Crosslinked Poly(Ionic Liquid) Pentablock Terpolymer Electrolytes for Lithium Metal Batteries

ABSTRACT In this study, solid polymer electrolytes (SPEs) containing crosslinked poly(ionic liquid) pentablock terpolymer (X‐PILPTP) (at varying crosslinking degrees from 1% to 20% [mol%]), ionic liquid, and lithium salt are investigated with respect to morphology, ionic conductivity, mechanical properties, electrochemical stability, and lithium metal battery performance. Selective crosslinking is used to covalently connect the middle block of ABCBA pentablock terpolymers with an ionic crosslinker to minimize the loss of microphase separation and self‐assembled morphology. Interestingly, all X‐PILPTP SPEs with absorption of lithium salt and ionic liquid exhibit lamellar morphologies in the presence of crosslinked networks. Additionally, mechanical strength is well preserved despite the high absorption of lithium salt and ionic liquid, providing outstanding ionic conductivity and mechanical properties. High ionic conductivity is achieved at a 5% crosslinking degree without significant mechanical loss, improving its electrochemical stability. X‐PILPTP SPE as the separator within lithium metal batteries delivers an initial discharge capacity of 128 mAh g −1 at room temperature with outstanding capacity retention of 96.8% after the 100th cycle, highlighting the prospect of crosslinked PIL multiblock polymers as a potential candidate for SPEs in solid‐state lithium metal batteries.