Li　metal　batteries　based　on　solid　polymer　electrolytes　offer　the　benefits　of　high　energy　density　and　safety,　as　well　as　extended　cycling　life,　making　them　an　excellent　candidate　for　the　next-generation　battery　system.　However,　current　solid　polymer　electrolytes　still　suffer　from　low　ion　conductivity　and　Li+　transfer　number,　which　seriously　restricts　its　practical　application.　Herein,　a　self-supporting　composite　solid　polymer　electrolyte　was　prepared,　where　phenolic　resin　rich　in　hydroxyl　groups　(BR)　and　polyethylene　oxide　(PEO)　are　mixed　evenly　and　poured　onto　a　cellulose　membrane　in　one　step.　In　such　an　electrolyte,　PEO　and　BR　combine　to　form　intermolecular　hydrogen　bonds,　lowering　the　crystallinity　of　PEO　and　increasing　the　Li+　transfer　number.　Lastly,　the　obtained　solid　electrolytes　exhibited　a　high　ion　conductivity　(1.1×10−4　S　cm−1)　and　Li+　transfer　number　(0.53),　as　well　as　improved　electrochemical　window.　Consequently,　Li　||　Li　symmetrical　cells　can　run　stably　for　more　than　700　h　at　0.1　mA　cm−2/0.25　mAh　cm−2.　And　full　cells　with　LiFePO4　cathode　can　also　demonstrate　high　discharge　capacity　of　152.12　mAh　g−1　and　rate　performance.　We　believe　that　such　a　design　based　on　supramolecular　interaction　offer　a　new　avenue　to　advanced　solid　polymer　electrolytes.　©　2024　Wiley-VCH　GmbH.