An efficient, convenient and flexible polyvinylidene fluoride/tetrabutylammonium hexafluorophosphate hierarchical nanofiber membrane (PVDF/TBAPF6 HNM) was successfully fabricated by one-step electrospinning and used as the separator of Li-ion capacitor (LIC). The PVDF/TBAPF6 HNMs displayed high ion conductivity of 4.28 × 10−3 S/cm, high mechanical strength, porosity, wettability and excellent thermal performance. Furthermore, the separator of PVDF/TBAPF6 HNM possessed lower interfacial resistance (134Ω) and better electrochemical stability, which exhibits better capacity retention and coulombic efficiency, compared with the commercial celgard 2340 separator. We believe that the gel polymer PVDF/TBAPF6 HNMs separator will have great potential in the field of the separator of LIC.