Asymmetric bond modulation at electronically coupled Bi/SnS heterointerfaces enables high-rate and durable sodium-ion storage.

Abstract

The conversion- and alloying-type materials are promising anode candidates of sodium-ion batteries (SIBs) due to their high theoretical capacities. However, they still suffer from trade-off between structural stability and reaction kinetics, which limits the practical applications of SIBs. Herein, we report an efficient strategy to break such trade-off by asymmetric bond modulation. A Bi/SnS heterostructure encapsulated in N,S co-doped carbon frameworks (Bi/SnS@NSC) is designed and constructed. Metallic screening predominantly localizes the electronic perturbation on the SnS side. Density functional theory (DFT) calculations and crystal orbital Hamilton population (COHP) analyses reveal that the interfacial charge polarization weakens SnS bonds, maintains stable BiBi interactions, and effectively reduces the diffusion barriers of Na+. In situ X-ray diffraction (XRD) characterization further confirms highly reversible multistep phase evolution of both components during sodiation/desodiation. As a result, Bi/SnS@NSC delivers a high capacity of 358.9 mAh g-1 at 40 A g-1, and maintains 310.6 mAh g-1 after 2500 cycles at 20 A g-1. This work provides an effective way to achieve a synergistic enhancement in the electrochemical performance and stability of SIBs by modulating the metal-semiconductor structure to control interfacial charge distribution.

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