Abstract: Cathode materials of Li Li_0.15Mn_0.575Ni_{0.2751 -x}Si_xO₂ (0≤x≤0.04)were synthesized through mixing lithium carbonated with precursor manganese nickel magnesium hydroxide complex prepared by liquid co -precipitation technique. Layered Li Li0.15Mn0.575Ni0.2751-xSixO2 powder materials were characterized by X-ray diffraction (XRD) and scanning electron microscope(SEM). The results show that the dopant can improve the cycling behavior of materials. The degree of crystal lattice disfigurement grows which reflects the full width half maximum increases of doping Si4+. x=1 % was confirmed as having the optimum electrochemical performance. The first discharge capacity of 4.2 V at 146.7 mAh/g,200 times cycles remained at 135.7 mAh/g and the capacity keep rates was 92 %.