Wood‐Derived Monolithic Ultrathick Porous Carbon Electrodes Filled with Reduced Graphene Oxide for High‐Performance Supercapacitors with Ultrahigh Areal Capacitances

Abstract A monolithic ultrathick and dense carbon electrode with high specific surface area and high hydrophilicity is fabricated for high‐performance supercapacitors with ultrahigh areal capacitance by infiltration of graphene oxide inside the aligned pores of the wood followed by lyophilization, carbonization, thermal reduction at 800 °C, and activation with KOH. The porous and vertical microchannels in the wood‐derived carbon facilitate the transport of ions and electrons, while the presence of reduced graphene oxide provides the electrode with high specific surface area, high electrochemical stability, and compactness. Benefiting from the efficient pores resulted from the KOH activation, the monolithic electrode exhibits a high specific surface area of 1049.9 m 2 g −1 with an enhanced permeability, and remains its primary structure as a freestanding electrode without the use of conductive additives or binders. Consequently, the directly sliced pellet electrode with a thickness of 2.2 mm delivers a high areal capacitance of 26.6 F cm −2 at a current density of 1 mA cm −2 in 6 M KOH electrolyte. The resultant symmetrical supercapacitor with a KOH gel electrolyte reaches an energy density of 0.91 mWh cm −2 and a maximum power density of 11.90 W cm −2 .