The increasing demand for supercapacitors with high energy and power density has attracted extensive attention in designing advanced carbon materials with high accessible surface area, hierarchical porosity, and 2D/3D morphology. Here, we report a new approach to tune the morphology and structure of the nanocarbons by using methyl cellulose as the precursor. Due to the varying effect of different activating agents, the interconnected sheet-like carbon with a high surface area of up to 2285 m(2) g(-1) and a thickness down to similar to 4 nm can be obtained. These important characteristics make the nanocarbons demonstrate a high capacitance of 144 F g(-1) at 1 A g(-1) and 20 degrees C, and an excellent capacitance retention ratio of 64% at 100 A g(-1) in ionic liquid. Because of the high fraction of meso/macropores for nano carbons, an outstanding capacitance of 116 F g(-1) can be achieved at 0 degrees C, with a high capacitance retention ratio of 39% at 100 A g(-1). A high energy of 16-17 and 9-10 W h kg(-1) can be maintained at 20 and 0 degrees C when the supercapacitor is charged in less than 1s. The excellent electrochemical response of nanocarbons suggests that the proposed preparation process is promising for developing advanced carbon electrodes. (C) 2017 Elsevier B.V. All rights reserved.