Heat transfer suppression sheet for battery pack and battery pack

Abstract

Provided are a heat transfer suppression sheet for a battery assembly, which is used in a battery assembly in which a plurality of battery cells are connected in series or parallel, and which can cool each battery cell during normal use while suppressing heat transfer between the battery cells during abnormal conditions, and a battery assembly. [Solution] A heat-transfer-suppressing sheet (10) for a battery assembly is used in a battery assembly in which multiple battery cells are connected in series or parallel, and is interposed between the battery cells. The heat-transfer-suppressing sheet (10) for a battery assembly includes a heat insulating material (11) containing at least one of inorganic particles and inorganic fibers, and a covering material (12) that covers at least a portion of the heat insulating material (11), with a sealed void (14) formed between the heat insulating material (11) and the covering material (12), and the covering material (12) is configured so that a communication opening is formed in the covering material (12) that connects the void (14) to the outside of the covering material (12) at a temperature of 60°C or higher.

Description

[Technical field]

[0001] The present invention relates to a heat transfer-suppressing sheet for a battery assembly that is suitably used in a battery assembly that serves as a power source for an electric motor that drives, for example, an electric vehicle or a hybrid vehicle, and to a battery assembly that uses the heat transfer-suppressing sheet for a battery assembly. [Background technology]

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

[0003] These battery cells mainly use lithium-ion secondary batteries, which have higher capacity and higher output than lead-acid batteries or nickel-metal hydride batteries. However, if thermal runaway occurs in one battery cell due to an internal short circuit or overcharging (i.e., in the event of an "abnormality"), heat can be transmitted to other adjacent battery cells, potentially causing thermal runaway in the other battery cells as well.

[0004] For example, Patent Document 1 discloses an electricity storage device capable of realizing effective thermal insulation between a plurality of electricity storage elements such as lithium ion secondary batteries. The electricity storage device described in Patent Document 1 has a first plate and a second plate disposed between a first electricity storage element and a second electricity storage element adjacent to each other. In addition, a low thermal conductive layer, which is a layer of a material having a lower thermal conductivity than the first plate and the second plate, is formed between the first plate and the second plate.

[0005] In the energy storage device of Patent Document 1 configured as above, the radiant heat from the first energy storage element toward the second energy storage element or the radiant heat from the second energy storage element toward the first energy storage element is blocked by the first plate and the second plate, and the transfer of heat from one of these two plates to the other is suppressed by the low thermal conductive layer.

[0006] However, because the above-mentioned energy storage device only has a heat insulating layer provided between the first energy storage element and the second energy storage element, it is not possible to effectively cool the battery cells that generate heat during charge and discharge cycles.

[0007] Therefore, Patent Document 2 proposes a heat absorbing sheet for a battery pack that can cool each battery cell during normal use while suppressing the transfer of heat between the battery cells during abnormal conditions. The heat absorbing sheet described in Patent Document 2 contains two or more substances with different dehydration temperatures. At least one of the two or more substances is configured to be dehydrated during normal use of the battery cells, and at least the other is configured to be dehydrated when an abnormality occurs in the battery cells. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2015-211013 A [Patent Document 2] JP 2019-175806 A Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, when a charge / discharge cycle is performed on battery cells assembled into a battery pack (i.e., during "normal use"), in order to fully utilize the charge / discharge performance of the battery cells, it is necessary to maintain the temperature of the battery cell surface below a predetermined value (e.g., below 150°C). Furthermore, in the event of an abnormal event in which the battery cells reach a temperature of, for example, 200° C. or higher, it is necessary to effectively cool the battery cells. As described above, there has been a demand in recent years for further improvements in heat transfer suppression means that can maintain the temperature of the battery cell surface during normal use while also providing effective cooling in the event of an abnormal high temperature.

[0010] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a heat transfer suppression sheet for a battery assembly, which is used in a battery assembly in which multiple battery cells are connected in series or parallel, and which is capable of cooling each battery cell during normal use while suppressing the transfer of heat between the battery cells in the event of an abnormality, and a battery assembly. [Means for solving the problem]

[0011] The above object of the present invention can be achieved by the heat-transfer-suppressing sheet for a battery pack having the following configuration [1].

[0012] [1] A heat transfer-suppressing sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel and interposed between the battery cells, comprising: A heat insulating material containing at least one of inorganic particles and inorganic fibers; A covering material that covers at least a portion of the thermal insulation material, A sealed gap is formed between the heat insulating material and the covering material, the covering material is configured so that a communication opening is formed between the void portion and the outside of the covering material at a temperature of 60° C. or higher.

[0013] Further, preferred embodiments of the present invention relating to the heat transfer-suppressing sheet for a battery pack relate to the following [2] to [8].

[0014] [2] The heat transfer-suppressing sheet for a battery assembly according to [1], wherein at least one of the inorganic particles and the inorganic fibers contained in the insulating material contains a material that releases moisture when heated.

[0015] [3] The heat transfer-suppressing sheet for a battery assembly according to [1] or [2], wherein the insulating material and the covering material are bonded to each other with an adhesive that melts at a temperature of 60°C or higher.

[0016] [4] The heat transfer-suppressing sheet for a battery assembly according to any one of [1] to [3], wherein the covering material is made of a polymer film that melts at a temperature of 60° C. or higher.

[0017] [5] The heat transfer-suppressing sheet for a battery assembly according to any one of [1] to [3], wherein the covering material is made of a metal plate, and the insulating material and the covering material are bonded together with an adhesive that melts at a temperature of 60°C or higher.

[0018] [6] The heat transfer-suppressing sheet for a battery assembly according to any one of [1] to [3], wherein the covering material is made of metal plates, and the metal plates are bonded together with an adhesive that melts at a temperature of 60°C or higher.

[0019] [7] The heat transfer-suppressing sheet for a battery assembly according to any one of [3], [5], and [6], wherein a plurality of adhesives having different melting temperatures are used in the plurality of regions so that the adhesive melts gradually in the plurality of regions as the temperature increases.

[0020] [8] The heat transfer-suppressing sheet for a battery assembly according to any one of [3], [5], and [6], wherein the adhesive is applied to the multiple regions in different application amounts so that the adhesive melts in stages in the multiple regions as the temperature increases.

[0021] The above object of the present invention can be achieved by the following configuration [9] relating to a battery pack.

[0022] [9] An assembled battery in which a plurality of battery cells are connected in series or parallel, the assembled battery having the heat-transfer-suppressing sheet for a battery according to any one of [1] to [8] interposed between the battery cells. Effect of the Invention

[0023] The heat-transfer-suppressing sheet for a battery pack of the present invention is used in a battery pack in which multiple battery cells are connected in series or parallel, and has a sealed gap formed between the insulating material and the covering material. Therefore, during normal use of the battery pack, moisture that evaporates from the insulating material can be retained in the gap, and the heat of vaporization at this time can be used to effectively cool the battery cells. In addition, when an abnormality occurs in the battery pack, a communication hole is formed between the gap and the outside of the covering material, allowing heated steam to be released to the outside through the communication hole, thereby suppressing the transfer of heat between the battery cells.

[0024] The battery pack of the present invention has the above-mentioned heat transfer suppression sheet interposed between multiple battery cells, so that during normal use, each battery cell can be cooled, and in the event of an abnormality, the transfer of heat between the battery cells can be suppressed, preventing a chain reaction of thermal runaway. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a heat-transfer-suppressing sheet for a battery assembly according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view that typically shows a heat insulating material used in the heat-transfer-suppressing sheet for a battery assembly according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view that typically shows a battery assembly to which the heat-transfer-suppressing sheet for a battery assembly according to the first embodiment of the present invention is applied. [Figure 4] FIG. 4 is a cross-sectional view that typically shows the state of the heat-transfer-suppressing sheet for a battery assembly according to the first embodiment of the present invention when an abnormality occurs. [Diagram 5] FIG. 5 is a cross-sectional view that typically shows a heat-transfer-suppressing sheet for a battery assembly according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view that illustrates a heat-transfer-suppressing sheet for a battery assembly according to a third embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view that illustrates a heat-transfer-suppressing sheet for a battery assembly according to a fourth embodiment of the present invention. [Figure 8A] FIG. 8A is a cross-sectional view that typically shows a heat-transfer-suppressing sheet for a battery assembly according to a fifth embodiment of the present invention. [Figure 8B] FIG. 8B is a cross-sectional view that typically shows the state of the heat-transfer-suppressing sheet for a battery assembled according to the fifth embodiment of the present invention when an abnormality occurs. [Figure 9A]FIG. 9A is a cross-sectional view that typically shows a heat-transfer-suppressing sheet for a battery assembly according to a sixth embodiment of the present invention. [Figure 9B] FIG. 9B is a cross-sectional view that typically shows the state of the heat-transfer-suppressing sheet for a battery assembled in accordance with the sixth embodiment of the present invention when an abnormality occurs. [Figure 10] FIG. 10 is a plan view that typically shows another example of a heat insulating material used in the heat-transfer-suppressing sheets for a battery assembly according to the first to sixth embodiments of the present invention. [Figure 11] FIG. 11 is a plan view that typically shows still another example of a heat insulating material used in the heat-transfer-suppressing sheets for a battery assembly according to the first to sixth embodiments of the present invention. [Figure 12] FIG. 12 is a plan view that typically shows a heat-transfer-suppressing sheet for a battery assembly that uses two types of adhesives that have different melting temperatures. [Figure 13] FIG. 13 is a plan view that shows a schematic diagram of another example of a heat-transfer-suppressing sheet for a battery assembly in which two types of adhesives having different melting temperatures are used. [Figure 14] FIG. 14 is a plan view that shows a schematic diagram of still another example of a heat-transfer-suppressing sheet for a battery assembly that uses two types of adhesives having different melting temperatures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The inventors have conducted extensive research in order to provide a heat transfer suppression sheet for a battery pack that can suppress the transfer of heat between battery cells during abnormal conditions in which high-temperature heat is generated, while cooling each battery cell during normal use in which relatively low-temperature heat is generated.

[0027] As a result, the inventors discovered that the above problem can be solved by configuring the insulating material and the covering material so that during normal use, a sealed gap is formed between the insulating material and the covering material, and a communication opening is formed that connects the gap with the outside of the covering material at a temperature of 60°C or higher.

[0028] In other words, during normal use when the temperature of the battery cell is relatively low, the presence of the sealed gap allows the moisture that evaporates from the insulation material to remain in the gap, and the heat of vaporization generated during evaporation can be used to effectively cool the battery cell. In addition, in the event of an abnormality in which the temperature of the battery cells becomes high, a communication hole is formed that connects the gap with the outside of the covering material, and heated steam is released to the outside through the communication hole, thereby suppressing the transmission of heat between each battery cell.

[0029] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below, and can be modified and carried out as desired without departing from the gist of the present invention. In the following, the symbol "to" means that the range is equal to or greater than the lower limit and equal to or less than the upper limit.

[0030] [1. Heat transfer suppression sheet for battery packs] Hereinafter, the heat-transfer-suppressing sheet for a battery assembly according to the present embodiment will be described in order from the first embodiment to the sixth embodiment. After that, other examples of the heat-insulating material according to the present embodiment, and the heat-insulating material and covering material constituting the heat-transfer-suppressing sheet for a battery assembly according to the present embodiment will be described. Furthermore, a method for manufacturing the heat-transfer-suppressing sheet for a battery assembly according to the present embodiment will be described.

[0031] <First embodiment> Fig. 1 is a cross-sectional view that typically shows a heat-transfer-suppressing sheet for a battery assembly according to the first embodiment. Fig. 2 is a plan view that typically shows a heat insulating material used in the heat-transfer-suppressing sheet for a battery assembly according to the first embodiment. Hereinafter, the heat-transfer-suppressing sheet 10 for a battery assembly may simply be referred to as the heat-transfer-suppressing sheet 10. The heat-transfer-inhibiting sheet 10 for a battery assembly according to this embodiment has a thermal insulator 11 and a covering material 12 that covers the front surface 11a and back surface 11b, which are the main surfaces of the thermal insulator 11. In this embodiment, the covering material 12 does not cover the end surfaces 11c of the thermal insulator 11. Note that the front surface 11a and back surface 11b of the thermal insulator 11 refer to the surfaces that face the battery cells when the heat-transfer-inhibiting sheet 10 and the battery cells are stacked, as described below, and the end surfaces 11c refer to the four surfaces of the heat-transfer-inhibiting sheet 10 that are parallel to the thickness direction.

[0032] The heat insulating material 11 contains, for example, inorganic particles and inorganic fibers containing water of crystallization or water of adsorption, and the water of crystallization or water of adsorption has the property of releasing moisture when heated. As shown in Figures 1 and 2, a plurality of recesses 13a are regularly formed on the surface 11a of the heat insulating material 11, and the regions where the recesses 13a are not formed substantially constitute the protrusions 13b. The recesses 13a are, for example, rectangular in a plan view, and as shown in Figure 2, recesses whose longitudinal direction is parallel to one side of the insulation material 11 and recesses whose longitudinal direction is perpendicular to one side of the insulation material 11 are arranged alternately.

[0033] The covering material 12 is a polymer film that melts at a temperature of, for example, 60° C. or higher, and the protruding portion 13b of the heat insulating material 11 and the covering material 12 are bonded with an adhesive (not shown). In this embodiment, an adhesive made of an organic or inorganic substance is used, and this adhesive has the property of melting at a temperature of 60° C. or higher. The region where the recesses 13a are formed is not in contact with the covering material 12, and as a result, a gap 14 is formed between the insulating material 11 and the covering material 12. Furthermore, the protrusions 13b located around the gap 14 are bonded to the covering material 12, so that the gap 14 is always sealed at temperatures below 60°C.

[0034] 3 is a cross-sectional view showing a schematic diagram of a battery assembly to which the heat-transfer-suppressing sheet for a battery assembly according to the first embodiment is applied. The battery assembly 100 has a battery case 30, a plurality of battery cells 20 housed inside the battery case 30, and a heat-transfer-suppressing sheet 10 interposed between the battery cells 20. The plurality of battery cells 20 are connected in series or parallel by bus bars (not shown) or the like. The battery cell 20 is preferably, for example, a lithium ion secondary battery, but is not limited to this and may be other secondary batteries.

[0035] In the heat-transfer-suppressing sheet 10 thus configured, when the temperature rises in the relatively low-temperature region from room temperature (about 20° C.) to about 150° C., which is the temperature range of the battery cells 20 during normal use, heat is also transmitted to the insulating material 11. In this embodiment, the insulating material 11 contains inorganic particles containing water of crystallization or adsorbed water. Since water of crystallization or adsorbed water is a material that releases moisture when heated, when the insulating material 11 is heated, moisture evaporates from the inorganic particles. Some of the evaporated moisture then remains in the voids 14, and the other part is released from the end face 11c of the heat-transfer-suppressing sheet 10. At this time, the insulating material 11 is cooled by absorbing heat of vaporization, and the heat-transfer-suppressing sheet 10 can effectively cool the battery cells 20.

[0036] When the use of the battery pack 100 (i.e., charging and discharging) is stopped after the battery cells 20 have been effectively cooled, the water vapor that had been retained in the gaps 14 is cooled and turns into water droplets, which are absorbed into the insulating material 11 over time. Then, at the next use, the water in the insulating material 11 evaporates again, and the insulating material 11 loses heat of vaporization, cooling the battery cells 20, repeating this cycle.

[0037] 4 is a cross-sectional view that typically illustrates the state of the heat-transfer-suppressing sheet for a battery assembly according to the first embodiment when an abnormality occurs. Note that front surface 11a of thermal insulation material 11 illustrates a state in which part of covering material 12 has melted, and back surface 11b illustrates a state in which the adhesive that bonds covering material 12 to thermal insulation material 11 has melted due to an increase in temperature. 4, in the event of an abnormality, for example, when the temperature of battery cell 20 rises to 200° C. or higher, covering material 12 melts and communication opening 15 is formed that connects gap 14 to the outside. Even when covering material 12 that does not melt at high temperatures is used, communication opening 15 is formed that connects gap 14 to the outside of heat-transfer-suppressing sheet 10 when the adhesive melts.

[0038] When communication openings 15 are formed in this manner, the steam that evaporates from the inorganic particles and accumulates in voids 14 and becomes hot is released to the outside of heat-transfer-suppressing sheet 10 through communication openings 15. Therefore, even if a battery cell 20 causes thermal runaway, the transfer of heat between each battery cell 20 can be effectively suppressed.

[0039] The polymer film and adhesive used in this embodiment both have the property of melting at any temperature equal to or higher than 60° C. In other words, in a temperature range below the melting temperature of the polymer film and adhesive used, the gap 14 is always sealed. Since the polymer film and adhesive have various melting temperatures depending on the type, a polymer film or adhesive having a desired melting temperature in the range of 60° C. or higher can be selected as necessary.

[0040] The temperature at which a communication port that connects gap 14 to the outside of covering material 12 is formed is preferably 80° C. or higher, and more preferably 100° C. or higher. On the other hand, there is no particular upper limit to the temperature at which a communication hole is formed that connects the void portion 14 to the outside of the coating material 12, but it is preferably 500°C or less, more preferably 350°C or less, even more preferably 300°C or less, and particularly preferably 250°C or less.

[0041] <Second embodiment> FIG. 5 is a cross-sectional view that illustrates a heat-transfer-suppressing sheet for a battery assembly according to a second embodiment. 5 to 9B showing the second to sixth embodiments below, the same or equivalent parts as those in the first embodiment above are denoted by the same reference numerals in the drawings, and their description will be omitted or simplified. Furthermore, all of the embodiments shown below can be used in place of the heat-transfer-suppressing sheet 10 shown in the battery assembly 100 shown in FIG. 3, so the effects and the like will be described assuming that the heat-transfer-suppressing sheets according to the second to sixth embodiments are applied to the battery assembly 100.

[0042] A heat transfer-suppressing sheet 40 for a battery assembly according to the second embodiment has a thermal insulator 11 and a covering material 12 that covers a front surface 11a, a back surface 11b, and an end surface 11c of the thermal insulator 11. In this embodiment, a recess 13a and a protrusion 13b are also formed on the end surface 11c of the thermal insulator 11. That is, the covering material 12 formed in a bag shape with an adhesive or the like (not shown) covers the entire surface of the thermal insulator 11, and the thermal insulator 11 is completely sealed by the covering material 12.

[0043] The heat-transfer-suppressing sheet 40 configured in this manner can also provide the same effects as the first embodiment during normal use. In the second embodiment, the insulating material 11 is completely covered by the covering material 12. Therefore, when the insulating material 11 is heated during normal use and moisture evaporates from the inorganic particles, all of the evaporated moisture remains in the voids 14 and is not released to the outside from the heat-transfer-suppressing sheet 40. However, as the moisture evaporates, the insulating material 11 is cooled by absorbing heat of vaporization, and the heat-transfer-suppressing sheet 10 can effectively cool the battery cells 20.

[0044] Furthermore, in the second embodiment, since the evaporated water is not released to the outside, when the use of the battery pack is stopped, most of the evaporated water is reabsorbed into the insulating material 11. Therefore, the heat transfer-suppressing sheet 40 for a battery pack according to the second embodiment can maintain the effect of cooling the battery cells 20 for a long period of time.

[0045] Furthermore, in the event of an abnormality, the adhesive bonding the coating materials 12 together or the coating material 12 melts, forming a communication opening 15 between the gap 14 and the outside, as in the case shown in Figure 4, thereby obtaining the same effect as in the first embodiment.

[0046] <Third embodiment> FIG. 6 is a cross-sectional view that illustrates a heat-transfer-suppressing sheet for a battery assembly according to a third embodiment. A heat transfer-suppressing sheet 50 for a battery assembly according to the third embodiment has a thermal insulator 51 and a covering material 52 that covers a front surface 51a and a back surface 51b of the thermal insulator 51. In this embodiment, similar to the first embodiment, the covering material 52 does not cover an end surface 51c of the thermal insulator 51.

[0047] In the third embodiment, the surface of the heat insulating material 51 is flat, and no recesses or protrusions are formed. On the other hand, the covering material 52 is made of a film, and the surface thereof is textured, with recesses 53a and protrusions 53b formed on the surface facing the heat insulating material 51. The protrusions 53b of the covering material 52 and the heat insulating material 51 are bonded with an adhesive (not shown), and a sealed gap 14 is formed between the recesses 53a and the heat insulating material 51.

[0048] The heat-transfer-suppressing sheet 50 configured in this manner can also provide the same effects as the first embodiment during normal use and under abnormal conditions. By configuring the heat-transfer-suppressing sheet using the covering material 52 shown in the third embodiment to cover the entire surface of the insulating material 51, the effect of cooling the battery cells 20 can be maintained for a long period of time, as in the second embodiment.

[0049] <Fourth embodiment> FIG. 7 is a cross-sectional view that illustrates a heat-transfer-suppressing sheet for a battery assembly according to a fourth embodiment. A heat transfer-suppressing sheet 60 for a battery assembly according to the fourth embodiment includes a thermal insulator 11 and a covering material 52 covering the entire surface of the thermal insulator 11. In this embodiment, a recess 13a and a protrusion 13b are formed in the thermal insulator 11. The covering material also has, on its surface facing the thermal insulator 11, a recess 53a recessed in a direction away from the thermal insulator 11 and a protrusion 53b protruding toward the thermal insulator 11. The protrusion 53b of the covering material 52 and the protrusion 13b of the thermal insulator 11 are bonded together with an adhesive (not shown), and a sealed gap 14 is formed between the recess 53a of the covering material 52 and the recess 13a of the thermal insulator 11.

[0050] The heat-transfer-suppressing sheet 60 configured in this manner can also provide the same effects as the second embodiment described above during normal use and under abnormal conditions. Furthermore, because the recesses 13a and 53a form the gaps 14, the volume of the gaps 14 is larger than in the heat-transfer-suppressing sheets for a battery pack according to the second and third embodiments. This makes it easier for moisture to evaporate from the insulating material 11, and the effect of cooling the battery cells 20 during normal use can be further improved.

[0051] In the fourth embodiment, the covering material 52 is configured to cover the end face 11c of the heat insulating material 11, but as in the first embodiment, the end face 11c of the heat insulating material 11 may be open. By opening the end face 11c, part of the evaporated moisture is released to the outside during normal use, so that the moisture in the heat insulating material 11 can evaporate more easily, and the cooling effect by the heat of vaporization can be improved. Furthermore, even if a coating material 52 that does not melt at high temperatures is used in the event of an abnormality, when the adhesive melts, a communication opening 15 is formed that connects the gap 14 to the outside of the heat transfer suppression sheet 60, thereby achieving the effect of cooling the battery cell 20.

[0052] <Fifth embodiment> Fig. 8A is a cross-sectional view that shows a schematic diagram of a heat-transfer-reducing sheet for a battery assembly according to a fifth embodiment, and Fig. 8B is a cross-sectional view that shows a schematic diagram of a heat-transfer-reducing sheet for a battery assembly according to the fifth embodiment when an abnormality occurs. A heat transfer-suppressing sheet 70 for a battery assembly according to the fifth embodiment has a thermal insulator 11 and a covering material 72 that covers a front surface 11a and a back surface 11b of the thermal insulator 11. In this embodiment, unlike the first embodiment, a covering material (metal plate) 72 made of metal is used as the covering material. The protruding portion 13b of the thermal insulator 11 and the metallic covering material 72 are bonded with an adhesive (not shown), and a sealed gap portion 14 is formed between the recessed portion 13a of the thermal insulator 11 and the covering material 72.

[0053] The heat-transfer-suppressing sheet 70 thus configured can also provide the same effects as those of the first embodiment during normal use. 8B, in the event of an abnormality, the adhesive bonding protrusions 13b of thermal insulation material 11 to covering material 72 melts, causing covering material 72 to peel off from thermal insulation material 11. As a result, communication openings 15 are formed that connect gaps 14 to the outside of heat-transfer-suppressing sheet 70, allowing battery cells 20 to be cooled effectively.

[0054] Sixth embodiment Fig. 9A is a cross-sectional view that typically shows a heat-transfer-reducing sheet for a battery assembly according to a sixth embodiment, and Fig. 9B is a cross-sectional view that typically shows a state of the heat-transfer-reducing sheet for a battery assembly according to the sixth embodiment when an abnormality occurs. In a heat transfer-suppressing sheet 80 for a battery assembly according to the sixth embodiment, not only the front surface 11a and back surface 11b of the heat insulating material 11 but also the end surfaces 11c are covered with a metallic covering material (metal plate) 82. That is, in this embodiment, all of the surfaces of the heat insulating material 11, namely the front surface 11a, back surface 11b and the end surfaces 11c in all four directions, are covered with a plurality of covering materials 82, and the covering materials are also bonded together with an adhesive (not shown).

[0055] The heat-transfer-suppressing sheet 80 configured in this manner can also provide the same effects as those of the second embodiment during normal use. 9B, in the event of an abnormality, the adhesive bonding protrusions 13b of insulation 11 to covering material 82 melts, separating insulation 11 from covering material 82. At the same time, the adhesive bonding covering materials 82 together also melts, separating each covering material 82. This forms communication openings 15 that connect gaps 14 to the outside of heat-transfer-suppressing sheet 80, enabling battery cells 20 to be effectively cooled.

[0056] In the sixth embodiment, the front surface 11a, the back surface 11b and the end surface 11c of the heat insulating material 11 are covered with a plurality of covering materials 82, and the covering materials 82 are bonded together with an adhesive. However, the present invention may use a single metal sheet. For example, a heat insulating material 11 may be sandwiched between a single metal sheet folded in half, and the metal sheet covering the front surface 11a side of the heat insulating material 11 and the metal sheet covering the back surface 11b side of the heat insulating material 11 may be bonded together with an adhesive in the region where they contact each other near the end surface 11c. Even with this configuration, the same effect as in the sixth embodiment can be obtained.

[0057] The heat-transfer-suppressing sheets for a battery assembly according to the first to sixth embodiments have been described above in order. Next, other examples of the heat insulating material used in the heat-transfer-suppressing sheets for a battery assembly according to the first to sixth embodiments will be described.

[0058] <Other examples of insulation materials> Fig. 10 is a plan view showing a schematic diagram of another example of the heat insulating material used in the heat transfer-suppressing sheet for a battery assembly according to the first to sixth embodiments. Note that, although the first to sixth embodiments have been described above as examples in which the heat insulating material 11 shown in Fig. 2 is used, the shape of the heat insulating material is not particularly limited. As shown in FIG. 10, a plurality of recesses 13a are regularly formed on a surface 21a of a heat insulating material 21, and the regions where the recesses 13a are not formed substantially constitute protrusions 13b. In this embodiment, the recesses 13a are, for example, rectangular in plan view, and all of the recesses 13a are arranged such that the longitudinal direction thereof is parallel to one side of the thermal insulation material 21. The heat insulating material 21 configured in this manner can also be applied to the heat transfer-suppressing sheets for a battery assembly according to the first to sixth embodiments, and can provide the same effects as those of the first to sixth embodiments.

[0059] <More examples of insulation materials> FIG. 11 is a plan view that illustrates still another example of a heat insulating material used in the heat-transfer-suppressing sheets for a battery assembly according to the first to sixth embodiments. In the heat insulating material 11 shown in FIG. 2 and the heat insulating material 21 shown in FIG. 10, all of the recesses 13a are structured to be sealed with a covering material, but the present invention is not limited to this. 11, a plurality of recesses 13a are regularly formed on a surface 31a of the heat insulating material 31, and the area where the recesses 13a are not formed substantially constitutes a protrusion 13b. However, the recesses 13c formed in the vicinity of an end face 31c of the heat insulating material 31 reach the end face 31c of the heat insulating material 31.

[0060] For example, when the heat insulating material 11 in the first embodiment is replaced with the heat insulating material 31, the recesses 13c formed in the vicinity of the end face 31c of the heat insulating material 31 do not form a sealed gap. However, a sealed gap is formed between some of the recesses 13a and the covering material 12, so that the same effects as those of the first to sixth embodiments can be obtained.

[0061] Next, the heat insulating material, covering material, adhesive, and thickness of the heat-transfer-suppressing sheet that constitutes the heat-transfer-suppressing sheet for a battery pack according to this embodiment will be described in detail.

[0062] <Thermal insulation> The heat insulating material used in the heat transfer-suppressing sheet for a battery assembly according to this embodiment contains at least one of inorganic particles and inorganic fibers. The inorganic particles are preferably inorganic hydrates or water-containing porous bodies. When the inorganic hydrate receives heat from the battery cell 20 and reaches or exceeds the thermal decomposition starting temperature, it undergoes thermal decomposition and releases its own water of crystallization, thereby cooling the battery cell 20. After releasing the water of crystallization, the inorganic hydrate becomes a porous body, and the innumerable air holes provide effective heat insulation. In addition, as the inorganic particles, a single inorganic particle may be used, or two or more kinds of inorganic hydrate particles may be used in combination. Since the thermal decomposition start temperature differs depending on the type of inorganic hydrate, by using two or more kinds of inorganic hydrate particles in combination, the battery cell 20 can be cooled in multiple stages.

[0063] 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). Furthermore, examples of fibrous inorganic hydrates include fibrous calcium silicate hydrate.

[0064] Specific examples of the hydrous porous body include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, sepiolite, wet silica, dry silica, aerogel, mica, and vermiculite.

[0065] Further, examples of inorganic fibers include alumina fibers, silica fibers, alumina silicate fibers, rock wool, magnesium silicate fibers, alkaline earth silicate fibers, glass fibers, zirconia fibers, potassium titanate fibers, etc. Among these inorganic fibers, magnesium silicate fibers can be suitably used as a material that releases moisture when heated. As for the inorganic fibers, a single inorganic fiber may be used, or two or more kinds of inorganic fibers may be used in combination.

[0066] In addition to the inorganic particles and inorganic fibers, the heat insulating material may contain organic fibers, organic binders, etc., as necessary. These are all useful for the purpose of reinforcing the heat insulating material and improving its moldability.

[0067] The inorganic particles and inorganic fibers contained in the insulating material do not necessarily need to contain a material that releases moisture when heated. Since a small amount of moisture is inevitably contained during the manufacturing process of the insulating material, when the temperature of the battery cells 20 rises during normal use or under abnormal conditions, the moisture contained in the insulating material evaporates, thereby providing the effect of cooling the battery cells 20.

[0068] In this embodiment, the heat insulating material may contain at least one of inorganic particles and inorganic fibers, and the content of inorganic particles is preferably 20% by mass to 80% by mass, and the content of inorganic fibers is preferably 5% by mass to 70% by mass, relative to the total mass of the heat transfer-suppressing sheet. By setting the contents at such levels, the shape retention, pressure resistance, and wind pressure resistance can be improved by the inorganic fibers, and the retention ability of the inorganic particles can be ensured.

[0069] The heat-transfer-suppressing sheet according to the present embodiment may contain organic fibers, organic binders, and the like, as necessary. Any of these are useful for the purpose of reinforcing the heat-transfer-suppressing sheet and improving its formability.

[0070] <Coating material> The covering material may be a polymer film or a metal film (metal plate). Examples of polymer films include polyimide, polycarbonate, PET, p-phenylene sulfide, polyetherimide, crosslinked polyethylene, flame-retardant chloroprene rubber, polyvinyl denfluoride, rigid polyvinyl chloride, polybutylene terephthalate, PTFE, PFA, FEP, ETFE, rigid PCV, flame-retardant PET, polystyrene, polyethersulfone, polyamideimide, polyacrylonitrile, polyethylene, polypropylene, and polyamide.

[0071] In the present invention, the covering material is configured so that a communication opening that connects the gap with the outside of the covering material is formed at a temperature of 60° C. or higher. As described above, the communication opening may be formed when the polymer film used as the covering material melts, or when the adhesive that bonds the covering materials together or the covering material and the insulating material melts. To form a communication opening that connects the gap with the outside of the covering material at a temperature of 60° C. or higher, for example, the polymer film may be melted at any temperature of 60° C. or higher. Since the melting point of the polymer film is 60° C. to 600° C., the covering material (polymer film) can always seal the gap at a temperature below 60° C., and can form a communication opening at any temperature of 60° C. or higher.

[0072] In this embodiment, when a polymer film is used as the covering material, the melting temperature of the polymer film is preferably 60° C. or higher, more preferably 80° C. or higher, and even more preferably 100° C. or higher. On the other hand, the melting temperature of the polymer film is preferably 500° C. or lower, more preferably 350° C. or lower, further preferably 300° C. or lower, and particularly preferably 250° C. or lower.

[0073] Examples of the metal film include aluminum foil, stainless steel foil, and copper foil.

[0074] <Adhesive> In this embodiment, a method of bonding the insulating material and the covering material, or a method of bonding covering materials together, can be applied as a method of sealing the gap formed between the insulating material and the covering material. Adhesives for bonding the insulating material and the covering material include those made from raw materials such as urethane, polyethylene, polypropylene, polystyrene, nylon, polyester, vinyl chloride, vinylon, acrylic resin, and silicone. The adhesive can also be used to bond coating materials together.

[0075] In this embodiment, even if a covering material that does not melt at temperatures of 60° C. or higher is used, it is sufficient that the melting temperature of the adhesive that bonds the covering materials together or the covering material to the insulating material is 60° C. or higher. In other words, if the adhesive melts at a temperature of 60° C. or higher, the covering material can always seal the gap at a temperature below 60° C., and can form a communication opening that communicates the gap with the outside of the covering material at any temperature of 60° C. or higher.

[0076] In this case, the melting temperature of the adhesive is preferably 60° C. or higher, more preferably 80° C. or higher, and even more preferably 100° C. or higher. On the other hand, the melting temperature of the adhesive is preferably 500° C. or lower, more preferably 350° C. or lower, further preferably 300° C. or lower, and particularly preferably 250° C. or lower.

[0077] As a method for sealing the gap formed between the insulating material and the covering material, a method of covering the entire insulating material with the covering material can also be applied. Methods for covering the entire heat insulating material with a covering material include lamination (dry lamination, thermal lamination), pouch lamination, vacuum packing, vacuum lamination, shrink packaging, caramel packaging, and the like.

[0078] Note that, as adhesives for bonding the insulating material and the covering material, or bonding covering materials together, a plurality of adhesives having different melting temperatures may be used so that they melt stepwise in a plurality of regions as the temperature rises. An example of using a plurality of adhesives will be described below with reference to the drawings. Note that the examples shown in the following Figs. 12 to 14 are modified versions of the heat-transfer-suppressing sheet 10 for a battery assembly according to the first embodiment shown in Figs. 1 and 2.

[0079] FIG. 12 is a plan view that typically shows a heat-transfer-suppressing sheet for a battery assembly that uses two types of adhesives that have different melting temperatures. 12, in the heat-transfer-suppressing sheet 110 for a battery pack, adhesive 16b is used in the peripheral portion near the end face of the region of the protruding portion 13b of the thermal insulation material 11, and adhesive 16a is used in the region inside the peripheral portion. The adhesives 16a and 16b have different melting temperatures, and specifically, the melting temperature of adhesive 16b is designed to be higher than the melting temperature of adhesive 16a. The melting temperature of the covering material is also designed to be higher than the melting temperature of adhesive 16b.

[0080] In heat-transfer-suppressing sheet 110 configured in this manner, in the first stage, the gaps between each recess 13a and the covering material are sealed at a temperature below the melting temperature of adhesive 16a. Therefore, when heat insulating material 11 is heated and moisture evaporates from the inorganic particles, all of the evaporated moisture remains in the gaps and is not released to the outside from heat-transfer-suppressing sheet 110, but the evaporation of the moisture removes heat of vaporization from heat insulating material 11, causing it to cool.

[0081] Then, in the second stage, when the temperature of the battery cells rises further and reaches or exceeds the melting temperature of adhesive 16a but falls below the melting temperature of adhesive 16b, the areas that were bonded by adhesive 16a are separated and the volume of the voids increases, making it easier for moisture to evaporate from thermal insulation material 11. In addition, the heated steam does not remain in a fixed position but can move over a wider area than in the first stage, allowing heat-transfer-suppressing sheet 110 to effectively cool the battery cells.

[0082] Furthermore, after that, in the third stage, when the temperature of the battery cells reaches or exceeds the melting temperature of adhesive 16b, the area bonded by adhesive 16b is separated, and a communication port is formed that connects the gap to the outside of heat-transfer-suppressing sheet 110. As a result, the high-temperature steam that has been retained inside the area of ​​adhesive 16b is released all at once. Therefore, even if a battery cell causes thermal runaway, the transfer of heat between the battery cells can be effectively suppressed.

[0083] FIG. 13 is a plan view that shows a schematic diagram of another example of a heat-transfer-suppressing sheet for a battery assembly in which two types of adhesives having different melting temperatures are used. 13, in heat-transfer-suppressing sheet 120, adhesive 16b with a higher melting temperature is used on the peripheral portion of the region of protrusion 13b of thermal insulation material 11, similar to heat-transfer-suppressing sheet 110 shown in Fig. 12. However, in only a portion of the peripheral portion, adhesive 16a with a lower melting temperature, which is the same as that used in the inner region, is used.

[0084] In heat-transfer-suppressing sheet 120 configured in this manner, in the first stage, the gap between recess 13a and covering material 12 is sealed at a temperature below the melting temperature of adhesive 16a. Therefore, similar to heat-transfer-suppressing sheet 110 shown in Fig. 12, moisture evaporates from heat insulating material 11 toward the gap, and heat insulating material 11 is cooled by absorbing heat of vaporization.

[0085] Then, in the second stage, when the temperature of the battery cells rises further and reaches or exceeds the melting temperature of adhesive 16a, the areas that were bonded by adhesive 16a are separated, making it easier for moisture to evaporate from thermal insulation material 11. Also, because adhesive 16a, which has a low melting temperature, is used only in a portion of the periphery, this area becomes a communication port that connects the gap with the outside of heat-transfer-suppressing sheet 110. Therefore, as shown by the arrows in Fig. 13, high-temperature steam is released from the communication port, making it possible to effectively suppress the transfer of heat between battery cells.

[0086] As shown in Fig. 13, if adhesive 16a with a lower melting temperature is used only in a part of the periphery as in the inner region, the position from which high-temperature steam (moisture) is released can be easily controlled, and thus it is possible to prevent water from reaching certain parts in the battery pack.

[0087] FIG. 14 is a plan view that shows a schematic diagram of still another example of a heat-transfer-suppressing sheet for a battery assembly that uses two types of adhesives having different melting temperatures. As shown in Fig. 14, in the heat-transfer-suppressing sheet 130, similar to the heat-transfer-suppressing sheet 120 shown in Fig. 13, adhesive 16b having a high melting temperature is used in the peripheral portion of the region of the protrusion 13b of the thermal insulation material 11. However, adhesive 16a having a low melting temperature is used only in a part of the peripheral portion, and this region becomes a communication port at high temperatures. Also, adhesive 16c having the same melting temperature as adhesive 16b is used in a region spaced a predetermined distance from the peripheral portion on the inside of the region where adhesive 16b is used. Note that even in the region where adhesive 16c is used, adhesive 16a having a partially low melting temperature is used on the side opposite the region that becomes the communication port.

[0088] In the heat-transfer-inhibiting sheet 130 configured in this manner, in the first stage, similar to the heat-transfer-inhibiting sheet 120 shown in FIG. 13 above, moisture evaporates from the insulating material 11 toward the gap, and the insulating material 11 is cooled by the heat of vaporization being absorbed. Then, in the second stage, when the adhesive 16a melts, a moisture release path is formed as shown by the arrow in Fig. 14. As a result, the high-temperature steam moves along the release path and is released to the outside through the communication port, thereby further improving the cooling effect. The adhesives 16a, 16b, and 16c may all have different melting temperatures, and the areas in which each adhesive is used may be determined arbitrarily depending on the purpose.

[0089] As described above, the heat-transfer-suppressing sheets 110, 120, and 130 shown in FIGS. 12 to 14 are designed so that the adhesive melts in stages in multiple regions as the temperature of the battery cell increases. Therefore, it is possible to adjust the timing for releasing the steam accumulated in the gap, provide a steam release port at any position, and provide any release path.

[0090] In order to obtain the above-mentioned effect, the adhesive can be designed so that it melts in stages in multiple regions as the temperature increases. In addition to using adhesives having different melting temperatures, it is also possible to use a method in which the adhesive is applied in different amounts to multiple regions. 12 to 14, a case has been described in which the adhesive that bonds the heat insulating material 11 and the covering material melts in stages in a heat-transfer-suppressing sheet in which a covering material is bonded to the front and back sides of the heat insulating material 11, but the present invention is not limited to such a case. For example, even in a configuration in which the heat insulating material 11 is completely covered with a covering material, a method of adjusting the melting temperature or application amount of the adhesive depending on the region can be applied. Specifically, in a case in which the covering materials are bonded to each other near the end faces of the heat insulating material 11, the same effect as the heat-transfer-suppressing sheet 110 can be obtained by setting the melting temperature of the adhesive that bonds the covering materials to each other high and setting the melting temperature of the adhesive that bonds the heat insulating material 11 and the covering material low.

[0091] <Thickness of heat transfer suppression sheet> In this embodiment, the thickness of the heat-transfer-suppressing sheet is not particularly limited, but is preferably in the range of 0.05 to 6 mm. If the thickness of the heat-transfer-suppressing sheet is less than 0.05 mm, the heat-transfer-suppressing sheet cannot be provided with sufficient mechanical strength. On the other hand, if the thickness of the heat-transfer-suppressing sheet exceeds 6 mm, the molding of the heat-transfer-suppressing sheet itself may become difficult.

[0092] Next, a method for producing the heat-transfer-suppressing sheet for a battery assembly according to this embodiment will be described.

[0093] <Method of manufacturing heat transfer suppression sheet> The heat insulating material used in the heat transfer-suppressing sheet according to the present embodiment can be manufactured, for example, by molding a material containing at least one of inorganic particles and inorganic fibers by a dry molding method or a wet molding method. As the dry molding method, for example, a press molding method (dry press molding method) and an extrusion molding method (dry extrusion molding method) can be used.

[0094] (Method of manufacturing insulation material using dry press molding) In the dry press molding method, inorganic particles and inorganic fibers, and optionally organic fibers, organic binders, etc. are charged into a mixer such as a V-type mixer in a predetermined ratio. After the materials charged into the mixer are thoroughly mixed, the mixture is charged into a predetermined mold and press molded to obtain a heat insulating material. Heating may be performed during press molding as necessary. A heat insulating material having recesses and protrusions can be formed, for example, by a method of pressing the material using a mold having recesses and protrusions during press molding.

[0095] The pressing pressure during press molding is preferably in the range of 0.98 MPa to 9.80 MPa. If the pressing pressure is less than 0.98 MPa, the strength of the resulting insulating material cannot be ensured and it may collapse. On the other hand, if the pressing pressure exceeds 9.80 MPa, excessive compression may cause a decrease in processability, or the bulk density may increase, increasing solid heat transfer and decreasing insulating properties.

[0096] When the dry press molding method is used, it is preferable to use an ethylene-vinylacetate copolymer (EVA) as the organic binder, but there are no particular limitations as long as it is an organic binder that is generally used when the dry press molding method is used.

[0097] (Method of manufacturing insulation material using dry extrusion molding) In the dry extrusion molding method, water is added to inorganic particles and inorganic fibers, and if necessary, organic fibers and organic binders as binding materials, and the mixture is kneaded in a kneader to prepare a paste. The paste obtained is then extruded from a slit-shaped nozzle using an extrusion molding machine, and further dried to obtain a heat insulating material. When using the dry extrusion molding method, it is preferable to use methyl cellulose, water-soluble cellulose ether, etc. as the organic binder, but any organic binder that is generally used when using the dry extrusion molding method can be used without any particular limitation. In addition, as a method for producing an insulating material having concave and convex portions by dry extrusion molding, for example, a method can be mentioned in which the surface of a sheet extruded from a slit-shaped nozzle and before drying is cut into the desired concave and convex shape.

[0098] (Method of manufacturing insulation material using wet molding method) In the wet molding method, inorganic particles, inorganic fibers, and optionally an organic binder are mixed in water and stirred with a stirrer to prepare a mixture. The mixture is then poured into a molding machine with a filtering mesh on the bottom, and the mixture is dehydrated through the mesh to produce a wet sheet. The resulting wet sheet is then heated and pressurized to obtain a thermal insulation material. Prior to the heating and pressurizing step, a through-drying treatment may be carried out in which hot air is passed through the wet sheet to dry the sheet, but the sheet may also be heated and pressed in a wet state without carrying out this through-drying treatment. When a wet molding method is used, an acrylic emulsion using polyvinyl alcohol (PVA) can be selected as the organic binder. An example of a method for producing a heat insulating material having concave and convex portions by a wet molding method is a method in which a wet sheet is press molded using a mold having concaves and convexes before heating and pressurizing.

[0099] (Method of manufacturing coating material) As a method for producing a coating material having concave and convex portions, a general-purpose polymer film or a metal film produced to a desired thickness can be used, and a method of press molding using a mold having concave and convex portions can be mentioned.

[0100] (Method of manufacturing heat transfer suppression sheet) The heat-transfer-suppressing sheet according to this embodiment can be produced, for example, by applying an adhesive to the heat insulating material or covering material obtained as described above and adhering the heat insulating material and the covering material together. In addition, examples of methods for covering the entire insulation with a covering material include a method in which the insulation is sandwiched between two sheets of covering material cut to a size larger than the surface of the insulation, or between folded covering materials, and the covering materials are bonded together around the insulation by thermocompression or with an adhesive.

[0101] [2. Battery pack] The battery pack according to this embodiment is an assembled battery in which a plurality of battery cells are connected in series or parallel, and a heat-transfer-suppressing sheet for a battery pack according to this embodiment is interposed between the battery cells. Specifically, for example, as shown in Fig. 3, an assembled battery 100 has a plurality of battery cells 20 arranged side by side, connected in series or parallel, and housed in a battery case 30, and a heat-transfer-suppressing sheet 10 is interposed between the battery cells 20.

[0102] In such a battery pack 100, since the heat-transfer-suppressing sheets 10 are interposed between the battery cells 20, the battery cells 20 can be cooled during normal use. Furthermore, even if one of the multiple battery cells 20 experiences thermal runaway, becomes too hot, expands, or catches fire, the presence of the heat-transfer-suppressing sheet 10 according to this embodiment can suppress the transfer of heat between the battery cells 20. This makes it possible to prevent a chain reaction of thermal runaway, and minimize adverse effects on the battery cells 20. [Explanation of symbols]

[0103] 10,40,50,60,70,80,110,120,130 Heat transfer suppression sheet for battery packs 11,21,31,51 Insulation material 12,52,72,82 Covering material 13a, 13c, 53a Recess 13b,53b convex part 14 Cavity 15 Communication port 20 Battery Cells 30 Battery case 100 battery packs

Claims

1. A heat transfer-suppressing sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the heat transfer-suppressing sheet being interposed between the battery cells, A heat insulating material containing at least one of inorganic particles and inorganic fibers; A covering material that covers at least a portion of the thermal insulation material, A sealed gap is formed between the heat insulating material and the covering material, And the end surface of the heat insulating material is open, the covering material is configured so that a communication opening is formed between the void portion and the outside of the covering material at a temperature of 60° C. or higher.

2. 2 . The heat transfer-suppressing sheet for a battery assembly according to claim 1 , wherein at least one of the inorganic particles and the inorganic fibers contained in the heat insulating material includes a material that releases moisture when heated.

3. 3 . The heat transfer-suppressing sheet for a battery assembly according to claim 1 , wherein the insulating material and the covering material are bonded together with an adhesive that melts at a temperature of 60° C. or higher.

4. 4. The heat transfer-suppressing sheet for a battery assembly according to claim 1, wherein the covering material is made of a polymer film that melts at a temperature of 60° C. or higher.

5. 4. The heat transfer suppressing sheet for a battery assembly according to claim 1, wherein the covering material is made of a metal plate, and the insulating material and the covering material are bonded together with an adhesive that melts at a temperature of 60° C. or higher.

6. 4. The heat transfer suppressing sheet for a battery assembly according to claim 1, wherein the covering material is made of metal plates, and the metal plates are bonded to each other with an adhesive that melts at a temperature of 60° C. or higher.

7. 7. The heat transfer-suppressing sheet for a battery assembly according to claim 3, wherein a plurality of adhesives having different melting temperatures are used in the plurality of regions so that the adhesive melts stepwise in the plurality of regions as the temperature increases.

8. 7. The heat transfer-suppressing sheet for a battery assembly according to claim 3, wherein the adhesive is applied to the plurality of regions in mutually different application amounts so that the adhesive melts stepwise in the plurality of regions as a temperature increases.

9. 9. An assembled battery comprising a plurality of battery cells connected in series or parallel, the heat transfer-suppressing sheet for an assembled battery according to claim 1 being interposed between the battery cells.

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