Three-dimensional flexible nitrogen-doped carbon monoliths (3DNC) were prepared by one-step carbonization method of commercially available melamine foam. The carbonization temperature effect on the electrochemical performance of nitrogen-doped carbon monoliths was investigated. With the increase of carbonization temperature, the specific capacitance of binder-free 3DNC electrode intensifies up to 221 F g(-1) at a current density of 0.5 A g(-1) at 950 degrees C in 2 M NaOH and weaken for higher temperature, which can be explained by the balance between nitrogen doping concentration and the specific surface area at different carbonization temperature. Further, the optimized 3DNC exhibits 96% retention after 5000 cycles measurements, indicating its superior long-term stability. Moreover, the assembled symmetric device outputs the maximum energy density of 9.34 Wh kg(-1) as well as the maximum power density of 6.9 kW kg(-1). These results demonstrate the potential application of the designed 3DNC structures for energy storage devices. (C) 2017 Elsevier Ltd. All rights reserved.