Thermal barrier system for use within traction battery pack

Abstract

The present disclosure provides a thermal barrier system for use within a traction battery pack. A thermal barrier system for use within a traction battery pack is provided. An exemplary thermal barrier system may include one or more expandable gap fillers configured to transition from a compressed state to an uncompressed state when a temperature proximate the expandable gap filler exceeds a predefined temperature threshold. In the uncompressed state, the expandable gap filler reduces the free air volume of the void space of the traction battery pack, thereby managing or even preventing the transfer of thermal energy to nearby structures.

Description

Technical Field

[0001] The present disclosure relates generally to electrified vehicle traction battery packs and, more particularly, to a thermal barrier system for managing the transfer of thermal energy within a traction battery pack. Background Art

[0002] A high-voltage traction battery pack typically supplies power to the electric motor and other electrical loads of an electrified vehicle. The traction battery pack includes multiple battery cells and various other battery internal components that support the vehicle's electric propulsion. Summary of the Invention

[0003] A traction battery pack according to an exemplary aspect of the present disclosure includes, among other things, a void space and an expandable gap filler disposed within the void space and configured to transition from a compressed state to an uncompressed state when a temperature proximate the expandable gap filler exceeds a predefined temperature threshold, thereby reducing a free air volume of the void space.

[0004] In another non-limiting embodiment of the foregoing traction battery pack, the void space extends between a first cell tab terminal of the first battery cell and a second cell tab terminal of the second battery cell.

[0005] In a further non-limiting embodiment of any of the foregoing traction battery packs, the void space extends between the battery array and the array housing roof.

[0006] In a further non-limiting embodiment of any of the foregoing traction battery packs, the void space extends between the battery array and the electronics housing.

[0007] In another non-limiting embodiment of any of the foregoing traction battery packs, the expandable gap filler includes a foam portion and a binding wrapped around the foam portion.

[0008] In a further non-limiting embodiment of any of the foregoing traction battery packs, the binding is configured to melt when the temperature exceeds the predefined temperature threshold to allow the foam portion to expand.

[0009] In a further non-limiting embodiment of any of the foregoing traction battery packs, the predefined temperature threshold is a melting point of the binding.

[0010] In another non-limiting embodiment of any of the foregoing traction battery packs, the foam portion is comprised of a flexible, high-temperature resistant solid foam material.

[0011] In another non-limiting embodiment of any of the foregoing traction battery packs, the flexible, high temperature resistant solid foam material comprises silicone rubber foam.

[0012] In another non-limiting embodiment of any of the foregoing traction battery packs, the flexible, high temperature resistant solid foam material includes an expansion aid.

[0013] In another non-limiting embodiment of any of the foregoing traction battery packs, the binding is comprised of a low melting point material.

[0014] In another non-limiting embodiment of any of the foregoing traction battery packs, the low melting point material includes polyethylene terephthalate (PET).

[0015] In another non-limiting embodiment of any of the foregoing traction battery packs, the low melting point material includes a polyolefin.

[0016] In a further non-limiting embodiment of any of the foregoing traction battery packs, in the uncompressed state, the expandable gap filler establishes a thermal barrier within the void space.

[0017] According to another exemplary aspect of the present disclosure, a traction battery pack includes, inter alia, a battery stack comprising at least a first battery cell and a second battery cell. The first battery cell includes a first battery cell terminal, and the second battery cell includes a second battery cell terminal. An expandable gap filler is disposed within a void space extending between the first battery cell terminal and the second battery cell terminal. The expandable gap filler is configured to transition from a compressed state to an uncompressed state when a temperature within the void space exceeds a melting point of a binding member of the expandable gap filler.

[0018] In a further non-limiting embodiment of any of the foregoing traction battery packs, the binding wraps around a foam portion of the expandable gap filler.

[0019] In a further non-limiting embodiment of any of the foregoing traction battery packs, the binding is made of polyethylene terephthalate (PET).

[0020] In a further non-limiting embodiment of any of the foregoing traction battery packs, the foam portion is made of silicone rubber foam.

[0021] In another non-limiting embodiment of any of the foregoing traction battery packs, the expandable gap filler is secured to a surrounding structure positioned adjacent to the cell stack.

[0022] In another non-limiting embodiment of any of the foregoing traction battery packs, the surrounding structure is an array housing plate or a busbar module frame.

[0023] The embodiments, examples and alternatives of the preceding paragraphs, claims or following description and drawings (including any of their various aspects or corresponding 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.

[0024] The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description.The drawings that accompany the detailed description can be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 An electrified vehicle including a traction battery pack is schematically shown.

[0026] Figure 2 The expandable gap filler is shown in a compressed state.

[0027] Figure 3 Shown Figure 2 Expandable gap filler in an uncompressed state.

[0028] Figure 4 FIG2 is a top view of a selected portion of a battery array of a traction battery pack. The battery array is equipped with a thermal barrier system comprising a plurality of expandable gap fillers.

[0029] Figure 5 Shown Figure 4 An expandable gap filler in an uncompressed state to create a thermal barrier within a battery array.

[0030] Figure 6 Shown are selected portions of another exemplary thermal barrier system for a battery array.

[0031] Figure 7 A thermal barrier system is shown disposed within a traction battery pack. DETAILED DESCRIPTION

[0032] This disclosure details a thermal barrier system for use within a traction battery pack. An exemplary thermal barrier system may include one or more expandable gap fillers configured to transition from a compressed state to an uncompressed state when the temperature proximate the expandable gap filler exceeds a predefined temperature threshold. In the uncompressed state, the expandable gap filler reduces the free air volume of the void space of the traction battery pack, thereby managing or even preventing the transfer of thermal energy to nearby structures. These and other features are discussed in greater detail in the following sections of this detailed description.

[0033] Figure 1An electrified vehicle 10 is schematically shown. The electrified vehicle 10 may include any type of electrified powertrain. In an 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, and the like. Thus, 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.

[0034] 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 figures of the present disclosure, the illustrations 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 figures accompanying the present disclosure are not necessarily drawn to scale, and some features may be exaggerated or minimized to emphasize certain details of a particular component or system.

[0035] In the illustrated 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 assistance from an internal combustion engine. The electric machines 12 can operate as electric motors, generators, or both. The electric machines 12 receive electrical power and can convert the power into torque that is used to drive one or more wheels 14 of the electrified vehicle 10.

[0036] 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 electrified vehicle battery. The traction battery pack 18 can be a high-voltage traction battery pack assembly that includes a plurality of battery cells 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 can alternatively or additionally be used to power the electrified vehicle 10.

[0037] The traction battery pack 18 may be secured to an underbody 20 of the electrified vehicle 10. However, the traction battery pack 18 may be located elsewhere on the electrified vehicle 10 within the scope of the present disclosure.

[0038] The traction battery pack 18 may include one or more battery arrays 22 (e.g., battery assemblies or groups of rechargeable battery cells 24) 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.

[0039] The one or more battery arrays 22 of the traction battery pack 18 may each include a plurality of battery cells 24 that store energy for powering various electrical loads of the electrified vehicle 10. Within the scope of the present disclosure, the traction battery pack 18 may employ any number of battery cells 24. Therefore, the present disclosure should not be limited to Figure 1 A highly schematic configuration is shown in FIG.

[0040] In an embodiment, the battery cells 24 of each battery array 22 are lithium-ion pouch cells. However, battery cells having other geometries (cylindrical, prismatic, etc.), other chemistries (nickel-metal hydride, lead acid, etc.), or both may alternatively be used within the scope of the present disclosure.

[0041] The battery array 22 and various other battery internal components (e.g., bus electrical center, battery electrical control module, wiring, connectors, etc.) can be housed within an interior region 26 of a housing assembly 28. The housing assembly 28 can include, for example, a housing cover and a housing tray. The housing cover can be secured (e.g., bolted, welded, bonded, etc.) to the housing tray to provide the interior region 26. The size, shape, and overall configuration of the housing assembly 28 are not intended to limit the present disclosure.

[0042] One or more of the battery cells 24 enclosed within the traction battery pack 18 may periodically release exhaust byproducts, such as during an overcharge condition, an over-discharge condition, a short circuit, etc. The exhaust byproducts may be released from the battery cells 24 through a vent. An increase in pressure within one of the battery cells 24 may cause the vent to rupture, thereby creating a path for the exhaust byproducts to be released from within the battery cell 24. The present disclosure generally relates to a thermal barrier system designed to manage the transfer of thermal energy when one or more of the battery cells 24 release exhaust byproducts.

[0043] Figure 2 and Figure 3 An exemplary expandable gap filler 30 is shown. The expandable gap filler 30 may be strategically positioned anywhere it is desired to reduce the free air volume of the void space of the traction battery pack 18, thereby significantly minimizing convective transfer of thermal energy within the traction battery pack 18 during a battery cell venting event.

[0044] The expandable gap filler 30 may include an inner foam portion 32 and an outer binding 34. In an embodiment, the expandable gap filler 30 includes a block shape. However, the specific size and shape of the expandable gap filler 30 is not intended to limit the present disclosure.

[0045] The foam portion 32 can be compressed and wrapped or otherwise bound by the binding 34. The foam portion 32 can be completely or partially wrapped by the binding 34. In an embodiment, the binding 34 is vacuum formed around the foam portion 32. However, other manufacturing techniques can be utilized to apply the binding 34 around the foam portion 32 within the scope of the present disclosure.

[0046] The foam portion 32 can be made of a flexible, high-temperature resistant solid foam material. Exemplary foam materials suitable for the foam portion 32 include, but are not limited to, silicone rubber foam, polyurethane foam, polyethylene foam, ethylene propylene diene monomer (EPDM) foam, polyvinyl chloride (PVC) foam, or acrylic-based polymer materials. However, within the scope of the present disclosure, other foam materials or material combinations may be utilized alternatively or additionally.

[0047] In an embodiment, the high temperature resistant solid foam material of the foam portion 32 may include an expansion aid, such as expandable graphene or monoammonium phosphate, for example, which may undergo an endothermic reaction when exposed to heat. However, other materials or combinations of materials may be used as part of the foam portion 32 within the scope of the present disclosure.

[0048] The binding 34 can be made of a relatively low melting point material compared to the foam portion 32. Exemplary materials suitable for the binding 34 include, but are not limited to, polyethylene terephthalate (PET) or polyolefins such as polyethylene or polypropylene. However, other low melting point materials or material combinations may be utilized alternatively or additionally within the scope of the present disclosure.

[0049] The expandable gap filler 30 may be configured to expand from a compressed state S1 (see Figure 2 ) into the uncompressed state S2 (see Figure 3 For example, when the temperature near the expandable gap filler 30 exceeds a predefined temperature threshold (such as the melting point of the binding member 34), the binding member 34 can quickly melt and allow the foam portion 32 to expand, thereby increasing its effective volume. In the uncompressed state S2, the expandable gap filler 30 can create a thermal barrier within the environment in which it is encapsulated. The thermal barrier can better manage or even prevent the transfer of thermal energy to nearby structures.

[0050] Figure 4 and Figure 5An exemplary implantation is shown in which a plurality of expandable gap fillers 30 establish a thermal barrier system 36 within the cell array 22. The total number of expandable gap fillers 30 provided as part of the thermal barrier system 36 may vary and, therefore, is not intended to limit the present disclosure.

[0051] The battery array 22 may include a plurality of battery cells 24. The total number of battery cells 24 disposed within the battery array 22 may vary and is not intended to limit the present disclosure. The battery cells 24 may be grouped together in a cell stack 38. The cell stack 38 may optionally further include one or more inter-cell compressible barriers 40 and / or one or more inter-cell thermal barriers 42 that may be disposed between adjacent battery cells 24 of the cell stack 38. Although not specifically shown for simplicity and clarity, the array housing (e.g., top plate, bottom plate, end plates, side plates, etc.) of the battery array 22 may be disposed to substantially surround the cell stack 38.

[0052] Each expandable gap filler 30 of the thermal barrier system 36 may be disposed within a void space 44 of the battery array 22. The void space 44 may extend between the battery cell stack 38 and a surrounding structure 46 of the battery array 22. The surrounding structure 46 may be a portion of the array housing, a portion of a busbar module frame, or any combination of these and / or other structures of the battery array 22.

[0053] In an embodiment, the expandable gap filler 30 is positioned between the cell tab terminals 48 of adjacent battery cells 24 of the cell stack 38 (see, e.g., Figure 4 The expandable gap filler 30 may be directly secured (eg, adhered) to the surrounding structure 46 , or alternatively may not be attached to any nearby structure and thus free float between adjacent cell tab terminals 48 .

[0054] In another embodiment, the expandable gap filler 30 is positioned in one or more void spaces 44 extending between the cell stack 38 and the array housing top plate 52 (see, e.g., Figure 6 However, other arrangements are contemplated within the scope of the present disclosure, and it should be understood that the expandable gap filler 30 may be arranged within any void space of the battery array 22 where it is desired to limit thermal energy transfer.

[0055] Each expandable gap filler 30 of the thermal barrier system 36 may be configured to Figure 4 The compression state shown is transformed into Figure 5The uncompressed state is shown. In the compressed state, the expandable gap filler 30 does not substantially fill the void space 44 and thus provides sufficient gap space to accommodate normal battery functions, such as, for example, accommodating battery cell expansion forces. In the uncompressed state, the expandable gap filler 30 substantially fills the void space 44 and thus provides near-zero gap to constrain the movement of gas, debris, and energy associated with the exhaust byproducts V released when one or more of the battery cells 24 are vented.

[0056] The expandable gap fillers 30 can each be configured to transition from a compressed state to an uncompressed state when the temperature proximate the expandable gap filler 30 exceeds the melting point (e.g., approximately 120 degrees Celsius) of the material of the corresponding binding members 34 of the expandable gap filler 30. For example, when one or more battery cells 24 of the battery stack 38 are venting and releasing exhaust byproducts V, the temperature proximate the expandable gap filler 30 may exceed the melting point of the binding members 34. When this occurs, the binding members 34 of the expandable gap filler 30 may quickly melt and allow the foam portion 32 to expand, thereby effectively reducing the free air volume of the void space 44 (e.g., Figure 5 ). Thus, the uncompressed expandable gap filler 30 may create a thermal barrier within the void space 44 to mitigate inter-cell and / or inter-array convective heat transfer.

[0057] Figure 7 Another exemplary implementation of a thermal barrier system 36 within a traction battery pack 18 is shown in which one or more expandable gap fillers 30 may be provided. The expandable gap fillers 30 of the thermal barrier system 36 may be disposed within a void space 44 within the interior region 26 within the housing assembly 28 of the traction battery pack 18. For example, the void space 44 may extend between the battery array 22 and an electronics housing 50 of the traction battery pack 18. The electronics housing 50 may house internal battery components, such as a bus electrical center, a battery electrical control module, and the like.

[0058] The expandable gap filler 30 of the thermal barrier system 36 can be configured to transition from a compressed state S1 to an uncompressed state S2 (shown in dashed lines). In the compressed state S1, the expandable gap filler 30 does not substantially fill the void space 44 and thus provides sufficient gap space to accommodate normal battery function. In the uncompressed state S2, the expandable gap filler 30 substantially fills the void space 44 and thus creates a thermal barrier that prevents heat energy from being transferred from the battery array 22 to the electronics housing 50.

[0059] The expandable gap filler 30 can transition from the compressed state S1 to the uncompressed state S2 when the temperature proximate the expandable gap filler 30 exceeds the melting point of the material of the binding members 34 of the expandable gap filler 30 (e.g., approximately 120 degrees Celsius). For example, when one or more battery cells of the battery array 22 vent and release vent byproducts V, the temperature proximate the expandable gap filler 30 may exceed the melting point of the binding members 34. When this occurs, the binding members 34 of the expandable gap filler 30 can quickly melt and allow the foam portion 32 to expand, thereby effectively reducing the free air volume of the void space 44. As a result, the uncompressed expandable gap filler 30 can create a thermal barrier between the battery array 22 and the electronics housing 50.

[0060] The exemplary thermal suppression system of the present disclosure is designed to incorporate expandable gap fillers to mitigate thermal energy transfer within a battery array and / or traction battery pack. The system can offer numerous advantages over known solutions, including, but not limited to, a non-conductive configuration that rapidly slows or even prevents thermal energy transfer between cells and / or arrays.

[0061] Although different non-limiting embodiments are shown as having specific components or steps, the embodiments of the present disclosure are not limited to these specific combinations. Some components or features from any one of the non-limiting embodiments can be used in combination with features or components from any one of the other non-limiting embodiments.

[0062] It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings.It should be understood that although particular component arrangements are disclosed and shown in these exemplary embodiments, other arrangements may also benefit from the teachings of this disclosure.

[0063] The foregoing description should be interpreted as illustrative and not limiting. Those skilled in the art will appreciate that certain modifications may occur within the scope of this disclosure. For these reasons, the appended claims should be studied to determine the true scope and content of this disclosure.

Claims

1. A traction battery pack comprising: void space; as well as An expandable gap filler is disposed within the void space and is configured to transition from a compressed state to an uncompressed state when a temperature proximate the expandable gap filler exceeds a predefined temperature threshold, thereby reducing a free air volume of the void space. 2 . The traction battery pack of claim 1 , wherein the void space extends between a first cell tab terminal of a first battery cell and a second cell tab terminal of a second battery cell.

3. The traction battery pack of claim 1 or 2, wherein the void space extends between the battery array and the array housing top plate.

4. A traction battery pack as claimed in any preceding claim, wherein the void space extends between the battery array and the electronics housing.

5. A traction battery pack according to any preceding claim, wherein the expandable gap filler comprises a foam portion and a binding wrapped around the foam portion. 6 . The traction battery pack of claim 5 , wherein the binding member is configured to melt to allow the foam portion to expand when the temperature exceeds the predefined temperature threshold. 7 . The traction battery pack of claim 6 , wherein the predefined temperature threshold is a melting point of the binding member. 8 . The traction battery pack according to claim 5 , wherein the foam portion is made of a flexible, high-temperature resistant solid foam material.

9. The traction battery pack of claim 8, wherein the flexible, high temperature resistant solid foam material comprises silicone rubber foam, and optionally wherein the flexible, high temperature resistant solid foam material comprises an expansion aid.

10. The traction battery pack of claim 5, wherein the binding is constructed of a low-melting-point material, and optionally wherein the low-melting-point material comprises polyethylene terephthalate (PET) or a polyolefin.

11. A traction battery pack as claimed in any preceding claim, wherein in the uncompressed state the expandable gap filler creates a thermal barrier within the void space.

12. A traction battery pack comprising: A battery cell stack, the battery cell stack comprising at least a first battery cell and a second battery cell; The first battery cell includes a first cell tab terminal; The second battery cell includes a second cell tab terminal; and An expandable gap filler is arranged in a void space extending between the first battery cell tab terminal and the second battery cell tab terminal, wherein the expandable gap filler is configured to transition from a compressed state to an uncompressed state when a temperature within the void space exceeds a melting point of a binding member of the expandable gap filler.

13. The traction battery pack of claim 12, wherein the binding wraps around a foam portion of the expandable gap filler.

14. The traction battery pack of claim 13, wherein the binding member is composed of polyethylene terephthalate (PET) and the foam portion is composed of silicone rubber foam.

15. The traction battery pack of any one of claims 12 to 14, wherein the expandable gap filler is secured to a surrounding structure located adjacent to the cell stack, and optionally wherein the surrounding structure is an array housing plate or a busbar module frame.

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