Laser Beam Welding of Aluminium: Process Optimisation to Achieve Hermetic Sealing for Electrochemical Energy System Containers

Abstract

Hermetic sealing is essential for long cycle life and calendar life of Lithium ion cells. Ingress of moisture and leaking of electrolyte in Lithium ion cells deteriorates the electrochemical performance. Nickel coated mild steel, Stainless steel, Aluminium and its alloys are generally used as case material. Pure Aluminium and Aluminium alloys are used to improve energy density of Lithium ion cells. High heat input is required for aluminium to obtain a sound weld because of the high thermal conductivity of the Aluminium. High heat input results in increased heat affected zone (HAZ) and transfer of heat into internal components during welding. Laser Beam Welding (LBW) results in very narrow heat affected zone (HAZ) and it is possible to have dissimilar metal welding. In the present work, experimental studies conducted to optimise the laser beam welding parameters for welding of Li-ion AA3003 cell case to lid without defects viz porosity and required weld strength. Hermeticity and strength of the weld bead were analysed in detail to ensure the adequacy of the process. It has been demonstrated that laser beam welding is a viable process for joining of cell case to its cover.