Built-in anionic equilibrium for atom-economic recycling of spent lithium-ion batteries


Recycling spent lithium-ion batteries (LIBs) is crucial to address environmental and global sustainability issues. Wet chemical extraction of valuable metals is currently the most practical disposal technology, but it is challenging due to excessive chemical consumption and concomitant secondary pollution. In this study, a built-in anionic equilibrium strategy was proposed to recycle spent LiFePO4 (sLFP) cathodes with high atom economy. The selective extraction of lithium and phosphorus was successfully achieved in deionized water under oxygen pressure by the anionic equilibrium between OH- produced by oxygen reduction and PO43- released from sLFP. The formed LiFePO4OH phase limited the lithium leaching efficiency to 65.6%, so the trapped lithium was further extracted by rebuilding the anionic equilibrium after adding phosphoric acid with a low H3PO4/Li molar ratio. The degraded LiFePO4 evolved into a fusiform Fe5(PO4)4(OH)3·2H2O crystal, and 90.19% of lithium and 19.88% of phosphorus in sLFP can be recovered as Li3PO4 products. Therefore, this built-in anionic equilibrium mechanism contributes to reduce chemical consumption and high-saline wastewater, thus providing a sustainable hydrometallurgical recycling route for spent lithium-ion batteries.



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