LiFePO₄ (LFP) has attracted much attention as a promising candidate for cathode materials in new generation of Li-ion batteries due to its good thermal stability, being environmentally friendly and abundance in nature. Many synthetic routes, such as solid state, sol-gel, hydrothermal, co-precipitation, and microwave preparations, have been used for preparing LFP. In 2003, Gauthier et al. advanced the concept of melt synthesis. The process operating above 1000°C in the liquid phase, benefits from fast reaction kinetics and the thermodynamic stability of LiFePO₄ in a reducing atmosphere. This approach allows the use of a wide range of simple raw materials as well as a possible purification strategy in the melt or upon solidification, potentially enabling for usage of less pure non-expensive raw materials.

Fundamental aspects will be addressed as this work is only feasible with a good understanding of the thermodynamics of the Li-Fe-P-O system. A model has been developed and it is supported by our experimental data. On this basis, recent experimental observations and progress on raw material selection and systems will be then reported. Melt-synthesis conditions and the latest result in controlling the purification of LiFePO₄ from major phase impurities will also be covered. All these considerations allow the selection of the best conditions to prepare a high purity LiFePO₄ by melt-process.

This work is part of an Automotive Partnership of Canada supported program to develop and pilot the molten-synthesis process to make high purity C-LiFePO₄ with excellent electrochemical properties for using as a cathode material in Li-ion batteries for EVs and PHEVs application.