LiCoO 2 , Mg-doped LiCoO 2 , and Zr doped LiCoO 2 , are manufactured by a sol–gel method, and are used as cathode active materials for lithium rechargeable batteries. The structural characteristics of the synthesized electrodes are analyzed by X-ray diffraction. The materials have a layered structure with the space gropu R3¯m of hexagonal systems. LiCoO 2 prepared by sol–gel method shows a capacity decay over 4.3V but LiCoO 2 doped with Mg and Zr give an improvement in charge–discharge cycling performance. This effect may attribute to the fact that Mg 2+ and Zr 4+ ions have the same size as the Li + ion and they locate at the inter-slab space. Therefore, they provide a pathway for the intercalation–deintercalation of Li + during the charge and the discharge processes and prevent distortion of the structure. Also, the formation of a solid solution on the surface of the electrode acts as the buffer to phase transition and the structure becomes very stable.