Rational engineering of ionic liquid electrolyte: a revolutionary paradigm shift toward advanced lithium batteries

The increasing demand for high-performance lithium-ion batteries (LIBs) in portable electronics and electric vehicles has driven extensive research into advanced electrolytes. Ionic liquids (ILs) and their derived electrolytes, including poly(ionic liquids), ionogels, and IL-functionalized systems, provide significant potential for enhancing the safety and electrochemical performance of LIBs due to their unique properties, such as non-volatility, wide electrochemical windows, and excellent thermal stability. These properties enable safer, high-energy, and long-lasting batteries. In order to benchmark the important development of the new concepts and technologies emerging in IL-based electrolytes, this review conducts a thorough analysis of the physicochemical properties of ILs and their versatile applications in electrolytes, particularly emphasizing their adaptability to fulfill the specific needs of different battery systems. In liquid electrolyte systems, ILs can function as solvents, interfacial modifiers, and critical components for constructing artificial solid electrolyte interphase (SEI). In (quasi-)solid-state electrolyte systems, ILs can be polymerized to form poly(ionic liquid)s or integrated with organic, inorganic, or composite materials to develop IL-based electrolytes, demonstrating multifunctional electrochemical performance. Finally, the review critically examines the challenges and opportunities in this field, offering insightful perspectives for future advancements.