Composition-Dependent Interlayer Stability and Oxygen-Vacancy Formation in Ni–Co–Mn Layered Oxides: Implications for Lithium-Ion Battery Cathode Recycling

Layered transition-metal oxides are key cathode materials for lithium-ion batteries and promising feedstocks for direct recycling. Their recycling behavior is strongly governed by oxide-framework stability, interlayer interactions, defect formation, and residual lithium content. In this work, spin-polarized density functional theory calculations were employed to investigate the composition-dependent structural stability of Mn- and Co-doped NiO2-based systems. The Co and Mn contents were systematically varied to evaluate interlayer distances, interlayer binding energies, oxygen-vacancy formation energies, and the influence of residual lithium. The results indicate that transition-metal composition strongly affects both the interlayer coupling strength and the energetic preference for oxygen-vacancy formation. In particular, compositional changes modify the balance between structural integrity and layer separability, while residual lithium further alters the stability of the layered framework. These findings clarify the roles of cation chemistry and defect formation in governing the propensity for delamination in spent layered cathodes. The results provide atomistic design principles for selecting recycling routes, direct reduction, or liquid-phase delamination for the studied cathode materials and may support the development of more efficient, composition-specific recycling strategies.