Welding method for realizing positive and negative electrode tabs in a single battery and battery head.

Abstract

This invention provides a welding method for realizing positive and negative electrode tabs in a single battery and a battery head. [Solution] The device includes a steel case 1, a cap 2 with a second positive terminal on its upper side, a positive terminal tab 3, a negative terminal tab 4, and a protective plate 5 with a first positive terminal 51 and a first negative terminal 52. The folded portion at the top of the steel case is formed as the second negative terminal. One end of the positive terminal tab is connected to the first positive terminal, and the other end bypasses the protective plate and is connected to the second positive terminal. The negative terminal tab includes a welded portion and a bent portion. The welded portion is annular or semi-annular, extending outward to form a bent portion, with its lower side connected to the second negative terminal. The bent portion bypasses the protective plate and is connected to the first negative terminal. An annular insulating gasket 6 is provided between the upper side of the connection portion and the bottom of the positive terminal tab. By providing an annular or semi-annular welded portion, the negative terminal tab can be provided at the top of the steel case, solving the problems of increasing the maximum diameter of the battery and increasing the internal resistance of the battery in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and particularly to a welding method for realizing positive and negative electrode tabs in a single battery and a battery head part.

Background Art

[0002] A single lithium battery refers to a single lithium-ion battery unit, which is the basic unit constituting a battery cell or a battery pack and can be combined in series or parallel to provide the required voltage and capacity. Depending on the packaging method, single lithium batteries can be classified into cylindrical, rectangular, soft package, etc.

[0003] The operating principle of a lithium-ion battery is based on the movement of lithium ions between the positive and negative electrodes. During charging, lithium ions are released from the positive electrode material, pass through the separator, and are occluded in the negative electrode material. During discharging, lithium ions are released from the negative electrode material, pass through the separator, and return to the positive electrode material. This process is accompanied by the flow of electrons in the external circuit, generating an electric current.

[0004] A single battery includes a steel case and a cap. The top of the steel case is open and filled with materials such as electrolyte inside. The cap is attached to the opening, connecting the steel case opening and the cap to complete the sealing. In the prior art, a conventional single battery usually has a protective plate provided above the cap, with a positive electrode port and a negative electrode port provided on the protective plate. A positive electrode tab is provided to connect the cap and the positive electrode port. As shown in FIG. 1, a negative electrode tab is provided to connect the bottom of the steel case and the negative electrode port. This type of single battery has the following defects.

[0005] (1) Because the protective plate is placed on the positive electrode cap, the negative electrode tab has a long, flat structure and needs to extend from the bottom of the steel case to the negative electrode port of the protective plate at the top of the steel case, and most of the area of ​​the negative electrode tab needs to be in close contact with the entire battery body. When connecting, the negative electrode tab needs to be bent. However, due to its flat shape, the negative electrode tab cannot be completely in close contact with a normal cylindrical steel case after being bent, and is prone to forming corners, which ultimately increases the maximum diameter of the finished cylindrical battery by about 1 mm.

[0006] (2) The long structure of the negative electrode tab makes the electron flow path longer, which significantly increases the internal resistance of the finished battery.

[0007] Therefore, in order to solve the above problem, it is necessary to provide a welding method that realizes positive and negative electrode tabs in a single battery and a battery head. [Overview of the project] [Problems that the invention aims to solve]

[0008] In response to the problems of the prior art, the present invention provides a welding method for realizing positive and negative electrode tabs in a single battery and a battery head, in order to solve the technical problems of increasing the maximum diameter and internal resistance of a finished battery. [Means for solving the problem]

[0009] The technical solution of the present invention is realized as follows.

[0010] A single battery comprising a steel case, a cap, a positive electrode tab, a negative electrode tab, and a protective plate having a first positive terminal and a first negative terminal on its upper surface, The upper surface of the cap is provided with a protruding second positive pole, the circumferential side of which is a connecting portion; the top of the steel case is open, the cap is provided in the opening, the opening is folded inward and fitted in, and is connected to the connecting portion; the outer surface of the folded portion of the steel case has a second negative pole formed on the outer circumferential side of the second positive pole; the protective plate is located above the cap. The positive electrode tab has an elongated structure, one end of which is connected to the first positive electrode terminal, and the other end of which bypasses the protective plate and is connected to the second positive electrode terminal located below the protective plate. The negative electrode tab includes a welded portion and a bent portion, the welded portion being annular or semi-annular and extending outward to form a strip-shaped bent portion, the lower surface of the welded portion being connected to the second negative electrode end, and the bent portion being bent and bypassing the protective plate and connected to the first negative electrode end. An annular insulating gasket is further provided between the upper part of the connection and the lowest part of the positive electrode tab.

[0011] The first positive pole and the first negative pole are both metal sheets.

[0012] By providing an annular or semi-annular welded section, the negative electrode tab can be completely connected to the top of the steel case without being connected to the bottom of the steel case. This solves the problem of increased maximum battery diameter due to the inability to achieve complete contact between the strip-shaped structure and the side of the cylindrical steel case, and also solves the problem of increased internal battery resistance due to the excessive length of the negative electrode tab of the strip-shaped structure.

[0013] Both the positive and negative electrode tabs are located at the top of the steel case, partially positioned below the protective plate, and by providing an insulating gasket, a short circuit between them and the second positive terminal can be avoided.

[0014] Furthermore, the protective plate has positive and negative leads that extend outward for connection to external power-consuming devices.

[0015] Furthermore, the cap, positive electrode tab, and negative electrode tab are all made of metal.

[0016] As a further optimization of the above plan, an angled or arc-shaped release groove is provided at the connection point between the bent portion and the welded portion.

[0017] A release groove is provided so that the bent portion and the welded portion contract at the connection point, making it easier to bend the bent portion relative to the welded portion.

[0018] Further optimization of the above plan involves providing a hole in the middle of the protective plate, with the first positive pole and the first negative pole both located on the outer circumference side of the hole. One end of the positive electrode tab is connected to the first positive electrode, and the other end is bent upward and bypasses from the hole to the upper side of the second positive electrode, or from the outer edge of the protective plate to the upper side of the second positive electrode, and finally connects to the second positive electrode.

[0019] The positive electrode tab can be folded from a hole, and compared to being folded from the edge of the protective plate, the length of the positive electrode tab can be effectively reduced, which in turn reduces battery impedance and further lowers the risk of short circuits during the battery manufacturing process.

[0020] Further optimization of the above plan is as follows: The positive electrode tab, after being bent, includes a long end and a short end that are parallel to each other, and a high-temperature tape is provided to wrap around the connection portion between the long end and the short end, the long end having a length of 2 to 5 mm, and the short end having a length of 2 to 5 mm. When the long end is connected to the first positive terminal, the short end bypasses from the outer edge of the protective plate to the upper side of the second positive terminal and is connected to the second positive terminal. When the shorter end is connected to the first positive terminal, the longer end bypasses the hole to the upper side of the second positive terminal and is connected to the second positive terminal.

[0021] High-temperature tape is a special type of tape that can maintain its viscosity in high-temperature environments, is resistant to detachment and melting, and is commonly used in industrial fields such as electronics, automotive, and aerospace where it is necessary to withstand high temperatures, ensuring strong connections and insulating protection between components. In this solution, the high-temperature tape plays an additional role in preventing short circuits.

[0022] For further optimization of the above solution, the positive electrode tab has a width of 2 - 6 mm, the hole is rectangular, has a width of 0.3 - 1 mm, and the length is 0.5 mm or more greater than the width of the positive electrode tab, or the hole is circular, and the diameter is 0.5 mm or more greater than the width of the positive electrode tab.

[0023] For further optimization of the above solution, the bending part has a width of 3 - 5 mm and a length of 4 - 8 mm, the welding part has an outer diameter 0 - 1.5 mm smaller than the outer diameter of the steel case, a width of 0.5 - 3 mm, and the thicknesses of the positive electrode tab and the negative electrode tab are 0.1 - 0.2 mm. The end of the bending part is two right angles or two rounded corners.

[0024] For further optimization of the above solution, the insulating gasket has a thickness of 0.04 - 1 mm, an outer diameter the same as that of the welding part, and is made of PET / PE material or vulcanized fiber.

[0025] For further optimization of the above solution, an annular flat part with an upward-facing surface is provided along the second negative terminal, and the welding part is closely connected to the annular flat part.

[0026] When the opening of the steel case is closed, it is folded inward to lock the connection part of the cap. The part that is folded in the normal state is arc-shaped, so the contact between the second negative terminal and the welding part is almost a line contact, and it is very easy to occur soldering defects in the subsequent soldering process. Therefore, by further processing the folded part, that is, the second negative terminal, to form an annular flat part, and forming a surface contact with the welding part, the soldering defect problem can be effectively avoided. The outer peripheral side of the annular flat part is formed as an r corner / rounded corner.

[0027] The present invention is applied to the above single cell, and is a welding method for realizing the positive and negative electrode tabs in the battery head part where the positive electrode tab, the negative electrode tab, the insulating gasket, and the protection plate are further attached to the steel case and the cap after assembly. Step 1 involves aligning the welded portion of the negative electrode tab with the second negative electrode end, pressing the welded portion with an auxiliary cover plate, ensuring close contact between the welded portion and the second negative electrode end, and then applying pressure using the auxiliary cover plate to further avoid soldering defects. Step 2 involves performing a welding operation along the aforementioned weld to form multiple uniformly distributed bonding fins, a corrugated annular bonding wire, or one or multiple corrugated stripe-shaped bonding wires, Step 3 involves placing the insulating gasket above the welded portion, aligning one end of the positive electrode tab with the second positive electrode end, and welding the two together. Step 4 involves positioning the protective plate above the positive electrode tab and the negative electrode tab such that both the first positive electrode and the first negative electrode are facing directly upwards. The present invention further provides a welding method for realizing positive and negative electrode tabs in a battery head, which includes step 5: bending the bent portion relative to the welded portion so that the bent portion bypasses the protective plate and is connected to the first negative electrode; performing a welding operation on the bent portion and the first negative electrode; bending the positive electrode tab so that one end of the positive electrode tab bypasses the protective plate and is connected to the first positive electrode; and performing a welding operation on one end of the positive electrode tab and the first positive electrode.

[0028] Further optimization of the above plan is as follows: In step 1, when the auxiliary cover plate is pushed downward, the pressure on the cap is 0.5 to 1.5 kg, where 1 kg is approximately equal to 9.8066 newtons, or 4.9033 N to 14.71 N. In step 2, the amplitude of the formed corrugated bonding wire is 0.2 to 1 mm, and the welding method used is continuous laser welding or pulsed laser welding. In step 3, pulsed laser welding is used between the second positive electrode and the positive electrode tab. In step 5, continuous laser welding or pulsed laser welding is used on the first positive electrode or the first negative electrode. [Effects of the Invention]

[0029] Compared to conventional technology, the present invention provides the following beneficial effects.

[0030] The present invention provides a welding method for realizing positive and negative electrode tabs in a single battery and battery head. By providing an annular or semi-annular weld, the negative electrode tab can be completely connected to the top of the steel case without being connected to the bottom of the steel case. This solves the problem of increased maximum battery diameter due to inability to achieve complete contact between the strip-shaped structure and the side surface of the cylindrical steel case, and also solves the problem of increased internal battery resistance due to the excessive length of the negative electrode tab in the strip-shaped structure. [Brief explanation of the drawing]

[0031] [Figure 1] This is a schematic cross-sectional view of a conventional battery. [Figure 2] This is a schematic diagram of a disassembled single battery according to Embodiment 1 of the present invention. [Figure 3] This is a partially enlarged schematic diagram of area a in Figure 1. [Figure 4] This is a schematic diagram illustrating the fitting of the positive electrode tab, negative electrode tab, cap, and steel case according to Embodiment 1 of the present invention. [Figure 5] This is a schematic diagram illustrating the fitting of the positive electrode tab, the negative electrode tab, and the protective plate according to Embodiment 1 of the present invention. [Figure 6] This is a schematic diagram of the welding process after unfolding the negative electrode tab according to Embodiment 1 of the present invention. [Figure 7] This is a schematic diagram of the welding process after unfolding the negative electrode tab according to Embodiment 2 of the present invention. [Figure 8] This is a schematic diagram of the welding process after unfolding the negative electrode tab according to Embodiment 3 of the present invention. [Figure 9] This is a schematic diagram of the welding process after unfolding the negative electrode tab according to Embodiment 4 of the present invention. [Figure 10] This is a schematic diagram of the welding process after unfolding the negative electrode tab according to Embodiment 5 of the present invention. [Figure 11] This is a schematic diagram of the negative electrode tab after unfolding according to Embodiment 6 of the present invention. [Figure 12]This is a schematic diagram of the negative electrode tab after unfolding according to Embodiment 7 of the present invention. [Modes for carrying out the invention]

[0032] To further clarify the object, technical solution, and advantages of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments that can be obtained by those skilled in the art without creative work based on the embodiments of the present invention are within the scope of the protection of the present invention.

[0033] <Example 1> As shown in Figures 2 to 6, this embodiment provides a single battery, which includes a steel case 1, a metal cap 2, a positive electrode tab 3, a negative electrode tab 4, and a protective plate 5 on its upper side, each having a first positive terminal 51 and a first negative terminal 52 made of a metal sheet. The protective plate 5 further includes positive and negative leads extending outward for connection to an external power-consuming device.

[0034] The upper surface of the cap 2 is provided with a protruding second positive end 21, the circumferential side of which is a connecting portion 22. The top of the steel case 1 is open, and the cap 2 is placed in the opening, which is folded inward and fitted into place, connecting to the connecting portion 22. The outer surface of the steel case 1 at the folded portion is formed as a second negative end 11. In this embodiment, an annular planar portion 12 with an upward-facing surface is provided along the second negative end 11, and the outer circumference of the annular planar portion 12 is formed as an r-angle 13. The second negative end 11 is located on the outer circumference side of the second positive end 21, and the protective plate 5 is located on the upper side of the cap 2.

[0035] The positive electrode tab 3 has a strip-like structure. In this embodiment, after being bent, the positive electrode tab 3 includes a long end 31 and a short end 32 that are parallel to each other, and a high-temperature tape is provided to wrap around the connection portion 22 between the long end 31 and the short end 32. The high-temperature tape is a special tape that can maintain its viscosity in high-temperature environments, is resistant to detachment and melting, and is often used in industrial fields that need to withstand high-temperature environments such as electronics, automobiles, and aerospace, ensuring a strong connection and insulating protection between components. In this solution, the high-temperature tape plays a role in further preventing short circuits.

[0036] In this embodiment, the positive electrode tab 3 has a width of 3 mm and a thickness of 0.1 mm, with a long end 31 having a length of 5 mm and a short end 32 having a length of 2 mm. The long end 31 is connected to the first positive terminal 51, and the short end 32 bypasses from the outer edge of the protective plate 5 to the upper side of the second positive terminal 21 and is connected to the second positive terminal 21.

[0037] The negative electrode tab 4 includes a welded portion 41 and a bent portion 42. The welded portion 41 is annular and extends outward, forming a strip-shaped bent portion 42 with two right angles 422 at its ends. In this embodiment, the bent portion 42 has a width of 3 mm and a length of 4 mm, the welded portion 41 has an outer diameter 1.5 mm smaller than the outer diameter of the steel case 1 and a width of 0.5 mm, and the negative electrode tab 4 has a thickness of 0.1 mm.

[0038] The lower surface of the welded portion 41 is in close contact with the annular planar portion 12 of the second negative pole 11, and the bent portion 42 is bent and bypasses the protective plate 5 to connect to the first negative pole 52. The annular planar portion 12 of the second negative pole 11 forms a surface contact with the welded portion 41, effectively avoiding soldering defects.

[0039] An annular insulating gasket is further provided between the upper side of the connection portion 22 and the lowest side of the positive electrode tab 3. In this embodiment, the insulating gasket has a thickness of 1 mm, an outer diameter the same as the outer diameter of the welded portion 41, and is made of PET material. Both the positive electrode tab 3 and the negative electrode tab 4 are provided at the top of the steel case 1, and both are partially located below the protective plate 5. By providing insulating gaskets, short circuits between both and the second positive terminal 21 can be avoided.

[0040] Both the positive electrode tab 3 and the negative electrode tab 4 are made of metal. By providing a welded joint 41, the negative electrode tab 4 can be connected to the top of the steel case 1 without being connected to the bottom of the steel case 1. This solves the problem of increased maximum battery diameter due to the inability to achieve complete contact between the strip-shaped structure and the side surface of the cylindrical steel case 1, and also solves the problem of increased internal battery resistance due to the excessive length of the negative electrode tab 4 of the strip-shaped structure.

[0041] This embodiment further provides a welding method for realizing the positive and negative electrode tabs 4 in the battery head portion, which is applied to the above-mentioned single battery and further attaches the positive electrode tab 3, negative electrode tab 4, insulating gasket and protective plate 5 to the assembled steel case 1 and cap 2, and the method includes the following steps.

[0042] In step 1, the welded portion 41 of the negative electrode tab 4 is aligned with the second negative electrode end 11 and the welded portion 41 is pressed against the second negative electrode end 11 using the auxiliary cover plate. In this embodiment, when the auxiliary cover plate is pushed downward in step 1, the pressure exerted on the cap 2 is 1.5 kg. By providing the auxiliary cover plate and applying pressure, soldering defects can be further avoided.

[0043] In step 2, a welding operation is performed along the welded area 41 to form multiple uniformly distributed bonding fins 7. The welding method used in this area is pulsed laser welding.

[0044] In step 3, an insulating gasket is placed on the upper side of the weld 41, one end of the positive electrode tab 3 is aligned with the second positive electrode end, and the two are welded together. The welding method used at this location is pulsed laser welding.

[0045] In step 4, the protective plate 5 is placed above the positive electrode tab 3 and the negative electrode tab 4 such that both the first positive electrode 51 and the first negative electrode face directly upwards.

[0046] In step 5, the bent portion 42 is bent relative to the weld portion 41 so that the bent portion 42 bypasses the protective plate 5 and connects to the first negative pole end 52, and a welding operation is performed on the bent portion 42 and the first negative pole end 52. The positive pole tab 3 is bent so that one end of the positive pole tab 3 bypasses the protective plate 5 and connects to the first positive pole end 51, and a welding operation is performed on one end of the positive pole tab 3 and the first positive pole end 51. The welding method used at this location is continuous laser welding.

[0047] In this example, the relevant parameters for continuous laser welding are: laser wavelength 1070±100nm, laser frequency 3~8KHz, output power 600~1000w, welding speed 50~100mm / s, defocus amount ±1.5mm, and depth of bonding fin 7 to the molten pool 0.1~0.3mm.

[0048] In this embodiment, the pulsed laser device is a YAG-WF350 model, and the welding parameters are as follows: laser wavelength 1064nm, laser frequency ≤200Hz, optical fiber core diameter 0.4mm, maximum welding power 3.5~4.0KW, maximum average power 310W, single-stage welding time 0.3~0.6ms, single-stage welding power 70%~100%, double-stage welding time 0.9~1.2ms, double-stage welding power 75%~100%, and defocus amount ±2.0mm.

[0049] In single-stage welding, a short time and high power are used to achieve rapid melting and passage of the material. This stage is typically used to start the welding process, aiming to achieve the required melting depth in the shortest time and lay the foundation for the next weld. In double-stage welding, a longer time and slightly lower power are used to complete the welding process. This stage is typically used at the end of the weld, ensuring sufficient melting of the material by extending the welding time.

[0050] <Example 2> This embodiment is shown in Figure 7. Features not interpreted in this embodiment will be interpreted using the method from Embodiment 1 and will not be explained further here. The differences between this embodiment and Embodiment 1 are as follows.

[0051] The end of the folded portion 42 has two rounded sections 421.

[0052] <Example 3> This embodiment is shown in Figure 8. Features not interpreted in this embodiment will be interpreted using the method from Embodiment 2 and will not be explained further here. The differences between this embodiment and Embodiment 2 are as follows.

[0053] In step 2, a welding operation is performed along the weld area 41 to form a wavy annular bonding wire 8 with an amplitude of 0.2 mm. The welding method used at this location is continuous laser welding.

[0054] <Example 4> This embodiment is shown in Figure 9. Features not interpreted in this embodiment will be interpreted using the method from Embodiment 3 and will not be explained further here. The differences between this embodiment and Embodiment 3 are as follows.

[0055] The welded section 41 has a semi-annular structure. In step 2, a welding operation is performed along the welded section 41 to form two multi-stage wavy stripe-shaped bonding wires 8.

[0056] <Example 5> This embodiment is shown in Figure 10. Features not interpreted in this embodiment will be interpreted using the method described in Embodiment 4 and will not be explained further here. The differences between this embodiment and Embodiment 4 are as follows.

[0057] In step 2, a welding operation is performed along the welded area 41 to form a single wavy, striped bonding wire 8.

[0058] <Example 6> This embodiment is shown in Figure 11. Features not interpreted in this embodiment will be interpreted using the method from Embodiment 1 and will not be explained further here. The differences between this embodiment and Embodiment 1 are as follows.

[0059] An angled release groove 43 is provided at the connection point between the bent portion 42 and the welded portion 41. The release groove 43 is provided so that the bent portion 42 and the welded portion 41 contract at the connection point, making it easier for the bent portion 42 to bend relative to the welded portion 41.

[0060] <Example 7> This embodiment is shown in Figure 12. Features not interpreted in this embodiment will be interpreted using the method from Embodiment 1 and will not be explained further here. The differences between this embodiment and Embodiment 1 are as follows.

[0061] An arc-shaped release groove 43 is provided at the connection point between the bent portion 42 and the welded portion 41.

[0062] Those skilled in the art can modify and alter the above embodiments based on the disclosures and teachings of the specification. Therefore, the present invention is not limited to the specific embodiments disclosed and described herein, and several modifications and alterations to the present invention should also be included within the scope of protection of the technical solutions of the present invention. Furthermore, certain terms are used herein, but these terms are for illustrative purposes only and do not limit the present invention. [Explanation of symbols]

[0063] 1. Steel case 11 2nd negative terminal 12 Annular planar section 13 r angle 2 caps 21 2nd positive end 22 Connection part 3 Positive Tab 31 Long end 32 Short end 4 Negative electrode tabs 41 Welded section 42 Folded section 421 Roundness 422 right angle 43 Release groove 5 Protective plate 51 1st positive end 52 1st negative terminal 53 holes 6. Insulating gasket 7 Bonding Fins 8 Bonding wire

Claims

1. A single battery comprising a steel case, a cap, a positive electrode tab, a negative electrode tab, and a protective plate having a first positive terminal and a first negative terminal on its upper surface, The upper surface of the cap is provided with a protruding second positive pole, the circumference of which is a connecting portion; the top of the steel case is open, the cap is provided in the opening, the opening is folded inward and fitted in, and is connected to the connecting portion; the outer surface of the folded portion of the steel case has a second negative pole formed on the outer circumference side of the second positive pole; the protective plate is located above the cap. The positive electrode tab has an elongated structure, one end of which is connected to the first positive electrode terminal, and the other end of which bypasses the protective plate and is connected to the second positive electrode terminal located below the protective plate. The negative electrode tab includes a welded portion and a bent portion, the welded portion being annular or semi-annular and extending outward to form a strip-shaped bent portion, the lower surface of the welded portion being connected to the second negative electrode end, and the bent portion being bent and bypassing the protective plate and connected to the first negative electrode end. A single battery characterized in that an annular insulating gasket is further provided between the upper side of the connection portion and the lowest side of the positive electrode tab.

2. The single battery according to claim 1, characterized in that an angled or arc-shaped release groove is provided at the connection point between the bent portion and the welded portion.

3. A hole is provided in the middle of the protective plate, and both the first positive pole and the first negative pole are located on the outer circumference side of the hole. The single battery according to claim 1, characterized in that one end of the positive electrode tab is connected to the first positive electrode, and the other end is bent upward and bypasses from the hole to the upper side of the second positive electrode, or bypasses from the outer edge of the protective plate to the upper side of the second positive electrode, and is finally connected to the second positive electrode.

4. The positive electrode tab, after being bent, includes a long end and a short end that are parallel to each other, and a high-temperature tape is provided to wrap around the connection portion between the long end and the short end, the long end having a length of 2 to 5 mm, and the short end having a length of 2 to 5 mm. When the long end is connected to the first positive pole, the short end bypasses from the outer edge of the protective plate to the upper side of the second positive pole and is connected to the second positive pole. The single battery according to claim 3, characterized in that when the shorter end is connected to the first positive terminal, the longer end bypasses from the hole to the upper side of the second positive terminal and is connected to the second positive terminal.

5. The positive electrode tab has a width of 2 to 6 mm. The single battery according to claim 3, characterized in that the hole is rectangular in shape, has a width of 0.3 to 1 mm, and is at least 0.5 mm longer than the width of the positive electrode tab, or the hole is circular in shape and is at least 0.5 mm larger in diameter than the width of the positive electrode tab.

6. The bent portion has a width of 3 to 5 mm and a length of 4 to 8 mm, the welded portion has an outer diameter 0 to 1.5 mm smaller than the outer diameter of the steel case and a width of 0.5 to 3 mm, and the thickness of the positive electrode tab and the negative electrode tab is 0.1 to 0.2 mm. The single battery according to claim 1, characterized in that the end of the bent portion has two right angles or two curves.

7. The single battery according to claim 1, characterized in that the insulating gasket has a thickness of 0.04 to 1 mm, an outer diameter the same as the outer diameter of the welded part, and is made of PET / PE material or vulcanized fiber.

8. The single battery according to claim 1, characterized in that an annular planar portion with an upward-facing surface is provided along the second negative pole, and the welded portion is connected in close contact with the annular planar portion.

9. A welding method for realizing positive and negative electrode tabs in a battery head portion, applicable to a single battery according to any one of claims 1 to 8, wherein the positive electrode tab, the negative electrode tab, the insulating gasket, and the protective plate are further attached to the assembled steel case and the cap, Step 1 involves aligning the welded portion of the negative electrode tab with the second negative electrode end, pressing the welded portion with an auxiliary cover plate, and bringing the welded portion into close contact with the second negative electrode end. Step 2 involves performing a welding operation along the aforementioned weld to form multiple uniformly distributed bonding fins, a corrugated annular bonding wire, or one or multiple corrugated stripe-shaped bonding wires, Step 3 involves placing the insulating gasket above the welded portion, aligning one end of the positive electrode tab with the second positive electrode end, and welding the two together. Step 4 involves positioning the protective plate above the positive electrode tab and the negative electrode tab such that both the first positive electrode and the first negative electrode are facing directly upwards. A welding method for realizing positive and negative electrode tabs in a battery head, characterized by including step 5: bending the bent portion relative to the welded portion so that the bent portion bypasses the protective plate and is connected to the first negative electrode; performing a welding operation on the bent portion and the first negative electrode; bending the positive electrode tab so that one end of the positive electrode tab bypasses the protective plate and is connected to the first positive electrode; and performing a welding operation on one end of the positive electrode tab and the first positive electrode.

10. In step 1, when the auxiliary cover plate is pushed downward, the pressure exerted on the cap is 0.5 to 1.5 kg. In step 2, the amplitude of the formed corrugated bonding wire is 0.2 to 1 mm, and the welding method used is continuous laser welding or pulsed laser welding. In step 3, pulsed laser welding is used between the second positive electrode and the positive electrode tab. A welding method for realizing positive and negative electrode tabs in a battery head portion according to claim 9, characterized in that, in step 5, continuous laser welding or pulsed laser welding is used on the first positive or first negative electrode.

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