Preparation and Electrochemical Performance of Yttrium-doped Li[Li0.20Mn0.534Ni0.133Co0.133]O2 as Cathode Material for Lithium-Ion Batteries

To improve the cycling performance and rate capability of the promising layered lithium-rich cathode materials, we substitute Co3+ in Li[Li0.20Mn0.534Ni0.133 Co0.133]O2 with unusually large Y3+ during coprecipitation and synthesize Li[Li0.20Mn0.534 Ni0.133Co0.133-x Yx]O2 (0 ≤ x ≤ 0.0665). The influences of yttrium content on the electrochemical properties of the lithium-rich materials are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), galvanostatic charge-discharge tests and electrochemical impedance spectroscopy (EIS) techniques. The charge-discharge cycling tests suggest that after heating at 1223 K in air for 10 h, the material with x = 0.00665 deliver a high discharge capacity of 349.7 mAhg−1 after 1 cycle and 225.2 mAhg−1 after 80 cycles with a current rate of 0.1 C between 2.0 and 4.6 V vs. Li/Li+. Electrochemical impedance spectroscopy indicates that Li[Li0.20Mn0.534Ni0.133Co0.133-xYx]O2 electrode has lower impedance during cycling. The higher capacity retention and high-rate capability of yttrium-substituted materials can be ascribed to the expanded Li+ diffusing channels in the layered structure, lower surface film resistance and lower charge transfer resistance of the electrode during cycling.