KOH Chemical-Activated Porous Carbon Sponges for Monolithic Supercapacitor Electrodes

Developing monolithic electrodes with high capacitor performance remains a challenge in energy storage field. KOH is applied to chemically activated commercial melamine sponges, and it can prepare monolithic N-/O-doped carbon sponge (NOCS) electrodes. The graphitization degree, heteroatom content, and pore size distribution can be regulated by adjusting the KOH/melamine sponge mass ratio. The optimal electrode demonstrates specific capacitances of 440 F g–1 at 1.0 mV s–1 and 273 F g–1 at 0.5 A g–1, and the capacitance retention remains 85.0% after 10,000 charging–discharging cycles at 10 A g–1. The charge storage mechanism in NOCSs is systematically studied by separating the capacitive effect (pseudo-capacitance) from the diffusion-controlled contribution (electrical double-layer capacitance). Moreover, the capacitance performances of NOCSs in a polyvinyl alcohol/KOH electrolyte are also investigated by assembling all-solid-state supercapacitors, which can output an energy density of 5.61 W h kg–1 at 250 W kg–1 and power three light-emitting diodes with different colors.