Abstract
A Li[Co 0 . 1 7 Li 0 . 2 8 Mn 0 . 5 5 ]O 2 cathode compound was prepared by a simple combustion method. The X-ray diffraction pattern showed that this compound could be classified as α-NaFeO 2 structure type with the latticeconstants of a = 2.8405(9) A and c = 14.228(4) A. 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 Li 2 MnO 3 and LiMnO 2 (M=Ni, Cr...). 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.
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