Research And Application Of Iron And Tin-Based Oxide/Carbon Composites As Anode Materials For Lithium-Ion Batteries

The lithium-ion battery has attracted much attention because of its excellent overall performance. With rapid developments of small and portable electronic devices (mobile phones,digital cameras,notebook computers etc) and comercialization of electric vehicles,requirements for the performance of lithium-ion batteries(LIBs) have been increased. Graphite as the anode material of the commercial lithium-ion battery has a low capacity that can not meet the growing demand for lithium-ion battery performance. Therefore, the development of new anode materials with better performance and low price is particularly urgent. Iron oxide and tin oxide have the characteristics of high capacity, low price and environmental friendliness, thus they are potential anode materials for lithium-ion batteries. However, these oxides as anode materials of lithium-ion batteries have the shortcomings of short cycle life and poor rate performance. To overcome these shortcomings, the most effective mean is to modify the nanostructure for functional purposes.In this thesis, iron oxide Fe3O4 and tin oxide SnO2 nanoparticles were prepared and their composites with carbon materials (graphene,amorphous carbon,conductive polymer)were synthesized. The main research work is divided into three parts as follows:1. By heat treatment of iron based xerogels, Fe3O4 composites with mesoporous carbon were synthesized, and their performance as the anode materials of LIBs were evaluated. The effects of heating temperature, heating rate and holding time on the microstructure and electrochemical properties of the composites were studied. The experimental results show that the composites prepared under the conditions of 600℃-5℃/min and 6 h have the best electrochemical performance.2. The binary composites of Fe3O4/para-phenylene(PPP), Fe3O4/(PPP-700,PPP heated to 700℃ for lh),SnO2/(PPP-700) and the ternary composite of SnO2/(PPP-700)/reduced graphene oxide(rGO) were prepared through the hydrothermal method. The experimental results show that (PPP-700) is better than PPP in modifying metal oxides. The ternary composite of tin SnO2/(PPP-700)/rGO has better electrochemical properties than the binary composites of SnO2/(PPP-700).3. Ternary SnO2/rGO/polyaniline(PANI) composite materials (SnO2-rGO-PANI) were synthesized. The experiments show that polyaniline has the effect of preventing the aggregation of SnO2/rGO. The optimal mass ratio of SnO2 and graphene oxide(GO) in the ternary composites was 2:1. At the same time,the particle size of SnO2 has a great influence on electrochemical properties of the composite materials and the composite using SnO2 nano particals prepared under hydrothermal conditions of 120℃-28 h exhibits the best electrochemical performance.