Synthesis and Electrochemical Performances of Y-Doped Lithium-Rich Layered Li[Li0.2Ni0.2Mn0.6]O2Cathode Material

A series of lithium-rich cathode materials Li[Li0.2Ni0.2−x/2Mn0.6−x/2Yx]O2 (x = 0, 0.01, 0.02, 0.03 and 0.05) were synthesized by the carbonate co-precipitation method. The influence of Y3+ doping on the structural and morphological characterizations was examined by means of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). The results show that the crystal structure and morphology of the powders are not distinctly changed with the incorporation of Y ions. Charge-discharge tests show that materials doped with a proper amount of yttrium display good cycling stability and good rate capability, compared with un-doped material. When the doped content is 0.03 (Li[Li0.2Ni0.185Mn0.585Y0.03]O2), it delivers initial coulombic efficiency of 77.6%, a highly reversible capacity of 235.5 mAh g−1 and a capacity retention of 92.7% at the 50th cycle, which is much better than the pristine materials (74.8%, 185.5 mAh g−1, and 81.0%). The cyclic voltammetry (CV) and AC impedance (EIS) results indicate that Y-doping can decrease electrochemical polarization and the charge-transfer resistance and enhance the ability of Li+ diffusion in both the Li2MnO3 and LiNi1/2Mn1/2O2 components. Yttrium substitution is a convenient and effective method for improving the electrochemical performance of Lithium-rich layered Li[Li0.2Ni0.2Mn0.6]O2 cathode material.