The electrochemical experiment was conducted in 6 M KOH electrolyte, which showed the specific capacitance values of 334, 349, 330, and 347 F g -1 for NCS-900, NCS-850, NCS-800, and NCS-750 electrodes at 0.2 A g -1 , respectively. NCS-850 delivered the highest specific capacitance value, and displayed the high cycling stability of 97% after 11000 cycles at 10 A g -1 . Further, ionic liquid EMIMBF4 electrolyte was utilized, and the NCS-850 electrode showed higher specific capacitance of 244 F g -1 at 0.2 A g -1 , and a capacitance retention of about 71 %, and delivered the specific energy density of 104 Wh Kg -1 at 0.2 A g -1 . The high capacity, and superior rate capacity performance of NCS-850 electrode was attributed to ultrahigh SBET (3326 m 2 g -1 ) in providing plenty of active sites for charge storage, optimized proportion of small-mesopores, and micropores for fast ion transport, thin 2D-nanosheets for short diffusion paths, and the introduction of heteroatoms, and defects to enhance the active sites as well as the ion-accessible surface area by wettability.