Enhanced Charging Kinetics of Porous Electrodes: Surface Conduction as a Short-Circuit Mechanism

Mohammad Mirzadeh, Frederic Gibou, and Todd M. Squires
Phys. Rev. Lett. 113, 097701 – Published 25 August 2014

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.

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  • Received 13 April 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.097701

© 2014 American Physical Society

Authors & Affiliations

Mohammad Mirzadeh and Frederic Gibou

  • Department of Mechanical Engineering, University of California, Santa Barbara, California 93106, USA

Todd M. Squires*

  • Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA

  • *squires@engineering.ucsb.edu

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Vol. 113, Iss. 9 — 29 August 2014

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