Heat transfer suppression member and battery pack

Abstract

To provide a heat transfer suppression member that maintains the distance between battery cells, can prevent the destruction of a battery case due to deformation of the battery cells and can reduce deterioration of battery performance, and can prevent the propagation of heat between battery cells in the event of an abnormality, and to provide a battery pack that can prevent the destruction of the battery case and deterioration of battery performance while preventing the propagation of heat between battery cells.SOLUTION: A heat transfer suppression member 50 has: a frame 53 that surrounds the outer circumference in a plan view; and a sheet-like heat insulating material 10 with a pair of main surfaces 10s arranged inside the frame 53. In a cross-sectional view perpendicular to the plan view of the heat transfer suppression member 50, the thickness of the heat insulating material 10 is smaller than the thickness of the frame 53.SELECTED DRAWING: Figure 1B

Description

[Technical field]

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

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

[0003] Furthermore, these battery cells mainly use lithium-ion secondary batteries, which are capable of higher capacity and higher output than lead-acid batteries, nickel-metal hydride batteries, etc. If a battery cell experiences thermal runaway, in which the temperature rises suddenly and continues to generate heat due to an internal short circuit or overcharging of the battery (i.e., in the case of an "abnormality"), the heat from the battery cell experiencing thermal runaway may propagate to other adjacent battery cells, causing thermal runaway in the other battery cells. Furthermore, if thermal runaway occurs in a battery cell, gas is generated inside the battery, causing the internal pressure to rise, resulting in deformation of the battery cell.

[0004] As a countermeasure against the occurrence of thermal runaway as described above, for example, Patent Document 1 discloses a heat-transfer-suppressing sheet that has excellent heat-transfer suppression effect and is capable of suppressing a decrease in the thickness of the insulating material even when the battery cell expands, thereby maintaining high insulating performance. 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] Patent Document 2 proposes a heat insulating material that maintains its structure and suppresses deterioration of thermal conductivity against compressive stress. The heat insulating material described in Patent Document 2 includes a composite layer containing fibers and silica aerogel, and resin struts arranged in the thickness direction in the composite layer.

[0006] The heat-transfer-suppressing sheets and insulating materials described in the above Patent Documents 1 and 2 both prevent the insulating material from being compressed and narrowing the gaps between the battery cells, thereby making it possible to suppress a decrease in thermal conductivity. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-187869 A [Patent Document 2] JP 2017-215014 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the deformation of the battery cell due to thermal runaway is large, if a heat insulating material with high compressive strength or a resin support is arranged in the area where the battery cell and the heat insulating material are in contact with each other as in Patent Documents 1 and 2, a repulsive force is generated against the battery cell. When the battery cell undergoes thermal runaway, the central area of ​​the main surface is most likely to deform, so if the spacing between the cells in the central area is fixed by a heat insulating material, the outermost battery cell of the multiple connected battery cells will be pressed against the battery case. As a result, the pressed battery cell or the case may be destroyed. In addition, even when the battery cells in the assembled battery are subjected to a charge / discharge cycle (i.e., during "normal use"), slight deformation of the battery cell occurs. Therefore, when the internal pressure of the battery cell repeatedly rises and falls during charging and discharging, the battery cell is repeatedly pressed and relaxed by the case and the heat insulating material, which causes the performance of the battery to deteriorate.

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

[0010] The present invention has been made in consideration of the above-mentioned problems, and has an object 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. [Means for solving the problem]

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

[0012] [1] A frame body surrounding the outer periphery in a plan view; A sheet-like insulating material having a pair of main surfaces and disposed inside the frame, A heat transfer suppressing member, characterized in that, 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] Further, preferred embodiments of the present invention relating to the heat transfer suppressing member relate to the following items [2] to

[15] .

[0014] [2] The heat transfer suppressing member described in [1], characterized in having a film covering the main surface of the insulation 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] A heat transfer suppression member as described in [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.

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

[0018] [6] The heat transfer suppressing member described in [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 includes at least one material selected from the group consisting of synthetic rubber, natural rubber, and thermoplastic elastomer.

[0020] [8] Further, a partition wall is provided to divide the inside of the frame body into a plurality of regions, The heat-transfer suppressing member according to any one of [1] to [7], comprising a plurality of the heat insulating materials arranged in the plurality of regions.

[0021] [9] The heat transfer suppressing member described in [8], characterized in that the multiple insulating materials include a first insulating material and a second insulating material having different properties from each other.

[0022]

[10] The heat transfer suppressing member described in [9], characterized in that 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 described in

[10] , characterized in that the first insulating material is arranged in a region including a center among the multiple regions.

[0024]

[12] A heat transfer suppressing member described in any one of [8] to

[11] , 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.

[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 can be 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. Effect of the Invention

[0030] The heat transfer suppressing member of the present invention has a frame surrounding the outer periphery, and therefore ensures spacing between battery cells. In addition, since a thermal insulating material is disposed inside the frame and is formed to be thinner than the frame, damage to the battery case and deterioration of battery performance due to deformation of the battery cells can be suppressed, and heat transfer between the battery cells in the event of an abnormality can be suppressed.

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

[0032] [Figure 1A] FIG. 1A is a plan view showing a heat-transfer suppressing member according to a first embodiment of the present invention. [Figure 1B] FIG. 1B is a cross-sectional view taken along line II in FIG. 1A. [Diagram 2] FIG. 2 is a cross-sectional view that typically illustrates a battery pack having a heat-transfer-suppressing sheet according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view showing a heat-transfer suppressing member according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view showing a heat-transfer suppressing member according to a third embodiment of the present invention. [Figure 5A] FIG. 5A is a plan view showing a heat-transfer suppressing member according to a fourth embodiment of the present invention. [Figure 5B] FIG. 5B is a cross-sectional view taken along line II-II in FIG. 5A. [Figure 6] FIG. 6 is a plan view showing a first modified example of a heat transfer suppressing member according to the fourth embodiment of the present invention. [Figure 7] FIG. 7 is a plan view showing Modification 2 of the heat transfer suppressing member according to the fourth embodiment of the present invention. [Figure 8] FIG. 8 is a photograph showing a first example of a structure of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention. [Figure 9] FIG. 9 is a photograph showing an enlarged view of a part of the heat insulating material shown in FIG. [Figure 10] FIG. 10 is a photograph showing a second example of the structure of a heat insulating material used in a heat-transfer suppressing member according to an embodiment of the present invention. [Figure 11] FIG. 11 is a schematic diagram showing a third example of a structure of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention. [Figure 12] FIG. 12 is a schematic diagram showing an enlarged portion of FIG. [Figure 13] FIG. 13 is a photograph showing the heat insulating material shown in FIG. [Figure 14]FIG. 14 is a photograph showing a fourth example of a structure of a heat insulating material used in a heat-transfer suppressing member according to an embodiment of the present invention. [Figure 15] FIG. 15 is a photograph showing an enlarged view of the structure of the heat insulating material shown in FIG. [Figure 16] FIG. 16 is a photograph showing a cross section of the heat insulating material shown in FIG. [Figure 17] FIG. 17 is a schematic diagram showing a fifth example structure of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention. [Figure 18] FIG. 18 is an enlarged schematic view of part A of the heat insulating material shown in FIG. [Figure 19] FIG. 19 is a photograph showing a sixth example of a structure of a heat insulating material used in a heat-transfer suppressing member according to an embodiment of the present invention. [Figure 20] FIG. 20 is a photograph showing another area of ​​the heat insulating material shown in FIG. [Figure 21] FIG. 21 is a photograph showing a cross section of the heat insulating material shown in FIGS. [Figure 22] FIG. 22 is a photograph substituting a drawing showing a seventh example of a structure of a heat insulating material used in a heat-transfer suppressing member according to an embodiment of the present invention. [Diagram 23] FIG. 23 is a photograph showing an enlarged view of a part of the heat insulating material shown in FIG. [Figure 24] FIG. 24 is a schematic diagram showing an example of a method for defining the length of a fiber bundle. [Diagram 25] FIG. 25 is a photograph showing another example of the structure of the heat insulating material shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The present inventors conducted extensive research to obtain a heat transfer suppressing member that can suppress the application of unnecessary pressure to battery cells while maintaining the desired thermal insulation properties, thereby preventing deterioration of battery performance. As a result, they found that the above problem can be solved by arranging a thermal insulating material inside a frame that surrounds the outer periphery and making the thickness of the thermal insulating material thinner than the thickness of the frame. In other words, by arranging a thermal insulating material thinner than the frame inside the frame while ensuring spacing between the battery cells using the frame, it is possible to ensure an escape route for the expansion of the battery cells, and to reduce the pressure applied to the battery cells when the battery cells expand.

[0034] A heat transfer suppressing member according to an embodiment of the present invention, a manufacturing method thereof, and a battery pack will be described in detail below. Note that the present invention is not limited to the embodiment described below, and can be modified as desired without departing from the gist of the present invention. First, a heat transfer suppressing member according to an embodiment of the present invention will be described.

[0035] [Heat transfer suppression 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. 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 heat insulating material 10 arranged 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 surface of the heat insulating material 10. In this specification, the "plan view" refers to a state in which the heat transfer suppressing member is viewed from above when the main surface of the heat insulating material 10 is arranged in the vertical direction. In addition, the "cross-sectional view" refers to a state in which the cross section of the heat transfer suppressing member is viewed from a direction perpendicular to the plan view. In this embodiment, the thickness of the heat insulating material 10 is formed to be thinner than the thickness of the frame 53. Therefore, a gap portion 54 is formed between the main surfaces 10s on both sides of the heat insulating material 10 and the film 52.

[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 that shows a schematic diagram of a battery pack having 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, 20c. The battery pack 100 is configured by storing the plurality of battery cells 20a, 20b, 20c in a state in which they are connected in series or parallel (the connected state is not shown). Note that, for example, lithium ion secondary batteries are preferably used as the battery cells 20a, 20b, 20c, but the present invention is not limited thereto and may also be applied to other secondary batteries.

[0037] In the heat transfer suppressing member 50 according to the first embodiment configured as described above, the frame body 53 is disposed between the battery cell 20a and the battery cell 20b, and between the battery cell 20b and the battery cell 20c. Therefore, by adjusting the thickness of the frame body 53, the interval between the battery cells can be secured at a desired interval. In addition, the heat insulating material 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 heat insulating material 10 and the battery cells 20a, 20b, and 20c, a gap portion 54 is formed. When the battery cells 20a, 20b, and 20c expand, the center portion of the main surface having the largest area of ​​the battery cells 20a, 20b, and 20c generally protrudes, and therefore, when the battery cells 20a, 20b, and 20c expand, the gap portion 54 serves as an escape route for the expansion. Therefore, it is possible to suppress the application of unnecessary pressure to the battery cells 20a, 20b, and 20c, and to suppress the deterioration of the battery performance.

[0038] In addition, while the insulating material 10 has a certain level of insulating properties, 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, when the insulating material 10 contains, for example, inorganic particles, it is possible to prevent the inorganic particles from falling off, i.e., powder falling, and thereby contaminating the inside of the battery case 30.

[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 configuration of the film 52 in the present invention is not limited to this. 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, and gaps may be formed between the film 52 and the battery cells 20a, 20b, 20c.

[0041] Moreover, 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 that a step is 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 portion 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 a heat-transfer suppressing member 120 shown in Fig. 3, the same components as those shown in Fig. 1A and Fig. 1B are denoted by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0043] 3, the heat transfer suppressing member 120 according to the second embodiment has elastic materials 51 laminated on both main surfaces 10s of the heat insulating material 10. That is, the heat insulating material 10 is sandwiched between the pair of elastic materials 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 so as to cover the outer main surface 111s of the laminate 111. Therefore, most of both outer main surfaces 111s of the laminate 111 and the film 52 are in contact with each other, and no voids are formed. In addition, when the thickness of the laminate 111 and the thickness of the frame body 53 are "approximately the same," this means that the difference between the two thicknesses is acceptable up to ±5% of the average value of the two, preferably up to ±3%, and more preferably up to ±1%.

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

[0045] In this embodiment as well, since the heat transfer suppressing member 120 has a frame body 53, the thickness of the frame body 53 can be adjusted to ensure a desired spacing between the battery cells. Furthermore, since the elastic material 51 is laminated on both main surfaces 10s of the thermal insulation material 10 and furthermore the film 52 is present on the outer surface thereof, powder falling 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 falling 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 disposed instead of the void portion 54 shown in the first embodiment. The elastic material 51 has elasticity, and when the heat transfer suppressing member 120 is pressed by the expansion of the battery cells 20a, 20b, and 20c, 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 are deformed, 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, in the heat transfer suppressing member 120 according to the second embodiment, as in the first embodiment in which the void portion 54 is formed, the deterioration of the battery performance caused by repeated pressing and relaxing of the battery cells 20a, 20b, and 20c can be suppressed.

[0047] In the second embodiment, the elastic material 51 is laminated on both main surfaces 10s of the heat insulating 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 heat insulating materials 10. The elastic material 51 may be laminated only on one main surface of the heat insulating material 10. In this case, the thickness of the two-layered laminate 111 of the heat insulating material 10 and the elastic material 51 can be made thinner than that of a three-layered laminate. Specifically, the two-layered 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 heat insulating 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 arranged. When using a two-layer laminate 111 of the heat insulating material 10 and the elastic material 51, the film 52 is preferably arranged so as to cover at least the main surface of the heat insulating material 10 on which the elastic material 51 is not laminated. This results in both main surfaces 10s of the heat insulating material 10 being covered with the elastic material 51 or the film 52, and an effect of suppressing powder falling can be obtained. In addition, the film 52 may be arranged so as to enclose all of the frame 53, the heat insulating material 10, and the elastic material 51, or may be arranged so as to enclose the laminate 111 of the heat insulating material 10 and the elastic material 51, or may be arranged so as to enclose only the heat insulating material 10.

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

[0050] 4, in the third embodiment, a laminate 111 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 applied instead 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. In addition, since the laminate 111 has the voids 54 on both outer main surfaces 111s, the heat insulation can be improved compared to the second embodiment. It is preferable that the voids 54 are present between at least one of the outer main surfaces 111s of the laminate 111 and the film 52, and it is more preferable that the voids 54 are present between both outer main surfaces 111s and the film 52. In the third embodiment, the laminate 111 may be configured by laminating the elastic material 51 only on one main surface 10s of the heat insulating material 10. In addition, the presence or absence and the arrangement of the film 52 are the same as those of the first and second embodiments.

[0052] [Fourth embodiment] Fig. 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. 5. In the heat-transfer suppressing member 140 shown in Figs. 5A and 5B, 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.

[0053] The heat transfer suppressing member 140 according to the fourth embodiment has partition walls 58a and 58b that divide the inside of the frame body 53 into a plurality of regions. More specifically, the partition walls 58a and 58b are formed in 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 the battery cells. As a result, the inside of the frame body 53 is divided into three regions, a first region 57a, a second region 57b, and a third region 57c. Then, the second insulating material 10b, the first insulating material 10a, and the second insulating material 10b that are thinner than the thickness of the frame body 53 are arranged 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 that has a smaller 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 can ensure 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, it is possible to suppress the application of unnecessary pressure to the battery cells even if the battery cells expand. Furthermore, the air present in the gaps 54 can provide even better thermal insulation.

[0055] As described above, the battery cells 20a, 20b, and 20c are more likely to protrude due to expansion at the center than at the end of the widest outer surface (main surface). In addition, terminals and exhaust valves are generally provided above the battery cells, and in the event of an abnormality, the exhaust valve side is more likely to become hot and deform. 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 small elastic modulus is arranged in the second region 57b that is in the center and extends vertically, and the second insulating material 10b with a larger elastic modulus than the first insulating material 10a is arranged on both sides of the second region 57b. In other words, the first insulating material 10a arranged in the second region 57b located in the center is softer and has a higher restoring force. Therefore, when the battery cells 20a, 20b, and 20c expand in the event of an abnormality and their central and upper parts are deformed, the first insulating material 10a with a small elastic modulus can further absorb the deformation of the battery cells.

[0056] In this embodiment, the insulating materials arranged in the regions divided by the partition walls have different elastic moduli, but insulating materials having different properties can be used as necessary. For example, an insulating material having extremely excellent thermal insulation properties can be arranged in the region that is the hottest, and insulating materials that take costs into consideration can be arranged in the other regions. When insulating materials having different properties are arranged in the regions, the types of insulating materials are not limited to two types, the first insulating material 10a and the second insulating material 10b, and three or more types of insulating materials having different properties can be used. In addition, insulating materials having the same elastic modulus can be arranged in all the 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, so that it is possible to suppress unnecessary pressure from being applied to the battery cells when the battery cells expand.

[0057] In addition, by disposing a plurality of insulating materials in a plurality of regions, the volume of each insulating material can be reduced, making manufacturing easier and improving handling. Furthermore, it is also preferable to form the partition walls 58a, 58b so that all of the plurality of regions have substantially the same shape and size. In the 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 insulating materials that are not damaged can be reused in other heat transfer suppressing members, thereby reducing the burden on the environment. In addition, "substantially the same" as mentioned above means that differences in shape or size of each of the multiple regions are acceptable up to ±5% of the average value of all the multiple regions, preferably up to ±3%, and more preferably up to ±1%.

[0058] In this embodiment, similarly to the first to third embodiments, the elastic material 51 may be disposed on both main surfaces of each of the first insulating material 10a and the second insulating material 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 is disposed only in the first insulating material 10a disposed, for example, on the inside of the second region 57b among the multiple regions.

[0059] Similarly 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 is no particular limitation on the method of disposing the film.

[0060] <Modification 1 of the Fourth Embodiment> 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. In a 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 is formed with partition walls 58a and 58b so as 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. As a result, the inside of the frame body 53 is divided into three regions, a first region 57a, a second region 57b, and a third region 57c, in that order from the top. Then, a first insulating material 10a, a first insulating material 10a, and a second insulating material 10b, each of which is thinner than the thickness of the frame body 53, are arranged 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 having a smaller elastic modulus than the second insulating material 10b.

[0062] The heat transfer suppressing member 150 configured as above can also provide the same effect as the fourth embodiment when used in place of the heat transfer suppressing member 50 of the battery pack 100. As described above, the battery cells 20a, 20b, and 20c are easily deformed at the center of the main surface of the battery cells and at the upper portion where the exhaust valve (not shown) is formed, so it is preferable that the first insulating material 10a with a small elastic modulus is disposed in the second central region 57b and the first upper region 57a. Note that the exhaust valve of the battery cell is not limited to the upper portion, and may be disposed at the lower portion. Therefore, when the heat transfer suppressing member 150 is incorporated 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, etc.

[0063] <Modification 2 of the Fourth Embodiment> Fig. 7 is a plan view showing Modification 2 of a heat-transfer suppressing member according to the fourth embodiment of the present invention. In a 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 the second modification, the frame body 53 is formed with partition walls 58a and 58b so as to connect a pair of frame members 53a facing each other in the vertical direction when the heat transfer suppressing member 160 is interposed between the battery cells. In addition, partition walls 58c and 58d are formed so as to connect a pair of frame members 53b facing 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, namely, 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, in that order from the upper left to the right of FIG. 7. A first insulating material 10a that is thinner than the thickness of the frame body 53 is disposed in the second region 57b and the fifth region 57e. Meanwhile, a second insulating material 10b that is thinner than the thickness of the frame body 53 is disposed in the regions other than the above-mentioned regions. In this embodiment, the first insulating material 10a is made of an insulating material having a smaller 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 in the fourth embodiment can be obtained. In this embodiment, the first insulating material 10a with a small elastic modulus is disposed in the central fifth region 57e that faces the positions where the battery cells 20a, 20b, 20c are likely to deform, and in the second region 57b above it. That is, in the regions 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 small elastic modulus, so that unnecessary pressure applied to the battery cells can be further reduced.

[0066] In addition, since a heat insulating material is disposed in each of the nine divided regions, various heat insulating materials can be combined as necessary for design, improving the degree of freedom in design. Furthermore, since the size of each heat insulating material in the nine divided heat transfer suppressing member 160 is small, there is a high possibility that undamaged heat insulating materials can be reused in the event of an abnormality such as thermal runaway, and the burden on the environment can be further reduced.

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

[0068] Furthermore, the partition wall has the effect of dividing the inside of the frame body into a plurality of regions. However, if the partition wall is present near the center of the heat transfer suppression member in a plan view, the partition wall acts as a resistance and repeatedly presses and releases the battery cell during charging and discharging of the battery cell, causing a decrease in battery performance. Therefore, it is preferable that the partition wall is not present in the center or a region close to the center of the inside of the frame body. Referring to FIG. 7, when a pair of frame members 53a facing each other in the vertical direction are connected by a partition wall, it is preferable to form the partition wall so as to divide the inner region of the frame body 53 into equal parts by the partition wall, taking into consideration the possibility of reusing the insulating material. At this time, in order to prevent the partition wall from being present in the center or a region close to the center of the inside of the frame body, it is preferable to connect the pair of opposing frame members 53a by an even number of partition walls. Similarly, when a partition wall is formed between a pair of frame members 53b facing each other in the horizontal direction, it is preferable to connect the frame members 53b by an even number of partition walls.

[0069] The widths of the partition walls 58a to 58d in the heat transfer suppressing members 140, 150, and 160 are not particularly limited. However, depending on the material constituting the partition walls, the heat insulating properties may be inferior to those of the first heat insulating material 10a and the second heat insulating material 10b. In addition, if the partition walls are made mainly of, for example, a resin material, the resin material will burn and disappear if the temperature around the heat transfer suppressing member becomes extremely high in an abnormal event. In such a case, in order to maintain the heat insulating properties of the heat insulating material, it is preferable that the width of the partition walls in a direction perpendicular to the longitudinal direction in a plan view is small. Specifically, it is preferable that the width of the partition walls 58a to 58d in a direction perpendicular to the longitudinal direction is smaller than the width of the frame body 53 in a 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 a gap between adjacent battery cells under normal conditions. Therefore, the frame is preferably made mainly of an insulating material, and more preferably made of a material having appropriate hardness and heat insulation. The main material constituting the frame is preferably at least one insulating material selected from, for example, a resin material, an oxide ceramic, a non-oxide ceramic, a silicate mineral such as mica, and a composite material of resin and ceramic. Of these, it is more preferable to use a resin material as the main material, since it has excellent workability in addition to properties such as hardness and heat insulation. The shape of the frame is not particularly limited as long as it provides the above-mentioned effects, and may be made of, for example, an inorganic fiber mat material.

[0072] <Partition wall> When the heat transfer suppressing member according to the present embodiment has a partition wall, the partition wall divides the inside of the frame body into a plurality of regions and has the effect of holding a plurality of heat insulating materials together with the frame body. Therefore, like the frame body, the partition wall is preferably made mainly of an insulating material, and more preferably made of a material having appropriate hardness and heat insulating properties. That is, the partition wall is preferably made mainly of at least one insulating material selected from a resin material, an oxide ceramic, a non-oxide ceramic, a silicate mineral such as mica, and a composite material of resin and ceramic. In addition, from the viewpoints of hardness, heat insulating properties, processability, and the like, it is more preferable that the partition wall is made mainly of a resin material. The frame body and the partition wall may be integrally molded or may be formed by combining a plurality of members. These materials may also be formed of the same material or different materials. The partition wall may have any shape as long as it can achieve the above-mentioned functions and effects, and may be made of, for example, an inorganic fiber mat material.

[0073] <Thermal insulation> The heat insulating material is not particularly limited as long as it can obtain the desired heat insulating effect. Thermal conductivity can be mentioned as an index showing the heat insulating effect. In the present embodiment, the heat conductivity of the heat insulating material is preferably less than 1 (W / m·K), more preferably less than 0.5 (W / m·K), and more preferably less than 0.2 (W / m·K). Furthermore, the heat conductivity of the heat insulating material is more preferably less than 0.1 (W / m·K), more preferably less than 0.05 (W / m·K), and particularly preferably less than 0.02 (W / m·K). As a heat insulating material capable of obtaining a desired heat insulating effect, for example, a heat insulating material containing silicon-based rubber and aerogel, a heat insulating material containing fiber and aerogel, a heat insulating material containing inorganic particles and organic fibers, etc. can be used. The heat conductivity of the heat insulating material can be measured in accordance with the "Test method for heat conductivity of refractory materials" described in JIS R 2251.

[0074] (Insulation size) When laminating an insulating material and an elastic material, the size of the main surface of the 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 smaller than the insulating material. In addition, the above term "substantially the same" means that the difference in size of the main surfaces of both can be up to ±5% of the average value of both, preferably up to ±3%, and more preferably up to ±1%.

[0075] (Thermal insulation material containing silicon rubber and aerogel) An example of a heat insulating material containing silicon rubber and aerogel is one in which silicon rubber is used as a framework and SiO2 is impregnated. Silicone and rubber with a heat resistance of 170°C or higher can be used as the silicon rubber. Aerogel has many cavities, so it can provide excellent heat insulating properties.

[0076] (Insulation material containing fiber and aerogel) An example of a heat insulating material containing fiber and aerogel is one in which a fiber framework is impregnated with SiO2. As the fiber, polyacrylonitrile (PAN) fiber, glass fiber, ceramic fiber, etc. can be used. In addition, since aerogel has many cavities, it can obtain excellent heat insulating properties.

[0077] (Thermal insulation material containing inorganic particles and organic fibers) When a thermal insulation material containing inorganic particles and organic fibers, particularly a thermal insulation material having the structure shown below, is used, it is possible to obtain even better thermal insulation properties than a 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 (Structure example 1)> FIG. 8 is a photograph showing a structural example 1 of an insulating material used in a heat transfer suppressing member according to an embodiment of the present invention, and FIG. 9 is a photograph showing an enlarged portion of the insulating material shown in FIG. 8.

[0079] As shown in Figures 8 and 9, the heat insulating material 10 has inorganic particles 4 and organic fibers 1. The heat insulating material 10 also has a plurality of three-dimensionally connected pores 7 between the inorganic particles 4 and the organic fibers 1. The organic fibers 1 have welded parts 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 parts 5. As a result, the surfaces of the organic fibers 1 are configured to be covered with the inorganic particles 4.

[0080] In the heat insulating material 10 configured in this manner, since it has a plurality of three-dimensionally connected pores 7, it is possible to obtain the effect of air insulation, and it is possible to further improve the heat insulating performance. In addition, since the heat insulating material 10 contains the organic fibers 1 having high flexibility, it is possible to increase the flexibility of the heat insulating material 10, and it is possible to obtain the effect of improving the strength of the heat insulating material by making it easier for the organic fibers 1 to be entangled with each other. Therefore, it is possible to suppress the destruction of the heat transfer suppressing member having such a heat insulating material 10. Furthermore, since the heat insulating material 10 has the pores 7, the cushioning property of the entire sheet is improved, so that 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 heat insulating material 10, and it is possible to further suppress the deterioration of the performance of the battery cells.

[0081] Furthermore, in this embodiment, it is preferable that at least some of the pores 7 communicate with the surface of the insulating material 10 and open outward. With the pores 7 configured in this manner, even if the insulating material 10 becomes hot and the organic fibers 1 and the like are decomposed when the adjacent battery cells 20a, 20b, 20c experience thermal runaway, the decomposition gas is not retained inside the sheet but is released to the outside via the pores 7. Therefore, from this point of view as well, the effect of preventing destruction of the sheet can be obtained.

[0082] Furthermore, when the welded portion 5 on the outer peripheral surface of the organic fibers 1 fixes 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 compressive stress or impact is applied to the heat transfer suppressing member 50, the effect of maintaining the shape of the insulating material 10 can be further enhanced, and a decrease in the insulating effect due to compressive deformation of the insulating material 10 can be prevented.

[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 described below. 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 large, which supports the shape of the thermal insulation material 10 and provides high strength.

[0084] The welded portion 5 does not need to completely cover the outer periphery of the organic fiber 1, and there may be some areas where the welded portion 5 is not present. In the thermal insulation material 10, binder fibers having 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 organic fiber 1, which is the core portion, 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 described in the following structural example 2 of the heat insulating material.

[0086] <Thermal insulation (Structure example 2)> Fig. 10 is a drawing substitute photograph showing a second structural example of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention. In the second structural example shown in Fig. 10, the same components as those in the first structural example shown in Fig. 8 and Fig. 9 are given the same reference numerals, and detailed description thereof will be omitted. The heat insulating material 40 shown in Fig. 10 can be used, for example, as the heat 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 heat insulating material 10a and the second heat insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in Figs. 5A, 5B, 6, and 7.

[0087] As shown in Fig. 10, the heat insulating material 40 has inorganic fibers 15. The heat insulating material 40 has a fiber layer 11 formed on at least a part of a first surface 40a and a second surface (not shown) perpendicular to the thickness direction of the heat insulating material 40. The fiber layer 11 is formed by welding at least a part of a plurality of organic fibers 1 to each other at welding parts, and is formed in a layer on the surface (first surface and second surface) of the heat insulating material 40. That is, the fiber layer 11 is a layer formed by gathering 10 or more organic fibers 1 on the surface of the heat insulating material 40, and extends, for example, in stripes, in a direction approximately parallel to the surface.

[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 parts, and inorganic particles 4 welded to the organic fibers 1 by welded parts.

[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, so they are not shown.

[0090] Furthermore, the thermal insulation material 40 has fiber bundles 6 formed by at least some of the organic fibers 1 being welded together by welded parts 5. The "fiber bundles 6" are formed by entangling 10 or more organic fibers 1 with one another and welding the organic fibers 1 to one another at some parts, and are arranged in any direction in the thermal insulation material 40.

[0091] The insulating material 40 configured in this manner contains inorganic fibers 15 that are difficult to decompose 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 insulating material 40 decompose, the inorganic fibers 15 remain, so that the shape of the insulating material 40 can be reliably maintained. In addition, the flexible organic fibers 1 tend to become entangled with the relatively hard inorganic fibers 15, and the inorganic fibers 15 and the organic fibers 1 form a three-dimensional skeleton, so that the strength of the insulating material 40 can be further improved.

[0092] Furthermore, when the heat insulating material 40 has a fiber layer 11 on its surface and a fiber bundle 6 inside, it can obtain a higher strength than when the organic fiber 1 is dispersed and arranged. The fiber layer 11 is not simply arranged on the base layer 13, but has a composite layer between the fiber layer 11 and the base layer 13 in which a part of the fiber layer 11 and a part of the inorganic particles 4 are mixed, so that the fiber layer 11 is securely bound to the surface of the heat insulating material 40. Therefore, only the fiber layer 11 does not fall off, and a heat insulating material 40 having high strength can be obtained. In addition, when an elastic material 51 is laminated on the heat insulating material, for example, as shown in the second embodiment, 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 insulation material 40, this fiber layer 11 can absorb impacts applied to the insulation material 40, so that 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 insulation material 40 from falling off.

[0094] <Thermal insulation (Structure example 3)> FIG. 11 is a schematic diagram showing a structural example 3 of a heat 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 heat insulating material shown in FIG. 11. In the structural example 3 shown in FIG. 11 to FIG. 13, the same components as those in the structural example 1 shown in FIG. 8 and FIG. 9 are given the same reference numerals, and detailed description thereof is omitted. Note that the heat insulating material 60 shown in FIG. 11 to FIG. 13 can be used, for example, as the heat insulating material 10 of the heat transfer suppressing members 50, 120, and 130 shown in FIG. 1A, FIG. 1B, FIG. 3, and FIG. 4, or as the first heat insulating material 10a and the second heat insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in FIG. 5A, FIG. 5B, FIG. 6, and FIG. 7.

[0095] As shown in FIG. 11 to FIG. 13, the heat insulating material 60 according to this embodiment has inorganic particles 4, organic fibers 1 made of a first organic material, and a welded portion 5 covering the outer circumferential surface of the organic fibers 1. As described above, the welded portion 5 includes a second organic material 17 having a melting point lower than that of the first organic material, and inorganic particles 4. In this embodiment, a binder fiber 3 having a core-sheath structure with a core and a sheath covering the outer circumferential surface of the core is used as the organic fiber, and the organic fiber 1 corresponds to the core. The welded portion 5 is formed by melting the sheath of the binder fiber 3 having a core-sheath structure by heating and then cooling it. Furthermore, as shown in FIG. 13, a fiber portion 16 is formed by the organic fiber 1 and the welded portion 5 including the inorganic particles 4, and a matrix portion 18 including the inorganic particles is formed between the multiple fiber portions 16. When the melted sheath portion is cooled, the adjacent organic fibers 1 are fused to each other at the contact portion 31 to form a three-dimensional skeleton.

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

[0097] Although the mechanism by which the insulating material 60 can prevent the inorganic particles 4 from falling off (powdering) is not clear, one of the reasons is believed to be that the organic fibers 1 and the welded parts 5 form a three-dimensional, strong skeleton, which maintains the shape of the insulating material 60 and thus prevents deformation or compression of the insulating material 60. Furthermore, as shown in the second and third embodiments, when 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 believed to further prevent the inorganic particles 4 from falling off.

[0098] It is considered that the reason why the inorganic particles 4 are held is that the fiber portion 16 exposed on the surface of the insulating material 60 can absorb impacts given to the insulating material 60, regardless of the presence or absence of the elastic material 51 on the surface of the insulating material 60. Furthermore, in this embodiment, since the insulating material is formed to be thinner than the frame body 53, it is possible to absorb impacts given to the insulating material, similar to the effect of the fiber portion 16, and the effect of holding the inorganic particles 4 can be improved.

[0099] 13, in the insulating material 60, the welded portion 5 does not need to completely cover the outer peripheral surface of the organic fiber 1, and the organic fiber 1 may be partially exposed. Since the insulating material 60 uses binder fiber 3 with a core-sheath structure, the sheath portion may peel off during the manufacturing process of the insulating material 60, but even if the organic fiber 1 is partially exposed, the effect of the present invention can be sufficiently obtained.

[0100] <Thermal insulation (Structure example 4)> FIG. 14 is a drawing substitute photograph showing a structural example 4 of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention, and FIG. 15 is a drawing substitute photograph showing an enlarged structure of the heat insulating material shown in FIG. 14. FIG. 16 is a drawing substitute photograph showing a cross section of the heat insulating material shown in FIG. 14. In the structural example 4 shown in FIGS. 14 to 16, the same components as those in the structural example 1 shown in FIGS. 8 and 9 are given the same reference numerals, and detailed description thereof is omitted. Note that the heat insulating material 70 shown in FIGS. 4 to 16 can be used, for example, as the heat insulating material 10 of the heat transfer suppressing members 50, 120, and 130 shown in FIGS. 1A, 1B, 3, and 4, and as the first heat insulating material 10a and the second heat insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in FIGS. 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 oriented three-dimensionally in the 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] As shown in the cross-sectional view of Fig. 16, a plurality of voids 7 are formed in the matrix 14 of the thermal insulation material 70. Furthermore, at least some of the organic fibers 1 in the matrix 14 are welded to each other by welded parts 5 not shown in Fig. 16 to form fiber bundles 6, and voids 8 are formed between the organic fibers 1 constituting the fiber bundles 6.

[0103] Furthermore, a fiber layer 11 is formed on at least a part of the first surface 70a and the second surface (not shown) perpendicular to the thickness direction of the heat insulating material 70. The fiber layer 11 is formed in a layer on the surface (first surface and second surface) of the heat insulating material 70 by welding at least a part of the organic fibers 1 to each other by the welding parts 5. In addition, a composite layer 12 is formed between the fiber layer 11 and the base layer 13 containing the matrix 14 and the organic fibers 1. The composite layer 12 is a layer in which a part of the fiber layer 11 and a part of the matrix 14 are mixed. Specifically, the composite layer 12 is a region including a plurality of organic fibers 1 at least a part of which are welded to each other by the welding parts 5, and inorganic particles 4 welded to the organic fibers 1 by the welding parts 5.

[0104] The fiber bundles 6 are formed by entangling 10 or more organic fibers 1 with one another and by welding the organic fibers 1 to one another in some places, and are arranged in an arbitrary 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 insulating material 70 configured in this manner, the organic fibers 1 are oriented three-dimensionally in the matrix 14, and the organic fibers 1 have welded parts 5 that cover at least a portion of their surfaces. The "welded parts 5" refer to parts where the surfaces of the organic fibers 1 melt and then solidify again, and are formed during the manufacturing process of the insulating material 70. In the insulating material 70, the three-dimensionally oriented organic fibers 1 are welded to each other by the welded parts 5, and this structure serves as a skeleton to support the shape of the insulating material 70, thereby enabling it to obtain high strength.

[0106] Similarly, in the thermal insulation material 70, the welded parts 5 on the outer peripheral surface of the organic fibers 1 also fix the inorganic particles 4 to the organic fibers 1, so that an even greater effect of suppressing powder falling can be obtained. 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 due to the effects of the welded parts 5 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 thermal insulation material 70 due to compressive deformation.

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

[0108] In the heat insulating material 70, the welded parts 5 do not need to completely cover the outer circumferential surface of the organic fibers 1, and there may be some areas where the welded parts 5 are 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, which has the effect of improving the sheet strength.

[0110] Furthermore, the heat insulating material 70 has a plurality of holes 7 in the matrix 14 and has voids 8 between the plurality of organic fibers 1 constituting the fiber bundle 6, so that the heat insulating performance can be improved. In addition, due to the presence of the voids 8, the organic fibers 1 are less likely to be constrained in the matrix 14, so that the flexibility and strength of the heat insulating material 70 can be further improved. The voids 8 do not need to be formed in the entire area between the plurality of organic fibers 1, and as long as the voids 8 are formed in at least a part of the areas between the organic fibers 1, the effect of suppressing heat transfer can be obtained. Note that, as shown in the first and third embodiments, if the heat insulating material has voids 54 on the main surface side, the effect of suppressing heat transfer can be further improved.

[0111] Furthermore, since the insulating material 70 has the fiber bundles 6 and the fiber layer 11, it is possible to obtain a much higher strength than when the organic fibers 1 are arranged in a dispersed manner. Moreover, the fiber layer 11 is not simply arranged on the base layer 13, but has a composite layer 12 between the fiber layer 11 and the base layer 13 in which a part of the fiber layer 11 and a part of the inorganic particles 4 constituting the matrix 14 are mixed, so that the fiber layer 11 is securely bound to the surface of the insulating material 70. Therefore, it is possible to obtain an insulating material 70 having high strength.

[0112] <Thermal insulation (Structure example 5)> Fig. 17 is a schematic diagram showing a fifth structural example of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention, and Fig. 18 is a schematic diagram showing an enlarged view of part A of the heat insulating material shown in Fig. 17. In the fifth structural example shown in Figs. 17 and 18, the same components as those in the first structural example of the heat insulating material shown in Figs. 8 and 9 are given the same reference numerals, and detailed description thereof will be omitted. The heat insulating material 80 shown in Figs. 17 to 18 can be used, for example, as the heat 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 heat insulating material 10a and the second heat insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in Figs. 5A, 5B, 6, and 7.

[0113] As shown in Figs. 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 in a part around the inorganic fibers 15. The organic fibers 1 have a welded portion 5 on a part of the surface, and at least a part of the inorganic fibers 15 is welded to the organic fibers 1 by the welded portion 5. Furthermore, at least a part of the inorganic particles 4 is welded to the organic fibers 1 by the welded portion 5.

[0114] In this specification, the term "dispersed" of the inorganic fibers 15 refers to a state in which 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 the inorganic fibers 15 are intertwined with each other to form a three-dimensional web structure, and this structure serves as a skeleton, thereby providing high strength. Therefore, even if the heat transfer suppressing member 50 is compressed due to the expansion of the battery cells during charging and discharging of the battery cells 20a, 20b, and 20c, the shape of the insulating material 80 can be maintained due to the effect of the skeleton structure of the organic fibers 1 and the inorganic fibers 15 and the frame 53. As a result, it is possible to prevent 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 deformation.

[0116] Furthermore, since the heat insulating material 80 contains the organic fibers 1 having high flexibility, the flexibility of the heat insulating material 80 can be increased, and the organic fibers 1 are easily entangled with the inorganic fibers 15 to form a three-dimensional web structure, thereby improving the strength. Furthermore, if the inorganic fibers 15 are contained in the heat insulating material 80, for example, when the battery cell 20a experiences thermal runaway and the heat-transfer-suppressing member disposed adjacent to the battery cell 20a is exposed to high temperatures, the shape of the heat-transfer-suppressing member can be maintained even if the organic fibers 1 are decomposed. Therefore, by having the heat insulating material 80 contain the organic fibers 1 having high flexibility and the inorganic fibers 15 that do not decompose even at high temperatures, it is possible to obtain a heat-transfer-suppressing member that has a good balance between flexibility and strength.

[0117] Furthermore, in this embodiment, an air layer 28 is provided 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 is formed around the inorganic fibers 15, thereby suppressing heat transfer between the inorganic fibers 15 and the matrix 14. The air layer 28 is formed in the manufacturing process of the heat insulating 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 part 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, so that the heat insulating material 80 can obtain high heat insulating properties evenly. Note that, as shown in the first and third embodiments, when the heat insulating material has voids 54 on the main surface side, even higher heat insulating properties can be obtained.

[0119] Furthermore, in the insulating material 80, the organic fibers 1 have welded parts 5 covering at least a part of the surface. The "welded parts 5" refer to the parts 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 part of the inorganic fibers 15 is welded to the organic fibers 1 by the welded parts 5, the entangled organic fibers 1 and the inorganic fibers 15 are fixed, so that an insulating material 80 with even higher strength can be obtained.

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

[0121] In this embodiment, the mechanism by which the inorganic particles 4 can be prevented from falling off from the sheet surface is believed to be that the organic fibers 1 and the inorganic fibers 15 are welded by the welded parts 5 to form a three-dimensional, strong skeleton, which maintains the shape of the insulating material 80 and prevents deformation or compression of the heat-transfer suppressing member. Furthermore, regardless of the presence or absence of the elastic material 51 on the surface of the insulating material 80, when the organic fibers 1 and the inorganic fibers 15 are exposed on the surface of the insulating material 80, it is believed that the impact given to the insulating material 80 can be absorbed and the inorganic particles 4 are held in place.

[0122] Furthermore, in this embodiment, the thickness of the insulating material is formed to be thinner than the frame body 53, so that, similar to the effect of the fiber portion 16, it is possible to absorb impacts applied to the insulating material, and the effect of retaining the inorganic particles 4 can be improved.

[0123] In the heat insulating material 80, the welded parts 5 do not need to completely cover the outer circumferential surface of the organic fibers 1, and there may be some areas where the welded parts 5 are not present. Even in such a case, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0124] <Thermal insulation (Structure example 6)> FIG. 19 is a drawing substitute photograph showing a sixth structural example of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention, and FIG. 20 is a drawing substitute photograph showing another region of the heat insulating material shown in FIG. 19. FIG. 21 is a drawing substitute photograph showing a cross section of the heat insulating material shown in FIGS. 19 and 20. In the sixth structural example shown in FIGS. 19 to 21, the same components as those in the fourth structural example of the heat insulating material shown in FIGS. 14 to 16 are given the same reference numerals, and detailed description thereof is omitted. The heat insulating material 90 shown in FIGS. 19 to 21 can be used, for example, as the heat 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 heat insulating material 10a and the second heat insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in FIGS. 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, namely, directions D1, D2, D3, and 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 each have a base 32 and branches 33 extending from the base 32 in five directions, namely, directions D1, D2, D3, D4, and D5, and the base 32 is thicker than the multiple branches 33.

[0127] Furthermore, in this embodiment, as shown in FIGS. 19 and 20, inorganic particles 4 are fused 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] As shown in the cross-sectional view of Fig. 21, a plurality of voids 7 are formed in the heat insulating material 90. Furthermore, in the heat insulating material 90, a fiber bundle 6 is formed by at least partially welding a plurality of organic fibers 1 to each other, and gaps 8 are formed between the plurality of organic fibers 1 constituting the fiber bundle 6. Note that, also in Fig. 21, it is possible to confirm the organic fibers 1 having 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 part of the first surface and the second surface perpendicular to the thickness direction of the heat insulating material 90. The fiber layer 11 is formed in a layer on the surface (first surface and second surface) of the heat insulating material 90 by welding at least a part of the organic fibers 1 to each other. In addition, a composite layer 12 may be formed between the fiber layer 11 and the base layer 13 containing the inorganic particles 4 and the organic fibers 1. The composite layer 12 is a layer in which a part of the fiber layer 11 and a part 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 the 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 one another and by welding the organic fibers 1 to one another in some places, and are arranged in an arbitrary 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 heat insulating material 90 configured in this manner, at least a portion of the organic fibers 1 has a branched structure consisting of a base 32 and a branch 33, and therefore the organic fibers 1 serve as a skeleton to maintain the shape of the heat insulating material 90. In this embodiment, the base 32 is configured by a fused portion in which the organic fibers 1 are fused to each other. Specifically, the base 32 is a portion in which a plurality of organic fibers 1 are brought into contact with each other, melted together, and then solidified, and is therefore thicker than the branch 33. Therefore, the entire skeleton can be firmly supported by the base 32, and the strength of the heat insulating material 90 can be significantly improved.

[0132] In the thermal insulation material 90, at least a part of the organic fibers 1 has 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 insulation material 90, but an easier way to confirm the branched structure is to observe a cross-section of the thermal insulation 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 the branches 33 will be described in more detail below.

[0133] (Base (fusion part)) The fused portion is formed when the sheath portion of the binder fiber is heated and melted once and then cooled in a portion where a plurality of binder fibers are in contact with each other when a binder fiber with a core-sheath structure is used as the material of the thermal insulation material 90. When a binder fiber with a core-sheath structure is used as the material of the thermal insulation material 90, the fused portion contains the second organic material that constitutes the sheath portion. Thus, in the manufacturing process of the heat-transfer-suppressing member 50, when the sheath in the region where the binder fibers are in contact is melted by heating, the amount of the melted sheath (second organic material) becomes greater than when the sheath of a single binder fiber is melted, and a thick fused portion (base 32) is formed after cooling. As a result, the skeleton is firmly supported by the base 32.

[0134] (Branch) The support portions 33 extend in at least three directions from the base portion 32 and have the effect of holding the inorganic particles 4. In addition, 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 makes it possible to obtain a high powder-fall suppression effect. When a binder fiber having a core-sheath structure is used as the organic fiber 1, the branch 33 is a part of the binder fiber having a core-sheath structure, and has a core made of a first organic material and a sheath 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. In addition, it is preferable that these multiple branches 33 each extend in a different three-dimensional direction, which allows a three-dimensional, strong skeleton to be formed.

[0136] In the above-mentioned heat insulating material 90, since a plurality of support parts 33 extend from the base part 32, the inorganic particles 4 can be held by these support parts 33, and a high powder fall suppression effect can be obtained by a synergistic effect with the effect of improving the sheet strength by forming a skeleton. Therefore, for example, even if a part of the battery cells 20a, 20b, 20c expands during charging and discharging, causing compressive stress or impact on the heat transfer suppressing member, the shape of the heat insulating material 90 can be maintained by the effect of the skeleton structure of the heat insulating material 90 and the frame body 53 of the heat transfer suppressing member. As a result, it is possible to suppress the inorganic particles 4 from falling off (powder fall), and to prevent a decrease in the insulating effect of the heat insulating material 90 due to compression deformation.

[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 fact that, in addition to the same effect as the insulating material 60 of Structural Example 3 above, the support parts 33 also have a holding effect on the inorganic particles 4. Furthermore, when the inorganic particles 4 are fused to the surface of the organic fibers 1, the organic fibers 1 appear to have a thicker fiber diameter, so that the strength is higher than that of the organic fibers 1 alone, and a high holding effect on the inorganic particles 4 can be obtained.

[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, which has the effect of improving the sheet strength.

[0140] Furthermore, the heat insulating material 90 preferably has a plurality of holes 7 and also has gaps 8 between the plurality of organic fibers 1 constituting the fiber bundle 6, thereby obtaining the effect of air insulation and improving the heat insulating performance. In addition, the presence of the gaps 8 makes the organic fibers 1 completely unconstrained, so that the flexibility and strength of the heat insulating material 90 can be further improved. The gaps 8 do not need to be formed in the entire area between the plurality of organic fibers 1, and as long as the gaps 8 are formed in at least a part of the organic fibers 1, the effect of suppressing heat transfer can be obtained. Note that, as shown in the first and third embodiments, if the heat insulating material has gaps 54 on the main surface side, even higher heat insulating properties can be obtained.

[0141] Furthermore, since the insulating material 90 has the fiber bundles 6 and the fiber layer 11, it is possible to obtain a sheet strength that is even higher than when the organic fibers 1 are arranged in a dispersed manner. Furthermore, when the fiber layer 11 is present, the fiber layer 11 is not simply arranged 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 (Structure example 7)> Fig. 22 is a drawing substitute photograph showing a structural example 7 of a heat insulating material used in a heat transfer suppressing member according to an embodiment of the present invention, and Fig. 23 is a drawing substitute photograph showing an enlarged portion of the heat insulating material shown in Fig. 22. In structural example 7 shown in Figs. 22 and 23, the same components as those in structural example 2 of the heat insulating material shown in Fig. 10 are given the same reference numerals, and detailed description thereof will be omitted. Note that the heat insulating material 110 shown in Figs. 22 and 23 can be used, for example, as the heat 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 heat insulating material 10a and the second heat insulating material 10b of the heat transfer suppressing members 140, 150, and 160 shown in Figs. 5A, 5B, 6, and 7.

[0143] 22 and 23, the thermal insulation 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 in which no fiber bundles 47 are present are formed on the surface of the thermal insulation material 110. In this specification, the "fiber bundles 47" are 10 or more organic fibers 1 intertwined with each other, and extend in a streak-like manner in a direction approximately parallel to the surface of the thermal insulation material 110.

[0144] That is, when the surface of the thermal insulation material 110 is observed, a state in which a plurality of organic fibers 1 are entangled is observed in the first region 42, as shown in Fig. 23. On the other hand, in the second region 43, although there are some places where a few organic fibers 1 are observed, fiber bundles 47 in which a plurality of organic fibers 1 are entangled are not observed. In this embodiment, the first region 42 and the second region 43 have a sea-island structure, and the second region 43 corresponding to an island portion is formed so as to be surrounded by the first region 42 corresponding to a sea portion.

[0145] In the heat insulating material 110, the fiber bundles 47 in which the organic fibers 1 are entangled are present on the surface of the heat insulating material 110 in a streaky manner, so that the strength of the heat insulating material 110 can be improved. In addition, the entire surface is not covered with the fiber bundles 47, and there are a first region 42 in which the fiber bundles 47 are present and a second region in which the fiber bundles 47 are not present, so that the flexibility of the heat insulating material 110 is also excellent. Furthermore, in this embodiment, the heat insulating material is formed with a thickness thinner than the frame body, and the fiber bundles 47 are present on the surface of the heat insulating material 110. Therefore, even if an impact or pressure is applied to the heat insulating material 110, the voids on the main surface side of the heat insulating 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, it is possible to suppress the inorganic particles 4 from falling off (powdering off), and it is possible to prevent a decrease in the heat insulating performance of the heat transfer suppressing member.

[0146] In the heat insulating material 110, the organic fibers 1 and the fiber bundles 47 in which the organic fibers 1 are entangled 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 so as to extend over the surface of the heat insulating material 110 is relatively long. An example of a method for determining the length of the fiber bundles 47 will be described with reference to FIG. 24, rectangular imaginary frames 21 are arranged along the streak-like fiber bundles 47 on the surface of the thermal insulation material 110. In this embodiment, the size of the imaginary frames 21 is 5 mm square, and these imaginary frames 21 are arranged so 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 effect of improving the strength of the thermal insulation material 110 is sufficient.

[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 the preferred contents thereof will be described in more detail below.

[0151] <Organic fiber> The organic fiber 1 gives flexibility to the heat insulating material, and has the effect of maintaining the strength and shape of the sheet by welding the inorganic particles 4 and other organic fibers 1 to the surface of the organic fiber 1. Although a single-component organic fiber can be used as the material of the organic fiber 1 in the heat insulating 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 peripheral surface of the core. In addition, the core is made of a first organic material, the sheath is made of a second organic material, and the melting point of the first organic material is higher than the melting point 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 heat insulating material. In addition, during the production of the heat insulating material, the second organic material constituting the sheath melts and then solidifies again, so that the sheath becomes the welded part 5 in the heat insulating material.

[0152] When a binder fiber having a core-sheath structure is used as the material of the organic fiber 1, the core, i.e., the first organic material constituting 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 peripheral 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 the organic fiber 1 in the heat insulating material is appropriately controlled, the effect of reinforcing the skeleton can be sufficiently obtained. The content of the organic fibers 1 is preferably 2% by mass or more, more preferably 4% by mass or more, based on the total mass of the heat insulating material. If the content of the organic fibers 1 is too high, the content of the inorganic particles 4 will relatively decrease, so in order to obtain the desired heat insulating performance, the content of the organic fibers is preferably 10% by mass or less, more preferably 8% by mass or less, based on the total mass of the heat insulating material.

[0154] (Organic fiber length) The fiber length of the organic fibers 1 is not particularly limited, but from the viewpoint of ensuring moldability and processability, it is preferable that the average fiber length of the organic fibers is 10 mm or less. On the other hand, from the viewpoint of making the organic fibers 1 function as a skeleton and ensuring the compressive strength of the heat insulating material, it is preferable that the average fiber length of the organic fibers 1 is 0.5 mm or more.

[0155] <Welded part> The welded portion 5 is formed by heating and melting the surface of the organic fiber 1 or the sheath 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 contains the second organic material that constitutes the sheath.

[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. The second organic material may be at least one selected from the group consisting of 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, and specifically, silica nanoparticles, metal oxide particles, inorganic balloons such as microporous particles and hollow silica particles, particles made of thermally expandable inorganic materials, particles made of water-containing porous bodies, etc. can also be used.

[0158] If 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. If 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 kinds of inorganic particles having different heat transfer suppression effects are used in combination, the heating body can be cooled in multiple stages, and the heat absorption effect can be expressed in 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 inorganic particle, it is preferable to include inorganic particles made of 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 particle> (Oxide particles) Since oxide particles have a high refractive index and a strong effect of scattering light, when oxide particles are used as the first inorganic particles, radiation 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 insulation properties, and titania is a component with a high refractive index compared to other metal oxides, and has a high effect of scattering light and blocking radiant heat in high temperature regions of 500°C or more, so it is most preferable to use silica and titania as the oxide particles.

[0161] (Average primary particle size of oxide particles: 0.001 μm to 50 μm) The particle size of the oxide particles can affect the effect of reflecting radiant heat, so if the average primary particle size is limited to a predetermined range, even higher heat insulation can be obtained. In other words, when the average primary particle diameter of the oxide particles is 0.001 μm or more, it is sufficiently larger than the wavelength of light that contributes to heating and efficiently diffuses the light, thereby suppressing the radiation heat transfer within the insulation material in the high temperature range of 500°C or more, thereby further improving the insulation properties. On the other hand, if the average primary particle size of the oxide particles is 50 μm or less, the number and number of contact points between the particles do not increase even when compressed, making it difficult to form a conductive heat transfer path, thereby reducing the impact on insulation, especially in the normal temperature range 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 ten particles.

[0163] (Nanoparticles) In the present invention, the term "nanoparticles" refers to particles of the order of nanometers that are spherical or nearly spherical and have an average primary particle diameter of less than 1 μm. Nanoparticles have a low density and therefore suppress conductive heat transfer. When nanoparticles are used as the first inorganic particles, the three-dimensionally connected pores 7 are further refined, and excellent heat insulation properties that suppress convective heat transfer can be obtained. For this reason, it is preferable to use nanoparticles in that heat transfer between adjacent nanoparticles can be suppressed when the battery is used in the normal room temperature range. Furthermore, if nanoparticles with a small average primary particle size are used as the oxide particles, the increase in conductive heat transfer of the insulating material can be suppressed even if the insulating material is compressed due to expansion caused by thermal runaway of the battery cell and the internal density increases. This is thought to be because nanoparticles are prone to forming fine gaps between particles due to electrostatic repulsion, and because they have a low bulk density, the particles are packed together to provide cushioning properties.

[0164] In the present invention, when nanoparticles are used as the first inorganic particles, there is no particular limitation on the material as long as it meets the above definition of nanoparticles. For example, silica nanoparticles are a material with high heat insulation properties, and since the contact points between particles are small, the amount of heat conducted by silica nanoparticles is smaller than that when silica particles with a large particle size are used. Furthermore, silica nanoparticles that are generally available 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 contacts 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 particles are aggregated, whereas dry silica particles can be dispersed. In the temperature range below 300℃, heat conduction is dominated by conductive heat transfer, so dry silica particles can be dispersed, which provides better heat insulation performance than wet silica. In addition, the heat insulating material according to the present embodiment is preferably produced by a manufacturing method in which a mixture containing the material 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 size of nanoparticles: 1 nm to 100 nm) By limiting the average primary particle size of the nanoparticles to a predetermined range, even higher heat insulation properties can be obtained. That is, when the average primary particle size of the nanoparticles is 1 nm or more and 100 nm or less, it is possible to suppress convective heat transfer and conductive heat transfer within the insulating material, particularly in the temperature range below 500° C., and to further improve the insulating properties. Even when compressive stress is applied, the gaps remaining between the nanoparticles and the contact points between many particles suppress conductive heat transfer, and the insulating properties of the insulating material can be maintained. The average primary particle size of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more, while the average primary particle size of the nanoparticles is more preferably 50 nm or less, and even more preferably 10 nm or less.

[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 and release their own water of crystallization to lower the temperature of the heating element and its surroundings, thus exerting the so-called "endothermic effect". After releasing the water of crystallization, the particles become porous and exert a heat insulating effect 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), and gallium hydroxide (Ga(OH)3).

[0168] For example, aluminum hydroxide has about 35% water of crystallization, and as shown in the formula below, it decomposes thermally and releases the water of crystallization, exerting an endothermic effect. After releasing the water of crystallization, it becomes a porous material called alumina (Al2O3), and functions as a heat insulating material. 2Al(OH)3 → Al2O3 + 3H2O

[0169] It should be noted that the heat transfer suppressing member 50 according to this embodiment is preferably interposed between battery cells, for example, but in a battery cell that has experienced thermal runaway, the temperature rises 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 sudden temperature rise in a battery cell that has experienced thermal runaway, and can efficiently suppress the temperature rise, making these inorganic hydrates preferable.

[0170] (Average secondary particle diameter of inorganic hydrate particles: 0.01 μm or more and 200 μm or less) In addition, when inorganic hydrate particles are used as the first inorganic particles, if the average particle size is too large, the first inorganic particles (inorganic hydrate) near the center of the heat insulating material require a certain amount of time to reach their thermal decomposition temperature, and the first inorganic particles near the center of the sheet may not be completely thermally decomposed. For this reason, the average secondary particle size of the inorganic hydrate particles is preferably 0.01 μm or more and 200 μm or less, and more preferably 0.05 μm or more and 100 μm or less.

[0171] (Particles made of thermally expandable inorganic material) Examples of the thermally expandable inorganic material include vermiculite, bentonite, mica, and perlite.

[0172] (Particles made of water-containing porous material) Specific examples of the hydrous porous body include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

[0173] (Inorganic balloon) The heat insulating material used in the present invention may contain inorganic balloons as the first inorganic particles. When inorganic balloons are contained, convective or conductive heat transfer within the insulating material can be suppressed in the temperature range below 500° C., and the insulating properties of the insulating material can be further improved. As the inorganic balloons, at least one selected from the group consisting of shirasu balloons, silica balloons, fly ash balloons, barite balloons, and glass balloons can be used.

[0174] (Inorganic balloon content: 60% or less by mass of the total mass of the insulation material) The content of the inorganic balloons is preferably 60 mass % or less based on the total mass of the heat insulating material.

[0175] (Average particle size of inorganic balloons: 1 μm to 100 μm) The average particle size of the inorganic balloons is preferably 1 μm or more and 100 μm or less.

[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. As the second inorganic particles, 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, particles made of a water-containing porous body, etc. can be used, and the details of these are as described above.

[0177] In addition, nanoparticles have extremely low conductive heat transfer and can maintain excellent heat insulation even when compressive stress is applied to the heat insulating material. Metal oxide particles such as titania have a high effect of blocking radiant heat. Furthermore, when large-diameter inorganic particles and small-diameter inorganic particles are used, the small-diameter inorganic particles enter the gaps between the large-diameter inorganic particles, resulting in a denser structure and improving the heat transfer suppression effect. Therefore, when nanoparticles are used as the first inorganic particles, for example, it is preferable to further include particles made of a metal oxide larger in diameter than the first inorganic particles as the second inorganic particles in the heat insulating material. Examples of metal oxides include silicon oxide, titanium oxide, aluminum oxide, barium titanate, zinc oxide, zircon, zirconium oxide, etc. In particular, titanium oxide (titania) is a component with a higher refractive index than other metal oxides, and is highly effective in scattering light and blocking radiant heat in a high temperature range of 500°C or higher, so it is most preferable to use titania.

[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 first inorganic particles are preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more of the total mass of the inorganic particles. In addition, the first inorganic particles are preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less of the total mass of the inorganic particles.

[0179] On the other hand, in order to obtain excellent heat insulating performance within a temperature range exceeding 300° C., the second inorganic particles are preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on the total mass of the inorganic particles. Also, the second inorganic particles are 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 size of second inorganic particles) When second inorganic particles made of a metal oxide are contained in a heat insulating material, if the average primary particle size of the second inorganic particles is 1 μm or more and 50 μm or less, radiation heat transfer can be efficiently suppressed in a high temperature range of 500° C. or more. The average primary particle size of the second inorganic particles is more preferably 5 μm or more and 30 μm or less, and most preferably 10 μm or less.

[0181] (Inorganic particle content) In this embodiment, when the total content of the inorganic particles 4 in the heat insulating material is appropriately controlled, the heat insulating property of the heat insulating material can be sufficiently ensured. The total content of the inorganic particles 4 is preferably 60% by mass or more, and more preferably 70% by mass or more, based on the total mass of the heat insulating material. If the total content of the inorganic particles 4 is too high, the content of the organic fibers is relatively reduced, so that in order to sufficiently obtain the effect of reinforcing the skeleton and the effect of retaining the inorganic particles, the total content of the inorganic particles 4 is preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total mass of the heat insulating 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 matter, and then measuring the mass of the remaining part.

[0183] <Inorganic fibers> A single inorganic fiber may be used, or two or more types of inorganic fibers may be used in combination as the inorganic fiber 15. Examples of the inorganic fiber include ceramic fibers such as silica fiber, alumina fiber, alumina silicate fiber, zirconia fiber, carbon fiber, soluble fiber, refractory ceramic fiber, aerogel composite material, magnesium silicate fiber, alkaline earth silicate fiber, potassium titanate fiber, silicon carbide fiber, and potassium titanate whisker fiber, glass fibers such as glass fibers, glass wool, and slag wool, and mineral fibers other than these fibers such as rock wool, basalt fiber, and mullite fiber, and mineral fibers other than the above such as natural mineral fibers such as wollastonite. These inorganic fibers are preferred in terms of heat resistance, strength, availability, etc. Among the inorganic fibers, silica-alumina fibers, alumina fibers, silica fibers, rock wool, alkaline earth silicate fibers, and glass fibers are particularly preferred in terms of ease of handling.

[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 them, 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, and the more preferred lower limit is 0.5 mm. On the other hand, the preferred upper limit of the average fiber length of the inorganic fibers is 50 mm, and the more preferred upper limit is 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, and the mechanical strength of the insulating material may be reduced. On the other hand, if it exceeds 50 mm, although a reinforcing effect is obtained, the inorganic fibers may not be able to be tightly entangled with each other, or may be curled up with only a single inorganic fiber, which may lead to continuous voids, which may lead to a decrease in thermal insulation.

[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. In addition, from the viewpoint of the effect on human health, it is preferable that the average fiber diameter of the inorganic fibers is 3 μm or more. On the other hand, if the average fiber diameter of the inorganic fibers is more than 15 μm, the solid heat transfer through the inorganic fibers may increase, leading to a decrease in heat insulation, and the moldability and strength of the heat insulating material may be deteriorated.

[0187] (Inorganic fiber content) In this embodiment, when the heat insulating material contains inorganic fibers, the content of the inorganic fibers is preferably 3 mass % or more and 15 mass % or less 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 based on the total mass of the heat insulating material. By setting the content at such a level, the shape retention, pressing force resistance, wind pressure resistance, and inorganic particle retention ability of the inorganic fibers are expressed in a well-balanced manner. In addition, 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, so that the effect of retaining the inorganic particles 4 and other compounding materials described later can be further improved.

[0189] <Other compounding materials> The heat insulating material according to the present embodiment may further contain a binder, a colorant, etc., as necessary. All of these are useful for the purpose of reinforcing the heat insulating material, improving its formability, etc., and the total amount of these is preferably 10 mass % or less based on the total mass of the heat insulating material.

[0190] Although the insulating material Structural Examples 1 to 7 have been described above, the structure of the insulating material containing inorganic particles and organic fibers is not limited thereto, and insulating materials having various structures can be used. In particular, the insulating materials of Structural Examples 1 to 7 have a more excellent insulating effect than other insulating materials and insulating materials containing fibers and aerogel.

[0191] Here, we will explain the results of comparing the insulating effect using 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 of the other main surface when the temperature of the heater is increased. When the temperature of the heater is increased to 800°C, the temperature of the other main surface of the insulating material reaches the maximum temperature after a certain period of time. At this time, it can be seen that the insulating material with the lower maximum temperature has better insulating properties. The results of the comparison of insulating effects are shown in Table 1 below.

[0192] [Table 1]

[0193] In Table 1, the heat insulating materials A-1 and A-2 are heat insulating materials of the structural example 3 shown in Fig. 11 to Fig. 13, and are formed by molding organic fibers with a core-sheath structure and inorganic particles into a sheet shape by a dry method. In the heat insulating materials A-1 and A-2, the organic fibers used are those with a core-sheath structure 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 the inorganic particles. The heat insulating material B is impregnated with SiO2 using a fiber as a framework.

[0194] As shown in Table 1 above, the insulating performance of the insulating material A-1 with a thickness of 2.0 mm is equal to that of the insulating material B with a thickness of 4.5 mm. Also, 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 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 frame 53, and therefore the insulating materials can be suitably used as the insulating materials for the heat transfer suppressing members according to the embodiments of the present invention.

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

[0197] <Film> As shown in the first to third embodiments above, when the heat transfer suppression 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), polyphenylsulfide, polycarbonate, and aramid.

[0198] Shrink packaging may be used when only the insulating material is covered with a film, or when the insulating material and the frame, or the entire surface of the laminate and the frame, are covered with film 52. Materials suitable 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 heat insulating material and to prevent the heat insulating material from falling off the frame 53. The film also preferably has appropriate flexibility. If the thickness of the film exceeds 1 mm, the film is prone to cracks and breaks. Therefore, the thickness of the film is preferably 1 mm or less, more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. On the other hand, there is no particular lower limit to the thickness of the film, but in order to prevent tearing due to friction with battery cells and the like and to obtain the desired strength, the thickness is preferably 0.005 mm or more, and more preferably 0.01 mm or more.

[0200] (Other materials contained in the film) In addition, since the film is required to be resistant to the high temperatures of the battery cells 20a, 20b, and 20c, it is preferable that the film has flame retardancy, and specifically, it is preferable that the film contains an inorganic substance or a flame retardant. Other materials contained 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 retardants 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 constituting the elastic material 51. Specifically, a sheet formed of rubber or a thermoplastic elastomer having elasticity that flexibly deforms 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. 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 the thermoplastic elastomer 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 type or open cell type.

[0204] (Elastic material size) 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 be 1 mm or more and 10 mm or less.

[0205] [Method of manufacturing heat transfer suppression member] A method for manufacturing a heat-transfer suppressing 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 a heat-transfer suppressing member 130 according to a third embodiment.

[0206] <Insulation material manufacturing> For example, binder fibers (not shown) having a core-sheath structure, inorganic particles 4, and inorganic fibers 15 are put into a mixer such as a V-type mixer in a predetermined ratio to prepare a mixture. As described above, it is preferable to use, as the binder fiber, fibers having a core-sheath structure with a core made of a first organic material and a sheath made of a second organic material, in which the melting point of the first organic material is higher than that of the second organic material.

[0207] The mixture is then placed in a predetermined mold and pressed with a press or the like, and the resulting molded body is heated to melt the sheath of the binder fiber. The heated molded body is then cooled, and the second organic material constituting the molten sheath and the inorganic particles 4 present around the binder fiber are fused to the core (organic fiber 1), and are also fused to each other in the region where the binder fibers 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 not including inorganic fibers 15 can be obtained in the same manner 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 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 has the effect of improving the strength of the heat insulating material 40 and mitigating impacts on the surface of the heat insulating material 40.

[0210] <Assembly of laminated bodies> Thereafter, the elastic material 51 is placed on the main surface of the heat insulating material 40, and the two are fixed together. There is no particular limitation 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 adhering with an adhesive or the like, a method of sewing with thread or the like, a method of clamping and fixing with a fixing jig, a method of covering with a film or the like, a method of covering with a thermocompressive film and then heating to shrink the film and fix it, etc. It is not necessarily necessary to laminate the elastic material 51, and as shown in the first embodiment, only the heat insulating material may be used.

[0211] <Frame manufacturing> Further, a frame 53 is prepared to surround the outer periphery of the heat insulating material. The frame 53 may be made of, for example, a resin, and may be molded as a single unit or may be prepared by combining a plurality of frame members. As shown in the fourth embodiment and its modified example shown in Fig. 5A and Fig. 5B, when the heat transfer suppressing member has a partition wall, the frame and the partition wall may be molded as a single unit or may be prepared by combining a plurality of members.

[0212] <Inserting the laminate into the frame> Thereafter, the heat insulating material is fitted and fixed in the frame body 53. The method for fixing the heat insulating material to the frame body 53 is not particularly limited, and the heat insulating material may be fixed using a fixing material such as an adhesive, or a groove or the like may be formed in the frame body 53 and the heat insulating material may be fixed by fitting into the groove.

[0213] <Film application> Thereafter, two sheets of film 52 having a size approximately equal to the outer diameter of frame body 53 in a plan view are prepared, film 52 is laid over frame body 53, and frame body 53 and film 52 are heat-sealed. In this manner, film 52 may be heat-sealed to frame body 53, may completely cover frame body 53 and the heat insulating material, or may cover only the heat insulating material. Also, as shown in the fourth embodiment, film 52 does not have to be disposed. In addition, when the outer diameter of frame body 53 and the size of film 52 are "approximately the same," this means that the difference between their sizes is acceptable up to ±5% of the average value of the two, preferably up to ±3%, and more preferably up to ±1%.

[0214] The above-mentioned heat insulating material is preferably manufactured by a dry method. When using a dry method, inorganic particles 4 suitable for the dry method are used, and a solvent such as water, which is necessary when forming by a wet method, is not added to the above mixture. However, in order to prevent powder such as inorganic particles 4 from flying around during the manufacture of the heat insulating material and making it difficult to handle the raw material, a small amount of solvent such as water can be added within the range of 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 the manufacture.

[0215] Next, the binder fiber 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 binder fibers 3 with a core-sheath structure as a material for the heat insulating material, there is no particular limitation 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 may be at least one selected from polyethylene terephthalate, polypropylene, and nylon. The second organic material constituting the sheath may 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, and the temperature setting for obtaining a desired structure can be made easier. 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-mentioned 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, and 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, but softening accompanied by a change in shape is also considered to be a type of melting deformation. The melting point of the sheath of the binder fiber can be measured, for example, by the following method. The binder fiber to be measured is placed in contact with the glass fiber having a higher melting point, heated from room temperature to, for example, 200°C at a heating rate of 5°C / min, and then cooled to room temperature. At this time, if the surface of the binder fiber melts and deforms and is fused at the part in contact with the glass fiber or 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 less. In this embodiment, the heating temperature is changed in various ways, 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 by the above-mentioned method, whereby the melting point of the second organic material constituting the sheath can be specified.

[0220] (Binder fiber content) When using binder fiber 3 having a core-sheath structure as a material for an insulating material, if the content of the binder fiber in the mixture is appropriately controlled, the skeleton of the resulting insulating material can be sufficiently reinforced. The content of the binder fibers 3 is preferably 5% by mass or more, and more preferably 10% by mass or more, based on the total mass of the mixture. If the content of the binder fibers 3 is too high, the content of the inorganic particles 4 is relatively reduced, so in order to obtain the desired heat insulating performance, the content of the binder fibers 3 is preferably 25% by mass or less, and more preferably 20% by mass or less, based on the total mass of the mixture.

[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. By adding the hot melt powder to the mixture and heating it, the hot melt powder melts, and when cooled, it hardens in a state including the surrounding inorganic particles 4. Therefore, it is possible to further suppress the falling off of the inorganic particles 4 from the heat insulating material.

[0222] There are various types of hot melt powders having various melting points, and a hot melt powder having an appropriate melting point can be selected in consideration of the melting points of the core and sheath of the binder fiber to be used. Specifically, if the third organic material, which is a component 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 the melting point 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] On the other hand, the type of hot melt powder used can be selected so that the melting point of the hot melt powder is between the melting points of the core and the sheath. When a hot melt powder having such a melting point is used, when the sheath and the hot melt powder are both melted and then cooled and hardened, the organic fiber (core) 1 and 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 welded to the organic fiber, making it easier to form a three-dimensional skeleton. Therefore, the strength of the entire sheet can be further improved.

[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, and the temperature setting for obtaining a desired structure can be made easier. For example, the melting point of the first organic material is preferably 60° C. or more higher than the melting point 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. Components constituting the hot melt powder include polyethylene, polyester, polyamide, ethylene vinyl acetate, and the like.

[0226] (Hot melt powder content) When hot melt powder is added to the mixture to suppress the falling off of inorganic particles, the effect of suppressing powder falling can be obtained even with a small amount of hot melt powder. Therefore, the content of hot melt powder is preferably 0.5% by mass or more, more preferably 1% by mass or more, based on the total mass of the mixture. On the other hand, when the content of the hot melt powder is increased, the content of the inorganic particles 4 and the like is relatively decreased, so in order to obtain the desired heat insulating performance, the content of the hot melt powder is preferably 5 mass % or less, and more preferably 4 mass % or less, relative to the total mass of the mixture.

[0227] <Heating conditions> When using binder fibers with a core-sheath structure as the material for the heat 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 the heating temperature in this manner, 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 by the fused parts 5.

[0228] Specifically, the heating temperature in the heating step is set preferably 10° C. or more higher, more preferably 20° C. or more higher, than the melting point of the second organic material constituting the sheath, while the heating temperature is set preferably 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 it is preferable to set the heating time so that the sheath can be sufficiently melted, for example, from 3 minutes to 15 minutes.

[0230] When the heat insulating material contains hot melt powder, the heating temperature in the heating step is preferably set to be 10°C or more 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, and more preferably set to be 20°C or more higher. On the other hand, the heating temperature is preferably set to be 10°C or more lower than the melting point of the first organic material constituting the core, and more preferably set to be 20°C or more lower. By setting the heating temperature at such a level, a strong skeleton can be formed, the strength of the sheet can be further improved, and the inorganic particles 4 can be prevented from falling off by the fused parts 5, etc.

[0231] <Insulation thickness> In this embodiment, the thickness of the heat insulating material is not particularly limited as long as it is thinner than the thickness of the frame body, but it is preferably 0.05 mm or more and 10 mm or less. If the thickness is 0.05 mm or more, sufficient compressive strength can be obtained. On the other hand, if the thickness is 10 mm or less, good heat insulating properties of the heat transfer suppressing member can be obtained.

[0232] [Battery pack] An example of a battery pack to which the heat-transfer-suppressing member 50 according to the first embodiment of the present invention is applied is as shown in FIG. 2. The configuration and effects of the battery pack will now be specifically described 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, 160 having other structures, as well as with heat-transfer-suppressing members having other structures within the scope of the present invention. In addition to the heat insulating materials 10, 40, 60, 70, 80, 90, 110 having the various structures described above, the heat insulating material can also be replaced with other heat insulating materials 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, and the plurality of battery cells are connected in series or in 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. Furthermore, 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, so that the spacing between the battery cells can be secured. Also, 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 the transfer of heat 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 catches fire, it is possible to prevent the flame from spreading outside the battery case 30. For example, the battery pack 100 according to this embodiment may be used in an electric vehicle (EV) or the like, and may be placed under the floor of a passenger compartment. In this case, even if a battery cell catches fire, the safety of the passengers can be ensured. Furthermore, since the heat transfer suppression member 50 can be disposed not only between each battery cell but also between the battery cells 20a, 20b, 20c and the battery case 30, there is no need to fabricate new flame retardant materials, etc., and a safe battery pack 100 can be easily constructed 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, in addition to prismatic batteries, it can also be applied to cylindrical batteries, flat batteries, etc. [Explanation of symbols]

[0238] 1. Organic Fibers 3. Binder Fiber 8,54 void 10,40,60,70,80,90,110 Insulation 10a First insulation material 10b Second insulation material 20a, 20b, 20c Battery cells 30 Battery case 50,120,130,140,150,160 Heat transfer suppression material 51 Elastic material 52,112,312 film 53 Frame 53a, 53b Frame members 58a, 58b, 58c, 58d Partition walls 100 battery packs

Claims

1. A frame body surrounding the outer periphery in a plan view; A sheet-like insulating material having a pair of main surfaces and disposed inside the frame, A heat transfer suppressing member, characterized in that, 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 a main surface of the heat insulating material.

3. The heat transfer suppressing member according to claim 2 , further comprising a gap between at least one of the pair of main surfaces and the film.

4. The heat transfer suppression member 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 laminate has a pair of outer main surfaces perpendicular to a thickness direction, The heat transfer suppressing member according to claim 4 , further comprising a film covering the pair of outer main surfaces.

6. The heat transfer suppressing member according to claim 5 , further comprising a gap between at least one of the pair of outer main surfaces and the film.

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

8. Further, a partition wall is provided to divide the inside of the frame into a plurality of regions, The heat transfer suppressing member according to claim 1 , further comprising 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 first insulating material has a modulus of elasticity smaller than a modulus of elasticity 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 of the plurality of regions.

12. 9. The heat transfer suppressing member according to claim 8, wherein in a plan view, a width of the partition wall in a direction perpendicular to the longitudinal direction is smaller than a width of the frame in the direction perpendicular to the longitudinal direction.

13. The heat transfer suppressing member according to any one of claims 8 to 12, wherein the partition wall is made mainly of an insulating material.

14. The heat transfer suppressing member according to any one of claims 1 to 12, wherein the frame body is made mainly of an insulating material.

15. 13. The heat transfer suppressing member according to claim 1, wherein the heat insulating material contains inorganic particles and organic fibers.

16. 13. A battery pack comprising: a plurality of battery cells; and the heat transfer suppressing member according to claim 1, the plurality of battery cells being connected in series or in parallel.

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