The development of all-solid state batteries is of significant interest as a solid electrolyte enables the removal of the flammable solvent phase and is stable to much higher potentials than modern batteries. We wish to perform in situ measurements on two all solid-state batteries to develop our fundamental understanding of the diffusion processes that occur during cycling. The all solid-state garnet materials under investigation offer excellent structural stability, high ionic conductivities, and do not react in contact with lithium metal anode. By studying the interfacial diffusion with a structurally equivalent electrode we hope to greatly enhance our understanding of the lithium diffusion mechanisms and rates, enabling further structural modifications to enhance the beneficial properties within a future all solid-state battery.