Nanoscaled Na3PS4 Solid Electrolyte for All-Solid-State FeS2/Na Batteries with Ultrahigh Initial Coulombic Efficiency of 95% and Excellent Cyclic Performances

Nanosized Na3PS4 solid electrolyte with an ionic conductivity of 8.44 x 10(-5) S cm(-1) at room temperature is synthesized by a liquid-phase reaction. The resultant all-solid-state FeS2/Na3PS4/Na batteries show an extraordinary high initial Coulombic efficiency of 95% and demonstrate high energy density of 611 Wh kg(-1) at current density of 20 mA g(-1) at room temperature. The outstanding performances of the battery can be ascribed to good interface compatibility and intimate solid-solid contact at FeS2 electrode/nanosized Na3PS4 solid electrolytes interface. Meanwhile, excellent cycling stability is achieved for the battery after cyding at 60 mA g(-1) for 100 cydes, showing a high capacity of 287 mAh g(-1) with the capacity retention of 80%.