Surface treatment of LiNi 0.8Co 0.2O 2 cathode material for lithium secondary batteries

Abstract

The harmful side reactions between the cathode materials and liquid electrolyte within the lithium secondary batteries will deteriorate the performance of the cathode materials and batteries. The Li 2O–2B 2O 3 glass with high Li + conductivity and stability can be coated on the surface of LiNi 0.8Co 0.2O 2 powders by mixing LiNi 0.8Co 0.2O 2, LiOH·H 2O and H 3BO 3 and heating the mixture at 500°C for 10 h. The structure of the surface-treated and base LiNi 0.8Co 0.2O 2 powders was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET. It is shown the Li 2O–2B 2O 3 layer can prevent LiNi 0.8Co 0.2O 2 from contacting directly with liquid electrolyte, and minimize the side reactions within the batteries. The surface-treated LiNi 0.8Co 0.2O 2 cathode material has increased reversible capacity, decreased irreversible capacity, stabilized cycling performance, reduced self-discharge, especially the improved high temperature performance. The results indicated that the surface treatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium secondary batteries.