Herein, a novel core@sheath nanofibrous membrane with ultrahigh strength, superior fire resistance and high wettability is prepared for lithium-ion batteries separator via self-bonding and self-compression technique, using the polyimide nanofiber as the core material and polybenzimidazole as the reinforced sheath material. The self-bonding and self-compression make the polyimide@polybenzimidazole-reinforced nanofibrous membrane possess ultrahigh strength up to 59 MPa and more compact porous structure, which is an exciting finding. The assynthesized nanofibrous membrane exhibits super high thermal dimensional stability up to 300 degrees C and satisfying wettability. Furthermore the good thermal stability of as-synthesized membrane enables it to preserve the integrity of backbone at temperatures as high as 540 degrees C. More significantly, the unique fire resistance of polybenzimidazole also ensures the high security of batteries. Notably, the battery using the as-synthesized separator displays much higher capability (130.2 mAh g(-1), 5 C) than that with Celgard separator (95.4 mAh g(-1), 5 C), and it can work steadily at 120 degrees C. Therefore, we believe that this work is really a significant breakthrough for the polyimide nonwoven separators, especially the ultrahigh mechanical strength, indicating the promising applications for the next generation high-safety and high-performance lithium-ion batteries.