BATTERY MODULE WITH AT LEAST ONE STORAGE CONTAINING A PHASE-CHANGING METAL POWDER TO LIMIT THE SPREAD OF THERMAL RUNAWAY AND THE PRESSURE INCREASE RELATING TO IT

Description

technical field

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

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

[0003] It is recalled here that a busbar is a strip (strip) or bar of electrically conductive material, possibly laminated with one or more electrically insulating materials, which is fixed, preferably screwed or welded, to an output terminal of at least one electrochemical accumulator to ensure the electrical connection with another electrochemical accumulator of a battery pack or other electrical input / output element.

[0004] The invention is mainly aimed at optimizing the cooling of the accumulators in a battery pack such that the energy of a thermal runaway of a given accumulator within the pack cannot propagate to the other accumulators.

[0005] Although described with reference to a Lithium-ion battery, the invention applies to any metal-ion electrochemical battery, i.e. also sodium-ion, Magnesium-ion, Aluminium-ion batteries... or more generally to any electrochemical battery.

[0006] A battery pack according to the invention can be either mobile or stationary. For example, the fields of electric and hybrid transportation and grid-connected energy storage systems can be considered within the scope of the invention. Previous technique

[0007] As schematically illustrated in figures 1 and 2, a lithium-ion battery or accumulator usually comprises at least one electrochemical cell consisting of an electrolyte constituent 1 between a positive electrode or cathode 2 and a negative electrode or anode 3, a current collector 4 connected to the cathode 2, a current collector 5 connected to the anode 3 and finally, a package 6 arranged to contain the electrochemical cell with sealing while being traversed by part of the current collectors 4, 5.

[0008] The architecture of conventional lithium-ion batteries consists of an anode, a cathode, and an electrolyte. Several types of conventional battery architecture geometries are known: a cylindrical geometry as disclosed in patent application US2006 / 0121348, a prismatic geometry as disclosed in patents US 7348098, US 7338733; a stacking geometry as disclosed in patent applications US2008 / 060189, US 2008 / 0057392, and patent US 7335448.

[0009] The electrolyte component 1 can be in solid, liquid, or gel form. In the latter form, the component may include a polymer, ceramic, or microporous composite separator impregnated with organic or ionic liquid electrolyte(s) that allows the movement of lithium ions from the cathode to the anode for charging and vice versa for discharging, thereby generating the current. The electrolyte is generally a mixture of organic solvents, for example, carbonates, to which a lithium salt, typically LiPF6, is added.

[0010] The positive electrode or cathode 2 is made of Lithium cation insertion materials which are generally composite, such as LiFePO4, LiCoO2, LiNi 0.33Mn 0.33Co 0.33O2.

[0011] The negative electrode or anode 3 is very often made of graphite carbon or Li 4 TiO 5 O 12 (titanate material), possibly also made of silicon or silicon-based composite.

[0012] The current collector 4 connected to the positive electrode is usually made of aluminum.

[0013] The current collector 5 connected to the negative electrode is generally made of copper, nickel-plated copper, or aluminum.

[0014] A lithium-ion battery or accumulator can obviously contain a plurality of electrochemical cells that are stacked one on top of the other.

[0015] Traditionally, a Li-ion battery or accumulator uses a pair of materials at the anode and cathode, enabling it to operate at a high voltage level, typically equal to 3.6 Volts.

[0016] Depending on the type of application targeted, the aim is to produce either a thin and flexible lithium-ion battery or a rigid battery: the packaging is then either flexible or rigid and in the latter case constitutes a kind of casing.

[0017] Flexible packaging is usually made from a multi-layered composite material, consisting of a stack of aluminum layers covered by one or more polymer film(s) laminated by bonding.

[0018] Rigid packaging is used when the applications are demanding, requiring a long service life, for example with much higher pressures to withstand and a stricter level of sealing required, typically less than 10⁻⁸ mbar.l / s, or in highly demanding environments such as the aeronautical or space sector.

[0019] Also, to date, rigid packaging used consists of a metal case, typically made of stainless steel (316L or 304 stainless steel) or aluminum (Al 1050 or Al 3003), or even titanium.

[0020] The geometry of most rigid Li-ion battery packaging cases is cylindrical, as most electrochemical cells in batteries are wound in a cylindrical shape around a cylindrical core. Prismatic case shapes have also been achieved by winding around a prismatic core or by stacking electrochemical cells.

[0021] Patent application FR3004292 describes the use of the inside of the mandrel as an air blade to core-cool a wound cell of a metal-ion battery.

[0022] One type of rigid, cylindrical case, usually manufactured for a high-capacity Li-ion battery, is illustrated in figure 3 .

[0023] A rigid, prismatic-shaped case is also shown in figure 4 .

[0024] The housing 6 has a cylindrical side casing 7, a bottom 8 at one end, a cover 9 at the other end, the bottom 8 and the cover 9 being assembled to the casing 7. The cover 9 supports the current output poles or terminals 4, 5. One of the output terminals (poles), for example the negative terminal 5 is soldered to the cover 9 while the other output terminal, for example the positive terminal 4, passes through the cover 9 with the interposition of a seal not shown which electrically isolates the positive terminal 4 from the cover.

[0025] The commonly manufactured rigid casing type also consists of a stamped cup and a lid, welded together around their perimeter. In contrast, current collectors include a feedthrough with a portion protruding from the top of the casing, forming a terminal also known as the exposed battery pole.

[0026] A battery pack P consists of a variable number of accumulators, up to several thousand, which are electrically connected in series or in parallel with each other and generally by connection bars, usually called busbars.

[0027] An example of a P battery pack is shown in figure 5 This pack consists of two identical Li-ion A accumulator modules M1, M2 connected in series, each module M1, M2 consisting of four rows of accumulators connected in parallel, each row consisting of six Li-ion accumulators.

[0028] As shown, the mechanical and electrical connection between two Li-ion batteries in the same row is achieved by screwing on busbars B1, advantageously made of copper, each connecting a positive terminal 4 to a negative terminal 5. The connection between two rows of batteries in parallel within the same module M1 or M2 is ensured by a busbar B2, also advantageously made of copper. The connection between the two modules M1 and M2 is ensured by a busbar B3, also advantageously made of copper.

[0029] In the development and manufacture of lithium-ion batteries, for each profile / new demand, regardless of the market players, precise sizing (series / parallel electrical architectures, mechanical, thermal...) is required to optimally design a high-performance and safe battery pack.

[0030] In particular, the safety of lithium-ion batteries must be taken into consideration both at the level of a single battery, a module and a battery pack.

[0031] Various passive or active devices with a safety function can also be integrated at the level of a cell (accumulator), and / or a module and / or the battery pack to prevent problems when the battery is subjected to conditions of abusive operation.

[0032] A lithium electrochemical system, whether at the cell (battery), module, or pack level, produces exothermic reactions regardless of the cycling profile. Thus, at the scale of a single battery, depending on the chemistries involved, the optimal operation of lithium-ion batteries is limited to a certain temperature range.

[0033] An electrochemical battery must operate within a defined temperature range, typically generally below 70°C on its outer casing surface, otherwise its performance will be degraded, or it may even be physically degraded to the point of destruction.

[0034] Lithium iron-phosphate batteries are a good example, as their operating range is generally between -20°C and +60°C. Above 60°C, the materials can undergo significant degradation, reducing cell performance. Beyond a temperature known as thermal runaway, which can range from 70°C to 110°C, exothermic internal chemical reactions begin. When the battery is no longer able to dissipate sufficient heat, the temperature of the electrochemical cell rises until it is destroyed; this phenomenon is commonly referred to as thermal runaway. "Thermal Runaway").

[0035] In other words, thermal runaway occurs in a cell (accumulator) when the energy released by the exothermic reactions taking place inside it exceeds the capacity to dissipate it to the outside. This runaway can be followed by the generation of gas and an explosion and / or fire.

[0036] Also, maintaining a temperature below 70°C helps to increase the lifespan of a battery, because the higher the operating temperature of a battery, the shorter its lifespan will be.

[0037] In addition, some battery chemistries require an operating temperature well above ambient temperature and therefore it is necessary to regulate their temperature level by initial preheating of the batteries, or even by maintaining a permanent temperature of the batteries.

[0038] For reasons of volumetric compactness, it is chosen to use assemblies of X accumulators in series and Y in parallel; a widely adopted mechanical integration of rigid-cased cylindrical accumulators 6 within a module or battery pack is that illustrated in the figure 6 .

[0039] In this integration, the accumulators A1, A2...A42 are arranged parallel to each other in contact with each other by their casing 6 and in a staggered arrangement forming a matrix which extends along the Z direction. A staggered arrangement allows a high energy density.

[0040] The assembly of this matrix is ​​most often done by gluing the accumulators A1, A2... A42 together.

[0041] As part of a functional risk analysis study, the inventors highlighted that one of the most critical risks for a module such as that of the figure 6, was the internal short circuit of an accumulator, following a manufacturing defect (with a failure rate of 10 -7< / h).

[0042] Thus, when a fault of this type is detected, as mentioned above, thermal runaway of a battery within the module can occur. Following this runaway of an individual battery, it can propagate to adjacent batteries within the module.

[0043] It is therefore important to implement a mitigation solution that eliminates the risk of propagation during the accidental runaway of a battery, and also limits any propagation outside the module, in particular by the expulsion of flame or incandescent particles.

[0044] However, all existing cooling devices according to the prior art do not allow for the actual mitigation of a thermal runaway of an accumulator within a battery pack, that is to say, they do not allow for the attenuation of the transmission of energy dissipated by a thermal runaway of the accumulator to the other accumulators in the pack, in order to prevent them from entering a situation of thermal runaway.

[0045] Patent application WO2022 / 090575 A1 proposed a multilayer film, arranged along the predetermined path of hot gases released under pressure in the event of thermal runaway in one of the cells of a battery module. The aqueous gel layer in this film, positioned opposite the cells, limits the propagation of thermal runaway from one cell to the others. This multilayer film solution, incorporating an aqueous gel layer, is satisfactory because it effectively cools the hot gases and is also optimized in terms of weight and size to maintain the pack's performance. However, it has the drawback of potentially contributing to pressure increases in certain configurations due to its phase change within the module casing.

[0046] Document DE 10 2020 133231 A1 describes a phase-change metallic powder placed in at least one zone intended for the passage of hot gases released by one of the accumulators during a thermal runaway, the powder being adapted to change phase in the zone and thus limit the thermal convection of the hot gases released.

[0047] There is therefore a need to improve thermal runaway mitigation solutions for any accumulator within a module or battery pack, which does not increase pressure.

[0048] In addition, the improvement must also be optimized in terms of weight and size to preserve the performance of the module or battery pack.

[0049] The purpose of the invention is to meet at least part of this need(s). Description of the invention

[0050] To this end, the invention relates, in one of its aspects, to a battery module comprising: a plurality of accumulators each comprising at least one electrochemical cell formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode, a case arranged to contain the electrochemical cell with a seal and two output terminals protruding from the cover and / or the bottom of the case; preferably at least one busbar fixed to one of the output terminals of at least some of the accumulators, in order to connect them electrically together; at least one phase-change metallic powder, placed in at least one area intended for the passage of hot gases released by one of the accumulators during a thermal runaway, the powder being adapted to change phase in the area and thus limit the thermal convection of the hot gases released.

[0051] Preferably at least some of the powder should be deposited on the busbar.

[0052] According to the invention, the phase-change metal powder material is adapted to change phase at a temperature between 150 and 700°C, preferably between 250 and 500°C.

[0053] According to the invention, the phase-change metal powder material is chosen from potassium fluoroborate (KBF4), potassium magnesium chloride (KMgCl3), NaKMgCl, KMgZnCl or a mixture thereof.

[0054] Batteries can have a cylindrical geometry.

[0055] According to an advantageous embodiment, the module includes at least one means of sealing between the accumulators and the area intended for the passage of hot gases released by one of the accumulators during a thermal runaway.

[0056] According to this method and an advantageous configuration, the module includes a housing called a battery housing containing the cylindrical accumulators and a sealed retaining plate, as a means of sealing, which holds the cylindrical accumulators in the battery housing and the seal between one of their terminals, in particular their positive terminals, electrically connected in series and / or in parallel and the rest of the cylindrical accumulators, the powder filling at least in part the delimited volume between the battery housing and the sealed retaining plate which contains the connected terminals.

[0057] The powder grains can be loose or agglomerated.

[0058] According to an advantageous variant, the powder is, prior to its placement, compacted under pressure or agglomerated by a polymer binder, preferably chosen from carboxymethylcellulose (CMC) or polyvinyl acetate (PVAC).

[0059] Advantageously, the thickness of the deposited metal powder is between 10 and 50mm.

[0060] In an advantageous embodiment, the metal powder is encapsulated between two encapsulation films or in an encapsulation envelope sealed by a film. These envelopes and encapsulation films prevent the powder from leaking out over time or due to vibrations that the battery module may experience.

[0061] Preferably, one of the two encapsulation films is intended to be applied directly against the busbar.

[0062] To allow for proper gas venting, an encapsulation film is designed to deteriorate upon opening an accumulator vent and the eventual ejection of electrolyte. Advantageously, one or both of the encapsulation films are made of a polymer selected from polyethylene (PE) or polyether.

[0063] The thickness of each encapsulation film is preferably at most equal to 50µm.

[0064] Thus, the invention essentially consists of a phase-change metallic powder, arranged on the previously determined path of hot gases released under pressure in the event of thermal runaway of one of the accumulators of a battery module.

[0065] The powder in relation to the accumulators will limit, by its phase change, the effect of thermal convection when incandescent gases are released from an accumulator and by thermal conduction, notably through a busbar, and thus prevent the propagation of a thermal runaway from one of them to the others.

[0066] Thus, during the thermal runaway of one of the accumulators, which can be designated as the "trigger accumulator", the local melting of the powder will greatly limit the temperature increase of the neighboring accumulators.

[0067] The primary function of the powder is to form a true thermal protection barrier for the other batteries, i.e. those that are not in runaway mode, by preventing the hot gases released by the safety vent(s) of the trigger battery from heating the other batteries very strongly.

[0068] The area(s) of passage of the hot gases released during a thermal runaway of one of the accumulators of the module (M), is / are determined beforehand.

[0069] During a thermal runaway, the powder can advantageously separate the hot gases released from the trigger accumulator from the rest of the accumulators by forming a thermal barrier limiting the heat exchange between the vent gases that have passed through the powder and the accumulators.

[0070] Hot gases can pass through the powder, which then changes phase.

[0071] At least one of the accumulators, preferably each accumulator, may include at least one safety vent configured to release hot gases under pressure during a thermal runaway of said accumulator, with the powder positioned opposite the safety vent. Advantageously, such an arrangement increases the quantity of hot gases that can pass through the powder during degassing. Advantageously, the powder is arranged as close as possible to the safety vent, or even deposited directly onto it.

[0072] Preferably, the safety vent(s) is / are located on one of the accumulator's output terminals, preferably the positive output terminal. Hot gas venting can take place through the busbar.

[0073] It should be noted here that for the phenomenon of thermal runaway, reference should be made to publication [2] and the protocol described therein. The temperatures referred to as "self-heating" and "thermal runaway" are denoted T1 and T2 respectively in this publication.

[0074] The temperature T1, typically 70°C, in the figure 2 of the publication, is the temperature from which the accumulator heats up without an external source at a typical rate of 0.02 °C / min under adiabatic conditions.

[0075] The temperature T2, typically 150°C, in the figure 2 of the publication, is the temperature from which the accumulator heats up at a typical heating rate of 10°C / min under adiabatic conditions, which leads to the melting of the separator in the electrochemical bundle of the accumulator, to a short circuit and therefore to the collapse of the voltage.

[0076] By "thermal runaway", we can thus understand here and within the framework of the invention, a ratio between the value of the derivative of the heating temperature and that of the time at least equal to 0.02°C per min.

[0077] In other words, thanks to the phase-change powder according to the invention, the energy of the thermal runaway of the trigger accumulator is not entirely transmitted to the adjacent accumulators of the pack, thus limiting their temperature.

[0078] Therefore, a powder according to the invention makes it possible to prevent the neighboring accumulators of a trigger accumulator from also going into thermal runaway.

[0079] Compared to a known solution using liquid water, the implementation of a phase-change powder according to the invention is simpler. Indeed, it does not require a perfectly sealed container throughout the entire runaway process of a battery. The powder also helps to limit the potential risk of short circuits within a battery module.

[0080] More generally, the phase-change powder according to the invention differs from prior art solutions by its action at a higher temperature than the materials generally used, due to its phase change, and by the fact that it does not produce additional gas. The volume increase associated with the phase change of the powder from solid to liquid is much less than that of a phase change to a gaseous phase. The powder therefore limits the maximum pressure within a module housing, which is not the case with prior art solutions, such as water.

[0081] The inventors have overcome a technical prejudice because until now it was accepted that only materials with phase change at around 100°C could prevent the runaway of a trigger battery.

[0082] But by analyzing the types of thermal runaway, the inventors highlighted that such materials are not actually effective for internal short-circuit faults in a battery.

[0083] That is why the inventors chose a powder whose phase change occurs at a higher temperature to prioritize limiting propagation and the amount of gas released in a battery module casing.

[0084] Ultimately, the invention offers numerous advantages, including: The implementation of a powder is simpler than state-of-the-art solutions because it does not require perfectly sealed solutions throughout the runaway of a battery; the limitation of potential short-circuit risks; a simple and effective safety solution to prevent the propagation of thermal runaway within a module or battery pack; a solution that does not increase the weight of a module or battery pack, as a phase-change powder according to the invention can be very light, which is very advantageous for embedded applications; the possibility of implementing a phase-change powder very quickly and easily in a module or battery pack, either from its design or as a retrofit to an existing module or battery pack.

[0085] For an application to a Li-ion battery pack, each cell is a Li-ion cell in which: the negative electrode material(s) is chosen from the group including graphite, lithium, titanate oxide Li 4 TiO 5 O 12; the positive electrode material(s) is chosen from the group including LiFePO 4 , LiCoO 2 , LiNi 0.33 Mn 0.33 Co 0.33 O 2 .

[0086] Other advantages and features of the invention will become clearer upon reading the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0087] [ Fig 1 ] there figure 1 is a schematic exploded perspective view showing the different components of a lithium-ion battery. Fig 2 ] there figure 2 This is a front view showing a lithium-ion battery with its state-of-the-art flexible packaging. Fig 3 ] there figure 3This is a perspective view of a state-of-the-art lithium-ion battery with its rigid, cylindrical casing. Fig 4 ] there figure 4 This is a perspective view of a state-of-the-art lithium-ion battery with its rigid packaging consisting of a prismatic-shaped casing. Fig 5 ] there figure 5 This is a perspective view of a state-of-the-art assembly of lithium-ion battery packs using busbars. Fig 6 ] there figure 6 is a perspective view of a plurality of cylindrical lithium-ion accumulators pre-assembled together according to the state of the art, forming a matrix intended for a battery module or battery pack. Fig 7 ] there figure 7 is a side view of a battery module equipped with a busbar on which a phase-change metallic powder according to the invention is deposited. Detailed description

[0088] THE figures 1 to 6 are related to different examples of Li-ion batteries, flexible packaging and battery cases, as well as a state-of-the-art battery pack. figures 1 to 6 have already been commented on in the preamble and are therefore not commented on further below.

[0089] For the sake of clarity, the same references designating the same elements according to the state of the art and according to the invention are used for all the figures 1 to 7 .

[0090] Throughout this application, the terms "lower", "upper", "bottom", "top", "below" and "above" are to be understood by reference to vertically arranged Li-ion battery cases, i.e. with a multilayer film according to the invention horizontally.

[0091] We represented in figure 7, an example of phase change metal powder 10 according to the invention deposited on a busbar B3 of a Li-ion battery module M, A1, A2, A3, A4.

[0092] In the illustrated examples, the A1-A4 batteries shown may have cylindrical cases, typically in 18650 or 21700 format.

[0093] The A1-AA4 accumulators are electrically connected by their output terminal in groups by the busbar B3.

[0094] According to one variant of the invention, a phase-change metal powder 10 according to the invention is deposited directly against the busbar B3.

[0095] Powder 10 is preferably in KBF4.

[0096] Powder 10 can be encapsulated between two polymer films.

[0097] The thickness of each encapsulation film is typically around 50µm.

[0098] The thickness of the powder 10 can be between 10 and 50mm.

[0099] As regards the placement of a powder10 according to the invention within a battery module M, it can be carried out in several forms.

[0100] A first alternative is to pour the powder 10 by gravity flow so that it is deposited at least on the busbar B3 of the positive terminals 4.

[0101] The poured powder can at least partially fill a volume between the wall of the module's housing 100 and a retaining and sealing plate 11, arranged below the busbar B3 and the positive terminals 4, as shown in the figure 7 .

[0102] This plate 11 holds the accumulators A1 to A4 and hermetically seals the output terminals 4 from the rest of the accumulators.

[0103] A second alternative is to encapsulate the powder 10 between two encapsulation films, as indicated above, and to place the encapsulated assembly directly in contact with the busbar B3.

[0104] A third alternative is to agglomerate the powder 10 to make a solid part, in particular by compaction under pressure or by pre-mixing with a polymer binder, of the type CMC or PVAC, and then to position the solid part made directly in contact with the busbar B3.

[0105] During the thermal runaway of an 18650 format battery, approximately 80 kJ of thermal energy can be released.

[0106] Generally, the energy released is shared between the ejected gases and molten materials, which account for about 70% of the heat, and the energy emitted by the battery casing due to the materials used in the battery's construction, which accounts for the remaining 30% of the heat.

[0107] It is therefore important to implement a heat transfer mitigation solution between the accumulators, taking into account thermal convection via the gases as well as conduction through the busbars.

[0108] As shown schematically in figure 7 Adding a phase-change powder 10 to a busbar B3, typically connected to the positive terminals 4 of accumulators A1-A4, limits these two modes of heat transfer. The hot gases from the trigger accumulator are vented through its safety vent.

[0109] The safety vent of the accumulators can be located on their positive terminal 4. The hot gases expelled by the safety vent then pass through the busbar B3 and then through the phase change metal powder 10.

[0110] The powder 10 then limits conduction by the busbar B3 as well as the effect of thermal convection of hot gases on the accumulators adjacent to the trigger accumulator.

[0111] In order to validate the safety of the KBF4 powder according to the invention, the inventors carried out tests.

[0112] Each of the tests consisted of housing 18650 type accumulators in a canister simulating a battery module case and then causing these accumulators to go into thermal runaway.

[0113] In one comparative test, no powder was placed in the canister. In the other test, a quantity of KBF4 powder was added, in accordance with the invention.

[0114] Visually, the inventors observed that large incandescent flames emerged from the canister in the comparative test, whereas no flame emerged from it containing the KBF4 powder.

[0115] This aspect, i.e. that no flame comes out of a module casing, in case of thermal runaway, is very important, especially because new automotive standards will bring additional constraints on the presence of flame outside a battery pack casing.

[0116] In addition, in each of the two tests, the pressure and temperature were also measured inside the canister. Table 1 summarizes the measurements taken. [Table 1] Essay KBF4 Powder-Free Test Test according to the invention, with KBF4 powder Temperature (°C) 1300 600 Pressure (bar) 7,5 3,2

[0117] The results clearly show that adding KBF4 powder reduces both the temperature and the maximum pressure in the canister.

[0118] These results are particularly important because the maximum temperature has a direct impact on the risk of thermal runaway propagation and pressure is a value directly used for the mechanical dimensioning of a module or battery pack housing.

[0119] Thus, the reduction of maximum pressure with the addition of KBF4 powder leads to considering mass optimization: the addition of a small mass of KBF4 powder can lead to the removal of a relatively large mass from a module housing.

[0120] Other variations and improvements can be considered without going outside the scope of the invention.

[0121] The examples given above relating to the positive pole of the batteries are also transferable to the application on a busbar on the negative pole side.

[0122] In the illustrated embodiments, the batteries are cylindrical, for example type 18650, with a safety vent in the positive terminal of each battery. Other battery shapes and / or other arrangements of safety vents are possible.

[0123] The pressures and temperatures at the outlet of the gases through the vents are, however, such that the phase-change powder according to the invention is chosen so as not to represent a significant barrier to the evacuation of incandescent gases from the vents of the accumulators. List of cited references :

[0124] [1] https: / / www.mersen.com / sites / default / files / publications-media / 16-markets-transportation-ev-hev-emobility-presentation-mersen.pdf. [2] Xuning Fenga, et al. “Key Characteristics for Thermal Runaway of Li-ion Batteries” Energy Procedia, 158 (2019) 4684-4689.

Claims

1. Battery module (M) comprising: - a plurality of accumulators (A1, A2...A8) each comprising at least one electrochemical cell C formed of a cathode (2), an anode (3) and an electrolyte interposed between the cathode and the anode, a casing (6) arranged to contain the electrochemical cell in a leaktight manner and two output terminals (4, 5) projecting from the lid and / or bottom of the casing; - preferably at least one busbar (B1, B2, B3) attached to one of the output terminals (4 or 5) of at least some of the accumulators, so as to electrically interconnect them; - at least one phase-change metal powder (10), placed in at least one area intended for the passage of hot gases released by one of the accumulators during thermal runaway, the powder being suitable for changing phase in the area and thus limiting thermal convection of the released hot gases, characterized in that the phase-change metal powder material is suitable for phase change at a temperature of between 150 and 700°C, preferably between 250 and 500°C, and in that the phase-change metal powder material is chosen from potassium fluoroborate (KBF4), magnesium potassium chloride (KMgCl3), NaKMgCl, KMgZnCl or a mixture thereof.

2. Battery module (M) according to Claim 1, at least some of the powder being deposited on the busbar.

3. Battery module (M) according to either of the preceding claims, the accumulators having a cylindrical geometry.

4. Battery module (M) according to one of the preceding claims, comprising at least one leaktightness means between the accumulators and the area intended for the passage of hot gases released by one of the accumulators during thermal runaway.

5. Battery module (M) according to Claim 4 in combination with Claim 3, comprising a casing, known as a battery casing, housing the cylindrical accumulators and a leaktight retaining plate, as a leaktightness means, which holds the cylindrical accumulators in the battery casing and ensures the leaktightness between one of their terminals, notably their positive terminals, electrically connected in series and / or parallel, and the rest of the accumulators, the powder at least partly filling the volume delimited between the battery casing and the leaktight retaining plate containing the connected terminals.

6. Battery module (M) according to one of the preceding claims, the powder grains being loose or agglomerated.

7. Battery module (M) according to Claim 6, the powder, prior to its insertion, being compacted under pressure or agglomerated with a polymeric binder, preferably chosen from carboxymethylcellulose (CMC) or polyvinyl acetate (PVAC) .

8. Battery module (M) according to one of the preceding claims, the thickness of the metal powder being between 10 and 50 mm.

9. Battery module (M) according to one of the preceding claims, the metal powder being encapsulated between two encapsulation films or in an encapsulation envelope closed by a film.

10. Battery module (M) according to Claim 9, one and / or the other of the encapsulation films being made of a polymer chosen from polyethylene (PE) or polyether.

11. Battery module (M) according to Claim 9 or 10, the thickness of an encapsulation film being not more than 50 µm.

12. Battery module (M) according to one of the preceding claims, each accumulator being an Li-ion accumulator in which: - the material of negative electrode(s) is chosen from the group including graphite, lithium, titanate oxide Li4TiO5O12; - the material of positive electrode(s) is chosen from the group including LiFePO4, LiCoO2 and LiNi0.33Mn0.33Co0.33O2.