Closed-loop recycling of lithium iron phosphate cathodic powders via citric acid leaching

Martina Bruno; Carlotta Francia; Silvia Fiore

doi:10.1007/s11356-024-32837-6

Closed-loop recycling of lithium iron phosphate cathodic powders via citric acid leaching

Environ Sci Pollut Res Int. 2024 Mar 11. doi: 10.1007/s11356-024-32837-6. Online ahead of print.

Authors

Martina Bruno¹, Carlotta Francia², Silvia Fiore³

Affiliations

¹ Department of Environment, Land and Infrastructure Engineering, DIATI, Politecnico Di Torino, Corso Duca Degli Abruzzi 24, 10129, Turin, Italy.
² DISAT, Department of Applied Sciences and Technology, Politecnico Di Torino, 10129, Turin, Italy.
³ Department of Environment, Land and Infrastructure Engineering, DIATI, Politecnico Di Torino, Corso Duca Degli Abruzzi 24, 10129, Turin, Italy. silvia.fiore@polito.it.

PMID: 38468005
DOI: 10.1007/s11356-024-32837-6

Abstract

Lithium recovery from Lithium-ion batteries requires hydrometallurgy but up-to-date technologies aren't economically viable for Lithium-Iron-Phosphate (LFP) batteries. Selective leaching (specifically targeting Lithium and based on mild organic acids and low temperatures) is attracting attention because of decreased environmental impacts compared to conventional hydrometallurgy. This study analysed the technical and economic performances of selective leaching with 6%vv. H₂O₂ and citric acid (0.25-1 M, 25 °C, 1 h, 70 g/l) compared with conventional leaching with an inorganic acid (H₂SO₄ 1 M, 40 °C, 2 h, 50 g/l) and an organic acid (citric acid 1 M, 25 °C, 1 h, 70 g/l) to recycle end of life LFP cathodes. After conventional leaching, chemical precipitation allowed to recover in multiple steps Li, Fe and P salts, while selective leaching allowed to recover Fe and P, in the leaching residues and required chemical precipitation only for lithium recovery. Conventional leaching with 1 M acids achieved leaching efficiencies equal to 95 ± 2% for Li, 98 ± 8% for Fe, 96 ± 3% for P with sulfuric acid and 83 ± 0.8% for Li, 8 ± 1% for Fe, 12 ± 5% for P with citric acid. Decreasing citric acid's concentration from 1 to 0.25 M didn't substantially change leaching efficiency. Selective leaching with citric acid has higher recovery efficiency (82 ± 6% for Fe, 74 ± 8% for P, 29 ± 5% for Li) than conventional leaching with sulfuric acid (69 ± 15% for Fe, 70 ± 18% for P, and 21 ± 2% for Li). Also, impurities' amounts were lower with citric acid (335 ± 19 335 ± 19 of S mg/kg of S) than with sulfuric acid (8104 ± 2403 mg/kg of S). In overall, the operative costs associated to 0.25 M citric acid route (3.17€/kg) were lower compared to 1 M sulfuric acid (3.52€/kg). In conclusion, citric acid could be a viable option to lower LFP batteries' recycling costs, and it should be further explored prioritizing Lithium recovery and purity of recovered materials.

Keywords: Citric acid; Leaching; Lithium iron phosphate; Lithium recovery; Recycling.