Hierarchical nanotubes assembled from MoS₂-carbon monolayer sandwiched superstructure nanosheets for high-performance sodium ion batteries

Interface engineering on 2D layered nanomaterials plays pivotal roles in achieving novel properties and superior device performance. In this work, hierarchical nanotubes consisting of 2D monolayer MoS₂ and carbon (MoS₂:C) interoverlapped superstructure nanosheets have been synthesized, in which the MoS₂ and carbon layers are alternately sandwiched. The hierarchical architectures assembled from the MoS₂:C superstructures are beneficial for: (i) providing substantially expanded (002) interlayer spacing (0.98 nm) of 2H-MoS₂ which facilitates fast Na⁺ insertion/extraction reaction kinetics, (ii) improving electrical conductivity of MoS₂ by carbon monolayer insertion with ideal heterointerface contact, (iii) preventing aggregation of MoS₂ nanosheets, and (iv) accommodating volume change upon sodiation/desodiation. The superstructure nanotubes are demonstrated as a robust anode material for sodium storage with superior electrochemical performance. They deliver a high rate-capability and maintain discharge capacities of 295 and 187 mAh g^-1 at high current densities of 10.0 and 20.0 A g^-1, respectively. Furthermore, they show durable cycling life (capacity retention of 101.3%, 108.2% and 107.8% after 200 cycles at current densities of 0.2, 0.5 and 1.0 A g^-1, respectively, in comparison to those of the 2^nd cycles), and an initial Coulombic efficiency as high as 84%. The MoS₂:C superstructure nanotubes perform among the best of current MoS₂-based electrode materials.