Flame-spread prevention sheet, method for producing same, and battery including the same

Abstract

To provide a flame-spread prevention sheet, a method for producing the same, and a battery including the same, the sheet exhibiting excellent thermal insulation and adaptability to pressure variation in the thickness direction while maintaining high heat resistance.SOLUTION: The present invention relates to a flame-spread prevention sheet 1 that is disposed at least between a plurality of heat sources and is capable of preventing flame spread by suppressing heat transfer to other heat sources when any of the heat sources is in an overheated state. The flame-spread prevention sheet 1 is formed by laminating two elastic foam sheets 2 and a heat-insulating sheet 3 containing a metal oxide. The heat-insulating sheet 3 is sandwiched between the two elastic foam sheets 2, and the outer periphery of the elastic foam sheets 2 is sealed. The present invention also relates to a method for producing the sheet and to a battery including the flame-spread prevention sheet 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fire prevention sheet, a method for manufacturing the same, and a battery including the same. [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] Some batteries may experience thermal runaway during discharge or charging, resulting in fire, smoke, or other problems. Recently, automotive batteries with multiple battery cells arranged in a housing have become known. In such a battery with multiple battery cells arranged in a row, if one battery cell were to catch fire or emit smoke, the heat could be transferred to the surrounding battery cells, potentially causing further fires, smoke, explosions, or other problems. To minimize damage caused by such problems, methods have been developed to prevent the transfer of heat from abnormally hot battery cells to the surrounding battery cells. For example, a known method involves providing a fire-prevention sheet, such as a fire-resistant material or a heat-insulating layer, between multiple battery cells (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] As a fire prevention sheet, for example, a ceramic fire-resistant sheet can be placed between battery cells (also simply called "cells"). However, the cell containers that make up a battery expand when overheated during discharge and / or charging. Therefore, even if a high-hardness ceramic sheet has excellent heat resistance (fire resistance), it is not suitable for preventing the spread of fire between cells because it has poor cushioning properties.

[0006] On the other hand, although resin sheets have excellent heat insulation and cushioning properties, they are inferior to ceramic sheets in terms of heat resistance (fire resistance). There is a demand in the market for heat spread prevention sheets that can provide heat insulation and cushioning properties as well as high heat resistance. Meeting this demand will also contribute to the achievement of the applicant's Sustainable Development Goal of "ensuring access to affordable, reliable, sustainable and modern energy for all."

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a heat spread prevention sheet that can exhibit heat insulation and cushioning properties and has high heat resistance, a method for manufacturing the same, and a battery equipped with the same. [Means for solving the problem]

[0008] (1) In order to achieve the above object, one embodiment of a fire spread prevention sheet is a fire spread prevention sheet that is disposed at least between a plurality of heat sources and that can prevent the spread of fire by suppressing heat transfer to other heat sources when the heat sources are in an overheated state, Two elastic foam sheets and a heat insulating sheet containing a metal oxide; and The heat insulating sheet is sandwiched between two of the elastic foam sheets, and the outer peripheries of the elastic foam sheets are sealed. (2) In another embodiment of the fire spread prevention sheet, the elastic foam sheets may each be a foamed silicone rubber sheet. (3) In another embodiment of the fire prevention sheet, the heat insulating sheet may preferably contain at least one of silica, aerogel, diatomaceous earth, and talc as the metal oxide or material containing the metal oxide. (4) In another embodiment of the fire prevention sheet, the heat insulating sheet may preferably contain at least one of silica, diatomaceous earth, and talc in an amount of 50 mass % or more based on the total mass of the heat insulating sheet. (5) To achieve the above object, one embodiment of a method for manufacturing a fire spread prevention sheet includes a lamination step of producing a laminate in which uncured sheets containing a foaming agent are attached to both sides of the heat insulating sheet; and a foaming and curing step of heating the laminate to foam and cure the uncured sheets. (6) In another embodiment of the method for manufacturing a fire spread prevention sheet, the foaming and curing step may preferably include a foaming step in which the uncured sheet is heated to foam it, and a subsequent curing step in which the sheet is heated at a higher temperature than in the foaming step to promote curing of the foamed sheet. (7) In another embodiment of the method for producing a fire spread prevention sheet, the heat insulating sheet may preferably contain at least one of silica, diatomaceous earth, and talc in an amount of 50 mass % or more relative to the total mass of the heat insulating sheet. (8) In order to achieve the above object, a battery according to one embodiment includes a plurality of battery cells in a housing, Any one of the fire spread prevention sheets described above is provided at least between the battery cells, among between the battery cells and between the battery cells and the housing. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a heat spread prevention sheet that can exhibit heat insulation and cushioning properties and has high heat resistance, a method for manufacturing the same, and a battery including the same. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows a front view and a side view (1A) of the fire spread prevention sheet according to the first embodiment, and an AA cross-sectional view (1B). [Figure 2] FIG. 2 shows vertical cross-sectional views (2A, 2B, 2C, 2D) illustrating the manufacturing process of the fire spread prevention sheet according to the first embodiment. [Figure 3] FIG. 3 is a vertical cross-sectional view showing a heat treatment process when manufacturing a fire spread prevention sheet according to the second embodiment. [Figure 4] FIG. 4 shows a longitudinal cross-sectional view of a battery according to one embodiment and an enlarged view of one fire spread prevention sheet sandwiched between battery cells in the longitudinal cross-sectional view. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, various embodiments of the present invention will be described with reference to the drawings. Note that the various embodiments described below do not limit the scope of the invention as claimed, and not all of the elements and combinations thereof described in the various embodiments are necessarily essential to the solution of the present invention.

[0012] 1. Fire prevention sheet FIG. 1 shows a front view and a side view (1A) of the fire spread prevention sheet according to the first embodiment, and an AA cross-sectional view (1B).

[0013] The fire spread prevention sheet 1 according to this embodiment is a sheet that is placed at least between multiple heat sources and can prevent the spread of fire while suppressing heat transfer to other heat sources when a heat source is overheated. Here, examples of "heat sources" include battery cells placed inside an automobile battery, batteries used in devices other than automobiles, or battery cells placed inside such batteries. However, "heat sources" also include, in addition to batteries or battery cells, heaters or their components, and components in electrical or electronic devices (circuit boards, circuit components, etc.).

[0014] As shown in the figure, the fire spread prevention sheet 1 comprises two elastic foam sheets 2 and one heat insulating sheet 3 between them. More specifically, the fire spread prevention sheet 1 has a configuration in which the heat insulating sheet 3 is sandwiched between the two elastic foam sheets 2, with the outer periphery of the elastic foam sheets 2 sealed. The elastic foam sheet 2 has a bag-like configuration with its outer periphery sealed. Therefore, even if a portion of the heat insulating sheet 3 chips or turns into powder, the chipped portion or powder will not spill out of the fire spread prevention sheet 1. The elastic foam sheet 2 is a porous elastic sheet and contains numerous pores 2a. The elastic foam sheet 2 functions as a cushioning material that can compress and expand in response to the thermal expansion and subsequent contraction of battery cells, which are an example of a heat source. Furthermore, the pores 2a present inside and on the surface of the elastic foam sheet 2 provide space for air to be stored when a heat source is present on both sides of the elastic foam sheet 2 in the thickness direction, or when a heat source and a non-heat source are present on both sides. This contributes to the high heat insulating properties of the fire spread prevention sheet 1 due to the air's high insulating properties.

[0015] The heat insulating sheet 3 is a sheet containing a metal oxide and preferably has higher heat resistance than the elastic foam sheet 2. By enclosing the heat insulating sheet 3 within the fire spread prevention sheet 1, even if a battery cell overheats and, in the worst case, catches fire, it is possible to prevent heat transfer to other battery cells adjacent to the battery cell in question. The heat insulating sheet 3 may be a sheet containing only a metal oxide, but is preferably a composite sheet of a metal oxide and a resin or rubber. As described below, the heat insulating sheet 3 preferably contains silica, aerogel (including silica aerogel), diatomaceous earth, talc, mica, aluminum hydroxide, and / or magnesium hydroxide as a metal oxide or a material containing a metal oxide. The heat insulating sheet 3 can be obtained, for example, by a manufacturing method including a molding process and a process similar to papermaking.

[0016] The ratio of the thickness of one of the two elastic foam sheets 2 to the thickness of the heat insulating sheet 3 is preferably elastic foam sheet:heat insulating sheet = 0.3 to 3:1, more preferably 0.5 to 2.5:1, and even more preferably 1 to 2:1.

[0017] The total thickness of the fire spread prevention sheet 1 is not particularly limited. It can be selected appropriately depending on the type and size of the heat source, the size of the space in which the fire spread prevention sheet 1 is placed, and the number of fire spread prevention sheets 1 to be used. For example, if the heat source is a battery cell for an automobile, which is subject to large vibrations, the elastic foam sheet 2, which acts as a cushion, may be made thicker. If the heat source is a heater or a component in an electronic device, which is not subject to large vibrations, the heat insulating sheet 3 may be made thicker.

[0018] Considering the productivity and versatility of the fire spread prevention sheet 1, the total thickness of the fire spread prevention sheet 1 is preferably 2 to 20 mm, more preferably 3 to 10 mm. The thickness of one of the two elastic foam sheets 2 and the thickness of the heat insulating sheet 3 can be set within the following ranges, for example: The thickness of one elastic foam sheet 2 can be set within the range of 1 to 3 mm, and the thickness of the heat insulating sheet 3 can be set within the range of 0.5 to 2 mm.

[0019] The ratio of the volume of the pores (also referred to as "voids") 2a in the elastic foam sheet 2 to the volume of the elastic foam sheet 2 (the external volume including the pores 2a) is preferably 50 / 100 to 95 / 100, more preferably 60 / 100 to 85 / 100. The pores 2a contribute to the function of enhancing the heat insulating property of the elastic foam sheet 2 and also contribute to the function of facilitating elastic deformation of the elastic foam sheet 2 during compression and release. Unlike the elastic foam sheet 2, the heat insulating sheet 3 preferably does not have pores, but may have pores.

[0020] The elastic foam sheet 2 is made of an elastomer to provide elastic deformation properties to the elastic foam sheet 2. As described below, the elastic foam sheet 2 is preferably obtained through a foaming and curing process using heat. Therefore, the elastomer is preferably a thermosetting elastomer. Examples of thermosetting elastomers include silicone rubber, urethane rubber, isoprene rubber, ethylene propylene rubber, ethylene propylene diene rubber, nitrile rubber (NBR), and styrene butadiene rubber (SBR). Among these, silicone rubber, which has relatively high heat resistance, is preferred. Preferably, both of the two elastic foam sheets 2 are foamed silicone rubber sheets.

[0021] The heat insulating sheet 3 preferably has higher heat resistance than the elastic foam sheet 2. The heat insulating sheet 3 is made of a resin or rubber containing a filler such as mica, silica, aerogel (including silica aerogel), diatomaceous earth, talc, or glass fiber. Of these fillers, silica, aerogel (including silica aerogel), diatomaceous earth, and talc are more preferred. The filler may be one type or two or more types.

[0022] When the heat insulating sheet 3 contains a resin, the resin is preferably polyphenylene sulfide (PPS) or polyether ether ketone (PEEK), which have excellent heat resistance. When the heat insulating sheet 3 contains rubber, the rubber is preferably a thermosetting elastomer such as silicone rubber, urethane rubber, isoprene rubber, ethylene propylene rubber, ethylene propylene diene rubber, nitrile rubber (NBR), or styrene butadiene rubber (SBR).

[0023] When the heat insulating sheet 3 contains a metal oxide such as silica, aerogel (including silica aerogel), diatomaceous earth, talc, and / or mica, but does not contain resin or rubber, the mass ratio of the metal oxide in the heat insulating sheet 3 is preferably 80 to 100 mass%, more preferably 85 to 99 mass%. When the heat insulating sheet 3 contains a resin or rubber in addition to the metal oxide, the mass ratio of the metal oxide in the heat insulating sheet 3 is preferably 50 to 80 mass%, more preferably 60 to 75 mass%. That is, the heat insulating sheet 3 preferably contains at least one of silica, diatomaceous earth, and talc in an amount of 50 mass% or more relative to the total mass of the heat insulating sheet 3. The filler may also be surface-treated. For example, a silane coupling agent can be used to surface treat the filler.

[0024] 2. Manufacturing method of fire prevention sheet First Embodiment A method for manufacturing a fire spread prevention sheet according to the first embodiment will now be described. This manufacturing method includes a lamination step in which uncured sheets 4 containing a foaming agent are bonded to both sides of a heat insulating sheet 3 to produce a laminate, and a foaming and curing step in which the laminate is heated to foam and cure the uncured sheets 4. The foaming agent may preferably be a known organic or inorganic foaming agent. Here, the "uncured sheet 4" refers to a sheet that will become the elastic foam sheet 2 upon curing, and refers to a molded or unmolded product before it is completely cured.

[0025] FIG. 2 shows vertical cross-sectional views (2A, 2B, 2C, 2D) illustrating the manufacturing process of the fire spread prevention sheet according to the first embodiment.

[0026] An insulating sheet 3 is placed on an uncured sheet 4 containing a foaming agent (FIG. 2(2A)). This results in a laminate in which the insulating sheet 3 is laminated on the uncured sheet 4. An uncured sheet 4 containing a foaming agent is then placed on top of this (FIG. 2(2B)). The uncured sheet 4 is larger than the insulating sheet 3 and is large enough to completely cover the insulating sheet 3. This process results in a laminate in which the insulating sheet 3 is sandwiched between two uncured sheets 4. Next, the resulting laminate is heated to a temperature equal to or higher than the curing temperature of the thermosetting elastomer contained in the sheet 4 (FIG. 2(2C)). The heating temperature is preferably 190 to 230°C, more preferably 200 to 230°C. This heating causes the uncured sheet 4 to foam and cure. This process also promotes the adhesion and integration of the two elastic foam sheets 2 and the insulating sheet 3, and the sealing of the outer peripheries of the two elastic foam sheets 2. This results in a fire prevention sheet 1 having two elastic foam sheets 2 and a heat insulating sheet 3 laminated together, with the heat insulating sheet 3 sandwiched between the two elastic foam sheets 2 (FIG. 2(2D)).

[0027] In the manufacturing process for the fire spread prevention sheet 1 described above, two uncured sheets 4 sandwiching the heat insulating sheet 3 are laminated together so that they are in contact with each other at their outer peripheries. This results in a fire spread prevention sheet 1 in which the heat insulating sheet 3 is wrapped in a bag of elastic foam sheet 2. When the fire spread prevention sheet 1 is used, filler or fine particles containing filler may fall out of the heat insulating sheet 3. Even in such cases, the fire spread prevention sheet 1 can retain the filler or fine particles inside because the heat insulating sheet 3 is enclosed inside the elastic foam sheet 2.

[0028] Second Embodiment Next, we will explain the manufacturing method of the fire spread prevention sheet according to the second embodiment. In this manufacturing method, the foaming and curing steps in the manufacturing method according to the first embodiment are divided into a foaming step in which the uncured sheet 4 is heated to foam it, and a curing step in which the sheet is subsequently heated at a higher temperature than in the foaming step to promote curing of the foamed sheet.

[0029] FIG. 3 is a vertical cross-sectional view showing a heat treatment process when manufacturing a fire spread prevention sheet according to the second embodiment.

[0030] In the manufacturing method according to this embodiment, foaming is preferentially carried out at a temperature of, for example, 120 to 160°C. Next, the foamed sheet is preferentially cured at a higher temperature, for example, 190 to 230°C. Here, "preferentially carried out" means that although both foaming and curing may occur, either foaming or curing proceeds more rapidly. To obtain a fire-preventing sheet 1 containing an elastic foam sheet 2 in a sufficiently foamed state, the foaming step and the curing step are carried out at different heating temperatures, which prevents the progress of foaming from being hindered by the curing of the elastomer.

[0031] 3. Battery FIG. 4 shows a longitudinal cross-sectional view of a battery according to one embodiment and an enlarged view of one fire spread prevention sheet sandwiched between battery cells in the longitudinal cross-sectional view.

[0032] The battery 10 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") 20 arranged side by side. In this embodiment, the number of battery cells 20 is eight, but may be two to seven, or nine or more. The battery 10 is a storage battery, preferably a lithium-ion battery. The battery 10 includes a housing 11 with a bottom that is open on one side. The battery cells 20 are disposed inside 12 of the housing 11. The plurality of battery cells 20 are preferably pressed against each other by applying compressive force from both sides of the housing 11 using screws or the like (not shown). The bottom of the housing 11 is provided with a through-hole 13 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 20 are disposed inside the housing 11 with a fire-prevention sheet 1 sandwiched between adjacent battery cells 20.

[0033] As described above, the battery 10 according to the present invention includes a plurality of battery cells 20 in a housing 11, and includes the fire prevention sheet 1 at least between the battery cells 20, either between the battery cells 20 or between the battery cells 20 and the housing 11. The fire prevention sheet 1 does not have to be disposed between the battery cells 20 and the housing 11.

[0034] The fire spread prevention sheet 1, which is disposed between the battery cells 20, is a sheet formed by laminating an elastic foam sheet 2 and a heat insulating sheet 3 in its thickness direction. When the battery cells 20 are set in the casing 11, the fire spread prevention sheet 1 is sandwiched and compressed between the battery cells 20, and the repulsive force of the fire spread prevention sheet 1 holds the battery cells 20 in the battery casing 11. Because the fire spread prevention sheet 1 includes the elastic foam sheet 2, it elastically deforms in its thickness direction and easily recovers to its original thickness even if it is subsequently released from compression multiple times. Furthermore, the fire spread prevention sheet 1 is compressed in its thickness direction when it is stored in the casing 11 in a compressed state between the battery cells 20, and is further compressed when the battery cells 20 heat and expand during subsequent charging and / or discharging of the battery 10. Because the elastic foam sheet 2 is a porous sheet, it reduces its thickness significantly when it is sandwiched and compressed between the battery cells 20.

[0035] The heat insulating sheet 3 is less likely to deform than the elastic foam sheet 2 and exhibits almost no cushioning properties. However, the heat insulating sheet 3 contains a non-flammable metal oxide. Therefore, even if a battery cell 20 overheats or even ignites, the fire spread prevention sheet 1 can prevent the fire from spreading to other battery cells 20 due to the presence of the heat insulating sheet 3.

[0036] 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.

[0037] For example, the fire spread prevention sheet 1 may be produced by sandwiching the heat insulating sheet 3 between two elastic foam sheets 2 and sealing the outer peripheries of the two elastic foam sheets by adhesive or other means. Adhesion can also be performed between the heat insulating sheet 3 and the elastic foam sheet 2.

[0038] The features of the claims may be combined in any combination except where they are incombinable with one another. [Industrial Applicability]

[0039] The present invention can be used in the field of preventing the spread of fire caused by an overheated state of a heat source. [Explanation of symbols]

[0040] 1 Fire prevention sheet, 2 Elastic foam sheet, 3 Heat insulating sheet, 4 Uncured sheet, 10 Battery, 11 Housing, 20 Battery cell (an example of a heat source).

Claims

1. A fire prevention sheet that is disposed at least between a plurality of heat sources and that can prevent the spread of fire by suppressing heat transfer to other heat sources when the heat sources are in an overheated state, Two elastic foam sheets; a heat insulating sheet containing a metal oxide; and A fire prevention sheet characterized in that the heat insulating sheet is sandwiched between two of the elastic foam sheets and the outer periphery of the elastic foam sheets is sealed.

2. 2. The fire spread prevention sheet according to claim 1, wherein the elastic foam sheets are all made of foamed silicone rubber.

3. 2. The fire prevention sheet according to claim 1, wherein the heat insulating sheet contains at least one of silica, diatomaceous earth, and talc as the metal oxide or material containing the metal oxide.

4. 4. The fire prevention sheet according to claim 3, wherein the heat insulating sheet contains at least one of silica, aerogel, diatomaceous earth, and talc in an amount of 50% by mass or more relative to the total mass of the heat insulating sheet.

5. A method for producing the fire spread prevention sheet according to any one of claims 1 to 4, a lamination step of laminating uncured sheets containing a foaming agent to both sides of the heat insulating sheet to produce a laminate; a foaming and curing step of heating the laminate to foam and harden the unhardened sheet.

6. The method for manufacturing a fire spread prevention sheet according to claim 5, characterized in that the foaming and curing step includes a foaming step in which the uncured sheet is heated to foam it, and a subsequent curing step in which the sheet is heated at a higher temperature than in the foaming step to promote hardening of the foamed sheet.

7. The method for manufacturing a fire spread prevention sheet according to claim 5, wherein the heat insulating sheet contains at least one of silica, diatomaceous earth and talc in an amount of 50 mass% or more based on the total mass of the heat insulating sheet.

8. A battery having a plurality of battery cells in a housing, A battery comprising the fire spread 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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