Thermal and electrical insulators for battery packs

Abstract

A flexible thermal insulator for an electric vehicle battery pack and an electric vehicle battery pack including the same are provided. The flexible thermal insulator has a composite wall including a sheet of fire-resistant material having first and second opposing sides. A first pressure-sensitive adhesive layer is bonded to the first side of the sheet of fire-resistant material. Additionally, either a scrim-reinforced polyetheretherketone layer is bonded to the second side of the fire-resistant material or a silicone rubber layer is bonded to the second side of the fire-resistant material.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 223,481, filed July 19, 2021, and priority to U.S. Application No. 17 / 866,316, filed July 15, 2022, which are incorporated herein by reference in their entireties.

[0002] Background of the Invention 1.Technical Field The present invention relates generally to thermal and electrical insulators, and more particularly to thermal and electrical insulators for inhibiting flame propagation in and out of battery packs.

[0003] 2. Related technologies It is known to encase or shield battery packs, such as those used in electric vehicle applications, in thermal insulation. A common material used to form such thermal insulation is woven fiberglass. While woven fiberglass insulation provides a satisfactory level of protection against contamination and environmental temperatures during normal use, woven fiberglass insulation does not provide a desired level of protection against flame propagation from the battery pack to the outside or between the cells of the battery pack, which may be encountered, for example, during a thermal runaway condition of one or more cells of the battery pack in an electric vehicle. It is desirable to provide thermal insulation that also provides electrical insulation protection to the battery pack while preventing flame propagation from the battery pack and flame propagation between the cells of the battery pack.

[0004] Summary of the Invention It is an object of the present disclosure to provide a thermal insulator for use in an electric vehicle battery pack that addresses the desire to prevent at least the propagation of flame from the battery pack and between cells of the battery pack.

[0005] A further objective is to prevent flame propagation in the battery pack and between the cells of the battery pack at a temperature of 1000°C for 5 minutes.

[0006] A further objective is to prevent flame propagation in the battery pack and between the cells of the battery pack at temperatures of 1000°C for up to 10 minutes.

[0007] It is a further object of the present disclosure to provide a thermal insulator for use in an electric vehicle battery pack that addresses the desire to provide electrical isolation protection at least between the battery pack and the cells of the battery pack.

[0008] It is a further object of the present disclosure to provide a thermal insulator for use in an electric vehicle battery pack that is flexible so that the thermal insulator can be easily conformed around the perimeter of the battery pack and between cells of the battery pack.

[0009] A further object of the present disclosure is to further facilitate placement of thermal insulation around the perimeter of the battery pack and between the cells of the battery pack.

[0010] It is a further object of the present disclosure to provide a thermal insulator for an electric vehicle battery pack that is lightweight, has a low profile to minimize the amount of space it occupies, and is economical to manufacture and use.

[0011] One aspect of the invention provides a thermal insulator for an electric vehicle battery pack having a wall including a scrim-reinforced polyetheretherketone layer, a first pressure-sensitive adhesive layer applied to a face of the scrim-reinforced polyetheretherketone layer, and a silica fabric bonded to the pressure-sensitive adhesive.

[0012] According to another aspect of the invention, a second pressure-sensitive adhesive layer can be bonded onto the silica fabric to facilitate securing the thermal insulator in the desired location.

[0013] According to another aspect of the invention, a release film can be releasably secured to the second pressure-sensitive adhesive layer, the release film configured to be removed to expose the underlying second pressure-sensitive adhesive layer for securement to a surface of an electric vehicle battery pack and / or a housing of an electric vehicle battery pack.

[0014] According to another aspect of the present invention, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be provided as an acrylic pressure-sensitive adhesive.

[0015] According to another aspect of the invention, the wall prevents flame propagation when exposed to 1000° C. for 10 minutes.

[0016] According to another aspect of the invention, the wall has an electrical insulation resistance of 4000 Mohm or greater before and after exposure to 1000° C. for 10 minutes.

[0017] According to another aspect of the invention, the walls have a maximum thickness of 5 mm, thereby providing a thin profile which allows for greater design options and reduced weight.

[0018] According to another aspect of the invention, the walls have a maximum thickness of 2 mm, thereby having a minimized profile which allows for greater design options and minimizes weight.

[0019] According to another aspect of the invention, the wall has a dielectric strength of 2 kV after exposure to 1000° C. for 10 minutes.

[0020] According to another aspect of the invention, a flexible thermal insulator for an electric vehicle battery pack has a composite wall including a sheet of silica fabric having first and second opposing surfaces and a first pressure-sensitive adhesive layer bonded to the first surface of the silica fabric sheet.

[0021] According to another aspect of the present invention, there is provided a flexible thermal insulator for an electric vehicle battery pack having a composite wall including a sheet of flame-retardant material having first and second opposing surfaces. A first pressure-sensitive adhesive layer is bonded to the first surface of the sheet of flame-retardant material. Further, either a scrim-reinforced polyetheretherketone layer is bonded to the second surface of the flame-retardant material, or a silicone rubber layer is bonded to the second surface of the flame-retardant material.

[0022] In accordance with another aspect of the invention, a second pressure-sensitive adhesive layer may be bonded to the scrim-reinforced polyetheretherketone layer.

[0023] According to another aspect of the invention, a release film can be releasably secured to the first pressure-sensitive adhesive layer, the release film configured to be removed to expose the underlying first pressure-sensitive adhesive layer for securement to a surface of an electric vehicle battery pack and / or a housing of an electric vehicle battery pack.

[0024] According to another aspect of the present invention, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be provided as an acrylic pressure-sensitive adhesive.

[0025] According to another aspect of the invention, the composite wall resists flame propagation when exposed to 1000° C. for 10 minutes.

[0026] According to another aspect of the invention, the composite wall has an electrical insulation resistance of 4000 Mohm or greater before and after exposure to 1000° C. for 10 minutes.

[0027] According to another aspect of the invention, the composite wall has a maximum thickness of 5 mm. According to another aspect of the invention, the composite wall has a maximum thickness of 2 mm.

[0028] According to another aspect of the invention, the composite wall has a dielectric strength of 2 kV after being exposed to 1000° C. for 10 minutes.

[0029] According to another aspect of the invention, the composite wall of the flexible thermal insulator includes a silicone layer bonded to a second surface of a sheet of silica fabric.

[0030] According to another aspect of the present invention, there is provided an electric vehicle battery pack. The electric vehicle battery pack includes a housing that bounds a plurality of cells. Further, a composite wall encases the plurality of cells. The composite wall includes a sheet of silica fabric having first and second opposing surfaces, and a first pressure-sensitive adhesive layer bonded to the first surface of the silica fabric sheet.

[0031] According to another aspect of the invention, the electric vehicle battery pack can further include a second pressure-sensitive adhesive layer bonded to the scrim-reinforced polyetheretherketone layer.

[0032] According to another aspect of the invention, the electric vehicle battery pack can further include a release film releasably secured to the first pressure-sensitive adhesive layer, the release film configured to be removed to expose the underlying first pressure-sensitive adhesive layer for operable securing to a surface of the housing.

[0033] According to another aspect of the present invention, the first and second pressure-sensitive adhesive layers of the electric vehicle battery pack may be provided as acrylic pressure-sensitive adhesives.

[0034] According to another aspect of the invention, a composite wall of an electric vehicle battery pack prevents flame propagation when exposed to 1000° C. for 10 minutes.

[0035] According to another aspect of the present invention, a composite wall of an electric vehicle battery pack has an electrical insulation resistance of 4000 Mohm or greater before and after exposure to 1000° C. for 10 minutes.

[0036] According to another aspect of the invention, the composite wall of the battery pack of the electric vehicle has a maximum thickness of 5 mm.

[0037] According to another aspect of the invention, the composite wall of the battery pack of the electric vehicle has a maximum thickness of 2 mm.

[0038] According to another aspect of the invention, a composite wall of an electric vehicle battery pack has a dielectric strength of 2 kV after being exposed to 1000° C. for 10 minutes.

[0039] According to another aspect of the invention, the composite wall of the electric vehicle battery pack further includes a silicone layer bonded to the second surface of the sheet of flame retardant material, the flame retardant material being a silica fabric.

[0040] According to another aspect of the invention, a silica fabric is woven from silica multifilament yarns.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects, features, and advantages will become readily apparent to those skilled in the art in light of the following detailed description of the presently preferred embodiments and best mode, the appended claims, and the accompanying drawings. [Brief explanation of the drawings]

[0042] [Figure 1] 1 is a schematic perspective view of an electric motor vehicle having a battery pack with a plurality of thermal insulators constructed in accordance with one aspect of the present invention; [Figure 2A] 2A and 2B show schematic diagrams of multiple cells in an electric vehicle battery pack without a thermal insulator according to the present invention, in a thermal runaway state where the flame propagates unimpeded from the flame initiation point (FIG. 2A) throughout the battery pack (FIG. 2C). [Figure 2B] 2A and 2B show schematic diagrams of multiple cells in an electric vehicle battery pack without a thermal insulator according to the present invention, in a thermal runaway state where the flame propagates unimpeded from the flame initiation point (FIG. 2A) throughout the battery pack (FIG. 2C). [Figure 2C]2A and 2B show schematic diagrams of multiple cells in an electric vehicle battery pack without a thermal insulator according to the present invention, in a thermal runaway state where the flame propagates unimpeded from the flame initiation point (FIG. 2A) throughout the battery pack (FIG. 2C). [Figure 3A] 2A-2C, but showing the battery pack including multiple thermal insulators, which inhibit and prevent flame propagation from the location of the thermal runaway condition (FIG. 3A) to the entire battery pack (FIG. 3C). [Figure 3B] 2A-2C, but showing the battery pack including multiple thermal insulators, which inhibit and prevent flame propagation from the location of the thermal runaway condition (FIG. 3A) to the entire battery pack (FIG. 3C). [Figure 3C] 2A-2C, but showing the battery pack including multiple thermal insulators, which inhibit and prevent flame propagation from the location of the thermal runaway condition (FIG. 3A) to the entire battery pack (FIG. 3C). [Figure 4] 1 is a schematic perspective view of a thermal insulator according to one embodiment of the present disclosure. [Figure 4A] 5 is a graph showing the housing surface temperature of a battery pack including the thermal insulator of FIG. 4, the battery pack being exposed to 1000° C. for 10 minutes. [Figure 5] FIG. 2 is a schematic perspective view of a thermal insulator according to another embodiment of the present disclosure. [Figure 5A] 6 is a graph showing the housing surface temperature of a battery pack including the thermal insulator of FIG. 5, the battery pack being exposed to 1000° C. for 10 minutes. DETAILED DESCRIPTION OF THE INVENTION

[0043] Detailed Description of the Preferred Embodiments Referring more particularly to the drawings, Figure 1 illustrates a motor vehicle (also referred to as an electric vehicle 11) shown as an electric motor vehicle having a battery pack 12, such as a lithium-ion battery pack, configured with at least one thermal insulator 10 (shown as multiple thermal insulators 10) in accordance with one embodiment of the present invention. The electric vehicle's battery pack 12 includes a housing 14 with multiple battery modules 15, each battery module 15 defining multiple cells 16. During normal use or under abnormal circumstances, such as a vehicle crash or any other condition that causes an impact force on the battery pack 12, a thermal runaway condition that begins in any one of the cells 16 is controlled and suppressed by the thermal insulator 10, thereby preventing flame propagation between the cells 16 and to the exterior of the battery pack 12 for at least 10 minutes, and maintaining the exterior temperature of the battery housing, also referred to as the case, 14 below 500°C, as evidenced by testing at a temperature of 1000°C for 10 minutes. (FIG. 4A shows the exterior surface temperature 17, indicated at 19, of a first embodiment of the thermal insulator 10 constructed in accordance with one aspect of the present disclosure when exposed to a temperature of 1000°C for 10 minutes, and FIG. 5A shows the exterior surface temperature 117, indicated at 119, of a second embodiment of the thermal insulator 110 constructed in accordance with another aspect of the present disclosure when exposed to a temperature of 1000°C for 10 minutes; the differences between the thermal insulators 10, 100 are explained in more detail below.)

[0044] As shown schematically in FIG. 4 , the thermal insulator 10 includes a generally flat composite sheet (also referred to as a composite wall, laminate wall, or wall 18) that overlies and extends between a plurality of cells 16 to effectively insulate each cell 16 from adjacent cells 16. The composite wall 18 includes a sheet of insulating fabric 20 having opposite first and second surfaces 22, 24. The insulating fabric 20 is formed from a flame-retardant material, such as tightly woven flame-retardant filaments (also referred to as multifilament yarns); in one preferred embodiment, the insulating fabric 20 is formed entirely from tightly interwoven silica multifilament yarns 25, preferably woven using a tight plain weave pattern for maximum density. Additionally, a first pressure-sensitive adhesive layer 26 can be bonded to the first surface 22 of the sheet of silica fabric 20 to facilitate securing the composite wall 18 to desired surfaces of the battery pack 12, including between adjacent cells 16 and / or around the interior and / or exterior surfaces of the housing 14. Additionally, a silicone rubber layer 28 is coated or otherwise bonded to the second surface 24 of the sheet of silica fabric 20. The silicone rubber layer 28 is a fluid-impermeable layer that significantly improves the flame retardancy of the wall 18 while providing additional protection against the ingress of contaminants, thereby further preventing flame propagation from the cells 16 to the outside and between adjacent cells 16, thereby extending the useful life of the battery pack 12 in the event of an emergency.

[0045] According to another aspect of the present invention, the composite wall 118 of the thermal insulator 110 of the electric vehicle battery pack 12 may further include a second pressure-sensitive adhesive layer 30 bonded to the second side 24 of the woven fabric sheet of silica fabric 20, as shown in FIG. 5 , in place of the silicone rubber layer 28 described above with respect to the thermal insulator 10, and may further include a scrim-reinforced polyetheretherketone layer 32 bonded to the second pressure-sensitive adhesive layer 30, such that the second pressure-sensitive adhesive layer 30 is sandwiched between the second side 24 of the sheet of silica fabric 20 and the scrim-reinforced polyetheretherketone layer 32.

[0046] According to another aspect of the present invention, the electric vehicle battery pack can further include a release film 34 releasably secured to the first pressure-sensitive adhesive layer 26, the release film 34 being configured to be removed to expose the underlying first pressure-sensitive adhesive layer 26 for operably securing to a surface of each cell 16 and housing 14.

[0047] According to another aspect of the present invention, the first and second pressure-sensitive adhesive layers 26, 30 of the electric vehicle battery pack 12 may be provided as acrylic pressure-sensitive adhesives.

[0048] According to another aspect of the present invention, the composite walls 18, 118 of the electric vehicle battery pack 12 resist flame propagation when exposed to 1000° C. for 10 minutes.

[0049] According to another aspect of the present invention, the composite walls 18, 118 of the electric vehicle battery pack 12 have an electrical insulation resistance of 4000 Mohm or greater before and after exposure to 1000° C. for 10 minutes.

[0050] According to another aspect of the present invention, the composite walls 18, 118 of the electric vehicle battery pack 12 have a maximum thickness (t) of 5 mm.

[0051] According to another aspect of the present invention, the composite walls 18, 118 of the electric vehicle battery pack 12 have a maximum thickness (t) of 2 mm.

[0052] According to another aspect of the present invention, the composite walls 18, 118 of the electric vehicle battery pack 12 have a dielectric strength of 2 kV after being exposed to 1000° C. for 10 minutes.

[0053] Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is contemplated that all features of all claims and all embodiments may be combined with each other, provided such combinations are not mutually inconsistent. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.

Claims

1. 1. A flexible thermal insulator for an electric vehicle battery pack, comprising: a sheet of flame retardant material having first and second opposed surfaces; a first pressure-sensitive adhesive layer directly bonded to the first surface of the sheet of flame-retardant material; a second pressure-sensitive adhesive layer directly bonded to the second surface of the sheet of flame-retardant material; a scrim-reinforced polyetheretherketone layer directly bonded to the second pressure-sensitive adhesive layer; Composite wall including 1. A flexible thermal insulator comprising:

2. a release film releasably secured to the first pressure-sensitive adhesive layer; further comprising 10. The flexible thermal insulator of claim 1, wherein the release film is configured to be removed to expose the underlying first pressure-sensitive adhesive layer for fastening to a surface of a battery pack of the electric vehicle.

3. 3. The flexible thermal insulator of claim 2, wherein the first and second pressure-sensitive adhesive layers are acrylic pressure-sensitive adhesives.

4. 10. The flexible thermal insulator of claim 1, wherein the wall prevents flame propagation when exposed to 1000°C for 10 minutes.

5. 10. The flexible thermal insulator of claim 1, wherein the wall has an electrical insulation resistance of 4000 Mohm or greater before and after exposure to 1000°C for 10 minutes.

6. 10. The flexible thermal insulator of claim 1, wherein the wall has a maximum thickness of 5 mm.

7. 7. The flexible thermal insulator of claim 6, wherein the wall has a maximum thickness of 2 mm.

8. 10. The flexible thermal insulator of claim 1, wherein the wall has a dielectric strength of 2 kV after exposure to 1000°C for 10 minutes.

9. 3. The flexible thermal insulator of claim 2, wherein the sheet of flame retardant material is a woven sheet of silica multifilament yarn.

10. Housing and a plurality of cells bounded by the housing; Multiple compound walls and It consists of Each of the composite walls comprises: a sheet of fire-resistant material having first and second opposed surfaces; a first pressure-sensitive adhesive layer bonded to the first surface of the sheet of fire-resistant material; a silicone rubber layer bonded directly to the second surface of the fire-resistant material; and It contains At least some of the composite walls separate adjacent ones of the cells from each other.

11. A housing; a plurality of cells bounded by the housing; Multiple compound walls and Equipped with Each of the composite walls comprises: a sheet of fire-resistant material having first and second opposed surfaces; a first pressure-sensitive adhesive layer directly bonded to the first surface of the sheet of fire-resistant material; a second pressure-sensitive adhesive layer bonded directly to the second surface of the scrim-reinforced polyetheretherketone layer; and a scrim-reinforced polyetheretherketone layer bonded to the second pressure-sensitive adhesive layer; and It contains At least some of the composite walls separate adjacent ones of the cells from each other.

12. a release film releasably secured to the first pressure-sensitive adhesive layer; further comprising 12. The electric vehicle battery pack of claim 11, wherein the release film is configured to be removed to expose the underlying first pressure-sensitive adhesive layer for operable fastening to a surface of the housing.

13. 13. The electric vehicle battery pack according to claim 12, wherein the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are acrylic pressure-sensitive adhesives.

14. 11. The electric vehicle battery pack of claim 10, wherein the composite wall prevents flame propagation when exposed to 1000°C for 10 minutes.

15. 11. The electric vehicle battery pack of claim 10, wherein the composite wall has an electrical insulation resistance of 4000 Mohm or greater before and after exposure to 1000°C for 10 minutes.

16. 16. The electric vehicle battery pack of claim 15, wherein the composite wall has a maximum thickness of 2 mm.

17. 11. The electric vehicle battery pack of claim 10, wherein the composite wall has a dielectric strength of 2 kV after exposure to 1000°C for 10 minutes.

18. 11. The electric vehicle battery pack of claim 10, wherein the sheet of fire-resistant material is a silica fabric.

19. 20. The electric vehicle battery pack of claim 18, wherein the silica fabric sheet is a woven fabric sheet, the woven fabric sheet being woven from silica multifilament yarn.

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