Steering Bidirectional Sulfur Redox via Geometric/Electronic Mediator Comodulation for Li-S Batteries.

Ding, Yifan; Shi, Zixiong; Sun, Yingjie; Wu, Jianghua; Pan, Xiaoqing; Sun, Jingyu · ACS Nano · 2023

basic_science · Level V

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Abstract

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<sup>-2</sup>, the cell could sustain a durable areal capacity of 4.63 mAh cm<sup>-2</sup>. 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.