Concentration-controlled morphology of LiFePO4 crystals with an exposed (100) facet and their enhanced performance for use in lithium-ion batteries

Abstract

A study of the morphology-controlled growth of olivine LiFePO4 particles by varying the precursor concentration via a facile solvothermal synthesis was carried out. The influences of the solvent product on the structure, morphology and electrochemical performance were systematically investigated by X-ray diffraction, scanning/transmission electron microscopy and charge-discharge tests. It was found that as the precursor concentration increased from 0.15 M to 0.90 M, the morphology of the LiFePO4 particles changed from spindle-shape to plate-type and then to a hierarchical club-shaped structure, and the predominantly exposed facet of all LiFePO4 samples was (100). The shape of LiFePO4 particles remained as nanoplates while synthesized at different reaction temperatures and time with a precursor concentration of 0.30 M. This in turn confirms that the precursor concentration plays an important role in controlling the morphology of LiFePO4 particles. To illustrate the phenomenon caused by variations in the concentration, a possible morphological transformation mechanism was demonstrated. With the optimal precursor concentration of 0.3 M, the obtained LiFePO4 shows square nanoplates with uniform particle size and carbon coating, resulting in excellent electrochemical performance: a discharge capacity of 157.3 mAh/g at 1 C with 95% capacity retention after 1000 cycles and a high-rate capacity of 140.8 mAh/g at 10 C. This facile and precursor concentration-controlled solvothermal method is anticipated to be a guide for large-scale cathode material manufacturing and can fulfil the requirements for its application to high-power lithium-ion batteries.