Controllable synthesis of reduced graphene oxide/nickel hydroxide composites with different morphologies for high performance supercapacitors

This work aims to synthesize reduced graphene oxide/nickel hydroxide composites, recorded as rGO/Ni(OH)(2), with different morphologies (nanoflakes, sticks, flowers and cubes) and analyze how different additional agents (tween-80 and sodium oxalate) affect their microstructure and electrochemical performance. We put forward here a simple, low cost and controllable chemical reaction method to large-scale production of rGO/Ni(OH)(2) composites with high performance. At a charge and discharge current density of 1 A/g, the specific capacitance of the rGO/Ni(OH)(2) composite electrodes is 1670.4, 1866.8, 890.6 and 366.9 F/g for nanoflakes, sticks, flowers and cubes, respectively. Comparatively, the specific capacitance of the rGO/Ni(OH)(2) nanoflakes, sticks, flowers and cubes keep 79.5%, 29.2%, 85.3% and 34.9%, respectively, when the current density changes from 1 to 20 A/g, and the capacitance remains respectively 172%, 15%, 90% and 100% of their initial values after 3000 cycles. Furthermore, the assembled rGO/Ni(OH)(2) nanoflakes//rGO asymmetric supercapacitor shows a wide voltage window (0-1.6 V), stable cycling performance (capacitance retains 158% after 3000 cycles), excellent specific energy density (54.1 Wh/kg at a power density of 1.0 kW/kg and 26.79 Wh/kg at a power density of 30.9 kW/kg). The successful preparation of rGO/Ni(OH)(2) with various morphologies paves a new way for tailoring the microstructure and optimizing the electrochemical performance of graphene-based composite electrodes for high performance supercapacitor applications. (C) 2019 Elsevier B.V. All rights reserved.