Vacancy‐Ordered Superstructure‐Induced Delocalized States Enable Superior Sodium Ion Storage

Abstract

AbstractTransition metal sulfides (TMSs) are perceived as competitive candidate anodes for sodium‐ion batteries (SIBs) on account of their high capacity and admirable reversibility. However, a majority of TMSs suffer from huge volume expansion and poor kinetics so they cannot achieve durable and fast Na+ storage. Herein, a cation vacancy‐ordered Cr2/3S is fabricated by extracting quantitative Cr atoms from nickel arsenide type CrS via sulfur “atomic pump,” that is, sulfur and particular sit Cr atoms are bonded to extend a new structure. The ordered vacancies not only construct a loosely‐packed crystal structure but also induce delocalized electron states of Cr atoms, hence effectively accelerating Na+ diffusion and releasing volume strain to enable high‐rate and longevous SIBs. The new Cr2/3S anode presents a high reversible capacity of 544 mAh g−1 after 100 cycles at 1 A g−1 and excellent high‐rate performance of ≈100% capacity retention after 7000 cycles at 20 A g−1. Subsequent in situ and ex situ characterizations reveal the Na+ storage mechanism of Cr2/3S. The proposed cation exaction strategy through an innovative sulfur “atomic pump” can be an efficient way to achieve loosely‐packed structure material for large‐capacity and fast‐kinetics anodes.