A new synthesis route of high-performance P′2-Na0.67Fe0.1Mn0.9O2-δ and its sodium storage properties for sodium-ion batteries

The P2-Na 0.67 Fe 0.1 Mn 0.9 O 2 materials with P 6 3 /mmc space group structure is a promising cathode material for sodium-ion batteries due to its low cost and high capacity. However, the occurrence of various phase transitions reduces the cycle reversibility of the compound. In this study, P′2-Na 0.67 Fe 0.1 Mn 0.9 O 2-δ with C mcm space group structure is synthesized by regulating oxygen vacancies content for the first time. The effect of oxygen vacancies on the structural evolution of the material during charge-discharge processes is further investigated by in-situ X-ray diffraction (XRD) techniques. Compared to P2-Na 0.67 Fe 0.1 Mn 0.9 O 1.98 , P′2-Na 0.67 Fe 0.1 Mn 0.9 O 2-δ experiences smaller Jahn-Teller distortion when intercalating and deintercalting Na + . Meanwhile, it exhibits better electrochemical performance . The initial discharge capacity reaches 200 mAh g −1 at a current density of 20 mA g −1 with the capacity retention of 70.8% after 200 cycles at the current density of 400 mA g −1 .