Heat transfer suppression sheet, heat transfer suppression sheet with pedestal, and battery pack

Abstract

Provided is a heat transfer suppression sheet that is capable of effectively suppressing heat transfer of high heat from a battery cell in which thermal runaway has occurred, and is excellent in adapting to battery cell expansion and contraction. Also provided is a highly safe battery pack comprising said heat transfer suppression sheet. In the heat transfer suppression sheet (1), an insulating layer (10) and heat conduction layers (30) are laminated with organic elastic layers (20) interposed therebetween. A heat transfer suppression sheet (60) with a pedestal is formed by providing, in an integrated manner on one surface or both surfaces of the heat transfer suppression sheet (1), a battery cell pedestal (70) made of an insulating material on which battery cells (40) are to be placed. In a battery pack (100), a plurality of battery cells (40) have the heat conduction layers (30) of the heat transfer suppression sheet (1) interposed therebetween so at to be in contact with main surfaces of the battery cells (40), and the battery cells (40) are connected in series or in parallel. In the battery pack (100), the battery cells (40) are placed on the battery cell pedestal (70) of the heat transfer suppression sheet (60) with a pedestal.

Description

Heat transfer suppression sheet, heat transfer suppression sheet with base, and battery pack

[0001] The present invention relates to a heat-transfer-suppressing sheet and a pedestal-equipped heat-transfer-suppressing sheet that are suitable for use in a battery pack, and also to a battery pack including such a heat-transfer-suppressing sheet.

[0002] In recent years, from the viewpoint of environmental protection, active development has been made of electric vehicles, hybrid vehicles, and the like that are driven by electric motors. These electric vehicles, hybrid vehicles, and the like are equipped with assembled batteries in which multiple battery cells are connected in series or parallel to serve as the power source for the driving electric motor.

[0003] Lithium-ion secondary batteries, which offer higher capacity and power output than lead-acid batteries or nickel-metal hydride batteries, are primarily used for battery cells. If a battery cell experiences thermal runaway, such as a sudden temperature rise caused by an internal short circuit or overcharging, and continues to generate heat, the high heat and flames from the battery cell experiencing thermal runaway may spread to other adjacent battery cells. Therefore, heat-transfer-suppressing sheets are placed between battery cells to prevent the transfer of thermal runaway and the spread of fire.

[0004] For example, Patent Document 1 discloses a heat transfer suppression sheet that is a multilayer body including a rubber sheet made of a rubber-like elastic material, heat insulating sheets laminated on both sides of the rubber sheet, and a heat conductive sheet laminated on the outside of the heat insulating sheet and having better thermal conductivity than the rubber sheet and the heat insulating sheet. The rubber sheet has a function of providing cushioning to improve adhesion between the heat source (battery cell) and the heat conductive sheet, and a function as a protective member to prevent the heat conductive sheet and the heat insulating sheet from being damaged by loads applied to them.

[0005] Japanese Patent Application Publication No. 2021-98308

[0006] However, in the heat-transfer-suppressing sheet of Patent Document 1, the elasticity of the rubber sheet is transferred to the thermally conductive sheet via the insulating sheet, and therefore the heat-transfer sheet does not adhere sufficiently to the heat source. In battery packs, in addition to measures to prevent thermal runaway in battery cells, the heat-transfer-suppressing sheet must also be able to follow the expansion and contraction of battery cells during charging and discharging.

[0007] The present invention has been made in consideration of the above problems, and aims to provide a heat-transfer-suppressing sheet that can effectively suppress the transfer of high heat from a battery cell that has experienced thermal runaway and that is also highly compliant with the expansion and contraction of the battery cell. Another aim of the present invention is to provide a highly safe battery pack that includes a heat-transfer-suppressing sheet that effectively suppresses the transfer of heat from a battery cell that has experienced thermal runaway and is also highly compliant with the expansion and contraction of the battery cell.

[0008] The above object of the present invention is achieved by the heat transfer-suppressing sheet having the following configuration [1].

[0009] [1] A heat transfer-suppressing sheet, comprising a heat insulating layer and a heat conductive layer laminated together with an organic elastic layer interposed therebetween.

[0010] A preferred embodiment of the present invention relating to the heat transfer suppression sheet relates to the following [2].

[0011] [2] The heat conduction layer is made of SiC, BN, or Al. ２ O ３ , AlN, Si ３ N ４ and a carbon-based material.

[0012] The above object of the present invention is achieved by the following configuration [3] relating to the pedestal-equipped heat transfer-suppressing sheet.

[0013] [3] A heat-transfer-suppressing sheet with a pedestal, wherein the pedestal is made of a heat-insulating material and is interposed between a battery cell and a cooling plate to support the battery cell in an assembled battery, and is integrally provided on one or both sides of the heat-transfer-suppressing sheet in which a heat-insulating layer and a heat-conductive layer are laminated with an organic elastic layer interposed therebetween.

[0014] A preferred embodiment of the present invention relating to the pedestal-equipped heat transfer suppression sheet relates to the following [4].

[0015] [4] The heat conduction layer is made of SiC, BN, or Al. ２ O ３ , AlN, Si ３ N ４and a carbon-based material.

[0016] The above object of the present invention is achieved by the following configuration [5] or [6] relating to the battery pack.

[0017] [5] An assembled battery, wherein the heat transfer-suppressing sheet according to [1] or [2] is inserted between battery cells with the thermally conductive layer in contact with a main surface of the battery cell, and the battery cells are connected in series or in parallel.

[0018] [6] A battery pack comprising: a base-attached heat transfer-suppressing sheet according to [3] or [4] disposed on a cooling plate; battery cells placed on the base; the thermally conductive layer is inserted and abuts against a main surface of the battery cell; and the battery cells are connected in series or parallel.

[0019] In the heat transfer-suppressing sheet of the present invention, the elastic force of the organic elastic layer is effectively transferred to the thermally conductive layer, improving adhesion between the thermally conductive layer and the battery cell, thereby improving compliance with the expansion and contraction of the battery cell. Furthermore, high heat and flames from a battery cell experiencing thermal runaway are transferred to the organic elastic layer via the thermally conductive layer, causing the organic elastic layer to disappear and creating a space. This space is an air layer, providing high thermal insulation, which, combined with the thermal insulation provided by the thermally insulating layer, provides even higher thermal insulation. Furthermore, the thermally conductive layer can be made of SiC, BN, or Al. ２ O ３ , AlN, Si ３ N ４ When the heat conductive layer is made of a resin containing at least one material selected from the group consisting of a carbon-based material and a char (carbon substance), the heat insulating properties are further improved.

[0020] Furthermore, the heat-transfer-suppressing sheet with base of the present invention is the heat-transfer-suppressing sheet having a base made of a heat-insulating material integrally formed therewith for placing the battery cell thereon. Therefore, in addition to the effects of the heat-transfer-suppressing sheet, the heat from the bottom surface of the battery cell can be effectively insulated, thereby further improving the heat-insulating performance.

[0021] Furthermore, a battery pack equipped with the heat transfer suppression sheet or base-attached heat transfer suppression sheet of the present invention effectively prevents high heat and flames from a battery cell experiencing thermal runaway from being transmitted to adjacent battery cells, and also has excellent ability to follow the expansion and contraction of the battery cells, making it highly safe.

[0022] Fig. 1 is a cross-sectional view schematically showing one embodiment of the heat-transfer-suppressing sheet of the present invention. Fig. 2 is a diagram illustrating the effect of suppressing heat transfer on a battery cell that has experienced thermal runaway in the heat-transfer-suppressing sheet shown in Fig. 1. Fig. 3 is a cross-sectional view schematically showing one embodiment of the pedestal-equipped heat-transfer-suppressing sheet of the present invention. Fig. 4 is a schematic diagram showing a battery assembly (part 1) including the heat-transfer-suppressing sheet of the present invention shown in Fig. 1. Fig. 5 is a schematic diagram showing a battery assembly (part 2) including the pedestal-equipped heat-transfer-suppressing sheet of the present invention shown in Fig. 3.

[0023] Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below, and can be implemented with any modifications within the scope of the gist of the present invention.

[0024] [Heat Transfer-Suppressing Sheet] Figure 1 is a cross-sectional view schematically illustrating one embodiment of a heat transfer-suppressing sheet 1 of the present invention. The heat transfer-suppressing sheet 1 is configured by laminating thermally conductive layers 30 on both sides of a heat insulating layer 10 with organic elastic layers 20 interposed therebetween. The layers are integrated by bonding with adhesive or double-sided adhesive tape, or by thermal fusion bonding. In a battery pack, the heat transfer-suppressing sheet 1 is inserted between battery cells 40, as indicated by the dotted lines in the figure.

[0025] There are no particular restrictions on the insulating material that constitutes the insulating layer 10, and any conventionally used material can be used, but it is preferable that the insulating material contains the following compound.

[0026] The thermal insulating material may be a thermal insulating material having inorganic particles and organic fibers. The thermal insulating material has a plurality of three-dimensionally connected pores between the inorganic particles and the organic fibers. The organic fibers have welded portions covering at least a portion of their surfaces, and at least a portion of the inorganic particles are welded to the surfaces of the organic fibers by the welded portions. As a result, the surfaces of the organic fibers are covered with the inorganic particles.

[0027] The insulating material configured in this manner has multiple three-dimensionally connected pores, which provide the effect of air insulation and improve its insulating performance. Furthermore, the insulating material contains highly flexible organic fibers, which not only enhances the flexibility of the insulating material but also makes it easier for the organic fibers to entangle with each other, improving the overall strength of the insulating material. Furthermore, the presence of pores improves the cushioning properties of the insulating material as a whole, allowing the insulating material to absorb the expansion of the battery cells 40 when they expand during charging and discharging. Therefore, damage to the insulating layer 10 containing such insulating material can be suppressed.

[0028] It is also preferable that at least some of the pores are connected to the surface of the thermal insulation material and open outward. With the pores configured in this manner, when the battery cell 40 experiences thermal runaway, high heat is transferred to the thermal insulation layer 10 via the thermal conduction layer 30. Even if the organic fibers or the like are decomposed, the decomposition gases do not remain inside the thermal insulation material but are released to the outside via the pores. Therefore, this also contributes to preventing destruction of the thermal insulation layer 10.

[0029] As described above, when the welded portions on the outer peripheral surface of the organic fibers fix the inorganic particles to the organic fibers, it is possible to obtain the effect of suppressing the inorganic particles from falling off (powdering). Therefore, for example, even if the battery cell 40 expands and compressive stress or impact is applied to the insulating layer 10, the effect of maintaining the shape of the insulating material can be further improved, and it is possible to prevent a decrease in the insulating effect due to compressive deformation of the insulating material.

[0030] The insulating material preferably contains inorganic fibers. Since inorganic fibers are resistant to decomposition even at high temperatures, even if the battery cell 40 experiences thermal runaway and the organic fibers of the insulating material decompose, the inorganic fibers remain, allowing the insulating material to reliably maintain its shape. Furthermore, the flexible organic fibers tend to become entangled with the relatively hard inorganic fibers, forming a three-dimensional skeleton between the inorganic and organic fibers, further improving the strength of the insulating material.

[0031] The heat insulating material may be produced by either a wet method or a dry method.

[0032] Furthermore, a mica sheet may be laminated on at least one of the first and second surfaces of the insulating material, which are perpendicular to the thickness direction. Mica has excellent heat resistance and insulating properties, and mica sheets, which are made by processing a mica-containing material into a sheet, also have excellent impact resistance. Therefore, if the battery cell 40 explodes due to high temperatures and generates debris, the mica sheet protects the insulating material, thereby preventing damage to the insulating layer 10.

[0033] The organic elastic layer 20 may be a sponge-like material having air bubbles therein or a rubber-like elastic material not having air bubbles, but a sponge-like material is more preferable in terms of elasticity and heat insulation performance due to the air bubbles. Examples of organic materials constituting the organic elastic layer 20 include thermosetting elastomers such as urethane rubber, isoprene rubber, ethylene propylene rubber, natural rubber, ethylene propylene diene rubber, nitrile rubber (NBR), and styrene butadiene rubber (SBR), thermoplastic elastomers such as urethane-based, ester-based, styrene-based, olefin-based, butadiene-based, fluorine-based, and siloxane-based elastomers, and composites thereof.

[0034] The thermally conductive layer 30 contacts the battery cells 40 to transfer heat from the battery cells 40. Because it contacts the battery cells 40, it must also have high insulating properties. Therefore, any material with excellent thermal conductivity and insulating properties can be used. Examples of suitable materials include graphite films made by baking resins and sheets containing carbon and resin. Examples of suitable resins include thermoplastic resins such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyamide-imide (PAI), and aromatic polyamide (aramid fiber). Examples of suitable carbon include graphite, carbon black, diamond, and diamond-like carbon.

[0035] In addition, to further improve thermal conductivity, SiC, BN, and Al ２ O ３ , AlN, Si ３ N ４ A thermally conductive filler such as the above may be dispersed in the resin.

[0036] The heat-transfer-suppressing sheet 1 is a laminate of the heat-insulating layer 10, organic elastic layer 20, and thermally conductive layer 30, and is interposed between the battery cells 40. As shown in Fig. 4 , in a battery pack 100, the battery cells 40 are generally placed on a cooling plate 50, and as shown in Fig. 1 , one end face (the lower end face in Fig. 1 ) of the heat-transfer-suppressing sheet 1 abuts against the cooling plate 50 indicated by the dashed line. As a result, part of the heat from the battery cells 40 is conducted directly to the cooling plate 50 through the bottom faces of the battery cells 40, while the remaining heat is conducted to the cooling plate 50 via the thermally conductive layer 30 of the heat-transfer-suppressing sheet 1 or to the heat-insulating layer 10 via the organic elastic layer 20.

[0037] The cooling plate 50 is not particularly limited as long as it has a cooling function. For example, it may have a structure in which a circulation path is provided inside a metal plate such as aluminum or an aluminum alloy, and a coolant is circulated through the circulation path. Alternatively, a gel plate or the like may be used.

[0038] As shown in FIG. 2 , when a battery cell 40A experiences thermal runaway, high heat from the battery cell 40A is transferred to the organic elastic layer 20A adjacent to the thermally conductive layer 30A via the thermally conductive layer 30A adjacent to the battery cell 40A. Because the organic elastic layer 20A is made of an organic material, it easily melts, decomposes, and disappears at relatively low temperatures. At the same time, the blast (pressure due to cell expansion) from the battery cell 40A pushes the thermally conductive layer 30A toward the insulating layer 10, creating spaces between the battery cell 40A and the thermally conductive layer 30A and between the insulating layer 10 and the thermally conductive layer 30A. Because these spaces are air spaces, they provide high thermal insulation, which, combined with the insulation provided by the insulating layer 10, provides even higher thermal insulation.

[0039] The thermally conductive layer 30A also generates char (carbon material) to prevent the spread of flames from the battery cell 40A.

[0040] In this way, the heat transfer-suppressing sheet 1 is constructed by laminating the heat conductive layers 30 on both sides of the heat insulating layer 10 with the organic elastic layers 20 interposed therebetween, thereby achieving superior elasticity and heat insulating properties.

[0041] [Heat-transfer-suppressing sheet with pedestal] Battery cell pedestals 70 for placing battery cells 40 on the heat-transfer-suppressing sheet 1 can also be integrally attached to the heat-transfer-suppressing sheet 1 described above. Figure 3 shows one embodiment of a heat-transfer-suppressing sheet 60 with pedestals integrated with battery cell pedestals 70. In the heat-transfer-suppressing sheet 60 with pedestals, the battery cell pedestals 70 are attached to the lower ends of both sides of the thermally conductive layer 30 of the heat-transfer-suppressing sheet 1. The battery cell pedestals 70 are attached using an adhesive or double-sided adhesive tape.

[0042] Battery cell pedestal 70 is made of a heat insulating material and protects the surrounding area from high heat and flames from the bottom surface of a thermally runaway battery cell 40. High heat and flames from other parts of a thermally runaway battery cell 40 are also prevented in the same way as heat transfer-suppressing sheet 1 described above.

[0043] The heat insulating material that makes up the battery cell pedestal 70 may be the heat insulating material that makes up the heat insulating layer 10 of the heat transfer-suppressing sheet 1 described above, or may be another heat insulating material.

[0044] [Battery Assembly (Part 1)] Fig. 4 is a schematic diagram showing a battery assembly 100 including the heat-transfer-reducing sheet 1 shown in Fig. 1. As shown in the figure, the battery assembly 100 has multiple battery cells 40 placed on the surface of a cooling plate 50, with the heat-transfer-reducing sheet 1 interposed between the battery cells 40. The battery cells 40 are connected in series or in parallel by bus bars. The heat-transfer-reducing sheet 1, battery cells 40, and cooling plate 50 are housed in a battery case 110.

[0045] The heat transfer-suppressing sheet 1 can ensure safety even when a certain battery cell 40 experiences thermal runaway due to the air layer generated by the disappearance of the organic elastic layer 20 and the generation of char in the thermal conduction layer 30 as described above.

[0046] [Battery Assembly (Part 2)] Fig. 5 is a schematic diagram showing a battery assembly 100 including the pedestal-attached heat-transfer-reducing sheet 60 shown in Fig. 3. As shown in the figure, the battery assembly 100 has the pedestal-attached heat-transfer-reducing sheet 60 placed on the surface of a cooling plate 50, and battery cells 40 placed on battery cell pedestals 70. Heat-transfer-reducing sheets 1 are interposed between the battery cells 40. The battery cells 40 are connected in series or in parallel by bus bars, and the pedestal-attached heat-transfer-reducing sheet 60, battery cells 40, and cooling plate 50 are housed in a battery case 110.

[0047] The heat transfer suppression sheet 60 with base provides an insulating effect due to the air layer generated by the disappearance of the organic elastic layer 20 and the generation of char in the thermal conduction layer 30, and in addition, the insulating effect of the battery cell base 70 made of an insulating material is also taken into account, thereby further enhancing safety.

[0048] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0049] This application is based on a Japanese patent application (Patent Application No. 2023-142914) filed on September 4, 2023, the contents of which are incorporated herein by reference.

[0050] REFERENCE SIGNS LIST 1 heat transfer suppressing sheet 10 heat insulating layer 20, 20A organic elastic layer 30 thermally conductive layer 40 battery cell 50 cooling plate 60 heat transfer suppressing sheet with base 70 battery cell base 100 battery pack 110 battery case

Claims

1. A heat transfer suppression sheet comprising a heat insulating layer and a heat conductive layer laminated with an organic elastic layer interposed therebetween.

2. The heat conductive layer is made of SiC, BN, or Al. ２ O ３ , AlN, Si ３ N ４ 2. The heat transfer-suppressing sheet according to claim 1, comprising a resin containing at least one material selected from the group consisting of a carbon-based material and a carbon-based material.

3. A heat-transfer-suppressing sheet with a base, in which a base made of a heat-insulating material for supporting a battery cell is interposed between a battery cell and a cooling plate and is provided integrally on one or both sides of a heat-transfer-suppressing sheet in which a heat-insulating layer and a heat-conductive layer are laminated with an organic elastic layer interposed therebetween in a battery pack.

4. The heat conductive layer is made of SiC, BN, or Al. ２ O ３ , AlN, Si ３ N ４ 4. The pedestal-equipped heat-transfer-suppressing sheet according to claim 3, comprising a resin containing at least one material selected from the group consisting of a carbon-based material and a carbon-based material.

5. A battery pack comprising: a heat transfer suppressing sheet according to claim 1 or 2 interposed between battery cells with the heat conductive layer abutting against the main surface of the battery cell; and the battery cells are connected in series or parallel.

6. A battery pack comprising a heat transfer suppressing sheet with a base as described in claim 3 or 4, which is disposed on a cooling plate, a battery cell is placed on the base, and the thermally conductive layer is inserted and abuts against the main surface of the battery cell, and the battery cells are connected in series or parallel.

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