On-surface lithium donor reaction enables decarbonated lithium garnets and compatible interfaces within cathodes

Lithium garnets have been widely studied as promising electrolytes that could enable the next-generation all-solid-state lithium batteries. However, upon exposure to atmospheric moisture and carbon dioxide, insulating lithium carbonate forms on the surface and deteriorates the interfaces within electrodes. Here, we report a scalable solid sintering method, defined by lithium donor reaction that allows for complete decarbonation of Li6.4La₃Zr1.4Ta0.6O₁₂ (LLZTO) and yields an active LiCoO₂ layer for each garnet particle. The obtained LiCoO₂ coated garnets composite is stable against air without any Li₂CO₃. Once working in a solid-state lithium battery, the LiCoO₂-LLZTO@LiCoO₂ composite cathode maintains 81% of the initial capacity after 180 cycles at 0.1 C. Eliminating CO₂ evolution above 4.0 V is confirmed experimentally after transforming Li₂CO₃ into LiCoO₂. These results indicate that Li₂CO₃ is no longer an obstacle, but a trigger of the intimate solid-solid interface. This strategy has been extended to develop a series of LLZTO@active layer materials.