Unraveling the Origin of Grain Boundary Lithium Deficiency in Ceramic Solid Electrolytes

Realizing solid electrolytes with low grain-boundary (GB) resistance is critical for advancing all-solid-state batteries. High GB resistance in SEs is often attributed to deficiencies in mobile ions at these boundaries; yet, when and how these deficiencies form during synthesis remain unclear. Here, we use a unique in situ scanning transmission electron microscopy setup to guide solid electrolyte crystallization during annealing, enabling real-time observation of GB formation at the atomic scale, with Li0.33La0.56TiO3 as a model SE. We reveal an ultrathin, less than 1.5 nm thick, lithium-deficient layer that emerges at the crystallization front upon crystallization and persists as two adjacent crystals fuse to form a GB. We offer two hypotheses for the origin of the lithium-deficient layer, one based on thermodynamic stabilization and the other on kinetic constraints. Our results provide guidelines for designing synthesis strategies to reduce GB resistance in solid electrolytes.

Duke Scholars

Author Miaofang Chi Thomas Lord Department of Mechanical Engineering and Materia ...