Properties Of Ionic Liquids Research Articles

Polymer electrolytes based on PEO and lithium tetraalkoxyborate salts with ionic liquid properties for lithium-based batteries

The development of lithium-ion batteries (LIBs) with improved safety features is crucial due to the inherent risks associated with liquid electrolytes, such as fires, explosions, and leakage. This study explores the potential of solid polymer electrolytes (SPEs) based on poly(ethylene oxide) (PEO) and lithium tetraalkoxyborate salts (LiTAB) with ionic liquid properties as a safer alternative. Ionic liquids (ILs) are examined for their high ionic conductivity, wide electrochemical window, and excellent thermal stability, despite their high synthesis costs and viscosity challenges. The study proposes the use of a novel LiTAB salt with an oligomeric star-shaped anion structure that reduces mobility, enhancing lithium ion transference numbers. This IL serves as both a lithium salt and an active plasticizer in PEO-based SPEs, offering potential for 3D printing applications. Experimental results demonstrate that these electrolytes exhibit favorable rheological properties, high ionic conductivities, and significant lithium ion transference numbers, addressing the key limitations of conventional PEO-based electrolytes. The findings suggest that incorporating these LiTAB salts in SPEs could significantly enhance the safety and performance of LIBs, particularly for applications in miniaturized consumer electronics and electronic implants.

Improvement of the properties of ionic liquids for the absorption refrigeration cycle

Ionic liquids (ILs), recognized as environmentally friendly green reagents, have good application prospects in many fields. However, their high viscosity has hindered their widespread application. Currently, an effective solution is to introduce a solvent as an additive. In this work, ethanol with different molar fractions was chosen to form working pairs with three ILs ([emim]BF4, [bmim]BF4 and [hmim]BF4), to reduce their viscosities. The densities and viscosities of the three working pairs were obtained in a temperature range of 293.15∼338.15 K, thereby determining the thermal expansion coefficients. The effects of ethanol on the volumetric and viscometric characteristics of the three ILs are discussed. To further analyze the interactions between ethanol and the ILs, excess mole volume and viscosity deviations were introduced. The interactions between different molecules were stronger than those between the same molecules in the working pairs. This is the main reason why the addition of ethanol reduces the viscosity of the three ILs. Finally, the hard-sphere model was applied to predict the viscosities of the working pairs. Upon introducing an adjustable argument, the average absolute relative deviation of the prediction for the aforementioned three ILs decreased to 4.4%, 5.9%, and 5.0%, respectively.

Predicting the solubility of CO2 and N2 in ionic liquids based on COSMO-RS and machine learning.

As ionic liquids (ILs) continue to be prepared, there is a growing need to develop theoretical methods for predicting the properties of ILs, such as gas solubility. In this work, different strategies were employed to obtain the solubility of CO2 and N2, where a conductor-like screening model for real solvents (COSMO-RS) was used as the basis. First, experimental data on the solubility of CO2 and N2 in ILs were collected. Then, the solubility of CO2 and N2 in ILs was predicted using COSMO-RS based on the structures of cations, anions, and gases. To further improve the performance of COSMO-RS, two options were used, i.e., the polynomial expression to correct the COSMO-RS results and the combination of COSMO-RS and machine learning algorithms (eXtreme Gradient Boosting, XGBoost) to develop a hybrid model. The results show that the COSMO-RS with correction can significantly improve the prediction of CO2 solubility, and the corresponding average absolute relative deviation (AARD) is decreased from 43.4% to 11.9%. In contrast, such an option cannot improve that of the N2 dataset. Instead, the results obtained from coupling machine learning algorithms with the COSMO-RS model agree well with the experimental results, with an AARD of 0.94% for the solubility of CO2 and an average absolute deviation (AAD) of 0.15% for the solubility of N2.

Analysis of the Effects of Ionic Liquid Properties on Electrospray Thruster Performance.

Ionic liquids (ILs) have proven extremely useful for a wide variety of roles, including as propellants for electrospray thrusters (ETs), due to their unique physical and chemical properties, as well as the potential tunability of those properties, through chemical engineering. However, there is a lack of literature exploring the effects of IL properties on ET operation. This paper presents experimental results investigating key physical properties of the common ILs 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMI-TFO), EAN, and Bmpyr-DCA not provided by manufacturers or reported in the literature, namely, their electrochemical stability windows (ESWs) and contact angles. Cyclic voltammetry experiments were employed to define the ESW of each IL, which is necessary for long-term ET operation while avoiding chemical breakdown. Contact-angle measurements were also conducted to study the wettability of the ILs on glass surfaces to be used for ET thruster substrates [Howell, J. H.; . J. Electrost. 2023, 122, 103799]. In addition, an analytical discussion is presented using established parametric relationships and scaling laws to examine the effects of relevant IL physical properties, such as surface tension and ion molecular weights, on ET performance. The results demonstrate the relative impact of IL properties on important ET figures of merit such as thrust density, power density, and specific impulse, which provide key insights into the future development of novel ILs specifically tailored for use as ET propellants.

Improvement of tetracycline removal using amino acid ionic liquid modified magnetic biochar based on theoretical design

In current research, biochar is widely used to remove antibiotic contamination from the environment. However, original biochar produced through direct pyrolysis has significant limitations in removing antibiotics. In this paper, response surface methodology provided the laudable choice for magnetic poplar biochar (MPBC) considering the synergistic effect of multi-factors as well as the restrictions abundance experiments during the preparation of MPBC. Amino acid ionic liquids (AAILs) are a class of ionic liquids in which amino acids act as the anionic component, combining the tunable properties of ionic liquids with the biocompatibility and functionality of amino acids. To ameliorate adsorption capacity of MPBC, tetra-ethylammonium glycinate ([TEA][Gly]) with the best affinity for tetracycline (TC) were screened from 600 AAILs based on theoretical predictions using the conductor-like screening model for real solvents (COSMO-RS) without extensive experimental. Furthermore, AAILs-modified magnetic biochar (MPBC-AAIL) was synthesized chemically for the first time. Adsorption kinetics, isotherms, and thermodynamic analyses revealed that TC adsorption by both MPBC and MPBC-AAIL is a monolayer, spontaneous, and exothermic chemical process. Moreover, MPBC-AAIL exhibited a maximum adsorption capacity of 305.9 mg·g−1. Meanwhile, MPBC-AAIL maintains superior adsorption performance for TC in different impurity solutions as well as in real water samples. The excellent reusability and selective adsorption capacity of the material demonstrate the superiority of the theoretical based design. The characterization reveals that the adsorption mechanisms include pore filling, π-π interactions, surface complexation, hydrogen bonding, and electrostatic interactions. In addition, theoretical calculations showed that ionic liquid modification altered the adsorption sites between TC and MPBC-AAIL, leading to enhanced adsorption. This comprehensive study introduces an innovative modification of biochar, providing a novel approach to designing biochar composites and promoting their application in the remediation of complex environmental pollution.

Molecular Dynamic Simulations of the Physical Properties of Four Ionic Liquids

In this study, the molecular structure models of four ionic liquids were created, the reverse nonequilibrium molecular dynamics simulation (RNEMD) approach was used to predict their densities and viscosities, and their thermal conductivity was simulated using the non-equilibrium molecular dynamic simulation method (NEMD). The calculated results of ionic liquid densities were compared with the data in the literature; most of the variances are around 2.5%, and the maximum relative deviation was less than 6.27%; viscosity values were compared with the experimental data, with a maximum relative deviation of −8.96% and a minimum relative deviation of −2.72%. The simulated thermal conductivity has a good linear relationship with respect to temperature and pressure, which is in good agreement. This study provides a reference for molecular dynamics simulation to measure the physical properties of ionic liquids, which is important for the development of ionic liquids.

Investigating the Role of Anions in the Adsorption of Pyrrolidinium Based Ionic Liquids on Pt(111) Surface Using Density Functional Theory

ABSTRACTThe adsorption properties of ionic liquids containing pyrrolidinium cations and various inorganic anions as electrolytes on a platinum surface were analyzed using first principle density functional theory. Three different orientations of the alkyl cation chain were observed during the adsorption process. The strength and structural stability varied between non‐fluorinated and fluorinated anions upon adsorption, with oxygen atoms influencing the mechanism of adsorption and driving the structural stability of the anion, while fluorine atoms played a role in determining the orientation of the cation during adsorption. Net atomic charges analysis, electron density difference methods, and electron density accumulation for this complex system were utilized to further investigate these phenomena. The results of this study provide valuable insights into the role of anions in the adsorption behavior of pyrrolidinium‐based ionic liquids on platinum surfaces, shedding light on the factors that influence their adsorption properties and structural stability on a molecular level. The findings of this study contribute to a better understanding of the interplay between anions and platinum surfaces in the adsorption of pyrrolidinium based ionic liquids, which can have implications for various applications such as electrochemistry, catalysis, and energy storage.

Boosting cesium retention efficiency with polyoxometalate-ionic liquid composites: Insights into {WO6} octahedral affinity

Commonly used polyoxometalate (POM) adsorbents exhibit high cesium (Cs) adsorption capacity. However, its impotent ability to sequester adsorbates poses a risk of Cs migration in radioactive waste decontamination and disposal. By leveraging the cesium affinity of POMs and the regulatory properties of ionic liquids (ILs), POM-IL composites hold promise for mitigating the risk of cesium migration through efficient adsorption and retention. Herein, we designed two POM-ILs composed of the phosphotungstate anion (PW) and tetrabutylammonium cation (TBA), i.e., the {WO6}-saturated TBA-PW12 and mono-lacunary TBA-PW11, for the capture and retention of aqueous Cs. The composites were then characterized, and the performance and mechanism of Cs uptake were investigated. TBA-PW12 exhibited ∼300 nm aggregate of particles around 20–60 nm. TBA-PW12 retained the Keggin structural features of PW12O403−, which was proven essential for the binding of Cs+. With a retention efficiency of 97.3% in an NH4Cl eluent and a maximum adsorption capacity of 400.9 mg/g at 338 K, TBA-PW12 exhibited superior Cs capture and retention compared to the POM-IL derived from common Cs adsorbent phosphomolybdate. The Cs adsorption onto TBA-PWs achieved equilibrium within 180 min. Cs uptake by TBA-PWs was monolayer chemisorption of Cs+ accompanied by H+ release, and the removal efficiencies stabilized around initial pH 5–10. Due to intense affinity between {WO6} and Cs+, TBA-PW12 efficiently sequestered Cs + through {WO6} octahedra so that the {WO6}-saturated TBA-PW12 presented better Cs uptake performance than the mono-lacunary TBA-PW11. The IL anion [N(C4H9)4]+ provided a composite-water biphasic interface for aqueous Cs adsorption, while retaining the ability of POM cation PW12O403− to form a stable structure with Cs via its affinity to {WO6} octahedra. These findings support the design of POM-IL composites as efficient adsorbents for capturing and retaining Cs, aiding in the decontamination and safe disposal of radioactive waste, thereby minimizing the risk of nuclide leakage into the environment.

Flipping Water Orientation at the Surface of Water-in-Salt and Salt-in-Water Solutions.

Salt-in-water and water-in-salt mixtures are promising for battery applications and fine-tuning of room-temperature ionic liquid (RTIL) properties. Although critical processes take place at interfaces of these systems, including charge transfer and heterogeneous catalytic reactions, the microscopic interfacial structures remain unclear. Here, we apply heterodyne-detected sum-frequency generation spectroscopy to aqueous solutions of imidazolium-based RTILs to unveil the microscopic structure of the interfaces of these solutions with air. Our results show that, under salt-in-water conditions, the orientation of the OH group hydrogen-bonded to the other water molecules flips from the OH group pointing down into the liquid for pure water to up due to the accumulation of anions in the cation-rich interfacial region. However, under the water-in-salt condition, the interfacial water molecules are confined by RTIL, and their orientation is down. Details of the water organization depend critically on the alkyl chain length of the imidazolium cation. Our results demonstrate that the surface structure can be tuned by altering the molecular structure and concentration of the RTIL.

Relationship between structure and properties of bio-based aromatic ionic liquids for tribological applications

This study examined six phosphonium-based room-temperature ionic liquids (PRTILs) having trihexyltetradecyl- or tributyltetradecyl-phosphonium cations with saccharinate, salicylate, or benzoate anions, and obtained a feature parameter to correlate their cationic chain length, anionic ring size, and contact angle with tribological properties. PRTILs with trihexyltetradecyl-phosphonium cations had lower coefficient of friction (COF) and wear than PRTILs with tributyltetradecyl- phosphonium cations, a trend attributed to the additional methylene groups providing lower contact angle. For either cation, PRTILs with the saccharinate anion exhibited much lower COF and wear than single-ring anions, due to the formation of a low-shear-strength-tribofilm facilitated by the double-ring structure and sulfur of saccharinate. Overall, this study revealed PRTIL interfacial mechanisms that can be used to identify anion-cation combinations with optimal tribological performance.

Possibilities For Using Ionic Liquids In The Polymerization Process

Abstract The paper investigates the polymerization of various methacrylate esters in different ionic liquids (ILs) and compares the results with those obtained in traditional organic solvents, particularly benzene. The study highlights the influence of ILs on the polymerization process, focusing on factors such as polymer yield, average molecular weight, and thermal stability. The results indicate a relatively higher degree of polymerization in ILs compared to benzene under identical conditions. Additionally, polymers synthesized in ILs exhibit higher average molecular weights and thermal stability. The observed differences are attributed to the unique properties of ILs, such as low chain transfer rate constants and the ability to stabilize active radicals during polymerization. The findings underscore the potential of ILs as promising reaction media for polymer synthesis, offering improved efficiency and polymer properties compared to conventional organic solvents.

Investigating the ions emitted by multiply charged ionic liquids from a porous electrospray ion source

A porous electrospray ion source was tested with three ionic liquids in order to investigate the effects of ionic liquid properties on the sizes of ion clusters emitted by purely ionic electrospray sources. Two of the ionic liquids, bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate and 1,6-bis(3-methylimidazolium-1-yl)hexane bis(trifluoromethylsulfonyl)amide, were selected due to them having a dication or dianion, which were termed multiply charged ionic liquids due to them containing anions or cations with more than one charge within them. These were selected in order to investigate ionic clustering within electrospray ion emission and were compared against one of the most common ionic liquids, EMI-BF4. The current–voltage data showed that EMI-BF4 emitted similar levels of current to bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate, even though the latter liquid had significantly lower conductivity and higher viscosity, suggesting an improvement in current speculated to be due to the extra charges contained by the ions. Time-of-flight and retarding potential analysis data are provided, showing all three liquids emitting ions comprising of monomers, dimers, trimers, and quadramers, with some of the 1,6-bis(3-methylimidazolium-1-yl)hexane bis(trifluoromethylsulfonyl)amide data showing heavier species emission. The data also suggested that the multiply charged ionic liquids produced ions that have two anions or cations attached, termed “double ions,” with these ions not been previously reported using porous electrospray sources. Furthermore, it was found that the dimers emitted by both of the multiply charged ionic liquids seemed to be more stable than EMI-BF4 dimers, providing insight into ion cluster formation.

Dependence of Carboxylate Anions on Physicochemical Properties of Tributyloctylphosphonium-Based Ionic Liquids

A new group of tributyloctylphosphonium-based ionic liquids containing several carboxylate anions was designed, prepared and physicochemically characterized. All phosphonium carboxylates obtained in this study became viscous liquids at room temperature. The formate-based ionic liquid exhibited the highest density and number density due to the smallest anion size. All ionic liquids exhibited typical ionic conduction behavior, since the viscosity decreased and the conductivity increased with increasing temperature. It was also found that the viscosity tended to decrease with increasing the carbon numbers of the alkyl chains of lower carboxylate anions. Compared to the propionate-based ionic liquids, lactate-based ionic liquids exhibited higher viscosity. The phosphonium ionic liquids based on carboxylate anions showed higher thermal stability than nitrogen-based counterpart ionic liquids.

Physicochemical and Thermal Behaviors of Room-Temperature Phosphonium Ionic Liquids Based on Fluorosulfonyl(trifluoromethylsulfonyl)Amide Anion As Potential Electrolytes

The physicochemical properties of novel room-temperature ionic liquids based on quaternary phosphonium cations in combination with asymmetric fluorosulfonyl(trifluoromethylsulfonyl)amide anion were reported. It was found that such phosphonium ionic liquids showed lower melting points than those of the conventional amide anion-based ionic liquids. Typical density and transport property behaviors for ionic liquids were observed. Several phosphonium ionic liquids based on fluorosulfonyl(trifluoromethylsulfonyl)amide anion exhibited low viscosities. The phosphonium ionic liquids based on fluorosulfonyl(trifluoromethylsulfonyl)amide anion exhibited relatively low thermal stability when compared to the corresponding conventional amide anion-based ionic liquids.

Predicting imidazolium ionic liquid properties with a simple molecular volume-based SAFT-VR Mie approach

Each thermodynamic model requires a distinct set of parameters for each component and these parameters must be transferable beyond their original estimation domain to accurately predict a variety of thermodynamic properties. Previous work introduced and evaluated a novel parametrization method for the solubility of ionic liquids in CO2 or CH4 [Chem. Eng. Sci. 2024, 285, 119610]. This methodology provides a fast and efficient way to evaluate ionic liquids by requiring only their molecular volume. In this study, the approach is extended to include both pure ionic liquids, examining properties such as density, isobaric heat capacity, isobaric expansivity, isothermal compressibility, and speed of sound, as well as their mixtures with ethanol or water, focusing on speed of sound, and excess enthalpy. Ionic liquids are modeled as both non-associating and associating components. Overall, the approach demonstrates good estimates and holds potential for extension to other models and systems.

Nitric oxide shifts the impact of ionic liquid on microbial community structure in rhizosphere of Arabidopsis

ABSTRACT Ionic liquids (ILs) are widely used in various fields due to their excellent properties. Despite their utility, there is limited knowledge regarding the phytotoxic properties of ILs and the mechanisms by which plants develop resistance to them. This is particularly true when considering the role of nitric oxide (NO) in response to ILs stress. Herein, we investigated the mechanism by which endogenous NO reduces the ILs’ phytotoxicity in Arabidopsis from the perspective of rhizosphere microorganisms. We investigated the impact of 1,3-dibutyl imidazole bromide (DIB) on microbial diversity and community in the rhizosphere of Arabidopsis lines with varying endogenous NO levels, using a high throughput sequencing method. DIB did not affect microbial taxon numbers, richness, or evenness; however, it did alter microbial beta diversity and community structure in the rhizosphere of Arabidopsis. Elevated endogenous NO increased fungal richness and evenness, shifted DIB’s impact on microbial community structure, and enriched more resistant species and toxin-decomposing species. These findings suggest a potential mechanism for plants to resist IL stress. Our study not only elucidates the toxicological mechanisms of ILs but also reveals the involvement of NO in plant responses to IL stress, providing valuable insights for future environmental risk assessments and mitigation strategies.

Thermophysical and transport properties of a pyrrolidinium-based ionic liquid confined in silica

Ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyrrTFSI) was confined in silica (Aerosil A380) by direct mixing. The resulting BMPyrrTFSI/xSiO2 ionogel (x – from 2.3 to 6.7 wt%) was studied by TG, DSC, conductometry and viscometric methods. For confined IL, a decrease in the Tm and Ts-s by 14–16 °C and an increase in the Tg, and Tcc by 4–5 °C were found. With an increase in xSiO2, the opposite dynamics of the decomposition temperatures Tonset and Tpeak, and a disproportionate decrease in ionic conductivity were observed. The change in the properties of BMPyrrTFSI under conditions of limited geometry of the silica matrix is explained in the terms by the interaction of the IL and SiO2, as well as the conformation features of the cation and anion. In the first time, parameters such as the fragility index D and the formation factor F were also discussed for such systems. As a result, BMPyrrTFSI/4.5 wt% SiO2 ionogel (0.2 S m−1, 20 °C) was proposed as a promising electrolyte for application in electrochemical devices. This study may be useful for creating quasi-solid electrolytes based on ILs and inorganic materials.

Structural effect on physicochemical properties of ethanolamine carboxylate ionic liquids by experimental and theoretical study

The hydroxylammonium ionic liquids (ILs) falling within the category of protic ionic liquids (PILs) have garnered attention from researchers, owing to their outstanding solubility properties. A one-step method was employed to synthesize a series of ethanolamine ILs. The thermodynamic properties of the ILs, including surface tension, density, and electrical conductivity, were measured across varying temperatures. Essential parameters such as thermal expansion coefficient, molecular volume, surface entropy, and surface energy were estimated using empirical equations. In order to elucidate the intermolecular interactions within the ethanolamine carboxylate ILs, the sigma profiles of ILs were determined using COSMO-RS. It was observed that the ethanolamine cation has a strong potential as a H-bond donor, while the carboxylate anion demonstrates significant capability as a hydrogen bond acceptor. By DFT calculations, it was observed that the NH in the ethanolamine cation can form H-bonds with the oxygen atom in the carboxylate anion.

Stable hierarchical ionic liquid nanochannels for highly efficient CO2 adsorption, separation and conversion

Constructing stable nanochannels and nanoconfined environments for ionic liquids holds significant application value in gas separation, ion channels, and related fields. The functional polyionic liquid synthesized in this study exhibits a controllable assembly structure and demonstrates liquid crystal properties. Through heating and water treatment, the polyionic liquids crosslink to form multi-hierarchical nanopores, including sub-nanochannels with pore sizes similar to CO2, without the need for a catalyst. The specific surface area and pore size of the polyionic liquid network (PILC) were adjusted by regulating the self-assembly of polyionic liquids in water. The unique PILC, combining ionic liquid nanopores and liquid crystal structure properties, shows high CO2 adsorption performance and excellent CO2/N2 selectivities, surpassing commonly reported ionic liquid porous materials. Furthermore, PILC-2 exhibits good catalytic performance for CO2 cycloaddition, and its catalytic activity and selectivity did not significantly decrease after five cycles. This study successfully introduces hierarchical ionic liquid nanochannels into porous networks without involving any inorganic ordered nanomaterials. This provides a simple and effective approach for the highly selective adsorption and separation of CO2, as well as for the preparation of catalytic materials.

A-priori framework of viscosity and ionic conductivity estimation of ionogel

A-priori framework has been developed to estimate the viscosity and ionic conductivity of ionogel. Six imidazolium-class of ionic liquids (ILs) form ionogels with tetraethyl orthosilicate (TEOS) matrix. Group contribution parameters of TEOS are estimated with the fitting of the density dataset in the predictive Soave−Redlich−Kwong equation of state with the NSM1 alpha function model. Later the parameters are used to estimate the critical property of ILs and TEOS. These facilitate the formulation of the predictive framework of viscosity estimation through the geometric similitude concept with the Valderrama-Patel-Teja cubic equation of state. Later the viscosity of ionogels is estimated through a mixture form of geometric similitude framework as well as the Arrhenius model. Additionally, the estimated viscosities from both frameworks are used to estimate the ionic conductivities of ionogels. The compositional and temperature variance of ionic conductivity reveals the superior ionic conductivity of tetrafluoroborate-based ionogels than the bis(trifluoromethanesulfonyl) imide-based counterparts. Both models estimate the decrease in viscosity as well as incremental trends in ionic conductivity with temperature. However, the concentration of IL rather plays a different trend in the estimation model as well as the class of IL. Such a priori framework shall lead to the design of the ionogels focusing on the physicochemical properties.