Power storage device

Abstract

A power storage device comprises: a bottomed tubular case (16); an electrode element (14) which is disposed in the case (16) and has a first electrode, a second electrode having a polarity different from that of the first electrode, and a separator (13), and in which the first electrode and the second electrode are wound with the separator (13) interposed therebetween; and a current collector plate (19) which is fixed to the bottom (68) of the case (16) and is fixed to the axial end of the electrode element (14). The current collector plate (19) has: a body (60) fixed to an end portion of the electrode element (14); a covering part (90) protruding from an outer circumferential portion (62) of the body (60) in a direction toward the center of the body (60); and a bent part (91) provided between the outer circumferential portion (62) of the body (60) and the covering part (90). The case (16) and the current collector plate (19) are welded. The body (60), the covering part (90), and the bent part (91) are the same member. The current collector plate (19) is folded at the bent part (91) as the turning point.

Description

Power storage device

[0001] The present disclosure relates to a power storage device, for example, a cylindrical battery, a prismatic battery, or a capacitor.

[0002] Power storage devices typified by cylindrical lithium-ion batteries are adopted in a wide range of fields such as electric vehicles and power storage systems. In the future, with the expansion of applications, various functions will be required, and as the batteries become larger, higher output, and higher capacity, the provision of safer batteries is demanded.

[0003] Generally, when electrically connecting the members constituting a battery, fixing is performed by laser welding or the like. In the welding operation, so-called welding spatters occur where the object melts and scatters in a droplet shape. If the welding spatters are cooled and adhere to the inside of the battery as foreign matter, it can cause voltage defects due to short circuits.

[0004] Patent Document 1 describes that by passing a cut core body exposed portion through a through hole provided in a current collector plate and folding the core body exposed portion, a uniform contact area in the welding region can be ensured, and a reduction in welding spatters when welding the current collector plate and the core body exposed portion can be achieved.

[0005] Japanese Patent Translation No. 2023-549100

[0006] In recent years, with the increase in the capacity of batteries, the weight of the electrode body has also increased, and it is required to weld the current collector plate and the battery case more firmly so as to withstand vibration and impact. However, in Patent Document 1, measures to suppress welding spatters generated when welding the case and the current collector plate are not examined. Also, welding of the case and the current collector plate generally requires irradiating a laser from the thick case side toward the inside of the battery, so it is inevitable that welding spatters will occur inside the battery.

[0007] An energy storage device according to one aspect of the present disclosure comprises a bottomed cylindrical case, an electrode body disposed inside the case and having a first electrode, a second electrode having a different polarity from the first electrode, and a separator, with the first electrode and the second electrode wound around the separator, and a current collector plate fixed to the bottom of the case and fixed to the axial end of the electrode body, wherein the current collector plate has a main body fixed to the end of the electrode body, a covering portion protruding from the outer periphery of the main body toward the center of the main body, and a bent portion provided between the outer periphery of the main body and the covering portion, the case and the current collector plate are welded together, the main body, the covering portion and the bent portion are the same material, and the current collector plate is bent starting from the bent portion.

[0008] Another embodiment of the present disclosure is an energy storage device comprising a bottomed cylindrical case, an electrode body disposed inside the case and having a first electrode, a second electrode having a different polarity from the first electrode, and a separator, with the first electrode and the second electrode wound around the separator, and a current collector plate fixed to the bottom of the case and fixed to the axial end of the electrode body, wherein the current collector plate has a main body fixed to the end of the electrode body, a support member disposed between the main body and the electrode body, and a connecting portion to which the main body and the support member are fixed, the case and the current collector plate are welded together, the main body and the support member are separate members, and the axial thickness of the support member decreases from the inner circumferential surface of the case toward the radially inward side.

[0009] According to the energy storage device described herein, by bending the current collector plate, it becomes more difficult for the laser beam to penetrate the current collector plate, thereby suppressing the decrease in the reliability of the energy storage device due to the generation of welding spatter.

[0010] This is an axial cross-sectional view of a cylindrical battery, which is an example of an embodiment. This is a perspective view showing part of the electrode body and positive electrode lead. This is an enlarged cross-sectional view of the negative electrode current collector plate and the bottom of the case in Figure 1. This is an enlarged cross-sectional view of the covering portion of the negative electrode current collector plate and the bottom of the case, which is an example of an embodiment. This is a perspective view of the negative electrode current collector plate viewed from diagonally above. This is an enlarged cross-sectional view of the negative electrode current collector plate and the bottom of the case, which is another example of an embodiment. This is an enlarged cross-sectional view of the negative electrode current collector plate and the bottom of the case, which is yet another example of an embodiment. This is an enlarged cross-sectional view of the negative electrode current collector plate and the bottom of the case, which is yet another example of an embodiment. This is an enlarged cross-sectional view of the negative electrode current collector plate and the bottom of the case, which is yet another example of an embodiment. This is a plan view and a cross-sectional view of the negative electrode current collector plate viewed from above, which is yet another example of an embodiment.

[0011] Hereinafter, an example of an embodiment of the energy storage device according to this disclosure will be described in detail with reference to the drawings. Note that configurations obtained by selectively combining the various components of the multiple embodiments and modified examples described below are included within the scope of this disclosure.

[0012] In the following, a cylindrical secondary battery using a non-aqueous electrolyte, more specifically a lithium-ion cylindrical secondary battery, is given as an example of an embodiment, but the energy storage device of this disclosure is not limited to this. The energy storage device of this disclosure is not limited to a battery using a non-aqueous electrolyte, but may also be a battery using an aqueous electrolyte. Furthermore, the energy storage device of this disclosure is not limited to a secondary battery, but may also be a primary battery. Furthermore, the energy storage device of this disclosure may be a battery other than a cylindrical battery, for example, a prismatic battery, etc. Furthermore, the energy storage device of this disclosure is not limited to a battery, but may also be a capacitor.

[0013] In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. In this specification, the axial (height) side of the sealing body 17 (the opening side of the case) 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. Also, 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. Similarly, the circumferential direction refers to the circumferential direction of the case 16, which coincides with the circumferential direction of the cylindrical battery 10. Furthermore, among the components described below, components not described in the independent claim representing the highest-level concept are optional components and not essential components.

[0014] The components of a cylindrical battery 10, which is an example of an embodiment, will be described using Figures 1 and 2. Figure 1 is an axial cross-sectional view of a cylindrical battery, which is an example of an embodiment. Figure 2 is a perspective view showing part of the electrode body and positive electrode lead. As shown in Figure 1, the cylindrical battery (hereinafter simply referred to as "battery") 10 comprises an electrode body 14, a non-aqueous electrolyte (not shown), a bottomed cylindrical case 16 that houses the electrode body 14 and the non-aqueous electrolyte, and a sealing body 17 that seals the opening 29 of the case 16 via a gasket 28.

[0015] As shown in Figure 2, the electrode body 14 is a wound electrode body having a long positive electrode 11, a long negative electrode 12, and two long separators 13, with the positive electrode 11 and negative electrode 12 wound around the separators 13, and is placed inside the case 16 (see Figure 1). In Figure 2, the positive electrode mixture layer 32 and the negative electrode mixture layer 42 are shown with diagonal hatching.

[0016] In this embodiment, the negative electrode 12 constitutes the first electrode, and the positive electrode 11 constitutes the second electrode. One or more positive electrode leads 20 are joined to the positive electrode 11, preferably six or more positive electrode leads 20 are joined, and in this embodiment, eight positive electrode leads 20 are joined to the positive electrode 11 with spacing between them in the longitudinal direction of the positive electrode.

[0017] The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. The negative electrode 12 is formed to be longer than the positive electrode 11 in the winding direction and axial direction. The two separators 13 are formed to be slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The separators 13 protrude above the positive electrode 11 and the negative electrode 12, and the negative electrode 12 protrudes below the positive electrode 11 and the separators 13.

[0018] In this embodiment, the negative electrode core body exposed portion 41 is provided at the lower end in the negative electrode width direction, from the winding start end to the winding end in the negative electrode longitudinal direction, where the negative electrode mixture layer 42 is not disposed on the negative electrode core body 40. The axial lower end of the electrode body 14 is formed by the negative electrode core body exposed portion 41. The negative electrode core body exposed portion 41 is, for example, a foil portion that is part of the first electrode. The negative electrode 12 may constitute the winding start end of the electrode body 14. However, generally, the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode body 14. The negative electrode core body exposed portion 41 protrudes downward from the positive electrode 11 and the separator 13.

[0019] Non-aqueous electrolytes are ionic conductive (e.g., lithium ion conductive). Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes. Liquid electrolytes contain a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. Non-aqueous solvents may contain halogen-substituted compounds (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms in these solvents are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0020] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0021] The positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 32 formed on both sides of the positive electrode core 30. The positive electrode core 30 can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film on which the metal is arranged on the 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 manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core 30, drying the coating film, and then compressing it to form the positive electrode mixture layer 32 on both sides of the positive electrode core 30.

[0022] 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. A preferred example of a lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0023] Examples of conductive agents included in the positive electrode mixture layer 32 include carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. Examples of binders included 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 carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0024] The positive electrode 11 has one or more exposed positive electrode core portions (not shown) where the positive electrode core is exposed. In this embodiment, it has eight exposed positive electrode core portions that are spaced apart in the longitudinal direction of the positive electrode. One positive electrode lead 20 is joined to each exposed positive electrode core portion by ultrasonic welding or the like. Since the reduction in electrical resistance is increased by effectively shortening the positive electrode side current path, it is preferable that the center positions of the eight positive electrode leads 20 in the longitudinal direction of the positive electrode are arranged at approximately equal intervals in the longitudinal direction of the positive electrode.

[0025] The negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode core 40. In this embodiment, the negative electrode core 40 is made of a metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy. A film with the metal arranged on its surface may also be used as the negative electrode core 40. The negative electrode mixture layer 42 contains a negative electrode active material and a binder. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 42 on both sides of the negative electrode core 40.

[0026] Generally, carbon materials that reversibly intercalate and release lithium ions are used as the negative electrode active material. Preferred carbon materials are graphites such as natural graphite such as flake graphite, lump graphite, and clay graphite, and artificial graphite such as lump graphite and graphitized mesophase carbon microbeads. Since it is easy to increase the capacity, it is preferable that the negative electrode active material of the negative electrode mixture layer 42 contains a Si material containing silicon (Si) particles, and it is preferable that the mass ratio of Si elements in the negative electrode mixture layer 42 is 5.0% by mass or more. It is also preferable that 3.0% by mass or more of the negative electrode mixture layer 42 is composed of silicon oxide. Other metals that alloy with lithium besides Si, alloys containing such metals, compounds containing such metals, etc., may also be used as the negative electrode active material.

[0027] The binder in the negative electrode mixture layer 42 may be a fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, etc., as in the case of the positive electrode 11, but preferably styrene-butadiene rubber (SBR) or a modified version thereof is used. In addition to SBR, the negative electrode mixture layer 42 may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, etc.

[0028] The separator 13 is made of a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably polyethylene, polyolefin resins such as polypropylene, or 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.

[0029] As shown in Figure 1, the battery 10 is equipped with an annular insulating plate 18 on the upper side of the electrode body 14. The positive electrode lead 20 attached to the positive electrode 11 extends towards the sealing body 17 through a through hole in the insulating plate 18. The sealing body 17 has a positive electrode current collector plate 26 and a terminal cap 27. The positive electrode current collector plate 26 is a metal annular plate member and has a through hole 26a in the radial center.

[0030] The terminal cap 27 is a metal plate-like member without a through hole and is 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, and this exposed portion constitutes the positive terminal. The sealing body 17 further has a metal plate 25. The metal plate 25 is a metal annular member and has a through hole.

[0031] Each positive electrode lead 20 is bent from the positive electrode 11 through the through hole 26a of the positive electrode current collector plate 26 so as to follow the upper surface of the positive electrode current collector plate 26. The tip of each positive electrode lead 20 is sandwiched between the upper surface of the positive electrode current collector plate 26 and the lower surface of the metal plate 25. Each positive electrode lead 20 is joined to the upper surface of the positive electrode current collector plate 26. The positive electrode current collector plate 26 and the metal plate 25 are also joined, and each positive electrode lead 20 is also joined to the metal plate 25. These joining can be achieved, for example, by laser welding the metal plate 25 by irradiating it axially from above with a laser beam while the tip of each positive electrode lead 20 is sandwiched between the positive electrode current collector plate 26 and the metal plate 25. In this case, the positive electrode leads 20 can be welded to the positive electrode current collector plate 26 reliably and easily.

[0032] The sealing body 17 has a laminated portion 35 on its outer edge in which a terminal cap 27 and a positive electrode current collector plate 26 are stacked. By irradiating the laminated portion 35 from above with laser light, the terminal cap 27 and the positive electrode current collector plate 26 are laser-welded and electrically connected. The annular upper surface of the positive electrode current collector plate 26 has an annular recess 31 that is radially inward from the laminated portion 35. Because the upper surface of the positive electrode current collector plate 26 has a recess 31 that is recessed downward, a space is provided between the terminal cap 27 and the recess 31 of the positive electrode current collector plate 26. Each positive electrode lead 20 is joined to the positive electrode current collector plate 26 within the recess 31. The positive electrode current collector plate 26 does not have to be joined to the metal plate 25, and the positive electrode leads 20 do not have to be joined to the metal plate 25. Also, the battery does not have to have the metal plate 25. Also, the positive electrode leads 20 may be joined to the lower surface of the positive electrode current collector plate 26.

[0033] The case 16 has a cylindrical portion 39 and a bottom portion 68. The cylindrical portion 39 includes an annular grooved portion 22 and an annular opening (shoulder portion) 29. The grooved portion 22 is formed by spinning a part of the cylindrical portion 39 to create a recess radially inward along its entire circumference. The sealing body 17 is placed on the grooved portion 22 and is crimped and fixed to the opening 29 of the case 16 via a resin gasket 28. The opening 29 is formed when the upper end of the cylindrical portion 39 is bent radially inward and crimped to the outer edge of the sealing body 17, and extends radially inward at the upper end of the cylindrical portion 39.

[0034] The space between the case 16 and the sealing body 17 is sealed with an annular gasket 28. This seals the internal space of the battery 10. The gasket 28 is sandwiched between the case 16 and the sealing body 17, insulating 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.

[0035] The battery 10 further comprises 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 on the case 16, more specifically, to the outer surface of the opening 29. The metal plate 80 extends substantially in the radial direction. The terminal cap 27 electrically connected to the positive electrode lead 20 becomes the positive electrode terminal, and the metal plate 80 electrically connected to the negative electrode core body exposed portion 41 via the negative electrode current collector plate 19 and the case 16 becomes the negative electrode terminal. The metal plate 80 is electrically connected, for example, to an external current collector plate (not shown) that connects multiple batteries 10 in series or parallel using the leads of the current collector plate, and the multiple batteries 10 are electrically connected via the current collector plate. The battery 10 may be used individually.

[0036] 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 an extended portion 28a extending radially from between the opening 29 and the sealing body 17 at its tip, and the radially outward outer peripheral edge 81a of the insulating plate 81 may be located above the extended portion 28a and in contact with the gasket 28. In this way, the gasket 28 can reliably insulate 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 27a of the terminal cap 27 located in the radially central part of the sealing body 17. The cylindrical portion 83 is connected to the radially inward end of the flange portion 82. The battery does not necessarily have to have a metal plate 80 and an insulating plate 81.

[0037] The battery 10 has a metal negative electrode current collector plate 19 located axially below the electrode body 14. As will be described in detail in Figure 3, the negative electrode current collector plate 19 is welded and fixed to the bottom 68 of the case 16. Furthermore, the surface of the negative electrode current collector plate 19 facing the electrode body 14 is joined to the axial end of the electrode body 14, i.e., the exposed negative electrode core portion 41.

[0038] Next, the bottom 68 of the case 16 and the negative electrode current collector plate 19 will be described in detail using Figures 3 to 5. Figure 3 is an enlarged cross-sectional view of the negative electrode current collector plate and the bottom of the case. Figure 4 is an enlarged cross-sectional view of the covering portion of the negative electrode current collector plate and the bottom of the case, which is an example of an embodiment. Figure 5 is a perspective view of the negative electrode current collector plate when viewed from diagonally above. As shown in Figure 3, the negative electrode current collector plate 19 is formed from a metal plate and installed inside the case 16. The negative electrode current collector plate 19 has a main body portion 60 fixed to the axial end of the electrode body 14 (see Figure 1), a covering portion 90 protruding from the outer peripheral portion 62 of the main body portion 60 toward the center of the main body portion 60, and a bent portion 91 provided between the outer peripheral portion 62 of the main body portion 60 and the covering portion 90. The main body portion 60, the covering portion 90, and the bent portion 91 are integrally constructed from the same material, and the covering portion 90 is formed when the negative electrode current collector plate 19 is bent starting from the bent portion 91.

[0039] The thickness of the negative electrode current collector plate 19 is preferably thinner than the thickness of the parts of the bottom portion 68 other than the weak portion 72 and the thin portion 78, which will be described later. The preferred thickness of the negative electrode current collector plate 19 is 0.2 mm or more and 0.5 mm or less. When the thickness of the negative electrode current collector plate 19 is within a predetermined range, a larger internal space can be secured in the battery 10, and a larger electrode body can be placed, thus reducing energy loss. In addition, it has the effect of making the negative electrode current collector plate 19 easier to bend. In this embodiment, the thickness of the negative electrode current collector plate 19 is about 0.3 mm.

[0040] The main body portion 60 is the central, disc-shaped portion of the negative electrode current collector plate 19, excluding the portion corresponding to the covering portion 90. The diameter of the main body portion 60 is larger than the diameter of the electrode body 14 and smaller than the inner diameter of the case 16. The main body portion 60 is fixed to the axial end of the electrode body 14, i.e., the negative electrode core body exposed portion 41 (see Figure 1). Specifically, with the negative electrode core body exposed portion 41 pressed against the main body portion 60, laser light is irradiated from the bottom of the main body portion 60 toward the axial upward direction. This irradiation of laser light causes the negative electrode core body exposed portion 41 to be joined to the main body portion 60 by laser welding over a wide radial area. In other words, the negative electrode core body exposed portion 41 is a conductive portion that electrically connects the electrode body 14 and the negative electrode current collector plate 19.

[0041] With the lower surface of the main body 60 of the negative electrode current collector plate 19 in contact with the inner surface of the bottom 68 of the case 16, the negative electrode current collector plate 19 is fixed to the bottom 68 by laser welding when laser light is irradiated from the bottom of the case 16. The preferred thickness of the bottom 68 of the case 16 is 0.3 mm or more and 0.7 mm or less. If the thickness of the bottom 68 is less than 0.3 mm, it will expand due to the increase in internal pressure of the battery 10 and will not be able to maintain its shape sufficiently, which is undesirable. If the thickness of the bottom 68 is greater than 0.7 mm, the mass of the battery 10 will increase, making it difficult to discharge the contents in the event of abnormal heat generation, as described later, which is also undesirable. In this embodiment, the thickness of the bottom 68 of the case 16 is about 0.6 mm.

[0042] The covering portion 90 is formed by bending a negative electrode current collector plate 19, which is a plate-shaped member made of metal, from the outer peripheral portion 62 of the main body portion 60 toward the center direction starting from the bending portion 91. The covering portion 90 covers the outer peripheral portion 62 of the main body portion 60. By covering the outer peripheral portion 62 of the main body portion 60 with the covering portion 90, it is possible to increase the thickness only of the portion of the negative electrode current collector plate 19 that is welded to the bottom portion 68 of the case 16. Although details will be described later, when the thickness of the welded portion of the negative electrode current collector plate 19 is large, it becomes difficult for the laser beam to penetrate the negative electrode current collector plate 19, so that the generation of welding spatter can be suppressed.

[0043] As shown in FIG. 4, the bending portion 91 includes a thin plate portion 94 having a thickness smaller than that of the main body portion 60, and the bending portion 91 is preferably bent such that the thin plate portion 94 is on the inner side. When the bending portion 91 of the negative electrode current collector plate 19 includes the thin plate portion 94, the generation of wrinkles can be suppressed when the negative electrode current collector plate 19 is bent. The thin plate portion 94 may be formed, for example, by providing a groove at the bending location (inner surface or outer surface) of the negative electrode current collector plate 19.

[0044] The thickness (t1) of the thin plate portion 94 is, for example, about half of the thickness (t2) of the main body portion 60. The cross-sectional shape of the thin plate portion 94 is not particularly limited, but is, for example, a V shape. Note that the thickness, length, and cross-sectional shape of the thin plate portion 94 may vary in the stretching direction. In this case, the thickness and length of the thin plate portion 94 each mean the average value of the values measured at a plurality of points along the stretching direction.

[0045] As shown in FIG. 5, the covering portion 90 may be formed, for example, by bending from the entire outer periphery of the main body portion 60 toward the center direction of the main body portion 60. When the main body portion 60 is provided in a disc shape, the covering portion 90 formed by bending the negative electrode current collector plate 19 from the outer peripheral portion 62 (see FIG. 3) of the main body portion 60 toward the center direction has an annular shape and projects from the entire outer periphery of the main body portion 60 toward the center direction of the main body portion 60.

[0046] The covering portion 90 may be formed by cutting the outer periphery of the negative electrode current collector plate 19 in the radial direction into a plurality of segments and then bending each segment toward the center. When the outer periphery of the negative electrode current collector plate 19 is divided into a plurality of segments, wrinkles and the like in the covering portion 90 can be suppressed when forming the covering portion 90 by bending, and the thickness of the negative electrode current collector plate 19 after bending can be kept substantially uniform.

[0047] The covering portion 90 is not limited to a shape that covers the entire outer peripheral portion 62 of the main body portion 60. For example, the covering portion 90 may be in the shape of tongues provided at at least two locations at the end of the outer peripheral portion 62 of the main body portion 60, and may be formed by bending the tongue shape toward the center of the main body portion 60. Also, the folded shape of the covering portion 90 may be polygonal. Furthermore, the covering portion 90 may be provided in a flaring shape toward the tip.

[0048] The length of the covering portion 90 in the radial direction of the battery 10 is preferably 1.0 mm or more and 3.0 mm or less. When the length of the covering portion 90 is shorter than half the length of the outer peripheral portion 62 in the radial direction, it becomes difficult to sufficiently weld the case 16 and the negative electrode current collector plate 19. Also, when the length of the covering portion 90 is longer than the outer peripheral portion 62, it interferes with the welding location between the protruding portion 61 and the electrode body 14, which is not preferable. Also, when the radial length of the protruding portion 61 is made short to ensure the length of the covering portion 90, the area of contact with the electrode body 14 decreases, and it becomes difficult to weld the protruding portion 61 and the electrode body 14, which is not preferable.

[0049] The covering portion 90 may contact the electrode body 14. When the covering portion 90 and the electrode body 14 contact each other, when an impact is applied to the battery 10, vibration of the electrode body 14 can be suppressed. Thereby, a connection failure between the electrode body 14 and the negative electrode current collector plate 19 is less likely to occur. Here, the contact between the covering portion 90 and the electrode body 14 does not necessarily mean constant contact. It may be such that they contact when the battery 10 is tilted and the electrode body 14 moves. Also, by providing the covering portion 90 above the protruding portion 61, when an impact is applied to the battery 10, the movable region of the electrode body 14 becomes narrow, and vibration of the electrode body 14 can be suppressed. Thereby, a connection failure between the electrode body 14 and the negative electrode current collector plate 19 is less likely to occur.

[0050] The main body portion 60 and the covering portion 90 may be welded together. By welding the main body portion 60, which is the central part of the negative electrode current collector plate 19, to the covering portion 90, which is formed by bending the negative electrode current collector plate 19 from the outer circumference 62 of the main body portion 60 toward the center, the main body portion 60 and the covering portion 90 can be reliably welded together, making it less likely to generate welding spatter.

[0051] The bent portion 91 is provided between the outer periphery 62 of the main body 60 and the covering portion 90. If the covering portion 90 is formed around the entire circumference of the main body 60, the bent portion 91 is formed around the entire circumference. If the covering portion 90 is formed at multiple intervals around the main body 60 in the circumferential direction, the bent portion 91 is formed intermittently around the main body 60 in the circumferential direction.

[0052] When welding the bottom 68 of the case 16 to the negative electrode current collector plate 19, the laser beam is emitted from the bottom of the case 16 to a position where the main body 60 and the covering portion 90 overlap in the axial direction, that is, to a position where the covering portion 90 covers the main body 60. The laser beam may be scanned in an annular manner, or it may be scanned intermittently at intervals in the circumferential direction. Through such scanning, the main body 60 is welded to the bottom 68 in a circular shape over its entire circumference, or it is welded to the bottom 68 intermittently at multiple points at intervals in the circumferential direction. As a result, the negative electrode 12 of the electrode body 14 is electrically connected to the case 16 via the negative electrode current collector plate 19. By joining the exposed portion 41 of the negative electrode core to the upper surface 65 of the negative electrode current collector plate 19 over a wide area in the longitudinal direction of the negative electrode, it is possible to suppress the flow of current over long distances in the longitudinal direction of the negative electrode 12, thereby reducing the electrical resistance of the battery 10.

[0053] When a laser beam is emitted axially from the bottom of the case 16 at a position where the covering portion 90 covers the main body portion 60 in the axial direction of the battery 10, welding spatter does not occur. Conventionally, when a laser beam was emitted from the bottom of the case 16, welding spatter was generated because the laser beam penetrated the negative electrode current collector plate 19, which is thinner than the thickness of the bottom portion 68 of the case 16, and it is thought that the welding spatter adhered to the inside of the battery. By having the covering portion 90 on the negative electrode current collector plate 19, the thickness of the welded portion of the negative electrode current collector plate 19 becomes about twice that of the conventional design, making it difficult for the laser beam to penetrate the negative electrode current collector plate 19, and thus the generation of welding spatter can be suppressed. By suppressing the generation of welding spatter, it is also possible to suppress an unintended drop in the voltage of the battery 10.

[0054] By welding the case 16 and the negative electrode current collector plate 19 at a position where a covering portion 90, formed by bending a part of the negative electrode current collector plate 19, covers the main body portion 60, the generation of welding spatter can be suppressed. In this case, it is not necessary to increase the overall thickness of the negative electrode current collector plate 19, and the internal space of the battery 10 can be used more widely, so the volume of the electrode body 14 placed inside can be increased, and energy loss is less likely to occur.

[0055] When a laser beam is emitted axially from the bottom of the case 16, the laser beam is focused in a cone shape toward the upward axial direction. Compared to the case where only the bottom 68 of the case 16 and the main body 60 of the negative electrode current collector plate 19 are welded, when the bottom 68, the main body 60, and the covering portion 90 covering the main body 60 are welded together, the thickness of the welded portion of the negative electrode current collector plate 19 increases, resulting in a larger melting width at the contact point between the case 16 and the lower surface of the main body 60. In other words, by welding at the position where the bottom 68, the main body 60, and the covering portion 90 overlap, the case 16 and the negative electrode current collector plate 19 can be connected more firmly.

[0056] The negative electrode current collector plate 19 may have a projection 61 that protrudes inward from the inner circumference of the main body 60 toward the case 16. The projection 61 protrudes in the direction toward the electrode body 14 from the bottom 68. The projection 61 may be plate-shaped, or it may be strip-shaped and multiple projections may be arranged at equal intervals in the circumferential direction. The projection 61 may also be arranged at uneven intervals in the circumferential direction.

[0057] The protruding portion 61 is fixed to the axial end of the electrode body 14, i.e., the exposed negative electrode core portion 41 (see Figure 1). Specifically, with the exposed negative electrode core portion 41 pressed against the protruding portion 61, laser light is irradiated from the lower side of the protruding portion 61 toward the upper side in the axial direction. This irradiation of laser light causes the exposed negative electrode core portion 41 to be joined to the protruding portion 61 by laser welding over a wide radial area. In other words, the exposed negative electrode core portion 41 electrically connects the electrode body 14 and the negative electrode current collector plate 19. Since the protruding portion 61 is provided so as to be convex upward, the pressing force applied to the exposed negative electrode core portion 41 against the protruding portion 61 can be increased, and the exposed negative electrode core portion 41 can be reliably welded to the protruding portion 61. Furthermore, since the protruding portion 61 is provided so as to be convex upward, high-temperature gas and molten material generated by abnormal heat generation of the battery can be smoothly guided downward along the protruding portion 61, and the high-temperature gas and molten material can be smoothly discharged.

[0058] The main body 60 may have a through hole in a position that overlaps with the hollow portion 14a (see Figure 1), which is a space provided at the winding center of the electrode body 14 when viewed from above. The bottom portion 68 has a weak portion 72 (described later) and a separation portion 74 surrounded by the weak portion 72 in a position that overlaps with the hollow portion 14a and the through hole when viewed from above. Because the main body 60 has a through hole, the cross-sectional area of ​​the negative electrode current collector plate 19 through which high-temperature gas and molten material generated when the battery overheats is increased, so that when at least a part of the weak portion 72 breaks, the high-temperature gas and molten material can be smoothly discharged to the outside, further increasing the safety of the battery 10.

[0059] As shown in Figure 3, the bottom portion 68 has a fixing portion 71 to which the main body portion 60 is fixed, and a projection portion 75 that protrudes upward. The main body portion 60 is electrically connected to the bottom portion 68 by welding to the fixing portion 71. In this embodiment, when viewed from above (axial direction), the projection portion 75 is completely surrounded by the annular fixing portion 71. The upper surface of the projection portion 75 is located above the upper surface of the fixing portion 71, and the lower surface of the projection portion 75 is also located above the lower surface of the fixing portion 71.

[0060] The protrusion 75 has a weak portion 72 that is thinner than the protrusion 75. The weak portion 72 is formed by providing a groove on the lower surface of the bottom portion 68. In this embodiment, in a plan view seen from above, the weak portion 72 is located radially inward from the covering portion 90 and is formed in an annular shape that forms a closed curve. In a plan view seen from the axial direction, the annular weak portion 72 has a polygonal outer edge shape, for example, a quadrilateral outer edge shape. Preferably, the annular weak portion 72 is formed in a regular polygonal outer edge shape.

[0061] The center of the outer edge of the polygon formed by the weak portion 72 substantially coincides with the center of the base portion 68. The depth of the groove constituting the weak portion 72 is, for example, 0.1 mm or more and 0.5 mm or less, and the width of the groove constituting the weak portion 72 is, for example, 0.1 mm or more and 1.0 mm or less. The cross-sectional shape of the groove constituting the weak portion 72 is not particularly limited, but is, for example, V-shaped. The depth, width, and cross-sectional shape of the groove constituting the weak portion 72 may change in the stretching direction. In this case, the depth and width of the groove constituting the weak portion 72 represent the average value of values ​​measured at multiple points along the stretching direction, respectively.

[0062] The protrusion 75 includes a fragile portion 72 arranged in an annular shape, as well as a separation portion 74 that is completely surrounded by the fragile portion 72. When the battery 10 overheats abnormally, pressure from high-temperature gas or molten material is applied to the separation portion 74, causing the separation portion 74 to separate from the bottom portion 68, thereby allowing the high-temperature gas and other substances to be discharged to the outside.

[0063] The protrusion 75 may further have a plurality of thin-walled portions 78 located between the separation portion 74 and the fixing portion 71. The thickness of the thin-walled portions 78 is thinner than the thickness of the fixing portion 71 and the separation portion 74. The thin-walled portions 78 are connected to the fragile portion 72 and extend in the direction from the fragile portion 72 toward the fixing portion 71. The thin-walled portions 78 are formed by providing grooves on the lower surface of the bottom portion 68.

[0064] The depth of the grooves constituting the thin-walled portion 78 is, for example, 0.1 mm or more and 0.7 mm or less, and the width of the grooves constituting the thin-walled portion 78 is, for example, 0.1 mm or more and 1.0 mm or less. The cross-sectional shape of the grooves constituting the thin-walled portion 78 is not particularly limited, but is, for example, V-shaped. The depth, width, and cross-sectional shape of the grooves constituting the thin-walled portion 78 may change in the stretching direction. In this case, the depth and width of the grooves constituting the thin-walled portion 78 refer to the average value of values ​​measured at multiple points along the stretching direction, respectively. The grooves constituting the weak portion 72 and the grooves constituting the thin-walled portion 78 may all be the same in depth, width, and cross-sectional shape, or at least one of the depth, width, and cross-sectional shape may be different. It is preferable that the thickness of the weak portion 72 and the thin-walled portion 78 are about the same (about ±0.04 mm).

[0065] The multiple thin-walled sections 78 extend in the same rotational direction relative to the center of the base 68. The rotational direction may be either clockwise or counterclockwise. The ends of the multiple thin-walled sections 78 are located, for example, on approximately the same circumference. The ends of the thin-walled sections 78 are the ends on the side of the thin-walled section 78 that are not in contact with the weak portion 72. Preferably, the center of the circle on which the ends of the multiple thin-walled sections 78 are located approximately coincides with the center of the base 68.

[0066] If the battery 10 overheats abnormally and the internal pressure continues to rise, at least a portion of the weak point 72 and the multiple thin-walled sections 78 will preferentially rupture, allowing the contents, i.e., high-temperature gas and molten material, to be discharged to the outside. This prevents a situation where the internal pressure of the battery becomes excessively high and there is a risk of the battery rupturing, thereby increasing the safety of the battery 10.

[0067] In this embodiment, the design ensures that when the internal pressure of the battery continues to rise, at least a portion of the fragile portion 72 and at least a portion of the multiple thin-walled portions 78 will rupture. As a result, not only at least a portion of the fragile portion 72 but also at least a portion of the thin-walled portions 78 will rupture, making it easier to discharge the contents to the outside more smoothly. In addition, a large opening for venting high-temperature gas is formed at the bottom 68, thereby improving the safety of the battery 10. Preferably, each thin-walled portion 78 is in contact with only one vertex of the polygon formed by the fragile portion 72. As a result, when the thin-walled portion 78 ruptures, the separation portion 74 surrounded by the fragile portion 72 is less likely to scatter from the bottom 68 and is more likely to be secured to the case 16.

[0068] Next, the negative electrode current collector plate 19 and the bottom 68 of the case 16 will be described in detail using Figures 6 to 10. Figure 6 is an enlarged cross-sectional view of the negative electrode current collector plate and the bottom of the case, which is another example of the embodiment. Figures 7 to 10 are enlarged cross-sectional views of the covering portion of the negative electrode current collector plate and the bottom of the case, which is yet another example of the embodiment.

[0069] As shown in Figure 6, the covering portion 90 of the negative electrode current collector plate 19 may be formed to be located between the main body portion 60 and the bottom portion 68. When the case 16 and the negative electrode current collector plate 19 are laser-welded at a position where the bottom portion 68, the covering portion 90, and the main body portion 60 overlap when viewed from above, the thickness of the welded negative electrode current collector plate 19 becomes approximately twice that of the conventional method, making it more difficult for the laser light to penetrate the negative electrode current collector plate 19, thereby suppressing the generation of welding spatter. By suppressing the generation of welding spatter, it is also possible to prevent an unintended drop in the voltage of the battery 10.

[0070] When the bottom portion 68, the main body portion 60, and the covering portion 90 are welded together, the melting width at the contact point between the case 16 and the lower surface of the main body portion 60 increases, similar to the case where the covering portion 90 is located between the main body portion 60 and the electrode body 14 (see Figure 1). In other words, by welding at a position where the main body portion 60 and the covering portion 90 overlap, it is possible to connect the case 16 and the negative electrode current collector plate 19 more firmly.

[0071] As shown in Figure 7, the extension direction of the main body 60 of the negative electrode current collector plate 19 and the extension direction of the covering portion 90 intersect, and a gap 92 surrounded by the main body 60 and the covering portion 90 may be provided. In other words, the covering portion 90 and the main body 60 are not arranged parallel to each other. In this case, when the bottom portion 68 of the case 16 and the main body 60 are laser welded, the laser beam penetrates the main body 60 of the negative electrode current collector plate 19, which is thinner than the bottom portion 68, causing welding spatter to be generated on the inside of the main body 60. However, the generated welding spatter remains in the gap 92 surrounded by the main body 60 and the covering portion 90, making it less likely to adhere to the inside of the battery.

[0072] If the extension direction of the main body 60 and the extension direction of the covering portion 90 intersect, the ends of the main body 60 and the covering portion 90 may be connected by a welded joint (not shown). In this case, a gap is provided surrounded by the main body 60, the covering portion 90, and the welded joint. When the bottom 68 of the case 16 and the main body 60 are laser-welded, welding spatter is generated inside the main body 60, but since the welding spatter remains in the gap surrounded by the main body 60, the covering portion 90, and the welded joint, adhesion to the inside of the battery can be suppressed.

[0073] As shown in Figure 8, the negative electrode current collector plate 19 may have a support portion 93 that protrudes outward from the case 16 from the tip of the covering portion 90, which is formed by bending it starting from the bent portion 91. The support portion 93 is integrally constructed from the same material as the main body portion 60 and the covering portion 90, and is formed by bending the tip of the covering portion 90 of the negative electrode current collector plate 19 so that it protrudes outward from the case 16. The support portion 93 and the electrode body 14 (see Figure 1) are in contact.

[0074] The electrode body 14 that contacts the support portion 93 has a shape that is convex downward toward the center because the exposed negative electrode core portion 41 is folded toward the center. Because the support portion 93, which has an upward-opening shape, contacts the electrode body 14, which has a downward-convex shape, the support portion 93 supports the electrode body 14 even when vibration or shock occurs in the battery 10, and the connection between the negative electrode current collector plate 19 and the electrode body 14 can be made stable.

[0075] As shown in Figure 9, the negative electrode current collector plate 19 may have a support member 95 placed between it and the electrode body 14 to support the electrode body 14. In this case, the support member 95 may be positioned so as to overlap the covering portion 90, or it may be positioned so as to be adjacent to the tip of the covering portion 90 and in contact with the upper surface of the main body portion 60, but in either case the support member 95 and the electrode body 14 are in contact. By welding the overlapping portions of the case 16, main body portion 60, covering portion 90 and support member 95, the thickness of the welded portion becomes thicker than in the conventional method, making it more difficult for the laser beam to penetrate the negative electrode current collector plate 19, thus suppressing the generation of welding spatter. In addition, because the melting width at the contact portion between the case 16 and the lower surface of the main body portion 60 becomes larger, the case 16 and the negative electrode current collector plate 19 can be strongly welded together.

[0076] As shown in Figure 10, the negative electrode current collector plate 19 may have a main body portion 60 fixed to the end of the electrode body 14, a support member 95 positioned between the main body portion 60 and the electrode body 14, and a connecting portion 96 to which the main body portion 60 and the support member 95 are fixed. The case 16 and the negative electrode current collector plate 19 are connected by welding, and the main body portion 60 and the support member 95 are separate components. The support member 95 is, for example, an annular metal member and is fixed by welding to a portion that covers the outer circumference 62 of the main body portion 60. The connecting portion 96 is the welding point between the support member 95 and the main body portion 60 and is provided between the main body portion 60 and the support member 95. When the bottom portion 68 of the case 16, the main body portion 60, and the support member 95 are laser welded, the thickness of the welded portion becomes thicker than in the conventional method, making it more difficult for the laser light to penetrate the negative electrode current collector plate 19, thus suppressing the generation of welding spatter. Furthermore, because the melting width at the contact point between the case 16 and the lower surface of the main body 60 is increased, the case 16 and the negative electrode current collector plate 19 can be firmly welded together. The connecting portion 96 to which the main body 60 and the support member 95 are fixed is preferably provided around the entire circumference of the main body 60.

[0077] Preferably, the axial thickness of the support member 95 decreases from the inner circumferential surface of the case 16 toward the radially inward direction. The electrode body 14 that contacts the support member 95 is arranged so that the exposed portion 41 of the negative electrode core is folded toward the center and joined to the negative electrode current collector plate 19. In this case, the electrode body 14 has a shape that is convex downward toward the center. The support member, which has an upward-opening shape, supports the electrode body 14, which has a downward-convex shape, thereby enabling a good connection between the negative electrode current collector plate 19 and the electrode body 14.

[0078] This disclosure is not limited to the embodiments and their variations described above, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents. For example, the case described above has a case in which the bottom 68 of the case 16 has a fixing portion 71 and a protrusion 75. However, the bottom of the case does not have to have a protrusion. Also, having both the thin-walled portion 78 and the fragile portion 72 makes it easier to discharge the contents when the internal pressure rises unintentionally, but only one of them may be provided.

[0079] The case described above has been one in which the negative electrode current collector plate 19 has a protruding portion 61 that extends inward from the inner circumference of the main body portion 60 into the case 16. However, as shown in Figure 11, the negative electrode current collector plate 19 does not have to have a protruding portion. In this case, the lower surface of the negative electrode current collector plate 19 is flush with the lower surface of the main body portion 60. The main body portion 60 of the negative electrode current collector plate 19 without a protruding portion may have a through hole (not shown) at a position that overlaps with the hollow portion 14a (see Figure 1) of the electrode body 14 (see Figure 1) when viewed from above. Providing a through hole makes it easier to discharge the contents when the internal pressure rises unintentionally. Note that it is not necessary to have a through hole. If the main body portion 60 does not have a through hole, the main body portion 60 may discharge the contents by providing an easily breakable portion (not shown) in an annular or arc shape at a position that overlaps with the hollow portion 14a (see Figure 1) of the electrode body 14 (see Figure 1) when viewed from above.

[0080] The case described above has been in which the vulnerable portion 72 is configured as having a polygonal outer edge shape in a plan view from the axial direction. However, the vulnerable portion may have a circular or C-shaped shape in a plan view from the axial direction, and may be provided, for example, by engraving a circular or C-shaped mark on the bottom surface of the case. Furthermore, although the vulnerable portion was configured by providing a groove on the bottom surface of the case, the vulnerable portion may also be configured by providing a groove on the top surface of the case.

[0081] The case described above is when the conductive portion electrically connecting the electrode body 14 and the negative electrode current collector plate 19 is the exposed negative electrode core portion 41 that constitutes the lower end of the electrode body 14. However, when the negative electrode has a strip shape, the conductive portion electrically connecting the electrode body and the negative electrode current collector plate may be a plurality of negative electrode leads, each with one end joined to the negative electrode at intervals in the longitudinal direction of the negative electrode. Alternatively, the other end of each negative electrode lead may be joined to the upper surface of the negative electrode current collector plate.

[0082] The case in which the positive electrode 11 is electrically connected to the sealing body 17 via one or more positive electrode leads 20 has been described. However, the upper end of the electrode body may be configured as a positive electrode core exposed portion, and this positive electrode core exposed portion may be joined to the positive electrode current collector plate by welding or the like. Then, the positive electrode may be electrically connected to the upper surface of the sealing body by electrically connecting the positive electrode current collector plate to a conductive member that includes the upper surface of the sealing body and has conductivity.

[0083] The case in which the negative electrode 12 constitutes the first electrode and the positive electrode 11 constitutes the second electrode has been described, and the case in which the case 16 is electrically connected to the negative electrode 12 and the negative electrode current collector plate 19 is placed on the bottom 68 side of the case 16 in the electrode body 14 has been described. However, the positive electrode may constitute the first electrode and the negative electrode may constitute the second electrode, and the case may be electrically connected to the positive electrode and the positive electrode current collector plate may be placed on the bottom side of the case in the electrode body.

[0084] Furthermore, the case in which the sealing body 17 does not have a rupture plate that bursts when the pressure inside the battery reaches a set pressure and temperature has been described. However, the sealing body may include two rupture plates (lower valve body and upper valve body) and a convex terminal cap that covers the rupture plates. Alternatively, the sealing body may consist only of rupture plates. Alternatively, the sealing body may have a structure in which an internal terminal plate, an insulating plate, and a rupture plate are stacked in that order from the electrode body side.

[0085] Furthermore, the energy storage device of this disclosure may have the following configurations: Configuration 1: An energy storage device comprising a bottomed cylindrical case, an electrode body disposed inside the case and having a first electrode, a second electrode having a different polarity from the first electrode, and a separator, with the first electrode and the second electrode wound around the separator, and a current collector plate fixed to the bottom of the case and fixed to the axial end of the electrode body, wherein the current collector plate has a main body fixed to the end of the electrode body, a covering portion protruding from the outer periphery of the main body toward the center of the main body, and a bent portion provided between the outer periphery of the main body and the covering portion, the case and the current collector plate are welded together, the main body, the covering portion and the bent portion are the same material, and the current collector plate is bent starting from the bent portion. Configuration 2: The energy storage device according to Configuration 1, wherein the covering portion is located between the main body and the electrode body. Configuration 3: The energy storage device according to Configuration 1, wherein the covering portion is located between the main body and the bottom. Configuration 4: The energy storage device according to Configuration 2, wherein the extension direction of the main body and the extension direction of the covering intersect, and a gap is provided between the main body and the covering. Configuration 5: The energy storage device according to Configuration 2, wherein the tip of the main body and the covering are connected by a welded joint, and a gap is provided between the main body, the covering, and the welded joint. Configuration 6: The energy storage device according to Configuration 2, wherein the main body and the covering are welded together. Configuration 7: The energy storage device according to Configuration 4 or 5, wherein the covering is in contact with the electrode body. Configuration 8: The energy storage device according to any one of Configurations 1 to 7, wherein the electrode body has a hollow portion provided at the center of the winding, the main body has a through hole at a position that overlaps with the hollow portion when viewed from above, the bottom has a fixing portion to which the main body is fixed, a separation portion that overlaps with the hollow portion and the through hole when viewed from above, and a fragile portion surrounding the separation portion, the fragile portion is located radially inward from the covering portion when viewed from above. Configuration 9: The main body has a projection that protrudes inward from the inner circumference of the main body toward the case, the projection protrudes in a direction toward the electrode body from the bottom, and the projection is fixed to the end of the electrode body, as described in any one of Configurations 1 to 8. Configuration 10: The current collector plate has a support portion that protrudes outward from the tip of the covering portion toward the case, the support portion is made of the same material as the main body and the covering portion, and the support portion is in contact with the electrode body, as described in Configuration 7.Configuration 11: The energy storage device according to Configuration 7, further comprising a support member disposed between a current collector plate and an electrode body, wherein the support member and the electrode body are in contact. Configuration 12: An energy storage device comprising a bottomed cylindrical case, an electrode body disposed inside the case and having a first electrode, a second electrode having a different polarity from the first electrode, and a separator, with the first electrode and the second electrode wound around the separator, and a current collector plate fixed to the bottom of the case and fixed to the axial end of the electrode body, wherein the current collector plate has a main body fixed to the end of the electrode body, a support member disposed between the main body and the electrode body, and a connecting portion to which the main body and the support member are fixed, the case and the current collector plate are welded together, the main body and the support member are separate components, and the axial thickness of the support member decreases from the inner circumferential surface of the case toward the radially inward direction. Configuration 13: The energy storage device according to any one of Configurations 1 to 12, wherein the thickness of the current collector plate is thinner than the thickness of the part other than the weak part at the bottom. Configuration 14: The energy storage device according to any one of Configurations 1 to 11, wherein the bent portion includes a thin plate portion that is thinner than the main body portion, and the bent portion is folded so that the thin plate portion is on the inside. Configuration 15: The energy storage device according to any one of Configurations 1 to 11, wherein the main body portion is provided in a disc shape, the covering portion protrudes from the entire outer circumference of the main body portion toward the center of the main body portion, and the bent portion is provided around the entire circumference between the main body portion and the covering portion. Configuration 16: The energy storage device according to Configuration 12, wherein the main body portion is provided in a disc shape, the covering portion protrudes from the entire outer circumference of the main body portion toward the center of the main body portion, and the connecting portion is provided around the entire circumference of the main body portion between the main body portion and the support member.

[0086] 10 Battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Case, 17 Sealing body, 18 Insulating plate, 19 Negative electrode current collector plate, 20 Positive electrode lead, 22 Grooved portion, 25 Metal plate, 26 Positive electrode current collector plate, 26a Through hole, 27 Terminal cap, 27a Terminal portion, 28 Gasket, 28a Extending portion of gasket, 29 Opening, 30 Positive electrode core, 31 Recess, 32 Positive electrode mixture layer, 35 Laminated portion, 39 Cylindrical portion, 40 Negative electrode core, 41 Negative electrode core exposed portion, 42 Negative electrode mixture layer, 60 Main body portion, 61 Protruding portion, 62 Outer circumference portion, 65 Top surface of protruding portion, 68 Bottom portion, 72 Weak portion, 74 Separation portion, 80 Metal plate, 81 Insulating plate, 81a outer edge portion, 82 flange portion, 83 cylindrical portion, 90 covering portion, 91 bent portion, 92 gap, 93 support portion, 94 thin plate portion, 95 support member, 96 connection portion

Claims

1. An energy storage device comprising: a bottomed cylindrical case; an electrode body disposed inside the case and having a first electrode, a second electrode having a different polarity from the first electrode, and a separator, with the first electrode and the second electrode wound around the separator; and a current collector plate fixed to the bottom of the case and fixed to the axial end of the electrode body, wherein the current collector plate has a main body fixed to the end of the electrode body, a covering portion protruding from the outer periphery of the main body toward the center of the main body, and a bent portion provided between the outer periphery of the main body and the covering portion, the case and the current collector plate are welded together, the main body, the covering portion and the bent portion are made of the same material, and the current collector plate is bent starting from the bent portion.

2. The energy storage device according to claim 1, wherein the covering portion is located between the main body portion and the electrode body.

3. The energy storage device according to claim 1, wherein the covering portion is located between the main body portion and the bottom portion.

4. The energy storage device according to claim 2, wherein the extension direction of the main body and the extension direction of the covering portion intersect, and a gap is provided enclosed by the main body and the covering portion.

5. The main body and the tip of the covering are connected by a welded joint, and a gap is provided between the main body, the covering, and the welded joint, as described in claim 2.

6. The energy storage device according to claim 2, wherein the main body and the covering are welded together.

7. The energy storage device according to claim 4 or 5, wherein the covering portion is in contact with the electrode body.

8. The electrode body has a hollow portion provided at the center of the winding, the main body has a through hole at a position that overlaps with the hollow portion when viewed from above, the bottom has a fixing portion to which the main body is fixed, a separating portion that overlaps with the hollow portion and the through hole when viewed from above, and a fragile portion surrounding the separating portion, the fragile portion is located radially inward from the covering portion when viewed from above, the energy storage device according to claim 1.

9. The energy storage device according to claim 1, wherein the main body portion has a projection portion that protrudes from the inner circumference of the main body portion toward the inside of the case, the projection portion protrudes in a direction toward the electrode body from the bottom portion, and the projection portion is fixed to the end of the electrode body.

10. The current collector plate has a support portion that protrudes outward from the tip of the covering portion toward the outside of the case, the support portion is made of the same material as the main body portion and the covering portion, and the support portion and the electrode body are in contact, as described in claim 7.

11. The energy storage device according to claim 7, further comprising a support member disposed between the current collector plate and the electrode body, wherein the support member and the electrode body are in contact.

12. An energy storage device comprising: a bottomed cylindrical case; an electrode body disposed inside the case and having a first electrode, a second electrode having a different polarity from the first electrode, and a separator, with the first electrode and the second electrode wound around the separator; and a current collector plate fixed to the bottom of the case and fixed to the axial end of the electrode body, wherein the current collector plate has a main body fixed to the end of the electrode body, a support member disposed between the main body and the electrode body, and a connecting portion to which the main body and the support member are fixed; the case and the current collector plate are welded together; the main body and the support member are separate components; and the axial thickness of the support member decreases from the inner circumferential surface of the case toward the radially inward side.

13. The energy storage device according to claim 1 or 12, wherein the thickness of the current collector plate is thinner than the thickness of the portion of the bottom other than the weak portion.

14. The energy storage device according to claim 1, wherein the bent portion includes a thin plate portion that is thinner than the main body portion, and the bent portion is folded so that the thin plate portion is on the inside.

15. The energy storage device according to claim 1, wherein the main body is provided in the shape of a disc, the covering portion protrudes from the entire outer circumference of the main body toward the center of the main body, and the bent portion is provided around the entire circumference between the main body and the covering portion.

16. The energy storage device according to claim 12, wherein the main body is provided in the shape of a disc, the covering portion protrudes from the entire outer circumference of the main body toward the center of the main body, and the connecting portion is provided between the main body and the support member around the entire circumference of the main body.

Images