Recycling nickel-rich cathodes toward structural and functional circularity: a perspective

The increasing use of nickel-rich (Ni ≥ 0.6) layered oxide cathodes in lithium-ion batteries creates an urgent need for recycling, for which existing elemental-recovery methods are not well suited. Unlike process-based classifications, the present framework evaluates recycling routes by whether they recover only the elemental inventory, preserve the layered crystal framework, or restore and intentionally improve electrochemical function. Here, we reconceptualize cathode recycling as three progressive levels of material circularity: elemental recovery, structural preservation, and functional restoration. The specific degradation modes of Ni-rich cathodes, including surface rock-salt reconstruction, cation disorder, and intergranular fracture, not only limit the effectiveness of conventional pyrometallurgical and hydrometallurgical processes but also define the precise materials science targets that higher-level recycling strategies must address. Against this framework, we critically assess advances in direct recycling and upcycling, highlighting relithiation chemistry, molten-salt recrystallization, and Artificial Intelligence-guided process control as the most capable approaches for achieving structural and functional circularity at scale. Closing the loop for Ni-rich cathodes requires more than just incremental improvements to existing recovery methods. It calls for a strategic shift in recycling research to preserve and restore the cathode's crystal structure.