Porosity and tortuosity: Keys for accurate modeling of porous electrodes in supercapacitors

Abstract

Modeling of porous electrodes in supercapacitors (SCs) is rather important for both characterizing and improving the charging/discharging process of SCs, but the current models fail to balance accuracy, flexibility, and detail characterization of the electrode structure, especially the porosity and tortuosity. In this work, we develop a porous tortuous electrode (PTE) model consisting of a stack of multiple parallel plate capacitors with adjustable structural parameters for accurate modeling of SCs. By solving the equivalent circuit of the PTE model, the influence of the electrode structures on electric capacity and relaxation time are characterized with experimental validation, signifying the keys for accurate modeling of SCs as tortuosity and porosity and offering a general formula for describing the relaxation time of SCs. Based on the adjustable parameters in the PTE model, the spatial heterogeneity of the electrodes enables more intricate electrode structure designs. The PTE model facilitates various electrode designs and provides insight into the charging and discharging kinetics of porous electrodes.