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

Abstract

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.

Hydrogels with highly concentrated salt solution as electrolytes for solid-state supercapacitors with a suppressed self-discharge rate

“…This change may be explained with the decreased activation-controlled faradaic side reactions involving water in the LiCl-PAAm hydrogel electrolytes at higher concentrations. [40][41][42][43][44][45][46][47][48] With aqueous electrolytes, side reactions such as oxidation/reduction of the functional groups on the surface of activated carbons, corrosion of carbons, and water oxidation/reduction in the electrolyte may occur. 41 For example, Corrosion of carbon:…”

Supercapacitors (electrochemical capacitors)

“…This measurement quite often follows the leakage current measurement where the system is hold at the certain voltage for a given time (1-12 hours) and the current response is recorded. Both measurements complement each other, although the leakage current in only one of the components causing capacitor self-discharge [27][28][29][30][31][32][33] .…”

Lifetime assessment of solid-state hybrid supercapacitors based on cotton fabric electrodes

“…8b reports the voltage decay in the self-discharge behavior after 4 h of charging at constant voltage of 1.6 V of both aged SCs for 10 k cycles. This decrease of cell voltage can be caused by charge redistribution and various parasitic redox processes due to the presence of inorganic or organic impurities in the electrodes, which can produce undesired parallel chemical reactions, mass transport limitations and additional ohmic resistances [52][53][54]. In any case and despite the self-discharge rate is not completely eliminated in our SCs, it is small enough to be considered as negligible for practical devices.…”