Reaction-field-regulated Fe₂O₃/carbon-paper cathodes for reliable lithium–oxygen energy-storage materials

Abstract

Emerging energy-storage materials require electrode architectures that not only enhance electrochemical activity but also regulate transport, reaction distribution, discharge-product accumulation, and structural reliability. Lithium–oxygen batteries are attractive high-energy-density systems; however, their practical performance is strongly limited by oxygen depletion, heterogeneous Li₂O₂ deposition, pore blockage, film-resistance growth, charge polarization, and mechanically induced degradation within porous cathodes. Herein, ultralow Fe₂O₃ loading (~ 1 wt%) on P50 carbon-paper cathodes is investigated as a reaction-field-regulating material strategy for improving Li–O₂ cathode operation. A coupled physicochemical framework was developed to resolve oxygen transport, lithium-ion migration, electronic and ionic charge conservation, Butler–Volmer interfacial kinetics, Li₂O₂ deposition/decomposition, porosity evolution, film-resistance growth, and Li₂O₂-induced stress formation. Compared with pristine P50, the Fe₂O₃/P50 cathode increased final oxygen availability by 26.8% and improved the Reaction Uniformity Index by 28.6%, demonstrating that dispersed Fe₂O₃ domains redistribute electrochemical activity across the porous carbon-paper network. This redistribution reduced mean Li₂O₂ thickness by 24.1%, improved porosity retention by 13.0%, decreased film resistance by 31.7%, and lowered charge overpotential by 7.4%. Mechanically, Fe₂O₃/P50 reduced maximum Von Mises stress by 33.4%, high-risk stressed area by 46.5%, and the Mechanical Reliability Index by 41.1%. The predicted 7.4% reduction in charge overpotential was quantitatively consistent with the experimentally reported ~ 7.0% reduction for Fe₂O₃/P50 cathodes, corresponding to a normalized RMSE of 0.0028. Additional qualitative agreement was obtained with reported XRD evidence of reversible Li₂O₂ formation/decomposition and SEM observations of less localized Li₂O₂ deposition. These results indicate that ultralow Fe₂O₃ loading acts beyond conventional catalytic acceleration, functioning as a materials-level regulator of reaction uniformity, transport preservation, Li₂O₂ distribution, and mechanical reliability. The study provides a design principle for developing reliable metal-oxide-modified carbon cathodes for next-generation Li–O₂ energy-storage materials.