Oxygen vacancy-mediated amorphous GeO_x assisted polysulfide redox kinetics for room-temperature sodium-sulfur...

The practical applications of room-temperature sodium-sulfur (RT Na-S) batteries have been greatly hindered by the natural sluggish reaction kinetics of sulfur and the shuttle effect of sodium polysulfide (NaPSs). Herein, oxygen vacancy (OV)-mediated amorphous GeO_x/nitrogen doped carbon (donated as GeO_x/NC) composites were well designed as sulfur hosts for RT Na-S batteries. Experimental and density functional theory studies show that the introduction of oxygen vacancies on GeO_x/NC can effectively immobilize polysulfides and accelerate the redox kinetics of polysulfides. Meanwhile, the micro-and mesoporous framework, acting as a reactor for storing active S, is conducive to alleviating the expansion of S during the charging/discharging process. Consequently, the S@GeO_x/NC cathode affords a reversible capacity of 1017 mA h g^-1 at 0.1 A g^-1 after 100 cycles, outstanding rate capability of 333 mA h g^-1 at 10.0 A g^-1 and long lifespan cyclability of 385 mAh g^-1 at 1 A g^-1 after 1200 cycles. This work furnishes a new way for the rational design of metal oxides with oxygen vacancies and boosts the application for RT Na-S batteries.