Effect of Particle Size of FePO4•2H2O on the Physical and Electrochemical Properties of LiFePO4/C Cathode for LIBs

Particle size is a very important factor for the electrochemical performance of materials. However, the effect of the particle size of FePO 4 ·2H 2 O on the properties of LiFePO 4 remains unclear during carbon thermal reduction using FePO 4 ·2H 2 O as a raw material. Here, LiFePO 4 /C composites are synthesized by an aqueous rheological phase-assisted carbon thermal reduction method using FePO 4 ·2H 2 O with different particle sizes as raw materials. The particle size of LiFePO 4 is positively correlated with the particle size of FePO 4 ·2H 2 O. The LiFePO 4 materials prepared using small-sized FePO 4 ·2H 2 O show high purity and small particle size, thus exhibiting an improved rate capacity of 160 mA h g –1 at 0.1 C and 135 mA h g –1 at 5 C and cycling stability with a capacity retention of 98.9% after 100 cycles at 2 C. Intriguingly, the LiFePO4 materials prepared using large-sized FePO 4 show a longer slope voltage at the end of the discharge curve, which could be accounted for by an Fe 3+ phase on the surface of the large-sized LiFePO 4 . Our studies provide a new understanding of the effect of the particle size of FePO 4 ·2H 2 O on the properties of LiFePO 4 materials during carbon thermal reduction.