TiO2 nanotube arrays annealed in N2 for efficient lithium-ion intercalation

Anatase titania nanotube arrays were fabricated by means of anodization and annealed at 300, 400, and 500 degrees C in N-2. Lithium-ion intercalation measurements revealed that annealing in nitrogen resulted in much enhanced lithium-ion insertion capacity and improved cyclic stability. TiO2 nanotube arrays annealed at 300 degrees C exhibited the best lithium-ion intercalation property with an initial high discharge capacity up to 240 mA . h/g at a high current density of 320 mA/g. The excellent discharge capacity at a high charge/discharge rate could be attributed to the large surface area of the nanotube arrays and a short facile diffusion path for lithium-ion intercalation as well as improved electrical conductivity. As the annealing temperature increased, the discharge capacity decreased, but the cyclic stability improved; 400 degrees C annealed TiO2 nanotube arrays possessed an initial discharge capacity of 163 mA.h/g and retained 145 mA.h/g at the 50th cycle. The relationship between the annealing conditions, microstructure, and lithium-ion intercalation properties of TiO2 nanotube arrays was discussed.