Ionic interplay of lithium salts in binary mixtures of acetonitrile and diethyl carbonate probed by physicochemical approach

• Triple-ion formation of LiI, LiClO4 and LiAsF6 in 0.25 mass fraction of AN in DEC.
• Ion-pair formation of LiI, LiClO4 and LiAsF6 in 0.50 and 0.75 mass fraction of AN in DEC.
• Ion–solvent interaction is strongest in LiI and weakest in LiAsF6.

Electrolytic conductivities, densities and viscosities of lithium salts (LiI, LIClO4 and LiAsF6) have been studied in (0.25, 0.50 and 0.75) mass fraction of acetonitrile (AN) in diethyl carbonate (DEC) at 298.15 K. The limiting molar conductivities (Λ0), association constants (KA) and the distance of closest approach of the ions (R) have been evaluated using the Fuoss conductance equation (1978). The Walden product is obtained and discussed. However, the deviation of the conductometric curves (Λ versus √c) from linearity for the electrolytes in 0.25 mass fraction of acetonitrile (AN) in diethyl carbonate (DEC) indicated triple-ion formation, and therefore the corresponding conductance data have been analysed by the Fuoss–Kraus theory of triple-ions. The observed molar conductivities were explained by the ion-pair (M+ + X− ⇆ MX) and triple-ion (2 M+ + X− ⇆ M2X+, M+ + 2X− ⇆ MX2−) formation. The limiting apparent molar volumes (ϕV0), experimental slopes (SV*) derived from the Masson equation and viscosity A and B-coefficients using the Jones–Dole equation have been interpreted in terms of ion–ion and ion–solvent interactions respectively.