Pyridinic-N-rich single-atom vanadium catalysts boost conversion kinetics of polysulfides for high performance lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries are promising next-generation energy storage devices possessing a high theoretical energy density, but their practical deployment has been hindered by the notorious shuttle effect and sluggish conversion kinetics of soluble lithium polysulfides (LiPSs). In this work, single-atom vanadium catalysts (V-SACs) embedded in pyridinic-N-rich carbon are developed through a simple one-step polymer-assisted pyrolysis approach, which can effectively adsorb LiPSs and remarkably boost the kinetics of LiPSs conversion. The Li-S cells comprising pyridinic-N-rich V-SACs as the sulfur host display an initial discharge capacity of 921.1 mAh g−1 at 1 C and retain a capacity of 605.8 mAh g−1 after 500 cycles, showing a low decay rate of 0.068 % per cycle. Even with a high sulfur loading of 6.5 mg cm−2 and a low electrolyte/sulfur ratio of 7.5 μL mg−1, the cell still delivers a high initial areal capacity of 8.1 mAh cm−2 at 0.05 C. Comprehensive experimental studies and density functional theory (DFT) calculations demonstrate that the abundant pyridinic-N sites and vanadium single atoms afford more chemisorption sites for LiPSs and synergistically promote LiPSs conversion kinetics, resulting in enhanced electrochemical performance compared to the Li-S cells without V-SACs.