A novel approach for Al-doped sintering of garnet solid electrolyte

Abstract

Garnet based solid-state electrolyte Li6.75La3Zr1.75Ta0.25O12 (LLZTO) is one of the most promising electrolytes for advanced all-solid-state lithium batteries. However, the ceramic electrolyte is difficult to densify under normal sintering conditions, and hence the Li+ transportation via grain boundary is significantly limited by the loose contact between electrolyte granules, resulting in a high Li+ ionic impedance. Herein, we report a novel 2-step approach to obtain a relatively dense LLZTO ceramic pellet by a special Al-doping method, in which the Al was derived from the erosion of the corundum milling beads by LiOH during ball milling. This approach enables the simultaneous distribution of the aluminum (Al) within the LLZTO lattice and uniformly within the grain boundary, serving as a sintering aid, effectively boosts the fusion of grain boundary and reduced the failure rate during the sintering process. The ceramic pellet had a conductivity of 8.13 × 10−4 S cm−1, higher than that without Al-doping or using Al2O3 as dopant. This method provides an easier way to sinter the garnet ceramic electrolyte.