P‐Band Center Engineering of Sulfur to Weaken Fe─S Bond Toward Superior Sodium‐Ion Storage
Yuhang Li, Xia Wen, Yinuo Li, Yulin Jiang, Xiaohui Li, Du Zhu, Hang Sun, Yanan Peng, Luying Song, Rui‐Hua Xu, Ling Huang, Chuxuan Xiao, Jianping Shi
Abstract
Abstract Iron‐based sulfides are appealing anodes of sodium‐ion batteries (SIBs) due to the high theoretical capacity, low‐cost, and excellent mechanical/thermal stability. However, achieving high electrochemical performances in such anodes is hindered by the strong Fe─S bonds and sluggish kinetics. Here, a unique carbon‐coated iron sulfide composite with abundant S vacancies (v‐FeS 2 @C) is designed, the spin polarization and S vacancy lift the p‐band center ( ɛ p ) of S and then decouple it from the d‐band center ( ɛ d ) of Fe, which weakens Fe─S bond and strengthens Na─S interaction. The obtained v‐FeS 2 @C anode exhibits ultrahigh rate capability of 438.0 mAh g −1 at 70 A g −1 and remarkable long‐life cycle performance (512.5 mAh g −1 after 8000 cycles at 40 A g −1 ). Particularly, the sodium‐ion full cell composed of v‐FeS 2 @C anode and Na 3 V 2 (PO 4 ) 3 cathode delivers the best specific capacity (211.5 mAh g −1 at 40 A g −1 ) and long cyclic stability (459.5 mAh g −1 after 2000 cycles at 5 A g −1 ). Such performances are much more superior to those of the other iron‐based sulfides. This work provides a new paradigm for boosting SIBs' performances of iron‐based sulfides by regulating p‐band center ( ɛ p ) of S and weakening Fe─S bonds.