Rational fabrication of semi-interpenetrating three-dimensional hierarchical carbon materials for high-performance symmetric supercapacitor

Porous carbon materials, characterized by variable surface morphologies, pore structures, crystallinity, and corresponding mechanisms for ion and electron storage and transport, are one of the promising electrode materials for supercapacitors. In this study, ammonium alginate, phenolic resin and calcium ions were introduced to form a nanoscale semi-interpenetrating network structure by sol-gel method. Further, porous carbon materials were prepared through carbonization and KOH activation. By adjusting the activation temperature and alkali-to‑carbon ratio, the activation rules and electrochemical properties of the porous carbon were obtained. Eventually, a coral-like three-dimensional (3D) porous carbon with high specific surface area was constructed. The alkali-to‑carbon ratio and the activation temperature can influence the specific surface area. When the alkali-to‑carbon ratio was 1:4 and the activation temperature was 800 °C, the activated carbon material used as supercapacitor electrode material achieved the highest specific capacitance in an aqueous electrolyte. Moreover, the capacitive performance of a two-electrode capacitor using an organic system as the electrolyte was investigated, and the specific capacitance reached 125.1 F/g at a current density of 0.5 A/g. The carbon material showed good cycling stability in the organic supercapacitor, maintaining >94 % of the initial specific capacitance in a voltage window of 0–2.5 V for 10,000 cycles. This investigation provides a reference for the construction of high-performance 3D hierarchical carbon materials for supercapacitors.