Ionic Liquid Components Research Articles

Quantitative Raman spectroscopy for the Ioncell\xae process: Part 2\u2014quantification of ionic liquid degradation products and improvement of prediction performance through interval PLS

One of the main issues associated with ionic liquids (ILs) is their recyclability. Viable recycling concepts can only be developed if one knows what is in the IL mixtures and solutions. In our previous work, we showed that it is possible to quantify water and 1.5-diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] IL components in liquid mixtures using Raman spectroscopy. In this regard, we considered Raman spectroscopy as a promising analytical method for the inline monitoring and control of the Ioncell® process. In the present work, we push the limits of this analytical method further by extending it to more complex and realistic liquid mixtures including the hydrolysis product 1-(3-aminopropyl)-2-pyrrolidone (APP) that can be formed upon the reaction of 5-diazabicyclo[4.3.0]non-5-ene (DBN) with water. Quantifying APP is important in order to measure the extent of the hydrolysis reaction and apply the right corrective measures to reverse the reaction and to maintain the process within the optimal working conditions. The simultaneous quantification of the four components (Acetic acid, DBN, APP and H2O) in typical Ioncell® liquid streams is investigated using Raman spectroscopy. The sensitivity of the Raman method in quantifying APP is also highlighted in comparison with refractometry, which is widely applied to measure IL concentration in aqueous mixtures. Finally, we propose simple modifications on the multivariate partial least square regression model based on a variable selection algorithm to enhance the accuracy of the predicted calibration values.

Interfacial Structures in Ionic Liquid-Based Ternary Electrolytes for Lithium-Metal Batteries: A Molecular Dynamics Study

Lithium-metal batteries are promising candidates to fulfill the future performance requirements for energy storage applications. However, the tendency to form metallic dendrites and the undesirable side reactions between the electrolyte and the Li electrode lead to poor performance and safety issues in these batteries. Therefore, understanding the interfacial properties and the Li-metal surface/electrolyte interactions is crucial to resolve the remaining obstacles and make these devices feasible. Here, we report a computational study on the interface effects in ternary polymer electrolytes composed by poly(ethylene oxide) (PEO), lithium salts, and different ionic liquids (ILs) confined between two Li-metal slabs. Atomistic simulations are used to characterize the local environment of the Li+ ions and the transport properties in the bulk and at the interface regions. Aggregation of ions at the metal surface is seen in all investigated systems; the structure and composition are directly correlated to the IL components. The strong interactions between the electrolyte species and the Li-metal atoms result in the structuring of the electrolyte at the interface region, in which comparatively small and flat ions result in a well-defined region with extensive Li+ populations and high self-diffusion coefficients. In contrast, large ions such as [P222mom]+ increase the PEO density in the bulk due to large steric effects at the interface. Therefore, the choice of specific ILs in ternary polymer electrolytes can tune the structure-dynamic properties at the Li-metal surface/electrolyte interface, controlling the SEI formation at the electrode surface, and thereby improve battery performance.

Influence of Carbonate-Based Additives on the Electrochemical Performance of Si NW Anodes Cycled in an Ionic Liquid Electrolyte.

Addition of electrolyte additives (ethylene or vinylene carbonate) is shown to dramatically improve the cycling stability and capacity retention (1600 mAh g-1) of Si nanowires (NWs) in a safe ionic liquid (IL) electrolyte (0.1LiTFSI-0.6PYR13FSI-0.3PYR13TFSI). We show, using postmortem SEM and TEM, a distinct difference in morphologies of the active material after cycling in the presence or absence of the additives. The difference in performance is shown by postmortem XPS analysis to arise from a notable increase in irreversible silicate formation in the absence of the carbonate additives. The composition of the solid electrolyte interphase (SEI) formed at the active material surface was further analyzed using XPS as a function of the IL components revealing that the SEI was primarily made up of N-, F-, and S-containing compounds from the degradation of the TFSI and FSI anions.

THE VERSATILITY OF DABCO: SYNTHETIC APPLICATIONS OF ITS BASIC, NUCLEOPHILIC, AND CATALYTIC PROPERTIES. PART 4. IONIC LIQUIDS AND REAGENTS (SELECTFLUOR, DABSO) DERIVED FROM DABCO, DABCO AS PIPERAZINE SOURCE

The fourth part of our review is devoted to comprehensive analysis of literature data on the applications of DABCO as a component of ionic liquids, the design and use of new reagents derived from DABCO, as well as its chemical modifications and role as a building block for the preparation of substituted piperazines. The available data on the biological properties of DABCO derivatives are also presented. Literature sources from the previous 5 years are covered in this review. Authors: Dmitry I. Bugaenko, Alexander V. Karchava, Marina A. Yurovskaya*

Graphene oxide grafted hyperbranched poly (vinyl imidazole) with ionic liquid components as a potential carbon dioxide scrubber

The present work focuses on the design of a CO2 scavenger, capable of adsorbing a low concentration of CO2 from a mixed gas composition. Typically, vinyl imidazole and an ionic liquid brancher were copolymerized by “Strathclyde methodology” and grafted from graphene oxide; GO-g-(HB) PVIm-co-PIL (Cl). The chain transfer agent maintained short chains and developed hyperbranched architecture in GO-g-(HB) PVIm-co-PIL (Cl). The structure and the properties of GO-g-(HB) PVIm-co-PIL (Cl) was established from FTIR, 1HNMR, Raman, XRD and rheology. A metathesis reaction was carried out to exchange chloride anions with hexafluorophosphate anions; GO-g-(HB) PVIm-co-PIL (PF6). GO-g-(HB) PVIm-co-PIL (PF6) selectively captured a low concentration of CO2 from a mixed gas. The surface functionalities/ properties of GO, hyperbranched architecture, porosity, nitrogen content and surface charge distribution together played a significant role in efficient and selective CO2 capture.

Quantitative Raman spectroscopy for the Ioncell\u2122 process. Part 1: comparison of univariate and multivariate calibration methods for the quantification of water and protic ionic liquid components

We investigate in this paper the potential of Raman spectroscopy for the quantification of protic ionic liquid components (acid and base) and water, in ionic liquid/water mixtures, taking 1.5-Diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]) as a case study. We show that the combination of Raman spectroscopy and chemometrics is quite successful for the quantitative analysis of the ionic liquid components and water in mixtures over wide concentration ranges. The finding of the present work suggest that Raman spectroscopy should be considered more universally for the in-line monitoring and control of processes involving ionic liquid/H2O mixtures.

Binary mixtures of ionic liquids based on EMIm cation and fluorinated anions: physico-chemical characterization in view of their application as low-temperature electrolytes

Binary mixtures of ionic liquids (ILs) consisting of 1-ethyl-3-methylimidazolium [EMIm]+ cation coupled with fluorinated anions: bis(fluorosulfonyl)imide [FSI]-, bis(trifluoromethanesulfonyl)imide [TFSI]- and tetrafluoroborate [BF4]-, were formulated to obtain ionic fluids which are liquid at low temperature and to understand their properties. The thermal behaviour of [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x) mixtures with various molar ratios of IL components was investigated with differential scanning calorimetry (DSC). They exhibited reduced enthalpy of the phase transitions and lower melting temperature compared to the parent ILs, or only vitrification/devitrification occurring below −90 °C in some cases where x ranges from 0.5 to 0.8, 0.1 to 0.6 or 0.2 to 0.8 for [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x), respectively. For the formulations showing solely a glass transition, considered to be prospective low-temperature electrolytes, the density, viscosity and conductivity values were determined in a wide temperature range. The density demonstrated linear temperature dependence, whilst the dynamic viscosity and ionic conductivity followed the Vogel-Tamman-Fulcher equation. The corresponding Walden plot for pure ILs and their mixtures revealed a high degree of ionicity classifying them as “good ionic liquids” even down to −25 °C. The [EMIm][FSI]x[BF4](1-x) mixtures with x ranging from 0.5 to 0.6 displayed the lowest viscosity and highest conductivity, indicating them as promising electrolytes for IL-based electrochemical capacitors operating at low temperature, down to at least −40 °C.

Mesoscale Organization and Dynamics in Binary Ionic Liquid Mixtures.

The impact of mesoscale organization on dynamics and ion transport in binary ionic liquid mixtures is investigated by broad-band dielectric spectroscopy, dynamic-mechanical spectroscopy, X-ray scattering, and molecular dynamics simulations. The mixtures are found to form distinct liquids with macroscopic properties that significantly deviate from weighted contributions of the neat components. For instance, it is shown that the mesoscale morphologies in ionic liquids can be tuned by mixing to enhance the static dielectric permittivity of the resulting liquid by as high as 100% relative to the neat ionic liquid components. This enhancement is attributed to the intricate role of interfacial dynamics associated with the changes in the mesoscopic aggregate morphologies in these systems. These results demonstrate the potential to design the physicochemical properties of ionic liquids through control of solvophobic aggregation.

Si Anode in High-Salt Concentration Ionic Liquid Electrolytes Based on Pyrrolidinium and Phosphonium Systems for High-Energy Li-Ion Batteries

In order to push further the development of next generation Li-ion batteries (LiBs), high energy density, good capacity retention and increased safety are key features that need to be taken into account when designing energy storage devices. To this date, commercial batteries for portable devices mainly use graphite as anode. However, with the advent of electric vehicles and intelligent power grids, there is an increasing demand for high capacity materials to meet the energy and power requirement of these applications. More recently, Si anode has received considerable attention because of its natural abundance and its ability to deliver high energy density, with a gravimetric capacity of 3579 mAhg-1 which is almost 10 times that of graphite (372 mAhg-1) [1-2]. Bearing in mind that commercial LiBs use carbonate electrolytes which are recognized to pose safety issues and have been identified to suffer from degradation during charge-discharge cycles, we explored in this study the performance of Si anode in ionic liquid electrolytes based on phosphonium and pyrrolidinium cations, systems that are currently the most studied in the field of Li batteries [3-4]. Ionic liquid electrolytes are an appealing alternative to carbonates mainly because of their low volatility and better stability. In the recent years, good electrochemical behavior has been observed in ionic liquids with high salt concentration [3-5]. In this work, we were able to demonstrate better electrochemical performance of Si anode in ionic liquid electrolytes with 3.2 m LiFSI compared to conventional carbonate electrolytes in terms of capacity and capacity retention at 50°C. Electrochemical performance obtained in the phosphonium and pyrrolidinium systems are compared for different concentrations and temperatures. Moreover, initial investigation of the SEI using NMR and XPS spectroscopy revealed that less degradation products are formed upon cycling in ionic liquid electrolytes compared to usual carbonates electrolytes. Overall, these results highlight the stability of ionic liquids which translate to good cycling performance and show promising potential of Si anode as a high-capacity material for high-energy and high-temperature applications. Cyclability and capacity retention for the phosphonium and pyrrolidinium system will be discussed in terms of ionic liquids components degradation and SEI formation and evolution, as probed by combined 19F, 7Li MAS-NMR, XPS and impedance spectroscopy.

Spectroscopic Assessment of Intra- and Intermolecular Hydrogen Bonding in Ether-Functionalized Imidazolium Ionic Liquids.

Functionalization of the imidazolium (Im+) cationic component of ionic liquids (ILs) with ether chains affords the possibility of tuning their properties through manipulation of the resulting interion and intramolecular interactions. Herein, we quantify these interactions at the molecular level through analysis of the vibrational spectra displayed by size-selected and cryogenically cooled ions. These spectra are obtained using the "tagging" approach carried out with photofragmentation tandem mass spectrometry. In the isolated cations, we find that the oxygen atom on the ether chain binds exclusively to the acidic C(2)H position on the Im+ ring. Upon complexation with BF4- to form the ternary (ether-MIm+)2(BF4-) cation, however, the less acidic C(4,5)H groups also participate as contact points for the ionic assembly, in contrast to the behavior of the closely related (EMIm+)2(BF4-) system. These experimental results support the conclusions derived from earlier X-ray scattering and molecular dynamics results on bulk ILs regarding interactions with the ring CH groups and their implications on tuning the viscosities of this class of functionalized ILs.

Role of Cation Structure in CO2 Separation by Ionic Liquid/Sulfonated Polyimide Composite Membrane.

The development of suitable separation technologies for the separation of carbon dioxide is a pressing technological requirement. The application of ion gel membranes for this purpose continues to stimulate a great deal of research, and in this study we focus on the chemical structure of the ionic liquid component in the ion gel, and its interactions with the sulfonated polyimide polymer. Whilst such membranes are known to give promising carbon dioxide separation properties together with mechanical strength and thin-film-processability, we further elaborate on how changing the cation of the ionic liquid from a typical imidazolium cation to a protic variant effects the physicochemical, thermal, and structural properties of the membranes, and how these changes further influence the carbon dioxide separation properties. We compare and contrast our findings with our earlier study on protic and aprotic ammonium-based ionic liquids, and highlight that for CO2 absorption behavior in the imidazolium systems, the importance of directionality of interactions (ion pairs exhibit a large energy stabilization only for a specific geometrical arrangement of cation and anion, e.g., hydrogen bonding rather than Coulombic interaction) between cation and anion applies not only to the protic system, but also to the nominally aprotic cation. Finally, we demonstrate that the phase separation behavior in the ion gels is an important factor in determining the carbon dioxide separation behavior.

Crystal Structures and Melting Behaviors of 2D and 3D Anionic Coordination Polymers Containing Organometallic Ionic Liquid Components.

Although coordination polymers generally do not melt, several that do melt have been synthesized recently and have drawn much attention. In this study, two- and three-dimensional coordination polymers that melt were synthesized, [Ru(Cp)(C6 H5 R)][M{C(CN)3 }2 ] (R=H, Me, Et; M=K, Rb; Cp=C5 H5 ), which are complex salts comprising M[C(CN)3 ] and organometallic ionic liquids [Ru(Cp)(C6 H5 R)][C(CN)3 ]. They have anionic [M{C(CN)3 }2 ]n - coordination polymer frameworks, whose dimensionalities depend on the size of the organometallic cation inside. Their melting points decreased with increasing cation substituent length and size of the alkali metal ion (Tm =102-239 °C), and these low-melting-point coordination polymers exhibited incongruent melting, forming mixtures of solid M[C(CN)3 ] and ionic liquid upon melting. Using the same method, coordination polymers were synthesized with various bridging ligands, [Co(Cp)2 ][MX2 ] (X=B(CN)4 , C(CN)3 , N(CN)2 ; M=K, Na), as well as a paramagnetic coordination polymer, [Fe(Cp)2 ][K{C(CN)3 }2 ].

Effect of Ionic Liquid Components on the Coil Dimensions of PEO

Small-angle neutron scattering is used to measure the infinite dilution radius of gyration (Rg,0) for a range of molecular weights (10–250 kg/mol) of perdeuterated poly(ethylene oxide) (d-PEO) in v...

Ionic Liquids as Solvents for SN2 Processes. Demonstration of the Complex Interplay of Interactions Resulting in the Observed Solvent Effects

Bimolecular nucleophilic substitution reactions between triphenylphosphine and benzylic electrophiles have been examined in an ionic liquid to probe interactions with species along the reaction coordinate. Trends in the rate constant were found on both varying the leaving group and the electronic nature of the aromatic ring. In all the cases considered, interactions between the components of the ionic liquid and the transition state were shown to be more significant in determining reaction outcome than previously observed for this class of reaction. This demonstrates the importance of considering interactions of the ionic liquid components with all species along the reaction coordinate when investigating the origin of ionic liquid solvent effects, along with how such effects might be exploited.

Azolate Anions in Ionic Liquids: Promising and Under-Utilized Components of the Ionic Liquid Toolbox.

Owing to their ease of synthesis, diffuse positive charge, and chemical stability, 1-alkyl-3-methylimidazolium cations (i.e., [Cn mim]+ ) are one of the most routinely utilized and historically important components in ionic liquid (IL) chemistry. However, while this is a routinely encountered member of the IL family as cations, relatively few workers have explored the versatile chemistry of azoles to allow their use as an anionic component in ILs, as azolates. Azolate anions possess many of the desired properties for IL formation, including a diffuse ionic charge, tailorable asymmetry, and synthetic flexibility, with the added advantages of not relying on halogen atoms for electron-withdrawing effects, as is commonly encountered with IL anions such as hexafluorophosphate. This review explores the 122 azolate-containing ILs known in the literature (prepared from only 39 disparate azolate anions), with a view to highlighting not only their demonstrated utility as an IL component, but the ways in which the larger scientific community may utilize their advantageous properties for new tailored materials.

Microemulsion-Based One-Step Electrochemical Fabrication of Mesoporous Catalysts

Electrochemical technology has been proposed as an alternative or complementary method to classical inorganic synthesis for the fabrication of effective metallic solid catalysts. Microemulsion-based electrodeposition is a novel, fast, and one-step procedure to obtain mesoporous catalysts with extraordinarily effective areas, which can be used in heterogeneous catalysis for degradation of pollutants and clean energy production. The fabrication process involves conducting microemulsions containing ionic species (dissolved in aqueous solutions) as precursors of the metallic catalysts. The presence of nanometric droplets of organic or ionic-liquid components in the microemulsion defines the mesoporosity of the catalysts during a one-step electrodeposition process. This method also allows the fabrication of metal catalysts as supported mesoporous films or mesoporous nanowires with very high effective areas. Additionally, reactants have excellent accessibility to the overall surface of the catalysts. The different catalysts fabricated with the help of this technology have been tested for competitive degradation of organic pollutants and anodes' materials for fuel cell devices.

Ionic Liquids as Fragrance Precursors: Smart Delivery Systems for Volatile Compounds

The low volatility of many ionic liquids (ILs) can be used to design a specific delivery system with a triggered release mechanism for volatile fragrances. We present two different strategies for IL-supported profragrance compounds based on common fragrance alcohols. When the fragrance was attached to the cation, its release was triggered by heat, while the fragrance attached to the anion was released under basic conditions. Selection of the counterion allowed not only control of the physical properties of the resulting compound but also addition of a second functionality. Our design strategy shows that the choice of the IL components can result in safe, biocompatible ionic profragrances suitable for applications such as topical nutraceutical or cosmetic formulations.

Nanoemulsions with All Ionic Liquid Components as Recyclable Nanoreactors

Nanoemulsions (NEs) comprising ionic liquids (ILs); ethanolammonium formate (HO-EOAF), proliniumisopropylester dioctylsulfosuccinate ([ProC3][AOT]), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, ([Bmim][NTf2]) as insoluble hydrophilic, surface active, and hydrophobic components have been constructed. This novel class of colloidal formulations exhibited several contrasting properties vis-à-vis conventional water-in-oil or water-in-ionic liquid or nonaqueous NEs such as (i) spontaneous formation, (ii) thermodynamic stability and isotropic nature, (iii) decrease of droplet size with increase in polar medium concentration, and (iv) high thermal and kinetic stability. Mechanisms and characteristics for such anomalies have been investigated by physical, spectroscopic, and imaging techniques. NEs have been demonstrated as versatile recyclable nanoreactors for user-friendly synthesis of materials such as metal-organic frameworks/light harvesting hybrid systems. We anticipate that this development will lead to the construction of several other need-based "all ionic-liquid nanoemulsions" in view of the flexibility provided by the tailoring nature of ILs.

Highly Active TiO2 Microspheres Formation in the Presence of Ethylammonium Nitrate Ionic Liquid

Spherical microparticles of TiO2 were synthesized by the ionic liquid-assisted solvothermal method at different reaction times (3, 6, 12, and 24 h). The properties of the prepared photocatalysts were investigated by means of UV-VIS diffuse-reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of the phenol degradation was related to the time of the solvothermal synthesis, as determined for the TiO2_EAN(1:1)_24h sample. The microparticles of TiO2_EAN(1:1)_3h that formed during only 3 h of the synthesis time revealed a really high photoactivity under visible irradiation (75%). This value increased to 80% and 82% after 12 h and 24 h, respectively. The photoactivity increase was accompanied by the increase of the specific surface area, thus the poresize as well as the ability to absorb UV-VIS irradiation. The high efficiency of the phenol degradation of the ionic liquid (IL)–TiO2 photocatalysts was ascribed to the interaction between the surface of the TiO2 and ionic liquid components (carbon and nitrogen).

Metal sols in ionic liquids: synthesis, properties, and application

This review contains the analysis of the state-of-the-art data on synthesis, structure, and practical application of metal sols in ionic liquids. Problems related to stabilization of metallic nanoparticles by the components of ionic liquids are analyzed in detail. Information on catalytic properties of metal sols in ionic liquids is generalized. Examples illustrating practical application of these systems in diverse areas of science and technology are presented.