title: Enhanced charging kinetics of porous electrodes: surface conduction as a short-circuit mechanism.
abstract: We use direct numerical simulations of the Poisson-Nernst-Planck equations to study the charging kinetics of porous electrodes and to evaluate the predictive capabilities of effective circuit models, both linear and nonlinear. The classic transmission line theory of de Levie holds for general electrode morphologies, but only at low applied potentials. Charging dynamics are slowed appreciably at high potentials, yet not as significantly as predicted by the nonlinear transmission line model of Biesheuvel and Bazant. We identify surface conduction as a mechanism which can effectively "short circuit" the high-resistance electrolyte in the bulk of the pores, thus accelerating the charging dynamics and boosting power densities. Notably, the boost in power density holds only for electrode morphologies with continuous conducting surfaces in the charging direction.
authors.affiliation: Department of Mechanical Engineering, University of California, Santa Barbara, California 93106, USA.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Mirzadeh
authors.affiliation: Department of Mechanical Engineering, University of California, Santa Barbara, California 93106, USA.
authors.forename: Frederic
authors.initials: F
authors.lastname: Gibou
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Squires