Green Phosphate Route of Regeneration of LiFePO₄ Composite Materials from Spent Lithium-Ion Batteries

Abstract

To develop efficient, viable, and promising routes to regenerate nano-LiFePO4 (nano-LFP) composite materials from spent LFP batteries, this paper studied phosphate approaches by taking Li3PO4 and FePO4 as raw materials. The crystalline structure, morphology, and physicochemical properties of regenerated LiFePO4 nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurement. Regenerated LiFePO4 owned a good olivine structure with a space group of Pnma. After being coated with carbon, rectangular-structured LiFePO4 prepared by hydrothermal synthesis exhibited high specific capacity, excellent rate capability, and good Li+ diffusivity. When the pH value was around 8.0 and the amount of the Li3PO4 raw material was 14 mmol, the discharge capacity at 0.1C was 158.6 mAh g–1 and the capacity retention rate was 99.19% at 1C after 300 cycles. Meanwhile, flake-like LiFePO4/C synthesized by the carbothermal method at 700 °C and a 14 wt % carbon mass fraction showed an initial discharge capacity of 159.0 mAh g–1 at 0.1C and a capacity retention rate of 97.45% after 300 cycles at 1C, exhibiting excellent electrochemical performance. Overall, this study provides a facile, feasible, and sustainable recovery method for the battery industry for recovering phosphate products from spent LFP cathode materials and subsequent large-scale regeneration of LiFePO4 composite materials.