Toward Cost-Effective High-Energy Lithium-Ion Battery Cathodes: Covalent Bond Formation Empowers Solid-State Oxygen Redox in Antifluorite-Type Lithium-Rich Iron Oxide

Affordable and high-energy lithium-ion batteries are pivotal for advances in sustainability. To this end, antifluorite-type Li 5 FeO 4 cathodes have recently gained attention due to their cost-effectiveness and theoretical capacity exceeding 300 mAh g –1 . Notably, metastable cubic Li 5 FeO 4 has achieved a reversible capacity of 346 mAh g –1, utilizing cationic iron and anionic oxygen redox reactions. However, the cyclability of solid-state oxygen redox in this system is hindered by concurrent, irreversible, and simultaneous evolution of the O 2 gas evolution. In this study, we enhance the cyclability through the incorporation of earth-abundant p -block elements into cubic Li 5 FeO 4 . We find that the covalent bonding between the oxygen species and the p -block element elevates the oxidation potential of the O 2 gas release without altering the solid-state oxygen redox potential.