Method for manufacturing cylindrical battery, and cylindrical battery

Abstract

A method for manufacturing a cylindrical battery according to one embodiment of the present disclosure includes: a step for irradiating at least a portion of an inner surface (31a) of a bottom portion (31) of an outer can (16) with laser light before an electrode body is housed, so as to improve the reflectivity of light; and a step for joining, on the inner surface (31a), a lead wire extending from the electrode body, by ultrasonic welding, to a laser irradiation section irradiated with laser light. It is preferable that the surface roughness Ra of the laser irradiation section is reduced by irradiation with the laser light. According to this method for manufacturing a cylindrical battery, variation in the bonding strength between a lead wire and an outer can (16) when the lead wire is bonded to the bottom (31) of the outer can (16) by ultrasonic bonding can be suppressed.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a cylindrical battery and the cylindrical battery. Background Art

[0002] Patent Document 1 describes a conventional cylindrical battery. This cylindrical battery comprises an electrode assembly formed by winding a positive electrode and a negative electrode with a separator interposed therebetween; a bottomed, cylindrical outer can housing the electrode assembly; and a sealing member that closes the opening of the outer can. A positive electrode lead extending from the positive electrode is welded to the sealing member, forming the positive electrode terminal. Furthermore, a negative electrode lead extending from the negative electrode is welded to the inner surface of the bottom of the outer can, forming the negative electrode terminal.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 09-274923 Summary of the Invention

[0006] Resistance welding or laser welding is commonly used to join the negative electrode lead to the bottom of the outer can. However, the spatter generated during welding can reduce battery quality. In contrast, ultrasonic welding eliminates spatter and improves battery quality. However, ultrasonic welding requires a long, thin, rod-shaped horn inserted into the hollow portion of the wound electrode assembly to transmit ultrasonic vibrations to the bottom of the outer can, which houses the wound electrode assembly. This makes joining the negative electrode lead to the bottom of the outer can difficult, and the strength of the joint can easily vary.

[0007] Therefore, an object of the present disclosure is to provide a method for manufacturing a cylindrical battery that can suppress variations in the bonding strength between a lead and the bottom of an outer can, and a cylindrical battery that has small variations in the bonding strength between a lead and an outer can and excellent quality and battery performance.

[0008] In the manufacturing method of the cylindrical battery involved in the present disclosure, the cylindrical battery comprises: an electrode body, which is formed by winding a first electrode and a second electrode with a separator interposed therebetween; an outer can with a bottom and a cylindrical shape, which houses the electrode body; and a sealing body, which blocks the opening of the outer can and electrically connects the first electrode and the inner surface of the bottom of the outer can via a lead wire. In the manufacturing method of the cylindrical battery, laser light is irradiated on at least a portion of the inner surface of the bottom of the outer can before housing the electrode body, so as to increase the reflectivity of light.

[0009] The cylindrical battery disclosed herein comprises: an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween; a bottomed cylindrical outer can housing the electrode body; a sealing member for closing the opening of the outer can; and a negative electrode lead formed by a covering member formed by laminating a copper plate and a nickel plate, with a copper layer disposed on one side in the thickness direction, and the copper layer of the negative electrode lead being bonded to the inner surface of the bottom of the outer can.

[0010] The cylindrical battery manufacturing method disclosed herein can suppress variations in the bond strength between the lead and the outer can when the lead is ultrasonically welded to the bottom of the outer can. Furthermore, the cylindrical battery disclosed herein can improve quality and battery performance while suppressing variations in the bond strength between the lead and the outer can. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view in the axial direction of a cylindrical battery according to one embodiment of the present disclosure.

[0012] Figure 2 This is a diagram illustrating an example of a method for producing the cylindrical battery.

[0013] Figure 3 This is a schematic plan view showing a state in which the center portion of the bottom inner surface of the outer can is irradiated with laser light.

[0014] Figure 4 This is a diagram illustrating ultrasonic welding of a lead wire to a laser-irradiated portion of the bottom of an outer can. DETAILED DESCRIPTION

[0015] Below, with reference to the accompanying drawings, embodiments of the cylindrical battery disclosed herein are described in detail. Furthermore, the cylindrical battery disclosed herein may be a primary battery or a secondary battery. Furthermore, it may be a battery utilizing an aqueous electrolyte or a battery utilizing a non-aqueous electrolyte. Below, a non-aqueous electrolyte secondary battery (lithium-ion battery) utilizing a non-aqueous electrolyte is exemplified as one embodiment of the cylindrical battery 10. However, the cylindrical battery disclosed herein is not limited thereto, and the electrolyte may also be an aqueous electrolyte.

[0016] It was originally envisioned that the characteristic parts of the embodiments and modifications described below would be appropriately combined to construct new embodiments. In the embodiments described below, the same structures are marked with the same figure marks in the drawings, and repeated descriptions are omitted. In addition, schematic diagrams are included in multiple drawings, and the dimensional ratios of the vertical, horizontal, and height of each component are not necessarily the same between different drawings. In this specification, the axial (height direction) side of the sealing body 17 of the cylindrical battery 10 is set as "upper", and the axial side of the bottom 31 of the outer can 16 is set as "lower". Among the constituent elements described below, the constituent elements that are not recorded in the independent claims representing the highest concept are arbitrary constituent elements and are not essential constituent elements. In addition, the present disclosure is not limited to the embodiments described below and their modifications, and various improvements and changes can be made within the scope of the matters recorded in the claims of this application and their equivalents.

[0017] Figure 1 FIG is a cross-sectional view of the cylindrical battery 10 according to one embodiment of the present disclosure in the axial direction. Figure 1 As shown, the cylindrical battery 10 includes an electrode body 14; a bottomed cylindrical outer can 16 that houses the electrode body 14; and a sealing member 17 that closes the opening of the outer can 16. The outer can 16 houses the non-aqueous electrolyte along with the electrode body 14. The outer can 16 has a shoulder 29 whose upper end is bent radially inward and extends inward. The outer can 16 has a groove 22 formed in its side wall. The sealing member 17 is supported by the groove 22 and closes the opening of the outer can 16.

[0018] The cylindrical battery 10 further includes a gasket 28 interposed between the outer can 16 and the sealing member 17. The gasket 28 is an annular resin member attached to the outer periphery of the sealing member 17, insulating the sealing member 17 from the outer can 16. The gasket 28 closes the gap between the outer can 16 and the sealing member 17, thereby sealing the interior of the battery. The gasket 28 is made of, for example, polyolefin.

[0019] The non-aqueous electrolyte includes 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 mixed solvents of two or more of these. The non-aqueous solvent may also contain a halogen-substituted form in which at least a portion of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and mixed solvents thereof. Examples of electrolyte salts include lithium salts such as LiPF6. In addition, the non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte.

[0020] The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a winding structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The negative electrode 12 is an example of a first electrode, and the positive electrode 11 is an example of a second electrode. The positive electrode 11, the negative electrode 12, and the separator 13 are all strip-shaped elongated bodies, and are alternately stacked in the radial direction of the electrode body 14 by being spirally wound. In order to prevent the precipitation of lithium, the negative electrode 12 is formed to be one size larger than the positive electrode 11. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in the length direction and the width direction. The separator 13 is formed to be at least one size larger than the positive electrode 11, and for example, two pieces are configured so as to sandwich the positive electrode 11.

[0021] A positive electrode lead 20 and a negative electrode lead 21 are connected to the electrode body 14. The positive electrode lead 20 electrically connects the positive electrode 11 to the sealing body 17, and the negative electrode lead 21 electrically connects the negative electrode 12 to the bottom 31 of the outer can 16. Figure 1 In the illustrated example, positive electrode lead 20 extends through the opening of upper insulating plate 18 toward sealing body 17 , and negative electrode lead 21 extends through the outside of lower insulating plate 19 toward bottom 31 of outer can 16 .

[0022] The positive electrode 11 includes a positive electrode core and a positive electrode mixture layer formed on at least one surface of the positive electrode core. The positive electrode core can be made of a foil of a metal such as aluminum or an aluminum alloy that is stable within the potential range of the positive electrode 11, or a film of such a metal disposed on the surface. 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 (PVdF), and is preferably formed on both surfaces of the positive electrode core. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc. is used as the positive electrode active material. The positive electrode lead 20 is connected to the positive electrode 11, but is preferably directly bonded to the positive electrode core by ultrasonic welding or the like.

[0023] The negative electrode 12 comprises a negative electrode core and a negative electrode mixture layer formed on at least one surface of the negative electrode core. The negative electrode core can be made of a metal foil such as copper or a copper alloy that is stable within the potential range of the negative electrode 12, or a film having such a metal disposed on the surface. The negative electrode mixture layer comprises a negative electrode active material and a binder such as styrene-butadiene rubber (SBR) or PVdF, and is preferably formed on both surfaces of the negative electrode core. Examples of the negative electrode active material include graphite and silicon-containing compounds. The negative electrode lead 21 is preferably directly bonded to the negative electrode core by ultrasonic welding or other methods.

[0024] The outer can 16 is generally made of a metal primarily composed of iron, such as iron plated with nickel, but may also be made of a metal primarily composed of aluminum or the like. The outer can 16 includes a cylindrical portion 39 and a bottom portion 31. The cylindrical portion 39 includes an annular groove 22 and an annular shoulder 29. The groove 22 is formed by spinning a portion of the cylindrical portion 39 radially inwardly. The shoulder 29 is formed by bending the upper end of the cylindrical portion 39 radially inwardly and riveting it to the peripheral edge 33 of the sealing body 17, and extends radially inward.

[0025] The sealing body 17 is secured to the outer can 16 by riveting, sandwiched between the shoulder 29 and the groove 22 via the gasket 28. The groove 22 is formed a predetermined distance from the upper end of the outer can 16. The predetermined distance is, for example, 1 to 20% of the axial length of the outer can 16. The gasket 28 is strongly compressed by the shoulder 29, and a portion of it protrudes radially inward from between the shoulder 29 and the sealing body 17.

[0026] The sealing body 17 has a structure in which a terminal plate 23, a lower valve body 24, an insulating plate 25, an upper valve body 26, and a sealing plate 27 are stacked in this order from the electrode body 14 side. The components constituting the sealing body 17 have, for example, a disc shape or a ring shape, and the components other than the insulating plate 25 are electrically connected to each other. The sealing plate 27 has a convex shape with a radially central portion protruding outward. The convex portion 27a of the sealing plate 27 includes: an inclined portion formed in an annular shape; and a flat top portion surrounded by the inclined portion. One or more vent holes 27b are formed on the top portion.

[0027] The lower valve body 24, insulating plate 25, and upper valve body 26 constitute the current interruption mechanism. The lower valve body 24 and upper valve body 26 are connected at their respective centers, with the insulating plate 25 interposed between their respective peripheral edges. If an abnormality occurs in the cylindrical battery 10 and the internal pressure rises, the lower valve body 24 deforms, pushing the upper valve body 26 toward the sealing plate 27, causing it to rupture, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 ruptures, allowing gas to escape through the vent holes 27b in the sealing plate 27.

[0028] One end of the positive electrode lead 20 is joined to the positive electrode core by ultrasonic welding or the like, and the other end of the positive electrode lead 20 is joined to the lower surface of the terminal plate 23 by laser welding, ultrasonic welding or the like. As a result, the top plate of the sealing body 17, i.e., the sealing plate 27 electrically connected to the terminal plate 23, becomes the positive electrode terminal.

[0029] The negative electrode lead 21 is formed by laminating a nickel plate and a copper plate. For example, the negative electrode lead 21 is formed by pressing one side of the nickel plate and one side of the copper plate together, then heat-treating them. A nickel layer 21a is provided on one side of the negative electrode lead 21 in the thickness direction, and a copper layer 21b is provided on the other side of the negative electrode lead 21 in the thickness direction.

[0030] One end of the negative electrode lead 21 is joined to the negative electrode core by ultrasonic welding or the like, while the copper layer 21b at the other end of the negative electrode lead 21 is joined to the inner surface of the bottom 31 of the outer can 16 by ultrasonic welding. As a result, the outer can 16 electrically connected to the negative electrode 12 serves as the negative electrode terminal. While the sealing member 17 has been described as forming the positive electrode terminal and the outer can 16 as the negative electrode terminal, the sealing member may also form the negative electrode terminal and the outer can may form the positive electrode terminal.

[0031] Next, an example of a method for manufacturing the cylindrical battery 10 is described. Figure 2 As shown, before accommodating the electrode assembly 14 , at least a portion of the inner surface 31 a of the bottom 31 of the bottomed cylindrical outer can 16 is irradiated with laser light to increase the reflectivity of light.

[0032] Figure 3 : is a schematic top view showing the state of the inner surface 31a after the laser is irradiated to the circular area in the center of the inner surface 31a. Figure 3 , irradiating the laser so that gloss is generated in the laser irradiated portion 41. By confirming that gloss is generated in the laser irradiated portion 41, it can be confirmed that the reflectivity of light in the laser irradiated portion 41 is improved. Preferably, the surface roughness Ra of the laser irradiated portion 41 is reduced by irradiating the laser.

[0033] Ultraviolet laser is preferably used as the laser for irradiation, but the wavelength of the laser for irradiation may be longer than that of ultraviolet laser.

[0034] Next, the copper layer 21 b of the negative electrode lead 21 extending from the electrode assembly 14 is joined to the laser irradiation portion 41 by ultrasonic welding. Figure 4 is a schematic diagram for explaining the ultrasonic welding. Figure 4 In the figure, the electrode body 14 is omitted.

[0035] like Figure 4As shown, the bottom 31 of the outer can 16 is placed on the upper surface 51a of the anvil 51. Next, the slender, rod-shaped horn (ultrasonic welding nozzle) 61 of the ultrasonic welding device is inserted into the hollow portion (not shown) of the electrode body 14. The horn tip 61a is used to press the nickel layer 21a of the negative electrode lead 21 extending from the electrode body 14 toward the laser-irradiated portion 41 of the bottom 31. Finally, in this pressed state, ultrasonic vibrations are transmitted through the horn 61 to the lead portion sandwiched between the horn tip 61a and the bottom 31. In this manner, the copper layer 21b of the negative electrode lead 21 is ultrasonically welded to the laser-irradiated portion 41 of the bottom 31. Subsequently, the groove 22 is formed and the opening of the outer can 16 is sealed using known techniques, thereby completing the cylindrical battery 10.

[0036] [Joint strength measurement test]

[0037] <Experimental Example 1>

[0038] A cylindrical outer can with a bottom was produced. On the same date as the outer can was manufactured, the copper layer of the lead wire, formed from the aforementioned sheathing, was ultrasonically welded to the inner surface of the outer can's bottom using the method described above. The bond strength between the lead wire and the outer can was then measured using a lead pull test. An ultrasonic welding apparatus was used, using a rod-shaped horn with a maximum outer diameter of 3 mm, a tip outer diameter of 1.4 mm, and a horn length of 105 mm. The lead wire was 0.1 mm thick, and the outer can's bottom was 0.4 mm thick. The outer can was made of nickel-plated iron. Ultrasonic welding was performed at an energy of 2.1 J.

[0039] <Experimental Example 2>

[0040] The bonding strength of the joint between the lead and the outer can was measured in the same manner as in Experimental Example 1, except that the lead was bonded to the bottom of the outer can by ultrasonic welding 90 days after the outer can was produced.

[0041] <Experimental Example 3>

[0042] The bond strength between the lead and the outer can was measured in the same manner as in Experimental Example 1, except that the center of the inner surface of the outer can bottom was irradiated with laser light 90 days after the outer can was manufactured and before the lead was ultrasonically welded to the bottom. Laser conditions were set to increase the reflectivity of the laser-irradiated area of ​​the outer can. Specifically, an ultraviolet laser with a wavelength of 355 nm was used, and the laser focus was aligned at a depth of 2 mm from the inner surface of the bottom. Furthermore, the laser pulse repetition frequency was set to 80 kHz, and the laser scanning speed was set to 300 mm / s.

[0043] (Measurement results)

[0044] [Table 1]

[0045]

[0046] In Table 1, the bond strength is expressed as a relative value, with the bond strength in Experimental Example 1 being set to 100. As shown in Experimental Examples 1 and 2, the bond strength between the lead wire and the outer can decreases when the bottomed cylindrical outer can is left for a long period of time after fabrication. On the other hand, as shown in Experimental Example 3, even when the outer can is left for a long period of time after fabrication, laser pretreatment can ensure a bond strength comparable to that obtained by ultrasonic welding immediately after fabrication of the outer can 16. Based on these results, the variation in the bond strength between the lead wire and the outer can during ultrasonic welding is believed to be due to changes in the outer can's surface condition over time, presumably due to the effects of the laser pretreatment removing the oxide film formed on the outer can.

[0047] The inventors of this application have confirmed that, when ultrasonic welding is used, welding the copper layer of the lead to the outer can increases the bond strength between the lead and the outer can compared to welding the nickel layer of the lead to the outer can. Furthermore, since the lead contains a copper layer, the internal resistance of the battery is reduced. Therefore, the cylindrical battery of this embodiment can suppress variations in the bond strength between the lead and the outer can, while improving quality and battery performance.

[0048] Description of Reference Signs

[0049] 10: Cylindrical battery, 11: Positive electrode, 12: Negative electrode, 13: Separator, 14: Electrode body, 16: Outer can, 17: Sealing body, 18: Upper insulating plate, 19: Lower insulating plate, 20: Positive electrode lead, 21: Negative electrode lead, 21a: Nickel layer, 21b: Copper layer, 22: Grooved portion, 23: Terminal plate, 24: Lower valve body, 25: Insulating plate, 26: Upper valve body, 27: Sealing plate, 27a: Protrusion, 27b: Vent, 28: Gasket, 29: Shoulder, 31: Bottom, 31a: Inner surface, 33: Peripheral portion, 39: Cylindrical portion, 41: Laser irradiation portion, 51: Anvil, 51a: Upper surface of anvil, 61: Amplitude transformer, 61a: Front end portion of amplitude transformer.

Claims

1. A method for manufacturing a cylindrical battery, the cylindrical battery comprising: An electrode body is formed by winding a first electrode and a second electrode with a separator interposed therebetween; a bottomed cylindrical outer can housing the electrode assembly; and a sealing body for sealing the opening of the outer can, The first electrode is electrically connected to the inner surface of the bottom of the outer can via a lead wire. The method for manufacturing the cylindrical battery comprises: a step of irradiating at least a portion of the inner surface of the bottom of the outer can before accommodating the electrode assembly with laser light to increase the reflectivity of light; and and joining the lead extending from the electrode body to the laser irradiated portion irradiated with the laser beam on the inner surface by ultrasonic welding.

2. The method for manufacturing a cylindrical battery according to claim 1, wherein: The surface roughness of the laser irradiated portion is reduced by the irradiation of the laser.

3. The method for manufacturing a cylindrical battery according to claim 1 or 2, wherein: The lead is composed of a covering member formed by laminating a copper plate and a nickel plate. The copper layer disposed on one side of the lead in the thickness direction is bonded to the laser irradiation portion by the ultrasonic welding.

4. A cylindrical battery comprising: The electrode body is formed by winding the positive electrode and the negative electrode with a separator between them; An outer container having a bottom and a cylindrical shape, housing the electrode body; a sealing body for sealing the opening of the outer can; and The negative electrode lead is made of a covering made by laminating a copper plate and a nickel plate, with a copper layer arranged on one side in the thickness direction. The copper layer of the negative electrode lead is joined to the inner surface of the bottom of the outer can.

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