(694h) Nonlinear Charging Dynamics of Porous Electrodes

Porous electrodes have many uses, ranging from energy storage to seawater desalination, but their theoretical description remains challenging. In 1963, Newman and Tobias pioneered the continuum theory of transport and reactions in porous electrodes, based on formal volume averaging, and in the same year De Levie derived equivalent circuit models (RC transmission lines) for linear response. These approaches have been successfully applied for decades, e.g. to supercapacitors and batteries, but various nonlinear effects have yet to be analyzed. Here, we extend the continuum theory of porous electrodes by taking into account double-layer salt adsorption (for capacitive desalination) and pseudo-capacitance (for electrochemical energy storage in nanoparticles). Scaling arguments, analytical approximations, and numerical solutions serve to describe different dynamical regimes, and comparisons are made with experimental data.