Comprehensive analysis and correlation of ionic liquid conductivity data for energy applications

Abstract Ionic liquids have emerged as potentially safer and more sustainable electrolytes for energy storage and renewable energy applications, such as Li-ion batteries, Na-ion batteries, supercapacitors and fuel cells. Conductivity is one of the key physical properties influencing the performance of an electrolyte in such applications. In this study, an extensive database for conductivity of ionic liquids was compiled, containing around 3800 data points over the temperature range from 234 K to 484 K, from 134 previously published literature sources. A total of 285 unique ionic liquids consisting of 152 unique cations and 82 unique anions, were included. The data were systematically analyzed to gain a deeper understanding of the relationships between the ionic liquid conductivity and various structural parameters, such as cation type, anion type, hydrocarbon chain length and functional groups. The correlations between conductivity and several other transport and thermodynamic properties of ionic liquids were also investigated and the COSMO-RS method was evaluated as a predictive tool for IL conductivity. Finally, the temperature dependence for each individual ionic liquid was correlated using the Arrhenius equation and the VTF equations. This work will assist in improving the design of ionic liquids as electrolytes in energy storage and renewable energy applications.