Mechanochemical upcycling of spent LiCoO 2 to new LiNi 0.80 Co 0.15 Al 0.05 O 2 battery: An atom economy strategy

The use of strong acids and low atom efficiency in conventional hydrometallurgical recycling of spent lithium-ion batteries (LIBs) results in significant secondary wastes and CO 2 emissions. Herein, we utilize the waste metal current collectors in spent LIBs to promote atom economy and reduce chemicals consumption in a conversion process of spent Li 1- x CoO 2 (LCO) → new LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) cathode. Mechanochemical activation is employed to achieve moderate valence reduction of transition metal oxides (Co 3+ →Co 2+,3+ ) and efficient oxidation of current collector fragments (Al 0 →Al 3+ , Cu 0 →Cu 1+,2+ ), and then due to stored internal energy from ball-milling, the leaching rates of Li, Co, Al, and Cu in the ≤4 mm crushed products uniformly approach 100% with just weak acetic acid. Instead of corrosive precipitation reagents, larger Al fragments (≥4 mm) are used to control the oxidation/reduction potential (ORP) in the aqueous leachate and induce the targeted removal of impurity ions (Cu, Fe). After the upcycling of NCA precursor solution to NCA cathode powders, we demonstrate excellent electrochemical performance of the regenerated NCA cathode and improved environmental impact. Through life cycle assessments, the profit margin of this green upcycling path reaches about 18%, while reducing greenhouse gas emissions by 45%.