Tailoring electronic state of sulfur electrocatalysis via dual defects for accelerated redox kinetics in advanced...

The lithium polysulfides (LiPSs) shuttle effect and sluggish sulfur redox kinetics hinder the cycling stability and sulfur utilization of lithium‑sulfur (Li-S) batteries. Herein, a dual-defect engineering strategy is proposed to tailor the electronic state of sulfur electrocatalysts. This is exemplified by synthesizing a dual-defect electrocatalyst of oxygen-deficient manganese-doped Fe₃O₄ and carbon nanotubes (Mn_dFe₃O_4-x@CNTs) via a one-step hydrothermal route. Theoretical analyses reveal the dual defects synergistically optimize the electronic structure of Fe₃O₄ by modulating its spin state. This leads to an upshift of the d-band center, strengthening the d-p orbital hybridization with LiPSs and significantly accelerating the bidirectional conversion kinetics. The interconnected mesoporous framework acts as a multifunctional host, offering ample space for sulfur loading and working synergistically with the catalytic centers to concentrate LiPSs for efficient conversion. Consequently, the composite cathode exhibits excellent performance, including a low capacity fading rate of 0.07 % per cycle over 500 cycles at 1C, a high-rate capacity of 892.1 mAh g^-1 at 3C, and an initial capacity of 582.7 mAh g^-1 at 0.2C under a high sulfur loading of 9.1 mg cm^-2. This work establishes a paradigm for developing high-performance Li-S batteries through precise defect engineering of mesoporous transition metal oxides.