Lithium metal batteries (LMBs) are promising candidates for next-generation energy storage systems due to their high theoretical energy density. However, lithium dendrite growth and safety concerns remain critical challenges. To address these issues, we propose a novel gel polymer electrolyte (GPE) design strategy by coating a PEGDE/PEA-based crosslinked polymer (PEGA) electrolyte onto a commercial polypropylene (PP) separator, which serves as a structural substrate. The PEGA gel polymer electrolyte exhibited enhanced mechanical properties, representing an improvement of 15% compared to the bare PP separator, and demonstrated excellent flame retardancy as confirmed by the self-extinguishing time (SET) test. Furthermore, the PEGA polymer matrix coordinates with Li⁺ to form direct ion transport pathways, achieving enhanced ionic conductivity (1.02 mS/cm) and a high Li⁺ transference number (0.602) compared to the liquid electrolyte (LE, 0.358). As a result, the PEGA gel polymer electrolyte demonstrated stable cycling for over 500 hours and effective dendrite suppression in the Li||Li symmetric cell test. Moreover, the Li||NCM622 cells employing the PEGA gel polymer electrolyte achieved a high capacity retention of 97.54% after 50 cycles, demonstrating its practical applicability in battery systems.