Effect of Cerium Substitution on Structural and Electrochemical Performance of Li[Li0.2Mn0.54Co0.13Ni0.13]O2 Cathode Material for Lithium-Ion Battery

To enhance the cyclic stability and high rate performance of the advanced Lithium-rich and manganese-based layered structure cathode materials, the Li1.20[Mn0.54-xNi0.13Co0.13Cex] O2 (x = 0, 0.01, 0.02, 0.03) were synthesized by partially substituting Mn4+ with different amounts of Ce3+ via the traditional co-precipitation method. The effect of Ce3+ doping on the crystal structure, particles morphology and electrochemical properties of the Li1.20[Mn0.54Co0.13Ni0.13]O2 was studied by X-ray diffraction (XRD), scanning electron microscope (SEM), galvanostatic charge-discharge tests and electrochemical impedance spectroscopy (EIS) measurement. The XRD, SEM and EDS results demonstrated that the cathodes after Ce3+ doping delivered the larger crystal lattice parameters, the lower cation mixing between Ni2+ and Li+ and the smaller size of cathode particles. Therefore, the superior rate capacity and cyclic performance were obtained for the Ce3+ doped cathodes. Particularly, the Li1.20[Mn0.52Ni0.13Co0.13Ce0.02]O2 demonstrated the optimal electrochemical properties, which delivered a high discharge capacity of 136.7 mAhg-1 at 5C high rate and a high capacity retention of 91.2% at 2C rate after 100 cycles. While the pristine cathode only exhibited a discharge capacity of 92.8 mAhg-1 at 5C rate, 43.9 mAhg-1 smaller than that of the Li1.20[Mn0.52Ni0.13Co0.13Ce0.02]O2. In addition, it retained a discharge capacity of 112.3 mAhg-1 with a capacity retention of only 81.5% after 100 cycles at 2C rate. The larger capacity retention and superior rate performance of Ce3+ doped cathodes could be ascribed to the fast Li+ diffusing speed, the high cation ordering and lower charge transfer resistance during cycling.