Simulating the influence of Cu impurities on the performance of NMC811 cathodes for re-synthesis from recycling

The recycling of Lithium-Ion Batteries (LIBs) has gained increasing significance but presents considerable challenges. During the mechanical crushing and sorting of spent LIBs, the resulting black mass exhibits a complex chemical composition. Despite costly purification processes, impurities can easily contaminate the final recycled materials. Understanding the role of these impurities is crucial, as they can impact the electrochemical performance, material stability, and durability of the recovered active materials. This study aims to investigate the impact of copper impurities from spent LIBs on the physical-chemical and electrochemical properties of NMC811 (LiNi0.8Mn0.1Co0.1O2) and evaluate how crystallization procedures influence these properties. NMC811 was synthesized via oxalate co-precipitation, enabling precipitation without additional complexing agents or an inert atmosphere, aspects that make the synthesis promising for integration into closed-loop recycling of LIBs. Specifically, two levels of Cu2+ doping (0.66 at.% and 1.09 at.%, relative to the total metal concentration in the precursor blend) were investigated and compared with NMC synthetized in absence of Cu. These doping levels were chosen based on the copper concentrations in leachates obtained from dust in a pilot plant. Physical-chemical analysis revealed that copper can be incorporated into the NMC structure without phase segregation, and low copper concentrations can enhance the electrochemical performance, improving both specific capacity and capacity retention.