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