The preparation and electrochemical properties of the Li-excess cathode material Li1 + x(Mn0.7Fe0.3)1 − xO2 by coprecipitation method

The Fe-substituted Li2MnO3 cathode materials were synthesized by the coprecipitation method. The effects of the different precipitants of Na2CO3 and NaOH on the structure, morphology, and electrochemical performance were investigated by X-ray diffractometry, scanning electron microscopy, dQ/dV plots, and charge–discharge tests. The results indicate that the materials prepared using both precipitants possess layered α-NaFeO2 structure with R-3m space group. However, the material prepared using Na2CO3 shows smaller primary particle size as well as higher discharge capacity. The cycling test shows that the initial discharge capacity is 206 mAh g−1 in the voltage range of 2.5–4.8 V under current density of 30 mA g−1 at 30 °C and 231 mAh g−1 in the voltage range of 2.0–4.8 V. Meanwhile, the discharge capacity fades to 191 mAh g−1 after 20 cycles. The activated Mn4+ was confirmed to contribute to the high reversible capacities.