In Operando XRD and TXM Study on the Metastable Structure Change of NaNi 1/3 Fe 1/3 Mn 1/3 O 2 under Electrochemical Sodium‐Ion Intercalation

In operando XRD and TXM-XANES approaches demonstrate that structure evolution in NaNi1/3Fe1/3Mn1/3O2 during cycling follows a continuous change, and the formation of a nonequilibrium solid solution phase in the existence of two phases. An O3′ and P3′ monoclinic phase occur, and redox couples of Ni3+/Ni4+ and Fe3+/Fe4+ are mainly responsible in the charge voltage range from 4.0 to 4.3 V.