A new concept of ternary aqueous electrolytes based on lithium 4,5-dicyanoimidazolate hydrates

Abstract

A new concept of aqueous electrolytes based on heterocyclic anions (hydrated anionic triplet electrolyte, HATE) has been presented. Structural studies showed that dimeric lithium 4,5-dicyanoimidazolate (LiTDI) dihydrate molecules, in the presence of acetonitrile, form an ionic system preserved in high concentrations and solid states. X-ray diffraction measurements show that electroneutral dihydrate units can coordinate additional lithium cations acting as charge carriers. The crystalline ionic phase was characterized using spectroscopic, thermal, and electrochemical methods and was used to prepare model electrolytes based on LiTDI hydrates. Linear sweep voltammetry and impedance spectroscopy measurements show, in this system, the depletion of water activity, high conductivity, and reversible cycling of full cells comprising examined electrolytes. We will prove that a concentrated triplet solution acts similarly to the anhydrous electrolyte; regardless of the concentration, it reaches high ionic conductivity values (12-16 mS/cm at room temperature) and is electrochemically stable.