Aqueous solution-gel precursors for LiFePO4 lithium ion battery cathodes, their decomposition and phase formation

Abstract

Several aqueous solution-gel precursors for the Li ion battery cathode material LiFePO4, were synthesized. These differ in their composition, both regarding their Fe source, as well as in the complexing agent present. Fe(II) lactate hydrate is for the first time used as Fe2+ source. The ability to use an Fe3+ source (Fe(III) nitrate nonahydrate) for the synthesis of LiFePO4 is also investigated. Our results show that it is possible to reduce the Fe3+ to Fe2+, necessary to enable LiFePO4 phase formation, during annealing under specific conditions. The decomposition behavior for these precursors in dry air, as well as in an inert atmosphere, is shown. Raman spectroscopy is used to evaluate the structure of the carbon phases present after annealing of the precursor powders.