Li[Li0.2Mn0.56Ni0.16Co0.08]O2 cathode materials with well-formed layered structure are synthesized by sol–gel process with different metal sources. Two normal metal salts (acetate and nitrate) are performed as the metal sources, and the effect of particle morphology on the electrochemical performance of the Li-rich layered oxide is investigated to show the importance of the choice of metal sources. Porosity with high specific surface area of 10.09m2 g−1 is only observed for the oxide powder synthesized with nitrate. Simultaneously, high discharge capacity of 247.8mAhg−1 and 135.5mAhg−1 are obtained at current densities of 200mAg−1 and 2000mAg−1, respectively. In addition, the results of electrochemical impedance spectroscopy (EIS) indicate that such porous morphology with good particle contact can efficiently reduce the impedance of the oxide electrode.