The influence of the Li+ addition rate during the hydrothermal synthesis of LiFePO4 on the average and local structure

Abstract

A hydrothermal method was used to synthesize LiFePO4 to explore the effect of the rate of addition of the Li+ precursor to a mixture of the Fe2+ and PO43− precursors. Both the average and local structures were investigated using powder X-ray diffraction, Mössbauer spectroscopy and X-ray absorption spectroscopy. Slower addition rates led to increased oxidation of Fe2+ to Fe3+ despite purging all solutions constantly, as well as increased defects. The local structure as determined by extended X-ray absorption fine structure displayed far less variation between the samples. The formation of a Li3PO4 impurity appeared to be independent of the Li+ addition rate.