To enable large-scale applications of lithium ion batteries for transportation and storage of renewable energy high energy densities, high power, reduced costs and, most importantly, safety are required. The use of liquid organic electrolytes that exhibit high vapor pressures and flammability poses a substantial safety issue in particular for large-scale systems. Solid electrolytes offer a potential solution due to their inherent chemical stability. Recently, several material systems such as Li_7-3xLa₃Zr₂Al_xO₁₂ (LLZO) have been identified that exhibit a large electrochemical window, ionic conductivities similar to those of liquid electrolytes at moderate temperatures and are stable against lithium metal, paving the way to the integration in high energy density battery cells.

In this work the synthesis and processing of fine-grained Li_7-3xLa₃Zr₂Al_xO₁₂ solid electrolyte is performed for the first time using a combination of nebulized spray pyrolysis (NSP) and field assisted sintering technique (FAST). The microstructure, i.e. grain size and microstrain, has a crucial influence on the electrochemical properties of the solid electrolyte and thereby on the all-solid-state battery performance. During sintering using FAST, the grain growth is suppressed and dense ceramics with 93 % of the theoretical density are obtained. The microstructure and the phase composition are characterized using scanning electron microscopy and X-ray diffraction, respectively. The total lithium ion conductivity of the solid electrolyte at room temperature is found to be in the order of 10^-4 Scm^-1, which is in very good agreement with the literature values. The total conductivity is determined in a wide temperature range from 220 K to 393 K for the determination of the activation energy. Galvanostatic cycling of symmetrical cells using lithium electrodes shows a good cycling stability over 100 hours. The interfacial resistance in contact with lithium metal is determined using alternating current impedance spectroscopy and is amongst the best reported values so far. Several techniques for the integration of Li_7-3xLa₃Zr₂Al_xO₁₂ solid electrolyte in an all-solid-state battery are presented and discussed.