Multi‐functional TiO 2 nanosheets/carbon nanotubes modified separator enhanced cycling performance for lithium‐sulfur batteries

TiO2 nanosheets (TiO2NSs) have been investigated for lithium-sulfur (Li-S) batteries as strategically designed TiO2 nanosheet/carbon nanotube (TiO2NS/CNT) composite modified polypropylene (PP) separator to inhibit the shuttling of the intermediate polysulfides. The modified separator was fabricated by the vacuum filtration method using the exfoliation TiO2NSs and untreated carbon nanotube (CNT) composites. The multi-functional TiO2NS/CNT coating not only reduced the electrochemical resistance but also localized the migrating polysulfides by the cooperative effect of physical adsorption and chemical binding. Specifically, the composition ratio of TiO2NSs/CNTs and the interface character have been studied. It was found that the optimum ratio and perfect electrolyte wettability of the TiO2NS/CNT layers were all the critical reasons to achieve good battery performance. The high initial discharge capacity of 1247 mA h g−1 at 0.2 C rate, which was 75% of the theoretical capacity of sulfur, 98% average coulombic efficiency, and 627 mA h g−1 discharge capacity retention after 100 cycles were obtained with the TiO2NS/CNT coating separator.