Role of deviation from Li stoichiometry in synthesis of LiFePO4 cathode material

Olivine-structured LiFePO4 was successfully synthesized by co-precipitation method as the cathode material for Li-ion battery application. In this study, deviation from nominal stoichiometry of LiFePO4 and its effects on the final phase composition and powder particle morphology have been investigated using X-ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM), respectively. The XRD results revealed that the molar composition of Li : Fe : PO4 = 1.25 : 1 : 1 in the precipitation stage is the proper stoichiometry for achieving single phase LiFePO4 with orthorhombic crystal structure after calcination at 700˚C under reductive atmosphere. Scanning electron microscopy studies confirmed formation of ultrafine spherical particles of LiFePO4 phase for the above sample.