The role of the solid electrolyte interphase layer in preventing Li dendrite growth in solid-state batteriesElectronic supplementary information (ESI) available: Fig. S1-S14 and Tables S1 and S2. See DOI: 10.1039/c8ee00540k

Lithium (Li) metal anodes have regained intensive interest in recent years due to the ever-increasing demand for next-generation high energy battery technologies. Li metal, unfortunately, suffers from poor cycling stability and low efficiency as well as from the formation of dangerous Li dendrites, raising safety concerns. Utilizing solid-state electrolytes (SSEs) to prevent Li dendrite growth provides a promising approach to tackle the challenge. However, recent studies indicate that Li dendrites easily form at high current densities, which calls for full investigation of the fundamental mechanisms of Li dendrite formation within SSEs. Herein, the origin and evolution of Li dendrite growth through SSEs have been studied and compared by using Li 6.1 Ga 0.3 La 3 Zr 2 O 12 (LLZO) and NASICON-type Li 2 O-Al 2 O 3 -P 2 O 5 -TiO 2 -GeO 2 (LATP) pellets as the separators. We discover that a solid electrolyte interphase (SEI)-like interfacial layer between Li and SSE plays a critical role in alleviating the growth of dendritic Li, providing new insights into the interface between SSE and Li metal to enable future all solid-state batteries. The fundamental role of the solid electrolyte interphase (SEI) layer in preventing dendritic Li growth has been investigated in solid-state batteries.