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

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 2Na3SbS4·Na2WS4 with a conductivity of 1.55 mS cm−1 was obtained, which was identified as superior to the 2Na3SbS4·Na4XS4 (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 2Na3SbS4·Na2WS4 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 W6+ in 2Na3SbS4·Na2WS4 glass–ceramic electrolyte, resulting in the improved electrochemical performance. In addition, the air stability of the 2Na3SbS4·Na2WS4 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 Na3PS4 electrolyte. The origins of aliovalent ion doping and thermal effect on the electrochemical performance were discussed in detail.