Synergistic selenium substitution and interfacial confinement in indium-based chalcogenide anodes enabling rapid and stable sodium storage

Indium sulfide (In₂S₃), which has garnered sufficient attention as a highly promising anode host for sodium-ion batteries (SIBs) owing to its considerable theoretical capacity and widespread availability, is nevertheless characterized by sluggish reaction kinetics, inadequate electronic conductivity, and severe volumetric expansion, yielding inferior rate capability and a short cyclic lifespan. Atomic-scale interface and anion-defect engineering, via introducing a foreign anion ligand combined with conductive carbon matrix to fabricate carbon-confined dual-anion indium-based chalcogenide, offers a powerful strategy to tune their physicochemical characteristics. Herein, we report a precisely designed and engineered Se-introduced hollow In₂S₃ microspindles confined within a N, S-codoped carbon matrix (In₂S_3‒xSe_x@NSC HMS) via an asynchronous sulfidation and selenidation method using MIL-68-In precursor as the template. Systematic electrochemical investigation reveals that the synergistic implantation of Se introduction and nanospace confinement design endows the In₂S₃ host with multiple favourable characteristics for sodium storage, including improved reaction reversibility, high electrical conductivity, robust structural durability and enriched vacancy defects, thereby facilitating rapid Na⁺ transport and endowing remarkable electrochemical characteristics. Leveraging these advantages, In₂S_3‒xSe_x@NSC HMS features exceptional rate capability and prolonged cycling stability exceeding 8000 cycles at 20.0 A·g^–1. Furthermore, comprehensive kinetic analyses coupled with ex-situ characterizations afford deep insight into the fundamental origins of ion-transport kinetics and fully elucidate the phase-transformation mechanism of In₂S_3‒xSe_x. Notably, In₂S_3‒xSe_x@NSC HMS, when employed in progressive SIBs full-cell configuration, yields satisfactory performance over 300 cycles at 5.0 A·g^–1, providing preliminary verification of the practical feasibility of In₂S_3–xSe_x@NSC HMS anode for high-rate SIBs applications.