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Model and Measurement Based Insights into Double Layer Capacitors: Voltage-Dependent Capacitance and Low Ionic Conductivity in Pores

Madabattula, G and Kumar, S (2020) Model and Measurement Based Insights into Double Layer Capacitors: Voltage-Dependent Capacitance and Low Ionic Conductivity in Pores. In: Journal of the Electrochemical Society, 167 (8).

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Official URL: https://dx.doi.org/10.1149/1945-7111/ab90aa


Electrochemical double layer capacitors (EDLCs) store electrical energy by accumulating ions near charged interfaces in porous electrodes. The available transport models for their characteristics often ignore the associated complexities: electrode-specific capacitance, its dependence on local potential difference and electrolyte concentration, and ionic conductivity in charged pores. As a result, modelling efforts are yet to be supported, supplemented, and validated with measurements. Detailed electrode specific measurements are reported in this work on discharge of porous carbon-H2SO4 EDLCs. A substantially decreased charge recovery at high currents and subsequent prolonged potential recovery in open circuit mode are salient features. These are compared with predictions of a comprehensive transport model, which uses potential dependent electrode capacitances retrieved from measurements. The model, with no fitted parameters and Bruggeman correction for ionic conductivity in pores, fails to capture observed features, unless an order of magnitude decrease beyond Bruggeman correction is effected. The required decrease is larger at higher electrolyte concentrations and for electrode with double layer of larger size ions. The corrected model quantitatively explains the unusual features observed, in addition to matching measured cyclic-voltammograms with substantial charge-redistribution as the cause of lag between current and voltage. © 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

Item Type: Journal Article
Publication: Journal of the Electrochemical Society
Publisher: Institute of Physics Publishing
Additional Information: Copy right for this article belongs to Institute of Physics Publishing
Keywords: Capacitance; Electric discharges; Electrolytes; Ionic conductivity; Porous materials, Charge redistribution; Cyclic voltammograms; Double layer capacitor; Electrochemical double-layer capacitors; Electrode capacitance; Electrolyte concentration; Modeling and measurement; Voltage-dependent capacitances, Electrochemical electrodes
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Date Deposited: 17 Nov 2020 09:52
Last Modified: 17 Nov 2020 10:14
URI: http://eprints.iisc.ac.in/id/eprint/65753

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