Storage element

Abstract

The present embodiment is characterized in being provided with an electrode body, a case in which the electrode body is housed, and a metal external terminal positioned in the case, the external terminal having a flange part spreading along the case on the outside of the case, and a shaft part extending from the flange part and penetrating through the case, the flange part being configured from a cladding material having a plurality of metal layers stacked in the direction in which the shaft part penetrates, and having a through hole through which the shaft part is inserted, the shaft part having an expanded diameter part spreading along the hole peripheral edge part of the through hole of a second metal layer, which is at the case-side end from among the plurality of metal layers, and a crimped part that spreads along the hole peripheral edge part of the through hole of a first metal layer, which is at the end on the opposite side from the case from among the plurality of metal layers, and that sandwiches, between the crimped part and the expanded diameter part, the peripheral edge part of the through hole of the flange part, and the hole peripheral edge part of the first metal layer indenting towards the case side relative to other portions of the first metal layer, and being formed at a position, when viewed from the penetration direction, at which the crimped part is included on the inner side.

Description

Technical Field

[0001] The present invention relates to a power storage element provided with external terminals.

Background Art

[0002] Conventionally, a lithium-ion secondary battery provided with external terminals composed of a plurality of members has been known (see Patent Document 1). In this lithium-ion secondary battery, as shown in FIG. 12, in the external terminal 100, a shaft portion 101 and a flange portion 102 that extends from the shaft portion 101 and to which other members such as a bus bar are welded are formed of separate members. The shaft portion 101 and the flange portion 102 are connected by caulking.

[0003] In the external terminal 100 in which the shaft portion 101 and the flange portion 102 are formed of separate members, a clad material in which a plurality of metal layers are laminated on the flange portion 102 may be used depending on the material of a member such as a bus bar welded to the flange portion 102.

[0004] In this external terminal 100, an end portion of the shaft portion 101 is inserted into a through hole provided in the flange portion 102, and the inserted end portion is caulked and spreads along the flange portion 102, whereby the flange portion 102 and the shaft portion 101 are connected. At the time of this caulking, the peripheral edge portion of the hole of the metal layer constituting the surface (the surface opposite to the case side) of the flange portion 102 is compressed and tends to extend in a direction away from the through hole. However, since the metal layer is fixed to an adjacent metal layer, the compressed portion cannot extend. As a result, when the end portion of the shaft portion 101 is caulked and spreads, the periphery of the caulked portion bulges.

[0005] When such a bulge occurs on the surface of the flange portion 102, it may be difficult to connect other members due to the bulge when connecting a member such as a bus bar.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] Therefore, an object of the present embodiment is to provide a storage element in which, even if a bulge caused by caulking occurs around the caulking portion at the flange portion of the external terminal, another member can be easily connected to the flange portion. MEANS FOR SOLVING THE PROBLEMS

[0008] The storage element of the present embodiment includes an electrode body, a case for housing the electrode body, and a metal external terminal disposed on the case, The external terminal includes a flange portion that extends along the case outside the case, and a shaft portion that extends from the flange portion, penetrates the case, and is electrically connected to the electrode body. The flange portion is composed of a clad material having a plurality of metal layers laminated in the penetrating direction of the shaft portion, and has a through hole through which the shaft portion is inserted. The shaft portion includes a diameter-expanded portion that extends along the surface of the flange portion on the case side, and a caulking portion that extends along the surface of the flange portion on the side opposite to the case and sandwiches the peripheral edge portion of the through hole in the flange portion between the diameter-expanded portion. A first metal layer, which is a metal layer at the end on the side opposite to the case in the penetrating direction among the plurality of metal layers, has a concave portion that is recessed in the penetrating direction or a through hole that penetrates in the penetrating direction in a region that is larger than the caulking portion and includes the caulking portion when viewed from the penetrating direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0009]

Figure 1

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Figure 12

DETAILED DESCRIPTION OF THE INVENTION

[0010] The energy storage element of this embodiment includes an electrode body, a case that houses the electrode body, and an external terminal made of metal disposed on the case. The external terminal has a flange portion that extends along the case on the outside of the case, and a shaft portion that extends from the flange portion, penetrates the case, and is electrically connected to the electrode body. The flange portion is composed of a clad material having a plurality of metal layers laminated in the penetrating direction of the shaft portion, and has a through hole through which the shaft portion is inserted. The shaft portion has a diameter-expanded portion that extends along the surface of the flange portion on the case side, and a caulked portion that extends along the surface of the flange portion opposite to the case and sandwiches the peripheral portion of the through hole in the flange portion between the diameter-expanded portion. The first metal layer, which is the metal layer at the end opposite to the case in the penetrating direction among the plurality of metal layers, has a concave portion that is recessed in the penetrating direction or a through hole that penetrates in the penetrating direction in a region that is larger than the caulked portion and includes the caulked portion when viewed from the penetrating direction.

[0011] According to such a configuration, even if a convex portion caused by caulking occurs around the caulked portion on the surface of the flange portion opposite to the case, since the position of the caulked portion and its periphery on the surface of the flange portion are recessed, the convex portion does not get in the way when connecting another member to the flange portion, and it is easy to connect.

[0012] In the energy storage element, the flange portion has two metal layers, namely, the first metal layer and the second metal layer, which is the metal layer at the end on the case side in the penetrating direction among the plurality of metal layers. The electrical resistance of the metal constituting the second metal layer may be smaller than the electrical resistance of the metal constituting the first metal layer.

[0013] According to such a configuration, compared with the case where the first metal layer has a uniform thickness, the electrical resistance between the second metal layer and the diameter-expanded portion is suppressed, and thereby the electrical conductivity between the shaft portion and the flange portion is improved.

[0014] The energy storage element of this embodiment includes an electrode body, a case that houses the electrode body, and an external terminal made of metal disposed on the case. The external terminal has a flange portion that extends along the outer surface of the case on the outside of the case, and a shaft portion that extends from the flange portion, penetrates the case, and is electrically connected to the electrode body. The flange portion is composed of a clad material having a plurality of metal layers laminated in the penetrating direction of the shaft portion, and has a through hole through which the shaft portion is inserted. The shaft portion is formed between the flange portion and the outer surface of the case, and has a diameter-expanded portion that extends along the outer surface of the case and a caulked portion that extends along the surface of the flange portion opposite to the case and sandwiches the peripheral edge of the through hole in the flange portion between the diameter-expanded portion. The first metal layer, which is the metal layer opposite to the case in the penetrating direction among the plurality of metal layers, has a concave portion that is recessed in the penetrating direction or a through hole that penetrates in the penetrating direction in a region that is larger than the caulked portion and includes the caulked portion when viewed from the penetrating direction.

[0015] According to such a configuration, even if a convex portion caused by caulking occurs around the caulked portion on the surface of the flange portion opposite to the case, since the position of the caulked portion and its periphery on the surface of the flange portion are recessed, the convex portion does not get in the way when connecting other members to the flange portion, and it is easy to connect.

[0016] The flange portion has two metal layers, namely the first metal layer and the second metal layer, which is the metal layer facing the case in the penetrating direction among the plurality of metal layers. The electrical resistance of the metal constituting the second metal layer may be smaller than the electrical resistance of the metal constituting the first metal layer.

[0017] According to such a configuration, compared with the case where the first metal layer has a uniform thickness, the electrical resistance between the second metal layer and the diameter-expanded portion is suppressed, and thereby the conductivity between the shaft portion and the flange portion is improved.

[0018] The flange portion has a convex portion that protrudes in the penetrating direction in the concave portion of the first metal layer. The convex portion is located between the outer peripheral edge of the concave portion and the caulked portion in a direction orthogonal to the penetrating direction. It may be arranged between the outer periphery.

[0019] According to such a configuration, it is easy for other members to be connected to the flange portion.

[0020] The first metal layer has the through hole, the flange portion has a convex portion protruding in the through direction, and the convex portion may be arranged between the outer peripheral edge of the through hole and the outer peripheral edge of the caulked portion in a direction orthogonal to the through direction.

[0021] According to such a configuration, it is easy for other members to be connected to the flange portion.

[0022] The second metal layer has a peripheral end surface which is an end surface in a direction orthogonal to the through direction, and the first metal layer may have a cover portion protruding in the through direction along the peripheral end surface of the second metal layer.

[0023] The external terminal is a negative electrode, the first metal layer may contain aluminum or an aluminum-based metal, and the second metal layer may contain copper or a copper-based metal.

[0024] As described above, according to the present embodiment, it is possible to provide a storage element in which, even if a bulge caused by caulking occurs around the caulked portion in the flange portion of the external terminal, it is easy for other members to be connected to the flange portion.

[0025] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 9. Note that the names of the constituent members (each component) of the present embodiment are those in the present embodiment and may be different from the names of the constituent members (each component) in the background art.

[0026] The energy storage element of this embodiment is a non-aqueous electrolyte secondary battery. More specifically, the energy storage element is a lithium-ion secondary battery that utilizes electron transfer generated by the movement of lithium ions. This type of energy storage element supplies electrical energy. The energy storage elements are used singly or in plurality. Specifically, when the required output and the required voltage are small, the energy storage element is used singly. On the other hand, when at least one of the required output and the required voltage is large, the energy storage element is combined with other energy storage elements and used in an energy storage device. In the said energy storage device, the energy storage element used in the energy storage device supplies electrical energy.

[0027] As shown in FIGS. 1 and 2, the energy storage element includes an electrode body 2, a case 3 that houses the electrode body 2, and a metal external terminal 4 disposed on the case 3. Further, the energy storage element 1 also includes a current collector 5 that electrically connects the electrode body 2 and the external terminal 4, and an insulating member 6 disposed between the electrode body 2 and the case 3. Note that the external terminal 4 shown in FIG. 2 (specifically, the negative electrode shaft portion 42B of the negative electrode terminal 4B) is in the shape before caulking.

[0028] As shown in FIG. 3, the electrode body 2 has wound electrodes (a positive electrode 23 and a negative electrode 24). Specifically, the electrode body 2 has a winding core 21 and a laminate 22 formed by electrodes wound around the winding core 21. In this laminate 22, the positive electrode 23 and the negative electrode 24 are laminated in a state of being insulated from each other. In the electrode body 2, lithium ions move between the positive electrode 23 and the negative electrode 24, whereby the energy storage element 1 is charged and discharged.

[0029] The positive electrode 23 has a strip-shaped metal foil 231 and a positive electrode active material layer 232 laminated on the metal foil 231. This positive electrode active material layer 232 is laminated on the metal foil 231 with one edge portion (uncovered portion) in the width direction of the metal foil 231 exposed. The metal foil 231 of this embodiment is, for example, an aluminum foil.

[0030] The negative electrode 24 has a strip-shaped metal foil 241 and a negative electrode active material layer 242 laminated on the metal foil 241. This negative electrode active material layer 242 is laminated on the metal foil 241 in a state where the edge portion (uncovered portion) on the other side in the width direction of the metal foil 241 (the side opposite to the uncovered portion of the metal foil 231 of the positive electrode 23) is exposed. The metal foil 241 of the present embodiment is, for example, a copper foil.

[0031] In the electrode body 2 of the present embodiment, the positive electrode 23 and the negative electrode 24 are wound in a state of being insulated by the separator 25. That is, in the laminate 22 of the present embodiment, the positive electrode 23, the negative electrode 24, and the separator 25 are laminated.

[0032] The separator 25 is a member having insulating properties and is disposed between the positive electrode 23 and the negative electrode 24. Thereby, in the electrode body 2 (specifically, the laminate 22), the positive electrode 23 and the negative electrode 24 are insulated from each other. Further, the separator 25 holds the electrolytic solution in the case 3. Thereby, during charging and discharging of the power storage element 1, lithium ions can move between the positive electrode 23 and the negative electrode 24 that are alternately laminated with the separator 25 interposed therebetween.

[0033] This separator 25 is strip-shaped and is composed of, for example, a porous film such as polyethylene, polypropylene, cellulose, or polyamide. The separator 25 of the present embodiment has a base material formed of a porous film and an inorganic layer provided on the base material. This inorganic layer contains inorganic particles such as SiO2 particles, Al2O3 particles, and boehmite (aluminum hydrate). Further, the base material is formed of, for example, polyethylene.

[0034] The dimension of the separator 25 in the width direction is larger than the width of the negative electrode active material layer 242. The separator 25 is disposed between the positive electrode 23 and the negative electrode 24 which are overlapped in the width direction in a state of being displaced in the width direction so that the positive electrode active material layer 232 and the negative electrode active material layer 242 overlap in the thickness direction (lamination direction). At this time, the non-coated portion of the positive electrode 23 and the non-coated portion of the negative electrode 24 do not overlap. That is, the non-coated portion of the positive electrode 23 protrudes in the width direction (direction orthogonal to the lamination direction) from the overlapping region of the positive electrode 23 and the negative electrode 24, and the non-coated portion of the negative electrode 24 protrudes in the width direction (direction opposite to the protruding direction of the non-coated portion of the positive electrode 23) from the overlapping region of the positive electrode 23 and the negative electrode 24. The electrode body 2 is formed by winding the positive electrode 23, the negative electrode 24, and the separator 25 around the winding core 21 so as to be in such a laminated state (relative position). Further, in the electrode body 2 of the present embodiment, the non-coated laminated portion 26 in the electrode body 2 is constituted by a portion where only the non-coated portion of the positive electrode 23 or the non-coated portion of the negative electrode 24 is laminated.

[0035] The non-coated laminated portion 26 is provided at each pole of the electrode body 2. That is, the non-coated laminated portion 26 where only the non-coated portion of the positive electrode 23 is laminated constitutes the non-coated laminated portion of the positive electrode in the electrode body 2, and the non-coated laminated portion 26 where only the non-coated portion of the negative electrode 24 is laminated constitutes the non-coated laminated portion of the negative electrode in the electrode body 2.

[0036] The case 3 houses the electrolytic solution together with the electrode body 2. Specifically, the case 3 has a case body 31 having an opening and a cover plate 32 for closing (sealing) the opening of the case body 31. This case 3 is formed of a metal having resistance to the electrolytic solution. The case 3 of the present embodiment is formed of an aluminum-based metal such as aluminum or an aluminum alloy, for example.

[0037] The electrolytic solution is a non-aqueous electrolytic solution. The electrolytic solution is obtained by dissolving an electrolyte salt in an organic solvent. The organic solvent is, for example, cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The electrolyte salt is LiClO 4 、LiBF4 and LiPF 6 and the like. The electrolyte of this embodiment is obtained by dissolving 1 mol / L of LiPF 6 in a mixed solvent in which ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are adjusted at a ratio of ethylene carbonate:dimethyl carbonate:ethyl methyl carbonate = 3:2:5.

[0038] The case body 31 includes a plate-shaped closing portion 311 and a cylindrical body portion (peripheral wall) 312 connected to the periphery of the closing portion 311.

[0039] The closing portion 311 is a portion located at the lower end of the case body 31 when the case body 31 is arranged with the opening facing upward (that is, the bottom wall of the case body 31 when the opening faces upward). The closing portion 311 is rectangular when viewed from the normal direction of the closing portion 311. Hereinafter, the long side direction of the closing portion 311 is defined as the X-axis of the rectangular coordinate system, the short side direction of the closing portion 311 is defined as the Y-axis of the rectangular coordinate system, and the normal direction of the closing portion 311 is defined as the Z-axis of the rectangular coordinate system.

[0040] The body portion 312 has a rectangular tube shape, more specifically, a flat rectangular tube shape. The body portion 312 has a pair of long wall portions 313 extending from the long side of the periphery of the closing portion 311 and a pair of short wall portions 314 extending from the short side of the periphery of the closing portion 311. That is, the pair of long wall portions 313 face each other with a space therebetween in the Y-axis direction (specifically, a space corresponding to the short side of the periphery of the closing portion 311), and the pair of short wall portions 314 face each other with a space therebetween in the X-axis direction (specifically, a space corresponding to the long side of the periphery of the closing portion 311). The rectangular tube-shaped body portion 312 is formed by connecting the short wall portions 314 to the corresponding (specifically, facing in the Y-axis direction) ends of the pair of long wall portions 313.

[0041] As described above, the case body 31 has a rectangular tube shape (that is, a bottomed rectangular tube shape) in which one end in the opening direction (Z-axis direction) is closed. The electrode body 2 is accommodated in the case body 31 with the winding center axis C direction facing the X-axis direction.

[0042] The cover plate 32 is a plate-shaped member that closes the opening of the case body 31. The cover plate 32 of the present embodiment is a rectangular plate member that is long in the X-axis direction when viewed from the Z-axis direction. This cover plate 32 is overlapped with the peripheral edge portion of the opening of the case body 31 so as to close the opening of the case body 31. In a state where the cover plate 32 is overlapped with the peripheral edge portion 34 of the opening, the boundary portion between the cover plate 32 and the case body 31 is welded, whereby the case 3 is formed.

[0043] The external terminal 4 is a portion where the power storage element 1 is electrically connected to the external terminal of another power storage element or an external device, etc. The external terminal 4 is formed of a conductive member. The power storage element 1 of the present embodiment includes two types of external terminals 4, a positive electrode terminal 4A and a negative electrode terminal 4B. These two external terminals 4 are arranged in the case 3 in a state where a part 42A, 42B thereof penetrates the case 3 at positions spaced apart in the X-axis direction, more specifically, at each end position of the case 3 in the X-axis direction.

[0044] In addition, in the power storage element 1 of the present embodiment, insulating members 7A, 7B are arranged between the external terminal 4 and the case 3, and between the case 3 and the current collector 5. This insulating member 7A insulates between the external terminal 4 and the case 3 (in the example of the present embodiment, the cover plate 32), and seals between the portions 42A, 42B where the external terminal 4 penetrates the case 3 and the case 3. Further, the insulating member 7B insulates between the case 3 (in the example of the present embodiment, the cover plate 32) and the current collector 5.

[0045] As shown in FIG. 4, the positive electrode terminal 4A has a positive electrode flange portion 41A that extends along the case 3 outside the case 3, and a positive electrode shaft portion 42A that extends from the positive electrode flange portion 41A, penetrates the case 3, and is electrically connected to the electrode body 2. In the positive electrode terminal 4A, the positive electrode flange portion 41A and the positive electrode shaft portion 42A are integral. The positive electrode terminal 4A of the present embodiment is made of an aluminum-based metal such as aluminum or an aluminum alloy, for example.

[0046] The positive electrode flange portion 41A extends along the cover plate 32 of the case 3. Specifically, the positive electrode flange portion 41A is a rectangular plate shape that is long in the X-axis direction. This positive electrode flange portion 41A has a welding surface 411A on the side opposite to the case 3. This welding surface 411A faces the outside in the Z-axis direction (the side opposite to the case 3), and it is the surface to which a member (a conduction member such as a bus bar) for conducting the positive electrode terminal 4A to the external terminal of another power storage element, an external device, etc. is welded.

[0047] The positive electrode shaft portion 42A extends in the Z-axis direction and penetrates the case 3. That is, the positive electrode shaft portion 42A penetrates the case 3 (cover plate 32) in the Z-axis direction. Specifically, the positive electrode shaft portion 42A has a positive electrode shaft portion main body 420A that extends in the Z-axis direction, and a positive electrode diameter-expanded portion 421A that extends from the positive electrode shaft portion main body 420A as viewed in the Z-axis direction.

[0048] The positive electrode shaft portion main body 420A is a columnar portion that extends in the Z-axis direction and penetrates the case 3 (specifically, the cover plate 32). The positive electrode shaft portion main body 420 of the present embodiment is cylindrical and penetrates the insulating member 7A, the cover plate 32, the insulating member 7B, and the current collector 5.

[0049] The positive electrode diameter-expanded portion 421A sandwiches the case 3 and the current collector 5 between it and the positive electrode flange portion 41A in the Z-axis direction. The positive electrode diameter-expanded portion 421A of the present embodiment sandwiches the insulating member 7A, the cover plate 32, the insulating member 7B, and the current collector 5 between it and the positive electrode flange portion 41A. This positive electrode diameter-expanded portion 421A extends (expands in diameter) along the current collector 5 inside the case 3.

[0050] As shown in FIGS. 1, 2, 5 to 7, the negative electrode terminal 4B has a negative electrode flange portion (flange portion) 41B that extends along the case 3 outside the case 3, and a negative electrode shaft portion (shaft portion) 42B that extends from the negative electrode flange portion 41B, penetrates the case 3, and conducts with the electrode body 2. In the negative electrode terminal 4B, the negative electrode flange portion 41B and the negative electrode shaft portion 42B are separate bodies (separate members).

[0051] The negative electrode flange portion 41B extends along the cover plate 32 of the case 3. Specifically, the negative electrode flange portion 41B is in the shape of a rectangular plate that is long in the X-axis direction. Further, the negative electrode flange portion 41B has a through-hole 412B through which the negative electrode shaft portion 42B is inserted. This through-hole 412B penetrates the negative electrode flange portion 41B in the Z-axis direction (in other words, the thickness direction of the negative electrode flange portion 41B). The through-hole 412B of the present embodiment is circular and is disposed at the center of the negative electrode flange portion 41B.

[0052] Also, the negative electrode flange portion 41B has a welding surface 411B on the side opposite to the case 3. Similar to the welding surface 411A of the positive electrode terminal 4A, the welding surface 411B faces outward in the Z-axis direction and is a surface to which a conductive member such as a bus bar is welded.

[0053] This negative electrode flange portion 41B is composed of a clad material having a plurality (two in the example of the present embodiment) of metal layers 411 laminated in the Z-axis direction. Adjacent metal layers 411 among these plurality of metal layers 411 are made of different types of metals.

[0054] In the negative electrode flange portion 41B, the metal layer (second metal layer) 411a at one end (the lower side in FIGS. 6 and 7) of the plurality of metal layers 411 in the Z-axis direction is made of the same type of metal as the negative electrode shaft portion 42B. Also, in the negative electrode flange portion 41B, the metal layer (first metal layer) 411b at the other end (the upper side in FIGS. 6 and 7) of the plurality of metal layers 411 in the Z-axis direction is made of a different type of metal from the negative electrode shaft portion 42B. Further, in the negative electrode flange portion 41B, the second metal layer 411a or the first metal layer 411b covers the peripheral end surface 411c of the remaining metal layers among the plurality of metal layers 411.

[0055] The negative electrode flange portion 41B of this embodiment has two metal layers, namely a second metal layer 411a and a first metal layer 411b. In this negative electrode flange portion 41B, the first metal layer 411b covers the peripheral end face 411c of the remaining metal layer (second metal layer) 411a. Also, the electrical resistance of the metal constituting the first metal layer 411b is greater than the electrical resistance of the metal constituting the second metal layer 411a. In the negative electrode flange portion 41B of this embodiment, for example, the second metal layer 411a is made of a copper-based metal such as copper or a copper alloy, and the first metal layer 411b is made of an aluminum-based metal such as aluminum or an aluminum alloy.

[0056] The second metal layer 411a is located on the case 3 side with respect to the first metal layer 411b in the negative electrode flange portion 41B. This second metal layer 411a extends along the X-Y plane (a plane including the X-axis direction and the Y-axis direction), and the dimension (thickness) in the Z-axis direction at each position in the X-Y plane direction excluding the through hole 412B is constant. The second metal layer 411a of this embodiment is rectangular with a dimension of 20 mm in the X-axis direction and a dimension of 8.3 mm in the Y-axis direction, and a thickness of 0.5 mm.

[0057] The first metal layer 411b is located on the side opposite to the case 3 with respect to the second metal layer 411a in the negative electrode flange portion 41B. This first metal layer 411b extends along the X-Y plane (a plane including the X-axis direction and the Y-axis direction), and has a thin portion (recess) 4111 that is recessed in the Z-axis direction or a through hole that penetrates in the Z-axis direction. The first metal layer 411b of this embodiment has a recess. The first metal layer 411b of this embodiment has a thin portion 4111 surrounding the through hole 412B and a portion (thick portion) 4112 excluding the thin portion 4111 in the first metal layer 411b.

[0058] The thin portion 4111 is thinner than the thick portion 4112 in the first metal layer 411b. The width (the dimension in the radial direction of the through hole 412B) at each position in the circumferential direction of this thin portion 4111 is constant. That is, when viewed from the Z-axis direction, the outer peripheral edge (the boundary position with the thick portion 4112) 4111a (see FIG. 7) of the thin portion 4111 and the inner peripheral edge (the boundary position with the through hole 412B) 4111b (see FIG. 7) are concentric circles. For example, the diameter of the outer peripheral edge 4111a in this embodiment is 7.3 mm, and the diameter of the inner peripheral edge 4111b is 4 mm.

[0059] The thick portion 4112 is a portion that surrounds the thin portion 4111 in the first metal layer 411b. The thick portion 4112 has a cover portion 4112c that extends to the second metal layer 411a side at the peripheral edge and covers the circumferential end surface 411c of the second metal layer 411a. In this thick portion 4112, except for the cover portion 4112c, the dimension (thickness) in the Z-axis direction at each position in the X-Y plane direction is constant. The thickness of the thick portion (excluding the peripheral edge) 4112 in this embodiment is the same as the thickness of the second metal layer 411a. For this reason, the thin portion 4111 is thinner than the second metal layer 411a. Also, in the thick portion 4112 of this embodiment, the cover portion 4112c is provided over the entire circumferential direction of the thick portion 4112.

[0060] In the first metal layer 411b, the thin portion 4111 is a portion where the dimension in the Z-axis direction at each position in the radial direction of the through hole 412B is substantially the same, and the portion where the dimension in the Z-axis direction is larger than that of the thin portion 4111 is the thick portion 4112. In the first metal layer 411b of this embodiment, a step 4111d is formed at the boundary between the thin portion 4111 and the thick portion 4112 (see FIG. 7). Also, the welding surface 411B of the negative electrode flange portion 41B is constituted by the outer surface (the surface facing away from the case 3) of the thick portion 4112 of the first metal layer 411b.

[0061] The negative electrode shaft portion 42B extends in the Z-axis direction and penetrates the case 3. That is, the negative electrode shaft portion 42B penetrates the case 3 (cover plate 32) in the Z-axis direction. Specifically, the negative electrode shaft portion 42B includes a negative electrode shaft portion main body 420B that extends in the Z-axis direction, and a plurality of enlarged diameter portions (a first enlarged diameter portion (crimping portion) 421B, a second enlarged diameter portion (enlarged diameter portion) 422B, and a third enlarged diameter portion 423B) that spread from the negative electrode shaft portion main body 420B when viewed in the Z-axis direction. The negative electrode shaft portion main body 420B and the plurality of enlarged diameter portions 421B, 422B, and 423B are integrally formed. The negative electrode shaft portion 42B is made of, for example, a copper-based metal such as copper or a copper alloy.

[0062] The negative electrode shaft portion main body 420B is a columnar portion that extends in the Z-axis direction and penetrates the case 3 (specifically, the cover plate 32). The negative electrode shaft portion main body 420B of the present embodiment is cylindrical and penetrates the insulating member 7A, the cover plate 32, the insulating member 7B, and the current collector 5.

[0063] The first diameter-expanded portion (crimped portion) 421B extends (has an expanded diameter) along the first metal layer 411b of the negative electrode flange portion 41B on the outer side (opposite to the case 3) of the negative electrode flange portion 41B in the Z-axis direction. Specifically, the first diameter-expanded portion 421B extends along the thin portion 4111 of the first metal layer 411b. The first diameter-expanded portion 421B is formed at a position smaller than the thin portion 4111 and included within the region where the thin portion 4111 is formed when viewed from the Z-axis direction. That is, the first metal layer 411b has the thin portion 4111 in a region larger than the first diameter-expanded portion 421B and including the first diameter-expanded portion 421B when viewed from the Z-axis direction. This first diameter-expanded portion 421B includes, on its surface, a first conduction surface (conduction surface) 4210B that faces the case 3 side and is in contact with (conductive to) the thin portion 4111 (see FIG. 6). The first diameter-expanded portion 421B of the present embodiment extends within the range of the thin portion 4111 from the other end (the upper side in FIG. 6) of the negative electrode shaft portion main body 420B in the Z-axis direction, and the contour when viewed from the Z-axis direction is a circular shape concentric with the negative electrode shaft portion main body 420B. As described above, this first diameter-expanded portion 421B is smaller than the thin portion 4111 when viewed from the Z-axis direction. That is, when viewed from the Z-axis direction, there is a gap (a portion recessed in a groove shape) between the contour of the first diameter-expanded portion 421B and the boundary position 4111a between the thin portion 4111 and the thick portion 4112 in the first metal layer 411b.

[0064] The second diameter-expanded portion (diameter-expanded portion) 422B sandwiches the peripheral edge portion of the through hole 412B in the negative electrode flange portion 41B (through hole peripheral edge portion 413B: see FIG. 7) between it and the first diameter-expanded portion 421B in the Z-axis direction. This second diameter-expanded portion 422B extends (has an expanded diameter) along the second metal layer 411a of the negative electrode flange portion 41B on the inner side (the case 3 side) of the negative electrode flange portion 41B in the Z-axis direction. Specifically, the second diameter-expanded portion 422B extends along the peripheral edge portion of the through hole 412B in the second metal layer 411a (the portion overlapping the thin portion 4111). This second diameter-expanded portion 422B includes, on its surface, a second conduction surface 4220B that faces the side opposite to the case 3 and is in contact with (conductive to) the second metal layer 411a (see FIG. 6). The second diameter-expanded portion 422B of the present embodiment extends from an intermediate position of the negative electrode shaft portion main body 420B in the Z-axis direction, and the contour when viewed from the Z-axis direction is a circular shape concentric with the negative electrode shaft portion main body 420B.

[0065]

[0066] The third diameter-expanding portion 423B sandwiches the case 3 and the current collector 5 between it and the second diameter-expanding portion 422B in the Z-axis direction. The third diameter-expanding portion 423B of the present embodiment sandwiches the insulating member 7A, the cover plate 32, the insulating member 7B, and the current collector 5 between it and the second diameter-expanding portion 422B. Specifically, the third diameter-expanding portion 423B spreads (expands in diameter) along the current collector 5 inside the case 3. This third diameter-expanding portion 423B includes, on its surface, a third conduction surface 4230B that faces the case 3 side in the Z-axis direction and is in contact with (conductive to) the current collector 5 (see FIG. 6). The third diameter-expanding portion 423B of the present embodiment spreads from one end (the lower side in FIG. 6) of the negative electrode shaft portion main body 420B in the Z-axis direction, and the contour seen from the Z-axis direction is a circular shape concentric with the negative electrode shaft portion main body 420B.

[0067]

[0068] In the negative electrode shaft portion 42B, the portion corresponding to the first enlarged diameter portion 421B before the negative electrode flange portion 41B is attached (fixed) is, as shown in FIGS. 2 and 8, a columnar portion (portion corresponding to the first enlarged diameter portion) 421B' through which the through hole 412B of the negative electrode flange portion 41B can be inserted. The portion corresponding to the first enlarged diameter portion 421B' is caulked in a state where the through hole 412B of the negative electrode flange portion 41B is inserted and the peripheral edge portion 413B of the through hole of the negative electrode flange portion 41B abuts against the second enlarged diameter portion (portion having a diameter larger than the through hole 412B) 422B (see FIG. 8). As a result, the portion corresponding to the first enlarged diameter portion 421B' spreads along the peripheral edge portion 413B (thin wall portion 4111), and as a result, the first enlarged diameter portion 421B is formed, and the negative electrode flange portion 41B is connected (fixed) to the negative electrode shaft portion 42B.

[0069] At this time, since the first metal layer 411b is made of an aluminum-based metal and is soft, when caulking the portion corresponding to the first enlarged diameter portion 421B', the peripheral edge portion of the through hole 412B in the first metal layer 411b is compressed and a part thereof tends to extend in a direction away from the through hole 412B. However, since the negative electrode flange portion 41B is made of a clad material and the first metal layer 411b and the second metal layer (second metal layer made of a hard copper-based metal) 411a are fixed, the compressed portion (peripheral edge portion of the through hole 412B in the first metal layer 411b) cannot extend. As a result, when the first enlarged diameter portion 421B is formed, the periphery thereof (the first metal layer 411b around the first enlarged diameter portion 421B) bulges (see reference sign α in FIG. 9). Even if a bulge α is formed around the first enlarged diameter portion 421B in this way, in the X-Y plane direction, the first enlarged diameter portion 421B is smaller than the thin wall portion 4111, that is, a gap is formed between the peripheral edge of the first enlarged diameter portion 421B and the boundary position 4111a between the thick wall portion 4112 and the thin wall portion 4111 in the thin wall portion 4111. Therefore, the formed bulge α is located in the gap (that is, inside the thin wall portion 4111). As a result, it is possible to prevent the formation of a bulge α caused by caulking when forming the first enlarged diameter portion 421B on the outer surface of the thick wall portion 4112 (welding surface 411B of the negative electrode flange portion 41B).

[0070] Also, in the negative electrode shaft portion 42B, the portion corresponding to the third enlarged diameter portion 423B before being attached (fixed) to the case 3 is a cylindrical portion (portion corresponding to the third enlarged diameter portion) 423B' that can penetrate through the insulating member 7A, the case 3 (the lid plate 32 in the example of this embodiment), the insulating member 7B, and the through holes provided in the current collector 5, as shown in FIGS. 2 and 8. The third enlarged diameter portion corresponding portion 423B' is caulked and enlarged in a state of passing through the through holes of the insulating member 7A, the case 3, the insulating member 7B, and the current collector 5 (in other words, in a state of passing through each member 7A, 3, 7B, 5; see FIG. 8), thereby forming the third enlarged diameter portion 423B.

[0071] In addition, the order in which the first enlarged diameter portion 421B and the third enlarged diameter portion 423B are formed is not limited. They may be formed in the order of the first enlarged diameter portion 421B and the third enlarged diameter portion 423B, or in the order of the third enlarged diameter portion 423B and the first enlarged diameter portion 421B. Also, the first enlarged diameter portion 421B and the third enlarged diameter portion 423B may be formed at the same timing.

[0072] Returning to FIG. 2, the current collector 5 is disposed in the case 3 and is directly or indirectly connected to the electrode body 2 in a conductive manner. The current collector 5 of this embodiment is connected to the electrode body 2 in a conductive manner via the clip member 50. That is, the power storage element 1 includes the clip member 50 that connects the electrode body 2 and the current collector 5 in a conductive manner.

[0073] The current collector 5 is formed of a conductive member. The current collector 5 is disposed along the inner surface of the case 3. The current collector 5 of the present embodiment connects the external terminal 4 and the clip member 50 in a conductive manner. Specifically, the current collector 5 has a first connection portion 51 that is conductively connected to the external terminal 4, a second connection portion 52 that is conductively connected to the electrode body 2, and a bent portion 53 that connects the first connection portion 51 and the second connection portion 52. In the current collector 5, the bent portion 53 is disposed near the boundary between the cover plate 32 and the short wall portion 314 in the case 3, the first connection portion 51 extends along the cover plate 32 from the bent portion 53, and the second connection portion 52 extends along the short wall portion 314 from the bent portion 53. The first connection portion 51 has a through hole 51a, and in a state where the shaft portion (positive electrode shaft portion 42A or negative electrode shaft portion 42B) of the external terminal 4 is inserted through the through hole 51a, it is conductively connected to the enlarged diameter portion (positive electrode enlarged diameter portion 421A or third enlarged diameter portion 423B). Further, the second connection portion 52 of the present embodiment is joined to the clip member 50 by, for example, ultrasonic welding.

[0074] The current collector 5 configured as described above is disposed on the positive electrode and the negative electrode of the power storage element 1, respectively. In the power storage element 1 of the present embodiment, the current collector 5 is disposed along the non-coated laminated portion 26 of the positive electrode and the non-coated laminated portion 26 of the negative electrode of the electrode body 2 in the case 3, respectively. The current collector 5 for the positive electrode and the current collector 5 for the negative electrode are formed of different materials. Specifically, the current collector 5 for the positive electrode is formed of an aluminum-based metal such as aluminum or an aluminum alloy, and the current collector 5 for the negative electrode is formed of a copper-based metal such as copper or a copper alloy.

[0075] The clip member 50 sandwiches the positive electrode 23 or the negative electrode 24 laminated in the non-coated laminated portion 26 of the electrode body 2 so as to bundle them. Thereby, the clip member 50 surely conducts the positive electrodes 23 or the negative electrodes 24 laminated in the non-coated laminated portion 26. The clip member 50 of the present embodiment is formed by bending a plate-like metal material so that the cross section is U-shaped.

[0076] The insulating member 6 is disposed between the case 3 (specifically, the case main body 31) and the electrode body 2. This insulating member 6 is formed in a bag shape by bending a sheet-like member having insulation that is cut into a predetermined shape.

[0077] In the above-described power storage element 1, even if a convex portion α due to caulking occurs around the first diameter-expanded portion 421B on the surface 411B on the side opposite to the case 3 of the negative electrode flange portion 41B, the position of the first diameter-expanded portion 421B and its periphery on the surface 411B of the negative electrode flange portion 41B are recessed, that is, since the thin portion 4111 is formed, when connecting another member to the negative electrode flange portion 41B, the convex portion α does not get in the way and is easy to connect.

[0078] In the power storage element 1 of the present embodiment, in the negative electrode flange portion 41B, the first metal layer 411b covers the peripheral end surface 411c of the remaining metal layer (second metal layer) 411a (see FIG. 6). In this way, in the negative electrode flange portion (clad material) 41B, by covering the peripheral end surfaces 411c of the remaining metal layers (second metal layers) 411a with the outermost metal layer (first metal layer 411b) among the plurality of metal layers 411, the intrusion of moisture between the metal layers 411a and 411b from the peripheral end of the negative electrode flange portion 41B is effectively suppressed.

[0079] Further, in the power storage element 1, since the side opposite to the case 3 (the upper side in FIG. 6) of the negative electrode flange portion 41B is more liberated without the arrangement of other members or the like than the case 3 side, moisture is likely to approach from the opposite side to the negative electrode flange portion 41B. For this reason, like the power storage element 1 of the present embodiment, in the negative electrode flange portion 41B, the first metal layer 411b at the end on the side opposite to the case 3 covers the peripheral end surface 411c of the remaining metal layer (second metal layer) 411a from the side opposite to the case 3 toward the case 3, so that the intrusion of moisture between the metal layers 411a and 411b from the liberated side (the side opposite to the case 3) is more effectively suppressed.

[0080] Further, in the negative electrode flange portion 41B of the negative electrode terminal 4B of the present embodiment, the electrical resistance of the metal constituting the first metal layer 411b (aluminum-based metal in the example of the present embodiment) is greater than the electrical resistance of the metal constituting the second metal layer 411a (copper-based metal in the example of the present embodiment). Also, in the portion of the negative electrode flange portion 41B that is electrically connected to the negative electrode shaft portion 42B, specifically, in the portion (peripheral portion 413B of the through hole) sandwiched between the first enlarged diameter portion 421B (first conduction surface 4210B) and the second enlarged diameter portion 422B, the first metal layer 411b (thin portion 4111) is thinner than the second metal layer 411a (see FIG. 7). According to such a configuration, compared with the case where the two metal layers 411a and 411b have the same thickness at the peripheral portion 413B of the through hole, the electrical resistance (electrical resistance value) between the first metal layer 411b and the first enlarged diameter portion 421B (first conduction surface 4210B) is suppressed, and thereby, the conduction between the negative electrode shaft portion 42B and the negative electrode flange portion 41B is improved.

[0081] Also, in the power storage element 1 of the present embodiment, in the first metal layer 411b, the portion (thin portion) 4111 that is electrically connected to the negative electrode shaft portion 42B (first conduction surface 4210B) is thinner than the thick portion 4112. Further, the surface of the thick portion 4112 constitutes the welding surface 411B. That is, the thick portion 4112 has the welding surface 411B. In this way, by making the portion (thin portion) 4111 that is electrically connected to the negative electrode shaft portion 42B (first conduction surface 4210B) in the first metal layer 411b thin and making the thick portion 4112 thick, while achieving good conduction between the negative electrode shaft portion 42B and the negative electrode flange portion 41B, the influence of heat due to the welding on the second metal layer 411a when another member is welded to the welding surface 411B of the first metal layer 411b is suppressed.

[0082] Note that the power storage element of the present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the gist of the present invention. For example, the configuration of another embodiment can be added to the configuration of a certain embodiment, and a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment. Further, a part of the configuration of a certain embodiment can be deleted.

[0083] In the energy storage element 1 of the above-described embodiment, only the negative electrode terminal 4B has a flange portion (negative electrode flange portion 41B) and a shaft portion (negative electrode shaft portion 42B) configured by separate members, but the present invention is not limited to this configuration. Also in the positive electrode terminal 4A, the flange portion (positive electrode flange portion 41A) and the shaft portion (positive electrode shaft portion 42A) may be configured by separate members.

[0084] Further, the negative electrode flange portion 41B is configured by a clad material having two metal layers 411 (specifically, a first metal layer 411b and a second metal layer 411a), but the present invention is not limited to this configuration. As shown in FIG. 10, the negative electrode flange portion 41B may be configured by a clad material having three or more metal layers 411. In this case, if adjacent metal layers 411 are made of different types of metal, the clad material may have a plurality of metal layers 411 made of the same type of metal.

[0085] When the negative electrode flange portion 41B is configured by three or more metal layers 411 in this way, the first metal layer (the metal layer at the end opposite to case 3 in the Z-axis direction among the plurality of metal layers 411) 411b may have a through hole penetrating in the Z-axis direction at a portion corresponding to the thin portion 4111. Even in this case, when the first enlarged diameter portion 421B is formed, a convex portion α is formed around the first enlarged diameter portion 421B. However, since the first metal layer 411b has the through hole, the convex portion α does not interfere when connecting another member to the negative electrode flange portion 41B, and it is easy to connect.

[0086] Also, in the negative electrode flange portion 41B of the above-described embodiment, the metal layer (cover portion 4112c of the first metal layer 411b) at the other end in the Z-axis direction covers the entire peripheral end surface 411c of the remaining metal layer (second metal layer 411a) (up to the lower end (one end in the Z-axis direction) in FIG. 7), but the present invention is not limited to this configuration. As shown in FIG. 10, the cover portion 4112c only needs to cover up to one side in the Z-axis direction from the boundary position P between adjacent metal layers 411. For example, in the example shown in FIG. 10, the cover portion 4112c covers from the boundary position P between the peripheral end surface 411c of the lowermost metal layer 411 and the peripheral end surface 411c of the second metal layer 411 from the bottom, to a position above the lower end of the peripheral end surface 411c of the lowermost metal layer 411.

[0087] Further, in the negative electrode flange portion 41B of the above-described embodiment, although the peripheral edge portion (cover portion 4112c) of the first metal layer 411b covers the peripheral end surface 411c (boundary position P between adjacent metal layers 411) of the second metal layer 411a over the entire circumferential direction (see FIGS. 5 and 7), the present invention is not limited to this configuration. The cover portion 4112c may be configured to cover the boundary position P between adjacent metal layers 411 in a part of the circumferential direction (the circumferential direction of the negative electrode flange portion 41B).

[0088] Also, at the peripheral end portion of the negative electrode flange portion 41B, the metal layer 411b at the end on the other side (the side opposite to the case 3: the upper side in FIG. 6) of the plurality of metal layers 411 in the Z-axis direction covers the peripheral end surface 411c of the metal layer 411a at the end on one side (the case 3 side: the lower side in FIG. 6) of the plurality of metal layers 411 in the Z-axis direction, but the present invention is not limited to this configuration. As shown in FIG. 11, the metal layer 411 at the end on one side (the case 3 side) of the plurality of metal layers in the Z-axis direction may cover the peripheral end surface 411c of the metal layer 411 at the end on the other side (the side opposite to the case 3) of the plurality of metal layers in the Z-axis direction. That is, the cover portion 4112c may be configured to extend in the Z-axis direction from the metal layer 411a at the end on the case 3 (cover plate 32) side in a direction away from the case 3.

[0089] Further, in the above-described embodiment, the case where the power storage element is used as a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) capable of charging and discharging has been described, but the type and size (capacity) of the power storage element are arbitrary. Also, in the above-described embodiment, a lithium ion secondary battery has been described as an example of the power storage element, but the present invention is not limited thereto. For example, the present invention is applicable to various secondary batteries, other primary batteries, and power storage elements of capacitors such as electric double layer capacitors.

[0090] The power storage element (for example, a battery) 1 may be used in a power storage device (when the power storage element is a battery, a battery module) 11 as shown in FIG. 11. The power storage device 11 includes at least two power storage elements 1 and a bus bar member 12 that electrically connects the two (different) power storage elements 1 to each other. In this case, it is sufficient that the technology of the present invention is applied to at least one power storage element 1.

Explanation of Reference Numerals

[0091] 1... Power storage element, 2... Electrode body, 21... Winding core, 22... Laminate, 23... Positive electrode, 231... Metal foil, 232... Positive electrode active material layer, 24... Negative electrode, 241... Metal foil, 242... Negative electrode active material layer, 25... Separator, 26... Uncoated laminated portion, 3... Case, 31... Case body, 311... Closing portion, 312... Barrel portion, 313... Long wall portion, 314... Short wall portion, 32... Cover plate, 34... Opening peripheral edge portion, 4... External terminal, 4A... Positive electrode terminal (external terminal), 41A... Positive electrode flange portion, 411A... Welding surface, 42A... Positive electrode shaft portion, 420A... Positive electrode shaft portion body, 421A... Positive electrode enlarged diameter portion, 4B... Negative electrode terminal (external terminal), 41B... Negative electrode flange portion (flange portion), 411B... Welding surface, 412B... Through hole, 413B... Through hole peripheral edge portion, 411... Metal layer, 411a... Second metal layer, 411b... First metal layer, 411c... Peripheral end surface, 4111... Thin portion, 4111a... Outer peripheral edge of the thin portion (boundary position between the thin portion and the thick portion), 4111b... Inner peripheral edge of the thin portion, 4111d... Step, 4112... Thick portion, 4112c... Cover portion, 42B... Negative electrode shaft portion (shaft portion), 420B... Negative electrode shaft portion body, 421B... First enlarged diameter portion (crimped portion), 421B’... Portion corresponding to the first enlarged diameter portion, 4210B... First conduction surface, 422B... Second enlarged diameter portion (enlarged diameter portion), 4220B... Second conduction surface, 423B... Third enlarged diameter portion, 423B’... Portion corresponding to the third enlarged diameter portion, 4230B... Third conduction surface, 4250B... Conduction surface, 5... Current collector, 50... Clip member, 51... First connection portion, 51a... Through hole, 52... Second connection portion, 53... Bent portion, 6... Insulating member, 7A, 7B... Insulating member, 11... Power storage device, 12... Bus bar member, 100... External terminal, 101... Shaft portion, 102... Flange portion, C... Winding center axis, P... Boundary position, α... Bulge (protrusion)

Claims

1. An electrode body, a case for housing the electrode body, and a metal external terminal disposed on the case, comprising: the external terminal has, a flange portion that extends along the case outside the case, and a shaft portion that extends from the flange portion, penetrates the case, and conducts with the electrode body, the flange portion is composed of a clad material having a plurality of metal layers laminated in the penetration direction of the shaft portion, and has a through hole through which the shaft portion is inserted, the shaft portion has, a diameter-expanded portion that extends along the surface of the flange portion on the case side, and a caulked portion that extends along the surface of the flange portion opposite to the case and sandwiches the peripheral edge portion of the through hole in the flange portion between the diameter-expanded portion, a first metal layer, which is a metal layer at the end opposite to the case in the penetration direction among the plurality of metal layers, has a recess recessed in the penetration direction or a through hole penetrating in the penetration direction in a region larger than the caulked portion and including the caulked portion when viewed from the penetration direction, an energy storage element.

2. The flange portion has two metal layers, namely, the first metal layer and a second metal layer, which is a metal layer at the end on the case side in the penetration direction among the plurality of metal layers, The electrical resistance of the metal constituting the second metal layer is smaller than the electrical resistance of the metal constituting the first metal layer. The energy storage element according to claim 1.

3. An electrode body, a case for housing the electrode body, and a metal external terminal disposed on the case, comprising: the external terminal has, a flange portion that extends along the outer surface of the case outside the case, and a shaft portion that extends from the flange portion, penetrates the case, and conducts with the electrode body, the flange portion is composed of a clad material having a plurality of metal layers laminated in the penetration direction of the shaft portion, and has a through hole through which the shaft portion is inserted, the shaft portion has, a diameter-expanded portion formed between the flange portion and the outer surface of the case and extending along the outer surface of the case, and a caulked portion that extends along the surface of the flange portion opposite to the case and sandwiches the peripheral edge portion of the through hole in the flange portion between the diameter-expanded portion, a first metal layer, which is a metal layer opposite to the case in the penetration direction among the plurality of metal layers, has a recess recessed in the penetration direction or a through hole penetrating in the penetration direction in a region larger than the caulked portion and including the caulked portion when viewed from the penetration direction, an energy storage element.

4. The flange portion has two metal layers, namely, the first metal layer and a second metal layer which is a metal layer among the plurality of metal layers and faces the case in the through direction. The electric resistance of the metal constituting the second metal layer is smaller than the electric resistance of the metal constituting the first metal layer. The power storage element according to claim 3.

5. The flange portion has a convex portion protruding in the through direction in the concave portion of the first metal layer. The convex portion is located between the outer peripheral edge of the concave portion and the outer peripheral edge of the caulked portion in a direction orthogonal to the through direction. The power storage element according to claim 3 or 4.

6. The first metal layer has the through hole. The flange portion has a convex portion protruding in the through direction. The convex portion is located between the outer peripheral edge of the through hole and the outer peripheral edge of the caulked portion in a direction orthogonal to the through direction. The power storage element according to claim 3 or 4.

7. The second metal layer has a peripheral end face which is an end face in a direction orthogonal to the through direction. The first metal layer has a cover portion protruding in the through direction along the peripheral end face of the second metal layer. The power storage element according to any one of claims 3 to 6.

8. The external terminal is a negative electrode. The first metal layer contains aluminum or an aluminum-based metal, and the second metal layer contains copper or a copper-based metal. The power storage element according to any one of claims 3 to 7.

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