Improved electrical transport properties in Ga/Ta co-doped LLZO under high temperature and pressure

Abstract

As a solid electrolyte for all-solid-state lithium-ion batteries, Ga/Ta co-doped LLZO has garnered significant interest because of its high conductivity and dense microstructure. However, its conductivity is still lower than that of liquid organic electrolytes. In this work, Li6.4Ga0.2La3Zr1.75Ta0.25O12 (Ga/Ta-LLZO) was synthesized by solid-state reaction, and the combined effects of elevated temperature and pressure on the electrical transport and dielectric properties of Ga/Ta-LLZO were systematically investigated over the temperature range of 24–150 °C and the pressure range of 3.3–30.2 GPa. The findings indicate that grain boundary resistance is the main contributor affecting the total resistance. Under a given pressure, as the temperature increases from 24 to 150 °C, the grain conductivity, grain boundary conductivity, and total conductivity of Ga/Ta-LLZO increase by about two orders of magnitude. At room temperature, when the pressure increases from 3.3 to 30.2 GPa, the grain conductivity, grain boundary conductivity, and total conductivity all increase by approximately one order of magnitude. The dielectric loss of Ga/Ta-LLZO decreases with the increase in temperature and pressure. In addition, this paper reveals the dielectric relaxation behavior of Ga/Ta-LLZO under high temperature and high pressure. At low frequencies, a dielectric relaxation with a giant dielectric constant is observed, which is associated with the relaxation of dipole formation due to the spatial charge polarization of lithium ions.