Challenges and Opportunities of Ionic Liquid Electrolytes for Rechargeable Batteries

Ionic liquids (ILs) feature excellent thermal stability, high safety, high conductivity, wide electrochemical window, low vapor pressure, structural designability, and noncombustibility. For secondary batteries serving as green electrolyte solvents, their performance, including thermal stability and capacity, can be greatly improved. Therefore, the application of an ionic liquid in a battery has increasingly become a hot spot for current research. To better understand the roles that ILs play in battery systems, this review on ILs as electrolytes is categorized into several parts: solvents for related electrolyte salts; compounded with conventional electrolytes; IL-based polymer electrolytes; functionalized ILs; and other IL-based solid electrolytes that are expected to be alternatives for organic solvents. The progress of research related to ILs in battery systems, the prospects of their applications, and the development aspects are discussed.