Flameproof sheet and method for manufacturing the same, and battery pack

Abstract

To provide a flameproof sheet where a heat insulation material and an elastic body are combined with each other, which has no problem of falling of powder from the heat insulation material, prevents breakage of the elastic body, prevents hole opening, and can thin the elastic body.SOLUTION: A flameproof sheet 1 has a heat insulation sheet 50, and an elastic coating 60 composed of a foam of a thermosetting resin, wherein the elastic coating 60 coats the whole heat insulation sheet 50 without having a joint part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fireproof sheet, a manufacturing method thereof, and a battery pack including the fireproof sheet. [Background technology]

[0002] In recent years, from the viewpoint of environmental protection, active development of electric vehicles, hybrid vehicles, etc. that are driven by electric motors is underway. These electric vehicles, hybrid vehicles, etc. are equipped with assembled batteries in which multiple battery cells are connected in series or parallel to serve as the power source for the driving electric motor.

[0003] The battery cells mainly used are lithium-ion secondary batteries, which have higher capacity and higher output than lead-acid batteries, nickel-metal hydride batteries, etc. If a certain battery cell experiences thermal runaway, where the temperature rises suddenly and continues to generate heat due to an internal short circuit or overcharging of the battery, the heat from the battery cell experiencing thermal runaway may propagate to other adjacent battery cells, causing thermal runaway in the other battery cells.

[0004] A common method for suppressing the transmission of heat from a battery cell that has experienced the above-mentioned thermal runaway is to place a fireproof sheet (also called a "heat transfer suppression sheet") between the battery cells.

[0005] In addition, even during normal use other than when thermal runaway occurs, battery cells repeatedly expand and contract during charging and discharging, and therefore may be used in combination with an elastic body to accommodate this expansion and contraction. The elastic body also has the effect of increasing adhesion to the battery cell. For example, Patent Document 1 describes an insulator 13 that includes a foam sheet 11 made of a thermoplastic resin, an insulating sheet 12 provided inside the foam sheet 11, and a heat-sealed portion 15, as shown in FIG. 5. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Patent Publication No. 2021 / 079601 Summary of the Invention [Problem to be solved by the invention]

[0007] The heat insulator 13 in Patent Document 1 is bag-shaped with cuts 14 formed along the edge of the foam sheet 11, and the heat insulating sheet 12 is inserted and housed inside the bag, and the opening made by the cuts 14 is sealed by forming a heat fused part 15. Since the heat insulating sheet 12 is a fiber sheet impregnated with silica gel, the heat fused part 15 is formed and sealed to prevent the silica gel from falling off (powdering). However, since the heat fused part 15 is formed by heating the overlapping part of the two upper and lower foam sheets 11 in the figure while applying pressure, stress remains in the heat fused part 15 and there is a risk of it peeling off when subjected to an external force.

[0008] In addition, since the heat insulating sheet 12 is inserted through the slits 14 in the foam sheet 11, tension is easily applied to the sliding contact portion between the foam sheet 11 and the edge portion of the heat insulating sheet 12, which may cause damage. When the heat insulating sheet 12 is inserted, the foam sheet is partially stretched, and tensile stress remains in the stretched portion. Thus, the foam sheet 11 may be torn or have holes due to the manufacturing process.

[0009] In a battery pack, it is desirable to make the volume of the components other than the battery cells as small as possible, and in a heat insulating material having an elastic portion, the entire battery pack can be made small by reducing the thickness of the elastic portion and increasing the elastic modulus. However, as the thickness of the elastic portion is reduced, the risk of tearing or holes increases.

[0010] As described above, in the heat insulator 13 of Patent Document 1, there is a risk of breakage or holes being formed in the foam sheet 11, and the thinner the foam sheet 11, the more likely it is to break or have holes. In addition, since tensile stress is also generated from both sides in the heat fusion portion 15, it is necessary to ensure a sufficient width, which is not sufficient to accommodate compactification of the heat insulator 13. Furthermore, since the heat insulator sheet 12 is inserted by making cuts in the foam sheet 11, if there are bubbles that reach a depth of 1 / 2 or more of the thickness from the surface layer of the foam sheet 11 before the cuts, only a very thin portion of the surface remains after the cuts, making the foam sheet 11 more likely to break or have holes.

[0011] Therefore, the present invention aims to provide a fireproof sheet which is made by combining a heat insulating material and an elastomer, which is free from the problem of powder falling off the heat insulating material, in which the elastomer is not easily torn or torn, and which is also not easily punctured, and in which the elastomer can be made thin. [Means for solving the problem]

[0012] The above object of the present invention is achieved by the following configuration [1] relating to a flame retardant sheet.

[0013] [1] A thermal insulation sheet and an elastic covering made of a thermosetting resin foam, A fireproof sheet, characterized in that the elastic covering covers the entire heat insulating sheet without any joints.

[0014] Further, preferred embodiments of the present invention relating to the flame retardant sheet relate to the following [2] to [8].

[0015] [2] The flame-retardant sheet according to [1], characterized in that the average thickness of the elastic coating covering the main surface of the heat-insulating sheet is 0.01 to 10 mm. [3] A flame-retardant sheet according to [1] or [2], characterized in that the average width of the frame region of the elastic coating located outside the end face of the insulating sheet is 0.1 to 2 mm. [4] The flame-retardant sheet according to any one of [1] to [3], wherein the elastic coating contains a silicone resin. [5] The flame-retardant sheet according to any one of [1] to [4], wherein the elastic coating contains a flame retardant. [6] The flame-retardant sheet according to any one of [1] to [5], wherein the heat insulating sheet contains ceramic particles. [7] The flame-retardant sheet according to [6], characterized in that the ceramic particles include one or more particles selected from metal oxide particles, inorganic hydrates, thermally expandable inorganic materials and hydrous porous bodies. [8] The flame-retardant sheet according to any one of [1] to [7], wherein the elastic coating has a compression rate of 40 to 99% when compressed at 2 MPa.

[0016] The above object of the present invention is achieved by the following configuration [9] relating to a method for producing a flame-retardant sheet.

[0017] [9] A method for producing a fireproof sheet according to any one of [1] to [8], A coating step of covering the heat insulating sheet with an elastic coating raw material containing a thermosetting resin precursor and a foaming agent; a foaming step of foaming the elastic covering raw material in a state where the thermal insulation sheet is covered with the elastic covering raw material; a hardening step of foaming and then hardening the elastic coating raw material; A method for producing a fireproof sheet, comprising the steps of:

[0018] Further, preferred embodiments of the present invention relating to a method for producing a fireproof sheet relate to the following

[10] to

[15] .

[0019]

[10] A first coating step of covering one side of the heat insulating sheet with the elastic coating material; a first foaming step of foaming the elastic covering raw material in a state where the thermal insulation sheet is covered with the elastic covering raw material; a first curing step of foaming and then curing the elastic covering raw material; A first step having A second coating step of covering the other side of the heat insulating sheet, one side of which is coated with an elastic coating, obtained in the first step with the elastic coating raw material; A second foaming step of foaming the elastic covering raw material while the thermal insulation sheet is covered with the elastic covering raw material; a second curing step of foaming and then curing the elastic coating raw material; and a second step having The method for producing a flame-retardant sheet according to [9], characterized in that it has

[11] In the first step, the first covering step is carried out by injecting the elastic covering raw material into a first molding frame with the heat insulating sheet accommodated inside the first molding frame, and then the first foaming step and the first curing step are carried out inside the first molding frame, The method for manufacturing a fire-retardant sheet described in

[10] is characterized in that in the second step, the second covering step is carried out by injecting the elastic covering raw material into a second molding frame while the insulation sheet after the first step is placed inside the second molding frame with the front and back sides inverted, and then the second foaming step and the second curing step are carried out inside the second molding frame.

[12] The method for producing a flame-retardant sheet according to any one of [9] to

[11] , wherein the thermosetting resin precursor contains a silicone-based raw material.

[13] The method for producing a flame-retardant sheet according to any one of [9] to

[12] , wherein the elastic coating raw material contains a flame retardant.

[14] The method for producing a flame-retardant sheet according to any one of [9] to

[13] , wherein the heat insulating sheet contains ceramic particles.

[15] The method for producing a flame-retardant sheet described in

[14] , characterized in that the ceramic particles include one or more selected from metal oxide particles, inorganic hydrates, thermally expandable inorganic materials and hydrous porous bodies.

[0020] The above object of the present invention is achieved by the following configuration

[16] relating to a battery pack.

[0021]

[16] An assembled battery, characterized in that a fireproof sheet according to any one of [1] to [8] is inserted between battery cells, and the battery cells are connected in series or in parallel. Effect of the Invention

[0022] The flame-retardant sheet of the present invention is a heat insulating sheet entirely covered with an elastic coating, and there is no problem with powder falling off the flame-retardant sheet. Moreover, when covering with the heat insulating sheet, the elastic coating raw material is foamed and hardened after covering with the heat insulating sheet, so there is no joint such as a heat-sealed part in the elastic coating, and the material is directly bonded without an adhesive layer, etc. Therefore, the joint does not peel off due to external forces such as heat and vibration, as occurs when heat is fused or an adhesive is used.

[0023] In addition, no parts for forming joints are required, and the fireproof sheet can be made more compact. Furthermore, the elastic covering has no sliding contact with the heat insulating sheet, so there is no risk of it tearing or having holes, and the elastic covering is made of a thermosetting resin foam, so it does not creep even when heated, and can be made thinner. This, together with the lack of joints, contributes to making the fireproof sheet more compact.

[0024] The battery pack of the present invention has the insulating sheet of the present invention disposed between the battery cells, so that even if thermal runaway occurs, the battery pack can more reliably prevent the spread of fire to the outside, and can smoothly follow the expansion and contraction of the battery cells during normal charging and discharging. In addition, the elastic covering does not tear or develop holes, and can be made thin, which, combined with the absence of joints, allows the battery pack to be made more compact. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the flame-retardant sheet of the present invention. [Diagram 2] FIG. 2 is a process diagram showing an example of a method for producing a fireproof sheet of the present invention, illustrating the first step. [Diagram 3] FIG. 3 is a process diagram showing an example of the method for producing a fireproof sheet of the present invention, illustrating the second step which is carried out following the first step. [Figure 4] FIG. 4 is a cross-sectional view showing an embodiment of a battery pack according to the present invention. [Diagram 5] FIG. 5 is a cross-sectional view showing the heat insulator of Patent Document 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and can be modified and implemented as desired without departing from the gist of the present invention.

[0027] [Flame-retardant sheet] As shown in the cross-sectional view of FIG. 1, the fireproof sheet 1 of this embodiment is formed by covering a heat insulating sheet 50 entirely with an elastic covering 60 .

[0028] <Elastic coating 60> Since the elastic covering 60 is made of a thermosetting resin foam, countless closed cells 65 made of air and foaming gas are dispersed throughout the elastic covering 60. Since the cells in the foam are closed and the gas is not released to the outside, even if the gas is compressed when an external force is applied, the gas tends to return to its original shape due to the repulsive force of the gas, and the elastic action is maintained. On the other hand, in the case of an open-cell structure, the gas is released when an external force is applied, so the only stress is the force of the resin trying to return to its original shape, and the elastic action is also weak.

[0029] In addition, the foam does not need to have any pores penetrating the elastic coating to prevent powder from falling off, and it is not necessary for all of the bubbles to be closed cells. There is nothing to prevent some of the bubbles present in the thermosetting resin from being multiple and interconnected.

[0030] In addition, since the thermosetting resin is crosslinked, it is less likely to be deformed by heat even when heated, and is less likely to develop holes or breakage due to thermal fatigue.

[0031] Furthermore, the elastic covering 60 does not have a heat-sealed portion (reference numeral 15 in FIG. 5) as in Patent Document 1, or a "joint" such as that bonded using an adhesive. Therefore, there is no problem of peeling originating from the joint. Furthermore, there is no need for a portion for forming a joint, making the fireproof sheet 1 compact, which in turn contributes to making the battery pack more compact. Note that the heat-sealed portion as in Patent Document 1 destroys bubbles that have been formed and forms a layer (joint) whose mechanical properties are different from those of the surrounding area, which is likely to become a starting point for stress generation.

[0032] 1, the average width (D1) of the frame region located outside the end face 50a of the heat insulating sheet 50, which corresponds to the conventional joint, can be made thin, and specifically, is preferably made 2 mm or less. If the average width (D1) of the frame region located outside the end face of the heat insulating sheet is 2 mm or less, the area between the battery cells without the heat insulating sheet can be reduced, making it possible to prevent flames from spreading to adjacent battery cells in the event of thermal runaway. The average width (D1) is preferably 0.01 mm or more. If the average width (D1) of the frame region located outside the end face 50a of the heat insulating sheet 50 is 0.01 mm or more, a sufficient thickness can be ensured for the closed bubbles 65, so that the heat insulating sheet 50 is completely covered and particle generation from the heat insulating sheet 50 can be prevented.

[0033] Since the elastic covering 60 is shaped to fit the outer surface of the insulating sheet 50, there is no deformation or tension that occurs when the insulating sheet 50 is inserted as in Patent Document 1, and there is no risk of tearing, particularly at the edges, due to sliding contact with the insulating sheet 50. Furthermore, by reducing the average film thickness (D2) of the part in contact with the main surface 50b of the insulating sheet 50 and the average width (D1) of the frame region located outside the end surface 50a of the insulating sheet 50, the flame retardant sheet 1 and the battery pack can be made more compact, and the capacity per volume of the entire battery pack can be increased.

[0034] It is also preferable that the elastic covering 60 and the heat insulating sheet 50 are integrally joined. If they are integrally joined, even if a dimensional difference occurs between the heat insulating sheet 50 and the elastic covering 60 due to a thermal expansion difference or expansion / contraction, no local tension is generated in the elastic covering 60 around the edge portion of the heat insulating sheet 50.

[0035] The average thickness (D2) of the portion of the heat insulating sheet 50 in contact with the main surface 50b is preferably 0.01 mm or more. If the average thickness (D2) is 0.01 mm or more, powder falling off can be prevented. It is more preferable that the average thickness (D2) of the portion of the heat insulating sheet 50 in contact with the main surface 50b is 0.5 mm or more. If the average thickness (D2) is 0.5 mm or more, appropriate elasticity can be imparted, and further, since the size can be made sufficiently larger than the size of the closed bubbles 65, powder falling off can be prevented.

[0036] Moreover, the average thickness (D2) of the portion in contact with the main surface 50b of the heat insulating sheet 50 is preferably 10 mm or less. When the average thickness (D2) is 10 mm or less, the battery pack can be made more compact, and the capacity per volume of the entire battery pack can be increased. The average film thickness (D2) covering the main surface 50b of the heat insulating sheet 50 is the distance between the main surface 50b of the heat insulating sheet 50 and the surface of the elastic coating 60 measured in an uncompressed state.

[0037] There are no limitations on the thermosetting resin that is the base material of the elastic covering 60, and any known thermosetting resin can be used, such as phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, silicone resin, urethane resin, and thermosetting polyimide resin, but silicone resin is preferred. Silicone resin is ceramicized at high temperatures and will not disappear, protecting the fireproof sheet 1 in the event of thermal runaway in the battery cell.

[0038] A foaming agent is used to foam the thermosetting resin, but there is no limitation on the foaming agent, and for example, known foaming agents such as hydrocarbons, halogenated hydrocarbons such as halogenated saturated hydrocarbons and halogenated unsaturated hydrocarbons, low boiling point gases such as nitrogen, argon, carbon dioxide gas, and air, chemical foaming agents such as sodium bicarbonate, sodium carbonate, calcium carbonate, magnesium carbonate, azodicarboxylic acid amide, azobisisobutyronitrile, barium azodicarboxylate, N,N'-dinitrosopentamethylenetetramine, p,p'-oxybisbenzenesulfonylhydrazide, and trihydrazinotriazine, and porous solid materials can be used. There is no limitation on the amount of the foaming agent, but it is appropriate that the amount is 1 to 5 mass% in total, including the thermosetting resin.

[0039] The elastic covering 60 preferably contains a flame retardant to enhance its own fire resistance. There are no limitations on the flame retardant, and known flame retardants can be used, such as red phosphorus, guanidine phosphate compounds, polyphosphate compounds such as ammonium polyphosphate, boron compounds such as organic boron compounds, boric acid, boron oxide, boric acid esters, and metaboric acid, aluminum oxide, aluminum hydroxide, boehmite, dolomide, hydrotalcite, calcium hydroxide, basic magnesium carbonate, zirconium hydroxide, and tin oxide, metal compounds, and halogen compounds. Standards such as UL94V-0 can be satisfied by appropriately adjusting the amount of the flame retardant. The elastomeric coating 60 may further include additives such as plasticizers, surface treatments, fillers, heat resistance agents, adhesion promoters, and the like. Examples of the filler that can be used include silica particles such as dry silica, wet silica, and crystalline silica, calcium carbonate, talc, diatomaceous earth, etc. These fillers can increase the strength and hardness of the elastic coating. When using these fillers, a plasticizer such as polyorganosiloxane or an organosiloxane oligomer may be used, and a surface treatment agent for enhancing the adhesive strength of the filler surface may be a silicon-based surface treatment agent such as silane, silazane or a silane coupling agent.

[0040] Furthermore, for example, iron oxide, cerium oxide, titanium oxide, and rare earth compounds may be used to increase the heat resistance of the elastic coating 60, and flame retardants such as titanium oxide, carbon black, and aluminum hydroxide may be used to impart flame retardancy. Furthermore, organometallic compounds and the like may be used as adhesion promoters.

[0041] In terms of the physical properties of the elastic covering 60, in order to ensure and maintain sufficient elastic properties, it is preferable that the compression rate when compressed at 2 MPa is 40% or more. The compression ratio when compressed at 2 MPa is obtained by taking the initial thickness of the flame-retardant sheet 1 (at 0 MPa) as 100% and measuring the thickness when a pressure of 2 MPa is applied. If the compression rate when compressed at 2 MPa is 40% or more, sufficient compressibility can be ensured for the entire fireproof sheet 1 even when a heat insulating sheet with poor compressibility is used, allowing for greater design freedom. An upper limit of the compression rate is appropriately set to 99%. If the upper limit of the compression rate is 99%, sufficient repulsive force can be ensured when multiple battery cells are arranged to form a stack, allowing the battery cells to be securely fixed. It is more preferable that the upper limit of the compression rate is 80%. If the upper limit of the compression rate is 80%, the ratio of closed cells can be increased, ensuring sufficient strength for the cell walls.

[0042] <Thermal insulation sheet 50> Although there is no limitation on the heat insulating sheet 50, it is preferable that the sheet contains ceramic particles because of its high heat insulating performance. As the ceramic particles, metal oxide particles such as silica, titania, alumina, magnesia, etc., inorganic hydrates such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, manganese hydroxide, etc., thermally expandable inorganic materials such as vermiculite, bentonite, mica, perlite, etc., and hydrous porous bodies such as zeolite, kaolinite, montmorillonite, acid clay, and diatomaceous earth can be used. In addition, the form of the ceramic particles can include, in addition to ordinary powders having an average particle size of about 1 to 100 μm, spherical or nearly spherical nanoparticles having an average particle size of 1 μm or less, hollow particles such as shirasu balloons, silica balloons, fly ash balloons, perlite balloons, and glass balloons, and each of them can be used alone or in a mixture. As the nanoparticles, silica nanoparticles such as wet silica, dry silica, and aerogel can be used.

[0043] Below are preferred examples of formulations containing ceramic particles.

[0044] (fibrous materials) The heat insulating sheet 50 contains ceramic particles and a fibrous material for holding the ceramic particles. The fibrous material is not particularly limited as long as it can hold the ceramic particles with high thermal insulation properties, and organic fibers, inorganic fibers, etc. can be used. By including the fibrous material, the mechanical strength of the heat insulating sheet 50 and the ability to hold the ceramic particles can be improved. Specific examples of inorganic fibers that can be used include ceramic fibers such as silica fibers, alumina fibers, alumina silicate fibers, zirconia fibers, carbon fibers, soluble fibers, refractory ceramic fibers, aerogel composite materials, magnesium silicate fibers, alkaline earth silicate fibers, potassium titanate fibers, silicon carbide fibers, and potassium titanate whisker fibers; glass fibers such as glass fibers, glass wool, and slag wool; rock wool, basalt fibers, and mullite fibers; and mineral fibers other than those mentioned above, such as natural mineral fibers such as wollastonite.

[0045] Moreover, fibers having a melting point exceeding 1000° C. can be preferably used because they do not melt or soften and can maintain their shape even if thermal runaway occurs in the battery cell. Of the above fibers, it is more preferable to use ceramic fibers such as silica fibers, alumina fibers, and alumina silicate fibers, as well as natural mineral fibers, and among these, it is even more preferable to use fibers having a melting point exceeding 1000° C. As the organic fiber, for example, at least one selected from polyvinyl alcohol (PVA) fiber, polyethylene fiber, nylon fiber, polyurethane fiber, and ethylene-vinyl alcohol copolymer fiber can be used. When organic fiber is used, it is difficult to break even when bent, so that it is possible to obtain a heat insulating sheet that is resistant to deformation and does not easily fall off.

[0046] (Other compounding materials) In addition to the above-mentioned fibrous material and ceramic particles, additives may be contained in the heat insulating sheet 50. The additives may include a resin binder, a pH adjuster, and a flocculant.

[0047] Resin binder The fibrous material can also be bound by a resin binder. There is no particular limitation on the resin binder as long as it has a glass transition point lower than that of the fibrous material described below. For example, a resin binder 9 containing at least one selected from styrene-butadiene resin, acrylic resin, silicon-acrylic resin, and styrene resin can be used.

[0048] The glass transition point of the resin binder is not particularly specified, but is preferably -10°C or higher. If the glass transition point of the resin binder 9 is room temperature or higher, the strength of the heat insulating sheet 50 can be further improved when a heat insulating material having the resin binder is used at room temperature. Therefore, the glass transition point of the resin binder is more preferably 20°C or higher, even more preferably 30°C or higher, even more preferably 50°C or higher, and particularly preferably 60°C or higher.

[0049] The content of the resin binder is preferably 0.5% by mass or more, and more preferably 1% by mass or more, relative to the total mass of the heat insulating sheet 50. Also, the content is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0050] (Method of manufacturing the heat insulating sheet 50) The heat insulating sheet 50 can be manufactured by a papermaking method, in which the materials forming the heat insulating sheet 50, such as ceramic particles, fibrous materials, and other compounding materials, are dispersed in water, and the dispersion is dehydrated, molded, and dried to produce the sheet.

[0051] Alternatively, the heat insulating sheet 50 may be produced by a dry method, in which the ceramic particles, fibrous material, and other ingredients that form the heat insulating sheet 50 are put into a suitable mixer, thoroughly dispersed, and preformed.

[0052] [Method of manufacturing fireproof sheet 1] To manufacture the flame-retardant sheet 1, a coating process is carried out in which the heat insulating sheet 50 is coated with an elastic coating raw material containing a thermosetting resin precursor, a foaming agent, and, if necessary, a flame retardant; a foaming process is carried out in which the elastic coating raw material is foamed while the heat insulating sheet 50 is coated with the elastic coating raw material; and a curing process is carried out in which the elastic coating raw material is foamed and then cured. Since the elastic covering raw material is foamed and cured in the presence of the heat insulating sheet, the elastic covering 60 and the heat insulating sheet can be integrally bonded.

[0053] It is preferable that the viscosity of the thermosetting resin precursor in the elastic coating raw material is high, and a low viscosity leads to coarsening of the closed cells 65. For example, in the case of a silicone resin, it is preferable to adjust the temperature and the component ratio of the elastic coating raw material so that the viscosity is 10 to 1000 Pa s.

[0054] The insulation sheet 50 can be covered with the elastic coating material by a dipping method, an insert molding method, etc. The dipping method is effective when a relatively thin elastic coating is formed on the surface of the insulation sheet, while the insert molding method is effective when a relatively thick elastic coating is formed. The dipping method can be performed by immersing the insulation sheet 50 in a storage container of the liquid elastic coating material and then pulling it out. After pulling it out, the elastic coating material is foamed and hardened by heating it to the foaming temperature of the foaming agent. This results in a fireproof sheet 1 in which the entire insulation sheet 50 is covered with a continuous elastic coating 60 without any joints such as heat-sealed parts.

[0055] The above series of steps can also be carried out by an "insert molding method." For example, it can be carried out in a two-step method as shown in Figures 2 and 3. Figure 2 is a process diagram showing the first step, and Figure 3 is a process diagram showing the second step.

[0056] (1st step) In the first step, as shown in FIG. 2(A), a frame 75A is attached on a release paper 70A, and the heat insulating sheet 50 is placed on the release paper 70A. The height of the frame 75A is made higher than the thickness of the heat insulating sheet 50. Next, as shown in FIG. 2(B), the elastic coating raw material 80 is injected into the gap between the heat insulating sheet 50 and the frame 75A. Then, as shown in FIG. 2(C), the frame 75A and the elastic coating raw material 80 are covered with the release paper 70B to seal, and are foamed and cured. After curing, the release papers 70A and 70B are peeled off, and the material is subjected to the second step described later. At this time, in order to make the thickness of the elastic coating 60A and the width of the frame region constant, a positioning pin may be used, or the base may have a positioning recess. For example, the positioning pin may be provided so as to penetrate the release paper 70A and pierce the heat insulating sheet 50, or may be provided at the end face position of the heat insulating sheet 50 for positioning. Furthermore, if the base has a recess, the heat insulating sheet 50 can be placed in the recess and the heat insulating sheet 50 can be surrounded by release paper 70A, allowing the heat insulating sheet 50 to be positioned accurately at the desired position.

[0057] (2nd process) In the second step, first, as shown in FIG. 3(D), the one-sided covering body 55 obtained in the first step, one of the main surfaces and the end surface of which is covered with the elastic covering 60A, is turned over and placed on the release paper 70C of the frame body 75B. The height of the frame body 75B is made higher than the thickness of the one-sided covering body 55. Next, as shown in FIG. 3(E), the elastic covering raw material 80 is injected into the gap between the one-sided covering body 55 and the frame body 75B. Then, as shown in FIG. 3(F), the frame body 75B and the elastic covering raw material 80 are covered with the release paper 70D to seal, and are foamed and cured. After curing, the release papers 70C and 70D are peeled off to obtain the fireproof sheet 1 as shown in FIG. 1. In this way, since the elastic covering is formed in the second step following the first step, the entire heat insulating sheet 50 can be covered without having any joints. In addition, since the elastic covering 60 is formed by foaming around the heat insulating sheet 50, tension is less likely to remain at the edge portions of the heat insulating sheet 50, making it less likely for tears or holes to occur. Furthermore, since the elastic coating raw material is foamed and then cured, the crosslinking makes it difficult for the elastic coating raw material to be creep-deformed, and difficult for the elastic coating raw material to be broken or have holes formed due to thermal fatigue.

[0058] [Battery module (assembled battery)] 4, the battery pack 100 has multiple battery cells 110 housed in a battery case 120. In this embodiment, the fireproof sheet 1 is disposed between the battery cells 110. The battery cells 110 are connected in series or parallel by bus bars (not shown). [Explanation of symbols]

[0059] 1. Flame retardant sheet (heat transfer suppression sheet) 50 Insulation Sheet 50a end face 50b Main surface 55 Single-sided coating 60, 60A Elastic coating 65 Closed bubble 70A, 70B, 70C, 70D Release paper 75A, 75B frame 80 Elastic coating materials 100 battery packs 110 Battery Cell 120 Battery case

Claims

1. The insulating sheet and the elastic covering made of a foam of a thermosetting resin are included. A fireproof sheet, characterized in that the elastic covering covers the entire heat insulating sheet without any joints.

2. 2. The flame retardant sheet according to claim 1, wherein the average thickness of the elastic coating covering the main surface of the heat insulating sheet is 0.01 to 10 mm.

3. 2. The fireproof sheet according to claim 1, characterized in that the average width of the frame region of the elastic covering located outside the end face of the heat insulating sheet is 0.01 to 2 mm.

4. 2. The fireproof sheet according to claim 1, wherein the elastic coating comprises a silicone resin.

5. 2. The fireproof sheeting according to claim 1, wherein the elastic coating comprises a fire retardant.

6. The fireproof sheet according to claim 1, characterized in that the heat insulating sheet contains ceramic particles.

7. 7. The flame-retardant sheet according to claim 6, wherein the ceramic particles include one or more particles selected from the group consisting of metal oxide particles, inorganic hydrates, thermally expandable inorganic materials, and water-containing porous bodies.

8. The fireproof sheet according to claim 1, characterized in that the elastic coating has a compression rate of 40 to 99% when compressed at 2 MPa.

9. A method for producing a fireproof sheet according to any one of claims 1 to 8, A coating step of covering the heat insulating sheet with an elastic coating raw material containing a thermosetting resin precursor and a foaming agent; a foaming step of foaming the elastic covering raw material in a state where the thermal insulation sheet is covered with the elastic covering raw material; a hardening step of foaming and then hardening the elastic coating raw material; A method for producing a fireproof sheet, comprising the steps of:

10. A first covering step of covering one side of the heat insulating sheet with the elastic covering material; a first foaming step of foaming the elastic covering raw material in a state where the thermal insulation sheet is covered with the elastic covering raw material; a first curing step of foaming and then curing the elastic coating raw material; A first step having A second coating step of covering the other surface of the heat insulating sheet obtained in the first step, one surface of which is coated with an elastic coating, with the elastic coating raw material; a second foaming step of foaming the elastic covering raw material while the thermal insulation sheet is covered with the elastic covering raw material; a second curing step of foaming and then curing the elastic coating raw material; and a second step having The method for producing a fireproof sheet according to claim 9, further comprising:

11. In the first step, the first covering step is carried out by injecting the elastic covering raw material into a first molding frame with the heat insulating sheet accommodated therein, and then the first foaming step and the first curing step are carried out in the first molding frame. In the second step, the second covering step is performed by injecting the elastic covering raw material into a second molding frame in a state where the heat insulating sheet after the first step is inverted and accommodated inside the second molding frame, and then the second foaming step and the second curing step are performed inside the second molding frame. A method for producing a fireproof sheet according to claim 10.

12. The method for producing a fireproof sheet according to claim 9, characterized in that the thermosetting resin precursor contains a silicone-based raw material.

13. The method for producing a fireproof sheet according to claim 9, characterized in that the elastic coating raw material contains a fire retardant.

14. The method for producing a fireproof sheet according to claim 9, wherein the heat insulating sheet contains ceramic particles.

15. The method for producing a fireproof sheet according to claim 14, characterized in that the ceramic particles contain one or more selected from the group consisting of metal oxide particles, inorganic hydrates, thermally expandable inorganic materials, and water-containing porous bodies.

16. An assembled battery comprising: a fireproof sheet according to any one of claims 1 to 8 interposed between battery cells; and the battery cells are connected in series or in parallel.

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