Chemically Reactivatable Sulfide Interfaces for Low-Pressure Thick-Cathode Solid-State Na-S Batteries

Low-pressure solid-state Na-S batteries with thick sulfur cathodes are attractive for high-energy storage, but their operation is fundamentally constrained by the progressive loss of solid-solid contact during sulfur conversion. Once insulating sulfides become poorly connected to the electronic network, charge recovery becomes incomplete and cathode passivation rapidly accumulates. Here, we construct chemically reactivatable sulfide interfaces by embedding Fe₃C-MnO heteropoints within nitrogen-doped hollow carbon nanotubes. The heterointerface integrates carbon-side electronic coupling, sulfide-side affinity, and interfacial polarization, thereby suppressing localized sulfide accumulation and sustaining charge-stage sulfur recovery as mechanical confinement weakens. This effect is strongly pressure dependent. Under high compression, the electrochemical responses of different hosts converge, whereas under contact-limited conditions the Fe₃C-MnO architecture preserves markedly higher sulfur utilization, lower polarization, and superior cycling stability. Consequently, the operational pressure required to retain ≥80% of the 10 MPa discharge capacity decreases from approximately 2 MPa for the control cathodes to 0.2 MPa for Fe₃C-MnO/NC@S. A 200 µm cathode with 8.3 mg cm^-2 sulfur sustains reversible cycling at 0.2 MPa, together with a pouch-cell energy density of 696 Wh kg_cathode ^-1. These results establish sulfide-interface reactivation as a route to decouple reversible sulfur chemistry from stringent mechanical confinement.