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

Abstract

BackgroundThe 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 TiO2 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 TiO2, resulting in the non-ideal cycling performances of LSBs. Compared with other TiO2 phase, nanotube structured TiO2-Bronze (TiO2(B)) owns characteristic required for ideal separator modifications. However, there are relatively few studies about ultrathin-walled TiO2(B) nanotubes as separator modifications. MethodsIn this paper, ultrathin-walled TiO2(B) nanotubes (TiO2(B)-NTs) were constructed through a facile hydrothermal synthesis combined with high-temperature calcination method. Significant findingsThe DFT calculations and electrochemical tests of LSBs proved that the ultrathin-walled TiO2(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 TiO2(B) and CNTs, the TiO2(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.