Power storage device

Abstract

The present invention comprises: an electrode body (14) in which a first electrode (positive electrode (11)) and a second electrode (negative electrode (12)) are disposed with a separator (13) therebetween; and an exterior body (16) that accommodates the electrode body (14). The first electrode (positive electrode (11)) has a tip portion that extends beyond an end portion of the second electrode (negative electrode (12)) in a first direction. After bending, the tip portion is connected to a first current collector plate (upper current collector plate (19)). A plurality of openings are formed in the tip portion.

Description

Power storage device

[0001] The present disclosure relates to power storage devices, such as batteries and capacitors.

[0002] A cylindrical secondary battery described in Patent Document 1 has been known as a conventional energy storage device. This cylindrical secondary battery includes an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a bottomed cylindrical exterior body that houses the electrode assembly, and a sealing body that closes the opening of the exterior body. The positive electrode of the electrode assembly is electrically connected to the bottom surface of the sealing body via a positive electrode lead, and the negative electrode of the electrode assembly is electrically connected to the bottom of the exterior body via a negative electrode lead.

[0003] US Patent Application Publication No. 2022 / 0278431

[0004] In order to further improve the capacity and output of power storage devices and to enable more stable charging and discharging, further improvements in reliability are required. Therefore, an object of the present disclosure is to provide a highly reliable power storage device.

[0005] The energy storage device of the present disclosure comprises an electrode body in which a first electrode and a second electrode are arranged with a separator interposed therebetween, and an outer casing that houses the electrode body, wherein the first electrode has a tip portion that extends beyond the end of the second electrode in the first direction, the tip portion is bent and then connected to a first current collector plate, and the tip portion has a plurality of openings formed therein.

[0006] According to the power storage device according to the present disclosure, a highly reliable power storage device can be provided.

[0007] FIG. 1 is an axial cross-sectional view of a battery according to an embodiment of the energy storage device according to the present disclosure; FIG. 2 is a diagram illustrating the configuration of the tip end of a positive electrode; FIG. 3 is a diagram illustrating bending; FIG. 4 is a schematic diagram illustrating the state after the upper current collecting plate has been laser welded, viewed from above; FIG. 5 is a diagram illustrating the formation of an opening; FIG. 6 is a diagram illustrating various examples of openings; FIG. 7 is a diagram illustrating yet another example of openings; and FIG. 8 is a flowchart illustrating the manufacturing process of a positive electrode.

[0008] Hereinafter, an embodiment of an energy storage device according to the present disclosure will be described in detail with reference to the drawings. The energy storage device according to the present disclosure may be a secondary battery using an aqueous electrolyte or a secondary battery using a nonaqueous electrolyte. The energy storage device according to the present disclosure may be a cylindrical battery having a cylindrical (e.g., bottomed cylindrical) exterior body, a prismatic battery having a prismatic exterior body, or a pouch-type battery having an exterior body made of a laminate sheet. In these batteries, the cylindrical exterior body, the prismatic exterior body, and the laminate sheet constitute the exterior body. Alternatively, the energy storage device according to the present disclosure may be a capacitor that is repeatedly charged and discharged. Below, a cylindrical secondary battery (lithium ion battery) using a regulated nonaqueous electrolyte is illustrated as an example of an energy storage device according to one embodiment, but the energy storage device according to the present disclosure is not limited thereto.

[0009] When multiple embodiments and variations are included below, it is anticipated from the beginning that new embodiments can be constructed by appropriately combining their characteristic features. In the following embodiments, the same components are designated 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 sealing body side in the axial direction (height direction) of a cylindrical battery is referred to as "upper," and the bottom plate side of the exterior body 16 in the axial direction is referred to as "lower." The axial direction of a cylindrical battery coincides with the height direction of the electrode assembly. Among the components described below, components not recited in the independent claims representing the highest concept are optional and not required.

[0010] 1 is an axial cross-sectional view of a battery 10 according to an embodiment of the energy storage device of the present disclosure. The battery 10 includes a wound electrode assembly 14, a non-aqueous electrolyte (not shown), a cylindrical metal exterior body 16 with a bottom that houses the electrode assembly 14 and the non-aqueous electrolyte, and a sealing body 17.

[0011] The electrode assembly 14 is a wound electrode assembly having a wound structure in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound with two strip-shaped separators 13 interposed therebetween. The positive electrode constitutes a first electrode, and the negative electrode 12 constitutes a second electrode.

[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] The positive electrode 11 includes 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 constitutes a first core, and the positive electrode mixture layer 32 constitutes a first mixture layer. The positive electrode core 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 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 produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc. to the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 32 on both sides of the positive electrode core 30. The positive electrode mixture layer 32 may be formed on only one side of the positive electrode core 30. Alternatively, the positive electrode mixture layer 32 may be formed by laminating a layered sheet to the positive electrode core 30. When laminating them, a conductive adhesive containing conductive particles may be interposed between the positive electrode mixture layer 32 and the positive electrode core 30.

[0015] 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.

[0016] Examples of the conductive agent contained in the positive electrode mixture layer 32 include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of the binder contained in the positive electrode mixture layer 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, or polyethylene oxide (PEO).

[0017] The negative electrode 12 includes a negative electrode core 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode core 40. The negative electrode core 40 constitutes a second core, and the negative electrode mixture layer 42 constitutes a second mixture layer. The negative electrode core 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 the surface. The negative electrode mixture layer 42 contains a negative electrode active material and a binder. The negative electrode 12 can be fabricated, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to 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. The negative electrode mixture layer 42 may be formed on only one side of the negative electrode core 40. Alternatively, a layered negative electrode mixture layer may be attached to the negative electrode core. When bonding them together, a conductive adhesive containing conductive particles may be interposed between the negative electrode substrate 40 and the negative electrode mixture layer 42 .

[0018] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials are graphites such as 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 may contain a silicon (Si) material as the negative electrode active material. In addition, the negative electrode active material may be a metal other than Si that alloys with lithium, an alloy containing such a metal, or a compound containing such a metal.

[0019] As in the case of the positive electrode 11, fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like may be used as the binder contained in the negative electrode mixture layer 42, but styrene-butadiene rubber (SBR) or a modified product thereof is preferably used. In addition to SBR or the like, the negative electrode mixture layer may also contain, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0020] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Preferred materials 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.

[0021] The battery 10 includes a lower current collector plate (negative current collector plate) 18 made of a metal such as copper, iron, nickel, or a nickel alloy, located axially below the electrode assembly 14. In this embodiment, the lower current collector plate 18 includes a disk-shaped base 18a and a cylindrical, bottomed protrusion 18b located at the center of the base 18a and protruding downward in the axial direction. While the upper surface of the base 18a is pressed against the negative electrode exposed portion 41 that constitutes the axial lower end of the electrode assembly 14, a laser beam is irradiated from below onto the lower surface of the base 18a. This laser welding joins the negative electrode exposed portion 41 to the upper surface of the base 18a. Furthermore, a bottom plate portion 18c located at the tip of the protrusion 18b is placed on the upper surface of a bottom plate portion 68 of the exterior body 16, and then a laser beam is irradiated onto the bottom plate portion 68 from below. This laser welding joins the lower current collector plate 18 to the bottom plate portion 68 and electrically connects it to the exterior body 16. The lower current collector plate (negative electrode current collector plate) 18 constitutes a second current collector plate.

[0022] In addition, in the drawing, the negative electrode exposed portion 41 is bent radially inward, but it may be bent radially from the outside to the inside.

[0023] The case where the negative electrode exposed portion 41 is electrically connected to the exterior body 16 via the lower current collecting plate 18 has been described. However, the negative electrode may be electrically connected to the exterior body via one or more negative electrode leads protruding from the lower end of the electrode assembly. Alternatively, in addition to or instead of being electrically connected to the exterior body via one or more negative electrode leads, the negative electrode may be electrically connected to the exterior body by contacting a negative electrode exposed portion provided on the outermost periphery of the electrode assembly with the inner circumferential surface of the exterior body. The negative electrode exposed portion 41 may also be directly joined to the bottom plate of the exterior body using a laser or the like. The negative electrode exposed portion 41 may also be joined to the lower current collecting plate 18 in a radially bent state. Furthermore, the negative electrode exposed portions 41 aligned radially may be joined to the lower current collecting plate 18 in a state where they overlap each other.

[0024] The battery 10 includes an upper current collector 19 (positive electrode current collector) made of a metal such as aluminum or an aluminum alloy, located axially above the electrode assembly 14. The upper current collector 19 has a base 19a electrically connected to the positive electrode 11 and a through-hole 19b located at the center of the base 19a. A spacer 37 made of an insulating material that prevents connection between the upper current collector 19 and the exterior housing 16 is provided between the base 19a and the exterior housing 16. While the lower surface of the base 19a is pressed against a positive electrode exposed portion 31 that constitutes the upper end of the electrode assembly 14, a laser beam is irradiated from above onto the upper surface of the base 19a. This laser welding joins the positive electrode exposed portion 31 to the lower surface of the base 19a. The positive electrode exposed portion 31 constitutes the first exposed portion. The upper current collector (positive electrode current collector) 19 constitutes the first current collector.

[0025] Here, the tip side of the positive electrode exposed portion 31 is bent radially outward by bending, and is joined to the upper current collecting plate 19 in a bent state in the radial direction. Note that the tip portion of the positive electrode exposed portion 31 may be bent radially inward. Furthermore, the positive electrode exposed portions aligned in the radial direction may be joined to the upper current collecting plate 19 in a state where they overlap each other.

[0026] A protective layer 33 is formed around the end of the positive electrode exposed portion 31 on the side of the positive electrode mixture layer 32 to prevent short-circuiting with the adjacent negative electrode 12 .

[0027] The sealing body 17 is composed of a gasket 28 and a terminal cap 27. The terminal cap 27 is made of metal. The terminal cap 27 has a disk-shaped base 27a and a protrusion 27b, and the protrusion 27b includes, for example, a cylindrical protrusion. The base 27a of the terminal cap 27 may be connected to the upper surface of the base 19a of the upper current collector plate 19 via a strip-shaped lead 55. Welding can be used as a method for joining the lead 55 to the base 27a and the base 19a. For example, the terminal cap 27 and the upper current collector plate 19 are electrically connected by laser welding.

[0028] The exterior body 16 is generally made of a metal primarily composed of iron, such as a material obtained by plating iron with nickel. The exterior body 16 may also be made of a metal primarily composed of aluminum or the like. The exterior body 16 has a cylindrical portion 65 and a bottom plate portion 68. The cylindrical portion 65 includes an annular groove portion 36 and an annular shoulder portion 38. The groove portion 36 is formed by spinning a portion of the cylindrical portion 65 to recess it radially inward around the entire circumferential direction. The shoulder portion 38 is formed when the upper end portion of the cylindrical portion 65 is bent radially inward and crimped to the peripheral edge portion 48 of the sealing body 17, and extends radially inward at the upper end portion of the cylindrical portion 65.

[0029] The sealing body 17 is fixed to the exterior body 16 by crimping the peripheral edge 48 of the terminal cap 27 between the shoulder 38 and the groove 36 via the gasket 28. The gasket 28 serves as a sealing material to maintain airtightness inside the battery and as an insulating material to insulate the exterior body 16 from the sealing body 17. The gasket 28 is made of, for example, polyolefin. The groove 36 is formed at a position a predetermined distance from the upper end of the exterior body 16. The predetermined length is, for example, a length equivalent to 1 to 20% of the axial length of the exterior body 16. The gasket 28 is compressed by the shoulder 38. The gasket 28 has a protrusion 28a that protrudes radially inward from between the shoulder 38 and the sealing body 17.

[0030] A thin, easily breakable portion 69 is provided on the bottom plate portion 68. The easily breakable portion 69 is provided, for example, by stamping a circle or a C-shape on the underside of the bottom plate portion 68. When the battery 10 generates abnormal heat and the internal pressure of the battery 10 rises to a predetermined pressure, the easily breakable portion 69 breaks and gas is released from the bottom plate portion 68. This gas release prevents the internal pressure of the battery 10 from rising excessively, which could cause the battery 10 to explode, thereby increasing the safety of the battery 10.

[0031] The battery 10 further includes an annular metal plate 80 and an annular insulating plate 82 made of an insulating material. The metal plate 80 extends in a generally radial direction. The metal plate 80 is joined to the upper surface of the shoulder portion 38. The terminal cap 27, to which the positive electrode exposed portion 31 is electrically connected via the upper current collector plate 19, serves as a positive electrode terminal, and the metal plate 80, to which the negative electrode exposed portion 41 is electrically connected via the lower current collector plate 18 and the outer casing 16, serves as a negative electrode terminal. The metal plate 80 is electrically connected to a current collector plate (not shown) that connects multiple batteries 10 in series or parallel, for example, using a tongue portion (lead) of the current collector plate. This configuration allows multiple cylindrical batteries 10 to be easily electrically connected to the current collector plate.

[0032] The insulating plate 82 is interposed between the metal plate 80 and the sealing body 17 to insulate the metal plate 80 from the sealing body 17. The outer peripheral edge of the insulating plate 82 on the radially outer side may be located above the protruding portion 28a of the gasket 28 and may be in contact with the gasket 28. In this manner, the metal plate 80 is insulated from the sealing body 17 by the gasket 28 and the insulating plate 82. The periphery of the hollow portion of the insulating plate 82 includes a cylindrical portion 83 that covers the outer peripheral surface of the protruding portion 27b of the terminal cap 27. The cylindrical portion 83 is connected to the radially inner end of the plate-shaped base of the insulating plate 82. Note that the battery does not necessarily have to have a metal plate and an insulating plate.

[0033] "Configuration of the tip portion of the positive electrode" Fig. 2 is a diagram showing the configuration of the tip portion of the positive electrode 11. The positive electrode 11 includes a positive electrode core 30 and a positive electrode mixture layer 32 coated on both side surfaces thereof. The upper end side does not have the positive electrode mixture layer 32 formed thereon, forming a positive electrode exposed portion 31 where the positive electrode core 30 is exposed. In addition, a protective layer 33 is provided at a predetermined distance from the upper end of the positive electrode mixture layer 32 on the positive electrode exposed portion 31. This protective layer 33 is made of an insulating material, which is a water-insoluble polymer mixed with a filler. The inorganic filler may be alumina (aluminum oxide (Al ２ O ３ )), inorganic oxides such as silica, zirconia, and titania can be used. In addition, to prevent the protective layer 33 from melting during laser welding of the positive electrode core 30 and the upper current collector plate 19, it is preferable that the melting point of the protective layer 33 be higher than that of the positive electrode core 30. However, the protective layer 33 may not be necessary in the electricity storage device of the present disclosure.

[0034] A plurality of openings 35 are formed in the tip end portion of the positive electrode exposed portion 31 where the protective layer 33 is not formed. When a plurality of openings 35 are formed in this manner, the rigidity of that region decreases, making the positive electrode exposed portion 31 more likely to bend. Note that the openings may be formed not only in the positive electrode exposed portion 31 but also in the portion of the positive electrode core where the positive electrode mixture layer is formed.

[0035] In this example, the plurality of openings 35 are not formed dispersedly over the entire portion of the positive electrode exposed portion 31 that protrudes from the protective layer 33, but are formed only in one-third of the region in the width direction. This limits the region that is prone to bending to the region where the plurality of openings 35 are formed, making it possible to perform the desired bending formation. The plurality of openings 35 may be formed over the entire portion, or may be formed in a band shape only in the central region in the width direction.

[0036] 1, the tip of the positive electrode exposed portion 31 is pressed against the upper current collector plate 19 and bent inward in the radial direction of the electrode body. The bent tip of the positive electrode exposed portion 31 is then connected to the upper current collector plate 19 by laser welding. Note that the positive electrode exposed portion 31 may also be bent outward in the radial direction.

[0037] For this purpose, the wound electrode body 14 is bent. Fig. 3 is a diagram illustrating the bending process. In this manner, the jig 95 with the curved lower surface 95a is moved while being pressed against the tip of the positive electrode exposed portion 31. As a result, the portion of the positive electrode exposed portion 31 on which the protective layer 33 is formed that is pressed by the jig 95 is bent.

[0038] As described above, the positive electrode exposed portion 31 has a plurality of openings 35 provided discretely in a predetermined portion thereof, and the strength of that region is relatively small. For this reason, as shown in Fig. 3 , the positive electrode exposed portion 31 is bent in the direction of travel of the jig 95 around the region where the plurality of openings 35 are provided.

[0039] After the bending process, the upper current collector plate 19 is pressed against the tip of the bent positive electrode exposed portion 31, and a laser is irradiated onto the upper current collector plate 19 from above. As a result, the portion of the upper current collector plate 19 irradiated with the laser becomes hot and melts. The positive electrode exposed portion 31 in contact with the upper current collector plate 19 also melts, and the two are fused together and integrated.

[0040] According to the energy storage device (battery) of this embodiment, the tip of the positive electrode exposed portion 31 can be reliably bent, and the positive electrode exposed portion 31 and the upper current collecting plate 19 can be reliably joined, thereby providing a highly reliable energy storage device.

[0041] After the bending is completed, the upper current collecting plates 19 are pressed against the grooves 97 from above and laser-welded. Fig. 4 is a schematic diagram showing the state after the upper current collecting plates 19 have been laser-welded, as viewed from above. Four upper current collecting plates 19 are attached to the grooves 97.

[0042] "Configuration of Opening" Fig. 5 is a diagram illustrating the formation of the opening 35. The mold 96 has a flat portion 96a and a conical protrusion 96b that protrudes from the center of the flat portion 96a. By pressing such a mold 96 against the positive electrode exposed portion 31 of the positive electrode core 30, the protrusion 96b penetrates the positive electrode exposed portion 31, forming the opening 35. The inner peripheral edge of the opening 35 has a shape that corresponds to the flat portion 96a and the conical protrusion 96b (first protrusion, second protrusion), and the opening 35 is formed at the top of the protruding portion.

[0043] The mold 96 may include one flat portion 96a and one protruding portion 96b as shown in the figure, or may include multiple flat portions 96a and one protruding portion 96b. Furthermore, by pressing two molds 96 against the positive electrode exposed portion 31 from both sides to form an opening having a protruding portion (first protruding portion) protruding from a first surface of the positive electrode exposed portion 31 and a protruding portion (second protruding portion) protruding from a second surface opposite the first surface, the pressing forces of the two can be offset. Furthermore, by having the protruding portions protrude from both surfaces, it is possible to eliminate the need to distinguish between the front and back sides, making handling easier in subsequent processes.

[0044] In this way, the protrusion 96b of the mold 96 penetrates the positive electrode exposed portion 31 to form the opening 35. When the opening 35 is formed using such a mold, the opening 35 is formed by deformation of the periphery, and the generation of chips corresponding to the opening 35 can be suppressed.

[0045] For example, when the opening 35 is formed by hollowing out using a punching process or the like, chips are generated corresponding to the opening 35. Furthermore, when laser processing or the like is performed, spatters are scattered. In this embodiment, it is possible to avoid the adverse effects of such residues on the electrode body 14.

[0046] "Examples of openings" Figure 6 is a diagram showing various examples of openings 35. (a) shows an example in which the openings 35 are horizontally elongated holes. (a) shows an example in which the openings 35 are horizontally elongated holes. (b) shows an example in which the openings 35 are vertically elongated holes. (c) shows an example in which the openings 35 are cross-shaped holes. (d) shows an example in which openings 35 of different diameters are included. In this example, the diameters of the openings 35 on the base side are larger than those on the tip side. However, openings 35 of various diameters may be mixed randomly. (e) shows an example in which the openings 35 are arranged in a single row. (f) shows an example in which the openings 35 on the tip side are located on the edge, and the tip side of the openings 35 is open.

[0047] As described above, various modifications are possible for the opening 35. These modifications can also be combined as appropriate.

[0048] FIG. 7 is a diagram showing yet another example of the openings 35. In this example, the openings 35 are densely arranged on the inner circumferential side (toward the center of the electrode body 14) and the density of the openings 35 is lower on the outer circumferential side (outside the electrode body 14). Because the positive electrode exposed portion 31 tends to deform on the inner circumferential side of the electrode body 14, increasing the density of the openings 35 on the inner side of the winding makes it possible to equalize the ease of deformation between the inner circumferential side portion, which is particularly resistant to collapse, and the outer circumferential side portion of the positive electrode exposed portion 31. The density of the openings 35 may be varied continuously or in stages. Alternatively, openings may be provided only on the inner circumferential side of the positive electrode exposed portion 31, with no openings provided on the outer circumferential side.

[0049] 8 is a flowchart illustrating the manufacturing process of the positive electrode 11. First, a core foil (for example, a base material of the positive electrode core 30) is prepared (S11). It is preferably a roll of long metal foil, and its width is the same as the width of the target positive electrode core 30.

[0050] Next, a mixture layer (e.g., positive electrode mixture layer 32) is formed on the core foil, and a protective layer (protective layer 33) is also formed (S12). These are performed by applying a slurry and drying it, as described above. Then, the dried mixture layer (positive electrode mixture layer 32) and the like are compressed and molded (S13).

[0051] Thereafter, slits are formed in the long core foil, and the core foil is cut to the length used for one electrode body 14, and multiple openings 35 are formed at the same time as this cutting (S14). The formation of the slits and the formation of the openings 35 can be performed separately, but can also be performed simultaneously, which can prevent an increase in the number of steps.

[0052] In this way, a positive electrode or a negative electrode is formed for one electrode assembly 14. Then, the electrode assembly 14 is produced by stacking and winding up a separately produced negative electrode or positive electrode and a separator (S15).

[0053] "Others" In the above-described embodiment, a plurality of openings 35 is provided in the positive electrode exposed portion 31 of the positive electrode core 30 of the positive electrode 11. However, this can also be applied to the negative electrode 12 instead of the positive electrode 11. That is, a plurality of openings 35 can also be provided in the negative electrode exposed portion 41 of the negative electrode core 40 of the negative electrode 12. Furthermore, the above-described exposed portion may not be formed in one of the positive electrode 11 and the negative electrode 12, and this one electrode may be electrically connected to the sealing body or the outer can via a ribbon-shaped lead.

[0054] REFERENCE SIGNS LIST 10 battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 exterior body, 17 sealing body, 18 lower current collector plate, 18a base, 18b protruding portion, 18c bottom plate portion, 19 upper current collector plate, 19a base, 19b through hole, 27 terminal cap, 27a base, 27b protruding portion, 28 gasket, 28a protruding portion, 30 positive electrode core, 31 exposed portion, 31 positive electrode exposed portion, 32 positive electrode mixture layer, 33 protective layer, 35 opening, 36 groove portion, 37 spacer, 38 shoulder portion, 40 negative electrode core, 41 negative electrode exposed portion, 42 negative electrode mixture layer, 48 peripheral portion, 55 lead, 65 cylindrical portion, 68 bottom plate portion, 69 Easy-to-break portion, 80 metal plate, 82 insulating plate, 83 cylindrical portion, 95 jig, 95a lower surface, 96 mold, 96a flat portion, 96b protrusion portion, 97 groove portion

Claims

1. A power storage device comprising: an electrode body in which a first electrode and a second electrode are arranged with a separator therebetween; and an exterior body that houses the electrode body, wherein the first electrode has a tip portion that extends beyond an end portion of the second electrode in a first direction, the tip portion is connected to a first current collector after being bent, and a plurality of openings are formed in the tip portion.

2. The power storage device according to claim 1, wherein the first electrode, the second electrode, and the separator are each strip-shaped, and the electrode body is a wound electrode body in which the first electrode and the second electrode are wound with the separator therebetween.

3. The power storage device according to claim 1 or 2, wherein the first electrode has a strip-shaped first core body and a first mixture layer disposed on the first core body, the second electrode has a strip-shaped second core body and a second mixture layer disposed on the second core body, a first exposed portion in which the first mixture layer is not formed and the first core body is exposed is formed at the tip portion of the first electrode, the first current collector is joined to the first exposed portion, and the plurality of openings are formed in the first exposed portion of the first electrode.

4. The power storage device according to claim 1 or 2, further comprising a second current collector that is electrically connected to the second electrode, wherein the second electrode has a tip portion that extends beyond an end portion of the second electrode in a first direction, and the tip portion is connected to the first current collector.

5. The power storage device according to claim 1, wherein the plurality of openings are formed more in the inner peripheral side portion than in the outer peripheral side portion of the tip portion.

6. The power storage device according to claim 1, wherein a plurality of protrusions are formed on each inner peripheral edge of the plurality of openings, the plurality of protrusions include a first protrusion that protrudes from a first surface at the tip portion and a second protrusion that protrudes from a second surface located on the opposite side of the first surface at the tip portion, and the plurality of openings include an opening in which the first protrusion is formed and an opening in which the second protrusion is formed.

Images