High performance aqueous supercapacitor based on nitrogen-doped coal-based activated carbon electrode materials

[Display omitted] •N-doped micropores carbon is used for high performance aqueous supercapacitors.•The MACN electrode exhibits a high specific capacitance of 323 F/g.•MACN symmetric cell exhibits an energy density up to 9.8 Wh/kg.•N-doped surface enhances the interaction of ion adsorption by DFT calculation. 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 (MACN) 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 MACN internal disorder increases (ID/IG 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 MACN possesses high specific surface area (SBET: 2129 m2/g), abundant micropores (Vmic: 0.62 cm3/g), appropriate mesopores (Vmes: 0.39 cm3/g, Vmes ratio: 38.6%), low impurity content, and highly N-doping (9.59 wt%). These characteristics of the MACN provide for a high C of 323 F/g at a current density of 0.5 A/g. The enhanced MACN is 64.8% higher than the undoped MAC. Furthermore, a high energy density of 10 Wh/kg can be achieved with a MACN-assembled symmetrical cell when the power density of 250 W/kg in 6 M KOH.