A novel sol–gel method based on FePO4·2H2O to synthesize submicrometer structured LiFePO4/C cathode material

Carbon coated LiFePO4/C cathode material is synthesized with a novel sol–gel method, using cheap FePO4·2H2O as both iron and phosphorus sources and oxalic acid (H2C2O4·2H2O) as both complexant and reductant. In H2C2O4 solution, FePO4·2H2O is very simple to form transparent sols without controlling the pH value. Pure submicrometer structured LiFePO4 crystal is obtained with a particle size ranging from 100 to 500 nm, which is also uniformly coated with a carbon layer, about 2.6 nm in thickness. The as-synthesized LiFePO4/C sample exhibits high initial discharge capacity 160.5 mAh g−1 at 0.1 C rate, with a capacity retention of 98.7% after 50th cycle. The material also shows good high-rate discharge performances, about 106 mAh g−1 at 10 C rate. The improved electrochemical properties of as-synthesized LiFePO4/C are ascribed to its submicrometer scale particles and low electrochemical impedance. The sol–gel method may be of great interest in the practical application of LiFePO4/C cathode material.