Fire spread prevention sheet and production method of the same, and battery

Abstract

To provide a fire spread prevention sheet capable of realizing elastic deformation which efficiently absorbs inflation of a heat source while realizing reflection of heat from the heat source, and a battery provided with the same.SOLUTION: A fire spread prevention sheet 10 capable of preventing the spread of a fire between heat sources 5 by being interposed between the heat sources 5, has a laminate structure constituted by interposing a metal film 13 between a first rubber sheet 11 and a second rubber sheet 12, where the metal film 13 is a film in a state in which metal particles 15 are deposited. There are also provided a production method of the same, and a battery.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a fire prevention sheet, a manufacturing method thereof, and a battery. [Background technology]

[0002] The power source of automobiles is shifting from engines that use fossil fuels such as gasoline and diesel to motors that use electricity from batteries. A lithium-ion battery, one type of battery, generally has multiple battery cells (also simply called "cells") arranged inside a housing.

[0003] Battery cells may generate heat during charging and discharging. If a battery cell overheats abnormally, the heat is transferred to adjacent battery cells, resulting in overheating of the entire battery and increasing the risk of fire. To prevent such an event, it is preferable to interpose a material between the battery cells that reduces heat conduction between the battery cells. On the other hand, when a battery cell overheats, the battery cell container expands. To absorb such expansion, it is preferable to interpose a material that is highly elastically deformable between the battery cells.

[0004] Prior to the present invention, the inventor of the present application developed a fire spread prevention sheet comprising a rubber sheet made of a rubber-like elastic body, heat insulating sheets laminated on both sides of the rubber sheet capable of reducing heat transfer between a plurality of adjacent heat sources, and adhesive layers interposed between the rubber sheet and the heat insulating sheet for adhering the heat insulating sheet to both sides of the rubber sheet (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2023-062546 A Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors of the present invention have further developed the fire prevention sheet based on the above-mentioned knowledge of the conventionally known fire prevention sheet, and have come up with the following improvements. One is to make it easier to reflect heat emitted from a heat source such as a battery cell. The other is to make the fire prevention sheet capable of elastic deformation sufficient to more reliably absorb the expansion of the heat source.

[0007] When a laminated sheet in which metal plates with high thermal conductivity, such as aluminum, are placed on both sides of the rubber sheet in the thickness direction is sandwiched between heat sources, the heat from the overheated heat source is immediately transferred to the metal plates. As a result, the metal plates themselves become hot, which is not preferable. In addition, if a normal metal plate is used, the elastic deformation of the rubber sheets that make up the laminated sheet is hindered. As a result, when the heat source expands, the rubber cannot exhibit elastic deformation corresponding to the expansion.

[0008] Based on the above findings, the present invention aims to provide a fire spread prevention sheet that can reflect heat from a heat source while also achieving elastic deformation that efficiently absorbs the expansion of the heat source, and a battery equipped with the same. [Means for solving the problem]

[0009] (1) In one embodiment for achieving the above object, a fire spread prevention sheet is a sheet that can be placed between heat sources to prevent the spread of fire between the heat sources, and has a laminate structure in which a metal film is sandwiched between a first rubber sheet and a second rubber sheet, and the metal film is a film in which metal particles are deposited. (2) In the fire spread prevention sheet according to another embodiment, at least one of the first rubber sheet and the second rubber sheet may preferably be a sponge-like porous sheet. (3) In the fire spread prevention sheet according to another embodiment, at least one of the first rubber sheet and the second rubber sheet may be made of silicone rubber. (4) In the fire spread prevention sheet according to another embodiment, the metal film may preferably be one or more films of aluminum, copper, tin, or an alloy containing at least one of these elements. (5) In one embodiment for achieving the above-mentioned object, a method for manufacturing a fire spread prevention sheet is a method for manufacturing any of the fire spread prevention sheets described above, and includes a metal film formation process for forming a metal film on one thickness-wise side of a first rubber sheet, and a lamination process for laminating a second rubber sheet on the surface of the metal film of the first rubber sheet. (6) In another embodiment of the method for manufacturing a fire spread prevention sheet, preferably, prior to the metal film formation process, a primer treatment process may be performed on one surface of the first rubber sheet in the thickness direction to facilitate the formation of the metal film. (7) In the method for producing a fire spread prevention sheet according to another embodiment, the metal film forming step may be preferably carried out by a deposition or sputtering process for forming the metal film. (8) In order to achieve the above object, one embodiment of a battery is a battery having a plurality of battery cells arranged in a row, and any of the above-mentioned fire prevention sheets is interposed between the battery cells. Effect of the Invention

[0010] According to the present invention, it is possible to provide a fire spread prevention sheet that is capable of reflecting heat from a heat source while also achieving elastic deformation that efficiently absorbs the expansion of the heat source, and a battery equipped with the same. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows an enlarged view of a main part and a part A of a battery according to an embodiment of the present invention. [Diagram 2] FIG. 2 shows a perspective view of a fire spread prevention sheet according to an embodiment of the present invention. [Diagram 3] FIG. 3 shows the main manufacturing steps of the fire prevention sheet of FIG. [Figure 4]FIG. 4 shows the first stage of the manufacturing process of the fire prevention sheet of FIG. [Diagram 5] FIG. 5 shows the stage following the situation in FIG. [Figure 6] FIG. 6 shows the stage following that of FIG. [Figure 7] FIG. 7 shows an evaluation method (7A) for the fire spread prevention performance of one example of the fire spread prevention sheet according to this embodiment, and the evaluation results (7B). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below does not limit the invention according to the claims, and all of the elements and combinations thereof described in the embodiment are not necessarily essential to the solution of the present invention.

[0013] FIG. 1 shows an enlarged view of a main part and a part A of a battery according to an embodiment of the present invention.

[0014] The battery 1 according to this embodiment is, for example, a battery for an electric vehicle, and is preferably a lithium-ion battery. The battery 1 has a large number of battery cells (also simply referred to as "cells") 5 arranged side by side, and a fire spread prevention sheet 10 is sandwiched between the battery cells 5. The fire spread prevention sheet 10 is a sheet for minimizing the spread of fire to adjacent battery cells 5 even if some of the battery cells 5 overheat and, in the worst case, catch fire. The fire spread prevention sheet 10 is also a sheet that can be elastically deformed in its thickness direction. The battery cells 5 are compressed in the arranging direction and set in the battery 1. At this time, the fire spread prevention sheet 10 is compressed and deformed by being compressed by the battery cells 5. On the other hand, when the compression of the battery cells 5 is released, the fire spread prevention sheet 10 recovers to its original thickness. Furthermore, when the battery cells 5, which are an example of a heat source, thermally expand, the fire spread prevention sheet 10 can be elastically deformed in response to the deformation of the battery cells 5 accompanying the expansion.

[0015] FIG. 2 shows a perspective view of a fire spread prevention sheet according to an embodiment of the present invention.

[0016] The fire spread prevention sheet 10 according to this embodiment is provided inside the battery 1 so that both sides in the thickness direction of the sheet 10 contact the battery cells 5. However, one of the multiple fire spread prevention sheets 10 may be provided inside the battery 1 so that one side in the thickness direction of the sheet 10 contacts the battery cell 5 and the other side contacts the housing (not shown) of the battery 1. The fire spread prevention sheet 10 is a sheet that can be interposed between battery cells 5, which are an example of a heat source, to prevent the spread of fire between the heat sources.

[0017] The fire spread prevention sheet 10 has a laminate structure in which a metal film 13 is sandwiched between a first rubber sheet 11 and a second rubber sheet 12. The metal film 13 is a film in which metal particles are deposited. In the present application, the metal particles are broadly interpreted to include metal atoms.

[0018] The thicknesses of the first rubber sheet 11 and the second rubber sheet 12 may be relatively larger or the same, but are preferably the same. As a result, the metal film 13 is disposed exactly in the center of the thickness of the fire spread prevention sheet 10. The range of the thicknesses of the first rubber sheet 11 and the second rubber sheet 12 is not particularly limited, but is preferably 1 mm or more and 10 mm or less, more preferably 2 mm or more and 5 mm or less. The total thickness of the metal film 13 is preferably 0.1 μm or more and 4.0 μm or less, more preferably 0.2 μm or more and 1.5 μm or less. The average diameter of the metal particles constituting the metal film 13 is preferably 0.1 μm or more and 2.0 μm or less, more preferably 0.5 μm or more and 1.5 μm or less. The metal film 13 has a form in which one or more layers of metal particles are deposited. Here, the "average diameter" refers to the average value of the diameters obtained by arbitrarily selecting 100 particles from an SEM image.

[0019] The first rubber sheet 11 and the second rubber sheet 12 are configured to include, for example, a thermosetting elastomer such as silicone rubber, urethane rubber, isoprene rubber, ethylene propylene rubber, natural rubber, ethylene propylene diene rubber, nitrile rubber (NBR), or styrene butadiene rubber (SBR); a thermoplastic elastomer such as a urethane-based, ester-based, styrene-based, olefin-based, butadiene-based, or fluorine-based elastomer, or a composite thereof. The first rubber sheet 11 and the second rubber sheet 12 are preferably silicone rubber sheets having excellent heat resistance. The first rubber sheet 11 and the second rubber sheet 12 may contain a filler such as silica or graphite. In addition, the first rubber sheet 11 and the second rubber sheet 12 are preferably porous sheets (also called sponge-like porous sheets) having high elasticity. In this embodiment, a more preferable form of the first rubber sheet 11 and the second rubber sheet 12 is a porous sheet made of silicone rubber. If the first rubber sheet 11 and the second rubber sheet 12 have small pores containing air inside, the heat insulating properties of the sheets can be further improved.

[0020] The first rubber sheet 11 and the second rubber sheet 12 do not have to be made of the same type of rubber. For example, only either the first rubber sheet 11 or the second rubber sheet 12 may be made of silicone rubber, and the other may be made of non-silicone rubber. Also, only either the first rubber sheet 11 or the second rubber sheet 12 may be a sponge-like porous sheet, and the other may be a non-sponge-like sheet.

[0021] The metal film 13 is not particularly limited in terms of the type of metal, but is preferably a film of aluminum, copper, tin, or an alloy containing at least one of these elements. The metal film 13 may be a film of one type of component, or a film in which films of two types of components are laminated. The metal film 13 may be, for example, an aluminum film, a copper film, a tin film, an aluminum alloy film, a copper alloy film, a tin alloy film, or a film in which two or more of the above single films are laminated. The metal film 13 is a thin film formed by depositing metal particles (preferably crystal grains) in an island shape. As can be seen from the above-mentioned exemplary thickness, the metal film 13 is very thin. Therefore, the risk that the metal film 13 inhibits the elastic deformation of the fire spread prevention sheet 10 in the thickness direction can be reduced. In addition, the metal film 13 is present inside the fire spread prevention sheet 10 in the thickness direction. Therefore, when the battery cell 5, which is a heat source, generates heat, the risk of reflecting the heat back to the battery cell 5 can be reduced.

[0022] Fig. 3 shows the main manufacturing process of the fire spread prevention sheet of Fig. 2. Fig. 4 to Fig. 6 show, in perspective views, the manufacturing process of the fire spread prevention sheet of Fig. 2 in stages. Fig. 5 shows an enlarged view of a part B1 of the metal film 13, and further shows an enlarged view of B2 in B1.

[0023] The manufacturing method of the fire spread prevention sheet 10 according to this embodiment preferably includes a primer treatment (S100), a metal film forming step (S200), and a lamination step (S300), as shown in Fig. 3. The primer treatment is an optional step and is not a required step.

[0024] (1) Primer treatment (S100) This step is a step for facilitating the formation of the metal film 13 on one surface in the thickness direction of the first rubber sheet 11 prior to the metal film forming step (S200). The primer treatment can be selected from various methods depending on the material of the first rubber sheet 11. For example, when the first rubber sheet 11 is made of silicone rubber, the primer treatment can be exemplified by application of a silane coupling agent. Examples of the silane coupling agent include epoxy-functional alkoxysilanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, mercapto-functional alkoxysilanes such as γ-mercaptopropyltrimethoxysilane, amine-functional alkoxysilanes such as γ-aminopropyltrimethoxysilane and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and methacryl-functional alkoxysilanes such as 3-methacryloxypropyltrimethoxysilane.

[0025] (2) Metal film formation process (S200) As shown in FIG. 5, this step is a step of forming a metal film 13 on one surface in the thickness direction of the first rubber sheet 11. When the primer treatment step (S100) is performed, the metal film 13 is formed on the primer-treated surface of the first rubber sheet 11. The metal film formation step (S200) is preferably performed by a metal deposition film formation or sputtering film formation process. Deposition is a method of forming a metal film 13 on one surface of the first rubber sheet 11 by evaporating a metal in a vacuum chamber. Examples of methods for depositing a metal include a resistance heating method, an electron beam irradiation method, a laser heating method, and a high-frequency induction method. Sputtering is a method of forming a metal film 13 on the first rubber sheet 11 by using a metal as a target in a vacuum chamber and colliding an inert gas such as argon as ions with the target to cause metal atoms to fly out of the target. Examples of types of sputtering include magnetron sputtering, RF sputtering, reactive sputtering, and DC sputtering.

[0026] As shown in the enlarged view of a portion B1 in FIG. 5 and the enlarged view of a portion B2 therein, the metal film 13 is a film on which metal particles 15 are deposited. When the first rubber sheet 11 is a sponge-like porous sheet, the metal film 13 is formed on the surface of the first rubber sheet 11 other than the holes 14. The metal particles 15 also penetrate into the holes 14. For this reason, a part of the metal film 13 may be formed inside the holes 14 as well.

[0027] (3) Lamination process (S300) As shown in Fig. 6, this step is a step of laminating a second rubber sheet 12 on the surface of the metal film 13 of the first rubber sheet 11. Prior to this step, the surface of the second rubber sheet 12 that comes into contact with the metal film 13 may be subjected to a treatment similar to the primer treatment step (S100). In addition, in the lamination step (S300), heating or a combination of heating and pressure may be performed. Also, lamination may be performed using a heat-resistant adhesive.

[0028] 7A and 7B show an evaluation method (7A) and evaluation results (7B) of the fire spread prevention performance of an example of the fire spread prevention sheet according to this embodiment. The horizontal axis of the graph (7B) shows elapsed time (sec), and the vertical axis shows temperature (°C).

[0029] The fire spread prevention performance was measured by sandwiching the sample X between the heating element (800°C) 20 and the temperature measurement plate 21 as shown in (7A), and applying pressure between the heating element 20 and the temperature measurement plate 21 when the heating element reached 800°C. The pressure during pressing was 0.1 MPa. The temperature was measured at the position of the temperature measurement plate 21. The following three types of sample X were used. The first sample was a 4.2 mm thick foamed silicone rubber sheet (specific gravity: 0.36) used as a comparative material (Sample A). The second sample was a sheet used as an example of this embodiment (Sample B), and was a sheet in the form of a laminated film of a 1 μm thick copper thin film and a 0.3 μm thick tin alloy (Sn-Ag-P alloy) thin film sandwiched between two 2.1 mm thick foamed silicone rubber sheets (specific gravity: 0.36). The copper thin film was formed by deposition on one side of the 2.1 mm thick foamed silicone rubber sheet. The above-mentioned thin film of tin-based alloy was formed by deposition on the surface of the thin copper film. Deposition was performed using a batch-type deposition apparatus (model number: LP1300BSD) manufactured by ULVAC, with the degree of vacuum in the chamber set to 1×10 ―4 ~1×10 ―6 The deposition was performed at a pressure in the range of 10 Pa. The deposition was performed by heating the metal for deposition using a resistance heating method. The third sample was a sheet used as a comparative material (Sample C), and was a sheet in which 10 μm thick aluminum foil was sandwiched between two 2.1 mm thick foamed silicone rubber sheets (specific gravity: 0.36).

[0030] As shown in (7B), Sample A, Sample B and Sample C all showed a rise in temperature over time. All samples maintained a temperature below 400°C, which was a significant effect in suppressing temperature rise compared to the temperature of the heating element (800°C). Sample B also showed a greater effect in suppressing temperature rise than Sample A. Furthermore, Sample C showed a greater effect in suppressing temperature rise than Sample B. However, in the case of a structure in which aluminum foil is sandwiched between foamed silicone rubber sheets as in Sample C, it was found that compression is difficult even when a load is concentrated in the center of the laminated sheet. This is thought to be because the aluminum foil is difficult to stretch, and the foil suppresses the deformation of the foamed silicone rubber sheet. This phenomenon was not observed in the structure of Sample B. From the above results, it was determined that Sample B, which has a relatively large heat shielding effect and does not suppress the deformation of the silicone rubber as much as possible, is an overall superior structure.

[0031] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified in various ways.

[0032] In the above-described embodiment, both the first rubber sheet 11 and the second rubber sheet 12 are sponge-like porous sheets, but only one of the rubber sheets 11, 12 may be a sponge-like porous sheet. Also, both the rubber sheets 11, 12 may be non-sponge rubber sheets.

[0033] In the above-described embodiment, the metal film 13 is formed on the entire area of ​​one side of the first rubber sheet 11. However, the metal film 13 may be formed on one or more parts of a portion of the one side.

[0034] The fire spread prevention sheet 10 may be disposed not only between the battery cells 5, but also between the battery cells 5 and a housing that stores the battery cells 5. Furthermore, the fire spread prevention sheet 10 may be used not only to be installed on the battery 1, but also to be disposed between circuit boards, between electronic components, or between a circuit board and an electronic component in an electronic device. [Industrial Applicability]

[0035] The present invention can be used, for example, in automobile batteries. [Explanation of symbols]

[0036] 1... battery, 5... battery cell (an example of a heat source), 10... fire prevention sheet, 11... first rubber sheet (e.g., a sponge-like porous sheet), 12... second rubber sheet (e.g., a sponge-like porous sheet), 13... metal film, 14... hole, 15... metal particles.

Claims

1. A fire prevention sheet that can be interposed between heat sources to prevent the spread of fire between the heat sources, The laminate structure has a metal film sandwiched between a first rubber sheet and a second rubber sheet, A fire spread prevention sheet, wherein the metal film is a film in which metal particles are deposited.

2. 2. The fire spread prevention sheet according to claim 1, wherein at least one of the first rubber sheet and the second rubber sheet is a sponge-like porous sheet.

3. 2. The fire spread prevention sheet according to claim 1, wherein at least one of the first rubber sheet and the second rubber sheet is made of silicone rubber.

4. 2. The fire spread prevention sheet according to claim 1, wherein the metal film is one or more films of aluminum, copper, tin or an alloy containing at least one of these elements.

5. A method for producing the fire spread prevention sheet according to any one of claims 1 to 4, a metal film forming step of forming a metal film on one surface in a thickness direction of the first rubber sheet; a lamination step of laminating a second rubber sheet on the surface of the metal film of the first rubber sheet; A method for producing a fire spread prevention sheet comprising the steps of:

6. The method for manufacturing a fire spread prevention sheet according to claim 5, characterized in that, prior to the metal film forming process, a primer treatment process is carried out on one surface of the first rubber sheet in the thickness direction to facilitate the formation of the metal film.

7. The method for manufacturing a fire spread prevention sheet according to claim 5, wherein the metal film forming step is carried out by a process of vapor deposition or sputtering of the metal.

8. A battery including a plurality of battery cells arranged in a row, A battery comprising the fire spread prevention sheet according to any one of claims 1 to 4 interposed between the battery cells.

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