Gallium-Doped LiLaZrO Garnet-Type Electrolytes with High Lithium-Ion Conductivity.

Owing to their high conductivity, crystalline LiGaLaZrO garnets are promising electrolytes for all-solid-state lithium-ion batteries. Herein, the influence of Ga doping on the phase, lithium-ion distribution, and conductivity of LiGaLaZrO garnets is investigated, with the determined concentration and mobility of lithium ions shedding light on the origin of the high conductivity of LiGaLaZrO. When the Ga concentration exceeds 0.20 Ga per formula unit, the garnet-type material is found to assume a cubic structure, but lower Ga concentrations result in the coexistence of cubic and tetragonal phases. Most lithium within LiGaLaZrO is found to reside at the octahedral 96h site, away from the central octahedral 48g site, while the remaining lithium resides at the tetrahedral 24d site. Such kind of lithium distribution leads to high lithium-ion mobility, which is the origin of the high conductivity; the highest lithium-ion conductivity of 1.46 mS/cm at 25 °C is found to be achieved for LiGaLaZrO at x = 0.25. Additionally, there are two lithium-ion migration pathways in the LiGaLaZrO garnets: 96h-96h and 24d-96h-24d, but the lithium ions transporting through the 96h-96h pathway determine the overall conductivity.