Vanadium nitride nanocrystals decorated ultrathin, N-rich and hierarchically porous carbon nanosheets as superior polysulfides mediator for stable lithium-sulfur batteries

The diligent exploitation of high-efficiency polysulfides mediators have exhibited enormous prospects to pro-mote the cycling performance of lithium-sulfur (Li-S) batteries with desirable sulfur loading and high sulfur utilization efficiency. Herein, we craft an elaborated catalyst of ultrafine vanadium nitride nanocrystals confined hierarchically porous, ultrathin nitrogen-doped carbon nanosheets (denoted as VN@NC) via a simple approach. Owing to the highly conductive porous carbon framework integrated with enriched V-N-C active sites, well-heterostructured VN@NC can actively favor the entrapping-adsorption-catalytic conversion of the poly -sulfides intermediates for boosted surface redox kinetics. As the separator interlayer, VN@NC dedicates to high-performance Li-S batteries with high discharge capacities (1594.8 mAh g-1 at 0.1 C), excellent rate capabilities (766.5 mAh g-1 at 5.0 C) and exceptional cyclic durability by a slight decay of 0.067% per cycle upon 500 cycles at 1.0 C. Interestingly, two cycled Li-S batteries after 100 cycles at 0.5 C can be connected to charge a daily smartphone. Even under elevated sulfur loading of 4.5 mg cm-2 and lean electrolyte of 8 mu L mg -1, the assembled Li-S battery still maintains a stable cycling performance. The cost-effective VN@NC catalyst could offer a viable avenue to construct applicable sulfur catalysts for advanced Li-S batteries.

Automated summary

The diligent exploitation of high-efficiency polysulfides mediators can promote the cycling performance of lithium-sulfur batteries. In this study, a catalyst composed of ultrafine vanadium nitride nanocrystals confined in hierarchically porous, nitrogen-doped carbon nanosheets was developed. The catalyst showed excellent redox kinetics and stability, making it a viable option for advanced lithium-sulfur batteries.