TiO₂@Porous carbon nanotubes modified separator as polysulfide barrier for lithium-sulfur batteries

The severe shuttle effect of polysulfides in lithium-sulfur (Li-S) batteries leads to rapid performance deterioration. Herein, a functional separator composed of TiO₂@surface-modified carbon nanotubes composite on polypropylene (PP) separator (donated as TiO₂@SCNT/PP) is developed toward the effective blocking of polysulfide shuttle. The as-assembled Li-S batteries using this functional separator with the strongly polar TiO₂ and highly conductive CNTs demonstrated considerably enhanced reversible capacity, cycling performance and reaction kinetics. The corresponding simple sulfur cathode with 70 wt% elemental sulfur powders exhibits a high initial discharge capacity of 1103.9 mAh g⁻¹, a high capacity of 848.0 mAh g⁻¹ after 200 cycles at 0.5 C, and a capacity decay of only 0.066% per cycle over 900 cycles. Moreover, a high reversible capacity of 746.5 mAh g⁻¹ is maintained after 300 cycles at 1 C. In contrast, the low reversible capacity of 218.5 mAh g⁻¹ at 0.5 C is obtained without the use of the TiO₂@SCNT/PP.