Electrospun TiO2 Nanofibers Featuring Surface Oxygen Vacancies as a Multifunctional Interlayer for High-Performance Lithium-Sulfur Batteries in a Wide Temperature Range.

ABSTRACT

Despite great achievements having been made in lithium-sulfur batteries (LSBs), further improvements regarding rate performance, cycle life, and operating temperature are needed for realistic applications. Herein, we developed a simple electrospun method for the preparation of TiO2 coaxial nanofiber (TCNFs)-modified Celgard separators to suppress the polysulfide shuttling. LSBs with a TCNF/Celgard separator display excellent electrochemical performance. For an areal sulfur loading of 2.5 mg cm-2, the cells exhibited a capacity of 1279 mA h g-1 at 0.5 A g-1, remained 798 mA h g-1 at 2.5 A g-1, and low-capacity decay of 0.057% per cycle within 1000 cycles. At 50 and -10 °C, the capacity of the cells is maintained at 932 and 931 mA h g-1 after 80 cycles at 0.5 A g-1, respectively. Detailed structural analysis and theoretical calculations revealed that the hollow-structured TCNFs offer high density of accessible electropositive Ti sites and oxygen vacancies and thus enables efficient trapping of polysulfides and facilitates Li+ transfer, leading to excellent performance. The simplicity of this strategy and the diversity of hollow-structured metal oxides holds great promise to design separators for high-performance LSBs.