Preparation and characterization of 2Na(3)SbS(4)center dot Na2WS4 and 2Na(3)SbS(4)center dot 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 2Na(3)SbS(4)center dot Na2WS4 with a conductivity of 1.55 mS cm(-1) was obtained, which was identified as superior to the 2Na(3)SbS(4)center dot 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 2Na(3)SbS(4)center dot Na2WS4 glass-ceramic electrolyte. The high crystallinity after heat treatment at 380 degrees C facilitated the migration of Na+ together with large sodium vacancies formed by doping with W6+ in 2Na(3)SbS(4)center dot Na2WS4 glass-ceramic electrolyte, resulting in the improved electrochemical performance. In addition, the air stability of the 2Na(3)SbS(4)center dot Na2WS4 glass-ceramic electrolyte decreased monotonically with increase of the annealing temperature, and heat application at 380 degrees 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.