Sulfur in amorphous silica for advanced room-temperature sodium-sulfur battery.

Room-temperature (RT) sodium-sulfur (Na/S) battery has been considered as a promising energy storage system due 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 the help of amorphous porous silica as a sulfur host. The sulfur is loaded into amorphous silica by a facile dipping method, and the optimal sulfur loading can be as high as 73.48 wt.%. The 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 (i.e., average discharge capacities of 1106, 1074, 1060, 1036, and 1000 mAh·g -1 at 1, 2, 3, 5, and 10 A·g -1 , respectively.) and an excellent cyclability even at 10 A·g -1 (nearly 100% coulomb efficiency and high reversible capacity of 955.8 mAh·g -1 after 1460 cycles). The present results introduce new insights into the inhibition of "shuttle effect" of sodium polysulfide and develop a promising sulfur electrode for advanced RT sodium-sulfur batteries.