Superior energy‐power performance of N‐doped carbon nano‐onions‐based asymmetric and symmetric supercapacitor devices

Summary Highly graphitic nitrogen‐doped carbon nano‐onions (N‐CNO) have attracted much attention in the field of energy storage device applications. Herein, we have synthesized N‐CNO by a simple flame pyrolysis method for symmetric and asymmetric (ASC) supercapacitor devices. The nitrogen doping is performed in‐situ during the pyrolysis of pyrrole. The synthesized N‐CNO has a high surface area of 49 m2 g−1 with 4 at% nitrogen content. The structural properties have confirmed the formation of graphitic N‐CNO with highly ordered concentric graphene layers with proper lattice spacing. The fabricated symmetric and asymmetric devices have shown high specific capacitance and excellent energy‐power performance. Especially, the ASC device shows a specific capacitance value 205 F g−1 with a high energy density (60 Wh kg−1) and power density (5.5 kW kg−1), leading to an increase in the power density by 260% for a mere 60% decrease in the energy density. In addition, both the novel symmetric and asymmetric devices have shown excellent capacity retention of 96% to 98% over 5000 cycles. The demonstrated results show the superior electrochemical performance of the active material, which indicates that the N‐rich‐CNOs can be used as a novel anode material in energy storage devices with high energy density and high power performance. Symmetric and Asymmetric supercapacitor devices of N‐CNOs.