Battery pack

Abstract

Provided is a battery pack with which size reduction is possible and in which a heat insulating material is less likely to peel off even if a battery cell undergoes 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 having a first main surface on the module side and a second main surface on the case side, and an adhesive layer laminated on the first main surface side of the first heat insulating sheet; and the adhesive layer is formed so as not to overlap the safety valves in a plan view of the heat insulating material.

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] Patent Document 1 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, and further discloses a battery module using said fireproof cover.

[0005] Chinese Utility Model Publication No. 216529122 Specification

[0006] In the battery module described in Patent Document 1, the heat insulating plate (4) is fixed using a wire harness snap (8), but this requires space to attach the wire harness snap (8), which has the problem of making the battery module larger.

[0007] One way to secure the insulation plate (4) without increasing the size of the battery module is to use adhesive instead of wire harness snaps (8). However, when the cell (2) overheats and high-temperature gas is discharged from the explosion-proof valve (21), the heat and pressure reduce the adhesive strength of the adhesive, causing the insulation plate (4) to peel off.

[0008] This invention was made to solve the above problems, and the present invention provides a battery pack that can be miniaturized and in which the heat insulating material is less likely to peel off even if the battery cells overheat.

[0009] The present invention relates to 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 having a first main surface on the module side and a second main surface on the case side, and an adhesive layer laminated on the first main surface side of the first heat insulating sheet, and the adhesive layer is formed to avoid the safety valve when the heat insulating material is viewed in plan view.

[0010] In the battery pack of the present invention, the first heat insulating sheet is bonded with an adhesive. Therefore, the heat insulating material can be fixed without using other components. As a result, the battery pack of the present invention can be miniaturized.

[0011] In the battery pack of the present invention, when the above-mentioned insulating material is viewed from above, the adhesive layer is formed to avoid the safety valve. Therefore, even if the battery cell experiences thermal runaway and generates high-temperature gas, the insulating material is unlikely to peel off. This principle is explained below.

[0012] For example, suppose that when the above-mentioned insulation material is viewed from above, the adhesive layer is also located at the position of the safety valve. In this case, if the battery cell overheats and generates high-temperature gas, and the gas is released from the safety valve, the gas will hit the adhesive layer. The adhesive strength of the part of the adhesive layer that is hit by the gas will decrease due to the heat of the gas. Furthermore, that heat will be conducted to the surrounding adhesive layer, and the adhesive strength of the surrounding adhesive layer will also decrease. In other words, when gas is released from the safety valve, the adhesive strength will decrease not only in the part of the adhesive layer that is directly hit by the gas, but also in the surrounding area. Furthermore, the adhesive layer in the part that is hit by the gas will become more prone to peeling due to the pressure of the gas. The surrounding adhesive layer will also become more prone to peeling in conjunction. As a result, the insulation material will become more prone to peeling from other components such as modules in these areas. On the other hand, in the battery pack of the present invention, when the above-mentioned insulation material is viewed from above, the adhesive layer is formed to avoid the safety valve. Therefore, even if the battery cell overheats and generates high-temperature gas, and the gas is released from the safety valve, the gas will not directly hit the adhesive layer. Therefore, the heat from the gas is not easily conducted to the adhesive layer. Also, since the gas does not directly contact the adhesive layer, the gas pressure is not easily transmitted to the adhesive layer. As a result, the adhesive strength of the adhesive layer is maintained, and the insulation material is less likely to peel off from components such as modules.

[0013] In the battery pack of the present invention, when the module is viewed from above, the plurality of battery cells are arranged in the module such that the safety valves are aligned in a line along the first direction, and the first adhesive layer may be formed so as to avoid the area where the safety valves are aligned in a line, and so as to be continuous with the first direction. In this case, when the module is viewed from above, it is preferable that at least two of the adhesive layers are formed at different positions, and the safety valves are positioned between the two adhesive layers. Since such a battery pack of the present invention can be manufactured by arranging strip-shaped adhesive layers, manufacturing efficiency is increased.

[0014] In the battery pack of the present invention, when the module is viewed from above, the plurality of battery cells are arranged in the module such that the safety valves are aligned in a line along the first direction, and the adhesive layer may be formed so as to surround each of the safety valves. When the adhesive layer is formed in this way, the area of ​​the adhesive layer can be increased, making it more difficult for the heat insulating material to peel off.

[0015] In the battery pack of the present invention, the thickness of the first heat insulating sheet is preferably 0.05 to 2.0 mm. If the thickness of the first heat insulating sheet is less than 0.05 mm, the strength of the first heat insulating sheet will be low and it will be easily damaged. If the thickness of the first heat insulating sheet exceeds 2.0 mm, the first heat insulating sheet will be too thick, making it difficult to miniaturize the entire battery pack.

[0016] In the battery pack of the present invention, when the first heat insulating sheet is viewed in plan, the first 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, wherein one of the covering portions is positioned to overlap with at least a part of one of the safety valves, and preferably 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.

[0017] In this battery pack of the present invention, it is possible to 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.

[0018] 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 discharged from the safety valve then reaches the insulating material.

[0019] The insulation material includes a first insulation sheet. When viewed from above, the first insulation sheet consists of multiple covering portions that cover each of the multiple safety valves, and a main body portion other than the covering portions. Therefore, the gas discharged from the safety valves will come into contact with the covering portions.

[0020] In the battery pack of the present invention, 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. When gas discharged from the safety valve hits the covering portion, the pressure causes the connection portion to break, and the covering portion separates from the main body along the cut portion.

[0021] The gas then passes through the area where the first insulation sheet was covering and is discharged between the insulation material and the case.

[0022] Furthermore, the gas discharged between the insulation material and the case also reaches other covering parts of the first insulation sheet. However, these other covering parts of the first insulation sheet are connected to the main body, and these covering parts do not detach from the main body due to the pressure of the gas discharged between the insulation material and the case. Therefore, even if the gas reaches other covering parts of the first insulation sheet, the gas is blocked by the covering parts. Consequently, it is possible to prevent the gas from flowing back through the safety valves of other battery cells.

[0023] In the battery pack of the present invention, it is preferable that the first heat insulating sheet has at least one first notch formed therein, at least a portion of which is inside the contour of the covering portion. When the first heat insulating sheet has a first notch formed therein, the covering portion is more likely to tear along the first notch. Therefore, when the battery cell experiences thermal runaway and high-temperature gas is generated, the gas can be quickly discharged.

[0024] 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.

[0025] 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.

[0026] In the battery pack of the present invention, the heat insulating material may further include a second heat insulating sheet disposed on the first main surface side of the first heat insulating sheet. When such a second heat insulating sheet is provided, gas released from an abnormal battery cell passes through the second heat insulating sheet before reaching the first heat insulating sheet. As the gas passes through the second heat insulating sheet, its temperature and pressure decrease. Therefore, even if the gas passes through the area where the first heat insulating sheet was covering and comes into contact with the case, the case is less likely to be heated or damaged by the gas.

[0027] In the battery pack of the present invention, the adhesive layer may be positioned at the location where the second heat insulating sheet is bonded to the first heat insulating sheet, and / or at the location where the second heat insulating sheet is bonded to the module. Even when the adhesive layer is positioned in this manner, since the adhesive layer is formed to avoid the safety valve, the heat insulating material is unlikely to peel off even if the battery cell experiences thermal runaway and generates high-temperature gas.

[0028] In the battery pack of the present invention, when the first heat insulating sheet is viewed from above, the first 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 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, and the second heat insulating sheet has a second notch portion that is continuous from the main surface on the first heat insulating sheet side to the other main surface, and when the heat insulating material is viewed from above from the first heat insulating sheet side, it is preferable that at least a part of the second notch portion is located inside the covering portion. When the second heat insulating sheet has a second notch portion, high-temperature gas from the module side can easily reach the covering portion through the second notch portion.

[0029] In the battery pack of the present invention, when the heat insulating material is viewed from above from the first heat insulating sheet side, it is preferable that the second cut portion is formed in a linear shape. The linear second cut portion can be easily formed with a cutter or the like.

[0030] In the battery pack of the present invention, the first heat insulating sheet has at least one first notch formed therein, at least a portion of which is inside the contour of the covering portion, and it is preferable that when the heat insulating material is viewed in plan view from the first heat insulating sheet side, the first notch and the second notch overlap in the same shape. Such a first notch and a second notch can be formed simultaneously by punching out the first heat insulating sheet and the second heat insulating sheet while they are stacked on top of each other.

[0031] In the battery pack of the present invention, the second heat insulating sheet may be at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth. Among these, the inorganic fiber mat is preferred. These can be easily molded, and the inorganic fiber mat exhibits excellent performance as the second heat insulating sheet.

[0032] According to the present invention, it is possible to provide a battery pack that can be miniaturized and in which the heat insulating material is less likely to peel off even if the battery cells experience thermal runaway.

[0033] 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 a cross-sectional view taken along line B-B in Figure 1A. Figure 1D is an exploded view of the battery pack shown in Figure 1A. Figure 2A 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 2B is a plan view of the heat insulating material included in the battery pack according to the first embodiment of the present invention, as seen from the case side. Figure 2C is a plan view of the heat insulating material included in the battery pack according to the first embodiment of the present invention, as seen from the module side. Figure 3A 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 3B 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 3C 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 4A is a plan view of another example of the thermal insulation material according to the first embodiment of the present invention, as seen from the module side. Figure 4B is a plan view of another example of the thermal insulation material according to the first embodiment of the present invention, as seen from the module side. Figure 4C is a plan view of another example of the thermal insulation material according to the first embodiment of the present invention, as seen from the module side. Figure 5 is a schematic cross-sectional view showing an example of a battery pack according to the second embodiment of the present invention.

[0034] 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.

[0035] (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 a cross-sectional view taken along line B-B in Figure 1A. Figure 1D is an exploded view of the battery pack shown in Figure 1A.

[0036] The battery pack 10 shown 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 houses the module 20 with a heat insulating material 40 provided between the module 20 and the case 65 30.

[0037] As shown in FIGS. 1A to 1C, the case 30 includes a housing portion 31 formed by a bottom portion 31b and side walls 31s, and a lid portion 32 that covers the housing portion 31. In the battery pack 10, a heat insulating material 40 is provided between the module 20 and the case 30. The heat insulating material 40 includes a first heat insulating sheet 41 having a first main surface S on the module 20 side and a second main surface S on the case 30 side, and an adhesive layer 81 laminated on the first main surface S of the first heat insulating sheet 41. The first heat insulating sheet 41 is adhered to the module 20 by the adhesive layer 81. Therefore, the heat insulating material 40 can be fixed without using other members. Thus, the battery pack 10 can be miniaturized. The adhesive layer 81 is formed so as to avoid the safety valve 22 (details will be described later). １ And a second main surface S on the case 30 side ２ And a first heat insulating sheet 41 having a first main surface S １ Side, and includes an adhesive layer 81 laminated on the first main surface S of the first heat insulating sheet 41. The first heat insulating sheet 41 is adhered to the module 20 by the adhesive layer 81. Therefore, the heat insulating material 40 can be fixed without using other members. Thus, the battery pack 10 can be miniaturized. The adhesive layer 81 is formed so as to avoid the safety valve 22 (details will be described later).

[0038] The battery cell 21 stores electric power and is preferably, for example, a so-called secondary battery that can be charged. Examples of the secondary battery include a lithium ion battery, a nickel hydrogen battery, and a sodium ion battery. The battery cells 21 shown in FIGS. 1B to 1D are rectangular parallelepiped. 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).

[0039] As shown in FIGS. 1B to 1D, in the module 20, a plurality of battery cells 21 are arranged in a row and fixed by a connection module member 20a. Further, the safety valves 22 of the battery cells 21 are arranged in a row along the first direction D. As shown in FIG. 1D, the battery cell 21 has terminals 23, and adjacent battery cells 21 are electrically connected by connecting the respective terminals 23 to a bus bar 20b arranged on the connection module member 20a.

[0040] The bus bar 20b is a flat member made of metal and having 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, etc.).

[0041] Examples of the material constituting the case 30 include steel materials and aluminum. As the steel material, stainless steel (SUS) is preferable.

[0042] FIG. 2A is a cross-sectional view schematically showing an example of one safety valve and a heat insulating material in the vicinity thereof in the battery pack according to the first embodiment of the present invention. FIG. 2B is a plan view of the heat insulating material included in the battery pack according to the first embodiment of the present invention as viewed from the case side. FIG. 2C is a plan view of the heat insulating material included in the battery pack according to the first embodiment of the present invention as viewed from the module side.

[0043] As shown in FIG. 2A, the first heat insulating sheet 41 includes a plurality of covering portions 41a covering each of the plurality of safety valves 22 and a main body portion 41b other than the covering portions 41a. One covering portion 41a is positioned so as to overlap one safety valve 22.

[0044] As shown in FIG. 2B, 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. Further, in the first heat insulating sheet 41, two first cut portions 60 are formed in a cross shape by two line segments inside the contour C of the covering portion 41a.

[0045] As shown in FIG. 2C, in the battery pack 10, the covering portions 41a are arranged in a row, but the region (in FIG. 2C, A １The adhesive layer 81 is formed so as to avoid the area indicated by the arrow and to be continuous with the first direction D. In other words, two adhesive layers 81 are formed in a strip shape along the first direction D, and the covering portion 41a is positioned so as to be sandwiched between the two adhesive layers 81. In the battery pack 10, the first heat insulating sheet 41 is bonded to the module 20 by the adhesive layer 81, so in the battery pack 10, each safety valve 22 is positioned so as to be sandwiched between the two adhesive layers 81. Since such a heat insulating material 40 can be manufactured by arranging strip-shaped adhesive layers 81, the manufacturing efficiency is high.

[0046] 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.

[0047] Figures 3A to 3C 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. As shown in Figure 3A, when one battery cell 21a experiences thermal runaway and high-temperature gas is generated from the battery cell 21a, gas G (in Figure 3A, 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. The gas discharged from the safety valve 22a then reaches the heat insulating material 40 (first heat insulating sheet 41).

[0048] The first heat insulating sheet 41 consists of multiple covering portions 41a that cover each of the multiple safety valves 22, and a main body portion 41b other than the covering portions 41a. Therefore, the gas G released from the safety valve will come into contact with the covering portions 41a.

[0049] As shown in Figure 3B, when the gas G released from the safety valve 22a hits the covering portion 41a, the pressure causes the connection portion 41c to rupture, and the covering portion 41a separates from the main body portion 41b along the contour C of the covering portion 41a. Since the first insulation sheet 41 has a first cut portion 60 formed therein, the covering portion 41a will rip open along the first cut portion 60. Therefore, when the battery cell 21 experiences thermal runaway and generates high-temperature gas G, the gas can be quickly discharged.

[0050] 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 first insulation sheet 41 and the case 30.

[0051] Furthermore, as shown in Figure 3C, the gas G released between the first insulation sheet 41 and the case 30 also reaches other covering portions 41a of the first insulation sheet 41. However, these other covering portions 41a of the first insulation sheet 41 are connected to the main body portion 41b by a connecting portion 41c, and the connecting portion 41c does not rupture under the pressure of the gas G released between the first insulation sheet 41 and the case 30. Therefore, even if the gas reaches other covering portions 41a of the first insulation 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.

[0052] In the battery pack 10, when the insulating material 40 is viewed from above, the adhesive layer 81 is formed to avoid the safety valve 22. Therefore, even if the battery cell 21 experiences thermal runaway and generates high-temperature gas G, the insulating material 40 is unlikely to peel off from the module 20. This principle is explained below.

[0053] For example, suppose that when viewing the insulation material in a plan view, the adhesive layer is also located at the position of the safety valve. In this case, if the battery cell experiences thermal runaway and generates high-temperature gas, and the gas is released from the safety valve, the gas will hit the adhesive layer. The adhesive strength of the part of the adhesive layer that is hit by the gas will decrease due to the heat of the gas. Furthermore, this heat will be conducted to the surrounding adhesive layer, reducing the adhesive strength of that layer as well. In other words, when gas is released from the safety valve, the adhesive strength decreases not only in the part of the adhesive layer that was directly hit by the gas, but also in the surrounding area. In addition, the adhesive layer in the part that is hit by the gas becomes more prone to delamination due to the pressure of the gas. The surrounding adhesive layer also becomes more prone to delamination in conjunction with this. As a result, the insulation material becomes more likely to delaminate from other components such as modules in these areas.

[0054] On the other hand, in the battery pack 10, when the insulation material 40 is viewed from above, the adhesive layer 81 is formed to avoid the safety valve 22. Therefore, even if the battery cell 21 experiences thermal runaway and generates high-temperature gas G, and the gas G is discharged from the safety valve 22, the gas G will not directly come into contact with the adhesive layer 81. Consequently, the heat from the gas G is not easily conducted to the adhesive layer 81. Also, since the gas G does not directly come into contact with the adhesive layer 81, the pressure from the gas G is not easily transmitted to the adhesive layer 81. As a result, the adhesive strength of the adhesive layer 81 is maintained, and the insulation material 40 is less likely to peel off from the module 20.

[0055] The following describes preferred embodiments of the heat insulating material for the battery pack according to the first embodiment of the present invention.

[0056] In the battery pack 10, the first 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 the first heat insulating sheet.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Furthermore, the average fiber length of the second inorganic fiber is preferably less than 1 μm in order to avoid impairing moldability.

[0065] Furthermore, the inorganic fiber paper may also contain other components such as organic fibers, inorganic particles, organic particles, and resin binders.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] Examples of particles made from thermally expandable inorganic materials that constitute the inorganic particles contained in inorganic fiber paper include vermiculite, bentonite, and perlite.

[0079] 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.

[0080] 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.

[0081] Inorganic fiber cloth is made by weaving inorganic fibers into a cross shape. Such inorganic fiber cloth has high strength and high heat resistance.

[0082] 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.

[0083] When the first heat insulation sheet 41 is a mica sheet or a heat-resistant resin sheet, the thickness of the first heat insulation 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. When the thickness of the first heat insulation sheet composed of a mica sheet or a heat-resistant resin sheet is less than 0.05 mm, the strength of the first heat insulation sheet becomes low, and it becomes easy to break. When the thickness of the first heat insulation sheet composed of a mica sheet or a heat-resistant resin sheet exceeds 2.0 mm, the first heat insulation sheet becomes too thick, making it difficult to miniaturize the entire battery pack.

[0084] Also, when the first heat insulation sheet 41 is inorganic fiber paper, the thickness of the first heat insulation sheet 41 is preferably 0.5 to 5.0 mm, and more preferably 0.8 mm to 3.0 mm. In this case, the first heat insulation sheet 41 composed of inorganic fiber paper can obtain sufficient mechanical strength.

[0085] Also, when the first heat insulation sheet 41 is an inorganic fiber cloth, the thickness of the first heat insulation sheet 41 is preferably 0.1 to 5.0 mm, and more preferably 0.3 mm to 1.4 mm. In this case, it is possible to balance the mechanical strength and flexibility of the first heat insulation sheet 41 composed of inorganic fiber cloth. Therefore, the first heat insulation sheet 41 composed of inorganic fiber cloth can be bent along a predetermined shape and used.

[0086] The area of the planar shape of the covering portion 41a is preferably 1.0 to 18 cm ２ and more preferably 3 to 12 cm ２ When the area of the planar shape of the covering portion is less than 1.0 cm ２ , it becomes difficult for the gas to pass through the portion where the covering portion 41a is located. When the area of the planar shape of the covering portion exceeds 18 cm ２ , the covering portion tends to be wider than the range where the gas reaches. Therefore, it becomes difficult for the covering portion to separate from the main body portion.

[0087] 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.

[0088] 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.

[0089] In the battery pack 10, the adhesive layer 81 may contain an adhesive resin such as a polyamide-based organic material, an acrylic-based organic material, an epoxy-based organic material, or a silicone-based organic material.

[0090] In the battery pack 10, the thickness of the adhesive layer 81 is not particularly limited, but it is preferably 50 to 500 μm.

[0091] Next, preferred placement positions of the adhesive layer in the battery pack according to the first embodiment of the present invention will be described. Figures 4A to 4C are plan views of another example of the heat insulating material according to the first embodiment of the present invention, as seen from the module side.

[0092] In the thermal insulation material 40A shown in Figure 4A, adhesive layers 81A are arranged in a strip shape at both ends in the first direction D on the first main surface of the first thermal insulation sheet 41.

[0093] Furthermore, in the thermal insulation material 40B shown in Figure 4B, an adhesive layer 81B is arranged in a ring shape at the edge of the first main surface of the first thermal insulation sheet 41.

[0094] Furthermore, in the insulation material 40C shown in Figure 4C, the adhesive layer 81C is arranged so as to surround the covering portion 41a of the first main surface of the first insulation sheet 41. Since the first insulation sheet 41 is bonded to the module 20 by the adhesive layer 81C, in the battery pack 10, the adhesive layer 81C is arranged so as to surround each of the safety valves 22.

[0095] In the battery pack according to the first embodiment of the present invention, even with the adhesive layer formed in this manner, miniaturization is possible, and the effects of the present invention can be obtained, such as the fact that the heat insulating material is less likely to peel off even if the battery cell experiences thermal runaway.

[0096] Next, the uses and arrangement methods of the battery pack according to the first embodiment of the present invention will be described.

[0097] 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.

[0098] 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).

[0099] 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.

[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, in the heat insulating material, the second heat insulating sheet is arranged on the first main surface side of the first heat insulating sheet, and adhesive layers are arranged between the first heat insulating sheet and the second heat insulating sheet, and between the second heat insulating sheet and the module. This battery pack according to the second embodiment of the present invention will be described with reference to the drawings.

[0101] Figure 5 is a schematic cross-sectional view showing an example of a battery pack according to a second embodiment of the present invention. In the battery pack 110 shown in Figure 5, the first main surface S of the first heat insulating sheet 141 in the heat insulating material 140 １ A second heat insulating sheet 142 is positioned on the side. Furthermore, in the battery pack 110, an adhesive layer 181 is formed between the first heat insulating sheet 141 and the second heat insulating sheet 142, and an adhesive layer 182 is formed between the second heat insulating sheet 142 and the module 20. Both adhesive layers 181 and 182 are formed to avoid the safety valve 22. The configuration of the battery pack 110 other than this configuration is preferably the same as the configuration of the battery pack 10 described above.

[0102] The preferred position of the adhesive layer 181 is the same as the preferred position of the adhesive layer 81. Furthermore, it is preferable that the adhesive layer 182 is positioned so as to overlap exactly with the adhesive layer 181 when the insulation material 140 is viewed from above.

[0103] With the second insulation sheet 142 in place, the gas G released from the abnormal battery cell passes through the second insulation sheet 142 before reaching the first insulation sheet 141. The gas pressure of the gas G then causes the covering portion 141a to separate from the main body portion 141b. Furthermore, the temperature and pressure of the gas G decrease as it passes through the second insulation sheet 142. Therefore, even if the gas G passes through the area where the covering portion 141a of the first insulation sheet 141 was located and comes into contact with the case 30, the case 30 is less likely to be heated or damaged by the gas G.

[0104] Furthermore, since both adhesive layers 181 and 182 are formed to avoid the safety valve 22, the gas G does not directly come into contact with adhesive layers 181 and 182. Therefore, the heat from the gas G is not easily conducted to adhesive layers 181 and 182. Also, since the gas G does not directly come into contact with adhesive layers 181 and 182, the pressure from the gas G is not easily transmitted to adhesive layers 181 and 182. As a result, the adhesive strength of adhesive layers 181 and 182 is maintained, and the insulation material 140 is less likely to peel off from the module 20.

[0105] In the battery pack 110, the second insulation sheet 142 has a second notch formed that extends from the main surface on the first insulation sheet 141 side to the other main surface, and when the insulation material 140 is viewed from above from the first insulation sheet 141 side, it is preferable that at least a part of the second notch is located inside the covering portion 141a. When the second insulation sheet 142 has a second notch, high-temperature gas G from the module 20 side can easily reach the covering portion 141a by passing through the second notch. When the insulation material 140 is viewed from above from the first insulation sheet 141 side, the second notch may be located only inside the covering portion 141a, or it may be located so as to intersect with the contour of the covering portion 141a.

[0106] In the battery pack 110, when the heat insulating material 140 is viewed from above from the first heat insulating sheet 141 side, the second cut portion may be formed in a linear shape or a curved shape, but it is preferable that it be formed in a linear shape. A linear second cut portion can be easily formed with a cutter or the like.

[0107] In the battery pack 110, the second insulation sheet 142 may have multiple second notches. Also, in the battery pack 110, when the insulation material 140 is viewed from the first insulation sheet 141 side, the multiple second notches may be separated from each other or may intersect each other. In either case, gas G generated from an abnormal battery cell can easily reach the first insulation sheet 141 quickly through the second notches.

[0108] In the battery pack 110, the first insulation sheet 141 has at least one first notch formed therein, at least a portion of which is inside the contour of the covering portion, and when the insulation material 140 is viewed from the first insulation sheet 141 side, the first notch and the second notch may overlap and have the same shape. Such a first notch and a second notch can be formed simultaneously by punching out the first insulation sheet 141 and the second insulation sheet 142 while they are stacked on top of each other. Note that the first notch and the second notch do not have to overlap and may have different shapes.

[0109] In the battery pack 110, the second heat insulating sheet 142 may be at least one selected from the group consisting of inorganic fiber mat, inorganic fiber paper, and inorganic fiber cloth. Among these, the inorganic fiber mat is preferred. These can be easily molded, and the inorganic fiber mat exhibits excellent performance as the second heat insulating sheet.

[0110] The thickness of the inorganic fiber mat is preferably 0.5 to 10 mm, and more preferably 1 to 4 mm. If the inorganic fiber mat is less than 0.5 mm thick, the gas temperature and pressure do not decrease easily as the gas passes through the mat. As a result, the gas reaches the case quickly at a high temperature, causing the case to deteriorate easily. If the inorganic fiber mat is more than 10 mm thick, it becomes too thick, making it difficult to miniaturize the entire battery pack.

[0111] 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. ３ If the bulk density is less than 1.0 g / cm³, the gaps between the inorganic fibers become larger, so the gas temperature and pressure do not decrease easily as the gas passes through the inorganic fiber mat. As a result, the gas reaches the case with high pressure while still at a high temperature, making the case more prone to deterioration. ３If the temperature exceeds a certain level, the gas will have difficulty passing through the inorganic fiber mat, causing the high-temperature gas to remain inside the battery cell and making it difficult for the temperature inside the battery cell to decrease. This makes it easier for a chain reaction of thermal runaway to occur.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] Furthermore, the preferred forms of inorganic fiber paper and inorganic fiber cloth as the second heat insulating sheet 142 are the same as those described in the first embodiment of the present invention as preferred inorganic fiber paper and inorganic fiber cloth as the first heat insulating sheet.

[0116] (Other Embodiments) In the battery packs according to the first and second embodiments of the present invention described above, the adhesive layer was formed so as to avoid the covering portion of the first heat insulating sheet when the heat insulating material was viewed in plan. However, in the battery pack of the present invention, when the heat insulating material was viewed in plan, the adhesive layer only needs to be formed so as to avoid the safety valve, and for example, the adhesive layer may be formed on a part of the covering portion.

[0117] In the battery pack according to the first embodiment of the present invention described above, a first notch was formed in the covering portion, but in the battery pack of the present invention, a first notch may not be formed in the covering portion.

[0118] In the battery pack according to the second embodiment of the present invention described above, adhesive layers were formed between the first and second heat insulating sheets, and between the second heat insulating sheet and the module. However, in the battery pack of the present invention, the adhesive layer may be formed only between the first and second heat insulating sheets. In this case, the heat insulating material may be fixed to the module using a separate component. Alternatively, the adhesive layer may be formed only between the second heat insulating sheet and the module. In this case, the first and second heat insulating sheets may be fixed using a separate component.

[0119] This specification describes the following inventions:

[0120] (1) The present invention relates to 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 having a first main surface on the module side and a second main surface on the case side, and an adhesive layer laminated on the first main surface side of the first heat insulating sheet, and the adhesive layer is formed to avoid the safety valve when the heat insulating material is viewed in plan view.

[0121] The present invention (2) is a battery pack according to the present invention (1), wherein, when the module is viewed from above, the plurality of battery cells are arranged in the module such that the safety valves are lined up in a row along the first direction, and the adhesive layer is formed so as to avoid the area where the safety valves are lined up in a row and so as to be continuous with the first direction.

[0122] The present invention (3) is a battery pack according to the present invention (2), wherein, when the module is viewed from above, at least two of the adhesive layers are formed at different positions, and the safety valve is arranged to be sandwiched between the two adhesive layers.

[0123] The present invention (4) is a battery pack according to the present invention (1), wherein, when the module is viewed from above, the plurality of battery cells are arranged in the module such that the safety valves are lined up in a row along the first direction, and the adhesive layer is formed so as to surround each of the safety valves.

[0124] The present invention (5) is a battery pack according to any one of the present inventions (1) to (4), wherein the thickness of the first heat insulating sheet is 0.05 to 2.0 mm.

[0125] The present invention (6) is a battery pack according to any one of the present inventions (1) to (5), wherein, when the first heat insulating sheet is viewed in plan, the first 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.

[0126] The present invention (7) is a battery pack according to the present invention (6), wherein the first heat insulating sheet has at least one first notch formed therein, at least a portion of which is inside the contour of the covering portion.

[0127] The present invention (8) is a battery pack according to the present invention (6) or (7), 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.

[0128] The present invention (9) is a battery pack according to any one of the present inventions (1) to (8), 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.

[0129] The present invention (10) is a battery pack according to any one of the present inventions (1) to (9), wherein the heat insulating material further comprises a second heat insulating sheet disposed on the first main surface side of the first heat insulating sheet.

[0130] The present invention (11) is a battery pack according to the present invention (10) wherein the adhesive layer is positioned at a location where the second heat insulating sheet is bonded to the first heat insulating sheet, and / or at a location where the second heat insulating sheet is bonded to the module.

[0131] The present invention (12) is a battery pack according to the present invention (10) or (11), wherein, when the first heat insulating sheet is viewed in plan, the first 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, 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, the second heat insulating sheet has a second notch formed that is continuous from the main surface on the first heat insulating sheet side to the other main surface, and when the heat insulating material is viewed in plan from the first heat insulating sheet side, at least a part of the second notch is located inside the covering portion.

[0132] The present invention (13) is a battery pack according to the present invention (12), wherein when the heat insulating material is viewed in plan view from the first heat insulating sheet side, the second cut portion is formed in a linear shape.

[0133] The present invention (14) is a battery pack according to the present invention (12) or (13), wherein the first heat insulating sheet has at least one first notch formed therein, at least a part of which is inside the contour of the covering portion, and when the heat insulating material is viewed in plan view from the first heat insulating sheet side, the first notch and the second notch overlap in the same shape.

[0134] The present invention (15) is a battery pack according to any one of the present inventions (10) to (14), 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.

[0135] 10, 110 Battery pack 20 Module 20a Connection module component 20b Busbar 21 Battery cell 21a Abnormal battery cell 22, 22a Safety valve 23 Terminal 30 Case 31 Housing section 31b Bottom section 31s Side wall 32 Lid section 40, 40A, 40B, 40C, 140 Insulation material 41, 141 First insulation sheet 41a, 141a Covering section 41b, 141b Main body section 41c Connection section 50 Cutting section 60 First cut section 81, 81A, 81B, 81C, 181, 182 Adhesive layer 142 Second insulation sheet S １ First main surface of the first insulation sheet S ２ Second main surface of the first insulation sheet

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 heat insulating material provided between the module and the case, wherein the heat insulating material includes a first heat insulating sheet having a first main surface on the module side and a second main surface on the case side, and an adhesive layer laminated on the first main surface side of the first heat insulating sheet, and the adhesive layer is formed to avoid the safety valve when the heat insulating material is viewed from above.

2. The battery pack according to claim 1, wherein, when the module is viewed from above, the plurality of battery cells are arranged in the module such that the safety valves are aligned in a line along the first direction, and the adhesive layer is formed so as to avoid the area where the safety valves are aligned in a line and so as to be continuous with the first direction.

3. The battery pack according to claim 2, wherein, when the module is viewed from above, at least two of the adhesive layers are formed at different positions, and the safety valve is positioned between the two adhesive layers.

4. The battery pack according to claim 1, wherein, when the module is viewed from above, the plurality of battery cells are arranged in the module such that the safety valves are aligned in a line along the first direction, and the adhesive layer is formed so as to surround each of the safety valves.

5. The battery pack according to any one of claims 1 to 4, wherein the thickness of the first heat insulating sheet is 0.05 to 2.0 mm.

6. The battery pack according to any one of claims 1 to 5, wherein, when the first heat insulating sheet is viewed in plan, the first 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.

7. The battery pack according to claim 6, wherein the first heat insulating sheet has at least one first notch formed therein, at least a portion of which is inside the contour of the covering portion.

8. The battery pack according to claim 6 or 7, 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.

9. The battery pack according to any one of claims 1 to 8, 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.

10. The battery pack according to any one of claims 1 to 9, further comprising a second insulating sheet disposed on the first main surface side of the first insulating sheet.

11. The battery pack according to claim 10, wherein the adhesive layer is positioned to bond the second heat insulating sheet to the first heat insulating sheet, and / or to bond the second heat insulating sheet to the module.

12. The battery pack according to claim 10 or 11, wherein, when the first heat insulating sheet is viewed in plan, the first 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, 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, the second heat insulating sheet has a second notch formed that is continuous from the main surface on the first heat insulating sheet side to the other main surface, and when the heat insulating material is viewed in plan from the first heat insulating sheet side, at least a part of the second notch is located inside the covering portion.

13. The battery pack according to claim 12, wherein the second cut portion is formed in a linear shape when the insulating material is viewed in plan view from the first insulating sheet side.

14. The battery pack according to claim 12 or 13, wherein the first heat insulating sheet has at least one first notch formed therein, at least a portion of which is inside the contour of the covering portion, and when the heat insulating material is viewed in plan view from the first heat insulating sheet side, the first notch and the second notch overlap in the same shape.

15. The battery pack according to any one of claims 10 to 14, 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.

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