Battery pack and heat insulating material

Abstract

Provided is a battery pack that makes it possible to quickly discharge a high-temperature gas that is emitted from an abnormal battery cell during thermal runaway, and prevent a thermal runaway cascade that is caused by backflow of the high-temperature gas to an adjacent battery cell. The battery pack according to the present invention comprises a module that has a plurality of battery cells that are each provided with a safety valve, a case for accommodating the module, and a heat insulating material that is provided between the module and the case, the battery pack being characterized in that: the heat insulating material includes a first heat insulating sheet; when the first heat insulating sheet is viewed in plan view, the heat insulating sheet is composed of a plurality of covering portions that cover each of the plurality of safety valves, and a main portion other than the covering portions; one covering portion is positioned so as to overlap at least a portion of one safety valve; each covering portion is formed so that a plurality of connection portions and a plurality of cutoff portions are alternately arranged along the contour of the covering portion, and the plurality of cutoff portions are arranged in a broken line shape; and the ratio of the length of one of the connection portions to the length of one of the cutoff portions (connection portion length / cutoff portion length) is 0.5–2.0.

Description

Battery pack and insulation

[0001] This invention relates to a battery pack and a thermal insulation material.

[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 such a battery pack, Patent Document 1 discloses an energy storage device comprising: an energy storage stack including a plurality of energy storage cells, each having an exhaust valve on its upper surface; an upper case covering the energy storage stack from above; and a first heat-resistant sheet and a second heat-resistant sheet having heat resistance to exhaust gas discharged from the exhaust valves and being disposed between the upper case and the energy storage stack, wherein the first heat-resistant sheet has a plurality of holes in positions that overlap vertically with each of the exhaust valves, and the second heat-resistant sheet is disposed above the first heat-resistant sheet so as to cover the plurality of holes.

[0005] Furthermore, Patent Document 2 discloses a battery module composed of multiple stacked battery cells, each battery cell having an explosion-proof valve, an insulating cover covering the battery cell group, the insulating cover having an integral structure, the explosion-proof valves facing the insulating cover, and the insulating cover having a vulnerable region corresponding to each explosion-proof valve.

[0006] Japanese Patent Publication No. 2023-59480, Chinese Utility Model Publication No. 219457784, Specification

[0007] Patent Document 1 describes the need to discharge gas from abnormal cells during thermal runaway, and for this purpose, the first heat-resistant sheet is provided with multiple holes. However, there is a possibility that the gas discharged from the abnormal cell may flow back through the holes and exhaust valves of adjacent cells and come into contact with them. In this case, ignition (heat chain reaction) of adjacent cells may be triggered.

[0008] In Patent Document 2, the heat-insulating cover does not have a hole at the position corresponding to the explosion-proof valve of the battery cell, but a vulnerable area is provided. In the event of thermal runaway, the structure is designed so that the vulnerable area at the position corresponding to the explosion-proof valve of the abnormal battery cell ruptures due to the pressure of the gas discharged from the abnormal battery cell. However, there were cases where the vulnerable area did not rupture sufficiently and the high-temperature gas could not be sufficiently discharged, or where the vulnerable area ruptured too much, exposing the explosion-proof valve of a normal battery cell, and high-temperature gas could flow back into the normal battery cell from the exposed explosion-proof valve.

[0009] The present invention was made to solve the above problems, and aims to provide a battery pack that can quickly discharge high-temperature gas when it is ejected from an abnormal battery cell during thermal runaway, and can prevent a chain reaction of thermal runaway caused by the backflow of high-temperature gas to adjacent battery cells.

[0010] 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, and when 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, wherein one of the covering portions is positioned to overlap with at least a part of one of the safety valves, and the covering portion is formed such that a plurality of connection portions and a plurality of cut portions are arranged alternately along the contour of the covering portion, and the plurality of cut portions are arranged in a dashed line pattern, and the ratio of the length of one connection portion to the length of one cut portion ([length of connection portion] / [length of cut portion]) is 0.5 to 2.0.

[0011] The battery pack of the present invention can prevent a chain reaction of thermal runaway caused by high-temperature gases from abnormal battery cells that occur during thermal runaway. The principle is explained below.

[0012] 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.

[0013] 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.

[0014] In the battery pack of the present invention, the covering portion has multiple connection portions and multiple cut portions formed alternately along the contour of the covering portion, and the multiple cut portions are arranged in a dashed line pattern. When gas discharged from the safety valve hits the covering portion, the pressure causes the connection portions to break, and the covering portion separates from the main body along the cut portions.

[0015] In particular, in the battery pack of the present invention, the ratio of the length of one connection part to the length of one cut part ([length of connection part] / [length of cut part]) is 0.5 to 2.0. When the above ratio ([length of connection part] / [length of cut part]) is within the above range, the maximum stress when gas hits the coating part tends to increase, and the coating part tends to separate from the main body part.

[0016] The gas then passes through the area where the first insulation sheet was covering and is discharged between the insulation material and the case.

[0017] 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.

[0018] In the battery pack of the present invention, the length of one of the cut sections is preferably 2.0 mm to 16.0 mm, and the length of one of the connection sections is preferably 2.0 mm to 8.0 mm. When the lengths of the cut sections and connection sections are within the above ranges, the covering portion is more easily separated from the main body when the battery cell experiences thermal runaway and generates high-temperature gas.

[0019] 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. Furthermore, in the battery pack of the present invention, the thickness of the main body is preferably 0.3 to 2.0 mm, and the thickness of the covering is preferably 0.05 to 0.3 mm.

[0020] 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.

[0021] In the battery pack of the present invention, the first notch and the cut portion may be separated. If the first notch and the cut portion are separated, the portion between the first notch and the cut portion becomes a support portion for the covering portion. Therefore, when gas pressure is applied to the covering portion, the pressure is also distributed to the portion between the first notch and the cut portion, making it difficult for the covering portion to separate from the main body. As a result, even if gas discharged from a faulty battery cell ruptures one part of the covering portion, and the gas is discharged between the insulation material and the case and reaches other parts of the covering portion, the pressure of the gas will not be sufficient to prevent the other parts of the covering portion from separating from the main body.

[0022] In the battery pack of the present invention, the shortest distance between the first notch and the cut portion is preferably 2.0 to 20.0 mm. When the shortest distance between the first notch and the cut portion is within this range, the covering portion can be separated from the main body portion with appropriate pressure.

[0023] 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.

[0024] 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.

[0025] In the battery pack of the present invention, the thermal insulation material further includes a second thermal insulation sheet and an adhesive layer that adheres the second thermal insulation sheet to the first thermal insulation sheet, and it is preferable that the thermal insulation material is arranged such that the second thermal insulation sheet is located on the module side and the first thermal insulation sheet is located on the case side. When such a second thermal insulation sheet is arranged, gas discharged from an abnormal battery cell passes through the second thermal insulation sheet before reaching the first thermal insulation sheet. As the gas passes through the second thermal insulation sheet, its temperature and gas pressure decrease. Therefore, even if the gas passes through the area where the covering portion of the first thermal insulation sheet was located and comes into contact with the case, the case is less likely to be heated or damaged by the gas.

[0026] In the battery pack of the present invention, the second heat insulating sheet has a second notch formed therein that extends from the main surface to which the first heat insulating sheet is bonded to the other main surface, and it is preferable that at least a part of the second notch is located inside the covering portion when the heat insulating material is viewed from the first heat insulating sheet side. When the second notch is formed in the second heat insulating sheet, high-temperature gas from the module side can easily reach the covering portion through the second notch.

[0027] 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.

[0028] 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 when the heat insulating material is viewed from the first heat insulating sheet side, the first notch and the second notch may overlap in the same shape. Such first and second notches can be formed simultaneously by punching them out while the first and second heat insulating sheets are stacked on top of each other.

[0029] 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.

[0030] The present invention provides a sheet-like thermal insulation material comprising a main body and a covering portion formed on the inside of the main body, wherein the covering portion has a plurality of connecting portions and a plurality of cutting portions alternately formed along the contour of the covering portion, the plurality of cutting portions are arranged in a dashed line pattern, and the ratio of the length of one connecting portion to the length of one cutting portion ([length of connecting portion] / [length of cutting portion]) is 0.5 to 2.0.

[0031] The thermal insulation material of the present invention is used in the battery pack of the present invention described above. In this case, the covering portion of the thermal insulation material is positioned to cover the safety valves of the multiple battery cells arranged in the module. By positioning the thermal insulation material of the present invention in this manner, the effects of the battery pack of the present invention described above can be achieved.

[0032] According to the present invention, it is possible to provide a battery pack that can quickly discharge high-temperature gas when it is ejected from an abnormal battery cell during thermal runaway, and can also prevent a chain reaction of thermal runaway caused by the backflow of high-temperature gas to adjacent battery cells.

[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 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 shown in Figure 2A, viewed from the bottom side of the housing portion of the case. 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 a 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 a 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 4 is a schematic plan view showing an example of the vicinity of the covering portion of the first heat insulating sheet in a battery pack according to the second embodiment of the present invention. Figure 5A is a schematic plan view showing another example of the vicinity of the covering portion of the first heat insulating sheet in a battery pack according to a second embodiment of the present invention. Figure 5B is a schematic plan view showing another example of the vicinity of the covering portion of the first heat insulating sheet in a battery pack according to a second embodiment of the present invention. Figure 5C is a schematic plan view showing another example of the vicinity of the covering portion of the first heat insulating sheet in a battery pack according to a second embodiment of the present invention. Figure 6 is a schematic cross-sectional view showing an example of a battery pack according to a third 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 an exploded view of the battery pack shown in Figure 1A.

[0036] The battery pack 10 shown in FIGS. 1A, 1B, and 1C 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.

[0037] As shown in FIGS. 1A and 1B, the case 30 includes a housing portion 31 composed of a bottom portion 31b and side walls 31s, and a lid portion 32 that covers the housing portion 31, and the module 20 is housed in the housing portion 31. In the battery pack 10, a heat insulating material 40 is provided between the module 20 and the case 30.

[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 and 1C 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 or a deformed shape).

[0039] As shown in FIGS. 1B and 1C, in the module 20, the plurality of battery cells 21 are arranged in a row and fixed by a connection module member 20a. Further, as shown in FIG. 1C, the battery cell 21 has a terminal 23, and adjacent battery cells 21 are electrically connected by connecting each terminal 23 with a bus bar 20b arranged on the connection module member 20a.

[0040] The bus bar 20b is a flat plate 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] 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 shown in Figure 2A, seen from the bottom side of the housing portion of the case.

[0043] As shown in Figure 2A, the thermal insulation material 40 consists of a first thermal insulation sheet 41. Also, as shown in Figure 2B, when the first thermal insulation sheet 41 is viewed from above, it 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. Furthermore, one covering portion 41a is positioned to overlap with one of the safety valves 22.

[0044] The covering portion 41a is formed such that multiple connecting portions 41c and multiple cutting portions 50 are arranged alternately along the contour C of the covering portion 41a, and the multiple cutting portions 50 are arranged in a dashed line pattern. The shape of the contour C of the covering portion 41a is rectangular, and the connecting portions 41c connect the covering portion 41a to the main body portion 41b. The cutting portions 50 can be easily formed with a cutter or the like.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] In the battery pack 10, the covering portion 41a is formed such that multiple connection portions 41c and multiple cutting portions 50 are arranged alternately along the contour C of the covering portion 41a, and the multiple cutting portions 50 are arranged in a dashed line pattern (i.e., perforated pattern). 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 portions 41c to break, and the covering portion 41a separates from the main body portion 41b along the contour C of the covering portion 41a.

[0049] In the battery pack 10, the length L of one cut section 50 ５０ Length L of one connection part 41c ４１ｃ The ratio ([length of connection] / [length of cut]) is 0.5 to 2.0. A ratio of 0.75 to 1.5 is more preferable. When the ratio ([length of connection] / [length of cut]) is within the above range, the maximum stress when the gas G hits the covering portion 41a tends to be high, and the covering portion 41a tends to separate from the main body portion 41b.

[0050] The gas G then 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 detach from the main body due to 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] Length L of one cut section 50 ５０ The length L of one connecting portion 41c is preferably 2.0 mm to 16.0 mm, and more preferably 2.0 to 8.0 mm. ４１ｃ The length of the cut portion 50 is preferably 2.0 mm to 8.0 mm, and more preferably 3.0 mm to 6.0 mm.５０ and the length L of the connecting portion 41c ４１ｃ If the above range is maintained, the covering portion 41a will readily separate from the main body portion 41b when the battery cell 21a experiences thermal runaway and generates high-temperature gas G. The length of each cut portion 50 may be uniform or different, but it is preferable that it be uniform. The length of each connecting portion 41c may be uniform or different, but it is preferable that it be uniform.

[0053] The following describes preferred embodiments of the thermal insulation material for the battery pack according to the first embodiment of the present invention. Note that the thermal insulation material used in the battery pack according to the first embodiment of the present invention is also an embodiment of the present invention.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] The inorganic fibers constituting the inorganic fiber paper preferably have an average fiber length of 0.1 to 100 mm. Within this range, problems with moldability and processability caused by excessively long average fiber lengths, and a decrease in mechanical strength due to excessively short average fiber lengths, are less likely to occur.

[0060] 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.

[0061] 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.

[0062] Furthermore, the average fiber length of the second inorganic fiber is preferably less than 1 μm in order to avoid impairing moldability.

[0063] Furthermore, the inorganic fiber paper may also contain other components such as organic fibers, inorganic particles, organic particles, and resin binders.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] Examples of particles made from thermally expandable inorganic materials that constitute the inorganic particles contained in inorganic fiber paper include vermiculite, bentonite, and perlite.

[0077] 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.

[0078] 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.

[0079] Inorganic fiber cloth is made by weaving inorganic fibers into a cross shape. Such inorganic fiber cloth has high strength and high heat resistance.

[0080] 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.

[0081] When the first heat insulating sheet 41 is a mica sheet or a heat-resistant resin sheet, the thickness of the first 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 first heat insulating sheet, which is made of a mica sheet or a heat-resistant resin sheet, is less than 0.05 mm, the strength of the first heat insulating sheet will be low and it will be easily damaged. If the thickness of the first heat insulating sheet, which is made of a mica sheet or a heat-resistant resin sheet, exceeds 2.0 mm, the first heat insulating sheet will be too thick, making it difficult to miniaturize the entire battery pack.

[0082] Furthermore, when the first heat insulating sheet 41 is inorganic fiber paper, the thickness of the first 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 first heat insulating sheet 41 made of inorganic fiber paper can obtain sufficient mechanical strength.

[0083] Furthermore, when the first heat insulating sheet 41 is an inorganic fiber cloth, the thickness of the first 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 first heat insulating sheet 41 made of inorganic fiber cloth. Therefore, the first heat insulating sheet 41 made of inorganic fiber cloth can be bent to fit a predetermined shape and used.

[0084] In the battery pack 10, the thickness of the covering portion 41a is preferably thinner than the thickness of the main body portion 41b, with the thickness of the covering portion 41a being 0.05 to 0.3 mm and the thickness of the main body portion 41b being 0.3 to 2.0 mm. With this thickness relationship, the covering portion 41a is more likely to separate from the main body portion 41b. Methods for making the thickness of the covering portion 41a thinner than the thickness of the main body portion 41b include molding a mica sheet, heat-resistant resin sheet, inorganic fiber paper, inorganic fiber cloth, etc. in advance so that the area to be the covering portion is thin, or molding a mica sheet, heat-resistant resin sheet, inorganic fiber paper, inorganic fiber cloth, etc. of uniform thickness and then cutting the area to be the covering portion.

[0085] The area of the planar shape of the covering portion 41a is preferably 1.0 to 18 cm ２ and more preferably 3.0 to 12 cm ２ If 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 was. If 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.

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

[0087] Next, the use and arrangement method of the battery pack according to the first embodiment of the present invention will be described.

[0088] The use of the battery pack according to the first embodiment of the present invention is not particularly limited, but for example, it may be used as a power source for an electric vehicle.

[0089] Also, the battery pack according to the first embodiment of the present invention is preferably arranged such that the safety valve provided in the battery cell is located on the upper side in the vertical direction or the lower side in the vertical direction. When the battery pack is arranged such that the safety valve is located in this way, the high-temperature gas from the abnormal battery cell is naturally and quickly dispersed, and the chain reaction of thermal runaway is less likely to occur. That is, from the perspective of fail-safe, it can be said that this is a preferable arrangement of the battery pack.

[0090] In the battery pack according to the first embodiment of the present invention, the safety valve may be positioned on the bottom side or on the lid 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 on the vertically upper side or vertically lower side. Since the battery pack is often arranged so that the bottom of the case or the lid is on the lower side, arranging the safety valve to be positioned on the bottom side or the lid side of the case makes it easier to position the safety valve on the vertically upper side or vertically lower side. In addition, 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 the vertically upper side and the vertically lower side (i.e., laterally).

[0091] (Second Embodiment) The battery pack according to the second embodiment of the present invention differs from the battery pack according to the first embodiment of the present invention in that the 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. The first heat insulating sheet included in the battery pack according to the second embodiment of the present invention will be described with reference to the drawings.

[0092] Figure 4 is a schematic plan view showing an example of the vicinity of the covering portion of the first heat insulating sheet in a battery pack according to a second embodiment of the present invention. The first heat insulating sheet 141 shown in Figure 4 consists of a covering portion 141a and a main body portion 141b other than the covering portion 141a.

[0093] The covering portion 141a is formed such that multiple connecting portions 141c and multiple cutting portions 150 are arranged alternately along the contour C of the covering portion 141a, and the multiple cutting portions 150 are arranged in a dashed line pattern. The connecting portions 141c connect the covering portion 141a and the main body portion 141b.

[0094] The first heat insulating sheet 141 has a single linear first cut portion 160 formed inside the contour C of the covering portion 141a. More specifically, the first cut portion 160 is formed along a minor axis passing through the center of gravity of the covering portion 141a.

[0095] If a first notch 160 is formed in the first insulation sheet 141, the covering portion 141a is more likely to tear along the first notch 160. Therefore, when a battery cell experiences thermal runaway and generates high-temperature gas, the gas can be released more quickly.

[0096] In the first heat insulating sheet 141, the length of the first cut portion 160 is preferably 50 to 90% of the widthwise length of the covering portion 141a.

[0097] In the first insulation sheet 141, the first notch 160 is separated from the cut portion 150. Because the first notch 160 and the cut portion 150 are separated, the portion between the first notch 160 and the cut portion 150 becomes a support portion for the covering portion 141a. Therefore, when gas pressure is applied to the covering portion 141a, the pressure is also distributed to the portion between the first notch 160 and the cut portion 150, making it difficult for the covering portion 141a to separate from the main body portion 141b. As a result, even if gas discharged from an abnormal battery cell ruptures one of the covering portions 141a, and the gas is discharged between the first insulation sheet 141 and the case and reaches other covering portions 141a, the pressure of the gas will not be sufficient to prevent the other covering portions 141a from separating from the main body portion 141b.

[0098] In the first heat insulating sheet 141, the shortest distance between the first notch 160 and the cut portion 150 is preferably 2.0 to 20.0 mm, and more preferably 2.0 to 8.0 mm. When the shortest distance between the first notch 160 and the cut portion 150 is within the above range, the covering portion 141a can be separated from the main body portion 141b with appropriate pressure.

[0099] In the first heat insulating sheet according to the second embodiment of the present invention, two or more first notches may be formed. The first notches may be continuous with the cut portion. The first notches may intersect with the contour of the covering portion. The first notches may be formed in a straight line, a curved shape, or a perforated shape. Such configurations are illustrated below with reference to the drawings. Figures 5A to 5C are schematic plan views showing another example of the vicinity of the covering portion of the first heat insulating sheet of the battery pack according to the second embodiment of the present invention.

[0100] In the first heat insulating sheet 141A shown in Figure 5A, two linear first cuts 160 are formed inside the contour C of the covering portion 141a. More specifically, the first cuts 160 are formed along the short axis and long axis passing through the center of gravity of the covering portion 141a. In addition, in the first heat insulating sheet 141A, the first cuts 160 are separated from the cut portion 150.

[0101] In the first heat insulating sheet 141B shown in Figure 5B, a single linear first cut portion 160 is formed inside the contour C of the covering portion 141a. More specifically, the first cut portion 160 is formed along the short axis passing through the center of gravity of the covering portion 141a. In addition, in the first heat insulating sheet 141B, both ends of the first cut portion 160 are continuous with the cut portion 150.

[0102] In the first heat insulating sheet 141C shown in Figure 5C, a single linear first cut portion 160 is formed inside the contour C of the covering portion 141a. More specifically, the first cut portion 160 is formed along the short axis passing through the centroid of the covering portion 141a. Furthermore, in the first heat insulating sheet 141C, the first cut portion 160 is formed to intersect with the contour C of the covering portion 141a.

[0103] (Third Embodiment) The battery pack according to the third embodiment of the present invention further includes a second heat insulating sheet and an adhesive layer for bonding the second heat insulating sheet to the first heat insulating sheet, and the heat insulating material is arranged such that the second heat insulating sheet is located on the module side and the first heat insulating sheet is located on the case side, which is different from the battery pack according to the first embodiment of the present invention. This battery pack according to the third embodiment of the present invention will be described with reference to the drawings.

[0104] Figure 6 is a schematic cross-sectional view showing an example of a battery pack according to a third embodiment of the present invention. The battery pack 210 shown in Figure 6 differs from the battery pack 10 in that the heat insulating material 240 consists of a first heat insulating sheet 241, a second heat insulating sheet 242, and an adhesive layer (not shown) that adheres the first heat insulating sheet 241 and the second heat insulating sheet 242 together. The heat insulating material 240 is arranged such that the second heat insulating sheet 242 is located on the module 20 side and the first heat insulating sheet 241 is located on the case 30 side.

[0105] With such a second insulation sheet 242 in place, the gas G released from the abnormal battery cell passes through the second insulation sheet 242 before reaching the first insulation sheet 241. The gas G then thermally decomposes the adhesive layer, causing the covering portion 241a to peel off from the second insulation sheet, and the gas pressure separates the covering portion 241a from the main body portion 241b. Furthermore, the temperature and pressure of the gas G decrease as it passes through the second insulation sheet 242. Therefore, even if the gas G passes over the area where the covering portion 241a was located on the first insulation sheet 241 and comes into contact with the case 30, the case 30 is less likely to be heated or damaged by the gas G.

[0106] In the battery pack 210, it is preferable that the adhesive layer includes an organic adhesive layer. When the adhesive layer includes an organic adhesive layer, it becomes easier for the adhesive layer to decompose thermally when high-temperature gas G from an abnormal battery cell reaches it. The organic adhesive layer is preferably thermally decomposed at 80°C or higher, and examples include adhesive layers containing polyamide-based organic materials.

[0107] In the battery pack 210, the second insulation sheet 242 has a second notch formed therein that extends from the main surface to which the first insulation sheet 241 is bonded to the other main surface, and when the insulation material 240 is viewed from above from the first insulation sheet 241 side, it is preferable that at least a part of the second notch is located inside the covering portion 241a. When the second insulation sheet 242 has a second notch formed therein, high-temperature gas G from the module 20 side can easily reach the covering portion 241a through the second notch. When the insulation material 240 is viewed from above from the first insulation sheet 241 side, the second notch may be located only inside the covering portion 241a, or it may be located so as to intersect with the contour of the covering portion 241a.

[0108] In the battery pack 210, when the heat insulating material 240 is viewed from above from the first heat insulating sheet 241 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.

[0109] In the battery pack 210, the second insulation sheet 242 may have multiple second notches. Also, in the battery pack 210, when the insulation material 240 is viewed from the first insulation sheet 241 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 241 quickly through the second notches.

[0110] In the battery pack 210, the first insulation sheet 241 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 240 is viewed from the first insulation sheet 241 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 241 and the second insulation sheet 242 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.

[0111] In the battery pack 210, the second heat insulating sheet 242 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.

[0112] 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.

[0113] 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. ３It 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. ３ If 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] Furthermore, the preferred forms of inorganic fiber paper and inorganic fiber cloth as the second heat insulating sheet 242 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.

[0118] This specification describes the following inventions:

[0119] (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, and 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 is formed such that a plurality of connection portions and a plurality of cut portions are arranged alternately along the contour of the covering portion, and the plurality of cut portions are arranged in a dashed line shape, and the ratio of the length of one connection portion to the length of one cut portion ([length of connection portion] / [length of cut portion]) is 0.5 to 2.0.

[0120] The present invention (2) is a battery pack according to the present invention (1), wherein the length of one of the above-mentioned cut sections is 2.0 mm to 16.0 mm, and the length of one of the above-mentioned connecting sections is 2.0 mm to 8.0 mm.

[0121] The present invention (3) is a battery pack according to the present invention (1) or (2), wherein the thickness of the first heat insulating sheet is 0.05 to 2.0 mm.

[0122] The present invention (4) is a battery pack according to any one of the present inventions (1) to (3), wherein the thickness of the main body is 0.3 to 2.0 mm and the thickness of the covering is 0.05 to 0.3 mm.

[0123] The present invention (5) is a battery pack according to any one of the present inventions (1) to (4), 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.

[0124] The present invention (6) is a battery pack according to any one of the present inventions (1) to (5), wherein the first notch portion and the cutting portion are separated.

[0125] The present invention (7) is a battery pack according to the present invention (6), wherein the shortest distance between the first notch and the cutting portion is 2.0 to 20.0 mm.

[0126] The present invention (8) is a battery pack according to any one of the present inventions (1) to (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.

[0127] 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.

[0128] 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 and an adhesive layer for bonding the second heat insulating sheet to the first heat insulating sheet, and the heat insulating material is arranged such that the second heat insulating sheet is located on the module side and the first heat insulating sheet is located on the case side.

[0129] The present invention (11) is a battery pack according to the present invention (10), wherein the second heat insulating sheet has a second notch formed therein that is continuous from the main surface to which the first heat insulating sheet is bonded 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.

[0130] The present invention (12) is a battery pack according to the present invention (11), 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.

[0131] The present invention (13) is a battery pack according to the present invention (11) or (12), 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.

[0132] The present invention (14) is a battery pack according to any one of the present inventions (10) to (13), 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.

[0133] The present invention (15) is a sheet-like thermal insulation material comprising a main body and a covering portion formed on the inside of the main body, wherein the covering portion has a plurality of connecting portions and a plurality of cut portions alternately formed along the contour of the covering portion, the plurality of cut portions are arranged in a dashed line pattern, and the ratio of the length of one connecting portion to the length of one cut portion ([length of connecting portion] / [length of cut portion]) is 0.5 to 2.0.

[0134] (Steady-state stress analysis) A steady-state stress analysis was performed using Ansys Mechanical. A first thermal insulation sheet model consisting of a covering part and a main body part was set as the analysis model. The density of the first thermal insulation sheet was set to 2.0 g / cm³ to mimic mica. ３ The modulus of elasticity was set to 40 GPa and the Poisson's ratio to 0.3. The thickness of the first insulation sheet model was set to 1.0 mm.

[0135] (Examples 1) to (Example 13) and (Comparative Example 1) to (Comparative Example 3) The shape of the covering portion was a rectangle with dimensions of 140 mm x 18 mm, as shown in Figure 4. In the first thermal insulation sheet model, multiple connection portions and multiple cut portions were arranged alternately along the contour of the covering portion, and the multiple cut portions were arranged in a dashed line pattern. The lengths of the connection portions and cut portions were set as shown in Table 1, and this constituted the first thermal insulation sheet model according to Examples 1 to 13. In Comparative Example 1, no cut portions were formed. In the first thermal insulation sheet model, a first cut portion with a length of 12 mm was formed. The cut portion and the first cut portion were separated, with the shortest distance between them being 3 mm.

[0136]

[0137] A simulation was conducted in which a pressure of 100 kPa was applied to a circular area with a radius of 20 mm from the center of the covering portion of each first insulation sheet model. The maximum stress generated in each first insulation sheet model and the area where stress of 169 MPa or higher occurred were calculated. The results are shown in Table 1. The pressure in this simulation is modeled after the gas injection that occurs during thermal runaway of a battery cell. Furthermore, "stress of 169 MPa or higher" refers to the fracture strength of the mica sheet with the above physical properties.

[0138] As shown in Table 1, the maximum stress was higher in the simulations for each embodiment than in the simulations for each comparative example. From these results, it was found that when the ratio of the length of one connection to the length of one cut section ([length of connection section] / [length of cut section]) is between 0.5 and 2.0, the maximum stress increases and the connection section becomes more prone to fracture. In other words, it was found that the covering section becomes more likely to separate from the main body.

[0139] Furthermore, when comparing Examples 1-6 and Comparative Examples 2-3, where the length of the connection portion was 4 mm, the simulations for Examples 1-6 showed a larger area where stress of 169 MPa or more occurred compared to the simulations for Comparative Examples 2-3. This indicates that when the ratio of the length of one connection portion to the length of one cut portion ([length of connection portion] / [length of cut portion]) is between 0.5 and 2.0, stress is more likely to occur, and the connection portion is more likely to break.

[0140] 10, 210 Battery pack 20 Module 20a Connection module member 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, 140, 240 Insulation material 41, 141, 141A, 141B, 141C, 241 First insulation sheet 41a, 141a, 241a Covering section 41b, 141b, 241b Main body section 41c, 141c Connection section 50, 150 Cutting section 160 First cut section 242 Second insulation sheet C Contour of the covering section

Claims

1. A battery pack comprising: a module having a plurality of battery cells, each provided with a safety valve; a case housing the module; and a heat insulating material provided between the module and the case, wherein the heat insulating material includes a first heat insulating sheet, and 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, one of the covering portions is positioned to overlap with at least a part of one of the safety valves, and the covering portion is formed such that a plurality of connection portions and a plurality of cut portions are arranged alternately along the contour of the covering portion, and the plurality of cut portions are arranged in a dashed line pattern, and the ratio of the length of one connection portion to the length of one cut portion ([length of connection portion] / [length of cut portion]) is 0.5 to 2.

0.

2. The battery pack according to claim 1, wherein the length of one of the cut portions is 2.0 mm to 16.0 mm, and the length of one of the connecting portions is 2.0 mm to 8.0 mm.

3. The battery pack according to claim 1 or 2, wherein the thickness of the first heat insulating sheet is 0.05 to 2.0 mm.

4. The battery pack according to any one of claims 1 to 3, wherein the thickness of the main body is 0.3 to 2.0 mm, and the thickness of the covering is 0.05 to 0.3 mm.

5. The battery pack according to any one of claims 1 to 4, 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.

6. The battery pack according to any one of claims 1 to 5, wherein the first notch and the cut portion are separated.

7. The battery pack according to claim 6, wherein the shortest distance between the first notch and the cutting portion is 2.0 to 20.0 mm.

8. The battery pack according to any one of claims 1 to 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, wherein the insulating material further comprises a second insulating sheet and an adhesive layer for bonding the second insulating sheet to the first insulating sheet, and the insulating material is arranged such that the second insulating sheet is located on the module side and the first insulating sheet is located on the case side.

11. The battery pack according to claim 10, wherein the second heat insulating sheet has a second notch formed therein that is continuous from the main surface to which the first heat insulating sheet is adhered 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.

12. The battery pack according to claim 11, 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.

13. The battery pack according to claim 11 or 12, 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 from the first heat insulating sheet side, the first notch and the second notch overlap in the same shape.

14. The battery pack according to any one of claims 10 to 13, 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.

15. A sheet-like thermal insulation material comprising a main body and a covering portion formed on the inside of the main body, wherein the covering portion has a plurality of connecting portions and a plurality of cut portions alternately formed along the contour of the covering portion, the plurality of cut portions are arranged in a dashed line pattern, and the ratio of the length of one connecting portion to the length of one cut portion ([length of connecting portion] / [length of cut portion]) is 0.5 to 2.0.

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