Abstract
LiCoO 2 spinel is one of the most promising cathode materials for Li-ion batteries. However, the capacity fading is aggravated at high voltage, resulting from cathode degradation and electrolyte decomposition owing to over-charging. To improve structural stability, surface modification is an effective method. In this study, nano-crystallized ZnO was coated on the surface of commercial LiCoO 2 powders via sol-gel method. The correlation among the amount of coated ZnO, microstructure of modified cathode and the cycling behavior of surface-treated LiCoO 2 powders is discussed. Moreover, the effects of cycling for cathodes with as-derived powders on the phase and morphology are also considered. The surface morphology observed from the scanning electron microscope (SEM) images shows that nano-crystallized and spherical ZnO particles with an average size of about 20 nm have developed after coating. The size of ZnO nanocrystallites is related to the initial concentration of Zn 2+ cations. In comparing the characteristics of bare and coated LiCoO 2 powders, improvement in cyceability of the ZnO-coated cathode is explored. It is confirmed that Zn 2+ ions diffuse into the surface region of LiCoO 2 particles. To reveal the effects of Zone coating on enhancing the electrochemical properties of LiCoO 2 cathode during charge and discharge, the morphological differences between the cathode material before and after cycling are discussed.