Asymmetric Li-Coated PEO–PVDF-co-HFP Membrane with Graphene Oxide as Next-Generation Gel Polymer Electrolytes for Li-Ion Batteries

The pursuit of safer and more efficient electrolytes is central to the development of next-generation lithium batteries. In this work, a hybrid gel polymer electrolyte (GPE) was engineered by combining poly(ethylene oxide) (PEO) with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) and functionalized with graphene oxide (GO). The introduction of GO disrupted PEO crystallinity and enhanced segmental motion, yielding a fourfold increase in ionic conductivity compared to the pristine polymer matrix. At an optimal loading of 1.5 wt%, the GPE achieved 1.29 × 10⁻⁴ S·cm⁻¹ while maintaining structural integrity and interfacial stability. To further boost performance, a thin lithium coating was deposited on the GPE surface, promoting uniform ion flux and reducing interfacial resistance. When paired with ZnO–Zn₃N₂ thin-film anodes, the modified GPE delivered stable cycling with capacities of 350–370 mAh g⁻¹ and 264 mAh g⁻¹ retained after 200 cycles at 0.1C, alongside Coulombic efficiencies exceeding 97 %. These findings highlight a synergistic design strategy that combines nanofiller engineering with interfacial modification to advance solid-state and gel-based lithium batteries.