However, it is still a huge challenge to achieve the desired
MnO2 structures with a controlled phase. Few reports have
focused on the relation between the structure and the electrochemical properties. In the work reported here, we
successfully synthesized MnO2 with a-, b- and d-type structures by controlling the concentration of metallic cations and
H+
. The effects of different ions on the structures and
morphologies of MnO2 were systematically investigated. The
relation between the structure and the electrochemical
properties was studied by evaluating the capacitance of these
materials. The results show that the loose tunnel or layer
structures (a- and d-type) decrease the effective diffusion path
and increase the effective space for insertion and extraction,
which favors the movement of charged particles (ions, electrons and protons) in the crystal lattice. The unique structures
effectively relieve structural destruction and local volumetric
variations during the charge/discharge (CD) process, which
leads to good electrochemical properties.