Single battery, welding device and welding method

Abstract

The invention provides a single battery, a welding device and a welding method, the single battery comprises: an electrode assembly, the electrode assembly comprises a plurality of tabs, and the plurality of tabs are stacked along a first direction and connected to form a furling part; wherein the furling part comprises a first area and a second area, the plurality of tabs are connected in the second area through ultrasonic welding, the first area at least partially surrounds the second area, the thickness of the second area is smaller than that of the first area, a plurality of concave parts which are arranged at intervals are formed in the second area, and the plurality of tabs have uniform thickness in the first area along the first direction. According to the technical scheme, at least the risk that the tab is easy to crack due to stress concentration at the corner of the furling part can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and more particularly to a single battery, a welding device and a welding method. Background Art

[0002] In the field of new energy power batteries, secondary batteries refer to rechargeable batteries, also known as renewable batteries or storage batteries. Unlike primary batteries, secondary batteries can undergo multiple charge and discharge cycles through reverse charging for reuse. Power batteries include several battery cells, and the multiple tabs of the electrode assembly of the battery cells are usually stacked and welded together. However, existing battery cells still need further improvement in certain aspects (such as tab welding). Summary of the Invention

[0003] In view of the problems existing in the related art, the object of the present invention is to provide a single battery, a welding device and a welding method, so as to at least reduce the risk of easy rupture of the tab due to stress concentration at the corners of the gathered portion.

[0004] To achieve the above-mentioned objectives, the present invention provides a single cell battery, which includes: an electrode assembly, the electrode assembly includes multiple tabs, the multiple tabs are stacked along a first direction and connected to form a gathered portion; wherein the gathered portion includes a first region and a second region, the multiple tabs are ultrasonically welded together in the second region, the first region at least partially surrounds the second region, the thickness of the second region is less than the thickness of the first region, and a plurality of spaced-apart recesses are formed in the second region.

[0005] In some embodiments, the gathered portion further includes a transition region between the first region and the second region, and the thickness of the second region is 90%-95% of the thickness of the first region.

[0006] In some embodiments, multiple tabs are connected to the main body of the electrode assembly, each tab has a top edge away from the main body, and in a first direction, the multiple tabs include a bottommost tab and a topmost tab, the top edge of the topmost tab is closer to the main body than the top edge of the bottommost tab, the first edge of the second region is closer to the top edge of the bottommost tab than the other edges, and the first region surrounds the other edges of the second region except the first edge.

[0007] In some embodiments, the second region extends beyond the top edge of the topmost tab in a second direction from the top edge of the topmost tab to the top edge of the bottommost tab.

[0008] In some embodiments, in the second direction, the distance between the first side of the second region and the top edge of the topmost tab is at most 1 / 3 of the width of the gathered portion.

[0009] In some embodiments, the single battery further includes: a shell, in which the electrode assembly is accommodated; and a pole, which is provided in the shell, wherein the second area of ​​the folded portion is fixedly connected to the pole, and the first area is not fixedly connected to the pole.

[0010] In some embodiments, the second region is rectangular in shape, and / or each recess of the first region is a spherical groove.

[0011] The single cell battery also includes a shell; a first pole and a second pole are arranged on the shell; the electrode assembly is accommodated in the shell; the electrode assembly includes a main body, and multiple pole tabs extend from the main body, the multiple pole tabs include multiple first pole tabs and multiple second pole tabs, the multiple first pole tabs are arranged at intervals from the multiple second pole tabs, the material of the multiple first pole tabs includes a first metal, the material of the multiple second pole tabs includes a second metal, the thickness of the multiple first pole tabs is greater than the thickness of the multiple second pole tabs, and the projected area of ​​each first recess in the stacking direction of the first pole tabs is greater than the projected area of ​​each second recess in the stacking direction of the second pole tabs.

[0012] The hardness of the first metal of the first tab is less than the hardness of the second metal of the second tab.

[0013] The thickness of the single-layer first electrode tab is greater than the thickness of the single-layer second electrode tab.

[0014] In some embodiments, the first electrode tab includes a first electrode tab body composed of a first metal and a first metal oxide layer located on the surface of the first electrode tab body, and the second electrode tab includes a second electrode tab body composed of a second metal and a second metal oxide layer located on the surface of the second electrode tab body, wherein the first metal oxide layer is denser or thicker than the second metal oxide layer.

[0015] The thermal conductivity of the first metal of the first electrode tab is lower than the thermal conductivity of the second metal of the second electrode tab, and the melting point of the first metal is lower than the melting point of the second metal.

[0016] In some embodiments, the second depth of each second recess is less than the first depth of each first recess, the first depth is greater than 50% of the thickness of the plurality of first tabs, and the second depth is greater than 50% of the thickness of the plurality of second tabs.

[0017] In some embodiments, the number of the plurality of first recesses is less than the number of the plurality of second recesses.

[0018] Each first electrode tab has a first top edge away from the main body, and each second electrode tab has a second top edge away from the main body. In the stacking direction of the first electrode tabs, the plurality of first electrode tabs include a bottommost first electrode tab and a topmost first electrode tab, and the first top edge of the topmost first electrode tab is closer to the main body than the first top edge of the bottommost first electrode tab. In the stacking direction of the second electrode tabs, the plurality of second electrode tabs include a bottommost second electrode tab and a topmost second electrode tab, and the second top edge of the topmost second electrode tab is closer to the main body than the second top edge of the bottommost second electrode tab. In the direction from the first top edge of the topmost first electrode tab to the first top edge of the bottommost first electrode tab, a portion of the first welding zone is located between the first top edge of the topmost first electrode tab and the first top edge of the bottommost first electrode tab, and in the direction from the second top edge of the topmost second electrode tab to the second top edge of the bottommost second electrode tab, a portion of the second welding zone is located between the second top edge of the topmost second electrode tab and the second top edge of the bottommost second electrode tab.

[0019] The projection of each first recess in the first tab stacking direction is circular, and the projection of each second recess in the second tab stacking direction is circular.

[0020] In some embodiments, the plurality of recesses are arranged in 1 to 4 rows in the second welding region, and the recesses in each row are spaced apart in a direction parallel to the top edge of the tab away from the main body.

[0021] In some embodiments, the first electrode tab is a positive electrode tab, and the first metal is aluminum; the second electrode tab is a negative electrode tab, and the second metal is copper.

[0022] According to another aspect of an embodiment of the present application, a welding device is also provided for processing the above-mentioned single battery, the welding device including a welding head, the welding head having a first welding tooth and a plurality of second welding teeth arranged at intervals, the first welding tooth having a welding plane, the welding plane at least partially surrounding the plurality of second welding teeth, the plurality of second welding teeth protruding from the welding plane, the first welding tooth being used to form a first area, and the plurality of second welding teeth being used to form a plurality of recesses in the second area.

[0023] In some embodiments, the first welding tooth further includes a rounded corner area connected to the welding plane away from the periphery of the plurality of second welding teeth.

[0024] In some embodiments, the radius of the rounded corner area ranges from 0.5 mm to 2 mm.

[0025] According to another aspect of an embodiment of the present application, a welding method is also provided for processing a pole tab using the above-mentioned welding device, the welding method comprising: stacking a plurality of pole tabs; and welding the stacked plurality of pole tabs once using a welding head to form a first area and a second area of ​​the folded portion.

[0026] In the above technical solution, for the second area formed by ultrasonic welding, a compressed first area is used to at least partially surround the second area, which can disperse the stress at the outer edge of the second area, thereby reducing the risk of the tab rupture caused by stress concentration. In addition, if the first area is not provided, the welding teeth on the periphery of the welding head cannot achieve the desired welding technical effect, and the upper and lower flow areas of the welded tabs are different. By using a compressed first area to at least partially surround the second area, the welding teeth on the periphery can achieve a good welding effect. On the other hand, in the welding device, a first welding tooth with a welding plane and a plurality of second welding teeth protruding from the welding plane are provided on the welding head to process the tabs of the single cell, which can reduce the risk of the tab rupture caused by stress concentration and improve the welding effect. On the other hand, the welding method uses the welding device provided by the present application to weld the tab once, which can avoid the use of two welding processes of initial welding and final welding, and can reduce the risk of the tab rupture caused by stress concentration and improve the welding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 is a schematic diagram of an electronic device for a vehicle according to an embodiment of the present application.

[0029] Figure 2A A schematic perspective view of a secondary battery according to an embodiment of the present application is shown.

[0030] Figure 2B A schematic cross-sectional view of a secondary battery according to an embodiment of the present application is shown.

[0031] Figure 2C yes Figure 2B Schematic cross-sectional view of an electrode assembly of a secondary battery.

[0032] Figure 2D yes Figure 2B Schematic top view of the electrode assembly of the secondary battery.

[0033] Figure 3 This is a partial schematic diagram of a tab of an electrode assembly according to an embodiment of the present application.

[0034] Figure 4 Schematic cross-sectional view of an electrode tab of an electrode assembly according to an embodiment of the present application.

[0035] Figure 5Aand Figure 5B They are respectively a plan view schematic diagram and a cross-sectional view schematic diagram of a welding head of a welding device according to an embodiment of the present application.

[0036] Figure 6 4 is a flow chart of a welding method according to an embodiment of the present application.

[0037] Figure 7A and Figure 7B They are partial schematic diagrams of tabs of different polarities of an electrode assembly according to an embodiment of the present application.

[0038] Figure 8 1 is a schematic cross-sectional view of a first recess and a second recess according to an embodiment of the present application.

[0039] Figure 9A and Figure 9B They are partial schematic diagrams of tabs of different polarities of an electrode assembly according to another embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to better understand the spirit of the embodiments of the present application, some preferred embodiments of the present application are further described below.

[0041] The embodiments of the present application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are represented by similar reference numerals. The embodiments described herein with respect to the accompanying drawings are illustrative and diagrammatic and are intended to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.

[0042] As used herein, the terms "substantially," "substantially," "essentially," and "about" are used to describe and account for small variations, such as variations within the margin of error for manufacturing processes. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurred precisely as well as instances where the event or circumstance occurred very approximately.

[0043] In this specification, unless otherwise specified or limited, relative terms such as "central", "longitudinal", "lateral", "front", "rear", "right", "left", "inner", "outer", "lower", "higher", "horizontal", "vertical", "above", "below", "above", "below", "top", "bottom" and their derivatives (such as "horizontally", "downwardly", "upwardly", etc.) should be interpreted as referring to the directions described in the discussion or depicted in the drawings. These relative terms are only used for convenience of description and do not require that the present application be constructed or operated in a specific orientation.

[0044] For ease of description, “first,” “second,” “third,” etc. may be used herein to distinguish different components in a figure or a series of figures. “First,” “second,” “third,” etc. are not intended to describe the corresponding components.

[0045] The multiple tabs of a battery cell's electrode assembly are stacked and welded together. Typically, multiple welding teeth (e.g., spherical welding teeth) arranged in an array are used to weld the tabs. However, this welding method causes stress concentration at the corners of the welded portion, which can easily cause the tabs to crack. To address this technical problem, the present application provides a single battery, welding device, and welding method.

[0046] Single cells can be used in electronic devices, such as Figure 1 In the electronic device 1000 shown in FIG. 1 , for the convenience of description, the following embodiments are described by taking the electronic device 1000 as a vehicle as an example. Figure 1 The vehicle is equipped with a battery pack 1002 inside. Battery pack 1002 can be located at the bottom, front, or rear of the vehicle body 1001. Battery pack 1002 can be used to power the vehicle, for example, as the vehicle's operating power source. The working portion of the electronic device 1000 is electrically connected to battery pack 1002 to obtain electrical energy. The vehicle can be a fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, among others, but is not limited thereto. The working portion is the vehicle body, with battery pack 1002 located at the bottom of the vehicle body and providing electrical energy for the vehicle's operation and for the operation of its electrical components. However, in other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or electric tool, among others. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, among others. The working portion can draw electrical energy from battery pack 1002 and perform corresponding operations, such as the blade rotation unit of a fan or the dust collection unit of a vacuum cleaner. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present embodiment of the present application does not impose any particular limitation on the electronic device 1000.

[0047] In this application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application do not limit this. Battery cells may be cylindrical, flat, rectangular, or other shapes, etc., and the embodiments of this application do not limit this. Battery cells are generally divided into three types based on the packaging method: cylindrical battery cells, prismatic battery cells, and soft-pack battery cells, and the embodiments of this application do not limit this.

[0048] Figure 2A A schematic perspective view of a secondary battery according to an embodiment of the present application is shown. Figure 2B A schematic cross-sectional view of a secondary battery according to an embodiment of the present application is shown. Figure 2C yes Figure 2B Schematic cross-sectional view of an electrode assembly of a secondary battery. Figure 2D yes Figure 2B Schematic top view of the electrode assembly of the secondary battery.

[0049] Combine Figures 1 to 2D As shown, the single battery 100 may include a housing 200, which includes a peripheral sidewall 109 and an end wall 111 connected to one end of the peripheral sidewall 109. The other end of the peripheral sidewall 109 opposite the end wall 111 is provided with an opening 205. The top cover assembly 220 covers the opening 205 of the housing 200 to define a receiving cavity together with the housing 200. The electrode assembly 120 is located in the receiving cavity.

[0050] The direction Z from the end wall 111 toward the top cover assembly 220 represents the height of the battery cell 100. In this embodiment, two electrode assemblies 120 are stacked and disposed within the housing 200 along their thickness. In other embodiments, more than two electrode assemblies 120 may be disposed within the housing 200. The battery cell 100 may be a rectangular parallelepiped as shown, or it may be cylindrical, flat, or have other shapes.

[0051] In some embodiments, the electrode assembly 120 is a wound body formed by winding a first electrode sheet 201, a second electrode sheet 202, and a separator 204 positioned between the first electrode sheet 201 and the second electrode sheet 202. In other embodiments, the electrode assembly 120 may also be a laminated body formed by sequentially stacking the first electrode sheet 201, the second electrode sheet 202, and the separator 204 positioned between the first electrode sheet 201 and the second electrode sheet 202. The electrode assembly 120 may be flat. The electrode assembly 120 may include a main body 124, with a tab 121 (which may be referred to as a first tab) and a tab 122 (which may be referred to as a second tab) extending from the main body 124 along a direction Z. The multiple tabs 121 of the first electrode sheet 201 and the multiple tabs 122 of the second electrode sheet 202 may be stacked in the thickness direction of the electrode assembly 120. In some embodiments, the first electrode sheet 201 may be a positive electrode sheet, and the second electrode sheet 202 may be a negative electrode sheet. Accordingly, the tab 121 may be a positive electrode tab, and the tab 122 may be a negative electrode tab.

[0052] The positive electrode plate may include a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is coated on a portion of the surface of the positive electrode current collector. The negative electrode plate may include a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is coated on a portion of the surface of the negative electrode current collector. In some embodiments, for example, in a lithium-ion battery, the material of the positive electrode current collector may be aluminum. The positive electrode active material layer may include a positive electrode active material, and the positive electrode active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. For a high-nickel ternary lithium battery, the positive electrode active material may be a ternary material composed of three elements: nickel, cobalt, and manganese (or aluminum). The material of the negative electrode current collector may be copper. The negative electrode active material layer may include a negative electrode active material, and the negative electrode active material may be carbon or silicon, etc. The material of the diaphragm may be, for example, PP (polypropylene) or PE (polyethylene, polyethylene), etc.

[0053] The top cover assembly 220 includes a top cover body 221 and a pole 223 and a pole 224 disposed on the top cover body 221. The pole 223 and the pole 224 can pass through the top cover body 221 and can be insulated from the top cover body 221. One of the pole 223 and the pole 224 is a positive terminal, and the other is a negative terminal. In this embodiment, the pole tab 121 and the pole tab 122 at one end of the electrode assembly 120 are respectively connected to the corresponding pole 223 and the pole 224. The pole tab 121 and the pole tab 122 can be directly or indirectly electrically connected to the pole 223 and the pole 224. In some embodiments, the pole tab 121 and the pole 223, and the pole tab 122 and the pole 224 can be electrically connected via corresponding adapter plates 226. The pole tab 121 and the pole tab 122 can be welded to the adapter plates 226 after being bent, for example, by ultrasonic welding. In some other embodiments, the tabs 121 and 122 may also be directly connected to the corresponding poles 223 and 224 by welding.

[0054] Figure 3 1 is a partial schematic diagram of a tab 121 of an electrode assembly according to an embodiment of the present application. Figure 4 1 is a schematic cross-sectional view of a tab 121 of an electrode assembly according to an embodiment of the present application. In some embodiments, tab 122 may have the same configuration as tab 121, as shown below. Figures 3 to 6 The description is given with the tab 121 as an example. Figure 3 and Figure 4 As shown, the tab 121 includes multiple tabs 121 stacked along the thickness direction (direction Y) of the electrode assembly. Figure 3 and Figure 4 The topmost tab 121t and the bottommost tab 121b are marked in FIG. Multiple tabs 121 form a gathered portion 400. For example, multiple tabs 121 are stacked and welded to form the gathered portion 400. During the welding process, the tabs 121 in the gathered portion 400 are compressed and plastically deformed, resulting in a thickness of the gathered portion 400 that is less than the thickness of the uncompressed tabs 121. In other words, the thickness of the gathered portion 400 is less than the thickness of the area surrounding the gathered portion 400. Therefore, it can be understood that the gathered portion 400 refers to the portion of the stacked tabs 121 that is compressed and has a reduced thickness.

[0055] The gathered portion 400 includes a first region 410 and a second region 420. The plurality of tabs 121 in the second region 420 are welded together. Specifically, the plurality of tabs 121 in the second region 420 are connected by ultrasonic welding. The second region 420 can be fixedly connected to the corresponding pole 223. Fixed connection means that the second region 420 can be welded to the bottom plate of the pole 223 and directly fixedly connected to the pole 223; or, the second region 420 can be connected to the adapter plate (e.g., Figure 2BThe adapter plate 226 in the first region 410 is welded to be connected to the pole 223 indirectly. In other embodiments, welding can be performed through the second region 420 in other ways to achieve a fixed connection between the second region 420 and the pole 223. In addition, the first region 410 is not fixedly connected to the pole 223. That is, the first region 410 is not welded to the bottom plate or the adapter plate of the pole 223. The multiple tabs 121 in the first region 410 are compressed and not welded. Among them, the thickness of the multiple tabs 121 in the first region 410 is less than the theoretical thickness T of the multiple tabs 121. This shows that the multiple tabs 121 in the first region 410 are compressed and plastically deformed, the thickness of the multiple tabs 121 is thinned, and the multiple tabs 121 in the first region 410 are tightly combined together, and the gap between layers is relatively small, so that the first region 410 can be formed as a compacted region. The compaction degree refers to the degree of tightness between the layers of the tabs 121. The smaller the compaction degree, the greater the thickness, and the greater the compaction degree, the smaller the thickness. The first region 410 may have a uniform thickness T1.

[0056] The ratio of the thickness T1 of the first region 410 to the theoretical thickness T of the tab 121 is T1 / T. The theoretical thickness T refers to the stacked thickness of the multiple tabs 121 before connection (e.g., welding), that is, the thickness of the multiple tabs 121 when they are not compressed. The thickness of the multiple tabs 121 in the area around the gathered portion 400 can be the theoretical thickness T (i.e., a×b). For example, the thickness of a single tab 121 is a (i.e., a is the thickness of a single layer of current collector foil), and b is the number of stacked tabs 121 (i.e., b is the number of layers of current collector foil). Then, the stacked thickness of b tabs 121 before connection is a×b, and therefore the theoretical thickness T of the tab 121 is a×b. In some embodiments, the value range of T1 / T is 95%-98%, that is, the value range of T1 is a×b×95% to a×b×98%. In some embodiments, a is 12 μm-15 μm, and b is 30 μm-100 μm.

[0057] The degree of compaction of the multiple tabs 121 in the second region 420 is greater than that in the first region 410. As described above, a lower degree of compaction results in a greater thickness, such that the thickness T2 of the second region 420 is less than the thickness T1 of the first region 410. The second region 420 may have a uniform thickness T2. The ratio of the thickness T2 of the second region 420 to the theoretical thickness T of the tab 121 is T2 / T. In some embodiments, T2 / T ranges from 90% to 95%, meaning that T2 ranges from a×b×90% to a×b×95%. In some embodiments, the ratio T2 / T1 of the thickness T2 of the second region 420 to the thickness T1 of the first region 410 ranges from 90% to 95%, meaning that the thickness T2 of the second region 420 is 90% to 95% of the thickness T1 of the first region 410.

[0058] The second region 420 may include a plurality of spaced-apart recesses 422 . The recesses 422 may be arranged in a multi-row array. The recesses 422 may be formed by welding teeth on a welding head of a welding device pressing down on the multiple tabs 121 . The multiple tabs 121 may have a uniform thickness along direction Y in the first region 410 . The multiple tabs 121 in the first region 410 are merely compressed, not welded together. The first region 410 at least partially surrounds the second region 420 .

[0059] If only the second area 420 with multiple recesses 422 is used to weld multiple tabs 121, the stress concentration at the periphery of the second area 420 (for example, at each corner) of the ultrasonic welding is likely to cause the tab to rupture. The present application uses a compressed first area 410 to at least partially surround the second area 420, which can disperse the stress at the peripheral edge of the second area 420, thereby reducing the risk of tab rupture caused by stress concentration. In addition, if the first area 410 is not provided, the welding teeth at the periphery of the welding head cannot achieve the desired welding technical effect, and the upper and lower flow areas of the welded tabs are different. By using a compressed first area 410 to at least partially surround the second area 420, the welding teeth at the periphery can achieve a good welding effect.

[0060] In some embodiments, the gathered portion 400 may further include a transition zone 430 located between the first region 410 and the second region 420. The transition zone 430 also at least partially surrounds the second region 420. The thickness of the second region 420 differs from the thickness of the first region 410. In some embodiments, as described above, the thickness of the second region 420 may be 90%-95% of the thickness of the first region 410. The transition zone 430 can provide a smooth transition between the first and second regions 410, 420, of different thicknesses. In other words, the thickness of the transition zone 430 gradually decreases from the first region 410 to the second region 420. In some embodiments, the height difference between the ends of the transition zone 430 connecting the first and second regions 410, 420 is Td, and the value of Td may range from 0.05 mm to 0.2 mm.

[0061] Specifically, such as Figure 3In the top view shown, each tab 121 may have a top edge Sa that is away from the main body 124. The top edge Sa of the topmost tab 121t is closer to the main body 124 than the top edge Sa of the bottommost tab 121b. The second region 420 may be rectangular in shape. Each recess 422 in the first region 410 is a spherical groove. In other embodiments, the second region 420 may have other shapes. In this embodiment, the second region 420 may be rectangular in shape, with one long side 420a and the other long side 420b of the second region 420 being parallel to the top edge Sa of the bottommost tab 121b (within the process tolerance range), and the distance between the edge 420a and the top edge Sa of the bottommost tab 121b is closer than the other edges 420b, 420c, and 420d. The first region 410 surrounds the other long side 420b and the two short sides 420c and 420d of the second region 420. That is, the first region 410 surrounds the sides of the second region 420 except the side 420 a .

[0062] Since the edge 420a of the second region 420 is generally parallel to the top edge Sa of the tab 121, the edge 420a usually falls in the staggered area between the top edge Sa of the top tab 121t and the top edge Sa of the bottom tab 121b. There is no need to form a foil compression connection along the position of the edge 420a, so it is only necessary to ensure that the other edges except the edge 420a have a compression effect.

[0063] In the direction from the top edge Sa of the topmost tab 121t to the top edge Sa of the bottommost tab 121b (i.e., along the length of the tab), the edge 420a of the second region 420 extends beyond the top edge Sa of the topmost tab 121t. Because edge 420a extends beyond the top edge Sa of the topmost tab 121t, compression is not required at that location, eliminating the need for the first region 410. This reduces the length of the gathered portion 400 along the length of the tab. This ensures weld strength while reducing the length of the tab 121.

[0064] Along the length of the tab, the distance D1 between the edge 420a of the second region 420 and the top edge Sa of the topmost tab 121t is at most 1 / 3 of the width D2 of the gathered portion 400, i.e., D1 / D2 ≤ 1 / 3. In some embodiments, the positioning tolerance of the gathered portion 400 is less than 0.5 mm. Along the length of the tab, the distance between the top edge Sa of the topmost tab 121t and the top edge Sa of the bottommost tab 121b is less than 6 mm. This means that the stagger tolerance is less than 6 mm. The region between the top edge Sa of the topmost tab 121t and the top edge Sa of the bottommost tab 121b can be referred to as the tab stagger region. Along the length of the tab, the minimum reserved distance D3 between the gathered portion 400 and the top edge Sa of the bottommost tab 121b is greater than 3 mm, and the minimum reserved distance D4 between the gathered portion 400 and the main body 124 is greater than 3 mm. This ensures the maximum length of the gathered portion 400. In some embodiments, the second region 420 may have a size of 45 mm×22 mm, and the gathered portion 400 may have a size of 5 mm×22 mm.

[0065] According to another aspect of the embodiments of the present application, a welding device is also provided. Figure 5A and Figure 5B They are respectively a plan view and a cross-sectional view of the welding head 500 of the welding device according to an embodiment of the present application. Figure 5A and Figure 5B As shown, the welding device for processing the tabs 121 and 122 includes a welding head 500. In some embodiments, the welding head 500 can be a welding head of an ultrasonic welding device.

[0066] The welding head 500 can compact the multiple tabs 121 during the welding process for welding. Specifically, the welding head 500 has a first welding tooth 510 and a plurality of second welding teeth 520 arranged at intervals. The first welding tooth 510 has a welding plane 512. The welding plane 512 at least partially surrounds the plurality of second welding teeth 520, for example, surrounding two short sides and one long side of the region of the plurality of second welding teeth 520. The plurality of second welding teeth 520 protrude from the welding plane 512. The first welding tooth 510 is used to form the first region 410 described above, and the plurality of second welding teeth 520 is used to form the plurality of recesses 422 of the second region 420 described above. By providing the welding head 500 with the first welding tooth 510 having the welding plane 512 and the plurality of second welding teeth 520 protruding from the welding plane 512 to process the tabs of a single battery cell, the risk of tab rupture caused by stress concentration can be reduced, thereby improving the welding effect.

[0067] During welding, the plurality of second welding teeth 520 on the welding head 500 first contact the tab 121 to achieve downward pressure on the second region 420 of the tab 121. As the welding head 500 continues to apply pressure, the downward pressure depth increases, and the plurality of tabs 121 in the first region 410 and the second region 420 are simultaneously pressed downward, thereby reducing the thickness of the plurality of tabs 121 in the first region 410 and further reducing the thickness of the plurality of tabs 121 in the second region 420. This makes the plurality of tabs 121 more compact in the second region 420 than in the first region 410, ultimately forming the aforementioned first region 410, second region 420, and plurality of recesses 422. In some embodiments, a transition region 430 may also be formed between the first region 410 and the second region 420.

[0068] In some embodiments, each second welding tooth 520 may be a spherical welding tooth. In some embodiments, the height of each second welding tooth 520 protruding from the welding plane 512 is in the range of 0.4 mm to 0.8 mm. The maximum width of each second welding tooth 520 (e.g., the diameter of each second welding tooth 520) may be in the range of 1.0 mm to 1.8 mm. The spacing between two adjacent second welding teeth 520 may be in the range of 1.2 mm to 2.0 mm.

[0069] In addition, the first welding tooth 510 may further include a fillet area 514 connected to the outer periphery of the welding plane 512 away from the plurality of second welding teeth 520. The fillet area 514 can reduce the stress at the corner of the welding plane when the welding plane 512 presses the tab, thereby preventing the tab from cracking.

[0070] In some embodiments, the radius of the fillet region 514 ranges from 0.5 mm to 2 mm. If the radius of the fillet region 514 is too large, the edge pressing effect will be relatively poor. In addition, if the radius of the fillet region 514 is too large, the width of the weld head will increase, thereby further widening the width of the welding device, which may cause damage to the tab stacking fault area.

[0071] According to another aspect of the embodiments of the present application, a welding method is also provided. Figure 6 is a flow chart of a welding method according to an embodiment of the present application. The welding head 500 of the welding device can be used to process multiple tabs to implement the welding method. Figure 6 As shown, the welding method may include step S610 of stacking multiple tabs (such as the multiple tabs 121 described above). Then, at step S620, the stacked multiple tabs are welded using a welding head (such as the welding head 500 described above) to form the gathered portion 400 and its first region 410 and second region 420. In some embodiments, a transition region 430 may also be formed between the first region 410 and the second region 420.

[0072] By using a welding device with a welding head 500 to weld the tab, the tab can be welded once, thereby avoiding the need for two welding operations, namely, initial welding and final welding, and reducing the risk of tab rupture caused by stress concentration, thereby improving the welding effect.

[0073] In addition, the prior art generally uses the same welding device and process parameters to weld the positive and negative electrode tabs. However, due to the different materials and thicknesses of the positive and negative electrode tabs, the existing welding method can easily cause different welding strengths between the positive and negative electrode tabs and the adapter or the electrode column, or local stress concentration, which can lead to rupture of the tab foil. To address such technical issues, in other embodiments, different welding devices are used for welding the positive and negative electrode tabs, and thus the weld marks formed in the second region 420 are also different (the presence and shape of the first region 410 and the transition region 430 are not limited). Figure 7A and Figure 7B They are partial schematic diagrams of the tabs 121 and 122 of the electrode assembly according to an embodiment of the present application. Figure 7A and Figure 7B As shown, multiple (also referred to as multiple layers) tabs 121 are stacked and connected to form a first welding region 420A. Multiple tabs 121 can be welded and connected in the first welding region 420A. Tabs 121 can be connected to corresponding poles 223 via adapters 226 in the first welding region 420A, or can be directly connected to poles 223 in the first welding region 420A. Multiple tabs 122 are stacked and connected to form a second welding region 420B. Multiple tabs 122 can be welded and connected in the second welding region 420B. Tabs 122 can be connected to corresponding poles 224 via adapters 226 in the second welding region 420B, or can be directly connected to poles 224 in the second welding region 420B. The first welding region 420A and the second welding region 420B can correspond to the second region 420 described above.

[0074] The tab 121 has a top edge Sa away from the main body 124, and the tab 122 has a top edge Sa' away from the main body 124. The width of the tab 121 may gradually decrease from the main body 124 to the top edge Sa. The width of the tab 122 may gradually decrease from the main body 124 to the top edge Sa'.

[0075] A plurality of first recesses 422A are formed in the first welding region 420A and a plurality of second recesses 422B are formed in the second welding region 420B. The first welding region 420A and the second welding region 420B may each be rectangular.

[0076] The multiple first recesses 422A and the multiple second recesses 422B can be formed by protruding welding teeth on the welding head of the welding device pressing down on the tab. In this embodiment, the multiple first recesses 422A and the multiple second recesses 422B can be formed by spherical welding teeth. In some embodiments, ultrasonic spherical welding can be used to form the first welding area 420A and the second welding area 420B. In some cases, the total welding area of ​​the welding teeth is greater than 80% of the total welding area to avoid affecting the overcurrent calculation. The projection of each first recess 422A in the stacking direction of the tab 121 is circular, and the projection of each second recess 422B in the stacking direction of the tab 122 is circular. In other embodiments, the first recesses 422A and the second recesses 422B can also be formed by welding teeth of other shapes to form other suitable shapes.

[0077] Each tab 121 is made of a first metal. Each tab 122 is made of a second metal. In some embodiments where tab 121 is a positive electrode tab and tab 122 is a negative electrode tab, the first metal of tab 121 is aluminum and the second metal of tab 122 is copper. That is, the positive electrode current collector is aluminum (the first metal) and the negative electrode current collector is copper (the second metal).

[0078] In some embodiments, the thickness of the single-layer tab 121 is greater than the thickness of the single-layer tab 122. The thickness of the single-layer tab 121 formed by the first metal can be 10μm-15μm, for example, the thickness of the single-layer aluminum positive electrode current collector of the positive electrode tab can be 10μm-15μm. The thickness of the single-layer tab 122 formed by the second metal can be 4μm-8μm, for example, the thickness of the single-layer copper negative electrode current collector of the negative electrode tab can be 4μm-8μm. Generally, the number of layers of the multiple tabs 121 is the same as the number of layers of the multiple tabs 122, so the total thickness of the multiple tabs 121 is greater than the total thickness of the multiple tabs 122.

[0079] The projected area of ​​each first recess 422A in the stacking direction of the tabs 121 is larger than the projected area of ​​each second recess 422B in the stacking direction of the tabs 122. Larger welding teeth can be used to form the first recesses 422A with larger projected areas in the first welding region 420A, and smaller welding teeth can be used to form the second recesses 422B with smaller projected areas in the second welding region 420B.

[0080] Because the tabs 121 and 122 are made of different metal materials and have different thicknesses (for example, when the number of layers of the tabs 121 and 122 is greater than 60, the thickness difference between the two is significant), during the welding process between the tabs and the adapter plate or the corresponding pole, if the same welding equipment and process parameters are used to weld the tabs 121 and 122, the same size of welding teeth can easily cause different welding strengths between the tabs 121 and 122 and the adapter plate or the pole, or local stress concentration, which can lead to rupture of the tab foil. For example, a thicker tab 121 is more likely to crack or produce a cold weld during welding.

[0081] Thicker tabs 121 are prone to cracking or cold welds during welding. By using larger welding teeth to form the first recess 422A with a larger projected area in the first welding region 420A, the larger welding teeth can reduce the risk of tab 121 fracture through a larger contact area, thereby improving yield. Since thicker tabs 121 require greater welding energy input, using larger welding teeth to form the first welding region 420A allows for greater ultrasonic vibration energy transfer through a larger contact area, while also reducing energy loss and avoiding energy attenuation caused by the thickness of the tab 121. On the other hand, for thinner tabs 122, excessive indentations should be avoided. By using smaller welding teeth to form the second recess 422B with a smaller projected area in the second welding region 420B, the indentation depth of the second recess 422B can be precisely controlled, preventing loss of conductive cross-sectional area due to excessive deformation of the tab 122. Furthermore, by using smaller welding teeth to form the second welding region 420B, the smaller size of the welding teeth can better concentrate welding energy. Therefore, the different welding requirements of tabs with different materials and thicknesses are met. For example, when the total thickness of the aluminum foil of tab 121 is 100 μm and the total thickness of the copper foil of tab 122 is 50 μm, this technical effect can be achieved.

[0082] Figure 8 FIG is a cross-sectional view of the first recess 422A of the tab 121 and the second recess 422B of the tab 122 according to an embodiment of the present application. Figure 8 As shown, the cross-sectional view of the first recess 422A is along Figure 7A The cross-sectional view of the second concave portion 422B is taken along the line X1 in the first welding area 420A. Figure 7BThe line X2 in FIG. 4 is taken at the second welding region 420B. In some embodiments, the second depth H2 of each second recess 422B is less than the first depth H1 of each first recess 422A. That is, the depth of the first recess 422A with a larger projected area may also be greater. Specifically, in some embodiments, the first depth H1 may be greater than 50% of the thickness of the multiple tabs 121. The second depth H2 may be greater than 50% of the thickness of the multiple tabs 122. The thickness of the multiple tabs 121 is the sum of the thicknesses of each tab 121, and the thickness of the multiple tabs 122 is the sum of the thicknesses of each tab 122. By setting the thickness of the recess to be greater than 50% of the thickness of the corresponding tab, the problem of incomplete welding through the total thickness of the tab can be prevented.

[0083] In this embodiment, the plurality of first recesses 422A and the plurality of second recesses 422B can be formed by spherical welding teeth. The first recesses 422A and the second recesses 422B can each be a spherical groove. The projection of the first recesses 422A in the direction in which the tabs 121 are stacked is circular, and the projection of the second recesses 422B in the direction in which the tabs 122 are stacked is also circular. The radius of the circular projection of the first recesses 422A is greater than the radius of the circular projection of the second recesses 422B.

[0084] The plurality of first recesses 422A and the plurality of second recesses 422B may be arranged in arrays of multiple rows and multiple columns, respectively. In some embodiments, the plurality of first recesses 422A may be arranged in 1 to 4 rows in the first welding region 420A, and the plurality of second recesses 422B may be arranged in 1 to 4 rows in the second welding region 420B. Figure 7A and Figure 7B The first recesses 422A and the second recesses 422B are shown as two rows as an example. The first recesses 422A in each row are spaced apart in a direction parallel to the top side Sa of the tab 121, and the second recesses 422B in each row are spaced apart in a direction parallel to the top side Sa' of the tab 122.

[0085] In some embodiments, the number of first recesses 422A is less than the number of second recesses 422B. For example, in this embodiment, there are 16 first recesses 422A arranged in two rows of eight columns, while there are 20 second recesses 422B arranged in two rows of ten columns. The greater number of first recesses 422A, with their larger projected areas, and the smaller number of second recesses 422B, with their smaller projected areas, ensure that the total weld area of ​​the welding teeth exceeds 80% of the total area of ​​the welding teeth, thereby preventing any impact on the overcurrent calculation.

[0086] In some embodiments, the hardness of the first metal of tab 121 is less than the hardness of the second metal of tab 122. For example, in some embodiments where tab 121 is a positive tab and tab 122 is a negative tab, the first metal of tab 121 is aluminum and the second metal of tab 122 is copper. Aluminum has a hardness of approximately 25 HV (Vickers hardness), while copper has a hardness of approximately 90 HV. The hardness of the aluminum of tab 121 is lower than the hardness of the copper of tab 122. Tab 121 with lower hardness has higher ductility and is more susceptible to plastic deformation. By using larger welding teeth to form the first recess 422A of tab 121, the larger welding teeth can provide a more uniform contact area, thereby preventing local stress concentration in tab 121 from causing tearing or excessive deformation of the tab foil. On the other hand, tab 122 has higher hardness and good conductivity, requiring higher ultrasonic energy to achieve plastic flow. By using smaller welding teeth to form the second recess 422B of the tab 122 , the smaller welding teeth can increase local pressure (ie, higher pressure per unit area), thereby promoting metallurgical bonding between the foil of the tab 122 and the weld.

[0087] In some embodiments, the thermal conductivity of the first metal of tab 121 is lower than the thermal conductivity of the second metal of tab 122, and the melting point of the first metal is lower than the melting point of the second metal. For example, in some embodiments where tab 121 is a positive tab and tab 122 is a negative tab, the thermal conductivity of the aluminum of tab 121 is approximately 237 W / m·K and the melting point of aluminum is approximately 660°C, while the thermal conductivity of the copper of tab 122 is approximately 401 W / m·K and the melting point of copper is approximately 1085°C. In such embodiments, using large-sized welding teeth to weld tab 121 can reduce localized heat accumulation, prevent overheating and melting of the first metal of tab 121, which has a lower melting point, while also distributing ultrasonic mechanical energy across the surface. Furthermore, the second metal of tab 122 requires a higher instantaneous energy density. By using small-sized welding teeth for the second metal of tab 122, which has a higher melting point, the temperature can be quickly raised to the welding temperature.

[0088] In some embodiments, different metal oxide layers may be formed on the foil surfaces of the tabs 121 and 122. Specifically, the tab 121 may include a tab body composed of a first metal (e.g., aluminum) and a first metal oxide layer located on the surface of the tab body. The first metal oxide layer may be formed by oxidation of the first metal. The first metal layer may be, for example, an aluminum oxide (e.g., Al2O3) layer. The tab 122 may include a tab body composed of a second metal (e.g., copper) and a second metal oxide layer located on the surface of the tab body. The second metal oxide layer may be formed by oxidation of the second metal. The second metal layer may be, for example, a copper oxide (e.g., CuO or Cu2O) layer.

[0089] The first metal oxide layer of tab 121 can be denser or thicker than the second metal oxide layer of tab 122. Because the first metal oxide layer is denser or thicker (for example, the natural oxide layer of aluminum is dense and insulating), the first metal oxide layer (for example, Al2O3) is more stubborn. By using large-sized welding teeth, the first metal oxide layer can be more effectively broken down through a larger friction contact area and a longer ultrasonic action time, thereby promoting welding between pure first metals. In addition, because the second metal oxide layer of tab 122 is sparser or thinner, it is easily damaged. For example, the natural oxide layer of copper (for example, CuO or Cu2O) is thinner and easier to damage and remove. By using the high pressure of small-sized welding teeth (without excessive contact area), the second metal oxide layer can be quickly destroyed. Small-sized welding teeth can also concentrate energy to quickly break through the surface second metal oxide layer (for example, CuO or Cu2O) and achieve efficient welding.

[0090] In some embodiments, different welding process parameters are used for tabs 121 and 122 of different materials and thicknesses. For example, for a tab 121 made of aluminum and having a relatively thick thickness, the welding process parameters are: energy 450 J, amplitude 40 μm, and pressure 30 PSI (pounds force per square inch); for a tab 122 made of copper and having a relatively thin thickness, the welding process parameters are: energy 450 J, amplitude 45 μm, and pressure 30 PSI.

[0091] Figure 9A and Figure 9B The multiple tabs 121 and 122 can be stacked in staggered layers. Figure 9A and Figure 9B As shown, the bottommost tab 121 t and the bottommost tab 121 b of the plurality of tabs 121 in the stacking direction, and the bottommost tab 122 t and the bottommost tab 122 b of the plurality of tabs 122 in the stacking direction are marked.

[0092] Each tab 121 has a top side Sa away from the main body 124. The top side Sa of the topmost tab 121 t is closer to the main body 124 than the top side Sa of the bottommost tab 121 b. Each tab 122 has a second top side Sa′ away from the main body 124. The top side Sa′ of the topmost tab 122 t is closer to the main body 124 than the top side Sa′ of the bottommost tab 122 b.

[0093] In this embodiment, if Figure 9AAs shown, in the direction from the top edge Sa of the topmost tab 121t to the top edge Sa of the bottommost tab 121b (i.e., the length direction of the tabs), a portion of the first welding region 420A is located between the top edge Sa of the topmost tab 121t and the top edge Sa of the bottommost tab 121b. Specifically, at least a portion of the plurality of first recesses 422A in the first welding region 420A, which are away from the body 124, are located between the top edge Sa of the topmost tab 121t and the top edge Sa of the bottommost tab 121b.

[0094] like Figure 9B As shown, in the direction from the top edge Sa' of the topmost tab 122t to the top edge Sa' of the bottommost tab 122b (i.e., the length direction of the tabs), a portion of the second welding region 420B is located between the top edge Sa' of the topmost tab 122t and the top edge Sa' of the bottommost tab 122b. Specifically, at least a portion of the plurality of second recesses 422B in the second welding region 420B, which are located away from the body 124, are located between the top edge Sa' of the topmost tab 122t and the top edge Sa' of the bottommost tab 122b.

[0095] The area between the top edge Sa of the topmost tab 121t and the top edge Sa of the bottommost tab 121b can be called the tab staggered region. Along the length direction of the tab 121, the distance between the top edge Sa of the topmost tab 121t and the top edge Sa of the bottommost tab 121b is less than 6mm, that is, the staggered tolerance is less than 6mm. Similarly, the area between the top edge Sa' of the topmost tab 122t and the top edge Sa' of the bottommost tab 122b can be called the tab staggered region. Along the length direction of the tab 122, the distance between the top edge Sa' of the topmost tab 122t and the top edge Sa' of the bottommost tab 122b is less than 6mm, that is, the staggered tolerance is less than 6mm.

[0096] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A single battery, characterized in that: include: An electrode assembly, the electrode assembly comprising a plurality of tabs, the plurality of tabs being stacked along a first direction and connected to form a gathered portion; The gathered portion includes a first area and a second area, and a plurality of tabs are ultrasonically welded together in the second area. The first area at least partially surrounds the second area, and the thickness of the second area is less than that of the first area. A plurality of recesses are formed in the second area.

2. The single cell according to claim 1, characterized in that: The gathered portion further includes a transition zone between the first region and the second region, and a thickness of the second region is 90% to 95% of a thickness of the first region.

3. The single cell according to claim 1 or 2, characterized in that: A plurality of tabs are connected to the main body of the electrode assembly, and each tab has a top edge away from the main body. In the first direction, the plurality of tabs include a bottom tab and a top tab, wherein a top edge of the top tab is closer to the main body than a top edge of the bottom tab. The first side of the second region is closer to the top side of the bottommost tab than the other sides, and the first region surrounds the other sides of the second region except the first side.

4. The single cell according to claim 3, characterized in that: In a second direction from the top edge of the topmost tab to the top edge of the bottommost tab, the second region extends beyond the top edge of the topmost tab.

5. The single cell according to claim 4, characterized in that: In the second direction, the distance between the first side of the second region and the top edge of the topmost tab is at most 1 / 3 of the width of the gathered portion.

6. The single cell according to claim 1, characterized in that: Also includes: a housing in which the electrode assembly is housed; A pole, provided on the housing, The second region of the gathered portion is fixedly connected to the pole, and the first region is not fixedly connected to the pole.

7. The single cell according to claim 1, characterized in that: The second area is rectangular in shape, and / or Each of the recesses in the second region is a spherical groove.

8. The single cell according to claim 1, characterized in that: Also includes a housing; A first pole and a second pole are provided on the housing; The electrode assembly is accommodated in the shell, and the electrode assembly further includes a main body, the plurality of tabs include a plurality of first tabs and a plurality of second tabs extending from the main body, the plurality of first tabs and the plurality of second tabs are spaced apart, the plurality of first tabs are stacked and connected to form the second region connected to the first pole as a first welding region, the plurality of second tabs are stacked and connected to form the second region connected to the second pole as a second welding region, the first welding region has a plurality of first recesses spaced apart, and the second welding region has a plurality of second recesses spaced apart. The material of the multiple pieces of the first pole tabs includes a first metal, the material of the multiple pieces of the second pole tabs includes a second metal, the thickness of the multiple pieces of the first pole tabs is greater than the thickness of the multiple pieces of the second pole tabs, and the projected area of ​​each of the first recesses in the stacking direction of the first pole tabs is greater than the projected area of ​​each of the second recesses in the stacking direction of the second pole tabs.

9. The single cell according to claim 8, characterized in that: The hardness of the first metal of the first electrode tab is smaller than the hardness of the second metal of the second electrode tab, and the thickness of a single layer of the first electrode tab is larger than the thickness of a single layer of the second electrode tab.

10. The single cell according to claim 8, characterized in that: The second depth of each second recess is smaller than the first depth of each first recess. The first depth is greater than 50% of the thickness of the first tabs. The second depth is greater than 50% of the thickness of the second tabs.

11. The single cell according to any one of claims 8 to 10, characterized in that: The first electrode tab is a positive electrode tab, and the first metal is aluminum; The second electrode tab is a negative electrode tab, and the second metal is copper.

12. A welding device, characterized in that: For processing a single battery according to any one of claims 1 to 7, the welding device comprises a welding head, The welding head comprises a first welding tooth and a plurality of second welding teeth arranged at intervals, wherein the first welding tooth has a welding plane, the welding plane at least partially surrounds the plurality of second welding teeth, and the plurality of second welding teeth protrude from the welding plane. The first welding teeth are used to form the first region, and the second welding teeth are used to form the recessed portions in the second region.

13. The welding device according to claim 12, characterized in that The first welding tooth further includes a rounded corner area connected to the welding plane away from the periphery of the plurality of second welding teeth.

14. The welding device according to claim 13, characterized in that The radius of the rounded corner area ranges from 0.5 mm to 2 mm.

15. A welding method, characterized in that: The tab is processed using the welding device according to any one of claims 12 to 14, wherein the welding method comprises: stacking a plurality of tabs; The welding head is used to weld the stacked plurality of electrode tabs once to form the first region and the second region of the gathered portion.

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