As-grown vertically aligned amorphous TiO2 nanotube arrays as high-rate Li-based micro-battery anodes with improved long-term performance

• Amorphous TiO2 nanotube (NT) arrays are fabricated by fast and facile anodic oxidation.
• Near-theoretical initial specific capacity and remarkable rate capability.
• Very long-term cycling stability (>2000 cycles) at a very high C-rate.
• High surface area and improved interfacial characteristics for fast diffusion kinetics.
• NTs show promising prospects in storage devices conceived for high power applications.

Vertically oriented arrays of high surface area TiO2 nanotubes (NTs) are fabricated by the fast and facile anodic oxidation of a titanium foil. The formation of well-defined one-dimensional nanotubular carpets is assessed by means of morphological Field Emission Scanning Electron Microscopy characterisation, while X-ray diffraction analysis and Transmission Electron Microscopy imaging confirm the amorphous nature of the samples. The electrochemical response evaluated in lab-scale lithium cells is highly satisfying with near-theoretical initial specific capacity and remarkable rate capability, noteworthy in the absence of binders and conductive agents, which would affect the overall energy density. A specific capacity exceeding 200 mAh g−1 is observed at very high 24 C and approx. 80 mAh g−1 are retained even at very high 96 C rate, thus accounting for the promising prospects in storage devices conceived for high power applications. Moreover, the NTs can perform with good cycling stability and capacity retention approaching 50% of the initial value after very long-term operation along with improved durability (> 2000 cycles).

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