Prioritized Lithium Extraction From Spent Lithium‐Ion Batteries via Low‐Temperature Chlorination Mediated by Seawater‐Derived Chlorides

ABSTRACT Chlorination roasting has emerged as a promising pyrometallurgical strategy for the selective recovery of lithium from spent lithium‐ion batteries (LIBs). In this study, a natural roasting agent, seawater‐derived chlorides, was employed to selectively extract lithium from spent LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode. MgCl 2 ·6H 2 O, a main component of seawater desalination by‐products, was investigated as a roasting agent to explore its chlorination mechanism and optimal roasting conditions. Under optimal roasting conditions (550°C, 4 h, NCM523/MgCl 2 ·6H 2 O mass ratio of 1:3, air atmosphere), lithium was selectively converted into soluble LiCl with a leaching efficiency of 98.36%, whereas over 99.99% of the transition metals remained in the form of insoluble metal oxides, achieving the highly selective pre‐extraction of lithium. In contrast, the roasting of anhydrous MgCl 2 is difficult to achieve the selective conversion of lithium, accompanied by the formation of partial transition metal chlorides. Thermodynamic analysis reveals that the formation of LiCl is thermodynamically more favorable, and the DFT calculation indicates that longer Li‐O bonds within the NCM523 structure break more easily, facilitating lithium to escape from the lattice to achieve selective conversion. Unlike the solid–solid reaction of anhydrous MgCl 2 with NCM523, the roasting process of MgCl 2 ·6H 2 O that occurs due to its own thermal hydrolysis is a gas–solid chlorination process, which selectively chlorinates Li in NCM523 using the released HCl and Cl 2 gases. Additionally, the chlorides extracted from the seawater as a chlorination agent further confirmed the effectiveness of the recovery process. Economic and environmental assessments demonstrate that this strategy reduces energy consumption and greenhouse gas (GHG) emissions, confirming its sustainability and cost‐effectiveness. Overall, this work offers an efficient and economic approach for recovering valuable metals from spent LIB cathode.