Macroscopic Modeling of Porous Electrodes

Introduction

It is well known that for optimal performance of electrochemical energy storage and conversion devices, it is necessary to have a nonplanar electrode to increase reaction area. One requires a porous electrode with multiple phases that can transport the reactant and products in the electrode while also undergoing reaction [1]; an analogy in heterogeneous catalysis is reaction through a catalyst particle [2]. For traditional devices, porous electrodes are often comprised of an electrolyte (which can be solid or liquid) that carries the ions or ionic current and a solid phase that carries the electrons or electronic current. In addition, there may be other phases such as a gas phase (e.g., fuel cells). Schematically one can consider the porous electrode as a transmission-line model as shown in Fig. 1.

Macroscopic Modeling of Porous Electrodes, Fig. 1

Simple equivalent-circuit representation of a porous electrode. The total current density, i, flows through the separator or...