Separating member and battery pack

Abstract

Provided are: a partition member that partitions between unit cells and has excellent shape stability even at high temperatures; and a battery pack using the same. An inner packaging body is formed by holding a layer for controlling heat movement in a holding part having compressibility, and the inner packaging body is sealed in an outer packaging body to form a partition member. The holding part is preferably formed in a tray shape, the thickness of the holding part is set to be larger than that of a layer for controlling heat movement, and the area of the outer packaging body in contact with the inner packaging body is increased along with the increase of external pressure applied to the partition member.

Description

Technical Field

[0001] The present invention relates to a partition member housed in a battery pack to partition between single cells, and the battery pack.

[0002] This application claims priority based on Japanese Patent Application No. 2023-21298 filed in Japan on February 15, 2023, the contents of which are incorporated herein by reference. Background Art

[0003] In recent years, research into increasing the energy density of secondary batteries, whose use as power sources for vehicles and other applications has been rapidly increasing, has been underway to improve their flexibility when installed in confined spaces such as vehicles and to extend the range that can be traveled on a single charge. On the other hand, the safety of secondary batteries tends to be inversely proportional to their energy density, with higher energy densities associated with lower safety. For example, in electric vehicles with ranges of hundreds of kilometers, the surface temperature of secondary batteries can exceed several hundred degrees Celsius, sometimes reaching over 1000 degrees Celsius, when damaged by overcharging, internal short circuits, or other factors.

[0004] Since secondary batteries used in power sources for vehicles and other applications are typically used in battery packs composed of multiple cells, if one of the cells forming the battery pack is damaged and reaches the temperature range described above, the resulting heat release could damage adjacent cells, potentially causing a chain reaction of damage to the entire battery pack. To prevent this chain reaction of cell damage, various technologies have been proposed that use separators between cells.

[0005] For example, there is a partition member having a structure in which a heat transfer control layer and a compressibility control layer are sealed in an outer casing (see, for example, Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-119679 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The aforementioned prior art partition member has the characteristic that the paste material constituting the heat transfer control layer becomes unstable in shape at high temperatures. Furthermore, the time from when the water contained in the heat transfer control layer reaches its boiling point until it completely evaporates (hereinafter also referred to as the "plateau time," and the region during this time is also referred to as the "plateau region") is short.

[0011] An object of the present invention is to provide a partition member having excellent shape stability even at high temperatures, and a battery pack obtained by using the partition member.

[0012] Solutions for solving problems

[0013] The present inventors conducted intensive research to solve the above-mentioned problems and found that providing a composition portion containing at least one of inorganic particles and inorganic fibers and a binder in the inner packaging of a separator disposed between cells can solve the above-mentioned problems, thereby completing the present invention.

[0014] That is, the present invention includes the following aspects.

[0015] [1] A partition member having a thickness direction and a plane direction perpendicular thereto, and partitioning the cells in the thickness direction.

[0016] The partition member includes an outer packaging body and an inner packaging body covered by the outer packaging body.

[0017] The inner package body includes a composition portion composed of a composition containing at least one of inorganic particles and inorganic fibers and a binder.

[0018] [2] The partition member according to [1], wherein the composition portion further contains a liquid.

[0019] [3] The partition member according to [1] or [2], wherein the inner package further comprises a holding portion.

[0020] The holding portion includes an outer wall portion that contacts at least a portion of an outer peripheral end surface in a plane direction of the composition portion and extends in a thickness direction.

[0021] [4] The partition member according to [3], wherein both ends of the outer wall portion of the holding portion in the thickness direction are in contact with the outer packaging body.

[0022] [5] The partition member according to any one of [1] to [4], wherein a deformation rate of the partition member in the thickness direction when the partition member is pressurized at 0.2 MPa in the thickness direction is 6.0% or more.

[0023] [6] The partition member according to any one of [3] to [5], wherein the length of the holding portion in the thickness direction is greater than the length of the combining portion in the thickness direction.

[0024] [7] The partition member according to any one of [3] to [6], wherein the holding portion has a space having a depth in the thickness direction, and the composition portion is held in the space.

[0025] [8] The partition member according to any one of [3] to [6], wherein the holding portion has a space having a depth in the thickness direction, the space includes a plurality of first spaces partitioned into a grid shape, and the composition portion is held in each of the first spaces.

[0026] [9] A partition member according to any one of [3] to [6], wherein the retaining portion has a space having a depth in the thickness direction, the space includes a plurality of first spaces partitioned into a grid shape, the combination portion is retained in each of the first spaces, and a third space is formed between the adjacent first spaces on the back side of the retaining portion.

[0027]

[10] The partition member according to [9], wherein the ratio of the volume of the third space to the volume of 100% by volume of the smallest rectangular parallelepiped capable of accommodating the holding portion is 0.1 to 15% by volume.

[0028]

[11] The partition member according to any one of [3] to

[10] , wherein the holding portion is a tray-shaped member having a frame-shaped outer wall portion and a bottom portion, the frame-shaped outer wall portion surrounding the composition portion, and the bottom portion closing an opening of the frame-shaped outer wall portion.

[0029] The composition portion is held in the recessed portion inside the outer wall portion.

[0030]

[12] The partition member according to

[11] , wherein the tray-shaped member further comprises a lattice-shaped partition wall for partitioning the inner side of the frame-shaped outer wall portion.

[0031] A plurality of recesses are formed on the inner side of the frame-shaped outer wall by the partition wall.

[0032] The composition portion is held in each of the recessed portions.

[0033]

[13] The partition member according to

[11] , wherein the tray-shaped member further comprises a lattice-shaped partition wall for partitioning the inner side of the frame-shaped outer wall portion.

[0034] A plurality of recesses are formed on the inner side of the frame-shaped outer wall by the partition wall.

[0035] The partition wall is composed of two side walls rising from the bottom between the two recessed portions and a connecting portion connecting the upper portions of the side walls to each other, and a recessed strip opening toward the bottom is formed between the two side walls.

[0036] The combination portion is held in each of the recessed portions, and the combination portions are connected to each other at the low-position portion.

[0037]

[14] The partition member according to any one of

[11] to

[13] , wherein the ratio of the area of ​​the composition portion to the total area of ​​the tray-shaped member and the composition portion when the tray-shaped member is viewed from above in the thickness direction is 50 to 100% by volume.

[0038]

[15] The partition member according to any one of

[11] to

[14] , wherein the tray-shaped member has a rectangular shape when viewed from above in the thickness direction.

[0039] When the XYZ coordinate axes are defined by setting the thickness direction as the Z axis, the direction parallel to one side of the outer periphery of the tray-shaped member in the surface direction as the X axis, and the direction perpendicular to the X axis in the surface direction as the Y axis,

[0040] In a cross section of the tray-shaped member cut along an XZ plane passing through the composite portion, the ratio of the area occupied by the space to the area of ​​the smallest rectangle surrounding the tray-shaped member is 15% by volume or less, and

[0041] In a cross section of the tray-shaped member cut along a YZ plane passing through the composition portion, a ratio of an area occupied by the space to an area of ​​a minimum rectangle surrounding the tray-shaped member is 15 volume % or less.

[0042]

[16] A battery pack comprising: a plurality of single cells; and the partition member according to any one of [1] to

[15] disposed between the single cells.

[0043]

[17] The battery pack according to

[16] , wherein a unit structure composed of the two single cells and the partition member disposed between the two single cells satisfies the following condition (i).

[0044] (i) The thermal conductivity of the partition member when the surface average temperature of the partition member in contact with the two cells is 200° C. is reduced to 70% or less relative to the thermal conductivity of the partition member when the surface average temperature of the partition member is 25° C.

[0045]

[18] The battery pack according to

[16] or

[17] , wherein a unit structure composed of two of the single cells and the partition member disposed between the two single cells satisfies the following condition (ii).

[0046] (ii) Under a pressure of 0.2 MPa applied between the two unit cells, the deformation rate of the partition member disposed between the unit cells is 6.0% or more.

[0047] [A1] A partition member having a thickness direction and a plane direction perpendicular thereto, and partitioning electric cells in the thickness direction, the partition member comprising an outer casing and an inner casing covered by the outer casing.

[0048] [A2] The partition member according to [A1], wherein the thermal conductivity in the thickness direction of the partition member is 0.20 [W / (m·K)] or more when the average surface temperature of the partition member is 25°C.

[0049] [A3] The partition member according to [A1] or [A2], wherein when the partition member is pressurized at 1.0 MPa in the thickness direction for one minute, the inner package remains contained within the outer package.

[0050] [A4] The partition member according to any one of [A1] to [A3], wherein when the temperature is increased to 100°C at a rate of 1.7°C / min, the inner package body remains contained within the outer package body.

[0051] [B1] The partition member according to any one of [A1] to [A4], wherein the inner package includes a composition portion containing a thermal resistance variable material.

[0052] [B2] The partition member according to any one of [B1], wherein the thermal resistance of the thermal resistance variable material increases after heating relative to the thermal resistance before heating.

[0053] [B3] The partition member according to [B1] or [B2], wherein the thermal resistance of the thermal resistance variable material after heating increases to 1.5 times or more relative to the thermal resistance before heating.

[0054] [B4] The partition member according to any one of [B1] to [B3], wherein the composition portion includes a composition portion containing a phase change material.

[0055] [B5] The partition member according to any one of [B1] to [B4], wherein the phase change material undergoes an irreversible phase change at a predetermined temperature.

[0056] [B6] The partition member according to any one of [B1] to [B5], wherein the phase change material undergoes a reversible phase change at a predetermined temperature.

[0057] [B7] The partition member according to any one of [B1] to [B6], wherein the phase change material undergoes a phase change accompanied by an endothermic reaction at a predetermined temperature.

[0058] [C1] The partition member according to any one of [A1] to [A4] and [B1] to [B7], wherein the inner package includes a composition portion containing at least one of inorganic particles and inorganic fibers and a binder.

[0059] [C2] The partition member according to [C1], wherein the adhesive includes a material that solidifies by a hydration reaction.

[0060] [C3] The partition member according to [C1] or [C2], wherein the composition portion includes at least one of inorganic particles and inorganic fibers and includes a hydrated product.

[0061] [C4] The partition member according to any one of [C1] to [C3], wherein the composition part further contains a liquid.

[0062] [C5] The partition member according to any one of [C1] to [C4], wherein the boiling point of the liquid is 50 to 200°C.

[0063] [C6] The partition member according to any one of [C1] to [C5], wherein the liquid is water.

[0064] [C7] The partition member according to any one of [C1] to [C6], wherein the composition portion further contains a liquid.

[0065] The content of the liquid is 1 to 90% by mass relative to 100% by mass of the composition.

[0066] [C8] The partition member according to any one of [C1] to [C7], comprising 1 to 70% by mass of at least one of the inorganic particles and the inorganic fibers relative to 100% by mass of the composition portion.

[0067] [C9] The partition member according to any one of [C1] to [C8], comprising 1 to 90% by mass of a liquid relative to 100% by mass of the composition portion.

[0068] [C10] The partition member according to any one of [C1] to [C9], comprising 1 to 70% by mass of the binder relative to 100% by mass of the composition portion.

[0069] [C11] The partition member according to any one of [C1] to [C10], comprising 1 to 70% by mass of a hydrate relative to 100% by mass of the composition portion.

[0070] [C12] The partition member according to any one of [C1] to [C11], wherein the composition does not become suspended even when immersed in water for 10 minutes after being stored at 25°C for 24 hours.

[0071] [C13] The partition member according to any one of [C1] to [C12], wherein the composition used in the composition part has a viscosity at 25° C. of 10 to 200 Pa·s as measured by a Brookfield viscometer.

[0072] [C14] The partition member according to any one of [C1] to [C13], wherein the composition used in the composition part has a viscosity at 25° C. of 15 to 100 Pa·s as measured by a Brookfield viscometer.

[0073] [D1] The partition member according to any one of [A1] to [A4], [B1] to [B7], and [C1] to [C14], wherein the inner package comprises a combining portion and a holding portion.

[0074] The holding portion includes an outer wall portion that contacts at least a portion of an outer peripheral end surface in a plane direction of the composition portion and extends in a thickness direction.

[0075] [D2] The partition member according to [D1], wherein both ends of the outer wall portion in the thickness direction are in contact with the outer casing.

[0076] [D3] The partition member according to [D1] or [D2], wherein the holding portion includes a thermoplastic resin.

[0077] [D4] The partition member according to any one of [D1] to [D3], wherein a deformation rate (X) of the partition member in the thickness direction when the partition member is pressurized at 0.2 MPa in the thickness direction is 6.0% or more.

[0078] [D5] The partition member according to any one of [D1] to [D4], wherein a deformation rate (Y) of the partition member in the thickness direction when the partition member is pressurized at 1.0 MPa in the thickness direction is 12% or more.

[0079] [D6] A partition member according to any one of [D1] to [D5], wherein the difference (XY) between the deformation rate (X) in the same direction when an external pressure of 0.2 MPa is applied along the thickness direction of the partition member and the deformation rate (Y) in the same direction when an external pressure of 1.0 MPa is applied along the same direction is 3.0 to 60%.

[0080] [D7] A partition member according to any one of [D1] to [D6], wherein the ratio (Y / X) of the deformation rate (X) in the same direction when an external pressure of 0.2 MPa is applied along the thickness direction of the partition member to the deformation rate (Y) in the same direction when an external pressure of 1.0 MPa is applied along the same direction is 0.10 to 2.0.

[0081] [E1] A partition member according to any one of [A1] to [A4], [B1] to [B7], [C1] to [C14] and [D1] to [D7], wherein the inner packaging body comprises a combining portion and a retaining portion, and the length of the retaining portion in the thickness direction is greater than the length of the combining portion in the thickness direction.

[0082] [E2] The partition member according to [E1], wherein the holding portion has a space having a depth in the thickness direction.

[0083] [E3] The partition member according to [E1] or [E2], wherein the holding portion has a space having a depth in the thickness direction.

[0084] The aforementioned space includes a plurality of first spaces divided into a grid shape.

[0085] [E4] The partition member according to any one of [E1] to [E3], wherein the holding portion has a space having a depth in the thickness direction.

[0086] The space includes a plurality of first spaces partitioned into a grid shape, and further includes a second space partially connecting adjacent first spaces.

[0087] [E5] The partition member according to any one of [E1] to [E4], wherein the holding portion is a tray-shaped member having a frame-shaped outer wall portion and a bottom portion, the frame-shaped outer wall portion surrounding the combination portion, and the bottom portion closing an opening of the frame-shaped outer wall portion.

[0088] The composition portion is held in the recessed portion inside the outer wall portion.

[0089] [E6] The partition member according to [E5], wherein the tray-shaped member further includes a lattice-shaped partition wall for partitioning the inner side of the frame-shaped outer wall portion.

[0090] A plurality of recesses are formed on the inner side of the frame-shaped outer wall by the partition wall.

[0091] The composition portion is held in each of the recessed portions.

[0092] [E7] The partition member according to [E5], wherein the tray-shaped member further includes a lattice-shaped partition wall for partitioning the inner side of the frame-shaped outer wall portion.

[0093] The partition wall has a low portion in part.

[0094] A plurality of recesses are formed on the inner side of the frame-shaped outer wall by the partition wall.

[0095] The combination portion is held in each of the recessed portions, and the combination portions are connected to each other at the low-position portion.

[0096] [F1] A partition member according to any one of [A1] to [A4], [B1] to [B7], [C1] to [C14], [D1] to [D7] and [E1] to [E6], which is constructed in such a way that the contact area between the outer packaging body and the inner packaging body increases as the external pressure applied to the partition member increases.

[0097] [F2] The partition member according to [F1], wherein the inner package includes a combining portion and a holding portion, and the holding portion is in partial or entire contact with one side in the thickness direction of the combining portion.

[0098] [F3] The partition member according to [F1] or [F2], wherein the ratio of the contact area between the outer packaging body and the inner packaging body when the external pressure is 0.2 MPa to the contact area between the outer packaging body and the inner packaging body when the external pressure is 0 MPa is 1.0 to 200.

[0099] [F4] The partition member according to any one of [F1] to [F3], wherein a ratio of an area of ​​the holding portion to a total area of ​​the combination portion and the holding portion when viewed from above in the thickness direction is 0.01 to 0.50.

[0100] [S1] A battery pack comprising a plurality of cells, and [A1] to [A4], [B1] to [B7], [C1] to [C14], [D1] to [D7], and [E1] to [E6] disposed between the cells.

[0101] and the partition member according to any one of [F1] to [E4].

[0102] [S2] The battery pack according to [S1], wherein a unit structure composed of the two unit cells and the partition member disposed between the two unit cells satisfies the following condition (i).

[0103] (i) The thermal conductivity of the partition member when the surface average temperature of the partition member in contact with the two cells is 200° C. is reduced to 70% or less relative to the thermal conductivity of the partition member when the surface average temperature of the partition member is 25° C.

[0104] [S3] The battery pack according to [S1] or [S2], wherein a unit structure composed of the two unit cells and the partition member disposed between the two unit cells satisfies the following condition (ii).

[0105] (ii) Under a pressure of 0.2 MPa applied between the two unit cells, the deformation rate of the partition member disposed between the unit cells is 6.0% or more.

[0106] Effects of the Invention

[0107] According to the present invention, a partition member having excellent shape stability even at high temperatures and a battery pack incorporating the partition member can be configured. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] Figure 1 This is a diagram showing a schematic longitudinal cross-section obtained by cutting an example of the partition member of the present invention in the thickness direction.

[0109] Figure 2A This figure shows a configuration of an example of an inner package constituting a partitioning member in a schematic longitudinal sectional view cut along the thickness direction.

[0110] Figure 2B This figure shows a configuration of an example of an inner package constituting a partitioning member in a schematic longitudinal sectional view cut along the thickness direction.

[0111] Figure 2C This figure shows a configuration of an example of an inner package constituting a partitioning member in a schematic longitudinal sectional view cut along the thickness direction.

[0112] Figure 3A This is a diagram showing a configuration of an example of an inner package constituting a partitioning member in a schematic plan view viewed from above in the thickness direction.

[0113] Figure 3B This is a diagram showing a configuration of an example of an inner package constituting a partitioning member in a schematic plan view viewed from above in the thickness direction.

[0114] Figure 4 This figure shows a configuration of an example of an inner package constituting a partitioning member in a schematic longitudinal sectional view cut along the thickness direction.

[0115] Figure 5AThis is a diagram showing a configuration of an example of an inner package constituting a partitioning member in a schematic plan view viewed from above in the thickness direction.

[0116] Figure 5B yes Figure 5A AA cross-sectional view of the inner packaging body shown in .

[0117] Figure 5C yes Figure 5A BB cross-sectional view of the inner packaging body shown in .

[0118] Figure 6 This is a diagram showing a configuration of an example of an inner package constituting a partitioning member in a schematic plan view viewed from above in the thickness direction.

[0119] Figure 7 This figure shows a configuration of an example of an inner package constituting a partitioning member in a schematic longitudinal sectional view cut along the thickness direction.

[0120] Figure 8 This is a conceptual diagram showing the battery pack of the present invention.

[0121] Figure 9 It is a plan view showing an example of a single cell.

[0122] Figure 10 yes Figure 9 Front view of a single battery.

[0123] Figure 11 yes Figure 9 Side view of a single battery.

[0124] Figure 12 This is a conceptual diagram of a thermal insulation evaluation test device. DETAILED DESCRIPTION

[0125] Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiment described below, and can be implemented with any modifications without departing from the spirit of the present invention.

[0126] It should be noted that in this specification, when "X to Y" (X and Y are arbitrary numbers) is described, unless otherwise specified, it includes the meaning of "X or more and Y or less" and "preferably greater than X" or "preferably less than Y". In addition, when "X or more" (X is an arbitrary number) is described, it includes the meaning of "preferably greater than X" unless otherwise specified, and when "Y or less" (Y is an arbitrary number) is described, it includes the meaning of "preferably less than Y" unless otherwise specified.

[0127] [Separator]

[0128] The partition member of the present invention has a thickness direction and a plane direction perpendicular to the thickness direction, and partitions the cells in the thickness direction.

[0129] One embodiment of the partition member of the present invention includes an outer packaging body and an inner packaging body covered by the outer packaging body. The inner packaging body preferably further includes a holding portion that contacts and holds at least a portion of the outer peripheral end surface of the composition portion in the plane direction.

[0130] It should be noted that the inner package may not have a holding portion.

[0131] Figure 1 This is a schematic cross-sectional view showing an embodiment of an example of the partition member of the present invention.

[0132] The partition member 1 shown in the figure is a flat plate-shaped member, which is formed by accommodating an inner package 2 in an outer package 6 that is sealed around the periphery. The inner package 2 is formed by accommodating and retaining a composition part 4 in a retaining part 3, and the retaining part 3 is provided in a frame shape at the outer peripheral part in the surface direction. Figure 1 In the example shown, the thickness of the holding portion 3 is set to be larger than the thickness of the composition portion 4 , and the upper portion of the composition portion 4 surrounded by the holding portion 3 serves as the void layer 5 .

[0133] The partition member 1 is placed between the cells 200 so as to contact the surface of the cells 200 along a plane direction perpendicular to the thickness direction thereof.

[0134] When the battery pack is assembled by placing the partition member 1 between the cells 200, external pressure is applied to the partition member 1 to constrain the rows of cells 200. However, the external pressure is mainly absorbed by the compression and deformation of the retaining portion 3 and the void layer 5. Figure 1 As indicated by the dashed line in FIG. 2 , when the cell 200 expands, the combination portion 4 is mainly deformed, and thereby the partition member 1 disposed between the cells 200 is deformed following the change in the spacing in the thickness direction.

[0135] Hereinafter, each member constituting the partition member will be described.

[0136] <Inner packaging>

[0137] The inner package includes at least one of a combining portion and a holding portion.

[0138] The inner package preferably does not become suspended even when immersed in water after being stored at 25°C for 24 hours. "Not suspended" means that the composition is neither dissolved nor dispersed in water due to physical and / or chemical interactions between the components, and the shape of the composition is unlikely to change.

[0139] (Composition Department)

[0140] In the partition member according to the embodiment, the composition portion functions as a thermal resistance variable layer or a phase change layer.

[0141] The variable thermal resistance layer is a layer that, when a partition member is placed between the cells, functions normally as a thermally conductive material that efficiently transfers heat released by adjacent cells to the adjacent cells. Furthermore, when the cells reach abnormally high temperatures, the layer functions as a thermally insulating material that exerts insulating properties to control the transfer of heat to the adjacent cells.

[0142] The phase change layer undergoes a phase change with an endothermic reaction when the temperature rises or the pressure drops. When the cell transitions from normal to abnormal state, the temperature rise around the separator causes a phase change with an endothermic reaction, thereby mitigating the sudden temperature rise.

[0143] (Thermal resistance variable layer)

[0144] The composition portion may be a variable thermal resistance layer. The variable thermal resistance material is a material whose thermal resistance after heating increases relative to the thermal resistance before heating.

[0145] When the temperature of the thermal resistance variable material is increased to 100° C. at a rate of 1.7° C. / min, the thermal resistance after heating is preferably increased to 1.5 times or more, more preferably to 1.7 times or more, relative to the thermal resistance before heating.

[0146] The thermal resistance variable material has low thermal resistance in normal conditions, allowing heat generated by adjacent cells to be efficiently transferred to adjacent cells. In abnormal conditions, the thermal resistance becomes high, preventing heat from being transferred to adjacent cells.

[0147] The thermal resistance variable material may be a material whose thermal resistance changes. For example, a material such as a foam material may be used whose volume change due to temperature increase increases the thermal resistance. Alternatively, a material whose thermal resistance changes due to phase change due to temperature increase may be used.

[0148] As a different method from the above, there is a method in which the aforementioned thermal resistance changing material uses two or more materials with different thermal resistances. It is possible to design in a way that a specific material presents a dominant thermal resistance at a specific time. For example, a high thermal conductivity material and a low thermal conductivity material can be used, and the design is carried out in a way that the low thermal conductivity material is covered or impregnated with the high thermal conductivity material. If the high thermal conductivity material melts, evaporates or sublimates at a specific temperature, the thermal conductivity of the low thermal conductivity material becomes dominant. In this case, the thermal resistance of the partition member at a specific temperature is reduced. Utilizing this mechanism, it is possible to control the temperature at which the thermal resistance of the partition member increases and the thermal resistance before and after its change.

[0149] In the aforementioned embodiment, it is preferable that the low thermal conductive material contains at least one of inorganic particles and inorganic fibers described below, and the high thermal conductive material contains a liquid or gel described below.

[0150] (Phase change layer)

[0151] The composite portion may be a phase change layer. A phase change material is a material that undergoes a phase change accompanied by an endothermic reaction when the temperature is increased.

[0152] The phase change material may be a material that undergoes irreversible phase change at a predetermined temperature, or a material that undergoes reversible phase change at a predetermined temperature.

[0153] The phase change material preferably undergoes a phase change accompanied by an endothermic reaction at a predetermined temperature because the phase change accompanied by the endothermic reaction can mitigate a rapid temperature rise when the ambient temperature rises from normal to abnormal conditions.

[0154] As the phase change material, a known phase change material such as an endothermic polymer can be used.

[0155] As a different method from the above, there is a method of combining two or more materials with different phase change temperatures in the aforementioned phase change material. It can be designed in a way that a specific material undergoes an endothermic reaction at a specific time. For example, a high-temperature phase change material and a low-temperature phase change material can be used, and the low-temperature phase change material can be designed in a way that is covered or impregnated with the high-temperature phase change material. If the low-temperature phase change material melts, evaporates or sublimates at a specific temperature, the endothermic reaction associated with the phase change can be utilized. In this case, the rapid temperature rise of the partition member in the specific temperature range is reduced. Using this mechanism, the temperature of the partition member can be controlled to reduce the rapid temperature rise.

[0156] As the aforementioned embodiment, it is preferable that the high-temperature phase change material includes at least one of inorganic particles and inorganic fibers described below, and the low-temperature phase change material includes a liquid or gel described below.

[0157] (Inorganic particles and inorganic fibers)

[0158] The inorganic particles are not particularly limited as long as they can exhibit the effects of the present invention, and examples thereof include silica, alumina, calcium silicate, zeolite, diatomaceous earth, Shirasu Balloon, clay minerals, vermiculite, mica, cement, pearlite, fumed silica, and aerosols. Among these, silica particles, alumina particles, calcium silicate, zeolite, and vermiculite are preferred. From the perspective of easily containing more liquid within and between the particles, calcium silicate and zeolite are more preferred, and calcium silicate is even more preferred.

[0159] Among the types of calcium silicate, xonotlite, tobermorite, wollastonite, and leucoglossite are preferred, and leucoglossite is more preferred. Leucoglossite, which has a petal-like structure, maintains a porous structure even during compression deformation and therefore has excellent water retention. Clay minerals are mainly magnesium silicate (including talc and sepiolite), montmorillonite, and kaolinite. The particle size of the inorganic particles is preferably a particle size of 1 / 5 or less of the thickness of the composition. These inorganic particles can be used alone or in a mixed state.

[0160] As inorganic fibers, there is no particular limitation as long as they are within the scope of the present invention, and examples thereof include glass fibers, alumina fibers, rock wool, etc. As the fiber system of the inorganic fibers, a fiber diameter of 1 / 5 or less of the thickness of the composition part is preferred. These inorganic fibers can be used alone or in a mixed state.

[0161] (liquid)

[0162] The boiling point of the liquid is preferably 50 to 200°C, more preferably 80 to 180°C.

[0163] As liquid, for example, it is preferred to include at least one selected from the group consisting of water, alcohols, esters, ethers, ketones, hydrocarbons, fluorine compounds and silicone oils. They can be only one kind or can be used in the form of a mixture of two or more. The liquid can include additives such as a substance (antifreeze agent) imparting antifreeze properties, a preservative, a pH regulator, etc. By imparting antifreeze properties, it is possible to avoid the outer packaging from being damaged by the expansion associated with freezing. In addition, by adding a pH regulator, the pH of the liquid can be reduced due to changes in the components dissolved from the powdered inorganic substance, the powdered inorganic substance, the outer packaging, and the possibility of the powdered inorganic substance, the outer packaging, and the liquid (water) itself being deteriorated. The substance contained in the water is not limited thereto and can be added as needed.

[0164] The composition part preferably contains the remaining water in addition to the hydration water of the hydration product described later.

[0165] (Binder)

[0166] From the perspective of improving the shape retention of the aforementioned composition part, the aforementioned composition part preferably further comprises a binder. The binder is not particularly limited as long as it solidifies the composition part, and known materials can be used. From the perspective of using the aforementioned liquid in combination, the binder preferably comprises a material that solidifies by a hydration reaction.

[0167] The material that solidifies by a hydration reaction is not particularly limited, and examples thereof include gypsum and hydraulic materials.

[0168] Examples of gypsum include natural gypsums such as dihydrate gypsum and hemihydrate gypsum, and chemical gypsums such as phosphate gypsum, flue gas desulfurization gypsum, titanium gypsum, smelting gypsum, and hydrofluoric acid gypsum. Of these, natural gypsum is preferred, and calcium sulfate is more preferred.

[0169] Examples of the hydraulic material include Portland cement, mixed cement, alumina cement, quicklime, slaked lime, and mixtures thereof, of which alumina cement is preferred.

[0170] From the viewpoint of controlling the curing time, two or more materials that cure by a hydration reaction may be mixed, and preferably gypsum and a hydraulic material are mixed.

[0171] In one embodiment, the composition is preferably a composition that becomes solid when dried for 24 hours at 25° C. “Solid” in this specification means a state in which the viscosity at 25° C. measured by a Brookfield viscometer is 200 Pa·s or more.

[0172] In the prior art, when cells are separated by a separator and the cells reach abnormally high temperatures, the composite portion may fluidize due to heat release, causing the outer packaging to rupture and escape. If the composite portion escapes from the outer packaging, the thermal insulation performance of the separator is impaired. In contrast, the separator described in one embodiment includes a binder in the composite portion, resulting in excellent shape stability even at high temperatures. Therefore, even when the cells reach abnormally high temperatures, the composite portion is less likely to fluidize, maintaining stable thermal insulation performance at high temperatures.

[0173] (Hydration product)

[0174] The composition part preferably includes a hydration product. That is, it is preferred that the composition part includes a hydration product obtained by using a material that solidifies by a hydration reaction as a binder and solidifying the material.

[0175] By making the composition partially contain hydration products, the energy required for the vaporization of hydrated water can be utilized. Therefore, the time from when the water contained in the inner packaging reaches the boiling point to when it is completely volatilized, the so-called plateau time, becomes longer, which makes it easier to suppress the heat transfer when the single battery reaches abnormally high temperature.

[0176] The content of the binder in the composition is preferably 1 to 70% by mass, more preferably 20 to 50% by mass, relative to the total mass (100% by mass) of the composition.

[0177] When gypsum and a hydraulic material are used in combination as a binder, the mixture preferably contains 15 to 40 mass% of gypsum and 5 to 30 mass% of the hydraulic material relative to the total mass (100 mass%) of the mixture.

[0178] The composition preferably contains a liquid in addition to the water of hydration of the hydration product. By including the remaining liquid in addition to the water of hydration, the plateau time is extended, thereby further improving the effect of suppressing heat propagation when the cell reaches abnormally high temperatures.

[0179] In one embodiment of the composition section, the composition includes a paste and a binder, wherein the paste includes at least one of inorganic particles and inorganic fibers, and the remainder includes a liquid.

[0180] The content of at least one of the inorganic particles and the inorganic fibers is preferably 1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass, relative to 100% by mass of the paste.

[0181] The paste preferably contains 1 to 70% by mass of the liquid relative to 100% by mass of the paste, more preferably 1 to 50% by mass, and even more preferably 1 to 30% by mass.

[0182] The ratio of the content of at least one of the inorganic particles and the inorganic fibers to the content of the binder is preferably 1 to 10, more preferably 1 to 7, and more preferably 1 to 5.

[0183] The thickness of the composite portion is not particularly limited, but is preferably less than the thickness of the holding portion described later, and more preferably less than the thickness of the holding portion. By making the thickness of the composite portion less than the thickness of the holding portion, one or both sides of the thickness direction of the composite portion held by the holding portion form a void layer. By having this void layer, the composite portion held by the holding portion is less likely to collapse, thereby ensuring shape retention.

[0184] The viscosity of the composition used in the composition section before curing, as measured with a Brookfield viscometer at 25°C, is preferably 10 to 200 Pa·s, more preferably 15 to 100 Pa·s. When the viscosity of the composition is at least the lower limit, excellent shape retention is achieved. When the viscosity of the composition is at most the upper limit, excellent handling is achieved.

[0185] The viscosity of the cured composition or the binder-free composition used in the composition portion, as measured with a Brookfield viscometer at 25°C, is preferably 200 Pa·s or more, more preferably 500 Pa·s or more. When the viscosity of the composition is at least the lower limit, excellent shape retention is achieved.

[0186] (Maintaining part)

[0187] The retaining portion of the inner packaging body is the part within which the aforementioned composite portion resides, accommodates, and retains. Furthermore, when assembling the battery pack by sandwiching the separator member between the cells, the following operation is performed: pressure is applied between the cells to clamp the separator member. With the cells and separator member stacked side by side within the housing, the surrounding area is constrained with a band-like member to adjust the overall length of the battery pack. The retaining portion also serves to buffer the pressing force applied to the surface of the cells when the separator member is sandwiched between the cells during this assembly process. The retaining portion is preferably designed to compress and deform when subjected to external force.

[0188] One embodiment of the holding portion includes a thermoplastic resin.

[0189] Examples of thermoplastic resins include olefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and polystyrene (PS). Silicone rubber and its foams can also be used.

[0190] Among these, olefin resins are preferred, and polypropylene is particularly preferred from the viewpoints of versatility, cost, etc. In addition, these resins may contain heat-resistant fillers such as alumina particles and glass fibers.

[0191] The retaining portion is in contact with at least a portion of the composite portion. The retaining portion may be arranged in contact with the composite portion's outer peripheral end surface in the surface direction, covering a portion or multiple regions of the composite portion's outer peripheral end surface in the surface direction, or in contact with the composite portion's outer peripheral end surface in the entirety of the aforementioned outer peripheral end surface. The retaining portion may be arranged in contact with a portion or the entirety of a surface in the thickness direction of the composite portion.

[0192] For example, the retaining portion may be provided on either side or both sides of the composite portion, or may be provided along the entire periphery of the composite portion, or may be provided locally on a portion of the periphery of the composite portion. In these cases, the retaining portion is configured such that the area of ​​the composite portion in contact with the retaining portion is larger than the area not in contact with the retaining portion.

[0193] In the partition member 1, as Figure 2A and Figure 3A As shown, the holding portion 3 includes a frame-shaped outer wall portion 3a that contacts the entire outer peripheral end surface of the composite portion 4 in the surface direction and extends in the thickness direction. A space having a depth in the thickness direction is provided inside the outer wall portion 3a. In this example, the outer wall portion 3a is formed in a substantially rectangular shape so as to surround the periphery of the composite portion 4 in the surface direction, but the present invention is not limited thereto.

[0194] The length in the thickness direction of the retaining portion 3 having a space with depth in the thickness direction, that is, the length in the thickness direction (t3) of the outer wall portion 3a in contact with the outer peripheral end surface of the composition portion 4 is not particularly limited, and is preferably greater than the thickness (t4) of the composition portion 4, and more preferably exceeds the length (t4) in the thickness direction of the composition portion 4.

[0195] exist Figure 1 and Figure 2A In the example shown, the length (t3) of the retaining portion 3 in the thickness direction is greater than the length (t4) of the composition portion 4 in the thickness direction. When the retaining portion 3 accommodates and retains the composition portion 4, both ends of the outer wall portion 3a of the retaining portion 3 in the thickness direction are in contact with the outer packaging body 6, and a gap layer 5 surrounded by the retaining portion 3 is ensured on the upper surface side of the composition portion 4.

[0196] The void layer 5 functions to cushion and absorb the pressing force applied across the surfaces of the cells 200 when the battery pack is assembled by placing the separator members 1 between the cells 200, as well as the pressing force applied directly from the surfaces of the cells 200 when the cells 200 expand. The presence of the void layer 5 prevents the composite portion 4 housed within the retaining portion 3 from collapsing, ensuring shape retention. Furthermore, the presence of the void layer 5 decouples the contributions of the retaining portion and the composite portion to compression under external pressure.

[0197] The inner packaging body in which the length of the retaining part in the thickness direction is greater than the length of the composition part in the thickness direction is assembled by the composition part that controls heat transfer and the retaining part that controls compressibility, thereby improving the following effects: its shape stability is excellent even at high temperatures and it is not easy to break, and the single battery stably shows excellent thermal insulation when reaching high temperatures.

[0198] In an inner packaging body where the length of the retaining portion in the thickness direction is greater than the length of the composite portion in the thickness direction, only the retaining portion is compressed up to a certain external pressure. When the external pressure is greater than or equal to the certain external pressure, both the retaining portion and the composite portion are compressed. By separating the contribution of compression under external pressure, a partition member with desired compression characteristics can be designed.

[0199] <Outer packaging>

[0200] The outer packaging has a sealed peripheral portion, and the inner packaging is housed within the sealed internal space. The outer packaging is flexible and can deform in response to the expansion of the cells. Furthermore, the outer packaging is capable of returning to its original state when the cells shrink. Specifically, with separators positioned between the cells, the outer packaging compresses to absorb the expansion during charging, and returns to its original state when the cells shrink during discharge.

[0201] The outer packaging body can be formed using a resin sheet, a resin film, etc. For example, the composition portion and the holding portion can be contained by sandwiching and accommodating the composition portion and the holding portion between two or two folded resin sheets or resin films, or by heat-melting and / or bonding the peripheral edges of the outer packaging body where the two resin sheets or resin films are in contact, thereby enabling the composition portion and the holding portion to be sealed and contained therein.

[0202] In addition, the outer packaging can be made of, for example, resin or metal. Outer packaging obtained by laminating metal foil and resin is preferred due to its high heat resistance and strength. The metal foil and resin laminate is preferably a laminate comprising three or more layers, including a resin layer, a metal foil layer, and a resin sealant layer.

[0203] The metal constituting the metal foil is preferably at least one of aluminum, copper, tin, nickel, stainless steel, lead, tin-lead alloy, bronze, silver, iridium, and phosphor bronze. Specifically, aluminum foil, copper foil, tin foil, nickel foil, stainless steel foil, lead foil, tin-lead alloy foil, bronze foil, silver foil, iridium foil, and phosphor bronze foil are examples. In particular, aluminum foil, copper foil, and nickel foil are preferred, with aluminum foil being even more preferred.

[0204] The resin may be at least one of a thermosetting resin and a thermoplastic resin, with a thermoplastic resin being particularly preferred. Examples of the resin include polyethylene, polypropylene, polystyrene, nylon, acrylic resins, epoxy resins, polyurethane, polyetheretherketone, polyethylene terephthalate, polyphenylene sulfide, polycarbonate, and aramid. At least one selected from polypropylene, nylon, and polyethylene terephthalate is particularly preferred.

[0205] The thickness of the outer packaging is not particularly limited, but is, for example, 5 to 200 μm. In the case of a laminate, the metal foil can be 3 to 50 μm thick, and the resin layer can be 2 to 150 μm thick. This allows the metal foil to exhibit its heat resistance and low water vapor permeability, while the resin layer can enhance sealing properties.

[0206] As described above, the outer packaging body can be provided by joining the peripheral portions of two outer packaging bodies into a ring shape by heat-melting and / or bonding, so that the composite portion and the retaining portion are sealed (sealed) within the outer packaging body. Alternatively, one outer packaging body can be bent and the peripheral portions can be joined by heat-melting and / or bonding, so that the composite portion and the retaining portion are sealed.

[0207] <Deformation Characteristics>

[0208] During manufacturing, pressure is applied to the individual cells, constraining the battery pack. Pressure is also applied due to electrode expansion during charging and gas generation from the electrolyte during charge and discharge. One embodiment of the present invention provides a separator member having specific deformation properties that can withstand these external pressures.

[0209] Here, the “deformation ratio” refers to the ratio of the thickness when external pressure is applied in the thickness direction under a predetermined pressure to the thickness when the external pressure is 0 MPa.

[0210] In one embodiment, when an external pressure of 0.2 MPa is applied to the partition member in its thickness direction, the deformation rate in the same direction relative to the shape before the external pressure is 6.0% or more, preferably 6.0 to 60%, and more preferably 10 to 60%.

[0211] In one embodiment, when an external pressure of 1.0 MPa is applied to the partition member in its thickness direction, the deformation rate in the same direction relative to the shape before the external pressure is applied is 12% or more, preferably 12 to 90%, more preferably 12 to 85%, and even more preferably 15 to 75%.

[0212] In one embodiment, when an external pressure of 0.2 MPa is applied to the partition member in the thickness direction, the deformation rate (X) in the same direction is 6.0 to 60%, and when an external pressure of 1 MPa is applied in the same direction, the deformation rate (Y) in the same direction is 12 to 90%.

[0213] In a certain embodiment, the difference (XY) between the deformation rate (X) in the same direction when an external pressure of 0.2 MPa is applied in the thickness direction of the partition member and the deformation rate (Y) in the same direction when an external pressure of 1 MPa is applied in the same direction is 3.0 to 60%, preferably 20 to 55%, and more preferably 35 to 50%.

[0214] In addition, in a certain embodiment, the ratio (Y / X) of the deformation rate (Y) in the same direction when an external pressure of 1 MPa is applied in the same direction relative to the deformation rate (X) in the same direction when an external pressure of 0.2 MPa is applied in the thickness direction of the partition member is 0.10 to 2.0, preferably 0.10 to 0.50, and more preferably 0.10 to 0.25.

[0215] The partition member preferably does not rupture even when pressurized at 1.0 MPa in the thickness direction, and the inner body remains contained within the outer body. Furthermore, the partition member preferably does not rupture even when heated to 100° C. at 1.7° C. / min, and the inner body remains contained within the outer body.

[0216] The thermal conductivity of the partition member in the thickness direction at an average surface temperature of 45°C is preferably 0.20 [W / (m·K)] or higher, and more preferably 0.25 to 5.0 [W / (m·K)]. When the thermal conductivity is at least the lower limit, the partition member can more easily function as a thermally conductive material that efficiently conducts heat generated by the cells during normal operation to adjacent cells sandwiching the partition member.

[0217] Furthermore, the thermal conductivity is preferably measured under the condition that the composition is partially in contact with the outer packaging.

[0218] The thermal conductivity of the partition member at 45°C was measured simultaneously with the partition member by heating a thermally resistive sheet (previously evaluated for thermal conductivity) to 45°C. The thermal conductivity of the partition member was calculated using the equation "Δt1 x thermal conductivity of thermally resistive sheet / Δt2," assuming the temperature difference between the front and back of the thermally resistive sheet and the front and back of the partition member were Δt1 and Δt2, respectively. The difference in thickness between the partition member and the thermally resistive sheet was appropriately converted.

[0219] The thermal conductivity of the partition member at an average surface temperature of 200°C is preferably reduced to 90% or less, more preferably to 80% or less, even more preferably to 70% or less, particularly preferably to 60% or less, and most preferably to 50% or less, relative to the thermal conductivity of the partition member at an average surface temperature of 25°C. This facilitates the function of the thermal insulation material, which, when a cell reaches abnormally high temperatures, exhibits thermal insulation properties and controls heat transfer to adjacent cells.

[0220] The thermal conductivity of the partition member decreases due to the vaporization of hydration water and other liquids contained in the composition portion.

[0221] <Varied Example>

[0222] The partition member described in the embodiment is not limited to the partition member 1 described above.

[0223] For example, Figure 2B As shown, the retaining portion 3 can include a frame-shaped outer wall portion 3a and a bottom 3b, wherein the frame-shaped outer wall portion 3a contacts the entire outer peripheral end surface of the surface direction of the composition portion 4 and surrounds the composition portion 4, and the bottom 3b blocks an opening of the frame-shaped outer wall portion 3a.

[0224] Figure 2B In the example of inner packaging body 2 shown, the retaining portion 3, which is a bottomed cylindrical portion with an open top, has a recessed portion inside, which accommodates and retains the composition portion 4. In this case, the length of the outer wall portion 3a in the thickness direction is also made greater than the length of the composition portion 4 in the thickness direction. When the retaining portion 3 accommodates and retains the composition portion 4, a void layer 5 surrounded by the retaining portion 3 can be ensured on the upper side of the composition portion 4.

[0225] Furthermore, if Figure 2C As shown, the inner packaging body 2 has a retaining portion 3 composed only of a frame-shaped outer wall portion 3a that is in contact with the entire peripheral end face in the surface direction of the composition portion 4, and can be arranged in a manner that ensures a gap layer 5 on both sides of the thickness direction of the composition portion 4 on the inner side of the outer wall portion 3a.

[0226] In one embodiment, the holding portion is preferably configured such that the contact area between the outer package and the inner package increases as the external pressure applied to the partition member increases. Figure 1 and Figures 2A to 2C The inner package body 2 having the void layer 5 shown in FIG. 1 is an example thereof.

[0227] The ratio of the contact area between the outer package and the inner package at an external pressure of 0.2 MPa to the contact area between the outer package and the inner package at an external pressure of 0 MPa is preferably 1.0-200, more preferably 2.0-150, and even more preferably 2.5-100.

[0228] It should be noted that, in Figure 1 and Figures 2A to 2C The illustrated void layer 5 houses a compressible member that cushions and absorbs external pressure applied to the inner packaging body 2 .

[0229] In a certain embodiment, the holding portion is preferably configured in a lattice shape. Here, "lattice shape" includes: when the inner packaging body 2 is observed from its thickness direction, Figure 3A As shown, a substantially rectangular frame-shaped holding portion 3 surrounds a shape of the surrounding composition portion 4; as Figure 3B As shown, the plurality of composition parts 4 are surrounded by the holding part 3 divided into a plurality of substantially rectangular shapes in the vertical and horizontal directions.

[0230] exist Figure 3B The inner packaging body 2 of the example shown includes a retaining portion 3 having a frame-shaped outer wall portion 3a and a grid-shaped partition wall 3c that divides the inner space of the outer wall portion 3a into a plurality of first spaces, and a composition portion 4 is accommodated and retained in each first space.

[0231] In one embodiment, the ratio of the area of ​​the holding portion to the total area of ​​the composition portion and the holding portion when viewed from above in the thickness direction is preferably 0.01 to 0.50, more preferably 0.01 to 0.30, and even more preferably 0.10 to 0.30.

[0232] (Tray-shaped holding portion)

[0233] A preferred example of the holding portion is a tray-shaped member having one or more recessed portions (hereinafter also referred to as a "tray-shaped member"). That is, the holding portion preferably has a recessed portion as a space having a depth in the thickness direction. Figure 2B The holding portion 3 shown in the figure, which includes a frame-shaped outer wall portion 3 a and a bottom portion 3 b that closes one opening of the frame-shaped outer wall portion 3 a, is an example thereof.

[0234] As a tray-like member, such as Figure 4As shown in FIG, a holding portion 3 having a frame-shaped outer wall portion 3a, a bottom portion 3b that blocks one opening of the frame-shaped outer wall portion 3a, and a lattice-shaped partition wall 3c that divides the inner space of the outer wall portion 3a into a plurality of first spaces (recesses) can also be illustrated. In this example, the composite portion 4 is held in each recess, but a void layer 5 can be ensured on the opening side of the composite portion 4 in each recess.

[0235] By configuring the holding portion to be in the shape of a tray having a recess, the process of accommodating and holding the aforementioned composite portion within the recess can be simplified. Furthermore, the use of a tray-shaped member is preferred because it enhances the ability to control the compression characteristics of the partition member accommodating the heat-resistant composite portion.

[0236] As described above, the tray-shaped member has the function of accommodating and filling the composition portion for controlling heat transfer in the recessed portion thereof and retaining it, and also has the function of serving as a layer for controlling compression characteristics.

[0237] It should be noted that in the present invention, even when the composition portion is filled into the tray-shaped member, the tray-shaped member is defined as a layer for controlling compression characteristics, and the composition portion filled into its recessed portion is defined as a layer for controlling heat conduction caused by heat release from the single cells.

[0238] In addition, it is not essential to hold the composition portion in all the recessed portions provided in the tray-shaped member.

[0239] The size of the recess of the tray-shaped member is not particularly limited as long as it is within the range that the effect of the present invention is exerted. The ratio of the area of ​​the recess when the tray-shaped member is viewed from above in the thickness direction to the total area of ​​the tray-shaped member is preferably 1 to 99%, more preferably 3 to 95%, and even more preferably 5 to 90%. If the area ratio of the aforementioned recess is above the aforementioned lower limit, a sufficient amount of the composition part can be maintained in the recess, thereby maintaining the control of heat transfer and the insulation effect. On the other hand, if the area ratio of the aforementioned recess is below the aforementioned upper limit, sufficient strength of the tray-shaped member can be ensured, and good compressibility can be obtained. In addition, if the area ratio of the aforementioned recess is below the aforementioned upper limit, when external pressure is applied to the partition member, the internal pressure of the partition member is not easy to rise, and the pressure resistance of the partition member becomes better.

[0240] The area of ​​the recessed portion refers to the opening area of ​​the recessed portion. In addition, when the tray-shaped member has a plurality of recessed portions, the area ratio of the recessed portions refers to the ratio of the total area of ​​the plurality of recessed portions to the total area of ​​the tray-shaped member.

[0241] The depth of the recess is not particularly limited, but is preferably 0.1 to 20 mm, more preferably 0.5 to 10 mm, and even more preferably 0.8 to 7 mm. If the depth of the recess is above the lower limit, a sufficient amount of the composition portion can be retained within the recess, thereby maintaining heat transfer control and thermal insulation effects. On the other hand, if the depth of the recess is below the upper limit, sufficient strength of the tray-shaped member can be ensured, good compressibility can be achieved, and the battery pack can be made more compact. Furthermore, if the depth is below the upper limit, more expansion of the single cells can be absorbed.

[0242] There is no particular limitation on the shape of the recess, and it can be Figure 3A and Figure 3B The rectangle shown in the figure may also be a square, a rhombus or other rectangle, or may be a circle, an ellipse, a honeycomb or the like. In addition, when there are a plurality of recesses, the shapes of the plurality of recesses may all be the same shape or a combination of different shapes.

[0243] The thickness (sheet thickness) of the tray-shaped member is preferably 50 to 1000 μm, more preferably 100 to 500 μm. If the thickness of the tray-shaped member is at least the lower limit, sufficient compressibility can be achieved. On the other hand, if the depth of the recess is at most the upper limit, the thickness of the partition member can be reduced, increasing the proportion of cells occupied, and improving energy efficiency. This also contributes to a more compact battery pack.

[0244] It should be noted that the thickness of the tray-shaped member refers to the maximum thickness of the tray-shaped member. Figure 2B and Figure 4 In the case of the holding portion 3 exemplified in FIG, the thickness of the tray-shaped member corresponds to the length of the outer wall portion 3 a in the thickness direction.

[0245] The recessed portion may have through holes along the thickness direction of the component. By having through holes, more composite parts can be retained, and the control of heat transfer and the insulation effect become higher. The ratio of the area occupied by the through holes relative to the area of ​​the recessed portion when the tray-shaped component is observed from the thickness direction is preferably about 10 to 100%, more preferably 50 to 90%. If the ratio of the area occupied by the through holes is above the aforementioned lower limit, a higher control of heat transfer and insulation effect can be obtained. If the ratio of the area occupied by the through holes is below the aforementioned upper limit, the retention of the composite part in the tray-shaped component becomes good.

[0246] When the spaces having depth in the thickness direction of the retaining portion are divided into a grid pattern to form a plurality of first spaces, a second space can be formed to partially connect adjacent first spaces to each other, thereby partially connecting the composite parts held by each first space. More specifically, in the case of a tray-shaped member having a plurality of recessed portions (first spaces), a lowered portion can be provided in the partitions between the recessed portions, and the space above the lowered portion can be used as the second space for partially connecting the composite parts to each other.

[0247] By partially connecting the composite sections held in adjacent first spaces using the second space, the shape retention of the composite sections is improved. When cells reach abnormally high temperatures, the tray-shaped member may melt due to the heat, losing its shape. However, by connecting the composite sections held in the recesses (first spaces) using the second space, the tray-shaped member maintains its shape even when it melts, maintaining thermal insulation performance for a longer period of time.

[0248] For example, Figures 5A to 5C As shown in FIG. 1 , the holding portion (tray-shaped member) 3 may be formed as follows, namely, the holding portion includes a frame-shaped outer wall portion 3a surrounding the composition portion 4, a bottom portion 3b closing an opening of the frame-shaped outer wall portion 3a, and a grid-shaped partition wall 3c dividing the inner space of the frame-shaped outer wall portion 3a into a plurality of recessed portions (first spaces), wherein the partition wall 3c has a low portion 3d in a local area. In the inner packaging body 2 having the holding portion 3, as shown in FIG. Figure 5B As shown, the lower portion 3d of the partition wall 3c within the inner space of the outer wall portion 3a of the retaining portion 3 forms a second space. The composite portions 2 held by each recess are partially connected to each other at the lower portion 3d. In the aforementioned embodiment, the composite portions are connected at the lower portion of the partition wall, so the lower portion of the partition wall does not appear on the surface of the composite portion when viewed from above in the thickness direction.

[0249] Alternatively, a cavity may be formed in the partition wall so that the composite portions are connected via the cavity. In the aforementioned embodiment, the partition wall exists above the connected portion of the composite portion, so that the partition wall appears on the surface of the composite portion when viewed from above in the thickness direction.

[0250] The holding portion having the recess including the first space and the second space is not limited to Figures 5A to 5C For example, Figure 6 As shown, when viewed from above in the thickness direction, the cross-shaped portion including the lattice points in the lattice-shaped partition wall 3c is set as the low-position portion 3d, and the respective composition portions 4 held by the four recesses around the low-position portion 3d are connected to each other on the low-position portion 3d.

[0251] When viewing the tray-shaped member from the thickness direction, the ratio of the area of ​​the composition portion to the total area of ​​the tray-shaped member and the composition portion is preferably 50 to 100 volume%, more preferably 55 to 95 volume%, further preferably 60 to 90 volume%, and particularly preferably 65 to 90 volume%. If the area ratio of the composition portion is above the lower limit, even when the composition portion is compressed due to the expansion of the single cell, it is easy to ensure a gap within the inner package, and the remaining liquid discharged as the composition portion is compressed easily escapes into this gap, thus making the partition member less likely to rupture. If the area ratio of the composition portion is below the upper limit, it is possible to achieve both high rupture pressure and compressibility.

[0252] In a tray-shaped component whose top view shape in the thickness direction is roughly rectangular, the thickness direction is set as the Z-axis direction, the direction parallel to one side of the outer periphery of the tray-shaped component in the surface direction is set as the X-axis direction, and the direction orthogonal to the X-axis direction in the surface direction is set as the Y-axis direction to define the XYZ coordinate axis.

[0253] In this case, in a cross-section of the tray-shaped member obtained by cutting the tray-shaped member along an XZ plane so as to pass through the combined portion, the ratio of the area occupied by the space relative to the area of ​​the smallest rectangle surrounding the tray-shaped member is preferably 15% or less, more preferably 12% or less, even more preferably 10% or less, particularly preferably 7% or less, and most preferably 5% or less. When the tray-shaped member is provided with a third space, the lower limit of the ratio of the area occupied by the space relative to the area of ​​the smallest rectangle surrounding the tray-shaped member is preferably 0.1% or more, preferably 0.5% or more, and preferably 1% or more.

[0254] Furthermore, in a cross-section of the tray-shaped member obtained by cutting the tray-shaped member along a YZ plane so as to pass through the combined portion, the ratio of the area occupied by the space relative to the area of ​​the smallest rectangle surrounding the tray-shaped member is preferably 15% or less, more preferably 12% or less, even more preferably 10% or less, particularly preferably 7% or less, and most preferably 5% or less. When the tray-shaped member is provided with a third space, the lower limit of the ratio of the area occupied by the space relative to the area of ​​the smallest rectangle surrounding the tray-shaped member is preferably 0.1% or more, preferably 0.5% or more, and preferably 1% or more.

[0255] If the ratio of the area occupied by the aforementioned space in the cross-section taken along the XZ and YZ planes is at or above the aforementioned lower limit, even when the composite portion is compressed due to expansion of the cells, a gap can be easily maintained within the inner package. Excess liquid expelled as the composite portion is compressed can easily escape into this gap, making the partition member less likely to rupture. If the ratio of the area occupied by the aforementioned space in the cross-section taken along the XZ and YZ planes is at or below the aforementioned upper limit, it is easier to achieve both the resistance to rupture and the properties imparted to the composite portion.

[0256] It should be noted that the "space in the cross-section of the XZ plane and the YZ plane" refers to a space where neither the tray-shaped member nor the combination part exists, including a void layer that may be formed on the combination part in the recessed portion of the tray-shaped member, and / or the space within the recessed strip when a recessed strip is formed in a portion corresponding to the recessed portion on the bottom side of the tray-shaped member.

[0257] Examples of the tray-shaped member having concave lines on the bottom side include: Figure 7 The holding portion 3 shown. In the holding portion 3 of this example, the partition wall 3c is composed of two side walls rising from the bottom 3b between the two recesses and a connecting portion connecting the upper portions of these side walls to each other, and a groove 3e opened on the bottom 3b side is formed between these side walls. On the back side of the holding portion 3, a third space is provided in the groove e between the adjacent first spaces. In this example, the "space in the cross section of the XZ plane and the YZ plane" includes the void layer 5 on the composite portion 4 and the third space in the groove 3e. In other words, in the cross section of the XZ plane and the YZ plane, the ratio of the area occupied by the void layer 5 and the space in the groove 3e to the area of ​​the minimum rectangle 7 surrounding the holding portion (tray-shaped member) 3 can be controlled to be within the aforementioned range.

[0258] In the case where the holding portion is a tray-shaped member having a third space on the back side, when assuming the smallest rectangular parallelepiped that can accommodate the holding portion, the ratio of the volume of the third space to the volume of the rectangular parallelepiped (100 volume %) is preferably 0.1 to 15 volume %, more preferably 0.1 to 12 volume %, further preferably 0.1 to 10 volume %, particularly preferably 0.1 to 7 volume %, and most preferably 0.1 to 5 volume . If the ratio of the volume of the aforementioned third space is above the aforementioned lower limit, even if the tray-shaped member melts, the composite portion is easy to maintain its shape and can maintain thermal insulation performance for a longer period of time. If the volume ratio of the aforementioned third space is below the aforementioned upper limit, it is easy to maintain a sufficient amount of the composite portion and it is easy to give full play to the control of heat transfer and the thermal insulation effect.

[0259] The method for manufacturing the tray-shaped retaining portion is not particularly limited, and suitable methods include: pre-fabricating a resin sheet such as polypropylene and performing vacuum forming or press molding; pre-fabricating a mold of a tray-shaped member and injecting molten resin into it into the mold; etc.

[0260] [Battery Pack]

[0261] The battery pack of the present invention includes the separator member of the present invention and a plurality of single cells.

[0262] As an example, Figure 8As shown, a plurality of single cells 200 and a partition member 1 for partitioning the single cells 200 are stacked, and are housed in a housing 300, for example. The partition member 1 is provided at least between the single cells 200 constituting the battery pack 100, so that the single cells 200 do not come into contact with each other. In addition to being arranged between the single cells 200, the partition member of the present invention can also be used as a partition member (1A) for separating the single cells 200 from components other than the single cells. Here, "components other than the single cells" refers to, for example, a housing having a bottom surface and four side surfaces, and accommodating the single cells and partition members constituting the battery pack. Figure 8 The middle is the bottom of the shell.

[0263] The orientation of the partition member 1 in the battery pack during use is not particularly limited, and the thickness direction of the partition member 1 may be parallel to or intersect with the horizontal plane.

[0264] As described above, the partition member 1 includes an inner packaging body having a combining portion and a holding portion used as needed, and an outer packaging body that accommodates the inner packaging body.

[0265] The compression deformation rate in the thickness direction of the partition member is preferably in the range of 0.1 to 20 MPa. By setting the compression deformation rate to 0.1 MPa or more, it is possible to apply appropriate stress to the single cell and reliably fix the single cell. From the above viewpoint, the compression deformation rate is more preferably 0.2 MPa or more, and further preferably 0.5 MPa or more. On the other hand, as for the upper limit, from the viewpoint of being able to extend the life of the battery cell by absorbing the stress from the expansion during charge and discharge and the expansion during time degradation, it is preferably 20 MPa or less, more preferably 15 MPa or less, and further preferably 10 MPa or less.

[0266] It should be noted that the compression deformation rate (23°C) is usually measured in accordance with JIS K7181, but in the present invention, it simply means: the pressure and thickness of the partition member are measured when the pressure applied is such that the thickness of the partition member becomes about 95% to 50% of the thickness when no pressure is applied, and the value is calculated and evaluated based on the ratio relative to the thickness when no pressure is applied.

[0267] The partition member can be used directly to separate single cells and / or single cells from other members, but when separating single cells and / or single cells from other members, in order to facilitate fixation, an adhesive and / or double-sided tape can be affixed to its surface, or a resin sheet can be installed on its surface.

[0268] [Single battery]

[0269] The single cell is preferably a lithium ion secondary battery having a positive electrode and a negative electrode capable of absorbing and releasing lithium ions, and an electrolyte. In addition to lithium ion secondary batteries, the present invention can be applied to secondary batteries such as lithium ion all-solid-state batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and lead-acid batteries.

[0270] Furthermore, as the form of the cell, a square cell, a pouch cell, a cylindrical cell, or the like can be applied regardless of the battery form.

[0271] Figure 9 1 is a plan view showing an example of a single cell 200 constituting a battery pack. Figure 10 yes Figure 9 The front view of the single cell 200 is shown in FIG. Figure 11 This is a right side view of the cell 200. The cell 200 is formed in a rectangular parallelepiped shape having a height direction (H), a width direction (W), and a thickness direction (D), and terminals 210 and 220 are provided on the upper surface thereof.

[0272] The battery pack described in the present embodiment as described above is applicable to battery packs installed in, for example, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric motorcycles, electric-assisted bicycles, ships, aircraft, trains, uninterruptible power supplies (UPSs), household power storage systems, and power system stabilization battery systems that utilize renewable energy sources such as wind power, solar power, tidal waves, and geothermal energy. The battery pack can also be used as a power source to supply power to devices other than the aforementioned EVs.

[0273] The unit structure of the battery pack, which is composed of two single cells and the aforementioned partition member disposed between the two single cells, preferably satisfies the following condition (i).

[0274] (i) The thermal conductivity of the partition member when the average surface temperature of the partition member in contact with the two cells is 200°C is reduced to 70% or less relative to the thermal conductivity of the partition member when the average surface temperature is 25°C.

[0275] By ensuring that the above-mentioned unit structure of the battery pack satisfies condition (i), the following effects are fully exerted: under normal circumstances, the partition member functions as a heat conductive material that efficiently conducts the heat released by the single cell to the adjacent single cell, and when the single cell reaches an abnormally high temperature, it functions as a heat insulating material that exerts its insulating properties to control the transfer of heat to the adjacent single cell.

[0276] The thermal conductivity of the partition member at an average surface temperature of 200°C is preferably reduced to 60% or less, and further preferably reduced to 50% or less relative to the thermal conductivity at an average surface temperature of 25°C.

[0277] The unit structure composed of two single cells and a partition member disposed between the two single cells preferably satisfies the following condition (ii).

[0278] (ii) Under a pressure of 0.2 MPa applied between two cells, the deformation rate of the partition member disposed between the cells is 6.0% or more.

[0279] By ensuring that the above-mentioned unit structure of the battery pack satisfies condition (ii), even if external pressure is applied to the partition member due to the expansion of the single cell, the expansion of the electrode during charging, or the generation of gas from the electrolyte during charging and discharging, the partition member will deform and be able to absorb the external pressure, so there is a tendency for the partition member to be less likely to rupture.

[0280] The deformation rate in the condition (ii) is more preferably 6.0 to 60%, and even more preferably 10 to 60%.

[0281] Example

[0282] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description.

[0283] [Experimental Example 1]

[0284] As the holding portion 3 of the inner packaging body 2 constituting the partition member 1, a polypropylene sheet having a thickness of 0.3 mm was used and a vacuum forming method was used to produce the Figure 3B and Figure 4 A tray-shaped member with a bottom having multiple recesses as shown.

[0285] The tray-shaped member was set to be 60 mm in length and 120 mm in width, and the shape of the lowest portion of the recessed portion of the tray-shaped member was set to be a square of 7.79 mm×7.79 mm, with a depth of 1.5 mm.

[0286] 0.09 g of sodium carboxymethylcellulose was added to 9 g of water and kneaded at room temperature using a stirrer for 30 minutes. 0.9 g of calcium silicate was added to this mixture and kneaded at room temperature using a stirrer for 5 minutes to obtain a slurry. 3.4 g of calcium sulfate and 1.7 g of alumina cement were added to this slurry as a binder to obtain a calcium silicate paste (composition).

[0287] Then, if Figure 4 As shown, the calcium silicate paste is filled into each recess of the tray-shaped member and solidified by a hydration reaction to form the composition portion 4 , thereby constituting the inner package 2 .

[0288] The depth of the recess of the tray-shaped member and the height of the filled composition part 4 are such that the height from the bottom of the recess having a depth of 1.5 mm is 1.0 mm, and a void layer 5 having a height of 0.5 mm is formed above the composition part 4 .

[0289] When the combination part 4 is formed in the recess, the ratio of the area of ​​the holding part to the total area of ​​the combination part 4 and the holding part (tray-shaped member) 3 when the partition member 1 is viewed from the thickness direction is 39%.

[0290] As the outer package 6 , an aluminum laminate film including resin layers of polyethylene terephthalate (outer side) with a thickness of 0.012 mm, nylon (inner side) with a thickness of 0.015 mm, and polypropylene (innermost side) with a thickness of 0.06 mm was prepared.

[0291] The inner package 2 having the composition portion 4 formed in the recess of the tray-shaped member was placed inside the outer package 6 and sealed using a vacuum degassing sealer to obtain the partition member 1 .

[0292] [Experimental Example 2]

[0293] In Experimental Example 1, the depth of the recess of the tray-shaped member serving as the retaining portion was set to 1.3 mm, a composite portion 4 was formed from the bottom of the recess to a height of 1.0 mm, and a gap layer 5 with a height of 0.3 mm was formed above the composite portion 4. Except for this, the same operations as in Experimental Example 1 were performed to obtain a partition member 1.

[0294] [Experimental Example 3]

[0295] In Experimental Example 1, the depth of the recess of the tray-shaped member serving as the retaining portion was set to 2.0 mm, and the composite portion 4 was formed from the bottom of the recess to a height of 2.0 mm. No void layer 5 was formed above the composite portion 4. A partition member 1 was obtained in the same manner as in Experimental Example 1.

[0296] [Experimental Example 4]

[0297] In Experimental Example 1, a partition member 1 was obtained in the same manner as in Experimental Example 1 except that a composition prepared without using a binder was used.

[0298] [Experimental Example 5]

[0299] In Experimental Example 1, a partition member 1 was obtained in the same manner as in Experimental Example 1 except that the composition was filled into the outer packaging body without using a tray.

[0300] [Experimental Example 6]

[0301] In Experimental Example 1, a partition member was obtained by the same operation as in Experimental Example 1 except that the depth of the recess of the tray-shaped member serving as the holding portion was set to 2.0 mm and the composition prepared without using a binder was filled from the bottom of the recess to a height of 2.0 mm to form a composition portion 4.

[0302] [Experimental Example 7]

[0303] In Experimental Example 5, a partition member was obtained in the same manner as in Experimental Example 5 except that a composition prepared without using a binder was used.

[0304] [Evaluation 1]

[0305] For the partition members produced in each experimental example, a pressure of 2.5 MPa was applied along the thickness direction and one side was heated to 100°C at a heating rate of 1.7°C / min. Visual confirmation was made to confirm whether liquid was observed to flow from the inside to the outside of the partition member during heating, or whether solid components were observed to flow out except for a trace amount of powder.

[0306] The case where the outflow of the liquid or powder was not observed was evaluated as "1 (no breakage)", and the case where the outflow of the liquid or powder was observed was evaluated as "2 (breakage)".

[0307] [Evaluation 2]

[0308] For the partition members produced in each experimental example, Figure 12 The thermal insulation performance was evaluated using the test apparatus shown.

[0309] Specifically, the partition member 1 is placed on a 1 mm thick brass metal plate 403, and a 5 mm thick brass metal block 402 is placed on top of the partition member 1. The metal plate 403, the partition member 1, and the metal block 402 are covered with a heat insulating material 401, except for the lower portion of the metal plate 403.

[0310] Nitrogen gas heated to 300°C by two tube heaters 404 was blown from below toward the metal plate 403, and the temperature of the metal block 402 located above the partition member 1 was measured. The time during this heating test during which the temperature of the metal block 402 was maintained within the range of 100°C ± 5°C was measured as the plateau time.

[0311] 〔Evaluation 3〕

[0312] For each experimental example, the thickness of the partition member produced was measured without external pressure, and then with an external pressure of 0.2 MPa applied along the thickness direction. Based on these measured thickness values, the deformation rate of the partition member in the thickness direction when a pressure of 0.2 MPa was applied along the thickness direction was calculated.

[0313] [Evaluation 4]

[0314] For the partition members produced in each experimental example, an external pressure of 1.0 MPa was applied along the thickness direction for 1 minute to visually confirm whether liquid was observed to flow out from the inside of the partition member or whether solid components were observed to flow out except for a trace amount of powder.

[0315] The case where the outflow of the liquid or powder was not observed was evaluated as "1 (no breakage)", and the case where the outflow of the liquid or powder was observed was evaluated as "2 (breakage)".

[0316] The results of evaluations 1, 2, and 4 of each experimental example are shown in Table 1, and the results of evaluation 3 are shown in Table 2.

[0317] [Table 1]

[0318]

[0319] [Table 2]

[0320]

[0321] The results of Evaluation 1 show that the partition members of Experimental Examples 1 to 3 and 5, in which the composition portion was formed using a composition containing a binder, exhibited excellent shape retention at high temperatures. On the other hand, the partition members of Experimental Examples 6 and 7, in which no binder was used in the composition portion, exhibited poor shape retention at high temperatures.

[0322] Furthermore, the results of Evaluation 2 show that the partition members of Experiments 1 to 3 and 5, which used a composition containing a binder to form the composition portion, exhibited a longer plateau region during the temperature rise process compared to the partition members of Experiments 6 and 7, which did not use a binder. Because a longer plateau region means that it takes longer for internal moisture to evaporate, this means that heat transfer during abnormal cell conditions takes longer.

[0323] The results of Evaluation 3 and Evaluation 4 show that the partition members of Experimental Examples 1 to 3 and 5, in which the composition portion was formed using a composition containing a binder, had a large deformation rate when compressed at 0.2 MPa, did not break even when compressed at 1.0 MPa, and had excellent shape retention during compression.

[0324] In addition, in the partition member of Experimental Example 4, in which the thickness of the holding portion was greater than that of the composition portion, a void layer was formed, and the composition portion was separated from the outer package, the deformation rate under 0.2 MPa pressure could be further increased.

[0325] Industrial applicability

[0326] The partition member of the present invention can efficiently transfer heat released from adjacent cells to adjacent cells under normal conditions. In addition, it can prevent chain reactions between cells when adjacent cells are damaged and the damage could spread to the entire battery pack.

[0327] Therefore, the battery pack obtained by using the separator of the present invention is useful as a secondary battery having high safety even though having a high energy density, for example, as a power source for vehicle use.

[0328] Description of Reference Numerals

[0329] 1 Separator

[0330] 2 Inner packaging

[0331] 3. Holding portion (tray-shaped member)

[0332] 4. Combination part (heat transfer control layer)

[0333] 5 Void layer

[0334] 6 Outer packaging

[0335] 7The smallest rectangle that encloses the tray-shaped component

[0336] 100 battery pack

[0337] 200 single batteries

[0338] 210 terminal

[0339] 220 terminal

[0340] 300 shell

[0341] 400 Thermal Insulation Evaluation Tester

[0342] 401 Insulation Materials

[0343] 402 Metal Block

[0344] 403 Metal Plate

[0345] 404 Tube Heater

[0346] D thickness direction

Claims

1. A partition member having a thickness direction and a plane direction perpendicular thereto, and partitioning a single cell in the thickness direction. The partition member includes an outer packaging body and an inner packaging body covered by the outer packaging body. The inner package body includes a composition portion composed of a composition containing at least one of inorganic particles and inorganic fibers and a binder.

2. The partition member according to claim 1, wherein The composition further comprises a liquid.

3. The partition member according to claim 1 or 2, wherein: The inner packaging body further comprises a holding portion, The holding portion includes an outer wall portion that contacts at least a portion of an outer peripheral end surface of the combination portion in a plane direction and extends in a thickness direction.

4. The partition member according to claim 3, wherein Both ends in the thickness direction of the outer wall portion of the holding portion are in contact with the outer packaging body.

5. The partition member according to claim 1 or 2, wherein When the partition member is pressurized at 0.2 MPa in the thickness direction, the deformation rate of the partition member in the thickness direction is 6.0% or more. The partition member according to claim 3 , wherein: The length of the holding portion in the thickness direction is greater than the length of the combining portion in the thickness direction.

7. The partition member according to claim 3, wherein The holding portion has a space having a depth in a thickness direction, and the combination portion is held in the space.

8. The partition member according to claim 3, wherein The holding portion has a space having a depth in a thickness direction, the space includes a plurality of first spaces partitioned into a grid shape, and the combination portion is held in each of the first spaces.

9. The partition member according to claim 3, wherein The holding portion has a space having a depth in the thickness direction, the space including a plurality of first spaces partitioned into a grid shape, each of the first spaces holding the combination portion, and a third space formed between adjacent first spaces on the back side of the holding portion.

10. The partition member according to claim 9, wherein The ratio of the volume of the third space to the volume of 100 volume % of the smallest rectangular parallelepiped capable of accommodating the holding portion is 0.1 to 15 volume %.

11. The partition member according to claim 3, wherein The holding portion is a tray-shaped member having a frame-shaped outer wall portion and a bottom portion, wherein the frame-shaped outer wall portion surrounds the composition portion and the bottom portion closes an opening of the frame-shaped outer wall portion. The combination portion is held in the recessed portion inside the outer wall portion.

12. The partition member according to claim 11, wherein The tray-shaped member further includes a grid-shaped partition wall for partitioning the inner side of the frame-shaped outer wall portion. A plurality of recesses are formed on the inner side of the frame-shaped outer wall portion by the partition wall. The combination portion is held in each of the recessed portions.

13. The partition member according to claim 11, wherein The tray-shaped member further includes a grid-shaped partition wall for partitioning the inner side of the frame-shaped outer wall portion. A plurality of recesses are formed on the inner side of the frame-shaped outer wall portion by the partition wall. The partition wall is composed of two side walls rising from the bottom between the two recessed portions and a connecting portion connecting the upper portions of the side walls to each other, and a recessed strip opened toward the bottom is formed between the two side walls. The combined portion is held in each of the recessed portions, and the combined portions are connected to each other at the low portion.

14. The partition member according to claim 11, wherein When the tray-shaped member is viewed in plan from the thickness direction, a ratio of the area of ​​the combination portion to the total area of ​​the tray-shaped member and the combination portion is 50 to 100%.

15. The partition member according to claim 11, wherein The tray-shaped member has a rectangular shape when viewed from above in the thickness direction. When the XYZ coordinate axes are defined by setting the thickness direction as the Z axis direction, the direction parallel to one side of the outer periphery of the tray-shaped member in the surface direction as the X axis direction, and the direction perpendicular to the X axis direction in the surface direction as the Y axis direction, In a cross section of the tray-shaped member cut along an XZ plane passing through the combined portion, a ratio of an area occupied by the space to an area of ​​a minimum rectangle surrounding the tray-shaped member is 15% or less, and In a cross section of the tray-shaped member cut along a YZ plane passing through the combined portion, a ratio of an area occupied by the space to an area of ​​a minimum rectangle surrounding the tray-shaped member is 15% or less. 16 . A battery pack comprising: a plurality of unit cells; and the partition member according to claim 1 or 2 arranged between the unit cells.

17. The battery pack according to claim 16, wherein: A unit structure composed of two of the single cells and the partition member disposed between the two single cells satisfies the following condition (i): (i) The thermal conductivity of the partition member when the average surface temperature of the partition member in contact with the two cells is 200° C. is reduced to 70% or less relative to the thermal conductivity of the partition member when the average surface temperature of the partition member is 25° C.

18. The battery pack according to claim 16, wherein: A unit structure composed of two of the single cells and the partition member disposed between the two single cells satisfies the following condition (ii): (ii) Under a pressure of 0.2 MPa applied between the two cells, the deformation rate of the partition member disposed between the cells is 6.0% or more.

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