Spinel-Based Solid-State Reactions: From Spinel Oxides to Lithium or Sodium Layered Oxides.

Precise synthesis of multi-component layered oxides via conventional solid-state routes remains a fundamental challenge, often constrained by the disparate reaction windows and mass transport kinetics of heterogeneous precursors. In this study, leveraging the close topological relationship between spinel and layered oxides that share close-packed oxygen frameworks, we develop a spinel-templated solid-state strategy to redirect phase-evolution pathways. By integrating in situ x-ray diffraction with density functional theory calculations, we reveal distinct lithiation and sodiation pathways across mono- and multi-component spinel systems. Crucially, the anti-site defect formation energy (Eas) serves as the key energetic descriptor that captures the accessibility of cation-mixed intermediate configurations, thereby accounting for this pathway divergence. Relative to traditional multi-precursor routes, the spinel-based strategy promotes a more integrated reaction pathway, improving elemental homogeneity and suppressing impurity formation in layered cathodes. These findings highlight how precursor topology and defect-related energetics can be coupled to steer phase evolution in solid-state reactions, offering a design perspective for compositionally complex oxides and related functional materials.