A novel promotion strategy for microstructure and electrical performance of garnet electrolytes via Li₄GeO₄ additive

Cubic Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (c-LLZTO) electrolyte is one of the most promising solid electrolytes. However, it is rather difficult to promote its electrical performance while reducing process parameters. Therefore, Li₄GeO₄ is applied as the additive in liquid sintering of LLZTO ceramics in this study. The LLZTO@Li₄GeO₄/Li₂O composite electrolyte sintered at 1180 °C for 3 h performs a significantly promoted microstructure and electrical performance, the ionic conductivity of which reaches 5.77 × 10⁻⁴ S cm⁻¹ at 25 °C. The Li₄GeO₄/Li₂O eutectic phase contributed prominently, in which the high concentration of Li⁺ seaming the LLZTO grains tightly. Meanwhile, Li⁺ conduction in the consecutive conductive pathways constructed by [GeO₄] groups among the grains was greatly stimulated. With the modification of the grain boundary, an improved garnet electrolytes/Li anode interface performance is produced. The Li/Au|LLZTO@Li₄GeO₄/Li₂O|Au/Li symmetrical cell is able to cycle stably for more than 500 h at the current density of 0.1 mA cm⁻² at room temperature.