Laser welding can greatly improve the safety and service life of power batteries.
In the manufacturing process of power battery, laser welding has many parts, including pole lugs, flip tabs, sealing, busbar, PACK module, injection hole encapsulation, etc., which can realize battery series and parallel connection. Also, it involves cells, modules and packages, and can also weld steel, aluminum, copper, nickel and many other materials.
The advantage of laser welding is that it effectively improves the reliability of the connection, facilitates the module light weight, reduces the battery resistance and reduces its own heat loss. It also cannot stop continuous work, has good welding quality and high flexibility. The difficulty and pain point is the high accuracy of the assembly of the welded parts and the position of the beam on the workpiece cannot be significantly shifted. At the same time, the cost of laser and its related systems is high.
There are two main types of laser welding for square cells, deep fusion welding and pulse welding. On soft packaged cells, it is pulse welding. The principle is to weld high energy density laser elements using a heat source with good reliability, low contact resistance and high automation, which can greatly improve production efficiency.
At present, lithium laser welding equipment manufacturers in the market, such as Da Zumotang laser, Haimuxing, Hyunshuo wisdom, Tide laser, Siqqi, Xin intelligence, and so on, of which the market share Da Zumotang laser, Haimuxing and other head enterprises market share of about 30-40%.
At the same time, Ningde Times, BYD, Guoxuan High-tech, Yiwei lithium, Panasonic, Samsung and other well-known lithium battery companies are involved in the use of laser welding.
Laser welding process, the more prominent are sealed nail welding, cap welding, continuous welding.
Seal nail welding, for pulse welding, the reason is the intermittent heat input, less tin hydrogen, and good results. The development of sealing nail welding is divided into two stages, the first stage is 7-8mm/s, the second stage is the speed has reached 30mm/s, the future will be faster.
The first stage is top cover welding, which can only be done at 60-80mm/s. Due to the deep fusion welding, it is easy to have a sight hole during the welding process and the end of the sight hole is easy to close. How electronic vapor leaks out, and it is easy to cause surface roughness.
The second stage is the commonly used composite welding and high-frequency swing welding, which can solve the problem of rapid closure of the view hole and greatly improve the welding speed.
The third stage is the start of new attempts by some companies. For example, high-speed welding round point and composite welding, which can reach 300mm / s.
Continuous welding is characterized by high speed, but it is easy to form heat accumulation and no microfracture during the instantaneous cooling of the molten pool. Continuous laser welding up to 15mm/s, physical welding up to 300mm /s
Generally speaking, the laser head and oscillating laser processing head welding are commonly used in lithium equipment, which can achieve high-speed welding of complex trajectories such as s-shaped and spiral, increasing the welding intensity while increasing the weld area. During the welding process, the MES system can also be connected to record and adjust various welding parameters in real time to ensure more stable welding and higher quality.
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