Preparations And Properties Of Sb And SbSn Thin Film Anode Materials In Thin Film Lithium-ion Batteries

To find the materials with high capacity, high cycleability and easy process is an important issue in developing thin-film lithium-ion battery. The research was initiated by this issue to study the synthesis, microstructures and properties of the thin films based on antimony metal and antimony-tin alloy. The parameters to prepare thin films and the theory relevant to electrochemical properties were investigated to realize the applications in thin film lithium-ion battery.Two approaches, magnetron sputtering and electrochemical deposition, were used to prepare Sb thin film. After the results were compared, magnetron sputtering was adopted to prepare the SbSn thin film with a variety of structures and properties under different synthesizing parameters. The plateaus of Sb thin film was at 0.8 V for intercalation and 1.0 V for deintercalation, respectively, and both were very flat. However, both the intercalation of SbSn and that of Sn were stepwise. and each product has different potential of intercalation.The initial intercalation capacity of the thin film prepared by electrochemical deposition could give 1290 mAhg"1. However, its cycleability below 300 mAhg"1 is uncomfortable. The thin film made by magnetron sputtering offered 872 mAhg'1 initial capacity and beyond 400mAhg"' upon 15 cycles. Compared with their corresponding powders, both approaches making thin films can much improve the properties in the initial capacity and cycleability because the volume effect was decreased. These two thin films made by magnetron sputtering show better microstructures, leading to better electrochemical properties than those prepared by electrochemical deposition.Thin film made by magnetron sputtering with shorter length of run gave more than 400 mAhg"1 upon 15 cycles while that run with longer time only had 200 mAhg"1 upon 15 cycles. It shows that the thinner the film thickness is, the finer is the microstructures and it decreased the volume effect to improve the cycleability.Sn and Sb can form complete solid solution, so no single phase of either Sb or Sn was found in SbSn thin film. The initial capacity of SbSn thin film was 1552 mAhg"1, and its irreversibility was 24%. Changing the length of run could cause glow discharge to form continuously thin film in a short time. Higher sputtering voltage made larger crystallites in the film and it decreased electrochemical properties. Electrochemical impedance spectroscopy was performed to test the thin film. It is found that the diffusion in thin-film electrode was similar to that of the powder under the equivalent circuit investigation.