Synergistic engineering of selenium vacancies and heterojunctions in MoSe2/Sb2Se3/C for fast and ultra-stable sodium-ion storage

Metal selenides are promising anode materials for sodium-ion batteries due to their high theoretical capacity, but their practical application is hindered by sluggish reaction kinetics and structural instability. Herein, a MoSe 2 /Sb 2 Se 3 heterostructure embedded in a carbon matrix with abundant heterojunctions and selenium vacancies is synthesized via solid-state selenization using polyvinylpyrrolidone as both carbon source and nucleation inducer. The heterojunctions induce lattice distortion and generate internal electric fields to accelerate charge transfer, while selenium vacancies enhance Na + adsorption and create additional active sites. Density functional theory calculations reveal a reduced bandgap (1.25 eV) and optimized electronic structure, synergistically boosting conductivity and ion diffusion kinetics. Benefiting from these features, the MoSe 2 /Sb 2 Se 3 /C anode delivers a reversible capacity of 405.7 mAh g −1 at 0.2 A g −1 after 100 cycles and maintains 261.7 mAh g −1 at 5 A g −1 over 3000 cycles, outperforming most reported sodium-ion anodes. In situ XRD and TEM analyses confirm reversible phase evolution (MoSe 2 /Sb 2 Se 3 ↔ Na 3 Sb/Mo) and robust structural stability. This study demonstrates a synergistic defect-interface engineering strategy to advance heterostructured materials for durable energy storage.