P2-type Na0.53MnO2 nanorods with superior rate capabilities as advanced cathode material for sodium ion batteries

Layered P2-type Na 0.53 MnO 2 nanorods is prepared by a simple solution reaction. When used as cathode material for sodium ion batteries, the P2-Na 0.53 MnO 2 delivers a high reversible capacity up to 135.7   mA   h   g −1 (theoretical capacity is 140   mA   h   g −1 ) at 0.1   C in the voltage range of 2–4.3   V vs. Na + /Na, corresponding to 0.51   mol of Na insertion/extraction. It presents good cycling performance and high rate capabilities. After 50 cycles, the capacity is just fading about 6.8% at the rate of 2   C. The significant behaviour of fast charging makes it be very attractive for practical application. The electrochemical impedance spectroscopy and galvanostatic intermittent titration technique are employed to investigate its sodium diffusion kinetics. The ex-situ X-ray diffraction technology is also used to study the intercalation/de-intercalation of sodium ions and the phase transition in the charging/discharging processes.