Critical interphase overpotential as a lithium dendrite-suppression criterion for all-solid-state lithium battery design

Critical current density (CCD) is currently used to evaluate Li dendrite-suppression capability of solid-state electrolytes (SSEs). However, CCD values vary with engineering parameters, resulting in a large deviation of CCD values for the same SSE. Herein we evaluate lithium dendrite-suppression capability of SSEs using critical interphase overpotential (CIOP). The CIOP is the intrinsic property of the interphase, which depends on electronic/ionic conductivity, lithiophobicity and mechanical strength. When the applied interphase overpotential (AIOP) is larger than CIOP, Li will grow into interphase as dendrites. To reduce AIOP but increase CIOP, we design a mix-conductive Li2NH-Mg interlayer between Li6PS5Cl SSE and Li-1.0 wt% La anode, which transfers into Li6PS5Cl/LiMgSx/LiH-Li3N/LiMgLa after Mg migration during annealing and activation cycles. The LiMgSx interphase increases the CIOP from ~10 mV (for Li6PS5Cl) to ~220 mV. The Li plates on the LiMgLa surface, and reversible penetration into formed porous LiH-Li3N reduces AIOP. The CIOP provides a design guideline for high-energy and room temperature all-solid-state lithium-metal batteries.