Electrochemical and magnetic properties of Li4Â /Â 3Mn2Â /Â 3O2-LiCoO2 solid solution

The compounds Li(4−x)/3Mn2(1−x)/3CoxO2 (0 < x < 0.5) were prepared by the sol-gel technique. X-ray diffraction patterns of these compounds were identified as α-NaFeO2 type layered structure, though some super-structure lines, related to the ordered array of Li and transition metal ions in the transition metal layer, were observed. The magnetic susceptibility exhibited an antiferromagnetic transition around 40 K for x < 0.2, however the specimens with x > 0.3 had no magnetic transition. The magnetic percolation may explain these magnetic variations. The electrochemical performances were evaluated for the compound of x = 0.5, and it was seen that the electrochemical properties were sensitive to the potential window. Additionally, it was also found that the discharge capacity strongly depended on the preparation temperature; it took a maximum value at the preparation temperature of 900 °C. The discharge capacity is sensitive not only to the cation mixing degree but also to the particle size.