Synthesis of honeycomb MnO2 nanospheres/carbon nanoparticles/graphene composites as electrode materials for supercapacitors

Improving the electrochemical performance of manganese dioxide (MnO2) electrodes is of great significance for supercapacitors. In this study, a novel honeycomb MnO2 nanospheres/carbon nanoparticles/graphene composites has been fabricated through freeze-drying method. The honeycomb MnO2 nanospheres are well inserted and dispersed on the graphene. Carbon nanoparticles in the composites act as spacers to effectively prevent graphene from restacking and agglomeration, construct efficient 3D conducting architecture with graphene for honeycomb MnO2 nanospheres, and alleviate the aggregation of honeycomb MnO2 nanospheres by separating them from each other. As a result, such honeycomb MnO2 nanospheres/carbon nanoparticles/graphene composites display much improved electrochemical capacitive performance of 255 F g(-1) at a current density of 0.5 A g(-1), outstanding rate capability (150 F g-1 remained at a current density of 20 A g(-1)) and good cycling stability (83% of the initial capacitance retained after 1000 charge/discharge cycles). The strategy for the synthesis of these composites is very effective. (C) 2015 Elsevier B.V. All rights reserved.