The application of laser to battery welding is the current market development trend, which is also determined by the technical advantages of laser itself. It is one of the important welding technologies that will replace traditional welding in the future. 

1. The advantages of laser welding batteries are mainly reflected in the following points:

1. Concentrated energy, high welding efficiency, and high processing precision and large weld depth-to-width ratio. The laser beam is easy to focus, align and be guided by optical instruments. It can be placed at an appropriate distance from the work piece and can be redirected between fixtures or obstacles around the work piece. Other welding methods cannot be used due to the above-mentioned space restrictions.

2. The heat input is small, the heat affected zone is small, and the residual stress and deformation of the work piece are small; the welding energy can be precisely controlled, the welding effect is stable, and the welding appearance is good;

3. Non-contact welding, optical fiber transmission, good accessibility and high degree of automation. When welding thin materials or fine-diameter wires, there is no melt back problem like arc welding.

Since the cells used in power batteries follow the "lightweight" principle, they usually use lighter aluminum materials and also need to be made "thinner". Generally, the shell, cover, and bottom are basically required to be less than 1.0mm. The current basic material thickness of mainstream manufacturers is around 0.8mm, which can provide high-strength welding for various material combinations, especially when welding copper materials and aluminum materials. This is also the only technique that can solder electroplated nickel to copper materials.

2. Difficulties in laser welding process

At present, aluminum alloy battery shells account for more than 90% of the entire power battery. The difficulty in welding lies in the extremely high reflectivity of aluminum alloy to laser and the high sensitivity of pores during the welding process. Some problems and defects will inevitably occur during welding, the most important of which are pores, hot cracks and explosions.

1. Porosity is easy to occur during the laser welding process of aluminum alloy. There are two main types: hydrogen pores and pores caused by bubble bursting. Because the cooling rate of laser welding is too fast, the problem of hydrogen holes is more serious, and there is an additional type of holes caused by the collapse of small holes in laser welding.

2. Thermal crack problem. Aluminum alloy is a typical eutectic alloy. Hot cracks are prone to occur during welding, including weld crystallization cracks and HAZ liquefaction cracks. Due to component segregation in the weld area, eutectic segregation will occur and grain boundary melting will occur. Under stress, it wills Liquefaction cracks form at grain boundaries, reducing the performance of welded joints.

3. Explosion (also called splashing) problem. There are many factors that cause explosions, such as the cleanliness of the material, the purity of the material itself, the characteristics of the material itself, etc. The decisive factor is the stability of the laser.

Shell surface bulges, pores, and internal bubbles. The main reason is that the fiber core diameter is too small or the laser energy setting is too high. It is not "the better the beam quality, the better the welding effect" promoted by some laser equipment suppliers. Good beam quality is suitable for superposition welding with larger penetration depth. Finding the right process parameters is the key to solving the problem.