Electrospun TiO<sub>2</sub> Nanofibers Featuring Surface Oxygen Vacancies as a Multifunctional Interlayer for High-Performance Lithium–Sulfur Batteries in a Wide Temperature Range
Xuan Du, Dan Ma, Yuefeng Zhang, Jianmin Ma, Jianyi Wang, Qinggui Xiao, Bin Wang, Liangliang Tian, Jinliang Zhuang
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 TiO 2 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.