The　safety　problem　of　lithium-ion　batteries　(LIBs)　has　restricted　their　further　large-scale　application,　especially　in　electrical　vehicles.　As　a　key　component　of　LIBs,　separators　are　commonly　used　as　an　inert　component　to　provide　a　migration　path　for　the　ions　and　prevent　direct　contact　of　the　cathodes　with　the　anodes.　However,　the　separator　damage　caused　by　external　impact　puncture,　local　overheating,　and　internal　and　external　short　circuit　leads　to　the　thermal　runaway　and　explosion　accidents　of　LIBs.　Therefore,　how　to　enhance　separator　safety　has　been　a　challenge　in　the　development　of　high-performance　LIBs.　In　this　review,　the　recent　advance　of　high-safety　separators　with　high　mechanical　strength,　high　thermal　stability　and　good　lithium　dendritic　resistance　is　the　main　focus.　Various　factors　affecting　the　separator＇s　safety　are　discussed,　including　the　species　of　the　polymer　substrate,　structure,　synthesis　and　modification　processes.　More　importantly,　the　designed　strategies　towards　high　safety　separator　are　comprehensively　addressed　in　terms　of　various　aspects:　(i)　to　composite　ceramic　materials　or　organic　polymers　to　improve　thermal　stability,　(ii)　to　modify　the　polymer　and　composite　structure　to　increase　mechanical　strength,　(iii)　to　design　a　functional　separator　to　regulate　ion　transport　and　lithium　deposition　for　mitigating　lithium　dendrites,　and　(iv)　to　intelligently　control　the　thermal　runaway　of　LIBs　by　flame　retardant　and　thermal　shutdown　function.　Furthermore,　the　component-structure-performance　relationship　of　separators　is　summarized,　and　the　impact　of　separator　compositions　and　structures　on　the　safety　of　LIBs　is　emphasized.　In　addition,　the　future　challenges　and　perspectives　of　separators　are　provided　for　building　high　safety　rechargeable　lithium　batteries.　©　2024　The　Royal　Society　of　Chemistry.