Electrochemical impedance analysis of the Li/Au-Li7La3Zr2O12 interface during Li dissolution/deposition cycles: Effect of pre-coating Li7La3Zr2O12 with Au

The influence of pre-coating Li7La3Zr2O12 (LLZ) with Au on the charge transfer resistance (Rint) at the interface of LLZ and lithium (Li) is examined by AC impedance spectroscopy using a three-electrode system. The Au diffuses into Li after physical contact with Li, and the open-circuit potential reaches approximately 0 mV (vs. Li/Li+) accompanied by a decrease in Rint. During the Li dissolution/deposition cycles, the electrode potential changes with 0 mV as the central potential, indicating that Li metal dissolution/deposition on Li metal proceeds predominantly at the interface. Rint increases and decreases during Li dissolution and deposition, respectively, regardless of the presence or absence of the Au coating; however, the increase in Rint during Li dissolution is suppressed at the Li/Au-coated LLZ (Au-LLZ) interface. The decreased Rint is considered to be due to an increase in the effective contact area at the electrode/LLZ interface, which is achieved by pre-coating Au onto the LLZ surface.