Construction of high-performance electrode materials of NiCo2O4 nanoparticles encapsulated in ultrathin N-doped carbon nanosheets for supercapacitors.

Highly dispersed nitrogen doped carbon (N-C) is decomposed by 2-methylimidazole (C4H6N2) and is used as a composite material with nickel cobaltite (NiCo2O4). The N-C and NiCo2O4 composites are obtained by a one-step hydrothermal method and subsequent calcination. In addition, N-C is used to control the morphology and structure of NiCo2O4 to obtain excellent capacitor materials. The N-C/NiCo2O4 electrode shows an excellent specific capacitance of 157.97 mA h g-1 (1263.75 F g-1) at 1 A g-1. Herein, we successfully develop a N-C/NiCo2O4//AC asymmetric supercapacitor (ASC), which is prepared using N-C/NiCo2O4 as a cathode coupled with activated carbon (AC) as an anode at a voltage of 1.6 V. The prepared N-C/NiCo2O4//AC device shows an excellent volumetric energy density of 66.44 mW h kg-1. The promising performance of N-C/NiCo2O4//AC illustrated its potential for portable supercapacitor applications.