Predictions of specific energies and specific powers of double-layer capacitors using a simplified model

Authors
Citation
D. Dunn et J. Newman, Predictions of specific energies and specific powers of double-layer capacitors using a simplified model, J ELCHEM SO, 147(3), 2000, pp. 820-830
Citations number
20
Categorie Soggetti
Physical Chemistry/Chemical Physics","Material Science & Engineering
Journal title
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
ISSN journal
00134651 → ACNP
Volume
147
Issue
3
Year of publication
2000
Pages
820 - 830
Database
ISI
SICI code
0013-4651(200003)147:3<820:POSEAS>2.0.ZU;2-K
Abstract
A model based on dilute-solution porous-electrode theory is proposed to des cribe electrochemical devices that store energy in the double layer (double -layer capacitors). Various assumptions, such as neglecting concentration p olarization, potential-dependent capacitance, and micropore effects, are ma de in the model. For constant-current discharges, the model reduces to a re sistance-capacitance (RC) series circuit model after the initial dischargin g transients. The RC series circuit model is seen to fit existing experimen tal data for the discharge times available. The specific energy for constan t-current and constant-power discharges is maximized over a range of discha rge times by optimizing the electrode thickness, electrode porosity, and th e final voltage constrained by the cutoff voltage. This maximization allows predictions of the attainable specific energies and powers for these devic es and shows the influence of the various cell properties. Energy efficienc ies are found for cycles when the capacitor is discharged in a given time a nd then charged infinitely slowly, and when the capacitor is discharged and charged in the same amount of time. Limitations to the model are discussed . (C) 2000 The Electrochemical Society. S0013-4651(99)05-100-9. All rights reserved.