Characterization and modelling of Al and Cu busbar during charging and discharging of Li-ion battery for electric vehicles

Abstract

• The simulated temperature of the Al-Cu busbar attached to the Li-ion pouch cell is validated with the experimental result. • The temperature generation in the Li-ion cell is influenced by the electrical contact resistance of the weld joint. • The joint resistance of a busbar is mainly dependent on intermetallic formation and grain size at the weld joint of a busbar. The electrical components such as bimetallic busbar joints of the lithium-ion (Li-ion) batteries should be able to withstand high voltages during charge and discharge processes. The busbar is an essential component that transmits high power to electrify the vehicle. The present study describes the sustainability of friction stir welded (FSW) busbar at different C-rates by simulating a Li-ion battery attached to a busbar, then correlating the heat generation of simulation results with an experimental result at 1, 1.5, and 2C-rates. The change in process parameters of FSW samples varies with electrical conductivity at the weld interface. The variation in electrical conductivity with different busbars is due to the formation of various intermetallic and changes in the grain size of the Al and Cu joints. However, the busbar with Cu-rich intermetallic exhibits smaller electrical resistivity. The specific electrical contact resistance of a busbar is obtained from simulation by validating the heat generated during constant time charge-discharge cycles. The temperature rises due to contact resistance in the Al-Cu busbar which can lead to thermal runaway and, eventually, short circuits in the Li-ion battery pack. Based on previous simulation parameters, the Li-ion cells are simulated at 5 and 10C-rates to understand thermal runaway behaviour.