Effect of ZrO₂coating on structures and properties of LiNi_0.8Co_0.2O₂

Abstract：In order to improve the comprehensive electrochemical properties of LiNi_0.8Co_0.2O₂cathode for lithium ion battery, the cathode material was coated with ZrO₂by a high temperature solid-state method.The materials were characterized by X-ray diffraction, scanning electron microscope and electrochemical test methods.The results showed that ZrO₂, which could be uniformly distributed on the surface of the material without changing the crystal structure of LiNi_0.8Co_0.2O₂, could influence the electrochemical performances of the cathode obviously.The initial discharge capacity was slightly decreased from 168.25 mAh/g for pristine LiNi_0.8Co_0.2O₂to 157.43 mAh/g for coated-ZrO₂material.However, the (1 C, 2 C) rate capability of the positive electrode was improved clearly by the coated-ZrO₂.In addition, great improvement in the cycleability of the coated-ZrO₂cathode could be obtained.After 100 cycles, the capacity retention of the coated-ZrO₂LiNi_0.8Co_0.2O₂was 97.70%while that of the pristine cathode was 90.68%.The reasons for this were that the coatings effectively prevented the electrolyte from contacting with the cathode directly and reduced the side reaction, on the other hand, ion conductivity of the material could be increased by the existence of Li₂ZrO₃which was produced during the the process of ZrO₂surface coating.This study could provide a simple and effective method for improving the comprehensive electrochemical performance of cathode materials for lithium ion batteries.

Keyword：LiNi_0.8Co_0.2O₂;ZrO₂coating;high temperature solid-state method;micro structure;electrochemical performance;