Impurity Impacts of Recycling NMC Cathodes

The skyrocketing demands for electric vehicles cause large quantities of spent lithium-ion batteries (LIBs) and pressure on the global supply chain, leading to raw materials shortages and cost increases. In LIBs, LiNi_xMn_yCo_zO₂(NMC) cathodes are one of the major cathode materials. Thus, recycling NMC cathodes from spent lithium-ion batteries is emerging because they contain abundant valuable materials, which can be considered unique “mineral” sources. Impurities are one of the main concerns for introducing recovered materials back into new battery manufacture because impurities are typically considered to impair the properties of recovered materials. However, some impurities can beneficially act as dopants or coatings. To comprehensively understand the effects of different impurities and treat impurities properly, this review summarizes the origin and species of possible impurities which can be introduced during different pretreatment processes, analyzes the methods to remove impurities, and discusses the effects of impurities on the regeneration process and recovered materials. This work also outlines future perspectives for fundamental research about impurities and relevant challenges of the recycling industry, helps academia and manufacturers to create new impurity standards of recovered cathode materials, and suggests opportunities for achieving a circular economy for the lithium-ion batteries industry.