Sealed battery

Abstract

A sealed battery that is an example of an embodiment comprises: an electrode body; an outer can that houses the electrode body; and a seal body that closes an opening of the outer can. The seal body includes: a cap; and a current collector plate that is located closer to the electrode body than the cap and that is welded to the cap. The current collector plate has, in a portion thereof welded to the cap, a recess protruding toward the cap.

Description

Technical Field

[0001] The present disclosure relates to a sealed battery, particularly to a cylindrical sealed battery.

Background Art

[0002] Sealed batteries such as cylindrical batteries are used not only for mobile applications but also for in-vehicle applications in recent years, and further higher output is required. A sealed battery generally includes an electrode body, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes the opening of the outer can. The sealing body includes a cap and a current collector plate to which an electrode lead extending from the electrode body is connected, and has a structure in which the cap and the current collector plate are welded together.

[0003] In a sealed battery, preventing leakage of the electrolytic solution and enhancing the hermeticity inside the battery are important issues. For example, Patent Document 1 discloses a sealed battery in which an uneven portion is formed on the outer surface of the outer peripheral portion of the cap to produce an anchor effect on the gasket, thereby improving the liquid leakage resistance and hermeticity. Further, Patent Document 2 discloses a sealed battery in which a gasket is brought into contact with the inner wall of the outer can inside the grooved portion of the outer can, thereby reducing the upward flow of the electrolytic solution along the inner wall of the outer can and enhancing the airtightness.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, sealed batteries are manufactured, for example, by housing the electrode body in an outer casing, pouring in the electrolyte, and then welding the cap and current collector plate to the sealing body. However, the inventors' research has shown that the electrolyte adhering to the current collector plate can cause welding defects between the cap and the current collector plate. When laser welding the cap and current collector plate, if the electrolyte is present at the welding site, the vaporized electrolyte can cause tiny holes to form in the cap.

[0006] The purpose of this disclosure is to provide a sealed battery in which the sealing cap and current collector plate are in good welding condition. [Means for solving the problem]

[0007] A sealed battery according to one aspect of the present disclosure comprises an electrode body, an outer casing housing the electrode body, and a sealing body that closes the opening of the outer casing, wherein the sealing body includes a cap and a current collector plate positioned on the electrode body side of the cap and welded to the cap, and the current collector plate has a protrusion projecting toward the cap at the portion welded to the cap. [Effects of the Invention]

[0008] The sealed battery according to this disclosure has good welding conditions between the cap of the sealing body and the current collector plate, and for example, has excellent airtightness. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of a sealed battery, which is an example of an embodiment. [Figure 2] This is a front view of the electrode with the electrode leads connected. [Figure 3] This is an enlarged view of section A in Figure 1. [Figure 4] This is a plan view of the first insulating plate, showing the first insulating plate placed on the electrode body. [Figure 5] This is a plan view of the second insulating plate, showing the second insulating plate placed on the electrode body. [Figure 6] This figure shows an enlarged view of a portion of the cross-section of a sealing body, which is another example of the embodiment, and shows the state before welding the cap and the current collector plate. [Figure 7] This figure shows an enlarged view of a portion of the cross-section of a sealing body, which is another example of the embodiment, showing the cap and current collector plate welded together. [Modes for carrying out the invention]

[0010] Hereinafter, an example of an embodiment of the sealed battery according to this disclosure will be described in detail with reference to the drawings. Note that configurations obtained by selectively combining the multiple embodiments and modifications described below are included in this disclosure.

[0011] The configuration of the sealed battery according to this disclosure is suitable for a cylindrical battery equipped with a bottomed cylindrical outer casing. However, the outer casing constituting the sealed battery is not limited to a cylindrical outer casing, and may be, for example, a rectangular outer casing (rectangular battery). Furthermore, the electrode body is not limited to a wound electrode body, and may be a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators in between.

[0012] Figure 1 is a cross-sectional view of a cylindrical battery 1, which is an example of an embodiment. As shown in Figure 1, the cylindrical battery 1 comprises an electrode body 10, a bottomed cylindrical outer casing 20 that houses the electrode body 10, and a sealing body 30 that closes the opening of the outer casing 20. The outer casing 20 contains an electrolyte together with the electrode body 10. The electrolyte may be an aqueous electrolyte, but in this embodiment, a non-aqueous electrolyte is used. The outer casing 20 has grooves 23 formed in its side wall 21, and the sealing body 30 is supported by the grooves 23 and closes the opening of the outer casing 20. For the sake of explanation, in the following, the side of the cylindrical battery 1 with the sealing body 30 is considered the top, and the side of the outer casing 20 with the bottom 22 is considered the bottom. In this specification, the vertical direction of the cylindrical battery 1 and the thickness direction of the sealing body 30 are the same.

[0013] The cylindrical battery 1 further includes an electrode lead extending from a position opposite the grooved portion 23 on the outer circumference of the electrode body 10, directly connecting the first electrode constituting the electrode body 10 to the current collector plate 32 of the sealing body 30, and an upper insulating plate 40 disposed between the electrode body 10 and the sealing body 30. The electrode body 10 is a wound-type electrode body in which the first electrode and the second electrode are wound around a separator, and in this embodiment, the first electrode is the positive electrode 11 (see Figure 2 below), the second electrode is the negative electrode, and the electrode lead is the positive electrode lead 12. The cylindrical battery 1 may also have a lower insulating plate disposed between the electrode body 10 and the bottom of the can 22.

[0014] As will be explained in more detail later, the positive lead 12 electrically connects the positive electrode 11 to the sealing body 30, and the negative lead electrically connects the negative electrode to the outer casing 20. Therefore, the sealing body 30 functions as the positive electrode external terminal, and the outer casing 20 functions as the negative electrode external terminal. The upper insulating plate 40 prevents the positive electrode 11 and the positive lead 12 from touching the outer casing 20, and also prevents the positive lead 12 from touching the negative electrode of the electrode body 10.

[0015] The electrode body 10 includes a positive electrode 11, a negative electrode, and a separator, and has a wound structure in which the positive electrode 11 and the negative electrode are wound in a spiral shape with the separator in between. The positive electrode 11, the negative electrode, and the separator are all elongated strip-shaped bodies, and are alternately stacked in the radial direction of the electrode body 10 by being wound in a spiral shape. The negative electrode is formed to be slightly larger in dimensions than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode is formed to be longer in the longitudinal direction and the width direction (short direction) than the positive electrode 11. The separator is formed to be at least slightly larger in dimensions than the positive electrode 11, and for example, two separators are arranged so as to sandwich the positive electrode 11.

[0016] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on at least one surface of the core. For the positive electrode core, a foil of a metal stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with such a metal disposed on the surface layer can be used. The positive electrode mixture layer contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride, and is preferably formed on both surfaces of the positive electrode core. For the positive electrode active material, for example, a lithium transition metal composite oxide is used. The positive electrode lead 12 is connected to the positive electrode 11, and is preferably directly joined to the positive electrode core by welding or the like.

[0017] The negative electrode has a negative electrode core and a negative electrode mixture layer formed on at least one surface of the core. For the negative electrode core, a foil of a metal stable within the potential range of the negative electrode, such as copper or a copper alloy, or a film with such a metal disposed on the surface layer can be used. The negative electrode mixture layer contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is preferably formed on both surfaces of the negative electrode core. For the negative electrode active material, for example, graphite, a silicon-containing compound, or the like is used. The negative electrode lead is preferably directly joined to the negative electrode core by welding or the like. It is also possible to electrically connect the negative electrode core and the exterior can 20 without using the negative electrode lead.

[0018] The non-aqueous electrolyte contained in the exterior can 20 contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, for example, esters, ethers, nitriles, amides, and a mixed solvent of two or more of these can be used. The non-aqueous solvent may contain a halogen-substituted product in which at least a part of the hydrogen of these solvents is substituted with a halogen atom such as fluorine. As an example of the non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and a mixed solvent of these can be mentioned. For the electrolyte salt, for example, a lithium salt such as LiPF6 is used.

[0019] The outer can 20 is a bottomed cylindrical metal container with one end (upper end) in the axial direction open, and has a cylindrical side wall 21 and a bottom 22 circular in plan view. The outer can 20 is generally made of a metal mainly composed of iron, but may also be made of a metal mainly composed of aluminum or the like. Further, the outer can 20 has a grooved portion 23 formed along the circumferential direction of the side wall 21. The grooved portion 23 is formed at a position separated by a predetermined length from the opening edge (upper end of the outer can 20) in the vicinity of the opening of the outer can 20. The predetermined length is, for example, a length corresponding to 1 to 20% of the axial length of the outer can 20.

[0020] In the present embodiment, a safety valve mechanism that operates when an abnormality occurs in the cylindrical battery 1 is provided on the bottom 22 of the outer can 20. On the other hand, the sealing body 30 is not provided with a safety valve mechanism. For example, a thin portion is formed on the bottom 22. When an abnormality occurs in the cylindrical battery 1 and the internal pressure rises, this thin portion is preferentially broken, and a gas discharge port is formed in the bottom 22.

[0021] The grooved portion 23 is a portion where a part of the side wall 21 projects inside the outer can 20, and is formed, for example, by spinning the side wall 21 from the outside. At the formation position of the grooved portion 23, the outer can 20 is reduced in diameter, and a thin linear groove is formed on the outer peripheral surface of the side wall 21. The grooved portion 23 preferably has a substantially U-shaped cross section and is formed annularly 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 outer can 20.

[0022] The inner diameter of the outer can 20 at the formation position of the grooved portion 23 is, for example, 80 to 99% of the maximum inner diameter of the outer can 20. An example of the length of the grooved portion 23 along the radial direction of the outer can 20 is 0.5 to 2.0 mm. Since the diameter of the electrode body 10 is approximately the same as the maximum inner diameter of the outer can 20, the electrode body 10 and the grooved portion 23 overlap in the vertical direction of the cylindrical battery 1. Although details will be described later, in the present embodiment, a plurality of positive electrode leads 12 are provided at predetermined intervals along the longitudinal direction of the positive electrode 11, and extend from a position facing the grooved portion 23 on the outer peripheral side of the electrode body 10.

[0023] The sealing body 30 comprises a cap 31, a current collector plate 32, and a gasket 33, and is formed in a disc shape overall. The sealing body 30 is positioned on the grooved portion 23 of the outer can 20 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 to the sealing body 30. In other words, the sealing body 30 is fixed to the upper end of the outer can 20 by the grooved portion 23 and the crimped portion of the outer can 20, closing the opening of the outer can 20. The crimped portion is formed in an annular shape along the circumferential direction of the outer can 20 and, together with the grooved portion 23, clamps the sealing body 30.

[0024] The cap 31 is a disc-shaped metal component that is exposed to the outside of the outer casing 20 and forms the top surface of the cylindrical battery 1. The cap 31 has a shape in which its radial center protrudes outward from the cylindrical battery 1. Wiring material is connected to the cap 31 when the cylindrical battery 1 is modularized to form a battery pack. For this reason, the cap 31 functions as an external terminal of the cylindrical battery 1 and is also called an external terminal or top cover. In this embodiment, the positive electrode lead 12 is connected to the current collector plate 32, and the cap 31 functions as a positive electrode external terminal.

[0025] The current collector plate 32 is a metal member having a diameter similar to that of the cap 31, and is positioned closer to the electrode body 10 than the cap 31. The current collector plate 32 has an opening 32a in its radial center and is formed in a ring shape. The cap 31 and the current collector plate 32 are welded together, with the current collector plate 32 welded, for example, closer to the outer edge than the radial center of the cap 31. A protrusion 32b, described later, is formed on the current collector plate 32, and the protrusion 32b becomes the welded portion with the cap 31. As described above, a positive electrode lead 12 connected to the positive electrode 11 of the electrode body 10 is connected to the current collector plate 32, so the current collector plate 32 functions as a positive electrode current collector plate.

[0026] The gasket 33 is provided on the outer periphery of the laminate of the cap 31 and the current collector plate 32. The gasket 33 is a resin component that prevents contact between the cap 31 and the current collector plate 32 and the outer casing 20, thereby ensuring insulation between the outer casing 20 and the sealing body 30. The gasket 33 covers the upper surface of the cap 31, the sides of the cap 31 and the current collector plate 32, and the lower surface of the current collector plate 32 on the outer periphery of the laminate. The gasket 33 also seals the gap between the outer casing 20 and the sealing body 30, thereby sealing the inside of the cylindrical battery 1.

[0027] The gasket 33 is a ring-shaped resin component formed to cover most of the lower surface of the current collector plate 32 and interposed between the current collector plate 32 and the upper insulating plate 40. An opening 33a is formed in the radial center of the gasket 33, which overlaps vertically with the opening 32a of the current collector plate 32. The gasket 33 also has through holes 33b formed in the portion located below the current collector plate 32. Although electrolyte is expected to accumulate on the upper surface of the gasket 33, the through holes 33b allow this electrolyte to be efficiently returned to the electrode body 10. Multiple through holes 33b are formed, for example, along the circumferential direction of the gasket 33.

[0028] The configuration of the positive electrode 11 and the positive electrode lead 12 will be explained in detail below with reference to Figure 2. Figure 2 is a front view of the positive electrode 11 to which the positive electrode lead 12 is connected, showing the positive electrode 11 in an unfolded state.

[0029] As shown in Figure 2, the positive electrode 11 is a long, strip-shaped body, and a plurality of positive electrode leads 12 are connected along the longitudinal direction of the positive electrode 11 at predetermined intervals L1. As described above, the positive electrode 11 includes a positive electrode core and a positive electrode mixture layer. Preferably, the positive electrode leads 12 are joined to the exposed portion of the positive electrode core where the positive electrode mixture layer is not formed, by welding or the like. In Figure 2, each positive electrode lead 12 is shown to be the same length, but adjacent positive electrode leads 12 may have different lengths. For example, when a wound electrode body 10 is formed, the positive electrode leads 12 located on the outer circumference side of the electrode body 10 are formed to be longer than the positive electrode leads 12 located on the inner circumference side.

[0030] The positive electrode lead 12 is a strip-shaped conductive member, made of a metal, for example, primarily composed of aluminum. All of the multiple positive electrode leads 12 extend in the same direction, extending from one end of the positive electrode 11 in the width direction. In this embodiment, one longitudinal end of each positive electrode lead 12 is joined to the positive electrode 11, and the other longitudinal end is joined to the current collector plate 32 of the sealing body 30, so that the positive electrode 11 and the current collector plate 32 are directly connected by the positive electrode lead 12. This simplifies the current collection structure from the electrode body 10. Furthermore, the structure in which the positive electrode 11 and the current collector plate 32 are directly connected by the positive electrode lead 12 is also preferable from the viewpoint of reducing resistance and improving output characteristics.

[0031] The number of positive electrode leads 12 is not particularly limited, but examples include 3 to 15 leads, or 6 to 10 leads. Preferably, the positive electrode leads 12 are provided at approximately equal intervals along the longitudinal direction of the positive electrode 11. Approximately equal intervals means, for example, that the difference between the maximum and minimum values ​​of the spacing L1 between positive electrode leads 12 is within 10%. In this case, the effect of improving the output characteristics becomes more pronounced. An example of the spacing L1 between adjacent positive electrode leads 12 is 400 to 600 mm, or 450 to 550 mm. In addition, at both ends in the longitudinal direction of the positive electrode 11, the positive electrode leads 12 are provided at a distance of length L2 from the longitudinal end of the positive electrode mixture layer. Preferably, length L2 corresponds to approximately half of the spacing L1.

[0032] Furthermore, since the positive electrode leads 12 are arranged at approximately equal intervals along the longitudinal direction of the positive electrode 11, they extend not only from the inner circumference side of the electrode body 10 but also from the outer circumference side toward the sealing body 30. At least one of the positive electrode leads 12 extends toward the sealing body 30 from a position facing the grooved portion 23 of the outer can 20. In this embodiment, multiple positive electrode leads 12 are joined to the positive electrode 11 at a position facing the grooved portion 23.

[0033] The configuration of the current collector plate 32 of the sealing body 30 to which the positive lead 12 is connected, and the cap 31 to which the current collector plate 32 is welded, will be explained in detail below with reference to Figure 3. Figure 3 is an enlarged view of section A in Figure 1.

[0034] As shown in Figure 3, the positive electrode lead 12 wraps around to the upper surface of the current collector plate 32 through the openings 32a and 33a of the current collector plate 32 and gasket 33, and is joined to the upper surface of the current collector plate 32 facing the cap 31. Preferably, the positive electrode lead 12 is joined to the current collector plate 32 by welding. The periphery of the opening 32a of the current collector plate 32 is curved toward the center of the opening 32a and is rounded. In other words, the wall of the opening 32a along the thickness direction of the current collector plate 32 is curved as a whole and formed in a circular arc shape in cross-section. It is expected that the positive electrode lead 12 will come into contact with the periphery of the opening 32a, but by curving the periphery of the opening 32a and eliminating the corners, damage to the positive electrode lead 12 caused by such contact can be suppressed.

[0035] The current collector plate 32 is bent toward the sealing body 30 at a position radially outward from the periphery of the opening 32a. The current collector plate 32 also has a protrusion 32b near the bent portion that projects toward the sealing body 30 (details of the protrusion 32b will be described later). A first region 32c is formed around the opening 32a of the current collector plate 32, closer to the electrode body 10 than the outer circumference of the current collector plate 32. The first region 32c is formed in an annular shape surrounding the opening 32a and is positioned with a gap between it and the cap 31. The positive electrode lead 12 is welded to the upper surface of the first region 32c. The upper surface of the first region 32c is formed flat, for example, along the radial direction of the outer can 20. A space is formed between the lower surface of the cap 31 and the upper surface of the first region 32c in which the positive electrode lead 12 can be placed. This space is also in communication with the opening 32a.

[0036] A second region 32d is formed on the outer circumference of the current collector plate 32, located above the battery compared to the first region 32c. The second region 32d is formed in an annular shape along the outer edge of the current collector plate 32. The upper surface of the second region 32d is, for example, approximately parallel to the upper surface of the first region 32c and abuts against the lower surface of the cap 31. Note that the upper surface of the second region 32d is not welded to the lower surface of the cap 31. In Figure 3, the width (radial length) of the second region 32d is smaller than the width of the first region 32c, but the relationship between the widths of each region is not particularly limited.

[0037] The current collector plate 32 has a protrusion 32b that projects toward the cap 31 at the welded portion with the cap 31. The protrusion 32b only needs to protrude toward the cap 31 more than the surrounding area, but preferably it is the part of the current collector plate 32 that protrudes the most toward the cap 31. In this embodiment, the protrusion 32b is formed between the first region 32c and the second region 32d, and the upper surface of the protrusion 32b is located above the second region 32d. The protrusion 32b is formed to improve the welded state between the cap 31 and the current collector plate 32.

[0038] A cylindrical battery 1 is manufactured, for example, by housing the electrode body 10 in an outer casing 20, pouring in the electrolyte, and then laser welding the cap 31 of the sealing body 30 to the current collector plate 32. At this time, the electrolyte may adhere to the area of ​​the current collector plate that is to be welded, and this adhered electrolyte may cause welding defects between the cap and the current collector plate. If the electrolyte is present at the welding area, the vaporized electrolyte may cause tiny holes to form in the cap. The joining of the positive electrode lead 12 to the current collector plate 32 is performed by ultrasonic welding or the like before the electrolyte is poured in.

[0039] The adhesion of electrolyte to the upper surface of the current collector plate 32 occurs when the electrolyte rises from the outer edge of the current collector plate 32 and the periphery of the opening 32a during the electrolyte injection process. However, since the upper surface of the protrusion 32b is higher than other parts, electrolyte adhesion is less likely to occur there. Furthermore, by welding the upper surface of the protrusion 32b to the cap 31, welding is performed without electrolyte present, resulting in a good weld. Even if electrolyte adheres to the upper surface of the protrusion 32b, the proportion of the upper surface of the protrusion 32b to the upper surface of the current collector plate 32 is small, so the adhered electrolyte can be easily wiped off. Moreover, even if electrolyte remains on the upper surface of the protrusion 32b during welding, a good weld can be formed by providing the gap 34 described later.

[0040] The protrusions 32b may be scattered on the upper surface of the current collector plate 32, but it is preferable that they be formed along the circumferential direction of the current collector plate 32. Furthermore, the protrusions 32b may be formed intermittently along the circumferential direction of the current collector plate 32, but it is preferable that they be formed continuously in an annular shape. For example, the protrusions 32b are formed in a circular shape in a plan view of the current collector plate 32. When the protrusions 32b are formed in an annular shape, the welded portion with the cap 31 may be formed intermittently along the protrusions 32b, or it may be formed continuously. When the welded portion between the cap 31 and the protrusions 32b is formed in an annular shape, the sealing function of the sealing body 30 is further improved, and the airtightness of the cylindrical battery 1 is enhanced. The welded portion may be formed at approximately equal intervals along the circumferential direction of the protrusions 32b, which are formed in an annular shape in a plan view.

[0041] The protrusion 32b is preferably formed in a levee shape surrounding the opening 32a at a position approximately equidistant from the outer edge of the current collector plate 32 and the periphery of the opening 32a. Furthermore, the protrusion 32b is preferably formed with a flat upper surface. A flat upper surface facilitates the formation of a welded joint with high joint strength. The upper surface of the protrusion 32b is formed, for example, parallel to the upper surfaces of the first region 32c and the second region 32d. The width W of the flat upper surface of the protrusion 32b is, for example, 1.0 to 2.5 mm, preferably 1.2 to 1.5 mm. The protrusion 32b is preferably formed with a constant width W along the circumferential direction of the current collector plate 32.

[0042] The height H1 of the protrusion 32b is not particularly limited, but is preferably at least 50% of the thickness of the current collector plate 32, and more preferably 50-150% of the thickness of the current collector plate 32. Here, height H1 refers to the length along the vertical direction of the battery (thickness direction of the sealing body 30) from the upper surface of the second region 32d to the upper surface of the protrusion 32b. A preferred example of height H1 is 0.2-0.5 mm. In this embodiment, the height H2 from the upper surface of the first region 32c is higher than the height H1 from the upper surface of the second region 32d. Since the electrolyte can easily rise from the inside of the current collector plate 32, increasing the height H2 can more effectively prevent the electrolyte from adhering to the upper surface of the protrusion 32b. A preferred example of height H2 is 1-3 mm.

[0043] The cap 31 preferably has a recess 31a into which the protrusion 32b of the current collector plate 32 fits. Providing the recess 31a makes it easier to align and weld the cap 31 and the current collector plate 32, and also improves the sealing function of the sealing body 30. The recess 31a is formed on the lower surface of the cap 31 facing the current collector plate 32, and preferably the thickness of the cap 31 in the part where the recess 31a is formed is thinner than other parts. The recess 31a becomes the welded part with the current collector plate 32, but by thinning the part where the recess 31a is formed, the output of the laser used for welding can be reduced, and the condition of the welded part becomes more stable.

[0044] The recess 31a, like the protrusion 32b, is formed in an annular shape along the circumferential direction of the current collector plate 32. Preferably, the recess 31a has a depth and width that allows the entire protrusion 32b to be inserted. The bottom (lower surface) of the recess 31a is formed flat so as to make broad contact with the upper surface of the protrusion 32b. Preferably, the depth of the recess 31a (the length along the vertical direction of the battery from the lower surface of the cap 31 to the bottom of the recess 31a) is equal to the height H1 of the protrusion 32b. In this case, with the protrusion 32b inserted into the recess 31a, the upper surface of the second region 32d contacts the lower surface of the cap 31.

[0045] In the example shown in Figure 3, the entire upper surface of the convex portion 32b is in contact with the lower surface of the concave portion 31a. A portion of the upper surface of the convex portion 32b is welded to the lower surface of the concave portion 31a. Although the welded portion is not shown in Figure 3, a welded portion is formed where the metal constituting the cap 31 and the current collector plate 32 are fused and solidified at the point where the concave portion 31a and the convex portion 32b meet. The thickness of the cap 31 in the portion where the concave portion 31a is formed is, for example, 30-70% or 40-60% of the thickness of the other portions. A preferred example of this thickness is 0.4-0.8 mm or 0.5-0.7 mm.

[0046] The configuration of the upper insulating plate 40, which is placed between the electrode body 10 and the sealing body 30, will be explained in detail below with reference to Figures 3 to 5. Figure 4 is a plan view of the first insulating plate 41, and Figure 5 is a plan view of the second insulating plate 42, showing them in their respective positions on the electrode body 10. Since Figure 5 also shows the first insulating plate 41, it can be said to be a plan view of the upper insulating plate 40.

[0047] As shown in Figures 3 to 5, the upper insulating plate 40 includes a first insulating plate 41 and a second insulating plate 42 positioned closer to the sealing body 30 than the first insulating plate 41. That is, the upper insulating plate 40 has a two-layer structure including two insulating plates. The first insulating plate 41 is interposed between the electrode body 10 and the positive electrode lead 12 to prevent contact between the negative electrode constituting the electrode body 10 and the positive electrode lead 12. The second insulating plate 42 is interposed between the grooved portion 23 of the outer can 20 and the positive electrode lead 12 to prevent contact between the outer can 20, which functions as a negative electrode external terminal, and the positive electrode lead 12.

[0048] As described above, multiple positive electrode leads 12 are provided at approximately equal intervals along the longitudinal direction of the positive electrode 11. Therefore, some of the positive electrode leads 12 extend from a position on the outer circumference of the electrode body 10 that overlaps with the grooved portion 23 in the vertical direction. It is conceivable to prevent electrical contact between the positive electrode leads 12 and the grooved portion 23 by applying insulating tape to the part of the positive electrode lead 12 that may come into contact with the grooved portion 23. However, in this case, it is conceivable that the tape may peel off after prolonged use. With the cylindrical battery 1, by providing the second insulating plate 42, electrical contact between the positive electrode leads 12 and the grooved portion 23 can be prevented more reliably.

[0049] At least one positive electrode lead 12 is sandwiched between the first insulating plate 41 and the second insulating plate 42. Of the multiple positive electrode leads 12, at least the positive electrode leads 12 positioned to overlap the grooved portion 23 in the vertical direction are bent in the direction of the central axis of the electrode body 10 and extend radially along the upper surface of the first insulating plate 41 to the outer casing 20. At least a portion of these positive electrode leads 12 is sandwiched between the first insulating plate 41 and the second insulating plate 42. The positive electrode leads 12 located on the outer circumference side of the electrode body 10 beyond the periphery of the opening 32a of the current collector plate 32 are bent in the direction of the central axis of the electrode body 10 and extend through the opening 32a to the upper surface of the current collector plate 32.

[0050] The first insulating plate 41 has an opening 41a formed on the central axis of the electrode body 10. The opening 41a has, for example, a roughly circular shape and serves as a hole for inserting a retaining rod when welding the negative electrode current collector plate and the bottom of the can 22 together. The first insulating plate 41 also has an opening 41b through which the positive electrode lead 12 extending from the inner circumference of the electrode body 10 passes, and is positioned on the electrode body 10 with the region on the outer circumference of the electrode body 10 from which the positive electrode lead 12 extends exposed. In the example shown in Figure 4, the openings 41a and 41b are formed as independent through holes that do not communicate with each other.

[0051] The opening 41b is a through-hole positioned away from the outer peripheral edge of the first insulating plate 41, and it is preferable that the periphery of the opening 41b is formed in an annular shape. In this case, the mechanical strength of the first insulating plate 41 is increased. The opening 41b has, for example, a substantially arched or substantially semicircular shape in plan view. In the example shown in Figure 4, five positive electrode leads 12 extend through the opening 41b toward the sealing body 30. An arc-shaped curved strip region is formed between the outer peripheral edge of the first insulating plate 41 and the opening 41b, and this strip region covers a part of the outer peripheral side of the electrode body 10.

[0052] The outer circumference of the first insulating plate 41 is shorter than the outer circumference of the electrode body 10, and the outer edge of the first insulating plate 41 is formed in a substantially semicircular shape in plan view. For this reason, the first insulating plate 41 does not cover a portion of the outer circumference of the electrode body 10, and the positive electrode leads 12 extend from the portion of the outer circumference of the electrode body 10 that is not covered by the first insulating plate 41. In the example shown in Figure 4, three positive electrode leads 12 extend from a portion of the outer circumference of the electrode body 10 that is not covered by the first insulating plate 41 toward the sealing body 30, and two of them extend from a position opposite the grooved portion 23. In addition, a portion of the outer edge of the first insulating plate 41 bulges outwards toward the three positive electrode leads 12. This bulge more reliably prevents contact between the negative electrode of the electrode body 10 and the positive electrode leads 12.

[0053] In a plan view of the electrode body 10, the positive electrode leads 12 extending from the inner circumference of the electrode body 10 are biased towards one radial side of the electrode body 10, while the positive electrode leads 12 extending from the outer circumference of the electrode body 10 are biased towards the other radial side of the electrode body 10. In other words, a predetermined spacing of the positive electrode leads 12 along the longitudinal direction of the positive electrode 11 is set so that the positive electrode leads 12 are arranged in this manner, while taking into consideration the improvement of the battery's output characteristics.

[0054] The second insulating plate 42 has an opening 42a formed in its radial center so as to overlap vertically with a portion of the opening 41b of the first insulating plate 41. The opening 42a has a circular shape, for example, with the center (radial center) of the second insulating plate 42 as its center. The second insulating plate 42 is formed in a ring shape that covers the electrode body 10 on its outer periphery. The ring-shaped second insulating plate 42 covers the positive electrode lead 12 extending from the outer periphery of the electrode body 10 and is interposed between the positive electrode lead 12 and the grooved portion 23. The opening 41b overlaps vertically with the entire opening 41b of the first insulating plate 41.

[0055] The second insulating plate 42 is positioned below the grooved portion 23 and covers substantially the entire area of ​​the grooved portion 23. Preferably, the inner peripheral edge of the second insulating plate 42 (the peripheral edge of the opening 42a) is located radially towards the center of the outer can 20, rather than towards the inner end of the grooved portion 23. On the other hand, preferably, the inner peripheral edge of the second insulating plate 42 is located radially outward of the outer can 20, rather than towards the peripheral edges of the openings 32a and 33a of the current collector plate 32 and gasket 33. The inner and outer peripheral edges of the second insulating plate 42 are formed concentrically in plan view, and cover the outer circumference of the electrode body 10 with the same width over its entire circumference. The second insulating plate 42 is in contact with, for example, the lower surface of the grooved portion 23. The second insulating plate 42 may also be joined to the upper surface of the first insulating plate 41.

[0056] The thicknesses of the first insulating plate 41 and the second insulating plate 42 are, for example, 0.2 to 0.6 mm. In Figure 3, the first insulating plate 41 is shown to be thicker than the second insulating plate 42, but the relationship between the thicknesses of each insulating plate is not particularly limited.

[0057] In the manufacturing process of the cylindrical battery 1, the electrode body 10 to which the positive electrode leads 12 are connected is inserted into the outer casing 20 and the electrolyte is poured in, after which the upper insulating plate 40 is placed on the electrode body 10. At this time, the first insulating plate 41 is placed on the electrode body 10 and some of the positive electrode leads 12 are bent toward the central axis of the electrode body 10. Then, the second insulating plate 42 is placed on the bent positive electrode leads 12, sandwiching the positive electrode leads 12 between the two insulating plates. All of the positive electrode leads 12 then extend toward the sealing body 30 through the opening 42a of the second insulating plate 42, and the tip of each lead is bent toward the opposite side of the central axis so that it lies along the upper surface of the current collector plate 32 and is joined to the upper surface of the current collector plate 32. Some of the positive electrode leads 12 extending from the inner circumference of the electrode body 10 are not bent toward the center of the electrode body 10, but extend toward the sealing body 30 through the opening 42a.

[0058] Hereinafter, a modified example of the sealing body 30 will be described with reference to Figures 6 and 7. Figures 6 and 7 are enlarged cross-sectional views showing the protrusion 32b of the current collector plate 32 and its vicinity, with Figure 6 showing the state before welding the cap 31 and the current collector plate 32, and Figure 7 showing the state after the welded portion has been formed.

[0059] As shown in Figures 6 and 7, a gap 34 is formed between the recess 31a of the cap 31 and the protrusion 32b of the current collector plate 32 in the thickness direction of the sealing body 30 (the vertical direction of the battery). In the example shown in Figure 3, the entire upper surface of the protrusion 32b is in contact with the lower surface of the recess 31a even before the weld is formed, but in the example shown in Figure 6, the upper surface of the protrusion 32b and the lower surface of the recess 31a are separated in the vertical direction and are not in contact with each other. Note that the embodiment illustrated in Figure 6 is the same as the embodiment illustrated in Figure 3 (before welding), except that a gap 34 exists between the upper surface of the protrusion 32b and the lower surface of the recess 31a.

[0060] As shown in Figure 7, the gap 34 is formed at least around the welded area 35, between the upper surface of the convex portion 32b and the lower surface of the concave portion 31a. The gap 34 may be formed locally to surround the welded area, but preferably it is formed in an annular shape along the convex portion 32b. When laser welding is performed, if a certain amount of electrolyte is present on the upper surface of the convex portion 32b, vapor generated by the vaporization of the electrolyte may scatter the molten metal, causing porosity. However, by providing the gap 34, an escape route for the vapor can be secured, and porosity in the welded area can be suppressed to a high degree. The effect of the convex portion 32b suppresses the adhesion of electrolyte to the welded area, but by providing the gap 34, porosity in the welded area 35 can be prevented even if a large amount of electrolyte is present at the welded area for some reason.

[0061] The welded joint 35 is formed when the metal constituting the cap 31 melts due to laser irradiation of the cap 31. In this embodiment, the molten metal of the cap 31 connects to the upper surface of the opposing protrusion 32b across the gap 34, melting the metal of the current collector plate 32 to form the welded joint 35. In other words, the molten metal of the cap 31 connects the cap 31 and the current collector plate 32 across the gap 34.

[0062] The spacing G of the gap 34 is preferably less than 1 / 3 of the thickness of the cap 31 in the portion where the recess 31a is formed (laser-irradiated portion), and more preferably 1 / 4 or less. The spacing G is the length along the thickness direction of the sealing body 30 from the upper surface of the convex portion 32b to the lower surface of the recess 31a. If the spacing G exceeds 1 / 3 of the thickness of the laser-irradiated portion, for example, the metal of the cap 31 that melts and falls may be cut in the middle, making it impossible to form a welded portion connecting the cap 31 and the current collector plate 32.

[0063] The lower limit of the gap G of the gap 34 is not particularly limited, but one example is that it is 3% or more of the thickness of the cap 31 in the portion where the recess 31a is formed. A preferred range for the gap G is, for example, 3 to 30% or 5 to 25%. If the gap G is within this range, even if electrolyte is present at the welding site for some reason, a cleaner weld without holes can be formed more reliably. The gap 34 can be formed, for example, by slightly reducing the height of the protrusion 32b compared to the embodiment illustrated in Figure 3.

[0064] In this embodiment, a space wider than the gap 34 is formed between the portion of the current collector plate 32 located inside the protrusion 32b and the cap 31. The gap 34 communicates with this space. The current collector plate 32 is bent toward the electrode body 10 at the inner circumference end of the protrusion 32b and has a first region 32c that is lower than the protrusion 32b. The distance between the lower surface of the cap 31 and the upper surface of the first region 32c is greater than the gap G of the gap 34, and a relatively large space exists inside the protrusion 32b of the sealing body 30. This space is also connected to the inside of the outer can 20 through the opening 32a of the current collector plate 32.

[0065] The upper surface of the protrusion 32b is not in contact with the lower surface of the recess 31a, nor is the portion located between the protrusion 32b and the first region 32c in contact with the lower surface of the cap 31. Therefore, a passage for steam is secured from the gap 34 to the space. By connecting the gap 34 and the space, steam can be released more effectively, improving the stability of the welding. [Examples]

[0066] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited to these examples.

[0067] <Example 1> A wound electrode assembly, with multiple positive electrode leads connected, was housed in a bottomed cylindrical outer casing. A non-aqueous electrolyte was then poured in, and an upper insulating plate was placed on top of the electrode assembly. The outer casing was then spun to form grooves. A current collector plate was placed on the grooves via a gasket, and the positive electrode leads were ultrasonically welded to the upper surface of the current collector plate. After degassing under reduced pressure, a cap was placed on the current collector plate, and the cap and current collector plate were welded together by irradiating the upper surface of the cap with a laser. Finally, the upper end of the outer casing was crimped to the cap to obtain a cylindrical battery.

[0068] The sealing body, consisting of a cap, a current collector plate, and a gasket, closes the opening of the outer can. An annular protrusion is formed on the upper surface of the current collector plate, and a recess into which the protrusion fits is formed on the lower surface of the cap. The upper surface of the protrusion and the lower surface of the recess are laser-welded. The sealing body has the structure shown in Figure 1. The height of the protrusion, etc., are as follows. Height of the protrusion H1: 0.4 mm Height of the protrusion H2: 1.2 mm Width of the top surface of the protrusion: W: 2.0 mm Thickness of the cap in the recessed area: 0.6 mm

[0069] <Comparative Example 1> A cylindrical battery was manufactured in the same manner as in Example 1, except that the sealing body was constructed using a cap without the aforementioned recess and a current collector plate without the aforementioned protrusion.

[0070] [Evaluation of welded joints] Ten batteries each were prepared for Example 1 and Comparative Example 1. The presence or absence of perforations in the welded joints (presence or absence of leaking through-holes) was evaluated by visual inspection of the welded joints between the cap and the current collector plate. As a result, no perforations were found in any of the ten batteries of Example 1. On the other hand, perforations were found in six of the batteries of Comparative Example. In the batteries of Comparative Example, it is thought that, for example, electrolyte adhered to the welded joint of the current collector plate during the degassing process, and that the vaporized electrolyte due to laser irradiation caused tiny holes in the cap.

[0071] As described above, with the cylindrical battery 1 (battery of Example 1) having the above configuration, by forming a protrusion 32b on the upper surface of the current collector plate 32 that constitutes the sealing body 30, the welding state between the cap 31 and the current collector plate 32 is stabilized and a good welding state is obtained. The electrolyte does not rise to the upper surface of the protrusion 32b during the battery manufacturing process, and it is difficult for the electrolyte to adhere to it. Furthermore, even if the electrolyte adheres, it can be easily wiped off. For this reason, it is possible to more reliably prevent the occurrence of holes when a laser is irradiated onto the part to which the electrolyte has adhered.

[0072] Furthermore, even when a small amount of electrolyte was intentionally applied to the upper surface of the convex portion of the current collector plate used in Example 1 using a cotton swab, no holes were observed in the welded area of ​​any of the 10 batteries (Application Experiment 1).

[0073] <Example 2> A cylindrical battery was manufactured in the same manner as in Example 1, except that the protrusions on the current collector plate were polished down to reduce their height by 0.05 mm, and a gap (gap G = 0.05 mm) was formed between the upper surface of the protrusions and the lower surface of the recesses of the cap, as shown in Figure 6.

[0074] <Example 3> A cylindrical battery was fabricated in the same manner as in Example 2, except that the gap G was changed to 0.10 mm.

[0075] <Example 4> A cylindrical battery was fabricated in the same manner as in Example 2, except that the gap G was changed to 0.15 mm.

[0076] <Comparative Example 2> A cylindrical battery was fabricated in the same manner as in Example 2, except that the gap G was changed to 0.20 mm.

[0077] [Evaluation of welded joints] Ten batteries each were prepared for Examples 1-4 and Comparative Example 2. Electrolyte was intentionally applied to the upper surface of the protrusions on each current collector plate using a cotton swab. Then, a cap was placed on the current collector plate so that the protrusions fit into the recesses of the caps. A welding laser was then shone onto the recessed portion of the cap from the upper surface opposite the recess. The amount of electrolyte applied was approximately twice (for Experiment 2) and approximately four times (for Experiment 3) the amount applied in Experiment 1. The presence or absence of holes in the welded area and the formation of a weld were evaluated by observing the appearance of the laser-irradiated area. The evaluation results are shown in Table 1. The numbers in each row for each experiment represent the number of batteries out of 10 in which holes were confirmed in the welded area.

[0078] [Table 1]

[0079] As shown in Table 1, when there is no gap between the upper surface of the convex portion of the current collector plate and the lower surface of the concave portion of the cap, i.e., when the laser is irradiated with the upper surface of the convex portion and the lower surface of the concave portion in contact, perforation of the welded portion was confirmed in one battery in coating experiment 2 and in three batteries in coating experiment 3 (Example 1). In the battery of Example 1, the effect of the convex portion of the current collector plate makes it unlikely for electrolyte to adhere to the welded area, but if a large amount of electrolyte is present at the welded area for some reason, perforation of the welded portion may occur in the battery of Example 1 as well.

[0080] In contrast, no holes were observed in the welded areas of any of the 10 batteries in Examples 2-4. It is believed that by creating a gap between the upper surface of the convex part and the lower surface of the concave part, this gap acts as a venting path for the electrolyte vapor generated by laser irradiation, reducing the amount of molten metal scattered and preventing holes from forming. As can be understood from the results of Example 1, if no gap is present, the amount of molten metal scattered may increase due to the vapor released through the welded area.

[0081] On the other hand, when the gap G widened to 0.20 mm, which corresponds to 1 / 3 of the thickness of the cap in the area irradiated by the laser, no weld was formed connecting the current collector plate and the cap (Comparative Example 2). In other words, in order to form a clean weld without holes when there is a certain amount of electrolyte present in the laser irradiation area, under the conditions of this embodiment and comparative example, it is necessary to provide a gap of less than 0.20 mm between the upper surface of the convex portion and the lower surface of the concave portion.

[0082] The above embodiments can be modified as appropriate without impairing the purpose of this disclosure. For example, the first electrode can be made the negative electrode and the second electrode the positive electrode of the electrode body. It is also possible to use a single-layer insulating plate as the upper insulating plate and to attach insulating tape to the part that may come into contact with the grooved portion of the positive electrode tab. [Explanation of Symbols]

[0083] 1 Cylindrical battery, 10 Electrode body, 11 Positive electrode, 12 Positive electrode lead, 20 Outer can, 21 Side wall, 22 Can bottom, 23 Grooved section, 30 Sealing body, 31 Cap, 31a Recess, 32 Current collector plate, 32a, 33a, 41a, 41b, 42a Opening, 32b Protrusion, 32c First region, 32d Second region, 33 Gasket, 33b Through hole, 34 Gap, 35 Welded section, 40 Upper insulating plate, 41 First insulating plate, 42 Second insulating plate

Claims

1. Electrode body and An outer container housing the electrode body, A sealing body that closes the opening of the outer can, Equipped with, The sealing body includes a cap and a current collector plate positioned on the electrode body side of the cap and welded to the cap. The current collector plate has a protrusion that extends toward the cap at the welded portion with the cap, The cap is a sealed battery having a recess into which the protrusion of the current collector plate fits.

2. A sealed battery according to claim 1, wherein a gap is formed between the convex portion and the concave portion, at least around the welded portion, in the thickness direction of the sealing body.

3. A space wider than the gap is formed between the portion of the current collector plate located inside the protrusion and the cap. The gap is in communication with the space, as described in claim 2 of the sealed battery 。

4. The sealed battery according to any one of claims 1 to 3, wherein the protrusion of the current collector plate is formed in an annular shape.

5. The electrode body comprises electrode leads that connect the electrodes and the current collector plate, The sealed battery according to any one of claims 1 to 3, wherein a plurality of electrode leads are provided at predetermined intervals along the longitudinal direction of the electrode.

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