One-Dimensional Nanostructured Titanium Oxides: Preparation, Characterization And Electrochemical Properties As Lithium Insertion Hosts

Lithium ion batteries have rapidly taken over the markets of high performance rechargeable batteries for portable electronic devices, however, their applications in electric vehicles (EV) or hybrid electric vehicles (HEV) are limited by unsatisfied safety and high-rate capability. In general, the low lithium diffusivity in solid-state body is the limiting factor of rate capability. The nanostructured materials as lithium intercalation hosts may greatly reduce the lithium ion diffusion distance in solid-state body, thus can improve the rate capability of as prepared electrode. On the other hand, the construction of quick lithium ion diffusion channel in the solid-state body of electrode materials, apparently, can also dramatically improve the high-rate capabilities of as prepared electrode. The present study will focus on the preparation of a series of one-dimensional nanostructured titanium oxide and the electrochemical investigation of lithium intercalation properties.On materials preparation, we developed a facile and economic way to prepare H-titanate nanotubes/nanowires by sonochemical-hydrothermal processes from commercial TiO₂ and NaOH solution. By directly examining the micro-structural and morphological changes of intermediate products derived from the different stage, we provided an explicit formation mechanism for the initial reaction stage, i.e., the amorphous Na-titanate formation and the crystallization into layered Na-titanate, which provided an experimental evidence for"rolling"formation mechanism of H-titanate nanotubes form layered titanate.Anatase TiO₂ nanotubes were prepared from H-titanate nanotubes by controlled heat treatment. At the same time, C-doped TiO₂ nanotubes/nanowires were prepared by pyrolysis small organic molecule intercalated into H-titanate nanotubes in N2 stream. It is showed that the carbon has successfully incorporated into the TiO₂ lattice and the substitution is on nano-scale based on the detailed analyses by Raman scattering spectra and XPS. Furthermore, the doping contents and the level of band-gap narrowing are controllable by varying the calcining temperature.