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.　(Figure　presented.)　©　Science　China　Press　2025.