Battery separators made of inorganic powders and polymeric substrates have attracted intensive attention from both industry and academia. However, existing technology suffers from an inherent limitation in that the aggregation of powders during manufacturing and the escape of powders in use are inevitable. In this work, we report for the first time, a novel separator prepared by blending inorganic ZrO₂ staple fibers with poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP). Through a unique phase inversion process, the separator shows a skinless surface, a highly porous internal structure and a uniform distribution of pore size. Systematical comparison of a fiber-based separator and a powder-based separator demonstrates that the reinforcement from the fiber skeleton can provide the separator with desired porosity, sufficient mechanical strength, superior thermal stability and improved electrochemical performance. We anticipate that the concept of combining inorganic fiber substrates with polymeric media will offer a platform strategy towards the fabrication of high-safety separators for lithium-ion batteries and other energy storage systems.