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.