Selenium Doping Enhances the Conductivity of Liquid Phase Synthesized Na3PS4 as a Solid Electrolyte for All Solid State Sodium Batteries

Abstract

A scalable, cost-effective liquid-phase synthesis method has shown promise for producing Na3PS4 solid electrolytes. However, the ionic conductivity of the resulting solid electrolyte has been insufficient for applications in all-solid state sodium batteries. In this work, solid electrolytes in which selenium (Se) partially substitutes phosphorus (P) in the series Na3+xP1-xSexS4 (0.000 ≤ x ≤ 0.150) are successfully synthesized via the liquid-phase method. The newly synthesized solid electrolytes retain the cubic structure of the glass-ceramic and demonstrate ionic conductivity comparable to Na3PS4 prepared by the ball-milling method. The synthesized samples are effectively applied in all-solid-state sodium batteries containing a TiS2-solid electrolyte composite as the cathode and Na15Sn4 as the anode, achieving an initial capacity of ≈125 mAh g−1 based on the weight of the TiS2.