Graphene-Regulated K-Ion Transport in Hierarchically Porous Biomass-Derived Carbon for High-Power Aqueous Supercapacitors

Abstract Understanding how graphitic structures evolve in biomass-derived carbon and regulate ion transport is critical for designing high-power aqueous supercapacitors. However, the evolution of graphene-like domains during chemical activation of biomass-derived carbons and their subsequent influence on ion-specific charge-storage kinetics remain poorly understood. This study elucidates the activation-induced evolution of graphene-like domains in hierarchically porous carbon derived from balsa wood and establishes their role in regulating electrolyte-dependent ion storage. Structural evolution during activation involves the selective removal of disordered sp3-rich carbon and K-mediated intercalation/exfoliation, followed by liquid-phase-assisted reconstruction of exfoliated graphitic sheets into extended graphene-like layers at 900 °C. In neutral K2SO4, the optimized Act.900 electrode maintains an energy density of 9.4 Wh kg−1 even at a high power density of 21.1 kW kg−1, demonstrating its rapid charge-storage capability. Comparative electrochemical analysis using Li+, Na+, and K+ electrolytes reveals a distinct K+ advantage under high-rate conditions, arising from its low hydration energy, rapid desolvation, and favorable interaction with graphene interlayers. Electrodes with different degrees of graphene evolution further demonstrate that continuous graphene-like domains critically regulate high-rate K-ion storage, providing a mechanistic basis for designing biomass-derived high-power aqueous supercapacitors.