Fig. 2. Schematic diagram of the entire in situ experimental processes in this work.

a, b Polished LLZO pellet was vacuum annealing at 350 °C for 30 min to remove surface Li₂CO₃, but surface contaminated carbon species cannot be removed. c During the cooling process, a small amount of Li₂CO₃ will be generated on the surface of LLZO. d,e Most of the surface contaminated carbon species can be removed by annealing in 1 × 10⁻⁶ mbar O₂ at 350 °C for 30 min. f–h The clean LLZO surface then be used to investigate the reaction with CO₂ and H₂O.