Improving electron and ion transport by constructing 3D graphene nanosheets sandwiched between porous carbon nanolayers produced from resorcinol-formaldehyde resin for high-performance supercapacitor electrodes

An ideal supercapacitor electrode should contain three-dimensional (3D) interpenetrating electron and ion pathways with a short transport distance. Graphene-based carbon materials offer new and fascinating opportunities for high performance supercapacitor electrodes due to their excellent planar conductivity and large surface area. 3D graphene nanosheets coated with carbon nanolayers of controllable thickness from resorcinol-formaldehyde (RF) resin are constructed and activated by KOH to develop pores. Such a sandwich structure provides abundant transport channels for ions with short paths. The porous carbon nanolayers accelerate ion transport, while the graphene networks improve the conductivity, boosting electron transport. As expected, the prepared porous carbon has a high surface area of 690 m² g⁻¹ and a high specific capacitance of up to 324 F g⁻¹ in a 6 mol L⁻¹ KOH aqueous electrolyte at a current density of 0.2 A g⁻¹. More than 99% of the capacitance is retained after 8000 charge–discharge cycles at a high current density of 5 A g⁻¹, indicating good cycling stability. This research provides an effective strategy for the development of outstanding electrode materials for the enhanced transport of both electrons and ions.