Novel Synthesis and Characterization of Flexible MnO2/CNT Composites Co-deposited on Graphite Paper as Supercapacitor Electrodes

Although MnO 2 possesses many advantages, such as a high theoretical specific capacity, resource abundance, easy synthesis and environmental friendliness, its poor electrical conductivity and low utilization seriously hinder its large-scale application as an electrode in supercapacitors. A MnO 2 and carbon nanotube (CNT) composite is co-deposited on flexible expanded graphite paper (EGP) by a facile method of composite brush plating. The three-dimensional conductive net of CNT in the composite greatly improves the supercapacitve and mechanical properties of MnO 2 electrode. The paper mainly studied (i) the choice of composite brush plating voltage and (ii) the effect of the concentration of active substance CNTs deposited on the performance of supercapacitor. When the current density is 20 A g –1 , the mass specific capacitance of the flexible CNT@MnO 2 /EGP electrode with an operation potential of 10 V in an electrolyte of 1.5 g L –1 CNTs dropped is 146 F g –1 . The CNT@MnO 2 /EGP/active carbon (AC)/carbon fibre cloth (CFC) flexible aqueous asymmetric supercapacitor (ASC) exhibits an energy density of 36.3 Wh kg –1 at a power density of 126.2 W kg –1 and high cycling stability with 91% capacitance retention after 4000 cycles. This study paves the way to provide a simple and novel technique for the mass production of flexible MnO 2 supercapacitor electrodes. Graphic Abstract The composite brush electroplating technology is successfully developed for fabricating flexible carbon nanotube@MnO 2 composite co-deposited on expanded graphite paper, which displays excellent capacitive performance and cycling stability in an aqueous media.