Preperation Of Carbon Coated Mixed Crystal Type Titanium Dioxide Nanotubes And Its Study As Anode Material Of Lithium Ion Batteries

In recent years, as environmental problems gradually got attention of the public, great importance has been attached to lithium ion batteries(LIBs), which is a kind of clean car power source. On the same time, electronic products such as smart phones, their screens are becoming larger and larger, so that the speed of power consumption of their batteries is becoming faster and faster. As a result,energe density, safty, cycling capacity and rate performance have become the keys to mesuring the quality of LIBs.With the characteristics of cheap and green, titanium dioxide (TiO2) is suitable to be the anode of LIBs. Nanosized TiO2 has the advantages of high theoretical capacity, good safty performance, high energe density, high charge and discharge platform, fast charge and discharge speed, so it is a very promising anode material. Especially, one-dimensional(1D) nanosized TiO2 can meet the requirements of fast charge and discharge for electric vehicles and digital products with very large current density due to its unique lithium ion transport channel on two directions, Moreover, the ID nanosized TiO2 materials are often prepared with hydrothermal method, which is easy to implement industrial production.In this research, one dimensional nanosized TiO2 is prepared by hydrothermal method, the affects of hydrothermal temperature and sintering temperature on its morphology, crytal type and electrochemical properties are discussed. Two kinds of ID TiO2 nanotubes(TiO2-400 and TiO2500) with a mixed crystal type of TiO2 anatase and TiO2-B are obtained, which have high cycling capacity and excellent rate performance.In order to further improve the electorchemical performance of mixed crystal type TiO2 nanotubes, graphene and dopamine-derived carbon coating were carried out on them. TiO2@Dopa-6, the carbon coated mixed crystal type TiO2 nanotubes, is prepared by carbonizing dopamine coated H2Ti3O7 nanotubes at 700?. It is tubulous, consists of anatase and TiO2-B, and have a proper thickness(about 2nm) of the carbon coating layer, which contribute to excellent rate performance, high capacity and good cycling stability. The TiO2@Dopa-6 keeps the capacity of 177.5mAh·g-1 with current density of 200mAg-1 after 500 cycles. In large current density of 2000mA·g-1, the capacity is as high as 141.2mAh·g-1. And with large current density of 2000mA·g-1 after 600 cycles, the capacity remains 140.5mAh·g-1.