Detailed analysis of the self-discharge of supercapacitors

Kowal, Julia; Avaroglu, Esin; Chamekh, Fahmi; Šenfelds, Armands; Thien, Tjark; Wijaya, Dhanny; Sauer, Dirk Uwe

doi:10.1016/j.jpowsour.2009.12.028

Cited by 204 publications

(151 citation statements)

References 6 publications

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“…Besides, the study of negative electrode SD at 0.0 V, in absence and presence of di-oxygen in the bulk solution by bubbling either nitrogen or oxygen gas, revealed that an increment of oxygen concentration caused a significant potential drop with time of the negative electrode at open circuit, in addition to a diffusion-controlled SD; hence, it is likely that O2 reduction on the negative electrode is the main cause of SD [12]. As already demonstrated in the literature, SD depends on parameters such as temperature, maximum cell potential reached and hold time at this value, and the charge/discharge history [20,23]. To date, the majority of studies were focused on SD dependence with the kind of aqueous electrolyte , in absence [6,[24][25][26][27] or presence of certain surfactants [26,27] or redox couple (redox-active electrolyte) [28], and type of separator [24,29].…”

Section: H2so4mentioning

confidence: 65%

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Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

García‐Cruz

Ratajczak

Iniesta

et al. 2016

Electrochimica Acta

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Please cite this article as: L.García-Cruz, P.Ratajczak, J.Iniesta, V.Montiel, F.Béguin, Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte, Electrochimica Acta http://dx.doi.org/10. 1016/j.electacta.2016.03.159 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe self-discharge (SD) of electrochemical capacitors based on activated carbon electrodes (AC/AC capacitors) in aqueous lithium sulfate was examined after applying a three-hour cell potential hold at Ui values from 1.0 to 1.6 V. The leakage current measured during the potentiostatic period as well as the amplitude of self-discharge increased with Ui; the cell potential drop was approximately doubled by 10°C increase of temperature. The potential decay of both negative and positive electrodes was explored separately, by introducing a reference electrode and it was found that the negative electrode contributes essentially to the capacitor self-discharge. A diffusion controlled mechanism was found at Ui ≤ 1.4 V and Ui ≤ 1.2 V for the positive and negative electrodes, respectively. At higher Ui of 1.6 V, both electrodes display an activation controlled mechanism due to water oxidation and subsequent carbon oxidation at the positive electrode and water or oxygen reduction at the negative electrode.

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Section: H2so4mentioning

confidence: 65%

“…Also, internal ohmic leakage currents generated by a faulty construction and Faradaic reactions with either activation or diffusion controlled mechanism might be the causes of SD process [11,15,19,20]. Activation controlled SD takes place with high concentration species such as electrolyte or functionality on the carbon surface.…”

Section: H2so4mentioning

confidence: 99%

Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

García‐Cruz

Ratajczak

Iniesta

et al. 2016

Electrochimica Acta

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“…Considerable effort has been reported on the modeling of the electrodes in terms of transmission lines with distributed capacitance and resistance [33,34,35]. This approach has been extended to consider networks going from macro-to micro-pores, as in [36,37].…”

Section: Introductionmentioning

confidence: 99%

Predictions of the maximum energy extracted from salinity exchange inside porous electrodes

Jiménez

Fernández

Ahualli

et al. 2013

Journal of Colloid and Interface Science

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Capacitive energy extraction based on double layer expansion (CDLE) is the name of a new method devised for extracting energy from the exchange of fresh and salty water in porous electrodes. It is based on the change of the capacitance of electrical double layers (EDLs) at the electrode/solution interface when the concentration of the bulk electrolyte solution is modified. The use of porous electrodes provides huge amounts of surface area, but given the typically small pore size, the curvature of the interface and EDL overlap should affect the final result. This is the first aspect dealt with in this contribution: we envisage the electrode as a swarm of spherical particles, and from the knowledge of their EDL structure, we evaluate the stored charge, the differential capacitance and the extracted energy per CDLE cycle. In all cases, different pore radii and particle sizes and possible EDL overlap are taken into account. The second aspect is the consideration of finite ion size instead of the usual point-like ion model: given the size of the pores and the relatively high potentials that can be applied to the electrode, excluded volume effects can have a significant role. We find an extremely strong effect: the double layer capacitance is maximum for a certain value of the surface potential. This is a consequence of the limited ionic concentration at the particle-solution interface imposed by the finite size of ions, and leads to the presence of two potential ranges: for low electric potentials the capacitance increases with the ionic strength, while for large potentials we find the opposite trend. The consequences of these facts on the possibility of net energy extraction from porous electrodes, upon changing the solution in contact with them, are evaluated.

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“…The law of energy preservation suggests that the voltage drop can generate energy exchange with the environment. Recent papers describe a model of charge redistribution in porous electrodes as the reason for EDLC voltage changes [3][4][5]. The model does not assume energy dissipation, in contrast to leakage current and faradaic mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Heat generated during electrochemical double-layer capacitor “self-discharge”

et al. 2014

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Eight commercial 10F electrochemical doublelayer capacitors (EDLCs) were connected together and placed in a container filled with mineral oil. The whole system was placed into a Dewar container. Temperature variation and heat exchanged between the test EDLC and the environment during its charging, discharging, and ''self-discharge'' were measured, together with voltage U changes. Charge separation during charging was equivalent to a transition into a more ordered system, which results in entropy decrease, while discharging caused entropy increase (the Peltier-Seebeck effect). Consequently, a number of charging/discharging cycles led to a corresponding series of entropy and temperature changes. The final shape of temperature versus time curve during charging/discharging cycles was due to overlapping of irreversible Joule-Lenz and reversible Peltier heats. When charged EDLC was kept under the open-circuit condition, measured heat flow was negligible in comparison to energy loss calculated from potential drop, assuming that energy E accumulated is proportional at any time to voltage to the second power (i.e., E * U 2 ). The result was interpreted assuming that the EDLC ''self-discharge'' phenomenon is not associated with energy loss by the device, but rather with charge redistribution between EDLC particles characterized by different time constants.

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Detailed analysis of the self-discharge of supercapacitors

Cited by 204 publications

References 6 publications

Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

Predictions of the maximum energy extracted from salinity exchange inside porous electrodes

Heat generated during electrochemical double-layer capacitor “self-discharge”

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