Schottky-type oxygen defect and orbital engineering of bismuth oxide for boosting sulfur redox kinetics

Lithium-sulfur (Li||S) batteries face significant challenges due to the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs). In this work, Schottky-type oxygen vacancies-enriched p-block bismuth oxide (S-O_VS-Bi₂O₃) is integrated onto lignin-derived carbon nanofibers (CNFs), forming a functional layer (S-O_VS-Bi₂O₃@CNFs) on the separator of high-performance Li||S batteries. Schottky-type oxygen vacancies induce localized crystal lattice distortions, which in turn alter the spatial distribution of the local electronic density, modify the band structures of S-O_VS-Bi₂O₃, narrow the band gap, and enhance electronic conductivity by promoting interband electron transfer. In situ characterizations confirm that S-O_VS-Bi₂O₃ effectively mitigates the shuttle effect and facilitates the redox reactions of LiPSs. The S-Ovs-Bi₂O₃@CNFs-based cells exhibit a cyclability of 630 mAh g⁻¹ at 1 C over 1000 cycles with a degradation rate of 0.032 % per cycle, and a high areal capacity of 4.36 mAh cm⁻² under a high sulfur loading of 7.0 mg cm⁻². This work highlights the influence of Schottky-type-vacancy-induced modulation of the p-orbital electronic configuration and p-band center, which lowers antibonding energy, improves electron occupancy in antibonding orbitals, and optimizes the chemical adsorption for LiPSs, offering valuable insights for the design of future electrocatalysts in energy storage applications.