Electricity storage device

Abstract

A power storage device includes: an electrode body (10); an outer can (20) that has a cylindrical part (21) and an opening part formed on one end side of the cylindrical part (21), and that houses the electrode body; and a sealing member (24) that closes the opening. In the height direction of the outer can (20), an annular groove portion (23) recessed inward is formed on the opening portion side of the cylindrical portion (21), a bent portion (210) folded inward is formed on the peripheral edge portion of the opening portion, the peripheral edge portion of the sealing member (24) is sandwiched from both sides by the groove portion (23) and the bent portion, and in the bent portion (210), the groove portion (23) and the bent portion (210) are folded inward. The thickness of the tip section located on the inside in the radial direction of the outer can (20) increases with respect to at least the thin section located on the outside in the radial direction of the outer can (20) than the tip section, and the tip section protrudes toward the sealing member (24) in the height direction of the outer can (20).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a power storage device such as a secondary battery. BACKGROUND

[0002] In a power storage device such as a lithium ion battery, a power storage device having an outer can that houses an electrode body that generates electricity and a sealing member that seals an opening of the outer can is widely used.

[0003] In such a power storage device, it is necessary to prevent moisture from entering the inside of the outer can or the like, and a high airtightness is required. Therefore, the contact portion of the outer can and the sealing member is sealed by crimping and fixing the peripheral portion of the sealing member to the upper portion of the outer can.

[0004] That is, a circular groove portion that is recessed inward is formed around a portion near the upper end of the outer can. Further, the upper end portion of the outer can is crimped so as to be folded inward in a state in which the peripheral portion of the sealing member is placed on the upper side of the groove portion, and thus the sealing member is sandwiched by the groove portion and the folded portion and the peripheral portion of the sealing member is fixed.

[0005] Further, in Patent Document 1, a notch is formed in advance in the upper end portion of the outer can, and thus the tip end is prevented from being wrinkled when the upper end portion is folded inward.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Publication No. 2006-261083 SUMMARY

[0009] With the above-described power storage device, the sealing reliability is high. However, as the capacity and high output of the power storage device are improved, it is expected that the reliability of the power storage device will be further improved. Therefore, an object of the present disclosure is to provide a power storage device that is excellent in reliability.

[0010] The power storage device of the present disclosure includes an electrode body, an outer can that has a cylindrical portion and an opening portion formed on one end side of the cylindrical portion, the outer can housing the electrode body, and a sealing member that seals the opening portion, a circular groove portion that is recessed inward is formed on the opening portion side of the cylindrical portion in the height direction of the outer can, a folded portion that is folded inward is formed on the peripheral portion of the opening portion, the peripheral portion of the sealing member is sandwiched by the groove portion and the folded portion from both sides, in the folded portion, the thickness of a tip end portion that is located on the radially inner side of the outer can is increased relative to at least a thin-walled portion that is located on the radially outer side of the outer can than the tip end portion, and the tip end portion protrudes toward the sealing member in the height direction of the outer can.

[0011] With the power storage device of the present disclosure, it is possible to improve reliability. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a sectional view of a battery that is an example of the power storage device of the embodiment.

[0013] Figure 2 is a diagram that illustrates a wound state of the electrode body.

[0014] Figure 3 is a longitudinal sectional view of a bent portion that is an example of a case where the upper end of the exterior can is bent inward.

[0015] Figure 4 is a diagram that shows bent portions of different lengths, Figure 4 (a) of FIG. 8 shows a case where the bent portion is relatively long, Figure 4 (b) of FIG. 8 shows a case where the bent portion is relatively short. DETAILED DESCRIPTION

[0016] Hereinafter, an example of an embodiment of the power storage device of the present disclosure will be described in detail with reference to the drawings. Further, structures obtained by selectively combining a plurality of embodiments and modifications described below are included in the present disclosure.

[0017] "Overall Structure"

[0018] Figure 1 is a sectional view of a battery 1 that is an example of the power storage device of the embodiment. Further, in the power storage device, a capacitor or the like is also included.

[0019] As shown in Figure 1 , the battery 1 is provided with an electrode body 10 and an exterior can 20 that houses the electrode body 10. The exterior can 20 includes a cylindrical portion 21 and a bottom portion 22 that seals one end of the cylindrical portion 21, and an opening portion is formed at the other end of the cylindrical portion 21, which is sealed by a sealing member 24. In addition, in the exterior can 20, an electrolyte is housed together with the electrode body 10. The electrolyte can be an aqueous electrolyte, but a non-aqueous electrolyte is used in the present embodiment. In addition, a solid electrolyte can also be used instead of the electrolyte. As the solid electrolyte, for example, a polymer electrolyte in a solid or gel state, an inorganic solid electrolyte, or the like is used.

[0020] A circular ring-shaped groove portion 23 protruding to the radially inner side of the battery (or the outer can) is provided on the opening portion side of the cylindrical portion 21 in the height direction. A sealing member 24 is supported by the groove portion 23 and seals the opening portion of the outer can 20. Hereinafter, for convenience of explanation, the sealing member 24 side of the battery 1 is set as the upper side, and the bottom portion 22 side of the outer can 20 is set as the lower side. Further, it is also possible that the outer can used in the power storage device of the present disclosure is open at both ends in the height direction, and a pair of openings are each sealed by a sealing member.

[0021] The battery 1 also has a plurality of electrode leads extending from each portion of the electrode body 10 toward the sealing member 24 side and directly connecting the first electrode constituting the electrode body 10 and the current collecting plate 26 of the sealing member 24. In addition, for example, an upper insulating plate 34 is disposed between the electrode body 10 and the sealing member 24.

[0022] The electrode body 10 is a jelly-roll type electrode body in which the first electrode and the second electrode are wound with the separator interposed therebetween, and in the present embodiment, the first electrode is a positive electrode, the second electrode is a negative electrode, and the above-described electrode lead is a positive electrode lead 19. Further, it is also possible that the first electrode is a negative electrode, and the second electrode is a positive electrode. As will be described later, the positive electrode lead 19 is provided in a plurality of numbers at a prescribed interval in the longitudinal direction of the positive electrode and extends upward from the upper portion of the positive electrode.

[0023] The positive electrode lead 19 electrically connects the positive electrode and the metal member of the sealing member 24. In addition, the negative electrode is electrically connected to the outer can 20, for example, by making the protruding portion of the core material thereof contact the outer can 20 via the negative electrode current collecting plate. Thus, the sealing member 24 functions as a positive electrode terminal, and the outer can 20 functions as a negative electrode terminal. The upper insulating plate 34 prevents the positive electrode and the positive electrode lead 19 from contacting the outer can 20, and in addition, prevents the positive electrode lead 19 from contacting the negative electrode of the electrode body 10. Further, the negative electrode can also be electrically connected to the bottom portion of the outer can via a lead.

[0024] Figure 2 is a view illustrating the winding state of the electrode body 10. The electrode body 10 includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, each of which is a long strip body in a band shape. The positive electrode 11, the negative electrode 12, and the separator 13 are alternately laminated in the radial direction of the electrode body 10 by being wound in a spiral shape. The positive electrode 11 and the negative electrode 12 each have an agent layer on the respective surfaces. Generally, in order to prevent precipitation of lithium, the composite material layer of the negative electrode 12 is formed in a size larger by one turn than the composite material layer of the positive electrode 11. That is, the composite material layer of the negative electrode 12 is formed longer than the composite material layer of the positive electrode 11 in the longitudinal direction and the width direction (short side direction). In the present embodiment, the positive electrode lead 19 is provided in a plurality of numbers at a prescribed interval in the longitudinal direction of the positive electrode 11 and extends upward from the upper portion of the positive electrode 11. Figure 2In the example of FIG. 1, the inner starting end of the positive electrode 11 is located outward of the starting end of the negative electrode 12, and the central portion of the electrode body 10 is wound only with the negative electrode 12 and the separator 13. In addition, the separator 13 is formed in a size of at least one turn larger than the positive electrode 11, and two pieces are arranged in a manner of sandwiching the positive electrode 11. Thus, the separator 13 is interposed between the positive electrode 11 and the negative electrode 12 at the time of winding.

[0025] The positive electrode 11 has a positive electrode core in a band shape and a positive electrode composite material layer formed on at least one face of the core. For the positive electrode core, a foil of a metal stable in the potential range of the positive electrode such as aluminum, an aluminum alloy, or the like, a film in which the metal is arranged on the surface layer, or the like can be used. Preferably, the positive electrode composite material layer contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride, and is formed on both faces of the positive electrode core. For the positive electrode active material, for example, a lithium transition metal complex oxide is used. The positive electrode lead 19 is connected to the positive electrode, but is preferably directly joined to the positive electrode core by welding or the like.

[0026] The negative electrode 12 has a negative electrode core in a band shape and a negative electrode composite material layer formed on at least one face of the core. For the negative electrode core, a foil of a metal stable in the potential range of the negative electrode such as copper, a copper alloy, or the like, a film in which the metal is arranged on the surface layer, or the like can be used. Preferably, the negative electrode composite material layer contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is formed on both faces of the negative electrode core. For the negative electrode active material, for example, graphite, a silicon-containing compound, or the like is used. Furthermore, a tongue-shaped negative electrode lead can be directly joined to the negative electrode core and to the current collector plate by welding or the like.

[0027] The nonaqueous electrolyte accommodated in the exterior can 20 contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. For the nonaqueous solvent, for example, an ester-based solvent, an ether-based solvent, a nitrile-based solvent, an amide-based solvent, and a mixed solvent of two or more kinds thereof, or the like can be used. The nonaqueous solvent can contain a halogen-substituted body obtained by substituting at least a part of hydrogens of these solvents with a halogen atom such as fluorine. As an example of the nonaqueous solvent, ethylene carbonate (EC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), and a mixed solvent thereof, or the like can be given. For the electrolyte salt, for example, a lithium salt such as LiPF6 can be used.

[0028] Returning to Figure 1The outer can 20 is a bottomed cylindrical metal container having an opening at an upper end in the axial direction, and has a cylindrical portion 21 and a bottom portion 22 which is circular in plan view. The outer can 20 is generally made of a metal having iron as a main component, and in particular, when the outer can 20 is electrically connected to the positive electrode, the outer can 20 can be made of a metal having aluminum or the like as a main component. Further, the outer can 20 has a groove portion 23 formed along the circumference of the cylindrical portion 21. The groove portion 23 is formed at a position separated from the opening edge portion (upper end of the outer can 20) by a predetermined length in the lower direction thereof in the vicinity of the opening of the outer can 20. The predetermined length is, for example, a length corresponding to 1 to 20% of the axial length of the outer can 20.

[0029] In the present embodiment, the bottom portion 22 of the outer can 20 is provided with a safety valve mechanism which operates when the battery 1 generates an abnormality. A thin-walled portion is formed in the bottom portion 22, for example. When the battery 1 generates an abnormality and the internal pressure rises, the thin-walled portion is preferentially broken, and a gas discharge port is formed in the bottom portion 22.

[0030] The groove portion 23 is a portion in which a part of the cylindrical portion 21 protrudes to the inside of the outer can 20, and is formed by, for example, spinning the cylindrical portion 21 from the outside. Further, at the position where the groove portion 23 is formed, the outer can 20 is reduced in diameter, and a thin-line groove is formed in the outer peripheral surface of the cylindrical portion 21. It is preferable that the groove portion 23 have a substantially U-shaped cross section, and be formed in a ring shape over the entire length in the circumferential direction of the cylindrical portion 21. It is more preferable that the groove portion 23 be formed by processing the cylindrical portion 21 after the electrode body 10 is housed in the outer can 20.

[0031] The inner diameter of the outer can 20 at the position where the groove portion 23 is formed is, for example, 80 to 99% of the maximum inner diameter of the outer can 20. An example of the length of the groove portion 23 in the radial direction of the outer can 20 is 0.5 to 2.0 mm. Since the diameter of the electrode body 10 is the same order as the maximum inner diameter of the outer can 20, the electrode body 10 and the groove portion 23 overlap in the vertical direction of the battery 1. In the present embodiment, the lower end of the positive electrode lead 19 is connected to the upper end of the positive electrode at a plurality of positions, and the other end of the positive electrode lead 19 is connected to the lid 25 via the current collecting plate 26.

[0032] The sealing member 24 includes, for example, a lid 25, a current collecting plate 26, and an electrically insulating gasket 33, and is formed in a disc shape as a whole. The sealing member 24 is arranged on the groove portion 23 of the outer can 20 and is fixed to the opening portion of the outer can 20. The upper end of the opening portion is bent inward and is crimped to the sealing member 24 with the gasket 33 interposed therebetween to form a bent portion. In other words, the sealing member 24 is fixed to the upper end portion of the outer can 20 by the groove portion 23 and the bent portion of the outer can 20, and seals the opening portion of the outer can 20. The bent portion is formed in a ring shape along the circumferential direction of the outer can 20, and holds the sealing member 24 together with the groove portion 23. Further, the sealing member 24 includes a member such as an upper insulating plate 34 for covering the upper opening portion of the outer can 20. In addition, the sealing member 24 can include a metal rupture plate or the like.

[0033] The lid 25 is a disc-shaped metal member exposed to the outside of the outer can 20 and forms the top surface of the battery 1. The lid 25 has a shape in which the radially central portion protrudes outward of the battery 1 (raised portion). When the battery 1 is modularized to constitute a battery pack, a wiring material is connected to the lid 25. Therefore, the lid 25 functions as an external terminal of the battery 1, and is also referred to as an external terminal or a top cover. In the present embodiment, the positive electrode lead 19 is connected to the current collecting plate 26, and the lid 25 functions as a positive electrode external terminal.

[0034] The current collecting plate 26 is a metal member having a diameter equal to that of the lid 25, and is arranged at a position closer to the electrode body 10 than the lid 25. The current collecting plate 26 has an opening portion 26a in the radially central portion, and is formed in a ring shape. The lid 25 and the current collecting plate 26 are welded together, and the current collecting plate 26 is welded, for example, to the lid 25 at a position at which the distance from the radially central portion is greater than the distance from the outer peripheral edge. The current collecting plate 26 has a ring-shaped protrusion 26b described later formed therein, and the protrusion 26b serves as a welding portion to be welded to the lid 25. Since the positive electrode lead 19 connected to the positive electrode of the electrode body 10 is connected to the current collecting plate 26 as described above, the current collecting plate 26 functions as a positive electrode current collecting plate. Further, it is also possible that the positive electrode current collecting plate is not provided, and the positive electrode lead is directly joined to the lid.

[0035] The gasket 33 is provided so as to surround the outer peripheral portion of the laminate of the lid 25 and the current collecting plate 26. The gasket 33 is a ring-shaped resin or rubber member for preventing the lid 25 and the current collecting plate 26 from coming into contact with the outer can 20, thereby ensuring the electrical insulation of the outer can 20 from the sealing member 24. The gasket 33 covers the upper surface of the lid 25, the side surfaces of the lid 25 and the current collecting plate 26, and the lower surface of the current collecting plate 26 at the outer peripheral portion of the above-described laminate. In addition, the gasket 33 seals the gap between the outer can 20 and the sealing member 24, thereby sealing the inside of the battery 1.

[0036] The gasket 33 is formed to cover most of the lower surface of the current collector plate 26 and is interposed between the current collector plate 26 and the upper insulating plate 34. An opening portion 33a overlapping the opening portion 26a of the current collector plate 26 in the vertical direction is formed in the radial central portion of the gasket 33. In addition, a through-hole 33b can also be formed in the portion of the gasket 33 located below the current collector plate 26. It is assumed that electrolyte solution is present on the upper surface of the gasket 33, but by providing the through-hole 33b, the electrolyte solution can be efficiently returned to the electrode body 10 side. The through-hole 33b is formed, for example, in a plurality of numbers along the circumferential direction of the gasket 33. Also, the gasket 33 has an inner side extending portion 33c extending inward from the outer peripheral portion of the cover 25.

[0037] The upper end of the outer can 20 is bent (flanged) toward the inside to form a bent portion 210. This bent portion 210 can be used as a negative electrode terminal.

[0038] "Structure of the Bent Portion 210"

[0039] Figure 3 is a longitudinal (radial) sectional view of an example of the bent portion 210 in which the upper end of the outer can 20 is bent inward. In this way, the bent portion 210 is formed by bending inward from the portion 211 of the cylindrical portion 21 extending in the axial direction (vertical direction) at the upper end portion. This bent portion 210 is formed by flange bending as described later.

[0040] The bent portion 210 includes a curved portion 212 bent inward, an intermediate portion 213 extending inward from the curved portion 212, and a tip end portion 214 which is the inner side end. Also, the tip end portion 214 is thicker than the thin-walled portion at a position located radially outward of the tip end portion. Also, the tip end portion 214 protrudes toward the closure member in the height direction of the outer can than the thin-walled portion. Also, the curved portion 212 and the intermediate portion 213 can also be thick-walled portions. Also, the intermediate portion 213 has a thin-walled portion 213-2 on the side close to the tip end portion 214, a thick-walled portion 213-1 near the center of the intermediate portion 213, and a thin-walled portion 213-3 on the side close to the curved portion 212.

[0041] In addition, the portion of the tip end of the bent portion 210 on the closure member 24 side extends to a position further inward and forms an annular inclined surface. By this shape, the tip end portion is thick-walled, so that the inner side extending portion 33c of the gasket 33 is easily inhibited (caught).

[0042] Thus, the bent portion 210 has the thick-walled tip portion 214 and the thin-walled portion 213-2 near the inner side thereof. By providing the tip portion 214 with a thick wall, the pressing force on the gasket below the tip portion 214 can be increased. With this increase in the pressing force, the reaction force of the inner side extension 33c of the gasket 33 becomes greater, and the portion of the inner side extension 33c of the gasket 33 near the tip portion 214 can be more reliably sealed. On the other hand, since the thin-walled portion 213-2 is formed on the outer can radial outer side of the tip portion 214, the reaction force of the gasket 33 can be maintained by receiving the material pressed by the tip portion 214. In addition, even if the radial dimension of the bent portion is lengthened, the upper surface (the surface facing outward in the thickness direction of the bent portion) of the bent portion 210 can be made relatively flat. Thus, a sufficient welding area can be ensured when welding the negative electrode terminal or the like to the bent portion 210. In addition, it can be that, on the surface of the bent portion 210 on the radial inner side of the thin-walled portion 213, which faces the gasket 33, there is an inclined surface that faces inward in the radial direction and approaches the gasket, and the thicker the area is on the inner side, the better.

[0043] Here, as shown in the drawing, when the thickness of the portion 211 (a portion other than the bent portion, and a portion located above the groove portion) corresponding to the upper portion of the cylindrical portion 21 is set to W1, the thickness of the curved portion 212 is set to W2, the thickness of the thin-walled portion 213-3 near the front of the intermediate portion 213 is set to W3, the thickness of the thick-walled portion 213-1 of the intermediate portion is set to W4, the thickness of the thin-walled portion 213-2 of the tip side of the intermediate portion 213 is set to W5, and the thickness of the tip portion is set to W6, the bent portion 210 satisfies the condition W5 < W6. In addition, further, the bent portion 210 can satisfy the condition W5 < W4. In addition, the bent portion can satisfy the condition W3 < W4, can satisfy the condition W3 < W2, and can satisfy the condition W1 < W2. In addition, with respect to the sloped inclined surface of the tip portion 214, when the thickness in the inclined direction is set to W7, W6 < W7 is obtained. In addition, W2 > W4 can be obtained.

[0044] When the size of the bending amount of the bent portion 210 is set to A as in Figure 3 When the size of the bending amount of the bent portion 210 is set to A as in

[0045] In addition, in this example, the curved portion 212 is thicker than the surrounding portions. By making the curved portion 212 thick-walled, the mechanical strength of the curved portion 212 can be improved.

[0046] "Edge bending processing"

[0047] Here, the thickness of the bent portion 210 varies in the radial direction. Such thickness can be formed by a flanging device. Since the flanging device performs flanging processing while rotating the body portion by a motor, this is called spinning flanging.

[0048] A motor is fixed to a stand of the flanging device, and a rotation axis of the motor extends in the vertical direction. A body portion is fixed to a lower end of the rotation axis, and the body portion rotates in a horizontal plane.

[0049] Around the lower end of the body portion, a roller is rotatably shaft-supported to a shaft extending in the horizontal direction. Also, the stand is vertically movable, and the flanging device as a whole is vertically movable. In addition, the shaft can extend in a direction other than the horizontal direction.

[0050] The flanging device is positioned above the outer can 20, and the body portion is rotated by rotating the motor. In this state, when the flanging device is moved downward, the roller comes into contact with the upper end of the peripheral portion of the outer can 20. The roller, which functions as a die for flanging, is rotatable, and the roller moves while being passively rotated above the upper end of the outer can 20. Also, by further lowering the flanging device in this state, the upper end of the cylindrical portion 21 is gradually bent inward.

[0051] By gradually lowering the roller, the upper end of the cylindrical portion 21 is bent inward to form the bent portion 210, and the bent portion 210 is pressed against the gasket 33 together with the closure member 24. A notch is formed in the outer peripheral surface of the roller, which is an abutting surface that abuts against the cylindrical portion. The inner surface of the notch is in line contact with the cylindrical portion. The notch has a first surface that opposes the upper end of the cylindrical portion 21 in the height direction of the outer can, a second surface that is apart from the outer peripheral surface of the cylindrical portion in the radial direction, and a curved R portion that is located at a corner portion where one end of the first surface and one end of the second surface are connected. At this time, in the initial stage of flanging where the tip end portion abuts against the notch of the roller, the tip end portion of the bent portion 210 is thickened. When the tip end portion is thickened, with respect to the R portion that abuts against the tip end portion, in a cross section of the roller obtained by cutting along the radial direction, the R portion is represented by a circular arc of a circle having a radius of 3 mm or less. Also, it can be a circular arc of a circle having a radius of 2.5 mm or less, and it can also be a circular arc of a circle having a radius of 2.0 mm or less. In the first surface, with respect to the slope of the line segment that is in line contact with the cylindrical portion, the farther it is from the R portion and the closer it is to the cylindrical portion, the more it can be inclined in parallel with the radial direction of the cylindrical portion or at an angle of less than 15° with respect to the radial direction of the cylindrical portion.

[0052] "Length of the Bent Portion"

[0053] The length of the bent portion 210 is described in FIG. 6. A length from the outer periphery of the outer can 20 to the inner side end of the bent portion 210 is set as A. In addition, as described above, the length of the bent portion 210 is set as B. Figure 1As shown, the outer diameter of the outer can 20 is set to X0, and the inner diameter of the inner side top end of the bent portion 210 is set to X1. Further, the length A of the bent portion is (X0-X1) / 2.

[0054] In the example of (a) of Fig. 6, X1 / X0 = 0.823 (A = 4.09 mm), and in the example of (b) of Fig. 6, X1 / X0 = 0.885 (A = 2.63 mm). In the example of (a) of Fig. 6, compared to the example of (b) of Fig. 6, a higher and sufficient sealing can be performed.

[0055] From the results of experiments in which the A dimension was varied, it was found that by setting X1 / X0 ≤ 0.85, a sufficient sealing can be performed. That is, it was found that by satisfying the condition X1 / X0 ≤ 0.85, a thick wall portion is formed in the middle portion of the bent portion 210, and the material of the gasket 33 can be suppressed from flowing to the inner side, and a sufficient reaction force can be obtained. Further, regardless of whether the thick wall portion is present in the middle portion, by making the A dimension of the bent portion 210 longer than the bent portion having a shorter A dimension, the force that restrains the sealing member is increased.

[0056] Thus, in the present embodiment, the bent portion 210 has a prescribed size with respect to the outer diameter of the outer can 20. Further, a thick wall portion 213-1 is formed in the middle portion of the bent portion 210. Thereby, the bent portion 210 can sufficiently press the gasket 33, and the direction pressure resistance can be increased.

[0057] Further, in the power storage device of the present disclosure, an outer can in which the angle formed by the bent portion and the axis extending in the height direction of the cylindrical portion is acute is described. However, the bent portion of the present disclosure is not limited to this structure, and the bent portion can extend in a manner in which the above-described angle is obtuse.

[0058] In the present embodiment, during the flanging of the outer can, a thick wall portion can be formed in the top end of the bent portion 210. When the gasket is subjected to a load in the compression direction, the material of the gasket flows to the inner side where there is no restraint. Therefore, if the bent portion 210 is flat, the reaction force of the gasket decreases, and the sealing effect is reduced. By forming a thick wall portion in the top end of the bent portion 210, the material of the gasket can be suppressed from flowing to the inner side, the reaction force is increased, and the sealing effect is increased.

[0059] Further, since the top end portion is not bent toward the lower side, the upper surface of the bent portion 210 can be maintained relatively flat. Therefore, a welding region for welding the external terminal can be maintained on the upper surface.

[0060] Explanation of Reference Signs

[0061] 1. battery; 10. electrode body; 11. positive electrode; 12. negative electrode; 13. separator; 19. positive electrode lead; 20. outer can; 21. cylindrical portion; 22. bottom portion; 23. groove portion; 24. sealing member; 25. lid; 26. current collector plate; 26a. opening portion; 26b. protrusion; 33. gasket; 34. upper insulating plate; 210. bent portion; 211. portion; 212. curved portion; 213. intermediate portion; 213-1. thick wall portion; 213-2. thin wall portion; 213-3. thin wall portion; 214. top end portion.

Claims

1. A power storage device, wherein: The power storage device comprises: Electrode body; an outer can having a cylindrical portion and an opening formed at one end of the cylindrical portion, the outer can housing the electrode assembly; and a sealing member that seals the opening, An annular groove portion that is recessed inward is formed on the opening side of the cylindrical portion in the height direction of the outer can. A bent portion folded inward is formed at the periphery of the opening. The peripheral edge of the sealing member is sandwiched from both sides by the groove and the bent portion. In the bent portion, the thickness of the tip portion located radially inward of the outer can is greater than that of at least the thin-walled portion located radially outward of the outer can. The top end portion protrudes toward the sealing member in a height direction of the outer can.

2. The power storage device according to claim 1, wherein The end surface of the tip end portion of the bent portion has an annular slope surface formed by extending the portion thereof closer to the sealing member to a further inner position.

3. The power storage device according to claim 1, wherein In a region of the bent portion radially inward of the thin portion, a surface of the bent portion on the sealing member side in the thickness direction is inclined so that the bent portion becomes thicker as it moves radially inward of the outer can.

4. The power storage device according to claim 1, wherein The bent portion has a thick portion in the middle portion thereof which is thicker than thicknesses on both sides thereof.

5. The power storage device according to any one of claims 1 to 4, wherein The sealing member comprises a cover and a gasket, An electrically insulating gasket is disposed between the cover and the outer body. The cover is electrically insulated from the outer can, The top end portion abuts against a portion of the gasket located between the bent portion and the cover.

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