New Na-Ion Solid Electrolytes Na4-xSn1-xSbxS4 (0.02 x 0.33) for All-Solid-State Na-Ion Batteries

Sulfide Na-ion solid electrolytes (SEs) are key to enable room-temperature operable all-solid-state Na-ion batteries that are attractive for large-scale energy storage applications. To date, few sulfide Na-ion SEs have been developed and most of the SEs developed contain P and suffer from poor chemical stability. Herein, discovery of a new structural class of tetragonal Na4-xSn1-xSbxS4 (0.02 x 0.33) with space group I4(1)/acd is described. The evolution of a new phase, distinctly different from Na4SnS4 or Na3SbS4, allows fast ionic conduction in 3D pathways (0.2-0.5 mS cm(-1) at 30 degrees C). Moreover, their excellent air stability and reversible dissolution in water and precipitation are highlighted. Specifically, TiS2/Na-Sn all-solid-state Na-ion batteries using Na3.75Sn0.75Sb0.25S4 demonstrates high capacity (201 mA h (g of TiS2)(-1)) with excellent reversibility.