Growth of rutile TiO2 on the convex surface of nanocylinders: from nanoneedles to nanorods and their electrochemical propertiesElectronic supplementary information (ESI) available: FESEM image of carbonized electrospinning-derived carbon nanofibers. FESEM images of TiO2 nanostructures grown on carbon nanofibers using titanium(iv) isopropoxide and titanium(iv) butoxide as precursors. TGA curves of the samples from 24 h hydrothermal growth at 90 °C, 130 °C and 180 °C. The cycling capacity of pure

• Main Authors: Kong, Junhua, Wei, Yuefan, Zhao, Chenyang, Toh, Meng Yew, Yee, Wu Aik, Zhou, Dan, Phua, Si Lei, Dong, Yuliang, Lu, Xuehong
• Format: Journal Article
• Language: English
• Published: 27.03.2014
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c3nr04308h

In this work, bundles of rutile TiO 2 nanoneedles/nanorods are hydrothermally grown on carbon nanofibers (CNFs), forming free-standing mats consisting of three dimensional hierarchical nanostructures (TiO 2 -on-CNFs). Morphologies and structures of the TiO 2 -on-CNFs are studied using a field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) and thermogravimetric analyzer (TGA). Their electrochemical properties as electrodes in lithium ion batteries (LIBs) are investigated and correlated with the morphologies and structures. It is shown that the lateral size of the TiO 2 nanoneedles/nanorods ranges from a few nanometers to tens of nanometers, and increases with the hydrothermal temperature. Small interspaces are observed between individual nanoneedles/nanorods, which are due to the diverging arrangement of nanoneedles/nanorods induced by growing on the convex surface of nanocylinders. It is found that the growth process can be divided into two stages: initial growth on the CNF surface and further growth upon re-nucleation on the TiO 2 bundles formed in the initial growth stage. In order to achieve good electrochemical performance in LIBs, the size of the TiO 2 nanostructures needs to be small enough to ensure complete alloying and fast charge transport, while the further growth stage has to be avoided to realize direct attachment of TiO 2 nanostructures on the CNFs, facilitating electron transport. The sample obtained after hydrothermal treatment at 130 °C for 2 h (TiO 2 -130-2) shows the above features and hence exhibits the best cyclability and rate capacity among all samples; the cyclability and rate capacity of TiO 2 -130-2 are also superior to those of other rutile TiO 2 -based LIB electrodes. Hydrothermal growth of diverging rutile TiO 2 nanoneedles/nanorods from a convex surface is investigated. With optimized TiO 2 content as well as size and morphology tailoring, TiO 2 -on-CNFs exhibit excellent cyclability and rate capacity.