A stepwise co-precipitation route (precipitation with different ratios of Ni

Mn elements in three steps)has been adopted to synthesize the precursor of LiNi0.5Co0.2Mn0.3(OH)2

which was mixed with Li2CO3 afterwards in a certain proportion. After post-heat treatment

the obtained LiNi0.5Co0.2Mn0.3O2 spherical cathode materials exhibit a gradient element distribution (nickel-rich in centre and manganese-rich around surface). The structure

morphology and chemical composition of the samples were characterized by X-Ray Diffraction (XRD)

Field Emission Scanning Electron Microscopy (FESEM)

Energy Dispersive Spectrometer (EDS) and Inductively Coupled Plasma Mass Spectrometry(ICP-MS)

respectively. The electrochemical performances of the as-prepared LiNi0.5Co0.2Mn0.3O2 cathode materials were studied by galvanostatic charge/discharge measurements

Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The testing results show that the materials derived from stepwise co-precipitation exhibit higher rate capability (104.1 mAh·g-1 at 20 C)

better cycle performance (with capacity retention of 95.8% after 200 cycles at 0.5 C) and more efficient fast charge and discharge performance (85.4 mAh·g-1 at 20 C/20 C)

compared with the counterparts obtained from the conventional co-precipitation. In summary

this stepwise co-precipitation strategy is extremely promising for the preparation of LiNi0.5Co0.2Mn0.3O2 electrode materials with enhanced electrochemical performances.