On the temperature dependence of the double layer capacitance of ionic liquids

Chen, Ming; Goodwin, Zachary A. H.; Feng, Guang; Kornyshev, Alexei A.

doi:10.1016/j.jelechem.2017.11.005

Cited by 79 publications

(100 citation statements)

References 105 publications

(302 reference statements)

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“…4d). This is interesting since recently Chen et al [27] extended the steric-only lattice-gas model (i.e, K = 0 in Eq. (10)) to account for the temperature dependence and studied the capacitance in a wide range of temperature, but they did not observe the bird-like capacitance.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…In general, such variation of ǫ shall also depend on the affinity of ions/solvent towards electrode (electrode's ionophilicity, see below), as well as on the applied potential. To avoid such complications, and to capture generic effects, unobscured by the chemical complexity, we have decided to take a position-independent dielectric constant, as in the majority of studies [10,11,13,14,16,20,27,38,39,42]; clearly, the change of ǫ close to the surface will affect the results quantitatively, but it is reasonable to expect that the qualitative behaviour will not be altered.…”

Section: Modelmentioning

confidence: 99%

“…Lockett et al [21] found the same behaviour for imidazolium-based ionic liquids in contact with glassy carbon electrodes. More careful theoretical work suggested that both trends are possible [25][26][27], but there is no general agreement on the origin of this behaviour.…”

mentioning

confidence: 99%

“…For instance, Holovko et al [25] proposed that the increase of capacitance is related to the decreased inter-ionic interactions and weaker ion associations, while Chen et al [27] argued that the temperature dependence of EDLs is chiefly determined by the strength and extent of the van der Waals interactions. Interestingly, it was shown that the transition between the camel and bell-like capacitances can be induced also by varying temperature [27,28], with the bell shape emerging at high temperatures due to breaking of 'ion pairs' and consequently stronger screening [27].…”

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confidence: 99%

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Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Cruz

Kondrat

Lomba

et al. 2019

Journal of Molecular Liquids

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There is a growing interest in the properties of ionic liquids (ILs) and IL-solvent mixtures at metallic interfaces, particularly due to their applications in energy storage. The main focus so far has been on electrical double layers with ILs far from phase transitions. However, the systems in the vicinity of their phase transformations are known to exhibit some remarkable features, such as wetting transitions and capillary condensation. Herein, we develop a mean-field model suitable for the IL-solvent mixtures close to demixing, and combine it with the Carnahan-Starling (CS) and lattice-gas expressions for the excluded volume interactions. This model is then solved analytically, using perturbation expansion, and numerically. We demonstrate that, besides the well-known camel and bell-shaped capacitances, there is a bird-shaped capacitance, having three peaks as a function of voltage, which emerge due to the proximity to demixing. In addition, we find that the camel-shaped capacitance, which is a signature of dilute electrolytes, can appear at high IL densities for ionophobic electrodes. We also discuss the differences and implications arising from the CS and lattice-gas expressions in the context of our model.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Cruz

Kondrat

Lomba

et al. 2019

Journal of Molecular Liquids

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“…Independent of data interpretation, the work by Gebbie et al had an immediate effect. The interpretation of compacity, γ, defined initially as the ratio of the average concentration of ions to their maximal local concentration, was reconsidered and the mean-field theory of EDL was modified [23,41]. Instead, it was considered as a ratio of the number of free charge carriers to the total number of ions.…”

Section: Nature Of Compacity and Overscreening Vs Underscreeningmentioning

confidence: 99%

Free and Bound States of Ions in Ionic Liquids, Conductivity, and Underscreening Paradox

et al. 2019

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Using molecular dynamics simulations and theoretical analysis of velocity-autocorrelation functions, we study ion transport mechanisms in typical room-temperature ionic liquids. We show that ions may reside in two states: free and bound with an interstate exchange. We investigate quantitatively the exchange process and reveal new qualitative features of this process. To this end, we propose a dynamic criterion for free and bound ions based on the ion trajectory density and demonstrate that this criterion is consistent with a static one based on interionic distances. Analyzing the trajectories of individual cations and anions, we estimate the time that ions spend in bound "clustered states" and when they move quasifreely. Using this method, we evaluate the average portion of "free" ions as approximately 15%-25%, increasing with temperature in the range of 300-600 K. The ion diffusion coefficients and conductivities as a function of the temperature calculated from the velocity and electrical-current autocorrelation functions reproduce the reported experimental data very well. The experimental data for the direct-current conductivity (constant ionic current) is in good agreement with theoretical predictions of the Nernst-Einstein equation based on the concentrations and diffusion coefficients of free ions obtained in our simulations. In analogy with electronic semiconductors, we scrutinize an "ionic semiconductor" model for ionic liquids, with valence and conduction "bands" for ions separated by an energy gap. The obtained band gap for the ionic liquid is small, around 26 meV, allowing for easy interchange between the two dynamic states. Moreover, we discuss the underscreening paradox in the context of the amount of free charge carriers, showing that the obtained results do not yet approve its simplistic resolution.

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Retrospective and Prospective Views of Electrochemical Electron Transfer Processes: Theory and Computations

Nazmutdinov

Ulstrup

2021

Atomic‐Scale Modelling of Electrochemical Systems

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On the temperature dependence of the double layer capacitance of ionic liquids

Cited by 79 publications

References 105 publications

Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Free and Bound States of Ions in Ionic Liquids, Conductivity, and Underscreening Paradox

Retrospective and Prospective Views of Electrochemical Electron Transfer Processes: Theory and Computations

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