Battery pack multilayer thermal barrier

Abstract

The invention provides a battery pack multi-layer thermal barrier. A multi-layer thermal barrier for a traction battery pack includes an inner sandwich structure provided by first and second ceramic layers sandwiching a core layer, and first and second foam layers sandwiching the inner sandwich structure. The core layer may be glass or mica. A mica layer may be positioned between the inner sandwich structure and the foam layer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 585,443, filed on September 26, 2023, and incorporated herein by reference. This application additionally claims the benefit of U.S. Provisional Application No. 63 / 594,623, filed on October 31, 2023, and incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to thermal barriers for use within battery packs, and more particularly to multi-layer thermal barriers. Background Art

[0004] The battery pack may include a cell stack having a plurality of battery cells. Within the cell stack, the mica layer may be positioned between the battery cell groups. The mica layer may slow down heat propagation between the battery cell groups.

[0005] For example, referring to FIG1 , a prior art battery pack includes a cell stack having a plurality of battery cells 2. The prior art thermal barrier 4 includes a mica layer 6 disposed between the groups of battery cells 2. A foam layer 8 positioned on opposite sides of the mica layer 6 can accommodate the expansion of the battery cells 2. Summary of the invention

[0006] In some aspects, the technology described herein relates to a multilayer thermal barrier for a traction battery pack, comprising: an inner sandwich structure provided by first and second ceramic layers sandwiching a core layer; and first and second foam layers sandwiching the inner sandwich structure.

[0007] In some aspects, the technology described herein relates to a multi-layer thermal barrier in which the core layer is glass.

[0008] In some aspects, the technology described herein relates to a multi-layer thermal barrier in which the core layer is mica.

[0009] In some aspects, the technology described herein relates to a multi-layer thermal barrier in which a first ceramic layer and a second ceramic layer are each thinner than a core layer.

[0010] In some aspects, the technology described herein relates to a multi-layer thermal barrier in which a first ceramic layer and a second ceramic layer are adhesively secured directly to a core layer.

[0011] In some aspects, the technology described herein relates to a multilayer thermal barrier, which also includes a first mica layer and a second mica layer, wherein the first mica layer is disposed between the first ceramic layer and the first foam layer, and the second mica layer is disposed between the second ceramic layer and the second foam layer.

[0012] In some aspects, the technology described herein relates to a multi-layer thermal barrier in which the core layer is a third mica layer.

[0013] In some aspects, the technology described herein relates to a multi-layer thermal barrier in which the core layer is glass.

[0014] In some aspects, the technology described herein relates to a multilayer thermal barrier wherein the first mica layer is adhesively secured to both the first foam layer and the first ceramic layer, wherein the second mica layer is adhesively secured to both the second foam layer and the second ceramic layer.

[0015] In some aspects, the technology described herein relates to a multi-layer thermal barrier, wherein the first foam layer is a first polyurethane foam layer, wherein the second foam layer is a second polyurethane foam layer.

[0016] In some aspects, the technology described herein relates to a traction battery pack assembly having a multi-layer thermal barrier and also including a cell stack having a plurality of battery cells arranged along an axis of the cell stack, the multi-layer thermal barrier being axially positioned between at least one first battery cell of the plurality of battery cells and at least one second battery cell of the plurality of battery cells.

[0017] In some aspects, the technology described herein relates to a traction battery pack assembly, comprising: a cell stack, the cell stack comprising at least one first battery cell, at least one second battery cell, and a multi-layer thermal barrier assembly, the multi-layer thermal barrier assembly being arranged to limit the transfer of thermal energy between the at least one first battery cell and the at least one second battery cell, the multi-layer thermal barrier assembly comprising an inner sandwich structure sandwiched between a first foam layer and a second foam layer.

[0018] In some aspects, the technology described herein relates to a traction battery pack assembly in which an inner sandwich structure includes a first ceramic layer and a second ceramic layer sandwiching a core layer.

[0019] In some aspects, the technology described herein relates to a traction battery pack assembly wherein the core layer is mica.

[0020] In some aspects, the technology described herein relates to a traction battery pack assembly in which the core layer is glass.

[0021] In some aspects, the technology described herein relates to a traction battery pack assembly wherein the at least one first battery cell includes four first battery cells and wherein the at least one second battery cell includes four second battery cells.

[0022] In some aspects, the technology described herein relates to a traction battery pack assembly, which also includes a first mica layer and a second mica layer, wherein the first mica layer is disposed between the inner sandwich structure and the first foam layer, and the second mica layer is disposed between the inner sandwich structure and the second foam layer.

[0023] In some aspects, the technology described herein relates to a traction battery pack assembly wherein the inner sandwich structure includes a third mica layer.

[0024] The embodiments, examples and alternatives of the preceding paragraphs, claims or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in conjunction with one embodiment apply to all embodiments, unless such features are incompatible. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a schematic side view of a portion of a prior art battery cell stack including a thermal barrier.

[0026] Figure 2 An electrified vehicle is schematically shown.

[0027] Figure 3 Shows Figure 2 Traction battery packs for electrified vehicles.

[0028] Figure 4 Shows Figure 3 The cell stack of the traction battery pack.

[0029] Figure 5 Shows Figure 4 A close-up view of an area of ​​a battery cell stack.

[0030] Figure 6 The exemplary embodiment according to the present disclosure is shown Figure 5 A perspective view of the multi-layer thermal barrier assembly of a battery cell stack.

[0031] Figure 7 yes Figure 6 Schematic end view of a multi-layer thermal barrier assembly.

[0032] Figures 8 to 23 Multilayer thermal barriers according to other exemplary embodiments of the present disclosure are shown. DETAILED DESCRIPTION

[0033] The present disclosure details a multi-layer thermal barrier assembly for a traction battery pack. The multi-layer thermal barrier assembly can inhibit the transfer of thermal energy within the traction battery pack. In some embodiments, the multi-layer thermal barrier provides a barrier to effluent particles as well as heat dissipation and thermal insulation to contain thermal energy and delay or stop heat propagation between battery cell packs. The multi-layer thermal barrier can extend the time for thermal energy to be transferred through the thermally conductive connection. This may result in a longer propagation time or at least a delay in heat propagation to the cells within the battery cell stack.

[0034] Figure 2An electrified vehicle 10 is schematically shown. The electrified vehicle 10 may include any type of electrified powertrain. In one embodiment, the electrified vehicle 10 is a battery electric vehicle (BEV). However, the concepts described herein are not limited to BEVs and may be extended to other electrified vehicles, including but not limited to hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles, etc. Therefore, although not specifically shown in the exemplary embodiment, the powertrain of the electrified vehicle 10 may be equipped with an internal combustion engine, which may be employed alone or in combination with other power sources to propel the electrified vehicle 10.

[0035] In the illustrated embodiment, the electrified vehicle 10 is depicted as an automobile. However, the electrified vehicle 10 may alternatively be a sport utility vehicle (SUV), a van, a pickup truck, or any other vehicle configuration. Although specific component relationships are shown in the drawings of the present disclosure, the drawings are not intended to limit the present disclosure. The placement and orientation of the various components of the electrified vehicle 10 are shown schematically and may vary within the scope of the present disclosure. In addition, the various drawings attached to the present disclosure are not necessarily drawn to scale, and some features may be enlarged or minimized to emphasize certain details of a particular component or system.

[0036] In one embodiment, the electrified vehicle 10 is a pure electric vehicle that is propelled solely by electricity, such as by one or more electric machines 12, without any assistance from an internal combustion engine. The electric machines 12 can operate as electric motors, generators, or both. The electric machines 12 receive electricity and can convert the electricity into torque for driving one or more wheels 14 of the electrified vehicle 10.

[0037] The voltage bus 16 may electrically couple the electric machine 12 to a traction battery 18. The traction battery 18 is an exemplary electrified vehicle battery. The traction battery 18 may be a high voltage traction battery assembly that includes a plurality of battery cell groups capable of outputting electrical power to power the electric machine 12 and / or other electrical loads of the electrified vehicle 10. Other types of energy storage devices and / or output devices may alternatively or additionally be used to power the electrified vehicle 10.

[0038] The traction battery pack 18 may be secured to an underbody 20 of the electrified vehicle 10 . However, in other examples, the traction battery pack 18 may be located elsewhere in the electrified vehicle 10 .

[0039] Figures 3 to 5Additional details associated with the traction battery pack 18 of the electrified vehicle 10 are shown. The traction battery pack 18 may include one or more cell stacks 22 (e.g., one is shown) housed within an interior area 30 of a housing assembly 24. The housing assembly 24 of the traction battery pack 18 may include a housing cover 26 and a housing tray 28. The housing cover 26 is vertically positioned above the housing tray 28. However, the housing cover 26 may be disposed below or to the side of the housing tray 28. Various terms such as "above," "below," "top," and "bottom" are used in the various figures with respect to the arrangement of components of the traction battery pack 18 and should not be considered limiting in other ways. These terms are in reference to the general orientation of the traction battery pack 18 when mounted on the electrified vehicle 10 of FIG. For purposes of this disclosure, vertical also refers to the ground and how the traction battery pack 18 is oriented when mounted on the electrified vehicle 10.

[0040] The housing cover 26 may be secured (e.g., bolted, welded, adhered, etc.) to the housing tray 28 to provide an interior area 30 for housing the cell stack 22 and other battery internal components (e.g., bus bars, control modules and other electronic devices, etc.) of the traction battery pack 18. The size, shape, and configuration of the housing assembly 24 may vary within the scope of the present disclosure.

[0041] Each stack 22 may include a plurality of individual battery cells 32 arranged together along a stack axis A between opposing end plates 48 . The battery cells 32 store and supply electrical power to power various components to support electric propulsion of the electrified vehicle 10 .

[0042] In one embodiment, the battery cells 32 are lithium-ion pouch cells. However, within the scope of the present disclosure, battery cells having other geometries (prismatic, cylindrical, etc.) and / or chemistries (nickel-metal hydride, lead acid, etc.) may alternatively be utilized.

[0043] Although a specific number of cell stacks 22 and battery cells 32 are shown in the various figures of this disclosure, the traction battery pack 18 may include any number of cell stacks 22 , with each cell stack 22 having any number of individual battery cells 32 .

[0044] Each battery cell 32 may include a first face 34, a second face 36 opposite the first face 34, a first end 38, a second end 40 opposite the first end 38, a top side 42, and a bottom side 44 opposite the top side 42. The first face 34 and the second face 36 establish a major side surface of the battery cell 32, and the first end 38, the second end 40, the top side 42, and the bottom side 44 establish a minor side surface of the battery cell 32. Thus, the first face 34 and the second face 36 present a larger surface area than any of the first end 38, the second end 40, the top side 42, and the bottom side 44.

[0045] Tab terminals 46 protrude outwardly from each of the first end 38 and the second end 40 of the battery cells 32. Thus, the battery cells 32 may be considered to be "sideways oriented" within the cell stack 22. The tab terminals 46 may be connected to bus bars (not shown) to electrically connect the battery cells 32 of each cell stack 22.

[0046] The cell stacks 22 include one or more multi-layer thermal barrier assemblies 60 arranged along the respective cell stack axis A of each cell stack 22. In one embodiment, groups of four individual battery cells 32 are separated by the multi-layer thermal barrier assemblies 60 along the cell stack axis A. However, other configurations are contemplated within the scope of the present disclosure, and it should be apparent to those having the benefit of the present disclosure that the cell stacks 22 may include any number and any arrangement of battery cells 32 and multi-layer thermal barrier assemblies 60.

[0047] The battery cells 32 can be arranged so that the faces 34, 36 of one battery cell 32 are in direct contact with one of the faces 34 or 36 of an adjacent battery cell 32 or an adjacent thermal barrier assembly 60 of the cell stack 22. The battery cells 32, thermal barrier assembly 60, and cell expansion pad 62 can be held in compression relative to each other within the cell stack 22 to provide a face-to-face arrangement. For example, the compression can be applied by the end plates 48 of the cell stack 22. However, other configurations are contemplated within the scope of the present disclosure.

[0048] refer to Figure 7 And continue to refer to Figures 2 to 6 In this example, the multilayer thermal barrier 60 includes an inner sandwich structure 62 provided by a core layer 64 sandwiched between a first ceramic layer 66 and a second ceramic layer 68. The multilayer thermal barrier 60 has an inner sandwich structure 62 sandwiched between a first foam layer 70 and a second foam layer 72.

[0049] In this example, the core layer 64 is a glass silicone layer approximately 0.5 mm thick. The first ceramic layer 66 and the second ceramic layer 68 are both thinner than the core layer 64. The first ceramic layer 66 and the second ceramic layer 68 can be directly adhesively secured to the core layer 64 using, for example, adhesive tape.

[0050] In a variation of the multi-layer thermal barrier 60, the core layer 64 may be a mica layer rather than glass silicone.

[0051] The first foam layer 70 and the second foam layer 72 may accommodate expansion of the battery cell 32 along the axis A. The first foam layer 70 and the second foam layer 72 may be polyurethane foams. The first foam layer 70 and the second foam layer 72 may have a smaller vertical height than other portions of the multi-layer thermal barrier 60 .

[0052] The exemplary multilayer thermal barrier 60 additionally includes a first mica layer 76 and a second mica layer 78. The first mica layer 76 is disposed between the first ceramic layer 66 and the first foam layer 70. The second mica layer is disposed between the second ceramic layer 68 and the second foam layer 72.

[0053] The first mica layer 76 may be adhesively secured directly to both the first foam layer 70 and the first ceramic layer 66 , and the second mica layer 78 may be adhesively secured to both the second foam layer 72 and the second ceramic layer 68 .

[0054] Now combine Figures 8 to 18 Additional exemplary embodiments of multilayer thermal barriers 60 are described. Some exemplary multilayer thermal barriers may include layers of intumescent heat absorbing aerogel in a sandwich configuration. The multilayer thermal barriers may also include fiberglass, steel, graphene layers, or some combination of these. Adhesives such as tape may be used to join the layers.

[0055] The intumescent material in some of these examples can be activated in response to a thermal event in one or more battery cells when the temperature exceeds 200° C. In some of these examples, the aerogel layer is endothermic in nature and can absorb thermal energy during a thermal event and can contain a portion of the convective effects of the hot gas to minimize impacts on adjacent cells.

[0056] The metal layer and / or graphene layer in some of these examples helps to dissipate the thermal energy and distribute the thermal energy on the heat absorbing aerogel layer to activate the heat absorbing aerogel layer.

[0057] Examples including a mica outer layer may rely on the layer to provide a barrier to cell particle outflow that may be expelled from one or more of the battery cells 32 during a thermal event.

[0058] refer to Figure 8 Another exemplary embodiment of a multi-layer thermal barrier 80 for use in a battery pack 18 includes two aerogel layers 81, 82 sandwiched between steel layers 83, 84. Foam layers 85, 86 sandwich the aerogel layers 81, 82 and the steel layers 83, 84.

[0059] refer to Fig. 9 Another exemplary embodiment of a multi-layer thermal barrier 90 for use in a battery pack 18 includes three mica layers 91, 92, 93 alternating with fiberglass layers 94, 95. The mica layers 91, 92, 93 and the fiberglass layers 94, 95 are sandwiched between foam layers 96, 97.

[0060] refer to Fig.10Another exemplary embodiment of a multi-layer thermal barrier 100 for use in a battery pack 18 includes an adhesive layer 101 , which may be a glass silicone tape with an adhesive backing, sandwiched between foam layers 102 , 103 .

[0061] refer to Fig.11 Another exemplary embodiment of a multi-layer thermal barrier 110 for use in a battery pack 18 includes a steel layer 111 and two aerogel layers 112 , 113 sandwiched between foam layers 114 , 115 .

[0062] refer to Fig.12 Another exemplary embodiment of a multi-layer thermal barrier 120 for use in a battery pack 18 includes a ceramic layer 121 sandwiched between two steel layers 122, 123, which are then sandwiched between foam layers 125, 126. The multi-layer thermal barrier 120 may also include a PET film layer.

[0063] refer to Fig.13 Another exemplary embodiment of a multi-layer thermal barrier 130 for use in a battery pack 18 includes a ceramic layer 131 sandwiched between two soft mica layers 132 , 133 , which are then sandwiched between foam layers 134 , 135 .

[0064] refer to Fig.14 Another exemplary embodiment of a multilayer thermal barrier 140 for use in a battery pack 18 includes a mica layer 141, which may be hard mica, sandwiched between PET / graphene layers 142, 143 and aerogel layers 144, 145, which are then sandwiched between foam layers 146, 147. The mica layer 141 extends outwardly from the axis A of the battery cell stack 22 through the PET / graphene layers 142, 143. The mica layer 141 provides a picture frame structure around the PET / graphene layers 142, 143. The PET / graphene layers 142, 143 can be laminated together.

[0065] When a multi-layer thermal barrier (such as multi-layer thermal barrier 140) has a picture frame structure, the frame layer (here, mica layer 141) extends outward beyond another inner layer. The inner layer, PET / graphene layer 142, 143 can be embedded in the frame layer. The edges of the inner layer (which can be sharp) are protected by the frame layer. This configuration omits the tape, which can save space.

[0066] refer to Fig.15, another exemplary embodiment of a multilayer thermal barrier 150 for use in a battery pack 18 includes a hard mica layer 151 sandwiched between PET / steel layers 152, 153 and then aerogel layers 154, 155. These layers are then sandwiched between foam layers 156, 157. The hard mica 151 and aerogel layers 154, 155 extend outwardly from the axis A of the battery cell stack 22 through the PET / steel layers 152, 153. The mica 151 and aerogel layers 154, 155 provide a picture frame structure around the PET / steel layers 152, 153.

[0067] refer to Fig.16 Another exemplary embodiment of a multi-layer thermal barrier 160 for use in a battery pack 18 includes a hard mica layer 161 sandwiched between steel layers 162 , 163 and soft mica layers 164 , 165 , which are then sandwiched between foam layers 166 , 167 .

[0068] refer to Fig.17 , another exemplary embodiment of a multilayer thermal barrier 170 for use in a battery pack 18 includes an aerogel layer 171 sandwiched between steel layers 172, 173 and soft mica layers 174, 175. These layers are then sandwiched between foam layers 176, 177. The soft mica layers 174, 175 and the aerogel layer 171 extend outwardly from the axis A of the battery cell stack 22 through the steel layers 172, 173. The soft mica layers 174, 175 and the aerogel layer 171 provide a picture frame structure around the steel layers 172, 173.

[0069] refer to Fig.18 , another exemplary embodiment of a multilayer thermal barrier 180 for use in a battery pack 18 includes dual aerogel layers 181, 182 sandwiched between graphene layers 183, 184, steel layers 185, 186, and then PET layers 187, 188. These layers are then sandwiched between two foam layers 189.

[0070] Reference now Figures 19 to 23 , other exemplary multilayer thermal barriers may include at least one heat absorbing glass silicone layer sandwiched between layers of another material. The heat absorbing layer may be activated in response to a thermal event in one or more battery cells when the temperature exceeds 200°C. The aerogel layer is endothermic in nature and may absorb thermal energy during a thermal event and may contain a portion of the convective effect of the hot gas to minimize the impact on adjacent cells.

[0071] The ceramic coating and the glass silicone layer can help dissipate the thermal energy and distribute the thermal energy over the heat absorbing aerogel layer to activate the heat absorbing aerogel layer.

[0072] refer to Fig.19Another exemplary embodiment of a multilayer thermal barrier 190 for use in a battery pack 18 includes a square mica layer 191 sandwiched between hard mica layers 192, 193 and then foam layers 194, 195. The square mica layer 191 may include a mica material or heat absorbing filler surrounded by air gaps, such as a mixture of sodium silicate (40% to 65%) and aluminum nitride (25% to 35%), or a mixture of sodium silicate (40% to 65%) and aluminum oxide (25% to 35%). The foam layers 194, 195 do not extend as far from the axis A as the other layers.

[0073] refer to Fig. 20 Another exemplary embodiment of a multilayer thermal barrier 200 for use in a battery pack 18 includes a heat absorbing bag layer 201 sandwiched between hard mica layers 202, 203 and then foam layers 204, 205. The heat absorbing bag layer 201 includes a bag made of, for example, polyimide or polyethylene terephthalate, filled with a heat absorbing material such as, for example, sodium silicate. The bag of the heat absorbing bag layer 201 may additionally include foam and electrically insulating materials such as aluminum nitrate and aluminum oxide. The foam layers 204, 205 do not extend as far as the other layers.

[0074] refer to Fig.21 , another exemplary embodiment of a multi-layer thermal barrier 210 for use in a battery pack 18 includes a mica layer 211 sandwiched between ceramic layers 212, 213, which is then sandwiched between other mica layers 214, 215 and then foam layers 216, 217. The foam layers 216, 217 do not extend as far as the other layers.

[0075] refer to Fig. 22 Another exemplary embodiment of a multilayer thermal barrier 220 for use in a battery pack 18 includes an aerogel layer 221 sandwiched between ceramic layers 222, 223, which are then sandwiched between mica layers 224, 225 and then foam layers 226, 227. The foam layers 226, 227 do not extend as far as the other layers.

[0076] refer to Fig.23 Another exemplary embodiment of a multilayer thermal barrier 230 for use in a battery pack 18 includes a glass / silicone layer 231 sandwiched between ceramic layers 232, 233, which is then sandwiched between mica layers 234, 235 and then foam layers 236, 237. The foam layers 236, 237 do not extend as far as the other layers. In this example, the thickness of the glass / silicone layer 231 is 0.3 mm.

[0077] Features of some disclosed examples may include a multi-layer thermal barrier having an intumescent heat absorbing aerogel layer to reduce thermal conductivity and absorb heat. The activation temperature of the layer may be about 200 degrees Celsius. Various combinations of steel layers, graphene layers, mica and / or aerogel may be used to achieve high heat dissipation and insulation values ​​at high temperatures using different combinations of steel, graphene with mica and aerogel. The multi-layer thermal barrier may include at least one square mica layer. The multi-layer thermal barrier may include at least one ceramic layer.

[0078] Features of the disclosed examples may include a multi-layer thermal barrier having an intumescent heat absorbing aerogel layer to reduce thermal conductivity and absorb heat. The activation temperature of the layer may be about 200 degrees Celsius. Various combinations of steel layers, graphene layers, mica, and / or aerogel may be used to achieve high heat dissipation and insulation values ​​at high temperatures using different combinations of steel, graphene with mica and aerogel.

[0079] The foregoing description is illustrative rather than restrictive in nature. Changes and modifications to the disclosed examples may become apparent to those skilled in the art, and the changes and modifications do not necessarily depart from the essence of the present disclosure. Therefore, the scope of protection granted to the present disclosure can only be determined by studying the attached claims.

Claims

1. A multi-layer thermal barrier for a traction battery pack, comprising: An inner sandwich structure, the inner sandwich structure being provided by a first ceramic layer and a second ceramic layer sandwiching a core layer; as well as A first foam layer and a second foam layer, wherein the first foam layer and the second foam layer sandwich the inner sandwich structure.

2. The multilayer thermal barrier of claim 1, wherein the core layer is glass.

3. The multilayer thermal barrier of claim 1 wherein the core layer is mica.

4. The multilayer thermal barrier of claim 1, wherein the first ceramic layer and the second ceramic layer are each thinner than the core layer.

5. The multilayer thermal barrier of claim 1 wherein the first ceramic layer and the second ceramic layer are adhesively secured directly to the core layer.

6. The multilayer thermal barrier of claim 1 further comprising a first mica layer and a second mica layer, the first mica layer being disposed between the first ceramic layer and the first foam layer, the second mica layer being disposed between the second ceramic layer and the second foam layer, and optionally wherein the core layer is a third mica layer.

7. The multilayer thermal barrier of claim 6, wherein the core layer is glass.

8. The multilayer thermal barrier of claim 6, wherein the first mica layer is adhesively secured to both the first foam layer and the first ceramic layer, wherein the second mica layer is adhesively secured to both the second foam layer and the second ceramic layer, and optionally, wherein the first foam layer is a first polyurethane foam layer, wherein the second foam layer is a second polyurethane foam layer.

9. A traction battery pack assembly having a multi-layer thermal barrier as described in claim 1, and further comprising a battery stack having a plurality of battery cells arranged along an axis of the battery stack, the multi-layer thermal barrier being axially positioned between at least one first battery cell among the plurality of battery cells and at least one second battery cell among the plurality of battery cells.

10. A traction battery pack assembly, comprising: A battery cell stack, the battery cell stack comprising at least one first battery cell, at least one second battery cell and a multi-layer thermal barrier assembly, wherein the multi-layer thermal barrier assembly is arranged to limit the transfer of thermal energy between the at least one first battery cell and the at least one second battery cell, and the multi-layer thermal barrier assembly comprises an inner sandwich structure sandwiched between a first foam layer and a second foam layer.

11. The traction battery pack assembly of claim 10, wherein the inner sandwich structure comprises a first ceramic layer and a second ceramic layer sandwiching a core layer.

12. The traction battery pack assembly of claim 11, wherein the core layer is mica or glass.

13. The traction battery pack assembly of claim 10, wherein the at least one first battery cell comprises four first battery cells, and wherein the at least one second battery cell comprises four second battery cells.

14. The traction battery pack assembly of claim 10, further comprising a first mica layer and a second mica layer, wherein the first mica layer is disposed between the inner sandwich structure and the first foam layer, and the second mica layer is disposed between the inner sandwich structure and the second foam layer.

15. The traction battery pack assembly of claim 14, wherein the inner sandwich structure includes a third mica layer.

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