Ambient Temperature Ionic Liquids Research Articles

A Sodium-Aluminum Hybrid Battery

To effectively harvest the energy from renewable sources such as solar and wind, cheap and long-lasting electric energy storage (EES) devices are essential.1 Among various EES technologies, lithium ion batteries (LIBs) are the most mature technologies with high energy density, high coulombic efficiency and long cycle life. Unfortunately, their high cost and the unevenly distributed global lithium source are major concerns. 2 Thus, beyond lithium technologies based on cheap and naturally abundant elements such as sodium (Na), magnesium (Mg), and aluminum (Al) ion batteries 3, 4 have been intensively studied during the last few years. Among different metals, Al is one of the most earth abundant elements, only second to silicon, resulting in its low price of $0.52/kg, 100 times lower than Li. In addition, Al with three electrons redox couple has distinct advantage over one electron redox couple such as Li and Na and two electrons redox couple such as Mg and Ca, providing a high theoretical specific capacity of 2980 mAh g-1 and a high volumetric capacity of 8040 mAh cm-3. The development of rechargeable Al ion batteries has been hampered by the electrolyte and cathode materials. Due to the low reduction potential of Al (-1.68 V vs. SHE), aqueous electrolytes cannot be used when Al is being used as the anode, since hydrogen will be released before Al can be plated during the reduction process. As an alternative, ambient room temperature ionic liquids with high ionic conductivity and wide electrochemical windows are good candidates for rechargeable Al batteries. Currently, the ionic liquids used for Al deposition are still based on mixtures of anhydrous AlCl3 and organic halide salts.5 It is well-known that only the acidic mixtures show reversible Al deposition/stripping, which poses stringent requirement for the hardwares of the Al batteries.6 To avoid the corrosion issue, pouch cell and special cell configuration have been used.7 Besides electrolytes, Al batteries also face challenges from the cathodes due to the high charge density of the Al3+ ion, making its insertion/extraction into/from the cathode host very difficult. An alternative way to take advantage of metallic Al anode but bypasses the need for efficient Al insertion cathodes is hybrid Al battery.7 It was demonstrated that high voltage and high capacity were possible in a hybrid Al battery with LiFePO4 as the cathode in an acidic ionic liquid electrolyte.7 However, a switch to the more earth-abundant sodium chemistry is more desirable due to the limited Li resources. In this presentation, we report a new hybrid battery using earth-abundant Na and Al chemistry, that is, Al as the anode, Na3V2(PO4)3 (NVP) as the cathode and NaAlCl4 dissolved in acidic ionic liquid as the electrolyte.8 The hybrid battery exhibits a discharge voltage of 1.25 V and a cathodic capacity of 99 mAh g-1 under a current rate of C/10. In addition, the hybrid battery exhibits good rate performance and long cycling stability while maintaining a high coulombic efficiency of 98 %. It is also demonstrated that increasing salt concentration can further enhance the cycling performance of the hybrid battery. X-ray diffraction analysis of the NVP electrodes under different conditions confirms that the main cathode reaction is indeed the Na extraction/insertion. 1. B. Dunn, H. Kamath and J. M. Tarascon, Science, 2011, 334, 928-935. 2. H. L. Pan, Y. S. Hu and L. Q. Chen, Energy Environ. Sci. , 2013, 6, 2338-2360. 3. G. A. Elia, K. Marquardt, K. Hoeppner, S. Fantini, R. Y. Lin, E. Knipping, W. Peters, J. F. Drillet, S. Passerini and R. Hahn, Adv. Mater. , 2016, 28, 7564-7579. 4. T. Gao, X. G. Li, X. W. Wang, J. K. Hu, F. D. Han, X. L. Fan, L. M. Suo, A. J. Pearse, S. B. Lee, G. W. Rubloff, K. J. Gaskell, M. Noked and C. S. Wang, Angew. Chem. Int. Ed. , 2016, 55, 9898-9901. 5. J. S. Wilkes, J. A. Levisky, R. A. Wilson and C. L. Hussey, Inorg. Chem. , 1982, 21, 1263-1264. 6. L. D. Reed and E. Menke, J. Electrochem. Soc., 2013, 160, A915−A917. 7. X. G. Sun, Z. H. Bi, H. S. Liu, Y. X. Fang, C. A. Bridges, M. P. Paranthaman, S. Dai and G. M. Brown, Chem. Commun., 2016, 52, 1713-1716. 8. X. G. Sun, Z. Z. Zhang, H. Y. Guan, C. A. Bridges, Y. X. Fang, Y.-S. Hu, G. M. Veith and S. Dai, J. Mater. Chem. A, 2017, 5, 6589-6596. Figure 1

Ionic Liquid Redox Catholyte for High Energy Efficiency, Low‐Cost Energy Storage

An approach to energy storage using ionic liquids as joint ion‐conducting medium and redox active catholyte material is described. The earth‐abundant ferric ion is incorporated as an oxidizing agent in the form of the low‐melting NaFeCl4 in a 1:1 mixture with ethylmethylimidazolium tetrachloraluminate, an ambient temperature ionic liquid. Different possible anode types are considered, and the most obvious one involving liquid sodium (with special wetting of a sodium ion‐conducting ceramic separator) is tested. The high voltage >3.2 V predicted for this cell is verified, and its cyclability is confirmed. Operating at 180 °C, an unexpectedly high energy efficiency >96%, is recorded. This establishes this type of cell as an attractive candidate for energy storage. For optimum energy storage, high energy efficiency is mandated for thermal management, as well as economic reasons. The theoretical capacity of the cell is 288 Wh kg−1 (418 Wh L−1) of which 73% is realized. The cell is shown to be fail‐safe against internal shorts. As there are many degrees of freedom for developing this type of cell, it is suggested as a promising area of future research effort in the energy storage area.

Direct electroreduction of solid cuprous chloride to copper powder in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

Direct electroreduction of solid cuprous chloride to prepare copper powder in a “neutral” ambient-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid (BMIMBF4) was investigated. Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid. Chronoamperometry of the salt powder filled Mo-cavity electrode (current collector) in the ionic liquid further demonstrated the conversion of chloride-to metal inside the cavity, as confirmed by scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction spectra.

Ionic liquids as oxidic media for electron transfer studies

We review the basic ideas underlying the electron free energy level diagrams that have been found useful in considering the thermodynamics of redox processes in molten silicates and related high temperature ionic liquid (IL) solvents, and then show how closely they link to behavior observable in ambient temperature ionic liquids. Much of the information available on redox levels in molten oxides has been gleaned from chemical analysis and spectroscopic species distribution studies, but it is simpler to obtain the data electrochemically. Here, we report some cyclic voltammetry measurements of the Fe(II)∕Fe(III) redox equilibrium in aprotic ionic liquids whose anions provide oxide environments for the redox species that are of different electronic polarizability character from the high temperature solvents, and relate the observations to those of the earlier studies. Quasi-reversible behavior is found in each of the cases studied. As might be expected, the Fe(II)∕Fe(III) equilibrium experiences a more basic environment in an acetate IL than it experiences in any of the common glassforming oxide media, while triflate anions contrast by providing a more acid environment than does the most acid of the molten oxide glassformers studied (an alkali phosphate). The difference can amount to well over 1 V, suggesting the possibility of a "basicity cell" where the same redox couple locates in anode and cathode compartments of the cell, and only the anion environment is different.

ChemInform Abstract: Proton Speciation in Ambient-Temperature Chloroaluminate Ionic Liquids

Proton speciation in ambient-temperature chloroaluminate ionic liquids, composed of 1-ethyl-3-methylimidazolium chloride (ImCl) and aluminum chloride has been examined by 2 H NMR and FT-IR spectroscopies. In oxide free basic melts (excess ImCl), two proton-containing species, HCl and HCl 2 - , exist which are in an equilibrium that strongly favors the formation of the dichloride ion. In oxide free acidic melts (excess AlCl 3 ) HCl is the only proton-containing species.

Immobilization of Chiral Quininium Salt in Ionic Liquid for Enantioselective Epoxidation of Chalcones

An ionic liquid mediated novel protocol for enantioselective epoxidation of α,β-unsaturated ketones employing hydrogen peroxide as an oxidant in the presence of phase transfer catalyst has been developed. The protocol is essentially mild, rapid and environmentally benign employing ambient temperature ionic liquids. The use of ionic liquids facilitates ease of product isolation and catalyst recovery. Keywords: Enantioselective Epoxidation, α,β-Unsaturated ketone, Quaternized quininium salt, Hydrogen peroxide, Phasetransfer catalyst, Ionic liquid

Electrochemical Lithium Insertion/Extraction for Carbon Electrodes in FSI-based Ionic Liquids

Introduction of bis(fluorosulfonyl)imide (FSI) as an anion to an ambient-temperature ionic liquid electrolyte based on 1-ethyl-3-methylimidazolium and lithium (Li) as cations can provide a reversible Li intercalation into a graphitized electrode, while the intercalation is completely irreversible without FSI. Laser desorption/ionization mass spectroscopy and ac impedance spectroscopy suggest that FSI-coordinated Li+ is facilely mobile even without any solvents and is reversibly accessible to a graphite interior.

Anions for Lithium Battery Electrolytes: A Spectroscopic and Theoretical Study of the B ( CN ) 4 − Anion of the Ionic Liquid C2mim [ B ( CN ) 4

On the basis of computations, the (bison) anion is shown to be of interest as a fluorine-free alternative in lithium-conducting electrolytes. Compared to the bison anion has an equally high stability toward oxidation, while at the same time offering a large reduction of the lithium-ion pair dissociation energy. The bison anion is readily available in a number of ambient-temperature ionic liquids (ILs). In this work, the Raman spectrum of the IL reveals an almost unperturbed bison anion and, consequently, the effects of the anion on the Raman shifts of are also very small.

Oxidation of Cyclohexane Catalyzed by TS-1 in Ionic Liquid with Tert-butyl-hydroperoxide

An efficient and environmentally friendly procedure was described for easy product isolation for the oxidation of cyclohexane with tert-butyl-hydroperoxide catalyzed by titanium silicalite 1 (TS-1) in ambient-temperature ionic liquid [emim]BF 4. Good yield and higher selectivity of products were found in the ionic liquid compared with in molecular solvent. The research results showed 13.2% conversion of cyclohexane, 97.6% cyclohexanol and cyclohexanone selectivity were obtained in ionic liquid under mild conditions of 90°C.

Ionic liquid electrolytes compatible with graphitized carbon negative without additive and their effects on interfacial properties

Introduction of bis(fluorosulfonyl)imide (FSI) as an anion to an ambient-temperature ionic liquid electrolyte based on 1-ethyl-3-methylimidazolium (EMI) as well as lithium (Li) cations can provide a reversible Li intercalation into a graphitized electrode, while such intercalation is completely irreversible without FSI. The surface-layer components on the graphitized electrodes, cycled in the ionic liquid electrolytes with and without FSI, were found to be chemically similar based on X-ray photoelectron spectroscopy. Ac impedance spectroscopy revealed that the resistance of the electrode charged with FSI was much lower even than that charged in a solvent electrolyte system containing ethylene carbonate (EC) and dimethyl carbonate (DMC). On the basis of these physicochemical analyses, the origins of cycleability in the presence of FSI are discussed.

An imidazolium tosylate salt as efficient and recyclable catalyst for acetylation in an ionic liquid

A novel non-metallic salt, 1-butyl-3-methylimidazolium tosylate ([bmim][OTs]) dissolved in the ambient temperature ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), was found to be the efficient catalyst for acetylation with the advantages of good recyclability, avoidance of metal contamination, mild reaction conditions, and wide availability for substrates (alcohols, phenols, and amines), could completely replace organic bases, metal Lewis acids, or metallic triflates to fulfill acetylation by a nucleophilic catalytic mechanism, which was supported by 13C NMR analysis.

LiFePO 4 and graphite electrodes with ionic liquids based on bis(fluorosulfonyl)imide (FSI) − for Li-ion batteries

Ambient-temperature ionic liquids (IL) based on bis(fluorosulfonyl)imide (FSI) as anion and 1-ethyl-3-methyleimidazolium (EMI) or N-methyl- N-propylpyrrolidinium (Py13) as cations have been investigated with natural graphite anode and LiFePO 4 cathode in lithium cells. The electrochemical performance was compared to the conventional solvent EC/DEC with 1 M LiPF 6 or 1 M LiFSI. The ionic liquid showed lower first coulombic efficiency (CE) at 80% compared to EC–DEC at 93%. The impedance spectroscopy measurements showed higher resistance of the diffusion part and it increases in the following order: EC–DEC–LiFSI < EC–DEC–LiPF 6 < Py13(FSI)–LiFSIE = MI(FSI)–LiFSI. On the cathode side, the lower reversible capacity at 143 mAh g −1 was obtained with Py13(FSI)–LiFSI; however, a comparable reversible capacity was found in EC–DEC and EMI(FSI)–LiFSI. The high viscosity of the ionic liquids suggests that different conditions such as vacuum and 60 °C are needed to improve impregnation of IL in the electrodes. With these conditions, the reversible capacity improved to 160 mAh g −1 at C/24. The high-rate capability of LiFePO 4 was evaluated in polymer–IL and compared to the pure IL cells. The reversible capacity at C/10 decreased from 155 to only 126 mAh g −1 when the polymer was present.

A Study on Friedel-Crafts Alkylation in Ambient Temperature Ionic Liquids

Alkylation of naphthalene, α-methylnaphthalene, and β-methylnaphthalene with different alkylating agents, such as olefins, bromoalkane, and fatty alcohol, in novel environmentally friendly ambient temperature ionic liquid, ethyl-containing amine chloroaluminate (anhydrous aluminum chloride mole fraction, X = 0.67–0.75), has been investigated. On the basis of optimal reaction conditions, high conversion of alkylating agent and excellent selectivity for monoalkylated product were obtained. The products and unreacted reactants were easily isolated by extraction with cyclohexane.

Pure ionic liquid electrolytes compatible with a graphitized carbon negative electrode in rechargeable lithium-ion batteries

Ambient temperature ionic liquids composed of bis(fluorosulfonyl)imide (FSI) as an anion and 1-ethyl-3-methylimidazolium (EMI) or N-methyl- N-propylpyrrolidinium (P-13) as a cation have the following desirable physicochemical properties, particularly for a battery electrolyte: a high ionic conductivity, low viscosity, and a low melting point. While an irreversible cationic intercalation into graphene interlayers at ca. 0.5 V versus Li/Li + has been a significant and common problem with usual ionic liquids, we found that ionic liquids containing FSI with the Li cation can prevent such an irreversible reaction and provide reversible Li intercalation into graphene interlayers. Our experimental results found the reversible capacity of a graphite negative electrode, in a half-cell with EMI-FSI containing the Li cation as an electrolyte, to be a stable value of approximately 360 mAh g −1 during 30 cycles at a charge/discharge rate of 0.2 C, The present paper may be the first report that a “pure” ionic liquid can provide a stable, reversible capacity for a graphitized negative electrode at an ambient temperature without any additives or solvents when an appropriate counter anion, e.g., FSI, is selected.

Processing metal oxides using ionic liquids

A eutectic formed between choline chloride and urea is shown to be a good solvent for the dissolution of a range of metal oxides. It is demonstrated that this ambient temperature ionic liquid can be applied to the processing of electric arc furnace dust. Zinc and lead can be selectively removed and subsequently electrowon from the liquid. This leaves the insoluble iron and aluminosilicates, which can be recycled through the electric arc furnace.

Understanding Reactions in Ionic Liquids

AbstractFor Abstract see ChemInform Abstract in Full Text.

Butyl-3-methylimidazolium Chloride Preparation in Supercritical Carbon Dioxide

A novel process for preparing an ambient-temperature ionic liquid precursor (1-butyl-3-methylimidazolium chloride) was developed. The reaction of 1-methyl imidazole with butyl chloride was conducted in supercritical carbon dioxide (scCO2) and followed by in situ scCO2 extraction for purifying the product, 1-butyl-3-methylimidazolium chloride. The yield of 1-butyl-3-methylimidazolium chloride could be >90%, according to the reaction in a scCO2 reaction environment. The residual reactants could be, in situ, removed completely using scCO2 extraction after the required reaction time. The conversion of the reaction is dependent positively and strongly on the pressure. The kinetics of the reaction in scCO2 could be described using the two-order irreversible reaction model. The reaction rate constant (k) is linearly dependent on the density of CO2 in the logarithmic coordinates. The 1H nuclear magnetic resonance (1H NMR) spectral data of the prepared 1-butyl-3-methylimidazolium chloride product was satisfactoril...

Model for the Conductivity of Ionic Liquids Based on an Infinite Dilution of Holes

Charge transport in an ambient-temperature ionic liquid is limited by the mobility of suitably sized voids into which ions can migrate (see figure). This allows conductivity data to be simply analyzed by using the Stokes–Einstein equation. The mechanism of charge transport is contrasted with that in high-temperature molten salts, which is different from that in low-temperature systems.

Novel Ionic Liquids—Imidazolium Salts with a Difluoromethylene Fragment Directly Bonded to the Nitrogen Atom.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel ionic liquids—Imidazolium salts with a difluoromethylene fragment directly bonded to the nitrogen atom

Alkylation of N-(1,1,2,2-tetrafluoroethyl)imidazole ( 1) by alkyl iodides and metathesis resulting in corresponding tetrafluoroborates and bis(trifluoromethanesulfonyl)amides led to the formation of new type stable ambient temperature ionic liquids 3 and 4 with a difluoromethylene fragment directly bonded to the nitrogen atom.