An Ammonium Solvate Ionic Liquid

Abstract

The first example of ammonium (NH4 +) solvate ionic liquids (ILs) is reported. The compound is ammonium bis(trifluoromethylsulfonyl)amide-18-crown-6 (1/1), i.e. [NH4 +][Tf2N–]−18C6 (1/1), where Tf represents SO2CF3. Raman spectra, NMR spectra, and DFT calculations support the conclusion that the compound can be described as an ammonium solvate IL [NH4 +·18C6][Tf2N–], which consists of 18C6-coordinated NH4 + cations and Tf2N– anions. The conductivity of the ammonium solvate IL reaches as high as 10 mS cm–1 at 150 °C. The negligible volatility below 200 °C is confirmed by thermogravimetry. Compared with a hydronium (H3O+) solvate IL [H3O+·18C6][Tf2N–], the ammonium solvate IL shows better thermal stability, which strongly suggests long residence time of 18C6 with NH4 + cation. The stability may lead to the vehicular-type translational motions of NH4 + cations with 18C6 solvents as proved by their self-diffusion coefficients. The findings regarding this ammonium solvate IL can provide the guidelines to design new NH4 + or proton conductors for ammonium ion batteries and fuel cells, which work at medium-low temperatures of 150 °C–200 °C.

Glyme-Lithium Bis(trifluoromethylsulfonyl)amide Super-concentrated Electrolytes: Salt Addition to Solvate Ionic Liquids Lowers Ionicity but Liberates Lithium Ions

“…1a, COC stretching and CH 2 rocking modes of oligoethers appear between 760 cm -1 and 900 cm -1 . 2,3,12,17,18,23 In the solvate IL, i.e., [G3]/[LiTf 2 N] = 1/1, a peak appears at 872 cm -1 , proving a change from pure G3 as a result of G3-Li + complex formation similar to the literatures. 2,3,23 The Raman spectra of the super-concentrated electrolyte [G3]/[LiTf 2 N] = 3/4 displayed a peak at 873 cm -1 , which also indicates complex formation.…”

“…Classification by iconicity.-Ionicity is expressed as a molar conductivity ratio Λ imp /Λ NMR . [15][16][17][18]23,24,33,34 This is a useful metric for evaluating the extent to which the self-diffusion of ionic species (Λ NMR ) contributes to the actual ionic conduction (Λ imp ). The molar conductivity Λ NMR is given by the Nernst-Einstein equation, Λ NMR = (F 2 /RT) (D cation + D anion ), where F is Faraday constant, R is the gas constant, T is the absolute temperature.…”

“…Highly concentrated electrolytes have been studied for various kinds of electrochemical applications such as next-generation batteries, [1][2][3][4][5][6][7][8][9][10][11][12] fuel cells, [13][14][15][16][17][18] and surface finishing. [19][20][21][22] Compared to conventional electrolytes with normal salt concentrations, a practical merit is safety, especially in the cases of non-aqueous media, because vapor pressure of solvent is lowered and electrochemical stability is extended.…”