Mechanochemical synthesis of Na<sub>3</sub>NbS<sub>4</sub> metastable phase as positive electrode materials for all-solid-state sodium batteries

Transition metal sulfides have been reported to be active materials with high capacities by using anionic redox reactions. Modifying the structure favor extraction/insertion of sodium is beneficial in achieving theoretical capacity these sulfides. In this study, we synthesized three new phases Na3NbS4 via a mechanochemical (MC) process. Under moderate MC conditions, amorphous was obtained. harsher metastable I and II were obtained at different process times 10 40 h, respectively. The conductivities higher than that orthorhombic Na3NbS4. particular, phase showed highest conductivity 3.2 × 10−6 S cm−1, all-solid-state cells as an electrode material 240 mAh g−1. Thus, useful for synthesizing positive on transition advantageous achieve capacity.