A Scalable Strategy To Develop Advanced Anode for Sodium-Ion Batteries: Commercial FeO-Derived FeO@FeS with Superior Full-Cell Performance.

A novel core-shell FeO@FeS composed of FeO core and FeS shell with the morphology of regular octahedra has been prepared via a facile and scalable strategy via employing commercial FeO as the precursor. When used as anode material for sodium-ion batteries (SIBs), the prepared FeO@FeS combines the merits of FeS and FeO with high Na-storage capacity and superior cycling stability, respectively. The optimized FeO@FeS electrode shows ultralong cycle life and outstanding rate capability. For instance, it remains a capacity retention of 90.8% with a reversible capacity of 169 mAh g after 750 cycles at 0.2 A g and 151 mAh g at a high current density of 2 A g, which is about 7.5 times in comparison to the Na-storage capacity of commercial FeO. More importantly, the prepared FeO@FeS also exhibits excellent full-cell performance. The assembled FeO@FeS//NaV(PO)OF sodium-ion full battery gives a reversible capacity of 157 mAh g after 50 cycles at 0.5 A g with a capacity retention of 92.3% and the Coulombic efficiency of around 100%, demonstrating its applicability for sodium-ion full batteries as a promising anode. Furthermore, it is also disclosed that such superior electrochemical properties can be attributed to the pseudocapacitive behavior of FeS shell as demonstrated by the kinetics studies as well as the core-shell structure. In view of the large-scale availability of commercial precursor and ease of preparation, this study provide a scalable strategy to develop advanced anode materials for SIBs.