Elastic member

Abstract

An elastic member (10) is configured by laminating, in a lamination direction, a first member (10a) which has an elastic modulus, and a second member (10b) and a third member (10c) which each have a lower elastic modulus than the first member (10a). The area of a surface that has the smallest area among surfaces perpendicular to the lamination direction of the first member (10a), the second member (10b), and the third member (10c) is larger than that of a surface perpendicular to the lamination direction of an all-solid-state battery (20) in a restraint region. The first member (10a) is laminated between the second member (10b) and the third member (10c), and the thickness of the second member (10b) abutting against the surface of the all-solid-state battery (20) is thinner than thickness of the third member (10c).

Description

Elastic member

[0001] The present application claims priority from Japanese Patent Application No. 2023-210264, filed on December 13, 2023, and the contents of the above application are incorporated by reference into this application in designated states where incorporation by reference of documents is permitted.

[0002] A pair of fastening end plates are known that are arranged at both ends of a battery body to stack and fix the battery body together, and that are configured to include a base plate with bolt insertion holes, an elastic body fixed to the inner surface of the base plate, and a pressure plate fixed to the inside of the elastic body (Patent Document 1).

[0003] Japanese Utility Model Application Laid-Open Publication No. 6-15264

[0004] However, in the clamping end plate described in Patent Document 1, a pressure plate made of a hard material abuts against the battery body, which has the problem that if the surface of the battery body is uneven, stress concentration may occur on part of the surface of the battery body, resulting in a decrease in battery performance.

[0005] The problem to be solved by the present invention is to provide an elastic member that can prevent a decrease in battery performance due to stress concentration on a portion of the surface of the battery that comes into contact with the elastic member when the battery is restrained.

[0006] The present invention solves the above-mentioned problems by providing an elastic member constructed by stacking a first member having an elastic modulus and a second member and a third member having an elastic modulus lower than that of the first member in a stacking direction, wherein the area of ​​the smallest surface among surfaces perpendicular to the stacking direction of the first member, the second member, and the third member is larger than the area of ​​the surface perpendicular to the stacking direction of the all-solid-state battery within a constrained region, and the first member is stacked between the second member and the third member, and the thickness of the second member abutting on the surface of the all-solid-state battery is thinner than the thickness of the third member.

[0007] According to the present invention, it is possible to prevent a decrease in battery performance due to stress concentration occurring on a portion of the surface of the battery that comes into contact when the battery is restrained.

[0008] FIG. 1 is a perspective view schematically illustrating a battery module including an elastic member according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the battery module taken along line A-A' in FIG. 1. FIG. 3 is a plan view illustrating a battery module according to an embodiment of the present invention and an example cross-sectional view of the upper part of the battery module taken along line B-B' in the plan view. FIG. 4 is a diagram illustrating an example of the state of a conventional elastic member and an all-solid-state battery when a load is applied from above to the elastic member and all-solid-state battery. FIG. 5 is a diagram illustrating an example of the state of the elastic member according to an embodiment of the present invention when a convex portion occurs on the surface of the all-solid-state battery. FIG. 6 is a plan view illustrating a battery module according to an embodiment of the present invention and an example cross-sectional view of the upper part of the battery module taken along line B-B' in the plan view. FIG. 7 is a diagram illustrating an example of the state of the elastic member according to an embodiment of the present invention when a convex portion occurs on the surface of the all-solid-state battery. FIG. 8 is a plan view illustrating a battery module according to an embodiment of the present invention and an example cross-sectional view of the upper part of the battery module taken along line B-B' in the plan view.

[0009] An elastic member according to an embodiment of the present invention will be described with reference to the drawings. The elastic member according to this embodiment is provided in an all-solid-state battery assembly. The all-solid-state battery assembly is mounted, for example, on an automobile, although not particularly limited thereto. The all-solid-state battery assembly includes a battery module and a load application mechanism. In the all-solid-state battery assembly, a load is applied to the battery module by the load application mechanism. The battery module will be described below.

[0010] FIG. 1 is a perspective view schematically illustrating a battery module including an elastic member according to an embodiment of the present invention. As shown in FIG. 1 , the battery module 1 includes an elastic member 10 and an all-solid-state battery 20. In FIG. 1 , the X-axis and Y-axis are directions along the top surfaces of the elastic member 10 and the all-solid-state battery 20. The Y-axis is perpendicular to the X-axis in the XY plane. The Z-axis is perpendicular to the XY plane. The elastic member 10 and the all-solid-state battery 20 are stacked in the Z-axis direction (stacking direction). The elastic member 10 is configured to apply uniform surface pressure to the all-solid-state battery 20 on the contact surface while suppressing displacement of the elastic member 10. The elastic member 10 is composed of a first member 10a, a second member 10b, and a third member 10c. The first member 10a, the second member 10b, and the third member 10c are each elastic bodies having a predetermined elastic modulus. Details of these members will be described later. The bottom surface of the second member 10b contacts the top surface of the all-solid-state battery 20. The area of ​​the surface of the elastic member 10 along the XY plane is larger than the area of ​​the surface of the all-solid-state battery 20 along the XY plane. The bottom surface of the first member 10a contacts the top surface of the second member 10b. The bottom surface of the third member 10c contacts the top surface of the first member 10a. Note that in the example of FIG. 1 , the battery module 1 includes one elastic member 10 and one all-solid-state battery 20, but the battery module 1 may include a plurality of elastic members 10 and a plurality of all-solid-state batteries 20. In this case, the elastic members 10 and the all-solid-state batteries 20 are stacked alternately along the Z direction (stacking direction).

[0011] FIG. 2 is a cross-sectional view of the battery module taken along line A-A' in FIG. 1. The XZ axes in FIG. 2 correspond to the XYZ axes in FIG. 1. The all-solid-state battery 20 is configured by stacking an anode current collector foil 22, an anode layer 23, an intermediate layer 24, a solid electrolyte layer 25, a cathode layer 26, and a cathode current collector foil 27 in the stacking direction (Z-axis direction). Laminate layers 21 and 21' are disposed above and below the power-generating element. The laminate layers 21 and 21' are formed of flexible materials, such as resin films such as polyethylene or polypropylene, or resin-metal thin film laminates in which both sides of a metal foil such as aluminum are laminated with resins such as polyethylene or polypropylene. Although not shown in FIG. 2, the laminate layers 21 and 21' function as exterior members, sealing the power-generating element stacked between these layers. At this time, the power generating element is sealed with the positive electrode tab and the negative electrode tab (not shown) exposed to the outside. The upper principal surface of the laminate layer 21 contacts the second member 10b of the elastic member 10. In other words, the principal surface of the laminate layer 21 is the surface of the all-solid-state battery 20 that abuts against the elastic member 10.

[0012] The anode layer 23 is an alkali metal layer mainly composed of alkali metal that is released from the cathode layer 26, reaches the anode current collector foil 22 via the solid electrolyte layer 25, and deposits thereon as the all-solid-state battery 20 is charged. The anode layer 23 deposits on the anode current collector foil 22 during charging of the all-solid-state battery 20, increasing in volume and decreasing in volume during discharge. The anode layer 23 is, for example, a lithium metal layer. The anode layer 23 may include a layer other than the lithium metal layer, such as an auxiliary layer that assists the deposition of the lithium metal layer. The anode layer 23 is interposed between the anode current collector foil 22 and the intermediate layer 24. The length of the anode layer 23 in the planar direction is shorter than the length of the anode current collector foil 22 and the length of the intermediate layer 24 in the planar direction. That is, the surface of the anode layer 23 is smaller than the surface of the anode current collector foil 22 and the surface of the intermediate layer 24. The negative electrode layer 23′ has the same material and structure as the negative electrode layer 23. The negative electrode layer 23′ is interposed between the intermediate layer 24′ and the negative electrode current collector foil 22′. The negative electrode current collector foil 22 is a conductive foil-like member. The negative electrode current collector foil 22 is, for example, a metal foil, and an example of this metal foil is copper foil. The negative electrode current collector foil 22 may be made of a conductive resin. The negative electrode current collector foil 22 is bonded to a negative electrode tab (not shown). The negative electrode current collector foil 22 is interposed between the laminate layer 21 and the negative electrode layer 23. The negative electrode current collector foil 22′ has the same material and structure as the negative electrode current collector foil 22. The negative electrode current collector foil 22′ is interposed between the negative electrode layer 23′ and the laminate layer 21′.

[0013] The intermediate layer 24 contains at least one material selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of absorbing lithium ions, and a binder. By containing the metal material capable of alloying with lithium, the intermediate layer 24 can more uniformly deposit lithium metal on the current collector surface. Furthermore, by containing the carbon material capable of absorbing lithium ions, the intermediate layer 24 can suppress the deposition and growth of lithium dendrites. The type of binder is not particularly limited, and binders known in the art can be appropriately used. The intermediate layer 24 is preferably conductive as a whole. The intermediate layer 24 is not an essential component and may be omitted as appropriate. The intermediate layer 24 is interposed between the anode layer 23 and the solid electrolyte layer 25. Specifically, the intermediate layer 24 is formed to cover the upper principal surface 25a of the solid electrolyte layer 25. The intermediate layer 24' has the same material and configuration as the intermediate layer 24. The upper principal surface of the intermediate layer 24' is formed to cover the lower bottom surface 25b of the solid electrolyte layer 25.

[0014] The solid electrolyte layer 25 may be, for example, a sulfide solid electrolyte or an oxide solid electrolyte, but preferably a sulfide solid electrolyte. The top surface of the solid electrolyte layer 25 contacts the bottom surface of the intermediate layer 24. The positive electrode layer 26 contains at least a positive electrode active material capable of absorbing and releasing lithium (Li). While not particularly limited, it preferably contains a sulfur-containing positive electrode active material. The sulfur-containing positive electrode active material may be any material capable of utilizing a sulfur oxidation-reduction reaction to release lithium ions during charging and absorb the lithium ions during discharging. The type of sulfur-containing positive electrode active material is not particularly limited, but particles or thin films of elemental sulfur (S), organic sulfur compounds, or inorganic sulfur compounds may be used. The positive electrode current collector foil 27 is a conductive foil-like member. The positive electrode current collector foil 27 is, for example, a metal foil, such as copper foil. The positive electrode current collector foil 27 may also be made of a conductive resin. The positive electrode current collector foil 27 is joined to a positive electrode tab (not shown).

[0015] The solid electrolyte layer 25 has a main surface 25a, a bottom surface 25b opposite the main surface 25a, and a first side surface 25c and a second side surface 25d interposed between the main surface 25a and the bottom surface 25b. The positive electrode layer 26 has a main surface 26a located on the upper side, a bottom surface 26b opposite the main surface 26a, and a first side surface 26c and a second side surface 26d interposed between the main surface 26a and the bottom surface 26b. The main surface 25a and the bottom surface 25b of the solid electrolyte layer 25 are covered by intermediate layers 24 and 24', respectively. The solid electrolyte layer 25 is formed so as to cover the main surface 26a, the bottom surface 26b, the first side surface 26c, and the second side surface 26d of the positive electrode layer 26. The positive electrode current collector foil 27 extends in the plane direction (X-axis direction) so as to penetrate the first side surface 26 c and the second side surface 26 d of the positive electrode layer 26 and the first side surface 25 c and the second side surface 25 d of the solid electrolyte layer 25. The positive electrode current collector foil 27 is exposed from the first side surface 25 c and the second side surface 25 d of the solid electrolyte layer 25. Note that the solid electrolyte layer 25 does not necessarily have to cover the first side surface 26 c and the second side surface 26 d of the positive electrode layer 26, and as long as it covers at least the main surface 26 a and the bottom surface 26 b of the positive electrode layer 26, it does not have to cover the first side surface 26 c and the second side surface 26 d of the positive electrode layer 26. Even in this case, the plane length of the solid electrolyte layer 25 is longer than the plane lengths of the main surface 26 a and the bottom surface 26 b of the positive electrode layer 26.

[0016] The elastic member 10 and the all-solid-state battery 20 are constrained by a constraining pressure in the stacking direction. Specifically, a load is applied to the elastic member 10 and the all-solid-state battery 20 in the Z-axis direction by a load application mechanism (not shown) that sandwiches the elastic member 10 and the all-solid-state battery 20. As a result, a constraining pressure is applied in a direction in which the layers of the elastic member 10 and the all-solid-state battery 20 approach each other. In the example of FIGS. 1 and 2 , the direction in which the elastic member 10 is positioned relative to the all-solid-state battery 20 is defined as "upward," and the direction opposite to "upward" relative to the all-solid-state battery 20 is defined as "downward." That is, the +Z-axis direction is "upward," and the -Z-axis direction is "downward." In this embodiment, for example, a pressure plate constituting the load application mechanism is located above the elastic member 10. Specifically, the pressure plate is placed on the top surface of the third member 10c of the elastic member 10. The pressure plate is a rigid plate-like member. A spring is installed on the surface (upper surface) of the pressure plate opposite the surface (lower surface) that abuts against the elastic member 10. The spring biases the pressure plate downward in the Z-axis direction (the -Z-axis direction in FIGS. 1 and 2), and is, for example, a compression coil spring. Furthermore, a bottom plate constituting the load application mechanism is disposed below the all-solid-state battery 20. The bottom plate abuts against the bottom surface of the all-solid-state battery 20 and supports the all-solid-state battery 20 from below. The bottom plate is a rigid plate-like member. The all-solid-state battery 20 sandwiched between the pressure plate and the bottom plate is pressed by the application of the spring load. As a result, the surface pressure from the pressure plate is applied to the all-solid-state battery 20 via the elastic member 10.

[0017] The elastic member 10 and the all-solid-state battery 20 have a region subjected to the confining pressure (hereinafter also referred to as the confining region) and a region not subjected to the confining pressure when confined by the confining pressure in the stacking direction. The confining region is a region overlapping the positive electrode layer 26 and the negative electrode layer 23 in the planar direction of the elastic member 10 and the all-solid-state battery 20. The region not subjected to the confining pressure is a region outside the confining region that does not overlap the positive electrode layer 26 and the negative electrode layer 23. FIG. 3 shows a plan view of a battery module according to this embodiment and an example cross-sectional view of the upper part of the battery module taken along line B-B' in the plan view. The XYZ axes in FIG. 3 correspond to the XYZ axes in FIG. 1. As shown in the plan view of FIG. 3, the elastic member 10 has an outer portion 101 outside the confining region 1a (region 1b not subjected to the confining pressure) and an inner portion 102 within the confining region 1a. The outer portion 101 is a portion that is outer than the outer edges 30 of the negative electrode layer 23 and the positive electrode layer 26 when viewed from the stacking direction (in a plan view). The inner portion 102 is a portion that is inner than the outer edges 30 of the negative electrode layer 23 and the positive electrode layer 26. That is, in the XY plane, the inner portion 102 is a portion that overlaps with the negative electrode layer 23 and the positive electrode layer 26, and the outer portion 101 is a portion that does not overlap with the negative electrode layer 23 and the positive electrode layer 26.

[0018] The elastic member 10 is formed by stacking multiple members in the stacking direction (Z-axis direction). The elastic member 10 is composed of a first member 10a, a second member 10b, and a third member 10c. These members are stacked in the following order from top to bottom: third member 10c, first member 10a, and second member 10b. That is, the first member 10a is stacked between the second member 10b and the third member 10c. The second member 10b abuts against the surface (top surface) of the all-solid-state battery 20 with its bottom surface located below the second member 10b. The third member 10c abuts against the lower surface of a pressure plate that constitutes the load application mechanism with its main surface located above the third member 10c. Note that the number of members constituting the elastic member 10 is not limited to three layers, and may be three or more layers.

[0019] The first member 10a has a first elastic modulus. The first elastic modulus is higher than a predetermined elastic modulus. The predetermined elastic modulus is, for example, an elastic modulus necessary to suppress deformation of the first member when a load is applied from above the elastic member 10. The predetermined elastic modulus is set through experiments, etc. By including the first member 10a with a high elastic modulus, the elastic member 10 can suppress deformation of the ends of the second member 10b and the third member 10c. The second member 10b and the third member 10c have elastic moduli lower than that of the first member 10a. Specifically, the second member 10b has a second elastic modulus. The second elastic modulus is lower than a predetermined elastic modulus. The third member 10c has a third elastic modulus. The third elastic modulus is lower than the predetermined elastic modulus. In other words, the first elastic modulus is higher than the second elastic modulus and the third elastic modulus. The second elastic modulus and the third elastic modulus may be the same or different.

[0020] The areas of the planes (planes along the X and Y axes) perpendicular to the stacking direction (Z-axis direction) of the first member 10a, the second member 10b, and the third member 10c may be the same or different. In the examples of FIGS. 1, 2, and 3, the areas of the planes perpendicular to the stacking direction of the first member 10a, the second member 10b, and the third member 10c are the same. In this case, the area of ​​the planes perpendicular to the stacking direction of the first member 10a, the second member 10b, and the third member 10c is larger than the area of ​​the planes perpendicular to the stacking direction of the all-solid-state battery 20 within the constrained region 1a. The planes perpendicular to the stacking direction of the all-solid-state battery 20 within the constrained region 1a are planes perpendicular to the stacking direction of the positive electrode layer 26 and the negative electrode layer 23. Even if the areas are different, the area of ​​the smallest plane among the planes perpendicular to the stacking direction of the first member 10a, the second member 10b, and the third member 10c is larger than the area of ​​the planes perpendicular to the stacking direction of the all-solid-state battery 20 within the constrained region 1a.

[0021] FIG. 4 shows an example of the state of the elastic member and the all-solid-state battery when a load is applied from above to a battery module including a conventional elastic member and an all-solid-state battery. FIG. 4 shows a partially enlarged view including a state in which the bottom surface of the elastic member is in contact with a corner portion of the all-solid-state battery. The Z-axis direction is the stacking direction of the elastic member 10′ and the all-solid-state battery 20′. The X-axis direction is the direction perpendicular to the Z-axis direction. Surface pressure is applied to the all-solid-state battery 20′ through the elastic member to maintain contact over the entire surface. In this case, the surface size of the elastic member 10′ is larger than the surface sizes of the anode layer 23′ and the cathode layer 26′ so that there are no portions of the all-solid-state battery 20′ that are not subjected to surface pressure even if the arrangement of each component is misaligned. Therefore, as shown in FIG. 4, the elastic member 10′ has an outer portion 101′ that is outside the outer edges 30′ of the negative electrode layer 23′ and the positive electrode layer 26′, and an inner portion 102′ that is inside the outer edges 30′ of the negative electrode layer 23′ and the positive electrode layer 26′, when viewed from the stacking direction (Z-axis direction).

[0022] When a load is applied from above in the load direction LD to a battery module having the structure shown in FIG. 4 , the outer portion 101′ of the elastic member 10′ deforms and sags to cover the all-solid-state battery 20′. As a result, the downwardly sagging outer portion 101′ of the elastic member 10′ comes into contact with a corner portion 201′ of the all-solid-state battery 20′, causing stress to concentrate at the corner portion 201′. If the intermediate layer 24′ or the solid electrolyte layer 25′ breaks due to the partial stress concentration at the corner portion 201′, the positive electrode layer 26′ may be exposed and short-circuited with the negative electrode layer 23′. In contrast, in this embodiment, the elastic member includes a material with a high elastic modulus, which prevents the outer portion of the elastic member from sagging to cover the all-solid-state battery, thereby preventing a decrease in battery performance due to a short-circuit between the positive electrode layer and the negative electrode layer.

[0023] In the present embodiment, when the battery module 1 is configured by alternately stacking a plurality of elastic members 10 and a plurality of all-solid-state batteries 20, the elastic member 10 that abuts against the pressure plate of the load application mechanism, i.e., the elastic member 10 located between the pressure plate and the all-solid-state battery 20, is configured by stacking a first member 10a, a second member 10b, and a third member 10c, but the configuration of the elastic member 10 located between the all-solid-state batteries 20 is not limited to this. The elastic member 10 located between the all-solid-state batteries 20 may be configured by stacking the second member 10b, the first member 10a, and the second member 10b in this order.

[0024] The thickness of the second member 10b is thinner than the thickness of the third member 10c. By reducing the thickness of the second member 10b, the variation in displacement of the elastic member 10 that occurs when a load is applied is suppressed. Furthermore, the thickness of the second member 10b is equal to or greater than the maximum depth of the irregularities on the surface of the all-solid-state battery 20 with which the second member 10b abuts. The maximum depth of the irregularities on the surface of the all-solid-state battery 20 is a value that is set in advance through experiments, etc. FIG. 5 is a diagram illustrating an example of the state of the elastic member according to this embodiment when protrusions are formed on the surface of the all-solid-state battery. In FIG. 5, protrusions 211 are formed on the surface of the all-solid-state battery 20. In this case, the second member 10b has a thickness equal to or greater than the maximum depth of the irregularities on the surface of the all-solid-state battery 20, and therefore, can deform to match the protrusions 211 on the surface of the all-solid-state battery 20, thereby absorbing the effects of deformation caused by the protrusions. This prevents stress from concentrating locally on the first member 10a due to the protrusions 211 on the surface of the all-solid-state battery 20. As described above, the second member 10b acts to prevent local variations in the surface pressure applied to the surface (top surface) of the all-solid-state battery 20. The thickness of the third member 10c may be equal to or greater than the maximum value of the fluctuation range. The fluctuation range is the range by which the position of the surface (top surface) of the all-solid-state battery 20 abutting against the second member 10b in the stacking direction (Z-axis direction) fluctuates due to expansion and contraction of the all-solid-state battery 20. The maximum value of the fluctuation range is a value that is set in advance through experiments, etc. In this embodiment, when tilt occurs on the pressure plate and / or the surface of the all-solid-state battery 20, the third member 10c absorbs the influence of the tilt.

[0025] When the all-solid-state battery 20 and the elastic member 10 are constrained by the constraining pressure in the stacking direction, the solid electrolyte layer 25 has an outer portion 251 outside the constrained region 1a (region 1b not subjected to the constraining pressure) and an inner portion 252 within the constrained region 1a. The outer portion 251 is a portion outer than the outer edges 30 of the anode layer 23 and the cathode layer 26 when viewed from the stacking direction. The inner portion 252 is a portion inner than the outer edges 30 of the anode layer 23 and the cathode layer 26 when viewed from the stacking direction. That is, the solid electrolyte layer 25 has corner portions extending to portions that do not overlap with the cathode layer 26 and the anode layer 23 in a plan view. The area of ​​a surface of the solid electrolyte layer 25 perpendicular to the stacking direction is larger than the area of ​​a surface of the all-solid-state battery 20 perpendicular to the stacking direction within the constrained region 1a. Furthermore, the intermediate layer 24 covers the main surface 25a of the solid electrolyte layer 25, and therefore has an outer portion 241 and an inner portion 242, similar to the solid electrolyte layer 25. The outer portion 241 of the intermediate layer 24 may have a portion that extends further outward than the outer portion 251 of the solid electrolyte layer 25 along the surface direction.

[0026] Furthermore, in this embodiment, the first member 10a, the second member 10b, and the third member 10c may each have a uniform thickness, or may have portions with different thicknesses. FIG. 6 shows an example of a plan view of a battery module according to this embodiment and a cross-sectional view of the upper portion of the battery module taken along line B-B' in the plan view. The XYZ axes in FIG. 6 correspond to the XYZ axes in FIG. 1. FIG. 6 shows an example in which the first member 10a and the third member 10c each have portions with different thicknesses. For example, the inner portion 102 of the first member 10a may be formed so that the thickness of the first member 10a decreases from the peripheral edge 102a to the central portion 102b of the inner portion 102.

[0027] The thickness of the first member 10a is not limited to this, and may be any thickness as long as the thickness of the central portion 102b of the inner portion 102 is thinner than the thickness of the peripheral portion 102a of the inner portion 102. For example, as shown in FIG. 6 , the main surface 11 located on the upper side of the first member 10a has an inclined portion 103 that slopes downward from the peripheral portion 102a of the inner portion 102 toward the central portion 102b in a cross-sectional view. That is, the first member 10a has a concave shape in which the main surface 11 is recessed in a cross-sectional view. The thickness of the outer portion 101 of the first member 10a is constant and is the same as or thicker than the thickness of the peripheral portion 102a of the inner portion 102 of the first member 10a. The thickness of the second member 10b is constant. The inner portion 102 of the third member 10c is formed so that the thickness of the third member 10c increases from the peripheral edge 102a toward the central portion 102b of the inner portion 102 in accordance with the change in thickness of the first member 10a. For example, as shown in FIG. 6 , the bottom surface 12 of the third member 10c has an inclined portion 103 that slopes downward from the peripheral edge 102a toward the central portion 102b of the inner portion 102 in a cross-sectional view. That is, the third member 10c has a convex shape in a cross-sectional view with the bottom surface 12 being convex. The outer portion 101 of the third member 10c has a constant thickness that is the same as or thinner than the thickness of the peripheral edge 102a of the inner portion 102 of the third member 10c.

[0028] FIG. 7 is a diagram illustrating an example of the state of the elastic member according to this embodiment when a convex portion occurs on the surface of the all-solid-state battery. The left diagram of FIG. 7 illustrates an example in which the thickness of the first member 10a of the elastic member 10 is constant. Even if a convex portion 211 occurs on the surface of the all-solid-state battery 20, deformation of the first member 10a, to which a load is applied from above, is suppressed. Therefore, the elastic member 10 does not deform to conform to the shape of the convex portion 211, resulting in a portion where no surface pressure is applied to the surface of the all-solid-state battery 20, such as the portion 212 indicated by the dashed line in FIG. 7 . Therefore, in this embodiment, the thickness of the central portion of the first member 10a is formed thinner than the peripheral portion. As a result, as shown in the right diagram of FIG. 7 , the first member 10a, to which a load is applied from above, is more likely to deform in the central portion to conform to the shape of the convex portion 211 on the surface of the all-solid-state battery 20, thereby applying uniform surface pressure to the surface of the all-solid-state battery 20.

[0029] Furthermore, the outer portion 101 of the second member 10b may be formed so that the thickness of the second member 10b decreases from the inner edge 101a to the outer edge 101b of the outer portion 101 of the second member 10b. FIG. 8 shows a plan view of a battery module according to this embodiment and an example cross-sectional view of the upper portion of the battery module taken along line B-B' in the plan view. The XYZ axes in FIG. 8 correspond to the XYZ axes in FIG. 1. As shown in FIG. 8, the bottom surface 13 located on the lower side of the second member 10b slopes upward from the inner edge 101a to the outer edge 101b of the outer portion 101 in a cross-sectional view. That is, the second member 10b has a trapezoidal shape in which the main surface 14 located on the upper side of the second member 10b is wider than the bottom surface 13 of the second member 10b in a cross-sectional view. The thickness of the inner portion 102 of the second member 10b is constant and is the same as or thicker than the thickness of the outer portion 101 of the second member 10b.

[0030] As described above, the elastic member according to the present embodiment is an elastic member arranged to overlap in the stacking direction with respect to an all-solid-state battery configured by stacking a cathode layer, a solid electrolyte layer, and an anode layer, wherein the solid electrolyte layer has an outer portion outside a constrained region that receives constraining pressure when the all-solid-state battery and the elastic member are constrained by the constraining pressure in the stacking direction, the elastic member is configured by stacking a first member having an elastic modulus with second and third members having elastic moduli lower than that of the first member in the stacking direction, the smallest surface area among the surfaces perpendicular to the stacking direction of the first member, second member, and third member is larger than the surface area of ​​the surfaces perpendicular to the stacking direction of the all-solid-state battery within the constrained region, and the first member is stacked between the second and third members, and the thickness of the second member abutting the surface of the all-solid-state battery is thinner than the thickness of the third member. This prevents a decrease in battery performance due to stress concentration on a portion of the surface of the battery that abuts when the battery is constrained.

[0031] Furthermore, in the elastic member according to this embodiment, the thickness of the second member is equal to or greater than the maximum depth of the unevenness on the surface of the all-solid-state battery with which the second member abuts. As a result, the second member of the elastic member, which has a low elastic modulus and is in contact with the all-solid-state battery, deforms to conform to the unevenness on the surface of the all-solid-state battery, so that even if the surface of the all-solid-state battery has a convex shape, stress can be prevented from concentrating on a portion of the all-solid-state battery, and a load can be applied uniformly to the all-solid-state battery.

[0032] Furthermore, in the elastic member according to this embodiment, the first member and the third member have, when viewed from the stacking direction, an outer portion outside the constrained region and an inner portion within the constrained region, the inner portion of the first member is formed such that the thickness of the first member decreases from the periphery of the inner portion toward the center, the thickness of the second member is constant, and the inner portion of the third member is formed such that the thickness of the third member increases from the periphery of the inner portion toward the center in accordance with the change in thickness of the first member. As a result, the first member is more likely to deform at the center of the inner portion than at the outer portion when a load is applied, and therefore, even if unevenness occurs on the surface of the all-solid-state battery near the center, the first member deforms along the unevenness, thereby preventing loss of surface pressure applied to the surface of the all-solid-state battery when a load is applied.

[0033] Furthermore, in the elastic member according to this embodiment, the second member has, when viewed from the stacking direction, an outer portion outside the constrained region and an inner portion within the constrained region, and the outer portion of the second member is formed so that the thickness of the second member decreases from the inner edge of the outer portion toward the outer edge. As a result, when a load is applied, the central portion of the second member deforms in accordance with the irregularities on the surface of the all-solid-state battery, and deformation of the end portions of the second member is suppressed, thereby making it possible to uniformize the surface pressure on the surface of the all-solid-state battery and prevent a decrease in battery performance due to stress concentration at the corners of the all-solid-state battery.

[0034] Furthermore, in the elastic member according to the present embodiment, the thickness of the third member is equal to or greater than the maximum value of the fluctuation range, and the fluctuation range is the range by which the position of the surface of the all-solid-state battery that abuts against the second member in the stacking direction fluctuates due to expansion and contraction of the all-solid-state battery. As a result, even if the surface of the all-solid-state battery deforms due to expansion and contraction of the all-solid-state battery during use, the contact surface of the third member deforms in accordance with the deformation of the surface of the all-solid-state battery, and therefore the influence of the deformation of the surface of the all-solid-state battery can be absorbed.

[0035] It should be noted that the above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above-described embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0036] REFERENCE SIGNS LIST 1 battery module 20 all-solid-state battery 21 laminate layer 22 negative electrode current collector foil 23 negative electrode layer 24 intermediate layer 25 solid electrolyte layer 26 positive electrode layer 27 positive electrode current collector foil 10 elastic member 10a first member 10b second member 10c third member

Claims

1. An elastic member that is arranged to overlap in a stacking direction with an all-solid-state battery configured by stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, wherein the solid electrolyte layer has an outer portion outside a constrained region that receives a constraining pressure in a state in which the all-solid-state battery and the elastic member are constrained by the constraining pressure in the stacking direction, the elastic member is configured by stacking in the stacking direction a first member having an elastic modulus, and a second member and a third member having an elastic modulus lower than that of the first member, the area of ​​a surface that is smallest among surfaces perpendicular to the stacking direction of the first member, the second member, and the third member is larger than an area of ​​a surface of the all-solid-state battery perpendicular to the stacking direction within the constrained region, the first member is stacked between the second member and the third member, and the thickness of the second member in contact with a surface of the all-solid-state battery is thinner than the thickness of the third member.

2. An elastic member according to claim 1, wherein the thickness of the second member is equal to or greater than the maximum depth of the irregularities on the surface of the all-solid-state battery with which the second member comes into contact.

3. An elastic member as described in claim 1 or 2, wherein the first member and the third member have, when viewed in the stacking direction, an outer portion outside the restraint area and an inner portion within the restraint area, the inner portion of the first member is formed such that the thickness of the first member becomes thinner from the periphery to the center of the inner portion, the thickness of the second member is constant, and the inner portion of the third member is formed such that the thickness of the third member becomes thicker from the periphery to the center of the inner portion in accordance with the change in thickness of the first member.

4. An elastic member as claimed in claim 1 or 2, wherein the second member has, when viewed in the stacking direction, an outer portion outside the restraint area and an inner portion within the restraint area, and the outer portion of the second member is formed such that the thickness of the second member becomes thinner from the inner edge portion to the outer edge portion of the outer portion.

5. An elastic member as claimed in claim 1 or 2, wherein the thickness of the third member is equal to or greater than the maximum value of a fluctuation range, and the fluctuation range is a range within which the position of the surface of the all-solid-state battery in contact with the second member in the stacking direction fluctuates due to expansion and contraction of the all-solid-state battery.

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