A general synthesis of inorganic nanotubes as high-rate anode materials of sodium ion batteries

Ino rganic tubular materials have an exceptionally wide range of applications,yet developing a simple and universal method to controllably synthesize them remains challenging.In this work,we report a vaporphase-etching hard-template method that can directly fabricate tubes on various thermally stable oxide and sulfide materials.This synthesis method features the introduction of a vapor-phase-etching process to greatly simplify the steps involved in preparing tubular materials and avoids complicated postprocessing procedures.Furthermore,the in-situ heating transmission electron microscopy(TEM) technique is used to observe the dynamic formation process of TiO2-xtubes,indicating that the removal process of the Sb2S3templates first experienced the Rayleigh instability,then vapor-phase-etching process.When used as an anode for sodium ion batteries,the TiO2-xtube exhibits excellent rate performance of134.6 mA h g-1at the high current density of 10 A g-1and long-term cycling over 7000 cycles.Moreover,the full cell demonstrates excellent cycling performance with capacity retention of 98% after 1000 cycles,indicating that it is a promising anode material for batteries.This method can be expanded to the design and synthesis of other thermally-stable tubular materials such as ZnS,MoS2,and SiO2.