Nanoscaled Na₃PS₄ Solid Electrolyte for All-Solid-State FeS₂/Na Batteries with Ultrahigh Initial Coulombic Efficiency...

Nanosized Na₃PS₄ solid electrolyte with an ionic conductivity of 8.44 × 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 cycling at 60 mA g^-1 for 100 cycles, showing a high capacity of 287 mAh g^-1 with the capacity retention of 80%.