Dual-engineering of tungsten doping and carbon incorporation in vanadium carbide arrays to accelerate the polysulfide conversion for lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries are promising candidates for next-generation electrochemical energy storage systems by virtue of the high energy density, low-cost, and ecofriendliness. Unfortunately, the sluggish sulfur conversion kinetics, notorious shuttle effect of lithium polysulfides (LiPSs) and severe volumetric variation during the lithiation/delithiation process result in insufficient sulfur utilization and fast capacity degradation. Herein, tungsten-doped vanadium carbide nanosheet arrays strongly coupled with a thin nitrogen-doped carbon layer directly grown on carbon cloth substrate (denoted as CC/W-VC@NC) have been conceptually designed as an advanced sulfur host to resolve the aforementioned problems. Specifically, the binder-free CC/W-VC@NC sulfur host not only strongly interacts with LiPSs, but also presents superior electrocatalytic activity for rapid LiPSs conversion. Additionally, the arrayed architecture provides sufficient space for sulfur loading and simultaneously accommodates its volumetric variation. Furthermore, theoretical calculations elucidate that tungsten doping can regulate the electronic structure, improve the electrical conductivity and strengthen the chemisorption toward LiPSs. Attributing to the multifarious advantages, Li-S batteries assembled with CC/W-VC@NC/S cathode exhibit a high initial discharge capacity of 1305.9 mAh/g at 0.1 C, as well as superior rate capability (709.8 mAh/g at 5 C) and good long-term durability (capacity decay rate of only 0.063 % per cycle over 500 cycles at 1 C). This study presents an effective approach to construct transition metal carbides as high-performance sulfur hosts for Li-S batteries.