Recycling phosphorus from spent LiFePO4 battery for multifunctional slow-release fertilizer preparation and simultaneous recovery of Lithium

Comprehensive utilization of phosphorus from spent LiFePO4 (LFP) battery has aroused considerable interest aiming to enhance the economic profit of recycling this type of low value-added battery. In the current study, a green and novel process was developed to recover phosphorus from spent LFP battery, which was further directly converted into phosphorus grafted slow-release fertilizer (P-SRF) with acid-resistance. Meanwhile, Li was simultaneously recovered. Effect of several parameters on the leaching efficiency of P was investigated, and the properties of P-SRF in acid and neutral conditions were clarified. In the whole process, the recovery efficiencies of Li and P were more than 99.5%, and furthermore, the synthesized P-SRF had high water-absorbing capacity and low release rate in both acid and neutral conditions. Mechanism study indicated phosphorus was recovered in the form of HPO42-/H2PO4- from spent LFP battery. HPO42-/H2PO4- reduced the activation energy of the condensation reaction between urea and acrylic acid to accelerate the reaction. Meanwhile, the low release rate of P-SRF in low pH was ascribed to the buffering effects of HPO42-/H2PO4- . Furthermore, pot experiments showed P-SRF effectively promoted the growth of maize. This study provided a profitable approach for high value-added recovery of spent LFP battery, and the recovered hydrophosphate could be further transferred into P-SRF with considerable acid-resistance, which has potential application in acid soil, horticulture and slope treatment.