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.