Electron Filling Control Mechanism Triggered by the Penetration Effect in Fe 3 N/Fe Accelerates Sulfur Redox Kinetics

Abstract This study designs a Fe 3 N/Fe‐NC catalyst with a dual internal‐external structure to address polysulfide conversion in Li‐S batteries. Derived from ZIF precursors, the catalyst features a hollow cavity and star‐like tip structure, where the high‐curvature exterior enhances electron transfer at Fe 3 N/Fe heterointerfaces and stabilizes Fe‐Nx sites for sulfur adsorption. Multivalent Fe increases effective nuclear charge via the penetration effect, promoting 3d orbital electron tunneling into inner layers. This reduces energy levels, populates non‐bonding orbitals with single electrons, and enables efficient d‐p hybridization with minimized antibonding states, strengthening polysulfide interactions. DFT calculations reveal Fe 3 N/Fe's d band center (ɛ d ) proximity to the Fermi level and reduced work function, facilitating charge transfer. The optimized Fe 3 N/Fe‐NC@PP‐based battery exhibits a low capacity decay rate of 0.0603% after 600 cycles at 2C and maintains high capacity under 6.668 mg cm⁻² sulfur loading. The pouch cell delivers an initial capacity of 1511.57 mAh g⁻¹ at 0.1 C with 50 cycle stability.