Construction of E-pH diagram and experimental study on wet synthesis of FePO4 as the precursor of cathode materials

The preparation of FePO4 as a precursor by co-precipitation method is widely used, Due to the lack of the guidance of thermodynamic theory, The prepared FePO4 often contains impurity phase, which leads to unsatisfactory performance of LiFeO4. The E-pH diagram of Fe-P-H2O system at the temperature of 25℃ were drawn through the basic E-pH principle with a number of thermodynamic data. According to the E-pH Diagram, the pH value is approximately 2.5, and the FePO4 with less impurity can be prepared by adding proper oxidant. Base on the above mentioned condition, a simple verification experiment was carried out. The results showed that the prepared iron FePO4 had fewer impurities, which provided a theoretical basis for preparing high-performance LiFeO4.