Suppressing Li3PO4 impurity formation in LiFePO4/Fe2P by a nonstoichiometry synthesis and its effect on electrochemical properties

Lithium iron phosphate (LiFePO4) was synthesized by a solid-state reaction from a nonstoichiometric mixture of starting materials with an iron: phosphorus excess ratio of 2:1 at a high temperature. The nonstoichiometry synthesis did not affect conductive Fe2P formation, lattice constants of LiFePO4 and materials morphology, but could effectively suppress insulating Li3PO4 impurity formation which was clearly observed in the stoichiometric sample. Our results demonstrate that the positive effect of the conductive Fe2P could be masked by the insulating Li3PO4 impurity presence, and the creation of Fe2P without Li3PO4 formation from carbothermal reduction could be successfully achieved by our nonstoichiometry synthesis.