Lattice Model of an Ionic Liquid at an Electrified Interface

Girotto, Matheus; Colla, Thiago; Santos, Alexandre Pereira dos; Levin, Yan

doi:10.1021/acs.jpcb.7b02258

Cited by 20 publications

(20 citation statements)

References 77 publications

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“…where we recall the definitions of the inverse length scales a and b in Eq. 14 We proceed with a physical interpretation of our predictions, especially the formation of layered domains with excess anions and cations that can even lead to a negative differential capacitance. Clearly, growing χ increases the tendency of like-charged ions to cluster.…”

Section: (Lb)mentioning

confidence: 97%

Differential capacitance of ionic liquids according to lattice-gas mean-field model with nearest-neighbor interactions

Downing

Berntson

Bossa

et al. 2018

The Journal of Chemical Physics

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The Bragg-Williams free energy is used to incorporate nearest-neighbor interactions into the lattice gas model of a solvent-free ionic liquid near a planar electrode. We calculate the differential capacitance from solutions of the mean-field consistency relation, arriving at an explicit expression in the limit of a weakly charged electrode.The two additional material parameters that appear in the theory -the degree of nonideality and the resistance to concentration changes of each ion type -give rise to different regimes that we identify and discuss. As the nonideality parameter, which becomes more positive for stronger nearest-neighbor attraction between like-charged ions, increases and the electrode is weakly charged, the differential capacitance is predicted to transition through a divergence and subsequently adopt negative values just before the ionic liquid becomes structurally unstable. This is associated with the spontaneous charging of an electrode at vanishing potential. The physical origin of the divergence and the negative sign of the differential capacitance is a nonmonotonic relationship between surface potential and surface charge density, which reflects the formation of layered domains alternatingly enriched in counterions and coions near the electrode. The decay length of this layered domain pattern, which can be many times larger than the ion size, is reminiscent of the recently introduced concept of "underscreening".

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Section: (Lb)mentioning

confidence: 97%

Differential capacitance of ionic liquids according to lattice-gas mean-field model with nearest-neighbor interactions

Downing

Berntson

Bossa

et al. 2018

The Journal of Chemical Physics

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“…[22][23][24][25][26] The mPB equation approximately accounts for the finite size of both ions and solvent and has been used to calculate differential capacitance of RTILs. However it has been shown [27][28][29] that the mPB equation does not accurately predict the double layer structure of electrified interfaces. Therefore more sophisticated approaches based on the Density Functional Theory (DFT) 30-34 must be used.…”

Section: Introductionmentioning

confidence: 99%

“…54 In various applications, the simulation box must be made sufficiently large to achieve a bulk-like regime in between the surfaces, 23 requiring a large number of particles, which further slows down simulations. 29 If the confining surfaces are polarizable, there are additional complications connected with the induced surface charge. [55][56][57] The usual methods for simulating metallic surfaces of electrodes are computationally very expensive, relying on a minimization procedure to calculate the induced surface charge at every simulation time step.…”

Section: Introductionmentioning

confidence: 99%

Lattice model of ionic liquid confined by metal electrodes

Girotto

Malossi

Santos

et al. 2018

The Journal of Chemical Physics

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“…At high concentrations, as in the case of ILs, ionic correlations that are neglected in the PB theory become important [23,24]. Nevertheless, in the attempt to construct an effective theory for ILs, the PB equation has been often used with further modifications that were supposed * andelman@tauex.tau.ac.il to account for deviations from the dilute regime [25][26][27][28]. Other approaches include liquid-state theory [29,30] and one-dimensional lattice-gas models [31,32].One of the significant contributions to describe theoretically ILs has been suggested by Bazant, Storey and Kornyshev (BSK) [33], who developed an equation that modifies the PB equation in two important ways.…”

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confidence: 99%

Charge oscillations in ionic liquids: A microscopic cluster model

2020

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In spite of their enormous applications as alternative energy storage devices and lubricants, room temperature ionic liquids (ILs) still pose many challenges from a pure scientific view point. We develop an IL microscopic theory in terms of ionic clusters, which describes the IL behavior close to charged interfaces. The full structure factor of finite-size clusters is considered and allows us to retain fine and essential details of the system as a whole. Beside the reduction in the screening, it is shown that ionic clusters cause the charge density to oscillate near charged boundaries, with alternating ion-size thick layers, in agreement with experiments. We distinguish between short-range oscillations that persist for a few ionic layers close to the boundary, as opposed to long-range damped oscillations that hold throughout the bulk. The former can be captured by finite-size ion pairs, while the latter is associated with larger clusters with pronounced quadrupole (or higher) moment. The long-wavelength limit of our theory recovers the well-known Bazant-Storey-Kornyshev (BSK) equation in the linear regime, and elucidates the microscopic origin of the BSK phenomenological parameters.Room-temperature ionic liquids (ILs) have been recently a subject of intense research due to their numerous applications as electrolytes in batteries, fuel cells and supercapacitors, and as molecular "green" lubricants [1-6]. In addition, being a highly interacting coulomb system, the statistical mechanics modelling of ILs, especially near electrified interfaces, continues to pose a great theoretical challenge [7,8].As ILs are solvent-free electrolyte systems, they can be modelled as concentrated ionic solutions. Although ILs are frequently compared with dilute ionic solutions, for which the theoretical understanding and fits to experiments are well established [9], experiments and simulations reveal key differences between these two systems. Unlike dilute solutions, the IL charge distribution near charged interfaces is often non-monotonic and can decay in an oscillatory manner. A combination of x-ray structure measurements [10], force measurements [11][12][13][14] and molecular dynamics simulations [15][16][17] revealed that close to charged interfaces, cations and anions form alternating layers of about one ionic diameter in thickness. When confined between two charged surfaces, ILs can even go through a phase transition into a solid-like phase [18]. Another distinct feature is under-screening. Namely, the screening in ILs and in concentrated ionic solutions is much weaker than the dilute-solution prediction [19][20][21][22].The most common theory of ionic solutions is the Poisson-Boltzmann (PB) theory. This is a mean-field (MF) theory [9] that is valid for low ionic concentrations. At high concentrations, as in the case of ILs, ionic correlations that are neglected in the PB theory become important [23,24]. Nevertheless, in the attempt to construct an effective theory for ILs, the PB equation has been often used with further modific...

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Lattice Model of an Ionic Liquid at an Electrified Interface

Cited by 20 publications

References 77 publications

Differential capacitance of ionic liquids according to lattice-gas mean-field model with nearest-neighbor interactions

Differential capacitance of ionic liquids according to lattice-gas mean-field model with nearest-neighbor interactions

Lattice model of ionic liquid confined by metal electrodes

Charge oscillations in ionic liquids: A microscopic cluster model

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