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

Abstract

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=12.98043Å and 129.8nm and a=12.97568Å and 394.5nm, respectively. The parameters for the Al-doped LLZO congener synthesized with the Couette–Taylor reactor were a=13.10758Å, c=12.67279Å, and 132.5nm. 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 1.2–1.75×10−3S/cm at 25°C. This value contrasts sharply with that of the sample from the batch reactor (3.9×10−4S/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.