Surface modification of LiNi0.8Co0.2O2 with La2O3 for lithium-ion batteries

The surface of LiNi0.8Co0.2O2 cathode particles was coated with various wt.% of La2O3 through a polymeric process, followed by calcination at 973 K for 5 h in air. The coated layer prevents the surface of the cathode materials from direct contact with the electrolyte and has demonstrated sustainable extended cycle stability. XRD patterns of the coated materials indicated no effect on the crystal structure (alpha-NaFeO2) of the cathode material compared to the pristine material. The O 1s XPS data revealed that the presence of two different oxygen ions corresponds to the surface coated La2O3 and core material. ESCA depth profiles of the constituent elements in the coated particles showed their levels. A compact coating layer on the surface of the core material was observed from TEM image and had an average thickness of similar to 20 nm. Galvanostatic cycling studies suggest that 1.0 wt.% coated La2O3 on LiNi0.8Co0.2O2 quadrupled cycle stability over the pristine material. Impedance spectroscopy and cyclic voltammetry demonstrated that the improved performance is attributed to a suppression of the impedance growth and cycle-limiting phase transitions. (c) 2005 Elsevier B.V. All rights reserved.