One-Pot Template-Free Strategy toward 3D Hierarchical Porous Nitrogen-Doped Carbon Framework in Situ Armored Homogeneous NiO Nanoparticles for High-Performance Asymmetric Supercapacitors.

The composites based on graphitic carbon and transitional metal oxides are regarded as one of the most promising electrochemical materials owing to the synergistic combination of the advantages of both superior electrical conductivity and high pseudocapacitance. In this work, a simple one-pot template-free strategy for the preparation of three-dimensional hierarchical porous nitrogen-doped carbon framework in situ armored NiO nanograins (NCF/NiO) by an ammonia-induced method assisted by the pyrolysis of a decomposable salt is reported. Due to such unique architecture and homogeneously dispersed nanoparticles, the as-prepared NCF/NiO-2 hybrid exhibits a large specific surface area (412.3 m2 g-1), a high specific capacitance (1074 F g-1 at 1 A g-1), good rate capability (820 F g-1 at 20 A g-1), and outstanding cycling performance (almost no decay after 5000 cycles). Moreover, the solid-state asymmetric supercapacitor, assembled with NCF/NiO-2 and NCS electrodes, can achieve a high cell potential of 1.6 V and deliver a superior specific capacitance of 113 F g-1 at 1 A g-1 with a maximum energy density of 40.18 W h kg-1 at a power density of 800 W kg-1, consequently, giving rise to stable cycling performance (94.3% retention over 5000 cycles). The prepared devices are shown to power 20 green light-emitting diodes efficiently. These encouraging results open up a wide horizon for developing novel carbon-supported metal oxide electrode materials for high rate energy conversion and storage devices.