Ultrathin MnO2 nanoflakes deposited on carbon nanotube networks for symmetrical supercapacitors with enhanced performance

Abstract

Abstract Manganese dioxide is a promising electrode material for electrochemical supercapacitors, but its poor electronic conductivity (10 −5 ∼10 −6 S cm −1 ) limits the fast charge/discharge rate for practical applications. In the present work, we use the chemical vapor deposition (CVD) method to grow highly conductive carbon nanotube (CNT) networks on flexible Ni mesh, on which MnO 2 nanoflake layers are deposited by a simple solution method, forming a hierarchical core-shell structure. Under the optimized mass loading, the as-fabricated MnO 2 nanoflake@CNTs/Ni mesh electrode exhibits a high specific capacitance of 1072 F g −1 at 1 A g −1 in three-electrode configuration. Due to advantageous features of these core-shell electrodes (e.g., high conductivity, direct current path, structure stability), the as-assembled symmetric supercapacitor (SSC) based on MnO 2 @CNTs/Ni mesh has a wide working voltage (2.0 V) in 1 M Na 2 SO 4 aqueous electrolyte. Finally an impressive energy density of 94.4 Wh kg −1 at 1000 W kg −1 and a high power density of 30.2 kW kg −1 at 33.6 Wh kg −1 have been achieved for the as-assembled SSC, which exhibits a great potential as a low-cost, high energy density and attractive wearable energy storage device.