Unravelling the Oxygen Evolution Mechanism of Lithium‐Rich Antifluorite Prelithiation Agent Based on Anionic Oxidation

Developing sacrificial cathode prelithiation technology to compensate for irreversible lithium loss is crucial for enhancing the energy density of lithium-ion batteries. Antifluorite Li-rich Li₅FeO₄ (LFO) is a promising prelithiation agent due to its high theoretical capacity (867 mAh g^-1) and superior decomposition dynamic (<4.0 V vs. Li/Li⁺). However, the oxygen evolution mechanism in LFO remains unclear, limiting its application as an ideal prelithiation agent. Herein, we systematically track the full lifecycle oxygen footprint in LFO lattice, electrolyte and solid electrolyte interface (SEI). We demonstrate the lattice mismatch induced by the quasi-disorder rocksalt intermediate phase can activate the lattice oxygen oxidation promoting the dimerization to O₂. Specifically, in contrast to the O─O dimers formed within typical anionic-redox active cathodes, the oxidation of lattice oxygen in LFO generates O^- stabilized in Li₆-O configuration. Significantly, a pair of edge-sharing Li₆-O configurations transforms into a superoxo dimer, which further evolves into O₂ via a ligand-to-metal charge transfer process. Moreover, we demonstrate that nucleophilic intermediates threaten the stability of electrolytes and SEI. Leveraging the insights above, we offer comprehensive perspectives for the modification of ideal prelithiation agents.