Process development of electrode-tab welds for aerospace, lithium-ion cells

This paper describes the design and process development of internal, electrode-tab connections for an aerospace, prismatic, 50-Ah, lithium-ion cell. The objective of this investigation was to formulate designs and processes that result in high-quality and uniform welds. Such welds must be sufficiently robust to withstand launch and operational environments and to support cell life in excess of 15 years. Electron beam welding (EBW), laser beam welding (LEW), plasma arc welding (PAW), tungsten inert gas (TIG) welding and ultrasonic welding (USW) were evaluated. Alternative current-collection schemes were also tried. In addition, the effects of process variables on weld quality were investigated. A feeder tab to a comb connection system was developed for the internal cell connections. The challenges of welding thin sections of aluminum and copper were met by using an ultrasonic weld for joining the electrode tabs to an intermediate feeder tab. A pulsed Nd:YAG (neodymium: yttrium aluminum garnet) laser was chosen to weld collector tabs to combs and combs to terminals.