Electrode body and cylindrical battery using same

Abstract

An electrode body 4 according to the present disclosure comprises a first electrode, a second electrode, and a separator disposed between the first electrode and the second electrode. At least one selected from the first electrode and the second electrode includes a strip-shaped current collector and a mixture layer disposed on the current collector. An end portion of the current collector in the width direction includes an exposed portion 162 on which the mixture layer is not disposed, and the exposed portion 162 includes a first weakened portion 31 provided along the longitudinal direction of the current collector so as to reduce the bending rigidity of the exposed portion 162, and is bent toward the central axis of the electrode body 4.

Description

Electrode Assembly and Cylindrical Battery Using the Same

[0001] The present disclosure relates to an electrode assembly and a cylindrical battery using the same.

[0002] In conventional cylindrical batteries, the current collector of an electrode is connected to a battery can or a sealing plate via a tab lead. On the other hand, as described in Patent Document 1, a structure is also known in which the current collector of an electrode is electrically connected to a battery can or a sealing plate without using a tab lead. Such a structure is often also referred to as "end face current collection".

[0003] Patent Document 1 describes a belt-shaped positive electrode foil or negative electrode foil having an uncoated portion where no active material is disposed. The uncoated portion of the positive electrode foil or negative electrode foil is bent toward the central axis of the wound structure and overlaps with each other. Thereby, a flat surface is formed, and a current collector plate is joined to the flat surface by laser welding.

[0004] Japanese Patent No. 7074263

[0005] As described in Patent Document 1, prior to the step of joining the current collector plate to the current collector, a step of bending the end portion of the current collector is performed so as to form a flat surface. At this time, it is difficult to control the bending position of the end portion of the current collector. If the bending position is not stable and there is large variation in the difference in height of the end portions after bending, the step of joining the current collector plate to the bent end portion is adversely affected.

[0006] The present disclosure provides a technique for controlling the bending position of an end portion of a current collector.

[0007] The present disclosure provides a wound electrode assembly comprising: a first electrode; a second electrode; and a separator disposed between the first electrode and the second electrode, wherein at least one selected from the first electrode and the second electrode comprises a belt-shaped current collector and a mixture layer disposed on the current collector, an end portion in the width direction of the current collector comprises an exposed portion where the mixture layer is not disposed, the exposed portion comprises a first weakened portion provided along the longitudinal direction of the current collector so as to reduce the bending rigidity of the exposed portion, and is bent toward the central axis of the electrode assembly.

[0008] According to the technology disclosed herein, the bending position of the end of the current collector can be controlled.

[0009] Figure 1 is a cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. Figure 2 is a plan view of the negative electrode. Figure 3A shows the process of bending the exposed portion of the negative electrode current collector toward the central axis. Figure 3B shows the process of bending the end of a conventional current collector that does not have a weakened portion. Figure 4 is another diagram showing the process of bending the exposed portion of the negative electrode current collector toward the central axis. Figure 5 is a bottom view of the electrode body showing the bent exposed portion. Figure 6 is a schematic diagram of the bent exposed portion viewed from the side of the electrode body. Figure 7 is a perspective view of the electrode body showing a current collector member joined to the exposed portion of the negative electrode current collector. Figure 8 is a plan view of the positive electrode.

[0010] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below.

[0011] (Embodiment) Figure 1 is a cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. The cylindrical battery 100 comprises a container 1 and an electrode body 4. The container 1 has a cylindrical shape. The electrode body 4 has a wound structure. The electrode body 4 is housed in the container 1. The electrode body 4 comprises a positive electrode 5, a negative electrode 6, and a pair of separators 7. The separators 7 are arranged between the positive electrode 5 and the negative electrode 6. The positive electrode 5 and the negative electrode 6 are wound around the separators 7. The electrode body 4 is impregnated with a non-aqueous electrolyte. The opening of the container 1 is sealed with a sealing plate 2. An insulating packing 3 is arranged around the sealing plate 2.

[0012] The electrode body 4 further includes current collectors 8 and 18. The current collector 8 is provided on the upper side of the electrode body 4 and is electrically connected to the positive electrode 5. The current collector 18 is provided on the lower side of the electrode body 4 and is electrically connected to the negative electrode 6.

[0013] The positive electrode 5 includes a positive electrode current collector 15 and a positive electrode composite layer 25. The positive electrode composite layer 25 is supported by the positive electrode current collector 15. The positive electrode 5 has a strip-like shape. The positive electrode current collector 15 also has a strip-like shape. The ends of the positive electrode current collector 15 in the width direction protrude from between the separators 7 and are bent toward the central axis O of the electrode body 4. A current collector member 8 is joined to the bent ends by welding or the like. The current collector member 8 is electrically connected to the sealing plate 2 via a tab lead 9. The current collector member 8 is, for example, a metal plate.

[0014] The negative electrode 6 includes a negative electrode current collector 16 and a negative electrode composite layer 26. The negative electrode composite layer 26 is supported by the negative electrode current collector 16. The negative electrode 6 has a strip-like shape. The negative electrode current collector 16 also has a strip-like shape. The ends of the negative electrode current collector 16 in the width direction protrude from between the separators 7 and are bent toward the central axis O of the electrode body 4. A current collector member 18 is joined to the bent ends by welding or the like. The current collector member 18 is further joined to the container 1. The current collector member 18 may be welded to the container 1. The current collector member 18 is, for example, a metal plate.

[0015] In this embodiment, the end of the positive electrode current collector 15 in the width direction is directly joined to the current collector member 8. Similarly, the end of the negative electrode current collector 16 in the width direction is directly joined to the current collector member 18. Such a structure is suitable for high-capacity and high-output batteries.

[0016] Figure 2 is a plan view of the negative electrode 6. The negative electrode current collector 16 includes a covered portion 161 and an exposed portion 162. The covered portion 161 is the portion on which the negative electrode composite layer 26 is arranged and is covered by the negative electrode composite layer 26. The exposed portion 162 is the end portion of the negative electrode current collector 16 in the width direction WD, and is the portion on which the negative electrode composite layer 26 is not arranged. As shown in Figure 1, the exposed portion 162 is bent toward the central axis O of the electrode body 4. The exposed portion 162 includes a first weakening portion 31 provided along the longitudinal direction LD of the negative electrode current collector 16 to reduce the bending rigidity of the exposed portion 162. The bending rigidity of the exposed portion 162 at the location where the first weakening portion 31 is provided is lower than the bending rigidity of other parts of the exposed portion 162.

[0017] In this embodiment, the first weakening portion 31 includes a plurality of through holes provided along the longitudinal direction LD of the negative electrode current collector 16. Preferably, the through holes include slits extending along the longitudinal direction LD of the negative electrode current collector 16. The longitudinal direction of the slits is parallel to the longitudinal direction LD of the negative electrode current collector 16. In this embodiment, the plurality of slits as the first weakening portion 31 are provided at predetermined intervals along the longitudinal direction LD of the negative electrode current collector 16. Through holes, in particular slits, can easily reduce the bending rigidity of the exposed portion 162.

[0018] The through-holes can be pre-formed in the negative electrode current collector 16 by processing methods such as laser cutting or roller cutting. If the first weakened portion 31 has a structure other than a through-hole, for example, a thin-walled portion, a line-shaped thin-walled portion can be pre-formed in the negative electrode current collector 16 by press working.

[0019] Figure 3A shows the process of bending the exposed portion 162 of the negative electrode current collector 16 toward the central axis O. After winding the positive electrode 5, negative electrode 6 and a pair of separators 7, the exposed portion 162 of the negative electrode current collector 16 is bent to form a flat welding surface. The current collector member 18 is welded to the welding surface by laser welding. This gives rise to the electrode body 4.

[0020] In detail, the exposed portion 162 of the negative electrode current collector 16 is bent by pressing the bending jig 49 against the exposed portion 162 of the negative electrode current collector 16 and moving it from the outer circumference of the electrode workpiece 14 toward the central axis O. In this embodiment, since the first weakening portion 31 is provided along the longitudinal direction LD of the negative electrode current collector 16, the exposed portion 162 is bent starting from the first weakening portion 31. In other words, the bending position of the exposed portion 162 of the negative electrode current collector 16 can be controlled to the position of the dashed line SL. By controlling the bending position, a flat welding surface with the same height is formed, making it easier for the bent exposed portion 162 and the current collector member 18 to come into contact. Therefore, the current collector member 18 can be welded to the exposed portion 162 without applying a large load to the current collector member 18. In addition, since the exposed portion 162 can be bent at the target position, damage to the negative electrode composite layer 26 can be prevented.

[0021] Figure 3B shows the process of bending the end of a conventional current collector that does not have a weakened section. With a conventional current collector that does not have a weakened section at the end, the bending position of the current collector by the bending jig 49 is unstable. As a result, the height of the end after bending is not uniform, and it is difficult to form a flat welding surface. In this case, a large gap tends to occur between the end of the current collector and the current collector member, making it difficult to weld the current collector member to the welding surface. In addition, if the current collector bends near the boundary between the covered part and the exposed part, there is a possibility that damage such as cracks will occur in the asphalt layer.

[0022] Here, even if the height of the ends of the current collector is not uniform, it seems that the contact between the end of the current collector and the current collector can be improved and the welding quality improved by applying a large load to the current collector when welding the current collector to the end of the current collector. However, if the load applied to the current collector during welding is too large, the asphalt layer will be damaged. Therefore, the load during welding should be limited. On the other hand, if the load is too small, the contact between the end of the current collector and the current collector deteriorates, and welding is performed with a gap between the two. As a result, the welding quality is unstable. Thus, there is a trade-off relationship between reducing the load during welding and stabilizing the welding quality. According to the technology disclosed herein, it is possible to achieve both a reduction in the load during welding and stabilization of the welding quality.

[0023] As shown in Figure 2, the exposed portion 162 further includes a second weakening portion 32 provided along the longitudinal direction LD of the negative electrode current collector 16 to reduce the bending rigidity of the exposed portion 162. The second weakening portion 32 is located outward in the width direction WD compared to the first weakening portion 31.

[0024] In this embodiment, the second weakening portion 32 includes a plurality of through holes provided along the longitudinal direction LD of the negative electrode current collector 16. Preferably, the through holes include slits extending along the longitudinal direction LD of the negative electrode current collector 16. The longitudinal direction of the slits is parallel to the longitudinal direction LD of the negative electrode current collector 16. In this embodiment, the plurality of slits as the second weakening portion 32 are provided at predetermined intervals along the longitudinal direction LD of the negative electrode current collector 16. Through holes, in particular slits, can easily reduce the bending rigidity of the exposed portion 162.

[0025] The effects obtained when a second weakening portion 32 is provided on the exposed portion 162 in addition to the first weakening portion 31 will be explained.

[0026] Figure 4 is another diagram showing the process of bending the exposed portion 162 of the negative electrode current collector 16 toward the central axis O. In the example shown in Figure 4, the exposed portion 162 is bent using two types of bending jigs 50 and bending jig 51. Multiple bending jigs 50 are arranged at equal angular intervals (for example, 90-degree intervals) along the circumferential direction of the electrode workpiece 14. Similarly, multiple bending jigs 51 are arranged at equal angular intervals (for example, 90-degree intervals) along the circumferential direction of the electrode body 4. The bending jigs 50 and bending jigs 51 are arranged alternately along the circumferential direction of the electrode workpiece 14. First, the multiple bending jigs 50 are moved toward the central axis O of the electrode workpiece 14 to bend the exposed portion 162 of the negative electrode current collector 16. Next, while holding the exposed portion 162 with the multiple bending jigs 50, the multiple bending jigs 51 are moved toward the central axis O of the electrode workpiece 14. At this time, there is a height difference between the bending position of the exposed portion 162 by the bending jig 50 and the bending position of the exposed portion 162 by the bending jig 51. The bending position of the exposed portion 162 by the bending jig 51 is slightly higher than the bending position of the exposed portion 162 by the bending jig 50. The exposed portion 162 is bent by the bending jig 50 starting from the first weakening portion 31. The exposed portion 162 is bent by the bending jig 51 starting from the second weakening portion 32. In other words, the distance between the first weakening portion 31 and the second weakening portion 32 corresponds to the difference in bending height Δh. The first weakening portion 31 and the second weakening portion 32 make it easy to create a difference in bending height Δh.

[0027] Figure 5 is a bottom view of the electrode workpiece 14 showing the bent exposed portion 162. Figure 6 is a schematic diagram of the bent exposed portion 162 as seen from the side of the electrode workpiece 14. Figure 7 is a perspective view of the electrode body 4 showing the current collector member 18 joined to the exposed portion 162 of the negative electrode current collector 16.

[0028] As shown in Figures 5 and 6, the height of the second portion 162b of the exposed portion 162, which is bent starting from the second weakened portion 32, exceeds the height of the first portion 162a, which is bent starting from the first weakened portion 31. A height difference Δh exists between the first portion 162a and the second portion 162b. Therefore, when a plate-shaped current collector 18 is placed on the bent exposed portion 162, the current collector 18 preferentially contacts the second portion 162b.

[0029] As shown in Figure 7, in this embodiment, the current collector 18 includes a plurality of radially extending portions 18a. The position of each of the radially extending portions 18a is aligned with the position of the second portion 162b of the bent exposed portion 162. Therefore, when the current collector 18 is placed on the electrode workpiece 14, the current collector 18 easily comes into contact with the second portion 162b of the exposed portion 162. As a result, a gap is less likely to occur between the current collector 18 and the exposed portion 162, making it easier to weld (for example, laser weld) the current collector 18 to the exposed portion 162.

[0030] In this embodiment, the first weakening portion 31 includes a plurality of first slits provided along the longitudinal direction LD of the negative electrode current collector 16. The second weakening portion 32 includes a plurality of second slits provided along the longitudinal direction LD of the negative electrode current collector 16. The plurality of first slits and the plurality of second slits are arranged in a staggered pattern. With this configuration, as described above, it is easy to create a difference in bending height.

[0031] The technique described with reference to Figures 2 to 7 for the negative electrode current collector 16 can also be applied to the positive electrode 5.

[0032] Figure 8 is a plan view of the positive electrode 5. The positive electrode current collector 15 includes a covered portion 151 and an exposed portion 152. The covered portion 151 is the portion on which the positive electrode composite layer 25 is arranged and is covered by the positive electrode composite layer 25. The exposed portion 152 is the end portion of the positive electrode current collector 15 in the width direction WD, and is the portion on which the positive electrode composite layer 25 is not arranged. As shown in Figure 1, the exposed portion 152 is bent toward the central axis O of the electrode body 4. The exposed portion 152 includes a first weakening portion 33 provided along the longitudinal direction LD of the positive electrode current collector 15 to reduce the bending stiffness of the exposed portion 152. The bending stiffness of the exposed portion 152 at the location where the first weakening portion 33 is provided is lower than the bending stiffness of the other parts of the exposed portion 152.

[0033] As shown in Figure 8, the exposed portion 152 may further include a second weakening portion 34 provided along the longitudinal direction LD of the positive electrode current collector 15 to reduce the bending rigidity of the exposed portion 152. The second weakening portion 34 is located outward in the width direction WD compared to the first weakening portion 33.

[0034] (Modification) The spacing between adjacent slits may vary in the circumferential direction of the electrode body 4. That is, the spacing between adjacent slits on the inner circumference of the electrode body 4 may be different from the spacing between adjacent slits on the outer circumference of the electrode body 4. The spacing between adjacent slits refers to the length of the positive electrode 5 or negative electrode 6 in the longitudinal direction LD.

[0035] The length of the slit may vary in the circumferential direction of the electrode body 4. That is, the length of the slit on the inner circumference of the electrode body 4 may differ from the length of the slit on the outer circumference of the electrode body 4. The length of the slit refers to the length in the longitudinal direction LD of the positive electrode 5 or the negative electrode 6.

[0036] The following describes the other components of the cylindrical battery 100.

[0037] In this embodiment, the container 1 has negative polarity and the sealing plate 2 has positive polarity. However, the container 1 may have positive polarity and the sealing plate 2 may have negative polarity.

[0038] As the positive electrode current collector 15, a sheet or film made of a metallic material such as aluminum, aluminum alloy, stainless steel, titanium, or titanium alloy may be used. The sheet or film may be porous or non-porous. As the sheet or film, metal foil or metal mesh may be used. A carbon material may be coated on the surface of the positive electrode current collector 15 as a conductive auxiliary material.

[0039] The positive electrode composite layer 25 contains a positive electrode active material. The positive electrode active material may be a material that has the ability to intercept and release lithium ions. As the positive electrode active material, lithium-containing transition metal oxides, lithium-containing transition metal phosphates, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, transition metal oxynitrides, etc., can be used. In particular, when lithium-containing transition metal oxides or lithium-containing transition metal phosphates are used as the positive electrode active material, the manufacturing cost of the battery can be reduced and the average discharge voltage can be increased. Examples of lithium-containing transition metal oxides include lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium nickel manganese oxide. Examples of lithium-containing transition metal phosphates include lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, and lithium nickel phosphate. One or more combinations of these positive electrode active materials can be used.

[0040] The positive electrode composite layer 25 may contain other materials such as conductive materials and binders.

[0041] Conductive materials are used to reduce the resistance of the positive electrode 5. Examples of conductive materials include carbon materials and conductive polymer compounds. Examples of carbon materials include carbon black, graphite, fibrous carbon materials, graphene, fullerene, and graphite oxide. Examples of carbon black include acetylene black. Examples of fibrous carbon materials include carbon nanotubes and carbon nanofibers. Examples of conductive polymer compounds include polyaniline, polypyrrole, and polythiophene. One or more combinations of these conductive materials can be used.

[0042] A binder is used to improve the bonding properties of the materials constituting the positive electrode 5. Examples of binders include polymer materials such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, styrene-butadiene copolymer rubber, polypropylene, polyethylene, and polyimide. One or more combinations of these binders may be used.

[0043] As the negative electrode current collector 16, a sheet or film made of a metallic material such as stainless steel, nickel, nickel alloy, copper, or copper alloy may be used. The sheet or film may be porous or non-porous. As the sheet or film, metal foil or metal mesh may be used. A carbon material may be coated on the surface of the negative electrode current collector 16 as a conductive auxiliary material.

[0044] The negative electrode composite layer 26 contains a negative electrode active material. The negative electrode active material may be a material having the ability to intercept and release lithium ions. The negative electrode active material includes, for example, at least one selected from the group consisting of carbon materials and materials capable of forming alloys with lithium. Examples of carbon materials include graphite. Examples of materials capable of forming alloys with lithium include silicon, silicon-containing oxides, tin, zinc alloys, bismuth, and germanium. One or more combinations of these negative electrode active materials may be used.

[0045] The negative electrode mixture layer 26 may contain other materials such as a conductive material and a binder. As the conductive material and the binder, materials usable for the positive electrode mixture layer 25 can also be used for the negative electrode mixture layer 26.

[0046] The electrolytic solution is a non-aqueous electrolyte with which the positive electrode 5, the negative electrode 6, and the separator 7 are impregnated. The electrolytic solution may fill the internal space of the container 1. Lithium ions can travel back and forth between the positive electrode 5 and the negative electrode 6 by the action of the electrolytic solution.

[0047] The electrolytic solution contains a non-aqueous solvent and a lithium salt.

[0048] Examples of the non-aqueous solvent include cyclic carbonic acid esters, chain carbonic acid esters, cyclic ethers, chain ethers, nitriles, and amides. One solvent selected from these solvents may be used, or two or more thereof may be used in combination.

[0049] Examples of the lithium salt include lithium hexafluorophosphate (LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate (LiClO₄), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(perfluoroethylsulfonyl)imide (LiN(SO₂C₂F₅)₂), LiAsF₆, LiCF₃SO₃, and lithium difluoro(oxalato)borate. One or a combination of two or more selected from these lithium salts can be used.

[0050] The separator 7 is lithium ion conductive. The material of the separator 7 is not particularly limited as long as the passage of lithium ions is permitted. The material of the separator 7 may be at least one selected from the group consisting of gel electrolytes, ion exchange resin membranes, semipermeable membranes, and porous membranes. If the separator 7 is made of these materials, the safety of the cylindrical battery 100 can be sufficiently ensured. Examples of gel electrolytes include gel electrolytes containing fluororesins such as PVDF. Examples of ion exchange resin membranes include cation exchange membranes and anion exchange membranes. Examples of porous membranes include porous membranes made of polyolefin resin and porous membranes containing glass paper obtained by weaving glass fibers into a nonwoven fabric.

[0051] (Other Embodiments) (Note) The above description of embodiments discloses the following technologies.

[0052] (Technical 1) An electrode body that is wound up, comprising: a first electrode; a second electrode; and a separator disposed between the first electrode and the second electrode, wherein at least one selected from the first electrode and the second electrode includes a strip-shaped current collector and an asphalt layer disposed on the current collector, the end of the current collector in the width direction includes an exposed portion where the asphalt layer is not disposed, the exposed portion includes a first weakening portion provided along the longitudinal direction of the current collector to reduce the bending rigidity of the exposed portion, and is bent toward the central axis of the electrode body.

[0053] According to the technology disclosed herein, the bending position of the end of the current collector can be controlled.

[0054] (Technology 2) The electrode body according to Technology 1, further comprising a current collector member joined to the exposed portion. Such a structure is suitable for high-capacity and high-output batteries.

[0055] (Technology 3) The electrode body according to Technology 1 or 2, wherein the first weakening portion includes a plurality of through holes provided along the longitudinal direction of the current collector. The through holes make it easy to reduce the bending rigidity of the exposed portion.

[0056] (Technical 4) The electrode body according to Technical 3, wherein the through hole includes a slit extending in the longitudinal direction of the current collector. The slit makes it easy to reduce the bending rigidity of the exposed portion.

[0057] (Technical 5) The electrode body according to any one of Technical 1 to 4, wherein the exposed portion further includes a second weakening portion provided along the longitudinal direction of the current collector so as to reduce the bending rigidity of the exposed portion, and the second weakening portion is located outward in the width direction from the first weakening portion. The first weakening portion and the second weakening portion make it easy to create a difference in bending height.

[0058] (Technical 6) The electrode body according to Technical 5, wherein the second weakening portion includes a plurality of through holes provided along the longitudinal direction of the current collector. The through holes make it easy to reduce the bending rigidity of the exposed portion.

[0059] (Technical 7) The electrode body according to Technical 6, wherein the through hole includes a slit extending in the longitudinal direction of the current collector. The slit makes it easy to reduce the bending rigidity of the exposed portion.

[0060] (Technical 8) The electrode body according to any one of Technical 5 to 7, wherein the first weakening portion includes a plurality of first slits provided along the longitudinal direction of the current collector, and the second weakening portion includes a plurality of second slits provided along the longitudinal direction of the current collector, and the plurality of first slits and the plurality of second slits are arranged in a staggered pattern. With such a configuration, it is easy to create a difference in bending height.

[0061] (Technical 9) A cylindrical battery comprising: a cylindrical container; and an electrode body according to any one of Technical 1 to 8 disposed inside the container.

[0062] The technology disclosed herein can be applied to non-aqueous electrolyte secondary batteries such as lithium secondary batteries, sodium secondary batteries, and magnesium secondary batteries.

Claims

1. An electrode body that is wound up, comprising: a first electrode; a second electrode; and a separator disposed between the first electrode and the second electrode, wherein at least one selected from the first electrode and the second electrode includes a strip-shaped current collector and an asphalt layer disposed on the current collector, the end of the current collector in the width direction includes an exposed portion where the asphalt layer is not disposed, the exposed portion includes a first weakening portion provided along the longitudinal direction of the current collector to reduce the bending rigidity of the exposed portion, and is bent toward the central axis of the electrode body.

2. The electrode body according to claim 1, further comprising a current collector member joined to the exposed portion.

3. The electrode body according to claim 1, wherein the first weakening portion includes a plurality of through holes provided along the longitudinal direction of the current collector.

4. The electrode body according to claim 3, wherein the through hole includes a slit extending in the longitudinal direction of the current collector.

5. The electrode body according to claim 1, wherein the exposed portion further includes a second weakening portion provided along the longitudinal direction of the current collector to reduce the bending rigidity of the exposed portion, and the second weakening portion is located outward in the width direction from the first weakening portion.

6. The electrode body according to claim 5, wherein the second weakening portion includes a plurality of through holes provided along the longitudinal direction of the current collector.

7. The electrode body according to claim 6, wherein the through hole includes a slit extending in the longitudinal direction of the current collector.

8. The electrode body according to claim 5, wherein the first weakening portion includes a plurality of first slits provided along the longitudinal direction of the current collector, and the second weakening portion includes a plurality of second slits provided along the longitudinal direction of the current collector, and the plurality of first slits and the plurality of second slits are arranged in a staggered pattern.

9. A cylindrical battery comprising a cylindrical container and an electrode body according to claim 1 disposed inside the container.

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