Electric power storage device

Abstract

A battery (10) comprises: a bottomed cylindrical case (16) that accommodates an electrode body (14); and a second collector plate (70) having a ridge portion (73) that is electrically connected to a negative electrode (12) and a joining portion that is electrically connected to a bottom portion (68) of the case (16), the second collector plate (70) being disposed between the bottom portion (68) and the electrode body (14). The bottom portion (68) is provided with a first exhaust portion (88) that deforms and opens when the interior of the case (16) has reached a pressure greater than or equal to a prescribed pressure. The joining portion is connected to the first exhaust portion (88). In the radial direction, a fragile portion (75) is provided between the ridge portion and the joining portion of the second collector plate (70).

Description

Power storage device

[0001] The present disclosure relates to an electricity storage device.

[0002] Conventional energy storage devices include a cylindrical battery described in, for example, Patent Document 1. In this cylindrical battery, the axial end of the electrode assembly facing the bottom of the case is formed of a negative electrode current collector, and this end is joined to the flat surface of a plate-shaped negative electrode current collector. The negative electrode current collector has a tongue portion that is bent into a U-shape. The tip of the bent tongue portion is joined to the bottom surface of the case. In this way, a wide longitudinal area of ​​the strip-shaped negative electrode current collector is electrically connected to the case via the negative electrode current collector, thereby shortening the current path on the negative electrode side and reducing the electrical resistance of the cylindrical battery.

[0003] This cylindrical battery has a thin-walled section stamped on the bottom of the case. If the battery experiences abnormal heat generation and the internal pressure of the battery continues to rise, the thin-walled section will rupture first, allowing the contents (e.g., high-temperature gas and molten material) to be expelled. This prevents the internal pressure of the battery from becoming excessively high, which could lead to battery explosion, thereby increasing the safety of the cylindrical battery.

[0004] Patent No. 7380825

[0005] A certain level of reliability can be achieved by using the above-described power storage device. However, further improvement in the reliability of the power storage device is required in preparation for cases where the operating conditions and operating environment of the power storage device become more severe. Therefore, an object of the present disclosure is to provide a power storage device with improved reliability.

[0006] In order to solve the above problem, the energy storage device of the present disclosure comprises an electrode body including a first electrode and a second electrode facing each other in a first direction, a tubular portion extending in a second direction substantially perpendicular to the first direction, and a bottom portion closing one end of the tubular portion in the second direction, a case for accommodating the electrode body, and a current collector plate having a first connection portion electrically connected to the first electrode and a second connection portion electrically connected to the bottom portion, the current collector plate being arranged between the bottom portion and the electrode body, the bottom portion being provided with an exhaust portion that deforms and opens when the pressure inside the case reaches a predetermined level or higher, the second connection portion being connected to the exhaust portion, and the current collector plate having a weak portion between the first connection portion and the second connection portion in the first direction.

[0007] According to the present disclosure, the reliability of the power storage device is further improved.

[0008] 9A is an axial cross-sectional view of a cylindrical battery according to a first embodiment of the energy storage device of the present disclosure; FIG. 9B is a perspective view showing a portion of an electrode body and a positive electrode lead; FIG. 9C is a perspective view of a second current collector plate as viewed from an obliquely lower side; FIG. 9D is an enlarged cross-sectional view of the periphery of the center of the second current collector plate and a portion of the bottom of the case in FIG. 1; FIG. 9E is a plan view of the lower surface of the bottom of the case as viewed from the axial direction; FIG. 9F is a perspective view of a second current collector plate of a cylindrical battery according to a second embodiment, corresponding to FIG. 3; FIG. 9G is a plan view of a battery according to a second embodiment, corresponding to FIG. 9H; FIG. 9H is a diagram illustrating the relationship between a first thin-walled portion having a substantially square outer edge shape, an annular fragile portion, and an annular joint portion when the second current collector plate of the second embodiment is viewed in the axial direction from the can bottom side; FIG. 9G is a plan view of a second current collector plate of a first modified example of the second embodiment, corresponding to FIG. 9A; 9(a) of a second current collector plate of a second modified example of the second embodiment. FIG. 9(a) of a second current collector plate of a third modified example of the second embodiment. FIG. 9(a) of a second current collector plate of a fourth ...

[0009] Hereinafter, an embodiment of the power storage device according to the present disclosure will be described in detail with reference to the drawings. Hereinafter, a cylindrical secondary battery using a non-aqueous electrolyte, more specifically a lithium-ion cylindrical secondary battery, will be exemplified as the power storage device of the embodiment, but the power storage device of the present disclosure is not limited to this. The power storage device of the present disclosure is not limited to a battery using a non-aqueous electrolyte, but may also be a battery using an aqueous electrolyte. Furthermore, the power storage device of the present disclosure is not limited to a secondary battery, but may also be a primary battery. Furthermore, the power storage device of the present disclosure may also be a battery other than a cylindrical battery, such as a prismatic battery. Furthermore, the power storage device of the present disclosure may also be a capacitor (condenser) instead of a battery.

[0010] When multiple embodiments and variations are included below, it is assumed from the beginning that new embodiments can be constructed by appropriately combining their characteristic features. In the following embodiments, the same components are denoted by the same reference numerals in the drawings, and redundant explanations are omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. In this specification, the axial (height) side of the sealing body 17 (the opening side of the case 16) is referred to as the upper side, and the axial side of the bottom 68 of the case 16 is referred to as the lower side. However, when using the energy storage device of the present disclosure, the bottom may be the upper side and the sealing body side may be the lower side. The up-down direction may be reversed. Furthermore, in the following description, the radial direction refers to the radial direction of the case 16, which coincides with the radial direction of the cylindrical battery 10. Furthermore, the circumferential direction refers to the circumferential direction of the case 16, which coincides with the circumferential direction of the cylindrical battery 10. In this embodiment, the first direction coincides with the radial direction, and the second direction coincides with the axial direction.

[0011] 1 is an axial cross-sectional view of a cylindrical battery 10 according to a first embodiment of the energy storage device of the present disclosure. As shown in Fig. 1, the cylindrical battery (hereinafter simply referred to as battery) 10 includes a wound electrode assembly 14, a non-aqueous electrolyte (not shown), a bottomed cylindrical case (external can) 16 that houses the electrode assembly 14 and the non-aqueous electrolyte, and a sealing body 17 that closes the opening of the case 16 via a gasket 28.

[0012] The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte. The liquid electrolyte (electrolytic solution) includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted compound (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. The electrolyte salt may include, for example, LiPF ６ Lithium salts such as

[0013] Examples of the solid electrolyte include solid or gel polymer electrolytes and inorganic solid electrolytes. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. Examples of the matrix polymer include a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesin, acrylic resin, and polyether resin. Examples of the inorganic solid electrolyte include materials known in all-solid-state lithium ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0014] FIG. 2 is a perspective view showing a portion of the electrode assembly 14 and the positive electrode lead 20. FIG. 2 shows the positive electrode 11, negative electrode 12, and separator 13 at the end of the wound electrode assembly 14 in a developed state. Also, in FIG. 2, the positive electrode mixture layer 32 and the negative electrode mixture layer 42 are indicated by diagonal hatching. As shown in FIG. 2, the electrode assembly 14 has a long (strip-shaped) positive electrode 11, a long (strip-shaped) negative electrode 12, and two long (strip-shaped) separators 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. In this embodiment, the negative electrode 12 constitutes the first electrode, and the positive electrode 11 constitutes the second electrode. In the energy storage device of the present disclosure, the positive electrode 11 may constitute the first electrode, and the negative electrode 12 may constitute the second electrode. A plurality of positive electrode leads 20 are joined to the positive electrode 11 at intervals from one another in the longitudinal direction of the positive electrode 11 for electrical connection. For example, as shown in FIG. 2 , eight positive electrode leads 20 are joined to the positive electrode 11 in a state where they are lined up at intervals in the longitudinal direction.

[0015] The negative electrode 12 is formed to have dimensions slightly larger than the positive electrode 11 in order to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction (short direction) than the positive electrode 11. Furthermore, two separators 13 are formed to have dimensions slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The separator 13 protrudes upward beyond the positive electrode 11 and the negative electrode 12, and one end of the negative electrode 12 in the width direction protrudes downward beyond the positive electrode 11 and the separator 13 (toward the second current collector plate).

[0016] The negative electrode 12 has an exposed portion 41 at one end in the width direction of the negative electrode current collector 40 where the negative electrode mixture layer 42 is not provided and the surface of the negative electrode current collector 40 is exposed. This exposed portion 41 is formed at the axial lower end of the long negative electrode 12 in the longitudinal direction, from the winding start end to the winding end end. The axial lower end of the electrode assembly 14 is formed by the exposed portion 41. The exposed portion 41 is an example of a first electrode current collector exposed portion. The negative electrode 12 may form the winding start end of the electrode assembly 14. However, the separator 13 may extend beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 may be the winding start end of the electrode assembly 14.

[0017] The positive electrode 11 has a strip-shaped positive electrode current collector 30 and positive electrode mixture layers 32 formed on both sides of the positive electrode current collector 30. The positive electrode current collector 30 can be made of a metal foil, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on its surface. The positive electrode mixture layer 32 contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., onto the positive electrode current collector 30, drying the coating, and then compressing it to form the positive electrode mixture layers 32 on both sides of the positive electrode current collector 30.

[0018] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a preferred lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0019] Examples of the conductive agent contained in the positive electrode mixture layer 32 include carbon black such as ketjen black and acetylene black, and carbon materials such as graphite. Examples of the binder contained in the positive electrode mixture layer 32 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, and polyolefin resin. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.

[0020] The positive electrodes 11 are arranged in a line in the longitudinal direction and have exposed portions (not shown) in the same number as the positive electrode leads 20. These exposed portions are portions of the positive electrode current collector where the positive electrode mixture layer is not applied and the positive electrode current collector is exposed. The positive electrode leads 20 are joined to the exposed portions. By joining multiple positive electrode leads 20 at intervals in the longitudinal direction of the strip-shaped positive electrode current collector 30, preferably at approximately equal intervals in the longitudinal direction, the current path in the longitudinal direction of the positive electrode 11 can be shortened and the internal resistance of the battery 10 can be reduced. The positive electrode leads 20 may be covered with, for example, insulating tape (not shown), thereby suppressing short circuits between the positive electrode 11 and the negative electrode 12. The insulating tape may cover all of the exposed portions.

[0021] The negative electrode 12 has a strip-shaped negative electrode current collector 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode current collector 40. The negative electrode current collector 40 can be made of a metal foil, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on its surface. The negative electrode mixture layer 42 contains a negative electrode active material and a binder. The negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing the negative electrode active material and the binder onto the negative electrode current collector 40, drying the coating, and then compressing it to form the negative electrode mixture layer 42 on both sides of the negative electrode current collector 40.

[0022] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Examples of the carbon material include natural graphite, such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite, such as lump artificial graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer 42 may contain, in addition to the carbon material, a silicon (Si)-containing Si material as the negative electrode active material. Furthermore, the negative electrode active material may also include a metal other than Si that alloys with lithium, an alloy containing such a metal, or a compound containing such a metal.

[0023] The binder contained in the negative electrode mixture layer 42 may be a fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, as in the case of the positive electrode 11. Alternatively, styrene-butadiene rubber (SBR) or a modified product thereof may be used. The negative electrode mixture layer 42 may contain, in addition to SBR or the like, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0024] The separator 13 is long (strip-shaped) and is made of a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Materials used for the separator 13 include polyolefin resins such as polyethylene and polypropylene, and cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13.

[0025] As shown in Figure 1, the battery 10 includes an annular insulating plate 18 on the upper side of the electrode body 14. A positive electrode lead 20 attached to the positive electrode 11 passes through a through-hole in the insulating plate 18 and extends toward the sealing body 17. The sealing body 17 includes a first current collector plate 50 and a terminal cap 27. The first current collector plate 50 is a metal annular plate member and has an insertion hole 50a in its radial center.

[0026] The terminal cap 27 is a metal plate-like member located axially above the sealing body 17. The axially upper end face of the terminal cap 27 is exposed to the outside except for the outer edge. The radially central portion of the exposed portion of the terminal cap 27 is a terminal portion 19 that protrudes outward in the axial direction, and this terminal portion 19 constitutes the positive electrode terminal. The sealing body 17 further has an auxiliary current collector 51. The auxiliary current collector 51 is a metal annular plate member. The auxiliary current collector 51 has a through-hole 51a.

[0027] Each positive electrode lead 20 passes from the positive electrode 11 through an insertion hole 50a in the first current collector 50 and is bent along the upper surface of the first current collector 50. The tip of each positive electrode lead 20 is sandwiched between the upper surface of the first current collector 50 and the lower surface of the auxiliary current collector 51. Each positive electrode lead 20 is joined to the upper surface of the first current collector 50. The first current collector 50 and the auxiliary current collector 51 are also joined, and each positive electrode lead 20 and the auxiliary current collector 51 are also joined.

[0028] These joinings can be achieved, for example, by laser welding the tip end of each positive electrode lead 20 sandwiched between the first current collector plate 50 and the auxiliary current collector plate 51 by irradiating a laser beam onto the surface (back surface) of the auxiliary current collector 51 opposite the opposing surface of the first current collector 50 in the thickness direction. By laser welding the tip end of the positive electrode lead 20 sandwiched between the first current collector plate 50 and the auxiliary current collector 51, the positive electrode lead 20 can be joined to the first current collector 50 more reliably and more easily.

[0029] The sealing body 17 has a laminated portion 36 at its outer periphery, in which a terminal cap 27 and a first current collector plate 50 are laminated. By irradiating the laminated portion 36 with a laser beam from above, the terminal cap 27 and the first current collector plate 50 are laser-welded and electrically connected. The annular upper surface of the first current collector plate 50 has an annular recess 54 radially inward from the laminated portion 36. Because the upper surface of the first current collector plate 50 has the recess 54 recessed downward, a space is provided between the terminal cap 27 and the recess 54 of the first current collector plate 50. Each positive electrode lead 20 is joined to the first current collector plate 50 and the auxiliary current collector plate 51 within the recess 54.

[0030] The power storage device of the present disclosure does not need to use an auxiliary current collector plate. Furthermore, the positive electrode lead 20 may be connected directly to the terminal cap 27 without using the first current collector plate 50. When the first current collector plate 50 is not used, the terminal cap 27 may be the only part of the sealing body 17 that is interposed between the crimping portion 38 (described later) and the groove 35 (described later). Furthermore, when the first current collector plate 50 is used, the first current collector plate 50 may be the only part of the sealing body 17 that is interposed between the crimping portion 38 and the groove 35, and the outer peripheral edge of the terminal cap 27 does not need to be located between the crimping portion 38 and the groove 35.

[0031] As shown in FIG. 1 , the case 16 houses the electrode assembly 14 and the nonaqueous electrolyte and has a crimped portion 38, a groove 35, a cylindrical portion 31, and a bottom 68. The groove 35 is formed, for example, by spinning a portion of the outer surface of the cylindrical portion 31 of the case 16 radially inward to form an annular recess radially inward, and by protruding the corresponding inner surface of the cylindrical portion 31 radially. The sealing body 17 is placed on the groove 35 via a gasket 28 and is fixed to the crimped portion 38 of the case 16 via the gasket 28. The crimped portion 38 is formed by bending the upper end of the case 16 inward toward a peripheral edge 48 of the sealing body 17 when fixing the sealing body 17 to the case 16.

[0032] The space between the case 16 and the sealing body 17 is sealed with an annular gasket 28, thereby sealing the internal space of the battery 10. The gasket 28 is sandwiched between the case 16 and the sealing body 17, and insulates the sealing body 17 from the case 16. The gasket 28 serves as a sealing material to maintain airtightness inside the battery and as an insulating material to insulate the case 16 and the sealing body 17.

[0033] The battery 10 further includes an annular metal plate 80 and an annular insulating plate 81 made of an insulating material. The metal plate 80 is joined to the outer surface of the axial opening side of the case 16, more specifically, to the outer surface of the crimped portion 38. The metal plate 80 extends in a substantially radial direction. The metal plate 80 is electrically connected to a current collector (not shown) outside the battery, which connects multiple batteries (not shown) in series or parallel, using a tongue portion (lead) of the current collector, and the multiple batteries 10 are electrically connected via the current collector. The battery 10 may be used alone.

[0034] The insulating plate 81 is interposed between the metal plate 80 and the sealing body 17 to insulate the metal plate 80 from the sealing body 17. The gasket 28 has a protrusion 28a at its tip end that extends radially from between the crimping portion 38 and the sealing body 17, and the outer peripheral edge 81a on the radially outer side of the insulating plate 81 may be located above the protrusion 28a and in contact with the gasket 28. In this manner, the gasket 28 reliably insulates the metal plate 80 from the sealing body 17. In this embodiment, the insulating plate 81 includes a flange portion 82 and a cylindrical portion 83 that covers the outer peripheral surface of the terminal portion 19 located at the radial center of the sealing body 17. The cylindrical portion 83 is connected to the radially inner end of the flange portion 82. The battery does not necessarily have to include the metal plate and insulating plate described above.

[0035] The battery 10 further includes a metal second current collector plate 70 axially below the electrode body 14. Fig. 3 is a perspective view of the second current collector plate 70 as viewed obliquely from below. As shown in Fig. 3, the second current collector plate 70 includes a central portion 71 and one or more tongue portions (radially extending portions) 72 that are connected to the central portion 71 at one end and extend in the radial direction (first direction).

[0036] In this embodiment, the center portion 71 is provided at the radial center of the second current collector plate 70 and is configured as a flat plate portion that is approximately circular in plan view. The center portion 71 may have any flat plate shape other than a circle, such as a rectangular shape. The number of tongue portions 72 must be at least one. The second current collector plate 70 has multiple tongue portions 72 connected to the center portion 71, and in the example shown in FIG. 3, the second current collector plate 70 has four tongue portions 72. Each of the tongue portions 72 has a plate shape. It is preferable that the multiple tongue portions 72 are arranged at equal intervals in the circumferential direction.

[0037] As shown in FIG. 3 , the tongue portion 72 has a protrusion 73 as an example of a first connection portion on its upper side. The protrusion 73 is provided in the widthwise center of the tongue portion 72 and protrudes in the thickness direction. The protrusion 73 extends radially. A groove 74 extending radially is provided on the underside of the tongue portion 72 at a location that overlaps the protrusion 73 in the thickness direction. The widthwise center of the underside of the plate-shaped tongue portion 72 is pressed upward in the thickness direction by a predetermined radial distance. This press forming forms the protrusion 73 and the groove 74.

[0038] The exposed portion 41 (see FIG. 2 ) is joined to the protrusion portion 73. More specifically, while the exposed portion 41 is pressed against the protrusion portion 73, a laser beam is irradiated toward the bottom of the groove portion 74. This laser beam irradiation joins the exposed portion 41 to the protrusion portion 73 by laser welding over a wide radial range, thereby forming a first connection portion. A circular weakened portion 75 is provided on the underside of the central portion 71, with the center of the central portion 71 at its center. The weakened portion 75 is a circular, thin-walled portion, and is configured by providing a circular groove in part of the central portion 71 by engraving or the like. Note that the thin-walled portion of the weakened portion 75 may also be configured by providing a groove on the upper surface of the central portion 71.

[0039] Fig. 4 is an enlarged cross-sectional view of the periphery of the center portion 71 of the second current collector plate 70 and a portion of the bottom portion 68 of the case 16 in Fig. 1. Fig. 5 is a plan view of the lower surface 68a of the bottom portion 68 of the case 16 as viewed in the axial direction. As shown in Fig. 4, a presser rod (not shown) inserted from above into the hollow portion 14a of the electrode body 14 (see Fig. 1) presses the upper surface of the center portion 71 against the inner surface of the bottom portion 68 of the case 16, and laser light L is irradiated from below the case 16 to join the bottom portion 68 to the second current collector plate 70 by laser welding, thereby forming a second connection portion.

[0040] As a result, the wound negative electrode 12 of the electrode body 14 is electrically connected to the case 16 via the second current collector plate 70. By providing a first connection portion extending radially, the exposed portion 41 of the wound negative electrode 12 can have multiple connection points with the second current collector plate in the range from the winding start end to the winding end in the winding direction at the first connection portion. By joining the wound exposed portion 41 to the upper surface of the second current collector plate 70 over a wide area in the longitudinal direction of the negative electrode, the current collection path of the negative electrode 12 in the longitudinal direction can be shortened, and the electrical resistance of the battery 10 can be reduced. In this embodiment, a metal plate 80 (see FIG. 1 ) electrically connected to the case 16 to which the exposed portion 41 is electrically connected via the second current collector plate 70 constitutes the negative electrode terminal.

[0041] As shown in FIGS. 4 and 5 , in the first embodiment, the center portion 71 is welded to the bottom portion 68 in a circular shape by irradiating the lower surface 68a with laser light L in the axial direction while scanning the lower surface 68a in a circular shape centered at the center of the lower surface 68a. The annular portion 95 (see FIG. 5 ) is the portion of the lower surface 68a that is irradiated with laser light. The annular joint portion 77 (see FIG. 4 ) that is joined (welded) to the bottom portion 68 at the center portion 71 is an example of a second connection portion. The bottom portion 68 has a linear thin-walled portion 87 radially outward from the joint portion 77 on the lower surface 68a. The thin-walled portion 87 is provided in a circular shape centered at the center of the lower surface 68a. Note that the thin-walled portion 87 may be configured by providing a groove in the upper surface of the bottom portion 68.

[0042] The depth of the groove that constitutes the thin-walled portion 87 is, for example, 0.1 mm or more and 0.5 mm or less, and the width of the groove that constitutes the thin-walled portion 87 is, for example, 0.1 mm or more and 1.0 mm or less. The cross-sectional shape of the groove that constitutes the thin-walled portion 87 is not particularly limited, but is, for example, V-shaped. The depth, width, and cross-sectional shape of the groove that constitutes the thin-walled portion 87 may vary in the stretching direction. In this case, the depth and width of the groove that constitutes the thin-walled portion 87 each mean the average values ​​of values ​​measured at multiple points along the stretching direction.

[0043] In the first embodiment, the thin-walled portion 87 is constituted by only a first thin-walled portion extending in an annular shape. The thin-walled portion 87 is provided by, for example, stamping the bottom portion 68. The portion of the bottom portion 68 surrounded by the annular thin-walled portion 87 constitutes a first exhaust portion (exhaust valve) 88. The bottom portion 68 may have an annular step portion 89 (see also FIG. 1 ) centered on the center of the lower surface 68a, radially outward from the thin-walled portion 87 on the lower surface 68a.

[0044] As shown in FIG. 4 , the fragile portion 75 is provided in the radial direction (first direction) between the protrusion portion (first connection portion) 73 and the joint portion (second connection portion) 77 of the second current collector plate 70, and more specifically, between the thin-walled portion 87 and the joint portion 77 in the radial direction. In the second current collector plate 70, the joint portion 77 is disposed more inward than the protrusion portion 73. The joint portion 77 of the second current collector plate 70 is surrounded by the annular fragile portion 75. The joint portion 77 overlaps in the axial direction (second direction) with a first exhaust portion 88 that is surrounded by the annular thin-walled portion 87. When the thin-walled portion 87 breaks, the first exhaust portion 88 is opened.

[0045] In conventional energy storage devices, when the current collector plate is located on the bottom side of the case of the electrode body, it is easy to effectively reduce the electrical resistance of the energy storage device, but there is a risk that if the energy storage device generates abnormal heat and the thin-walled part breaks, the current collector plate will hinder the smooth discharge of the contents to the outside.

[0046] In contrast, the battery 10 according to one embodiment of the present disclosure includes a second current collector 70 that is electrically connected to the negative electrode 12 below the electrode assembly 14, making it easy to electrically connect the negative electrode 12 of the electrode assembly 14 to the second current collector 70 over a wide area. This makes it easy to shorten the current path on the negative electrode side, making it easy to effectively reduce electrical resistance and improve battery performance.

[0047] Furthermore, the second current collecting plate 70 has a fragile portion 75 between the radial protrusion 73 and the joint portion 77, and the joint portion 77 is connected to a first vent portion 88 at the bottom 68 of the case 16. Therefore, if the battery 10 generates abnormal heat and the pressure inside the case 16 exceeds a predetermined level, causing the first vent portion 88 to vent, the fragile portion 75 may break or the second current collecting plate 70 may be easily displaced starting from the fragile portion 75, creating a passage due to the break in the second current collecting plate 70. Therefore, when the first vent portion 88 vents, the contents can be smoothly discharged to the outside through the passage, improving the reliability of the battery 10.

[0048] Furthermore, the thin-walled portion 87 has an annular portion, the first exhaust portion 88 is formed by a portion of the bottom portion 68 that is surrounded by the annular thin-walled portion 87, and the joint portion 77 is connected to the first exhaust portion 88. Therefore, it is easier to open the first exhaust portion 88 more smoothly and reliably, and the opening area of ​​the first exhaust portion 88 is also easier to increase.

[0049] Furthermore, since the fragile portion 75 is disposed between the thin-walled portion 87 and the joint portion 77 in the radial direction, the first exhaust portion 88 can be effectively separated from the bottom portion 68. Furthermore, since the joint portion 77 constituting the second connection portion in the second current collector plate 70 is located more inward than the protrusion portion 73 constituting the first connection portion, it is easy to effectively shorten the current path and to effectively reduce electrical resistance. Furthermore, since the fragile portion 75 in the second current collector plate 70 extends in an annular shape and the joint portion 77 is surrounded by the fragile portion 75, it is possible to reliably interrupt current on the negative electrode side when the first exhaust portion 88 is evacuated.

[0050] Second Embodiment Fig. 6 is a perspective view corresponding to Fig. 3 of a second current collector plate 170 of a cylindrical battery (hereinafter referred to as battery) according to a second embodiment, and Fig. 7 is a plan view corresponding to Fig. 5 of a battery 110 according to the second embodiment. Note that in the second embodiment, explanations of the same effects and modifications as in the first embodiment will be omitted. As shown in Fig. 6, the second current collector plate 170 has a central portion 171 provided at the radial center of the second current collector plate 70 and configured as a flat plate portion having a substantially square shape in a plan view. A circular fragile portion 175 centered at the center of the central portion 171 is provided on the underside of the central portion 171. The fragile portion 175 is a circular thin-walled portion configured by providing a circular groove in part of the central portion 171 by engraving or the like.

[0051] The second current collecting plate 170 has a plurality of tongue portions 172 that are connected to the center portion 171 at one end and extend in the radial direction (first direction). The tongue portions 172 have a pair of wing portions 192 that protrude radially outward on both sides in the circumferential direction. By abutting this pair of wing portions 192 against the inner surface (not shown) of the bottom portion 168 (see FIG. 7 ) of the case 116, the second current collecting plate 170 can be stably and reliably joined to the inner surface of the bottom portion 168. In particular, the portion of the exposed portion 41 that faces the tongue portions is tilted in the radial direction to form an upwardly recessed depression, and when the protrusion is accommodated in this depression and abutted against it for joining, the wing portions 192 make it easy to align the position of the second current collecting plate on the exposed portion 41.

[0052] As shown in FIG. 7 , the bottom portion 168 has a linear thin-walled portion 187, which includes a linear first thin-walled portion 187a and a linear second thin-walled portion 187b. The first thin-walled portion 187a and the second thin-walled portion 187b are each provided by forming a groove on the lower surface 168a of the bottom portion 168 by engraving or the like. The first thin-walled portion 187a extends in an annular shape and has a polygonal outer edge shape in a plan view when viewed from the axial direction; in this embodiment, it has a rectangular outer edge shape. The area surrounded by the first thin-walled portion 187a constitutes a first exhaust portion 188.

[0053] The annular first thin-walled portion 187a is preferably configured with the outer edge shape of a regular polygon. The second thin-walled portion 187b is connected to the first thin-walled portion 187a. The second thin-walled portion 187b extends radially outward from the first thin-walled portion 187a. The area surrounded by one of the multiple second thin-walled portions 187b and the first thin-walled portion 187a connected to this second thin-walled portion 187b constitutes the second exhaust portion 197. The second exhaust portion 197 is configured, for example, as the area indicated by the hatched area in FIG. 5. Note that the area of ​​the second exhaust portion 197 may be smaller or larger than the hatched area in FIG. 7.

[0054] More specifically, the second thin-walled portion 187b is formed by grooves extending outward from each of the vertices of a polygon. This improves safety while suppressing deformation of the bottom portion 168 in the battery 110. The second thin-walled portion 187b may also be connected to the portions between the vertices of the first thin-walled portion 187a. In the example shown in FIG. 7 , the second thin-walled portion 187b extends outward from each vertex of the rectangular groove that constitutes the first thin-walled portion 187a. The groove shape connecting the vertices in the annular portion that constitutes the first thin-walled portion 187a does not have to be the straight line shown in FIG. 7 but may be a curve, and in this case, the curve preferably has an outward convex shape.

[0055] The center of the outer edge of the polygon formed by the first thin-walled portion 187a substantially overlaps with the center C of the bottom portion 168. The depth of the groove forming the first thin-walled portion 187a is, for example, 0.1 mm to 0.5 mm, and the width of the groove forming the first thin-walled portion 187a is, for example, 0.1 mm to 1.0 mm. The cross-sectional shape of the groove forming the first thin-walled portion 187a is not particularly limited, but may be, for example, a V-shape. The depth, width, and cross-sectional shape of the groove forming the first thin-walled portion 187a may vary in the extension direction. In this case, the depth and width of the groove forming the first thin-walled portion 187a each represent the average values ​​measured at multiple points along the extension direction.

[0056] The depth of the groove constituting the second thin-walled portion 187b is, for example, 0.1 mm to 0.5 mm, and the width of the groove constituting the second thin-walled portion 187b is, for example, 0.1 mm to 1.0 mm. The cross-sectional shape of the groove constituting the second thin-walled portion 187b is not particularly limited, but may be, for example, a V-shape. The depth, width, and cross-sectional shape of the groove constituting the second thin-walled portion 187b may vary in the extension direction. In this case, the depth and width of the groove constituting the second thin-walled portion 187b each represent the average values ​​measured at multiple points along the extension direction. The depth, width, and cross-sectional shape of the groove constituting the first thin-walled portion 187a and the groove constituting the second thin-walled portion 187b may all be the same, or at least one of the depth, width, and cross-sectional shape may be different.

[0057] The multiple second thin-walled portions 187b extend in the same rotational direction relative to the center C of the bottom portion 168. The rotational direction may be either clockwise or counterclockwise. Ends 179 of the multiple second thin-walled portions 187b are located, for example, on approximately the same circumference. The end 179 is the end of the second thin-walled portion 187b that is not in contact with the first thin-walled portion 187a. It is preferable that the center of the circle on which the multiple end points 179 are located approximately overlaps with the center C of the bottom portion 168.

[0058] When the battery 110 generates abnormal heat and the internal battery pressure continues to rise, at least some of the first thin-walled portion 187a and the plurality of second thin-walled portions 187b are preferentially broken, and the contents, i.e., high-temperature gas and molten material, are discharged to the outside. This prevents the internal battery pressure from becoming excessively high, which may cause the battery to explode, and improves the safety of the battery 110.

[0059] In this embodiment, the battery is designed so that at least a portion of the first thin-walled portion 187a and at least a portion of each of the plurality of second thin-walled portions 187b break when the battery internal pressure continues to rise. This causes not only at least a portion of the first thin-walled portion 187a but also at least a portion of the second thin-walled portion 187b to break, venting the second exhaust portion 197, making it easier to discharge the contents to the outside. Furthermore, a large opening for discharging high-temperature gas is formed in the bottom portion 168, improving the safety of the battery 110. Each second thin-walled portion 187b preferably contacts only one vertex of the polygon formed by the first thin-walled portions 187a. This prevents the first exhaust portion 188, surrounded by the first thin-walled portions 187a, from scattering from the bottom portion 168 when the second thin-walled portion 187b breaks, making it easier to secure the first exhaust portion 188 to the case.

[0060] 8 is a diagram illustrating the relationship between the first thin-walled portion 187a, which has a substantially square outer edge shape, the annular fragile portion 175, and the annular joint portion 177, when viewed in the axial direction from the can bottom side. As shown in Fig. 8, the centers of the first thin-walled portion 187a, the fragile portion 175, and the joint portion 177 are all substantially aligned. Furthermore, the fragile portion 175 is located radially outward from the joint portion 177, and the first thin-walled portion 187a is located radially outward from the fragile portion 175.

[0061] Fig. 9(a) is a plan view of the second current collector 170 as viewed in the axial direction from the bottom side, and Fig. 9(b) is a diagram illustrating the relative position of the thin-walled portion 187 with respect to the second current collector 170 as viewed in the axial direction from the can bottom side. Note that in Fig. 9(b), all lines are drawn in solid lines to clarify the relative positional relationship.

[0062] 9(b), in this embodiment, first thin-walled portion 187a having a substantially square outer edge shape in the plan view in Fig. 9(b) is configured to have region 187c where it does not overlap with second current collector plate 170, thereby enabling efficient exhaust of air from inside the can to the outside. Note that in Fig. 9(b), non-overlapping region 187c that constitutes part of first thin-walled portion 187a is depicted darker.

[0063] FIG. 10 is a plan view of a second current collector 270 of the first modified example, corresponding to FIG. 9( a). The second current collector 270 differs from the second current collector 170 in that it has a pair of notches 206 (weak portions) recessed inward on both sides in the width direction on the outer edge of the tongue portion 272 between the first and second connection portions. The formation of the recesses 206 reduces the strength and rigidity of the center portion 271 of the second current collector 270. This allows the center portion 271 to break or deform more smoothly and easily in the event of abnormal battery heat generation. These notches are deeper and narrower than the recesses formed on the edges of the other tongue portions. Note that the weak portion in the center may be omitted.

[0064] FIG. 11 is a plan view corresponding to FIG. 9( a) of a second current collector plate 370 of the second modified example. The second current collector plate 370 differs from the second current collector plate 170 in that the center portion 371 has a slot 306 at a position where the center portion 371 radially overlaps the tongue portion 372. The formation of the slot 306 (weak portion) reduces the strength and rigidity of the center portion 371 of the second current collector plate 370. This allows the center portion 371 to break or deform more smoothly and easily in the event of abnormal battery heat generation. In the plan view of FIG. 11 , it is preferable that at least a portion of the slot 306 is located on the circumference where the weak portion 375 is located. Note that the weak portion 375 may be omitted.

[0065] FIG. 12 is a plan view of a second current collector plate 470 of a third modified example, corresponding to FIG. 9( a). The second current collector plate 470 differs from the second current collector plate 170 in that a central portion 471 has a plurality of through-holes 406 (weak portions) arranged to surround the joint. The formation of the through-holes 406 reduces the strength and rigidity of the central portion 471 of the second current collector plate 470. This allows the central portion 471 to break or deform more smoothly and easily in the event of abnormal battery heat generation. In the plan view of FIG. 12, it is preferable that at least a portion of the through-holes 406 is located on the circumference where the weak portions 475 are located. Note that the weak portions 475 may be omitted.

[0066] FIG. 13 is a plan view of a second current collector plate 570 of a fourth modification, corresponding to FIG. 9( a). This second current collector plate 570 differs from the second current collector plate 170 in that the center portion 571 has multiple fused portions 506 arranged around the joint. The fused portions 506 may be welded portions joining the center portion 571 to the tongue portion 572. The formation of the fused portions 506 reduces the strength and rigidity of the center portion 571 of the second current collector plate 570. Therefore, the center portion 571 can be more smoothly and easily fractured in the event of abnormal battery heat generation. In the plan view of FIG. 13 , at least a portion of the fused portion 506 (weak portion) whose crystal structure has changed from the rest of the second current collector plate 570 (e.g., grain boundary growth) is preferably located on the circumference where the weak portion 575 is located. The weak portion 575 may be omitted.

[0067] (Modifications) The present disclosure is not limited to the above-described embodiment and its modifications. Various improvements and modifications are possible within the scope of the claims of the present application and their equivalents. FIG. 14 is a diagram illustrating variations of the weak portion in the second current collector plate, showing a cross-sectional view in the thickness direction of the weak portion periphery of the second current collector plate. As in the weak portion 675 shown in FIG. 14( a), the groove 675 a formed in the weak portion 675 may open upward. As in the weak portion 775 shown in FIG. 14( b), the groove 775 a formed in the weak portion 775 may open downward. Furthermore, as in the weak portion 875 shown in FIG. 14( c), the weak portion 875 may not have a uniform thickness.

[0068] 15A and 15B are diagrams illustrating variations in the planar shape of the weak portion when the second current collector plate is viewed in the axial direction. Like the weak portion 975 shown in FIG. 15A, the weak portion 975 may have a circular planar shape. Like the weak portion 1075 and the weak portion 1175 shown in FIGS. 15B and 15C, the weak portion 1075 and the weak portion 1175 may have a square planar shape. Or, like the weak portion 1275 shown in FIG. 15D, the weak portion 1275 may have a regular hexagonal planar shape. Alternatively, although not shown, the weak portion may have a C-shaped planar shape.

[0069] 16A and 16B are diagrams illustrating variations in the planar shape of the joint when the second current collector plate is viewed in the axial direction. The joint 1377 shown in Fig. 16A may have a circular planar shape, and the joint 1477 shown in Fig. 16B may have a linear planar shape.

[0070] In the above description, the positive electrode 11 is electrically connected to the sealing body 17 via one or more positive electrode leads 20. However, the upper end of the electrode body may be configured as an exposed portion of the positive electrode current collector, and the exposed portion of the positive electrode current collector may be joined to the positive electrode current collector plate by welding or the like. The positive electrode current collector plate may then be electrically connected to a conductive member that includes the upper surface of the sealing body and has conductivity, thereby electrically connecting the positive electrode to the upper surface of the sealing body.

[0071] In the above description, the case has been described in which the case 16 is electrically connected to the negative electrode 12, and the second current collector 70 is disposed on the bottom 68 side of the case 16 in the electrode assembly 14. However, the case may be electrically connected to the positive electrode, and the positive current collector may be disposed on the bottom side of the case in the electrode assembly.

[0072] The case where the sealing body 17 does not have a rupture plate has been described. However, the sealing body may also have two rupture plates (a lower valve body and an upper valve body) and a convex terminal cap that covers the rupture plates. Alternatively, the sealing body may be composed of only a rupture plate. Alternatively, the sealing body may have a structure in which an internal terminal plate, an insulating plate, and a rupture plate are stacked in this order from the electrode body side.

[0073] The case where the tongue portion 72 is formed so as to be convex upward and has a protrusion 73 on the upper side has been described, and the case where a groove 74 extending in the radial direction is provided on the underside of the tongue portion 72 at a location overlapping the protrusion 73 in the thickness direction has been described. However, the tongue portion 72 does not have to be formed so as to be convex upward, and does not have to have a protrusion on the upper side. Furthermore, the thin-walled portion provided on the bottom of the case may be configured by providing a groove on the bottom that is C-shaped in plan view, or may have a C-shape in plan view. Furthermore, the electrode body may be a stacked electrode body, and the stacking direction may coincide with the first direction.

[0074] The power storage device of the present disclosure may also have the following configurations: Configuration 1: A power storage device comprising: an electrode assembly including a first electrode and a second electrode facing each other in a first direction, a tubular portion extending in a second direction substantially perpendicular to the first direction, and a bottom portion closing one end of the tubular portion in the second direction, the case accommodating the electrode assembly; and a current collector plate having a first connection portion electrically connecting to the first electrode and a second connection portion electrically connecting to the bottom portion, the current collector plate being disposed between the bottom portion and the electrode assembly, the bottom portion being provided with an exhaust portion that deforms and opens when a pressure inside the case reaches a predetermined level or higher, the second connection portion being connected to the exhaust portion, and the current collector plate having a fragile portion between the first connection portion and the second connection portion in the first direction. Configuration 2: The power storage device according to Configuration 1, wherein at least one linear thin-walled portion is formed on a surface of the exhaust portion, and the thin-walled portion breaks when the exhaust portion is opened. Configuration 3: The energy storage device of Configuration 2, wherein the thin-walled portion includes a first thin-walled portion extending in an annular shape, the exhaust portion includes a first exhaust portion provided in a region surrounded by the first thin-walled portion, and the second connection portion overlaps the exhaust portion in the second direction. Configuration 4: The energy storage device of Configuration 3, wherein the fragile portion is disposed between the first thin-walled portion and the second connection portion with respect to the first direction. Configuration 5: The energy storage device of Configuration 3 or 4, wherein the thin-walled portion further includes one or more linear second thin-walled portions having one end connected to the first thin-walled portion and the other end provided at a position farther from the exhaust portion than the one end. Configuration 6: The energy storage device of Configuration 5, wherein the exhaust portion has a second exhaust portion provided in a region surrounded by a predetermined second thin-walled portion of the one or more second thin-walled portions and a portion of the first thin-walled portion connected to the predetermined second thin-walled portion. Configuration 7: The electricity storage device according to any one of configurations 1 to 6, wherein the second connection portion is disposed more inward than the first connection portion on the current collecting plate.Configuration 8: The electricity storage device according to any one of configurations 1 to 7, wherein the current collecting plate has a center portion and one or more tongue portions connected to the center portion at one end and extending in the first direction, the first connection portion being provided on the tongue portion, and the weak portion being provided on the center portion.Configuration 9: The electricity storage device according to any one of configurations 1 to 8, wherein the weak portion on the current collecting plate extends in an annular shape, and the second connection portion is surrounded by the weak portion.Configuration 10: The electricity storage device according to any one of configurations 1 to 9, wherein the first electrode includes a strip-shaped first electrode current collector and a first electrode mixture layer disposed on the surface of the first electrode current collector, the first electrode having a first electrode current collector exposed portion at one end in the second direction where the first electrode current collector is exposed, the first electrode current collector exposed portion protruding from the second electrode toward the one end in the second direction and joined to the current collector plate. Configuration 11: The electricity storage device according to any one of configurations 1 to 10, wherein the fragile portion includes a notch provided in the outer peripheral edge of the current collector plate. Configuration 12: The electricity storage device according to any one of configurations 1 to 11, wherein the fragile portion includes an elongated hole. Configuration 13: The electricity storage device according to any one of configurations 1 to 12, wherein the fragile portion includes a plurality of through holes spaced apart from one another. Configuration 14: The electricity storage device according to any one of configurations 1 to 13, wherein the fragile portion includes a region having a crystal structure different from that of the remainder of the current collector plate.

[0075] REFERENCE SIGNS LIST 10,110 battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 14a hollow portion, 16,116 case, 17 sealing body, 18 insulating plate, 19 terminal portion, 20 positive electrode lead, 27 terminal cap, 28 gasket, 28a gasket protrusion, 30 positive electrode current collector, 31 cylindrical portion, 32 positive electrode mixture layer, 35 groove portion, 36 stacked portion, 38 crimped portion, 40 negative electrode current collector, 41 exposed portion, 42 negative electrode mixture layer, 48 sealing body peripheral portion, 50 first current collector, 50a insertion hole, 51 auxiliary current collector, 51a through hole, 54 recessed portion 68,168 Bottom portion, 68a,168a Lower surface, 70,170,270,370,470,570 Second current collecting plate, 71,171,271,371,471,571 Center portion, 72,172,272,372,572 Tongue portion, 73 Protrusion portion, 74 Groove portion, 75,175,375,475,575,675,775,875,975,1075,1175,1275 Weak portion, 77,177,1377,1477 Joint portion, 80 Metal plate, 81 Insulating plate, 81a Outer peripheral edge portion of insulating plate, 82 Flange portion, 83 Cylindrical portion, 87,187 Thin portion, 88, 188 First exhaust portion, 89 Step portion, 95 Annular portion, 179 End portion, 187a First thin-walled portion, 187b Second thin-walled portion, 192 Wing portion, 197 Second exhaust portion, 206 Recess, 306 Slot, 406 Through hole, 506 Melted portion, 675a, 775a Groove, C Center of bottom, L Laser light.

Claims

1. An electricity storage device comprising: an electrode body including a first electrode and a second electrode facing each other in a first direction; a case containing the electrode body, the case having a tubular portion extending in a second direction substantially perpendicular to the first direction and a bottom portion closing one end of the tubular portion in the second direction; and a current collector plate having a first connection portion electrically connecting to the first electrode and a second connection portion electrically connecting to the bottom portion, the current collector plate being disposed between the bottom portion and the electrode body; wherein the bottom portion is provided with an exhaust portion that deforms and opens when the pressure inside the case reaches or exceeds a predetermined level, the second connection portion being connected to the exhaust portion; and wherein the current collector plate has a weak portion between the first connection portion and the second connection portion in the first direction.

2. The electricity storage device according to claim 1, wherein at least one linear thin-walled portion is formed on a surface of the exhaust portion, and the thin-walled portion breaks when the exhaust portion is opened.

3. The energy storage device according to claim 2, wherein the thin-walled portion includes a first thin-walled portion extending in an annular shape, the exhaust portion includes a first exhaust portion provided in an area surrounded by the first thin-walled portion, and the second connection portion overlaps the exhaust portion in the second direction.

4. The energy storage device according to claim 3, wherein the weak portion is disposed between the first thin portion and the second connection portion in the first direction.

5. The energy storage device according to claim 3 or 4, wherein the thin-walled portion further includes one or more linear second thin-walled portions having one end connected to the first thin-walled portion and the other end provided at a position farther from the exhaust portion than the one end.

6. The energy storage device according to claim 5, wherein the exhaust section has a second exhaust section provided in an area surrounded by a predetermined second thin-walled section among the one or more second thin-walled sections and a portion of the first thin-walled section connected to the predetermined second thin-walled section.

7. The electricity storage device according to claim 1, wherein the second connection portion is disposed on the current collecting plate more inward than the first connection portion.

8. The electricity storage device according to claim 1, wherein the current collecting plate has a center portion and one or more tongue portions connected to the center portion at one end and extending in the first direction, the first connecting portion being provided on the tongue portion, and the fragile portion being provided in the center portion.

9. The electricity storage device according to claim 1, wherein the weak portion of the current collector plate extends in an annular shape, and the second connection portion is surrounded by the weak portion.

10. The electricity storage device according to claim 1, wherein the first electrode comprises a strip-shaped first electrode current collector and a first electrode mixture layer disposed on the surface of the first electrode current collector, the first electrode has a first electrode current collector exposed portion at one end in the second direction where the first electrode current collector is exposed, and the first electrode current collector exposed portion protrudes from the second electrode at one end side in the second direction and is joined to the current collector plate.

11. The electricity storage device according to claim 1, wherein the weakened portion includes a notch provided on the outer periphery of the current collector plate.

12. The electricity storage device according to claim 1, wherein the weakened portion includes a slot.

13. The electricity storage device according to claim 1, wherein the weakened portion includes a plurality of through holes spaced apart from one another.

14. The electricity storage device according to claim 1, wherein the weakened portion includes a region having a different crystal structure from the remainder of the current collector plate.

Images