Enhancing Ionic Conductivity and Electrochemical Stability of Li₃PS₄ via Zn, F Co-Doping for All-Solid-State Li–S Batteries

Abstract

Sulfide solid-state electrolytes have garnered considerable attention owing to their notable ionic conductivity and mechanical properties. However, achieving an electrolyte characterized by both high ionic conductivity and a stable interface between the electrode and electrolyte remains challenging, impeding its widespread application. In this work, we present a novel sulfide solid-state electrolyte, Li_3.04P_0.96Zn_0.04S_3.92F_0.08, prepared through a solid-phase reaction, and explore its usage in all-solid-state lithium sulfur batteries (ASSLSBs). The findings reveal that the Zn, F co-doped solid-state electrolyte exhibits an ionic conductivity of 1.23 × 10^-3 S cm^-1 and a low activation energy (<i>E</i>_a) of 9.8 kJ mol^-1 at room temperature, illustrating the aliovalent co-doping's facilitation of Li-ion migration. Furthermore, benefiting from the formation of a LiF-rich interfacial layer between the electrolyte and the Li metal anode, the Li/Li_3.04P_0.96Zn_0.04S_3.92F_0.08/Li symmetrical cell exhibits critical current densities (CCDs) of up to 1 mA cm^-2 and maintains excellent cycling stability. Finally, the assembled ASSLSBs exhibit an initial discharge capacity of 1295.7 mAh g^-1 at a rate of 0.05 C and at room temperature. The cell maintains a capacity retention of 70.5% for more than 600 cycles at a high rate of 2 C, representing a substantial improvement compared to the cell with Li₃PS₄. This work provides a new idea for the design of solid-state electrolytes and ASSLSBs.