Solvate Structures and Computational/Spectroscopic Characterization of LiBF₄ Electrolytes

Crystal structures have been determined for both LiBF4 and HBF4 solvates: (acetonitrile)2:LiBF4, (ethylene glycol diethyl ether)1:LiBF4, (diethylene glycol diethyl ether)1:LiBF4, (tetrahydrofuran)1:LiBF4, (methyl methoxyacetate)1:LiBF4, (succinonitrile)1:LiBF4, (N,N,N′,N″,N″-pentamethyldiethylenetriamine)1:HBF4, (N,N,N′,N′-tetramethylethylenediamine)3/2:HBF4, and (phenanthroline)2:HBF4. These, as well as other known LiBF4 solvate structures, have been characterized by Raman vibrational spectroscopy to unambiguously assign the anion Raman band positions to specific forms of BF4–···Li+ cation coordination. In addition, complementary DFT calculations of BF4–···Li+ cation complexes have provided additional insight into the challenges associated with accurately interpreting the anion interactions from experimental Raman spectra. This information provides a crucial tool for the characterization of the ionic association interactions within electrolytes.