Nanosized silver-coated and doped manganese dioxide for rechargeable lithium batteries

Nanosized pure, Ag-coated and doped manganese dioxides (MDO) were prepared through a redox reaction between KMnO4 and fumaric acid. XRD analysis showed cryptomelane crystal structure for pure, coated and doped α-phases. Chemical analysis detected the presence of silver in doped and coated MDO. Scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) analyses confirmed the presence of silver in doped and coated oxides. Transmission electron microscope (TEM) images confirmed the nanosized particles of the prepared oxides. Magnetic measurements showed reduction in Mn3+ ions in the crystal structure after coating and doping with silver. The electrochemical performance showed that Ag-coated and doped MnO2 samples have better initial capacities than pristine MnO2. Ag-coated MnO2 material showed the best capacity retention upon cycling among all prepared MnO2 oxides, i.e. 140 mAh/g after the 40th cycle at C/5 rate in the potential window 1.5–4.0 V vs. Li/Li+.