Abstract Next-Generation batteries requires more energy and output power due to the high demands of applications to large-size vehicles, e.g. SUVs and trucks. As a result, multiple dissimilar battery cell tabs are joined together in parallel and carry larger currents in the electrical circuit. Ultrasonic and laser welding have been the two dominant battery cell joining processes in the automotive industry. However, both of them have limitations for joining a large number of stacked battery tabs at one time. Since failure of a single joint can impact the battery and eventually the vehicle, it is important to ensure process robustness and soundness of the resulting battery tab joints. In this study a new joining method, resistive joining (RJ), has been developed for welding multiple dissimilar (copper and aluminum) battery tabs. First, nickel-phosphorus (Ni-P, with ~7 wt% phosphorus) is electroless plated on both sides of selected tabs. In the subsequent resistive joining process, heat is concentrated at the high-electrical-resistivity Ni-P coatings as an electric current is passed through the joint. Aluminum is melted adjacent to the Ni-P coating due to its low melting temperature, and a portion of the Ni-P coating is dissolved into the liquid aluminum and a metallurgical bond is formed as the aluminum re-solidifies. In the meantime, solid-state bonds are formed between the Ni-P coating and copper due to material interdiffusion. Consequently, no Al-Cu intermetallic compound (IMC) is generated at the joint, and the strengths of RJ joints are higher than the base metal when tested in a lap-shear configuration.
Resistive Joining – A Novel Dissimilar Welding Method for Thin Sheet Metals