Electrochemical Cyclability Mechanism For Mno_2 Electrodes Utilized As Electrochemical Supercapacitors

摘要

The electrochemical cyclability mechanism of nanocrystalline MnO_2 electrodes with rock salt-type and hexagonal e-type structures was investigated to determine the relationship between physicochemical feature evolution and the corresponding electrochemical behaviour of MnO_2 electrodes. Rock salt MnO_2 and hexagonal ε-MnO_2 electrodes, with fibrous and porous morphologies, evolve into the antifluorite-type MnO_2 with a petal-shaped nanosheet structure after electrochemical cycling, similar to that observed in nanocrystalline antifluorite-type MnO_2 electrodes after electrochemical cycling. However, a different impedance response was observed for the rock salt MnO_2 and hexagonal ε-MnO_2 electrodes during the charge-discharge cycles, compared with the improved impedance response observed for the cycled antifluorite-type MnO_2. A dissolution-redeposition mechanism is proposed to account for the impedance response of the MnO_2 electrodes with different morphologies and crystal structures.