Fibrous Separator with Surface Modification and Micro-Nano Fibers Lamination Enabling Fast Ion Transport for Lithium-Ion Batteries

Appropriate materials collaborated with reasonable structure can significantly increase the separator performance for lithium-ion batteries. In this work, taking the advantages of microfibrous and nanofibrous membranes and compensating for their defects, we developed a composited separator (GOPPH) with excellent overall performance by first wetting-modifying the polyethylene terephthalate microfibers and then laminating a polyvinylidene fluoride-hexafluoropropylene nanofiber layer. Such a combination not only offers the GOPPH separator, from the perspective of structure, with high porosity and hierarchical structure in terms of fiber diameter and pore size, but also provides satisfactory features including wettability, mechanical strength and thermal shutdown function that benefit from the selected materials. Meanwhile, as determined by experimental and theoretical approaches, the obtained GOPPH separator exhibits considerably enhanced lithium ion transport ability with a high lithium ion transference number and transport rate, which thereby endowing the cell with superior cycling stability with a capacity retention of 93% after 200 cycles at 1 C. Therefore, considering battery safety and performance, the GOPPH fibrous membrane could be a promising separator candidate for lithium-ion batteries.