Chloroaluminate Ionic Liquids Research Articles

Throwing Power in Chloroaluminate Ionic Liquids: Effects of Metal Concentration, Additives and Waveform on Aluminum/Aluminum Alloy Deposition on Complex Geometries

Al deposition from chloroaluminate ionic liquids necessitates the use of consumable anodes and near 100% plating efficiency in order prevent irreversible breakdown of the electrolyte. A significant side effect of this high plating efficiency is poor deposit thickness uniformity across current density gradients. For simple or axisymmetric geometries under ideal plating conditions it is straight forward to mitigate such issues through traditional thieving or shielding. However, as part geometries become more complex, and plating conditions less ideal (i.e. barrel plating of small parts), methods of improving poor throwing power resulting from secondary current density effects become less obvious. Addressing this issue is critical in enabling Al plating technologies to progress commercially. We have explored the effects of metal concentration, additives and plating waveform on deposit thickness uniformity for rack and barrel plated parts of increasing geometric complexity in order to minimize plating thickness distribution and improve throwing power of [AlCl3:EMIMCl] chloroaluminate electrolytes into high aspect ratio features.

Segregation in Aluminum-Zirconium Alloys, Electrodeposited from Ionic Liquids, and Its Modification By Pulse Plating

It is quite typical for aluminum-zirconium alloys, obtained by electrodeposition in chloroaluminate ionic liquids, to have two or more distinct phases with different Zr concentrations. The Zr content in one phase can be several times higher than in the other. In the present work we have studied this segregation in [EMIM]Cl*AlCl3 ionic liquid. Factors like temperature, current density, agitation, and concentrations of both zirconium and aluminum in the electrolyte were investigated. A proposed mechanism for this phenomenon is based on a possibility of two different pathways of zirconium reduction. One pathway is a 4-electron process, taking Zr4+ directly to metal. Another way is a 2-electron reaction via intermediate Zr2+ ions formed in the solution. The difference between these pathways includes variations in chloride ions concentration in the vicinity of the electrode surface, as well as variations in charge and structure of the double layer. The above variations exist only near the cathode surface, and have a limited life time. One approach to eliminating the segregation in the alloy is to utilize pulsed electrodeposition methods, allowing re-mixing and equilibration of the electrolyte during the off periods. As expected, shorter pulses and longer off times lead to more compositionally uniform deposits. Figure 1. Backscatter SEM image of a cross section of Al-Zr deposit. Light areas are zirconium-rich. Figure 1

Electrodeposition of Aluminum Nanoplatelet from AlCl3–1-Ethyl-3-Methylimidazolium Chloride–Urea Mixtures

Aluminum electrodeposition is generally conducted in nonaqueous solvents because of its negative electrode potential (-1.66 V (vs. NHE)). Among the solvents, Lewis acidic chloroaluminate ionic liquids (ILs) and deep eutectic solvents (DESs), which contain AlCl3 over 50 mol% and are handled at room temperature, are commonly employed for the electrodeposition process. Recently, these solvents are also expected as the electrolyte for Al-anion secondary battery.1 A great number of articles on Al technologies using AlCl3–1-ethyl-3-methylimidazolium chloride ([C2mim]Cl) IL2 and AlCl3–urea DES3 have been reported so far. However, there is no report on Al electrodeposition from the Lewis acidic chloroaluminate ternary mixtures consisting of AlCl3, [C2mim]Cl, and urea. In this study, we examine the electrochemical behavior of Al deposition process and the association between the morphology variations in the Al electrodeposits and electrodeposition conditions. The procedures used for the preparation and purification of the AlCl3, [C2mim]Cl, and urea, were identical with those described in previous articles.2,3 The molar fraction of AlCl3 in each mixture was 60 mol%. The sum of molar fraction for the [C2mim]Cl and urea was 40 mol%. Their molar fraction was changed in the range of 0 ~ 40 mol%. The electroanalytical measurements were conducted using a three-electrode cell. The working electrode was a Pt disk electrode. An Al plate was used for the counter electrode. The reference electrode was an Al wire immersed directly in the electrolyte. Galvanostatic electrodeposition was conducted using Cu plate electrodes. All the experiments were carried out in an Ar gas-filled glove box with O2 and H2O < 1 ppm. The resulting Al samples were characterized by SEM, EDX, and XRD. Operando digital microscope observation for the Al electrodeposition process was performed by using the specially designed two-electrode airtight electrochemical cell. Figure 1 shows SEM images of the pure Al electrodeposits prepared in 60.0-40.0 mol% AlCl3–[C2mim]Cl IL and 60.0-40.0 mol% AlCl3–urea DES under the same electrodeposition conditions. EDX analysis of the electrodeposits revealed that they are pure Al without chloride contamination. When the IL electrolyte was used, the Cu substrate surface was covered with dense crystals. Meanwhile, in the case of the DES electrolyte, surprisingly Al nanoplatelets having very smooth surface were yielded at 333 K but not 293 K, when the applied current density was -5 ~ -20 mA cm-2. The Al nanoplatelets were readily obtained at the bath temperature over 313 K. The surface morphology of the electrodeposit obtained at 293 K was similar to that shown in Fig. 1a. XRD patterns of the Al deposits revealed that specimens shown in Fig. 1a and 1b were Al polycrystalline Al and (111)-preferentially oriented Al, respectively (Fig. 2a and 2e). The unexpected electrodeposition behavior recognized in the DES solvent has not been observed in the chloroaluminate IL. In order to get further insights concerning the interesting behavior, the electrodeposition was conducted in the ternary AlCl3–[C2mim]Cl–urea mixtures under the same condition that can produce Al nanoplatelet in the AlCl3–urea DES. Here we used three types of mixtures, 60.0-30.0-10.0 mol%, 60.0-20.0-20.0 mol%, and 60.0-10.0-30.0 mol% AlCl3–[C2mim]Cl–urea. As we expected, the increase in the urea molar faction in the ternary mixture caused the variation in the surface morphology. The nanoplatelet structure appeared in only the 60.0-10.0-30.0 mol% AlCl3–[C2mim]Cl–urea. It suggests that the urea contributes the formation of unique platelet structure. Because direct observation of the electrodeposition process enables to propose the plausible formation mechanism, airtight electrochemical cell for the operando digital microscope was newly designed. From the video clip during the electrodeposition process, two-dimensional crystal growth of the Al deposits was visually recognized in the 60.0-40.0 mol% AlCl3–urea DES. The detailed information obtained from the operando observation including the video clip will be given in our presentation. References T. Tsuda, G. R. Stafford, and C. L. Hussey, J. Electrochem. Soc., 164, H5007 (2017) and references therein.J. S.Wilkes, J. A. Levisky, R. A.Wilson, and C. L. Hussey, Inorg. Chem., 21, 1263 (1982).H. M. A. Abood, A. P. Abbott, A. D. Ballantyne, and K. S. Ryder, Chem. Commun., 47, 3523 (2011). Figure 1

Adherent Light-Induced Al Plating on Si for Substitution of Ag in Si Solar Cells

Silver (Ag) is one of the most expensive materials used in the manufacture of silicon (Si) solar cells today as the front electrode. The current Si cell manufacturing cost from Si wafers is ~$0.10 per cell and Ag accounts for about half of that cost. Another key issue is the limited reserve of Ag on our planet, with a US Geological Survey estimated amount of 530,000 metric tons [1]. Even if the entire Ag reserve was used for cell manufacturing, we could only supply ~5% of the 2100 global energy demand [2]. Based on material cost, abundance, and resistivity, only two suitable replacements for Ag exist, Cu and Al. Al bears the advantage over Cu since it eliminates the need for a barrier layer such as Ni. Al is also less prone to oxidization often experienced by Cu. We reported light-induced Al electroplating on Si solar cells using a Lewis acidic chloroaluminate ionic liquid [3], demonstrating direct Al plating on Si without a seed layer. This talk focuses on surface preparation and Al plating processes to promote strong adhesion and low contact resistance between plated Al and cell emitter. Sheet resistance and surface morphology of the emitter were monitored as a function of laser power for SiNx removal. Electrochemical capacitance-voltage profiling determined the laser power at which the emitter surface dopant profiles were preserved. A process to remove laser damage and clean the Si surface after laser patterning was developed by etching Si in 1 wt% NaOH. It was found by atomic force microscopy that ~23 s was the minimum time to completely remove the original Si surface which was damaged and contaminated. Al deposits on substrates prepared by this surface cleaning process showed strong adherence in the Scotch tape test. Al plating was performed at different temperatures. The resulting film thickness and morphology were investigated with scanning electron microscopy. The lowest film resistivity was less than 8 µΩ-cm which was obtained at a plating temperature of 50°C and showed a grain size of 2–5 µm. [1] U.S. Geological Survey, Mineral Commodity Summaries (2017). [2] M. Tao, Terawatt Solar Photovoltaics: Roadblocks and Opportunities (Springer, London, 2014). [3] L. Wang, W.-H. Huang, W. J. Shin, M. Tao, B. Deng, and D. Wang, J. Electrochem. Soc., 165, D381 (2018).

Materials Compatibility in Rechargeable Aluminum Batteries: Chemical and Electrochemical Properties between Vanadium Pentoxide and Chloroaluminate Ionic Liquids

To demonstrate the importance of electrode/electrolyte stability in rechargeable aluminum (Al) batteries, we investigate the chemical compatibility between vanadium pentoxide (V2O5), a proposed pos...

A safe and non-flammable sodium metal battery based on an ionic liquid electrolyte

Rechargeable sodium metal batteries with high energy density could be important to a wide range of energy applications in modern society. The pursuit of higher energy density should ideally come with high safety, a goal difficult for electrolytes based on organic solvents. Here we report a chloroaluminate ionic liquid electrolyte comprised of aluminium chloride/1-methyl-3-ethylimidazolium chloride/sodium chloride ionic liquid spiked with two important additives, ethylaluminum dichloride and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide. This leads to the first chloroaluminate based ionic liquid electrolyte for rechargeable sodium metal battery. The obtained batteries reached voltages up to ~ 4 V, high Coulombic efficiency up to 99.9%, and high energy and power density of ~ 420 Wh kg−1 and ~ 1766 W kg−1, respectively. The batteries retained over 90% of the original capacity after 700 cycles, suggesting an effective approach to sodium metal batteries with high energy/high power density, long cycle life and high safety.

Electrochemical study on the rechargeability of TiO2 as electrode material for Al-ion batteries with chloroaluminate ionic liquid electrolyte

The renewal of research interest in rechargeable aluminum-ion batteries could be seen as a massive boost for the exploration of Al3+-ion electroactive electrode materials in recent times. Titanium dioxide (TiO2) is less explored but could be a promising electrode material for aluminum-ion battery. Here, we demonstrate the rechargeability of an Al-ion cell with anatase TiO2 as cathode in chloroaluminate ionic liquid electrolyte. The Al-TiO2 cell exhibited excellent long-term stability with maximum specific capacity of 25 mAh g−1 at current rate of 500 mA g−1 at room temperature. The electroactive nature of TiO2 in the chloroaluminate electrolyte is clearly demonstrated both by cyclic voltammetry and galvanostatic cycling studies. The synergistic effect of current collector in improving the long-term stability of Al-TiO2 cell is also revealed.

Electrodeposition of Aluminum Using Chloroaluminate Ionic Liquids Under Dry Air Conditions

Electrodeposition of Al at near room temperature using chloroaluminate ionic liquids, represented by the 1-ethyl-3-methylimidazolium chloride−AlCl3 system, has been extensively investigated as a technique for the fabrication of Al coatings. Such coatings have many potential applications, e.g., as corrosion-protective and decorative coatings. The electrodeposition of Al is usually performed under an inert gas atmosphere such as nitrogen and argon in a closed system using a glove box to protect the bath from absorbing moisture. Exposure of chloroaluminate ionic liquids to ambient air readily causes hydrolysis, which makes Al electrodeposition impossible. However, operation in a closed system reduces the productivity and increases the cost of the electrodeposition process, making it unsuitable for a large-scale production in industry. In this study, the feasibility of the electrodeposition of Al using chloroaluminate ionic liquids under dry air conditions was examined. Such dry air conditions can be maintained in a system that is half-open to ambient air using a dehumidifier. As the electrodeposition process in dry air does not require the use of a glove box, it should be much more productive than in inert atmosphere. Four kinds of chloroaluminate ionic liquids composed of different organic cations ([cation]Cl−AlCl3) with a molar ratio of [cation]Cl:AlCl3 = 1:2 were employed as the bath for Al electrodeposition. The cations employed were 1-ethyl-3-methylimidazolium, 1-butylpyridinium, 1-butyl-1-methylpyrrolidinium, and trimethylphenylammonium. Electrochemical behavior of Al in these baths in dry air was examined by cyclic voltammetry. Galvanostatic electrodeposition was performed and deposits from these baths in dry air were inspected by X-ray diffraction, scanning electron microscopy, and elemental analysis. The current efficiency was also assessed. These experiments clarified the baths that can produce Al films in dry air with as good quality as the ones obtained in an inert atmosphere. The reactivity between the organic cation and superoxide ion generated by the cathodic reduction of dissolved oxygen seemed to be responsible for the difference in the quality of the Al films electrodeposited from these baths in dry air. The reactions of dissolved oxygen in these baths are discussed.

Rechargeable Aluminum Battery Cathode/Electrolyte Compatibility and Room Temperature Aluminum Deposition from Organic Solvent of AlCl3

Lacking viable electrolytes is one of the fundamental obstacles preventing the realization of rechargeable aluminum batteries. To date, the only electrolytes which can enable allowing reversible Al deposition-stripping with excellent chemical and electrochemical stability are the chloroaluminate ionic liquids (ILs). However, these kind of ILs are extremely corrosive due to the high concentration of chloride. To demonstrate the importance of the cathode/electrolyte interfacial stability in emerging rechargeable aluminum (Al) batteries, chemical compatibility between vanadium(V) oxide (V2O5), a widely studied cathode material for Al batteries, and the most common chloroaluminate ionic liquid electrolyte are studied. The potential reactions between V2O5 and Lewis acidic species (Al2Cl7 -) and Lewis neutral species (AlCl4 -), respectively, and the resulting electrochemical properties are investigated with electrochemical analysis, spectroscopic characterizations including Raman and nuclear magnetic resonance (NMR) spectroscopy, supported by computational studies using methods based on density functional theory (DFT). Our studies clearly demonstrate that V2O5 reacts to both Al2Cl7 - and AlCl4 -, and the reaction mechanisms are proposed and validated. We also developed new organic electrolyte for Al deposition at room temperature based on AlCl3/g-butyrolactone (GBL) mixture in benzene. It is found that the solubility of AlCl3 in GBL can be significantly enhanced by adding benzene as diluent. Besides, the coordination structure between AlCl3 and GBL would change when the molar ratio of AlCl3/GBL increased above 1:1, which lead to the generation of active species for Al deposition.

Lewis Acidity and Basicity of Mixed Chlorometallate Ionic Liquids: Investigations from Surface Analysis and Fukui Function.

Mixed chlorometallate ionic liquids (ILs) have been regarded as potential solvents, catalysts, and reagents for many organic processes. The acidity and basicity of these ILs were correlated with theoretically estimated parameters such as electrostatic surface potential maxima and minima, average local surface ionization energy, and Fukui and dual descriptor functions. The introduction of metal chloride into the anions would influence the acidity/basicity of ILs by withdrawing the electron density from the cationic counterpart. For the [C4mim]-based ILs with the mixed-metal anions, the acidity tends to attenuate while the basicity becomes stronger, as compared to the corresponding chloroaluminate ILs. However, the acidity of [(C2H5)3NH]-based ILs with the mixed-metal anions are greater than that of the net chloroaluminate ILs. The Fukui function values showed that most of the mixed chlorometallate ILs belong to bifunctional distribution. The mixed chlorometallate ILs both have electrophilic and nucleophilic sites, which would be beneficial for their applications.

The Catalytic Performance Study of Chloroaluminate Ionic Liquids on Long-Chain Alkenes Alkylation

Friedel–Crafts alkylation of long-chain alkenes (mixed C16–24 olefins) with toluene catalyzed by chloroaluminate ionic liquids was investigated systematically in this work. The catalysts were chara...

Interaction of 3D Conductive Polymer-Reticulated Vitreous Carbon Composites in Ionic Liquid As Energy Storage Material

Energy storage technologies, which combine high specific energy and power with sustainability and low costs, are fundamental drivers for an energy sustainable society. Conductive polymers in highly stable and non-toxic ionic liquid (IL) electrolytes have been proposed as possible systems that combine these advantages. Recently, it has been demonstrated that poly(3,4-ethylenedioxythiophene) (PEDOT) can undergo a redox reaction like in a battery and at the same time perform the characteristics of a capacitor by being doped/charged (de-doped/discharged) by anions from the IL. The storable amount of charges depends on the generated doping/de-doping sites in the polymer, which is a function of the electrode potential. These so called “hybrid-battery-capacitor” system combines the faradaic and capacitive properties in a single electrode [1,2], providing the possibility to improve cell voltages and energy densities. High surface area materials such as three-dimensional conductive reticulated vitreous carbon (RVC) substrate, provide large surface area for electro-polymerisation of a thin film nano/micro-porous PEDOT active material (“footprint-area” [3]). The resulting composite has large capacitance supported by the rigid carbon substrate which helps to stabilise the typical swelling/contraction process observed in conducting polymers during the electrochemical charge/discharge process. This study focuses on the synthesis and characterisations of thin electro-active PEDOT films on RVC substrates by electro-polymerisation in IL. The polymer synthesis produced a uniform film on the RVC with a high number of doping/de-doping sites in Lewis neutral 1-ethyl-3-methylimidazolium chloride aluminum chloride (EMImCl-AlCl3) IL with AlCl4 - as doping/de-doping anion. The interaction of the conductive polymer films with the ionic liquid electrolyte are characterised by combined in-operando atomic force microscopy (AFM) and electrochemical quartz crystal microbalance measurements (EQCM), distinguishing the predominant battery or capacitor behaviour per doping/de-doping site and the correlated changes of the polymer structure as function of the electrode potential. [1] Chemical Reviews 110 (2010) 4724–4771. [2] Chemical Society Reviews 44 (2015) 1777–1790. [3] Advanced Materials 26 (2014) 2440–2445. Graphical abstract: (A-C) PEDOT electro-polymerised on RVC and (D) schematic illustration of the three-dimensional RVC-PEDOT composite, which is doped (charged) and de-doped (discharged) with AlCl4 - anions of a chloroaluminate ionic liquid. Figure 1

Solvation effect of [BMIM]Cl/AlCl3 ionic liquid electrolyte

Four kinds of solvents, methylene chloride (CH2Cl2), toluene (TOL), ethyl acetate (EtoAc), and dimethyl carbonate (DMC), were added into the 1-butyl-3-methylimidazolium chloroaluminate ionic liquid ([BMIM]Cl/AlCl3 IL) to improve the property of the IL-based electrolyte for aluminum (Al) electrolysis. Solvation effects of these solvents on the physical properties, electrochemical properties, and electroactive ion of the [BMIM]Cl/AlCl3 IL-based electrolyte were investigated. It was found that the viscosity of the IL electrolyte decreased after adding CH2Cl2 or TOL, and the conductivity increased while the change of the conductivity and the viscosity moved in the opposite direction with the addition of EtoAc or DMC. The UV-Vis spectra showed that the electroactive Al ion continued existence after adding CH2Cl2 or TOL, but there was solvation effect between TOL and BMIM+. On the other hand, both EtoAc and DMC had solvation effects with electroactive Al ion and BMIM+. The results illustrated that solvation effect was the key effect on the reduction of Al on the cathode, and further influenced the morphology of the Al deposits. In addition, the concentration polarization reduced and the efficiency of electrolysis improved after adding CH2Cl2 or TOL. Furthermore, bright Al coatings were obtained finally by adding CH2Cl2 into [BMIM]Cl/AlCl3 IL electrolyte (when the mole ratio of CH2Cl2 is around 66.7~75%).

Deactivation mechanism and activity-recovery approach of composite ionic liquids for isobutane alkylation

The deactivation mechanism and the activity recovery approach of composite ionic liquid (CIL), a kind of acidic chloroaluminate ionic liquids (ILs) modified with CuCl for the in 2013 successfully commercialized catalysis of isobutane alkylation are being discussed in this paper. CIL showed catalytic activity only in the presence of both Brønsted and Lewis acids. CIL deactivation was caused by the loss of Brønsted acidity and/or Lewis acidity. Brønsted acidity decreased by the loss of trace amount of formed chlorohydrocarbons with the outflowing alkylate. Lewis acidity was deactivated mainly due to the complexation of the formed acid soluble oil (ASO) with the CIL anions. Brønsted acidity was maintained by the continuous addition of hydrogen chloride (HCl) or tert-butyl chloride, and Lewis activity was recovered by AlCl3 addition. However, Brønsted acidity could not be recovered when Lewis acidity was lost and was thus dependent on Lewis acidity. Furthermore, ASO interacted with active components of CIL, causing the loss of copper via precipitation of CuCl which is the major contributor to the high selectivity. Therefore, CuCl was added simultaneously with AlCl3 to maintain the high selectivity of alkylate.

Polypyrenes as High-Performance Cathode Materials for Aluminum Batteries.

The pressing need for low-cost and large-scale stationary storage of electricity has led to a new wave of research on novel batteries made entirely of components that have high natural abundances and are easy to manufacture. One example of such an anode-electrolyte-cathode architecture comprises metallic aluminum, AlCl3 :[EMIm]Cl (1-ethyl-3-methylimidazolium chloride) ionic liquid and graphite. Various forms of synthetic and natural graphite cathodes have been tested in recent years in this context. Here, a new type of compelling cathode based on inexpensive pyrene polymers is demonstrated. During charging, the condensed aromatic rings of these polymers are oxidized, which is accompanied by the uptake of aluminum tetrachloride anions (AlCl4- ) from the chloroaluminate ionic liquid. Discharge is the fast inverse process of reduction and the release of AlCl4- . The electrochemical properties of the polypyrenes can be fine-tuned by the appropriate chemical derivatization. This process is showcased here by poly(nitropyrene-co-pyrene), which has a storage capacity of 100 mAh g-1 , higher than the neat polypyrene (70 mAh g-1 ) or crystalline pyrene (20 mAh g-1 ), at a high discharge voltage (≈1.7 V), energy efficiency (≈86%), and cyclic stability (at least 1000 cycles).

Development and application of composite ionic liquid catalyzed isobutane alkylation technology

Alkylate from isobutane alkylation is an ideal blending component of motor gasoline. In China its blending ratio in gasoline is continuously increased with upgrading the gasoline quality standards. A series of studies on ionic liquid catalyzed isobutane alkylation were carried out around a new industrial process of alkylate production. The composition, structure and catalytic performance of chloroaluminate ionic liquids were studied, and a composite ionic liquid (CIL) with high catalytic activity and high selectivity was designed and synthesized. The deactivation mechanism of CIL during isobutane alkylation was studied and a feasible regeneration scheme was developed, including a Lewis acid activity monitoring method of chloroaluminate ionic liquids. A long period (2 months) operation test was carried out in a pilot plant, and then the initial process development of CIL catalyzed isobutane alkylation technology (CILA) was completed. A new type static mixing reactor and a hydrocyclone were developed. The first industrial plant of CILA was designed and constructed. The plant includes feed pretreatment, alkylation reaction, catalyst regeneration, product separation and clean-up systems. The industrial operation results were excellent. Butene conversion reached 100%, research octane number of alkylate maintained stably at above 95 and could reached up to above 98 at optimal operating conditions, end boiling point of alkylate was below 198 °C, and Cl content in alkylate was below 5 mg/L. CILA can produce clean alkylate with clean process, having a good application prospect and promotion value.

Electro-polymerisation of 3,4-ethylenedioxythiophene on reticulated vitreous carbon in imidazolium-based chloroaluminate ionic liquid as energy storage material

This work shows the electro-polymerisation of thin film poly(3,4-ethylenedioxythiophene) on three-dimensional reticulated vitreous carbon substrates by cyclic voltammetry and pulsed polymerisation methods from a Lewis neutral chloroaluminate ionic liquid containing 3,4-ethylenedioxythiophene monomer. The polymer composite is attractive as an energy storage electrode for sustainable and high-performance technologies due to its unique properties of battery and capacitor in one system, i.e., the redox reaction occurring simultaneously with the anion doping/de-doping of the conductive polymer with AlCl4− ionic species contained in the ionic liquid. The structure of the polymer films, their doping/de-doping mechanism and the stability in the ionic liquid were characterised by scanning electron microscopy and cyclic voltammetry and compared with films electro-polymerised on planar vitreous carbon. The typical granular and nano/micro-porous polymer structure observed on planar vitreous carbon was successfully replicated on the macro-porous reticulated vitreous carbon surface. The polymer films show approximately 45% higher capacity than films on planar substrates and similar efficient redox behaviour, proving that the material has hybrid battery-capacitor properties enhanced by the higher area per unit volume of reticulated vitreous carbon.

Aluminum Chloride-Graphite Batteries with Flexible Current Collectors Prepared from Earth-Abundant Elements.

In the search for low‐cost and large‐scale stationary storage of electricity, nonaqueous aluminum chloride‐graphite batteries (AlCl3‐GBs) have received much attention due to the high natural abundances of their primary constituents, facile manufacturing, and high energy densities. Much research has focused on the judicious selection of graphite cathode materials, leading to the most notable recent advances in the performance of AlCl3‐GBs. However, the major obstacle to commercializing this technology is the lack of oxidatively stable, inexpensive current collectors that can operate in chloroaluminate ionic liquids and are composed of earth‐abundant elements. This study presents the use of titanium nitride (TiN) as a compelling material for this purpose. Flexible current collectors can be fabricated by coating TiN on stainless steel or flexible polyimide substrates by low‐cost, rapid, scalable methods such as magnetron sputtering. When these current collectors are used in AlCl3‐GB coin or pouch cells, stable cathodic operation is observed at voltages of up to 2.5 V versus Al3+/Al. Furthermore, these batteries have a high coulombic efficiency of 99.5%, power density of 4500 W kg−1, and cyclability of at least 500 cycles.

Electro-polymerisation and characterisation of PEDOT in Lewis basic, neutral and acidic EMImCl-AlCl3 ionic liquid

This work studied the electro-polymerisation of 3,4-ethylenedioxythiophene (EDOT) and its electrochemical behavior in Lewis acidic, neutral and basic chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride aluminum chloride (EMImCl-AlCl3) by cyclic voltammetry. It was found that the electro-polymerisation on vitreous carbon only occurs in Lewis neutral EMImCl-AlCl3 as a dark blue-violet film whereas the electro-polymerisation in a Lewis acidic or basic compositions is not possible due to the interactions between the conductive polymer and the ionic liquid as well as the potential stability limits of the electrolyte. PEDOT films synthesised in Lewis neutral ionic liquid were tested in monomer-free Lewis acidic, basic and neutral EMImCl-AlCl3 and show different doping and de-doping behavior for chloride ionic species. The PEDOT films in a Lewis neutral composition showed higher doping levels due to the higher potential stability window, up to 2.6 V vs. Al|Al(III) than in a Lewis acidic and basic solutions. Furthermore, it was shown that the doping and de-doping levels are predefined during the electro-polymerisation of PEDOT. The anion doping and de-doping reaction reached 97% reversibility in the neutral composition, which suggests that PEDOT is a suitable electrode material to store charged species in this media and could be used in rechargeable energy storage devices.

Communication—Light-Induced Plating of Aluminum on Silicon in a Lewis Acidic Chloroaluminate Ionic Liquid

Conventional electroplating of aluminum on silicon often requires a seed layer to overcome the high resistivity of the substrate. In this paper, light-induced plating of aluminum directly on a silicon substrate in an ionic liquid is reported. Without any seed layer, the deposited aluminum has good adhesion to the silicon surface. The resistivity of the aluminum deposits is as low as 4 × 10−6 Ω-cm, which is only about 1.5 times that of bulk aluminum. The suitable wavelength for the light source is 600 nm to 1,000 nm. The effect of plating temperature on morphology of the aluminum deposits is analyzed.