Mediator design has stimulated ever-increasing attention to help tackle a surge of detrimental caveats in Li-S realms, mainly pertaining to rampant polysulfide shuttling and sluggish redox kinetics. Nevertheless, universal designing philosophy, despite being highly sought-after, remains still elusive to date. Herein, we present a generic and simple material strategy to allow the target fabrication of advanced mediator toward boosted sulfur electrochemistry. This trick is done by the geometric/electronic comodulation of a prototype VN mediator, where the interplay of its triple-phase interface, favorable catalytic activity, and facile ion diffusivity is conducive to steering bidirectional sulfur redox kinetics. In laboratory tests, the thus-derived Li-S cells manifest impressive cyclic performances with a capacity decay rate of 0.07% per cycle over 500 cycles at 1.0 C. Moreover, under a sulfur loading of 5.0 mg cm-2, the cell could sustain a durable areal capacity of 4.63 mAh cm-2. Our work is anticipated to lay a theory-to-application foundation for rationalizing the design and modulation of reliable polysulfide mediators in working Li-S batteries.
Keywords: Li−S battery; bidirectional sulfur redox; comodulation; mediator; polysulfide conversion.