The　growing　awareness　of　the　environmental　risks　associated　with　spent　lithium-ion　battery　(LIB)　disposal　underscores　the　urgent　need　for　sustainable　solutions.　Commercial　polyolefins　separators　for　LIBs　cannot　naturally　degrade　at　end　of　life,　which　is　often　destroyed　by　pyrolysis,　causing　considerable　environment　issue.　Therefore,　developing　green　and　sustainable　separators　for　LIBs　seems　necessary.　Herein,　a　degradable　polyester　separator　(extended-chain-crystal　poly(butylene　succinate),　E-PBS)　is　successfully　developed　through　crystal　engineering　for　long-life　LIBs.　Such　an　E-PBS　separator　possesses　an　ionic　conductivity　of　up　to　3.19　mS　&　sdot;cm-1.　The　assembled　LIBs　using　this　E-PBS　separator　can　achieve　much　superior　capacity　retention　rates　after　long　cycles　to　those　with　commercial　polyethylene　separators.　Moreover,　the　spent　E-PBS　separator　can　be　dissolved　in　lye,　which　allows　the　cathode　and　anode　to　easily,　quickly　and　efficiently　separate.　A　life　cycle　assessment　shows　that　this　E-PBS　separator　is　more　environmentally　friendly　than　the　polyethylene　separator,　with　can　reduce　CO2　and　SO2　emissions　by　42.8　%　and　38.0　%,　respectively.　This　work　clearly　demonstrates　that　the　E-PBS　separator　is　a　more　sustainable　option　for　next-generation　sustainable　LIBs.