Cylindrical battery

Abstract

A cylindrical battery (10) comprises: an electrode body (14) that has a positive electrode (11), a negative electrode (12), and a separator (13), and that is formed by winding the positive electrode (11) and the negative electrode (12) with the separator (13) therebetween; a bottomed cylindrical outer can (15) that houses the electrode body (14); and an opening-sealing body (17) that closes an opening of the outer can (15). The opening-sealing body (17) includes: an opening-sealing plate (24) which has formed therein a through-hole (25) that penetrates the same in the vertical direction; and a sealing plug body (26) that closes the through-hole (25). On the upper surface of the opening-sealing plate (24), a welded part (28) at which the opening-sealing plate (24) and the sealing plug body (26) are welded is formed. The opening-sealing plate (24) and / or the sealing plug body (26) has an oxide film (40) formed at a portion of the surface from the through-hole (25) to the welded part (28).

Description

Cylindrical battery

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

[0002] A cylindrical battery generally comprises an electrode assembly, an outer can that accommodates the electrode assembly, and a sealing body that closes an opening of the outer can, and includes a conductive member that electrically connects the electrode assembly and the sealing body (for example, Patent Document 1). In addition, a plug sealing structure is sometimes adopted to reduce the time of the electrolyte injection process. The plug sealing structure is formed by sealing an opening of the outer can with a sealing body having an electrolyte injection port, evacuating air from the inside of the outer can through the electrolyte injection port, injecting electrolyte through the electrolyte injection port, and then sealing the electrolyte injection port with a plug.

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

[0004] In a cylindrical battery having a plug sealing structure, the plug and the sealing body are welded after the electrolyte is injected. At this time, electrolyte may seep out to the welded portion due to capillary action between the plug and the sealing plate. In this case, if welding is performed when electrolyte remains in the portion to be welded, there is a problem that welding defects such as pinholes occur. The above problem cannot be solved even with the cylindrical battery according to the prior art document 1.

[0005] The cylindrical battery according to the present disclosure comprises a positive electrode, a negative electrode, a separator, an electrode assembly formed by winding the positive electrode and the negative electrode with the separator interposed therebetween, a bottomed cylindrical outer can that accommodates the electrode assembly, and a sealing body that closes an opening of the outer can, wherein the sealing body has a sealing plate formed with a through-hole penetrating in a vertical direction, and a plug that closes the through-hole; a welded portion where the sealing plate and the plug are welded is formed on an upper surface of the sealing plate; and an oxide film is formed on a part of a surface between the through-hole and the welded portion on at least one of the sealing plate and the plug.

[0006] According to the cylindrical battery of the present disclosure, electrolyte can be prevented from seeping out to the welded portion between the sealing body and the plug, and the occurrence of welding defects can be suppressed.

[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 showing a sealing body, which is an example of an embodiment.

[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. 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 that is positioned above the electrode body 14 and closes the opening of the outer casing 15. The cylindrical battery 10 contains an electrolyte, and the electrolyte 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 in the vertical direction and connects the internal space and the external space of the outer casing 15.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] The thickness of the inclined portion 24c is thinner than that of the central portion 24a and 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.

[0034] 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 outward 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Referring further to Figures 3 and 4, an example of an embodiment will be described in detail, showing the oxide film 40 formed on a portion of the sealing plate 24 and the sealing body 26. Figure 3 is a view of the sealing plate 24 from above. Figure 4 is a view of the sealing body 26 from below.

[0039] An oxide film 40 is formed on a portion of the surface between the through hole 25 and the welded portion 28 on at least one of the sealing plate 24 and the sealing body 26. In the example shown in Figures 1 to 4, the oxide film 40 is formed on the first stage 25a of the sealing plate 24 and on the flange portion 26b of the sealing body 26 at a position that contacts the first stage 25a. This prevents the electrolyte from seeping out onto the upper surface of the sealing plate 24, especially to the welded portion 28, due to capillary action. Specifically, when an oxide film 40 is formed on the surface of the sealing plate 24 or the sealing body 26, the wettability of the region where the oxide film 40 is formed differs from that of other regions. Therefore, a large capillary force is required when the electrolyte enters or leaves the region where the oxide film 40 is formed, thus suppressing the movement of the electrolyte. As a result, since the seepage of the electrolyte can be suppressed, defects in the welded portion 28 can be suppressed.

[0040] The location where the oxide film 40 is formed is not particularly limited, as long as it is a part of the surface between the through hole 25 and the welded portion 28. For example, as shown in Figure 2, the oxide film 40 is formed on the first stage 25a of the sealing plate 24 and on the flange portion 26b of the sealing body 26, in the region that contacts the first stage 25a. That is, in the example shown in Figure 2, the oxide film 40 formed on the sealing plate 24 and the oxide film 40 formed on the sealing body 26 are arranged to be in contact with each other. This allows for more effective suppression of capillary action, and thus more effective suppression of welding defects.

[0041] The oxide film 40 formed on the sealing plate 24 may, for example, be formed on the second stage 25b. Alternatively, the oxide film 40 may be formed on the vertical wall between the second stage 25b and the first stage 25a, and on the vertical wall between the first stage 25a and the upper surface of the sealing plate 24. Furthermore, the oxide film 40 may be formed on the inner wall of the through hole 25 that contacts the radially outer surface of the projection 26a. Also, the oxide film 40 may be formed at multiple locations. For example, the oxide film 40 may be formed on the first stage 25a and on the vertical wall between the first stage 25a and the upper surface of the sealing plate 24. From the viewpoint of ease of oxide film formation, it is preferable that the oxide film 40 formed on the sealing plate 24 be formed on the first stage 25a or the second stage 25b.

[0042] The oxide film 40 formed on the sealing body 26 may be formed, for example, on the radially outer surface of the flange portion 26b, in a position where the weld portion 28 is not formed. It may also be formed in multiple positions. Preferably, the oxide film 40 is formed on the surface of the sealing body 26 that is in contact with the sealing plate 24. This suppresses the movement of electrolyte that crawls up the gap between the sealing plate 24 and the sealing body 26 by capillary action, and effectively suppresses the leakage of electrolyte.

[0043] When the oxide film 40 is provided on both the sealing plate 24 and the sealing body 26, it is preferable that the oxide film 40 provided on the sealing plate 24 and the oxide film 40 provided on the sealing body 26 be in contact with each other. For example, as shown in Figure 2, the oxide film 40 formed on the first stage 25a of the sealing plate 24 and the oxide film 40 formed on the flange portion 26b of the sealing body 26 are in contact with each other. This makes it possible to suppress the movement of the electrolyte more effectively because the wettability of the region where the oxide film 40 is formed is significantly different compared to when the oxide film 40 is formed on only one of the sealing plate 24 or the sealing body 26.

[0044] It is preferable that the oxide film 40 is formed so as to surround the entire circumference of the through-hole 25. Specifically, it is preferable that the oxide film 40 is formed so as to surround the entire circumference of the through-hole 25 regardless of whether the oxide film 40 is formed on either the sealing plate 24 or the plug body 26. According to this configuration, even when the electrolytic solution creeps up from the through-hole 25, the oxide film 40 is formed in all directions, so the seepage of the electrolytic solution can be effectively suppressed.

[0045] It is preferable that the oxide film 40 is formed in a substantially hollow circular shape when viewed from the thickness direction of the sealing body 17. That is, as shown in FIG. 3 and FIG. 4, the oxide film 40 preferably has a substantially hollow circular shape that surrounds the entire circumference of the through-hole 25. According to this configuration, since the oxide film 40 is formed so as to surround the entire circumference of the through-hole 25, the seepage of the electrolytic solution can be suppressed more effectively.

[0046] A plurality of substantially hollow circular oxide films 40 may be formed. That is, the oxide film 40 may have a multiple hollow circular shape. According to this configuration, the movement of the electrolytic solution is suppressed by the plurality of oxide films 40, so the seepage of the electrolytic solution can be effectively suppressed.

[0047] The relationship between the width W of the oxide film 40 and the outer diameter D of the oxide film 40 preferably satisfies W≧D / 4. In the case of the oxide film 40 provided on the sealing plate 24, as shown in FIG. 3, it is preferable that the relationship between the width W1 and the outer diameter D1 satisfies W1≧D1 / 4. Further, in the case of the oxide film 40 provided on the plug body 26, as shown in FIG. 4, it is preferable that the relationship between the width W2 and the outer diameter D2 satisfies W2≧D1 / 4. According to this configuration, since the length of the oxide film 40 in the radial direction of the sealing body 17 is ensured, the movement of the electrolytic solution that has entered the region where the oxide film 40 is formed can be effectively suppressed. As a result, seepage can be effectively suppressed, and welding defects can be effectively suppressed.

[0048] The thickness of the oxide film 40 is preferably 5 µm or more. Further, the thickness of the oxide film 40 is preferably 10 µm or more. When the oxide film 40 satisfies the above conditions, the wettability of the surface of the oxide film 40 can be stabilized. Therefore, the movement of the electrolytic solution can be effectively suppressed. From the viewpoint of shortening manufacturing time, the thickness of the oxide film 40 is preferably 50 µm or less.

[0049] The oxide film 40 may be formed by anodizing or high-temperature oxidation. Furthermore, since the oxide film 40 is formed on at least a portion of the sealing plate 24 and the sealing body 26, the oxide film 40 may be partially formed by covering the portion other than the portion where the oxide film 40 is not to be formed with paint or masking tape.

[0050] As described above, with a cylindrical battery having the above configuration, an oxide film is formed between the through hole and the welded part, which changes the wettability of the surface, thereby preventing electrolyte from seeping out of the welded part between the sealing plate and the sealing body, and suppressing the occurrence of welding defects.

[0051] The present 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 therein that penetrates 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 an oxide film formed on a part of the surface between the through hole and the welded portion on at least one of the sealing plate and the sealing body. Configuration 2: The cylindrical battery according to Configuration 1, wherein the oxide film is formed to surround the entire circumference of the through hole. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the oxide film is formed on the surface of the sealing body that is in contact with the sealing plate. Configuration 4: A cylindrical battery according to any one of Configurations 1 to 3, wherein the thickness of the oxide film is 5 μm or more. Configuration 5: A cylindrical battery according to any one of Configurations 1 to 4, wherein the oxide film is formed in a substantially hollow circular shape when viewed from the thickness direction of the sealing body. Configuration 6: A cylindrical battery according to Configuration 5, wherein the relationship between the width W of the oxide film and the outer diameter D of the oxide film is W ≥ D / 4. Configuration 7: A cylindrical battery according to any one of Configurations 1 to 6, wherein the oxide film is formed by anodizing or high-temperature oxidation.

[0052] 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 Oxide film W, W1, W2 Width D, D1, D2 Outer diameter

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 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 an oxide film formed on a portion of the surface between the through hole and the welded portion on at least one of the sealing plate and the sealing body.

2. The cylindrical battery according to claim 1, wherein the oxide film is formed to surround the entire circumference of the through hole.

3. The cylindrical battery according to claim 1, wherein the sealing body has the oxide film formed on the surface that contacts the sealing plate.

4. The cylindrical battery according to claim 1, wherein the thickness of the oxide film is 5 μm or more.

5. The cylindrical battery according to claim 1, wherein the oxide film is formed in a substantially hollow circular shape when viewed from the thickness direction of the sealing body.

6. The cylindrical battery according to claim 5, wherein the relationship between the width W of the oxide film and the outer diameter D of the oxide film is W ≥ D / 4.

7. The cylindrical battery according to any one of claims 1 to 6, wherein the oxide film is formed by anodizing or high-temperature oxidation.

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