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 (La 2 O 3 ─Ru) as a cathode catalyst. During discharge, high‐energy La 2 O 3 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 La 2 O 3 formation‐decomposition, but also modulates the O 2p electronic states of La 2 O 3 near the Fermi level. This La 2 O 3 ─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, La 2 O 3 ─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.