Constructing dendrite suppressing mixed sulfide solid electrolyte for high-rate lithium metal batteries

All-solid-state lithium metal batteries (ASSLMBs) have received much attention because of their potential for high energy density and high safety performance. However, the poor compatibility of the lithium/solid electrolytes (SEs) interface and the penetration of lithium dendrites during cycling prevent them from achieving current densities that are capable of commercialization. In this work, a lithium-metastable solid electrolyte and a lithium-unstable solid electrolyte have been mixed to obtain mix-structured solid electrolyte. In particular, Li5.5PS4.5Cl1.5 acts as a lithium-compatible matrix, and Li10SnP2S12 as a dendrite-scavenger. The synergy between the two generates a stable interface with the Li anode and effectively suppresses the penetration of lithium dendrites. Li symmetric cells can operate stably for 160 h at a current density of 0.5 mA cm-2 at room temperature. The critical current density can reach 5 mA cm-2 and the overpotential is less than 0.5 V. The Li/SEs/Li4Ti5O12 all-solid-state cells show a high capacity of 174 mAh g-1 at 0.2 C and 148 mAh g-1 at 2 C. High-capacity retentions of 97.3% and 94.4% are shown after 75 cycles at 1 C and 2 C at room temperature, respectively. This work highlights the advantages of the electrolyte with mixed structure and provides a new strategy to resist lithium dendrites and improve the critical current density and cycle life of ASSLMBs.