Adsorption, diffusion and electrocatalytic triple effect from ultrathin-walled TiO2(B) nanotubes for lithium–sulfur batteries

The shuttling of lithium polysulfides (LiPSs) between anode and cathode in lithium-sulfur batteries (LSBs) has been seriously restricted their actual electrochemical performances. Coating modifications on the surface of separators is considered an effective strategy to improve the battery performances. Metal oxides, especially TiO 2 as separator modifications can restrain the shuttle effect of LiPSs to a certain extent. It could be the inappropriate microstructure or limited crystal structure of TiO 2 , resulting in the non-ideal cycling performances of LSBs. Compared with other TiO 2 phase, nanotube structured TiO 2 -Bronze (TiO 2 (B)) owns characteristic required for ideal separator modifications. However, there are relatively few studies about ultrathin-walled TiO 2 (B) nanotubes as separator modifications. In this paper, ultrathin-walled TiO 2 (B) nanotubes (TiO 2 (B)-NTs) were constructed through a facile hydrothermal synthesis combined with high-temperature calcination method. The DFT calculations and electrochemical tests of LSBs proved that the ultrathin-walled TiO 2 (B)-NTs as separator modifications have several advantages: strong chemical entrapment for LiPSs; fast lithium-ion diffusivity and strong catalytic activity. Consequently, compared with nanorod structured TiO 2 (B) and CNTs, the TiO 2 (B)-NTs as separator modifications deliver superior cycling performances with ∼805 mAh g −1 at 1.0 C after 80 cycles and ∼235 mAh g −1 at 5.0 C after 600 cycles, and good rate capabilities in LSBs.