A laser welding device and method for a large cylindrical battery with multiple tabs

Abstract

A laser welding device and method for a large cylindrical battery with all tabs and a current collector, belonging to the field of new energy vehicle battery welding technology, is disclosed. This invention aims to solve the problem of low workpiece preheating efficiency in existing technologies. The device includes a pressure ring assembly, which comprises an outer cylinder and a retaining ring. The outer end of the retaining ring is connected to the upper end of the outer cylinder. An annular groove is formed along the inner circumference of the outer cylinder. Several heating plates are radially arranged along the outer cylinder, with their outer ends slidingly engaging with the annular groove. The number of heating plates is the same as the number of areas to be welded. A magnetic pressure head is located at the center of the retaining ring, connected to the retaining ring via a fastening plate. The inner end of each heating plate has a magnetically attached pressure head, which attracts the magnetic pressure head. By pressing the current collector and the battery's all tabs together with the pressure ring assembly, and by heating the areas to be welded with the heating plates, localized heating at precise locations is achieved.

Description

Technical Field

[0001] This invention belongs to the field of new energy vehicle battery welding technology, specifically relating to a laser welding device and method for a large cylindrical battery with multiple tabs and a current collector. Background Technology

[0002] Compared to other types of lithium batteries, the large cylindrical battery structure boasts higher total energy. Its all-tab design shortens the electrode busbar path, significantly reducing ohmic internal resistance and improving fast-charging performance. Furthermore, it enhances charging performance by reducing battery polarization effects and ohmic heat generation, lowering heat generation rate and increasing heat dissipation rate, thus improving battery uniformity. Because it requires fewer individual cells to assemble and interconnect, large cylindrical batteries can reduce production costs in battery pack assembly while achieving the same battery pack characteristics, making them a promising candidate for application in the new energy vehicle industry.

[0003] Currently, in the welding process of positive and negative tabs and current collectors of large cylindrical batteries, some manufacturers use preheating before welding to improve the absorption rate of highly reactive materials and thus improve welding quality. However, a single heating method is generally used, which has low preheating efficiency and uneven temperature distribution of the material from the outside to the inside. Furthermore, the temperature distribution difference between the start and end points of the weld is not distinguished in the welding direction, making it difficult to control heat accumulation at the end point of the weld, resulting in poor improvement of defects at the start and end points. Although the welding quality is slightly improved, defects such as blasting and spatter still exist. Summary of the Invention

[0004] The purpose of this invention is to provide a laser welding device and method for large cylindrical batteries with multiple tabs, to solve problems such as low preheating efficiency of the workpiece before welding, uneven temperature distribution during welding, and low material absorption rate in existing technologies. The technical solution adopted by this invention is as follows:

[0005] A laser welding device for a large cylindrical battery with all tabs, the large cylindrical battery with all tabs includes a cell to be welded, the cell to be welded includes a current collector, a battery tab, and a core. The core is a cylindrical component, a second positioning hole is provided in the center of the upper end face of the core, the battery tab is provided on the upper end face of the core, and a central hole matching the second positioning hole is left in the center of the battery tab. The current collector is a circular plate component, a first positioning hole is provided in the center of the current collector, and several through stress relief grooves are radially opened on the current collector. The stress relief grooves are evenly distributed around the outer periphery of the first positioning hole, and the stress relief grooves divide the current collector into several segments to be welded.

[0006] The welding device includes a pressure ring device, a moving mechanism, a contact heating device, and an induction heating device. The moving mechanism includes a moving device and a movable connecting rod. The pressure ring device is connected to the output end of the moving device through the movable connecting rod.

[0007] The pressure ring device includes a pressure ring outer edge, which includes an outer cylinder and a retaining ring. The outer end of the retaining ring is connected to the upper end of the outer cylinder. The inner circumference of the outer cylinder is provided with an annular groove opened in the circumferential direction. A plurality of heating plates are respectively arranged radially along the outer cylinder. The outer ends of the plurality of heating plates are respectively slidably engaged with the annular groove. The number of heating plates is the same as the number of areas to be welded. A magnetic pressure head is provided in the center of the retaining ring. The magnetic pressure head is connected to the retaining ring through a fastening plate. The inner end of the heating plate is provided with a pressure head made of magnetic material. The pressure head is attracted to the magnetic pressure head.

[0008] The current collector is mounted on the battery tabs. The inner circumference of the outer cylinder mates with the outer circumference of the current collector and the core, respectively. Several heating plates correspond to several of the areas to be welded. A circular boss is coaxially provided at the lower end of the magnetic pressure head. The circular boss is inserted into the first positioning hole and the second positioning hole, respectively. The contact heating device heats the heating plates, and the induction heating device heats the outer edge of the pressure ring. When the current collector reaches the required temperature, the laser system is controlled to emit a multi-mode laser through the diaphragm head to perform welding in the areas to be welded.

[0009] Furthermore, the inner circumferential diameter of the outer cylinder is 47.5mm to 48mm, and the wall thickness is 7mm to 10mm.

[0010] Furthermore, a resistance wire is threaded inside the heating plate, and the contact heating device is electrically connected to the resistance wire. The diameter of the resistance wire changes from small to large along the direction from the outer end to the inner end of the heating plate.

[0011] Furthermore, the heated pressing sheet can be triangular, rectangular, or irregularly shaped with openwork.

[0012] Furthermore, a temperature measuring device is installed above the battery cell to be welded, and the temperature measuring device is electrically connected to both the contact heating device and the induction heating device.

[0013] Furthermore, the multimode laser consists of a central beam, an inner ring beam, and an outer ring beam arranged sequentially from the inside out. The central beam is a blue laser with a wavelength of 450nm, and the inner and outer ring beams are both infrared lasers with a wavelength of 1064nm.

[0014] Furthermore, the galvanometer lens is a 2D high-power galvanometer lens.

[0015] This invention also provides a method for using a laser welding device for a large cylindrical battery with all tabs, which is based on the aforementioned laser welding device for a large cylindrical battery with all tabs, and includes the following steps:

[0016] Step 1: Before welding, wipe the oil and impurities on the current collector and battery tabs with alcohol. Keep the core vertical with the side to be welded facing upward. Then, put the current collector and battery tabs together and align the first positioning hole with the second positioning hole. Adjust the movable connecting rod and the pressure ring device so that the movable connecting rod is tilted at an angle of 30° to 60°. Control the moving device to move the pressure ring device directly above the cell to be welded and keep the pressure ring device parallel to the current collector.

[0017] Step 2: First, rotate several heating plates so that each heating plate is placed on one side of the corresponding area to be welded, exposing the area to be welded. Then, move the pressure ring device downward so that the retaining ring presses on the current collector, thereby pressing and fixing the current collector and the battery tabs. Plan to weld 3 to 5 welds in each area to be welded. Each heating plate is 2mm to 4mm away from any weld position in the corresponding area to be welded in the horizontal direction.

[0018] Step 3: Turn on the induction heating device and the contact heating device, and use staged heating. In the first stage, set the temperature to 200℃~400℃ and the heating time to 2 minutes~5 minutes. In the second stage, set the temperature to 600℃~800℃ and the heating time to 8 minutes~12 minutes. In both the first and second stages, use a temperature measuring device to measure whether the temperature of the current collector and the battery tabs has reached the required temperature.

[0019] Step 4: Set the power of the central beam to 300W-500W, the power of the inner ring beam to 400W-600W, and the power of the outer ring beam to 500W-700W. Set the welding speed to 16m / min-26m / min and the defocusing amount to +3mm-8+mm. During welding, use a protective gas to isolate the current collector and battery tabs from the air. The protective gas flow rate is 10L / min-20L / min. Emits a multi-mode laser through the galvanizing head to weld the weld seam next to the heated pressing sheet. The weld seam length is 7mm-10mm.

[0020] Step 5: Lift the pressure ring device and adjust the position of each heating plate so that the heating plate is 2mm to 4mm away from the next weld position in the corresponding welding area. Repeat steps 3 and 4. When repeating step 3, adjust the heating time of the first and second stages according to the measurement results of the temperature measuring device until all welds are completed and the current collector and battery tabs are welded together.

[0021] Furthermore, in the first and second stages, the induction heating device and the contact heating device are turned on simultaneously, or, in the first stage, only the induction heating device is turned on, and in the second stage, both the induction heating device and the contact heating device are turned on simultaneously.

[0022] Furthermore, the protective gas is nitrogen or argon with a purity of 99.9% or higher, or the protective gas is a mixture of nitrogen and argon in a mass ratio of 3:1, 2:1, 1:1, 1:2, or 1:3.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This invention uses a rotating and moving heating plate to place two adjacent heating plates on both sides of the area to be welded. Then, by controlling the contact heating device, the heating program of these two heating plates is started individually to raise the temperature to the desired temperature, thus achieving localized heating of a precise location.

[0025] 2. This invention provides a trapezoidal distribution of preheating temperature by changing the diameter of the heating resistance wire in the heating plate, which effectively improves the problem of incomplete welding caused by low material temperature and insufficient heat input at the starting position of laser welding, and avoids spatter and pit defects caused by excessive heat accumulation at the ending position.

[0026] 3. This invention improves the preheating efficiency of workpieces before welding by combining induction heating and contact heating. Induction heating mainly targets the surface of the workpiece, while contact heating mainly targets the interior of the workpiece. This combined heating method significantly improves the uniformity of temperature distribution in the workpiece to be welded. At the same time, the staged heating method can avoid the drastic thermal expansion of the workpiece to be welded caused by rapid heating and can reduce energy loss and save energy.

[0027] 4. This invention uses a temperature measuring device as a feedback system. The temperature measuring device monitors and determines the deviation between the actual temperature and the required temperature in real time, and feeds the signal back to the heating device. The induction heating device and the contact heating device adjust the heating temperature in real time according to the feedback result, thereby achieving consistency of preheating temperature and achieving a constant temperature effect. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the device for welding the battery tabs and current collector of the present invention;

[0029] Figure 2 Schematic diagram of a large cylindrical battery

[0030] Figure 3 This is a schematic diagram of the pressure ring device;

[0031] Figure 4 for Figure 3 A diagram showing the view from below;

[0032] Figure 5 This is a schematic diagram illustrating the method of using the device of the present invention.

[0033] In the diagram: 1. Battery cell to be welded; 2. Pressure ring device; 3. Moving mechanism; 4. Contact heating device; 5. Induction heating device; 6. Multimodal laser; 7. Grinding head; 8. Weld seam; 9. Temperature measuring device; 11. Current collector; 12. Battery tabs; 13. Core winding; 21. Outer cylinder; 22. Fastening plate; 23. Magnetic pressure head; 24. Heating plate; 25. Retaining ring; 26. Circular boss; 31. Movable connecting rod; 32. Moving device; 111. First positioning hole; 112. Stress relief groove. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Example 1: As Figures 1-5 As shown, a laser welding device for a large cylindrical battery with full tabs is disclosed. The large cylindrical battery with full tabs includes a cell 1 to be welded. The cell 1 includes a current collector 11, battery tabs 12, and a core 13. The core 13 is a cylindrical component. A second positioning hole is provided in the center of the upper end face of the core 13. Battery tabs 12 are provided on the upper end face of the core 13. A central hole matching the second positioning hole is left in the center of the battery tabs 12. The current collector 11 is a circular plate component. A first positioning hole 111 is provided in the center of the current collector 11. Several through stress relief grooves 112 are radially opened on the current collector 11. The stress relief grooves 112 are evenly distributed around the outer periphery of the first positioning hole 111. The stress relief grooves 112 divide the current collector 11 into several segments to be welded.

[0038] The welding device includes a pressure ring device 2, a moving mechanism 3, a contact heating device 4, and an induction heating device 5. The moving mechanism 3 includes a moving device 32 and a movable connecting rod 31. The pressure ring device 2 is connected to the output end of the moving device 32 through the movable connecting rod 31. The contact heating device 4 is fixed on the moving mechanism 3.

[0039] The pressure ring device 2 includes a pressure ring outer edge, which includes an outer cylinder portion 21 and a retaining ring portion 25. The outer end of the retaining ring portion 25 is connected to the upper end of the outer cylinder portion 21. The inner circumference of the outer cylinder portion 21 is provided with an annular groove opened in the circumferential direction. A plurality of heating pressure plates 24 are respectively arranged radially along the outer cylinder portion 21. The outer ends of the plurality of heating pressure plates 24 are respectively slidably engaged with the annular groove. The number of heating pressure plates 24 is the same as the number of the areas to be welded. A magnetic pressure head 23 is provided in the center of the retaining ring portion 25. The magnetic pressure head 23 is connected to the retaining ring portion 25 through a fastening pressure plate 22. The inner end of the heating pressure plate 24 is provided with a pressure plate head of magnetic material. The pressure plate head is attracted to the magnetic pressure head 23.

[0040] The current collector 11 is mounted on the battery tabs 12. The inner circumference of the outer cylinder 21 mates with the outer circumference of the current collector 11 and the core 13, respectively. Several heating plates 24 correspond to and abut against several of the areas to be welded. A circular boss 26 is coaxially provided at the lower end of the magnetic pressure head 23. The circular boss 26 is inserted into and mates with the first positioning hole 111 and the second positioning hole, respectively. The contact heating device 4 heats up the heating plates 24, and the induction heating device 5 heats up the outer edge of the pressure ring. When the current collector 11 reaches the required temperature, the laser system is controlled to emit a multi-mode laser through the diaphragm head 7 to perform welding in the areas to be welded.

[0041] The battery cell 1 to be soldered comprises three parts: a core 13, battery tabs 12, and a current collector 11. The core 13 in this invention has a diameter of 46 mm. The battery tabs 12 are composed of multiple layers of stacked metal foils. The positive tab of the battery tab 12 is made of aluminum, and the negative tab is made of copper. The thickness of each tab is 6 to 13 micrometers. The current collector 11 is divided into a six-lobed current collector and a four-lobed current collector according to the number of lobes in the area to be soldered. The cathode material of the current collector 11 is aluminum with a thickness of 0.3 to 0.4 mm, and the anode material is nickel-plated copper with a thickness of 0.2 to 0.3 mm and a nickel plating layer of 1 to 2 micrometers.

[0042] The moving mechanism 3 can be mounted on the vibrating head 7, including a moving device 32 and a movable connecting rod 31. Its movement accuracy in each direction can be controlled within 0.1mm to achieve precise alignment between the pressing ring device 2 and the cell to be welded. The moving device 32 is existing technology, capable of moving the pressing ring device 2 in three mutually perpendicular directions (x, y, z), for example, a three-axis slide module. The two ends of the movable connecting rod 31 connect the pressing ring device 2 and the moving device 32 respectively via bolts, and the relative angles of the three are adjustable. By adjusting the position and angle of the moving device 32 and the movable connecting rod 31, the pressing ring device 2 can be precisely positioned on the upper end of the cell 1 to be welded, achieving the clamping of the current collector 11, the battery tabs 12, and the winding core 13 before welding.

[0043] The main function of the stress relief groove 112 is to release residual stress during the welding process and avoid severe deformation after welding. The outer edge of the pressure ring can press the outer edge of the current collector 11 against the battery tab 12. The annular groove can realize the rotational movement of the heating plate 24. The magnetic pressure head 23 has magnetic attraction and its polarity is opposite to that of the magnetic material of the pressure head. Multiple heating plates 24 can be fixed by magnetic attraction. The circular boss 26 can be used for positioning. The contact heating device 4 is used to heat up several heating plates 24. The induction heating device 5 is used to heat up the outer edge of the pressure ring.

[0044] During pre-welding clamping, first, the lower end face of the current collector 11 is aligned with the battery tabs 12. Then, the first positioning hole 111 is aligned with the second positioning hole. Next, the pressure ring device 2 is engaged with the cell to be welded 1, so that the retaining ring 25 is pressed against the outer edge of the current collector 11, and the outer cylinder 21 is fitted onto the top of the core 13. The circular boss 26 is inserted into the first positioning hole 111 and the second positioning hole respectively. Several heating plates 24 are rotated so that the heating plates 24 correspond one-to-one with the several areas to be welded.

[0045] After clamping, the contact heating device 4 and the induction heating device 5 are turned on. The combined heating method of induction heating and contact heating increases the temperature of the current collector 11 to be welded and the battery tabs 12, thereby achieving complete evaporation of residual moisture in the area to be welded and the surrounding area, and improving the absorption rate of the battery tabs 12. Finally, high-quality weld seam 8 is achieved by multimodal laser welding 6.

[0046] The inner diameter of the outer cylinder 21 is 47.5mm to 48mm, the wall thickness is 7mm to 10mm, and it is connected to the induction heating device 5. The required properties of its material include: high melting point, strong oxidation resistance, high magnetic permeability, high resistivity and low temperature coefficient of resistance. For example, the outer cylinder 21 is made of high temperature resistant materials such as brass, nickel-based alloys and silicon carbide.

[0047] A resistance wire is threaded inside the heating plate 24. The contact heating device 4 is electrically connected to the resistance wire. Current flows through the resistance wire, generating resistance heat, which is then conducted through the heating plate 24 to raise the temperature of the area to be welded. The resistance wire possesses physical properties such as high melting point, strong oxidation resistance, high resistivity, and low temperature coefficient of resistance. Optional low-temperature heating materials include nickel-chromium alloys, iron-chromium-aluminum alloys, and copper-nickel alloys, with heating temperatures reaching 1100 to 1400°C. Optional high-temperature heating materials include platinum, molybdenum disilicide, and silicon carbide, with heating temperatures reaching 1900 to 2100°C. Preferably, the diameter of the resistance wire increases from the outer end to the inner end of the heating plate 24; the smaller the wire diameter, the higher the resistance value, generating more heat under constant current heating; conversely, the larger the wire diameter, the less heat is generated. When the laser welds along the direction of the resistance wire's diameter from small to large, this varying wire diameter provides a gradient temperature distribution: a higher temperature at the welding start point and a lower preheating temperature at the end point.

[0048] The heating plate 24 is triangular, rectangular, or irregularly shaped with a hollow design. Preferably, the heating plate 24 is a replaceable element and is set up separately in the process of contacting the heating device 4, so that the temperature rise of each heating plate 24 can be controlled individually. The number of heating plates 24 varies depending on the number of areas to be welded and the number of weld seams 8, generally ranging from 3 to 6. The heating plates 24 are not fixedly connected to the outer edge of the pressure ring; instead, they can rotate and move along the annular groove around the axis of the pressure ring device 2, allowing for flexible adjustment to the desired heating area. The heating plates 24 can be machined into triangular, rectangular, or irregularly shaped hollow designs to adapt to different welding paths and the width of the areas to be welded, ensuring uniform heating around the weld seams 8. The rotatable range of the heating plates 24 is limited by their number and shape, but the sum of the maximum rotation ranges of all heating plates 24 should be 360°. For example, when the pressure ring device 2 is equipped with 3 heating plates 24, the maximum rotation range of each heating plate 24 is 120°. Each heating plate 24 has a thickness of 3–5 mm and a total length of 42–45 mm.

[0049] A temperature measuring device 9 is provided above the electrode cell 1 to be welded. The temperature measuring device 9 is electrically connected to the contact heating device 4 and the induction heating device 5 respectively. It is used to measure whether the actual temperature value has reached the required temperature value. The temperature measuring device 9 can measure the deviation between the actual temperature and the required temperature, and as a feedback system, it feeds the signal back to the contact heating device 4 and the induction heating device 5. Then, the contact heating device 4 and the induction heating device 5 adjust the heating temperature in real time.

[0050] The multimode laser 6 is a three-beam laser, consisting of a central beam, an inner ring beam, and an outer ring beam arranged sequentially from the inside out. The central beam is a blue laser with a wavelength of 450nm, and the inner and outer ring beams are both infrared lasers with a wavelength of 1064nm.

[0051] The aforementioned galvanometer 7 is a 2D high-power galvanometer, which can realize the oscillation of three-beam lasers and the setting of different welding paths.

[0052] Preferably, during the preheating process, the induction heating device 5 and the contact heating device 4 can be turned on simultaneously, or either the induction heating device 5 or the contact heating device 4 can be turned on separately to achieve different preheating effects. When the induction heating device 5 and the contact heating device 4 are turned on at the same time, the combined heating method of contact heating and induction heating greatly improves the heating speed and efficiency.

[0053] Example 2: Figures 1-5 As shown, a method for using a laser welding device for a large cylindrical battery with all tabs is implemented based on the laser welding device for a large cylindrical battery with all tabs described in Example 1, and includes the following steps:

[0054] Step 1: Before welding, wipe the oil and impurities from the current collector 11 and the battery tabs 12 with alcohol. Keep the core 13 vertical with the side to be welded facing upward. Then, put the current collector 11 and the battery tabs 12 together and align the first positioning hole 111 with the second positioning hole. Adjust the movable connecting rod 31 and the pressure ring device 2 so that the movable connecting rod 31 is tilted at an angle of 30° to 60°. Control the moving device 32 to move the pressure ring device 2 directly above the cell 1 to be welded and keep the pressure ring device 2 parallel to the current collector 11.

[0055] Step 2: First, rotate several heating plates 24 so that each heating plate 24 is placed on one side of the corresponding area to be welded, exposing the area to be welded. Then, move the pressure ring device 2 downward so that the retaining ring 25 presses onto the current collector 11, thereby pressing and fixing the current collector 11 and the battery tabs 12. Plan to weld 3 to 5 welds 8 in each area to be welded. Each heating plate 24 is 2mm to 4mm away from any weld 8 to be welded in the corresponding area in the horizontal direction.

[0056] Step 3: Turn on the induction heating device 5 and the contact heating device 4, and adopt staged heating. In the first stage, the temperature is set to 200℃~400℃ and the heating time is 2 minutes to 5 minutes. In the second stage, the temperature is set to 600℃~800℃ and the heating time is 8 minutes to 12 minutes. In both the first and second stages, the temperature measuring device 9 is used to measure whether the temperature of the current collector 11 and the battery tabs 12 has reached the required temperature.

[0057] Step 4: Set the power of the central beam to 300W-500W, the power of the inner ring beam to 400W-600W, and the power of the outer ring beam to 500W-700W. Set the welding speed to 16m / min-26m / min and the defocusing amount to +3mm-8+mm. During welding, use a protective gas to isolate the current collector 11 and the battery tab 12 from the air. The protective gas flow rate is 10L / min-20L / min. Emits a multi-mode laser through the galvanizing head 7 to weld the weld seam 8 next to the heated pressing plate 24. The length of the weld seam 8 is 7mm-10mm.

[0058] Step 5: Lift the pressure ring device 2 and adjust the position of each heating plate 24 so that the heating plate 24 is 2mm to 4mm away from the position of the next weld seam 8 to be welded in the corresponding welding area. Repeat steps 3 and 4. When repeating step 3, shorten the heating time of the first and second stages according to the measurement results of the temperature measuring device 9 until all weld seams 8 are welded and the current collector 11 is welded to the battery tab 12 as one unit.

[0059] In the first and second stages, the induction heating device 5 and the contact heating device 4 are turned on simultaneously, or, in the first stage, only the induction heating device 5 is turned on, and in the second stage, both the induction heating device 5 and the contact heating device 4 are turned on simultaneously.

[0060] The protective gas is nitrogen or argon with a purity of 99.9% or higher, or the protective gas is a mixture of nitrogen and argon in a mass ratio of 3:1, 2:1, 1:1, 1:2 or 1:3.

[0061] 1. The present invention rotates and moves the heating plate 24 to place two adjacent heating plates 24 on both sides of the area to be welded, and then controls the contact heating device to start the heating program of the two heating plates individually to raise the temperature to the desired temperature, thereby realizing local heating of a precise location.

[0062] 2. This invention provides a trapezoidal distribution of preheating temperature by changing the diameter of the heating resistance wire inside the heating plate 24, which effectively improves the problem of incomplete welding caused by low material temperature and insufficient heat input at the starting position of laser welding, and avoids spatter and pit defects caused by excessive heat accumulation at the ending position.

[0063] 3. This invention improves the preheating efficiency of workpieces before welding by combining induction heating and contact heating. Induction heating mainly targets the surface of the workpiece, while contact heating mainly targets the interior of the workpiece. This combined heating method significantly improves the uniformity of temperature distribution in the workpiece to be welded. At the same time, the staged heating method can avoid the drastic thermal expansion of the workpiece to be welded caused by rapid heating and can reduce energy loss and save energy.

[0064] 4. In this invention, the temperature measuring device 9 is used as a feedback system. The temperature measuring device 9 monitors and judges the deviation between the actual temperature and the required temperature in real time, and feeds the signal back to the heating device. The induction heating device 5 and the contact heating device 4 adjust the heating temperature in real time according to the feedback result, thereby achieving the consistency of the preheating temperature and achieving the effect of constant temperature.

[0065] The invention will be further illustrated below with application examples:

[0066] Example 1: The collector plate 11 is a six-lobed collector plate made of T2 pure copper with a thickness of 0.2mm; it has 6 areas to be soldered, each with a fan-shaped outline and a central angle of 60°; the pressure ring device 2 is equipped with 6 heating plates 24, each triangular in shape, with a rotation range of 60°, a total length of 44mm, and a thickness of 3mm; the inner diameter of the outer edge of the pressure ring is 46.5mm, and the wall thickness is 10mm; the specific implementation method is as follows:

[0067] Step 1: Before welding, wipe the oil and impurities on the current collector 11 and the battery tabs 12 with alcohol. Keep the core 13 vertical and the side to be welded facing upward. Then, put the current collector 11 and the battery tabs 12 together and align the first positioning hole 111 with the second positioning hole. Adjust the movable connecting rod 31 and the pressure ring device 2 so that the movable connecting rod 31 is tilted at a 45° angle. Control the moving device 32 to move the pressure ring device 2 directly above the cell 1 to be welded and keep the pressure ring device 2 parallel to the current collector 11.

[0068] Step 2: First, rotate several heating plates 24 so that each heating plate 24 is placed on one side of the corresponding area to be welded, exposing the area to be welded. Then, move the pressure ring device 2 downward so that the retaining ring 25 presses onto the current collector 11, thereby pressing and fixing the current collector 11 and the battery tabs 12. Three welds 8 are planned to be welded in each area to be welded. Each heating plate 24 is 2.5mm away from any weld 8 to be welded in the corresponding area in the horizontal direction.

[0069] Step 3: Turn on the induction heating device 5 and the contact heating device 4, and use staged heating. In the first stage, the temperature is set to 200℃ and the heating time is 3 minutes. In the second stage, the temperature is set to 600℃ and the heating time is 8 minutes. In both the first and second stages, the temperature measuring device 9 is used to measure whether the temperature of the current collector 11 and the battery tabs 12 has reached the required temperature.

[0070] Step 4: Set the power of the central beam to 450W, the power of the inner ring beam to 500W, and the power of the outer ring beam to 600W. Set the welding speed to 24m / min and the defocusing amount to +5mm. During welding, use 99.99% pure argon protective gas to isolate the current collector 11 and the battery tab 12 from the air. The protective gas flow rate is 15L / min. Emits a multi-mode laser through the galvanizing lens 7 to weld the weld seam 8 next to the heated pressing plate 24. The length of the weld seam 8 is 8mm.

[0071] After testing, weld 8 was found to be free of defects such as blast points, porosity, and spatter. The width of weld 8 was 0.37 mm and the depth was 0.29 mm. The workpiece deformation was small and the welding process did not affect other battery components. No short circuit occurred during the post-weld battery short circuit test.

[0072] Example 2: The collector plate 11 is a four-lobed collector plate 11, made of T2 pure copper, with a nickel plating layer thickness of 0.2 micrometers and a total thickness of 0.3 mm; it has 4 areas to be soldered, each with a fan-shaped outline and a central angle of 90°; the pressure ring mechanism 2 is equipped with 4 heating plates 24, each rectangular in shape, with a rotation range of 90°, a total length of 45 mm, and a thickness of 4 mm; the inner diameter of the outer edge 21 of the pressure ring is 46.5 mm, and the wall thickness is 8 mm; the specific implementation method is as follows:

[0073] like Figure 5 As shown, in this embodiment, the workpiece to be welded is a four-lobed manifold 11, made of pure copper, with a nickel plating layer thickness of 0. micrometers and a total thickness of 0. mm; it has a total of 10 welding areas, each with a fan-shaped outline and a central angle of 90°; the pressure ring device 2 is equipped with 10 heating plates 24, each rectangular in shape, with a rotation range of 90°, a total length of 1 mm, and a thickness of 1 mm; the inner diameter of the outer edge of the pressure ring is 0. mm, and the wall thickness is 1 mm; the specific implementation method is as follows:

[0074] Step 1: Before welding, wipe the oil and impurities on the current collector 11 and the battery tabs 12 with alcohol. Keep the core 13 vertical and the side to be welded facing upward. Then, put the current collector 11 and the battery tabs 12 together and align the first positioning hole 111 with the second positioning hole. Adjust the movable connecting rod 31 and the pressure ring device 2 so that the movable connecting rod 31 is tilted at a 60° angle. Control the moving device 32 to move the pressure ring device 2 directly above the cell 1 to be welded and keep the pressure ring device 2 parallel to the current collector 11.

[0075] Step 2: First, rotate several heating plates 24 so that each heating plate 24 is placed on one side of the corresponding area to be welded, exposing the area to be welded. Then, move the pressure ring device 2 downward so that the retaining ring part 25 presses on the current collector 11, thereby pressing and fixing the current collector 11 and the battery tabs 12. Three welds 8 are planned to be welded in each area to be welded. Each heating plate 24 is 3.5mm away from any weld 8 to be welded in the corresponding area in the horizontal direction.

[0076] Step 3: Use staged heating. In the first stage, only the induction heating device 5 is turned on and the temperature is set to 300℃ for 4 minutes. In the second stage, both the induction heating device 5 and the contact heating device 4 are turned on and the temperature is set to 650℃ for 10 minutes. In both the first and second stages, the temperature measuring device 9 is used to measure whether the temperature of the current collector 11 and the battery tabs 12 has reached the required temperature.

[0077] Step 4: Set the power of the central beam to 400W, the power of the inner ring beam to 550W, and the power of the outer ring beam to 650W. Set the welding speed to 20m / min and the defocusing amount to +6mm. During welding, use 99.99% pure nitrogen protective gas to isolate the current collector 11 and the battery tab 12 from the air. The protective gas flow rate is 12L / min. Emits a multi-mode laser through the galvanizing head 7 to weld the weld seam 8 next to the heated pressing plate 24. The length of the weld seam 8 is 9mm.

[0078] After testing, weld 8 was found to be free of defects such as blast points, porosity, and spatter. The width of weld 8 was 0.41 mm and the depth was 0.28 mm. The workpiece deformation was small and the welding process did not affect other battery components. No short circuit occurred during the short circuit test of the battery after welding.

[0079] In summary, for welding the tabs and current collectors 11 of large cylindrical batteries of various structures, preheating before welding can improve welding quality and reduce welding defects, resulting in a more aesthetically pleasing weld 8 after welding. By adopting different welding parameters for workpieces of different sizes, it is possible to prevent thermal damage and short circuits in other battery structures after welding.

[0080] 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. A laser welding device for full-tab large cylindrical batteries, the full-tab large cylindrical battery comprising a battery cell (1) to be welded, the battery cell (1) to be welded comprising a current collector plate (11), a battery full-tab (12) and a winding core (13), the winding core (13) being a cylindrical member, a second positioning hole being provided in the center of the upper end face of the winding core (13), the battery full-tab (12) being provided on the upper end face of the winding core (13), a center hole matching the second positioning hole being left in the center of the battery full-tab (12), the current collector plate (11) being a circular plate member, a first positioning hole (111) being provided in the center of the current collector plate (11), a plurality of through stress release grooves (112) being provided on the current collector plate (11) in the radial direction, the plurality of stress release grooves (112) being circumferentially distributed on the outer periphery of the first positioning hole (111), and the plurality of stress release grooves (112) separating the current collector plate (11) into a plurality of lobe welding areas; characterized in that the welding device comprising a pressure ring device (2), a moving mechanism (3), a contact heating device (4) and an induction heating device (5), the moving mechanism (3) comprising a moving device (32) and a movable connecting rod (31), the pressure ring device (2) being connected to the output end of the moving device (32) through the movable connecting rod (31); the pressure ring device (2) comprising a pressure ring outer edge, the pressure ring outer edge comprising an outer cylinder portion (21) and a blocking ring portion (25), the outer end of the blocking ring portion (25) being connected to the upper end of the outer cylinder portion (21), the inner periphery of the outer cylinder portion (21) being provided with an annular sliding groove opened in the circumferential direction, a plurality of heating pressure pieces (24) being respectively provided in the radial direction of the outer cylinder portion (21), the outer ends of the plurality of heating pressure pieces (24) being respectively in sliding fit with the annular sliding groove, the number of the heating pressure pieces (24) being the same as the number of the welding areas, a magnetic pressure head (23) being provided in the center of the blocking ring portion (25), the magnetic pressure head (23) being connected to the blocking ring portion (25) through a fastening pressure piece (22), the inner end of the heating pressure piece (24) being provided with a pressure piece head of magnetic material, the pressure piece head being attracted to the magnetic pressure head (23); the current collector plate (11) being provided on the battery full-tab (12), the inner periphery of the outer cylinder portion (21) being fitted with the current collector plate (11) and the winding core (13) respectively, the plurality of heating pressure pieces (24) being respectively corresponding to the plurality of welding areas, the lower end of the magnetic pressure head (23) being coaxially provided with a circular boss (26), the circular boss (26) being respectively in plug fit with the first positioning hole (111) and the second positioning hole, the contact heating device (4) being used to heat the plurality of heating pressure pieces (24), and the induction heating device (5) being used to heat the pressure ring outer edge, when the current collector plate (11) reaches the required temperature, a laser system is controlled to emit multi-modal laser through a galvanometer head (7) to weld the welding areas.

2. The laser welding apparatus for full tab large cylindrical batteries of claim 1, wherein: The inner periphery diameter of the outer cylinder portion (21) is 47.5mm-48mm, and the wall thickness is 7mm-10mm.

3. The laser welding apparatus for full tab large cylindrical batteries of claim 1, wherein: A resistance wire is provided in the heating pressure piece (24), the contact heating device (4) is electrically connected to the resistance wire, and the wire diameter of the resistance wire changes from small to large in the direction from the outer end to the inner end of the heating pressure piece (24).

4. The laser welding apparatus for full tab large cylindrical batteries of claim 1, wherein: The heating pressing piece (24) is in the shape of a triangle, a rectangle or an irregular hollow shape.

5. The laser welding apparatus for full tab large cylindrical batteries of any one of claims 1-4, wherein: The temperature measuring device (9) is arranged above the welding cell (1) and is electrically connected with the contact heating device (4) and the induction heating device (5).

6. The laser welding apparatus for full tab large cylindrical batteries of claim 5, wherein: The multi-mode laser (6) is composed of a central light beam, an inner ring light beam and an outer ring light beam arranged from inside to outside, the central light beam is a blue laser with a wavelength of 450 nm, and the inner ring light beam and the outer ring light beam are both infrared lasers with a wavelength of 1064 nm.

7. The method of using a full-tab large cylindrical battery laser welding apparatus of claim 6, wherein: The galvanometer head (7) is a 2D high-power galvanometer.

8. A method for using a laser welding device for full-tab large cylindrical batteries, implemented by means of a laser welding device for full-tab large cylindrical batteries according to claim 7, characterized in that, The method comprises the following steps: In step one, before welding, the collector plate (11) and the battery full tab (12) are wiped with alcohol to remove oil stains and impurities, the winding core (13) is placed vertically with the side to be welded upward, then the collector plate (11) and the battery full tab (12) are attached to each other with the first positioning hole (111) aligned with the second positioning hole, the movable connecting rod (31) and the pressing ring device (2) are adjusted to make the movable connecting rod (31) form an angle of 30°-60°, the moving device (32) is controlled to move the pressing ring device (2) to the upper side of the welding cell (1) and make the pressing ring device (2) parallel to the collector plate (11); In step two, a plurality of heating pressing pieces (24) are rotated to make each heating pressing piece (24) arranged on one side of the corresponding welding area to expose the welding area, then the pressing ring device (2) is moved downward to make the blocking ring (25) press on the collector plate (11) to realize the compression and fixation of the collector plate (11) and the battery full tab (12), 3-5 welds (8) are planned for each welding area, and each heating pressing piece (24) is 2-4 mm away from the position of any weld (8) of the corresponding welding area in the horizontal direction; In step three, the induction heating device (5) and the contact heating device (4) are turned on, and stage heating is adopted, the temperature in the first stage is set to 200-400℃, and the heating time is 2-5 minutes; the temperature in the second stage is set to 600-800℃, and the heating time is 8-12 minutes, and the temperature measuring device (9) is used to measure whether the temperature of the collector plate (11) and the battery full tab (12) reaches the required temperature in the first stage and the second stage; In step four, the power of the central light beam is set to 300-500W, the power of the inner ring light beam is set to 400-600W, the power of the outer ring light beam is set to 500-700W, the welding speed is set to 16-26 m / min, the defocusing amount is set to +3-8 mm, the collector plate (11) and the battery full tab (12) are isolated from air by using a protective gas with a flow rate of 10-20 L / min during welding, the multi-mode laser is emitted by the galvanometer head (7) to weld the welds (8) at the positions beside the heating pressing piece (24), and the length of the welds (8) is 7-10 mm. Step five, lift the pressure ring device (2), adjust the position of each heating tablet (24), make the heating tablet (24) 2mm-4mm away from the next to be welded weld (8) in the corresponding to be welded area, repeat step three and step four, repeat three times, shorten the heating time of the first stage and the second stage according to the measurement result of the temperature measuring device (9), until all the welds (8) are welded, and the current collector plate (11) is welded with the battery full tab (12).

9. The method of using a full-tab large cylindrical battery laser welding apparatus of claim 8, wherein: In the first stage and the second stage, the induction heating device (5) and the contact heating device (4) are turned on at the same time, or only the induction heating device (5) is turned on in the first stage, and the induction heating device (5) and the contact heating device (4) are turned on at the same time in the second stage.

10. The method of using a full-tab large cylindrical battery laser welding apparatus of claim 8, wherein: The protective gas is nitrogen or argon, and the purity is 99.9% or above, or the protective gas is a mixed gas of nitrogen and argon, and the mixing mass ratio is 3:1, 2:1, 1:1, 1:2 or 1:3.

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