KOH Chemical-Activated Porous Carbon Sponges for Monolithic Supercapacitor Electrodes
Xiangxia Jing, Lei Wang, Konggang Qu, Rui Li, Wenjun Kang, Haibo Li, Shenglin Xiong
Abstract
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.