Dissimilar laser welding of copper and aluminum alloys in multilayer configuration for battery applications

Abstract

The joining process of copper and aluminum has become a key topic especially in the field of electro-mobility due to the fact that batteries, based especially on pouch Li-ion cells, are often manufactured in a way that involves joining together copper and aluminum tabs that constitute the anode and the cathode. Car manufacturers, in order to create more compact and performing batteries, are looking to stack more cells in small spaces and then weld the copper and aluminum tabs in multilayer configuration. However, welding those materials poses several challenges due to their differences in chemical and physical properties, such as melting temperature, thermal conductivity, and thermal expansion coefficient. One of the main challenges is represented by the formation of hard and brittle intermetallic compounds, which reduce both mechanical and electrical properties. The present paper addresses dissimilar laser welding of copper and aluminum in multilayer configuration by means of an infrared laser source equipped with galvanometric scanner optics, which allows us to obtain a spatial beam oscillation (circular wobbling) of the beam. The results confirmed that a larger wobbling amplitude does not enhance the properties of the connection. A maximum tensile load of about 1000 N and low electrical contact resistance were obtained with optimized parameters, while the presence of harder and brittle intermetallic compounds was reduced. Scanning electron microscope-energy dispersive x-ray spectrometer analysis confirmed the results obtained with the metallographic and mechanical tests.