Immobilization and accelerated conversion of polysulfides by vanadium-regulated metal sulfide catalysts for Li-S battery

Abstract

Lithium-sulfur batteries possess significant potential due to their high energy density and cost-effectiveness. However, sluggish redox kinetics, polysulfide shuttle effects, and the inadequate oxidation of Li2S impede their practical application. To overcome these challenges, electrocatalysts with high intrinsic activity are essential for enhancing performance. Herein, by using an innovative double-solvent method (DSM), we synthesized the vanadium-doped Co9S8 encapsulated in porous carbon nanoflowers (V-Co9S8), which are designed to serve as sulfur hosts. Nanoflower structures can shorten the path of electron transmission, increase the migration rate of electrons in electrode materials, and simultaneously enhance the exposure of active sites. The theoretical calculations and experimental investigations consistently discover that vanadium atoms enhance the binding energies between lithium polysulfides (LiPSs) and Co9S8, while also mitigating the sluggish kinetics of LiPSs in Li-S batteries. As a result, the V-Co9S8 cathode demonstrates remarkable cycling stability, achieving a capacity of 1458 mAh g-1 at 0.1 C and 588 mAh g-1 at 2.0 C. This study highlights the significance of atomic engineering in catalyst design and advances the potential for practical application of Li-S batteries.