Three‐Dimensional Morphology of Iron Phosphide Phases in a Polycrystalline LiFePO4 Matrix

The three-dimensionally isolated morp­hology of secondary iron phosphide phases in a polycrystalline LiFePO4 matrix is determined using a combination of electron tomography in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), and electron energy-loss spectroscopy (EELS). The present evidence shows that the enhanced bulk electronic conductivity in LiFePO4 has no relation to secondary metallic phases at the grain boundaries.