FTIR spectroscopic study of Li+ solvation in the solutions of LiBF4 in propylene carbonate, dimethyl sulfoxide, and their mixtures

Abstract

Ionic solvation in solutions of lithium tetrafluoroborate (LiBF₄) in propylene carbonate (PC) + dimethyl sulfoxide (DMSO) mixtures has been studied using Fourier transformed infrared (FTIR) spectroscopy. Dimerization of DMSO molecules in the solutions was taken into account. The obtained results are discussed with respect to the electrolyte concentration and properties of the cations of the electrolyte. Band changes due to solvation interaction were detected in the region of the C=O stretching vibrations and ring deformation for PC, and the S=O stretching vibrations and C–S–C skeleton stretching modes for DMSO, indicating that there is a strong interaction between lithium cations and solvent molecules. In addition, Li⁺ was preferentially solvated by DMSO in these binary solvents as a result of the large difference in their donor number (DN) values. The structures of PC, DMSO, Li⁺-PC, Li⁺-DMSO, and Li⁺-PC+DMSO were given.