Synthesis and electrochemical properties of spherical LiFePO₄ with various particle sizes as cathode material for lithium batteries

Spherical FePO₄ particles with various sizes were synthesized using controlled crystallization method, then LiFePO₄ materials were prepared with FePO₄ as precursor by carbothermal reduction method. The crystal structure, microstructure and electrochemical properties of samples were characterized by XRD, SEM and galvanostatically charge-discharge experiments, and the tap-densities of samples with different paticle sizes were measeured. The samples remained the spherical shape successfully and LiFePO₄ with large size had a tap density reach to 2.03g/cm³ but poor electrochemical properties. The small size LiFePO₄ had the best gravimetric capacity at different discharge rate, the discharge capacity is up to 160.6mAh/g at 0.1C. However, the volumetric capacity of the medium size LiFePO₄ were relatively higher, which were 230.4mAh/cm³ at 0.1C. Generally, spherical LiFePO₄ with small size has better gravimetric capacity and the volumetric capacity of the medium size LiFePO₄ is higher, we should choose spherical LiFePO₄ with appropriate size according to practical situation.