Electroanalytical Measurement of Interphase Formation at a Li Metal–Solid Electrolyte Interface

The interphase between Li metal and solid electrolytes dictates performance in Li metal batteries. For the solid electrolyte Lipon, we electroanalytically measure a capacity loss of 1.03 ± 0.16 μAh/cm2 when Lipon first contacts Li metal. Assuming this capacity is all lost to interphase formation, this corresponds to a maximum Li consumption of 5.0 ± 0.8 nm to form an interphase ∼4.7 nm thick. From dynamic electrochemical impedance spectroscopy (dEIS) during Li plating, we determine that nonlinear chaotic spectra demark this interphase formation and that this occurs immediately upon initiation of Li plating. dEIS also reveals interfacial resistance during both plating and stripping that decreases as the amount of plated Li increases.