Structure, morphology and electrochemistry of doped lithium cobalt oxides

Abstract

The structure, morphology and electrochemical performance of LiCoO₂ powders doped with various trivalent cations such as M³⁺=Ni³⁺, Al³⁺, and B³⁺ have been investigated. X-ray diffraction patterns and FTIR data show that LiCo_1−yNi_yO₂ oxides display a solid solution in the whole range 0≤y≤1, while the solubility limit of LiCo_1−yAl_yO₂ and LiCo_1−yB_yO₂ materials is about y=0.35. Electrochemical features of LiCo_1−yNi_yO₂ cathode materials show remarkable stability in their charge-discharge profiles. Aluminum substitution also stabilizes the two-dimensional framework and induces an increasing average cell potential than for LiCoO₂. The overall capacity of the LiCo_1−yB_yO₂ oxides has been reduced due to the sp metal substitution, however, a more stable charge-discharge cycling characteristic has been observed when electrodes are charged up to 4.4 V as compared to the performances of the native oxides.