Estimation of Ion Pairs Formation Constants of Lithium Salts in 1,2-dimethoxyethane and 1,4-dioxane Mixtures

摘要

In this paper the 19{sup left}F NMR spectroscopy and conductivity measurements by means of impedance spectroscopy together with Fuoss-Krauss formalism calculations are used as two independent methods to determine the ion pair formation constants for lithium tetrafluoroborate and lithium trifluoromethylsulfonate solutions in mixtures of 1,2-dimethoxyethane and 1,4-dioxane. These liquid systems have very similar coordinating properties (donor and acceptor numbers) as liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide) and can be tailored to have identical dielectric constants. Thus, they can be used as a model system for discussion of the role of the chain length in cation and anion coordination and conduction mechanism in polymeric electrolytes. Similar experiments were performed for "theoretically unassociated" tetraalkylamonium salts with identical anions. The results are compared with literature data for liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide) in the field of ion-ion and ion-solvent interactions.