Ultrafine Mn-rich P2-type Na0.67Fe0.1Mn0.9O2 particles via combustion synthesis as high-performance sodium-ion battery cathode

Layered transition metal oxide is considered as one of the most promising cathode materials for sodium-ion batteries due to the abundant reserves of Na, Fe, and Mn. Moreover, the trivalent Fe substitution weakens the Jahn–Teller effect and enhance the crystal structure during the de/intercalation of Na+. Herein, a series of Mn-rich P2-type Na0.67Fe0.1Mn0.9O2 (NFMO-600, NFMO-700 and NFMO-800) are prepared using combustion synthesis followed by calcinating at 600, 700 and 800 °C, respectively. As confirmed by XRD and SEM, NFMO-700 owns ultrafine high-purity crystal particles with a larger layer spacing and a smaller crystal size. Owing to these unique structures, NFMO-700 exhibits excellent electrochemical performance, delivering an impressive 179 mA h g−1 at 0.2C, with a capacity retention of 84.43 % after 100 cycles at 0.5C.