Fig. 2: Operando XPS of metal | LLZO | Li cells.

a Charge/discharge profiles and corresponding XPS spectrum according to the Li plating/stripping states during the first cycle and spectra from four cycles along with their composition profiles: b Li 1 s with Au 4 f, c Li 1 s with Ag 3 d, and d Li 1 s with Zn 2p3. Red and green profiles correspond to the intermediate states between the pristine state and EoLP and EoLS.