Quantifying the role of ultrasonic welding and press contacts on electrical resistance for developing battery interconnects

Abstract

This paper investigates the comparative study of electrical resistance between press contact and ultrasonic welding techniques for similar and dissimilar Al and Cu combinations, which are primarily used in electric vehicle (EV) battery interconnects. The effect of surface roughness, pressure, and the number of nuggets on electrical resistance was quantified for press contact and ultrasonic welding. The results showed that AlAl, CuAl, and CuCu tab-to-tab material combinations exhibited the ultrasonic welding exhibited up to 80 % reduction in electrical contact resistance in comparison to press contacts. The changes in resistance from single ultrasonic nugget to three ultrasonic nuggets for AlAl, CuAl, and CuCu combinations were 31.4 %, 9.5 % and 14.37 %, respectively. This multi-nugget configuration can significantly improve the performance and life of the battery joint when considering large-scale applications like energy storage systems and electric vehicles. A multiphysics model of electrical contact resistance was developed and verified with experimental results to predict the electrical behaviours for press contact and ultrasonic joints. The developed simulation models for press contacts and ultrasonic welding were able to predict the electrical resistance within 4 % - 27 % deviation from experimental results. Using a mathematically modelled case study, the paper also highlighted the effect of such electrical resistance offered by different joint configurations and its industrial importance. These findings revealed the importance of material selection, joint configuration, and joint strategy to reduce the resistance offered for niche applications like electric vehicles and energy storage systems.