Regulating the Front-Line Orbital Energy Level Enables a High-Rate Performance for Lithium–Sulfur-Containing Polymer Batteries

Sulfur-containing polymers are promising cathode materials for lithium batteries, offering a novel pathway toward high-energy batteries. Moreover, tuning the frontier orbital energy levels of sulfur-containing polymers can accelerate the electrochemical reaction kinetics. Herein, an organic cathode material containing selenium is synthesized using a selenium sulfide solid solution via a previously proposed thiol-sulfur click chemistry reaction, which is a rubber-like material with good mechanical properties. According to front-line orbital theory, the introduction of a selenium group VI element like sulfur leads to sp 3 hybridization and S–Se covalent bond formation. Owing to the electronegativity disparity between sulfur and selenium, electrons accumulate near sulfur atoms, creating nucleophilic sites and continuous negative regions that promote Li + transport. As a result, the Li + diffusion coefficient increases from 9.7 × 10 –13 cm 2 S –1 to 2.7 × 10 –12 cm 2 S –1 . The bandgap narrows from 4.14 to 3.89 eV, facilitating the lithiation process and enhancing electrochemical performance. Among the cathode materials with different selenium contents, the fabricated materials exhibit a superior initial capacity of 580 mAh g –1 at 0.05 C and longer cycle stability. This study reveals how doping-modulated frontier orbital energy levels can be employed to enhance reaction kinetics, offering insights for improving sulfur containing polymers–lithium batteries’ performance.