Synthesis of micro and nanostructured MnO2 and their comparative study in lithium battery

Abstract

Micro and nanostructured γ-MnO2 are synthesized to investigate the size effect of cathode active materials in battery performance. MnSO4 and (NH4)2S2O8 were used as starting materials to prepare micro and nanostructured samples in the presence of stirring and ultrasonic irradiation, respectively. Structure optimization is done by changing values for temperature and manganese sulphate concentration. The MnO2 micro and nanoparticles are characterized by scanning electron microscopy and X-ray diffraction (XRD). The XRD results reveal that only γ-MnO2 is formed under the reaction conditions. Under the optimized conditions, manganese dioxide nanoparticles, with an average particle size of 56 nm, are obtained. Both micro and nanostructured MnO2 is used as the cathode active material in Li/MnO2 battery. Discharge profiles of stirrer-based cathode material (micro) and ultrasonic instrument-based one (nano) compared with each other in constant discharge currents of 50 and 100 mA g−1. The results demonstrated that nanosized materials show higher specific capacities and energies. Electrochemical impedance spectroscopy is used to investigate the size effect of cathode material on battery resistance and the results show a copious decrease in total resistance.