Li metal anode has regained intensive interest in recent years in order to develop high energy next-generation battery technologies. Unfortunately, Li metal suffers from poor cycling stability and low efficiency as well as the formation of dangerous Li dendrites raising safety concerns. The employment of solid state electrolyte (SSE) to prevent Li dendrite growth provides a promising approach to address the dendrite issue. However, recent studies indicate that Li dendrites easily form at elevated current densities, while the fundamental mechanisms of forming Li dendrites within SSE is still unknown. This calls for further investigation to understand, and control the detrimental observation.

The origin and evolution of Li dendrite growth through SSE will be discussed in this talk by using two different SSE membranes, garnet and phosphate-type, as the separators. During cycling, Li is repeatedly deposited on SSE. Although a good SSE should not react with the deposited Li, the reactions between Li deposits and SSE generate a self-terminating interface, which stops the fast propagation of dendritic Li through the SSE membrane. New insights are provided on the further modification and/or incorporation of interfacial layers between SSE and Li metal to enable future solid state batteries.