Inorganic-Shell Reinforcement: TiO2-Coated Polyimide Nanofibers Membrane as Advanced Separator for Lithium-Ion Batteries

Herein, we report a series of titania (TiO 2 )-coated polymeric nanofibers membranes with superb strength, excellent thermal stability, and admirable wettability via in situ coating TiO 2 nano-shells on the surface of polyimide (PI) nanofibers. TiO 2 nano-shells are able to weld the PI nanofibers and serve as a reinforcement layer, endowing the TiO 2 -coated PI separator with high tensile strength of 43.94 MPa. Specifically, the in situ coating technique is a simple and controllable method to fabricate high-performance hybrid separator and meet the demand of low-cost industrial production. Moreover, TiO 2 -coated PI separator displays preferable wettability, thermal stability, and ion conductivity than the Celgard separator. Importantly, the unique thermal dimensional stability of TiO 2 -nanoshells and PI materials also improves the safety of lithium ion battery (LIB). Notably, TiO 2 -coated PI separator exhibit superior LIB capability of 140.1 mAh g −1 at 5 C compared to the commercial Celgard separator (95.4 mAh g −1 , 5 C). Besides, the present battery with TiO 2 -coated PI separator can operate stably after being tested at 1 C for 100 cycles. Thus, we believe that this work provides a significant contribution for realizing industrial production preparation of high-performance hybrid separators for LIBs.