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−yCoyO4 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 3d6 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.