Battery pack

Abstract

Provided is a battery pack capable of preventing moisture from entering a battery cell and preventing propagation of thermal runaway caused by high-temperature gas generated from an abnormal battery cell during thermal runaway.　A battery pack according to the present invention comprises a module having a plurality of battery cells each provided with a safety valve, a case for accommodating the module, and a heat insulating material provided between the module and the case. The battery pack is characterized in that: the heat insulating material includes a first heat insulating sheet, a second heat insulating sheet laminated on the first heat insulating sheet, and a seal member bonding the first heat insulating sheet and the second heat insulating sheet together; the heat insulating material is disposed such that the second heat insulating sheet is positioned on the module side and the first heat insulating sheet is positioned on the case side; the first heat insulating sheet includes, in a plan view of the heat insulating material, a plurality of covering portions respectively covering the plurality of safety valves and a body portion other than the covering portions; one of the covering portions is positioned so as to overlap with at least a part of one of the safety valves; the covering portion has a first cut portion formed along the contour of the covering portion and a second cut portion at least a part of which is located inside the contour of the covering portion; the second heat insulating sheet has a third cut portion formed to be continuous from a main surface on the first heat insulating sheet side to the other main surface; at least a part of the third cut portion is located inside the covering portion; and the seal member is disposed so as to overlap with at least a part of at least one cut portion selected from the group consisting of the first cut portion, the second cut portion, and the third cut portion.

Description

Battery pack

[0001] This invention relates to a battery pack.

[0002] In battery packs where modules containing multiple battery cells are housed in a case, high-temperature gases and flames can be generated during thermal runaway. These gases and flames can spread to the surrounding area, potentially inducing further thermal runaway. To prevent a chain reaction of thermal runaway, safety valves have traditionally been installed in the modules to release the high-temperature gases generated during thermal runaway.

[0003] Furthermore, to effectively prevent a chain reaction of thermal runaway, an opening is provided in the case, connecting the internal space of the battery pack to an external exhaust path. This allows the gas discharged from the safety valve to pass through the opening in the case and be vented to the external exhaust path.

[0004] As such a battery pack, Patent Document 1 discloses a battery pack characterized by comprising: at least one battery cell having a vent portion for discharging gas; and a pack case that houses the at least one battery cell such that the vent portion faces the lower part of the battery pack, and the vent portion is exposed to the outside of the battery pack.

[0005] Special Publication No. 2023-528515

[0006] In the battery pack described in Patent Document 1, the vent portion is exposed to the outside of the battery pack, so there is a risk that moisture from the outside may enter the inside of the battery pack. Patent Document 1 describes sealing the opening of the pack case that exposes the vent portion to the outside with a thin film in order to prevent moisture from entering.

[0007] This film is designed to rupture under a predetermined gas pressure, so it does not obstruct the release of gas to the outside during thermal runaway of a battery cell. However, if the film is susceptible to heat and impact, the film at the location corresponding to the vent of an adjacent battery cell may also rupture. If the film at the location corresponding to the vent of an adjacent battery cell ruptures in this way, gas backflow occurs, which can cause ignition (thermal chain reaction) in the adjacent battery cell. On the other hand, if the film is made of a material with high heat resistance and impact resistance, there is a problem that the film will not rupture during thermal runaway of a battery cell, preventing the release of gas into a safe space.

[0008] The present invention was made to solve the above problems, and aims to provide a battery pack that can prevent moisture from entering the battery cells and prevent a chain reaction of thermal runaway caused by high-temperature gases from abnormal battery cells that occur during thermal runaway.

[0009] The battery pack of the present invention comprises a module having a plurality of battery cells, each provided with a safety valve; a case housing the module; and a heat insulating material provided between the module and the case, wherein the heat insulating material includes a first heat insulating sheet, a second heat insulating sheet laminated on the first heat insulating sheet, and a sealing member for bonding the first heat insulating sheet and the second heat insulating sheet, and the heat insulating material is arranged such that the second heat insulating sheet is located on the module side and the first heat insulating sheet is located on the case side, and when the heat insulating material is viewed through a plane, the first heat insulating sheet has a plurality of covering portions that cover each of the plurality of safety valves, and The invention is characterized in that it consists of a main body portion other than the covering portion, one of the covering portions is positioned to overlap with at least a part of one of the safety valves, the covering portion has a first notch along the contour of the covering portion and a second notch which at least a part of which is inside the contour of the covering portion, the second heat insulating sheet has a third notch which is continuous from the main surface on the first heat insulating sheet side to the other main surface, at least a part of the third notch which is located inside the covering portion, and the sealing member is positioned to overlap with at least a part of at least one notch selected from the group consisting of the first notch, the second notch and the third notch.

[0010] The battery pack of the present invention can prevent a chain reaction of thermal runaway caused by high-temperature gases from abnormal battery cells that occur during thermal runaway. The principle is explained below.

[0011] In the battery pack of this invention, a safety valve is provided in the module. Therefore, when the battery cell experiences thermal runaway and generates high-temperature gas, the gas is discharged from the safety valve. The gas released from the safety valve then reaches the insulating material.

[0012] Since the second insulation sheet is located on the module side of the insulation material, the gas will pass through the third cut in the second insulation sheet and reach the first insulation sheet. At this time, the temperature and pressure of the gas will decrease to some extent.

[0013] The gas that reaches the first insulation sheet will come into contact with the covering portion of the first insulation sheet. In the battery pack of the present invention, the covering portion has a first notch along the contour of the covering portion and a second notch located inside the contour of the covering portion. When the gas comes into contact with the covering portion, the pressure causes the covering portion to separate from the main body along the first notch. At this time, the covering portion also separates into multiple parts along the second notch. In the battery pack of the present invention, the sealing member is arranged to overlap the first notch, the second notch, and the third notch, but the pressure of the gas causes the sealing member to break, and the covering portion also separates from the second insulation sheet.

[0014] The gas then passes through the area where the first insulation sheet was covering and is released between the insulation material and the case.

[0015] Furthermore, the gas released between the insulation material and the case reaches other covering parts of the first insulation sheet. However, the pressure of the gas released between the insulation material and the case prevents the other covering parts of the first insulation sheet from separating from the main body. Therefore, even if the gas reaches other covering parts of the first insulation sheet, the gas is blocked by the covering parts. This prevents the gas from flowing back through the safety valves of other battery cells.

[0016] Furthermore, the battery pack of the present invention can prevent moisture from entering the battery cells. The principle is explained below. The first, second, and third notches can serve as pathways for moisture from the outside into the battery cells. In the battery pack of the present invention, the sealing member is positioned to overlap with at least a portion of at least one notch selected from the group consisting of the first, second, and third notches. In other words, the sealing member blocks at least a portion of the first, second, and third notches, which serve as pathways for moisture. Therefore, the battery pack of the present invention can prevent moisture from entering the battery cells.

[0017] In the battery pack of the present invention, when the heat insulating material is viewed through from above, it is preferable that the sealing member is positioned so as to overlap the entirety of the first and second notches, or the entirety of the third notch. When the sealing member is positioned so as to overlap the entirety of the first and second notches, it is possible to prevent moisture from entering the battery cell side from the first heat insulating sheet. Furthermore, when the sealing member is positioned so as to overlap the entirety of the third notch, it is possible to prevent moisture from entering the battery cell side from the second heat insulating sheet.

[0018] In the battery pack of the present invention, when the heat insulating material is viewed through from above, it is preferable that the sealing member is arranged so as to overlap the entirety of the first cut portion, the second cut portion, and the third cut portion. By arranging the sealing member in this manner, the entirety of each cut portion, which serves as a passage for moisture, can be covered with the sealing member, thereby preventing moisture from entering through each cut portion.

[0019] In the battery pack of the present invention, it is preferable that the first cut portion, the second cut portion, and the third cut portion are formed such that they do not overlap when the insulating material is viewed through from above. If the first cut portion, the second cut portion, and the third cut portion overlap, the cut portions become continuous in the thickness direction of the insulating material. In this case, moisture can easily penetrate into the inside of the battery cell from the continuous cut portions. However, by forming the first cut portion, the second cut portion, and the third cut portion so that they do not overlap, it is possible to prevent moisture from penetrating into the inside of the battery cell.

[0020] Another embodiment of the present invention is a battery pack comprising: a module having a plurality of battery cells, each provided with a safety valve; a case housing the module; and a heat insulating material provided between the module and the case, wherein the heat insulating material includes a first heat insulating sheet, and when viewed from above, the first heat insulating sheet consists of a plurality of covering portions covering each of the plurality of safety valves and a main body portion other than the covering portions, one of the covering portions is positioned to overlap with at least a part of one of the safety valves, and the covering portion has a first notch along the contour of the covering portion and a second notch, at least a part of which is inside the contour of the covering portion, and the end face of at least a part of at least one notch selected from the group consisting of the first notch and the second notch is bonded by a sealing member.

[0021] In another embodiment of the present invention, a battery pack can prevent a chain reaction of thermal runaway caused by high-temperature gases from abnormal battery cells that occur during thermal runaway. The principle is explained below.

[0022] In the battery pack of the present invention, a safety valve is provided in the module. Therefore, when the battery cell experiences thermal runaway and generates high-temperature gas, the gas is discharged from the safety valve. The gas released from the safety valve then reaches the first heat insulating sheet.

[0023] The gas that reaches the first insulation sheet will come into contact with the covering portion of the first insulation sheet. In the battery pack of the present invention, the covering portion has a first notch along the contour of the covering portion and a second notch located inside the contour of the covering portion. When the gas comes into contact with the covering portion, the pressure causes the covering portion to separate from the main body along the first notch. At this time, the covering portion also separates into multiple parts along the second notch. In the battery pack of the present invention, at least a portion of the end face of at least one notch selected from the group consisting of the first notch and the second notch is bonded by a sealing member, but the sealing member breaks due to the pressure of the gas.

[0024] The gas then passes through the area where the first insulation sheet was covering and is released between the insulation material and the case.

[0025] Furthermore, the gas released between the insulation material and the case reaches other covering parts of the first insulation sheet. However, the pressure of the gas released between the insulation material and the case prevents the other covering parts of the first insulation sheet from separating from the main body. Therefore, even if the gas reaches other covering parts of the first insulation sheet, the gas is blocked by the covering parts. This prevents the gas from flowing back through the safety valves of other battery cells.

[0026] Furthermore, the battery pack of the present invention can prevent moisture from entering the battery cells. The principle is explained below. The first and second notches can serve as pathways for moisture from the outside into the battery cells. In the battery pack of the present invention, at least a portion of the end face of at least one notch selected from the group consisting of the first and second notches is bonded by a sealing member. In other words, the sealing member blocks at least a portion of the end faces of the first and second notches that serve as pathways for moisture. Therefore, the battery pack of the present invention can prevent moisture from entering the battery cells.

[0027] In the battery pack of the present invention, it is preferable that the entire end faces of the first and second notches are bonded together by the sealing member. By arranging the sealing member in this manner, the entire end faces of the notches, which serve as pathways for moisture, are sealed by the sealing member, thereby preventing moisture from entering through each notch.

[0028] In the battery pack of the present invention, the first heat insulating sheet is preferably at least one selected from the group consisting of mica sheets, heat-resistant resin sheets, inorganic fiber paper, and inorganic fiber cloth. These materials are suitable as the first heat insulating sheet from the viewpoint of heat resistance and strength.

[0029] In the battery pack of the present invention, the second heat insulating sheet is preferably at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth. Inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth can be easily molded and exhibit excellent performance as a second heat insulating sheet.

[0030] In the battery pack of the present invention, the plan view shape of the covering portion is preferably at least one selected from the group consisting of polygons, circles, ellipses, and racetrack shapes. Covering portions of such shapes can be easily formed.

[0031] In the battery pack of the present invention, it is preferable that the sealing member includes an adhesive. By using an adhesive, the first heat insulating sheet and the second heat insulating sheet can be bonded together while easily forming a sealing member that overlaps with the first cut portion, the second cut portion, and the third cut portion. Furthermore, by using an adhesive, the end faces of the first cut portion and the second cut portion can be easily bonded together.

[0032] In the battery pack of the present invention, it is preferable that the adhesive includes at least one selected from the group consisting of acrylic adhesives, silicone rubber adhesives, polyester adhesives, epoxy adhesives, polyolefin adhesives, polyamide adhesives, polyurethane adhesives, and synthetic rubber adhesives. These adhesives are water-resistant and make it easier to prevent moisture from entering the battery cells.

[0033] In the battery pack of the present invention, the case comprises a housing portion consisting of a bottom portion and a side wall portion, and a lid portion covering the housing portion, and it is preferable that the module is arranged such that the safety valve faces the bottom portion, the safety valve faces the side wall portion, or the safety valve faces the lid portion. In the battery pack of the present invention, the safety valve of the battery cell may face in any direction.

[0034] In the battery pack of the present invention, the case comprises a housing portion consisting of a bottom portion and side walls, and a lid portion covering the housing portion. The module is arranged such that the safety valve faces the bottom portion, and a plurality of openings are formed in the bottom portion. Preferably, when the bottom portion of the case is viewed from above, one of the openings is positioned to overlap with at least a portion of one of the safety valves. In such a battery pack, high-temperature gas from a malfunctioning battery cell can be released to the outside through the openings formed in the bottom portion of the case. In particular, since one of the openings is positioned to overlap with at least a portion of one of the safety valves, high-temperature gas from a malfunctioning battery cell is quickly released to the outside. Furthermore, if openings are formed in the bottom portion of the case, moisture can easily enter the battery pack from the outside. However, as described above, the battery pack of the present invention has a sealing member, so it is possible to prevent moisture from entering the inside of the battery cell from the outside of the battery pack.

[0035] In the battery pack of the present invention, the case comprises a housing portion consisting of a bottom portion and a side wall portion, and a lid portion covering the housing portion. The module is arranged such that the safety valve faces the side wall portion, and a plurality of openings are formed in the side wall portion. Preferably, when the side wall portion of the case is viewed from above, one of the openings is positioned to overlap with at least a portion of one of the safety valves. In such a battery pack, high-temperature gas from a faulty battery cell can be released to the outside through the openings formed in the side wall portion of the case. In particular, since one of the openings is positioned to overlap with at least a portion of one of the safety valves, high-temperature gas from a faulty battery cell is quickly released to the outside. Furthermore, if openings are formed in the side wall portion of the case, moisture can easily enter the battery pack from the outside. However, as described above, the battery pack of the present invention has a sealing member, so it is possible to prevent moisture from entering the inside of the battery cell from the outside of the battery pack.

[0036] According to the present invention, it is possible to provide a battery pack that can prevent moisture from entering the battery cells and can prevent a chain reaction of thermal runaway caused by high-temperature gases from abnormal battery cells that occur during thermal runaway.

[0037] Figure 1A is a schematic perspective view showing an example of a battery pack according to the first embodiment of the present invention. Figure 1B is a cross-sectional view taken along line A-A in Figure 1A. Figure 1C is an exploded view of the battery pack shown in Figure 1A. Figure 1D is a plan view of the battery pack shown in Figure 1A, viewed from the bottom. Figure 2 is a schematic cross-sectional view showing an example of a safety valve and its vicinity in a battery pack according to the first embodiment of the present invention. Figure 3A is an exploded view showing an example of an insulating material in a battery pack according to the first embodiment of the present invention. Figure 3B is a plan perspective view of the insulating material shown in Figure 3A, viewed from the first insulating sheet material side. Figure 4A is an explanatory diagram illustrating the principle by which a chain reaction of thermal runaway is prevented when one battery cell experiences thermal runaway in a battery pack according to the first embodiment of the present invention. Figure 4B is an explanatory diagram illustrating the principle by which a chain reaction of thermal runaway is prevented when one battery cell experiences thermal runaway in a battery pack according to the first embodiment of the present invention. Figure 4C is an explanatory diagram illustrating the principle by which a chain reaction of thermal runaway is prevented when one battery cell experiences thermal runaway in a battery pack according to the first embodiment of the present invention. Figure 5A is a schematic plan perspective view of the heat insulating material, illustrating another example of the arrangement position of the seal portion in the battery pack according to the first embodiment of the present invention. Figure 5B is a schematic plan perspective view of the heat insulating material, illustrating another example of the arrangement position of the seal portion in the battery pack according to the first embodiment of the present invention. Figure 5C is a schematic plan perspective view of the heat insulating material, illustrating another example of the arrangement position of the seal portion in the battery pack according to the first embodiment of the present invention. Figure 6A is a schematic perspective view illustrating an example of a battery pack according to the second embodiment of the present invention. Figure 6B is a cross-sectional view taken along line B-B in Figure 6A. Figure 6C is an exploded view of the battery pack shown in Figure 6A. Figure 6D is a plan view of the battery pack shown in Figure 6A, viewed from the bottom. Figure 7 is a schematic cross-sectional view illustrating an example of a safety valve and its vicinity in a battery pack according to the second embodiment of the present invention. Figure 8 is a plan view of an example of the heat insulating material in a battery pack according to the second embodiment of the present invention.

[0038] Hereinafter, the battery pack of the present invention will be specifically described. However, the present invention is not limited to the following configuration, and can be appropriately modified and applied without changing the gist of the present invention. Note that the present invention also includes any combination of two or more individual preferable configurations of the present invention described below.

[0039] (First Embodiment) A battery pack according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a perspective view schematically illustrating an example of the battery pack according to the first embodiment of the present invention. FIG. 1B is a cross-sectional view taken along line A-A of FIG. 1A. FIG. 1C is an exploded view of the battery pack illustrated in FIG. 1A. FIG. 1D is a plan view of the battery pack illustrated in FIG. 1A as seen from the bottom.

[0040] The battery pack 10 illustrated in FIGS. 1A to 1D includes a module 20 having a plurality of battery cells 21 each provided with a safety valve 22, and a case 30 that accommodates the module 20.

[0041] As illustrated in FIGS. 1A and 1B, the case 30 includes a housing portion 31 including a bottom portion 31b and a side wall 31s, and a lid portion 32 that covers the housing portion 31, and the module 20 is accommodated in the housing portion 31. Further, in the battery pack 10, a heat insulating material 40 is provided between the module 20 and the case 30.

[0042] As illustrated in FIGS. 1B and 1C, the module 20 is arranged such that the safety valve 22 faces toward the bottom 31b side, and a plurality of openings 33 are formed in the bottom 31b. As illustrated in FIG. 1D, when the bottom 31b of the housing portion 31 is viewed in plan, one opening 33 is positioned so as to overlap with one safety valve 22. As will be described later in detail, when the battery cell 21 undergoes thermal runaway and high-temperature gas is generated, the gas is discharged from the safety valve 22. When the opening 33 is positioned so as to overlap with the safety valve 22, the high-temperature gas is rapidly discharged to the outside of the case 30 through the opening 33.

[0043] The battery cell 21 stores electric power, and is preferably, for example, a rechargeable so-called secondary battery. Examples of the secondary battery include a lithium ion battery, a nickel hydrogen battery, a sodium ion battery, and the like. The battery cell 21 shown in FIGS. 1B and 1C has a rectangular parallelepiped shape. In the battery pack of the present invention, the battery cell may have a three-dimensional shape other than a rectangular parallelepiped shape (for example, a cubic shape, a deformed shape).

[0044] As shown in FIGS. 1B and 1C, in the module 20, the plurality of battery cells 21 are arranged in a line and fixed by the connecting module member 20a. Further, as shown in FIG. 1C, the battery cell 21 has a terminal 23, and adjacent battery cells 21 are electrically connected in that each terminal 23 is connected by a bus bar 20b disposed on the connecting module member 20a.

[0045] The bus bar 20b is a flat plate-shaped member made of metal and having electrical conductivity. Examples of the material of the bus bar 20b include copper, copper alloy, stainless steel (SUS), and aluminum. The bus bar 20b may be fixed to the terminal 23 by any fixing means (for example, screwing, welding, or the like).

[0046] Examples of the material forming the case 30 include steel, aluminum, and the like. As the steel material, stainless steel (SUS) is preferable.

[0047] FIG. 2 is a cross-sectional view schematically illustrating an example of one safety valve and the vicinity thereof in the battery pack according to the first embodiment of the present invention. As shown in FIG. 2, the heat insulating material 40 includes a first heat insulating sheet 41, a second heat insulating sheet 42 laminated on the first heat insulating sheet 41, and a sealing member 43 that bonds the first heat insulating sheet 41 and the second heat insulating sheet 42. The heat insulating material 40 is disposed such that the first heat insulating sheet 41 is located on the case 30 side, and the second heat insulating sheet 42 is located on the module 20 side.

[0048] As shown in Figure 2, the first heat insulating sheet 41 consists of a covering portion 41a that covers the safety valve 22 and a main body portion 41b other than the covering portion 41a. The covering portion 41a is positioned so as to overlap with a part of the safety valve 22. The covering portion 41a has a first cut portion 51 along the contour of the covering portion 41a and a second cut portion 52 located inside the contour of the covering portion 41a.

[0049] The second insulation sheet 42 has a third cutout 53 that extends from the main surface on the side of the first insulation sheet 41 (the lower main surface in Figure 2) to the other main surface (the upper main surface in Figure 2).

[0050] Here, the configuration of the insulation material 40 will be explained with reference to the drawings. Figure 3A is a schematic exploded view showing an example of the insulation material of a battery pack according to the first embodiment of the present invention. Figure 3B is a plan perspective view of the insulation material shown in Figure 3A, as seen from the first insulation sheet material side.

[0051] As shown in Figure 3A, in the thermal insulation material 40, the sealing member 43 has a sheet-like shape and is placed over the entire surface of the first thermal insulation sheet 41 and the second thermal insulation sheet 42.

[0052] As shown in Figures 3A and 3B, the first heat insulating sheet 41 consists of a covering portion 41a that covers the safety valve and a main body portion 41b other than the covering portion 41a. The covering portion 41a also has a first notch 51 that follows the contour of the covering portion 41a and a second notch 52 that is inside the contour of the covering portion 41a.

[0053] The covering portion 41a is racetrack-shaped, and the second notch portion 52 is cross-shaped, overlapping with the long and short axes of the racetrack-shaped covering portion 41a.

[0054] Furthermore, as shown in Figures 3A and 3B, when the insulation material 40 is viewed from above, the third notch 53 is located inside the covering portion 41a. More specifically, the third notch 53 is formed linearly in the direction along the long axis of the covering portion 41a, in the center of a part of the covering portion 41a that is divided into four by the second notch 52. Note that the third notch 53 does not intersect with the first notch 51 and the second notch 52. In other words, the first notch 51, the second notch 52, and the third notch 53 are formed so that when the insulation material 40 is viewed from above, the first notch 51, the second notch 52, and the third notch 53 do not overlap.

[0055] As described above, since the sealing member 43 has a sheet-like shape, when the heat insulating material 40 is viewed through from above, the sealing member 43 is positioned to overlap with the entirety of the first cut portion 51, the second cut portion 52, and the third cut portion 53.

[0056] The battery pack 10 can prevent a chain reaction of thermal runaway caused by high-temperature gases from abnormal battery cells that occur during thermal runaway. The principle is explained below.

[0057] Figures 4A to 4C are explanatory diagrams illustrating, in order, the principle by which a chain reaction of thermal runaway is prevented when one battery cell experiences thermal runaway in a battery pack according to the first embodiment of the present invention.

[0058] As shown in Figure 4A, when the battery cell 21 experiences thermal runaway and generates high-temperature gas (in Figure 4A, gas is indicated by the symbol "G," and the direction of gas flow is indicated by an arrow), the gas G is discharged from the safety valve 22. The gas G released from the safety valve 22 then reaches the insulation material 40.

[0059] Since the second insulation sheet 42 is located on the module 20 side of the insulation material 40, the gas G passes through the third cut portion 53 of the second insulation sheet 42 and reaches the first insulation sheet 41. At this time, the temperature and pressure of the gas G decrease to some extent.

[0060] The gas G that reaches the first insulation sheet 41 will come into contact with the covering portion 41a of the first insulation sheet 41. In the battery pack 10, the covering portion 41a has a first cut portion 51 along the contour of the covering portion 41a and a second cut portion 52 located inside the contour of the covering portion.

[0061] As shown in Figure 4B, when gas G hits the covering portion 41a, the pressure causes the covering portion 41a to separate from the main body portion 41b along the first notch 51. At this time, the covering portion 41a also separates into multiple parts along the second notch 52. In the battery pack 10, the sealing member 43 is positioned to overlap with the first notch 51, the second notch 52, and the third notch 53, but the pressure of gas G causes the sealing member 43 to break, and the covering portion 41a also separates from the second heat insulating sheet 42.

[0062] Then, the gas G passes through the area where the covering portion 41a of the first insulation sheet 41 was located and is released between the insulation material 40 and the case 30.

[0063] As shown in Figure 4C, some of the gas G released between the insulation material 40 and the case 30 reaches other covering portions 41a of the first insulation sheet 41. However, the pressure of the gas G released between the insulation material 40 and the case 30 prevents the other covering portions 41a of the first insulation sheet 41 from separating from the main body portion 41b. Therefore, even if the gas G reaches other covering portions 41a of the first insulation sheet 41, the gas G is blocked by the covering portions 41a. This prevents the gas G from flowing back through the safety valves 22 of other battery cells 21.

[0064] A portion of the gas G released between the insulation material 40 and the case 30 is released to the outside of the case 30 through an opening 33 formed in the bottom 31b of the case 30. This reduces the amount of gas G that reaches other covering parts 41a of the first insulation sheet 41, making it easier to prevent a chain reaction of thermal runaway.

[0065] The battery pack 10 can prevent moisture from entering the battery cells 21. The principle behind this is explained below.

[0066] In the battery pack 10, an opening 33 is formed in the bottom 31b of the case 30, making it easy for moisture from the outside to pass through the opening 33 and enter the inside of the battery pack 10. Such moisture will come into contact with the first insulation sheet 41 of the insulation material 40. The first cutout 51, second cutout 52, and third cutout 53 of the insulation material 40 can become pathways for such moisture from the outside. In other words, the first cutout 51, second cutout 52, and third cutout 53 can cause moisture to penetrate into the inside of the battery cell 21.

[0067] However, in the battery pack 10, the sealing member 43 is positioned to overlap the first notch 51, the second notch 52, and the third notch 53. In other words, the sealing member 43 blocks the first notch 51, the second notch 52, and the third notch 53, which would otherwise be pathways for moisture. Therefore, the battery pack 10 can prevent moisture from entering the battery cells 21.

[0068] Furthermore, in the battery pack 10, when the insulation material 40 is viewed through from above, the first notch 51 and the second notch 52 do not overlap with the third notch 53. If the first notch 51 and the second notch 52 and the third notch 53 overlap, the notches will be continuous in the thickness direction of the insulation material 40. In this case, moisture can easily penetrate into the inside of the battery cell 21 from the continuous notch area. However, in the battery pack 10, since the first notch 51 and the second notch 52 and the third notch 53 do not overlap, it is possible to prevent moisture from penetrating into the inside of the battery cell 21.

[0069] The area of ​​the plan view shape of the covering portion 41a is 1.0 to 18 cm². ２ Preferably, it is 3 to 12 cm ２ It is more preferable that the area of ​​the planar shape of the covered portion is 1.0 cm². ２ If it is less than 18 cm², the gas will have difficulty passing through the area where the covering portion 41a was located. ２ Beyond a certain point, the covered area tends to extend beyond the range the gas can reach. As a result, the covered area becomes less likely to separate from the main body.

[0070] In the battery pack 10, when the first heat insulating sheet 41 is viewed through from above, it is sufficient that one covering portion 41a overlaps with at least a part of one safety valve 22, but it is preferable that one covering portion 41a is positioned so that it fits inside the contour of one safety valve 22. When the covering portion 41a is positioned in this way, the gas released from the safety valve 22 can easily reach the covering portion 41a.

[0071] In the battery pack 10 described above, the sealing member 43 was in the form of a sheet and was arranged across the entire surface of the first heat insulating sheet 41 and the second heat insulating sheet 42. However, in the battery pack according to the first embodiment of the present invention, the sealing member does not have to be in the form of a sheet. Also, in the battery pack 10 described above, when the heat insulating material 40 was viewed through from above, the sealing member 43 was arranged to overlap with the entirety of the first cut portion 51, the second cut portion 52 and the third cut portion 53. However, in the battery pack according to the first embodiment of the present invention, the sealing member only needs to be arranged to overlap with at least a part of at least one cut portion selected from the group consisting of the first cut portion, the second cut portion and the third cut portion. An example of such a heat insulating material will be described below with reference to the drawings.

[0072] Figures 5A to 5C are schematic plan views of the heat insulating material, illustrating another example of the arrangement of the sealing portion in a battery pack according to the first embodiment of the present invention. In Figures 5A to 5C, the sealing member and the third notch are shown in a transparent view so that their arrangement can be understood.

[0073] The insulation material 40A shown in Figure 5A differs from the insulation material 40 in that the sealing member 43A is arranged in a strip shape along the first cut portion 51, the second cut portion 52, and the third cut portion 53. Even with the sealing member 43A arranged in this way, the covering portion 41a can be adhered to the second insulation sheet 42, and it is possible to prevent ingress into the battery cell 21 from the first cut portion 51, the second cut portion 52, and the third cut portion 53. In this case, the main body portion 41b and the second insulation sheet 42 may be adhered to each other at a different location with an adhesive or the like.

[0074] The insulating material 40B shown in Figure 5B differs from the insulating material 40 in that the sealing member 43B is arranged in a strip shape along the first notch 51 and the second notch 52. Even with the sealing member 43B arranged in this way, the covering portion 41a can be adhered to the second insulating sheet 42, and it is possible to prevent moisture from entering the inside of the battery cell 21 from the first notch 51 and the second notch 52. In other words, it is possible to prevent moisture from entering the battery cell 21 from the first insulating sheet 41. In this case, the main body portion 41b and the second insulating sheet 42 may be adhered to each other at a different location with an adhesive or the like.

[0075] The insulating material 40C shown in Figure 5C differs from the insulating material 40 in that the sealing member 43C is arranged in a strip shape along the third notch 53. Even with the sealing member 43C arranged in this way, the covering portion 41a can be adhered to the second insulating sheet 42, and it is possible to prevent moisture from entering the inside of the battery cell 21 from the third notch 53. In other words, it is possible to prevent moisture from entering the battery cell 21 from the second insulating sheet 42. In this case, the main body portion 41b and the second insulating sheet 42 may be adhered to each other with an adhesive or the like at another location.

[0076] In the battery pack 10 described above, the plan view shape of the covering portion 41a was racetrack-shaped. However, in the battery pack according to the first embodiment of the present invention, the plan view shape of the covering portion is not particularly limited and may be, for example, polygonal, circular, elliptical, etc.

[0077] In the battery pack 10 described above, the first notch 51 was formed along the entire contour of the covering portion 41a. However, in the battery pack according to the first embodiment of the present invention, the first notch may be formed along only a part of the contour of the covering portion, as long as the covering portion can separate from the main body when gas hits the covering portion. In other words, the covering portion and the main body may be connected in part.

[0078] In the battery pack 10 described above, the second notch 52 was formed in a cross shape. However, in the battery pack according to the first embodiment of the present invention, the second notch is formed inside the contour of the covering portion and is not particularly limited as long as it is formed in such a way that the covering portion is divided into two or more parts when gas strikes the covering portion. For example, if the plan view shape of the covering portion is a racetrack shape, the second notch may be formed along only the long axis of the covering portion, or along only the short axis of the covering portion, or multiple second notches may be formed parallel to the short axis of the covering portion.

[0079] In the battery pack according to the first embodiment of the present invention, the first notch and the second notch may or may not be in contact. Note that contact between the first notch and the second notch includes the case where the first notch and the second notch intersect. When the first notch and the second notch are in contact, the covering is more likely to be separated when gas hits the covering. When the first notch and the second notch are not in contact, the covering is less likely to be separated even if an external impact is applied to the covering. Therefore, even if an adjacent battery cell experiences thermal runaway and gas is released between the insulation material and the case, and the gas reaches the covering from the first insulation sheet side, the covering will not be separated, and gas backflow from the safety valve can be prevented. Whether or not to make the first notch and the second notch in contact is preferably designed appropriately according to the required performance and function.

[0080] In the battery pack 10 described above, the first notch 51 and the second notch 52 and the third notch 53 were formed so that they did not overlap when the insulating material 40 was viewed through from above. However, in the battery pack according to the first embodiment of the present invention, the first notch 51 and the second notch 52 and the third notch 53 may overlap. Even in this case, the sealing member 43 can prevent moisture from entering the battery cell 21, improving the design flexibility.

[0081] Next, preferred materials for the first heat insulating sheet in the battery pack according to the first embodiment of the present invention will be described.

[0082] The first insulation sheet is preferably at least one selected from the group consisting of mica sheets, heat-resistant resin sheets, inorganic fiber paper, and inorganic fiber cloth. These materials are suitable as the first insulation sheet from the viewpoint of heat resistance and strength.

[0083] Examples of resins that make up heat-resistant resin sheets include polybutylene terephthalate, polyamide, and polypropylene. These resins may also contain glass fibers or silica fibers as fillers.

[0084] Inorganic fiber paper is preferably given a thermal conductivity of less than 1 (W / m·K). The thermal conductivity can be measured in accordance with the "Test Method for Thermal Conductivity of Refractories" described in JIS R 2251.

[0085] The inorganic fibers that make up inorganic fiber paper include alumina fiber, carbon fiber, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, glass wool, slag wool, and SiO ２ At least one of the following can be used: fibers containing [unspecified material], silica fibers, mullite fibers, alumina silicate fibers, ceramic fibers, rock wool, alkali earth silicate fibers, zirconia fibers, silicon carbide fibers, magnesium silicate fibers, potassium titanate fibers, aerogel composites, and mineral fibers. These inorganic fibers have excellent heat resistance.

[0086] The inorganic fibers constituting the inorganic fiber paper preferably have an average fiber diameter of 1 to 20 μm, and more preferably 3 to 15 μm. Within this range, inorganic fiber paper can be manufactured without impairing moldability or processability.

[0087] The inorganic fibers constituting the inorganic fiber paper preferably have an average fiber length of 0.1 to 100 mm. Within this range, problems such as impaired moldability and processability due to an average fiber length that is too long, and a decrease in mechanical strength due to an average fiber length that is too short, are less likely to occur.

[0088] Furthermore, in addition to the inorganic fibers mentioned above (hereinafter also referred to as the first inorganic fibers), inorganic fibers with an average fiber diameter smaller than that of the first inorganic fibers (hereinafter referred to as the second inorganic fibers) may also be used. By using two inorganic fibers with different fiber diameters, the flexibility of the inorganic fiber paper can be improved, and the retention of other components, such as inorganic particles and organic particles, which will be described later, can be improved.

[0089] The average fiber diameter of the second inorganic fiber is preferably 1 nm or more and less than 1 μm, and more preferably 10 nm or more and 0.1 μm or less. Within this range, the second inorganic fiber can maintain flexibility while retaining mechanical strength.

[0090] Furthermore, the average fiber length of the second inorganic fiber is preferably less than 1 μm in order to avoid impairing moldability.

[0091] Furthermore, the inorganic fiber paper may also contain other components such as organic fibers, inorganic particles, organic particles, and resin binders.

[0092] The organic fibers contained in the inorganic fiber paper may be at least one selected from polyethylene terephthalate fibers, polybutylene terephthalate fibers, polytrimethylene terephthalate fibers, polyacetal fibers, polytetrafluoroethylene fibers, polyether ether ketone fibers, polyphenylene sulfide fibers, polyamide fibers, poly-p-phenylphthalamide fibers, polyvinyl alcohol fibers, polyethylene fibers, nylon fibers, polyurethane fibers, polypropylene fibers, and ethylene-vinyl alcohol copolymer fibers.

[0093] The average fiber length of the organic fibers is not particularly limited, but is preferably 0.5 to 10 mm. Within this range, sufficient compressive strength can be obtained without impairing the moldability or shape retention of the inorganic fiber paper.

[0094] The inorganic particles contained in the inorganic fiber paper can be materials with an average secondary particle diameter in the range of 0.01 to 200 μm. If the average secondary particle diameter is within this range, the material is readily available and the desired heat insulation effect can be obtained. Furthermore, it is preferable that the average secondary particle diameter of the inorganic particles is 0.05 to 100 μm.

[0095] Inorganic particles contained in inorganic fiber paper include oxide particles, nanoparticles, inorganic hydrate particles, particles made of thermally expandable inorganic materials, and water-containing porous materials.

[0096] The inorganic particles contained in the inorganic fiber paper may consist of two or more types of inorganic particles with different average secondary particle sizes. Since different sizes of inorganic particles result in different heat transfer suppression effects, heat transfer from the battery cell can be cooled in multiple stages, and a heat absorption effect can be achieved over a wide temperature range.

[0097] When the inorganic particles contained in inorganic fiber paper are oxide particles, at least one particle selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina can be used as the oxide particle. Because these oxide particles have a high refractive index, they can prevent radiant heat generated by thermal runaway of battery cells from propagating to adjacent cells or outside the battery pack.

[0098] When the inorganic particles contained in inorganic fiber paper are oxide particles, the average primary particle diameter of the oxide particles is preferably 1 to 50 μm in order to maximize the radiant heat shielding effect. The average primary particle diameter is determined by measuring the particle diameter of 10 arbitrary particles with a standard scale using a microscope and averaging the particle diameters of the measured 10 particles.

[0099] The nanoparticles that make up the inorganic particles contained in inorganic fiber paper have an average primary particle diameter of less than 1 μm. Nanoparticles have extremely low conductive heat transfer and excellent thermal insulation properties.

[0100] For example, if oxide particles are used as nanoparticles, even if the internal density increases due to compression of the inorganic fiber paper caused by expansion resulting from thermal runaway of the battery cell, the electrostatic repulsive force of the nanoparticles easily creates fine voids between the particles, and the particles are filled in a cushioning manner, thereby suppressing the increase in conductive heat transfer.

[0101] Silica nanoparticles are preferred as nanoparticles. Silica nanoparticles have high thermal insulation properties and are characterized by small contact points between particles, resulting in low heat conduction between particles. Therefore, using silica nanoparticles can further improve the thermal insulation properties of inorganic fiber paper. Wet silica, dry silica, aerogel, etc., can be used as silica nanoparticles.

[0102] The average primary particle size of the nanoparticles is preferably 1 to 100 nm. Within this range, convective and conductive heat transfer in the inorganic fiber paper can be suppressed in the temperature range during thermal runaway of the battery cell. Furthermore, even when compressive stress is applied to the inorganic fiber paper due to the expansion of the battery pack, the voids between the nanoparticles and the contact points between many particles suppress heat transfer in the inorganic fiber paper, maintaining the thermal insulation properties of the inorganic fiber paper. The average primary particle size of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. On the other hand, the average primary particle size of the nanoparticles is preferably 50 nm or less, and even more preferably 10 nm or less.

[0103] Examples of inorganic hydrate particles that make up the inorganic particles contained in inorganic fiber paper include particles of aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, manganese hydroxide, zirconium hydroxide, and gallium hydroxide. If the inorganic hydrate particles are as described above, they will start thermal decomposition in the thermal runaway environment of the battery cell and release crystalline water, thereby releasing heat from the heat source and suppressing a rapid temperature rise inside the battery pack.

[0104] Examples of particles made from thermally expandable inorganic materials that constitute the inorganic particles contained in inorganic fiber paper include vermiculite, bentonite, and perlite.

[0105] Examples of particles made of water-containing porous materials that constitute the inorganic particles contained in inorganic fiber paper include zeolite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

[0106] When an inorganic fiber paper contains a resin binder, its mechanical strength is improved. This allows the inorganic fiber paper to maintain its shape even when compressed due to the expansion of battery cells during thermal runaway, thereby suppressing the deterioration of its thermal insulation performance. Examples of resin binders that can be included in inorganic fiber paper include styrene-butadiene resin, acrylic resin, silicone-acrylic resin, and styrene resin.

[0107] Furthermore, the inorganic fiber paper may be an impact-absorbing material containing inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers. The average fiber diameter of the small-diameter fibers is preferably 0.2 times or less, more preferably 0.1 times or less, and even more preferably 0.05 times or less, than the average fiber diameter of the large-diameter inorganic fibers.

[0108] The effects of using such shock-absorbing materials will now be explained. If paper made of inorganic fibers without inorganic particle fragments is used as a shock-absorbing material, the inorganic fibers will break due to the impact of high-temperature crushed material, making it prone to damage from continuous impacts. In contrast, even when high-temperature crushed material impacts the above-mentioned shock-absorbing material, the impact is absorbed by the broad surface area of ​​the inorganic particle fragments. Therefore, it is possible to obtain the effect of suppressing damage to the shock-absorbing material and to prevent damage to the area in which the shock-absorbing material is placed.

[0109] The inorganic particle fragments preferably have the following predetermined size (shape). Specifically, when the length of the long side of the inorganic particle fragment is L1 and the length of the short side is L2, the length ratio R calculated by the formula L1 / L2 is preferably 20 or less, more preferably 15 or less, even more preferably 12 or less, and even more preferably 8 or less.

[0110] Examples of inorganic particle shapes include cylindrical, prismatic, flaky, plate-like, and flake-like shapes.

[0111] To obtain the above-mentioned effects from inorganic particle fragments, the inorganic particle fragment content is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on the total mass of the shock absorber. Furthermore, if the inorganic particle fragment content becomes too high, the content of large-diameter inorganic fibers and small-diameter fibers, described later, decreases, making it difficult to obtain the desired effects. Therefore, the inorganic particle fragment content is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, based on the total mass of the shock absorber.

[0112] Examples of inorganic particulate materials include boehmite, flaky silica, vermiculite, mica, plate-like alumina, wollastonite, talc, limestone, and kaolin. These materials possess heat resistance and high impact strength, thus providing high strength to the shock absorber. In particular, the use of wollastonite, talc, and mica is more preferable due to their heat resistance, quality stability, and cost.

[0113] Wollastonite has a short, rod-like form, for example, with an average diameter of about 5 μm and an average length of about 15 μm, and the length ratio R calculated by formula L1 / L2 is about 3. Talc, on the other hand, is flaky, with the length of the longer side of the two-dimensional surface being about 15 μm and the thickness being 1 μm, and the length ratio R calculated by formula L1 / L2 is about 15.

[0114] The average fiber diameter of the large-diameter inorganic fibers is preferably 1 μm or more, and more preferably 3 μm or more. However, if the large-diameter inorganic fibers are too thick, the moldability and processability of the shock-absorbing material may decrease, so the average fiber diameter of the large-diameter inorganic fibers is preferably 20 μm or less, and more preferably 15 μm or less.

[0115] The content of large-diameter inorganic fibers is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to the total mass of the shock absorber. However, if the content of large-diameter inorganic fibers becomes too high, the content of inorganic particle fragments decreases, making it difficult to obtain the desired effect. Therefore, the content of large-diameter inorganic fibers is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, relative to the total mass of the shock absorber.

[0116] Examples of large-diameter inorganic fiber materials include glass fibers, basalt fibers, silica fibers, alumina fibers, and alkali earth silicate (AES fibers). Of these inorganic fibers, it is more preferable to use at least one of alumina fibers, glass fibers, and basalt fibers, particularly from the viewpoint of heat resistance. It is also preferable to use at least one of glass fibers and basalt fibers from the viewpoint of availability and cost. When using basalt fibers as the large-diameter inorganic fiber, it is more preferable that the basalt fiber content be 5 to 35% by mass or less of the total mass of the impact absorber.

[0117] The average fiber diameter of the small-diameter fibers is preferably 1 μm or less, more preferably 0.8 μm or less, and even more preferably 0.5 μm or less. However, if the average fiber diameter of the small-diameter fibers is too small, they are prone to breakage and their ability to hold inorganic particle fragments decreases. Therefore, the average fiber diameter of the small-diameter fibers is preferably 1 nm or more, more preferably 10 nm or more, and even more preferably 50 nm or more.

[0118] The content of small-diameter fibers is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total mass of the shock absorber. However, if the content of small-diameter fibers becomes too high, the moldability of the shock absorber decreases, and the content of inorganic particles decreases, making it difficult to obtain the desired effect. Therefore, the content of small-diameter fibers is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, relative to the total mass of the shock absorber.

[0119] Examples of small-diameter fiber materials include cellulose fibers (including pulp fibers), sepiolite, attapulgite, and microglass fibers. In particular, the use of sepiolite is more preferable from the viewpoint of heat resistance.

[0120] The shock-absorbing material may also contain organic fibers.

[0121] When organic fibers are included in shock-absorbing materials, they form the framework of the material and increase its flexibility, thereby improving its strength and impact resistance. Furthermore, depending on their melting point, organic fibers can also be used as a binder. For example, when shock-absorbing materials are manufactured using a wet molding method, the wet paper strength is low after papermaking, which may cause the sheet to break before drying. Also, the outer surface of shock-absorbing materials may be covered by lamination. Therefore, it is preferable to use organic fibers to improve strength and adhesion to films.

[0122] The average fiber diameter of the organic fibers is preferably 3 to 30 μm. The average fiber length of the organic fibers is preferably 3 to 6 mm.

[0123] Examples of organic fibers include polyethylene terephthalate fibers, polypropylene fibers, polyethylene fibers, and polyvinyl alcohol fibers.

[0124] As for organic fibers, it is also preferable to use fibers with a core-sheath structure. An organic fiber with a core-sheath structure has a core portion extending in the longitudinal direction of the fiber and a sheath portion formed to cover the outer surface of the core portion. The core portion and the sheath portion are made of organic materials having different melting points, with the melting point of the organic material constituting the core portion being higher than that of the organic material constituting the sheath portion. When the shock absorber contains organic fibers with a core-sheath structure, the sheath portion functions as a binder that fuses the inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers together, and the core portion functions as a skeleton.

[0125] In an organic fiber with a core-sheath structure, the organic material constituting the core is not particularly limited, as long as its melting point is higher than that of the organic material constituting the sheath. For example, the organic material constituting the core can be at least one selected from polyethylene terephthalate, polypropylene, and nylon. The organic material constituting the sheath can be at least one selected from polyethylene terephthalate, polyethylene, polypropylene, and nylon.

[0126] The shock-absorbing material may further contain a resin binder.

[0127] When a resin binder is included in the shock-absorbing material, it is possible to bind inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers together, and to improve the strength and impact resistance of the shock-absorbing material.

[0128] The resin binder content is preferably 3% by mass or more, and more preferably 5% by mass or more, relative to the total mass of the shock absorber. However, if the resin binder content is too high, the heat resistance may decrease, so the resin binder content is preferably 35% by mass or less, and more preferably 25% by mass or less, relative to the total mass of the shock absorber.

[0129] Examples of resin binders include acrylic resins, vinyl acetate resins, phenolic resins, silicone resins, epoxy resins, styrene-butadiene resins, silicone-acrylic resins, and styrene resins. Of these resin binders, using a thermoplastic resin provides greater flexibility after molding compared to using a thermosetting resin, allowing it to be deformed into various shapes and positioned as desired. Therefore, it is more preferable to select a resin binder that includes at least one selected from acrylic resins, vinyl acetate resins, styrene-butadiene resins, silicone-acrylic resins, and styrene resins.

[0130] Inorganic fiber cloth is made by weaving inorganic fibers into a cross shape. Such inorganic fiber cloth has high strength and high heat resistance.

[0131] Examples of inorganic fibers that make up inorganic fiber cloth include silica fibers, alumina fibers, aluminosilicate fibers, ceramic fibers such as zirconia fibers, glass fibers, and basalt fibers. These inorganic fibers may be used individually or in mixtures of two or more types. For example, when producing inorganic fiber cloth, the warp and weft threads may be made of different types of inorganic fibers and then knitted together to form the inorganic fiber cloth.

[0132] When the first insulation sheet is a mica sheet or a heat-resistant resin sheet, the thickness of the first insulation sheet is preferably 0.05 to 2.0 mm, more preferably 0.1 to 1.0 mm, and even more preferably 0.1 to 0.5 mm. If the thickness of the first insulation sheet, which is made of a mica sheet or a heat-resistant resin sheet, is less than 0.05 mm, the strength of the first insulation sheet will be low and it will be easily damaged. If the thickness of the first insulation sheet, which is made of a mica sheet or a heat-resistant resin sheet, exceeds 2.0 mm, the first insulation sheet will be too thick, making it difficult to miniaturize the entire battery pack.

[0133] Furthermore, when the first insulation sheet is inorganic fiber paper, the thickness of the first insulation sheet is preferably 0.5 to 5.0 mm, and more preferably 0.8 mm to 3.0 mm. In this case, the first insulation sheet made of inorganic fiber paper can obtain sufficient mechanical strength.

[0134] Furthermore, when the first insulation sheet is an inorganic fiber cloth, the thickness of the first insulation sheet is preferably 0.1 to 5.0 mm, and more preferably 0.3 mm to 1.4 mm. In this case, both mechanical strength and flexibility of the first insulation sheet made of inorganic fiber cloth can be achieved. Therefore, the first insulation sheet made of inorganic fiber cloth can be bent to fit a predetermined shape and used.

[0135] Next, preferred materials for the second heat insulating sheet in the battery pack according to the first embodiment of the present invention will be described. The second heat insulating sheet is preferably at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth. Inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth can be easily molded and exhibit excellent performance as a second heat insulating sheet.

[0136] If the second insulation sheet is an inorganic fiber mat, the thickness of the inorganic fiber mat is preferably 0.5 to 10 mm, and more preferably 1 to 4 mm. If the thickness of the inorganic fiber mat is less than 0.5 mm, the inorganic fiber mat is thin, so when the gas passes through the inorganic fiber mat, the temperature of the gas does not decrease easily, and the gas pressure does not decrease easily either. As a result, the gas reaches the case quickly while still at a high temperature, making the case more prone to deterioration. If the thickness of the inorganic fiber mat exceeds 10 mm, the inorganic fiber mat becomes too thick, making it difficult to miniaturize the entire battery pack.

[0137] The bulk density of inorganic fiber mats is 0.1 to 1.0 g / cm³. ３ Preferably, it is 0.2 to 0.7 g / cm³. ３ It is more preferable that the bulk density of the inorganic fiber mat be 0.1 g / cm³. ３If the bulk density is less than the aforementioned value, the gaps between the inorganic fibers become large. Therefore, when gas passes through the inorganic fiber mat, the temperature of the gas is unlikely to decrease, and the gas pressure is also unlikely to decrease. As a result, the gas reaches the case vigorously while remaining at a high temperature, and the case is likely to deteriorate. If the bulk density of the inorganic fiber mat is 1.0 g / cm ３ 3, it becomes difficult for gas to pass through the inorganic fiber mat, and high-temperature gas remains in the battery cell, making it difficult for the temperature inside the battery cell to decrease. Therefore, a chain of thermal runaway is likely to occur.

[0138] The inorganic fiber mat is preferably obtained by processing into a mat shape inorganic fibers containing at least one fiber selected from the group consisting of silica fibers, glass fibers, alumina fibers, aluminosilicate fibers, basalt fibers, rock wool, and biosoluble fibers. An inorganic fiber mat made of such a material can be easily processed.

[0139] The inorganic fiber mat may be obtained by processing into a mat shape inorganic fibers including fibers having a melting point of 1000°C or higher. When the inorganic fiber mat contains fibers having a melting point of 1000°C or higher, the inorganic fibers have high heat resistance. Therefore, even if high-temperature gas from an abnormal battery cell reaches the inorganic fiber mat, the inorganic fiber mat is less likely to deteriorate.

[0140] The inorganic fiber mat may be obtained by processing into a mat shape inorganic fibers including fibers having a melting point of less than 1000°C. When the inorganic fiber mat contains fibers having a melting point of less than 1000°C, when high-temperature gas from an abnormal battery cell reaches the inorganic fiber mat, the inorganic fiber mat melts, and gas flow paths are easily formed.

[0141] Preferred embodiments of the inorganic fiber paper and inorganic fiber cloth constituting the second heat insulating sheet are the same as the preferred embodiments of the inorganic fiber paper and inorganic fiber cloth constituting the first heat insulating sheet.

[0142] Next, preferable materials for the sealing member in the battery pack according to the first embodiment of the present invention will be described. The type of the sealing member is not particularly limited as long as it can bond the first heat insulating sheet and the second heat insulating sheet, and for example, it may be a member including a double-sided adhesive sheet or an adhesive.

[0143] By using an adhesive, the first insulation sheet and the second insulation sheet can be bonded together while easily forming a sealing member that overlaps with the first, second, and third cutouts.

[0144] Examples of adhesives include acrylic adhesives, silicone rubber adhesives, polyester adhesives, epoxy adhesives, polyolefin adhesives, polyamide adhesives, polyurethane adhesives, and synthetic rubber adhesives.

[0145] (Second Embodiment) Next, a battery pack according to the second embodiment of the present invention will be described. The battery pack according to the second embodiment of the present invention differs from the battery pack according to the first embodiment of the present invention in that the heat insulating material does not include a second heat insulating sheet, and at least a portion of the end face of at least one cut portion selected from the group consisting of a first cut portion and a second cut portion formed in the first heat insulating sheet is bonded by a sealing member.

[0146] A battery pack according to this second embodiment of the present invention will be described below with reference to the drawings. Figure 6A is a schematic perspective view showing an example of a battery pack according to the second embodiment of the present invention. Figure 6B is a cross-sectional view taken along line B-B in Figure 6A. Figure 6C is an exploded view of the battery pack shown in Figure 6A. Figure 6D is a plan view of the battery pack shown in Figure 6A, viewed from the bottom.

[0147] The battery pack 110 shown in Figures 6A to 6D comprises a module 120 having a plurality of battery cells 121, each of which is provided with a safety valve 122, and a case 130 that houses the module 120.

[0148] As shown in Figures 6A and 6B, the case 130 comprises a housing section 131 consisting of a bottom section 131b and side walls 131s, and a lid section 132 that covers the housing section 131, with the module 120 housed in the housing section 131. In addition, in the battery pack 110, an insulating material 140 is provided between the module 120 and the case 130.

[0149] As shown in Figures 6B and 6C, the module 120 is positioned such that the safety valve 122 faces the bottom 131b, and multiple openings 133 are formed in the bottom 131b. As shown in Figure 6D, when the bottom 131b of the housing 131 is viewed from above, one opening 133 is positioned to overlap with one safety valve 122. If the battery cell 121 experiences thermal runaway and generates high-temperature gas, the gas is released from the safety valve 122. If the openings 133 are positioned to overlap with the safety valves 122, the high-temperature gas is quickly released from the openings 133 to the outside of the case 130.

[0150] As shown in Figures 6B and 6C, in module 120, multiple battery cells 121 are arranged in a row and fixed by a connecting module member 120a. Also, as shown in Figure 6C, each battery cell 121 has terminals 123, and adjacent battery cells 121 are electrically connected by busbars 120b located on the connecting module member 120a, with each terminal 123 connected to the busbar 120b.

[0151] In the battery pack 110, the preferred materials for the battery cell 121, busbar 120b, and case 130 are the same as the preferred materials for the battery cell 21, busbar 20b, and case 30 of the battery pack 10.

[0152] Figure 7 is a schematic cross-sectional view showing an example of a safety valve and its vicinity in a battery pack according to a second embodiment of the present invention. As shown in Figure 7, the heat insulating material 140 consists of a first heat insulating sheet 141. The first heat insulating sheet 141 consists of a covering portion 141a that covers the safety valve 122 and a main body portion 141b other than the covering portion 141a. The covering portion 141a is positioned to overlap with a part of the safety valve 122.

[0153] Figure 8 is a plan view of an example of a heat insulating material for a battery pack according to a second embodiment of the present invention. As shown in Figure 8, the first heat insulating sheet 141 consists of a covering portion 141a that covers the safety valve and a main body portion 141b other than the covering portion 141a. The covering portion 141a is formed with a first cut portion 151 along the contour of the covering portion 141a and a second cut portion 152 located inside the contour of the covering portion 141a.

[0154] The covering portion 141a is racetrack-shaped, and the second notch portion 152 is cross-shaped, overlapping with the long and short axes of the racetrack-shaped covering portion 141a.

[0155] In the battery pack 110, the entire end faces of the first notch 151 and the second notch 152 are bonded together by the sealing member 143.

[0156] Herein, the principle by which the battery pack according to the second embodiment of the present invention can prevent a chain reaction of thermal runaway caused by high-temperature gas from abnormal battery cells that occur during thermal runaway will be explained below.

[0157] In the battery pack 110, a safety valve 122 is provided in the module 120. Therefore, when the battery cell 121 experiences thermal runaway and generates high-temperature gas G, the gas G is discharged from the safety valve 122. The gas G released from the safety valve 122 then reaches the first insulation sheet 141.

[0158] When gas G reaches the first insulation sheet 141, it comes into contact with the covering portion 141a of the first insulation sheet 141. In the battery pack 110, the covering portion 141a has a first notch 151 along the contour of the covering portion 141a and a second notch 152 located inside the contour of the covering portion 141a. When gas G comes into contact with the covering portion 141a, the pressure causes the covering portion 141a to separate from the main body portion 141b along the first notch 151. At this time, the covering portion 141a also separates into multiple parts along the second notch 152. In the battery pack 110, the end faces of the first notch 151 and the second notch 152 are bonded together by a sealing member 143, but the pressure of gas G causes the sealing member 143 to break.

[0159] The gas G then passes through the area where the covering portion 141a of the first insulation sheet 141 was located and is released between the insulation material 140 and the case 130.

[0160] Furthermore, the gas G released between the insulation material 140 and the case 130 also reaches other covering portions 141a of the first insulation sheet 141. However, the pressure of the gas G released between the insulation material 140 and the case 130 prevents the other covering portions 141a of the first insulation sheet 141 from separating from the main body portion 141b. Therefore, even if the gas G reaches other covering portions 141a of the first insulation sheet 141, the gas G is blocked by the covering portions 141a. This prevents the gas G from flowing back through the safety valve 122 of other battery cells 121.

[0161] The battery pack 110 can prevent moisture from entering the battery cells 121. The principle is explained below.

[0162] In the battery pack 110, an opening 133 is formed in the bottom 131b of the case 130, making it easy for moisture from the outside to pass through the opening 133 and enter the inside of the battery pack 110. Such moisture will come into contact with the first insulation sheet 141 of the insulation material 140. The first cutout 151 and the second cutout 152 can become pathways for such moisture from the outside. In other words, the first cutout 151 and the second cutout 152 can cause moisture to penetrate into the inside of the battery cell 121.

[0163] However, in the battery pack 110, the end faces of the first notch 151 and the second notch 152 are bonded together by the sealing member 143. In other words, the sealing member 143 blocks at least a portion of the end faces of the first notch 151 and the second notch 152, which would otherwise be pathways for moisture. Therefore, the battery pack 110 can prevent moisture from entering the battery cells 121.

[0164] In the battery pack 110 described above, the covering portion 141a was racetrack-shaped, and the second notch portion 152 was cross-shaped, overlapping the long and short axes of the racetrack-shaped covering portion 141a. However, in the battery pack according to the second embodiment of the present invention, the shapes of the covering portion, the first notch portion and the second notch portion are not limited to these, and may be the same as the preferred shapes of the covering portion, the first notch portion and the second notch portion of the battery pack according to the first embodiment of the present invention.

[0165] In the battery pack according to the second embodiment of the present invention, the first notch 151 and the second notch 152 may or may not be in contact, similar to the battery pack according to the first embodiment of the present invention.

[0166] In the battery pack 110 described above, the entire end faces of the first notch 151 and the second notch 152 are bonded by the sealing member 143. However, in the battery pack according to the second embodiment of the present invention, at least a portion of the end face of at least one notch selected from the group consisting of the first notch and the second notch may be bonded by the sealing member. Since the sealing member closes a portion of the first notch and the second notch, it can prevent moisture from entering the battery cell.

[0167] The preferred materials for the first heat insulating sheet in the battery pack according to the second embodiment of the present invention are the same as the preferred materials for the first heat insulating sheet in the battery pack according to the first embodiment of the present invention.

[0168] In the battery pack according to the second embodiment of the present invention, the sealing member preferably includes an adhesive. Examples of adhesives include acrylic adhesives, silicone rubber adhesives, polyester adhesives, epoxy adhesives, polyolefin adhesives, polyamide adhesives, polyurethane adhesives, and synthetic rubber adhesives.

[0169] These adhesives can suitably bond the end faces of the first and second notches. Furthermore, when placing the sealing member on the first insulation sheet, the sealing member can be easily formed by allowing the adhesive to penetrate through the first and second notches.

[0170] (Other Embodiments) In the battery pack according to the first and second embodiments of the present invention described above, a plurality of openings were formed in the bottom of the case. In the battery pack of the present invention, a plurality of openings may be formed in the side wall of the case. In this case, the module is arranged so that the safety valve faces the side wall, and when the side wall of the case is viewed from above, one opening may be positioned to overlap with at least a part of one safety valve. In such a battery pack, high-temperature gas from an abnormal battery cell can be released to the outside through the opening formed in the side wall of the case. Also, since one opening is positioned to overlap with at least a part of one safety valve, high-temperature gas from an abnormal battery cell is quickly released to the outside. However, if openings are formed in the side wall of the case, moisture can easily enter the battery pack from the outside. However, as described above, the battery pack of the present invention has a sealing member, so it is possible to prevent moisture from entering the inside of the battery cell from the outside of the battery pack.

[0171] In the battery pack of the present invention, it is not necessary to have an opening in the case. In this case, it is possible to prevent moisture from entering the inside of the case through the opening.

[0172] In the battery pack of the present invention, the case comprises a housing section consisting of a bottom section and a side wall section, and a lid section covering the housing section. The module may be positioned so that the safety valve faces the bottom section, the side wall section, or the lid section. High-temperature gas from an abnormal battery cell is released from the safety valve and hits the case, causing a part of the case to become hot. If electrical wiring or the like is located near the hot part of the case, it may cause the electrical wiring to malfunction. Also, if there is a living space near the hot part of the case, it may lead to burns or other injuries. Therefore, from a safety standpoint, it is preferable to appropriately set the direction of the safety valve according to the design and location of the device in which the battery pack is installed.

[0173] This specification contains the following information:

[0174] (1) The present disclosure is a battery pack comprising a module having a plurality of battery cells, each provided with a safety valve; a case housing the module; and a thermal insulation material provided between the module and the case, wherein the thermal insulation material includes a first thermal insulation sheet, a second thermal insulation sheet laminated on the first thermal insulation sheet, and a sealing member for bonding the first thermal insulation sheet and the second thermal insulation sheet, wherein the thermal insulation material is arranged such that the second thermal insulation sheet is located on the module side and the first thermal insulation sheet is located on the case side, and when the thermal insulation material is viewed through a plane, the first thermal insulation sheet has a plurality of covering portions that cover each of the plurality of safety valves, and the portion other than the covering portions. The battery pack comprises a main body and a covering portion, where one covering portion is positioned to overlap with at least a part of one safety valve, the covering portion has a first notch along the contour of the covering portion and a second notch, at least a part of which is inside the contour of the covering portion, the second heat insulating sheet has a third notch that is continuous from the main surface on the first heat insulating sheet side to the other main surface, at least a part of the third notch is located inside the covering portion, and the sealing member is positioned to overlap with at least a part of at least one notch selected from the group consisting of the first notch, the second notch, and the third notch.

[0175] The present disclosure (2) is a battery pack according to the present disclosure (1), wherein, when the thermal insulation material is viewed through from above, the sealing member is arranged to overlap with the entirety of the first cut portion and the second cut portion, or the entirety of the third cut portion.

[0176] The present disclosure (3) is a battery pack according to the present disclosure (1), wherein, when the thermal insulation material is viewed through from above, the sealing member is arranged to overlap with the entirety of the first cut portion, the second cut portion, and the third cut portion.

[0177] Disclosure (4) is a battery pack according to any one of Disclosures (1) to (3) wherein the first cut portion, the second cut portion and the third cut portion are formed such that when the thermal insulation material is viewed from above, the first cut portion and the second cut portion and the third cut portion do not overlap.

[0178] (5) The present disclosure is a battery pack comprising a module having a plurality of battery cells, each provided with a safety valve; a case housing the module; and a thermal insulation material provided between the module and the case, wherein the thermal insulation material includes a first thermal insulation sheet, and when viewed in plan, the first thermal insulation sheet consists of a plurality of covering portions that cover each of the plurality of safety valves, and a main body portion other than the covering portions, and one of the covering portions is positioned to overlap with at least a part of one of the safety valves, and the covering portion has a first notch along the contour of the covering portion and a second notch that at least a part of is inside the contour of the covering portion, and the end face of at least a part of at least one notch selected from the group consisting of the first notch and the second notch is bonded by a sealing member.

[0179] The present disclosure (6) is a battery pack according to the present disclosure (5), wherein the entire end faces of the first cut portion and the second cut portion are bonded together by the sealing member.

[0180] Disclosure (7) is a battery pack according to any one of Disclosures (1) to (6), wherein the first heat insulating sheet is at least one selected from the group consisting of mica sheet, heat-resistant resin sheet, inorganic fiber paper, and inorganic fiber cloth.

[0181] Disclosure (8) is a battery pack according to any one of Disclosures (1) to (4), wherein the second heat insulating sheet is at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth.

[0182] Disclosure (9) is a battery pack according to any one of Disclosures (1) to (8), wherein the plan view shape of the covering portion is at least one selected from the group consisting of polygons, circles, ellipses and racetrack shapes.

[0183] Disclosure (10) is a battery pack according to any one of Disclosures (1) to (9) wherein the sealing member includes an adhesive.

[0184] The present disclosure (11) is a battery pack according to the present disclosure (10) wherein the adhesive comprises at least one selected from the group consisting of acrylic adhesives, silicone rubber adhesives, polyester adhesives, epoxy adhesives, polyolefin adhesives, polyamide adhesives, polyurethane adhesives, and synthetic rubber adhesives.

[0185] (12) The present disclosure is a battery pack according to any one of the present disclosures (1) to (11), wherein the case comprises a housing portion consisting of a bottom portion and a side wall portion, and a lid portion covering the housing portion, and the module is arranged such that the safety valve faces the bottom portion, the safety valve faces the side wall portion, or the safety valve faces the lid portion.

[0186] (13) The present disclosure is a battery pack according to any one of the present disclosures (1) to (11), wherein the case comprises a housing portion consisting of a bottom portion and a side wall portion, and a lid portion covering the housing portion, the module is arranged such that the safety valve faces the bottom portion, a plurality of openings are formed in the bottom portion, and when the bottom portion of the case is viewed from above, one of the openings is positioned to overlap with at least a portion of one of the safety valves.

[0187] The present disclosure (14) is a battery pack according to any one of the present disclosures (1) to (11), wherein the case comprises a housing portion consisting of a bottom portion and a side wall portion, and a lid portion covering the housing portion, the module is arranged such that the safety valve faces the side wall portion, a plurality of openings are formed in the side wall portion, and when the side wall portion of the case is viewed from above, one of the openings is positioned to overlap with at least a portion of one of the safety valves.

[0188] 10, 110 Battery pack 20, 120 Module 20a, 120a Connection module member 20b, 120b Busbar 21, 121 Battery cell 22, 122 Safety valve 23, 123 Terminal 30, 130 Case 31, 131 Housing section 31b, 131b Bottom section 31s, 131s Side wall 32, 132 Lid section 33, 133 Opening 40, 40A, 40B, 40C, 140 Insulation material 41, 141 First insulation sheet 41a, 141a Covering section 41b, 141b Main body section 42 Second insulation sheet 43, 43A, 43B, 43C, 143 Sealing member 51, 151 First cut section 52, 152 Second cut section 53 Third cut section

Claims

1. A battery pack comprising: a module having a plurality of battery cells, each provided with a safety valve; a case housing the module; and a thermal insulation material provided between the module and the case, wherein the thermal insulation material includes a first thermal insulation sheet, a second thermal insulation sheet laminated on the first thermal insulation sheet, and a sealing member for bonding the first thermal insulation sheet and the second thermal insulation sheet, the thermal insulation material is arranged such that the second thermal insulation sheet is located on the module side and the first thermal insulation sheet is located on the case side, and when the thermal insulation material is viewed through from above, the first thermal insulation sheet consists of a plurality of covering portions that cover each of the plurality of safety valves and a main body portion other than the covering portions, one of the covering portions is positioned to overlap with at least a part of one of the safety valves, the covering portion has a first notch along the contour of the covering portion and a second notch which at least a part of is inside the contour of the covering portion, and the second thermal insulation sheet has a third notch which is continuous from the main surface on the side of the first thermal insulation sheet to the other main surface. The battery pack is characterized in that at least a portion of the third notch is located inside the covering portion, and the sealing member is arranged to overlap with at least a portion of at least one notch selected from the group consisting of the first notch, the second notch, and the third notch.

2. The battery pack according to claim 1, wherein, when the insulating material is viewed through from above, the sealing member is arranged to overlap with the entirety of the first cut portion and the second cut portion, or the entirety of the third cut portion.

3. The battery pack according to claim 1, wherein, when the insulating material is viewed through from above, the sealing member is arranged to overlap with the entirety of the first cut portion, the second cut portion, and the third cut portion.

4. The battery pack according to any one of claims 1 to 3, wherein the first cut portion, the second cut portion, and the third cut portion are formed such that when the insulating material is viewed through from above, the first cut portion and the second cut portion do not overlap.

5. A battery pack comprising: a module having a plurality of battery cells, each provided with a safety valve; a case housing the module; and a heat insulating material provided between the module and the case, wherein the heat insulating material includes a first heat insulating sheet, and when viewed from above, the first heat insulating sheet consists of a plurality of covering portions covering each of the plurality of safety valves and a main body portion other than the covering portions, one of the covering portions is positioned to overlap with at least a part of one of the safety valves, the covering portion has a first notch along the contour of the covering portion and a second notch which at least a part of is inside the contour of the covering portion, and the end face of at least a part of at least one notch selected from the group consisting of the first notch and the second notch is bonded by a sealing member.

6. The battery pack according to claim 5, wherein the entire end faces of the first cut portion and the second cut portion are bonded together by the sealing member.

7. The battery pack according to any one of claims 1 to 6, wherein the first heat insulating sheet is at least one selected from the group consisting of mica sheet, heat-resistant resin sheet, inorganic fiber paper, and inorganic fiber cloth.

8. The battery pack according to any one of claims 1 to 4, wherein the second heat insulating sheet is at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth.

9. The battery pack according to any one of claims 1 to 8, wherein the plan view shape of the covering portion is at least one selected from the group consisting of polygons, circles, ellipses, and racetrack shapes.

10. The battery pack according to any one of claims 1 to 9, wherein the sealing member includes an adhesive.

11. The battery pack according to claim 10, wherein the adhesive comprises at least one selected from the group consisting of acrylic adhesives, silicone rubber adhesives, polyester adhesives, epoxy adhesives, polyolefin adhesives, polyamide adhesives, polyurethane adhesives, and synthetic rubber adhesives.

12. The battery pack according to any one of claims 1 to 11, wherein the case comprises a housing portion consisting of a bottom portion and a side wall portion, and a lid portion covering the housing portion, and the module is arranged such that the safety valve faces the bottom portion, the safety valve faces the side wall portion, or the safety valve faces the lid portion.

13. The battery pack according to any one of claims 1 to 11, wherein the case comprises a housing portion consisting of a bottom portion and side wall portions, and a lid portion covering the housing portion, the module is arranged such that the safety valve faces the bottom portion, a plurality of openings are formed in the bottom portion, and when the bottom portion of the case is viewed from above, one of the openings is positioned to overlap with at least a portion of one of the safety valves.

14. The battery pack according to any one of claims 1 to 11, wherein the case comprises a housing portion consisting of a bottom portion and a side wall portion, and a lid portion covering the housing portion, the module is arranged such that the safety valve faces the side wall portion, a plurality of openings are formed in the side wall portion, and when the side wall portion of the case is viewed from above, one of the openings is positioned to overlap with at least a portion of one of the safety valves.

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