Effects of Al doping on the microstructure of LiCoO2 cathode materials

LiCo1−xAlxO2 (0≤x≤0.3, R3m) 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 α-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−xAlxO2 was higher than that of LiCoO2 because of a smaller variation in the longer c-axis.