Abstract
Ultrasonic welding is characterized by its energy-saving and environmentally friendly nature. Compared to conventional molten welding technology, the intermetallic compounds formed by diffusion during ultrasonic welding are thinner, and material deformation is reduced. This process has become a primary welding technique for assembling lithium batteries in electric vehicles. Aluminum and copper ultrasonic welding has increasingly gained attention as a research hotspot. The research on aluminum and copper ultrasonic welding primarily focuses on the interfacial microstructure evolution, mechanical performance during the welding process, and numerical simulations to investigate macro- and micro-scale physical phenomena. Given the aluminum and copper multi-layer structures used in lithium battery packaging, numerous studies have been conducted on aluminum and copper multi-layer ultrasonic welding. For Al/Cu joints, advancements in understanding the microstructure evolution, joint performance, and finite element modeling of the welding process have been systematically reviewed and summarized. Moreover, significant progress has been made in molecular dynamics simulations of Al/Cu ultrasonic welding and hybrid welding techniques based on Al/Cu ultrasonic welding. Finally, several new research directions for Al/Cu ultrasonic welding and joining have been proposed to guide further in-depth studies.