Co-doped In-Situ Engineered Carbon Nano-Onions Enabled High-Performance Supercapacitors

The feasibility of achieving in situ sulfur (S) and nitrogen (N) co-doped carbon nano-onions (CNOs and SN–CNOs) via a simple flame-pyrolysis technique without using sophisticated high-vacuum annealing or expensive nanodiamond-based complex processes is demonstrated for the first time. The characteristic onion-like feature of 0.34 nm remained intact with a high degree of ordering and graphitization, even though the S and N heteroatoms were co-doped simultaneously. The in situ co-doped SN–CNO demonstrated high supercapacitor device performance with a high energy density of 25 Wh kg−1 at a maximum power density of 18 kW kg−1, maintaining 98% specific capacitance over 10,000 cycles at 10 A g−1. These are the highest achieved device performance values of a fullerene family electrode material to date.