Heat transfer suppression member and battery pack

Abstract

The present invention provides a heat transfer suppression member that can achieve sufficient heat insulation required during normal use, maintain spacing between battery cells during abnormal situations, suppress damage to the battery case and degradation of battery performance due to deformation of battery cells, and suppress heat transfer between each battery cell. [Solution] The heat transfer suppression member 50 has a frame 53 that surrounds the outer periphery in a plan view, and a sheet-like functional member 9 that is arranged inside the frame 53 and has a pair of main surfaces 9s. The functional member 9 also has an insulating sheet, and in a cross-sectional view perpendicular to the plan view, the thickness of the functional member 9 is greater than the thickness of the frame 53.

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 Art

[0002] In recent years, development of electric vehicles, hybrid vehicles and the like driven by electric motors has been actively promoted from the viewpoint of environmental protection. These electric vehicles, hybrid vehicles and the like are each equipped with a battery pack in which a plurality of battery cells are connected in series or in parallel to serve as a power source for the driving electric motor.

[0003] In addition, as these battery cells, lithium ion secondary batteries capable of higher capacity and higher output than lead-acid batteries, nickel-metal hydride batteries and the like are mainly used. When a certain battery cell rapidly rises in temperature due to an internal short circuit, overcharge or the like of the battery and then undergoes thermal runaway that continues to generate heat (that is, in an "abnormal state"), the heat from the thermally runaway battery cell propagates to other adjacent battery cells, which may cause thermal runaway in the other battery cells. Further, when thermal runaway occurs in a battery cell, gas is generated inside the battery, and the internal pressure rises, causing 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 an excellent heat transfer suppressing effect, can suppress a decrease in the thickness of a heat insulating material even when a battery cell expands, and can maintain high heat insulating performance. The heat transfer suppressing sheet described in Patent Document 1 includes a first heat insulating material and a second heat insulating material, and the thermal conductivity of the first heat insulating material is lower than the thermal conductivity of the second heat insulating material. Further, the compressive strength of the second heat insulating material is higher than the compressive strength of the first heat insulating material, and the first heat insulating material is sandwiched between a plurality of the second heat insulating materials.

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

[0006] The heat transfer suppression sheet and thermal insulation material described in Patent Documents 1 and 2 above both prevent the thermal insulation material from being compressed and narrowing the gap between battery cells, thereby suppressing a decrease in thermal conductivity. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-187869 [Patent Document 2] Japanese Patent Publication No. 2017-215014 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, under normal use, the areas where the frame and resin supports are located have low thermal insulation properties, making it difficult to obtain sufficient thermal insulation.

[0009] Furthermore, even if a battery cell expands during thermal runaway, it is required to maintain the spacing between adjacent battery cells.

[0010] The present invention has been made in view of the above problems, and aims to provide a heat transfer suppression member that can obtain sufficient heat insulation required during normal use, maintain the spacing between battery cells in abnormal situations, suppress damage to the battery case and deterioration of battery performance due to deformation of battery cells, and suppress heat transfer between each battery cell, and a battery pack that can suppress heat transfer between each battery cell and suppress damage to the battery case and deterioration of battery performance. [Means for solving the problem]

[0011] The above objective of the present invention is achieved by the configuration of the heat transfer suppression member described below [1].

[0012] [1] A frame that surrounds the outer perimeter in plan view, A heat transfer suppression member having a sheet-like functional member disposed inside the frame and having a pair of main surfaces, The functional member has a heat insulating sheet, A heat transfer suppressing member characterized in that, in a cross-sectional view perpendicular to the plan view, the thickness of the functional member is greater than the thickness of the frame.

[0013] Furthermore, preferred embodiments of the present invention relating to the heat transfer suppression member are described in the following [2] to

[14] .

[0014] [2] The heat transfer suppression member according to [1], characterized in that the functional member consists only of the heat insulating sheet.

[0015] [3] The heat transfer suppression member according to [1], characterized in that the functional member comprises a heat insulating sheet having a pair of main surfaces and an elastic sheet laminated on at least one of the main surfaces of the heat insulating sheet.

[0016] [4] The heat transfer suppression member according to any one of [1] to [3], characterized by having a film covering the main surface of the functional member.

[0017] [5] The heat transfer suppressing member according to any one of [1] to [4], characterized in that, in the cross-sectional view, there is a step between the functional member and the frame, and at least one main surface of the functional member protrudes in the thickness direction relative to the frame.

[0018] [6] The heat transfer suppression member according to any one of [1] to [5], characterized in that the frame is mainly made of an insulating material.

[0019] [7] The heat transfer suppressing member according to any one of [1] to [6], wherein the heat insulating sheet contains inorganic particles and organic fibers.

[0020] [8] The heat transfer suppressing member according to [3], wherein the elastic sheet contains at least one selected from synthetic rubber, natural rubber and thermoplastic elastomer.

[0021] [9] Further, the heat transfer suppressing member has a partition wall that divides the inner side of the frame body into a plurality of regions, and has a plurality of the functional members arranged in the plurality of regions, The heat transfer suppressing member according to any one of [1] to [8], wherein in the cross-sectional view, the thickness of the functional member is larger than the thickness of the partition wall.

[0022]

[10] The heat transfer suppressing member according to [9], wherein the plurality of functional members include a first functional member and a second functional member having properties different from each other.

[0023]

[11] The heat transfer suppressing member according to

[10] , wherein the elastic modulus of the first functional member is smaller than the elastic modulus of the second functional member.

[0024]

[12] The heat transfer suppressing member according to

[11] , wherein the first functional member is arranged in at least a central region among the plurality of regions.

[0025]

[13] The heat transfer suppressing member according to any one of [9] to

[12] , wherein in the plan view, the width of the partition wall in the direction orthogonal to the longitudinal direction is smaller than the width of the frame body in the direction orthogonal to the longitudinal direction.

[0026]

[14] The heat transfer suppressing member according to any one of [9] to

[13] , wherein the partition wall is mainly made of an insulating material.

[0027] Furthermore, the above-mentioned objective of the present invention is achieved by the following configuration of the battery pack

[15] .

[0028]

[15] A battery pack comprising a plurality of battery cells and a heat transfer suppression member described in any one of [1] to

[14] , wherein the plurality of battery cells are connected in series or in parallel. [Effects of the Invention]

[0029] The heat transfer suppressing member of the present invention has a frame surrounding its outer circumference, and the thickness of the functional member placed inside the frame is greater than the thickness of the frame. Therefore, when the heat transfer suppressing member is placed between battery cells, a gap is formed between the frame and the battery cells. Consequently, under normal use, heat transfer through the frame can be suppressed, and sufficient thermal insulation can be obtained. Furthermore, even if the thickness of the functional member decreases under abnormal conditions, the spacing between battery cells can be maintained, preventing damage to the battery case due to deformation of the battery cells and a decrease in battery performance, and suppressing heat propagation between each battery cell.

[0030] Because the battery pack of the present invention has the heat transfer suppressing member described above, it is possible to suppress the propagation of heat between each battery cell, thereby suppressing the destruction of the battery case and the deterioration of battery performance, and thus obtain a battery pack that can maintain excellent battery performance. [Brief explanation of the drawing]

[0031] [Figure 1A] Figure 1A is a plan view showing a heat transfer suppression member according to a first embodiment of the present invention. [Figure 1B] Figure 1B is a cross-sectional view along line II in Figure 1A. [Figure 2] Figure 2 is a schematic cross-sectional view showing a battery pack having a heat transfer suppression sheet according to the first embodiment of the present invention. [Figure 3] Figure 3 is a cross-sectional view showing a heat transfer suppression member according to a second embodiment of the present invention. [Figure 4] Figure 4 is a cross-sectional view showing a heat transfer suppression member according to a third embodiment of the present invention. [Figure 5A] Figure 5A is a plan view showing a heat transfer suppression member according to a fourth embodiment of the present invention. [Figure 5B] Figure 5B is a cross-sectional view taken along the line II-II in Figure 5A. [Figure 6] Figure 6 is a plan view showing a modified example 1 of the heat transfer suppression member according to the fourth embodiment of the present invention. [Figure 7] Figure 7 is a plan view showing a modified example 2 of the heat transfer suppression member according to the fourth embodiment of the present invention. [Figure 8] Figure 8 is a photograph that serves as a substitute for a drawing, showing an example of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention. [Figure 9] Figure 9 is a photograph used as a substitute for a drawing, showing a magnified view of a portion of the insulation sheet shown in Figure 8. [Figure 10] Figure 10 is a photograph that serves as a substitute for a drawing, showing an example of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention. [Figure 11] Figure 11 is a schematic diagram showing example 3 of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention. [Figure 12] Figure 12 is a schematic diagram showing an enlarged portion of Figure 11. [Figure 13] Figure 13 is a photograph used as a substitute for a drawing, showing the insulation sheet shown in Figure 11. [Figure 14] Figure 14 is a photographic substitute for a drawing showing example 4 of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention. [Figure 15] Figure 15 is a photograph used as a substitute for a diagram, showing an enlarged view of the structure of the insulation sheet shown in Figure 14. [Figure 16] Figure 16 is a photograph used as a substitute for a drawing, showing a cross-section of the insulation sheet shown in Figure 14. [Figure 17] Figure 17 is a schematic diagram showing an example of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention. [Figure 18] Figure 18 is a schematic diagram showing an enlarged view of section A of the insulation sheet shown in Figure 17. [Figure 19]Figure 19 is a photographic substitute for a drawing showing example 6 of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention. [Figure 20] Figure 20 is a photographic representation of a drawing showing other areas of the insulation sheet shown in Figure 19. [Figure 21] Figure 21 is a photographic representation of a cross-section of the insulation sheet shown in Figures 19 and 20. [Figure 22] Figure 22 is a photograph that serves as a substitute for a drawing, showing an example of the structure 7 of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention. [Figure 23] Figure 23 is a photograph used as a substitute for a drawing, showing a magnified view of a portion of the insulation sheet shown in Figure 22. [Figure 24] Figure 24 is a schematic diagram illustrating an example of a method for defining the length of a fiber bundle. [Figure 25] Figure 25 is a photographic substitute for a drawing, showing another structural example of the insulation sheet shown in Figure 22. [Modes for carrying out the invention]

[0032] The inventors diligently studied to obtain a heat transfer suppression member that can maintain the desired heat insulation performance during normal use while suppressing the application of unnecessary pressure to battery cells during abnormal conditions, thereby preventing a decrease in battery performance. As a result, they found that the above problem can be solved by making the frame surrounding the outer periphery thinner than the thickness of the functional member placed inside it. In other words, during normal use, a decrease in heat insulation performance through the frame can be suppressed, and during abnormal conditions, the spacing between battery cells can be secured to provide an escape route for the expansion of the battery cells, thereby reducing the pressure applied to the battery cells when they expand.

[0033] The following describes in detail a heat transfer suppressing member, a method for manufacturing the same, and a battery pack according to an embodiment of the present invention. It should be noted that the present invention is not limited to the embodiments described below, and can be modified and implemented as desired without departing from the spirit of the invention. First, the heat transfer suppressing member according to an embodiment of the present invention will be described.

[0034] [Heat transfer suppression member] [First Embodiment] Figure 1A is a plan view showing a heat transfer suppressing member according to the first embodiment of the present invention, and Figure 1B is a cross-sectional view along line II. As shown in Figures 1A and 1B, the heat transfer suppressing member 40 according to the first embodiment includes a frame 53 that surrounds the outer periphery in a plan view, a functional member 9 disposed inside the frame 53 and having a pair of main surfaces 9s, and a film 52 attached to the surface of the frame 53 parallel to the main surfaces 9s of the functional member 9. In the first embodiment, the functional member 9 consists only of an insulating sheet, but the functional member 9 only needs to have an insulating sheet, and as will be described later, it may be a laminate of an insulating sheet and other sheets. In this embodiment, the thickness of the functional member 9 is formed to be thicker than the thickness of the frame 53. Therefore, in a cross-sectional view, there is a step between the functional member 9 and the frame 53, and both main surfaces 9s of the functional member 9 protrude in the thickness direction relative to the frame 53.

[0035] In this specification, "plan view" refers to a view of the heat transfer suppressing member from above when the main surface of the functional member 9 is positioned with its main surface facing vertically. "Cross-sectional view" refers to a view of the cross-section of the heat transfer suppressing member from a direction perpendicular to the above plan view.

[0036] The specific usage of the heat transfer suppression member 40 according to the first embodiment described above will be explained below. Figure 2 is a schematic cross-sectional view showing a battery pack having a heat transfer suppression sheet according to the first embodiment of the present invention. As shown in Figure 2, the heat transfer suppression member 40 can be used by interposing it between a plurality of battery cells 20a, 20b, and 20c. The plurality of battery cells 20a, 20b, and 20c are then connected in series or in parallel (the connected state is not shown in the figure) and stored in the battery case 30 to form the battery pack 100. For example, lithium-ion secondary batteries are preferably used as the battery cells 20a, 20b, and 20c, but are not particularly limited to this and can be applied to other secondary batteries as well.

[0037] Furthermore, as shown in Figure 2, when heat transfer suppression members 40 are placed between battery cells 20a and 20b, and between battery cells 20b and 20c, gaps 54 are formed between the frame 53 and the battery cells 20a, 20b, and 20c. More specifically, gaps 54 are formed between the frame 53 and the film 52, and between the film 52 and the battery cells 20a, 20b, and 20c on both sides of the frame 53 in the thickness direction.

[0038] If the frame 53 were to have the same thickness as the functional member 9 in cross-section, then during normal use, when the temperature of a battery cell rises, heat would be more easily transferred to adjacent battery cells through the frame 53, reducing its function as a heat transfer suppression member. In contrast, the battery pack 100 according to this embodiment has a functional member 9 made of an insulating sheet, a frame 53, and an air gap 54 between adjacent battery cells. Therefore, an insulating effect can be obtained from the insulating sheet and air, and the desired insulation performance between battery cells can be ensured.

[0039] Furthermore, in the event of an abnormality, that is, when the temperature of a particular battery cell rises significantly, the functional component 9 may burn out due to combustion or its thickness may decrease. In such cases, the presence of the frame 53 allows adjacent battery cells to be maintained at a desired distance, thereby suppressing the propagation of heat from the battery cell experiencing thermal runaway to other adjacent battery cells. In addition, the presence of the frame 53 also suppresses the application of unnecessary pressure to the battery cell experiencing thermal runaway and the adjacent battery cells due to the expansion of the battery cell.

[0040] Furthermore, in this embodiment, since the film 52 covers the main surface 9s of the functional member 9, if the heat insulating sheet constituting the functional member 9 contains, for example, inorganic particles, it is possible to prevent contamination of the inside of the battery case 30 by the shedding of inorganic particles, i.e., powder.

[0041] In this embodiment, the film 52 is heat-sealed to a part of the frame 53, so that the film 52 covers the main surface 9s of the functional member 9. However, the configuration of the film 52 is not limited to this in the present invention. For example, the film 52 may be arranged to enclose the frame 53 and the functional member 9 as a whole, or the film 52 may be arranged to cover only the functional member 9.

[0042] Furthermore, the film 52 is not necessarily required in this invention. Even if the heat transfer suppression member does not have the film 52, a step is created between the frame 53 and the functional member 9 in cross-sectional view because the thickness of the functional member 9 is formed to be greater than that of the frame 53. Specifically, the main surface 9s of the functional member 9 protrudes more in the thickness direction than the frame 53. Therefore, when the heat transfer suppression member 40 is interposed between the battery cells 20a, 20b, and 20c, gaps 54 are formed on both sides of the frame 53 in the thickness direction. As a result, it is possible to suppress the application of unnecessary pressure to the battery cells when adjacent battery cells expand via the frame 53.

[0043] [Second Embodiment] Figure 3 is a cross-sectional view showing a heat transfer suppression member according to a second embodiment of the present invention. In the heat transfer suppression member 120 shown in Figure 3, the same reference numerals are used for parts that are the same as those shown in Figures 1A and 1B, and their detailed descriptions are omitted or simplified.

[0044] As shown in Figure 3, the heat transfer suppression member 120 according to the second embodiment includes a frame 53 that surrounds the outer periphery in plan view, a functional member 111 disposed inside the frame 53 and having a pair of main surfaces 111s, and a film 52 attached to the surface of the frame 53 parallel to the main surfaces 111s of the functional member 111. In this embodiment, the functional member 111 is composed of a heat insulating sheet 10 having a pair of main surfaces and an elastic sheet 51 laminated on both main surfaces 40s of the heat insulating sheet 10. And, as in the first embodiment, the thickness of the functional member 111 in cross-sectional view is designed to be thicker than the thickness of the frame 53.

[0045] The following will specifically describe the case where the heat transfer suppression member 120 configured as described above is applied to a battery pack. Here, we will describe the case where the heat transfer suppression member 120 shown in Figure 3 is applied instead of the heat transfer suppression member 40 of the battery pack 100 shown in Figure 2.

[0046] In this embodiment as well, since the frame 53 has voids 54 on both sides in the thickness direction, it is possible to suppress the transfer of heat from one battery cell to another via the frame 53. Furthermore, in the second embodiment, elastic sheets 51 are laminated on both main surfaces 40s of the heat insulating sheet 10. The elastic sheets 51 are elastic, and when the heat transfer suppression member 120 is pressed by the expansion of the battery cells 20a, 20b, and 20c, the elastic sheets 51 deform by an appropriate amount, thereby suppressing the repulsive force on the battery cells. That is, when the battery cells 20a, 20b, and 20c deform, the elastic sheets 51 deform flexibly 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 themselves. Therefore, in the second embodiment, it is possible to suppress the deterioration of battery performance due to repeated pressing and releasing of the battery cells 20a, 20b, and 20c.

[0047] Furthermore, in the event of an abnormality, the presence of the frame 53 allows adjacent battery cells to be maintained at a desired distance, thereby suppressing the propagation of heat from a battery cell experiencing thermal runaway to other adjacent battery cells.

[0048] Furthermore, in this embodiment, since the elastic sheet 51 and film 52 are present on both main surfaces 40s of the heat insulating sheet 10, powder shedding can be further suppressed when the heat insulating sheet 10 contains inorganic particles, etc. In particular, even if the film 52 tears in an abnormal situation, contamination due to powder shedding can be prevented because the main surface 40s of the heat insulating sheet 10 is covered with the elastic sheet 51.

[0049] In the second embodiment, the elastic sheet 51 is laminated on both main surfaces 40s of the heat insulating sheet 10, but the present invention is not limited thereto, and the elastic sheet 51 may be laminated so as to be sandwiched between a pair of heat insulating sheets 10. Alternatively, the elastic sheet 51 may be laminated on only one main surface of the heat insulating sheet 10. In this case, the thickness of the heat insulating sheet 10 can be increased compared to a three-layer laminate, thereby improving heat insulation performance.

[0050] Similar to the first embodiment, in the second embodiment, the film 52 may or may not be provided. When using a functional member 111 with a two-layer structure of a heat insulating sheet 10 and an elastic sheet 51, it is preferable that the film 52 be provided so as to cover at least the main surface of the heat insulating sheet 10 that is not laminated with the elastic sheet 51. This ensures that both main surfaces 40s of the heat insulating sheet 10 are covered with either the elastic sheet 51 or the film 52, thereby suppressing powder shedding. Furthermore, the film 52 may be provided so as to enclose all of the frame 53, the heat insulating sheet 10, and the elastic sheet 51, or it may be provided so as to enclose the functional member 111, which is a laminate of the heat insulating sheet 10 and the elastic sheet 51. In addition, the film 52 may be provided so as to enclose only the heat insulating sheet 10.

[0051] [Third Embodiment] Figure 4 is a cross-sectional view showing a heat transfer suppression member according to a third embodiment of the present invention. In the heat transfer suppression member 130 shown in Figure 4, the same reference numerals are used for parts that are the same as those shown in Figures 1B and 3, and their detailed descriptions are omitted or simplified.

[0052] As shown in Figure 4, in the third embodiment, the heat transfer suppression member 130 includes a frame 53 that surrounds the outer periphery in a plan view, a heat insulating sheet (functional member) 10 disposed inside the frame and having a pair of main surfaces, and a film 52 laminated on one of the main surfaces 10s of the heat insulating sheet 10. In this embodiment, the heat insulating sheet 10 is formed to be thicker than the frame 53, but there is no step between one of the main surfaces 10s of the heat insulating sheet 10 and the frame 53, and a step is formed only between the other main surface 10t and the frame 53. Therefore, the other main surface 10t of the heat insulating sheet 10 protrudes in the thickness direction relative to the frame 53.

[0053] Even when the heat transfer suppression member 130 configured as described above is applied in place of the heat transfer suppression member 40 of the battery pack 100, a gap is formed between one end face in the thickness direction of the frame 53 and the battery cells 20a, 20b, and 20c. Therefore, it is possible to suppress the transfer of heat to adjacent battery cells via the frame 53. Furthermore, in the event of an abnormality, the frame 53 can maintain the desired spacing between adjacent battery cells, thereby suppressing the occurrence of a chain reaction of thermal runaway. Moreover, since there is no step between the frame 53 and one main surface 10s of the heat insulation sheet 10, the film 52 can be efficiently attached.

[0054] The functional member consisting of the heat insulating sheet 10 shown in Figure 4 may also be composed of a laminate of the heat insulating sheet 10 and the elastic sheet 51 as shown in Figure 3, and the combinations thereof are as described in the second embodiment. Furthermore, the presence or absence and arrangement of the film 52 are the same as in the first and second embodiments.

[0055] [Fourth Embodiment] Figure 5A is a plan view showing a heat transfer suppressing member according to a fourth embodiment of the present invention, and Figure 5B is a cross-sectional view along the line II-II thereof. In the heat transfer suppressing member 140 shown in Figures 5A and 5B, the same reference numerals are used for parts that are the same as those shown in Figures 1A and 1B, and their detailed descriptions are omitted or simplified.

[0056] The heat transfer suppression member 140 according to the fourth embodiment has partition walls 58a and 58b that divide the inside of the frame 53 into a plurality of regions. More specifically, when the heat transfer suppression member 140 is interposed between battery cells, the frame 53 has a pair of frame members 53a that extend in the horizontal direction, and partition walls 58a and 58b are formed to connect the pair of frame members 53a. As a result, the inside of the frame 53 is divided into three regions: a first region 57a, a second region 57b, and a third region 57c. A second functional member 10b, a first functional member 10a, and a second functional member 10b, which are thicker than the thickness of the frame 53, are arranged in each of the first region 57a, the second region 57b, and the third region 57c. In this embodiment, the first functional member 10a is configured to have a lower elastic modulus than the second functional member 10b.

[0057] Here, the elastic modulus of the functional member is the value measured by the usual method for measuring the elastic modulus of a functional member as a whole, whether it consists of a single layer of thermal insulation sheet or a laminate of thermal insulation sheet and elastic sheet.

[0058] When the heat transfer suppression member 140 configured as described above is applied in place of the heat transfer suppression member 40 of the battery pack 100, heat transfer to adjacent battery cells via the frame 53 can be suppressed, similar to the first to third embodiments. Furthermore, in the event of an abnormality, the frame 53 can ensure spacing between adjacent battery cells, thereby suppressing the occurrence of a chain reaction of thermal runaway.

[0059] Furthermore, in the battery cells 20a, 20b, and 20c, the central part of the widest outer surface (main surface) is more prone to protrusion due to expansion than the edges. Also, generally, terminals and exhaust valves are provided above the battery cells, and in the event of a malfunction, the exhaust valve side tends to become hot and is prone to deformation. Therefore, in this embodiment, of the three divided regions (first region 57a, second region 57b, and third region 57c), the first functional member 10a with a low modulus of elasticity is placed in the central second region 57b, which extends vertically, and the second functional members 10b having a higher modulus of elasticity than the first functional member 10a are placed on both sides of it. In other words, the first functional member 10a placed in the central second region 57b is softer and has higher restorative force. Therefore, when the battery cells 20a, 20b, and 20c expand in the event of a malfunction and their central and upper parts deform, the first functional member 10a with a low modulus of elasticity can absorb the deformation of the battery cells.

[0060] One method for making the elastic modulus of the first functional member 10a smaller than that of the second functional member 10b is to use different materials for the heat insulating sheets that constitute each functional member. Also, since the first functional member 10a and the second functional member 10b may be laminates of a heat insulating sheet and an elastic sheet, as in the second embodiment, different materials may be used for the elastic sheets. Furthermore, it is also preferable to use a laminate of a heat insulating sheet and an elastic sheet only in the first functional member 10a, which is located inside the second region 57b, among multiple regions. Note that the elastic sheet may be placed on only one main surface of the heat insulating sheet, or the elastic sheet may be placed so as to be sandwiched between a pair of heat insulating sheets.

[0061] In this embodiment, the multiple functional members arranged in the multiple regions divided by partition walls 58a and 58b have different elastic moduli, but functional members with different properties can be used as needed. For example, a functional member with extremely excellent heat insulation properties can be placed in the region that becomes the hottest, and functional members that take cost into consideration can be placed in the other regions. When functional members with different properties are arranged in multiple regions, the types of functional members are not limited to the two types of first functional member 10a and second functional member 10b, but three or more types of functional members with different properties may be used. Alternatively, the same functional member may be placed in all of the multiple regions.

[0062] Furthermore, by arranging multiple insulation sheets in multiple regions, the volume per functional component can be reduced, making manufacturing easier and improving handling. It is also preferable to form partition walls 58a and 58b such that all multiple regions have substantially the same shape and size. In a heat transfer suppression member configured in this way, even if some insulation sheets are damaged in the event of an abnormality such as thermal runaway, the undamaged insulation sheets can be reused in other heat transfer suppression members, thereby reducing the environmental burden. In addition, "approximately identical" as used above means that the difference in shape or size between multiple regions is acceptable up to ±5%, preferably up to ±3%, and more preferably up to ±1%, of the average value of all multiple regions.

[0063] Furthermore, similar to the first to third embodiments, a film may be placed to directly or indirectly cover the surfaces of the first functional member 10a and the second functional member 10b, and the method of placing the film is not particularly limited.

[0064] <Modification 1 of the 4th embodiment> Figure 6 is a plan view showing a modified example 1 of the heat transfer suppressing member according to the fourth embodiment of the present invention. In the heat transfer suppressing member 150 shown in Figure 6, the same reference numerals are used for parts identical to those of the heat transfer suppressing member 140 shown in Figure 5A, and their detailed descriptions are omitted or simplified.

[0065] In the modified example 1, when the heat transfer suppression member 150 is interposed between the battery cells, the frame 53 has a pair of vertically extending frame members 53b, and partition walls 58c and 58d are formed to connect the pair of frame members 53b. As a result, the inside of the frame 53 is divided into three regions from top to bottom: a first region 57a, a second region 57b, and a third region 57c. In each of the first region 57a, second region 57b, and third region 57c, a first functional member 10a, a second functional member 10b, and a second functional member 10b, which are thicker than the thickness of the frame 53, are arranged. In this embodiment, the first functional member 10a is configured to have a lower elastic modulus than the second functional member 10b.

[0066] Even with the heat transfer suppression member 150 configured as described above, the same effects as in the fourth embodiment can be obtained when applied in place of the heat transfer suppression member 40 of the battery pack 100. As described above, the parts of the battery cells 20a, 20b, and 20c that are prone to deformation are the central part of the main surface of the battery cell and the upper part where an exhaust valve (not shown) is formed. Therefore, it is preferable to arrange the first functional member 10a, which has a low modulus of elasticity, in the central second region 57b and the upper first region 57a. Note that the exhaust valve of the battery cell is not limited to the upper part and may be located at the bottom. For this reason, when incorporating the heat transfer suppression member 150 between the battery cell 20a and the battery cell 20b, and between the battery cell 20b and the battery cell 20c, the combination of the first functional member 10a and the second functional member 10b can be designed taking into account the position of the exhaust valve, etc.

[0067] <Modification 2 of the 4th embodiment> Figure 7 is a plan view showing a modified example 2 of the heat transfer suppressing member according to the fourth embodiment of the present invention. In the heat transfer suppressing member 160 shown in Figure 7, the same reference numerals are used for parts identical to those of the heat transfer suppressing member 140 shown in Figure 5A, and their detailed descriptions are omitted or simplified.

[0068] In the modified example 2, when the heat transfer suppression member 160 is interposed between the battery cells, the frame 53 has a pair of frame members 53a extending horizontally and a pair of frame members 53b extending vertically. Partition walls 58a and 58b are formed to connect the pair of frame members 53a, and partition walls 58c and 58d are formed to connect the pair of frame members 53b. As a result, the inside of the frame 53 is divided into nine regions, in order from the upper left to the right in Figure 7: the first region 57a, the second region 57b, the third region 57c; in order from the middle left to the right: the fourth region 57d, the fifth region 57e, the sixth region 57f; and in order from the lower left to the right: the seventh region 57g, the eighth region 57h, and the ninth region 57i. Furthermore, the first functional member 10a, which is thicker than the frame 53, is placed in the second region 57b and the fifth region 57e. On the other hand, the second functional member 10b, which is thicker than the frame 53, is placed in the regions other than those mentioned above. In this embodiment, the first functional member 10a is configured to have a lower elastic modulus than the second functional member 10b.

[0069] Even with the heat transfer suppression member 160 configured as described above, the same effects as in the fourth embodiment can be obtained when applied in place of the heat transfer suppression member 40 of the battery pack 100. In this embodiment, the first functional member 10a with a low modulus of elasticity is placed in the central fifth region 57e and the second region 57b above it, which are opposite the positions where the battery cells 20a, 20b, and 20c are prone to deformation. In other words, the first functional member 10a placed in the region where the battery cells are prone to deformation can further reduce the unnecessary pressure applied to the battery cells.

[0070] Furthermore, since functional components are placed in each of the nine divided regions, various functional components can be combined as needed in the design, thereby increasing the degree of design freedom. In addition, because the size of each insulation sheet is smaller in the nine divided heat transfer suppression members 160, there is a higher possibility of reusing the insulation sheets that have not been damaged in the event of abnormalities such as thermal runaway, further reducing the burden on the environment.

[0071] Furthermore, in the heat transfer suppression members 140, 150, and 160 having partition walls, it is preferable that the first functional member 10a, which has a low elastic modulus, be placed in at least the central region among the multiple regions divided by the partition walls. Also, when the heat transfer suppression members 140, 150, and 160 are placed between the battery cells 20a, 20b, and 20c, it is also preferable that the first functional member 10a be placed near the exhaust valves of the battery cells 20a, 20b, and 20c.

[0072] Furthermore, while partition walls serve to divide the inside of the frame into multiple regions, if a partition wall is located near the center of the heat transfer suppression member in a plan view, it can cause repeated pressure and release on the battery cell during charging and discharging, leading to a decrease in battery performance. Therefore, it is preferable that partition walls are not located in the center or near the center of the inside of the frame. Referring to Figure 7, when connecting a pair of horizontally extending frame members 53a with partition walls, considering the possibility of reusing functional members, it is preferable to form the partition walls so as to equally divide the inside region of the frame 53. In this case, in order to prevent partition walls from being located in the center or near the center of the inside of the frame, it is preferable to connect a pair of opposing frame members 53a with an even number of partition walls. Similarly, when forming partition walls between a pair of opposing frame members 53b in the left-right direction, it is preferable to connect the frame members 53b with an even number of partition walls.

[0073] Furthermore, the width of partition walls 58a to 58d in the heat transfer suppression members 140, 150, and 160 is not particularly limited. However, when the partition walls are molded integrally with the frame 53, the partition walls have inferior thermal insulation properties compared to the functional members. Therefore, in order to maintain the thermal insulation properties of the functional members, it is preferable that the width of the partition walls in the direction perpendicular to the longitudinal direction in a plan view is small. Specifically, it is preferable that the width of partition walls 58a to 58d in the direction perpendicular to the longitudinal direction is smaller than the width of the frame 53 in the direction perpendicular to the longitudinal direction.

[0074] Furthermore, if the thickness of partition walls 58a to 58d is designed to be thinner than that of the functional member, similar to the frame 53, then when the heat transfer suppression member is interposed between the battery cells, gaps will be formed on both sides in the thickness direction of the partition walls. Therefore, it is possible to suppress the transfer of heat to adjacent battery cells through the partition walls. However, from the viewpoint of the strength of the partition walls and the holding force of the functional member, the thickness of partition walls 58a and 58b may be the same as that of the functional member.

[0075] The following describes the materials that constitute the heat transfer suppression member according to this embodiment.

[0076] <Frame> The frame has the effect of ensuring the spacing between adjacent battery cells under normal conditions. Therefore, it is preferable that the frame be made primarily of an insulating material, and more preferably of a material having appropriate hardness and heat insulation properties. As the main material constituting the frame, it is preferable to use at least one insulating material selected from, for example, resin materials, oxide ceramics, non-oxide ceramics, silicate minerals such as mica, and composite materials of resin and ceramic. Of these, using resin materials as the main material is more preferable because, in addition to properties such as hardness and heat insulation, it also has excellent processability. The form of the frame is not particularly limited as long as it achieves the above-mentioned effects, but for example, it may be made of an inorganic fiber mat material.

[0077] <Partition wall> When the heat transfer suppression member according to this embodiment has a partition wall, the partition wall has the effect of dividing the inside of the frame into multiple regions and holding multiple heat insulating sheets together with the frame. Therefore, it is preferable that the partition wall, like the frame, be mainly made of an insulating material, and more preferably made of a material having appropriate hardness and heat insulating properties. That is, it is preferable that the partition wall be mainly made of at least one insulating material selected from resin materials, oxide ceramics, non-oxide ceramics, silicate minerals such as mica, and composite materials of resin and ceramic. Furthermore, it is more preferable that the partition wall be mainly made of a resin material from the viewpoint of hardness, heat insulating properties and processability. Note that the frame and the partition wall may be integrally molded or may be formed by combining multiple members. These materials may also be formed from the same material or from different materials. The form of the partition wall is not particularly limited as long as it achieves the above-mentioned effects, but for example, it may be made of an inorganic fiber mat material.

[0078] <Insulation sheet> The thermal insulation sheet of the functional component is not particularly limited as long as it can achieve the desired thermal insulation effect. Thermal conductivity can be used as an indicator of thermal insulation effect, but in this embodiment, the thermal conductivity of the thermal insulation sheet 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 thermal conductivity of the thermal insulation sheet 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 thermal insulation sheet that can achieve the desired thermal insulation effect, for example, a thermal insulation sheet containing silicone rubber and aerogel, a thermal insulation sheet containing fibers and aerogel, or a thermal insulation sheet containing inorganic particles and organic fibers can be used. The thermal conductivity of the thermal insulation sheet can be measured in accordance with the "Test method for thermal conductivity of refractories" described in JIS R 2251.

[0079] (Size of the insulation sheet) When the functional component is a laminate of a thermal insulation sheet and an elastic sheet, even if the size of the main surface of the thermal insulation sheet and the size of the main surface of the elastic sheet perpendicular to the thickness direction are approximately the same, the elastic sheet may be formed to be smaller than the thermal insulation sheet. In addition, "approximately identical" as used above means that the difference in the size of the main surfaces of the two is acceptable up to ±5%, preferably up to ±3%, and more preferably up to ±1%, of the average value of the two.

[0080] (Insulation sheet containing silicone rubber and aerogel) An example of an insulating sheet containing silicone rubber and aerogel is one in which SiO2 is impregnated into a silicone rubber framework. As the silicone rubber, silicone and rubber with a heat resistance of 170°C or higher can be used. Furthermore, because aerogel has numerous cavities, excellent insulating properties can be obtained.

[0081] (An insulating sheet containing fibers and aerogel) An example of an insulating sheet containing fibers and aerogel is one in which SiO2 is impregnated with fibers as a framework. Polyacrylonitrile (PAN) fibers, glass fibers, and ceramic fibers can be used as the fibers. Furthermore, because aerogel has numerous cavities, excellent insulating properties can be obtained.

[0082] (Insulating sheet containing inorganic particles and organic fibers) When using an insulating sheet containing inorganic particles and organic fibers, particularly one with the structure described below, even better thermal insulation can be obtained compared to an insulating sheet containing the above-mentioned fibers and aerogel. Examples of such specific insulating sheets are described in detail below.

[0083] <Insulation sheet (Structural example 1)> Figure 8 is a photograph used as a substitute for a drawing, showing an example of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention, and Figure 9 is a photograph used as a substitute for a drawing, showing a magnified view of a part of the heat insulating sheet shown in Figure 8.

[0084] As shown in Figures 8 and 9, the heat insulating sheet 10 has inorganic particles 4 and organic fibers 1. The heat insulating sheet 10 also has a plurality of three-dimensionally connected voids 7 between the inorganic particles 4 and the organic fibers 1. The organic fibers 1 have welded portions 5 that cover at least a portion of their surface, and at least a portion of the inorganic particles 4 are welded to the surface of the organic fibers 1 by the welded portions 5. As a result, the surface of the organic fibers 1 is covered with inorganic particles 4.

[0085] In the heat insulating sheet 10 configured in this way, since it has multiple three-dimensionally connected voids 7, the effect of air insulation can be obtained, and the heat insulating performance can be further improved. In addition, since the heat insulating sheet 10 contains organic fibers 1 that have high flexibility, the flexibility of the heat insulating sheet 10 can be increased, and the organic fibers 1 can be more easily intertwined with each other, resulting in an effect of improving the strength of the heat insulating sheet. Therefore, the destruction of the heat transfer suppression member having such a heat insulating sheet 10 can be suppressed. Furthermore, because the voids 7 in the heat insulating sheet 10 improve the cushioning of the entire sheet, when the battery cells 20a, 20b, and 20c expand during charging and discharging, the voids 54 can absorb the expansion, and the heat insulating sheet 10 also absorbs the expansion of the battery cells, further suppressing the deterioration of the battery cell performance.

[0086] Furthermore, in this embodiment, it is preferable that at least a portion of the voids 7 communicate with the surface of the heat insulating sheet 10 and open outwards. With the voids 7 configured in this way, even if the heat insulating sheet 10 becomes hot and the organic fibers 1 etc. decompose when adjacent battery cells 20a, 20b, and 20c experience thermal runaway, the decomposition gas will not remain inside the sheet but will be released to the outside through the voids 7. Therefore, from this point as well, the effect of preventing damage to the sheet can be obtained.

[0087] Furthermore, if the welded portion 5 on the outer surface of the organic fiber 1 fixes the inorganic particles 4 to the organic fiber 1, it is possible to suppress the shedding (dropping of powder) of the inorganic particles 4. Therefore, for example, even if a part of the battery cells 20a, 20b, and 20c expands and compressive stress or impact is applied to the heat transfer suppression member 40, the effect of maintaining the shape of the heat insulating sheet 10 can be further enhanced, and a decrease in the heat insulating effect due to compressive deformation of the heat insulating sheet 10 can be prevented.

[0088] In this specification, "welded portion 5" refers to a portion where the surface of the organic fiber 1 has melted and then solidified again, and is formed in the manufacturing process of the heat insulating sheet 10 described later. In this embodiment, 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 thicker, supporting the shape of the heat insulating sheet 10 and providing high strength.

[0089] Furthermore, the welded portion 5 does not need to completely cover the outer surface of the organic fiber 1, and there may be areas where the welded portion 5 is not present. In the heat insulating sheet 10, binder fibers with a core-sheath structure, as described later, can be used as the material for the organic fiber 1, but if the sheath peels off during the manufacturing process, the core portion of the organic fiber 1 may be partially exposed. Even in such cases, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0090] Furthermore, it is preferable that the heat insulating sheet 10 contains inorganic fibers. The effects obtained by including inorganic fibers will be explained in the following example of the heat insulating sheet structure 2.

[0091] <Insulation sheet (Structural example 2)> Figure 10 is a photographic substitute for a drawing showing a structural example 2 of a heat insulating sheet used in a heat transfer suppressing member according to an embodiment of the present invention. In structural example 2 shown in Figure 10, the same reference numerals are used for parts identical to those in structural example 1 shown in Figures 8 and 9, and detailed explanations are omitted. The heat insulating sheet 50 shown in Figure 10 can be used, for example, as a heat insulating sheet constituting the functional member 9 shown in Figures 1A, 1B, and 2, as well as as a heat insulating sheet constituting the heat insulating sheet 10 shown in Figures 3 and 4, as well as a heat insulating sheet constituting the first functional member 10a and the second functional member 10b shown in Figures 5A, 5B, 6, and 7.

[0092] As shown in Figure 10, the heat insulating sheet 50 has inorganic fibers 15. Furthermore, the heat insulating sheet 50 has a fiber layer 11 formed on at least a portion of the first surface 50a and a second surface (not shown) perpendicular to its thickness direction. The fiber layer 11 is formed in a layered manner on the surface (first and second surfaces) of the heat insulating sheet 50 by welding at least a portion of multiple organic fibers 1 to each other at welding points. That is, the fiber layer 11 is a layer formed by the aggregation of 10 or more organic fibers 1 on the surface of the heat insulating sheet 50, and extends, for example, in a streaky manner in a direction substantially parallel to the surface.

[0093] Furthermore, a composite layer (not shown) is formed between the fiber layer 11 and the base layer 13 containing inorganic particles 4 and organic fibers 1, in which a portion of the fiber layer 11 and a portion of the inorganic particles 4 are mixed. Specifically, the composite layer is a region containing a plurality of organic fibers 1, at least a portion of which are welded to each other by welding portions, and inorganic particles 4 welded to the organic fibers 1 by welding portions.

[0094] In the heat insulating sheet 50 shown in Figure 10, the inorganic fibers 15 are contained in the base layer 13 which contains inorganic particles 4 and organic fibers 1, but they may also be contained in the fiber layer 11. In Figure 10, the inorganic fibers 15 in the fiber layer 11 cannot be distinguished and are therefore not shown.

[0095] Furthermore, the heat insulating sheet 50 has fiber bundles 6 formed by welding at least a portion of multiple organic fibers 1 together at welding points 5. A "fiber bundle 6" is formed by 10 or more organic fibers 1 intertwining with each other and welding some of the organic fibers 1 together, and is arranged in any direction within the heat insulating sheet 50.

[0096] The heat-insulating sheet 50 constructed in this manner contains inorganic fibers 15 that are resistant to decomposition even at high temperatures. Therefore, for example, if a battery cell 20a experiences thermal runaway and a heat transfer suppression member 40 adjacent to the battery cell 20a is exposed to high temperatures, even if the organic fibers 1 in the heat-insulating sheet 50 decompose, the inorganic fibers 15 remain, thus reliably maintaining the shape of the heat-insulating sheet 50. Furthermore, the relatively hard inorganic fibers 15 easily intertwine with the flexible organic fibers 1, forming a three-dimensional skeleton with the inorganic fibers 15 and organic fibers 1, thereby further improving the strength of the heat-insulating sheet 50.

[0097] Furthermore, if the heat insulating sheet 50 has a fiber layer 11 on its surface and a fiber bundle 6 inside, it can obtain even higher strength compared to the case where the organic fibers 1 are dispersed. Note that the fiber layer 11 is not simply placed on the base layer 13, but rather there is 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 the fiber layer 11 is securely constrained to the surface of the heat insulating sheet 50. Therefore, the fiber layer 11 alone will not fall off, and a heat insulating sheet 50 with high strength can be obtained. Also, for example, as shown in the second embodiment, if an elastic sheet 51 is laminated to the heat insulating sheet, the pressure on the base layer 13 can be reduced even further.

[0098] Furthermore, if a fiber layer 11 is formed on the surface of the heat insulating sheet 50, this fiber layer 11 can absorb the impact applied to the heat insulating sheet 50. Therefore, even if the elastic sheet 51 is not laminated, the fiber layer 11 can prevent inorganic particles contained in the heat insulating sheet 50 from falling off.

[0099] <Insulation sheet (Structural example 3)> Figure 11 is a schematic diagram showing a structural example 3 of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention, and Figure 12 is a schematic diagram showing an enlarged portion of Figure 11. Figure 13 is a photograph used as a substitute for a drawing showing the heat insulating sheet shown in Figure 11. In structural example 3 shown in Figures 11 to 13, the same reference numerals are used for parts that are the same as those in structural example 1 shown in Figures 8 and 9, and detailed explanations are omitted. The heat insulating sheet 60 shown in Figures 11 to 13 can be used, for example, as a heat insulating sheet constituting the functional member 9 shown in Figures 1A, 1B, and 2, or as a heat insulating sheet constituting the heat insulating sheet 10 shown in Figures 3 and 4, or as a heat insulating sheet constituting the first functional member 10a and the second functional member 10b shown in Figures 5A, 5B, 6, and 7.

[0100] As shown in Figures 11 to 13, the heat insulating sheet 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 surface of the organic fibers 1. As described above, the welded portion 5 contains a second organic material 17 having a melting point lower than that of the first organic material, and the inorganic particles 4. In this embodiment, a binder fiber 3 with a core-sheath structure having a core and a sheath that covers the outer surface of the core is used as the organic fiber, with the organic fiber 1 corresponding to the core. The welded portion 5 is formed when the sheath of the binder fiber 3 having a core-sheath structure is melted by heating and then cooled. Furthermore, as shown in Figure 13, a fiber portion 16 is composed of the organic fiber 1 and the welded portion 5 containing the inorganic particles 4, and a base material portion 18 containing inorganic particles is formed between multiple fiber portions 16. Also, when the molten sheath is cooled, adjacent organic fibers 1 are fused together at the contact portion 31, forming a three-dimensional skeleton.

[0101] In the heat insulating sheet 60 constructed in this manner, the organic fibers 1 and the welded portion 5 act as a framework, thus providing excellent strength and shape retention. Furthermore, on both the surface and center sides of the heat insulating sheet 60, the welded portion 5 covering the outer surface of the organic fibers fixes the inorganic particles 4 to the organic fibers 1, thus suppressing powder shedding. Therefore, for example, even if a heat transfer suppression member including the heat insulating sheet 60 is placed between multiple battery cells, and the battery cells expand, applying compressive stress or impact to the heat transfer suppression member, excellent heat insulating performance can be maintained.

[0102] In the above-described heat insulating sheet 60, the mechanism by which the shedding (powder fall) of inorganic particles 4 can be suppressed is not clear, but it is thought that one reason is that the organic fibers 1 and the welded portion 5 form a three-dimensional and strong skeleton, and the shape of the heat insulating sheet 60 is maintained, thereby suppressing deformation or compression of the heat insulating sheet 60. Furthermore, as shown in the second and third embodiments above, if an elastic sheet 51 is laminated on at least one surface of the heat insulating sheet 60, it is thought that the pressure on the heat insulating sheet 60 is reduced, and the shedding of inorganic particles 4 can be further suppressed.

[0103] Furthermore, regardless of the presence or absence of the elastic sheet 51 on the surface of the heat insulating sheet 60, the fiber portion 16 exposed on the surface of the heat insulating sheet 60 can absorb the impact applied to the heat insulating sheet 60, which is also considered to be a reason why the inorganic particles 4 are retained. Moreover, in this embodiment, since the thickness of the heat insulating sheet is formed to be thinner than that of the frame 53, it is possible to absorb the impact applied to the heat insulating sheet in the same way as the effect of the fiber portion 16, thereby improving the effect of retaining the inorganic particles 4.

[0104] As shown in Figure 13, in the heat insulating sheet 60, the welded portion 5 does not need to completely cover the outer surface of the organic fiber 1, and the organic fiber 1 may be partially exposed. Since the heat insulating sheet 60 uses binder fibers 3 with a core-sheath structure, the sheath portion may peel off during the manufacturing process of the heat insulating sheet 60, but even if the organic fiber 1 is partially exposed, the effects of the present invention can be fully obtained.

[0105] <Insulation sheet (Structural example 4)> Figure 14 is a photographic substitute for a drawing showing structural example 4 of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention, and Figure 15 is a photographic substitute for a drawing showing an enlarged view of the structure of the heat insulating sheet shown in Figure 14. Figure 16 is a photographic substitute for a drawing showing a cross-section of the heat insulating sheet shown in Figure 14. In structural example 4 shown in Figures 14 to 16, the same reference numerals are used for parts that are the same as those in structural example 1 shown in Figures 8 and 9, and detailed explanations are omitted. The heat insulating sheet 70 shown in Figures 4 to 16 can be used, for example, as a heat insulating sheet constituting the functional member 9 shown in Figures 1A, 1B, and 2, or as a heat insulating sheet constituting the first functional member 10a shown in Figures 3 and 4, or the second functional member 10b shown in Figures 5A, 5B, 6, and 7.

[0106] As shown in Figures 14 and 15, the heat insulating sheet 70 has a matrix 14 containing inorganic particles 4 and organic fibers 1 oriented three-dimensionally within the matrix 14. The organic fibers 1 have welded portions 5 that cover at least a portion of their surface, and the organic fibers 1 are welded to each other by the welded portions 5. Similarly, the inorganic particles 4 are also welded to the surface of the organic fibers 1, so that the surface of the organic fibers 1 is covered with inorganic particles 4.

[0107] Furthermore, as shown in the cross-sectional view of Figure 16, multiple voids 7 are formed in the matrix 14 of the heat insulating sheet 70. In addition, at least a portion of multiple organic fibers 1 are welded together in the matrix 14 by welding portions 5 (not shown in Figure 16), thereby forming fiber bundles 6, and voids 8 are formed between the multiple organic fibers 1 that make up the fiber bundles 6.

[0108] Furthermore, a fiber layer 11 is formed on at least a portion of the first surface 70a and a second surface (not shown) perpendicular to the thickness direction of the heat insulating sheet 70. The fiber layer 11 is formed in layers on the surface (first and second surfaces) of the heat insulating sheet 70 by welding at least a portion of a plurality of organic fibers 1 to each other by welding portions 5. In addition, a composite layer 12 is formed between the fiber layer 11 and the base layer 13 containing the matrix 14 and organic fibers 1. The composite layer 12 is a layer in which a portion of the fiber layer 11 and a portion of the matrix 14 are mixed. Specifically, the composite layer 12 is a region containing a plurality of organic fibers 1 that are welded to each other at least a portion of the welding portions 5, and inorganic particles 4 that are welded to the organic fibers 1 by the welding portions 5.

[0109] The fiber bundle 6 is formed by 10 or more organic fibers 1 intertwining with each other, and in some cases, the organic fibers 1 are welded to each other, and is arranged in any direction within the matrix 14 of the heat insulating sheet 70. On the other hand, the fiber layer 11 is a layer formed by 10 or more organic fibers 1 gathering on the surface of the heat insulating sheet 70, and extends in a direction substantially parallel to the surface, for example, in a streak.

[0110] In the heat insulating sheet 70 constructed in this manner, the organic fibers 1 are oriented three-dimensionally within the matrix 14, and the organic fibers 1 have welded portions 5 that cover at least a portion of their surface. The "welded portion 5" refers to a portion where the surface of the organic fiber 1 has melted and then solidified again, and is formed during the manufacturing process of the heat insulating sheet 70. In the heat insulating sheet 70, the three-dimensionally oriented organic fibers 1 are welded together by the welded portions 5, so this structure acts as a framework to support the shape of the heat insulating sheet 70, and high strength can be obtained.

[0111] Similarly, in the heat insulating sheet 70, the welded portion 5 on the outer surface of the organic fiber 1 also fixes the inorganic particles 4 to the organic fiber 1, thus achieving an even higher powder shedding suppression effect. Therefore, for example, even when a part of the battery cells 20a, 20b, and 20c expand during charging and discharging, applying compressive stress or impact to the heat transfer suppression member 40, in this embodiment, the shape of the heat insulating sheet 70 can be maintained by the effect of the welded portion 5 and the frame 53. As a result, the shedding (powder shedding) of inorganic particles 4 can be suppressed, and a decrease in the heat insulating effect due to compressive deformation of the heat insulating sheet 70 can be prevented.

[0112] In the heat insulating sheet 70, the mechanism for suppressing the shedding of inorganic particles 4 from the sheet surface is considered to be the same as that of the heat insulating sheet 60 in the structural example 3 described above.

[0113] Furthermore, even in the heat insulating sheet 70, the welded portion 5 does not need to completely cover the outer surface of the organic fiber 1, and there may be areas where the welded portion 5 is not present. Even in such cases, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0114] Furthermore, since the heat-insulating sheet 70 contains organic fibers 1 that have high flexibility, the flexibility of the heat-insulating sheet 70 can be increased, and the organic fibers 1 become more likely to intertwine with each other, resulting in an effect of improving the strength of the sheet.

[0115] Furthermore, the thermal insulation sheet 70 has multiple voids 7 in the matrix 14 and voids 8 between the multiple organic fibers 1 that constitute the fiber bundle 6, thereby improving thermal insulation performance. In addition, the presence of voids 8 makes it less likely for the organic fibers 1 to be constrained in the matrix 14, thus further improving the flexibility and strength of the thermal insulation sheet 70. The voids 8 do not need to be formed in the entire area between the multiple organic fibers 1; the heat transfer suppression effect can be obtained if the voids 8 are formed in at least a part of the area between the organic fibers 1. As shown in the first and third embodiments above, the heat transfer suppression effect can be obtained even further if the thermal insulation sheet has voids 54 on the main surface side.

[0116] Furthermore, because the thermal insulation sheet 70 has fiber bundles 6 and fiber layers 11, it can achieve even higher strength compared to the case where organic fibers 1 are dispersed. In addition, the fiber layers 11 are not simply placed on the base layer 13, but rather there is a composite layer 12 between the fiber layers 11 and the base layer 13 in which a part of the fiber layers 11 and a part of the inorganic particles 4 constituting the matrix 14 are mixed, so the fiber layers 11 are securely constrained to the surface of the thermal insulation sheet 70. Therefore, a thermal insulation sheet 70 with high strength can be obtained.

[0117] <Insulation sheet (Structural example 5)> Figure 17 is a schematic diagram showing example 5 of the structure of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention, and Figure 18 is a schematic diagram showing an enlarged view of part A of the heat insulating sheet shown in Figure 17. In example 5 of the structure shown in Figures 17 and 18, the same reference numerals are used for parts that are the same as those in example 1 of the heat insulating sheet shown in Figures 8 and 9, and detailed explanations are omitted. The heat insulating sheet 80 shown in Figures 17 to 18 can be used, for example, as a heat insulating sheet constituting the functional member 9 shown in Figures 1A, 1B, and 2, or as a heat insulating sheet constituting the heat insulating sheet 10 shown in Figures 3 and 4, or as a heat insulating sheet constituting the first functional member 10a and the second functional member 10b shown in Figures 5A, 5B, 6, and 7.

[0118] As shown in Figures 17 and 18, the heat insulating sheet 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 inorganic fibers 15 are intertwined with each other to form a three-dimensional web structure. In this embodiment, an air layer 28 is formed in part around the inorganic fibers 15. The organic fibers 1 also have welded portions 5 on part of their surface, and at least a portion of the inorganic fibers 15 is welded to the organic fibers 1 by the welded portions 5. Furthermore, at least a portion of the inorganic particles 4 is welded to the organic fibers 1 by the welded portions 5.

[0119] In this specification, "dispersed" of the inorganic fibers 15 means that the inorganic fibers 15 are spread out and arranged evenly without being extremely concentrated in one area.

[0120] In the heat insulating sheet 80 constructed in this manner, the organic fibers 1 and inorganic fibers 15 intertwine to form a three-dimensional web structure, and since this structure serves as the framework, high strength can be obtained. Therefore, even when the heat transfer suppression member 40 is compressed due to the expansion of the battery cells 20a, 20b, and 20c during charging and discharging, the shape of the heat insulating sheet 80 can be maintained by the skeletal structure of the organic fibers 1 and inorganic fibers 15 and the effect of the frame 53. As a result, the shedding (dropping of powder) of inorganic particles 4 can be suppressed, and the decrease in the heat insulating effect due to the compression deformation of the heat insulating sheet 80 can be prevented.

[0121] Furthermore, since the heat insulating sheet 80 contains highly flexible organic fibers 1, the flexibility of the heat insulating sheet 80 can be increased, and the organic fibers 1 can easily intertwine with the inorganic fibers 15 to form a three-dimensional web structure, thereby improving its strength. In addition, if the heat insulating sheet 80 contains inorganic fibers 15, for example, if the battery cell 20a experiences thermal runaway and the heat transfer suppression member located adjacent to the battery cell 20a is exposed to high temperatures, even if the organic fibers 1 decompose, the heat transfer suppression member can maintain its shape. Therefore, by having both highly flexible organic fibers 1 and inorganic fibers 15 that do not decompose even at high temperatures, a heat transfer suppression member with a good balance of flexibility and strength can be obtained.

[0122] Furthermore, in this embodiment, an air layer 28 is provided around the inorganic fibers 15 dispersed within the matrix 14. Although the inorganic fibers 15 have a higher thermal conductivity than the organic fibers 1, as described above, the formation of an air layer 28 around the inorganic fibers 15 suppresses heat transfer between the inorganic fibers 15 and the matrix 14. The air layer 28 is formed during the manufacturing process of the heat insulating sheet 80, but it is not necessary for the air layer 28 to be formed around the entire periphery of the inorganic fibers 15. The heat transfer suppression effect can be obtained if the air layer 28 is formed on at least a portion of the outer surface of the inorganic fibers 15.

[0123] When the inorganic fibers 15 are uniformly dispersed in the matrix 14, the air layers 28 in the matrix 14 are also uniformly dispersed, so the heat insulating sheet 80 can achieve uniform and high heat insulating properties. Furthermore, as shown in the first and third embodiments above, if the heat insulating sheet has voids 54 on the main surface side, even higher heat insulating properties can be obtained.

[0124] Furthermore, in the heat insulating sheet 80, the organic fiber 1 has a welded portion 5 that covers at least a part of its surface. The "welded portion 5" refers to a part where the surface of the organic fiber 1 has melted and then solidified again, and is formed in the manufacturing process of the heat insulating sheet 80. If at least a part of the inorganic fiber 15 is welded to the organic fiber 1 by the welded portion 5, the entangled organic fiber 1 and inorganic fiber 15 are fixed together, so an even higher-strength heat insulating sheet 80 can be obtained.

[0125] Similarly, in this embodiment, the welded portion 5 on the outer surface of the organic fiber 1 also fixes the inorganic particles 4 to the organic fiber 1, thus achieving an even higher powder shedding suppression effect. Therefore, for example, even if a portion of the battery cells 20a, 20b, and 20c expands and compressive stress or impact is applied to the heat transfer suppression member, excellent heat insulation performance can be maintained.

[0126] In this embodiment, the mechanism by which the shedding of inorganic particles 4 from the sheet surface can be suppressed is thought to be that the organic fibers 1 and inorganic fibers 15 are welded together by the welding portion 5 to form a three-dimensional and strong framework, thereby maintaining the shape of the heat insulating sheet 80 and suppressing deformation or compression of the heat transfer suppression member. Furthermore, regardless of the presence or absence of the elastic sheet 51 on the surface of the heat insulating sheet 80, if the organic fibers 1 and inorganic fibers 15 are exposed on the surface of the heat insulating sheet 80, they can absorb the impact applied to the heat insulating sheet 80, and thus the inorganic particles 4 are retained.

[0127] Furthermore, in this embodiment, since the thickness of the heat insulating sheet is thinner than that of the frame 53, it is possible to absorb impacts applied to the heat insulating sheet, similar to the effect of the fiber portion 16, and improve the effect of holding the inorganic particles 4.

[0128] Furthermore, even in the heat insulating sheet 80, the welded portion 5 does not need to completely cover the outer surface of the organic fiber 1, and there may be areas where the welded portion 5 is not present. Even in such cases, the effect of holding the inorganic particles 4 can be sufficiently obtained.

[0129] <Insulation sheet (Structural example 6)> Figure 19 is a photographic substitute for a drawing showing structural example 6 of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention, and Figure 20 is a photographic substitute for a drawing showing another area of ​​the heat insulating sheet shown in Figure 19. Figure 21 is a photographic substitute for a drawing showing a cross-section of the heat insulating sheet shown in Figures 19 and 20. In structural example 6 shown in Figures 19 to 21, the same reference numerals are used for parts identical to those in structural example 4 of the heat insulating sheet shown in Figures 14 to 16, and detailed explanations are omitted. The heat insulating sheet 90 shown in Figures 19 to 21 can be used, for example, as a heat insulating sheet constituting the functional member 9 shown in Figures 1A, 1B, and 2, or as a heat insulating sheet constituting the heat insulating sheet 10 shown in Figures 3 and 4, or as a heat insulating sheet constituting the first functional member 10a and the second functional member 10b shown in Figures 5A, 5B, 6, and 7.

[0130] As shown in Figure 19, the heat insulating sheet 90 has inorganic particles 4 and organic fibers 1. In addition, at least some of the organic fibers 1 have a branched structure consisting of a base portion 32 and branches 33 extending from the base portion 32. In this embodiment, the branches 33 extend from the base portion 32 in four directions: D1, D2, D3, and D4. The base portion 32 and the multiple branches 33 form a skeleton.

[0131] Furthermore, in other regions of the heat insulating sheet 90 shown in Figure 20, the organic fiber 1 also contains a branched structure consisting of a base portion 32 and branch portions 33 extending from the base portion 32. The organic fiber 1 shown in Figure 20 has a base portion 32 and branch portions 33 extending from the base portion 32 in five directions: D1, D2, D3, D4, and D5, and the base portion 32 is thicker compared to the multiple branch portions 33.

[0132] Furthermore, as shown in Figures 19 and 20, in this embodiment, inorganic particles 4 are welded to the surface of the organic fiber 1, thereby creating a configuration in which the surface of the organic fiber 1 is covered with inorganic particles 4.

[0133] Furthermore, as shown in the cross-sectional view of Figure 21, multiple voids 7 are formed in the heat insulating sheet 90. In addition, a fiber bundle 6 is formed in the heat insulating sheet 90 by welding at least a portion of multiple organic fibers 1 together, and voids 8 are formed between the multiple organic fibers 1 that make up the fiber bundle 6. In Figure 21, an organic fiber 1 having a branched structure consisting of a base portion 32 and branch portions 33 extending in three directions from the base portion 32 can also be seen.

[0134] Furthermore, a fiber layer 11 may be formed on at least a portion of the first and second surfaces of the heat insulating sheet 90 that are perpendicular to the thickness direction. The fiber layer 11 is formed in layers on the surface (first and second surfaces) of the heat insulating sheet 90 by welding at least a portion of a plurality of 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 inorganic particles 4 and organic fibers 1. The composite layer 12 is a layer in which a portion of the fiber layer 11 and a portion of the inorganic particles 4 are mixed. Specifically, the composite layer 12 is a region containing a plurality of organic fibers 1 that are welded to each other and inorganic particles 4 that are welded to these organic fibers 1.

[0135] The fiber bundle 6 is formed by 10 or more organic fibers 1 intertwining with each other, and in some cases, the organic fibers 1 are welded to each other, and is arranged in any direction within the heat insulating sheet 90. On the other hand, the fiber layer 11 is a layer formed by 10 or more organic fibers 1 gathering on the surface of the heat insulating sheet 90, and extends in a direction substantially parallel to the surface, for example, in a streak.

[0136] In the heat insulating sheet 90 constructed in this manner, at least a portion of the organic fibers 1 has a branched structure consisting of a base portion 32 and a support portion 33, so that the organic fibers 1 can act as a skeleton to maintain the shape of the heat insulating sheet 90. In this embodiment, the base portion 32 is composed of a fused portion in which the organic fibers 1 are fused together. Specifically, the base portion 32 is a portion that has solidified after a portion of multiple organic fibers 1 have come into contact with each other and melted together, and is therefore thicker than the support portion 33. As a result, the entire skeleton can be firmly supported by the base portion 32, and thus the strength of the heat insulating sheet 90 can be significantly improved.

[0137] In the thermal insulation sheet 90, at least a portion of the organic fiber 1 has a branched structure consisting of a base portion 32 and branch portions 33 extending from the base portion 32 in at least three directions. The branched structure can be confirmed in cross-sectional photographs of the thermal insulation sheet 90, but a simpler way to confirm the branched structure is to observe the cross-section obtained by tearing the thermal insulation sheet 90 in a plane direction perpendicular to its thickness direction. By observing the cross-section in this way, the organic fiber 1 having a branched structure consisting of a base portion 32 and branch portions 33 extending from the base portion 32 in at least three directions can be easily confirmed. The base portion 32 and branch portions 33 will be described in more detail below.

[0138] (Base (fusion part)) The fused portion is formed when a core-sheath binder fiber is used as the material for the heat insulating sheet 90, by melting the sheath portion of the binder fiber upon heating and then cooling it in the area where multiple binder fibers are in contact with each other. When a core-sheath binder fiber is used as the material for the heat insulating sheet 90, the fused portion includes a second organic material that constitutes the sheath portion. Thus, in the manufacturing process of the heat-insulating sheet 50, when the sheath portion in the area where multiple binder fibers are in contact melts due to heating, the amount of melted sheath portion (second organic material) is greater than when the sheath portion of a single binder fiber melts, and after cooling, a thick fused portion (base portion 32) is formed. As a result, the skeleton is firmly supported by the base portion 32.

[0139] (branch) The support portion 33 extends from the base portion 32 in at least three directions and has the effect of holding inorganic particles 4. Furthermore, since the base portion 32 and the support portion 33 form a framework, the strength of the heat insulating sheet 50 can also be improved. As a result, a high powder shedding suppression effect can be obtained. When a binder fiber with a core-sheath structure is used as the organic fiber 1, the branch portion 33 is part of the binder fiber with a core-sheath structure and has a core portion made of a first organic material and a sheath portion made of a second organic material.

[0140] If the branches 33 extending from the base 32 extend in at least three directions, they can form a skeleton made of organic fibers 1. Furthermore, it is preferable that these multiple branches 33 each extend in different three-dimensional directions, thereby forming a three-dimensional and robust skeleton.

[0141] In the above-described heat insulating sheet 90, since multiple support parts 33 extend from the base part 32, these multiple support parts 33 can hold the inorganic particles 4, and a high powder shedding suppression effect can be obtained through a synergistic effect with the effect of improving the sheet strength due to the formation of the framework. Therefore, for example, even if a part of the battery cells 20a, 20b, and 20c expand during charging and discharging and compressive stress or impact is applied to the heat transfer suppression member, the shape of the heat insulating sheet 90 can be maintained due to the framework structure of the heat insulating sheet 90 and the effect of the frame 53 in the heat transfer suppression member. As a result, the shedding (powder shedding) of inorganic particles 4 can be suppressed, and a decrease in the heat insulating effect due to compressive deformation of the heat insulating sheet 90 can be prevented.

[0142] The mechanism that can suppress the shedding of inorganic particles 4 from the surface of the heat insulating sheet 90 is thought to be due to the same effect as the heat insulating sheet 60 in structural example 3 described above, as well as the holding effect of the support 33 on the inorganic particles 4. Furthermore, when inorganic particles 4 are welded to the surface of the organic fibers 1, the organic fibers 1 appear to have a thicker fiber diameter, resulting in higher strength than the organic fibers 1 alone, and a high holding effect on the inorganic particles 4 can be obtained.

[0143] Furthermore, in the heat insulating sheet 90, there may be areas on the outer surface of the organic fiber 1 where the inorganic particles 4 are not partially welded. Even in such cases, the effect of retaining the inorganic particles 4 can be sufficiently obtained.

[0144] Furthermore, since the heat insulation sheet 90 contains organic fibers 1 that have high flexibility, the flexibility of the heat insulation sheet 90 can be increased, and the organic fibers 1 become more likely to intertwine with each other, resulting in an effect of improving the strength of the sheet.

[0145] Furthermore, it is preferable that the heat insulating sheet 90 has multiple voids 7 and gaps 8 between the multiple organic fibers 1 that constitute the fiber bundle 6, thereby providing an air insulation effect and improving heat insulating performance. In addition, because the organic fibers 1 are not completely constrained due to the presence of the gaps 8, the flexibility and strength of the heat insulating sheet 90 can be further improved. The gaps 8 do not need to be formed in the entire area between the multiple organic fibers 1; a heat transfer suppression effect can be obtained if the gaps 8 are formed in at least a part between the organic fibers 1. As shown in the first and third embodiments above, if the heat insulating sheet has gaps 54 on the main surface side, even higher heat insulating performance can be obtained.

[0146] Furthermore, because the thermal insulation sheet 90 has fiber bundles 6 and fiber layers 11, it can achieve even higher sheet strength compared to the case where organic fibers 1 are dispersed. Also, when the fiber layer 11 is present, the fiber layer 11 is not simply placed on top of the base layer 13, but rather there is 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 are mixed, so the fiber layer 11 is reliably constrained to the surface of the thermal insulation sheet 90. Therefore, the strength of the thermal insulation sheet 90 can be improved.

[0147] <Insulation sheet (Structural example 7)> Figure 22 is a photographic substitute for a drawing showing an example of the structure 7 of a heat insulating sheet used in a heat transfer suppression member according to an embodiment of the present invention, and Figure 23 is a photographic substitute for a drawing showing an enlarged view of a part of the heat insulating sheet shown in Figure 22. In the structure example 7 shown in Figures 22 and 23, the same reference numerals are used for parts that are the same as those in the structure example 2 of the heat insulating sheet shown in Figure 10, and detailed explanations are omitted. The heat insulating sheet 110 shown in Figures 22 and 23 can be used, for example, as a heat insulating sheet constituting the functional member 9 shown in Figures 1A, 1B, and 2, or as a heat insulating sheet constituting the heat insulating sheet 10 shown in Figures 3 and 4, or as a heat insulating sheet constituting the first functional member 10a and the second functional member 10b shown in Figures 5A, 5B, 6, and 7.

[0148] As shown in Figures 22 and 23, the heat insulating sheet 110 has inorganic particles 4 and organic fibers 1. The surface of the heat insulating sheet 110 has a first region 42 having striated fiber bundles 47 made up of multiple organic fibers 1, and a second region 43 where no fiber bundles 47 are present. In this specification, "fiber bundles 47" are made up of 10 or more organic fibers 1 intertwined with each other, and extend in striated directions in a direction substantially parallel to the surface of the heat insulating sheet 110.

[0149] In other words, when the surface of the heat insulating sheet 110 is observed, as shown in Figure 23, in the first region 42, multiple organic fibers 1 are observed to be entangled. On the other hand, in the second region 43, although there are some areas where several organic fibers 1 are observed, fiber bundles 47 in which multiple 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, with the second region 43, which corresponds to the island, being formed so as to be surrounded by the first region 42, which corresponds to the sea.

[0150] In the heat insulating sheet 110, the fiber bundles 47, which are entangled organic fibers 1, are present on the surface of the heat insulating sheet 110 in a streaky manner, thereby improving the strength of the heat insulating sheet 110. Furthermore, since the entire surface is not covered with fiber bundles 47, and there is a first region 42 where fiber bundles 47 are present and a second region where fiber bundles 47 are not present, the heat insulating sheet 110 also exhibits excellent flexibility. Moreover, in this embodiment, the heat insulating sheet is formed with a thickness thinner than the frame, and the fiber bundles 47 are present on the surface of the heat insulating sheet 110. Therefore, even when impact or pressure is applied to the heat insulating sheet 110, the voids on the main surface side of the heat insulating sheet as shown in the first and third embodiments, the elastic sheet 51 as shown in the second embodiment, and the fiber bundles 47 can absorb and mitigate the impact or compressive force. Therefore, the shedding (dropping of powder) of inorganic particles 4 can be suppressed, and a decrease in the heat insulating performance of the heat transfer suppression member can be prevented.

[0151] Furthermore, in the heat-insulating sheet 110, the organic fibers 1 and the fiber bundles 47 in which the organic fibers 1 are intertwined are present not only on the surface of the heat-insulating sheet 110 but also inside. This allows for even greater strength to be obtained.

[0152] The length of the fiber bundles 47, which are formed to extend across the surface of the heat insulating sheet 110, is preferably somewhat long. An example of a method for defining the length of the fiber bundles 47 is explained using Figure 24. As shown in Figure 24, a rectangular virtual frame 21 is arranged on the surface of the heat insulating sheet 110 along the fiber bundles 47 that extend in a striated pattern. In this embodiment, the size of the virtual frame 21 is 5 mm square, and these virtual frames 21 are arranged to be continuous with each other. In this case, if there are fiber bundles 47 that penetrate at least three continuous virtual frames 21, it can be determined that this has a sufficient effect in improving the strength of the heat insulating sheet 110.

[0153] Furthermore, it is also possible to simply measure the length of the fiber bundles 47 that extend in a striated manner. For example, a method can be used in which a string or the like is placed on the surface of the heat-insulating sheet 110 along the fiber bundles 47, and then the length of the string is measured. If the length of a continuous fiber bundle 47 is measured and there are fiber bundles 47 with a length of 20 mm or more, a sufficient effect of improving the strength of the heat-insulating sheet 110 can be obtained.

[0154] Furthermore, as shown in Figure 25, the sheet strength of the heat insulating sheet 110 can be further improved if the fiber bundles 47 are arranged in a mesh-like pattern on its surface.

[0155] The following provides a more detailed explanation of the materials that constitute the thermal insulation sheets of the above structural examples 1 to 7, as well as their preferred content.

[0156] <Organic Fibers> The organic fiber 1 provides flexibility to the heat insulating sheet and, by welding inorganic particles 4 and other organic fibers 1 to its surface, has the effect of maintaining the strength and shape of the sheet. As the material for the organic fiber 1 in the heat insulating sheet, a single-component organic fiber can be used, but it is preferable to use a binder fiber with a core-sheath structure. The binder fiber with a core-sheath structure has a core portion that extends in the longitudinal direction of the fiber and a sheath portion formed to cover the outer surface of the core portion. The core portion is made of a first organic material, and the sheath portion 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 a binder fiber with a core-sheath structure is used as the material, the core portion in the heat insulating sheet corresponds to the organic fiber 1. Also, during the manufacture of the heat insulating sheet, the second organic material constituting the sheath portion melts and then solidifies again, so in the heat insulating sheet, the sheath portion becomes a welded portion 5.

[0157] When a binder fiber with a core-sheath structure is used as the material for the organic fiber 1, the core portion, i.e., the first organic material constituting the organic fiber 1, is not particularly limited as long as its melting point is higher than that of the sheath portion, i.e., the second organic material present on the outer surface of the organic fiber 1. Examples of the first organic material include at least one selected from polyethylene terephthalate, polypropylene, and nylon.

[0158] (Organic fiber content) In this embodiment, if the content of organic fibers 1 in the heat insulating sheet is appropriately controlled, a sufficient reinforcing effect on the framework can be obtained. The content of organic fiber 1 is preferably 2% by mass or more, and more preferably 4% by mass or more, relative to the total mass of the heat insulating sheet. Furthermore, if the content of organic fiber 1 becomes too high, the content of inorganic particles 4 will relatively decrease. Therefore, in order to obtain the desired heat insulating performance, the content of organic fiber is preferably 10% by mass or less, and more preferably 8% by mass or less, relative to the total mass of the heat insulating sheet.

[0159] (Fiber length of organic fibers) While there are no particular limitations on the fiber length of organic fiber 1, it is preferable that the average fiber length of the organic fiber be 10 mm or less from the viewpoint of ensuring moldability and processability. On the other hand, from the viewpoint of using the organic fiber 1 as a framework and ensuring the compressive strength of the heat insulating sheet, it is preferable that the average fiber length of the organic fiber 1 be 0.5 mm or more.

[0160] <Welded part> The welded portion 5 is formed when the surface of the organic fiber 1, or the sheath portion of a binder fiber having a core-sheath structure, is heated, melted, and then cooled. It welds inorganic particles 4 to the surface of the organic fiber 1 and also welds the organic fibers 1 to each other. When a binder fiber with a core-sheath structure is used as the material for the organic fiber 1, the welded portion 5 includes a second organic material that constitutes the sheath portion.

[0161] (Second organic material) The second organic material is not particularly limited, as long as its melting point is lower than that of the first organic material constituting the organic fiber 1. Examples of the second organic material include at least one selected from polyethylene terephthalate, polyethylene, polypropylene, and nylon. The melting point of the second organic material is preferably 90°C or higher, and more preferably 100°C or higher. Furthermore, the melting point of the second organic material is preferably 150°C or lower, and more preferably 130°C or lower.

[0162] <Inorganic particles> As inorganic particles, a single inorganic particle may be used, or a combination of two or more inorganic particles may be used. From the viewpoint of 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. Furthermore, there are no particular limitations on the shape, but it is preferable to include at least one selected from nanoparticles, hollow particles, and porous particles. 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 materials, etc., can be used.

[0163] If the average secondary particle diameter of the inorganic particles is 0.01 μm or more, they are readily available and manufacturing costs can be kept down. Furthermore, if it 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.

[0164] Furthermore, by using two or more inorganic particles with different heat transfer suppression effects, the heat-generating element can be cooled in multiple stages, and the endothermic effect can be exhibited over a wider temperature range. Specifically, it is preferable to use a mixture of large-diameter and small-diameter particles. For example, when nanoparticles are used as one type of inorganic particle, it is preferable to include inorganic particles made of metal oxides as the other type of inorganic particle. Below, the inorganic particles will be described in more detail, with small-diameter inorganic particles referred to as the first inorganic particles and large-diameter inorganic particles as the second inorganic particles.

[0165] <First inorganic particle> (Oxide particles) Oxide particles have a high refractive index and a strong effect of diffusely reflecting light. Therefore, using oxide particles as the first inorganic particles can suppress radiative heat transfer, especially in high-temperature regions such as abnormal heat generation. As oxide particles, at least one particle selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina can be used. That is, only one of the above oxide particles that can be used as inorganic particles may be used, or two or more oxide particles may be used. In particular, silica is a component with high thermal insulation properties, and titania is a component with a high refractive index compared to other metal oxides. Since they have a high effect of diffusely reflecting light and blocking radiant heat in high-temperature regions of 500°C or higher, it is most preferable to use silica and titania as oxide particles.

[0166] (Average primary particle size of oxide particles: 0.001 μm or more and 50 μm or less) Since the particle size of oxide particles can affect the effect of reflecting radiant heat, limiting the average primary particle size to a predetermined range can result in even higher thermal insulation. In other words, if the average primary particle diameter of the oxide particles is 0.001 μm or larger, it is sufficiently larger than the wavelength of light that contributes to heating, and efficiently diffusely reflects the light. As a result, radiative heat transfer within the insulating sheet is suppressed in the high-temperature region of 500°C or higher, further improving the insulating properties. On the other hand, if the average primary particle diameter of oxide particles is 50 μm or less, the number of contact points between particles does not increase even when compressed, making it difficult to form conductive heat transfer paths. This reduces the impact on thermal insulation, especially in the normal temperature range where conductive heat transfer is dominant.

[0167] In this invention, the average primary particle diameter can be determined by observing the particles under a microscope, comparing them to a standard scale, and taking the average of 10 arbitrary particles.

[0168] (Nanoparticles) In this invention, "nanoparticles" refers to particles that are spherical or nearly spherical, with an average primary particle diameter of less than 1 μm and on the order of nanometers. Because nanoparticles have low density, they suppress conductive heat transfer, and when nanoparticles are used as the first inorganic particles, the three-dimensionally connected pores 7 are further refined, resulting in excellent heat insulation that suppresses convective heat transfer. For this reason, it is preferable to use nanoparticles when using a battery in the normal room temperature range, as it can suppress heat conduction between adjacent nanoparticles. Furthermore, by using nanoparticles with a small average primary particle diameter as oxide particles, even if the insulating sheet is compressed due to expansion caused by thermal runaway of the battery cell, and the internal density increases, the increase in conductive heat transfer of the insulating sheet can be suppressed. This is thought to be because nanoparticles easily create fine voids between particles due to electrostatic repulsion, and because their bulk density is low, the particles are packed in a way that provides cushioning.

[0169] In this invention, when nanoparticles are used as the first inorganic particles, the material is not particularly limited as long as it conforms to the above definition of nanoparticles. For example, silica nanoparticles are a material with high thermal insulation properties, and because the contact points between particles are small, the amount of heat conducted by silica nanoparticles is smaller compared to when silica particles with a larger particle size are used. Also, commonly available silica nanoparticles have a bulk density of 0.1 g / cm³. 3 Because of this, for example, even if battery cells arranged on both sides of the heat insulating sheet undergo thermal expansion and a large compressive stress is applied to the heat insulating sheet, the size (area) and number of contact points between silica nanoparticles will not increase significantly, and the heat 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.

[0170] Generally, wet silica has aggregated particles, while dry silica allows for particle dispersion. In the temperature range below 300°C, conduction is the dominant method of heat transfer, so dry silica, which allows for particle dispersion, can provide superior thermal insulation compared to wet silica. In this embodiment, it is preferable to use a manufacturing method in which a mixture containing the materials is processed into a sheet by a dry process. Therefore, it is preferable to use dry silica, silica aerogel, or the like as the inorganic particles, as they have low thermal conductivity.

[0171] (Average primary particle size of nanoparticles: 1 nm to 100 nm) By limiting the average primary particle size of nanoparticles to a predetermined range, even higher thermal insulation can be achieved. In other words, by setting the average primary particle diameter of the nanoparticles to 1 nm or more and 100 nm or less, convective and conductive heat transfer within the insulating sheet can be suppressed, especially in the temperature range below 500°C, thereby further improving the insulating properties. Furthermore, even when compressive stress is applied, the voids remaining between the nanoparticles and the numerous contact points between particles suppress conductive heat transfer, maintaining the insulating properties of the insulating sheet. Furthermore, the average primary particle diameter of the nanoparticles is more preferably 2 nm or larger, and even more preferably 3 nm or larger. On the other hand, the average primary particle diameter of the nanoparticles is more preferably 50 nm or smaller, and even more preferably 10 nm or smaller.

[0172] (Inorganic hydrate particles) Inorganic hydrate particles, when exposed to heat from a heat source and exceeding their decomposition start temperature, undergo thermal decomposition, releasing their crystalline water and lowering the temperature of the heat source and its surroundings—a phenomenon known as "endothermic action." After releasing the crystalline water, they become porous, exhibiting insulating properties through their numerous air pores. 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).

[0173] For example, aluminum hydroxide contains approximately 35% crystal water, and as shown in the formula below, it undergoes thermal decomposition to release crystal water, exhibiting an endothermic effect. After releasing the crystal water, it becomes a porous alumina (Al2O3) and functions as an insulating sheet. 2Al(OH)3 → Al2O3 + 3H2O

[0174] In this embodiment, the heat insulating sheet is preferably interposed between battery cells, for example. However, in a battery cell experiencing thermal runaway, the temperature rapidly rises to over 200°C and continues to rise to around 700°C. Therefore, it is preferable that the inorganic particles consist of inorganic hydrates whose thermal decomposition initiation temperature is 200°C or higher. The thermal decomposition initiation temperatures for the inorganic hydrates listed above are approximately 200°C for aluminum hydroxide, 330°C for magnesium hydroxide, 580°C for calcium hydroxide, 200°C for zinc hydroxide, 350°C for iron hydroxide, 300°C for manganese hydroxide, 300°C for zirconium hydroxide, and 300°C for gallium hydroxide. These temperatures largely overlap with the temperature range of rapid temperature increases in battery cells experiencing thermal runaway, and can effectively suppress temperature rise, making them desirable inorganic hydrates.

[0175] (Average secondary particle diameter of inorganic hydrate particles: 0.01 μm or more and 200 μm or less) Furthermore, when inorganic hydrate particles are used as the first inorganic particles, if their average particle size is too large, it may take a certain amount of time for the first inorganic particles (inorganic hydrates) near the center of the heat insulating sheet to reach their thermal decomposition temperature, and the first inorganic particles near the center of the sheet may not be completely 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.

[0176] (Particles made of thermally expandable inorganic material) Examples of thermally expandable inorganic materials include vermiculite, bentonite, mica, and perlite.

[0177] (Particles made of a water-containing porous material) Specific examples of water-containing porous materials include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

[0178] (Inorganic balloon) The heat insulating sheet used in the present invention may contain inorganic balloons as the first inorganic particles. The inclusion of inorganic balloons can suppress convective or conductive heat transfer within the insulating sheet at temperatures below 500°C, thereby further improving the insulating properties of the insulating sheet. As the inorganic balloon, at least one selected from shirasu balloons, silica balloons, fly ash balloons, barlite balloons, and glass balloons can be used.

[0179] (Inorganic balloon content: 60% or less by mass relative to the total mass of the insulation sheet) The inorganic balloon content is preferably 60% by mass or less relative to the total mass of the heat insulating sheet.

[0180] (Average particle size of inorganic balloons: 1 μm to 100 μm) The average particle size of the inorganic balloons is preferably between 1 μm and 100 μm.

[0181] <Second inorganic particle> When the heat insulating sheet contains two types of inorganic particles, the second inorganic particle is not particularly limited as long as it differs from the first inorganic particle in terms of material, particle size, etc. The second inorganic particle can be 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 thermally expandable inorganic materials, particles made of water-containing porous materials, etc. Details of these are as described above.

[0182] Furthermore, nanoparticles exhibit extremely low conductive heat transfer and can maintain excellent thermal insulation even when compressive stress is applied to the thermal insulation sheet. In addition, metal oxide particles such as titania have a high effect in blocking radiant heat. Moreover, by using both large-diameter and small-diameter inorganic particles, the small-diameter inorganic particles can fill the gaps between the large-diameter inorganic particles, resulting in a denser structure and improving the heat transfer suppression effect. Therefore, when nanoparticles are used as the first inorganic particles, it is preferable to further include particles made of metal oxides, which are larger in diameter than the first inorganic particles, as second inorganic particles in the thermal insulation sheet. Examples of metal oxides include silicon dioxide, titanium dioxide, aluminum oxide, barium titanate, zinc oxide, zircon, and zirconium oxide. In particular, titanium dioxide (titania) has a higher refractive index compared to other metal oxides, and is highly effective in scattering light and blocking radiant heat in the high-temperature range of 500°C or higher, so using titania is most preferable.

[0183] When using at least one particle selected from dry silica particles and silica aerogel as the first inorganic particle, and at least one particle selected from titania, zircon, zirconia, silicon carbide, zinc oxide, and alumina as the second inorganic particle, in order to obtain excellent thermal insulation performance within a temperature range of 300°C or less, the first inorganic particle is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total mass of the inorganic particles. Furthermore, the first inorganic particle is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on the total mass of the inorganic particles.

[0184] On the other hand, in order to obtain excellent heat insulation performance in a temperature range exceeding 300°C, the amount of the second inorganic particles is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on the total mass of the inorganic particles. Furthermore, the amount of the second inorganic particles is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total mass of the inorganic particles.

[0185] (Average primary particle diameter of the second inorganic particle) When a second inorganic particle consisting of a metal oxide is incorporated into the heat insulating sheet, if the average primary particle diameter of the second inorganic particle is 1 μm or more and 50 μm or less, radiant heat transfer can be efficiently suppressed in the high-temperature region of 500°C or higher. It is more preferable that the average primary particle diameter of the second inorganic particle is 5 μm or more and 30 μm or less, and most preferably 10 μm or less.

[0186] (Content of inorganic particles) In this embodiment, if the total content of inorganic particles 4 in the heat insulating sheet is appropriately controlled, the heat insulating properties of the heat insulating sheet can be sufficiently ensured. The total content of inorganic particles 4 is preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the total mass of the heat insulating sheet. Furthermore, if the total content of inorganic particles 4 becomes too high, the content of organic fibers will relatively decrease. Therefore, in order to obtain sufficient reinforcing effects on the framework and retention effects on inorganic particles, the total content of inorganic particles 4 is preferably 95% by mass or less, and more preferably 90% by mass or less, relative to the total mass of the heat insulating sheet.

[0187] The amount of inorganic particles 4 in the heat-insulating sheet can be calculated, for example, by heating the heat-insulating sheet to 800°C to decompose the organic components and then measuring the mass of the remaining material.

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

[0189] The cross-sectional shape of inorganic fibers is not particularly limited and includes circular, flat, hollow, polygonal, and core cross-sections. Among these, fibers with irregular cross-sections, such as hollow, flat, or polygonal cross-sections, can be suitably used because they slightly improve thermal insulation.

[0190] The preferred lower limit for the average fiber length of inorganic fibers is 0.1 mm, and the more preferred lower limit is 0.5 mm. On the other hand, the preferred upper limit for the average fiber length of inorganic fibers is 50 mm, and the more preferred upper limit is 10 mm. If the average fiber length of inorganic fibers is less than 0.1 mm, entanglement between inorganic fibers is unlikely to occur, which may reduce the mechanical strength of the insulation sheet. On the other hand, if it exceeds 50 mm, although a reinforcing effect can be obtained, the inorganic fibers may not be able to entangle tightly with each other, or individual inorganic fibers may curl up, which may lead to the creation of continuous voids and thus reduce the insulation performance.

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

[0192] (Inorganic fiber content) In this embodiment, when the heat insulating sheet contains inorganic fibers, it is preferable that the inorganic fiber content is 3% by mass or more and 15% by mass or less of the total mass of the heat insulating sheet.

[0193] Furthermore, it is more preferable that the inorganic fiber content be between 5% and 10% by mass relative to the total mass of the heat-insulating sheet. By using such a content, the shape retention, compressive force resistance, wind pressure resistance, and inorganic particle holding ability of the inorganic fibers are well-balanced. In addition, by appropriately controlling the inorganic fiber content, the organic fibers 1 and inorganic fibers intertwine to form a three-dimensional network, thereby further improving the effect of holding the inorganic particles 4 and other compounding materials described later.

[0194] <Other ingredients> Furthermore, the heat insulating sheet according to this embodiment may contain binders, colorants, etc., as needed. These are all useful for purposes such as reinforcing the heat insulating sheet and improving its moldability, and it is preferable that the total amount of these is 10% by mass or less of the total mass of the heat insulating sheet.

[0195] The above describes structural examples 1 to 7 of the thermal insulation sheet, but the structure of the thermal insulation sheet containing inorganic particles and organic fibers is not limited to these, and thermal insulation sheets with various structures can be used. In particular, the thermal insulation sheets of structural examples 1 to 7 have an even better thermal insulation effect compared to other thermal insulation sheets and thermal insulation sheets containing fibers and aerogel.

[0196] Here, we will explain the results of comparing the thermal insulation effects of various thermal insulation sheets of different types and thicknesses. The thermal insulation effect test can be performed by placing a heater in contact with one main surface of the thermal insulation sheet and a thermometer on the other main surface, and measuring the temperature change of the other main surface when the heater temperature is increased. When the heater temperature is raised to 800°C, the temperature of the other main surface of the thermal insulation sheet reaches its maximum temperature after a certain period of time. At this point, it can be seen that the thermal insulation sheet with a lower maximum temperature has better thermal insulation performance. The results of the thermal insulation effect comparison are shown in Table 1 below.

[0197] [Table 1]

[0198] In Table 1 above, insulation sheets A-1 and A-2 are insulation sheets of structural example 3 shown in Figures 11 to 13, and are formed into a sheet shape by a dry method using organic fibers with a core-sheath structure and inorganic particles. In insulation sheets A-1 and A-2, the organic fibers used are organic fibers with a core-sheath structure in which the core and sheath parts are made of polyethylene terephthalate and the melting points of the two parts differ by 90°C or more, and silica nanoparticles and titania are used as inorganic particles. Insulation sheet B is made by impregnating SiO2 with fibers as a framework.

[0199] As shown in Table 1 above, the thermal insulation performance of thermal insulation sheet A-1, which has a thickness of 2.0 mm, is equal to that of thermal insulation sheet B, which has a thickness of 4.5 mm. Furthermore, by increasing the thickness of thermal insulation sheet A-2, it is possible to obtain higher thermal insulation performance than thermal insulation sheet B at a thinner thickness than thermal insulation sheet B.

[0200] These results are not limited to structural example 3, but similar thermal insulation performance can be obtained with all thermal insulation sheets from structural examples 1 to 7. Therefore, by using thermal insulation sheets from structural examples 1 to 7 that contain inorganic particles and organic fibers, the thickness of the thermal insulation sheet can be easily made thinner than that of the frame 53, making them suitable for use as thermal insulation sheets for the heat transfer suppression member according to the embodiments of the present invention.

[0201] Furthermore, in the heat transfer suppression member according to this embodiment, the constituent materials other than the frame, partition wall, and heat insulation sheet will be described below.

[0202] <film> As shown in the first to third embodiments above, when the heat transfer suppression member has a film 52, at least one material selected from polyethylene, polypropylene, polystyrene, vinyl chloride, nylon, acrylic, epoxy resin, polyurethane, polyetheretherketone, polyetherimide, polyethylene terephthalate, polytetrafluoroethylene (PTFE), polyphenyl sulfide, polycarbonate, and aramid can be used to constitute the film 52.

[0203] Furthermore, shrink wrapping may be used when covering the functional component with film, or when covering the entire surface of the functional component and frame with film 52. Suitable materials for shrink wrapping include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride.

[0204] (Film thickness) The film has the effect of preventing particles from falling off the heat insulating sheet and preventing the heat insulating sheet from falling off the frame 53, so it is preferable that it has an appropriate thickness. It is also preferable that the film has appropriate flexibility. If the thickness of the film exceeds 1 mm, cracks and splits are more likely to occur in the film. 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, while there is no particular lower limit to the film thickness, it is preferably 0.005 mm or more, and more preferably 0.01 mm or more, in order to prevent tearing due to friction with battery cells, etc., and to obtain the desired strength.

[0205] (Other materials included in the film) Furthermore, since the film is required to withstand high temperatures from the battery cells 20a, 20b, and 20c, it is preferable that it be flame-retardant, and specifically, it is preferable that it contains inorganic substances or flame retardants. Other materials that can be included in the film include, as inorganic substances, talc, calcium carbonate, aluminum hydroxide, titanium dioxide, vermiculite, zeolite, synthetic silica, zirconia, zircon, barium titanate, zinc oxide, and alumina, and as flame retardants, brominated flame retardants, chlorine-based flame retardants, phosphorus-based flame retardants, boron-based flame retardants, silicone-based flame retardants, and nitrogen-containing compounds.

[0206] <Elastic Sheet> The elastic sheet is made by processing an elastic material into a sheet. As shown in the second embodiment above, when the heat transfer suppression member is a laminate of a heat insulating sheet 10 and an elastic sheet 51, known elastic materials can be used to constitute the elastic sheet 51. Specifically, a sheet made of rubber or thermoplastic elastomer that has elasticity that allows it to deform flexibly in response to the deformation of the battery cells 20a, 20b, and 20c can be used.

[0207] The rubber may be either synthetic rubber 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, echochlorohydrin rubber, and foamed silicone.

[0208] Examples of thermoplastic elastomers include polystyrene-based, polyolefin-based, vinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, and polybutadiene-based thermoplastic elastomers. Furthermore, the elastomer may be either porous or non-porous. In the case of porous elastomers, the cell structure may be either closed-cell or open-cell.

[0209] (Size of the elastic sheet) The thickness of the elastic sheet is not particularly limited, but it is preferable to set it to 1 mm or more and 10 mm or less in order to effectively obtain the effects of the elastic sheet.

[0210] [Method for manufacturing a heat transfer suppression member] The method for manufacturing the heat transfer suppressing member according to this embodiment will be described in detail below, in particular, with regard to an example in which the heat insulating sheet 50 of structural example 2 shown in Figure 10 is applied to the heat transfer suppressing member 120 according to the second embodiment.

[0211] <Manufacturing of insulation sheets> For example, binder fibers having a core-sheath structure (not shown), inorganic particles 4, and inorganic fibers 15 are put into a mixer such as a V-type mixer in a predetermined ratio to produce a mixture. As mentioned above, it is preferable to use a core-sheath structure fiber as the binder fiber, which has a core made of a first organic material and a sheath made of a second organic material. In this case, the melting point of the first organic material is higher than the melting point of the second organic material.

[0212] Subsequently, the resulting mixture is placed into a predetermined mold and pressurized using a press or the like to heat the resulting molded body, causing the sheath portion of the binder fibers to melt. Then, by cooling the heated molded body, the second organic material constituting the molten sheath portion and the inorganic particles 4 present around the binder fibers are welded to the core portion (organic fiber 1), and the areas where the binder fibers were in contact with each other are also welded to each other. As a result, a heat insulating sheet 50 processed into a sheet shape with a thickness thinner than the frame can be obtained.

[0213] Furthermore, a heat insulating sheet that does not contain inorganic fibers 15 can also be obtained by the same manufacturing method as the heat insulating sheet 50 described above, and the use of inorganic fibers 15 can be arbitrarily selected.

[0214] Furthermore, when the materials for the above-mentioned heat-insulating sheet are mixed, 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 sheet 50. The fiber layer 11 thus obtained has the effect of improving the strength of the heat-insulating sheet 50 and mitigating impacts to the surface of the heat-insulating sheet 50.

[0215] <Assembly of laminated structures> Subsequently, the elastic sheet 51 is placed on both main surfaces of the heat insulating sheet 50 and fixed together to produce the functional member 111. The method of fixing the heat insulating sheet 50 and the elastic sheet 51 to each other is not particularly limited, and various methods can be used, such as bonding with an adhesive, sewing with thread, clamping and fixing with a fixing jig, covering with a film, or covering with a heat-compressible film and then heating to shrink the film and fix it in place. Note that the elastic sheet 51 does not necessarily need to be laminated, and as shown in the first embodiment, a functional member consisting only of a heat insulating sheet may be used.

[0216] <Frame manufacturing> Furthermore, a frame 53 is fabricated to surround the outer perimeter of the heat-insulating sheet. The material for the frame 53 can be, for example, resin, and it may be integrally molded or made by combining multiple frame members. As shown in the fourth embodiment in Figures 5A and 5B, and its modified examples, when the heat transfer suppression member has a partition wall, the frame and partition wall may be integrally molded or made by combining multiple members.

[0217] <Integrating the laminated structure into the frame> Subsequently, the functional member 111 is fitted into the frame 53 and fixed in place. The method of fixing the functional member 111 to the frame 53 is not particularly limited; it may be fixed using a fixing material such as adhesive, or grooves may be processed into the frame 53 and the functional member may be fixed by fitting it into the grooves.

[0218] <Applying the film> Subsequently, two films 52 having a size approximately equal to the outer diameter of the frame 53 in plan view are prepared, and these films 52 are placed on top of the frame 53, and the frame 53 and the films 52 are heat-sealed together. In this way, the films 52 may be heat-sealed to the frame 53, or they may be used to completely cover the frame 53 and the insulation sheet, or they may be used to cover only the insulation sheet. Furthermore, as shown in the fourth embodiment, the films 52 may not be provided at all. Furthermore, "approximately equivalent" means that the outer diameter of the frame 53 and the size of the film 52 are acceptable if the difference between their sizes is up to ±5%, preferably up to ±3%, and more preferably up to ±1% of the average value of the two.

[0219] The above-mentioned heat-insulating sheet is preferably manufactured by a dry process. When using a dry process, inorganic particles 4 suitable for the dry process are used, and no solvents such as water required for molding by a wet process are added to the mixture. However, in order to prevent the inorganic particles 4 and other powders from becoming airborne and making it difficult to handle the raw materials during the manufacture of the heat-insulating sheet, a small amount of solvent such as water may be added within the scope of the dry process. For example, by adding a small amount of solvent such as water to the mixture, the scattering of inorganic particles during manufacturing can be suppressed.

[0220] Next, we will describe the binder fibers and heating conditions that are preferable to use in the manufacture of the above-mentioned heat-insulating sheet, as well as other binder materials.

[0221] <Binder Fiber> When using a core-sheath binder fiber 3 as the material for the heat insulating sheet, the material is not particularly limited 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 that forms the core can be selected from at least one of polyethylene terephthalate, polypropylene, and nylon. The second organic material that forms the sheath can be selected from at least one of polyethylene terephthalate, polyethylene, polypropylene, and nylon.

[0222] If the melting point of the first organic material constituting the core is sufficiently higher than the melting point of the second organic material constituting the sheath, the margin for setting the heating temperature in the heating process can be widened, making it easier to set the temperature to obtain the desired structure. For example, the melting point of the first organic material is preferably 60°C or more higher than the melting point of the second organic material, more preferably 70°C or more higher, and even more preferably 80°C or more higher.

[0223] The binder fiber 3 having the core-sheath structure described above is generally available on the market, and the materials constituting the core and sheath may be the same or different. Examples of binder fibers in which the core and sheath are made of the same material but have different melting points include those in which the core and sheath are made of polyethylene terephthalate, polypropylene, or nylon. Examples of binder fibers in which the core and sheath are made of different materials include those in which the core is made of polyethylene terephthalate and the sheath is made of polyethylene, or those in which the core is made of polypropylene and the sheath is made of polyethylene.

[0224] In this embodiment, the melting point of the second organic material constituting the sheath of the binder fiber 3 represents the melting temperature at which the second organic material begins to melt and deform. However, softening accompanied by a change in shape is also considered a type of melting deformation. The melting point of the sheath of the binder fiber can be measured, for example, by the following method. The binder fiber to be measured is placed in contact with a glass fiber that has a higher melting point, and heated from room temperature to, for example, 200°C at a heating rate of 5°C / min, and then cooled back to room temperature. At this time, if the surface of the binder fiber melts and deforms, and fuses with the glass fiber at the point of contact, or if the cross-sectional shape of the binder fiber changes, it can be determined that the melting point of the second organic material constituting the sheath is 200°C or lower. In this embodiment, by varying the heating temperature and observing the fusion state between the binder fiber and the glass fiber after cooling using the method described above, or by observing the cross-sectional shape of the binder fiber, the melting point of the second organic material constituting the sheath can be determined.

[0225] (Binder fiber content) When using binder fibers 3 with a core-sheath structure as the material for the heat insulating sheet, if the content of binder fibers in the mixture is appropriately controlled, a sufficient reinforcing effect on the framework of the resulting heat insulating sheet can be obtained. The content of binder fibers 3 is preferably 5% by mass or more, and more preferably 10% by mass or more, relative to the total mass of the mixture. Furthermore, if the content of binder fibers 3 is too high, the content of inorganic particles 4 will decrease relatively. Therefore, in order to obtain the desired thermal insulation performance, the content of binder fibers 3 is preferably 25% by mass or less, and more preferably 20% by mass or less, relative to the total mass of the mixture.

[0226] (Hot melt powder) In this embodiment, in addition to the binder fibers 3 and inorganic particles 4, the mixture may also 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 and second organic materials, and has the property of melting when heated. By including the hot melt powder in the mixture and heating it, the hot melt powder melts, and then when cooled, it hardens while containing the surrounding inorganic particles 4. Therefore, the shedding of inorganic particles 4 from the heat insulating sheet can be further suppressed.

[0227] While various types of hot melt powders have different melting points, it is best to select a hot melt powder with an appropriate melting point, taking into account the melting points of the core and sheath of the binder fiber used. Specifically, if the melting point of the third organic material constituting the hot melt powder is lower than that of the first organic material constituting the organic fiber, the heating temperature can be set to melt the sheath and the hot melt powder while leaving the core intact. For example, if the melting point of the hot melt powder is lower than or equal to the melting point of the sheath, the heating temperature during manufacturing can be set between the melting points of the core and the sheath, making it even easier to set the heating temperature.

[0228] Alternatively, the type of hot melt powder used can be selected so that its melting point falls between the melting point of the core and the melting point of the sheath. When a hot melt powder with such a melting point is used, after both the sheath and the hot melt powder melt and then cool and harden, the hot melt powder present in the gaps between the organic fiber (core) 1, the surrounding molten sheath, and the inorganic particles 4 hardens first. As a result, the position of the organic fiber 1 can be fixed, and then the molten sheath fuses to the organic fiber, making it easier to form a three-dimensional structure. Therefore, the overall strength of the sheet can be further improved.

[0229] If the melting point of the third organic material constituting the hot melt powder is sufficiently lower than the melting point of the first organic material constituting the core, the margin for setting the heating temperature in the heating process can be widened, making it easier to set the temperature to obtain the desired structure. For example, the melting point of the first organic material is preferably 60°C or more higher than the melting point of the third organic material, more preferably 70°C or more higher, and even more preferably 80°C or more higher.

[0230] The melting point of the hot melt powder (third organic material) is preferably 80°C or higher, and more preferably 90°C or higher. Furthermore, the melting point of the hot melt powder (third organic material) is preferably 180°C or lower, and more preferably 150°C or lower. Examples of components constituting the hot melt powder include polyethylene, polyester, polyamide, and ethylene vinyl acetate.

[0231] (Hot melt powder content) When hot melt powder is included in the mixture to suppress the shedding of inorganic particles, even a small amount of the powder can be used to suppress shedding. Therefore, the hot melt powder content is preferably 0.5% by mass or more, and more preferably 1% by mass or more, relative to the total mass of the mixture. On the other hand, increasing the content of hot melt powder relatively decreases the content of inorganic particles 4, etc. Therefore, in order to obtain the desired thermal insulation performance, the content of hot melt powder is preferably 5% by mass or less, and more preferably 4% by mass or less, relative to the total mass of the mixture.

[0232] <Heating conditions> When using binder fibers with a core-sheath structure as the material for the heat insulating sheet, it is preferable that the heating temperature in the heating process be 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 way, as described above, the strength of the sheet can be ensured by the core on both the surface and the center side of the sheet, and the inorganic particles 4 can be held in place by the welded portion 5.

[0233] Specifically, the heating temperature in the heating process is preferably set at least 10°C higher than the melting point of the second organic material constituting the sheath, and more preferably at least 20°C higher. On the other hand, the heating temperature is preferably set at least 10°C lower than the melting point of the first organic material constituting the core, and more preferably at least 20°C lower.

[0234] While there are no particular limitations on the heating time, it is preferable to set a heating time that allows the sheath to melt sufficiently. For example, it can be set to between 3 minutes and 15 minutes.

[0235] When the heat insulating sheet material includes hot melt powder, the heating temperature in the heating process is preferably set at least 10°C higher than the higher of the melting point of the second organic material constituting the sheath and the melting point of the third organic material constituting the hot melt powder, and more preferably at least 20°C higher. On the other hand, the heating temperature is preferably set at least 10°C lower than the melting point of the first organic material constituting the core, and more preferably at least 20°C lower. By setting the heating temperature in this manner, a strong framework can be formed, further improving the strength of the sheet, and preventing the inorganic particles 4 from falling off at the welded parts 5, etc.

[0236] <Thickness of the insulation sheet> In this embodiment, the thickness of the heat insulating sheet is not particularly limited as long as it is thinner than the thickness of the frame, but it is preferably 0.05 mm or more and 10 mm or less. 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.

[0237] [Battery pack] An example of a battery pack to which the heat transfer suppression member 40 according to the first embodiment of the present invention is applied is shown in Figure 2 above. Here, the configuration and effects of the battery pack will be specifically explained using Figure 2. As described above, the heat transfer suppression member 40 shown in Figure 2 can be replaced with other heat transfer suppression members 120, 130, 140, 150, 160 having other structures, as well as other heat transfer suppression members having other structures within the scope of the present invention. Furthermore, as the heat insulating sheet, in addition to the heat insulating sheets 10, 50, 60, 70, 80, 90, 110 having the various structures described above, other heat insulating sheets can be replaced within the scope of the present invention.

[0238] As shown in Figure 2, the assembled battery 100 includes a plurality of battery cells 20a, 20b, 20c, and the heat transfer suppressing member 40 according to the present embodiment, wherein the plurality of battery cells are connected in series or in parallel. For example, the heat transfer suppressing member 40 according to the present embodiment is interposed between the battery cell 20a and the battery cell 20b, and between the battery cell 20b and the battery cell 20c. Further, the battery cells 20a, 20b, 20c and the heat transfer suppressing member 40 are accommodated in a battery case 30. Note that the heat transfer suppressing member 40 is as described above.

[0239] In the assembled battery 100 configured as described above, since the functional member 9 is formed to be thicker than the frame body 53, it is possible to suppress heat from being transferred to the adjacent battery cells via the frame body 53 in a normal state. In addition, since the heat transfer suppressing member 40 has a frame body with a predetermined thickness, the interval between the battery cells can be ensured in an abnormal state. Further, when the battery cells 20a, 20b, 20c are deformed, it is possible to suppress destruction of the battery case and deterioration of battery performance, and also to suppress heat propagation between the respective battery cells in an abnormal state.

[0240] Note that the assembled battery 100 of the present embodiment is not limited to the assembled battery illustrated in Figure 2. For example, the heat transfer suppressing member 40 may be disposed not only between the battery cell 20a and the battery cell 20b and between the battery cell 20b and the battery cell 20c, but also between the battery cells 20a, 20b, 20c and the battery case 30, or may be attached to the inner surface of the battery case 30.

[0241] In the assembled battery 100 configured as described above, when a certain battery cell catches fire, it is possible to suppress the flame from spreading to the outside of the battery case 30. For example, the assembled battery 100 according to the present embodiment is used in an electric vehicle (EV) or the like, and may be disposed under the floor of a passenger. In this case, even if the battery cell catches fire, the safety of the passenger can be ensured. Furthermore, since the heat transfer suppression member 40 can be placed not only between each battery cell, but also between the battery cells 20a, 20b, and 20c and the battery case 30, there is no need to newly manufacture flame retardant materials, and a safe battery pack 100 can be easily constructed at low cost.

[0242] Furthermore, the heat transfer suppressing member according to this embodiment can be manufactured in various shapes depending on the manufacturing method. Therefore, it is not affected by the shape of the battery cells 20a, 20b, 20c and the battery case 30, and can be used with any shape. Specifically, it can be applied not only to prismatic batteries but also to cylindrical batteries, flat-plate batteries, and the like. [Explanation of Symbols]

[0243] 1. Organic Fibers 3 Binder Fibers 4 Inorganic particles 8,54 void 9,111 Functional components 10, 50, 60, 70, 80, 90, 110 Insulation Sheets 10a First functional component 10b Second functional component 15 Inorganic Fibers 20a, 20b, 20c battery cells 30 Battery Cases 40, 120, 130, 140, 150, 160 Heat transfer suppression member 51 Elastic Sheet 52 film 53 Frame 53a, 53b Frame members 58a, 58b, 58c, 58d Partition wall 100 battery packs

Claims

1. A frame that surrounds the outer perimeter in a plan view, A heat transfer suppression member having a sheet-like functional member disposed inside the frame and having a pair of main surfaces, The functional member has a heat insulating sheet, A heat transfer suppressing member characterized in that, in a cross-sectional view perpendicular to the plan view, the thickness of the functional member is greater than the thickness of the frame.

2. The heat transfer suppression member according to claim 1, characterized in that the functional member consists only of the heat insulating sheet.

3. The heat transfer suppression member according to claim 1, characterized in that the functional member comprises a heat insulating sheet having a pair of main surfaces, and an elastic sheet laminated on at least one of the main surfaces of the heat insulating sheet.

4. The heat transfer suppressing member according to claim 1, characterized in that it has a film covering the main surface of the functional member.

5. The heat transfer suppressing member according to claim 1, characterized in that, in the cross-sectional view, there is a step between the functional member and the frame, and at least one main surface of the functional member protrudes in the thickness direction relative to the frame.

6. The heat transfer suppressing member according to claim 1, characterized in that the frame is mainly made of an insulating material.

7. The heat transfer suppressing member according to claim 1, characterized in that the heat insulating sheet contains inorganic particles and organic fibers.

8. The heat transfer suppressing member according to claim 3, characterized in that the elastic sheet includes at least one selected from synthetic rubber, natural rubber, and thermoplastic elastomer.

9. Furthermore, the frame has partition walls that divide the inside of the frame into multiple regions, Having a plurality of functional members arranged in the plurality of regions, The heat transfer suppressing member according to claim 1, characterized in that, in the cross-sectional view, the thickness of the functional member is greater than the thickness of the partition wall.

10. The heat transfer suppressing member according to claim 9, characterized in that the plurality of functional members include a first functional member and a second functional member having different properties from each other.

11. The heat transfer suppressing member according to claim 10, characterized in that the elastic modulus of the first functional member is smaller than the elastic modulus of the second functional member.

12. The heat transfer suppressing member according to claim 11, characterized in that the first functional member is arranged in at least the central region of the plurality of regions.

13. The heat transfer suppressing member according to claim 9, characterized in that, in the plan view, the width of the partition wall in the direction perpendicular to the longitudinal direction is smaller than the width of the frame in the direction perpendicular to the longitudinal direction.

14. The heat transfer suppression member according to claim 9, characterized in that the partition wall is mainly made of an insulating material.

15. A battery pack comprising a plurality of battery cells and a heat transfer suppression member according to any one of claims 1 to 14, wherein the plurality of battery cells are connected in series or in parallel.

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