Chloroaluminate Ionic Liquids Research Articles

Rechargeable aluminum-selenium batteries with high capacity.

Rechargeable aluminum (Al) batteries are emerging as a promising post lithium-ion battery technology. Herein, we demonstrate a conceptually new design of rechargeable aluminum-selenium (Al-Se) batteries by understanding the selenium chemistry and controlling the electrode reaction. The Al-Se battery consists of a composite cathode including selenium nanowires and mesoporous carbon (CMK-3) nanorods, an Al metal anode and chloroaluminate ionic liquid electrolyte. The working mechanism of the Al-Se battery is the reversible redox reaction of the Se2Cl2/Se pair confined in the mesopores of CMK-3 nanorods. Al-Se batteries deliver a high reversible capacity of 178 mA h g-1 (by Se mass), high discharge voltages (mainly above 1.5 V), and good cycling/rate performances.

Stability, Deactivation, and Regeneration of Chloroaluminate Ionic Liquid as Catalyst for Industrial C4 Alkylation

Alkylation of isobutane and 2-butene was carried out in a continuous unit using triethylamine hydrochloride (Et3NHCl)-aluminum chloride (AlCl3) ionic liquid (IL) as catalyst. The effects of impurities such as water, methanol, and diethyl ether on the stability of the catalytic properties and deactivation of the ionic liquid were studied in the continuous alkylation. In the Et3NHCl-2AlCl3 ionic liquid, only one half of the aluminum chloride could act as the active site. With a molar ratio of 1:1, the active aluminum chloride in the ionic liquid was deactivated by water by reaction or by diethyl ether through complexation while the complexation of aluminum chloride with two molecular proportions of methanol inactivated the active aluminum chloride in the ionic liquid. The deactivation of chloroaluminate ionic liquid was observed when the active aluminum chloride, i.e., one half of the total aluminum chloride in the ionic liquid, was consumed completely. The regeneration of the deactivated ionic liquid was also investigated and the catalytic activity could be recovered by means of replenishment with fresh aluminum chloride.

Alkylation of Isobutane with Butene over Ether-functionalized Composited Chloroaluminate Ionic Liquids

Alkylation of Isobutane with Butene over Ether-functionalized Composited Chloroaluminate Ionic Liquids

Electroplating of Al-Nb Alloys from the Lewis Acidic Chloroaluminate Ionic Liquid

Currently ionic liquid (IL) is a common technical term. A great number of scientists and engineers in various fields are using it to create new technologies because of IL’s interesting features, e.g., relatively high ionic conductivity, high electrochemical stability, low-flammability, negligible vapor pressure, and antistatic property.1 Although the chloroaluminate IL system consisting of organic halide and aluminum halide seems to be outdated one, only this IL system gives a high quality Al electroplating.2 To date, many chloroaluminate ILs have been reported for obtaining pure Al and Al alloy electroplating with a high coulomb efficiency. Usually Lewis acidic AlCl3–1-ethyl-3-methylimidazolium chloride ([C2mim]Cl) IL containing more than 50 mol% AlCl3 is employed. However, there is no report on Al-Nb alloy electroplating in the chloroaluminate IL while in inorganic AlCl3–NaCl molten salt it can be obtained.3 In this study, we examined to clarify the electrochemical behavior of Nb(V) in the Lewis acidic AlCl3–[C2mim]Cl IL. Based on the results, Al-Nb alloy electroplating was carried out under various experimental conditions. The procedures used for the preparation and purification of the AlCl3−[C2mim]Cl IL were identical to those described in previous articles.2 All the electrochemical experiments were conducted using a three-electrode cell. A Teflon® sheathed platinum rotating disk electrode was employed for the working electrode. A coil of 1.00 mm diameter aluminum wire was used for the counter electrode. The reference electrode was an aluminum wire immersed in a neat 66.7-33.3 mol % AlCl3–[C2mim]Cl. These two electrodes were separated from the bulk IL by porosity E glass frits. All experiments were carried out in an Ar gas-filled glove box with O2 and H2O < 1 ppm. The Nb ion was electrochemically supplied by anodic dissolution of pure Nb metal to the chloroaluminate IL. Alloy samples were electroplated from the 66.7-33.3 m/o AlCl3−[C2mim]Cl with different Nb(V) concentrations onto Teflon®-sheathed 2.0 mm diameter copper cylinder electrodes. Figure 1 shows cyclic voltammograms recorded at a Pt stationary disk electrode in the 66.7 mol % AlCl3–[C2mim]Cl with and without 19.6 mmol L-1 Nb(V). In the neat melt, Al deposition/stripping waves appeared at 0 V vs. Al(III)/Al by the known electrode reactions.2 After addition of Nb(V) to the neat IL, in a negative sweep initiated from the rest potential, four reduction waves appeared except the reduction wave for Al electroplating. Electrochemical analytical techniques revealed that the first two reduction waves correspond to electrode reactions for Nb(V)/Nb(IV) and Nb(IV)/Nb(III), respectively. Diffusion coefficient for the Nb(V) estimated from Levich equation and Cottrell equation was ca. 1.9 × 10-6 cm2 s-1 at 353 K. However, it was difficult for us to conduct further investigation on the other two reduction waves due to probably the precipitation of NbCl3 derived from the subsequent chemical reaction of the Nb(IV)/Nb(III) electrode reaction onto the electrode. In fact, electrochemistry of vanadium, which is the homologous elements of niobium, also shows a similar behavior.4 In this case, the alloying mechanism is likely different from that obtained by direct reduction from the transition metal ions dissolved in the chloroaluminate ILs, but nevertheless Al alloy can be obtained the same.2 Therefore, the Al-Nb alloy was prepared on Cu substrates rotated at a fixed rate of 2,000 rpm in the 66.7 mol % AlCl3–[C2mim]Cl with 5 ~ 48 mmol L-1 Nb(V) by a dc galvanostatic method at 353 K. As shown in Figure 2, Nb content in the Al-Nb alloys decreased with increasing the applied current density in all Nb(V) concentrations and with decreasing the Nb(V) concentration in all applied current density. The highest Nb content reached 65 at% when the Nb(V) concentration in the solution was 48 mmol L-1 and the applied current density was -5 mA cm-2. XRD patterns for the resulting Al-Nb alloys revealed that the alloys have a solid solution phase with an fcc structure because those for Al slightly shifted to lower angle with increasing the Nb content. When the content is 9.3 at%, XRD patterns for Al completely disappeared. It suggests that Al-Nb alloy forms microcrystalline or amorphous phase. T. Torimoto, T. Tsuda, K. Okazaki, and S. Kuwabata, Adv. Mater., 22, 1196 (2010).T. Tsuda, G. R. Stafford, and C. L. Hussey, J. Electrochem. Soc., 164, H5007 (2017) and references therein.G. R. Stafford and G. M. Haarberg, Plasmas & Ions, 1, 35 (1999).T. Tsuda and C. L. Hussey, J. Min. Metall. B, 39, 3 (2003). Figure 1

Kish Graphite Flakes as a Cathode Material for an Aluminum Chloride–Graphite Battery

Nonaqueous, ionic liquid-based aluminum chloride-graphite batteries (AlCl3-GBs) are a highly promising post-Li-ion technology for low-cost and large-scale storage of electricity because these batteries feature exclusively highly abundant chemical elements and simple fabrication methods. In this work, we demonstrate that synthetic kish graphite, which is a byproduct of steelmaking, can be used as a cathode in AlCl3-GB and exhibits high capacities of ≤142 mAh g-1. The comprehensive characterization of kish graphite flakes and other forms of graphite by X-ray diffraction, Raman spectroscopy, and Brunauer-Emmett-Teller surface area analysis provides solid evidence that the exceptional electrochemical behavior of kish graphite flakes is mainly determined by the high structural order of carbon atoms, a low level of defects, and a unique "crater morphology". In view of the nonrocking chair operation mechanism of AlCl3-GB, we have tested the achievable energy densities as a function of the composition of chloroaluminate ionic liquid (AlCl3 content) and have obtained energy densities of up to 65 Wh kg-1. In addition, the kish graphite flakes can rapidly charge and discharge, offering high power densities of up to 4363 W kg-1.

Synthesis of butyl-octyl-diphenylamine as lubricant antioxidant additive by ionic liquids

Ionic liquid used in Friedel-Crafts reaction catalytic of dialkyl diphenylamine is a green environmental method. In this paper, butyl-octyl-diphenylamine (BODPA) was synthesized by the series of 1-butyl-3-methylimidazolium chloroaluminate (BMIM-AlCl3) ionic liquids catalysts. Pressure differential scanning calorimetry (PDSC) was used to test antioxidant properties of BODPA in lubricating oil. The influences of various reaction parameters such as dosage of catalysts, molar ratio of diphenylamine to chloralkane, reaction temperature, and time on the alkylation catalyzed by BMIM-AlCl3 have been studied. The molecular structure and content of alkyl diphenylamine were also characterized by FT-IR/GC-MS.

A Raman spectroscopic study of graphene cathodes in high-performance aluminum ion batteries

Few layer graphene is a promising cathode material for aluminum-ion batteries that use chloroaluminate (AlCl4-) ionic liquids as the electrolyte. A fundamental understanding of interactions between the few layer graphene cathode and the ionic liquid electrolyte is key for realizing the full potential of these systems. Through in situ Raman spectroscopy and density functional theory calculations, we show that the cathode is capable of achieving stage-one intercalation within the operating voltage window, leading to improved cell performance. We also show that the presence of structural defects in few layer graphene such as pores induced via plasma exposure or nitrogen dopants can deteriorate the cell performance by either decreasing the electrical connectivity or precluding stage-one intercalation respectively. The cathodes made with highly crystalline few layer graphene display high power and energy densities (~ 200Whkg−1 at 200Wkg−1 and ~ 160Whkg−1 at 5000Wkg−1), and are stable with no loss in performance up to 1000 cycles while fully charging to 2.4V.

Preparation and characterization of a rechargeable battery based on poly-(3,4-ethylenedioxythiophene) and aluminum in ionic liquids

This paper presents a feasibility study of a non-aqueous rechargeable battery based on aluminum and poly-(3,4-ethylenedioxythiophene) conductive polymer in a chloroaluminate ionic liquid. The polymer was electrodeposited on a vitreous carbon working electrode in a chloride aqueous solution and the structure was analyzed by scanning electron microscopy. The doping/de-doping mechanism of chloride ions into the polymer structure was studied using a quartz crystal microbalance and cyclic voltammetry. The deposition/dissolution of the aluminum negative electrode were investigated by electrochemical and microscopic methods. Performance data were obtained with a laboratory-scale aluminum-conductive polymer battery at constant current showing an average cell discharge voltage of 1 V and specific energies of at least 84 Wh kg−1 referred to the mass of the polymer and aluminum. The system is novel and the paper outlines further research to improve the cell performance.Graphical

Electrodeposition of Al from chloroaluminate ionic liquids with different cations

Four typical chloroaluminate ionic liquids (ILs) with different cations, namely 1-butyl-3-methylimidazoliumchloride [Bmim]Cl/AlCl3 (33.3/66.7 mol%), 1-butyl-3-methylpyridinium chloride [BMPyri]Cl/AlCl3 (33.3/66.7 mol%), 1-butyl-1-methylpyrrolidiniumchloride [Py1,4]Cl/AlCl3 (33.3/66.7 mol%), and trimethylphenylammonium chloride [TMPA]Cl/AlCl3 (33.3/66.7 mol%), were employed to deposit Al. The viscosity and ionic conductivity of these ILs were measured. The results showed that [Bmim]Cl/AlCl3 (33.3/66.7 mol%) had the lowest viscosity and the highest conductivity. Raman spectra showed that Al2Cl7 − was the main anion in the four systems. Cyclic voltammetry indicated that [Bmim]Cl/AlCl3 (33.3/66.7 mol%) had the highest reduction current for Al deposition in the four ILs. By comparing the quality of the Al coatings prepared at the same current density and temperature, it was found that compact and smooth Al deposits could be obtained from [Bmim]Cl/AlCl3 (33.3/66.7 mol%) at 303 K, while the temperature needed was higher than 333 K for the other three ILs to obtain Al deposits with the same quality. Based on the density functional theory (DFT) calculations, the differences in these properties were attributed to the different molecular structure and cation-anion interaction induced by the cations of these ILs.

The cellulose aluminum oxide composite-supported imidazolium chloroaluminate ionic liquid as a novel and stable heterogeneous catalyst

ABSTRACT1-Methyl-3-(triethoxysilylpropyl)imidazolium chloroaluminate ionic liquid anchored on a composite of cellulose and aluminum oxide was easily synthesized and tested for its catalytic activity in one-pot Knoevenagel condensation, Michael addition, and cyclodehydration of 5,5-dimethyl-1,3-cycloheanedione (dimedone) with aromatic aldehydes. The catalyst was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, energy-dispersive spectroscopy, elemental analysis, and atomic absorption technique. It is a non-hygroscopic (as a bench top catalyst), reusable, and environmentally compatible heterogeneous catalyst.

Zeolite-Templated Carbon as an Ordered Microporous Electrode for Aluminum Batteries.

High surface area porous carbon frameworks exhibit potential advantages over crystalline graphite as an electrochemical energy storage material owing to the possibility of faster ion transport and up to double the ion capacity, assuming a surface-based mechanism of storage. When detrimental surface-related effects such as irreversible capacity loss due to interphase formation (known as solid-electrolyte interphase, SEI) can be mitigated or altogether avoided, the greatest advantage can be achieved by maximizing the gravimetric and volumetric surface area and by tailoring the porosity to accommodate the relevant ion species. We investigate this concept by employing zeolite-templated carbon (ZTC) as the cathode in an aluminum battery based on a chloroaluminate ionic liquid electrolyte. Its ultrahigh surface area and dense, conductive network of homogeneous channels (12 Å in width) render ZTC suitable for the fast, dense storage of AlCl4- ions (6 Å in ionic diameter). With aluminum as the anode, full cells were prepared which simultaneously exhibited both high specific energy (up to 64 Wh kg-1, 30 Wh L-1) and specific power (up to 290 W kg-1, 93 W L-1), highly stable cycling performance, and complete reversibility within the potential range of 0.01-2.20 V.

Effects of Metal Ions on the Aluminum Electrodeposition from Ionic Liquids

In this study, we report on the effects of three common transition metal ions, i.e., Ni2+, Cu2+ and Fe3+ on the electrodeposition of aluminum from a chloroaluminate ionic liquid, evaluated by means of electrochemical and morphological investigation. Aiming at the determination of the morphological and chemical effects on the aluminum coatings, variable amounts of ions were introduced into the electroplating bath. Thick (about 20 μm) Al coatings were obtained by direct deposition (galvanostatic, 10 mA cm2, 2 h) on brass or carbon steel substrates (10 mm diameter disks), and their morphology was examined via rugosimetry, optical and electron microscopy. The chemical composition of the deposits was provided by EDX analysis. Nickel and iron resulted to have only moderate effects on the coatings properties, but copper affected the process even in tiny amounts being detected in the deposits for bath content as low as 10 ppm.

Graphene-Coated Activated Carbon Fiber Cloth Positive Electrodes for Aluminum Rechargeable Batteries with a Chloroaluminate Room-Temperature Ionic Liquid

Functional carbon materials have recently attracted attention as positive electrode active materials for Al rechargeable batteries in conjunction with an Al negative electrode and a chloroaluminate ionic liquid electrolyte. This study explores a new carbon material, a graphene-decorated activated carbon fiber cloth (ACFC), for the positive electrode. Graphene-decorated ACFCs can be used in a binder-free manner and will directly contribute to increased gravimetric capacity of the whole electrode [mAh (gelectrode)−1, not per the active material]. Specifically, the positive electrode behaviors of three types of ACFC-based electrodes are examined in a Lewis acidic AlCl3−1-ethyl-3-methylimidazolioum chloride ([C2mim]Cl) room-temperature ionic liquid. Uncoated and low-loading graphene-coated ACFC electrodes show an electric double layer capacitor (EDLC)-like behavior, whereas the intercalation/deintercalation reaction of chloroaluminate anion (e.g., [AlCl4]−) is observed for the high-loading graphene-coated one. These electrodes exhibit a good cyclability and satisfactory coulombic efficiency up to 800 cycles at a current density of 500 mA g−1.

Quantitative Characterization of Lewis Acidity and Activity of Chloroaluminate Ionic Liquids

Pyridine can act as a basic indicator for both Bronsted and Lewis acids forming different types of bonds. Infrared spectroscopy, in combination with 27Al NMR spectroscopy, was employed to study the interaction mechanism of pyridine and chloroaluminate ionic liquids (ILs). The acid type, acid amount, acidity, and even activity of chloroaluminate ILs could be determined. An in situ infrared complexometric titration was developed as a quantitative characterization method for determining the different acidities and catalyst activity. The method is based on the principle that Lewis acidic chloroaluminate [Al2Cl7]− anion reacts with pyridine to form the [AlCl4]− anion and pyridine–AlCl3 ([PyAlCl3]) complexes, while the Bronsted acid forms a pyridinium salt. Both product types showed characteristic shifts of the pyridine peaks in the infrared spectrum.

Carbon Material-Based Positive Electrodes for Aluminum Secondary Battery with a Chloroaluminate Ionic Liquid

Secondary batteries have already been utilized widely in various equipment, e.g., electric vehicle and cell-phone, but higher power density and capacity are required for supporting our modern life more than ever before. In order to achieve it, novel battery systems that are expected to take the place of conventional Li-ion battery (LIB) are proposed by a great number of research groups around the world. Above all, secondary battery using a multivalent-metal ion, e.g., Mg(II) and Al(III), has been expected to be a next generation battery because it can flow a larger current exceeding a conventional LIB. In a Lewis acidic haloaluminate ionic liquid (IL), it is well-known that aluminum can be electrochemically deposited with a high current efficiency. It suggests that the electrode reaction is a favorable one for constructing the Al secondary battery with the chloroaluminate IL. In fact, some remarkable researches on the Al secondary battery with haloaluminate ILs have been reported since the 1980.1-4 In this study, we have investigated the electrochemical behaviors of the various carbon positive electrodes in the Lewis acidic 60.0-40.0 mol % AlCl3–1-ethyl-3-methylimidazolium chloride (AlCl3–[C2mim]Cl) IL. The procedures used for the preparation and purification processes on the AlCl3−[C2mim]Cl IL were identical to those described in our articles. All the electrochemical experiments were conducted using a three-electrode beaker cell. A coiled Al wire was employed for the negative electrode. Five types of carbon materials were exploited to fabricate the positive electrode for an Al secondary battery. Those were an activated carbon fiber cloth covered with or without a graphene layer, a basal or an edge plane pyrolytic graphite, and a graphite-leaf powder. The reference electrode was an Al wire immersed in a neat 60.0-40.0 mol % AlCl3–[C2mim]Cl, if needed, but was separated from the bulk IL by porosity E glass frits. All experiments were carried out in an Ar gas-filled glove box with O2 and H2O < 1 ppm. Cyclic voltammograms recorded at different carbon positive electrodes in the 60.0 mol % AlCl3–[C2mim]Cl are shown in Fig. 1. At an activated carbon fiber cloth electrode, only an oxidation reaction appeared at the potential over ca. 2.25 V, and then electric double layer capacitance was also recognized due to the porous properties. But if the graphite (not shown) and graphene-coated electrodes were employed, several redox waves appeared. A small oxidation wave observed at ca. 1.70 V (vs. Al(III)/Al) should be the following electrochemical intercalation reaction. n C + [AlCl4]- ⇄ C n +[AlCl4]- + e- However, graphite electrodes, especially an edge plane pyrolytic one, were seriously damaged by the voltage sweep over 2.30 V. After the experiment, carbon powder precipitated in the IL electrolyte. In order to improve the behavior, graphite-leaf powder composite electrode was fabricated by using polymer binders that are stable in the IL. A typical voltammogram recorded at the electrode are shown in Fig. 1. Two clear oxidation waves appeared before increasing the oxidation current corresponding to the electrochemical oxidation of [AlCl4]-. It suggests that graphite intercalation compounds with different stages, e.g., stage 4, are produced during the anodic potential sweep.3 Based on the findings described above, we designed several Al secondary battery systems with different positive electrodes. Of these, use of the graphite-leaf powder composite electrode enabled high coulomb efficiency and discharge capacity up to 99 % and 80 mAh g-1, respectively, when the cut-off voltages were 0.80 and 2.10 V at the charge-discharge rate of the 50 mA g-1. The electrode performance strongly depended on the amount of the active material. This positive electrode will be one of the choices for designing the Al secondary battery. Acknowledgement Part of this research was supported by the Grant-in-Aid for Scientific Research, Grant Numbers 15H03591, 15K13287, and 15H2202 from the Japanese Ministry of Education, Culture, Sports, Science and Technology and by the ALCA-SPRING program, Japan Science and Technology Agency. References N. Takami and N. Koura, J. Electrochem. Soc., 140, 928 (1993).P. R. Gifford and J. B. Palmisano, J. Electrochem. Soc., 135, 650 (1988).M.-C. Lin, M. Gong, B. Lu, Y. Wu, D.-Y. Wang, M. Guan, M. Angell, C. Chen, J. Yang, B.-J. Hwang, and H. Dai, Nature, 520, 324 (2015).T. Tsuda, I. Kokubo, M. Kawabata, M. Yamagata, M. Ishikawa, S. Kusumoto, A. Imanishi, and S. Kuwabata, J. Electrochem. Soc., 161, A908 (2014). Figure 1

Electrochemical Deposition of Aluminum and Aluminum-Manganese Alloys in Ionic Liquids

Aluminum and aluminum-manganese alloys were electrodeposited from chloroaluminate ionic liquids on low carbon steel substrates. The properties of the deposited films were analyzed, with regard to their morphology, structure, composition and corrosion behavior in neutral 3.5% NaCl solution. The effect of the deposition time and of the current density chosen on the above mentioned properties of the deposits was systematically investigated. Both the Al and the Al-Mn layers showed excellent corrosion protection to the steel substrates.

Low-temperature Electrolysis of Aluminium from 1-Butyl-3-methylimidazolium Chloroaluminate Ionic Liquids with Inert Anode

Low-temperature Electrolysis of Aluminium from 1-Butyl-3-methylimidazolium Chloroaluminate Ionic Liquids with Inert Anode

Physiochemical Properties of Dialkylimidazolium Chloroaluminate Ionic Liquids Under Dynamic Conditions

Aluminum deposition is an industrially important process that is often not optimized in an electrochemical sense. One method of growing thin aluminum films is electrodeposition; this process has been gaining traction in ionic liquids over the last two decades, although details of the process are still under debate. These inconsistencies are largely attributed to widely variable results based on electrolyte purity and a strong dependence on a multitude of parameters including composition, temperature and even experimental set up. This work is targeted to elucidate some of these properties with electrochemical and rheological measurements, alongside NMR and microscopy techniques. Some of the most promising aluminum deposition is done in chloroaluminate ionic liquids. These solutions have high aluminum concentration and low vapor pressure but typically higher viscosity then molecular solvents or aqueous chemistries. 1-ethyl-3-methyl imidazolium chloride (EMIC) and AlCl3 in acidic ratios will readily deposit aluminum. This electrolyte deposits aluminum by the reduction of Al2Cl7 - to aluminum and produces AlCl4 - anions in a relatively complex 3 electron transfer mechanism. The composition of the electrolyte is determined by the ratio of AlCl3 to EMIC and is confirmed by NMR. The varying compositions of the ionic liquid influence both the physical and electrochemical properties. The Walden rule applies well to most ionic liquids and states that the conductivity and viscosity are related, and as a corollary the mobility of ions is dependent as well. We systematically investigate the diffusion parameters that lead to insight of reaction kinetics of the chloroaluminate system. There are methods that have been developed for this type of investigation that do not apply to this system because of a few complications. For example, the Cottrell model indicates a diffusion controlled system, while attempting Koutecky-Levich does not apply because the system cannot reach a diffusion limited regime in the window of the electrolyte. We assert that in a quiescent system the ionic interactions of the electrolyte become quite strong and resistant to cleavage, leading to restricted Al2Cl7 - diffusion. The structuring and interaction of the ionic liquid may be shown in the rheological data, indicating that the solutions are thixotropic. Since the conductivity and diffusivity are dependent on the viscosity, we assert that as the solution is allowed to rest and coordinate in a preferred structure the diffusivity would decrease significantly. This implies that the measured diffusion rates in a quiescent experiment are not relevant in a system that implements convection, which is almost any real system. We apply data derived from the quiescent system experiments to dynamic systems by understanding how the macroscale physical properties change as the system goes from static to dynamic. As mentioned above, the Cottrell equation can measure the diffusion rates of an electrochemically active species, which allows measurement of transport for Al2Cl7 -. Proton pulse field gradient spin echo nuclear magnetic resonance spectroscopy (PGSE NMR) can measure the diffusivity of the cationic species in the system (EMIm+), and the bulk conductivity was used to determine the combined mobility of ions in solution. The anions and cations contribute to the bulk conductivity separately, which necessitates the multiple methods of investigation, as well as the redundancy of using solutions of varying compositions. All of these experiments give results based on a static solution. We apply the viscosity dependence to the data gathered in static solutions to predict properties in dynamic conditions. A close approximation of zero shear viscosity was determined through falling ball experiments. The dynamic viscosity was measured by a rheometer at varying shear rates. The diffusion properties and conductivity are related to viscosity. Composition and temperature variation in the viscosity studies gave insight to the mobility of both the anions and cations under all static or dynamic conditions, and point to complex interaction at the electrode interface for deposition from the Al2Cl7 - in this ionic liquid. Using the diffusivity and composition data gathered from this set of experiments allows for investigation of the reaction kinetics, and optimization of the kinetics to diffusion balance. Increasing the plating rate reduces fabrication times but infringing on the precursor diffusion limits leads to dendritic and poor quality deposits. Adjusting the parameters to give similar kinetic and diffusion properties of the Al2Cl7 - in this electrolyte will give the best deposition properties based on both rate and dense, compact and level morphologies. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Ionic Liquid Electrolytes for Rechargeable Aluminum Batteries

Rechargeable aluminum battery is considered as a promising battery system used in energy storage devices, due to its abundant natural resources and high capacity. However, fabrication of this battery working at room temperature didn’t succeed until haloaluminate contained ionic liquids were used as electrolytes. Therefore, electrolytes are expected to have a great effect on performance of rechargeable aluminum battery. For ionic liquid electrolytes, anions play a major role in its electrochemical properties. Anion-effect of haloaluminate contained ionic liquids prepared with different halogenated imidazole salt and AlCl3/imidazolium chloride mole ratio are studied. Electrochemical window is found narrowing with reducibility of halide ion and AlCl3 mole fraction. When used as electrolyte in rechargeable aluminum battery with V2O5 nanowire cathode, AlCl3/[BMIM]Cl ionic liquid with the mole ration of 1.1:1 shows the best performance. The as-assembled cell exhibits a high discharge voltage platform (1 V) and capacity (288 mAh/g) at the first cycle. Concentration of Al2Cl7 - is considered as a key factor in chloroaluminate ionic liquids when used as electrolyte. A slightly corrosion is found on the surface of Al metal foil immerged in acid AlCl3/[BMIM]Cl ionic liquids after 24 h. It means this kind of ionic liquids may help to remove the oxide film on Al metal foil. The oxide film is considered as a mainly hinder to performance of aluminum battery. Performance of battery using ionic liquid with other anions (such as BF4 -, PF6 - and CF3SO3 -) has not been reported, which is probably due to the dense Al2O3 film formed on surface of Al anode. It prevents the oxidation of Al in discharge process of battery and causes a failure. Figure 1

Copper Dissolution in Chloroaluminate Ionic Liquids

The anodic dissolution of metal substrates under convective mass-transport conditions can often lead to considerable improvement of the surface roughness of the substrate through a process known as electropolishing. Electropolishing processes, which are a cornerstone of metal surface finishing, are most commonly carried out in aqueous electrolyte solutions, especially mixtures of concentrated sulfuric and/or phosphoric acids, or in the single acids. However, depending on the metal and conditions used, anodic dissolution in aqueous solutions sometimes results in the formation of unwanted passive films of insoluble salts and/or metal oxides, which limit the efficacy of the electropolishing process. In some circumstances, ionic liquids or room-temperature molten salts may be suitable replacement electrolytes for the aqueous acids commonly used for electropolishing. Among these ionic liquids are the organic salt-based chloroaluminates, such as AlCl3-1-ethyl-3-methylimidazolium chloride (EtMeImCl). Because of their adjustable Lewis acidity, chloroaluminate ionic liquids offer a unique solvation environment for many metals. The Lewis basic AlCl3-EtMeImCl ionic liquids, which contain unbound chloride ion, provide a solvation environment that is not unlike aqueous NaCl, except without the H2O. On the other hand, the AlCl3-rich Lewis acidic ionic liquids are a very different story because there are no “hard” ligands available to form isolable anionic complexes. Nevertheless, many metal ions are very soluble in these ionic liquids. In this investigation, we have focused on the anodic dissolution of copper, not only to assess the utility of acidic and basic chloroaluminates as electrolytes for electropolishing metals, but to understand the kinetics of the electrodissolution of metals in these versatile solvents. As is well known, copper is vitally important in the electronics industry, especially with regard to the preparation of interconnects for computer chips by electrodeposition. As with all electrochemical deposition processes, anode dissolution must be considered in the overall cell reaction. There is also an extensive body of information about the kinetics and mechanism of the anodic dissolution of copper and its alloys under simulated marine conditions, i.e., in aqueous NaCl solutions. Thus, another goal of this investigation is to compare the dissolution of copper in the chloride-rich ionic liquids with dissolution in aqueous chloride solutions. In this presentation, we will describe a kinetic analysis of the anodic dissolution of copper in the Lewis acidic and basic compositions of the AlCl3-EtMeImCl ionic liquid. An example of our research results is given in the figures below. Figure 1 shows current density-time transits recorded at a copper RDE in the Lewis acidic ionic liquid at different potentials and at a fixed rotation rate. Clearly, the current density, j, is potential dependent, but independent of time. Plots of j versus the square root of electrode rotation rate, w1/2, which were constructed from data resulting from a series of experiments similar to those used to produce Fig. 1, are shown in Fig. 2. According to the Levich equation, for a mass transport-limited process, j should show a linear dependence on w1/2 with the line passing through the origin of the plot. This is obviously not the case here, indicating that the dissolution process probably proceeds under mixed control. Figure 3 shows plots of 1/j versus 1/w1/2 based on the Koutecky-Levich equation for a one-electron reaction, 1/j=1/j k + kc /k a [1.61(FD 2/3)-1 ν1/6 ] ω-1/2. These plots clearly show a potential-dependent intercept, indicating a kinetic step in the dissolution process. The interpretation of this data, as well as that resulting from similar experiments conducted in Lewis basic ionic liquids, will be discussed in this presentation. This work was funded by the Strategic Environmental Research and Development Program (SERDP) through contract DE-AC05-00OR22725 to ORNL with subcontract to the University of Mississippi. Figure 1