Charging dynamics in a laminate-electrode model for graphene-based supercapacitors

Abstract

Development of porous electrode materials for high-performance supercapacitors depends on the efficiency of pore utilization for charge storage. It remains an experimental and theoretical challenge to quantitatively relate the porous structure to charging dynamics. Here, based on a laminate-electrode model of graphene-based supercapacitors, we perform the equivalent circuit model to characterize the structure-charging dynamics relationship of porous electrodes by coupling key structural features in a mathematical expression for the Resistor-Capacitor (RC) time. This theoretical description is validated by direct numerical calculations of the Poisson-Nernst-Planck (PNP) equations. We discover that the charging dynamics of graphene-based supercapacitors is dominated by the ion diffusion from the electrolyte region into the layered structure. The predicted charging time compares well with the experimental investigations reported in the literature on graphene-based supercapacitors. Our work bridges nanoscopic transport behaviors with macroscopic devices, providing theoretical insights of the structure-dependent ion transport in two-dimensional materials-based films for compact energy storage.