Design of Cu‐Substituted O3‐Type NaFe0.5Mn0.5O2 Cathode Materials for Sodium‐Ion Batteries

Abstract O3‐type Fe/Mn‐based layered oxide cathode materials with abundant reserves have a promising prospect in sodium‐ion batteries. However, the electrochemical reversibility of most O3‐type Fe/Mn‐based oxide cathode materials is still not high enough. Herein, the effect of different Cu contents on the electrochemical properties of O3‐NaFe 0.50 Mn 0.50 O 2 materials is systematically investigated. The as‐prepared NaFe 0.30 Mn 0.50 Cu 0.20 O 2 cathode achieves the synergistic optimization of the interface and bulk phase. It shows superior electrochemical performance, with an initial discharge specific capacity of 114 mAh g −1 at 0.1 C, a capacity retention rate of 94 % after 100 cycles at 0.5 C, and excellent chemical stability in air and water. In addition, the sodium ion full battery based on NaFe 0.30 Mn 0.50 Cu 0.20 O 2 cathode and hard carbon anode has a capacity retention rate of 81 % after 100 cycles. This research provides a useful approach for the preparation of low‐cost and high‐performance O3‐type layered cathode materials.