Fig. 4. The mRAS and XAS spectra of pure LiOH, Li₂O, Li₂CO₃ and LLZO surface at different states.

a The color-coded mRAS spectra comparison of clean LLZO with pure LiOH, Li₂O, Li₂CO₃. b The color-coded mRAS spectra comparison of LLZO surface at different states, corresponding to the process a, e, f, h in flowchart Fig. 2. The pressure of CO₂ and H₂O are 1 mbar and 0.5 mbar separately. c Distribution of LLZO surface at different states in photon energy direction. d Distribution of LLZO surface at different states in kinetic energy direction. LLZO (blue line) is extracted from h$\nu$ = 531.9 eV, Li₂CO₃ (red line) is extracted from h$\nu$ = 533.7 eV and LiOH (green line) is extracted from h$\nu$ = 532.8 eV.