Synthesis and Electrochemical Performances of Y-Doped Lithium-Rich Layered Li[Li_0.2Ni_0.2Mn_0.6]O₂Cathode Material

A series of lithium-rich cathode materials Li[Li 0.2 Ni 0.2− x /2 Mn 0.6− x /2 Y x ]O 2 ( x = 0, 0.01, 0.02, 0.03 and 0.05) were synthesized by the carbonate co-precipitation method. The influence of Y 3+ 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[Li 0.2 Ni 0.185 Mn 0.585 Y 0.03 ]O 2 ), 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 Li 2 MnO 3 and LiNi 1/2 Mn 1/2 O 2 components. Yttrium substitution is a convenient and effective method for improving the electrochemical performance of Lithium-rich layered Li[Li 0.2 Ni 0.2 Mn 0.6 ]O 2 cathode material.