Dilute Ionic Liquid Research Articles

Effect of Pore Size Distribution on Energy Storage of Nanoporous Carbon Materials in Neat and Dilute Ionic Liquid Electrolytes.

This study investigates three carbide-derived carbon (CDC) materials (TiC, NbC, and Mo2C) characterized by uni-, bi-, and tri-modal pore sizes, respectively, for energy storage in both neat and acetonitrile-diluted 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A distribution of micro- and mesopores was studied through low-temperature N2 and CO2 adsorption. To elucidate the relationships between porosity and the electrochemical properties of carbon materials, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements were conducted using three-electrode test cells. The ultramicroporous TiC-derived carbon is characterized by a high packing density of 0.85 g cm-3, resulting in superior cathodic and anodic capacitances for both neat ionic liquid (IL) and a 1.9 M IL/acetonitrile electrolyte (93.6 and 75.8 F cm-3, respectively, in the dilute IL). However, the bi-modal pore-sized microporous NbC-derived carbon, with slightly lower cathodic and anodic capacitances (i.e., 85.0 and 73.7 F cm-3 in the dilute IL, respectively), has a lower pore resistance, making it more suitable for real-world applications. A symmetric two-electrode capacitor incorporating microporous CDC-NbC electrodes revealed an acceptable cycle life. After 10,000 cycles, the cell retained approximately 75% of its original capacitance, while the equivalent series resistance (ESR) only increased by 13%.

Amino Acid Ester based Phenolic Ionic Liquids as a Potential Solvent for the Bioactive Compound Luteolin: Synthesis, Characterization, and Food Preservation Activity

Ionic liquids (ILs) have gained great attention as potent solubilizing agents of poorly soluble bioactive compounds. The use of Luteolin (LUT) – a natural bioactive compound – is limited because of its poor aqueous solubility. To address this issue, this study reports potential ILs for effectively solubilizing LUT at ambient temperature. First, promising ILs were screened from a potential 180 ILs that were proposed by the combination of 20 standard amino acid ethyl esters cations and nine phenolic acids anions using the conductor-like screening model for real solvents (COSMO-RS); the activity coefficients of LUT at infinite dilution in ILs were used as the screening criteria. Four proline ethyl ester phenolate ILs (PEEP-ILs) composed of a biocompatible proline ethyl ester and bioactive phenolic acids (trans-ferulic, vanillic, p-coumaric, and 4-hydroxybenzoic acid) were selected and synthesized. The synthesized PEEP-ILs were characterized through 1H NMR, FT-IR, elemental analysis, TGA, and DSC. The experimental solubility of LUT in PEEP-ILs (60% IL in water) showed excellent solubility. Among the PEEP-ILs, proline ethyl ester ferulate (IL[ProEt][Fer]) exhibited the best LUT solubility, followed by ILs with p-coumarate (IL[ProEt][Cou]), vanillate (IL[ProEt][Van]), and 4-hydroxybenzoate (IL[ProEt][Ben]). 1H NMR assessment and COSMO-RS prediction confirmed that the ILs facilitated the solubilization of LUT through multiple hydrogen bonding, π − π, and cation − π interactions between the LUT and the ILs. The biocompatibility study revealed that PEEP-ILs were relatively harmless and low toxicity compared with conventional imidazolium, pyridinium, pyrrolidinium, piperidinium, and morpholinium-based ILs. The LUT dissolved in the newly-synthesized PEEP-ILs and demonstrated better organoleptic properties on red apple slices. These results indicate that PEEP-ILs can be potential green alternatives to conventional toxic solvents for dissolving poorly water-soluble bioactive natural preservatives.

QSPR modeling of selectivity at infinite dilution of ionic liquids

The intelligent choice of extractants and entrainers can improve current mixture separation techniques allowing better efficiency and sustainability of chemical processes that are both used in industry and laboratory practice. The most promising approach is a straightforward comparison of selectivity at infinite dilution between potential candidates. However, selectivity at infinite dilution values are rarely available for most compounds so a theoretical estimation is highly desired. In this study, we suggest a Quantitative Structure–Property Relationship (QSPR) approach to the modelling of the selectivity at infinite dilution of ionic liquids. Additionally, auxiliary models were developed to overcome the potential bias from big activity coefficient at infinite dilution from the solute. Data from SelinfDB database was used as training and internal validation sets in QSPR model development. External validation was done with the data from literature. The selection of the best models was done using decision functions that aim to diminish bias in prediction of the data points associated with the underrepresented ionic liquids or extreme temperatures. The best models were used for the virtual screening for potential azeotrope breakers of aniline + n-dodecane mixture. The subject of screening was a combinatorial library of ionic liquids, created based on the previously unused combinations of cations and anions from SelinfDB and the test set extractants. Both selectivity at infinite dilution and auxiliary models show good performance in the validation. Our models’ predictions were compared to the ones of the COSMO-RS, where applicable, displaying smaller prediction error. The best ionic liquid to extract aniline from n-dodecane was suggested.

Heterogeneous dynamics in [BMIM][PF6] + Cosolvent binary Mixtures: Does It depend upon cosolvent Polarity?

It is known that dilution of ionic liquid with appropriate cosolvents modifies a number of physicochemical properties that include surface tension, viscosity, ion diffusivity and many others. The cosolvents, particularly when present in low concentrations, also undergo substantial changes in their inherent dynamics. The work reported here explores, via molecular dynamics simulations, the composition dependence of modifications on motional features of both the neutral cosolvent molecules and the charged molecular ions constituting the ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM] [PF6]). The cosolvents have been carefully chosen so that the polarities differ widely; they are acetonitrile (dipolar), 1,4-dioxane (quadrupolar) and n-hexane (non-polar). Mixture compositions studied are, FIL = 1.00, 0.90, 0.75, 0.50, 0.25, 0.10 and 0, FIL being the IL mole fraction. Signature of heterogeneous relaxations have been searched via examining several dynamical markers, such as, four-point density-time correlation functions, overlap functions, self-intermediate scattering functions, and other motional features arising from the deviations of displacements from Gaussian distributions. The presence of cosolvents affects the diffusivity of both the ions and the cosolvents, with dipolar acetonitrile causing the fastest ion diffusion in the mixture. Interestingly, all the dynamical heterogeneity features studied here have been found to respond significantly to both the cosolvent polarity and the mixture composition.

Cosolvent polarity dependence of solution structure in [BMIM] [PF6] + acetonitrile/1, 4-dioxane/hexane binary mixtures: Insights from composition dependent Voronoi polyhedra analyses, iso-surfaces and radial distribution functions

We investigate in this paper, via molecular dynamics simulations, the composition dependent solution structures in the binary mixtures composed of the ionic liquid (IL), 1-butyl-3methyl-imidazolium hexafluorophosphate, ([BMIM] [PF6]), and three different co-solvents of comparable sizes but with differing polarities. These cosolvents are acetonitrile (dipolar), 1,4-dioxane (quadrupolar) and hexane (non-polar). Five different IL mole fractions for the binary mixtures (FIL = 0.90, 0.75, 0.50, 0.25, 0.10) along with the neat solvents have been studied. The cosolvent polarity and concentration dependencies have been assessed through the examination of the composition dependent spatial and radial distribution functions, coordination numbers and the Voronoi polyhedra analyses. The solution structure is found to be dominated by the cosolvent clustering at high IL concentrations, and segregation of the IL into polar and non-polar domains in dilute IL solutions, their extent being strongly dependent upon cosolvent polarity. The aggregation behavior of the IL in the non-polar and dipolar binary mixtures is explained in terms of the Debye screening length (DSL). Such an explanation, however, fails to explain the comparable solubility of 1,4-dioxane in this IL. Isodensity surfaces constructed from the simulated spatial distribution functions show a dramatic cosolvent polarity dependence for the binary solution structure and reflects that microscopic phase segregation is the most pronounced for IL + hexane binary mixtures. The Voronoi polyhedra (VP) analyses indicate broader void and neck distributions upon dilution of the IL by cosolvents, suggesting increased heterogeneity in the solution structure of the binary mixtures. The severe phase segregation observed for [BMIM] [PF6] + hexane mixtures at the low IL concentrations did not allow similar VP analyses for this binary mixture for all the mixture compositions considered.

On the Effects of Diluted and Mixed Ionic Liquids as Liquid Substrates for the Sputter Synthesis of Nanoparticles.

The synthesis of nanoparticles by combinatorial sputtering in ionic liquids is a versatile approach for discovering new materials. Whereas the influence on nanoparticle formation of different pure ionic liquids has been addressed, the influence of (I) dilution of ionic liquid with solvents and (II) different mixtures of ionic liquids is less known. Therefore, mixtures of the ionic liquid [Bmim][(Tf)2N] with the organic solvent anisole and other ionic liquids ([Bmim][(Pf)2N], [BmPyr][(Tf)2N]) were used as liquid substrates for the sputter synthesis of nanoparticles, in order to investigate the influence of these mixtures on the size of the nanoparticles. First, mixtures of anisole with a suspension of sputtered Ag nanoparticles in [Bmim][(Tf)2N] were prepared in different volumetric steps to investigate if the stabilization of the NPs by the ionic liquid could be reduced by the solvent. However, a continuous reduction in nanoparticle size and amount with increasing anisole volume was observed. Second, Ag, Au and Cu were sputtered on ionic liquid mixtures. Ag nanoparticles in [Bmim][(Tf)2N]/[Bmim][(Pf)2N] mixtures showed a decrease in size with the increasing volumetric fraction of [Bmim][(Tf)2N], whereas all nanoparticles obtained from [Bmim][(Tf)2N]/[BmPyr][(Tf)2N] mixtures showed increasing size and broadening of the size distribution. Maximum sizes of sputtered Ag and Au NPs were reached in mixtures of [Bmim][(Tf)2N] with 20 vol.% and 40 vol.% [BmPyr][(Tf)2N]. The results indicate that ionic liquid mixtures with different portions of cations and anions have the capability of influencing the ionic liquid stabilization characteristics with respect to, e.g., nanoparticle size and size distribution.

Cellulose hydrolysis using ionic liquids and inorganic acids under dilute conditions: morphological comparison of nanocellulose.

The preparation of cellulose nanocrystals (CNCs) from cellulose extracted from cotton gin motes (CGM) using an ionic liquid (1-butyl-3-methylimidazolium chloride, [BMIm]Cl) under dilute conditions is reported. The concurrent process involves minimal swelling of cellulose with an ionic liquid and hydrolysis of the cellulose initiated by the addition of either phosphoric (H3PO4), hydrochloric (HCl), or sulfuric (H2SO4) acid. The obtained nanocrystals had similar physical properties (e.g. crystallinity) to the counterparts prepared under conventional conditions and exhibited superior thermal properties for sulfate CNCs. Additionally, the obtained CNCs had low surface functionalization, yet were colloidally stable for >90 days, which is a desirable trait for post-functionalization of CNCs. This process represents a general strategy utilizing dilute ionic liquids in the preparation of nanocellulose under mildly acidic conditions.

Developing a new correlation for the aliphatic and aromatic hydrocarbon diffusion coefficients at infinite dilution in ionic liquids

In this work the Taylor dispersion technique has been used to measure the diffusion coefficients of n-heptane and toluene at infinite dilution in four ionic liquids, namely 1-ethyl-3-methylimidazolium thiocyanate ([emim][SCN]), 1-ethyl-3-methylimidazolium tricyanomethanide ([emim][TCM]), 1-butyl-3-methylimidazolium tricyanomethanide ([bmim][TCM]), and 1-butyl-4-methylpyridinium tricyanomethanide ([4bmpy][TCM]), at the range temperatures from (298.2–333.2) K. The hydrocarbon diffusion is faster at higher temperatures because of the lower ionic liquid viscosity, and toluene diffuses faster than n-heptane due to its smaller molecular volume. In addition, it is seen that the values of the n-heptane diffusion coefficients decrease with an increase in the molecular weight and molar volume of the ionic liquid. The same is observed for the diffusion coefficients of toluene in the most viscous ionic liquids ([bmim][TCM], [4bmpy][TCM] and [4empy][Tf2N]), but, conversely, they increase for the least viscous ionic liquids ([emim][SCN], [emim][DCA], and [emim][TCM]). This behavior suggests that the strength of the toluene-ionic liquid chemical interactions have a significant effect on diffusion. A new empirical correlation has been proposed as a variation of the Wilke-Chang equation. Two additional variables have been introduced in this correlation; the molar fraction of the maximum hydrocarbon solubility, to take into account the toluene-ionic liquid interactions, as well as the molar volume of the ionic liquid, because of the huge difference between them and the solute. This new correlation satisfactorily fits the experimental data with an average deviation of 9.6%.

Ion dissociation in aqueous 1-alkyl-3-methyl-imidazolium chlorides and the impact of microstructure formation

ABSTRACTWe study ion dissociation in four aqueous 1-alkyl-3-methyl-imidazolium chloride ([amim][Cl]) (where a = alkyl) ionic liquids (ILs) focusing on the effects of microstructure formation. We calculate ion dissociation using precise density, viscosity, and ionic conductivity measurements taken in this work as well as values reported by Rogac et al. (M. Bešter-Rogač, M. V. Fedotova, S.E. Kruchinin, and M. Klähn, Mobility and association of ions in aqueous solutions: The case of imidazolium based ionic liquids, Phys. Chem. Chem. Phys. 18, 28594–28605 (2016); R. Toma, A. Tot, J. Kuhar, and M. Be, Interactions in aqueous solutions of imidazolium chloride ionic liquids [C n mim][Cl] (n=0, 1, 2, 4, 6, 8) from volumetric properties, viscosity B-coefficients and molecular dynamics simulations, 254, 267–271 (2018)) in conjunction with our estimation framework presented previously (O. Nordness, L.D. Simoni, M.A. Stadtherr, and J.F. Brennecke, Characterization of Aqueous 1-Ethyl-3-Methylimidazolium Ionic Liquids for Calculation of Ion Dissociation, J. Phys. Chem. B 123, 1348–1358 (2019); L.D. Simoni, Predictive Modeling of Fluid Phase Equilibria for Systems Containing Ionic Liquids (University of Notre Dame, Notre Dame, IN, 2009)). We first consider ion dissociation at dilute IL concentrations below the critical aggregate concentrations . We introduce a combined Stokes radii term calculated from limiting molar conductivity data, which more accurately estimates ion dissociation in dilute IL systems than radii estimated from a group contribution method. Incorporating the new radii term in the existing model, we study ion dissociation across a wide IL concentration range. Even if prior knowledge of aggregation were not available, as is the case for aqueous [amim][Cl] systems, aggregation is apparent from this analysis because the increased viscous forces of microstructure formation lead to unrealistic estimates of ion dissociation.

Overview of Activity Coefficient of Methanol at Infinite Dilution in Ionic Liquids and their Modeling using Group Contribution Model

A predictive model is developed by using a group contribution method for the estimation of the infinite dilution activity coefficient (IDAC) of methanol in ionic liquids (ILs). A simple van’t Hoff ...

Characterization of Aqueous 1-Ethyl-3-Methylimidazolium Ionic Liquids for Calculation of Ion Dissociation.

We employ precise measuring techniques to determine the densities, viscosities, and ionic conductivities of three aqueous 1-ethyl-3-methylimidazolium [emim]+ ionic liquid (IL) systems with minimal experimental uncertainty. We simultaneously present a novel method for estimating ion dissociation relying only on these three measurements and the estimated Stokes radii of the ions based on the Stokes-Einstein and Nernst-Einstein equations. Ion dissociation values are estimated across a range of IL concentrations, emphasizing dilute IL regions, using ionic radii calculated from widely used UNIQUAC and UNIFAC values. With these approximations and assuming the presence of only ion pairs, the ion dissociation of all three ILs reaches a minimum value at a water mole fraction of about 0.98. Upon further dilution with water, the ion dissociation increases as the system approaches infinite dilution of the IL. We postulate that the apparent minimum in the ion dissociation is caused by the Stokes radii of the cation and anion increasing as the concentration becomes more dilute, due to the formation of ion triplets.

Effect of cation structure of tetraalkylammonium- and imidazolium-based ionic liquids on their conductivity

Electrical conductivities of pure tetraalkylammonium- (N+Me4, N+Et4, N+Bu4, N+Me3Hex) and imidazolium- (EMIM+, BMIM+) based ionic liquids (ILs) with bis(trifluoromethylsulfonyl)imide (TFSI−) anion and their acetonitrile solutions were measured in two temperature ranges of 298–368 and 298–348 K. Acetonitrile was used as an organic solvent to decrease the viscosity of ILs and, therefore, to increase the mobility of charge carriers. The maximum conductivity of acetonitrile solutions of both tetraalkylammonium- and imidazolium-based ILs was found to decrease with cation size. The conductivity – temperature dependencies of pure ILs and their acetonitrile solutions were analyzed using three approaches based on the Arrhenius equation for non-associating electrolytes, the Vogel-Fulcher-Tammann equation for ionic conductivity of glass-forming liquids and the Litovitz equation for associated liquids. The dilution of ILs with acetonitrile significantly reduced their activation energies of conductivity. At the same time, the activation energy decreased with increasing the alkyl chain length because of the deceleration of the ion transfer and the growth of the viscosity.

Influence of different concentrations of ionic solutions on coal spontaneous combustion

ABSTRACTConsidering the high cost of ionic liquids, this paper proposed to dilute ionic liquids with purified water to suppress coal spontaneous combustion based on an in-depth study on the mechanism of ionic liquids for suppressing coal spontaneous combustion. Three kinds of ionic liquids, namely, [HOEMIm][BF4] (HOE), [BMIm][BF4] (BM), and [AMIm]Cl (AM), were mixed with purified water to form ionic solutions with different concentrations. The differences in gas products of raw coal and samples treated with ionic solutions were comparatively analyzed, and then their mechanism of inhibiting coal spontaneous combustion was studied by calculating inhibition rates and apparent activation energy of samples. Furthermore, the molecular structure of coal was further studied by means of Fourier transform infrared spectroscopy. The results show that ionic solutions can not only absorb heat through water evaporation, but also reduce the alkyl chain content of coal by inerting hydrogen bonds in coal. Among the three kinds of ionic solutions with different concentrations, AM with a mass ratio of 1:10 achieves the best inhibitory effect.

Aqueous ionic liquids in comparison with standard co-solutes : Differences and common principles in their interaction with protein and DNA structures.

Ionic liquids (ILs) are versatile solvents for a broad range of biotechnological applications. Recent experimental and simulation results highlight the potential benefits of dilute ILs in aqueous solution (aqueous ILs) in order to modify protein and DNA structures systematically. In contrast to a limited number of standard co-solutes like urea, ectoine, trimethylamine-N-oxide (TMAO), or guanidinium chloride, the large amount of possible cation and anion combinations in aqueous ILs can be used to develop tailor-made stabilizers or destabilizers for specific purposes. In this review article, we highlight common principles and differences between aqueous ILs and standard co-solutes with a specific focus on their underlying macromolecular stabilization or destabilization behavior. In combination with statistical thermodynamics theories, we present an efficient framework, which is used to classify structure modification effects consistently. The crucial importance of enthalpic and entropic contributions to the free energy change upon IL-assisted macromolecular unfolding in combination with a complex destabilization mechanism is described in detail. A special focus is also set on aqueous IL-DNA interactions, for which experimental and simulation outcomes are summarized and discussed in the context of previous findings.

Aqueous solutions of [EMIM] 1,1,2,2-tetrafluoroethanesulfonate and [EMIM] trifluoromethanesulfonate: A thermodynamic study

Abstract While ionic liquids (ILs) based on a trifluoromethanesulfonate ([OTF] − ) anion and their mixtures with other compounds have been relatively well explored, the information about structurally similar 1,1,2,2-tetrafluoroethanesulfonate-based ([TFES] − ) ILs is either very scarce or, as in the case of their mixtures with water, totally lacking. We herein thus present a broad thermodynamic characterization of aqueous solutions of [EMIM][TFES] and [EMIM][OTF], with the study of aqueous solutions of the latter serving as a benchmark. First, the peculiar solid-liquid phase transition behavior of the neat [EMIM][TFES] was examined and its density was determined over a temperature range encompassing both the subcooled and the stable liquid. For the aqueous solutions of the two ILs, we performed extensive measurements at several temperatures in the range from (288.15 to 318.15) K of water activity ( a w ) across the entire composition range, mixing enthalpy and density specifically in the highly dilute IL region, and the solution freezing temperatures at water mole fractions greater than 0.6. The ample a w data were fitted ( i ) by a two-step procedure and ( ii ) simultaneously with the excess enthalpy data using an extended NRTL-type model. Although both treatments provide adequate representations of the data and prove to yield reasonable estimates of derivative thermal properties, the latter approach to the global description of energetics of the systems is preferred for its handiness in practical calculations. We duly proved its reliability in extrapolation and/or prediction against experimental data on various properties, among others, SLE. The analysis of volumetric data by the Redlich-Meyer equation allowed us to obtain accurate values of infinite dilution partial molar volumes of the ILs and revealed the nature of their hydration as rather hydrophobic. The solution behavior of the systems studied was found to be essentially non-ideal: their small S-shaped excess Gibbs energy ( G E ) actually results from the compensation of their large positive excess enthalpy ( H E ) and entropy ( S E ). Thus, despite being completely miscible with water, the two ILs are not typically hydrophilic, but intermediate on an imaginary (hydrophobicity/hydrophilicity) scale. The structural variation in the anion, though influencing H E and S E considerably, is only subtly reflected in G E and activity coefficients. Due to their somewhat lower values and a weaker decrease of apparent molar volume with increasing molality observed for [EMIM][TFES], [TFES] − is identified to be slightly more hydrophilic than [OTF] − .

Direct Measurement of the Differential Capacitance of Solvent-Free and Dilute Ionic Liquids

Differential capacitance is a key quantity in the understanding of electrical double-layer charging of electrolytes. However, experimental observations of ionic liquid systems are controversial, inconsistent, and often unable of confirming or refuting existing theories as well as highlighting discrepancies between the measurement techniques. We study the differential capacitance in both pure and dilute ionic liquids at room temperature. Using chronoamperometry to measure the differential capacitance of the liquids at a polycrystalline platinum electrode, we find good agreement between the measured capacitance curves and the extended mean-field model of Goodwin–Kornyshev [Goodwin, Z. A.; et al. Electrochim. Acta.2017, 225, 190–197]. A crossover is found from the pure to the dilute regime, as shown by a transition from a camel-shape capacitance curve to a U-like one, together with a nonmonotonic dependence of capacitance with electrolyte concentration.

From Solvent-Free to Dilute Electrolytes: Essential Components for a Continuum Theory.

The increasing number of experimental observations on highly concentrated electrolytes and ionic liquids show qualitative features that are distinct from dilute or moderately concentrated electrolytes, such as self-assembly, multiple-time relaxation, and underscreening, which all impact the emergence of fluid/solid interfaces, and the transport in these systems. Because these phenomena are not captured by existing mean-field models of electrolytes, there is a paramount need for a continuum framework for highly concentrated electrolytes and ionic liquid mixtures. In this work, we present a self-consistent spatiotemporal framework for a ternary composition that comprises ions and solvent employing a free energy that consists of short- and long-range interactions, along with an energy dissipation mechanism obtained by Onsager's relations. We show that the model can describe multiple bulk and interfacial morphologies at steady-state. Thus, the dynamic processes in the emergence of distinct morphologies become equally as important as the interactions that are specified by the free energy. The model equations not only provide insights into transport mechanisms beyond the Stokes-Einstein-Smoluchowski relations but also enable qualitative recovery of three distinct regions in the full range of the nonmonotonic electrical screening length that has been recently observed in experiments in which organic solvent is used to dilute ionic liquids.

Near-Wall Molecular Ordering of Dilute Ionic Liquids.

The interfacial behavior of ionic liquids promises tunable lubrication as well as playing an integral role in ion diffusion for electron transfer. Diluting the ionic liquids optimizes bulk parameters, such as electric conductivity, and one would expect dilution to disrupt the near-wall molecular ordering. We study this ordering in the ionic liquids [Emim]+[NTf2]−, [Emim]+[DCA]−, and [C4mpyr]+[NTf2]−, diluted in the solvent dimethyl sulfoxide. We found a structural crossover from well-ordered ionic liquids to a well-ordered solvent with increasing dilution, but this occurs nonlinearly, with solvent molecules initially space-filling and solvating and later disrupting the ionic layers. This is of key importance for ionic liquids as optimized tunable nanolubricants.

Structural-dynamic properties of infinitely dilute ionic liquid–nonpolar compound systems

The effect of nonpolar solvents (argon, methane, and benzene) on the structural-dynamic properties of an ionic liquid (IL), dimethylimidazolium chloride, is studied at 400 K by the method of molecular dynamics using DL_POLY _4.05 software package. The energy and structural-dynamic parameters of infinitely dilute liquid ternary systems are calculated and analyzed. The pattern of motion of the molecules of dilute compound in the IL is described. It is demonstrated that increased size of a solvent molecule enhances the effect on the ionic liquid structure, which also influences the solubility of nonpolar compounds and IL.

Ionic Liquid-Based Non-Aqueous Electrolytes for Nickel/Metal Hydride Batteries

The voltage of an alkaline electrolyte-based battery is often limited by the narrow electrochemical stability window of water (1.23 V). As an alternative to water, ionic liquid (IL)-based electrolyte has been shown to exhibit excellent proton conducting properties and a wide electrochemical stability window, and can be used in proton conducting batteries. In this study, we used IL/acid mixtures to replace the 30 wt % KOH aqueous electrolyte in nickel/metal hydride (Ni/MH) batteries, and verified the proton conducting character of these mixtures through electrochemical charge/discharge experiments. Dilution of ILs with acetic acid was found to effectively increase proton conductivity. By using 2 M acetic acid in 1-ethyl-3-methylimidazolium acetate, stable charge/discharge characteristics were obtained, including low charge/discharge overpotentials, a discharge voltage plateau at ~1.2 V, a specific capacity of 161.9 mAh·g−1, and a stable cycling performance for an AB5 metal hydride anode with a (Ni,Co,Zn)(OH)2 cathode.