Physical and electrochemical properties of LiFePO4/C thin films deposited by direct current and radiofrequency magnetron sputtering

In this study, LiFePO4/C thin films with various contents of carbon were prepared by direct current (DC), radiofrequency (RF) and combined (DC/RF) magnetron sputtering methods. Influences of the composition, morphology and microstructure on the electrochemical properties of LiFePO4/C thin films are investigated by studying charge-discharge curves, cyclic voltammetry and electrochemical impedance spectroscopy. Cyclic voltammogram of the LiFePO4/C thin film showed the typical redox reaction peaks characterizing the electrochemical lithium insertion/extraction reactions in LiFePO4. Obtained LiFePO4/C thin films have relatively high charge capacities (127 rnAh g(-1)). It was found that optimal magnetron sputtering conditions use a combined CD/RF process to obtain LiFePO4/C thin films with the best electrochemical performance. (C) 2010 Elsevier B.V. All rights reserved.