Na4Co3(PO4)2P2O7 through Correlative Operando X-ray Diffraction and Electrochemical Impedance Spectroscopy

Na4Co3(PO4)(2)P2O7, a high-voltage positive Na-ion electrode material, is thoroughly analyzed by coupling operando X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) measurements. Na4Co3(PO4)(2)P2O7 follows a complex structural evolution upon electrochemical cycling four consecutive biphasic reactions followed by a single-phase process at the end of the charge. The coupling of XRD and EIS techniques allows the correlation between the phase transformation sequence and transport properties so as to unlock the factors governing the electrochemical performance of Na4Co3(PO4)(2)P2O7.