Insights into the Synergistic Roles of Microwave and Fluorination Treatments towards Enhancing the Cycling Stability of P2-Type Na0.67[Mg0.28Mn0.72]O2Cathode Material for Sodium-Ion Batteries

P2-type Na0.67Mg0.28Mn0.72O2 based cathode materials for sodium-ion batteries were prepared using combustion synthesis. The effect of microwave irradiation and fluorination was investigated with the aim to improve the electrochemical performance. Four samples were considered: samples were prepared by the combustion method (NaMgMnO-a) and then either microwave-irradiated or fluorinated (NaMgMnO-ma and NaMgMnO-af, respectively) or both microwave-irradiated and fluorinated (NaMgMnO-maf). The powder XRD analyses showed that pure single phase P2-type powders were successfully prepared. SEM analyses revealed an impact of microwave irradiation and fluorination on the morphology of the materials, suggesting a change in the electrochemical performance. The galvanostatic charge-discharge studies revealed that both microwave irradiation and fluorination improved the capacity and cycle performance. The electrochemical data (from first discharge capacity to coulombic efficiency, capacity retention, cyclability and impedance) show that microwave- and fluorine-treated samples performed better. The key finding clearly shows the impact of microwave irradiation and fluorination processes in suppressing the P2-O2 phase transformation process and the Mn3+-induced Jahn-Teller distortion effect.