LiMn2-yCOyO4 (0 ≤ y ≤1) intercalation compounds synthesized from wet-chemical route

We present the synthesis, characterization and electrode behaviour of LiMn2-yCoyO4 (0 <= y <= 1) spinel oxides prepared by the wet-chemical route assisted by carboxylic acid. The phase evolution was studied as a function of the cobalt substitution and the modification on the intercalation and deintercalation of Li ions. Characterization methods include TG-DTA, XRD, SEM, Raman, FTIR, and SQUID. LiMn2-yCoyO samples crystallize with the cubic spinel-like structure (Fd3m S.G.). Raman scattering and FT-infrared spectroscopy indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Co, Mn)-O bonds. MEB micrographs show that the particle dimension of the LiMn2-yCoyO4 powders ranges in the sub-micron-sized domain with a narrow grain-size distribution. The overall electrochemical capacity of LiMn2-yCoyO4 oxides have been reduced due to the 3d(6) metal substitution. However, a more stable charge-discharge cycling performances has been observed when the electrodes are charged up to 4.3 V as compared to the performance of the native oxide. For such a cut-off voltage, the charge capacity of the Li//LiMn1.8CO0.2O4 cell is ca. 101 mA h/g. Differences and similarities between LiMn2O4 and Co-substituted oxides are discussed there from. (c) 2006 Elsevier B.V All rights reserved.