Synthesis of LiFePO4/C Composites Based on Natural Iron Stone Using a Sol Gel Method

Synthesis of LiFePO4/C composites has been carried out using a sol gel method. The Fe precursor was made from a natural iron stone of Tanah Laut, South Kalimantan, while the other raw materials were commercial Li2CO3 powder and NH4H2PO4 powder with HCl and water as solvents. Citric acid was used as the carbon source in the synthesis. This study used a molar ratio of 1: 1: 2 for Li: Fe: P with variation of added citric acid of 1.5 and 2.5 g. The solutions were dried in air at 100 degrees C. The dried powders were characterized using DSC-TGA and then calcined at 600 and 700 degrees C under argon environment for 10 hours. The calcined powders were characterized by X-ray diffractometry (XRD), scanning electron microscopy-energy dispersive x-ray (SEM-EDX), and LCR meter. It was found that the samples contained LiFePO4 as the dominant phase and LiFeP2O7 and Fe2O3 as secondary phases. The analysis showed that the addition of citric acid influenced the electronic conductivity of the composites. A Rietveld relative weight fraction of up to 94.7% was achieved in the synthesis at temperature 600 degrees C. The LFP/C sample exhibited electronic conductivity of 4.56x10(-3) Scm(-1) which was six times of that of the pure LFP.