Improvement of PEO-based composite solid electrolyte sheet using particle-size-controlled Ga-Rb-doped LLZO with high ion conductivity

In this study, a Li_6.5Ga_0.2La_2.95Rb_0.05Zr₂O₁₂ garnet-type solid electrolyte with high ion conductivity was prepared. The particle size was reduced to the nano size through a ball milling process, and the effect of the change in particle size on the all-solid-state batterie was investigated. As all-solid-state batteries have better stability than liquid electrolytes and serve as separators to help increase energy density, much research has been conducted recently. However, their conductivity is much lower than that of the liquid electrolyte. Therefore, an experiment was conducted on the difference in particle size to improve the ionic conductivity and energy density. Reducing the average particle size of the LLZO samples from approximately 10 to 0.6 μm using a ball milling process increased the ionic conductivity of the pellet from 1.27 × 10–3 to 1.58 × 10–3 S cm-1 at 25 °C. The ionic conductivity of the sheet decreased from 2.96 × 10–4 to 2.60 × 10–4 S cm-1 at 70 °C, but lithium transference number increased from 0.56 to 0.64. Therefore, the structural and electrochemical properties of the LLZO-bare and LLZO-ball-milled were investigated using powder X-ray diffraction analysis, field-emission scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic measurements.