1,721,006 research outputs found
Nanoscale organization in the fluorinated room temperature ionic liquid: Tetraethyl ammonium (trifluoromethanesulfonyl)(nonafluorobutylsulfonyl)imide
No full textFluorinated Room Temperature Ionic Liquids (FRTILs) are a branch of ionic liquids that is the object of growing interest for a wide range of potential applications, due to the synergic combination of specifically ionic features and those properties that stem from fluorous tails. So far limited experimental work exists on the micro- and mesoscopic structural organization in this class of compounds. Such a work is however necessary to fully understand morphological details at atomistic level that would have strong implications in terms of bulk properties. Here we use the synergy between X-ray and neutron scattering together with molecular dynamics simulations to access structural details of a technologically relevant FRTIL that is characterised by an anion bearing a long enough fluorinated tail to develop specific morphological features. In particular, we find the first experimental evidence that in FRTILs bearing an asymmetric bis(perfluoroalkyl)sulfonyl-imide anion, fluorous side chains tend to be spatially segregated into nm-scale spatial heterogeneities. This feature together with the well-established micro-segregation of side alkyl chains in conventional RTILs leads to the concept of triphilic ILs, whose technological applications are yet to be fully developed. © 2018 Author(s)
Multiple points of view of heteronuclear NOE: Long range vs short range contacts in pyrrolidinium based ionic liquids in the presence of Li salts
No full textThe nuclear Overhauser enhancement (NOE) is a powerful tool of NMR spectroscopy extensively used to gain structural information in ionic liquids (ILs). A general model for the distance dependence of intermolecular NOE in ILs was recently proposed showing that NOE spots beyond the first solvation shell and accounts for long-range effects. This conclusion prompted for a deep rethinking of the NOE data interpretation in ILs. In this paper we present an extensive and quantitative study of N-propyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI), the homologue with bis(fluorosulfonyl)imide (PYR13FSI), and their mixtures with LiTFSI based on {1H-19F} and {1H-7Li}NOE correlation experiments (HOESY). The former is mainly tuned on long-range interactions, the latter on short-range ones, due to the small and large Larmor frequency differences of the involved nuclei. The collected data are discussed in two different way: long-range {1H-19F}NOEs spot on the polar/apolar domains within the ILs, whereas short-range (e.g. regarding the first coordination shell) {1H-7Li}NOEs describe the contacts between first neighbors, with interesting correlation with the distances' statistics derived by crystallographic data of related systems. © 2015 Elsevier B.V.All rights reserved
From Nanoscale to Microscale: Crossover in the Diffusion Dynamics within Two Pyrrolidinium-Based Ionic Liquids
No full textKnowledge of the ion motion in room temperature ionic liquids (RTILs) is critical for their applications in a number of fields, from lithium batteries to dye-sensitized solar cells. Experiments on a limited number of RTILs have shown that on macroscopic time scales the ions typically undergo conventional, Gaussian diffusion. On shorter time scales, however, non-Gaussian behavior has been observed, similar to supercooled fluids, concentrated colloidal suspensions, and more complex systems. Here we characterize the diffusive motion of ionic liquids based on the N-butyl-N-methylpyrrolidinium (PYR14) cation and bis(trifluoro methanesulfonyl)imide (TFSI) or bis(fluorosulfonyl)imide (FSI) anions. A combination of pulsed gradient spin-echo (PGSE) NMR experiments and molecular dynamics (MD) simulations demonstrates a crossover from subdiffusive behavior to conventional Gaussian diffusion at ∼10 ns. The deconvolution of molecular displacements into a continuous spectrum of diffusivities shows that the short-time behavior is related to the effects of molecular caging. For PYR14FSI, we identify the change of short-range ion-counterion associations as one possible mechanism triggering long-range displacements. © 2017 American Chemical Society
Influence of Alkyl Chain Length on Microscopic Configurations of the Anion in the Crystalline Phases of PYR1A-TFSI
No full textThe infrared spectra and their temperature dependence are measured for a series of pyrrolidinium based ionic liquids (ILs) sharing the bis(trifluoromethanesulfonyl)imide (TFSI) anion and having alkyl chains of different length. While in the liquid or glassy state, both conformers of TFSI are retained for all compounds, in the solid state a strong predominance of trans-TFSI occurs in ionic liquids with alkyl chains shorter than five C-H groups; on the contrary, for alkyl chain longer than six C-H groups crystalline phases display only cis-TFSI, which is a rare configuration in solids. Moreover, a mixed system composed of a short chain liquid (PYR14-TFSI) with one having a longer chain (PYR18-TFSI) in a mass ratio of 1:1 is studied. The competition between the two conformers of TFSI hinders the crystallization and gives rise to a glass transition around 183 K. © 2017 American Chemical Society
Sodium-conducting ionic liquid-based electrolytes
No full textMixtures, based on the N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) ionic liquid and the NaTFSI salt, as low flammability and volatility electrolytes for safer sodium electrochemical energy storage devices, were prepared and investigated in terms of thermal and ion-transport properties. The PYR14TFSI-NaTFSI electrolytes showed melting point down to - 30 C. No difference in terms of ion-transport properties was observed with respect to analogous lithium electrolyte systems. Conductivity values above 1 × 10- 3 S cm- 1 were observed at room temperature. © 2014 Elsevier B.V
Thermal and electrochemical properties of PEO-LiTFSI-Pyr 14TFSI-based composite cathodes, incorporating 4 V-class cathode active materials
No full textPoly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PEO-LiTFSI-Pyr14TFSI)-based 4 V-class composite cathodes, incorporating either Li(Ni1/3Co1/3Mn1/3)O 2 or Li(Ni0.8Co0.15Al0.05)O 2 were prepared by a hot-pressing process and successively investigated in terms of their morphological, thermal, and electrochemical properties. Thereby, excellent mechanical and thermal properties could be demonstrated for all composite cathodes. The electrochemical performance of truly dry all-solid-state Li/P(EO)10LiTFSI-(Pyr14TFSI) 2/composite cathode batteries at temperatures as low as 40 C revealed high delivered capacities. However, in comparison with LiFePO4, the 4 V-class composite cathodes also indicated much lower capacity retention. In-depth investigations on the interfacial properties of Li(Ni 0.8Co0.15Al0.05)O2 composite cathodes revealed a strong dependence on the anodic cut-off potential and the presence of current flow through the cell, whereby different degradation mechanisms could be characterized upon cycling, according to which the finite growth of a surface films at both electrode/polymer electrolyte interfaces inhibited continuous decomposition of the polymer electrolyte even at potentials as high as 4.3 V. Moreover, the presence of Pyr14TFSI in the 4 V-class composite cathodes sustainably reduced the cathode interfacial resistance and presumably diminished the corrosion of the aluminum current collector. © 2013 Elsevier B.V. All rights reserved
An advanced ionic liquid-lithium salt electrolyte mixture based on the bis(fluoromethanesulfonyl)imide anion
No full textAn innovative electrolyte mixture, based on the novel N-butyl-N- ethylpyrrolidinium bis(fluoromethanesulfonyl)imide (PYR24FSI) ionic liquid and the LiFSI lithium salt, was prepared and its thermal and ion-transport properties were investigated. The FSI-based mixture showed fast crystallization kinetics with melting point around - 40 C. A conductivity close to 4 � 10- 3 S cm- 1 was reached at room temperature. This PYR24FSI-LiFSI mixture family has been found to be an appealing electrolyte for high safety and performance lithium battery systems. � 2014 Elsevier B.V
Mesoscopic organization in ionic liquids
No full textWe discuss some published results and provide new observations concerning the high level of structural complexity that lies behind the nanoscale correlations in ionic liquids (ILs) and their mixtures with molecular liquids. It turns out that this organization is a consequence of the hierarchical construction on both spatial (from ångström to several nanometer) and temporal (from fraction of picosecond to hundreds of nanosecond) scales, which requires joint use of experimental and computational tools. © 2017, Springer International Publishing Switzerland
Mesoscopic structural organization in triphilic room temperature ionic liquids
No full textRoom temperature ionic liquids are one of the most exciting classes of materials in the last decade. The interest for these low melting, ionic compounds stems from both their technological impact and the stimulating plethora of structural and dynamic peculiarities in the mesoscopic space-time scales. It is nowadays well-established that they are characterised by an enhanced degree of mesoscopic order originating from their inherent amphiphilicity. In this contribution we highlight the existence of a further degree of mesoscopic complexity when dealing with RTILs bearing a medium length fluorous tail: such triphilic materials (they simultaneously contain polar, hydrophobic and fluorophilic moieties that mutually segregate from each other) turn out to be highly structurally compartmentalised at the mesoscopic level, thus paving the way to new smart applications for this new class of RTILs. This journal is © The Royal Society of Chemistry
Ionic liquid mixtures with tunable physicochemical properties
No full textInnovative ionic liquids (ILs) can be prepared by properly combining pure ILs, thus obtaining materials with improved characteristics. For instance, three different mixture families, namely PYR11TFSI-PYR14TFSI, PYR11TFSI-PYR18TFSI and PYR14TFSI-PYR18TFSI, were prepared and investigated in terms of thermal behavior, ionic conductivity and ion self-diffusion coefficient as a function of the mole composition. The physicochemical properties, including mechanical consistency, of these mixed ionic liquids were found to be enhanced and/or finely tuned by properly varying the aliphatic chain length and/or the mole ratio of the pyrrolidinium cations. This issue might be profitably exploited to match the electrolyte requirements of electrochemical devices operating under particular or hard conditions, not always achievable by single materials. © 2014 Elsevier Ltd. All rights reserved
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