Synergistic Cation-Anion Vacancies and Topological Morphology Tuning on TiO Nanoflower Spheres for Efficient Polysulfide Confinement and Catalysis in Lithium Sulfur Batteries.

Lithium─sulfur (Li─S) batteries are promising next-generation energy storage systems but are plagued by the Lithium Polysulfides (LiPSs) shuttle and sluggish redox kinetics. Titanium monoxide (TiO) is an attractive material for mitigating these issues, while conventional synthesis methods often lead to particle agglomeration and reduced active sites. This work presents a novel strategy for fabricating TiO nanoflower spheres (TiO-NFSs) rich in both Ti and O vacancies. The synthesis involves a magnesiothermic reduction of TiO2@SiO2 nanospheres followed by a controlled NaOH etching process, which simultaneously removes impurities and modulates the surface topology. When applied as a functional coating on the commercial polypropylene separator (TiO-NFSs@PP), the material demonstrates exceptional capability in anchoring LiPSs and accelerating their conversion kinetics. Consequently, Li─S cells equipped with TiO-NFSs@PP separator achieve a high initial discharge capacity of 1097 mAh g-1 at 0.2C with a capacity retention of 83% after 80 cycles, and an ultralow decay rate of 0.035% per cycle over 1000 cycles at 1C. This study elucidates the synthesis-structure-performance relationship of vacancy-engineered TiO, providing a new approach to the designing of highly efficient functional modified separators for advanced Li─S batteries.