Mesoporous Graphitic Carbon‐Encapsulated Fe2O3 Nanocomposite as High‐Rate Anode Material for Sodium‐Ion Batteries

: A mesoporous graphitic carbon-encapsulated Fe2 O3 nanocomposite is synthesized as a superior anode material for sodium-ion batteries. A threefold strategy is adopted to achieve a high rate performance. First, the mesoporous structure with high specific surface area and large pore volume facilitates the transfer of electrolyte and accommodates the large volume change. Secondly, graphitic carbon encapsulation further improves the electronic conductivity of the nanocomposite. Finally, ultrafine Fe2 O3 nanocrystals effectively shorten the Na+ diffusion length. Consequently, this nanocomposite exhibits stable and fast Na+ storage, thus leading to excellent rate capability and cyclability. Pseudocapacitive behavior is found to dominate in the redox reactions, accounting for the outstanding rate and cycling performance. In addition, full cells, assembled with O3-Na0.9 [Cu0.22 Fe0.30 Mn0.48 ]O2 as cathodes, present good electrochemical performance.