Electron-RicInterfacial layer mediates synergistic enhancement of kinetics and long-term stability in Sb/carbon composite anodes for sodium-ion batteries.

The strategic design of electrode materials is essential for advancing sodium-ion batteries (SIBs). In this study, an electron-rich interfacial layer formed between antimony (Sb) and carbon (C) is introduced as a key mediator to synergistically enhance both sodium storage kinetics and long-term stability. Density functional theory (DFT) calculations reveal a strong Na+ adsorption energy of -2.19 eV at the SbC interface, more negative than that on pure carbon (-0.81 eV), thermodynamically favoring Sb as the preferential sodium reservoir. This mechanism is directly visualized by In situ Raman spectroscopy, which shows that Sb alloying precedes Na+ storage in the carbon matrix, thereby suppressing metallic plating. The engineered interface, achieved by confining about 10 nm Sb nanoparticles within a conductive carbon host, concurrently accelerates charge transfer (more than 50% lower Rct) and, together with a bimodal porous structure, accommodates volume expansion. The optimized Sb/C composite delivers a capacity approximately 60% higher capacity than that of pure carbon and exhibits outstanding cycling stability. Notably, the Sb/Carbon electrode remains its structural integrity after 1000 charge-discharge cycles at a current density of 1000 mA g-1 and maintains a specific capacity of 170 mAh g-1 even after 2000 cycles. In contrast, the pure carbon electrode fails after 1100 cycles. This work highlights the crucial role of interfacial engineering in alloy-based anode materials and offers a viable strategy for developing high-performance and long-life SIBs.