Design and synthesis of highly efficient nitrogen-doped carbon nano-onions for asymmetric supercapacitors

The preparation of highly graphitic carbon materials encourages the synthesis of sustainable energy storage for fast charging power applications. In this consideration, at present work, porous nitrogendoped carbon nano-onions (N-CNO) were prepared by a different strategic, simple, low-cost, one-step pyrolysis technique. The fabricated material was characterized by various physical and electroanalytical measurements. The D, G, and 2D bands from Raman and pyridinic-N, pyrrolic-N, graphitic-N, and pyridinic-N-O from the X-ray photoelectron spectroscopy confirmed the graphitic nature of the N-CNO material. The results of specific capacitance for the as-grown materials containing N-CNO at a current density of 1 A/g have achieved a specific capacitance of 234 F g- 1. Moreover, the retention of N-CNO after 5000 long charge/discharge was 98%. The utilizing voltages of the synthesized asymmetric devices were expanded to 1.6 V in 2 M KOH solution, providing a notable specific capacitance of 79 F g-1 and higher energy densities of 27.2 Wh kg-1 at 1 A g-1. Mainly, even at higher current densities (10 A/g) this device still holds higher power densities (7.5 kW kg-1) while keeping 12 Wh kg-1 energy densities. Nevertheless, the well-being asymmetric device explores notable electrochemical cycling stabilities and capacitance retention of 98% over 5000 at 8 A g-1. These values evident that N-CNO will have been utilized as a surrogate electrode source and a potential candidate in SCs with higher specifical energy/power densities.