Enhanced electrochemical properties of Y2O3-coated-(lithium-manganese)-rich layered oxides as cathode materials for use in lithium-ion batteries

Abstract

In this study, a 5–10-nm-thick Y2O3 layer is employed as a surface-coating layer on (lithium-manganese)-rich Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) cathode materials for the first time. The results indicate that the bulk structure of LMNCO is unchanged with the additional Y2O3 coating, and the electrochemical properties, including initial coulombic efficiency, cycle stability and rate performance, are greatly enhanced in these coated materials. In particular, the 2.0 wt% Y2O3-coated LMNCO expresses an initial discharge capacity of 280.3 mAhg−1 with capacity retention of 89.1% at a 0.5 C rate after 200 cycles, which is much better than that of 76.3% of the pristine sample. Furthermore, electrochemical impedance spectroscopy demonstrates that the Y2O3-coating layer can protect the LMNCO from being impaired by the electrolyte and can make contributions to reduce the cathode charge-transfer resistance at the delithiated condition. These findings offer new research directions for solving serious defects, such as a large proportion of initial nonreversible capacity loss and poor cycling stability, in lithium-rich cathode materials used for lithium-ion batteries.