Cyclic Properties of Li[Co_0,17Li_0,28Mn_0,55]O₂ Cathode Material

摘要

A Li[Co_0.17Li_0.28Mn_0.55]O₂ cathode compound was prepared by a simple combustion method. The X-ray diffraction pattern showed that this compound could be classified as メ-NaFeO₂ structure type with the lattice constants of a = 2.8405(9) ∈ and c = 14.228(4) ∈. According to XANES analysis, the oxidation state of Mn and Co ions in the compound were 4+ and 3+, respectively. During the first charge process, the irreversible voltage plateau at around 4.65 V was observed. The similar voltage-plateau was observed in the initial charge profile of other solid solution series between Li₂MnO₃ and LiMnO₂ (M=Ni, Crˇ). The first discharge capacity was 187 mAh/g and the second discharge capacity increased to 204 mAh/g. As the increase of cycling number, one smooth discharge profile was converted to two distinct sub-plateaus and the discharge capacity was slowly decreased. From the Co and Mn K-edge XANES spectra measured at different cyclic process, it can be concluded that irreversible transformation of phase is occurred during continuous cycling process.