While solid-state batteries promise to enhance the energy density and power density of conventional lithium-ion batteries, the morphological instability of the lithium metal anode persists to be a major challenge. During plating and stripping, the dynamic evolution of the lithium metal-solid electrolyte interface is governed by a coupled set of electrochemical-mechanical-transport processes. This mechanistic interaction is influenced by several factors including the mechanical properties of the solid electrolyte and lithium, presence of heterogeneities such as grain boundaries, defects and voids, and external pressure/temperature. In this presentation, the underlying role of microstructural and interfacial heterogeneities on the reaction kinetics, morphological growth, and the origin of electrochemical-mechanical failure will be examined. A fundamental analysis on how such heterogeneity-driven implications scale with plating and stripping currents, and their mechanistic dependence on the interfacial stress-temperature fields will be presented.