Thermal diffusion prevention sheet and method for manufacturing the same, and battery

Abstract

To provide a thermal diffusion prevention sheet which is excellent in thermal diffusion reduction effect and cushioning property, and a battery including the same.SOLUTION: There are provided a thermal diffusion prevention sheet that is arranged at least between a plurality of heat sources, and can reduce thermal diffusion between the heat sources and relax the pressure when the heat sources are expanded, which has such a structure that powder fixed sheets 25 and 26 where powder 20a and 21a is fixed to one surfaces of resin or rubber porous sheets 10 and 11 are bonded to each other so that the surfaces of the fixed powder layer side face each other, and has an air layer 30 between the powder layers 20 and 21 and a method for manufacturing the same; and a battery including the thermal diffusion prevention sheet 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal diffusion prevention sheet, a method for producing the same, and a battery. [Background technology]

[0002] Currently, there is a growing movement around the world to gradually replace conventional gasoline or diesel vehicles with electric vehicles in order to reduce the burden on the global environment. Electric vehicles are becoming increasingly popular, particularly in European countries such as France, the Netherlands, and Germany, as well as in China. The widespread use of electric vehicles requires high-performance batteries.

[0003] Conventionally, automotive batteries have been known in which multiple battery cells (also simply referred to as "cells") are arranged in a housing. The battery cell housing expands when overheated during discharge and / or charging. When the battery cells expand, they come into contact with each other, and there is a risk of abnormal overheating and even fire due to a chain reaction of heat transfer. To address this problem, a method is known in which a sheet is provided between multiple battery cells to prevent heat diffusion (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-206604 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventionally known sheets do not necessarily provide sufficient cushioning and effective reduction of heat diffusion between cells. These problems are common not only to battery cells for automobiles, but also to batteries used in other mobile vehicles such as trains and ships, electronic components built into electronic devices, and circuit boards on which these electronic components are mounted. Furthermore, developing a heat diffusion prevention sheet that meets these requirements will also contribute to achieving the applicant's sustainable development goal of "ensuring access to affordable, reliable, sustainable, and modern energy for all."

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a thermal diffusion prevention sheet that is excellent in the effect of reducing thermal diffusion and in cushioning properties, and a battery including the same. [Means for solving the problem]

[0007] (1) To achieve the above object, one embodiment of a thermal diffusion prevention sheet is a thermal diffusion prevention sheet that is disposed at least between a plurality of heat sources and that can reduce thermal diffusion between the heat sources and relieve pressure when the heat sources expand, The structure is such that two powder-fixed sheets, each having powder fixed on one side of a porous resin or rubber sheet, are bonded together with the fixed powder layer sides facing each other, and an air layer is provided between the two powder layers. (2) In another embodiment of the thermal diffusion prevention sheet, preferably, an insulating sheet having higher insulating properties than the porous sheet is sandwiched between the powder fixing sheets, and the air layer may be formed between the powder layer and the insulating sheet. (3) In another embodiment of the thermal diffusion prevention sheet, the heat insulating sheet may be a sheet that mainly contains talc, silica, aerogel, mullite, cordierite, steatite, forsterite, titania, or zirconia. (4) In the thermal diffusion prevention sheet according to another embodiment, the powder may preferably be a powder of silicone rubber, silica, or aerogel. (5) In the thermal diffusion prevention sheet according to another embodiment, the porous sheet may preferably be a silicone rubber sponge sheet. (6) To achieve the above object, a method for producing a thermal diffusion prevention sheet according to one embodiment is a method for producing any of the above-mentioned thermal diffusion prevention sheets, comprising the steps of: a paste preparation step of preparing a paste by mixing the powder with a dispersion medium; a coating step of coating one surface of the porous sheet with the paste; a volatilization step of volatilizing the dispersion medium from the applied paste; a lamination step of laminating the powder-fixed sheets, each having a powder fixed thereon, with the fixed powder layer sides facing each other; Includes. (7) In another embodiment of the method for producing a thermal diffusion prevention sheet, preferably, in the laminating step, a heat insulating sheet having a higher heat insulating property than the porous sheet may be sandwiched between the opposing powder layer sides. (8) In one embodiment of a battery for achieving the above object, the battery has a plurality of battery cells in a housing, and includes any of the above-mentioned heat diffusion prevention sheets between the battery cells and between the battery cells and the housing, at least between the battery cells. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a thermal diffusion prevention sheet that is excellent in the effect of reducing thermal diffusion and in cushioning properties, and a battery including the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows a plan view, a side view, and a bottom view of the thermal diffusion prevention sheet according to the first embodiment. [Figure 2] FIG. 2 shows a cross-sectional view of the thermal diffusion prevention sheet of FIG. 1 taken along line AA and an enlarged view of part B thereof. [Figure 3] FIG. 3 shows the flow of the main steps in the method for producing the thermal diffusion prevention sheet according to the first embodiment. [Figure 4] FIG. 4 shows a photograph of the powder fixing sheet and an enlarged photograph of a part C thereof after the volatilization step has been completed in the manufacturing process of the thermal diffusion prevention sheet according to the first embodiment. [Figure 5] FIG. 5 shows a cross-sectional view of the thermal diffusion prevention sheet according to the second embodiment taken along line AA in the same view as FIG. 1, and an enlarged view of a part B thereof. [Figure 6] FIG. 6 shows a longitudinal cross-sectional view of a battery according to one embodiment and an enlarged view of one heat diffusion prevention sheet sandwiched between battery cells in the longitudinal cross-sectional view. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the invention according to the claims, and not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0011] 1. Thermal diffusion prevention sheet and its manufacturing method First Embodiment Fig. 1 shows a plan view, a side view, and a bottom view of the thermal diffusion barrier sheet according to the first embodiment. Fig. 2 shows a cross-sectional view of the thermal diffusion barrier sheet taken along line AA in Fig. 1 and an enlarged view of part B thereof.

[0012] The thermal diffusion prevention sheet 1 according to this embodiment is a sheet that is disposed at least between multiple heat sources, and that can reduce thermal diffusion between the heat sources and relieve pressure when the heat sources expand. The thermal diffusion prevention sheet 1 has a structure in which powder-fixed sheets 25, 26, each having powder 20a, 21a fixed on one surface of a resin or rubber porous sheet 10, 11, are bonded together with the surfaces of the fixed powder layers 20, 21 facing each other, and an air layer 30 is provided between the powder layers 20, 21.

[0013] In this application, examples of a "heat source" include a battery cell disposed inside a battery for an automobile, a battery used for a device other than an automobile, or a battery cell disposed inside the battery. However, the term "heat source" also includes, in addition to a battery or battery cell, a heater or a component thereof, and a component in an electrical or electronic device (such as a circuit board or a component on a circuit).

[0014] The thermal diffusion barrier sheet 1 is not particularly limited in its shape or size. It may be in any shape, such as a rectangular parallelepiped, a cylinder, or an elliptical cylinder that is thin in the thickness direction. A preferred shape for the thermal diffusion barrier sheet 1 is a rectangular parallelepiped, particularly a sheet-like rectangular parallelepiped with one of its three sides (the side in the thickness direction) being very small. In this case, the long side (the longest side) is preferably 100 mm or more and 800 mm or less, more preferably 200 mm or more and 500 mm or less. The short side (the second longest side), provided it is shorter than the long side, is preferably 50 mm or more and 300 mm or less, more preferably 100 mm or more and 250 mm or less. The thickness (shortest side) is not particularly limited, but is preferably 1 mm or more and 40 mm or less, more preferably 2 mm or more and 20 mm or less.

[0015] In this embodiment, the outer peripheries 15 of two porous sheets 10, 11 are closed by applying an adhesive or by thermocompression bonding, and powder layers 20, 21 are provided in the internal space. The powder layers 20, 21 are fixed to the surfaces of the porous sheets 10, 11 facing the internal space, respectively. The porous sheets 10, 11, the powders 20a, 21a, and the powder layers 20, 21 will be described below.

[0016] (1) Perforated sheet The porous sheets 10, 11 are mainly composed of resin or rubber. The porous sheets 10, 11 contain a plurality of air bubbles inside the resin or rubber, and are preferably molded sheets of foamed resin or foamed rubber. The porous sheets 10, 11 having such a structure may also be called sponge sheets or foamed sheets. Here, "mainly" means that the ratio of resin or rubber in the porous sheets 10, 11 (excluding holes) exceeds 50% by volume. The porous sheets 10, 11 may contain a filler such as silica in the resin or rubber matrix (base material).

[0017] The matrix material constituting the porous sheets 10 and 11 is not particularly limited, but is preferably a material with high heat resistance. When resin is used as the matrix material, suitable resins include polypropylene, polyvinylidene fluoride, polyamide, polycarbonate, polyphenylene sulfide, polyimide, polyetherimide, polytetrafluoroethylene, polyamideimide, phenolic resin, allyl resin, epoxy resin, furan resin, and silicone resin. When rubber is used as the matrix material, suitable rubbers include silicone rubber, acrylic rubber, styrene rubber, butyl rubber, ethylene propylene rubber, and fluororubber.

[0018] The air in the cells of the porous sheets 10, 11 improves the heat insulating performance of the thermal diffusion prevention sheet 1 and contributes to improving the cushioning properties (ability to significantly shrink from its original size) of the thermal diffusion prevention sheet 1. The porous sheets 10, 11 are preferably silicone rubber sponge sheets. Silicone rubber sponge sheets are particularly preferred materials because they combine the insulating properties of the air in the cells with the insulating properties and elastic deformability of silicone rubber. The ratio of the volume of the cells to the volume of the matrix material (including the cells) is preferably 30 / 100 to 97 / 100, more preferably 40 / 100 to 90 / 100.

[0019] (2) powder The powders 20a, 21a are composed of a plurality of particles 20b, 21b. The particles 20b, 21b constituting the powders 20a, 21a may have any shape, such as a spherical, rectangular, cubic, octahedral, or irregular shape. The suitable average equivalent spherical diameter of the particles 20b, 21b is not particularly limited, but is preferably 100 μm or more and 3000 μm or less, and more preferably 300 μm or more and 2000 μm or less. Here, the "equivalent spherical diameter" refers to the diameter when the particle 20b, 21b is converted into a sphere having the same volume as the particle 20b, 21b. The "average" refers to the average measured by observing 50 particles under a microscope (optical microscope or scanning electron microscope).

[0020] The powders 20a, 21a preferably have the same or higher heat resistance as the matrix material of the porous sheets 10, 11. Here, the heat resistance is preferably determined by the melting point (or the sublimation point if there is no melting point). Examples of the powders 20a, 21a include silicone rubber, silica, and aerogel. When the matrix material of the porous sheets 10, 11 is silicone rubber, the powders 20a, 21a are preferably silicone rubber powder, and more preferably powder obtained by shaving molded silicone rubber for recycling purposes.

[0021] (3) Powder layer The powder layers 20, 21 are aggregates of particles 20b, 21b constituting the powders 20a, 21a, in one or more layers. The particles 20b, 21b may be bonded to each other by any method, such as physical adsorption or bonding via a binder component. The powder layers 20, 21 are fixed to one side of each of the porous sheets 10, 11 (i.e., the side of the internal space when the porous sheets 10, 11 are bonded together). The surfaces of the powder layers 20, 21 facing each other have numerous irregularities caused by the particles 20b, 21b. When the powder fixing sheets 25, 26 are bonded to the powder layers 20, 21 so that they face each other, gaps always occur between the powder layers 20, 21, and the powder layers 20, 21 are not in contact without gaps. These gaps are called air layers 30. The air layers 30 contribute to improving the thermal insulation of the thermal diffusion prevention sheet 1.

[0022] There is a possibility that the particles 20b, 21b constituting the powders 20, 21a may fall off during use of the thermal diffusion prevention sheet 1. However, since the porous sheets 10, 11 have a bag-like shape with a closed outer periphery 15, the possibility of the particles 20b, 21b spilling out can be reduced or prevented.

[0023] FIG. 3 shows the flow of the main steps in the method for producing the thermal diffusion prevention sheet according to the first embodiment.

[0024] The method for manufacturing the thermal diffusion prevention sheet according to this embodiment includes a paste preparation step (S110), an application step (S120), a volatilization step (S130), and a bonding step (S140).

[0025] (Paste production process) This step involves mixing the powders 20a and 21a with a dispersion medium to prepare a paste. The dispersion medium is not particularly limited as long as it is a liquid capable of dispersing the particles 20b and 21b that make up the powders 20a and 21a, and examples thereof include organic solvents and water. Examples of organic solvents include ethanol, propanol, and acetone. The powders 20a and 21a may be simply dispersed in the dispersion medium, or may be slightly dissolved in the dispersion medium.

[0026] (Coating process) This step involves applying the paste to one side of the porous sheets 10 and 11. There are no particular restrictions on the application method, and examples include brush application and spraying.

[0027] (Volatilization process) This step is a step of volatilizing the dispersion medium from the applied paste. The volatilization does not have to be to the extent that the dispersion medium is completely removed, but a method that leaves a small amount of dispersion medium components remaining is also acceptable. Furthermore, the method of volatilizing the dispersion medium in this step may be any method, such as drying at a temperature lower than that of heating, heating, or leaving at room temperature. Powder fixing sheets 25, 26 are completed by this step.

[0028] (Lamination process) In this step, powder fixing sheets 25, 26, each having powder 20a, 21a fixed thereto, are bonded together with the surfaces of the fixed powder layers 20, 21 facing each other. The bonding is performed by sealing the outer peripheries 15 of the porous sheets 10, 11 by adhesive bonding or thermocompression bonding, but no adhesive component such as an adhesive is supplied between the powder layers 20, 21. This is because it is necessary to ensure an air layer 30 between the powder layers 20, 21. With this step, the thermal diffusion prevention sheet 1 is completed.

[0029] FIG. 4 shows a photograph of the powder fixing sheet and an enlarged photograph of a part C thereof after the volatilization step has been completed in the manufacturing process of the thermal diffusion prevention sheet according to the first embodiment.

[0030] 4, the surfaces of the powder fixing sheets 25, 26 facing the powder layers 20, 21 have numerous irregularities. In addition, the surfaces facing the powder layers 20, 21 have irregular irregularities. Therefore, even when the powder layers 20, 21 are placed face to face, the irregularities do not completely overlap, and an air layer 30 is formed.

[0031] Second Embodiment Next, a description will be given of a thermal diffusion prevention sheet and a method for manufacturing the same according to a second embodiment. In the second embodiment, duplicated descriptions of parts common to the first embodiment will be omitted.

[0032] 5 shows a cross-sectional view of the thermal diffusion barrier sheet according to the second embodiment taken along line AA in the same view as in FIG. 1, and an enlarged view of part B. The plan view, side view, and bottom view of the thermal diffusion barrier sheet 1a according to the second embodiment are the same as those of the thermal diffusion barrier sheet 1 according to the first embodiment (see FIG. 1).

[0033] The thermal diffusion prevention sheet 1a according to the second embodiment has a heat insulating sheet 40, which has higher heat insulating properties than the porous sheets 10 and 11, sandwiched between two powder fixing sheets 25 and 26, more specifically, between two powder layers 20 and 21. Air layers 30 are formed between the two powder layers 20 and 21, between the powder layer 20 and the heat insulating sheet 40, and between the powder layer 21 and the heat insulating sheet 40. High heat insulating properties mean low thermal conductivity. Therefore, the heat insulating sheet 40 is a member with lower thermal conductivity than the porous sheets 10 and 11.

[0034] The heat insulating sheet 40 may or may not have excellent electrical conductivity. The heat insulating sheet 40 preferably exhibits high insulation properties. The heat insulating sheet 40 is preferably a sheet that has excellent flexibility (or bendability). There are no restrictions on the thickness of the heat insulating sheet, but it is preferably 0.2 mm or more and 5 mm or less, more preferably 0.5 mm or more and 2 mm or less.

[0035] The heat insulating sheet 40 is preferably a sheet containing primarily talc, silica, aerogel (e.g., silica aerogel), mullite, cordierite, steatite, forsterite, titania, or zirconia, and more preferably a sheet containing primarily talc, silica, or aerogel. Talc is generally a ceramic whose main component is hydrous magnesium silicate and contains small amounts of impurities such as iron oxide. The type and amount of impurities vary depending on the source of the talc ore, but the talc contained in the heat insulating sheet 40 is not particularly limited in these respects.

[0036] The term "mainly" used herein means that the mass ratio of the metal oxides of talc, silica, aerogel, mullite, cordierite, steatite, forsterite, titania, or zirconia to the total mass of the heat insulating sheet 40 exceeds 50 mass%. The content of the metal oxides in the heat insulating sheet 40 as a whole is preferably 51 mass% or more, more preferably 70 mass% or more, and even more preferably 90 mass% or more. In addition to the metal oxides, the heat insulating sheet 40 may contain relatively heat-resistant materials such as silicone rubber, aramid fiber, and polyphenylene sulfide. Alternatively, the heat insulating sheet 40 may be composed almost entirely or entirely of the metal oxides.

[0037] Both surfaces of the heat insulating sheet 40 in the thickness direction are preferably smoother than the surfaces of the powder layers 20, 21. However, these surfaces may be rougher than the surfaces of the powder layers 20, 21. The roughness of these surfaces does not matter as long as they do not adhere closely to the surfaces of the powder layers 20, 21. The air layer 30 formed between the heat insulating sheet 40 and each powder layer 20, 21 contributes to improving the heat insulating properties of the thermal diffusion prevention sheet 1a.

[0038] When the thermal diffusion prevention sheet 1a is used, there is a possibility that the particles 20b, 21b constituting the powders 20, 21a may fall off. However, since the porous sheets 10, 11 have a bag-like shape with a closed outer periphery 15, the possibility of the particles 20b, 21b spilling out can be reduced or prevented.

[0039] Next, a method for producing the thermal diffusion prevention sheet 1a will be described.

[0040] The thermal diffusion barrier sheet 1a can be manufactured by steps similar to those for the thermal diffusion barrier sheet 1. That is, the method for manufacturing the thermal diffusion barrier sheet according to the second embodiment includes a paste preparation step (S110), an application step (S120), a volatilization step (S130), and a bonding step (S140) (see FIG. 3). However, the bonding step in the second embodiment differs from that in the first embodiment in that a heat insulating sheet 40, which has higher heat insulating properties than the porous sheets 10 and 11, is sandwiched between the opposing surfaces of the powder layers 20 and 21.

[0041] 2. Battery FIG. 6 shows a longitudinal cross-sectional view of a battery according to one embodiment and an enlarged view of one heat diffusion prevention sheet sandwiched between battery cells in the longitudinal cross-sectional view.

[0042] The battery 50 according to this embodiment is, for example, a battery for an electric vehicle, and includes a plurality of battery cells (also simply referred to as "cells") 60 arranged side by side. In this embodiment, the number of battery cells 60 is eight, but may be two to seven, or nine or more. The battery 50 is a storage battery, preferably a lithium-ion battery. The battery 50 includes a housing 51 with a bottom that is open on one side. The battery cells 60 are disposed inside 52 of the housing 51. The plurality of battery cells 60 are preferably pressed against each other by applying compressive force from both sides of the housing 51 using screws or the like (not shown). The bottom of the housing 51 is provided with a through-hole 53 for allowing the flow of cooling water, which is an example of a coolant. The coolant may also be referred to as a cooling medium or a coolant. The battery cells 60 are disposed inside the housing 51 with a thermal diffusion prevention sheet 1 or a thermal diffusion prevention sheet 1a sandwiched between adjacent battery cells 60.

[0043] As described above, the battery 50 according to this embodiment includes a plurality of battery cells 60 in the housing 51, and includes the heat diffusion prevention sheets 1, 1a at least between the battery cells 60, either between the battery cells 60 or between the battery cells 60 and the housing 51. The heat diffusion prevention sheets 1, 1a do not necessarily have to be disposed between the battery cells 60 and the housing 51.

[0044] The thermal diffusion prevention sheets 1, 1a are sandwiched and compressed between the battery cells 60 when the battery cells 60 are set in the housing 51, and even if the compression is repeated several times, the thermal diffusion prevention sheets 1, 1a elastically deform in the thickness direction and easily recover to their original thickness. Furthermore, the thermal diffusion prevention sheets 1, 1a are compressed in the thickness direction when stored in the housing 51 in a compressed state between the battery cells 60. They are further compressed when the battery cells 60 heat and expand during charging and / or discharging of the battery 50. The thermal diffusion prevention sheets 1, 1a include the porous sheets 10, 11, which allow them to contract when compressed, thereby contributing to the relaxation of stress on the battery cells 60. The air layer 30 also contributes to the reduction of thermal diffusion (also known as thermal conduction) between the battery cells 60. The heat insulating sheet 40 of the thermal diffusion prevention sheet 1a further contributes to the reduction of thermal diffusion.

[0045] 3. Other embodiments Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be practiced in various modified forms.

[0046] The powder layers 20 and 21 are preferably layers in which a plurality of particles 20b or a plurality of particles 21b are in contact with each other, i.e., layers in which a plurality of particles 20b or a plurality of particles 21b are integrated. However, the plurality of particles 20b or a plurality of particles 21b may be separated into two or more islands. Alternatively, the particles 20b or the particles 21b may not be in contact with other islands. Furthermore, one or more particles 20b or 21b may have fallen off the powder layers 20 and 21.

[0047] In the thermal diffusion prevention sheet 1a according to the second embodiment described above, one of the powder layers 20, 21 (for example, powder layer 21) may be omitted, and an air layer 30 may be formed only between the powder layer 20 and the heat insulating sheet 40.

[0048] The features of the claims may be combined in any combination except where they are incombinable with one another. [Industrial Applicability]

[0049] The present invention can be used as a sheet that can be compressed and deformed in response to the expansion of a heat source. [Explanation of symbols]

[0050] 1,1a···Heat diffusion prevention sheet, 10,11···Perforated sheet, 15···Outer periphery, 20,21···Powder layer, 20a,21a···Powder, 20b,21b···Particles, 25,26···Powder fixing sheet, 30···Air layer, 40···Insulating sheet, 50···Battery, 51···Enclosure, 60···Battery cell (an example of a heat source).

Claims

1. A thermal diffusion prevention sheet that is disposed at least between a plurality of heat sources and that can reduce thermal diffusion between the heat sources and relieve pressure when the heat sources expand, A thermal diffusion prevention sheet having a structure in which two powder-fixed sheets, each having a powder fixed on one side of a porous resin or rubber sheet, are bonded together with the fixed powder layer sides facing each other, and characterized by having an air layer between the two powder layers.

2. The thermal diffusion prevention sheet according to claim 1, characterized in that an insulating sheet having higher insulating properties than the porous sheet is sandwiched between the powder fixing sheets, and the air layer is formed between the powder layer and the insulating sheet.

3. 3. The heat diffusion prevention sheet according to claim 2, wherein the heat insulating sheet is a sheet containing primarily talc, silica, aerogel, mullite, cordierite, steatite, forsterite, titania, or zirconia.

4. 2. The thermal diffusion prevention sheet according to claim 1, wherein the powder is silicone rubber, silica, or aerogel.

5. 2. The thermal diffusion prevention sheet according to claim 1, wherein the porous sheet is a silicone rubber sponge sheet.

6. A method for producing the thermal diffusion prevention sheet according to any one of claims 1 to 5, comprising the steps of: a paste preparation step of preparing a paste by mixing the powder with a dispersion medium; a coating step of coating one surface of the porous sheet with the paste; a volatilization step of volatilizing the dispersion medium from the applied paste; a lamination step of laminating the powder-fixed sheets, each having a powder fixed thereon, with the fixed powder layer sides facing each other; A method for producing a thermal diffusion prevention sheet, comprising:

7. 7. The method for manufacturing a thermal diffusion prevention sheet according to claim 6, wherein in the laminating step, a heat insulating sheet having a higher heat insulating property than the porous sheet is sandwiched between the opposing powder layer sides.

8. A battery having a plurality of battery cells in a housing, A battery comprising the thermal diffusion prevention sheet according to claim 1 , at least between the battery cells, among between the battery cells and between the battery cells and the housing.

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