Integrating Energy Band Alignment and Oxygen Vacancies Engineering of TiO₂ Anatase/Rutile Homojunction for Kinetics‐Enhanced Li–S Batteries

Abstract

Abstract The inferior shuttle effect of intermediate lithium polysulfides and the sluggish kinetics of sulfur redox reaction are two serious puzzles for the application of lithium–sulfur batteries. Herein, energy band alignment is combined with oxygen vacancies engineering to obtain TiO 2 anatase/rutile homojunction (A/R‐TiO 2 ) with effective immobilization and high‐efficiency catalytic conversion of polysulfides. Theoretical calculations and experiments reveal that the near perfect energy band alignment in A/R‐TiO 2 is conducive to fluent charge transfer and high catalytic activity, while the rich oxygen vacancies are engineered to provide abundant active sites for anchoring and accelerating conversion of soluble polysulfides. As a result, a battery with A/R‐TiO 2 ‐modified separator delivers a marked sulfur utilization (1210 mAh g −1 at 0.1 C and 689 mAh g −1 at 1 C, 3.75 mg cm −2 ) and a high capacity retention of 63% over 300 cycles at 0.5 C (3.25 mg cm −2 ). More importantly, the A/R‐TiO 2 ‐modified separator endows the pouch cell with a high capacity of 128.5 mAh at 0.05 C with a lean electrolyte/sulfur ratio for practical application (S loading: 4 mg cm −2 ).