2, Argonne National Laboratory, Lemont, Illinois, United States
All-solid state lithium ion batteries (LIB) are promising solutions for portable electronics and electric vehicle applications because of their achievable energy densities, safety, and compatibility with metallic lithium. Li metal is thermodynamically unstable in conventional liquid electrolytes and is a limiting component for achieving high volumetric capacity LIBs. However, garnet-type solid electrolytes are believed to be stable against Li-metal and demonstrate fast ion conductivity (~1 mS/cm at 298K). Furthermore, theoretical studies (Monroe-Newman model) have predicted that solid electrolytes with shear moduli (~60 GPa) can suppress Li dendrite growth. Recent experimental studies have contradicted these findings and revealed preferential lithium growth along grain boundaries in ceramic electrolytes. Although, significant work has realized rationally designed interfacial coatings, the origin and growth mechanisms behind lithium in a solid electrolyte is largely not well understood. Herein, we examine for the first time the internal structural effects lithium deposition has on the solid electrolyte microstructure ex situ, and connect these findings to processing conditions.