The Sustainability Assessment of Second Life Applications of Automotive Batteries (SASLAB) exploratory research project of the European Commission’s Joint Research Centre (JRC) aims at developing and applying a methodology to analyse the sustainability of deploying electrified vehicles (xEV) batteries in second use applications. A mapping of industrial demonstration and publicly-funded research projects in the area is presented, followed by an experimental assessment of the capacity and impedance change of lithium-ion cells during calendar and cycle ageing. Fresh cells and cells aged in the laboratory, as well as under real-world driving conditions, have been characterised to understand their application-specific remaining lifetime, beyond the 70% to 80% end-of-first-use criterion. For this purpose, pre-aged cells were examined under duty-cycles that resemble those of second use grid-scale applications.