Active Component Design of Amorphous SnP _x /SnS _x and Interfacial Bonding Engineering in N/P/S‐Doped Hard Carbon for High‐Rate Sodium‐Ion Hybrid Capacitors

Abstract Sodium‐ion hybrid capacitors （SIC）face critical challenges from the kinetic mismatch and cycling life imbalance between battery‐type anodes and capacitive cathodes. A slope‐dominant N/P/S‐doped hard carbon anode (Sn0.1@NSPC) with nearly plateau‐free sloping charge–discharge curves, embedded with amorphous SnP _x /SnS _x composites, is developed. This unique design delivers a high reversible capacity of 412.8 mAh g⁻¹ at 0.05 A g⁻¹ while retaining 180.7 mAh g⁻¹ at 10 A g⁻¹, coupled with 90% capacity retention over 10 000 cycles. The amorphous SnP _x /SnS _x enables isotropic Na⁺ diffusion and volume expansion suppression, while interfacial Sn─P/Sn─S bonding activates the redox potential of P/S for sodium storage through reversible Na₃P/Na₂S formation. Density functional theory calculations demonstrate that Sn doping enhances electronic states near the Fermi level and reduces sodium‐ion diffusion barriers, improving conductivity and ion transport. Pseudocapacitive‐dominated kinetics with reduced charge transfer resistance are achieved, synergizing with alloying/conversion reactions. In SIC paired with activated carbon, the system exhibits an energy density of 360 Wh kg⁻¹ (anode‐mass‐based), a power density of 38 kW kg⁻¹, and 91% capacity retention after 3000 cycles. This work establishes a universal heterostructure design via amorphous engineering and interfacial coupling, addressing trade‐offs between high capacity, rapid kinetics, and long‐term cycling stability in advanced SIC.