A Green Recyclable Process for Selective Recovery of Li and Fe from Spent Lithium Iron Phosphate Batteries by Synergistic Effect of Deep Eutectic Solvent and Oxygen

This work designs a new method for recovering spent LiFePO4 cathode materials, aiming to address issues with traditional hydrometallurgy processes such as complex operations, low lithium recovery rates, and high wastewater discharge. The method involves using a deep eutectic solvent (DES) composed of chloroacetic acid and ethanol, and oxygen as an oxidant, for the cooperative leaching of LiFePO4 powders. Based on the acidic nature of the DES and the oxidizing properties of oxygen, LiFePO4 was undergone an in-situ transformation into solid FePO4, while 100% of lithium was dissolved in the DES with high selectivity. The FePO4 product can be recovered by filtration, and the addition of oxalic acid to the filtrate allows for lithium recovery. Importantly, the structure of the DES remained unchanged after use, allowing for three recycling cycles without a significant decrease in LiFePO4 recovery efficiency. This process is environmentally friendly, with no generation of acidic or alkaline wastewater, and boasts high metal recovery rates, showcasing its huge potential for application.