Raman spectroscopy is a powerful method for identifying ion-ion interactions, but only if the vibrational band signature for the anion coordination modes can be accurately deciphered. The present study characterizes the PF6- anion P-F Raman symmetric stretching vibrational band for evaluating the PF6-...Li+ cation interactions within LiPF6 crystalline solvates to create a characterization tool for liquid electrolytes. To facilitate this, the crystal structures for two new solvates—(G3)1:LiPF6 and (DEC)2:LiPF6 with triglyme and diethyl carbonate, respectively—are reported. The information obtained from this analysis provides key guidance about the ionic association information which may be obtained from a Raman spectroscopic evaluation of electrolytes containing the LiPF6 salt and aprotic solvents. Of particular note is the overlap of the Raman bands for both solvent-separated ion pair (SSIP) and contact ion pair (CIP) coordination in which the PF6- anions are uncoordinated or coordinated to a single Li+ cation, respectively.
Revised: September 18, 2015 |
Published: April 23, 2015
Citation
Han S.D., S. Yun, O. Borodin, D.M. Seo, R.D. Sommer, V.G. Young, and W.A. Henderson. 2015.Solvate Structures and Computational/Spectroscopic Characterization of LiPF6 Electrolytes.Journal of Physical Chemistry C 119, no. 16:8492-85.PNNL-SA-107628.doi:10.1021/acs.jpcc.5b00826