Cycling performance of LiFePO4 cathode material for lithium secondary batteries

Lithium iron phosphate (LiFePO4) cathode material has been synthesized by a solid-state reaction which uses Li3PO4 and Fe3(PO4)2·8H2O as starting materials. These materials were mixed with alumina balls and treated thermally at various temperatures in an argon and hydrogen atmosphere. The crystalline intensity of LiFePO4 powder prepared at 700 °C is higher than that of powders prepared at 600 and 800 °C. The particle size increases as the heat-treatment temperature increases. The material prepared at 700 °C gives a higher discharge capacity than the other materials, namely, 100 mAh g−1 at the C/5 rate, which corresponds to 0.25 mA cm−2 and at room temperature. Although the capacity increases as the operating temperature is raised, the degree of capacity fade also increases.