Progress on iron oxides and chalcogenides as anodes for sodium-ion batteries

As one of the most promising candidate devices in large-scale energy storage applications for renewable energy, sodium-ion batteries (NIBs) have attracted great attention due to the inexpensive cost and abundant sodium sources in earth's crust. To exert the cost advantage for NIBs, earth-abundant electrode materials are essential. Recent studies have demonstrated that various iron-based materials, such as iron oxides and chalcogenides can be regarded as potential anode candidates for NIBs. In this review, recent progress on iron-based materials as anodes for NIBs is summarized. The corresponding structural designs, achievable capacities and electrochemical mechanisms are also briefly discussed. Based on this extensive literature review, there are still some existing challenges for these anode materials. In addition, outlooks on the possible further research directions are presented.