Insulator for multilayer battery packs

Abstract

An insulator for a flexible multilayer battery pack for electric vehicles, having a multilayer wall comprising multiple layers. The multiple layers include an inner layer made of a mineral material having an inner surface and an outer surface, and an outer layer made of a mineral material having an inner surface and an outer surface. A flame-retardant coating containing silicone and mica is bonded to at least one of the multiple layers. An adhesive layer is bonded to the outer surface of the inner layer, and at least one filament fixes the multiple layers together.

Description

Technical Field

[0001] Cross-Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 541,775 filed on September 29, 2023 and the priority of U.S. Application No. 18 / 898,496 filed on September 26, 2024, the entire disclosures of which are incorporated herein by reference in their entirety.

[0002] Background of the Invention 1. Technical Field The present invention relates generally to heat insulators, and more particularly to multilayer heat insulators for suppressing flame propagation from battery packs of electric vehicles.

Background Art

[0003] 2. Background Art It is known to enclose or shield battery packs, including those used in electric vehicle applications, with heat insulators. A common material used to form such heat insulators is glass fiber fabric. While glass fiber fabric heat insulators provide an acceptable level of protection against contamination and ambient temperatures during normal use, they do not provide the desired level of protection against flame propagation, as may be experienced during a thermal runaway condition of one or more cells in an electric vehicle battery pack. Glass fiber insulators may lead to a thermal runaway condition occurring in any one cell of the battery pack, and flames may propagate outward from the battery pack at a temperature of 1000°C in less than 5 minutes.

[0004] It is desirable to provide a heat insulator that suppresses flame propagation from the battery case of a battery pack to the outside for 10 minutes or more at a temperature of 800°C to 1500°C.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Summary of the Invention The purpose of this disclosure is to provide a multilayer material for use in electric vehicle battery packs that at least addresses the requirement of suppressing flame propagation from the battery pack at temperatures of 800 to 1500°C for more than 10 minutes.

[0006] A further objective of this disclosure is to provide a multilayer material for use in electric vehicle battery packs that minimizes the amount of flame fuel present within the multilayer material.

[0007] A further object of this disclosure is to provide a multilayer material for use in electric vehicle battery packs that is flexible, lightweight, thin and low profile to minimize the amount of space occupied by the insulation, and economical in manufacturing and use. [Means for solving the problem]

[0008] One aspect of the present invention provides an insulator for a flexible multilayer battery pack for an electric vehicle, the insulator for a flexible multilayer battery pack comprising a multilayer wall, the multilayer wall comprising a plurality of layers including an inner layer made of a mineral material having an inner surface and an outer surface, and an outer layer made of a mineral material having an inner surface and an outer surface. At least one flame-retardant coating comprising silicone and mica is bonded to at least one of the plurality of layers. An adhesive layer is bonded to the outer surface of the outer layer, and at least one filament fastens the plurality of layers to each other.

[0009] Another aspect of the present invention provides an insulator for a flexible multilayer battery pack for electric vehicles. The insulator has an inner layer made of a mineral material. The inner layer has an outer surface and an inner surface. A first flame-retardant coating is bonded to the inner surface of the inner layer. The insulator further includes an intermediate layer made of a mineral material and an outer layer made of a mineral material. The intermediate layer is located between the outer layer and the inner layer. A pressure-sensitive adhesive is bonded to the outer layer. The pressure-sensitive adhesive is oriented in the opposite direction to the intermediate layer. The insulator has at least one filament that fastens the outer layer, the intermediate layer and the inner layer together.

[0010] According to another aspect of the present invention, the entangled mineral material may be provided as mineral filaments that are entangled with one another.

[0011] According to another aspect of the present invention, the entangled mineral filament is silica.

[0012] According to another aspect of the present invention, the entangled mineral yarn is woven or knitted.

[0013] According to another aspect of the present invention, the first flame-retardant coating is a silicone-based coating.

[0014] According to another aspect of the present invention, the first flame-retardant coating comprises silicone and mica.

[0015] According to another aspect of the present invention, the mica is in the range of 1 to 35% by weight of the first flame-retardant coating.

[0016] According to another aspect of the present invention, the outer layer, the intermediate layer, and the inner layer are not joined to each other by an adhesive material.

[0017] According to another aspect of the present invention, the pressure-sensitive adhesive layer is the sole adhesive layer of the multilayer wall.

[0018] According to another aspect of the present invention, a flexible multilayer wall prevents the propagation of flames when exposed to a temperature of approximately 800 to 1500°C for a continuous period of 10 minutes.

[0019] According to another aspect of the present invention, the multilayer wall has a thickness of 1.5 mm to 2.5 mm.

[0020] According to another aspect of the present invention, an insulator for a flexible multilayer battery pack for an electric vehicle comprises a multilayer wall, the multilayer wall including a plurality of layers made of interlaced mineral material. The plurality of layers includes an outer layer having a first exposed outwardly facing surface and an inner layer having a second exposed inwardly facing surface. A flame-retardant coating is bonded to at least one of the plurality of layers. A pressure-sensitive adhesive is bonded to the first exposed outwardly facing surface. At least one filament secures the plurality of layers to one another.

[0021] According to another aspect of the present invention, a method for constructing an insulator for a flexible multilayer battery pack comprises: interlacing a mineral material to form an inner layer having an outer surface and an inner surface; bonding a first flame-retardant coating to the inner surface of the inner layer; interlacing a mineral material to form an intermediate layer; interlacing a mineral material to form an outer layer; disposing the intermediate layer between the inner layer and the outer layer; stitching at least one filament to secure the inner layer, the intermediate layer, and the outer layer to one another to form a multilayer wall; bonding a pressure-sensitive adhesive to the outer layer; and cutting the multilayer wall to a predetermined size.

[0022] According to another aspect of the present invention, the method further comprises maintaining the outer layer, the intermediate layer, and the inner layer in a separated relationship with one another except at locations where the outer layer, the intermediate layer, and the inner layer are stitched together by the at least one filament.

[0023] According to another aspect of the present invention, the method further comprises using a mineral yarn coated with a flame-retardant coating for the at least one filament.

[0024] According to another aspect of the present invention, the method further comprises using polytetrafluoroethylene for the flame-retardant coating.

[0025] According to another aspect of the present invention, the method further comprises using glass fibers or silica for the mineral yarn of the at least one filament.

[0026] These and other aspects, features, and advantages will be readily apparent to those skilled in the art upon consideration of the following detailed description of the presently preferred embodiments and best mode, the appended claims, and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] [Figure 1] 1 is a schematic perspective view of an electric vehicle equipped with a battery pack having a multilayer heat insulator constructed in accordance with one aspect of the present invention. [Figure 2] 2 is a schematic cross-sectional side view generally taken along line 2-2 of FIG. 3 of a multilayer heat insulator according to non-limiting embodiments of the present disclosure. [Figure 3] 3 is a partial perspective view of a multilayer heat insulator according to non-limiting embodiments of the present disclosure. [Figure 4] FIG. 4 is an exploded view similar to the multilayer heat insulator of FIG. 3. DETAILED DESCRIPTION OF EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0028] Detailed Description of the Preferred Embodiments As an example, with closer reference to the drawings, Figure 1 shows, but is not limited to, an electric vehicle (also referred to as an electric vehicle EV) having a battery pack 12 such as a lithium-ion battery pack made of a flexible multilayer battery pack insulator (hereinafter referred to as insulator 10) constructed according to one aspect of the present invention. The electric vehicle battery pack 12 comprises a housing member (also referred to as a housing or case 14) which, as is commonly known in electric vehicle battery packs, includes a busbar for connecting and interconnecting a plurality of cells 16 (shown hidden within a single cell pack in Figure 1 to avoid cluttering the drawings), a high-voltage electrical connector, a cell interface, low-voltage signal lines, a high-voltage cable, and a cooling system having cooling tubes through which a coolant can flow. In contrast to a battery pack 12 without a multilayer insulator 10 as disclosed herein, thermal runaway conditions occurring in any one cell 16 of the battery pack 12 during normal use and in abnormal conditions such as a vehicle collision or any other condition causing an impact force to the battery pack 12 are controlled and contained within the battery pack 12 via the multilayer insulator 10, as shown in the partial diagram of Figure 2, by having the multilayer insulator 10 positioned on the inner surface of the case 14 and around the cell 16. As a result, the propagation of flames from the case 14 to the outside is blocked for at least 10 minutes at the cell internal temperature in the range of 800-1500°C, and the outer surface temperature of the case 14 is maintained below 500°C for 5 minutes. Thus, occupants in the passenger compartment 17 of the vehicle EV are shielded from flames and exposure to high temperatures from flames, and similarly, ignition of any dielectric material 19 along the outer surface of the case 14, such as cationic electrodeposition coating (but not limited to this), is shielded. It should be understood that the insulator 10 may, if desired, be positioned along the inner surface of the upper case wall 14a, or around any other surface including the entire case 14.

[0029] The insulator 10 is in the form of a relatively thin, flexible multilayer wall (hereinafter also referred to as wall 18), for example, having a total thickness of about 1.5 mm to 2.5 mm. Because the wall 18 is thin and flexible, it can be contoured as desired to provide an external protective barrier around the upper surface of the cell 16, or around the entire outer periphery of the cell 16.

[0030] In the illustrated non-limiting embodiments, as best schematically shown in the partial view of Figure 2, the wall 18 includes a first layer (also referred to as the inner layer 20) made of a mineral material. The mineral material of the inner layer 20 may be formed of entangled mineral filaments. For example, the mineral filaments of the inner layer 20 may be entangled in a weaving process using a dense plain weave structure to form a dense woven structure, but is not limited to this. Otherwise, the mineral filaments or fibers may be entangled in a knitting process or interwoven in a nonwoven process. When assembled to form the wall 18, the inner layer 20 has an inner surface 20a and an outer surface 20b that form the innermost surface of the wall 18, and the first flame-retardant coating 22 is bonded to the inner surface 20a. According to one non-limiting embodiment, the inner layer 20 is woven from silica multifilaments, but other materials are also possible, such as glass fibers, aramid, ceramics, or other mineral materials. The first flame-retardant coating 22 is a silicone-based coating, which in one exemplary embodiment is provided as a generally homogeneous mixture of silicone and mica, where the mica functions as a flame retardant and is present in the range of 1 to 35% by weight of the first flame-retardant coating mixture. The silicone-based coating 22 is very thin, having a thickness of about 0.1 to 0.9 mm, and therefore does not significantly increase the overall thickness of the insulator 10. Since the silicone-based coating 22 is in direct contact with the cells 16, if a flame is present from one or more cells 16, the flame first comes into contact with the silicone-based coating 22, thereby causing the silicone in the coating 22 to undergo a phase change and change to silica, which forms a strong flame barrier to prevent the direct flame from passing through the inner layer 20. The silicone-based coating 22 may be applied to have a coating weight of 50 gsm to 600 gsm, and the first layer 20 may be made to have a weight of 100 gsm to 1,200 gsm.

[0031] The wall 18 further includes a second layer (also referred to as the intermediate layer 24) made of mineral material. The mineral material of the intermediate layer 24 may be formed of entangled mineral or ceramic yarns. For example, the mineral yarns of the intermediate layer 24 may be provided of the same material as described above for the mineral yarns of the first layer 20, and may be entangled in a weaving process using a dense plain weave structure to form a dense woven structure, but is not limited to this. Otherwise, the mineral yarns or fibers may be entangled in a knitting process or interwoven in a nonwoven process. The second layer 24 may be made to have a weight of 50 gsm to 1,000 gsm.

[0032] The wall 18 further includes a third layer (also referred to as the outer layer 28) made of mineral material. The mineral material of the outer layer 28 may be formed of entangled mineral yarns. For example, the mineral yarns of the outer layer 28 may be provided of the same material as described above for the mineral yarns of the first layer 20, and may be entangled in a weaving process using a dense plain weave structure to form a dense woven structure, but is not limited to this. Otherwise, the mineral yarns or fibers may be entangled in a knitting process or intertwined in a nonwoven process. A second flame-retardant coating 26 may be bonded to the third layer 28, and the second flame-retardant coating 26 may be provided of a mica-containing silicone material, the same as the silicone material described above for the first flame-retardant coating 22. Otherwise, the second flame-retardant coating 26 may simply be provided as a silicone coating. As shown in Figure 2, the second flame-retardant coating 26 is bonded to the inner surface of the third layer 28 facing the second layer 24, and as a result, the second flame-retardant coating 26 is sandwiched between the inner surface of the third layer 28 and the outward-facing surface of the second layer 24.

[0033] To facilitate fixing the insulator 10 to the case 14, the insulator 10 may include an adhesive layer, such as a pressure-sensitive adhesive 30, bonded to the outward-facing outer surface of the outer layer 28, the adhesive 30 facing in the opposite direction to the intermediate layer 24 in order to bond directly to the case 14. To fix all of the aforementioned layers 20, 24, and 28 together, at least one filament 32 is stitched together in a quilting process or the like, thereby fixing the outer layer 20, the intermediate layer 24, and the inner layer 28 together.

[0034] The outer layer 28 is woven to form a low gsm mineral cloth to facilitate adhesion of the pressure-sensitive adhesive 30 thereon, according to one non-limiting embodiment, and is woven from glass fiber multifilaments.

[0035] The pressure-sensitive adhesive layer 30 faces outward from the outer layer 28, and as a result, the pressure-sensitive adhesive layer 30 can be exposed for adhesion to the inner surface of the case 14, thereby orienting the first flame-retardant coating 22 to face the cell 16 directly. Since the pressure-sensitive adhesive layer 30 is the only adhesive layer to the insulator 10, the amount of fuel for the flame can be minimized. The pressure-sensitive adhesive layer 30 may be supplied as an acrylic material, thereby providing heat resistance. Prior to use and application, the pressure-sensitive adhesive layer 30 can be covered and protected with a release layer, which, if desired, can be selectively removed from the pressure-sensitive adhesive layer 30 for use.

[0036] For example, but not limited to, filaments 32 such as polymers, for example nylon yarn, or mineral yarns such as glass fiber, Nomex, or aramid filaments coated with polytetrafluoroethylene (PTFE) or silica, are stitched together in the quilting process to fix the inner layer 20, the intermediate layer 24, and the outer layer 28 to each other. To avoid contamination of the stitching needles during quilting, a pressure-sensitive adhesive layer 30 is preferably applied to the outer layer 28 after quilting is complete, along with a release layer if desired. The quilted wall 18 can then be cut to a predetermined size. The quilted wall 18 reduces heat conduction by allowing the individual layers 20, 24, and 28 to shift relative to each other between the stitched filaments, and the air layers between the layers 20, 24, and 28 provide further insulation against heat transfer through the insulator 10.

[0037] In another embodiment, a method for constructing an insulator 10 for a flexible multilayer battery pack includes entangling mineral threads or fibers to form an inner layer 20 having an inner surface 20a and an outer surface 20b. Furthermore, as described above, it includes bonding a first flame-retardant coating 22 to at least the inner surface 20a of the inner layer 20. Furthermore, it includes entangling mineral threads or fibers to form an intermediate layer 24. Furthermore, it includes entangling mineral threads or fibers to form an outer layer 28. Furthermore, it includes placing the intermediate layer 24 between the inner layer 20 and the outer layer 28, then stitching at least one filament 32 to fix the inner layer 20, the intermediate layer 24, and the outer layer 28 to each other to form a multilayer wall 18. Then, it includes bonding a pressure-sensitive adhesive 30 to the outer layer 28 and cutting the multilayer wall 18 to a predetermined size.

[0038] The method further includes keeping the outer layer 20, the intermediate layer 24, and the inner layer 28 separate from each other, except where they are stitched together by at least one filament 32. The stitching step may include stitching the outer layer 20, the intermediate layer 24, and the inner layer 28 through a plurality of filaments 32, each of which is spaced apart from the others, allowing relative movement of the outer layer 20, the intermediate layer 24, and the inner layer 28 between the stitched filaments 32. The stitching step further includes forming air pockets between the stitched filaments 32 to enhance the thermal insulation properties of the insulator 10.

[0039] In view of the above teachings, it is clear that many modifications and variations of the present invention are possible. All features of all claims and all embodiments are considered to be combinable with each other, as long as the combination is not contradictory. Therefore, it should be understood that the present invention may be carried out in embodiments other than those specifically described, within the scope of the appended claims.

Claims

1. An insulator for flexible multilayer battery packs for electric vehicles, It has a multilayer wall, and the multilayer wall is The multilayer wall comprises multiple layers, each of which includes an inner layer made of a mineral material having an inner surface and an outer surface, and an outer layer made of a mineral material having an inner surface and an outer surface, and the multilayer wall further comprises, The multilayer wall comprises at least one flame-retardant coating, the at least one flame-retardant coating comprising a first flame-retardant coating of silicone and mica, the first flame-retardant coating bonded to at least one of the plurality of layers, and the multilayer wall further comprises An adhesive layer bonded to the outer surface of the outer layer, An insulator for a flexible multilayer battery pack, comprising at least one filament for fixing the plurality of layers together.

2. The insulator for a flexible multilayer battery pack according to claim 1, wherein the first flame-retardant coating is bonded to the inner surface of the inner layer.

3. The insulator for a flexible multilayer battery pack according to claim 2, wherein the plurality of layers include an intermediate layer made of a mineral material disposed between the outer layer and the inner layer.

4. The insulator for a flexible multilayer battery pack according to claim 3, wherein the at least one flame-retardant coating includes a second flame-retardant coating bonded to the intermediate layer.

5. The insulator for a flexible multilayer battery pack according to claim 3, wherein the mineral material of the outer layer includes entangled silica mineral filaments.

6. The insulator for a flexible multilayer battery pack according to claim 5, wherein the mineral material of the intermediate layer includes entangled ceramic mineral filaments.

7. The insulator for a flexible multilayer battery pack according to claim 6, wherein the mineral material of the inner layer includes entangled mineral filaments of glass fibers.

8. The insulator for a flexible multilayer battery pack according to claim 3, wherein the outer layer, the intermediate layer, and the inner layer are not joined to each other by an adhesive material.

9. The insulator for a flexible multilayer battery pack according to claim 1, wherein the adhesive layer is the only adhesive layer of the multilayer wall.

10. The insulator for a flexible multilayer battery pack according to claim 1, wherein the mica is in the range of 1 to 35% by weight in the at least one flame-retardant coating.

11. An insulator for flexible multilayer battery packs for electric vehicles, It has a multilayer wall, and the multilayer wall is It includes an inner layer made of mineral material, the inner layer having an outer surface and an inner surface, and the multilayer wall further comprises, A first flame-retardant coating comprising a mixture of silicone and mica is bonded to the inner surface of the inner layer, An intermediate layer made of mineral material, The multilayer wall comprises an outer layer made of mineral material, the intermediate layer being positioned between the outer layer and the inner layer, and the multilayer wall further comprises The multilayer wall includes a pressure-sensitive adhesive layer bonded to the outer layer, the pressure-sensitive adhesive being oriented in the opposite direction to the intermediate layer, and the multilayer wall further comprises, An insulator for a flexible multilayer battery pack, comprising at least one filament for fixing the outer layer, the intermediate layer, and the inner layer together.

12. The insulator for a flexible multilayer battery pack according to claim 11, wherein at least one of the inner layer, the intermediate layer, and the outer layer of the mineral material includes entangled mineral filaments.

13. The insulator for a flexible multilayer battery pack according to claim 11, wherein each of the mineral materials in the inner layer, the intermediate layer, and the outer layer includes entangled mineral filaments.

14. The insulator for a flexible multilayer battery pack according to claim 12, wherein the entangled mineral yarn is woven or knitted.

15. The insulator for a flexible multilayer battery pack according to claim 11, wherein the outer layer, the intermediate layer, and the inner layer are not joined to each other by an adhesive material.

16. The insulator for a flexible multilayer battery pack according to claim 11, wherein the pressure-sensitive adhesive layer is the only adhesive layer of the multilayer wall.

17. The insulator for a flexible multilayer battery pack according to claim 11, wherein the mica is in the range of 1 to 35% by weight in the first flame-retardant coating.

18. The insulator for a flexible multilayer battery pack according to claim 11, wherein the inner layer has a weight of 100 gsm to 1,200 gsm, and the intermediate layer has a weight of 50 gsm to 1,000 gsm.

19. The insulator for a flexible multilayer battery pack according to claim 11, further comprising a second flame-retardant coating sandwiched between the outer layer and the intermediate layer.

20. The process involves intertwining mineral materials to form an inner layer having an outer surface and an inner surface, The first flame-retardant coating is bonded to the inner surface of the inner layer, The process involves intertwining mineral materials to form an intermediate layer, The formation of the outer layer by intertwining mineral materials, The intermediate layer is placed between the inner layer and the outer layer, Stitching at least one filament to fix the inner layer, the intermediate layer, and the outer layer to each other to form a multilayer wall, The aforementioned outer layer is bonded to a pressure-sensitive adhesive, A method for constructing an insulator for a flexible multilayer battery pack, comprising cutting the multilayer walls to a predetermined size.

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