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A TiO2/carbon nanotubes (TiO2/CNTs) composite was synthesized by chemical vapor deposition method with in situ growth of CNTs using hydrothermally treated TiO2 as the starting material. The nanocomposite was characterized by powder x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Raman spectrum, and nitrogen adsorption/desorption isotherms and was investigated as an anode material for lithium-ion batteries. The underlying mechanism for the improvement was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. The in situ synthesized composite showed better electrochemical performance than the pristine TiO2. The in situ formed CNTs not only supply an efficient conductive network but also keep the structural stability of the TiO2 particles, leading to improved electrochemical performance.

I. INTRODUCTION

Titanium dioxide (TiO2) as anode material for Li-ion batteries has been found to be very alluring because of its open crystal structure and flexible electronic structure of titanium ion. Recently, nanostructured titania has obtained tremendous attention owing to its unique physicochemical properties.1–5 However, the electrochemical performance of TiO2 at high rates is still poor due to its intrinsic poor electron transport.6 To obtain a large reversible capacity and a good rate capability, various methods have been adopted by coupling TiO2 with other materials,7,8 such as coating carbon or graphene on TiO2 particles,9,10 loading Ag on ordered TiO2 nanotube,11 or by synthesizing TiO2 with various nanostructures.12,13 The carbon-based materials are considered as best choice as the matrices to form TiO2-based composites, among which carbon nanotubes (CNTs) have received special interest due to its facile fabrication and high electronic conductivity.14–16 In addition, CNTs can also contribute to the overall capacity of the composites. The improvement in electrochemical performance has been realized in some composites such as MnO2/CNTs,17,18 SnO2/CNTs,19 NiO/CNTs,20 and V2O5/CNTs.21,22 CNTs were also used as matrices to form composites with TiO2, leading to the improved electrochemical performance of TiO2.23,24 However, in the above work, the CNTs were introduced into TiO2 by an ex situ route, namely, the CNTs were presynthesized before adding to the TiO2.

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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.406 J. Mater. Res., Vol. 27, No. 2, Jan 28, 2012

http://journals.cambridge.org

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Iron or iron compounds are commonly used as catalysts in the growth of CNTs. In this work, we proposed a facile in situ chemical vapor deposition (CVD) route in N2/C2H2 to synthesize TiO2/CNTs nanocomposite using hydrothermally treated TiO2 and Fe(NO3)3 as the starting materials. This method is adopted for the first time for the in situ growth of TiO2/CNTs composite. The content of Fe(NO3)3 in the starting materials is well controlled so as to grow CNTs wit