scholarly journals Erratum: Corrigendum: Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Anis Allagui ◽  
Todd J. Freeborn ◽  
Ahmed S. Elwakil ◽  
Brent J. Maundy
Keyword(s):  
Cyclic Voltammetry ◽  
Double Layer ◽  
Electric Double Layer ◽  
Constant Current ◽  
Constant Current Charge ◽  
Double Layer Capacitors ◽  
Charge Discharge ◽  
Electric Double Layer Capacitors

scholarly journals Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Anis Allagui ◽  
Todd J. Freeborn ◽  
Ahmed S. Elwakil ◽  
Brent J. Maundy
Keyword(s):  
Cyclic Voltammetry ◽  
Double Layer ◽  
Time Domain ◽  
Electric Double Layer ◽  
Constant Current ◽  
Step Response ◽  
Current Voltage ◽  
The Time Domain ◽  
Double Layer Capacitors ◽  
Electric Double Layer Capacitors

Abstract The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal S s C behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance R s in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (R s , Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical R s C model. We validate our formulae with the experimental measurements of different EDLCs.

scholarly journals How to Measure and Calculate Equivalent Series Resistance of Electric Double-Layer Capacitors

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1452 ◽  
Author(s):  
Rafael Vicentini ◽  
Leonardo Morais Da Silva ◽  
Edson Pedro Cecilio Junior ◽  
Thayane Almeida Alves ◽  
Willian Gonçalves Nunes ◽  
...  
Keyword(s):  
Double Layer ◽  
Electric Double Layer ◽  
Series Resistance ◽  
Voltage Drop ◽  
Equivalent Series Resistance ◽  
Galvanostatic Charge ◽  
Applied Current ◽  
Double Layer Capacitors ◽  
Charge Discharge ◽  
Electric Double Layer Capacitors

Electric double-layer capacitors (EDLCs) are energy storage devices that have attracted attention from the scientific community due to their high specific power storage capabilities. The standard method for determining the maximum power (Pmax) of these devices uses the relation Pmax = U2/4RESR, where U stands for the cell voltage and RESR for the equivalent series resistance. Despite the relevance of RESR, one can observe a lack of consensus in the literature regarding the determination of this parameter from the galvanostatic charge-discharge findings. In addition, a literature survey revealed that roughly half of the scientific papers have calculated the RESR values using the electrochemical impedance spectroscopy (EIS) technique, while the other half used the galvanostatic charge discharge (GCD) method. RESR values extracted from EIS at high frequencies (>10 kHz) do not depend on the particular equivalent circuit model. However, the conventional GCD method better resembles the real situation of the device operation, and thus its use is of paramount importance for practical purposes. In the latter case, the voltage drop (ΔU) verified at the charge-discharge transition for a given applied current (I) is used in conjunction with Ohm’s law to obtain the RESR (e.g., RESR = ΔU/ΔI). However, several papers have caused a great confusion in the literature considering only applied current (I). In order to shed light on this important subject, we report in this work a rational analysis regarding the GCD method in order to prove that to obtain reliable RESR values the voltage drop must be normalized by a factor of two (e.g., RESR = ΔU/2I).

Preparation and Electrochemical Properties of Fluorinated Mesoporous Carbon Foams for Electric Double-Layer Capacitors

2011 ◽  
Vol 239-242 ◽  
pp. 3190-3193 ◽  
Author(s):  
Yong Jie Cao ◽  
Ming Xian Liu ◽  
Li Hua Gan ◽  
Yao Kang Lv ◽  
Zi Jie Xu ◽  
...  
Keyword(s):  
Contact Angle ◽  
Electrochemical Properties ◽  
Double Layer ◽  
Electric Double Layer ◽  
Mesoporous Carbon ◽  
Galvanostatic Charge ◽  
Carbon Foams ◽  
Double Layer Capacitors ◽  
Charge Discharge ◽  
Electric Double Layer Capacitors

We reported the preparation and electrochemical properties of fluorinated mesoporous carbon foams (F-MCFs) for application as electric double-layer capacitors (EDLCs). By using fluorinated resol which was obtained from the polymerization of formaldehyde, phenol, and 3-fluorophenol as the carbon source and fluorin precursor, and triblock copolymer F127 as a template, F-MCFs were prepared through evaporation induced self-assembly strategy. The F-MCFs were characterized by N2 adsorption and desorption, transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The results indicate that the F-MCFs possess highly ordered mesostructure with a specific surface area of 675 m2/g, a uniform pore size of 2.2 nm and a pore volume of 0.12 cm3/g. The wettability of F-MCFs was investigated by contact angle analysis. The contact angle of F-MCFs for water is 111.5o, much lower than that of mesoporous carbon foams (MCFs) (141o), indicating that the surface wettability of F-MCFs is improved by the introduction of fluorin into the carbon matrix. The enhancement of wettability would increase the surface contact of electrolyte and electrode and accelerate the ion transfer within the pore channel, and thus improve the electrochemical properties of F-MCFs. The electrochemical properties of the F-MCFs have been investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge in electrolyte of 6 mol/L KOH with a three-electrode system. F-MCFs present linear galvanostatic charge-discharge curve at a loading current of 10 mA, and possess good charge-discharge efficiency over 98%. The specific capacitance of the F-MCFs is 220 F/g, significantly higher than that of the MCFs (140 F/g). F-MCFs show important prospect as electrode materials for the application in EDLCs.

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