Solvents Of High Dielectric Constant Research Articles

Functional Electrolyte: Highly-Safe LIB Using Branched Carboxylic Acid Ester as Electrolyte Additive

The electrolyte in current automotive lithium-ion batteries is a mixture of ethylene carbonate (EC), which has a high dielectric constant, and ethyl methyl carbonate or dimethyl carbonate, which have a low viscosity. However, the flash point of these mixed solvents is as low as 25 °C, so safety precautions must be taken. On the other hand, if only EC or propylene carbonate with a high flash point is used, the flash point will be 120 °C or higher. However, the high dielectric constant solvent cannot wet the hydrophobic separator whose material is polyethylene and/or polypropylene. Therefore, there is a problem that the battery does not work. In 1999, we proposed a “functional electrolyte” in which a small amount of an additive with a new function is added to the electrolyte, and many additives have since been commercialized. In recent work, we focused on a low viscosity linear carboxylic acid esters, designed an electrolyte with a flash point above 120 °C that provides wettability to the separator even in an electrolyte with a high dielectric constant solvent.

Lateral Electron and Hole Hopping between Dyes on Mesoporous ZrO2: Unexpected Influence of Solvents with a Low Dielectric Constant

Lateral intermolecular charge transfer between photosensitizers on metal oxide substrates is important for the understanding on the overall working principles of dye-sensitized systems. Such studies usually concentrate on either hole or electron transfer separately and are conducted in solvents with a high dielectric constant (εs) that are known, however, to show a drastic decrease of the local dielectric constant close to the metal oxide surface. In the present study, both hole and electron hopping between organic donor-acceptor photosensitizers was experimentally investigated on PB6 dye-sensitized mesoporous ZrO2 films. The donor (close to the surface) and acceptor (away from surface) subunit of the PB6 dye were observed to be involved in hole and electron hopping, respectively. Hole and electron transfer kinetics were found to differ remarkably in high-εs solvents, but similar in solvents with εs < 12. This finding indicates that low-εs solvents maintain similar local dielectric constant values close to, and further away from, the semiconductor surface, which is different from the previously observed behavior of high dielectric constant solvents at a metal oxide interface.

Proton Transfer in Phosphoric Acid-Based Protic Ionic Liquids: Effects of the Base.

Electronic structure calculations were performed to understand highly decoupled conductivities recently reported in protic ionic liquids (PILs). To develop a molecular-level understanding of the mechanisms of proton conductivity in PILs, minimum-energy structures of trimethylamine, imidazole, lidocaine, and creatinine (CRT) with the addition of one to three phosphoric acid (PA) molecules were determined at the B3LYP/6-311G** level of theory with the inclusion of an implicit solvation model (SMD with ε = 61). The proton affinity of the bases and zero-point energy corrected binding energies were computed at a similar level of theory. Proton dissociation from PA occurs in all systems, resulting in the formation of ion pairs due to the relatively strong basicity of the bases (proton acceptors) and the effect of the high dielectric constant solvent in stabilizing the charge separation. The second and third PA molecules preferentially form "ring-like" hydrogen bonds with one another instead of forming hydrogen bonds at the donor and acceptor sites of the bases. Potential energy scans reveal that the bases with stronger proton affinity exert greater influence on the energetics of proton transfer between the individual PA molecules. However, the effects are minimal when shifted into a single-well from a double-well potential. Barrierless proton transfer was observed to occur in the CRT system with several PA molecules present, implying that the CRT may be a promising PA-based PIL.

Solvothermal synthesis of porous organic cage CC3 in the presence of dimethylformamide as solvent

Morphology, and crystal product of porous organic cage CC3, was modified by the use of a novel and non-traditional high dielectric constant solvent dimethyl formamide.

Approaches to Complex Electrolyte Formulation Optimization

Lithium ion battery electrolytes are complex formulations of solvents, salts, and additives. Each component can contribute to the battery performance in a unique way. For example, high dielectric constant solvents are necessary to dissolve the lithium salt, but are high viscosity. Therefore, low viscosity solvents are required to reduce the bulk electrolyte viscosity. Salt type and concentration can affect properties such as conductivity and thermal stability. Finally, many additives may be considered for use in formulations – with functions such as anode solid electrolyte interphase (SEI) formers, cathode SEI formers, acid scavengers, thermal stabilizers, and more. Development of optimized electrolyte formulations can require many experiments to find the best components and ratios/concentrations of components. Using Wildcat’s high throughput battery workflow, we can apply combinatorial chemistry approaches to screen hundreds of new electrolyte components and study their interactions for electrolyte formulation development. Combining statistical models for formulation optimization, and component substitution, the function of a single component in a complex electrolyte and its interaction with other components can be elucidated. In this presentation, we will demonstrate the power of these tools to rapidly improve and optimize complex electrolyte formulations.

Symmetrical and Nonsymmetrical Meso-Meso Directly Linked Hydroporphyrin Dyads: Synthesis and Photochemical Properties.

A series of a rigid meso-meso directly linked chlorin-chlorin, chlorin-bacteriochlorin, and bacteriochlorin-bacteriochlorin dyads, including free bases as well as Zn(II), Pd(II), and Cu(II) complexes, has been synthesized, and their absorption, emission, singlet oxygen (1O2) photosensitization, and electronic properties have been examined. Marked bathochromic shifts of the long-wavelength Q y absorption band and increase in fluorescence quantum yields in dyads, in comparison to the corresponding monomers, are observed. Nonsymmetrical dyads (except bacteriochlorin-bacteriochlorin) show two distinctive Q y bands, corresponding to the absorption of each dyad component. A nearly quantitative S1-S1 energy transfer between hydroporphyrins in dyads, leading to an almost exclusive emission of hydroporphyrin with a lower S1 energy, has been determined. Several symmetrical and all nonsymmetrical dyads exhibit a significant reduction in fluorescence quantum yields in solvents of high dielectric constants; this is attributed to the photoinduced electron transfer. The complexation of one macrocycle by Cu(II) or Pd(II) enhances intersystem crossing in the adjacent, free base dyad component, which is manifested by a significant reduction in fluorescence and increase in quantum yield of 1O2 photosensitization.

Wide-Temperature Electrolytes for Lithium-Ion Batteries.

Formulating electrolytes with solvents of low freezing points and high dielectric constants is a direct approach to extend the service-temperature range of lithium (Li)-ion batteries (LIBs). In this study, we report such wide-temperature electrolyte formulations by optimizing the ethylene carbonate (EC) content in the ternary solvent system of EC, propylene carbonate (PC), and ethyl methyl carbonate (EMC) with LiPF6 salt and CsPF6 additive. An extended service-temperature range from -40 to 60 °C was obtained in LIBs with lithium nickel cobalt aluminum oxide (LiNi0.80Co0.15Al0.05O2, NCA) as cathode and graphite as anode. The discharge capacities at low temperatures and the cycle life at room temperature and elevated temperatures were systematically investigated together with the ionic conductivity and phase-transition behaviors. The most promising electrolyte formulation was identified as 1.0 M LiPF6 in EC-PC-EMC (1:1:8 by wt) with 0.05 M CsPF6, which was demonstrated in both coin cells of graphite∥NCA and 1 Ah pouch cells of graphite∥LiNi1/3Mn1/3Co1/3O2. This optimized electrolyte enables excellent wide-temperature performances, as evidenced by the high capacity retention (68%) at -40 °C and C/5 rate, significantly higher than that (20%) of the conventional LIB electrolyte, and the nearly identical stable cycle life as the conventional LIB electrolyte at room temperature and elevated temperatures up to 60 °C.

Size change of silica nanoparticles induced by non-alcoholic solvent addition during sol–gel reaction

The effect of solvent addition on particle size was investigated for silica nanoparticles synthesized by sol–gel reaction. In order to prepare solvent mixtures having a wide range of solvent polarity, non-alcoholic organic solvents with various dielectric constants were selected, such as toluene, N-methylformamide, chlorobenzene, methyl isobutyl ketone, and N,N-dimethylacetamide, which are firstly tested in this study as cosolvents for controlling the particle size of sol–gel silica. The role of the solvent dielectric constant during the sol–gel reaction is further clarified by experimental observation of increased particle size with low dielectric constant solvents (toluene, chlorobenzene, and methyl isobutyl ketone), and decreased particle size with high dielectric constant solvent (N-methylformamide and N,N-dimethylacetamide). Contradictory observations of particle size change according to water content are discussed in terms of its two competing roles—as a high-dielectric constant solvent and a hydrolysis reactant.

On-site crosslinked quaternized poly(vinyl alcohol) as ionomer binder for solid alkaline fuel cells

Water-soluble polyvinyl alcohol functionalized with quaternary ammonium groups and crosslinked quaternized polyvinyl alcohol were synthesized and used to prepare an ionomer binder solution having a low boiling point and high dielectric constant solvent to be used in electrodes for solid alkaline fuel cells. The polyvinyl alcohol was quaternized to have anion-conducting ability using glycidyltrimethylammonium chloride. To prevent washing-out of the water-soluble anion-conducting ionomer during fuel cell operations, the quaternized poly(vinyl alcohol) was successfully crosslinked by using an on-site crosslinking method. The highest ionic conductivity of the ionomer was 2.3 × 10−2 S cm−1, and its ion exchange capacity was 1.2 meq g−1 at room temperature. The electrodes were fabricated by a spray method on anion-exchangeable membranes, and membrane-electrode assemblies were operated at 50 °C in ambient pressure and were characterized by voltage–current relationship and cyclic voltammetry. The highest performance of the membrane-electrode assemblies having the electrode with the ionomer of 25 wt.% in dry weight basis was 172.8 mW cm−2 at 0.485 V. As a result, the anionic binder electrodes introduced by the on-site crosslinking were successfully functioned both to conduct OH− ions between electrodes and an electrolyte and to move electron to an external circuit by forming three phase boundary at the electrode of the membrane-electrode assemblies.

Design and screening of suitable ligand/diluents systems for removal of Sr2+ ion from nuclear waste: Density functional theoretical modelling

Density functional theoretical (DFT) calculation has been used for the design and screening of ligand/solvent systems for the selective and efficient extraction of Sr2+ ion from aqueous solution using free energy analysis. Present DFT study has shown that the metal ion selectivity cannot be predicted using intrinsic gas phase interaction energy alone. Even implicit solvation employing conductor like screening model (COSMO) approach unable to predict the correct trend of experimental selectivity. The COSMO solvation model when used explicitly by considering first solvation sphere around the metal ion it captures the correct trend of experimental selectivity. Organic solvent of high dielectric constant was found to be suitable for the extraction of the metal ion. Further, COSMO for real solvent (COSMO-RS) was successfully used to predict the solubility and partition coefficients of the ligands for screening. Presence of nitrate anion in the complexation reaction was shown to increase the gas as well as solvent phase complexion energy. The calculated theoretical extraction energy was found to be well correlated to the experimentally observed distribution constant of Sr2+ ion in the biphasic systems. The preferential selectivity of Sr2+ ion over other competing ions towards macrocyclic ligands was demonstrated by calculating free energy of extraction in the biphasic systems. Natural bond order (NBO) analysis was also performed to investigate the nature of bonding in Sr2+ ion-crown ether interaction.

Kinetics of Methylene Green and Ascorbic Acid Reaction in Aqueous 2-propanol at Different Temperatures

The kinetics of reaction of methylene green with ascorbic acid was carried out spectrophotometrically in mixed solvent system by using aqueous 2 -propanol ratios as a solvent in the presenceof hydrochloric acid. The pseudo -first order rate constants were proposed on the basis of the experimental kinetic data. The reaction was carried out in 10%, 20%, 30%, 40%, 50% aqueous 2 -propanol ratios at different ionic strength. The effects of these sol vent compositions and ionic strength on rate of reaction were studied. The effect of concentration of ascorbic acid on the rate of reduction was also determined. The values of rate constants at all initial concentrations of methylene green revealed that re action follows 1 st order kinetics with respect to ascorbic acid and relatively higher value of the rate of the reaction was observed in the solvent of high dielectric constant. The reaction was found to be zero order dependence on the concentration of methylene green, and the variation of hydrochloric acid concentration did not bring about significant changes in the values of rate constants in various aqueous propanol mixtures.

Synthesis and Characterization of Lithium Bis(fluoromalonato)borate for Lithium‐Ion Battery Applications

A new orthochelated salt, lithium bis(monofluoromalonato)borate (LiBFMB), is synthesized and purified for application in lithium‐ion batteries. The presence of fluorine in the borate anion of LiBFMB increases its oxidation potential and also facilitates ion dissociation, as reflected by the ratio of ionic conductivity (σexp) and ion diffusivity coefficients (σNMR). Half‐cell tests using 5.0 V lithium nickel manganese oxide (LiNi0.5Mn1.5O4) as a cathode and ethylene carbonate (EC)/dimethyl carbonate (DMC)/diethyl carbonate (DEC) as a solvent reveals that the impedance of the LiBFMB cell is much larger than those of LiPF6‐ and lithium bis(oxalato)borate (LiBOB)‐based cells, which results in lower capacity and poor cycling performance of the former. X‐ray photoelectron spectroscopy (XPS) results for the cycled cathode electrode suggest that because of the stability of the LiBFMB salt, the solid electrolyte interphase (SEI) formed on the cathode surface is significantly different from those of LiPF6 and LiBOB based electrolytes, resulting in more solvent decomposition and a thicker SEI layer. Initial results also indicate that using a high dielectric constant solvent, propylene carbonate, alters the surface chemistry, reduces the interfacial impedance, and enhances the performance of LiBFMB‐based 5.0 V cell.

Free allyl radical: Catalytic generation and subsequent immobilization onto Au, Pd, Pt, and carbon cathodes

The cathodic reduction of allyl bromide (AllBr) in polar solvents of high dielectric constant containing tetraalkylammonium iodide at precious metals (Au, Pd, Pt, Rh) permits the one-electron scission of the C Br bond easily generating allyl radical. Glassy carbon (GC) used as cathode material also allows splitting the two one-electron transfers, usually observed with most of organic halides. A facile and dense allylation of several solid surfaces (in particular, at GC, Au and Pt) is obtained. The level of ethylenic moiety coverage was calculated by means of bromine and iodine indices (coulometric reduction of halogenated surface-grafted layers) and found to be between 1 and 6 × 10 −9 mol cm −2 of the original electrode area.

Visible Detection of Water in Oil Using Solvatochromism of Organic Fluorescent Dye

A method for simply measuring water mixed into oil is restricted. In the present study, we synthesized a solvatochromic organic fluorescence dye. Changes in the fluorescence spectra and the luminescent color to change of the amount of water in the oil of this fluorescence dye were investigated. In dioxane, which is a low dielectric constant solvent, the color changed from green to yellow and a bathochromic shift of the fluorescence spectra was observed by the increase in moisture. These results suggested that the water selectively solvated to the fluorescence dye. On the other hand, in acetonitrile, which is a high dielectric constant solvent, the bathochromic shift observed by the increase in water showed almost the same tendency as the bathochromic shift accompanying the increase in the dielectric constant. However, the color showed only yellow in a visible observation. The visual detection of water will be applied to some low-dielectric organic solvents and lubricating oils.

Utilizing an ionic liquid for synthesizing a soft matter polymer “gel” electrolyte for high rate capability lithium-ion batteries

A cross-linked polymer “gel” electrolyte obtained from free radical polymerization of a vinyl monomer (acrylonitrile; AN) in a room temperature ionic liquid electrolyte (N,N-methyl butyl pyrrolidinium-bis(trifluoromethanesulphonyl)imide-lithium bis(trifluoromethanesulphonyl)imide; LiTFSI-[Py1,4-TFSI]) for application in high rate capability rechargeable lithium-ion batteries is discussed here. This is a novel alternative compared to the often employed approach of using a molecular liquid as the medium for performing the polymerization reaction. The polymer “gel” electrolytes (AN:Py1,4-TFSI = 0.16–0.18, w/w) showed remarkable compliable mechanical strength and higher thermal stability compared to LiTFSI-[Py1,4-TFSI]. Despite two orders increase in magnitude of viscosity of polymer “gels”, the room temperature ionic conductivity of the “gels” (1.1 × 10−3–1.7 × 10−3 Ω−1 cm−1) were nearly identical to that of the ionic liquid (1.8 × 10−3 Ω−1 cm−1). The present “gel” electrolytes did not exhibit any ageing effects on ionic conductivity similar to the conventional polymer gel electrolytes (e.g. high molecular weight polymer + salt + high dielectric constant molecular solvent). The disorder (ionic liquid) to a relative order (cross-linked polymer electrolyte) transformation does not at all influence the concentration of conducting species. The polymer framework is still able to provide efficient pathways for fast ion transport. Unlike the ionic liquid which is impossible to assemble without a conventional separator in a cell, the polymer “gel” electrolyte could be conveniently assembled without a separator in a Li|lithium iron phosphate (LiFePO4) cell. Compared to the ionic liquid, the “gel” electrolyte showed exceptional cyclability and rate capability (current density: 35–760 mA g−1 with LiFePO4 electronically wired with carbon (amorphous or multiwalled nanotube [MWCNT]).

The ground state structure and properties of erythritol in gas phase and in different solvents: A DFT / SC-IPCM approach

Quantum mechanical study of the ground state structure and properties of erythritol was carried out in gas phase and in different solvents at the hybrid B3LYP DFT level with complete geometry optimization and varying basis sets [6-311G (d,p) and 6-311++G (d,p)] in order to provide detailed information of the model molecule in solvents of low, medium and high dielectric constant. It was found that the molecule is stabilized by solvation in all cases, the order of stability being water > DMSO > carbontetrachloride. The dipole moment was increased. The charge density on O-atoms were increased almost as per above order indicating that there are two types of O-H groups in the molecule in agreement with the reported experimental findings. Carbon skeleton were planar in water and DMSO by 6-311++G (d,p) basis set gave non planar structure in CCl4. The geometries in water and DMSO were in excellent agreement with the experiment. The calculated IR frequencies are well when compared with the experimental results. The HOMO-LUMO gap remained almost same on solvation. Key words: B3LYP DFT, GAUSSIAN, erythritol, charge distribution, gas phase.

Synthesis and characterization of gallium colloidal nanoparticles

In this work, gallium colloidal nanoparticles (Ga-Nps) were synthesized by chemical liquid deposition (CLD). This method involved the deposition of metallic atoms with organic solvents (THF, acetone and 2-propanol) in a freezing matrix of the solvent at 77 K, in order to obtain core–shell Ga-Nps which were characterized by: FT-IR, UV–Vis, TEM, SAED and electrophoretic mobility measurements. TEM images revealed a wide distribution of the apparent size of the particles and apparent average size of 5.65, 8.11 and 13.87 nm for Ga-Nps obtained with 2-propanol, THF and acetone, respectively. UV spectra showed absorption bands of metal plasmons, interesting quantum size effects and plasmon absorption bands of particles aggregated to λ 280 and λ 325. Electrophoretic mobility allowed to evidence that nanoparticles had a negative charge as well as to observe that the zeta potential of the colloidal dispersions decreased over time, showing a significant tendency to the aggregation of Ga-Nps. The importance of the functionalization of metal nanoparticles with high dielectric constant solvents in the stabilization of colloidal systems was also observed. FT-IR spectroscopy revealed that the interaction of Ga surface with the solvent possibly produces a (Ga C) bond. Experimental details, structural and thermal stability studies were also analyzed in this work.

Self‐Assembly of ZnO Nanocrystals in Colloidal Solutions

The self-organization in solution of ZnO nanocrystals into superlattices is monitored by dynamic light scattering. When long-alkyl-chain amines or carboxylic acids are used as stabilizing ligands, no organization is observed. In contrast, when binary mixtures of long-alkyl-chain amines and carboxylic acids are used, the presence of a thermodynamic equilibrium between free and organized ZnO nanoparticles is detected in THF or toluene. The superlattices of organized ZnO nanoparticles are independently observed by TEM and SEM. The coordination mode of the ligands at the surface of the ZnO nanoparticles is evidenced by NMR studies. The presence of ion-paired ammonium carboxylate surrounding the surface of ZnO nanoparticles appears to be a necessary requirement to govern this reversible organization. This is substantiated by the absence of organization of ZnO nanoparticles when either a solvent of high dielectric constant, such as acetone, or a strong hydrogen-bond acceptor is used.

SOLVENT EFFECTS ON THE DISPERSION OF LINEAR POLARIZABILITY AND FIRST HYPERPOLARIZABILITY OF PARA-NITROANILINE USING POLARIZABLE CONTINUUM MODEL

The results of ab-initio calculation of frequency dependent linear polarizability α and first hyperpolarizability β of para-nitroaniline (p-NA) in the presence of different solvents are presented using polarizable continuum model (PCM). Geometry of p-NA in different solvents was optimized using HF/6-31 + G(d,p). Both static and frequency dependent α and β initially increase with an increase in the dielectric constant of the solvent used with p-NA, but subsequently attain an almost constant value. With solvents of higher dielectric constant, the value of static β is more compared to the β value at 1.17 eV but less than the value at 2 eV. Even though the existence of the solvent effect is confirmed from the results, the β values calculated at both 1.17 eV and 2 eV do not show any linear relationship with the dielectric constant and the reaction field factor of the solvents. The first excitation energies of both α and β of p-NA are considerably different in the presence of solvents as compared to their values in the gas phase, but the change with dielectric constant of the solvent is not very significant. The effect of hydrogen bonding between the solute and the solvent molecule on the first excitation energy of hyperpolarizability has been included using the explicit solvent method. The values of the first excitation energy calculated using the explicit method are lower than those obtained by the implicit method.

Amino acids as selective acylating agents: regioselective N 1-acylation of imidazolidin-4-one derivatives of the antimalarial drug primaquine

The acylation of bioactive primaquine-based imidazolidin-4-ones was studied using N α-Boc-protected glycine as acylating agent. Two synthesis routes, eight different coupling methods and seven distinct solvents were compared. Mild carbodiimide-based couplings on high dielectric constant solvents such as DMF or MeCN increased acylation yields, whereas alcohols inhibited carbodiimide-mediated acylations to take place. Achievement of the synthetic goals was limited by the size of the imidazolidin-4-one ring substituents R 1, R 2 and R 3, but resort to MW-assisted synthesis allowed overcoming such obstacle, though with very modest reaction yields. All reactions involving a Boc-protected amino acid were regioselective, independent of reaction conditions employed. In contrast, regioselective acetylation of the imidazolidin-4-ones could only be achieved by resort to very mild coupling procedures.