Solvate Structures and Computational/Spectroscopic Characterization of LiBF₄ Electrolytes

Crystal structures have been determined for both LiBF 4 and HBF 4 solvates: (acetonitrile) 2:LiBF 4, (ethylene glycol diethyl ether) 1:LiBF 4, (diethylene glycol diethyl ether) 1:LiBF 4, (tetrahydrofuran) 1:LiBF 4, (methyl methoxyacetate) 1:LiBF 4, (succinonitrile) 1:LiBF 4, ( N, N, N ′, N ″, N ″-pentamethyldiethylenetriamine) 1:HBF 4, ( N, N, N ′, N ′-tetramethylethylenediamine) 3/2:HBF 4, and (phenanthroline) 2:HBF 4 . These, as well as other known LiBF 4 solvate structures, have been characterized by Raman vibrational spectroscopy to unambiguously assign the anion Raman band positions to specific forms of BF 4 – ···Li + cation coordination. In addition, complementary DFT calculations of BF 4 – ···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.