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

Abstract Electrochemical properties of LiFePO 4 /carbon composites were investigated to achieve a high-rate lithium electrode performance. LiFePO 4 /carbon composites were synthesized by a hydrothermal reaction of a solution of FeSO 4 ·7H 2 O, H 3 PO 4 , and LiOH·H 2 O mixed with carbon powders under nitrogen atmosphere followed by annealing under 1% H 2 –99% Ar atmosphere. Particle size of the obtained LiFePO 4 /carbon composites observed by scanning electron microscopy was less than 100 nm. At a high current density of 1000 mA g −1 , the LiFePO 4 /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 LiFePO 4 cathodes. Homogeneous microstructure consisting of small particles contributed to the high-rate properties of the LiFePO 4 /carbon composites.