Influence of Solvent Addition on the Properties of Ionic Liquids
Résumé
The effects of the incorporation of ethylene carbonate (EC) or dimethyl carbonate on the physicochemical and electrochemical properties of ionic liquids (ILs) based on aliphatic quaternary ammonium and imide anion were studied. The evolution of the melting point, glass transition, ionic conductivity, diffusion coefficient, and electrochemical stability were evaluated. The addition of a low amount of solvent, that is, 20 wt %, allows us to improve significantly the conductivity values, reaching 12 mS/cm at 40 °C. The incorporation of a polar solvent, EC, has no positive effect on the IL dissociation. Moreover, the incorporation of EC in ILs improves the electrochemical stability toward reduction, whereas the high anodic stability is maintained. The addition of LiTFSI in IL + solvent electrolytes has been investigated. Although this addition reduces the ionic conductivity, this decrease is less pronounced than in pure ILs, showing the beneficial effect of the additive solvent.