This study presents a facile and low-cost method to prepare core-shell nano-structured b-MnO 2 @d-MnO 2 , in which b-MnO 2 nano-wires act as the cores to form 3D networks and d-MnO 2 as the shells. A uniform hierarchical b-MnO 2 @d-MnO 2 core-shell structure can be obtained after layered structured dMnO 2 is deposited on the surface of the needle-like b-MnO 2 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 b-MnO 2 @d-MnO 2 was $200 F g À1 and the specific capacitance retention was almost 100% after 5000 cycles at a current density of 1 A g À1 in 1 M LiOH electrolyte. The excellent cycling stability of b-MnO 2 @d-MnO 2 showed that the new material has great potential for use in electrochemical supercapacitors, and the facile wet chemistry method used to synthesize b-MnO 2 @d-MnO 2 could be a promising method to produce highly stable MnO 2 -based electrode materials in large batches.