Preparation of ultrafine MnO2 powders by the solid state method reaction of KMnO4 with Mn(II) salts at room temperature

A novel route was used to prepare ultrafine powders of MnO2, i.e. the solid state reaction of KMnO4 with manganese acetate or manganese chloride at or near room temperature. The results of XPS and chemical analysis revealed that the main valence state of synthesized manganese oxides was 4. TEM and XRD showed that the average particle sizes were in the range 10–50 nm with two kinds of shapes: acicular and spherical; and the crystalline form was α+δ-phase. It has been confirmed that the existence of crystalline water was the key factor for the occurrence of the solid phase preparation of nano-particles at low temperature. It has also established that the discharge performance of nano-sized MnO2 electrode was different from that of normal-sized MnO2 electrode.