Studies On The Tin Oxide-Based Anode Materials For Lithium Ion Batteries

On the basis of reviewing the developments of lithium ion battery and anode materials in detail,with tin oxide-based anode materials as objects of the study, focusing studies on the specific capacity, cyclability and rate capability of materials, the tin oxide-based materials were prepared by sol-gel and homogeneous precipitation methods, and characterized by various electrochemical methods in combination with powder X-ray diffraction(XRD), Transmission Electron Microscope(TEM), Infrared (IR) spectroscopy and so on.Nanosized SnO₂ powders were successfully prepared by sol-gel approach combined with heat treatments using tin tetrachloride and Ammonia water as starting materials.The reaction mechanisms of the sol-gel process are proposed. Results indicate that powders with uniform size around 10-15 nm can be obtained at 500℃for 6 hours.Results on the electrochemical properties of nanosized SnO₂ powders show that heat treatment temperature, voltage windows, current density for charge and discharge, and particle size effect on their specific capacities, cyclability and rate capability. The powders obtained at 500℃for 6 hours shows the best electrochemical properties: a reversible capacity of more than 746mAh/g was obtained and the rate of capacity fading only 0.77% after 25 cycles at 0.1 C rate in the potential range of 0～2.0V; and the reversible capacity was 531mAh/g with a rate of capacity fading of 0.28% after 25 cycles at 0.5C rate in the potential range of 0～1.2V. The interface processes of lithium insertion into nanosized SnO₂ electrode was studied by A.C. impedance, and different A.C. impedance spectrum at different charge states were studied.SnO₂ -graphite composites were prepared by homogeneous precipitation method, the structure and electrochemical properties were studied. Stuides suggest that the composites of 30%SnO₂-70%graphite heat-treated at 600℃for 6 hours have a reversible capacity of 494mAh/g and 82% of the reversible capacity can be retained after 30 cycles. 90.5% and 82.3% of the capacity discharged at 0.1 C can be obtained when discharge at 1.0 C and 2.0 C respectively. These results show that SnO₂-graphite composites have good reversible capacities, rate capability and cyclability. But the specific capacities are not the sums of the capacities of SnO₂ and graphite, suggests the presence of synergistic interaction between the two constituents.