High-performance P2-type Na_0.7Co_0.1Fe_0.1Mn_0.8O₂ cathode materials for sodium-ion batteries

Sodium-ion batteries are gaining broad application prospects in the field of new energy due to their high energy density, low cost, and good safety. However, the irreversible phase transformation of layered oxides during charge and discharge cycles limits their long-term cycling performance and practicality. This article utilizes the sol–gel method to prepare a stable Na_0.7MnO₂ (NMO) crystal phase and explores the effects of double doping with Fe and Co on the microstructure and electrochemical properties of Na_0.7MnO₂. The XRD pattern indicates that Fe and Co ions were successfully incorporated into the lattice of the Na-Mn–O system, stabilizing the P2 crystal phase and increasing the sodium layer spacing. Na_0.7Co_0.1Fe_0.1Mn_0.8O₂(NCFMO) can deliver an initial capacity of 109.78 mAh/g, with an average operating voltage of 3 V, and retains a capacity retention rate of 96.31% after 100 cycles. Moreover, at a current density of 0.2 C and a voltage range of 1.5–4.5 V, the cycle charge–discharge specific capacity reaches 226.08 and 159.3 mAh/g, respectively, demonstrating excellent cycle and rate performance.

The cycle performance of the material Na_0.7Co_0.1Fe_0.1Mn_0.8O₂ in different voltage ranges is tested in the figure, and it shows excellent performance in the voltage range of 1.5–4.5 V.