LiMn 2− yCo yO 4 (0 ≤ y ≤ 1) intercalation compounds synthesized from wet-chemical route

Abstract

We present the synthesis, characterization and electrode behaviour of LiMn 2− y Co y O 4 (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. LiMn 2− y Co y O 4 samples crystallize with the cubic spinel-like structure ( Fd3 m 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 LiMn 2− y Co y O 4 powders ranges in the sub-micron-sized domain with a narrow grain-size distribution. The overall electrochemical capacity of LiMn 2− y Co y O 4 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//LiMn 1.8Co 0.2O 4 cell is ca. 101 mA h/g. Differences and similarities between LiMn 2O 4 and Co-substituted oxides are discussed there from.