Dredging sodium polysulfides using a Fe3C electrocatalyst to realize improved room-temperature Na-S batteries

The shuttle effect of soluble polysulfides is a critical challenge that hinders the realization of pragmatic room-temperature sodium-sulfur (RT Na-S) batteries. To surmount this intractable issue, carbon nanorods decorated with highly sulfiphilic nanosized cementite (nano-Fe3C) are employed to serve as the role of S host. The nano-Fe3C strongly interacts with soluble polysulfide intermediates via Fe-S bonds to block their shuttling action. More significantly, the nano-Fe3C enables the dredging of these polysulfides via its electrocatalytic effect, which is accompanied by improved redox kinetics. Moreover, the hierarchical porous carbon nanorod substrate promotes the fast transport of electrons and accommodates the dramatic volumetric fluctuation of the active materials. As a result, the nano-Fe3C-decorated S cathode demonstrates outstanding cyclability (capacity retention of 373 mA h g−1 over 900 cycles at 1.0 A g−1). This work presents an excellent highly efficient electrocatalyst that realizes improved RT Na-S batteries.