Novel Electrode Materials and Redox-Active Electrolyte for High-Performance Supercapacitor

Heteroatom doping has been increasingly applied to enhance the electrochemical performance of carbon materials when used as supercapacitor electrodes. However, the use of doped electrode by itself often does not provide sufficiently high performance for aqueous-based supercapacitor. Here, a high-performance supercapacitor was developed, using nitrogen-doped microporous carbon spheres-based materials and a redox-active electrolyte as electrodes and electrolyte, respectively. The doped electrode, which was produced via template and self-assembly routes, exhibited a well-developed microporous structure, large specific surface area, and abundant heteroatoms. The combination of the heteroatom-doped electrode and KI-H2SO4 electrolyte in supercapacitor substantially increased the specific capacitance, from 230 F g(-1) to 532 mAh g(-1). Such a large enhancement was attributed to the addition of KI as a redox mediator in the aqueous electrolyte. The NCS-800 supercapacitor has a specific capacity as high as 68 mAh g(-1) (at a 1 A g(-1) current density) in KI-H2SO4 electrolyte. It could retain 57 % of capacitance even after maintaining a constant voltage of 1 V for 5 hours, highlighting its good electrochemical performance of NCS-800 as a supercapacitor electrode material.