Here, we fabricate poly(vinylidene fluoride- co-hexafluoropropene) (PVDF- co-HFP) by electrospinning for a gel polymer electrolyte (GPE) for use in flexible Li-ion batteries (LIBs). As a solvent, we use N-methyl-2-pyrrolidone (NMP), which helps produce the cross-linked morphology of PVDF- co-HFP separator, owing to its low volatility. The cross-linked PVDF- co-HFP separator shows an uptake rate higher than that of a commercialized polypropylene (PP) separator. Moreover, the PVDF- co-HFP separator shows an ionic conductivity of 2.3 × 10 −3 S/cm at room temperature, comparable with previously reported values. An LIB full-cell assembled with the PVDF- co-HFP-based GPE shows capacities higher than its counterpart with the commercialized PP separator, confirming that the cross-linked PVDF- co-HFP separator provides highly efficient ionic conducting pathways. In addition, we integrate a flexible LIB cell using the PVDF- co-HFP GPE with a flexible organic light emitting diode (OLED), demonstrating a fully flexible unit of LIB and OLED.