Cylindrical battery

Abstract

This cylindrical battery comprises: an electrode body (10); an outer can (20) that has a bottomed cylindrical shape and accommodates the electrode body (10) and an electrolyte solution; and a sealing body (30) that closes the opening in the outer can (20). The cylindrical battery includes a positive electrode lead (11) that is connected to a positive electrode constituting the electrode body (10). The cylindrical battery further comprises: a positive electrode current collector plate (40) that is formed in an annular shape, has the positive electrode lead (11) connected thereto, and is welded to the outer can (20); and a gasket (50) that is arranged between the outer can (20) and the sealing body (30) and covers the lower surface of the positive electrode current collector plate (40), which faces the direction of the electrode body (10). The gasket (50) has an inner peripheral wall section (51) that covers an inner peripheral surface (44) forming the peripheral edge of an opening (41) in the positive electrode current collector plate (40).

Description

Cylindrical battery

[0001] The present disclosure relates to cylindrical batteries.

[0002] A cylindrical battery generally includes a wound electrode assembly in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, a cylindrical outer can with a bottom that houses the electrode assembly, and a sealing body that closes the opening of the outer can, with leads extending from the electrode assembly connected to the sealing body (see, for example, Patent Document 1).The cylindrical battery in Patent Document 1 also includes an annular current collecting member to which the leads are connected and which is welded to the sealing body, and a gasket that is placed between the outer can and the sealing body.

[0003] International Publication No. WO2022 / 270432

[0004] However, as a result of investigations by the present inventors, it was found that poor welding occurs due to electrolyte adhering to the current collecting member. If electrolyte is present at the welded portion when welding the sealing member and the current collecting member, the vaporized electrolyte can cause poor welding.

[0005] The cylindrical battery according to the present disclosure is a cylindrical battery comprising an electrode body, a cylindrical outer can with a bottom that houses the electrode body and an electrolyte, and a sealing body that closes the opening of the outer can, and including leads connected to the electrodes that constitute the electrode body, and further comprising: an annular current collecting member to which the leads are connected and which is welded to the sealing body; and a gasket that is disposed between the outer can and the sealing body and covers the underside of the current collecting member that faces toward the electrode body, and the gasket has an inner wall portion that covers the inner surface that forms the periphery of the opening of the current collecting member.

[0006] In the cylindrical battery according to the present disclosure, the sealing body and the current collecting member are welded in a good state.

[0007] 1 is a cross-sectional view of a cylindrical battery according to an embodiment; FIG. 2 is an enlarged view of part A in FIG. 1; FIG. 3 is a diagram showing a process of injecting an electrolyte solution into an outer can of a cylindrical battery according to an embodiment (the positive electrode lead and insulating plate are not shown); and FIG. 4 is a diagram showing a modified example of a gasket.

[0008] Hereinafter, an example of an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. Note that configurations formed by selectively combining the components of the multiple embodiments and variations described below are included within the scope of the present disclosure.

[0009] FIG. 1 is a cross-sectional view of a cylindrical battery 1 according to an embodiment. As shown in FIG. 1 , the cylindrical battery 1 includes an electrode assembly 10, a cylindrical outer can 20 with a bottom that houses the electrode assembly 10 and an electrolyte, and a sealing member 30 that closes the opening of the outer can 20. The electrode assembly 10 includes a positive electrode, a negative electrode, and a separator, and has a wound structure in which the positive electrode and negative electrode are spirally wound with the separator interposed therebetween. While the electrolyte may be an aqueous electrolyte, a nonaqueous electrolyte is used in this embodiment. The outer can 20 has a groove 23 formed in its sidewall 21, and the sealing member 30 is supported by the groove 23 and closes the opening of the outer can 20. For ease of explanation, the sealing member 30 side of the cylindrical battery 1 is referred to as the top, and the can bottom 22 side of the outer can 20 is referred to as the bottom.

[0010] The cylindrical battery 1 further includes a positive current collector plate 40, which is an annular current collecting member to which the positive lead 11 is connected and which is welded to the sealing body 30, and a gasket 50 that is disposed between the outer can 20 and the sealing body 30 and covers the underside of the positive current collector plate 40 facing toward the electrode body 10. The cylindrical battery 1 also includes an insulating plate 60 that is disposed between the electrode body 10, the grooved portion 23, and the positive current collector plate 40. The insulating plate 60 prevents the positive electrode and positive lead 11 from contacting the outer can 20 and also prevents the positive lead 11 from contacting the negative electrode of the electrode body 10. The cylindrical battery 1 may also include a lower insulating plate that is disposed between the electrode body 10 and the can bottom 22.

[0011] As will be described in detail later, the gasket 50 has an inner peripheral wall 52 that covers the inner peripheral surface that forms the periphery of the opening 43 of the positive current collector plate 40. The cylindrical battery 1 is manufactured by accommodating the electrode assembly 10 and the positive current collector plate 40 in the outer can 20, pouring an electrolyte solution into the can 20, and then welding the sealing body 30 and the positive current collector plate 40 together. The gasket 50, which has the inner peripheral wall 52, prevents the electrolyte solution from coming into contact with the positive current collector plate 40. During the manufacturing process of the cylindrical battery 1, the electrolyte solution is poured so as not to exceed the upper end of the inner peripheral wall 52. In this embodiment, the positive current collector plate 40 to which the positive lead 11 is connected is exemplified as the current collecting member, but the current collecting member may also be a negative current collecting member to which a negative lead is connected.

[0012] As described above, the electrode assembly 10 has a wound structure in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween. The positive electrode, negative electrode, and separator are all strip-shaped, long bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 10. The negative electrode is formed to be slightly larger than the positive electrode in order to prevent lithium deposition. That is, the negative electrode is formed to be longer in the longitudinal direction and width direction (short direction) than the positive electrode. The separator is formed to be at least slightly larger than the positive electrode, and for example, two separators are arranged to sandwich the positive electrode.

[0013] The electrode body 10 has a positive electrode lead 11 connected to the positive electrode by welding or the like, and a negative electrode lead connected to the negative electrode by welding or the like. The positive electrode lead 11 electrically connects the positive electrode and the sealing body 30 via the positive electrode current collector plate 40. The positive electrode lead 11 extends from the upper end of the electrode body 10, passes through the insulating plate 60, the gasket 50, and each opening of the positive electrode current collector plate 40, and is welded to the upper surface of the positive electrode current collector plate 40 facing the sealing body 30. The negative electrode lead electrically connects the negative electrode and the outer can 20. Therefore, the sealing body 30 functions as a positive electrode external terminal, and the outer can 20 functions as a negative electrode external terminal.

[0014] The positive electrode has a positive electrode core and a positive electrode mixture layer disposed on the positive electrode core. The positive electrode core can be made of a foil of a metal stable within the potential range of the positive electrode, such as aluminum, an aluminum alloy, stainless steel, or titanium, or a film with such a metal disposed on the surface. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder, and is preferably provided on both sides of the positive electrode core except for the portion to which the positive electrode lead 11 is connected. The positive electrode active material is a lithium transition metal composite oxide containing a transition metal element such as Ni, Co, or Mn.

[0015] The positive electrode lead 11 is a rectangular conductive member made of, for example, a metal primarily composed of aluminum. In this embodiment, multiple positive electrode leads 11 are connected to the positive electrode. One longitudinal end of each positive electrode lead 11 is welded to the positive electrode, and the other longitudinal end is welded to the positive electrode current collector plate 40. The cylindrical battery 1 has a simple current collection structure in which the positive electrode and the positive electrode current collector plate 40 are directly connected by the positive electrode lead 11, and has excellent output characteristics. The positive electrode has multiple core exposed portions spaced apart in the longitudinal direction of the positive electrode, where no positive electrode mixture layer is present on the positive electrode core and the surface of the positive electrode core is exposed. One positive electrode lead 11 is connected to each exposed portion by welding or the like.

[0016] The spacing between each exposed portion to which the positive electrode lead 11 is welded may be constant or may vary, but for example, the layout of the positive electrode lead 11 is set appropriately depending on the battery performance such as the capacity and output characteristics of the cylindrical battery 1. Therefore, the spacing between each exposed portion of the core is determined depending on the layout, etc. The number of cylindrical batteries 1 may be one, but for large batteries, it is preferable to have multiple batteries, and may be, for example, 3 to 15 or 6 to 10.

[0017] The negative electrode has a negative electrode core and a negative electrode mixture layer disposed on the negative electrode core. The negative electrode core can be made of a foil of a metal stable within the potential range of the negative electrode, such as copper, copper alloy, stainless steel, nickel, or nickel alloy, or a film with such a metal disposed on its surface. The negative electrode mixture layer contains a negative electrode active material and a binder, and is preferably provided on both sides of the negative electrode core except for the portion where the negative electrode lead is connected. The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. The negative electrode active material may also use an element that alloys with Li, such as Si or Sn, or a material containing such an element. It is also possible to electrically connect the negative electrode core and the outer can 20 without using a negative electrode lead.

[0018] The separator is a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator include polyolefins such as polyethylene and polypropylene, and cellulose. The separator may have a single-layer structure or a multi-layer structure. The separator may have, for example, a multi-layer structure including a thermoplastic resin layer such as polyolefin and a cellulose fiber layer, a two-layer structure of polyethylene (PE) / polypropylene (PP), or a three-layer structure of PE / PP / PE.

[0019] The non-aqueous electrolyte contained in the exterior can 20 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. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms in these solvents are substituted with halogen atoms such as fluorine. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and mixed solvents thereof. Examples of the electrolyte salt include LiPF ６ Lithium salts such as

[0020] The outer can 20 is a cylindrical metal container with a bottom and an open axial end (top end), and has a cylindrical side wall 21 and a can bottom 22 that is circular in bottom view. The outer can 20 is generally made of a metal primarily containing iron, but may also be made of a metal primarily containing aluminum or the like. The outer can 20 also has a grooved portion 23 formed along the circumferential direction of the side wall 21. The grooved portion 23 is formed near the opening of the outer can 20, at a position a predetermined length away from the top end of the outer can 20. The predetermined length is, for example, a length equivalent to 1% to 20% of the axial length of the outer can 20.

[0021] In this embodiment, the can bottom 22 of the exterior can 20 is provided with a safety valve mechanism that activates in the event of an abnormality in the cylindrical battery 1. On the other hand, the sealing body 30 is not provided with a safety valve mechanism. For example, a thin-walled portion is formed in the can bottom 22. When an abnormality occurs in the cylindrical battery 1 and the internal pressure rises, this thin-walled portion breaks first, forming a gas outlet in the can bottom 22.

[0022] The grooved portion 23 is a portion of the side wall 21 that protrudes inwardly from the exterior can 20, and is formed, for example, by spinning the side wall 21 from the outside. At the position where the grooved portion 23 is formed, the exterior can 20 is reduced in diameter, and a thin groove is formed in the outer circumferential surface of the side wall 21. The grooved portion 23 preferably has a substantially U-shaped cross section and is formed in an annular shape over the entire circumferential length of the side wall 21. The grooved portion 23 is formed by processing the side wall 21 after the electrode body 10 is housed in the exterior can 20.

[0023] The sealing body 30 is a disk-shaped metal member. The sealing body 30 has a shape in which the radial center portion protrudes outward from the cylindrical battery 1. Wiring material is connected to the sealing body 30 when the cylindrical batteries 1 are modularized to form a battery pack. For this reason, the sealing body 30 functions as the positive electrode external terminal of the cylindrical battery 1 and is also called an external terminal or top cover. The sealing body 30 is placed on the grooved portion 23 of the outer can 20 via a gasket 50 and is fixed to the upper end of the outer can 20. The upper end of the outer can 20 is bent inward and crimped against the sealing body 30.

[0024] The positive electrode current collector 40 is a metal member having a diameter approximately the same as that of the sealing body 30, and is disposed closer to the electrode body 10 than the sealing body 30. The positive electrode current collector 40 has an opening 43 in the radial center and is formed in an annular shape. The positive electrode lead 11 is welded to the inner peripheral portion of the positive electrode current collector 40, and the sealing body 30 is welded to the outer peripheral portion thereof. As will be described in detail later, the positive electrode lead 11 is welded to the positive electrode current collector 40 before the electrolyte is poured into the outer can 20, and the sealing body 30 is welded after the electrolyte is poured.

[0025] The gasket 50 is a resin member that prevents contact between the outer can 20 and the sealing body 30 and the positive current collector plate 40, thereby ensuring insulation between the positive and negative electrodes. The gasket 50 is interposed between the outer can 20 and the sealing body 30 and the positive current collector plate 40, and covers the bottom surface and inner peripheral surface of the positive current collector plate 40. The gasket 50 also seals the gap between the outer can 20 and the sealing body 30, sealing the interior of the cylindrical battery 1. The gasket 50 is formed in an annular shape and has an opening 51 in its radial center that vertically overlaps with the opening 43 in the positive current collector plate 40.

[0026] The configuration of the positive electrode current collector plate 40 and the gasket 50 will be described in detail below with reference to Fig. 2. Fig. 2 is an enlarged view of part A in Fig. 1 .

[0027] As shown in FIG. 2 , the positive electrode current collector 40 is bent toward the sealing body 30 at a position radially outwardly spaced from the periphery of the opening 43. The positive electrode current collector 40 includes a first region 41 located radially outward from the bent portion and a second region 42 located radially inward from the bent portion and one step lower than the first region 41. The first region 41 is in contact with the sealing body 30, and a portion of the first region 41 is welded to the sealing body 30. The upper surface of the second region 42 is located closer to the electrode body 10 than the upper surface of the first region 41, and a gap exists between the second region 42 and the sealing body 30. The first region 41 and the second region 42 are formed, for example, in an annular shape with a constant width along the circumferential direction and flat along the radial direction.

[0028] The positive current collector 40 is a conductive member having an opening 43 and an annular step that forms the boundary between the first region 41 and the second region 42. The thickness of the positive current collector 40 is, for example, 0.3 mm to 1.0 mm, or 0.4 mm to 0.8 mm, and is substantially constant throughout the first region 41 and the second region 42. The step of the positive current collector 40 may be formed to be higher than the thickness of the current collector. The difference in height between the top surfaces of the first region 41 and the second region 42 (the height of the step) is, for example, 0.8 mm to 1.5 mm.

[0029] The opening 43 in the positive current collector plate 40 is a through-hole for passing the positive electrode lead 11 and the electrolyte. The opening 43 is formed, for example, in a substantially circular shape in a plan view, but the shape is not particularly limited. The multiple positive electrode leads 11 pass through the openings 43 and 51 in the positive current collector plate 40 and the gasket 50, wrap around to the upper surface of the positive current collector plate 40, and are welded to the upper surface of the second region 42. The welded portion with the sealing body 30 formed in the first region 41 may be formed, for example, in a continuous annular shape, or may be formed intermittently in multiple portions on the same circumference.

[0030] The inner peripheral surface 44 of the positive current collector plate 40 that forms the periphery of the opening 43 is, for example, a surface along the thickness direction (vertical direction) of the current collector plate, but may be gently curved or inclined with respect to the vertical direction. In this embodiment, the inner peripheral surface 44 is a surface that is approximately perpendicular to the upper and lower surfaces of the positive current collector plate 40. The height (length along the vertical direction) of the inner peripheral surface 44 corresponds to the thickness of the second region 42.

[0031] In the cylindrical battery 1, the lower surface and inner peripheral surface 44 of the positive current collector 40 are covered with a gasket 50. In the manufacturing process of the cylindrical battery 1, as described above, the electrode assembly 10 and the positive current collector 40 are housed in the outer can 20, and then an electrolyte is poured into the can. If the electrolyte comes into contact with the positive current collector 40, capillary action can cause the electrolyte to creep up to the first region 41, which is the welded portion with the sealing body 30, potentially resulting in a welding defect. However, the gasket 50 covering the lower surface and inner peripheral surface 44 of the positive current collector 40 prevents the current collector from becoming wet with the electrolyte. As a result, welding defects between the sealing body 30 and the positive current collector 40 due to the electrolyte are prevented.

[0032] A portion of the gasket 50 is inserted into the opening 43 from below to cover the inner circumferential surface 44. The gasket 50 has an opening 51 for passing the positive electrode lead 11 and the electrolyte, and an inner circumferential wall portion 52 that covers the inner circumferential surface 44 of the positive electrode current collector 40. The inner circumferential wall portion 52 is a wall that stands on the periphery of the opening 51 and prevents the positive electrode current collector 40 from becoming wet with the electrolyte. In the electrolyte injection step, for example, the electrolyte is injected to a height that exceeds the lower surface of the positive electrode current collector 40. At this time, it is preferable that the electrolyte is injected so as not to exceed the upper end of the inner circumferential wall portion 52 (see FIG. 3 described below).

[0033] The gasket 50 covers the entire lower surface of the positive current collector plate 40. The gasket 50 does not have any openings that expose the lower surface of the positive current collector plate 40. The only opening formed in the gasket 50 is an opening 51 in the radial center, and there are no gaps through which the electrolyte can penetrate on the lower surface of the gasket 50 facing the electrode body 10. In this embodiment, a bent portion is also formed on the lower surface of the gasket 50 corresponding to the bent portion formed on the positive current collector plate 40. The bent portion of the gasket 50 bends in the thickness direction, forming a step on the lower surface of the gasket 50.

[0034] The outer peripheral edge of gasket 50 wraps around the upper surface of sealing body 30 and is pressed down from above by the upper end of crimped outer can 20. Gasket 50 covers the peripheral edge of the upper surface of sealing body 30, the outer peripheral surfaces and lower surfaces of sealing body 30 and positive current collector plate 40, and is attached across inner peripheral surface 44 of positive current collector plate 40.

[0035] The gasket 50 is made of a resin material that has excellent chemical resistance (electrolyte resistance). One example of a suitable material for the gasket 50 is polypropylene. The thickness of the gasket 50 is not particularly limited, but is, for example, 0.3 mm to 1.0 mm at the portion covering the lower surface of the positive electrode current collector plate 40 and at the inner peripheral wall portion 52.

[0036] The inner circumferential wall portion 52 is formed in an annular shape along the inner circumferential surface 44 of the positive current collector plate 40. In other words, the inner circumferential wall portion 52 is formed in an annular shape along the periphery of the opening 51. The inner circumferential wall portion 52 is, for example, a standing wall formed perpendicular to the upper surface of the gasket 50 that faces the lower surface of the positive current collector plate 40. The height H1 of the inner circumferential wall portion 52 may vary along the circumferential direction, but in this embodiment, it is constant along the circumferential direction. Note that the height H1 of the inner circumferential wall portion 52 refers to the length in the vertical direction from the upper surface of the gasket 50 to the upper end of the inner circumferential wall portion 52.

[0037] The inner circumferential wall portion 52 is preferably formed to cover 50% or more of the height of the inner circumferential surface 44 of the positive current collector plate 40 and to have a height that does not exceed the upper end of the inner circumferential surface 44. By making the upper end position of the inner circumferential wall portion 52 lower than the upper surface of the second region 42 of the positive current collector plate 40, welding of the positive electrode lead 11 to the upper surface of the second region 42 becomes easier. In the example shown in FIG. 2 , the upper surface of the gasket 50 contacts the lower surface of the positive current collector plate 40, but a small gap may exist between the two surfaces. If a gap exists between the upper surface of the gasket 50 and the lower surface of the second region 42 of the positive current collector plate 40, the inner circumferential wall portion 52 preferably has a height that is at least equivalent to 50% of the height of the inner circumferential surface 44 plus the height corresponding to the gap.

[0038] The inner circumferential wall portion 52 is formed high without exceeding the upper end of the inner circumferential surface 44. The inner circumferential wall portion 52 is formed to a height that covers, for example, 60% or more, 70% or more, or 80% or more of the height of the inner circumferential surface 44. When the upper surface of the gasket 50 contacts the lower surface of the second region 42 of the positive electrode current collector plate 40, the height H1 of the inner circumferential wall portion 52 is preferably 50% or more of the height of the inner circumferential surface 44, and may be 60% or more, 70% or more, or 80% or more. Note that, because the height of the inner circumferential surface 44 is the same as the thickness of the second region 42, this can be rephrased as saying that the height H1 of the inner circumferential wall portion 52 is preferably 50% or more of the thickness of the second region 42.

[0039] The inner peripheral wall portion 52 may be formed in an annular shape along the inner peripheral surface 44 of the positive current collector plate 40 and may cover substantially the entire inner peripheral surface 44. In the example shown in Fig. 2, the upper surface of the second region 42 of the positive current collector plate 40 and the upper end surface of the inner peripheral wall portion 52 are flush with each other, and the annular inner peripheral wall portion 52 covers the entire inner peripheral surface 44. The positive current collector plate 40 is, for example, assembled to the gasket 50 and placed on the grooved portion 23 of the outer can 20. The inner peripheral wall portion 52 may be joined to the inner peripheral surface 44 of the positive current collector plate 40.

[0040] Hereinafter, a method for manufacturing the cylindrical battery 1 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the electrolyte injection step, and for clarity of the drawing, the positive electrode lead 11 and the insulating plate 60 are omitted from the illustration.

[0041] The cylindrical battery 1 is manufactured, for example, through the following steps: (1) The electrode assembly 10 and the insulating plate 60 are housed in the exterior can 20. For example, if insulation can be ensured by the separator constituting the electrode assembly 10 alone, the insulating plate 60 can be omitted. (2) A groove 23 is formed in the side wall 21 of the exterior can 20, and the gasket 50 and the positive current collector plate 40 are placed on the groove 23. At this time, the positive current collector plate 40 and the gasket 50 may be pre-assembled and then placed on the groove 23. (3) An electrolyte is poured into the exterior can 20 housing the electrode assembly 10, the positive current collector plate 40, and the gasket 50. The electrolyte enters the can interior through the openings 43, 51 in the positive current collector plate 40 and the gasket 50 and is absorbed by the electrode assembly 10. (4) The sealing body 30 is placed on the positive current collector plate 40, and the sealing body 30 is welded to the first region 41 of the positive current collector plate 40. The sealing body 30 is preferably laser-welded, and a laser beam is irradiated from the top surface of the sealing body 30. (5) The top end of the outer can 20 is bent inward, and the sealing body 30 is crimped and fixed. The sealing body 30 may be crimped and fixed before welding the sealing body 30 to the positive current collector plate 40.

[0042] 3 , in the above step (2), the lower surface and inner peripheral surface 44 of the positive current collector plate 40 are covered with the gasket 50. Furthermore, before the electrolyte solution 70 is poured, the positive electrode lead 11 is welded to the upper surface of the second region 42 of the positive current collector plate 40. The welding of the positive electrode lead 11 can be performed by, for example, ultrasonic welding.

[0043] 3 , in the above step (3), the electrolyte 70 is poured to a height exceeding the lower surface of the positive current collector plate 40. Meanwhile, the liquid level of the electrolyte 70 is controlled so that it does not exceed the upper end of the inner circumferential wall portion 52 of the gasket 50. In this case, since the inner circumferential surface 44 of the positive current collector plate 40 is covered by the inner circumferential wall portion 52, the electrolyte 70 does not adhere to the inner circumferential surface 44. Furthermore, since the lower surface of the positive current collector plate 40 is also covered by the gasket 50, the electrolyte does not penetrate between the positive current collector plate 40 and the gasket 50.

[0044] If the inner peripheral surface of the positive current collector plate is exposed and not covered by a gasket, the electrolyte will creep up to the first region, which is the welded portion with the sealing body, due to capillary action, and laser welding will be performed in the presence of the electrolyte. In this case, the vaporized electrolyte may cause welding defects. In contrast, in the embodiment illustrated in FIG. 3, the positive current collector plate 40 is covered by the gasket 50, and the electrolyte 70 does not adhere to the positive current collector plate 40. Therefore, welding can be performed in the absence of the electrolyte, achieving a good welded state.

[0045] The above embodiment may be modified as needed within the scope of the present disclosure. For example, as shown in FIG. 4 , the inner peripheral wall portion 52 of the gasket 50 may extend beyond the upper end of the inner peripheral surface 44 of the positive current collector plate 40 and wrap around to the upper surface of the positive current collector plate 40.

[0046] 4 , the inner circumferential wall portion 52 formed on the inner periphery of the gasket 50 is formed in an annular shape along the inner circumferential surface 44 of the positive current collector plate 40, covers the entire inner circumferential surface 44 from the lower end to the upper end of the inner circumferential surface 44, and wraps around to the upper surface of the second region 42 to cover the upper surface of the second region 42 located on the periphery of the opening 43. In this case, adhesion of the electrolyte to the positive current collector plate 40 can be more reliably prevented. On the other hand, since the inner circumferential wall portion 52 protrudes above the upper surface of the second region 42, the portion of the positive electrode lead 11 that overlaps with the inner circumferential wall portion 52 is bent so as to be convex upward.

[0047] REFERENCE SIGNS LIST 1 Cylindrical battery, 10 Electrode body, 11 Positive electrode lead, 11 Outer can, 21 Side wall, 22 Can bottom, 23 Grooved portion, 30 Sealing body, 40 Positive electrode current collector plate, 41 First region, 42 Second region, 43 Opening, 44 Inner peripheral surface, 50 Gasket, 51 Opening, 52 Inner peripheral wall portion, 60 Insulating plate

Claims

1. A cylindrical battery comprising an electrode body, a cylindrical outer can with a bottom that contains the electrode body and an electrolyte, and a sealing body that closes the opening of the outer can, and including leads connected to the electrodes that constitute the electrode body, further comprising: an annular current collecting member to which the leads are connected and which is welded to the sealing body; and a gasket that is disposed between the outer can and the sealing body and covers the underside of the current collecting member that faces toward the electrode body, wherein the gasket has an inner wall portion that covers the inner surface that forms the periphery of the opening of the current collecting member.

2. The cylindrical battery according to claim 1, wherein the inner peripheral wall portion is formed in an annular shape along the inner peripheral surface of the current collecting member.

3. A cylindrical battery as described in claim 1 or 2, wherein the inner wall portion covers 50% or more of the height of the inner surface of the current collecting member and is formed with a height that does not exceed the upper end of the current collecting member.

4. The cylindrical battery according to claim 3, wherein the inner peripheral wall portion is formed in an annular shape along the inner peripheral surface of the current collecting member and covers substantially the entire area of ​​the inner peripheral surface of the current collecting member.

5. A cylindrical battery as set forth in claim 1 or 2, wherein the inner peripheral wall portion extends beyond the upper end of the inner peripheral surface and wraps around to the upper surface of the current collecting member.

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