Laser beam welding of electrical interconnections for lithium-ion batteries

Lithium-ion batteries are growing in popularity for automotive applications due to their high energy density. The cells used in such batteries are often so called pouch bag cells which are equipped with two conductors made of copper and aluminum for anode and cathode. When multiple cells are mounted to a battery pack several electrical interconnections must be made between these conductors to achieve a serial connection of the cells. Nowadays this is mostly done by screwing.Laser welding is an interesting alternative to automate the battery pack fabrication, though a couple of restrictions must be considered. For a serial connection mostly copper and aluminum sheets must be welded to each other with minimum energy input to avoid overheating the cells. The prevailing difficulty in this process is the formation of brittle intermetallic compounds which cause cracks in the welds and impede the electrical conductivity.The use of high brilliance laser sources offers promising opportunities for this application....