An investigation of mechanical and electrical properties of friction stir welded Al and Cu busbar for battery pack applications

Abstract

The aluminum and copper (Al–Cu) busbar is widely used as a core component in Lithium-Ion (Li-ion) batteries. The Al–Cu busbar is challenging to fabricate with the traditional welding processes because of its high thermal conductivity. The Al–Cu busbar is fabricated using the friction stir welding method in the present study. The effect of temperature and vibration generated during the welding process on intermetallic compounds (IMCs) is studied using the effective formation model and found that Al2Cu is the first to form at the interface. The IMC formation at the joint interface had detrimental (Al-rich IMC) and beneficial (Cu-rich IMC) effects. The presence of detrimental IMCs affects the joint strength of about 36% as compared to the sample with the highest tensile load. The surface electrical conductivity is measured by using a Gaussian profile method and found in the range of 0.94–5.37 μ Ω·mm. The welded samples with the presence of Al2Cu3 and Al4Cu9 IMC at the interface are found to have higher electrical conductivity. Interestingly, the sample with a higher tensile load had observed higher electrical conductivity due to the formation of Cu-rich IMC, i.e., Al4Cu9.