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

Abstract

To provide 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 that is excellent in adapting to battery cell expansion and contraction, and also to provide a highly safe battery pack including the heat transfer suppression sheet.SOLUTION: In a heat transfer suppression sheet 1, a heat insulation 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 a heat insulation material on which battery cells 40 are to be placed. Furthermore, 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 as 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 addition, 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.SELECTED DRAWING: Figure 1

Description

[Technical field]

[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. [Background technology]

[0002] In recent years, from the viewpoint of environmental protection, active development of electric vehicles, hybrid vehicles, etc. that are driven by electric motors is underway. These electric vehicles, hybrid vehicles, etc. 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 have higher capacity and output than lead-acid batteries or nickel-metal hydride batteries, are mainly used for battery cells. If a battery cell experiences thermal runaway, where the temperature rises suddenly and continues to generate heat due to an internal short circuit or overcharging, the high heat and flames from the battery cell experiencing thermal runaway may spread to other adjacent battery cells. For this reason, heat transfer suppression sheets are placed between battery cells to prevent the transfer of thermal runaway and the spread of fire.

[0004] As an example of a heat transfer suppression sheet, Patent Document 1 discloses a multilayer body including a rubber sheet made of a rubber-like elastic material, a heat insulating sheet 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 heat conductivity than the rubber sheet and the heat insulating sheet. The rubber sheet has a function of enhancing adhesion between the heat source (battery cell) and the heat conductive sheet by exerting cushioning properties, and a function as a protective member that prevents the heat conductive sheet and the heat insulating sheet from being damaged by a load applied to them. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-98308 Summary of the Invention [Problem to be solved by the invention]

[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, so the heat-transfer sheet does not adhere sufficiently to the heat source. In a battery pack, in addition to measures against thermal runaway battery cells, the heat-transfer-suppressing sheet is also required to 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 has an object 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 also has excellent follow-up ability to the expansion and contraction of the battery cell. Another object of the present invention is to provide a highly safe assembled battery that includes a heat-transfer-suppressing sheet that can effectively suppress the transfer of heat from a battery cell that has experienced thermal runaway, and that also has excellent follow-up ability to the expansion and contraction of the battery cell. [Means for solving the problem]

[0008] The above object of the present invention can be 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 with an organic elastic layer interposed therebetween.

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

[0011] [2] The heat-transfer-suppressing sheet according to [1], wherein the thermally conductive layer is made of a resin containing at least one material selected from the group consisting of SiC, BN, Al2O3, AlN, Si3N4, and a carbon-based material.

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

[0013] [3] In the battery pack, a base made of a heat insulating material is interposed between the battery cells and a cooling plate to support the battery cells, A heat-transfer-suppressing sheet with a pedestal, comprising a heat insulating layer and a heat conductive layer integrally provided on one or both sides of a heat-transfer-suppressing sheet laminated with an organic elastic layer therebetween.

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

[0015] [4] The pedestal-equipped heat transfer-suppressing sheet according to [3], wherein the thermally conductive layer is made of a resin containing at least one material selected from the group consisting of SiC, BN, Al2O3, AlN, Si3N4, and a carbon-based material.

[0016] The above object of the present invention can be achieved by the following configuration [5] or [6] of a battery pack.

[0017] [5] 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, The battery pack is characterized in that the battery cells are connected in series or in parallel.

[0018] [6] A heat-transfer-suppressing sheet with a base according to [3] or [4] is disposed on a cooling plate, and a battery cell is placed on the base, and the thermally conductive layer is inserted in contact with a main surface of the battery cell; and The battery pack is characterized in that the battery cells are connected in series or in parallel. Effect of the Invention

[0019] In the heat-transfer-suppressing sheet of the present invention, the elastic force of the organic elastic layer is effectively transmitted 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. In addition, high heat and flames from a battery cell that has experienced thermal runaway are conducted to the organic elastic layer via the thermal conductive layer, causing the organic elastic layer to disappear and creating a space. This space is an air layer, which provides high thermal insulation, and in combination with the insulation provided by the insulating layer, provides even higher thermal insulation. Furthermore, when the thermally conductive layer is made of a resin containing at least one selected from SiC, BN, Al2O3, AlN, Si3N4, and a carbon-based material, the thermally conductive layer generates char (carbon substance), thereby further improving the thermal insulation properties.

[0020] Furthermore, the heat-transfer-inhibiting sheet with base of the present invention is the heat-transfer-inhibiting sheet having an integrated base made of an insulating material on which a battery cell is placed. Therefore, in addition to the above-mentioned effects of the heat-transfer-inhibiting sheet, the heat from the bottom surface of the battery cell can be effectively insulated, thereby further improving the insulating performance.

[0021] Furthermore, a battery pack equipped with the heat-transfer-inhibiting sheet or pedestal-attached heat-transfer-inhibiting sheet of the present invention effectively prevents the high heat and flames from a battery cell experiencing thermal runaway from being transmitted to adjacent battery cells, and also has excellent compliance with the expansion and contraction of the battery cells, making it extremely safe. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic diagram of one embodiment of a heat transfer-suppressing sheet of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating the effect of suppressing heat transfer to a battery cell that has experienced thermal runaway in the heat-transfer-suppressing sheet shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view that illustrates a schematic diagram of one embodiment of a pedestal-equipped heat-transfer-suppressing sheet of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a battery pack (part 1) provided with the heat-transfer-suppressing sheet of the present invention shown in FIG. [Diagram 5] FIG. 5 is a schematic diagram showing a battery pack (part 2) including the pedestal-equipped heat-transfer-suppressing sheet of the present invention shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the 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 modified and implemented as desired without departing from the gist of the present invention.

[0024] [Heat transfer suppression sheet] 1 is a cross-sectional view showing a schematic diagram of 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 an adhesive or double-sided adhesive tape, or by thermal fusion. In a battery pack, the heat-transfer-suppressing sheet 1 is inserted between battery cells 40, as indicated by dotted lines in the figure.

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

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

[0027] In the insulating material configured in this manner, since it has a plurality of three-dimensionally connected pores, it is possible to obtain the effect of air insulation and improve the insulating performance. In addition, since the insulating material contains highly flexible organic fibers, it is possible to increase the flexibility of the insulating material and the organic fibers are easily entangled with each other, improving the strength of the insulating material as a whole. Furthermore, since the presence of pores improves the cushioning properties of the insulating material as a whole, when the battery cells 40 expand during charging and discharging, the insulating material can absorb the expansion of the battery cells 40. Therefore, it is possible to suppress the destruction of the insulating layer 10 having such insulating material.

[0028] It is also preferable that at least some of the pores communicate with the surface of the insulating material and open outward. With the pores configured in this way, when the battery cell 40 experiences thermal runaway, high heat is transferred to the insulating layer 10 via the thermally conductive layer 30, and even if the organic fibers or the like are decomposed, the decomposition gas is not retained inside the insulating material but is released to the outside via the pores. Therefore, from this point of view as well, the effect of preventing destruction of the insulating layer 10 can be obtained.

[0029] As described above, when the fusion zone on the outer peripheral surface of the organic fiber fixes the inorganic particles to the organic fibers, it is possible to obtain the effect of suppressing the falling off (powdering) of the inorganic particles. 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 a decrease in the insulating effect due to compressive deformation of the insulating material can be prevented.

[0030] The insulating material preferably contains inorganic fibers. Since inorganic fibers are not easily decomposed even at high temperatures, even if the battery cell 40 experiences thermal runaway and the organic fibers of the insulating material are decomposed, the inorganic fibers remain, so the shape of the insulating material can be reliably maintained. Furthermore, flexible organic fibers tend to be entangled with relatively hard inorganic fibers, and the inorganic fibers and organic fibers form a three-dimensional skeleton, which further improves 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 perpendicular to the thickness direction of the insulating material. Mica has excellent heat resistance and insulation properties, and a mica sheet made by processing a material containing mica into a sheet also has excellent impact resistance. Therefore, if the battery cell 40 explodes due to high temperature and debris is generated, the insulating material is protected by the mica sheet, so that damage to the insulating layer 10 can be suppressed.

[0033] The organic elastic layer 20 may be either a sponge-like material having air bubbles therein or a rubber-like elastic body not containing air bubbles, but a sponge-like material is more preferable in terms of elasticity and heat insulation performance due to the air that becomes 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 is a member that contacts the battery cells 40 to transfer heat from the battery cells 40, and is also required to have high insulation properties because it contacts the battery cells 40. Therefore, there are no limitations on the material as long as it has excellent thermal conductivity and insulation properties, and a graphite film obtained by baking a resin, a sheet containing carbon and a resin, etc. can be used. Examples of the resin include thermoplastic resins such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyamide imide (PAI), and aromatic polyamide (aramid fiber). Examples of the carbon include graphite, carbon black, diamond, and diamond-like carbon.

[0035] In order to further increase the thermal conductivity, a thermally conductive filler such as SiC, BN, Al2O3, AlN, or Si3N4 may be dispersed in the resin.

[0036] The heat-transfer-suppressing sheet 1 is a laminate of the above-mentioned heat insulating layer 10, organic elastic layer 20, and heat 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 shown by the dashed line. Therefore, part of the heat from the battery cells 40 is directly conducted to the cooling plate 50 through the bottom faces of the battery cells 40, and the remaining heat is conducted to the cooling plate 50 via the heat 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 has a structure in which a circulation path is provided inside a metal plate such as aluminum or an aluminum alloy, and a cooling liquid is circulated through the circulation path. Alternatively, a gel plate or the like can be used.

[0038] As shown in FIG. 2, when a certain battery cell 40A experiences thermal runaway, high heat from the battery cell 40A is transferred to the organic elastic layer 20A adjacent to the thermal conductive layer 30A via the thermal conductive layer 30A adjacent to the battery cell 40A. The organic elastic layer 20A is made of an organic material and is easily melted, decomposed, and disappeared at a relatively low temperature. At the same time, the blast (pressure due to cell expansion) from the battery cell 40A pushes the thermal conductive layer 30A toward the insulating layer 10, creating a space between the battery cell 40A and the thermal conductive layer 30A and between the insulating layer 10 and the thermal conductive layer 30A. This space is an air layer, so it has high insulating properties, and in combination with the insulation by the insulating layer 10, a higher insulating property is obtained.

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

[0040] In this manner, the heat-transfer-suppressing sheet 1 is constructed by laminating the heat-conducting 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 suppression sheet with pedestal] Furthermore, battery cell pedestals 70 for placing battery cells 40 on can also be attached integrally to the above-described heat-transfer-suppressing sheet 1. Fig. 3 shows one embodiment of a pedestal-attached heat-transfer-suppressing sheet 60 integrated with a battery cell pedestal 70. In the heat-transfer-suppressing sheet 60 with pedestal, 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 with an adhesive or double-sided adhesive tape.

[0042] Battery cell base 70 is made of a heat insulating material and protects the surrounding area from high heat and flames from the bottom surface of a thermal runaway battery cell 40. High heat and flames from other parts of a thermal 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 it may be another heat insulating material.

[0044] [Battery pack (part 1)] Fig. 4 is a schematic diagram showing a battery pack 100 including the heat-transfer-restricting sheet 1 shown in Fig. 1. As shown in the figure, the battery pack 100 has a plurality of battery cells 40 placed on the surface of a cooling plate 50, with the heat-transfer-restricting 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-restricting 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 pack (part 2)] Fig. 5 is a schematic diagram showing a battery pack 100 including the pedestal-attached heat-transfer-reducing sheet 60 shown in Fig. 3. As shown in the figure, the battery pack 100 has the pedestal-attached heat-transfer-reducing sheet 60 placed on the surface of a cooling plate 50, and further has battery cells 40 placed on battery cell pedestals 70. In addition, a heat-transfer-reducing sheet 1 is 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, the battery cells 40, and the cooling plate 50 are housed in a battery case 110.

[0047] The heat transfer-inhibiting sheet 60 with base has 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 conductive layer 30, as well as the insulating effect of the battery cell base 70 made of an insulating material, thereby further enhancing safety. [Explanation of symbols]

[0048] 1. Heat transfer suppression sheet 10. Insulation Layer 20, 20A Organic Elastic Layer 30 Thermal Conductive Layer 40 Battery Cells 50 Cooling Plate 60 Heat transfer suppression sheet with base 70 Battery cell stand 100 battery packs 110 Battery case

Claims

1. A heat transfer-suppressing sheet comprising a heat insulating layer and a heat conductive layer laminated via an organic elastic layer.

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. In the battery pack, a base made of a heat insulating material is interposed between the battery cells and a cooling plate to support the battery cells, A heat-transfer-suppressing sheet with a pedestal, comprising a heat insulating layer and a heat conductive layer integrally provided on one or both sides of a heat-transfer-suppressing sheet laminated with an organic elastic layer therebetween.

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. The heat transfer-suppressing sheet according to claim 1 or 2 is inserted between battery cells with the thermally conductive layer in contact with a main surface of the battery cell, The battery pack is characterized in that the battery cells are connected in series or in parallel.

6. The heat transfer-suppressing sheet with a pedestal according to claim 3 or 4 is disposed on a cooling plate, a battery cell is placed on the pedestal, and the thermally conductive layer is inserted and abuts against a main surface of the battery cell; The battery pack is characterized in that the battery cells are connected in series or in parallel.

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