Cu-Doped Spherical P2-Type Na_0.7Fe_{0.23- x}Cu _x Mn_0.77O₂ Cathode for High-Performance Sodium-Ion Batteries

Sodium-ion batteries (SIBs), owing to their abundant resources and cost-effectiveness, have garnered considerable interest in the realm of large-scale energy storage. The properties of cathode materials profoundly affect the cycle stability and specific capacity of batteries. Herein, a series of Cu-doped spherical P2-type Na_0.7Fe_0.23-xCu_xMn_0.77O₂ (x = 0, 0.05, 0.09, and 0.14, x-NFCMO) was fabricated using a convenient hydrothermal method. The successful doping of Cu efficaciously mitigated the Jahn-Teller effect, augmented the electrical conductivity of the material, and diminished the resistance to charge transfer. The distinctive spherical structure remained stable and withstood considerable volumetric strain, thereby improving the cyclic stability of the material. The optimized 0.09-NFCMO cathode exhibited a high specific capacity of 168.6 mAh g^-1 at 100 mA g^-1, a superior rate capability (90.9 mAh g^-1 at 2000 mA g^-1), and a good cycling stability. This unique structure design and doping approach provides new insights into the design of advanced electrode materials for sodium-ion batteries.