A unified lattice-surface engineering strategy stabilizing oxygen redox in Li-rich cathodes for all-solid-state batteries

Li-rich Mn-based layered oxides (LRMOs) are promising high-energy cathodes for all-solid-state batteries (ASSBs), but their application is limited by irreversible O₂ evolution during lattice O^2-/O₂^2- redox and interfacial degradation at high voltages. Here we report a "coat-sinter-wash" synthetic strategy that simultaneously modulates bulk oxygen redox and stabilizes the cathode surface. An ammonium tungstate precursor is first coated onto LRMO particles. The subsequent sintering generates Li vacancies and enables W incorporation into the lattice, which acts as a "chemical rivet" and enhances the reversibility of lattice oxygen redox. A final washing step reconstructs the Li-deficient surface into an in-situ spinel layer, suppressing oxygen release from the surface and mitigating structural decomposition. The resulting ASSBs achieve remarkable cycling stability with 80% capacity retention over 500 cycles (0.5 C, 25°C) and an outstanding reversible capacity of 278.2 mAh g^-1 (0.1 C, 40°C). Furthermore, an all-solid-state pouch cell with Si anode demonstrates an areal capacity of 4.55 mAh cm^-2 and a high energy density of 543 Wh kg^-1. This work provides a scalable synthetic framework for stabilizing oxygen-redox cathodes in solid-state batteries.