Determination of the Lamb-Mossbauer factors of LiFePO4 and FePO4 for electrochemical in situ and operando measurements in Li-ion batteries

Fe-57 Mossbauer spectroscopy is a powerful tool to investigate redox reactions during in electrochemical lithium insertion/extraction processes. Electrochemical oxidation of (LiFeO4)-O-II (triphylite) in Li-ion batteries results in (FePO4)-P-III (heterosite). LiFePO4 Was synthesized by solid state reaction at 800 degrees C under At How from Li2CO3, FeC2O4 center dot 2H(2)O and NH4H2PO4 precursors in stoichicimetric composition. FePO4 was prepared from chemical oxidation of LiFePO4 using bromine as oxidative agent. For both materials a complete Fe-57 Mossbauer study as a function of the temperature has been carried out. The Debye temperatures are found to be theta(m)=336K for LiFePO4 and theta(m)=3591 < for FePO4, leading to Lamb-Mossbauer factors f(300 K) = 0.73 and 0.77, respectively. These data will be useful for a precise estimation of the relative amounts of each species in a mixture. (C) 2009 Elsevier Inc. All rights reserved.