Nitrogen-doped porous carbon composite with three-dimensional conducting network for high rate supercapacitors

Nitrogen-doped porous carbon materials are widely used as electrode materials for supercapacitors. However, the electrodes based on these materials generally suffer from poor conductivity due to point-to-point contact of granular materials, especially at high charging/discharging rates. Herein, nitrogen-doped porous carbon composite (N-PC/CNT) with three-dimensional (3D) conducting network is prepared by carbonizing carbon nanotube (CNT) thread zeolitic imidazolate framework-8 (ZIF-8) composite. In this construction, the carbonized ZIF-8 with rich pore structure serves as a “reservoir” to provide storage space for electrolyte ions, while CNTs act as “wires” to form internal 3D conducting network for rapid electron transfer. As a result, the obtained N-PC/CNT exhibits a high specific capacitance of 334.5 F g−1 at 1 A g−1, excellent rate capability (195.5 F g−1 at 100 A g−1, capacitance retention of 58%), remarkable cycling stability (almost 100% capacitance retention after 20000 cycles) and outstanding frequency response with an ultrahigh rate up to 3 V s−1 in 6 M KOH electrolyte. These prominent performances result from the synergy of high nitrogen doping content (12.1 at.%), large specific surface area (980.2 m2 g−1), suitable pore size distribution and excellent conductivity. The assembled N-PC/CNT//N-PC/CNT symmetric supercapacitor exhibits a maximal energy density of 17 Wh kg−1 at a power density of 533 W kg−1 in 1 M Na2SO4 electrolyte. Evidently, the nitrogen-doped porous carbon composite has a great development potential for advanced supercapacitors or other electrochemical energy storage devices.