Complex capacitance analysis on rate capability of electric-double layer capacitor (EDLC) electrodes of different thickness

Yoon, Seung Soo; Jang, Jong Hyun; Ka, Bok H.; Oh, Seung M.

doi:10.1016/j.electacta.2004.10.009

Cited by 115 publications

(90 citation statements)

References 21 publications

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“…As reported earlier by us, the complex capacitance analysis can be a useful technique to assess the EDLC parameters, such as capacitance, rate capability, and degree of side reactions. [38][39][40][41] In this analysis, impedance data are converted to complex capacitance and the imaginary part of complex capacitance is plotted as a function of frequency on a semilogarithmic scale ͑imaginary capacitance plots, C im vs log f͒. In this plot, the capacitive component appears as a peak and the capacitance value is proportional to the area of this peak.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Activation of Expanded Graphite Electrode for Electrochemical Capacitor

Ka¹,

Oh²

2008

J. Electrochem. Soc.

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An expanded graphite ͑e-MCMB, mesocarbon microbeads͒ having a wider interlayer spacing ͑d 002 = 0.404 nm͒ than that of common graphites is prepared by heat-treatment of an oxidized MCMB. When the e-MCMB electrode, which gives a negligible capacitance due to a small surface area, is polarized over a certain onset potential ͓4.6-4.8 V ͑vs Li/Li + ͒ for positive and 1.3-1.0 V for negative direction͔, it is electrochemically activated to be a high-capacitance positive and negative electrode for electrochemical capacitor. The activation process involves an ion intercalation into the interlayer space to generate ion-accessible sites. The intercalation is evidenced by the presence of a voltage plateau in the charge-discharge profiles, and by the widening of the interlayer distance ͑by in situ X-ray diffraction study͒ and concomitant electrode swelling ͑by electrochemical dilatometry͒ that occur at the same potential region. The electrochemically activated e-MCMB particles carry slitlike pores of ca. 0.45 nm in the mean interlayer distance, into which ions very likely enter either bare or with partial solvent shells with a mixed adsorption/ intercalation charge storage behavior. A full cell fabricated with two e-MCMB electrodes delivers a volume specific capacitance of 30-24 F mL Until now, electric double-layer capacitors ͑EDLCs͒, which deliver a higher rate capability and longer cycle life as compared to the modern secondary batteries, have been used as the energy storage device for memory back-up systems. [1][2][3][4][5][6] Recently, the markets for EDLCs have been extended to the higher power and higher energy systems such as hybrid electric vehicles. Energy density of the present EDLC, however, does not meet the market's need. Hence, to exploit such new applications, it is necessary to develop electrode materials having a higher energy density than the conventional ones.The energy density of EDLC is given by E = 1/2 CV 2 , where C stands for the capacitance per volume or weight, and V the working voltage. An enlargement in either C or V can thus be the way to achieve a high energy density in EDLCs. 3,5,7 One way to increase the cell voltage is the use of nonaqueous electrolytes. Normally, the cell voltage of EDLCs employing aqueous electrolytes is below 1.2 V, which can, however, be enlarged up to 3.0 V by using nonaqueous electrolytes. The other approach to increase the energy density is the employment of high-capacitance electrode materials, which are normally high-surface-area conductive materials as the electric double layer is formed at the electrode/electrolyte interface.

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Section: Resultsmentioning

confidence: 99%

Electrochemical Activation of Expanded Graphite Electrode for Electrochemical Capacitor

Ka¹,

Oh²

2008

J. Electrochem. Soc.

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“…RC circuit and homogeneous models.-Numerous equivalent RC circuit models [53][54][55][56][57] have been proposed and used to numerically investigate and predict the performance of EDLCs. They include but are not limited to (i) the simple series RC circuit, (ii) the so-called classical equivalent circuit 58 consisting of a resistor in parallel with a capacitor with an additional resistance in series, (iii) the three branch model with one voltage-dependent capacitance, 59 and (iv) the transmission line network model with an arbitrary number of equivalent RC circuit stages.…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Continuum Modeling of Interfacial and Transport Phenomena in Electric Double Layer Capacitors

Pilon

Wang

d’Entremont

2015

J. Electrochem. Soc.

117

105

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This paper reviews recent advances in physical modeling of interfacial and transport phenomena in electric double layer capacitors (EDLCs) under both equilibrium and dynamic cycling. The models are based on continuum theory and account for (i) the Stern layer at the electrode/electrolyte interface, (ii) finite ion sizes, (iii) steric repulsions, (iv) asymmetric electrolytes featuring ions with different valencies, effective diameters, or diffusion coefficients, (v) electric-field-dependent dielectric permittivity of the electrolyte, and/or (vi) porous three-dimensional morphology of the electrodes. Typical characterization methods such as electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic cycling were reproduced numerically to identify the dominant physical phenomena and to gain insight into experimental observations. In addition, recent thermal models derived from first principles for EDLCs under constant-current cycling accounting for irreversible Joule heating and reversible heat generation rates due to ion diffusion, steric effects, and changes in entropy are discussed. Scaling analyses of both equilibrium and dynamic models are also presented as a way to identify self-similar and asymptotic behaviors as well as to develop design rules for electrodes and electrolytes of next generation EDLCs. Electrical double layer capacitors (EDLCs) store energy by ion adsorption in the electrical double layer (EDL) forming at the electrode/electrolyte interfaces.1,2 This process is highly reversible and the cycle life of EDLCs exceeds 100,000 cycles.2,3 EDLCs can operate in a wide range of specific energy and power densities. This versatility is a key feature for electrical energy storage, energy harvesting, and energy regeneration applications. 2The performance of EDLCs is determined by the combination of the electrode material and morphology and of the electrolyte. In general, the key attributes of a good electrode include 1,3-7 (i) large surface area accessible to ions to maximize charge storage, (ii) optimum pore size, short pore length, and good pore connectivity to facilitate ion transport, (iii) large electrical conductivity to enable fast charging and discharging and low ohmic resistance, (iv) thin electrodes and current collectors to reduce the total resistance of the device, (v) small leakage current, (vi) small self-discharge, (vii) environmentally friendly materials, and (viii) low price. However, satisfying all these criteria simultaneously is challenging. For example, increasing surface area often results in larger electrode electrical resistivity.1 Micropores with diameter less than 2 nm contribute greatly to EDLCs capacitance.2 But pores smaller than the ion size are typically inactive and do not contribute to charge storage. 1,8 Porous electrodes must also be electrochemically accessible to ions. Then, interconnected mesopores with diameter ranging from 2 to 50 nm are necessary for fast charging thanks to their easier accessibility to ions. 1,6,[9][10][11] In practice, electrode...

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“…The use of complex capacitance data for analysis of dielectric systems and calculation of the effective capacitance of a blocking system has been reported by Orazem and Tribollet [24]. Likewise, a number of researchers have utilized complex capacitance data for the evaluation of adsorption and double layer capacitance [25][26][27][28].…”

Section: Particle-wall Interaction At Acidic and Alkaline Phmentioning

confidence: 99%

Interfacial electrochemistry study of particle–wall interaction using electrochemical impedance spectroscopy

Zebardast

Rogak

Asselin

2012

Journal of Electroanalytical Chemistry

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Complex capacitance analysis on rate capability of electric-double layer capacitor (EDLC) electrodes of different thickness

Cited by 115 publications

References 21 publications

Electrochemical Activation of Expanded Graphite Electrode for Electrochemical Capacitor

Electrochemical Activation of Expanded Graphite Electrode for Electrochemical Capacitor

Recent Advances in Continuum Modeling of Interfacial and Transport Phenomena in Electric Double Layer Capacitors

Interfacial electrochemistry study of particle–wall interaction using electrochemical impedance spectroscopy

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