Gel polymer electrolytes (GPEs) have attracted extensive attention in lithium-ion batteries due to their high security and excellent electrochemical performance. However, their inferior Li-ion transference number, low room-temperature ionic conductivity, and poor long cycle stability raise challenges in practical applications. Herein, a flexible poly(vinylidene fluoride-co-hexafluoropropylene)-butanedinitrile (PVDF-HFP-SN)-based GPE (PSGPE) is synthesized successfully by a general immersion precipitation method. The resultant PSGPEs have numerous connecting pores to ensure sufficient space for liquid electrolytes. Moreover, the reduced crystallinity of PVDF-HFP and the high polarity of SN can reduce the energy barrier of Li-ions shuttling between pores. The synergistic effect possesses a high ionic conductivity of 1.35 mS·cm⁻¹ at room temperature with a high Li-ion transference number of 0.69. The PVDF-HFP-SN-based GPE is applied in a LiFePO₄/graphite battery, which can realize stable cycling performance for 350 cycles and good rate performance at room temperature. These results demonstrate that the novel PSGPE possesses advantage in simplified production process, which can improve the practicability of gel polymer lithium-ion batteries.