Enhanced cyclability and thennal stability of LiCoO2 coated with cobalt oxides

Improved cycling properties and thermal stability of LiCoO2 coated with cobalt oxides by a wet chemical process are described. XRD studies showed that the values of the lattice parameters, a and c, were altered by the coating, indicating that substitutional compounds might have formed on the surface upon calcination. TEM studies on 0.3-wt.% cobalt oxide-coated LiCoO2 suggested that cobalt oxides formed a uniform coating over the cathode material. SEM images, R-factor values from XRD studies and galvanostatic cycling studies indicated that a coating level of 0.3 wt.% produced optimal performance in terms of capacity and cyclability. Cyclic voltammetric curves suggested that the coating suppressed the cycle-limiting phase transitions that occur at potentials above 4.1 V vs. Li+/Li. Charge-discharge studies with a 0.3wt.% cobalt oxide-coated LiCoO2 material showed a 12-fold improvement in cyclability. Differential scanning calorimetric data revealed the higher thermal stability of the coated cathode materials. (C) 2004 Elsevier B.V. All rights reserved.