High-rate properties of LiFePO4/carbon composites as cathode materials for lithium-ion batteries

Electrochemical properties of LiFePO4/carbon composites were investigated to achieve a high-rate lithium electrode performance. LiFePO4/carbon composites were synthesized by a hydrothermal reaction of a solution of FeSO4·7H2O, H3PO4, and LiOH·H2O mixed with carbon powders under nitrogen atmosphere followed by annealing under 1% H2–99% Ar atmosphere. Particle size of the obtained LiFePO4/carbon composites observed by scanning electron microscopy was less than 100 nm. At a high current density of 1000 mA g−1, the LiFePO4/carbon composites showed a high discharge capacity of 113 mA h g−1, and a flat discharge potential plateau was observed around 3.4 V. The discharge capacity at the high current density, 85% of that at a low current density of 30 mA g−1, is a quite high value for LiFePO4 cathodes. Homogeneous microstructure consisting of small particles contributed to the high-rate properties of the LiFePO4/carbon composites.