Growth of ultrathin Ni-Co-Al layered double hydroxide on reduced graphene oxide and superb supercapacitive performance of the resulting composite

Ultrathin Ni-Co-Al layered double hydroxide (LDH) sheets directly grew on reduced graphene oxide (RGO) nanosheets by a facile hydrothermal route in a mixed solvent of water and ethylene glycol, yielding the RGO/Ni0.75-xCoxAl0.25-LDH (x = 0, 0.05, 0.15) composites. Structural analyses revealed that the resulting composites presented a unique morphology of crumpled silk veil waves, in which the ultrathin Ni0.75-xCoxAl0.25-LDH sheets, composed of 2-3 host layers, were entangled with the rippled RGO nanosheets. Electrochemical analyses demonstrated that the RGO/Ni0.70Co0.05Al0.25-LDH composite showed superior supercapacitive performance, as compared with the pure Ni0.70Co0.05Al0.25-LDH and the RGO/Ni0.75-xCoxAl0.25-LDH (x = 0, 0.15) composites. It exhibited not only ultrahigh cycling stability and good rate capability, but also considerably high specific capacitance. It possessed a high specific capacitance of 1544 F g(-1) at current densities of 1 A g(-1), still delivering a high capacitance of 1081 F g(-1) at an increased current density of 40 A g(-1). After cycled at 10 A g(-1) for 2000 cycles, it retained a capacitance of 1343 F g(-1) without capacitance decay observed. The superb supercapacitive performance along with the facile synthesis method adopted suggested that the RGO/Ni0.70Co0.05Al0.25-LDH composite was promising for supercapacitor applications. (C) 2016 Elsevier B. V. All rights reserved.