Li-ion battery technology has advanced significantly in the last two decades. However, future energy storage demands will require safer, cheaper and higher performance electrochemical energy storage. The development of advanced energy storage batteries such as solid-state and Li – S batteries, could enable a significant increase in energy density compared to Li-ion batteries. While the primary strategy for improving performance has focused on state-of-the-art Li-ion components, this work seeks to develop solid-state batteries employing Li metal anodes. One approach entails the replacement of a liquid with a solid electrolyte. Recently, the ceramic electrolyte, Li₇La₃Zr₂O₁₂ (LLZO) cubic garnet, has shown promise owing to its unique combination of properties such as high Li-ion conductivity (~1 mS/cm at room temperature) and electrochemical stability between 0-6 V vs. Li/Li⁺. The purpose of this work was to characterize the LLZO interface stability upon air exposure and its effect on the Li-LLZO interface charge transfer resistance. Specific attention was given to LLZO phase purity, and relative density. The LLZO was densified using a rapid densification process achieving > 97% relative density, with < 10% grain boundary resistance; effectively consisting of an ensemble of single LLZO crystals. Furthermore, the LLZO interface-charge-transfer has been related to the LLZO surface preparation by Electrochemical Impedance Spectroscopy (EIS) with equivalent modeling to understand the conduction mechanism at the Li-LLZO interface. X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Raman Spectroscopy were used in a concerted effort to determine the reaction pathways that govern chemical reactions between LLZO and ambient air. It will be shown that while several days of exposure to air results in high Li-LLZO interface charge transfer resistance, 24 hours of exposure to air (50 % relative humidity) had a negligible effect on interface resistance.