Research on the extraction mechanism of dibenzo-14-crown-4 ether to specific recovery Li+ from spent lithium-ion battery raffinate

The flourishing growth of electric vehicle market has led to pile of spent lithium-ion batteries (LIB), efficient treatment and recovery of retired LIBs is crucial for ecological environment and human health, especially the terminal treatment of spent lithium-ion battery raffinate (SLR). For selectively recycle Li + from SLR (the lithium and sodium concentration reaches up to 1000 mg/L and 31,200 mg/L, respectively), dibenzo 14-crown-4 ether (DB14C4) is synthesized as extractant for lithium due to the excellent size-match effect. The extraction performance of DB14C4 is evaluated from aspects of dosage, temperature, organic/aqueous phase (O/A) ratio, adsorption kinetics, adsorption selectivity and reusability through liquid-liquid extraction. The results manifested that DB14C4 exhibited fast adsorption kinetics and reached saturation in 1 h, and reached the highest adsorption capacity of 22.1 mg/g with concentration of 0.03 mol/L, O/A ratio of 1:4 and temperature of 25 °C. Besides, DB14C4 has excellent selective adsorption for Li + with lithium partition coefficient of 10.2 mL/g and Li + /Na + separation factor of 13.2. Furthermore, the selectivity of DB14C4 to Li + is studied by density functional theory calculation, including structure optimization, molecular orbital analysis, charger transfer and natural bond orbital (NBO) analysis. The results show that DB14C4 preferentially complex with Li + with lithium ion lies in the center plane of crown ether ring, and the DB14C4-Li + complex has higher charge transfer and bigger stabilization energy than DB14C4-Na + . This paper provides a feasible method for lithium recovery from SLR to guarantee sustainable lithium supply for electric vehicles, and offers brand-new perspectives to evaluate the full life cycle of LIBs.