Surface treatment of LiNi0.8Co0.2O2 cathode material for lithium secondarybatteries

The harmful side reactions. between the cathode, materials and liquid elect rolyte within the lithium secondary batteries, will deteriorate the perform ance of the cathode materials and batteries. The Li2O-2B(2)O(3) glass with high Li+ conductivity and stability can be coated on the, surface of LiNi0. 8Co0.2O2 powders by Mixing LiNi0.8Co0.2O2, LiOH .H2O and H3BO3 and heating the mixture at 500 degreesC for 10 h. The structure of the surface-treated and base LiNi0.8Co0.2O2 powders was characterized by X-ray photoelectron sp ectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SE M) and BET. It is shown the Li2O-2B(2)O(3) layer can prevent LiNi0.8Co0.2O2 from contacting directly with liquid electrolyte, and minimize the side re actions within the batteries. The surface-treated LiNi0.8Co0.2O2 cathode ma terial has increased reversible capacity, decreased irreversible capacity; stabilized cycling performance, reduced self-discharge, especially the impr oved high temperature performance. The results indicated that the surface t reatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium secondary batteries. (C) 2001 Elsevie r Science B.V. All rights reserved.