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

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-B-Mo₂C@NC) is designed <i>via</i> facile boron-doping engineering, which simultaneously mitigates LiPS shuttling and facilitates sulfur conversion reactions. The incorporation of boron dopants into the δ-B-Mo₂C@NC framework significantly increases active sites and enhances electron/ion pathways, synergistically promoting strong adsorption and efficient catalytic conversion for LiPSs. Moreover, the electronic structure of δ-B-Mo₂C is optimized by upshifting the Mo d-band center. This enhancement promotes stronger Mo 4d/S 3p orbital hybridization between δ-B-Mo₂C@NC and LiPSs, thus accelerating sulfur redox kinetics. Consequently, the LSB equipped with the δ-B-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 Mo₂C-based catalysts in suppressing the shuttle effect and pave the way for designing advanced electrocatalysts toward high-energy and long-life LSBs.