Interfacial modulation of heterogeneous W/WN crystals enable efficient sulfur redox reactions in lithium‑sulfur...

Lithium‑sulfur (Li-S) batteries are considered as potential candidates for future-oriented energy storage system. However, its practical application still is hindered by the sluggish conversion kinetics and the notorious shuttle effect of lithium polysulfides (LiPSs). Here, a flexible interlayer consisting of heterogeneous W/WN crystals confined into porous nitrogen-doped carbon fibers (W/WN@PNCF) is developed to address above challenges. Specifically, the abundant porous structure in carbon fibers resulted from the Zn-template method provides sufficient exposed W/WN catalytically active sites and the strong physical capturing effect for the polysulfide intermediates. More important, the rich heterogeneous interface in the formed W/WN heterojunction presents unique electronic modulation effect, which as the actual active area enables moderate but efficient chemical-adsorption and remarkable catalytic activity for lithium polysulfides (LiPSs). Consequently, by using this W/WN@PNCF interlayer, the assembled Li-S batteries exhibit high specific capacity (1412.3 mAh g^-1 at 0.2C), excellent rate performance (814.5 mAh g^-1 at 5C) and stabled cycling capability. Moreover, a high areal capacity of 4.8 mAh cm^-2 is maintained after 120 cycles at 0.2C under a high sulfur loading of 7.1 mg cm^-2 and a low electrolyte/sulfur ratio of 6.0 μL mg^-1. This work provides insights into designing rational electronic structures of hetero-catalysts for the high-performance Li-S batteries.