Battery pack

Abstract

Provided is a battery pack that can quickly discharge a high-temperature gas emitted from an abnormal battery cell during thermal runaway and prevent a thermal runaway cascade caused by backflow of the high-temperature gas to an adjacent battery cell. This battery pack comprises a module that includes a plurality of battery cells that each have a safety valve, a case that accommodates the module, and a heat insulation material that is provided between the module and the case. The battery pack is characterized in that the heat insulation material includes a first heat insulation sheet that, as seen in plan view, comprises a plurality of covering parts that respectively cover the plurality of safety valves and a body part that is outside the covering parts, each of the covering parts being positioned so as to overlap at least a portion of one safety valve and having a first slit part that is formed along the outline of the covering part and a second slit part that is at least partially formed inside the outline of the covering part, the outline of the covering part including at least two connection parts that connect the covering part and the body part where the first slit part is not formed.

Description

Battery pack

[0001] The present invention relates to a battery pack.

[0002] In battery packs, which consist of modules containing multiple battery cells 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 and potentially trigger further thermal runaway. To prevent a chain reaction of thermal runaway, a safety valve has traditionally been installed in the module to release the high-temperature gases generated during thermal runaway.

[0003] Furthermore, if the high-temperature gas released from the safety valve hits the case directly, the temperature of the case will rise, which may cause thermal damage to the area around the battery pack.To prevent this, it has been common practice to place a heat insulating material between the module and the case.

[0004] As such a battery pack, Patent Document 1 discloses a storage device comprising: a storage stack including a plurality of storage cells, each having an exhaust valve on its upper surface; an upper case covering the storage stack from above; and first and second heat-resistant sheets that are heat-resistant to exhaust gases discharged from the exhaust valves and are arranged between the upper case and the storage stack, wherein the first heat-resistant sheet has a plurality of holes formed in positions that overlap each of the exhaust valves in the vertical direction, and the second heat-resistant sheet is arranged above the first heat-resistant sheet so as to cover the plurality of holes.

[0005] Patent Document 2 also discloses an energy storage module that includes at least one cylindrical energy storage device, a holder that holds the energy storage device, and an insulating plate that is provided on one side of the holder, wherein an exhaust valve is provided at one end of the energy storage device, and a first opening that exposes the exhaust valve is formed in the holder, and the insulating plate has a flat main body portion, a second opening that is formed in the main body portion and communicates with the first opening, a lid portion that closes part of the second opening, and a connecting portion that connects the lid portion to the main body portion, and the main body portion is provided with a fixing portion that fixes the insulating plate to the holder.

[0006] JP 2023-59480 A International Publication No. 2023 / 054498

[0007] In Patent Document 1, it is necessary to exhaust gas from a defective cell in the event of thermal runaway, and for this purpose, multiple holes are provided in the first heat-resistant sheet. However, there is a possibility that the gas exhausted from the defective cell may flow back through the holes and exhaust valve of an adjacent cell and come into contact with the adjacent cell. In this case, there is a possibility that the adjacent cell may ignite (thermal chain reaction).

[0008] In Patent Document 2, a cover is provided over the hole (opening) in the sheet, and in the event of thermal runaway, the pressure of the gas exhausted from the abnormal cell causes the cover to peel off (fly off) or open at a position corresponding to the exhaust valve of the abnormal cell. However, there is room for improvement in the ease with which the cover peels off.

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

[0010] The battery pack of the present invention is a battery pack comprising a module having a plurality of battery cells, each having a safety valve, a case for accommodating 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 in a plane, the first heat insulating sheet is composed 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 covering portion is positioned so as to overlap with at least a portion of one of the safety valves, and the covering portion has a first cut portion formed along the outline of the covering portion and a second cut portion at least a portion of which is inside the outline of the covering portion, and the outline of the covering portion does not have the first cut portion formed therein, and there are at least two connection portions that connect the covering portion and the main body portion.

[0011] The battery pack of the present invention can prevent a chain reaction of thermal runaway caused by high-temperature gas from an abnormal battery cell during thermal runaway. The principle behind this is explained below.

[0012] In the battery pack of the present invention, the module is provided with a safety valve. Therefore, when a battery cell experiences thermal runaway and generates high-temperature gas, the gas is released from the safety valve and reaches the insulating material.

[0013] The heat insulating material includes a first heat insulating sheet. When viewed from above, the first heat insulating sheet is composed of a plurality of covering portions that respectively cover the plurality of safety valves and a main body portion other than the covering portions. Therefore, gas released from the safety valves hits the covering portions.

[0014] In the battery pack of the present invention, the covering portion has a first cutout along the contour of the covering portion and a second cutout inside the contour of the covering portion. The contour of the covering portion does not have the first cutout, and there are at least two connecting portions connecting the covering portion and the main body portion. When gas released from the safety valve hits the covering portion, the pressure breaks the connecting portions, and the covering portion separates from the main body portion along the first cutout. At this time, the covering portion also separates into multiple portions along the second cutouts.

[0015] The gas then passes through the area where the covering portion of the first heat insulating sheet was located and is released between the heat insulating material and the case.

[0016] Furthermore, gas released between the insulation material and the case also reaches the other covering portions of the first insulation sheet. However, the other covering portions of the first insulation sheet are connected to the main body by connectors, and these connectors are not broken by the pressure of the gas released between the insulation material and the case. Therefore, even if gas reaches the other covering portions of the first insulation sheet, the gas is blocked by the connectors. This prevents gas from flowing back through the safety valves of other battery cells.

[0017] In the battery pack of the present invention, the covering is connected to the main body by at least two connections. For example, if the covering were connected to the main body by only one connection, pressure would be applied to the connection, easily causing it to break. Therefore, even the pressure of gas released between the insulation and the case could cause the covering to separate from the main body. In this case, it would be impossible to prevent backflow of gas. However, if the covering is connected to the main body by at least two connections, the pressure applied to the connections is dispersed, making the connections less likely to break. Therefore, even if gas released from an abnormal battery cell breaks one covering and is released between the insulation and the case to reach other coverings, the pressure of the gas is less likely to break the connections of the other coverings, making it less likely for the coverings to separate from the main body.

[0018] Furthermore, as described above, the gas released from the safety valve causes the covering portion to split into multiple pieces along the second cutout. If the covering portion separated from the main body remains as a single large piece without splitting, it may block the gas flow path and inhibit gas diffusion. However, if the covering portion separated from the main body splits into multiple pieces, each piece becomes smaller, making it less likely for each piece to inhibit gas diffusion.

[0019] In the battery pack of the present invention, the first cutout and the second cutout may be spaced apart. When the first cutout and the second cutout are spaced apart, the area between the first cutout and the second cutout supports the covering. Therefore, when gas pressure is applied to the covering, the pressure is dispersed to the area between the first cutout and the second cutout, making the connection less likely to break. Therefore, even if gas released from an abnormal battery cell breaks one covering and is released between the insulation and the case to reach another covering, the gas pressure is less likely to break the connection of the other covering, making it less likely for the covering to separate from the main body.

[0020] In the battery pack of the present invention, when the first insulation sheet is viewed in a plan view, the second cutouts may be formed in multiple locations on intersecting straight lines. The second cutouts may be formed so as to intersect at the intersection of the intersecting straight lines. The second cutouts may be formed on one of the straight lines at the intersection of the intersecting straight lines. The second cutouts may not be formed at the intersection of the intersecting straight lines. When the second cutouts are intersecting, there is no support at the intersection, making the connection more likely to break and the covering more likely to separate from the main body. When the second cutouts are not intersecting, there is a support at the intersection, making the connection less likely to break and the covering less likely to separate from the main body. In this way, the ease of breaking the connection can be controlled by whether or not the second cutouts are intersecting.

[0021] In the battery pack of the present invention, when the first insulating sheet is viewed in plan, the covering portion has a shape including a minor axis passing through the center of gravity of the covering portion and being the shortest portion, and a major axis passing through the center of gravity of the covering portion and being the longest portion, and one of the intersecting lines may be the minor axis and the other may be the major axis. If the second cut portions are formed along such a minor axis and a major axis, the covering portion is more likely to separate evenly. This makes it possible to prevent only a portion of the covering portion from separating from the main body portion.

[0022] In the battery pack of the present invention, the thickness of the first insulating sheet is preferably 0.05 to 2.0 mm. If the thickness of the first insulating sheet is less than 0.05 mm, the strength of the first insulating sheet is low and it becomes easily broken. If the thickness of the first insulating sheet is more than 2.0 mm, the first insulating sheet becomes too thick, making it difficult to miniaturize the entire battery pack.

[0023] In the battery pack of the present invention, the length of each connection portion is preferably 50% or less of the total length of the contour of the covering portion, and 1.0 mm or more. If the length of each connection portion exceeds 50% of the total length of the contour of the covering portion, the connection portion becomes less likely to break and the covering portion becomes less likely to separate from the main body portion. If the length of each connection portion is less than 1.0 mm, the connection portion becomes too easily broken and the covering portion becomes too easily separated from the main body portion.

[0024] In the battery pack of the present invention, the inside of the outline of the covering portion is divided into multiple portions by the second cutouts, and the intersecting straight lines have no second cutouts at the intersections of the intersecting straight lines, and there is at least one internal connection portion connecting the multiple portions, and the length of each internal connection portion is preferably 50% or less of the length of the covering portion on the intersecting straight line where the internal connection portion is located, and the length of each internal connection portion is preferably 1.0 mm or more. If the length of the internal connection portion exceeds 50% of the length of the covering portion on the intersecting straight line where the internal connection portion is located, the connection portion becomes less likely to break and the covering portion becomes less likely to separate from the main body portion. If the length of the internal connection portion is less than 1.0 mm, the connection portion becomes too easily broken and the covering portion becomes too easily separated from the main body portion.

[0025] In the battery pack of the present invention, the shape of the covering portion in a plan view is preferably at least one selected from the group consisting of a polygon, a circle, an ellipse, and a racetrack shape. Covering portions having such shapes can be easily formed.

[0026] In the battery pack of the present invention, the first insulating sheet is preferably at least one selected from the group consisting of a mica sheet, a heat-resistant resin sheet, inorganic fiber paper, and inorganic fiber cloth. These materials are suitable for the first insulating sheet.

[0027] In the battery pack of the present invention, the thermal insulation material preferably further includes a second insulating sheet and an adhesive layer that bonds the second insulating sheet to the first insulating sheet, and the thermal insulation material is arranged so that the second insulating sheet is located on the module side and the first insulating sheet is located on the case side. When the second insulating sheet is arranged in this manner, gas released from an abnormal battery cell passes through the second insulating sheet before reaching the first insulating sheet. The gas's temperature and pressure decrease as it passes through the second insulating sheet. Therefore, even if the gas passes through the area where the covering portion of the first insulating sheet was located and comes into contact with the case, the case is less likely to be heated or damaged by the gas.

[0028] In the battery pack of the present invention, it is preferable that the second insulating sheet has a third cutout formed therein that continues from the main surface to which the first insulating sheet is adhered to the other main surface, and that at least a portion of the third cutout is located inside the covering portion when the insulating material is viewed in plan from the first insulating sheet side. When the second insulating sheet has a third cutout formed therein, high-temperature gas from the module side can easily reach the covering portion through the third cutout.

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

[0030] In the battery pack of the present invention, the second cutout and the third cutout may be overlapped and have the same shape when the heat insulating material is viewed in plan from the first heat insulating sheet side. Such second cutout and third cutout can be formed simultaneously by punching out the first heat insulating sheet and the second heat insulating sheet in a stacked state.

[0031] In the battery pack of the present invention, the second insulating sheet is preferably at least one selected from the group consisting of an inorganic fiber mat, an inorganic fiber paper, and an inorganic fiber cloth, which can be easily molded and exhibit excellent performance as the second insulating sheet.

[0032] The thermal insulation material of the present invention is a sheet-like thermal insulation material comprising a main body portion and a covering portion formed inside the main body portion, and is characterized in that a first cut portion is formed along the outline of the covering portion and a second cut portion at least partially inside the outline of the covering portion, and the outline of the covering portion is not formed with the first cut portion, and there are at least two connection portions connecting the covering portion and the main body portion. The thermal insulation material of the present invention is used in the battery pack of the present invention. The covering portion of the thermal insulation material is arranged so as to cover the safety valves of multiple battery cells arranged in a module. By arranging the thermal insulation material of the present invention in this manner, the effects of the battery pack of the present invention can be achieved.

[0033] 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 that occurs during thermal runaway, and that can prevent a chain reaction of thermal runaway caused by high-temperature gas flowing back into adjacent battery cells.

[0034] FIG. 1A is a perspective view schematically illustrating an example of a battery pack according to a first embodiment of the present invention. FIG. 1B is a cross-sectional view taken along line A-A in FIG. 1A. FIG. 1C is an exploded view of the battery pack shown in FIG. 1A. FIG. 2A is a cross-sectional view schematically illustrating an example of one safety valve and its vicinity in the battery pack according to the first embodiment of the present invention. FIG. 2B is a plan view of the safety valve shown in FIG. 2A as viewed from the insulating material side. FIG. 3A is an explanatory diagram sequentially 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. FIG. 3B is an explanatory diagram sequentially 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. FIG. 3C is an explanatory diagram sequentially 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. FIG. 4A is a plan view schematically illustrating another example of the vicinity of the covered portion of the first insulating sheet in the battery pack according to the first embodiment of the present invention. Fig. 4B is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4C is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4D is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4E is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4F is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4G is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4H is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4I is a plan view schematically showing another example of the vicinity of the covered portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 4J is a plan view schematically showing another example of the vicinity of the covering portion of the first insulating sheet of the battery pack according to the first embodiment of the present invention. Fig. 5 is an explanatory diagram of a preferred length of the second cutout portion according to the first embodiment of the present invention.Fig. 6 is a cross-sectional view schematically showing an example of a battery pack according to a second embodiment of the present invention. Fig. 7 is a plan view schematically showing the vicinity of a covered portion of a mica sheet according to Example 1. Fig. 8 is a plan view schematically showing the vicinity of a covered portion of a mica sheet according to Example 2. Fig. 9 is a schematic diagram showing an overview of a thermal runaway test. Fig. 10 is a graph showing the results of the thermal runaway test.

[0035] The battery pack of the present invention will be specifically described below. However, the present invention is not limited to the following configuration, and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual preferred configurations of the present invention described below also constitutes the present invention.

[0036] (First embodiment) A battery pack according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1A is a perspective view schematically showing an example of a battery pack according to the first embodiment of the present invention. Fig. 1B is a cross-sectional view taken along line A-A in Fig. 1A. Fig. 1C is an exploded view of the battery pack shown in Fig. 1A. A battery pack 10 shown in Figs. 1A, 1B, and 1C includes a module 20 having a plurality of battery cells 21, each of which is provided with a safety valve 22, and a case 30 that houses the module 20.

[0037] 1A and 1B , the case 30 includes a housing portion 31 consisting of a bottom portion 31 b and a side wall 31 s, and a lid portion 32 that covers the housing portion 31. 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 cells 21 store power and are preferably, for example, rechargeable so-called secondary batteries. Examples of secondary batteries include lithium ion batteries, nickel-metal hydride batteries, and sodium ion batteries. The battery cells 21 shown in Figures 1B and 1C are rectangular parallelepiped. However, in the battery pack of the present invention, the battery cells may have a three-dimensional shape other than a rectangular parallelepiped shape (for example, a cube or a modified shape).

[0039] 1B and 1C, in the module 20, a plurality of battery cells 21 are arranged in a row and fixed by a connecting module member 20a. Also, as shown in Fig. 1C, the battery cells 21 have terminals 23, and adjacent battery cells 21 are electrically connected by connecting each terminal 23 to a bus bar 20b arranged on the connecting module member 20a.

[0040] The bus bar 20b is a flat, electrically conductive metal member. Examples of materials for 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 (e.g., screwing, welding, etc.).

[0041] Examples of materials that can be used to form the case 30 include steel and aluminum. As the steel, stainless steel (SUS) is preferred.

[0042] Fig. 2A is a cross-sectional view schematically illustrating an example of one safety valve and its vicinity in the battery pack according to the first embodiment of the present invention, and Fig. 2B is a plan view of the safety valve shown in Fig. 2A as viewed from the heat insulating material side.

[0043] As shown in FIG. 2A, the heat insulating material 40 is made of a first heat insulating sheet 41. As shown in FIG. 2B, when the first heat insulating sheet 41 is viewed from above, the first heat insulating sheet 41 is made of a plurality of covering portions 41a that cover the plurality of safety valves 22, and a main body portion 41b other than the covering portions 41a. Each covering portion 41a is positioned so as to overlap with one safety valve 22. The covering portion 41a has first cutouts (51a and 51b) that follow the contour C of the covering portion 41a, and second cutouts (52a and 52b) that are inside the contour C of the covering portion 41a. Furthermore, the contour C of the covering portion 41a does not have the first cutouts (51a and 51b), and two connection portions (41c) that connect the covering portion 41a and the main body portion 41b are not formed. １ , 41c ２ ) is available.

[0044] More specifically, the contour C of the covering portion 41a is defined by two line segments (Ls １ , Ls ２ ) and two arcs (Cs１ , Cs ２ ) The covering portion 41a has a racetrack shape consisting of a minor axis Sa passing through the center of gravity of the covering portion 41a and being the shortest portion, and a major axis La passing through the center of gravity of the covering portion 41a and being the longest portion. In the covering portion 41a, the minor axis Sa and the major axis La intersect at a right angle.

[0045] In the first heat insulating sheet 41, two first cutouts (51a and 51b) are formed along the contour C of the covering portion 41a so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a. In addition, two second cutouts (52a and 52b) are formed along the major axis La and minor axis Sa of the covering portion 41a. Both ends of the second cutout 52a formed along the major axis La contact the first cutouts (51a, 51b). In addition, both ends of the second cutout 52b formed along the minor axis Sa do not contact the first cutouts (51a, 51b).

[0046] In the contour C of the covering portion 41a, the portion where the first cut portions (51a, 51b) are not formed near the intersection of the minor axis Sa and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. １ , 41c ２ )

[0047] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) there are two connecting parts (41c １ , 41c ２ ) and two arcs (Cs １ , Cs ２ ) and the inside of the outline C of the covering portion 41a is divided into four parts by the second cutouts (52a, 52b), and there is no part connecting the parts.

[0048] The battery pack 10 can prevent a chain reaction of thermal runaway caused by high-temperature gas from an abnormal battery cell that occurs during thermal runaway. The principle behind this is explained below.

[0049] 3A to 3C are explanatory diagrams sequentially illustrating the principle of preventing a chain reaction of thermal runaway when one battery cell experiences thermal runaway in the battery pack according to the first embodiment of the present invention. As shown in Fig. 3A, when one battery cell 21a experiences thermal runaway and generates high-temperature gas from the battery cell 21a, gas G (in Fig. 3A, the 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 released from the safety valve 22a then reaches the thermal insulation material 40 (first insulation sheet 41).

[0050] The first heat insulating sheet 41 is made up of a plurality of covering portions 41a that cover the plurality of safety valves 22, respectively, and a main body portion 41b that is the portion other than the covering portions 41a. Therefore, the gas G released from the safety valves hits the covering portions 41a.

[0051] In the battery pack 10, the covering portion 41a has first notches (51a, 51b) formed along the contour C of the covering portion 41a and second notches (52a, 52b) formed inside the contour C of the covering portion 41a. In addition, the first notches (51a, 51b) are not formed along the contour C of the covering portion 41a, and two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b are not formed along the contour C of the covering portion 41a. １ , 41c ２ 3B, when the gas G released from the safety valve 22a hits the covering portion 41a, the pressure causes the connecting portion 41c to break, and the covering portion 41a separates from the main body portion 41b along the first cut portions (51a, 51b). At this time, the covering portion 41a also separates into four along the second cut portions (52a, 52b).

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

[0053] 3C , the gas G released between the first insulating sheet 41 and the case 30 also reaches the other covering portion 41a of the first insulating sheet 41. However, the other covering portion 41a of the first insulating sheet 41 is connected to the main body portion 41b by a connecting portion 41c, and the connecting portion 41c is not broken by the pressure of the gas G released between the first insulating sheet 41 and the case 30. Therefore, even if the gas reaches the other covering portion 41a of the first insulating sheet 41, the gas G is blocked by the covering portion 41a. This prevents the gas G from flowing back through the safety valves 22 of the other battery cells 21.

[0054] In the battery pack 10, the covering portion 41a is connected to the main body portion 41b with two connecting portions 41c. For example, if the covering portion were connected to the main body portion with only one connecting portion, pressure would be applied to the connecting portion, which would easily break. Therefore, even the pressure of gas released between the insulation material and the case could cause the covering portion to separate from the main body portion. In this case, it would be impossible to prevent backflow of gas. However, if the covering portion 41a is connected to the main body portion 41b with two connecting portions 41c, the pressure applied to the connecting portions 41c is dispersed, making the connecting portions 41c less likely to break. Therefore, even if gas G released from an abnormal battery cell 21a breaks one covering portion 41a and is released between the first insulation sheet 41 and the case 30 to reach other covering portions 41a, the pressure of the gas G is less likely to break the connecting portions 41c of the other covering portions 41a, making it less likely for the covering portions 41a to separate from the main body portion 41b.

[0055] Furthermore, as described above, the gas G released from the safety valve 22 causes the covering portion 41a to split into multiple pieces along the second cutouts (52a, 52b). If the covering portion separated from the main body portion remains as one large piece without splitting, it may block the gas flow path and inhibit the diffusion of the gas. However, if the covering portion 41a separated from the main body portion 41b splits into four pieces, each piece becomes smaller, and each piece is less likely to inhibit the diffusion of the gas G.

[0056] Furthermore, the first heat insulating sheet 41 has the second cut portions (52a, 52b) formed along the minor axis Sa and the major axis La, which facilitates the separation of the covering portion 41a evenly. This prevents only a portion of the covering portion 41a from separating from the main body portion 41b.

[0057] A preferred embodiment of the heat insulating material of the battery pack according to the first embodiment of the present invention will be described below.

[0058] In the battery pack 10, the first insulating sheet 41 is preferably at least one selected from the group consisting of a mica sheet, a heat-resistant resin sheet, inorganic fiber paper, and inorganic fiber cloth. These materials are suitable for the first insulating sheet.

[0059] Examples of resins that can be used to form the heat-resistant resin sheet include polybutylene terephthalate, polyamide, polypropylene, etc. These resins may also contain glass fiber or silica fiber as a filler.

[0060] The inorganic fiber paper preferably has a thermal conductivity of less than 1 (W / m·K). The thermal conductivity can be measured in accordance with JIS R 2251 "Test method for thermal conductivity of refractories."

[0061] Examples of inorganic fibers that constitute inorganic fiber paper include alumina fiber, carbon fiber, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, glass wool, slag wool, and SiO ２ At least one selected from fibers containing methyl methacrylate, silica fibers, mullite fibers, alumina silicate fibers, ceramic fibers, rock wool, alkaline earth silicate fibers, zirconia fibers, silicon carbide fibers, magnesium silicate fibers, potassium titanate fibers, aerogel composites, and mineral fibers can be used. These inorganic fibers have excellent heat resistance.

[0062] The inorganic fibers constituting the inorganic fiber paper preferably have an average fiber diameter of 1 to 20 μm, more preferably 3 to 15 μm. Within the above range, the inorganic fiber paper can be produced without impairing moldability or processability.

[0063] The inorganic fibers constituting the inorganic fiber paper preferably have an average fiber length of 0.1 to 100 mm. This range prevents problems with moldability and processability that are caused by an average fiber length that is too long, and reduces the reduction in mechanical strength that is caused by an average fiber length that is too short.

[0064] In addition to the inorganic fibers (hereinafter also referred to as first inorganic fibers), inorganic fibers (hereinafter referred to as second inorganic fibers) having an average fiber diameter smaller than that of the first inorganic fibers may 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 inorganic particles and organic particles, which are other components described below, can be improved.

[0065] The average fiber diameter of the second inorganic fibers 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 fibers can have flexibility while maintaining mechanical strength.

[0066] The average fiber length of the second inorganic fibers is preferably less than 1 μm so as not to impair moldability.

[0067] Furthermore, the inorganic fiber paper may contain other components such as organic fibers, inorganic particles, organic particles, and a resin binder.

[0068] The organic fibers contained in the inorganic fiber paper can 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, polyparaphenylphthalamide fibers, polyvinyl alcohol fibers, polyethylene fibers, nylon fibers, polyurethane fibers, polypropylene fibers, and ethylene-vinyl alcohol copolymer fibers.

[0069] The average fiber length of the organic fibers is not particularly limited, but is preferably 0.5 to 10 mm. If the average fiber length is within this range, sufficient compressive strength can be obtained without impairing the moldability and shape retention of the inorganic fiber paper.

[0070] The inorganic particles contained in the inorganic fiber paper can be made of a material having an average secondary particle diameter in the range of 0.01 to 200 μm. If the average secondary particle diameter is in the above range, the material is easily available and the desired heat insulating effect can be obtained. Furthermore, the average secondary particle diameter of the inorganic particles is preferably 0.05 to 100 μm.

[0071] Examples of inorganic particles contained in the inorganic fiber paper include oxide particles, nanoparticles, inorganic hydrate particles, particles made of thermally expandable inorganic materials, and hydrous porous bodies.

[0072] The inorganic particles contained in the inorganic fiber paper may be a combination of two or more types of inorganic particles with different average secondary particle diameters. Different sizes of inorganic particles have different heat transfer suppression effects, so that the heat transfer from the battery cell can be cooled in multiple stages, and the heat absorption effect can be achieved over a wide temperature range.

[0073] When the inorganic particles contained in the inorganic fiber paper are oxide particles, the oxide particles can be at least one type selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina. These oxide particles have a high refractive index, and therefore can prevent radiant heat generated by thermal runaway in a battery cell from propagating to adjacent cells or outside the battery pack.

[0074] When the inorganic particles contained in the 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 blocking effect. The average primary particle diameter is determined by measuring the particle diameters of 10 random particles under a microscope by comparing them with a standard scale and averaging the particle diameters of the 10 measured particles.

[0075] The nanoparticles constituting the inorganic particles contained in the inorganic fiber paper have an average primary particle diameter of less than 1 μm. Nanoparticles have extremely low conductive heat transfer and excellent heat insulation properties.

[0076] For example, if oxide particles are used as nanoparticles, even if the internal density increases due to the compression of the inorganic fiber paper caused by expansion associated with thermal runaway in the battery cell, the electrostatic repulsion force of the nanoparticles tends to create small gaps between the particles, and the particles are packed together to provide cushioning, thereby suppressing an increase in conductive heat transfer.

[0077] Silica nanoparticles are preferred as nanoparticles. Silica nanoparticles have high heat insulating properties and are characterized by small contact points between particles, which reduces the amount of heat transfer between particles. Therefore, using silica nanoparticles as nanoparticles can further improve the heat insulating properties of inorganic fiber paper. Wet silica, dry silica, aerogel, etc. can be used as silica nanoparticles.

[0078] The average primary particle diameter of the nanoparticles is preferably 1 to 100 nm. This range allows for suppression of convective and conductive heat transfer through the inorganic fiber paper 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 within the inorganic fiber paper, thereby maintaining the insulating properties of the inorganic fiber paper. The average primary particle diameter of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. Meanwhile, the average primary particle diameter of the nanoparticles is preferably 50 nm or less, and even more preferably 10 nm or less.

[0079] Examples of inorganic hydrate particles that constitute the inorganic particles contained in the inorganic fiber paper include particles of aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, manganese hydroxide, zirconium hydroxide, gallium hydroxide, etc. The aforementioned inorganic hydrate particles begin to thermally decompose in a thermal runaway environment of the battery cell, releasing water of crystallization, thereby releasing heat from the heating element, thereby suppressing a sudden rise in temperature inside the battery pack.

[0080] Examples of particles made of a thermally expandable inorganic material that constitute the inorganic particles contained in the inorganic fiber paper include particles of vermiculite, bentonite, perlite, and the like.

[0081] Examples of particles made of a hydrous porous material that constitute the inorganic particles contained in the inorganic fiber paper include particles of zeolite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

[0082] When inorganic fiber paper contains a resin binder, the mechanical strength of the inorganic fiber paper is improved, and therefore the inorganic fiber paper can maintain its shape even when pressure is generated due to the expansion of the battery cell during thermal runaway of the battery cell, thereby preventing a decrease in thermal insulation performance. Examples of resin binders contained in inorganic fiber paper include styrene-butadiene resin, acrylic resin, silicone-acrylic resin, and styrene resin.

[0083] The inorganic fiber cloth is made by weaving inorganic fibers into a cross shape. Such inorganic fiber cloth has high strength and high heat resistance.

[0084] Examples of inorganic fibers constituting the inorganic fiber cloth include ceramic fibers such as silica fiber, alumina fiber, aluminosilicate fiber, and zirconia fiber, as well as glass fiber and basalt fiber. These inorganic fibers may be used alone or in combination of two or more. For example, when producing the inorganic fiber cloth, different types of inorganic fibers may be used for the warp and weft, and these may be woven together to form the inorganic fiber cloth.

[0085] When the first insulating sheet 41 is a mica sheet or a heat-resistant resin sheet, the thickness of the first 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 insulating sheet made of a mica sheet or a heat-resistant resin sheet is less than 0.05 mm, the strength of the first insulating sheet is low and it becomes easily damaged. If the thickness of the first insulating sheet made of a mica sheet or a heat-resistant resin sheet exceeds 2.0 mm, the first insulating sheet becomes too thick, making it difficult to miniaturize the entire battery pack.

[0086] Furthermore, when the first heat insulating sheet 41 is made of 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 to 3.0 mm. In this case, the first heat insulating sheet 41 made of inorganic fiber paper can obtain sufficient mechanical strength.

[0087] 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 to 1.4 mm. In this case, the first heat insulating sheet 41 made of inorganic fiber cloth can have both mechanical strength and flexibility. Therefore, the first heat insulating sheet 41 made of inorganic fiber cloth can be bent into a predetermined shape for use.

[0088] The area of ​​the covering portion 41a in plan view is 1.0 to 18 cm ２ It is preferable that the length is 3 to 12 cm. ２ It is more preferable that the area of ​​the planar shape of the covering portion is 1.0 cm ２ If the area of ​​the planar shape of the covering portion is less than 18 cm 2 , the gas will have difficulty passing through the portion where the covering portion 41a was located. ２ If the distance exceeds this, the covering portion is likely to be wider than the range that the gas can reach, making it difficult for the covering portion to separate from the main body portion.

[0089] In the battery pack 10, when the first insulating sheet 41 is viewed from above, each covering portion 41a may be positioned so as to overlap at least a portion of each safety valve 22, but it is preferable that each covering portion 41a is positioned so as to fit within the outline of each safety valve 22. When the covering portion 41a is positioned in this manner, gas released from the safety valve 22 can easily reach the covering portion 41a.

[0090] In the battery pack 10, the length of each connection portion 41c is preferably 50% or less of the total length of the contour C of the covering portion 41a, and the length of each connection portion 41c is preferably 1.0 mm or more. The length of each connection portion 41c is more preferably 40% or less, and even more preferably 30% or less, of the total length of the contour C of the covering portion 41a. The length of each connection portion 41c is more preferably 3.0 mm or more, even more preferably 5.0 mm or more, and even more preferably 7.0 mm or more. If the length of each connection portion exceeds 50% of the total length of the contour of the covering portion, the connection portion becomes less likely to break, and the covering portion becomes less likely to separate from the main body portion. If the length of each connection portion is less than 1.0 mm, the connection portion becomes too easily broken, and the covering portion becomes too easily separated from the main body portion.

[0091] In the battery pack 10, the first cutouts (51a, 51b) may be formed to penetrate the first insulating sheet 41 in the thickness direction, or may be formed partway through the thickness direction. Moreover, the second cutouts (52a, 52b) may be formed to penetrate the first insulating sheet 41 in the thickness direction, or may be formed partway through the thickness direction.

[0092] In the battery pack according to the first embodiment of the present invention, the covering portion has a first notch that follows the contour of the covering portion and a second notch that is at least partially inside the contour of the covering portion, and the covering portion, the connecting portion, the first notch, and the second notch may have other configurations as long as the contour of the covering portion does not have the first notch and there are at least two connecting portions that connect the covering portion and the main body portion.

[0093] For example, in the battery pack according to the first embodiment of the present invention, the first cutout and the second cutout may be spaced apart. When the first cutout and the second cutout are spaced apart, the area between the first cutout and the second cutout supports the covering. Therefore, when gas pressure is applied to the covering, the pressure is dispersed to the area between the first cutout and the second cutout, making the connection less likely to break. Therefore, even if gas released from an abnormal battery cell breaks one covering and is released between the insulating material and the case to reach another covering, the gas pressure is less likely to break the connection of the other covering, making it less likely for the covering to separate from the main body.

[0094] Furthermore, in the battery pack according to the first embodiment of the present invention, when the first insulation sheet is viewed in plan, the second cutouts may be formed in multiple locations on the intersecting straight lines. The second cutouts may be formed so as to intersect at the intersection of the intersecting straight lines. The second cutouts may be formed on one of the straight lines at the intersection of the intersecting straight lines. The second cutouts may not be formed at the intersection of the intersecting straight lines. When the second cutouts are intersecting, there is no support at the intersection, making the connection more likely to break and the covering more likely to separate from the main body. When the second cutouts are not intersecting, there is a support at the intersection, making the connection less likely to break and the covering less likely to separate from the main body. In this way, the ease of breaking the connection can be controlled by whether or not the second cutouts are intersecting.

[0095] In the battery pack according to the first embodiment of the present invention, two or more connection portions may be formed.

[0096] Such an embodiment will be described below with reference to the drawings.

[0097] 4A to 4J are plan views each showing a schematic view of another example of the vicinity of the covering portion of the first heat insulating sheet of the battery pack according to the first embodiment of the present invention.

[0098] In the first heat insulating sheets 41A to 41J shown in FIGS. 4A to 4J, the contour C of the covering portion 41a is defined by two line segments (Ls １ , Ls ２) and two arcs (Cs １ , Cs ２ ) The covering portion 41a has a racetrack shape consisting of a minor axis Sa passing through the center of gravity of the covering portion 41a and being the shortest portion, and a major axis La passing through the center of gravity of the covering portion 41a and being the longest portion. In the covering portion 41a, the minor axis Sa and the major axis La intersect at a right angle.

[0099] In the first heat insulating sheet 41A shown in FIG. 4A, two line segments (Ls １ , Ls ２ ), four first cutouts (51a, 51b, 51c, 51d) are formed along the contour C of the covering portion 41a. １ , Ls ２ ) at each end thereof are four connectors (41c １ , 41c ２ , 41c ３ , 41c ４ ) is formed.

[0100] In the first heat insulating sheet 41A shown in Fig. 4A, both ends of the second cutout 52a formed along the major axis La are in contact with the first cutouts (51a, 51b). Also, both ends of the second cutout 52b formed along the minor axis Sa are in contact with the first cutouts (51a, 51b). In other words, the inside of the contour C of the covering portion 41a is divided into four parts by the second cutouts (52a, 52b), and there are no parts connecting the individual parts.

[0101] In the first heat insulating sheet 41B shown in FIG. 4B, two first cutouts (51a and 51b) are formed along the contour C of the covering portion 41a so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a. Two second cutouts (52a and 52b) are formed along the major axis La and the minor axis Sa of the covering portion 41a. Both ends of the second cutout 52a formed along the major axis La do not contact the first cutouts (51a, 51b). Both ends of the second cutout 52b formed along the minor axis Sa contact the first cutouts (51a, 51b).

[0102] In the contour C of the covering portion 41a, the portion where the first notch portions (51a, 51b) are not formed near the intersection of the major axis La and the contour C of the covering portion 41a is formed as two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. １ , 41c ２ )

[0103] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) and there is no connection on the two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ２ The inside of the outline C of the covering portion 41a is divided into four parts by the second cutouts (52a, 52b), and there is no part connecting the parts.

[0104] In the first heat insulating sheet 41C shown in FIG. 4C , four first cutouts (51a, 51b, 51c, and 51d) are formed along the contour C of the covering portion 41a so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a, and so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a. Two second cutouts (52a and 52b) are formed along the major axis La and the minor axis Sa of the covering portion 41a. Both ends of the second cutout 52a formed along the major axis La do not contact the first cutouts (51a, 51b, 51c, and 51d). Both ends of the second cutout 52b formed along the minor axis Sa do not contact the first cutouts (51a, 51b, 51c, and 51d).

[0105] In the contour C of the covering portion 41a, the portion where the first cutout portions (51a, 51b, 51c, and 51d) are not formed near the intersection of the major axis La and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. １ , 41c ３ ), and the portion where the first cutouts (51a, 51b, 51c, and 51d) are not formed near the intersection of the minor axis Sa and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. ２ , 41c ４ )

[0106] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on two connectors (41c ２ , 41c ４ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ３ The inside of the outline C of the covering portion 41a is divided into four parts by the second cutouts (52a, 52b), and there is no part connecting the parts.

[0107] In the first heat insulating sheet 41D shown in FIG. 4D, the first cutouts (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h) are arranged so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a, so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a, and so as not to contact the intersection of the two line segments (Ls １ , Ls ２ Eight second cutouts (52a and 52b) are formed along the contour C of the covering portion 41a, excluding the ends of the first cutouts (52a and 52b). Two second cutouts (52a and 52b) are formed along the major axis La and the minor axis Sa of the covering portion 41a. Both ends of the second cutout 52a formed along the major axis La do not contact the first cutouts. Both ends of the second cutout 52b formed along the minor axis Sa do not contact the first cutouts.

[0108] In the contour C of the covering portion 41a, the portion where the first notches (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h) are not formed is provided with eight connecting portions (41c) that connect the covering portion 41a and the main body portion 41b. １ , 41c ２ , 41c ３ , 41c ４ , 41c ５ , 41c ６ , 41c ７ and 41c ８ )

[0109] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on the six connections (41c ２ , 41c ３, 41c ４ , 41c ６ , 41c ７ , 41c ８ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ５ The inside of the outline C of the covering portion 41a is divided into four parts by the second cutouts (52a, 52b), and there is no part connecting the parts.

[0110] In the first heat insulating sheet 41E shown in FIG. 4E, four first cutouts (51a, 51b, 51c, and 51d) are formed along the contour C of the covering portion 41a so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a and so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a. In addition, two second cutouts (52a) are formed along the major axis La of the covering portion 41a and so as to avoid the intersection of the major axis La and the minor axis Sa. １ and 52a ２ Furthermore, two second cutouts (52b) are formed along the minor axis Sa and in a manner to avoid the intersection of the major axis La and the minor axis Sa. １ and 52b ２ In addition, the first heat insulating sheet 41E has a second cutout portion (52a １ , 52a ２ , 52b １ and 52b ２ ) are not in contact with the first notches (51a, 51b, 51c and 51d).

[0111] In the contour C of the covering portion 41a, the portion where the first cutout portions (51a, 51b, 51c, and 51d) are not formed near the intersection of the major axis La and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. １ , 41c ３ ), and the portion where the first cutouts (51a, 51b, 51c, and 51d) are not formed near the intersection of the minor axis Sa and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. ２ , 41c ４ )

[0112] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on two connectors (41c ２ , 41c ４ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ３ ) The inside of the contour C of the covering portion 41 a is divided into four parts by the major axis La and the minor axis Sa, but one internal connection portion 44 is formed at the intersection of the major axis La and the minor axis Sa to connect the respective parts.

[0113] In the first heat insulating sheet 41F shown in FIG. 4F, four first cutouts (51a, 51b, 51c, and 51d) are formed along the contour C of the covering portion 41a so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a and so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a. In addition, two second cutouts (52a) are formed along the major axis La of the covering portion 41a and so as to avoid the intersection of the major axis La and the minor axis Sa. １ and 52a ２ ) is formed. Furthermore, one second cut portion 52b is formed along the minor axis Sa. In addition, in the first heat insulating sheet 41F, the second cut portion (52a １ , 52a ２ , 52b) are not in contact with the first notches (51a, 51b, 51c and 51d).

[0114] In the contour C of the covering portion 41a, the portion where the first cutout portions (51a, 51b, 51c, and 51d) are not formed near the intersection of the major axis La and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. １ , 41c ３ ), and the portion where the first cutouts (51a, 51b, 51c, and 51d) are not formed near the intersection of the minor axis Sa and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. ２ , 41c ４ )

[0115] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on two connectors (41c ２ , 41c ４ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ３ The inside of the contour C of the covering portion 41a is divided into two by the second cutout portion 52b, and each portion is １ and 52a ２ 4F, the second cutout 52a is further divided into two (a total of four). １ The upper two sections divided by the second cutout 52a are connected by an internal connection portion 44a at the intersection of the major axis La and the minor axis Sa. ２ The two lower portions divided by are connected by an internal connector 44b at the intersection of the major axis La and the minor axis Sa.

[0116] In the first heat insulating sheet 41G shown in FIG. 4G, four first cutouts (51a, 51b, 51c, and 51d) are formed along the contour C of the covering portion 41a so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a and so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a. Also, one second cutout 52a is formed along the major axis La of the covering portion 41a. Furthermore, two second cutouts (52b) are formed along the minor axis Sa and so as to avoid the intersection of the major axis La and the minor axis Sa. １ and 52b ２ In addition, the first heat insulating sheet 41G has second cutouts (52a, 52b) １ and 52b ２ ) are not in contact with the first notches (51a, 51b, 51c and 51d).

[0117] In the contour C of the covering portion 41a, the portion where the first cutout portions (51a, 51b, 51c, and 51d) are not formed near the intersection of the major axis La and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b.１ , 41c ３ ), and the portion where the first cutouts (51a, 51b, 51c, and 51d) are not formed near the intersection of the minor axis Sa and the contour C of the covering portion 41a is formed by two connecting portions (41c) connecting the covering portion 41a and the main body portion 41b. ２ , 41c ４ )

[0118] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on two connectors (41c ２ , 41c ４ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ３ The inside of the contour C of the covering portion 41a is divided into two by the second cutout portion 52a, and each portion is separated by the second cutout portion (52b １ and 52b ２ 4G, the second cutout 52b is further divided into two (a total of four). １ The two left portions divided by the second cutout 52b are connected by an internal connection portion 44a at the intersection of the major axis La and the minor axis Sa. ２ The two right portions divided by are connected by an internal connection portion 44b at the intersection of the major axis La and the minor axis Sa.

[0119] In the first heat insulating sheet 41H shown in FIG. 4H, the first cutouts (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h) are arranged so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a, so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a, and so as not to contact the intersection of the two line segments (Ls １ , Ls ２ ) are formed along the contour C of the covering portion 41a, excluding the ends of the covering portion 41a. Also, one second cutout 52a is formed along the major axis La of the covering portion 41a. Furthermore, two second cutouts (52b) are formed along the minor axis Sa and so as to avoid the intersection of the major axis La and the minor axis Sa. １ and 52b ２In addition, the first heat insulating sheet 41H has second cutouts (52a, 52b) １ and 52b ２ ) are not in contact with the first notches (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h).

[0120] In the contour C of the covering portion 41a, the portion where the first notches (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h) are not formed is provided with eight connecting portions (41c) that connect the covering portion 41a and the main body portion 41b. １ , 41c ２ , 41c ３ , 41c ４ , 41c ５ , 41c ６ , 41c ７ and 41c ８ )

[0121] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on the six connections (41c ２ , 41c ３ , 41c ４ , 41c ６ , 41c ７ , 41c ８ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ５ The inside of the contour C of the covering portion 41a is divided into two by the second cutout portion 52a, and each portion is separated by the second cutout portion (52b １ and 52b ２ 4H, the second cutout 52b is further divided into two (a total of four). １ The two left portions divided by the second cutout 52b are connected by an internal connection portion 44a at the intersection of the major axis La and the minor axis Sa. ２ The two right portions divided by are connected by an internal connection portion 44b at the intersection of the major axis La and the minor axis Sa.

[0122] In the first heat insulating sheet 41I shown in FIG. 4I, the first cutouts (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h) are arranged so as not to contact the intersection of the major axis La and the contour C of the covering portion 41a, so as not to contact the intersection of the minor axis Sa and the contour C of the covering portion 41a, and so as not to contact the intersection of the two line segments (Ls １ , Ls ２ ) are formed along the contour C of the covering portion 41a, excluding the ends of the covering portion 41a. In addition, two second cutouts (52a) are formed along the major axis La of the covering portion 41a and so as to avoid the intersection of the major axis La and the minor axis Sa. １ and 52a ２ ) is formed. Furthermore, one second cut portion 52b is formed along the minor axis Sa. In addition, in the first heat insulating sheet 41I, the second cut portion (52a １ , 52a ２ and 52b) are not in contact with the first notches (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h).

[0123] In the contour C of the covering portion 41a, the portion where the first notches (51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h) are not formed is provided with eight connecting portions (41c) that connect the covering portion 41a and the main body portion 41b. １ , 41c ２ , 41c ３ , 41c ４ , 41c ５ , 41c ６ , 41c ７ and 41c ８ )

[0124] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on the six connections (41c ２ , 41c ３ , 41c ４ , 41c ６ , 41c ７ , 41c ８ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ５The inside of the contour C of the covering portion 41a is divided into two by the second cutout portion 52b, and each portion is １ and 52a ２ 4I, the second cutout 52a is further divided into two (a total of four). １ The upper two portions divided by the second cutout 52a are connected by an internal connection portion 44a at the intersection of the major axis La and the minor axis Sa. ２ The two lower portions divided by are connected by an internal connector 44b at the intersection of the major axis La and the minor axis Sa.

[0125] In the first insulation sheet 41J shown in Figure 4J, four first cutouts (51a, 51b, 51c, and 51d) are formed along the contour C of the covering portion 41a so as not to contact the intersection between the long axis La and the contour C of the covering portion 41a, and so as not to contact the intersection between the short axis Sa and the contour C of the covering portion 41a.

[0126] In the first heat insulating sheet 41J shown in FIG. 4J, three second cutouts parallel to the minor axis Sa are formed at positions that divide the major axis La into four equal parts (for convenience, the upper horizontal second cutouts 52b １ , the second horizontal cutout 52b in the middle ２ and the lower second horizontal cutout 52b ３ (hereinafter referred to as "second lateral cutout 52b") １ The second horizontal cutout 52b in the middle is in contact with the first cutouts (51a and 51d). ２ The lower horizontal second cutout 52b is not in contact with the first cutouts (51a, 51b, 51c, and 51d). ３ is in contact with the first notch portions (51b and 51c).

[0127] In the first heat insulating sheet 41J shown in FIG. 4J, three second cut portions are formed along the long axis La (for convenience, from the top, the upper vertical second cut portion 52a １ , the second vertical cut portion 52a in the middle ２ and the lower second vertical cutout 52a ３ (hereinafter referred to as "second vertical cut portion 52a") １and the lower second vertical cutout 52a ３ The vertical second cutout 52a in the middle is formed so as not to come into contact with the first cutout and other second cutouts. ２ The second horizontal cutout 52b in the middle １ It is formed so as to intersect with

[0128] In the contour C of the covering portion 41a, two line segments (Ls １ , Ls ２ ) on two connectors (41c ２ , 41c ４ ) and two arcs (Cs １ , Cs ２ ) on which there are two connectors (41c １ , 41c ３ ) is available.

[0129] The covering portion is, from the top, the upper second horizontal cut portion 52b １ , the second horizontal cutout 52b in the middle ２ , the lower second horizontal cutout 52b ３ , upper vertical second cut portion 52a １ , the second vertical cut portion 52a in the middle ２ and the lower second vertical cutout 52a ３ The upper second horizontal cutout 52b is divided into eight sections. １ The upper second vertical cutout 52a １ The lower second horizontal cutout 52b does not intersect with the ３ The second vertical cutout 52a at the bottom ３ Therefore, at these intersections, the sections are connected by four internal connections 44.

[0130] In the battery pack according to the first embodiment of the present invention, when the covering portion has a racetrack shape as described above, the two line segments (Ls １ , Ls ２ ) each have one or more connections, and two arcs (Cs １ , Cs ２In the battery pack according to the first embodiment of the present invention, when the second cutouts are formed on the minor axis Sa and the major axis La and the covering portion is divided, it is preferable that each portion be connected by one or more internal connecting portions inside the outline of the covering portion.

[0131] In the battery pack according to the first embodiment of the present invention, the second cutout portion may be formed in a straight line or a curved line.

[0132] The preferred length of the second cutouts will be described below using the first heat insulating sheet 41E as an example. FIG. 5 is an explanatory diagram of the preferred length of the second cutouts according to the first embodiment of the present invention. In the first heat insulating sheet 41E shown in FIG. 5, two second cutouts (52a) are formed along the major axis La of the covering portion 41a. １ and 52a ２ ) are formed along the minor axis Sa. １ and 52b ２ ) is formed.

[0133] In the first heat insulating sheet 41E, two second cut portions (52a １ and 52a ２ ) have the same length L ５２ａ In addition, two second cut portions (52b １ and 52b ２ ) have the same length L ５２ｂ In the battery pack according to the first embodiment of the present invention, when a plurality of second cutouts are formed in a straight line, the lengths of the second cutouts may be the same or different.

[0134] The second cutout portion (52a １ and 52a ２ ) the length I of the internal connection portion 44 between ５２ａ is the length L of the covering portion 41a on the major axis La ４１ａ－１ It is preferable that the length I of the internal connection portion 44 is 50% or less and 1.0 mm or more. ５２ａ is the length L of the covering portion 41a on the major axis La ４１ａ－１It is more preferable that the length I of the internal connection portion 44 is 40% or less, and even more preferable that the length I of the internal connection portion 44 is 30% or less. ５２ａ The length I of the internal connection portion 44 is more preferably 3.0 mm or more, even more preferably 5.0 mm or more, and even more preferably 7.0 mm or more. ５２ａ is the length L of the covering portion 41a on the major axis La. ４１ａ－１ If the length I of the internal connection portion 44 exceeds 50%, the connection portion is less likely to break and the covering portion is less likely to separate from the main body portion. ５２ａ However, if the thickness is less than 1.0 mm, the connection portion becomes too easily broken and the covering portion becomes too easily separated from the main body portion.

[0135] Second cutout portion (52b １ and 52b ２ ) the length I of the internal connection portion 44 between ５２ｂ is the length L of the covering portion 41a on the minor axis Sa ４１ａ－２ It is preferable that the length I of the internal connection portion 44 is 50% or less and 1.0 mm or more. ５２ｂ is the length L of the covering portion 41a on the minor axis Sa ４１ａ－２ It is more preferable that the length I of the internal connection portion 44 is 40% or less, and even more preferable that the length I of the internal connection portion 44 is 30% or less. ５２ｂ The length I of the internal connection portion 44 is more preferably 3.0 mm or more, even more preferably 5.0 mm or more, and even more preferably 7.0 mm or more. ５２ｂ is the length L of the covering portion 41a on the minor axis Sa. ４１ａ－２ If the length I of the internal connection portion 44 exceeds 50%, the connection portion is less likely to break and the covering portion is less likely to separate from the main body portion. ５２ｂ However, if the thickness is less than 1.0 mm, the connection portion becomes too easily broken and the covering portion becomes too easily separated from the main body portion.

[0136] When the length of the second cut portion is within the above range, the covering portion is easily divided into multiple portions along the second cut portion.

[0137] In the above description, the second cutouts are formed along the minor axis Sa and the major axis La, respectively. However, in the battery pack according to the first embodiment of the present invention, the second cutouts may be formed on intersecting straight lines other than the minor axis Sa and the major axis La. Furthermore, in the battery pack according to the first embodiment of the present invention, only one second cutout may be formed.

[0138] Furthermore, in the explanation so far, the second cutout portion has been formed only inside the outline of the covering portion, but in the battery pack according to the first embodiment of the present invention, it is sufficient that at least a portion of the second cutout portion is inside the outline of the covering portion, and for example, the second cutout portion may be formed so as to intersect with the outline of the covering portion.

[0139] The first cut portion and the second cut portion may be formed by punching with a Thomson blade or the like having a predetermined structure, or may be formed by cutting or laser processing.

[0140] In the battery pack according to the first embodiment of the present invention, the planar shape of the covering portion is not limited to a racetrack shape, but may be a triangle, a polygon such as a rectangle or a hexagon, a circle, or an ellipse.

[0141] Next, the use and arrangement method of the battery pack according to the first embodiment of the present invention will be described. The use of the battery pack according to the first embodiment of the present invention is not particularly limited, but it may be used as a power source for an electric vehicle, for example.

[0142] Furthermore, the battery pack according to the first embodiment of the present invention is preferably arranged so that the safety valves provided on the battery cells are located vertically either on the upper or lower side. When the battery pack is arranged so that the safety valves are located in this way, high-temperature gas from an abnormal battery cell is naturally and quickly dispersed, making it less likely that a chain reaction of thermal runaway will occur. In other words, this is a preferable battery pack arrangement from the viewpoint of fail-safety.

[0143] In the battery pack according to the first embodiment of the present invention, the safety valve may be disposed on the bottom side or the lid side. As described above, when the battery pack according to the first embodiment of the present invention is disposed, from the viewpoint of fail-safe, the battery pack may be disposed so that the safety valve is disposed on the vertically upper side or the vertically lower side. Since battery packs are often disposed so that the bottom or the lid of the case is disposed on the lower side, disposing the safety valve 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 the vertically lower side.

[0144] Second Embodiment A battery pack according to a second embodiment of the present invention differs from the battery pack according to the first embodiment of the present invention in that the heat insulating material further includes a second heat insulating sheet and an adhesive layer that bonds the second heat insulating sheet to the first heat insulating sheet, and the heat insulating material is arranged so that the second heat insulating sheet is located on the module side and the first heat insulating sheet is located on the case side. The battery pack according to the second embodiment of the present invention will be described below with reference to the drawings.

[0145] Fig. 6 is a cross-sectional view schematically illustrating an example of a battery pack according to a second embodiment of the present invention. The battery pack 110 shown in Fig. 6 differs from the battery pack 10 in that the heat insulating material 140 is made up of a first heat insulating sheet 141, a second heat insulating sheet 142, and an adhesive layer (not shown) that bonds the first heat insulating sheet 141 and the second heat insulating sheet 142 together. The heat insulating material 140 is arranged such that the second heat insulating sheet 142 is located on the module 20 side and the first heat insulating sheet 141 is located on the case 30 side.

[0146] With this second insulating sheet 142 in place, gas G released from the abnormal battery cell 21 passes through the second insulating sheet 142 before reaching the first insulating sheet 141. The gas G then thermally decomposes the adhesive layer, causing the covering portion 141a to peel off from the second insulating sheet, and the gas pressure causes the covering portion 141a to separate from the main body portion 141b. The temperature of the gas G drops as it passes through the second insulating sheet 142, and the gas pressure also decreases. Therefore, even if the gas G passes through the portion of the first insulating sheet 141 where the covering portion 141a was located and comes into contact with the case 30, the case 30 is unlikely to be heated or damaged by the gas G.

[0147] In the battery pack 110, the adhesive layer preferably includes an organic adhesive layer. If the adhesive layer includes an organic adhesive layer, the adhesive layer is likely to be thermally decomposed when high-temperature gas G from an abnormal battery cell reaches the adhesive layer. Organic adhesives that are thermally decomposed at 80°C or higher are preferred, and examples thereof include adhesives containing polyamide-based organic materials.

[0148] In the battery pack 110, the second insulating sheet 142 has a third cutout formed therein that continues from the main surface to which the first insulating sheet 141 is adhered to the other main surface, and it is preferable that at least a portion of the third cutout be located inside the covering portion 141a when the insulating material 140 is viewed in plan from the first insulating sheet 141 side. When the second insulating sheet 142 has the third cutout formed therein, high-temperature gas G from the module 20 side can easily pass through the third cutout and reach the covering portion 141a. Note that when the insulating material 140 is viewed in plan from the first insulating sheet 141 side, the third cutout may be located only inside the covering portion 141a, or may be located so as to intersect with the outline of the covering portion 141a.

[0149] In the battery pack 110, when the heat insulating material 140 is viewed in plan from the side of the first heat insulating sheet 141, the third cut portion may be formed in a linear shape or a curved shape, but is preferably formed in a straight line. A linear third cut portion can be easily formed using a cutter or the like.

[0150] In the battery pack 110, a plurality of third cutouts may be formed in the second insulating sheet 142. Furthermore, in the battery pack 110, the plurality of third cutouts may be separated from one another or may intersect with one another when the insulating material 140 is viewed in plan from the first insulating sheet 141 side. In either case, gas G generated from an abnormal battery cell 21 a is likely to quickly reach the first insulating sheet 141 through the third cutouts.

[0151] In the battery pack 110, the second cutout and the third cutout may be overlapping and have the same shape when the heat insulating material 140 is viewed in a plan view from the first heat insulating sheet 141 side. Such second cutout and third cutout can be formed simultaneously by punching out the first heat insulating sheet 141 and the second heat insulating sheet 142 in an overlapping state. Note that the second cutout and the third cutout do not have to overlap and may have different shapes.

[0152] In the battery pack 110, the second insulating sheet 142 is preferably at least one selected from the group consisting of an inorganic fiber mat, an inorganic fiber paper, and an inorganic fiber cloth. The inorganic fiber mat, the inorganic fiber paper, and the inorganic fiber cloth can be easily molded and exhibit excellent performance as the second insulating sheet.

[0153] The thickness of the inorganic fiber mat is preferably 0.5 to 10 mm, and more preferably 1 to 4 mm. If the thickness of the inorganic fiber mat is less than 0.5 mm, the inorganic fiber mat is so thin that the gas temperature and gas pressure are not easily reduced as the gas passes through the inorganic fiber mat. As a result, the gas reaches the case with force while still hot, which makes the case more susceptible to deterioration. If the thickness of the inorganic fiber mat exceeds 10 mm, the inorganic fiber mat becomes too thick, making it difficult to miniaturize the entire battery pack.

[0154] The bulk density of the inorganic fiber mat is 0.1 to 1.0 g / cm ３ is preferably 0.2 to 0.7 g / cm ３ It is more preferable that the bulk density of the inorganic fiber mat is 0.1 g / cm ３If the bulk density of the inorganic fiber mat is less than 1.0 g / cm, the gaps between the inorganic fibers become large, and as the gas passes through the inorganic fiber mat, the temperature of the gas is less likely to decrease, and the gas pressure is less likely to decrease. As a result, the gas reaches the case with force while still at a high temperature, which makes the case more likely to deteriorate. ３ If the temperature exceeds this value, it becomes difficult for the gas to pass through the inorganic fiber mat, and the high-temperature gas remains inside the battery cell, making it difficult for the temperature inside the battery cell to decrease. This makes it more likely that a chain reaction of thermal runaway will occur.

[0155] The inorganic fiber mat is preferably a mat-shaped inorganic fiber containing at least one fiber selected from silica fiber, glass fiber, alumina fiber, aluminosilicate fiber, basalt fiber, rock wool, and biosoluble fiber. Inorganic fiber mats made of such materials can be easily processed.

[0156] The inorganic fiber mat may be a mat made of inorganic fibers containing fibers with a melting point of 1000° C. or higher. When the inorganic fiber mat contains fibers with a melting point of 1000° C. or higher, the inorganic fibers have high heat resistance, so the inorganic fiber mat is less likely to deteriorate even if high-temperature gas from an abnormal battery cell reaches the inorganic fiber mat.

[0157] The inorganic fiber mat may be formed by processing inorganic fibers containing fibers with a melting point of less than 1000° C. 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 melts and a gas flow path is easily formed.

[0158] The preferred embodiments of the inorganic fiber paper and inorganic fiber cloth constituting the second heat insulating sheet are the same as the preferred embodiments of the inorganic fiber paper and inorganic fiber cloth constituting the first heat insulating sheet.

[0159] This specification describes the following inventions:

[0160] The present invention (1) is a battery pack comprising a module having a plurality of battery cells, each having a safety valve, a case for accommodating 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 in a plane, the first heat insulating sheet is composed 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, each covering portion being positioned so as to overlap with at least a portion of each safety valve, the covering portion having a first cutout portion that follows the contour of the covering portion and a second cutout portion at least a portion of which is inside the contour of the covering portion, the contour of the covering portion not having the first cutout portion, and the battery pack having at least two connection portions that connect the covering portion to the main body portion.

[0161] A second aspect of the present invention is the battery pack according to the first aspect of the present invention, wherein the first cutout and the second cutout are spaced apart from each other.

[0162] The present invention (3) is a battery pack according to the present invention (1) or (2), in which, when the first insulating sheet is viewed in a plane, the second cutouts are formed in multiple numbers on intersecting straight lines.

[0163] A fourth aspect of the present invention is the battery pack according to the third aspect of the present invention, wherein the second cutouts are formed so as to intersect at the intersections of the intersecting straight lines.

[0164] A fifth aspect of the present invention is the battery pack according to the third aspect of the present invention, wherein the second cutout is formed on one of the straight lines at the intersection of the intersecting straight lines.

[0165] A sixth aspect of the present invention is the battery pack according to the third aspect of the present invention, wherein the second cutout is not formed at the intersection of the intersecting straight lines.

[0166] The present invention (7) is a battery pack according to any one of the present inventions (3) to (6), wherein, when the first insulating sheet is viewed in a plan view, the covering portion has a shape including a minor axis that passes through the center of gravity of the covering portion and is the shortest part, and a major axis that passes through the center of gravity of the covering portion and is the longest part, and one of the intersecting straight lines is the minor axis and the other is the major axis.

[0167] The present invention (8) is the battery pack according to any one of the present inventions (1) to (7), wherein the thickness of the first heat insulating sheet is 0.05 to 2.0 mm.

[0168] The present invention (9) is the battery pack according to any one of the present inventions (1) to (8), wherein the length of one of the connection parts is 50% or less of the total length of the outline of the covering part, and the length of one of the connection parts is 1.0 mm or more.

[0169] The present invention (10) is a battery pack according to any one of the present inventions (3) to (7), wherein the inside of the outline of the covering portion is divided into a plurality of portions by the second cutouts, the second cutouts are not formed on the intersecting straight lines at the intersections of the intersecting straight lines, there is at least one internal connection portion connecting the plurality of portions, the length of one internal connection portion is 50% or less of the length of the covering portion on the intersecting straight line where the internal connection portion is located, and the length of one internal connection portion is 1.0 mm or more.

[0170] The present invention (11) is the battery pack according to any one of the present inventions (1) to (10), wherein the planar shape of the covering portion is at least one selected from the group consisting of a polygon, a circle, an ellipse, and a racetrack shape.

[0171] The present invention (12) is the battery pack according to any one of the present inventions (1) to (11), wherein the first heat insulating sheet is at least one selected from the group consisting of a mica sheet, a heat-resistant resin sheet, inorganic fiber paper, and inorganic fiber cloth.

[0172] The present invention (13) is a battery pack according to any one of the present inventions (1) to (12), wherein the heat insulating material further includes a second heat insulating sheet and an adhesive layer that adheres the second heat insulating sheet to the first heat insulating sheet, and the heat insulating material is arranged so that the second heat insulating sheet is located on the module side and the first heat insulating sheet is located on the case side.

[0173] The present invention (14) is a battery pack according to the present invention (13), in which the second insulating sheet has a third cutout portion formed therein that continues from the main surface to which the first insulating sheet is adhered to the other main surface, and when the insulating material is viewed in a plane from the first insulating sheet side, at least a portion of the third cutout portion is located inside the covering portion.

[0174] The present invention (15) is the battery pack according to the present invention (14), wherein the third cutout is formed linearly when the heat insulating material is viewed in plan from the first heat insulating sheet side.

[0175] The present invention (16) is a battery pack according to the present invention (14) or (15), in which, when the insulating material is viewed in a plane from the first insulating sheet side, the second cutout portion and the third cutout portion overlap with each other and have the same shape.

[0176] The present invention (17) is the battery pack according to any one of the present inventions (13) to (16), wherein the second heat insulating sheet is at least one selected from the group consisting of an inorganic fiber mat, an inorganic fiber paper, and an inorganic fiber cloth.

[0177] The present invention (18) is a sheet-like insulating material consisting of a main body and a covering formed inside the main body, characterized in that a first cutout portion is formed along the contour of the covering part, and a second cutout portion at least a portion of which is inside the contour of the covering part, the first cutout portion is not formed on the contour of the covering part, and there are at least two connecting portions connecting the covering part and the main body.

[0178] Example 1 Fig. 7 is a plan view schematically illustrating the vicinity of the covering portion of the mica sheet according to Example 1. First, a mica sheet having a thickness of 0.1 mm was prepared. Next, as shown in Fig. 7, first cut portions 51 were formed along a rectangular outline C having dimensions of 70 mm x 20 mm. In this case, the first cut portions 51 were formed so that connection portions 41c were formed near the midpoints of the long sides of the rectangular outline C, near the midpoints of the short sides of the rectangular outline C, and near the ends of the long sides where the long and short sides of the rectangular outline C meet.

[0179] Furthermore, two more first cutouts 51 (not shown) were formed in different positions on the mica sheet so that the covering portion 41a would cover the safety valve of the battery cell in the thermal runaway test described below.

[0180] Next, a 4.0 mm thick silica sheet made of silica fiber was prepared, and the mica sheet and the silica sheet were laminated together with the adhesive disposed between them, followed by thermocompression bonding under conditions of 100 kPa, 180°C, and 20 seconds.

[0181] Next, as shown in Fig. 7, second cuts 52 were formed in the mica sheet. At this time, cuts were also formed in the silica sheet. The second cuts 52 were formed along the line connecting the midpoints of the short sides of the rectangular outline C and the line connecting the midpoints of the long sides of the rectangular outline C (excluding the vicinity of the line connecting the midpoints of the short sides of the rectangular outline C). In this way, the covering portion 41a, the main body portion 41b, the connecting portion 41c, and the internal connecting portion 44 were formed.

[0182] Through the above steps, the heat insulating material of Example 1 was produced, in which the mica sheet (first heat insulating sheet) and the silica sheet (second heat insulating sheet) were laminated.

[0183] (Example 2) Fig. 8 is a plan view schematically showing the vicinity of the covering portion of the mica sheet according to Example 2. The heat insulating material according to Example 2 was produced in the same manner as in Example 1, except that the first cut portion 51 and the second cut portion 52 were formed at the positions shown in Fig. 8.

[0184] 8, first cutouts 51 were formed along the rectangular outline C. At this time, first cutouts 51 were formed so that connection portions 41c were formed near the midpoint of the long side of the rectangular outline C, near the midpoint of the short side of the rectangular outline C, and near the end of the long side where the long side and short side of the rectangular outline C meet.

[0185] As shown in FIG. 8, the second cutouts 52 are formed along the lines connecting the midpoints of the short sides of the rectangular outline C and the lines connecting the midpoints of the long sides of the rectangular outline C.

[0186] Example 3 A heat insulating material according to Example 3 was produced in the same manner as in Example 1, except that a mica sheet having a thickness of 0.3 mm was used.

[0187] (Thermal Runaway Test) A thermal runaway test was carried out according to the following procedure: Fig. 9 is a schematic diagram showing an outline of the thermal runaway test.

[0188] (Test Example 1) First, as shown in FIG. 9 , a heat insulator 240, a heater 270, a thermal runaway battery cell 221a, a first adjacent battery cell 221b, and a second adjacent battery cell 221c were arranged in a test apparatus 260 having a wall portion 261, a bottom portion 262, and a lid portion 263. In the test apparatus 260, the heat insulator 240 was arranged so that the mica sheet 241 was located closer to the bottom portion 262 than the silica sheet 242. Furthermore, on the heat insulator 240, the heater 270, the thermal runaway battery cell 221a, the first adjacent battery cell 221b, and the second adjacent battery cell 221c were arranged in this order from left to right. The thermal runaway battery cell 221a, the first adjacent battery cell 221b, and the second adjacent battery cell 221c were connected in series. Furthermore, the safety valves 222 of each battery cell were arranged so as to be located on the bottom portion 262 side. The heat insulator 240 used was the heat insulator according to Example 1.

[0189] Next, current was made to flow from the thermal runaway battery cell 221a, the first adjacent battery cell 221b, and the second adjacent battery cell 221c. After that, the thermal runaway battery cell 221a was heated by the heater 270, causing the thermal runaway battery cell 221a to go into thermal runaway, and high-temperature gas was sprayed from the safety valve of the thermal runaway battery cell 221a.

[0190] And, the thermal runaway battery cell 221a has a safety valve P １ , P directly below the safety valve of the first adjacent battery cell 221b ２ , and P directly below the safety valve of the second adjacent battery cell 221c ３ was measured. １ ~P ３ The maximum temperatures are shown in Table 1 and Fig. 10. Fig. 10 is a graph showing the results of the thermal runaway test.

[0191]

[0192] Test Examples 2 and 3 Test Examples 2 and 3 were carried out in the same manner as Test Example 1, except that the heat insulating material according to Example 2 and the heat insulating material according to Example 3 were used as the heat insulating material 240. The results are shown in Table 1 and FIG.

[0193] Comparative Test Example 1 Comparative Test Example 1 was carried out in the same manner as Test Example 1, except that no heat insulating material was used. The results are shown in Table 1 and FIG.

[0194] From the results of the thermal runaway test, １ It was shown that the maximum temperature in Comparative Test Example 1, where no heat insulating material was provided, was lower than that in Test Examples 1 to 3, where heat insulating material was provided. This is because in Test Examples 1 to 3, it takes a little time for the covering part of the mica sheet of the heat insulating material to break, and high-temperature gas accumulates during that time, １ In Comparative Test Example 1, P ２ 2. Since the maximum temperature in the first adjacent battery cell 221b exceeds 700°C, high-temperature gas flows back from the safety valve 222 of the first adjacent battery cell 221b, making the first adjacent battery cell 221b prone to thermal runaway.

[0195] On the other hand, in Test Examples 1 to 3, P ２ and P ３ The maximum temperature at P was less than 700°C, which indicated that the first adjacent battery cell 221b and the second adjacent battery cell 221c were unlikely to experience thermal runaway. ２ and P ３ The maximum temperature at the first adjacent battery cell 221b was less than 200°C, which indicates that the first adjacent battery cell 221b and the second adjacent battery cell 221c are less susceptible to thermal runaway.

[0196] REFERENCE SIGNS LIST 10, 110 Battery pack 20 Module 20a Connection module member 20b Bus bar 21 Battery cell 21a Abnormal battery cell 22, 22a Safety valve 23 Terminal 30 Case 31 Storage section 31b Bottom section 31s Side wall 32 Lid section 40, 240 Heat insulating material 41, 41A, 41B, 41C, 41D, 41E, 41F, 41G, 41H, 141 First heat insulating sheet 41a, 141a Cover section 41b, 141b Main body section 41c, 41c １ , 41c ２ , 41c ３ , 41c ４ , 41c ５ , 41c ６ , 41c ７ and 41c ８Connection portions 44, 44a, 44b Internal connection portions 51, 51a, 51b, 51c, 51d, 51e, 51f, 51g, and 51h First cut portions 52, 52a, 52a １ , 52a ２ , 52a ３ , 52b, 52b １ , 52b ２ , 52b ３ Second cutout 221a: Thermal runaway battery cell 221b: First adjacent battery cell 221c: Second adjacent battery cell 222: Safety valve 241: Mica sheet 242: Silica sheet 260: Test device 261: Wall 262: Bottom 263: Lid 270: Heater

Claims

1. A battery pack comprising: a module having a plurality of battery cells, each having a safety valve; a case that houses the module; and a heat insulating material that is 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 in a plane, the first heat insulating sheet is made up 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 covering portion is positioned so as to overlap with at least a portion of one of the safety valves, and the covering portion has a first notch that follows the outline of the covering portion and a second notch that is at least partially inside the outline of the covering portion, and the outline of the covering portion does not have the first notch, and there are at least two connecting portions that connect the covering portion and the main body portion.

2. The battery pack according to claim 1, wherein the first cutout and the second cutout are spaced apart.

3. The battery pack according to claim 1 or 2, wherein, when the first heat insulating sheet is viewed in a plan view, a plurality of the second cutouts are formed on intersecting straight lines.

4. The battery pack according to claim 3, wherein the second cutout is formed so as to intersect at the intersection of the intersecting straight lines.

5. The battery pack according to claim 3, wherein the second cutout is formed on one of the straight lines at the intersection of the intersecting straight lines.

6. The battery pack according to claim 3, wherein the second cutout is not formed at the intersection of the intersecting straight lines.

7. A battery pack as described in any one of claims 3 to 6, wherein, when the first heat insulating sheet is viewed in a plane, the covering portion has a shape including a minor axis that passes through the center of gravity of the covering portion and is the shortest part, and a major axis that passes through the center of gravity of the covering portion and is the longest part, and one of the intersecting straight lines is the minor axis and the other is the major axis.

8. A battery pack according to any one of claims 1 to 7, wherein the thickness of the first heat insulating sheet is 0.05 to 2.0 mm.

9. A battery pack as set forth in any one of claims 1 to 8, wherein the length of each said connection portion is 50% or less of the total length of the outline of said covering portion, and the length of each said connection portion is 1.0 mm or more.

10. A battery pack as described in any one of claims 3 to 7, wherein the inside of the outline of the covering portion is divided into a plurality of portions by the second cutouts, and on the intersecting straight lines, at the intersection of the intersecting straight lines, there is at least one internal connection portion connecting the plurality of portions, where the second cutouts are not formed, and the length of one internal connection portion is 50% or less of the length of the covering portion on the intersecting straight line where the internal connection portion is located, and the length of one internal connection portion is 1.0 mm or more.

11. The battery pack according to any one of claims 1 to 10, wherein the planar shape of the covering portion is at least one selected from the group consisting of a polygon, a circle, an ellipse, and a racetrack shape.

12. A battery pack according to any one of claims 1 to 11, wherein the first heat insulating sheet is at least one selected from the group consisting of a mica sheet, a heat-resistant resin sheet, inorganic fiber paper, and inorganic fiber cloth.

13. A battery pack as described in any one of claims 1 to 12, wherein the heat insulating material further includes a second heat insulating sheet and an adhesive layer that bonds the second heat insulating sheet to the first heat insulating sheet, and the heat insulating material is arranged so that the second heat insulating sheet is located on the module side and the first heat insulating sheet is located on the case side.

14. A battery pack as described in claim 13, wherein the second insulating sheet has a third cutout portion formed therein that continues from the main surface to which the first insulating sheet is adhered to the other main surface, and when the insulating material is viewed in a plane from the first insulating sheet side, at least a portion of the third cutout portion is located inside the covering portion.

15. The battery pack according to claim 14, wherein the third cutout is formed linearly when the heat insulating material is viewed from the first heat insulating sheet side in a plan view.

16. A battery pack according to claim 14 or 15, wherein when the heat insulating material is viewed in a plan view from the first heat insulating sheet side, the second cutout and the third cutout have the same shape and overlap.

17. A battery pack according to any one of claims 13 to 16, 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.

18. A sheet-like insulating material consisting of a main body and a covering formed inside the main body, wherein a first cutout is formed along the contour of the covering and a second cutout is formed at least partially inside the contour of the covering, and the first cutout is not formed on the contour of the covering, and there are at least two connecting parts connecting the covering and the main body.

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