Modelling the effects of charge redistribution during self-discharge of supercapacitors

Kaus, Maximilian; Kowal, Julia; Sauer, Dirk Uwe

doi:10.1016/j.electacta.2010.01.002

Cited by 222 publications

(163 citation statements)

References 21 publications

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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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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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“…These models characterise the non-linear behaviour of the leakage current, which is a function of the discharge dynamic pattern and the internal chemistry of the device. A full electrochemical model of self-discharge studies the reactions on the electrode surface, through which electrons cross its double layer, as per the rule of the leakage and mathematical model of [19]. The model combines quantum mechanical and electrochemical phenomena that occur in the self-discharge process.…”

Section: Mathematical Modelmentioning

confidence: 99%

Supercapacitor Electro-Mathematical and Machine Learning Modelling for Low Power Applications

et al. 2018

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Low power electronic systems, whenever feasible, use supercapacitors to store energy instead of batteries due to their fast charging capability, low maintenance and low environmental footprint. To decide if supercapacitors are feasible requires characterising their behaviour and performance for the load profiles and conditions of the target. Traditional supercapacitor models are electromechanical, require complex equations and knowledge of the physics and chemical processes involved. Models based on equivalent circuits and mathematical equations are less complex and could provide enough accuracy. The present work uses the latter techniques to characterize supercapacitors. The data required to parametrize the mathematical model is obtained through tests that provide the capacitors charge and discharge profiles under different conditions. The parameters identified are life cycle, voltage, time, temperature, moisture, Equivalent Series Resistance (ESR) and leakage resistance. The accuracy of this electro-mathematical model is improved with a remodelling based on artificial neuronal networks. The experimental data and the results obtained with both models are compared to verify and weigh their accuracy. Results show that the models presented determine the behaviour of supercapacitors with similar accuracy and less complexity than electromechanical ones, thus, helping scaling low power systems for given conditions.

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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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Modelling the effects of charge redistribution during self-discharge of supercapacitors

Cited by 222 publications

References 21 publications

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

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

Supercapacitor Electro-Mathematical and Machine Learning Modelling for Low Power Applications

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

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