Surface redox on Li[Ni1/3Mn1/3Co1/3]O2 characterized by in situ X-ray photoelectron spectroscopy and in situ Auger electron spectroscopy

This work applies in situ Auger electron spectroscopy and X-ray photoelectron spectroscopy to the study of surface redox on LiNi1/3Mn1/3Co1/3O2 during charging and overcharging. We observe that all three transition metals are surface redox active, and that oxygen oxidation occurs for voltages above ≈4.2 V O2 loss above ≈4.7 V, mediated by carbon redox, leads to partial reduction of the transition metals at the surface during overcharging.