Ionic conductivity of Ga-doped LLZO prepared using Couette-Taylor reactor for all-solid lithium batteries

A Couette-Taylor reactor and a batch reactor were used to synthesize garnet-related LLZO materials (Li7-3xMxLa3Zr2O12, M = Ga, Al) for all-solid batteries, and the properties of the resulting samples were compared. Ga-doped LLZO synthesized with the Couette-Taylor reactor comprised cubic phase primary nanoparticles; the calculated lattice parameter and crystallite size for the Couette-Taylor and batch reactor samples were a = 12.98043 Å and 129.8 nm and a = 12.97568 Å and 394.5 nm, respectively. The parameters for the Al-doped LLZO congener synthesized with the Couette-Taylor reactor were a = 13.10758 Å, c = 12.67279 Å, and 132.5 nm. The cross-section of the Ga-doped LLZO pellet synthesized with the Couette-Taylor reactor showed a denser microstructure than that of the other pellets, with a relative density of 98%. The total ionic conductivity of the Ga-doped LLZO pellets synthesized with the Couette-Taylor reactor was 1.2-1.75 × 10−3 S/cm at 25 °C. This value contrasts sharply with that of the sample from the batch reactor (3.9 × 10−4 S/cm). This is may be related to the large size of Ga doped into the LLZO crystallite structure and the primary nanoparticles, which promoted sintering of the pellet.