Comparison of Nanoarchitecture to Porous Media Diffusion Models in Reduced Graphene Oxide/Aramid Nanofiber Electrodes for Supercapacitors

Structural electrodes made of reduced graphene oxide (rGO) and aramid nanofiber (ANF) are promising candidates for future structural supercapacitors. In this study, the influence of nanoarchitecture on the effective ionic diffusivity, porosity, and tortuosity in rGO/ANF structural electrodes is investigated through multiphysics computational modeling. Two specific nanoarchitectures, namely, "house of cards" and "layered" structures, are evaluated. The results obtained from nanoarchitecture computational modeling are compared to the porous media approach and show that the widely used porous electrode theories, such as Bruggeman or Millington-Quirk relations, overestimate the effective diffusion coefficient. Also, the results from nanoarchitecture modeling are validated with experimental measurements obtained from electro-chemical impedance spectroscopy and cyclic voltammetry. The effective diffusion coefficients obtained from nanoarchitectural modeling show better agreement with experimental measurements. Evaluation of microscopic properties such as porosity, tortuosity, and effective diffusivity through both experiment and simulation is essential to understand the material behavior and to improve its performance.