Liquid electrolytes based on new lithium conductive imidazole salts

In the present paper new generation of imidazole-derived lithium salts (LiTDI—lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide, LiPDI—lithium 4,5-dicyano-2-(pentafluoroethyl)imidazolide and LiHDI—lithium 4,5-dicyano-2-(n-heptafluoropropyl)imidazolide) applied in a model liquid electrolyte, with propylene carbonate used as a solvent, is described. Room temperature ionic conductivities measured by Impedance Spectroscopy are as high as 10−2 to 10−3 S cm−1 for the 0.1–1 mol dm−3 salt concentration range. Lithium cation transference numbers calculated using the Bruce–Vincent method exceed 0.4 at salt concentration equal to 1 mol dm−3. Interface resistance measurements showed good stability at high—0.5 mol dm−3 or low—0.01 mol dm−3 salt concentrations. Ionic associations were estimated using Fuoss–Kraus semiempirical method revealing relatively low association rates. The effect of anion structure on ionic interactions and electrochemical characteristics of the studied electrolytes is discussed.