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

Abstract

Affordable and high-energy lithium-ion batteries are pivotal for advances in sustainability. To this end, antifluorite-type Li5FeO4 cathodes have recently gained attention due to their cost-effectiveness and theoretical capacity exceeding 300 mAh g-1. Notably, metastable cubic Li5FeO4 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 O2 gas evolution. In this study, we enhance the cyclability through the incorporation of earth-abundant p-block elements into cubic Li5FeO4. We find that the covalent bonding between the oxygen species and the p-block element elevates the oxidation potential of the O2 gas release without altering the solid-state oxygen redox potential.