Earth‐Abundant Fe‐Mn‐Based Compound Cathodes for Sodium‐Ion Batteries: Challenges and Progress

Abstract Sodium‐ion batteries (SIBs) with high energy/power density and low‐cost characteristics are deemed to be one of the best replacements to lithium‐ion batteries for utilizing in large‐scale electric energy storage (EES) devices. Fe‐Mn‐based cathode materials take the leading position in realizing high‐performance SIBs because of their high capacity, environment‐friendly, earth abundant, and low‐cost features, exhibiting huge commercial potential. However, the energy density and cyclic stability are still limited so far, considering the increasing demands for practical applications. In this review, aiming to better understanding the research level and currently existed sore points, the research progress is overviewed for several types of Fe‐Mn‐based cathode materials, including layered oxides, polyanionic compounds and Prussian blue analogues, and refine the electrochemical storage mechanism and structure–performance relationship. Finally, the representative electrochemical performances of these three kinds of cathode materials is summarized, compare the advantages and disadvantages of various materials, point out the existing key scientific problems of these materials, and propose the direction of development in near future. This review makes a thoroughly understanding for Fe‐Mn‐based cathode materials, providing new guidance for future research on SIBs toward real‐world applications.