A hierarchical nano-MoS2 flake/micro-MXene lamellar complex structure within a carbon coating for rapid sodium-ion storage

Abstract

A single two-dimensional material often struggles to satisfy all the performance requirements of electrode materials for sodium-ion batteries. However, constructing a hierarchical heterogeneous two-dimensional stacking structure can effectively combine the advantages of multiple materials and make up for the insufficiency of a single element. This work applied a pre-intercalation–sulphuration concept and liquid-phase coating modification by constructing a hierarchical nano-flake/micro-lamellar complex structure. In this composite material, MoS₂ nanosheets and V₂C MXene layers overlap and interact to prevent nanoparticle agglomeration and micron flakes collapse simultaneously. The MoS₂/MXene hierarchical structure is sandwiched between ultrathin and dense carbon layers to form a multifaceted conductive skeleton and a twofold protection mechanism. The coating reduces the electrolyte contact area and prevents the escape of polysulfide byproducts. Accordingly, the designed MSVC@C demonstrates superior Na⁺ storage capacities (612.4 mA h g⁻¹ at 0.5 A g⁻¹ after 600 cycles) and outstanding rate performance (304.42 mA h g⁻¹ at 10 A g⁻¹). Experimental results and theoretical calculations verify that the MoS₂ and V₂C heterostructure promotes the electrochemical performance owing to the better electronic conductivity and lower ion diffusion energy barrier. Moreover, this structure optimization strategy applies to various MXene guests (e.g., V₂C and Nb₂C) to prepare a variety of hierarchical nano–micro structures that are expected to be promising two-dimensional electrode materials for SIBs with application prospects in the future.