The performance of a supercapacitor (SCs) fabricated from coal-based activated carbon was studied in terms of its specific capacitance (C), life cycle and rate performance. In this work, a low cost modified nitrogen-doped coal-based activated carbon (MAC N ) was prepared by KOH/H2O co-activation from lignite. Experimental results and density functional theory (DFT) calculations showed that introducing nitrogen atoms into the coal-based activated carbon leads to a rearrangement of the carbon skeleton structure and changes the surface chemical environment. Leading to the MAC N internal disorder increases (I-D/I-G is up to 0.99), structural stability improves (TGA curves shift right), and various nitrogen functional groups (N-5, N-6, N-Q) are formed on the carbon surface. In addition, the MAC(N) possesses high specific surface area (S-BET: 2129 m(2)/g), abundant micropores (V-mic: 0.62 cm(3)/g), appropriate mesopores (V-mes: 0.39 cm(3) /g, V-mes ratio: 38.6%), low impurity content, and highly N-doping (9.59 wt%). These characteristics of the MAC N provide for a high C of 323 F/g at a current density of 0.5 A/g. The enhanced MAC N is 64.8% higher than the undoped MAC. Furthermore, a high energy density of 10 Wh/kg can be achieved with a MAC N -assembled symmetrical cell when the power density of 250 W/kg in 6 M KOH. (C) 2020 Elsevier Inc. All rights reserved.