Mesoporous manganese dioxide cathode prepared by an ambient temperature synthesis for Na-ion batteries

A manganese dioxide ( gamma -MnO sub(2)) cathode was prepared by a simple ambient temperature redox reaction method for Na-ion batteries. The X-ray diffraction (XRD) pattern of the as-prepared sample annealed to low-temperatures ( similar to 200 degree C) revealed diffraction peaks confined to the orthorhombic phase of gamma -MnO sub(2). The particle morphology of the sample, as revealed by the electron microscopy studies, was comprised of aggregated nanowire crystallites with diameters and lengths in the range of 2-3 and 25-40 nm, respectively. From the N sub(2) adsorption and Brunauer Emmett Teller (BET) studies, the average pore diameter and the surface area of the annealed gamma -MnO sub(2) was determined to be 3.77 nm and 148 m super(2) g super(-1) respectively and thereby the mesoporous sample characteristics were confirmed. When employed in a Na/MnO sub(2) cell, the mesoporous gamma -MnO sub(2) cathode registered initial discharge and charge capacities of 234 and 233 mA h g super(-1) with almost 100% Coulombic efficiency. Although gradual capacity fading was observed on successive electrochemical cycling, the present study confirms the use of mesoporous electrodes as suitable Na-intercalation/de-intercalation hosts for emerging sodium battery applications.