Enhanced cyclability of LiCoO2 cathodes coated with alumina derived from carboxylate?alumoxanes

Abstract

LiCoO2 cathodes coated with Al2O3 generated from carboxylate–alumoxanes have demonstrated sustainable extended cyclability. The carboxylate–alumoxanes were prepared by reacting boehmite with acetic and substituted acetic acids. TEM images of the coated powders revealed that the coatings were compact and had an average thickness of about 20nm. XRD data on the coated materials indicated minor changes in the values of the lattice parameters, suggesting the formation of solid solutions of the composition LiAl y Co1– y O2 on the surface during calcination. ESCA depth profiles of the constituent elements in the coated particles support this theory. R-factor values from XRD analysis and galvanostatic cycling studies suggest that a 1.0 wt.% coating formed from a (methoxyethoxy)acetate-alumoxane enhanced the cyclability by a factor of 12. The improved performance is attributed to suppression of the cycle-limiting phase transitions accompanying the charge–discharge processes. Being without environmentally hazardous organic chemicals and by-products, the coating procedure based on carboxylate–alumoxanes is a clean and benign process for industrial exploitation.