Thermodynamic of LiF dissolution in alkylcarbonates and some of their mixtures with water

The solubility of lithium fluoride has so far never been studied in alkylcarbonate solvents. These data is essential to understand the behavior of this salt in solution, in particular in the field of lithium-ion batteries. The solubility of lithium fluoride (LiF) was measured at various temperatures in propylene carbonate (PC), ethylene carbonate (EC) and dimethyl carbonate (DMC) by atomic absorption spectroscopy. The LiF free enthalpy, enthalpy and entropy of dissolution in these solvents were deduced from the results. The solubility of LiF differs significantly with the nature of the solvent, EC being by far the most solubilizing media. The high solubilizing power of EC towards LiF cannot be explain by any of the physico-chemical properties of the solvent, but by an entropy-driven phenomenon. The solubilities of LiF in water–alkylcarbonates mixtures were determined by conductimetry at several temperatures leading to the corresponding LiF thermodynamic properties in these media. Results are discussed and compared to those obtained by atomic absorption measurements. Finally, a scheme representing the different stages for the dissolution of LiF in alkylcarbonates is proposed.