Abstract: X-ray diffraction (XRD), the traditional characterization method to detect the electrochemical properties of LiCoO₂, was doubted. The XRD patterns of three types of LiCoO₂, with similar electrochemical properties, present differences. For the same type of LiCoO₂, different XRD patterns were obtained when the sample preparing methods were different, because of preferred orientation. The nonstandard method to prepare XRD powder samples can eliminate preferred orientation. The reliable evidence to detect electrochemical properties is still charge and discharge curves.