Reinforced Quaternized Poly(crown ether)-Based Solid Polymer Electrolyte for Highly Durable Lithium–Metal Batteries

All-solid-state lithium metal batteries (LMBs) are recognized as prospective next-generation energy storage systems due to their high energy density and inherent safety. However, as a critical component of LMBs, solid polymer electrolytes (SPEs) face challenges, such as low ionic conductivity and a low Li+ transference number, leading to severe interfacial polarization and lithium dendrite growth. Herein, we develop a mechanically reinforced composite solid polymer electrolyte (QPCE-SPE) by impregnating a PEO/LiTFSI matrix blended with quaternized poly(crown ether) into an ultrathin porous polypropylene substrate. The cationic polymer immobilizes TFSI- anions while crown ether moieties promote lithium salt dissociation, enabling an enhanced ionic conductivity of 1.05 × 10-4 S cm-1 at 80 °C and a Li+ transference number of 0.56. Consequently, QPCE-SPE delivers stable cycling performance (>1300 h at 0.1 mA cm-2) in Li symmetric cells, and the Li|QPCE-SPE|LFP battery retains 81.9% of its capacity after 1000 cycles at 0.5C and 60 °C. Pouch cells based on QPCE-SPE remain stable under mechanical abuse, demonstrating robust mechanical resilience and intrinsic safety. This study presents an effective strategy for developing high-performance SPEs for LMBs.