Sustainable Upcycling of Spent LiCoO 2 Toward High‐Stability NCM Cathode via Eutectic Molten Salt Synthesis

ABSTRACT Spent LiCoO 2 (S‐LCO) cathode materials from retired lithium‐ion batteries (LIBs) pose severe environmental threats and represent a noteworthy waste of strategic resources. The emerging regeneration/upcycling approach for S‐LCO mainly adopts solid‐state treatment, showing significant potential of short‐range, high‐efficient reactivation of S‐LCO materials. Yet it suffers from the complex pre‐determination of lithium content as well as the varying degradation degrees of S‐LCO materials from different batches of retired LIBs. Meanwhile, the cost‐effective ternary layered oxides have become the mainstream cathode materials for LIBs due to the rapid popularization of electric vehicles. Herein, we use a LiOH‐LiNO 3 eutectic molten salt as the reaction medium to upcycle S‐LCO for single‐crystalline LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM111) cathode materials. The molten salt treatment not only achieves self‐saturating relithiation and direct transformation of S‐LCO toward stoichiometric NCM111 materials but also rejuvenates the product with structural and compositional integrity for outstanding electrochemical performance. The product delivers a specific capacity of 161.6 mAh g −1 at 0.1 C and a 92.4% capacity retention after 200 cycles at 1 C, outperforming those of commercial NCM111 materials. This study provides a simple, green, and scalable approach for handling those S‐LCO materials, suggesting a sustainable and transformative solution for recycling retired LIBs.