Waste minimization in all-solid-state battery production via re-lithiation of the garnet solid electrolyte LLZO

Abstract

Oxide-ceramic based electrolytes such as Li7La3Zr2O12 (LLZO), are one of the most promising solid electrolytes for application in all-solid-state batteries. However, most of its constituents are listed as critical raw materials, highlighting the need to minimize waste during synthesis and processing. Therefore, we investigated the re-use of aged LLZO powder and aged LLZO green foils produced by tape-casting, an industrial processing route suitable for ASSBs. We established a new synthesis route to fully recovery Li-poor LLZO and pyrochlore phase La2Zr2O7 by simply adding a Li source during firing. By using recycled LLZO powder in a <200 μm thick cast tape, we were able to prove a similar ionic conductivity of 2.1 × 10−4 S cm−1 at room temperature and a critical current density of 0.75 mA cm−2 at 60 °C compared to fresh powder. This simple and efficient re-synthesis strategy might hold the potential to minimize waste streams of critical raw materials in future industrial production processes of solid-state batteries.