Searching for low-cost Li MO compounds for compensating Li-loss in sintering of Li-Garnet solid electrolyte

Cubic Li-Garnet Li7La3Zr2O12 (c-LLZO) is one of the promising solid-state electrolyte candidates for the next generation high safety solid-state batteries. However, preparing the electrolyte has many challenges. Li-loss during high temperature sintering is one of them. Mother powder with the same component of green garnet pellets is often used to co-fire with the pellets to compensate the Li-loss. Due to the high weight ratio of rare earth element La and non-recyclability of mother powder, it is worthy to explore low-cost mother powders to replace them. In this paper, low cost compounds such as Li5AlO4, Li2TiO3, Li2SiO3, Li4SiO4 and (Li2O)x-(ZrO2)1-x (x = 0.6–0.8) are investigated for substitution of the mother powder for compensating Li-loss during the sintering of LLZO. Dense Li6.4La3Zr1.4Ta0.6O12 (LLZTO) samples have been prepared by sintering with (Li2O)0.733(ZrO2)0.267 powder at 1150 °C for 5 h with the relative density of 95% and conductivity of 5.7 × 10−4 S cm−1 at 25 °C, which show same performance with LLZTO ceramics sintered with LLZO mother powder.