Continuous hydrothermal synthesis of lithium iron phosphate particles in subcritical and supercritical water

We have investigated the continuous hydrothermal synthesis of lithium iron phosphate (LiFePO4) nanoparticles by reacting iron sulfate, phosphoric acid, and lithium hydroxide in a flow system. The effects of temperature, flowrate of water, and reactant concentration on the size and morphology of particles were investigated. In general, particle size increased with temperature and with increasing reactant concentration. Particle morphology, on the other hand, became more regular at high flowrates of water. Possible reasons for this behavior are given, and differences with batch hydrothermal synthesis of LiFePO4 are highlighted. The different mechanisms in the two methods results in much smaller and more uniform particles being obtained in continuous hydrothermal synthesis than via batch hydrothermal synthesis.