In Situ Thermally-Driven Radial Heterophase Evolution of δ-Bi<sub>2</sub>O<sub>3</sub> Modulates the p-Block Bi 6p Orbitals and p-Band Center for Enhancing Sulfur Redox Reactions.

Hu, Shunyou; Li, Yancen; Zhang, Huanchun; Huang, Xueyan; Wang, Xing; Sun, Shaochao; Yi, Mingjie; Yan, Qiang et al. · Adv Mater · 2026

basic_science · Level V

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Abstract

The commercialization of lithium-sulfur batteries is hindered by challenges such as the shuttle effect of lithium polysulfides (LiPSs), slow sulfur redox reaction kinetics, and poor electrical conductivity. The electronic configuration of the p-block Bi 6p orbitals is modulated through an in situ thermally-induced reduction strategy using lignin-based carbon nanofibers (CNFs). This approach enables the radial gradient heterophase transformation of δ-Bi<sub>2</sub>O<sub>3</sub>, leading to the formation of a high-density heterojunction network composite (δ-Bi<sub>2</sub>O<sub>3</sub>-O<sub>VS</sub>/Bi@CNFs) rich in oxygen vacancies (O<sub>VS</sub>), which effectively moderates the adsorption of LiPSs and enhances the kinetics of sulfur redox reactions. Based on the δ-Bi<sub>2</sub>O<sub>3</sub>-O<sub>VS</sub>/Bi@CNFs, a high-energy-density (377 Wh kg<sup>-1</sup>) pouch cell with a capacity of 1.8 Ah is fabricated and successfully used in drone flights, highlighting its potential for practical applications. This work elucidates the mechanism of in situ thermally-induced radial-gradient heterophase evolution of p-block metal oxides and the influence of 6p-orbital electron modulation on the sulfur redox reaction.