GISAXS and TOF-GISANS studies on surface and depth morphology of self-organized TiO₂nanotube arrays: model anode material in Li-ion batteries

Abstract

Self‐organized anodic titania (TiO2) nanotube arrays are an interesting model anode material for use in Li‐ion batteries owing to their excellent rate capability, their cycling stability and their enhanced safety compared to graphite. A composite material where carbothermally treated conductive TiO2 nanotubes are used as support for a thin silicon film has been shown to have the additional advantage of high lithium storage capacity. This article presents a detailed comparison of the structure, surface and bulk morphology of self‐organized conductive TiO2 nanotube arrays, with and without silicon coating, using a combination of X‐ray diffraction, X‐ray reflectivity, grazing‐incidence small‐angle X‐ray scattering (GISAXS) and time‐of‐flight grazing‐incidence small‐angle neutron scattering (TOF‐GISANS) techniques. X‐ray diffraction shows that the nanotubes crystallize in the anatase structure with a preferred (004) orientation. GISAXS and TOF‐GISANS are used to study the morphology of the nanotube arrays, delivering values for the inner nanotube radius and intertubular distances with high statistical relevance because of the large probed volume. The analyses reveal the distinct signatures of a prominent lateral correlation of the TiO2 nanotubes of ∼94 nm and a nanotube radius of ∼46 nm. The porosity averaged over the entire film using TOF‐GISANS is 46%. The inner nanotube radius is reduced to half (∼23 nm) through the silicon coating, but the prominent lateral structure is preserved. Such in‐depth morphological investigations over large sample volumes are useful towards development of more efficient battery electrode morphologies.

Recent Progress in Understanding Ion Storage in Self‐Organized Anodic TiO2 Nanotubes

“…The Li insertion characteristics of anodic TiO 2 NTs have been subject of numerous studies . The most relevant performance data to describe the Li storage capacities of self‐organized TiO 2 NTs are summarized in Figure .…”

Tailoring morphology, structure and photoluminescence properties of anodic TiO2nanotubes

“…Thus, one can determine that the SLD = 1.6 Â 10 À5 Å À2 . Typically, the SLD for TNT is around 3.07 Â 10 À5 Å À2 (Paul et al, 2015). This clearly indicates a porosity…”

“…In addition to the FESEM studies, further information regarding the degree of lateral ordering, grain sizes and porosity in the materials can be obtained from the GISAXS measurements (Paul et al, 2015;Ziegler et al, 2014). GISAXS is an experimental technique that combines both grazing incidence and scattering at low angles.…”

Recent progress in Li-ion batteries with TiO2 nanotube anodes grown by electrochemical anodization

“…The reason why the electrochemical performance decreases with the increase in tube length is generally divided into two aspects: on the one hand, the surface morphology can change with the rise in tube length and the long tube is usually covered with a layer of nanograss [24,26]. On the other hand, when NTs are grown in an organic electrolyte, an inner carbon-rich layer is formed in NT which will reduce the efficiency of lithium insertion [28,69].…”