Anchoring Ligand Electron Enables Robust Metal‐Oxygen Coordination Toward 4.5 V O3‐Type Sodium‐Ion Battery Cathodes

Abstract High‐voltage operation enables sodium‐sufficient O3‐type layered oxides to approach the maximum achievable energy densities for practical sodium‐ion batteries (SIBs). This high‐voltage regime, however, induces structural degradation strongly correlated with oxygen redox activity, a mechanism still incompletely resolved. Using prototypical O3‐type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM) as a model system, we identify the origin of this instability as a detrimental feedback loop between σ‐type oxygen redox and cation migration. We thus propose an “anchoring ligand electron (ALE)” strategy, employing a multi‐level screening protocol to identify optimal anchor agents that confine oxygen redox to stable π‐type configurations with robust metal‐oxygen coordination. The ALE‐engineered NFM cathode mitigates excessive oxygen ligand electron transfer, achieving record capacity retention at an ultrahigh voltage of 4.5 V after 300 cycles. The superior cyclic stability is demonstrated to be closely associated with the stable π‐type oxygen redox and suppressed metal‐oxygen decoordination. This ALE strategy expands the optimization pathway toward ultrahigh‐voltage and high‐energy‐density cathodes.