Preparation and characterization of 2Na3SbS4·Na2WS4 and 2Na3SbS4·Na4XS4 (X = Si, Ge, Sn) glass–ceramic electrolytes

Abstract Solid Na‐ion‐conducting sulfides exhibited potential applications for commercial solid‐state rechargeable batteries because of their low cost and good contact with the electrode. In the present work, a sulfide sodium‐ion conductor 2Na 3 SbS 4 ·Na 2 WS 4 with a conductivity of 1.55 mS cm −1 was obtained, which was identified as superior to the 2Na 3 SbS 4 ·Na 4 XS 4 (X = Si, Ge, Sn) systems. Further exploration of the heat treatment to improve the crystallinity of the glass resulted in a high conductivity of 1.9 mS cm −1 and low activation energy of 0.24 eV for the 2Na 3 SbS 4 ·Na 2 WS 4 glass–ceramic electrolyte. The high crystallinity after heat treatment at 380°C facilitated the migration of Na + together with large sodium vacancies formed by doping with W 6+ in 2Na 3 SbS 4 ·Na 2 WS 4 glass–ceramic electrolyte, resulting in the improved electrochemical performance. In addition, the air stability of the 2Na 3 SbS 4 ·Na 2 WS 4 glass–ceramic electrolyte decreased monotonically with increase of the annealing temperature, and heat application at 380°C effectively improved the electrolyte tolerance to the air compared with pure Na 3 PS 4 electrolyte. The origins of aliovalent ion doping and thermal effect on the electrochemical performance were discussed in detail.