Bi2S3 spheres coated with MOF-derived Co9S8 and N-doped carbon composite layer for half/full sodium-ion batteries with superior performance

Bismuth sulfide (Bi2S3) has attracted particular interest as a potential anode material for sodium-ion batteries (SIBs). However, the low electrical conductivity and dramatic volumetric change greatly restrict its practical applications. In view of the apparent structural and compositional advantages of metal-organic frameworks (MOFs) derived carbon-based composite, herein, as a proof of concept, Bi2S3 spheres coated with the MOF-derived Co9S8 and N-doped carbon composite layer (Bi2S3@Co9S8/NC composite spheres) have been rational designed and synthesized. As expected, the core-shell Bi2S3@Co9S8/NC composite spheres exhibit remarkable electrochemical performance in terms of high reversible capacity (597 mAh g−1 after 100 cycles at 0.1 A g−1), good rate capability (341 mAh g−1 at 8 A g−1) and long-term cycling stability (458 mAh g−1 after 1000 cycles at 1 A g−1) when investigated as anode materials for SIBs. Electrochemical analyses further reveal the favorable reaction kinetics in the Bi2S3@Co9S8/NC composite spheres. In addition, the possible sodium storage mechanism has been studied by ex-situ X-ray diffraction technique. More importantly, a sodium-ion full cell based on Na3V2(PO4)3/rGO as cathode and Bi2S3@Co9S8/NC as anode is also fabricated, suggesting their potential for practical applications. It is anticipated that the present work could be extended to construct other advanced electrode materials using MOFs-derived carbon-based composites as surface coating materials for various energy storage-related applications.