LiCo1-xAlxO2(0 less than or equal to x less than or equal to 0.3, R (3) over barm) powders by the emulsion drying method and their microstructure studies were carried out in order to understand Al-doping effect on the electrochemical properties. Through X-ray diffraction experiment; we confirmed that Co was well substituted by Al while maintaining the alpha -NaFeO2 layer structure type. The substitution of Al was effective on suppressing cobalt dissolution at 4.5 V versus Li/Li+ and on diminishing changes in a- and c-axes during lithium intercalation. For x = 0.1, the open-circuit voltage was slightly higher than that of undoped LiCoO2. Chemical diffusion coefficient of lithium in LiCo1-xAl2O3 was higher than that of LiCoO2 because of a smaller variation in the longer c-axis. (C) 2001 Elsevier Science B.V. All rights reserved.