Mitigating the polysulfides “shuttling” with TiO₂ nanowires/nanosheets hybrid modified separators for robust lithium-sulfur batteries

Abstract

The “shuttling” of the dissolved lithium polysulfides (LPSs) has been a major impediment to the development of a robust lithium-sulfur batteries (LSBs). Functionalization of commercial polypropylene (PP) separators has been considered as a promising alternative strategy for further mitigation of the “shuttle effect” of LPSs. Herein, we re-engineer the surface of PP separator with a sodium-containing TiO2 hybrid composed of nanowires and nanosheets (STO-W/S), forming a unique sandwich-like surface layer. The polar nature of STO surface layer indubitably improves its wettability to electrolyte, subsequently enhancing Li+ conductivity. Meanwhile, the synergistic effect of the sandwiched sheet/nanowire hybrid structure, its strong chemical adsorption and the regeneration capability of STO-W/S to LPSs effectively suppresses the “shuttling” of LPSs. As expected, LSBs coupled with STO-W/S modified PP separators show superior electrochemical performance. They deliver high discharge capacity of 813 mAh·g−1 at 1C and superior cycling stability with a capacity fading rate of 0.067% for each cycle, and the capacity was still maintained at ~541 mAh·g−1 for 500 cycles. Based on the aforementioned advantages, this newly-proposed functionalization strategy for separators can be a promising route to develop the next-generation multifunctional separators for high-performance LSBs.