LiCo1−yMyO2 positive electrodes for rechargeable lithium batteries: I. Aluminum doped materials

Several substituted layered cobaltates of formula LiCo1−yAlyO2 (0.05≤y≤0.30) were synthesized and investigated as cathode materials in rechargeable lithium batteries. These materials were investigated by X-ray powder diffraction, spectroscopic measurements (Raman and FTIR), and galvanostatic cycling. Structural data have shown that single phase impurity free can be made through careful selection of precursors. The voltage profiles of electrochemical cells including substituted oxides were monitored against lithium electrode. The overall capacity of the oxides have been reduced due to the sp metal substitution, however, a more stable charge–discharge cycling performances have been observed when electrodes are charged to 4.4 V as compared with the performances of the native oxides. At this cut-off voltage, the charge capacity of the Li//LiCo0.80Al0.20O2 cell is ca. 128 mAh g−1. Kinetics were characterized by the galvanostatic intermittent titration technique. Al substitution also provides an increase of the chemical diffusion coefficients of Li ions in the LiCo1−yAlyO2 matrix.