Construction of MnO2 nanosheets@graphenated carbon nanotube networks core-shell heterostructure on 316L stainless steel as binder-free supercapacitor electrodes

Carbon nanotubes are regarded as typical and promising electrode materials in supercapacitors. However, small specific capacitance of carbon nanotubes restricts the practical application in high energy density devices. Herein, MnO2 nanosheets@graphenated carbon nanotube networks are synthesized directly on 316L stainless steel as binder-free electrodes for high-performance supercapacitors. Graphenated carbon nanotube networks are grown in-situ on stainless steel by chemical vapor deposition method followed by annealing treatment. Subsequently, MnO2 nanosheets are uniformly deposited on graphenated carbon nanotube networks to construct core-shell heterostructure based on the facile hydrothermal reaction using KMnO4 as the precursor. Core carbon nanotube networks can offer a stable structural backbone and shell MnO2 nanosheets can shorten diffusion paths of ions. The MnO2 nanosheets@graphenated carbon nanotube networks exhibit a high specific capacitance of 575.4 F g(-1) (areal capacitance of 274 mF cm(-2)) at the current density of 0.5 mA cm(-2) and good cycling stability (93% of capacity retention after 6000 cycles), due to the synergistic effects between pseudocapacitive MnO2 nanosheets and conductive carbon nanotube networks. The developed synthetic strategy offers design guidelines for the construction of advanced binder-free electrodes for high-performance supercapacitors. (C) 2019 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.