Recent development of ionic liquid-based electrolytes in lithium-ion batteries

Lithium-ion batteries are promising technologies for large-scale energy storage due to their high energy densities. However, the safety concerns of traditional lithium-ion batteries caused by usage of flammable organic-based electrolytes have severely hindered their practical applications. Ionic liquids (ILs) are molten salts with melting points lower than 100 degrees C. The unique physiochemical properties of ionic liquids include wide electrochemical stability window, high ionic conductivity, superior thermal stability, and non-flammability. When employing as electrolyte components, ionic liquids have demonstrated improved safety and electrochemical performances in lithium-ion batteries. This review summarizes the recent development of ionic liquids and ionic liquid-based electrolytes in terms of physiochemical properties, interphase formation ability, and electrochemical performance in lithium-ion batteries. The applications of pure ionic liquid-based electrolytes, ionic liquid-hybrid electrolytes, and (quasi) solid-state ionic liquid electrolytes are discussed in detail. Finally, the challenges and perspectives for the application of ionic liquid-based electrolytes in lithium-ion batteries are also presented for further development.