Morphology engineering and interface electron modulation of crystalline-amorphous CoS-MoS heterostructure with N-doped carbon for fast and stable sodium-ion storage.

Rational design and synthesis of robust and reversible anode materials are critical for sodium-ion storage; however, further development remains hindered by sluggish kinetics, volume expansion, and unsatisfactory cycling stability. To address these issues, precise structural optimization and interface modulation are highly desirable. Herein, a hierarchical hollow crystalline-amorphous CoS-MoS heterojunction coated with N-doped carbon (CoS-MoS@NC) is designed and prepared via facile reduction/oxidation reactions, polydopamine coating, and sulfurization processes. The hierarchical hollow structure along with N-doped carbon provides internal buffering space, relieves volume variations, and enhances the conductivity. Moreover, crystalline-amorphous CoS-MoS heterostructure offers the abundant active sites and induces an interfacial electric field via electron redistribution, thus enhancing Na adsorption and diffusion abilities and overall electrochemical performances as evidenced by experimental and theoretical results. Benefiting from these structural and interfacial advantages, CoS-MoS@NC exhibits superior rate performance (362.3 mAh g at 10.0 A g) and excellent cycling stability (511.1 mAh g at 2.0 A g after 1000 cycles). In addition, CoS-MoS@NC//NaV(PO) full cell evinces impressive performance and practical application potential. Furthermore, various ex-situ characterizations verify a reversible intercalation-conversion storage mechanism throughout the sodiation/desodiation processes. The strategic integration of rational morphology engineering and heterostructure construction in this work provides valuable insights into the development of advanced anodes for efficient and durable energy storage systems.