Device and method for improving quality of laser welding of large cylindrical battery tabs

Abstract

The application relates to a device and method for improving the quality of laser welding of the pole ears of large cylindrical batteries, and belongs to the technical field of battery welding of new energy vehicles. The device comprises a fastening pressing block, the fastening pressing block is used for fixing the battery and the current collecting disc, the fastening pressing block is provided with an internal gas passage, the gas blowing nozzle of the fastening pressing block is connected with a plasma activator, a gas heating device, a gas flow controller and a protective gas cylinder in sequence, the gas suction nozzle of the fastening pressing block is connected with a gas suction device, nitrogen gas blown out of the gas blowing nozzle sweeps the surface of the to-be-welded area of the current collecting disc, a protective gas curtain is formed in the to-be-welded area, the nitrogen gas is ionized and activated by the plasma activator, nitrogen radicals formed by the ionization and activation of the nitrogen gas form a nitriding layer with the to-be-welded surface through a chemical method, and the material absorption rate of laser can be obviously improved; the surface of the preheated workpiece can accelerate the reaction with the nitrogen radicals, and a double-effect mechanism of "physical preheating and chemical activation" is formed.

Description

Technical Field

[0001] This invention belongs to the field of new energy vehicle battery welding technology, specifically relating to a device and method for improving the quality of laser welding of large cylindrical battery tabs, and particularly to a method for pre-welding workpiece surface treatment modified by nitrogen plasma. Background Technology

[0002] Compared to other types of lithium batteries, large cylindrical batteries exhibit higher total energy density under the same volume or mass conditions. A key feature is their all-tab design, which effectively reduces ohmic internal resistance by shortening the electrode current-carrying path, significantly improving fast-charging performance. Simultaneously, this design reduces polarization effects and ohmic heat generation during charging and discharging, thereby simultaneously optimizing charging efficiency. By reducing the rate of heat generation per unit time and optimizing the heat conduction path, this design significantly improves heat dissipation efficiency, ensuring uniform temperature distribution within the battery pack. These technical features make this product particularly suitable for new energy vehicle power battery systems with high requirements for energy density, charging rate, and thermal control, demonstrating significant industrial application value.

[0003] The following challenges remain in the actual connection process between the electrode tabs and the current collector: the low laser absorption rate of the materials to be welded and the non-linear response of their surface reflectivity to temperature changes make them prone to defects such as spatter and explosions during welding, resulting in poor process stability. Current battery electrode tab welding processes do not involve surface modification of the workpieces to improve the material's laser absorption rate; moreover, most welding shielding gases are applied at room temperature, offering limited protection; furthermore, dust and spatter generated during welding are easily blown onto other surfaces by the shielding gas, thus failing to achieve the optimal welding effect. Summary of the Invention

[0004] The purpose of this invention is to provide an apparatus and method for improving the quality of laser welding of tabs in large cylindrical batteries, thereby solving problems such as low material absorption rate and weak welding protection in existing technologies. This invention achieves surface modification and preheating of the large cylindrical battery before welding of all tabs, and enhances the protective effect of nitrogen gas, thus improving the quality of laser welding of all tab batteries and the yield rate after welding. The technical solution adopted in this invention is as follows:

[0005] A device for improving the quality of laser welding of tabs in large cylindrical batteries, wherein the large cylindrical battery includes a cell and a current collector, the cell is a cylindrical component and the current collector is a circular plate component, the current collector is coaxially disposed on the upper end surface of the cell, and the device includes a fastening block, a plasma activator, a protective gas cylinder, a gas heating device and a gas extraction device.

[0006] The fastening block includes a block body with an inner hole that is open at both ends. A centering block is located in the center of the inner hole. The centering block and the block body are connected by several circumferentially arranged limiting plates. The limiting plates press on the collector plate. The centering block is coaxially arranged with the collector plate and is connected to the block body through a ventilation beam. The block body is equipped with an air blowing nozzle and an air extraction nozzle. A gas flow controller is provided on the protective gas cylinder. The air blowing nozzle is connected in sequence to a plasma activator, a gas heating device, a gas flow controller, and a protective gas cylinder. The protective gas cylinder contains nitrogen. The air extraction nozzle is connected to an extraction device. The nitrogen blown out through the air blowing nozzle sweeps across the surface of the area to be welded on the collector plate and forms a protective gas curtain in the area to be welded. Excess nitrogen is extracted in sequence through the ventilation beam, the air extraction nozzle, and the extraction device. The galvanometer emits a laser beam and performs welding in the nitrogen-protected area to be welded.

[0007] Furthermore, the current collector is divided into three-lobed current collectors and six-lobed current collectors according to the number of areas to be soldered. The number of limiting pressure plates is the same as the number of areas to be soldered in the current collector. When the current collector is a three-lobed current collector, a three-lobed fastening block with three limiting pressure plates is used to press the battery cell and the current collector. When the current collector is a six-lobed current collector, a six-lobed fastening block with six limiting pressure plates is used to press the battery cell and the current collector.

[0008] Furthermore, a limiting sleeve is connected to the lower part of the six-petal fastening block body. The limiting sleeve is respectively fitted with the battery cell and the current collector. An air outlet groove and an air inlet groove are respectively opened on both sides of the limiting plate. The air outlet groove is connected to the air blowing nozzle. The centering block is a hollow structure. The air inlet groove is connected to the ventilation beam through the centering block. The air outlet groove of any limiting plate is arranged opposite to the air inlet groove of the adjacent limiting plate on one side. The air blowing nozzle, air outlet groove, air inlet groove, centering block, ventilation beam and the air extraction nozzle are connected in sequence to form a gas passage. The gas is discharged by the air extraction device through the ventilation beam.

[0009] Furthermore, a limiting sleeve is connected to the lower part of the three-lobed fastening block body. The limiting sleeve is respectively engaged with the battery cell and the current collector. The inner wall of the block body is provided with an annular air outlet groove in the circumferential direction. The air blowing nozzle is connected to the air outlet groove. The centering block is a hollow structure and is connected to the ventilation beam. Several air inlet grooves are provided on the centering block. The air blowing nozzle, air outlet groove, air inlet groove, centering block, ventilation beam and air extraction nozzle are connected in sequence to form a gas passage.

[0010] Furthermore, the laser beam is generated by a laser, transmitted through an optical fiber, and emitted through a galvanizing head. The laser beam mode is a dual-beam laser combining a central laser and a ring laser. The power of the central laser and the ring laser can be adjusted separately. The optical fiber is an adjustable ring mode laser fiber, including an inner core fiber and an outer ring fiber. The diameter of the inner core fiber is 12 micrometers to 16 micrometers, and the diameter of the outer ring fiber is 100 micrometers to 120 micrometers.

[0011] Furthermore, the galvanometer is a 2D high-power galvanometer.

[0012] Furthermore, the limiting pressure plate is arranged radially along the inner hole of the pressure block body.

[0013] Furthermore, the air extraction device is connected to the air extraction nozzle via an air extraction pipe, which is a replaceable air pipe.

[0014] This invention also provides a method for improving the quality of laser welding of tabs in large cylindrical batteries, which is based on the aforementioned device for improving the quality of laser welding of tabs in large cylindrical batteries, and includes the following steps:

[0015] Step 1: Before welding, wipe the oil and impurities from the battery cell and current collector with alcohol. Keep the battery cell vertical with the side to be welded facing up and in contact with the current collector. Place the fastening block on top of the battery cell and current collector. Use the limiting sleeve to achieve the first-level alignment between the battery cell and current collector. Then, use the centering block to fine-tune the position of the current collector to achieve the second-level alignment, fully exposing the area of ​​the current collector to be welded. Then, apply a vertical downward pressure of 30N to 150N to the fastening block to ensure that the position of the part to be welded and the current collector remain unchanged and are firmly attached.

[0016] Step 2: Sequentially turn on the protective gas cylinder, the airflow controller, and the gas heating device. Set the gas flow rate of the airflow controller to 10L / min to 30L / min, and the heating temperature of the gas heating device to 500℃ to 800℃, maintaining this temperature for 2 to 5 minutes to ensure sufficient preheating and to provide a nitrogen environment for the gas path. Then, turn on the plasma activator, setting its discharge frequency to 20kHz to 50kHz and its power density to 50W / cm³. 2 ~200W / cm 2 After 1 to 3 minutes, the plasma activator is turned off.

[0017] Step 3: Set the center laser power of the laser beam to 550W-850W and the ring laser power to 650W-950W. Set the welding speed of the galvanometer to 15m / min-25m / min and the defocusing amount to +3mm-+10mm. Then turn on the air extraction device and set the air extraction flow rate to 5L / min-10L / min. Finally, turn on the laser and weld 3-6 welds in each area to be welded, with a weld length of 6mm-10mm.

[0018] Furthermore, the gas heating device provides intermittent heating.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention uses a plasma activator to ionize and activate nitrogen gas, and the resulting nitrogen free radicals form a nitriding layer with the surface to be welded through a chemical process, which can significantly improve the absorption rate of the material to laser; and heats the nitrogen gas to preheat the workpiece to be welded, and the surface of the preheated workpiece can accelerate the reaction with nitrogen free radicals, forming a dual synergistic mechanism of "physical preheating and chemical activation".

[0021] 2. This invention utilizes heated nitrogen gas to protect the welding process, reducing the cooling rate of the molten pool and enhancing its fluidity, which helps gases and impurities escape from the molten pool. Simultaneously, the density of the protective gas decreases after heating, increasing its flow rate and diffusivity, resulting in more uniform gas coverage. Furthermore, the coupling effect of the protective gas and dust removal makes the gas flow more stable, reducing fluctuations in the molten pool during welding. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0023] Figure 2 This is a schematic diagram of a six-lobed fastening block structure;

[0024] Figure 3 A half-sectional schematic diagram of the three-lobed fastening block;

[0025] Figure 4 This is a schematic diagram of a three-lobed fastening block structure;

[0026] Figure 5 The image shows the weld morphology of the battery positive electrode tab and current collector welded under active nitrogen protection using the apparatus and method of the present invention.

[0027] Figure 6 This image shows the weld morphology of the battery positive electrode tab and current collector plate welded under nitrogen protection using the apparatus and method of this invention.

[0028] In the diagram, 1. Battery cell; 2. Current collector; 3. Fastening block; 4. Laser beam; 5. Gamma lens; 6. Protective gas cylinder; 7. Airflow controller; 8. Gas heating device; 9. Plasma activator; 10. Evacuation device; 11. Evacuation pipe; 31. Centering block; 32. Ventilation beam; 33. Limiting plate; 34. Gas outlet groove; 35. Gas inlet groove; 36. Block body; 37. Limiting sleeve. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0030] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as bolted connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can be found to achieve this function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a bolted connection can be chosen for detachable connections.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0032] Example 1: As Figures 1-6 As shown, an apparatus for improving the quality of laser welding of tabs in a large cylindrical battery is provided. The large cylindrical battery includes a cell 1 and a current collector 2. The cell 1 is a cylindrical component, and the current collector 2 is a circular plate component. The current collector 2 is coaxially disposed on the upper end surface of the cell 1. The apparatus includes a fastening block 3, a plasma activator 9, a protective gas cylinder 6, a gas heating device 8, and a gas extraction device 10.

[0033] The fastening block 3 includes a block body 36, which has an inner hole that is open at both the top and bottom. A centering block 31 is located in the center of the inner hole. The centering block 31 and the block body 36 are connected by several circumferentially arranged limiting plates 33. The limiting plates 33 press on the collecting plate 2. The centering block 31 is coaxially arranged with the collecting plate 2 and is connected to the block body 36 through a ventilation beam 32. The block body 36 is equipped with an air blowing nozzle and an air suction nozzle. An airflow controller is provided on the protective gas cylinder 6. 7. The blowing nozzle is connected in sequence to the plasma activator 9, the gas heating device 8, the airflow controller 7 and the protective gas cylinder 6. The protective gas cylinder 6 contains nitrogen. The suction nozzle is connected to the suction device 10. The nitrogen blown out by the blowing nozzle sweeps across the surface of the area to be welded on the collector plate 2 and forms a protective gas curtain in the area to be welded. Excess nitrogen is successively drawn away through the ventilation beam 32, the suction nozzle and the suction device 10. The galvanizing head 5 emits a laser beam 4 and performs welding in the nitrogen-protected area to be welded.

[0034] In this invention, the battery cell 1 to be welded has a diameter of 46 mm, and its upper and lower end faces have a full tab structure formed by multi-layer stacking of metal foil sheets. The positive electrode tab material is aluminum, and the thickness of each tab is 8-16 micrometers; the negative electrode tab material is copper, and the thickness of each tab is 4-10 micrometers. The current collector 2 has two types: a cathode current collector and an anode current collector. The cathode current collector is made of aluminum with a thickness of 0.2 mm-0.6 mm; the anode current collector is made of nickel-plated copper with a total thickness of 0.2 mm-0.5 mm and a nickel plating layer thickness of 1-10 micrometers. The ventilation beam 32 has a hollow structure for guiding airflow; the centering block 31 is set concentrically with the current collector 2, which can completely expose the area to be welded. The airflow controller 7 can precisely control the gas flow rate of nitrogen gas flowing out of the protective gas cylinder 6. The suction flow rate of the extraction device 10 must not exceed the gas flow rate set by the airflow controller; otherwise, most of the blown nitrogen will be drawn away by the extraction device 10, losing its function of protecting the area to be welded. When blowing and extraction are performed simultaneously, in addition to removing spatter, dust, and other impurities generated during the welding process, a stable protective air curtain can also be formed above the welding area to reduce molten pool fluctuations.

[0035] Turn on the airflow controller 7, gas heating device 8, and plasma activator 9. Nitrogen gas can flow out from the protective gas cylinder 6. The nitrogen gas reaches a specific flow rate after passing through the airflow controller 7, then reaches the set temperature after passing through the gas heating device 8, and then is ionized and activated by the plasma activator 9. Finally, it is blown onto the surface of the area to be welded on the manifold 2. When the nitrogen gas passes through the plasma activator 9, it is ionized and activated into highly reactive nitrogen free radicals. The reaction formula is:

[0036] ;(ionization)

[0037] (Surface nitriding)

[0038] Nitrogen gas is ionized and activated by plasma activator 9. The resulting nitrogen free radicals form a nitriding layer on the surface of the collector disk 2 to be welded through chemical means, which can significantly improve the absorption rate of laser by the collector disk 2. The gas heating device 8 heats nitrogen gas, which also has the function of preheating the workpiece to be welded. The preheated surface of the collector disk 2 can accelerate the reaction with nitrogen free radicals, forming a dual-effect mechanism of "physical preheating and chemical activation".

[0039] The current collector 2 is divided into a three-lobed current collector and a six-lobed current collector according to the number of areas to be welded. The number of limiting pressure plates 33 is the same as the number of areas to be welded in the current collector 2. When the current collector 2 is a three-lobed current collector, a three-lobed fastening block 3 with three limiting pressure plates 33 is used to press the battery cell 1 and the current collector 2. When the current collector 2 is a six-lobed current collector, a six-lobed fastening block 3 with six limiting pressure plates 33 is used to press the battery cell 1 and the current collector 2.

[0040] The six-lobed fastening block 3 has a limiting sleeve 37 connected to the lower part of the block body 36. The limiting sleeve 37 is respectively fitted with the battery cell 1 and the current collector 2 to achieve primary centering. The limiting plate 33 has an air outlet groove 34 and an air inlet groove 35 on both sides. The air outlet groove 34 is connected to the air blowing nozzle. The centering block 31 has a hollow structure. The air inlet groove 35 is connected to the ventilation beam 32 through the centering block 31. The air outlet groove 34 of any limiting plate 33 is arranged opposite to the air inlet groove 35 of the adjacent limiting plate 33 on one side. The air blowing nozzle, air outlet groove 34, air inlet groove 35, centering block 31, ventilation beam 32 and the suction nozzle are connected in sequence to form a gas passage. The gas is discharged by the suction device 10 through the ventilation beam 32. Figure 2 The arrows shown indicate the approximate direction of gas flow. The pressure block body 36 also serves to facilitate the application of pressure to fix the manifold 2 to be welded.

[0041] The three-lobed fastening block 3 has a limiting sleeve 37 connected to its lower part on the block body 36. The limiting sleeve 37 is respectively fitted with the battery cell 1 and the current collector 2 to achieve primary centering. The inner wall of the block body 36 has an annular air outlet groove 34 circumferentially opened. The air blowing nozzle is connected to the air outlet groove 34. The centering block 31 has a hollow structure and is connected to the ventilation beam 32. The centering block 31 has several air inlet grooves 35. The air blowing nozzle, air outlet groove 34, air inlet groove 35, centering block 31, ventilation beam 32 and air extraction nozzle are sequentially connected to form a gas passage. Figure 3 As shown, the inner diameter of the limiting sleeve 37 is slightly larger than the diameters of the battery cell 1 and the current collector 2, and its main function is to keep the battery cell 1 and the current collector 2 to be welded in an aligned position. Different types of fastening blocks 3 are mainly used to deal with different welding paths and current collectors 2 with different structures.

[0042] The laser beam 4 is generated by a laser, transmitted through an optical fiber, and emitted through a diaphragm head 5. The laser beam mode is a dual-beam laser consisting of a central laser and a ring laser. The power of the central laser and the ring laser can be adjusted separately. The optical fiber is an adjustable ring mode laser fiber, including an inner core fiber and an outer ring fiber. The diameter of the inner core fiber is 12 micrometers to 16 micrometers, and the diameter of the outer ring fiber is 100 micrometers to 120 micrometers.

[0043] The galvanometer 5 is a 2D high-power galvanometer, which can realize the oscillation of the laser beam 4 and the setting of different welding paths.

[0044] The limiting pressure plate 33 is arranged radially along the inner hole of the pressure block body 36.

[0045] The air extraction device 10 is connected to the air extraction nozzle through the air extraction pipe 11. The air extraction pipe 11 is a replaceable air pipe. The welding dust and spatter extracted will inevitably adhere to the inner wall of the air extraction pipe. When the impurities accumulate to a certain extent, the air extraction pipe needs to be replaced.

[0046] Example 2: Figures 1-6 As shown, a method for improving the quality of laser welding of tabs in large cylindrical batteries is implemented based on the device for improving the quality of laser welding of tabs in large cylindrical batteries described in Embodiment 1, and includes the following steps:

[0047] Step 1: Before welding, wipe the oil and impurities from the battery cell 1 and the current collector 2 with alcohol. Keep the battery cell 1 vertical with the side to be welded facing up and in contact with the current collector 2. Place the fastening block 3 on top of the battery cell 1 and the current collector 2. Use the limiting sleeve 37 to achieve the first-level alignment of the battery cell 1 and the current collector 2. Then, use the centering block 31 to finely adjust the position of the current collector 2 to achieve the second-level alignment, so that the area to be welded on the current collector 2 is completely exposed. Then, apply a vertical downward pressure of 30N to 150N to the fastening block 3 to ensure that the position of the battery cell 1 and the current collector 2 remains unchanged and is tightly attached.

[0048] Step 2: Sequentially turn on the protective gas cylinder 6, the airflow controller 7, and the gas heating device 8. Set the gas flow rate of the airflow controller 7 to 10L / min to 30L / min, and set the heating temperature of the gas heating device 8 to 500℃ to 800℃, maintaining this temperature for 2 to 5 minutes to ensure sufficient preheating and to provide a nitrogen environment for the gas path. Then, turn on the plasma activator 9, setting its discharge frequency to 20kHz to 50kHz and its power density to 50W / cm³. 2 ~200W / cm 2 After 1 to 3 minutes, the plasma activator 9 is turned off;

[0049] Step 3: Set the center laser power of laser beam 4 to 550W-850W and the ring laser power to 650W-950W. Set the welding speed of the galvanometer head 5 to 15m / min-25m / min and the defocusing amount to +3mm-+10mm. Then turn on the air extraction device 10 and set the air extraction speed to 5L / min-10L / min. Finally, turn on the laser and weld 3-6 welds in each area to be welded, with a weld length of 6mm-10mm.

[0050] The gas heating device 8 provides intermittent heating, meaning the heating process is not continuous but intermittent, making it suitable for heating during specific time periods. Its maximum heating temperature can reach 1000℃. Its function is not only to heat nitrogen, but also to provide a high-energy state for nitrogen ionization.

[0051] Compared with the prior art, the advantages of the present invention are as follows:

[0052] 1. This invention uses a plasma activator 9 to ionize and activate nitrogen gas, and the resulting nitrogen free radicals form a nitriding layer with the surface to be welded through a chemical process, which can significantly improve the absorption rate of the material to laser; and heats the nitrogen gas to preheat the workpiece to be welded, and the surface of the preheated workpiece can accelerate the reaction with nitrogen free radicals, forming a dual-effect mechanism of "physical preheating and chemical activation".

[0053] 2. This invention utilizes heated nitrogen gas to protect the welding process, reducing the cooling rate of the molten pool and enhancing its fluidity, which helps gases and impurities escape from the molten pool. Simultaneously, the density of the protective gas decreases after heating, increasing its flow rate and diffusivity, resulting in more uniform gas coverage. Furthermore, the coupling effect of the protective gas and dust removal makes the gas flow more stable, reducing fluctuations in the molten pool during welding.

[0054] The invention will be further illustrated below with application examples:

[0055] Example 1: The positive electrode tab of cell 1 and the current collector 2 are both made of 1060 aluminum. The thickness of the electrode tab is 13 micrometers, and the thickness of the current collector 2 is 0.3 mm. There are 6 areas to be soldered, all with a fan-shaped outline of 60° central angle. The fastening block 3 used is a six-lobed fastening block with 6 limiting plates 33. Each adjacent limiting plate is at a 60° angle, with a length of 44 mm and a thickness of 3 mm. Figure 2 As shown, both the exhaust groove 34 and the inlet groove 35 are located on the side wall of the limiting pressure plate 33. Each pair of adjacent exhaust grooves 34 and inlet grooves 35 forms a stable airflow above the area to be welded. The inner diameter of the limiting sleeve 37 is 46.5 mm, and the wall thickness is 9 mm. The specific implementation method is as follows:

[0056] Step 1: Before welding, wipe the oil and impurities from the battery cell 1 and the current collector 2 with alcohol. Keep the battery cell 1 vertical with the side to be welded facing upwards and in contact with the current collector 2. Place the fastening block 3 on top of the workpiece, and use the limiting sleeve 37 of the fastening block 3 to achieve primary alignment between the battery cell 1 and the current collector 2. Then, slightly adjust the position of the current collector 2 using the centering block 31 to achieve secondary alignment, fully exposing the area to be welded to the air. Subsequently, apply a pressure of 60N vertically to the fastening block 3 above the block body 36 to ensure that the position of the battery cell 1 to be welded and the current collector 2 remain unchanged and are firmly attached.

[0057] Step 2: Connect the air nozzle of the fastening block 3 to the plasma activator 9, gas heating device 8, airflow controller 7, and protective gas cylinder 6 in sequence using the air hose. Connect one end of the suction pipe 11 to the suction nozzle of the fastening block 3, and the other end to the suction device 10. Turn on the protective gas cylinder 6, airflow controller 7, and gas heating device 8 in sequence, set the gas flow rate to 12 L / min, set the heating temperature to 600℃, and maintain this for 3 minutes to ensure sufficient preheating and provide a nitrogen environment for the gas path. Then, while keeping the protective gas cylinder 6, airflow controller 7, and gas heating device 8 in working condition, turn on the plasma activator 9, set the discharge frequency to 30 kHz, and the power density to 150 W / cm³. 2 After 2 minutes, the plasma activator 9 is turned off.

[0058] Step 3: Set the center laser power to 530W, the ring laser power to 750W, the welding speed to 22m / min, the defocusing amount to +7mm, and the weld length to 6mm. Set 3 welds for each area to be welded. Then turn on the exhaust device 10 and set the exhaust flow rate to 10L / min. Finally, turn on the laser and start welding. The heat generated by the laser beam 4 will melt the preheated workpiece to form the weld.

[0059] like Figure 5 As shown, the weld was tested and found to be free of defects such as blast points, porosity, and spatter; the weld width was 0.28 mm and the depth was 0.36 mm; the workpiece deformation was small and the welding process did not affect other battery components; no short circuit occurred in the post-weld battery short circuit test.

[0060] Example 2: This example is a comparative experiment of nitrogen ionization activation without using plasma activator 9. The positive electrode tab of cell 1 and the current collector 2 are both made of 1060 aluminum, with a tab thickness of 10 micrometers and a current collector 2 thickness of 0.3 mm. There are three areas to be soldered, each with a fan-shaped outline and a central angle of 120°. The fastening block 3 used is a three-lobed fastening block with three limiting plates 33, each adjacent limiting plate forming a 120° angle, a length of 45 mm, and a thickness of 4 mm. Figure 4 As shown, the vent groove 34 is located on the inner wall of the annulus where the limiting pressure plate 33 is located, and the inlet groove 35 is directly located on the centering block 31, forming a gas passage with the interior of the ventilation beam 32. The annularly distributed vent grooves 34 and the inlet groove 35 at the center form a stable airflow above the area to be welded; the inner diameter of the limiting sleeve 37 is 46.5 mm, and the wall thickness is 8 mm; the specific implementation method is as follows:

[0061] Step 1: Before welding, wipe the oil and impurities from the battery cell 1 and the current collector 2 with alcohol. Keep the battery cell 1 vertical with the side to be welded facing upwards and in contact with the current collector 2. Place the fastening block 3 on top of the workpiece, and use the limiting sleeve 37 of the fastening block 3 to achieve primary alignment between the battery cell 1 and the current collector 2. Then, slightly adjust the position of the current collector 2 using the centering block 31 to achieve secondary alignment, fully exposing the area to be welded to the air. Subsequently, apply a pressure of 60N vertically to the fastening block 3 above the block body 36 to ensure that the position of the battery cell 1 to be welded and the current collector 2 remain unchanged and are firmly attached.

[0062] Step 2: Connect the air nozzle of the fastening block 3 to the gas heating device 8, the airflow controller 7, and the protective gas cylinder 6 in sequence using the air hose. Connect one end of the suction pipe 11 to the suction nozzle of the fastening block 3, and the other end to the suction device 10. Then turn on the protective gas cylinder 6, the airflow controller 7, and the gas heating device 8, setting the gas flow rate to 12L / min and the heating temperature to 160℃. The heated nitrogen gas will be sprayed out from the gas outlet 34 and cover the area to be welded, achieving protection. Then maintain this for 5 minutes to ensure sufficient heating and preheating of the workpiece to be welded.

[0063] Step 3: Set the center laser power to 530W, the ring laser power to 750W, the welding speed to 22m / min, the defocusing amount to +7mm, and the weld length to 8mm. Set 6 weld seams for each area to be welded. Then turn on the exhaust device 10 and set the exhaust flow rate to 10L / min. Finally, turn on the laser and start welding. The heat generated by the laser beam 4 will melt the preheated workpiece to form the weld seam.

[0064] like Figure 6 As shown, the weld tested showed no obvious defects such as spatter or blasting, but it did have small internal porosity; the weld width was 0.21 mm and the depth was 0.29 mm; compared with the weld in Example 1, its cross-sectional dimensions were smaller. The comparison revealed that using a plasma activator to modify the surface to be welded resulted in better welding performance.

[0065] In summary, for large cylindrical battery tabs and current collectors of various structures, surface modification through nitrogen activation and the formation of a nitrided layer on the surface to be welded before welding improves the material's absorption rate of laser light, increases the weld cross-sectional size, and reduces weld defects. The stable airflow created by high-temperature nitrogen protection and dust removal reduces molten pool fluctuations and avoids the influence of dust and metal vapors, resulting in a more aesthetically pleasing weld after welding. By adopting different welding parameters for workpieces of different materials and sizes, it is possible to prevent thermal damage and short circuits in other battery structures after welding.

[0066] The above embodiments are merely illustrative examples of the present invention and do not limit its scope of protection. Those skilled in the art can make partial changes to them, as long as they do not exceed the spirit and essence of the present invention, they are all within the scope of protection of the present invention.

Claims

1. An apparatus for improving the quality of laser welding of tabs in a large cylindrical battery, the large cylindrical battery comprising a cell (1) and a current collector (2), the cell (1) being a cylindrical component and the current collector (2) being a circular plate component, the current collector (2) being coaxially disposed on the upper end surface of the cell (1), characterized in that: The device includes a fastening block (3), a plasma activator (9), a protective gas cylinder (6), a gas heating device (8), and a gas extraction device (10). The fastening block (3) includes a block body (36), which has an inner hole that is open at both the top and bottom. A centering block (31) is provided in the center of the inner hole. The centering block (31) and the block body (36) are connected by several circumferentially arranged limiting plates (33). The limiting plates (33) press on the collecting plate (2). The centering block (31) is coaxially arranged with the collecting plate (2). The centering block (31) is connected to the block body (36) through a ventilation beam (32). The block body (36) is provided with an air blowing nozzle and an air suction nozzle. The protective gas cylinder (6) is provided with a gas cylinder. The flow controller (7) is connected in sequence to the plasma activator (9), the gas heating device (8), the airflow controller (7) and the protective gas cylinder (6). The protective gas cylinder (6) contains nitrogen. The suction nozzle is connected to the suction device (10). The nitrogen blown out by the suction nozzle sweeps across the surface of the welding area of ​​the collector plate (2) and forms a protective gas curtain in the welding area. The excess nitrogen is successively drawn away through the ventilation beam (32), the suction nozzle and the suction device (10). The galvanizing head (5) emits a laser beam (4) and performs welding in the welding area protected by nitrogen. When nitrogen passes through the plasma activator (9), it is ionized and activated into highly reactive nitrogen free radicals, as shown in the following reaction formula: ； The nitrogen free radicals chemically form a nitrided layer on the surface of the manifold (2) to be welded, and the reaction formula is as follows: 。 2. The device for improving the quality of laser welding of tabs in large cylindrical batteries according to claim 1, characterized in that: The current collector (2) is divided into a three-lobed current collector and a six-lobed current collector according to the number of areas to be welded. The number of limiting pressure plates (33) is the same as the number of areas to be welded in the current collector (2). When the current collector (2) is a three-lobed current collector, a three-lobed fastening block (3) with three limiting pressure plates (33) is used to press the battery cell (1) and the current collector (2). When the current collector (2) is a six-lobed current collector, a six-lobed fastening block (3) with six limiting pressure plates (33) is used to press the battery cell (1) and the current collector (2).

3. The device for improving the quality of laser welding of large cylindrical battery tabs according to claim 2, characterized in that: The six-petaled fastening block (3) has a limiting sleeve (37) connected to the lower part of the block body (36). The limiting sleeve (37) is fitted with the battery cell (1) and the current collector (2) respectively. The limiting plate (33) has an air outlet groove (34) and an air inlet groove (35) on both sides respectively. The air outlet groove (34) is connected to the air blowing nozzle. The centering block (31) is a hollow structure. The air inlet groove (35) is connected to the ventilation beam (32) through the centering block (31). The air outlet groove (34) of any limiting plate (33) is set opposite to the air inlet groove (35) of the adjacent limiting plate (33) on one side. The air blowing nozzle, air outlet groove (34), air inlet groove (35), centering block (31), ventilation beam (32) and the suction nozzle are connected in sequence to form a gas passage. The gas is discharged by the suction device (10) through the ventilation beam (32).

4. The device for improving the quality of laser welding of large cylindrical battery tabs according to claim 2, characterized in that: The three-lobed fastening block (3) has a limiting sleeve (37) connected to the lower part of the block body (36). The limiting sleeve (37) is respectively fitted with the battery cell (1) and the collector plate (2). The inner wall of the block body (36) has an annular air outlet groove (34) in the circumferential direction. The air blowing nozzle is connected to the air outlet groove (34). The centering block (31) is a hollow structure. The centering block (31) is connected to the ventilation beam (32). Several air inlet grooves (35) are opened on the centering block (31). The air blowing nozzle, air outlet groove (34), air inlet groove (35), centering block (31), ventilation beam (32) and air extraction nozzle are connected in sequence to form a gas passage.

5. The device for improving the quality of laser welding of tabs in large cylindrical batteries according to claim 3 or 4, characterized in that: The laser beam (4) is generated by a laser, transmitted through an optical fiber, and emitted through a diaphragm (5). The laser beam mode is a dual-beam laser consisting of a central laser and a ring laser. The power of the central laser and the ring laser can be adjusted separately. The optical fiber is an adjustable ring mode laser fiber, including an inner core fiber and an outer ring fiber. The diameter of the inner core fiber is 12 micrometers to 16 micrometers, and the diameter of the outer ring fiber is 100 micrometers to 120 micrometers.

6. The device for improving the quality of laser welding of large cylindrical battery tabs according to claim 5, characterized in that: The galvanometer (5) is a 2D high-power galvanometer.

7. The device for improving the quality of laser welding of tabs in large cylindrical batteries according to claim 6, characterized in that: The limiting pressure plate (33) is arranged radially along the inner hole of the pressure block body (36).

8. The device for improving the quality of laser welding of tabs in large cylindrical batteries according to claim 7, characterized in that: The air extraction device (10) is connected to the air extraction nozzle through the air extraction pipe (11), which is a replaceable air pipe.

9. A method for improving the quality of laser welding of tabs on large cylindrical batteries, implemented using the apparatus for improving the quality of laser welding of tabs on large cylindrical batteries as described in claim 8, characterized in that... Includes the following steps: Step 1: Before welding, wipe the oil and impurities of the battery cell (1) and the current collector (2) with alcohol. Keep the battery cell (1) in a vertical position with the side to be welded facing up and in contact with the current collector (2). Place the fastening block (3) on top of the battery cell (1) and the current collector (2). Use the limiting sleeve (37) to achieve the first-level alignment of the battery cell (1) and the current collector (2). Then, use the centering block (31) to finely adjust the position of the current collector (2) to achieve the second-level alignment, so that the area to be welded on the current collector (2) is completely exposed. Then, apply a vertical downward pressure of 30N to 150N to the fastening block (3) to ensure that the position of the battery cell (1) and the current collector (2) remains unchanged and is tightly attached. Step 2: Sequentially turn on the protective gas cylinder (6), the airflow controller (7), and the gas heating device (8). Set the gas flow rate of the airflow controller (7) to 10L / min to 30L / min, and set the heating temperature of the gas heating device (8) to 500℃ to 800℃. Maintain this temperature for 2 to 5 minutes to ensure sufficient preheating and to provide a nitrogen environment for the gas path. Then turn on the plasma activator (9) and set the discharge frequency of the plasma activator (9) to 20kHz to 50kHz and the power density to 50W / cm³. 2 ~200W / cm 2 After 1 to 3 minutes, the plasma activator is turned off (9). Step 3: Set the center laser power of the laser beam (4) to 550W~850W and the ring laser power to 650W~950W. Set the welding speed of the diaphragm head (5) to 15m / min~25m / min and the defocusing amount to +3mm~+10mm. Then turn on the air extraction device (10) and set the air extraction flow rate to 5L / min~10L / min. Finally, turn on the laser and weld 3~6 welds in each area to be welded, with a weld length of 6mm~10mm.

10. A method for improving the quality of laser welding of tabs in large cylindrical batteries according to claim 9, characterized in that, Gas heating device (8) intermittent heating.

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