Operando GI-WAXS and in-situ GI-XAS characterisation of the Li metal - garnet solid electrolyte interface degradation in solid-state batteri

Solid-state batteries (SSBs) based on garnet solid electrolytes (SE) and lithium metal anodes promise safe, high-energy storage devices. While bulk properties of garnet SEs are well-characterised, their reaction mechanisms with Li metal remain poorly understood. Traditional analysis methods, limited by the buried nature of the Li-SE interface, rely on destructive techniques that hinder mechanistic insights. To overcome these limitations, we propose operando grazing incidence wide-angle x-ray scattering (GI-WAXS) and in-situ near-edge x-ray absorption spectroscopy (GI-XAS) on symmetric Li-SE-Li cells to non-destructively identify interface decomposition products, their orientation and spatial distribution, and track element oxidation states in-situ during cycling. Since these degradation mechanisms exacerbate Li-metal dendrite initiation and voids (contact loss) at the Li-SE interface, our results will enable the rational design of stable Li-SE interfaces thereby extending cycle life.