Regenerated Natural Minerals towards Double‐layers Heterojunctions Metal@metal‐sulfides with Remarkable Conductivity for Ultra‐fast Sodium‐ion Storage

Abstract Attracted by the high specific capacity and energy density, transition metal‐sulfides exhibit great application potential as sodium‐ion batteries anode, but still suffer from the uncontrolled separation of M/S phase and inferior conductivity. Herein, the flower‐like Fe_1‐xS@Sb@C (FF) is rationally tailored, accompanied by double‐layer heterojunctions and C–S–Sb/Sb–S–Fe “bridge” bonds. Meanwhile, the bimetallic phases/boundary defects and built‐in electric fields are formed with a strong electronic coupling effect, effectively alleviating the separation of the M/S phase (Fe/Sb and S), and significantly enhancing ion/e⁻ conductivity. As expected, FF delivers an ultra‐fast sodium‐ions storage rate capacity of 436.5/334.3 mAh g⁻¹ even at 10.0/20.0 A g⁻¹. When the operation temperature is lowered to ‐5 °C, the reversible capacity can still remain at ≈349.7 mAh g⁻¹. Assisted by the detailed kinetic analysis and theoretical calculations, their great ion‐storage abilities mainly derive from improved interfacial Na⁺/e⁻ transfer and surface/near‐surface redox behaviors. Moreover, the reassembling evolution of active phases is revealed by in/ex situ techniques, further demonstrating the stable adsorption/anchoring of intermediate reaction products Fe/Sb–S phases on the heterointerface, accompanying high reversible conversion‐alloying reaction. Given this, this interesting work is anticipated to offer an in‐depth insight into capacity fading mechanism, and effective strategy to design metal‐sulfur anodes for advanced sodium‐ion systems.