Carbon Thin Film Wrapped around a Three‐Dimensional Nitrogen‐Doped Carbon Scaffold for Superior‐Performance Supercapacitors

A carbon thin film/carbon foam core/sheath structure was synthesized by chemical vapor deposition (CVD) on carbonized melamine foam. It has a specific capacitance of 310 F g −1 at a current density of 1 A g −1 and shows outstanding electrochemical performance in both aqueous and water‐in‐salt electrolytes. Electrochemical analysis by cyclic voltammetry and galvanostatic charge/discharge testing revealed a large capacitive contribution up to more than 90 % of its total capacitance. The core/sheath structure has advantages in ion transport and a high degree of utilization of the electrode surface, and the synthetic process provides a way to coat carbon thin film on any substrate by nickel‐catalyzed CVD.