Tungsten and Boron Codoping toward High Ionic Conductivity and Stable Sodium Solid Electrolyte for All-Solid-State Sodium Batteries.

Sodium solid electrolytes with high ionic conductivity and good interfacial stability with sodium metal are crucial to realize high-performance all-solid-state sodium batteries. In this work, W and B-codoped Na 3 Sb 1- x W x S 4- x B x solid electrolytes are prepared by melt-quenching with further annealing. The synthesized Na 3 Sb 0.95 W 0.05 S 3.95 B 0.05 solid electrolyte possesses a high ionic conductivity of 11.06 mS cm -1 under 25 °C and shows significantly improved interface compatibility with metal sodium. Specifically, Na/Na 3 Sb 0.95 W 0.05 S 3.95 B 0.05 /Na symmetric cell can stable cycle for 500 h under a current density of 0.05 mA cm -2 . In addition, the resultant TiS 2 /Na 3 Sb 0.95 W 0.05 S 3.95 B 0.05 /Na battery exhibits an initial charge capacity of 164.1 mAh g -1 at 0.1 C with a capacity retention of 76.4% after 100 cycles. This work provides a new strategy to realize the high ionic conductivity of sodium solid electrolytes with improved interfacial stability with sodium anode.