Dynamically Constructing Lanthanum Oxide on Ruthenium to Enhance Lithium-Oxygen Interfacial Reactions

Reversibly tuning the active structure of air cathodes in response to dynamic electrochemical conditions has long been sought for aprotic lithium-oxygen batteries (LOBs). Here, we report a charge/discharge-regulated transformation of lanthanum oxide nanocrystals on ruthenium nanoparticles (La₂O₃─Ru) as a cathode catalyst. During discharge, high-energy La₂O₃ nanocrystals are electrochemically formed, whereas in the subsequent charge process they undergo catalytic decomposition, enabling autonomous regeneration of active catalytic sites throughout cycling. Integrated experimental characterization and first-principles calculations reveal that the supported Ru not only dictates the reversible La₂O₃ formation-decomposition, but also modulates the O 2p electronic states of La₂O₃ near the Fermi level. This La₂O₃─Ru heterojunction electronic restructuring establishes a direct electron-transfer channel from the heterojunction catalyst to discharged products, which accelerates lithium-oxygen interfacial reaction kinetics and enhances discharge capacity. Consequently, La₂O₃─Ru-based LOBs exhibit low charge overpotential, improved reversibility, and high discharge capacity, achieving 5000 mAh g^-1 for 46 cycles and markedly outperforming either solid-phase or liquid-phase systems. Leveraging the reversible nature of this heterojunction catalyst resolves the long-standing trade-off between limited capacity and cycling stability, offering a paradigm for designing adaptive catalysts that advance LOBs toward practical high-capacity, durable operation.