Pulse Laser Deposition and Electrochemical Characterization of LiFePO4−C Composite Thin Films

• Published in: Journal of physical chemistry. C 2008-05, Vol.112 (17), p.7069-7078
• Main Authors: Lu, Z. G, Lo, M. F, Chung, C. Y
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp0744735

Conductive carbon was codeposited with LiFePO4 to enhance the electrical conductivity of the olivine-type LiFePO4 thin films. In this approach, poly(vinyl alcohol) was used as the source for carbon as well as the binder for target densification. After a highly densified (>80%) LiFePO4−C target was fabricated, pulse laser deposition (PLD) technique was employed to deposit the LiFePO4−C composite thin films on the Si/SiO2/Ti/Pt substrates. The as-deposited LiFePO4−C composite films were characterized by techniques of X-ray diffraction, scanning electron microscopy, Raman scattering spectroscopy, X-ray photoelectron spectroscopy, DC conductivity measurement, as well as cyclic voltammograms, electrochemical impedance spectroscopy, and galvanostatics. The effects of carbon content and postdeposition annealing treatments on the electrochemical performances of the as-deposited film electrodes were carefully investigated. The results showed that the codeposited carbon was homogeneously distributed throughout the LiFePO4 films. It was found that 2 mol% carbon was the optimized amount for the highest capacity. Postdeposition annealing at 600 °C for 6 h in the same vacuum chamber could considerably improve the Coulombic efficiency as well as the high rate capability of the PLD-deposited LiFePO4−C composite thin films. However, the specific capacity would be reduced.