Towards large-scale, fully ab initio calculations of ionic liquids

Ionic liquids have attracted a substantial amount of interest as replacement of traditional electrolytes in high efficiency electrochemical devices for generation and storage of energy due to their superior physical and chemical properties, especially low volatility and high electrochemical stability. For enhanced performance of the electrochemical devices ionic liquids are required to be highly conductive and low viscous. Long-range Coulomb and short-range dispersion interactions between ions affect physical and chemical properties of ionic liquids in a very complex way, thus preventing direct correlations to the chemical structure. Considering a vast combination of available cations and anions that can be used to synthesize ionic liquids, development of predictive theoretical approaches that allow for accurate tailoring of their physical properties has become crucial to further enhance the performance of electrochemical devices such as lithium batteries, fuel and solar cells. This perspective article gives a thorough overview of current theoretical approaches applied for studying thermodynamic (melting point and enthalpy of vapourisation) and transport (conductivity and viscosity) properties of ionic liquids, emphasizing their reliability and limitations. Strategies for improving predictive power and versatility of existing theoretical approaches are also outlined.