Characterization and Electrochemical Properties of Nanostructured Zr-Doped Anatase TiO2 Tubes Synthesized by Sol-Gel Template Route

A series of nanostructured Zr-doped anatase TiO2 tubes with the Zr/Ti molar ratio of 0.01, 0.02, 0.03, and 0.09 were prepared by a sol-gel technology on a carbon fiber template. The electrochemical performance of Zr-doped anatase TiO2 as anodes for rechargeable lithium batteries was investigated and compared with undoped titania. Tests represented that after 35-fold charge/discharge cycling at C/10 the reversible capacity of Zr-doped titania (Zr/Ti = 0.03) reaches 135 mA h g−1, while the capacity of undoped titania (Zr/Ti = 0) yielded only 50 mA h g−1. Based on the results of the physicochemical investigation, three reasons of improving electrochemical performance of Zr-doped titania were suggested. According to the scanning electron microscopy and transmission electron microscopy, Zr4+ doping induces a decrease in nanoparticle size, which facilitates the Li+ diffusion. The Raman investigations show the more open structure of Zr-doped TiO2 as compared to undoped titania due to changing of the unit cell parameters, that significantly affects on the reversibility of the insertion/extraction process. The electrochemical impedance spectroscopy results indicate that substitution of Zr4+ for Ti4+ into anatase TiO2 has favorable effects on the conductivity.