Ionic Liquid Analogues Research Articles

(Digital Presentation) Electrode and Electrolyte Materials for Thin Film Microbatteries

Electrode and Electrolyte Materials for Thin Film Microbatteries, Aaron O’Donoghue, Louise McGrath, Ian Povey and James Rohan In this work we assess the electrochemical performance of electrodeposited, binder-free V2O5 thin films with Li metal anodes in liquid and polymer gel electrolytes based on a pyrrolidinium based ionic liquid (C4mpyrTFSI). Coulombic efficiencies >99%, with electrode capacities >120 mAh g-1 are obtained in cyclic voltammetry analysis of crystalline V2O5 with C4mpyr-based Ionic liquid (IL) electrolytes. A polymer gel electrolyte suited to layer by layer microbattery fabrication was synthesised and tested with the crystalline V2O5 and gave large electrode capacities at a relatively high rate (110 mAh g-1 at 2 C) similar to those obtained in liquid electrolytes. Stable long-term cycling (up to 400 cycles) is obtained with Li metal anodes without capacity fade or short circuits developing in either the VC containing IL or the polymer gel analogue. In addition, no V2O5 deterioration is observed with the polymer gel electrolyte as the capacity recovered to ~125 mAh g-1 after cycling at 5 C.Furthermore, we assess surface modification of V2O5 by depositing 3nm Al2O3 via ALD which has been shown to improve the charge-discharge kinetics of oxide electrode materials. Coulombic efficiencies >99%, with peak electrode capacities >120 mAh g-1 are obtained and long-term cycling stabilities up to 625 cycles.1) L. M. McGrath and J. F. Rohan, Batteries & Supercaps, 4 (2021) 485 – 492, High rate lithium ion cycling in electrodeposited binder-free thin film vanadium oxide cathodes with lithium metal anodes in ionic liquid and polymer gel analogue electrolytes.2) L. M. McGrath and J. F. Rohan, Molecules, (2020), 25. 6002, Pyrrolidinium containing ionic liquid electrolytes for Li-based batteries.3) T. Teranishi, Y. Yoshikawa, M. Yoneda, A. Kishimoto, J. Halpin, S. O’Brien, M. Modreanu and I. M. Povey, (2018), ACS Applied Energy Materials, 1(7), pp. 3277-3282, Aluminum Interdiffusion into LiCoO2 Using Atomic Layer Deposition for High Rate Lithium Ion Batteries. Figure 1: Charge/Discharge capacity of 3nm Al2O3 coated V2O5 vs Li foil in 1M LiPF6 in EC:DEC (1:1) Figure 1

Physicochemical and acoustic characterization of binary mixtures of tetraalkylammonium bromide: PEG based DES and water

In modern green chemistry, Deep eutectic solvents (DESs) have gain appreciable recognition as an analogues of ionic liquids (ILs) due to inexpensive and easy to handle preparation method. DESs exhibit similar physiochemical properties to ILs and considered as a suitable alternative to volatile organic solvents. In present study, DESs were formulated by complexing HBA: Tetraethylammonium bromide and Tetrapropylammonium bromide and HBD: Polyethylene glycol of average molecular weight (200/400/600) in 1:2 M ratio. The densities (ρ), speeds of sound (u) of pure DESs and their binary mixtures with H2O were collected as a function of DES concentration and temperature. The excess molar properties: VmE and Ks,mE were calculated using these data and fitted to the Redlich-Kister equation to estimate standard deviation between the experimental and calculated values of excess molar properties. The trends of variation in calculated values of VmE and Ks,mE were interpreted in light of temperature and DES: H2O interactions occurring within the binary mixtures. The PFPT (Prigogine-Flory-Patterson Theory) and ERAS (Extended Real Associated Solution Model) were applied to evaluate the validity of theories to predict VmE for presently studied binary mixtures.

Multiscale Structure of Poly(ionic liquid)s in Bulk and Solutions by Small-Angle Neutron Scattering

Poly(ionic liquid)s (PILs), similar to their ionic liquid (IL) analogues, present a nanostructure arising from local interactions. The influence of this nanostructure on the macromolecular conformation of polymer chains is investigated for the first time by means of an extensive use of small angle neutron scattering on a series of poly(1-vinyl-3-alkylimidazolium)s with varying alkyl side-chain length and counter-anion both in bulk and in dilute solutions. Radii of gyration are found to increase with the side-chain length in solution as a consequence of crowding interactions between neighboring monomers. In bulk, however, a non monotonic evolution of the radius of gyration reflects a change in chain flexibility and a potential screening of electrostatic interactions. Additionally at smaller scale, SANS provides an experimental estimation of both the chain diameter and the correlation length between neighboring chains, comparison of which unveils clear evidence of interdigitation of the alkyl side-chains. These structural features bring precious insights in the understanding of the dynamic properties of PILs.

Physical Properties of Betaine-1,2-Propanediol-Based Deep Eutectic Solvents.

Due to their splendid advantages, deep eutectic solvents have attracted high attention and are considered as analogues of ionic liquids. Deep eutectic solvents (DESs) are homogeneous mixtures formed by two or three green and cheap components through hydrogen bond, which is divided into hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD). Recently, Betaine has been widely used as a hydrogen bond acceptor. In this work, four DESs were synthesized by blending betaine as HBA and 1,2-propanediol as HBD in four molar ratios (1:3.5, 1:4, 1:5, 1:6). Then, the physical properties of these DESs were measured. The density values were measured within the temperature range (293.15 K to 363.15 K) at atmospheric pressure, whereas the surface tension and viscosity data were determined in four and seven temperatures between 293.15 K and 353.15 K. The relationship between the density and surface tension with temperature have been analyzed and have been fitted as a linear function. The commonly used Arrhenius model was used to describe the dependence between viscosity and temperature. The results of this study are important not only for the DESs’ industrial applications but also for the research on their synthesis mechanism and microstructure.

Choline chloride-based deep eutectic solvents for ultrasonic-assisted oxidative desulfurization of actual heavy crude oil

Deep eutectic solvents (DESs) are acquiring increasing interest as ionic liquid analogues because of their wide application, low-cost characteristics and environmentally friendly. In this study, choline chloride-based (ChCl) as a type of DESs were synthesized using polyethylene glycol (PEG), and applied to reduce sulfur content of actual heavy crude oil with sulfur content 37900 ppm (3.79 wt%). The synthesized DESs were characterized using Fourier-transform infrared spectroscopy (FTIR), as well as viscosity and density measurements. The DESs were evaluated for extractive ultrasound-assisted oxidative desulfurization (EUAODS), with 30 wt% H2O2 as the oxidant and formic acid as the catalyst. This study looked at the effects of oxidative desulfurization (ODS) and single ODS under ultrasonic treatment. Different systems for DESs were tested to find the desulfurization selectivity of the better reaction system; and it was found that extractive desulfurization (EDS) removed 24.57% of the sulfur, followed by extractive and ultrasonic-assisted desulfurization (EUADS) at 26.78%, then ODS at 37.28%, with ultrasonic-assisted oxidative desulfurization (EUAODS) providing the best result of 62%. According to the comparison trials, combining DESs with ultrasonic treatment improved processing. This study contributes to the body of information on the use of ultrasonic treatment in heavy crude oil desulfurization.

Revisiting the Physicochemical Properties and Applications of Deep Eutectic Solvents.

Recently, deep eutectic solvent (DES) or ionic liquid (IL) analogues have been considered as the newest green solvent, demonstrating the potential to replace harsh volatile organic solvents. DESs are mainly a combination of two compounds: hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD), which have the ability to interact through extensive hydrogen bonds. A thorough understanding of their physicochemical properties is essential, given their successful applications on an industrial scale. The appropriate blend of HBA to HBD can easily fine-tune DES properties for desired applications. In this context, we have reviewed the basic information related to DESs, the two most studied physicochemical properties (density and viscosity), and their performance as a solvent in (i) drug delivery and (ii) extraction of biomolecules. A broader approach of various factors affecting their performance has been considered, giving a detailed picture of the current status of DESs in research and development.

Molecular and Spectroscopic Insights into a Metal Salt-Based Deep Eutectic Solvent: A Combined Quantum Theory of Atoms in Molecules, Noncovalent Interaction, and Density Functional Theory Study.

Deep eutectic solvents (DESs) based on metal halide salts are highly catalytic, low toxic, reusable, cost-effective, and have higher thermal stability than their analogue ionic liquids (ILs). In this work, we have reported the formation mechanism of metal salt-based DESs at the molecular level along with their charge-transfer analysis and thermodynamics associated with their formation using density functional theory. The DES systems analyzed in the present work were choline chloride and tin(II)chloride (DES1) and choline chloride and zinc(II)chloride (DES2), both in a molar ratio of 1:2, respectively. An excellent correlation is obtained between the theoretically calculated IR spectra of the DES systems and the previously reported experimental findings for the formation of the complex systems. The DESs were found to be stable systems due to traditional hydrogen bonding and electrostatic interactions resulting in the ionic species [Sn2Cl5]- and [Zn2Cl5]- and are elucidated with the help of electronic structure calculations. CHELPG partial charge analysis and natural bond orbital analysis suggest a charge transfer from Cl- (chloride) to Ch+ (choline) and metal salts in the DES structures. The atom-in-molecules and noncovalent interaction (NCI) analysis suggest a strong electrostatic interaction within the DES2 system as compared to DES1. Higher stability and reactivity are observed in the DES2 system based on the frontier molecular orbital analysis. Our analysis offers important insights into the formation mechanism of these economic IL analogues.

Electrolyte Speciation and Electrochemical Performance of Idinium Based Ionic Liquid Analogues for Aluminium Battery Applications

The development of non-aqueous electrolyte chemistries for aluminium (Al) battery systems has recently received renewed attention to address some of the challenges associated with lithium-ion batteries. Of particular importance in this development is the electrolyte, which governs the battery chemistry. Chloroaluminate room temperature ionic liquid (RTIL) electrolytes made by mixing Lewis acidic aluminium chloride (AlCl3) salt with a (often chloride-containing) Lewis basic salt e.g. 1-ethyl-3-methylimidazolium chloride (EMIM-Cl), 1-butyl-3-methylimidazolium chloride (BMIM-Cl), and 1-butyl-1-methylpyrrolidinium chloride (BMP-Cl) have been studied. These tuneable electrolytes provide good thermal stability, good ionic conductivity, and a wide polarisable potential window. While these traits are advantageous the Lewis basic salt precursors are often very costly, challenging to synthesise and in some instances can be toxic. Recently, ionic liquid analogues (ILA) that are made from abundant, inexpensive and often non-toxic materials have begun to be explored. To date the two most common Lewis basic salts examined have been urea and acetamide (both contain oxygen functionality) but their rheological properties need to be improved to complete with the RTIL-based electrolytes.Our group has recently examined a range of different chloroaluminate ILA electrolytes, and we have identified a class of Lewis base salt precursors that show promise over urea, acetamide and BMP-Cl based electrolytes. Specifically, –idinium chloride salts with nitrogen functionality (i.e. guanidinium chloride [Guan-Cl], acetamidinium chloride [Acet-Cl], and formamidinium chloride [Form-Cl]) display reversible electrochemical plating/stripping of Al, good ionic conductivities (10 – 14 mS cm-1), and viscosities (50 – 80 cP). The choice of Lewis base salt can have a profound impact on not only the electrochemical performance but also the chemical and rheological properties of the electrolyte.As such, this contribution will highlight our efforts in studying the chemical functionality of the Lewis base by changing from oxygen-, nitrogen- and sulphur-based ligands. We will also examine the compositional differences and determine the liquidus range by systematically varying the molar ratios of the Lewis acid : Lewis base. We will report how this affects the chemical speciation of the electrolyte, the ionic conductivity, and the electrolyte viscosity. This will help us identify an optimal electrolyte composition for testing in a coin cell configuration. Temperature-dependent electrochemical performance of these electrolytes will be evaluated using cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), and electrochemical impedance spectroscopy (EIS). The chemical speciation of Al in the different electrolytes will be analysed using 27Al NMR and Raman spectroscopy. This will help identify if Al2Cl7 -, AlCl4 - or other ionic species are responsible for their behaviour. Overall, this work will provide a deeper, fundamental understanding of these novel electrolytes and their application in aluminium-based batteries.

Synthesis and characterization of analogues of glycine-betaine surface-active ionic liquids

With the goal of finding sustainable solvents, novel ionic liquids (ILs) with low ecotoxicity features have been a target of research. Among these, ILs with surface-active characteristics play a significant role in the food, cosmetic, pharmaceutical, household cleaning and other detergent industries. Most surface-active ILs reported up to date are imidazolium-based, which may raise some environmental and health-related concerns. Aiming the development of ILs with surfactant properties and low ecotoxicity, in this work, novel surface-active analogues of glycine-betaine ILs (AGB-SAILs) combined with the dodecylbenzenesulfonate ([DBS]-) anion have been synthesized and characterized. The synthesized AGB-SAILs were characterized chemically by elemental analysis and spectroscopic methods. Their thermal properties, critical micellar concentration, micelle diameter and ecotoxicity against Aliivibrio fischeri were determined, being these properties compared with the commercial surfactant sodium dodecylbenzenesulfonate (SDBS). It is shown that all investigated AGB-SAILs are liquid at room temperature and thermally stable. Furthermore, most of them display a lower critical micellar concentration and lower toxicity towards Aliivibrio fischeri than SDBS, thus being good alternatives to the commercial surfactant in a wide range of applications.

Mono-, Bi-, and Tri-Metallic DES Are Prepared from Nb, Zr, and Mo for n-Butane Selective Oxidation via VPO Catalyst

In recent work, deep eutectic solvents (DESs) as ionic liquid analogues have been abundantly used in catalysis. Herein, vanadium phosphorus oxide (VPO) catalysts were synthesized from mono-, bi-, and tri- metallic DES of Nb, Zr, and Mo metal dopants as structure-directing agents and electronic promoters for n-butane selective oxidation towards maleic anhydride. Higher MA selectivity and larger n-butane conversion was successfully obtained using the newly developed catalysts, while oxidation by-product COx (CO, CO2) was minimized. Characterization techniques including FTIR, DSC, XRD, TEM, SEM, EDS, Raman spectroscopy, TGA, XPS, and NH3-TPD were employed to fully characterize the DESs, precursors and catalysts. This work led to an increase of 7.8% in MA mass yield with 16% more n-butane conversion as compared to an unpromoted VPO catalyst. Moreover, the utilization of a low-carbon alkane brought in a green impact on the chemical plant as well as the environment.

Comparative Study of Water-soluble and Non-water-soluble Wool Keratin from Ionic Liquid Analogue

Comparative Study of Water-soluble and Non-water-soluble Wool Keratin from Ionic Liquid Analogue

A Low‐Cost Al‐Graphite Battery with Urea and Acetamide‐Based Electrolytes

AbstractAl‐ion batteries employing natural graphite cathodes have been proposed as a valid alternative to Li‐ion systems due to their low‐cost and sustainability, as well as a stable long‐term cycle life. In contrast to commonly used but typically expensive ionic‐liquid‐based electrolytes, our reported Al‐graphite batteries use AlCl3/urea and AlCl3/acetamide deep eutectic solvents (DES, also known as ionic liquid analogues) as low‐cost alternative. By carefully selecting amide composition, Al speciation in the DES electrolyte can be modified, as confirmed by Raman, NMR and IR spectroscopy. We correlate the speciation changes to resulting battery performance by systematic electrochemical investigations of Al‐graphite batteries employing urea and acetamide eutectics of different compositions. The practical applicability was demonstrated using long‐term cycling experiments with >8000 cycles, exhibiting a specific capacity of around 50 mAh/g at a current rate of 2 A/g.

Insights into the interactions and dynamics of a DES formed by phenyl propionic acid and choline chloride

Deep eutectic solvents (DESs) have received much attention in modern green chemistry as inexpensive and easy to handle analogous ionic liquids. This work employed molecular dynamics techniques to investigate the structure and dynamics of a DES system composed of choline chloride and phenyl propionic acid as a hydrogen bond donor and acceptor, respectively. Dynamical parameters such as mean square displacement, liquid phase self-diffusion coefficient and viscosity are calculated at the pressure of 0.1 MPa and temperatures 293, 321 and 400 K. The system size effect on the self-diffusion coefficient of DES species was also examined. Structural parameters such as liquid phase densities, hydrogen bonds, molecular dipole moment of species, and radial and spatial distribution functions (RDF and SDF) were investigated. The viscosity of the studied system was compared with the experimental values recently reported in the literature. A good agreement was observed between simulated and experimental values. The electrostatic and van der Waals nonbonding interaction energies between species were also evaluated and interpreted in terms of temperature. These investigations could play a vital role in the future development of these designer solvents.

Novel Phosphorous-Based Deep Eutectic Solvents for the Production of Recyclable Macadamia Nutshell–Polymer Biocomposites with Improved Mechanical and Fire Safety Performances

Deep eutectic solvents (DESs), a new class of ionic liquid analogue solvents, provide excellent opportunities to chemically solubilize and functionalize wood components. Here, we synthesized a nove...

Spectroscopic analysis of acetamide-AlCl3-based ionic liquid analog and their catalytic performance in isobutene oligomerization

The spectral structures of acetamide-AlCl3-based ionic liquid (IL) analogs were determined in detail through IR, NMR, and Raman spectroscopy. IR spectroscopy showed that 0.65AA-1.0AlCl3 was the coordination structure of Al and O atoms because of the resonance structure of acetamide. The mutual verification of the results of 27Al NMR and 1H NMR indicated that acetamide coexisted mainly in the form of cationic Al species and molecular Al species in xAA-1.0AlCl3, and AA/AlCl3 molar ratio affected the transformation of cationic Al species to molecular Al species. xAA-1.0AlCl3 was used as a green acidic catalyst for isobutene oligomerization, and the effects of AA/AlCl3 molar ratio, reaction temperature, reaction time, and volumetric ratio between IL analog and isobutene on product distribution were investigated. Optimal reaction conditions were AA/AlCl3 molar ratio of 0.75, reaction temperature of 60 °C, reaction time of 30 min, and catalyst/i-C4= volumetric ratio of 1.4 v/v. Under optimal conditions, isobutene conversion, (C8= + C12=) selectivity, (C16= + C20=) selectivity, and by-product selectivity were 85.26, 80.20, 6.80, and 13.00 wt%, respectively.

Zwitterionic compounds are less ecotoxic than their analogous ionic liquids

Zwitterionic compounds are less ecotoxic than their analogous ionic liquids.

Amidine-based ionic liquid analogues with AlCl3: a credible new electrolyte for rechargeable Al batteries.

Here we demonstrate the generation of novel ionic liquid analogue (ILA) electrolytes for aluminium (Al) electrodeposition that are based on salts of amidine Lewis bases. The electrolytes exhibit reversible voltammetric plating/stripping of Al, good ionic conductivities (10-14 mS cm-1), and relatively low viscosities (50-80 cP). The rheological properties are an improvement on analogous amide-based ILAs and make these liquids credible alternatives to ILAs based on urea or acetamide, or conventional chloroaluminate ionic liquids (IL) for Al battery applications.

(Invited) Evolution of Structural, Transport and Electrical Properties of Binary Ionic Liquids in the Presence of Graphite

The flexibility to manipulate various interactions in ionic liquids by changing the cation, anion, or the various functional groups on the ions has drawn researchers to design tailor-made ionic liquids for a given application. Another approach that is gaining importance in tuning the properties of ionic liquids is to form binary, ternary, and reciprocal ionic liquid mixtures. Results from molecular simulations conducted in our research group have demonstrated that the binary ionic liquid mixtures in which two anions are combined in different molar ratios for a given cation can lead to either native or non-native structures in the bulk depending on the difference between the hydrogen bonding ability of the participating anions. The non-native structures differ markedly from those for the pure ionic liquid analogues and impact the physical dissolution mechanism for gases such as CO2.Given the importance of ionic liquids as electrolytes in the next-generation of batteries, it is likely that such ionic liquid mixtures will increasingly be investigated for their ability to transport ions to and from charged surfaces. However, very little is currently known regarding how the presence of a surface or an interface affects the local and long-range structures of binary ionic liquids. In this talk, we will present our findings from molecular simulation studies by examining the structural response of binary ionic liquid mixtures comprised of a single cation in combination with two anions when presented with a graphite surface. We will compare and contrast these structures to those obtained when binary ionic liquid mixtures are formed with a single anion and two cations and a graphite surface is introduced. Additionally, we will elucidate the influence of graphite on the transport and electrical properties of binary ionic liquids.

High‐Rate Lithium‐Ion Cycling in Electrodeposited Binder‐Free Thin‐Film Vanadium Oxide Cathodes with Lithium Metal Anodes in Ionic Liquid and Polymer Gel Analogue Electrolytes

AbstractHigh rate and long cycle life performance for electrodeposited, binder‐free V2O5 thin film cathodes and lithium metal anodes is described using liquid and polymer gel electrolytes of the pyrrolidinium based (C4mpyrTFSI) ionic liquid (IL). Sharp well‐defined voltammetric peaks typically seen with nanostructured V2O5 materials in organic electrolytes, support the fast kinetics observed. The addition of vinylene carbonate (VC) stabilises the electrolyte interface leading to higher electrode capacities than for the additive‐free electrolyte, ∼120 versus ∼90 mAh g−1 at 0.75 C. Polymer gel electrolytes based on the IL yield similar electrode capacities, coulombic efficiencies and high rate performances without the VC‐additive. The polymer gel option delivers the better long‐term stability up to 400 cycles with lithium metal anodes with minimal capacity fade at elevated charge and discharge rates up to 5 C.

Corrosion behavior of AA2024-T6 and AA6065-T6 alloys in reline

Deep eutectic solvents have been widely acknowledged as ionic liquid analogues, since they share many characteristics and properties with ionic liquids. The two major application areas of deep eutectic solvents have been metal processing and synthesis media; however, plenty of other applications have already been reported and predicted for these liquids. Reline, an eutectic mixture of choline chloride and urea, is a well known representative of deep eutectic solvents. Despite their importance in the contemporary technologies, the knowledge about the corrosivity of deep eutectic solvents is remarkably scarce. This article reports the results on the corrosivity of reline towards two Al alloys, namely AA2024-T6 and AA6065-T6. To measure the corrosion rates and characterize the passive film on the alloys in reline, electrochemical impedance and inductively coupled plasma optical emission spectroscopy methods were used, and the corrosion product composition was analyzed by X-ray photoelectron spectroscopy. Surface morphology and Volta potential were imaged by scanning electron microscopy, atomic force microscopy and scanning Kelvin probe force microscopy. The corrosion tests show that the two alloys are extremely stable in reline, and the passive layer is formed in the first three hours of immersion in the corrosive media. There is no evidence that electrolyte species are incorporated into the Al oxide protective layer through chemical bonding.