Thermal insulating mat for an electrical energy storage device

Abstract

There is described a thermal insulating member (8) for an electrical energy storage device (1), the thermal insulating member (8) has a layered configuration and comprises: a first layer (10) made of an elastomeric material including silicone elastomer; a second layer (11) coupled to the first layer and made of carbon fiber.

Description

[0001] THERMAL INSULATING MAT FOR AN ELECTRICAL ENERGY STORAGE DEVICE

[0002] Cross-Reference to Related Applications

[0003] This Patent Application claims priority from Italian Patent Application No . 102024000019459 filed on August 30 , 2024 , the entire disclosure of which is incorporated herein by reference .

[0004] Technical Field

[0005] The present invention relates to a thermal insulating member, in particular a thermal insulating mat , for an electrical energy storage device , more in particular for a battery pack having a housing and a plurality of battery cells enclosed within the housing .

[0006] Background Art

[0007] Battery cells are known, which are used as electrical energy accumulators .

[0008] In particular, so-called primary batteries are known, which cannot be easily recharged and are therefore destined to single-use , and so-called secondary batteries are known, which can be repeatedly charged after each cycle of usage .

[0009] Single-cell batteries of the secondary type are known which are used for various portable small-si zed electronic devices , such as cellular phones , watches , smartwatches , smart bands , etc .

[0010] Also , battery packs which include a plurality o f battery cells connected in series or in parallel are known, for example as increasingly used in the automotive industry .

[0011] The present invention will refer to a battery pack for the use in a hybrid or full-electric vehicle , for example an electric car, without however loss of generality .

[0012] A single battery cell typically comprises a hollow casing, for example in the shape of a hollow parallelepiped and usually made of metallic material , generally open on at least one side ( for example on the top ) and a lid for closing the casing .

[0013] The casing internally defines an inner compartment of the cell and houses the cell electrodes ( cathode and anode ) , which are provided for example in the form of sheets , and a separator material electrically interposed between the electrodes .

[0014] Within the compartment , the electrodes and the separator are immersed in an electrolytic material , usually liquid or gelatinous .

[0015] The lid is coupled to the housing at an opening thereof for closing the inner compartment in a fluid- tight manner, thereby maintaining electrodes and separator in place and preventing the outflow of the electrolytic material .

[0016] Typically, the lid carries the electrical poles , i . e . the positive and negative terminals of the respective battery cell which are configured to be connected with a consumer device to be powered by the battery pack .

[0017] A typical battery pack essentially comprises a housing and a plurality of such battery cells enclosed within the housing .

[0018] As it is known, the unlikely event of a so called "thermal runway" may occur for one or more battery cells of the battery pack .

[0019] During such a thermal runway event , gas developed within the battery cell may abruptly outflow from the casing thereof .

[0020] In some cases , the thermal runway event may lead to a development of a fire within the battery pack housing .

[0021] Such type of events may also occur without a development of a fire . However, the gases which outburst from the damaged cell may reach high temperatures .

[0022] Therefore , it must be ensured that either the flames or the hot gases ( or both) are at least temporarily contained within the housing, for example for a reasonable amount of time necessary for the fire rescue reaching the battery pack or for a driver to exit from the vehicle .

[0023] To this end, a typical battery pack is provided with a thermal insulating member, usually in the form of a mat , arranged within the housing and interposed between the lids of the battery cells and the upper inner wall of the housing facing the lids .

[0024] The thermal insulating mat is configured to withstand high temperatures , such as the temperature reached during a fire , and high pressure .

[0025] Hence , the thermal insulating mat defines a fire barrier element of the battery pack .

[0026] Typically, the thermal insulating mat comprises at least one layer comprising silicone elastomer . In some cases , such silicone layer may be reinforced with a metallic mesh and / or with basaltic compounds .

[0027] JP7416613B2 describes a multilayer sheet which reduces heat conduction between a plurality of heat sources , namely battery cells .

[0028] EP4024589A1 describes a battery protection composite construction, and in particular a thermal barrier assembly, having a multilayer structure configured for protect against thermal runway events .

[0029] Although the known thermal insulating members described above work satis fyingly well , the Applicant has observed that they are still open for further improvement , in particular as per their thermal insulating performance and as per their cost and ease of manufacturing .

[0030] Disclosure of Invention

[0031] It is therefore an obj ect of the present invention to provide a thermal insulating member for an electrical energy storage device , in particular a thermal insulating mat , which is designed to meet the above-mentioned need in a straightforward and low-cost manner .

[0032] This obj ect is achieved by a thermal insulating member for an electrical energy storage device as claimed in the appended independent claim 1 . Preferred embodiments of the present invention are laid down in the appended dependent claims .

[0033] Brief Description of the Drawings

[0034] Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings , in which : Figure 1 is a schematic, sectioned side view, with parts removed for clarity, of an electrical energy storage device , in particular a battery pack, comprising a thermal insulating member, in particular a thermal insulating mat , according to the present invention;

[0035] Figure 2a is a larger-scale , schematic crosssection, with parts removed for clarity, of the thermal insulating member according to a first preferred embodiment of the present invention;

[0036] Figure 2b is a larger-scale , schematic crosssection, with parts removed for clarity, of the thermal insulating member according to a second preferred embodiment of the present invention;

[0037] Figure 2c is a larger-scale , schematic crosssection, with parts removed for clarity, of the thermal insulating member according to a third preferred embodiment of the present invention .

[0038] Best Mode for Carrying Out the Invention

[0039] With reference to Figure 1 , number 1 indicates as a whole an electrical energy storage device , in particular a battery pack, to which the present description will refer without loss of generality .

[0040] In the following, the expressions "electrical energy storage device" and "battery pack" may be used interchangeably, without however loss of generality .

[0041] Battery pack 1 includes a housing ( or outer casing) 2 and a plurality of energy storage cells 3 , in particular battery cells , arranged within housing 2 , and in particular enclosed in housing 2 . Without loss of generality, battery pack 1 is preferably destined for the use in a vehicle , in particular a full-electric or hybrid vehicle , such as a car, a van, or the like .

[0042] In Figure 1 only a portion of housing 2 is shown . In particular, only a portion of an upper wall of housing 2 is shown .

[0043] It is stated that , in the following description, terms as "upper" and " lower" are to be intended as defined with respect to the direction of gravity, or with respect to a direction perpendicular to the ground, during use of the battery pack 1 .

[0044] Each battery cell 3 is of the known type and includes a casing which internally defines a compartment containing electrodes ( cathode and anode ) and a separator . The electrodes and the separator are immersed in an electrolytic solution .

[0045] In the preferred embodiment shown, each battery cell 3 is a prismatic battery cell , to which the present invention will refer without loss of generality .

[0046] However, each battery cell 3 may alternatively present a cylindric shape or any other shape .

[0047] Each battery cell 3 includes two electrical poles 4 , which define the positive and negative terminals of the cell .

[0048] The electrical poles 4 of each battery cell 3 are configured to be connected in series or in parallel to the electrical poles 4 of the other battery cells 3 .

[0049] Furthermore , the electrical poles 4 are configured to be connected with the connector of a consumer device ( such as an electric motor of a vehicle ) to be powered by the battery pack 1 .

[0050] Each battery cell 3 has a lid 5 coupled to the respective casing at an opening thereof for closing the inner compartment in a fluid-tight manner, thereby maintaining electrodes and separator in place and preventing the outflow of the electrolytic material .

[0051] In particular, electrical poles 4 are carried by lid 5 .

[0052] More in particular, electrical poles 4 protrude externally from lid 5 .

[0053] Each electrical pole 4 is connected to a respective electrode , according to a manner known and not described in detail .

[0054] Lid 5 is fixedly coupled to the casing of the battery cell 3 , preferably is welded thereto .

[0055] Each battery cell 3 further includes a safety venting port 6 , which is defined by a through hole obtained in lid 5 and is closed and sealed, during normal operation of the battery cell 3 , by a thin membrane , such as an aluminum foil .

[0056] The membrane defines a rupturable element which during a so-called thermal runway event ruptures , thereby allowing the gas (usually hot gas ) to outflow from the casing of battery cell 3 .

[0057] In a preferred embodiment , each venting port 6 has a substantially oval or elliptical shape .

[0058] However, venting port 6 may have a rectangular, circular or otherwise polygonal shape or elongated shape .

[0059] According to the non-limiting embodiment shown, electrical poles 4 are arranged at opposite longitudinal ends of lid 5 , and venting port 6 is arranged on lid 5 in between the electrical poles 4 .

[0060] In light of the above , each battery cell 3 has a lid 5 carrying the respective electrical poles 4 and on which the respective venting port 6 is obtained .

[0061] Preferably, battery pack 1 further comprises a support plate 7 which is arranged on top of the battery cells 3 .

[0062] In particular, support plate 7 rests on top of the lids 5 .

[0063] Support plate 7 i s configured to maintain the battery cells 3 in their predetermined positions .

[0064] Conveniently, support plate 7 is provided with openings 7a which are aligned to correspondingly venting ports 6 , so as to allow the passage of gas or flames therethrough .

[0065] In one embodiment , battery pack 1 may be devoid of support plate 7 , i . e . support plate 7 may not be present .

[0066] In the event of the aforementioned thermal runway occurring in one or more of the battery cells 3 , each venting port 6 allows (hot ) gas and / or flames to burst out of the casing of the relative battery cell 3 , thereby avoiding an explosion .

[0067] It is therefore desirable to provide a thermal and fire-proof insulation between the battery cells 3 and the aforementioned upper wall of the housing 2 , and in particular to an inner wall 2a of housing 2 facing the lids 5 ( and therefore the venting ports 6 ) of the battery cells 3 .

[0068] To this end, battery pack 1 further comprises a thermal insulating member 8 arranged within housing 2 and interposed between the battery cells 3 and inner wall 2a of housing 2 ( as schemati zed in Figure 1 ) .

[0069] Thermal insulating member 8 defines a fire barrier element of battery pack 1 and is configured to insulate thermally and in a fire-proof manner inner wall 2a from the battery cells 3 .

[0070] According to the preferred embodiment shown, thermal insulating member 8 has a substantially flat and planar configuration, thereby defining an insulating mat .

[0071] This allows for saving space and decreasing the overall si ze of the battery pack 1 , which is crucial in some applications like in hybrid or electric vehicles , especially in vehicles of small si ze .

[0072] In the following, the expressions "thermal insulating member" , "thermal insulating mat" and "mat" may be used interchangeably .

[0073] As visible in Figure 2a, thermal insulating mat 8 has a layered configuration and comprises a first layer 10 made of an elastomeric material including silicone elastomer .

[0074] Preferably, first layer 10 is made of silicone elastomer .

[0075] According to an important aspect of the present invention, thermal insulating mat 8 further comprises a second layer 11 coupled to first layer 10 and made of carbon fiber .

[0076] In particular, second layer 11 is defined by a fabric material made of carbon fibers woven with a predetermined orientation .

[0077] The Applicant has observed that the presence of a carbon fiber, and particularly a carbon fiber fabric layer, j ointly with the silicone elastomer layer in the thermal insulating mat 8 allows for enhancing the overall resistance to venting beams due to hot gases or flames coming from one of more venting ports 6 during a thermal runway event .

[0078] Moreover, the presence of a carbon fabric layer is particularly useful in case of adoption of high capacity NMC generations or solid-state Li-cells .

[0079] Furthermore , the overall mechanical resistance of mat 8 is increased due to the presence of carbon fibers . Speci fically, the Applicant has observed an improved resistance against hard particles produced during a thermal runway event .

[0080] In addition, the carbon fabric layer enables a lightweight construction of mat 8 , especially compared to other reinforcing layers known in the art such as metallic meshes or basaltic fillers , and consequently a more lightweight architecture of the entire battery module 1 .

[0081] As shown in Figure 2 a, first layer 10 has a first surface 10a configured to face , in use , battery cells 3 and a second surface 10b opposite to first surface 10a .

[0082] Second surface 10b faces , in use , inner wall 2a . Conveniently, second layer 11 is arranged on second surface 10b .

[0083] That is , second layer 11 is arranged on the side o f mat 8 which is opposite to lids 5 , venting ports 6 and, therefore , of hot gases and flames during a thermal runway event .

[0084] By means of an extensive empirical campaign, the Applicant has noted that such configuration represents the optimal compromise between thermal and fire resistance and cost and ease of manufacture .

[0085] Preferably, second layer 11 completely covers second surface 10a .

[0086] In this way, the insulation performance of mat 8 are even more improved and ensured .

[0087] According to a further aspect of the invention, second layer 11 is partially embedded in first layer 10 .

[0088] In detail , second layer 11 is partially embedded in first layer 10 at the second surface 10b thereof .

[0089] In other words , an outer surface of second layer 11 is not covered by first layer 10 and directly faces inner wall 2a without interposition of any part of first layer 10 .

[0090] In greater detail , while a portion ( and an inner wall ) of the second layer 11 is embedded in the silicone elastomer material of the first layer 10 , the other portion ( and the outer wall opposite the inner wall ) of the second layer 11 is arranged outside the silicone elastomer material of the first layer 10 .

[0091] This is schemati zed in Figure 2a . Thanks to the partially embedded arrangement of second layer 11 , an optimal compromise between ease of manufacturing process and insulation performance is obtained .

[0092] In fact , the woven "mesh" configuration of the carbon fabric may make it di fficult for the silicone elastomer to ef fectively penetrate inside the mesh of the fabric itsel f , making high compression forces necessary to obtain a total immersion . Accordingly, the partially embedded configuration according to the invention, solves this problem .

[0093] Moreover, the partial exposure of the carbon fabric due to the partially embedded configuration of second layer 11 , allows a better adhesion of the adhesive which is advantageously provided between the thermal insulating mat 8 and inner wall 2a of housing 2 . In fact , if the carbon fabric is completely immersed and embedded in the silicone elastomer , the aforementioned adhesive would have to be applied to the silicone , making it necessary to use a higher performance adhesive , which then entails higher production costs .

[0094] Ultimately, the embedding of second layer 11 in first layer 10 allows for avoiding a further adhesive for fixing second layer 11 on second surface 10b . This results in avoiding a further production step and also in a leaner and more robust construction of mat 8 . Also , the presence of a further adhesive may impact the insulation performance of mat 8 .

[0095] As said, first layer 10 comprises silicone elastomer .

[0096] Advantageously, first layer 10 is made of a silicone elastomer compound .

[0097] An example of silicone elastomer compound for first layer 10 may advantageously be one of the compounds disclosed in WO-A-2024028367 , from the same Applicant .

[0098] The silicone elastomer compound preferably includes high-temperature crosslinking silicone elastomer compound (HTV silicone elastomer compound) or a liquid silicone elastomer ( LSR) .

[0099] In one embodiment , first layer 10 may contain a first filler, the first filler being formed from organic material .

[0100] Such organic materials may include materials such as polyimides , thermosets , polyacrylonitrile ( PAN) , oxidi zed PAN, aramids , cotton or cellulose . These materials show high temperature stable properties and improve the resistance of the protective element to temperature loads .

[0101] Preferably, first filler comprises fibers . The elastomeric material serves as an elastomeric matrix and the fibers are bonded to the elastomeric matrix by vulcani zation . The fibers are present as a fiber mixture with fiber lengths between 2 pm and 50 mm and fiber diameters between 2 pm and 400 pm . The fibers are largely embedded in the matrix and 95% surrounded by the elastomer matrix .

[0102] In one embodiment , f irst layer 10 may contain a second filler, the second filler being formed from inorganic material. Inorganic fillers of a first group are, for example, glass or ceramics, in particular basalt, aluminum oxide, mullite or ZrO2. Inorganic fillers of a second group include, for example, oxides, hydroxides or oxide hydroxides. Minerals such as mica, silicates, alkaline earth carbonates or silicon dioxide are also conceivable. In principle, the second filler can be composed of a combination of the aforementioned materials .

[0103] Preferably, ATH (Aluminiumtrihydroxide) is used as a filler, which may be combined with different iron oxides (preferably Fe2O3) and silica (of different surface activity and structure including silicates) and often CaO. All variants of crystalwater and OH groups containing Metalhydxides may be used: ATH, A100H, Mg (OH) 2.

[0104] The first filler and / or the second filler may contain fillers in the form of fibers. The elastomeric material forms an elastomer matrix and the fibers are preferably bonded to the elastomer matrix by vulcanization.

[0105] This allows the advantageous properties of the fiber material to be combined with the advantageous properties of the elastomer matrix. The fibers preferably have a fiber length between 5 pm and 50 mm and a fiber diameter between 2 pm and 500 pm.

[0106] In one embodiment, the first filler and / or the second filler may also additionally comprise further fibers whose fiber length and / or fiber diameter lie outside the specified ranges. Preferably, all fibers of the first filler and / or the second filler have a fiber length and / or a fiber diameter in the specified range. Preferably, the fibers are at least 90% surrounded by the elastomer matrix, based on the sum of the surfaces of all fibers. The fibers preferably comprise organic material and / or inorganic material of the first group.

[0107] Preferably, such fibers are mostly inorganic: basalt fiber, glass fiber, special HT resistant silicate-glass fibers or mixtures thereof. Fibers like PAN oxidized PAN aramids, cotton or cellulose may be used too.

[0108] In one embodiment, the first filler and / or the second filler may contain fillers in the form of particles. The elastomeric material forms an elastomer matrix. Preferably, the particles are at least 90% surrounded by the elastomer matrix, based on the sum of the surfaces of all particles. The particles preferably have a spherical, platelet-shaped or amorphous shape. Furthermore, the particles preferably have endothermic properties. The endotherm can come about, for example, through a phase transition or through a chemical reaction. The desired temperature range for endothermy is between 100°C and 800°C. This allows the temperature properties of the protective element to be further improved. The particles preferably comprise inorganic material of the second group .

[0109] In one embodiment, first layer 10 may contain an adhesion promoter. In this embodiment, silanes or resins are preferably used as adhesion promoters. This makes it possible to achieve an improved connection of the first and / or second filler to the elastomer matrix. The Applicant has observed, through an extensive empirical campaign, that the thermal isolation and the flame resistance of thermal insulating mat 8 made of the aforementioned material is largely improved .

[0110] Thus , the safety degree of thermal insulating mat 8 is improved, as well as the overall safety of battery pack 1 and the vehicle in which battery pack 1 is installed, in use .

[0111] Figure 2b shows a second preferred embodiment of thermal insulating mat 8 according to the present invention . Since thermal insulating mat 8 according to such second embodiment is similar to the thermal insulating mat 8 according to the embodiment already described above , only the di f ferences between them will be described hereinafter, using same reference numbers for similar or corresponding parts .

[0112] In particular, thermal insulating mat 8 according to such second embodiment further comprises a third layer 12 coupled to first layer 10 and made of carbon fiber , particularly of carbon fiber fabric .

[0113] Third layer 12 is arranged on first surface 10a .

[0114] Hence , third layer 12 is opposite to second layer 11 .

[0115] Thanks to the presence of such third layer 12 , the thermal insulation properties and the fire-barrier performance of mat 8 are further improved .

[0116] Preferably, third layer 12 is similar, and in particular equal and corresponding, to second layer 11 , with the only di f ference that it is arranged on first surface 10a instead of second surface 10b .

[0117] Hence , also third layer 12 is conveniently partially embedded in first layer 10 , at first surface 10a . The advantages connected to such partially embedded configuration are the same as described above in connection with second layer 11 .

[0118] In one embodiment , the second layer 11 and the third layer 12 may not be partially embedded, i . e . they may not be embedded at all , in first layer 10 . Accordingly, second layer 11 and third layer 12 may be fixed, and in particular attached, onto the respective second surface 10b and first surface 10a of the first layer 10 .

[0119] Figure 2c shows a third preferred embodiment of thermal insulating mat 8 according to the present invention . Since thermal insulating mat 8 according to such third embodiment is similar to the thermal insulating mat 8 according to the second embodiment already described above , only the di f ferences between them will be described hereinafter, using same reference numbers for similar or corresponding parts .

[0120] In particular, thermal insulating mat 8 according to such third embodiment further comprises a fourth layer 13 made of carbon fiber, particularly of carbon fiber fabric .

[0121] Fourth layer 13 is completely embedded in first layer 10 , so as to be fully incorporated into first layer 10 , and so as to be arranged between second layer 11 and third layer 12 .

[0122] Conveniently, fourth layer 13 is arranged along a middle symmetry line of first layer 10 . Preferably, fourth layer 13 is similar, and in particular equal and corresponding, to second layer 11 and third layer 12 , with the only di f ference that it is arranged within first layer 10 .

[0123] Thanks to the presence of such fourth layer 13 , the insulation properties and the fire-barrier performance of mat 8 are even further improved, albeit entailing a slight increase in production costs and time compared to the second embodiment .

[0124] The advantages of thermal insulating member 8 , i . e . of thermal insulating mat 8 , according to the present invention will be clear from the foregoing description .

[0125] In particular, thanks to the presence of a carbon fiber fabric layer j ointly with the silicone elastomer layer the overall resistance of mat 8 to venting beams due to hot gases or flames coming from one of more venting ports 6 during a thermal runway event is enhanced .

[0126] Furthermore , the overall mechanical resistance of mat 8 is increased due to the presence of carbon fibers . Speci fically, the Applicant has observed an improved resistance against hard particles produced during a thermal runway event .

[0127] In addition, the carbon fabric layer enables a lightweight construction of mat 8 , especially compared to other reinforcing layers known in the art such as metallic meshes , and consequently a more lightweight architecture of battery module 1 .

[0128] Moreover, the partially embedded configuration of the carbon fabric layer into the silicone layer allows to obtain an optimal compromise between ease of manufacturing process and insulation performance . In fact , the woven "mesh" configuration of the carbon fabric would make it di f ficult for the silicone elastomer to ef fectively penetrate inside the mesh of the fabric itsel f , making high compression forces necessary to obtain a total immersion . Moreover, the partial exposure of the carbon fabric , due to the partially embedded configuration of second layer 11 , allows a better adhesion of the adhesive which is advantageously provided between the thermal insulating mat 8 and inner wall 2a of housing 2 . In fact , i f the carbon fabric is completely immersed and embedded in the silicone elastomer, the aforementioned adhesive would have to be applied to the silicone , making it necessary to use a higher performance adhesive , which then entails higher production costs . Ultimately, the embedding of second layer 11 in first layer 10 allows for avoiding a further adhesive for fixing second layer 11 on second surface 10b . This results in avoiding a further production step and also in a leaner and more robust construction of mat 8 . Also , the presence of a further adhesive may impact the insulation performance of mat 8 .

[0129] Clearly, changes may be made to thermal insulation mat 8 as described herein without , however, departing from the scope of protection as defined in the accompanying claims .

Claims

CLAIMS1.- Thermal insulating member (8) for an electrical energy storage device (1) , the thermal insulating member (8) having a layered configuration and comprising:- a first layer (10) made of an elastomeric material including silicone elastomer;- a second layer (11) coupled to the first layer and made of carbon fiber; wherein the second layer (11) is partially embedded in the first layer (10) .2.- Thermal insulating member as claimed in claim 1, wherein the second layer (11) is defined by a fabric material made of carbon fibers woven with a predetermined orientation .3.- Thermal insulating member as claimed in claim 1 or 2, wherein the first layer (10) has a first surface (10a) configured to face, in use, electrical energy storage cells (3) of said electrical energy storage device (1) , and a second surface (10b) opposite to the first surface (10a) ; and wherein the second layer (11) is arranged on said second surface (10b) .4.- Thermal insulating member as claimed in claim 3, wherein the second layer (11) completely covers said second surface (10b) .5.- Thermal insulating member as claimed in claim 3 or 4, and comprising a third layer (12) coupled to the first layer (10) and made of carbon fiber, the third layer(12) being arranged on said first surface (10a) .6.- Thermal insulating member as claimed in claim 5, and comprising a fourth layer (13) made of carbon fiber, the fourth layer (13) being completely embedded in the first layer (10) so as to be fully incorporated into the first layer (10) , and so as to be arranged between the second layer (11) and the third layer (12) .7 Thermal insulating member as claimed in any one of the foregoing claims, wherein the first layer (10) comprises a first filler and a second filler, wherein the first filler is formed from inorganic material and the second filler is formed from organic material ; and / or wherein the first filler and / or the second filler contains fillers in fiber form; and / or wherein the first filler and / or the second filler contains fillers in particle form.8.- Thermal insulating member as claimed in any one of the foregoing claims, wherein the thermal insulating member (8) has a substantially flat and planar configuration, thereby defining an insulating mat.9.- Thermal insulating member (8) for an electrical energy storage device (1) , the thermal insulating member (8) having a layered configuration and comprising:- a first layer (10) made of an elastomeric material including silicone elastomer;- a second layer (11) coupled to the first layer and made of carbon fiber; wherein the first layer (10) has a first surface(10a) configured to face, in use, electrical energy storage cells (3) of said electrical energy storage device (1) , and a second surface (10b) opposite to the first surface (10a) ; wherein the second layer (11) is arranged on said second surface (10b) ; wherein the thermal insulating member (8) further comprises :- a third layer (12) coupled to the first layer (10) and made of carbon fiber, the third layer (12) being arranged on said first surface (10a) ;- a fourth layer (13) made of carbon fiber, the fourth layer (13) being completely embedded in the first layer (10) so as to be fully incorporated into the first layer (10) , and so as to be arranged between the second layer (11) and the third layer (12) .10.- Electrical energy storage device (1) comprising a housing (2) , a plurality of electrical energy storage cells (3) arranged within the housing (2) , and a thermal insulating member (8) as claimed in any one of the foregoing claims, the thermal insulating member (8) being arranged within the housing (2) and being interposed between the electrical energy storage cells (3) and an inner wall (2a) of the housing (2) for defining a fire barrier element of the electrical energy storage device (1) configured to insulate thermally and in a fire-proof manner said inner wall (2a) from the electrical energy storage cells (3) .

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