LiCo1-yByO2 as cathode materials for rechargeable lithium batteries
Résumé
LiCo1-yByO2 (0.05≤y≤0.35) samples were synthesized free of any impurity, except residual concentration of Ni present in the commercial products used as the precursors. They were characterized by X-ray powder diffraction, FTIR spectroscopy, and magnetic measurements. Structural data have shown that the limit of solubility of boron is y ~ 0.25. The voltage profiles of electrochemical cells including these compounds as the cathode were monitored against Li anode. The overall capacity of the oxides has been reduced by the sp metal substitution, but more stable cycling performances have been observed, compared to the performances of the native oxides. At 4.4 V cut-off voltage, the Li//LiCo0.75B0.25O2 cell exhibits an almost constant capacity of ca. 127 mAh/g up to the 16th cycle. The origin of the benefit of boron doping is discussed.