Observation of Order and Disorder in Solid-Electrolyte Interphases of Lithium-Metal Anodes

Battery interfaces critically influence lithium-metal battery performance through their role in ion diffusion and dendrite formation. However, structural characterization of these interfaces has remained challenging due to limitations in high-resolution methods and artifacts induced by electron irradiation. Using cryogenic conditions for both specimen preparation and scanning electron nanobeam diffraction, we can determine the structural organization at the interface between the vitrified electrolyte and adjacent layers. We identified two distinct interface types: one showing short-range order adjacent to lithium metal and another displaying a mixed structure of short-range ordering and defective, nanoscale lithium fluoride crystallites at a copper current collector. Notably, short-range order appeared exclusively in electrolytes, demonstrating high reversibility. Our results establish that solid-electrolyte-interphase structure directly influences lithium deposition morphology and battery performance. This methodology opens new possibilities for the high-resolution characterization of interfaces in energy storage materials, advancing our understanding of their critical structural properties.