Chloroaluminate Ionic Liquids Research Articles

Characterizing the electronic structure of ionic liquid/benzene catalysts for the isobutane alkylation

When a small amount of benzene was introduced into the chloroaluminate ionic liquid (IL), the IL − alkylation can produce premium alkylation gasoline. In order to deepen our understanding of IL − alkylation in general, the electronic properties of [BMIm][AlCl4]/benzene/reactant system were analyzed by the ADCH charge analysis, DOS analysis, frontier molecular orbital analysis, non − covalent interactions (NCI), and energy decomposition analysis (EDA). ADCH analysis reveals that benzene could markedly affect the charge transfer of alkanes and chloroaluminate anions, which weakened the super−acidity of the IL. Frontier molecular orbital analysis shows that the IL system has a significant decrease of H − Lgap, and it increases the sensitivity of the reactants. The anchoring effect of [BMIm]+ cation was observed in the DOS spectra, which enhanced stabilization of the IL structure. NCI analysis shows that π − H bonds could be formed between benzene and the IL. It is believed that better alkylation performance of IL/benzene system is due to these weak interactions.

The Friedel-Crafts sulfonylation catalyzed by chloroaluminate ionic liquids

Friedel-Crafts sulfonylation is one of the most common methods to prepare sulfone. With the development of Green Chemistry, chemical processes have been improved towards being environmentally friendly by using of organic solvents in the limit, using recoverable catalysts, reducing energy ... are getting more attention. Therefore, in this study, several types of ionic liquids such as [Bmim]BF4, [Bmim]PF6, [Bpy]Cl2AlCl3, [Pyrro]I2AlCl3, [Mth]I2AlCl3, [Bmim]Cl2AlCl3 which catalysed for the Friedel-Crafts sulfonylation of toluene and benzenesulfonyl chloride have been investigated. Besides, most factors which have influenced on the reaction yield such as the temperature, the reaction time, the amount of catalyst have been studied. The reaction was carried out under solvent-free and mild conditions; moreover, the catalyst was able to be recovered and reused without significant loss of its activity. The main product phenyl p-tolyl sulfone was easily isolated after the reaction and obtained in high yield 97% after four-hour heating at 100 oC by using Nbutylpyridinium chloroaluminate, [Bpy]Cl.2AlCl3, as catalyst. Microwave irradiation has been used to improve many organic syntheses as a green and efficient activation method in order to reduce reaction times and save energy. Compared to the conventional heating, phenyl p-tolyl sulfone was synthesized with the excellent yield in the short reaction time under the microwave assistance.

Measurement of Dissolved Oxygen Concentrations of Chloroaluminate Ionic Liquids in Dry Air

The electrodeposition of Al has been studied in various ionic liquids represented by the 1-ethyl-3-methylimidazolium chloride-AlCl3 system. However, AlCl3-based (chloroaluminate) ionic liquids are generally handled in an inert atmosphere of nitrogen or argon because they are highly hygroscopic and susceptible to hydrolysis through the reaction with moisture in the air. To maintain an inert atmosphere, a closed system that typically uses a glove box is required, but operation in a closed system leads to low productivity and high cost. Therefore, electrodeposition in an inert atmosphere is unsuitable for mass production on an industrial scale. To alleviate this problem, we have previously studied the feasibility of Al electrodeposition in dry air using chloroaluminate ionic liquids. Because the electrodeposition process in dry air does not require a glove box, it is considered to be more productive than the electrodeposition process under an inert atmosphere.In our previous study, four different chloroaluminate ionic liquids consisting of different organic cations ([cation]Cl-AlCl3) with a molar ratio of [cation]Cl : AlCl3 = 1 : 2 were used as Al electrodeposition baths to study Al electrodeposition behavior in dry air. The cations used were 1-ethyl-3-methylimidazolium (EMI+), 1-butylpyridinium (BP+), 1-butyl-1-methylpyrrolidinium (BMP+), and trimethylphenylammonium (TMPA+). We found that electrodeposition in dry air using the bath composed of EMI+ or BP+ could not produce an Al film covering the entire surface of the substrate, whereas electrodeposition using the bath composed of BMP+ or TMPA+ could produce an Al film covering the entire surface of the substrate in dry air as well as in an inert atmosphere.The reason for the difference in the results of Al electrodeposition in dry air according to cationic species has not yet been ascertained, but it is speculated that dissolved oxygen has some influence on the Al electrodeposition. In the present study, we measured the concentration of oxygen dissolved in four types of ionic liquids in dry air.For measuring the dissolved oxygen concentration, ionic liquids with a composition of [cation] Cl: AlCl3 = 1: 0.9 were used. This composition was chosen because only AlCl4 −, which is an ionic species that is difficult to be reduced to Al metal, is present in the bath when the AlCl3 mole fraction is less than 50 mol% (Lewis base)in chloroaluminate ionic liquids. Consequently, Al electrodeposition does not occur, and low extent of electrochemical reaction other than Al electrodeposition at a potential of 0 V vs. Al / Al (III) or less can be investigated. The concentration of dissolved oxygen was measured by chronoamperometry using two types of electrodes, a macroelectrode and a microelectrode, both of which have a circular active area with a diameter in the order of millimeter and micrometer, respectively. In the case of chronoamperometric measurement with a macroelectrode, the reduction current of oxygen follows the equation in the upper row in Table 1, assuming that the reaction rate is controlled by the planar diffusion of oxygen from the bulk electrolyte to the surface of the electrode. Upon measuring the current–time response, two unknowns remain, namely, the concentration and the diffusion coefficient of dissolved oxygen; and it is not possible to determine the dissolved oxygen concentration through the chronoamperometric measurement using the macroelectrode alone. In the case of chronoamperometric measurement with a microelectrode, the geometry of the diffusion of the reactant to the electrode surface changes to semi-spherical, and the reduction current of oxygen thus follows the equation in the lower row in Table 1. The concentration and diffusion coefficient of dissolved oxygen can thus be determined through the two chronoamperometric measurements.The chronoamperometric measurements revealed that there was no significant difference in the oxygen concentrations of the ionic liquids with different cationic species. The results that we have obtained so far are as follows: 1) In an inert atmosphere, an Al film covering the entire surface of the substrate can be electrodeposited from a bath containing any cation species. 2) In dry air, an Al film covering the entire surface of the substrate can only be electrodeposited from some baths composed of specific cation species. 3) There is no significant difference in the dissolved oxygen concentrations of the baths in dry air, even though the cation species in the baths are different. In consideration of these results, the reason for the different results of Al electrodeposition in dry air according to the cationic species is neither dissolved oxygen alone nor cationic species alone but the combined action of both dissolved oxygen and the cation. Figure 1

Influence of Additive Inclusion on Hardness of Electroplated Al Film with Nanometer-Level Flatness from Chloroaluminate Ionic Liquid

In this study, we report the influence of additive inclusion on the hardness of an Al film electrochemically deposited from the chloroaluminate ionic liquid. The additive inclusion drastically increased the hardness as well as the surface flatness. The measured elastic modulus and mechanical hardness of Al on Au seed layer were 71.9 GPa and 10.3 GPa, respectively. Introduction Electrochemical deposition (ECD) process is widely used for micro-electro mechanical system (MEMS) fabrication and packaging to form a relatively thick metallization. The process is often selected owing to its low-cost, high deposition rate and availability to tune various properties of the resulting deposit. Its application spans from the structural material of sensors [1] to wafer-level bonding [2].The emergence of ionic liquid as a solvent has allowed ECD of various materials which are impossible to reduce in water, including Al. Additive inclusion has been introduced to reduce the surface roughness of the resulting deposit [4]. On the other hand, material properties are also of importance for designing MEMS based on the film. However, the influence of additive inclusion on the material property has not been investigated yet. Therefore, this study aims to close the gap. Experimental method The ECD process was performed on a Si substrate with Au or Pt seed layer using a commercially available AlCl3–1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) (3:2) ionic liquid electrolyte. A 0.5 g/L 2-chloronicotinyl chloride was introduced as the additive to improve the surface roughness. The deposition was carried out using direct current (DC) at 10 mA/cm2 current density under room temperature for 60 min, which resulted in around 7 μm thickness of deposits. To avoid the degradation of the ionic liquid solvent, the deposition was performed inside a glove box with continuous flow of an inert and dry N2 gas. Results and discussions Scanning electron micrographs (SEMs) of the deposited films are shown in Fig. 1 (a), (b) and (c). The difference of surface roughness between films deposited in electrolyte without and with the additive inclusion is quite significant. Fig. 1 (d) shows the quantitative comparison. The surface roughness was reduced to a few nm, which is 2 orders magnitude less than that of without additive. The additive inclusion also introduces a 15% reduction of the deposition rate.The influence of the additive inclusion in the electrolyte to the mechanical properties of the resulting film is shown in Fig. 1 (e). The hardness and elastic modulus of the deposited films were characterized by nanoindentation using a diamond tetrahedron indenter, i.e. Berkovich tip. The indentation depth was maintained to be more than 100 nm and less than 10% of the film thickness to avoid the influence of the native oxide layer and the substrate.The evaluation results are compared to previously reported values of bulk Al and thin films deposited using other techniques [5,6]. Compared to the bulk, thin films have a higher nanoindentation hardness. This might be partly attributed to the grain size refining, which is in agreement with the Hall-Petch relation. The nanoindentation hardness became further higher for films deposited with additive inclusion. This significant strengthening can also be partly attributed to the grain size refining [4].The elastic modulus of the electrodeposited Al film on the Au seed layer without additive inclusion and the film deposited on the Pt seed layer with additive inclusion were significantly lower compared to other conditions. The significantly low elastic modulus regardless of high hardness can be caused by the existence of pores as well as other defects in the grain boundaries, including vacancies, dislocations, impurities and the local distribution of strain [7]. The difference in the deposition mechanism between the Au and Pt seed layers is to be investigated in the future. Conclusion In this study, the evolution of mechanical properties of the electrodeposited Al films with the inclusion of additive has been investigated. Enhancement of nanoindentation hardness was observed, mainly due to the grain boundary hardening. This result is useful as a design guide for future MEMS application of the film. References S. Alper et al., Sens. Act. A Phys. 132 (1), pp. 171–181 (2006).M. S. Al Farisi et al., J. Micromech. Microeng. 27 (1), p. 015029 (2017).F. Endres ChemPhysChem 3 (2), pp. 144–154 (2002).P. Sheng et al., Mater. Corr. 66 (11), pp. 1338–1443 (2015).Y. Y. Lim et al., J. Mat er . Res. 14 (6), pp. 2314–2327 (1999).M.F. Doerner et al., J. Mat er . Res. 1 (6), pp. 845–851 (1986).Y. Nakoshi et al., Jpn. J. Appl. Phys. 58, p. SBBC04 (2019). Figure 1

Sulfur-Carbon Composite Cathodes for Aluminum-Anion Rechargeable Battery with an Inorganic AlCl3–NaCl–KCl Ionic Liquid

Aluminum-anion rechargeable battery (AARB), in which chloroaluminate anions control the cathodic and anodic reactions, has been getting a lot of attention recently, because Al metal has several advantages, such as very high theoretical capacity (2980 mAh g-1, 8046 mAh cm-3), less expensive and mass consumable material, and moderate reactivity in air. It is known that Al metal deposition/stripping reversibly proceeds in Lewis acidic chloroaluminate melts.1 4[Al2Cl7]- + 3e- ⇌ Al + 7[AlCl4]- In general, AARB uses layered sp2 carbon materials as cathode active materials that can cause the following electrochemical reaction.1 nC + [Al anion]- ⇌ C n [Al anion] + e- (Al anion: [AlCl4]- and [Al2Cl7]-)These materials show a favorable coulomb efficiency over 99 % and are available for rapid charge-discharge. But, the charge-discharge capacities are only 60 ~ 90 mAh g-1, if the electrolyte is Lewis acidic organic chloroaluminate ionic liquids (ILs). Although, in the inorganic ones, e.g., AlCl3–NaCl–KCl, the capacities are over ca. 130 mAh g-1,2 it is still disportionate to high capacity of Al metal anode. Therefore, novel high capacity cathode active materials are required to design appealing AARBs. In this study, we have applied the sulfur-carbon composite material (SPEG) synthesized from the mixture of sulfur and polyethylene glycol3 to the cathode active material for AARB. Electrochemical behavior of the SPEG electrodes was examined in an inorganic 61.0-26.0-13.0 mol% AlCl3–NaCl–KCl IL (eutectic point: 366 K).The procedure used for the preparation of SPEG was identical with that described in previous articles.2 SPEG composite electrodes were prepared by pressing the mixtures of x wt% SPEG, 100-x-5 wt% conductive additive (ketjen black (KB) or multi-walled carbon nanotube (MWCNT), and 5 wt% polytetrafluoroethylene (PTFE) onto molybdenum (Mo) plate current collectors. Al metal plates were employed as anodes. After purification of AlCl3, NaCl, and KCl, the inorganic AlCl3–NaCl–KCl IL was obtained by heating the mixture consisting of 61.0 mol% AlCl3, 26.0 mol% NaCl, and 13.0 mol% KCl at 403 K. The final product was clear and colorless. Electrochemical experiments were carried out using a two-electrode type sealed cell set up in an electric furnace with a temperature-control device. The experimental temperature was 393 K. All the procedures are conducted in an Ar gas-filled glove box with O2 and H2O < 1 ppm.Figure 1 shows cyclic voltammograms recorded at Mo and SPEG composite electrodes in the two-electrode type sealed cell with a 61.0-26.0-13.0 mol% AlCl3–NaCl–KCl electrolyte at 393 K. There is no change in current density in the voltammograms at the Mo electrode, implying that Mo electrode is usable for the current collector in AARB. As to the SPEG composite electrodes, a pair of reduction and oxidation waves appeared at ca. 1.05 V and 1.25 V, respectively. However, the shapes of voltammograms depended on the conductive additive species and their weight ratio. In the case of the KB conductive additive, redox waves with the influence of electric double layer capacitance were observed, when the weight ratio was over 45 wt%. It was difficult to see the waves below 45 wt%. Meanwhile, the use of MWCNT was very effective to improve the cathode performance, and clear redox waves appeared at the additive amount of 10 wt%. Given the fact that electrochemical behavior of the sulfur in an organic AlCl3–[C2mim]Cl (1-ethyl-3-methylimidazolium chloride) IL,4 the redox waves observed in Fig. 1 would originate in the following reaction.8[Al2Cl7]- + 6e- + 3S ⇌ Al2S3 + 14[AlCl4]- These results suggest that the SPEG composite electrodes can work as the cathode in AARB. Charge-discharge tests were conducted under various conditions. Favorable rate capability comparable to the layered sp2 carbon materials was recognized.1 Besides, the SPEG electrodes had very high cathode capacities. The SPEG cathode with KB (45 wt%) showed 323 mAh (g-SPEG)-1 at 5000 mA (g-SPEG)-1. If the MWCNT was employed as a conductive additive, the capacity was decreased to 266 mAh (g-SPEG)-1 at 5000 mA (g-SPEG)-1, but the cyclability was stable up to 600 cycles. From these findings, we concluded that SPEG composite electrodes prepared in this research are promising cathodes for AARB.This research was supported by the MIRAI program (grant number JPMJMI17E9), JST. References T. Tsuda, G. R. Stafford, and C. L. Hussey, J. Electrochem. Soc., 164, H5007 (2017) and references therein.C.-Y. Chen, T. Tsuda, S. Kuwabata, and C. L. Hussey, Chem. Commun., 54, 4164 (2018).T. Kojima, H. Ando, N. Takeichi, and H. Senoh, ECS Trans., 75, 201 (2017).T. Gao, X. Li, X. Wang, A. J. Pearse, K. J. Gaskell, et al., Angew. Chem. Int. Ed., 55, 9898 (2016). Figure 1

Understanding Electrochemical Reaction Mechanisms and Properties of Rechargeable Aluminum-Sulfur and Aluminum-Selenium Batteries

The continual rise in global energy demands coupled with recent incremental advances in the cost and energy density of lithium-ion batteries have given researchers an impetus to investigate high-energy-density batteries such as those that use multivalent-ions. Rechargeable Al metal batteries have recently garnered significant interest due to its low cost, earth abundance, inherent safety, and high volumetric (8040 mAh cm -3) and gravimetric (2980 mAh g -1) capacities due to the trivalent nature of Al3+ ions (3-electron redox). Commercialization of rechargeable aluminum battery systems has been limited, however, due to the small number of (i) electrolytes that enable reversible electrodeposition of Al metal at room temperature and (ii) positive electrode materials that are compatible with the electrolytes while providing high capacity and cycle life. Sulfur (S) and selenium (Se) are promising positive electrode materials for rechargeable battery systems as they exhibit very high specific capacities during electrochemical conversion reactions.Sulfur is a very low-cost material due to its earth abundance and generation as a byproduct of the petroleum industry, while it can provide a very high specific capacity up to 1675 mAh g-1. Commercialization of battery systems with sulfur electrodes has been hindered due to its low electrical conductivity, high volume expansion during galvanostatic cycling, and deleterious polysulfide shuttle reactions during charge and discharge1-3. Selenium, like sulfur, is also a chalcogen and is expected to exhibit similar electrochemical reactions. Although Se is a heavier element and consequently exhibits lower specific capacity (675 mAh g-1), it possesses significantly higher electronic conductivity compared to sulfur4 that would be beneficial in mitigating key challenges that faces sulfur electrodes, such as low active material utilization and high charge transfer overpotentials during galvanostatic cycling. To date, there are few reports of Al-S2,3, and Al-Se4,5 systems. There is no clear consensus on the electrochemical reaction mechanism during the charge/discharge process, while capacity fade plagues both systems during galvanostatic cycling.Here, aluminum-sulfur (Al-S) and aluminum-selenium (Al-Se) cells were investigated with a chloroaluminate ionic liquid electrolyte, AlCl3:[EMIm][Cl] (molar ratio of 1.5:1), whose electrochemical reaction mechanisms and ensuing reaction products were analyzed via a combination of bulk (XRD, NMR) and surface (XPS) analyzation techniques. Electrochemical experiments for Al-S batteries showed high initial capacities close to 1200 mAh g-1, which exhibited a inverse correlation with galvanostatic cycling rate. For Al-S batteries a higher capacity was observed upon charge, compared to discharge, pointing towards either an unwanted side reaction or polysulfide-shuttle-like behavior. This behavior occurred predominately at low current densities and affected the reversibility of the system. For the Al-Se batteries, the two different reaction mechanisms that have been previously reported were found to be dependent on (i) the applied current density and (ii) the crystallinity of the active material, as shown by XRD. We demonstrate that, with appropriate cycling conditions, both reaction mechanisms can occur during a single charge/discharge step, thus significantly increasing the capacity and the electrochemical window of the Al-Se cell. A significant capacity fade was also observed over a course of multiple cycles showing similar behavior compared to Al-S cells.To understand the reaction mechanisms of Al-S and Al-Se batteries at a molecular level, solid-state and liquid-state 27Al NMR and 77Se NMR measurements (on Al-Se systems) were acquired on the electrodes and electrolyte at different states-of-charge, respectively. XPS was also performed on cycled chalcogen electrodes to understand surface compositions. The combination of electrochemical, spectroscopic, and X-ray diffraction data yield insights into the reaction mechanisms and products, including the aluminum coordination environments and relative populations in these environments. This work establishes the potential of conversion-type aluminum-chalcogen batteries as high-energy-density energy storage systems and highlights the importance that molecular-level analytical tools like NMR spectroscopy can have in clarifying electrochemical mechanisms in emerging electrochemical systems.Reference L. Ellis, K. T. Lee, and L. F. Nazar, Chemistry of Materials, 22, 691 (2010).Gao et al., Angew. Chemie - Int. Ed., 55, 9898–9901 (2016).. X. Yu, M. J. Boyer, G. S. Hwang, and A. Manthiram, Chem, 4, 586–598 (2018).Liu et al., Nano Energy, 66, 104159 (2019)Li, J. Liu, X. Huo, J. Li, and F. Kang, ACS Appl. Mater. Interfaces, 11, 45709–45716 (2019).

The alkylation of oil fractions rich in aromatic hydrocarbons with C6, C8 and C10 \u03b1 - olefins in the presence of ionic liquids catalytic systems

The article is dedicated to the development of processes for (oligo)alkylation of petroleum fractions rich in aromatic hydrocarbons, with α-olefins (hexene-1, octene-1, decene-1) in the presence of ionic-liquid catalytic systems and the study of the properties of the products obtained. Alkylation reactions were carried out in the presence of chloroaluminate ionic liquids; for the first time a (nano)metal-polymer composite (NMPC) was used in the catalytic system as a modifier, and zinc chloride (ZnCl2) was used in the catalytic system as a component and the results were compared. It has been shown that these ionic liquid catalytic systems (ILCS) are suitable for (oligo)alkylation reactions and the use of these additives in their composition will lead to efficient alkylation. The products obtained were analyzed by IR-, NMR- spectroscopy, fluorescent indicator adsorption methods, and size exclusion chromatography. It was shown that these petroleum fractions rich in aromatic hydrocarbons can be used as alkylation components, and depending on the composition of the ILCS, it is possible to regulate the molecular, thermophysical and other characteristics of the products obtained based on them. The alkylated products obtained have been tested as plasticizing additives in polyolefin composites.

Tailoring material properties of electrochemically deposited Al film from chloroaluminate ionic liquid for microsystem technology using pulsed deposition

To practically utilize an electrochemically deposited Al film in microsystems, its material properties have to be elucidated, along with the influence of different deposition conditions. In this study, microstructure, electrical, mechanical and thermal properties of electrochemically deposited Al film from a chloroaluminate ionic liquid electrolyte are comprehensively investigated. The nanoindentation hardness and elastic modulus of the film varied between 486–908 MPa and 41–102 GPa, respectively, depending on the deposition condition. The electrical resistivity and the coefficient of thermal expansion varied between 51–160 nΩ m and 2–20 ppm/K, respectively. The results are compared to those of Al thin films deposited using other techniques. The characterized properties were found to be associated to the microstuctures of the deposits, which can be tailored by the deposition conditions. The microstructures of the deposits were comprehensively characterized by cross-sectional scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) spectroscopy. These results are useful as a design guide for the future applications of the film.

Fast-charged aluminum-ion battery with aluminum-graphene nanocomposite anode

Currently, aluminum-ion batteries are considered attractive energy storage devices because aluminum is an inexpensive, widely available, environmentally friendly, low-flammable, and high recyclable electrode material. Electrochemical cell simulating the work of an aluminum-ion battery with aluminum-graphene nanocomposite–negative electrode, positive graphene electrode, and chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride has been designed and tested. The cell exhibits excellent performance and long shelf life. The aluminum-graphene composite is not prone to oxidation over a long period of time. Consequently, the negative electrode surface does not undergo passivation by trace amounts of water and oxygen in the electrolyte during storage, which considerably prolongs the battery shelf life. The analyzed cell delivered stable performance across a wide range of charge/discharge rates for several thousands of cycles without any noticeable loss in capacity and Coulombic efficiency. It has almost 100% Coulombic efficiency at high charge/discharge current densities and retains its characteristics after a 7-day current-free period.

Influence of FeCl3‐modified chloroaluminate ionic liquids on long‐chain alkenes alkylation

The influence of anhydrous ferric chloride on the catalytic properties of chloroaluminate ionic liquids catalyst for Friedel–Crafts alkylation was investigated. The catalysts were characterized by Fourier‐transform infrared (FT‐IR) (acetonitrile molecule as probe), specific gravity, and 27Al NMR. Besides, the effect of the mass ratio of FeCl3 to AlCl3, catalysts dosage, toluene/olefin molar ratio, reaction temperature, and reaction time on long‐chain alkenes alkylation were investigated thoroughly. And bromine value and high‐performance liquid chromatography (HPLC) were employed as the evaluation method for alkylation products. It was observed that the addition of anhydrous ferric chloride results in improvement in terms of Lewis acid and its catalytic recyclability. Among these catalysts studied, the catalyst modified with 1.0 wt.% anhydrous FeCl3 showed the best catalytic performance in terms of yield and stability, which can be attributed to the formation of new stronger acidic ions [Al2FeCll0]− when the added ferric chloride reacts with acidic ions [Al2Cl7]−.

Charge Transport and Dynamics in Imidazolium Chloroaluminate Ionic Liquids

Imidazolium based chloroaluminates were the first widely studied room-temperature ionic liquids. However, work in these systems has waned over the past 25 years in favor of ionic liquids with less reactive anions. Researchers are beginning to rediscover chloroaluminates because they possess some very advantageous properties that hold significant promise for applications such as energy storage, electrodeposition, and chemical synthesis. Chloroaluminates are not simple mixtures of a single cation with a single anion. It is more appropriate to think of these systems as binary mixtures of two ionic liquids which share the same cation. The binary nature of the chloroaluimates leads to highly tunable physical and chemical properties including liquidus range, electrochemical stability window, dc ionic conductivity, zero-shear viscosity, and static dielectric permittivity. However, the binary nature also leads to significant experimental challenges with respect to characterization of the structure and anion speciation in the chloroaluminates. The majority of work characterizing the imidazolium based chloroaluminate was conducted more than 25 years ago and focused on physical property measurements across limited compositions and/or narrow temperature/frequency ranges. The data from these early studies revealed important aspects of chloroaluminate physical properties; however, due to their limited scope they failed to make significant progress in understanding underlying structure-property relationships which are critical to realizing the full potential of chloroaluminate ionic liquids as electrolyte systems. Our current work seeks to reexamine imidazolium chloroaluminate ionic liquids leveraging the improved experimental tools and capabilities available today. In this presentation we will discuss our initial studies of imidazolium chloroaluminate ionic liquids using broadband dielectric spectroscopy, oscillatory shear rheology, and Raman spectroscopy. We will present preliminary work on the impact of changes in cation structure and ionic liquid composition on anion speciation, transport properties, and dynamics.

Electrochemical Behavior of Silver Halogenocomplexes in an Amide-Type Ionic Liquid

Silver halides, AgX (X = Cl–, Br–, and I–), are known to be typical poorly soluble salts in aqueous solution. AgX is also almost insoluble in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonly)amide (BMPTFSA). However, AgX has been known to dissolve in the media in the presence of X– by forming halogenocomplexes, [AgX n ](n–1)–. Dissolution of AgCl has been reported in basic chloroaluminate ionic liquids[1] and deep eutectic solvents containing Cl–. In these reports, however, electrochemical behavior of [AgX n ](n–1)– has not been studied in detail. We have already reported that some metal chlorides are soluble in BMPTFSA in the presence of Cl– and that electrodeposition of the metals is possible[2,3]. In the present study, dissolution of AgX has been investigated in BMPTFSA with addition of BMPX. Furthermore, electrodeposition of Ag and electrochemical preparation of Ag nanoparticles have been examined in the Lewis basic ionic liquids. AgX was found to dissolve in BMPTFSA containing 0.5 M BMPX. The dissolved species was determined to be [AgX3]2– by potentiometric technique. The deposition and dissolution of Ag were observed in cyclic voltammetry. The redox potential of [AgX3]2–/Ag was more negative than that of [Ag(TFSA)3]–/Ag and dependent on the kind of halide. The diffusion coefficient of [AgX3]2– was determined by chlonoamperometry. The initial stage of electrodeposition of Ag on a glassy carbon electrode was regarded as progressive. Potentiostatic cathodic reduction of [AgX3]2– resulted in deposition of Ag. The morphology of Ag deposits depended on the reduction potential. Formation of Ag nanoparticles dispersed in the ionic liquid was confirmed after potentiostatic cathodic reduction at a negative potential using transmission electron microscopy[2].

Investigation on Operating Conditions Influencing the Aluminum Electrolysis Using Chloroaluminate Ionic Liquids

Our group has focused on the Al electrolysis using room-temperature ionic liquids (RTILs). Al can be deposited from the chloroaluminate ILs, but a practical technology for depositing Al from even the ILs has not been established. There are several problems such as the low limiting current density and the deposition in a dendritic form. In particular, the surface smoothness of electrolytic Al foil is required for practical application. Many articles on the Al electrodeposition using the ILs have ever been reported. However, few articles systematically investigate the correlation between the Al electrodeposits and the operating conditions (parameters). Ueda and co-workers reported that the surface smoothness was improved by adding 1,10-phenanthroline anhydrate (OP) to a Lewis acidic AlCl3-EMIC (1-ethyl-3-methylimidazolium chloride) melt [1]. In order to effectively scale up from the laboratory level to the practical level, it is desirable to make the above correlation clear sufficiently. In this study, we investigated on the parameters influencing to obtain a smooth electrolytic Al foil.The chloroaluminate ionic liquids consisting of anhydrous AlCl3 and 1-ethyl-3-methylimidazolium chloride (EMIC) for 2:1 molar ratio were prepared as an electrolyte in an Ar-filled glove box. 20 mmol dm−3 OP (1,10-phenanthroline anhydrate) was added to the electrolyte as an additive. Galvanostatic electrolysis method was carried out in a conventional three-electrode cell with stirring at room temperature (RT) and 50 ℃. A Ti plate was employed as a cathode. The electricity was controlled to 30 C cm−2. Surface morphology was observed using a field-emission scanning electron microscope (FE-SEM). Arithmetic mean roughness (Sa) was observed using an atomic force microscope (AFM).The current efficiency of the resulting Al foil at the operating temperature of RT and 50 oC was 99.6% in the latter as compared to 84.8% in the former at a current density of 52.6 mA cm−2. The current efficiencies at the operating temperature of 50 oC were higher than those of RT also at other current densities. The Al foil was obtained without the reductive decomposition of EMI+ cation (-2.2 V vs. Al / Al (Ⅲ)) even at the high current density (63.2 mA cm−2) by increasing the operating temperature to 50 oC. Regardless of the addition of OP, the current efficiencies were more than 90% even at the current density of 50 mA cm-2.Fig. 1 shows the FE-SEM images of the Al foil obtained at the various operating conditions. The crystal grain shape was the same, like a texture, regardless of the operating conditions. In contrast, the crystal grain size became larger with increasing the operating temperature. Moreover, the addition of OP to the AlCl3-EMIC melt at 50 oC also affected the crystal grain size to be small while the addition of OP did not affect the overpotential for the electrolysis. The AEM images showed that the Sa value became larger with increasing the operating temperature. By adding OP to the melt, the Sa value became extremely smaller, indicating that the addition of OP strongly suppresses the roughness.These results indicate that the smooth electrolytic Al foil would be obtained even with high operating temperature and high current density by adding OP to the AlCl3-EMIC melt. Acknowledgements This work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Charge Transport and Dynamics in Imidazolium Chloroaluminate Ionic Liquids

Ion dynamics and charge transport in 1-alkyl-3-methylimidazolium chloroaluminate ionic liquids were investigated over broad temperature and frequency ranges by broadband dielectric spectroscopy and differential scanning calorimetry. The timescale of ion dynamics, as captured by the imaginary component of the complex dielectric modulus as well as the calorimetric glass transition temperature (Tg), is strongly composition-dependent, with the fastest dynamics, lowest Tg, and highest fragility observed for the Lewis acidic 67 mol% AlCl3 + 1-ethyl-3-methylimidazolium chloride composition. The DC ionic conductivity scales directly by the ion dynamics for all compositions indicating the primary effect of ion speciation is an alteration of the underlying ion mobility. The fragility (m) of the 67 mol% AlCl3 + 1-ethyl-3-methylimidazolium chloride ionic liquid, m=148, is among the highest reported fragilities for a glass-forming liquid.

High performance aluminum ion battery using polyaniline/ordered mesoporous carbon composite

Aluminum-ion battery (AIB) is intriguing for electrochemical power sources due to its potentially high capacity and high safety. However, the most investigated graphitic and metal dichalcogenide cathode materials normally possess moderate capacity and inferior cycling stability, respectively, which limit the performance of current AIBs. Here, we develop a polyaniline (PANI)/ordered mesoporous carbon (OMC) composite as a cathode material of AIB using chloroaluminate ionic liquid as an electrolyte. During the charging/discharging process, two obvious platforms are observed at high voltages of 1.1 V and 1.5–1.7 V. The PANI/OMC cathode exhibits outstanding performance in terms of high specific capacity (140 mAh g−1 at 100 mA g−1), good rate performance (118 mAh g−1 at 2000 mA g−1) and excellent cycling stability (only 12% loss of capacity after 5000 cycles). Based on the ex-situ characterizations, the charge storage of PANI is found to be via the doping/de-doping of anions such as AlCl4−.

Facile and Selective Mono Benzylation of Naphthalene Using Atom Efficient Chloroaluminate Ionic Liquid

Benzyl naphthalenes are versatile compounds having multiple applications in dyes, fine chemicals, and pharmaceuticals etc. Herein, we present benzylation of naphthalene with benzyl chloride using a chloroaluminate ionic liquid which we have reported recently. The catalyst is highly active, selective and required in very low quantity i.e., 0.5% w/w to drive the reaction. The reaction was carried out at ambient temperature and pressure which has an edge over other existing catalysts that requires elevated temperature. The conversion of benzyl chloride and selectivity toward mono-benzylated product was found to be more than 95% and 90%, respectively. The formation of the product was confirmed by GC-MS. Various reaction parameters like temperature, catalyst concentration, mole ratio of benzyl chloride and naphthalene were investigated to optimize the best operating conditions to obtain the mono benzylated naphthalene. The catalyst was efficiently recyclized up to 5 times. The easy single-step synthesis of the catalysts, use of hydrophobic neutral ligand, better atom economy, makes the process more attractive for its application in benzylation reaction of naphthalene.

Deep compositional understanding of TBA: AlCl3 ionic liquid for its applications

Chloroaluminate ionic liquids (ILs) have been immensely used as homogeneous catalyst in Friedel-Crafts reaction. We have recently synthesized chloroaluminate ILs by reacting aluminium chloride with a hydrophobic neutral ligand i.e. tributylamine (TBA:AlCl3). The current study elaborates on the investigations of the composition of the ionic liquids at various stages of their formation. The ionic liquids were synthesized using various mole ratios of tributyl amine and aluminium chloride in range of 1:1 to 1:2.3, in presence of an aromatic solvent in a one pot reaction. Various characterization techniques like Mass spectrometry, 27Al Nuclear Magnetic Resonance, 31P Nuclear Magnetic Resonance and Fourier Transform Infrared spectroscopy were used to elucidate the formation of various moieties of the TBA:AlCl3 Ionic Liquid. This study also elaborates on the investigations of the cationic and anionic moieties and their structure-property relationship for various applications. Various Friedel-Crafts reaction of industrial importance were performed using the ionic liquid having (Al2Cl7)−moiety to assess its performance and compared with conventional processes. The synthesized products were characterised by sophisticated analytical techniques like 1H NMR, 13C NMR, FTIR, GC–MS, GC-FID, to name a few. This class of ionic liquids also have importance in various electrochemical applications like aluminium deposition and aluminium batteries.

Replacing HF or AlCl3 in the Acylation of Isobutylbenzene with Chloroaluminate Ionic Liquids

The two most common commercial catalysts for the acylation of isobutylbenzene to produce the major ibuprofen intermediate 4-isobutylacetophenone are HF and AlCl3; however, both of these catalysts suffer from significant drawbacks including the stringent safety issues associated with using volatile/toxic HF and the requirement for additional processing for deacidification of AlCl3. Here, two chloroaluminate-based catalysts, the ionic liquid (IL) [HN222][Al2Cl7] ([HN222] = triethylammonium) and the liquid coordination complex (LCC, here an IL analog) AlCl3/O-NMPχAlCl30.6 (O-NMP = N-methyl-2-pyrrolidone), were investigated and found to be efficient in the acylation of isobutylbenzene. Of the tested catalysts, the LCC, which along with neutral species has both a Lewis acidic cation ([AlCl2(O-NMP)2]+) and anion ([Al2Cl7]−), had the best catalytic performance (99% conversion with 96% selectivity).

Structure, microstructure and electrodeposition behaviours of aluminium from AlCl3-EMIC and AlCl3-BMIC ionic liquid electrolytes – a comparative study

ABSTRACT Electrodeposition of aluminium on the copper substrate using two different chloroaluminate ionic liquid electrolytes such as AlCl3/1-Butyl-3-methylimidazolium chloride electrolyte (AlCl3-BMIC) and AlCl3/1-Ethyl-3-methylimidazolium chloride electrolyte (AlCl3-EMIC) were studied. Cyclic voltammetry studies reveal the aluminium deposition process follows two steps mechanism in AlCl3-EMIC electrolytes and in AlCl3-BMIC electrolytes, it follows single-step mechanism. The AlCl3-EMIC electrolytes permit wide deposition current density window than the AlCl3-BMIC electrolytes for aluminium deposition with good properties. The aluminium deposits obtained from AlCl3-EMIC electrolyte have better surface properties than the deposits obtained from AlCl3-BMIC electrolyte. Detailed comparative studies of deposits obtained from these two electrolytes with respect to deposition mechanism, deposition efficiency and deposition current density window were done. The deposit properties such as surface morphology, microstructure and crystal structures were also compared. From this study, we observed the AlCl3-EMIC electrolyte gives good quality deposits than AlCl3-BMIC electrolyte.

High‐Performance Aluminum Ion Battery Using Cost‐Effective AlCl3‐Trimethylamine Hydrochloride Ionic Liquid Electrolyte

AbstractThe critical need for cost‐effective and sustainable large‐scale battery technologies for harvesting renewable energy has led to a new research wave on novel batteries made of low‐cost, high‐abundance, high‐performance, and safe components. Among the emerging candidates for post‐lithium‐ion batteries, aluminum‐based batteries are particularly promising due to the high theoretical capacities, low cost, and high abundance of raw materials. Most advanced nonaqueous rechargeable Al batteries rely on costly dialkylimidazolium chloride‐based chloroaluminate ionic liquids and this added cost inevitably diminishes various benefits of utilizing Al as the anode material. Here, a high‐performance Al battery made of Al anode, graphene nanoplatelets (GNPs) cathode, and a cost‐effective AlCl3‐trimethylamine hydrochloride (AlCl3‐TMAHCl) ionic liquid electrolyte is reported. The battery delivers a high specific capacity of 134 mAh g−1at 2000 mA g−1while maintaining Coulombic efficiency (CE) above 98% over 3000 cycles. Moreover, it delivers a specific capacity of 83 mAh g−1with a CE of 97% under ultrafast charging at 4000 mA g−1(1 min) and slow discharging at 100 mA g−1(50 min) conditions. Considering the low cost and high performance, AlCl3‐TMAHCl electrolyte opens up a new avenue for the development of next‐generation Al batteries.