Investigation on the combined effect of thermal cycling and corrosion behavior on pulsed laser spot-welded Al-Cu joints for battery applications

Laser spot-welded Al Cu joints are widely used in battery interconnects, but their long-term reliability under severe service conditions is less understood. Therefore, this study investigates the combined effects of thermal cycling and corrosion on pulsed laser spot-welded Al Cu joints for battery applications. Ni-assisted Al Cu joints were thermally cycled at 120, 150, and 180 A for 200 and 1000 cycles, corresponding to stabilized peak temperatures of 116 ± 3.0 °C, 156 ± 3.0 °C, and 233 ± 4.0 °C, respectively. The results showed that degradation strongly depended on thermal severity and cycle exposure. The 120 A condition showed relatively stable behavior, with low corrosion rates (6.96 and 7.30 mpy after 200 and 1000 cycles, respectively) and tensile strengths (753 ± 18 N and 749 ± 21 N) comparable to the as-welded joint (5.64 mpy and 754 ± 20 N). In contrast, severe degradation occurred at 180 A, where extensive pore formation and crack propagation increased the corrosion rate to 18.92 mpy and reduced the tensile strength to 350 ± 30 N after 1000 cycles. XRD analysis confirmed progressive evolution of the Al₂Cu intermetallic compound (IMC) with increasing thermal exposure. These thermally induced defects promoted localized corrosion and increased electrical resistance from 187 ± 3 μΩ in the as-welded condition to 338 ± 23 μΩ after 1000 cycles at 180 A. The results demonstrate a strong coupling between thermal fatigue, corrosion degradation, and IMC evolution, providing insight into the durability of Al Cu battery interconnects under severe service conditions.