Spacer and assembled battery

Abstract

To provide a spacer excellent in restorability after compressive deformation, and a battery pack using the spacer.SOLUTION: A spacer for partitioning a single cell, the spacer comprising an exterior body and an encapsulated body enclosed in the exterior body, the encapsulated body comprising a tray-shaped holding portion, wherein when a plane parallel to an inner bottom surface of the holding portion is defined as an XY plane and a direction perpendicular to the XY plane is defined as a Z-axis direction, the holding portion comprises an outer wall portion rising in the Z-axis direction from at least a part of an outer edge portion of the inner bottom surface, A cross-sectional shape of the outer wall portion is a tapered shape in which a width of the outer wall portion gradually increases from a distal end toward a proximal end in a cross section obtained by cutting the outer wall portion along a plane parallel to both a width direction of the outer wall portion and the Z-axis direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spacer and a battery pack. [Background technology]

[0002] In recent years, secondary batteries have seen a rapid increase in use as power sources for vehicles and other applications. Research is underway to increase the energy density of secondary batteries in order to improve the flexibility of installation in limited spaces and to extend the driving range per charge. However, the higher the energy density of secondary batteries, the more likely they are to malfunction. For example, in the case of secondary batteries installed in electric vehicles with driving ranges of several hundred kilometers, if the secondary battery is damaged by overcharging or an internal short circuit, the battery surface temperature can exceed several hundred degrees Celsius, sometimes reaching 1,000 degrees Celsius or more.

[0003] Since secondary batteries used as power sources for vehicles and the like are generally used as battery packs consisting of multiple cells, if one of the cells constituting the battery pack is damaged and reaches the temperature range described above, the heat generated by the damaged cell may also damage adjacent cells, potentially causing a chain reaction of damage to the entire battery pack. To prevent this chain reaction of damage to the cells, various techniques have been proposed that provide spacers between the cells.

[0004] For example, Patent Document 1 discloses a spacer in which a tray-shaped member is enclosed within an outer casing, and a paste containing at least one selected from the group consisting of particles and heat-resistant fibers and a liquid is contained in a recess of the tray-shaped member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-119679 Summary of the Invention [Problem to be solved by the invention]

[0006] Spacers such as those described in Patent Document 1 are capable of compressing and deforming when subjected to external pressure that constrains the row of unit cells or pressure due to cell expansion, thereby absorbing the pressure. However, conventional spacers do not have sufficient recovery ability after compressive deformation, and their ability to absorb external pressure that constrains the row of unit cells or pressure due to cell expansion tends to decrease.

[0007] A primary object of the present invention is to provide a spacer that is excellent in restoring ability after compressive deformation, and a battery pack using the spacer. [Means for solving the problem]

[0008] The present invention includes the following configurations. [1] A spacer for separating unit cells, comprising an outer casing and an inner casing enclosed within the outer casing, The inner container has a tray-shaped holding portion, When a plane parallel to the inner bottom surface of the holding portion is defined as an XY plane, and a direction perpendicular to the XY plane is defined as a Z-axis direction, the holding portion includes an outer wall portion rising in the Z-axis direction from at least a part of the outer edge portion of the inner bottom surface, A spacer in which, in a cross section of the outer wall portion cut by a plane parallel to both the width direction of the outer wall portion and the Z-axis direction, the cross-sectional shape of the outer wall portion is a tapered shape whose width gradually increases from the tip to the base end. [2] The spacer according to [1], wherein the cross-sectional shape of the outer wall portion is trapezoidal or semicircular. [3] The spacer according to [1] or [2], wherein the contact area between the holding portion and the exterior body increases when pressure is applied in the Z-axis direction. [4] The spacer according to any one of [1] to [3], wherein the angle θ formed between the XY plane and the side surface of the outer wall portion satisfies θ>90°. [5] The spacer according to any one of [1] to [4], wherein the holding portion has a composition portion containing at least one of inorganic particles and inorganic fibers. [6] The spacer according to any one of [1] to [5], wherein the cross-sectional shape of the outer wall portion is symmetrical with respect to a line that passes through the center of the outer wall portion in the width direction and is parallel to the Z-axis direction. [7] The outer wall portion is arranged in a rectangular frame shape having two sides parallel to the X-axis direction and two sides parallel to the Y-axis direction, The spacer according to any one of [1] to [6], wherein the holding portion further includes a first partition wall extending in the Y-axis direction inside the outer wall portion. [8] The spacer according to [7], wherein the XZ cross-sectional shape of the first partition wall is a tapered shape whose width gradually narrows from the base end to the tip end. [9] The spacer according to [8], wherein the XZ cross-sectional shape of the first partition wall is trapezoidal or semicircular.

[10] The spacer according to any one of [7] to [9], wherein the first partition wall has a trapezoidal, semicircular or wavy shape when viewed from the X-axis direction.

[11] The outer wall portion is arranged in the shape of a quadrangular frame having two sides parallel to the X-axis direction and two sides parallel to the Y-axis direction, The spacer according to any one of [1] to

[10] , wherein the holding portion further includes a second partition wall extending in the X-axis direction inside the outer wall portion.

[12] The spacer according to

[11] , wherein the YZ cross-sectional shape of the second partition wall is a tapered shape whose width gradually narrows from the base end to the tip end.

[13] The spacer according to

[12] , wherein the YZ cross-sectional shape of the second partition wall is trapezoidal or semicircular.

[14] The spacer according to any one of

[11] to

[13] , wherein the second partition wall has a trapezoidal, semicircular or wavy shape when viewed from the Y-axis direction.

[15] The spacer according to any one of [1] to

[14] , wherein the recovery rate of the holding portion measured by the following measurement method (1) is 70 to 100%.

[16] A battery pack comprising a plurality of unit cells and the spacer according to any one of [1] to

[15] arranged between the unit cells. [Effects of the Invention]

[0009] According to the present invention, there are provided a spacer that has excellent restorability after compressive deformation, and a battery pack using the spacer. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view schematically illustrating a general configuration of a spacer according to an example of an embodiment. [Figure 2] 2 is an XY plan view schematically showing the general configuration of a holding portion of the spacer in FIG. 1. FIG. [Figure 3] 2 is an XZ cross-sectional view schematically showing the general configuration of a holding portion of the spacer of FIG. 1. FIG. [Figure 4] 2 is a YZ cross-sectional view schematically showing the general configuration of a holding portion of the spacer in FIG. 1. FIG. [Figure 5] FIG. 10 is an XZ cross-sectional view schematically showing a schematic configuration of a holding portion of another example of a spacer. [Figure 6] FIG. 10 is an XY plan view schematically showing a schematic configuration of a holding portion of another example of a spacer. [Figure 7] 7 is an XZ cross-sectional view schematically showing the general configuration of a holding portion of the spacer in FIG. 6. FIG. [Figure 8] 7 is a YZ cross-sectional view schematically showing the general configuration of the holding portion of the spacer in FIG. 6. [Figure 9] FIG. 10 is an XY plan view schematically showing a schematic configuration of a holding portion of another example of a spacer. [Figure 10] 10 is an XZ cross-sectional view schematically showing the general configuration of the holding portion of the spacer in FIG. 9. FIG. [Figure 11] 10 is a YZ cross-sectional view schematically showing the general configuration of the holding portion of the spacer in FIG. 9. FIG. [Figure 12] FIG. 10 is an XY plan view schematically showing a schematic configuration of a holding portion of another example of a spacer. [Figure 13] 13 is an XZ cross-sectional view schematically showing the general configuration of the holding portion of the spacer in FIG. 12. FIG. [Figure 14] 13 is a YZ cross-sectional view schematically showing the general configuration of the holding portion of the spacer in FIG. 12. FIG. [Figure 15]FIG. 10 is a YZ cross-sectional view schematically showing the schematic configuration of a holding portion of another example of a spacer. [Figure 16] FIG. 10 is an XY plan view schematically showing a schematic configuration of a holding portion of another example of a spacer. [Figure 17] 17 is a YZ cross-sectional view schematically showing the general configuration of the holding portion of the spacer in FIG. 16. FIG. [Figure 18] 1 is a conceptual diagram illustrating a battery pack according to an embodiment; [Figure 19] FIG. 2 is a plan view showing an example of a unit cell. [Figure 20] FIG. 20 is a front view of the cell of FIG. 19. [Figure 21] FIG. 20 is a side view of the cell of FIG. 19. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiment described below, and can be implemented by modifying it as desired within the scope of the gist of the present invention. In this specification, when it is written "A to B" (A and B are any numbers), it means "A or more and B or less" unless otherwise specified, and also means "preferably greater than A" or "preferably smaller than B." Furthermore, when it is written "A or more" (A is any number), it means "preferably greater than A" unless otherwise specified, and when it is written "B or less" (B is any number), it also means "preferably smaller than B" unless otherwise specified.

[0012] [Spacer] A spacer according to an embodiment is a spacer for separating unit cells, and includes an exterior body and an inner body enclosed within the exterior body. The inner body includes a tray-shaped holder. When a plane parallel to the inner bottom surface of the holder is defined as an XY plane and a direction perpendicular to the XY plane is defined as a Z-axis direction, the holder includes an outer wall portion rising in the Z-axis direction from at least a part of the outer edge of the inner bottom surface. In a cross section of the outer wall portion cut along a plane parallel to both the width direction of the outer wall portion and the Z-axis direction, the cross-sectional shape of the outer wall portion is a tapered shape whose width gradually increases from the tip to the base end. The spacer according to the embodiment is typically plate-shaped, with its surface direction parallel to the XY plane and its thickness direction coinciding with the Z-axis direction.

[0013] FIG. 1 is a cross-sectional view showing a schematic configuration of a spacer 1 according to an example of the embodiment. As shown in FIG. 1, spacer 1 is flat and configured by housing inner body 2 in outer body 6 whose periphery is sealed. Inner body 2 is configured with holding portion 3 and composition portion 4 housed in holding portion 3. In the example shown in FIG. 1, holding portion 3 is thicker than composition portion 4, and the upper portion of composition portion 4 surrounded by holding portion 3 forms void layer 5.

[0014] The spacer 1 is disposed between the cells 200 in contact with the surfaces of the cells 200 along a plane direction perpendicular to the thickness direction of the spacer 1 . When assembling a battery pack by disposing the spacers 1 between the cells 200, external pressure that restrains the row of the cells 200 is applied to the spacers 1 in the Z-axis direction, but the external pressure is absorbed by mainly the retaining portion 3 and the void layer 5 compressing and deforming. Also, as shown by the dashed dotted line in Figure 1, when the cells 200 expand, mainly the composition portion 4 deforms, and the spacers 1 disposed between the cells 200 deform in accordance with the change in the spacing in the thickness direction.

[0015] <Inclusion body> The inner case has a tray-shaped holding section. The holding section can accommodate and hold the composition section or porous sheet described below. It is preferable that the holding section accommodate and hold the composition section.

[0016] (holding part) The retaining portion is a portion that houses and holds the composition portion or porous sheet described below. When assembling a battery pack by sandwiching the spacer between the cells, the spacer is sandwiched between the cells under pressure, and the cells and spacers are aligned and stacked inside the housing, and then the periphery is constrained with a belt-like member to adjust the overall length of the battery pack. The retaining portion also functions to buffer the pressure applied to the surfaces of the cells when sandwiching the spacer between the cells during this assembly process. The holding portion preferably has a property of being compressively deformed when subjected to an external force and restoring its shape when the external force is removed.

[0017] One embodiment of the holding portion includes a thermoplastic resin. 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 foam can also be used. Among these, olefin resins are preferred, and polypropylene is particularly preferred, from the viewpoints of versatility, cost, etc. Furthermore, these resins may contain heat-resistant fillers such as alumina particles and glass fibers.

[0018] The retaining portion is in contact with at least a portion of the composition portion or the porous sheet. The retaining portion may be arranged in contact with the outer peripheral end surface in the surface direction of the composition portion so as to cover a part or a plurality of regions of the outer peripheral end surface in the surface direction of the composition portion, or to cover the entire outer peripheral end surface. The retaining portion may be arranged in contact with one surface in the thickness direction of the composition portion partially or entirely. For example, the retaining portion may be provided on one or both sides of the composition portion, around the entire periphery of the composition portion, or partially around a portion of the periphery of the composition portion. In these cases, the retaining portion may be configured so that the area of ​​the composition portion that contacts the retaining portion is larger than the area that does not contact the retaining portion.

[0019] 2 to 4 is tray-shaped and includes a rectangular bottom surface 10 and an outer wall 12 arranged in the shape of a rectangular frame around the outer edge of the bottom surface 10. If a plane parallel to the inner bottom surface 10a of the holder 3 is defined as the XY plane and a direction perpendicular to the XY plane is defined as the Z-axis direction, then the outer wall 12 rises in the Z-axis direction from the outer edge of the bottom surface 10 all along the length of the holder 3. The XY plane shape of the holding unit 3 is typically rectangular, but is not limited to this. When the XY plane shape of the holding unit 3 is rectangular, the direction perpendicular to the short side is the X-axis direction, and the direction parallel to the long side is the Y-axis direction.

[0020] 1 again, the retaining portion 3 has an outer wall portion 12 that contacts the entire outer peripheral end face in the surface direction of the composition portion 4, and has a space with a depth in the Z-axis direction inside the outer wall portion 12. In this example, the outer wall portion 12 is provided in a substantially rectangular shape so as to surround the periphery of the composition portion 4 in the surface direction, but is not limited thereto. The length in the Z-axis direction of the retaining portion 3 having a space with depth in the Z-axis direction, i.e., the length in the Z-axis direction of the outer wall portion 12 that contacts the outer peripheral end surface of the composition portion 4, is not particularly limited, but is preferably equal to or greater than the thickness of the composition portion 4, and more preferably is greater than the length in the Z-axis direction of the composition portion 4.

[0021] In this example, the length of the holding portion 3 in the Z-axis direction is greater than the length of the composition portion 4 in the Z-axis direction, and when the composition portion 4 is contained and held in the holding portion 3, both ends of the outer wall portion 12 of the holding portion 3 in the Z-axis direction contact the outer casing 6, and a void layer 5 surrounded by the holding portion 3 is secured on the upper surface side of the composition portion 4. The void layer 5 functions to buffer and absorb the pressing force applied through the surface of the cells 200 when assembling a battery pack by disposing the spacers 1 between the cells 200, and the pressing force applied directly from the surface of the cells 200 when the cells 200 expand. The presence of the void layer 5 makes the composition portion 4 housed in the holding portion 3 less likely to collapse, ensuring shape retention. Furthermore, the presence of the void layer 5 makes it possible to separate the contribution of compression to external pressure from that of the holding portion and the composition portion.

[0022] The encapsulant, in which the length of the retaining portion in the Z-axis direction is greater than the length of the composition portion in the Z-axis direction as described above, incorporates a composition portion that controls heat transfer and a retaining portion that controls compressibility, thereby enhancing the effects of having excellent shape stability even at high temperatures, being less likely to burst, and consistently exhibiting excellent insulating properties when the single cell becomes hot. In an encapsulation body in which the length of the retaining portion in the Z-axis direction is greater than the length of the composition portion in the Z-axis direction, only the retaining portion is compressed up to a certain external pressure, and above that external pressure, both the retaining portion and the composition portion are compressed. By separating the contribution of compression to external pressure, it is possible to design a spacer with desired compression characteristics.

[0023] The outer wall portion 12 may be provided on at least a portion of the inner bottom surface 10a of the holder 3, and is not limited to being provided on the outer edges of all sides of the bottom portion 10. For example, the outer wall portion 12 may be provided on only the outer edge of one side of the bottom portion 10, or on the outer edges of two parallel sides, or on the outer edges of two adjacent sides. Since this makes the holder 3 harder and reduces the compressive deformation rate, it is preferable that the outer wall portion 12 be provided on the outer edges of at least two adjacent sides of the bottom portion 10, and it is more preferable that the outer wall portion 12 be provided in a frame shape on the outer edges of all sides of the bottom portion 10.

[0024] The outer wall portion 12 in this example consists of two side walls and a connecting portion connecting the upper parts of the side walls, and a recessed strip with an open bottom between the two side walls, but is not limited to this. In a cross section of the outer wall portion 12 cut along a plane parallel to both the width direction and the Z-axis direction of the outer wall portion 12, the cross-sectional shape of the outer wall portion 12 is a tapered shape whose width gradually increases from the tip to the base end. As a result, when pressure is applied in the Z-axis direction, the contact area between the holding portion 3 and the exterior body 6 increases. More specifically, when the holding portion 3 is compressed and deformed in the Z-axis direction due to external pressure or expansion of the cell, the contact area between the outer wall portion 12 of the holding portion 3 and the exterior body 6 increases as the holding portion 3 is compressed in the Z-axis direction. Therefore, as the holding portion 3 deforms, its resistance to compression increases, resulting in excellent resilience.

[0025] In the example shown in Fig. 3, the cross-sectional shape of the outer wall portion 12 parallel to the Y-axis direction when cut along a plane parallel to both the width direction (X-axis direction) and the Z-axis direction is a trapezoid whose width gradually narrows from the base end to the tip. Note that the cross-sectional shape of the outer wall portion 12 parallel to the Y-axis direction is not limited to a trapezoid, and may be, for example, a semicircular shape whose width gradually narrows from the base end to the tip, as in the example shown in Fig. 5. 3, the cross-sectional shape of the outer wall portion 12 parallel to the Y-axis direction is preferably symmetrical with respect to a line k parallel to the Z-axis direction that passes through the center of the width direction of the outer wall portion 12. This further improves the restorability of the holding portion 3.

[0026] 4, the cross-sectional shape of outer wall portion 12 parallel to the X-axis direction when cut along a plane parallel to both the width direction (Y-axis direction) and the Z-axis direction is a trapezoid whose width gradually narrows from the base end to the tip. The cross-sectional shape of outer wall portion 12 parallel to the X-axis direction is not limited to a trapezoid, and may be, for example, a semicircular shape whose width gradually narrows from the base end to the tip. As shown in Fig. 4, the cross-sectional shape of the outer wall portion 12 parallel to the X-axis direction is preferably symmetrical with respect to a line parallel to the Z-axis direction that passes through the center of the width of the outer wall portion 12. This further improves the restorability of the holding portion 3.

[0027] The angle θ (FIG. 3) formed between the XY plane and the side surface 12a of the outer wall portion 12 satisfies θ>90°. Since this improves the restorability after compressive deformation, θ>95° is preferable, θ>100° is more preferable, θ>105° is even more preferable, and θ>110° is particularly preferable. In terms of ensuring the volume of the holding portion, the angle θ is preferably θ<140°, more preferably θ<130°, even more preferably θ<120°, and particularly preferably θ<110°. The lower and upper limits of the angle θ can be combined arbitrarily. In addition, when the cross-sectional shape of the outer wall portion 12 is semicircular, the angle θ means the angle between the tangent at the center in the Z-axis direction of the side surface 12a of the outer wall portion 12 and the inner bottom surface 10a in a cross section parallel to both the width direction and the Z-axis direction of the outer wall portion 12. The angle θ of the side surfaces 12a on both sides in the width direction of the outer wall portion 12 may be the same or different, but is preferably the same.

[0028] When the cross-sectional shape of the outer wall portion 12 is trapezoidal, the ratio of the total area of ​​the tip surface of the outer wall portion 12 to the total area of ​​the outer wall portion 12 on the surface parallel to the XY plane of the inner bottom surface 10a of the holding portion 3 is preferably 0.5% or more, more preferably 1% or more, and even more preferably 1.5% or more. If the area ratio of the outer wall portion 12 is equal to or greater than the lower limit, the compressive deformation rate in the Z-axis direction tends to be smaller. The area ratio of the outer wall portion 12 is preferably 15% or less, more preferably 12% or less, and even more preferably 9% or less. The lower and upper limits of the area ratio of the outer wall portion 12 can be combined arbitrarily.

[0029] The length of the outer wall portion 12 in the Z-axis direction, i.e., the length from the inner bottom surface 10a of the holding portion 3 to the tip of the outer wall portion 12 in the Z-axis direction, is preferably 2 mm or more, more preferably 3 mm or more, and even more preferably 5 mm or more. If the length of the outer wall portion 12 in the Z-axis direction is equal to or greater than the above-mentioned lower limit, it is easy to increase the elastic recovery rate. The length of the outer wall portion 12 in the Z-axis direction is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 6 mm or less. The lower limit and upper limit of the length of the outer wall portion 12 in the Z-axis direction can be combined arbitrarily.

[0030] (Composition part) The inner shell preferably comprises a composition portion held by a holding portion. It is preferable that the composition part does not become suspended even when immersed in water after storage for 24 hours at 25° C. The phrase "does not become suspended" means that the composition part does not dissolve or disperse in water due to at least one of physical interactions and chemical interactions between the components, and the shape of the composition part is unlikely to change.

[0031] In the spacer according to the embodiment, the composition portion functions as a thermal resistance change layer or a phase change layer. The thermal resistance change layer is a layer that, when a spacer is placed between the cells, functions as a heat transfer material that efficiently transfers heat generated from adjacent cells to nearby cells under normal conditions, and also functions as a heat insulating material that exhibits insulating properties and controls the transfer of heat to adjacent cells when the temperature of a cell becomes abnormally high. The phase-change layer undergoes a phase change accompanied by an endothermic reaction when the temperature rises or the pressure drops. When the unit cell goes from normal to abnormal, the temperature rise around the spacer causes a phase change accompanied by an endothermic reaction, which can mitigate the sudden temperature rise.

[0032] (1) Thermal resistance change layer The composition portion may be a thermal resistance variable layer. A thermal resistance variable material is a material whose thermal resistance after heating increases compared to its thermal resistance before heating. When the temperature of the thermal resistance change material is raised to 100°C at a rate of 1.7°C / min, the thermal resistance after heating preferably increases to 1.5 times or more, and more preferably increases to 1.7 times or more, the thermal resistance before heating.

[0033] The thermal resistance variable material has low thermal resistance under normal conditions, allowing it to efficiently transfer heat generated from adjacent cells to nearby cells, and in the event of an abnormality, its thermal resistance increases, allowing it to suppress the transfer of heat to adjacent cells. The thermal resistance variable material can be a material whose thermal resistance changes. For example, a material such as a foam material whose volume changes with increasing temperature to increase its thermal resistance can be used. Alternatively, a material whose phase changes with increasing temperature can be used. In a different embodiment from the above, the thermal resistance change material may use two or more materials with different thermal resistances. A specific material may be designed to become the dominant thermal resistance at a specific time. For example, a high thermal conductivity material and a low thermal conductivity material may be used, with the low thermal conductivity material being designed to be coated or impregnated into the high thermal conductivity material. If the high thermal conductivity material melts, evaporates, or sublimes at a specific temperature, the thermal conductivity of the low thermal conductivity material becomes dominant. In this case, the thermal resistance of the spacer decreases at a specific temperature. This mechanism makes it possible to control the temperature at which the thermal resistance of the spacer increases, as well as the thermal resistance before and after that change. In this embodiment, it is preferable that the low thermal conductive material contains at least one of inorganic particles and inorganic fibers, which will be described later, and the high thermal conductive material contains a liquid or gel, which will be described later.

[0034] (2) Phase change layer The composition 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 heated. The phase change material may be a material that undergoes an irreversible phase change at a specified temperature, or may be a material that undergoes a reversible phase change at a specified temperature. It is preferable that the phase change material undergoes a phase change accompanied by an endothermic reaction at a specified temperature, because when the ambient temperature rises from normal to abnormal, the phase change accompanied by an endothermic reaction can mitigate a sudden temperature rise.

[0035] The phase change material may be a known phase change material such as a heat absorbing polymer. In a different embodiment from the above, the phase change material may be combined with two or more materials with different phase transition temperatures. A specific material may be designed to undergo an endothermic reaction at a specific timing. For example, a high-temperature phase transition material and a low-temperature phase transition material may be used, with the low-temperature phase transition material being designed to be coated or impregnated into the high-temperature phase transition material. If the low-temperature phase transition material melts, evaporates, or sublimes at a specific temperature, the endothermic reaction associated with the phase transition can be utilized. In this case, the spacer reduces a sudden temperature rise in a specific temperature range. This mechanism allows the temperature at which the spacer reduces a sudden temperature rise to be controlled. In this embodiment, it is preferable that the high-temperature phase transition material contains at least one of inorganic particles and inorganic fibers, which will be described later, and the low-temperature phase transition material contains a liquid or gel, which will be described later.

[0036] (3) Inorganic particles and inorganic fibers The inorganic particles are not particularly limited as long as they achieve the effects of the present invention, and examples thereof include silica, alumina, calcium silicate, zeolite, diatomaceous earth, shirasu balloons, clay minerals, vermiculite, mica, cement, perlite, fumed silica, and aerogel. Among these, silica particles, alumina particles, calcium silicate, zeolite, and vermiculite are preferred, and calcium silicate and zeolite are more preferred, with calcium silicate being even more preferred, as they allow a larger amount of liquid to be easily contained within and between particles. Among the types of calcium silicate, xonotlite, tobermorite, wollastonite, and gyrolite are preferred, with gyrolite being more preferred. Gyrolite, which has a petal-like structure, maintains its porous structure even when compressed and deformed, resulting in excellent water retention. Clay minerals are primarily magnesium silicate (including talc and sepiolite), montmorillonite, and kaolinite. The particle size of the inorganic particles is preferably 1 / 5 or less of the thickness of the composition. These inorganic particles can be used alone or in a mixture of multiple types.

[0037] The inorganic fibers are not particularly limited as long as they achieve the effects of the present invention, and examples thereof include glass fibers, alumina fibers, and rock wool. The inorganic fibers preferably have a fiber diameter of 1 / 5 or less of the thickness of the composition. These inorganic fibers can be used alone or in a mixture of two or more types.

[0038] (4)Liquid The boiling point of the liquid is preferably 50 to 200°C, more preferably 80 to 180°C. The liquid preferably contains at least one selected from the group consisting of water, alcohols, esters, ethers, ketones, hydrocarbons, fluorine-based compounds, and silicone oils. These may be used alone or as a mixture of two or more. The liquid may contain additives such as substances that provide antifreeze properties (antifreeze agents), preservatives, and pH adjusters. By providing antifreeze properties, damage to the exterior body due to expansion caused by freezing can be prevented. Furthermore, the addition of a pH adjuster can reduce the possibility of the pH of the liquid being changed by components eluted from the powdered inorganic material, which can lead to deterioration of the powdered inorganic material, the exterior body, and the liquid (water) itself. The water may contain other substances as needed, and these may be added as needed. It is more preferable that the composition portion further contains excess water in addition to the water of hydration of the hydration product described below.

[0039] (5) Binder From the viewpoint of improving the shape retention of the composition part, it is preferable that the composition part further contains a binder. There are no particular limitations on the binder as long as it hardens the composition part, and known materials can be used. From the viewpoint of using the liquid in combination, it is preferable that the binder contains a material that hardens by a hydration reaction.

[0040] The material that hardens by hydration reaction is not particularly limited, and examples thereof include gypsum and hydraulic materials. Examples of gypsum include natural gypsum such as gypsum dihydrate and gypsum hemihydrate, and chemical gypsum such as phosphate gypsum, flue gas desulfurization gypsum, titanic gypsum, smelted gypsum, and hydrofluoric gypsum. Of these, natural gypsum is preferred, and calcium sulfate is more preferred. Examples of hydraulic materials include portland cement, mixed cement, alumina cement, quicklime, slaked lime, and mixtures thereof. Among these, alumina cement is preferred. From the viewpoint of controlling the setting time, two or more materials that set by hydration reaction may be mixed, and it is preferable to mix gypsum and a hydraulic material. In one embodiment, the composition preferably becomes solid when dried for 24 hours at 25° C. In this specification, the term "solid" refers to a state in which the viscosity at 25° C. measured with a Brookfield viscometer is 200 Pa s or more.

[0041] In conventional technology, when unit cells separated by a spacer become abnormally hot, the heat generated by the cells can cause the composition portion to fluidize, causing the outer casing to burst and be ejected to the outside. If the composition portion escapes from the outer casing, the heat insulating performance of the spacer is impaired. In contrast, in one embodiment of the spacer, a binder is blended into the composition portion, resulting in excellent shape stability even at high temperatures. Therefore, even if the unit cells become abnormally hot, the composition portion is less likely to fluidize, and stable heat insulating performance can be maintained even at high temperatures.

[0042] (6) Hydration products The composition part preferably contains a hydration product. That is, it is preferable that the composition part contains a hydration product obtained by using a material that hardens by hydration reaction as a binder. By including a hydration product in the composition portion, the energy required for the hydration water to evaporate can be utilized, thereby lengthening the time from when the water contained in the encapsulant reaches its boiling point until it completely evaporates, known as the plateau time, and making it easier to suppress heat propagation when the single cell becomes abnormally hot.

[0043] The content of the binder in the composition is preferably from 1 to 70% by mass, more preferably from 20 to 50% by mass, relative to the total mass (100% by mass) of the composition. When gypsum and a hydraulic material are used in combination as a binder, the mixture thereof 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.

[0044] The composition part preferably further contains a liquid other than the hydrated water of the hydration product. When the composition part contains an excess liquid other than the hydrated water, the plateau time is longer, and the effect of suppressing heat propagation when the unit cell becomes abnormally hot is further enhanced.

[0045] A composition according to one embodiment of the composition part contains at least one of inorganic particles and inorganic fibers, and preferably contains a paste containing at least one of inorganic particles and inorganic fibers, excess liquid, and a binder. With respect to 100% by mass of the paste, 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. The liquid content is preferably 1 to 70% by mass, more preferably 1 to 50% by mass, and even more preferably 1 to 30% by mass, relative to 100% by mass of the paste. 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 1-10, more preferably 1-7, and even more preferably 1-5.

[0046] The thickness of the composition part is not particularly limited, but is preferably equal to or less than the thickness of the holding part described below, and more preferably less than the thickness of the holding part. By making the thickness of the composition part smaller than the thickness of the holding part, one or both sides in the thickness direction of the composition part held by the holding part become void layers. The presence of this void layer makes the composition part held by the holding part less likely to collapse, ensuring shape retention.

[0047] The viscosity of the composition used in the composition part before curing, 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 equal to or greater than the lower limit, the shape retention is excellent. When the viscosity of the composition is equal to or less than the upper limit, the handleability is excellent. The viscosity at 25°C of the cured composition used in the composition part, or of the composition part not containing a binder, as measured with a Brookfield viscometer is preferably 200 Pa s or more, more preferably 500 Pa s or more. When the viscosity of the composition is equal to or higher than the lower limit mentioned above, the shape retention is excellent.

[0048] (porous sheet) The inner envelope may comprise a porous sheet held by a holding portion. The porous sheet preferably contains fibrous materials (also referred to as fibrous inorganic materials) and / or inorganic particles (also referred to as powdered inorganic materials). Examples of fibrous materials (fibrous inorganic materials) include organic fibers such as paper, cotton sheets, polyimide fibers, aramid fibers, and polytetrafluoroethylene (PTFE) fibers, and inorganic fibers such as glass fibers, rock wool, ceramic fibers, and biosoluble inorganic fibers. Specific examples of ceramic fibers that can be used include silica-alumina fibers (silica:alumina ratio of 40:60 to 1:99), mullite fibers, and alumina fibers.

[0049] The inorganic particles (powdered inorganic material) are preferably at least one selected from the group consisting of silica particles, alumina particles, calcium silicate, aluminum hydroxide, clay minerals, vermiculite, mica, cement, perlite, fumed silica, and aerogel, and among these, at least one selected from silica particles, alumina particles, calcium silicate, aluminum hydroxide, and vermiculite is particularly preferred. More preferred inorganic particles are calcium silicate or aluminum hydroxide. Among the types of calcium silicates, xonotlite, tobermorite, wollastonite, and gyrolite are preferred, with gyrolite being particularly preferred. Gyrolite, which has a petal-like structure, maintains its porous structure even when compressed and deformed, and therefore has excellent water retention properties. Clay minerals are mainly magnesium silicate (including talc and sepiolite), montmorillonite, and kaolinite.

[0050] Among these, the porous sheet is preferably an inorganic fiber sheet, an inorganic particle sheet, paper, or a combination thereof, and more preferably at least one selected from paper, glass fiber, rock wool, ceramic fiber, and biosoluble inorganic fiber.

[0051] The thickness of the porous sheet can be 0.2 to 10 mm, preferably 0.5 to 8 mm, and more preferably 0.8 to 4 mm. If the thickness of the porous sheet is equal to or less than the upper limit, the volumetric energy density of the assembled battery tends to be improved. If the thickness of the porous sheet is equal to or more than the lower limit, the amount of water absorption tends to be large.

[0052] <Exterior body> The exterior body has a sealed peripheral portion and accommodates the inner body in an internal space formed by the sealing. The exterior body is flexible and can deform in response to the expansion of the unit cells. Furthermore, the exterior body can return to its original state when the unit cells contract. Specifically, when the unit cells expand as the spacers are placed between the unit cells and the unit cells are charged, the exterior body is compressed to absorb the expansion, and when the unit cells contract as they are discharged, the exterior body returns to its original state. The exterior body can be formed using a resin sheet, a resin film, etc. For example, the composition part and the holding part can be sandwiched between two or two-folded resin sheets or resin films, or the peripheral part of the exterior body where the two resin sheets or resin films come into contact can be heat-sealed or glued, thereby sealing and housing the composition part and the holding part inside.

[0053] The outer casing may be made of, for example, resin or metal. A laminate of metal foil and resin is preferred because of its high heat resistance and strength. As the laminate of metal foil and resin, a laminate of three or more layers including a resin layer, a metal foil layer, and a resin sealant layer is preferred.

[0054] 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. Specific examples include 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. Aluminum foil, copper foil, and nickel foil are particularly preferred, with aluminum foil being even more preferred.

[0055] 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, epoxy resin, polyurethane, polyether ether ketone, polyethylene terephthalate, polyphenyl sulfide, polycarbonate, and aramid. At least one selected from polypropylene, nylon, and polyethylene terephthalate is particularly preferred.

[0056] The thickness of the exterior body 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 heat resistance and low water vapor permeability, while the resin can improve sealing properties.

[0057] As described above, the exterior body can be provided so that the composition portion and the holding portion are hermetically sealed within the exterior body by joining the peripheral portions of two exterior bodies into a ring shape by heat fusion, adhesive, etc. Alternatively, one exterior body can be folded and the peripheral portions joined by heat fusion, adhesive, etc., so that the composition portion and the holding portion are sealed.

[0058] <Deformation characteristics> The cells are subjected to pressure during the manufacturing process to constrain the battery pack. Pressure is also applied due to the expansion of the electrodes during charging and the generation of gas from the electrolyte during charging and discharging. One aspect of the present invention is a spacer that has specific deformation characteristics that can withstand these external pressures. Here, the "compressive deformation ratio" refers to the ratio of the thickness when a predetermined external pressure is applied in the Z-axis direction (thickness direction) to the thickness when the external pressure is 0 MPa.

[0059] In one embodiment, when an external pressure of 0.2 MPa is applied to the spacer in its Z-axis direction, the compressive deformation rate in the same direction relative to the shape before the external pressure was applied is 20% or more, preferably 20 to 35%, and more preferably 20 to 30%. In one embodiment, when an external pressure of 1.0 MPa is applied to the spacer in its Z-axis direction, the compressive deformation rate in the same direction relative to the shape before the external pressure was applied is 50% or more, preferably 50 to 85%, and more preferably 60 to 75%. In one embodiment, the compressive deformation rate (X) in the Z-axis direction of the spacer when an external pressure of 0.2 MPa is applied in the same direction is 20 to 30%, and the compressive deformation rate (Y) when an external pressure of 1.0 MPa is applied in the same direction is 60 to 75%.

[0060] In one embodiment, the difference (YX) between the compressive deformation rate (X) in the Z-axis direction of the spacer when an external pressure of 0.2 MPa is applied in the same direction and the compressive deformation rate (Y) in the same direction when an external pressure of 1.0 MPa is applied in the same direction is 20 to 55%, preferably 30 to 55%, and more preferably 40 to 50%. In one embodiment, the ratio (Y / X) of the compressive deformation rate (X) in the Z-axis direction of the spacer when an external pressure of 0.2 MPa is applied to the same direction to the compressive deformation rate (Y) in the same direction when an external pressure of 1.0 MPa is applied to the same direction is 1 to 10, preferably 1.2 to 7, and more preferably 1.5 to 5.

[0061] It is preferable that the spacer does not burst when pressurized in the Z-axis direction at 1.0 MPa, and that the inner casing remains housed in the outer packaging.It is also preferable that the spacer does not burst when heated to 100°C at 1.7°C / min, and that the inner casing remains housed in the outer packaging.

[0062] The recovery rate of the holding part measured by the measuring method (1) described below is preferably 70 to 100%, more preferably 85 to 99%.

[0063] (Measurement method (1)) A hydraulic press (AS ONE high pressure jack 1t, 5t) is used to apply a load to the sample, while measuring the sample thickness using a film thickness meter. The recovery rate in this specification is calculated as the ratio of the sample thickness after the load is released in the 10th cycle to the initial sample thickness before the load is applied, after 10 cycles of applying and releasing the load, each cycle consisting of applying and releasing the load.

[0064] The thermal conductivity of the spacer in the Z-axis direction when the average surface temperature is 45°C is preferably 0.20 [W / (m K)] or more, and more preferably 0.25 to 5.0 [W / (m K)]. If the thermal conductivity is equal to or greater than the lower limit, the spacer is likely to function as a heat transfer material that efficiently transfers heat generated by a cell under normal conditions to an adjacent cell sandwiched between the spacer. The thermal conductivity is preferably measured under conditions where the composition portion is in contact with an exterior body. The thermal conductivity of the spacer at 45°C is measured by heating a thermally conductive resistance sheet whose thermal conductivity has been evaluated in advance to 45°C and measuring it simultaneously with the spacer. If the temperature difference between the front and back of the thermally conductive resistance sheet is Δt1 and the temperature difference between the front and back of the spacer is Δt2, the thermal conductivity of the spacer is calculated using the relationship "Δt1 × thermal conductivity of the thermally conductive resistance sheet / Δt2". The difference in thickness between the spacer and the thermally conductive resistance sheet is converted appropriately.

[0065] The thermal conductivity of the spacer when the average surface temperature is 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, of the thermal conductivity of the spacer when the average surface temperature is 25° C. This makes it easier for the spacer to function as a heat insulator that exhibits heat insulating properties and controls heat transfer to adjacent cells when the temperature of the cells becomes abnormally high. The thermal conductivity of the spacer decreases as the hydrated water and other liquids contained in the composition portion evaporate.

[0066] <Modified Example> The spacer according to the embodiment is not limited to the spacer 1 described above. 6 to 8, the spacer may include a holder 3 in which an outer wall 12 is arranged in the shape of a rectangular frame having two sides parallel to the X-axis direction and two sides parallel to the Y-axis direction, and a first partition wall 14 is further provided inside the outer wall 12, the first partition wall 14 rising from the inner bottom surface 10a in the Z-axis direction and extending in the Y-axis direction. In this example, both ends of the first partition wall 14 in the Y-axis direction are connected to the outer wall 12.

[0067] In the example shown in FIG. 6, one first partition wall 14 is provided in the center of the holding portion 3 in the X-axis direction so as to extend in the Y-axis direction, but the present invention is not limited to this configuration. The number of first partition walls 14 may be two or more. The number of first partition walls 14 may be, for example, 1 to 29, 1 to 14, or 1 to 5. The position of the first partition wall 14 may be shifted from the center of the holding portion 3 in the X-axis direction. The shape of the first partition wall 14 as viewed in the X-axis direction is rectangular in this example, but is not limited thereto. The shape of the first partition wall 14 as viewed in the Z-axis direction is linear in this example, but may also be wavy.

[0068] In this example, the first partition wall 14 consists of two side walls and a connecting portion connecting the upper parts of the side walls, and between the two side walls there is a recessed strip with an open bottom, but this is not limited to this. The XZ cross-sectional shape of the first partition wall 14, i.e., the shape of a cross section taken along a plane parallel to both the width direction and the Z-axis direction of the first partition wall 14, is a tapered shape whose width gradually increases from the tip to the base end. Because the first partition wall 14 has such an XZ cross-sectional shape, when pressure is applied from the Z-axis direction, the contact area with the exterior body 6 increases as the holding portion 3 deforms. More specifically, when the holding portion 3 is compressed and deformed in the Z-axis direction due to external pressure or expansion of the cell, the contact area with the exterior body 6 increases as the first partition wall 14 is compressed in the Z-axis direction. Therefore, as the holding portion 3 deforms, its resistance to compression increases, resulting in even better recovery.

[0069] 7, the XZ cross-sectional shape of the first partition wall 14 is a trapezoid whose width gradually narrows from the base end to the tip. Note that the XZ cross-sectional shape of the first partition wall 14 is not limited to a trapezoid, and may be, for example, a semicircular shape whose width gradually narrows from the base end to the tip. The XZ cross-sectional shape of the first partition wall 14 is preferably symmetrical with respect to a line m1 that is parallel to the Z-axis direction and passes through the center in the width direction of the first partition wall 14. This further improves the restorability of the holding portion 3.

[0070] The angle φ1 ( FIG. 7 ) formed between the XY plane and the side surface 14a of the first partition wall 14 satisfies φ1 > 90°. To improve the restorability after compressive deformation, φ1 > 95° is preferable, φ1 > 100° is more preferable, φ1 > 105° is even more preferable, and φ1 > 110° is particularly preferable. To ensure the volume of the holding portion, the angle φ is preferably φ1 < 140°, more preferably φ1 < 130°, even more preferably φ1 < 120°, and particularly preferably φ1 < 110°. The lower and upper limits of the angle φ1 can be combined arbitrarily. In addition, when the XZ cross-sectional shape of the first partition wall 14 is semicircular, the angle φ1 means the angle between the tangent at the center in the Z-axis direction of the side surface 14a of the first partition wall 14 in the XZ cross-section and the inner bottom surface 10a.

[0071] The angle φ1 of the side surfaces 14a on both sides in the width direction of the first partition wall 14 may be the same or different, but is preferably the same. The angle φ1 of the side surface 14a of the first partition wall 14 and the angle θ of the side surface 12a of the outer wall portion 12 may be the same or different, but are preferably the same.

[0072] When the cross-sectional shape of the first partition wall 14 is trapezoidal, the ratio of the total area of ​​the tip surfaces of the first partition wall 14 to the total area of ​​the first partition wall 14 on the surface parallel to the XY plane of the inner bottom surface 10a of the holding portion 3 is preferably 0.5% or more, more preferably 1% or more, and even more preferably 1.5% or more. If the area ratio of the first partition wall 14 is equal to or greater than the lower limit, the compressive deformation rate in the Z-axis direction tends to be smaller. The area ratio of the first partition wall 14 is preferably 15% or less, more preferably 12% or less, and even more preferably 9% or less. The lower and upper limits of the area ratio of the first partition wall 14 can be combined arbitrarily.

[0073] The length of the first partition wall 14 in the Z-axis direction, i.e., the length from the inner bottom surface 10a of the holding portion 3 to the tip of the first partition wall 14 in the Z-axis direction, is preferably 2 mm or more, more preferably 3 mm or more, and even more preferably 5 mm or more. If the length of the first partition wall 14 in the Z-axis direction is equal to or greater than the above-mentioned lower limit, it is easy to increase the elastic recovery rate. The length of the first partition wall 14 in the Z-axis direction is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 6 mm or less. The lower limit and upper limit of the length of the first partition wall 14 in the Z-axis direction can be combined arbitrarily. The length of the first partition wall 14 in the Z-axis direction is preferably the same as the length of the outer wall portion 12 in the Z-axis direction, but is not limited thereto.

[0074] The spacer may also include a holding portion provided with a second partition wall extending in the X-axis direction inside the outer wall portion. 9 to 11, the spacer may be provided with a retaining portion 3 in which the outer wall portion 12 is arranged in the shape of a rectangular frame having two sides parallel to the X-axis direction and two sides parallel to the Y-axis direction, and in addition to the first partition wall 14, a second partition wall 16 that rises from the inner bottom surface 10a in the Z-axis direction and extends in the X-axis direction is further provided inside the outer wall portion 12. In this example, both ends of the second partition wall 16 in the Y-axis direction are connected to the outer wall portion 12. It is also possible to provide a spacer including a holding portion 3 in which the first partition wall 14 is not provided inside the outer wall portion 12 but the second partition wall 16 is provided.

[0075] In the example shown in FIG. 9, one second partition wall 16 is provided in the center of the holding portion 3 in the Y-axis direction so as to extend in the X-axis direction, but the present invention is not limited to this configuration. The number of second partition walls 16 may be 2 or more. The number of second partition walls 16 may be, for example, 1 to 29, 1 to 23, or 1 to 11. The position of the second partition wall 16 may be shifted from the center of the holding portion 3 in the Y-axis direction. The shape of the second partition wall 16 when viewed from the Y-axis direction is rectangular in this example, but is not limited to this. The shape of the second partition wall 16 when viewed in the Z-axis direction is linear in this example, but may also be wavy.

[0076] The second partition wall 16 in this example consists of two side walls and a connecting portion connecting the upper parts of the side walls, and a recessed strip with an open bottom between the two side walls, but is not limited to this. In the YZ cross section of the second partition wall 16, i.e., a cross section cut along a plane parallel to both the width direction and the Z-axis direction of the second partition wall 16, the cross-sectional shape of the second partition wall 16 is a tapered shape whose width gradually increases from the tip to the base end. Because the second partition wall 16 has such a cross-sectional shape, when pressure is applied from the Z-axis direction, the contact area with the exterior body 6 increases as the holding portion 3 deforms. More specifically, when the holding portion 3 is compressed and deformed in the Z-axis direction due to external pressure or expansion of the cell, the contact area with the exterior body 6 increases as the second partition wall 16 is compressed in the Z-axis direction. Therefore, as the holding portion 3 deforms, its resistance to compression increases further, resulting in even better recovery.

[0077] 7, the YZ cross section of the second partition wall 16 is a trapezoid whose width gradually narrows from the base end to the tip. Note that the YZ cross section of the second partition wall 16 is not limited to a trapezoid, and may be, for example, a semicircular shape whose width gradually narrows from the base end to the tip. The YZ cross section of the second partition wall 16 is preferably symmetrical with respect to a line m2 that is parallel to the Z axis direction and passes through the center of the second partition wall 16 in the width direction. This further improves the restorability of the holding part 3.

[0078] The angle φ2 ( FIG. 11 ) formed between the YZ plane and the side surface 16a of the second partition wall 16 satisfies φ2 > 90°. Since this improves the restorability after compressive deformation, φ2 > 95° is preferable, φ2 > 100° is more preferable, φ2 > 105° is even more preferable, and φ2 > 110° is particularly preferable. In terms of ensuring the volume of the holding portion, the angle φ is preferably φ2 < 140°, more preferably φ2 < 130°, even more preferably φ2 < 120°, and particularly preferably φ2 < 110°. The lower and upper limits of the angle φ2 can be combined arbitrarily. In addition, when the YZ cross-sectional shape of the second partition wall 16 is semicircular, the angle φ2 means the angle between the tangent at the center of the Z-axis direction of the side surface 16a of the second partition wall 16 in the YZ cross-section and the inner bottom surface 10a.

[0079] The angles φ2 of the side surfaces 16a on both sides in the width direction of the second partition wall 16 may be the same or different, but are preferably the same. The angle φ1 of the side 14a of the first partition wall 14, the angle φ2 of the side 16a of the second partition wall 16, and the angle θ of the side 12a of the outer wall portion 12 may be the same or different, but it is preferable that they are the same.

[0080] When the cross-sectional shape of the second partition wall 16 is trapezoidal, the ratio of the total area of ​​the tip surfaces of the second partition wall 16 to the total area of ​​the second partition wall 16 on the surface parallel to the XY plane of the inner bottom surface 10a of the holding portion 3 is preferably 0.5% or more, more preferably 1% or more, and even more preferably 1.5% or more. If the area ratio of the second partition wall 16 is equal to or greater than the lower limit, the compressive deformation rate in the Z-axis direction tends to be smaller. The area ratio of the second partition wall 16 is preferably 15% or less, more preferably 12% or less, and even more preferably 9% or less. The lower and upper limits of the area ratio of the second partition wall 16 can be combined arbitrarily.

[0081] The length of the second partition wall 16 in the Z-axis direction, i.e., the length from the inner bottom surface 10a of the holding portion 3 to the tip of the second partition wall 16 in the Z-axis direction, is preferably 2 mm or more, more preferably 3 mm or more, and even more preferably 5 mm or more. If the length of the second partition wall 16 in the Z-axis direction is equal to or greater than the above-mentioned lower limit, the compressive deformation rate in the Z-axis direction tends to be smaller. The length of the first partition wall 14 in the Z-axis direction is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 6 mm or less. The lower and upper limits of the length of the second partition wall 16 in the Z-axis direction can be combined in any manner. The length of the second partition wall 16 in the Z-axis direction is preferably the same as the length of the outer wall portion 12 in the Z-axis direction, but is not limited thereto.

[0082] The spacer may include a retaining portion provided with a first partition wall whose both ends are not connected to the outer wall portion. When the first partition wall is not connected to the outer wall portion, the composition portions on both sides of the first partition wall are connected at the portion between the first partition wall and the outer wall portion, thereby improving the shape retention of the composition portion. More specifically, when the unit cell becomes abnormally hot, the retaining portion may melt and lose its shape due to the heat. However, if the composition portions are connected to each other at the portion between the first partition wall and the outer wall portion, the shape of the composition portion is more likely to be maintained even if the retaining portion melts, and the heat insulating performance is maintained for a longer period of time.

[0083] For example, as shown in Figures 12 to 14, the spacer may have a retaining portion 3 in which a first partition wall 14 is provided inside an outer wall portion 12 arranged in a rectangular frame shape, and further, between the first partition wall 14 and the outer wall portions 12 on both sides, a first partition wall 14A is provided, the both ends of which are not connected to the outer wall portions 12.

[0084] In the example shown in FIGS. 12 to 14, two first partition walls 14A are provided so as to extend in the Y-axis direction midway between the first partition wall 14 and the outer wall portion 12, but the present invention is not limited to this configuration. The number of first partition walls 14A that are not connected to the outer wall portion 12 may be two or more. The number of first partition walls 14 may be, for example, 1 to 28, 2 to 13, or 2 to 4. The position of the first partition wall 14A that is not connected to the outer wall portion 12 may be shifted from the midpoint between the first partition wall 14 and the outer wall portion 12. The shape of the first partition wall 14A that is not connected to the outer wall portion 12 when viewed in the Z-axis direction is linear in this example, but may also be wavy.

[0085] In the example shown in Fig. 14, the shape of the first partition wall 14A that is not connected to the outer wall portion 12 when viewed from the X-axis direction is trapezoidal. As a result, when pressure is applied from the Z-axis direction, the contact area of ​​the exterior body 6 increases as the holding portion 3 deforms. More specifically, when the holding portion 3 is compressed and deformed in the Z-axis direction due to external pressure or expansion of the cell, the contact area of ​​the first partition wall 14A with the exterior body 6 increases as it is compressed in the Z-axis direction. Therefore, as the holding portion 3 deforms, its resistance to compression further increases, resulting in even better recovery. The shape of the first partition wall 14A as viewed in the X-axis direction is not limited to a trapezoidal shape, and may be a semicircular shape or a wavy shape as shown in the example of Fig. 15. The first partition wall 14A having a wavy shape as viewed in the X-axis direction has an upper edge that moves up and down in a wavy shape as viewed in the X-axis direction.

[0086] In the example shown in Figure 13, the XZ cross-sectional shape of the first partition wall 14A, i.e., the shape of the cross section cut by a plane parallel to both the width direction and the Z-axis direction of the first partition wall 14A, is rectangular, but this is not limited to this.

[0087] 16, a spacer may be provided with a first partition wall 14 provided inside an outer wall portion 12 arranged in a rectangular frame shape, and further with a retaining portion 3 in which first partition walls 14A, both ends of which are not connected to the outer wall portions 12, are provided between the first partition wall 14 and the outer wall portions 12 on both sides and have a wavy shape when viewed from the Z-axis direction. As shown in FIG. 17, the shape of the first partition wall 14A in this example when viewed from the X-axis direction is rectangular, but this is not limited to this.

[0088] The length of the first partition wall 14A in the Z-axis direction, i.e., the length from the inner bottom surface 10a of the holding portion 3 to the tip of the first partition wall 14 in the Z-axis direction, is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 3 mm or more. If the length of the first partition wall 14A in the Z-axis direction is equal to or greater than the above-mentioned lower limit, it is easy to increase the elastic recovery rate. The length of the first partition wall 14A in the Z-axis direction is preferably 9 mm or less, more preferably 6 mm or less, and even more preferably 5 mm or less. The lower and upper limits of the length of the first partition wall 14A in the Z-axis direction can be combined in any manner. The length of the first partition wall 14A in the Z-axis direction can be, but is not limited to, shorter than the length of the outer wall portion 12 in the Z-axis direction. The length of the first partition wall 14A in the Z-axis direction may be the same as the length of the outer wall portion 12 in the Z-axis direction, or may be longer than the length of the outer wall portion 12 in the Z-axis direction.

[0089] Furthermore, the first partition wall 14A that is not connected to the outer wall portion 12 may have a semicircular XZ cross section and a semicircular YZ cross section. Typically, such a first partition wall 14 may have the shape of a cut-out portion of a sphere. The second partition wall may also be configured so as not to be connected to the outer wall portion, similar to the first partition wall. In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate.

[0090] [Battery pack] The battery pack according to the embodiment includes the spacer according to the embodiment described above and a plurality of unit cells. As an example, as shown in FIG. 18, a plurality of cells 200 and spacers 1 disposed between the cells 200 are stacked and housed in, for example, a housing 300. The spacers 1 are disposed at least between the cells 200 constituting the battery pack 100 to prevent the cells 200 from contacting each other. In addition to being disposed between the cells 200, the spacer of the present invention can also be used as a spacer (1A) to separate the cells 200 from components other than the cells. Here, "components other than cells" refers to, for example, a housing having a bottom and four side surfaces that houses the cells and spacers constituting the battery pack, and in FIG. 18, it is the bottom of the housing. The orientation of the spacer 1 in the battery pack during use is not particularly limited, and the thickness direction of the spacer 1 may be parallel to the horizontal plane or may intersect with the horizontal plane.

[0091] As described above, the spacer 1 comprises an inner body having a composition portion and a holding portion that is used as needed, and an outer body that houses the inner body. The compressive deformation ratio of the spacer in the thickness direction is preferably in the range of 0.1 to 20 MPa. By setting the compressive deformation ratio to 0.1 MPa or more, an appropriate stress can be applied to the unit cells, and the unit cells can be securely fixed. From the above viewpoints, the compressive deformation ratio is more preferably 0.2 MPa or more, and even more preferably 0.5 MPa or more. On the other hand, the upper limit is preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less, from the viewpoint of being able to absorb stress due to swelling during charge and discharge and further expansion during deterioration over time, thereby enabling a longer life of the cell.

[0092] The compressive deformation rate (23°C) is generally a value measured in accordance with JIS K7181, but in the present invention, the value is evaluated by simply measuring the pressure and the spacer thickness when pressure is applied so that the spacer thickness becomes approximately 95% to 50% of the thickness when no pressure is applied, and calculating the ratio to the thickness when no pressure is applied. The spacer can be used as it is to separate the cells or the cells from other components, but to make it easier to fix the spacer when separating the cells or the cells from other components, adhesive or double-sided tape may be attached to the surface, or a piece of resin or the like may be attached to the surface.

[0093] [Single cell] The unit 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 the lithium ion secondary battery, other secondary batteries such as a lithium ion all-solid-state battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, etc. may also be used. Furthermore, the type of the cell may be a prismatic cell, a pouch-shaped cell, a cylindrical cell, or the like, and the present invention is applicable regardless of the type of battery.

[0094] Fig. 19 is a plan view showing an example of a cell 200 constituting a battery pack, Fig. 20 is a front view of the cell 200 shown in Fig. 19, and Fig. 21 is a right side view of the cell 200. The cell 200 is formed in the shape of a rectangular parallelepiped 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.

[0095] The battery pack according to the present embodiment as described above is applied to battery packs mounted in, for example, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric heavy machinery, electric motorcycles, electrically assisted bicycles, ships, aircraft, trains, uninterruptible power supplies (UPSs), home energy storage systems, and storage battery systems for stabilizing power systems that utilize renewable energy sources such as wind, solar, tidal, and geothermal energy. However, the battery pack can also be used as a power source that supplies power to devices other than the above-mentioned EVs.

[0096] It is preferable that the unit structure of the battery pack, which is made up of two cells and the spacer disposed between the two cells, satisfies the following condition (i). (i) When the average surface temperature of the spacer in contact with the two cells is 25°C, the thermal conductivity of the spacer drops to 70% or less when the average surface temperature is 200°C.

[0097] When the unit structure of the battery pack satisfies condition (i), the spacer normally functions as a heat transfer material that efficiently transfers heat generated from a cell to an adjacent cell, and when a cell becomes abnormally hot, the spacer fully exerts its effect of functioning as a heat insulator that exhibits insulating properties and controls the transfer of heat to the adjacent cell. The thermal conductivity of the spacer when the average surface temperature is 200°C is more preferably reduced to 60% or less, and even more preferably reduced to 50% or less, of the thermal conductivity when the average surface temperature is 25°C.

[0098] It is preferable that the unit structure consisting of two unit cells and a spacer disposed between the two unit cells satisfies the following condition (ii). (ii) When a pressure of 0.2 MPa is applied between two unit cells, the deformation rate of the spacer disposed between the unit cells is 6.0% or more.

[0099] When the unit structure of the battery pack satisfies the condition (ii), even if external pressure is applied to the spacer due to expansion of the cells, expansion of the electrodes during charging, or gas generation from the electrolyte during charging and discharging, the spacer can deform and absorb the external pressure, which tends to make the spacer even less likely to burst. The deformation rate of the condition (ii) is more preferably 6.0 to 60%, and even more preferably 10 to 60%. [Explanation of symbols]

[0100] 1 spacer 2. Inclusion bodies 3 Holding part 4. Composition part (heat transfer control layer) 5 void layer 6. Exterior body 10 Bottom part 12 Exterior wall 14,14A First Partition Wall 16 Second Partition Wall 100 battery packs 200 cells 210 terminal 220 terminal 300 cabinets

Claims

1. A spacer for separating unit cells, the spacer comprising an outer casing and an inner casing enclosed within the outer casing, The inner container has a tray-shaped holding portion, When a plane parallel to the inner bottom surface of the holding portion is defined as an XY plane, and a direction perpendicular to the XY plane is defined as a Z-axis direction, the holding portion includes an outer wall portion rising in the Z-axis direction from at least a part of the outer edge portion of the inner bottom surface, A spacer in which, in a cross section of the outer wall portion cut by a plane parallel to both the width direction of the outer wall portion and the Z-axis direction, the cross-sectional shape of the outer wall portion is a tapered shape whose width gradually increases from the tip to the base end.

2. The spacer according to claim 1 , wherein the cross-sectional shape of the outer wall portion is trapezoidal or semicircular.

3. The spacer according to claim 1 , wherein a contact area between the holding portion and the exterior body increases when pressure is applied in the Z-axis direction.

4. The spacer according to claim 1 or 2, wherein an angle θ formed between the XY plane and the side surface of the outer wall portion satisfies θ>90°.

5. The spacer according to claim 1 or 2, wherein the holding portion contains a composition portion containing at least one of inorganic particles and inorganic fibers.

6. 3. The spacer according to claim 1, wherein the cross-sectional shape of the outer wall portion is symmetrical with respect to a line passing through the center of the outer wall portion in the width direction and parallel to the Z-axis direction.

7. the outer wall portion is arranged in the shape of a rectangular frame having two sides parallel to the X-axis direction and two sides parallel to the Y-axis direction, The spacer according to claim 1 or 2, wherein the holding portion further comprises a first partition wall extending in the Y-axis direction inside the outer wall portion.

8. 8. The spacer according to claim 7, wherein the XZ cross-sectional shape of said first partition wall is a tapered shape whose width gradually narrows from the base end to the tip end.

9. The spacer according to claim 8 , wherein the XZ cross section of the first partition wall is trapezoidal or semicircular.

10. The spacer according to claim 7 , wherein the first partition wall has a trapezoidal, semicircular or wavy shape when viewed from the X-axis direction.

11. the outer wall portion is arranged in the shape of a quadrangular frame having two sides parallel to the X-axis direction and two sides parallel to the Y-axis direction, The spacer according to claim 1 or 2, wherein the holding portion further comprises a second partition wall extending in the X-axis direction inside the outer wall portion.

12. The spacer according to claim 11 , wherein the YZ cross-sectional shape of the second partition wall is a tapered shape whose width gradually narrows from the base end to the tip end.

13. The spacer according to claim 12 , wherein the YZ cross section of the second partition wall is trapezoidal or semicircular.

14. The spacer according to claim 11 , wherein the second partition wall has a trapezoidal, semicircular or wavy shape when viewed from the Y-axis direction.

15. 3. The spacer according to claim 1, wherein the recovery rate of the retaining portion measured by the following measurement method (1) is 70 to 100%.

16. A battery pack comprising a plurality of unit cells and the spacer according to claim 1 or 2 disposed between the unit cells.

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