(Invited) New Ionic Liquids (ILs) for Secondary Batteries: Interplay between Structure, Electrical Response and Conductivity Mechanism

Abstract

The main bottleneck towards the development of high-performing “beyond Lithium ion” batteries in the portable electronic, electric automotive, and stationary applications [1] is the lack of electrolytes that are safe, electrochemically stable, and compatible with the electrode materials [2-3].Recently published papers demonstrated that halo-aluminate ionic liquids (ILs) can provide an appealing alternative to conventional ethereal solvent-based electrolytes due to their low volatility, negligible flammability, and excellent electrochemical performance [4-7].Following this, an overview on recent advancements on electrolytes for secondary batteries is presented, with a particular reference to imidazolium- and pyrrolidinium-based ILs. Insights on the interplay between thermal properties, structure and conductivity of BF4 -, Cl-/AlCl3, Cl-/TiCl4, and I-/AlI3-based systems are given, thus providing an in-depth understanding of the relation existing between ion speciation, long-range charge transfer mechanism, conductivity mechanisms and electrochemical performance of this very promising class of materials.