Adopting　ultra-thin　copper　foil　as　the　current　collector　is　one　of　the　most　important　strategies　for　improving　the　gravimetric　energy　density　of　lithium-ion　batteries　(LIBs),　however,　stumbled　by　the　quality-control　of　physicochemical　properties　for　ultra-thin　foils.　Herein,　by　utilizing　combinative　additives,　the　≤　4.5　µm　ultra-thin　electrolytic　copper　foil　with　appealing　physicochemical　properties　is　prepared,　presenting　very　low　Rz　(surface　roughness)　of　1.74　µm　and　extraordinarily　high　tensile　strength　of　435.65　MPa.　When　being　used　as　the　current　collector　in　LIBs,　a　high　gravimetric　energy　density　of　323.19　Wh/kg　was　achieved,　outperforming　both　the　commercial　9　µm　candidate　(205.81　Wh/kg)　and　the　purchased　4.5　µm　counterpart　(310.48　Wh/kg).　Also,　decreasing　the　thickness　of　commercial　copper　foil　(9　µm)　to　4.5　µm　demonstrates　superiorities　in　both　resources　saving　and　environmental　benignity,　contributing　to　∼32　million　tons　copper　savings　in　2030　and　40.6　%　elimination　in　carbon　footprint　for　copper　foil　preparation.　The　results　herein　can　provide　guidance　for　quality-controlled　preparation　of　ultra-thin　copper　foil　as　well　as　new　insights　for　resource　savings　and　environmentally　friendly　manufacturing.　©　2023　Elsevier　Ltd