Thermal control sheet for battery pack and battery pack

Abstract

To provide a thermal control sheet for a battery pack used for a battery pack in which a plurality of battery cells are connected in series or in parallel, and that can efficiently disperse generated heat to the exterior in normal use, and can suppress heat propagation between the battery cells in the event of abnormality to prevent a chain reaction of thermorunaway.SOLUTION: A thermal control sheet 10 for a battery pack is used for a battery pack in which a plurality of battery cells are connected in series or in parallel, being interposed between the battery cells. The thermal control sheet 10 for a battery pack has: a pair of surface layers 11a and 11b in contact with the battery cells; at least one intermediate layer 12 arranged between the pair of surface layers 11a and 11b; and thermal insulation materials 13a and 13b arranged between the surface layers 11a and 11b and the intermediate layer 12, respectively. All of the surface layers 11a and 11b and the intermediate layer 12 have an emissivity lower than that of the thermal insulation materials 13a and 13b and have a thermal conductivity higher than that of the thermal insulation materials 13a and 13b.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a thermal control sheet for a battery assembly that is suitably used in a battery assembly that serves as a power source for an electric motor that drives, for example, an electric vehicle or a hybrid vehicle, and to a battery assembly using the thermal control sheet for a battery assembly. [Background technology]

[0002] In recent years, from the viewpoint of environmental protection, active development of electric vehicles and hybrid vehicles driven by electric motors has been underway. These electric vehicles and hybrid vehicles 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] These battery cells mainly use lithium-ion secondary batteries, which have higher capacity and higher output than lead-acid batteries or nickel-metal hydride batteries. However, if thermal runaway occurs in one battery cell due to an internal short circuit or overcharging (i.e., in the event of an "abnormality"), heat can be transmitted to other adjacent battery cells, potentially causing thermal runaway in the other battery cells as well.

[0004] For example, Patent Document 1 discloses an electricity storage device capable of realizing effective thermal insulation between a plurality of electricity storage elements such as lithium ion secondary batteries. The electricity storage device described in Patent Document 1 has a first plate material and a second plate material having thermal insulation properties disposed between a first electricity storage element and a second electricity storage element adjacent to each other. In addition, a low thermal conductive layer, which is a layer of a material having a lower thermal conductivity than the first plate material and the second plate material, is formed between the first plate material and the second plate material.

[0005] In the energy storage device of Patent Document 1 configured as above, the radiant heat from the first energy storage element toward the second energy storage element, or a portion of the radiant heat from the second energy storage element toward the first energy storage element, is blocked by the first plate and the second plate. In addition, the transfer of heat from one of these two plates to the other is suppressed by the low thermal conductivity layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-211013 A Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, when a charge / discharge cycle is performed on battery cells assembled into a battery pack (i.e., during "normal use"), in order to fully utilize the charge / discharge performance of the battery cells, it is necessary to maintain the temperature of the battery cell surface below a predetermined value (e.g., below 150°C). Furthermore, if an abnormality occurs in which a battery cell reaches a temperature of, for example, 200°C or higher, it is necessary to effectively cool the battery cell while suppressing the transfer of heat to adjacent battery cells and preventing thermal runaway.

[0008] However, the above-mentioned energy storage device only has a heat insulating member and a low thermal conductive layer between the first energy storage element and the second energy storage element, and therefore cannot efficiently dissipate heat generated during charge / discharge cycles to the outside. Furthermore, when thermal runaway occurs in one battery cell, it is difficult to effectively suppress the chain reaction of thermal runaway with only the above-mentioned structure. As such, there has been a demand in recent years for further improvements in heat control means that can efficiently diffuse generated heat to the outside during normal use and suppress a chain reaction of thermal runaway.

[0009] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a thermal control sheet for a battery assembly, and a battery assembly, which can be used in a battery assembly in which multiple battery cells are connected in series or parallel, and which can efficiently diffuse heat generated during normal use to the outside, while suppressing the transmission of heat between the battery cells in the event of an abnormality, and preventing a chain reaction of thermal runaway. [Means for solving the problem]

[0010] The above object of the present invention can be achieved by the following configuration [1] relating to a thermal control sheet for a battery pack.

[0011] [1] A thermal control sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the sheet being interposed between the battery cells, A pair of surface layers in contact with the battery cell; At least one intermediate layer disposed between the pair of surface layers; a heat insulating material disposed between the surface layer and the intermediate layer, The thermal control sheet for a battery pack, wherein the surface layer and the intermediate layer each have a lower emissivity and a higher thermal conductivity than the insulating material.

[0012] Further, preferred embodiments of the present invention relating to the thermal control sheet for a battery pack relate to the following items [2] to

[16] .

[0013] [2] Two or more intermediate layers; The thermal control sheet for a battery pack according to [1], further comprising a heat insulating material disposed between adjacent intermediate layers.

[0014] [3] The thermal control sheet for a battery pack according to [1] or [2], wherein the thermal conductivity of the insulating material is less than 1 (W / m K).

[0015] [4] The thermal control sheet for a battery pack according to any one of [1] to [3], wherein the thermal conductivity of the surface layer and the thermal conductivity of the intermediate layer are both at least 10 times the thermal conductivity of the insulating material.

[0016] [5] The thermal control sheet for a battery pack according to any one of [1] to [4], wherein the thermal conductivity of the intermediate layer is equal to or higher than the thermal conductivity of the surface layer.

[0017] [6] The thermal control sheet for a battery pack according to any one of [1] to [5], wherein the intermediate layer has an emissivity equal to or higher than the emissivity of the surface layer.

[0018] [7] The thermal control sheet for a battery pack according to any one of [1] to [6], wherein the surface layer is made of a metal having a melting point of 600° C. or higher, or a ceramic.

[0019] [8] The thermal control sheet for a battery pack according to [7], wherein the surface layer is made of one metal selected from stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

[0020] [9] The thermal control sheet for a battery pack according to [7], wherein the surface layer is a composite layer formed by laminating two or more metals selected from stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

[0021]

[10] The thermal control sheet for a battery pack according to [8], wherein the surface layer is made of one metal selected from stainless steel, and silver or a silver alloy.

[0022]

[11] The thermal control sheet for a battery pack according to any one of [1] to

[10] , wherein the intermediate layer is made of a metal or a ceramic.

[0023]

[12] The thermal control sheet for a battery pack according to

[11] , wherein the intermediate layer is made of one metal selected from aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

[0024]

[13] The thermal control sheet for a battery pack according to

[11] , wherein the intermediate layer is a composite layer formed by laminating two or more metals selected from aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

[0025]

[14] The thermal control sheet for a battery pack according to

[12] , wherein the intermediate layer is made of one metal selected from aluminum or an aluminum alloy, copper or a copper alloy, and silver or a silver alloy.

[0026]

[15] The thermal control sheet for a battery pack according to any one of [1] to

[14] , wherein the insulating material contains at least one type selected from inorganic fibers, organic fibers, inorganic particles, and organic particles.

[0027]

[16] The thermal control sheet for a battery pack according to

[15] , wherein the insulating material contains at least one selected from alumina fiber, carbon fiber, mica, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, an aerogel composite, microporous particles, hollow silica particles, thermally expandable inorganic materials, and aerogel.

[0028] The above object of the present invention can be achieved by the following configuration

[17] relating to a battery pack.

[0029]

[17] A battery case; A plurality of battery cells housed inside the battery case and connected in series or parallel; and a thermal control sheet for a battery pack according to any one of [1] to

[16] interposed between the plurality of battery cells; A battery pack, wherein a surface layer of the thermal control sheet for the battery pack is in contact with the battery cells. Effect of the Invention

[0030] The thermal control sheet for a battery pack of the present invention is a thermal control sheet used for a battery pack in which a plurality of battery cells are connected in series or parallel, and the surface layer and intermediate layer have a lower emissivity and a higher thermal conductivity than the insulating material disposed between them. Therefore, the heat generated from the battery cell is reduced through the surface layer and intermediate layer by the suppression effect of radiative heat transfer and the heat diffusion effect by conductive heat transfer, and can be reduced stepwise through the insulating material. As a result, the heat generated from one battery cell can be suppressed from propagating to an adjacent battery cell, and a chain reaction of thermal runaway can be prevented.

[0031] Since the battery pack of the present invention has the above-mentioned thermal control sheet interposed between multiple battery cells, it can efficiently diffuse heat during normal use and in the event of an abnormality, and can suppress the transmission of heat between battery cells, thereby preventing a chain reaction of thermal runaway. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a thermal control sheet for a battery pack according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view that illustrates a schematic diagram of an assembled battery to which the thermal control sheet for an assembled battery according to the first embodiment is applied. [Diagram 3] FIG. 3 is a cross-sectional view that illustrates a thermal control sheet for a battery pack according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view that illustrates a method for evaluating the effect of thermal control. [Diagram 5] FIG. 5 is a perspective view showing the size of the thermal control sheet used in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The inventors conducted extensive research to provide a thermal control sheet for a battery pack that can suppress the transmission of heat between battery cells in abnormal conditions when high-temperature heat is generated, while also efficiently diffusing heat generated from the battery cells to the outside during normal use when relatively low-temperature heat is generated.

[0034] As a result, the inventors discovered that the above problem can be solved by configuring a thermal control sheet for an assembled battery to be interposed between multiple battery cells, by disposing an intermediate layer between a pair of surface layers and disposing insulating material between each surface layer and the intermediate layer, and by making the emissivity of the surface layer and intermediate layer lower than that of the insulating material and making the thermal conductivity higher than that of the insulating material.

[0035] That is, when the temperature of a battery cell rises, the surface layer in contact with the battery cell has the effect of suppressing radiative heat transfer from the battery cell and diffusing the heat that reaches the surface layer by conductive heat transfer. Then, the amount of heat generated from the battery cell is reduced by the surface layer and the insulating material before it reaches the intermediate layer, and the intermediate layer further suppresses radiative heat transfer to the next layer and diffuses the heat that reaches the intermediate layer by conductive heat transfer. In this way, by utilizing the surface layer and intermediate layer to suppress radiative heat transfer and to diffuse heat by conductive heat transfer, when a battery cell becomes hot, heat transfer is gradually suppressed before it reaches an adjacent battery cell, and the heat can be diffused to the outside, thereby suppressing a chain reaction of thermal runaway.

[0036] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below, and can be modified and carried out as desired without departing from the gist of the present invention.

[0037] [1. Thermal control sheet for battery packs] Hereinafter, the thermal control sheet for a battery pack according to the embodiment of the present invention will be described in order of a first embodiment and a second embodiment. After that, the surface layer, intermediate layer, heat insulating material, etc. constituting the thermal control sheet for a battery pack according to this embodiment will be described. Furthermore, the manufacturing method of the thermal control sheet for a battery pack according to this embodiment will be described.

[0038] <First embodiment> 1 is a cross-sectional view that typically shows a thermal control sheet for a battery assembly according to a first embodiment of the present invention. Hereinafter, the thermal control sheet for a battery assembly may be simply referred to as a "thermal control sheet." The thermal control sheet 10 for a battery pack according to the first embodiment has a pair of surface layers 11a, 11b, an intermediate layer 12 disposed between the surface layers 11a and 11b, and insulating materials 13a, 13b disposed between the surface layer 11a and the intermediate layer 12, and between the surface layer 11b and the intermediate layer 12, respectively. In the first embodiment, the surface layers 11a and 11b are made of a material having a lower emissivity and a higher thermal conductivity than the heat insulating materials 13a and 13b, for example, a stainless steel plate. The intermediate layer 12 is also made of a material having a lower emissivity and a higher thermal conductivity than the heat insulating materials 13a and 13b, for example, an aluminum plate. The heat insulating materials 13a and 13b are, for example, alumina fibers.

[0039] 2 is a cross-sectional view showing a schematic diagram of an assembled battery to which the thermal control sheet for an assembled battery according to the first embodiment is applied. The assembled battery 100 has a battery case 30, a plurality of battery cells 20a, 20b, and 20c housed inside the battery case 30, and a thermal control sheet 10 interposed between the battery cells 20a and 20b and between the battery cells 20b and 20c. The plurality of battery cells 20a, 20b, and 20c are connected in series or in parallel by bus bars (not shown) or the like. The battery cells 20a, 20b, and 20c are preferably, for example, lithium ion secondary batteries, but are not limited thereto and may also be other secondary batteries.

[0040] In a typical conventional battery pack, a sheet disposed between a plurality of battery cells has a heat insulating material disposed on the surface closest to the battery cells. In contrast, in the thermal control sheet 10 according to the first embodiment, the surface layers 11a and 11b are disposed so as to be in contact with the battery cells 20a, 20b, and 20c. Furthermore, as the surface layers 11a and 11b, stainless steel plates having a lower emissivity and a higher thermal conductivity than the thermal insulators 13a and 13b are used.

[0041] In the first embodiment configured as described above, for example, when the temperature of the battery cell 20a rises, the surface layer 11a provided at a position in contact with the battery cell 20a has a lower emissivity than the thermal insulators 13a and 13b, and therefore can suppress radiative heat transfer to the thermal insulator 13a side. Also, the surface layer 11a has a higher thermal conductivity than the thermal insulators 13a and 13b, and therefore a part of the heat propagated to the surface layer 11a is propagated in the planar direction of the surface layer 11a. In this way, the amount of heat generated from the battery cell 20a is reduced through the surface layer 11a, and heat transfer to the thermal insulator 13a side is suppressed. The surface direction of the surface layer 11a refers to the direction of a surface perpendicular to the thickness direction of the surface layer 11a. Similarly, the surface direction of the intermediate layer 12 described below refers to the direction of a surface perpendicular to the thickness direction of the intermediate layer 12.

[0042] The remaining heat reduced by the surface layer 11a is further reduced by passing through the insulating material 13a and then reaches the intermediate layer 12. The intermediate layer 12, like the surface layer 11a, has a lower emissivity than the insulating materials 13a and 13b, and therefore can suppress radiative heat transfer to the next layer, i.e., the insulating material 13b. In addition, the intermediate layer 12 has a higher thermal conductivity than the insulating materials 13a and 13b, so a part of the heat that reaches the intermediate layer 12 is propagated in the surface direction of the intermediate layer 12 and diffused to the outside of the thermal control sheet 10.

[0043] Similarly, the heat dissipated by the intermediate layer 12 is further dissipated through the insulating material 13b and the surface layer 11b. Therefore, by arranging battery cell 20a and battery cell 20b via thermal control sheet 10, when heat is generated from battery cell 20a, the heat can be efficiently diffused and the transmission of heat between the battery cells can be suppressed, thereby preventing a chain reaction of thermal runaway.

[0044] The thermal control sheet 10 is configured symmetrically in the thickness direction with respect to the intermediate layer 12. Therefore, even if heat is generated from the battery cell 20b, the heat is gradually reduced toward the battery cell 20a by passing through the surface layer 11b, the insulating material 13b, the intermediate layer 12, the insulating material 13a, and the surface layer 11a in this order, thereby suppressing the propagation of heat to the battery cell 20a. Similarly, the heat generated from battery cell 20b is gradually reduced by passing through surface layer 11a, insulating material 13a, intermediate layer 12, insulating material 13b, and surface layer 11b, in that order, toward battery cell 20c, thereby suppressing the transmission of heat to battery cell 20c.

[0045] <Second embodiment> In the above first embodiment, the thermal control sheet 10 for the battery pack has a five-layer structure in which a surface layer 11a, an insulating material 13a, an intermediate layer 12, an insulating material 13b, and a surface layer 11b are arranged in this order, but the thermal control sheet for the battery pack of the present invention is not limited to five layers. For example, it may have two intermediate layers and a heat insulating material disposed between two adjacent intermediate layers.

[0046] 3 is a cross-sectional view showing a schematic diagram of a thermal control sheet for a battery assembly according to a second embodiment of the present invention. In the second embodiment shown in FIG. 3, the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals in the drawing, and their description will be omitted or simplified. In addition, since the second embodiment can be used in place of the thermal control sheet 10 described in the battery assembly 100 shown in FIG. 2, the effects and the like will be described assuming that the thermal control sheet according to the second embodiment is applied to the battery assembly 100.

[0047] The thermal control sheet 15 for a battery pack according to the second embodiment has a pair of surface layers 11a, 11b, two intermediate layers 12a, 12b disposed between the surface layers 11a and 11b, and insulating materials 13a, 13b, 13c disposed between the respective layers. In the second embodiment, similarly to the first embodiment, the surface layers 11a and 11b are made of a material having a lower emissivity and a higher thermal conductivity than the thermal insulators 13a, 13b, and 13c, and the intermediate layers 12a and 12b are also made of a material having a lower emissivity and a higher thermal conductivity than the thermal insulators 13a, 13b, and 13c.

[0048] In the second embodiment configured as described above, when the temperature of the battery cell 20a rises, the surface layer 11a provided at the position in contact with the battery cell 20a has a lower emissivity than the insulating material, so that it is possible to suppress the radiative heat transfer to the insulating material 13a side. In addition, since the surface layer 11a has a higher thermal conductivity than the insulating material, a part of the heat transferred to the surface layer 11a is transferred in the planar direction of the surface layer 11a and diffused to the outside of the thermal control sheet 15. The heat that reaches the insulating material 13a is then further reduced by the insulating material 13a before reaching the intermediate layer 12a. The intermediate layer 12a suppresses radiative heat transfer to the insulating material 13a side, and also diffuses the heat that reaches the intermediate layer 12a in the surface direction of the intermediate layer 12a, thereby suppressing the transfer of heat to the insulating material 13c side.

[0049] Similarly, through the insulating material 13c, the intermediate layer 12b, the insulating material 13b, and the surface layer 11b, the radiation heat transfer is suppressed in stages to the adjacent battery cell 20b, and the heat is diffused by the conductive heat transfer. Therefore, the heat transfer between the battery cells can be efficiently suppressed, and the chain reaction of thermal runaway can be suppressed.

[0050] The effects of the present invention can be obtained even if the intermediate layers are, for example, three or more layers, and a heat insulating material is disposed between each intermediate layer. However, since increasing the number of layers increases the overall thickness of the thermal control sheet and decreases the thickness of each heat insulating material, it is preferable to appropriately select the number of intermediate layers and the thickness of the heat insulating material according to the required performance.

[0051] Next, the surface layer, intermediate layer, heat insulating material, etc. that constitute the thermal control sheet for a battery pack according to the present invention will be described in detail.

[0052] (Surface layer) The surface layer used in the thermal control sheet for a battery pack according to this embodiment has the effect of suppressing radiative heat transfer from the battery cells in contact with it, and the effect of diffusing heat that reaches the surface layer by conductive heat transfer. Therefore, the surface layer has a lower emissivity and a higher thermal conductivity than the insulating material described below. The specific value of the emissivity of the surface layer is preferably less than 0.5, and more preferably less than 0.2. The specific value of the thermal conductivity of the surface layer is preferably 5 (W / m·K) or more, and more preferably 15 (W / m·K) or more.

[0053] The thermal conductivity of the surface layer can be calculated by a laser flash method and a differential scanning calorimetry (DSC) method, as shown in the following (1) to (3). (1) Thermal diffusivity is measured in accordance with the "Method for measuring thermal diffusivity of metals by laser flash method" described in JIS H 7801. (2) The specific heat capacity is measured in accordance with "Method for measuring specific heat capacity of long fiber reinforced ceramic composite material by differential scanning calorimetry" described in JIS R 1672. (3) Calculate the thermal conductivity based on the values ​​obtained in (1) and (2). The emissivity of the surface layer can be measured in accordance with "Method of measuring emissivity of fine ceramics and ceramic composite materials" described in JIS R 1693.

[0054] The surface layer is preferably made of, for example, a metal or ceramic. In order to prevent the surface layer in contact with the battery cell from being damaged by melting or the like in the event of a significant rise in the temperature of the battery cell due to an abnormality, the surface layer is more preferably made of a metal or ceramic having a melting point of 600°C or higher. It is even more preferable that the surface layer be made of a metal having a melting point of 900°C or higher.

[0055] Specifically, it is preferable to use one metal selected from stainless steel, copper or copper alloy, silver or silver alloy, nickel or nickel alloy, and titanium or titanium alloy, or one ceramic selected from AlN, SiC, and TiN as the material of the surface layer. Of these materials, stainless steel and silver have melting points of about 1400°C and about 960°C, respectively, and are unlikely to melt even if the battery cell becomes hot. In addition, stainless steel and silver are less likely to oxidize compared to other metals, and the increase in emissivity is small even when exposed to high temperatures. Therefore, in this embodiment, stainless steel, silver, or a silver alloy can be suitably used as the material of the surface layer.

[0056] The surface layer may be a composite layer formed by laminating two or more metals selected from the above-mentioned surface layer materials. When a composite layer is used as the surface layer, the above-mentioned two or more metal layers are selected to have a lower emissivity than the insulating material and a higher thermal conductivity than the insulating material. Examples of such surface layers include a [silver / copper / silver] composite layer, a [nickel / copper / nickel] composite layer, a [nickel / stainless steel / nickel] composite layer, and a [silver / stainless steel / silver] composite layer. The silver, copper, and nickel in the composite layer may each be in the form of an alloy. The composite layer can be obtained by forming metal layers on both sides of a central base layer by wet plating or vapor deposition, or by laminating metal foils made of different materials.

[0057] The thermal conductivity of the metals mentioned above as the material for the surface layer is 5 to 450 (W / m K), which is sufficiently greater than the thermal conductivity of the insulating material described below (e.g., 0.05 (W / m K)), and therefore the heat that reaches the surface layer can be efficiently diffused. In terms of specific thermal conductivity compared to the insulating material, the thermal conductivity of the surface layer is preferably 10 times or more, and more preferably 100 times or more, of the thermal conductivity of the insulating material.

[0058] In order to fully obtain the effect of suppressing radiative heat transfer by the surface layer and the effect of diffusing heat by conductive heat transfer, the thickness of the surface layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. On the other hand, in consideration of the overall thickness of the thermal control sheet, the thickness of the surface layer is preferably 300 μm or less, and more preferably 200 μm or less.

[0059] Furthermore, the surface layer may be a single layer or a laminate of multiple thin layers made of the same material. When the surface layer is made of multiple thin layers made of the same material, the same effect can be obtained as long as the total thickness of the multiple layers is the same as the thickness of the surface layer made of a single layer. Therefore, even if the surface layer is made of multiple layers, it is preferable that the total thickness is within the above range.

[0060] (Middle class) The intermediate layer used in the thermal control sheet for a battery pack according to this embodiment has the effect of suppressing radiation heat transfer to the next layer and diffusing the heat that reaches the intermediate layer by conductive heat transfer. Therefore, like the surface layer, it is important that the intermediate layer has a lower emissivity and a higher thermal conductivity than the insulating material described below. The specific value of the emissivity of the intermediate layer is preferably less than 0.5, and more preferably less than 0.2. In addition, the specific value of the thermal conductivity of the intermediate layer is preferably 10 (W / m K) or more, and more preferably 100 (W / m K) or more. The intermediate layer is preferably made of, for example, a metal or a ceramic.

[0061] The thermal conductivity and emissivity of the intermediate layer can be calculated in the same manner as the thermal conductivity and emissivity of the surface layer.

[0062] When a metal is used as the material for the intermediate layer, it is preferable to use one metal selected from, for example, aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

[0063] The intermediate layer may be a composite layer formed by laminating two or more metals selected from the materials for the intermediate layer. When a composite layer is used as the intermediate layer, the two or more metal layers are selected to have a lower emissivity than the insulating material and a higher thermal conductivity than the insulating material. Examples of such intermediate layers include an aluminum / copper / aluminum composite layer, an aluminum / silver / aluminum composite layer, a nickel / stainless steel / nickel composite layer, and a silver / stainless steel / silver composite layer. The aluminum, copper, and silver in the composite layer may each be in the form of an alloy. The composite layer can be obtained by forming metal layers on both sides of a central base layer by wet plating or vapor deposition, or by laminating metal foils made of different materials.

[0064] When ceramic is used as the material for the intermediate layer, one type of ceramic selected from AlN, SiC, and TiN can be used.

[0065] As with the surface layer, the thermal conductivity of the metals mentioned above as materials for the intermediate layer is 5 to 450 (W / m K), which is sufficiently greater than the thermal conductivity of the insulating material described below (e.g., 0.05 (W / m K)), and therefore the heat that reaches the intermediate layer can be efficiently diffused. In terms of specific thermal conductivity compared to the insulating material, the thermal conductivity of the intermediate layer is preferably 10 times or more, and more preferably 100 times or more, of the thermal conductivity of the insulating material.

[0066] Furthermore, when the intermediate layer is made of metal, in order to obtain a sufficient heat diffusion effect by conductive heat transfer, the thickness of the intermediate layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. On the other hand, in consideration of the overall thickness of the thermal control sheet, the thickness of the intermediate layer is preferably 300 μm or less, and more preferably 200 μm or less. Furthermore, the intermediate layer may be a single layer, or may be a laminate of multiple thin films made of the same material, as shown in Fig. 1. When the intermediate layer is made of laminated thin films made of the same material, the same effect can be obtained as long as the total thickness of the multiple layers is the same as the thickness of the intermediate layer made of a single layer. Therefore, even when the intermediate layer is made of multiple layers, it is preferable that the total thickness is within the above range.

[0067] In addition, it is preferable that the intermediate layer has a high effect of transmitting heat that has reached one surface in the planar direction and diffusing it to the outside of the thermal control sheet. Therefore, it is preferable that the thermal conductivity of the intermediate layer is equal to or higher than the thermal conductivity of the surface layer. For the same reason, it is preferable that the emissivity of the intermediate layer is equal to or higher than the emissivity of the surface layer. Therefore, among the above-mentioned intermediate layer materials, aluminum or aluminum alloy, and copper or copper alloy are more suitable for use because they have higher thermal conductivity than stainless steel, which is a suitable material for the surface layer. However, since emissivity varies depending on the type of material and the surface condition, it is preferable to select a material taking into consideration the surface condition, etc.

[0068] (Thermal insulation) The heat insulating material used in the thermal control sheet for a battery pack according to this embodiment is not particularly limited as long as it has a heat insulating effect. Thermal conductivity can be given as an index showing the heat insulating effect, and in this embodiment, the heat conductivity of the heat insulating material is preferably less than 1 (W / m·K), more preferably less than 0.5 (W / m·K), and even more preferably less than 0.2 (W / m·K). Furthermore, the heat conductivity of the heat insulating material is more preferably less than 0.1 (W / m·K), more preferably less than 0.05 (W / m·K), and particularly preferably less than 0.02 (W / m·K). As such a heat insulating material, for example, a material containing at least one selected from inorganic fibers, organic fibers, inorganic particles, and organic particles can be used.

[0069] The thermal conductivity of the insulating material can be measured in accordance with the "Test method for thermal conductivity of refractories" described in JIS R 2251.

[0070] As the inorganic fiber, alumina fiber, carbon fiber, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, aerogel composite material, and the like can be used. As the organic fiber, cellulose fiber or the like can be used. Incidentally, these fibers may be used alone or in combination of two or more kinds.

[0071] As inorganic particles, mica, microporous particles, hollow silica particles, thermally expandable inorganic materials, and aerogels can be used. Examples of the thermally expandable inorganic material include vermiculite, bentonite, mica, and perlite. As the organic particles, hollow polystyrene particles or the like can be used.

[0072] Of these materials as heat insulating materials, alumina fiber, glass fiber, aerogel composite material, etc. can be suitably used.

[0073] <Thickness of thermal control sheet> In this embodiment, the thickness of the thermal control sheet is not particularly limited, but is preferably in the range of 0.05 to 6 mm. If the thickness of the thermal control sheet is 0.05 mm or more, sufficient mechanical strength can be imparted to the thermal control sheet. On the other hand, if the thickness of the thermal control sheet is 6 mm or less, good assembly properties can be obtained.

[0074] Next, a method for producing the thermal control sheet for a battery pack according to this embodiment will be described.

[0075] <Method of manufacturing the thermal control sheet> The thermal control sheet according to the present embodiment can be obtained, for example, by preparing a pair of metal plates as surface layers, disposing a metal plate as an intermediate layer between the pair of surface layers, and disposing a heat insulating material between the surface layers and the intermediate layer. These layers may or may not be bonded to each other. When they are bonded, for example, a method of fixing the peripheral portions of the laminated sheets by adhesion or welding can be used.

[0076] [2. Battery pack] The battery pack according to this embodiment is a battery pack in which a plurality of battery cells are connected in series or parallel, and a thermal control sheet for a battery pack according to this embodiment is interposed between the battery cells. Specifically, for example, as shown in Fig. 3, a battery pack 100 is a battery pack in which a plurality of battery cells 20a, 20b, 20c are arranged side by side, connected in series or parallel, and stored in a battery case 30, and a thermal control sheet 10 is interposed between the battery cells 20a, 20b, 20c.

[0077] In such a battery pack 100, since the thermal control sheet 10 is interposed between the battery cells 20a, 20b, 20c, the transfer of heat between the battery cells 20a, 20b, 20c can be suppressed during normal use. Furthermore, even if one of the multiple battery cells 20a, 20b, and 20c experiences thermal runaway, becomes too hot, expands, or catches fire, the presence of the thermal control sheet 10 according to this embodiment can suppress the transfer of heat between the battery cells 20a, 20b, and 20c. This makes it possible to prevent a chain reaction of thermal runaway, and minimize adverse effects on other battery cells.

[0078] The thermal control sheet according to this embodiment can be easily bent depending on the type and thickness of the surface layer, intermediate layer, and heat insulating material. Therefore, it can be adapted to any shape without being affected by the shape of the battery cells 20a, 20b, and 20c and the battery case 30. Specifically, it can be applied to cylindrical batteries, flat batteries, etc. in addition to square batteries. EXAMPLES

[0079] An example of the thermal control sheet for a battery pack according to the present embodiment and a comparative example will be described below.

[0080] [Example 1: Effect of heat control depending on the presence or absence of a surface layer or intermediate layer, and the type of intermediate layer] A stainless steel plate or a silver plate was prepared as the surface layers 11a and 11b shown in FIG. 1, and an aluminum plate, a copper plate, a stainless steel plate, a silver plate, or an [aluminum / silver / aluminum] composite layer was prepared as the intermediate layer 12. An alumina fiber sheet, an aerogel blanket, or a glass fiber was prepared as the heat insulating materials 13a and 13b, and the surface layer, the intermediate layer, and the heat insulating material were laminated to produce a thermal control sheet 10 for a battery pack according to the invention. As a comparative example, a test piece was prepared in which either one or both of the surface layer 11a and the intermediate layer 12 was not laminated, in comparison with the above-mentioned invention example. Then, the effect of thermal control on the presence or absence of the surface layer or the intermediate layer was evaluated for the obtained thermal control sheet.

[0081] Fig. 4 is a cross-sectional view showing a typical method for evaluating the effect of thermal control, and Fig. 5 is a perspective view showing the size of the thermal control sheet used in this example. As shown in FIG. 4, an Fe jig 16 heated to 800° C. in an electric furnace was placed on one side (surface of the surface layer 11a) of the thermal control sheet 10 so that it was moved from the electric furnace within 5 seconds. Thereafter, the temperature was measured 90 seconds after placement using a thermocouple 17 placed on the other side (surface of the surface layer 11b) of the thermal control sheet 10 to evaluate the effect of thermal control. Similarly, for the comparative examples, the thermal control sheet 10 shown in FIG. 4 and FIG. 5 was replaced with the test piece of the comparative example to evaluate the effect of thermal control. However, for some comparative examples in which the surface layer was not laminated, the surface layer 11b was disposed on the other side for measurement by the thermocouple 17.

[0082] 5, the thermal control sheet 10 thus produced was a square with a side of 50 mm and a total thickness of 1.5 mm. On one side of the thermal control sheet 10, the width of the contact area A with the Fe jig 16 was 25 mm, and the length in the direction perpendicular to the width direction was 50 mm from one side of the thermal control sheet 10 to the opposite side.

[0083] Detailed measurement conditions are shown in Table 1 below, and lamination conditions and measurement results are shown in Table 2 below. In the tables shown below, "SUS" stands for stainless steel, and [Al / Ag / Al] stands for an [aluminum / silver / aluminum] composite layer. Also, "AF" stands for alumina fiber, and "AG-F" stands for aerogel blanket, both trade names made by SHENZHEN AEROGEL TECHNOLOGY CO., LTD. "GF" stands for glass fiber. Note that "-" indicates that there is no lamination. The thermal conductivity of the alumina fiber used was 0.05 (W / m K) and the emissivity was 0.8. The thermal conductivity of the aerogel blanket (AG-F) was 0.02 (W / m K) and the emissivity was 0.8. The thermal conductivity of the glass fiber (GF) was 0.05 (W / m K) and the emissivity was 0.8. Furthermore, the emissivity of the stainless steel plate as the surface layer, and the aluminum plate, copper plate, and stainless steel plate as the intermediate layer was all about 0.2.

[0084] [Table 1]

[0085] [Table 2]

[0086] As shown in Table 2 above, since Invention Examples No. 1 to 9 are thermal control sheets according to an embodiment of the present invention, the surface layer and intermediate layer are able to provide a suppression effect of radiative heat transfer and a diffusion effect through conductive heat transfer, and all of them have excellent insulating effects. In contrast, Comparative Examples Nos. 1 to 6 did not have either or both of the surface layer and the intermediate layer laminated therein, and therefore had a lower heat insulating effect than the invention examples.

[0087] In addition, when comparing invention examples Nos. 1 to 4 and 7 with comparative example No. 2, the surface layer and the heat insulating material are all the same, and the only difference is the presence or absence of an intermediate layer, but invention examples Nos. 1 to 4 and 7 showed superior heat insulating effects. This shows that regardless of the type of intermediate layer, having the intermediate layer described in the present invention is effective in obtaining superior heat insulating effects. In addition, when comparing Example No. 3 and Comparative Example No. 3, both of which share the same insulating material and intermediate layer, and differ only in the presence or absence of one surface layer, Example No. 3 showed superior insulating effect, demonstrating that having the surface layer according to the present invention in the position in contact with the heated battery cell is effective in obtaining superior insulating effect.

[0088] [Example 2: Effect of thermal control on total number of layers and thickness of intermediate layer]

[0089] A thermal control sheet 15 according to the second embodiment of the present invention was produced by preparing stainless steel plates as the surface layers 11a and 11b, aluminum plates as the intermediate layers 12a and 12b, and alumina fiber sheets as the heat insulating materials 13a, 13b, and 13c shown in Fig. 3, and laminating the surface layers, intermediate layers, and heat insulating materials. A thermal control sheet with a total of nine layers was also produced by adding one intermediate layer and one heat insulating material. Note that for the nine-layer structure, thermal control sheets with different thicknesses of the intermediate layer were also produced. Thereafter, in the same manner as in Example 1 above, the temperature of the surface of the thermal control sheet opposite to the surface on which the Fe jig was placed was measured to evaluate the effect of thermal control due to the total number of layers or the thickness of the intermediate layer.

[0090] The size of the thermal control sheet produced was the same as that of the above-mentioned Example 1. The lamination conditions and the measurement results are shown in the following Table 3. For comparison, the results of the invention example No. 1 in the above-mentioned Example 1 are also shown in Table 3.

[0091] [Table 3]

[0092] As shown in Table 3 above, in invention examples No. 10 to 12, in which two or more intermediate layers were arranged, the surface layer and intermediate layer were able to provide the effect of suppressing radiative heat transfer and the diffusion effect through conductive heat transfer, and a superior insulation effect was obtained compared to comparison examples No. 1 to 6 shown in Table 2 above.

[0093] Moreover, compared to invention sample No. 1, invention sample No. 10 shows superior heat insulation. This is thought to be due to the fact that the number of intermediate layers was increased from one to two, which enhanced the heat diffusion effect. Invention sample No. 11 further increases the number of intermediate layers, but since it is necessary to reduce the basis weight of the insulation material as the number of layers is increased, invention sample No. 11 has the same heat insulation effect as invention sample No. 1. In addition, in Example No. 11, the thickness of each intermediate layer was thicker than in Example No. 12, so the heat diffusion effect of the intermediate layer was high and excellent heat insulation effects were obtained.

[0094] [Example 3: Effect of thermal control on thickness of each layer]

[0095] A five-layered thermal control sheet 10 for a battery pack was produced as an example of the invention, using stainless steel plates as the surface layers 11a and 11b, an aluminum plate as the intermediate layer 12, and an alumina fiber sheet or an aerogel blanket (AG-F) as the heat insulating materials 13a and 13b, and varying the thickness of the surface layer 11a and the intermediate layer 12, or the type and basis weight of the heat insulating materials 13a and 13b. The thickness of each of the surface layers 11b was 50 μm, and the total thickness was 1.5 mm. Thereafter, in the same manner as in Example 1 above, the temperature of the surface of the thermal control sheet opposite to the surface on which the Fe jig was placed was measured to evaluate the effect of thermal control due to the thickness of each layer.

[0096] The size of the thermal control sheet produced was the same as that of the above-mentioned Example 1. The lamination conditions and the measurement results are shown in the following Table 4. For comparison, the results of the invention example No. 1 in the above-mentioned Example 1 are also shown in Table 4.

[0097] [Table 4]

[0098] As shown in Table 4 above, the thickness of the surface layer is 50 μm or 150 μm, the thickness of the intermediate layer is 11 μm, 50 μm, or 165 μm, and the basis weight of the heat insulating material is 150 (g / m 2 ), 190(g / m 2 ) or 280(g / m 2 In the case of invention examples Nos. 13 to 18, in which the surface layer and intermediate layer were used, the effect of suppressing radiative heat transfer and the diffusion effect due to conductive heat transfer were obtained, and superior insulation effects were obtained compared to comparative examples Nos. 1 to 6 shown in Table 2 above. In addition, since invention examples No. 1, 13, and 14 have different thicknesses of the intermediate layer per layer, the thicker the intermediate layer, the greater the insulating effect, and invention example No. 14 achieved the best insulating effect.

[0099] In addition, since invention samples No. 1 and 15 have different thicknesses of the surface layer per layer, invention sample No. 15, which has a thicker surface layer, exhibited a superior heat insulating effect. Similarly, since invention samples Nos. 14 and 16 differ in the thickness of the surface layer per layer, invention sample No. 16, which has a thicker surface layer, exhibited a superior heat insulating effect. Furthermore, although invention examples Nos. 13, 17, and 18 differ from one another in type and basis weight of insulation material and have the thinnest intermediate layer, no matter which insulation material was used, excellent insulation effects were obtained compared to comparative examples Nos. 1 to 6 shown in Table 2 above.

[0100] As described above, the thermal control sheet of the present invention has different insulating effects depending on the total number of layers, the basis weight of the insulating material, and the thickness of the intermediate layer, so that by appropriately controlling these, an even better insulating effect can be obtained. [Explanation of symbols]

[0101] 10,15 Thermal control sheet for battery packs 11a,11b surface layer 12,12a,12b middle layer 13a, 13b, 13c Insulation material 17 Thermocouple 20a, 20b, 20c Battery cells 30 Battery case 100 battery packs

Claims

1. A thermal control sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the thermal control sheet being interposed between the battery cells, A pair of surface layers in contact with the battery cell; At least one intermediate layer disposed between the pair of surface layers; a heat insulating material disposed between the surface layer and the intermediate layer, The thermal control sheet for a battery pack, wherein the surface layer and the intermediate layer each have a lower emissivity and a higher thermal conductivity than the insulating material.

2. Two or more intermediate layers; 2. The thermal control sheet for a battery pack according to claim 1, further comprising a heat insulating material disposed between adjacent intermediate layers.

3. 3. The thermal control sheet for a battery pack according to claim 1, wherein the thermal insulation material has a thermal conductivity of less than 1 (W / m·K).

4. The thermal control sheet for a battery pack according to any one of claims 1 to 3, characterized in that the thermal conductivity of the surface layer and the thermal conductivity of the intermediate layer are both 10 times or more higher than the thermal conductivity of the insulating material and are in the range of 5 to 450 (W / m K).

5. 5. The thermal control sheet for a battery pack according to claim 1, wherein the thermal conductivity of the intermediate layer is equal to or higher than the thermal conductivity of the surface layer.

6. 6. The thermal control sheet for a battery pack according to claim 1, wherein the intermediate layer has an emissivity equal to or higher than the emissivity of the surface layer.

7. 7. The thermal control sheet for a battery pack according to claim 1, wherein the surface layer is made of a metal having a melting point of 600° C. or higher, or a ceramic.

8. 8. The thermal control sheet for a battery pack according to claim 7, wherein the surface layer is made of one metal selected from the group consisting of stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

9. 8. The thermal control sheet for a battery pack according to claim 7, wherein the surface layer is a composite layer formed by laminating two or more metals selected from stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

10. 9. The thermal control sheet for a battery pack according to claim 8, wherein the surface layer is made of one metal selected from the group consisting of stainless steel, and silver or a silver alloy.

11. 11. The thermal control sheet for a battery pack according to claim 1, wherein the intermediate layer is made of a metal or a ceramic.

12. 12. The thermal control sheet for a battery pack according to claim 11, wherein the intermediate layer is made of one metal selected from the group consisting of aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

13. 12. The thermal control sheet for a battery pack according to claim 11, wherein the intermediate layer is a composite layer formed by laminating two or more metals selected from aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, and titanium or a titanium alloy.

14. 13. The thermal control sheet for a battery pack according to claim 12, wherein the intermediate layer is made of one metal selected from the group consisting of aluminum or an aluminum alloy, copper or a copper alloy, and silver or a silver alloy.

15. The thermal control sheet for a battery pack according to any one of claims 1 to 14, characterized in that the heat insulating material contains at least one type selected from inorganic fibers, organic fibers, inorganic particles, and organic particles.

16. The thermal control sheet for a battery pack according to claim 15, characterized in that the heat insulating material contains at least one selected from alumina fiber, carbon fiber, mica, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, an aerogel composite material, microporous particles, hollow silica particles, thermally expandable inorganic materials, and aerogel.

17. A battery case; A plurality of battery cells housed inside the battery case and connected in series or parallel; and a thermal control sheet for a battery pack according to any one of claims 1 to 16, which is interposed between the plurality of battery cells; A battery pack, wherein a surface layer of the thermal control sheet for the battery pack is in contact with the battery cells.

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