Improving the Electrochemical Properties of Self-Organized Titanium Dioxide Nanotubes in Lithium Batteries by Surface Polyacrylonitrile Electropolymerization

The surface of the amorphous TiO2 nanotubes is critical to achieve high capacity, cycling stability and high rate performance. In order to improve the stability of nanotubular titanium dioxide electrodes in lithium batteries, polyacrylonitrile (PAN) has been deposited by electropolymerization. Self-organized TiO2 nanotubes were prepared by titanium anodization with different aspect ratios. After electropolymerization, electron microscopy, composition mapping and XPS data confirmed that electrododeposited PAN covered the complete surface of open ends of the nanotubes, exclusively. The resulting electrode material was tested in lithium cells, and showed reversible areal capacities in the order of 0.5 mAhcm(-2) and good cycling behavior and within a wide potential window (0.0-3.0 V). The improvement of the electrochemistry is more evident for the lower aspect ratio nt-TiO2, with capacity values normalized by the nanotubes length of around 0.25 mAh cm(-2) mu m(-1) at slow rate. An areal capacity of 0.26 mAh cm(-2) is delivered at 75C rate. The ion-conducting PAN layer ensures lithium ion access to the nanotubes, protects the open end surface from undesirable reactions with the electrolyte and provides enhanced mechanical stability to the electrode and lower charge transfer resistance. (C) 2013 The Electrochemical Society.