MD Simulations of the Formation of Stable Clusters in Mixtures of Alkaline Salts and Imidazolium-Based Ionic Liquids

Abstract

Structural and dynamical properties of room-temperature ionic liquids containing the cation 1-butyl-3-methylimidazolium ([BMIM](+)) and three different anions (hexafluorophosphate, [PF6](-), tetrafluoroborate, [BF4](-), and bis(trifluoromethylsulfonyl)imide, [NTf2](-)) doped with several molar fractions of lithium salts with a common anion at 298.15 K and 1 atm were investigated by means of molecular dynamics simulations. The effect of the size of the salt cation was also analyzed by comparing these results with those for mixtures of [BMIM][PF6] with NaPF6. Lithium/sodium solvation and ionic mobilities were analyzed via the study of radial distribution functions, coordination numbers, cage autocorrelation functions, mean-square displacements (including the analysis of both ballistic and diffusive regimes), self-diffusion coefficients of all the ionic species, velocity and current autocorrelation functions, and ionic conductivity in all the ionic liquid/salt systems. We found that lithium and sodium cations are strongly coordinated in two different positions with the anion present in the mixture. Moreover, [Li](+) and [Na](+) cations were found to form bonded-like, long-lived aggregates with the anions in their first solvation shell, which act as very stable kinetic entities within which a marked rattling motion of salt ions takes place. With very long MD simulation runs, this phenomenon is proved to be on the basis of the decrease of self-diffusion coefficients and ionic conductivities previously reported in experimental and computational results.

Ionic liquid based lithium battery electrolytes: fundamental benefits of utilising both TFSI and FSI anions?

“…The usual reference, an aqueous solution of KCl with completely dissociated ions, g = 1, is also added. 61,62 The data for the mixed electrolytes, however, propose an advantage of having both FSI and TFSI present at a certain ratio. LiTFSI 0.2 EMIFSI 0.8 is an exception with almost the same g as LiTFSI 0.1 EMIFSI 0.9 (see Table 2).…”

“…33,48 The addition of LiTFSI to TFSI based ILs introduces a new spectral feature at ca. 60,61 This complex has a coordination number (CN) of 4, by virtue of doubly bidentate coordination, and hence a solvation number (SN) of 2. 60,61 This complex has a coordination number (CN) of 4, by virtue of doubly bidentate coordination, and hence a solvation number (SN) of 2.…”

“…60,61 This complex has a coordination number (CN) of 4, by virtue of doubly bidentate coordination, and hence a solvation number (SN) of 2. 34,61 There is also some controversy on the exact nature of the complexation, bidentate or not, based on conflicting results of MD simulations. 34,61 There is also some controversy on the exact nature of the complexation, bidentate or not, based on conflicting results of MD simulations.…”

Molecular Modeling of Electrolytes

“…[53,[85][86][87][88] and nonpolarizable [89,90] force fields were used in these simulations. MD simulations employing polarizable force fields predicted Li + transport in pyr 14 TFSI doped with LiTFSI below experimental values [86], while MD using nonpolarizable force fields predicted significantly slower ion transport.…”

Effects of imidazolium-based ionic surfactants on the size and dynamics of phosphatidylcholine bilayers with saturated and unsaturated chains

“…Imidazoliumbased ionic surfactants such as 1-ethyl-3-methylimidazolium (C 2 MIM), 1-butyl-3-methylimidazolium (C 4 MIM), and 1-hexyl-3-methylimidazolium (C 6 MIM) were modeled using the OPLS ionic-liquid FF developed by Sambasivarao and Acevedo [37] ( Fig. 1), which has accurately predicted the experimentally observed or theoretically derived structural and thermodynamic properties of ionic surfactants and their solvent effects on the polymer conformation [38], and thus has been widely used for many previous simulations [39][40][41][42]. For lipids, potential parameters for dimyristoylglycerophosphocholine (DMPC), palmitoyloleoylglycerophosphocholine (POPC), and dioleoylglycerophosphocholine (DOPC) were taken directly from the Berger lipid FF modified by Tieleman et al [43,44] We equilibrated pure bilayers without ionic surfactants, showing the area per lipid of 62.3 ± 1.5, 64.6 ± 0.2, and 67.7 ± 0.2 Å 2 , respectively, for DMPC, POPC, and DOPC bilayers.…”