Electrochemical characteristics of Y₂O₃-Coated LiCo_1/3Ni_1/3Mn_1/3O₂

LiCo_1/3Ni_1/3Mn_1/3O₂ was coated by a layer of Y₂O₃ via a simple method. The bared sample was immersed into Y(NO₃)₃· 6H₂O solution and then calcined at a certain temperature to get the coated material. The coated and bared LiCo_1/3Ni_1/3Mn_1/3O₂ meterials were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), cyclic voltammetry (CV), and galvanotactic charge-discharge test. It was showed that Y₂O₃ existed only on the surface, and had no effect on the crystal structure; the LiCo_1/3Ni_1/3Mn_1/3O₂ coated with Y₂O₃ exhibited better capacity retention than the bared LiCo_1/3Ni_1/3Mn_1/3O₂ in the higher cutoff voltage and had higher thermal stability. CV results suggested that the Y₂O₃ coating suppressed the phase transitions and prevented the surface of cathode materials from direct contact with the electrolyte.