Facile Design and Synthesis of Co-Free Layered P2-Na2/3Fe1/2Mn1/2O2 as Advanced Cathode Material for Sodium-Ion Batteries

Co-free Fe/Mn-based cathodes have become a popular choice for sodium-ion batteries (SIBs) due to their affordability and impressive theoretical capacity. Nevertheless, the issue of their terrible battery life and rate capability continues to be their hindrances. A set of three-factor, three-level orthogonal experiments was adopted, including the calcination temperature, calcination time, and heating rate. And two single-factor experiments were carried out to further optimize the preparation conditions. Finally, the optimal conditions were obtained as follows: the calcination temperature was 900 °C, the calcination time was 12 h, and the heating rate was 5 °C min^–1. The layered oxide cathode material Co-free P2-Na_2/3Fe_1/2Mn_1/2O₂ was synthesized by the solid phase method. Under the control of the optimal conditions, the P2-Na_2/3Fe_1/2Mn_1/2O₂ cathode could yield a remarkable initial discharge specific capacity (179.3 mAh g^–1, 0.1 C) and cycle stability (54.6% over 50 cycles). These findings further declared that it was feasible to design Co-free Fe/Mn-based cathode materials with superior performance, which might offer guidance for popularizing cost-effective Fe/Mn-based cathode materials in the future.