Vacancy‐Engineered Ceria Enables 4f‐Orbital‐Driven Redox Catalysis for Bidirectional Sulfur Conversion in Li─S Batteries
Jiaqin Liu, Han Zhuo, Xiaofei Zhang, Yulei Li, Yan Yu, Tongzhen Wang, Jiewu Cui, Yue Tian, Jian Yan, Yan Yu, Yucheng Wu
Abstract
Abstract Redox‐flexible rare‐earth catalysts featuring partially filled 4f orbitals enable orbital‐level modulation of sulfur electrochemistry. Here, an oxygen‐vacancy‐engineered CeO 2 /carbon nanotube (O v ‐CeO 2 /CNT) composite is reported, configured as a conformal catalytic layer on a commercial separator, to regulate polysulfide redox reactions in lithium‐sulfur (Li─S) batteries. In situ and ex situ characterizations, corroborated by DFT calculations, reveal that oxygen vacancies dynamically modulate the Ce electronic environment, enabling reversible Ce 3+ (4f 1 )/Ce 4+ (4f 0 ) redox cycling and interfacial charge transfer. This vacancy‐induced orbital hybridization between Ce‐4f/S‐3p and Li‐2s/O‐2p states enhances LiPS adsorption, lowers the barriers for Li 2 S nucleation and decomposition, and facilitates ion transport, thereby accelerating bidirectional sulfur conversion and ensuring stable redox reversibility. As a result, the designed cell achieves long‐term durability (743.2 mAh g −1 after 1000 cycles at 0.5C), high‐rate capability (up to 5C), and high energy density in pouch cells. This work establishes 4f‐orbital‐mediated defect engineering as a scalable and effective strategy for designing redox‐regulating catalysts in high‐performance Li─S batteries.