Ionic Conductivity and Viscosity of Solvate Ionic Liquids Composed of Glymes and Excess Lithium Bis(Trifluoromethylsulfonyl)Amide

Abstract

Ionic conductivity and viscosity of lithium bis(trifluoromethylsulfonyl)amide (LiTFSA)-glyme solvate ionic liquids with the mole fraction of LiTFSA from 50.0 to 54.5 mol% were investigated at 298-323 K. The ionic conductivity of the solvate ionic liquids was found to be inversely proportional to the viscosity, as expected from Walden's rule. The ionic conductivity of the solvate ionic liquid decreased with increasing the mole fraction of LiTFSA, probably due to formation of a bulky lithium species, [Li(TFSA) 2 ] − , which forms at the compositions of more than 50 mol% of LiTFSA.

Towards a High‐Performance Lithium‐Metal Battery with Glyme Solution and an Olivine Cathode

“…The electrolytes display an ionic conductivity ranging from 10 −3 to 10 −2 S cm −1 within the temperature window from 0 to 80 °C, that is, a promising response for a possible application in lithium batteries . Based on the literature, the temperature dependence of the ionic conductivity of glyme‐based solutions may follow either an Arrhenius or a Vogel‐Tamman‐Fulcher (VTF) trend, according to the investigated temperature range along with the electrolyte formulation in terms of chemical composition and lithium salt concentration. Herein, the conductivity values may be interpolated by the VTF equation (see Figure a) with squared correlation factors ( R 2 ) higher than 0.99.…”

Glyme-based electrolytes: suitable solutions for next-generation lithium batteries

“…Thus, a decrease in ionic conductivity with increasing concentration of LiTFSI was observed and associated with the formation of a bulky lithium species, i.e., [Li(TFSI) 2 ] − . 51 The [Li(G 4 )][TFSI] complex was employed in a quasi-solid-state electrolyte with fumed silica nanoparticles. This electrolyte was used in double-layered and triple-layered high-voltage bipolar stacked batteries, which showed a working voltage of 6.7 and 10.0 V, respectively, that is, two and three times that of the single-layered device (3.4 V).…”

“…Along with the initial conceptualization and pioneering studies of glyme-based electrolytes, Li–metal batteries using the most common intercalation electrodes, such as LiCoO 2 and graphite, as well as other insertion cathodes such as LiFePO 4 , were proposed with promising results, in spite of several issues which were firstly identified. 43–60 Afterwards, “high-concentration” glyme-based electrolytes have attracted a great deal of attention due to their favorable properties, and there is an intriguing dilemma on the actual nature of these mixtures, which have been described as either solvent-in-salt solutions or solvated ionic liquids (SILs). 61–82 Moreover, glyme-based electrolytes have been gaining renewed interest due to a possible suitability for the emerging high-energy lithium–sulfur (Li–S) battery, which is formed by combining a lithium–metal anode and a sulfur-based cathode.…”

Four Phosphonium‐based Ionic Liquids. Synthesis, Characterization and Electrochemical Performance as Electrolytes for Silicon Anodes

“…As with all the properties of ILs, viscosity varies with different combinations of cations and anions [23] since it depends on intermolecular forces such as van der Waals forces, hydrogen bonding, and Coulombic forces [24–26] . Similarly, the ionic conductivity of a solvent is fundamental in its selection for any electrochemical application, [9] mainly because the performance of these devices is strongly dependent on the rate of transport or diffusion of the electroactive species to and from the electrode [25,27] . Other properties, such as melting point (T m ) and thermal decomposition (T d ) temperatures, are required to establish the feasible temperature operating range for any electrolyte [28] .…”