Preparation And Electrochemical Properties Of Pure And Sn/Li Doped Titania Nanotubes

Lithium-ion battery is a new generation green non-pollution battery when it was used in the 1990s. It is widely used in portable electron, telephone, computer and electric car, due to its highlights such as high voltage, low discharge rate by little volume, light weight and nonmemeory effect. But the anode materials for lithium-ion battery are the key to constrain its whole performance.The lithium-ion batteries which used early almost select carbon as the anode material. But when discharge for the time, there are passivation membrane on the surface of carbon, which will cause capacity lose. Moreover, the potential of carbon is very close to that of lithium, when overcharge, the metal lithium will separate out on the surface of carbon, which is the intrinsic safety we must concern. while, for TiO2 nanotubes, when used as negative material for Li-ion battery, there is no such problem, and there are almost no structure change and small polarization during discharge, that is why there are so small irreversible capacity lose and intrinsic safety. A 2.0-2.5V cell can be constructed when TiO2 nanotubes combined with positive electrode materials such as LiCO2, LiNiO2.TiO2 nanotubes and Sn, Li doped TiO2 nanotubes were prepared by hydrothermal method. We studied the electrochemical performance of them in lithium-ion battery. 1. TiO2 nanotubes were prepared by hydrothermal method. The appropriate temperature, the appropriate time and the effect to TiO2 nanotubes of heat treatment were researched. The perfect nanotubes were formed by the temperature of 110-130℃and 24h. TiO2 nanotubes (anatase ) showed a good stability below the temperature of 500℃.2. The electrode foils were prepared by mixing TiO2 nanotubes and other material. The electrochemical properties were studied by assembling there-electrode cell in a glove box. It shows that the TiO2 nanotubes owed the specific reversible capacity of 175 mAh/g and 339 mAh/g of the first cycle discharge, which are better capacity than nano-grain. CV curves showed that the electrode is norm reverse reaction. 3. TiO2 nanotubes of doped Li and Sn were prepared by sol-gel and hydrothermal (Li, Sn/TiO2 =5%), the microstructure and micrograph were investigated by XRD, TEM and investigated the electrochemical properties. X ray diffraction exhibited that the structure takes no changing when doped. The electrochemistry tests showed the discharge capacity increasing when doped, the cycling stability also improved by doping. There are three main reasons: firstly, TiO2 is a novel semiconductor, the Ti4+ depressing resulted in the improving conductivity when doped. Secondly, the length of the TiO2 nanotubes became short when doped, this improves the properties of electrode and electrolyte interface, and abridges the distance about lithium ion transmit. Thirdly, after the doping reinforced the lattice structure stability, reduced the change of the crystalline lattice volume in charging and discharging process, thus enhanced the specific reversible capacity.