Preparation Of Three - Dimensional Ordered TiO 2 Sub - Nanocomposite Composites And Their Lithium Performance

TiO2 is well known as one kind of semiconductor functional ceramic materials. As an anode active material for lithium ion batteries, TiO2 possesses many advantages such as low toxicity, high safety and structural stability, and thus it is a promising anode candidate material. In recent years, the development of micro-electro mechanical system (MEMS) and micro circuit have promoted the development of three-dimensional (3D) micro lithium ion battery, so the traditional electrode structure may not meet the double demands of small space and high capacity any more. Three-dimensional (3D) ordered TiO2 nanotubes array via anodization with large surface area was expected to shorten the Li+diffusion paths and meet the requirements as mentioned above. However, the poor electronic conductivity of TiO2 limited the wide application in lithium ion battery. For this purpose, the doping modification of TiO2 nanotube arrays with good conductive agents such as Ag nanoparticles and graphene nanosheets can be carried out as the following:(1) 3D ordered anatase TiO2 nanotube arrays were firstly modified with Ag nanoparticles via facile one-step electrodeposition. The microstructure and morphology of the as-prepared composite Ag/TiO2 nanotube arrays were studied in terms of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Furthermore, the electrochemical performances of Ag/TiO2 nanotube arrays were investigated in terms of galvanostatic charge/discharge, cyclic voltammograms (CV) and alternative current (AC) impedance spectroscope. The results showed that composite Ag/TiO2 nanotube electrode delivered an initial discharge capacity of about 177 mAh/g, higher than 130 mAh/g of the bare anatase TiO2 nanotubes electrode. Meanwhile, Ag/TiO2 nanotube electrode displayed better cycle stabilities and rate performances than bare TiO2 nanotubes electrode. Modified performances of composite Ag/TiO2 nanotubes electrode were not only benefit from increased conductivity but also from Li-storage activity of Ag nanoparticles.(2) Binder-free combination of graphene nanosheets with oriented TiO2 nanotube arrays was designed and achieved via one-step facile electrodeposition. The structure and morphology of the as-prepared composite graphene nanosheets/TiO2 nanotube arrays were studied in terms of SEM, FESEM, EDX, TEM, Raman and FTIR. Furthermore, the corresponding electrochemical performances were evaluated in terms of galvanostatic charge/discharge and AC impedance. The results showed that composite graphene nanosheets/TiO2 nanotube electrode delivered an initial discharge capacity of 499 mAh/g, higher than 277 mAh/g of the bare amorphous TiO2 nanotubes electrode. Meanwhile, the composite graphene nanosheets/TiO2 nanotube electrode displayed better cyclic stabilities and Li+diffusion coefficient than the bare noncrystal TiO2 nanotubes electrode. The modified performances of the composite graphene nanosheets/TiO2 nanotubes electrode were not only benefit from increased conductivity and Li-storage activity of graphene, but also the from synergistic effect between graphene nanosheets and 3D ordered TiO2 nanotube arrays.