Impact of multiple ultrasonic and laser welds on electro-thermal behaviours for connecting Li-ion battery cells

Abstract

The need for efficient manufacturing methods to produce battery packs is increasing with the growing demand for Electric Vehicles (EVs). A large number of individual battery cells are interconnected to meet the power and capacity requirements of EVs. As a result, several joining methods are under investigation to produce battery interconnects efficiently. Typically, ultrasonic metal welding is employed to produce pouch cell tab-to-tab interconnects. In addition, laser welding is also emerging as a fast and non-contact joining alternative. Detailed critical-to-quality investigations are needed to compare both joint types. This paper investigated the effect of multiple ultrasonic nuggets and laser seams on electrical resistance and thermal performance at the tab-to-tab interconnects. Multi-physics simulation models were developed to predict the joint resistance and temperature rise under different charge-discharge current values. Results show that electrical contact resistance was decreased by 54% when a 5 mm diameter circular laser weld-based tab-to-tab connection was replaced with six circular welds of the same diameter. Simulation-based comparative analysis showed that resistance and temperature rise obtained from the 3 or 6 circular laser welds were similar to 3 or 6 nuggets ultrasonic welds. As a result, both the ultrasonic and laser joints can be used as per need.