Multi-layer thermal barrier assemblies for traction battery packs

Abstract

Thermal barrier assemblies are provided for traction battery packs. An example thermal barrier assembly can be configured to inhibit the transfer of thermal energy within the traction battery pack. The thermal barrier assembly can include a first thermally insulating layer, a second thermally insulating layer, and an air gap extending between the first and second thermally insulating layers. The air gap can be formed by integrated features provided at an interface between the first and second thermally insulating layers. The air gap can be configured to increase thermal resistance across a thickness of the thermal barrier assembly, thereby reducing heat transfer from cell to cell and / or from cell stack to cell stack within the traction battery pack.

Description

AREA OF TECHNOLOGY

[0001] This disclosure relates generally to traction battery packs and in particular to multilayer thermal barrier assemblies for managing the transfer of thermal energy within traction battery packs. GENERAL STATE OF THE ART

[0002] Electrified vehicles include a traction battery pack to supply power to electric motors and other electrical components within the vehicle. The traction battery pack comprises a variety of battery cells and various other internal components that support the electric vehicle's propulsion system. SUMMARY

[0003] A traction battery pack according to an exemplary aspect of the present disclosure includes, among other things, a cell stack comprising a first battery cell, a second battery cell, and a thermal barrier assembly arranged to limit heat transfer between the first and second battery cells. The thermal barrier assembly includes a first heat-insulating layer, a second heat-insulating layer, and an air gap.

[0004] In a further non-restrictive embodiment of the aforementioned traction battery pack, the cell stack includes a cell expansion pad arranged between the first battery cell and a third battery cell.

[0005] In a further non-restrictive embodiment of one of the aforementioned traction battery packs, an inner surface of each of the first heat-insulating layer and the second heat-insulating layer includes a roughened surface having a plurality of peaks and a plurality of depressions.

[0006] In a further non-restrictive embodiment of any of the aforementioned traction battery packs, the air gap extends between a first recess of the plurality of recesses of the first heat-insulating layer and a second recess of the plurality of recesses of the second heat-insulating layer.

[0007] In a further non-restrictive embodiment of any of the foregoing traction battery packs, an inner surface of each of the first heat-insulating layer and the second heat-insulating layer includes a raised surface.

[0008] In a further non-restrictive embodiment of any of the aforementioned traction battery packs, the raised surface extends vertically over a height of the heat barrier assembly.

[0009] In a further non-restrictive embodiment of any of the aforementioned traction battery packs, the raised surface extends horizontally over a width W of the heat barrier assembly.

[0010] In a further non-restrictive embodiment of any of the foregoing traction battery packs, the air gap between adjacent sets of raised surfaces extends to the inner surface of each of the first heat-insulating layer and the second heat-insulating layer.

[0011] In a further non-restrictive embodiment of any of the foregoing traction battery packs, an inner surface of each of the first heat-insulating layer and the second heat-insulating layer includes a recess.

[0012] In a further non-restrictive embodiment of any of the aforementioned traction battery packs, the recess of the first heat-insulating layer adjoins the recess of the second heat-insulating layer to form the air gap.

[0013] In a further non-restrictive embodiment of any of the foregoing traction battery packs, the cell stack includes a third battery cell, a fourth battery cell and a second thermal barrier assembly arranged to limit heat transfer between the third battery cell and the fourth battery cell.

[0014] In a further non-restrictive embodiment of any of the aforementioned traction battery packs, the air gap forms a fluid flow channel through an internal volume of the heat barrier assembly.

[0015] In a further non-restrictive embodiment of any of the foregoing traction battery packs, the thermal barrier assembly includes a first thickness and the first heat-insulating layer includes a second thickness which is about 1 / 3 of the first thickness.

[0016] In a further non-restrictive embodiment of any of the foregoing traction battery packs, the heat barrier assembly includes a first thickness and the air gap includes a second thickness, which is about 1 / 3 of the first thickness.

[0017] In a further non-restrictive embodiment of any of the aforementioned traction battery packs, each of the first heat-insulating layer and the second heat-insulating layer is a mica film.

[0018] A traction battery pack according to another exemplary aspect of the present disclosure includes, among other things, a first battery cell, a second battery cell, and a thermal barrier assembly arranged between the first battery cell and the second battery cell. The thermal barrier assembly includes a first thermally insulating layer having a first integrated feature and a second thermally insulating layer having a second integrated feature. The first integrated feature and the second integrated feature interact to form an air gap between the first thermally insulating layer and the second thermally insulating layer.

[0019] In a further non-restrictive embodiment of any of the foregoing traction battery packs, the first integrated feature and the second integrated feature include roughened surfaces.

[0020] In a further non-restrictive embodiment of one of the aforementioned traction battery packs, the first integrated feature and the second integrated feature include raised surfaces.

[0021] In a further non-restrictive embodiment of any of the foregoing traction battery packs, the first integrated feature and the second integrated feature include recesses.

[0022] In a further non-limiting embodiment of any of the foregoing traction battery packs, the first thermally insulating layer comprises a first outer surface that is in close contact with the first battery cell and a first inner surface that provides the first integrated feature. The second thermally insulating layer comprises a second outer surface that is in close contact with the second battery cell and a second inner surface that provides the second integrated feature.

[0023] The embodiments, examples, and alternatives described in the preceding paragraphs, the claims, or the following description and drawings, including their various aspects or individual features, may be used independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, provided such features are not incompatible.

[0024] The various features and advantages of this disclosure will become apparent to the person skilled in the art from the following detailed description. The drawings accompanying the detailed description can be summarized as follows. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 schematically illustrates an electrified vehicle. Fig. Figure 2 illustrates a traction battery pack of the electrified vehicle from Fig. 1. Fig. Figure 3 illustrates a cell stack of the traction battery pack made of Fig. 2. Fig. Figure 4 is an enlarged view of selected sections of the cell stack. Fig. 3. Fig. Figure 5 illustrates an example of a heat barrier assembly. Fig. Figure 6 is an enlarged view of selected sections of the heat barrier assembly. Fig. 5. Fig. Figure 7 is a cross-sectional view along line 7-7 from Fig. 6. Fig. Figure 8 illustrates another example of a heat barrier assembly. Fig. Figure 9 is an enlarged view of selected sections of the heat barrier assembly. Fig. 8. Fig. Figure 10 illustrates another exemplary heat barrier assembly. Fig. Figure 11 is an enlarged view of selected sections of the heat barrier assembly. Fig. 10. Fig. Figure 12 illustrates another exemplary heat barrier assembly. Fig. Figure 13 is an enlarged view of selected sections of the heat barrier assembly. Fig. 12. DETAILED DESCRIPTION

[0025] This disclosure describes thermal barrier assemblies for traction battery packs in detail. An exemplary thermal barrier assembly may be configured to inhibit the transfer of thermal energy within the traction battery pack. The thermal barrier assembly may include a first thermally insulating layer, a second thermally insulating layer, and an air gap extending between the first and second thermally insulating layers. The air gap may be formed by integrated features provided at an interface between the first and second thermally insulating layers. The air gap may be configured to increase thermal resistance across a thickness of the thermal barrier assembly, thereby reducing heat transfer from cell to cell and / or from cell stack to cell stack within the traction battery pack. These and other features are discussed in more detail in the following paragraphs of this detailed description.

[0026] Fig. Figure 1 schematically illustrates an electrified vehicle 10. The electrified vehicle 10 can include any type of electrified powertrain. In one embodiment, the electrified vehicle 10 is a battery electric vehicle (BEV). However, the concepts described in this document are not limited to BEVs and could extend 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 could be equipped with an internal combustion engine, which can be used either alone or in combination with other power sources to propel the electrified vehicle 10.

[0027] In the illustrated embodiment, the electrified vehicle 10 is depicted as an automobile. However, the electrified vehicle 10 could alternatively be a sport utility vehicle (SUV), a van, a pickup truck, or any other vehicle configuration. Although a specific relationship of the components is illustrated in the figures of this disclosure, these illustrations are not intended to limit this disclosure. The placement and orientation of the various components of the electrified vehicle 10 are shown schematically and could vary within the scope of this disclosure. Furthermore, the various figures accompanying this disclosure are not necessarily drawn to scale, and some features may be enlarged or reduced to highlight certain details of a particular component or system.

[0028] In one embodiment, the electrified vehicle 10 is a fully electric vehicle powered exclusively by electrical power, such as from one or more electric machines 12, without any assistance from an internal combustion engine. The electric machine 12 can operate as an electric motor, an electric generator, or both. The electric machine 12 receives electrical power and can convert this power into torque to drive one or more wheels 14 of the electrified vehicle 10.

[0029] A voltage bus 16 can electrically couple the electric machine 12 to a traction battery pack 18. The traction battery pack 18 is an exemplary battery of an electrified vehicle. The traction battery pack 18 can be a high-voltage traction battery pack assembly comprising a variety of battery cell groupings capable of outputting electrical power to supply the electric machine 12 and / or other electrical consumers of the electrified vehicle 10. Alternatively or additionally, other types of energy storage devices and / or output devices could also be used to supply the electrified vehicle 10 with electrical power.

[0030] The traction battery pack 18 may be secured to an underbody 20 of the electrified vehicle 10. However, within the scope of this disclosure, the traction battery pack 18 could be located at a different location on the electrified vehicle 10.

[0031] Fig. 2, Fig. 3 and Fig. Figure 4 illustrates additional details associated with the traction battery pack 18 of the electrified vehicle 10. The traction battery pack 18 may include one or more cell stacks 22 (e.g., the one shown) housed within an interior space 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 shell 28. The housing cover 26 may be positioned vertically above the housing shell 28. However, the housing cover 26 could also be located below or on one side of the housing shell 28. Different terms, such as "above," "below," "top," and "bottom," are used in the various drawings with respect to the arrangement of the components of the traction battery pack 18 and should not otherwise be considered restrictive.These terms refer to the general orientation of the traction battery pack 18 when it is installed in the electrified vehicle 10. Fig. 1 is installed. In the context of this disclosure, vertical also refers to the ground and how the traction battery pack 18 is oriented when installed in the electrified vehicle 10.

[0032] The housing cover 26 can be secured to the housing shell 28 (e.g., screwed, welded, glued, etc.) to provide the interior 30 for accommodating the cell stacks 22 and other internal battery components (e.g., busbars, control modules, and other electronics, etc.) of the traction battery pack 18. The size, shape, and configuration of the housing assembly 24 may vary within the scope of this disclosure.

[0033] Each cell stack 22 can contain a plurality of individual battery cells 32, which are arranged together along a cell stack axis A between opposing end plates 48. The battery cells 32 store electrical energy to supply power to various components and supply this power to support the electric drive of the electrified vehicle 10.

[0034] In one embodiment, the battery cells are 32 lithium-ion pouch cells. However, within the scope of this disclosure, alternatively battery cells with other geometries (prismatic, cylindrical, etc.) and / or chemical compositions (nickel-metal hydride, lead-acid, etc.) could be used.

[0035] Although a specific number of cell stacks 22 and battery cells 32 are illustrated in the various figures of this revelation, the traction battery pack 18 could include any number of cell stacks 22, each cell stack 22 having any number of individual battery cells 32.

[0036] Each battery cell 32 can include a first end face 34, a second end face 36 opposite the first end face 34, a first end 38, a second end 40 opposite the first end 38, a top 42, and a bottom 44 opposite the top 42. The first end face 34 and the second end face 36 form the primary side faces of the battery cells 32, and the first end 38, the second end 40, the top 42, and the bottom 44 form secondary side faces of the battery cell 32. The first face 34 and the second face 36 therefore have a larger surface area than any of the first end 38, the second end 40, the top 42, and the bottom 44.

[0037] A flat terminal 46 can project outwards from each of the first end 38 and the second end 40 of the battery cells 32. The battery cells 32 can thus be considered to be "side-aligned" within the cell stacks 22. The flat terminals 46 can be connected to busbars (not shown) to electrically connect the battery cells 32 of each cell stack 22.

[0038] A cell expansion pad 62 can be arranged between some adjacent battery cells 32 within the cell stack 22. The cell expansion pads 62 can comprise a material (e.g., polyurethane foam, silicone foam, etc.) adapted to accommodate swelling of the battery cells.

[0039] One or more thermal barrier assemblies 60 can be 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 thermal barrier assemblies 60 along the cell stack axis A. However, other configurations within the scope of this disclosure are also considered, and it should be obvious to those who benefit from this disclosure that the cell stack 22 could include any number and any arrangement of battery cells 32, thermal barrier assemblies 60, and cell expansion pads 62.

[0040] The battery cells 32 can be arranged such that the surfaces 34, 36 of a battery cell 32 are in direct contact with one of the surfaces 34 or 36 of an adjacent battery cell 32, an adjacent thermal barrier assembly 60 of the cell stack 22, or an adjacent cell expansion pad 62 of the cell stack 22. The battery cells 32, thermal barrier assemblies 60, and cell expansion pads 62 can be held in compression relative to one another within the cell stack 22 to provide the opposing arrangement. The compression can be applied, for example, by the end plates 48 of the cell stack 22. However, other configurations within the scope of this disclosure are considered.

[0041] Thermal energy levels of the battery cells 32 of each cell stack 22 can increase while the electrified vehicle 10 is in operation. A thermal management system 50 (see Fig. 2) can be used to manage the thermal energy levels of the battery cells 32, cell stack 22, and other areas of the traction battery pack 18. The thermal management system 50 can be configured to circulate a coolant C through the traction battery pack 18 to manage the thermal energy within the cell stack 22, for example, by using the coolant C to absorb heat from the cell stack 22.

[0042] In one embodiment, the thermal management system 50 is an immersion thermal management system in which sections of the traction battery pack 18, here at least sections of the battery cells 32, are immersed in the coolant C. Thermal energy can be transferred between the coolant C and the battery cells 32 when the coolant C flows over and / or around the battery cells 32. The coolant C can help manage the thermal energy levels of the battery cells 32 as well as other components of the traction battery pack 18.

[0043] The thermal management system 50 can supply a coolant C through an inlet 52 to the interior 30 of the traction battery pack 18. The coolant C can fill one or more open areas within the interior 30, so that the battery cells 32 are immersed in the coolant C within the traction battery pack 18 and are in direct contact with it. The coolant C can absorb thermal energy from the battery cells 32 of the cell stacks 22 and other components of the traction battery pack 18 to manage thermal energy levels. The coolant C can exit the traction battery pack 18 through an outlet 54, which may be located at an end of the housing assembly 24 opposite the inlet 52. The coolant C exiting through the outlet 54 can move to a heat exchange device (not shown), such as a heat exchanger, where thermal energy can be transferred from the coolant C to the atmosphere.A pump (not shown) can be operated to selectively circulate the coolant C between the traction battery pack 18 and the heat energy exchange device.

[0044] The coolant C circulating in the immersion heat management system can be a dielectric fluid or another type of non-conductive fluid (e.g., oil) designed for immersion cooling of the battery cells 32. However, other non-conductive fluids may also be suitable, and the actual chemical composition and design properties (e.g., dielectric constant, maximum dielectric strength, boiling point, etc.) may vary depending on the environment in which the traction battery pack 18 is to be used.

[0045] In another embodiment, the thermal management system 50 is a conventional cold plate system in which the coolant C, such as glycol, is circulated through a cold plate (not shown) to thermally manage heat generated by the battery cells 32. The teachings of this disclosure are therefore not limited to immersion thermal management systems. In this type of thermal management system, the battery cells 32 are not immersed in the coolant C.

[0046] The heat barrier assemblies 60 can also function as part of the thermal management system 50. For example, the heat barrier assemblies 60 can be arranged to limit the conductive transfer of heat energy from cell to cell across each cell stack 22 of the traction battery pack 18.

[0047] Now mainly with reference to Fig. 5, Fig. 6 and Fig. 7. Each heat barrier assembly 60 can be configured as a multilayer structure designed to limit the conductive heat transfer of thermal energy across the cell stack 22. The multilayer structure of each heat barrier assembly 60 can include a first heat-insulating layer 64 and a second heat-insulating layer 66. Although two heat-insulating layers are shown in the exemplary embodiments, the heat barrier assemblies described in this document could include two or more heat-insulating layers within the scope of this disclosure.

[0048] The first and second heat-insulating layers 64, 66 can be made of one or more heat-resistant (and thus having low thermal conductivity) materials, such as mica, aerogel materials, refractory ceramic fibers, etc. However, other materials or combinations of materials could also be used to provide the heat-resistant material of each of the first and second heat-insulating layers 64, 66.

[0049] The first thermally insulating layer 64 and the second thermally insulating layer 66 can each include an outer surface 68 and an inner surface 70 opposite the outer surface 68. The outer surface 68 can be positioned in direct contact with the first surface 34 or the second surface 36 of an adjacent battery cell 32 within the cell stack 22, and the inner surface 70 can be positioned such that it forms an interface with the inner surface 70 of the other of the first thermally insulating layer 64 or the second thermally insulating layer 66.

[0050] How best to Fig. As illustrated in Figure 7, each inner surface 70 can include integrated features that interact with integrated features of the inner surface 70 of the adjacent thermally insulating layer to form one or more air gaps 72 within the thermal barrier assembly 60. In one embodiment, the integrated features are configured as a roughened surface 74 formed on each inner surface 70. The roughened surface 74 forms a plurality of peaks 76 and depressions 78 on the inner surface 70. When the first thermally insulating layer 64 and the second thermally insulating layer 66 are positioned adjacent to each other and joined, for example, by means of an adhesive, the peaks 76 and the depressions 78 are aligned with each other. The space between the depressions 78 of the first thermally insulating layer 64 and the depressions 78 of the second thermally insulating layer 66 forms the air gaps 72 of the thermal barrier assembly 60.

[0051] The air gaps 72 can be configured to increase the thermal resistance of the thermal barrier assembly 60, thereby reducing heat transfer from cell to cell across the cell stack 22. These thermal resistance benefits can be achieved while reducing the amount of material required to form each heat-insulating layer of the thermal barrier assembly 60.

[0052] If the heat management system 50 is configured as a conventional chilled plate system, the air gaps 72 can be filled with air to provide low thermal conductivity in one thickness direction of the heat barrier assembly 60. Alternatively, if the heat management system 50 is configured as an immersion heat management system, the air gaps 72 can form fluid flow channels for circulating the coolant C through an internal volume of the heat barrier assembly 60.

[0053] The heat barrier assembly includes a total thickness T1 (see Fig. 6), extending parallel to the length of the cell stack 22 along the cell stack axis A. The total thickness T1 can, for example, be between approximately 2 mm and approximately 4 mm. However, other thicknesses are considered within the scope of this disclosure. In this disclosure, the term "approximately" means that the specified quantities or ranges need not be exact, but may be approximate and / or larger or smaller, reflecting acceptable tolerances, conversion factors, measurement errors, etc.

[0054] In one embodiment, the first and second heat-insulating layers 64, 66 can each be made of a mica film having a thickness T2 that is approximately 1 / 3 of the total thickness T1 of the heat barrier assembly 60. Each air gap 72 can have a third thickness T3 that is also approximately 1 / 3 of the total thickness T1 of the heat barrier assembly 60. However, other thickness ratios for each sublayer of the heat barrier assembly 60 are considered within the scope of this disclosure.

[0055] Fig. 8 and Fig. Figure 9 illustrates another exemplary thermal barrier assembly 160, which can function as part of the thermal management system 50 of the traction battery pack 18 described above. The thermal barrier assembly 160 can include a first thermally insulating layer 164 and a second thermally insulating layer 166. The first and second thermally insulating layers 164, 166 can be made of one or more heat-resistant materials (and thus with low thermal conductivity), such as mica, aerogel materials, refractory ceramic fibers, etc.

[0056] The first thermally insulating layer 164 and the second thermally insulating layer 166 can each include an outer surface 168 and an inner surface 170 opposite the outer surface 168. The outer surface 168 can be positioned in direct contact with the first surface 34 or the second surface 36 of an adjacent battery cell 32 within the cell stack 22, and the inner surface 170 can be positioned such that it forms an interface with the inner surface 170 of the other of the first thermally insulating layer 164 or the second thermally insulating layer 166.

[0057] Each internal surface 170 can include integrated features that interact with integrated features of an adjacent internal surface 170 to form one or more air gaps 172 within the heat barrier assembly 60. In one embodiment, the integrated features are configured as raised surfaces 180 projecting outward from the internal surface 70. In this embodiment, the raised surfaces 180 extend vertically over a height H of the heat barrier assembly 160. In another embodiment, the raised surfaces 180 extend horizontally over a width W of the heat barrier assembly (see, for example, Figure 1). Fig. 10 and Fig. 11).

[0058] When the first heat-insulating layer 164 and the second heat-insulating layer 166 are mounted together, for example via an adhesive, the raised surfaces 180 lie against each other and the spaces between adjacent sets of raised surfaces 180 form the air gaps 172 of the heat barrier assembly 160.

[0059] The air gaps 172 can be configured to increase the thermal resistance of the thermal barrier assembly 160, thereby reducing heat transfer from cell to cell across the cell stack 22. These thermal resistance benefits can be achieved while reducing the amount of material required to form each heat-insulating layer of the thermal barrier assembly 160.

[0060] If the heat management system 50 is configured as a conventional chilled plate system, the air gaps 172 can be filled with air to provide low thermal conductivity in one thickness direction of the heat barrier assembly 160. Alternatively, if the heat management system 50 is configured as an immersion heat management system, the air gaps 172 can form fluid flow channels for circulating the coolant C through an internal volume of the heat barrier assembly 160.

[0061] Fig. 12 and Fig.Figure 13 illustrates another exemplary thermal barrier assembly 260, which can function as part of the thermal management system 50 of the traction battery pack 18 described above. The thermal barrier assembly 260 can include a first thermally insulating layer 264 and a second thermally insulating layer 266. The first and second thermally insulating layers 264, 266 can be made of one or more heat-resistant materials (and thus with low thermal conductivity), such as mica, aerogel materials, refractory ceramic fibers, etc.

[0062] The first thermally insulating layer 264 and the second thermally insulating layer 266 can each include an outer surface 268 and an inner surface 270 opposite the outer surface 268. The outer surface 268 can be positioned in direct contact with the first surface 34 or the second surface 36 of an adjacent battery cell 32 within the cell stack 22, and the inner surface 270 can be positioned such that it forms an interface with the inner surface 270 of the other of the first thermally insulating layer 264 or the second thermally insulating layer 266.

[0063] Each internal surface 270 can include integrated features that interact with integrated features of an adjacent internal surface 270 to form one or more air gaps 272 within the thermal barrier assembly 260. In one embodiment, the integrated features are configured as recesses 290 projecting outwards from the internal surfaces 270. When the first thermally insulating layer 264 and the second thermally insulating layer 266 are positioned side by side and joined together, for example by means of an adhesive, the recesses 290 abut each other, thereby forming the air gap 272 of the thermal barrier assembly 260.

[0064] The air gap 272 can be configured to increase the thermal resistance of the thermal barrier assembly 260, thereby reducing heat transfer from cell to cell across the cell stack 22. These thermal resistance benefits can be achieved while reducing the amount of material required to form each heat-insulating layer of the thermal barrier assembly 260.

[0065] If the heat management system 50 is configured as a conventional cold plate system, the air gap 272 can be filled with air to provide low thermal conductivity in one thickness direction of the heat barrier assembly 260. Alternatively, if the heat management system 50 is configured as an immersion heat management system, the air gap 272 can form fluid flow channels for circulating the coolant C through an interior of the heat barrier assembly 260.

[0066] The exemplary thermal barrier assemblies presented in this disclosure are configured to provide increased thermal resistance while requiring less thermal barrier material for the same installation space. The proposed thermal barrier designs can be used for both immersion and non-immersion cooling thermal arrangements, thus providing enhanced benefits compared to previous barrier systems.

[0067] Although the different non-restrictive embodiments are illustrated by showing specific components or steps, the embodiments of this disclosure are not limited to these specific combinations. It is possible to use some of the components or features from any of the non-restrictive embodiments in combination with features or components from any of the other non-restrictive embodiments.

[0068] It is understood that identical reference numerals denote corresponding or similar elements in the multiple views. It is understood that although a specific component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the lessons of this disclosure.

[0069] The foregoing description is to be interpreted as illustrative and not as limiting. A person skilled in the art will understand that certain modifications may be covered by the scope of this disclosure. For these reasons, the following patent claims should be read carefully to determine the true scope and content of this disclosure.

Claims

[1] Traction battery pack, comprising: a cell stack comprising a first battery cell, a second battery cell and a thermal barrier assembly arranged to limit heat transfer between the first battery cell and the second battery cell, wherein the heat barrier assembly includes a first heat-insulating layer, a second heat-insulating layer and an air gap. [2] Traction battery pack according to claim 1, wherein the cell stack includes a cell expansion pad arranged between the first battery cell and a third battery cell. [3] Traction battery pack according to claim 1 or 2, wherein an inner surface of each of the first heat-insulating layer and the second heat-insulating layer includes a roughened surface having a plurality of peaks and a plurality of depressions, and wherein the air gap optionally extends between a first depression of the plurality of depressions of the first heat-insulating layer and a second depression of the plurality of depressions of the second heat-insulating layer. [4] Traction battery pack according to one of the preceding claims, wherein an inner surface of each of the first heat-insulating layer and the second heat-insulating layer includes a raised surface. [5] Traction battery pack according to claim 4, wherein the raised surface extends vertically over a height of the heat barrier assembly or horizontally over a width W of the heat barrier assembly. [6] Traction battery pack according to claim 4, wherein the air gap between adjacent sets of raised surfaces extends through the inner surface of each of the first heat-insulating layer and the second heat-insulating layer. [7] Traction battery pack according to one of the preceding claims, wherein an inner surface of each of the first heat-insulating layer and the second heat-insulating layer includes a recess and wherein the recess of the first heat-insulating layer may optionally adjoin the recess of the second heat-insulating layer to form the air gap. [8] Traction battery pack according to any of the preceding claims, wherein the cell stack includes a third battery cell, a fourth battery cell and a second heat barrier assembly arranged to limit heat transfer between the third battery cell and the fourth battery cell. [9] Traction battery pack according to one of the preceding claims, wherein the air gap forms a fluid flow channel through an internal volume of the heat barrier assembly. [10] Traction battery pack according to one of the preceding claims, wherein the heat barrier assembly includes a first thickness and the first heat-insulating layer includes a second thickness which is about 1 / 3 of the first thickness. [11] Traction battery pack according to one of the preceding claims, wherein the heat barrier assembly includes a first thickness and the air gap includes a second thickness which is about 1 / 3 of the first thickness. [12] Traction battery pack according to one of the preceding claims, wherein each of the first heat-insulating layer and the second heat-insulating layer is a mica film. [13] Traction battery pack, comprising: a first battery cell; a second battery cell; and a thermal barrier assembly arranged between the first battery cell and the second battery cell, wherein the thermal barrier assembly includes a first thermally insulating layer having a first integrated feature and a second thermally insulating layer having a second integrated feature, wherein the first integrated feature and the second integrated feature work together to form an air gap between the first heat-insulating layer and the second heat-insulating layer. [14] Traction battery pack according to claim 13, wherein the first integrated feature and the second integrated feature comprise roughened surfaces, raised areas or depressions. [15] Traction battery pack according to claim 13 or 14, wherein the first heat-insulating layer comprises a first outer surface which is in adjacent contact with the first battery cell and a first inner surface which provides the first integrated feature, and the second heat-insulating layer comprises a second outer surface which is in adjacent contact with the second battery cell and a second inner surface which provides the second integrated feature.

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