Tab welding method, connecting piece and battery

Abstract

The present application relates to a tab welding method, a connecting sheet and a battery, wherein the tab welding method comprises: installing the connecting sheet on a welding tool, the connecting sheet comprising a connecting portion and welding portions arranged on both sides of the connecting portion, each welding portion comprising at least one first step and at least one second step, the first step being arranged away from the connecting portion and being lower than the second step; overlapping the first tab of the winding core on the first step to perform first welding; overlapping the second tab arranged on the same side as the first tab on the second step to perform second welding. The welding portion is matched with multiple tabs by arranging multiple steps, which can make the total tab layer number of the battery sufficient to meet the high power requirement of the battery core, and can keep the tab layer number of each welding single layer within a proper range without additional welding power, avoiding problems such as virtual welding caused by insufficient ultrasonic welding power, tab cracking caused by excessive ultrasonic welding power and the like, and improving the safety performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for welding tabs, a connecting piece, and a battery. Background Technology

[0002] The new energy market is becoming increasingly competitive, and the battery market is pursuing goals such as large single-cell capacity, high power, fast charging and discharging, and long cycle life, gradually optimizing the cell manufacturing process and cell structure. Currently, square cells generally use connecting tabs as a bridge connecting the cell tabs to the top cover terminals, and these connecting tabs are generally butterfly-shaped. To meet high-power charging and discharging requirements within the original cell size structure, the number of tab layers needs to be increased, even to a full tab configuration. During the cell manufacturing process, the increased number of tab layers and thickness when welding the tabs to the connecting tabs presents challenges for ultrasonic welding. Increasing the welding power can easily cause the tabs to crack; insufficient welding power cannot weld all the tabs to the connecting tab, resulting in incomplete welds, which can easily lead to thermal runaway safety issues during battery use.

[0003] Therefore, it is necessary to design a better electrode welding method to solve the above problems. Summary of the Invention

[0004] This invention provides a method for welding tabs, a connecting piece, and a battery. By setting a stepped structure on the connecting piece and welding the tabs in segments, the core tabs can be reliably welded to the connecting piece without the need for additional welding power. This avoids problems such as incomplete welding due to insufficient ultrasonic welding power and tab cracking due to excessive ultrasonic welding power, thereby improving the safety performance of the battery.

[0005] This invention provides a method for welding electrode tabs to a connecting piece, characterized in that it includes: The connecting piece is installed on the welding fixture, wherein the connecting piece includes a connecting part and welding parts disposed on both sides of the connecting part, each welding part includes at least one first step and at least one second step, the first step is disposed away from the connecting part, and the first step is lower than the second step; The first electrode lug of the core is overlapped with the first step for the first welding; The second electrode tab, which is located on the same side as the first electrode tab, is overlapped with the second step for a second welding.

[0006] In one embodiment, before welding, the first electrode lug and the second electrode lug on the same side of the core are first gathered together, and the length of the first electrode lug extending from the core is less than the length of the second electrode lug extending from the core, so that the first electrode lug matches the first step and the second electrode lug matches the second step.

[0007] In one embodiment, the core includes a first core and a second core stacked together, wherein a first tab is disposed on one side of the first core, a second tab is disposed on the same side of the second core as the first tab, and the length of the first tab extending from the first core is less than the length of the second tab extending from the second core. During welding, first place the first core so that the first electrode tab overlaps the first step, then place the second core on the first core, with the second core and the first core being flush in the stacking direction, so that the second electrode tab overlaps the second step.

[0008] In one embodiment, the first weld and / or the second weld is ultrasonic welding.

[0009] In one embodiment, after ultrasonic welding is completed, the connecting piece and the core are assembled onto the top cover, and the connecting part is laser welded to the pole of the top cover. After insulation treatment, the core is inserted into the outer shell and fully welded to form a seal, thereby completing the battery assembly.

[0010] In one embodiment, before the connecting piece is installed on the welding fixture, the welding portions on both sides of the connecting piece are bent at least once to form the first step, and the thickness of the first step is equal to the thickness of the second step.

[0011] In one embodiment, the height to which the first step bends downward is greater than the thickness of the first tab.

[0012] In one embodiment, the first tab and / or the second tab are pre-welded together from multiple layers of single-layer tabs.

[0013] The present invention also provides a connecting piece for connecting the tabs of a winding core, the connecting piece comprising: Connecting parts; and A welding portion is disposed on both sides of the connecting portion. The welding portion includes at least one first step and at least one second step. The first step is disposed away from the connecting portion and is lower than the second step. The electrode lugs include a first electrode lug and a second electrode lug disposed on the same side of the winding core. The first electrode lug is welded to the first step, and the second electrode lug is welded to the second step.

[0014] The present invention also provides a battery, comprising a casing, a core, a top cover, a positive electrode connecting piece, and a negative electrode connecting piece, wherein the core is installed inside the casing, and the core is provided with a positive electrode tab and a negative electrode tab respectively, the positive electrode tab being connected to the positive electrode connecting piece, and the negative electrode tab being connected to the negative electrode connecting piece, wherein the positive electrode connecting piece and the negative electrode connecting piece are the connecting pieces as described in claim 9; The positive electrode tab and the negative electrode tab each include a first electrode tab and a second electrode tab. The first electrode tab is welded to the first step of the connecting piece, and the second electrode tab is welded to the second step of the connecting piece.

[0015] Compared with the prior art, the advantages of this invention are that at least one first step and at least one second step are respectively provided on the welding portions on both sides of the connecting piece, and the first step is lower than the second step. During welding, the first tab of the core is first overlapped with the first step for welding, and then the second tab on the same side is overlapped with the second step for welding. This allows multiple first tabs and second tabs to be welded on the same side of the connecting piece. Each first tab or second tab may include multiple layers of single-layer tabs, and each first tab or second tab is welded separately. Therefore, it can ensure that the overall number of tab layers is sufficient to meet the high-power charging and discharging of the battery cell, and can also keep the number of single-layer tabs welded each time within an appropriate range without the need to increase the welding power. This avoids problems such as insufficient ultrasonic welding power leading to poor welding, and excessive ultrasonic welding power leading to tab cracking. By segmenting the tabs, the core tabs can be reliably welded to the connecting piece, thereby improving the safety performance of the battery. Furthermore, the structure of the first step and the second step can stagger the welding parts, avoiding the decrease in conductivity caused by multiple welding of the same part. Attached Figure Description

[0016] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the positive electrode connecting piece in an embodiment of the present invention; Figure 2 This is a schematic diagram of the negative electrode connecting piece in an embodiment of the present invention; Figure 3 This is a schematic diagram of the first layer of core being welded to the connecting piece in the electrode tab welding method of the present invention; Figure 4 This is a schematic diagram of the second layer of core being welded to the connecting piece in the electrode tab welding method of the present invention; Figure 5 This is a schematic diagram of the top cover being welded to the connecting piece in the electrode tab welding method of the present invention; Figure 6 This is a cross-sectional view after welding is completed in the electrode tab welding method of the present invention.

[0018] Figure label: 1. Connecting piece; 11. Positive electrode connecting piece; 12. Negative electrode connecting piece; 13. Connecting part; 14. Welding part; 141. First step; 142. Second step; 2. Core; 21. First core; 211. First tab; 22. Second core; 221. Second tab; 3. Ultrasonic welding section; 31. First ultrasonic weld mark; 32. Second ultrasonic weld mark; 4. Top cover; 5. Laser welding section. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0021] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0022] like Figures 3 to 5 As shown, the present invention provides a method for welding electrode tabs to a connecting piece 1, comprising the following steps: Step 1: Install connecting piece 1 onto the welding fixture. Specifically, place connecting piece 1 onto the ultrasonic welding fixture and fix it in place.

[0023] like Figure 1 and Figure 2As shown, the connecting piece 1 includes a connecting portion 13 and welding portions 14 disposed on both sides of the connecting portion 13. Each welding portion 14 includes at least one first step 141 and at least one second step 142. The first step 141 is disposed away from the connecting portion 13 and is lower than the second step 142.

[0024] The connecting piece 1 includes a positive electrode connecting piece 11 and a negative electrode connecting piece 12. In this embodiment, the positive electrode connecting piece 11 is an aluminum connecting piece 1, and the negative electrode connecting piece 12 is a copper connecting piece 1. The positive electrode connecting piece 11 and the negative electrode connecting piece 12 have basically the same structure, both including a connecting part 13 and a welding part 14 located on both sides of the connecting part 13.

[0025] Step 2: The first tab 211 of the core 2 is overlapped with the first step 141 and the first welding is performed to form the ultrasonic welded part 3.

[0026] In this embodiment, the two cores 2 are overlapped with the first tabs 211 extending toward each other on the first step 141, and the first tabs 211 cannot extend beyond the step surface inside the first step 141. Then, the first tabs 211 and the first step 141 are ultrasonically welded for the first time to form a first ultrasonic weld mark 31 at the welding point of the first tabs 211 and the first step 141.

[0027] like Figure 3 As shown, on the same side of each core 2, the first tab 211 of the positive electrode and the first tab 211 of the negative electrode extend outward, wherein the first tab 211 of the positive electrode is welded to the first step 141 of the positive electrode connecting piece 11, and the first tab 211 of the negative electrode is welded to the first step 141 of the negative electrode connecting piece 12.

[0028] Step 3: The second electrode 221, which is located on the same side as the first electrode 211, is overlapped with the second step 142 and a second welding is performed to form the ultrasonic welded part 3.

[0029] In this embodiment, the core 2 has a second electrode 221 extending in the same direction above each first electrode 211. The length of the second electrode 221 is greater than the length of the first electrode 211, so that the second electrode 221 can extend towards the inside of the connecting piece 1 relative to the first electrode 211 and overlap the second step 142. Then, the second electrode 221 and the second step 142 are ultrasonically welded a second time to form a second ultrasonic weld mark 32 at the welding site of the second electrode 221 and the second step 142.

[0030] like Figure 4As shown, each core 2 has a positive electrode first tab 211 and a second tab 221, and a negative electrode first tab 211 and a second tab 221 extending outward from the same side. The positive electrode first tab 211 is welded to the first step 141 of the positive electrode connecting piece 11, the positive electrode second tab 221 is welded to the first step 141 of the positive electrode connecting piece 11, the negative electrode first tab 211 is welded to the first step 141 of the negative electrode connecting piece 12, and the negative electrode second tab 221 is welded to the second step 142 of the negative electrode connecting piece 12.

[0031] Furthermore, the first step 141 is lower than the second step 142, and the first step 141 is located on the outer side of the connecting piece 1. During welding, welding is performed sequentially from the outer side to the inner side.

[0032] In this invention, during welding, the first tab 211 of the core 2 is first overlapped with the first step 141 for welding, and then the second tab 221 on the same side is overlapped with the second step 142 for welding. This allows multiple first tabs 211 and second tabs 221 to be welded on the same side of the connecting piece 1. Each first tab 211 or second tab 221 may include multiple layers of single-layer tabs, and each first tab 211 or second tab 221 is welded separately. Therefore, it can ensure that the overall number of tab layers is sufficient to meet the high power requirements of the battery cell, and it can also keep the number of single-layer tabs welded each time within an appropriate range (such as 35 layers). The thickness of each single first tab 211 or second tab 221 welded each time does not increase, so there is no need to increase the welding power. This avoids problems such as insufficient ultrasonic welding power leading to poor welding, and excessive ultrasonic welding power leading to tab cracking. By welding the tabs in segments, the core tabs can be reliably welded to the connecting piece, thereby improving the safety performance of the battery. Furthermore, the structure of the first step 141 and the second step 142 allows the welding parts to be staggered, avoiding the decrease in conductivity caused by multiple welding of the same part.

[0033] In one embodiment, the first weld and / or the second weld is ultrasonic welding.

[0034] In one embodiment, the first tab 211 and / or the second tab 221 are pre-welded together from multiple layers of single-layer tabs. Specifically, the multiple layers of single-layer tabs extending from the core 2 are pre-welded to form the first tab 211 and the second tab 221. Then, the first tab 211 and the second tab 221 are processed so that the length of the first tab 211 extending from the core 2 is less than the length of the second tab 221 extending from the core 2, thereby making the first tab 211 match the outer first step 141 and the second tab 221 match the inner second step 142. In this embodiment, the number of layers of the single-layer tab pre-welded to each first tab 211 or second tab 221 is 35-70 layers.

[0035] Since the tabs on the same side of the core 2 are divided into a first tab 211 and a second tab 221, the first tab 211 and the second tab 221 are welded separately. The number of tab layers welded each time is not high, so there is no need to increase the power of the welding equipment. Moreover, the overall number of tab layers is sufficient to meet the requirements of high power of the battery cell.

[0036] In one embodiment, before the connecting piece 1 is installed on the welding fixture, the welding portions 14 on both sides of the connecting piece 1 are bent at least once to form a first step 141, and the thickness of the first step 141 is equal to the thickness of the second step 142, so that the current flowing through them is the same.

[0037] In this embodiment, the second step 142 is flush with the connecting part 13. The edge of the second step 142 is bent downward to form a first step 141 with a height difference from the second step 142. Since the first step 141 and the second step 142 are formed by bending the same sheet, the thickness of the first step 141 is equal to the thickness of the second step 142.

[0038] In a preferred embodiment, the downward bending height of the first step 141 is greater than the thickness of the first tab 211. Therefore, after the first tab 211 is welded to the first step 141, the second tab 221 is then overlapped to the second step 142. At this time, the second tab 221 will not come into contact with the first tab 211.

[0039] like Figure 5 and Figure 6 As shown, after two ultrasonic welding processes, the connecting piece 1 and the core 2 are assembled onto the top cover 4, and the connecting part 13 is laser welded onto the pole of the top cover 4 to form the laser welding part 5. After applying insulating adhesive, the core 2 is closed, and after insulation treatment, the core 2 is installed into the outer shell and fully welded to form a seal, thus completing the battery assembly.

[0040] Example 1 like Figures 3 to 5 As shown, the electrode welding method of this embodiment is for welding the electrodes of a multi-core battery. The core 2 includes a first core 21 and a second core 22 stacked together. The first electrode 211 is disposed on one side of the first core 21, and the second electrode 221 is disposed on the same side of the second core 22 as the first electrode 211. The length of the first electrode 211 extending from the first core 21 is less than the length of the second electrode 221 extending from the second core 22.

[0041] During welding, the connecting piece 1 is first installed on the welding fixture, and then the lower first core 21 is placed in, so that the first tab 211 on one side of the first core 21 overlaps with the first step 141 of the connecting piece 1 for the first ultrasonic welding. Then, the upper second core 22 is placed on the first core 21, and the second core 22 is flush with the first core 21 in the stacking direction, so that the second tab 221 overlaps with the second step 142 for the second ultrasonic welding. After the two ultrasonic weldings are completed, the connecting piece 1 and the core 2 are installed together on the top cover 4, and the connecting part 13 is laser welded to the pole of the top cover 4. After applying insulating glue, the core 2 is closed, and after insulation treatment, the core 2 is installed into the outer shell and fully welded to form a seal, thus completing the assembly of the multi-core 2 battery.

[0042] The present invention can also set multiple layers (more than 2 layers) of core 2 according to the number of electrode tabs required. Correspondingly, each welding part 14 on the connecting piece 1 is provided with multiple steps. The electrode tab on the side of the bottom core 2 is the shortest. The length of the electrode tab increases from the bottom to the top. During welding, the bottom electrode tab is first overlapped with the outermost step and ultrasonically welded. Then, the electrode tabs are overlapped with the steps from the outside to the inside from the bottom to the top, and ultrasonic welding is performed from the outside to the inside.

[0043] By matching multiple layers of steps with multiple tabs, the total number of tab layers in the battery can be sufficiently large to meet the high power requirements of the cell, while ensuring that the number of single tab layers welded each time remains within an appropriate range. This eliminates the need for additional welding power, avoiding problems such as incomplete welds due to insufficient ultrasonic welding power and tab cracking due to excessive ultrasonic welding power, thus improving battery safety. Furthermore, the multi-layered step structure allows for staggered welding areas, preventing a decrease in conductivity caused by repeated welding of the same area.

[0044] Example 2 The tab welding method of this embodiment is for a dual-core battery. The dual-core battery has a core 2 set on each side of the connecting piece 1. A first tab 211 and a second tab 221 extend from the same side of the core 2. The length of the first tab 211 extending from the core 2 is less than the length of the second tab 221 extending from the core 2, so that the first tab 211 matches the first step 141 and the second tab 221 matches the second step 142.

[0045] Before welding, the first tab 211 and the second tab 221 on the same side of the core 2 are folded up respectively. During welding, the connecting piece 1 is first installed on the welding fixture, and then the core 2 is placed on both sides of the connecting piece 1, with the core side of the first tab 211 facing down and overlapping on the first step 141 of the connecting piece 1, for the first ultrasonic welding. During this process, the second tab 221 is located outside the range of the first ultrasonic welding to avoid affecting the welding within the welding area. After the first welding is completed, the second tab 221 is opened and overlapped on the second step 142 for the second ultrasonic welding. After the two ultrasonic weldings are completed, the connecting piece 1 and the core 2 are installed together on the top cover 4, and the connecting part 13 is laser welded to the pole of the top cover 4. After applying insulating glue, the core 2 is closed, and after insulation treatment, the core 2 is installed into the outer shell and fully welded to form a seal, thus completing the assembly of the dual-core 2 battery.

[0046] The present invention can also provide multiple (more than 2) electrodes on the same side of the core 2 according to the number of electrode layers. Correspondingly, each welding part 14 on the connecting piece 1 is provided with multiple steps. The electrode at the bottom layer of the core 2 is the shortest, and the length of the electrode from the bottom layer to the top layer increases sequentially. During welding, the bottom electrode is first overlapped with the outermost step and ultrasonically welded. Then, the electrodes are overlapped with the steps from the outside to the inside sequentially from the bottom layer to the top layer, and ultrasonic welding is performed sequentially from the outside to the inside.

[0047] By matching multiple layers of steps with multiple tabs, the total number of tab layers in the battery can be sufficiently large to meet the high power requirements of the cell, while ensuring that the number of single tab layers welded each time remains within an appropriate range. This eliminates the need for additional welding power, avoiding problems such as incomplete welds due to insufficient ultrasonic welding power and tab cracking due to excessive ultrasonic welding power, thus improving battery safety. Furthermore, the multi-layered step structure allows for staggered welding areas, preventing a decrease in conductivity caused by repeated welding of the same area.

[0048] Example 3 like Figure 1 and Figure 2 As shown, the present invention also provides a connecting piece 1 for connecting the tabs of the winding core 2. The connecting piece 1 includes a connecting portion 13 and welding portions 14 disposed on both sides of the connecting portion 13. The welding portion 14 includes at least one first step 141 and at least one second step 142. The first step 141 is disposed away from the connecting portion 13 and is lower than the second step 142.

[0049] like Figure 4 As shown, the electrode tabs include a first electrode tab 211 and a second electrode tab 221 disposed on the same side of the core 2. The first electrode tab 211 is welded to the first step 141, and the second electrode tab 221 is welded to the second step 142.

[0050] In this embodiment, the second step 142 is flush with the connecting part 13, and the first step 141 is formed by bending downward from the edge of the second step 142. The thickness of the first step 141 is equal to the thickness of the second step 142.

[0051] like Figure 6 As shown, in a preferred embodiment, the height difference between the first step 141 and the second step 142 is greater than the thickness of the first tab 211, so that when the second tab 221 is welded to the second step 142, it will not come into contact with the first tab 211 that has already been welded to the first step 141.

[0052] In a preferred embodiment, the extension length of the first electrode 211 is less than the extension length of the second electrode 221, and the length of the first electrode 211 does not exceed the step surface of the first step 141, so that the first electrode 211 matches the outer first step 141, and the second electrode 221 matches the inner second step 142.

[0053] The connecting piece 1 of the present invention, by providing multiple stepped structures on the welding portions 14 on both sides of the connecting portion 13, can match and weld with multiple tabs of the core 2, ensuring that the total number of tab layers in the battery is sufficient to meet the high power requirements of the cell, while also keeping the number of single tab layers welded each time within an appropriate range, without the need for additional welding power. This avoids problems such as incomplete welding due to insufficient ultrasonic welding power and tab cracking due to excessive ultrasonic welding power, thus improving the safety performance of the battery. Furthermore, the multi-layer stepped structure allows the welding parts to be staggered, avoiding the decrease in conductivity caused by multiple welding of the same part.

[0054] Example 4 like Figure 5 and Figure 6 As shown, the present invention also provides a battery, including a casing, a core 2, a top cover 4, a positive electrode connecting piece 11, and a negative electrode connecting piece 12. The core 2 is installed inside the casing, and the core 2 is provided with a positive electrode tab and a negative electrode tab respectively. The positive electrode tab is connected to the positive electrode connecting piece 11, and the negative electrode tab is connected to the negative electrode connecting piece 12. The positive electrode connecting piece 11 and the negative electrode connecting piece 12 are the connecting pieces 1 of the above embodiment, and will not be described again here.

[0055] The positive electrode tab and the negative electrode tab include a first electrode tab 211 and a second electrode tab 221, respectively. The first electrode tab 211 is welded to the first step 141 of the connecting piece 1, and the second electrode tab 221 is welded to the second step 142 of the connecting piece 1.

[0056] By matching multiple tabs with the multi-layered stepped structure of the connecting piece 1, the overall number of battery cores and tab layers can be increased, thereby increasing the overall battery power. Furthermore, the number of tab layers welded each time remains within an appropriate range, eliminating the need for additional welding power. This avoids issues such as incomplete welds due to insufficient ultrasonic welding power and tab cracking due to excessive ultrasonic welding power, thus improving battery safety. The multi-layered stepped structure also allows for staggered welding areas, preventing a decrease in conductivity caused by repeated welding of the same area.

[0057] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for welding electrode tabs to a connecting piece, characterized in that, include: The connecting piece is installed on the welding fixture, wherein the connecting piece includes a connecting part and welding parts disposed on both sides of the connecting part, each welding part includes at least one first step and at least one second step, the first step is disposed away from the connecting part, and the first step is lower than the second step; The first electrode lug of the core is overlapped with the first step for the first welding; The second electrode tab, which is located on the same side as the first electrode tab, is overlapped with the second step for a second welding.

2. The electrode tab welding method according to claim 1, characterized in that, Before welding, the first electrode lug and the second electrode lug on the same side of the core are first gathered together, and the length of the first electrode lug extending from the core is less than the length of the second electrode lug extending from the core, so that the first electrode lug matches the first step and the second electrode lug matches the second step.

3. The electrode tab welding method according to claim 1, characterized in that, The core includes a first core and a second core stacked together, wherein the first electrode tab is disposed on one side of the first core, the second electrode tab is disposed on the same side of the second core as the first electrode tab, and the length of the first electrode tab extending from the first core is less than the length of the second electrode tab extending from the second core. During welding, first place the first core so that the first electrode tab overlaps the first step, then place the second core on the first core, with the second core and the first core being flush in the stacking direction, so that the second electrode tab overlaps the second step.

4. The electrode tab welding method according to claim 2 or 3, characterized in that, The first weld and / or the second weld are ultrasonic welds.

5. The electrode tab welding method according to claim 4, characterized in that, After ultrasonic welding is completed, the connecting piece and the core are assembled on the top cover, and the connecting part is laser welded to the pole of the top cover. After insulation treatment, the core is installed into the outer shell and fully welded to form a seal, thereby completing the battery assembly.

6. The electrode tab welding method according to claim 1, characterized in that, Before the connecting piece is installed on the welding fixture, the welding portions on both sides of the connecting piece are bent at least once to form the first step, and the thickness of the first step is equal to the thickness of the second step.

7. The electrode tab welding method according to claim 6, characterized in that, The height of the downward bend of the first step is greater than the thickness of the first electrode tab.

8. The electrode tab welding method according to claim 1, characterized in that, The first electrode tab and / or the second electrode tab are pre-welded together from multiple layers of single-layer electrode tabs.

9. A connecting piece for connecting the tabs of a winding core, characterized in that, include: Connecting part; as well as A welding portion is disposed on both sides of the connecting portion. The welding portion includes at least one first step and at least one second step. The first step is disposed away from the connecting portion and is lower than the second step. The electrode lugs include a first electrode lug and a second electrode lug disposed on the same side of the winding core. The first electrode lug is welded to the first step, and the second electrode lug is welded to the second step.

10. A battery, comprising a casing, a winding core, a top cover, a positive electrode connector, and a negative electrode connector, wherein, The core is housed within the outer casing, and the core is provided with a positive electrode tab and a negative electrode tab respectively. The positive electrode tab is connected to the positive electrode connecting piece, and the negative electrode tab is connected to the negative electrode connecting piece. The positive electrode connecting piece and the negative electrode connecting piece are the connecting pieces as described in claim 9. The positive electrode tab and the negative electrode tab each include a first electrode tab and a second electrode tab. The first electrode tab is welded to the first step of the connecting piece, and the second electrode tab is welded to the second step of the connecting piece.

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