Liquid-Phase Synthesis of Nanosized Na11Sn2PS12 Solid Electrolytes for Room Temperature All-Solid-State Sodium Batteries

The nanosized Na11Sn2PS12 solid electrolyte with a particle size of around 200 nm is synthesized using the liquid-phase method using 1,2-dimethoxyethane. The sintering conditions for Na11Sn2PS12 crystallization are systematically optimized to maximize ionic conductivity. The highest room temperature ionic conductivity of the liquid-phase-synthesized Na11Sn2PS12 electrolytes (LP-Na11Sn2PS12) is 1.73 × 10–4 S cm–1, which is comparable with that of ball-milling samples (BM-Na11Sn2PS12) of 2.16 × 10–4 S cm–1. Both Na11Sn2PS12 electrolytes show an electrochemical window of 0.3–3.2 V. Moreover, the as-synthesized Na11Sn2PS12 electrolytes are employed as solid electrolytes in TiS2/Na11Sn2PS12/Na all-solid-state batteries. The TiS2/LP-Na11Sn2PS12/Na battery shows a higher reversible capacity of 142.4 mAh g–1 compared with 110.5 mAh g–1 for the TiS2/BM-Na11Sn2PS12/Na battery after 10 cycles under 20 mA g–1 at 25 °C. The better performance of the TiS2/LP-Na11Sn2PS12/Na battery can be ascribed to improved solid–solid contact between the electrolyte and the electrode arising from the nanosized particles of LP-Na11Sn2PS12 electrolytes.