Improved Ga-doped Li7La3Zr2O12 garnet-type solid electrolytes for solid-state Li-ion batteries

Li7La3Zr2O12 (LLZO) is one of the most competent candidates as a solid electrolyte for next-generation Li-ion batteries. Although the stabilization of the cubic phase is necessary to gain high ionic conductivity. This study applies the sol–gel combustion method to prepare Ga-doped LLZO solid electrolytes. The X-ray diffraction patterns revealed the evolution of the cubic phase with Ga content as a dopant. Densification properties were investigated using SEM. Adding 0.4 mol of gallium increased the relative density of the sample from 85 to 94% when sintered at 1150 °C. The effect of Ga-doping on electrochemical properties is investigated in detail using A.C. impedance spectroscopy at different temperatures. The result revealed that this study’s optimum concentration of the Ga dopant is 0.2 mol and exhibits the highest conductivity of 7.81 mS cm−1 at 30 °C. The distribution of relaxation times (DRT) method is used to define the time-constant responses for different resistive components in the solid electrolyte by characterizing them as a function of frequency and capacitance. The values are then quantified using the equivalent circuit model (ECM). The activation energies for bulk and grain boundary conductivity are extracted from the DRT plots to depict changes as a function of dopant concentration. The 0.2 mol-doped Ga sample with lower relative density showed the highest total conductivity of 5.85E − 03 S·cm−1 at 20 °C, at which the activation energy for grain boundary conductivity reached 0.39 eV. The highest activation energy of 0.78 eV for the grain boundary conductivity is reported for the 0.4 mol Ga-doped sample.