Microstructural effects on Charge Storage Properties in MnO{sub}2 based Electrochemical Supercapacitors

摘要

The present work provides a detailed study on the charge storage properties in MnO{sub}2 based electrochemical capacitors. Various crystallographic forms of MnO{sub}2 were investigated including pyrolusite, ramsdellite, cryptomelane, todorokite, birnessite, buserite and spinel. Prepared products have been characterized by XRD, SEM and BET. SEM photomicrographs revealed different surface morphologies depending on the prepared MnO{sub}2 form. According to BET measurements, surface areas vary from 29 m{sup}2/g for the cryptomelane to 156 m{sup}2/g for the spinel form. Electrochemical performances have been evaluated and commented regarding microstructural arrangements: 1D tunnels, 2D layers or 3D interconnected channels. Specific capacitances were found to decrease in the following order: spinel > birnessite approx= buserite > cryptomelane > ramsdellite > Ni-todorokite > pyrolusite or regarding microstructures with 3D > 2D > 1D.