pubs.acs.org/cm r XXXX American Chemical Society Chem. Mater. XXXX, XXX, 000–000 A DOI:10.1021/cm1020977 Niobium Doped TiO 2 with Mesoporosity and Its Application for Lithium Insertion Yude Wang,* ,† Bernd M. Smarsly, ‡ and Igor Djerdj § † Department of Materials Science and Engineering, Yunnan University, 650091 Kunming, People’s Republic of China, ‡ Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, and § Division of Materials Physics, Ru{ er Bo skovi c Institute, Bijeni  cka 54, 10000 Zagreb, Croatia Received July 28, 2010. Revised Manuscript Received November 8, 2010 The synthesis as well as the electrochemical properties study of niobium-doped TiO 2 (NTO) with mesoporosity and high surface area is presented. The mesoporous NTO was prepared using a novel poly(ethylene-co-butylene)-b-poly(ethylene oxide) amphiphilic diblock copolymer as a template and simple titanium reagents (TiCl 4 and Nb(OC 2 H 5 ) 5 ) by a polymer-assisted sol-gel process. The samples were characterized by differential scanning calorimetry and thermogravimetric analysis (DSC-TGA), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, scan- ning electron microscopy (SEM), transmission electron microscopy (including high-resolution imaging-HRTEM), and the Brunauer-Emmett-Teller (BET). All samples are highly crystalline and have pore-solid architectures after removal of the polymer template by calcination. The resulting mesoporous NTO shows a high porosity of 46% and a high surface area of 128 m 2 /g, respectively. The as-prepared samples were used as positive electrode materials for lithium-ion battery, whose charge-discharge properties, cyclic voltammetry, and cycle performance were examined and revealed very good properties. A highly stable capacity of 160 mA h g -1 was found after 100 cycles. Introduction Titanium dioxide (TiO 2 ) as an important, wide band gap semiconductor has been intensively studied as a key material for fundamental research and technological applications in the fields of semiconductors, optical devices, 1 photovoltaic cells, 2 photocatalysis, 3 gas sensing, 4 and electrochemical storage. 5 TiO 2 is a typical Li-ion inter- calation compound with a volume change <4% in the reaction described by eq 1: TiO 2 þ xLi þ þ xe - TLi x TiO 2 ð0exe1Þ ð1Þ Particularly, nanostructured TiO 2 for Li insertion has received much attention because of its low-voltage insertion host for Li and the fast Li insertion/extraction host. 6 These characteristics make it a potential anode material for high-power lithium-ion batteries, avoiding the neces- sity of a passivation layer at the contact to the liquid electrolyte. 7 However, TiO 2 has low electric conductivity that limits its use for high power output. 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