Study on the empirical parameter of solvent polarity - The E _T(30) scale of carbonate using Reichardt's Dye

The polarity of non-aqueous electrolyte solvent in lithium ion batteries has been studied by means of the solvatochromism of 2,6-diphenyl-4-(2,4,6- triphenyl-1-pyridium)phenolate (Reichardt's Dye), and the empirical parameter of solvent polarity-the E_T(30) scale of carbonate systematically determined. The obtained E_T(30) scale of ethylene carbonate is 48.6, propylene carbonate 46.1, 2,3-butylene carbonate 45.7, dimethyl carbonate 39.0, methyl ethyl carbonate 37.3, and diethyl carbonate 37.0. With the addition of lithium perchlorate to the different kinds of carbonates individually, the molecule of solvatochromic compound had an effect on halochromism. It showed that the E_T(30) scale was increased, and the solvent polarity of carbonate enlarged. Cyclic carbonate and linear carbonate have different charge tendency because of interaction among particles. Because the structure of Ar-O^-⋯solvent⋯Li⁺ is formed, there exists the damping effect in more polar solvents, which suppresses the interaction between the phenoxide moiety of Reichardt's dye and Li⁺.