Study Of Electrochemical Performance Of New Type Negative Electrode Materials For Lithium-ion Batteries

The over-exploiting of the fossil power such as coal and petroleum not only lead to the declining of the reserve level day by day, but also results in greenhouse effect and serious damage to the ecological environment. The incident of the oil spill in the Gulf of Mexico this year has caused serious concern to the world on the development of clean energy. If battery energy superseded fossil power, there would be a great reduction in both greenhouse gas emissions and the dependency on oil imports, which is of important economic and strategic meaning to our country. In comparison to other secondary batteries, Li-ion Battery has many advantages such as high voltage and specific capacity, long cycling life and environmental friendliness. Li-ion Battery is the most positive to be used in high power EV battery. However, the present commercialized carbon anode materials have reached their limit and could no longer meet the requirements of EV. To discover a new anode material which is of better safety, higher specific capacitance and longer cycling life has become the focus on Li-ion Battery research at present.Anatase TiO₂ has become one of the desirable choices for anode materials for Lithium-ion Batteries because of its many advantages such as good cycle performance and safety, good resistance to overcharge and etc. In this paper we have prepared anatase TiO₂ by hydrothermal process at low temperatures and studied the influences of the hydrothermal reaction factors (the temperatures, time and reactant concentration) on the morphology of the products. The investigation shows that when the volume ratio between TiOSO₄, glycerol, absolute alcohol and ethyl ether is 1:16:40:11 and reaction temperature is between 105℃and 120℃, uniform sized, well-dispersed spherical/core-shell TiO₂ is obtained. By means of controlling different reaction time, we discovered that the synthesis of core-shell TiO₂ falls into two phases, i.e. the formation of inner crystal nucleus and the growth of outer chips.We performed the roasting experiments upon the core-shell TiO₂ at 700℃under vacuum. With XRD,TEM and elemental analyser techniques we get to know that the carbon content in this product is about 18.35%, TEM pictures show that the core-shell TiO₂ is polycrstal.In this paper we made further studies on the electrochemical performance of core-shell TiO₂ roasted under vacuum at 700℃over three hours. The experimental results showed that the core-shell TiO₂ exhibited a high initial discharge capacity and excellent cycling performance. However,there are still large irreversible capacities in the first cycle and the cycling performance need some improvement.