Ionic Liquid Analogues Research Articles

Innovative ice mitigation: Exploring the potential of choline-based deep eutectic solvents and ionic liquids synergies

The development of anti-icing coatings for extremely low temperatures is still emerging. Deep eutectic solvents (DESs), as subset of ionic liquid (IL) analogues, have recently gained increasing attention for their unique and versatile applications. Given no investigation regarding anti-icing capabilities of DESs, our study focused on the exciting potential of choline-based DESs. The intriguing potential of hydrogen bonding through the synergistic combination of DESs and ILs offers significant promise for innovative solutions to ice-related challenges that remain largely unexplored. We conducted a comprehensive study on the anti-freezing properties of DESs by synthesizing choline-based ILs featuring both hydrophilic and hydrophobic anions. We aimed to explore how the diverse hydrogen-bond donors in DESs combined with the synthesized ILs to enhance the system’s ability to prevent ice formation. Substituting ethylene glycol (EG) with glycerol (GL) resulted in achieving an ice formation temperature of − 36 °C and an exceptionally low ice adhesion strength of 10 kPa, due to a thicker quasi-liquid layer on the coating surface, confirmed by solid-state NMR spectroscopy. The altered frost formation patterns of the DES-containing coatings demonstrated an enhance resistance against frost formation. This comprehensive study underscored the promising synergy between DESs and ILs for highly effective ice mitigation.

TMPAC-EG deep eutectic solvent for sustainable recovery of Nd by electrodeposition

The electrodeposition of neodymium (Nd) in a novel analogous ionic liquid (AIL), phenyltrimethylammonium chloride-ethylene glycol (TMPAC-EG), was investigated. The existence form and the electrochemical behavior of Nd(III) in TMPAC-EG were studied using spectroscopic, cyclic voltammetry and chronoamperometry analyses. The spectroscopic analyses indicates that Nd3+ interact with Cl− and EG to form complexes [Nd(EG)6-yCly]3-y as NdCl3 dissolves in TMPAC-EG IL. Cyclic voltammograms reveals that the overpotential for Nd electrodeposition in TMPAC-EG IL decreases with the rise of the temperature. The diffusion coefficient of Nd(III) ions is calculated to about 10−12 m2 s−1. The diffusion activation energy for Nd(III) ions is determined to be 22.8 kJ mol−1 from the temperature dependence of diffusion coefficient. The transient analysis indicates that initial nucleation behavior of Nd conforms to the three-dimensional instantaneous nucleation and growth model, which are largely independent of temperature. In addition, deposition temperature and deposition potential are found to have a great influence on the nucleation and growth kinetics of Nd electrodeposition. Depending on the temperature and potential of electrodeposition, metallic neodymium with caterpillar-shape, nodule, layered rock, or porous structures was obtained.

Ternary Ionic Liquid Analogues as Electrolytes for Ambient and Low-Temperature Rechargeable Aluminum Batteries.

Rechargeable aluminum (Al) metal batteries are enticing for the coming generation of electrochemical energy storage systems due to the earth abundance, high energy density, inherent safety, and recyclability of Al metal. However, few electrolytes can reversibly electrodeposit Al metal, especially at low temperatures. In this study, Al electroplating and stripping were investigated from 25 °C to -40 °C in mixtures of aluminum chloride (AlCl3), 1-ethyl-3-methyl-imidazolium chloride ([EMIm]Cl), and urea. The ternary ionic liquid analogue (ILA) consisting of AlCl3-urea-[EMIm]Cl in a molar ratio of 1.3:0.25:0.75 enabled reversible Al electrodeposition at temperatures as low as -40 °C while exhibiting the highest current density and the lowest overpotential among all of the electrolyte mixtures at 25 °C, including the AlCl3-[EMIm]Cl binary mixture. The ILA electrolyte was further tested in a rechargeable Al-graphite battery system down to -40 °C. The addition of urea to AlCl3-[EMIm]Cl binary mixtures can improve the Al electrodeposition, extend the liquid temperature window, and reduce the cost.

Insights into application of aqueous biphasic systems of deep eutectic solvents composed of benzyltrialkylammonium chloride in dye separation

Deep eutectic solvents (DES) are considered the newest entry in the list of green solvents and they are analogues of ionic liquids (ILs), with excellent solvent characteristics better than commonly used organic solvents and ILs. Owing to this, We have prepared DES using benzyltrialkylammonium chloride (BTAAC) including benzyltrimethylammonium chloride (BTMAC), benzyltriethylammonium chloride (BTEAC), and benzyltributylammonium chloride (BTBAC) as hydrogen bond acceptors (HBA) and glycols, like ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG) as hydrogen bond donors (HBD). Aqueous biphasic systems (ABS) were developed using the synthesized DESs and K3PO4, K2HPO4, and K2CO3 at 298.15 K and atmospheric pressure. The phase-forming ability of DES has been evaluated based on the nature of potassium salts, HBA and HBD. In most cases, the influence of salts on ABS formation was found to follow the order: K3PO4 > K2HPO4 > K2CO3, while HBAs follow: BTBAC > BTEAC > BTMAC. The performance of the ABSs was experimentally applied for the extraction of Methyl orange (MO), Eriochrome black T (EBT), and Eosin Y (EY). In most ABS, the extraction order for the studied dyes noticed was: MO < EBT < EY, consistent with their hydrophobic nature. ABS consisting of BTBAC:TEG + K2HPO4 and BTBAC:TEG + K3PO4 was found to lead to the complete extraction of MO, EBT, and EY. The recovery of extracted EY dye was performed by adsorption method using starch-modified chitosan as an adsrobent.

Competition-Induced Macroscopic Superlubricity of Ionic Liquid Analogues by Hydroxyl Ligands Revealed by in Situ Raman.

High load-bearing capacity is one of the crucial indicators for liquid superlubricants to move toward practicality. However, some of the current emerging systems not only have low contact pressures but also are highly susceptible to further degradation due to water adsorption and even superlubricity failure. Herein, a novel choline chloride-based ionic liquid analogues (ILAs) of a superlubricant with triethanolamine (TEOA) as the H-bond donor is reported for the first time; it obtains an ultralow coefficient of friction (0.005) and high load-bearing capacity (360 MPa, more than 2 times that of similar systems) due to adsorption of a small amount of water (<5 wt %) from the air. In situ Raman combined with 1H NMR and FTIR techniques reveals that adsorbed water competes with the hydroxyl group of TEOA for coordination with Cl-, leading to the conversion of some strong H-bonds to weak H-bonds in ILAs; the localized strong H-bonds and weak H-bonds endow the ILAs with high load-bearing capacity and the formation of ultralow shear-resistance sliding interfaces, respectively, under the shear motion. This study proposes a strategy to modulate the interactions between liquid species using adsorbed water from air as a competing ligand, which provides new insights into the design of ILA-based macroscopic liquid superlubricants with a high load-bearing capacity.

Electrolyte Mixtures and Organic Cathode Materials for Rechargeable Aluminum Batteries

Rechargeable aluminum (Al) metal batteries are an emerging energy storage technology ideal for use at a global scale: Al metal is energy dense, low cost, inherently safe, earth abundant, and highly recyclable. Despite such great promise, their technological progress has been hindered by the few electrolytes able to reversibly electrodeposit Al metal at room temperature, coupled with the limited number of positive electrode materials that are compatible with them. In this context, recent progress will be discussed in the development of electrolyte mixtures and organic cathode materials for rechargeable aluminum batteries. Chloroaluminate ionic liquid electrolytes and ionic liquid analogues prepared using mixtures of organic cations and/or neutral solvent species will be presented, which exhibit improved electrochemical properties for aluminum electrodeposition and in aluminum-graphite batteries, over temperatures ranging from ambient conditions down to -60 °C. Different organic structures will also be presented as organic cathode materials for aluminum batteries, where the effects of molecular structure on bulk energy storage properties will be discussed. Molecular-scale understanding of their ionic and electronic charge storage mechanisms will be elucidated through a combination of solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations. Lastly, by using different electrolytes in combination with an organic cathode, it will be shown that electrolyte speciation can affect the local environments of charge-compensating ions in cycled organic electrodes. Overall, the results and analyses are aimed at developing next-generation rechargeable aluminum metal batteries for diverse energy storage applications.

Zwitterionic liquid-based gel electrolyte for high performance lithium metal battery at low temperatures

Gel electrolyte (GE) gains intensive attentions for lithium metal battery, especially those targeting to use at low temperatures. The liquid medium, as the core component, of most gel electrolytes (GEs) is organic liquid or ionic liquid, always suffering from serious safety issue and low transference number (t+). The low t + aggravates concentration polarization and thus leads to the increase of overpotential and undesirable side reactions. Herein, zwitterionic liquid (ZIL) with high stability and safety is prepared by mixing zwitterion (ZI) and lithium salt. The ZIL is then encapsulated into a SiO2 matrix to fabricate novel gel electrolyte (SiGE-ZIL). The low freezing point and strong mobility of ZIL confer SiGE-ZIL a high conductivity of 3.36 × 10−4 S cm−1 at −40 °C. Importantly, the large dipole moment of ZI effectively accelerates the dissociation of lithium salt, permitting a high t+ of 0.553 at −40 °C, which is 2.3 times of that of the analogous ionic liquid. The assembled LiFePO4/Li battery exhibits an excellent cycling stability with a capacity of 91.6 mAh g−1 at 600th cycle at 0.5C and 0 °C. Especially at −20 °C, the capacity can reach 67.1 mAh g−1 at 600th cycle under 0.5C, surpassing most of GE-based batteries.

Deep eutectic solvents as sustainable solvents for industrial separation problems: A recent update

Deep eutectic solvents (DESs) are ionic liquid analogues that consist of Lewis or Brønsted acids and bases. These systems are characterized by a substantial decrease in melting points as compared to those of the neat constituents. Activity coefficients at infinite dilution of organic solutes is used as a screening tool for extracting solvents, an approach that is useful for identifying acceptable precursors and assessing separation performance in practical applications. This review assesses the effectiveness of DESs as solvents for chemical separations wherein the data is presented for the activity coefficients at infinite dilution for 33 solutes in different DESs at various temperatures. Additionally, the selectivities and capacities for various solute extraction problems are also appraised from the activity coefficients at infinite dilution at T = 323.15 K; capacity represents the solvent's ability to extract the component.

Comparative Study of Guanidine-, Acetamidine- and Urea-Based Chloroaluminate Electrolytes for an Aluminum Battery.

Aluminum-based batteries are a promising alternative to lithium-ion as they are considered to be low-cost and more friendly to the environment. In addition, aluminum is abundant and evenly distributed across the globe. Many studies and Al battery prototypes use imidazolium chloroaluminate electrolytes because of their good rheological and electrochemical performance. However, these electrolytes are very expensive, and so cost is a barrier to industrial scale-up. A urea-based electrolyte, AlCl3:Urea, has been proposed as an alternative, but its performance is relatively poor because of its high viscosity and low conductivity. This type of electrolyte has become known as an ionic liquid analogue (ILA). In this contribution, we proposed two Lewis base salt precursors, namely, guanidine hydrochloride and acetamidine hydrochloride, as alternatives to the urea-based ILA. We present the study of three ILAs, AlCl3:Guanidine, AlCl3:Acetamidine, and AlCl3:Urea, examining their rheology, electrochemistry, NMR spectra, and coin-cell performance. The room temperature viscosities of both AlCl3:Guanidine (52.9 cP) and AlCl3:Acetamidine (76.0 cP) were significantly lower than those of the urea-based liquid (240.9 cP), and their conductivities were correspondingly higher. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) showed that all three electrolytes exhibit reversible deposition/dissolution of Al, but LSV indicated that AlCl3:Guanidine and AlCl3:Acetamidine ILAs have superior anodic stability compared to the AlCl3:Urea electrolyte, as evidenced by anodic potential limits of +2.23 V for both AlCl3:Guanidine and AlCl3:Acetamidine and +2.12 V for AlCl3:Urea. Coin-cell tests showed that both AlCl3:Guanidine and AlCl3:Acetamidine ILA exhibit a higher Coulombic efficiency (98 and 97%, respectively) than the AlCl3:Urea electrolyte system, which has an efficiency of 88% after 100 cycles at 60 mA g-1. Overall, we show that AlCl3:Guanidine and AlCl3:Acetamidine have superior performance when compared to AlCl3:Urea, while maintaining low economic cost. We consider these to be valuable alternative materials for Al-based battery systems, especially for commercial production.

Influence of tetrabutylammonium bromide based ionic liquid on the aggregation behavior of dodecyltrimethylammonium bromide in the range (293.15 K–313.15 K): acoustic and volumetric investigation

Abstract The effect of the ionic liquid analogue tetrabutylammonium bromide on the aggregation behaviour of the cationic surfactant dodecyltrimethylammonium bromide in aqueous medium was investigated with volumetric and compressibility measurements over a wide temperature range (293.15–313.15) K. The data obtained were used to obtain density data. Based on the density data obtained, the volumetric properties (apparent molar volumes and partial molar volumes) of the surfactant in unimeric and micellar forms were evaluated and discussed in terms of the respective ionic and dipolar interactions. The data obtained were analysed to determine the effects of (i) temperature and (ii) salt added to the surfactant. The results were also interpreted in terms of the molecular interactions occurring in the binary mixtures of the present study. The addition of tetrabutylammonium bromide has a lowering effect on the CMC values of the surfactant studied in aqueous medium.

Aqueous biphasic systems comprising analogues of glycine-betaine ionic liquids: Toward greener separation platforms

The use of biobased and bioactive compounds has boosted the development of sustainable extraction and purification processes, in which ionic liquids have been playing a major role. Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have been raising significant interest as advantageous extraction and purification platforms; however, imidazolium-based ILs have been the primary option as phase-forming agents. Aiming the development of more sustainable IL-based ABS, in this work, six novel analogues of glycine-betaine ILs (AGB-ILs) were investigated. These ILs were synthesized and characterized in terms of purity, physico-chemical properties, ecotoxicity and ability to form ABS with tri-potassium citrate. The investigated AGB-ILs are composed of tri(n-alkyl[2-ethoxy-2-oxoethyl]ammonium/phosphonium and tri(n-alkyl[4-ethoxy-4-oxobutyl]ammonium/phosphonium cations with ethyl, n-propyl and n-butyl substituents, and the tosylate ([Tos]-) anion. The synthesized ILs present degradation temperatures in the range from 220 to 265 °C, and are classified as relatively harmless regarding their ecotoxicity. The studied AGB-ILs display slightly lower thermal stability, but yet a lower ecotoxicity compared to the commercial IL 1-butyl-3-methylimidazolium tosylate. Their ability to form ABS was assessed, allowing to conclude that an expansion in the alkyl side chain length and spacer, as well as the presence of phosphonium instead of ammonium as central atom, increase the ability for phase separation in presence of tri-potassium phosphate aqueous solutions. The extraction performance of the studied AGB-ILs-based ABS was finally assessed with furfural, a platform chemical. In the majority of the studied systems, furfural preferentially migrates to the AGB-IL-rich phase, obtaining extraction efficiencies in a single step to the IL-rich phase up to 98%. These results reveal that novel ABS comprising AGB-ILs can be potentially used as separation platforms of bioactive compounds.

In Situ Raman Study of Voltage Tolerance Up to 2.2 V of Ionic Liquid Analogue Supercapacitor Electrolytes Immune to Water Adsorption Conferred by Amphoteric Imidazole Additives.

Ionic liquid analogues (ILAs) are promising electrolytes for supercapacitors due to their low cost and considerable voltage (>2.0 V). However, the voltage is <1.1 V for water-adsorbed ILAs. Herein for the first time, an amphoteric imidazole (IMZ) additive is reported to address this concern by reconfiguring the solvent shell of ILAs. Addition of only 2 wt % IMZ increases the voltage from 1.1 to 2.2 V, with an increase in capacitance from 178 to 211 F g-1 and an increase in energy density from 6.8 to 32.6 Wh kg-1. In situ Raman reveals that the strong H-bonds formed by IMZ with completive ligands 1,3-propanediol and water induce a reversal of the polarity of the solvent shells, suppressing absorbed water electrochemical activity and thus increasing the voltage. This study solves the problem of low voltage for water-adsorbed ILAs and reduces the equipment cost of ILA-based supercapacitor assembly (e.g., assembly in air without a glovebox).

Stability Mechanism of Menthol and Fatty Acid Based Hydrophobic Eutectic Solvents: Insights from Nonbonded Interactions

Deep eutectic solvents (DESs), being ionic liquid (IL) analogues, are easy to prepare, cost-effective, recyclable, and biocompatible and have low toxicity. Hydrophobic deep eutectic solvents (HDESs) composed of natural compounds are highly effective in the extraction of micropollutants (metal ions, pharmaceuticals, and so on) from an aqueous stream. In this work, the formation mechanism of dl-menthol and carboxylic acid (acetic, butanoic, hexanoic, octanoic, nonanoic, decanoic, and dodecanoic acid) based DESs in a molar ratio of 1:1 has been presented along with their structural composition, charge transfer analysis, chemical stability, and aqueous phase solvation analysis using density functional theory (DFT) calculations. The intermolecular hydrogen bonding and dispersion interactions between menthol (−OH group) and carboxylic acids (−COOH) at a short to medium range are responsible for the stable DES formation. CHELPG and natural bonding orbital (NBO) analyses suggest that the acetic acid based DES is more closely structured and has lesser resistance to charge transfer as compared to higher chain length acid (C8 to C12) based DESs. Frontier molecular orbital (FMO) analysis confirms higher chemical stability and lesser reactivity of long-chain fatty acid based DESs as compared to their short-chain counterparts. The atom-in-molecules (AIM) and noncovalent interaction (NCI) analyses suggest that a strong network of hydrogen bonding and dispersion interactions are solely responsible for the formation and strength of the DESs. The DFT-based solvation study supported by spatial distribution function (SDF) from molecular dynamics (MD) indicates that the lower fatty acid (C1 to C6) based DESs are disrupted by water penetration to a higher extent as compared to the higher fatty acid (C8 to C12) based DESs. According to the solvation-based NCI analysis, van der Waals and dispersion connections are the interactions that are largely responsible for the chemical and physical stability of the DESs in the aqueous phase. The overall findings from the computational study have a remarkable degree of coherence with the findings of the experiments that were previously reported.

Electrorheological effect and dielectric properties of Poly(ionic liquid) microspheres with different length of alkyl chain spacer between ion pair and backbone

Imidazolium-based poly(ionic liquid) analogues having different lengths of alkyl chain spacer between ion pair and backbone, named as P[ECnVim][PF6] (n = 2, 3, 6), were synthesized. Then, P[ECnVim][PF6] were transformed into microspheres by an evaporation-induced phase separation method. The influence of the length of alkyl chain spacer on the electro-responsive electrorheological effect and dielectric property of P[ECnVim][PF6] microsphere suspensions were studied. It showed that as the length of alkyl chain spacer increased, the electrorheological effect increased but the working temperature range of electrorheological effect became narrow. By combining dielectric spectra analysis and activation energy measurement, it was clarified that the influence of the length of alkyl chain spacer on electrorheological effect was mainly associated with the change of ionic conductivity and interfacial polarization, which was further related to the change of elastic potential energy of ion motion in P[ECnVim][PF6] with different lengths of alkyl chain spacer between ion pair and backbone. However, the working temperature range of electrorheological effect depended on the change of glass transition temperature with the length of alkyl chain spacer. The result provides the structure-property relationship insight for the design of poly(ionic liquid)-based electro-responsive electrorheological materials.

Unravelling High-Load Superlubricity of Ionic Liquid Analogues by In Situ Raman: Incomplete Hydration Induced by Competitive Exchange of External Water with Crystalline Water

A high load-carrying capacity is the key to the practicality of liquid superlubricity, but it is difficult to achieve high load and low friction simultaneously by relying solely on a liquid film. Herein, a choline chloride-based ionic liquid analogue (ILA) macroscale superlubricant is first reported by tuning down strong hydrogen bonding in the ILA via introducing 2-10 wt % water, with a high load of 160 MPa and a low coefficient of friction of 0.006-0.008. In situ Raman reveals that competitive exchange between external water and crystalline water induces weak H-bond-dominated incomplete hydration, conferring a low-shear interface and considerable load-carrying capacity inside the lubricant. It is a hydrodynamic lubrication film rather than a tribochemical/physical adsorption film, allowing it to be applied to friction pairs of various materials. This study unveils the principle of water mediation of high-viscosity ILAs and also provides new insights into the design of practical ILA-based superlubrication materials with high load-carrying capacity.

High toxicity of amino acid-based deep eutectic solvents

Amino acid-based deep eutectic solvents (i.e., ionic liquids analogues (DESs)) have been deemed as green and low toxic materials for efficient CO2 capture, conversion and utilization. However, (1) are amino acid-based DESs really green and low toxic? (2) how to minimize the toxicity of amino acid-based DESs for a better CO2 capture, conversion and utilization? Herein, we for the first time unexpectedly find that amino acid-based DESs are super toxic. The toxicity of amino acid-based DESs could be 105 times that of conventional choline chloride-based DESs, which could be ascribed to the much higher toxicity of DESs than their individuals. The lower toxicity of amino acid-based DESs could be tuned by hydrogen-bonding acceptor, hydrogen-bonding donor, mole ratio and intermolecular interaction. This work would provide a basis for designing less or even no toxic green solvents for better and sustainable CO2 capture, conversion and utilization.

A Zinc-Bromine Battery with Deep Eutectic Electrolytes.

A deep eutectic solvent (DES) is an ionic liquid-analog electrolyte, newly emerging due to its low cost, easy preparation, and tunable properties. Herein, a zinc-bromine battery (ZBB) with a Zn-halide-based DES electrolyte prepared by mixing ZnBr2 , ZnCl2 , and a bromine-capturing agent is reported. The water-free DES electrolyte allows a closed-cell configuration for the ZBB owing to the prevention of Br2 evaporation and H2 evolution. It is found that the Cl- anion changes the structure of the zinc-halide complex anions and demonstrated that it improves the ion mobility and electrode reaction kinetics. The DES electrolyte with the optimized ZnCl2 composition shows much higher rate capability and a cycle life 90 times longer than that of a ZnCl2 -free DES electrolyte. A pouch-type flexible ZBB battery based on the DES electrolyte exhibits swelling-free operation for more than 120 cycles and stable operation under a folding test, suggesting its potential in consumer applications such as wearable electronics.

Perspectives for Deep Eutectic Solvents and Ionic Liquid Analogues in Metal Electroplating

Here we will specifically describe the opportunities and perspectives offered by non-aqueous so-called deep eutectic solvents (DES) and ionic liquid analogues (ILA) in the materials finishing and metal electroplating industries. We will describe a range of plating and dissolution processes from anti-corrosion coatings to new battery technologies. Details will be presented of the plating and characterisation techniques using some novel in-situ methods. These include electrochemical processing and characterisation as well as a number of cutting-edge surface methodologies including acoustic resonance methods, ESR, EXAFS, atomic force microscopy, neutron scattering techniques and magnetic resonance imaging.We will describe a number of case-studies including electrolytic deposition of nickel, alloys such as Ni/Zn, and galvanic methods associated with Au and Ag coatings for the electronics industry. 1, 2, 3 In all these studies we have focused on a combination of fundamental chemical, electrochemical, structural and spectroscopic studies, maintaining close links with industrial partners through collaboration and scale-up trials.We will include very recent updates and future prospects on the use of ILA's in energy storage vectors such as Al secondary batteries. We will describe the advantages and drawbacks of DES and ILA systems in terms of functionality, sustainability and economic cost.

(Digital Presentation) Conductivity Measured in Situ from I-E Curve Fitting in Chloroaluminate Electrolytes

Aluminium (Al) batteries are a promising, next-generation technology and current research efforts are aimed at positioning this technology to compete with existing lithium-ion batteries (LIB). The development of non-aqueous electrolyte chemistries for Al battery systems has received renewed attention to address some of the shortcomings associated with LIB. Of particular importance in this development is the liquid electrolyte as its rheology governs the battery chemistry. The goals are to generate a liquid that is compatible with the other (solid) battery components, stable long-term with repeated use, and to optimise the rheology (i.e. target high conductivity and low viscosity). 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) has been extensively studied. This tuneable electrolyte provides good thermal stability, good ionic conductivity, and a wide polarizable potential window. While these traits are advantageous these types of Lewis basic salt precursors are generally expensive, difficult to synthesize 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 but their rheological and electrochemical properties need to be improved in order to complete with RTIL-based electrolytes.Our group have recently revealed that amidine-based chloroaluminate ILA electrolytes show promise over urea-, acetamide-, and pyrrolidinium-based electrolytes.[1] Specifically, guanidinium chloride (Guan-Cl) and acetamidinium chloride (Acet-Cl) based salts display reversible electrochemical plating/stripping of Al, good ionic conductivities (e.g. 10 mS cm-1), and moderate viscosities (e.g. 50 cP). Also, in this work we initially proposed a mathematical model to extract the conductivity from these electrolytes by fitting the voltammetric i-E curve (from Al deposition/dissolution) to a linear, modified Butler-Volmer formalism. The characteristic, anodic i-E trace shows a striking linearity often over very large potential ranges (e.g. >2 V), and this response is used to extract ionic conductivity. This represents a novel, electroanalytical method to obtain this important rheological metric.As such, in this contribution we will highlight our latest efforts to expand, benchmark (to common methods for measuring conductivity), and determine the limits of our i-E curve fitting method to measure ionic conductivity.[2] Specifically, we have examined the AlCl3:Acet-Cl electrolyte in depth by looking at the potential scanning rate, potential range probed, and the compositional (mole ratio Lewis acid : Lewis base) effect on the conductivity extracted from our fitting method. We have also studied a range of other common chloroaluminate electrolytes to compare with published literature. All of these values are then benchmarked to conductivity data measured both from a traditional impedance-based method and that from a commercial conductivity probe. Lastly, we also have examined temperature-dependent conductivities from all three of these methods. Overall, we find good agreement between values measured from our in situ i-E curve fitting method to those from more traditional conductivity measurement methods. This electroanalytical work serves to deepen our understanding of the conductivity of chloroaluminate ILAs for Al battery applications.

(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