Enhanced electrochemical performance of LiNi0.4Co0.2Mn0.4O2 cathode materials via Y2O3 coating

An ultrathin Y2O3 layer is applied to improve the unsatisfactory cyclability and rate performance of LiNi0.4Co0.2Mn0.4O2 (NCM) cathodes for the first time. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were implemented to characterize the physical performance of synthetical materials. In addition, charge-discharge cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were executed to investigate the electrochemical actions. In particular, the 0.5 wt% Y2O3-coated NCM manifests a significantly upgraded initial specific capacity of 185.4 mAh g−1 at 1 C and a capacity retention as high as 93.7% after 100 cycles. Nevertheless, bare NCM manifests a capacity retention of 59.4%. Even at 5 C, modified NCM samples still have high capacity. The remarkably ameliorative electrochemical performance of Y2O3-coated NCM materials during cycling is because of the Y2O3 coating that may hinder the deleterious reactions between the electrolyte and the cathodes and decrease the charge-transfer resistance.