Synergistic optimization of electrochemical performance in P2-phase Na 0.67 MnO 2 through Fe doping and controlled calcination temperature

Abstract

Sodium-ion batteries are promising for large-scale storage due to low cost and good low-temperature performance. The development of P2-type Na₀.₆₇MnO₂ cathode materials, known for high capacity and stability, is challenged by their structural instability and performance decay upon cycling. The work investigated the structure and electrochemical properties of P2-type Na_0.67MnO₂ cathode materials through Fe doping and calcination temperature regulation. Fe doping could suppress phase transformation, increase interlayer spacing, and promote Na⁺ diffusion, which enhanced the specific capacity and cycling stability of the materials. Experiments showed that Na_0.7Fe_0.2Mn_0.8O₂ material with a Fe to Mn molar ratio of 0.2 : 0.8 calcined at 900 °C exhibited optimal performance, with an initial charge-discharge specific capacity of 132.2 mAh/g and excellent rate capability.