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

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 O₂ materials is systematically investigated. The as-prepared NaFe_0.30 Mn_0.50 Cu_0.20 O₂ 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 O₂ 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.