Heat transfer suppression sheet and its manufacturing method, as well as battery pack

Abstract

To provide a heat transfer suppression sheet having desired strength and heat insulation property and capable of flexibly coping with various designs in size and heat insulation property.SOLUTION: A heat transfer suppression sheet 50 includes a plurality of heat insulation materials 10 joined to one another, the heat insulation materials 10 each having a pair of main surfaces 10a, 10b and a connection surface 10c connecting the pair of main surfaces 10a, 10b. The connection surfaces 10c of the plurality of heat insulation materials 10 are arranged in opposition to each other, where joint surfaces 61 are formed to join the heat insulation materials 10 to each other. In a cross-section view perpendicular to the pair of main surfaces 10a, 10b and parallel to the direction of the heat insulation materials 10 neighboring each other, the joint surface has a heat transfer prevention part 62 between a first end 63a on the side of one main surface 10a and a second end 63b on the side of the other main surface 10b. The heat transfer prevention part 62 exists at a position shifted from at least one of the first end 63a and the second end 63b in the direction parallel to the main surfaces 10a, 10b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heat-transfer-suppressing sheet, a method for producing the same, and a battery pack including the heat-transfer-suppressing 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] Furthermore, these battery cells are mainly 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 the temperature rises suddenly and continues to rise due to an internal short circuit or overcharging, the heat from the battery cell experiencing thermal runaway may be transmitted to other adjacent battery cells, potentially causing thermal runaway in those cells.

[0004] A common method for suppressing the propagation of heat from a battery cell that has experienced thermal runaway as described above is to place a heat insulating sheet between the battery cells. For example, Patent Document 1 proposes a flame-resistant electrical insulating material for use in electric vehicles. The insulating material contains glass fiber, a particulate filler mixture containing a predetermined material, and an inorganic binder, and has a specified flammability rating.

[0005] Furthermore, Patent Document 2 also proposes a method for producing a heat-transfer-suppressing sheet by processing a mixture containing inorganic particles, binder fibers having a core-sheath structure, and hot-melt powder into a sheet by a dry method, as a method for obtaining strength and heat insulating performance superior to conventional heat insulating sheets.

[0006] In response to recent demands for larger battery cell capacities, long battery cells have been developed in which only one end surface of a plate-shaped battery cell is significantly longer than conventional battery cells. Therefore, the heat insulating sheets placed between such long battery cells must also be enlarged to match the size of the battery cells. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2021-531631 [Patent Document 2] Japanese Patent Application Publication No. 2023-132944 Summary of the Invention [Problem to be solved by the invention]

[0008] However, some of the long battery cells described above have longitudinal lengths exceeding 1 m. For example, if a conventional small-sized insulation sheet is joined to increase the size, the insulation performance at the joints may be reduced. On the other hand, manufacturing an insulation sheet with the desired strength and insulation performance to fit the size of a long battery cell requires new manufacturing equipment, which increases manufacturing costs. Even if a single large insulation sheet is manufactured, the insulation performance may vary depending on the region, or design may be difficult if different insulation performance is desired in different regions. Because these problems occur even with conventional small-sized insulation materials, there is a growing demand for the development of heat-transfer-suppressing sheets that can improve design flexibility.

[0009] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a heat-transfer-inhibiting sheet that has desired strength and heat insulating properties and can flexibly accommodate a variety of designs, such as size and heat insulating properties; a method for manufacturing the heat-transfer-inhibiting sheet that can easily and inexpensively manufacture the heat-transfer-inhibiting sheet; and a battery pack that includes the heat-transfer-inhibiting sheet. [Means for solving the problem]

[0010] The above object of the present invention is achieved by the heat transfer-suppressing sheet having the following configuration [1].

[0011] [1] A heat-transfer-suppressing sheet formed by bonding together a plurality of insulating materials containing inorganic particles, The heat insulating material has a pair of main surfaces and a connecting surface connecting the pair of main surfaces, The connecting surfaces of the plurality of heat insulating materials are arranged opposite to each other, and a connecting surface that connects the heat insulating materials to each other is formed, In a cross-sectional view perpendicular to the pair of main surfaces and parallel to the direction in which the thermal insulating materials are adjacent to each other, When an end portion of the joining surface on one main surface side is defined as a first end portion and an end portion of the joining surface on the other main surface side is defined as a second end portion, the joining surface has a heat transfer prevention portion between the first end portion and the second end portion, The heat transfer suppressing sheet, wherein the heat transfer blocking portion is located at a position offset from at least one of the first end portion and the second end portion in a direction parallel to the main surface.

[0012] Furthermore, preferred embodiments of the present invention relating to the heat transfer-suppressing sheet relate to the following [2] to [9].

[0013] [2] The heat transfer suppression sheet according to [1], characterized in that, in the cross-sectional view, the heat transfer prevention portion has an area extending in a direction different from the thickness direction of the heat insulating material.

[0014] [3] The heat transfer suppression sheet according to [1] or [2], characterized in that, in the cross-sectional view, the heat transfer prevention portion has an area that is at an angle of 20° or more and 160° or less with respect to the thickness direction of the heat insulating material.

[0015] [4] The heat-transfer-suppressing sheet according to any one of [1] to [3], wherein, in the cross-sectional view, the first end portion is shifted in a direction parallel to the main surface relative to the second end portion.

[0016] [5] In the cross-sectional view, the first end and the second end are located symmetrically in the thickness direction of the thermal insulation material, The heat transfer suppressing sheet according to any one of [1] to [3], characterized in that the connecting surface of one of the adjacent insulating materials has a convex portion, and the connecting surface of the other insulating material has a concave portion shaped to fit into the convex portion, and the adjacent insulating materials are joined by fitting the convex portion and the concave portion together.

[0017] [6] A heat transfer-suppressing sheet according to any one of [1] to [5], characterized in that, when the density of the heat insulating material in a region in the thickness direction of the heat insulating material that includes the heat transfer-preventing portion is M1, and the density of the heat insulating material in a region in the thickness direction that does not include the heat transfer-preventing portion is M2, the ratio (M1 / M2) of the density M1 to the density M2 is 1.2 or more.

[0018] [7] The heat-transfer-suppressing sheet according to [1], wherein the heat insulating material comprises organic fibers.

[0019] [8] The heat transfer-suppressing sheet according to any one of [1] to [7], characterized in that the connecting surfaces of adjacent pieces of the heat insulating material that make up the joining surface are bonded to each other in at least a portion of the joining surface.

[0020] [9] The heat transfer-suppressing sheet according to any one of [1] to [7], characterized in that in at least a portion of the bonding surface, the connecting surfaces of adjacent pieces of the heat insulating material that make up the bonding surface are heat-fused together.

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

[10] relating to a method for producing a heat transfer-suppressing sheet.

[0022]

[10] A method for producing the heat transfer-suppressing sheet according to any one of [1] to [7], a first processing step of processing an end surface of one of the two insulating materials to be joined together so that at least a portion of the end surface of the one of the insulating materials extends in a direction different from the thickness direction of the insulating material, thereby forming a first connecting surface; a second processing step of processing the end surface of the other insulating material to form a second connecting surface so that the end surface of the other insulating material is shaped to conform to the first connecting surface of the one insulating material; a bonding surface forming process for forming the bonding surface by arranging the one insulating material and the other insulating material so that the first connecting surface and the second connecting surface face each other, and forming the bonding surface by joining the first connecting surface and the second connecting surface.

[0023] Furthermore, preferred embodiments of the present invention relating to a method for producing a heat transfer-suppressing sheet relate to the following

[11] to

[12] .

[0024]

[11] The method for producing a heat transfer-suppressing sheet according to

[10] , wherein in the bonding surface forming step, at least a portion of the bonding surface is bonded with an adhesive.

[0025]

[12] The method for manufacturing a heat transfer-suppressing sheet according to

[10] , characterized in that in the joining surface forming step, the first joining surface and the second joining surface are heated while being pressed in a direction to bring them closer to each other, and at least a portion between the first joining surface and the second joining surface is fused by thermal fusion.

[0026] The above object of the present invention is also achieved by the following configuration

[13] relating to another method for producing a heat transfer-suppressing sheet.

[0027]

[13] A method for producing the heat transfer-suppressing sheet according to any one of [1] to [7], An arrangement process of arranging the two insulating materials so that a portion of a main surface of one insulating material overlaps a portion of a main surface of the other insulating material, among the two insulating materials to be joined together; A method for manufacturing a heat transfer suppressing sheet, characterized by including a bonding surface forming process in which the area where the two insulating materials overlap is pressed in the thickness direction of the two insulating materials to form the bonding surface in which a portion of the main surface of one insulating material is bonded to a portion of the main surface of the other insulating material.

[0028] Further, preferred embodiments of the present invention relating to other methods for producing a heat transfer-suppressing sheet relate to the following

[14] to

[15] .

[0029]

[14] The method for producing a heat transfer-suppressing sheet according to

[13] , wherein in the bonding surface forming step, at least a portion of the bonding surface is bonded with an adhesive.

[0030]

[15] A method for manufacturing a heat transfer-suppressing sheet according to

[13] , characterized in that in the bonding surface forming step, the area where the two insulating materials overlap is heated while being pressed in the thickness direction of the area, and a portion of the main surface of one insulating material and a portion of the main surface of the other insulating material are fused together by thermal fusion.

[0031] The above object of the present invention is also achieved by the following configuration

[16] relating to a battery pack.

[0032]

[16] A battery pack comprising a plurality of battery cells and the heat-transfer-suppressing sheet according to any one of [1] to [9], the plurality of battery cells being connected in series or in parallel. [Effects of the Invention]

[0033] The heat-transfer-suppressing sheet of the present invention has a heat-insulating material containing inorganic particles, and therefore can provide excellent heat insulation. Furthermore, because it has a structure in which multiple heat-insulating materials are combined, it can be easily manufactured to a desired size, and it is possible to minimize variations in heat insulation depending on the location and intentionally change the heat insulation depending on the location. This simplifies the design of the heat-transfer-suppressing sheet when manufacturing it, and improves the degree of design freedom.

[0034] Furthermore, the joining surface to which the insulating material is joined does not extend linearly in the thickness direction of the plate, but has a heat transfer prevention portion that extends in a direction different from the thickness direction of the plate in at least a portion thereof, so that even when multiple insulating materials are joined, the transfer of heat in the thickness direction of the insulating material can be suppressed.

[0035] Furthermore, according to the method for producing a heat-transfer-suppressing sheet of the present invention, even if the sheet has bonding surfaces of multiple insulating materials, it is possible to suppress a decrease in insulating properties, and it is possible to easily and inexpensively produce a heat-transfer-suppressing sheet in which the properties and size of the insulating materials can be freely designed.

[0036] The battery pack of the present invention has a heat transfer suppression sheet in which a heat transfer blocking portion is formed on the joining surface where multiple insulating materials are joined, which makes it possible to suppress the propagation of heat between battery cells and to flexibly adapt to the size and shape of the battery cells, thereby suppressing thermal runaway of the battery cells in the battery pack and the spread of flames outside the battery case. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a perspective view showing a heat-transfer-suppressing sheet according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a portion of the heat-transfer-suppressing sheet shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing a battery pack according to an embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing a portion of a heat-transfer-suppressing sheet according to a second embodiment of the present invention. [Figure 5] FIG. 5 is an enlarged cross-sectional view showing a portion of a heat-transfer-suppressing sheet according to a third embodiment of the present invention. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing a portion of a heat-transfer-suppressing sheet according to a fourth embodiment of the present invention. [Figure 7] FIG. 7 is a schematic diagram showing a method for manufacturing the heat transfer-suppressing sheet shown in FIGS. [Figure 8]FIG. 8 is a schematic diagram showing a method for manufacturing the heat transfer-suppressing sheet shown in FIG. [Figure 9] FIG. 9 is a photograph, substituted for a drawing, showing a structural example S1 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. [Figure 10] FIG. 10 is a photograph showing an enlarged view of a part of the heat insulating material shown in FIG. [Figure 11] FIG. 11 is a photograph, substituted for a drawing, showing a structural example S2 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. [Figure 12] FIG. 12 is a schematic diagram showing a structural example S3 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. [Figure 13] FIG. 13 is a schematic diagram showing an enlarged portion of FIG. [Figure 14] FIG. 14 is a photograph showing the heat insulating material shown in FIG. [Figure 15] FIG. 15 is a photograph, substituted for a drawing, showing a structural example S4 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. [Figure 16] FIG. 16 is a photograph showing an enlarged view of the structure of the heat insulating material shown in FIG. [Figure 17] FIG. 17 is a photograph showing a cross section of the heat insulating material shown in FIG. [Figure 18] FIG. 18 is a schematic diagram showing a structural example S5 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. [Figure 19] FIG. 19 is an enlarged schematic view of part A of the heat insulating material shown in FIG. [Figure 20] FIG. 20 is a photograph, substituted for a drawing, showing a structural example S6 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. [Figure 21] FIG. 21 is a photograph showing another area of ​​the heat insulating material shown in FIG. [Figure 22] FIG. 22 is a photograph showing a cross section of the heat insulating material shown in FIGS. 20 and 21. In FIG. [Figure 23]FIG. 23 is a photograph, substituted for a drawing, showing a structural example S7 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. [Figure 24] FIG. 24 is a photograph showing an enlarged view of a part of the heat insulating material shown in FIG. [Figure 25] FIG. 25 is a photograph used as a substitute for a drawing to explain a method for specifying the length of the fiber bundles contained in the thermal insulation material. [Figure 26] FIG. 26 is a photograph showing fiber bundles arranged in a mesh pattern on the surface of a heat insulating material. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present inventors have conducted extensive research into a heat-transfer-suppressing sheet that can solve the above-mentioned problems. For example, when a large heat-transfer-suppressing sheet is manufactured by butting the end faces of multiple thermal insulating materials together and bonding them with an adhesive or the like, the insulating properties of the adhesive portion of the bonded surfaces are lower than those of other areas, resulting in a decrease in the insulating properties of the heat-transfer-suppressing sheet itself. Therefore, the present inventors have discovered that by forming a heat-transfer-blocking portion on the bonding surface that joins the end faces, it is possible to suppress the decrease in insulating properties.

[0039] The following describes in detail a method for manufacturing a heat transfer-suppressing sheet, a heat transfer-suppressing sheet, and a battery pack according to embodiments of the present invention. Note that the present invention is not limited to the embodiments described below, and can be modified as desired without departing from the spirit and scope of the present invention.

[0040] [Heat transfer suppression sheet] [First embodiment] Fig. 1 is a perspective view showing a heat-transfer-suppressing sheet according to a first embodiment of the present invention, Fig. 2 is an enlarged cross-sectional view showing a portion of the heat-transfer-suppressing sheet shown in Fig. 1.

[0041] As shown in Fig. 1, the heat-transfer-suppressing sheet 50 according to the first embodiment is formed by bonding together a plurality of thermal insulating materials 10. The thermal insulating materials 10 contain inorganic particles, and the materials constituting the thermal insulating materials 10 will be described in detail later. Each thermal insulating material 10 has a pair of main surfaces 10a, 10b and a connecting surface 10c connecting the main surfaces 10a and 10b. The connecting surfaces 10c of adjacent thermal insulating materials 10 are arranged opposite each other to form a connecting surface 61 along which the thermal insulating materials 10 are bonded together, and the connecting surface 61 has a heat-transfer-blocking portion 62.

[0042] The heat transfer prevention portion 62 will be described in more detail using Figure 2. Figure 2 shows a cross section perpendicular to the pair of main surfaces 10a, 10b and parallel to the direction in which adjacent thermal insulators 10 adjoin each other. For ease of explanation, Figure 2 shows gaps between adjacent thermal insulators 10. However, in practice, it is preferable that there are no gaps between adjacent thermal insulators 10, and it is more preferable that the connecting surfaces 10c are in complete contact over the entire surface. In the cross-sectional view shown in Figure 2, if the end of the connecting surface 61 on one main surface 10a side is defined as a first end 63a and the end on the other main surface 10b side is defined as a second end 63b, the heat transfer prevention portion 62 is formed between the first end 63a and the second end 63b.

[0043] In this cross-sectional view, the first end 63a of the joining surface 61 of the heat transfer-suppressing sheet 50 is offset in a direction parallel to the main surfaces 10a, 10b relative to the second end 63b. The joining surface 61 has a first thickness-direction portion 64a extending from the first end 63a in the thickness direction (thickness direction) to approximately the center of the thickness of the thermal insulation material 10, and a second thickness-direction portion 64b extending from the second end 63b in the thickness direction to approximately the center of the thickness of the thermal insulation material 10. In addition, a heat transfer blocking portion 62 is formed to connect the first thickness-direction portion 64a and the second thickness-direction portion 64b near the center of the thickness. Thus, the heat transfer blocking portion 62 refers to a region of the joining surface 61 that is offset in a direction parallel to the main surfaces 10a, 10b from at least one of the first end 63a and the second end 63b.

[0044] The connecting surfaces 10c arranged opposite each other do not have to be joined, but because the heat-transfer-suppressing sheet 50 according to the first embodiment has a simple shape and the joining surfaces 61 are prone to slippage, it is preferable that adjacent heat insulating materials 10 are fixed in a joined state. For example, the connecting surfaces 10c of adjacent heat insulating materials 10 may be bonded together with an adhesive or the like, or may be joined by thermal fusion.

[0045] A specific use of the heat-transfer-suppressing sheet 50 shown in FIGS. 1 and 2 will be described below as an example. FIG. 3 is a schematic diagram showing a battery pack according to an embodiment of the present invention. As shown in FIG. 3, the heat-transfer-suppressing sheet 50 can be used by interposing the heat-transfer-suppressing sheet 50 between a plurality of battery cells 20a, 20b, and 20c. The battery pack 100 is constructed by storing the plurality of battery cells 20a, 20b, and 20c in a state where they are connected in series or in parallel (the connected state is not shown) in a battery case 30. Note that, for example, lithium-ion secondary batteries are preferably used as the battery cells 20a, 20b, and 20c, but the present invention is not limited thereto and other secondary batteries can also be used.

[0046] Furthermore, the battery cells 20a, 20b, and 20c may be of a normal size or may be larger than a normal size. If the battery cells 20a, 20b, and 20c shown in FIG. 3 are large, the battery cells 20a, 20b, and 20c may be assumed to extend elongatedly in a direction perpendicular to the page. Therefore, the heat transfer-suppressing sheet 50 is also arranged to extend elongatedly in a direction perpendicular to the page, and the joining surface 61 does not appear in FIG. 3.

[0047] The heat-transfer-suppressing sheet 50 according to the first embodiment includes the insulating material 10 containing inorganic particles, thereby achieving excellent thermal insulation between the multiple battery cells 20a, 20b, and 20c. Therefore, for example, if an abnormality occurs in the battery cell 20a and the temperature rises, the heat transfer to the battery cell 20b can be sufficiently suppressed. Furthermore, because the heat-transfer-suppressing sheet 50 can be formed by joining multiple insulating materials 10, it can be easily manufactured to a desired size. If the insulating material contains organic fibers, the effect of retaining the inorganic fibers can be improved.

[0048] Furthermore, when attempting to manufacture a large heat-transfer-suppressing sheet made from a single piece of thermal insulation material, there is a risk of variations in thermal insulation properties. However, by combining multiple small thermal insulation materials 10 to manufacture a heat-transfer-suppressing sheet, as in the present embodiment, it is possible to minimize variations in thermal insulation properties depending on the location. Furthermore, combining multiple small thermal insulation materials 10 also makes it possible to intentionally vary the thermal insulation properties. Therefore, the multiple thermal insulation materials may all have the same properties, or may have different properties. This simplifies design and increases the degree of freedom in design when manufacturing a heat-transfer-suppressing sheet with different thermal insulation properties depending on the region.

[0049] 2, in the heat-transfer-suppressing sheet 50 according to this embodiment, the joining surface 61 does not extend linearly in the thickness direction from one main surface 10a to the other main surface 10b, but has at least a portion of the joining surface 61 that extends in a direction different from the thickness direction. Therefore, even if there is a joining surface 61 that joins multiple pieces of thermal insulating material 10, the presence of the heat-transfer-suppressing portion 62 makes it possible to suppress heat transfer in the thickness direction of the thermal insulating material 10.

[0050] Second Embodiment Fig. 4 is an enlarged cross-sectional view of a portion of a heat-transfer-suppressing sheet according to a second embodiment of the present invention. In the second embodiment shown in Fig. 4, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted or simplified. Furthermore, the heat-transfer-suppressing sheet 52 according to the second embodiment can be used in place of the heat-transfer-suppressing sheet 50 of the battery pack 100 shown in Fig. 3. For ease of explanation, Fig. 4 also shows gaps between adjacent thermal insulators 10. However, in practice, it is preferable that there be no gaps between adjacent thermal insulators 10, and it is more preferable that the connecting surfaces be in complete contact over the entire surface.

[0051] In the heat transfer-suppressing sheet 52 according to the second embodiment, the first end 63a and the second end 63b are positioned symmetrically in the thickness direction of the thermal insulator 10, and the connecting surface of one of the thermal insulators 10 has a convex portion 65, while the connecting surface of the other of the thermal insulators 10 has a concave portion 66 shaped to fit into the convex portion 65. The convex portion 65 and the concave portion 66 fit together to form a connecting surface 61 where adjacent thermal insulators 10 are connected. Note that the convex portion 65 is positioned on the connecting surface 61 away from at least one of the first end 63a and the second end 63b in a direction parallel to the main surfaces 10a, 10b, and therefore this convex portion 65 constitutes a heat transfer-blocking portion 62.

[0052] The heat transfer-suppressing sheet 52 thus configured also has a structure in which a plurality of thermal insulating materials 10 are combined, thereby suppressing variations in functionality and improving design freedom. Furthermore, the joining surface 61 does not extend linearly in the thickness direction from one main surface 10a to the other main surface 10b, but has a convex portion 65 that serves as a heat transfer blocking portion 62. Therefore, even if there is a joining surface 61 that joins a plurality of thermal insulating materials 10, the presence of the heat transfer blocking portion 62 makes it possible to suppress heat transfer in the thickness direction of the thermal insulating materials 10.

[0053] Furthermore, in this embodiment, the convex portions 65 and the concave portions 66 are fitted together to join the insulating materials 10 together. Therefore, even if the joining surfaces 61 are not glued or fused together, the insulating materials 10 will not easily come apart, making them easy to handle. However, as in the first embodiment, if the connecting surfaces of adjacent insulating materials 10 are joined together by glueing or fusion, etc., the ease of handling can be further improved.

[0054] Third Embodiment Fig. 5 is an enlarged cross-sectional view of a portion of a heat-transfer-suppressing sheet according to a third embodiment of the present invention. In the third embodiment shown in Fig. 5, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted or simplified. Furthermore, the heat-transfer-suppressing sheet 53 according to the third embodiment can be used in place of the heat-transfer-suppressing sheet 50 of the battery pack 100 shown in Fig. 3. For ease of explanation, Fig. 5 shows gaps between adjacent thermal insulators 10, but in practice, it is preferable that there be no gaps between adjacent thermal insulators 10, and it is more preferable that the connecting surfaces be in complete contact over the entire surface.

[0055] In the heat-transfer-suppressing sheet 53 according to the third embodiment, the first end 63a is shifted in a direction parallel to the main surfaces 10a and 10b relative to the second end 63b, and a continuous inclined surface is formed from the first end 63a to the second end 63b. That is, the inclined surface is shifted in a direction parallel to the main surfaces 10a and 10b from at least one of the first end 63a and the second end 63b, and therefore this inclined surface constitutes the heat-transfer-blocking portion 62.

[0056] The heat transfer-inhibiting sheet 53 configured in this manner can also achieve the same effects as those of the first embodiment. In the cross-sectional view shown in FIG. 5, the heat transfer-inhibiting portion 62 is inclined with respect to the thickness direction V of the thermal insulation material 10, as indicated by the dashed line in the figure, and is formed at a predetermined angle with respect to the thickness direction V. If the angle A formed between the heat transfer-inhibiting portion 62 and the thickness direction V is 20° or more, a decrease in the thermal insulation performance of the thermal insulation material in the thickness direction can be suppressed. Furthermore, if the angle A formed between the two is 90°, the heat transfer-inhibiting portion 62 is parallel to the main surfaces 10a, 10b, as in the heat transfer-inhibiting portion 62 in the first embodiment. Furthermore, if the angle A formed between the two is greater than 90° and up to 160°, a decrease in thermal insulation performance can be suppressed. Therefore, it is preferable that the heat transfer prevention portion 62 has an area on at least a part of the joining surface 61 that is at an angle of 20° or more and 160° or less with respect to the thickness direction of the insulation material 10, and it is more preferable that the angle A between the heat transfer prevention portion 62 and the plate thickness direction V is in the above range over the entire joining surface 61.

[0057] [Fourth embodiment] Fig. 6 is an enlarged cross-sectional view of a portion of a heat-transfer-suppressing sheet according to a fourth embodiment of the present invention. In the fourth embodiment shown in Fig. 6, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted or simplified. The heat-transfer-suppressing sheet 54 according to the fourth embodiment can be used in place of the heat-transfer-suppressing sheet 50 of the battery pack 100 shown in Fig. 3. For ease of explanation, Fig. 6 shows gaps between adjacent thermal insulators 10, but in practice, it is preferable that there are no gaps between adjacent thermal insulators 10, and it is more preferable that the connecting surfaces are in complete contact over the entire surface.

[0058] In the heat-transfer-suppressing sheet 54 according to the fourth embodiment, the first end 63a is offset from the second end 63b in a direction parallel to the main surfaces 10a and 10b, and an inclined surface is formed from the first end 63a to the second end 63b. A detailed manufacturing method for the heat-transfer-suppressing sheet 54 will be described later. In this embodiment, the inclined surface is formed by overlapping a portion of the main surface 10a of one thermal insulator 10 with a portion of the main surface 10b of the other thermal insulator 10 and applying pressure in the thickness direction. Therefore, a joint surface 61 is formed by the portion of the main surface 10a and the portion of the main surface 10b, and the joint surface 61 constitutes a heat-transfer-blocking portion 62.

[0059] The heat-transfer-inhibiting sheet 54 configured in this manner can also achieve the same effects as the first embodiment. Note that the larger the heat-transfer-inhibiting sheet 54, the more likely it is that the areas away from its end faces will lack strength. Larger battery cells 20a, 20b, and 20c are more likely to bulge in the center of their main surfaces than smaller ones, so the heat-transfer-inhibiting sheet must also be strong enough to withstand pressure. In this embodiment, the end of the thermal insulation material 10 is compressed in the thickness direction. This means that the density M1 of the region R1 that includes the heat-transfer-inhibiting portion 62 in the thickness direction is higher than the density M2 of the region R2 that does not include the heat-transfer-inhibiting portion 62 in the thickness direction. Therefore, the presence of the high-density region R1 extending along the main surface of the heat-transfer-inhibiting sheet 54 not only maintains the strength of the heat-transfer-inhibiting sheet itself but also improves its strength against pressure from the battery cells 20a, 20b, and 20c.

[0060] Assuming that the density of the heat insulating material in region R1, which includes the heat transfer blocking portion 62 in the thickness direction, is M1, and the density of the heat insulating material in region R2, which does not include the heat transfer blocking portion 62 in the thickness direction, is M2, if the ratio of density M1 to density M2 (M1 / M2) is 1.2 or greater, the strength of the heat transfer-suppressing sheet can be improved as described above. Therefore, the ratio (M1 / M2) is preferably 1.2 or greater, and more preferably 1.5 or greater. However, as the density of the heat insulating material increases, the heat insulating properties tend to decrease. For this reason, it is preferable to control the ratio (M1 / M2) of density M1 to density M2, taking into account the required heat insulating properties and strength.

[0061] As in the first embodiment, in the third and fourth embodiments, if the connecting surfaces of adjacent heat insulating materials 10 are joined together by adhesion, fusion, or the like, the handling properties can be further improved.

[0062] [Method of manufacturing heat transfer suppression sheet] Methods for producing heat transfer-suppressing sheets having the various structures described above will be described below with reference to examples.

[0063] [Method for manufacturing the heat transfer-suppressing sheet according to the first embodiment] Fig. 7 is a schematic diagram showing a method for manufacturing the heat-transfer-suppressing sheet shown in Fig. 1 and Fig. 2. For convenience, Fig. 7 illustrates a method for manufacturing a heat-transfer-suppressing sheet using a heat insulating material 10 and a heat insulating material 9 bonded to this heat insulating material 10.

[0064] <1st processing step> As shown in Figure 7, a thermal insulating material 10 having main surfaces 10a and 10b and a thermal insulating material 9 having main surfaces 9a and 9b are prepared. Next, a first connecting surface 10e is machined on the end surface of one of the two thermal insulating materials 10, 9. Specifically, a notch 10d is formed at the corner between the end surface of the thermal insulating material 10 and the main surface 10b, thereby creating a first connecting surface 10e in at least a portion of which extends in a direction different from the thickness direction of the thermal insulating material.

[0065] <Second processing process> Thereafter, the end face of the insulating material 9 is processed to form a second connecting surface 9e so that the end face of the other insulating material 9 to be joined to the insulating material 10 has a shape that conforms to the first connecting surface 10e of one of the insulating materials 10. Specifically, a notch 9d is formed at the corner between the end face of the insulating material 9 and the main surface 9a. The notches 10d, 9d in the first processing step and the second processing step may be formed by cutting the end face of the plate-shaped insulating board, or may be formed by pressing the end faces of the insulating materials 10, 9 with a mold.

[0066] <Binding surface formation process> Thereafter, the thermal insulation material 10 and the thermal insulation material 9 are arranged so that the first connecting surface 10e of the thermal insulation material 10 faces the second connecting surface 9e of the thermal insulation material 9. As a result, as shown in FIG. 2, the first connecting surface 10e and the second connecting surface 9e are connected to form a connecting surface 61, and a heat transfer blocking portion 62 is formed in part of this connecting surface 61.

[0067] In the bonding surface forming step, at least a portion of the bonding surface 61 may be bonded with an adhesive or fused by thermal fusion. When fusion is performed by thermal fusion, the first connecting surface 10e and the second connecting surface 9e are heated while being pressed in a direction that brings them closer to each other, for example, in the direction of the arrows shown in FIG. 7. This allows at least a portion of the first connecting surface 10e and the second connecting surface 9e to be thermally fused. When the insulating material contains organic fibers, the heating temperature during thermal fusion is preferably set to a temperature at which the organic fibers melt, as described below. Furthermore, when fusion is performed between the first connecting surface 10e and the second connecting surface 9e, cutting is preferably used as a method for forming the notches 10d and 9d.

[0068] According to the method for manufacturing a heat-transfer-suppressing sheet according to the above embodiment, even if the heat-transfer-suppressing sheet has a bonding surface where multiple heat-insulating materials are bonded, it is possible to suppress a decrease in heat-insulating properties, and it is possible to easily manufacture a heat-transfer-suppressing sheet of a desired size at low cost. Furthermore, because the heat-transfer-suppressing sheet can be manufactured by combining multiple heat-insulating materials, the properties of the heat-insulating material can be freely designed by changing the position of the heat-transfer-suppressing sheet.

[0069] In this embodiment, the sizes of the notches 10d and 9d may be adjusted in advance, and pressure may be applied to the overlapping region of the thermal insulating material 10 and the thermal insulating material 9 to increase the density of this region. As described above, the strength of the heat-transfer-suppressing sheet can be improved by applying pressure so that the ratio (M1 / M2) of density M1 to density M2 is 1.2 or greater. Furthermore, even when the end faces of the thermal insulating materials 10 and 9 are pressed with a mold and processed into a desired shape, the density of the pressed region increases. Therefore, even when the first connecting surface 10e and the second connecting surface 9e, which have been pressed with a mold, are joined, a heat-transfer-suppressing sheet having excellent strength at the joining surface 61 can be obtained.

[0070] The heat-transfer-suppressing sheet 52 according to the second embodiment shown in FIG. 4 and the heat-transfer-suppressing sheet 53 according to the third embodiment shown in FIG. 5 can be manufactured in the same manner as the heat-transfer-suppressing sheet 50 according to the first embodiment, and therefore the manufacturing methods thereof will be omitted.

[0071] [Method for manufacturing heat transfer-suppressing sheet according to the fourth embodiment] Fig. 8 is a schematic diagram showing a method for manufacturing the heat-transfer-suppressing sheet 54 shown in Fig. 6. For convenience, Fig. 8 also illustrates a method for manufacturing the heat-transfer-suppressing sheet using the heat insulating material 10 and the heat insulating material 9 bonded to this heat insulating material 10.

[0072] <Placement process> As shown in FIG. 8, two thermal insulators 10 and 9 are arranged so that part of the main surface 10b of one thermal insulator 10 and part of the main surface 9a of the other thermal insulator 9 overlap with each other.

[0073] <Binding surface formation process> Pressure is applied to the area where the insulating materials 10 and 9 overlap in the thickness direction of the insulating materials 10 and 9, i.e., in the direction shown by the arrow in Figure 8. As a result, the insulating materials 10 and 9 are compressed as they approach their end faces, and as shown in Figure 6, a joint surface 61 is formed where a portion of the main surface 10b of one insulating material 10 is joined to a portion of the main surface 9a of the other insulating material 9. In this way, in this embodiment, the joint surface 61 is not the area where the end faces of the insulating materials 10 and 9 face each other, but the area where the main surfaces 10b and 9a face each other. Therefore, the joint surface 61 is formed by portions of the main surfaces 10b and 9a, and this joint surface 61 becomes a heat transfer blocking portion 62.

[0074] Like the heat-transfer-suppressing sheet according to the first embodiment, the manufacturing method for the heat-transfer-suppressing sheet according to the fourth embodiment allows for easy production of a heat-transfer-suppressing sheet of a desired size with excellent thermal insulation properties, while also improving design flexibility. Furthermore, unlike the manufacturing method shown in FIG. 7 , there is no need to preprocess the end faces of the heat insulating material. The joining surface forming step alone allows for simultaneous formation of the connecting surface and the joining surface, further simplifying the manufacturing process. Furthermore, because the end faces of the heat insulating material are compressed during the joining surface forming step, the density M1 of the heat insulating material in region R1 is increased, and the ratio of density M1 to density M2 (M1 / M2) can easily be set to 1.2 or greater. Therefore, according to this embodiment, a heat-transfer-suppressing sheet with excellent strength can be easily obtained.

[0075] When the manufacturing method for a heat-transfer-suppressing sheet according to the fourth embodiment is used, the shape of the joining surface 61 in cross section may change depending on the hardness of the thermal insulating materials 10 and 9, resulting in a stepped joining surface as shown in FIG. 2 . Furthermore, depending on the pressure with which the thermal insulating materials 10 and 9 are pressed together in their thickness direction, the ends of the thermal insulating materials 10 and 9 may protrude from the main surfaces 10a and 10b. However, regardless of the surface shape of the joining surface 61 or the heat-transfer-suppressing sheet, a decrease in the thermal insulation performance of the joining surface can be sufficiently suppressed as long as the heat-transfer-blocking portion 62 is formed at a position offset from at least one of the first end 63a and the second end 63b of the joining surface 61 in a direction parallel to the main surfaces 10a and 10b of the thermal insulating material 10.

[0076] In the bonding surface forming step, at least a portion of the bonding surface 61 may be adhered with an adhesive or the like, or may be fused by thermal fusion. When fusion is performed by thermal fusion, the area where the insulating material 10 and the insulating material 9 overlap is heated while being pressed in the thickness direction of this area. This allows a portion of the main surface 10b of one insulating material 10 to a portion of the main surface 9a of the other insulating material 9 to be fused by thermal fusion. When the insulating material contains organic fibers, the heating temperature during thermal fusion is preferably set to a temperature equal to or higher than the melting temperature of the organic fibers described below, as described above.

[0077] The components of the heat-transfer-suppressing sheet according to this embodiment will be described below. First, the heat insulating material will be described in detail.

[0078] [Insulation material] The heat insulating material used in the heat transfer-suppressing sheet according to this embodiment is not particularly limited as long as it has a heat insulating effect. Thermal conductivity can be used as an index of heat insulating effect, and in this embodiment, the heat conductivity of the heat insulating material is preferably less than 1 (W / m·K), more preferably less than 0.5 (W / m·K), and even more preferably less than 0.2 (W / m·K). Furthermore, the heat conductivity of the heat insulating material is more preferably less than 0.1 (W / m·K), more preferably less than 0.05 (W / m·K), and particularly preferably less than 0.02 (W / m·K). The thermal conductivity of the heat insulating material can be measured in accordance with the "Test method for thermal conductivity of refractories" described in JIS R 2251.

[0079] In the heat transfer-suppressing sheet according to an embodiment of the present invention, the heat insulating material may be any material containing inorganic particles, but an example of the structure of a heat insulating material containing organic fibers, which has even better heat insulating properties, will be described in detail below.

[0080] <Insulating material (Structure example S1)> Fig. 9 is a photograph substituting for a drawing showing a structural example S1 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 10 is a photograph substituting for a drawing showing an enlarged portion of the heat insulating material shown in Fig. 9. Note that the heat insulating material 10 in Figs. 9 and 10 can be used as the heat insulating material 10 in Figs. 1 to 8 and the heat insulating material 9 in Figs. 7 and 8.

[0081] As shown in Figures 9 and 10, the heat insulating material 10 has inorganic particles 4 and organic fibers 1. The heat insulating material 10 also has a plurality of three-dimensionally connected pores 7 between the inorganic particles 4 and the organic fibers 1. The organic fibers 1 have welded portions 5 that cover at least a portion of their surfaces, and at least a portion of the inorganic particles 4 are welded to the surfaces of the organic fibers 1 by the welded portions 5. As a result, the surfaces of the organic fibers 1 are covered with the inorganic particles 4.

[0082] The insulating material 10 configured in this manner has multiple three-dimensionally connected pores 7, which provide the effect of air insulation and improve the insulating performance. Furthermore, the insulating material 10 contains highly flexible organic fibers 1, which not only increases the flexibility of the insulating material 10 but also makes it easier for the organic fibers 1 to entangle with each other, thereby improving the sheet strength. Therefore, damage to a heat-transfer-suppressing sheet including such insulating material 10 can be suppressed. Furthermore, the presence of pores 7 in the insulating material 10 improves the cushioning properties of the entire sheet. Therefore, when the battery cells 20a, 20b, and 20c expand during charge and discharge, the insulating material 10 absorbs the expansion of the battery cells, further suppressing deterioration in battery cell performance.

[0083] Furthermore, in this embodiment, it is preferable that at least some of the pores 7 communicate with the surface of the thermal insulator 10 and open outward. With the pores 7 configured in this manner, even if the adjacent battery cells 20a, 20b, and 20c experience thermal runaway and the thermal insulator 10 becomes hot and the organic fibers 1 and the like are decomposed, the decomposition gas will not remain inside the sheet but will be released to the outside through the pores 7. Therefore, from this point of view as well, the effect of preventing destruction of the sheet can be obtained.

[0084] Furthermore, if the welded portions 5 on the outer peripheral surface of the organic fibers 1 fix the inorganic particles 4 to the organic fibers 1, it is possible to obtain the effect of suppressing the falling off (powdering) of the inorganic particles 4. Therefore, even if, for example, a portion of the battery cells 20a, 20b, 20c expands and applies compressive stress or impact to the heat transfer-suppressing sheet 50, it is possible to further enhance the effect of maintaining the shape of the thermal insulating material 10, and to prevent a decrease in the insulating effect due to compressive deformation of the thermal insulating material 10.

[0085] The welded portion 5 does not need to completely cover the outer surface of the organic fiber 1, and there may be areas where the welded portion 5 is not present. In the thermal insulation material 10, binder fibers with a sheath-core structure, which will be described later, can be used as the material for the organic fiber 1. However, if the sheath portion peels off during the manufacturing process, the core portion of the organic fiber 1 may be partially exposed. Even in such a case, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0086] In this specification, the welded portion 5 refers to a portion on the surface of the organic fiber 1, or a portion where the sheath portion of a binder fiber having a core-sheath structure is melted by heating and then cooled and solidified again, and is formed during the manufacturing process of the thermal insulating material 10 described below. The welded portion 5 welds the inorganic particles 4 to the surface of the organic fiber 1 and also welds the organic fibers 1 together. When a binder fiber having a core-sheath structure is used as the material for the organic fiber 1, the welded portion 5 contains a second organic material that constitutes the sheath portion. In this embodiment, the welded portion 5 welds the inorganic particles 4 to the surface of the organic fiber 1, thereby increasing the apparent fiber diameter of the organic fiber 1, supporting the shape of the thermal insulating material 10 and achieving high strength.

[0087] Furthermore, it is preferable that the heat insulating material 10 contains inorganic fibers. The effect obtained by containing inorganic fibers will be explained in the following structural example S2 of the heat insulating material.

[0088] <Insulating material (Structure example S2)> Fig. 11 is a photograph showing a structural example S2 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. In structural example S2 shown in Fig. 11, the same components as those in structural example S1 shown in Figs. 9 and 10 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the heat insulating material 40 shown in Fig. 11 can be used in place of, for example, the heat insulating material 10 of the heat-transfer-suppressing sheets 50, 52, 53, and 54, or the heat insulating material 9 shown in Figs. 7 and 8.

[0089] As shown in FIG. 11, the heat insulating material 40 has inorganic fibers 15. The heat insulating material 40 also has a fiber layer 11 formed on at least a portion of a first surface 40a and a second surface (not shown) perpendicular to the thickness direction of the heat insulating material 40. The fiber layer 11 is formed by welding at least some of the organic fibers 1 together at welding portions, and is layered on the surface (first surface and second surface) of the heat insulating material 40. That is, the fiber layer 11 is a layer formed by gathering 10 or more organic fibers 1 on the surface of the heat insulating material 40, and extends, for example, in stripes, in a direction approximately parallel to the surface.

[0090] Furthermore, a composite layer (not shown) containing a mixture of part of the fiber layer 11 and part of the inorganic particles 4 is formed between the fiber layer 11 and the base layer 13 containing the inorganic particles 4 and the organic fibers 1. Specifically, the composite layer is a region containing a plurality of organic fibers 1 at least partially welded to one another by welded portions, and inorganic particles 4 welded to the organic fibers 1 by welded portions.

[0091] In the heat insulating material 40 shown in Fig. 11, the inorganic fibers 15 are contained in the base layer 13 containing the inorganic particles 4 and the organic fibers 1, but may also be contained in the fiber layer 11. In Fig. 11, the inorganic fibers 15 in the fiber layer 11 cannot be distinguished and are therefore not shown.

[0092] Furthermore, the thermal insulating material 40 has fiber bundles 6 formed by welding at least some of the organic fibers 1 together at welding portions 5. The fiber bundles 6 are formed by entangling 10 or more organic fibers 1 with one another and welding some of the organic fibers 1 together, and are arranged in any direction within the thermal insulating material 40.

[0093] The thermal insulation material 40 configured in this manner contains inorganic fibers 15 that are resistant to decomposition even at high temperatures. Therefore, for example, if the battery cell 20a experiences thermal runaway and the heat-transfer-suppressing sheet 50 disposed adjacent to the battery cell 20a is exposed to high temperatures, even if the organic fibers 1 in the thermal insulation material 40 decompose, the inorganic fibers 15 remain, allowing the thermal insulation material 40 to reliably maintain its shape. Furthermore, the flexible organic fibers 1 easily become entangled with the relatively hard inorganic fibers 15, and the inorganic fibers 15 and organic fibers 1 form a three-dimensional skeleton, further improving the strength of the thermal insulation material 40.

[0094] Furthermore, when the insulating material 40 has a fiber layer 11 on its surface and fiber bundles 6 inside, it can obtain even higher strength compared to when the organic fibers 1 are dispersed. Note that the fiber layer 11 is not simply disposed on the base layer 13, but has a composite layer between the fiber layer 11 and the base layer 13, in which part of the fiber layer 11 and part of the inorganic particles 4 are mixed, so that the fiber layer 11 is securely bound to the surface of the insulating material 40. Therefore, the fiber layer 11 alone does not fall off, and an insulating material 40 having high strength can be obtained, and the pressure on the base layer 13 can be further reduced.

[0095] Furthermore, when a fiber layer 11 is formed on the surface of the insulating material 40, this fiber layer 11 can absorb impacts applied to the insulating material 40, thereby preventing the inorganic particles contained in the insulating material 40 from falling off.

[0096] <Insulating material (Structure example S3)> Fig. 12 is a schematic diagram showing a structural example S3 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 13 is a schematic diagram showing an enlarged portion of Fig. 12. Fig. 14 is a photograph showing the heat insulating material shown in Fig. 12. In structural example S3 shown in Figs. 12 to 14, the same components as those in structural example S1 shown in Figs. 9 and 10 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the heat insulating material 60 shown in Figs. 12 to 14 can be used in place of, for example, the heat insulating material 10 of the heat-transfer-suppressing sheets 50, 52, 53, and 54, or the heat insulating material 9 shown in Figs. 7 and 8.

[0097] As shown in FIGS. 12 to 14 , the heat insulating material 60 includes inorganic particles 4, organic fibers 1 made of a first organic material, and welded portions 5 covering the outer periphery of the organic fibers 1. As described above, the welded portions 5 include a second organic material 17 having a melting point lower than that of the first organic material, and inorganic particles 4. In this embodiment, binder fibers 3 having a sheath-core structure with a core and a sheath covering the outer periphery of the core are used as the organic fibers, and the organic fibers 1 correspond to the core. The welded portions 5 are formed by heating and then melting the sheath of the binder fibers 3 having a sheath-core structure, followed by cooling. Furthermore, as shown in FIG. 14 , the organic fibers 1 and the welded portions 5 containing the inorganic particles 4 form fiber portions 16, and matrix portions 18 containing inorganic particles are formed between the multiple fiber portions 16. When the melted sheath portions are cooled, adjacent organic fibers 1 are fused to each other at contact portions 31, forming a three-dimensional skeleton.

[0098] In the thermal insulation material 60 configured in this manner, the organic fibers 1 and the welded portions 5 act as a skeleton, thereby achieving excellent strength and shape retention. Furthermore, on both the surface and center sides of the thermal insulation material 60, the welded portions 5 covering the outer periphery of the organic fibers fix the inorganic particles 4 to the organic fibers 1, thereby preventing powder from falling off. Therefore, for example, if the heat-transfer-suppressing sheet 50 according to this embodiment is disposed between multiple battery cells, and the battery cells expand, applying compressive stress or impact to the heat-transfer-suppressing sheet 50, the excellent thermal insulation performance can be maintained.

[0099] The mechanism by which the above-mentioned insulating material 60 is able to prevent the inorganic particles 4 from falling off (powdering) is not clear, but one possible reason is that the organic fibers 1 and the welded parts 5 form a three-dimensional, strong skeleton, which maintains the shape of the insulating material 60 and therefore prevents deformation or compression of the insulating material 60. Another possible reason for the inorganic particles 4 being held in place is that the fiber parts 16 exposed on the surface of the insulating material 60 can absorb impacts applied to the insulating material 60.

[0100] 14, in the thermal insulation material 60, the welded portion 5 does not need to completely cover the outer surface of the organic fiber 1, and the organic fiber 1 may be partially exposed. Because the thermal insulation material 60 uses binder fiber 3 with a core-sheath structure, the sheath portion may peel off during the manufacturing process of the thermal insulation material 60, but even if the organic fiber 1 is partially exposed, the effect of suppressing powder fall-off can be sufficiently obtained.

[0101] <Insulating material (Structure example S4)> Fig. 15 is a photograph, substituted for a drawing, showing a structural example S4 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 16 is a photograph, substituted for a drawing, showing an enlarged view of the structure of the heat insulating material shown in Fig. 15. Fig. 17 is a photograph, substituted for a drawing, showing a cross section of the heat insulating material shown in Fig. 15. In structural example S4 shown in Figs. 15 to 17, the same components as those in structural example S1 shown in Figs. 9 and 10 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the heat insulating material 70 shown in Figs. 15 to 17 can be used, for example, in place of the heat insulating material 10 of the heat-transfer-suppressing sheets 50, 52, 53, and 54, or the heat insulating material 9 shown in Figs. 7 and 8.

[0102] 15 and 16, the heat insulating material 70 has a matrix 14 containing inorganic particles 4 and organic fibers 1 three-dimensionally oriented in this matrix 14. The organic fibers 1 have welded parts 5 covering at least a part of their surfaces, and the organic fibers 1 are welded to each other by the welded parts 5. Similarly, the inorganic particles 4 are welded to the surfaces of the organic fibers 1, so that the surfaces of the organic fibers 1 are covered with the inorganic particles 4.

[0103] As shown in the cross-sectional view of Fig. 17, a plurality of voids 7 are formed in the matrix 14 of the thermal insulating material 70. Furthermore, at least some of the plurality of organic fibers 1 are welded together in the matrix 14 by welded portions 5 not shown in Fig. 17, thereby forming fiber bundles 6, and voids 8 are formed between the plurality of organic fibers 1 constituting the fiber bundles 6.

[0104] Furthermore, a fiber layer 11 is formed on at least a portion of the first surface 70a and the second surface (not shown) perpendicular to the thickness direction of the thermal insulation material 70. The fiber layer 11 is formed in a layer on the surfaces (first and second surfaces) of the thermal insulation material 70, with at least some of the organic fibers 1 welded together by welded portions 5. A composite layer 12 is formed between the fiber layer 11 and a base layer 13 containing a matrix 14 and the organic fibers 1. The composite layer 12 is a layer in which some of the fiber layer 11 and some of the matrix 14 are mixed. Specifically, the composite layer 12 is a region containing a plurality of organic fibers 1 at least partially welded to each other by welded portions 5, and inorganic particles 4 welded to the organic fibers 1 by the welded portions 5.

[0105] The fiber bundles 6 are formed by entangling 10 or more organic fibers 1 with some of the organic fibers 1 being welded to one another, and are arranged in any direction in the matrix 14 of the thermal insulation material 70. On the other hand, the fiber layer 11 is a layer formed by assembling 10 or more organic fibers 1 on the surface of the thermal insulation material 70, and extends, for example, in stripes in a direction substantially parallel to the surface.

[0106] In the thermal insulation material 70 configured in this manner, the organic fibers 1 are oriented three-dimensionally in the matrix 14, and the organic fibers 1 have welded parts 5 that cover at least a portion of their surfaces. The welded parts 5 refer to areas where the surfaces of the organic fibers 1 have melted and then solidified again, and are formed during the manufacturing process of the thermal insulation material 70. In the thermal insulation material 70, the three-dimensionally oriented organic fibers 1 are welded together by the welded parts 5, and this structure serves as a skeleton to support the shape of the thermal insulation material 70, thereby achieving high strength.

[0107] Similarly, in the thermal insulating material 70, the welded portions 5 on the outer peripheral surface of the organic fibers 1 also fix the inorganic particles 4 to the organic fibers 1, thereby achieving an even greater powder shedding suppression effect. Therefore, for example, even if a portion of the battery cells 20a, 20b, and 20c expands during charging and discharging, causing compressive stress or impact on the heat transfer-suppressing sheet 50, the shape of the thermal insulating material 70 can be maintained. As a result, shedding (powder shedding) of the inorganic particles 4 can be suppressed, and a decrease in the insulating effect of the thermal insulating material 70 due to compressive deformation can be prevented.

[0108] The mechanism by which the heat insulating material 70 can prevent the inorganic particles 4 from falling off from the sheet surface is thought to be similar to that of the heat insulating material 60 of the above-mentioned structural example S3.

[0109] In the heat insulating material 70, the welded portions 5 do not need to completely cover the outer periphery of the organic fibers 1, and there may be areas where the welded portions 5 are not present. Even in such a case, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0110] Furthermore, since the insulating material 70 contains organic fibers 1 that have high flexibility, the flexibility of the insulating material 70 can be increased and the organic fibers 1 can be easily entangled with each other, which has the effect of improving the sheet strength.

[0111] Furthermore, the heat insulating material 70 has a plurality of pores 7 in the matrix 14 and voids 8 between the plurality of organic fibers 1 that make up the fiber bundle 6, thereby improving the heat insulating performance. Furthermore, the presence of the voids 8 makes it difficult for the organic fibers 1 to be constrained in the matrix 14, thereby further improving the flexibility and strength of the heat insulating material 70. The voids 8 do not need to be formed in the entire area between the plurality of organic fibers 1; as long as the voids 8 are formed in at least a portion of the area between the organic fibers 1, the effect of suppressing heat transfer can be obtained.

[0112] Furthermore, since the thermal insulation material 70 has the fiber bundles 6 and the fiber layer 11, it can have even higher strength than when the organic fibers 1 are dispersed. Furthermore, the fiber layer 11 is not simply disposed on the base layer 13, but has a composite layer 12 between the fiber layer 11 and the base layer 13, in which part of the fiber layer 11 and part of the inorganic particles 4 that make up the matrix 14 are mixed, so the fiber layer 11 is securely bound to the surface of the thermal insulation material 70. Therefore, a thermal insulation material 70 with high strength can be obtained.

[0113] <Insulation material (Structure example S5)> Fig. 18 is a schematic diagram showing a structural example S5 of the heat insulating material used in the heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 19 is a schematic diagram showing an enlarged view of part A of the heat insulating material shown in Fig. 18. In structural example S5 shown in Figs. 18 and 19, the same components as those in structural example S1 of the heat insulating material shown in Figs. 9 and 10 are given the same reference numerals, and detailed description thereof will be omitted. Note that the heat insulating material 80 shown in Figs. 18 and 19 can be used in place of, for example, the heat insulating material 10 of the heat-transfer-suppressing sheets 50, 52, 53, and 54, or the heat insulating material 9 shown in Figs. 7 and 8.

[0114] As shown in Figures 18 and 19, the heat insulating material 80 has a matrix 14 containing inorganic particles 4, inorganic fibers 15 dispersed in the matrix 14, and organic fibers 1. The organic fibers 1 and the inorganic fibers 15 are entangled with each other to form a three-dimensional web structure. In this embodiment, an air layer 28 is formed in a portion around the inorganic fibers 15. The organic fibers 1 also have welded portions 5 on a portion of their surface, and at least a portion of the inorganic fibers 15 is welded to the organic fibers 1 by the welded portions 5. Furthermore, at least a portion of the inorganic particles 4 is welded to the organic fibers 1 by the welded portions 5.

[0115] In this specification, the term "dispersed" of the inorganic fibers 15 means that the inorganic fibers 15 are not distributed unevenly but are spread out over the entire surface.

[0116] In the thermal insulation material 80 configured in this manner, the organic fibers 1 and the inorganic fibers 15 are entangled with each other to form a three-dimensional web structure, and this structure serves as the skeleton, providing high strength. Therefore, even if the heat-transfer-suppressing sheet 50 is compressed due to expansion of the battery cells 20a, 20b, and 20c during charging and discharging, the shape of the thermal insulation material 80 can be maintained. As a result, it is possible to prevent the inorganic particles 4 from falling off (powdering), and to prevent a decrease in the thermal insulation effect of the thermal insulation material 80 due to compression and deformation.

[0117] Furthermore, because the heat insulating material 80 contains highly flexible organic fibers 1, the flexibility of the heat insulating material 80 can be increased, and the organic fibers 1 become entangled with the inorganic fibers 15, making it easier to form a three-dimensional web structure, thereby improving strength. Furthermore, if the heat insulating material 80 contains inorganic fibers 15, the shape of the heat-transfer-suppressing sheet can be maintained even if, for example, the battery cell 20a experiences thermal runaway and the heat-transfer-suppressing sheet disposed adjacent to the battery cell 20a is exposed to high temperatures, causing the organic fibers 1 to decompose. Therefore, by including the highly flexible organic fibers 1 and the inorganic fibers 15 that do not decompose even at high temperatures in the heat insulating material 80, it is possible to obtain a heat-transfer-suppressing sheet that has a good balance of both flexibility and strength.

[0118] Furthermore, in this embodiment, air layers 28 are formed around the inorganic fibers 15 dispersed in the matrix 14. The inorganic fibers 15 have a higher thermal conductivity than the organic fibers 1, but as described above, the air layers 28 formed around the inorganic fibers 15 can suppress heat transfer between the inorganic fibers 15 and the matrix 14. The air layers 28 are formed in the manufacturing process of the thermal insulation material 80, but it is not necessary for the air layers 28 to be formed around the entire area around the inorganic fibers 15. As long as the air layers 28 are formed on at least a portion of the outer circumferential surface of the inorganic fibers 15, the effect of suppressing heat transfer can be obtained. When the inorganic fibers 15 are uniformly dispersed in the matrix 14, the air spaces 28 in the matrix 14 are also uniformly dispersed and disposed, so that the heat insulating material 80 can obtain high heat insulating properties evenly.

[0119] Furthermore, in the insulating material 80, the organic fibers 1 have welded portions 5 that cover at least a portion of their surfaces. The welded portions 5 refer to areas where the surfaces of the organic fibers 1 melt and then solidify again, and are formed during the manufacturing process of the insulating material 80. When at least a portion of the inorganic fibers 15 are welded to the organic fibers 1 by the welded portions 5, the entangled organic fibers 1 and inorganic fibers 15 are fixed, thereby making it possible to obtain an insulating material 80 with even higher strength.

[0120] Similarly, in this embodiment, the welded portions 5 on the outer peripheral surface of the organic fibers 1 also fix the inorganic particles 4 to the organic fibers 1, thereby achieving an even greater powder shedding suppression effect. Therefore, even if, for example, a portion of the battery cells 20a, 20b, 20c expands and applies compressive stress or impact to the heat transfer-suppressing sheet, excellent heat insulating performance can be maintained.

[0121] In this embodiment, the mechanism by which the inorganic particles 4 are prevented from falling off from the sheet surface is thought to be that the organic fibers 1 and the inorganic fibers 15 are welded to each other at the welded portions 5 to form a three-dimensional, strong skeleton, which maintains the shape of the heat insulating material 80 and prevents deformation or compression of the heat-transfer-suppressing sheet. Furthermore, when the organic fibers 1 and the inorganic fibers 15 are exposed on the surface of the heat insulating material 80, they are able to absorb impacts applied to the heat insulating material 80, and the inorganic particles 4 are thought to be held in place.

[0122] In the heat insulating material 80, the welded portions 5 do not need to completely cover the outer periphery of the organic fibers 1, and there may be areas where the welded portions 5 are not present. Even in such a case, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0123] <Insulating material (Structure example S6)> Fig. 20 is a photograph, substitute for a drawing, showing structural example S6 of the heat insulating material used in the heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 21 is a photograph, substitute for a drawing, showing another region of the heat insulating material shown in Fig. 20. Fig. 22 is a photograph, substitute for a drawing, showing a cross section of the heat insulating material shown in Figs. 20 and 21. In structural example S6 shown in Figs. 20 to 22, the same components as those in structural example S4 of the heat insulating material shown in Figs. 15 to 17 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the heat insulating material 90 shown in Figs. 20 to 22 can be used, for example, in place of the heat insulating material 10 of the heat-transfer-suppressing sheets 50, 52, 53, and 54, or the heat insulating material 9 shown in Figs. 7 and 8.

[0124] As shown in Fig. 20, the heat insulating material 90 includes inorganic particles 4 and organic fibers 1. At least some of the organic fibers 1 have a branched structure consisting of a base 32 and branches 33 extending from the base 32. In this embodiment, the branches 33 extend from the base 32 in four directions: direction D1, direction D2, direction D3, and direction D4. The base 32 and the multiple branches 33 form a skeleton.

[0125] 21 also contains organic fibers 1 having a branched structure consisting of a base 32 and branches 33 extending from the base 32. The organic fibers 1 shown in FIG. 21 have a base 32 and branches 33 extending from the base 32 in five directions, namely, directions D1, D2, D3, D4, and D5, and the base 32 is thicker than the multiple branches 33.

[0126] Furthermore, as shown in FIGS. 20 and 21, in this embodiment, inorganic particles 4 are welded to the surface of the organic fiber 1, so that the surface of the organic fiber 1 is covered with the inorganic particles 4.

[0127] As shown in the cross-sectional view of Figure 22, a plurality of voids 7 are formed in the thermal insulation material 90. Furthermore, a plurality of organic fibers 1 are at least partially welded together in the thermal insulation material 90 to form fiber bundles 6, and gaps 8 are formed between the plurality of organic fibers 1 that make up the fiber bundles 6. Note that, also in Figure 22, it is possible to see the organic fibers 1 having a branched structure consisting of a base 32 and branch portions 33 extending in three directions from the base 32.

[0128] Furthermore, a fiber layer 11 may be formed on at least a portion of the first and second surfaces of the thermal insulation 90 that are perpendicular to the thickness direction. The fiber layer 11 is formed by welding at least a portion of a plurality of organic fibers 1 to each other and forming a layer on the surface (first and second surfaces) of the thermal insulation 90. Furthermore, a composite layer 12 may be formed between the fiber layer 11 and a base layer 13 that contains inorganic particles 4 and the organic fibers 1. The composite layer 12 is a layer in which a portion of the fiber layer 11 and a portion of the inorganic particles 4 are mixed. Specifically, the composite layer 12 is a region that contains a plurality of organic fibers 1 that are welded to each other and inorganic particles 4 that are welded to the organic fibers 1.

[0129] The fiber bundles 6 are formed by entangling 10 or more organic fibers 1 with some of the organic fibers 1 being welded to one another, and are arranged in any direction inside the thermal insulation material 90. On the other hand, the fiber layer 11 is a layer formed by assembling 10 or more organic fibers 1 on the surface of the thermal insulation material 90, and extends, for example, in stripes in a direction substantially parallel to the surface.

[0130] In the thermal insulation material 90 configured in this manner, at least some of the organic fibers 1 have a branched structure consisting of bases 32 and branches 33, and the organic fibers 1 serve as a skeleton, allowing the shape of the thermal insulation material 90 to be maintained. In this embodiment, the bases 32 are formed by fused portions where the organic fibers 1 are fused to each other. Specifically, the bases 32 are portions where portions of the multiple organic fibers 1 come into contact with each other, melt together, and then solidify, and are therefore thicker than the branches 33. Therefore, the bases 32 can firmly support the entire skeleton, allowing the strength of the thermal insulation material 90 to be significantly improved.

[0131] In the thermal insulating material 90, at least some of the organic fibers 1 have a branched structure consisting of a base 32 and branch portions 33 extending from the base 32 in at least three directions. The branched structure can be confirmed in a cross-sectional photograph of the thermal insulating material 90, but an easier way to confirm the branched structure is to observe a cross section of the thermal insulating material 90 torn in a plane direction perpendicular to its thickness direction. In this way, by observing the cross section, it is possible to easily confirm that the organic fibers 1 have a branched structure consisting of a base 32 and branch portions 33 extending from the base 32 in at least three directions. The base 32 and branch portions 33 will be described in more detail below.

[0132] (Base (fusion part)) The fused portion is formed by heating and melting the sheath portion of the binder fiber at the portion where the plurality of binder fibers are in contact with each other when a binder fiber with a core-sheath structure is used as the material for the thermal insulation material 90, and then cooling the sheath portion. When a binder fiber with a core-sheath structure is used as the material for the thermal insulation material 90, the fused portion contains the second organic material that constitutes the sheath portion. Thus, in the manufacturing process of the heat transfer-suppressing sheet 50, when the sheaths in the contacting regions of the binder fibers are melted by heating, the amount of melted sheath (second organic material) is greater than when the sheath of a single binder fiber is melted, and a thick fused portion (base 32) is formed after cooling. As a result, the skeleton is firmly supported by the base 32.

[0133] (branch) The support portions 33 extend in at least three directions from the base portion 32 and have the effect of holding the inorganic particles 4. Furthermore, the base portion 32 and the support portions 33 form a skeleton, which can also improve the strength of the heat transfer-suppressing sheet 50. This makes it possible to obtain a high effect of suppressing powder falling. When a binder fiber with a core-sheath structure is used as the organic fiber 1, the branch portion 33 is a part of the binder fiber with a core-sheath structure, and has a core portion made of a first organic material and a sheath portion made of a second organic material.

[0134] As long as the branches 33 extending from the base 32 extend in at least three directions, a skeleton made of the organic fibers 1 can be formed. Furthermore, it is preferable that these multiple branches 33 extend in different three-dimensional directions, which allows the formation of a three-dimensional, strong skeleton.

[0135] In the thermal insulating material 90, the multiple support portions 33 extend from the base portion 32, allowing the inorganic particles 4 to be held by these support portions 33. This, combined with the improved sheet strength achieved by the formation of a skeleton, provides a high powder shedding prevention effect. Therefore, for example, even if a portion of the battery cells 20a, 20b, and 20c expands during charging and discharging, causing compressive stress or impact on the heat transfer-suppressing sheet, the shape of the thermal insulating material 90 can be maintained. As a result, shedding (powder shedding) of the inorganic particles 4 can be prevented, and a decrease in the insulating effect of the thermal insulating material 90 due to compressive deformation can be prevented.

[0136] The mechanism by which the inorganic particles 4 can be prevented from falling off from the surface of the insulating material 90 is thought to be due to the same effect as that of the insulating material 60 of the above structural example S3, as well as the effect of the support parts 33 to hold the inorganic particles 4. Furthermore, when the inorganic particles 4 are fused to the surface of the organic fibers 1, the organic fibers 1 appear to have a thicker fiber diameter, which makes them stronger than the strength of the organic fibers 1 alone, and also provides a high holding effect for the inorganic particles 4.

[0137] In the heat insulating material 90, there may be a region where the inorganic particles 4 are not partially welded to the outer peripheral surface of the organic fibers 1. Even in such a case, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0138] Furthermore, since the insulating material 90 contains organic fibers 1 that have high flexibility, the flexibility of the insulating material 90 can be increased and the organic fibers 1 can be easily entangled with each other, which has the effect of improving the sheet strength.

[0139] Furthermore, the heat insulating material 90 preferably has a plurality of pores 7 and voids 8 between the plurality of organic fibers 1 constituting the fiber bundle 6, thereby obtaining the effect of air insulation and improving the heat insulating performance. Furthermore, the presence of the voids 8 leaves the organic fibers 1 in a completely unconstrained state, further improving the flexibility and strength of the heat insulating material 90. The voids 8 do not need to be formed in the entire area between the plurality of organic fibers 1; as long as the voids 8 are formed in at least a portion of the area between the organic fibers 1, the effect of suppressing heat transfer can be obtained.

[0140] Furthermore, since the thermal insulation material 90 has the fiber bundles 6 and the fiber layer 11, it can obtain a sheet strength that is even higher than when the organic fibers 1 are dispersed. Furthermore, when the fiber layer 11 is present, the fiber layer 11 is not simply disposed on the base layer 13, but has a composite layer 12 between the fiber layer 11 and the base layer 13, in which part of the fiber layer 11 and part of the inorganic particles 4 are mixed, so that the fiber layer 11 is securely bound to the surface of the thermal insulation material 90. Therefore, the strength of the thermal insulation material 90 can be improved.

[0141] <Insulating material (Structure example S7)> Fig. 23 is a photograph, substituted for a drawing, showing a structural example S7 of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 24 is a photograph, substituted for a drawing, showing an enlarged portion of the heat insulating material shown in Fig. 23. In structural example S7 shown in Figs. 23 and 24, the same components as those in structural example S2 of the heat insulating material shown in Fig. 11 are given the same reference numerals, and detailed explanations will be omitted. Note that the heat insulating material 110 shown in Figs. 23 and 24 can be used, for example, in place of the heat insulating material 10 of the heat-transfer-suppressing sheets 50, 52, 53, and 54 described above, or the heat insulating material 9 shown in Figs. 7 and 8.

[0142] 23 and 24, the thermal insulating material 110 has inorganic particles 4 and organic fibers 1. On the surface of the thermal insulating material 110, a first region 42 having streak-like fiber bundles made of a plurality of organic fibers 1 and a second region 43 having no fiber bundles 47 are formed. In this specification, the fiber bundles 47 are 10 or more organic fibers 1 entangled with one another, and extend in streak-like fashion in a direction substantially parallel to the surface of the thermal insulating material 110.

[0143] That is, when the surface of the thermal insulating material 110 is observed, a state in which a plurality of organic fibers 1 are entangled is observed in the first region 42, as shown in Fig. 24. On the other hand, in the second region 43, although there are some places where a few organic fibers 1 are observed, fiber bundles 47 in which a plurality of organic fibers 1 are entangled are not observed. In this embodiment, the first region 42 and the second region 43 have a sea-island structure, and the second region 43, which corresponds to an island portion, is formed so as to be surrounded by the first region 42, which corresponds to a sea portion.

[0144] In the thermal insulating material 110, fiber bundles 47 formed by entanglement of organic fibers 1 are present on the surface of the thermal insulating material 110 in a streak-like manner, thereby improving the strength of the thermal insulating material 110. Furthermore, the entire surface is not covered with fiber bundles 47, and there are first regions 42 where fiber bundles 47 are present and second regions where fiber bundles 47 are not present, so the flexibility of the thermal insulating material 110 is also excellent. Furthermore, because the fiber bundles 47 are present on the surface of the thermal insulating material 110, even if an impact or pressure is applied to the thermal insulating material 110, the fiber bundles 47 can absorb and mitigate the impact or pressure. Therefore, it is possible to suppress the inorganic particles 4 from falling off (powdering), and it is possible to prevent a decrease in the thermal insulating performance of the thermal insulating material 110.

[0145] In the heat insulating material 110, the organic fibers 1 and the fiber bundles 47 formed by entanglement of the organic fibers 1 are present not only on the surface of the heat insulating material 110 but also inside the heat insulating material 110. This allows for even greater strength to be obtained.

[0146] It is preferable that the length of the fiber bundles 47 formed so as to extend on the surface of the heat insulating material 110 is relatively long. An example of a method for specifying the length of the fiber bundles 47 will be described with reference to FIG. 25, rectangular imaginary frames 21 are arranged along the streak-like fiber bundles 47 on the surface of the thermal insulation material 110. In this embodiment, the size of the imaginary frames 21 is 5 mm square, and these imaginary frames 21 are arranged so that they are continuous with each other. In this case, if there are fiber bundles 47 that penetrate at least three continuous imaginary frames 21, it can be determined that the effect of improving the strength of the thermal insulation material 110 is sufficient.

[0147] It is also possible to simply measure the length of the fiber bundles 47 extending in a stripe shape. For example, a method can be used in which a string or the like is placed on the surface of the thermal insulation material 110 along the fiber bundles 47, and then the length of the string is measured. When the length of continuous fiber bundles 47 is measured, if there are fiber bundles 47 with a length of 20 mm or more, the effect of improving the strength of the thermal insulation material 110 can be sufficiently obtained.

[0148] Furthermore, as shown in FIG. 26, if the fiber bundles 47 are connected in a mesh pattern on the surface of the heat insulating material 110, the sheet strength can be further improved.

[0149] While structural examples S1 to S7 of the heat insulating material have been described above, the structure of the heat insulating material is not limited thereto, and heat insulating materials having various structures can be used. Specifically, the heat insulating materials of structural examples S1 to S7 contain inorganic particles and organic fibers, and have excellent heat insulating properties as well as various properties such as suppressing powder shedding, further improving strength, and maintaining shape. Therefore, as shown in FIGS. 1 to 6, a heat-transfer-suppressing sheet formed by combining and bonding the heat insulating materials 9, 10, 40, 60, 70, 80, 90, and 110 described above can achieve excellent heat insulating properties and the various effects described above. However, in the present invention, the heat insulating material does not necessarily need to contain organic fibers; even a heat-transfer-suppressing sheet having a heat insulating material that does not contain organic fibers can achieve the effect of the present invention, which increases the design freedom for size and heat insulating properties.

[0150] As described above, the heat insulating material contains inorganic particles, and as other components, for example, at least one selected from organic fibers, inorganic fibers, and organic particles. Each material will be described with reference to Figs. 9 to 25.

[0151] <Inorganic particles> As the inorganic particles 4, a single inorganic particle may be used, or two or more types of inorganic particles may be used in combination. From the viewpoint of the heat transfer suppression effect, the type of inorganic particles 4 is preferably particles made of at least one inorganic material selected from oxide particles, carbide particles, nitride particles, and inorganic hydrate particles, and more preferably oxide particles. Furthermore, the shape of the inorganic particles 4 is not particularly limited, but preferably includes at least one type selected from nanoparticles, hollow particles, and porous particles. Specific examples of the inorganic particles that can be used include silica nanoparticles, metal oxide particles, inorganic balloons such as microporous particles and hollow silica particles, particles made of thermally expandable inorganic materials, and particles made of hydrous porous bodies.

[0152] When the average secondary particle diameter of the inorganic particles is 0.01 μm or more, they are easily available and the increase in production costs can be suppressed. Furthermore, when the average secondary particle diameter is 200 μm or less, the desired heat insulating effect can be obtained. Therefore, the average secondary particle diameter of the inorganic particles is preferably 0.01 μm or more and 200 μm or less, and more preferably 0.05 μm or more and 100 μm or less.

[0153] In addition, by using two or more inorganic particles 4 with different heat transfer suppression effects in combination, it is possible to cool a heat generating body in multiple stages, and the heat absorption effect can be exerted over a wider temperature range. Specifically, it is preferable to use a mixture of large-diameter particles and small-diameter particles. For example, when nanoparticles are used as one of the inorganic particles, it is preferable to include inorganic particles made of a metal oxide as the other inorganic particle. Hereinafter, the inorganic particles will be described in more detail, with the small-diameter inorganic particles referred to as the first inorganic particles and the large-diameter inorganic particles referred to as the second inorganic particles.

[0154] <First inorganic particle> (oxide particles) Oxide particles have a high refractive index and a strong effect of diffusely reflecting light. Therefore, using oxide particles as the first inorganic particles can suppress radiant heat transfer, particularly in high-temperature regions such as those caused by abnormal heat generation. The oxide particles can be at least one type of particle selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina. That is, among the above oxide particles that can be used as inorganic particles, only one type or two or more types of oxide particles can be used. In particular, silica is a component with high heat insulating properties, and titania is a component with a higher refractive index than other metal oxides, and is highly effective in diffusely reflecting light and blocking radiant heat in high-temperature regions of 500°C or higher. Therefore, it is most preferable to use silica and titania as the oxide particles.

[0155] (Average primary particle size of oxide particles: 0.001 μm to 50 μm) The particle size of the oxide particles can affect the effect of reflecting radiant heat, so if the average primary particle size is limited to a predetermined range, even higher heat insulating properties can be obtained. In other words, when the average primary particle diameter of the oxide particles is 0.001 μm or more, the particle diameter is sufficiently larger than the wavelength of light that contributes to heating, and the light is efficiently diffused, thereby suppressing the radiative heat transfer within the thermal insulation material in the high temperature range of 500°C or higher, thereby further improving the thermal insulation properties. On the other hand, if the average primary particle size of the oxide particles is 50 μm or less, the number and number of contact points between the particles do not increase even when compressed, making it difficult to form paths for conductive heat transfer. This reduces the impact on thermal insulation, particularly in the normal temperature range where conductive heat transfer is dominant.

[0156] In the present invention, the average primary particle size can be determined by observing particles under a microscope, comparing with a standard scale, and taking the average of any 10 particles.

[0157] (nanoparticles) In the present invention, nanoparticles refer to particles on the order of nanometers that are spherical or nearly spherical and have an average primary particle diameter of less than 1 μm. Nanoparticles have low density, which suppresses conductive heat transfer. When nanoparticles are used as the first inorganic particles, the three-dimensionally connected pores 7 become finer, resulting in excellent heat insulation that suppresses convective heat transfer. Therefore, it is preferable to use nanoparticles because they can suppress heat transfer between adjacent nanoparticles during normal use of the battery at room temperature. Furthermore, if nanoparticles with a small average primary particle size are used as oxide particles, the increase in conductive heat transfer through the insulating material can be suppressed even when the insulating material is compressed due to expansion caused by thermal runaway in the battery cell, increasing the internal density. This is thought to be because nanoparticles are prone to forming tiny voids between particles due to electrostatic repulsion, and because their bulk density is low, the particles are packed together to provide cushioning.

[0158] In the present invention, when nanoparticles are used as the first inorganic particles, there are no particular limitations on the material as long as they comply with the definition of nanoparticles. For example, silica nanoparticles are a material with high heat insulating properties, and the contact points between particles are small, so the amount of heat conducted by silica nanoparticles is smaller than when silica particles with a large particle diameter are used. Furthermore, commonly available silica nanoparticles have a bulk density of 0.1 (g / cm 3 ), for example, even if the battery cells arranged on both sides of the insulating material thermally expand and a large compressive stress is applied to the insulating material, the size (area) and number of contact points between the silica nanoparticles do not increase significantly, and the insulating properties can be maintained. Therefore, it is preferable to use silica nanoparticles as the nanoparticles. Examples of silica nanoparticles include wet silica, dry silica, and aerogel, but silica nanoparticles that are particularly suitable for this embodiment will be described below.

[0159] Generally, wet silica particles are aggregated, whereas dry silica particles can be dispersed. Because heat conduction is dominated by conductive heat transfer in the temperature range below 300°C, dry silica, which allows particles to be dispersed, can achieve superior insulating performance compared to wet silica. While the insulating materials shown in the structural examples S1 to S7 above are examples of insulating materials manufactured by a dry process, insulating materials may also be manufactured by a wet process. However, to further improve insulating properties, it is preferable to use a manufacturing method in which a mixture containing the materials is processed into a sheet by a dry process. Therefore, it is preferable to use dry silica, silica aerogel, or the like, which has low thermal conductivity, as the inorganic particles.

[0160] (Average primary particle diameter of nanoparticles: 1 nm to 100 nm) If the average primary particle size of the nanoparticles is limited to a predetermined range, even higher heat insulating properties can be obtained. That is, when the average primary particle diameter of the nanoparticles is 1 nm or more and 100 nm or less, convective heat transfer and conductive heat transfer within the thermal insulation material can be suppressed, particularly in the temperature range below 500°C, and the thermal insulation properties can be further improved. Furthermore, even when compressive stress is applied, the voids remaining between the nanoparticles and the contact points between many particles suppress conductive heat transfer, allowing the thermal insulation properties of the thermal insulation material to be maintained. The average primary particle size of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more, while the average primary particle size of the nanoparticles is more preferably 50 nm or less, and even more preferably 10 nm or less.

[0161] (Inorganic hydrate particles) When inorganic hydrate particles receive heat from a heating element and reach a temperature above their thermal decomposition initiation temperature, they undergo thermal decomposition and release their own water of crystallization, lowering the temperature of the heating element and its surroundings, thereby exhibiting a so-called "endothermic effect." After releasing the water of crystallization, the particles become porous, and the numerous air holes provide thermal insulation. Specific examples of inorganic hydrates include aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), zinc hydroxide (Zn(OH)2), iron hydroxide (Fe(OH)2), manganese hydroxide (Mn(OH)2), zirconium hydroxide (Zr(OH)2), and gallium hydroxide (Ga(OH)3).

[0162] For example, aluminum hydroxide has about 35% water of crystallization, and as shown in the following formula, it thermally decomposes, releasing the water of crystallization and exhibiting an endothermic effect. After releasing the water of crystallization, it becomes a porous alumina (Al2O3) and functions as a heat insulating material. 2Al(OH)3 → Al2O3 + 3H2O

[0163] The heat transfer-suppressing sheet 50 according to this embodiment is preferably interposed between battery cells, for example, but in a battery cell that has experienced thermal runaway, the temperature rises sharply to over 200°C and continues to rise to around 700°C. Therefore, the inorganic particles are preferably made of inorganic hydrates whose thermal decomposition temperature starts at 200°C or higher. The thermal decomposition starting temperatures of the inorganic hydrates listed above are approximately 200°C for aluminum hydroxide, approximately 330°C for magnesium hydroxide, approximately 580°C for calcium hydroxide, approximately 200°C for zinc hydroxide, approximately 350°C for iron hydroxide, approximately 300°C for manganese hydroxide, approximately 300°C for zirconium hydroxide, and approximately 300°C for gallium hydroxide.All of these temperatures roughly overlap with the temperature range in which a battery cell experiencing thermal runaway experiences a sudden rise in temperature, and can efficiently suppress temperature rise, making these inorganic hydrates preferable.

[0164] (Average secondary particle diameter of inorganic hydrate particles: 0.01 μm or more and 200 μm or less) Furthermore, when inorganic hydrate particles are used as the first inorganic particles, if their average particle size is too large, it takes some time for the first inorganic particles (inorganic hydrate) near the center of the heat insulating material to reach their thermal decomposition temperature, and the first inorganic particles near the center of the sheet may not be completely thermally decomposed. For this reason, the average secondary particle size of the inorganic hydrate particles is preferably 0.01 μm or more and 200 μm or less, and more preferably 0.05 μm or more and 100 μm or less.

[0165] (Particles made of thermally expandable inorganic material) Examples of thermally expandable inorganic materials include vermiculite, bentonite, mica, and perlite.

[0166] (Particles made of hydrous porous material) Specific examples of the hydrous porous material include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

[0167] (inorganic balloons) The heat insulating material used in the present invention may contain inorganic balloons as the first inorganic particles. When inorganic balloons are contained, convective or conductive heat transfer within the heat insulating material can be suppressed in the temperature range below 500°C, and the heat insulating properties of the heat insulating material can be further improved. As the inorganic balloons, at least one selected from shirasu balloons, silica balloons, fly ash balloons, barite balloons, and glass balloons can be used.

[0168] (Inorganic balloon content: 60% or less by mass of the total mass of the insulation material) The content of the inorganic balloons is preferably 60 mass % or less based on the total mass of the heat insulating material.

[0169] (Average particle size of inorganic balloons: 1 μm to 100 μm) The average particle size of the inorganic balloons is preferably 1 μm or more and 100 μm or less.

[0170] <Second inorganic particles> When two types of inorganic particles are contained in a heat insulating material, the second inorganic particles are not particularly limited as long as they are different from the first inorganic particles in terms of material, particle size, etc. Examples of the second inorganic particles that can be used include oxide particles, carbide particles, nitride particles, inorganic hydrate particles, silica nanoparticles, metal oxide particles, inorganic balloons such as microporous particles and hollow silica particles, particles made of a thermally expandable inorganic material, and particles made of a hydrous porous body, the details of which are as described above.

[0171] Nanoparticles have extremely low conductive heat transfer and can maintain excellent heat insulation even when compressive stress is applied to the insulating material. Metal oxide particles such as titania are also effective in blocking radiant heat. Furthermore, when large-diameter inorganic particles and small-diameter inorganic particles are used, the small-diameter inorganic particles penetrate into the gaps between the large-diameter inorganic particles, resulting in a denser structure and improving the heat transfer suppression effect. Therefore, when nanoparticles are used as the first inorganic particles, it is preferable to further include second inorganic particles made of a metal oxide that are larger in diameter than the first inorganic particles in the insulating material. Examples of metal oxides include silicon oxide, titanium oxide, aluminum oxide, barium titanate, zinc oxide, zircon, zirconium oxide, etc. In particular, titanium oxide (titania) is a component with a higher refractive index than other metal oxides, and is highly effective in scattering light and blocking radiant heat in a high temperature range of 500°C or higher, so it is most preferable to use titania.

[0172] When the first inorganic particles are at least one type of particles selected from dry silica particles and silica aerogel, and the second inorganic particles are at least one type of particles selected from titania, zircon, zirconia, silicon carbide, zinc oxide, and alumina, the first inorganic particles preferably account for 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more of the total mass of the inorganic particles, in order to obtain excellent heat insulating performance within a temperature range of 300° C. or less. Furthermore, the first inorganic particles preferably account for 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less of the total mass of the inorganic particles.

[0173] On the other hand, in order to obtain excellent heat insulating performance in a temperature range exceeding 300° C., the content of the second inorganic particles is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on the total mass of the inorganic particles. Also, the content of the second inorganic particles is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total mass of the inorganic particles.

[0174] (Average primary particle size of second inorganic particles) When second inorganic particles made of a metal oxide are contained in a thermal insulating material, if the average primary particle size of the second inorganic particles is 1 μm or more and 50 μm or less, radiation heat transfer can be efficiently suppressed in a high temperature range of 500° C. or more. The average primary particle size of the second inorganic particles is more preferably 5 μm or more and 30 μm or less, and most preferably 10 μm or less.

[0175] (Inorganic particle content) In this embodiment, if the total content of the inorganic particles 4 in the heat insulating material is appropriately controlled, the heat insulating property of the heat insulating material can be sufficiently ensured. The total content of the inorganic particles 4 is preferably 60% by mass or more, and more preferably 70% by mass or more, based on the total mass of the thermal insulation material. If the total content of the inorganic particles 4 is too high, the content of the organic fibers will relatively decrease, so in order to sufficiently obtain the skeleton reinforcing effect and the inorganic particle retention effect, the total content of the inorganic particles 4 is preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total mass of the thermal insulation material.

[0176] The content of the inorganic particles 4 in the heat insulating material can be calculated, for example, by heating the heat insulating material at 800° C., decomposing the organic components, and then measuring the mass of the remaining portion.

[0177] <Organic fiber> The organic fiber 1 provides flexibility to the thermal insulation material, and by welding the inorganic particles 4 and other organic fibers 1 to its surface, it has the effect of maintaining the strength and shape of the sheet. While single-component organic fibers can be used as the organic fiber 1 material in the thermal insulation material, it is preferable to use a binder fiber with a core-sheath structure. The binder fiber with a core-sheath structure has a core extending in the longitudinal direction of the fiber and a sheath formed to cover the outer surface of the core. The core is made of a first organic material, and the sheath is made of a second organic material, and the melting point of the first organic material is higher than that of the second organic material. When the binder fiber with a core-sheath structure is used as a material, the core in the thermal insulation material corresponds to the organic fiber 1. Furthermore, during the manufacturing of the thermal insulation material, the second organic material constituting the sheath melts and then solidifies again, so that the sheath becomes the welded portion 5 in the thermal insulation material.

[0178] (organic fiber content) In this embodiment, if the content of the organic fiber 1 in the heat insulating material is appropriately controlled, the skeleton can be sufficiently reinforced. The content of organic fiber 1 is preferably 2% by mass or more, and more preferably 4% by mass or more, based on the total mass of the thermal insulation material. If the content of organic fiber 1 is too high, the content of inorganic particles 4 will relatively decrease, so in order to obtain the desired thermal insulation performance, the content of organic fiber is preferably 10% by mass or less, and more preferably 8% by mass or less, based on the total mass of the thermal insulation material.

[0179] (fiber length of organic fiber) The fiber length of the organic fibers 1 is not particularly limited, but from the viewpoint of ensuring moldability and processability, it is preferable that the average fiber length of the organic fibers be 10 mm or less. On the other hand, from the viewpoint of making the organic fibers 1 function as a skeleton and ensuring the compressive strength of the heat insulating material, it is preferable that the average fiber length of the organic fibers 1 is 0.5 mm or more.

[0180] (binder fiber) When binder fibers having a core-sheath structure are used as the material for the organic fibers 1, the melting point of the first organic material constituting the core, i.e., the organic fibers 1, is not particularly limited as long as it is higher than the melting point of the second organic material constituting the sheath, i.e., the second organic material, present on the outer surface of the organic fibers 1. Binder fibers 3 having such a core-sheath structure are generally commercially available, and the materials constituting the core and sheath may be the same or different. Examples of binder fibers in which the core (first organic material) and sheath (second organic material) are made of the same material but have different melting points include those in which the core and sheath are made of polyethylene terephthalate, polypropylene, or nylon. Examples of binder fibers in which the core and sheath are made of different materials include those in which the core is made of polyethylene terephthalate and the sheath is made of polyethylene, and those in which the core is made of polypropylene and the sheath is made of polyethylene.

[0181] The melting point of the second organic material is preferably 90° C. or higher, and more preferably 100° C. or higher. The melting point of the second organic material is preferably 150° C. or lower, and more preferably 130° C. or lower.

[0182] If the melting point of the first organic material constituting the core is sufficiently higher than that of the second organic material constituting the sheath, the heating temperature setting margin in the heating step can be expanded, making it easier to set the temperature to obtain the desired structure. For example, the melting point of the first organic material is preferably 60°C or more higher than that of the second organic material, more preferably 70°C or more higher, and even more preferably 80°C or more higher.

[0183] When binder fibers with a core-sheath structure are used as the material for the thermal insulation, the sheath can be melted while leaving the core when the material mixture is heated during the production of the thermal insulation. After cooling, the outer surface of the core (organic fiber 1) is covered with a second organic material containing inorganic particles 4, thereby holding the inorganic particles 4 in place. The organic fiber 1 with the inorganic particles 4 fused to it appears to have a thicker fiber diameter, resulting in a strength greater than that of the organic fiber 1 alone. Furthermore, because the binder fibers are present in an irregular orientation in the mixture, the organic fibers 1 are fused to each other in the areas where the binder fibers are in contact with each other, forming a three-dimensional skeleton. As a result, the overall shape of the thermal insulation can be maintained with even greater strength.

[0184] Even when organic fibers without a core-sheath structure are used as binder fibers, it is possible to melt only the surface of the organic fibers while leaving the center of the organic fibers, thereby coating the surface with inorganic particles or fusing the organic fibers together, depending on the temperature setting. However, when manufacturing a heat insulating material, it is common to heat from one or both sides perpendicular to the thickness direction, and because a material with high heat insulating performance is used, strict temperature control is required to raise the temperature to the same level on the surface side and the center side in the thickness direction of the sheet.

[0185] In contrast, if binder fibers with a sheath-core structure in which the melting point of the first organic material constituting the core is higher than the melting point of the second organic material constituting the sheath are used, it is extremely easy to set the temperature to melt the sheath while leaving the core intact. As a result, the resulting insulating material has an ideal structure in which the organic fibers 1 are fused together on both the surface and center to form a skeleton that maintains the strength of the sheet, and fused portions 5 containing inorganic particles 4 are formed on the surfaces of the organic fibers 1. Therefore, it is preferable to use binder fibers with the above-mentioned sheath-core structure as a material for insulating materials.

[0186] In this embodiment, the melting point of the second organic material constituting the sheath of the binder fiber 3 refers to the melting temperature at which the second organic material begins to melt and deform, but softening accompanied by a change in shape is also considered to be a type of melting deformation. The melting point of the sheath of the binder fiber can be measured, for example, by the following method. The binder fiber to be measured is placed in contact with a glass fiber having a higher melting point, and is heated from room temperature to, for example, 200°C at a temperature increase rate of 5°C / min, and then cooled to room temperature. If the surface of the binder fiber melts and deforms, and the area in contact with the glass fiber is fused, or if the cross-sectional shape of the binder fiber changes, it can be determined that the melting point of the second organic material constituting the sheath is 200°C or lower. In this embodiment, the heating temperature is varied and the fusion state between the binder fiber and the glass fiber or the cross-sectional shape of the binder fiber after cooling is observed using the above method, thereby identifying the melting point of the second organic material constituting the sheath.

[0187] (Binder fiber content) In this embodiment, when binder fibers 3 having a core-sheath structure are used as the material, if the content of binder fibers in the mixture is appropriately controlled, the skeleton of the resulting insulating material can be sufficiently reinforced. The content of the binder fibers 3 is preferably 5% by mass or more, and more preferably 10% by mass or more, based on the total mass of the mixture. If the content of the binder fibers 3 is too high, the content of the inorganic particles 4 will relatively decrease. Therefore, in order to obtain the desired heat insulating performance, the content of the binder fibers 3 is preferably 25% by mass or less, and more preferably 20% by mass or less, based on the total mass of the mixture.

[0188] <Inorganic fibers> A single inorganic fiber may be used, or two or more types of inorganic fibers may be used in combination as the inorganic fiber 15. Examples of inorganic fibers include ceramic fibers such as silica fiber, alumina fiber, alumina silicate fiber, zirconia fiber, carbon fiber, soluble fiber, refractory ceramic fiber, aerogel composite material, magnesium silicate fiber, alkaline earth silicate fiber, potassium titanate fiber, silicon carbide fiber, and potassium titanate whisker fiber, glass fibers such as glass fiber, glass wool, and slag wool, and mineral fibers other than these fibers, such as rock wool, basalt fiber, wollastonite, and mullite fiber. These inorganic fibers are preferred in terms of heat resistance, strength, availability, etc. Among the inorganic fibers, silica-alumina fibers, alumina fibers, silica fibers, rock wool, alkaline earth silicate fibers, and glass fibers are particularly preferred in terms of ease of handling.

[0189] The cross-sectional shape of the inorganic fiber is not particularly limited, and examples thereof include a circular cross section, a flat cross section, a hollow cross section, a polygonal cross section, a core cross section, etc. Among these, modified cross section fibers having a hollow cross section, a flat cross section, or a polygonal cross section are preferably used because they have slightly improved heat insulation properties.

[0190] The preferred lower limit of the average fiber length of the inorganic fibers is 0.1 mm, more preferably 0.5 mm. Meanwhile, the preferred upper limit of the average fiber length of the inorganic fibers is 50 mm, more preferably 10 mm. If the average fiber length of the inorganic fibers is less than 0.1 mm, the inorganic fibers are less likely to intertwine with each other, which may reduce the mechanical strength of the insulating material. Meanwhile, if the average fiber length exceeds 50 mm, although a reinforcing effect is obtained, the inorganic fibers may not be able to intertwine tightly with each other, or may curl up with a single inorganic fiber, which may result in continuous voids and reduce the insulating properties.

[0191] The preferred lower limit of the average fiber diameter of the inorganic fibers is 1 μm, more preferably 2 μm, and even more preferably 3 μm. On the other hand, the preferred upper limit of the average fiber diameter of the inorganic fibers is 15 μm, and more preferably 10 μm. If the average fiber diameter of the inorganic fibers is less than 1 μm, the mechanical strength of the inorganic fibers themselves may be reduced. Furthermore, from the viewpoint of the effects on human health, the average fiber diameter of the inorganic fibers is preferably 3 μm or more. On the other hand, if the average fiber diameter of the inorganic fibers is greater than 15 μm, solid heat transfer through the inorganic fibers may increase, leading to a decrease in thermal insulation properties, and the moldability and strength of the thermal insulation material may be deteriorated.

[0192] (Inorganic fiber content) In this embodiment, when the heat insulating material contains inorganic fibers, the content of the inorganic fibers is preferably 3 mass % or more and 15 mass % or less relative to the total mass of the heat insulating material.

[0193] Furthermore, the content of inorganic fibers is more preferably 5% by mass or more and 10% by mass or less of the total mass of the thermal insulating material. By setting the content in this range, the shape retention, compressive force resistance, wind pressure resistance, and inorganic particle retention ability of the inorganic fibers are exhibited in a balanced manner. Furthermore, by appropriately controlling the content of inorganic fibers, the organic fibers 1 and the inorganic fibers are entangled with each other to form a three-dimensional network, which further improves the retention effect of the inorganic particles 4 and other compounding materials described below.

[0194] <Hot melt powder> In this embodiment, the insulating material may contain hot melt powder as a binder material in addition to the organic fibers 1 and inorganic particles 4. The hot melt powder is a powder that contains, for example, a third organic material different from the first and second organic materials and has the property of melting when heated. When the hot melt powder is added to the mixture used to manufacture the insulating material and heated, the hot melt powder melts, and when cooled, it hardens in a state that includes the surrounding inorganic particles 4. This further prevents the inorganic particles 4 from falling off from the insulating material.

[0195] Hot melt powders with various melting points can be used. A hot melt powder with an appropriate melting point can be selected based on the melting points of the core and sheath of the binder fiber used. Specifically, if the third organic material constituting the hot melt powder has a melting point lower than that of the first organic material constituting the organic fiber, the heating temperature can be set to melt the sheath and hot melt powder while leaving the core. For example, if the melting point of the hot melt powder is lower than that of the sheath, the heating temperature during production can be set between the melting points of the core and the sheath, making it even easier to set the heating temperature.

[0196] Alternatively, the type of hot melt powder used can be selected so that its melting point is between the melting points of the core and sheath. When a hot melt powder with such a melting point is used, the sheath and hot melt powder melt together, and then when they cool and harden, the organic fibers (core) 1, the molten sheath around them, and the hot melt powder present in the gaps between the inorganic particles 4 harden first. As a result, the position of the organic fibers 1 can be fixed, and then the molten sheath will fuse to the organic fibers, facilitating the formation of a three-dimensional skeleton. This further improves the strength of the entire sheet.

[0197] If the melting point of the third organic material constituting the hot melt powder is sufficiently lower than that of the first organic material constituting the core, the heating temperature setting latitude in the heating step can be expanded, making it easier to set the temperature to obtain the desired structure. For example, the melting point of the first organic material is preferably 60°C or more higher than that of the third organic material, more preferably 70°C or more higher, and even more preferably 80°C or more higher.

[0198] The melting point of the hot melt powder (third organic material) is preferably 80° C. or higher, and more preferably 90° C. or higher. The melting point of the hot melt powder (third organic material) is preferably 180° C. or lower, and more preferably 150° C. or lower. Components constituting the hot melt powder include polyethylene, polyester, polyamide, and ethylene vinyl acetate.

[0199] (Hot melt powder content) When hot-melt powder is added to the mixture to prevent the inorganic particles from falling off, even a small amount of hot-melt powder can be effective in preventing the particles from falling off. Therefore, the hot-melt powder content is preferably 0.5% by mass or more, and more preferably 1% by mass or more, based on the total mass of the mixture. On the other hand, when the content of the hot melt powder is increased, the content of the inorganic particles 4 and the like is relatively decreased, so in order to obtain the desired heat insulating performance, the content of the hot melt powder is preferably 5 mass% or less, and more preferably 4 mass% or less, relative to the total mass of the mixture.

[0200] <Other compounding materials> The heat insulating material may further contain binders, colorants, etc., as needed. These are all useful for reinforcing the heat insulating material and improving its formability, and the total amount of these additives is preferably 10 mass % or less based on the total mass of the heat insulating material.

[0201] <Insulating material manufacturing method> The method for manufacturing the heat insulating material will be described in detail below, particularly taking the method for manufacturing the heat insulating material of structural example S2 as an example. For example, binder fibers (not shown) having a core-sheath structure, inorganic particles 4, and inorganic fibers 15 are put into a mixer such as a V-type mixer in a predetermined ratio to prepare a mixture. As mentioned above, it is preferable to use a core-sheath fiber as the binder fiber, which has a core made of a first organic material and a sheath made of a second organic material, where the melting point of the first organic material is higher than that of the second organic material.

[0202] The resulting mixture is then placed in a mold and pressurized with a press or the like, and the resulting molded body is heated to melt the sheath of the binder fiber. The heated molded body is then cooled, and the second organic material constituting the molten sheath and the inorganic particles 4 present around the binder fiber are fused to the core (organic fiber 1), and the binder fibers are also fused to each other in the areas where they were in contact with each other. This allows for the production of a sheet-shaped insulating material 40.

[0203] The heat insulating material 10 that does not contain the inorganic fibers 15 can also be obtained by the same manufacturing method as the heat insulating material 40, and the use of the inorganic fibers 15 can be selected arbitrarily.

[0204] When the materials for the heat insulating material are mixed and then pressurized and heated, the entangled organic fibers 1 exposed on the surface are heated and formed as a fiber layer 11 on the surface of the heat insulating material 40. The fiber layer 11 thus obtained improves the strength of the heat insulating material 40 and also has the effect of mitigating impacts on the surface of the heat insulating material 40.

[0205] (Heating conditions) When a core-sheath binder fiber is used as the material for the thermal insulation material, the heating temperature in the heating step is preferably higher than the melting point of the second organic material constituting the sheath and lower than the melting point of the first organic material constituting the core. By setting such a heating temperature, as described above, the strength of the sheet can be ensured by the core on both the surface side and the center side of the sheet, and the inorganic particles 4 can be held in place by the fused parts 5.

[0206] Specifically, the heating temperature in the heating step is preferably set to be 10°C or more higher, more preferably 20°C or more higher, than the melting point of the second organic material constituting the sheath, while the heating temperature is preferably set to be 10°C or more lower, more preferably 20°C or more lower, than the melting point of the first organic material constituting the core.

[0207] The heating time is not particularly limited, but it is preferable to set the heating time so that the sheath can be sufficiently melted, for example, from 3 minutes to 15 minutes.

[0208] When the insulating material contains a hot melt powder, the heating temperature in the heating step is preferably set to be at least 10°C higher, and more preferably at least 20°C higher, than the higher of the melting point of the second organic material constituting the sheath and the melting point of the third organic material constituting the hot melt powder. Meanwhile, the heating temperature is preferably set to be at least 10°C lower, and more preferably at least 20°C lower, than the melting point of the first organic material constituting the core. Setting the heating temperature at this level allows for the formation of a strong skeleton, further improving the strength of the sheet, and preventing the inorganic particles 4 from falling off due to the welded portions 5, etc.

[0209] As described above, the insulating material may be manufactured by either a dry method or a wet method, but the dry method is preferred. When using the dry method, inorganic particles 4 suitable for the dry method are used, and a solvent such as water, which is required when forming by a wet method, is not added to the mixture. However, to prevent powder such as inorganic particles 4 from flying around during the manufacturing of the insulating material and making the raw materials difficult to handle, a small amount of solvent such as water can be added within the range required for the dry method. For example, adding a small amount of solvent such as water to the mixture can suppress the scattering of inorganic particles during manufacturing.

[0210] <Adhesive> In this embodiment, the joining surfaces 61 of the two thermal insulating materials can be bonded together using an adhesive or the like. The adhesive for bonding the joining surfaces 61 is not particularly limited, and a commonly used adhesive can be used, but it is preferable to use a flame-retardant adhesive. Specifically, the flame-retardant inorganic adhesive can be a heat-curing, heat-resistant inorganic adhesive whose main components are a fire-resistant ceramic such as alumina and an inorganic polymer. The flame-retardant organic adhesive can be an adhesive containing a halogen-based, phosphorus-based, silicone-based, or nitrogen-based flame-retardant material. It is also effective to use the flame-retardant inorganic adhesive in combination with a flame-retardant organic adhesive. By using an adhesive, the adhesive can penetrate into the pores in the joining surfaces 61 of the two thermal insulating materials, thereby more firmly bonding them together.

[0211] <Thickness of heat transfer suppression sheet> The thickness of the heat-transfer-suppressing sheet according to this embodiment is generally the same as that of the heat insulating material and is not particularly limited, but is preferably 0.05 mm or more and 10 mm or less. A thickness of 0.05 mm or more ensures sufficient compressive strength. On the other hand, a thickness of 10 mm or less ensures good heat insulating properties of the heat-transfer-suppressing sheet.

[0212] [Battery pack] An example of a battery pack using a heat-transfer-suppressing sheet 50 according to an embodiment of the present invention is shown in FIG. 3 above. The configuration and effects of the battery pack will now be described in detail with reference to FIG. 3. As mentioned above, the heat-transfer-suppressing sheet 50 shown in FIG. 3 can be replaced with heat-transfer-suppressing sheets 52, 53, and 54 having other structures, as well as with heat-transfer-suppressing sheets having other structures within the scope of the present invention. Furthermore, the heat insulating material 10 can be replaced with other heat insulating materials within the scope of the present invention, in addition to the heat insulating materials having the various structures described above.

[0213] 3, the battery pack 100 includes a plurality of battery cells 20a, 20b, and 20c and a heat-transfer-reducing sheet 50 according to the present embodiment, with the plurality of battery cells connected in series or parallel. For example, the heat-transfer-reducing sheet 50 according to the present embodiment is interposed between the battery cells 20a and 20b, and between the battery cells 20b and 20c. The battery cells 20a, 20b, and 20c and the heat-transfer-reducing sheet 50 are housed in a battery case 30. The heat transfer suppressing sheet 50 is as described above.

[0214] In the battery pack 100 configured in this manner, because the heat-transfer-suppressing sheet has high thermal insulation properties, even if a certain battery cell 20a becomes hot, the heat-transfer-suppressing sheet 50, which has a heat-transfer-suppressing effect, is present between the battery cell 20a and the battery cell 20b, thereby suppressing the transfer of heat to the battery cell 20b and preventing thermal runaway of the battery cells. Furthermore, because the battery pack according to this embodiment has a heat-transfer-suppressing sheet in which multiple thermal insulators are bonded together and in which a decrease in thermal insulation properties is suppressed at the bonded surfaces, it can flexibly accommodate various sizes of battery cells 20a, 20b, and 20c and can provide desired thermal insulation in desired areas.

[0215] The battery pack 100 of this embodiment is not limited to the battery pack illustrated in Fig. 3. For example, the heat transfer-suppressing sheet 50 may be disposed not only between the battery cells 20a and 20b and between the battery cells 20b and 20c, but also between the battery cells 20a, 20b, and 20c and the battery case 30, or may be attached to the inner surface of the battery case 30.

[0216] In the battery pack 100 configured in this manner, if a battery cell catches fire, it is possible to prevent the flame from spreading outside the battery case 30. For example, the battery pack 100 according to this embodiment may be used in an electric vehicle (EV) or the like and placed under the floor of a passenger compartment. In this case, even if a battery cell catches fire, the safety of the passengers can be ensured. Furthermore, the heat-transfer-suppressing sheet 50 can be disposed not only between the battery cells but also between the battery cells 20a, 20b, 20c and the battery case 30. The size and heat insulating performance of the heat-transfer-suppressing sheet according to this embodiment can be freely designed and it can be easily manufactured, so it can also be suitably used in places other than between the battery cells.

[0217] In the battery pack of this embodiment, the heat-transfer-suppressing sheet 50 disposed between the battery cells 20a, 20b, and 20c and the battery case 30 may be in contact with the battery cells or may have gaps between them. If gaps are undesirable, a thicker insulating material may be combined in areas where gaps are likely to occur than in other areas. In particular, when the battery cells 20a, 20b, and 20c are large, there is a variation in the contact between the battery cells 20a, 20b, and 20c and the heat-transfer-suppressing sheet 50 in some areas and not in other areas. Therefore, according to this embodiment, not only the insulating performance of the insulating material but also various characteristics such as thickness and elasticity can be combined to form a single heat-transfer-suppressing sheet that meets various requirements, thereby obtaining a battery pack with even better characteristics.

[0218] As described above, the heat transfer-suppressing sheet according to this embodiment can be manufactured into various shapes depending on the manufacturing method. Therefore, it can be adapted to any shape, regardless of the shapes of the battery cells 20a, 20b, 20c and the battery case 30. Specifically, it can be applied to cylindrical batteries, flat batteries, etc., in addition to prismatic batteries. [Explanation of symbols]

[0219] 1. Organic Fiber 3. Binder Fiber 4 Inorganic particles 5 Welded area 9,10,40,60,70,80,90,110 Insulation 9e 2nd connecting surface 10c Connecting surface 10e 1st connection surface 11 Fiber layer 12 composite layers 13 Base layer 14. Matrix 15 Inorganic fibers 16 Fiber section 20a, 20b, 20c battery cells 30 Battery case 32 Base 33 branches 42 First area 43 Second area 50, 52, 53, 54 Heat transfer suppression sheet 61 Bonding surface 62 Heat transfer blocking section 63a First end 63b Second end 65 Convex part 66 Concave part 100 battery packs

Claims

1. A heat transfer-suppressing sheet formed by bonding a plurality of heat insulating materials containing inorganic particles, The heat insulating material has a pair of main surfaces and a connecting surface connecting the pair of main surfaces, The connecting surfaces of the plurality of heat insulating materials are arranged opposite to each other, and a connecting surface that connects the heat insulating materials to each other is formed, In a cross-sectional view perpendicular to the pair of main surfaces and parallel to the direction in which the thermal insulating materials are adjacent to each other, When an end portion of the joining surface on one main surface side is defined as a first end portion and an end portion of the joining surface on the other main surface side is defined as a second end portion, the joining surface has a heat transfer prevention portion between the first end portion and the second end portion, The heat transfer suppressing sheet, wherein the heat transfer blocking portion is located at a position offset from at least one of the first end portion and the second end portion in a direction parallel to the main surface.

2. The heat transfer suppressing sheet according to claim 1 , wherein, in the cross-sectional view, the heat transfer blocking portion has a region that extends in a direction different from a thickness direction of the heat insulating material.

3. 3. The heat transfer suppressing sheet according to claim 2, wherein, in the cross-sectional view, the heat transfer blocking portion has a region that forms an angle of 20° to 160° with respect to the thickness direction of the heat insulating material.

4. The heat transfer suppressing sheet according to claim 1 , wherein, in the cross-sectional view, the first end portion is positioned offset in a direction parallel to the main surface with respect to the second end portion.

5. In the cross-sectional view, the first end and the second end are located symmetrically in a thickness direction of the thermal insulation material, The heat transfer suppression sheet of claim 1, characterized in that, of the adjacent insulating materials, the connecting surface of one insulating material has a convex portion, and the connecting surface of the other insulating material has a concave portion shaped to fit into the convex portion, and the adjacent insulating materials are joined by the convex portion and the concave portion fitting together.

6. The heat transfer suppression sheet of claim 1, characterized in that when the density of the insulating material in the region including the heat transfer prevention portion in the thickness direction of the insulating material is M1 and the density of the insulating material in the region not including the heat transfer prevention portion in the thickness direction is M2, the ratio of the density M1 to the density M2 (M1 / M2) is 1.2 or more.

7. The heat transfer suppressing sheet according to claim 1 , wherein the heat insulating material comprises organic fibers.

8. The heat transfer-suppressing sheet according to claim 1 , wherein the connecting surfaces of the adjacent heat insulating materials that make up the connecting surface are bonded together in at least a partial region of the connecting surface.

9. The heat transfer-suppressing sheet according to claim 1 , wherein the connecting surfaces of the adjacent insulating materials that form the connecting surface are thermally fused together in at least a partial region of the connecting surface.

10. A method for producing the heat transfer-suppressing sheet according to any one of claims 1 to 7, comprising: a first processing step of processing an end surface of one of the two insulating materials to be joined together so that at least a portion of the end surface of the one of the insulating materials extends in a direction different from the thickness direction of the insulating material, thereby forming a first connecting surface; a second processing step of processing the end surface of the other of the two insulating materials to be joined together so that the end surface of the other insulating material is shaped to follow the first connecting surface of the one insulating material, thereby creating a second connecting surface; a bonding surface forming process for forming the bonding surface by arranging the first connecting surface and the second connecting surface opposite each other, and forming the bonding surface by joining the first connecting surface and the second connecting surface.

11. The method for manufacturing a heat transfer-suppressing sheet according to claim 10, wherein in the bonding surface forming step, at least a part of the bonding surface is bonded with an adhesive.

12. 11. The method for manufacturing a heat transfer suppressing sheet according to claim 10, wherein in the joining surface forming step, the first joining surface and the second joining surface are heated while being pressed in a direction to bring them closer to each other, and at least a portion between the first joining surface and the second joining surface is fused by thermal fusion.

13. A method for producing the heat transfer-suppressing sheet according to any one of claims 1 to 7, comprising: an arrangement step of arranging the two sheets of insulating material to be joined together such that a portion of a main surface of one insulating material overlaps a portion of a main surface of the other insulating material; A method for manufacturing a heat transfer suppression sheet, characterized by comprising: a bonding surface formation process in which the area where the two insulating materials overlap is pressed in the thickness direction of the two insulating materials to form a bonding surface in which a portion of the main surface of one insulating material is bonded to a portion of the main surface of the other insulating material.

14. The method for manufacturing a heat transfer-suppressing sheet according to claim 13, wherein in the bonding surface forming step, at least a part of the bonding surface is bonded with an adhesive.

15. 14. The method for manufacturing a heat transfer suppressing sheet according to claim 13, characterized in that in the bonding surface forming process, the area where the two insulating materials overlap is heated while being pressed in the thickness direction of the area, and a portion of the main surface of one insulating material and a portion of the main surface of the other insulating material are fused by thermal fusion.

16. 10. A battery pack comprising a plurality of battery cells and the heat transfer-suppressing sheet according to claim 1, the plurality of battery cells being connected in series or in parallel.

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