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

Abstract

This study presents a facile and low-cost method to prepare core–shell nano-structured β-MnO₂@δ-MnO₂, in which β-MnO₂ nano-wires act as the cores to form 3D networks and δ-MnO₂ as the shells. A uniform hierarchical β-MnO₂@δ-MnO₂ core–shell structure can be obtained after layered structured δ-MnO₂ is deposited on the surface of the needle-like β-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 β-MnO₂@δ-MnO₂ was ∼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 β-MnO₂@δ-MnO₂ showed that the new material has great potential for use in electrochemical supercapacitors, and the facile wet chemistry method used to synthesize β-MnO₂@δ-MnO₂ could be a promising method to produce highly stable MnO₂-based electrode materials in large batches.