Batteries provided with a thermal management system comprising phase-change materials

Abstract

The invention relates to a battery comprising one or more electrochemical cells and solid-liquid phase-change material composites, the battery comprising a plurality of modules, each having a given composite, the modules having an individual configuration, in which each module has an opening used to surround part of a cell inserted into the opening, a cell being surrounded along its height by a plurality of individual modules stacked on top of one another, with at least two modules having different composites, this individual configuration being implemented for one or more cells, and / or having a collective configuration, in which each collective module has a plurality of openings used to surround part of a plurality of cells inserted into the openings, the cells being surrounded along their height by a plurality of horizontal collective modules stacked on top of one another, with at least two modules having different composites; or cells N are surrounded over their entire height by a single Nth vertical collective module composed of a composite N, and cells N+1 adjacent to the cells N are surrounded by a single Nth+1 vertical collective module composed of a composite N+1 that is different from the composite N.

Description

[0001] Batteries equipped with a thermal management system including phase change materials.

[0002] Description

[0003] The invention relates to the technical field of batteries, and may relate to any type of battery, in particular for example lithium-ion (Li-ion) batteries.

[0004] Batteries can be, for example, batteries for energy storage systems, telecom devices, space devices, renewable energy devices, electronic devices such as power inverters, electric vehicles, etc.

[0005] The invention is particularly suitable for electric vehicle batteries.

[0006] Electric vehicles are used here in particular to refer to vehicles equipped with an electric motor and a battery (BEV, Battery electric vehicle), rechargeable hybrid vehicles, equipped with an internal combustion engine and an electric motor, the battery of which can be recharged by connecting to an external source of electricity (PHEV, Plug-in hybrid electric vehicle). Electric vehicles are used here in particular to refer to two-wheeled or four-wheeled vehicles, scooters, private vehicles, utility vehicles or public transport vehicles, such as buses.

[0007] Lithium-ion (Li-ion) batteries are currently the most widely used in electric vehicles. A Li-ion battery is a set of Li-ion accumulators, called cells, connected in series or parallel in modules. The cells are cylindrical, prismatic, or pouch cells. Recent advances in lithium-ion batteries have led to a significant reduction in battery prices and an increase in battery range.

[0008] To increase the range of electric vehicles, manufacturers have increased the on-board energy, by increasing the size of the battery pack or by increasing the energy density of the batteries, which can now reach 60 kWh, and between 80 kWh and 100 kWh in some high-end models. The range of electric vehicles varies depending on the vehicle and driving conditions, but the energy densities of the batteries allow for at least 200 km in all cases, while most daily vehicle uses do not exceed 100 km.

[0009] To reduce charging times, manufacturers are increasing charger power from 100 kW to 400 kW, resulting in charging rates ranging from 1.5C to 10C at the battery cell level. Charging currents are, however, limited by cell operating mechanisms, particularly thermal effects and aging. Beyond a certain rate, increasing the charging current may lead to cell heating rather than reducing charging time. Fast charging can lead to degradation of lithium-ion cells, through various mechanisms, including the deposition of metallic lithium (lithium plating), degradation of the electrolyte by growth of a passive layer (solid electrolyte interphase), and mechanical degradation of the electrodes.

[0010] The increase in temperature of Li-ion batteries can also lead to thermal runaway of one of the battery cells, with a domino effect on the other cells. Thermal runaway results in an increase in the temperature of the cell, which causes an acceleration of exothermic reactions, generating a further increase in the internal temperature of the cell, with the risk of leakage of liquid electrolyte, release of chemical substances, fire, explosion.

[0011] Lead-acid batteries are widely used in this type of industry to equip railway vehicles, automobiles, aircraft, and satellites. A lead-acid battery is a series-connected set of lead-acid accumulators. Lead-acid batteries are also very sensitive to extreme temperatures. In hot weather, they release more energy than they do at normal temperatures. Heat causes the battery to lose electrolyte, leading to increased discharge and eventual failure.

[0012] Battery temperature control is therefore very important and is ensured by battery thermal management systems (BTMS), which can be classified into two main families: active management systems and passive management systems.

[0013] Hybrid thermal management systems are also known, comprising passive and active means. SGTB can also be classified into five categories, depending on the cooling medium used: air, liquid, phase change material (PCM), heat pipe, refrigerant compound. A power supply is required for active management systems, by forced convection or circulation of a heat transfer liquid.

[0014] The invention relates more particularly to thermal management systems for batteries using solid-liquid or solid-solid MCPs.

[0015] A review of MCPs considered for battery thermal management was presented in 2020 by Liu et al. Phase Change Materials Application in Battery Thermal Management System: A Review, Materials 2020, 13, 4622).

[0016] The thermal state of a battery depends on the individual thermal behavior of each cell and the collective thermal behavior of all cells in the battery.

[0017] There are technical solutions available today, but they are not satisfactory because they are based on a plate exchanger with a flow of heat transfer fluid, which does not take into account the individual behavior of each cell.

[0018] For example, it is known from Bloch et al. (Li-ion Batteries, from the Present to the Future, EDP 2020), thermal management systems for automotive batteries using MCPs, existing only in prototype form, with commercially available SGTBs for automotive vehicles implementing other means of thermal management, such as air cooling, cooling by contact with a liquid circulating in a cold plate.

[0019] The invention aims to solve this first main technical problem.

[0020] It also aims to solve the second technical problem described below, when the phase change material is solid-liquid.

[0021] El ldi et al. proposent l’emploi d’un composite paraffine RT27 / mousse d’aluminium (Hybrid cooling based battery thermal management using composite phase change materials and forced convection, Journal of Energy Storage, 2021, 102946), ou bien l’emploi d’un composite à base de paraffine RT27 et d’une mousse d’aluminium , de nickel ou de cuivre (A numerical investigation of the effects of metal foam characteristics and heating / cooling conditions on the phase change kinetic of phase change materials embedded in metal foam, Journal of Energy Storage, Elsevier, 2019, 26; A passive thermal management system of Li-ion batteries using PCM composites: Experimental and numerical investigations, International Journal of Heat and Mass Transfer Volume 169, April 2021, 120894) .

[0022] Zhengyuan et al. propose the use of a paraffin / expanded graphite composite in a battery thermal management system (BTMS) further comprising cooling by water circulation in micro-channels ( Thermal performance of thermal management system coupling composite phase change material to water cooling with double s-shaped micro-channels for prismatic lithium-ion battery, Journal of Energy Storage, 2022, 103490).

[0023] Liquid-solid PCMs offer the ability to store and release large amounts of heat during the phase change process in small volumes. However, liquid-solid PCMs have several drawbacks, making their use in battery thermal management systems difficult. The main disadvantages of PCMs are their low thermal conductivity, the significant risk of liquid PCM leaking into the battery, the need for PCM regeneration (solidification), and the difference in PCM volume during its phase change. Furthermore, using a PCM increases the mass and cost of the battery.

[0024] Invention

[0025] The present invention aims to propose a battery thermal management system which does not have the drawbacks of the systems proposed previously.

[0026] The invention is based on the exploitation of the thermodynamic properties of phase change materials (PCMs), mainly on their ability to store and release thermal energy at a constant temperature. This property makes it possible to envisage very precise control of the wall temperatures of the PCMs in order to guarantee better temperature homogeneity within the cells as well as the battery module. Heat absorption also makes it possible to gain autonomy by avoiding the use of costly and energy-intensive active systems.

[0027] The development of the innovative system is based in particular on stratified heat storage devices.

[0028] The invention allows for targeted thermal management by hot zone, adapted to the individual thermal behaviors of the cells as well as to their collective thermal behavior. It is based on the implementation of an original thermally activated composite that can be coupled to an intelligent microfluidic regeneration system.

[0029] Advantageously, the proposed system is coupled with a microfluidic thermal control circuit, based on heat transfer fluid. For example, each MCP stratum (layer) can have a circuit independent of the other circuits. In each circuit will circulate the same heat transfer fluid with a controlled temperature and an exchange coefficient (h) adapted to the power to be dissipated. For this, the optimized cooling circuit will be connected to an intelligent thermal control system, in order to ensure the regeneration of the MCPs in each layer and this according to the thermal cycles. This solution will ensure homogenization of the temperature of the cells (batteries) and can mitigate conditions that could lead to a thermal runaway event of the batteries.

[0030] For these purposes, there is proposed, according to a first aspect, a battery comprising one or more electrochemical cells and composites based on one or more solid-liquid or solid-solid MCPs, configured to produce a thermal management system, making it possible to maintain the temperature of one or more electrochemical cells in operation at a value lower than a given temperature, said composites being thermally conductive and comprising a heat-conducting material with a sealed structure allowing the encapsulation of MCPs when the MCP is solid-liquid, the battery comprising several modules each having a given composite, sealed when the MCP is solid-liquid, the modules having two possible configurations, possibly combined.

[0031] Encapsulation is synonymous with the sealed housing of PCMs in composite modules, when the PCM is solid-liquid. It is possible to use single-layer or multi-layer microencapsulation. Multi-layer microencapsulation can be accompanied by a "self-healing" effect in the event of cracking due to thermal or mechanical stress.

[0032] Advantageously, the encapsulation of the MCPs is watertight, allowing the MCPs to be kept inside the structure during their phase change without leakage or loss of MCP.

[0033] Advantageously, the encapsulation of the MCPs allows thermal conduction of the MCPs to be obtained, in order to facilitate heat transfer. Advantageously, the encapsulation is carried out in a module with openings, allowing the cells to pass through. This embodiment makes it possible to arrange the encapsulated MCPs as close as possible to the cells, and to arrange them according to their thermal and mechanical characteristics. Thus, thanks to this specific arrangement of the MCPs according to their capacities, it is possible to obtain the desired temperatures during the operation of the cells, to control the mechanical behavior, particularly near the cells, and to avoid possible liquid leaks.

[0034] In a first configuration, called individual configuration, each individual module has an opening allowing each individual module to surround a part of an electrochemical cell introduced into the opening, an electrochemical cell being surrounded along its height by several superimposed individual modules, at least two modules having different composites, this individual configuration being produced for a single or several cells.

[0035] In a second configuration, called the collective configuration, each collective module has several openings, allowing each collective module to surround a part of several electrochemical cells introduced into the openings, according to two arrangements.

[0036] Advantageously, the battery has air and / or liquid micro-exchangers which comprise conductive plates and air and / or liquid microcircuits in the conductive plates, allowing compartmentalization of the modules and regeneration of the MCPs, the micro-exchangers being configured to create a thermal conduction bridge between the MCPs.

[0037] Advantageously, the battery has air and / or liquid micro-exchangers along vertical and horizontal plates, in particular on the end plates outside the battery to evacuate heat outside the battery. Advantageously, these plates are aligned and / or perpendicular to the electrochemical cells and in contact with each other, to evacuate heat outside the battery.

[0038] Advantageously, the battery has air and / or liquid micro-exchangers along parallel plates along the length of the MCP modules and / or perpendicular to each other, the plates being in contact with each other to evacuate the heat extracted by the MCPs to the outside of the battery, in particular advantageously with internal plates located between the MCP modules to compartmentalize them and which are in contact with perpendicular plates located outside the MCP modules.

[0039] Advantageously, the exchangers are hybrid and comprise conductive plates with phase change materials and micro-channels within their thickness.

[0040] Advantageously, the plates are equipped with a system that controls the direction of flow, with valves to control the flow rates, the plates being able to have the same coefficient of performance or a different coefficient (KPI).

[0041] Advantageously, the plates are equipped with two air / liquid flow circuits or first liquid / second liquid flows.

[0042] In a first arrangement, the cells are surrounded, along their height, by several horizontal collective modules superimposed, with at least two modules which have different composites.

[0043] In a second arrangement, N cells are surrounded over their entire height by a single Nth vertical collective module, composed of an N composite, and N + 1 cells neighboring the N cells are surrounded by a single Nth + 1 vertical collective module, composed of an N + 1 composite different from the N composite. When using the solid-liquid phase change material, by sealed composite, we mean here a composite material comprising a solid-liquid PCM from which the PCM in the liquid state cannot substantially escape.

[0044] The composite material, for example, has very low porosity, particularly very low interconnected porosity.

[0045] In some implementations, the MCP is encapsulated in the composite material, particularly microencapsulated in the composite material.

[0046] In other embodiments, possibly combined, the composite material is enveloped by an advantageously sealed wall, for example made of a metal alloy.

[0047] According to various implementations, when the phase change material is solid-liquid, the waterproof composites are chosen from a composite A, a composite B or a composite C.

[0048] Composite A comprises a heat-conducting foam with at least one PCM, the foam being advantageously wrapped with a waterproof layer or a composite B or a composite C.

[0049] Composite B comprises a matrix with at least one polymer having heat-conducting fillers and at least one MCP.

[0050] Composite C comprises a matrix with at least one polymer having at least one MCP micro-encapsulated by a heat-conducting material, and which makes it possible to contain the MCP during its change of state.

[0051] Advantageously, the battery comprises one or more compartments, to receive and match the shape of the modules and electrochemical cells, with outer walls which match the outer periphery of the modules, and inner walls whose dimensions are configured to be in contact on one face with each inner wall of the openings of the modules, and on another face with the outer periphery of the electrochemical cells. Advantageously, the battery has air and / or liquid micro-exchangers, which allow compartmentalization of the modules, regeneration (solidification) of the MCPs. The micro-exchangers are advantageously configured to create a thermal conduction bridge between the MCPs.

[0052] In some implementations, micro-exchangers comprise plates which form at least one of the walls of the different compartment(s).

[0053] In certain particular implementations, the shape of the plates is configured to allow their placement perpendicular to the height of the electrochemical cells in the compartment(s), without obstructing the openings of the modules.

[0054] In certain particular implementations, the shape of the plates is configured to allow their placement parallel to the height of the electrochemical cells in the compartment(s), between neighboring electrochemical cells.

[0055] Advantageously, the composites surrounding the electrochemical cells located in the center of the battery are configured to have a greater latent heat than the latent heat of the composites located at the edges of the battery.

[0056] Alternatively or in combination, the composites surrounding the electrochemical cells located in the center of the battery comprise heat-conducting materials having a heat-conducting capacity greater than the heat-conducting capacity of the heat-conducting materials of the composites located at the edges of the battery.

[0057] Advantageously, the electrochemical cells are distributed in groups of adjacent electrochemical cells, and for at least one group of adjacent electrochemical cells, at least two different horizontal collective modules surrounding all the adjacent electrochemical cells of this group according to their height.

[0058] The horizontal collective modules are chosen for each group of adjacent electrochemical cells according to the following possibilities: collective module comprising a composite A and collective module comprising a composite B; or collective module comprising a composite A and collective module comprising a composite C; or collective modules comprising a composite B with compositional variations on the polymer matrices and / or conductive fillers and / or different PCMs; or collective modules comprising a composite C with compositional variations on the polymer matrices and / or different microencapsulated PCMs and / or different heat-conducting microencapsulation material.

[0059] Advantageously, air / liquid micro-exchangers have plates and air / liquid microcircuits in the plates, these plates having openings to allow the electrochemical cells to pass through.

[0060] In some implementations, the battery has three horizontal collective modules, with at least two different composites for the three horizontal collective modules.

[0061] In some implementations, the electrochemical cells are distributed in groups of electrochemical cells, each group of electrochemical cells having the same vertical collective module over the entire height of the group, different from a vertical collective module of at least one other group of electrochemical cells over the entire height of said group.The vertical collective modules are chosen according to the following possibilities: collective module comprising a composite A and collective module comprising a composite B; or collective module comprising a composite A and collective module comprising a composite C; or collective modules comprising a composite B, with compositional variations on the polymer matrices and / or conductive fillers and / or the different PCMs; or collective modules comprising a composite C, with compositional variations on the polymer matrices and / or the different microencapsulated PCMs and / or a different heat-conducting microencapsulation material.

[0062] Advantageously, the battery has different individual modules superimposed and / or different collective modules, to create horizontal and vertical compartments around the electrochemical cells.

[0063] In some implementations, the battery comprises several electrochemical cells, each cell being individually surrounded over its entire height by an individual module comprising a composite A, a composite B or a composite C with MCP, the composites being chosen for each cell according to its location relative to the other electrochemical cells in the battery.

[0064] Advantageously, the microcircuits are different per module surrounding the electrochemical cells and / or depending on the location of one or more electrochemical cells in the module.

[0065] Advantageously, next to a group of electrochemical cells surrounded by composite, there is at least one group of electrochemical cells without composite.

[0066] Advantageously, a conductive plate is located in the extreme part of the electrochemical cells.

[0067] The heat-conducting foams are advantageously chosen from the following list: aluminum foam, copper foam, nickel foam, graphite-based foam, all heat-conducting foams. The conductive fillers or conductive materials encapsulating the PCMs are advantageously chosen from the following list: fins, expanded graphite, heat-conducting fillers from recycled aluminum, copper, aluminum nitride, nano-silica.

[0068] The polymers are advantageously chosen from the following list: HDPE (high density polyethylene), LDPE (low density polyethylene), SE BS (polystyrene-b-poly(ethylene-butylene)-b-polystyrene), SEPS (poly(Styrene Ethylene Propylene Styrene)) or SEP (Poly(styrene-b-ethylene-co-propylene), PU (Polyurethane), PEG (polyethylene glycol), PP (polypropylene), POE (polyethylene octene co-elastomers), SBS (Styrene Butadiene Styrene), EPDM (ethylene propylene diene monomer), recycled polymers, biopolymers (e.g. lignocellulosics, chitosans, silicates, clay, etc.)

[0069] The possible association of polymers to constitute composites makes it possible to fulfill several functions: encapsulate the MCP "Shape Stabilized Phase Change Materials (SSPCM)" example Karkri et al. Polymer Testing 46 (2015), Thermochimica Acta 614 (2015) 218-225, Energy Conversion and Management Volume 77, January 2014, Pages 586-596. increase the rate of "stabilized form of MCP". increase the rigidity / or flexibility Karkri et al. Applied Thermal Engineering Volume 171, 5 May 2020, 1 15072).

[0070] MCPs are advantageously chosen from the following list: RT paraffins, hydrated salt, hexadecane, trademark BioMCP ®, trademark PureTemp ®.

[0071] Solid-Solid MCPs can be chosen from the following list: PEG4000, PEG6000, PEG8000, PU-SSPCM(PEG / 4' 4-diphenylmethane diisocyanate (MDI)), Polystyrene-g-PEG6000,

[0072] Sorbitol / Dipentaerythritol / Inositol / PEG. Advantageously, the composites are chosen so that the temperature of the electrochemical cells in operation is below a given temperature, for example 40°C.

[0073] In some implementations, the walls of the compartment(s) comprise different materials or a heat-conducting composite.

[0074] According to a second aspect, there is proposed a battery comprising one or more electrochemical cells, and composites based on one or more solid-liquid PCMs, configured to produce a thermal management system making it possible to maintain the temperature of one or more electrochemical cells in operation at a value below a given temperature, these composites being chosen when the phase change material is solid-liquid, from a composite A, a composite B, a composite C, a composite A comprising a heat-conducting foam with at least one PCM, advantageously wrapped in a sealed layer or a composite B or a composite C, a composite B comprising a matrix with at least one polymer having heat-conducting fillers and at least one PCM, a composite C comprising a matrix with at least one polymer having at least one PCM micro-encapsulated by a heat-conducting material.

[0075] Advantageously, the electrochemical cell(s) are surrounded by a composite block A which completely surrounds, envelops the electrochemical cell(s), the composite block A being completely surrounded, envelops by the composite B or by the composite C or by a heat-conducting material such as an aluminum alloy, the composite A being able to be reinforced by heat-conducting fillers.

[0076] Advantageously, composite B or C comprises several polymers.

[0077] Advantageously, composite B or C has a mixture of polymers from the following list: SEBS and POE; or SBS and EPDM; or HDPE and SBS. In a second arrangement, composite B or C has a mixture of polymers chosen from the following list: SEBS, SEPS, SEP, PU, ​​PEG, PP, PEBD, PEHD.

[0078] According to a third aspect, there is provided a system using a battery as presented above, the electrochemical cells being advantageously of the lithium-ion, lithium-manganese-cobalt (NMC), lithium-polymer (LiPo), lithium-iron-phosphate (LFP), lithium-cobalt-nickel-aluminium (NCA) type, lithium manganese (LMO), lithium-titanate (LTO), lithium-air, lithium-cobalt-oxide (LCO), lithium-sulfur (Li-S), lithium-metal-polymer (LMP), lithium-air, lithium-cobalt-oxide (LCO), sodium-ion (Na-ion) battery, nickel-cadmium (Ni-Cd) battery, nickel-metal hydride (Ni-MH) battery.

[0079] Other objects and advantages of the invention will appear in the light of the description of an embodiment, given below with reference to the appended drawings in which: Figure 1 is a schematic representation of a set of cells placed in a containing matrix, enveloped in a diffusing matrix, according to one implementation, Figure 2 is a schematic representation of a set of cells placed in a containing matrix, enveloped in a stratified diffusing matrix, according to one implementation, Figure 3 is a schematic representation of a cell block comprising cooling plates, Figure 4 is an exploded view of an embodiment of a cell block according to Figure 3, Figure 5 is an exploded view of an alternative embodiment of a cell block, Figure 6 is an exploded view of another alternative embodiment of a cell block,Figure 7 is a detailed view of a cooling panel that can be used in the blocks shown in Figures 3 to 6, Figure 8 is a schematic view of a thermal regulation of a cell, Figure 9 is a diagram of an experimental measurement device, Figure 10 is a view of a cell holder tube, Figure 11 is a diagram showing the installation of thermocouples in the cell holder tube of Figure 10, Figure 12 is a view illustrating the temperature variations as a function of time without the use of MCP, and with the use of MCP RT27, RT27 / aluminum foam, Figures 13, 14 and 15 respectively present the evolution of the temperature measured by the four thermocouples T1, T2, T3, T4, in the case of thermal management by pure paraffin RT27, for mold thicknesses of e= 3mm, e= 5mm and e= 7mm , respectively, Figure 1 6 represents the evolutions as a function of time of the cell temperature,without forced convection, with the use of pure paraffin RT27, for the three thicknesses of MCP considered (3 mm, 5 mm, 7 mm), figure 1 7 represents the evolutions as a function of time of the cell temperature, without forced convection, with the use of pure paraffin RT27, for a thickness of 3 mm, figure 1 8 represents the evolutions as a function of time of the cell temperature, without forced convection, with the use of paraffin RT27 and an aluminum foam, for a thickness of 7 mm, figures 19 and 20 respectively present the temporal evolution of the recorded temperature (T1, T2, T3, T4), for pure paraffin RT27, with a thickness e of 3 mm (figure 1 9) and a thickness e of 7 mm (figure 20), figure 21 presents the temporal evolution of the temperature of the surface of the cell measured by the thermocouple T1 for the different thicknesses studied,Figure 22 illustrates the impact of the metal foam on the thermal state of the cell for a thickness of 3mm, without and with forced convection, the measurements of the temperature T1 being presented in Figure 22, without forced convection, Figure 23 presents the temperature evolutions of the cell with pure RT27 paraffin and with a MA-RT27 composite with forced convection, Figure 24 presents the temporal evolution of the temperature of the cell without and with forced convection in the case of a MA-RT27 composite, e=7mm, Figure 25 presents the variation of the temperature and the thermal flux of the cells when the module operates without a thermal management system (without MCP), Figures 26 and 27 are representations similar to Figure 25, the system being stressed without air convection or with air convection.

[0080] GENERAL DESCRIPTION

[0081] The invention presents, according to a first aspect, a battery comprising one or more electrochemical cells and composites based on solid-liquid or solid-solid MCP, configured to produce a thermal management system, making it possible to maintain the temperature of one or more electrochemical cells in operation at a value lower than a given temperature, said composites being thermally conductive when the phase change material is solid-liquid, and comprising a heat-conducting material with a structure allowing the encapsulation of MCP when the phase change material is solid-liquid, the battery comprising several modules each having a given composite, the modules having two possible configurations, possibly combined.

[0082] According to a second aspect, there is provided a battery having one or more electrochemical cells, and composites based on solid-liquid or solid-solid PCMs, configured to produce a thermal management system making it possible to maintain the temperature of one or more electrochemical cells in operation at a value below a given temperature, these composites being chosen when the phase change material is solid-liquid, from a composite A, a composite B, a composite C, a composite A comprising a heat-conducting foam with at least one PCM, advantageously wrapped in a sealed layer or a composite B or a composite C, a composite B comprising a matrix with at least one polymer having heat-conducting fillers and at least one PCM, a composite C comprising a matrix with at least one polymer having at least one PCM micro-encapsulated by a heat-conducting material.Advantageously, the thermal management system is a stratified energy absorber for battery cooling.

[0083] Advantageously, the thermal management system is a generalized thermal control system in the form of a “3D cooling plate”.

[0084] Advantageously, the thermal management system is a hybrid MCP cooling system with a regeneration liquid allowing the durability of the batteries to be significantly improved.

[0085] Advantageously, the laminated absorber also relates to thermal management systems for batteries used in urban e-mobility such as bicycles, scooters and motorcycles.

[0086] Advantageously, this system has a thermal conductivity and heat storage capacity that can be modulated depending on the heat sources to be controlled. This thermal management system also offers flexibility in the layout (horizontal and / or vertical stratification), in the choice of PCMs and the quantity of conductive fillers to be used.

[0087] DETAILED DESCRIPTION OF THE INVENTION

[0088] In the remainder of the description, three types of composite materials are advantageously used, these composite materials being called composite A, composite B, composite C.

[0089] When the phase change material is solid-liquid, a composite A comprises a heat-conducting foam, for example a metal foam, containing at least one phase change material (PCM) and a sealing material. The metal foam is for example an aluminum foam, a copper foam or a nickel foam, graphite-based foams, all heat-conducting foams. When the phase change material is solid-liquid, a composite B comprises a polymer matrix with one or more polymers and at least one phase change material (PCM), the matrix advantageously comprising heat-conducting fillers.

[0090] A composite C comprises a polymer matrix with one or more polymers and at least one encapsulated phase change material (PCM), advantageously encapsulated in a heat-conducting material, the PCM being advantageously microencapsulated.

[0091] Advantageously, the microencapsulation of the three composites is single-layer or multi-layer.

[0092] Advantageously, multi-layer micro-encapsulation is accompanied by a “self-regenerating” effect, in the event of cracking due to thermal or mechanical stresses, for example.

[0093] Advantageously, multi-layer micro-encapsulation is accompanied by a “flame retardant” effect, in the event of thermal runaway, fire for example.

[0094] Composite A

[0095] A composite A is obtained, for example, by vacuum impregnation, according to the following process.

[0096] A solid-state MCP and a metal foam are cascaded into a Pyrex glass mold, before being introduced into an oven.

[0097] The oven is then placed under vacuum, while keeping the MCP in a solid state. The vacuum allows the air contained in the pores of the metal foam to be evacuated.

[0098] Then, the oven is heated for 140 min at a temperature above the melting temperature of the PCM, in order to ensure the immersion of the metal foam in the liquid PCM. Then the pressure in the oven is increased, for example by a value of 0.6 mbar to atmospheric pressure.

[0099] When the oven is at atmospheric pressure, the mold is removed from the oven to cool it, for example in a climatic chamber at a fixed temperature.

[0100] Once the MCP has completely solidified, the product is removed from the mold.

[0101] The MCP impregnation process is evaluated by calculating the impregnation rate, which is advantageously close to 100%.

[0102] Tables 1, 2 and 3 present the impregnation rates of the composites studied. These results reveal the success of the vacuum impregnation protocol.

[0103] A1 / RT21 93 0.55 98.55 (0.64)

[0104] Ni / RT21 95.2 0.9 97.39 (0.76)

[0105] Ni / RT21 95 2.3 97.53 (0.77)

[0106] Table 1. Impregnation rate of metal foam composites / RT21 c (%) dp (mm) a (%)

[0107] A1 / RT27 93 0.55 98.18 (0.65)

[0108] Ni / RT27 95.2 0.9 98.16 (0.73)

[0109] Ni / RT27 95 2.3 98.65 (0.75)

[0110] Table 2. Impregnation rate of metal foam composites / RT27 c (%) dp (mm) a (%)

[0111] A1 / RT35HC 93 0.55 97.76 (0.72)

[0112] Ni / RT35HC 95.2 0.9 97.28 (0.75)

[0113] Ni / RT35HC 95 2.3 97.87 (0.74)

[0114] Table 3. Impregnation rates of metal foam composites / RT35HC

[0115] Composite B A composite B is for example obtained as follows.

[0116] First, a PCM is dissolved in a solvent at 80°C, then SEBS (polystyrene-b-poly(ethylene-butylene)-b-polystyrene) and LDPE (low-density polyethylene) are added to the solution until the mixture is homogeneous. PCM is, for example, a paraffin, especially an RT42 paraffin.

[0117] Expanded graphite is then gradually added.

[0118] Sonication is applied, for example for 30 min at 100W, to decompose the graphite aggregates and ensure a homogeneous dispersion of the conductive fillers in the mixture.

[0119] In order to evaporate the solvent, the resulting mixture is left under a hood at a temperature of around 120°C.

[0120] Then the composite is dried in an oven, for example overnight at 130°C.

[0121] Finally, the mixture is hot pressed, for example at 130°C for 10 min in a steel mold using a heat press.

[0122] Table 4 shows an example of the mixture.

[0123] SEBS Hexadecane LDPE GE Thickness Mass

[0124] (%) (%) (%) (%) (mm) (g)

[0125] SI 15 75 5 5 6.01 8.669

[0126] S2 10 75 5 10 5.94 9.006

[0127] S3 5 75 5 15 6.08 9.593

[0128] S4 15 45 35 5 5.82 8.928

[0129] S5 15 45 30 10 6.08 9.392

[0130] S6 15 45 20 20 6.12 9.628

[0131] Table 4: Composition of SEBS / Hexadecane / LDPE / GE composites.

[0132] Composite C

[0133] A composite C is for example obtained by dispersion, as follows. A known quantity of polymer (example: SEBS / LDPE) is dispersed in a solvent loaded with heat-conducting microcapsules-MCP.

[0134] Microcapsules are, for example, made of polymer material, of natural, semi-synthetic or synthetic origin.

[0135] Microencapsulation is achieved, for example, by interfacial polymerization or spray drying. The spray drying process involves the formation of a solution, suspension, or emulsion containing a polymer and the MCP, an aerosol being formed by nebulization through a pneumatic, ultrasonic, or rotary nozzle. During this nebulization, solid microcapsules are formed after evaporation in a drying chamber, using a flow of air or nitrogen.

[0136] A container containing the solvent and MCP microcapsules is placed on a hot plate. Reflux heating is used to heat the reaction mixture. Reflux prevents loss of reactant or product through vaporization.

[0137] The microcapsules are gradually incorporated into the polymers, under magnetic stirring. Stirring is maintained, for example for about 60 min under reflux, so that the MCP-microcapsules are well dispersed in the LDPE / SEBS.

[0138] An additional amount of SEBS is added with stirring, for example for 30 min.

[0139] As the temperature increases, some chemical species vaporize. These chemical species then rise in a water cooler. In this cooler, cold water flows continuously, and upon contact with the walls, the gases cool and liquefy in the form of droplets on the walls of the cooler and eventually fall back into the container. In order to evaporate the solvent, the resulting mixture is left under a hood at a temperature of around 120°C. The composite is then placed in an oven, for example overnight at 120°C.

[0140] For shaping, the mixture is hot pressed, for example at 130°C for 10 min in a steel mold using a heat press.

[0141] Table 5 shows an example of the microcapsule-MCP mixture

[0142] SEBS / PEBD MCP SEBS sup

[0143] (%) (%) (%)

[0144] SI 65 30 5

[0145] S2 55 40 5

[0146] S3 45 50 5

[0147] Table 5: Composition of SEBS / MCP / LDPE composites

[0148] Possible implementation methods

[0149] Figure 1 illustrates an arrangement of the composites, according to a first implementation.

[0150] Figure 1 shows schematically 10 electrochemical cells of cylindrical shape. These cells are for example of type 18650, with a diameter of 18 mm and a length of 65 mm, or of type 26650 with a diameter of 26 mm, or of type 2170.

[0151] In Figure 1, a group of seventy cells is shown schematically, with the electrical connections not shown for simplification.

[0152] The number of cells depends in particular on the intended use of the battery (e.g. two-wheeled vehicle, automobile, truck). For example, forty-six cells can be connected in parallel to form a group of cells, the battery comprising two modules, each module comprising about twenty groups of cells, the modules and groups being connected in series.

[0153] The cells are for example of the Li-ion type. In the embodiment shown, the cells 10 are substantially equidistant and arranged in a square mesh.

[0154] In the embodiment shown, over substantially the entire height of the cells 10, the spaces existing between the cells are occupied by a composite A.

[0155] Advantageously, composite A completely surrounds all cells 10.

[0156] In one implementation, composite A contains heat-conducting fillers.

[0157] The block 11 of composite A containing the cells 10 is contained in an envelope 12 formed by a mass of composite B or a mass of composite C, or even by a heat-conducting material, for example an aluminum alloy.

[0158] Advantageously, the envelope 1 2 completely surrounds the composite A.

[0159] The envelope 12 forms a container, limiting the risks of leakage of the MCP in the liquid phase contained in the composite A.

[0160] The envelope 1 2 is heat conductive and promotes the regeneration (solidification) of the MCP contained in the composite A.

[0161] Figure 2 represents an alternative embodiment. In this alternative, the group of cells 10 is for example that described with reference to Figure 1, and this group of cells 10 is contained in a laminated envelope, comprising a first layer 13, a second layer 14 and a third layer 15 of composite material.

[0162] Each of the three layers 13, 14, 15 can be formed by a mass of composite A, or a mass of composite B or by a mass of composite C. In one implementation, one layer, for example the second layer 14, is formed by a composite A, the other two layers being formed by two masses of composite of type B, these two layers of composite of type B comprising different polymer matrices and / or different conductive fillers and / or different PCMs.

[0163] In another implementation, one layer, for example the second layer 14, is formed by a composite A, the other two layers being formed by two masses of composite of type C, these two layers of composite of type C comprising different polymer matrices and / or different microencapsulated MCPs, and / or a different microencapsulation material.

[0164] In the embodiment shown, the three layers 13, 14, 15 are substantially flat and of equal thickness, and extend substantially perpendicular to the slenderness axis of the cells 10.

[0165] Advantageously, the number of layers is greater than 2. Advantageously, the number of layers is adapted to the thermal state of the cell.

[0166] In other embodiments, the three layers 13, 14, 15 have different thicknesses from each other. For example, the intermediate layer 14 has a greater thickness than the lower layer 13 and the upper layer 15.

[0167] In other embodiments, the three layers 13, 14, 15 extend substantially parallel to the axis of slenderness of the cells 10. For example, a layer 14 advantageously surrounds the cells located at the center of a group of cells.

[0168] The properties of the composites used for the three layers are advantageously different. For example, one of the layers has a higher thermal conductivity than the other two layers, or a higher phase change temperature for the PCM. In other embodiments, the envelope contains two or more layers. The arrangement of different layers of composites in the envelope forms a lamination, each layer being able to be adapted to the thermal properties of the cells, in particular at a given height along the slenderness axis of the cells.

[0169] The laminated envelope forms a container limiting the risks of leakage of the liquid phase MCP contained in composite A.

[0170] The laminated envelope is heat conductive and promotes the regeneration of the MCP contained in composite A, taking into account a thermal gradient following the height of the cells 10.

[0171] Figure 3 illustrates a cell block comprising an envelope 20, at least one phase change material 21 contained in the envelope 20, and cooling panels 22.

[0172] The phase change material 21 may be a composite A, a composite B, or a composite C, or a variation of one of these composites.

[0173] In the embodiment shown in Figure 3, the block comprises nine cells 10 of cylindrical type, substantially identical and arranged equidistantly in three columns and three rows. It is understood that the number of cells 10 in the block may be less than nine, or greater than nine, depending on the intended applications for the battery.

[0174] In one implementation, the phase change material 21 is identical for the entire cell block.

[0175] In other embodiments, the phase change material 21 is adapted to the thermal behavior of each cell 10 of the block. For example, a type A composite is used for the cell(s) located in the center of the block, and a type B or type C composite is used for the cells located at the periphery of the block. Figure 4 illustrates an embodiment of the block shown in Figure 3.

[0176] As shown in Figure 4, a multiple selection of characteristics makes it possible to ensure temperature homogeneity within a block of cells 10.

[0177] A first selection advantageously concerns the material of the module 23 located in contact with the cells 10. As shown in FIG. 4, this material of the module 23 is in the form of a parallelepiped block, forming an individual composite module, provided with an axial hole 24, and can be selected for each cell 10. The material of the module 23 comprises, for example, a composite A, a composite B or a composite C. In the embodiment shown, the material of the module 23 extends along substantially the entire height of the cells 10. In other embodiments, the material of the module 23 is formed from at least two different materials, stacked along the height of the cells 10. The individual module 23 is thus laminated, allowing adaptation to a possible thermal gradient along the slenderness axis of the cell.

[0178] A second selection concerns the envelope. This second selection is advantageously combined with the first selection. In the embodiment shown, the envelope is formed of three superimposed elements, forming compartments 25, 26, 27. Each of the compartments 25, 26, 27 may be formed of a thermally conductive material, for example a metal alloy such as an aluminum alloy. In the embodiment shown in FIG. 4, the three compartments 25, 26, 27 are substantially identical. In other embodiments, one of the compartments has a greater thickness than that of the other compartments, this thickness being measured along the slenderness axis of the cells 10.

[0179] A third selection concerns the number and arrangement of cooling panels 22. This third selection is advantageously combined with the first selection and / or the second selection. In the embodiment shown in FIG. 4, the block comprises four substantially identical cooling panels 22, extending along the height of the cells 10, between two rows and between two columns of neighboring cells 10.

[0180] The panels 22 are thus arranged in two groups. In each group, the panels 22 are substantially parallel to each other. The panels of a first group are substantially perpendicular to the panels of the second group.

[0181] In the embodiment variant of Figure 5, the block comprises two substantially identical cooling panels 22, extending along the height of the cells 10, between two rows of neighboring cells 10. In this embodiment variant of Figure 5, the modules 23 are collective, collectively surrounding several cells 10, and comprise for example three passage holes for three cells 10. The cooling panels 22 extend between collective modules 23.

[0182] Advantageously, the modules 23 are different depending on the thermal state of the battery. Advantageously, the modules 23 are different per block within the battery.

[0183] Advantageously, the structure has a stratification by modules 23. For example, the stratification follows one of these combinations (from the lower layer to the upper layer, or from the upper layer to the lower layer): composite A - composite B - composite C; composite B - composite A - composite C; composite A - composite C - composite B; composite B - composite B' - composite B”; composite C - composite C' - composite C” composite A - composite B - composite B'; composite B - composite A - composite B'; composite A - composite

[0184] C - composite C'; composite C - composite A - composite C'; composite

[0185] C - composite B - composite B'; composite B - composite C - composite

[0186] B' ; composite B - composite C - composite C'; composite C - composite

[0187] B - composite C'.

[0188] Advantageously, the composite layers are composed of a mixture of at least one of the following composites: composite A; composite A'; composite A”; composite B; composite B'; composite B”; composite C; composite C'; composite C”. For example, a composite layer is: composite A+B; composite A+B'; composite A+B”; composite A+C; composite A+C', composite A+C”; composite A' + B'; composite A+B+C; composite A+B' + C; composite A+B+C'; composite A+B” + C; composite A+B'+C'; composite A+B'+C”; or composite A' + B'+C'.

[0189] Advantageously, the composite layers are different to ensure optimal management of the cells and to increase the lifespan of the cells.

[0190] Advantageously, a composite X' is different from composite X, such that composite X' has a different composition from X with a similar structure. X can be A, B or C.

[0191] Advantageously, the composite layers of the lamination have a particular shape, allowing nesting between the composite layers. Advantageously, the particular shape is composed of “male” triangles, “female” triangles, “male” rectangles, “female” rectangles, “male” pyramids, “female” pyramids, “male” cones, “female” cones, “male” columns, “female” columns, etc. For example, a first composite layer may have “male” triangles on a surface in contact with a second composite layer, while the second composite layer has “female” triangles on the surface in contact with the first composite layer.

[0192] Advantageously, when the phase change material is solid-liquid, the composite layers comprise at least two waterproof polymers for the MCPs.

[0193] Advantageously, the composite layers comprise at least three waterproof polymers for the MCPs.

[0194] Advantageously, the composite layers comprise at least four waterproof polymers for the MCPs. In the embodiment variant of Figure 6, the block comprises two substantially identical cooling panels 22, extending perpendicular to the slenderness axis of the cells 10, the material surrounding the cells 10 being formed of three modules 23, these three modules 23 being stacked along the slenderness axis of the cells 10. A panel 22 extends between two modules 23. Each module 23 is placed in a compartment 25, 26, 27.

[0195] Figure 7 shows a geometry of micro-channels 30 for circulation in the cooling panels 22, according to one embodiment. The micro-channels 30 comprise baffles (of variable dimensions), promoting heat exchanges. The micro-channels form micro-paths for heat exchange. The panels 22 allow the circulation of air or a cooling fluid.

[0196] Figure 8 shows a diagram of a hybrid thermal management for a cell 10. The cell 10 is surrounded by a sleeve formed by the stacking of at least two different composites. In the implementation shown, three rings 40, 41, 42 are stacked along the axis of the slenderness of the cell, each of the rings 40, 41, 42 being able to contain a composite A, or a composite B, or a composite C. A coil 50 wound in a helix around the sleeve formed by the rings 40, 41, 42 contains a heat transfer fluid.

[0197] The panels 22 or the coils 50 can be coupled to a micro-fluidic thermal control circuit based on heat transfer liquid.

[0198] Advantageously, each coil 50 or each layer of material 23 has a circuit independent of the other circuits.

[0199] In some implementations, the same heat transfer fluid circulates in each circuit with a controlled temperature and an exchange coefficient adapted to the power to be dissipated. For this, the optimized cooling circuit is connected to an intelligent thermal control system, in order to ensure the regeneration of the MCPs in each individual or collective module 23, according to the thermal cycles. These arrangements ensure homogenization of the temperature of the cells 1 0 and can mitigate conditions that could lead to a thermal runaway event of the batteries.

[0200] Advantageously, phase change materials are materials of natural origin.

[0201] Advantageously, the concentration of MCP is different from one layer of composites to another, while maintaining the same type of MCP.

[0202] Advantageously, the type of MCP is different from one layer of composites to another, while maintaining the same concentration of MCP.

[0203] Advantageously, the type of MCP and the concentration of MCP are different from one layer of composites to another.

[0204] Advantageously, in the same layer of composites there are at least two different types of MCP.

[0205] Advantageously, the microencapsulation of the MCPs of composite C is optimized according to the thermal state of the cell. For example, the composition of the microencapsulation can be of a different nature or of different thickness.

[0206] Advantageously, the microencapsulation of the MCPs of composite C has a multilayer structure. Advantageously, each layer that makes up the multilayer structure has a different function.

[0207] The results obtained will be presented with reference to figures 9 and following.

[0208] The results that will be presented concern the thermal phenomena in a Li-ion cell, and the sizing and optimization of a passive management system by an MCP-metal foam (MM) composite, the cell 10 being advantageously maintained at a temperature above 30°C under a stress of 1 C.

[0209] A test bench was developed to monitor the temperature evolution of a 10 Li-ion cell and its thermal flux released during stress.

[0210] The heat actually dissipated by cell 10 was calculated from the experimental results and using a calculation code developed in Matlab.

[0211] The simulation of the thermal behavior of MCP and MCP-metal foam composite MM is done under COMSOL Multiphysics and Matlab.

[0212] The experimental test bench is shown in Figure 9.

[0213] The electrochemical cell 10 studied, with a capacity of 2500 mAh, is connected to a direct current power supply which ensures charging and to an active load which ensures discharging. The cell 10 is cylindrical with a radius of 9.255 mm and a height of 70 mm.

[0214] Electromechanical relays are inserted, allowing the opening and closing of the electrical circuit. The surface temperature of cell 10 is measured by two T-type thermocouples. A cylindrical flux meter encases cell 10, to measure the dissipated heat flux as a function of time.

[0215] A LabVI EW program was developed to monitor battery charge / discharge cycles. It provides control of the relays, power supply and active load, as well as the acquisition of measured data.

[0216] The battery studied is suspended in order to avoid thermal exchanges by conduction between the surface of the battery and the external environment. The cell 10 studied is placed in an aluminum mold, shown in figure 10. The mold is in the form of two hollow coaxial aluminum cylinders, of height h and thickness e. The two cylinders form an inner tube (containing the cell) and an outer tube.

[0217] The inner tube is the same diameter as cell 10.

[0218] In the space between the inner and outer tube, the MCP with or without MM metal foam is inserted.

[0219] A groove is provided at the cell-internal tube interface, to house the temperature sensors and the flowmeter cables.

[0220] The mold sizing takes into account the volumetric expansion of the MCP. Aluminum is chosen for its good compromise between thermal properties, density and cost. In order to study the impact of the MCP mass, three molds with different thicknesses (3 mm, 5 mm and 7 mm) were manufactured. All the molds were manufactured by metal 3D printing.

[0221] Liquid paraffin is injected into the void designed to contain it. After filling, the assembly is cooled in the climatic chamber to a set temperature of 22°C.

[0222] Before inserting the 1 0 cell into the mold, protection of all connections is necessary, to avoid any direct contact between the aluminum mold and the accumulators.

[0223] In the case of a MM - MCP metal foam composite, the metal foam (e.g. MA aluminum foam) was cut by a laser cutting system into tubes of h*e dimension. The tubes are filled with paraffin following the vacuum impregnation protocol described above.

[0224] After filling and instrumentation, cell 10 and the mold are housed in a climatic chamber. The base of the mold is insulated by a layer of expanded polystyrene. To evaluate the effectiveness of the use of RT27 paraffin and the MA-RT27 composite and their ability to absorb the heat generated by cell 10 during the charge / discharge cycles, the evolution of the radial temperature was monitored at the interfaces, thanks to the four K-type thermocouples: T1, T2, T3 and T4, arranged according to Figure 11.

[0225] Thermocouple T1 is placed between cell 10 and the inner wall of the inner tube. Thermocouple T2 is placed between the outer wall of the inner tube and the composite. Thermocouple T3 is placed between the composite and the inner wall of the outer tube. Thermocouple T4 is placed on the outer wall of the outer tube.

[0226] Testing procedure and definition of the permanent regime

[0227] The tests were carried out for different currents and for a maximum voltage of 3.8V, without a break between two consecutive cycles. A cycle corresponds to a charge followed by a discharge. If the fully charged battery is discharged by a current of 2.5 A, it will reach its cut-off voltage after one hour of discharge. The tests are stopped once the steady state is reached. Indeed, the temperature increases at the beginning and tends towards a constant value which characterizes the steady state.

[0228] Evolution of cell temperature

[0229] Figure 1 2 shows the evolution of the temperature measured by the thermocouple T1 as a function of time. The results are presented for a 3 mm thick mold. For the three cases studied, namely natural convection (cell without thermal management system), RT27 paraffin and MA aluminum foam composite (porosity 0.93, pore density 40PPI) - RT27 paraffin, the results are obtained under the same conditions, namely: an imposed current of 1 C (2.6A) for ten charge / discharge cycles of 8 minutes. In the case of thermal management by pure RT27 paraffin and by a paraffin / MA aluminum foam composite, the imposed temperature is 22°C. For these cases, ventilation is active, to promote the heat exchange between the evaporator (condenser in the case of heating) and the air inside the climatic chamber.

[0230] The results show that the addition of a pure MCP or a MM-MCP composite allows to considerably reduce the temperature of the cell 1 0. In the case of management with pure RT27 paraffin or the MA-paraffin RT27 composite, the steady state is reached after two cycles compared to five cycles in the case of natural convection.

[0231] In steady state, the temperature of cell 1 0 with natural convection reached 36.7°C, compared to 26.5°C when pure RT27 paraffin was used and 25.6°C when a RT27 paraffin-Aluminum foam composite (0.93, 40PP I) was used.

[0232] Pure RT27 paraffin reduces cell temperature by 10.2°C (average steady-state deviation) and RT27 paraffin-MA aluminum foam composite (0.93, 40PPI) reduces cell temperature by 11.2°C (average steady-state deviation).

[0233] Temperature distribution without forced convection

[0234] In order to avoid thermal losses from cell 10 to the ambient air and to simulate the case where cell 10 is placed in a very confined place (battery module), tests without forced convection were carried out. The assembly is placed in the climatic chamber initially in thermal equilibrium at 22°C, isolated from any thermal exchange with the ambient environment.

[0235] Figures 13, 14 and 15 respectively present the evolution of the temperature measured by the four thermocouples T1, T2, T3, T4, in the case of thermal management by pure paraffin RT27, for mold thicknesses of e= 3mm, e= 5mm and e= 7mm, respectively. In Figures 13, 14 and 15, the evolutions of the temperatures measured by the thermocouples T2, T3 and T4 are substantially identical. The temperature curve measured by the thermocouple T1 (cell temperature) is separated from the three other superimposed curves T2, T3, T4 (PCM temperatures).

[0236] The results show the total melting of pure RT27 paraffin, in the case of a thickness of 3 mm, which leads to high temperatures compared to other cases. An underestimation of the amount of MCP to absorb the heat generated by cell 1 0 can therefore lead to high temperatures.

[0237] The difference between the cell temperature (T1) and the paraffin (T2) is inversely proportional to the thickness. The smallest difference is observed in the case of a thickness of 3 mm. Increasing the thickness of the paraffin increases the thermal resistance due to its low thermal conductivity, which leads to a less intense heat transfer in the case of a pure solid or a pure liquid.

[0238] Figure 1 6 represents the evolutions as a function of time of the cell temperature 1 0, without forced convection, with the use of pure paraffin RT27, for the three thicknesses of MCP considered (3 mm, 5 mm, 7 mm).

[0239] In the solid phase, a lower temperature is observed for a thickness e of 3 mm, compared to the other two cases. In addition, after the total melting of the RT27 paraffin, an inflection is observed at the level of the curve representing the evolution of the temperature of cell 10.

[0240] The evolution of temperatures T1, T2, T3, T4 in the case of a MM-MCP composite without forced convection was evaluated for thicknesses 3mm and 7mm. The results are presented in figures 17 (thickness 3mm) and 18 (thickness 7mm). The metal foam is an aluminum foam (MA). The results show that the addition of a MM metal foam made it possible to significantly reduce the temperature difference between cell 10 and the MM-MCP composite by improving the effective conductivity of the RT27 / Metal Foam composite.

[0241] The difference between T1 and T2 remains low for a MM-MCP composite thickness of 3 mm, of the order of 0.5°C (figure 1 7).

[0242] For a MCP thickness of 7 mm, the difference between the cell temperature T1 and the MCP temperature T2 is 2.5°C in the case of pure RT27 paraffin and 1.6°C in the case of MA-RT27 (figure 1 8). These results are in agreement with the results obtained by numerical study.

[0243] Temperature distribution, with forced convection

[0244] In order to test the effect of convection on the thermal state of cell 10, ventilation is activated, in order to ensure a homogeneous temperature in the climatic chamber (22°C).

[0245] Figures 19 and 20 respectively present the temporal evolution of the recorded temperature (T1, T2, T3, T4), for pure paraffin RT27, with a thickness e of 3 mm (figure 19) and a thickness e of 7 mm (figure 20).

[0246] The steady state is reached more quickly in the case of a thickness of 3 mm, with thermal homogeneity following the thickness (T2 = T3).

[0247] In both configurations studied, the paraffin was not completely melted at the end of the test. This can be attributed to thermal losses by forced convection.

[0248] The impact of the quantity of MCP used is evaluated for the three thicknesses studied (e= 3mm, e= 5mm and e= 7mm) in the case of an imposed ambient temperature with ventilation (forced convection). The tests are carried out under the same conditions: current 1 C (2.6A) for ten charge / discharge cycles of 8 minutes under an ambient temperature of 22°C.

[0249] Figure 21 shows the temporal evolution of the temperature of the surface of cell 10 measured by thermocouple T1, for the different thicknesses studied.

[0250] Increasing the thickness of the MCP has a negative impact on the thermal management of the cell 1 0. Indeed, the MCP has a low thermal conductivity, which reduces the intensity of heat transfer to the outside. In this case, this system must be combined with an active management system (air, heat transfer fluid).

[0251] Impact of adding metal foam and forced convection

[0252] The impact of the metal foam on the thermal state of cell 1 0 is evaluated for the mold e=3mm, without and with forced convection. The measurements of the temperature T1 are presented in Figure 22, without forced convection.

[0253] In this figure 22, we can see that the addition of the metal foam reduces the temperature of the cell 1 0 during the melting process. Indeed, the addition of a conductive foam intensifies the heat transfer. This gives - a priori - a greater impact in the case of the presence of forced convection.

[0254] To confirm or refute this, the temperature of cell 10 with pure RT27 paraffin was compared with that with a MA-RT27 composite (Figure 23, with forced convection). The comparison shows an average steady-state temperature difference of about 1.2°C between the temperature of cell 10 with pure RT27 and with the MA (0.93, 40PPI)-RT27 composite.

[0255] Figure 24 shows the time evolution of the temperature of cell 10 without and with forced convection in the case of a MA-RT27 composite, e=7mm. With forced convection, the steady state is reached after about 5 cycles, while with natural convection the temperature of cell 10 continues to increase. The temperature of cell 10 at the end of the test with insulation reaches 28.5°C, while that with convection reaches 26.3°C, a temperature difference of about 2.2°C.

[0256] Li-ion battery module thermal management

[0257] This section presents results obtained in the thermal management of a battery module composed of nine 10 Li-ion type cells assembled in 3S-3P.

[0258] The test protocol consists of a continuous discharge and charge cycle. The battery module is first discharged at a constant current of 6A to a minimum voltage of 8V, then recharged using the CC-CV method with a current of 6A to a maximum voltage of 12V.

[0259] In order to evaluate the temperature evolution within the module, a total of twenty thermocouples and fifteen flux meters are used. Only five cells 10 are instrumented. Before the installation of the flux meters and thermocouples, a thin layer of thermal grease is spread on the lateral surface of the cells 10 in order to facilitate the heat transfer to the flux meters and reduce the contact resistance.

[0260] Then, the 10 cells are placed in the climatic chamber where the temperature is set at 21.5°C; the Li-ion cells are then assembled in 3S-3P while maintaining a distance between cells of 3mm thanks to two 3D printed support plates.

[0261] Figure 25 shows the variation of the temperature and heat flow of the cells 1 0 when the module operates without a thermal management system (without MCP). It can be seen that the maximum temperature of the module is higher than 35°C, despite a forced convection system at a constant temperature of 21°C during charging and discharging.

[0262] Thermal management using MCP + Metal foam The MM metal foam composite / MCP phase change materials is introduced into the cell support mold.

[0263] The same tests as before are used (discharge-charge without pause). The temperature is maintained at 21.5°C, ventilation deactivated.

[0264] The experimental results show that the maximum temperature measured within the battery module is 27.8°C, with forced ventilation allowing the temperature to be reduced to a value of 25.22°C. It is also noted that the central cell always has the highest temperature within the module.

[0265] As for the flux densities, there is no major difference when the system is used without air convection and when air convection is activated (figures 26 and 27).

[0266] The invention has many advantages.

[0267] Advantageously, the invention makes it possible to provide a thermal management system for batteries, in particular Li-ion batteries, allowing the temperature of the batteries to be maintained below 40°C.

[0268] Advantageously, the invention makes it possible to provide a thermal management system for a battery, in particular a Li-ion battery, by using heat-conducting composites with phase change, allowing the battery temperature to be maintained close to the optimum operating temperature.

[0269] Advantageously, the invention makes it possible to provide a thermal management system for a battery, in particular a Li-ion battery, by using metal foams, conductive fillers and paraffins, allowing the cell temperature to be maintained between 15°C and 30°C.

[0270] Advantageously, the invention makes it possible to provide a thermal management system for a battery, in particular a Li-ion battery, preserving the durability of the battery and guaranteeing optimal operation for as long as possible. Advantageously, the invention makes it possible to provide a thermal management system for a battery, in particular a Li-ion battery, allowing uniformity of the temperature field in the battery.

[0271] Advantageously, the invention makes it possible to provide a thermal management system for a battery, in particular a Li-ion battery, making it possible to increase the lifespan of the battery and preserve its state of health.

[0272] A battery is thus proposed provided with at least one electrochemical cell and a composite material comprising a solid-liquid phase change material (PCM), the battery comprising a containing matrix surrounding the cell(s), and a diffusing matrix surrounding the containing matrix, the containing matrix comprising one or more blocks of composite material, each block of composite material surrounding at least one cell over at least part of its height.

[0273] The diffusing matrix and / or the containing matrix comprises at least two layers formed from different composite materials.

[0274] The composite materials are advantageously chosen from the group comprising: a composite A, comprising a heat-conducting foam containing a phase change material (PCM); a composite B, comprising a polymer matrix and a phase change material (PCM); a composite C, comprising a polymer matrix and an encapsulated phase change material (PCM).

[0275] The containing matrix surrounds the cell(s) and is thus directly subject to temperature increases of the cells, for example during rapid charging of the battery or during intensive use of an electric vehicle. Advantageously, a conductive material is placed between the containing matrix and the cells, for example a conductive grease. Heating of the cells causes the phase change of the PCM used in the containing matrix.

[0276] The risks of leakage of the liquid MCP are limited by the presence of the diffusing matrix, which surrounds the containing matrix. Advantageously, the diffusing matrix completely encompasses and envelops the containing matrix.

[0277] Alternatively or in combination, when the phase change material is solid-liquid, the composite of the containing matrix is ​​waterproof. By waterproof composite, here is meant a composite material comprising a solid-liquid MCP from which the MCP in the liquid state cannot substantially escape. The composite material has for example a very low porosity, in particular a very low interconnected porosity. In certain implementations, the MCP is encapsulated in the composite material, in particular micro-encapsulated in the composite material. In other embodiments, possibly combined, the composite material is enveloped by a waterproof wall, for example made of a metal alloy.

[0278] The presence of at least two layers in the containing matrix and / or the diffusing matrix, comprising different composite materials, allows adaptation to the heterogeneous thermal behavior of the cells.

[0279] When the cells have a slenderness axis, the layers of the containing matrix and / or the diffusing matrix extend substantially perpendicular to the slenderness axis of the cells. This arrangement makes it possible to take into account a thermal gradient of the cells according to their slenderness direction.

[0280] Advantageously, the MCPs contained in the layers of the diffusing matrix and / or the containing matrix have melting temperatures that are different from each other. Advantageously, the containing matrix and / or the diffusing matrix comprises heat-conducting fillers, chosen for example from the group comprising expanded graphite, copper, aluminum nitride.

[0281] Advantageously, the battery has air / liquid micro-exchangers which allow compartmentalization of the modules 23 and regeneration of the MCPs, the micro-exchangers being configured to create a thermal conduction bridge between the MCPs.

[0282] Advantageously, the micro-exchangers have optimized shapes to increase the efficiency (with a KPI “key performance indicator”) of the device.

[0283] Advantageously, the micro-exchangers have a given flow rate and circulation speed. Advantageously, the flow rate is adapted to the shape of the micro-exchangers and / or adapted to the thermal state of the cell and / or adapted to the number of cells.

[0284] Advantageously, the micro-exchangers are micro-channels in the direction of stratification and / or perpendicular to the plane of stratification.

[0285] Advantageously, the liquid circulating inside the micro-exchangers is air, water, or a heat transfer liquid. Advantageously, the liquid inside the micro-exchangers is changed / chosen according to the operating temperature and the usage constraints.

[0286] Advantageously, the system for activating the circulation of the fluid is based on a global management program, the input parameters of the program are multiple: temperature, volume expansion, etc.

[0287] An additional automated system may be associated to provide forced regeneration at a programmable time and temperature. The regeneration may be targeted, in identifiable blocks, by means of a network of sensors and actuators optimally located and managed by computer logic. Advantageously, the system of the present invention is coupled to another system. Advantageously, the system of the present invention transmits thermal energy to the coupled system. Advantageously, the system of the present invention is large enough to exploit the energy gain. For example, in the case of electric vehicles, the recovered heat is used to supplement the passenger compartment heating system.

[0288] The invention allows thermal management by zone of the battery, in particular for each group of cells. The invention thus allows a great homogeneity of temperature according to the height of each cell, or within a battery module. The invention makes it possible in particular to avoid the presence of a thermal gradient between the core of a battery and its periphery.

[0289] The invention significantly reduces the risk of MCP leakage in the liquid phase.

[0290] The invention makes it possible to maintain a battery, in particular a Li-ion battery, at a substantially uniform temperature, within the optimum operating range, advantageously between 15°C and 35°C for Li-ion batteries.

[0291] The thermal management system according to the invention is presented as a stratified energy absorber. Such a system finds particular application for batteries used in electric bicycles, electric scooters, and electric two-wheelers (scooters, motorcycles).

[0292] In one implementation, the thermal management system according to the invention is a hybrid MCP+ regeneration liquid cooling system, making it possible to significantly improve the durability of the batteries.

[0293] The invention finds advantageous application for electric vehicles, in particular motor vehicles or two-wheelers.

[0294] The invention also finds application in the cooling of microprocessors, or the conditioning of energy storage batteries in photovoltaic installations or solid hydrogen storage tanks.

[0295] Advantageously, the invention is used for batteries of energy storage systems, telecom devices, space devices, renewable energy devices, electronic devices such as power converters, Datacenters, electric vehicles, etc.

Claims

Demands 1. Battery comprising electrochemical cells (10) and composites (21) based on one or more solid-liquid or solid-solid phase change materials (PCMs), configured to implement a thermal management system for maintaining the temperature of one or more operating electrochemical cells (10) below a given temperature, characterized in that: - said composites (21) comprise one or more conductive materials and a sealed structure allowing the encapsulation of PCM when the PCM is solid-liquid, - the battery comprising several modules (23) each having a given composite (21) which is leak-proof when the PCM is solid-liquid, the composite modules (23) having: an individual configuration, in which each individual module (23) has an opening (24) allowing each individual module (23) to surround a part of an electrochemical cell (10) introduced into the opening (24), an electrochemical cell (10) being surrounded along its height by several superimposed individual modules (23), with at least two modules (23) which have different composites, this individual configuration being carried out for several cells (10); or a collective configuration, in which each collective module (23) has several openings (24) allowing each collective module (23) to surround a part of several adjacent electrochemical cells (10) introduced into the openings (24), according to one of the following two configurations: the cells (10) are surrounded along their height by several superimposed horizontal collective modules (23), with at least two modules (23) having different composites; or N cells are surrounded along their entire height by a single Nth vertical collective module composed of a composite N, and N+1 cells adjacent to the N cells are surrounded by a single Nth+1 vertical collective module composed of a composite N+1 different from the composite N, and wherein the battery has air and / or liquid micro-exchangers which include conductive plates and air and / or liquid microcircuits in the conductive plates (22), allowing compartmentalization of the modules (23) and regeneration of the MCPs, the micro-exchangers being configured to make a thermal conduction bridge between the MCPs and remove heat outside the battery.

2. Battery according to claim 1, wherein the battery has air and / or liquid micro-exchangers along plates advantageously parallel along the length of the MCP modules and / or perpendicular to each other, the plates being in contact with each other to evacuate the heat extracted by the MCPs outside the battery, in particular advantageously with inner plates located between the MCP modules to compartmentalize them and which are in contact with perpendicular plates located outside the MCP modules.

3. Battery according to claim 1 or 2, wherein the exchangers are hybrid and comprise conductive plates with phase change materials within their thickness, and micro-channels.

4. Battery according to any one of claims 1 to 3, in which the plates (22) are equipped with a system that controls the direction of flow, with valves to control the flow rates.

5. Battery according to any one of claims 1 to 4, wherein the plates (22) are equipped with two air / liquid flow circuits or first liquid / second liquid flow circuits.

6. Battery according to any one of claims 1 to 5, in which these plates (22) have openings to allow the passage of electrochemical cells (10).

7. Battery according to any one of claims 1 to 6, in which the battery comprises one or more compartments (25, 26, 27) for receiving and conforming to the shape of the modules (23) and the electrochemical cells (10), with: outer walls conforming to the outer perimeter of the modules (23) and inner walls whose dimensions are configured to be in contact on a first face with each inner wall of the openings (24) of the modules (23), and on a second face with the outer perimeter of the electrochemical cells (10).

8. Battery according to any one of claims 1 to 7, wherein the shape of the plates (22) is configured: with openings to allow the electrochemical cells (10) to pass through and to allow their placement perpendicular to the height of the electrochemical cells (10) in the compartment(s) (25, 26, 27), or to allow their placement parallel to the height of the electrochemical cells (10) in the compartment(s) (25, 26, 27), between adjacent electrochemical cells (10).

9. Battery according to any one of claims 1 to 8, wherein where the phase-change material is solid-liquid, said composites are sealed, and are selected from a composite A, a composite B, a composite C as defined: a composite A comprising a heat-conducting foam with at least one encapsulated PCM, wrapped in one or more sealed layers or of a composite (B) or of a composite (C), a composite B comprising a matrix with at least one polymer having heat-conducting fillers and at least one encapsulated MCP, a composite C comprising a matrix with at least one polymer having at least one MCP micro-encapsulated by at least one heat-conducting material, and which allows the MCP to be contained during its change of state.

10. Battery according to any one of claims 1 to 9, wherein the composites surrounding the electrochemical cells (10) located at the center of the battery are configured to have: a greater latent heat than the latent heat of the composites located at the edges of the battery; and / or heat-conducting materials having a heat conduction capacity greater than the heat conduction capacity of the heat-conducting materials of the composites located at the edges of the battery. 1 1. Battery according to any one of claims 1 to 1 0, wherein the electrochemical cells (1 0) are distributed in groups of adjacent electrochemical cells, and for at least one group of adjacent electrochemical cells, at least two different horizontal collective modules (23) surround all the adjacent electrochemical cells (10) of that group along their height or part of their height, the horizontal collective modules (23) being chosen for each group of adjacent electrochemical cells (10) according to the following possibilities: a collective module comprising a composite A and a collective module comprising a composite B; or a collective module comprising a composite A and a collective module comprising a composite C; or collective modules comprising a composite B, with variations in composition on the polymer matrices and / or conductive fillers and / or different PCMs;or collective modules comprising a C composite, with variations in composition on the polymer matrices and / or MCPs; different micro-encapsulated materials and / or a different heat-conducting micro-encapsulation material.

12. Battery according to any one of claims 1 to 11, wherein the electrochemical cells (10) are distributed in groups of electrochemical cells, each group of electrochemical cells having the same vertical collective module (23) over the entire height or part of their height of the group, different from another vertical collective module (23) of at least one other group of electrochemical cells over the entire height or part of their height of said group, the vertical collective modules (23) of composites being chosen according to the following possibilities: a collective module comprising a composite A and a collective module comprising a composite B; or a collective module comprising a composite A and a collective module comprising a composite C; or collective modules comprising a composite B, with variations in composition on the polymer matrices and / or conductive fillers and / or different PCMs;or collective modules comprising a composite C, with variations in composition on the polymer matrices and / or different micro-encapsulated MCPs and / or a different heat-conducting micro-encapsulation material.

13. Battery according to any one of claims 1 to 12, wherein the battery has different collective modules (23) to make horizontal and vertical compartments (25, 26, 27) around the electrochemical cells (10).

14. Battery according to any one of claims 1 to 13, having several electrochemical cells (10), each cell (10) being individually surrounded over its entire height by a module (23), the composites being chosen for each cell (10) according to its location relative to the other electrochemical cells (10) in the battery.

15. Battery according to any one of claims 1 to 14, wherein the microcircuits are different by module (23) surrounding the electrochemical cells (10) and / or according to the location of one or more electrochemical cells (10) in the module (23).

16. Battery according to any one of claims 1 to 15, in which, besides a group of electrochemical cells (10) surrounded by several modules, there is at least one group having electrochemical cells (10) without modules.

17. Battery according to any one of claims 1 to 16, wherein the exchangers conform to the shape of the cells.

18. Battery according to any one of claims 9 to 17, wherein: the heat-conducting foams are selected from the following list: aluminum foams, copper foams, nickel foams, graphite-based foams, any heat-conducting foams; and / or the conductive fillers or conductive materials encapsulating the MCPs are selected from the following list: fins, expanded graphite, heat-conducting fillers from recycled aluminum, copper, aluminum nitride, nano-silica; and / or the polymers are selected from the following list: HDPE, LDPE, SEBS, SEPS, SEP, PU, ​​PEG, PP, POE, SBS, EPDM, recycled polymers, biopolymers; and / or the MCPs are selected from the following list: RT paraffins, hexadecane, BioMCP® trademark, PureTemp® trademark, hydrated salts.

19. Battery according to any one of claims 9 to 17, wherein the Solid-Solid MCPs are selected from the following list: PEG4000, PEG6000, PEG8000, PU-SSPCM(PEG / 4'4-diphenylmethane diisocyanate), Polystyrene-g-PEG6000, Sorbitol / Dipentaerythritol / Inositol / PEG 20. Battery according to any one of claims 1 to 19, wherein the composites are chosen so that the temperature of the electrochemical cells (10) in operation is less than 40°C.

21. Battery according to any one of claims 7 to 20, wherein the walls of the compartment(s) (25, 26, 27) comprise different materials or a heat-conducting composite, for example these compartments being heat-conducting composites with one or more PCMs or hybrid micro-exchangers (PCM-micro-rings) or air or liquid micro-exchangers.

22. Battery according to any one of claims 9 to 21, wherein the composite B or C comprises several polymers.

23. Battery according to claim 22, wherein the composite B or C has • a mixture of polymers: SEBS and POE; SBS and EPDM; PEH D and SBS; • or a mixture of polymers chosen from the following list: SEBS, SEPS, SEP, PU, ​​PEG, PP, PEBD, PEHD.

24. System using a battery as defined in any one of claims 1 to 23, wherein the electrochemical cells (10) are of the lithium ion, lithium-manganese-cobalt (NMC), lithium-polymer (LiPo), lithium-iron-phosphate (LFP), lithium-cobalt-nickel-aluminium (NCA), lithium manganese (LMO), lithium-titanate (LTO), lithium-air, lithium-cobalt-oxide (LCO), lithium-sulfur (Li-S), lithium-metal-polymer (LMP), lithium-air, lithium-cobalt-oxide (LCO), sodium-ion (Na-ion), nickel-cadmium (Ni-Cd), or nickel-metal hydride (Ni-MH) type.

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