Regulating Capacitive Performance of Monolithic Carbon Sponges by Balancing Heteroatom Content, Surface Area and Graphitization Degree

Abstract Monolithic electrodes show a great advantage in energy storage devices. Nitrogen/oxygen co‐doped carbons sponges (NOCSs) prepared from carbonized melamine foams are directly applied as the supercapacitor electrodes without any additives and binders. The influence of carbonization temperatures from 650 to 950 °C on the heteroatom (N and O) content, surface area, graphitization degree, and capacitor performance of carbon sponges are systematically investigated, and it is found that NOCS‐850 delivers a better overall capacitive properties for its balanced heteroatom content, surface area, and graphitization degree. It possess specific capacitances of 338 F g −1 at a scan rate of 1.0 mV s −1 and 168.3 F g −1 at a current density of 0.5 A g −1 in 1.0 M H 2 SO 4 . After 5000 cycles of repeated charging/discharging process, the capacitance retention remains 107%. When being assembled into an all‐solid‐state supercapacitor, the NOCS‐850 has a energy density of 5.38 Wh kg −1 at a power density of 233 W kg −1 . A red light‐emitting diode can be successfully lighted by three connected all‐solid‐state supercapacitors of NOCS‐850, illustrating its potential application in energy storage field.