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Ionic Liquids: Properties and Applications

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: closed (30 September 2020) | Viewed by 16444

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Dr. Oriele Palumbo

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Italian National Research Council - Istituto Dei Sistemi Complessi, 00185 Rome, Italy
Interests: ionic liquids; structural and dynamical properties of materials; Lithium batteries; hydrogen storage
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Dear Colleagues,

Ionic liquids have been studied intensively in the last few years due to their properties, which make them attractive for a range of applications in green chemistry and electrochemistry. What really makes them charming, from a fundamental point of view, is the possibility of tailoring their properties by means of a proper choice of the constituent ions, by modification of the alkyl chains, or by mixing them with other liquids. Despite our efforts, our knowledge of the mechanisms that govern their physical properties remains incomplete. Moreover, new liquids are continuously being proposed and synthesized. This Special Issue aims to collect original research articles and review articles that describe new advances in the synthesis of ionic liquids, in the description of their structural and dynamic properties, and in their modification. New results that identify new challenges in their possible application are also welcome.

Dr. Oriele Palumbo
Guest Editor

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Keywords

ionic liquids
synthesis
structural and dynamical properties
electrolytes
modeling

Published Papers (7 papers)

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Research

7 pages, 880 KiB

Open AccessArticle

Renaturation of Lyophilized Concanavalin a Treated in Water Content Controlled Hydrated Ionic Liquids

by Kyoko Fujita, Ryota Fujii and Kimiyoshi Ichida

Appl. Sci. 2021, 11(1), 57; https://0-doi-org.brum.beds.ac.uk/10.3390/app11010057 - 23 Dec 2020

Cited by 1 | Viewed by 1770

Abstract

A fraction of commercially available lyophilized concanavalin A (ConA) shows low mannose binding activity. In this study, we investigated the effects of the component ion and water content of hydrated ionic liquids (ILs) as treatment solvent on the mannose binding ability of lyophilized ConA. While high mannose binding ability was observed treated in hydrated ILs composed of dihydrogen phosphate anion with three water molecules per ion pair, it decreased with increase in water content. In contrast, no increase in mannose binding ability was observed after treatment with hydrated ILs composed of bromide anions. A steady response in mannose binding was observed after treatment with hydrated cholinium dihydrogen phosphate ([ch][dhp]). Following treatment with hydrated [ch][dhp] with three water molecules per ion pair, the mannose binding ability of lyophilized ConA increased twofold, while the low and high mannose binding ConA fraction showed an increase of 3.3 and 1.8 in the binding response, respectively. Full article

(This article belongs to the Special Issue Ionic Liquids: Properties and Applications)

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8 pages, 1693 KiB

Open AccessCommunication

Pyr_1,xTFSI Ionic Liquids (x = 1–8): A Computational Chemistry Study

by Sergio Brutti

Appl. Sci. 2020, 10(23), 8552; https://0-doi-org.brum.beds.ac.uk/10.3390/app10238552 - 29 Nov 2020

Cited by 6 | Viewed by 1941

Abstract

Pyrrolidinium-based (Pyr) ionic liquids are a very wide family of molecular species. Pyrrolidinium cations are electrochemically stable in a large potential interval and their molecular size hinders their transport properties. The corresponding ionic liquids with trifluoromethyl sulphonyl imide anions are excellent solvents for lithium/sodium salts and have been demonstrated as electrolytes in aprotic batteries with enhanced safety standards. In this study, the analysis of the physicochemical properties of a homologous series of pyrrolidinium-based ionic liquids with general formula Pyr_1,xTFSI (x = 1–8) have been tackled by first principles calculations based on the density functional theory. The molecular structures of isolated ions and ion pairs have been predicted by electronic structure calculations at B3LYP level of theory in vacuum or in simulated solvents. Thermodynamic properties have been calculated to evaluate the ion pairs dissociation and oxidation/reduction stability. This is the first systematic computational analysis of this series of molecules with a specific focus on the impact of the length of the alkyl chain on the pyrrolidinium cation on the overall physicochemical properties of the ion pairs. Full article

(This article belongs to the Special Issue Ionic Liquids: Properties and Applications)

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12 pages, 1486 KiB

Open AccessArticle

Improved Loss-of-Lubrication Performance with Lubricants Containing Nano-Graphene Platelets and Ionic Liquids

by Nikhil Murthy, Amarendra K. Rai and Stephen Berkebile

Appl. Sci. 2020, 10(22), 7958; https://0-doi-org.brum.beds.ac.uk/10.3390/app10227958 - 10 Nov 2020

Cited by 5 | Viewed by 1781

Abstract

In this study, nano-graphene platelets (NG) and a phosphonium-phosphate-based ionic liquid (IL) were studied as additives to rotorcraft gearbox oil to improve the resistance to scuffing under starved lubricated conditions. Behavior under a loss of lubrication was evaluated using a high-speed ball-on-disk tribometer and a reciprocating cylindrical pin-on-disk tribometer. In addition, the scuffing load and friction over a wide range of sliding and entrainment speeds was determined. On the high-speed ball-on-disk tribometer, an oil blend containing both NG and IL additives was able to operate two times longer than an unadditivized oil before scuffing after the lubrication supply was removed. The increase in time to scuffing was larger for two additives together than the sum of their parts. The additives showed an increase in scuffing load individually but were detrimental when mixed together with a lower scuffing load. The combination of NG and IL show promise as additives to increase the operation time of gears during loss of lubrication, however at the potential cost of decreasing the load-carrying capacity of the oil. Full article

(This article belongs to the Special Issue Ionic Liquids: Properties and Applications)

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11 pages, 1807 KiB

Open AccessArticle

Synthesis and Use of Zwitterion Bearing Sulfonyl(trifluoromethane sylfonyl)imide Anion as Additive for Polymer Electrolytes

by Elisabetta Fedeli, Andriy Kvasha, Didier Gigmes and Trang N. T. Phan

Appl. Sci. 2020, 10(21), 7724; https://0-doi-org.brum.beds.ac.uk/10.3390/app10217724 - 31 Oct 2020

Cited by 4 | Viewed by 2720

Abstract

In order to improve the electrochemical properties of poly(ethylene oxide), a well-known-solid polymer electrolyte, by adding zwitterion molecules, the synthesis of a new zwitterion (ZN) having imidazolium cation and sulfonyl(trifluoromethane sulfonyl)imide anion is investigated. The addition of different amounts of ZN to the mixture of lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) and poly(ethylene glycol)dimethyl ether (PEGDM) of 1000 g mol⁻¹ does not significantly affect the transition temperature of PEGDM but causes a slight decrease in ionic conductivity of the electrolyte mixtures. However, even with the presence of only 0.05 mole fraction of ZN, the anodic stability of LiTFSI/PEGDM based electrolytes is improved to over 4.5 V vs. Li⁺/Li at 25 °C. This makes the new synthesized zwitterion a promising electrolyte’s additive for high voltage batteries. Full article

(This article belongs to the Special Issue Ionic Liquids: Properties and Applications)

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6 pages, 648 KiB

Open AccessCommunication

Ionic Liquid Electrolytes for Safer and More Reliable Sodium Battery Systems

by Mariangela Bellusci, Elisabetta Simonetti, Massimo De Francesco and Giovanni Battista Appetecchi

Appl. Sci. 2020, 10(18), 6323; https://0-doi-org.brum.beds.ac.uk/10.3390/app10186323 - 11 Sep 2020

Cited by 16 | Viewed by 2354

Abstract

Na⁺-conducting, binary electrolytic mixtures, based on 1-ethyl-3-methyl-imidazolium, trimethyl-butyl-ammonium, and N-alkyl-N-methyl-piperidinium ionic liquid (IL) families, were designed and investigated. The anions were selected among the per(fluoroalkylsulfonyl)imide families. Sodium bis(trifluoromethylsulfonyl)imide, NaTFSI, was selected as the salt. The NaTFSI-IL electrolytes, addressed to safer sodium battery systems, were studied and compared in terms of ionic conductivity and thermal stability as a function of the temperature, the nature of the anion and the cation aliphatic side chain length. Room temperature conductivities of interest for sodium batteries, i.e., largely overcoming 10⁻⁴ or 10⁻³ S cm⁻¹, are displayed. Similar conduction values are exhibited by the EMI-based samples even below −10 °C, making these electrolyte mixtures potentially appealing also for low temperature applications. The NaTFSI-IL electrolytes, with the exception of the FSI-ones, are found to be thermally stable up to 275 °C, depending on the nature of the cation and/or anion, thus extending their applicability above 100 °C and remarkably increasing the reliability and safety of the final device, especially in the case of prolonged overheating. Full article

(This article belongs to the Special Issue Ionic Liquids: Properties and Applications)

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11 pages, 3124 KiB

Open AccessArticle

Temperature and Pressure Dependence of the Infrared Spectrum of 1-Ethyl-3-Methylimidazolium Trifluoromethanesulfonate Ionic Liquid

by Francesco Trequattrini, Anna Celeste, Francesco Capitani, Oriele Palumbo, Adriano Cimini and Annalisa Paolone

Appl. Sci. 2020, 10(12), 4404; https://0-doi-org.brum.beds.ac.uk/10.3390/app10124404 - 26 Jun 2020

Cited by 1 | Viewed by 2622

Abstract

The infrared absorption spectrum of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI–TfO) was investigated at ambient pressure and variable temperatures between 120 and 330 K, or at room temperature and variable pressures up to 10 GPa. Upon cooling, the ionic liquid crystallizes; on the contrary, upon compression no evidence of crystallization can be obtained from the infrared spectra. Moreover, Density Functional Theory (DFT) calculations were applied to gain a better description of the ionic couple. The ωB97X-D functional, including not only the empirical dispersion corrections but also the presence of a polar solvent, gives a good agreement with the infrared spectrum and suggests that TfO resides above the plane of the imidazolium, with the shorter distance between the O atom of the anion and the C2 atom of the imidazolium ring equal to 2.23 Å. Full article

(This article belongs to the Special Issue Ionic Liquids: Properties and Applications)

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10 pages, 3133 KiB

Open AccessArticle

Study on Degradation of Benzothiazolium-Based Ionic Liquids by UV-H₂O₂

by Jianhui Gu, Huimin Zang, Shun Yao, Xuejiao Wang, Minghui Zhu and Hang Song

Appl. Sci. 2020, 10(3), 894; https://0-doi-org.brum.beds.ac.uk/10.3390/app10030894 - 29 Jan 2020

Cited by 12 | Viewed by 2415

Abstract

Ionic liquids (ILs) are considered to be a new type of solvent due to their low vapor pressure, some unique properties and are expected to be used widely in the following days. Given their water solubility, stable chemical structure, and biological toxicity, ILs probably reach aquatic environments and become long-term pollutants. We studied the fate of benzothiazolium-based ionic liquids catalyzed by UV-H₂O₂ in water. Due to the synergistic effect of UV and H₂O₂, the degradation efficiency can be significantly improved compared to any of them alone. Fitting results showed that the degradation reaction follows pseudo-first-order kinetics and reaction rate constants with hydroxyl radicals ranging from 0.0005 s⁻¹ to 0.0529 s⁻¹. The experimental data showed that satisfactory results can be obtained at a temperature of 45 ℃, an initial concentration of ionic liquid of 0.1 M, and a hydrogen peroxide concentration of 0.1 M. We also explored the effects of chloride ions and pH on degradation reactions. In an appropriate situation, the degradation yield of [C₄Bth]PF₆ could achieve 97% in 60 min and 99% in 90 min. The UV-H₂O₂ combination process could provide an effective technique for the treatment of benzothiazolium-based ionic liquids in wastewater. Full article

(This article belongs to the Special Issue Ionic Liquids: Properties and Applications)

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