<p>The performance of polymer electrolytes in Li-ion batteries depends on meeting several demanding criteria, including high ionic conductivity, strong mechanical integrity, thermal and electrochemical stability, and a high Li-ion transference number. However, pristine polymers often struggle to fulfill all these requirements simultaneously. One of the biggest challenges is balancing ionic conductivity with mechanical strength. While conductivity benefits from a more amorphous polymer structure, mechanical robustness usually requires greater structural order. To overcome these limitations, researchers have explored various enhancement strategies such as polymer blending, the addition of functional additives, cross linking, surface functionalization, and incorporating nanomaterials. These techniques help reinforce mechanical properties and optimize ionic transport pathways, addressing the inherent trade-offs in polymer electrolyte design. This review takes a deep dive into these enhancement methods, examining how they improve the performance of polymer electrolytes for energy storage applications. It also explores key factors influencing optimization, including solvent selection, polymer filler interactions, and electrode–electrolyte interface stability, all of which significantly impact the overall efficiency of Li-ion batteries. Additionally, the review covers various polymer electrolyte film fabrication techniques, such as solution casting, melt mixing, spin coating, hot pressing, and dip coating, providing insights into the most effective methods for developing high-performance polymer electrolytes tailored to specific battery needs.</p>