Single Atom‐Substituted Chalcogenides with Anion Vacancy Bonded on Graphene Nanotubes for Achieving “1+1+1>3” Synergistic Enhanced Sodium Storage

Developing distinctive composite anodes with multiple active components is critical for enhancing the charge storage capability of sodium-ion hybrid capacitors (SIHCs). Herein, In single atom-substituted SnS₂ with moderate sulfur vacancies in situ bonded on N-doped graphene nanotubes (In─SnS_2-x@NG) is ingeniously engineered as a superior anode. Theoretical calculations and in situ/ex situ characterizations illustrate that the introduced Sn(In)─N interfacial bonds immensely strengthen composites integration and boost charge transfer, then In single atom substitution effectively elevates d band center and enhances Na⁺ adsorption. Moreover, the sulfur vacancies reveal the bifunctional roles in accelerating Na⁺ diffusion and reinforcing structural thermodynamics. These merits guarantee deeply reversible conversion-alloying reaction and yield additional surface capacitive behavior of the In─SnS_2-x@NG anode, further realizing "1+1+1>3" synergistic enhanced sodium storage with ultrahigh reversible capacity (∼1211.8 mAh g^-1 at 0.1 A g^-1) and prominent rate performance of 417 mAh g^-1 at 5 A g^-1. Additionally, a SIHC device with the In─SnS_2-x@NG anode and the activated carbon cathode exhibits the high energy/power density of 278 Wh kg^-1/10.0 kW kg^-1 and long cycle lifespan, showing promising practical application. This work not only offers in-depth insights for designing SIHCs anodes, but also paves the way on practical applications for Na⁺ storage systems.