Modeling of the Electrical and Thermal Behaviors of  an Ultracapacitor

Lee, Jeongbin; Yi, Jaeshin; Kim, Dae-Yong; Shin, Chee Burm; Kyung-Seok, Min，; Choi, Jongrak; Lee, Ha-Young

doi:10.3390/en7128264

Cited by 22 publications

(19 citation statements)

References 22 publications

(43 reference statements)

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“…Approximations enter the theory at the level of (∂Ψ/∂T ) Q , so that more accurate estimates can be found by systematically improving the grand potential Eq. (3), by including, for instance, solvent polarizability [38], a better description of excluded volume interactions [39], and residual ion correlations [29] (see also Appendix C).Though oversimplified ideal-gas reasoning permeates 5 the reversible heating literature [9,11,[13][14][15], the main finding of this Letter is that the thermodynamic identity Eq. (2), and not Eq.…”

mentioning

confidence: 92%

“…Though oversimplified ideal-gas reasoning permeates the reversible heating literature [9,11,[13][14][15], the main finding of this Letter is that the thermodynamic identity Eq. (2), and not Eq.…”

mentioning

confidence: 96%

“…(2) in the limit of slow charging, thereby reconciling the thermodynamic and kinetic viewpoints. The ideal-gas reasoning, often used for illustration purposes [9,11,14], or even to fit to experiments [13,15], cannot reproduce the adiabatic temperature change.Consider a thermally insulated container with two planar parallel electrodes separated by an (incompressible) 1:1 electrolyte of dielectric constant (Fig. 1).…”

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confidence: 99%

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Reversible Heating in Electric Double Layer Capacitors

Janssen

Roij

2017

Phys. Rev. Lett.

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A detailed comparison is made between different viewpoints on reversible heating in electric double layer capacitors. We show in the limit of slow charging that a combined Poisson-Nernst-Planck and heat equation, first studied by d'Entremont and Pilon [J. Power Sources 246, 887 (2014)], recovers the temperature changes as predicted by the thermodynamic identity of Janssen et al. [Phys. Rev. Lett. 113, 268501 (2014)], and disagrees with the approximative model of Schiffer et al. [J. Power Sources 160, 765 (2006)] that predominates the literature. The thermal response to the adiabatic charging of supercapacitors contains information on electric double layer formation that has remained largely unexplored.With the relation between heat and entropy formulated by Clausius in 1855, and with the establishment of the importance of ion entropy to the electric double layer (EDL) by Gouy (1910) and Chapman (1913) [1], almost a century passed before reversible, adiabatic heating and cooling was measured in electric double layer capacitors (EDLCs) [2]. Unlike irreversible Joule heating, occurring everywhere in the electrolyte when an EDLC is charged at finite currents, it turns out that the sources of reversible heating are located only within the nanometerrange vicinity of the electrode's surface. Therefore, one needs EDLCs whose surface-to-volume ratio is as high as possible to notice an appreciable reversible temperature variation. This has become possible and relevant in recent years because electrodes can now be manufactured from porous carbon with internal surface areas up to 2000 m 2 g −1 . Electrolyte-filled supercapacitors made from these electrodes are characterized by a high capacitance, fast (dis)charging rates, and high cyclability [3]. These favorable properties have sparked a huge scientific interest in supercapacitors in recent years, and led to various applications [4][5][6][7][8]. The performance of supercapacitors for energy storage usually suffers, however, from increased temperatures causing aging of materials, increased internal resistance, decreased capacitance, parasitic electrochemical reactions, and self discharging [9][10][11]. Efforts were therefore made both in experiments [2, 10-13] and modeling [14][15][16][17] to gain insight in the thermal behavior of supercapacitors. However, a unified understanding of reversible heating effects occurring during EDL buildup is still lacking, and thermal response to charging has not yet been fully exploited. This Letter for the first time quantitatively reconciles two viewpoints on reversible heating. Within the thermodynamic viewpoint, two distinct identities for isentropic processes are discussed, only one of which (we show) agrees with the other, kinetic, viewpoint.For the thermodynamic viewpoint, consider an EDLC on which a potential is imposed by connecting it to a battery. The electrodes then obtain surface charges which are screened by diffuse clouds of counterionic charge (see Fig. 1), hence the ionic configuration entropy decreases. For a thermally ...

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Reversible Heating in Electric Double Layer Capacitors

Janssen

Roij

2017

Phys. Rev. Lett.

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“…7,[13][14][15][16][17] Irreversible heat generation has been attributed, both theoretically and experimentally, to Joule heating. 7,9,11,[13][14][15][16][17][18][19][20] It is constant throughout the EDLC cell and equal to the product of the EDLC internal resistance and the square of the imposed current. 7,[14][15][16] On the other hand, reversible heat generation rate in the entire device was theoretically and experimentally found to be exothermic during charging and endothermic during discharging.…”

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Effects of Constituent Materials on Heat Generation in Individual EDLC Electrodes

Munteshari

Lau

Ashby

et al. 2018

J. Electrochem. Soc.

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This study aims to investigate the effect of electrode composition on heat generation in electric double layer capacitor (EDLC) electrodes under galvanostatic cycling. EDLCs consist of two identical electrodes usually made of a mixture of (i) carbon-based material, (ii) binder, and (iii) other conductive additives. These constituents were found to influence the capacitance and internal resistance of the device and the heat generation rate in the positive and negative electrodes. Indeed, the heat generation rate was measured using an isothermal calorimeter in both electrodes of five EDLC devices with different electrode compositions but the same electrolyte consisting of 1 M LiPF 6 in EC:DMC. The reversible heat generation rates at the positive and negative electrodes were nearly identical in absence of CMC. However, in devices containing CMC, the reversible heat generation rate in the positive electrode was significantly larger than that in the negative electrode. Such asymmetric heating was attributed to asymmetry in the charging mechanism due to the overscreening effect caused by interactions between the anionic functional groups of CMC and the cations at the negative electrode. Electric double layer capacitors (EDLCs) have received significant attention in recent years for electrical energy storage applications in particular those requiring rapid charging/discharging, such as regenerative braking in electric vehicles, 1 smart grids, 2 and renewable energy harvesting systems.3-5 Indeed, EDLCs can provide higher power density, higher cycle efficiency, and longer lifetime than batteries. 4,6 EDLC devices consist typically of two carbon-based electrodes partitioned by a separator immersed in aqueous or organic electrolytes. EDLCs store electrical energy in the electrical double layer of ions forming at electrode/electrolyte interface.Heat generation in EDLC is a major concern since these devices are usually cycled under high current density resulting in excessive temperature rise.7 This, in turn, can lead to (i) accelerated cell aging, [8][9][10] (ii) increased self-discharge rates, 9,11 and possibly (iii) electrolyte decomposition and evaporation. 9,12 Heat generation in EDLCs can be classified into irreversible and reversible heat generation rates. 7,[13][14][15][16][17] Irreversible heat generation has been attributed, both theoretically and experimentally, to Joule heating. 7,9,11,[13][14][15][16][17][18][19][20] It is constant throughout the EDLC cell and equal to the product of the EDLC internal resistance and the square of the imposed current. 7,[14][15][16] On the other hand, reversible heat generation rate in the entire device was theoretically and experimentally found to be exothermic during charging and endothermic during discharging.7,14-16 The time-averaged reversible heat generation over a charging step was shown to be proportional to the imposed current under galvanostatic cycling.7,14-16 Experimentally, reversible heat generation has been assumed to be identical in both the positive and negative e...

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“…According to the above simplifications and assumptions, the transient two-dimensional equation of heat conduction can be written as follows [30,31]:…”

Section: Governing Equationsmentioning

confidence: 99%

Analyzing Electrical Performance and Thermal Coupling of Supercapacitor Assembled Using Phosphorus-Doped Porous Carbon/Graphene Composite

et al. 2019

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A novel phosphorus-doped porous carbon/graphene composite was adopted as electrode material of super-capacitor, which showed excellent electrochemical performance compared with carbon material without phosphorus heteroatom by means of cyclic voltammetry, the charge/discharge property, impedance characteristics, cycle life, and stability. The P-enriched carbons sample offered an outstanding capacitive behavior, which had specific capacitance 277 F/g and was able to withstand at a wide voltage window of 1.6 V with 90.8% performance retention after 10,000 cycles at a current density of 10 Ag−1, providing a higher energy density 26.42 Wh/kg. In addition, because the thermal effect in charge and discharge process can make the supercapacitor temperature rise rapidly in a short time and affect the electrical performance, temperature characteristic is one of the important characteristics to be considered in practical application. In this paper, a two-dimensional thermal model for commonly used coiling supercapacitor with p-doped porous carbon/graphene composite as electrode material was established, and the temperature distribution of supercapacitor and the variation of internal temperature under different conditions were analyzed by finite element method. The results show that the maximum temperature appears near the center, and the maximum temperature is related to the applied current and the number of cycles. With the increase of the current, the maximum internal temperature is increased sharply, and it is kept constant after the number of cycles reaches a certain value. Cooling measures should be taken when the maximum temperature exceeds the allowable temperature range.

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Modeling of the Electrical and Thermal Behaviors of an Ultracapacitor

Cited by 22 publications

References 22 publications

Reversible Heating in Electric Double Layer Capacitors

Reversible Heating in Electric Double Layer Capacitors

Effects of Constituent Materials on Heat Generation in Individual EDLC Electrodes

Analyzing Electrical Performance and Thermal Coupling of Supercapacitor Assembled Using Phosphorus-Doped Porous Carbon/Graphene Composite

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