Poly(vinyl　ethylene　carbonate)　(PVEC)　electrolyte　is　a　promising　option　for　high-performance　solid-state　lithium　metal　batteries　(SSLMBs).　However,　its　anti-oxidation　ability　is　still　too　low　to　match　high-voltage　cathode　materials.　Herein,　a　novel　copolymer　electrolyte,　poly(vinyl　ethylene　carbonate-3-sulfolene)　(P(VEC-SF)-PE)　has　been　developed　by　copolymerizing　3-sulfolene　(SF)　and　vinyl　ethylene　carbonate　(VEC)　monomer　precursors.　The　P(VEC-SF)-PE　possesses　a　wide　electrochemical　stability　window　of　5　V　(vs.　Li+/Li),　high　lithium　ion　transference　number　of　0.6　and　ionic　conductivity　of　7.97　×　10−4　S　cm−1　at　25　°C.　The　anti-oxidation　ability　is　enhanced　by　the　pre-degradation　of　sulfolene-based　functional　units　and　confirmed　by　multiple　techniques.　The　P(VEC-SF)-PE　based　SSLMBs　with　the　LiCoO2　cathode　exhibit　a　high　discharge　capacity　and　good　rate　performances　when　charged　to　4.5　V.　This　study　presents　an　efficient　strategy　to　improve　the　compatibility　of　the　cathode/electrolyte　interface　and　the　electrochemical　performances　of　high-energy　SSLMBs.　©　The　Royal　Society　of　Chemistry　2024.