Pyrrolidinium-based Ionic Liquid Research Articles

Thermophysical and transport properties of a pyrrolidinium-based ionic liquid confined in silica

Ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyrrTFSI) was confined in silica (Aerosil A380) by direct mixing. The resulting BMPyrrTFSI/xSiO2 ionogel (x – from 2.3 to 6.7 wt%) was studied by TG, DSC, conductometry and viscometric methods. For confined IL, a decrease in the Tm and Ts-s by 14–16 °C and an increase in the Tg, and Tcc by 4–5 °C were found. With an increase in xSiO2, the opposite dynamics of the decomposition temperatures Tonset and Tpeak, and a disproportionate decrease in ionic conductivity were observed. The change in the properties of BMPyrrTFSI under conditions of limited geometry of the silica matrix is explained in the terms by the interaction of the IL and SiO2, as well as the conformation features of the cation and anion. In the first time, parameters such as the fragility index D and the formation factor F were also discussed for such systems. As a result, BMPyrrTFSI/4.5 wt% SiO2 ionogel (0.2 S m−1, 20 °C) was proposed as a promising electrolyte for application in electrochemical devices. This study may be useful for creating quasi-solid electrolytes based on ILs and inorganic materials.

Entropy-Driven 60mol% Li Electrolyte for Li Metal-Free Batteries.

Highly Li-concentrated electrolytes are acknowledged for their compatibility with Li metal negative electrodes and high voltage positive electrodes to achieve high-energy Li metal batteries, showcasing stable and facile interfaces for Li deposition/dissolution and high anodic stability. This study aims to explore a highly concentrated electrolyte by adopting entropy-driven chemistry for Li metal-free (so-called anode-free) batteries. The combination of lithium bis(fluorosulfonyl)amide (LiFSA) and lithium trifluoromethanesulfonate (LiOTf)salts in a pyrrolidinium-based ionic liquid is found to significantly modify the coordination structure, resulting in an unprecedented 60mol% Li concentration and a low solvent-to-salt ratio of 0.67:1 in the electrolyte system. This novel 60mol% Li electrolyte demonstrates unique coordination stricture, featuring a high ratio of monodentate-anion structures and aggregates, which facilitates an enhanced Li+ transference number and improved anodic stability. Moreover, the developed electrolyte provides a facile de-coordination process and leads to the formation of an anion-based solid electrolyte interface, which enables stable Li deposition/dissolution properties and demonstrates excellent cycling stability in the Li metal-free full cell with a Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) positive electrode.

Fluorinated Linkers Enable High-Voltage Pyrrolidinium-based Dicationic Ionic Liquid Electrolytes.

Novel fluorinated, pyrrolidinium-based dicationic ionic liquids (FDILs) as high-performance electrolytes in energy storage devices have been prepared, displaying unprecedented electrochemical stabilities (up to 7 V); thermal stability (up to 370 °C) and ion transport (up to 1.45 mS cm-1). FDILs were designed with a fluorinated ether linker and paired with TFSI/FSI counterions. To comprehensively assess the impact of the fluorinated spacer on their electrochemical, thermal, and physico-chemical properties, a comparison with their non-fluorinated counterparts was conducted. With a specific focus on their application as electrolytes in next-generation high-voltage lithium-ion batteries, the impact of the Li-salt on the characteristics of dicationic ILs was systematically evaluated. The incorporation of a fluorinated linker demonstrates significantly superior properties compared to their non-fluorinated counterparts, presenting a promising alternative towards next-generation high-voltage energy storage systems.

Influence of Pyrrolidinium-Based Ionic Liquid on the Interfacial Activity and Droplet Leaf Surface Wettability of Nitenpyram: Experimental and Theoretical Approach

Influence of Pyrrolidinium-Based Ionic Liquid on the Interfacial Activity and Droplet Leaf Surface Wettability of Nitenpyram: Experimental and Theoretical Approach

Ternary Solid Polymer Electrolytes at the Electrochemical Interface: A Computational Study.

Polymer-based solid-like gel electrolytes have emerged as a promising alternative to improve battery performance. However, there is a scarcity of studies on the behavior of these media at the electrochemical interface. In this work, we report classical MD simulations of ternary polymer electrolytes composed of poly(ethylene oxide), a lithium salt [lithium bis(trifluoromethanesulfonyl)imide], and different ionic liquids [1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide] confined between two charged and uncharged graphene-like surfaces. The molecular solvation of Li+ ions and their diffusion as well as the polymer conformational picture were characterized in terms of the radial distribution functions, coordination numbers, number density profiles, orientations, displacement variance, polymer radius of gyration, and polymer end-to-end distance. Our results show that the layering behavior of the ternary electrolyte in the interfacial region leads to a decrease of Li+ mobility in the direction perpendicular to the electrodes and high energy barriers that hinder lithium cations from coming into direct contact with the graphene-like surface. The nature of the ionic liquid and its concentration were found to influence the structural and dynamic properties at the electrode/electrolyte interface, the electrolyte with low amounts of the pyrrolidinium-based ionic liquid being that with the best performance since it favors the migration of Li+ cations toward the negative electrode when compared to the imidazolium-based one.

Unravelling solvation structure and interfacial mechanism of pyrrolidinium-based ionic liquid electrolytes in potassium-ion batteries

Ionic liquid-based electrolytes (ILEs) show great potential in mitigating the dissolution of organic electrode materials as well as manipulating the interfacial electrochemistry for long lifespan of potassium-ion batteries (PIBs). Herein, KFSI/Pyr13FSI ILEs with varying K+ and Pyr13+ ratios were designed to match a novel organic K-storage anode of p-toluic acid/CMK3 (PTA/CMK3). These ILEs exhibited facilely manipulated solvation structures, resulting into excellent compatibility with K-metal as well as promotion of the generation of robust solid-electrolyte interphase (SEI) for stable K-storage. As a result, the optimized PTA/CMK3||KFSI/Pyr13FSI K-storage system delivered a reversible capacity of 190 mAh/g(composites) alongside high coulomb efficiency of 99.7 % at a current density of 200 mA/g for 600 cycles. This work provides a fresh insight on rational design of ILEs-based advanced PIBs with high energy density and safety.

Experimental investigation of pyrrolidinium-based ionic liquid as shale swelling inhibitor for water-based drilling fluids

This study evaluated the potential of 1-ethyl-1-methylpyrrolidinium bromide (1E1MPyBr) ionic liquid as a shale swelling inhibitor for water-based mud. Firstly, a linear shale swelling test was conducted to evaluate the ionic liquid's ability to inhibit clay hydration. Moreover, a capillary suction time test was performed to determine the fluid absorbance potential. Besides, particle size distribution analysis and zeta potential were evaluated to determine the ionic liquid effect on the base mud's colloidal distribution and surface charge. Furthermore, the rheological and filtration properties of the ionic liquid-mixed drilling mud were investigated. Finally, The X-ray diffraction analysis was conducted to evaluate the inhibition mechanism. The findings of this study revealed that the incorporation of 0.3 wt% of pyrrolidinium-based ionic liquid into the drilling mud resulted in a 20% reduction in shale swelling behaviour compared to conventional bentonite mud. The observed increase in particle size, decrease in zeta potential, and lower capillary suction timer values demonstrated the clay inhibition potential of ionic liquids. Moreover, adding the ionic liquid to bentonite mixed with water-based mud led to higher fluid loss and decreased rheological properties. These effects were attributed to the intercalation of ionic liquids into the clay layers, which inhibited swelling and hydration and reduced the water absorbance capacity of clay. Besides, the tested ionic liquid showed corrosion inhibition potential. Based on these results, the pyrrolidinium-based ionic liquid is proffered as an efficient shale swelling inhibition additive for water-based mud.

Composite of MIL-101(Cr) with a Pyrrolidinium-Based Ionic Liquid Providing High CO2 Selectivity.

Capturing CO2 selectively from flue gas and natural gas addresses the criteria of a sustainable society. In this work, we incorporated an ionic liquid (IL) (1-methyl-1-propyl pyrrolidinium dicyanamide, [MPPyr][DCA]) into a metal organic framework (MOF), MIL-101(Cr), by wet impregnation and characterized the resulting [MPPyr][DCA]/MIL-101(Cr) composite in deep detail to identify the interactions between [MPPyr][DCA] molecules and MIL-101(Cr). Consequences of these interactions on the CO2/N2, CO2/CH4, and CH4/N2 separation performance of the composite were examined by volumetric gas adsorption measurements complemented by the density functional theory (DFT) calculations. Results showed that the composite offers remarkably high CO2/N2 and CH4/N2 selectivities of 19,180 and 1915 at 0.1 bar and 15 °C corresponding to 1144- and 510-times improvements, respectively, as compared to the corresponding selectivities of pristine MIL-101(Cr). At low pressures, these selectivities reached practically infinity, making the composite completely CO2-selective over CH4 and N2. The CO2/CH4 selectivity was improved from 4.6 to 11.7 at 15 °C and 0.001 bar, yielding a 2.5-times improvement, attributed to the high affinity of [MPPyr][DCA] toward CO2, validated by the DFT calculations. These results offer broad opportunities for the design of composites where ILs are incorporated into the pores of MOFs for high performance gas separation applications to address the environmental challenges.

Understanding Li creep in Li-metal pouch cells and the role of separator integrity

To realize the advantages of high energy density lithium-metal batteries, their cycle life and safety need to be improved to meet practical and commercial demands. External compression has been shown to improve the performance of lithium-metal batteries through suppressing dendrite growth, densifying the lithium deposit, and improving the lithium deposition morphology. Here, we report the behavior of high-capacity Li||LFP pouch cells in pyrrolidinium-based ionic liquid electrolytes at elevated temperature (50 °C) under various levels of compression and discuss the compression-related mechanisms that affect the performance and failure of the cells. Using scanning electron microscopy, we observed more uniform and less dendritic Li deposition at high levels of compression. However, cell pressure evolution data shows significant lithium metal creep above 800 kPa, effectively limiting the maximum applicable compression. Reducing the testing temperature to 25 °C and maintaining high compression led to suppressed Li creep and extended the cell cycle life by 40%. The adverse effect of lithium creep on the separator is identified as an important mechanism on the pouch cell cycling behavior and is further discussed herein.

Assessing the Suitability of a Dicationic Ionic Liquid as a Stabilizing Material for the Storage of DNA in Aqueous Medium.

The present study has been undertaken with an objective to find out a suitable medium for the long-term stability and storage of the ct-DNA structure in aqueous solution. For this purpose, the potential of a pyrrolidinium-based dicationic ionic liquid (DIL) in stabilizing ct-DNA structure has been investigated by following the DNA-DIL interaction. Additionally, in order to understand the fundamental aspects regarding the DNA-DIL interaction in a comprehensive manner, studies are also done by employing structurally similar monocationic ionic liquids (MILs). The investigations have been carried out both at ensemble-average and single molecular level by using various spectroscopic techniques. The molecular docking study has also been performed to throw more light into the experimental observations. The combined steady-state and time-resolved fluorescence, fluorescence correlation spectroscopy, and circular dichroism measurements have demonstrated that DILs can effectively be used as better storage media for ct-DNA as compared to MILs. Investigations have also shown that the extra electrostatic interaction between the cationic head group of DIL and the phosphate backbone of DNA is primarily responsible for providing better stabilization to ct-DNA, retaining its native structure in aqueous medium. The outcomes of the present study are also expected to provide valuable insights in designing new polycationic IL systems that can be used in nucleic acid-based applications.

CO2 Adsorption Performance on Surface-Functionalized Activated Carbon Impregnated with Pyrrolidinium-Based Ionic Liquid

The serious environmental issues associated with CO2 emissions have triggered the search for energy efficient processes and CO2 capture technologies to control the amount of gas released into the atmosphere. One of the suitable techniques is CO2 adsorption using functionalized sorbents. In this study, a functionalized activated carbon (AC) material was developed via the wet impregnation technique. The AC was synthesized from a rubber seed shell (RSS) precursor using chemical activation and was later impregnated with different ratios of [bmpy][Tf2N] ionic liquid (IL). The AC was successfully functionalized with IL as confirmed by FTIR and Raman spectroscopy analyses. Incorporation of IL resulted in a reduction in the surface area and total pore volume of the parent adsorbent. Bare AC showed the largest SBET value of 683 m2/g, while AC functionalized with the maximum amount of IL showed 14 m2/g. A comparative analysis of CO2 adsorption data revealed that CO2 adsorption performance of AC is majorly affected by surface area and a pore-clogging effect. Temperature has a positive impact on the CO2 adsorption capacity of functionalized AC due to better dispersion of IL at higher temperatures. The CO2 adsorption capacity of AC (30) increased from 1.124 mmol/g at 25 °C to 1.714 mmol/g at 40 °C.

Physical and Electrochemical Properties of Pyrrolidinium-Based Ionic Liquid and Methyl Propionate Co-Solvent Electrolyte

Advancements in modern technology has led to increasing demand for high-capacity batteries. Lithium metal batteries have high specific capacity and are a promising candidate for post lithium-ion batteries. Traditional organic electrolytes have poor compatibility with lithium metal batteries. Ionic liquids (IL) with the addition of co-solvents have shown promised in lithium metal battery systems. In this work, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ([Pyr14][TFSI]) was selected for its large electrochemical window and methyl propionate (MP) for its low viscosity and melting point. The IL/MP mixture with 0.8m LiTFSI maintained a large electrochemical window (>5V), extended liquid range of the IL and noticeably improved conductivity (from 0.56 mS/cm for 0.8m LiTFSI in [Pyr14][TFSI] to 11 mS/cm for 0.8m LiTFSI in a mixture of 1 to 7 mole ratio of [Pyr14][TFSI] to MP at 25°C). Also, we have identified that the addition of cyclic carbonate is important to increase the columbic efficiency for lithium deposition and stripping.

Influence of temperature and concentration on the molecular interactions of pyrrolidinium-based ionic liquid with water and alcohols: An experimental and DFT studies

The purpose of the present work is to explore the influence of concentration and temperature on solute–solvent interactions of binary mixtures of ionic liquid (IL) 1-methyl-1-propyl pyrrolidinium tetrafluoroborate ([MPpyr][BF 4 ]) and water, alcohols (methanol and ethanol) at 298.15, 303.15, 308.15 and 313.15 K under atmospheric pressure. The thermophysical properties such as the apparent molar volume ( V ϕ ), apparent molar adiabatic compressibility ( κ ϕ ), and limiting apparent molar volumes ( V ϕ 0 ), limiting apparent molar adiabatic compressibility ( κ ϕ 0 ), the limiting apparent molar expansibility ( E ϕ 0 ), thermal expansion coefficients ( α P ) were evaluated from experimental density ( ρ ) and speed of sound ( u ) data using suitable Redlich–Mayer type equation. V ϕ 0 and ( κ ϕ 0 ) values explain that the IL-solvent interaction in water, are stronger than the those between either methanol or ethanol with IL. Density functional theory (DFT) results are performed using the B3LYP/6–31++G (d,p) method, shows that the prominent interactions within the IL which are aliphatic C–H···anion interactions while the prominent interactions between the IL and the selected solvents are O − H···anion solute–solvent interactions. More importantly, DFT results confirm the trends observed from experimental findings, that the interaction involving IL in water is stronger than those involving either methanol or ethanol solvent with IL.

Depth-Dependent Understanding of Cathode Electrolyte Interphase (CEI) on the Layered Li-Ion Cathodes Operated at Extreme High Temperature

The high-temperature operation of Li-ion batteries is highly dependent on the stability of the cathode electrolyte interphase (CEI) formed during lithiation–delithiation reactions. However, knowledge on the nature of the CEI is limited and its stability under extreme temperatures is not well understood. Therefore, herein, we investigate a proof-of-concept study on stabilizing CEI on model LiNi0.33Mn0.33Co0.33O2 (NMC333) at an extreme operation condition of 100 °C using the thermally stable pyrrolidinium-based ionic liquid electrolyte. The electrochemical lithiation–delithiation reactions at 100 °C and the CEI evolution upon different cycling conditions are investigated. Further, the depth-dependent CEI chemistry was investigated using energy-tunable synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). The results reveal that the high-temperature operation accelerated the CEI formation compared to room temperature, and the surface of the interphase layer is rich in boron-based inorganic moieties than the deeper surface. Further, bulk-sensitive X-ray absorption spectroscopy (XAS) was used to investigate the transition-metal redox contributors during high-temperature electrochemical reactions; similar to room temperature, the Ni2+/4+ redox couple is the only charge-compensating redox couple during high-temperature operation. Finally, the physical nature of the conformal CEI on the cathode particles was visualized with high-resolution transmission electron microscopy, which confirms that the significant degradation of cathode particles without conformal CEI is due to the transformation of a layer-to-spinel formation at extreme temperature. In this study, understanding this high-temperature interfacial chemistry of NMC cathodes through advanced spectroscopy and microscopy will shed light on transforming the ambient-temperature Li-ion chemistry into high-temperature applications.

Spectroscopic investigation of the structure of a pyrrolidinium-based ionic liquid at electrified interfaces.

The molecular structure of electric double layers (EDLs) at electrode-electrolyte interfaces is crucial for all types of electrochemical processes. Here, we probe the EDL structure of an ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPy-TFSI), using electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy. We extract the position and intensity of individual peaks corresponding to either intra- or inter-molecular vibrational modes and examine their dependence on the electrode potential. The observed trends suggest that the molecular reconfiguration mechanism is distinct between cations and anions. BMPy+ is found to always adsorb on the Au electrode surface via the pyrrolidinium ring while the alkyl chains strongly change their orientation at different potentials. In contrast, TFSI- is observed to have pronounced position shifts but negligible orientation changes as we sweep the electrode potential. Despite their distinct reconfiguration mechanisms, BMPy+ and TFSI- in the EDL are likely paired together through strong intermolecular interaction.

Unusual Lower Critical Solution Temperature Phase Behavior of Poly(benzyl methacrylate) in a Pyrrolidinium-Based Ionic Liquid.

Polymer/ionic liquid systems are being increasingly explored, yet those exhibiting lower critical solution temperature (LCST) phase behavior remain poorly understood. Poly(benzyl methacrylate) in certain ionic liquids constitute unusual LCST systems, in that the second virial coefficient (A2) in dilute solutions has recently been shown to be positive, indicative of good solvent behavior, even above phase separation temperatures, where A2 < 0 is expected. In this work, we describe the LCST phase behavior of poly(benzyl methacrylate) in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide for three different molecular weights (32, 63, and 76 kg/mol) in concentrated solutions (5–40% by weight). Turbidimetry measurements reveal a strong concentration dependence to the phase boundaries, yet the molecular weight is shown to have no influence. The critical compositions of these systems are not accessed, and must therefore lie above 40 wt% polymer, far from the values (ca. 10%) anticipated by Flory-Huggins theory. The proximity of the experimental cloud point to the coexistence curve (binodal) and the thermo-reversibility of the phase transitions, are also confirmed at various heating and cooling rates.

Zinc Stannate as anode and Pyrrolidinium-Based Room Temperature Ionic Liquid as electrolyte for Lithium-ion Cells

Zinc Stannate as anode and Pyrrolidinium-Based Room Temperature Ionic Liquid as electrolyte for Lithium-ion Cells

Electrodeposition of Cobalt in a Pyrrolidinium-Based Ionic Liquid Under a Magnetic Field

Cobalt (Co) is well-known as a hard-magnetic material for its tailorable magnetic properties. Nowadays, a pyrrolidinium-based ionic liquid, composed of 1-butyl-1-methylpyrrolidinium (BMP+) and bis(trifluromethylsulfonyl)amide (TFSA–), has drawn more attention for the electrodeposition of various transition metals because of its wide electrochemical potential window, acceptable ionic conductivity, and high stability against moisture. Although the redox reaction of Co species has been reported in BMPTFSA, the electrochemical behavior of Co species under a magnetic field has not been explored in this ionic liquid.1-3 In this study, the electrodeposition of Co has been performed in BMPTFSA under a static magnetic field. Co(TFSA)2 was prepared by the reaction of CoCO3 with HTFSA. A Teflon made, double compartment cell was used for the electrochemical measurements using a glassy carbon (GC) as a working electrode, a platinum mesh as a counter electrode, and a silver wire immersed in BMPTFSA containing 0.1 M AgCF3SO3 as a reference electrode. A neodymium magnet (NdFeB) was attached to the back of the GC electrode. The diameter of the magnet was 6 mm and the magnetic flux density was 530 mT. Potentiostatic cathodic reduction applying –1.6 and –2.0 V was conducted under the magnetic field in BMPTFSA containing Co(TFSA)2 at 25 °C. Nanowire-shaped deposits were obtained on the GC electrode after the electrodeposition at both potentials. The presence of Co in the deposits was confirmed by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. However, no diffraction peak was observed in the deposits by X-ray diffraction. The deposits were further examined by transmission electron microscopy. The lattice fringe corresponding to (111) plane of Co was found in the deposits, indicating the deposits were composed of metallic Co nanoparticles.References(1) R. Fukui, Y. Katayama, and T. Miura, Electrochemistry, 73, 567 (2005).(2) Y. Katayama, R. Fukui, and T. Miura, J. Electrochem. Soc., 154, D534 (2007).(3) Y. Katayama, R. Fukui, and T. Miura, Electrochemistry, 81, 532 (2013).

An investigation of commercial carbon air cathode structure in ionic liquid based sodium oxygen batteries

In order to bridge the gap between theoretical and practical energy density in sodium oxygen batteries challenges need to be overcome. In this work, four commercial air cathodes were selected, and the impacts of their morphologies, structure and chemistry on their performance with a pyrrolidinium-based ionic liquid electrolyte are evaluated. The highest discharge capacity was found for a cathode with a pore size ca. 6 nm; this was over 100 times greater than that delivered by a cathode with a pore size less than 2 nm. The air cathode with the highest specific surface area and the presence of a microporous layer (BC39) exhibited the highest specific capacity (0.53 mAh cm−2).

Solvent- and Catalyst-Free Carbon Dioxide Capture and Reduction to Formate with Borohydride Ionic Liquid.

The metal- and solvent-free capture and reduction of large amounts of CO2 to formate under ambient conditions is achieved by combining a pyrrolidinium-based ionic liquid with a borohydride anion. This material demonstrates one of the highest CO2 capacities at room temperature and 1 bar with up to 1 g g-1 IL . CO2 gas reacts with the BH4 - anion to give triformatoborohydride, [HB(OCHO)3 ]- . The reaction occurs without loss in capacity at low CO2 concentration (6 vol % diluted with N2 ). The thermodynamics and kinetics of the reaction were monitored by using a magnetic suspended balance. In addition, more than 1 mol mol-1 is captured and reduced if air is used as a CO2 source. The product can be then treated with HCl to give formic acid and the corresponding ionic liquid chloride, which can be recycled. This ionic liquid borohydride demonstrates great potential as a CO2 absorber and reducer to produce alternative fuels.