Chlorine-Rich NaPSCl: A Promising Sodium Solid Electrolyte for All-Solid-State Sodium Batteries.

Developing argyrodite-type, chlorine-rich, sodium-ion, solid-state electrolytes with high conductivity is a long-term challenge that is crucial for the advancement of all-solid-state batteries (ASSBs). In this study, chlorine-rich, argyrodite-type NaPSCl solid solutions were successfully developed with a solid solution formation range of 0 ≤ ≤ 0.5. NaPSCl ( = 0.5), displaying a highest ionic conductivity of 1.2 × 10 S/cm at 25 °C, which is more than a hundred times higher than that of NaPSCl. Cyclic voltammetry and electrochemical impedance spectroscopy results demonstrated that the rich chlorine significantly enhanced the ionic conductivity and electrochemical stability, in addition to causing a reduction in activation energy. The NaPSCl composite also showed the characteristics of a pure ionic conductor without electronic conductivity. Finally, the viability of NaPSCl as a sodium electrolyte for all-solid-state sodium batteries was checked in a lab-scale ASSB, showing stable battery performance. This study not only demonstrates new composites of sodium-ionic, solid-state electrolytes with relatively high conductivity but also provides an anion-modulation strategy to enhance the ionic conductivity of argyrodite-type sodium solid-state ionic conductors.