Preparation and characterization of manganese dioxides with nano-sized tunnel structures for zinc ion storage (Conference Paper)

摘要

α-, β-, γ-, and δ-types manganese dioxide (MnO _2) with different tunnel structures and morphologies have been successfully synthesized by a common liquid co-precipitation method based on the redox reactions of Mn ~4 and Mn ~2. The crystalline tunnel structure, particle size, and morphology of the manganese dioxides have been characterized by X-ray diffraction and scanning electron microscopy. It is found that the morphology of as-prepared MnO _2 changes with the concentration of raw materials. Depending on the procedure of preparation, spherical particles about 20 nm in diameter, nanorods of 40-100 nm in length and about 20 nm in diameter, or interlocked nanosheet of 10-20 nm in thickness are formed. The effect of crystallographic forms of MnO _2 on Zn ~2 ion storage properties has been revealed. The electrochemical performances of the α-, β-, γ-, and δ-MnO _2 were characterized by the galvanostatic charge-discharge and cyclic voltammetry tests. The δ-MnO _2 shows the highest specific capacity (269 mAh g ~(-1)) in the new zinc battery system Zn|ZnSO _4(aq)|MnO _2.