Battery pack

Abstract

This invention provides a battery pack that, during thermal runaway, rapidly discharges high-temperature gas generated from abnormal battery cells and prevents a chain reaction of thermal runaway caused by the backflow of high-temperature gas to adjacent battery cells. The battery pack of this invention comprises: a module having multiple battery cells each equipped with a safety valve; a housing housing the module; and a thermal insulation material disposed between the module and the housing. The battery pack of this invention is characterized in that the thermal insulation material includes a first thermal insulation sheet. Viewed from above, the first thermal insulation sheet is composed of multiple covering portions covering the multiple safety valves and a main body portion other than the covering portions. One of the covering portions is located at a position overlapping at least a portion of one of the safety valves. The covering portion has a first slit portion along its outline and at least a second slit portion located inside the outline of the covering portion. The first slit portion is not formed on the outline of the covering portion, but at least two connecting portions connecting the covering portion to the main body portion are provided.

Description

Technical Field

[0001] This invention relates to a battery pack. Background Technology

[0002] In battery packs, which consist of modules housing multiple individual cells, high-temperature gases and flames can sometimes be generated during thermal runaway. These gases and flames can spread to the surrounding area, potentially triggering further thermal runaway.

[0003] In order to prevent thermal runaway chain reactions, safety valves have been installed in modules to release high-temperature gases generated during thermal runaway.

[0004] In addition, when the high-temperature gas released from the safety valve directly collides with the casing, the temperature of the casing rises, sometimes generating a thermal effect around the battery pack.

[0005] In order to prevent high-temperature gas from directly colliding with the shell, thermal insulation material was previously placed between the module and the shell.

[0006] As such a battery pack, Patent Document 1 discloses an energy storage device comprising: an energy storage stack including a plurality of energy storage cells each having an exhaust valve on its upper surface; an upper housing covering the energy storage stack from above; and a first heat-resistant sheet and a second heat-resistant sheet having heat resistance to exhaust gas discharged from the exhaust valves and disposed between the upper housing and the energy storage stack, wherein the first heat-resistant sheet has a plurality of holes provided at positions overlapping with each of the exhaust valves in the vertical direction, and the second heat-resistant sheet is disposed above the first heat-resistant sheet in such a way as to cover the plurality of holes.

[0007] In addition, Patent Document 2 discloses an energy storage module comprising: at least one cylindrical energy storage device; a retainer for holding the energy storage device; and an insulating plate disposed on one side of the retainer, wherein an exhaust valve is provided at one end of the side of the energy storage device, and a first opening is formed on the retainer to expose the exhaust valve. The insulating plate has: a flat body portion; a second opening formed in the body portion and communicating with the first opening; a cover portion that closes a portion of the second opening; and a connecting portion that connects the cover portion and the body portion. A fixing portion for fixing the insulating plate to the retainer is provided in the body portion.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2023-59480

[0011] Patent Document 2: International Publication No. 2023 / 054498 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] In Patent Document 1, in the event of thermal runaway, it is necessary to vent the gas from the abnormal monomer, therefore multiple holes are provided on the first heat-resistant sheet. However, the gas vented from the abnormal monomer may flow back through the holes and exhaust valves of adjacent monomers and come into contact with them. In this case, it may cause the adjacent monomers to ignite (thermal chain reaction).

[0014] In Patent Document 2, the structure is configured such that a cover is provided at the hole (opening) of the sheet, and in the event of thermal runaway, under the pressure of the gas discharged from the abnormal monomer, the cover at the position corresponding to the exhaust valve of the abnormal monomer peels off (flies out) or opens. However, there is still room for improvement in the ease of peeling off the cover.

[0015] This invention was made to solve the above-mentioned problems. The purpose of this invention is to provide a battery pack that can quickly discharge high-temperature gas generated from abnormal battery cells during thermal runaway, and can prevent the high-temperature gas from flowing back to adjacent battery cells and causing a thermal runaway chain reaction.

[0016] Methods for solving problems

[0017] The battery pack of the present invention comprises: a module having a plurality of battery cells each having a safety valve; a housing housing the module; and a heat-insulating material disposed between the module and the housing. The battery pack is characterized in that the heat-insulating material includes a first heat-insulating sheet, which, when viewed from above, is composed of a plurality of covering portions covering the plurality of safety valves and a main body portion other than the covering portions. One of the covering portions is located at a position overlapping at least a portion of one of the safety valves. A first slit portion along the outline of the covering portion and at least a portion of a second slit portion located inside the outline of the covering portion are formed on the covering portion. At least two connecting portions on the outline of the covering portion connect the covering portion to the main body portion without forming the first slit portion.

[0018] The battery pack of this invention can prevent thermal runaway chain reactions caused by high-temperature gases from abnormal battery cells during thermal runaway. The principle is explained below.

[0019] In the battery pack of this invention, a safety valve is provided within the module. Therefore, when a single battery cell experiences thermal runaway and generates high-temperature gas, the gas is released through the safety valve. The gas released from the safety valve then reaches the thermal insulation material.

[0020] The insulation material includes a first insulation sheet.

[0021] Furthermore, when viewed from above, the first heat insulation sheet consists of multiple covering parts that cover multiple safety valves and a main body part other than the covering parts.

[0022] Therefore, the gas released from the safety valve collides with the cover.

[0023] In the battery pack of the present invention, a first slit along the outline of the cover portion and a second slit located inside the outline of the cover portion are formed on the cover portion. Furthermore, at least two connecting portions are provided on the outline of the cover portion that connect the cover portion to the main body portion without forming the first slit.

[0024] When the gas released from the safety valve hits the cover, the connecting part breaks under its pressure, and the cover detaches from the main body along the first slit. At this time, the cover also splits into multiple parts along the second slit.

[0025] Then, the gas is released between the insulation material and the shell through the covered portion of the first insulation sheet.

[0026] In addition, the gas released between the insulation material and the shell also reaches other covered parts of the first insulation sheet.

[0027] However, the other coverings of the first insulation sheet are connected to the main body via a connecting part that will not break due to the pressure of the gas released between the insulation material and the shell.

[0028] Therefore, even if gas reaches other covered portions of the first heat insulation sheet, the gas will be blocked by the covered portions. Thus, it is possible to prevent gas from flowing back through the safety valves of other battery cells.

[0029] In addition, in the battery pack of the present invention, the cover portion is connected to the main body portion through at least two connecting portions.

[0030] For example, if the cover is connected to the main body only by a single connection, pressure can easily be applied to the connection, making it prone to breakage. Therefore, even the pressure of gas released between the insulation material and the shell could cause the cover to detach from the main body. In this case, backflow of gas cannot be prevented.

[0031] However, if the cover is connected to the main body through at least two connecting parts, the pressure applied to the connecting parts is dispersed, and the connecting parts are not easily broken. Therefore, even if the gas released from the abnormal battery cell causes one cover to break, the gas is released between the heat insulation material and the shell and reaches other covers. The connecting parts of the other covers are not easily broken due to the pressure of the gas, and the covers are not easily detached from the main body.

[0032] Furthermore, as described above, under the action of the gas released from the safety valve, the cover is split into multiple parts along the second slit.

[0033] If the covering part that detaches from the main body does not split but remains a large fragment, it may sometimes block the gas flow path and hinder gas diffusion.

[0034] However, when the covering part that detaches from the main body splits into multiple parts, each fragment becomes smaller, and the fragments do not easily impede the diffusion of gas.

[0035] In the battery pack of the present invention, the first slit portion can be separated from the second slit portion.

[0036] If the first slit and the second slit are separated, the portion between them becomes part of the supporting cover. Therefore, when gas pressure is applied to the cover, the pressure is also distributed in the portion between the first and second slits, making the connection less prone to breakage.

[0037] Therefore, even if the gas released from the abnormal battery cell causes a certain cover to break, and the gas is released between the heat insulation material and the shell and reaches other covers, the connection of the other covers is not likely to break under the pressure of the gas, and the covers are not likely to detach from the main body.

[0038] In the battery pack of the present invention, when viewed from above, the first heat insulation sheet can be formed with a plurality of the second slits on intersecting straight lines.

[0039] Furthermore, the aforementioned second slit can be formed to intersect at the intersection of the aforementioned intersecting straight lines.

[0040] Furthermore, at the intersection of the aforementioned intersecting straight lines, the aforementioned second slit can be formed on a straight line.

[0041] Furthermore, at the intersection of the aforementioned intersecting straight lines, the aforementioned second slit may not be formed.

[0042] When the second slits intersect, the part that loses support at the intersection is prone to breakage, and the cover part is prone to detach from the main body.

[0043] Without intersecting the second slits, there is a supporting part at the intersection point, so the connection part is not easy to break and the cover part is not easy to detach from the main body.

[0044] In this way, the ease of breakage of the joint can be controlled by whether or not the second slit crosses.

[0045] In the battery pack of the present invention, when viewed from above, the covering portion can be shaped to include a short axis passing through the center of gravity of the covering portion and being the shortest portion, and a long axis passing through the center of gravity of the covering portion and being the longest portion. One of the intersecting straight lines can be the short axis, and the other is the long axis.

[0046] If a second slit is formed along such a short axis and a long axis, the covering part will easily split equally when it breaks.

[0047] Therefore, it is possible to prevent only a portion of the covering part from detaching from the main body.

[0048] In the battery pack of the present invention, the thickness of the first heat insulation sheet is preferably 0.05 to 2.0 mm.

[0049] If the thickness of the first heat insulation sheet is less than 0.05mm, the strength of the first heat insulation sheet will be lower and it will be easily damaged.

[0050] If the thickness of the first heat insulation sheet exceeds 2.0 mm, the first heat insulation sheet becomes too thick, making it difficult to miniaturize the battery pack as a whole.

[0051] In the battery pack of the present invention, it is preferable that the length of one of the connecting portions is less than 50% of the total length of the outline of the covering portion, and the length of one of the connecting portions is 1.0 mm or more.

[0052] When the length of a connecting part exceeds 50% of the total length of the outline of the covering part, the connecting part is difficult to break and the covering part is difficult to detach from the main body.

[0053] When the length of a connecting part is less than 1.0 mm, the connecting part is prone to breakage, and the cover part is prone to detach from the main body.

[0054] In the battery pack of the present invention, preferably, the inner side of the outline of the cover portion is divided into multiple portions by the second slit portion, and at the intersection of the intersecting straight lines, at least one internal connecting portion is provided to connect the multiple portions without forming the second slit portion, wherein the length of one of the internal connecting portions is less than 50% of the length of the cover portion on the intersecting straight lines where the internal connecting portion is located, and the length of one of the internal connecting portions is 1.0 mm or more.

[0055] When the length of the internal connecting part exceeds 50% of the length of the covering part on the intersecting straight line where the internal connecting part is located, the connecting part is difficult to break and the covering part is difficult to detach from the main body.

[0056] When the length of the internal connecting part is less than 1.0 mm, the connecting part is too easy to break and the covering part is too easy to detach from the main body.

[0057] In the battery pack of the present invention, the top view shape of the cover portion is preferably selected from at least one of the group consisting of polygons, circles, ellipses and racetrack shapes.

[0058] Such a shaped cover can be easily formed.

[0059] In the battery pack of the present invention, the first heat insulation sheet is preferably selected from at least one of the group consisting of mica sheet, heat-resistant resin sheet, inorganic fiber paper and inorganic fiber cloth.

[0060] These materials are suitable as primary insulation sheets.

[0061] In the battery pack of the present invention, the heat insulation material preferably further includes a second heat insulation sheet and an adhesive layer for bonding the second heat insulation sheet to the first heat insulation sheet, wherein the heat insulation material is arranged such that the second heat insulation sheet is located on the module side and the first heat insulation sheet is located on the housing side.

[0062] If such a second heat insulation sheet is provided, the gas released from the abnormal battery cell will reach the first heat insulation sheet after passing through the second heat insulation sheet.

[0063] The gas temperature decreases and the gas pressure decreases as it passes through the second heat insulation sheet. Therefore, even if the gas passes through the covered portion of the first heat insulation sheet and comes into contact with the housing, the housing is not easily heated by the gas and is not easily damaged.

[0064] In the battery pack of the present invention, preferably, a third slit portion is formed in the second heat insulation sheet, which extends from the main surface to which the first heat insulation sheet is bonded to to another main surface, and when the heat insulation material is viewed from the side of the first heat insulation sheet, at least a portion of the third slit portion is located inside the cover portion.

[0065] If a third slit is formed in the second heat insulation sheet, high-temperature gas from the module side can easily reach the cover through the third slit.

[0066] In the battery pack of the present invention, the third slit is preferably formed as a line when the heat insulation material is viewed from the side of the first heat insulation sheet.

[0067] The linear third slit can be easily formed using a tool or similar device.

[0068] In the battery pack of the present invention, when the heat insulation material is viewed from the first heat insulation sheet side, the second slit portion can overlap with the third slit portion in the same shape.

[0069] Such a second and third slit can be formed simultaneously by punching while the first and second heat insulation sheets are overlapping.

[0070] In the battery pack of the present invention, the second heat insulation sheet is preferably selected from at least one of the group consisting of inorganic fiber pad, inorganic fiber paper and inorganic fiber cloth.

[0071] Inorganic fiber pads, inorganic fiber paper, and inorganic fiber cloth can be easily molded and exhibit excellent performance as a second heat insulation sheet.

[0072] The heat insulation material of the present invention is a sheet-like heat insulation material composed of a main body and a cover formed on the inner side of the main body. It is characterized in that a first slit portion is formed along the outline of the cover portion and a second slit portion at least partly located on the inner side of the outline of the cover portion, and at least two connecting portions are provided on the outline of the cover portion to connect the cover portion and the main body without the first slit portion being formed.

[0073] The thermal insulation material of the present invention is used in the battery pack of the present invention described above. The covering portion of the thermal insulation material is configured to cover the safety valves of multiple battery cells disposed in the module.

[0074] By configuring the heat-insulating material of the present invention in this way, the effects of the battery pack of the present invention described above can be achieved.

[0075] Invention Effects

[0076] According to the present invention, a battery pack can be provided that, when high-temperature gas generated from abnormal battery cells during thermal runaway is ejected, can rapidly discharge the high-temperature gas and prevent thermal runaway chain reactions caused by the backflow of high-temperature gas to adjacent battery cells. Attached Figure Description

[0077] Figure 1A This is a perspective view schematically illustrating an example of a battery pack according to a first embodiment of the present invention.

[0078] Figure 1B yes Figure 1A A sectional view along line AA.

[0079] Figure 1C yes Figure 1A The diagram shown is an exploded view of the battery pack.

[0080] Figure 2A This is a schematic cross-sectional view illustrating a safety valve in a battery pack according to a first embodiment of the present invention and an example of its vicinity.

[0081] Figure 2B Viewed from the insulation material side Figure 2A The safety valve shown is shown in top view.

[0082] Figure 3AThese are explanatory diagrams illustrating the principle of preventing a thermal runaway chain reaction in a battery pack according to the first embodiment of the present invention when a single battery cell experiences thermal runaway.

[0083] Figure 3B These are explanatory diagrams illustrating the principle of preventing a thermal runaway chain reaction in a battery pack according to the first embodiment of the present invention when a single battery cell experiences thermal runaway.

[0084] Figure 3C These are explanatory diagrams illustrating the principle of preventing a thermal runaway chain reaction in a battery pack according to the first embodiment of the present invention when a single battery cell experiences thermal runaway.

[0085] Figure 4A This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0086] Figure 4B This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0087] Figure 4C This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0088] Figure 4D This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0089] Figure 4E This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0090] Figure 4F This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0091] Figure 4G This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0092] Figure 4H This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0093] Figure 4I This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0094] Figure 4JThis is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0095] Figure 5 This is an explanatory diagram of the preferred length of the second slit portion according to the first embodiment of the present invention.

[0096] Figure 6 This is a cross-sectional view schematically illustrating an example of a battery pack according to a second embodiment of the present invention.

[0097] Figure 7 This is a schematic top view showing the area near the cover of the mica sheet in Embodiment 1.

[0098] Figure 8 This is a schematic top view showing the area near the cover of the mica sheet in Embodiment 2.

[0099] Figure 9 This is a schematic diagram illustrating the overview of a thermal runaway test.

[0100] Figure 10 This is a graph showing the results of a thermal runaway test. Detailed Implementation

[0101] The battery pack of the present invention will now be described in detail. However, the present invention is not limited to the following configuration and can be applied by appropriate modifications without changing the spirit of the invention. Furthermore, inventions formed by combining two or more of the preferred configurations of the present invention described below are also part of the present invention.

[0102] (First Implementation)

[0103] The battery pack of the first embodiment of the present invention will be described with reference to the accompanying drawings.

[0104] Figure 1A This is a perspective view schematically illustrating an example of a battery pack according to a first embodiment of the present invention.

[0105] Figure 1B yes Figure 1A A sectional view along line AA.

[0106] Figure 1C yes Figure 1A The diagram shown is an exploded view of the battery pack.

[0107] Figure 1A , Figure 1B and Figure 1C The battery pack 10 shown includes: a module 20 having a plurality of battery cells 21 each having a safety valve 22; and a housing 30 for housing the module 20.

[0108] like Figure 1A and Figure 1B As shown, the housing 30 has a storage section 31 consisting of a bottom 31b and a side wall 31s, and a cover 32 covering the storage section 31, in which the module 20 is stored.

[0109] In addition, in the battery pack 10, a heat insulation material 40 is provided between the module 20 and the housing 30.

[0110] The battery cell 21 stores electricity, and is preferably a rechargeable secondary battery. Examples of secondary batteries include lithium-ion batteries, nickel-metal hydride batteries, and sodium-ion batteries.

[0111] Figure 1B and Figure 1C The battery cell 21 shown is rectangular parallelepiped. It should be noted that in the battery pack of the present invention, the battery cell can also be a three-dimensional shape other than a rectangular parallelepiped (e.g., a cube or deformed shape).

[0112] like Figure 1B and Figure 1C As shown, in module 20, multiple battery cells 21 are configured in a row and fixed by connecting module component 20a.

[0113] In addition, such as Figure 1C As shown, the battery cell 21 has a terminal 23, and adjacent battery cells 21 are electrically connected by connecting each terminal 23 with a busbar 20b disposed on the connection module member 20a.

[0114] Busbar 20b is a flat, conductive metal component. Examples of materials that can be used for busbar 20b include copper, copper alloys, stainless steel (SUS), and aluminum.

[0115] Busbar 20b can also be fixed to terminal 23 by any fixing method (such as screw fixing, welding, etc.).

[0116] Materials that make up the shell 30 include steel, aluminum, etc. As steel, stainless steel (SUS) is preferred.

[0117] Figure 2A This is a schematic cross-sectional view illustrating a safety valve in a battery pack according to a first embodiment of the present invention and an example of its vicinity.

[0118] Figure 2B Viewed from the insulation material side Figure 2A The safety valve shown is shown in top view.

[0119] like Figure 2A As shown, the heat insulation material 40 is composed of the first heat insulation sheet 41.

[0120] In addition, such as Figure 2BAs shown, when viewed from above, the first heat insulation sheet 41 is composed of multiple covering portions 41a that cover multiple safety valves 22 and a main body portion 41b other than the covering portions 41a.

[0121] Additionally, a cover 41a is located at a position that overlaps with a safety valve 22.

[0122] Furthermore, a first slit portion (51a and 51b) along the outline C of the cover portion 41a and a second slit portion (52a and 52b) located inside the outline C of the cover portion 41a are formed in the cover portion 41a.

[0123] Furthermore, the cover portion 41a has two connecting portions (41c1, 41c2) on its outline C that connect the cover portion 41a to the main body portion 41b without forming the first slit portions (51a and 51b).

[0124] More specifically, the outline C of the cover portion 41a is a racetrack shape formed by two line segments (Ls1, Ls2) and two circular arcs (Cs1, Cs2). In addition, the cover portion 41a has a short axis Sa that passes through the center of gravity of the cover portion 41a and is the shortest part, and a long axis La that passes through the center of gravity of the cover portion 41a and is the longest part.

[0125] In the cover portion 41a, the short axis Sa intersects the long axis La at a right angle.

[0126] In the first heat insulation sheet 41, two first slits (51a and 51b) are formed, which are formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the short axis Sa and the contour C of the cover portion 41a.

[0127] In addition, two second slits (52a and 52b) are formed along the long axis La and short axis Sa of the covering portion 41a.

[0128] The two ends of the second slit portion 52a formed along the long axis La are in contact with the first slit portions (51a, 51b). In addition, the two ends of the second slit portion 52b formed along the short axis Sa are not in contact with the first slit portions (51a, 51b).

[0129] On the outline C of the cover portion 41a, the portion near the intersection of the short axis Sa and the outline C of the cover portion 41a where the first slit portion (51a, 51b) is not formed is the two connecting portions (41c1, 41c2) that connect the cover portion 41a and the main body portion 41b.

[0130] On the outline C of the covering part 41a, there are two connecting parts (41c1, 41c2) on two line segments (Ls1, Ls2), but no connecting parts on two arcs (Cs1, Cs2).

[0131] Furthermore, the inner side of the outline C of the cover portion 41a is divided into four parts by the second slit portion (52a, 52b), and there is no part connecting the parts.

[0132] In battery pack 10, a thermal runaway chain reaction caused by high-temperature gases from abnormal battery cells can be prevented during thermal runaway. The principle is explained below.

[0133] Figures 3A-3C These are explanatory diagrams illustrating the principle of preventing a thermal runaway chain reaction in a battery pack according to the first embodiment of the present invention when a single battery cell experiences thermal runaway.

[0134] like Figure 3A As shown, when a battery cell 21a experiences thermal runaway and generates high-temperature gas from the battery cell 21a, gas G is discharged from safety valve 22a (in... Figure 3A In this diagram, the symbol "G" represents gas, and an arrow indicates the direction of gas flow.

[0135] Then, the gas released from safety valve 22a reaches the insulation material 40 (first insulation sheet 41).

[0136] The first heat insulation sheet 41 is composed of multiple covering portions 41a that cover multiple safety valves 22 respectively and a main body portion 41b other than the covering portions 41a.

[0137] Therefore, the gas G released from the safety valve collides with the cover 41a.

[0138] In the battery pack 10, a first slit (51a, 51b) is formed along the outline C of the cover portion 41a, and a second slit (52a, 52b) is formed inside the outline C of the cover portion 41a. In addition, two connecting portions (41c1, 41c2) are provided on the outline C of the cover portion 41a, which connect the cover portion 41a to the main body portion 41b without the first slit (51a, 51b) being formed.

[0139] like Figure 3B As shown, when the gas G released from the safety valve 22a collides with the cover portion 41a, the connecting portion 41c breaks under the pressure, and the cover portion 41a detaches from the main body portion 41b along the first slit portion (51a, 51b). At this time, the cover portion 41a also splits into four parts along the second slit portion (52a, 52b).

[0140] Then, the gas G is released between the first heat insulation sheet 41 and the outer casing 30 through the portion of the first heat insulation sheet 41 with the covering part 41a.

[0141] In addition, such as Figure 3CAs shown, the gas G released between the first heat insulation sheet 41 and the housing 30 also reaches the other covering parts 41a of the first heat insulation sheet 41.

[0142] However, the other covering portion 41a of the first heat insulation sheet 41 is connected to the main body portion 41b through the connecting portion 41c, and the connecting portion 41c will not break due to the pressure of the gas G released between the first heat insulation sheet 41 and the housing 30.

[0143] Therefore, even if the gas reaches other covering portions 41a of the first heat insulation sheet 41, the gas G will be blocked by the covering portions 41a. Thus, it is possible to prevent the gas G from flowing back from the safety valve 22 of other battery cells 21.

[0144] In addition, in the battery pack 10, the cover 41a is connected to the main body 41b via two connecting parts 41c.

[0145] For example, if the cover is connected to the main body only by a single connection, pressure can easily be applied to the connection, making it prone to breakage. Therefore, even the pressure of gas released between the insulation material and the shell could cause the cover to detach from the main body. In this case, backflow of gas cannot be prevented.

[0146] However, if the cover 41a is connected to the main body 41b via two connecting parts 41c, the pressure applied to the connecting parts 41c is dispersed, and the connecting parts 41c are not easily broken. Therefore, even if the gas G released from the abnormal battery cell 21a causes one of the cover parts 41a to break, the gas G is released between the first heat insulation sheet 41 and the housing 30 and reaches the other cover parts 41a. The connecting parts 41c of the other cover parts 41a are not easily broken due to the pressure of the gas G, and the cover parts 41a are not easily detached from the main body 41b.

[0147] Furthermore, as described above, under the action of the gas G released from the safety valve 22, the cover 41a splits into multiple parts along the second slit (52a, 52b).

[0148] If the covering part that detaches from the main body does not split but remains a large fragment, it may sometimes block the gas flow path and hinder gas diffusion.

[0149] However, when the covering part 41a, which detaches from the main body part 41b, splits into four parts, each fragment becomes smaller and each fragment is less likely to impede the diffusion of gas G.

[0150] In addition, in the first heat insulation sheet 41, a second slit portion (52a, 52b) is formed along the short axis Sa and the long axis La, so that it can easily split evenly when the covering portion 41a splits.

[0151] Therefore, it is possible to prevent only a portion of the cover 41a from detaching from the main body 41b.

[0152] Hereinafter, a preferred embodiment of the heat-insulating material of the battery pack according to the first embodiment of the present invention will be described.

[0153] In the battery pack 10, the first heat insulation sheet 41 is preferably at least one selected from the group consisting of mica sheet, heat-resistant resin sheet, inorganic fiber paper and inorganic fiber cloth.

[0154] These materials are suitable as primary insulation sheets.

[0155] Examples of resins that constitute heat-resistant resin sheets include polybutylene terephthalate, polyamide, and polypropylene.

[0156] In addition, these resins may also contain glass fibers or silica fibers as fillers.

[0157] The thermal conductivity of inorganic fiber paper is preferably less than 1 (W / m·K).

[0158] It should be noted that thermal conductivity can be measured according to the "Test Method for Thermal Conductivity of Refractory Materials" described in JIS R 2251.

[0159] The inorganic fibers constituting inorganic fiber paper may be at least one selected from the group consisting of alumina fibers, carbon fibers, basalt fibers, soluble fibers, refractory ceramic fibers, glass fibers, glass wool, slag wool, fibers containing SiO2, silica fibers, mullite fibers, aluminosilicate fibers, ceramic fibers, rock wool, alkaline earth silicate fibers, zirconium oxide fibers, silicon carbide fibers, magnesium silicate fibers, potassium titanate fibers, aerogel composite materials, and mineral fibers.

[0160] These inorganic fibers have excellent heat resistance.

[0161] The average fiber diameter of the inorganic fibers constituting the inorganic fiber paper is preferably 1 to 20 μm, more preferably 3 to 15 μm.

[0162] If it falls within the above range, inorganic fiber paper can be manufactured without compromising its formability and processability.

[0163] The inorganic fibers constituting the inorganic fiber paper preferably have an average fiber length of 0.1 to 100 mm.

[0164] If it falls within the above range, it is less likely to cause problems with formability and processability due to excessively long average fiber length of inorganic fibers, or a decrease in mechanical strength due to excessively short average fiber length.

[0165] In addition to the aforementioned inorganic fibers (hereinafter also referred to as the first inorganic fiber), inorganic fibers with an average fiber diameter smaller than that of the first inorganic fiber (hereinafter referred to as the second inorganic fiber) may also be used.

[0166] By using two types of inorganic fibers with different fiber diameters, the softness of inorganic fiber paper can be improved, as can the retention of inorganic and organic particles, which are other components described later, be enhanced.

[0167] In addition, the average fiber diameter of the second inorganic fiber is preferably 1 nm or more and less than 1 μm, more preferably 10 nm or more and less than 0.1 μm.

[0168] If it falls within the above range, the second inorganic fiber can maintain its mechanical strength while also being flexible.

[0169] In addition, in order not to impair formability, the average fiber length of the second inorganic fiber is preferably less than 1 μm.

[0170] In addition, inorganic fiber paper may also contain organic fibers, inorganic particles, organic particles, resin binders, etc. as other components.

[0171] The organic fibers contained in the inorganic fiber paper may be selected from at least one of the following groups: polyethylene terephthalate fiber, polybutylene terephthalate fiber, polypropylene terephthalate fiber, polyacetal fiber, polytetrafluoroethylene fiber, polyetheretherketone fiber, polyphenylene sulfide fiber, polyamide fiber, poly(p-phenylene terephthalamide) fiber, polyvinyl alcohol fiber, polyethylene fiber, nylon fiber, polyurethane fiber, polypropylene fiber, and ethylene-vinyl alcohol copolymer fiber.

[0172] The average fiber length of the organic fiber is not particularly limited, but is preferably 0.5 to 10 mm.

[0173] If it falls within the above range, sufficient compressive strength can be obtained without compromising the formability and shape retention of the inorganic fiber paper.

[0174] The inorganic particles contained in inorganic fiber paper can be materials with an average secondary particle size in the range of 0.01 to 200 μm.

[0175] If the average secondary particle size is within the above range, the material is readily available and the desired thermal insulation effect can be achieved. Furthermore, the average secondary particle size of the inorganic particles is preferably 0.05–100 μm.

[0176] Inorganic particles contained in inorganic fiber paper can include oxide particles, nanoparticles, inorganic hydrate particles, particles composed of thermally expandable inorganic materials, and hydrous porous bodies.

[0177] The inorganic particles contained in inorganic fiber paper can be of two or more types with different average secondary particle sizes. When the size of the inorganic particles is different, the effect of inhibiting heat transfer is also different. Therefore, it can perform multi-stage cooling of heat transfer from battery cells and exert heat absorption effect over a wide temperature range.

[0178] When the inorganic particles contained in the inorganic fiber paper are oxide particles, at least one particle selected from the group consisting of silicon dioxide, titanium dioxide, zircon, zircon, barium titanate, zinc oxide, and aluminum oxide can be used as the oxide particles. These oxide particles have a high refractive index, thus preventing the radiative heat generated by the thermal runaway of a single battery cell from propagating to adjacent battery cells or the battery pack.

[0179] When the inorganic particles contained in the inorganic fiber paper are oxide particles, in order to maximize the blocking effect of radiative heat, the average primary particle size of the oxide particles is preferably 1 to 50 μm.

[0180] It should be noted that the average particle size is determined by comparing any 10 particles with a standard scale using a microscope, and the average of the measured particle sizes of the 10 particles is taken.

[0181] The inorganic particles that make up inorganic fiber paper are nanoparticles with an average primary particle size of less than 1 μm. Nanoparticles have extremely low thermal conductivity and excellent thermal insulation properties.

[0182] For example, if oxide particles are used as nanoparticles, even if the internal density of the inorganic fiber paper increases due to the expansion caused by the thermal runaway of the battery cell, the electrostatic repulsion of the nanoparticles can easily form small gaps between the particles, which are filled in a buffering manner, thus suppressing the increase in conductive heat transfer.

[0183] Silica nanoparticles are preferred as nanoparticles. Silica nanoparticles have high thermal insulation properties and small contact points between particles, thus reducing heat transfer between particles. Therefore, using silica nanoparticles can further improve the thermal insulation of inorganic fiber paper. Wet-process silica, dry-process silica, and aerogels can be used as silica nanoparticles.

[0184] In addition, the average primary particle size of the nanoparticles is preferably 1 to 100 nm.

[0185] If the temperature falls within the aforementioned range, convective and conductive heat transfer in the inorganic fiber paper can be suppressed within the temperature range during thermal runaway of a single battery cell. Furthermore, even when compressive stress is applied to the inorganic fiber paper due to the expansion of the battery pack, the gaps between nanoparticles and the numerous contact points between particles can suppress heat transfer in the inorganic fiber paper, maintaining its thermal insulation properties.

[0186] Furthermore, the average primary particle size of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. On the other hand, the average primary particle size of the nanoparticles is preferably 50 nm or less, and even more preferably 10 nm or less.

[0187] Inorganic hydrate particles, which constitute inorganic particles contained in inorganic fiber paper, can be exemplified by particles such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, manganese hydroxide, zirconium hydroxide, and gallium hydroxide.

[0188] If the particles are inorganic hydrates, they will begin to decompose under the thermal runaway environment of the battery cell, releasing water of crystallization and thus releasing heat from the heat source, thereby suppressing the rapid temperature rise in the battery pack.

[0189] Examples of particles composed of thermally expandable inorganic materials that make up the inorganic particles contained in inorganic fiber paper include particles of vermiculite, bentonite, perlite, etc.

[0190] Examples of inorganic particles composed of hydrous porous bodies that constitute inorganic fiber paper include particles of zeolite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, vermiculite, etc.

[0191] If the inorganic fiber paper contains a resin binder, the mechanical strength of the inorganic fiber paper is improved. Therefore, even when the battery cell expands and is compressed during thermal runaway, the shape of the inorganic fiber paper can be maintained, thus suppressing the reduction of thermal insulation performance.

[0192] Examples of resin binders used in inorganic fiber paper include styrene-butadiene resin, acrylic resin, silicone-acrylic resin, and styrene resin.

[0193] Inorganic fiber cloth is a material made by weaving inorganic fibers into a cloth-like structure. Such inorganic fiber cloth has high strength and high heat resistance.

[0194] Inorganic fibers that make up inorganic fiber cloth can include silica fibers, alumina fibers, aluminosilicate fibers, zirconium oxide fibers and other ceramic fibers, glass fibers, basalt fibers, etc.

[0195] These inorganic fibers can be used alone or in combination of two or more.

[0196] For example, when making inorganic fiber cloth, the warp and weft yarns can be made of different kinds of inorganic fibers, and they can be woven into inorganic fiber cloth.

[0197] When the first heat insulation sheet 41 is a mica sheet or a heat-resistant resin sheet, the thickness of the first heat insulation sheet 41 is preferably 0.05 to 2.0 mm, more preferably 0.1 to 1.0 mm, and even more preferably 0.1 to 0.5 mm.

[0198] When the thickness of the first heat insulation sheet, which is composed of mica sheet and heat-resistant resin sheet, is less than 0.05 mm, the strength of the first heat insulation sheet decreases and it is easily damaged.

[0199] When the thickness of the first heat insulation sheet, which is composed of mica sheet and heat-resistant resin sheet, exceeds 2.0 mm, the first heat insulation sheet is too thick, making it difficult to miniaturize the battery pack as a whole.

[0200] In addition, when the first heat insulation sheet 41 is inorganic fiber paper, the thickness of the first heat insulation sheet 41 is preferably 0.5 to 5.0 mm, more preferably 0.8 mm to 3.0 mm.

[0201] In this case, the first heat insulation sheet 41, made of inorganic fiber paper, can obtain sufficient mechanical strength.

[0202] In addition, when the first heat insulation sheet 41 is an inorganic fiber cloth, the thickness of the first heat insulation sheet 41 is preferably 0.1 to 5.0 mm, more preferably 0.3 mm to 1.4 mm.

[0203] In this case, both the mechanical strength and flexibility of the first heat insulation sheet 41 made of inorganic fiber cloth can be taken into account. Therefore, the first heat insulation sheet 41 made of inorganic fiber cloth can be bent and used along a prescribed shape.

[0204] The area of ​​the top view of the covering part 41a is preferably 1.0 to 18 cm². 2 More preferably 3-12cm 2 .

[0205] If the area of ​​the top view of the covered part is less than 1.0 cm² 2 If so, the gas will have difficulty passing through the part with the covering part 41a.

[0206] If the top view area of ​​the covered part exceeds 18cm² 2 If the covered area is wider than the area reached by the gas, then the covered area is difficult to detach from the main body.

[0207] In the battery pack 10, when the first heat insulation sheet 41 is viewed from above, a cover 41a only needs to be located at a position that overlaps with at least a portion of a safety valve 22, preferably located at a position where a cover 41a is housed inside the outline of a safety valve 22.

[0208] When the cover 41a is in such a position, the gas released from the safety valve 22 can easily reach the cover 41a.

[0209] In the battery pack 10, it is preferable that the length of one connecting portion 41c is less than 50% of the total length of the outline C of the covering portion 41a, and the length of one connecting portion 41c is 1.0 mm or more.

[0210] Furthermore, the length of a connecting portion 41c is more preferably 40% or less of the total length of the outline C of the covering portion 41a, and even more preferably 30% or less.

[0211] Furthermore, the length of a connecting 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.

[0212] When the length of a connecting part exceeds 50% of the total length of the outline of the covering part, the connecting part is difficult to break and the covering part is difficult to detach from the main body.

[0213] When the length of a connecting part is less than 1.0 mm, the connecting part is too easy to break, and the cover part is too easy to detach from the main body.

[0214] In the battery pack 10, the first slit (51a, 51b) can be formed to penetrate the first heat insulation sheet 41 in the thickness direction, or it can be formed to the middle in the thickness direction.

[0215] In addition, the second slit (52a, 52b) can be formed to penetrate the first heat insulation sheet 41 in the thickness direction, or it can be formed to the middle in the thickness direction.

[0216] In the battery pack of the first embodiment of the present invention, as long as a first slit portion along the outline of the cover portion and a second slit portion at least partly located inside the outline of the cover portion are formed in the cover portion, and at least two connecting portions are formed on the outline of the cover portion without forming the first slit portion to connect the cover portion to the main body portion, the cover portion, connecting portions, first slit portion and second slit portion may also be other types.

[0217] For example, in the battery pack of the first embodiment of the present invention, the first slit portion and the second slit portion can also be separated.

[0218] When the first slit and the second slit separate, the portion between the first slit and the second slit becomes the supporting cover portion. Therefore, when gas pressure is applied to the cover portion, the pressure is also distributed in the portion between the first slit and the second slit, so the connection is less likely to break.

[0219] Therefore, even if the gas released from an abnormal battery cell causes a certain cover to break, and the gas is released between the heat insulation material and the shell and reaches other covers, the connection of the other covers is not easily broken due to the pressure of the gas, and the covers are not easily detached from the main body.

[0220] Furthermore, in the battery pack of the first embodiment of the present invention, when viewed from above, a plurality of second slits may be formed on intersecting straight lines.

[0221] Furthermore, the aforementioned second slit can be formed to intersect at the intersection of the aforementioned intersecting straight lines.

[0222] Furthermore, at the intersection of the aforementioned intersecting straight lines, the aforementioned second slit can be formed on a straight line.

[0223] Furthermore, at the intersection of the aforementioned intersecting straight lines, the aforementioned second slit may not be formed.

[0224] When the second slits intersect, the part that loses support at the intersection is prone to breakage, and the cover part is prone to detach from the main body.

[0225] Without intersecting the second slits, there is a supporting part at the intersection point, so the connection part is not easy to break and the cover part is not easy to detach from the main body.

[0226] In this way, the ease of breakage of the joint can be controlled by whether or not the second slit crosses.

[0227] Furthermore, in the battery pack of the first embodiment of the present invention, two or more connecting portions may be formed.

[0228] The following diagram illustrates this method.

[0229] Figures 4A to 4J This is a top view schematically showing another example near the cover portion of the first heat insulation sheet of the battery pack according to the first embodiment of the present invention.

[0230] exist Figures 4A to 4JIn the first heat insulation sheets 41A to 41J shown, the outline C of the covering portion 41a is a racetrack shape formed by two line segments (Ls1, Ls2) and two circular arcs (Cs1, Cs2). Furthermore, the covering portion 41a has a short axis Sa passing through its center of gravity and being the shortest part, and a long axis La passing through its center of gravity and being the longest part.

[0231] In the cover portion 41a, the short axis Sa intersects the long axis La at a right angle.

[0232] exist Figure 4A In the first heat insulation sheet 41A shown, in addition to the ends of the two line segments (Ls1, Ls2), four first slits (51a, 51b, 51c, 51d) are formed along the contour C of the covering portion 41a.

[0233] Four connecting parts (41c1, 41c2, 41c3, 41c4) are formed at each end of the two line segments (Ls1, Ls2).

[0234] exist Figure 4A In the first heat insulation sheet 41A shown, the two ends of the second slit portion 52a formed along the long axis La are in contact with the first slit portions (51a, 51b). In addition, the two ends of the second slit portion 52b formed along the short axis Sa are in contact with the first slit portions (51a, 51b).

[0235] That is, the inner side of the outline C of the covering part 41a is divided into four parts by the second slits (52a, 52b), and there is no part connecting the parts.

[0236] exist Figure 4B In the first heat insulation sheet 41B shown, two first slits (51a and 51b) are formed, which are formed along the contour C of the cover portion 41a in a manner that does not contact the intersection of the long axis La and the contour C of the cover portion 41a.

[0237] In addition, two second slits (52a and 52b) are formed along the long axis La and short axis Sa of the covering portion 41a.

[0238] The two ends of the second slit portion 52a formed along the long axis La do not contact the first slit portions (51a, 51b). In contrast, the two ends of the second slit portion 52b formed along the short axis Sa contact the first slit portions (51a, 51b).

[0239] In the outline C of the cover portion 41a, the portion near the intersection of the major axis La and the outline C of the cover portion 41a where the first slit portion (51a, 51b) is not formed is the two connecting portions (41c1, 41c2) connecting the cover portion 41a and the main body portion 41b.

[0240] In the outline C of the covering part 41a, there are no connecting parts on the two line segments (Ls1, Ls2), but there are two connecting parts (41c1, 41c2) on the two arcs (Cs1, Cs2).

[0241] Furthermore, the inner side of the outline C of the cover portion 41a is divided into four parts by the second slit portion (52a, 52b), and there is no part connecting the parts.

[0242] exist Figure 4C The first heat insulation sheet 41C shown has four first slits (51a, 51b, 51c and 51d) formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the long axis La and the contour C of the cover portion 41a and do not contact the intersection of the short axis Sa and the contour C of the cover portion 41a.

[0243] In addition, two second slits (52a and 52b) are formed along the long axis La and short axis Sa of the covering portion 41a.

[0244] The two ends of the second slit portion 52a formed along the long axis La do not contact the first slit portions (51a, 51b, 51c and 51d). In addition, the two ends of the second slit portion 52b formed along the short axis Sa do not contact the first slit portions (51a, 51b, 51c and 51d).

[0245] In the outline C of the cover portion 41a, the portion near the intersection of the major axis La and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is two connecting portions (41c1, 41c3) connecting the cover portion 41a and the main body portion 41b, and the portion near the intersection of the minor axis Sa and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is two connecting portions (41c2, 41c4) connecting the cover portion 41a and the main body portion 41b.

[0246] In the outline C of the covering part 41a, there are two connecting parts (41c2, 41c4) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c3) on two arcs (Cs1, Cs2).

[0247] Furthermore, the inner side of the outline C of the cover portion 41a is divided into four parts by the second slit portion (52a, 52b), and there is no part connecting the parts.

[0248] exist Figure 4DIn the first heat insulation sheet 41D shown, eight first slit portions (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h) are formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the major axis La and the contour C of the cover portion 41a, nor the intersection of the minor axis Sa and the contour C of the cover portion 41a.

[0249] In addition, two second slits (52a and 52b) are formed along the long axis La and short axis Sa of the covering portion 41a.

[0250] The two ends of the second slit portion 52a formed along the long axis La do not contact the first slit portion. Similarly, the two ends of the second slit portion 52b formed along the short axis Sa do not contact the first slit portion.

[0251] In the outline C of the cover portion 41a, the portion where the first slit portion (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h) is not formed is the eight connecting portions (41c1, 41c2, 41c3, 41c4, 41c5, 41c6, 41c7 and 41c8) connecting the cover portion 41a and the main body portion 41b.

[0252] In the outline C of the covering part 41a, there are six connecting parts (41c2, 41c3, 41c4, 41c6, 41c7, 41c8) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c5) on two arcs (Cs1, Cs2).

[0253] Furthermore, the inner side of the outline C of the cover portion 41a is divided into four parts by the second slit portion (52a, 52b), and there is no part connecting the parts.

[0254] exist Figure 4E The first heat insulation sheet 41E shown has four first slits (51a, 51b, 51c and 51d) formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the major axis La and the contour C of the cover portion 41a, nor do they contact the intersection of the minor axis Sa and the contour C of the cover portion 41a.

[0255] In addition, two second slits (52a1 and 52a2) are formed along the long axis La of the covering portion 41a, avoiding the intersection of the long axis La and the short axis Sa. Furthermore, two second slits (52b1 and 52b2) are formed along the short axis Sa, avoiding the intersection of the long axis La and the short axis Sa.

[0256] In addition, in the first heat insulation sheet 41E, the second slit portions (52a1, 52a2, 52b1 and 52b2) do not contact the first slit portions (51a, 51b, 51c and 51d).

[0257] In the outline C of the cover portion 41a, the portion near the intersection of the major axis La and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is the two connecting portions (41c1, 41c3) connecting the cover portion 41a and the main body portion 41b, and the portion near the intersection of the minor axis Sa and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is the two connecting portions (41c2, 41c4) connecting the cover portion 41a and the main body portion 41b.

[0258] In the outline C of the covering part 41a, there are two connecting parts (41c2, 41c4) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c3) on two arcs (Cs1, Cs2).

[0259] In addition, although the inner side of the outline C of the cover portion 41a is divided into four parts by the major axis La and the minor axis Sa, an internal connecting portion 44 is formed at the intersection of the major axis La and the minor axis Sa to connect the various parts.

[0260] exist Figure 4F The first heat insulation sheet 41F shown has four first slits (51a, 51b, 51c and 51d) formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the major axis La and the contour C of the cover portion 41a, nor do they contact the intersection of the minor axis Sa and the contour C of the cover portion 41a.

[0261] In addition, two second slits (52a1 and 52a2) are formed along the long axis La of the covering portion 41a, avoiding the intersection of the long axis La and the short axis Sa. Furthermore, a second slit 52b is formed along the short axis Sa.

[0262] In addition, in the first heat insulation sheet 41F, the second slit portion (52a1, 52a2, 52b) does not contact the first slit portion (51a, 51b, 51c and 51d).

[0263] In the outline C of the cover portion 41a, the portion near the intersection of the major axis La and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is the two connecting portions (41c1, 41c3) connecting the cover portion 41a and the main body portion 41b, and the portion near the intersection of the minor axis Sa and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is the two connecting portions (41c2, 41c4) connecting the cover portion 41a and the main body portion 41b.

[0264] In the outline C of the covering part 41a, there are two connecting parts (41c2, 41c4) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c3) on two arcs (Cs1, Cs2).

[0265] In addition, the inner side of the outline C of the cover portion 41a is divided into two parts by the second slit portion 52b, and each part is further divided into two parts by the second slit portions (52a1 and 52a2) (divided into a total of four parts).

[0266] In addition, Figure 4F In the middle, the two upper parts divided by the second slit 52a1 are connected by the internal connecting part 44a at the intersection of the major axis La and the minor axis Sa.

[0267] In addition, Figure 4F In the middle, the two lower parts divided by the second slit 52a2 are connected by the internal connecting part 44b at the intersection of the major axis La and the minor axis Sa.

[0268] exist Figure 4G The first heat insulation sheet 41G shown has four first slits (51a, 51b, 51c and 51d) formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the long axis La and the contour C of the cover portion 41a, nor do they contact the intersection of the short axis Sa and the contour C of the cover portion 41a.

[0269] Additionally, a second slit 52a is formed along the long axis La of the covering portion 41a. Furthermore, two second slits (52b1 and 52b2) are formed along the short axis Sa, avoiding the intersection of the long axis La and the short axis Sa.

[0270] In addition, in the first heat insulation sheet 41G, the second slit portions (52a, 52b1 and 52b2) do not contact the first slit portions (51a, 51b, 51c and 51d).

[0271] In the outline C of the cover portion 41a, the portion near the intersection of the major axis La and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is the two connecting portions (41c1, 41c3) connecting the cover portion 41a and the main body portion 41b, and the portion near the intersection of the minor axis Sa and the outline C of the cover portion 41a where the first slit portion (51a, 51b, 51c and 51d) is not formed is the two connecting portions (41c2, 41c4) connecting the cover portion 41a and the main body portion 41b.

[0272] In the outline C of the covering part 41a, there are two connecting parts (41c2, 41c4) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c3) on two arcs (Cs1, Cs2).

[0273] In addition, the inner side of the outline C of the cover portion 41a is divided into two parts by the second slit portion 52a, and each part is further divided into two parts by the second slit portions (52b1 and 52b2) (divided into a total of four parts).

[0274] In addition, Figure 4G In the middle, the two parts on the left side, which are divided by the second slit 52b1, are connected by the internal connecting part 44a at the intersection of the major axis La and the minor axis Sa.

[0275] In addition, Figure 4G In the middle, the two parts on the right side, which are divided by the second slit 52b2, are connected by the internal connecting part 44b at the intersection of the major axis La and the minor axis Sa.

[0276] exist Figure 4H The first heat insulation sheet 41H shown has eight first slits (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h) formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the major axis La and the contour C of the cover portion 41a, nor the intersection of the minor axis Sa and the contour C of the cover portion 41a.

[0277] Additionally, a second slit 52a is formed along the long axis La of the covering portion 41a. Furthermore, two second slits (52b1 and 52b2) are formed along the short axis Sa, avoiding the intersection of the long axis La and the short axis Sa.

[0278] In addition, in the first heat insulation sheet 41H, the second slit portions (52a, 52b1 and 52b2) do not contact the first slit portions (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h).

[0279] In the outline C of the cover portion 41a, the portion where the first slit portion (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h) is not formed is the eight connecting portions (41c1, 41c2, 41c3, 41c4, 41c5, 41c6, 41c7 and 41c8) connecting the cover portion 41a and the main body portion 41b.

[0280] In the outline C of the covering part 41a, there are six connecting parts (41c2, 41c3, 41c4, 41c6, 41c7, 41c8) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c5) on two arcs (Cs1, Cs2).

[0281] In addition, the inner side of the outline C of the cover portion 41a is divided into two parts by the second slit portion 52a, and each part is further divided into two parts by the second slit portions (52b1 and 52b2) (divided into a total of four parts).

[0282] In addition, Figure 4H In the middle, the two parts on the left side, which are divided by the second slit 52b1, are connected by the internal connecting part 44a at the intersection of the major axis La and the minor axis Sa.

[0283] In addition, Figure 4H In the middle, the two parts on the right side, which are divided by the second slit 52b2, are connected by the internal connecting part 44b at the intersection of the major axis La and the minor axis Sa.

[0284] exist Figure 4I The first heat insulation sheet 41I shown has eight first slits (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h) formed along the contour C of the cover portion 41a in a manner that does not contact the intersection of the major axis La and the contour C of the cover portion 41a, nor the intersection of the minor axis Sa and the contour C of the cover portion 41a.

[0285] In addition, two second slits (52a1 and 52a2) are formed along the long axis La of the covering portion 41a, avoiding the intersection of the long axis La and the short axis Sa. Furthermore, a second slit 52b is formed along the short axis Sa.

[0286] In addition, in the first heat insulation sheet 41I, the second slit portions (52a1, 52a2 and 52b) do not contact the first slit portions (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h).

[0287] In the outline C of the cover portion 41a, the portion where the first slit portion (51a, 51b, 51c, 51d, 51e, 51f, 51g and 51h) is not formed is the eight connecting portions (41c1, 41c2, 41c3, 41c4, 41c5, 41c6, 41c7 and 41c8) connecting the cover portion 41a and the main body portion 41b.

[0288] In the outline C of the covering part 41a, there are six connecting parts (41c2, 41c3, 41c4, 41c6, 41c7, 41c8) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c5) on two arcs (Cs1, Cs2).

[0289] In addition, the inner side of the outline C of the cover portion 41a is divided into two parts by the second slit portion 52b, and each part is further divided into two parts by the second slit portions (52a1 and 52a2) (divided into a total of four parts).

[0290] In addition, Figure 4I In the middle, the two upper parts divided by the second slit 52a1 are connected by the internal connecting part 44a at the intersection of the major axis La and the minor axis Sa.

[0291] In addition, Figure 4I In the middle, the two lower parts divided by the second slit 52a2 are connected by the internal connecting part 44b at the intersection of the major axis La and the minor axis Sa.

[0292] exist Figure 4J The first heat insulation sheet 41J shown has four first slits (51a, 51b, 51c and 51d) formed along the contour C of the cover portion 41a in such a way that they do not contact the intersection of the long axis La and the contour C of the cover portion 41a, nor do they contact the intersection of the short axis Sa and the contour C of the cover portion 41a.

[0293] exist Figure 4J In the first heat insulation sheet 41J shown, three second slits parallel to the short axis Sa are formed at the position that divides the long axis La into four equal parts (for convenience, they are referred to from top to bottom as the upper transverse second slit 52b1, the middle transverse second slit 52b2, and the lower transverse second slit 52b3).

[0294] The upper transverse second slit portion 52b1 contacts the first slit portions (51a and 51d).

[0295] The transverse second slit portion 52b2 in the middle does not contact the first slit portions (51a, 51b, 51c and 51d).

[0296] The lower transverse second slit portion 52b3 contacts the first slit portion (51b and 51c).

[0297] exist Figure 4J In the first heat insulation sheet 41J shown, three second slits are formed along the long axis La (for convenience, they are referred to from top to bottom as the upper longitudinal second slit 52a1, the middle longitudinal second slit 52a2, and the lower longitudinal second slit 52a3).

[0298] The upper longitudinal second slit portion 52a1 and the lower longitudinal second slit portion 52a3 are formed in a manner that does not contact the first slit portion or other second slit portions.

[0299] The longitudinal second slit portion 52a2 in the middle is formed in a manner that intersects with the transverse second slit portion 52b1 in the middle.

[0300] In the outline C of the covering part 41a, there are two connecting parts (41c2, 41c4) on two line segments (Ls1, Ls2) and two connecting parts (41c1, 41c3) on two arcs (Cs1, Cs2).

[0301] The covering portion is divided into eight parts from top to bottom by the upper transverse second slit portion 52b1, the middle transverse second slit portion 52b2, the lower transverse second slit portion 52b3, the upper longitudinal second slit portion 52a1, the middle longitudinal second slit portion 52a2, and the lower longitudinal second slit portion 52a3.

[0302] The upper transverse second slit portion 52b1 does not intersect with the upper longitudinal second slit portion 52a1.

[0303] The lower transverse second slit portion 52b3 does not intersect with the lower longitudinal second slit portion 52a3.

[0304] Therefore, at these intersections, the parts are connected by four internal connecting parts 44.

[0305] In the battery pack of the first embodiment of the present invention, when the cover portion is racetrack-shaped as described above, it is preferable to have one or more connecting portions on each of the two line segments (Ls1, Ls2) and one or more connecting portions on each of the two arcs (Cs1, Cs2).

[0306] Furthermore, in the battery pack of the first embodiment of the present invention, when the cover portion is divided by the second slit portion being formed on the short axis Sa and the long axis La, it is preferable that each part is connected by one or more internal connecting portions on the inner side of the outline of the cover portion.

[0307] In the battery pack of the first embodiment of the present invention, the second slit portion can be formed as a straight line or as a curve.

[0308] The preferred length of the second slit will be explained below, taking the first heat insulation sheet 41E as an example.

[0309] Figure 5 This is an explanatory diagram of the preferred length of the second slit portion according to the first embodiment of the present invention.

[0310] exist Figure 5 In the first heat insulation sheet 41E shown, two second slits (52a1 and 52a2) are formed along the long axis La of the covering portion 41a. In addition, two second slits (52b1 and 52b2) are formed along the short axis Sa.

[0311] In the first heat insulation sheet 41E, the two second slits (52a1 and 52a2) have the same length L. 52a In addition, the two second slits (52b1 and 52b2) have the same length L. 52b .

[0312] It should be noted that in the battery pack of the first embodiment of the present invention, when multiple second slits are formed in a straight line, the lengths of each second slit may be the same or different.

[0313] The length I of the internal connecting portion 44 between the second slit portions (52a1 and 52a2) 52a Preferably, the length L of the covering portion 41a on the long axis La is... 41a-1 Less than 50% and more than 1.0 mm.

[0314] In addition, the length I of the internal connecting part 44 52a More preferably, the length L of the covering portion 41a on the long axis La is... 41a-1 The percentage is less than 40%, and more preferably less than 30%.

[0315] In addition, the length I of the internal connecting part 44 52a More preferably, it is 3.0 mm or more; even more preferably, it is 5.0 mm or more; and still more preferably, it is 7.0 mm or more.

[0316] The length I of the internal connecting part 44 52a The length L of the cover portion 41a on the long axis La exceeds 41a-1 When the thickness reaches 50%, the connecting part is difficult to break, and the covering part is difficult to detach from the main body.

[0317] The length I of the internal connecting part 44 52a When the thickness is less than 1.0 mm, the connecting part is too easy to break, and the covering part is too easy to detach from the main body.

[0318] The length I of the internal connection portion 44 between the second slit portions (52b1 and 52b2) 52b Preferably, the length L of the covering portion 41a on the short axis Sa is... 41a-2 Less than 50% and more than 1.0 mm.

[0319] In addition, the length I of the internal connecting part 44 52b More preferably, the length L of the covering portion 41a on the short axis Sa is... 41a-2 The percentage is less than 40%, and more preferably less than 30%.

[0320] In addition, the length I of the internal connecting part 44 52b More preferably, it is 3.0 mm or more; even more preferably, it is 5.0 mm or more; and still more preferably, it is 7.0 mm or more.

[0321] The length I of the internal connecting part 44 52b The length L of the cover portion 41a on the short axis Sa exceeds 41a-2 When the thickness reaches 50%, the connecting part is difficult to break, and the covering part is difficult to detach from the main body.

[0322] The length I of the internal connecting part 44 52b When the thickness is less than 1.0 mm, the connecting part is too easy to break, and the covering part is too easy to detach from the main body.

[0323] When the length of the second slit is within the range described above, the cover is prone to split into multiple parts along the second slit.

[0324] In the description up to this point, the second slit portion is formed along the short axis Sa and the long axis La, respectively. However, in the battery pack of the first embodiment of the present invention, the second slit portion may also be formed on a straight line intersecting other than the short axis Sa and the long axis La.

[0325] Alternatively, in the battery pack of the first embodiment of the present invention, only one second slit may be formed.

[0326] Furthermore, in the description up to this point, the second slit portion is only formed inside the outline of the cover portion. However, in the battery pack of the first embodiment of the present invention, it is sufficient as long as at least a portion of the second slit portion is located inside the outline of the cover portion. For example, the second slit portion may also be formed to intersect with the outline of the cover portion.

[0327] The first and second slits can be formed by punching using a Thomson cutter or similar tool with a specified structure, or by machining with a cutting tool or by laser processing.

[0328] In the battery pack of the first embodiment of the present invention, the top view shape of the cover is not limited to a racetrack shape, but can also be a polygon such as a triangle, quadrilateral, or hexagon, a circle, or an ellipse.

[0329] Next, the use and configuration method of the battery pack according to the first embodiment of the present invention will be described.

[0330] The application of the battery pack in the first embodiment of the present invention is not particularly limited; for example, it can be used as a power source for electric vehicles.

[0331] Furthermore, the battery pack of the first embodiment of the present invention is preferably configured such that the safety valve of the individual battery cell is located on the upper or lower side in the vertical direction.

[0332] When the battery pack is configured with the safety valve in this position, the high-temperature gas from the abnormal battery cell disperses naturally and rapidly, making it less likely to cause a thermal runaway chain reaction. In other words, from a fail-safe point of view, this can be considered the preferred configuration for the battery pack.

[0333] In the battery pack of the first embodiment of the present invention, the safety valve may be configured either on the bottom side or on the cover side.

[0334] As described above, when configuring the battery pack of the first embodiment of the present invention, from the viewpoint of fail-safety, the battery pack is sometimes configured such that the safety valve is located on the upper or lower side of the vertical direction.

[0335] Since battery packs are mostly configured with the bottom of the casing or the cover on the lower side, if the safety valve is configured to be located on the bottom side of the casing or the cover side, it is easy for the safety valve to be located on the upper or lower side in the vertical direction.

[0336] (Second Implementation)

[0337] The battery pack of the second embodiment of the present invention differs from the battery pack of the first embodiment of the present invention in that the heat insulation material further includes a second heat insulation sheet and an adhesive layer for bonding the second heat insulation sheet and the first heat insulation sheet, and the heat insulation material is arranged such that the second heat insulation sheet is located on the module side and the first heat insulation sheet is located on the housing side.

[0338] The battery pack of such a second embodiment of the present invention will be described using the accompanying drawings.

[0339] Figure 6 This is a cross-sectional view schematically illustrating an example of a battery pack according to a second embodiment of the present invention.

[0340] Figure 6The battery pack 110 shown differs from the battery pack 10 described above in that the heat insulation material 140 is composed of a first heat insulation sheet 141, a second heat insulation sheet 142, and an adhesive layer (not shown) that bonds the first heat insulation sheet 141 and the second heat insulation sheet 142.

[0341] In addition, the heat insulation material 140 is configured such that the second heat insulation sheet 142 is located on the module 20 side and the first heat insulation sheet 141 is located on the housing 30 side.

[0342] When such a second heat insulation sheet 142 is configured, the gas G released from the abnormal battery cell 21 reaches the first heat insulation sheet 141 after passing through the second heat insulation sheet 142.

[0343] Then, the gas G causes the adhesive layer to thermally decompose, the cover 141a peels off from the second heat insulation sheet, and the cover 141a detaches from the main body 141b due to the gas pressure.

[0344] Furthermore, the gas G decreases in temperature and pressure as it passes through the second heat insulation sheet 142. Therefore, even if the gas G passes through the portion of the first heat insulation sheet 141 with the covering portion 141a and comes into contact with the housing 30, the housing 30 is not easily heated by the gas G and is not easily damaged.

[0345] In the battery pack 110, the adhesive layer preferably comprises an organic adhesive layer.

[0346] When the adhesive layer contains an organic adhesive layer, the high-temperature gas G from the abnormal battery cell is prone to thermal decomposition when it reaches the adhesive layer.

[0347] Organic adhesives are preferably thermally decomposed at temperatures above 80°C; for example, adhesives containing polyamide-based organic materials can be cited.

[0348] In the battery pack 110, preferably, a third slit is formed in the second heat insulation sheet 142, which extends from the main surface to which the first heat insulation sheet 141 is bonded to to another main surface, and at least a portion of the third slit is located inside the cover portion 141a when the heat insulation material 140 is viewed from the side of the first heat insulation sheet 141.

[0349] When a third slit is formed in the second heat insulation sheet 142, the high-temperature gas G from the module 20 side can easily reach the cover 141a through the third slit.

[0350] It should be noted that when the insulation material 140 is viewed from the side of the first insulation sheet 141, the third cut may be located only inside the cover portion 141a, or it may be located at a position that intersects with the outline of the cover portion 141a.

[0351] In the battery pack 110, when the heat insulation material 140 is viewed from the side of the first heat insulation sheet 141, the third slit can be formed as a line or a curve, and preferably as a straight line.

[0352] The linear third slit can be easily formed using a tool or similar device.

[0353] In the battery pack 110, multiple third slits may also be formed in the second heat insulation sheet 142.

[0354] In addition, in the battery pack 110, when the heat insulation material 140 is viewed from the side of the first heat insulation sheet 141, the multiple third slits can be separated from each other or intersected with each other.

[0355] Regardless of the method, the gas G generated from the abnormal battery cell 21a can easily and quickly reach the first heat insulation sheet 141 through the third slit.

[0356] In the battery pack 110, when the heat insulation material 140 is viewed from the side of the first heat insulation sheet 141, the second cut portion and the third cut portion can overlap in the same shape.

[0357] Such a second and third slit can be formed simultaneously by punching while the first heat insulation sheet 141 and the second heat insulation sheet 142 are overlapped.

[0358] In addition, the second and third slits may not overlap, or they may be different shapes.

[0359] In the battery pack 110, the second heat insulation sheet 142 is preferably at least one selected from the group consisting of inorganic fiber pad, inorganic fiber paper and inorganic fiber cloth.

[0360] Inorganic fiber pads, inorganic fiber paper, and inorganic fiber cloth can be easily molded and exhibit excellent performance as a second heat insulation sheet.

[0361] The thickness of the inorganic fiber pad is preferably 0.5 to 10 mm, and more preferably 1 to 4 mm.

[0362] If the thickness of the inorganic fiber pad is less than 0.5 mm, it is too thin, making it difficult to reduce the gas temperature and pressure when the gas passes through it. As a result, the gas violently reaches the shell at a high temperature, easily causing shell deterioration.

[0363] When the thickness of the inorganic fiber pad exceeds 10mm, the inorganic fiber pad becomes too thick, making it difficult to miniaturize the battery pack as a whole.

[0364] The bulk density of the inorganic fiber mat is preferably 0.1–1.0 g / cm³. 3More preferably, it is 0.2–0.7 g / cm³. 3 .

[0365] The bulk density of the inorganic fiber mat is less than 0.1 g / cm³. 3 In this condition, the gaps between the inorganic fibers increase, making it difficult to reduce the gas temperature and pressure when the gas passes through the inorganic fiber pad. As a result, the gas violently reaches the shell at a high temperature, easily causing shell deterioration.

[0366] The bulk density of the inorganic fiber mat exceeds 1.0 g / cm³. 3 At this time, the gas has difficulty passing through the inorganic fiber pad, and the high-temperature gas remains inside the battery cell, making it difficult to reduce the temperature inside the battery cell. Therefore, a thermal runaway chain reaction can easily occur.

[0367] The inorganic fiber mat is preferably a material obtained by processing inorganic fibers, which include at least one fiber selected from the group consisting of silica fiber, glass fiber, alumina fiber, aluminosilicate fiber, basalt fiber, rock wool and biosoluble fiber, into a mat shape.

[0368] Inorganic fiber mats made of such materials can be easily processed.

[0369] Inorganic fiber mats can be materials obtained by processing inorganic fibers containing fibers with a melting point of over 1000°C into a mat shape.

[0370] When inorganic fiber pads contain fibers with a melting point above 1000℃, the inorganic fibers have high heat resistance, so even if high-temperature gases from abnormal battery cells reach the inorganic fiber pads, the inorganic fiber pads are not easily degraded.

[0371] Inorganic fiber mats can also be materials obtained by processing inorganic fibers containing fibers with melting points below 1000°C into a mat shape.

[0372] When an inorganic fiber pad contains fibers with a melting point below 1000°C, the inorganic fiber pad melts when high-temperature gas from an abnormal battery cell reaches it, easily forming a gas flow path.

[0373] The preferred method for the inorganic fiber paper and inorganic fiber cloth constituting the second heat insulation sheet is the same as the preferred method for the inorganic fiber paper and inorganic fiber cloth constituting the first heat insulation sheet.

[0374] The following invention is described in this specification.

[0375] The present invention (1) is a battery pack comprising: a module having a plurality of battery cells each having a safety valve; a housing for housing the module; and a heat insulation material disposed between the module and the housing. The battery pack is characterized in that the heat insulation material includes a first heat insulation sheet, which, when viewed from above, is composed of a plurality of covering portions covering the plurality of safety valves and a main body portion other than the covering portions. One of the covering portions is located at a position overlapping at least a portion of one of the safety valves. A first slit portion along the outline of the covering portion and a second slit portion at least a portion located inside the outline of the covering portion are formed on the covering portion. At least two connecting portions are provided on the outline of the covering portion without the first slit portion, connecting the covering portion to the main body portion.

[0376] The present invention (2) is the battery pack described in the present invention (1), wherein the first slit portion is separated from the second slit portion.

[0377] The present invention (3) is the battery pack described in the present invention (1) or (2), wherein, when viewed from above, the first heat insulation sheet has a plurality of the second cut portions formed on intersecting straight lines.

[0378] The present invention (4) is the battery pack described in the present invention (3), wherein the second slit is formed to intersect at the intersection of the intersecting straight lines.

[0379] The present invention (5) is the battery pack described in the present invention (3), wherein the second slit portion is formed on a straight line at the intersection of the above-mentioned intersecting straight lines.

[0380] The present invention (6) is the battery pack described in the present invention (3), wherein the second slit is not formed at the intersection of the above-mentioned intersecting straight lines.

[0381] The present invention (7) is a battery pack according to any one of the present invention (3) to (6), wherein, when viewed from above, the covering portion has a shape that includes a short axis passing through the center of gravity of the covering portion and becoming the shortest portion and a long axis passing through the center of gravity of the covering portion and becoming the longest portion, and one of the intersecting straight lines is the short axis and the other is the long axis.

[0382] The present invention (8) is the battery pack of any one of the present invention (1) to (7), wherein the thickness of the first heat insulation sheet is 0.05 to 2.0 mm.

[0383] The present invention (9) is a battery pack according to any one of the present inventions (1) to (8), wherein the length of one of the above-mentioned connecting portions is less than 50% of the total length of the outline of the above-mentioned covering portion, and the length of one of the above-mentioned connecting portions is 1.0 mm or more.

[0384] The present invention (10) is a battery pack according to any one of the present invention (3) to (7), wherein the inner side of the outline of the cover portion is divided into multiple portions by the second slit portion, and at the intersection of the intersecting straight lines, at least one internal connecting portion is provided at the intersection of the intersecting straight lines without forming the second slit portion, the length of one of the internal connecting portions is less than 50% of the length of the cover portion on the intersecting straight lines where the internal connecting portion is located, and the length of one of the internal connecting portions is 1.0 mm or more.

[0385] The present invention (11) is a battery pack according to any one of the present inventions (1) to (10), wherein the top view shape of the covered part is selected from at least one of the group consisting of polygon, circle, ellipse and racetrack shape.

[0386] The present invention (12) is a battery pack according to any one of the present invention (1) to (11), wherein the first heat insulation sheet is selected from at least one of the group consisting of mica sheet, heat-resistant resin sheet, inorganic fiber paper and inorganic fiber cloth.

[0387] The present invention (13) is a battery pack according to any one of the present invention (1) to (12), wherein the heat insulation material further includes a second heat insulation sheet and an adhesive layer for bonding the second heat insulation sheet to the first heat insulation sheet, and the heat insulation material is configured such that the second heat insulation sheet is located on the module side and the first heat insulation sheet is located on the housing side.

[0388] The present invention (14) is the battery pack described in the present invention (13), wherein a third slit portion is formed in the second heat insulation sheet, which extends from the main surface to the other main surface where the first heat insulation sheet is bonded, and when the heat insulation material is viewed from the side of the first heat insulation sheet, at least a portion of the third slit portion is located inside the cover portion.

[0389] The present invention (15) is the battery pack described in the present invention (14), wherein, when the heat insulation material is viewed from the first heat insulation sheet side, the third slit portion is formed in a linear shape.

[0390] The present invention (16) is the battery pack described in the present invention (14) or (15), wherein, when the heat insulation material is viewed from the first heat insulation sheet side, the second cut portion and the third cut portion overlap in the same shape.

[0391] The present invention (17) is the battery pack of any one of the present inventions (13) to (16), wherein the second heat insulation sheet is selected from at least one of the group consisting of inorganic fiber pad, inorganic fiber paper and inorganic fiber cloth.

[0392] The present invention (18) is a heat insulation material, which is a sheet-like heat insulation material composed of a main body and a cover formed on the inner side of the main body. It is characterized in that a first slit portion is formed along the outline of the cover portion and a second slit portion at least partly located on the inner side of the outline of the cover portion, and at least two connecting portions are provided on the outline of the cover portion to connect the cover portion and the main body without the first slit portion being formed.

[0393] Example

[0394] (Example 1)

[0395] Figure 7 This is a schematic top view showing the area near the cover of the mica sheet in Embodiment 1.

[0396] First, prepare a mica sheet with a thickness of 0.1mm.

[0397] Next, as Figure 7 As shown, a first slit 51 is formed along the outline C of a rectangle with a length × width = 70mm × 20mm.

[0398] At this time, the first slit portion 51 is formed in such a way that a connecting portion 41c is 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 the short side of the rectangular outline C meet.

[0399] In addition, in the thermal runaway test described later, two first slits 51 (not shown) are further formed at other locations on the mica sheet in such a way that the safety valve of the battery cell is covered by the cover portion 41a.

[0400] Next, prepare a 4.0 mm thick silicon dioxide sheet made of silicon dioxide fibers.

[0401] Then, the mica sheet and the silica sheet are laminated by placing an adhesive between them, and then hot-pressed at 100 kPa, 180°C and 20 seconds.

[0402] Next, as Figure 7 As shown, a second slit 52 is formed on the mica sheet. At this time, a slit is also formed on the silicon dioxide sheet.

[0403] The second slit 52 is formed along the line connecting the midpoints of the short sides of the rectangular outline C to each other, and the line connecting the midpoints of the long sides of the rectangular outline C to each other (excluding the vicinity of the line connecting the midpoints of the short sides of the rectangular outline C to each other).

[0404] Thus, a covering part 41a, a main body part 41b, a connecting part 41c, and an internal connecting part 44 are formed.

[0405] Through the above processes, the heat insulation material of Example 1, which is composed of mica sheet (first heat insulation sheet) and silicon dioxide sheet (second heat insulation sheet) stacked together, is produced.

[0406] (Example 2)

[0407] Figure 8 This is a schematic top view showing the area near the cover of the mica sheet in Embodiment 2.

[0408] In addition to Figure 8 Except for the first slit portion 51 and the second slit portion 52 formed at the positions shown, the heat insulation material of Example 2 is made in the same manner as in Example 1.

[0409] That is, such as Figure 8 As shown, a first slit 51 is formed along the outline C of the rectangle.

[0410] At this time, the first slit portion 51 is formed in such a way that a connecting portion 41c is 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 the short side of the rectangular outline C meet.

[0411] In addition, such as Figure 8 As shown, a second slit 52 is formed along the lines connecting the midpoints of the short sides of the rectangle's outline C to each other and the lines connecting the midpoints of the long sides of the rectangle's outline C to each other.

[0412] (Example 3)

[0413] Except for using mica sheets with a thickness of 0.3 mm, the heat insulation material of Example 3 was made in the same manner as in Example 1.

[0414] (Thermal runaway test)

[0415] Perform a thermal runaway test by following these steps.

[0416] Figure 9 This is a schematic diagram illustrating the overview of a thermal runaway test.

[0417] (Experimental Example 1)

[0418] First, such as Figure 9 As shown, a thermal insulation material 240, a heater 270, a thermal runaway battery cell 221a, a first adjacent battery cell 221b, and a second adjacent battery cell 221c are arranged in a test apparatus 260 having a wall portion 261, a bottom portion 262, and a cover portion 263.

[0419] In the test apparatus 260, the heat insulation material 240 is arranged such that the mica sheet 241 is located on the side of the bottom 262 of the silicon dioxide sheet 242.

[0420] Additionally, on top of the thermal insulation material 240, from left to right, are arranged a heater 270, a thermal runaway battery cell 221a, a first adjacent battery cell 221b, and a second adjacent battery cell 221c. The thermal runaway battery cell 221a, the first adjacent battery cell 221b, and the second adjacent battery cell 221c are connected in series.

[0421] In addition, each battery cell is configured with a safety valve 222 located on the bottom side 262.

[0422] In addition, the heat insulation material of Example 1 is used as the heat insulation material 240.

[0423] Next, current is allowed to flow through the thermal runaway battery cell 221a, the first adjacent battery cell 221b, and the second adjacent battery cell 221c. Then, the thermal runaway battery cell 221a is heated by the heater 270, causing the thermal runaway battery cell 221a to thermally run away, and high-temperature gas is ejected from the safety valve of the thermal runaway battery cell 221a.

[0424] Then, measurements were taken at P1 directly below the safety valve of thermal runaway battery cell 221a, P2 directly below the safety valve of the first adjacent battery cell 221b, and P3 directly below the safety valve of the second adjacent battery cell 221c.

[0425] The highest temperatures at points P1 to P3 are shown in Table 1 and Figure 10 .

[0426] Figure 10 This is a graph showing the results of a thermal runaway test.

[0427] [Table 1]

[0428] (Experimental Example 2) and (Experimental Example 3)

[0429] As the insulation material 240 used, the insulation material of Example 2 and the insulation material of Example 3 were used. Otherwise, Example 2 and Example 3 were performed in the same manner as Example 1.

[0430] The results are shown in Table 1 and Figure 10 .

[0431] (Comparative Test Example 1)

[0432] Except that no thermal insulation material was used, the test was compared to Test Example 1 in the same way.

[0433] The results are shown in Table 1 and Figure 10 .

[0434] The results of the thermal runaway test showed that, compared with Test Examples 1 to 3 which were equipped with thermal insulation materials, the highest temperature at P1 in Comparative Test Example 1, which was not equipped with thermal insulation materials, was lower.

[0435] This is believed to be because, in Test Examples 1 to 3, the mica sheet covering the insulation material required a short time before breaking, during which time high-temperature gas accumulated and P1 was heated.

[0436] In addition, in Comparative Test Example 1, the highest temperature at P2 exceeded 700°C, indicating that the high-temperature gas flowed back from the safety valve 222 of the first adjacent battery cell 221b, and the first adjacent battery cell 221b was prone to thermal runaway.

[0437] On the other hand, in Test Examples 1 to 3, the highest temperatures at P2 and P3 were below 700°C, indicating that the first adjacent battery cell 221b and the second adjacent battery cell 221c are not prone to thermal runaway.

[0438] In particular, in Test Example 1, the highest temperature at P2 and P3 was below 200°C, indicating that the first adjacent cell 221b and the second adjacent cell 221c are less prone to thermal runaway.

[0439] Explanation of reference numerals in the attached figures

[0440] 10 and 110 battery packs

[0441] 20 modules

[0442] 20a Connection module component

[0443] 20b bus

[0444] 21 battery cells

[0445] 21a Abnormal battery cell

[0446] Safety valves 22 and 22a

[0447] 23 terminals

[0448] 30. Housing

[0449] 31 Storage Department

[0450] 31b Bottom

[0451] 31s sidewall

[0452] 32 cover

[0453] 40, 240 thermal insulation materials

[0454] 41, 41A, 41B, 41C, 41D, 41E, 41F, 41G, 41H, 141 First heat insulation sheet

[0455] 41a, 141a Cover Section

[0456] 41b, 141b Main body

[0457] Connecting parts of 41c, 41c1, 41c2, 41c3, 41c4, 41c5, 41c6, 41c7 and 41c8

[0458] 44, 44a, 44b Internal connecting parts

[0459] 51, 51a, 51b, 51c, 51d, 51e, 51f, 51g, 51h First seam section

[0460] 52, 52a, 52a1, 52a2, 52a3, 52b, 52b1, 52b2, 52b3 Second slit section

[0461] 221a Thermal runaway battery cell

[0462] 221b First adjacent cell

[0463] 221c Second Adjacent Cell

[0464] 222 Safety Valve

[0465] 241 Mica Sheets

[0466] 242 silicon dioxide wafer

[0467] 260 Test Apparatus

[0468] 261 Wall section

[0469] 262 Bottom

[0470] 263 cover

[0471] 270 Heater.

Claims

1. A battery pack comprising: a module having a plurality of battery cells each having a safety valve; a housing for receiving the module; and a thermal insulating material disposed between the module and the housing, characterized in that... The heat insulation material includes a first heat insulation sheet. When viewed from above, the first heat insulation sheet consists of multiple covering portions that respectively cover the multiple safety valves and a main body portion other than the covering portions. One of the covers is located at a position that overlaps with at least a portion of one of the safety valves. The covering portion has a first slit along the outline of the covering portion and a second slit at least a portion located inside the outline of the covering portion. The cover portion has at least two connecting portions on its outline that connect the cover portion to the main body portion without forming the first slit portion.

2. The battery pack according to claim 1, wherein, The first cut portion is separated from the second cut portion.

3. The battery pack according to claim 1 or 2, wherein, When viewed from above, the first heat insulation sheet has multiple second slits formed on intersecting straight lines.

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

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

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

7. The battery pack according to any one of claims 3 to 6, wherein, When viewed from above, the covering portion has a shape that includes a short axis passing through the center of gravity of the covering portion and becoming the shortest part, and a long axis passing through the center of gravity of the covering portion and becoming the longest part. One of the intersecting straight lines is the minor axis, and the other is the major axis.

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

9. The battery pack according to any one of claims 1 to 8, wherein, The length of one of the connecting portions is less than 50% of the total length of the outline of the covering portion. The length of one of the connecting parts is 1.0 mm or more.

10. The battery pack according to any one of claims 3 to 7, wherein, The inner side of the outline of the cover is divided into multiple parts by the second slit portion. On the intersecting straight lines, at the intersection of the intersecting straight lines, there is at least one internal connecting portion that connects the plurality of parts without forming the second slit portion. The length of one of the internal connecting portions is less than 50% of the length of the covering portion on the intersecting straight line where the internal connecting portion is located. The length of one of the internal connecting parts is 1.0 mm or more.

11. The battery pack according to any one of claims 1 to 10, wherein, The top view shape of the cover is selected from at least one of the group consisting of polygons, circles, ellipses and racetrack shapes.

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

13. The battery pack according to any one of claims 1 to 12, wherein, The thermal insulation material further includes a second thermal insulation sheet and an adhesive layer for bonding the second thermal insulation sheet to the first thermal insulation sheet, wherein the thermal insulation material is configured such that the second thermal insulation sheet is located on the module side and the first thermal insulation sheet is located on the housing side.

14. The battery pack according to claim 13, wherein, A third slit is formed in the second heat insulation sheet, extending from the main surface to which the first heat insulation sheet is bonded to to another main surface. When viewed from the side of the first heat insulation sheet, at least a portion of the third slit is located inside the cover portion.

15. The battery pack according to claim 14, wherein, When viewed from above the first heat insulation sheet side, the third slit is formed as a line.

16. The battery pack according to claim 14 or 15, wherein, When viewed from the side of the first heat insulation sheet, the second cut portion overlaps the third cut portion in the same shape.

17. The battery pack according to any one of claims 13 to 16, wherein, The second heat insulation sheet is selected from at least one of the group consisting of inorganic fiber pad, inorganic fiber paper and inorganic fiber cloth.

18. A heat-insulating material, which is a sheet-like heat-insulating material composed of a main body and a covering portion formed on the inner side of said main body, characterized in that, A first slit portion is formed along the contour of the covering portion, and a second slit portion is at least partially located inside the contour of the covering portion. The cover portion has at least two connecting portions on its outline that connect the cover portion to the main body portion without forming the first slit portion.

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