Sodium insertion/extraction investigations into zinc ferrite nanospheres as a high performance anode material

Abstract

Electrode materials with high fast charging and high capacity are urgently required for the realization of sodium-ion batteries (SIBs). In this work, zinc ferrite (ZnFe₂O₄) nanospheres have been prepared by the simple hydrothermal route and the structural analysis of ZnFe₂O₄ was evaluated by using X-ray diffraction. The morphology and microstructural characterizations are obtained using scanning electron microscopy and transmission electron microscopy. The results indicate that a single phase material was obtained with uniform sphere-like morphology and high crystallinity. The Brunauer–Emmett–Teller method was employed to determine the specific surface area of the ZnFe₂O₄ nanospheres which has been calculated to be 32 m² g⁻¹. The electrochemical results indicate that the composite possesses high sodium storage capability (478 mA h g⁻¹), and good cycling stability (284 mA h g⁻¹ at 100^th cycle) and rate capability (78 mA h g⁻¹ at 2 A g⁻¹). The high sodium storage performance of the ZnFe₂O₄ electrode is ascribed to the mesoporous nature of the ZnFe₂O₄ nanospheres. Further, sodium kinetics and the reaction mechanism in ZnFe₂O₄ nanospheres have been elucidated using electrochemical impedance spectroscopy, galvanostatic intermittent titration technique, ex situ TEM, and XAS. The acquired results indicate sluggish kinetics, reversibility of the material, and the stable structure of ZnFe₂O₄. Therefore, such a structure can be considered to be an attractive contender as a low cost anode for SIBs.