Preparation And Electrochemical Performace Of LiFePO₄

LiFePO4is a very hopeful positive electrode material for further lithium-ion batteries materials, because of abundance of raw materials, high theoretical capacity, stable structure, excellent cycling performance and pollution-free. On the base of reviewing the development of lithium ion battery and its cathode materials in brief, LiFePO4was chosen as cathode material and its synthesis was studied. In this paper, precursor FePO4was prepared via homogeneous precipitation, then LiFePO4was synthesized by carbon-thermal reduction method using obtained FePO4as precursor. The morphology, structure of particles and electrochemical performance were characterized by SEM, XRD, thermal gravimetric analysis and electrochemical performance testing.During preparing precursor by homogeneous precipitation, the effect of molar ratio of PO43-and Fe3+, dropping concentration and dropping speed of Fe3+, temperature and the amount of PEG on the shape of precursor was studied. The results demonstrated that, when the molar ratio of PO43-and Fe3+was4, dropping concentration of Fe3+was0.4mol/1, dropping speed was33.33ml/h, temperature was95℃and the amount of PEG was3%, the obtained FePO4was good dispersion,2μm in particle size and spherical in shape.During preparing LiFePO4, the effect of different precursors on electrochemical performance of LiFePO4was studied. The results demonstrated that LiFePO4synthesized by different precursors had certain electrochemical performance. When precursor was prepared by homogeneous at optimization conditions, the first discharge capacity of obtained LiFePO4can be up to132mA·h/g at0.2C charge-discharge rate. After20cycles, its discharge capacity still was129mA·h/g.