Restoring garnet oxide electrolytes via ultra-fast sintering

Garnet type solid-state electrolytes is one of the most promising electrolytes for solid-state lithium-metal batteries. However, the garnet electrolyte exhibits inadequate stability in air, leading to the formation of lithium carbonate. This reduction of lithium content in electrolytes can result in decreased ionic conductivity, increased interfacial resistance, and consequently, terrible electrochemical performance. Here, we report a fast and effective method for recovering long-time stored garnet oxide. The lithium carbonate in the long-time stored Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) is completely removed by immersing in LiOH solution followed by ultra-fast sintering. As a result, the garnet SSEs can obtain higher ionic conductivity and reduced electronic conductivity, compared with the counterpart before treatment. In addition, increased critical current density together with improved electrochemical performance of Li|LiNi_0.8Co_0.1Mn_0.1O₂ half cells are also achieved for the recovered LLZTO. This work proposes a simple strategy on recycling garnet electrolytes for the application in solid-state lithium-metal batteries.