Journal
ELECTROCHIMICA ACTA
Volume 56, Issue 13, Pages 4869-4875Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2011.02.119
Keywords
Lithium iron phosphate; Thin film; Chemical diffusion coefficient; Overpotential
Categories
Funding
- CAS [KJCX2- YW-W26]
- NSFC [50730005]
- 863 project [2009AA033101]
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LiFePO4 thin films were deposited on Ti substrates by pulsed laser deposition (PLD). The apparent chemical diffusion coefficients of lithium in the films, D-Li, were measured by cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS). The average D-Li values calculated from CV results were in the order of 10(-14) cm(2) s(-1). The D-Li values obtained by GITT, and EIS techniques were in the range of 10(-14)-10(-18) cm(2) s(-1), 10(-14)-10(-18) cm(2) s(-1), respectively.The D-Li values obtained by the two methods show a minimum point at x similar to 0.5 for Li1-xFePO4. However, the overpotential values of the LiFePO4 thin film electrodes obtained from the GITT results and the diffusion impedance deduced from the impedance spectra also show the minimum values at x similar to 0.5 for Li1-xFePO4. This contradict could be caused by the improper use of GITT and EIS techniques for measuring the chemical diffusion coefficient of Li in Li1-xFePO4 which constitutes two phase, i.e., LiFePO4 and FePO4 in this region. (C) 2011 Elsevier Ltd. All rights reserved.
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