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.