Spectroscopic characterization of the interaction of lithium with thin films of the ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide

Abstract

In this experimental investigation the interaction of lithium with 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([OMIm]Tf2N) is shown. For this purpose thin films of lithium and [OMIm]Tf2N were successively vapor deposited on a copper substrate and analyzed by X-ray Photoelectron Spectroscopy (XPS) as well as by Ultraviolet Photoelectron Spectroscopy (UPS). When [OMIm]Tf2N is evaporated on top of a thin lithium film a chemical shift analysis of XPS spectra shows a variety of reaction products like LiF, Li2O and LixCHy which reveals the instability of the IL against lithium. Time resolved XPS spectra were discussed to distinguish cation reactions from beam damage effects. In a second step lithium is deposited on a [OMIm]Tf2N layer. The XPS spectra are in agreement with the results of the previous step, but show some differences concerning the [OMIm] cation. In a third step [OMIm]Tf2N has been deposited on a passivated lithium layer. XPS results show nearly unaffected [Tf2N](-) anions and partially decomposed [OMIm](+) cations. Interestingly the cation reactions show similarities when compared to the interaction of [C4C1Pyrr]Tf2N (1-butyl-1-methylpyrrolidinium bis[trifluoromethylsulfonyl]amide) and lithium.

Chemical Analysis of Ionic Liquids Using Photoelectron Spectroscopy

“…Many research groups have investigated the effect of different cations with same anions or various anions with same cations on the properties of RTILs . To verify the properties of RTILs, many techniques such as liquid chromatography, grazing incidence X‐ray diffraction, soft X‐ray emission spectroscopy, high‐resolution electron energy‐loss spectroscopy (HREELS), low‐energy ion scattering (LEIS), high‐resolution Rutherford backscattering (HRBS), metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), and X‐ray photoelectron spectroscopy (XPS) have been utilized. Among them, photoelectron emission spectroscopy (XPS or UPS) would be a useful technique to confirm the qualitative and semiquantitative properties of solid materials in general.…”

Surface Science and Electrochemical Model Studies on the Interaction of Graphite and Li‐Containing Ionic Liquids

“…In contrast, [BMP] + is predominantly decomposed under surface science conditions, that is, upon post‐deposition of Li on a multilayer film of the IL. Preferential cation decomposition ([BMP] + and [OMIm] + ([OMIm]: 1‐octyl‐3‐methylimidazolium), respectively) on Li layers and after Li post‐deposition has also been reported previously . However, of all BE regions, the C 1s range is the one least suited for the (quantitative) interpretation of possible products, as it—except for the C−F peak—only features the characteristic IL and substrate peaks.…”

“…Interestingly, the cation peak intensity loss is much more pronounced than that of the N TFSI peak (about 80 %), indicating that most of the cations are decomposed and that the extent of [BMP] + decomposition even exceeds that of [TFSI] − decomposition. The new peak at 398.4 eV has been ascribed to Li 3 N although other nitrogen‐containing Li‐bound fragments, for example, linear LiC x H y N species resulting from a ring‐opening of the pyrrolidinium molecule, might be possible as well. Despite the strong changes in the individual peak intensities, however, the total peak intensity of the N 1s spectrum remains almost constant, similar to that in the O 1s region, but different from the F 1s signal.…”

Spectroscopic study of ionic liquid adsorption from solution onto gold

“…7 Conventional XPS has been used extensively to study IL layers on solids (and IL bulk interfaces 31,32 ), and this application of XPS was recently reviewed by Steinrück. [34][35][36][37][38] However, vapor deposited IL layers may not be representative of IL adsorbed from a solvent. This methodology has allowed the investigation of a number of ILs in sub-monolayer and mono/multilayer amounts on alumina, mica, gold, silver, lithium, and copper.…”