Fabrication of Ni-Al LDH/nitramine-N-doped graphene hybrid composites via a novel self-assembly process for hybrid supercapacitors

Abstract

The ingenious synthesis strategies have been highly desired to construct hybrid composites with intriguing properties for supercapacitors. Herein, Ni-Al LDH (layered double hydroxide)/NNDG (nitramine-N-doped graphene) hybrid composites with a layered structure were fabricated via a novel self-assembly process. Nitramine-N dopants anchored to graphene framework allow the self-immobilization of delaminated Ni-Al LDH nanolayers onto the surface of two-dimensional carbonaceous scaffolds and boost the abundance of Ni3+ within hybrid composites along with the removal of interlayer anions within Ni-Al LDH-NO3. Remarkably, the combination of Ni-Al LDH with NNDG can not only enhance the utilization of electrochemically active matrixes in dependence on the increase of electrolyte accessible active sites, but also maximize the electrochemically active contact between inorganic macromolecules and carbonaceous matrixes in favor of the establishment of conductive architectures. Furthermore, Ni-Al LDH/NNDG hybrid composites achieve a specific capacity of 975 C g−1 at a specific current of 1.0 A g−1 with a capacity retention of 75% as the increase of specific currents to 10 A g−1, superior to Ni-Al LDH-NO3 and Ni-Al LDH/rGO hybrid composites. The hybrid supercapacitor comprised of Ni-Al LDH/NNDG hybrid composites as a positive electrode and activated carbon as a negative electrode attains a high energy density of 59 Wh kg−1 with a power density of 1991 W kg−1 at a specific current of 2.5 A g−1 and retains 95% of the initial capacitance after 10 000 cycles at a specific current of 10 A g−1. The excellence electrochemical performance demonstrates clearly the potential application of self-assembled Ni-Al LDH/NNDG hybrid composites for hybrid supercapacitors.