• anodization;
  • arrays;
  • crystals;
  • iron oxide;
  • lithium ion batteries;
  • nanotubes

A comprehensive electrochemical study of crystalline iron oxide nanotube arrays grown in a highly ordered form with a high aspect ratio is presented. Nanotube arrays, thickness of ∼5 µm and tube diameter ∼100 nm, were synthesized through an optimized two-step anodization technique. The morphology and the chemical composition of the resulting materials were characterized by field-emission scanning electron microscopy, X-ray diffraction, Rietveld analysis and Raman spectroscopy. The electrochemical response was evaluated by cyclic voltammetry, galvanostatic charge/discharge cycling, and electrochemical impedance spectroscopy on cells with Li metal as the counter and reference electrodes. The results have shown an excellent electrochemical response in terms of charge/discharge capacity (2775 µAhcm−2 at 100 µAcm−2) and rate capability (150 µAhcm−2 at 800 µAcm−2). Cyclic performance was also exceptional as a high reversible capacity (350 µAhcm−2 at 200 µA cm−2) was retained for 100 charge/discharge cycles. Such an enhanced electrochemical response is attributed to the unidirectional morphology of the nanotubes with high aspect ratio, favoring fast Li+ ion diffusion and improved electron transport. Also, avoiding use of binder and conductive carbon agents contribute towards high energy density of the anode material.