High specific capacity Mg-doping LiNi1/3Mn1/3Co1/3O2 cathode materials synthesised by a simple stepwise co-precipitation method

The layered LiNi1/3Co1/3Mn1/3−x Mg x O2 (x = 0, 0.01, 0.02, 0.03) were synthesised by a stepwise co-precipitation method. The effects of Mg substitution on the crystal structure of the synthesised powder have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping. Their electrochemical properties were evaluated by charge/discharge and electrical impedance spectroscopy tests. The results of XRD, SEM and EDS mapping characterisation indicated that all the modified cathode materials with their Ni, Co and Mn components doped by magnesium without destroying the crystal structure. Electrochemical characterisation confirms that the materials have optimal cycling performance and the least capacity loss under the 2% Mg-doping. The specific capacity of the LiNi1/3Co1/3Mn1/3−0.02Mg0.02O2 was 180 mAh g−1 at 0.1 C and 138 mAh g−1 at 8 C, which compares favourably to 175 mAh g−1 at 0.1 C and 121 mAh g−1 at 8 C for the LiNi1/3Co1/3Mn1/3O2. The LiNi1/3Co1/3Mn1/3−0.02Mg0.02O2 also exhibited the best electrochemical performance with capacity retention of 89.4% after 50 cycles at 0.2 C between 2.5 and 4.3 V.