Cylindrical battery

Abstract

A cylindrical battery (10) comprises: an electrode body (14) that includes a positive electrode (11), a negative electrode (12), and a separator (13), and is formed by winding the positive electrode (11) and the negative electrode (12) with the separator (13) interposed therebetween; an outer can (15) that has a bottomed cylindrical shape and houses the electrode body (14); and a sealing body (17) that covers an opening in the outer can (15). The sealing body (17) includes: a sealing plate (24) in which is formed a through-hole (25) penetrating in the up-down direction; and a sealing plug body (26) that covers the through-hole (25). A welded portion (28) where the sealing plate (24) and the sealing plug body (26) are welded is formed on the upper surface of the sealing plate (24), and a peripheral hole (40) penetrating the sealing plate (24) at the periphery of the through-hole (25) is formed in a region between the through-hole (25) and the welded portion (28) in the sealing plate (24).

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery, and particularly to a sealing body structure of a cylindrical battery.

[0002] A cylindrical battery generally includes an electrode body, an outer can that accommodates the electrode body, and a sealing body that closes an opening of the outer can, and includes a conductive member that electrically connects the electrode body and the sealing body (for example, Patent Document 1). In addition, a plugging structure may be employed to shorten the time of the liquid injection process. The plugging structure is formed by sealing the opening of the outer can with a sealing body having a liquid injection port, evacuating air from inside the outer can through the liquid injection port, injecting an electrolytic solution through the liquid injection port, and then sealing the liquid injection port with a plugging body.

[0003] Japanese Patent Laid-Open No. 9-320562

[0004] In a cylindrical battery having a plugging structure, welding of the plugging body and the sealing body is performed after injecting the electrolytic solution. At this time, the electrolytic solution may seep out into the welded portion due to capillary action or the like between the plugging body and the sealing plate. In this case, if welding is performed with the electrolytic solution present in the welded portion, there is a problem that welding defects such as pinholes occur. Even the cylindrical battery according to Prior Document 1 cannot solve such a problem.

[0005] The cylindrical battery according to the present disclosure includes a positive electrode, a negative electrode, and a separator, and an electrode body formed by winding the positive electrode and the negative electrode with the separator interposed therebetween; a bottomed cylindrical outer can that houses the electrode body; and a sealing body that closes an opening of the outer can. The sealing body includes a sealing plate provided with a through-hole penetrating in a vertical direction, and a plugging body that closes the through-hole. A welded portion where the sealing plate and the plugging body are welded is formed on an upper surface of the sealing plate, and a peripheral hole penetrating the sealing plate is formed in a region between the through-hole and the welded portion and around the through-hole.

[0006] According to the cylindrical battery of the present disclosure, it is possible to prevent the electrolytic solution from seeping out into the welded portion between the sealing body and the plugging body, and suppress the occurrence of welding defects.

[0007] This is an axial cross-sectional view of a cylindrical battery, which is an example of an embodiment. This is an enlarged view of part A in Figure 1. This is a diagram showing a sealing plate, which is an example of an embodiment. This is a diagram illustrating a sealing body having a mounting projection. This is a diagram illustrating a sealing plate having a support projection. This is a diagram showing a first modified example of the peripheral hole. This is a diagram showing a second modified example of the peripheral hole.

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

[0009] In the following, a cylindrical secondary battery using a non-aqueous electrolyte, and more specifically a lithium-ion cylindrical secondary battery, are given as examples of embodiments, but the cylindrical battery of this disclosure is not limited to this. The cylindrical battery of this disclosure is not limited to a battery using a non-aqueous electrolyte, but may also be a battery using an aqueous electrolyte. Furthermore, the cylindrical battery of this disclosure is not limited to a secondary battery, but may also be a primary battery.

[0010] A cylindrical battery 10, which is an example of an embodiment, will be described in detail with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of a cylindrical battery 10, which is an example of an embodiment. Figure 2 is an enlarged view of part A in Figure 1, which shows the sealing body 17 of the cylindrical battery 10 in detail.

[0011] As shown in Figure 1, the cylindrical battery 10 has a positive electrode 11, a negative electrode 12, and a separator 13, and comprises an electrode body 14 formed by winding the positive electrode 11 and the negative electrode 12 via the separator 13, a bottomed cylindrical outer casing 15 that houses the electrode body 14, and a sealing body 17 positioned above the electrode body 14 and closing the opening of the outer casing 15. The cylindrical battery 10 contains an electrolyte, which is housed in the outer casing 15 together with the electrode body 14. As will be described in more detail later, the sealing body 17 has a through hole 25 that penetrates vertically and connects the internal space and the external space of the outer casing 15.

[0012] In this specification, "plan view" means the view of the bottomed cylindrical outer can 15 from the axial direction. The plan view may be the view from the electrode body 14 side or from the opening side of the outer can 15, both in the axial direction of the outer can 15. In this specification, the vertical direction means that when the sealing body 17 and the electrode body 14 are arranged from top to bottom, the direction from the electrode body 14 toward the sealing body 17 is considered up, and the direction from the sealing body 17 toward the electrode body 14 is considered down.

[0013] The electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via the separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies, and are alternately stacked in the radial direction of the electrode body 14 by being wound in a spiral shape. The negative electrode 12 is formed to be slightly larger in dimensions than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and the width direction (short direction) than the positive electrode 11. The separator 13 is formed to be at least slightly larger in dimensions than the positive electrode 11, and two separators are arranged so as to sandwich the positive electrode 11.

[0014] The outer casing 15 is a bottomed cylindrical metal container that houses the electrode body 14 and the electrolyte. A groove 16 is formed on the side of the outer casing 15, extending circumferentially and protruding radially inward. The radial length of the groove 16 on the outer casing 15 is preferably such that it does not come into contact with the positive electrode lead 20 extending from the electrode body 14. For the sake of explanation, the sealing body 17 side of the cylindrical battery 10 will be considered the top, and the bottom side of the outer casing 15 will be considered the bottom. The groove 16 is preferably formed in an annular shape along the circumferential direction of the outer casing 15, and its upper surface supports the sealing body 17. The sealing body 17 and gasket 30 are fixed to the upper part of the outer casing 15 by the groove 16 and the open end of the outer casing 15 that is crimped to the sealing body 17 and gasket 30. The opening of the outer casing 15 is circular in plan view, and the sealing body 17 is similarly circular in plan view.

[0015] The electrolyte may be an aqueous electrolyte, but in this embodiment, a non-aqueous electrolyte is used. The non-aqueous electrolyte has lithium-ion conductivity. The non-aqueous electrolyte is a liquid electrolyte (electrolyte). In the following, the cylindrical battery 10 will be described using a non-aqueous electrolyte secondary battery, and in particular a lithium-ion battery, as an example.

[0016] A liquid electrolyte (electrolyte solution) comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may also contain halogen-substituted solvents (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0017] The positive electrode 11 has a long positive electrode core and positive electrode mixture layers formed on both sides of the positive electrode core. The positive electrode core can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layers contain a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core, drying the coating, and then compressing it to form positive electrode mixture layers on both sides of the positive electrode core.

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

[0019] Examples of conductive agents included in the positive electrode mixture layer include acetylene black (AB), carbon black such as Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, graphene, metal fibers, metal powders, and conductive whiskers. Examples of binders included in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0020] The negative electrode 12 comprises a negative electrode core and a negative electrode mixture layer formed on both sides of the negative electrode core. In this embodiment, the negative electrode core is made of a metal foil that is stable within the potential range of the negative electrode 12, such as copper or a copper alloy. A film with the metal arranged on its surface may also be used as the negative electrode core. The negative electrode mixture layer contains a negative electrode active material and a binder. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core, drying the coating, and then compressing it to form the negative electrode mixture layer on both sides of the negative electrode core.

[0021] Generally, carbon materials that reversibly intercalate and release lithium ions are used as the negative electrode active material. Preferred carbon materials are graphites such as natural graphite such as flake graphite, lump graphite, and clay graphite, and artificial graphite such as lump graphite and graphitized mesophase carbon microbeads. Since it is easy to increase the capacity, it is preferable that the negative electrode active material of the negative electrode mixture layer contains a Si material containing silicon (Si) particles, and it is preferable that the mass ratio of Si elements in the negative electrode mixture layer is 5.0% by mass or more. It is also preferable that 3.0% by mass or more of the negative electrode mixture layer is composed of silicon oxide. Other metals that alloy with lithium besides Si, alloys containing such metals, compounds containing such metals, etc., may also be used as the negative electrode active material.

[0022] The binder included in the negative electrode mixture layer may be fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, etc., as in the case of the positive electrode 11, but preferably styrene-butadiene rubber (SBR) or a modified version thereof is used. In addition to SBR, the negative electrode mixture layer may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, etc.

[0023] The separator 13 is made of a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 (porous sheet) include polyethylene, polyolefins such as polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. In addition, a highly heat-resistant resin layer, such as aramid resin, may be formed on the surface of the separator 13.

[0024] The electrode body 14 further includes a positive electrode lead 20 that functions as a conductive member to electrically connect the positive electrode 11 of the electrode body 14 to the sealing body 17, and a negative electrode lead 21 that electrically connects the negative electrode 12 to the outer casing 15. One end of the positive electrode lead 20 is connected to the core of the positive electrode 11 by welding or the like, and the other end is connected to the lower surface of the sealing body 17 by welding or the like, so that the sealing body 17 becomes the positive electrode external terminal. One end of the negative electrode lead 21 is connected to the core of the negative electrode 12, and the other end is connected to the inner surface of the bottom of the outer casing 15 by welding or the like, so that the outer casing 15 becomes the negative electrode external terminal. In addition, an upper insulating plate 22 and a lower insulating plate 23 are arranged above and below the electrode body 14, respectively. The upper insulating plate 22 is provided between the electrode body 14 and the sealing body 17, and the lower insulating plate 23 is provided between the electrode body 14 and the bottom of the outer casing 15. In the example shown in Figure 1, the positive lead 20 extends through the through-hole in the upper insulating plate 22 towards the sealing body 17, and the negative lead 21 extends outside the lower insulating plate 23 towards the bottom of the outer can 15.

[0025] The outer container 15 is a bottomed cylindrical metal container with one end open in the axial direction, and the opening of the outer container 15 is sealed by a sealing body 17 via a gasket 30. The constituent material of the outer container 15 is not particularly limited, but examples of preferred constituent materials include carbon steel and stainless steel.

[0026] As shown in Figures 1 and 2, the sealing body 17 has a sealing plate 24 with a through hole 25 that penetrates vertically and a sealing body 26 that closes the through hole 25. In detail, the through hole 25 of the sealing plate 24 is closed by a projection 26a formed on the sealing body 26.

[0027] The sealing plate 24 has a circular shape in plan view. The sealing plate 24 can be manufactured, for example, by press-forming a sheet of aluminum or an aluminum alloy. Aluminum and aluminum alloys are preferred materials for the sealing plate 24, which functions as an explosion-proof valve, because they have excellent flexibility.

[0028] The sealing plate 24 has, for example, a through hole 25 in its central portion 24a. The through hole 25 has, for example, a circular shape in plan view. The through hole 25 penetrates the outer can 15 in the axial direction. The shape of the through hole 25 in plan view is not particularly limited.

[0029] The through-holes 25 are preferably provided in steps, as shown in Figures 1 and 2. That is, the sealing plate 24 is preferably shaped like steps around the through-holes 25. This allows the tip of a nozzle (not shown) used for removing air from inside the outer can 15 and for injecting electrolyte into the outer can 15 to be placed against the second step 25b. This improves the efficiency of exhaust and injection. Here, in this specification, exhaust means removing air from inside the outer can 15. Injection means injecting electrolyte into the outer can 15.

[0030] The first stage 25a is formed in a circular shape in plan view and has a diameter slightly larger than the diameter of the sealing body 26. Furthermore, it is preferable that the depth of the first stage 25a is the same as the thickness of the flange portion 26b of the sealing body 26. This facilitates the formation of the welded portion 28, which will be described later. Here, the first stage 25a functions as an arrangement surface on which the flange portion 26b of the sealing body 26 is positioned.

[0031] The sealing body 26 has a flange portion 26b and a projection 26a that protrudes downward from the flange portion 26b. The shape of the sealing body 26 is, for example, circular in plan view, with the projection 26a formed by the central portion protruding. With this, the through hole 25 can be sealed by inserting the projection into the through hole 25. It is preferable that the projection 26a is of a length that does not extend beyond the lower surface of the sealing plate 24. The material of the sealing body 26 is not particularly limited, but it may be made of the same material as the sealing plate 24.

[0032] A welded portion 28 is formed on the upper surface of the sealing plate 24, where the sealing plate 24 and the sealing body 26 are welded together. More specifically, the welded portion 28 is formed by welding the flange portion 26b of the sealing body 26 to the upper surface of the sealing plate 24. The welded portion 28 is formed, for example, on the upper surface of the sealing plate 24 near the boundary between the sealing plate 24 and the sealing body 26. The welded portion 28 is formed, for example, by laser welding.

[0033] The sealing plate 24 has a central portion 24a in which a through hole 25 is provided, an outer peripheral portion 24b extending radially outward from the central portion 24a toward the outer peripheral portion 15, and an inclined portion 24c connecting the central portion 24a and the outer peripheral portion 24b. In the sealing plate 24, the area radially inward from the inclined portion 24c is the central portion 24a.

[0034] The thickness of the inclined portion 24c is thinner than that of the outer peripheral portion 24b. The lower surface of the inclined portion 24c is located above the lower surface of the central portion 24a. The annular upper surface of the inclined portion 24c is an inclined surface that is located higher as it moves radially outward, and the annular lower surface of the inclined portion 24c is also an inclined surface that is located higher as it moves radially outward. The thickness of the inclined portion 24c is thinner as it moves radially outward.

[0035] With the above configuration of the sealing plate 24, when the internal pressure of the cylindrical battery 10 reaches a predetermined value, gas can be released. Specifically, when the internal pressure of the cylindrical battery 10 reaches a predetermined value, the central part 24a and the inclined part 24c of the sealing plate 24 invert upward in the height direction, using the radially outer annular end 24d, which has low rigidity in the inclined part 24c, as a fulcrum. Furthermore, as the internal pressure rises, the annular end 24d of the inclined part 24c ruptures, and the gas inside the battery is discharged to the outside from the rupture in the sealing plate 24. This prevents the battery from rupturing even when the internal pressure of the cylindrical battery 10 rises.

[0036] Although not shown in Figure 2, the sealing body 17 may also have a structure in which multiple components such as an internal terminal plate and an annular insulating plate are stacked in order from the electrode body 14 side. Each component constituting the sealing body 17 has a disc shape or a ring shape, and each component except the annular insulating plate is electrically connected. In this case, the positive electrode lead 20 is connected to the lower surface of the internal terminal plate, which is the electrode body 14 side of the sealing body 17.

[0037] As shown in Figures 1 and 2, the gasket 30 is a sealing member positioned on the opening side of the outer can 15, between the sealing body 17 and the outer can 15. The annular gasket 30 seals the space between the outer can 15 and the sealing body 17, thereby sealing the internal space of the outer can 15. The gasket 30 also insulates the sealing body 17 from the outer can 15. In other words, the gasket 30 serves as a sealing material to maintain airtightness inside the battery and as an insulating material to prevent short circuits between the outer can 15 and the sealing body 17.

[0038] The gasket 30 is fixed to the upper end of the outer can 15 by the grooved portion 16 of the outer can 15 and the crimped portion 18 of the opening edge of the outer can 15 which is crimped to the sealing body 17 and the gasket 30. After crimping and fixing, the gasket 30 is positioned between the sealing body 17 and the crimped portion 18, and between the sealing body 17 and the grooved portion 16. Note that the injection of electrolyte into the outer can 15 and the welding of the sealing plate 24 and the sealing body 26 are performed after crimping and fixing.

[0039] Referring further to Figure 3, a peripheral hole 40 formed in the sealing plate 24, which is an example of an embodiment, will be described in detail. Figure 3 is a view of the lower surface of the sealing plate 24.

[0040] The sealing plate 24 has a peripheral hole 40 that penetrates the sealing plate 24 in the region between the through hole 25 and the welded portion 28, around the through hole 25. In the example shown in Figure 3, the peripheral hole 40 is located in the central part 24a of the sealing plate 24, around the through hole 25. With this configuration, it is possible to suppress the electrolyte from seeping out from the through hole 25 toward the upper surface of the sealing plate 24. In particular, it is possible to suppress the electrolyte from crawling up the gap between the sealing plate 24 and the sealing body 26 by capillary action and seeping out to the upper surface of the sealing plate 24. Because the peripheral hole 40 is formed, the electrolyte that enters the sealing plate 24 side from the through hole 25 is directed toward the electrode body 14 side. Furthermore, because the peripheral hole 40 is formed, the area where the surfaces of the sealing plate 24 and the sealing body 26 face each other is reduced, and the gap between the sealing plate 24 and the sealing body 26 where capillary action occurs is reduced, thus suppressing the crawling up of the electrolyte. As a result, the electrolyte is prevented from seeping up to the upper surface of the sealing plate 24, thereby suppressing the occurrence of welding defects. As will be described in more detail later, the sealing plate 24 has a bridge portion 29 that connects the first stage 25a and the second stage 25b.

[0041] The number of peripheral holes 40 formed in the sealing plate 24 may be one, but it is preferable that multiple peripheral holes 40 are arranged to surround the through hole 25. For example, as shown in Figure 3, three peripheral holes 40 are arranged to surround the through hole 25. This makes it easier for the electrolyte that seeps up from the through hole 25 to fall towards the electrode body 14, thereby effectively suppressing the leakage of electrolyte.

[0042] The shape of the peripheral holes 40 is not particularly limited, but it is preferable that the peripheral holes 40 have an arc shape in plan view and are provided concentrically with the through-hole 25. In the example shown in FIG. 3, the three peripheral holes 40 each having an arc shape in plan view are arranged so as to be concentric with the through-hole 25. According to this configuration, since the electrolytic solution that crawls up the through-hole 25 can easily drop toward the electrode assembly 14 side, oozing of the electrolytic solution can be effectively suppressed. Furthermore, since the peripheral holes 40 have an arc shape in plan view, they can be arranged so as to surround the through-hole 25 having a circular shape in plan view along the shape thereof, so that oozing of the electrolytic solution can be effectively suppressed.

[0043] The peripheral holes 40 may be provided so as to penetrate through a parallel plane parallel to the radial direction of the sealing plate 24. For example, they may be provided so as to penetrate the first step 25a in the vertical direction. Further, the peripheral holes 40 may be provided so as to penetrate through a vertical plane perpendicular to the radial direction of the sealing plate 24. For example, they may be provided so as to penetrate, in the radial direction of the sealing plate 24, a vertical wall connecting the first step 25a and the second step 25b.

[0044] As shown in FIG. 2, the peripheral holes 40 are preferably opened in the thickness direction of the sealing plate 24 and the radial direction of the sealing plate 24. That is, the peripheral holes 40 are preferably provided so as to be open on both a parallel plane parallel to the radial direction of the sealing plate 24 and a vertical plane perpendicular to the radial direction of the sealing plate 24. According to this configuration, as compared with a case where the holes are opened on either the parallel plane or the vertical plane, the openings are formed larger, and the electrolytic solution can easily drop toward the electrode assembly 14 side, so that oozing of the electrolytic solution can be suppressed.

[0045] As shown in FIG. 2, the through-hole 25 and the peripheral holes 40 are preferably located closer to the electrode assembly 14 side than the first step 25a. In other words, the through-hole 25 and the peripheral holes 40 are preferably located lower than the first step 25a. According to this configuration, the electrolytic solution can be suppressed from crawling up to the first step 25a of the sealing plate 24 where capillary action may occur.

[0046] It is preferable that the through-hole 25 is located closer to the electrode assembly 14 side than the peripheral hole 40. In other words, it is preferable that the peripheral hole 40 is located above the through-hole 25. According to this structure, since the peripheral hole 40 is located between the through-hole 25 and the upper surface of the sealing plate 24, the movement of the electrolytic solution that tends to creep up from the through-hole 25 to the upper surface of the sealing plate 24 can be suppressed more effectively. As a result, poor welding can be effectively suppressed.

[0047] As described above, the sealing plate 24 has a first step 25a as an arrangement surface on which the flange portion 26b of the sealing plug 26 is arranged, and has a second step 25b as a contact surface with a nozzle. The sealing plate 24 also has a bridge portion 29 connecting the second step 25b and the first step 25a. That is, the first step 25a and the second step 25b are connected via the bridge portion 29. Although the shape and number of the bridge portions 29 are not particularly limited, it is preferable that a plurality of bridge portions are provided to ensure reliable connection between the first step 25a and the second step 25b.

[0048] As shown in FIG. 4, it is preferable that the flange portion 26b of the sealing plug 26 is provided with a plurality of installation protrusions 50 protruding toward the sealing plate 24. Further, it is preferable that the sealing plug 26 is installed on the first step 25a of the sealing plate 24 via the installation protrusions 50. According to this structure, even if the electrolytic solution creeps up via the bridge portion 29, a large gap is formed by the installation protrusions 50 between the flange portion 26b of the sealing plug 26 and the first step 25a of the sealing plate 24, so capillary phenomenon is less likely to occur. As a result, the seepage of the electrolytic solution to the welded portion 28 can be suppressed.

[0049] It is preferable that the installation protrusion 50 is provided at a position away from the outermost peripheral edge of the flange portion 26b. In other words, when the flange portion 26b is installed on the arrangement surface, the installation protrusion 50 is preferably provided at a position away from the vertical wall connecting the first step 25a and the upper surface of the sealing plate 24. According to this structure, the occurrence of capillary phenomenon between the installation protrusion 50 and the vertical wall can be prevented, so the seepage of the electrolytic solution can be suppressed more effectively.

[0050] The shape of the mounting projection 50 is not particularly limited, but it is preferable that it has a shape that tapers towards the tip. The mounting projection 50 may be hemispherical in shape, for example, as shown in Figure 4. This reduces the contact area between the sealing body 26 and the sealing plate 24, thereby suppressing the movement of the electrolyte due to capillary action.

[0051] The first stage 25a, which functions as the placement surface for the sealing plate 24, is preferably provided with a plurality of support protrusions 60 projecting toward the sealing body 26, as shown in Figure 5. Furthermore, it is preferable that the sealing plate 24 supports the sealing body 26 via the support protrusions 60. With this configuration, even if the electrolyte seeps up through the bridge portion 29, a large gap is formed between the flange portion 26b of the sealing body 26 and the first stage 25a of the sealing plate 24 by the support protrusions 60, making capillary action less likely to occur. As a result, it is possible to suppress the electrolyte from seeping out to the weld portion 28.

[0052] The support projection 60 is preferably provided at a position away from the outermost edge of the first stage 25a. In other words, the support projection 60 is preferably provided at a position away from the vertical wall connecting the first stage 25a and the upper surface of the sealing plate 24. This prevents capillary action from occurring between the support projection 60 and the vertical wall, thereby more effectively suppressing the leakage of the electrolyte.

[0053] The shape of the support projection 60 is not particularly limited, but it is preferable that it has a shape that becomes thinner towards the tip. The support projection 60 may be hemispherical, for example, as shown in Figure 5. This reduces the contact area between the sealing plate 24 and the sealing body 26, thereby suppressing the movement of the electrolyte due to capillary action.

[0054] As described above, with a cylindrical battery having the above configuration, a peripheral hole is formed in the region between the through hole and the welded part, around the through hole, which suppresses the leakage of electrolyte into the welded part between the sealing plate and the sealing body, thereby suppressing the occurrence of welding defects.

[0055] The above embodiments can be modified as appropriate without impairing the purpose of this disclosure. For example, in the above embodiments, a peripheral hole 40 having the shape shown in Figure 3 was used as an example for explanation, but peripheral holes 40 having other shapes may be selected. Hereinafter, modifications of the peripheral hole 40 will be explained with reference to Figures 6 and 7. Figure 6 is a diagram showing a first modification of the peripheral hole 40. Figure 7 is a diagram showing a second modification of the peripheral hole 40.

[0056] As shown in Figure 6, the sealing plate 24 may have a plurality of circular peripheral holes 70 in plan view. The peripheral holes 70 are located around the through hole 25 and are arranged to surround the through hole 25. Even with peripheral holes 70, electrolyte seepage can be suppressed by allowing the electrolyte that rises from the through hole 25 to fall towards the electrode body 14. Alternatively, as shown in Figure 7, the sealing plate 24 may have peripheral holes 80 connected to the through hole 25. In this case as well, electrolyte seepage can be suppressed because the rise of the electrolyte can be suppressed by the peripheral holes 80 and the holes connecting the through hole 25 and the peripheral holes 80. Note that the shape of the peripheral holes formed in the sealing plate 24 may be other shapes than those exemplified above, for example, a polygonal shape in plan view. Alternatively, it may have a shape that combines the shapes exemplified above.

[0057] This disclosure is further illustrated by the following embodiments. Configuration 1: A cylindrical battery comprising an electrode body having a positive electrode, a negative electrode, and a separator, formed by winding the positive electrode and the negative electrode via the separator; a bottomed cylindrical outer casing housing the electrode body; and a sealing body that closes the opening of the outer casing, wherein the sealing body has a sealing plate with a through hole formed therethrough in the vertical direction, and a sealing body that closes the through hole, a welded portion formed on the upper surface of the sealing plate where the sealing plate and the sealing body are welded, and peripheral holes that penetrate the sealing plate are formed in the region between the through hole and the welded portion, around the through hole. Configuration 2: The cylindrical battery according to Configuration 1, wherein a plurality of peripheral holes are arranged on the sealing plate so as to surround the through hole. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the peripheral holes are arc-shaped in plan view and arranged concentrically with the through hole. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the peripheral holes are open in the thickness direction and the radial direction of the sealing plate. Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the through holes are located closer to the electrode body than the peripheral holes. Configuration 6: The cylindrical battery according to any one of Configurations 1 to 5, wherein the sealing plate has an arrangement surface in the region between the through holes and the welded portion where the flange portion of the sealing body is arranged, and the through holes and the peripheral holes are located closer to the electrode body than the arrangement surface. Configuration 7: The cylindrical battery according to any one of Configurations 1 to 6, wherein the sealing plate has an arrangement surface in the region between the through holes and the welded portion where the flange portion of the sealing body is arranged, and the arrangement surface of the sealing plate is provided with a plurality of support protrusions projecting toward the sealing body side, and the sealing plate supports the sealing body via the support protrusions. Configuration 8: The cylindrical battery according to any one of Configurations 1 to 7, wherein the sealing plate has an arrangement surface in the region between the through hole and the welded portion on which the flange portion of the sealing body is arranged, the flange portion of the sealing body is provided with a plurality of mounting protrusions projecting toward the sealing plate, and the sealing body is installed on the arrangement surface of the sealing plate via the mounting protrusions.

[0058] 10 Cylindrical battery 11 Positive electrode 12 Negative electrode 13 Separator 14 Electrode body 15 Outer casing 16 Grooved section 17 Sealing body 18 Crimped section 20 Positive electrode lead 21 Negative electrode lead 22, 23 Insulating plate 24 Sealing plate 24a Center section 24b Outer periphery section 24c Inclined section 24d Annular end section 25 Through hole 25a First stage 25b Second stage 26 Sealing body 26a Projection 26b Flange section 28 Welded section 30 Gasket 40, 70, 80 Peripheral holes 50 Mounting protrusion 60 Supporting protrusion

Claims

1. A cylindrical battery comprising: an electrode body having a positive electrode, a negative electrode, and a separator, formed by winding the positive electrode and the negative electrode with the separator in between; a bottomed cylindrical outer casing for housing the electrode body; and a sealing body for closing the opening of the outer casing, wherein the sealing body comprises: a sealing plate having a through hole that penetrates vertically; and a sealing plug that closes the through hole; a welded portion formed on the upper surface of the sealing plate where the sealing plate and the sealing plug are welded; and a peripheral hole formed in the region between the through hole and the welded portion, penetrating the sealing plate around the through hole.

2. The cylindrical battery according to claim 1, wherein the sealing plate has a plurality of peripheral holes arranged to surround the through hole.

3. The cylindrical battery according to claim 1, wherein the peripheral holes are arc-shaped in plan view and arranged concentrically with the through holes.

4. The cylindrical battery according to claim 1, wherein the peripheral holes are open in the thickness direction and the radial direction of the sealing plate.

5. The cylindrical battery according to claim 1, wherein the through hole is located closer to the electrode body than the peripheral hole.

6. The cylindrical battery according to claim 1, wherein the sealing plate has an arrangement surface in the region between the through hole and the welded portion, on which the flange portion of the sealing body is arranged, and the through hole and the peripheral hole are located on the electrode body side of the arrangement surface.

7. The cylindrical battery according to claim 1, wherein the sealing plate has an arrangement surface in the region between the through hole and the welded portion on which the flange portion of the sealing body is arranged, the arrangement surface of the sealing plate is provided with a plurality of support protrusions projecting toward the sealing body side, and the sealing plate supports the sealing body via the support protrusions.

8. The cylindrical battery according to any one of claims 1 to 7, wherein the sealing plate has an arrangement surface in the region between the through hole and the welded portion on which the flange portion of the sealing body is arranged, the flange portion of the sealing body is provided with a plurality of mounting protrusions projecting toward the sealing plate, and the sealing body is installed on the arrangement surface of the sealing plate via the mounting protrusions.

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