Constructing Coupled Ion-Electron Pathways for Efficient Oxygen Chemistry in Solid-State Lithium-Oxygen Batteries

Solid-state lithium-oxygen batteries (SSLOBs) are ideal energy storage systems because of their intrinsic safety and ultrahigh theoretical energy density. However, practical implementation is severely hindered by sluggish oxygen-redox kinetics at solid-state air cathodes, where achieving fast ionic/electronic transport and high catalytic activity concurrently remains a formidable challenge. Here, we demonstrate a strategy to construct coupled ion-electron pathways within a monolithic mixed ionic-electronic catalyst (MMIEC) cathode. Using LiCoO₂ (LCO) as a model system, a seamless interface with the solid electrolyte is established via an ultrafast thermal integration process, creating continuous percolation networks for both Li⁺ and electrons. These coupled pathways ensure unimpeded charge transport at the electrochemical interface, while surface-enriched Co³⁺/Co⁴⁺ redox couples act as intrinsically active catalytic centers. This architecture mediates oxygen-redox reactions by accelerating LiO₂ ^* formation during discharge and promoting the reversible decomposition of Li₂O₂ upon charge. Consequently, the MMIEC-based SSLOB delivers an ultrahigh discharge capacity of 12970 mAh g^-1, maintains stable cycling for more than 400 cycles, and exhibits a reduced voltage polarization of 1.0 V. This work demonstrates that coupling catalytic activity with robust ionic-electronic pathways is crucial for advancing high-performance SSLOBs.