Solvothermal synthesis of lithium iron phosphate from a high concentration precursor

LiFePO₄ cathode material was synthesized using a solvothermal method at various relatively high concentration precursors. The samples were prepared using LiOH·H₂O, FeSO₄·7H₂O, H₃PO₄, and citric acid which are dissolved in ethylene glycol and water mixture solvent with various concentration of LiOH from 0.3 to 1.8 M while the Li:Fe:P molar ratio was fixed at 3:1:1. The precursors were heated in an autoclave at fixed temperature of 180°C for 8 hours. The prepared samples were characterized using an X-Ray Diffraction and Scanning Electron Microscopy to study the crystal structures and morphology of the prepared particles, respectively. It was found that LiFePO₄ structures were observed at all various concentrations. However, a small part of crystal structure impurity was detected for the samples that fabricated at concentration 0.3 M and some coagulated part of sample from 1.5 M and 1.8 M. We found that the optimum precursor concentration for the present method and preparation condition was at 1.2 M of LiOH precursor.