Polyol process for the synthesis of LiFePO4 rhombohedral particles

As a new approach, LiFePO4 nanoparticles were directly synthesized from precursors iron(III) nitrate and lithium dihydrogen phosphate by a polyol process without post heat treatment in one step. The obtained powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and combined thermogravimetry and differential scanning calorimetry and mass spectroscopy TG/DSC/MS. The X-ray diffraction showed the orthorhombic crystal structure of LiFePO4 without any impurity phases. The synthesized LiFePO4 has rhombohedral morphology with high aspect ratio with a thickness of less than 100 nm. TG/DSC/MS revealed a weight loss of only 10.9 wt.% when heating up to 1000 °C. Electrodes prepared from the LiFePO4 particles were electrochemically characterized by cycling at 0.1C current rate and temperatures in half cell measurements against lithium foil between 2 and 4.2 V in an EC/DMC electrolyte with 1 M LiPF6 as conductive salt. A reversible specific capacity of 146 mAh/g was achieved by applying carbon coating on the rhombohedral particles.