Fig. 2: Identification of incomplete oxygen redox activity.

a Initial charge and discharge curves of Li | |N36 coin cell in the voltage range of 2.0-4.7 V at 20 mA g−1 with specific points marked for ex-situ SXAS measurements. SXAS results of the (b) Ni L-edge, (c) Mn L-edge, and (d) O K-edge collected at pristine, charge to 4.45 V, charge to 4.7 V, and discharge to 2.0 V states. The FY mode was applied for Ni and O and the iFY mode was applied for Mn. e O K-edge RIXS spectra collected at an excitation energy of 531 eV at pristine, charge to 4.7 V, and discharged to 2.0 V states in the first cycle and (f) an enlarged view of the elastic region (0–1 eV).