Heat transfer suppression sheet and battery pack

Abstract

Provided are: a heat transfer suppression sheet capable of further suppressing propagation of heat between battery cells when an abnormality occurs and capable of suppressing destruction of a battery case and reduction in battery performance due to deformation of a battery cell; and a battery pack that can be easily designed and assembled and that is capable of suppressing the destruction of the battery case and the reduction in the battery performance while suppressing the propagation of heat between the battery cells. A heat transfer suppression sheet (50) has: a heat insulating material (10) that has inorganic particles (4) and organic fibers (1) or inorganic fibers (15); and an elastic sheet (51) laminated on at least one of a first surface (10a) and a second surface (10b), which are orthogonal to the thickness direction of the heat insulating material (10). A battery pack (100) includes: a plurality of battery cells (20a, 20b, 20c); and the heat transfer suppression sheet (50). The plurality of battery cells (20a, 20b, 20c) are connected in series or in parallel.

Description

Heat transfer suppression sheet and assembled battery

[0001] The present invention relates to a heat transfer-suppressing sheet and a battery pack including the heat transfer-suppressing sheet.

[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] As a countermeasure against the occurrence of thermal runaway, for example, Patent Document 1 proposes a battery pack that can prevent or suppress the spread of fire to adjacent battery cells when abnormal heat generation occurs due to an overcurrent flowing into a battery cell. The battery pack described in Patent Document 1 is composed of multiple battery cells and a block made of a metal material that holds the battery cells, and this block is composed of multiple small blocks. In addition, the size of the gap between the block and the battery cells is adjusted.

[0005] In the battery pack described in Patent Document 1, which is configured in this manner, the blocks that hold the battery cells are made of a metal material, and therefore, it is said that heat can be quickly diffused.

[0006] Furthermore, Patent Document 2 discloses a battery pack that aims to improve the heat dissipation of secondary batteries and prevent performance degradation. The battery pack described in Patent Document 2 houses multiple secondary batteries in a case, and a plate-shaped rubber sheet that has a thermal conductivity equal to or greater than a predetermined value and changes shape when pressure is applied is disposed between the multiple secondary batteries and the case.

[0007] According to Patent Document 2, the rubber sheet has a relatively high thermal conductivity, which allows heat from the secondary battery to be efficiently discharged through the case. In addition, the rubber sheet has elasticity, which prevents damage to the battery pack when it is dropped.

[0008] Japanese Patent Publication No. 2014-96271 Japanese Patent Publication No. 2004-146161

[0009] When thermal runaway occurs in a battery cell, gas is generated inside the battery, causing an increase in internal pressure, which causes deformation of the battery cell. If this deformation is significant, the case may be destroyed. Such battery cell deformation occurs slightly even when the assembled battery cells are subjected to charge / discharge cycles (i.e., during "normal use"). When the internal pressure of the battery cell repeatedly increases and decreases during charge / discharge, the case repeatedly presses and releases pressure on the battery cell, causing a decrease in battery performance.

[0010] The battery pack disclosed in Patent Document 1 uses blocks that hold battery cells and are made of metal, allowing for quick heat dissipation. However, the battery pack does not take into consideration the risk of battery case damage or battery performance degradation due to battery cell deformation. Furthermore, the battery pack described in Patent Document 1 requires multiple blocks, and the gaps between the blocks and the battery cells vary, requiring block design depending on the electronic device, power tool, or other device in which the battery pack is installed. This poses the problem of complex block design and battery pack assembly.

[0011] Furthermore, the battery pack described in Patent Document 2 does not take into consideration how to prevent thermal runaway in adjacent battery cells when thermal runaway occurs in one battery cell.

[0012] The present invention has been made in view of the above-mentioned problems, and aims to provide a heat transfer suppression sheet that can further suppress the propagation of heat between battery cells in the event of an abnormality and can suppress the destruction of the battery case and the deterioration of battery performance due to deformation of the battery cells, and an assembled battery that can suppress the propagation of heat between battery cells while suppressing the destruction of the battery case and the deterioration of battery performance, and that is easy to design and assemble.

[0013] The above object of the present invention is achieved by the heat transfer-suppressing sheet having the following configuration [1].

[0014] [1] A heat transfer-suppressing sheet comprising: a heat insulating material having inorganic particles and organic or inorganic fibers; and an elastic sheet laminated on at least one of a first surface and a second surface of the heat insulating material that are perpendicular to the thickness direction.

[0015] Furthermore, preferred embodiments of the present invention relating to the heat transfer-suppressing sheet relate to the following [2] to

[14] .

[0016] [2] The heat-transfer-suppressing sheet according to [1], wherein the heat insulating material has a plurality of pores that are three-dimensionally connected.

[0017] [3] The heat transfer-suppressing sheet according to [1] or [2], wherein, when the heat insulating material contains organic fibers, the organic fibers have welded portions covering at least a portion of a surface thereof, and at least a portion of the inorganic particles are welded to the organic fibers by the welded portions.

[0018] [4] The heat transfer-suppressing sheet according to [3], wherein in the heat insulating material, the organic fibers are made of a first organic material, the welded portion contains a second organic material, and the melting point of the second organic material is lower than the melting point of the first organic material.

[0019] [5] The heat-transfer-suppressing sheet according to [4], wherein the melting point of the second organic material in the heat insulating material is lower by 60° C. or more than the melting point of the first organic material.

[0020] [6] The heat transfer-suppressing sheet according to [4] or [5], wherein in the heat insulating material, the first organic material is at least one selected from polyethylene terephthalate, polypropylene, and nylon, and the second organic material is at least one selected from polyethylene terephthalate, polyethylene, polypropylene, and nylon.

[0021] [7] The heat-transfer-suppressing sheet according to any one of [1] to [6], wherein the heat insulating material essentially contains the inorganic fibers.

[0022] [8] The heat transfer-suppressing sheet according to [7], wherein the inorganic fibers are at least one selected from silica-alumina fibers, alumina fibers, silica fibers, rock wool, alkaline earth silicate fibers, and glass fibers.

[0023] [9] The heat-transfer-suppressing sheet according to any one of [3] to [6], wherein the heat insulating material has, on at least a portion of the first surface and the second surface, a fiber layer formed by welding at least some of the organic fibers together at the welding portion.

[0024]

[10] The heat transfer-suppressing sheet according to [9], wherein the heat insulating material further comprises inorganic fibers, and the fiber layer contains the inorganic fibers.

[0025]

[11] The heat-transfer-suppressing sheet according to any one of [1] to

[10] , wherein in the heat insulating material, the inorganic particles are particles made of at least one inorganic material selected from oxide particles, carbide particles, nitride particles, and inorganic hydrate particles.

[0026]

[12] The heat transfer-suppressing sheet according to any one of [1] to

[11] , wherein in the heat insulating material, the inorganic particles include at least one type of particles selected from dry silica particles and silica aerogel.

[0027]

[13] The heat transfer-suppressing sheet according to

[12] , wherein in the heat insulating material, the inorganic particles further include at least one type of particles selected from titania, zircon, zirconia, silicon carbide, zinc oxide, and alumina.

[0028]

[14] The heat transfer-suppressing sheet according to any one of [1] to

[13] , further comprising a resin film enclosing a laminate having the heat insulating material and the elastic sheet, the resin film having a plurality of holes and comprising a first-surface-side film and a second-surface-side film arranged on a first surface and a second surface of the laminate perpendicular to the thickness direction of the laminate, and an end-surface-side film arranged on an end surface parallel to the thickness direction of the laminate, wherein the area ratio of the holes in the first-surface-side film and the second-surface-side film to the total area of ​​the first-surface-side film and the second-surface-side film is greater than the area ratio of the holes in the end-surface-side film to the total area of ​​the end-surface-side film.

[0029] The above object of the present invention is also achieved by the following configuration

[15] relating to a battery pack.

[0030]

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

[14] , the plurality of battery cells being connected in series or in parallel.

[0031] The heat transfer-suppressing sheet of the present invention has an insulating material containing inorganic particles and organic or inorganic fibers, and therefore has excellent insulating properties. In addition, because the insulating material is laminated with an elastic sheet, the elastic sheet absorbs deformation of the battery cell, preventing breakage of the battery case and deterioration of battery performance.

[0032] As described above, the battery pack of the present invention has a simple structure, has high thermal insulation properties, and includes a heat transfer suppression sheet that can suppress destruction of the battery case and deterioration of battery performance. Therefore, it is possible to obtain a battery pack that is easy to design and assemble, and can suppress thermal runaway of the battery cells in the battery pack and the spread of flames to the outside of the battery case.

[0033] FIG. 1A is a schematic cross-sectional view showing a heat-transfer-suppressing sheet according to a first embodiment of the present invention. FIG. 1B is a schematic cross-sectional view showing another example of a heat-transfer-suppressing sheet according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a battery pack including a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 3 is a photograph showing a first structural example of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 4 is a photograph showing an enlarged view of a portion of the heat insulating material shown in FIG. 3. FIG. 5 is a photograph showing a second structural example of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 6 is a schematic diagram showing a third structural example of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 7 is a schematic diagram showing an enlarged view of a portion of FIG. 6. FIG. 8 is a photograph showing the heat insulating material shown in FIG. 6. FIG. 9 is a photograph showing a fourth structural example of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 10 is a photograph showing an enlarged view of the structure of the heat insulating material shown in FIG. 9. FIG. 11 is a photograph showing a cross section of the heat insulating material shown in FIG. 9. FIG. 12 is a schematic diagram showing a fifth structural example of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 13 is a schematic diagram showing an enlarged view of portion A of the heat insulating material shown in FIG. 12. FIG. 14 is a photograph, substitute for a drawing, showing a sixth structural example of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 15 is a photograph, substitute for a drawing, showing another region of the heat insulating material shown in FIG. 14. FIG. 16 is a photograph, substitute for a drawing, showing a cross section of the heat insulating material shown in FIGS. 14 and 15. FIG. 17 is a photograph, substitute for a drawing, showing a seventh structural example of a heat insulating material used in a heat-transfer-suppressing sheet according to an embodiment of the present invention. FIG. 18 is a photograph, substitute for a drawing, showing an enlarged view of a portion of the heat insulating material shown in FIG. 17. FIG. 19 is a schematic diagram showing an example of a method for specifying the length of the fiber bundles. FIG. 20 is a photograph, substitute for a drawing, showing another structural example of the heat insulating material shown in FIG. 17. FIG. 21 is a perspective view of a heat-transfer-suppressing sheet according to a second embodiment of the present invention. FIG. 22 is a cross-sectional view of a heat-transfer-suppressing sheet according to the second embodiment of the present invention. FIG. 23A is a top view of a heat-transfer-suppressing sheet according to a third embodiment of the present invention. Fig. 23B is a cross-sectional view of a heat-transfer-suppressing sheet according to a third embodiment of the present invention taken along line II. Fig. 24A is a top view showing a heat-transfer-suppressing sheet according to a fourth embodiment of the present invention.FIG. 24B is a cross-sectional view of a heat-transfer-inhibiting sheet according to a fourth embodiment of the present invention, taken along line II-II. FIG. 25A is a top view of a heat-transfer-inhibiting sheet according to a fifth embodiment of the present invention. FIG. 25B is a cross-sectional view in the thickness direction of a heat-transfer-inhibiting sheet according to the fifth embodiment of the present invention. FIG. 26A is a cross-sectional view in the thickness direction of a heat-transfer-inhibiting sheet according to a sixth embodiment of the present invention. FIG. 26B is a top view of a heat-transfer-inhibiting sheet according to the sixth embodiment of the present invention, viewed from the main surface side. FIG. 27 is a perspective view of a heat-transfer-inhibiting sheet according to a seventh embodiment of the present invention. FIG. 28 is a perspective view of a modified heat-transfer-inhibiting sheet according to the seventh embodiment of the present invention, showing a state below 90°C. FIG. 29 is a cross-sectional view of a modified heat-transfer-inhibiting sheet according to the seventh embodiment of the present invention, showing a state at 90°C or higher. FIG. 30 is a schematic cross-sectional view of a heat-transfer-inhibiting sheet according to an eighth embodiment of the present invention.

[0034] The present inventors conducted extensive research to solve the above-mentioned problems and found that by forming a heat-transfer-suppressing sheet including a heat insulating material containing inorganic particles and organic or inorganic fibers, and an elastic sheet laminated on the heat insulating material, it is possible to suppress the application of unnecessary pressure to the battery cell and to suppress a decrease in battery performance.

[0035] A heat-transfer-suppressing sheet, a manufacturing method thereof, and a battery pack according to an embodiment of the present invention will be described in detail below. Note that the present invention is not limited to the embodiment described below, and can be implemented with any modifications within the scope of the present invention. First, a heat-transfer-suppressing sheet according to an embodiment of the present invention will be described.

[0036] [Heat Transfer-Suppressing Sheet] [First Embodiment] Fig. 1A is a schematic cross-sectional view showing a heat transfer-suppressing sheet according to a first embodiment of the present invention. As shown in Fig. 1A, a heat transfer-suppressing sheet 50 according to the first embodiment includes a heat insulating material 10 and an elastic sheet 51 laminated on a first surface 10a of the heat insulating material 10, the first surface 10a being perpendicular to the thickness direction of the heat insulating material 10. The heat insulating material 10 includes inorganic particles and organic or inorganic fibers (not shown). The heat insulating material 10 will be described in detail later. The elastic sheet 51 is formed by processing an elastic material (described later) into a sheet shape.

[0037] Fig. 1B is a schematic cross-sectional view showing another example of the heat-transfer-suppressing sheet according to the first embodiment of the present invention. The heat-transfer-suppressing sheet 50 shown in Fig. 1B has a thermal insulating material 10 and an elastic sheet 51 laminated on a first surface 10a and a second surface 10b perpendicular to the thickness direction of the thermal insulating material 10. That is, in the heat-transfer-suppressing sheet 50 shown in Fig. 1B, the thermal insulating material 10 is sandwiched between a pair of elastic sheets 51. The thermal insulating material 10 and the elastic sheet 51 are the same as those of the heat-transfer-suppressing sheet 50 shown in Fig. 1A.

[0038] A specific use of the heat-transfer-suppressing sheet 50 shown in Fig. 1B will be described below as an example. As shown in Fig. 2, 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 plurality of battery cells 20a, 20b, and 20c are connected in series or parallel (the connected state is not shown) and housed in a battery case 30 to form a battery pack 100. Note that, while lithium-ion secondary batteries are preferably used as the battery cells 20a, 20b, and 20c, the present invention is not limited thereto and other secondary batteries may also be used.

[0039] The heat transfer-suppressing sheet 50 according to the first embodiment configured as described above includes the insulating material 10 containing inorganic particles and organic or inorganic fibers, thereby achieving excellent thermal insulation. Therefore, for example, when an abnormality occurs in the battery cell 20a and the temperature rises, heat transfer to the battery cell 20b can be sufficiently suppressed. In the embodiment shown in FIG. 1B , an elastic sheet 51 is laminated on the first surface 10a and the second surface 10b of the insulating material 10. The elastic sheet 51 has the effect of suppressing deformation of the battery cells 20a, 20b, and 20c and the effect of absorbing the deformation of the battery cells 20a, 20b, and 20c. In other words, when the battery cells 20a, 20b, and 20c deform during charging / discharging or an abnormality, the elastic sheet 51 flexibly deforms in response to the deformation of the battery cells 20a, 20b, and 20c while suppressing the deformation of the battery cells 20a, 20b, and 20c. Therefore, unnecessary pressure can be suppressed from being applied to the battery cells 20a, 20b, and 20c.

[0040] 1A , even if the elastic sheet 51 is laminated on only one of the first and second surfaces of the thermal insulation material, the presence of the elastic sheet 51 can suppress deformation of the battery cells 20a, 20b, and 20c and can also absorb that deformation. The elastic sheet 51 may also be disposed between a pair of thermal insulation materials 10. In either configuration, the properties of the elastic sheet 51 can be utilized to suppress damage to the battery case and deterioration of battery performance.

[0041] In the first embodiment, the insulating material 10 may be any material that contains inorganic particles and organic fibers or inorganic fibers (i.e., at least one of organic fibers and inorganic fibers), but an example of an insulating material 10 that has even better insulating properties will be described in detail below.

[0042] <Thermal Insulation Material (Structural Example 1)> FIG. 3 is a photograph, substitute for a drawing, showing structural example 1 of a thermal insulation material used in a heat transfer-suppressing sheet according to an embodiment of the present invention, and FIG. 4 is a photograph, substitute for a drawing, showing an enlarged view of a portion of the thermal insulation material shown in FIG. 3 .

[0043] 3 and 4 , the thermal insulation material 10 according to the thermal insulation material (Structural Example 1) includes inorganic particles 4 and organic fibers 1. The thermal insulation material 10 also includes 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.

[0044] The insulating material 10 configured in this manner has multiple three-dimensionally connected pores 7, which provide the effect of air insulation and improve thermal insulation performance. Furthermore, the insulating material 10 contains highly flexible organic fibers 1, which not only enhances the flexibility of the insulating material 10 but also makes it easier for the organic fibers 1 to entangle with each other, thereby improving 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 charging and discharging, the insulating material 10, together with the elastic sheet 51, absorbs the expansion of the battery cells, further suppressing deterioration in battery cell performance.

[0045] Furthermore, in this embodiment, it is preferable that at least some of the pores 7 communicate with the surface of the thermal insulation material 10 and open outward. With the pores 7 configured in this manner, even if the adjacent battery cells 20a, 20b, 20c experience thermal runaway and the thermal insulation material 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, this also has the effect of preventing the sheet from being destroyed.

[0046] Furthermore, when the welded portions 5 on the outer peripheral surfaces 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 insulation material 10, and to prevent a decrease in the thermal insulation effect due to compressive deformation of the thermal insulation material 10.

[0047] In this specification, the welded portion 5 refers to a portion where the surface of the organic fiber 1 melts and then solidifies again, and is formed in the manufacturing process of the thermal insulating material 10, which will be described later. In this embodiment, the inorganic particles 4 are welded to the surface of the organic fiber 1 by the welded portion 5, so that the apparent fiber diameter of the organic fiber 1 becomes larger, which supports the shape of the thermal insulating material 10 and allows for high strength to be obtained.

[0048] The welded portion 5 does not need to completely cover the outer periphery 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, but 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.

[0049] Furthermore, it is preferable that the thermal insulation material 10 according to the thermal insulation material (Structural Example 1) further contains inorganic fibers. The effects obtained by including inorganic fibers will be described in the following "Thermal insulation material (Structural Example 2)".

[0050] <Thermal Insulation (Structural Example 2)> Figure 5 is a photograph showing structural example 2 of a thermal insulator used in the heat-transfer-suppressing sheet according to an embodiment of the present invention. In structural example 2 shown in Figure 5, the same components as those in structural example 1 shown in Figures 3 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the thermal insulator 40 shown in Figure 5 can be used in place of the thermal insulator 10 of the heat-transfer-suppressing sheet 50 shown in Figure 1.

[0051] As shown in Figure 5, the thermal insulation material 40 has inorganic fibers 15. The thermal insulation 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 thermal insulation material 40. The fiber layer 11 is formed by welding at least a portion of a plurality of organic fibers 1 together at welding portions, and is formed in a layer on the surface (first surface and second surface) of the thermal insulation 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 thermal insulation material 40, and extends, for example, in stripes, in a direction approximately parallel to the surface.

[0052] 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.

[0053] In the heat insulating material 40 shown in Fig. 5, 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. 5, the inorganic fibers 15 in the fiber layer 11 cannot be distinguished, and are therefore not shown.

[0054] 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.

[0055] The thermal insulating material 40 configured in this manner contains inorganic fibers 15 that are resistant to decomposition even at high temperatures. Therefore, for example, if a 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 insulating material 40 decompose, the inorganic fibers 15 remain, thereby ensuring that the shape of the thermal insulating material 40 is maintained. Furthermore, the flexible organic fibers 1 easily become entangled with the relatively hard inorganic fibers 15, forming a three-dimensional skeleton between the inorganic fibers 15 and the organic fibers 1, thereby further improving the strength of the thermal insulating material 40. Note that in the "Thermal Insulating Material (Structural Example 2)," the thermal insulating material 40 contains organic fibers 1 in addition to inorganic fibers 15. However, even if the thermal insulating material 40 does not contain organic fibers 1 and only contains inorganic particles 4 and inorganic fibers 15, the above-described effect of the inorganic fibers 15 remaining and the thermal insulating material 40 being able to reliably maintain its shape can be achieved.

[0056] Furthermore, when the heat insulating material 40 contains both organic fibers 1 and inorganic fibers 15, it is particularly preferable because it can simultaneously achieve the effects of "Since it contains organic fibers 1 which have high flexibility, the flexibility of the heat insulating material 10 can be increased and the organic fibers 1 can be easily entangled with each other, thereby improving the sheet strength" and "When the heat transfer suppressing sheet 50 is exposed to high temperatures, even if the organic fibers 1 in the heat insulating material 40 decompose, the inorganic fibers 15 remain, so the shape of the heat insulating material 40 can be reliably maintained."

[0057] 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 since the elastic sheet 51 is laminated on this insulating material 40, the pressure on the base layer 13 can be further reduced.

[0058] Furthermore, when a fiber layer 11 is formed on the surface of the insulation material 40, this fiber layer 11 can absorb the impact given to the insulation material 40, and therefore, even on surfaces where the elastic sheet 51 is not laminated, the effect of preventing the inorganic particles contained in the insulation material 40 from falling off can be obtained.

[0059] <Thermal Insulation (Structural Example 3)> Fig. 6 is a schematic diagram showing structural example 3 of the thermal insulation used in the heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 7 is a schematic diagram showing an enlarged portion of Fig. 6. Fig. 8 is a photograph showing the thermal insulation shown in Fig. 6. In structural example 3 shown in Figs. 6 to 8, the same components as those in structural example 1 shown in Figs. 3 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the thermal insulation 60 shown in Figs. 6 to 8 can be used in place of the thermal insulation 10 of the heat-transfer-suppressing sheet 50 shown in Fig. 1.

[0060] As shown in FIGS. 6 to 8 , the insulating material 60 according to this embodiment includes inorganic particles 4, organic fibers 1 made of a first organic material, and welded portions 5 covering the outer surfaces 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 surface of the core are used as the organic fibers, with the organic fibers 1 corresponding to the core. The welded portions 5 are formed by heating and then cooling the sheath of the binder fibers 3 having a sheath-core structure. Furthermore, as shown in FIG. 8 , 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 molten sheath portions are cooled, adjacent organic fibers 1 are fused to each other at contact portions 31, forming a three-dimensional skeleton.

[0061] 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, the welded portions 5 covering the outer periphery of the organic fibers on both the surface and center sides of the thermal insulation material 60 fix the inorganic particles 4 to the organic fibers 1, thereby suppressing powder shedding. Therefore, for example, if the heat-transfer-suppressing sheet 50 according to this embodiment is disposed between multiple battery cells, excellent thermal insulation performance can be maintained even if the battery cells expand and apply compressive stress or impact to the heat-transfer-suppressing sheet 50.

[0062] Although 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, one possible reason is that the organic fibers 1 and the welded portions 5 form a three-dimensional, strong skeleton, which maintains the shape of the insulating material 60 and thus prevents deformation or compression of the insulating material 60. In addition, since the elastic sheet 51 is laminated on at least one of the first and second surfaces of the insulating material 60, the pressure on the insulating material 60 is reduced, which is also thought to contribute to preventing the inorganic particles 4 from falling off. Note that, regardless of whether the elastic sheet 51 is present on the surface of the insulating material 60, the fiber portion 16 exposed on the surface of the insulating material 60 can absorb impacts applied to the insulating material 60, which is also thought to be a reason why the inorganic particles 4 are retained.

[0063] 8, in the thermal insulation material 60, the welded portion 5 does not need to completely cover the outer periphery 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 the present invention can be fully obtained.

[0064] <Thermal Insulation (Structural Example 4)> Fig. 9 is a photograph substituting a drawing showing structural example 4 of a thermal insulator used in a heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 10 is a photograph substituting a drawing showing an enlarged view of the structure of the thermal insulator shown in Fig. 9. Fig. 11 is a photograph substituting a drawing showing a cross section of the thermal insulator shown in Fig. 9. In structural example 4 shown in Figs. 9 to 11, the same components as those in structural example 1 shown in Figs. 3 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the thermal insulator 70 shown in Figs. 9 to 11 can be used in place of the thermal insulator 10 of the heat-transfer-suppressing sheet 50 shown in Fig. 1.

[0065] 9 and 10 , 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.

[0066] 11, 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 welds 5 (not shown in FIG. 11) to form fiber bundles 6, and voids 8 are formed between the plurality of organic fibers 1 constituting the fiber bundles 6.

[0067] 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 a portion of a plurality of 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 a portion of the fiber layer 11 and a portion of the matrix 14 are mixed. Specifically, the composite layer 12 is a region containing a plurality of organic fibers 1 at least a portion of which are welded to each other by welded portions 5, and inorganic particles 4 welded to the organic fibers 1 by welded portions 5.

[0068] 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.

[0069] In the thermal insulation material 70 configured in this manner, the organic fibers 1 are three-dimensionally oriented in the matrix 14, and 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 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 to each other by the welded portions 5, and this structure serves as a skeleton to support the shape of the thermal insulation material 70, thereby achieving high strength.

[0070] 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.

[0071] 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 the same as that of the heat insulating material 60 of Structural Example 3 above.

[0072] In the heat insulating material 70, 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. Even in such a case, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0073] 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, thereby obtaining the effect of improving the sheet strength.

[0074] Furthermore, the thermal insulation material 70 has a plurality of voids 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 thermal insulation 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 thermal insulation material 70. The voids 8 do not need to be formed in the entire region between the plurality of organic fibers 1; as long as the voids 8 are formed in at least a portion of the regions between the organic fibers 1, the effect of suppressing heat transfer can be obtained.

[0075] 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 that 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.

[0076] <Thermal Insulation (Structural Example 5)> Figure 12 is a schematic diagram showing structural example 5 of the thermal insulation used in the heat-transfer-suppressing sheet according to an embodiment of the present invention, and Figure 13 is a schematic diagram showing an enlarged view of section A of the thermal insulation shown in Figure 12. In structural example 5 shown in Figures 12 and 13, the same components as those in structural example 1 of the thermal insulation shown in Figures 3 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the thermal insulation 80 shown in Figures 12 and 13 can be used in place of the thermal insulation 10 of the heat-transfer-suppressing sheet 50 shown in Figure 1.

[0077] 12 and 13 , 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 around a portion of 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.

[0078] 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.

[0079] In the thermal insulation material 80 configured in this manner, the organic fibers 1 and inorganic fibers 15 are entangled with each other to form a three-dimensional web structure, and this structure serves as a 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.

[0080] Furthermore, because the heat insulating material 80 contains the highly flexible organic fibers 1, the flexibility of the heat insulating material 80 can be increased, and the organic fibers 1 are more likely to become entangled with the inorganic fibers 15 to form a three-dimensional web structure, thereby improving strength. Furthermore, if the heat insulating material 80 contains the inorganic fibers 15, for example, when 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, the shape of the heat transfer-suppressing sheet can be maintained even if the organic fibers 1 are decomposed. 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, a heat transfer-suppressing sheet that has a good balance of both flexibility and strength can be obtained.

[0081] 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 formation of the air layers 28 around the inorganic fibers 15 can suppress heat transfer between the inorganic fibers 15 and the matrix 14. The air layers 28 are formed during the manufacturing process of the thermal insulation material 80, but the air layers 28 do not need to be formed around the entire area around the inorganic fibers 15. The heat transfer suppression effect can be obtained as long as the air layers 28 are formed on at least a portion of the outer surface of the inorganic fibers 15. If the inorganic fibers 15 are uniformly dispersed in the matrix 14, the air layers 28 in the matrix 14 will also be uniformly dispersed and disposed, allowing the thermal insulation material 80 to achieve high, uniform thermal insulation properties.

[0082] Furthermore, in the insulating material 80, the organic fibers 1 have welded portions 5 that cover at least a portion of the surface. 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.

[0083] Similarly, in this embodiment, the welded portions 5 on the outer peripheral surfaces 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 20 a, 20 b, 20 c expands and applies compressive stress or impact to the heat transfer-suppressing sheet, excellent heat insulating performance can be maintained.

[0084] 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 by 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, regardless of whether or not an elastic sheet 51 is present on the surface of the heat insulating material 80, 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.

[0085] In the heat insulating material 80, 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. Even in such a case, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0086] <Thermal Insulation (Structural Example 6)> Figure 14 is a photograph substituting a drawing showing structural example 6 of the thermal insulation used in the heat-transfer-suppressing sheet according to an embodiment of the present invention, and Figure 15 is a photograph substituting a drawing showing another region of the thermal insulation shown in Figure 14. Figure 16 is a photograph substituting a drawing showing a cross section of the thermal insulation shown in Figures 14 and 15. In structural example 6 shown in Figures 14 to 16, the same components as those in structural example 4 of the thermal insulation shown in Figures 9 to 11 are designated by the same reference numerals, and detailed description will be omitted. Note that the thermal insulation 90 shown in Figures 14 to 16 can be used in place of the thermal insulation 10 of the heat-transfer-suppressing sheet 50 shown in Figure 1.

[0087] 14 , 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 including 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.

[0088] 15 also contains organic fibers 1 having a branched structure made up of a base 32 and branches 33 extending from the base 32. The organic fibers 1 shown in Fig. 15 have a base 32 and branches 33 extending from the base 32 in five directions, i.e., directions D1, D2, D3, D4, and D5, and the base 32 is thicker than the multiple branches 33.

[0089] Furthermore, as shown in Figures 14 and 15, 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.

[0090] 16, 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 FIG. 16, the organic fibers 1 can be seen to have a branched structure consisting of a base 32 and branches 33 extending in three directions from the base 32.

[0091] Furthermore, a fiber layer 11 may be formed on at least a portion of the first and second surfaces perpendicular to the thickness direction of the thermal insulation material 90. 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 material 90. Furthermore, a composite layer 12 may be formed between the fiber layer 11 and a base layer 13 containing 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 containing a plurality of organic fibers 1 welded to each other and inorganic particles 4 welded to the organic fibers 1.

[0092] 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.

[0093] 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 to maintain the shape of the thermal insulation material 90. 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 a plurality of 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, and the strength of the thermal insulation material 90 can be significantly improved.

[0094] In the thermal insulating material 90, at least a portion of the organic fibers 1 have a branched structure consisting of a base 32 and branches 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 branches 33 extending from the base 32 in at least three directions. The base 32 and branches 33 will be described in more detail below.

[0095] (Base (Fused Portion)) When binder fibers with a sheath-core structure are used as the material for the thermal insulation material 90, the fused portion is formed by first melting the sheath of the binder fiber by heating and then cooling it in the area where multiple binder fibers are in contact with each other. When binder fibers with a sheath-core structure are used as the material for the thermal insulation material 90, the fused portion contains the second organic material that constitutes the sheath. In this way, when the sheath in the area where multiple binder fibers are in contact is melted by heating in the manufacturing process of the heat transfer-suppressing sheet 50, 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.

[0096] (Branch) The branch 33 extends in at least three directions from the base 32 and has the effect of holding the inorganic particles 4. Furthermore, the base 32 and branch 33 form a skeleton, which can also improve the strength of the heat transfer-suppressing sheet 50. This can achieve a high powder shedding suppression effect. When a core-sheath binder fiber is used as the organic fiber 1, the branch 33 is part of the core-sheath binder fiber and has a core made of a first organic material and a sheath made of a second organic material.

[0097] 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, thereby forming a three-dimensional, strong skeleton.

[0098] In the above-described thermal insulating material 90, the multiple support portions 33 extend from the base portion 32, and these multiple support portions 33 can hold the inorganic particles 4. This, combined with the improved sheet strength due to the formation of a skeleton, provides a high 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, the shape of the thermal insulating material 90 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 90 due to compressive deformation can be prevented.

[0099] 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 effect of the support parts 33 holding the inorganic particles 4 in addition to the same effect as that of the insulating material 60 of Structural Example 3. 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.

[0100] 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.

[0101] 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.

[0102] 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 causes the organic fibers 1 to be 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 region between the plurality of organic fibers 1; as long as the voids 8 are formed in at least a portion of the regions between the organic fibers 1, the effect of suppressing heat transfer can be obtained.

[0103] Furthermore, since the insulating 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 insulating material 90. Therefore, the strength of the insulating material 90 can be improved.

[0104] <Thermal Insulation (Structural Example 7)> Fig. 17 is a photograph, substitute for a drawing, showing structural example 7 of the thermal insulation used in the heat-transfer-suppressing sheet according to an embodiment of the present invention, and Fig. 18 is a photograph, substitute for a drawing, showing an enlarged portion of the thermal insulation shown in Fig. 17. In structural example 7 shown in Figs. 17 and 18, the same components as those in structural example 2 of the thermal insulation shown in Fig. 5 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the thermal insulation 110 shown in Figs. 17 and 18 can be used in place of the thermal insulation 10 of the heat-transfer-suppressing sheet 50 shown in Fig. 1.

[0105] 17 and 18 , the thermal insulation material 110 includes inorganic particles 4 and organic fibers 1. A first region 42 having streak-like fiber bundles 47 made of a plurality of organic fibers 1 and a second region 43 having no fiber bundles 47 are formed on the surface of the thermal insulation material 110. In this specification, the fiber bundles 47 are defined as 10 or more organic fibers 1 intertwined with one another, and extend in streak-like fashion in a direction substantially parallel to the surface of the thermal insulation material 110.

[0106] 18, 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. On the other hand, in the second region 43, although a few organic fibers 1 are observed in some places, 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 the island portion, is formed so as to be surrounded by the first region 42, which corresponds to the sea portion.

[0107] In the thermal insulation material 110, fiber bundles 47 formed by intertwining organic fibers 1 are present on the surface of the thermal insulation material 110 in a streak-like manner, thereby improving the strength of the thermal insulation 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, thereby improving the flexibility of the thermal insulation material 110. Furthermore, because the fiber bundles 47 are present on the surface of the thermal insulation material 110, even if the thermal insulation material 110 is subjected to impact or pressure, the fiber bundles 47 can absorb and mitigate the impact or pressure. Therefore, shedding (powdering) of the inorganic particles 4 can be suppressed, and a decrease in the thermal insulation performance of the thermal insulation material 110 can be prevented.

[0108] 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 makes it possible to obtain even greater strength.

[0109] It is preferable that the length of the fiber bundles 47 formed to extend on the surface of the thermal insulation material 110 be relatively long. An example of a method for specifying the length of the fiber bundles 47 will be described with reference to FIG. 19 . As shown in FIG. 19 , rectangular imaginary frames 21 are arranged along the fiber bundles 47 extending in stripes 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 they have a sufficient effect of improving the strength of the thermal insulation material 110.

[0110] 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.

[0111] Furthermore, as shown in FIG. 20, 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.

[0112] Although structural examples 1 to 7 of the thermal insulation material have been described above, the structure of the thermal insulation material is not limited thereto, and thermal insulation materials having various structures can be used. Specifically, the thermal insulation materials of structural examples 1 to 7 have excellent thermal insulation effects and also have various properties such as the effect of suppressing powder shedding, the effect of further improving strength, and the effect of maintaining shape. Therefore, as shown in FIG. 1 , a heat transfer-suppressing sheet 50 in which an elastic sheet 51 is laminated on the thermal insulation material can obtain the various effects described above and can also prevent unnecessary pressure from being applied to the battery cells 20 a, 20 b, and 20 c.

[0113] Second Embodiment The heat-transfer-suppressing sheet according to the present embodiment preferably has a film covering the outer peripheral surface. A heat-transfer-suppressing sheet having a film will be described below with reference to the drawings. Fig. 21A is a perspective view showing a heat-transfer-suppressing sheet according to a second embodiment of the present invention, and Fig. 21B is a cross-sectional view thereof.

[0114] 21A and 21B , a heat transfer-suppressing sheet 120 according to the second embodiment includes a thermal insulator 10, for example, as shown in FIG. 1B , elastic sheets 51 laminated on the first surface 10a and the second surface 10b of the thermal insulator 10, and a resin film 112 enclosing the laminate 111. The resin film 112 has a plurality of elliptical holes 113 formed therein. The resin film 112 is also configured with a first-surface-side film 112a and a second-surface-side film 112b, which respectively cover two main surfaces perpendicular to the thickness direction of the laminate 111, i.e., the first surface 111a and the second surface 111b of the laminate, and an end-surface-side film 112c, which covers four end surfaces 111c parallel to the thickness direction of the laminate 111. The area ratio of the holes 113 in the first-surface-side film 112a and the second-surface-side film 112b is designed to be greater than the area ratio of the holes in the end-surface-side film 112c.

[0115] Here, the area ratio of the holes 113 in the first surface side film 112a and the second surface side film 112b refers to the ratio of the area of ​​the holes 113 formed in the first surface side film 112a and the second surface side film 112b to the total area of ​​the first surface side film 112a and the second surface side film 112b. Also, the area ratio of the holes in the edge surface side film 112c refers to the ratio of the area of ​​the holes formed in the edge surface side film 112c to the total area of ​​the edge surface side film 112c.

[0116] In the second embodiment, the laminate 111 is wrapped in a planar resin film, and the resin films 112 are fused together near the end faces 111c of the laminate 111 to form the fused film portions 114. The resin films 112 are heated and shrink, so that the laminate first surface 111a, laminate second surface 111b, and end faces 111c of the laminate 111 are covered with the resin film 112, and the resin film 112 is in close contact with the surface of the laminate 111. Therefore, because the fused film portions 114 are formed mainly in the end face side film 112c, the thickness of the region where the fused film portions 114 are formed is increased, and as a result, the end face side film 112c has higher strength than the first face side film 112a and the second face side film 112b. Furthermore, even if holes 113 exist on the end surface 111c of the laminate 111 when the laminate 111 is wrapped in a flat resin film, the formation of the film fusion portion 114 reduces the area ratio of the holes 113 in the end surface side film 112c to be smaller than the area ratio of the holes 113 in the first surface side film 112a and the second surface side film 112b.

[0117] A specific example of application of the heat-transfer-reducing sheet 120 configured as described above to a battery pack will be described below. Here, the case where the heat-transfer-reducing sheet 120 shown in Figures 21A and 21B is applied instead of the heat-transfer-reducing sheet 50 of the battery pack 100 shown in Figure 2 will be described.

[0118] In the heat-transfer-suppressing sheet 120 according to the second embodiment, the laminate 111 is encapsulated in a resin film, which prevents particles from falling off when the sheet is incorporated into the battery pack 100. The elastic sheet 51 has a predetermined elasticity, and when the heat-transfer-suppressing sheet 120 is pressed by the expansion of the battery cells 20a, 20b, and 20c, the elastic sheet 51 deforms by an appropriate amount, thereby suppressing the repulsive force on the battery cells. This prevents a decrease in battery performance due to repeated pressing and releasing of the battery cells 20a, 20b, and 20c.

[0119] Furthermore, the insulating material 10 constituting the laminate 111 contains inorganic particles and organic fibers and has high thermal insulation properties, which can suppress the transfer of heat from a battery cell experiencing thermal runaway to adjacent battery cells. Furthermore, when the heat transfer-suppressing sheet 120 is incorporated into the battery pack 100, misalignment between the insulating material 10 and the elastic sheet 51 can be prevented.

[0120] Furthermore, for example, when the temperature of the battery cell 20a rises, the air contained within the thermal insulating material 10 in the laminate 111 disposed between the battery cells 20a and 20b, and between the laminate 111 and the resin film 112, expands, and is discharged through the holes 113 in the resin film 112. In this case, in the second embodiment, for example, the area ratio of the holes 113 in the first-surface-side film 112a and the second-surface-side film 112b that are in contact with the battery cells 20a and 20b is larger than the area ratio of the holes 113 in the end-surface-side film 112c. Therefore, air is easily discharged from the first-surface-side film 112a and the second-surface-side film 112b. As a result, air is slowly discharged from the gap between the battery cells 20a and 20b and the heat-transfer-suppressing sheet 120 via the holes 113 in the first-surface-side film 112a and the second-surface-side film 112b, thereby suppressing the spread of particle contamination within the battery case 30.

[0121] In order to allow as much air as possible to be discharged through the holes 113 in the first-surface-side film 112a and the second-surface-side film 112b, it is preferable that the area ratio of the holes 113 in the end-surface-side film 112c be as small as possible, and it is more preferable that the end-surface-side film 112c has no holes (i.e., an area ratio of 0%). Even if the end-surface-side film 112c has holes 113, it is preferable that the average area per hole 113 in the first-surface-side film 112a and the second-surface-side film 112b is larger than the average area per hole 113 in the end-surface-side film 112c.

[0122] One method for making the area ratio of the holes 113 in the edge-side film 112c smaller than the area ratio of the holes 113 in the first-side film 112a and the second-side film 112b is to form holes only in the regions corresponding to the first-side film 112a and the second-side film 112b during the manufacture of the heat transfer-suppressing sheet. Other methods include forming larger holes in the regions corresponding to the first-side film 112a and the second-side film 112b than in the regions corresponding to the edge-side film 112c, or forming a film fusion portion 114 in the edge-side film 112c by fusing resin films together. Forming the film fusion portion 114 in the edge-side film 112c also ensures the smoothness of the first-side film 112a and the second-side film 112b. However, depending on the manufacturing conditions, a portion of the film fusion portion 114 may be formed in the first-side film 112a and the second-side film 112b. However, if the majority of the film fusion portion 114 is formed in the end surface side film 112c, it is possible to obtain the effect of controlling the area ratio of the holes and the effect of ensuring the smoothness of the first surface side film 112a and the second surface side film 112b.

[0123] For example, the battery cell 20a and the heat-transfer-suppressing sheet 120, and the battery cell 20b and the heat-transfer-suppressing sheet 120, are not arranged in complete contact with each other, but rather there are areas where they are in close contact with each other and areas where they are slightly separated from each other. If the holes 113 were completely blocked by the areas where they are in close contact with each other, it would be difficult for air to be discharged through the holes 113, and the effective area ratio of the holes 113 in the first-surface-side film 112a and the second-surface-side film 112b would decrease. Therefore, to prevent the holes 113 from being completely blocked by adjacent battery cells, it is preferable that the shapes of the holes 113 be oval shapes that extend elongated in one direction.

[0124] Furthermore, when the laminate first surface 111a and the laminate second surface 111b of the laminate 111 are rectangular, if the holes 113 are elliptical with their major axes in the same direction as the longitudinal direction of the laminate first surface 111a and the laminate second surface 111b, adjacent holes 113 are too close to each other, reducing the strength and preventing cracks from occurring in the resin film 112. Similarly, if the holes 113 in the first surface-side film 112a and the second surface-side film 112b are arranged at equal intervals on the laminate first surface 111a and the laminate second surface 111b, adjacent holes 113 are too close to each other, preventing cracks from occurring in the resin film 112. Furthermore, if these multiple holes 113 are arranged along the longitudinal direction and a direction perpendicular to the longitudinal direction on the laminate first surface 111a and the laminate second surface 111b, cracks can be further prevented from occurring.

[0125] In the second embodiment, the laminate 111 may be formed by laminating an elastic sheet 51 on at least one of the first surface 10a and the second surface 10b of the thermal insulation material 10. As shown in FIG. 1A , the elastic sheet 51 may be laminated only on the first surface 10a of the thermal insulation material 10, or may be laminated on both the first surface 10a and the second surface 10b of the thermal insulation material 10. Alternatively, the elastic sheet 51 may be sandwiched between a pair of thermal insulation materials 10, or the thermal insulation material 10 may be sandwiched between a pair of elastic sheets 51. Furthermore, various sheets other than the thermal insulation material and the elastic sheet 51 may be laminated. For the thermal insulation material 10, any of the thermal insulation materials 10, 40, 60, 70, 80, 90, and 110 of Structural Examples 1 to 7 described above may be used, and the unique effects of each thermal insulation material can be obtained.

[0126] As shown in the above-mentioned insulating material 10, insulating material 70, and insulating material 90, when a plurality of voids 7 or gaps 8 are formed, it is preferable that these voids 7 or gaps 8 are in communication with the holes 113 in the resin film 112, since this facilitates the discharge of air from the insulating material through the holes 113. Furthermore, if inorganic hydrate particles are contained as inorganic particles in the insulating material 10, when the insulating material 10 is thermally decomposed by heating and releases water of crystallization, the water of crystallization is more likely to be discharged from the holes 113 in the resin film 112 through the voids 7 or gaps 8.

[0127] Furthermore, in the second embodiment, air is more easily expelled from the first surface side film 112a and the second surface side film 112b than from the end surface side film 112c, which further prevents inorganic particles and the like, which are used as materials for the insulating material 10, from being ejected into the inside of the battery case 30 and causing the spread of contamination.

[0128] 23A is a top view showing a heat-transfer-suppressing sheet according to a third embodiment of the present invention, and FIG. 23B is a cross-sectional view taken along line II of FIG. 1. A heat-transfer-suppressing sheet 130 according to the first embodiment includes, for example, a thermal insulating material 10 containing inorganic particles, an elastic sheet 51 laminated on the first surface 10a of the thermal insulating material 10, a resin film 312 enclosing a laminate 311 of these, and a covering material 313 laminated on the resin film 312. The laminate 311 has a pair of laminate main surfaces 311a perpendicular to its thickness direction and two pairs of opposing laminate end surfaces 311c substantially parallel to the thickness direction.

[0129] The resin film 312 has a main surface side portion 312a located on the laminate main surface 311a side of the laminate 311 and end surface side portions 312b, 312c covering the laminate end surfaces 311b, 311c, thereby covering the entire surface of the laminate 311. In the third embodiment, a heat-shrinkable resin film 312 is used, and the resin film 312 is heat-shrunk (shrink-wrapped) to adhere to the surface of the laminate 311. At this time, a plurality of first holes 314 are formed in the main surface side portion 312a of the resin film 312 to allow air in the internal region enclosed by the resin film 312 to be discharged to the outside. The resin films 312 are fused to each other at the end surface side portions 312b, 312c, thereby forming fused portions 316.

[0130] A covering material 313 is laminated on the outer surface of the main surface side portion 312 a of the resin film 312, and the covering material 313 and the resin film 312 are adhered together with an adhesive. As a result, at least a portion of the first hole 314 is covered with the covering material 313.

[0131] A specific example of application of the heat-transfer-reducing sheet 130 configured as described above to a battery pack will be described below. Here, the case where the heat-transfer-reducing sheet 130 shown in Figures 23A and 23B is applied instead of the heat-transfer-reducing sheet 50 of the battery pack 100 shown in Figure 2 will be described.

[0132] In the third embodiment, the laminate 311 is encapsulated in the resin film 312, which prevents particles from falling off when the heat transfer-suppressing sheet 130 is incorporated into the battery pack 100 or when the battery pack 100 is in use, and also prevents the laminate 311 from shifting position. Furthermore, the heat insulating material 10 that constitutes the laminate 311 contains inorganic particles and has high thermal insulation properties, which can suppress the propagation of heat from a battery cell that has experienced thermal runaway to adjacent battery cells. Furthermore, as in the second embodiment, the elastic sheet 51 can suppress a decrease in battery performance.

[0133] Furthermore, according to the third embodiment, the first hole 314 of the resin film 312 is covered with the covering material 313, so that even if the temperature inside the battery case changes and the atmosphere becomes highly humid, the heat insulating material 10 can be prevented from absorbing moisture. Therefore, the heat insulating property of the heat insulating material 10 can be prevented from decreasing.

[0134] In the third embodiment, the covering material 313 and the resin film 312 are bonded together with an adhesive. However, if the surface of the resin film 312 is not completely smooth, a gap 317 may be formed between the covering material 313 and the resin film 312. Furthermore, when the laminate 311 is covered with the resin film 312 by shrink-wrapping, a first hole (not shown) may also be formed in the end surface side portion 312c of the resin film 312, depending on the manufacturing method. In such a case, the internal region enclosed by the resin film 312 and the external region of the heat-transfer-suppressing sheet 130 are at least partially in communication with each other via the first hole 314 and the gap 317, or via the first hole 314, etc. As a result, when the heat-transfer-suppressing sheet 130 is heated to a high temperature due to an increase in the temperature of the battery cells 20a, 20b, and 20c, the gas inside the heat-transfer-suppressing sheet 130 can be discharged to the outside.

[0135] On the other hand, in the third embodiment, when the coating material 313 and the resin film 312 are completely adhered to each other without any gaps, and when no holes are formed in the end surface side portion 312c of the resin film 312, it is possible to completely prevent moisture in the battery case 30 from penetrating into the heat transfer suppression sheet 130.

[0136] In this embodiment, the covering material 313 having a size equivalent to that of the main surface side portion 312a of the resin film 312 is arranged by adhering it to the main surface side portion 312a. However, the position and size of the covering material 313 are not limited to this. For example, a covering material 313 having a size smaller than that of the main surface side portion 312a may be adhered to at least a portion of the main surface side portion 312a of the resin film 312. However, if there is a step between the resin film 312 and the covering material 313, the contact surface with the battery cells 20a, 20b, and 20c may become uneven, which may affect battery performance. Therefore, it is preferable to arrange the covering material 313 so that it has approximately the same size as or is larger than the main surface side portion 312a so that at least the entire main surface side portion 312a of the resin film 312 is covered by the covering material 313. Here, "substantially the same" means that the difference in size between the two is acceptable up to ±5% of the average value of the two, preferably up to ±3%, and more preferably up to ±1%.

[0137] Alternatively, the covering material 313 may be disposed between the laminate 311 and the resin film 312. Furthermore, the covering material 313 may be disposed so as to surround the pair of main surface side portions 312a and the pair of end surface side portions 312c of the resin film 312, thereby making it possible for all of the first holes 314 in the resin film 312 to be covered by the covering material 313. Furthermore, the covering material 313 may be disposed between the laminate 311 and the resin film 312. However, in order to obtain a sufficient effect of suppressing moisture penetration into the internal region enclosed in the resin film 312, it is preferable that the covering material 313 be disposed so as to cover the outer surface of the resin film 312.

[0138] [Fourth Embodiment] Fig. 24A is a top view showing a heat-transfer-suppressing sheet according to a fourth embodiment of the present invention, and Fig. 24B is a cross-sectional view taken along line II-II. In the fourth embodiment shown in Figs. 24A and 24B, the same components as those in the third embodiment shown in Figs. 23A and 23B are designated by the same reference numerals, and detailed descriptions thereof will be omitted or simplified. Furthermore, the fused portions 316 shown in Figs. 23A and 23B are omitted in Figs. 24A and 24B. The following description will be given assuming that the heat-transfer-suppressing sheet 140 according to the fourth embodiment is applied to the battery pack 100 shown in Fig. 2.

[0139] 24A and 24B , in the heat transfer-suppressing sheet 140 according to the fourth embodiment, a laminate main surface 311a and laminate end surfaces 311b, 311c of a laminate 311 are covered with a resin film 312 by shrink packaging. Furthermore, a main surface side portion 312a and end surface side portions 312b, 312c of the resin film 312 are covered with a covering material 323 by shrink packaging. A plurality of second holes 315 are formed in the main surface side portion 323a of the covering material 323 to allow internal air to be discharged to the outside when the covering material 323 is shrink-packaged. Furthermore, when viewed in the stacking direction of the resin film 312 and the covering material 323, i.e., when viewed from the top as shown in FIG. 24A , at least some of the plurality of second holes 315 are positioned offset from the plurality of first holes 314.

[0140] In the fourth embodiment configured as described above, the laminate 311 is covered with the resin film 312, thereby preventing powder fall and misalignment. Furthermore, the elastic sheet 51 that constitutes the laminate 311 prevents deterioration of battery performance. Furthermore, the first hole 314 and the second hole 315 are formed at positions offset from each other, and the first hole 314 of the resin film 312 is covered with the covering material 323, so the surface of the laminate 311 is not exposed. Therefore, moisture is prevented from penetrating into the insulating material 10 that constitutes the laminate 311, preventing deterioration of the insulating properties.

[0141] In the fourth embodiment, the covering material 323 and the resin film 312 are not completely bonded together. Instead, the covering material 323 is made of a heat-shrinkable film, and is heated and shrunk to adhere to the resin film 312. As a result, a small gap 317 exists between the resin film 312 and the covering material 323, and the region where the laminate 311 is contained in the resin film 312 communicates with the external region of the heat-transfer-suppressing sheet 140 via the first holes 314, the gap 317, and the second holes 315. Therefore, when the heat-transfer-suppressing sheet 140 is heated to a high temperature due to an increase in the temperature of the battery cells 20a, 20b, and 20c, the gas in the internal region contained in the resin film 312 can be discharged to the outside.

[0142] In the third and fourth embodiments, the laminate 311 may be formed by laminating an elastic sheet 51 on at least one of the first surface 10a and the second surface 10b of the thermal insulating material 10. Specifically, the elastic sheet 51 may be laminated only on the first surface 10a of the thermal insulating material 10, or may be laminated on both the first surface 10a and the second surface 10b of the thermal insulating material 10. The elastic sheet 51 may be sandwiched between a pair of thermal insulating materials 10, or the thermal insulating material 10 may be sandwiched between a pair of elastic sheets 51. Furthermore, various sheets other than the thermal insulating material 10 and the elastic sheet 51 may be laminated. For the thermal insulating material 10, any of the thermal insulating materials 10, 40, 60, 70, 80, 90, and 110 of Structural Examples 1 to 7 described above may be used, and the unique effects of each thermal insulating material can be obtained.

[0143] <Resin Film> In the third and fourth embodiments, the material constituting the resin film 112, 312 can be at least one resin selected from polyethylene, polypropylene, polystyrene, vinyl chloride, nylon, acrylic, epoxy resin, polyurethane, polyether ether ketone, polyetherimide, polyethylene terephthalate, polyphenyl sulfide, polycarbonate, and aramid.

[0144] As shown in the second to fourth embodiments, shrink packaging is preferably used when the entire surface of the laminate 111, 311 is covered with the resin film 112, 312. Therefore, it is more preferable to use a resin film 112, 312 made of a material suitable for shrink packaging. Examples of such materials include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and vinyl chloride.

[0145] (Thickness of Resin Film) The resin film preferably has an appropriate thickness to adhere to the outer surface of the laminate, preventing particles and the like from falling off and preventing misalignment between the insulating material and the elastic sheet 51. Furthermore, the resin film preferably has appropriate flexibility so that at least a portion of the resin film adheres to the shape of the laminate. If the resin film thickness exceeds 1 mm, it becomes difficult to conform to the shape of the laminate 111, 311, and cracks or breaks may occur in the resin film. Therefore, the thickness of the resin film is preferably 1 mm or less, more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. On the other hand, there is no particular lower limit to the thickness of the resin film, but in order to prevent tearing due to friction with the battery cell or the like and to obtain the desired strength, it is preferably 0.005 mm or more, more preferably 0.01 mm or more.

[0146] (Other Materials Included in the Resin Film) Furthermore, since the resin film is required to be resistant to high temperatures of the battery cells 20 a, 20 b, and 20 c, it is preferable that the resin film be flame-retardant, and specifically, it is preferable that the resin film include an inorganic substance or a flame-retardant material. Examples of other materials included in the resin film include inorganic substances such as talc, calcium carbonate, aluminum hydroxide, titanium oxide, vermiculite, zeolite, synthetic silica, zirconia, zircon, barium titanate, zinc oxide, and alumina, and flame-retardant materials such as bromine-based flame retardants, chlorine-based flame retardants, phosphorus-based flame retardants, boron-based flame retardants, silicone-based flame retardants, and nitrogen-containing compounds.

[0147] <Coating Material> In the third and fourth embodiments, the materials constituting the covering materials 313, 323 may be the same as those of the resin film 312, but they may be made of the same material as the resin film 312 or different materials. As shown in Figures 24A and 24B, when the covering material 323 is brought into close contact with the surface of the resin film 312 by shrink packaging, the covering material 323 preferably contains a material suitable for shrink packaging.

[0148] Fifth Embodiment FIG. 25A is a top view of a heat-transfer-inhibiting sheet according to a fifth embodiment of the present invention, and FIG. 25B is a cross-sectional view of the heat-transfer-inhibiting sheet 150 in the thickness direction. The heat-transfer-inhibiting sheet 150 according to the fifth embodiment includes a laminate 511 and a bulge-inhibiting sheet 512. The laminate 511 is formed by stacking the insulating material 10 and the elastic sheet 51 shown in the first to fourth embodiments. In FIG. 25A, the insulating material 10 and the elastic sheet 51 are not shown, and only the laminate 511 is shown. The laminate 511 has a pair of main surfaces 511a perpendicular to its thickness direction and end surfaces 511b substantially parallel to the thickness direction. In the fifth embodiment, the bulge-inhibiting sheet 512 is formed continuously along the end surfaces 511b of the laminate 511 so as to cover them. As described below, the bulge-inhibiting sheet 512 has specific physical properties and is effective in suppressing outward bulging of the end surfaces 511b of the laminate 511.

[0149] A specific example of application of the heat-transfer-reducing sheet 150 configured as described above to a battery pack will be described below. Here, the case where the heat-transfer-reducing sheet 150 shown in Figures 25A and 25B is applied instead of the heat-transfer-reducing sheet 50 of the battery pack 100 shown in Figure 2 will be described.

[0150] In the battery pack 100, when the temperature of at least one of the battery cells 20a, 20b, and 20c rises, the heat transfer-reducing sheet 150, which has a heat insulating material with excellent thermal insulation properties, is interposed between adjacent battery cells, thereby suppressing heat transfer between the battery cells. Furthermore, when the battery cells 20a, 20b, and 20c expand due to charging and discharging, a pressing force F1 is applied toward the main surface 511a of the stack 511, as shown in FIG. 25B . Because the stack 511 includes an elastic sheet, the main surface 511a is pressed, reducing the thickness of the elastic sheet. A portion of the elastic sheet's volume attempts to escape to unpressured areas, generating an expansion force F2. In the fifth embodiment, the expansion-reducing sheet 512 covers the end surface 511b of the stack 511. The expansion-reducing sheet 512 presses the end surface 511b of the stack 511 inward with a pressing force F3, thereby suppressing outward expansion of the end surface of the elastic sheet.

[0151] As a result, it is possible to prevent misalignment or rattle between the battery cells 20 a, 20 b, and 20 c and the heat-transfer-suppressing sheet 150, and to prevent a decrease in the performance of the battery pack. Furthermore, even if the main surface 511 a of the laminate 511 is pressed with a high pressing force F1, it is possible to prevent the elastic sheets constituting the laminate 511 from being significantly compressed and deformed, which would otherwise cause an excessive reduction in thickness, and it is possible to maintain the thermal insulation between the battery cells 20 a, 20 b, and 20 c.

[0152] Although it is possible to suppress bulging of the end faces of the elastic sheet by appropriately selecting the material of the elastic sheet and controlling the elastic modulus, according to this embodiment, regardless of the material of the elastic sheet, bulging can be suppressed simply by attaching the bulge suppression sheet 512. This increases the latitude in selecting the elastic sheet, allowing for the free selection of an elastic sheet having desired properties other than the elastic modulus.

[0153] The swell suppressing sheet 512 may or may not be in close contact with the end surface 511b of the laminate 511, but if it is in close contact, it can prevent the swell suppressing sheet 512 from separating from the laminate 511. Furthermore, it is sufficient that the swell suppressing sheet 512 is present at least on the end surface of the elastic sheet, but it is preferable that it be arranged so as to cover the end surface 511b of the laminate 511.

[0154] 26A is a cross-sectional view in the thickness direction showing a heat transfer-suppressing sheet according to a sixth embodiment of the present invention, and FIG. 26B is a top view seen from the main surface side. In the sixth embodiment shown in FIGS. 26A and 26B, the same components as those in the fifth embodiment shown in FIGS. 25A and 25B are designated by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0155] 26A , in a heat transfer-restricting sheet 160 according to the sixth embodiment, a pair of elastic sheets 51 are laminated on a pair of main surfaces 510a of a thermal insulator 10 to form a laminate 511. A bulge-restricting sheet 514 encases the laminate 511. Thus, the bulge-restricting sheet 514 is composed of outer main surface side portions 514a that cover the pair of main surfaces 511a of the laminate 511 and outer end surface side portions 514b that cover the end surfaces 511b of the laminate 511, and the outer main surface side portions 514a and the outer end surface side portions 514b are formed continuously.

[0156] Even in the sixth embodiment configured as described above, the insulating material 10 having excellent thermal insulation properties is disposed, thereby suppressing heat transfer between battery cells. Furthermore, the outer end surface side portion 514b of the bulge-suppressing sheet 514 is disposed on the end surface 511b side of the laminate 511, and the outer end surface side portion 514b presses the end surface of the elastic sheet 51 inward. Therefore, outward bulging of the end surface of the elastic sheet 51 is suppressed. As a result, when the heat-transfer-suppressing sheet 160 according to the sixth embodiment is applied to the battery pack 100, degradation of the battery pack performance due to misalignment or rattle between the battery cells 20a, 20b, and 20c and the heat-transfer-suppressing sheet 160 can be prevented. Furthermore, degradation of thermal insulation due to a reduction in the thickness of the elastic sheet 51 can be suppressed.

[0157] Furthermore, in the sixth embodiment, the expansion suppression sheet 514 encloses the entire laminate 511, and therefore, it is possible to prevent inorganic particles and the like contained in the heat insulating material from falling off.

[0158] The main surface 511a of the laminate 511 and the outer main surface side portion 514a of the swell-reducing sheet 514 may or may not be in contact with each other, and another functional member may be interposed between the main surface 511a of the laminate 511 and the outer main surface side portion 514a of the swell-reducing sheet 514. Similarly, the end surface 511b of the laminate 511 and the outer end surface side portion 514b of the swell-reducing sheet 514 may or may not be in direct contact with each other. Specifically, it is sufficient that the arrangement of the swell-reducing sheet 514 has the effect of suppressing swelling of the end surface of the elastic sheet 51, and another functional sheet may be interposed between the end surface of the elastic sheet 51 and the outer end surface side portion 514b of the swell-reducing sheet 514.

[0159] 26A, the elastic sheets 51 are arranged on both main surfaces of the thermal insulation material 10, but for example, the elastic sheets 51 may be arranged on only one main surface 11a of the thermal insulation material 10. Also, the thermal insulation material 10 may be arranged on both main surfaces of the elastic sheets 51.

[0160] Furthermore, as shown in FIG. 26B, it is preferable that the outer end surface side portion 514b of the expansion-suppressing sheet 514 of the heat transfer-suppressing sheet 160 has a linear thick portion 516 extending in a direction approximately parallel to the main surface 511a of the laminate 511.

[0161] The thickened portion 516 on the outer end surface side portion 514b of the bulge-suppressing sheet 514 can further improve the effect of suppressing outward bulging of the end surface of the elastic sheet 51. It is preferable that at least a portion of the thickened portion 516 is curved or serpentine. If the thickened portion 516 has a serpentine region, when the end surface of the elastic sheet 51 bulges, the outer end surface side portion 514b stretches slightly in response to the bulging, and the serpentine thickened portion 516 also stretches accordingly. Thereafter, when the pressure exerted by the battery cells 20a, 20b, and 20c on the heat transfer-suppressing sheet 160 decreases and the elastic sheet 51 contracts, the end surface of the elastic sheet 51 retreats inward. At this time, the thick portion 516 tries to return to its serpentine shape, and a force is generated on the outer end surface side portion 514b of the expansion suppression sheet 514 that follows the retreat of the end surface of the elastic sheet 51, so that the expansion suppression effect of the expansion suppression sheet 514 can be maintained for a long period of time.

[0162] Although thick portion 516 is effective in suppressing bulging if it is formed so as to go around outer end surface side portion 514b of bulge-suppressing sheet 514, it does not necessarily have to be formed so as to go around, and the above effect can be obtained as long as it is formed in at least a partial area of ​​outer end surface side portion 514b. Similarly, thick portion 516 does not have to be curved or meandering over the entire area, and the above effect can be obtained as long as at least a portion of the thick portion is curved or meandering.

[0163] In the fifth and sixth embodiments, the laminate 511 may be formed by laminating an elastic sheet 51 on at least one of the first surface 10a and the second surface 10b of the thermal insulating material 10. Specifically, the elastic sheet 51 may be laminated only on the first surface 10a of the thermal insulating material 10, or may be laminated on both the first surface 10a and the second surface 10b of the thermal insulating material 10. The elastic sheet 51 may be sandwiched between a pair of thermal insulating materials 10, or the thermal insulating material 10 may be sandwiched between a pair of elastic sheets 51. Furthermore, various sheets other than the thermal insulating material 10 and the elastic sheet 51 may be laminated. For the thermal insulating material 10, any of the thermal insulating materials 10, 40, 60, 70, 80, 90, and 110 of the above-described structural examples 1 to 7 may be used, and the effects unique to each thermal insulating material can be obtained.

[0164] <Swelling-suppressing sheet> The material constituting the swelling-suppressing sheet can be at least one resin selected from polyethylene, polypropylene, polystyrene, vinyl chloride, nylon, acrylic, epoxy resin, polyurethane, polyether ether ketone, polyetherimide, polyethylene terephthalate, polyphenyl sulfide, polycarbonate, and aramid.

[0165] 25A to 26B, it is preferable to use shrink packaging when covering the entire surface of the laminate 511 with expansion-control sheets 512 and 514. Therefore, it is more preferable to use an expansion-control sheet made of a material suitable for shrink packaging. Examples of such materials include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride.

[0166] (Characteristics of the swell-suppressing sheet) In the present embodiment, the swell-suppressing sheet preferably has an appropriate tensile strength in order to adhere closely to the end surface 511b of the laminate 511 (particularly the elastic sheet 51) and to have the effect of preventing swell at the end surface 511b. Furthermore, in order to fully obtain the effect of suppressing swell along the end surface of the elastic sheet 51, the swell-suppressing sheet also preferably has an appropriate tensile elongation.

[0167] (Tensile Strength of the Swell-Preventing Sheet) If the tensile strength of the swell-preventing sheet is less than 20 MPa, the sheet will be easily destroyed if the end faces of the elastic sheet 51 bulge outward, and the swell-preventing effect will not be fully achieved. Therefore, the tensile strength of the swell-preventing sheet is set to 20 MPa or more, preferably 30 MPa or more, and more preferably 40 MPa or more. On the other hand, if the tensile strength of the swell-preventing sheet is 150 MPa or less, the effect of preventing the end faces of the elastic sheet 51 from bulging can be appropriately controlled, and the effect of the elastic sheet 51 absorbing deformation of the battery cells 20a, 20b, and 20c can be fully achieved. Therefore, the tensile strength of the swell-preventing sheet is preferably 150 MPa or less, more preferably 130 MPa or less, and even more preferably 100 MPa or less.

[0168] (Thickness of the swell-suppressing sheet) If the thickness of the swell-suppressing sheet exceeds 1 mm, it becomes difficult for the sheet to conform to the shape of the laminate 511, and cracks or breaks may occur. Therefore, the thickness of the swell-suppressing sheet is preferably 1 mm or less, more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. On the other hand, there is no particular lower limit to the thickness of the swell-suppressing sheet, but in order to obtain the desired tensile strength, it is preferably 0.005 mm or more, and more preferably 0.01 mm or more.

[0169] <Other Materials Included in the Swell-Controlling Sheet> Furthermore, since the swell-controlling sheet comes into contact with the battery cells 20 a, 20 b, and 20 c, it is preferable that the sheet be flame-retardant, and specifically, it preferably includes an inorganic substance or a flame-retardant material. Examples of materials constituting the swell-controlling sheet include inorganic substances such as talc, calcium carbonate, aluminum hydroxide, titanium oxide, vermiculite, zeolite, synthetic silica, zirconia, zircon, barium titanate, zinc oxide, and alumina, and flame-retardant materials such as bromine-based flame retardants, chlorine-based flame retardants, phosphorus-based flame retardants, boron-based flame retardants, silicone-based flame retardants, and nitrogen-containing compounds.

[0170] Seventh Embodiment Fig. 27 is a perspective view showing a heat-transfer-suppressing sheet according to a seventh embodiment of the present invention. A heat-transfer-suppressing sheet 170 according to the seventh embodiment has an elastic sheet 751 laminated on one main surface of a thermal insulating material 10, and the elastic sheet 751 is formed to be smaller than the thermal insulating material 10 in a plan view. The elastic sheet 751 is made of an elastic body that maintains a compressed state below 90°C and releases the compressed state and expands when the temperature rises to 90°C or higher. A known elastic body can be used as the elastic body, and the elastic material that constitutes the elastic body will be described in detail below.

[0171] In this embodiment, to maintain the elastic sheet 751 in a compressed state, a binder substance is blended with the elastic material and processed into a sheet to form the elastic sheet 751. Considering that the binder substance melts at 90°C or higher to release the compressed state of the elastic body, an organic binder is preferred. Examples of organic binders include acrylic, methacrylic, styrene, and butadiene resins. The blending amount of the binder substance can be selected appropriately depending on the type of binder substance, the degree of compression of the elastic body, and the elastic capacity of the elastic body, but it is appropriate for the binder substance to be contained in an amount of 5 to 30 mass% of the total mass of the elastic sheet 751.

[0172] The elastic sheet 751 and the heat insulating material 10 may be bonded together over the entire surface, or may be bonded in spots. Bonding the elastic sheet 751 and the heat insulating material 10 improves the ease of handling of the heat transfer-suppressing sheet 170. Note that, because the elastic sheet 751 expands in the thickness direction and the surface direction when released from the compressed state, it is preferable that the elastic sheet 751 be partially bonded to the heat insulating material 10 so as not to hinder expansion in the surface direction. In this case, it is preferable that the center portion of the elastic sheet 751 be bonded to the heat insulating material 10.

[0173] 27, the elastic sheet 751 is shaped to be smaller than the thermal insulator 10 in consideration of expansion in the planar direction, but the elastic sheet 751 and the thermal insulator 10 may be the same size. If the elastic sheet 751 and the thermal insulator 10 are shaped to be the same size, when the elastic sheet 751 expands, the elastic sheet 751 also spreads into the space around the thermal insulator 10, and when applied to a battery pack, for example, it is expected that the elastic sheet 751 will protect battery cells adjacent to a battery cell that has experienced thermal runaway.

[0174] FIG. 28 is a perspective view of a modified heat-transfer-inhibiting sheet according to the seventh embodiment of the present invention, showing the sheet at temperatures below 90°C. FIG. 29 is a cross-sectional view of a modified heat-transfer-inhibiting sheet according to the seventh embodiment of the present invention, showing the sheet at temperatures above 90°C. As shown in FIG. 28 , in a heat-transfer-inhibiting sheet 180, an elastic sheet 751 may be composed of multiple divided elastic sheets 751A. The multiple divided elastic sheets 751A are arranged at approximately equal intervals on the surface of the thermal insulation material 10, with gaps 702 formed between adjacent divided elastic sheets 751A. When the divided elastic sheets 751A are in a compressed state, i.e., at temperatures below 90°C, the gaps 702 serve as air flow paths, providing a cooling effect and improving the heat insulating performance of the heat-transfer-inhibiting sheet 180.

[0175] On the other hand, at temperatures above 90°C, the individual divided elastic sheets 751A expand and close the gaps 702, thereby improving the elastic performance. Furthermore, as the divided elastic sheets 751A expand further, the end faces of adjacent divided elastic sheets 751A come into contact with each other, forming mountain-shaped gaps 702A, as shown in Fig. 29. These mountain-shaped gaps 702A act as air flow paths and provide a cooling effect, thereby improving the heat insulating performance of the heat-transfer-suppressing sheet 180 even in temperatures above 90°C.

[0176] 27 to 29, the heat transfer-suppressing sheets 170, 180 may be formed by laminating a compressed elastic sheet 751, a divided elastic sheet 751A, and a heat insulating material 10. Furthermore, as shown in the following eighth embodiment, the compressed elastic sheet 751 and the divided elastic sheet 751A may be formed by a heat-compressible packaging body.

[0177] Eighth Embodiment Fig. 30 is a schematic cross-sectional view showing a heat-transfer-suppressing sheet according to an eighth embodiment of the present invention. As shown in Fig. 30, a heat-transfer-suppressing sheet 190 according to the eighth embodiment includes a laminate in which an elastic sheet 751 is laminated on one main surface of a thermal insulating material 10, and this laminate is surrounded by a heat-shrinkable wrapping body 715. The wrapping body 715 is shrunk by heat, thereby maintaining the compressed state of the elastic sheet 751. In Fig. 30, the wrapping body 715 is indicated by a thick solid line. In this embodiment, the entire laminate of the thermal insulating material 10 and the elastic sheet 751 is surrounded with almost no gaps. Note that even when surrounded and shrunk by the wrapping body 715, the thermal insulating material 10 shows almost no change in shape, but the elastic sheet 751 has an area slightly smaller than that of the thermal insulating material 10 due to the shrinkage of the wrapping body 715.

[0178] The elastic sheet 751 may be made up of a plurality of divided elastic sheets 751A, as in the seventh embodiment, and the elastic sheet 751 and the heat insulating material 10 may be bonded to each other partially or entirely.

[0179] A sheet or film made of a heat-shrinkable resin can be used for the packaging body 715, and may be either non-porous or perforated. If the packaging body 715 is perforated, the perforations will cause the packaging body 715 to tear at temperatures above 90° C., making the elastic sheet 751 more likely to expand.

[0180] In the seventh embodiment, its modifications, and the eighth embodiment, the elastic sheet 751 and the divided elastic sheet 751A may be laminated on only one or both main surfaces of the thermal insulation material 10. The elastic sheet 751 or the divided elastic sheet 751A may also be sandwiched between a pair of thermal insulation materials 10. However, in a configuration in which the divided elastic sheet 751A is sandwiched between a pair of thermal insulation materials 10, even if the divided elastic sheet 751A further expands, the formation of a void 702A is less likely. Furthermore, various sheets other than the thermal insulation material 10, the elastic sheet 751, and the divided elastic sheet 751A may also be laminated. For the thermal insulation material 10, any of the thermal insulation materials 10, 40, 60, 70, 80, 90, and 110 of Structural Examples 1 to 7 described above can be used, and the unique effects of each thermal insulation material can be obtained.

[0181] Examples of heat-shrinkable resins that make up the packaging body 715 include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and vinyl chloride. There are no limitations on the thickness of the packaging body 715 as long as it can maintain the compressed state of the elastic sheet 751. However, if the thickness of the packaging body 715 exceeds 1 mm, it becomes difficult for the packaging body 715 to conform to the shape of the insulating material, and cracks and breaks may occur. Therefore, the thickness is preferably 1 mm or less, more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. On the other hand, the lower limit is preferably 0.005 mm or more, more preferably 0.01 mm or more, to prevent tearing due to friction with the battery cells when applied to, for example, an assembled battery.

[0182] The materials constituting the heat-transfer-suppressing sheet according to this embodiment will be described below. First, the materials constituting the heat insulating material will be described.

[0183] <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, with the melting point of the first organic material being higher than that of the second organic material. When the binder fiber with a core-sheath structure is used as a material, the core corresponds to the organic fiber 1 in the thermal insulation material. Furthermore, during the manufacturing process 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.

[0184] When a binder fiber having a core-sheath structure is used as the material for the organic fiber 1, the first organic material constituting the core, i.e., the organic fiber 1, is not particularly limited as long as it has a melting point higher than that of the sheath, i.e., the second organic material present on the outer surface of the organic fiber 1. The first organic material may be at least one selected from polyethylene terephthalate, polypropylene, and nylon.

[0185] (Organic Fiber Content) In this embodiment, if the content of organic fiber 1 in the thermal insulation material is appropriately controlled, a sufficient skeleton reinforcing effect can be obtained. The content of organic fiber 1 is preferably 5 mass% or more, and more preferably 10 mass% or more, relative to the total mass of the thermal insulation material. Furthermore, if the content of organic fiber 1 is too high, the content of inorganic particles 4 will relatively decrease. Therefore, in order to obtain the desired thermal insulation performance, the content of organic fiber is preferably 25 mass% or less, and more preferably 20 mass% or less, relative to the total mass of the thermal insulation material.

[0186] (Fiber length of organic fibers) The fiber length of the organic fibers 1 is not particularly limited, but from the viewpoint of ensuring moldability and processability, the average fiber length of the organic fibers is preferably 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 thermal insulating material, the average fiber length of the organic fibers 1 is preferably 0.5 mm or more.

[0187] <Welded portion> The welded portion 5 is formed by heating and melting the surface of the organic fiber 1 or the sheath portion of the binder fiber having a core-sheath structure, and then cooling it, and serves to weld the inorganic particles 4 to the surface of the organic fiber 1 and also to weld 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 will contain the second organic material that constitutes the sheath portion.

[0188] (Second Organic Material) The second organic material is not particularly limited as long as it has a melting point lower than that of the first organic material constituting the organic fiber 1. Examples of the second organic material include at least one selected from polyethylene terephthalate, polyethylene, polypropylene, and nylon. 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.

[0189] <Inorganic particles> As the inorganic particles, a single inorganic particle may be used, or two or more types of inorganic particles may be used in combination. As the type of inorganic particles, from the viewpoint of the heat transfer suppression effect, it is preferable to use particles made of at least one inorganic material selected from oxide particles, carbide particles, nitride particles and inorganic hydrate particles, and it is more preferable to use oxide particles. In addition, the shape is not particularly limited, but it is preferable to include at least one selected from nanoparticles, hollow particles and porous particles. Specifically, it is also possible to use inorganic balloons such as silica nanoparticles, metal oxide particles, microporous particles and hollow silica particles, particles made of thermally expandable inorganic materials, particles made of hydrous porous bodies, etc.

[0190] 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. 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.

[0191] In addition, when two or more inorganic particles having different heat transfer suppression effects are used in combination, the heat generating body can be cooled 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 being referred to as the first inorganic particles and the large-diameter inorganic particles being referred to as the second inorganic particles.

[0192] <First Inorganic Particles> (Oxide Particles) Oxide particles have a high refractive index and a strong effect of diffusely reflecting light. Therefore, when oxide particles are used as the first inorganic particles, radiant heat transfer can be suppressed, particularly in high-temperature regions such as abnormal heat generation. As the oxide particles, at least one type of particle selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina can be used. That is, among the above oxide particles that can be used as inorganic particles, only one type may be used, or two or more types of oxide particles may 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.

[0193] (Average primary particle diameter of oxide particles: 0.001 μm or more and 50 μm or less) The particle diameter of the oxide particles can affect the effect of reflecting radiant heat, so limiting the average primary particle diameter to a predetermined range can achieve even higher thermal insulation. That is, when the average primary particle diameter of the oxide particles is 0.001 μm or more, the particles are sufficiently larger than the wavelength of light that contributes to heating and efficiently diffusely reflect light, thereby suppressing radiant heat transfer within the thermal insulation material in high-temperature regions of 500°C or more, thereby further improving thermal insulation. On the other hand, when the average primary particle diameter of the oxide particles is 50 μm or less, the number and number of contact points between particles do not increase even when compressed, making it difficult to form a path for conductive heat transfer, thereby reducing the impact on thermal insulation, particularly in normal temperature regions where conductive heat transfer is dominant.

[0194] 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.

[0195] (Nanoparticles) In the present invention, nanoparticles refer to particles on the nanometer order that are spherical or nearly spherical and have an average primary particle diameter of less than 1 μm. Nanoparticles have a low density, which suppresses conductive heat transfer. Using nanoparticles as the first inorganic particles further refines the three-dimensionally connected pores 7, thereby achieving excellent thermal insulation that suppresses convective heat transfer. Therefore, nanoparticles are preferred because they can suppress heat conduction between adjacent nanoparticles during normal battery operation at room temperature. Furthermore, using nanoparticles with a small average primary particle diameter as oxide particles can suppress an increase in conductive heat transfer through the insulating material, even when the insulating material is compressed due to expansion associated with thermal runaway in the battery cell, increasing its internal density. This is thought to be because nanoparticles are prone to forming small voids between particles due to electrostatic repulsion, and their low bulk density allows the particles to be packed together to provide cushioning.

[0196] 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.

[0197] Generally, wet silica has agglomerated particles, whereas dry silica allows particles to be dispersed. In the temperature range of 300°C or less, heat conduction is dominated by conductive heat transfer, so dry silica, which allows particles to be dispersed, can provide superior heat insulating performance compared to wet silica. Note that the heat insulating material according to this embodiment is preferably produced using a manufacturing method in which a mixture containing the materials is processed into a sheet shape by a dry method. Therefore, it is preferable to use dry silica, silica aerogel, or the like, which has low thermal conductivity, as the inorganic particles.

[0198] (Average primary particle diameter of nanoparticles: 1 nm or more and 100 nm or less) Limiting the average primary particle diameter of nanoparticles to a predetermined range can achieve even higher thermal insulation. That is, when the average primary particle diameter of 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, thereby further improving thermal insulation. Furthermore, even when compressive stress is applied, the voids remaining between the nanoparticles and the contact points between many particles suppress conductive heat transfer, thereby maintaining the thermal insulation properties of the thermal insulation material. The average primary particle diameter of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. On the other hand, the average primary particle diameter of the nanoparticles is more preferably 50 nm or less, and even more preferably 10 nm or less.

[0199] (Inorganic hydrate particles) When inorganic hydrate particles receive heat from a heating element and reach a temperature above the thermal decomposition initiation temperature, they undergo thermal decomposition, releasing their own water of crystallization to lower the temperature of the heating element and its surroundings, thereby exhibiting the so-called "endothermic effect." After releasing the water of crystallization, they become porous, and exhibit heat insulating properties due to the countless air holes. 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 ), gallium hydroxide (Ga(OH) ３ ) etc.

[0200] For example, aluminum hydroxide contains 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 (Al ２ O ３ ) and functions as a heat insulating material. 2Al(OH) ３ →Al ２ O ３ +3H２ O

[0201] The heat transfer-suppressing sheet 50 according to this embodiment is preferably interposed between battery cells, for example. 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 onset temperature is 200°C or higher. The thermal decomposition onset 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. These inorganic hydrates are all preferred because they substantially overlap the temperature range of the rapid temperature rise in a battery cell that has experienced thermal runaway and can efficiently suppress temperature rise.

[0202] (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 the average particle diameter is too large, it takes a certain amount of 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 diameter 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.

[0203] (Particles Made of Thermally Expandable Inorganic Material) Examples of thermally expandable inorganic materials include vermiculite, bentonite, mica, and perlite.

[0204] (Particles Made of Hydrous Porous Material) Specific examples of hydrous porous materials include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

[0205] (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 heat transfer or conductive heat transfer within the heat insulating material can be suppressed in a temperature range of less than 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.

[0206] (Content of inorganic balloons: 60 mass % or less based on the total mass of the heat insulating material) The content of inorganic balloons is preferably 60 mass % or less based on the total mass of the heat insulating material.

[0207] (Average Particle Diameter of Inorganic Balloons: 1 μm or More and 100 μm or Less) The average particle diameter of the inorganic balloons is preferably 1 μm or more and 100 μm or less.

[0208] <Second inorganic particles> When two types of inorganic particles are contained in the 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.

[0209] 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 highly effective at 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 improved heat transfer suppression. Therefore, when nanoparticles are used as the first inorganic particles, it is preferable to further include second inorganic particles made of a metal oxide 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, zirconium oxide, and the like. Titanium oxide (titania), in particular, has a higher refractive index than other metal oxides and is highly effective at scattering light and blocking radiant heat in high-temperature regions above 500°C. Therefore, titania is the most preferable.

[0210] When at least one type of particles selected from dry silica particles and silica aerogel is used as the first inorganic particles and at least one type of particles selected from titania, zircon, zirconia, silicon carbide, zinc oxide, and alumina is used as the second inorganic particles, in order to obtain excellent heat insulating performance within a temperature range of 300° C. or less, the content of the first inorganic particles is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total mass of the inorganic particles. Furthermore, the content of the first inorganic particles is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on the total mass of the inorganic particles.

[0211] 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, and 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.

[0212] (Average primary particle diameter 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 diameter 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 diameter of the second inorganic particles is more preferably 5 μm or more and 30 μm or less, and most preferably 10 μm or less.

[0213] (Inorganic Particle Content) In this embodiment, if the total content of inorganic particles 4 in the thermal insulation material is appropriately controlled, the thermal insulation properties of the thermal insulation material can be sufficiently ensured. The total content of inorganic particles 4 is preferably 60 mass% or more, and more preferably 70 mass% or more, relative to the total mass of the thermal insulation material. Furthermore, if the total content of inorganic particles 4 is too high, the content of organic fibers will relatively decrease. Therefore, in order to sufficiently obtain the skeleton reinforcing effect and the inorganic particle retention effect, the total content of inorganic particles 4 is preferably 95 mass% or less, and more preferably 90 mass% or less, relative to the total mass of the thermal insulation material.

[0214] 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.

[0215] <Inorganic Fibers> As the inorganic fibers 15, a single inorganic fiber may be used, or two or more types of inorganic fibers may be used in combination. 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, 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 natural 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, and availability. From the standpoint of handleability, it is preferable that the insulating material contain at least one type of inorganic fiber selected from silica-alumina fiber, alumina fiber, silica fiber, rock wool, alkaline earth silicate fiber, and glass fiber.

[0216] 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.

[0217] The preferred lower limit of the average fiber length of the inorganic fibers is 0.1 mm, more preferably 0.5 mm. On the other hand, 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 be entangled with each other, which may reduce the mechanical strength of the insulating material. On the other hand, if the average fiber length exceeds 50 mm, although a reinforcing effect can be obtained, the inorganic fibers may not be able to be tightly entangled with each other, or may be curled up by a single inorganic fiber, which may result in continuous voids being easily generated, which may reduce the insulating properties.

[0218] 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.

[0219] (Inorganic Fiber Content) In the present 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 with respect to the total mass of the heat insulating material.

[0220] 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 effect of retaining the inorganic particles 4 and other compounding materials described below.

[0221] <Other Compounding Materials> The heat insulating material according to this embodiment may further contain, as necessary, a binder, a colorant, etc. All of these are useful for the purposes of reinforcing the heat insulating material, improving its formability, etc., and the total amount of these is preferably 10 mass % or less relative to the total mass of the heat insulating material.

[0222] <Elastic Sheet> The elastic sheet is made by processing an elastic material into a sheet shape. Any known elastic material can be used. Specifically, a sheet made of rubber or thermoplastic elastomer that has elasticity that allows it to flexibly deform in response to deformation of the battery cells 20 a, 20 b, and 20 c can be used.

[0223] The rubber may be either synthetic or natural rubber, and examples of synthetic rubber include styrene-butadiene rubber, butadiene rubber, chloroprene rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, nitrile rubber, silicone rubber, fluororubber, acrylic rubber, urethane rubber, polysulfide rubber, epichlorohydrin rubber, and foamed silicone.

[0224] Examples of thermoplastic elastomers include polystyrene-based, polyolefin-based, vinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, and polybutadiene-based thermoplastic elastomers. The elastomer may be either porous or non-porous. If the elastomer is porous, the cell structure may be either closed-cell or open-cell.

[0225] (Size of Elastic Sheet) The thickness of the elastic sheet is not particularly limited, but in order to effectively obtain the effects of the elastic sheet, it is preferable that the thickness is 1 mm or more and 10 mm or less.

[0226] [Thermal Insulation Material] The thermal insulation material used in the heat transfer-suppressing sheet according to this embodiment is not particularly limited as long as it has a thermal insulation effect. Thermal conductivity can be used as an index of the thermal insulation effect. In this embodiment, the thermal conductivity of the thermal insulation 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 thermal conductivity of the thermal insulation 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 thermal insulation material can be measured in accordance with the "Test Method for Thermal Conductivity of Refractories" described in JIS R 2251.

[0227] In addition, in this embodiment, a composite insulation material can be used in which the above-mentioned insulation material and a mica sheet are laminated. The mica sheet is a mica sheet material that contains mica and is processed into a sheet shape. Mica has excellent heat resistance and insulating properties, and mica sheets made by processing a material containing mica into a sheet shape also have excellent impact resistance. Therefore, for example, if the battery cell 20a explodes due to high temperature and generates debris, the composite insulation material can be prevented from being damaged. As a result, high insulation can be maintained between the battery cell 20a and the battery cell 20b.

[0228] The mica sheet material preferably contains oxide particles, oxide fibers, etc. in addition to mica. ２ , Al ２ O ３ , Ti ２ O ３ However, the present invention is not limited to these materials. It is more preferable to use a mica sheet made of a natural mineral. The sheet shape may be a flat sheet without holes or may have holes. If holes are provided in at least a portion of the center or other regions of the mica sheet, the mica sheet can follow the battery cells 20a, 20b, 20c without cracking when the battery cells 20a, 20b, 20c expand and contract.

[0229] (Size of Heat Insulating Material) When a heat insulating material and an elastic sheet are laminated together, the size of the main surface of the heat insulating material and the size of the main surface perpendicular to the thickness direction of the elastic sheet may be approximately the same, or the elastic sheet may be formed smaller than the heat insulating material, as in the seventh and eighth embodiments shown in Figures 27 to 30. Note that "approximately the same" means that the difference in size between the two is acceptable up to ±5% of the average value of the two, preferably up to ±3%, and more preferably up to ±1%.

[0230] [Method of Manufacturing Heat Transfer-Suppressing Sheet] The method of manufacturing a heat transfer-suppressing sheet according to this embodiment will be described in detail below, particularly with reference to an example using the insulating material of Structural Example 2. For example, a mixture is prepared by adding a core-sheath binder fiber (not shown), inorganic particles 4, and inorganic fibers 15 in a predetermined ratio to a mixer such as a V-type mixer. As described above, it is preferable to use a core-sheath fiber having a core made of a first organic material and a sheath made of a second organic material as the binder fiber. In this case, the melting point of the first organic material is higher than that of the second organic material.

[0231] The resulting mixture is then placed in a mold and pressurized with a press or the like. 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 are also fused to each other in areas where the binder fibers were in contact with each other. This allows for the production of a sheet-shaped insulating material 40.

[0232] Thereafter, the elastic sheet 51 is placed on one main surface of the heat insulating material 40, and the two are fixed together. There are no particular limitations on the method for fixing the heat insulating material 40 and the elastic sheet 51 to each other, and various methods can be used, such as a method of bonding them with an adhesive or the like, a method of sewing them using thread or the like, a method of clamping them with a fixing jig and fixing them, a method of covering them with a film or the like, and a method of covering them with a thermocompressible film and then heating the film to shrink and fix them.

[0233] In addition, the insulating material 10 that does not contain inorganic fibers 15 and the insulating material that does not contain organic fibers 1 can be obtained using the same manufacturing method as the insulating material 40, and the use of organic fibers 1 and inorganic fibers 15 can be selected arbitrarily.

[0234] 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.

[0235] The above-mentioned heat insulating material is preferably manufactured by a dry method. 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 production of the heat insulating material and making it difficult to handle the raw materials, a small amount of solvent such as water can be added within the range required for the dry method. For example, by adding a small amount of solvent such as water to the mixture, it is possible to suppress the scattering of inorganic particles during production.

[0236] Furthermore, the thermal insulation material uses binder fibers with a core-sheath structure. The melting point of the first organic material constituting the core is higher than that of the second organic material constituting the sheath. This allows the sheath to melt while leaving the core intact when the mixture is heated. After cooling, the outer surface of the core (organic fiber 1) is coated with the second organic material containing inorganic particles 4, thereby retaining the inorganic particles 4. The organic fiber 1 with the inorganic particles 4 fused to it appears to have a thicker fiber diameter, resulting in a higher strength than 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 areas where the binder fibers contact each other, forming a three-dimensional skeleton. As a result, the overall shape of the thermal insulation material can be maintained with even greater strength.

[0237] 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.

[0238] 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. 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 surface 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.

[0239] As described above, after laminating the heat insulating material and the elastic sheet 51, the surface of the laminate may be covered with a film or the like. Examples of polymer films include films made of polyimide, polycarbonate, PET, p-phenylene sulfide, polyetherimide, cross-linked polyethylene, flame-retardant chloroprene rubber, polyvinyl denfluoride, rigid polyvinyl chloride, polybutylene terephthalate, PTFE, PFA, FEP, ETFE, rigid PVC, flame-retardant PET, polystyrene, polyethersulfone, polyamideimide, polyacrylonitrile, polyethylene, polypropylene, polyamide, etc. The method for covering the surface with the film is not particularly limited, and examples include a method of attaching it with an adhesive or the like, a method of wrapping the heat insulating material and the elastic sheet 51 in a film, and a method of housing the heat insulating material and the elastic sheet 51 in a bag-shaped film.

[0240] As shown in Figures 21 and 22, in a configuration in which the resin film encases the laminate, a laminate including, for example, a thermal insulating material 10 and an elastic sheet 51 is placed on a planar resin film, and the planar resin film is folded, for example, to cover the top surface of the laminate. The planar film on the bottom surface of the laminate and the planar resin film on the top surface are then heated while applying pressure around the periphery of the laminate to form a film fusion zone 114. The resin film around the periphery of the laminate is then heated to shrink, thereby adhering the resin film 112 to the outer surface of the laminate. At any time before shrinking the resin film, multiple holes 113 are formed in the resin film in the regions that will become the first-surface film 112a and the second-surface film 112b. The heat transfer-suppressing sheet can be manufactured using the process described above.

[0241] In the second to fourth embodiments, the resin film 112, 312 and the covering material 323 have multiple elliptical holes. However, these holes may be formed in an elliptical shape beforehand, or circular holes may be formed and then the elliptical shape may be formed by heat-shrinking the resin film or the like. When forming an elliptical shape by heat-shrinking the resin film, a method can be used in which the length of a pair of sides of the laminate and the length of a pair of fused portions parallel to the pair of sides are adjusted, or the distance between the fused portions and the folded side of the planar resin film is adjusted. For example, by bringing the length of a pair of fused portions parallel to the pair of sides of the laminate closer to the length of the pair of sides of the laminate, the force of shrinkage of the resin film is strengthened, and elliptical holes having major axes perpendicular to the pair of sides can be formed.

[0242] The method for enclosing the laminate in the resin film 112, 312 is not particularly limited, and examples thereof include shrink packaging, in which the film is shrunk as described above, a method in which the laminate is wrapped in a resin film and then attached with an adhesive, or a method in which the laminate is housed in a bag-shaped film. Whichever method is used, as shown in Figures 21 and 22, the area ratio of the holes 113 in the first-surface-side film 112a and the second-surface-side film 112b can be made larger than the area ratio of the holes (not shown) in the end-surface-side film 112c. In Figures 21 and 22, it is preferable that the end-surface-side film 112c has a joint between the resin films.

[0243] Next, binder fibers and heating conditions that are preferably used in the method for producing the heat transfer-suppressing sheet 50 according to this embodiment, as well as other binder materials, will be described.

[0244] <Binder Fiber> In this embodiment, when using binder fiber 3 having a core-sheath structure, there are no particular limitations as long as 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. The first organic material constituting the core can be at least one selected from polyethylene terephthalate, polypropylene, and nylon. The second organic material constituting the sheath can be at least one selected from polyethylene terephthalate, polyethylene, polypropylene, and nylon.

[0245] If the melting point of the first organic material constituting the core is sufficiently higher than that of the second organic material constituting the shell, the heating temperature setting margin in the heating step can be expanded, making it easier to set the temperature to obtain a 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.

[0246] Note that binder fibers 3 having the above-described 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 and sheath 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.

[0247] 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. However, softening accompanied by a change in shape is also considered to be a type of melting deformation. The melting point of the binder fiber sheath can be measured, for example, by the following method. The binder fiber to be measured is placed in contact with glass fiber, which has a higher melting point, and heated from room temperature to, for example, 200°C at a heating 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 determining the melting point of the second organic material constituting the sheath.

[0248] (Binder Fiber Content) In this embodiment, when a core-sheath binder fiber 3 is used as a material, if the binder fiber content in the mixture is appropriately controlled, the skeleton of the resulting insulating material can be sufficiently reinforced. The binder fiber 3 content is preferably 5% by mass or more, and more preferably 10% by mass or more, relative to the total mass of the mixture. Furthermore, if the binder fiber 3 content is too high, the content of the inorganic particles 4 will relatively decrease. Therefore, in order to obtain the desired insulating performance, the binder fiber 3 content is preferably 25% by mass or less, and more preferably 20% by mass or less, relative to the total mass of the mixture.

[0249] (Hot Melt Powder) In this embodiment, in addition to the binder fibers 3 and inorganic particles 4, the mixture may contain hot melt powder as a binder material. The hot melt powder is a powder that contains, for example, a third organic material different from the first organic material and the second organic material, and has the property of melting when heated. When the hot melt powder is contained in the mixture 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.

[0250] Hot melt powders with various melting points can be used, but a hot melt powder with an appropriate melting point can be selected taking into account 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.

[0251] 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, when the sheath and hot melt powder melt together and then cool and harden, the organic fiber (core) 1, the molten sheath around it, and the hot melt powder present in the gaps between the inorganic particles 4 harden first. As a result, the position of the organic fiber 1 can be fixed, and then the molten sheath is fused to the organic fiber, facilitating the formation of a three-dimensional skeleton. This further improves the strength of the entire sheet.

[0252] 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 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 third organic material, more preferably 70°C or more higher, and even more preferably 80°C or more higher.

[0253] 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. Examples of components constituting the hot melt powder include polyethylene, polyester, polyamide, and ethylene vinyl acetate.

[0254] (Hot-melt powder content) When hot-melt powder is added to the mixture to suppress the shedding of inorganic particles, even a small amount of hot-melt powder can be used to suppress powder shedding. Therefore, the hot-melt powder content is preferably 0.5% by mass or more, more preferably 1% by mass or more, relative to the total mass of the mixture. On the other hand, since increasing the hot-melt powder content relatively reduces the content of inorganic particles 4 and the like, in order to obtain the desired heat insulating performance, the hot-melt powder content is preferably 5% by mass or less, more preferably 4% by mass or less, relative to the total mass of the mixture.

[0255] <Heating Conditions> When a binder fiber having a core-sheath structure is used as the material for the thermal insulating 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 welded parts 5.

[0256] 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. On the other hand, 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.

[0257] The heating time is not particularly limited, but is preferably set to a time sufficient to melt the sheath, for example, from 3 minutes to 15 minutes.

[0258] 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, more preferably 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. On the other hand, the heating temperature is preferably set to be at least 10°C lower, more preferably 20°C lower, than the melting point of the first organic material constituting the core. Setting the heating temperature at such a temperature allows a strong skeleton to be formed, further improving the strength of the sheet and preventing the inorganic particles 4 from falling off due to the welded portions 5, etc.

[0259] <Thickness of Heat-Transfer-Suppressing Sheet> The thickness of the heat-transfer-suppressing sheet according to this embodiment 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 insulation of the heat-transfer-suppressing sheet.

[0260] [Battery Assembly] An example of a battery assembly using the heat-transfer-suppressing sheet 50 according to an embodiment of the present invention is as shown in FIG. 2 above. The configuration and effects of the battery assembly will now be described in detail with reference to FIG. 2. As described above, the heat-transfer-suppressing sheet 50 shown in FIG. 2 can be replaced with heat-transfer-suppressing sheets 120, 130, 140, 150, 160, 170, 180, and 190 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.

[0261] 2, 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-reducing sheet 50 is as described above.

[0262] In the battery pack 100 configured in this manner, the heat-transfer-suppressing sheet has high thermal insulation properties, so even if a certain battery cell 20a becomes hot, the heat transfer to the battery cell 20b can be suppressed because 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. Furthermore, in the battery pack according to this embodiment, the heat-transfer-suppressing sheet is an elastic sheet, so unnecessary pressure is prevented from being applied to the battery cells during charging / discharging or in the event of an abnormality. As a result, deterioration of battery performance can be suppressed and durability can be improved.

[0263] The battery pack 100 of this embodiment is not limited to the battery pack illustrated in Fig. 2. 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.

[0264] In the battery pack 100 configured in this manner, if a battery cell ignites, the flame can be prevented 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 ignites, the safety of the passengers can be ensured. Furthermore, since the heat transfer suppression sheet 50 can be placed not only between the battery cells but also between the battery cells 20a, 20b, and 20c and the battery case 30, there is no need to fabricate additional flame retardant materials, and a safe battery pack 100 can be easily configured at low cost.

[0265] In the battery pack of this embodiment, the heat-transfer-suppressing sheet 50 disposed between the battery cells 20 a, 20 b, and 20 c and the battery case 30 may be in contact with the battery cells or may have a gap therebetween. The heat-transfer-suppressing sheet of this embodiment is an elastic sheet, and therefore can allow deformation of the battery cells even if the temperature of any of the multiple battery cells rises and the volume expands.

[0266] 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 without being affected by 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.

[0267] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0268] This application is based on a Japanese patent application filed on July 31, 2023 (Patent Application No. 2023-124840) and a Japanese patent application filed on July 19, 2024 (Patent Application No. 2024-115979), the contents of which are incorporated by reference into this application.

[0269] REFERENCE SIGNS LIST 1 organic fiber 3 binder fiber 4 inorganic particle 5 fused portion 6, 47 fiber bundle 7 hole 8 void portion 10, 40, 60, 70, 80, 90, 110 heat insulating material 11 fiber layer 15 inorganic fiber 16 fiber portion 20a, 20b, 20c battery cell 28 air layer 30 battery case 32 base portion 33 support portion 50, 120, 130, 140, 150, 160, 170, 180, 190 heat transfer suppressing sheet 51, 751 elastic sheet 100 assembled battery 111, 311, 511 laminate 112, 312 resin film 113 hole 114 film fused portion 313, 323 coating material 316 fused portion 317 Gap portion 512, 514 Bulge suppression sheet

Claims

1. A heat transfer-suppressing sheet comprising: an insulating material having inorganic particles and organic or inorganic fibers; and an elastic sheet laminated to at least one of a first surface and a second surface perpendicular to the thickness direction of the insulating material.

2. The heat transfer suppression sheet according to claim 1, wherein the heat insulating material has a plurality of pores that are three-dimensionally connected.

3. The heat transfer suppression sheet as described in claim 1, characterized in that when the insulating material contains organic fibers, the organic fibers have a fused portion covering at least a portion of their surface, and at least a portion of the inorganic particles are fused to the organic fibers by the fused portion.

4. The heat transfer suppression sheet according to claim 3, wherein in the heat insulating material, the organic fibers are made of a first organic material, the welded portion includes a second organic material, and the melting point of the second organic material is lower than the melting point of the first organic material.

5. The heat transfer suppressing sheet according to claim 4, wherein in said heat insulating material, the melting point of said second organic material is at least 60° C. lower than the melting point of said first organic material.

6. The heat transfer suppression sheet according to claim 4, characterized in that in the heat insulating material, the first organic material is at least one selected from polyethylene terephthalate, polypropylene and nylon, and the second organic material is at least one selected from polyethylene terephthalate, polyethylene, polypropylene and nylon.

7. The heat transfer suppressing sheet according to claim 1, wherein the heat insulating material essentially contains the inorganic fibers.

8. The heat transfer-suppressing sheet according to claim 7, wherein the inorganic fibers are at least one type selected from the group consisting of silica-alumina fibers, alumina fibers, silica fibers, rock wool, alkaline earth silicate fibers, and glass fibers.

9. The heat transfer suppression sheet described in claim 3, characterized in that the insulation material has a fiber layer on at least a portion of the first surface and the second surface, in which at least a portion of a plurality of the organic fibers are welded together by the welding portion.

10. The heat transfer suppression sheet according to claim 9, wherein the heat insulating material further comprises inorganic fibers, and the fiber layer contains the inorganic fibers.

11. The heat transfer suppression sheet according to claim 1, characterized in that in the heat insulating material, the inorganic particles are particles made of at least one type of inorganic material selected from the group consisting of oxide particles, carbide particles, nitride particles and inorganic hydrate particles.

12. The heat transfer suppression sheet according to claim 9, wherein in the heat insulating material, the inorganic particles include at least one type of particles selected from dry silica particles and silica aerogel.

13. The heat transfer suppression sheet according to claim 12, wherein in the heat insulating material, the inorganic particles further include at least one type of particles selected from the group consisting of titania, zircon, zirconia, silicon carbide, zinc oxide, and alumina.

14. A heat transfer inhibiting sheet as described in any one of claims 1 to 13, further comprising a resin film encapsulating a laminate having the insulating material and the elastic sheet, the resin film having a plurality of holes and being composed of a first surface side film and a second surface side film arranged on the first surface side and the second surface side of the laminate perpendicular to the thickness direction of the laminate, and an end surface side film arranged on the end surface side parallel to the thickness direction of the laminate, wherein the area ratio of the holes in the first surface side film and the second surface side film to the total area of ​​the first surface side film and the second surface side film is greater than the area ratio of the holes in the end surface side film to the total area of ​​the end surface side film.

15. An assembled battery comprising a plurality of battery cells and the heat transfer suppression sheet according to any one of claims 1 to 13, the plurality of battery cells being connected in series or in parallel.

16. A battery pack comprising a plurality of battery cells and the heat transfer suppression sheet according to claim 14, the plurality of battery cells being connected in series or parallel.

Images