Enhancing ionic conductivity of solid electrolyte by lithium substitution in halogenated Li-Argyrodite

The demand for batteries with high safety and high energy density produces considerable efforts toward the development of all-solid-batteries and solid state electrolytes. Halogen-substituted lithium argyrodites, Li6PS5X (X = Cl, Br), represent a class of promising and suitable sulfide-based solid electrolytes with high conductivity and good processability. To further extend the scope and better understand the structure-property relationship, we systematically explore the effect of partial substitution of Li+ by other cations in Li6PS5X (X = Cl, Br). The X-ray diffraction (XRD) analysis shows the possibility of successful substitution at Li+ position by various cations. Among them, substitution with a small amount of Al3+ in Li6PS5Br is confirmed by Rietveld refinements. The ionic conductivity is improved by almost three times to 2.4 × 10−3 S cm−1. This improvement is attributed to the shortened distances of inter-cage jumps. In addition, the substituted sample shows better electrochemical performance in all-solid-state batteries. This work demonstrates the feasibility of performance improvement by manipulating the position of Li+ in the structure of lithium argyrodites, which provides a versatile approach toward designing better performing solid electrolytes.