Effect of Ionic Size on Solvate Stability of Glyme-Based Solvate Ionic Liquids

Abstract

A series of binary mixtures composed of glymes (triglyme, G3; tetraglyme, G4; pentaglyme, G5) and alkali-metal bis(trifluoromethanesulfonyl)amide salts (M[TFSA]; M = Li, Na, and K) were prepared, and the correlation between the composition and solvate stability was systematically investigated. Their phase diagrams and Raman spectra suggested complexation of the glymes with M[TFSA] in 1:1 and/or 2:1 molar ratio(s). From isothermal stability measurements, it was found that the formation of structurally stable complexes in the solid state did not necessarily ensure their thermal stability in the liquid state, especially in the case of 2:1 complexes, where uncoordinating or highly exchangeable glyme ligands existed in the molten complexes. The phase-state-dependent Raman spectra also supported the presence of free glymes in certain liquid complexes. The effect of the electric field induced by the alkali-metal cations on the oxidative stability of certain glyme complexes was examined by linear sweep voltammetry and quantum chemical calculations. Although the actual oxidative stability of complexes did not necessarily reflect the calculated HOMO energy levels of the glymes, the strong electric field induced by the smaller M(+) cations and proper coordination structures impart high stability to the glyme complexes. The results of thermogravimetry of complexes with different M(+) cations revealed that a balance of competitive interactions of the M(+) ions with the glymes and [TFSA](-) anions predominates the thermal stability.

Progress in Mechanistic Understanding and Characterization Techniques of Li‐S Batteries

“…Many types of liquid organic solvents, including linear ethers such as glymes (monoglyme, diglyme, triglyme, and tetraglyme), [ 57,162,163 ] cyclic ethers (1,2-dioxolane and THF), [ 26,85 ] sulfone, [ 43,164 ] carbonates, [ 17,38,165,166 ] and ionic liquid, [ 75,167 ] have been investigated for their effect on the performance of sulfur cathodes. On the basis of knowledge about sulfur redox chemistry, early efforts focused on solvents with high solubility to polysulfi des for better utilization of the active material.…”

Pentaglyme–K salt binary mixtures: phase behavior, solvate structures, and physicochemical properties

“…8,9,19 Systematic studies on the glyme-Li salt mixtures identified their characteristic features. 22,23 These studies, and a subdivision of solvate ILs based on their structural stability, are summarized in our recent perspective article. 8,9,12,13,20 The ionic nature of the equimolar mixtures is dominated by the Lewis basicity of the paired anion species.…”

“…Brouillette's and Henderson's groups previously performed pioneering work on the phase diagrams and solvate a Department of Chemistry and Biotechnology, Yokohama National University, structures of a series of glyme-Li salt mixtures. 23 Glyme-Li and glyme-Na systems with equimolar mixtures of ClO 4 À or other imide anions can also be referred to as solvate ILs. 31,32 Bruce et al reported the selective ion transport behavior in glyme-LiAsF 6 complex-based solid electrolytes.…”

Categorizing Molten Salt Complexes as Ionic Liquids and Their Applications to Battery Electrolytes

“…[34][35][36][37] Given that a large number of combinations of metal salts and ligands are available to form a complex, we can play with different types of complexes, some of which have the potential to form solvate ILs. 38 Moreover, one may introduce a new functionality into the solvate ILs to form, for example, stimuli-responsible ILs by designing the components of the complexes. Of course, the application of the solvate ILs is not limited to electrochemical devices, but they have already been tested as reaction media for organic synthesis 39 and as the media for CO 2 capture.…”