Solvate Structures and Computational/Spectroscopic Characterization of Lithium Difluoro(oxalato)borate (LiDFOB) Electrolytes

Lithium difluoro­(oxalato)­borate (LiDFOB)
is a relatively new salt
designed for battery electrolyte usage. Limited information is currently
available, however, regarding the ionic interactions of this salt
(i.e., solvate formation) when it is dissolved in aprotic solvents.
Vibrational spectroscopy is a particularly useful tool for identifying
these interactions, but only if the vibrational bands can be correctly
linked to specific forms of anion coordination. Single crystal structures
of LiDFOB solvates have therefore been used to both explore the DFOB–...Li+ cation coordination interactions
and serve as unambiguous models for the assignment of the Raman vibrational
bands. The solvate crystal structures determined include (monoglyme)2:LiDFOB, (1,2-diethoxyethane)3/2:LiDFOB, (acetonitrile)3:LiDFOB, (acetonitrile)1:LiDFOB, (dimethyl carbonate)3/2:LiDFOB, (succinonitrile)1:LiDFOB, (adiponitrile)1:LiDFOB, (PMDETA)1:LiDFOB, (CRYPT-222)2/3:LiDFOB, and (propylene carbonate)1:LiDFOB. DFT calculations
have been incorporated to provide additional insight into the origin
(i.e., vibrational modes) of the Raman vibrational bands to aid in
the interpretation of the experimental analysis.