Flame-retardant coated fabric insulation

Abstract

A flexible heat insulator has a fabric layer, a flame retardant outer coating adhered to the outer side of the fabric layer, and a pressure sensitive adhesive layer adhered to the inner side of the fabric layer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 443,227, filed February 3, 2023, and priority to U.S. Application Serial No. 18 / 431,754, filed February 2, 2024, which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates generally to thermal insulation and, more particularly, to thermal insulation for inhibiting the propagation of flames between and from battery cells in electric vehicle battery packs. Background Art

[0004] It is well known to house or shield battery packs, including those used in electric vehicle applications, in insulation. A common material for forming such insulation is fiberglass fabric. While fiberglass fabric insulation provides an acceptable level of protection against contamination and ambient temperature during normal use, fiberglass fabric insulation does not provide the desired level of protection in suppressing the propagation of flames, such as in the event of thermal runaway of one or more cells in an electric vehicle battery pack. As shown in Figures 2A-2C, a battery pack 12 and its housing 14 have fiberglass insulation between and around the cells 16 of the battery pack 12. The fiberglass insulation may cause any one of the cells 16 of the battery pack 12 to enter a thermal runaway condition, causing a flame to spread over a range of 1000 to 1000°C. o C, spreading from a single cell 16 (FIG. 2A) to multiple cells (FIG. 2C) in less than 10 minutes.

[0005] It is desirable to provide a thermal insulator which can o C-1400 o C, when the battery cells of the battery pack are exposed to flames at a distance of about 25 mm for 10 minutes or more, the insulation can inhibit the spread of flames between the cells of the battery pack. Summary of the Invention

[0006] The purpose of this disclosure is to provide a thermal insulation material for electric vehicle battery packs that can at least meet the requirements of 1200-1400 o The need to suppress the spread of flame from or within the battery pack for 10 minutes or more at a temperature of 30°C.

[0007] Another object of the present disclosure is to provide a thermal insulation material for an electric vehicle battery pack that is flexible, lightweight, and has a slim profile, minimizing the space it occupies between and around the battery cells.

[0008] Another object of the present disclosure is to provide a thermal insulation material for an electric vehicle battery pack that has low manufacturing and use costs.

[0009] According to one aspect of the present invention, the insulation material is a coated fabric insulation having a fabric layer, a flame retardant outer coating bonded to the outside of the fabric layer, and a pressure sensitive adhesive layer bonded to the inside of the fabric layer, wherein the fabric layer is sandwiched between the flame retardant outer coating and the pressure sensitive adhesive layer.

[0010] According to another aspect of the present invention, the fabric layer may be a fabric woven from mineral fiber yarns.

[0011] According to another aspect of the present invention, the mineral fiber yarn of the fabric may be provided by at least one of silica multifilaments, glass fiber multifilaments, basalt multifilaments, and Nomex multifilaments.

[0012] According to another aspect of the present invention, a fabric is provided having an areal density of about 30-40 ounces per square yard.

[0013] According to another aspect of the present invention, a release layer is releasably bonded to a pressure-sensitive adhesive layer, and the release layer is removed to expose the pressure-sensitive adhesive layer for bonding to a surface of an electric vehicle battery pack.

[0014] According to another aspect of the present invention, the pressure sensitive adhesive is flame retardant.

[0015] According to another aspect of the present invention, the pressure sensitive adhesive is an acrylic adhesive.

[0016] According to another aspect of the present invention, the flame retardant outer coating is a composite comprising liquid silicone rubber (LSR) infused with a flame retardant material.

[0017] According to another aspect of the present invention, the composite includes about 5% to 30% by mass of the flame retardant material.

[0018] According to another aspect of the present invention, the flame retardant material injected into the LSR is mica powder.

[0019] According to another aspect of the present invention, the composite contains about 15% by mass of mica powder.

[0020] According to another aspect of the present invention, the flame retardant outer coating is cured.

[0021] According to another aspect of the present invention, the thickness of the flame retardant outer coating is between 0.5 mm and 1.0 mm.

[0022] According to another aspect of the present invention, the coated textile insulation has a thickness between about 1.0 mm and 2.0 mm.

[0023] According to another aspect of the present invention, the maximum thickness of the coated textile insulation is 2.0 mm.

[0024] According to another aspect of the present invention, an electric vehicle battery pack is provided. The electric vehicle battery pack includes a housing defining a plurality of battery cells. Furthermore, a coated textile thermal insulator is disposed between and / or around the plurality of battery cells. The coated textile thermal insulator includes a textile layer, a flame-retardant outer coating bonded to the outside of the textile layer, and a pressure-sensitive adhesive layer bonded to the inside of the textile layer, wherein the textile layer is sandwiched between the flame-retardant outer coating and the pressure-sensitive adhesive layer.

[0025] According to another aspect of the present invention, a method for manufacturing a thermal insulation material for electric vehicle battery packs is provided. The method includes interweaving mineral fiber yarns to form a fabric layer. Furthermore, a composite is formed by mixing liquid silicone rubber (LSR) with a flame-retardant material, bonding the composite to the outer side of the fabric layer, and curing the composite to form a flame-retardant outer coating. Furthermore, an adhesive is bonded to the inner side of the fabric layer, and a release layer is used to protect the adhesive.

[0026] According to another aspect of the present invention, the method may further comprise infusing the fabric layer with a composite material such that the composite material fills gaps between the interwoven mineral fiber yarns.

[0027] According to another aspect of the present invention, the method may further comprise providing a flame retardant material in the composite in the form of mica powder.

[0028] According to another aspect of the present invention, the method further comprises providing mica powder in an amount of about 5% to 30% by weight of the composite.

[0029] According to another aspect of the present invention, the method may further include providing mica powder in an amount between about 15% by mass of the composite.

[0030] According to another aspect of the present invention, the method further comprises providing a flame retardant outer coating having a thickness between about 0.5 mm and 1.0 mm.

[0031] According to another aspect of the present invention, the method further comprises providing the thermal insulation material with a maximum thickness of 2.0 mm.

[0032] According to another aspect of the present invention, the method may further include using an acrylic adhesive as the pressure-sensitive adhesive.

[0033] According to another aspect of the present invention, the method further comprises providing a pressure sensitive adhesive having a peel strength of about 5 N / 25 mm under normal operating conditions.

[0034] According to another aspect of the present invention, the method further includes providing the fabric layer having an areal density between about 30 oz / yd2 and 40 oz / yd2.

[0035] According to another aspect of the present invention, the method may further include forming the fabric layer by a weaving process.

[0036] According to another aspect of the present invention, the method may further include forming the fabric layer using at least one of silica multifilaments, glass fiber multifilaments, basalt multifilaments, and Nomex multifilaments.

[0037] According to another aspect of the present invention, the method may further include forming the fabric layer entirely of silica multifilaments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other aspects, features and advantages will be readily understood by those skilled in the art after considering the following: the detailed description of the preferred embodiments and best mode of implementation of the present invention, the appended claims and the accompanying drawings, in which: FIG1 is a schematic perspective view of an electric vehicle having a battery pack equipped with a multi-layer insulation constructed according to one aspect of the present invention; Figures 2A-2C schematically illustrate a thermal runaway situation in an electric vehicle battery pack according to the prior art, without the coated textile insulation disclosed in the present invention, where the flame spreads unhindered from the fire location (Figure 2A) to multiple cells of the battery pack (Figure 2C); Figure 3A-3C 2A-2C , wherein an electric vehicle battery pack includes a coated fabric insulation constructed according to one aspect of the present disclosure that can suppress and prevent flames from emanating from a single battery cell ( Figure 3A ) to multiple cells in the battery pack ( Figure 3C )spread; Figure 4 is a schematic side view of a flexible insulator according to a non-limiting embodiment of the present disclosure; and Figure 5 is based on Figure 4 A partially cutaway fragmentary perspective view of a flexible insulator is shown. DETAILED DESCRIPTION

[0039] Referring to the accompanying drawings in more detail, Figure 1A motor vehicle, shown as an electric motor vehicle (also referred to as an EV), is shown having a battery pack 12 (e.g., a lithium-ion battery pack). By way of example and not limitation, the battery pack is configured with an insulation material (also referred to as coated fabric insulation or flexible insulation 10) according to an aspect of the present invention. The EV battery pack 12 includes a housing member (also referred to as a casing or housing 14) that defines a plurality of battery cells 16 and includes busbars connecting the cells, high-voltage electrical connectors, cell interfaces, low-voltage signal lines, high-voltage electrical cables, and a cooling system having cooling tubes through which a coolant can flow, as is well known in EV battery packs. During normal use, including in abnormal situations (e.g., in the event of a vehicle crash or other impact force to the battery pack 12), compared to a battery pack 12 without the multi-layer insulation 10 disclosed herein (which may result in flame spread), propagation may result in a thermal runaway condition originating in any one of the battery cells 16 of the battery pack 12 being controlled and contained by the multi-layer insulation 10 when the multi-layer insulation 10 is disposed between and / or around the battery cells 16, as shown in Figures 3A-3C, thereby maintaining the internal temperature of the battery cell between 1200-1400°C. o C, the flame spread is arrested for at least 10 minutes and the outer surface temperature of the battery housing 14 (also called the shell) is maintained below 400 C for at least 10 minutes. o C, preferably 370 o C. The flexible insulator 10 can withstand a dielectric condition of 2000 V before and after exposure to flame for 10 minutes, and its tensile strength is not less than 200 N / cm.

[0040] As shown in Figures 3A-3C , the insulator 10 can be positioned between adjacent battery cells 16 to thermally isolate the battery cells 16 from one another and shield and protect the surfaces of the battery pack housing 14, the aforementioned busbars, high-voltage electrical connectors, cell interfaces, low-voltage signal lines, high-voltage cables, and cooling pipes from extreme thermal runaway conditions, contaminants (such as fluids or debris), and impact forces (such as those experienced in a crash). The insulator utilizes a relatively thin, flexible composite wall 18, for example, with a thickness of no greater than 2.0 mm. This thin and flexible composite wall 18 can be configured as needed, for example, to wrap around busbars, electrical wires, pipes, connectors, etc. into a hollow tubular sleeve structure. It can also be used in sheet form (e.g., a flat sheet) to provide a protective outer barrier around the periphery of the battery cells 16 and between adjacent battery cells 16, effectively thermally isolating each battery cell 16 from adjacent cells 16.

[0041] As shown in the schematic diagram of FIG4 and the photograph of FIG5 , the composite wall 18 includes a fabric layer 20, a flame-retardant outer coating 22 bonded to the outer surface (also referred to as outer side 24) of the fabric layer 20, and a pressure-sensitive adhesive layer 26 bonded to the inner surface (also referred to as inner side 28) of the fabric layer 20. Thus, the fabric layer 20 is sandwiched between the flame-retardant outer coating 22 and the pressure-sensitive adhesive layer 26.

[0042] The fabric layer 20 is provided in the form of a textile layer, such as a fabric woven from mineral fiber yarns 30. The fabric is woven using a tight weave pattern (such as, but not limited to, a plain weave pattern) to enhance flame retardancy, and has an areal density of approximately 30 to 40 ounces per square yard. By way of example and not limitation, the mineral fiber yarns 30 of the fabric 20 may be at least one of silica multifilaments, glass fiber multifilaments, basalt multifilaments, and Nomex multifilaments.

[0043] Pressure-sensitive adhesive layer 26 has flame-retardant properties and, in a preferred embodiment, is an acrylic adhesive. Release layer 32 is releasably bonded to the side of pressure-sensitive adhesive layer 26 facing away from fabric layer 20, allowing for selective removal to expose the underlying pressure-sensitive adhesive layer 26 for bonding to the desired surface of electric vehicle battery pack 12. Under normal operating conditions, pressure-sensitive adhesive layer 26 has a minimum peel strength of 5 N / 25 mm.

[0044] In Figure 5, the flame-retardant outer coating 22 is partially cut away to reveal only the underlying fabric layer 20. The flame-retardant outer coating 22 is a composite comprising liquid silicone rubber (LSR) infused with a flame-retardant material. According to one aspect of the present disclosure, the flame-retardant material infused into the LSR is mica powder. The flame-retardant outer coating 22 contains approximately 10% to 20% by mass of the flame-retardant material. In one exemplary embodiment, the flame-retardant outer coating 22 contains approximately 10% to 20% by mass of mica powder, more specifically approximately 15% mica powder. After being bonded to the fabric layer 20, the flame-retardant outer coating 22 is cured. The thickness of the flame-retardant outer coating 22 is between approximately 0.5 mm and 1.0 mm. The flame retardant outer coating 22 may be flush with or cover the periphery of the fabric layer 20 to enhance flame retardancy and prevent fabric edge fraying so that no fibers of the fabric layer 20 extend more than 5 mm beyond the periphery of the flexible insulation 10 .

[0045] According to another aspect of the present invention, an electric vehicle battery pack 12 is provided. The electric vehicle battery pack 12 includes a housing 14 that defines a plurality of battery cells 16. Furthermore, a coated textile insulation 10 is disposed between and / or around the plurality of battery cells 16. The coated textile insulation 10 includes a textile layer 20, a flame-retardant outer coating 22 bonded to an outer side 24 of the textile layer 20, and a pressure-sensitive adhesive layer 26 bonded to an inner side 28 of the textile layer 20, such that the textile layer 20 is sandwiched between the flame-retardant outer coating 22 and the pressure-sensitive adhesive layer 26. The flame-retardant outer coating 22 is a composite comprising approximately 5% to 30% (by mass) mica powder. The mica powder is infused into the composite's matrix (e.g., liquid silicone rubber (LSR)).

[0046] According to another aspect of the present invention, a method for manufacturing an insulator 10 for an electric vehicle battery pack 12 is provided. The method includes interweaving mineral fiber yarns 30 to form a fabric layer 20. Furthermore, a composite is formed by mixing liquid silicone rubber (LSR) with a flame-retardant material, bonding the composite to the outer surface (also referred to as outer side 24) of the fabric layer 20, and curing the composite to form a flame-retardant outer coating 22. Furthermore, an adhesive 26 is bonded to the inner surface (also referred to as inner side 28) of the fabric layer 20, and a release ply 32 is used to protect the adhesive 26 until it is removed to expose the adhesive for bonding to a desired surface.

[0047] According to another aspect of the present invention, the method may further include injecting a composite into the fabric layer 20 so that the composite fills the gaps between the interwoven mineral fiber yarns 30 .

[0048] The method further includes providing a flame retardant material in the composite in the form of mica powder, the mass of the mica powder being approximately 5% to 30% by mass of the composite.

[0049] According to another aspect of the present invention, in one exemplary embodiment, the method may further include providing mica powder in an amount of about 15% by mass of the composite.

[0050] According to another aspect of the present invention, the method further comprises providing the flame retardant outer coating having a thickness between about 0.5 mm and 1.0 mm.

[0051] 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 one another, provided such combinations do not conflict with one another. Therefore, it should be understood that, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.

Claims

1. A flexible thermal insulator for an electric vehicle battery pack, comprising: fabric layer; a flame retardant outer coating bonded to the outside of the fabric layer; as well as A pressure sensitive adhesive layer is bonded to the inner side of the fabric layer, wherein the fabric layer is sandwiched between the flame retardant outer coating and the pressure sensitive adhesive layer.

2. The flexible thermal insulation body according to claim 1, wherein: The fabric layer comprises woven mineral fiber yarns.

3. The flexible thermal insulator according to claim 2, wherein: The mineral fiber yarn includes at least one of silica multifilament, glass fiber multifilament, basalt multifilament and Nomex multifilament.

4. The flexible thermal insulator according to claim 2, wherein: The fabric layer is a woven structure having an areal density of between about 30 ounces per square yard and about 40 ounces per square yard.

5. The flexible thermal insulator according to claim 1, further comprising a release layer releasably bonded to the pressure-sensitive adhesive layer, the release layer being adapted to be removed to expose the pressure-sensitive adhesive layer for bonding to the surface of the electric vehicle battery pack.

6. The flexible thermal insulator according to claim 1, wherein The pressure sensitive adhesive is flame retardant.

7. The flexible thermal insulation body according to claim 6, wherein: The pressure-sensitive adhesive is an acrylic adhesive.

8. The flexible thermal insulation body according to any one of claims 1, wherein: The flame retardant outer coating is a composite comprising liquid silicone rubber (LSR) impregnated with a flame retardant material.

9. The flexible thermal insulation body according to claim 8, wherein: The composite includes about 5% to 30% by mass of a flame retardant material.

10. The flexible thermal insulation body according to claim 9, wherein: The flame retardant material is mica powder.

11. The flexible thermal insulation body according to claim 10, wherein: The composite includes about 15% by weight of mica powder.

12. The flexible thermal insulator according to claim 1, wherein The flame retardant outer coating is cured.

13. The flexible thermal insulator according to claim 1, wherein The thickness of the flame retardant outer coating is between about 0.5 mm and 1.0 mm.

14. The flexible insulator of claim 1, wherein the thickness of the flexible insulator is between about 1.0 mm and 2.0 mm.

15. An electric vehicle battery pack, comprising: shell; a plurality of battery cells defined by the housing; as well as a flexible thermal insulator fixed to at least one surface of the housing, the flexible thermal insulator having: fabric layer; a flame retardant outer coating bonded to the outside of the fabric layer; as well as A pressure sensitive adhesive layer is bonded to the inner side of the fabric layer, wherein the fabric layer is sandwiched between the flame retardant outer coating and the pressure sensitive adhesive layer.

16. The electric vehicle battery pack according to claim 15, wherein: The flame retardant outer coating is a composite comprising liquid silicone rubber (LSR) impregnated with a flame retardant material.

17. The electric vehicle battery pack according to claim 16, wherein: The flame retardant outer coating is cured.

18. The electric vehicle battery pack according to claim 17, wherein: The flame retardant material is mica powder.

19. The electric vehicle battery pack according to claim 18, wherein: The composite includes about 5 to 30% by mass of mica powder.

20. The electric vehicle battery pack according to claim 15, wherein: The fabric layer comprises woven mineral fiber yarns and has an areal density of between about 30 ounces per square yard and about 40 ounces per square yard.

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