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

Inorganic 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 vapor-phase-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 post-processing procedures. Furthermore, the in-situ heating transmission electron microscopy (TEM) technique is used to observe the dynamic formation process of TiO2−x tubes, indicating that the removal process of the Sb2S3 templates first experienced the Rayleigh instability, then vapor-phase-etching process. When used as an anode for sodium ion batteries, the TiO2−x tube exhibits excellent rate performance of 134.6 mA h g−1 at the high current density of 10 A g−1 and 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.