All solid-state Li batteries are foreseen as the future state of battery technology due to their safety, high energy density, and high potential window as compared to the present organic liquid electrolyte batteries. Li-ion conducting garnet-type electrolytes have received considerable research interests due to their compatibility with Li metal anode, good ionic conductivity (10^-3 S/cm) and wide electrochemical window (~ 6V vs. Li).¹ Garnet-type Li_6.5La_3-xA_xZr_1.5-xTa_x+0.5O₁₂ (A = Ca, Sr, Ba; x = 0.1, 0.5) solid electrolytes were prepared by conventional solid-state synthesis and spark plasma synthesis (SPS).^2-4 The formation of the cubic garnet-type structure was confirmed by powder X-ray diffraction (PXRD). Microstructure of the solid electrolytes were analysed by scanning electron microscopy (SEM) and cross-sectional analyses showed that the SPS processed samples are highly dense compared to the same compositions prepared by conventional solid-state route. The AC electrochemical impedance spectroscopy (EIS) was used to measure the impedance of solid electrolytes and found that all samples exhibit bulk conductivity in the order of 10^-4 S/cm at room temperature. SPS processed samples showed an excellent Li-ion charge transfer resistance and the highest critical current density compared to the samples prepared by conventional solid-state synthesis. X-ray photoelectron spectroscopy (XPS) analyses were conducted on SPS-processed samples to quantify the impurity layers on garnet surface. Electrochemical performance of a hybrid cell consisting of liquid Li-ion electrolytes and garnet electrolyte will be discussed.

References

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