Picosecond Dynamics of Molecular Entities in Lithium Salt Solutions in Dimethyl Sulfoxide, Propylene Carbonate, and Dimethyl Carbonate

Abstract

An analysis of the Raman spectra of the solutions of lithium salts in dimethyl sulfoxide, propylene carbonate, and dimethyl carbonate in a concentration range from diluted solutions to the mixtures of molten solvates with salts has been performed in terms of the dynamics, specifically, the dephasing (тv) and modulation (тw) times of all molecular entities present in solutions are determined and analyzed. It has been found that, in the picosecond time domain, the dephasing and modulation in solvent molecules hydrogen-bonded with an anion and/or solvating a cation are slower than in free solvent molecules. In solvent separated ion pairs, both тv and тw are much longer than in solvated anions, thus indicating the strong interactions between anions and their surrounding. In contact ion pairs, тv are great, whereas тw appear close to those for free anions. This reflects that the structure of the liquid tends to the structure of molten salts.

Electrochemically Driven Transformation of Olivine LiFePO4 to Olivine NaFePO4 in Cells with Sodium Anode and Carbonate Electrolyte

“…As expected, [46,47] the specific conductivity of NaClO 4 containing electrolytes appears to be higher than that of a LiClO 4 containing electrolyte. It is known that in lithium electrolytes in carbonate solvents, prevailing structure entities are solvent separated and contact ion pairs [48,49] . Therefore, the decrease in the specific conductivity upon growing concentration of FEC in solutions may be caused by its greater tendency to ion pairing.…”

“…It is known that in lithium electrolytes in carbonate solvents, prevailing structure entities are solvent separated and contact ion pairs. [48,49] Therefore, the decrease in the specific conductivity upon growing concentration of FEC in solutions may be caused by its greater tendency to ion pairing. This may be explained by great dielectric permittivity of FEC (107 at 25 °C) compared to EC (90 at 40 °C).…”