High Lithium Storage in Mixed Crystallographic Phase Nanotubes of Titania and Carbon-Titania

Abstract

Morphology and electrochemical performance of mixed crystallographic phase titania nanotubes for prospective application as anode in rechargeable lithium ion batteries are discussed. Hydrothermally grown nanotubes of titania (TiO2) and carbon-titania (C-TiO2) comprise a mixture of both anatase and TiO2 (B) crystallographic phases. The first cycle capacity (at current rate = 10 mAg−1) for bare TiO2 nanotubes was 355 mAhg−1 (approximately 1.06 Li), which is higher than both the theoretical capacity (335 mAhg−1) and the reported values for pure anatase and TiO2 (B) nanotubes. Higher capacity is attributed to a combination of the presence of mixed crystallographic phases of titania and trivial size effects. The surface area of bare TiO2 nanotubes was very high at 340 m2 g−1. C-TiO2 nanotubes showed a slightly lower first-cycle specific capacity of 307 mAhg−1, but the irreversible capacity loss in the first cycle decreased by half compared to bare TiO2 nanotubes. The C-TiO2 nanotubes also showed a better rate capability, that is, higher capacities compared to bare TiO2 nanotubes in the current range 0.1−2 Ag−1. Enhanced rate capability in the case of C-TiO2 is attributed to the efficient percolation of electrons as well as to the decrease in the anatase phase.