Effect of welding path on the weld quality of aluminum tab and steel battery case in lithium-ion battery

The choice of welding path in joining battery connections plays a crucial role in the bonding strength, which in turn affects battery performance. A commonly employed welding path in laser welding is the circular wobbling path. Our prior study revealed that the hatching path in laser welding, which is hardly reported in the literature, offers a flexible welding pattern and sufficient weld strength, especially for thin specimens. This study conducted a comparative analysis of circular and hatch welding paths concerning their microstructure, mechanical properties, and electrical characteristics. Upon observing the surfaces of the two types of welds, it becomes evident that the hatch welding path results in a superior weld appearance with less spatter formation near the welding zone in comparison to the circular path. Furthermore, an examination of the cross-sections reveals a significant disparity in the interdiffusion between the welding materials. While the circular path yields a non-uniform chemical diffusion of the case material within the welded tab, the hatching path exhibits a periodic upward penetration of the case material into the tab at the welding lines. This discrepancy leads to a distinctive distribution of hardness, electrical resistance, and mechanical strength in the welds, with the desired properties attributed to the hatch welding path. Through this comparative analysis, the study unveils the influence of the laser beam deflection path on the overall weld quality.