Flame-retardant sheet, manufacturing method of the same, and assembled battery

Abstract

To provide a flame-retardant sheet which is excellent in handleability and can prevent deterioration of heat insulation quality and falling of powder of a material from a heat insulation sheet, secure sufficient strength of an elastic material, and maintain an effect for easing stress on a member disposed adjacent to the flame-retardant sheet.SOLUTION: A flame-retardant sheet 1 includes: a heat insulation sheet 50 having a first major surface 51 and a second major surface 52 and end surfaces 53; and an elastic material 60 made of a material containing a thermosetting resin and covering the first major surface 51, the second major surface 52, and the end surfaces 53. The elastic material 60 has: a first major surface side elastic part 61 disposed on the first major surface 51 side of the heat insulation sheet 50; a second major surface side elastic part 62 disposed on the second major surface 52 side; and end surface side elastic parts 63 respectively disposed at the terminal surface 53 sides. The end surface side elastic part 63 is formed by the first major surface side elastic part 61 and the second major surface side elastic part 62 extending outward from the end surface 53 of the heat insulation sheet 50 to be integrated.SELECTED DRAWING: Figure 1B

Description

[Technical Field]

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

[0002] In recent years, from the viewpoint of environmental protection, active development has been made of electric vehicles, hybrid vehicles, and the like that are driven by electric motors. These electric vehicles, hybrid vehicles, and the like 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 battery cell experiences thermal runaway, where it suddenly rises in temperature and continues to generate heat due to an internal short circuit or overcharging, the heat from the battery cell experiencing thermal runaway may propagate to other adjacent battery cells, causing thermal runaway in those cells as well.

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

[0005] Furthermore, battery cells repeatedly expand and contract during charging and discharging, even during normal use, not during thermal runaway. Therefore, when multiple battery cells are installed inside a battery case, the battery cells themselves are repeatedly compressed and released, causing a decrease in battery performance. Therefore, in order to accommodate the expansion and contraction of battery cells, development is underway for insulators that combine insulating sheets and elastic bodies. In such insulators, the elastic body also has the effect of increasing adhesion to the battery cells.

[0006] For example, Patent Document 1 describes an insulator comprising a foam sheet made of a thermoplastic resin, a heat insulating sheet provided inside the foam sheet, and a heat-sealing portion. The foam sheet has a cut formed along its upper surface from one end face to the other. The heat insulating sheet is inserted into the cut, and the opening formed by the cut is heat-sealed to seal the heat insulating sheet, thereby preventing the material from detaching from the heat insulating sheet and scattering around. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Patent Publication No. 2021 / 079601 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in Patent Document 1, the heat-sealed portion formed by heat sealing is formed by applying pressure to the overlapping portion of the opening of the foam sheet while heating, so stress remains in the heat-sealed portion and there is a risk of peeling when subjected to external force. In particular, because the foam sheet is made of a thermoplastic resin, the heat-sealed portion is prone to peeling at high temperatures, causing the material of the insulation sheet to separate and reducing its elasticity. Furthermore, if the foam sheet melts due to high temperatures, the molten foam sheet may penetrate into the insulation sheet, reducing its insulation properties.

[0009] Furthermore, not only when the insulator is in use, but also when multiple insulators are transported, they may be placed with their end faces facing up or down, and if there are heat-sealed parts, stress is applied to the end faces, which may cause the heat-sealed parts to peel off. As a result, problems such as the foam sheet becoming detached from the heat-sealing sheet may occur, so care must be taken when handling them even during transportation.

[0010] Furthermore, when manufacturing the heat insulator described in Patent Document 1, the heat insulating sheet is inserted through the slits in the foam sheet, so tension is easily applied to the area where the foam sheet slides against the edge of the heat insulating sheet, which may cause damage.Furthermore, when the heat insulating sheet is inserted into the foam sheet, the foam sheet is partially stretched, and tensile stress remains in the stretched area, which may cause tears or holes in the foam sheet due to the manufacturing process.

[0011] Furthermore, when trying to reduce the thickness of a foam sheet during the manufacture of insulation, the risk of tearing or holes increases even more. For example, if there are bubbles that reach a depth of more than half the thickness from the surface of the foam sheet before the foam sheet is cut, extremely thin sections will be created in the foam sheet after cutting, which can cause breakage.

[0012] The present invention has been made in consideration of these problems, and aims to provide a flame-retardant sheet made by combining a heat insulating sheet and an elastic material, which is easy to handle, can prevent a decrease in heat insulating properties, prevents powder falling off of the material from the heat insulating sheet, ensures sufficient strength of the elastic material, and can maintain the effect of alleviating stress on adjacent components, as well as a method for easily manufacturing the flame-retardant sheet, and a battery pack having the flame-retardant sheet. [Means for solving the problem]

[0013] The above object of the present invention is achieved by the following configuration [1] relating to a flame-retardant sheet.

[0014] [1] A heat insulating sheet having a first main surface and a second main surface perpendicular to the thickness direction, and an end surface connecting the first main surface and the second main surface; A fireproof sheet made of a material containing a thermosetting resin and having an elastic material covering the first main surface, the second main surface, and the end surfaces, the elastic material has a first main surface side elastic portion arranged on the first main surface side of the heat insulating sheet, a second main surface side elastic portion arranged on the second main surface side of the heat insulating sheet, and an end surface side elastic portion arranged on the end surface side of the heat insulating sheet, A flame-retardant sheet characterized in that the end surface side elastic portion is formed by the first main surface side elastic portion and the second main surface side elastic portion each extending outward from the end surface of the insulating sheet and being integrated with each other.

[0015] Further, preferred embodiments of the present invention relating to the flame-retardant sheet relate to the following [2] to

[10] .

[0016] [2] The flame-retardant sheet described in [1], characterized in that the first main surface side elastic portion, the second main surface side elastic portion, and the end surface side elastic portion do not penetrate into the interior of the insulating sheet. [3] The flame-retardant sheet according to [1] or [2], characterized in that the first main surface side elastic portion, the second main surface side elastic portion and the end surface side elastic portion are not bonded to the first main surface, the second main surface and the end surface of the heat insulating sheet, respectively. [4] A flame-retardant sheet according to any one of [1] to [3], characterized in that the average thickness of the first main surface side elastic portion and the second main surface side elastic portion is 0.1 mm or more and 10 mm or less, respectively. [5] A flame-retardant sheet according to any one of [1] to [4], characterized in that the average distance from the end face of the heat insulating sheet to the outer end of the end face side elastic portion is 0.5 mm or more and 5 mm or less. [6] A flame-retardant sheet according to any one of [1] to [5], characterized in that the first main surface side elastic portion, the second main surface side elastic portion, and the end surface side elastic portion are all made of the same material. [7] The flame-retardant sheet according to any one of [1] to [6], characterized in that the elastic material contains at least one selected from silicone resin, phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, urethane resin, and thermosetting polyimide resin. [8] The flame-retardant sheet according to any one of [1] to [7], wherein the elastic material contains a flame retardant. [9] The flame retardant sheet according to any one of [1] to [8], characterized in that the heat insulating sheet contains ceramic particles.

[10] The flame-retardant sheet according to [9], characterized in that the ceramic particles contain at least one type of particles selected from metal oxide particles, inorganic hydrates, thermally expandable inorganic materials, and hydrous porous bodies.

[0017] The above object of the present invention is achieved by the following configuration

[11] relating to a method for producing a flame-retardant sheet.

[0018]

[11] A method for producing a flame-retardant sheet according to any one of [1] to

[10] , a foaming material sheet preparation step of preparing a first foaming material sheet and a second foaming material sheet so that the first foaming material sheet and the second foaming material sheet are larger in size than the first main surface and the second main surface of the heat insulating sheet, respectively; a foaming material sheet arranging step of arranging the first foaming material sheet so as to face the first main surface of the heat insulating sheet and arranging the second foaming material sheet so as to face the second main surface of the heat insulating sheet; a compression joining step of overlapping and compressing a surface of the first foaming material sheet facing the heat insulating sheet and a surface of the second foaming material sheet facing the heat insulating sheet at the end face side of the heat insulating sheet; a foaming and curing step of foaming and curing the first foaming material sheet and the second foaming material sheet to obtain the first main surface side elastic portion and the second main surface side elastic portion, as well as to obtain the integrated end surface side elastic portion.

[0019] Furthermore, preferred embodiments of the present invention relating to a method for producing a flameproof sheet relate to the following

[12] to

[14] .

[0020]

[12] The method for manufacturing a flame-retardant sheet according to

[11] , characterized in that the first foaming raw material sheet and the second foaming raw material sheet both contain a thermosetting resin precursor and a foaming agent or a foaming accelerator.

[13] The method for producing a flame-retardant sheet according to

[11] or

[12] , characterized in that the thermosetting resin precursor contains at least one selected from silicone-based raw materials, phenol-based raw materials, epoxy-based raw materials, melamine-based raw materials, urea-based raw materials, unsaturated polyester-based raw materials, alkyd-based raw materials, urethane-based raw materials, and thermosetting polyimide-based raw materials.

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

[11] to

[13] , wherein the first foaming raw material sheet and the second foaming raw material sheet both contain a flame retardant.

[0021] The above object of the present invention is achieved by the following configuration

[15] relating to a battery pack.

[0022]

[15] A battery pack comprising a plurality of battery cells and the flame-retardant sheet according to any one of [1] to

[10] , the plurality of battery cells being connected in series or in parallel. [Effects of the Invention]

[0023] In the flame-retardant sheet of the present invention, the insulating sheet is covered with an elastic material, which prevents powder from falling off the insulating sheet, and preferably the first main surface side elastic portion, the second main surface side elastic portion, and the end surface side elastic portion do not penetrate into the insulating sheet, which prevents a decrease in insulating properties. Furthermore, the end surface side elastic portion is formed by the first main surface side elastic portion and the second main surface side elastic portion each extending outward from the end surface of the insulating sheet and being integrated with each other, which provides excellent strength against pressure and impact.

[0024] Furthermore, according to the method for manufacturing a flame-retardant sheet of the present invention, the first foaming raw material sheet and the second foaming raw material sheet are compressed and bonded together, and then foaming and curing are carried out. This allows the two to be bonded together with a high bonding strength, and foaming and curing can be carried out simultaneously in a single process, thereby simplifying the manufacturing process.

[0025] Because the battery pack of the present invention contains the flame-retardant sheet of the present invention, it can more reliably prevent the fire from spreading to the outside even in the event of thermal runaway, and it can smoothly follow the expansion and contraction of the battery cells, resulting in excellent battery performance. [Brief explanation of the drawings]

[0026] [Figure 1A] FIG. 1A is a schematic cross-sectional view showing a fireproof sheet according to an embodiment of the present invention. [Figure 1B] FIG. 1B is a schematic diagram showing an enlarged portion of FIG. 1A. [Figure 2A] FIG. 2A is a diagram showing a method for producing a fireproof sheet according to an embodiment of the present invention, and is a cross-sectional view showing a foaming raw material sheet producing step and a foaming raw material sheet arranging step. [Figure 2B] FIG. 2B is a cross-sectional view showing a compression joining step in a method for producing a fireproof sheet according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing a battery pack according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, 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 implemented with any modifications within the scope of the gist of the present invention.

[0028] [Flame-retardant sheet] FIG. 1A is a schematic cross-sectional view showing a flame-retardant sheet according to an embodiment of the present invention. FIG. 1B is a schematic enlarged view of a portion of FIG. 1A. As shown in FIG. 1A, the flame-retardant sheet 1 includes a thermal insulation sheet 50 and an elastic member 60. The thermal insulation sheet 50 has a first main surface 51 and a second main surface 52 that are perpendicular to the thickness direction, and an end surface 53 that connects the first main surface 51 and the second main surface 52. The elastic member 60 is made of a material containing a thermosetting resin and covers the first main surface 51, the second main surface 52, and the end surface 53 of the thermal insulation sheet 50. Specifically, the elastic member 60 includes a first-main-surface-side elastic portion 61 disposed on the first main surface 51 side of the thermal insulation sheet 50, a second-main-surface-side elastic portion 62 disposed on the second main surface 52 side, and an end surface-side elastic portion 63 disposed on the end surface 53 side. The end surface side elastic portion 63 is formed by integrating the first main surface side elastic portion 61 and the second main surface side elastic portion 62, which each extend outward from the end surface 53 of the heat insulating sheet 50. In other words, the end surface side elastic portion 63 has a shape that protrudes outward from the end surface 53 side of the heat insulating sheet 50. The elastic material 60 is made of a foamed thermosetting resin, and has a large number of bubbles 65 formed therein.

[0029] 1B, the first main surface side elastic portions 61 do not penetrate into the interior of the heat insulating sheet 50 from the first main surface 51 side of the heat insulating sheet 50. Similarly, the end surface side elastic portions 63 do not penetrate into the interior of the heat insulating sheet 50 from the end surface 53 side of the heat insulating sheet 50. Furthermore, although not shown in FIG. 1B, the second main surface side elastic portions 62 also do not penetrate into the interior of the heat insulating sheet 50 from the second main surface 52 side of the heat insulating sheet 50.

[0030] Specifically, the surfaces of the first main surface side elastic portion 61 and the second main surface side elastic portion 62 facing the heat insulating sheet 50 do not have shapes that follow the shapes of the first main surface 51 and the second main surface 52 of the heat insulating sheet 50. Furthermore, the first main surface side elastic portion 61 and the second main surface side elastic portion 62 are not bonded to the first main surface 51 and the second main surface 52 of the heat insulating sheet 50, respectively. Therefore, the first main surface side elastic portion 61 and the second main surface side elastic portion 62 are partially in contact with the first main surface 51 and the second main surface 52, respectively, but are configured to be able to separate from them, and a plurality of gaps 71 are formed between them. The end surface side elastic portion 63 may or may not be in partial contact with the end surface 53 of the heat insulating sheet 50, and gaps 73 are formed in the non-contact region. Furthermore, the surface shape of the end face side elastic portion 63 does not follow the shape of the end face 53 of the heat insulating sheet 50, and the end face side elastic portion 63 and the end face 53 are not joined together.

[0031] In the flame-retardant sheet 1 configured in this manner, the first main surface 51, the second main surface 52, and the end surfaces 53 of the heat insulating sheet 50 are covered with the elastic material 60, which prevents the materials that make up the heat insulating sheet 50 from falling off. Furthermore, since the elastic material 60 is made of a material that contains a thermosetting resin, it will not melt even when exposed to high temperatures and can ensure the desired elasticity and strength, thereby maintaining the effect of alleviating stress on adjacent members.

[0032] Furthermore, since the insulating properties of the elastic material 60 are generally inferior to those of the insulating sheet 50, if the material of the elastic material 60 penetrates into the insulating sheet 50, the insulating properties of the flame-retardant sheet 1 will be reduced. In contrast, in the present embodiment, the first main surface side elastic portion 61, the second main surface side elastic portion 62, and the end face side elastic portion 63 do not penetrate into the interior of the insulating sheet 50 from the first main surface 51, the second main surface 52, and the end face 53 sides, and gaps 71 are formed between the first main surface 51 and the second main surface 52 of the insulating sheet 50 and the surfaces of the first main surface side elastic portion 61 and the second main surface side elastic portion 62 facing the insulating sheet 50. In the present embodiment, a gap 73 is also formed between the end face side elastic portion 63 and the end face 53 of the insulating sheet 50. Therefore, compared to a state in which the first main surface side elastic portion 61, the second main surface side elastic portion 62, and the end surface side elastic portion 63 penetrate into the interior of the insulating sheet 50, the insulating properties of the insulating sheet 50 can be maintained, and the void portions 71, 73 can further improve the insulating properties.

[0033] Furthermore, in this embodiment, the end surface side elastic portion 63 is formed by integrating the first main surface side elastic portion 61 and the second main surface side elastic portion 62 outside the end surface 53, and has no joints, so it has excellent strength against pressure and impact. Therefore, for example, when assembling the flame retardant sheet 1 into a battery pack or during transportation, it is possible to prevent the elastic material 60 from coming off the heat insulating sheet 50 due to peeling at the joints, and handleability can be improved.

[0034] The heat insulating sheet 50 and the elastic material 60 that constitute the flame-retardant sheet 1 according to this embodiment will be described in more detail below.

[0035] <Elastic material> The flame-retardant sheet 1 interposed between battery cells (described later) preferably maintains a minimum compressibility required to hold the battery cells while preventing excessive repulsive force against the battery cells when the battery cells expand. In this embodiment, the elastic material 60 is made of a material containing a thermosetting resin, such as a foamed thermosetting resin. Elastic materials made of foamed thermosetting resin have numerous independent bubbles 65 consisting of air or foaming gas dispersed throughout, providing excellent thermal insulation. Furthermore, since thermosetting resins are crosslinked, they are resistant to thermal deformation even when heated, providing excellent strength. Furthermore, the dispersed independent bubbles 65 prevent gas from being released to the outside. Therefore, even if the gas is compressed when an external force is applied, the repulsive force of the gas allows the material to easily return to its original shape, maintaining its elasticity.

[0036] Furthermore, the elastic material 60 has a large number of interconnected cells, which are structures in which air bubbles are connected. If these interconnected cells are connected to the outside of the elastic material, gas will be released when external force is applied. As a result, the only stress is the force that causes the resin to return to its original shape, weakening the elastic force of the elastic material. Therefore, it is preferable to use a thermosetting resin foam with countless independent air bubbles 65 dispersed therein as the elastic material, and it is even more preferable to use a material that contains silicone resin.

[0037] The air bubbles inside the elastic material 60 do not all need to be independent, and some of the air bubbles may be interconnected. However, it is preferable that there are no air bubbles that penetrate through the elastic material 60 in the thickness direction, which makes it possible to suppress powder falling from the first main surface 51, second main surface 52 and end surfaces 53 of the heat insulating sheet 50, for example, and to maintain heat insulating properties.

[0038] The thermosetting resin, which is one of the materials constituting the elastic material 60, is not particularly limited, and may be any known thermosetting resin, such as silicone resin, phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, urethane resin, or thermosetting polyimide resin. Of these thermosetting resins, silicone resin ceramicizes at high temperatures and does not disappear, and has the effect of protecting the heat insulating sheet 50 in the event of thermal runaway in the battery cells. Therefore, it is preferable that the elastic material 60 contain silicone resin as a thermosetting resin.

[0039] In the present invention, the first main surface side elastic portion 61 and the second main surface side elastic portion 62 do not necessarily have to be made of the same material. However, if the material of the raw material sheet is selected so that the first main surface side elastic portion 61, the second main surface side elastic portion 62, and the end surface side elastic portion 63 are all made of the same material. This further improves the strength of the end surface side elastic portion 63.

[0040] Furthermore, the elastic material 60 preferably contains a flame retardant to enhance its own fire resistance. The flame retardant contained in the elastic material 60 is not particularly limited, and examples thereof include known flame retardants 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, metal compounds such as aluminum oxide, aluminum hydroxide, boehmite, dolomide, hydrotalcite, calcium hydroxide, basic magnesium carbonate, zirconium hydroxide, and tin oxide, halogen compounds, platinum compounds, titanium oxide, carbon, metal carbonates, and iron oxide. By appropriately adjusting the amount of flame retardant added, standards such as UL94V-0 can be met.

[0041] The elastic material 60 may further contain additives such as plasticizers, surface treatment agents, fillers, heat resistance agents, and adhesion promoters. Examples of fillers that can be used include silica particles such as dry silica, wet silica, and crystalline silica, calcium carbonate, talc, and diatomaceous earth. 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 silicon-based surface treatment agent such as silane, silazane or a silane coupling agent may be used as a surface treatment agent to strengthen the adhesive strength of the filler surface.

[0042] Furthermore, in order to enhance the heat resistance of the elastic material 60, the elastic material 60 may contain, for example, iron oxide, cerium oxide, titanium oxide, or a rare earth compound, and in order to impart flame retardancy, the elastic material 60 may contain a flame retardant such as titanium oxide, carbon black, or aluminum hydroxide. Furthermore, the elastic material 60 may contain an organometallic compound or the like as an adhesion promoter.

[0043] The average thicknesses of the first and second main surface side elastic portions 61 and 62 are not particularly limited, but are preferably 10 mm or less. Having an average thickness of 10 mm or less allows the battery pack to be more compact, and when the flame-retardant sheet 1 is incorporated into the battery pack, the overall battery pack capacity per volume can be increased. The thicknesses of the first and second main surface side elastic portions 61 and 62 are measured in an uncompressed state by measuring the distance between the first main surface 51 of the insulating sheet 50 and the surface of the first main surface side elastic portion 61, and the distance between the second main surface 52 and the surface of the second main surface side elastic portion 62. These average thicknesses can be calculated by averaging the thicknesses measured at any five locations.

[0044] On the other hand, the average thickness of the first main surface side elastic portion 61 and the second main surface side elastic portion 62 is preferably 0.1 mm or more. If the average thickness of the first main surface side elastic portion 61 and the second main surface side elastic portion 62 is 0.1 mm or more, it is possible to obtain the effect of suppressing the falling off (powder shedding) of particles and the like contained in the heat insulating sheet 50. Furthermore, from the viewpoints of imparting appropriate elasticity and improving the effect of suppressing powder shedding, it is more preferable that the average thickness of the first main surface side elastic portion 61 and the second main surface side elastic portion 62 be 0.5 mm or more.

[0045] As with the first main surface side elastic portion 61 and the second main surface side elastic portion 62, when the average thickness of the end surface side elastic portion 63 is defined as the average distance from the end surface 53 of the heat insulating sheet 50 to the outer end of the end surface side elastic portion 63, the average thickness of the end surface side elastic portion 63 is preferably 5 mm or less. When the average thickness of the end surface side elastic portion 63 is 5 mm or less, it is possible to reduce the area between battery cells where the heat insulating sheet 50 is not present, thereby preventing flames from spreading to adjacent battery cells in the event of thermal runaway.

[0046] In addition, when the average thickness of the first main surface side elastic portion 61 and the second main surface side elastic portion 62 is, for example, 5 mm or more, it is conceivable that the average thickness of the end surface side elastic portion 63 will also exceed 5 mm. Therefore, one method for making the average thickness of the end surface side elastic portion 63 5 mm or less includes, for example, forming a thin region of the foaming raw material sheet that is the material for the elastic material to form the end surface side elastic portion 63.

[0047] On the other hand, the average thickness of the end surface side elastic portion 63 is preferably 0.5 mm or more. When the average thickness of the end surface side elastic portion 63 is 0.5 mm or more, the area where the first main surface side elastic portion 61 and the second main surface side elastic portion 62 are integrated can be made large, and the strength of the end surface side elastic portion can be ensured sufficiently. The thickness of the end surface side elastic portion 63 is measured as the distance from the end surface 53 of the heat insulating sheet 50 to the outer end of the end surface side elastic portion 63 in an uncompressed state. Furthermore, these average thicknesses can be the average value of the thicknesses of the end surface side elastic portion 63 measured at any five points on the end surface of the heat insulating sheet 50.

[0048] <Thermal insulation sheet> In this embodiment, the heat insulating sheet 50 is not particularly limited, but preferably has excellent heat insulating properties. Examples of materials that are preferably contained in the heat insulating sheet 50 are described below.

[0049] (ceramic particles) The heat insulating sheet 50 can achieve excellent heat insulation by including ceramic particles. Examples of ceramic particles include metal oxide particles such as silica, titania, alumina, and magnesia; inorganic hydrates such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, and manganese hydroxide; thermally expandable inorganic materials such as vermiculite, bentonite, mica, and perlite; and hydrous porous materials such as zeolite, kaolinite, montmorillonite, acid clay, and diatomaceous earth. The ceramic particles can take the form of ordinary powders with an average particle size of approximately 1 to 100 μm, as well as spherical or nearly spherical nanoparticles with an average particle size of 1 μm or less, and hollow particles such as shirasu balloons, silica balloons, fly ash balloons, perlite balloons, and glass balloons. These particles can be used alone or in combination. As the nanoparticles, silica nanoparticles such as wet silica, dry silica, and aerogel can be used.

[0050] (fibrous materials) The heat insulating sheet 50 preferably contains 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 a fibrous material, the mechanical strength of the heat insulating sheet 50 and its ability to hold the ceramic particles can be improved.

[0051] 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 composites, 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. Among 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. Furthermore, if the melting point of the fibrous material exceeds 1000°C, it will not melt or soften and will be able to maintain its shape even if thermal runaway occurs in the battery cell. Therefore, it is more preferable that the heat insulating sheet 50 contain a fibrous material with a melting point exceeding 1000°C.

[0052] The organic fiber may be at least one selected from the group consisting of polyvinyl alcohol (PVA) fiber, polyethylene fiber, nylon fiber, polyurethane fiber, and ethylene-vinyl alcohol copolymer fiber. When organic fiber is used, it is difficult to break even when bent, so that a heat insulating sheet that is resistant to deformation and powder shedding can be obtained.

[0053] (Other compounding materials) In addition to the ceramic particles and fibrous material, the heat insulating sheet 50 may contain additives such as a resin binder, a pH adjuster, and a flocculant.

[0054] If the heat insulating sheet 50 contains a resin binder as an additive, the other materials contained in the heat insulating sheet 50 can also be bound by the resin binder. There are no particular restrictions on the resin binder, as long as it has a glass transition point lower than that of the fibrous material. For example, a resin binder containing at least one resin selected from styrene-butadiene resin, acrylic resin, silicone-acrylic resin, and styrene resin can be used.

[0055] 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 is room temperature or higher, the strength of the heat insulating sheet 50 can be further improved when a heat insulating material containing 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.

[0056] When the heat insulating sheet 50 contains a resin binder, 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, it is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0057] (Method of manufacturing heat insulating sheets) Methods for producing the heat insulating sheet 50 include a wet method (papermaking method) and a dry method. When using the papermaking method, the ceramic particles, fibrous material, and other compounding materials that form the heat insulating sheet 50 are dispersed in water, and the dispersion is dehydrated, molded, and dried to produce the heat insulating sheet 50. When using the dry method, the ceramic particles, fibrous material, and other compounding materials that form the heat insulating sheet 50 are placed in an appropriate mixer, thoroughly dispersed, and then pressurized and heated in a predetermined mold to produce the heat insulating sheet 50.

[0058] [Fireproof sheet manufacturing method] FIG. 2A is a diagram showing a method for producing a fire-retardant sheet according to an embodiment of the present invention, and is a cross-sectional view showing a foam raw material sheet preparation step and a foam raw material sheet arrangement step. FIG. 2B is a diagram showing a method for producing a fire-retardant sheet according to an embodiment of the present invention, and is a cross-sectional view showing a compression joining step. The method for producing a fire-retardant sheet 1 according to this embodiment will be described in detail below with reference to FIGS. 1A, 2A, and 2B. The method for producing a fire-retardant sheet described below is one example of a method for producing the fire-retardant sheet 1.

[0059] <Foaming raw material sheet manufacturing process> As shown in FIG. 2A , the first foam raw sheet 91 and the second foam raw sheet 92 are prepared so as to be larger than the first main surface 51 and the second main surface 52 of the heat insulating sheet 50, respectively. The first foam raw sheet 91 and the second foam raw sheet 92 are raw material sheets for preparing the first main surface side elastic portion 61, the second main surface side elastic portion 62, and the end surface side elastic portion 63 of the elastic material 60. Such raw material sheets are called, for example, millable silicone rubber. Specifically, the first foam raw sheet 91 and the second foam raw sheet 92 can be prepared by kneading a thermosetting resin precursor, a foaming agent or foaming accelerator, a crosslinking agent, etc. at a low temperature and molding the mixture into a sheet. At this point, the first foam raw sheet 91 and the second foam raw sheet 92 are in a soft state, with no foaming or crosslinking occurring inside.

[0060] <Foaming material sheet placement process> Next, the first foaming raw material sheet 91 is placed so as to face the first main surface 51 of the heat insulating sheet 50, and the second foaming raw material sheet 92 is placed so as to face the second main surface 52 of the heat insulating sheet 50. At this time, the first foaming raw material sheet 91 and the second foaming raw material sheet 92 are placed so as to protrude from the position of the end surface 53 of the heat insulating sheet 50.

[0061] <Compression joining process> Then, as shown in Figure 2B, on the end face 53 side of the insulating sheet 50, the surface of the first foaming raw material sheet 91 facing the insulating sheet 50 and the surface of the second foaming raw material sheet 92 facing the insulating sheet 50 are overlapped, and pressure is applied in the direction of the arrow to compress and bond the two together.

[0062] <Foaming and curing process> Thereafter, the first foaming raw material sheet 91 and the second foaming raw material sheet 92 are foamed and cured to obtain the first main surface side elastic portion 61 and the second main surface side elastic portion 62, as well as the integrated end surface side elastic portion 63. As a result, as shown in Fig. 1A, the heat insulating sheet 50 is covered with the first main surface side elastic portion 61, the second main surface side elastic portion 62, and the end surface side elastic portion 63, and the fireproof sheet 1 can be manufactured.

[0063] According to the manufacturing method of the present embodiment, the first foaming raw material sheet 91 and the second foaming raw material sheet 92 are compressed and bonded together, and then foaming and curing are performed, so that the two can be bonded together with a high bonding strength. This makes it possible to easily form the end face side elastic portion 63 that has the effect of absorbing shock during transportation of the fireproof sheet 1. Furthermore, since the first foaming raw material sheet 91 and the second foaming raw material sheet 92 are foamed and cured simultaneously, foaming and curing can be performed simultaneously in a single step, thereby simplifying the manufacturing process.

[0064] Furthermore, in this embodiment, after the first foaming raw material sheet 91 and the second foaming raw material sheet 92 are produced, these raw material sheets are foamed and cured in a foaming and curing process. Therefore, unlike a method in which a single elastic material is divided along its main surface, it is possible to prevent stress from being applied to only a portion of the elastic material, and to prevent the first main surface side elastic portion 61 and the second main surface side elastic portion 62 from becoming extremely thin due to the shape of the bubbles. Therefore, it is possible to ensure sufficient strength of the elastic material 60, and to fully maintain the performance required of the elastic material 60, i.e., the effect of alleviating stress on adjacent members.

[0065] Furthermore, by making the first foaming raw material sheet 91 and the second foaming raw material sheet 92 from the same material, the process for making them can be simplified and an end face side elastic portion 63 with excellent strength can be easily obtained.

[0066] Hereinafter, raw materials used in the method for producing a fireproof sheet according to an embodiment of the present invention will be described.

[0067] (thermosetting resin precursor) The thermosetting resin precursor is contained in the first foaming raw material sheet 91 and the second foaming raw material sheet 92. In the foaming and curing process, the thermosetting resin precursor crosslinks, thereby improving heat resistance and strength. As the thermosetting resin precursor, known thermosetting resin precursors such as phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, silicone resin, urethane resin, and thermosetting polyimide resin, which are listed as the thermosetting resins above, can be used, i.e., pre-cured raw materials (at least one selected from silicone-based raw materials, phenolic-based raw materials, epoxy-based raw materials, melamine-based raw materials, urea-based raw materials, unsaturated polyester-based raw materials, alkyd-based raw materials, urethane-based raw materials, and thermosetting polyimide-based raw materials), and it is preferable to contain pre-cured silicone.

[0068] (Foaming agents and foaming accelerators) The raw material for the elastic material preferably contains a foaming agent or foaming accelerator for forming pores (bubbles) in the elastic material. The foaming agent used in the present invention is one that foams itself. The type of foaming agent is not particularly limited. Examples of suitable foaming agents include hydrocarbons, halogenated hydrocarbons such as halogenated saturated hydrocarbons and halogenated unsaturated hydrocarbons, low-boiling gases such as nitrogen, argon, carbon dioxide, 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. The amount of foaming agent is not limited, but is preferably 0.1 to 5% by mass based on the total amount of the thermosetting resin precursor and foaming agent used to produce the liquid foaming material or foaming material sheet.

[0069] The foaming accelerator refers to a catalyst or the like that generates hydrogen or the like as a by-product when a precursor of a thermosetting resin is cured, and examples thereof include platinum catalysts, aminoxy catalysts, organotin catalysts, etc. The raw material of the elastic material may contain either a foaming agent or a foaming accelerator, or may contain both.

[0070] (Flame retardant) The flame retardant material is the same as that explained in the "Flame Retardant Sheet" section above.

[0071] [Battery module (assembled battery)] FIG. 3 is a schematic diagram showing a battery pack according to an embodiment of the present invention. As shown in FIG. 3, the battery pack 100 includes a plurality of battery cells 20a, 20b, and 20c housed in a battery case 30. The battery cells 20a, 20b, and 20c are connected in series or in parallel by bus bars (not shown). In this embodiment, the fire-retardant sheets 1 are disposed between the battery cells 20a, 20b, and 20c. However, the fire-retardant sheets 1 can be disposed not only between the battery cells but also between the battery cells 20a, 20b, and 20c and the battery case 30. Note that various fire-retardant sheets can be used in the present invention without departing from the spirit and scope of the present invention.

[0072] The battery pack configured in this manner has a flame-retardant sheet that can prevent a decrease in thermal insulation properties, prevent powder falling off of the insulating sheet, ensure sufficient strength of the elastic material, and maintain the effect of alleviating stress on adjacent battery cells, etc. Furthermore, when assembling the flame-retardant sheet 1 to the battery pack 100, the elastic material 60 will not come off the insulating sheet 50. Therefore, the flame-retardant sheet 1 can be easily assembled, and a battery pack 100 with excellent performance can be obtained. [Explanation of symbols]

[0073] 1. Fire-retardant sheet 20a, 20b, 20c battery cells 30 Battery case 50 Heat insulation sheet 51 First main surface 52 Second main surface 53 End face 60 Elastic material 61 first main surface side elastic portion 62 second main surface side elastic portion 63 End surface elastic part 65 Bubbles 71,73 void 91 First foaming material sheet 92 Second foam material sheet 100 battery packs

Claims

1. a heat insulating sheet having a first main surface and a second main surface perpendicular to the thickness direction, and an end surface connecting the first main surface and the second main surface; A fireproof sheet made of a material containing a thermosetting resin and having an elastic material covering the first main surface, the second main surface, and the end surfaces, the elastic material has a first main surface side elastic portion arranged on the first main surface side of the heat insulating sheet, a second main surface side elastic portion arranged on the second main surface side of the heat insulating sheet, and an end surface side elastic portion arranged on the end surface side of the heat insulating sheet, A flame-retardant sheet characterized in that the end surface side elastic portion is formed by the first main surface side elastic portion and the second main surface side elastic portion each extending outward from the end surface of the insulating sheet and being integrated with each other.

2. The flame-retardant sheet according to claim 1, characterized in that the first main surface side elastic portion, the second main surface side elastic portion, and the end surface side elastic portion do not penetrate into the interior of the heat insulating sheet.

3. The flame-retardant sheet according to claim 1, characterized in that the first main surface side elastic portion, the second main surface side elastic portion and the end surface side elastic portion are not bonded to the first main surface, the second main surface and the end surface of the insulating sheet, respectively.

4. The flame-retardant sheet according to claim 1, wherein the first main surface side elastic portion and the second main surface side elastic portion each have an average thickness of 0.1 mm or more and 10 mm or less.

5. 2. The flame retardant sheet according to claim 1, wherein an average distance from the end face of the heat insulating sheet to the outer end of the end face side elastic portion is 0.5 mm or more and 5 mm or less.

6. The flame-retardant sheet according to claim 1, wherein the first main surface side elastic portion, the second main surface side elastic portion, and the end surface side elastic portion are all made of the same material.

7. 2. The flame-retardant sheet according to claim 1, wherein the elastic material comprises at least one selected from the group consisting of silicone resin, phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, urethane resin, and thermosetting polyimide resin.

8. The fire-resistant sheet according to claim 1, wherein the elastic material contains a fire retardant.

9. The fireproof sheet according to claim 1, wherein the heat insulating sheet contains ceramic particles.

10. 10. The fireproof sheet according to claim 9, wherein the ceramic particles include at least one type of particles selected from the group consisting of metal oxide particles, inorganic hydrates, thermally expandable inorganic materials, and water-containing porous bodies.

11. A method for producing a flame-retardant sheet according to any one of claims 1 to 10, a foaming material sheet preparation step of preparing a first foaming material sheet and a second foaming material sheet so that the first foaming material sheet and the second foaming material sheet are larger in size than the first main surface and the second main surface of the heat insulating sheet, respectively; a foaming material sheet arranging step of arranging the first foaming material sheet so as to face the first main surface of the heat insulating sheet and arranging the second foaming material sheet so as to face the second main surface of the heat insulating sheet; a compression joining step of overlapping and compressing a surface of the first foaming material sheet facing the heat insulating sheet and a surface of the second foaming material sheet facing the heat insulating sheet at the end face side of the heat insulating sheet; a foaming and curing step of foaming and curing the first foam raw material sheet and the second foam raw material sheet to obtain the first main surface side elastic portion and the second main surface side elastic portion, and to obtain the integrated end surface side elastic portion.

12. The method for manufacturing a fireproof sheet according to claim 11, wherein the first foaming raw material sheet and the second foaming raw material sheet each contain a thermosetting resin precursor, and a foaming agent or a foaming accelerator.

13. 13. The method for producing a fire-retardant sheet according to claim 12, wherein the thermosetting resin precursor contains at least one selected from the group consisting of a silicone-based raw material, a phenol-based raw material, an epoxy-based raw material, a melamine-based raw material, a urea-based raw material, an unsaturated polyester-based raw material, an alkyd-based raw material, a urethane-based raw material, and a thermosetting polyimide-based raw material.

14. The method for manufacturing a fireproof sheet according to claim 11, wherein both the first foaming material sheet and the second foaming material sheet contain a fire retardant.

15. An assembled battery comprising a plurality of battery cells and the fireproof sheet according to any one of claims 1 to 10, the plurality of battery cells being connected in series or in parallel.

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