Single battery and method for welding positive and negative tabs on battery head

Abstract

The invention discloses a single battery and a method for welding positive and negative tabs at the head of the battery, and relates to the technical field of batteries, the single battery comprises a steel shell, a cap, a positive tab, a negative tab and a protection plate, and the protection plate is provided with a first positive electrode end and a first negative electrode end; the upper side of the cap is provided with a second anode end; the top of the steel shell forms a second negative electrode end at the folding part; one end of the positive tab is connected with the first positive terminal, and the other end bypasses the protection plate and is connected with the second positive terminal; the negative tab comprises a welding part and a bending part; the welding part is in a full ring shape or a semi-ring shape; the welding part extends outwards to form a bent part; the lower side face of the welding part is connected with the second negative electrode end, and the bending part is bent, bypasses the protection plate and is connected with the first negative electrode end. And an annular insulating spacer is also arranged between the upper side of the connecting part and the lowermost side of the positive tab. By arranging the full-ring-shaped or semi-ring-shaped welding part, the negative tab can be arranged at the top of the steel shell, so that the problems that the maximum diameter of the battery is increased and the internal resistance of the battery is increased in the prior art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of batteries, and in particular to a method for welding positive and negative tabs of a single cell and a battery head. Background Art

[0002] A single lithium-ion battery is a single lithium-ion battery cell, which is the basic unit of a battery pack or battery pack. It can be connected in series or in parallel to provide the required voltage and capacity. According to different packaging methods, single lithium batteries can be divided into cylindrical, square and soft pack forms.

[0003] The working principle of lithium-ion batteries 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 embed into the negative electrode material; during discharge, 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, thus generating electric current.

[0004] The single cell includes a steel shell and a cap. The top of the steel shell is open and filled with electrolyte and other materials. The cap is installed at the opening, and the steel shell opening is connected to the cap to complete the sealing. In the prior art, a traditional single cell usually has a protective plate above the cap, the protective plate has a positive electrode port and a negative electrode port, and a positive electrode ear is provided to connect the cap and the positive electrode port; a negative electrode ear is provided to connect the bottom of the steel shell and the negative electrode port, as shown in the attached figure Figure 1 As shown. This type of single battery has the following defects:

[0005] (1) Because the protective plate is placed at the positive electrode cap, the negative electrode tab is a long flat structure that needs to extend from the bottom of the steel shell to the negative electrode port of the protective plate at the top of the steel shell, and most of the negative electrode tab needs to fit 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 fitted with the commonly used cylindrical steel shell after bending, and it is easy to form edges and corners, which ultimately increases the maximum diameter of the finished cylindrical battery by about 1mm;

[0006] (2) The long structure of the negative electrode tab results in a long electron flow path, which will significantly increase the internal resistance of the finished battery.

[0007] Therefore, there is an urgent need to provide a method for welding positive and negative tabs of a single cell and a battery head to solve the above problems. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for welding positive and negative tabs of a single cell and a battery head, so as to solve the technical problems of increased maximum diameter and increased internal resistance of the finished battery.

[0009] The technical solution of the present invention is achieved in this way:

[0010] A single cell battery comprises a steel shell, a cap, a positive electrode ear, a negative electrode ear and a protective plate, wherein the upper side of the protective plate is provided with a first positive terminal and a first negative terminal;

[0011] The upper side of the cap is provided with a protruding second positive terminal, and the peripheral side of the second positive terminal is a connecting portion; the top of the steel shell is open, and the cap is arranged at the opening; the opening is folded inwardly and connected to the connecting portion, and the outer side of the steel shell at the folded part forms a second negative terminal; the second negative terminal is located on the outer peripheral side of the second positive terminal; the protective plate is located on the upper side of the cap;

[0012] The positive electrode ear is a long strip structure, one end of the positive electrode ear is connected to the first positive terminal, and the other end bypasses the protection plate and is connected to the second positive terminal located at the lower side of the protection plate;

[0013] The negative electrode ear includes a welding portion and a bending portion; the welding portion is a full ring or a semi-ring; the welding portion extends outward to form a strip-shaped bending portion; the lower side of the welding portion is connected to the second negative terminal, and the bending portion is bent and bypasses the protection plate to be connected to the first negative terminal;

[0014] An annular insulating gasket is also provided between the upper side of the connecting portion and the lowermost side of the positive electrode ear.

[0015] The first positive terminal and the first negative terminal are both metal sheets;

[0016] By setting a full-annular or semi-annular welding portion, the negative electrode ear can be completely connected to the top of the steel shell without being connected to the bottom of the steel shell. This solves the problem of increased maximum diameter of the battery caused by the inability of the strip structure to fully fit the side of the cylindrical steel shell, and also solves the problem of increased internal resistance of the battery caused by the excessive length of the negative electrode ear of the strip structure.

[0017] Since the positive ear and the negative ear are both arranged on the top of the steel shell, and both are partially located under the protection plate, the provision of an insulating gasket can avoid a short circuit between the two and the second positive terminal.

[0018] Furthermore, the protection board has a positive lead and a negative lead extending outwardly for connecting to external electrical equipment.

[0019] Furthermore, the cap, the positive electrode ear and the negative electrode ear are all made of metal.

[0020] As a further optimization of the above solution, the bending portion and the welding portion are provided with a release groove at the connection, and the release groove is in an angle shape or an arc shape.

[0021] A release groove is provided to allow the bending portion and the welding portion to contract at the connection, thereby facilitating bending of the bending portion relative to the welding portion.

[0022] As a further optimization of the above solution, an opening is provided in the middle of the protection plate, and the first positive terminal and the first negative terminal are both located on the outer peripheral side of the opening;

[0023] One end of the positive electrode ear is connected to the first positive terminal, and the other end is bent upward and wrapped around from the opening to the upper side of the second positive terminal, or wrapped around from the outer edge of the protective plate to the upper side of the second positive terminal, and finally connected to the second positive terminal.

[0024] Compared with bending from the edge of the protective plate, the positive electrode ear is bent from the opening, which can effectively reduce the length of the positive electrode ear, that is, reduce the battery impedance, and further reduce the risk of short circuit in the battery manufacturing process.

[0025] As a further optimization of the above solution, after the positive electrode ear is bent, it includes a long end and a short end that are parallel to each other, and the connecting part between the long end and the short end is wrapped with high-temperature adhesive tape; the long end is 2 to 5 mm; the short end is 2 to 5 mm;

[0026] When the long end is connected to the first positive terminal, the short end is wound from the outer edge of the protection plate to the upper side of the second positive terminal and connected to the second positive terminal;

[0027] When the short end is connected to the first positive terminal, the long end is wound from the opening to the upper side of the second positive terminal and connected to the second positive terminal.

[0028] High temperature adhesive tape is a special tape that can maintain its stickiness in high temperature environments and is not easy to fall off or melt. It is often used in industrial fields such as electronics, automobiles, and aviation that need to withstand high temperature environments to ensure a firm connection or insulation protection between components. In this solution, high temperature adhesive tape plays a further role in preventing short circuits.

[0029] As a further optimization of the above solution, the width of the positive electrode ear is 2 to 6 mm; the opening is rectangular in shape, with a width of 0.3 to 1 mm, and a length that is more than 0.5 mm greater than the width of the positive electrode ear; or the opening is circular in shape, with a diameter that is more than 0.5 mm greater than the width of the positive electrode ear.

[0030] As a further optimization of the above scheme, the width of the bending portion is 3-5 mm, and the length is 4-8 mm; the outer diameter of the welding portion is 0-1.5 mm smaller than the outer diameter of the steel shell; the width of the welding portion is 0.5-3 mm; the thickness of the positive electrode ear and the negative electrode ear is 0.1-0.2 mm;

[0031] The ends of the bending portion are two right angles or two rounded corners.

[0032] As a further optimization of the above solution, the thickness of the insulating gasket is 0.04-1 mm, and the outer diameter is the same as the outer diameter of the welding part; the insulating gasket is made of PET / PE or highland barley paper.

[0033] As a further optimization of the above solution, an upward-facing annular plane portion is provided along the second negative terminal; and the welding portion is fitted and connected to the annular plane portion.

[0034] When the steel shell opening is closed, the inner side of the bend is folded to hold the connection part of the cap. Under normal conditions, the folded part is in an arc shape, so that the contact between the second negative terminal and the welding part is almost line contact, which is very likely to cause a cold weld in the subsequent welding process; for this reason, the folded part, that is, the second negative terminal, is further processed to form an annular plane part, so that the contact with the welding part is formed into a surface contact, which can effectively avoid the cold weld problem. The outer peripheral side of the annular plane part is formed into an r angle / rounded corner.

[0035] The present invention also provides a method for welding positive and negative tabs at the battery head, which is applied to the above-mentioned single battery, and further installs the positive tab, the negative tab, the insulating gasket and the protective plate on the assembled steel shell and the cap; the method comprises the following steps:

[0036] Step 1: align the welding part of the negative electrode ear and place it on the second negative terminal, and use the auxiliary cover plate to press the welding part so that the welding part and the second negative terminal are closely attached; the auxiliary cover plate is set to apply pressure to further avoid the occurrence of cold welding;

[0037] Step 2: Perform welding operation along the welding portion to form multiple uniformly distributed welding spots, or form a wavy annular welding line, or form one or multiple segmented wavy strip welding lines;

[0038] Step 3, pad the insulating gasket on the upper side of the welding part; align one end of the positive electrode ear with the second positive terminal, and weld the two;

[0039] Step 4: placing the protection plate above the positive electrode ear and the negative electrode ear, wherein the first positive terminal and the first negative terminal are both facing upward;

[0040] Step 5: bend the bent portion relative to the welding portion so that the bent portion bypasses the protection plate and is connected to the first negative terminal, and welds the bent portion and the first negative terminal; bend the positive ear so that one end of the positive ear bypasses the protection plate and is connected to the first positive terminal, and welds one end of the positive ear and the first positive terminal.

[0041] As a further optimization of the above scheme, in step one, when the auxiliary cover plate is pressed down, the pressure on the cap is 0.5 to 1.5 kg, 1 kg is approximately equal to 9.8066 newton, that is, 4.9033 N to 14.71 N; in step two, the amplitude of the formed wavy weld line is 0.2 to 1 mm; the welding method adopted is continuous laser welding or pulsed laser welding; in step three, pulsed laser welding is used between the second positive terminal and the positive ear; in step five, continuous laser welding or pulsed laser welding is performed at the first positive terminal or the first negative terminal.

[0042] Compared with the prior art, the present invention achieves the following beneficial effects:

[0043] The present invention provides a method for welding positive and negative pole ears of a single cell and a battery head. By setting a full-annular or semi-annular welding portion, the negative pole ear can be completely connected to the top of the steel shell without being connected to the bottom of the steel shell, thereby solving the problem of increased maximum diameter of the battery due to the inability of the strip structure to fully fit the side of the cylindrical steel shell, and also solving the problem of increased internal resistance of the battery due to the excessive length of the negative pole ear of the strip structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a cross-sectional schematic diagram of a conventional battery;

[0045] Figure 2 is an exploded schematic diagram of a single cell provided in Example 1 of the present invention;

[0046] Figure 3 yes Figure 2 A local enlarged schematic diagram at point a;

[0047] Figure 4 It is a schematic diagram of the coordination of the positive electrode ear, the negative electrode ear, the cap, and the steel shell provided in Example 1 of the present invention;

[0048] Figure 5 It is a schematic diagram of the coordination of the positive electrode ear, the negative electrode ear and the protection plate provided in Example 1 of the present invention;

[0049] Figure 6 is a schematic diagram of welding of the negative electrode ear after it is unfolded provided in Example 1 of the present invention;

[0050] Figure 7 is a schematic diagram of welding of the negative electrode ear after it is unfolded provided in Example 2 of the present invention;

[0051] Figure 8 is a schematic diagram of welding of the negative electrode ear after it is unfolded provided in Example 3 of the present invention;

[0052] Fig. 9is a schematic diagram of welding of the negative electrode ear after it is unfolded provided in Example 4 of the present invention;

[0053] Fig.10 is a schematic diagram of welding of the negative electrode ear after it is unfolded provided in Example 5 of the present invention;

[0054] Fig.11 is a schematic diagram of the unfolded negative electrode ear provided in Example 6 of the present invention;

[0055] Fig.12 It is a schematic diagram of the unfolded negative electrode ear provided in Example 7 of the present invention.

[0056] Reference numerals:

[0057] 1. Steel shell; 11. Second negative terminal; 12. Annular plane portion; 13. R angle;

[0058] 2. Cap; 21. Second positive terminal; 22. Connecting part;

[0059] 3. Positive ear; 31. Long end; 32. Short end;

[0060] 4. negative electrode ear; 41. welding portion; 42. bending portion; 421. rounded corner; 422. right angle; 43. release groove;

[0061] 5. Protection plate; 51. First positive terminal; 52. First negative terminal; 53. Opening

[0062] 6. Insulation gasket;

[0063] 7. Soldering points;

[0064] 8. Soldering wire. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solution and advantages of the present invention more clear, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] Example 1

[0067] like Figures 2 to 6 As shown, this embodiment provides a single cell battery, including a steel shell 1, a metal cap 2, a positive electrode ear 3, a negative electrode ear 4 and a protective plate 5; the upper side of the protective plate 5 is provided with a first positive terminal 51 and a first negative terminal 52, both of which are metal sheets; the protective plate 5 also has a positive lead and a negative lead extending outwardly for connecting to external electrical equipment.

[0068] The upper side of the cap 2 is provided with a protruding second positive terminal 21, and the surrounding side of the second positive terminal 21 is a connecting portion 22; the top of the steel shell 1 is open, and the cap 2 is arranged at the opening; the opening is folded inwards and connected to the connecting portion 22, and the outer side of the steel shell 1 at the folded part forms the second negative terminal 11; in this embodiment, an annular plane portion 12 facing upward is provided along the second negative terminal 11; the outer peripheral side of the annular plane portion 12 forms an r angle 13. The second negative terminal 11 is located on the outer peripheral side of the second positive terminal 21; the protective plate 5 is located on the upper side of the cap 2;

[0069] The positive electrode ear 3 is a strip structure. In this embodiment, after the positive electrode ear 3 is bent, it includes a long end 31 and a short end 32 that are parallel to each other, and the connecting portion 22 between the long end 31 and the short end 32 is wrapped with high-temperature adhesive tape; high-temperature adhesive tape is a special tape that can maintain its viscosity in a high-temperature environment and is not easy to fall off or melt. It is often used in industrial fields such as electronics, automobiles, and aviation that need to withstand high-temperature environments to ensure a firm connection or insulation protection between components. In this solution, the high-temperature adhesive tape plays a role in further preventing short circuits.

[0070] In this embodiment, the width of the positive ear 3 is 3 mm and the thickness is 0.1 mm; the long end 31 is 5 mm; the short end 32 is 2 mm; the long end 31 is connected to the first positive terminal 51, and the short end 32 is wrapped around the outer edge of the protective plate 5 to the upper side of the second positive terminal 21 and connected to the second positive terminal 21.

[0071] The negative electrode ear 4 includes a welding portion 41 and a bending portion 42; the welding portion 41 is a full ring; the welding portion 41 extends outward to form a strip-shaped bending portion 42; the ends of the bending portion 42 are two right angles 422. In this embodiment, the bending portion 42 has a width of 3 mm and a length of 4 mm; the outer diameter of the welding portion 41 is 1.5 mm smaller than the outer diameter of the steel shell 1; the width of the welding portion 41 is 0.5 mm; and the thickness of the negative electrode ear 4 is 0.1 mm.

[0072] The lower side of the welding portion 41 is connected to the annular plane portion 12 of the second negative terminal 11, and the bent portion 42 is bent and bypasses the protection plate 5 to connect to the first negative terminal 52. The annular plane portion 12 of the second negative terminal 11 makes surface contact with the welding portion 41, which can effectively avoid the problem of cold welding.

[0073] An annular insulating gasket is also provided between the upper side of the connecting portion 22 and the lowermost side of the positive electrode ear 3. In this embodiment, the thickness of the insulating gasket is 1 mm, and the outer diameter is the same as the outer diameter of the welding portion 41; the insulating gasket is made of PET. Since the positive electrode ear 3 and the negative electrode ear 4 are both provided on the top of the steel shell 1, and both are partially located on the lower side of the protective plate 5, the provision of the insulating gasket can avoid a short circuit between the two and the second positive terminal 21.

[0074] The positive electrode ear 3 and the negative electrode ear 4 are both made of metal. By providing the welding portion 41, the negative electrode ear 4 can be completely connected to the top of the steel shell 1 without being connected to the bottom of the steel shell 1, which solves the problem of the maximum diameter of the battery increasing due to the inability of the strip structure to fully fit the side of the cylindrical steel shell 1, and also solves the problem of the internal resistance of the battery increasing due to the excessive length of the negative electrode ear 4 of the strip structure.

[0075] This embodiment also provides a method for welding positive and negative tabs 4 at the head of a battery, which is applied to the above-mentioned single battery, and further installs positive tabs 3, negative tabs 4, insulating gaskets and protective plates 5 on the assembled steel shell 1 and cap 2; the method comprises the following steps:

[0076] Step 1: align the welding portion 41 of the negative electrode ear 4 and place it on the second negative terminal 11, and use the auxiliary cover plate to press the welding portion 41 so that the welding portion 41 is tightly fitted with the second negative terminal 11; in this embodiment, in step 1, when the auxiliary cover plate is pressed down, the pressure on the cap 2 is 1.5 kg; setting the auxiliary cover plate to apply pressure can further avoid the occurrence of cold welding;

[0077] Step 2: Perform welding operation along the welding portion 41 to form multiple uniformly distributed welding spots 7. The welding method used here is pulsed laser welding.

[0078] Step 3: Place an insulating gasket on the upper side of the welding portion 41; align one end of the positive electrode ear 3 with the second positive electrode terminal 21, and weld the two together; the welding method used here is pulsed laser welding;

[0079] Step 4: placing a protective plate 5 above the positive electrode ear 3 and the negative electrode ear 4, wherein the first positive terminal 51 and the first negative terminal 52 are both facing upward;

[0080] Step 5: bend the bent portion 42 relative to the welding portion 41 so that the bent portion 42 bypasses the protection plate 5 and is connected to the first negative terminal 52, and welds the bent portion 42 and the first negative terminal 52; bend the positive electrode ear 3 so that one end of the positive electrode ear 3 bypasses the protection plate 5 and is connected to the first positive terminal 51, and welds one end of the positive electrode ear 3 and the first positive terminal 51. The welding method used here is continuous laser welding.

[0081] In this embodiment, the relevant parameters of continuous laser welding are: laser wavelength 1070±100nm, laser frequency 3~8KHz, output power 600~1000w, welding speed 50~100mm / s, defocusing amount ±1.5mm, and the molten pool depth corresponding to weld point 7 is 0.1~0.3mm.

[0082] In this embodiment, the pulsed laser machine is a YAG-WF350 model, and the relevant parameters for welding are: the laser wavelength is 1064nm, the laser frequency is ≤200Hz, the optical fiber core diameter is 0.4mm, the maximum welding power is 3.5~4.0KW, the maximum average power is 310W, the first welding time is 0.3~0.6ms, the first welding power is 70%~100%, the second welding time is 0.9~1.2ms, the second welding power is 75%~100%, and the defocus is ±2.0mm.

[0083] In the first stage of welding, a shorter time and higher power are used to achieve rapid melting and penetration of the material. This stage is usually used at the beginning of the welding process, with the aim of achieving the required penetration in the shortest time and laying the foundation for the subsequent welding. The second stage of welding uses a longer time and slightly lower power to complete the welding process. This stage is usually used at the end of welding to ensure full fusion of the materials by extending the welding time.

[0084] Example 2

[0085] In this embodiment, Figure 7 As shown, the features not explained in this embodiment are explained in Example 1 and will not be described in detail here. The difference between this embodiment and Example 1 is that:

[0086] The ends of the bent portion 42 are two rounded corners 421 .

[0087] Example 3

[0088] In this embodiment, Figure 8 As shown, the features not explained in this embodiment are explained in Example 2, and will not be repeated here. The difference between this embodiment and Example 2 is:

[0089] In step 2, welding is performed along the welding portion 41 to form a wavy annular welding line 8 , and the amplitude of the formed wavy welding line 8 is 0.2 mm; the welding method used here is continuous laser welding.

[0090] Example 4

[0091] In this embodiment, Fig. 9 As shown, the features not explained in this embodiment are explained in Example 3, and will not be repeated here. The difference between this embodiment and Example 3 is:

[0092] The welding portion 41 is a semi-annular structure. In step 2, welding is performed along the welding portion 41 to form two segmented wavy strip welding lines 8 .

[0093] Example 5

[0094] In this embodiment, Fig.10As shown, the features not explained in this embodiment are explained in Example 4, and will not be repeated here. The difference between this embodiment and Example 4 is:

[0095] In step 2, welding is performed along the welding portion 41 to form a wavy strip welding line 8 .

[0096] Example 6

[0097] In this embodiment, Fig.11 As shown, the features not explained in this embodiment are explained in Example 1 and will not be described in detail here. The difference between this embodiment and Example 1 is that:

[0098] The bending portion 42 and the welding portion 41 are provided with a release groove 43 at the connection, and the release groove 43 is in an angle shape. The release groove 43 is provided to shrink the bending portion 42 and the welding portion 41 at the connection, so as to facilitate the bending portion 42 to bend relative to the welding portion 41.

[0099] Example 7

[0100] In this embodiment, Fig.12 As shown, the features not explained in this embodiment are explained in Example 1 and will not be described in detail here. The difference between this embodiment and Example 1 is that:

[0101] A release groove 43 is provided at the connection between the bending portion 42 and the welding portion 41 , and the release groove 43 is in an arc shape.

[0102] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A single cell battery, comprising a steel shell, a cap, a positive electrode ear, a negative electrode ear and a protective plate, wherein the upper side of the protective plate is provided with a first positive terminal and a first negative terminal; characterized in that: The upper side of the cap is provided with a protruding second positive terminal, and the peripheral side of the second positive terminal is a connecting portion; the top of the steel shell is open, and the cap is arranged at the opening; the opening is folded inwardly and connected to the connecting portion, and the outer side of the steel shell at the folded part forms a second negative terminal; the second negative terminal is located on the outer peripheral side of the second positive terminal; the protective plate is located on the upper side of the cap; The positive electrode ear is a long strip structure, one end of the positive electrode ear is connected to the first positive terminal, and the other end bypasses the protection plate and is connected to the second positive terminal located at the lower side of the protection plate; The negative electrode ear includes a welding portion and a bending portion; the welding portion is a full ring or a semi-ring; the welding portion extends outward to form a strip-shaped bending portion; the lower side of the welding portion is connected to the second negative terminal, and the bending portion is bent and bypasses the protection plate to be connected to the first negative terminal; An annular insulating gasket is also provided between the upper side of the connecting portion and the lowermost side of the positive electrode ear.

2. A single cell according to claim 1, characterized in that: The bending portion and the welding portion are provided with a release groove at the connection position, and the release groove is in an angle shape or an arc shape.

3. A single cell according to claim 1, characterized in that: An opening is provided in the middle of the protection plate, and the first positive terminal and the first negative terminal are both located on the outer periphery of the opening; One end of the positive electrode ear is connected to the first positive terminal, and the other end is bent upward and wrapped around from the opening to the upper side of the second positive terminal, or wrapped around from the outer edge of the protective plate to the upper side of the second positive terminal, and finally connected to the second positive terminal.

4. A single cell according to claim 3, characterized in that: After being bent, the positive electrode ear comprises a long end and a short end parallel to each other, and the connecting portion between the long end and the short end is wrapped with high-temperature adhesive tape; the long end is 2 to 5 mm; the short end is 2 to 5 mm; When the long end is connected to the first positive terminal, the short end is wound from the outer edge of the protection plate to the upper side of the second positive terminal and connected to the second positive terminal; When the short end is connected to the first positive terminal, the long end is wound from the opening to the upper side of the second positive terminal and connected to the second positive terminal.

5. A single cell according to claim 3, characterized in that: The width of the positive electrode ear is 2 to 6 mm; the opening is rectangular, with a width of 0.3 to 1 mm, and a length greater than the width of the positive electrode ear by more than 0.5 mm; or the opening is circular, with a diameter greater than the width of the positive electrode ear by more than 0.5 mm.

6. A single cell according to claim 1, characterized in that: The width of the bending portion is 3-5 mm, and the length is 4-8 mm; the outer diameter of the welding portion is 0-1.5 mm smaller than the outer diameter of the steel shell; the width of the welding portion is 0.5-3 mm; the thickness of the positive electrode ear and the negative electrode ear is 0.1-0.2 mm; The ends of the bending portion are two right angles or two rounded corners.

7. A single cell according to claim 1, characterized in that: The thickness of the insulating gasket is 0.04-1 mm, and the outer diameter is the same as the outer diameter of the welding part; the insulating gasket is made of PET / PE or highland barley paper.

8. A single cell according to claim 1, characterized in that: An upwardly facing annular plane portion is provided along the second negative terminal; the welding portion is fitted and connected with the annular plane portion.

9. A method for welding positive and negative tabs at the head of a battery, applied to a single battery as claimed in any one of claims 1 to 8, wherein the positive tab, the negative tab, the insulating gasket and the protective plate are further installed on the assembled steel shell and the cap; characterized in that: The steps include: Step 1: align the welding portion of the negative electrode ear and place it on the second negative terminal, and use an auxiliary cover plate to press the welding portion so that the welding portion is tightly fitted with the second negative terminal; Step 2: Perform welding operation along the welding portion to form multiple uniformly distributed welding spots, or form a wavy annular welding line, or form one or multiple segmented wavy strip welding lines; Step 3, pad the insulating gasket on the upper side of the welding part; align one end of the positive electrode ear with the second positive terminal, and weld the two; Step 4: placing the protection plate above the positive electrode ear and the negative electrode ear, wherein the first positive terminal and the first negative terminal are both facing upward; Step 5: bend the bent portion relative to the welding portion so that the bent portion bypasses the protection plate and is connected to the first negative terminal, and welds the bent portion and the first negative terminal; bend the positive ear so that one end of the positive ear bypasses the protection plate and is connected to the first positive terminal, and welds one end of the positive ear and the first positive terminal.

10. A method for welding positive and negative tabs at a battery head according to claim 9, characterized in that: In step one, when the auxiliary cover plate is pressed down, the pressure on the cap is 0.5 to 1.5 kg; in step two, the amplitude of the formed wavy weld line is 0.2 to 1 mm; the welding method adopted is continuous laser welding or pulsed laser welding; in step three, pulsed laser welding is used between the second positive terminal and the positive ear; in step five, continuous laser welding or pulsed laser welding is used at the first positive terminal or the first negative terminal.

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