Manganese dioxide core-shell nanostructure to achieve excellent cycling stability for asymmetric supercapacitor applications

This study presents a facile and low-cost method to prepare core-shell nano-structured beta-MnO2@delta-MnO2, in which beta-MnO2 nano-wires act as the cores to form 3D networks and delta-MnO2 as the shells. A uniform hierarchical beta-MnO2@delta-MnO2 core-shell structure can be obtained after layered structured delta-MnO2 is deposited on the surface of the needle-like beta-MnO2 particles via a simple wet chemistry method at room temperature. The as-prepared materials were physically and electrochemically characterized by nitrogen isotherm analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and potentiostatically/galvanostatically. Under our conditions, the electrochemical results showed that the specific capacitance of beta-MnO2@delta-MnO2 was similar to 200 F g(-1) and the specific capacitance retention was almost 100% after 5000 cycles at a current density of 1 A g(-1) in 1 M LiOH electrolyte. The excellent cycling stability of beta-MnO2\@delta-MnO2 showed that the new material has great potential for use in electrochemical supercapacitors, and the facile wet chemistry method used to synthesize beta-MnO2@delta-MnO2 could be a promising method to produce highly stable MnO2-based electrode materials in large batches.