On the LiCo_(2/3)Ni_(1/6)Mn_(1/6)O_2 positive electrode material

摘要

LiCo_(2/3)Ni_(1/6)Mn_(1/6)O_2 layered oxide was synthesized by the combustion method that led to a crystalline phase with good homogeneity and low particles size. The structural properties of the prepared positive electrode material were investigated by performing XRD Rietveld refinement. Practically no Li/Ni mixing was detected evidencing that the studied compound adopts almost an ideal α-NaFeO_2 type structure. The Li_‖LiCo_(2/3)Ni_(1/6)Mn_(1/6)O_2 cell showed a discharge capacity of 199 mAh g~(-1) when cycled in the 2.7-4.6 V potential range while the best cycling performances were recorded when the upper cut off is fixed at 4.5 V. Structural changes in Li_xCo_(2/3)Ni_(1/6)Mn_(1/6)O_2 with lithium electrochemical de-intercalation were studied using X-ray diffraction. This study clearly shows the existence of a solid solution domain in the 0.1 < x < 1.0 composition range while for x = 0.1, a new phase appears explaining the decrease of the electrochemical performance when the cell is cycled at high upper cut off voltage.