Battery pack

Abstract

Provided is a battery pack which comprises a thermal insulation material that can be installed even in small spaces and has excellent heat dissipation properties.　A battery pack according to the present invention comprises a module that has a plurality of battery cells in each of which a safety valve and a connection terminal are disposed on a first surface and a bus bar which connects the connection terminals and which electrically connects the plurality of battery cells, a case that accommodates the module, and a thermal insulation material that is disposed between the module and the case on the first surface side of the battery cells. The battery pack is characterized in that: the thermal insulation material includes a cushioning sheet, a thermal insulation sheet that is laminated on the cushioning sheet, and an adhesive layer that adheres the cushioning sheet and the thermal insulation sheet; the thermal insulation material is disposed such that the cushioning sheet is positioned on the module side and the thermal insulation sheet is positioned on the case side; and in a plan view of the thermal insulation material, the cushioning sheet is disposed so as not to overlap with the bus bar and the thermal insulation sheet is disposed so as to overlap with the bus bar.

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, if the high-temperature gas discharged from the safety valve directly hits the case, the case temperature will rise, potentially causing thermal effects around the battery pack. To prevent this direct contact between the high-temperature gas and the case, insulating material has traditionally been placed between the module and the case.

[0004] As an example of such a battery pack, Patent Document 1 discloses a battery module comprising a battery box (1) including a housing (11) and an upper cover (12), a plurality of cells (2) arranged in parallel within the housing (11), an electrical connection assembly (3) that electrically connects the plurality of cells (2), and heat insulating plates (4) installed on one side of the electrical connection assembly (3) that approaches the upper cover (12) or on both sides of the electrical connection assembly (3).

[0005] Furthermore, Patent Document 2 discloses a fireproof cover for a battery module, comprising a heat insulating cover and a top surface reinforcing plate, wherein the heat insulating cover is a polyhedron made of fire-resistant heat insulating material and is used to cover each surface of the battery module other than the bottom surface and conforms to the dimensions of the battery module, and the top surface reinforcing plate is made of fire-resistant, high-temperature resistant, and impact-resistant plate material and is installed above or below the top surface of the heat insulating cover and is used to enhance the impact resistance of the top surface of the heat insulating cover.

[0006] Chinese Utility Model Publication No. 218299959 Specification, Chinese Utility Model Publication No. 216529122 Specification

[0007] In the battery module described in Patent Document 1, an insulating plate is provided between the cell and the upper cover. However, in order to make the insulating plate sufficiently strong, it is necessary to increase its thickness, which increases its weight. Furthermore, in order to suppress vibration, it becomes necessary to make the insulating plate a predetermined three-dimensional shape, which increases the installation space and makes it difficult to fix with adhesive, thus requiring the use of fixing devices.

[0008] The fireproof cover for a battery module described in Patent Document 2 includes an insulating cover that covers the battery module. Such an insulating cover may hinder heat dissipation from the battery module.

[0009] This invention was made to solve the above problems, and the present invention provides a battery pack equipped with an insulating material that has excellent heat dissipation properties and can be installed even in a narrow space.

[0010] The present invention relates to a battery pack comprising: a module having a plurality of battery cells, each having a safety valve and connection terminals arranged on its first surface; a busbar connecting the connection terminals and electrically connecting the plurality of battery cells; a case housing the module; and a heat insulating material disposed between the module and the case on the first surface side of the battery cells, wherein the heat insulating material includes a cushioning sheet, a heat insulating sheet laminated on the cushioning sheet, and an adhesive layer for bonding the cushioning sheet and the heat insulating sheet, and the heat insulating material is arranged such that the cushioning sheet is located on the module side and the heat insulating sheet is located on the case side, and when the heat insulating material is viewed from above, the cushioning sheet is arranged so as not to overlap with the busbar, and the heat insulating sheet is arranged so as to overlap with the busbar.

[0011] In the battery pack of the present invention, the cushioning sheet can absorb steps and vibrations, eliminating the need to shape the heat insulating sheet into a predetermined three-dimensional shape to suppress vibrations. Therefore, heat insulating material can be placed even in narrow spaces.

[0012] In the battery pack of the present invention, the cushioning sheet is positioned so as not to overlap with the busbars. Therefore, heat can be efficiently dissipated from the busbars.

[0013] In the battery pack of the present invention, when the heat insulating material is viewed from above, the cushioning sheet may be arranged to cover the portion between the safety valve and the connection terminal on the first surface of the battery cell. Alternatively, in the battery pack of the present invention, when the heat insulating material is viewed from above, the cushioning sheet may be arranged to cover the portion between the safety valves of each of two adjacent battery cells. Furthermore, in the battery pack of the present invention, each battery cell has at least two connection terminals, and on the first surface of the battery cell, the safety valve is positioned between at least two connection terminals, and the heat insulating sheet may be arranged on the first surface to cover the portion outside the area between at least two connection terminals. When the cushioning sheet is arranged in this manner, steps and vibrations can be absorbed more effectively.

[0014] In the battery pack of the present invention, the heat insulating sheet may be arranged to overlap with the safety valve. In this case, it is possible to prevent high-temperature gas generated from the battery cells during thermal runaway from directly contacting the case.

[0015] In the battery pack of the present invention, when the heat insulating material is viewed from above, the buffer sheet may be positioned to overlap with the safety valve. In this case, the buffer sheet has a first notch formed thereon that extends from the main surface to which the heat insulating sheet is bonded to the other main surface, and when the heat insulating material is viewed from above from the heat insulating sheet side, at least a part of the first notch may be positioned to overlap with the safety valve. Furthermore, when the heat insulating material is viewed from above from the heat insulating sheet side, the first notch may be formed in a linear shape. In addition, in the battery pack of the present invention, when the heat insulating material is viewed from above, the buffer sheet may be positioned so as not to overlap with the safety valve. Regardless of the configuration, the effect of being able to place the heat insulating material in a narrow space and the effect of efficiently releasing heat from the busbar can be obtained.

[0016] In the battery pack of the present invention, the thickness of the heat insulating sheet is preferably 0.05 to 2.0 mm. If the thickness of the heat insulating sheet is less than 0.05 mm, the strength of the heat insulating sheet will be low and it will be easily damaged. If the thickness of the heat insulating sheet exceeds 2.0 mm, the heat insulating sheet will be too thick, making it difficult to miniaturize the entire battery pack.

[0017] In the battery pack of the present invention, the 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 heat insulating sheets.

[0018] In the battery pack of the present invention, the cushioning sheet may be at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth. Among these, inorganic fiber mat is preferred. These can be easily molded, and inorganic fiber mat exhibits excellent performance as a cushioning sheet.

[0019] In the battery pack of the present invention, when the heat insulating sheet is viewed in plan, it is preferable that the heat insulating 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 that one of the covering portions is positioned to overlap with at least a part of one of the safety valves, and that the covering portion has a cut portion formed along the contour of the covering portion and a connection portion formed along the contour of the covering portion other than the cut portion. In such a battery pack, it is possible to prevent a chain reaction of thermal runaway caused by high-temperature gas from abnormal battery cells that occur during thermal runaway. The principle is explained below. When a battery cell experiences thermal runaway and generates high-temperature gas, the gas is discharged from the safety valve. The gas discharged from the safety valve then reaches the heat insulating material. If the heat insulating 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, the gas discharged from the safety valve will hit the covering portion of the heat insulating sheet. When the gas discharged from the safety valve hits the covering portion, the pressure causes the connection portion of the covering portion to break, and the covering portion separates from the main body portion along the cut portion. The gas then passes through the area where the insulating sheet was covered and is released between the insulating material and the case. The gas released between the insulating material and the case also reaches other areas covered by the insulating sheet. However, these other areas of the insulating sheet are connected to the main body by a connector, and this connector will not rupture under the pressure of the gas released between the insulating material and the case. Therefore, even if the gas reaches other areas of the insulating sheet, it is blocked by the covering. This prevents the gas from flowing back through the safety valves of other battery cells.

[0020] 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.

[0021] In the battery pack of the present invention, it is preferable that the heat insulating sheet has at least one second notch formed therein, at least a portion of which is inside the contour of the covering portion. When the covering portion has a second notch formed therein, the covering portion is more likely to tear along the second notch. Therefore, when the battery cell experiences thermal runaway and high-temperature gas is generated, the gas can be quickly discharged.

[0022] In the battery pack of the present invention, the cushioning sheet has a first notch formed therein that extends from the main surface to which the heat insulating sheet is bonded to the other main surface, and it is preferable that the first notch and the second notch overlap in the same shape when the heat insulating material is viewed from the heat insulating sheet side. When the first notch is formed in the cushioning sheet, high-temperature gas from the module side can easily reach the covering through the first notch. Furthermore, such a first notch and a second notch can be formed simultaneously by punching them out while the cushioning sheet and the heat insulating sheet are stacked on top of each other.

[0023] According to the present invention, it is possible to provide a battery pack equipped with an insulating material that has excellent heat dissipation properties and can be installed even in narrow spaces.

[0024] 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 2 is a schematic top view showing an example of a module included in the battery pack according to the first embodiment of the present invention. Figure 3A is a schematic perspective view showing an example of a heat insulating material included in the battery pack according to the first embodiment of the present invention. Figure 3B is a schematic diagram of an example of a heat insulating material included in the battery pack according to the first embodiment of the present invention, viewed from the heat insulating sheet side. Figure 3C is a schematic diagram of an example of a heat insulating material included in the battery pack according to the first embodiment of the present invention, viewed from the buffer sheet side. Figure 4A is a schematic diagram of an example of a module in which the heat insulating material included in the battery pack according to the first embodiment of the present invention is arranged, viewed along the direction of the battery cell arrangement. Figure 4B is a side view of Figure 4A. Figure 5 is a schematic diagram viewed from above of an example of the arrangement position of a buffer sheet placed in a module included in the battery pack according to the first embodiment of the present invention. Figure 6A 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 the battery pack according to the first embodiment of the present invention. Figure 6B 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 6C 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 7 is a schematic diagram viewed from above of another example of the arrangement position of a buffer sheet placed in a module included in a battery pack according to the first embodiment of the present invention. Figure 8A is a schematic diagram viewed from the buffer sheet side of an example of a heat insulating material included in a battery pack according to the second embodiment of the present invention. Figure 8B is a schematic diagram viewed from the buffer sheet side of an example of a heat insulating material included in a battery pack according to the second embodiment of the present invention. Figure 9 is a schematic diagram viewed from above of an example of the arrangement position of a buffer sheet placed in a module included in a battery pack according to the second embodiment of the present invention.

[0025] The battery pack of the present invention will be described in detail below. However, the present invention is not limited to the following configuration, and can be modified and applied as appropriate without changing the gist of the invention. Furthermore, a combination of two or more of the individual preferred configurations of the present invention described below also constitutes the present invention.

[0026] (First Embodiment) A battery pack according to the first embodiment of the present invention will be described with reference to the drawings. 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.

[0027] The battery pack 10 shown in Figures 1A, 1B, and 1C comprises a module 20 having a plurality of battery cells 21, each having a safety valve 22 and connection terminals 23 arranged on a first surface S, and a case 30 that houses the module 20. In Figures 1A, 1B, and 1C, the first surface S of the battery cells 21 is positioned upwards.

[0028] As shown in Figures 1A and 1B, the case 30 comprises a housing section 31 consisting of a bottom section 31b and side walls 31s, and a lid section 32 that covers the housing section 31, with the module 20 housed in the housing section 31. In the battery pack 10, a heat insulating material 40 is placed between the module 20 and the case 30 on the first surface S side of the battery cell 21.

[0029] The battery cell 21 stores power and is preferably a rechargeable secondary battery, for example. Examples of secondary batteries include lithium-ion batteries, nickel-metal hydride batteries, and sodium-ion batteries. The battery cell 21 shown in Figures 1B and 1C is rectangular in shape. However, in the battery pack of the present invention, the battery cell may have a three-dimensional shape other than a rectangular parallelepiped (for example, a cube or an irregular shape).

[0030] Next, the structure of module 20 will be described. Figure 2 is a schematic top view showing an example of a module included in a battery pack according to the first embodiment of the present invention. As shown in Figure 2, module 20 has a plurality of battery cells 21, each having a safety valve 22 and a connection terminal 23 arranged on a first surface S, and a busbar 24 that connects the connection terminals 23 of each battery cell 21 and electrically connects the plurality of battery cells 21.

[0031] Focusing on a single battery cell 21, one safety valve 22 and two connection terminals 23 are arranged on the first surface S, with the safety valve 22 located in a position other than the part sandwiched between the two connection terminals 23. The safety valve 22 is located in the central part of the first surface S.

[0032] Furthermore, in module 20, each battery cell 21 is arranged such that the safety valve 22 and the connection terminal 23 are aligned in a straight line.

[0033] As shown in Figure 2, in module 20, the busbar 24 connects the connection terminals 23 of adjacent battery cells 21 to each other.

[0034] The busbar 24 is a flat, conductive metal component. Examples of materials for the busbar 24 include copper, copper alloy, stainless steel (SUS), and aluminum. The busbar 24 may be fixed to the connection terminal 23 by any fixing means (e.g., screwing, welding, etc.).

[0035] The materials that make up the case 30 include steel, aluminum, and the like. Stainless steel (SUS) is preferred as the steel material.

[0036] Next, the thermal insulation material 40 will be described. Figure 3A is a schematic perspective view showing an example of the thermal insulation material included in the battery pack according to the first embodiment of the present invention. Figure 3B is a schematic diagram of an example of the thermal insulation material included in the battery pack according to the first embodiment of the present invention, viewed from the thermal insulation sheet side. Figure 3C is a schematic diagram of an example of the thermal insulation material included in the battery pack according to the first embodiment of the present invention, viewed from the buffer sheet side.

[0037] As shown in FIG. 3A, the heat insulating material 40 includes a buffer sheet 42, a heat insulating sheet 41 laminated on the buffer sheet 42, and an adhesive layer (not shown) that adheres the buffer sheet 42 and the heat insulating sheet 41. The heat insulating material 40 is arranged such that the buffer sheet 42 is located on the module 20 side and the heat insulating sheet 41 is located on the case 30 side. Note that in FIG. 3A, for the sake of convenience, it is a perspective view of the heat insulating material 40 with the buffer sheet 42 on top, and it is upside down compared to the heat insulating material 40 shown in FIGS. 1B and 1C.

[0038] As shown in FIG. 3B, the heat insulating sheet 41 has a rectangular planar shape. When the heat insulating material 40 is viewed in plan, the heat insulating sheet 41 is arranged to overlap with the safety valve 22.

[0039] The heat insulating sheet 41 includes a covering portion 41a and a main body portion 41b other than the covering portion 41a. The covering portion 41a is arranged at a position overlapping at least a part of the safety valve 22 when the heat insulating material 40 is arranged on the module 20. Further, the covering portion 41a has a cutting portion 50 formed along the contour C of the covering portion 41a and a connecting portion 41c formed along the contour C of the covering portion 41a other than the cutting portion 50. Furthermore, two second cut portions 60 are formed in a cross shape by two line segments inside the contour C of the covering portion 41a of the heat insulating sheet 41.

[0040] As shown in FIG. 3C, the buffer sheet 42 has a rectangular planar shape with a shorter length in the width direction than the heat insulating sheet 41, and is formed along the longitudinal direction of the heat insulating sheet 41 at the central portion of the heat insulating sheet 41. That is, when the heat insulating material 40 is viewed from the buffer sheet 42 side, a part of the heat insulating sheet 41 is not covered by the buffer sheet 42.

[0041] When the heat insulating material 40 is arranged on the module 20 and the heat insulating material 40 is viewed in plan, the buffer sheet 42 is arranged at a position that does not overlap with the bus bar 24.

[0042] Note that two first cut portions 70 that are continuous from one main surface to the other main surface are formed in a cross shape by two line segments on the buffer sheet 42, and the first cut portions 70 are arranged at positions overlapping the covering portion 41a and the safety valve 22.

[0043] When the heat insulating material 40 is viewed from the heat insulating sheet 41 side in a plan view, the first cut portion 70 and the second cut portion 60 have the same shape and overlap each other.

[0044] Next, the case of arranging the heat insulating material 40 on the module 20 will be described. FIG. 4A is a schematic view of an example of a module in which a heat insulating material included in the battery pack according to the first embodiment of the present invention is arranged, as viewed along the arrangement direction of battery cells. FIG. 4B is a side view of FIG. 4A. As shown in FIGS. 4A and 4B, in the battery pack 10, the bus bar 24 is not covered with the buffer sheet 42 but is covered with the heat insulating sheet 41, and the bus bar 24 is exposed. That is, in the battery pack 10, when the heat insulating material 40 is viewed in a plan view, the buffer sheet 42 is arranged so as not to overlap with the bus bar 24, and the heat insulating sheet 41 is arranged so as to overlap with the bus bar 24.

[0045] The arrangement position of the buffer sheet 42 on the module 20 will be described in detail with reference to the drawings. FIG. 5 is a schematic view of an example of the arrangement position of the buffer sheet arranged on the module included in the battery pack according to the first embodiment of the present invention, as viewed from above. In FIG. 5, the heat insulating sheet 41 is not shown, and only the arrangement position of the buffer sheet 42 is shown. As shown in FIG. 5, the buffer sheet 42 is arranged so as to cover the safety valve 22 of the first surface S of the battery cell 21 and the portion between the safety valve 22 and the connection terminal 23. Further, the buffer sheet 42 is arranged so as to cover the portion between the safety valves 22 of two adjacent battery cells 21.

[0046] Since the battery pack 10 includes the heat insulating material 40, the following effects can be exhibited. That is, in the battery pack 10, since the buffer sheet 42 can absorb steps and vibrations, it is not necessary to make the shape of the heat insulating sheet 41 into a predetermined three-dimensional shape for vibration suppression. Therefore, the heat insulating material 40 can be arranged even in a narrow space. Further, since the bus bar 24 is exposed, heat can be efficiently released from the bus bar 24.

[0047] 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. Figures 6A to 6C 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 the battery pack according to the first embodiment of the present invention.

[0048] As shown in Figure 6A, when one abnormal battery cell 21a experiences thermal runaway and generates high-temperature gas from the abnormal battery cell 21a, gas G (in Figure 6A, gas is indicated by the symbol "G", and the direction of gas flow is indicated by an arrow) is discharged from the safety valve 22a.

[0049] The gas G released from the safety valve 22a forms in the buffer sheet 42 of the insulation material 40, passes through the first notch 70, and reaches the insulation sheet 41. As the gas G passes through the first notch 70 of the buffer sheet 42, its temperature decreases and its gas pressure also decreases.

[0050] Subsequently, the gas G released from the safety valve will come into contact with the covering portion 41a of the heat-insulating sheet 41.

[0051] In the battery pack 10, the covering portion 41a has a cut portion 50 and a connecting portion 41c formed along the contour C of the covering portion 41a. Therefore, as shown in Figure 6B, when the gas G released from the safety valve 22a hits the covering portion 41a, the pressure causes the connecting portion 41c to break, and the covering portion 41a separates from the main body portion 41b along the contour C of the covering portion 41a.

[0052] Then, the gas G passes through the area where the covering portion 41a of the heat insulating sheet 41 was located and is released between the heat insulating sheet 41 and the case 30.

[0053] Furthermore, as shown in Figure 6C, the gas G released between the heat insulating sheet 41 and the case 30 also reaches other covering portions 41a of the heat insulating sheet 41. However, these other covering portions 41a of the heat insulating sheet 41 are connected to the main body portion 41b by a connecting portion 41c, and the connecting portion 41c does not detach from the main body due to the pressure of the gas G released between the heat insulating sheet 41 and the case 30. Therefore, even if the gas reaches other covering portions 41a of the heat insulating sheet 41, the gas G is blocked by the covering portion 41a. This prevents the gas G from flowing back through the safety valve 22 of other battery cells 21.

[0054] The following describes preferred embodiments of the heat insulating material for the battery pack according to the first embodiment of the present invention.

[0055] In the battery pack 10, the heat insulating sheet 41 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 heat insulating sheets.

[0056] Examples of resins that make up heat-resistant resin sheets include polybutylene terephthalate, polyamide, polypropylene, silicone, and urethane. These resins may also contain inorganic fibers such as glass fiber or silica fiber, or inorganic particles such as alumina and calcium carbonate, as fillers.

[0057] 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.

[0058] 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 ２At 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] Furthermore, the average fiber length of the second inorganic fiber is preferably less than 1 μm in order to avoid impairing moldability.

[0064] Furthermore, the inorganic fiber paper may also contain other components such as organic fibers, inorganic particles, organic particles, and resin binders.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] Examples of particles made from thermally expandable inorganic materials that constitute the inorganic particles contained in inorganic fiber paper include vermiculite, bentonite, and perlite.

[0078] 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.

[0079] 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.

[0080] Inorganic fiber cloth is made by weaving inorganic fibers into a cross shape. Such inorganic fiber cloth has high strength and high heat resistance.

[0081] 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.

[0082] When the heat insulating sheet 41 is a mica sheet or a heat-resistant resin sheet, the thickness of the heat insulating sheet 41 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 heat insulating sheet made of a mica sheet or a heat-resistant resin sheet is less than 0.05 mm, the strength of the heat insulating sheet will be low and it will be easily damaged. If the thickness of the heat insulating sheet made of a mica sheet or a heat-resistant resin sheet exceeds 2.0 mm, the heat insulating sheet will be too thick, making it difficult to miniaturize the entire battery pack.

[0083] Furthermore, if the heat insulating sheet 41 is inorganic fiber paper, the thickness of the heat insulating sheet 41 is preferably 0.5 to 5.0 mm, and more preferably 0.8 mm to 3.0 mm. In this case, the heat insulating sheet 41 made of inorganic fiber paper can obtain sufficient mechanical strength.

[0084] Furthermore, when the heat insulating sheet 41 is an inorganic fiber cloth, the thickness of the heat insulating sheet 41 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 can be achieved for the heat insulating sheet 41 made of inorganic fiber cloth. Therefore, the heat insulating sheet 41 made of inorganic fiber cloth can be bent to fit a predetermined shape and used.

[0085] The area of ​​the planar shape of the covering portion 41a is 1.0 to 18 cm². ２ Preferably, 3.0 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 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.

[0086] In the battery pack 10, the plan view shape of the covering portion 41a is not particularly limited and may be a polygon, circle, ellipse, or racetrack shape, etc. It may also be a rounded polygon with rounded corners.

[0087] In the battery pack 10, the adhesive layer that adheres the buffer sheet 42 and the heat insulation sheet 41 preferably includes an organic adhesive layer. When the adhesive layer includes an organic adhesive layer, it is likely to thermally decompose when the high-temperature gas G from the abnormal battery cell reaches the adhesive layer. The organic adhesive layer preferably thermally decomposes at 80°C or higher. For example, an adhesive layer containing a polyamide-based organic material can be mentioned.

[0088] In the battery pack 10, the buffer sheet 42 may be at least one selected from the group consisting of an inorganic fiber mat, an inorganic fiber paper, and an inorganic fiber cloth. Among these, an inorganic fiber mat is preferable. These can be easily molded, and the inorganic fiber mat exhibits excellent performance as a buffer sheet.

[0089] The thickness of the inorganic fiber mat is preferably 0.5 to 10 mm, and more preferably 1 to 4 mm. When the thickness of the inorganic fiber mat is less than 0.5 mm, since the thickness of the inorganic fiber mat is thin, when the gas passes through the inorganic fiber mat, the temperature of the gas is not likely to decrease, and the gas pressure is also not likely to decrease. As a result, the gas reaches the case vigorously while remaining at a high temperature, and the case is likely to deteriorate. When 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.

[0090] The bulk density of the inorganic fiber mat is preferably 0.1 to 1.0 g / cm ３ and more preferably 0.2 to 0.7 g / cm ３ When the bulk density of the inorganic fiber mat is less than 0.1 g / cm ３ the gap between the inorganic fibers becomes large, so when the gas passes through the inorganic fiber mat, the temperature of the gas is not likely to decrease, and the gas pressure is also not likely to decrease. As a result, the gas reaches the case vigorously while remaining at a high temperature, and the case is likely to deteriorate. When the bulk density of the inorganic fiber mat exceeds 1.0 g / cm ３ the gas becomes difficult to pass through the inorganic fiber mat, and the high-temperature gas remains in the battery cell, making it difficult for the temperature in the battery cell to decrease. Therefore, a chain reaction of thermal runaway is likely to occur.

[0091] The inorganic fiber mat is preferably made by processing inorganic fibers into a mat shape, which include at least one fiber selected from silica fibers, glass fibers, alumina fibers, aluminosilicate fibers, basalt fibers, rock wool, and biosoluble fibers. Inorganic fiber mats made of such materials can be easily processed.

[0092] The inorganic fiber mat may be made by processing inorganic fibers containing fibers with a melting point of 1000°C or higher into a mat shape. When the inorganic fiber mat contains fibers with a melting point of 1000°C or higher, the inorganic fibers have high heat resistance, so even if high-temperature gas from an abnormal battery cell reaches the inorganic fiber mat, the inorganic fiber mat will be less likely to deteriorate.

[0093] The inorganic fiber mat may be made by processing inorganic fibers, including fibers with a melting point of less than 1000°C, into a mat shape. If the inorganic fiber mat contains fibers with 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 will melt, making it easier for gas channels to form.

[0094] Furthermore, the preferred embodiments of inorganic fiber paper and inorganic fiber cloth as the cushioning sheet 42 are the same as those described above for the preferred inorganic fiber paper and inorganic fiber cloth as the heat insulating sheet.

[0095] Next, the uses and arrangement methods of the battery pack according to the first embodiment of the present invention will be described.

[0096] The battery pack according to the first embodiment of the present invention is not particularly limited in its use, but may be used, for example, as a power source for an electric vehicle.

[0097] Furthermore, in the battery pack according to the first embodiment of the present invention, it is preferable that the safety valve provided on the battery cell is positioned either vertically upward or vertically downward. When the battery pack is positioned in this way, high-temperature gas from an abnormal battery cell is naturally and quickly dispersed, making it less likely for a chain reaction of thermal runaway to occur. In other words, from the viewpoint of fail-safe, this is a preferred arrangement for the battery pack. However, in the battery pack according to the first embodiment of the present invention, the safety valve provided on the battery cell may be positioned in a direction other than vertically upward and vertically downward (i.e., laterally).

[0098] In the battery pack according to the first embodiment of the present invention, the safety valve may be positioned on the lid side or on the bottom side. As described above, when arranging the battery pack according to the first embodiment of the present invention, from the viewpoint of fail-safe, the battery pack may be arranged so that the safety valve is positioned vertically upward or vertically downward. Since the battery pack is often arranged so that the lid or bottom of the case is on the downward side, arranging the safety valve to be on the lid side or bottom side of the case makes it easier to position the safety valve vertically upward or vertically downward.

[0099] (Modification of the First Embodiment) Next, a modification of the battery pack according to the first embodiment of the present invention will be described. Figure 7 is a schematic diagram viewed from above of another example of the arrangement position of the cushioning sheet placed in the module included in the battery pack according to the first embodiment of the present invention. Note that in Figure 7, the heat insulating sheet is not shown, and only the arrangement position of the cushioning sheet is shown. As shown in Figure 7, in the battery pack 10', which is a modification of the battery pack according to the first embodiment of the present invention, the cushioning sheet 42' is arranged on the first surface S to cover the outer part of the portion sandwiched between the two connection terminals 23, which is different from the battery pack 10 described above. Even with this configuration, the cushioning sheet 42' can absorb steps and vibrations, so there is no need to make the shape of the heat insulating sheet a predetermined three-dimensional shape in order to suppress vibrations, and the effect of the present invention is realized in that the heat insulating material can be placed even in a narrow space.

[0100] (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, when the insulating material is viewed in plan, the cushioning sheet is not arranged so as to overlap with the safety valve. The insulating material included in the battery pack according to the second embodiment of the present invention will be described in detail below with reference to the drawings.

[0101] Figure 8A is a schematic diagram showing an example of a heat insulating material included in a battery pack according to the second embodiment of the present invention, viewed from the heat insulating sheet side. Figure 8B is a schematic diagram showing an example of a heat insulating material included in a battery pack according to the second embodiment of the present invention, viewed from the cushioning sheet side.

[0102] As shown in Figure 8A, the thermal insulation sheet 141 of the thermal insulation material 140 has the same configuration as the thermal insulation sheet 41 of the battery pack 10 according to the first embodiment of the present invention. That is, the thermal insulation sheet 141 has a rectangular planar shape. The thermal insulation sheet 141 consists of a covering portion 141a and a main body portion 141b other than the covering portion 141a. The covering portion 141a is positioned to overlap with at least a part of the safety valve when the thermal insulation material 140 is placed on the module. The covering portion 141a also has a cut portion 150 formed along the contour C of the covering portion 141a and a connecting portion 141c formed along the contour C of the covering portion 141a other than the cut portion 150. Furthermore, the thermal insulation sheet 141 has a second cut portion 160 formed in a cross shape with two line segments inside the contour C of the covering portion 141a.

[0103] As shown in Figure 8B, the buffer sheet 142 is positioned to avoid the covering portion 141a. In other words, even if the insulation material 140 is viewed from the buffer sheet 142 side, the covering portion 141a is visible. Therefore, when the insulation material 140 is placed on the module, the buffer sheet 142 is positioned so as not to overlap with the safety valve.

[0104] More specifically, the relationship between the cushioning sheet 142 and the module when the insulation material 140 is placed on top of the module will be explained.

[0105] Figure 9 is a schematic diagram, viewed from above, showing an example of the placement of a buffer sheet in a module included in a battery pack according to a second embodiment of the present invention. Note that in Figure 9, the heat insulating sheet 141 is not shown, and only the placement of the buffer sheet 142 is shown. As shown in Figure 9, the buffer sheet 142 is positioned so as not to overlap with the safety valve 22 of the battery cell 21. Furthermore, the buffer sheet 142 is positioned so as not to overlap with the busbar 24 of the battery cell 21. In addition, the buffer sheet 142 is positioned to cover the portion of the first surface S of the battery cell 21 between the safety valve 22 and the connection terminal 23. Furthermore, the buffer sheet 142 is positioned to cover the portion between the safety valves 22 of two adjacent battery cells 21. Furthermore, on the first surface S, the buffer sheet 142 is positioned to cover the outer portion of the portion sandwiched between the two connection terminals 23.

[0106] Even if the cushioning sheet 142 is arranged in this manner, the cushioning sheet 142 can absorb steps and vibrations, so there is no need to make the shape of the heat insulating sheet 141 a predetermined three-dimensional shape to suppress vibrations, and the effect of the present invention is realized in that the heat insulating material 140 can be arranged even in a narrow space. Furthermore, since the cushioning sheet 142 is arranged so as not to overlap with the busbar 24, heat can be efficiently released from the busbar 24.

[0107] In addition, the preferred material configuration of the buffer sheet and the insulating sheet constituting the insulating material in the battery pack according to the second embodiment of the present invention is the same as the preferred material configuration of the buffer sheet and the insulating sheet constituting the insulating material in the battery pack according to the first embodiment of the present invention.

[0108] (Other Embodiments) In the battery packs according to the first and second embodiments described above, only one safety valve was located in the center of the first surface. Also, the battery cell had two connection terminals, and on the first surface, the safety valve was positioned so as to be sandwiched between at least two connection terminals. In the battery pack of the present invention, the number and position of the safety valve and connection terminals are not limited to the above. For example, two or more safety valves may be formed, and they may be located at the edges of the first surface. Also, the safety valve may be located in a place other than the portion sandwiched between the two connection terminals.

[0109] This specification describes the following inventions:

[0110] (1) The present invention relates to a battery pack comprising: a module having a plurality of battery cells, each having a safety valve and a connection terminal arranged on its first surface; a busbar connecting the connection terminals and electrically connecting the plurality of battery cells; a case housing the module; and a heat insulating material disposed between the module and the case on the first surface side of the battery cells, wherein the heat insulating material includes a cushioning sheet, a heat insulating sheet laminated on the cushioning sheet, and an adhesive layer for bonding the cushioning sheet and the heat insulating sheet, and the heat insulating material is arranged such that the cushioning sheet is located on the module side and the heat insulating sheet is located on the case side, and when the heat insulating material is viewed in plan view, the cushioning sheet is arranged so as not to overlap with the busbar, and the heat insulating sheet is arranged so as to overlap with the busbar.

[0111] The present invention (2) is a battery pack according to the present invention (1), wherein, when the heat insulating material is viewed in plan view, the cushioning sheet is arranged to cover the portion between the safety valve and the connection terminal on the first surface of the battery cell.

[0112] The present invention (3) is a battery pack according to the present invention (1) or (2), wherein, when the heat insulating material is viewed in plan, the cushioning sheet is arranged to cover the portion between the safety valves of each of the two adjacent battery cells.

[0113] The present invention (4) is a battery pack according to any one of the present inventions (1) to (3), wherein the battery cell has at least two of the connection terminals, the safety valve is positioned on the first surface of the battery cell so as to be sandwiched between at least two of the connection terminals, and the heat insulating sheet is arranged on the first surface so as to cover the outer portion of the portion sandwiched between at least two of the connection terminals.

[0114] The present invention (5) is a battery pack according to any one of the present inventions (1) to (4), wherein, when the above-mentioned heat insulating material is viewed in plan, the heat insulating sheet is arranged to overlap with the above-mentioned safety valve.

[0115] The present invention (6) is a battery pack according to any one of the present inventions (1) to (5), wherein, when the heat insulating material is viewed in plan, the cushioning sheet is arranged to overlap with the safety valve.

[0116] The present invention (7) is a battery pack according to the present invention (6), wherein the cushioning sheet has a first notch formed thereon that extends from one main surface to which the heat insulating sheet is bonded to the other main surface, and when the heat insulating material is viewed in plan from the heat insulating sheet side, at least a part of the first notch is positioned to overlap with the safety valve.

[0117] The present invention (8) is a battery pack according to the present invention (7), wherein when the heat insulating material is viewed in plan view from the heat insulating sheet side, the first cut portion is formed in a linear shape.

[0118] The present invention (9) is a battery pack according to any one of the present inventions (1) to (5), wherein, when the heat insulating material is viewed in plan, the cushioning sheet is arranged so as not to overlap with the safety valve.

[0119] The present invention (10) is a battery pack according to any one of the present inventions (1) to (9), wherein the thickness of the heat insulating sheet is 0.05 to 2.0 mm.

[0120] The present invention (11) is a battery pack according to any one of the present inventions (1) to (10), wherein the 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.

[0121] The present invention (12) is a battery pack according to any one of the present inventions (1) to (11), wherein the cushioning sheet is at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth.

[0122] The present invention (13) is a battery pack according to any one of the present inventions (1) to (12), wherein, when the heat insulating sheet is viewed in plan, the heat insulating 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, and the covering portion has a cut portion formed along the contour of the covering portion and a connecting portion formed along the contour of the covering portion other than the cut portion.

[0123] The present invention (14) is a battery pack according to the present invention (13), wherein the plan view shape of the covering portion is at least one selected from the group consisting of polygon, circle, ellipse and racetrack shape.

[0124] The present invention (15) is a battery pack according to the present invention (13) or (14), wherein the heat insulating sheet has at least one second notch formed therein, at least a portion of which is inside the contour of the covering portion.

[0125] The present invention (16) is a battery pack according to the present invention (15), wherein the cushioning sheet has a first notch formed that extends from the main surface to which the heat insulating sheet is adhered to the other main surface, and when the heat insulating material is viewed in plan view from the heat insulating sheet side, the first notch and the second notch overlap in the same shape.

[0126] 10, 10' Battery pack 20 Module 21 Battery cell 21a Abnormal battery cell 22, 22a Safety valve 23 Terminal 24 Busbar 30 Case 31 Housing section 31b Bottom section 31s Side wall 32 Lid section 40, 140 Insulation material 41, 141 Insulation sheet 41a, 141a Covering section 41b, 141b Main body section 41c, 141c Connection section 42, 42', 142 Cushioning sheet 50, 150 Cut section 60, 160 Second cut section 70 First cut section

Claims

1. A battery pack comprising: a module having a plurality of battery cells, each having a safety valve and connection terminals arranged on its first surface; a busbar connecting the connection terminals and electrically connecting the plurality of battery cells; a case housing the module; and a heat insulating material disposed between the module and the case on the first surface side of the battery cells, wherein the heat insulating material includes a cushioning sheet, a heat insulating sheet laminated on the cushioning sheet, and an adhesive layer bonding the cushioning sheet and the heat insulating sheet; the heat insulating material is arranged such that the cushioning sheet is located on the module side and the heat insulating sheet is located on the case side; and when the heat insulating material is viewed from above, the cushioning sheet is arranged so as not to overlap with the busbar; and the heat insulating sheet is arranged so as to overlap with the busbar.

2. The battery pack according to claim 1, wherein, when the insulating material is viewed from above, the cushioning sheet is arranged to cover the portion of the first surface of the battery cell between the safety valve and the connection terminal.

3. The battery pack according to claim 1 or 2, wherein, when the insulating material is viewed from above, the cushioning sheet is arranged to cover the portion between each of the safety valves of two adjacent battery cells.

4. The battery pack according to any one of claims 1 to 3, wherein the battery cell has at least two of the connection terminals, the safety valve is positioned on the first surface of the battery cell so as to be sandwiched between at least two of the connection terminals, and the heat insulating sheet is arranged on the first surface so as to cover the outer portion of the portion sandwiched between at least two of the connection terminals.

5. The battery pack according to any one of claims 1 to 4, wherein, when the insulating material is viewed in plan, the insulating sheet is arranged to overlap with the safety valve.

6. The battery pack according to any one of claims 1 to 5, wherein, when the insulating material is viewed from above, the cushioning sheet is arranged to overlap with the safety valve.

7. The battery pack according to claim 6, wherein the cushioning sheet has a first notch formed therein that is continuous from one main surface to which the heat insulating sheet is adhered to the other main surface, and when the heat insulating material is viewed in plan from the heat insulating sheet side, at least a part of the first notch is positioned to overlap with the safety valve.

8. The battery pack according to claim 7, wherein the first cut portion is formed in a linear shape when the insulating material is viewed in plan from the insulating sheet side.

9. The battery pack according to any one of claims 1 to 5, wherein the cushioning sheet is arranged so as not to overlap with the safety valve when the insulating material is viewed in plan.

10. The battery pack according to any one of claims 1 to 9, wherein the thickness of the heat insulating sheet is 0.05 to 2.0 mm.

11. The battery pack according to any one of claims 1 to 10, wherein the 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.

12. The battery pack according to any one of claims 1 to 11, wherein the cushioning sheet is at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth.

13. The battery pack according to any one of claims 1 to 12, wherein, when the heat insulating sheet is viewed in plan, the heat insulating sheet comprises 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, and the covering portion has a cut portion formed along the contour of the covering portion and a connecting portion formed along the contour of the covering portion other than the cut portion.

14. The battery pack according to claim 13, 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.

15. The battery pack according to claim 13 or 14, wherein the heat insulating sheet has at least one second notch formed therein, at least a portion of which is inside the contour of the covering portion.

16. The battery pack according to claim 15, wherein the cushioning sheet has a first notch formed therein that is continuous from the main surface to which the heat insulating sheet is adhered to the other main surface, and when the heat insulating material is viewed in plan view from the heat insulating sheet side, the first notch and the second notch overlap in the same shape.

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