Nanowire-templated formation of SnO2/carbon nanotubes with enhanced lithium storage properties

Abstract

In this work, we have designed and synthesized SnO₂ nanotubes wrapped by a porous carbon layer via a multistep method. Single-crystalline MnO_x nanowires are employed as the template. SnO₂ is grown on MnO_x nanowires by a simple hydrothermal method to generate MnO_x/SnO₂ core–shell nanocables, followed by further coating with a layer of polydopamine. After carbonization of polydopamine and selective removal of MnO_x nanowires, carbon coated SnO₂ nanotubes are obtained. This structure combines several advantages. First, the internal empty space of the tubular structure can buffer the huge volume variation during lithium insertion–extraction processes properly, leading to improved cycling performance. Second, the nanosized SnO₂ subunits and porous carbon coating not only shorten the distance for lithium ion diffusion but also offer large electrode–electrolyte contact area for fast Li⁺ crossing the interface, thus enabling improved rate capability. Third, the flexible carbon coating is closely covered onto the SnO₂ nanocrystals, which could facilitate the electronic transport and also significantly mitigate the pulverization. As a result, the as-synthesized SnO₂/C-NT nanocomposites exhibit a high reversible capacity of 596 mA h g⁻¹ after 200 cycles, as well as an outstanding rate capability.