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

Anatase titania nanotube arrayswere fabricated by means of anodization of Ti foil and annealed at 400 degrees C in respective CO and N-2 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 N-2 gas under otherwise the same conditions. TiO2 nanotube arrays annealed in CO possessed much improved lithium ion intercalation capacity and rate capability than N-2 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 N-2 annealed arrays, similar to 164 mAh g(-1). After 50 charge/discharge cycles, the discharge capacity in CO annealed arrays remained at similar to 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. (C) 2009 Elsevier Ltd. All rights reserved.