Battery module

Abstract

To provide a battery module which exhibits a function of a pad provided between battery cells even when the battery module is overheated.SOLUTION: The battery pack includes a plurality of battery cells 100, and a pad 200 sandwiched between the battery cells 100 adjacent to each other, whose expansion rate increases when a temperature reaches a predetermined temperature or higher, and which is compressible in a state of the predetermined temperature or lower, wherein when a temperature of a first battery cell 101 reaches the predetermined temperature or higher, a first pad 201 located adjacent to the first battery cell 101 expands, A second battery cell (102) located adjacent to the first battery cell (101) is moved or bent in a stacking direction (X direction) of the plurality of battery cells (100), and a second pad (202) located between the second battery cell (102) and a third battery cell (103) located adjacent to the second battery cell (102) is compressed in the stacking direction (X direction).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a battery module. [Background technology]

[0002] In recent years, various battery modules have been developed that include multiple battery cells and a cover that houses the multiple battery cells. Each battery cell may experience thermal runaway due to various factors, such as an internal short circuit or overcharging, and it is therefore necessary to suppress the heat transfer from a battery cell that has experienced thermal runaway to other battery cells.

[0003] One such technique is to provide heat insulating members (also called pads or compression pads) between battery cells (see, for example, Patent Document 1). Patent Document 1 proposes a structure in which a pad complex with swelling absorption and heat insulation functions is placed between the cells. This structure sandwiches a heat insulation pad with thermal expansion properties between a pair of swelling absorption pads. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2022-506014 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 has the problem of a complex structure, which leads to problems such as high costs and difficulty in miniaturizing the battery module.

[0006] An example of an object of the present invention is to provide a technique that can ensure a heat insulating structure between battery cells with a simple structure even in the event of thermal runaway. [Means for solving the problem]

[0007] The present invention provides the following techniques. 1. A plurality of cells; a heat insulating member sandwiched between the adjacent cells, the heat insulating member having an expansion rate that increases when the temperature reaches a predetermined temperature or higher and being compressible when the temperature is below the predetermined temperature; Equipped with When the temperature of the first cell reaches or exceeds the predetermined temperature, a first insulating member located adjacent to the first cell expands; A second cell located adjacent to the first cell moves or bends in the stacking direction of the plurality of cells, A battery module, wherein a second insulating material located between the second cell and a third cell located adjacent to the second cell is compressed in the stacking direction. 2. The battery module according to 1., wherein the predetermined temperature is 120°C or higher and 180°C or lower. 3. The battery module according to 1. or 2., wherein the heat insulating member contains an elastic material, pores, and an expanding agent that generates gas at or above the predetermined temperature. 4. A battery module described in 1. or 2., wherein the thermal insulating member has an expansion coefficient in the stacking direction of 200% or more and 9000% or less when heated from 25°C to 150°C when not sandwiched between adjacent cells and not compressed. 5. A battery module described in 1. or 2., wherein the thermal insulating member has an expansion coefficient of 100% or more and 500% or less in the stacking direction when heated from 25°C to 150°C while sandwiched between adjacent cells at a pressure of 20 kPa or more and 1 MPa or less. 6. A battery module described in 1. or 2., wherein the heat insulating member, when not sandwiched between adjacent cells and not compressed, has a compression rate of 20% or more and 95% or less when a final pressure of 1 MPa is applied at 25°C. 7. A battery module described in 1. or 2., wherein the heat insulating member has a compression rate of 15% or more and 90% or less when sandwiched between adjacent cells at a pressure of 20 kPa or more and 1 MPa or less at 25°C and when a final pressure of 1 MPa is applied. 8. The battery module described in 1. or 2., wherein the plurality of cells are fixed to the inner surface of the housing using a fixing layer so as to be movable in the stacking direction. [Effects of the Invention]

[0008] According to the present invention, a heat insulating structure between battery cells can be ensured with a simple structure even in the event of thermal runaway. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an exploded perspective view of the battery module according to the embodiment. [Figure 2] FIG. 2 is a top view of the battery module with the top cover removed. [Figure 3] 2 is a cross-sectional view along AA' in FIG. [Figure 4] FIG. 4 is an enlarged view of region Z in FIG. 3. [Figure 5] FIG. 4 is an enlarged view of region Z in FIG. 3, illustrating the internal structure when an abnormality occurs. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments and modifications of the present invention will be described with reference to the drawings. In all the drawings, like components are denoted by like reference numerals, and descriptions thereof will be omitted where appropriate.

[0011] In this specification, ordinal numbers such as "first," "second," and "third" are used merely to distinguish between similarly named configurations, unless otherwise specified, and do not imply any particular characteristics (e.g., order or importance) of the configurations.

[0012] <Battery module overview> FIG. 1 is an exploded perspective view of a battery module 10 according to an embodiment. FIG. 2 is a top view of the battery module 10 with the top cover 312 and the structure glue 220 removed. FIG. 3 is a cross-sectional view taken along the line AA' in FIG. 1. FIG. 4 is an enlarged view of area Z in FIG. 3. FIG. 5 is an enlarged view of area Z in FIG. 3, illustrating the internal structure in an abnormal state. In the following description, "normal state (or normal condition)" refers to a state in which the battery cells 100 are not exposed to high-temperature gases or the like and are within the recommended operating temperature range (for example, -30°C to 90°C), and "abnormal state (or abnormal condition)" refers to a state in which the battery cells 100 or pads 200 are at or above a predetermined temperature. The "predetermined temperature" will be described later.

[0013] 1 to 5, an arrow indicating the X, Y, or Z direction indicates that the direction from the base end of the arrow to the tip is the positive direction of the arrow, and that the direction from the tip of the arrow to the base end is the negative direction of the arrow. Furthermore, a white circle with a black dot indicating the X, Y, or Z direction indicates that the direction from the back of the paper to the front is the positive direction of the arrow, and that the direction from the front of the paper to the back is the negative direction of the arrow. Furthermore, a white circle with an X indicating the X, Y, or Z direction indicates that the direction from the front of the paper to the back is the positive direction of the arrow, and that the direction from the back of the paper to the front is the negative direction of the arrow.

[0014] 1 to 5, the X direction is a direction parallel to the horizontal direction perpendicular to the vertical direction, and is also referred to as the stacking direction of the battery cells 100. The positive X direction is the direction from the rear to the front of the battery module 10. The negative X direction is the direction from the front to the rear of the battery module 10. The Y direction is a direction parallel to the horizontal direction and perpendicular to the X direction. The positive Y direction is the direction from left to right when viewed from the front of the battery module 10. The negative Y direction is the direction from right to left when viewed from the front of the battery module 10. The Z direction is a direction parallel to the vertical direction. The positive Z direction is the direction from bottom to top. The negative Z direction is the direction from top to bottom. Note that the relationship between the vertical or horizontal direction and the X, Y, or Z direction of the battery module 10 is not limited to the example described above. The relationship between the vertical or horizontal direction and the X, Y, or Z direction of the battery module 10 may differ from the example described above depending on the arrangement of the battery module 10. For example, the X direction may be parallel to the vertical direction, and the Y and Z directions may be parallel to the horizontal direction.

[0015] The battery module 10 includes a laminate 190, a fixing layer 210, and a housing 300 (also referred to as a "casing").

[0016] The multiple battery cells 100 are stacked in the X direction to form a stack 190 with pads 200 interposed between each battery cell 100. The stack 190 is fixed to the inner surface of the housing 300 using a fixing layer 210 (structural glue 220, thermal glue 230). At this time, each battery cell 100 is movable to a certain extent in the stacking direction. The movement of the battery cells 100 will be described later.

[0017] Each battery cell 100 has a thickness in the X direction, a longitudinal direction in the Y direction, and a lateral direction in the Z direction. The multiple battery cells 100 are lined up in the X direction (that is, the stacking direction).

[0018] A first lead 110 is provided at the end of each battery cell 100 on the positive side in the Y direction. A second lead 120 is provided at the end of each battery cell 100 on the negative side in the Y direction. The polarity of the first lead 110 is positive or negative. The polarity of the second lead 120 is different from the polarity of the first lead 110. Note that both the first lead 110 and the second lead 120 may be located on the positive side in the Y direction or the negative side in the Y direction of the battery cell 100.

[0019] The storage section 300 has a top cover 312, a bottom cover 314, a first end cover 322, a second end cover 324, a first side cover 332, and a second side cover 334. The top cover 312, the bottom cover 314, the first end cover 322, the second end cover 324, the first side cover 332, and the second side cover 334 are made of a thermally conductive material such as metal.

[0020] As shown in FIGS. 1 and 3, the top cover 312 covers the ends of each battery cell 100 on the positive side in the Z direction. The bottom cover 314 covers the ends of each battery cell 100 on the negative side in the Z direction. As shown in FIGS. 1 and 2, the first end cover 322 covers the ends of each battery cell 100 on the positive side in the Y direction. The second end cover 324 covers the ends of each battery cell 100 on the negative side in the Y direction. As shown in FIGS. 1 to 3, the first side cover 332 covers the ends of each battery cell 100 on the positive side in the X direction. The second side cover 334 covers the ends of each battery cell 100 on the negative side in the X direction.

[0021] 1 and 3, each of the pads 200 is located between adjacent battery cells 100, except for pad 200a (pad 200) located at one end of the battery cells 100 on the positive side in the X direction, and pad 200b (pad 200) located at the other end of the battery cells 100 on the negative side in the X direction. The specific structure and function of the pad 200 will be described later with reference to FIGS. 4 and 5, but the pad 200 is a heat insulating member. When a battery cell 100 goes into an abnormal state and its temperature exceeds a predetermined level, the pad 200 expands due to the influence, maintaining the heat insulating state between the battery cells 100 and suppressing a chain reaction of thermal runaway.

[0022] The fixing layer 210 fixes the stack 190 to the inner surface of the housing 300. The battery cells 100 constituting the stack 190 can move to a certain extent in the stacking direction (X direction) while being fixed to the inner surface of the housing 300 by the fixing layer 210. For example, when a certain battery cell 100 is heated, if the adjacent pad 200 expands in the stacking direction due to the heating, the battery cell 100 moves and can absorb to a certain extent the influence of the expansion of the pad 200. This is because, as will be described later, the fixing layer 210 (structure glue 220, thermal glue 230) has elastic properties after hardening, allowing it to move to a certain extent.

[0023] The amount of movement of the battery cell 100 is, for example, 0.1 mm or more and 5 mm or less. The lower limit of the movable amount is preferably 0.3 mm or more, and more preferably 0.5 mm or more. The upper limit of the movable amount is preferably 5.0 mm or less, and more preferably 3 mm or less. The movable amount of the battery cell 100 is measured at the upper or lower end of the battery cell 100. The movable amount is based on the position when the stack 190 is formed in the normal state, and more specifically, on the positions (e.g., the first side cover 332 and the second side cover 334) that do not move in the stacking direction in the housing section 300 that houses the stack 190.

[0024] The amount of movement is determined by the dimensional limitations of the stack 190, which is composed of the battery cells 100 and the pads 200 (i.e., limitations on the storage space for the stack 190 inside the storage section 300), and the amount of expansion and compression of the pads 200. More specifically, it is determined taking into consideration the clearance in the stacking direction when the stack 190 is stored inside the storage section 300, the total amount of expansion of the expanded pads 200, and the total amount of compression of the compressed pads 200. In this embodiment, a state in which there is no clearance in the stacking direction is illustrated. The amount of expansion and compression of the pads 200 will be described later.

[0025] The fixing layer 210 includes a structural glue 220 and a thermal glue 230 . In the laminate 190, the portion on the -Z side is fixed to the bottom cover 314 by thermal glue 230, and the portion on the +Z side is fixed to the top cover 312 by structural glue 220. Hereinafter, the structural glue 220 and the thermal glue 230 are formed by curing an adhesive in a liquid or gel state before curing (hereinafter referred to as uncured adhesive).

[0026] As shown in FIG. 1 , the structure glue 220 is partially located between the +Z side surface of the stack 190 of battery cells 100 and the -Z side surface of the top cover 312 (i.e., the inner surface of the housing 300). The structure glue 220 is a collection of multiple strands extending in the X direction, and they are arranged at predetermined intervals in the Z direction. The structure glue 220 is, for example, a thermally conductive adhesive such as a silicone adhesive or a urethane adhesive. This structure allows heat generated from the stack 190 of battery cells 100 to be released toward the top cover 312 via the structure glue 220. However, the structure glue 220 does not have to be thermally conductive. Furthermore, if the structure glue 220 is a silicone adhesive, a urethane adhesive, or the like, it will have elastic properties after hardening, allowing the battery cells 100 to move to a certain extent.

[0027] 1 and 3, the thermal glue 230 (thermally conductive adhesive) is located between the bottom cover 314 and the ends of the multiple battery cells 100 on the negative Z-direction side. The thermal glue 230 is, for example, a thermally conductive adhesive such as a silicone adhesive or a urethane adhesive. Furthermore, if the thermal glue 230 is a silicone adhesive, a urethane adhesive, or the like, it will have elastic properties after hardening, allowing the battery cells 100 to move to a certain extent.

[0028] A gap is provided between the first end cover 322 and the end of each battery cell 100 on the positive side in the Y direction. A gap is also provided between the second end cover 324 and the end of each battery cell 100 on the negative side in the Y direction. When these gaps are provided, repeated thermal runaway between adjacent battery cells 100 can be suppressed in the following manner, compared to when the first end cover 322 and the end of each battery cell 100 on the positive side in the Y direction are in contact with each other and the second end cover 324 and the end of each battery cell 100 on the negative side in the Y direction are in contact with each other. Specifically, heat from the battery cell 100 on the most positive side in the X direction among the multiple battery cells 100 can be conducted to the first end cover 322 and the second end cover 324 via the first side cover 332. Heat from the battery cell 100 on the most negative side in the X direction among the multiple battery cells 100 can be conducted to the first end cover 322 and the second end cover 324 via the second side cover 334. However, when the above-mentioned gap is provided, heat is less likely to be transferred from the first end cover 322 or the second end cover 324 to the battery cells 100 compared to when the first end cover 322 and the end of each battery cell 100 on the positive side in the Y direction are in contact with each other and the second end cover 324 and the end of each battery cell 100 on the negative side in the Y direction are in contact with each other.

[0029] As shown in FIG. 3 , a pad 200a is located between the first side cover 332 and one end of the multiple battery cells 100 on the positive X-direction side. The pad 200a can function as a first cushioning material for cushioning physical forces such as vibrations and impacts. The compression characteristics of the pad 200a may be increased to absorb expansion of the pad 200 in the stacking direction (positive X-direction). The pad 200b is located between the second side cover 334 and the other end of the multiple battery cells 100 on the negative X-direction side. The pad 200b can function as a second cushioning material for cushioning physical forces such as vibrations and impacts. The compression characteristics of the pad 200b may be increased to absorb expansion of the pad 200 in the stacking direction (negative X-direction). Instead of the pad 200a, another member capable of functioning as a first cushioning material may be provided between the first side cover 332 and one end of the multiple battery cells 100 on the positive X-direction side. Also, instead of the pad 200b, another member capable of functioning as a second cushioning material may be provided between the second side cover 334 and the other end of the multiple battery cells 100 on the negative X-direction side.

[0030] 3, the multiple battery cells 100 are pressed in the negative direction of the X direction by the first side cover 332 via the pad 200a. The multiple battery cells 100 are pressed in the positive direction of the X direction by the second side cover 334 via the pad 200b. In this way, the multiple battery cells 100 are sandwiched by the housing section 300 via the pads 200a and 200b.

[0031] In this embodiment, heat conduction from a battery cell 100 that has experienced thermal runaway to other battery cells 100 can be sufficiently suppressed compared to when the end of each battery cell 100 on the positive side in the Z direction is thermally coupled to the top cover 312 and when the end of each battery cell 100 on the negative side in the Z direction is thermally coupled to the bottom cover 314. Specifically, heat generated from a battery cell 100 that has experienced thermal runaway is conducted to the top cover 312 or the bottom cover 314 via a pad 200 adjacent to the battery cell 100 that has experienced thermal runaway. Furthermore, the heat conducted to the top cover 312 or the bottom cover 314 is conducted to another pad 200 different from the pad 200 adjacent to the battery cell 100 that has experienced thermal runaway. In this embodiment, compared to when the end of each battery cell 100 on the positive side in the Z direction is thermally coupled to the top cover 312 and when the end of each battery cell 100 on the negative side in the Z direction is thermally coupled to the bottom cover 314, it is possible to suppress the heat conducted to the top cover 312 or the bottom cover 314 from being conducted toward the battery cells 100. Therefore, compared to when the end of each battery cell 100 on the positive side in the Z direction is thermally coupled to the top cover 312 and when the end of each battery cell 100 on the negative side in the Z direction is thermally coupled to the bottom cover 314, it is possible to suppress the heat conduction from a battery cell 100 that has experienced thermal runaway to other battery cells 100, and to disperse the heat throughout the entire battery module 10.

[0032] <Pat 200 Details> The pad 200 will be described in detail with reference to Figures 4 and 5. The following description will mainly focus on the shape change (expansion and compression) of the pad 200 and the accompanying movement of the battery cells 100.

[0033] The pads 200 are sandwiched between adjacent battery cells 100. As an example, the pads 200 are formed in a sheet shape that is approximately rectangular when viewed from the positive (or negative) side in the X direction and has a constant thickness in the stacking direction (X direction). The pads 200 are compressible within the recommended operating temperature range (for example, -30°C to 90°C) and expand when the temperature exceeds a predetermined temperature higher than the recommended operating temperature range. This allows the pads 200 to absorb the expansion and contraction of the battery cells 100 and provide a certain level of thermal insulation. Furthermore, the pad 200 is sandwiched between adjacent battery cells 100 at a pressure of 20 kPa or more and 1 MPa or less at 25°C, for example. The lower limit of the pressure is preferably 30 kPa or more, and more preferably 50 kPa or more. The upper limit of the pressure is preferably 900 kPa or less, and more preferably 800 kPa or less.

[0034] <Pat 200 expansion> A brief description will be given of the state of the laminated body 190 when the pad 200 expands. The principle of how the pad 200 expands will be described later. When the pad 200 reaches a predetermined temperature or higher due to a temperature rise caused by thermal runaway or the like of the battery cells 100, the expansion rate of the pad 200 increases. Furthermore, the pad 200 is compressible when the temperature is below the predetermined temperature. In other words, the pad 200 is normally sandwiched between adjacent battery cells 100 and is slightly compressed in the stacking direction. When the pad 200 is heated by thermal runaway or the like of the battery cells 100 and reaches a predetermined temperature or higher, it expands in the stacking direction.

[0035] The expanded pads 200 cause the battery cells 100 attached to the housing 300 by the fixing layer 210 (structure glue 220, thermal glue 230) to move or bend in the stacking direction. Here, we briefly explain what it means for the battery cells 100 to "bend." For example, a battery cell 100 that has experienced thermal runaway is fixed to the fixing layer 210 at its upper and lower ends, and its thickness may increase toward the center. As a result, the shape of the adjacent battery cells 100 changes, such as becoming concave on the side of the battery cell 100 that has experienced thermal runaway and convex on the opposite side. In this embodiment, this shape change is referred to as "bending." Note that the movement and bending of the battery cells 100 may occur simultaneously. Furthermore, the pads 200 other than the expanded pad 200 are compressible. The movement and bending of the battery cells 100 and the compression of the pads 200 allow the pads 200 that have reached a predetermined temperature or higher to sufficiently expand.

[0036] When the pad 200 reaches a predetermined temperature or higher, it expands in the stacking direction, improving the heat insulating properties of the expanded pad 200. As a result, it is possible to prevent the effects of the heated battery cell 100 from being transmitted to other battery cells 100 or other pads 200. As a result, it is possible to prevent a chain reaction of thermal runaway from progressing in the entire battery module 10. Furthermore, as will be described later, the pad 200 is a member with a simple structure including an elastic member, holes, and an expansion member, which helps to prevent increases in costs.

[0037] <Pat 200 expansion start temperature> The predetermined temperature at which the pad 200 starts to expand is 120°C or higher and 180°C or lower. The lower limit is preferably 125° C. or higher, more preferably 130° C. or higher. The upper limit is preferably 175° C. or lower, more preferably 170° C. or lower. By setting the lower limit of the predetermined temperature at which expansion starts to the above value, it is possible to prevent the expansion from starting too early. In other words, it is possible to prevent the pads 200 from expanding and causing the battery module 10 to stop functioning even when the temperature is still in a state where the battery module 10 can continue to function. By setting the upper limit of the predetermined temperature at which expansion starts to the above value, it is possible to prevent the expansion from starting too late. In other words, before thermal runaway of the battery module 10 progresses, the battery cell 100 that caused the thermal runaway or the like can be thermally separated from the other battery cells 100, thereby preventing a chain reaction of thermal runaway. The predetermined temperature at which the expansion starts can be adjusted by adjusting the material of the pad 200, which will be described next.

[0038] <Ingredients for Pat 200> The pad 200 includes an elastic material, voids, and an expansion agent. The elastic material and voids allow the pad 200 to be compressed. The elastic material, voids, and an expansion agent allow the pad 200 to be expanded.

[0039] The expanding agent generates gas or expands when it reaches a predetermined temperature or higher. Examples of pads 200 with this characteristic include thermally expanding rubber, which is a type of elastic material made of rubber material containing pores and an expanding agent, and thermally expanding sponge, which is a type of elastic material made of sponge material containing pores and an expanding agent.

[0040] The size of the pores and the occupancy rate per volume are adjusted according to the compression characteristics (amount of compression, compression ratio, etc.) and heat insulating characteristics set for the pad 200.

[0041] An expanding agent is a material that expands when heated. Examples of expanding agents include organic and inorganic blowing agents, which generate gas through a chemical reaction or thermal decomposition reaction when heated to a certain temperature. Examples of organic blowing agents include ADCA (azodicarbonamide), DPT (N,N'-dinitropentamethylenetetramine), and OBSH (4,4'-oxybisbenzenesulfonylhydrazide). Examples of inorganic blowing agents include bicarbonates and carbonates.

[0042] Alternatively, thermally expandable microcapsules (also called thermally decomposable microcapsules) may be used as the expanding agent. Thermally expandable microcapsules have a structure in which, for example, hydrocarbons are encapsulated in capsules made of gas-barrier plastic (generally, thermoplastic resin). When the thermally expandable microcapsules reach a predetermined temperature, they soften and simultaneously generate the encapsulated gas, such as hydrocarbon, causing the capsules to expand. The gas permeates and diffuses through the capsules.

[0043] By selecting the type of expanding agent, it is possible to adjust the temperature at which the pad 200 starts to expand. In addition, by selecting the type of expanding agent and adjusting the content, it is possible to adjust the amount of gas generated, and thereby adjust the amount and rate of expansion of the pad 200.

[0044] <Pat 200 thickness> The thickness T1 of the pad 200 in a normal state, more specifically, in a state where no external force is applied (uncompressed state) at 25° C., is, for example, 0.5 mm or more and 15 mm or less. In this embodiment, the state where no external force is applied (uncompressed state) will be described as a state where the pad 200 is not incorporated into the laminate 190 and is viewed as a standalone pad. The lower limit of the thickness T1 is preferably 1 mm or more, more preferably 1.5 mm or more, and the upper limit of the thickness T1 is preferably 10 mm or less, more preferably 5 mm or less. By setting the lower limit of the thickness T1 to such a value, it is possible to compress the cell 100 to a certain extent, and also to ensure heat insulation between the cells 100 when compressed. Setting the upper limit of the thickness T1 to this value can increase the stacking efficiency of the battery cells 100. Furthermore, when compression occurs due to the influence of the expanded pad 200, sufficient compression can be achieved.

[0045] Under normal conditions, more specifically at 25°C, the thickness T2 of the pad 200 in a compressed state sandwiched between the battery cells 100 is, for example, 0.45 mm or more and 13.5 mm or less. In this embodiment, the pad 200 is in a compressed state as described above, where the pad 200 is sandwiched between adjacent battery cells 100 as a component of the stack 190. The pressure when the pad 200 is sandwiched between the adjacent battery cells 100 is, for example, 20 kPa or more and 1 MPa or less, as described above. The lower limit of the thickness T2 is preferably 0.9 mm or more, and more preferably 1.45 mm or more. The upper limit of the thickness T2 is preferably 9 mm or less, and more preferably 4.5 mm or less. Setting the lower limit of the thickness T2 to such a value ensures heat insulation between the cells 100. Also, the pad 200 can be compressed to a certain degree. Setting the upper limit of the thickness T2 to this value can increase the stacking efficiency of the battery cells 100. Furthermore, when compression occurs due to the influence of the expanded pad 200, sufficient compression can be achieved.

[0046] <Expansion amount of Pad 200> When the pad 200 is not sandwiched between adjacent battery cells 100 and is not compressed, the amount of expansion V1 in the stacking direction (X direction) when heated from 25°C to 150°C is 0.5 mm or more and 1300 mm or less. The amount of expansion V1 is obtained by measuring the volume when the ambient temperature of the pad 200 reaches 150°C and then is left at that temperature for 5 minutes. The lower limit of the expansion amount V1 is preferably 5 mm or more, more preferably 10 mm or more, and the upper limit of the expansion amount V1 is preferably 50 mm or less, more preferably 40 mm or less. By setting the lower limit of the expansion amount V1 to the above value, a heat insulating space can be secured between the battery cells 100 when the battery cells 100 are heated, and heat transfer from the heated battery cell 100 to the adjacent battery cell 100 can be suppressed. As a result, heating of the battery cells 100 due to a thermal chain reaction can be suppressed. Setting the upper limit of the expansion amount to the above value makes it possible to prevent damage to the battery cells 100 due to the expansion of the pads 200. Furthermore, the battery cells 100 are able to move or bend to a certain extent in the stacking direction when the pads 200 expand. Setting the expansion amount V1 of the pads 200 to the above value makes it possible to keep the battery cells 100 within the range in which they can move or bend.

[0047] When the pad 200 is sandwiched between adjacent battery cells 100 and heated from 25°C to 150°C, the pad 200 expands in the stacking direction by an amount V2 of 0.5 mm or more and 10 mm or less. The expansion amount V2 is obtained by measuring the volume of the pad 200 when it is sandwiched between adjacent battery cells 100 after the ambient temperature reaches 150°C and the pad is left at that temperature for 5 minutes. Generally, the expansion amount V2 of the pad 200 is considered to be greater than that in the uncompressed state. However, when the pad 200 is incorporated into the stack 190, there is a limit to the storage space for the stack 190 in the storage section 300. Therefore, in this embodiment, the expansion amount V2 is smaller than the expansion amount V1, taking into account this storage space. The lower limit of the expansion amount V2 is preferably 0.5 mm or more, more preferably 1 mm or more, and the upper limit of the expansion amount V2 is preferably 7 mm or less, more preferably 5 mm or less. By setting the lower limit of the expansion amount V2 to the above value, a heat insulating space can be secured between the battery cells 100 when the battery cells 100 are heated, and heat transfer from the heated battery cell 100 to the adjacent battery cell 100 can be suppressed. As a result, heating of the battery cells 100 due to a thermal chain reaction can be suppressed. Setting the upper limit of the expansion amount V2 to the above value makes it possible to prevent damage to the battery cells 100 due to the expansion of the pads 200. Furthermore, the battery cells 100 are able to move or bend to a certain extent in the stacking direction when the pads 200 expand. Setting the expansion amount V2 of the pads 200 to the above value makes it possible to keep the battery cells 100 within the range in which they can move or bend.

[0048] <Expansion rate> When the pad 200 is not sandwiched between adjacent battery cells 100 and is not compressed, the expansion coefficient W1 in the stacking direction (X direction) when heated from 25°C to 150°C is 200% or more and 9000% or less. In other words, when the temperature reaches a predetermined level or higher, the pad 200 expands by 2 to 90 times. The expansion coefficient W1 can be obtained by measuring the volume of the pad 200 when the ambient temperature reaches 150°C and then leaving it at that temperature for 5 minutes. The lower limit of the expansion rate W1 is preferably 300% or more, and more preferably 500% or more. By setting the lower limit of the expansion coefficient W1 to the above value, a heat insulating space can be secured between the battery cells 100 when the battery cells 100 are heated, and heat transfer from a heated battery cell 100 to an adjacent battery cell 100 can be suppressed. As a result, heating of the battery cells 100 due to a thermal chain reaction can be suppressed. The upper limit of the expansion rate W1 is preferably 1200% or less, and more preferably 1000% or less. Setting the upper limit of the expansion rate W1 to this value makes it possible to prevent the battery cells 100 from being damaged by the expansion of the pad 200. Furthermore, the battery cells 100 are able to move or bend to a certain extent in the stacking direction when the pad 200 expands. Setting the expansion rate W1 of the pad 200 to this value makes it possible to keep the battery cells 100 within the range in which they can move or bend.

[0049] When the pad 200 is heated from 25°C to 150°C in a compressed state sandwiched between adjacent battery cells 100, the expansion coefficient W2 in the stacking direction (X direction) is 100% or more and 500% or less. The expansion coefficient W2 is obtained by measuring the volume of the pad 200 when it is sandwiched between adjacent battery cells 100 and the ambient temperature reaches 150°C, and then the pad is left at that temperature for 5 minutes. Generally, the expansion coefficient W2 of the pad 200 is considered to be greater than that in the uncompressed state. However, when the pad 200 is incorporated into the stack 190, there is a limit to the storage space for the stack 190 in the storage section 300. Therefore, in this embodiment, the expansion coefficient W2 is smaller than the expansion coefficient W1 in consideration of this storage space. The lower limit of the expansion rate W2 is preferably 175% or more, more preferably 200% or more. The upper limit of the expansion rate W2 is preferably 400% or less, more preferably 300% or less. By setting the lower limit of the expansion coefficient W2 to the above value, a heat insulating space can be secured between the battery cells 100 when the battery cells 100 are heated, and heat transfer from a heated battery cell 100 to an adjacent battery cell 100 can be suppressed. As a result, heating of the battery cells 100 due to a thermal chain reaction can be suppressed. Setting the upper limit of the expansion amount W2 to the above value makes it possible to prevent damage to the battery cells 100 due to the expansion of the pads 200. Furthermore, the battery cells 100 are able to move or bend to a certain extent in the stacking direction when the pads 200 expand. Setting the expansion rate W2 of the pads 200 to the above value makes it possible to keep the battery cells 100 within the range in which they can move or bend.

[0050] <Compression amount> When the pad 200 is not sandwiched between adjacent battery cells 100 and is not compressed, the compression amount C1 from when no pressure is applied to when a final pressure of 1 MPa is applied at 25°C is 0.45 mm or more and 13.5 mm or less. The lower limit of the compression amount C1 is preferably 0.5 mm or more, and more preferably 2 mm or more. The upper limit of the compression amount C1 is preferably 8 mm or less, and more preferably 6 mm or less. By setting the lower limit of the compression amount C1 to the above value, it is possible to absorb the influence of the pads 200 that have expanded due to heating. More specifically, when a pad 200 expands, the other pads 200 that have not expanded compress even slightly, thereby securing space for the expanded pad 200. In other words, the pads 200 can expand. By setting the lower limit of the compression amount C1 to the above value, the dimensions of the laminate 190 can be prevented from becoming excessively large.

[0051] When the pad 200 is sandwiched between adjacent battery cells 100 at a pressure of 20 kPa to 1 MPa (compressed state), the amount of compression C2 at 25°C up to a final pressure of 1 MPa is 0.05 mm to 13.5 mm. The amount of compression C2 is measured based on the dimensions before and after the pad 200 is sandwiched between the adjacent battery cells 100. The lower limit of the compression amount C2 is preferably 0.1 mm or more, more preferably 0.5 mm or more, and the upper limit of the compression amount C2 is preferably 13 mm or less, more preferably 10 mm or less. By setting the lower limit of the compression amount C2 to the above value, the pads 200 can be further compressed from the compressed state in the laminate 190. Therefore, the influence of the pads 200 that have expanded due to heating can be absorbed. More specifically, when a certain pad 200 expands, the other pads 200 that have not expanded compress even slightly, thereby ensuring space for the expanded pads 200. In other words, the pads 200 can expand. By setting the upper limit of the compression amount C2 to the above value, the dimensions of the laminate 190 can be prevented from becoming excessively large.

[0052] <Compression ratio> When the pad 200 is not sandwiched between adjacent battery cells 100 and is not compressed, the compression rate C3 from no pressure to a final pressure of 1 MPa at 25°C is 20% or more and 95% or less. The lower limit of the compression ratio C3 is preferably 25% or more, more preferably 30% or more, and the upper limit of the compression ratio C3 is preferably 90% or less, more preferably 85% or less. Setting the lower limit of the compression rate C3 to the above value makes it possible to absorb the effects of pads 200 that expand due to heating. More specifically, when a pad 200 expands, the other pads 200 that have not expanded compress even slightly, thereby ensuring space for the expanded pad 200. In other words, the pads 200 can expand. By setting the upper limit of the compression ratio C3 to the above value, the dimensions of the laminate 190 can be prevented from becoming excessively large.

[0053] When the pad 200 is sandwiched between adjacent battery cells 100 at a pressure of 20 kPa or more and 1 MPa or less (compressed state), the compression rate C4 from no pressure to when a final pressure of 1 MPa is applied at 25°C is 15% or more and 90% or less. The lower limit of the compression ratio C4 is preferably 20% or more, more preferably 25% or more, and the upper limit of the compression ratio C4 is preferably 85% or less, more preferably 80% or less. By setting the lower limit of the compression rate C4 to the above value, it is possible to absorb the influence of the pads 200 that have expanded due to heating. More specifically, when a certain pad 200 expands, the other pads 200 that have not expanded compress even slightly, thereby securing space for the expanded pad 200. In other words, the pads 200 can expand. By setting the upper limit of the compression rate C4 to the above value, the dimensions of the laminate 190 can be prevented from becoming excessively large.

[0054] <Changes in Pad 200 and Battery Cell 100 at High Temperatures> 4 and 5, a change in the laminate 190 will be described when a certain battery cell 100 goes into an abnormal state and exceeds a predetermined temperature, and the adjacent pad 200, influenced by the battery cell 100, exceeds the predetermined temperature and expands. Fig. 4 is an enlarged schematic diagram of the cross-sectional structure of the laminate 190 in a normal state. Fig. 5 is an enlarged schematic diagram of the cross-sectional structure of the laminate 190 in a state in which the pad 200 expands.

[0055] In Figures 4 and 5, for convenience, the battery cell 100 that heats up due to thermal runaway or the like is referred to as the "first battery cell 101," the battery cell 100 that does not heat up enough to affect other parts is referred to as the "second battery cell 100," the pad 200 adjacent to the first battery cell 101 that rises to a predetermined temperature and expands due to the influence of heating is referred to as the "first pad 201," and the pad 200 that does not reach the predetermined temperature and does not expand is referred to as the "second pad 202."

[0056] 4, in a normal state, the components of the stack 190 (battery cells 100 and pads 200) are within the recommended operating temperature range, and all of the pads 200 (first pad 201 and second pad 202) are not expanded and are in a constant compressed state sandwiched between the battery cells 100. In other words, the battery cells 100 and pads 200 are in a predetermined arrangement that constitutes the stack 190.

[0057] As shown in FIG. 5 , when the temperature of the first battery cell 101 rises above a predetermined temperature, the first pad 201 located next to the first battery cell 101 expands. Here, the first pads 201 on both sides of the first battery cell 101 are heated above the predetermined temperature and expand. Specifically, when the first pad 201 is exposed to high temperatures and reaches the predetermined temperature, the expansion agent contained in the first pad 201 expands or gas is generated from the expansion agent. Accordingly, the elastic material of the first pad 201 elastically deforms and stretches, expanding the volume of the pores. Because the pores have high insulating properties, the expanded pad 201 can exhibit high insulating properties. For example, if the temperature rise of the first battery cell 101 is uneven, only one of the first pads 201 may expand.

[0058] As the first pad 201 expands, the second battery cell 102 located next to the first battery cell 101 moves or bends in the stacking direction. The second battery cell 102 may move and bend at the same time. FIG. 5 illustrates an example in which the second battery cell 102 moves. Note that the third battery cell 103 may also move.

[0059] The second pad 202 located between the second battery cell 102 and the third battery cell 103 located next to the second battery cell 102 is compressed in the stacking direction. The second pad 202 also moves together with the second battery cell 102 that sandwiches it.

[0060] Since the laminate 190 housed inside the housing 300 has a dimensional limit in the stacking direction, the laminate 190 as a whole cannot expand in the stacking direction (or there is a limit to the amount of expansion). Therefore, the unexpanded pad 202 compresses, absorbing the expansion of the pad 201.

[0061] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various other configurations can also be adopted.

[0062] <Summary of the embodiment> The features of this embodiment can be summarized as follows: 1. A plurality of cells (battery cells 100); a heat insulating member (pad 200) sandwiched between adjacent cells (battery cells 100), whose expansion rate increases when the temperature exceeds a predetermined value and which is compressible when the temperature is below the predetermined value; Equipped with When the temperature of the first cell (first battery cell 101) reaches or exceeds the predetermined temperature, The first insulating member (first pad 201) located next to the first cell (first battery cell 101) expands, The second cell (second battery cell 102) located next to the first cell (first battery cell 101) moves or bends in the stacking direction (X direction) of the multiple cells (battery cells 100), The second insulating material (second pad 202) located between the second cell (second battery cell 102) and the third cell (third battery cell 103) located adjacent to the second cell (second battery cell 102) is compressed in the stacking direction (X direction). A battery module 10 comprising: 2. The battery module 10 according to 1., wherein the predetermined temperature is 120°C or higher and 180°C or lower. 3. The battery module 10 according to 1. or 2., wherein the heat insulating member (pad 200) contains an elastic material, pores, and an expanding agent that generates gas when the temperature reaches or exceeds the predetermined temperature. 4. The battery module 10 described in 1. or 2., wherein the thermal insulating member (pad 200) has an expansion coefficient W1 in the stacking direction (X direction) of 200% or more and 9000% or less when heated from 25°C to 150°C in a state where it is not sandwiched between adjacent cells (battery cells 100) and is not compressed. 5. The battery module 10 described in 1 or 2, wherein the thermal insulating member (pad 200) has an expansion coefficient W2 in the stacking direction (X direction) of 100% or more and 500% or less when heated from 25°C to 150°C in a state where the thermal insulating member (pad 200) is sandwiched between adjacent cells (battery cells 100) at a pressure of 20 kPa or more and 1 MPa or less. 6. A battery module 10 described in 1. or 2., wherein the compression rate C3 of the insulating member (pad 200) when not sandwiched between adjacent cells (battery cells 100) and not compressed is 20% or more and 95% or less when a final pressure of 1 MPa is applied at 25°C. 7. The battery module 10 described in 1. or 2., wherein the heat insulating member (pad 200) has a compression rate C4 of 15% or more and 90% or less when sandwiched between adjacent cells (battery cells 100) at a pressure of 20 kPa or more and 1 MPa or less at 25°C and when a final pressure of 1 MPa is applied. 8. A battery module 10 described in 1. or 2., in which the plurality of cells (battery cells 100) are fixed to the inner surface of the housing (accommodation section 300) using a fixing layer 210 (structural glue 220, thermal glue 230) so as to be movable in the stacking direction (X direction). [Explanation of symbols]

[0063] 10 Battery Module 100 battery cells 101 First battery cell 102 Second Battery Cell 110 First Lead 120 2nd Lead 200 putts 201 First Putt 202 Second Putt 210 Fixed layer 220 Structure Glue 230 Thermal Glue 300 storage unit 312 Top cover 314 Bottom cover 322 No. 1 End Cover 324 Second end cover 332 1st side cover 334 Second side cover

Claims

1. A plurality of cells; a heat insulating member sandwiched between the adjacent cells, the heat insulating member having an expansion rate that increases when the temperature reaches a predetermined temperature or higher and being compressible when the temperature is below the predetermined temperature; Equipped with When the temperature of the first cell becomes equal to or higher than the predetermined temperature, a first insulating member located adjacent to the first cell expands; a second cell located adjacent to the first cell moves or bends in the stacking direction of the plurality of cells; a second insulating material positioned between the second cell and a third cell positioned adjacent to the second cell, the second insulating material being compressed in the stacking direction;

2. The battery module according to claim 1 , wherein the predetermined temperature is 120° C. or higher and 180° C. or lower.

3. The battery module according to claim 1 , wherein the heat insulating member includes an elastic material, pores, and an expanding agent that generates gas at a temperature equal to or higher than the predetermined temperature.

4. 3. The battery module according to claim 1, wherein the thermal insulating member has an expansion coefficient in the stacking direction of 200% or more and 9000% or less when heated from 25°C to 150°C when not sandwiched between adjacent cells and not compressed.

5. 3. The battery module according to claim 1, wherein the thermal insulating member has an expansion coefficient in the stacking direction of 100% or more and 500% or less when heated from 25°C to 150°C while sandwiched between adjacent cells at a pressure of 20 kPa or more and 1 MPa or less.

6. 3. The battery module according to claim 1, wherein the insulating member has a compression rate of 20% or more and 95% or less when subjected to a final pressure of 1 MPa at 25°C when not sandwiched between adjacent cells and not compressed.

7. 3. The battery module according to claim 1, wherein the heat insulating member has a compression rate of 15% or more and 90% or less when sandwiched between adjacent cells at a pressure of 20 kPa or more and 1 MPa or less at 25°C and when a final pressure of 1 MPa is applied.

8. The battery module according to claim 1 , wherein the plurality of cells are fixed to an inner surface of the housing using a fixing layer so as to be movable in the stacking direction.

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