Design of cation doped Li7P2S8Br I sulfide electrolyte with improved conductivity and stable interfacial properties for all-solid-state lithium batteries

Sulfide-based lithium-ion solid electrolytes have attracted extensive attention due to their unique superiority such as high ionic conductivity, safety, and compatibility. In this work, the dual-halide anions and series cations like Zn, Si, Mo and Sb were first tried co-doping/substitution in sulfide solid electrolyte by ball milling process and low-temperature heat treatment (180°C). A series of cations was substituted for the P-site to further improve the conductive properties of the solid electrolytes. The optimized glass-ceramic phase LPSZn0.05Br0.2I0.8 solid electrolyte obtained a high ionic conductivity of 3.98 mS cm−1 at room temperature. Additionally, the LPSZn0.05Br0.2I0.8 solid electrolyte cycled stably for 500 h at a current density of 0.2 mA cm−2 with low and constant interfacial resistance (16 Ω). A series of characterization results indicated that the radius size effect of halides and cations enlarged ions transport channels, promoting the effective mobility of Li+ inside the channel structure. Meanwhile, the Br-I dual-doped electrolyte largely facilitated the formation of thio-LISICON II high ionic conducting phase. The addition of large Zn atoms partially occupied P-site further prolonged the lattice parameters of conductive crystals, thus wholly contributed to the ion movement inside the solid electrolyte.