Solvate Structures and Spectroscopic Characterization of LiTFSI Electrolytes

A Raman spectroscopic evaluation
of numerous crystalline solvates
with lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI or LiN­(SO2CF3)2) has been conducted over a wide
temperature range. Four new crystalline solvate structures(PHEN)3:LiTFSI, (2,9-DMPHEN)2:LiTFSI, (G3)1:LiTFSI and (2,6-DMPy)1/2:LiTFSI with phenanthroline,
2,9-dimethyl­[1,10]­phenanthroline, triglyme, and 2,6-dimethylpyridine,
respectivelyhave been determined to aid in this study. The
spectroscopic data have been correlated with varying modes of TFSI–···Li+ cation coordination
within the solvate structures to create an electrolyte characterization
tool to facilitate the Raman band deconvolution assignments for the
determination of ionic association interactions within electrolytes
containing LiTFSI. It is found, however, that significant difficulties
may be encountered when identifying the distributions of specific
forms of TFSI– anion coordination present in liquid
electrolyte mixtures due to the wide range of TFSI–···Li+ cation interactions possible and
the overlap of the corresponding spectroscopic data signatures.