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.