TiO2 nanotube arrays annealed in CO exhibiting high performance for lithium ion intercalation

Anatase titania nanotube arrays were fabricated by means of anodization of Ti foil and annealed at 400 ◦C in respective CO and N2 gases for 3 h. Electrochemical impendence spectroscopy study showed that CO annealed arrays possessed a noticeably lower charge-transfer resistance as compared with arrays annealed in N2 gas under otherwise the same conditions. TiO2 nanotube arrays annealed in CO possessed much improved lithium ion intercalation capacity and rate capability than N2 annealed samples. At a high charge/discharge current density of 320 mA g−1, the initial discharge capacity in CO annealed arrays was found to be as high as 223 mAh g−1, 30% higher than N2 annealed arrays, ∼164 mAh g−1. After 50 charge/discharge cycles, the discharge capacity in CO annealed arrays remained at ∼179 mAh g−1. The improved intercalation capacity and rate capability could be attributed to the presence of surface defects like Ti–C species and Ti3+ groups with oxygen vacancies, which not only improved the charge-transfer conductivity of the arrays but also possibly promoted phase transition. © 2009 Elsevier Ltd. All rights reserved.