Conductivities of 1?1 salts in 2-cyanopyridine

Effect of Concentration and Temperature on the Structure and Ion Transport in Diglyme-Based Sodium-Ion Electrolyte

Glyme-based sodium electrolytes show excellent electrochemical properties and good chemical and thermal stability compared with existing carbonate-based battery electrolytes. In this investigation, we perform classical molecular dynamics (MD) simulations to examine the effect of concentration and temperature on ion-ion interactions and ion-solvent interactions via radial distribution functions (RDFs), mean residence time, ion cluster analysis, diffusion coefficients, and ionic conductivity in sodium hexafluorophosphate (NaPF₆) salt in diglyme mixtures. The results from MD simulations show the following trends with concentration and temperature: The Na⁺---O(diglyme) interactions increase with concentration and decrease with temperature, while the Na⁺---F(PF₆^-) interactions increase with concentration and temperature. The mean residence time suggests that Na⁺---O(diglyme) are significantly longer lived compared with that of Na⁺---F(PF₆^-) and H (diglyme)---F(PF₆^-), which shows the affinity of diglyme to the Na⁺ ions. The ion cluster analysis suggests that the Na⁺ ions largely exist as solvated ions (coordinated to diglyme molecules), whereas some fractions exist as contact-ion pairs, and negligible fractions as aggregated ion pairs, with the latter two increasing slightly with temperature and more with ion concentration. The magnitude of the diffusion coefficients of Na⁺ and PF₆^- ions decreases with concentration and increases with temperature, where the Na⁺ ion has slightly lower mobility compared with the PF₆^- anion. The simulated total ionic conductivities show qualitative trends comparable to experimental data and highlight the need for the inclusion of ion-ion correlations in the Nernst-Einstein equation, especially at higher concentrations and lower temperatures.

Glymes as Versatile Solvents for Chemical Reactions and Processes: from the Laboratory to Industry

Glymes, also known as glycol diethers, are saturated non-cyclic polyethers containing no other functional groups. Most glymes are usually less volatile and less toxic than common laboratory organic solvents; in this context, they are more environmentally benign solvents. However, it is also important to point out that some glymes could cause long-term reproductive and developmental damages despite their low acute toxicities. Glymes have both hydrophilic and hydrophobic characters that common organic solvents are lack of. In addition, they are usually thermally and chemically stable, and can even form complexes with ions. Therefore, glymes are found in a broad range of laboratory applications including organic synthesis, electrochemistry, biocatalysis, materials, and Chemical Vapor Deposition (CVD), etc. In addition, glyme are used in numerous industrial applications, such as cleaning products, inks, adhesives and coatings, batteries and electronics, absorption refrigeration and heat pumps, as well as pharmaceutical formulations, etc. However, there is a lack of comprehensive and critical review on this attractive subject. This review aims to accomplish this task by providing an in-depth understanding of glymes' physicochemical properties, toxicity and major applications.