Formation of Contact Ion Pairs and Solvation of Li⁺Ion in Sulfones: Phase Diagrams, Conductivity, Raman Spectra, and Dynamics

Abstract

This work reports phase diagrams, conductivity isotherms, and data regarding the structure and dynamics of systems formed by lithium perchlorate and nitrate as solutes and sulfones as solvents. The LiClO4 + (CH3)2SO2 system behaves like typical electrolytic systems containing a lithium salt and a solvent and forms a 1:1 solvate; its conductivity isotherm demonstrates a maximum. Unlike typical systems, the phase diagrams of the LiNO3 + (CH3)2SO2 and LiNO3 + (C2H5)2SO2 systems appear to be simple eutectic. The dependences of specific conductivity on the concentration of LiNO3 are also uncommon showing no maximum characteristic to electrolyte solutions. Raman studies and analysis of dynamics performed using Raman data signify that, in the LiClO4 + (CH3)2SO2 system, solvated cations and contact ion pairs exist. In the LiNO3 + (CH3)2SO2 system, contact ion pairs are present as well, but signatures of cation solvation cannot be found.