Preparation of tank-like resin-derived porous carbon sphere for supercapacitor: The influence of KOH activator and activation temperature on structure and performance

Abstract

The resorcinol-melamine-formaldehyde (RMF) resin as a promising carbon precursor has aroused wide public concern due to its low cost, high nitrogen content, and ease of industrial production. In this work, the tank-like resorcinol–melamine-formaldehyde (RMF) resin spheres are synthesized via the hydrothermal method with the F127 assisting, and tank-like porous carbon spheres (TPCSs) are further prepared by pre‑carbonization and KOH treatment. The F127 is crucial in the formation of tank-like resin spheres and the influence of KOH dosage and activation temperature on morphology, particle size and structure-activity relationships for resin-based carbon spheres are explored in detail. The particle size of RMF resin and TPCSs-X-Y mainly locate at 1.75–2.75 μm and 1–1.8 μm, respectively. TPCSs-2-600 possesses a specific surface area of 1338 m2 g−1 and a high N content of 11.49 %. The specific surface area of resin-based carbon materials initially increases and then decreases with increasing KOH activator, which affects the specific capacitance in a similar trend. The rate performance of resin-based porous carbon materials gets better with increasing KOH dosage due to enhanced ion transport ability resulting from pore size getting larger. Increasing activation temperature enhances the specific surface area and pore size of the carbon electrode, but the specific capacitance reduces gradually in three-electrode system. The cycle stability of TPCSs-2-600 can be 87.8 % after 10,000 times charge-discharge cycles at 10 A g−1 in two-electrode system, and the symmetric supercapacitor assembled with TPCSs-2-700 electrode shows a good energy density of 6.68 Wh kg−1 with a power density of 484 W kg−1 in 6 M KOH aqueous electrolyte.