Nanostructured FexSbyOz Composites as Anode Materials for Sodium-Ion Batteries

Nanostructured FexSbyOz composites were developed via a galvanic replacement reaction. Two different galvanic replacement reaction times were used to control the morphology of the composite material. The structure, morphology, and composition of the as-prepared composites were characterized by X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. It was observed that the FexSbyOz composites consisted of the Sb/Sb2O3/Fe3O4 phases. When evaluated as anode materials for sodium-ion batteries, the composites exhibited a high coulombic efficiency, excellent cycling stability, and high rate capability. The excellent electrochemical performance of the composites could be ascribed to the synergistic effect involving conversion and alloying reactions between Sb/Sb2O3/Fe3O4 and Na+ ions. Specifically, conversion reactions between Na+-ions and Sb2O3 or Fe3O4 generated amorphous Na2O and the inactive conductive phase of Fe, which could act as an effective buffer against volume changes during cycling, resulting in improved cycling performance.