Hierarchically stacked reduced graphene oxide/carbon nanotubes for as high performance anode for sodium-ion batteries

Sodium has attracted an increasing amount of attention as an alternative element to lithium for energy storage due to its low cost and wide distribution, although the intercalation problem for sodium ions in conventional anode materials, due to their larger ionic size, still has to be overcome in order to utilize this element. Herein, we report a carbon-based hybrid material that is composed of stacked reduced graphene oxide/carbon nanotubes (rGO/CNTs) with a hierarchical and open structure to accommodate Na ions, which was fabricated by a liquid-phase oxidative exfoliation and subsequent reduction. This rGO/CNTs hybrid material features a hierarchical nanostructure with rGO nanosheets homogeneously spaced by monodisperse CNTs. The increased interlayer space between individual rGO nanosheets, which resulted from the inserted CNTs, is beneficial for highly efficient and reversible Na ion intercalation, leading to a high and stable capacity of 295 mAhg −1 at 50 mAg −1 for 200 cycles