pump or before the cell assemblies. (20) to protect them.

[0096] The hydraulic circuit comprises an exchanger (110) which allows the liquid (5) to be cooled or heated. This exchanger transfers the heat to a fluid (111) which may be air, glycolated water, a refrigerant fluid, or even a cryogenic fluid for space applications, or a mixture of these different fluids in different circuits. This exchanger (110) may be placed at different locations on the circuit: after the pump and before the cell assemblies (20) preferably in order to reduce the hydraulic pressure in the enclosure (104) of the battery (100).

[0097] The sealed enclosure (104) acts as an expansion vessel allowing thermal expansion of the liquid because it contains either a gas, for example air, or a deformable membrane.

[0098] The hydraulic circuit also includes a safety valve (105) to prevent pressure build-up in the circuit in the event of failure due to gas emission from the battery. This valve is placed on the sealed enclosure (104).

[0099] A filling device (114) and a purging device (115) are also placed on the enclosure. The filling device (114) may be in the form of a plug. This plug may contain an air purging system, for example a float, or contain a simple pressure equalization hole equipped or not with a particle filter and desiccant.

[0100] Detailed description of a prismatic cell battery module f 10)

[0101] Prismatic cells are blocks. Their outer casing is made of aluminum, as opposed to pouch cells. In this section, the figures illustrate a prismatic cell battery module.

[0102] In [Fig.6], the module (10) is composed of a housing (12) made of welded or extruded aluminum. A front face (11) and a rear face (17) close the housing (12). On the front face (11) are fixed sealed electrical power (13) and communication (16) connectors. Hydraulic inlet (14) and outlet (15) ports for liquid (5) are arranged respectively at the bottom and top in the front face. On the rear face, only the safety valve (18) is positioned.

[0103] In [Fig.7], an exploded view of the module (10) is presented. It shows the assembly of cells (20) having mechanical fixing means (78 and 79) on the front face (11) and on the support plate (19) which has holes (80) allowing guidance and stopping in translation in the plane normal to the rods (79). The prismatic cells are arranged vertically, their large faces facing each other in vertical planes.

[0104] An electronic circuit (34) allowing the measurement of cell voltages and temperature measurement is integrated in the module (10). An electrically insulating cover (35) prevents electrical contact between the cell assembly (20) and the enclosure (12). A bucket-shaped hydraulic conduit (22) collects the liquid near the upper internal face of the enclosure (12) to guide it towards the outlet port (15) so as to collect the gas bubbles and limit the height of any gaseous cloud in the module. The inlet of the valve (18) on the rear face (17) has a horizontally oblong shape so as to define the highest possible liquid level (5) in the module (10) when it is open.

[0105] In [Fig.8], an exploded view of the cell assembly (20) is shown. There finds a set of cells (29). Front (26) and rear (27) plates allow a compressive force to be applied to the set of cells (29). This force is maintained by steel strips (28) constituting a strapping of the set of cells.

[0106] Between each cell, spacers (24) are inserted to clear a path for the flow of the liquid (5), as well as a compressible thermal insulator (25) to prevent the propagation of combustion from one cell to another in the event of thermal runaway and allowing the inflation of the prismatic cells (29). The set of cells (29) is raised by shims (23) which free a space for the circulation of the liquid (5) under the module (10). The liquid (5) is guided from the hydraulic inlet connector (14) by a hydraulic conduit (21) which establishes a low-speed flow of liquid (5) under the set of cells (29).

[0107] On top of the cells is placed an electrically insulating support (30) which positions the bus bars (31) welded to the terminals of the cells (29). A flexible electronic circuit (33) is welded to the bus bars and mechanically fixed to the support (30). This circuit (33) allows the voltage and temperature readings read by the electronic card (34). A last bus bar (32) is riveted, welded or screwed in order to make the electrical connection between the two rows of cells.

[0108] Figures 9 and 10 show the inter-cell arrangement that allows the cooling of the large faces of the prismatic cells (70). Two spacers (71) delimit passages (74) for the liquid (5). Between the spacers, a thermal and electrical insulator (72) prevents the cells (70) from touching each other if they swell and also prevents the heat from one cell from being transferred mainly to the adjacent cell in the event of thermal runaway. This insulator (72) can be made of plastic, fiberglass, cork, or any other material compatible with the liquid, which retains these thermal and mechanical properties once immersed, which resists temperatures above 200°C and which has a thermal conductivity preferably less than 0.4 W / m / K. Its thickness is typically less than 3 mm.The spacer (71) has a thickness equivalent to the normal swelling of a cell, typically 7 to 8% of the thickness of the cell having a Lithium ion NMC type electrochemistry.

[0109] A spacer (71) is formed by a frame made of electrically insulating material, typically a plastic (eg. PA6) on which the cell rests and which absorbs the compressive force applied to the set of cells (29). The spacer allows the liquid (5) to communicate from the lower volume (73) to the upper volume (75). A pressure loss device is formed by calibrated slots (76) forming the inlet of the spacer (71). The hydraulic outlet of the spacer (71) is formed by wider slots (77) generating significantly less pressure loss than at the inlet (76) so as to promote a natural convection effect in the event of failure of the pump (109) or absence of supply of dielectric liquid (5). This effect is particularly sought during thermal runaway to distribute the heat generated by the combustion of a cell over the entire module and not only over adjacent cells.

[0110] Alternatively, a single spacer (71) can be positioned between the cells, without the presence of the insulator (72). Its thickness is then equivalent to 7 to 15% of the thickness of the cell having a Lithium ion NMC type electrochemistry. [YES] In [Fig. 11], spacer variants (71) show reinforcements (81) to absorb the compressive force applied to the cell assembly (29) on the large faces thereof in addition to the spacer frame. This allows the internal stresses to be distributed as well as possible within the cells while allowing the circulation of the liquid (5). The range of internal stresses acceptable to the cells is typically less than IMPa and greater than 0.001MPa. These spacers can be compressible in their thickness to accommodate the natural swelling of the cells using a compressible material while keeping the internal stresses within the desired range. In addition, in the event of thermal runaway of a cell, the reinforcements (81) prevent direct thermal contact between the burning cell and the adjacent cell.

[0112] In [Fig. 12], the compression holding device is isolated from the cell assembly (20). Two front (26) and rear (27) plates apply a uniform force to all surfaces. This force is maintained by a set of steel strips (28) which form a ring around the cell assembly (29). Mechanical fixing means allow anchoring on the front plate (26) by means of the bracket screw (78) in the front face (11) and a sliding connection in the support plate (19) formed by the rods (79) of the rear plate (27) which slide during assembly in the holes (80).

[0113] Detailed description of a module (10) with cylindrical cells

[0114] Cylindrical cells are cylinders with an aluminum shell.

[0115] In Figures 13 and 14, the module (10) is composed of a tank (41) and a cover (42) forming a liquid-tight enclosure (5). These parts are made of aluminum or composite material. The front face of the tank (41) has sealed electrical power (44) and communication (45) connectors as well as hydraulic inlet (46) ports at the bottom and outlet (47) ports at the top. A mechanical reinforcement (43) prevents the cover from deforming under the effect of vibrations or internal pressure. The rear face of the tank (41) has a safety valve (48) allowing the evacuation of gas or liquid (5) in the event of excessive internal pressure.

[0116] [Fig. 15] shows an exploded view of the module (10) with cylindrical cells. An as cell assembly (20) is contained in the tray (41) and the cover (42). Bus bars (51 and 52) electrically connect the cell assembly to the power electrical connectors (44). An electronic circuit (34) is integrated into the module. It communicates via the communication electrical connector (45) and is connected to the cell assembly (20). A bucket-shaped hydraulic conduit (50) collects the hot liquid (5) near the inner upper face of the module (10) and guides it to the outlet hydraulic connector (47). Holding rods (56) allow the mechanical fixing of the cell assembly (20) in the tray (41).

[0117] [Fig. 16] shows an exploded view of the cell assembly (20) and Figures 17 and 18 illustrate the liquid flows (5) in the module (10) and the details of the cell assembly (20) allowing the circulation of the liquid (5). It is composed of a set of cylindrical cells (59) enclosed in a cell support formed by two shells (57 and 58) whose joint is made watertight by a flat gasket (60). Bus bars (62 and 61) are welded to each end as well as a flexible electronic circuit (63 and 64) welded to the bus bars to take the voltage of the cells and having brazed thermistors to measure the temperatures. Two insulating plates (53 and 54) close the cell support by defining lower (65) and upper (66) volumes in which the liquid (5) circulates. A hydraulic conduit (49) supplies liquid to the lower volume (65).A pressure drop device is formed by orifices (67) present in the shells (57 and 58) which allow the liquid (5) to pass through and generate a pressure drop allowing the uniform distribution of the liquid over all the cells. These orifices (67) have a typical diameter between 0.5mm and 2mm. Holes are provided in the bus bars (62 and 61) to allow the liquid (5) to pass through. Each cell is surrounded by several orifices, between 3 and 6, totaling a surface area between 1mm2 and 12mm2.

[0118] Detailed description of a modular battery integrated into a vehicle

[0119] [Fig. 19] shows a battery divided into 9 modules (10) electrically connected in series to a junction box (102) by bus bars as well as by an electrical communication harness which transfers the information measured by the electronic cards (34) according to a CAN protocol. The modules and the junction box are immersion cooled and connected to a hydraulic circuit (113). This battery is presented in a flat frame (117) formed of hollow aluminum tubes manufactured by extrusion and aluminum profiles formed by molding.

[0120] The valves (18) of each of the modules are connected to the frame (117) composed of hollow tubes. In the event of thermal runaway, the gases generated by the combustion of the cells (an example of a position is represented by a black star in the figure) are channeled inside the hollow tubes of the frame (117) then directed towards a single outlet (118) (as illustrated by the black arrows in the figure) to be expelled from the battery without propagating in it. At this outlet, a temperature and pressure sensor (119) can be positioned in order to detect the triggering of the battery fire. The use of the aluminum tubes of the frame makes it possible to avoid the use of an additional pipe and to increase the compactness of the battery. Any cross members of the frame can also be used.

[0121] Detailed description of a sachet cell battery module (10)

[0122] Pouch cells are cobblestone-shaped cells whose outer envelope is made of plastic film (we then speak of “pouch” cells according to the English term).

[0123] In [Fig.20], the module (10) is composed of a housing (212) made of welded or extruded aluminum. A front face (211) and a rear face (217) close the housing (212). On the front face (211) are fixed sealed electrical power (213) and communication (216) connectors. Hydraulic inlet (214) and outlet (215) ports for dielectric liquid (5) are arranged respectively at the bottom and top in the front face. On the rear face, only the safety valve (218) is positioned.

[0124] In [Fig.21], an exploded view of the module (10) is shown. It shows the assembly of cells (220). The prismatic cells are arranged vertically, their large faces facing each other in vertical planes. The inlet of the valve (218) on the rear face (217) is served by a bucket-shaped hydraulic conduit (222) so as to define the highest possible liquid level (5) in the module (10) when said valve (218) is open.

[0125] In [Fig.22], an exploded view of the cell assembly (220) is shown. It shows a set of cells (229). Front (226) and rear plates allow a compressive force to be applied to the set of cells (229). This force is maintained by metal strips (228) constituting a strapping of the set of cells.

[0126] Between each cell (229), spacers (224) are inserted alternately to clear a path for the flow of the dielectric liquid (5), or a compressible thermal insulating foam (225) allowing the cells to swell and preventing the propagation of combustion from one cell to another in the event of thermal runaway. The spacers (224) and the compressible insulating foam (225) prevent thermal contact between the cells in the event of thermal runaway and thus limit its propagation. The cell assembly (229) is contained in a cell support (223) which defines a space for circulation of the dielectric liquid (5) below and above the cells (229). The dielectric liquid (5) is guided from the inlet hydraulic connector (214) by a hydraulic conduit which establishes a low-speed liquid flow (5) under the cell assembly (29). Then it passes through a pressure drop device (267), illustrated in [Fig.23], consisting of holes arranged so as to balance the liquid flow rates between the different spacers (224) and along the length of a single spacer. The dielectric liquid (5) passes through the cell assembly (229). It is collected by the cell support (223) at the top of the module without section restriction in order to promote natural convection, and is guided towards the outlet hydraulic connector (215).

[0127] [Fig.24] shows the flows of dielectric liquid (5), represented by the arrows, through a spacer (224), in the module (10) manufactured from sachet cells (229). The cell support (223) defines a lower volume (230) and an upper volume (231).

[0128] In Figures 25, a spacer variant is illustrated. It is a corrugated metal sheet forming a grid (224), for example of the type used as turbulators in certain plate exchangers. Because it is made by folding and cutting sheet metal strips, this type of grid (224) is economical to produce and has an offset crenellation pattern that is favorable in several respects:

[0129] - it has a lattice for fluid circulation

[0130] - it has a substantially flat surface, non-aggressive with respect to the face of the cells with which it is put in contact

[0131] - the grid comprising this type of pattern has a cumulative contact surface homogeneous and extensive, typically greater than 30%, and ideally greater than 50% of the surface area of ​​the large face of the cells, allowing the compression forces due to the manufacture of the cell assembly to be absorbed without causing localized stresses

[0132] - in the event of thermal runaway of a cell, the offset slot pattern allows to mobilize by natural convection all the dielectric liquid present between the cells (compared to only a fraction of the liquid in the case of a continuous corrugated sheet for example).

[0133] The arrow shows the direction of circulation of the dielectric liquid (5) through this grid (224). This grid (224) allows the compression forces due to the manufacture of the cell assembly and due to the swelling of the cells (229) to be absorbed while allowing the liquid (5) to pass through.

[0134] In [Fig.26], a grid variant (224) is shown in cross-section. between the large faces (232) of two cells (229) and capable of conforming to these same curved faces (233) when the cells are inflated. This grid (224) can have, by its sheet thickness and an adapted profile of its folding pattern, a compressibility rate which makes it possible to conform to the shape of the inflated cells and not to exceed a threshold value of compression force on the cells (229) by controlling it over a range of internal stresses of said cells between 0.001MPa and IMPa. A folding profile adapted to this function is for example a 'dovetail' profile shown [Fig.26], where at least one of the legs of the profile has an acute angle with respect to its base (as distinguished from trapezoidal profiles whose legs have an obtuse angle with respect to their base).

[0135] The acute angle between the leg and its base improves the profile's ability to be compressed, and thereby allows the spacer to be shaped in contact with the cell when the latter swells. Typically, the desired flexibility must be greater than 1mm per MPa. The thickness of the sheet metal used to produce the grid (224) is advantageously less than 0.2mm, ideally less than 0.1mm. The material of the sheet metal is preferably stainless steel, for its temperature resistance and its relatively low thermal conductivity, capable of limiting the conduction heat flow to the adjacent cells in the event of thermal runaway.

Claims

Claims

1. Electric battery module (10) comprising a housing (2, 12) in which a plurality of cells (1, 29, 59, 70, 229) are arranged in direct heat exchange with a dielectric coolant (5) circulating between interstices formed between said adjacent cells (1, 29, 59, 70, 229), characterized in that said housing (2, 12) has: • an intermediate volume (150) in which said adjacent cells (1, 29, 59, 70, 229) are arranged and between which said dielectric liquid (5) flows, • a lower volume (65, 73, 130, 230) located below said intermediate volume (150), and supplied by at least one inlet port (3, 14, 46) of dielectric liquid (5), • an upper volume (66, 75, 140, 231), located above said intermediate volume (150), and opening towards the outside of said housing by at least one outlet port (4, 15, 47) of dielectric liquid (5),said module further comprising a device (6, 67, 76, 267) creating a pressure drop greater than the other pressure drops experienced by the liquid when passing through the module (10) between the zone(s) closest to said at least one dielectric liquid (5) inlet port (3), and the opposite zone(s) of said lower volume (65, 73, 130, 230); said pressure drop device (6, 67, 76, 267) being arranged between said lower volume (65, 73, 130, 230) and said intermediate volume (150).,

2. Electric battery module (10) according to the preceding claim, characterized in that said load loss device (6) is constituted by a perforated wall.

3. Electric battery module (10) according to claim 1 characterized in that said pressure drop device (6) is composed of an assembly of parts sealed between them and having calibrated orifices, or slots, allowing the coolant to pass through, creating locally, a dissipation, by friction, of the mechanical energy of the coolant passing through the device, and a pressure drop varying according to the distance from the inlet port (3) coolant.

4. Electric battery module (10) according to claim 1 characterized in that the pressure drop between said intermediate volume (150) and said upper volume (66, 75, 140, 231) is substantially lower than between said lower volume (65, 73, 130, 230) and said intermediate volume (150) so as to promote natural convection in the event of an absence of supply of dielectric liquid (5) through said at least one inlet port (3, 14, 46)

5. Electric battery module (10) according to one of the preceding claims, characterized in that said pressure loss device (6, 67, 76, 267) is made up of orifices between 0.3mm2 and 2.3mm2 in section each.

6. Electric battery module (10) according to one of the preceding claims, characterized in that said cells (1, 29, 70, 229) are of the prismatic or sachet type and are arranged vertically in said intermediate volume (150).

7. Electric battery module (10) according to claim 6 characterized in that spacers (24, 71, 224) are interposed between two adjacent cells (1, 29, 70, 229).

8. Electric battery module (10) according to claim 7 characterized in that said spacers (24, 71, 224) form a lattice for absorbing the compression force applied to the set of cells (1, 29, 70, 229) on the large faces thereof.

9. Electric battery module (10) according to claim 7 or 8 characterized in that said spacers (24, 71, 224) have a flexibility in their thickness greater than 1 mm per MPa.

10. Electric battery module (10) according to claim 7, 8 or 9 characterized in that said spacers (24, 71, 224) have meshes less than 30% of the length of said cells (1, 29, 70, 229).

11. Electric battery module (10) according to claim 7, 8, 9 or 10 characterized in that said spacers (24, 71, 224): • are formed by a cut electrical insulating frame with a thickness of between 7 and 15% of the thickness of the cells (1, 29, 70, 229), • have lower slots (76) allowing a loss of charge, • have upper slots (77) substantially wider than said lower slots, • have reinforcements (81) configured to avoid direct thermal contact between cells, • are made of compressible material having a flexibility greater than 1 mm per MPa, • and have a window (74) for circulation of the liquid (5) from a lower volume (73, 130, 230) to an upper volume (75, 140, 231).

12. Electric battery module (10) according to claim 7, 8, 9 or 10 characterized in that said spacers (24, 71, 224) are grids obtained by folding-cutting according to a pattern with offset crenellations, from a metal sheet with a thickness of less than 0.2 mm.

13. Electric battery module (10) according to claim 7, 8, 9, 10 or 11 characterized in that said spacers (24, 71, 224): • are formed by a grid (224) with a thickness between 7 and 15% of the thickness of the cells (1, 29 70, 229) • have a contact surface with the cells greater than 30% of the surface of the large face of said cells • allow the circulation of the liquid (5) from a lower volume (73, 130, 230) to a higher volume (75, 140, 231)

14. Electric battery module (10) according to the preceding claim, characterized in that said spacers (24, 71, 224): • have a contact surface with the cells greater than 50% of the surface of the large face of said cells, • have a 'dovetail' folding pattern giving the grid (224) a compressibility allowing it to conform to the swelling of said cells (1, 29 70, 229), • are formed from a stainless steel sheet with a thickness of less than 0.1 mm.

15. Electric battery module (10) according to claim 1 or 2 characterized in that said cells (1, 59) are cylindrical in shape and are arranged vertically in said intermediate volume (150).

16. Electric battery module (10) according to the preceding claim, characterized in that said pressure loss device (6, 67) consists of orifices distributed around the periphery of each of said cylindrical cells, in each of the two shells (57 and 58) of the cell support and represents between 1mm2 and 12mm2 around each of said cylindrical cells.

17. Electric battery module (10) according to claim 1 characterized in that an internal hydraulic conduit (22, 50) in the form of a bucket collects the dielectric liquid (5) from the upper volume (66, 75, 140, 231) near the upper internal face of the enclosure (12, 42) to guide it towards the outlet port (4, 15, 47).

18. Electric battery module (10) according to claim 1 characterized in that an internal conduit (222) in the form of a bucket collects the gases emitted in the event of thermal runaway in the upper volume (66, 75, 140, 231) near the upper internal face of the enclosure (12, 42, 212) to guide them towards the safety valve (18, 48, 218), so as to define a level of dielectric liquid (5) in the upper volume (66, 75, 140, 231) as high as possible in the module (10) when said valve is open.

19. Electric battery characterized in that it comprises a plurality of battery modules (10) having the characteristics in claim 1 and in that they are sealed, said modules each having a safety valve (18) connected to a hollow tube of the chassis (117) so that the gases emitted during thermal runaway are directed inside said chassis and expelled from said battery without propagating therein.

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