Elastic sheets and battery modules

Abstract

This suppresses the deterioration of the elastic sheet due to localized stress concentration and the increase in the reaction force of the elastic sheet due to compression. [Solution] The elastic sheet 3 is an elastic sheet 3 applied to a battery module 100, and includes a flat base plate portion 30 including a first surface S1 and a first projection 31 protruding from the first surface S1, the first projection 31 being annular in plan view.

Description

Technical Field

[0001] The present disclosure relates to the technology of elastic sheets.

Background Art

[0002] A battery module used in a moving body such as an electric vehicle includes a stack of a plurality of battery cells. The battery cells expand due to heat generation during charging. As a result of each battery cell expanding, there is a risk that adjacent battery cells will push against each other and be damaged. In addition, it is necessary to pressurize the battery cells in order to suppress the precipitation of acicular crystals due to long-term use of the battery cells. Therefore, it has been conventionally proposed to install an elastic sheet between the battery cells. For example, Patent Document 1 discloses a buffer sheet for a battery module including a base portion and elastic protrusions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] A battery module according to one aspect of the present disclosure includes a first battery cell and a second battery cell, and an elastic sheet interposed between the first battery cell and the second battery cell, wherein the elastic sheet includes a base material portion on a flat plate including a first surface, and a first projection protruding from the first surface, the first projection being annular in plan view.

[0007] An elastic sheet according to one aspect of the present disclosure is an elastic sheet applied to a battery module, comprising a flat base plate portion including a first surface, and a first projection protruding from the first surface, wherein a first recess is formed in the first projection, and when the first projection is compressed toward the first surface, the inner wall surface of the first recess elastically deforms radially inward within the first recess. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a battery module. [Figure 2] This is a schematic diagram of the elastic sheet according to the first embodiment. [Figure 3] This is a plan view of the elastic sheet according to the first embodiment. [Figure 4] This is a cross-sectional view of the elastic sheet according to the first embodiment. [Figure 5] This is a perspective view of the elastic sheet relating to the proportionality 1 according to the first embodiment. [Figure 6] This is a cross-sectional view of the first projection relating to the proportionality 1 according to the first embodiment. [Figure 7] This is a correlation graph between the amount of compression and reaction force of the elastic sheet according to the first embodiment (comparison between proportionality 1 and the first embodiment). [Figure 8] This is a schematic diagram of the inclination angle α of the first outer surface and the inclination angle β of the first inner surface. [Figure 9] This is a cross-sectional view of the first projection according to the second embodiment. [Figure 10] This is a correlation graph between the compressibility and reaction force of the elastic sheet according to the second embodiment (comparison between proportionality 2 and the second embodiment). [Figure 11] This is a correlation graph between the compression ratio and reaction force of the elastic sheet according to the second embodiment (comparison based on the difference in outer diameter at the outer edge of the first bottom surface). [Figure 12] This is a correlation graph between the compressibility and reaction force of an elastic sheet according to the second embodiment (comparison based on differences in inclination angle α and inclination angle β). [Modes for carrying out the invention]

[0009] The embodiments for implementing this disclosure will be described with reference to the drawings. Note that the dimensions and scale of the elements in each drawing may differ from those of the actual product. Furthermore, the embodiments described below are illustrative examples of embodiments that may be envisioned when implementing this disclosure. Therefore, the scope of this disclosure is not limited to the embodiments exemplified below.

[0010] A: First Embodiment Figure 1 is a schematic diagram of a battery module 100. The battery module 100 is applied to batteries for electric vehicles, etc. As illustrated in Figure 1, the battery module 100 includes a plurality of battery cells 1, a housing 2, and a plurality of elastic sheets 3. Each of the plurality of elastic sheets 3 is interposed between each of the plurality of adjacent battery cells 1.

[0011] Each battery cell 1 is a flattened rectangular parallelepiped. Each battery cell 1 is stacked in a direction perpendicular to the flattened plane of each battery cell 1. For example, lithium-ion secondary batteries can be used as battery cells 1. The housing 2 is a hollow structure that houses the multiple battery cells 1 and the multiple elastic sheets 3. Specifically, the housing 2 is formed in a rectangular parallelepiped shape including a top surface 20, side surfaces 21 and a bottom surface 22. The top surface 20 and the bottom surface 22 are rectangular plate-like members that face each other with a predetermined distance between them. The side surfaces 21 are rectangular frame-like members that connect the periphery of the top surface 20 and the periphery of the bottom surface 22.

[0012] Each battery cell 1 expands in a direction perpendicular to its flattened surface due to the heat generated during charging. In a configuration where each battery cell 1 is installed in direct contact with each other, the expansion of each battery cell 1 may cause adjacent battery cells 1 to press against each other and be damaged. In addition, needle-shaped crystals may precipitate inside the battery cells 1 after prolonged use, but the precipitation of needle-shaped crystals can be suppressed by pressurizing the battery cells 1. To prevent adjacent battery cells 1 from directly contacting each other and to suppress the precipitation of needle-shaped crystals by pressurizing the battery cells 1, an elastic sheet 3 is interposed between each of the adjacent battery cells 1.

[0013] The elastic sheet 3 is a plate-shaped rubber elastic body. Examples of materials for the elastic sheet 3 include chloroprene rubber (CR), silicone rubber (SR), acrylic rubber (ACM), urethane rubber (U), polyurethane rubber (PUR), vinyl methyl silicone rubber (VMQ), ethylene propylene diene rubber (EPDM), or fluororubber (FKM). However, the material of the elastic sheet 3 is not limited to the above examples.

[0014] The elastic sheet 3 functions as a buffer that suppresses the propagation of pressure between the battery cells 1 by elastically deforming to follow the shape of each battery cell 1 when each battery cell 1 expands during charging. As each battery cell 1 contracts during discharge, the reaction force acting from the elastic sheet 3 on the battery cell 1 decreases. However, in order to suppress the deposition of needle-shaped crystals, it is necessary to maintain a reaction force acting from the elastic sheet 3 on the battery cell 1 above a certain level. Therefore, even when each battery cell 1 contracts during discharge, the elastic sheet 3 provides a sufficient reaction force to each battery cell 1 to suppress the deposition of needle-shaped crystals.

[0015] FIG. 2 is a schematic view of the elastic sheet 3. In the following description, the vertical direction in FIG. 2 is defined as the Z-axis. One direction along the Z-axis is defined as the Z1 direction, and the opposite direction of the Z1 direction is defined as the Z2 direction. One direction parallel to the plane perpendicular to the Z-axis is defined as the X direction, and one direction orthogonal to the X direction is defined as the Y direction. In the following description, observing an arbitrary object from the perspective along the Z-axis is denoted as "plan view".

[0016] As illustrated in FIG. 2, the elastic sheet 3 includes a base material portion 30 and a plurality of first protrusion portions 31. The elastic sheet 3 is formed by injection molding using a molding die such as a metal die or a resin die. Specifically, a liquid elastic material is injected into the molding die and cured by cooling to form the elastic sheet 3. That is, the elastic sheet 3 is a molded product in which the base material portion 30 and the plurality of first protrusion portions 31 are integrally formed.

[0017] The base material portion 30 is a flat plate-like portion in the elastic sheet 3. Specifically, the base material portion 30 is a flat plate-like portion parallel to the X-Y plane. The base material portion 30 includes a first surface S1 and a second surface S2. The first surface S1 and the second surface S2 are surfaces on opposite sides of each other. Note that the Z1 direction is the direction from the second surface S2 toward the first surface S1, and the Z2 direction is the direction from the first surface S1 toward the second surface S2.

[0018] The plurality of first protrusion portions 31 protrude in the Z1 direction from the first surface S1. The plurality of first protrusion portions 31 are arranged in a matrix pattern in the X direction and the Y direction on the first surface S1. Specifically, the plurality of first protrusion portions 31 are arranged vertically and horizontally (in the X direction and the Y direction). That is, the first protrusion portions 31 are arranged in the horizontal direction, and the first protrusion portions 31 are also arranged in the vertical direction. That is, the plurality of first protrusion portions 31 are evenly distributed over the entire area of the first surface S1. Note that the number and position of the first protrusion portions 31 (or the arrangement pattern of the plurality of protrusion portions) are appropriately changed according to the dimensions of the elastic sheet 3 and the like.

[0019] Figure 3 is a plan view of the first projection 31 according to the first embodiment. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3. The central axis C of the first projection 31 is shown in Figures 3 and 4. In the following description, the direction of the radius in a virtual circle of arbitrary diameter centered on the central axis C will be referred to as the "radial direction". In the radial direction, the direction opposite to the central axis C will be referred to as the "outside", and in the radial direction, the direction toward the central axis C will be referred to as the "inside". In the first embodiment, for convenience, we will focus on one first projection 31, but the shapes of multiple first projections 31 are common.

[0020] As illustrated in Figures 3 and 4, the first projection 31 is a portion that protrudes from the first surface S1 in the Z1 direction. The first projection 31 is annular in plan view. In this embodiment, "annular" means a shape obtained by removing other closed regions that exist inside one closed region when viewed from plan. A "closed region" is, for example, a region enclosed by one or both of a curve and / or a line segment. In other words, "annular" means a shape composed of straight lines or curves that loop around and enclose space.

[0021] The first projection 31 includes a first outer surface 32, a first top surface 33, a first inner surface 34, and a first bottom surface 35.

[0022] As illustrated in Figure 4, the first outer peripheral surface 32 is a side wall surface facing radially outward at the first projection 31. The first outer peripheral surface 32 protrudes from the first surface S1 in the Z1 direction. As illustrated in Figures 3 and 4, the first outer peripheral surface 32 is a surface of rotation about the central axis C.

[0023] In a plan view, the outer diameter Φ1 at the edge 32b (i.e., the lower edge) of the first outer circumferential surface 32 in the Z2 direction is larger than the outer diameter Φ2 at the edge 32a (i.e., the upper edge) of the first outer circumferential surface 32 in the Z1 direction. In other words, the first outer circumferential surface 32 is inclined with respect to the first surface S1. The first outer circumferential surface 32 can also be described as a frustoconical side surface protruding from the first surface S1. The edge 32b of the first outer circumferential surface 32 in the Z2 direction can also be described as the outer edge 31c of the first projection 31.

[0024] As illustrated in Figure 4, the first top surface 33 is the upper surface of the first projection 31 that is located in the Z1 direction relative to the first surface S1. The first top surface 33 is a flat surface parallel to the first surface S1. The outer peripheral edge 33c of the first top surface 33 corresponds to the edge 32a of the first outer peripheral surface 32 in the Z1 direction. When the elastic sheet 3 is interposed between each battery cell 1, the first top surface 33 is in contact with the battery cell 1.

[0025] The first inner circumferential surface 34 is a side wall surface facing radially inward at the first projection 31. That is, the first inner circumferential surface 34 is located inside the first outer circumferential surface 32 in a plan view. The first inner circumferential surface 34 protrudes from the first surface S1 in the Z1 direction. As illustrated in Figures 3 and 4, the edge 34a (i.e., the upper edge) of the first inner circumferential surface 34 in the Z1 direction corresponds to the inner circumferential edge 33d of the first apex surface 33. The first inner circumferential surface 34 is a plane of revolution about the central axis C. The first apex surface 33 is a plane connecting the edge 32a of the first outer circumferential surface 32 in the Z1 direction and the edge 34a of the first inner circumferential surface 34 in the Z1 direction.

[0026] In a plan view, both the inner periphery 33d and the outer periphery 33c of the first vertex 33 are circular in shape with respect to the central axis C. Therefore, the width from the inner periphery 33d to the outer periphery 33c of the first vertex 33 is equal around its entire circumference. Also, in a plan view, the first vertex 33 is annular.

[0027] In a plan view, the inner diameter Φ3 at the edge 34a (i.e., the upper edge) in the Z1 direction of the first inner surface 34 is larger than the inner diameter Φ4 at the edge 34b (i.e., the lower edge) in the Z2 direction of the first inner surface 34. In other words, the first inner surface 34 is inclined with respect to the first surface S1. The first inner surface 34 can also be described as a frustoconical side surface protruding from the first surface S1.

[0028] The first base surface 35 is a region located inside the first inner circumferential surface 34 in a plan view. The outer edge 35c of the first base surface 35 is circular in shape with respect to the central axis C in a plan view. The outer edge 35c of the first base surface 35 corresponds to the edge 34b (i.e., the lower edge) of the first inner circumferential surface 34 in the Z2 direction. The outer edge 35c of the first base surface 35 can also be described as the inner circumferential edge 31d of the first projection 31.

[0029] As illustrated in Figure 4, the first base surface 35 is located in the Z2 direction relative to the first top surface 33. The first base surface 35 is a flat surface parallel to the first surface S1. That is, the thickness D1 from the first base surface 35 to the second surface S2 is constant over the entire surface of the first base surface 35. Also, the position of the first base surface 35 in the Z-axis direction coincides with the position of the first surface S1 in the Z-axis direction. Specifically, the thickness D1 from the first base surface 35 to the second surface S2 is the same as the thickness D2 from the first surface S1 to the second surface S2 on the outside of the first projection 31. That is, the region of the first surface S1 outside the first projection 31 and the first base surface 35 of the first projection 31 are located in the same plane. The first base surface 35 may also be interpreted as a part of the first surface S1.

[0030] As described above, the elastic sheet 3 is formed by injection molding using a mold. In the molding process, if the thickness D1 from the first bottom surface 35 to the second surface S2 is greater than the thickness D2 from the first surface S1 to the second surface S2 on the outside of the first projection 31, the flow path of the mold becomes narrower in the region outside the first projection 31, making it difficult for the liquid elastic material to flow through that flow path. Also, if the thickness D1 from the first bottom surface 35 to the second surface S2 is smaller than the thickness D2 from the first surface S1 to the second surface S2 on the outside of the first projection 31, the flow path of the mold becomes narrower in the region inside the first projection 31, making it difficult for the liquid elastic material to flow through that flow path. In contrast, according to the first embodiment, since the thickness of the base material 30 is the same inside and outside the first projection 31, there is an advantage that the liquid elastic material can easily flow through the internal space of the mold.

[0031] As illustrated in Figures 3 and 4, a space (hereinafter referred to as the "first recess 36") is formed in the first projection 31, enclosed by the first inner circumferential surface 34 and the first bottom surface 35. As described above, the inner diameter Φ4 at the edge 34b in the Z2 direction of the first inner circumferential surface 34 (i.e., the outer peripheral edge 35c of the first bottom surface 35) is less than the inner diameter Φ3 at the edge 34a in the Z1 direction of the first inner circumferential surface 34 (i.e., the inner peripheral edge 33d of the first top surface 33). Therefore, the first recess 36 has a frustoconical shape that decreases in diameter toward the Z2 direction. The first inner circumferential surface 34 is an example of the "inner wall surface of the first recess".

[0032] Figure 5 is a perspective view of a configuration in which the first projection 31 does not have a first recess 36 (hereinafter referred to as "proportionality 1"). Figure 6 is a cross-sectional view of the first projection 31 in proportionality 1. As illustrated in Figures 5 and 6, in proportionality 1, a cylindrical portion protruding in the Z1 direction from the first surface S1 of the base material 30 is formed as the first projection 31. In contrast to proportionality 1, in the first embodiment, the first recess 36 is formed on the first projection 31, which has the effect of suppressing an excessive increase in the reaction force of the elastic sheet 3 compared to proportionality 1. The effects of the first embodiment compared to proportionality 1 are described in detail below.

[0033] As a result of the expansion of the battery cell 1, pressure is applied from the battery cell 1 to the first top surface 33, causing the first projection 31 to elastically deform in the Z-axis direction. Figure 7 is a graph showing the correlation between the amount of compression of the elastic sheet 3 and the reaction force. The vertical axis represents the magnitude (N) of the reaction force acting from the elastic sheet 3 to the battery cell 1. The horizontal axis represents the amount of compression (mm) of the elastic sheet 3 due to the expansion of the battery cell 1.

[0034] In Figure 7, the dotted line graph shows the relationship between the amount of compression and the reaction force in proportionality 1. In proportionality 1, since the first projection 31 is cylindrical, the first projection 31 elastically deforms outward in a plan view. Therefore, as the elastic sheet 3 is compressed, the reaction force acting from the elastic sheet 3 to the battery cell 1 increases.

[0035] On the other hand, the solid line graph shows the relationship between the amount of compression and the reaction force in the first embodiment. In the first embodiment, since the first projection 31 is annular, the first projection 31 elastically deforms not only on the outside but also on the inside when viewed in plan. Therefore, compared to proportionality 1, the increase in the reaction force accompanying the compression of the elastic sheet 3 is more gradual.

[0036] Here, we will explain the functions required of the elastic sheet 3.

[0037] As mentioned above, the elastic sheet 3 functions as a buffer that suppresses the propagation of pressure between the battery cells 1 by elastically deforming to follow the shape of each battery cell 1 when each battery cell 1 expands during charging. However, if the reaction force acting from the elastic sheet 3 to the battery cells 1 is too high, the battery cells 1 will be damaged. Therefore, a maximum value Rmax is set for the reaction force acting from the elastic sheet 3 to the battery cells 1.

[0038] When each battery cell 1 contracts, the reaction force acting on the battery cell 1 from the elastic sheet 3 decreases. However, in order to suppress the deposition of needle-shaped crystals, the elastic sheet 3 needs to act a constant reaction force on each battery cell 1 even when each battery cell 1 contracts. Therefore, a minimum value Rmin is set for the reaction force acting on the battery cell 1 from the elastic sheet 3. That is, the reaction force acting on the battery cell 1 from the elastic sheet 3 needs to be within the range from the minimum value Rmin to the maximum value Rmax.

[0039] The difference between the compression amount corresponding to the maximum value Rmax and the compression amount corresponding to the minimum value Rmin is called the displacement absorption amount A. The larger the displacement absorption amount A in the elastic sheet 3, the more the increase in reaction force due to compression by the battery cell 1 is suppressed. The displacement absorption amount A is the amount of displacement in the Z-axis direction that can occur in the elastic sheet 3 under the condition that the reaction force acting from the elastic sheet 3 to the battery cell 1 is limited between the maximum value Rmax and the minimum value Rmin.

[0040] In proportionality 1, where the first recess 36 is not formed on the first projection 31, deformation occurs only outward when compressed by the battery cell 1, making it difficult to secure a large displacement absorption amount A0, as shown in Figure 7. In contrast to proportionality 1, in the first embodiment, the first recess 36 is formed on the first projection 31, so deformation occurs not only outward but also inward within the first recess 36 when compressed by the battery cell 1. Therefore, as illustrated in Figure 7, it is possible to increase the displacement absorption amount A1 compared to proportionality 1. As described above, according to the first embodiment, a larger displacement absorption amount A1 can be secured than in proportionality 1 while limiting the reaction force acting from the elastic sheet 3 on the battery cell 1 between the maximum value Rmax and the minimum value Rmin. In other words, it is possible to achieve a high level of both suppression of excess or deficiency of the reaction force on the battery cell 1 and securing the displacement absorption amount A1. Therefore, according to the first embodiment, compared to proportionality 1, for example, an excessive increase in the reaction force of the elastic sheet 3 can be suppressed.

[0041] As described above with reference to Figure 1, the elastic sheet 3 is interposed between adjacent battery cells 1. In the first embodiment, the battery cell 1 facing the first surface S1 is in contact with the first top surface 33, and the battery cell 1 facing the second surface S2 is in contact with the second surface S2.

[0042] Since the first top surface 33 is a flat surface parallel to the first surface S1, the first top surface 33 makes uniform contact with the battery cell 1. Therefore, compared to a configuration in which the first top surface 33 is not parallel to the first surface S1, it is possible to suppress a local increase in the reaction force acting from the first top surface 33 to the battery cell 1.

[0043] When the expanded battery cell 1 exerts pressure on the first top surface 33, the first projection 31 elastically deforms inward in a plan view, resulting in compression of the air in the internal space of the first projection 31 (i.e., the first recess 36). If the internal space (i.e., the first recess 36) is sealed by the battery cell 1 contacting the first top surface 33, the pressure of the air in the internal space (i.e., the first recess 36) increases, resulting in an excessive reaction force acting from the elastic sheet 3 on the battery cell 1. Therefore, in the first embodiment, a first groove 37 is formed on the first top surface 33 to release the air in the internal space (i.e., the first recess 36) to the outside of the first projection 31.

[0044] As illustrated in Figures 3 and 4, the first groove 37 is a recess that is indented in the Z1 direction. The first groove 37 is located in the Z1 direction relative to the first bottom surface 35. The first groove 37 is formed in a rectangular shape with a constant width from the outer peripheral edge 33c to the inner peripheral edge 33d of the first top surface 33. The cross-sectional shape of the first groove 37 is a trapezoid that tapers in diameter in the Z2 direction. That is, the cross-sectional shape of the first groove 37 is a trapezoid where the upper base is larger than the lower base. Compared to a configuration in which the first groove 37 is not formed on the first top surface 33, it is possible to suppress an excessive increase in reaction force due to air compression in the internal space of the first projection 31 (i.e., the first recess 36).

[0045] Figure 8 is a schematic diagram showing the inclination angles of the first outer circumferential surface 32 and the first inner circumferential surface 34 with respect to the first surface S1. As illustrated in Figure 8, the inclination angle α of the first outer circumferential surface 32 with respect to the first surface S1 is acute. The inclination angle α of the first outer circumferential surface 32 is constant over its entire circumference. In a configuration where the inclination angle α of the first outer circumferential surface 32 is acute, the pressure exerted on the first projection 31 by the expansion of the battery cell 1 is distributed not only in the direction perpendicular to the first surface S1 but also in the inclination direction of the first outer circumferential surface 32. Therefore, compared to configurations where the inclination angle α of the first outer circumferential surface 32 is right or obtuse, an excessive increase in the reaction force of the elastic sheet 3 can be suppressed.

[0046] The inclination angle β of the first inner surface 34 with respect to the first surface S1 is acute. The inclination angle β of the first inner surface 34 is constant over its entire circumference. In a configuration where the inclination angle β of the first inner surface 34 is acute, the pressure exerted on the first projection 31 by the expansion of the battery cell 1 is distributed not only in the direction perpendicular to the first surface S1 but also in the inclination direction of the first inner surface 34. Therefore, compared to a configuration where the inclination angle β of the first inner surface 34 is right or obtuse, an excessive increase in the reaction force of the elastic sheet 3 can be suppressed.

[0047] The inclination angle α of the first outer surface 32 and the inclination angle β of the first inner surface 34 are equal. In a configuration where the inclination angle α of the first outer surface 32 is sufficiently larger than the inclination angle β of the first inner surface 34, the expansion of the battery cell 1 causes pressure to act from the battery cell 1 to the first top surface 33, which may cause the first projection 31 to tilt radially outward. Similarly, in a configuration where the inclination angle β of the first inner surface 34 is sufficiently larger than the inclination angle α of the first outer surface 32, the first inner surface 34 is more likely to deform radially inward than the first outer surface 32. Therefore, the first projection 31 may tilt radially inward. In contrast to these, according to the first embodiment, since the inclination angle α of the first outer surface 32 and the inclination angle β of the first inner surface 34 are equal, excessive deformation of the first projection 31 in either the outward or inward direction is suppressed. Therefore, compared to a configuration where the difference between the inclination angle α of the first outer surface 32 and the inclination angle β of the first inner surface 34 is large, the possibility of the first projection 31 tilting outward or inward can be reduced.

[0048] As illustrated in Figure 4, the first bottom surface 35 is a flat surface parallel to the first surface S1. In configurations where the thickness D1 between the first bottom surface 35 and the second surface S2 differs depending on the position within the first bottom surface 35 (for example, a configuration where the first bottom surface 35 is a curved surface, or a configuration where the first bottom surface 35 is inclined with respect to the second surface S2), the expansion of the battery cell 1 causes pressure to act from the battery cell 1 to the elastic sheet 3, resulting in uneven deformation of the first projection 31 due to the difference in thickness inside the first projection 31 of the base material 30. Therefore, according to the first embodiment, the uneven deformation of the first projection 31 is suppressed compared to a configuration where the thickness D1 between the first bottom surface 35 and the second surface S2 differs depending on the position within the first bottom surface 35. Consequently, an excessive increase in the reaction force of the elastic sheet 3 can be suppressed.

[0049] B: Second Embodiment A second embodiment of this disclosure will now be described. For elements whose function is the same as in the first embodiment in each of the embodiments described below, the same reference numerals as in the first embodiment will be used, and detailed descriptions of each will be omitted as appropriate.

[0050] The elastic sheet 3 according to the second embodiment further includes a plurality of second protrusions 41 in addition to elements similar to those of the first embodiment. The plurality of second protrusions 41 project from the second surface S2 toward the Z2 direction. Each of the plurality of second protrusions 41 corresponds to each of the plurality of first protrusions 31 (not shown). That is, there is a one-to-one correspondence between the plurality of second protrusions 41 and the plurality of first protrusions 31. Specifically, the plurality of second protrusions 41 and the plurality of first protrusions 31 overlap each other in a plan view, and both are centered on the central axis C.

[0051] Figure 9 is a cross-sectional view of the elastic sheet 3 according to the second embodiment. In the following description, a reference plane S3 is assumed. As illustrated in Figure 9, the reference plane S3 is a plane that passes through the midpoint of the first plane S1 and the second plane S2 and is parallel to the XY plane. The first projection 31 and the second projection 41 are formed symmetrically with respect to the reference plane S3. That is, the second projection 41 and the first projection 31 have the same configuration.

[0052] The second projection 41 is a portion that protrudes from the second surface S2 in the Z2 direction. The second projection 41 is annular in plan view. The second projection 41 includes a second outer surface 42, a second top surface 43, a second inner surface 44, and a second bottom surface 45.

[0053] The second outer circumferential surface 42 is a side wall surface facing radially outward at the second projection 41. The second outer circumferential surface 42 protrudes from the second surface S2 in the Z2 direction. The second outer circumferential surface 42 is a rotational surface about the central axis C.

[0054] The second outer surface 42 corresponds to the first outer surface 32. Therefore, the outer diameter of the edge 42a of the second outer surface 42 in the Z1 direction corresponds to the outer diameter Φ1 of the edge 32b of the first outer surface 32 in the Z2 direction. Also, the outer diameter of the edge 42b of the second outer surface 42 in the Z2 direction corresponds to the outer diameter Φ2 of the edge 32a of the first outer surface 32 in the Z1 direction. In other words, the second outer surface 42 is inclined with respect to the second surface S2. The angle of inclination of the second outer surface 42 with respect to the second surface S2 is the same as the angle of inclination α of the first outer surface 32 with respect to the first surface S1. The second outer surface 42 can also be described as a frustoconical side surface protruding from the second surface S2. The edge 42a of the second outer surface 42 in the Z1 direction can also be described as the outer edge 41c of the second projection 41.

[0055] The second top surface 43 is the lower surface of the second projection 41, located in the Z2 direction relative to the second surface S2. The second top surface 43 is a flat surface parallel to the second surface S2. The outer peripheral edge 43c of the second top surface 43 corresponds to the Z2 direction edge 42b of the second outer peripheral surface 42. The second top surface 43 corresponds to the first top surface 33. When the elastic sheet 3 is interposed between each battery cell 1, the second top surface 43 contacts the battery cell 1 facing the second surface S2.

[0056] The length L1 from the first apex 33 to the second apex 43 is smaller than the outer diameter Φ1 at the outer peripheral edge 31c of the first projection 31.

[0057] The second inner circumferential surface 44 is a side wall surface facing radially inward at the second projection 41. That is, the second inner circumferential surface 44 is located inside the second outer circumferential surface 42 in a plan view. The second inner circumferential surface 44 protrudes from the second surface S2 in the Z2 direction. The edge 44b of the second inner circumferential surface 44 in the Z2 direction corresponds to the inner circumferential edge 43d of the second top surface 43. The second inner circumferential surface 44 is a plane of revolution about the central axis C. The second top surface 43 is a plane connecting the edge 42b of the second outer circumferential surface 42 in the Z2 direction and the edge 44b of the second inner circumferential surface 44 in the Z2 direction.

[0058] The second inner surface 44 corresponds to the first inner surface 34. Therefore, the inner diameter of the edge 44b of the second inner surface 44 in the Z2 direction corresponds to the outer diameter Φ3 of the edge 34a of the first inner surface 34 in the Z1 direction. Also, the inner diameter of the edge 44a of the second inner surface 44 in the Z1 direction corresponds to the outer diameter Φ4 of the edge 34b of the first inner surface 34 in the Z2 direction. In other words, the second inner surface 44 is inclined with respect to the second surface S2. The angle of inclination of the second inner surface 44 with respect to the second surface S2 is the same as the angle of inclination β of the first inner surface 34 with respect to the first surface S1. The second inner surface 44 can also be described as a frustoconical side surface protruding from the second surface S2.

[0059] The second base surface 45 is a region located inside the second inner circumferential surface 44 in a plan view. The outer edge 45c of the second base surface 45 is circular in shape with respect to the central axis C in a plan view. The outer edge 45c of the second base surface 45 corresponds to the edge 44a of the second inner circumferential surface 44 in the Z1 direction. The outer edge 45c of the second base surface 45 can also be described as the inner circumferential edge 41d of the second projection 41. The second base surface 45 corresponds to the first base surface 35.

[0060] The second base surface 45 is located in the Z1 direction relative to the second top surface 43. The second base surface 45 is a flat surface parallel to the second surface S2. That is, the thickness D3 from the second base surface 45 to the first base surface 35 is constant over the entire area of ​​the second base surface 45. Also, the position of the second base surface 45 in the Z-axis direction coincides with the position of the second surface S2 in the Z-axis direction. Specifically, the thickness D3 from the second base surface 45 to the first base surface 35 is the same as the thickness D2 from the first surface S1 to the second surface S2 on the outside of the second projection 41. That is, the region of the second surface S2 outside of the second projection 41 and the second base surface 45 of the second projection 41 are located in the same plane. The second base surface 45 may also be interpreted as a part of the second surface S2.

[0061] A space (hereinafter referred to as the "second recess 46") is formed in the second projection 41, enclosed by the second inner circumferential surface 44 and the second bottom surface 45. The second recess 46 has a frustoconical shape that decreases in diameter in the Z1 direction. The second recess 46 corresponds to the first recess 36.

[0062] As described above with reference to Figure 1, the elastic sheet 3 is interposed between adjacent battery cells 1. In the second embodiment, the battery cell 1 facing the first surface S1 is in contact with the first top surface 33, and the battery cell 1 facing the second surface S2 is in contact with the second top surface 43. Note that since the first projection 31 and the second projection 41 are formed symmetrically with respect to the reference surface S3, the elastic sheet 3 may also be interposed between adjacent battery cells 1 with the first surface S1 and the second surface S2 reversed.

[0063] As illustrated in Figure 9, similar to the relationship between the first top surface 33 and the first groove 37, the second groove 47 is formed on the second top surface 43 to release the air inside the second projection 41 (i.e., the second recess 46) to the outside of the second projection 41.

[0064] The second groove 47 is a recess that is indented in the Z1 direction. The second groove 47 is located in the Z1 direction more than the second bottom surface 45. The second groove 47 is formed in a rectangular shape with a constant width from the outer peripheral edge 43c to the inner peripheral edge 43d of the second top surface 43. The cross-sectional shape of the second groove 47 is a trapezoid that tapers in diameter in the Z1 direction. That is, the cross-sectional shape of the second groove 47 is a trapezoid where the upper base is smaller than the lower base. The second groove 47 corresponds to the first groove 37.

[0065] For comparison with the second embodiment, we will consider a configuration (hereinafter referred to as "proportionality 2") in which, similar to proportionality 1, the first projection 31 does not have a first recess 36 and the second projection 41 does not have a second recess 46. In proportionality 2, the first projection 31 and the second projection 41 deform only outward when compressed by the battery cell 1. In contrast to proportionality 2, in the second embodiment, since recesses are formed on the top surfaces of the first projection 31 and the second projection 41, they deform not only outward but also inward when compressed by the battery cell 1. Therefore, compared to proportionality 2, there is an effect that, for example, excessive increases in the reaction force of the elastic sheet 3 can be suppressed.

[0066] As the battery cell 1 expands, pressure acts from the battery cell 1 onto the first top surface 33 and the second top surface 43, resulting in elastic deformation of the first projection 31 and the second projection 41 in the Z-axis direction. As the elastic sheet 3 is compressed, the reaction force acting from the elastic sheet 3 on the battery cell 1 increases. Figure 10 is a graph showing the correlation between the compressibility of the elastic sheet 3 and the reaction force. The vertical axis represents the magnitude (N) of the reaction force acting from the elastic sheet 3 on the battery cell 1. The horizontal axis represents the compressibility (%) of the elastic sheet 3 as the battery cell 1 expands.

[0067] In proportionality 2, the first projection 31 and the second projection 41 are cylindrical in shape with no recesses formed on their top surfaces, so the first projection 31 and the second projection 41 elastically deform outward in a plan view. On the other hand, in the second embodiment, the first projection 31 and the second projection 41 are annular in shape, so the first projection 31 and the second projection 41 elastically deform not only outward but also inward in a plan view. Therefore, as illustrated in Figure 10, similar to the relationship between the first embodiment and proportionality 1, the increase in reaction force associated with the compression of the elastic sheet 3 is more gradual compared to proportionality 2.

[0068] The relationship between the compressibility and reaction force of the elastic sheet 3 tends to depend on the outer diameter Φ4 of the first projection 31 or the second projection 41. Figure 11 is a graph showing the relationship between compressibility and reaction force for several cases in which the outer diameters Φ4 of the outer edge 35c of the first bottom surface 35 and the outer edge 45c of the second bottom surface 45 are different. In the measurement in Figure 11, a configuration is assumed in which the inclination angle α of the first outer surface 32 and the second outer surface 42 and the inclination angle β of the first outer surface 32 and the second outer surface 42 are both 90°.

[0069] The larger the outer diameter Φ4 at the outer edge 35c of the first base surface 35, the more space is secured for the first projection 31 to elastically deform inward. Therefore, as illustrated in Figure 11, the larger the outer diameter Φ4 at the outer edge 35c of the first base surface 35, the more the increase in reaction force due to compression by the battery cell 1 is suppressed. The same applies to the second projection 41.

[0070] Furthermore, the larger the outer diameter Φ4 at the outer peripheral edge 35c of the first bottom surface 35, the larger the volume of the first recess 36 and the second recess 46. Therefore, compared to a configuration in which the first recess 36 and the second recess 46 are not formed, the amount of material required to manufacture the elastic sheet 3 is reduced, making it possible to lighten and reduce the cost of the elastic sheet 3.

[0071] Furthermore, the relationship between the compressibility of the elastic sheet 3 and the reaction force tends to depend on the inclination angle α of the first outer surface 32 and the second outer surface 42, and the inclination angle β of the first outer surface 32 and the second outer surface 42. Figure 12 is a graph showing the relationship between compressibility and reaction force for several cases in which the inclination angles α and β are different. In the measurement in Figure 12, the outer diameter Φ4 of the outer edge 35c of the first bottom surface 35 and the outer edge 45c of the second bottom surface 45 is 4 mm, and the case in which the inclination angle α and the inclination angle β are equal is assumed.

[0072] The smaller the inclination angle α of the first outer surface 32 and the inclination angle β of the first inner surface 34, the more the pressure received by the first projection 31 is distributed not only in the direction perpendicular to the first surface S1 but also in the inclination direction of the first outer surface 32 and the first inner surface 34. Therefore, as illustrated in Figure 12, the smaller the inclination angle α of the first outer surface 32 and the second outer surface 42 and the inclination angle β of the first inner surface 34 and the second inner surface 44, the more the increase in reaction force due to compression by the battery cell 1 is suppressed. The same applies to the second projection 41.

[0073] C: Variant The following are examples of specific modifications that may be added to each of the embodiments exemplified above. Two or more embodiments may be arbitrarily selected from the following examples and merged as appropriate, provided they do not contradict each other.

[0074] (1) In the first embodiment, a molded product in which a base material portion 30 and a plurality of first protrusions 31 are integrally formed was illustrated. However, a plurality of first protrusions 31 formed separately from the base material portion 30 may be joined to the first surface S1 of the base material portion 30. Similarly, in the second embodiment, a plurality of second protrusions 41 formed separately from the base material portion 30 may be joined to the second surface S2 of the base material portion 30.

[0075] (2) In the embodiments described above, a configuration was shown in which a portion of the base material 30 is located inside the inner peripheral edge 31d of the first projection 31. However, the base material 30 may be removed over the entire area inside the inner peripheral edge 31d of the first projection 31. That is, a through hole may be formed inside the inner peripheral edge 31d of the first projection 31, penetrating from the first surface S1 to the second surface S2.

[0076] (3) In the first embodiment, a configuration in which the planar shape of the first vertex 33 is annular was illustrated. In the second embodiment, a configuration in which the planar shapes of the first vertex 33 and the second vertex 43 are annular was illustrated. However, the planar shape of the first vertex 33 may be polygonal. However, in the configuration in which the planar shape of the first vertex 33 is polygonal, when pressure is applied from the battery cell 1 to the elastic sheet 3, stress concentrates near the corners of the planar shape. In contrast, in the configuration in which the planar shape of the first vertex 33 is annular, localized stress concentration on the first vertex 33 is less likely to occur. Therefore, there is an advantage in that the possibility of damage to the elastic sheet 3 due to localized stress concentration is reduced. The same applies to the second vertex 43.

[0077] (4) In the first embodiment, a configuration in which the first bottom surface 35 is circular in shape with respect to the central axis C in a plan view was illustrated. In the second embodiment, a configuration in which the first bottom surface 35 and the second bottom surface 45 are circular in shape with respect to the central axis C in a plan view was illustrated. However, the planar shape of the first bottom surface 35 may be polygonal. However, in the configuration in which the planar shape of the first bottom surface 35 is polygonal, when pressure is applied from the battery cell 1 to the elastic sheet 3, stress concentrates near the corners of the planar shape. In contrast, in the configuration in which the planar shape of the first bottom surface 35 is circular, localized stress concentration on the first bottom surface 35 is less likely to occur. Therefore, there is an advantage in that the possibility of damage to the elastic sheet 3 due to localized stress concentration is reduced. The same applies to the second bottom surface 45.

[0078] (5) In the second embodiment, a configuration was shown in which the length L1 from the first top surface 33 to the second top surface 43 is smaller than the outer diameter Φ1 at the outer peripheral edge 31c of the first projection 31. However, the length L1 from the first top surface 33 to the second top surface 43 may be larger than the outer diameter Φ1 at the outer peripheral edge 31c of the first projection 31. However, in a configuration in which the length L1 from the first top surface 33 to the second top surface 43 is larger than the outer diameter Φ1 at the outer peripheral edge 31c of the first projection 31, when pressure is applied from the battery cell 1 to the elastic sheet 3, the first projection 31 and the second projection 41 tend to tilt radially outward or inward. Therefore, from the viewpoint of maintaining the posture of the first projection 31 and the second projection 41, a configuration in which the length L1 from the first top surface 33 to the second top surface 43 is smaller than the outer diameter Φ1 at the outer peripheral edge 31c of the first projection 31 is preferable. In other words, if the length L1 from the first top surface 33 to the second top surface 43 is smaller than the outer diameter Φ1 at the outer edge 31c of the first projection 31, the orientation of the first projection 31 and the second projection 41 can be maintained. Specifically, the ratio Φ1 / L1 of the outer diameter Φ1 at the outer edge 31c of the first projection 31 to the length from the first top surface 33 to the second top surface 43 is 2.15 or greater.

[0079] (6) In the second embodiment, the first projection 31 and the second projection 41 were shown to be the same annular shape in plan view. However, a configuration in which the planar shape of the first projection 31 and the planar shape of the second projection 41 are different may also be adopted.

[0080] (7) In the second embodiment, a configuration was shown in which the cross-sectional shapes of the first projection 31 and the second projection 41 are the same frustoconical shape. However, a configuration in which the cross-sectional shapes of the first projection 31 and the second projection 41 are different can also be adopted.

[0081] (8) In the embodiments described above, each of the multiple elastic sheets 3 was shown to be interposed between each of the multiple adjacent battery cells 1. However, each of the multiple elastic sheets 3 may be interposed between the battery cell 1 and the housing 2. For example, a configuration in which the elastic sheet 3 is interposed between the side portion 21 of the housing 2 and the battery cell 1 is conceivable.

[0082] (9) In the embodiments described above, a configuration in which the inclination angle α of the first outer peripheral surface 32 is acute was illustrated. However, the inclination angle α of the first outer peripheral surface 32 may be right angle. However, in the configuration in which the inclination angle α of the first outer peripheral surface 32 is acute, as a result of the expansion of the battery cell 1, pressure is applied from the battery cell 1 to the first top surface 33, and the pressure received by the first projection 31 is distributed not only in the direction perpendicular to the first surface S1 but also in the inclination direction of the first outer peripheral surface 32.

[0083] (10) In the embodiments described above, a configuration in which the inclination angle β of the first inner surface 34 is acute was illustrated. However, the inclination angle β of the first inner surface 34 may be right angle. However, in the configuration in which the inclination angle β of the first inner surface 34 is acute, as a result of the expansion of the battery cell 1, pressure is applied from the battery cell 1 to the first top surface 33, and the pressure received by the first projection 31 is distributed not only in the direction perpendicular to the first surface S1 but also in the inclination direction of the first inner surface 34.

[0084] (11) In the embodiments described above, a configuration in which the inclination angle α of the first outer surface 32 and the inclination angle β of the first inner surface 34 are equal was illustrated. However, a configuration in which the inclination angle α of the first outer surface 32 is greater than the inclination angle β of the first inner surface 34, or a configuration in which the inclination angle α of the first outer surface 32 is less than the inclination angle β of the first inner surface 34, can also be adopted. However, a configuration in which the inclination angle α of the first outer surface 32 and the inclination angle β of the first inner surface 34 are equal has the advantage that the possibility of the first projection 31 tilting outward or inward can be reduced.

[0085] (12) In the embodiments described above, an example was given in which, in a plan view, both the inner circumferential edge 33d and the outer circumferential edge 33c of the first top surface 33 are circular in shape with respect to the central axis C. However, in a plan view, the inner circumferential edge 33d and the outer circumferential edge 33c of the first top surface 33 may be circular in shape with respect to different central axes. However, in the former configuration, the width from the inner circumferential edge 33d to the outer circumferential edge 33c of the first top surface 33 is equal around the entire circumference. Therefore, compared to the latter configuration, there is an advantage in that when pressure is applied from the battery cell 1 to the elastic sheet 3, the uneven deformation of the first projection 31 is suppressed. The relationship between the inner circumferential edge 43d and the outer circumferential edge 43c of the second top surface 43 in the second embodiment is the same as the relationship between the inner circumferential edge 33d and the outer circumferential edge 33c of the first top surface 33.

[0086] (13) In the embodiments described above, the elastic sheet 3 is shown as being formed by injection molding, but the method of forming the elastic sheet 3 is arbitrary. For example, the elastic sheet 3 may be formed by compression molding. Specifically, the elastic sheet 3 is formed by compressing a heated elastic material between molds and then hardening it by cooling.

[0087] (14) The notation "nth" (where n is a natural number) in this application is used solely as a formal and convenient label to distinguish each element in notation and has no substantive meaning whatsoever. Therefore, there is no room for restrictive interpretation of the position or manufacturing order of each element based on the notation "nth".

[0088] D: Addendum From the forms exemplified above, the following configuration can be understood, for example.

[0089] An elastic sheet according to one aspect of the present disclosure (Aspect 1) is an elastic sheet applied to a battery module, comprising a flat base plate portion including a first surface and a first projection protruding from the first surface, wherein the first projection is annular in plan view. According to the above aspect, when pressure is applied to the elastic sheet from the battery module, the first projection elastically deforms not only outward in plan view but also inward. Therefore, compared to a configuration in which the first projection is not annular in plan view, an excessive increase in the reaction force of the elastic sheet can be suppressed. Note that a "battery module" comprises a laminate of a plurality of battery cells and a restraining member that restrains the laminate in the stacking direction. The elastic sheet applied to the battery module is installed between adjacent battery cells in the battery module, or between a battery cell and a restraining member. "Annular" refers to a shape obtained by removing other closed regions located inside one closed region from a closed region in plan view. A "closed region" refers to, for example, a region enclosed by one or both of a curve and a line segment. In other words, "ring-shaped" refers to a shape composed of straight or curved lines that loop around and enclose space.

[0090] In a specific example of Embodiment 1 (Embodiment 2), the inner circumferential surface of the first projection is inclined with respect to the first surface, and the angle of inclination of the inner circumferential surface with respect to the first surface is acute. According to the above embodiment, when pressure is applied from the battery module to the elastic sheet, the pressure received by the first projection is distributed not only in the direction perpendicular to the first surface but also in the direction of inclination of the inner circumferential surface of the first projection. Therefore, compared to a configuration in which the angle of inclination of the inner circumferential surface of the first projection is right angle, it is possible to suppress an excessive increase in the reaction force of the elastic sheet.

[0091] In a specific example of Embodiment 1 (Embodiment 3), the outer circumferential surface of the first projection is inclined with respect to the first surface, and the angle of inclination of the outer circumferential surface with respect to the first surface is acute. According to the above embodiment, when pressure is applied from the battery module to the elastic sheet, the pressure received by the first projection is distributed not only in the direction perpendicular to the first surface but also in the direction of inclination of the outer circumferential surface of the first projection. Therefore, compared to a configuration in which the angle of inclination of the outer circumferential surface of the first projection is right angle, it is possible to suppress an excessive increase in the reaction force of the elastic sheet.

[0092] In a specific example of Embodiment 2 or Embodiment 3 (Embodiment 4), the inclination angle of the inner circumferential surface is equal to the inclination angle of the outer circumferential surface. When pressure is applied to the elastic sheet from the battery module, in a configuration where the inclination angle of the inner circumferential surface is sufficiently larger than the inclination angle of the outer circumferential surface, the inner circumferential surface is more likely to deform inward than the outer circumferential surface. Therefore, the first projection may tilt inward. Similarly, in a configuration where the inclination angle of the outer circumferential surface is sufficiently larger than the inclination angle of the inner circumferential surface, the first projection may tilt outward. In contrast to these, according to Embodiment 4, since the inclination angle of the inner circumferential surface of the first projection is equal to the inclination angle of the outer circumferential surface of the first projection, excessive deformation of the first projection inward or outward is suppressed. Therefore, compared to a configuration where the difference between the inclination angle of the outer circumferential surface of the first projection and the inclination angle of the inner circumferential surface of the first projection is large, the possibility of the first projection tilting outward or inward can be reduced.

[0093] In any specific example of Embodiments 1 to 4 (Embodiment 5), the top surface of the first projection is parallel to the first surface. According to the above embodiments, when the battery cell and the elastic sheet come into contact, the top surface of the first projection makes uniform contact with the battery cell. Therefore, a localized increase in the reaction force of the elastic sheet can be suppressed.

[0094] In any specific example (6) of embodiments 1 to 5, the top surface includes a groove, which is formed extending from the inner periphery to the outer periphery of the top surface. According to the above embodiments, when pressure is applied from the battery module to the elastic sheet, the air inside the first projection, compressed by the elastic deformation of the first projection, is released to the outside of the first projection through the groove. Therefore, compared to a configuration without a groove on the top surface, it is possible to suppress an excessive increase in reaction force due to the compression of air inside the first projection.

[0095] In any specific example of Embodiments 1 to 6 (Embodiment 7), the first projection includes a bottom surface parallel to the first surface. According to the above embodiments, the deviation due to deformation of the first projection is suppressed compared to a configuration in which the bottom surface of the first projection is not parallel to the first surface of the base material (for example, a configuration in which the bottom surface is curved, or a configuration in which the bottom surface is inclined with respect to the first surface). Therefore, an excessive increase in the reaction force of the elastic sheet can be suppressed.

[0096] In a specific example of Embodiment 7 (Embodiment 8), in a plan view, the thickness of the base material on the inside of the first projection is the same as the thickness of the base material on the outside of the first projection. In the above embodiments, the thickness of the base material is the same on the inside of the first projection and on the outside of the first projection. Therefore, when injection molding an elastic sheet by pouring a liquid elastic material into a mold, there is an advantage that the liquid elastic material flows more easily throughout the mold compared to a configuration in which the thickness of the base material on the inside of the first projection is thinner than the thickness of the base material on the outside of the first projection.

[0097] In any specific example of Embodiments 1 to 8 (Embodiment 9), a second projection is further included that protrudes from a second surface opposite to the first surface, and the second projection is annular in plan view. According to the above embodiments, when pressure is applied from the battery module to the elastic sheet, the second projection elastically deforms not only on the outside but also on the inside in plan view. Therefore, compared to a configuration in which the second projection is not formed on the second surface, an excessive increase in the reaction force of the elastic sheet can be suppressed.

[0098] In a specific example of Embodiment 9 (Embodiment 10), the second projection overlaps the first projection in a plan view. According to the above embodiments, when pressure is applied from the battery module to the elastic sheet, the possibility of distorted deformation of the substrate due to the displacement of the positions of the pressure received by the first projection and the pressure received by the second projection in a plan view is reduced. Therefore, the reaction force of the elastic sheet is more stable compared to a configuration in which the first projection and the second projection do not overlap in a plan view.

[0099] In a specific example of Embodiment 10 (Embodiment 11), the ratio of the outer diameter of the first projection in a plan view to the length from the top surface of the first projection to the top surface of the second projection is 2.15 or greater. In this embodiment, when the first projection is subjected to pressure, the possibility of the pressure being biased in a particular direction and causing the first projection to tip over is reduced. As a result of the reduced possibility of the first projection tipping over, the reaction force of the elastic sheet becomes stable. Note that if the first projection has a shape other than a circle, "outer diameter of the first projection in a plan view" means the diameter of the circumscribed circle of the first projection in a plan view.

[0100] A battery module according to one aspect of the present disclosure (Aspect 12) includes a first battery cell and a second battery cell, and an elastic sheet interposed between the first battery cell and the second battery cell, wherein the elastic sheet includes a base material portion on a flat plate including a first surface, and a first projection protruding from the first surface, the first projection being annular in plan view. According to the above aspect, when pressure is applied to the elastic sheet from the battery module, the first projection elastically deforms not only outward in plan view but also inward. Therefore, compared to a configuration in which the first projection is not annular in plan view, an excessive increase in the reaction force of the elastic sheet can be suppressed.

[0101] An elastic sheet according to one aspect of the present disclosure (Aspect 13) is an elastic sheet applied to a battery module, comprising a flat base plate portion including a first surface and a first projection protruding from the first surface, wherein a first recess is formed in the first projection, and when the first projection is compressed toward the first surface, the inner wall surface of the first recess elastically deforms radially inward in the first recess. According to the above aspect, when pressure is applied to the elastic sheet from the battery module, the first projection elastically deforms inward in a plan view. Therefore, compared to a configuration in which the top surface of the first projection does not have a first recess, an excessive increase in the reaction force of the elastic sheet can be suppressed. Note that "elastically deforms radially inward" includes not only a configuration in which the first projection elastically deforms radially inward only, but also a configuration in which the first projection elastically deforms radially outward as well as inward. [Explanation of symbols]

[0102] 1...Battery cell, 2...Housing, 3...Elastic sheet, 20...Top surface, 21...Side surface, 22...Bottom surface, 30...Base material, 31...First projection, 31c...Outer peripheral edge of the first projection, 31d...Inner peripheral edge of the first projection, 32...First outer surface, 32a...Edge of the first outer surface in the Z1 direction, 32b...Edge of the first outer surface in the Z2 direction, 33...First top surface, 33c...Outer peripheral edge of the first top surface, 33d...Inner peripheral edge of the first top surface, 34...First inner surface, 34a...Edge of the first inner surface in the Z1 direction, 34 b... Z2 direction edge of the first inner surface, 35... first bottom surface, 35c... outer peripheral edge of the first bottom surface, 36... first recess, 37... first groove, 41... second projection, 41c... outer peripheral edge of the second projection, 41d... inner peripheral edge of the second projection, 42... second outer surface, 42a... Z1 direction edge of the second outer surface, 42b... Z2 direction edge of the second outer surface, 43... second top surface, 43c... outer peripheral edge of the second top surface, 43d... inner peripheral edge of the second top surface, 44... second inner surface, 44a... Z1 direction of the second inner surface Edge, 44b...Edge of the second inner circumferential surface in the Z2 direction, 45...Second bottom surface, 45c...Outer peripheral edge of the second bottom surface, 46...Second recess, 47...Second groove, 100...Battery module, A...Displacement absorption amount, A0...Proportional displacement absorption amount, A1...Displacement absorption amount of the first embodiment, C...Central axis, D1...Thickness from the first bottom surface to the second surface, D2...Thickness from the first surface to the second surface on the outside of the first projection, L1...Length from the first top surface to the second top surface, Rmax...From the elastic sheet to the battery Rmin…Maximum reaction force acting on the cell, Minimum reaction force acting from the elastic sheet to the battery cell, S1…First surface, S2…Second surface, α…Angle of inclination of the first outer surface relative to the first surface, β…Angle of inclination of the first inner surface relative to the first surface, Φ1…Outer diameter of the first outer surface at the edge in the Z2 direction, Φ2…Outer diameter of the first outer surface at the edge in the Z1 direction, Φ3…Inner diameter of the first inner surface at the edge in the Z1 direction, Φ4…Inner diameter of the first inner surface at the edge in the Z2 direction.

Claims

1. An elastic sheet applied to a battery module, A flat base plate portion including the first surface, Including a first projection protruding from the first surface, The first projection is annular in plan view. Elastic sheet.

2. The inner circumferential surface of the first projection is inclined with respect to the first surface, The inclination angle of the inner circumferential surface with respect to the first surface is acute. The elastic sheet according to claim 1.

3. The outer circumferential surface of the first projection is inclined with respect to the first surface, The angle of inclination of the outer circumferential surface with respect to the first surface is acute. The elastic sheet according to claim 1.

4. The inclination angle of the inner surface is equal to the inclination angle of the outer surface. An elastic sheet according to claim 2 or claim 3.

5. The top surface of the first projection is parallel to the first surface. The elastic sheet according to claim 4.

6. The aforementioned top surface includes a groove, The groove is formed extending from the inner edge to the outer edge of the top surface. The elastic sheet according to claim 5.

7. The first projection includes a bottom surface parallel to the first surface. The elastic sheet according to claim 6.

8. In a plan view, the thickness of the base material on the inside of the first projection is the same as the thickness of the base material on the outside of the first projection. The elastic sheet according to claim 7.

9. It further includes a second projection that protrudes from the second surface opposite to the first surface, The second projection is annular in plan view. The elastic sheet according to claim 1.

10. The second projection overlaps the first projection in a plan view. The elastic sheet according to claim 9.

11. The ratio of the outer diameter of the first projection in a plan view to the length from the top surface of the first projection to the top surface of the second projection is 2.15 or greater. The elastic sheet according to claim 10.

12. The device includes a first battery cell and a second battery cell, and an elastic sheet interposed between the first battery cell and the second battery cell. The elastic sheet comprises a base material portion on a flat plate including a first surface, Including a first projection protruding from the first surface, The first projection is annular in plan view. Battery module.

13. An elastic sheet applied to a battery module, A flat base plate portion including the first surface, Including a first projection protruding from the first surface, A first recess is formed in the first projection. When the first projection is compressed toward the first surface, the inner wall surface of the first recess elastically deforms radially inward within the first recess. Elastic sheet.

Images