Review: Ionic liquids as a potential electrolyte for energy devices

In the past decade, “ionic liquids (ILs)”, which are liquids at room temperature and contain only cations and anions without any molecular species, like water and organic solvents have attracted much attention as novel liquid electrolytes for electrochemical devices, such as the lithium ion battery (LIB), due to their unique physical and electrochemical properties. We have prepared low melting and low viscosity ILs to improve ion transport in the ILs and the resulting device performances. Especially, in the case of the LIBs, the structure of the negatively charged ion (anion) was found to be one of the key components that governs not only the ion transport resistance, but also the interfacial charge transfer resistance on both the negative and positive electrodes.