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 °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.