Synthesis and electrochemical performance of Na0.7Fe0.7Mn0.3O2 as a cathode material for Na-ion battery

A new technique was employed to synthesize Na0.7Fe0.7Mn0.3O2 precursor by adding citric acid to an aqueous solution of sodium, iron, and manganese salts. The rhombohedral Na0.7Fe0.7Mn0.3O2 was obtained by calcining the precursor in air. The precursor and its calcined products were characterized by X-ray powder diffraction and scanning electron microscopy. The results showed that a high-crystallized Na0.7Fe0.7Mn0.3O2 with a rhombohedral structure was obtained when the precursor was calcined over 600 °C in air for 8 h. The product obtained at 800 °C delivered a discharge capacity of about 130 mA h g−1 at the specific current of 13 mA g−1 in the 1st cycle between 1.5 V and 4.3 V.