Operando GI-WAXS characterisation of buried lithium metal-solid electrolyte interface degradation in solid-state batteries

Solid-state batteries (SSBs) based on solid electrolytes (SE) can enable safe and high-energy storage devices; however, their progress is significantly hampered by challenges at the lithium (Li) metal - SE interface. Void formation (contact loss) and dendrite-induced short-circuiting are exacerbated by high interfacial resistance stemming from poorly understood SE electrochemical decomposition with Li metal. Traditional analysis is limited by the buried interface, necessitating destructive profiling that obscures mechanistic understanding. To overcome these limitations, we propose operando grazing incidence wide-angle x-ray scattering (GIWAXS) on symmetric Li-SE-Li cells. This will directly identify interface decomposition products (orientation, spatial distribution) in-situ within oxide and sulphide SEs. Revealing these degradation mechanisms will enable the rational design of stable, high-performance SSBs with extended cycle life.