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

Herein, heterogeneous bimetallic sulfides BiS/MoS nanoparticles anchored on MXene (TiCT) nanosheets (MXene@BiS/MoS) were prepared through a solvothermal process and subsequent chemical vapor deposition process. Benefiting from the heterogeneous structure between BiS and MoS and the high conductivity of the TiCT nanosheets, the Na diffusion barrier and charge transfer resistance of this electrode are effectively decreased. Simultaneously, the hierarchical architectures of BiS/MoS and TiCT 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@BiS/MoS 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.