Fe3P impurity phase in high-quality LiFePO4: X-ray diffraction and neutron-graphical studies

Abstract

High discharge capacity and long life cycles of electrodes fabricated from various LiFePO4 powders have been used to select samples for detailed structural studies. In some samples, the presence of ferromagnetic Fe3P crystallites was revealed by the synchrotron X-ray diffraction analysis, with the integral intensity ratio of the peaks Fe3P (231) and LiFePO4 (112) equal to ∼1/12. Small-angle polarized neutron scattering (SAPNS) detected the presence of magnetic nuclear contrasting regions with size of 17 ± 1 nm. The average diameter of LiFePO4 crystallites is 230 nm, and Fe3P crystallites were found as 17 × 54 nm2 plates. The high quality of these samples was provided by their manufacturer via synthesis of the Fe3P impurity phase. It can be stated that the set of studies, developed in the study, is helpful in a search for new effective impurity phases and in optimization of their parameters.