Amorphous TiO2(a-TiO2) thin films were conformally coated onto the surface of hydroxyl functionalized multi-walled carbon nanotubes (CNTs) using atomic layer deposition (ALD). The electrochemical characteristics of the a-TiO2/CNT nanocomposites were then determined using cyclic voltammetry and galvanostatic charge/discharge curves. The ultrathin TiO2ALD films displayed high specific capacity and high rate capability. The specific capacities of the a-TiO2/CNT nanocomposites after 50 and 100 TiO2ALD cycles at 100 mA/g were 220 mAh/g and 240 mAh/g, respectively. For CNTs coated with 100 TiO2ALD cycles, 88% of the capacity at 100 mA/g could be maintained at 1 A/g. When the voltage window for the a-TiO2/CNT nanocomposites was extended down to 0.5 V versus Li/Li+, the CNTs coated with 50 and 100 TiO2ALD cycles exhibited specific capacities at 100 mA/g of 275 mAh/g and 312 mAh/g, respectively. These high capacities are higher than the bulk theoretical values and are attributed to additional interfacial charge storage resulting from the high surface area of the a-TiO2/CNT nanocomposites. Free-standing TiO2-CNT electrodes were also fabricated and displayed excellent capacity and rate capability. These results demonstrate that TiO2ALD on high surface area CNT substrates can provide high power and high capacity anodes for lithium ion batteries.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry