Construction of heterogeneous interface structures of a cobalt/iron sulfide derived from a binary metal–organic framework for ultra-stable sodium-ion storage

Metal sulfides, as anode materials for sodium-ion batteries, have attracted much attention from the scientific community due to their high theoretical capacity. However, in practical applications, they still face key challenges such as significant volume expansion and dynamic hysteresis. This work innovatively adopts the metal–organic framework (MOF) template method, and a CoS/FeS@C composite electrode with heterogeneous interface structures is successfully prepared through a controllable vulcanization process. Characterization analysis indicates that the rich heterogeneous interfaces constructed within the material not only significantly enhance the efficiency of electron transmission but also effectively promote the diffusion kinetics of Na⁺ through the interfacial electric field effect, enabling the composite electrode to maintain a reversible capacity of 498.1 mAh g⁻¹ at a high current density of 10 A g⁻¹. It also demonstrates excellent rate capability at the same time. In addition, a complete battery of CoS/FeS@C//Na₃V₂(PO₄)₃ is successfully assembled, and it demonstrated impressive performance (300.2 mAh g⁻¹ at 0.5 A g⁻¹ after 100 cycles).