Electrical Conductivity of Lithium Chloride, Lithium Bromide, and Lithium Iodide Electrolytes in Methanol, Water, and Their Binary Mixtures

Low-grade thermal energy can be converted to electricity by integrating multi-effect distillation and reverse electrodialysis technologies. The energy conversion efficiency of such a system is strongly influenced by the working solution. Here, six binary solutions (LiCl/LiBr/LiI in H2O and LiCl/LiBr/LiI in methanol) and three ternary solutions (LiCl/LiBr/LiI in methanol and H2O mixture) are assessed as candidate working solutions. Electrical conductivities of these solutions were measured over a wide concentration range (up to 12.4 mol·kg–1), and the results were examined with the Casteel–Amis equation and the modified Gaussian amplitude equation. Previous experimental results have shown that the electrical conductivity of solutions is influenced by the concentration, temperature, and characteristics of the solute and solvent. At 293.15 K, the maximum electrical conductivity was 201.6 ± 3.8 mS·cm–1 for an aqueous LiI solution at 6.38 mol·kg–1. Furthermore, the electrical conductivity decreased in the order: LiI–solvent > LiBr–solvent > LiCl–solvent (for the same solvent) and LiX (X = I, Br, or Cl)–H2O > LiX–methanol–H2O > LiX–methanol (for the same solute) under the same concentration and temperature conditions. Hence, LiX–methanol–H2O ternary solutions show good potential as working solutions considering their electrochemical and thermodynamic properties comprehensively.