Recently, many sorts of lithium batteries have been studied such as all solid and lithium-air batteries etc., for EV and ESS applications. Especially, all solid battery is one of the candidates for a large-sized battery in regard of the safety problem. Garnet-type LLZO electrolyte has good advantages with a high ionic conductivity and electrochemical potential window. However, it is reported that there are difficulties to prepare LLZO(Li₇La₃Zr₂O₁₂) pellets with high relative density. In this study, LLZO material was doped by the different elements of Al, Nb, Ta by co-precipitation process. Furthermore, we studied the effects of lithium excess concentration of Al-doped LLZO. We investigated not only the change of cubic and tetragonal structure but also electrochemical properties according to the synthesis conditions. As a result, ionic conductivity of Al-doped LLZO material was about 3x10^-4 S/cm at room temperature, indicating a wide electrochemical window of 0~5.5V. Furthermore, we will introduce the electrochemical properties of unit cell using LLZO material in more detail.