Cl Ionic Liquid Research Articles

Electrodeposition of Stoichiometric CdTe from a Reusable Ionic Liquid Bath

Electrodeposition (ED) from ionic liquid (IL) medium is of much importance because a variety of architectures can be synthesized by IL assisted growth. However, these liquids are relatively new for the fabrication of compounds and alloys with a great control over the stoichiometry and thickness. In this regard a well-defined route needs to be established for their wider acceptance as greener alternatives to deposit materials like CdTe, CdS, CdSe, etc. via ED. In this article, we have discussed the prerequisites, tricks and methodology to develop stoichiometric CdTe thin films from IL medium with required thicknesses in a highly controlled way compared to conventional ED techniques. This method provides a greener alternative to aqueous electrolytes which are considered to be hazardous media for the ED of CdTe films. We have found that the required precursor ratio of Te:Cd can be lower down to 1:10 for [Bmim]Cl IL medium which is 1:1000 for the aqueous electrolytes. As-grown nanostructured CdTe films can be directly utilized for the devices like IR sensors, Schottky rectifiers and Solar cells without any post-annealing. Moreover, the aspect ratio of nanostructures can be tuned by changing the precursors’ ratio in IL bath. Nevertheless, IL can be reused multiple times to develop identical thin films which guarantee the low cost pathway.

Mechanistic understanding of humin formation in the conversion of glucose and fructose to 5-hydroxymethylfurfural in [BMIM]Cl ionic liquid.

Humin formation is one of the key issues that hinders economical 5-HMF production from hexose sugars such as glucose and fructose. In this work, the mechanism of humin formation in glucose/fructose conversion to HMF was studied in an ionic liquid system (1-butyl-3-methylimidazolium chloride, [BMIM]Cl) with CrCl3 as the catalyst. Elemental analysis, XRD, FT-IR, and TEM were applied to study the molecular structure and morphology of the solid humins. The possible intermediates to form solid humins were investigated by HPLC-MS. We synthesized furanic model compounds that mimic the experimentally identified humin intermediates to investigate the mechanism of humin growth at an early stage. The results showed that a furan compound bearing a hydroxymethyl and an electron-donating group was unstable due to three types of reactions: (1) bimolecular ether formation reactions; (2) intermolecular addition reaction; (3) furan ring opening reaction with water. The stability of a furan compound in [BMIM]Cl was increased when the hydroxymethyl group of a furan compound was protected by a methyl group, and the stability was further enhanced with an additional electron-withdrawing group (such as an aldehyde group) on the furan ring. Protecting the hydroxymethyl group of 5-HMF with a methyl group allows easy separation of the products from the [BMIM]Cl solvent through extraction.

1-Butyl-3-Methylimidazolium Chloride Ionic Liquid as Inhibitor for Corrosion Protection of Mild Steel in Acidic Media

Corrosion inhibitor is a substance added to the corrosive environment in small quantities to reduce the corrosion a metal. The addition of inhibitors will reduce the corrosion rate of the metal by retarding the corrosion process on the metal surface. Thus, this study focused on the study of the effectiveness of 1- butyl-3-methylimidazolium chloride ([EMIM]Cl) ionic liquid as an inhibitor for corrosion protection of mild steel. Two different concentrations of [EMIM]Cl (0.05 M and 0.5 M) were tested into different concentrations of sulphuric acid (0.05M, 0.10 M, 0.15 M, 0.20 M and 0.25 M). Weight loss measurement was used to determine the effectiveness of the [EMIM]Cl as inhibitor for corrosion protection. Results showed that acid concentrations play an important role for the corrosion protection process in the presence of the inhibitor. The weight loss increases as the concentration of the acid increased. The study also revealed that the concentrations of [EMIM]Cl ionic liquid effect the performance of the inhibitor. From this study, 0.5 M of [EMIM]Cl ionic liquid shows better corrosion performance compared to 0.05 M of [EMIM]Cl. At 0.25 M of sulphuric acid, the weight loss of untreated metal increased drastically from 0.0075 g at 0.5 hour to 0.0974 g at 24 hours. After treated with 0.5 M of [EMIM]Cl, the weight loss measurement slightly increased from 0.0027 g at 0.5 hour to 0.0179 g at 24 hours. This weight loss value is lower compared to mild steel treated with 0.05 M [EMIM]Cl which is 0.0469 g at 24 hours. The performance of the inhibitor in two different type of acid was also investigated. The morphology of the untreated mild steel and mild steel treated with [EMIM]Cl was investigated by scanning electronic microscopy (SEM)

Graphite/copper phthalocyanine composite cathode for overcharge protection and gas evolution suppression in aluminum-ion batteries at room temperature

A rechargeable aluminum-graphite battery based on the conventional AlCl3−[EMIm]Cl ionic liquid electrolyte exhibits excellent electrochemical performance, but the relatively narrow electrochemical window (1–2.45 V vs. Al/Al3+) at room temperature. Therefore, overcharge and safety hazards could limit the operation of such batteries. In this study, the authors proposed the addition of organic compounds to the graphite cathode to improve protection when the battery is overcharged. In particular, copper phthalocyanine (CuPc) and natural graphite flakes were combined to form a novel cathode material that effectively increases the working potential window up to 2.82 V (vs. Al/Al3+). In the conventional graphite cathode, the specific capacity was reduced by 66.7% after 200 charge/discharge cycles in the range of 1–2.82 V, accompanied by obvious pouch swelling. After the addition of CuPc to the graphite cathode, no significant capacity degradation (less than 10%) was observed after 200 cycles, and the specific capacity decay was below ∼25% for the first 1000 cycles. Notably, the swelling phenomenon did not occur after 1000 charging/discharging cycles when the CuPc/graphite composite cathode was used.

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

WITHDRAWN: Electrodeposition of CdTe from a reusable ionic liquid bath

Abstract Electrodeposition (ED) from ionic liquid (IL) medium is of much importance due to a variety of architectures can be synthesized by IL assisted growth. However, these liquids are relatively new for the fabrication of compounds and alloys with a great control over the stoichiometry and thickness. In this regard a well-defined route needs to be established for their wider acceptance as greener alternatives to deposit materials like CdTe, CdS, CdSe, etc. via ED. In this MethodsX article, we have discussed the prerequisites, tricks and methodology to develop stoichiometric CdTe thin films from IL medium with required thicknesses in a highly controlled way compared to conventional ED techniques. This method provides a greener alternative to aqueous electrolytes which are considered to be hazardous media for the ED of CdTe films. We have found that the required precursor ratio of Te:Cd can be lower down to 1:10 for [Bmim]Cl IL medium which is 1:1000 for the aqueous electrolytes. As-grown nanostructured CdTe films can be directly utilized for the devices like IR sensors, schottky rectifiers and solar cells without any post-annealing. Moreover, the aspect ratio of nanostructures can be tuned by changing the precursors’ ratio in IL bath. Nevertheless, IL can be reused multiple times to develop identical thin films which guarantee the low cost pathway. • Nanostructured CdTe thin films • Low cost • Reuse of ionic liquid

Porous α‐MnSe Microsphere Cathode Material for High‐Performance Aluminum Batteries

AbstractAluminum batteries (ABs) have been considered as a viable candidate for new‐generation energy‐storage devices due to its low cost and high theoretical volumetric capacity. Despite these advantages, the large‐scale application of ABs is constrained by scarce options of suitable cathode materials. Herein, three‐dimensional nanostructured α‐MnSe microspheres with porous properties are reported as a cathode for ABs. The nanosized and porous structure of α‐MnSe could offer numerous open channels and the short ionic transport path, which would efficiently mitigate volume changes and enhance electrochemical reaction kinetics. Moreover, the pseudocapacitive characteristic of Al3+ storage in α‐MnSe contributes to the fast kinetics of the cathode. It is demonstrated that the reversible Al3+ insertion/extraction occurs in the α‐MnSe cathode during the cycling process. The resulting aluminum battery based on the α‐MnSe cathode, AlCl3/[EMIm]Cl ionic liquid electrolyte, and aluminum anode exhibits an ultrahigh reversible capacity of 408 mA h g−1 at 0.2 A g−1. Even for a current density at 1 A g−1, a discharge capacity of 131 mA h g−1 could be retained with a Coulombic efficiency of 97 % over 150 cycles. This strategy has referential significance in aspects of the selection of compatible cathode for ABs.

Effect of Lewis and Brønsted Acids on Conversion of Chitin Monomer &lt;i&gt;N&lt;/i&gt;-Acetyl-D-Glucosamine (GlcNAc) to Furan Derivatives in [Bmim]Cl Ionic Liquid

Effect of Lewis and Brønsted Acids on Conversion of Chitin Monomer &lt;i&gt;N&lt;/i&gt;-Acetyl-D-Glucosamine (GlcNAc) to Furan Derivatives in [Bmim]Cl Ionic Liquid

Magnetic hydrogel derived from wheat straw cellulose/feather protein in ionic liquids as copper nanoparticles carrier for catalytic reduction

Magnetic hydrogel derived from wheat straw cellulose (WSC) and feather protein (FP) was successfully derived from [Bmim]Cl ionic liquids for copper nanoparticles carrier to prepare magnetic hydrogel-Cu (m-WSC/FP-Cu). Morphology, structure and component of m-WSC/FP-Cu were characterized by different techniques (SEM, TEM, XRD, FTIR, VSM, etc.). The activity of m-WSC/FP-Cu were evaluated by employing them as catalysts for the reduction of 2-nitrobenzoic acid (2-NA) to a useful industrial intermediates, 2-aminobenzoic acid (2-ABA). Effect of experimental conditions, including m-WSC/FP-Cu dosage, 2-NA initial concentration, NaBH4 dosage and temperature, were investigated. The m-WSC/FP-Cu exhibited maximum catalytic activity under conditions of 1.00 g m-WSC/FP-Cu, 100 mg/L 2-NA and 0.3 g NaBH4. Besides, higher activity of m-WSC/FP-Cu was obtained at higher temperature. The activity of m-WSC/FP-Cu maintained 99.02% over 5 cycles utilization and 90.60% after 30 days storage, which exhibited excellent recyclability and stability. It is expected that the m-WSC/FP-Cu have the potential for treating organic wastewater cooperated with a catalyst regeneration device.

Real-Time Imaging Analysis on Dendrite Formation of Aluminium Metal Anodes

In recent years, rechargeable batteries are one of the most attractive options for both grid electrical energy storage and electrical vehicle (EV) applications due to the steadily increasing demands. Aluminum is the most abundant metal in the earth’s crust. Rechargeable aluminum-ion batteries (AIBs) is a promising research for future energy storage technologies due to its impressive advantages such as high anode capacity (gravimetric capacity of 2980 mAh g−1, and volumetric capacity of 8040 mAh cm−3), cost effectiveness, and safety. A recent study reported by Dai et al. cooperate with ITRI opened a new stage for this topic by employing an AlCl3/[EMIm]Cl ionic liquid electrolyte and graphitic cathode. This pioneering work has been stimulating various research enthusiasms in aluminum-ion batteries (AIBs). At present, there are multiple challenges that need to be overcome in AIBs, including, for example, decomposition of the electrolyte material, small charge-discharge voltage window of the battery, and small energy/power densities, (compared with commercially available lithium batteries). The occurrence of aluminum dendrites, which could cause safety hazards, on the other hand, has not drawn sufficient attention. In this study, we studied in real-time using optical microscopy the occurrence of dendritic aluminum electrochemical plating and its dendrite formation mechanisms. In particular, extensive real-time optical microscopy imaging and post mortem SEM analyses are carried out in conjunction with electrochemical characterizations to reveal the underlying mechanisms for the resulting effects. Figure 1

Ionic liquids with polychloride anions as effective oxidants for the dissolution of UO2.

Herein, polychloride ([Cl3]- or/and [Cl5]-) ionic liquids (ILs) were prepared from their imidazolium chloride precursors by the addition of chlorine gas. The highest storage ability of Cl2 was found in the [Bmim]Cl IL among the six imidazolium chlorides [Rmim]Cl (Rmim = Emim, 1-ethyl-3-methylimidazolium; Bmim, 1-butyl-3-methylimidazolium; Pmim, 1-propyl-3-methylimidazolium; Pnmim, 1-pentyl-3-methylimidazolium; Hmim, 1-hexyl-3-methylimidazolium; and Omim, 1-octyl-3-methylimidazolium). When a mixed IL of [Bmim][Tf2N] (1-butyl-3-methylimidazolium bistriflimide) and [Bmim]Cl was used, the IL cation could maintain good stability during the chlorination process, and the imidazolium cation [Bmim]+ could retain almost the same structure after the chlorine gas was introduced into the mixed IL according to 1H NMR spectroscopy. It has been found that the synthesized polychloride ILs not only can successfully dissolve UO2, but can also decrease the consumption of Cl2 and increase the chlorine efficiency. Spectroscopy studies indicate that [UO2Cl4]2- is the principal product in the IL reaction solution. The dissolved uranyl species can be easily recovered from the ILs by crystallization in the form of [Bmim]2[UO2Cl4]. Moreover, even if 57.1 wt% of the lanthanide element, when compared with the total amount of dissolved uranium and lanthanide elements, was dissolved in the IL mixture, only uranium-containing crystals could be isolated from the system.

Aluminum Patterned Electroplating from AlCl₃⁻[EMIm]Cl Ionic Liquid towards Microsystems Application.

Electroplating process is being used to deposit a relatively thick film of metallic materials for various microsystems applications, such as for the wafer-level bonding sealing frame and as a thermal actuator. Recently, the Al electroplating process from ionic liquid has been an attractive deposition method for anti-corrosion coatings. To extend the utilization of the film, in particular for microsystems application, a microstructure formation by patterned electroplating of Al from AlCl–1-ethyl-3-methylimidazolium chloride ((EMIm)Cl) ionic liquid is investigated in this study. The influences of each deposition parameters to the electroplating process as well as the resulting surface morphology are evaluated. Electroplated Al deposits on both Au and Al seed layers are both studied. It is also found that a recurrent galvanic pulse plating process yields in a higher current efficiency. Finally, Al electroplating on a 2 µm-trenched 100 mm-wafer is also demonstrated.

Extraction of Palladium(II) and Platinum(IV) from Hydrochloric Acid Solutions with Trioctylammonium Nitrate Ionic Liquid without Dilution

The fundamental properties and extraction capability of an ionic liquid (IL), trioctylammonium nitrate ([HTOA][NO3]), for PdII and PtIV, are investigated. At room temperature, [HTOA][NO3] is a solid (melting point: 30.7 °C), but it becomes a liquid (melting point: 16.7 °C) when saturated with water. Water-saturated [HTOA][NO3] exhibits a viscosity of 267.1 mPa·s and an aqueous solubility of 2.821 × 10−4 mol·dm−3 at 25 °C, and can be used as an extraction solvent without dilution. [HTOA][NO3] exhibits an extremely high extraction capability for PdII and PtIV in dilute hydrochloric acid (0.1–2 mol·dm−3 HCl); the distribution ratio reaches 3 × 104 for both the metals. From electrospray ionization mass spectrometry analysis, the species extracted in the IL phase are [PdCl3]− and [PdCl2(NO3)]− for PdII and [PtCl6]2− and [PtCl5]− for PtIV. A majority of the other transition metals are considerably less or marginally extracted into [HTOA][NO3] from a 0.1 mol·dm−3 hydrochloric acid solution. The extraction capacity of [HTOA][NO3] is greater than that of other hydrophobic ILs such as [HTOA]Cl and bis(trifluoromethanesulfonyl)imide-based ILs. The metals extracted into the IL phase are quantitatively back-extracted using an aqueous solution containing thiourea and nitric acid. By controlling the thiourea concentration and shaking time, PdII and PtIV are mutually separated to some extent in the back extraction process. The IL phase used for the back extraction can be reused for the forward extraction of these metals after scrubbing it with an aqueous nitric acid solution.

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).

Non-aqueous rechargeable Al–O2 battery with a bifunctional catalyst of carbon microspheres

ABSTRACTNon-aqueous secondary Al-O2 batteries have recently received much attention due to their high theoretical capacity, element richness, safety and low cost, although there are still many problems to be overcome. In this paper, a type of Al-O2 battery using AlCl3/[EMIm]Cl ionic liquid as electrolyte and carbon microspheres (CMs) as air electrode was considered. The batteries with CMs deliver a high specific capacity of 820 mAh g−1 in the first cycle at the current density of 25 mA g−1 and a low charge voltage. In addition, CMs show better redox catalytic activity for O2 compared with super-p (SP) and the Al-O2 batteries have two obvious oxygen reduction processes corresponding to two reductive peaks.

Green bio‐based synthesis of Fe2O3@SiO2‐IL/Ag hollow spheres and their catalytic utility for ultrasonic‐assisted synthesis of propargylamines and benzo[b]furans

A novel magnetic hybrid system containing nano‐magnetic Fe2O3 hollow spheres, silica shell, [pmim]Cl ionic liquid and silver nanoparticles was synthesized and characterized. The silver nanoparticles were prepared via biosynthesis using Achillea millefolium flower as reducing and stabilizing agent. The hybrid system was successfully used as an efficient and reusable catalyst for promoting green ultrasonic‐assisted A3 and KA2 coupling reactions as well as benzo[b]furan synthesis. It was found that decoration of the magnetic core with non‐magnetic moieties decreased the maximum saturation magnetization. However, the catalyst was still superparamagnetic and could be simply separated from the reaction mixture using an external magnet. The heterogeneous nature of the catalyst was also confirmed by studying its reusability and stability and the leaching of silver. Use of aqueous media, high yields, short reaction times, broad substrate tolerance and low required amount of catalyst are the merits of this protocol.

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

Novel Carbon-Based Intercalation Structures for Rechargeable Aluminum Batteries

Rechargeable aluminum-metal batteries promise low cost and and high energy density, as aluminum metal has a theoretical volumetric capacity (8040 mAh/cm3) that is almost four times higher than lithium metal. Various cathode materials (e.g., V2O5 nanowires, Mo6S8, etc.) have been shown to reversibly intercalate aluminum ions, but obstacles such as low working voltages, self-discharge, and low mobilities of intercalated ions are typically observed. Novel graphite-based cathodes have recently been developed that exhibit high cyclability, good discharge voltage plateaus (ca. 2 V), and high rate performances when paired with aluminum anodes and a AlCl3/[EMIm]Cl ionic liquid electrolyte. However, the relationship between the local carbon structure and electrochemical properties of the electrodes is not well understood. Here, we report novel graphene-based electrodes that exhibit high specific capacity (e.g., >100 mAh/g at a current density of 66 mA/g) and discuss how the structural features of various carbon-based cathodes (e.g. synthetic, natural, and exfoliated graphite compounds) correlate with the electrode’s electrochemical properties and cell performance. Galvanostatic cycling and cyclic voltammetry analyses were performed to track electrode performance at various current densities, cycle numbers, and states-of-charge. Ex situ solid-state magic-angle-spinning (MAS) NMR spectroscopy was used to probe the local environments, relative populations, and dynamics of chloroaluminate and solvent species within the carbon electrodes, while X-ray diffraction and electron microscopy were conducted to analyze how the intercalation processes affected their local structures, periodic layering, and morphologies. These studies seek to unveil correlations of local carbon structure with electrochemical performance to aid the development of rechargeable aluminum-carbon batteries.

Intercalation Cathodes for Rechargeable Aluminum-Ion Batteries

Rechargeable aluminum batteries have been a topic of great interest as aluminum metal has a high volumetric capacity and is the most abundant metal in the earth’s crust. However, few crystalline materials have been shown to reversibly intercalate aluminum ions into their structures. Recently, it has been shown that aluminum ions can reversibly intercalate/de-intercalate into the Chevrel Mo6S8 phase and the spinel Mn2O4 compound. However, the intercalation mechanisms are not well understood, particularly for the spinel Mn2O4, in part due to poor capacity retention and slow solid-state diffusion of the highly charged tri-valent aluminum ions within these crystalline structures. Better understanding of the intercalation mechanism of aluminum ions into these materials, including the dynamics and populations of aluminum ions, is important for the design and optimization of next-generation intercalation electrodes for aluminum batteries. Our research has focused on these intercalation electrode materials for use in aluminum batteries with AlCl3/[EMIm]Cl ionic liquid electrolyte to study the intercalation process of aluminum ions into crystalline host structures. Cyclic voltammetry was performed at low scan rates to identify oxidation and reduction peaks corresponding to different intercalation sites during the charge-discharge process. Galvanostatic cycling was performed to observe capacity retention at different current densities. Ex situ multi-dimensional solid-state 27Al magic-angle-spinning (MAS) NMR spectroscopy was used to observe changes in the populations and local environments of the aluminum ions, as well as their dynamics. X-ray diffraction and electron microscopy were also used to analyze structural changes in the cathode materials as a function of state-of-charge. Our studies shed light on the intercalation mechanisms of aluminum ions in crystalline transition metal oxide and sulfide host structures.

Polyaniline/sugarcane bagasse derived biocarbon composites with superior performance in supercapacitors

A coral-like polyaniline/activated biocarbon (PANI/AB) composites were prepared via in-site polymerization method. First, the activated biocarbon (AB) was derived from sugarcane bagasse, and then, the PANI/AB composites were obtained using AB as the scaffolds for PANI growth and [CMMIm]Cl ionic liquid as dopant. The results indicated that chemical composition and microstructure of PANI/AB were closely related to the mass ratio of aniline monomer (An) and AB, and which further impacted electrochemical performance of PANI/AB profoundly. Especially, the PANI/AB-4 (the mass ratio of An/AB is 40) exhibited a highest specific capacitance of 447Fg−1 at a current density of 0.5Ag−1. Furthermore, the asymmetric two-electrode system based on PANI/AB-4 as positive electrode and AB as negative electrode is successfully assembled with a voltage window of 0–1.6V, exhibiting high energy density (27.3Whkg−1) and power density (800Wkg−1), and excellent cycling stability (87% capacitance retention after 2000cycles).