From interlayer to lightweight capping layer: Rational design of mesoporous TiO₂ threaded with CNTs for advanced Li–S batteries

Lithium-sulfur (Li-S) battery with high theoretical energy density has been considered a promising candidate of the next-generation energy storage systems. Its commercialization, however, is mainly hindered by the fast capacity decay induced by the polysulfide shuttle behavior between two electrodes. Herein, we report a scalable production of mesoporous TiO₂-carbon nanotubes (MTO-CNTs) in which each mesoporous oval-shaped TiO₂ particle is threaded with a CNT in the axis direction. As its one dimensional structure with a self-weaving feature, two different approaches enlisting the use of MTO-CNTs as an interlayer between cathode and separator or a capping layer coated directly onto the sulfur cathode, both aiming to suppress the polysulfide shuttle. The threaded structure provides excellent interfacial contact between TiO₂ and CNTs allowing CNTs to provide fast and continuous electron pathway toward the TiO₂-polysulfide polar adsorption interface, thus dynamically accelerating the redox conversion of the trapped polysulfides. As a result of the synergetic effect, the cell with an ultra-lightweight MTO-CNTs capping layer (merely 0.06 mg cm⁻²) exhibits a long-term cyclability with a low capacity decay of 0.07% per cycle within 500 cycles at 0.5 C.