Li7La3Zr2O12 electrolytes doped with different amounts of Al (0, 0.2, 0.7, 1.2, and 2.5wt.%) were prepared by a polymerized complex (Pechini) method. The influence of aluminum on the structure and conductivity of Li7La3Zr2O12 were investigated by X-ray diffraction (XRD), impedance spectroscopy, scanning electron microscopy (SEM), and thermal dilatometry. It was found that even a small amount of Al (e.g. 0.2wt.%) added to Li7La3Zr2O12 can greatly accelerate densification during the sintering process. SEM micrographs showed the existence of a liquid phase introduced by Al additions which led to the enhanced sintering rate. The addition of Al also stabilized the higher conductivity cubic form of Li7La3Zr2O12 rather than the less conductive tetragonal form. The combination of these two beneficial effects of Al enabled greatly reduced sintering times for preparation of highly conductive Li7La3Zr2O12 electrolyte. With optimal additions of Al (e.g. 1.2wt.%), Li7La3Zr2O12 electrolyte sintered at 1200°C for only 6h showed an ionic conductivity of 2.0×10−4 Scm−1 at room temperature.