Facile synthesis of MnO2 grown on nitrogen-doped carbon nanotubes for asymmetric supercapacitors with enhanced electrochemical performance

Abstract Large reversible capacitance and rapid rate capability are crucial to the realization of the manganese dioxide (MnO 2 ) based electrode material but have been proved to be challenging to achieve due to the poor electronic conductivity of MnO 2 . Herein, the N-CNTs/MnO 2 composites are prepared by using PPy-derived nitrogen-doped carbon nanotubes (N-CNTs) as the support frameworks to load nanosized MnO 2 . Benefitting from the high electronic conductivity of N-CNTs and the large pseudocapacitance of MnO 2 , the N-CNTs/MnO 2 -2 electrodes exhibit high specific capacitance of 366.5 F g −1 at a current density of 0.5 A g −1 which maintains 245.5 F g −1 (67.0%) at 25 A g −1 , indicating excellent rate capability. Moreover, the as-fabricated asymmetric supercapaitors using N-CNTs/MnO 2 -2 and N-CNTs as the positive and negative electrodes achieve a wide stable operating voltage of 1.8 V and a high energy density of 20.9 Wh kg −1 , as well as outstanding cycling stability of 91.6% retention after 5000 cycles at a current density of 5 mA cm −2 . Therefore, these composites are promising electrode materials for the further high-power output energy storage and conversion devices.