Synthesis and electrochemical properties of chemically substituted LiMn2O4 prepared by a solution-based gel method

Lithium manganese oxide, LiMn2O4, and its substituted samples LiM0.05Mn1.95O4 (M = Al, Co, and Zn) were first prepared by a cost-saving and effective new solution-based gel method using a mixture of acetate and ethanol as the chelating agent. The physical properties of the synthesized samples were investigated by thermogravimetry/differential thermal analysis, X-ray diffraction, and scanning electronic microscopy. The as-prepared powders were used as positive materials for a lithium-ion battery, whose charge/discharge properties and cycle performance were examined. The results revealed that all the substituted samples had better cycle performance than pure LiMn2O4. Among these synthesized materials, the LiCo0.05Mn1.95O4 sample had the best cycle performance. After 30 cycles, its capacity loss was only 3%. Therefore, cyclic voltammetry and electrochemical impedance spectroscopy were employed to characterize the reactions of Li ion insertion into and extraction from LiCo0.05Mn1.95O4 electrodes.

The cyclic voltammograms of all samples show two symmetrical couples of peaks which represented two redox reactions for LiMn2O4 and LiCo0.05Mn1.95O4. As substitution manganese with cobalt, the redox peaks of the LiCo0.05Mn1.95O4 electrode are sharp and show well defined splitting, which indicates that the Co-doped LiCo0.05Mn1.95O4 powders are more crystalline than pure LiMn2O4 and also explains that the cycle performance of LiCo0.05Mn1.95O4 is better than LiMn2O4.Figure optionsDownload as PowerPoint slide