Critical Interphase Overpotential as a Lithium Dendrite Suppression Criterion for All-Solid-State Lithium Battery Design

Suppressing Li dendrite growth is a crucial challenge in the development of all-solid-state Li-metal batteries (ASSLBs). Penetration of Li dendrites through the solid-state electrolyte (SSE) can lead to short-circuiting of the cells, presenting a safety concern. The current density at which Li dendrites penetrate through the SSE and cause short-circuiting is termed the critical current density (CCD). The CCD not only depends on the intrinsic properties of the SSE but also on the thickness of the SSE. Furthermore, as the Li plating or stripping capacity, stack pressure, and interfacial resistance change the overpotential, which is the driving force for Li plating and stripping, these factors also change the CCD. Thus, because the CCD is not an intrinsic property of an SSE, it is difficult to use CCDs to design SSEs. Herein, we evaluate the lithium dendrite suppression capability of SSE 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-1.0wt%La anode, which transfers into Li₆PS₅Cl/LiMgS<i>_x</i>/LiH-Li₃N/LiMgLa after Mg migration during annealing and activation cycles. The LiMgS<i>_x </i>interphase increases the CIOP from 9~12mV (of Li₆PS₅Cl) to ~220mV. The Li plates on LiMgLa surface and reversible penetration into the formed porous LiH-Li₃N reducing AIOP. The CIOP provides design guidelines for high-energy and room-temperature all-solid-state lithium-metal batteries.