Fabrication of Cu-coated TiO2 nanotubes and enhanced electrochemical performance of lithium ion batteries

• The Cu-coated TiO2 nanotube arrays were firstly fabricated and reported as lithium ion batteries anode.
• The Cu-coated TiO2 nanotubes anode increased the specific capacity significantly.
• The Cu-coated TiO2 nanotube anode showed improved rate capability and cycleability.

Parent TiO2 nanotubes were synthesized through an anodizing process and Cu coating was applied on these nanotubes by electroplating to take advantage of their improved Li ion intercalation properties. The field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) results demonstrated that the products consisted of impurity-free, anatase-phase TiO2 nanotubes uniformly coated with a Cu layer. The charge-transfer resistance of the Cu-coated TiO2 nanotubes decreased by more than 39% compared to that of the parent TiO2 nanotubes. The first reversible capacity of the Cu-coated TiO2 nanotubes was 226.5 mA h g−1 at a high current density of 200 mA g−1. After the 300th cycle, the discharge capacity of the Cu-coated TiO2 nanotubes decreased by 18.1%, compared to the initial discharge capacity, to 185.6 mA h g−1. These results represent 23.6% and 35.3% improvements, respectively, over the parent TiO2 nanotubes. The enhanced electrical performances of the Cu-coated TiO2 nanotubes, ascribed to the increase in electrical conductivity, led to improvements in the reversible capacity and cycle stability of the anode materials. It is speculated that Cu-coated TiO2 nanotubes are a promising anode material for Li ion batteries.