Boron-doping engineering of molybdenum carbide on nitrogen-rich carbon nanosphere: A synergistic adsorption-conversion modifier for high-performance lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) hold significant promise for next-generation energy storage due to the ultrahigh potential energy density. However, their commercialization is hindered by the shuttle effect and sluggish reaction kinetics of lithium polysulfides (LiPSs). Herein, a hierarchical catalyst composed of cubic Mo2C nanoparticles anchored on N-doped carbon nanospheres (δ-Mo2C@NC) is designed via a facile boron-doping engineering, which simultaneously mitigates LiPSs shuttling and facilitates sulfur conversion reactions. The incorporation of boron dopant into the δ-Mo2C@NC framework significantly increases active sites and enhances electron/ion pathways, synergistically promoing strong adsorption and efficient catalytic conversion for LiPSs. Moreover, the electronic structure of δ-Mo2C is optimized by upshifting the Mo d-band center. This enhancement promotes stronger Mo 3d/S 2p orbital hybridization between δ-Mo2C@NC and LiPSs, thus accelerating sulfur redox kinetics. Consequently, the LSB equipped with the δ-Mo2C@NC catalyst exhibits remarkable rate capability (459 mAh g-1 at 3 A g-1) and long-term cycling stability (a capacity decay of 0.045% per cycle over 500 cycles at 1 A g-1). These findings highlight the potential of δ-Mo2C-based catalysts in suppressing shuttle effect and paves the way for designing advanced electrocatalysts toward high-energy and long-life LSBs.