Battery module with at least one accumulator comprising a phase-change metal powder to limit the propagation of thermal runaway and the associated increase in pressure.

Abstract

Battery module with at least one accumulator comprising a phase-change metal powder to limit the propagation of thermal runaway and the related increase in pressure. The invention relates to a battery module (M) comprising at least one phase-change metal powder (10), placed in at least one zone intended for the passage of hot gases released by one of the accumulators during thermal runaway, the powder being adapted to change phase in the zone and thus limit the thermal convection of the released hot gases. Figure for abstract: fig.7

Description

Title of the invention: Battery module with at least one accumulator comprising a phase-change metal powder to limit the propagation of thermal runaway and the associated increase in pressure. Technical field

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

[0002] More particularly, 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 (foil) or bar made 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 another electrical input / output element.

[0004] The invention aims mainly to optimize the cooling of the accumulators of 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 accumulator, the invention applies to any metal-ion electrochemical accumulator, i.e. also sodium-ion, Magnesium-ion, Aluminum-ion accumulators, etc., or more generally to any electrochemical accumulator.

[0006] A battery pack according to the invention may be on-board or stationary. For example, the fields of electric and hybrid transportation and grid-connected storage systems may be considered within the scope of the invention. Prior Art

[0007] As illustrated schematically 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 packaging 6 arranged to contain the electrochemical cell with sealing while being crossed by a part of the current collectors 4, 5.

[0008] The architecture of conventional lithium-ion batteries comprises an anode, a cathode and an electrolyte. Several types of conventional architectural geometry are known:

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

[0010] - a prismatic geometry as disclosed in US patents 7348098, US 7338733;

[0011] - a stacking geometry as disclosed in the patent applications US2008 / 060189, US 2008 / 0057392, and US patent 7335448.

[0012] The electrolyte component 1 may be in solid, liquid or gel form. In the latter form, the component may comprise a polymer, ceramic or microporous composite separator soaked in organic or ionic liquid electrolyte(s) which allows the movement of the Lithium ion from the cathode to the anode for charging and vice versa for discharging, which generates the current. The electrolyte is generally a mixture of organic solvents, for example carbonates to which a lithium salt, typically LiPF6, is added.

[0013] The positive electrode or cathode 2 is made of Lithium cation insertion materials which are generally composite, such as LiFePO4, LiCoO2, LiNi0.33Mn0.33Co0.33O 2-

[0014] The negative electrode or anode 3 is very often made of graphite carbon or Li4TiO5O12 (titanate material), possibly also based on silicon or a composite formed from silicon.

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

[0016] The current collector 5 connected to the negative electrode is generally made of copper, nickel-plated copper or aluminum.

[0017] A lithium-ion battery or accumulator can obviously comprise a plurality of electrochemical cells which are stacked on top of each other.

[0018] Traditionally, a Li-ion battery or accumulator uses a pair of materials at the anode and the cathode allowing it to operate at a high voltage level, typically equal to 3.6 Volts.

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

[0020] Flexible packaging is usually manufactured from a multi-layer composite material, consisting of a stack of aluminum layers covered by one or more polymer films laminated by bonding.

[0021] Rigid packaging is used when the intended applications are restrictive where a long lifespan is required, for example with much higher pressures to withstand and a stricter level of sealing required, typically less than 10 8mbar.l / s, or in environments with high constraints such as the aeronautical or space sector.

[0022] Also, to date, rigid packaging used consists of a metal case, typically made of stainless steel (316L stainless steel or 304 stainless steel) or aluminum (Al 1050 or Al 3003), or even titanium.

[0023] The geometry of most rigid Li-ion battery packaging cases is cylindrical, because most of the electrochemical cells of the batteries are wound by winding in a cylindrical geometry around a cylindrical mandrel. Prismatic shapes of cases have also already been produced by winding around a prismatic mandrel or by stacking electrochemical cells.

[0024] Patent application FR3004292 describes the use of the interior of the mandrel as an air blade to cool the core of a wound cell of a metal-ion accumulator.

[0025] One of the types of rigid cylindrical shaped case, usually manufactured for a high capacity Li-ion accumulator, is illustrated in [Fig.3].

[0026] A rigid prismatic shaped case is also shown in [Fig.4].

[0027] The housing 6 comprises a cylindrical side casing 7, a base 8 at one end, a cover 9 at the other end, the base 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 welded 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 insulates the positive terminal 4 from the cover.

[0028] The widely manufactured rigid housing type also consists of a stamped cup and a cover, welded together on their periphery. On the other hand, current collectors include a bushing with a portion projecting from the top of the housing and which forms a terminal also called the exposed pole of the battery.

[0029] A battery pack P is made up of a variable number of accumulators which can reach several thousand which are electrically connected in series or in parallel with each other and generally by connection bars, usually called busbars.

[0030] An example of a battery pack P is shown in [Fig.5]. This pack consists of two modules M1, M2 of identical Li-ion accumulators A connected together in series, each module M1, M2 consisting of four rows of accumulators connected in parallel, each row consisting of a number equal to six Li-ion accumulators.

[0031] As shown, the mechanical and electrical connection between two Li-ion accumulators of the same row is made by screwing busbars B1, advantageously in copper, each connecting a positive terminal 4 to a negative terminal 5. The connection between two rows of accumulators in parallel within the same module Ml or M2 is ensured by a busbar B2, also advantageously made of copper. The connection between the two modules Ml, M2 is ensured by a busbar B3, also advantageously made of copper.

[0032] In the development and manufacture of lithium-ion batteries, for each profile / new demand, regardless of the market players, this requires precise sizing (series / parallel electrical architectures, mechanical, thermal, etc.) to optimally design a high-performance and safe battery pack.

[0033] In particular, the safety of lithium-ion accumulators must be taken into consideration both at the scale of a single accumulator, a module and a battery pack.

[0034] Different passive or active devices having 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 finds itself in so-called abusive operating conditions.

[0035] A lithium electrochemical system, whether at the cell (accumulator), module or pack scale, produces exothermic reactions regardless of the given cycling profile. Thus, at the scale of a unit accumulator, depending on the chemistries considered, the optimal operation of lithium-ion accumulators is limited within a certain temperature range.

[0036] An electrochemical accumulator must operate within a defined temperature range, typically generally less than 70°C at its outer casing surface, otherwise its performance will be degraded, or even physically degraded to the point of destruction.

[0037] Examples include lithium iron-phosphate accumulators which have an operating range generally between -20°C and +60°C. Above 60°C, the materials may undergo significant degradation, reducing the performance of the cell. Beyond a so-called thermal runaway temperature which may be between 70°C and 110°C, exothermic internal chemical reactions begin. When the accumulator is no longer able to dissipate sufficient heat, the temperature of the electrochemical cell increases until it is destroyed, this phenomenon usually being referred to as thermal runaway.

[0038] In other words, thermal runaway occurs in a cell (accumulator) when the energy released by the exothermic reactions occurring inside it exceeds the capacity to dissipate it to the outside. This runaway may be followed by the generation of gas and explosion and / or fire.

[0039] Also, maintaining a temperature below 70°C makes it possible to increase the lifespan of an accumulator, because the higher the operating temperature of an accumulator, the more its lifespan will be reduced.

[0040] Furthermore, certain accumulator chemistries require an operating temperature well above ambient temperature and consequently, it proves necessary to regulate their temperature level by initial preheating of the accumulators, or even by permanently maintaining the temperature of the accumulators.

[0041] For reasons of volume compactness, it is chosen to use assemblies of X accumulators in series and Y in parallel, a mechanical integration of accumulators of cylindrical geometry with rigid casing 6 within a module or a battery pack widely retained is that illustrated in [Fig.6].

[0042] In this integration, the accumulators A1, A2...A42 are arranged parallel to each other in contact with each other by their housing 6 and in a staggered manner, forming a matrix which extends in the Z direction. A staggered arrangement allows for high energy density.

[0043] The assembly of this matrix is ​​most often done by gluing the accumulators A1, A2...A42 to each other.

[0044] As part of an operating risk analysis study, the inventors highlighted that one of the most critical risks for a module such as that of [Fig.6], was the internal short circuit of an accumulator, following a manufacturing defect (with a failure rate of 10 7 / h).

[0045] Thus, when a fault of this type is declared, as already mentioned above, a thermal runaway of an accumulator within the module may occur. Following this runaway of an individual accumulator, it may propagate to adjacent accumulators within a module.

[0046] It is therefore important to implement a mitigation solution which eliminates the risk of propagation during the accidental runaway of an accumulator, and also limits possible propagation outside the module, in particular by the expulsion of flame or incandescent particles.

[0047] However, all the existing cooling devices according to the prior art do not make it possible to actually mitigate thermal runaway of an accumulator within a battery pack, that is to say which make it possible to attenuate the transmission of the energy dissipated by thermal runaway of the accumulator to the other accumulators of the pack, in order to prevent them themselves from entering into a situation of thermal runaway.

[0048] Patent application WO2022 / 090575 A1 proposed a multilayer film, arranged on the previously determined path of the hot gases released under pressure in the event of thermal runaway of one of the accumulators of a battery module, the A layer of aqueous gel opposite the accumulators limits the spread of thermal runaway from one of them to the others. This multi-layer film solution, including a layer of aqueous gel, is satisfactory insofar as it effectively cools the hot gases and is also optimized in terms of weight and size to preserve the performance of the pack. However, it has the disadvantage of being able, in certain configurations, to contribute to the rise in pressure by its phase change in the module casing.

[0049] There is therefore a need to improve thermal runaway mitigation solutions for any accumulator within a module or battery pack, which does not increase the pressure.

[0050] Furthermore, the improvement must also be optimized in terms of weight and size to preserve the performance of the module or battery pack.

[0051] The aim of the invention is to respond at least in part to this(these) need(s). Statement of the invention

[0052] To do this, the invention relates, in one of its aspects, to a battery module comprising:

[0053] - a plurality of accumulators each comprising at least one electrolyte cell chemical formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode, a housing arranged to contain the electrochemical cell in a sealed manner and two output terminals projecting from the cover and / or the bottom of the housing;

[0054] - preferably at least one busbar attached to one of the output terminals of at least one part of the accumulators, in order to electrically connect them together; - at least one phase-change metal powder, placed in at least one zone intended for the passage of hot gases released by one of the accumulators during thermal runaway, the powder being adapted to change phase in the zone and thus limit the thermal convection of the released hot gases.

[0055] Preferably at least a portion of the powder being deposited on the busbar.

[0056] Preferably, the phase change metal powder material being suitable for phase change at a temperature between 150 and 700°C, preferably between 250 and 500°C.

[0057] Advantageously, the phase change material of the metal powder is chosen from potassium fluoroborate (KBF4), magnesium and potassium chloride (KMgC13), NaKMgCl, KMgZnCl or a mixture thereof.

[0058] The accumulators can be of cylindrical geometry.

[0059] According to an advantageous embodiment, the module comprises at least one sealing means between the accumulators and the zone intended for the passage of hot gases. released by one of the accumulators during thermal runaway.

[0060] According to this mode and an advantageous configuration, the module comprises a case called a battery case housing the cylindrical accumulators and a sealed holding plate, as a sealing means, which holds the cylindrical accumulators in the battery case 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 volume delimited between the battery case and the sealed holding plate which contains the connected terminals.

[0061] The grains of the powder can be free or agglomerated.

[0062] 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).

[0063] Advantageously, the thickness of the deposited metal powder is between 10 and 50 mm.

[0064] According to an advantageous embodiment variant, the metal powder is encapsulated between two encapsulation films or in an encapsulation envelope closed by a film. These envelopes and encapsulation films make it possible to prevent the flow of the powder over time or the vibrations that the battery module may undergo.

[0065] Preferably, one of the two encapsulation films is intended to be applied directly against the busbar.

[0066] In order to allow good evacuation of gases, an encapsulation film is configured to deteriorate at the time of opening of an accumulator vent and possible ejection of the electrolyte. Thus, advantageously, one and / or the other of the encapsulation films is (are) made of a polymer chosen from polyethylene (PE) or polyether.

[0067] The thickness of each encapsulation film is preferably at most equal to 50 μm.

[0068] Thus, the invention essentially consists of a phase-change metal powder, arranged on the previously determined path of the hot gases released under pressure in the event of thermal runaway of one of the accumulators of a battery module.

[0069] The powder opposite the accumulators will limit, by its phase change, the thermal convection effect when the incandescent gases are released from an accumulator and by thermal conduction, in particular by a busbar, and thus avoid the propagation of thermal runaway from one of them to the others.

[0070] Thus, during thermal runaway of one of the accumulators, which can be referred to as a “trigger accumulator”, the melting of the powder locally will make it possible to significantly limit the increase in the temperature of the neighboring accumulators.

[0071] The primary function of the powder is to form a real thermal protection barrier for the other accumulators, i.e. those which are not racing, by preventing the hot gases released by the safety vent(s) of the trigger accumulator from heating the other accumulators very strongly.

[0072] The zone(s) of passage of the hot gases released during thermal runaway of one of the accumulators of the module (M) is(are) previously determined.

[0073] During thermal runaway, the powder can advantageously separate the hot gases degassing from the trigger accumulator from the rest of the accumulators by forming a thermal barrier limiting the thermal exchanges between the vent gases having passed through the powder and the accumulators.

[0074] Hot gases can pass through the powder which then changes phase.

[0075] At least one of the accumulators, preferably each accumulator, may comprise at least one safety vent configured to release the hot gases under pressure during thermal runaway of said accumulator, the powder being placed opposite the safety vent. Advantageously, such an arrangement makes it possible to increase the quantity of hot gases that can pass through the powder during their degassing. Advantageously, the powder is arranged as close as possible to the safety vent, or even deposited on the latter.

[0076] Preferably, the safety vent(s) is(are) located on one of the output terminals of the accumulator(s), preferably on the positive output terminal. The degassing of hot gases can take place through the busbar.

[0077] It is specified here that for the thermal runaway phenomenon, reference will be made to publication [2] and to the protocol described in this publication. The so-called “self-heating” and “thermal runaway” temperatures are respectively denoted T1 and T2 in this publication.

[0078] The temperature Tl, typically 70°C, in [Fig.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 in adiabatic conditions.

[0079] The temperature T2, typically 150°C, in [Fig.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.

[0080] 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.

[0081] 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 integrated. generally transmitted to the adjacent accumulators in the pack, thus limiting their temperature.

[0082] Consequently, a powder according to the invention makes it possible to prevent the accumulators adjacent to a trigger accumulator from also going into thermal runaway.

[0083] Compared with a known solution using liquid water, the implementation of a phase change powder according to the invention is simpler. Indeed, it does not require having a perfectly sealed container throughout the racing of an accumulator. The powder also makes it possible to limit the potential risks of short circuit within a battery module.

[0084] More generally, the phase change powder according to the invention is distinguished from state-of-the-art solutions by an action at a higher temperature than the materials generally used, due to its phase change and that it does not produce additional gas. The increase in volume linked to the phase change of the powder between solid and liquid is much less than a phase change to a gaseous phase. The powder therefore limits the maximum pressure within a module housing, which is not the case with state-of-the-art solutions, such as water.

[0085] The inventors have overcome a technical prejudice because until now, it was accepted that only materials with a phase change at around 100°C made it possible to avoid the runaway of a trigger accumulator.

[0086] But by analyzing the types of thermal runaway, the inventors highlighted that such materials are not really effective for internal short circuit faults in an accumulator.

[0087] This is why the inventors chose a powder whose phase change occurs at a higher temperature to favor the limitation of propagation and the quantity of gases released in a battery module housing.

[0088] Ultimately, the invention provides 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 racing of an accumulator; - limiting potential short-circuit risks; - a simple to implement and effective safety solution to prevent the propagation of thermal runaway within a module or battery pack; - a solution which is not to the detriment of the weight of a module or a battery pack, a phase change powder according to the invention being able to be very light, which is very advantageous for on-board applications; - the possibility of implementing a very rapid phase change powder quickly and easily into a module or battery pack, from its design or on the contrary as a retrofit of an existing module or battery pack.

[0089] For application to a Li-ion battery pack, each accumulator is a Li-ion accumulator in which: - the negative electrode(s) material is chosen from the group comprising graphite, lithium, titanate oxide Li4TiO5Oi2; - the positive electrode(s) material is chosen from the group comprising LiFePO4, LiCoO2, LiNio.sshdno 33(2003302.

[0090] Other advantages and characteristics of the invention will become more apparent 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

[0091] [Fig-1] [Fig.l] is an exploded perspective schematic view showing the different elements of a lithium-ion battery.

[0092] [Fig.2] [Fig.2] is a front view showing a lithium-ion battery with its flexible packaging according to the state of the art.

[0093] [Fig.3] [Fig.3] is a perspective view of a lithium-ion accumulator according to state of the art with its rigid packaging consisting of a cylindrical shaped box.

[0094] [Fig.4] [Fig.4] is a perspective view of a lithium-ion accumulator according to state of the art with its rigid packaging consisting of a prismatic shaped box.

[0095] [Fig.5] [Fig.5] is a perspective view of an assembly using busbars state-of-the-art lithium-ion accumulators, forming a battery pack.

[0096] [Fig.6] [Fig.6] is a perspective view of a plurality of lithium-ion batteries ion of cylindrical geometry preassembled together according to the state of the art, forming a matrix intended for a battery module or a battery pack.

[0097] [Fig.7] [Fig.7] is a side view of a battery module equipped with a busbar on which a phase change metal powder according to the invention is deposited. Detailed description

[0098] Figures 1 to 6 relate to different examples of Li-ion accumulators, flexible packaging and accumulator cases as well as a battery pack according to the state of the art. These figures 1 to 6 have already been commented on in the preamble and are therefore not commented on further below.

[0099] 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 figures 1 to 7.

[0100] Throughout the present application, the terms “lower”, “upper”, “bottom”, “top”, “below” and “above” are to be understood by reference to Li-ion battery cases arranged vertically, i.e. with a film multilayers according to the invention horizontally.

[0101] [Fig.7] shows an example of phase-change metal powder 10 according to the invention deposited on a busbar B3 of a Li-ion, Al, A2, A3, A4 accumulator battery module M.

[0102] In the illustrated examples, the illustrated Al-A4 accumulators may have cylindrical format cases, typically 18650 or 21700 format.

[0103] The accumulators A1-AA4 are electrically connected by their output terminal in groups via the busbar B3.

[0104] According to the invention, a phase change metal powder 10 according to the invention is deposited directly against the busbar B3.

[0105] Powder 10 is preferably made of KBF4.

[0106] The powder 10 can be encapsulated between two polymer films.

[0107] The thickness of each encapsulation film is typically about 50 pm.

[0108] The thickness of the powder 10 can be between 10 and 50 mm.

[0109] As regards the installation of a powder 10 according to the invention within a battery module M, it can be carried out in several forms.

[0110] A first alternative consists of pouring the powder 10 by gravity flow so that it is deposited at least on the busbar B3 of the positive terminals 4.

[0111] The spilled powder can at least partially fill a volume between the wall of the housing 100 of the module and a holding and sealing plate 11, arranged below the busbar B3 and the positive terminals 4, as shown in [Fig.7].

[0112] This plate 11 holds the accumulators A1 to A4 and separates the output terminals 4 from the rest of the accumulators in a sealed manner.

[0113] A second alternative consists of encapsulating the powder 10 between two encapsulation films, as indicated above and placing the encapsulated assembly directly in contact with the busbar B3.

[0114] A third alternative consists of agglomerating the powder 10 to make a solid part, in particular by compaction under pressure or by prior mixing with a polymer binder, of the CMC or PVAC type, then positioning the solid part produced directly in contact with the busbar B3.

[0115] During thermal runaway of an 18650 size battery, approximately 80 kJ of thermal energy can be released.

[0116] Generally, the released energy is shared between the ejected gases and molten materials which represent approximately 70% of the heat, and the energy emitted by the accumulator casing due to the materials retained in the production of the accumulator, which represents the remaining 30% of heat.

[0117] It is therefore important to implement a solution for mitigating heat transfer between accumulators taking into consideration thermal convection via gases as well as conduction through the busbars.

[0118] As shown schematically in [Fig.7], the addition of a phase-change powder 10 on a busbar B3, typically connected to the positive terminals 4 of accumulators A1-A4, allows the limitation of these two heat transfer modes. The hot gases from the trigger accumulator are evacuated through its safety vent.

[0119] The safety vent of the accumulators can be located on their positive terminal 4. The hot gases evacuated by the safety vent then pass through the busbar B3 then pass through the phase change metal powder 10.

[0120] The powder 10 then limits the conduction by the busbar B3 as well as the thermal convection effect of the hot gases on the accumulators adjacent to the trigger accumulator.

[0121] In order to validate the safety of the KBF4 powder according to the invention, the inventors carried out tests.

[0122] 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.

[0123] In one test, for comparison, no powder was put into the canister. In the other test, a quantity of KBF4 powder was put in, in accordance with the invention.

[0124] Visually, the inventors observed that large incandescent flames emerged from the canister of the comparative test while no flames emerged from it containing the KBF4 powder.

[0125] This aspect, i.e. that no flame comes out of a module housing, in the event of thermal runaway, is very important, in particular because the new automotive standards will bring additional constraints on the presence of flame outside a battery pack housing.

[0126] In addition, in each of the two tests the pressure and temperature were also measured inside the canister. Table 1 summarizes the measurements carried out.

[0127] [Tableauxl] Test Test without KBF4 powder Test according to the invention, with KBF4 powder Temperature (°C) 1300 600 Pressure (bar) 7.5 3.2

[0128] The results clearly show that the addition of KBF4 powder decreases the temperature as well as the maximum pressure in the canister.

[0129] These results are particularly important because the maximum temperature has a direct impact on the risk of propagation of thermal runaway and the pressure is a value directly used for the mechanical dimensioning of a module or battery pack case.

[0130] Thus, the reduction in maximum pressure with the addition of KBF4 powder leads to considering mass optimization: the addition of a low mass of KBF4 powder can lead to the removal of a relatively large mass from a module housing.

[0131] The invention is not limited to the examples which have just been described; it is possible in particular to combine characteristics of the examples illustrated within non-illustrated variants.

[0132] Other variants and improvements may be envisaged without departing from the scope of the invention.

[0133] The examples given above relating to the positive pole of the accumulators are also transferable to the application on a busbar on the negative pole side.

[0134] In the illustrated embodiments, the accumulators are cylindrical, for example of the 18650 type, with a safety vent in the positive terminal of each accumulator. Other shapes of accumulators and / or other arrangements of the safety vents are conceivable.

[0135] The pressures and temperatures at which the gases exit 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:

[0136] [1] https: / / www.mersen.com / sites / default / files / publications-media / 16-markets-transportati on-ev-hev-emobility-presentation-mersen.pdf.

[0137] [2] Xuning Fenga, et al. « Key Characteristics for Thermal Runaway of Li-ion Batteries » Energy Procedia, 158 (2019) 4684-4689.

Claims

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 housing (6) arranged to contain the electrochemical cell in a sealed manner and two output terminals (4, 5) projecting from the cover and / or the bottom of the housing; - preferably at least one busbar (B1, B2, B3) fixed to one of the output terminals (4 or 5) of at least some of the accumulators, in order to electrically connect them together; - at least one phase-change metal powder (10), placed in at least one zone intended for the passage of hot gases released by one of the accumulators during thermal runaway, the powder being adapted to change phase in the zone and thus limit the thermal convection of the released hot gases.

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

3. Battery module (M) according to claim 1 or 2, the phase change metal powder material being adapted to change phase at a temperature between 150 and 700°C, preferably between 250 and 500°C.

4. Battery module (M) according to one of the preceding claims, the phase change material of the metal powder being chosen from potassium fluoroborate (KBF4), potassium magnesium chloride (KMgC13), NaKMgCl, KMgZnCl or a mixture thereof.

5. VI. Battery module (M) according to one of the preceding claims, the accumulators being of cylindrical geometry.

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

7. Battery module (M) according to claim 6 in combination with claim 5, comprising a housing called battery housing housing the cylindrical accumulators and a sealed holding plate, as sealing means, which holds the cylindrical accumulators

8.

9.

10.

11.

12.

13.

14. in the battery case and ensures sealing between one of their terminals, in particular their positive terminals, electrically connected in series and / or in parallel and the rest of the accumulators, the powder filling at least in part the volume delimited between the battery case and the sealed holding plate which contains the connected terminals. Battery module (M) according to one of the preceding claims, the grains of the powder being free or agglomerated. Battery module (M) according to claim 8, the powder being, prior to its installation, compacted under pressure or agglomerated by a polymer binder, preferably chosen from carboxymethylcellulose (CMC) or polyvinyl acetate (PVAC). Battery module (M) according to one of the preceding claims, the thickness of the metal powder being between 10 and 50 mm. 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. Battery module (M) according to claim 11, one and / or the other of the encapsulation films being made of a polymer chosen from polyethylene (PE) or polyether. Battery module (M) according to claim 11 or 12, the thickness of an encapsulation film being at most equal to 50 pm. Battery module (M) according to one of the preceding claims, each accumulator being a Li-ion accumulator in which: - the negative electrode(s) material is chosen from the group comprising graphite, lithium, titanate oxide Li4TiO5Oi2; the positive electrode(s) material is chosen from the group comprising LiFePO4, LiCoO2, LiNi0.33Mn0.33Co0.33O2.

Images