Rate capability of Li[Li_(0.17)Mn_(0.58)Ni_(0.25)]O_2 as high-capacity cathode materials

A carbonate co-precipitation method was used to synthesize Li[Li_(0.17)Mn_(0.58)Ni_(0.25)]O_2 samples with different morphologies via controlling the crystal process.The Li[Li_(0.17)Mn_(0.58)Ni_(0.25)]O_2 samples were characterized by X-ray diffraction(XRD),high resolution transmission electron microscopy(HRTEM),field emission scanning electron microscopy(FESEM),galvanostatic charge-discharge testing,and electrochemical impedance spectroscopy(EIS).It is found that the Li[Li_(0.17)Mn_(0.58)Ni_(0.25)]O_2 samples,with high crystallinity,can all be indexed as aα-NaFeO_2 phase(space group R3m).Moreover,the sample with the hexagonal primary particles aggregated along with the long axis shows a much better rate capability than the other.Li[Li_(0.17)Mn_(0.58)Ni_(0.25)]O_2 delivers the initial discharge capacities of 205.4, 195.5 and 158.5 mA·h·g~(-1),in the voltage range of 2.5～4.8 V at the rates of 0.5C,1.0C and 3.0C,respectively.After 100 cycles,the discharge capacities are 203.5,187.2and 151.2 mA·h·g~(-1),which correspond to 99%,96%and 95%retention of their initial capacities.The special aggregated morphology of Li[Li_(0.17)Mn_(0.58)Ni_(0.25)]O_2 particles contributes to the reduced charge transferring impedance and the improved rate capability.Additionally,the electrochemical properties of the materials in different potential windows were also comparatively studied.