Recent progress on nanostructured iron-based anodes beyond metal-organic frameworks for sodium-ion batteries

Considering the wide abundance and low cost of sodium resources and their similar electrochemistry to the well-established lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) have been regarded as potential alternatives to LIBs. Iron-based materials have attracted considerable attention as promising electrode materials for SIBs due to their high theoretical capacitance, natural abundance, and low cost. However, their sluggish reaction kinetics, accompanied with severe volume change during cycling sodiation/desodiation process and their unsatisfied electric conductivity, always leads to inferior long-term cycling stability and rate performance. To resolve these issues, significant and effective efforts have been made to improve their electrochemical performance, and great processes have been achieved. In this review, some recent progress on the development and design of nanostructured iron-based anodes, including oxides, chalcogenides, phosphides, nitrides, alloys, etc., are summarized, mainly focusing on the relationship between their structural features and sodium storage performance to understand the mechanisms behind the improvement of their sodium storage performance. In addition, the current challenges and future directions upon improving iron-based anodes for SIBs are briefly reviewed. These iron-based electrode materials are expected to be competitive and attractive electrodes for next-generation energy storage devices.