Battery module having at least one battery and phase change metal powder for limiting the propagation of

Abstract

The present invention relates to a battery module having at least one battery and a phase change metal powder that limits the propagation of thermal runaway and the associated pressure rise. The invention relates to a battery module (M) comprising at least one phase change metal powder (10) placed in at least one region for the passage of the hot gas released by one of the batteries during thermal runaway, said powder being adapted to take place a phase change in said region, thereby limiting the thermal convection of the released hot gas.

Description

Field of the Invention

[0001] The present invention relates to the field of electrochemical accumulators, and more particularly to metal ion accumulators.

[0002] More specifically, the present invention relates to a multilayer film for a busbar applied in a battery module.

[0003] Herein, it is recalled that a busbar is a strip (foil) or bar of conductive material, which strip (foil) or bar is optionally laminated with one or more electrically insulating materials, and which strip (foil) or bar is attached to, preferably screwed or welded to, the output terminals of at least one electrochemical accumulator to ensure an electrical connection with another electrochemical accumulator or another electrical input / output element of the battery pack.

[0004] The main object of the present invention is to optimize the cooling of the accumulators in a battery pack such that the thermal runaway energy of a given accumulator in the battery pack does not spread to other accumulators.

[0005] Although described with reference to lithium-ion accumulators, the present invention is applicable to any metal ion electrochemical accumulator, i.e., also applicable to sodium ion accumulators, magnesium ion accumulators, aluminum ion accumulators, etc., or more generally, to any electrochemical accumulator.

[0006] The battery pack according to the present invention can be airborne or stationary. For example, in the context of the present invention, the fields of electric and hybrid transportation and grid-connected storage systems can be envisaged. Background Art

[0007] As Figure 1 and Figure 2 Schematically shown, a lithium-ion battery or accumulator generally includes at least one electrochemical cell unit composed of an electrolyte component 1 between a positive electrode or anode 2 and a negative electrode or cathode 3, a current collector 4 connected to the positive electrode 2, a current collector 5 connected to the negative electrode 3, and finally a packaging 6, which packaging 6 is arranged to hermetically accommodate the electrochemical cell unit while being penetrated by a part of the current collector 4 and the current collector 5.

[0008] Conventional lithium-ion battery structures include a negative electrode, a positive electrode, and an electrolyte. Several types of conventional structural geometries are known:

[0009] - A cylindrical geometry as disclosed in patent application US2006 / 0121348,

[0010] - A prismatic geometry as disclosed in patents US 7348098 and US 7338733,

[0011] -The stacked geometric configurations disclosed in patent applications US2008 / 060189 and US2008 / 0057392 and patent US 7335448.

[0012] The electrolyte component 1 can be in solid, liquid or gel form. In the latter form, the component can include a separator made of a polymer, ceramic or microporous composite material, which is soaked with an electrolyte of the organic electrolyte or ionic liquid type, which allows lithium ions to move from the positive electrode to the negative electrode during charging and vice versa from the negative electrode to the positive electrode during discharging, thus generating an electric current. The electrolyte is usually a mixture of an organic solvent (such as carbonate) added with a lithium salt (usually LiPF 6 ).

[0013] The positive electrode or cathode 2 is composed of a lithium cation insertion material, which is usually a composite material, such as LiFePO 4 , LiCoO 2 or LiNi 0.33 Mn 0.33 Co 0.33 O 2 .

[0014] The negative electrode or anode 3 is usually composed of graphite carbon or Li 4 TiO 5 O 12 (titanate material), and can also optionally form a composite material based on silicon or silicon-based.

[0015] The current collector 4 connected to the positive electrode is usually made of aluminum.

[0016] The current collector 5 connected to the negative electrode is usually made of copper, copper treated with nickel or aluminum.

[0017] Obviously, a lithium-ion battery or accumulator can include a plurality of electrochemical battery cells stacked on top of each other.

[0018] Conventionally, a lithium-ion battery or accumulator uses two materials at the negative and positive electrodes to allow it to operate at a high voltage level usually equal to 3.6 volts.

[0019] Depending on the type of target application, the aim is to produce a thin flexible lithium-ion accumulator or a rigid accumulator: thus the packaging is flexible or rigid, and in the latter case the packaging constitutes a housing.

[0020] Flexible packaging is usually made of a multi-layer composite material, which consists of a stack of aluminum layers covered with one or more polymer films laminated by an adhesive.

[0021] Regarding rigid packaging, it is used in situations where the intended applications are restricted, such situations seeking a long service life, for example, to withstand higher pressures and require a more stringent level of sealing, usually less than 10 -8 mbar·L / s, or for a media environment with highly restrictive limitations, such as in the aviation or space fields.

[0022] Thus, hitherto, the rigid packaging used has been formed by a metal casing, which is typically made of stainless steel (316L stainless steel or 304 stainless steel) or aluminum (1050 aluminum or 3003 aluminum) or titanium.

[0023] The geometry of most rigid lithium-ion battery packaging casings is cylindrical because most electrochemical battery cells of accumulators are wound around a cylindrical mandrel into a cylindrical geometry. Prismatic casing shapes have also been produced by winding around a prismatic mandrel or by stacking electrochemical battery cells.

[0024] Patent application FR3004292 describes using the interior of the mandrel as an air knife for cooling the cores of wound battery cells of metal-ion accumulators.

[0025] Figure 3 Shown is a rigid cylindrical casing typically manufactured for high-capacity lithium-ion accumulators.

[0026] Figure 4 Also shown in is a rigid prismatic casing.

[0027] The casing 6 includes a cylindrical side enclosure 7, a bottom 8 at one end, and a lid 9 at the other end, with the bottom 8 and the lid 9 joined to the enclosure 7. The lid 9 supports the current output poles or terminals 4, 5. One output terminal (pole), such as the negative terminal 5, is welded to the lid 9, while the other output terminal, such as the positive terminal 4, passes through the lid 9, and a seal (not shown) is inserted between the positive terminal 4 and the lid 9, which electrically insulates the positive terminal 4 from the lid.

[0028] This widely manufactured rigid casing is also composed of a deep-drawn cup and a lid, which are welded together around their perimeters. On the other hand, the current collector includes a feedthrough, a part of which protrudes from the top of the casing to form a terminal also known as the visible pole of the battery.

[0029] The battery pack P is formed by a variable number of accumulators, up to several thousand, which are usually electrically connected in series or in parallel with each other through connecting bars (usually called busbars).

[0030] An example of the battery pack P is as Figure 5As shown. The battery pack is composed of two identical lithium-ion battery modules M1 and M2 connected in series. Each module M1 and M2 is composed of four rows of batteries connected in parallel, and each row consists of the same number of six lithium-ion batteries.

[0031] As shown in the figure, the mechanical and electrical connection between two lithium-ion batteries in the same row is achieved by screwing onto the bus bar B1, which is advantageously made of copper. Each bus bar connects the positive terminal 4 to the negative terminal 5. The connection between two parallel rows of batteries within the same module M1 or M2 is provided by the bus bar B2, which is also advantageously made of copper. The connection between the two modules M1 and M2 is provided by the bus bar B3, which is also advantageously made of copper.

[0032] During the development and manufacturing process of lithium-ion batteries, for each form factor / new application, regardless of the market participants involved, precise dimensions (electrical, mechanical, thermal architecture, etc. in series / parallel) are required to optimize the design of a safe and efficient battery pack.

[0033] In particular, the safety of lithium-ion batteries must be considered from the perspective of individual batteries, modules, and the battery pack.

[0034] Various passivators or activators with safety functions can also be incorporated into the battery cells (batteries) and / or modules and / or battery packs to prevent problems when the battery is subjected to "abusive" operating conditions.

[0035] Whether at the battery cell (battery), module, or battery pack level, lithium electrochemical systems generate exothermic reactions, which are independent of the given cycle characteristics. Therefore, at the level of individual batteries, the optimal operation of lithium-ion batteries is limited to a certain temperature range according to the chemical composition considered.

[0036] Electrochemical batteries must operate within a specified temperature range, usually below 70 °C at the outer surface of their housing. Otherwise, their performance will decline, or they may even be physically damaged to the point of destruction.

[0037] For example, lithium batteries with a lithium iron phosphate chemical composition typically have an operating temperature range between -20 °C and +60 °C. Above 60 °C, the material may undergo significant degradation, reducing the performance of the battery cells. Above the "thermal runaway" temperature (which may be between 70 °C and 110 °C), an exothermic internal chemical reaction will be triggered. When the battery can no longer dissipate sufficient heat, the temperature of the electrochemical battery cell rises to the destruction point, and this phenomenon is usually referred to as "thermal runaway".

[0038] In other words, thermal runaway occurs in a battery cell (accumulator) when the energy released by the exothermic reaction inside the cell exceeds its ability to dissipate this energy to the outside. After such a runaway, gas, explosion and / or fire may occur.

[0039] In addition, keeping the temperature below 70 °C can extend the service life of the accumulator, because the higher the operating temperature of the accumulator, the more its service life will be shortened.

[0040] In addition, some accumulator chemistries require operating temperatures far above room temperature, so it is necessary to regulate their temperature levels by initial preheating of the accumulator or even by permanently maintaining the temperature of the accumulator.

[0041] For reasons of volume compactness, an assembly of X accumulators in series and Y accumulators in parallel has been chosen. As Figure 6 shown, a widely chosen mechanical integration within a module or battery pack of accumulators with a rigid housing 6 having a cylindrical geometry has been made.

[0042] In this integration, the accumulators A1, A2......A42 are arranged parallel to each other, in contact with each other via their housing 6, and staggered to form a matrix extending in the Z direction. The staggered arrangement allows for a high energy density.

[0043] This matrix is generally assembled by gluing the accumulators A1, A2......A42 to each other.

[0044] In the context of a study on operational risk analysis, the inventors emphasize that for a module as Figure 6 shown, one of the most critical risks is an internal short circuit in the accumulator due to a manufacturing defect (failure rate of 10 -7 / h).

[0045] Thus, when such a type of failure is announced, as described above, thermal runaway may occur in the accumulators within the module. After such a runaway in a single accumulator, it may spread to adjacent accumulators within the module.

[0046] Therefore, it is important to implement a mitigation scheme to eliminate the risk of spread in the case of an accidental runaway of the accumulator and also to limit any spread outside the module, in particular by the discharge of flames or incandescent particles.

[0047] However, not all cooling devices existing in the prior art allow for effective mitigation of thermal runaway in the accumulators within a battery pack, i.e., to attenuate the transfer of the energy dissipated by the thermal runaway of an accumulator to other accumulators in the battery pack, thereby preventing other accumulators from also entering a thermal runaway state.

[0048] Patent application WO 2022 / 090575 A1 proposes a multi-layer film which is arranged in a predetermined path of hot gas released under pressure in the case of thermal runaway of a storage battery in a battery module, and its hydrogel layer facing the storage battery allows the spread of thermal runaway from one storage battery to other storage batteries to be restricted. This multi-layer film solution including a hydrogel layer is satisfactory in effectively cooling hot gas and is also optimized in terms of weight and size to maintain the performance of the battery pack. However, in some configurations, it does have the disadvantage of being prone to promoting a pressure rise in the module housing through its phase change.

[0049] Therefore, an improved solution is needed to mitigate thermal runaway of any storage battery in the module or battery pack without increasing pressure.

[0050] In addition, such improvement also needs to be optimized in terms of weight and size to maintain the performance of the module or battery pack.

[0051] The object of the present invention is to at least partly meet this or these requirements. Summary of the Invention

[0052] To this end, an aspect of the present invention relates to a battery module, which includes:

[0053] - A plurality of storage batteries, each storage battery including at least one electrochemical cell unit composed of a positive electrode, a negative electrode, and an electrolyte inserted between the positive electrode and the negative electrode, a housing configured to accommodate the electrochemical cell unit in a sealed manner, and two output terminals protruding from the cover and / or bottom of the housing;

[0054] - Preferably, at least one bus bar attached to one of the output terminals of at least some of the storage batteries to electrically interconnect these storage batteries;

[0055] - At least one phase change metal powder placed in at least one area through which hot gas released by one of the storage batteries during thermal runaway passes, and the powder is suitable for undergoing a phase change in this area, thereby restricting the heat convection of the released hot gas.

[0056] Preferably, at least some of the powder is deposited on the bus bar.

[0057] Preferably, the phase change metal powder material is suitable for undergoing a phase change at a temperature between 150°C and 700°C, preferably between 250°C and 500°C.

[0058] Advantageously, the phase change material of the metal powder is selected from potassium tetrafluoroborate (KBF 4 ), potassium magnesium chloride (KMgCl 3 ), NaKMgCl, KMgZnCl or a mixture thereof.

[0059] The geometry of the accumulator can be cylindrical.

[0060] According to an advantageous embodiment, the module comprises at least one sealing member between the accumulator and the area through which the hot gases released by one of the accumulators during thermal runaway pass.

[0061] According to this embodiment and an advantageous configuration, the module comprises a housing, called a battery housing, for receiving the cylindrical accumulator and a sealing retaining plate as a sealing member, which retains the cylindrical accumulator in the battery housing and maintains the sealing between one of its terminals for series and / or parallel electrical connection, in particular its positive terminal, and the rest of the cylindrical accumulator, and the volume defined between the battery housing and the sealing retaining plate containing the connected terminals is at least partially filled with powder.

[0062] The powder particles can be loose or agglomerated.

[0063] According to an advantageous variant, before insertion, the powder is compacted under pressure or agglomerated with a polymer binder, which is preferably selected from carboxymethyl cellulose (CMC) or polyvinyl acetate (PVAC).

[0064] Advantageously, the thickness of the deposited metal powder is between 10 mm and 50 mm.

[0065] According to an advantageous variant of the embodiment, the metal powder is encapsulated between two encapsulation films or in an encapsulation envelope closed by a film. These encapsulation envelopes and films prevent the powder from flowing over time or from being subjected to any vibrations to which the battery module may be exposed.

[0066] Preferably, one of the two encapsulation films is used for direct application to the busbar.

[0067] In order to allow good gas discharge, one of the encapsulation films is configured to deteriorate when the accumulator vent is opened and the electrolyte is optionally ejected. Thus, advantageously, one and / or the other of the encapsulation films is made of a polymer selected from polyethylene (PE) or polyether.

[0068] The thickness of each encapsulation film preferably does not exceed 50 μm.

[0069] Thus, the present invention mainly consists of a phase change metal powder, which is arranged in the predetermined path of the hot gases released under pressure in the event of thermal runaway of one of the accumulators in the battery module.

[0070] Due to the phase change of the powder, the powder facing the accumulator will limit the effect of thermal convection when the hot gases are released from the accumulator and limit the heat conduction, especially through the busbar, thereby preventing the spread of thermal runaway from one of these accumulators to the others.

[0071] Thus, in the case of thermal runaway of one of the accumulators (which may be denoted as "trigger accumulator"), the local melting of the powder allows a significant limitation of the temperature rise of adjacent accumulators.

[0072] The first function of the powder is to form a real thermal barrier, protecting the other accumulators, i.e., those not in runaway mode, by preventing the hot gases released from the safety vent of the trigger accumulator from heating the other accumulators very strongly.

[0073] The area through which the hot gases released during thermal runaway of one of the accumulators in the module (M) pass is predefined.

[0074] During thermal runaway, the powder advantageously allows the hot gases discharged from the trigger accumulator to be separated from the remaining accumulators by forming a thermal barrier that limits the heat exchange between the discharged gases that have passed through the powder and the accumulators.

[0075] The hot gases can pass through the powder, and then the powder undergoes a phase change.

[0076] At least one of the accumulators, preferably each accumulator, may include at least one safety vent configured to release hot gases under pressure in the case of thermal runaway of the accumulator, and the powder faces the safety vent. Advantageously, this arrangement allows an increase in the amount of hot gases that can pass through the powder during the exhaust process. Advantageously, the powder is arranged as close as possible to the safety vent, or even deposited on the safety vent.

[0077] Preferably, the safety vent is located on one of the output terminals of the accumulator, preferably on the positive output terminal. The discharge of the hot gases can be carried out through the busbar.

[0078] It should be noted here that for the phenomenon of thermal runaway, reference is made to publication [2] and the regulations described therein. The temperatures referred to as "self-heating" and "thermal runaway" in this publication are T1 and T2, respectively.

[0079] In this publication Figure 2 the temperature T1 (usually 70 °C) is the temperature at which the accumulator starts to heat up in adiabatic conditions at a typical rate of 0.02 °C / min without an external source.

[0080] In this publication Figure 2 the temperature T2 (usually 150 °C) is the temperature at which the accumulator starts to heat up in adiabatic conditions at a typical heating rate of 10 °C / min, causing the separator in the electrochemical bundle of the accumulator to melt and short-circuit, resulting in a voltage collapse.

[0081] Thus, in the context of the present invention, the term "thermal runaway" can be understood as the ratio between the derivative of the heating temperature and the derivative of time, being at least equal to 0.02 °C per minute.

[0082] In other words, due to the phase change powder according to the present invention, the thermal runaway energy triggering the accumulator is not fully transferred to the adjacent accumulators in the battery pack, thus limiting the temperature of the adjacent accumulators.

[0083] Therefore, the powder according to the present invention helps to prevent thermal runaway from occurring in the accumulators adjacent to the triggered accumulator.

[0084] Compared to known solutions using liquid water, using the phase change powder according to the present invention is simpler. In particular, throughout the entire process of accumulator runaway, it does not require a fully sealed container. The powder also helps to limit the potential short - circuit risk within the battery module.

[0085] More generally, the phase change powder according to the present invention differs from prior - art solutions in that, due to its phase change, the phase change powder actuates at a higher temperature than commonly used materials and does not generate additional gas. The volume increase associated with the phase change of the powder from solid to liquid is much lower than the volume increase to gas. Therefore, the powder limits the maximum pressure within the module housing, which is not the case for prior - art solutions (such as water).

[0086] The inventors have overcome a technical prejudice because, until now, it was thought that only materials that undergo a phase change at around 100 °C could prevent a triggered accumulator from running away.

[0087] However, by analyzing the type of thermal runaway, the inventors have emphasized that such materials are not really effective against short - circuit faults inside the accumulator.

[0088] This is why the inventors have chosen a powder that undergoes a phase change at a higher temperature to limit the spread and amount of gas released in the battery module housing.

[0089] Overall, the present invention offers many advantages, among which the following can be mentioned:

[0090] - The powder is easier to implement than prior - art solutions because the powder does not require a fully sealed solution throughout the entire process of accumulator runaway;

[0091] - Limits the potential short - circuit risk;

[0092] - Is a safe solution that is easy to implement and effectively prevents the spread of thermal runaway within the module or battery pack;

[0093] - Is a solution that does not compromise the weight of the module or battery pack because the phase change powder according to the present invention can be very light, which is highly advantageous for airborne applications;

[0094] - It is possible to install phase change powder very quickly and easily in a module or battery pack, both during the design phase and as a retrofit to an existing module or battery pack.

[0095] For applications in lithium-ion battery packs, each accumulator is a lithium-ion accumulator, wherein:

[0096] - The material of the negative electrode is selected from the group comprising: graphite, lithium titanate oxide Li 4 TiO 5 O 12 ;

[0097] - The material of the positive electrode is selected from the group comprising: LiFePO 4 、LiCoO 2 and LiNi 0.33 Mn 0.33 Co 0.33 O 2 .

[0098] After reading the detailed description of the embodiments in which the present invention is implemented, other advantages and features of the present invention will become more clearly apparent, and these embodiments are given by way of non-limiting example with reference to the following drawings. Description of the Drawings

[0099] Figure 1 is a schematic exploded perspective view showing various elements of a lithium-ion accumulator.

[0100] Figure 2 is a front view showing a lithium-ion accumulator with a flexible package according to the prior art.

[0101] Figure 3 is a perspective view of a lithium-ion accumulator according to the prior art, having a rigid package consisting of a cylindrical housing.

[0102] Figure 4 is a perspective view of a lithium-ion accumulator according to the prior art, having a rigid package consisting of a prismatic housing.

[0103] Figure 5 is a perspective view of a prior art assembly of lithium-ion accumulators forming a battery pack using busbars.

[0104] Figure 6 is a perspective view of a plurality of pre-assembled lithium-ion accumulators having a cylindrical geometry according to the prior art, which form a matrix for a battery module or battery pack.

[0105] Figure 7It is a side view of a battery module equipped with a bus bar, on which the phase change metal powder according to the present invention is deposited. Detailed Description

[0106] Figures 1 to 6 Different examples of lithium-ion storage batteries, flexible packaging and battery housings, and battery packs according to the prior art are shown. Figures 1 to 6 It has been discussed above, so it will not be further discussed below.

[0107] For clarity, the same reference numerals are used for the same elements according to the prior art and according to the present invention for all Figures 1 to 7 .

[0108] Throughout this patent application, the terms "lower", "upper", "bottom", "top", "below" and "above" should be understood by reference to a vertically arranged lithium-ion battery housing (i.e., the multilayer film according to the present invention is placed horizontally).

[0109] Figure 7 An example of the phase change metal powder 10 according to the present invention deposited on the bus bar B3 of the battery module M of the lithium-ion storage batteries A1, A2, A3, A4 is shown.

[0110] In the example shown, the storage batteries A1 to A4 shown may have a cylindrical housing, typically in the 18650 or 21700 format.

[0111] The storage batteries A1 to A4 are electrically connected in groups via their output terminals through the bus bar B3.

[0112] According to the present invention, the phase change metal powder 10 according to the present invention is directly deposited on the bus bar B3.

[0113] The powder 10 is preferably made of KBF 4 made.

[0114] The powder 10 can be encapsulated between two polymer films.

[0115] The thickness of each encapsulating film is typically about 50 μm.

[0116] The thickness of the powder 10 can be between 10 mm and 50 mm.

[0117] Regarding placing the powder 10 according to the present invention inside the battery module M, this can be done in several forms.

[0118] The first option consists of pouring the powder 10 by gravity flow so that it settles at least on the bus bar B3 of the positive terminal 4.

[0119] The powder can at least partially fill the volume between the walls of the module housing 100 and the holding and sealing plate 11 arranged below the bus bar B3 and the positive terminal 4, as Figure 7 shown.

[0120] The plate 11 holds the batteries A1 to A4 and separates the output terminal 4 from the rest of the batteries in a sealed manner.

[0121] A second option consists in encapsulating the powder 10 between two encapsulation films as described above and placing the encapsulated assembly in direct contact with the bus bar B3.

[0122] A third option consists in agglomerating the powder 10 to form a solid part, in particular by compacting under pressure or by premixing with a polymer binder (such as CMC or PVAC) to form a solid part, and then placing the resulting solid part in direct contact with the bus bar B3.

[0123] During thermal runaway of a battery in 18650 format, approximately 80 kJ of thermal energy is released.

[0124] In general, the energy released is distributed between the ejected gases and molten materials (approximately 70% of the heat) and the energy released by the battery housing due to the materials used to manufacture the battery (the remaining 30% of the heat).

[0125] Therefore, it is important to implement a solution to mitigate heat transfer between the batteries, taking into account heat convection through the gas and conduction through the bus bar.

[0126] As Figure 7 schematically shown, adding the phase change powder 10 to the bus bar B3 (the bus bar B3 is typically connected to the positive terminals 4 of the batteries A1 to A4) allows limiting heat transfer in these two modes. The hot gases from the triggered battery are discharged through its safety vent.

[0127] The safety vent of the battery can be located on its positive terminal 4. The hot gases discharged through the safety vent then pass through the bus bar B3 and then through the phase change metal powder 10.

[0128] The powder 10 then limits conduction through the bus bar B3 and the heat convection effect of the hot gases on the batteries adjacent to the triggered battery.

[0129] To verify the safety of the KBF 4 powder according to the present invention, the inventors conducted a series of tests.

[0130] Each test consisted of placing a 18650 format battery in a tank simulating the battery module housing and then allowing the battery to enter thermal runaway.

[0131] In one test, for comparison, no powder was placed in the can. In another test, a certain amount of KBF according to the present invention was added 4 powder.

[0132] Visually, the inventors found that in the comparative test, large hot flames emerged from the can, while no flames emerged from the can containing KBF 4 powder.

[0133] This aspect, namely that no flames emerge from the module housing in the case of thermal runaway, is very important, especially since new automotive standards will impose additional restrictions on the presence of flames outside the battery pack housing.

[0134] In addition, in both tests, the pressure and temperature inside the can were also measured. Table 1 summarizes the measured results.

[0135] [Table 1]

[0136]

[0137] The results clearly show that the addition of KBF 4 powder reduces both the temperature and the maximum pressure inside the can.

[0138] These results are particularly important because the maximum temperature has a direct impact on the risk of thermal runaway propagation, and the pressure is a value directly used for the mechanical dimensions of the module or battery pack housing.

[0139] Therefore, reducing the maximum pressure by adding KBF 4 powder can lead to mass optimization: adding a small amount of KBF 4 powder can lead to the removal of a relatively large mass from the module housing.

[0140] The present invention is not limited to the examples just described; the features of the shown examples can in particular be combined in variants not shown.

[0141] However, other variants and improvements can be envisaged without departing from the scope of the present invention.

[0142] The above example relating to the positive electrode of the storage battery can also be applied to the bus bar on the negative electrode side.

[0143] In the shown embodiment, the storage battery is cylindrical, for example of the 18650 type, and has a safety vent in the positive terminal of each storage battery. Other battery forms and / or arrangements of safety vents are also possible.

[0144] However, the gas outlet pressure and temperature through the vent are such that the phase change powder according to the present invention is selected so as not to pose a significant obstacle to the discharge of hot gas from the storage battery vent.

[0145] List of cited references:

[0146] [1]https: / / www.mersen.com / sites / default / files / publications-media / 16-markets-tra nsportation-ev-hev-emobility-presentation-mersen.pdf.

[0147] [2]Xuning Fenga et al., "Key Characteristics for Thermal Runaway of Li-ion Batteries", Energy Procedia, 158 (2019) 4684-4689.

Claims

1. A battery module (M), comprising: - a plurality of batteries (A1, A2, ... A8), each comprising at least one electrochemical cell C, a housing (6) arranged to contain the electrochemical cell in a sealed manner, and two output terminals (4, 5) protruding from the cover and / or the bottom of the housing, the electrochemical cell being composed of a positive electrode (2), a negative electrode (3) and an electrolyte interposed between the positive electrode and the negative electrode; - preferably at least one busbar (B1, B2, B3) attached to one of said output terminals (4 or 5) of at least some of the batteries in order to electrically interconnect these batteries; - at least one phase change metal powder (10), the at least one phase change metal powder being placed in at least one zone for passage of hot gases released by one of the batteries during thermal runaway, the powder being suitable for undergoing a phase change in the zone, thereby limiting thermal convection of the released hot gases, the phase change material of the metal powder being suitable for undergoing a phase change at a temperature between 150°C and 700°C, preferably between 250°C and 500°C, the phase change material of the metal powder being selected from potassium borofluoride (KBF4), potassium magnesium chloride (KMgCl3), NaKMgCl, KMgZnCl or a mixture thereof. 2 . The battery module (M) according to claim 1 , at least some of the powder being deposited on the bus bar.

3. The battery module (M) as claimed in claim 1, wherein the storage cells have a cylindrical geometry.

4. The battery module (M) according to any one of the preceding claims, comprising at least one sealing member between the accumulators and the zone for passage of hot gases released by one of the accumulators during thermal runaway.

5. The battery module (M) as described in claim 4 in combination with claim 3 comprises a housing called a battery housing, which accommodates cylindrical batteries and a sealing retaining plate as a sealing component, which retains the cylindrical batteries in the battery housing and ensures the sealing between one of the terminals of the batteries electrically connected in series and / or in parallel, in particular the positive terminal, and the rest of the batteries, and the powder at least partially fills the volume defined between the battery housing and the sealing retaining plate accommodating the connected terminals. 6 . The battery module (M) according to claim 1 , wherein the particles of the powder are loose or agglomerated.

7. Battery module (M) according to claim 6, wherein the powder is compacted under pressure or agglomerated with a polymer binder before insertion, the polymer binder preferably being selected from carboxymethylcellulose (CMC) or polyvinyl acetate (PVAC).

8. The battery module (M) according to any one of the preceding claims, wherein the thickness of the metal powder is between 10 mm and 50 mm.

9. The battery module (M) according to any of the preceding claims, the metal powder being encapsulated between two encapsulation films or in an encapsulation envelope closed by a film. 10 . The battery module (M) according to claim 9 , wherein one and / or the other of the packaging films is made of a polymer selected from polyethylene (PE) or polyether.

11. The battery module (M) according to claim 9 or 10, wherein the thickness of the packaging film does not exceed 50 μm.

12. A battery module (M) as claimed in any one of the preceding claims, each battery being a lithium-ion battery, wherein: - The negative electrode material is selected from the group consisting of graphite, lithium titanate oxide Li4TiO5O 12 ; - The material of the positive electrode is selected from the group consisting of LiFePO4, LiCoO2 and LiNi 0.33 Mn 0.33 Co 0.33 O2.

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