Sulfur in Amorphous Silica for an Advanced Room-Temperature Sodium-Sulfur Battery.

The room-temperature (RT) Na/S battery is a promising energy storage system owing to suitable operating temperature, high theoretical energy density, and low cost. However, it has a poor cycle life and low reversible capacity. In this work, we report a long-life RT-Na/S battery with amorphous porous silica as a sulfur host. The sulfur is loaded into amorphous silica by a dipping method; the optimal sulfur loading is up to 73.48 wt %. Molecular dynamics simulation and first-principles calculations suggest that the complex pores, acting as micro-containers and the formation of Na-O chemical bonds between amorphous silica and sodium polysulfide, give the electrodes a strong ability to inhibit sodium polysulfide shuttle. This would give rise to effectively avoiding the loss of active sulfur, corresponding to a superior capacity and an excellent cyclability even at 10 A gsulfur -1 (nearly 100 % coulomb efficiency and high reversible capacity of 955.8 mAh gsulfur -1 after 1460 cycles).