Selective recovery of valuable metals from NCM cathode scraps: A pretreatment-free process
Abstract
In the recycling of spent lithium-ion batteries, pretreatment methods for separating cathode materials from aluminum current collectors are essential to mitigate the impact of impurity aluminum. However, these methods are typically energy-intensive, consume organic reagents, or result in element loss. In this study, we proposed an endogenous hindering strategy to reduce the effect of Al impurities in the leaching process, thereby achieving the stepwise recovery of Li and transition metals without pretreatment. In a mildly acidic hydrothermal environment, the interaction between aluminum current collectors and cathode materials results in the formation of AlO(OH) interlayers, which preserves the sandwich-like structure of the leaching residue while selectively extracting lithium. After the lithium is extracted, the cathode materials are transformed into a low-valence transition metal hydroxide. In the sandwich-like structure, the majority of H+ are consumed by the transition metal hydroxide layers, which are also more prone to reacting with H+. Consequently, in an acidic environment, transition metals are preferentially leached compared to the aluminum current collectors. In the end, 90.0?% of Li and more than 95.0?% of transition metals were successfully recycled, with Al being conserved within the leaching residue. Consequently, the targeted leaching of valuable metals obviates the necessity for pretreatment, enhances the recovery rates of valuable metals, and mitigates substantial reagent consumption during separation processes. This study offers new perspectives on the recycling of valuable metals from spent lithium-ion batteries.