Is the Cation Innocent? An Analytical Approach on the Cationic Decomposition Behavior of N-Butyl-N-methylpyrrolidinium Bis(trifluoromethanesulfonyl)imide in Contact with Lithium Metal

Abstract

The stability of the ionic liquid (IL) N-butyl-N-methylpyrrolidinium bis­(trifluoro­methane­sulfonyl)­imide (Pyr14TFSI) against lithium metal at room temperature was investigated by gas chromatography/mass spectrometry (GC/MS), solid phase microextraction gas chromatography/mass spectrometry (SPME-GC/MS), and gas chromatography/high-resolution mass spectrometry (GC/HR-MS). The focus of this work is the degradation behavior and mechanism of the Pyr14 + cation in the presence of lithium metal as the anion participation in the formation of the solid electrolyte interphase (SEI) in IL-based systems has been, and continues to be, well described. N-Butyl-N-methyl-N-but-3-eneamine could be identified as a decomposition product for the first time. The existence of this compound was validated by chemical ionization (CI) experiments as well as with high-resolution results and the comparison with N,N-dibutyl-N-methylamine (DBMA) as a reference substance. Additionally, N-methylpyrrolidine (NMP) was identified as well as an analogue of N,N-dibutyl-N-methylamine, whose molecular structure could not be conclusively determined. The special feature of this finding is the terminal vinyl group of the N-butyl-N-methyl-N-but-3-eneamine which could generally enable polymerization reactions. It suggests that the Pyr14 + cation is not “innocent” and can participate in the formation of an organic layer at the surface of lithium metal. Therefore, this work contributes to a better understanding of the aging behavior of Pyr14TFSI or pyrrolidinium-based ILs in general.

Electrochemical Behaviour of Nb‐Doped Anatase TiO2 Microbeads in an Ionic Liquid Electrolyte

“…As the electrode is cycled the surface composition changes and spectral components corresponding to surface groups containing oxygen, sulfur and nitrogen appear. The presence of nitrogen is explained by the decomposition of both EMIM cations and TFSI anions, previously described [43,44] and sulfur originates only from the decomposition of the TFSI anion. These contributions are present from the initial cycles and shows that and interphase layer is formed directly upon cycling and that it is stable over extended cycling.…”

Pyrrolidinium Containing Ionic Liquid Electrolytes for Li-Based Batteries

“…This is attributed in part to the lack of understanding of the roles the cations, anions and lithium salt play in the electrochemical and physicochemical properties of ionic liquid electrolytes. This is being addressed by various research groups, where new breakdown products such as N -butyl- N -methyl- N -but-3-eneamine are being discovered [ 175 ]. N -methyl- N -but-3-eneamine has the potential to provide elastomeric properties to accommodate changes in the electrode volume, which could facilitate the use of group IV materials in commercial microbatteries, thus enabling their use within healthcare applications such as rechargeable implantable devices where high power is required for data transmission.…”

“…Molecules 2020, 25, x 13 of 34 room temperature ( Figure 7) recently studied by Preibisch et al [175]. They identified a new degradation product N-butyl-N-methyl-N-but-3-eneamine, which was previously unreported and suggested that it participates in the formation of an organic layer at the surface of Li metal.…”

“…Other characterization tests carried out have been mentioned in previous pyrrolidinium subsections [ 148 , 149 ]. Another important characterization carried out recently is the degradation of C 4 mpyrTFSI in the presence of Li metal at room temperature ( Figure 7 ) recently studied by Preibisch et al [ 175 ]. They identified a new degradation product N -butyl- N -methyl- N -but-3-eneamine, which was previously unreported and suggested that it participates in the formation of an organic layer at the surface of Li metal.…”

“…The ionic species (orange box) were identified by Pyschik et al [ 176 , 177 ] while Kroon et al [ 178 ] confirmed the presence of the neutral species (green box). The neutral vinyl species was identified by Preibisch et al [ 175 ] Reprinted with permission from Preibisch et al [ 175 ]. Copyright 2020 American Chemical Society.…”