An oxidation-preventing electrode for tab pre-welding, a pre-welding system and a pre-welding forming method

Abstract

The application provides an anti-oxidation electrode for tab pre-welding, a pre-welding system and a pre-welding forming method, and belongs to the technical field of welding devices. The anti-oxidation electrode comprises a mounting seat and an electrode head, the electrode head is detachably arranged on the mounting seat, a composite protective layer is arranged on the electrode head, and the composite protective layer comprises a barrier layer and a conductive anti-oxidation layer which are sequentially arranged in layers from the inside to the outer wall of the electrode head. The composite protective layer is also provided with raised lines. The electrode prevents its own oxidation through the arrangement of the conductive anti-oxidation layer, so as to always maintain a low and constant contact resistance, and can improve the consistency of pre-welding quality and the product yield. Moreover, the raised lines on the surface of the electrode head are transferred to the surface of the tab welding point during welding, forming a micro-rough structure and providing convenience for the subsequent laser repair welding process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding devices, in particular to an anti-oxidation electrode for tab pre-welding, a pre-welding system and a pre-welding forming method. BACKGROUND

[0002] In the process of manufacturing lithium batteries, the welding of tabs is one of the key processes. As an important component for connecting the internal battery cells and external circuits, the welding quality of tabs directly affects the conductivity, safety and cycle life of the battery. Especially for the pre-welding of multi-layer tabs (i.e. the structure of multi-layer metal foil stacking), the industry generally uses ultrasonic welding technology. Ultrasonic welding achieves plastic deformation and mechanical bonding between metal materials through high-frequency vibration, which has the advantages of fast welding speed and no need for adding welding materials.

[0003] However, since ultrasonic welding is a mechanical bonding method, the welding strength is relatively limited, and the phenomenon of "false welding" may occur at the welding interface, which leads to an increase in contact resistance and affects the performance of the battery. Secondly, high-frequency vibration during welding can easily cause small metal debris on the surface of the metal foil, which may fall into the battery and cause short circuit risk, reducing the safety and reliability of the battery. In addition, ultrasonic welding has high requirements for the stability of welding parameters, and parameter fluctuations can easily lead to poor welding consistency, affecting the yield of mass production.

[0004] Therefore, it is necessary to improve the existing tab welding method of lithium batteries to overcome the defects of the prior art. SUMMARY

[0005] To overcome the problems in the related art, one of the purposes of the present application is to provide an anti-oxidation electrode for tab pre-welding. The electrode prevents oxidation by setting a conductive anti-oxidation layer, thereby always maintaining a low and constant contact resistance, which can improve the consistency of pre-welding quality and product yield. The raised lines on the surface of the electrode head are transferred to the surface of the tab welding point during welding, forming a micro-rough structure, which provides convenience for the subsequent laser repair welding process.

[0006] An anti-oxidation electrode for tab pre-welding comprises an electrode body.

[0007] The electrode body comprises a mounting seat and an electrode head, the electrode head is detachably arranged on the mounting seat, and a composite protective layer is arranged on the electrode head, the composite protective layer comprises a barrier layer and a conductive anti-oxidation layer arranged in sequence from the inside to the outer wall of the electrode head.

[0008] The composite protective layer is also provided with raised lines.

[0009] In the preferable technical scheme of the present application, the conductive oxidation-preventing layer is made of any one of silver, gold, platinum or palladium or an alloy thereof.

[0010] The thickness of the conductive oxidation-preventing layer is 0.1-10 microns.

[0011] In the preferable technical scheme of the present application, the raised lines include a plurality of regularly arranged square raised lines arranged on the surface of the electrode tip.

[0012] The raised lines include stripe-shaped raised lines arranged on the surface of the electrode tip.

[0013] In the preferable technical scheme of the present application, the mounting base is provided with a mounting cavity, the electrode tip is detachably arranged in the mounting cavity, and the mounting base is provided with a clamping groove on the side away from the electrode tip.

[0014] One end of the electrode tip is exposed outside the mounting cavity, and the side of the electrode tip away from the mounting base is provided with the raised lines.

[0015] In the preferable technical scheme of the present application, the mounting base is provided with a mounting cavity, the electrode tip is detachably arranged in the mounting cavity, and the mounting base is provided with a clamping groove on the side away from the electrode tip.

[0016] The mounting base is provided with a cooling cavity, the cooling structure includes a sealing end cover, a water inlet pipe and a water outlet pipe, the sealing end cover is fixed to one end of the mounting base, a sealing gasket is arranged between the sealing end cover and the mounting base, one end of the water inlet pipe penetrates through the sealing end cover and extends into the cooling cavity.

[0017] The water outlet pipe is fixed to the outer wall of the mounting base and communicates with the cooling cavity.

[0018] In the preferable technical scheme of the present application, the cross section of the electrode tip is rectangular, and the length-width ratio of the cross section of the electrode tip is 1:1-5:1.

[0019] The second object of the present application is to provide a pre-welding system including a base plate, the base plate being provided with a pre-pressing structure and a welding structure, the welding structure being arranged on one side of the pre-pressing structure.

[0020] The pre-pressing structure is provided with a pressing head for pre-pressing and shaping the multi-layered tabs.

[0021] The welding structure is provided with the oxidation-preventing electrode as described above.

[0022] In the preferable technical scheme of the present application, the pre-pressing structure includes a pre-pressing rack, the pre-pressing rack is provided with a first driving device, the output end of the first driving device is arranged towards the base plate, the output end of the first driving device is provided with the pressing head, and the bottom of the pressing head is provided with a shaping raised portion.

[0023] The first bearing table is arranged on one side of the pre-pressing frame and is provided with a mold for bearing the workpiece.

[0024] In the preferred technical solution of the present application, the welding structure comprises a welding frame arranged on one side of the pre-pressing frame, and one side of the welding frame is further provided with a second bearing table, and the second bearing table is provided with a positioning jig for positioning the mold.

[0025] The second driving device is arranged on the welding frame, and the output end of the second driving device is located above the second bearing table, and the output end of the second driving device is provided with a mounting plate, and the mounting plate is provided with a clamping piece, and the mounting seat is clamped on the mounting seat.

[0026] One side of the positioning jig is further provided with a limiting structure, and the limiting structure comprises a first limiting frame and a second limiting frame arranged oppositely, and the second limiting frame is arranged above the first limiting frame, and the second limiting frame is provided with a through hole for the electrode head to pass through; the first limiting frame and the second limiting frame are further provided with a third driving device, and the third driving device drives the first limiting frame and the second limiting frame to move oppositely.

[0027] The third object of the present application is to provide a pre-welding forming method, which uses the pre-welding system as described above to implement.

[0028] The method comprises:

[0029] First, the negative tab is pre-pressed, and after pre-pressing, the negative tab is preheated, so that the temperature difference between the temperature of the negative tab and the temperature required for welding is controlled in the range of 50-200 DEG C.

[0030] After preheating, the negative tab is welded by using an anti-oxidation electrode, and then the welding state is maintained until the welding is completed.

[0031] The present application has the following advantages:

[0032] The application provides an anti-oxidation electrode for tab pre-welding, which comprises a mounting seat and an electrode head, the electrode head is detachably arranged on the mounting seat, a composite protective layer is arranged on the electrode head, and the composite protective layer comprises a barrier layer and a conductive anti-oxidation layer which are arranged in the order of from the inside of the electrode head to the outer wall. The composite protective layer is also provided with raised lines. In use, the conductive anti-oxidation layer does not oxidize itself, so that the contact resistance can be kept low and constant at all times. This makes the current through the negative tab and the generated Joule heat highly consistent each time of pre-welding, and finally a pre-welding plating layer with uniform thickness and bright and full appearance is obtained, which helps to improve the consistency of pre-welding quality and product yield. The internal barrier layer can effectively prevent the outward diffusion of internal copper atoms, and the barrier layer acts as a "shield" and the conductive anti-oxidation layer acts as a "helmet", which jointly resist the double attacks of high-temperature oxidation and flux chemical corrosion, so that the electrode can adapt to more severe and continuous pre-welding process requirements, and help to broaden the application range of pre-welding equipment. In addition, the raised lines on the surface of the electrode are transferred to the surface of the tab welding point during welding, forming a micro-rough structure. This provides convenience for the subsequent laser repair welding process. The rough surface can significantly reduce the laser reflectivity and improve the laser energy absorption efficiency, so that the laser welding is easier and more stable, and the strength of the final welding point can be improved.

[0033] The application also provides a pre-welding system and a pre-welding forming method comprising the above-mentioned anti-oxidation electrode for tab pre-welding, which can pre-weld the negative tab by the above-mentioned anti-oxidation electrode, and can improve the pre-welding effect of the negative tab, thereby helping to ensure the manufacturing quality of lithium batteries. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a perspective view of the anti-oxidation electrode for tab pre-welding provided in the embodiments of the application;

[0035] Figure 2 is a schematic view of the clamping position arranged on the electrode head provided in the embodiments of the application;

[0036] Figure 3 is a perspective view of the mounting seat provided in the embodiments of the application;

[0037] Figure 4 is a schematic view of the cooling cavity arranged in the mounting seat provided in the embodiments of the application;

[0038] Figure 5 is a perspective view of the pre-welding system provided in the embodiments of the application;

[0039] Figure 6 is a front view of the pre-welding system provided in the embodiments of the application;

[0040] Figure 7is a schematic view of the pressing head cooperating with the mold provided in the embodiment of the present application;

[0041] Figure 8 is a perspective view of the limiting structure provided in the embodiment of the present application;

[0042] Figure 9 is a schematic view of the electrode lug welded by the electrode provided in the present application.

[0043] Reference signs:

[0044] 1, electrode body; 11, mounting seat; 111, water outlet pipe; 112, mounting cavity; 113, cooling cavity; 12, electrode head; 121, convex lines; 2, clamping block; 21, clamping position; 3, sealing end cover; 31, water inlet pipe; 32, clamping groove; 100, bottom plate; 200, pre-pressing structure; 210, pre-pressing frame; 220, first driving device; 230, first bearing table; 240, mold; 250, pressing head; 2501, shaping convex; 300, welding structure; 310, welding frame; 320, second driving device; 3201, mounting plate; 330, second bearing table; 340, positioning jig; 400, limiting structure; 410, first limiting frame; 420, second limiting frame; 4201, through port; 430, third driving device. DETAILED DESCRIPTION

[0045] Preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application is more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0046] The lug, as an important component for connecting the internal cell and the external circuit of the battery, directly affects the conductivity, safety and cycle life of the battery. Especially for the pre-welding of multi-layer lugs (i.e. multi-layer metal foil laminated structure), the industry generally adopts ultrasonic welding process. Ultrasonic welding causes plastic deformation between metal materials through high-frequency vibration and realizes mechanical bonding, which has the advantages of fast welding speed and no need to add solder.

[0047] However, because ultrasonic welding is a mechanical bonding method, its welding strength is relatively limited, and it is prone to incomplete bonding ("false weld") at the welding interface, leading to increased contact resistance and affecting battery performance. Secondly, the high-frequency vibration during welding can easily generate tiny metal debris on the surface of the metal foil. This debris may fall into the battery, causing a short circuit risk and reducing battery safety and reliability. Furthermore, ultrasonic welding requires high stability of welding parameters; parameter fluctuations can easily lead to poor welding consistency, affecting the yield of mass production.

[0048] Based on this, this application provides an anti-oxidation electrode for pre-soldering of electrode tabs.

[0049] Example 1

[0050] like Figures 1-4 As shown, this embodiment provides an anti-oxidation electrode for pre-welding of tabs, comprising an electrode body 1;

[0051] The electrode body 1 includes a mounting base 11 and an electrode head 12. The electrode head 12 is detachably mounted on the mounting base 11. A composite protective layer is provided on the electrode head 12. The composite protective layer includes a barrier layer and a conductive anti-oxidation layer that are stacked sequentially from the inside to the outside of the electrode head 12.

[0052] The composite protective layer is also provided with raised texture 121.

[0053] Furthermore, the conductive anti-oxidation layer is made of any one of silver, gold, platinum or palladium or an alloy thereof;

[0054] The thickness of the conductive anti-oxidation layer is from 0.1 μm to 10 μm. 0.1 μm (100 nanometers) is the critical thickness to ensure a continuous, dense, and defect-free coating (e.g., free of pinholes). Below this thickness, the coating may be discontinuous, failing to form a complete protective barrier. The substrate or barrier layer may be exposed through micropores, leading to localized oxidation or diffusion and rendering the anti-oxidation function ineffective. Some coating technologies used in large-scale production (such as specific electroplating, thermal spraying, or thick-film printing) may require greater thickness tolerance to achieve a uniform, stress-free coating; therefore, the thickness of the conductive anti-oxidation layer needs to be increased to 10 μm. A thickness exceeding 10 μm may lead to increased internal stress in the coating, decreased adhesion, increased thermal resistance affecting heat dissipation, and potentially deterioration of the surface micro-texture (protrusion) morphology. In practical applications, for cutting-edge high-performance applications, a precision precious metal coating close to the lower limit (e.g., 0.1-1 μm) can be selected to achieve ultimate performance with minimal precious metal usage and control costs. For large-scale industrial applications, medium-thickness ranges (e.g., 1-5μm) can be selected, using more cost-effective coating materials (e.g., specific alloys) or processes to maximize production cost-effectiveness while ensuring reliability.

[0055] In practical applications, the barrier layer is directly deposited or plated onto the substrate of the electrode head 12. The preferred material is a high-hardness, high-melting-point ceramic or metallic compound, such as titanium nitride (TiN), chromium carbide (CrC), or alumina (Al2O3). The main function of the barrier layer is to act as a diffusion barrier, effectively preventing the diffusion of outer layer elements into the copper substrate during high-temperature welding (avoiding substrate softening or the formation of brittle phases), while simultaneously preventing copper substrate elements from diffusing outwards and affecting the outer layer performance. This fundamentally ensures the dimensional stability and mechanical integrity of the electrode head 12 substrate under long-term thermal cycling.

[0056] In another embodiment, the conductive anti-oxidation layer is a metallic gold layer with a thickness of approximately 0.5 μm. Because gold is chemically stable and does not easily oxidize at high temperatures, defects such as spark spatter, localized ablation (burn-through), or incomplete soldering caused by the oxide layer can be avoided. The welding process is quiet and stable, resulting in smooth and uniform solder joint morphology.

[0057] On the outer surface of the conductive anti-oxidation layer, raised textures 121 are formed by laser etching, micromachining, or template forming during the deposition process. These raised textures 121 can be regular micro-pyramid arrays, interlaced grids, or annular grooves. They are designed to be effectively embedded into the surface of the tab foil material during welding pressure.

[0058] In a preferred embodiment, the raised texture 121 comprises a plurality of regularly arranged square raised protrusions on the surface of the electrode head 12. Further, the electrode head 12 has a rectangular cross-section, and the aspect ratio of the cross-section is 1:1 to 5:1. In a specific embodiment, the aspect ratio of the cross-section of the electrode head 12 does not exceed 3.

[0059] The cross-section of the electrode head 12 is preferably rectangular. The rectangular shape is beneficial for controlling the shape of the welding area, especially for the more uniform expansion of the weld nugget. The raised texture 121 is specifically a number of square raised protrusions arranged regularly on the rectangular welding end face. These square raised protrusions can be integrally formed during the manufacturing of the electrode head 12 through machining, etching or laser forming processes.

[0060] During installation, the electrode head 12 is connected to the mounting base 11 via a detachable structure such as threads, snap-fit, or locking pin, which makes it easy to replace the electrode head 12 separately after wear or damage, without having to replace the entire electrode body 1.

[0061] Better yet, see Figure 1 , Figure 2 Clamping blocks 2 can also be provided on opposite sides of the electrode head 12, and clamping positions 21 for clamping the electrode tabs are formed between the two clamping blocks 2, so that the electrode head 12 and the electrode tabs can be in close contact, thereby improving the welding quality.

[0062] In the present application, the electrode head 12 with a rectangular cross-section and a specified length-width ratio (for example, no more than 3) can effectively control the shape of the welding heat-affected zone, reduce the diffusion of heat to non-welding areas, reduce the risk of oxidation of the tab foil, and at the same time facilitate the formation of a regular shape and uniform strength of the welding nugget.

[0063] The square grid protrusions on the end surface of the electrode head 12 not only enhance the microscopic contact with the tab surface during welding, improve the current distribution and heat dissipation conditions, but also form a rough structure similar to ultrasonic welding on the tab surface after welding, effectively reducing the laser reflectivity in the subsequent laser repair welding process, improving energy absorption and welding reliability, and achieving good connection between resistance pre-welding and laser repair welding process.

[0064] The electrode in use:

[0065] During the tab resistance pre-welding process, the electrode is pressed towards the multi-layered tab foil under the drive of the welding machine. The welding current flows through the mounting seat 11, the electrode head 12, the barrier layer, and the conductive anti-oxidation layer, and finally reaches the welded foil. The protruding pattern 121 provides local high pressure at the moment of contact, breaks the surface contaminants, and ensures initial conduction. During the entire welding cycle, the conductive anti-oxidation layer maintains a smooth surface and low contact resistance due to its intrinsic high-temperature oxidation resistance.

[0066] The protruding pattern 121 on the electrode head 12 of the electrode is reliably replicated to each welding point, forming a uniform microstructure. This provides an ideal optical absorption surface for subsequent laser welding, which can reduce laser reflectivity by more than 30%, making the laser welding process more stable, requiring less energy, and having more controllable weld depth, and overall improving the reliability and efficiency of the final welding of the battery tab.

[0067] In another embodiment, the protruding pattern 121 includes a stripe-shaped protrusion arranged on the surface of the electrode head 12.

[0068] Further, the mounting seat 11 is provided with a mounting cavity 112, and the electrode head 12 is detachably arranged in the mounting cavity 112. The mounting seat 11 is provided with a clamping groove 32 on the side away from the electrode head 12.

[0069] One end of the electrode head 12 is exposed outside the mounting cavity 112, and the protruding pattern 121 is arranged on the side wall of the electrode head 12 away from the mounting seat 11.

[0070] The shape of the mounting cavity 112 matches the cross-section of the electrode head 12, facilitating positioning and fixing. The mounting seat 11 is provided with a clamping groove 32 on the side away from the electrode head 12 (usually the end connected to the welding machine), which is used for quick positioning and locking with the electrode arm or mounting clamp of the welding equipment, facilitating the installation and replacement of the overall electrode.

[0071] One end of the electrode tip 12 protrudes from the installation cavity 112 and is exposed, directly facing the welding workpiece (negative electrode lug).

[0072] Further, the electrode further comprises a cooling structure;

[0073] The installation base 11 is provided with a cooling cavity 113; the cooling structure comprises a sealing end cover 3, a water inlet pipe 31 and a water outlet pipe 111; the sealing end cover 3 is fixed at one end of the installation base 11, and a sealing gasket is arranged between the sealing end cover 3 and the installation base 11; one end of the water inlet pipe 31 penetrates through the sealing end cover 3 and extends into the cooling cavity 113;

[0074] The water outlet pipe 111 is fixed on the outer wall of the installation base 11 and communicates with the cooling cavity 113.

[0075] The cooling structure specifically comprises a sealing end cover 3, a water inlet pipe 31 and a water outlet pipe 111. The sealing end cover 3 is fixed at one end of the installation base 11 by screws or buckles, and a sealing gasket (such as a rubber gasket or a polytetrafluoroethylene gasket) is arranged between the sealing end cover 3 and the end face of the installation base 11 to ensure the sealing property of the cooling cavity 113 and prevent the cooling liquid from leaking. One end of the water inlet pipe 31 penetrates through the side of the sealing end cover 3 and extends into the cooling cavity 113, and the extension depth can be adjusted according to the shape of the cooling cavity 113 to optimize the cooling liquid flow field. The water outlet pipe 111 is fixed on the outer wall of the installation base 11 and communicates with the outlet of the cooling cavity 113. The cooling liquid (such as water or special cooling oil) is pumped into the cooling cavity 113 from the water inlet pipe 31, flows through the high-temperature area of the electrode to absorb heat, and then flows out from the water outlet pipe 111, forming a continuous circulating cooling path.

[0076] Optionally, the cooling cavity 113 can be designed as a spiral flow channel, a series of cavities or other structures for enhancing heat exchange. The water inlet pipe 31 and the water outlet pipe 111 are made of high-temperature-resistant and corrosion-resistant materials, such as stainless steel or red copper, and can be connected to the external cooling system through quick-change joints.

[0077] After long-term use, the cooling system may be scaled or blocked by impurities. For a closed deep hole channel, it is extremely difficult to clean. However, according to the design, only the sealing end cover 3 needs to be disassembled to expose the inner wall of the entire cooling cavity 113 for direct and thorough cleaning. This openable maintenance design greatly prolongs the service life of the electrode and ensures the long-term stability of the cooling efficiency.

[0078] Through direct heat exchange between the built-in cooling cavity 113 and the circulating cooling liquid, a large amount of Joule heat and conduction heat accumulated in the electrode tip 12 and the body during resistance welding can be quickly removed, the working temperature of the electrode can be effectively controlled within a reasonable range, and the annealing, hardness reduction or deformation of the material caused by overheating can be avoided.

[0079] Example 2

[0080] like Figures 1-9 As shown, this embodiment provides a pre-welding system, including a base plate 100, on which a pre-pressing structure 200 and a welding structure 300 are provided, and the welding structure 300 is disposed on one side of the pre-pressing structure 200.

[0081] The pre-compression structure 200 is provided with a compression head 250 for pre-compressing and shaping the multi-layer electrode tabs;

[0082] The welding structure 300 is provided with an anti-oxidation electrode as described above.

[0083] Specifically, the pre-compression structure 200 includes a pre-compression frame 210, on which a first driving device 220 is provided. The output end of the first driving device 220 is disposed toward the base plate 100, and the pressing head 250 is disposed on the output end of the first driving device 220. A shaping protrusion 2501 is disposed at the bottom of the pressing head 250.

[0084] A first support platform 230 is provided on one side of the pre-pressing frame 210, and a mold 240 for supporting the workpiece is provided on the first support platform 230.

[0085] The pre-compression structure 200 operates as follows: The assembled battery cell electrode assembly (with its multi-layer metal foil tabs protruding for welding) is placed in a dedicated mold 240 on the first support platform 230. The mold 240 ensures the battery cell body is fixed and that the stacked tabs are accurately exposed within the stroke directly below the clamping head 250. After receiving a start signal, the first drive device 220 (typically a servo electric cylinder or precision cylinder) drives the clamping head 250 to move vertically downwards. The shaping protrusion 2501 at the bottom of the clamping head 250 contacts the multi-layer tabs. As the drive device continuously applies controllable pressure, the shaping protrusion 2501 squeezes the foil stack, breaking its original loose stacking state, causing it to undergo plastic deformation, tightly adhering, and expelling residual air or micro-gaps between layers. The shaping protrusion 2501 can also make dots on the surface of the multi-layer metal foil tabs, thereby aiding in subsequent welding positioning. After reaching the preset pressure or stroke, the pre-compression structure 200 maintains a short holding time. During this period, the deformation of the foil material is stabilized, and the shape of the shaping protrusion 2501 is partially "imprinted" on the electrode tab, forming a preliminarily integrated and regularly shaped area to be soldered.

[0086] The multi-layer tabs are mechanically compacted and shaped before welding. This step effectively eliminates air between the foils, corrects the initial misalignment and warping, and makes the tab stack entering the welding station uniform in height and compact. This provides a stable initial condition for subsequent welding and is the fundamental prerequisite for obtaining uniform and reliable welds, thus ensuring the consistency of product quality from the source.

[0087] Further, the welding structure 300 comprises a welding rack 310 arranged on one side of the pre-pressing rack 210, and a second bearing table 330 arranged on one side of the welding rack 310, and a positioning jig 340 for positioning the mold 240 is arranged on the second bearing table 330.

[0088] The second driving device 320 is arranged on the welding rack 310, and the output end of the second driving device 320 is located above the second bearing table 330, and the output end of the second driving device 320 is provided with a mounting plate 3201, and the mounting plate 3201 is provided with a clamping piece, and the mounting seat 11 is clamped on the mounting seat 11.

[0089] The positioning jig 340 is further provided with a limiting structure 400, and the limiting structure 400 comprises a first limiting frame 410 and a second limiting frame 420 arranged oppositely, and the second limiting frame 420 is arranged above the first limiting frame 410, and the second limiting frame 420 is provided with a passing hole 4201 for the electrode head 12 to pass through; and a third driving device 430 is further arranged between the first limiting frame 410 and the second limiting frame 420, and the third driving device 430 drives the first limiting frame 410 and the second limiting frame 420 to move oppositely. The passing hole 4201 on the second limiting frame 420 acts as a "guide rail" for the downward movement of the electrode head 12, and forcibly ensures that the electrode head 12 contacts the welding point in a vertical posture and a preset position, which can eliminate the welding position deviation caused by mechanical deviation. At the same time, this structure effectively limits the activity range of the electrode head 12, and provides physical protection to prevent collision with the surrounding jigs during high-speed movement. The upper and lower limiting frames also physically limit the transverse diffusion path of the current while clamping the tabs, forcing the welding current to flow more concentratedly through the to-be-welded points, improving the energy utilization rate and reducing the welding instability caused by "shunt". The compact clamping also reduces the air around the local area, providing an auxiliary air isolation effect for the welding area.

[0090] The working process of the pre-welding system is as follows:

[0091] Firstly, the workpiece with the tab to be welded is placed in the mold 240 of the first bearing table 230. The first driving device 220 is actuated to drive the pressing head 250 to press down, and the loose multi-layer tabs are pre-pressed by the shaping protrusion 2501 at the bottom of the pressing head 250 to make them initially integrated and shaped. Subsequently, the workpiece after pre-pressing is transferred together with the mold 240 to the second bearing table 330 of the welding structure 300, and is accurately positioned by the positioning jig 340. Then, the third driving device 430 is started to drive the first limiting frame 410 to move relative to the second limiting frame 420, so as to press and fix the multi-layer tabs from the top and bottom, and at the same time, the welding area to be welded is accurately aligned with the passing opening 4201 of the second limiting frame 420. After that, the second driving device 320 drives the mounting plate 3201 and the anti-oxidation electrode mounted thereon to press down, and the electrode head 12 contacts the tab after passing through the passing opening 4201, and the resistance pre-welding is completed by applying a welding current. Finally, the electrode is lifted, the limiting structure 400 is loosened, and the welded workpiece can be taken out

[0092] The system integrates the two independent processes of key pre-pressing shaping and resistance pre-welding in a compact work station. Seamless connection between processes is achieved by mechanical transfer, eliminating the intermediate handling and repeated positioning steps, significantly shortening the processing cycle of single product, especially suitable for high-speed automatic production lines, and greatly improving the overall production efficiency.

[0093] Embodiment 3

[0094] The embodiment provides a pre-welding forming method, which is implemented by using the pre-welding system as described above.

[0095] The pre-welding forming method comprises the following steps:

[0096] The negative tab is pre-pressed first, and after pre-pressing, the negative tab is pre-heated, so that the temperature difference between the temperature of the negative tab and the temperature required for welding is controlled in the range of 50-200℃.

[0097] After pre-heating, the negative tab is welded by using the anti-oxidation electrode, and then the welding state is maintained until the welding is completed.

[0098] Specifically, the pre-welding forming method is implemented in the following process:

[0099] The battery cell tab to be processed is assembled into the mold 240 on the first bearing table 230 of the pre-welding system, so that the multi-layer negative tab of the battery cell tab extends out of the mold 240 and is positioned below the pre-pressing structure 200. The pre-pressing structure 200 is started, and the first driving device 220 drives the pressing head 250 to press down, and the shaping protrusion 2501 at the bottom of the pressing head 250 applies controllable pressure to the superimposed multi-layer negative tab to perform pre-pressing and shaping. This step can compact the tab foil, remove air between the layers, and initially form a regular and dense welding area, and after completion, the pressing head 250 is reset.

[0100] After the pre-pressing shaping, the workpiece is transferred to the second carrying table 330 of the welding structure 300 and is precisely positioned by the positioning jig 340. Then, the pre-pressing negative electrode tab is preheated by the anti-oxidation electrode on the welding structure 300 or other independent preheating device. The preheating process needs to be precisely controlled to make the temperature of the negative electrode tab rise before welding and to ensure that the temperature difference between the temperature before welding and the final temperature required by the subsequent resistance welding is strictly controlled within the range of 50-200°C. This step provides a temperature rise buffer for the subsequent welding.

[0101] After the preheating is completed, resistance welding is performed. The third driving device 430 of the welding structure 300 first acts to drive the first limiting frame 410 of the limiting structure 400 to move relative to the second limiting frame 420, and the first limiting frame 410 tightly presses the multi-layer electrode tab. Then, the second driving device 320 drives the mounting plate 3201 and the anti-oxidation electrode mounted thereon to press down, and the electrode head 12 passes through the passing opening 4201 of the second limiting frame 420 to contact the clamped electrode tab. The welding current is applied, and resistance welding is performed by using the anti-oxidation electrode. After the welding starts, the system maintains the pressure of the electrode and the input state of the current until the preset welding time or energy is reached, the metallurgical bonding is completed, and then the electrode is lifted and the limiting structure 400 is loosened.

[0102] In this pre-welding shaping method, the pre-pressing physically eliminates the interlayer gap and gas that causes false welding; the preheating can alleviate the severe thermal shock in the welding instant; and the resistance welding itself forms a metallurgical bond with higher strength than mechanical bonding. The three work together to overcome the industry's stubborn problem of false welding and metal debris easily produced by traditional ultrasonic welding, greatly improving the internal quality and connection reliability of the welding points. The temperature design of the preheating avoids the risk of thermal stress concentration, local overburning or "welding through" caused by too large temperature difference from room temperature to high welding temperature, which is particularly beneficial to protect the integrity of the ultra-thin copper foil.

[0103] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and practice described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the following claims, along with full equivalents thereof. Unless otherwise indicated, the relative arrangement of components and steps in the embodiments set forth in the following examples does not limit the scope of the application. Also, it is to be understood that the dimensions of the various parts shown in the drawings are not to scale, and that the dimensions are merely illustrative of the relationships between the various parts. Techniques, methods, and apparatus known to those of ordinary skill are not discussed in detail, but are to be considered part of the present application, as described in the following claims. In all of the examples shown and discussed herein, any specific values should be interpreted as merely illustrative of the examples, and not as a limitation thereon. Thus, other examples of the exemplary embodiments can have different values. It is to be noted that like numbers and letters refer to like elements throughout the several views of the drawings, and that the use of or insertion of a reference number in one drawing does not preclude its use in another drawing. In the description of the application, it is to be understood that the terms "front," "back," "side," "top," "bottom," "up," "down," "vertical," "horizontal," and "lateral" merely describe the orientation in the drawings in which the application is shown and described, and are not meant to limit the position or orientation of the device or element being described to a particular position or orientation in the drawings, unless otherwise specifically noted. The terms "inner" and "outer" refer to the inner and outer contours of the components themselves.

[0104] For purposes of the description hereinafter, spatial or directional terms, such as "above," "below," "up," "down," "right," "left," "vertical," "horizontal," and the like, can be used where appropriate to describe the various examples. It is to be understood that such terms are not intended to limit the present application to the position or orientation shown in the drawings. It is also to be understood that the terms "front," "back," "side," "top," "bottom," "over," "under," and the like, in reference to a structure or element of a device, are intended to encompass various alternative positions or orientations of the structure or element, unless otherwise specifically noted. For example, a device that is described as "over" or "above" another device can also be positioned "under" or "below" the other device, unless otherwise specifically noted.

[0105] In addition, it should be noted that the use of "first", "second", and the like words to define parts is merely for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, and therefore cannot be understood as limiting the scope of protection of the present application. The above is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An oxidation-preventing electrode for tab pre-welding, characterized by: The electrode body comprises a mounting seat and an electrode head which is detachably arranged on the mounting seat, and a composite protective layer is arranged on the electrode head, wherein the composite protective layer comprises a barrier layer and a conductive anti-oxidation layer which are arranged in sequence from the inside to the outer wall of the electrode head; the barrier layer is a high-hardness and high-melting-point metal compound. The composite protective layer is further provided with raised lines. The conductive anti-oxidation layer is made of any one of silver, gold, platinum or palladium or an alloy thereof. The thickness of the conductive anti-oxidation layer is 0.1-10 μm. The raised lines comprise a plurality of regularly arranged square protrusions arranged on the surface of the electrode head; or The raised lines comprise stripe-shaped protrusions arranged on the surface of the electrode head. The anti-oxidation electrode further comprises a cooling structure. The mounting seat is provided with a cooling cavity; the cooling structure comprises a sealing end cover, a water inlet pipe and a water outlet pipe; the sealing end cover is fixed at one end of the mounting seat, and a sealing gasket is arranged between the sealing end cover and the mounting seat; one end of the water inlet pipe penetrates through the sealing end cover and extends into the cooling cavity; The water outlet pipe is fixed on the outer wall of the mounting seat and communicates with the cooling cavity; The cross section of the electrode head is rectangular, and the length-width ratio of the cross section of the electrode head is 1:1-5:

1.

2. The anti-oxidation electrode for tab pre-welding according to claim 1, wherein: The mounting seat is provided with a mounting cavity, and the electrode head is detachably arranged in the mounting cavity; a clamping groove is arranged on the side of the mounting seat away from the electrode head; One end of the electrode head is exposed outside the mounting cavity, and the side wall of the electrode head away from the mounting seat is provided with the raised lines. The bottom plate is provided with a pre-pressing structure and a welding structure, and the welding structure is arranged on one side of the pre-pressing structure; 3. A prewelding system characterized by: The pre-pressing structure is provided with a pressing head for pre-pressing and shaping the multi-layer tabs; The welding structure is provided with the anti-oxidation electrode according to claim 1 or 2.

4. The pre-welding system according to claim 3, wherein: The pre-pressing structure comprises a pre-pressing rack, and the pre-pressing rack is provided with a first driving device, and the output end of the first driving device is arranged towards the bottom plate, and the output end of the first driving device is provided with the pressing head, and the bottom of the pressing head is provided with a shaping protrusion; One side of the pre-pressing rack is provided with a first bearing table, and the first bearing table is provided with a mold for bearing the workpiece.

5. The pre-welding system according to claim 4, wherein: The welding structure comprises a welding rack, and the welding rack is arranged on one side of the pre-pressing rack, and one side of the welding rack is further provided with a second bearing table, and the second bearing table is provided with a positioning jig for positioning the mold; The welding rack is provided with a second driving device, and the output end of the second driving device is located above the second bearing table, and the output end of the second driving device is provided with a mounting plate, and the mounting plate is provided with a clamping piece, and the mounting seat is clamped on the mounting plate; ​ The positioning jig is further provided with a limiting structure on one side, the limiting structure comprises a first limiting frame and a second limiting frame arranged oppositely, the second limiting frame is arranged above the first limiting frame, and a passing opening for the electrode head to pass through is arranged in the second limiting frame; and a third driving device is further arranged between the first limiting frame and the second limiting frame, and the third driving device drives the first limiting frame and the second limiting frame to move oppositely.

6. A preweld forming method characterized by: The method is performed using the pre-welding system of any one of claims 3-5; The method comprises: The negative tab is first pre-pressed and shaped, and after the pre-pressing and shaping is completed, the negative tab is pre-heated, so that the temperature difference between the temperature of the negative tab and the temperature required for welding is controlled in the range of 50-200 DEG C; After the pre-heating is completed, the negative tab is welded using the anti-oxidation electrode, and then the welding state is maintained until the welding is completed.

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