Operando Scanning SAXS/WAXS Cell Design for Multiscale Analysis of All‐Solid‐State Battery Systems

Operando X‐ray scattering techniques, particularly small‐ and wide‐angle X‐ray scattering (SAXS/WAXS), have been key for elucidating the physicochemical processes governing liquid‐electrolyte batteries by providing real‐time insights into phase transformations and nanoscale structural evolution. However, extending these methods to all‐solid‐state batteries has been experimentally challenging due to high X‐ray absorption and nonideal operating pressures in transmission mode. Here a novel operando electrochemical cell design is presented that enables cross‐sectional scanning SAXS/WAXS measurements, while maintaining the pressure necessary for solid‐state operation. Applying this scanning SAXS/WAXS technique to all‐solid‐state lithium‐sulfur batteries, it enables simultaneous mapping of the crystalline phase evolution and the nanoscale structural changes across distinct cell components during cycling. Spatially resolved WAXS revealed significant heterogeneity in the formation and distribution of Li 2 S within the composite cathode. Simultaneously, WAXS captured an anisotropic lithiation mechanism in the Li–In anode, evidenced by the preferential disruption of In(110) planes and suggesting amorphous LiIn formation. Combined analysis of stable SAXS profiles and WAXS‐derived Li 2 S nanocrystallite sizes suggest that the sulfur conversion occurs within the nanopores of the templated carbon host. Control experiments using a liquid‐electrolyte Li–S system validated the technique's sensitivity to detect expected nanoscale changes, confirming the genuineness of the solid‐state observations.