Strong interface coupling and few-crystalline MnO2/Reduced graphene oxide composites for supercapacitors with high cycle stability

Long cycle life has been the key factor that inhibits the practical application of transition metal oxides (TMOs)-based pseduocapacitors, due to their poor electrical conductivity and the limited interface charge transfer between TMOs and conductive substrates. We here demonstrate a novel strategy to address this issue by constructing strongly coupled, few-crystalline MnO2 nanosheets/reduced graphene oxide (rGO) composites. The covalent linkage of C-O-Mn at the interface effectively improves the charge transfer efficiency, avoiding the detachment of MnO2 nanosheets from rGO surfaces during the charge/discharge. Meanwhile, the few-crystalline MnO2 nanosheets are able to retain good structural integrity for the long cycling duration at large current densities. In the process of galvanostatic charge/discharge, the resulting composite electrode reveals a specific capacitance up to 234.8 F g(-1) at 0.1 A g(-1) and a 100% of capacitance retention after 20,000 cycles at 10 A g(-1) in neutral Na2SO4 electrolyte. These extraordinary electrochemical properties reflect the synergistic role that the interface design and crystal structure control play in optimizing the performance of TMO-based pseduocapacitors. (C) 2018 Elsevier Ltd. All rights reserved.