Heat transfer suppression member and battery pack

Abstract

Provided are: a heat transfer suppression member capable of suppressing destruction of a battery case and deterioration of battery performance due to deformation of battery cells while ensuring an interval between the battery cells, and capable of suppressing propagation of heat between the battery cells at the time of abnormality; and a battery pack capable of suppressing destruction of the battery case and deterioration of battery performance while suppressing propagation of heat between the battery cells. The heat transfer suppression member (50) has: a frame body (53) that surrounds the outer periphery in a plan view; and a sheet-like heat insulation material (10) that is disposed inside the frame body (53) and is provided with a pair of main surfaces (10s). In a cross-sectional view orthogonal to the plan view of the heat transfer suppression member (50), the thickness of the heat insulation material (10) is thinner than the thickness of the frame body (53).

Description

Heat transfer suppression member and battery pack

[0001] The present invention relates to a heat transfer suppressing member and a battery pack having the heat transfer suppressing member.

[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 primarily lithium-ion secondary batteries, which offer higher capacity and power output than lead-acid batteries, nickel-metal hydride batteries, etc. If a battery cell experiences thermal runaway, such as a sudden rise in temperature due to an internal short circuit or overcharging, and continues to generate heat (i.e., an "abnormal event"), the heat from the battery cell experiencing thermal runaway may propagate to other adjacent battery cells, potentially causing thermal runaway in those cells. Furthermore, if a battery cell experiences thermal runaway, gas is generated inside the battery, causing an increase in internal pressure and resulting in deformation of the battery cell.

[0004] As a countermeasure against the occurrence of thermal runaway, for example, Patent Document 1 discloses a heat-transfer-suppressing sheet that has excellent heat-transfer suppression effects and can maintain high thermal insulation performance by suppressing a decrease in the thickness of the insulating material even when the battery cell expands. The heat-transfer-suppressing sheet described in Patent Document 1 includes a first insulating material and a second insulating material, and the thermal conductivity of the first insulating material is lower than that of the second insulating material. In addition, the compressive strength of the second insulating material is higher than that of the first insulating material, and the first insulating material is sandwiched between multiple second insulating materials.

[0005] Furthermore, Patent Document 2 proposes a thermal insulation material that maintains its structure and suppresses deterioration of thermal conductivity against compressive stress. The thermal insulation material described in Patent Document 2 includes a composite layer containing fibers and silica aerogel, and resin struts arranged in the thickness direction of the composite layer.

[0006] The heat transfer suppression sheet and the heat insulating material described in the above Patent Documents 1 and 2 are both intended to prevent the heat insulating material from being compressed and narrowing the gaps between the battery cells, thereby suppressing a decrease in thermal conductivity.

[0007] Japanese Patent Publication No. 2020-187869 Japanese Patent Publication No. 2017-215014

[0008] However, when battery cells undergo significant deformation due to thermal runaway, if a high-compression-strength insulating material or resin support is placed in the area where the battery cells contact the insulating material, as in Patent Documents 1 and 2, a repulsive force is generated against the battery cells. During thermal runaway, the central region of the battery cell's main surface is most susceptible to deformation. Therefore, if the spacing between the cells in the central region is fixed by insulating material, the outermost battery cells of multiple connected battery cells will be pressed against the battery case. This can result in destruction of the pressed battery cells or the case. Furthermore, even when battery cells are subjected to charge / discharge cycles (i.e., during "normal use"), slight deformation of the battery cells occurs. Therefore, when the internal pressure of the battery cells repeatedly increases and decreases during charge / discharge, the battery cells are repeatedly pressed and released by the case and insulating material, causing a decrease in battery performance.

[0009] Furthermore, the use of electric vehicles and hybrid vehicles is rapidly expanding, and in order to ensure high safety, there is a demand for the development of heat insulating materials with even better heat insulating properties.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a heat transfer suppression member that can suppress damage to the battery case and deterioration of battery performance due to deformation of the battery cells while ensuring spacing between the battery cells, and can suppress the propagation of heat between the battery cells in the event of an abnormality, and a battery pack that can suppress damage to the battery case and deterioration of battery performance while suppressing the propagation of heat between the battery cells.

[0011] The above object of the present invention is achieved by the following configuration [1] relating to a heat transfer suppressing member.

[0012] [1] A heat transfer suppression member comprising: a frame body surrounding an outer periphery in a plan view; and a sheet-like insulating material arranged inside the frame body and having a pair of main surfaces, wherein, in a cross-sectional view perpendicular to the plan view, the thickness of the insulating material is thinner than the thickness of the frame body.

[0013] Furthermore, preferred embodiments of the present invention relating to the heat transfer suppressing member relate to the following [2] to

[15] .

[0014] [2] The heat transfer suppressing member according to [1], further comprising a film covering a main surface of the heat insulating material.

[0015] [3] The heat transfer suppressing member according to [2], characterized in that a gap is provided between at least one of the pair of main surfaces and the film.

[0016] [4] The heat transfer suppressing member described in [1], characterized in that it has an elastic material laminated on at least one of the pair of main surfaces of the insulating material, and in the cross-sectional view, the thickness of the laminate of the insulating material and the elastic material is approximately the same as the thickness of the frame body or is thinner than the thickness of the frame body.

[0017] [5] The heat transfer suppressing member according to [4], wherein the laminate has a pair of outer main surfaces perpendicular to the thickness direction, and has a film covering the pair of outer main surfaces.

[0018] [6] The heat transfer suppressing member according to [5], characterized in that a gap is provided between at least one of the pair of outer principal surfaces and the film.

[0019] [7] The heat transfer suppressing member according to [4] or [5], wherein the elastic material contains at least one selected from synthetic rubber, natural rubber, and thermoplastic elastomer.

[0020] [8] The heat transfer suppressing member according to any one of [1] to [7], further comprising partition walls that divide the inside of the frame body into a plurality of regions, and a plurality of the heat insulating materials arranged in the plurality of regions.

[0021] [9] The heat transfer suppressing member according to [8], wherein the plurality of heat insulating materials include a first heat insulating material and a second heat insulating material having properties different from each other.

[0022]

[10] The heat transfer suppressing member according to [9], wherein the elastic modulus of the first insulating material is smaller than the elastic modulus of the second insulating material.

[0023]

[11] The heat transfer suppressing member according to

[10] , wherein the first insulating material is disposed in a region including a center of the plurality of regions.

[0024]

[12] The heat transfer suppressing member according to any one of [8] to

[11] , wherein, in a plan view, the width of the partition wall in a direction perpendicular to the longitudinal direction is smaller than the width of the frame in a direction perpendicular to the longitudinal direction.

[0025]

[13] The heat transfer suppressing member according to any one of [8] to

[12] , wherein the partition wall is made primarily of an insulating material.

[0026]

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

[13] , wherein the frame is made primarily of an insulating material.

[0027]

[15] The heat transfer suppressing member according to any one of [1] to

[12] , wherein the heat insulating material contains inorganic particles and organic fibers.

[0028] The above object of the present invention is also achieved by the following configuration

[16] relating to a battery pack.

[0029]

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

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

[0030] The heat transfer suppressing member of the present invention has a frame that surrounds the outer periphery, ensuring sufficient spacing between battery cells. Furthermore, since the heat insulating material is disposed inside the frame and is thinner than the frame, it is possible to suppress damage to the battery case and deterioration of battery performance due to deformation of the battery cells, as well as suppressing heat transfer between battery cells in the event of an abnormality.

[0031] Because the battery pack of the present invention has the above-mentioned heat transfer suppression member, it is possible to suppress the transfer of heat between each battery cell while suppressing damage to the battery case and deterioration of battery performance, thereby obtaining a battery pack that can maintain excellent battery performance.

[0032] FIG. 1A is a plan view showing a heat-transfer-suppressing member according to a first embodiment of the present invention. FIG. 1B is a cross-sectional view taken along line II in FIG. 1A. FIG. 2 is a cross-sectional view schematically showing a battery pack including a heat-transfer-suppressing sheet according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view showing a heat-transfer-suppressing member according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view showing a heat-transfer-suppressing member according to a third embodiment of the present invention. FIG. 5A is a plan view showing a heat-transfer-suppressing member according to a fourth embodiment of the present invention. FIG. 5B is a cross-sectional view taken along line II-II in FIG. 5A. FIG. 6 is a plan view showing a first modified example of a heat-transfer-suppressing member according to a fourth embodiment of the present invention. FIG. 7 is a plan view showing a second modified example of a heat-transfer-suppressing member according to the fourth embodiment of the present invention. FIG. 8 is a photograph showing a first structural example of a heat-transfer-suppressing member used in a heat-transfer-suppressing member according to an embodiment of the present invention. FIG. 9 is a photograph showing an enlarged view of a portion of the heat-transfer-suppressing member shown in FIG. 8. FIG. 10 is a photograph showing a second structural example of a heat-transfer-suppressing member used in a heat-transfer-suppressing member according to an embodiment of the present invention. FIG. 11 is a schematic diagram showing a third structural example of a heat-transfer-suppressing member used in a heat-transfer-suppressing member according to an embodiment of the present invention. FIG. 12 is a schematic diagram showing an enlarged portion of FIG. 11 . FIG. 13 is a photograph, substitute for a drawing, showing the insulating material shown in FIG. 11 . FIG. 14 is a photograph, substitute for a drawing, showing a fourth structural example of an insulating material used in a heat-transfer-suppressing member according to an embodiment of the present invention. FIG. 15 is a photograph, substitute for a drawing, showing an enlarged structure of the insulating material shown in FIG. 14 . FIG. 16 is a photograph, substitute for a drawing, showing a cross-section of the insulating material shown in FIG. 14 . FIG. 17 is a schematic diagram showing a fifth structural example of an insulating material used in a heat-transfer-suppressing member according to an embodiment of the present invention. FIG. 18 is a schematic diagram showing an enlarged view of portion A of the insulating material shown in FIG. 17 . FIG. 19 is a photograph, substitute for a drawing, showing a sixth structural example of an insulating material used in a heat-transfer-suppressing member according to an embodiment of the present invention. FIG. 20 is a photograph, substitute for a drawing, showing another region of the insulating material shown in FIG. 19 . FIG. 21 is a photograph, substitute for a drawing, showing a cross-section of the insulating material shown in FIGS. 19 and 20 . FIG. 22 is a photograph, substitute for a drawing, showing a seventh structural example of an insulating material used in a heat-transfer-suppressing member according to an embodiment of the present invention. Fig. 23 is a photograph showing an enlarged view of a portion of the thermal insulation material shown in Fig. 22. Fig. 24 is a schematic diagram showing an example of a method for specifying the length of the fiber bundle. Fig. 25 is a photograph showing another example of the structure of the thermal insulation material shown in Fig. 22.

[0033] The inventors conducted extensive research to develop a heat transfer suppressing member that can suppress the application of unnecessary pressure to battery cells while maintaining desired thermal insulation properties and prevent a decrease in battery performance. As a result, they discovered that the above-mentioned problems can be solved by placing a thermal insulating material inside a frame that surrounds the outer periphery and making the thickness of the thermal insulating material thinner than the frame. That is, by using the frame to ensure spacing between battery cells and placing a thermal insulating material thinner than the frame inside the frame, a space can be secured for expansion of the battery cells, thereby reducing the pressure applied to the battery cells when they expand.

[0034] A heat transfer suppressing member, a manufacturing method thereof, and a battery assembly 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 member according to an embodiment of the present invention will be described.

[0035] [Heat Transfer Suppressing Member] [First Embodiment] FIG. 1A is a plan view showing a heat transfer suppressing member according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line II of the heat transfer suppressing member. As shown in FIGS. 1A and 1B, a heat transfer suppressing member 50 according to the first embodiment includes a frame 53 surrounding the outer periphery in a plan view, a sheet-like insulating material 10 disposed inside the frame 53 and having a pair of main surfaces 10s, and a film 52 attached to a surface of the frame 53 parallel to the main surfaces of the insulating material 10. In this specification, "plan view" refers to the heat transfer suppressing member viewed from above when the main surfaces of the insulating material 10 are oriented vertically. Furthermore, "cross-sectional view" refers to the cross-section of the heat transfer suppressing member viewed from a direction perpendicular to the plan view. In this embodiment, the thickness of the insulating material 10 is thinner than the thickness of the frame 53. Therefore, gaps 54 are formed between the film 52 and the main surfaces 10s on both sides of the insulating material 10.

[0036] A specific use of the heat transfer-suppressing member 50 according to the first embodiment will be described below. FIG. 2 is a cross-sectional view schematically illustrating a battery pack including a heat transfer-suppressing sheet according to the first embodiment of the present invention. As shown in FIG. 2, the heat transfer-suppressing member 50 can be used by interposing the heat transfer-suppressing member 50 between a plurality of battery cells 20a, 20b, and 20c. The battery pack 100 is configured by storing the plurality of battery cells 20a, 20b, and 20c in a state in which they are connected in series or parallel (the connected state is not shown) in a battery case 30. The battery cells 20a, 20b, and 20c are preferably lithium-ion secondary batteries, for example, but are not limited thereto and may also be used with other secondary batteries.

[0037] In the heat transfer suppressing member 50 according to the first embodiment configured as described above, frame bodies 53 are disposed between the battery cells 20a and 20b, and between the battery cells 20b and 20c. Therefore, by adjusting the thickness of the frame bodies 53, the desired spacing between the battery cells can be ensured. Furthermore, a thermal insulator 10 having a thickness thinner than the frame body 53 is disposed inside the frame body 53. Therefore, although the film 52 exists between the thermal insulator 10 and the battery cells 20a, 20b, and 20c, a gap 54 is formed. When the battery cells 20a, 20b, and 20c expand, the central portions of the main surfaces of the battery cells 20a, 20b, and 20c, which have the largest areas, generally protrude. Therefore, when the battery cells 20a, 20b, and 20c expand, the gap 54 serves as a refuge for the expansion. Therefore, unnecessary pressure is prevented from being applied to the battery cells 20a, 20b, and 20c, and a decrease in battery performance is suppressed.

[0038] Furthermore, the insulating material 10 has a predetermined insulating property, but in this embodiment, there is a gap 54 between the insulating material 10 and the film 52, and since air is present in this gap 54, the air can provide an even better insulating effect.

[0039] Furthermore, in this embodiment, since the film 52 covers the main surface 10s of the insulating material 10, if the insulating material 10 contains, for example, inorganic particles, it is possible to prevent the inside of the battery case 30 from being contaminated by the inorganic particles falling off, i.e., powder falling off.

[0040] In this embodiment, the film 52 is heat-sealed to a portion of the frame 53, so that the film 52 covers the main surface 10s of the thermal insulation material 10, but the present invention is not limited to this configuration of the film 52. For example, the film 52 may be arranged so as to entirely enclose the frame 53 and the thermal insulation material 10, or the film 52 may be arranged so as to cover only the thermal insulation material 10, with gaps being formed between the film 52 and the battery cells 20a, 20b, 20c.

[0041] Furthermore, in the present invention, the film 52 is not necessarily required. Even if the heat transfer suppressing member does not have the film 52, the heat insulating material 10 is formed to be thinner than the frame body 53, so a step will be created between the frame body 53 and the heat insulating material 10 in a cross-sectional view. Specifically, the main surface 10s of the heat insulating material 10 has a concave shape that is more recessed than the frame body 53. Therefore, when the heat transfer suppressing member 50 is interposed between the battery cells 20a, 20b, and 20c, the presence of the frame body 53 can ensure a gap 54. As a result, it is possible to suppress the application of unnecessary pressure to the battery cells when the battery cells expand.

[0042] Second Embodiment Fig. 3 is a cross-sectional view showing a heat-transfer suppressing member according to a second embodiment of the present invention. In the heat-transfer suppressing member 120 shown in Fig. 3, the same components as those shown in Figs. 1A and 1B are designated by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0043] As shown in FIG. 3 , the heat transfer suppressing member 120 according to the second embodiment has elastic members 51 laminated on both main surfaces 10s of the thermal insulation material 10. That is, the thermal insulation material 10 is sandwiched between a pair of elastic members 51 to form a laminate 111. The thickness of the laminate 111 is configured to be substantially the same as the thickness of the frame 53, and the film 52 is disposed to cover the outer main surface 111s of the laminate 111. Therefore, both outer main surfaces 111s of the laminate 111 and the film 52 are in contact with each other over most of the surface, and no gaps are formed. Note that the "substantially the same" thickness of the laminate 111 and the frame 53 means that a difference in thickness between the two is acceptable within ±5% of the average value of the two, preferably ±3%, and more preferably ±1%.

[0044] A specific example of application of the heat transfer suppressing member 120 configured as described above to a battery pack will be described below. Here, the case where the heat transfer suppressing member 120 shown in Fig. 3 is applied instead of the heat transfer suppressing member 50 of the battery pack 100 shown in Fig. 2 will be described.

[0045] In this embodiment, the heat transfer suppressing member 120 also has a frame 53, so that the desired spacing between the battery cells can be ensured by adjusting the thickness of the frame 53. Furthermore, because the elastic material 51 is laminated on both main surfaces 10s of the thermal insulation material 10 and the film 52 is further provided on the outer surface thereof, powder shedding can be further suppressed when the thermal insulation material 10 contains inorganic particles or the like. In particular, even if the film 52 is torn in the event of an abnormality, contamination due to powder shedding can be prevented if the main surface 10s of the thermal insulation material 10 is covered with the elastic material 51.

[0046] Furthermore, in the second embodiment, an elastic material 51 is provided instead of the voids 54 shown in the first embodiment. The elastic material 51 has elasticity, and when the expansion of the battery cells 20a, 20b, and 20c presses on the heat transfer suppressing member 120, the elastic material 51 deforms by an appropriate amount, thereby suppressing the repulsive force on the battery cells. In other words, when the battery cells 20a, 20b, and 20c deform, the elastic material 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, similar to the first embodiment in which the voids 54 are formed, the heat transfer suppressing member 120 according to the second embodiment can also suppress a decrease in battery performance due to repeated pressing and releasing of the battery cells 20a, 20b, and 20c.

[0047] In the second embodiment, the elastic material 51 is laminated on both main surfaces 10s of the thermal insulation material 10, but the present invention is not limited to this. The elastic material 51 may be laminated so as to be sandwiched between a pair of thermal insulation materials 10. The elastic material 51 may also be laminated on only one main surface of the thermal insulation material 10. In this case, the thickness of the two-layer laminate 111 of the thermal insulation material 10 and the elastic material 51 can be made thinner than that of a three-layer laminate. Specifically, the two-layer laminate 111 is preferably thinner than the thickness of the frame 53, and the position of the laminate 111 in the thickness direction is preferably adjusted so that a gap is formed between the other main surface of the thermal insulation material 10 on which the elastic material 51 is not laminated and the battery cell.

[0048] As in the first embodiment, in the second embodiment, the film 52 may or may not be disposed. When using a two-layer laminate 111 of the thermal insulation material 10 and the elastic material 51, the film 52 is preferably disposed so as to cover at least the main surface of the thermal insulation material 10 on which the elastic material 51 is not laminated. This results in both main surfaces 10s of the thermal insulation material 10 being covered with the elastic material 51 or the film 52, thereby achieving the effect of suppressing powder shedding. Furthermore, the film 52 may be disposed so as to enclose all of the frame 53, the thermal insulation material 10, and the elastic material 51, or may be disposed so as to enclose the laminate 111 of the thermal insulation material 10 and the elastic material 51, or may be disposed so as to enclose only the thermal insulation material 10.

[0049] 4 is a cross-sectional view of a heat-transfer suppressing member according to a third embodiment of the present invention. In the heat-transfer suppressing member 130 shown in FIG. 4, the same components as those shown in FIGS. 1B and 3 are designated by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0050] 4, in the third embodiment, a laminate 111 made of a thermal insulating material 10 and elastic materials 51 laminated on both main surfaces 10s thereof is formed to be thinner than a frame body 53. In addition, a film 52 is disposed so as to cover an outer main surface 111s of the laminate 111 with a gap 54 interposed therebetween.

[0051] When the heat transfer suppressing member 130 configured as described above is used in place of the heat transfer suppressing member 50 of the battery pack 100, the same effects as those of the first and second embodiments can be obtained. Furthermore, since the laminate 111 has the voids 54 on both outer main surfaces 111s thereof, the thermal insulation performance can be improved compared to the second embodiment. It is preferable to have the voids 54 between at least one of the outer main surfaces 111s of the laminate 111 and the film 52, and it is more preferable to have the voids 54 between both outer main surfaces 111s thereof and the film 52. In the third embodiment, the laminate 111 may also be configured by laminating the elastic material 51 on only one main surface 10s of the thermal insulating material 10. The presence or absence and arrangement of the film 52 are also similar to those of the first and second embodiments.

[0052] 5A is a plan view showing a heat-transfer suppressing member according to a fourth embodiment of the present invention, and FIG. 5B is a cross-sectional view taken along line II-II of FIG. 5A. In the heat-transfer suppressing member 140 shown in FIG. 5A and FIG. 5B, the same components as those shown in FIG. 1A and FIG. 1B are designated by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0053] The heat transfer suppressing member 140 according to the fourth embodiment has partition walls 58a, 58b that divide the inside of the frame body 53 into multiple regions. More specifically, the partition walls 58a, 58b are formed on the frame body 53 so as to connect a pair of frame members 53a that face each other in the vertical direction when the heat transfer suppressing member 140 is interposed between battery cells. This divides the inside of the frame body 53 into three regions: a first region 57a, a second region 57b, and a third region 57c. A second insulating material 10b, a first insulating material 10a, and a second insulating material 10b that are thinner than the thickness of the frame body 53 are disposed in the first region 57a, the second region 57b, and the third region 57c, respectively. In this embodiment, the first insulating material 10a is made of an insulating material with a lower elastic modulus than the second insulating material 10b.

[0054] When the heat transfer suppressing member 140 configured as described above is used in place of the heat transfer suppressing member 50 of the battery pack 100, the frame 53 ensures spacing between the battery cells, as in the first and third embodiments. Furthermore, because gaps 54 are formed between the first and second insulating materials 10a and 10b and the battery cells 20a, 20b, and 20c, unnecessary pressure is prevented from being applied to the battery cells even if the battery cells expand. Furthermore, the air present in the gaps 54 provides even better thermal insulation.

[0055] As described above, the center of the widest outer surface (main surface) of the battery cells 20a, 20b, and 20c is more likely to protrude due to expansion than the edges. Furthermore, terminals and exhaust valves are typically provided above the battery cells, and the exhaust valve side is more likely to become hot and deform in the event of an abnormality. Therefore, in this embodiment, of the three divided regions (first region 57a, second region 57b, and third region 57c), the first insulating material 10a with a low elastic modulus is placed in the second region 57b, which is central and extends vertically, and the second insulating material 10b with a higher elastic modulus than the first insulating material 10a is placed on both sides of the second region 57b. In other words, the first insulating material 10a placed in the central second region 57b is softer and has a higher resilience. Therefore, when the battery cells 20a, 20b, and 20c expand and deform at their central and upper portions in the event of an abnormality, the first insulating material 10a with a low elastic modulus can better absorb the deformation of the battery cells.

[0056] In this embodiment, the multiple insulating materials arranged in the multiple regions separated by partition walls have different elastic moduli. However, insulating materials with different properties can be used as needed. For example, an insulating material with extremely high insulating properties can be arranged in the hottest region, and insulating materials that take cost into consideration can be arranged in the other regions. When insulating materials with different properties are arranged in multiple regions, the types of insulating materials are not limited to two types, the first insulating material 10a and the second insulating material 10b. Three or more types of insulating materials with different properties can be used. Furthermore, insulating materials with the same elastic modulus can be arranged in all multiple regions. Even with this configuration, in this embodiment, the thicknesses of the first insulating material 10a and the second insulating material 10b are thinner than the thickness of the frame body 53, thereby preventing unnecessary pressure from being applied to the battery cells when they expand.

[0057] Furthermore, by disposing multiple insulating materials in multiple regions, the volume per insulating material can be reduced, facilitating manufacturing and improving handling. Furthermore, it is also preferable to form the partition walls 58a, 58b so that all of the multiple regions have substantially the same shape and size. In a heat transfer suppressing member configured in this manner, even if some of the insulating materials are damaged in the event of an abnormality such as thermal runaway, the undamaged insulating materials can be reused in other heat transfer suppressing members, thereby reducing environmental impact. Note that the term "substantially the same" as used above means that differences in shape or size among the multiple regions can be tolerated up to ±5%, preferably ±3%, and more preferably ±1% of the average value of all the multiple regions.

[0058] In this embodiment, as in the first to third embodiments, the elastic material 51 may be disposed on both main surfaces of each of the first and second insulating materials 10a, 10b, or may be disposed on only one of the main surfaces. The elastic material 51 may also be disposed so as to be sandwiched between a pair of insulating materials. Furthermore, it is also preferable that the elastic material 51 be disposed only in the first insulating material 10a, which is disposed within the second region 57b, among the multiple regions.

[0059] Furthermore, similar to the first to third embodiments, a film may be disposed to directly or indirectly cover the surfaces of the first insulating material 10a and the second insulating material 10b, and there are no particular limitations on the method of disposing the film.

[0060] <Modification 1 of Fourth Embodiment> Fig. 6 is a plan view showing Modification 1 of a heat-transfer suppressing member according to the fourth embodiment of the present invention. In the heat-transfer suppressing member 150 shown in Fig. 6, the same components as those in the heat-transfer suppressing member 140 shown in Fig. 5A are denoted by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0061] In the first modification, the frame body 53 has partition walls 58a and 58b formed thereon to connect a pair of frame members 53b facing each other in the left-right direction when the heat transfer suppressing member 150 is interposed between the battery cells. This divides the inside of the frame body 53 into three regions, a first region 57a, a second region 57b, and a third region 57c, from top to bottom. A first insulating material 10a, a second insulating material 10b, and a first insulating material 10b each having a thickness thinner than the frame body 53 are disposed in the first region 57a, the second region 57b, and the third region 57c, respectively. In this embodiment, the first insulating material 10a is made of an insulating material with a lower elastic modulus than the second insulating material 10b.

[0062] When the heat transfer suppressing member 150 configured as described above is used in place of the heat transfer suppressing member 50 of the battery pack 100, the same effect as that of the fourth embodiment can be achieved. As described above, the battery cells 20a, 20b, and 20c are susceptible to deformation in the central portions of the main surfaces of the battery cells and in the upper portions where exhaust valves (not shown) are formed. Therefore, it is preferable to arrange the first insulating material 10a, which has a low elastic modulus, in the central second region 57b and the upper first region 57a. Note that the exhaust valves of the battery cells are not limited to being arranged in the upper portions, and may be arranged in the lower portions. Therefore, when incorporating the heat transfer suppressing member 150 between the battery cells 20a and 20b and between the battery cells 20b and 20c, the combination of the first insulating material 10a and the second insulating material 10b can be designed taking into account the positions of the exhaust valves and other components.

[0063] 7 is a plan view showing a heat-transfer-suppressing member according to a second modification of the fourth embodiment of the present invention. In the heat-transfer-suppressing member 160 shown in Fig. 7, the same components as those in the heat-transfer-suppressing member 140 shown in Fig. 5A are denoted by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0064] In Modification 2, the frame body 53 includes partition walls 58a and 58b that connect a pair of frame members 53a that face each other in the vertical direction when the heat transfer suppressing member 160 is interposed between the battery cells. Partition walls 58c and 58d also connect a pair of frame members 53b that face each other in the horizontal direction of the heat transfer suppressing member 160. As a result, the inside of the frame body 53 is divided into nine regions, from the upper left to the right in FIG. 7 : a first region 57a, a second region 57b, a third region 57c, a fourth region 57d, a fifth region 57e, a sixth region 57f, a seventh region 57g, an eighth region 57h, and a ninth region 57i. A first insulating material 10a that is thinner than the frame body 53 is disposed in the second region 57b and the fifth region 57e. A second insulating material 10b that is thinner than the frame body 53 is disposed in the remaining regions. In this embodiment, the first insulating material 10a is made of an insulating material having a lower elastic modulus than the second insulating material 10b.

[0065] When the heat transfer suppressing member 160 configured as described above is used in place of the heat transfer suppressing member 50 of the battery pack 100, the same effect as that of the fourth embodiment can be obtained. In this embodiment, the first insulating material 10a with a low elastic modulus is disposed in the central fifth region 57e, which faces the position where the battery cells 20a, 20b, 20c are likely to deform, and in the second region 57b above it. That is, in the region where the battery cells are likely to deform, there is a gap between the first insulating material 10a and the battery cells, and the first insulating material 10a has a low elastic modulus, so that unnecessary pressure on the battery cells can be further reduced.

[0066] Furthermore, since a thermal insulating material is disposed in each of the nine divided regions, various types of thermal insulating materials can be combined as needed, improving design flexibility. Furthermore, since the nine divided heat transfer suppressing member 160 has smaller sizes for each thermal insulating material, it is more likely that undamaged thermal insulating materials can be reused in the event of an abnormality such as thermal runaway, thereby further reducing the burden on the environment.

[0067] In heat transfer suppressing members 140, 150, 160 that have partition walls, it is preferable that the first insulating material 10a, which has a low elastic modulus, be placed in at least the central region of the multiple regions divided by the partition walls. Furthermore, when the heat transfer suppressing members 140, 150, 160 are placed between the battery cells 20a, 20b, 20c, it is also preferable that the first insulating material 10a be placed near the exhaust valves of the battery cells 20a, 20b, 20c.

[0068] Furthermore, the partition walls divide the interior of the frame body into multiple regions. However, if the partition walls are located near the center of the heat transfer suppression member in a plan view, they will act as a resistance, repeatedly compressing and releasing the battery cells during charging and discharging, resulting in reduced battery performance. Therefore, it is preferable that the partition walls not be located in the center or near the center of the interior of the frame body. Referring to FIG. 7 , when connecting a pair of vertically opposing frame members 53a with a partition wall, it is preferable to form the partition walls so as to divide the interior of the frame body 53 equally, taking into consideration the possibility of reusing the insulation material. In this case, to avoid the partition walls being located in the center or near the center of the interior of the frame body, it is preferable to connect the pair of opposing frame members 53a with an even number of partition walls. Similarly, when forming a partition wall between a pair of horizontally opposing frame members 53b, it is preferable to connect the frame members 53b with an even number of partition walls.

[0069] Furthermore, the widths of the partition walls 58a to 58d in the heat transfer suppression members 140, 150, and 160 are not particularly limited. However, depending on the material of the partition walls, their insulating properties may be inferior to those of the first insulating material 10a and the second insulating material 10b. Furthermore, if the partition walls are primarily made of, for example, a resin material, the resin material may burn and disappear if the temperature around the heat transfer suppression member becomes extremely high during an abnormality. In such cases, to maintain the insulating properties of the insulating material, it is preferable that the widths of the partition walls 58a to 58d in the direction perpendicular to the longitudinal direction in a plan view be small. Specifically, it is preferable that the widths of the partition walls 58a to 58d in the direction perpendicular to the longitudinal direction be smaller than the width of the frame 53 in the direction perpendicular to the longitudinal direction.

[0070] The materials constituting the heat transfer suppressing member according to this embodiment will be described below.

[0071] <Frame> The frame has the function of ensuring spacing between adjacent battery cells under normal conditions. Therefore, the frame is preferably primarily made of an insulating material, and more preferably made of a material with appropriate hardness and thermal insulation. The primary material constituting the frame is preferably at least one insulating material selected from the group consisting of resin materials, oxide ceramics, non-oxide ceramics, silicate minerals such as mica, and composite materials of resin and ceramic. Of these, resin materials are preferred as the primary material because they offer excellent processability in addition to properties such as hardness and thermal insulation. The shape of the frame is not particularly limited as long as it achieves the above-mentioned function and effect, but it may also be made of an inorganic fiber mat material, for example.

[0072] <Partition Wall> When the heat transfer suppressing member according to this embodiment has a partition wall, the partition wall divides the inside of the frame body into multiple regions and, together with the frame body, serves to hold multiple insulating materials. Therefore, like the frame body, the partition wall is preferably primarily made of an insulating material, and more preferably made of a material with appropriate hardness and insulating properties. That is, the partition wall is preferably primarily made of at least one insulating material selected from the group consisting of resin materials, oxide ceramics, non-oxide ceramics, silicate minerals such as mica, and composite materials of resin and ceramic. Furthermore, from the viewpoints of hardness, insulating properties, and processability, it is more preferable that the partition wall be primarily made of a resin material. The frame body and the partition wall may be integrally molded or may be formed by combining multiple components. These materials may be formed from the same material or different materials. The shape of the partition wall is not particularly limited as long as it achieves the above-described effects. For example, the partition wall may be formed from an inorganic fiber mat material.

[0073] <Thermal Insulation Material> The thermal insulation material is not particularly limited as long as it can achieve the desired thermal insulation effect. Thermal conductivity can be used as an indicator 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 even more preferably less than 0.02 (W / m·K). Examples of thermal insulation materials that can achieve the desired thermal insulation effect include those containing silicone rubber and aerogel, those containing fibers and aerogel, and those containing inorganic particles and organic fibers. The thermal conductivity of the thermal insulation material can be measured in accordance with JIS R 2251, "Test Method for Thermal Conductivity of Refractories."

[0074] (Size of Heat Insulating Material) When a heat insulating material and an elastic material are laminated, 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 material may be approximately the same, or the elastic material may be formed to be smaller than the heat insulating material. Note that "approximately the same" as mentioned above means that the difference in the sizes of the main surfaces of the two materials can be up to ±5% of the average value of the two materials, preferably up to ±3%, and more preferably up to ±1%.

[0075] (Thermal Insulation Material Containing Silicone Rubber and Aerogel) The thermal insulation material containing silicon rubber and aerogel is a material containing silicon rubber as a framework and SiO ２ Examples of the silicone rubber include silicone and rubber with a heat resistance temperature of 170°C or higher. Since aerogel has many cavities, it can provide excellent heat insulation.

[0076] (Thermal Insulation Material Comprising Fibers and Aerogel) The thermal insulation material comprising fibers and aerogel is a material comprising a fiber framework and SiO ２Examples of fibers that can be used include polyacrylonitrile (PAN) fibers, glass fibers, and ceramic fibers. Aerogels have many cavities, which allows them to have excellent heat insulating properties.

[0077] (Thermal insulation material containing inorganic particles and organic fibers) When the thermal insulation material containing inorganic particles and organic fibers, in particular the thermal insulation material having the structure shown below, is used, it is possible to obtain even better thermal insulation properties than the thermal insulation material containing the above-mentioned fibers and aerogel. Examples of such specific thermal insulation materials are described in detail below.

[0078] <Thermal Insulation Material (Structural Example 1)> FIG. 8 is a photograph, substitute for a drawing, showing structural example 1 of a thermal insulation material used in a heat transfer suppression member according to an embodiment of the present invention, and FIG. 9 is a photograph, substitute for a drawing, showing an enlarged portion of the thermal insulation material shown in FIG. 8 .

[0079] 8 and 9 , the thermal insulation material 10 has inorganic particles 4 and organic fibers 1. The thermal insulation material 10 also has a plurality of three-dimensionally connected pores 7 between the inorganic particles 4 and the organic fibers 1. The organic fibers 1 have welded portions 5 covering 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.

[0080] The insulating material 10 configured in this manner has multiple three-dimensionally connected voids 7, which provide the effect of air insulation and further improve its insulating 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 the strength of the insulating material. Therefore, damage to a heat transfer suppressing member that includes such insulating material 10 can be suppressed. Furthermore, the presence of voids 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 expansion can be absorbed by the voids 54, and the expansion of the battery cells can also be absorbed by the insulating material 10, further suppressing deterioration in battery cell performance.

[0081] 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.

[0082] 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 member 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.

[0083] 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 insulation 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 insulation material 10 and allows for high strength to be obtained.

[0084] 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.

[0085] Furthermore, it is preferable that the heat insulating material 10 contains inorganic fibers. The effect obtained by containing inorganic fibers will be explained in the following structural example 2 of the heat insulating material.

[0086] <Thermal Insulation (Structural Example 2)> Figure 10 is a photograph showing structural example 2 of a thermal insulator used in a heat transfer suppressing member according to an embodiment of the present invention. In structural example 2 shown in Figure 10, the same components as those in structural example 1 shown in Figures 8 and 9 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the thermal insulator 40 shown in Figure 10 can be used, for example, as the thermal insulator 10 of the heat transfer suppressing members 50, 120, and 130 shown in Figures 1A, 1B, 3, and 4, or as the first thermal insulator 10a and the second thermal insulator 10b of the heat transfer suppressing members 140, 150, and 160 shown in Figures 5A, 5B, 6, and 7.

[0087] As shown in Figure 10, 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. In other words, 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.

[0088] 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.

[0089] In the heat insulating material 40 shown in Fig. 10, 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. 10, the inorganic fibers 15 in the fiber layer 11 cannot be distinguished, and are therefore not shown.

[0090] 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.

[0091] The thermal insulation material 40 configured in this manner contains inorganic fibers 15 that are resistant to decomposition even at high temperatures. Therefore, for example, if the battery cell 20a experiences thermal runaway and the heat transfer suppressing member 50 disposed adjacent to the battery cell 20a is exposed to high temperatures, even if the organic fibers 1 in the thermal insulation material 40 decompose, the inorganic fibers 15 remain, thereby reliably maintaining the shape of the thermal insulation material 40. Furthermore, the flexible organic fibers 1 easily become entangled with the relatively hard inorganic fibers 15, and the inorganic fibers 15 and the organic fibers 1 form a three-dimensional skeleton, further improving the strength of the thermal insulation material 40.

[0092] Furthermore, when the insulating material 40 has a fiber layer 11 on its surface and fiber bundles 6 inside, it can achieve even higher strength than when the organic fibers 1 are dispersed. 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. This ensures that the fiber layer 11 is securely bound to the surface of the insulating material 40. Therefore, the fiber layer 11 alone will not fall off, and an insulating material 40 with high strength can be obtained. Furthermore, as shown in the second embodiment, for example, if an elastic material 51 is laminated on the insulating material, the pressure on the base layer 13 can be further reduced.

[0093] Furthermore, when a fiber layer 11 is formed on the surface of the insulating material 40, this fiber layer 11 can absorb the impact given to the insulating material 40, so even if the elastic material 51 is not laminated, the fiber layer 11 can have the effect of preventing the inorganic particles contained in the insulating material 40 from falling off.

[0094] <Insulating Material (Structural Example 3)> FIG. 11 is a schematic diagram showing Structural Example 3 of an insulating material used in a heat transfer suppressing member according to an embodiment of the present invention, and FIG. 12 is a schematic diagram showing an enlarged portion of FIG. 11 . FIG. 13 is a photograph showing the insulating material shown in FIG. 11 . In Structural Example 3 shown in FIGS. 11 to 13 , the same components as those in Structural Example 1 shown in FIGS. 8 and 9 are designated by the same reference numerals, and detailed descriptions thereof will be omitted. Note that the insulating material 60 shown in FIGS. 11 to 13 can be used, for example, as the insulating material 10 of the heat transfer suppressing members 50, 120, and 130 shown in FIGS. 1A , 1B , 3 , and 4 , or as the first insulating material 10a and the second insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in FIGS. 5A , 5B , 6 , and 7 .

[0095] As shown in FIGS. 11 to 13 , a heat 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. 13 , fiber portions 16 are formed by the organic fibers 1 and the welded portions 5 containing the inorganic particles 4, 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.

[0096] In the insulating material 60 configured in this manner, the organic fibers 1 and the welded portions 5 act as a skeleton, providing excellent strength and shape retention. Furthermore, the welded portions 5 covering the outer periphery of the organic fibers on both the surface and center of the insulating material 60 fix the inorganic particles 4 to the organic fibers 1, thereby preventing powder from falling off. Therefore, for example, if a heat-transfer-suppressing member 50 including the insulating material 60 is disposed between multiple battery cells, excellent insulating performance can be maintained even if the battery cells expand and apply compressive stress or impact to the heat-transfer-suppressing member 50.

[0097] Although the mechanism by which the 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. Furthermore, as shown in the second and third embodiments, if an elastic material 51 is laminated on at least one surface of the insulating material 60, the pressure on the insulating material 60 is reduced, which is thought to further prevent the inorganic particles 4 from falling off.

[0098] It is believed that the inorganic particles 4 are held in place because the fiber portion 16 exposed on the surface of the insulating material 60 can absorb impacts on the insulating material 60, regardless of whether or not the elastic material 51 is present on the surface of the insulating material 60. Furthermore, in this embodiment, the insulating material is formed to be thinner than the frame 53, and therefore, similar to the effect of the fiber portion 16, impacts on the insulating material can be absorbed, improving the effect of holding the inorganic particles 4.

[0099] 13, 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.

[0100] <Insulating Material (Structural Example 4)> Figure 14 is a photograph, substituted for a drawing, showing Structural Example 4 of an insulating material used in a heat transfer suppressing member according to an embodiment of the present invention. Figure 15 is a photograph, substituted for a drawing, showing an enlarged view of the structure of the insulating material shown in Figure 14. Figure 16 is a photograph, substituted for a drawing, showing a cross section of the insulating material shown in Figure 14. In Structural Example 4 shown in Figures 14 to 16, the same components as those in Structural Example 1 shown in Figures 8 and 9 are designated by the same reference numerals, and detailed descriptions will be omitted. Note that the insulating material 70 shown in Figures 4 to 16 can be used, for example, as the insulating material 10 of the heat transfer suppressing members 50, 120, and 130 shown in Figures 1A, 1B, 3, and 4, or as the first insulating material 10a and the second insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in Figures 5A, 5B, 6, and 7.

[0101] 14 and 15 , 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.

[0102] 16, 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. 16), thereby forming fiber bundles 6, and voids 8 are formed between the plurality of organic fibers 1 constituting the fiber bundles 6.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] Similarly, in the thermal insulation 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 member 50, in this embodiment, the shape of the thermal insulation material 70 can be maintained by the effects of the welded portions 5 and the frame 53. As a result, it is possible to suppress the inorganic particles 4 from falling off (powder shedding), and to prevent a decrease in the insulating effect of the thermal insulation material 70 due to compressive deformation.

[0107] The mechanism by which the heat insulating material 70 can prevent the inorganic particles 4 from falling off from the sheet surface is thought to be similar to that of the heat insulating material 60 of Structural Example 3 above.

[0108] 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.

[0109] 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.

[0110] 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 constituting 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 area between the plurality of organic fibers 1; as long as the voids 8 are formed in at least a portion of the areas between the organic fibers 1, a heat transfer suppression effect can be obtained. Note that, as shown in the first and third embodiments, if the thermal insulation material has voids 54 on the main surface side, an even greater heat transfer suppression effect can be obtained.

[0111] 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.

[0112] <Insulating Material (Structural Example 5)> Figure 17 is a schematic diagram showing Structural Example 5 of an insulating material used in a heat-transfer-suppressing member according to an embodiment of the present invention, and Figure 18 is a schematic diagram showing an enlarged view of section A of the insulating material shown in Figure 17. In Structural Example 5 shown in Figures 17 and 18, the same components as those in Structural Example 1 of the insulating material shown in Figures 8 and 9 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the insulating material 80 shown in Figures 17 and 18 can be used, for example, as the insulating material 10 of the heat-transfer-suppressing members 50, 120, and 130 shown in Figures 1A, 1B, 3, and 4, or as the first insulating material 10a and the second insulating material 10b of the heat-transfer-suppressing members 140, 150, and 160 shown in Figures 5A, 5B, 6, and 7.

[0113] 17 and 18 , 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.

[0114] 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.

[0115] In the insulating 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, thereby achieving high strength. Therefore, even if the heat transfer suppressing member 50 is compressed due to the expansion of the battery cells 20a, 20b, and 20c during charging and discharging, the shape of the insulating material 80 can be maintained by the effect of the skeleton structure of the organic fibers 1 and inorganic fibers 15 and the frame 53. As a result, it is possible to suppress the inorganic particles 4 from falling off (powdering), and to prevent a decrease in the insulating effect of the insulating material 80 due to compression and deformation.

[0116] Furthermore, because the insulating material 80 contains highly flexible organic fibers 1, the flexibility of the 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 insulating material 80 contains inorganic fibers 15, for example, in the event of thermal runaway in a battery cell 20a and the heat-transfer-suppressing member disposed adjacent to the battery cell 20a being exposed to high temperatures, the shape of the heat-transfer-suppressing member can be maintained even if the organic fibers 1 decompose. Therefore, by including highly flexible organic fibers 1 and inorganic fibers 15 that do not decompose even at high temperatures in the insulating material 80, a heat-transfer-suppressing member that has a good balance of both flexibility and strength can be obtained.

[0117] Furthermore, in this embodiment, an air layer 28 is formed around the inorganic fibers 15 dispersed in the matrix 14. The inorganic fibers 15 have a higher thermal conductivity than the organic fibers 1, but as described above, the air layer 28 formed around the inorganic fibers 15 can suppress heat transfer between the inorganic fibers 15 and the matrix 14. The air layer 28 is formed in the manufacturing process of the thermal insulation material 80, but it is not necessary for the air layer 28 to be formed around the entire area around the inorganic fibers 15. As long as the air layer 28 is formed on at least a portion of the outer circumferential surface of the inorganic fibers 15, the effect of suppressing heat transfer can be obtained.

[0118] When the inorganic fibers 15 are uniformly dispersed in the matrix 14, the air layers 28 in the matrix 14 are also uniformly dispersed and disposed, thereby enabling the thermal insulation material 80 to obtain high thermal insulation properties evenly. Note that, as shown in the first and third embodiments, when the thermal insulation material has voids 54 on the main surface side, even higher thermal insulation properties can be obtained.

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

[0120] Similarly, in this embodiment, the welded portions 5 on the outer peripheral 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, for example, even if a portion of the battery cells 20a, 20b, 20c expands and applies compressive stress or impact to the heat transfer suppressing member, excellent heat insulating performance can be maintained.

[0121] In this embodiment, the mechanism by which the inorganic particles 4 are prevented from falling off from the sheet surface is thought to be that the organic fibers 1 and the inorganic fibers 15 are welded 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 member. Furthermore, regardless of whether or not the elastic material 51 is present on the surface of the heat insulating material 80, if the organic fibers 1 and the inorganic fibers 15 are exposed on the surface of the heat insulating material 80, they can absorb impacts applied to the heat insulating material 80, and the inorganic particles 4 are thought to be retained.

[0122] Furthermore, in this embodiment, the thickness of the insulating material is made thinner than the frame body 53, so that, similar to the effect of the fiber section 16, it is possible to absorb impacts applied to the insulating material, thereby improving the effect of retaining the inorganic particles 4.

[0123] 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.

[0124] <Insulating Material (Structural Example 6)> Figure 19 is a photograph showing Structural Example 6 of an insulating material used in a heat transfer suppressing member according to an embodiment of the present invention, and Figure 20 is a photograph showing another region of the insulating material shown in Figure 19. Figure 21 is a photograph showing a cross section of the insulating material shown in Figures 19 and 20. In Structural Example 6 shown in Figures 19 to 21, the same components as those in Structural Example 4 of the insulating material shown in Figures 14 to 16 are designated by the same reference numerals, and detailed descriptions will be omitted. The insulating material 90 shown in Figures 19 to 21 can be used, for example, as the insulating material 10 of the heat transfer suppressing members 50, 120, and 130 shown in Figures 1A, 1B, 3, and 4, or as the first insulating material 10a and the second insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in Figures 5A, 5B, 6, and 7.

[0125] 19 , 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.

[0126] 20 also contains organic fibers 1 having a branched structure consisting of a base 32 and branches 33 extending from the base 32. The organic fibers 1 shown in Fig. 20 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.

[0127] Furthermore, as shown in Figures 19 and 20, 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.

[0128] 21 , 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. 21 , 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] (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 heating and melting the sheath of the binder fiber in the area where multiple binder fibers are in contact with each other, followed by cooling. 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 member 50, a larger amount of the sheath (second organic material) melts than when the sheath of a single binder fiber melts, and a thick fused portion (base 32) is formed after cooling. As a result, the skeleton is firmly supported by the base 32.

[0134] (Support Portions) The support portions 33 extend in at least three directions from the base portion 32 and have the effect of holding the inorganic particles 4. Furthermore, the base portion 32 and the support portions 33 form a skeleton, which can also improve the strength of the heat transfer suppressing member 50. This can achieve a high powder shedding suppression effect. When a binder fiber with a core-sheath structure is used as the organic fiber 1, the support portions 33 are part of the binder fiber with a core-sheath structure, and have a core portion made of a first organic material and a sheath portion made of a second organic material.

[0135] 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.

[0136] In the above-described insulating material 90, the multiple support portions 33 extend from the base portion 32, allowing the inorganic particles 4 to be held by these support portions 33. This, combined with the improved sheet strength provided by the skeletal structure, provides a high powder shedding prevention effect. Therefore, for example, even if a portion of the battery cells 20a, 20b, and 20c expands during charging and discharging, causing compressive stress or impact on the heat transfer suppressing member, the shape of the insulating material 90 can be maintained due to the skeletal structure of the insulating material 90 and the effect of the frame 53 of the heat transfer suppressing member. As a result, shedding (powder shedding) of the inorganic particles 4 can be prevented, and a decrease in the insulating effect of the insulating material 90 due to compressive deformation can be prevented.

[0137] 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.

[0138] 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.

[0139] 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, thereby obtaining the effect of improving the sheet strength.

[0140] Furthermore, the 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 providing an air insulation effect and improving the insulating performance. Furthermore, the presence of the voids 8 allows the organic fibers 1 to be completely unconstrained, further improving the flexibility and strength of the insulating material 90. The voids 8 do not need to be formed in the entire area between the plurality of organic fibers 1; as long as the voids 8 are formed in at least a portion of the organic fibers 1, a heat transfer suppression effect can be obtained. Incidentally, as shown in the first and third embodiments, if the insulating material has voids 54 on its main surface side, even higher insulating properties can be obtained.

[0141] 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.

[0142] <Thermal Insulation (Structural Example 7)> Figure 22 is a photograph, substitute for a drawing, showing Structural Example 7 of a thermal insulator used in a heat transfer suppressing member according to an embodiment of the present invention, and Figure 23 is a photograph, substitute for a drawing, showing an enlarged portion of the thermal insulator shown in Figure 22. In Structural Example 7 shown in Figures 22 and 23, the same components as those in Structural Example 2 of the thermal insulator shown in Figure 10 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that the thermal insulator 110 shown in Figures 22 and 23 can be used, for example, as the thermal insulator 10 of the heat transfer suppressing members 50, 120, and 130 shown in Figures 1A, 1B, 3, and 4, or as the first thermal insulator 10a and the second thermal insulator 10b of the heat transfer suppressing members 140, 150, and 160 shown in Figures 5A, 5B, 6, and 7.

[0143] 22 and 23 , the thermal insulating material 110 has 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 insulating material 110. In this specification, the "fiber bundles 47" are 10 or more organic fibers 1 entangled with one another, and extend in streak-like fashion in a direction substantially parallel to the surface of the thermal insulating material 110.

[0144] That is, when the surface of the thermal insulating material 110 is observed, as shown in Fig. 23, 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.

[0145] 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 pattern, thereby improving the strength of the thermal insulation material 110. Furthermore, the entire surface is not covered with fiber bundles 47. Since there are first regions 42 in which the fiber bundles 47 are present and second regions in which the fiber bundles 47 are not present, the flexibility of the thermal insulation material 110 is also excellent. Furthermore, in this embodiment, the thermal insulation material is formed with a thickness thinner than the frame body, and the fiber bundles 47 are present on the surface of the thermal insulation material 110. Therefore, even if the thermal insulation material 110 is subjected to impact or pressure, the voids on the main surface side of the thermal insulation material as shown in the first and third embodiments, the elastic material 51 as shown in the second embodiment, and 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 heat transfer suppressing member can be prevented.

[0146] 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.

[0147] 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. 24 . As shown in FIG. 24 , rectangular imaginary frames 21 are placed along the streak-like fiber bundles 47 on the surface of the thermal insulation material 110. In this embodiment, the size of the imaginary frames 21 is 5 mm square, and these imaginary frames 21 are placed so as to be continuous with each other. In this case, if there are fiber bundles 47 that penetrate at least three continuous imaginary frames 21, it can be determined that the fiber bundles 47 have a sufficient effect of improving the strength of the thermal insulation material 110.

[0148] 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.

[0149] Furthermore, as shown in FIG. 25, 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.

[0150] The materials constituting the heat insulating materials of Structural Examples 1 to 7 and their preferred contents will be described in more detail below.

[0151] <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.

[0152] 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.

[0153] (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 2 mass% or more, and more preferably 4 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 10 mass% or less, and more preferably 8 mass% or less, relative to the total mass of the thermal insulation material.

[0154] (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.

[0155] <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.

[0156] (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.

[0157] <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.

[0158] 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.

[0159] 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.

[0160] <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.

[0161] (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.

[0162] 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.

[0163] (Nanoparticles) In the present invention, "nanoparticles" refers to spherical or nearly spherical particles with an average primary particle diameter of less than 1 μm on the order of nanometers. 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.

[0164] 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.

[0165] 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.

[0166] (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.

[0167] (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.

[0168] 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

[0169] The heat transfer suppressing member 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 rapidly to over 200°C and continues to rise to around 700°C. Therefore, it is preferable that the inorganic particles be 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. All of these temperatures roughly overlap with the temperature range of the rapid temperature rise in a battery cell that has experienced thermal runaway, and can efficiently suppress the temperature rise. Therefore, these inorganic hydrates are preferable.

[0170] (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.

[0171] (Particles Made of Thermally Expandable Inorganic Material) Examples of thermally expandable inorganic materials include vermiculite, bentonite, mica, and perlite.

[0172] (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.

[0173] (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.

[0174] (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.

[0175] (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.

[0176] <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.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] (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.

[0181] (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.

[0182] 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.

[0183] <Inorganic Fibers> As the inorganic fibers 15, a single inorganic fiber may be used, or two or more 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 mineral fibers other than these fibers, such as rock wool, basalt fiber, and mullite fiber. Other mineral fibers include natural mineral fibers such as wollastonite. These inorganic fibers are preferred in terms of heat resistance, strength, and availability. Among the inorganic fibers, silica-alumina fiber, alumina fiber, silica fiber, rock wool, alkaline earth silicate fiber, and glass fiber are particularly preferred from the standpoint of ease of handling.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] (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.

[0188] 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.

[0189] <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.

[0190] Although structural examples 1 to 7 of the thermal insulating material have been described above, the structure of the thermal insulating material containing inorganic particles and organic fibers is not limited thereto, and thermal insulating materials having various structures can be used. In particular, the thermal insulating materials of structural examples 1 to 7 have even better thermal insulating effects than other thermal insulating materials and thermal insulating materials containing fibers and aerogel.

[0191] Here, we will explain the results of comparing the insulating effects of various insulating materials of different types and thicknesses. The insulating effect test can be performed by placing a heater in contact with one main surface of the insulating material, placing a thermometer on the other main surface, and measuring the temperature change on the other main surface as the heater temperature is increased. When the heater temperature is increased to 800°C, the temperature on the other main surface of the insulating material reaches its maximum temperature after a certain period of time. At this time, it can be seen that the insulating material with a lower maximum temperature has better insulating properties. The results of the comparison of insulating effects are shown in Table 1 below.

[0192]

[0193] In Table 1 above, thermal insulation materials A-1 and A-2 are thermal insulation materials of structural example 3 shown in Figures 11 to 13, and are obtained by molding core-sheath organic fibers and inorganic particles into a sheet shape by a dry method. In thermal insulation materials A-1 and A-2, the organic fibers used are core-sheath organic fibers in which the core and sheath are made of polyethylene terephthalate and the melting points of the two differ by 90°C or more, and silica nanoparticles and titania are used as inorganic particles. Thermal insulation material B is a thermal insulation material made of a fiber framework and SiO ２ It is impregnated with

[0194] As shown in Table 1 above, the insulating performance of the insulating material A-1, which is 2.0 mm thick, is equal to that of the insulating material B, which is 4.5 mm thick. Furthermore, when the thickness of the insulating material A-2 is further increased, it is possible to obtain higher insulating performance than the insulating material B, even with a thinner thickness.

[0195] These results are not limited to Structural Example 3, and similar insulating performance can be obtained with all of the insulating materials of Structural Examples 1 to 7. Therefore, when using the insulating materials of Structural Examples 1 to 7 that contain inorganic particles and organic fibers, the thickness of the insulating material can be easily made thinner than that of frame 53, and therefore these materials can be suitably used as insulating materials for the heat transfer suppressing members according to the above-described embodiments of the present invention.

[0196] Furthermore, the constituent materials of the heat transfer suppressing member according to this embodiment other than the frame, partition wall, and heat insulating material will be described below.

[0197] <Film> As shown in the first to third embodiments, when the heat transfer suppressing member has a film 52, the material constituting the film 52 can be at least one selected from polyethylene, polypropylene, polystyrene, vinyl chloride, nylon, acrylic, epoxy resin, polyurethane, polyether ether ketone, polyetherimide, polyethylene terephthalate, polytetrafluoroethylene (PTFE), polyphenyl sulfide, polycarbonate, and aramid.

[0198] Shrink packaging may be used when only the insulating material is covered with film, or when the insulating material and frame, or the entire surface of the laminate and frame, are covered with film 52. Suitable materials for shrink packaging include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride.

[0199] (Film Thickness) The film preferably has an appropriate thickness to prevent particles and the like from falling off the insulating material and to prevent the insulating material from falling off the frame 53. The film also preferably has appropriate flexibility. If the film thickness exceeds 1 mm, the film is prone to cracks and breaks. Therefore, the film 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, there is no particular lower limit to the film thickness, but in order to prevent tearing due to friction with the battery cell and the like and to obtain the desired strength, it is preferably 0.005 mm or more, and more preferably 0.01 mm or more.

[0200] (Other Materials Included in the Film) Furthermore, since the 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 film be flame-retardant, and specifically, it is preferable that the film contain an inorganic substance or a flame-retardant material. Examples of other materials included in the 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.

[0201] <Elastic Material> The elastic material is an elastic material processed into a sheet shape. As shown in the second and third embodiments, when the heat transfer suppressing member has the elastic material 51, a known elastic material can be used as the elastic material that constitutes the elastic material 51. 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 20a, 20b, and 20c can be used.

[0202] 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.

[0203] 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.

[0204] (Size of Elastic Material) The thickness of the elastic material is not particularly limited, but in order to effectively obtain the effect of the elastic material, it is preferable that the thickness is 1 mm or more and 10 mm or less.

[0205] [Method for manufacturing heat transfer suppression member] The method for manufacturing the heat transfer suppression member according to this embodiment will be described in detail below, particularly with respect to an example in which the heat insulating material 40 of structural example 2 shown in FIG. 10 is applied to the heat transfer suppression member 130 according to the third embodiment.

[0206] <Manufacturing of Heat Insulating Material> For example, a binder fiber (not shown) having a core-sheath structure, inorganic particles 4, and inorganic fibers 15 are added to a mixer such as a V-type mixer in a predetermined ratio to prepare a mixture. As described above, it is preferable to use a fiber having a core-sheath structure with 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 set to be higher than the melting point of the second organic material.

[0207] 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 the binder fibers are also fused to each other in areas where they were in contact with each other. This allows for the production of a heat insulating material 40 that is processed into a sheet shape with a thickness thinner than that of the frame body.

[0208] Incidentally, a heat insulating material that does not contain inorganic fibers 15 can also be obtained by the same manufacturing method as the heat insulating material 40, and the use of inorganic fibers 15 can be selected arbitrarily.

[0209] 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.

[0210] <Assembly of Laminate> Thereafter, the elastic material 51 is placed on the 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 material 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 and fixing them with a fixing jig, a method of covering them with a film or the like, and a method of covering them with a thermo-compressible film and then heating the film to shrink and fix them. Note that the elastic material 51 does not necessarily have to be laminated, and as shown in the first embodiment, only the heat insulating material may be used.

[0211] <Manufacture of Frame> Next, a frame 53 is manufactured to surround the outer periphery of the thermal insulating material. The frame 53 may be made of, for example, a resin, and may be integrally molded or manufactured by combining multiple frame members. As shown in the fourth embodiment and its modified examples shown in FIGS. 5A and 5B , when the heat transfer suppressing member has a partition wall, the frame and the partition wall may be integrally molded or manufactured by combining multiple members.

[0212] <Incorporating laminate into frame> Thereafter, the heat insulating material is fitted and fixed to the frame 53. There are no particular limitations on the method for fixing the heat insulating material to the frame 53, and the heat insulating material may be fixed using a fixing material such as an adhesive, or grooves or the like may be formed in the frame 53 and the heat insulating material may be fitted into the grooves.

[0213] <Attachment of Film> Then, two sheets of film 52 having a size substantially equal to the outer diameter of frame body 53 in a plan view are prepared, and these films 52 are overlapped on frame body 53, and frame body 53 and film 52 are heat-sealed together. In this manner, film 52 may be heat-sealed to frame body 53, or may completely encase frame body 53 and the insulating material, or may encase only the insulating material. Furthermore, as shown in the fourth embodiment, film 52 may not be provided. Note that "substantially equal" between the outer diameter of frame body 53 and film 52 means that a difference in size between the two is acceptable within ±5% of the average value of the two, preferably ±3%, and more preferably ±1%.

[0214] 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.

[0215] Next, binder fibers and heating conditions that are preferably used in the production of the above-mentioned insulating material, as well as other binder materials, will be described.

[0216] <Binder Fiber> When using a core-sheath structure binder fiber 3 as a material for a thermal insulating material, there are no particular limitations on the binder fiber 3 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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] (Binder Fiber Content) When using binder fibers 3 with a core-sheath structure as a material for a thermal insulation material, if the binder fiber content in the mixture is appropriately controlled, the skeleton of the resulting thermal insulation 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 thermal insulation 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.

[0221] (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.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] 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.

[0226] (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.

[0227] <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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] <Thickness of Insulating Material> In this embodiment, the thickness of the insulating material is not particularly limited as long as it is thinner than the thickness of the frame, but it 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 thermal insulation of the heat-transfer suppressing member.

[0232] [Battery Assembly] An example of a battery assembly using the heat transfer suppressing member 50 according to the first 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 member 50 shown in FIG. 2 can be replaced with heat transfer suppressing members 120, 130, 140, 150, and 160 having other structures, as well as heat transfer suppressing members having other structures within the scope of the present invention. Furthermore, as the thermal insulator, in addition to the thermal insulators 10, 40, 60, 70, 80, 90, and 110 having the various structures described above, it can also be replaced with other thermal insulators within the scope of the present invention.

[0233] 2, the battery pack 100 includes a plurality of battery cells 20a, 20b, and 20c and a heat transfer suppressing member 50 according to the present embodiment, with the plurality of battery cells connected in series or parallel. For example, the heat transfer suppressing member 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 suppressing member 50 are housed in a battery case 30. The heat transfer suppressing member 50 is as described above.

[0234] In the battery pack 100 configured in this manner, the heat transfer suppression member has a frame body, which ensures spacing between the battery cells. Furthermore, because the insulating material is formed thinner than the frame body, it is possible to suppress damage to the battery case and deterioration of battery performance when the battery cells 20a, 20b, 20c are deformed, and it is also possible to suppress heat transfer between the battery cells in the event of an abnormality.

[0235] The battery pack 100 of this embodiment is not limited to the battery pack illustrated in Fig. 2. For example, the heat transfer suppressing member 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.

[0236] 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 member 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.

[0237] The heat transfer suppressing member 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.

[0238] 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.

[0239] This application is based on a Japanese patent application (Patent Application No. 2023-124841) filed on July 31, 2023, the contents of which are incorporated herein by reference.

[0240] REFERENCE SIGNS LIST 1 organic fiber 3 binder fiber 8, 54 gap 10, 40, 60, 70, 80, 90, 110 heat insulating material 10a first heat insulating material 10b second heat insulating material 20a, 20b, 20c battery cell 30 battery case 50, 120, 130, 140, 150, 160 heat transfer suppressing member 51 elastic material 52, 112, 312 film 53 frame body 53a, 53b frame member 58a, 58b, 58c, 58d partition wall 100 battery pack

Claims

1. A heat transfer suppression member comprising: a frame body surrounding an outer periphery in a plan view; and a sheet-like insulating material arranged inside the frame body and having a pair of main surfaces, wherein in a cross-sectional view perpendicular to the plan view, the thickness of the insulating material is thinner than the thickness of the frame body.

2. The heat transfer suppressing member according to claim 1, further comprising a film covering the main surface of the heat insulating material.

3. The heat transfer suppressing member according to claim 2, characterized in that a gap is provided between at least one of the pair of main surfaces and the film.

4. A heat transfer suppression member as described in claim 1, characterized in that it has an elastic material laminated on at least one of the pair of main surfaces of the insulation material, and in the cross-sectional view, the thickness of the laminate of the insulation material and the elastic material is approximately the same as the thickness of the frame body or is thinner than the thickness of the frame body.

5. The heat transfer suppressing member according to claim 4, characterized in that the laminate has a pair of outer main surfaces perpendicular to the thickness direction, and has a film covering the pair of outer main surfaces.

6. The heat transfer suppressing member according to claim 5, characterized in that a gap is provided between at least one of the pair of outer main surfaces and the film.

7. The heat transfer suppressing member according to claim 4, characterized in that the elastic material contains at least one material selected from the group consisting of synthetic rubber, natural rubber, and thermoplastic elastomer.

8. The heat transfer suppressing member according to claim 1, further comprising a partition wall dividing the inside of the frame into a plurality of regions, and a plurality of the heat insulating materials arranged in the plurality of regions.

9. The heat transfer suppressing member according to claim 8, wherein the plurality of heat insulating materials include a first heat insulating material and a second heat insulating material having properties different from each other.

10. The heat transfer suppressing member according to claim 9, wherein the elastic modulus of the first insulating material is smaller than the elastic modulus of the second insulating material.

11. The heat transfer suppressing member according to claim 10, wherein the first insulating material is disposed in at least a central region among the plurality of regions.

12. A heat transfer suppression member as described in claim 8, characterized in that, in a plan view, the width of the partition wall in a direction perpendicular to the longitudinal direction is smaller than the width of the frame body in a direction perpendicular to the longitudinal direction.

13. A heat transfer suppressing member according to any one of claims 8 to 12, characterized in that the partition wall is made primarily of an insulating material.

14. A heat transfer suppressing member according to any one of claims 1 to 12, characterized in that the frame body is made primarily of an insulating material.

15. A heat transfer suppressing member according to any one of claims 1 to 12, characterized in that the heat insulating material contains inorganic particles and organic fibers.

16. A battery pack comprising a plurality of battery cells and a heat transfer suppression member according to any one of claims 1 to 12, the plurality of battery cells being connected in series or in parallel.

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