Electrode assembly and welding method thereof

Abstract

The present application discloses an electrode assembly and a welding method thereof. The electrode assembly includes a cover plate and a plurality of superimposed multi-layer pole ears, and the multi-layer pole ears are laser welded on the cover plate, wherein the laser welding forms a plurality of groups of laser welds superimposed in sequence along the welding direction on the multi-layer pole ears, and each group of laser welds includes two intersecting first welds and second welds; wherein, along the welding direction, two adjacent first welds partially overlap, and two adjacent second welds partially overlap. Through the above-mentioned method, the electrode assembly provided by the present application can avoid the problems of pole ear foil damage, high voids and gaps caused by ultrasonic pre-welding, avoid excessive heat input caused by long-term continuous output of laser welding, and prevent excessive accumulation of heat at the edge of the weld, thereby improving the problem of weld faults in welding, and the overlap and balance of each weld track, which is also conducive to reducing the risk of forming weld bulges and bubbles inside the weld.

Description

Technical Field

[0001] The present application relates to the technical field of electrode assembly welding, and in particular to an electrode assembly and a welding method thereof. Background Art

[0002] The current lithium battery cell assembly line process uses ultrasound to weld the tabs to the adapter, and then uses laser to weld the adapter to the cover. Although this process is currently used on a large scale by customers and the process is mature, the adapter increases the weight of the battery cell, occupies space and increases cost.

[0003] In order to reduce costs and improve efficiency, a new process of direct laser welding of the pole tabs and the battery top cover is now used. The specific process flow is to first weld the multi-layer pole tabs (foil thickness: 6-12um, number of layers: 20-140 layers or more) together through ultrasonic equipment, and then use laser welding to connect the pole tabs to the cover.

[0004] In traditional welding methods, such as linear welding, spiral welding and swing welding, continuous welding is usually used. Although the weld formation can be ensured by changing the welding process parameters, there are still problems such as large heat input and uneven start and end. This may cause the internal bubbles to fail to completely overflow, thus generating bubbles; in addition, excessive heat input at the junction of the weld and the foil may cause cracks in the foil and increase the fracture rate of the weld section.

[0005] Since the tab foil is thin and has many layers, there may be damage, high voids and gaps after ultrasonic pre-welding. In addition, the energy density of batteries is getting higher and higher, and there are higher requirements for charging and discharging efficiency, overcurrent and temperature rise. This makes the welding technology of multi-layer tabs and cover plates face more stringent challenges. Summary of the invention

[0006] The present application mainly provides an electrode assembly and a welding method thereof to solve the problem of insufficient welding performance between multi-layer electrode tabs and cover plates.

[0007] In order to solve the above technical problems, a technical solution adopted by the present application is to provide an electrode assembly. The electrode assembly includes a cover plate and a plurality of superimposed multi-layered pole tabs, wherein the multi-layered pole tabs are laser welded on the cover plate, wherein the laser welding forms a plurality of groups of laser welds superimposed in sequence along a welding direction on the multi-layered pole tabs, and each group of the laser welds includes two intersecting first welds and second welds; wherein, along the welding direction, two adjacent first welds partially overlap, and two adjacent second welds partially overlap.

[0008] In some embodiments, the overlap degree between two adjacent first welds is 60%-95%, and the overlap degree between two adjacent second welds is 60%-95%.

[0009] In some embodiments, the spacing between the center lines of two adjacent first welds is 0.05-1 mm, and the spacing between the center lines of two adjacent second welds is 0.05-1 mm.

[0010] In some embodiments, in each group of the laser welds, the first weld and the second weld are symmetrical about the welding direction, and an angle between the first weld and the welding direction is 30 to 60 degrees.

[0011] In some embodiments, the tail end of the first weld and the tail end of the second weld are located within a range defined by the head end of the first weld and the head end of the second weld, the offset spacing between the tail end of the first weld and the head end of the second weld in the width direction is 0.1mm-0.5mm, and the offset spacing between the tail end of the second weld and the head end of the first weld in the width direction is 0.1mm-0.5mm, and the width direction is perpendicular to the welding direction.

[0012] In some embodiments, the width of the weld marks formed by the multiple groups of laser welds in the width direction is 0.5-10 mm, and the width direction is perpendicular to the welding direction.

[0013] In order to solve the above technical problems, another technical solution adopted by the present application is: to provide a welding method for an electrode assembly. The welding method of the electrode assembly includes: setting a welding pattern adapted to the size of the multi-layer pole ear, the welding pattern including the centerline tracks of the intersecting first weld and second weld; setting the operating parameters of the pulsed welding laser, the operating parameters including welding direction, welding speed, idle speed, step spacing and welding angle; the welding speed is the operating speed when forming the first weld and the second weld, the idle speed is the operating speed when the first weld and the second weld are switched, the step spacing is the spacing between the centerlines of two adjacent first welds, the welding angle is the angle between the centerline of the first weld and the welding direction, and the centerline of the first weld and the centerline of the second weld are symmetrical about the welding direction; placing the multi-layer pole ear on the cover plate, and alternately forming the first weld and the second weld on the multi-layer pole ear along the welding direction, wherein the two adjacent first welds partially overlap, and the two adjacent second welds partially overlap.

[0014] In some embodiments, the step of setting the operating parameters of the pulsed welding laser includes:

[0015] The welding speed, the idle speed, the stepping pitch and the welding angle are set based on the material and the number of layers of the multi-layer tab and the type of laser.

[0016] In some embodiments, the degree of overlap between two adjacent first welds is 60%-95%, and the degree of overlap between two adjacent second welds is 60%-95%; the angle between the first weld and the welding direction is 30 to 60; the tail end of the first weld and the tail end of the second weld are located within the interval defined by the head end of the first weld and the head end of the second weld, and the misalignment spacing between the tail end of the first weld and the head end of the second weld in the width direction is 0.1mm-0.5mm, and the misalignment spacing between the tail end of the second weld and the head end of the first weld in the width direction is 0.1mm-0.5mm.

[0017] In some embodiments, the welding power of the pulsed welding laser is 1000W to 1800W, and the welding speed is 400 to 800 mm / s.

[0018] The beneficial effect of the present application is that, different from the prior art, the present application discloses an electrode assembly and a welding method thereof. In the welding process of the multi-layer pole ear and the cover plate, the present application cancels the ultrasonic pre-welding, and directly uses the pulsed laser to weld the multi-layer pole ear to the cover plate, thereby avoiding the problems of pole ear foil damage, high voids and gaps caused by ultrasonic pre-welding; further, by optimizing the weld bead structure, a plurality of groups of laser welds superimposed in sequence along the welding direction are formed on the multi-layer pole ear, wherein each group of laser welds includes two intersecting first welds and second welds, and along the welding direction, two adjacent first welds partially overlap, and two adjacent second welds partially overlap, that is, the pulsed laser welding can independently form each first weld and each second weld, and the formed first weld and second weld and the laser source can dissipate heat in the idle stroke of switching to form the first weld and the second weld, thereby avoiding excessive heat input caused by long-term continuous output of laser welding, preventing excessive accumulation of heat at the edge of the weld, thereby improving the weld fault problem in welding, and the overlap of each weld track is balanced, which is also conducive to reducing the risk of forming weld bulges and bubbles inside the weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0020] Figure 1 is a structural schematic diagram of an embodiment of an electrode assembly provided by the present application;

[0021] Figure 2 yes Figure 1A schematic structural diagram of an embodiment of weld bead forming in an electrode assembly shown;

[0022] Figure 3 yes Figure 1 A structural schematic diagram of another embodiment of weld bead forming in the electrode assembly shown;

[0023] Figure 4 It is a schematic flow chart of an embodiment of a welding method for an electrode assembly provided in the present application;

[0024] Figure 5 It is a physical schematic diagram of an embodiment of a weld on an electrode assembly provided in the present application. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] The terms "first", "second", "third" in the embodiments of the present application are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second", "third" can expressly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0027] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] The present application provides an electrode assembly 100, see Figure 1 and Figure 2 , Figure 1 is a schematic structural diagram of an embodiment of an electrode assembly provided in the present application, Figure 2 yes Figure 1 A schematic structural diagram of an embodiment of weld bead formation in an electrode assembly is shown.

[0029] The electrode assembly 100 includes a cover plate 30 and a plurality of stacked multi-layer pole ears 10, wherein the plurality of multi-layer pole ears 10 are welded to the cover plate 30 by laser welding, wherein the laser welding forms a plurality of groups of laser welds 20 stacked in sequence along a welding direction A on the plurality of multi-layer pole ears 10, wherein each group of laser welds 20 includes two intersecting first welds 21 and second welds 22; wherein, along the welding direction A, two adjacent first welds 21 partially overlap, and two adjacent second welds 22 partially overlap.

[0030] The multi-layered pole tabs 10 are gathered and stacked, and placed on the cover plate 30 , and then the multi-layered pole tabs 10 and the cover plate 30 are connected by laser welding.

[0031] Specifically, pulsed laser welding is used in the present application, so that each first weld 21 and each second weld 22 can be formed independently, avoiding excessive heat input caused by long-term continuous output of laser welding, and preventing excessive accumulation of heat at the edge of the weld, thereby improving the weld fault problem during welding.

[0032] Pulse laser welding, that is, controlling the laser welding output according to the duty cycle, forms the first weld or the second weld when the laser is output, and suspends the laser output when switching between the first weld and the second weld, thereby effectively reducing heat accumulation and avoiding excessive heat input caused by continuous laser output.

[0033] Pulse laser welding forms multiple groups of superimposed laser welds 20 in the welding direction A in sequence, and there is partial overlap between two adjacent groups of laser welds 20, that is, along the welding direction A, two adjacent first welds 21 partially overlap, and two adjacent second welds 22 partially overlap, so that the overlap of each weld trajectory is balanced, reducing the risk of forming weld bulges and bubbles inside the weld.

[0034] A weld bead for welding the multi-layered tab 10 and the cover plate 30 is formed by a plurality of first welds 21 and a plurality of second welds 22 superimposed along the welding direction A, and the first welds 21 and the second welds 22 are formed alternately and stepwise to finally form the weld bead as described above.

[0035] When the first weld 21 and the second weld 22 are formed alternately, multiple first welds 21 and multiple second welds 22 distributed in sequence along the welding direction A are formed non-continuously. During the switching process of the first weld 21 and the second weld 22, the formed first weld 21 and the second weld 22 and the laser source can dissipate heat in the idle stroke, thereby avoiding excessive heat input.

[0036] In the welding process of the multi-layer pole tab 10 and the cover plate 30, the present application cancels the ultrasonic pre-welding, and directly uses the pulsed laser to weld the multi-layer pole tab 10 to the cover plate 30, thereby avoiding the problems of pole tab foil damage, high voids and gaps caused by ultrasonic pre-welding; further, by optimizing the weld bead structure, a plurality of groups of laser welds 20 are formed on the multi-layer pole tab 10, which are sequentially superimposed along the welding direction A, wherein each group of laser welds 20 includes two intersecting first welds 21 and a second weld 22, and along the welding direction A, two adjacent first welds 21 are partially intersected. Overlap, two adjacent second welds 22 partially overlap, that is, pulsed laser welding can independently form each first weld 21 and each second weld 22, and the formed first weld 21 and second weld 22 and the laser source can dissipate heat in the idle stroke of switching to form the first weld 21 and the second weld 22, avoiding excessive heat input caused by long-term continuous output of laser welding, preventing excessive accumulation of heat at the edge of the weld, thereby improving the problem of weld faults in welding, and the overlap of each weld trajectory is balanced, which is also conducive to reducing the risk of forming weld bulges and bubbles inside the weld.

[0037] In this embodiment, the degree of overlap between two adjacent first welds 21 is 60%-95%, and thus the heat between the adjacent front and rear first welds 21 can be coordinated with each other, and there is appropriate heat accumulation in the local area, so that the subsequently superimposed first weld 21 can more efficiently and thermally evenly weld through the multi-layer pole ear 10, and the temperature of the molten pool formed during welding is balanced, thereby avoiding the generation of bulges in the weld and the generation of bubbles inside the weld; the degree of overlap between two adjacent second welds 22 is 60%-95%, and thus the heat between the adjacent front and rear second welds 22 can be coordinated with each other, and there is appropriate heat accumulation in the local area, so that the subsequently superimposed second weld 22 can more efficiently and thermally evenly weld through the multi-layer pole ear 10, and the temperature of the molten pool formed during welding is balanced, thereby avoiding the generation of bulges in the weld and the generation of bubbles inside the weld.

[0038] Specifically, the overlap between two adjacent first welds 21 can be 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, and the overlap between two adjacent second welds 22 can be 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, which can be considered based on the material, number of layers, thickness and welding material of the tab 10.

[0039] In this embodiment, the overlap degree between the first welds 21 and the overlap degree between the second welds 22 are the same, which further ensures that the weld trajectories overlap evenly and reduces the risk of forming weld protrusions and bubbles inside the welds.

[0040] In other embodiments, the overlapping degree between the first welds 21 and the overlapping degree between the second welds 22 may also be different.

[0041] Furthermore, the spacing a between the center lines of two adjacent first welds 21 is 0.05-1 mm, and the spacing b between the center lines of two adjacent second welds 22 is 0.05-1 mm. Under this spacing range, a good degree of overlap can be formed between adjacent welds.

[0042] The spacing a and the spacing b are the same, and are determined by the type of laser and the light spot it forms. Within this range, multiple types of lasers such as single-mode lasers, annular spot lasers and composite (blue light and infrared) lasers can be adapted.

[0043] Furthermore, in each group of laser welds 20, the first weld 21 and the second weld 22 are symmetrical about the welding direction A, and the angle c between the first weld 21 and the welding direction A is 30 to 60. This angle range can optimize the forming and morphology of the weld, improve the geometry of the weld bead, achieve smoothness and consistency of the weld, and effectively reduce defects in the welding process.

[0044] The angle between the first weld 21 and the welding direction A may specifically be 30, 35, 40, 45, 50, 55 or 60.

[0045] Furthermore, in the present embodiment, the weld trajectories are misaligned, that is, the tail end of the first weld 21 and the tail end of the second weld 22 are located within the interval defined by the head end of the first weld 21 and the head end of the second weld 22, and the misalignment spacing e between the tail end of the first weld 21 and the head end of the second weld 22 in the width direction B is 0.1mm-0.5mm, and the misalignment spacing f between the tail end of the second weld 22 and the head end of the first weld 21 in the width direction B is 0.1mm-0.5mm, and the width direction B is perpendicular to the welding direction A.

[0046] In other words, the distance between the starting point of the first weld 21 and the starting point of the second weld 22 in the width direction B is greater than the distance between the end point of the first weld 21 and the end point of the second weld 22 in the width direction B, the starting point of the first weld 21 and the end point of the second weld 22 are misaligned in the width direction B, and the starting point of the second weld 22 and the end point of the first weld 21 are misaligned in the width direction B to prevent excessive accumulation of heat at the edge of the weld, thereby improving the problem of weld faults during welding.

[0047] In this embodiment, the offset spacing e and the offset spacing f are equal in size, and may be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm.

[0048] In this embodiment, the weld width d formed by the plurality of laser welds 20 in the width direction B is 0.5-10 mm, which can be applied to tabs 20 of various sizes and form a good welding shape and morphology.

[0049] The weld width d can specifically be 0.5mm, 1mm, 1.5-mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm or 10mm.

[0050] Furthermore, the present application also provides a welding method for an electrode assembly 100, Figures 1 to 4 ,in Figure 4 1 is a schematic flow chart of an embodiment of a multi-layer electrode tab welding method provided in the present application. The welding method of the electrode assembly 100 includes:

[0051] Step 10: Setting a welding pattern adapted to the size of the multi-layer tab, the welding pattern including centerline tracks of the intersecting first weld seam and second weld seam.

[0052] In the operating system of the laser equipment, a welding pattern adapted to the size of the multilayer pole ear 10 is set. The welding patterns are multiple. In different welding images, the weld width d is different, the first weld 21 and the second weld 22, the distance between the tail end of the first weld 21 and the beginning end of the second weld 22 in the width direction B is different, and the distance between the tail end of the second weld 22 and the beginning end of the first weld 21 in the width direction B is also different.

[0053] Specifically, a visual camera may be used to identify the size of the multi-layer tab 10 , or the size of the multi-layer tab 10 may be manually input, so that a corresponding welding pattern may be automatically matched.

[0054] Furthermore, the welding pattern also includes an overlap degree between two adjacent first welds and an overlap degree between two adjacent second welds that can be matched based on the type of laser.

[0055] In this embodiment, the overlap degree between two adjacent first welds is 60%-95%, and the overlap degree between two adjacent second welds is 60%-95%.

[0056] Furthermore, the welding pattern also includes the weld trajectory misalignment size of the first weld 21 and the second weld 22 .

[0057] In this embodiment, the tail end of the first weld 21 and the tail end of the second weld 22 are located in the interval defined by the head end of the first weld 21 and the head end of the second weld 22, and the offset spacing between the tail end of the first weld 21 and the head end of the second weld 22 in the width direction B is 0.1mm-0.5mm, and the offset spacing between the tail end of the second weld 22 and the head end of the first weld 21 in the width direction B is 0.1mm-0.5mm.

[0058] Step 20: Set the operating parameters of the pulsed welding laser, including welding direction, welding speed, idle speed, step spacing and welding angle.

[0059] After the welding pattern is preliminarily matched, the operating parameters of the pulsed welding laser can be further set to make the weld bead higher in quality and better in forming efficiency.

[0060] The operating parameters include welding direction, welding speed, idle speed, step spacing and welding angle, wherein the welding speed is the operating speed of the laser when forming the first weld 21 and the second weld 22, the idle speed is the operating speed of the laser when the first weld 21 and the second weld 22 are switched, the step spacing is the spacing a between the center lines of two adjacent first welds 21, the welding angle is the angle c between the center line of the first weld 21 and the welding direction A, and the center line of the first weld 21 and the center line of the second weld 22 are symmetrical about the welding direction A.

[0061] Specifically, the welding speed, idle speed, stepping pitch and welding angle may be set based on the material and number of layers of the multi-layer tab 10 and the type of laser.

[0062] Among them, the angle c between the first weld 21 and the welding direction A is 30 to 60. By adaptively adjusting the angle c, the forming and morphology of the weld can be optimized, the geometry of the weld can be improved, the smoothness and consistency of the weld can be achieved, and defects in the welding process can be effectively reduced.

[0063] The operating parameters also include welding methods, which include forward method (such as Figure 2 as shown) and the back-off method (as shown Figure 3 As shown in the figure, the starting point of the weld in the forward method is after the end point, and the end point of the weld in the backward method is after the starting point.

[0064] Through pulsed laser welding and setting appropriate welding speed, idle speed and step spacing, the accumulation of heat at the edge of the weld can be reduced, and uneven heating of the tab foil can be avoided, thereby improving the porosity and fault problems in welding. The heat distribution during the welding process can be improved, and welding defects caused by heat concentration, such as undercut, burrs and spatter, can be reduced. A reasonable step spacing can also achieve balanced heat input to improve the flatness and consistency of the weld.

[0065] In this embodiment, the welding power of the pulsed welding laser is 1000W to 1800W, and the welding speed is 400 to 800mm / s. Within this parameter range, it can be adapted to multiple types of lasers and a wider range of lug sizes, thereby achieving good and reliable welding quality.

[0066] For example, a single-mode laser is used to output the pulsed welding laser, and the welding power of the single-mode laser is 1000W to 1800W. Alternatively, a ring-shaped spot laser is used to output the pulsed laser, and the center power of the ring-shaped spot laser is 1000W to 1800W, and its ring power is 1000W to 1800W.

[0067] Step 30: placing the multi-layer electrode tab on the cover plate, and alternately forming first welds and second welds on the multi-layer electrode tab along the welding direction, wherein two adjacent first welds partially overlap, and two adjacent second welds partially overlap.

[0068] After the above adjustment, the first weld seams 21 and the second weld seams 22 may be formed alternately along the welding direction A on the multi-layered tab 10 , which will not be described in detail.

[0069] See also Figure 5 , Figure 5 It is a physical schematic diagram of an embodiment of a weld on an electrode assembly provided in the present application. Figure 5 The weld on the electrode assembly shown in the figure is formed by a welding method as provided in the present application, which greatly improves the forming consistency and smooth morphology of the weld, effectively reduces heat input, prevents excessive accumulation of heat at the edge of the weld, improves the weld fault problem during welding, and effectively prevents the occurrence of weld bulges and internal bubbles.

[0070] It has been verified through experiments that, under the condition of forming the same weld mark size, the weld formed by the welding method provided in the present application can increase the peeling force between the multi-layer pole tab 10 and the cover plate 30 by more than 50%, thereby greatly improving the bonding force between the pole tab 10 and the cover plate 30.

[0071] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An electrode assembly, characterized in that: The electrode assembly includes a cover plate and a plurality of stacked electrode tabs, wherein the plurality of electrode tabs are laser welded to the cover plate, wherein the laser welding forms a plurality of groups of laser welds stacked in sequence along a welding direction on the plurality of electrode tabs, and each group of the laser welds includes two intersecting first welds and second welds; wherein, along the welding direction, two adjacent first welds partially overlap, and two adjacent second welds partially overlap.

2. The electrode assembly according to claim 1, characterized in that: The overlapping degree between two adjacent first welds is 60%-95%, and the overlapping degree between two adjacent second welds is 60%-95%.

3. The electrode assembly according to claim 2, characterized in that: The spacing between the center lines of two adjacent first welds is 0.05-1 mm, and the spacing between the center lines of two adjacent second welds is 0.05-1 mm.

4. The electrode assembly according to any one of claims 1 to 3, characterized in that: In each group of the laser welds, the first weld and the second weld are symmetrical about the welding direction, and an angle between the first weld and the welding direction is 30 to 60 degrees.

5. The electrode assembly according to claim 1, characterized in that: The tail end of the first weld and the tail end of the second weld are located within the interval defined by the head end of the first weld and the head end of the second weld, the offset spacing between the tail end of the first weld and the head end of the second weld in the width direction is 0.1mm-0.5mm, the offset spacing between the tail end of the second weld and the head end of the first weld in the width direction is 0.1mm-0.5mm, and the width direction is perpendicular to the welding direction.

6. The electrode assembly according to claim 1, characterized in that: The width of the weld marks formed by the multiple groups of laser welds in the width direction is 0.5-10 mm, and the width direction is perpendicular to the welding direction.

7. A welding method for an electrode assembly, characterized in that: include: Setting a welding pattern adapted to the size of the multi-layer tab, the welding pattern comprising centerline tracks of intersecting first welds and second welds; Setting the operating parameters of the pulsed welding laser, the operating parameters including welding direction, welding speed, idle speed, step spacing and welding angle; the welding speed is the operating speed when forming the first weld and the second weld, the idle speed is the operating speed when the first weld and the second weld are switched, the step spacing is the spacing between the center lines of two adjacent first welds, the welding angle is the angle between the center line of the first weld and the welding direction, and the center line of the first weld and the center line of the second weld are symmetrical about the welding direction; The multilayer tab is placed on a cover plate, and the first welds and the second welds are alternately formed on the multilayer tab along the welding direction, wherein two adjacent first welds partially overlap, and two adjacent second welds partially overlap.

8. The welding method of the electrode assembly according to claim 7, characterized in that: The operating parameters of the pulsed welding laser are set, including: The welding speed, the idle speed, the stepping pitch and the welding angle are set based on the material and the number of layers of the multi-layer tab and the type of laser.

9. The welding method of the electrode assembly according to claim 7, characterized in that: The degree of overlap between two adjacent first welds is 60%-95%, and the degree of overlap between two adjacent second welds is 60%-95%; the angle between the first weld and the welding direction is 30 to 60; the tail end of the first weld and the tail end of the second weld are located within the interval defined by the head end of the first weld and the head end of the second weld, the offset spacing between the tail end of the first weld and the head end of the second weld in the width direction is 0.1mm-0.5mm, and the offset spacing between the tail end of the second weld and the head end of the first weld in the width direction is 0.1mm-0.5mm.

10. The welding method of the electrode assembly according to claim 7, characterized in that: The welding power of the pulse welding laser is 1000W-1800W, and the welding speed is 400-800mm / s.

Images