First-Principles Calculation Study on the Interfacial Stability Between Zr and F Co-Doped Li6PS5Cl and Lithium Metal Anode

Li-Argyrodite-type Li6PS5Cl solid electrolyte is one of the most extensively investigated and promising materials in the field of all-solid-state batteries. However, its interfacial stability against lithium metal anodes remains challenging. Herein, first-principles calculations were employed to probe the effects of Zr and F co-doping on the interfacial structural characteristics of Li6P0.9Zr0.1S4.9F0.1Cl solid electrolytes in contact with lithium metal at the atomic scale. Systematic investigations were conducted on interfacial structural stability, electronic structure, lithium-ion transport properties, and stress–strain properties. Theoretical results demonstrate that the formation energy of sulfur on the lithium metal side in the Zr and F co-doped interface is significantly increased, which stems from the strong bonding interactions of Zr–S and P-F bonds. This effectively suppresses sulfur diffusion toward the lithium metal anode, thereby enhancing the interfacial structural stability. Moreover, Zr and F co-doping simultaneously improves both the lithium-ion migration capability and mechanical stress–strain properties at the interface. The maximum strain at the Li/Li6PS5Cl interface increases substantially from 6% to 12% with the implementation of Zr/F co-doping. The Li+ migration barrier at the interface exhibits a reduction of 36%. The insights from this study can serve as a design guideline for engineering high-performance solid electrolytes for all-solid-state batteries.