Photoemission Study on the Interaction Between LiCoO2 Thin Films and Adsorbed Water

Surface layers at the cathode-electrolyte interface strongly affect the performance of the Li-ion cell. Such surface layers are found during manufacturing and operation of the battery. As water can never be fully excluded from the manufacturing chain, it will form an additional surface layer situated between cathode and electrolyte. In this contribution, we investigate the interaction between the LiCoO2 electrode and H2O by a surface science approach. H2O was adsorbed stepwise onto a LiCoO2 thin film, and intermediate X-ray photoelectron spectroscopy analysis was performed after every step. Adsorption results in the formation of a Li2O/LiOH-type reaction layer on top of the electrode and downward band bending attributed to a Lit-ion transfer out of the electrode.