Sulfamides and Glymes as Aprotic Solvents for Lithium Batteries

Abstract

In view of the high reactivity of the lithium metal, lithium batteries must operate in an aprotic environment, which can either be a conducting polymer; a liquid solvent, or a mixture of them. Two families of aprotic liquids were considered as solvents for lithium bis(trifluoromethylsulfone)imide (LiCF3SO2NSO2CF3 or LiTFSI). The first one is the substituted sulfamides, R1R2NSO2NR3R4, where the R groups are either methyl, ethyl, or methoxyethyl (CH,CHOOCH,), and the second one is the glymes, CH3O(CH2CH3O)CH3, for n up to 10. The phase diagrams, potential windows, conductivities, and the lithium interfacial resistances of the solutions were investigated, often as a function of temperature. The potential use of these solvents for different types of batteries is discussed.* Electrochemical Society Active Member. * * Electrochemical Society Student Member.making the molecule unsymmetrical and more polar, i.e., by replacing the ethyl groups by methyl or methoxyethyl groups, i.e., CH3CH2OCH3. The present paper deals with the phase diagrams, conductivities, potential windows, and lithium interfacial resistances of LiTFSI in these substituted sulfamides. The synthesis and properties of these liquid sulfamides is described elsewhere.'6 The use of these sulfamides as diluents for a polymer electrolyte is reported elsewhere.'7 The sulfamides used in this investigation are summarized in Table I where a short abbreviation is given for each.Another family of aprotic liquids which has proven interesting as solvents for high-energy batteries is the glymes18 or (polyethyleneglycol) dimethylether, CH,O(CH2CH,O)CH3.Unfortunately, the first member of the series, also called Sulfamtdes Rl\ '1? 1R,

Chelate Effects in Glyme/Lithium Bis(trifluoromethanesulfonyl)amide Solvate Ionic Liquids. I. Stability of Solvate Cations and Correlation with Electrolyte Properties

“…Given the maximum ionicity results from an [O]/[Li + ] ratio of ∼4 or 5, these ratios may be sufficient for the dissociation of the solvated Li + and [TFSA] − . In a fashion similar to the mixtures of aprotic ILs and low-polarity solvents, further addition of glymes or THF with low permittivity (ε = 7−8) 56 Such behavior is common for the oligoethers studied in this work. However, this is probably not the case for other nonaqueous aprotic solvents with higher permittivitysuch as PC (ε ∼ 64)where Coulombic attractions between the solvated cation and the counteranions are more shielded.…”

Glymes as versatile solvents for chemical reactions and processes: from the laboratory to industry

“…These results further stimulated the infrared study of poly(ethylene oxide)-lithium triflate films, and enabled a more mechanistic understanding of polymer electrolyte materials. To provide an aprotic environment for lithium batteries, Choquette et al 160 studied the phase diagrams, potential windows, conductivities and the lithium interfacial resistances of Li[Tf 2 N] dissolved in sulfamides and glymes. They suggested that glymes or their mixtures with sulfamides could be useful for batteries whose cathode is not a 2D layer structure.…”

Rechargeable lithium battery using non-flammable electrolyte based on tetraethylene glycol dimethyl ether and olivine cathodes

“…Poly(ethylene glycol)dialkyl ethers (i.e., R1O(CH2CH2O)nR2), known as end-capped glymes, are characterized by a high flash point and suitable features as aprotic solvents for lithium salts [9]. However, glyme-based electrolytes have revealed poor electrode passivation properties, which limit their application in rechargeable Li-battery due to continuous solvent decomposition by cell operation [10,11].…”