Hetero-structural and hetero-interfacial engineering of MXene@Bi2S3/Mo7S8 hybrid for advanced sodium/potassium-ion batteries.

ABSTRACT

Herein, heterogeneous bimetallic sulfides Bi2S3/Mo7S8 nanoparticles anchored on MXene (Ti3C2Tx) nanosheets (MXene@Bi2S3/Mo7S8) were prepared through a solvothermal process and subsequent chemical vapor deposition process. Benefiting from the heterogeneous structure between Bi2S3 and Mo7S8 and the high conductivity of the Ti3C2Tx nanosheets, the Na+ diffusion barrier and charge transfer resistance of this electrode are effectively decreased. Simultaneously, the hierarchical architectures of Bi2S3/Mo7S8 and Ti3C2Tx not only effectively inhibit the re-stacking of MXene and the agglomeration of bimetallic sulfides nanoparticles, but also dramatically relieve the volume expansion during the periodic charge/discharge processes. As a result, the MXene@Bi2S3/Mo7S8 heterostructure demonstrated remarkable rate capability (474.9 mAh/g at 5.0 A/g) and outstanding cycling stability (427.3 mAh/g after 1400 cycles at 1.0 A/g) for sodium ion battery. The Na+ storage mechanism and the multiple-step phase transition in the heterostructures are further clarified by the ex-situ XRD and XPS characterizations. This study paves a new way to design and exploit conversion/alloying type anodes of sodium ion batteries with hierarchical heterogeneous architecture and high-performance electrochemical properties.