Nanosheet Iron Phosphate by an Efficient Route for LiFePO4 Cathode Material

Abstract

The precursor of FePO₄·2H₂O is prepared by a liquid phase conversion method with low-cost fine Fe₃O₄ ore powder from magnetite flotation, and the LiFePO₄/C is synthesized by sanding and spray followed by roasting technology. By controlling the excess coefficient of phosphate to Fe, the influence on the degree of chemical reaction and the preferred orientation of the precursor of nano sheet FePO₄·2H₂O on the (020) face is investigated. The results indicate that when the mole of phosphate is 2.5 times that of iron, the thickness of the FePO₄·2H₂O precursor nanosheet is the thinnest, resulting in the synthesis of LiFePO₄/C materials with the smallest primary particles and the best electrochemical properties. It can be observed that the specific discharge capacity of the as-prepared LiFePO₄/C can reach 150.5 mAh/g at 1 C, and the capacity retention rate is still over 96% after 450 cycles at 2 C. At the same time, the Re-LFP/C-2 synthesized with FePO₄·2H₂O by recycling H₃PO₄ mother liquor can achieve the same excellent electrochemical performance as the LFP/C-2 synthesized with fresh H₃PO₄. It is demonstrated that this route has promising development prospects and is easily scalable. At the same time, this synthetic route is cheaper to synthesize and produces less wastewater, which provides a basis for exploring the green, efficient, and low-cost synthesis route of LiFePO₄/C.