Structural and electrochemical properties of Fe-doped Na2Mn3-xFex(P2O7)2cathode material for sodium ion batteries

A series of Fe-doped Na2Mn3-xFex(P2O7)(2) (x = 0.0, 0.5, 1.0, 1.5 and 2.0) compounds have been successfullyprepared by using sol-gel method. Rietveld refinement results indicate that single phase Na2Mn3-xFex(P2O7)(2)with triclinic structure can be obtained within 0 <= x <= 2 although no Na2Fe3(P2O7)(2) existing under our experimental conditions, and the cell parameters (including a, b, c and V) are decreasing with the increasing of x. Our results reveal that Na2Mn3(P2O7)(2) exhibits an electrochemical activity in the voltage range of 1.5 V-4.5 V vs.Na+/Na when using as the cathode material for SIBS although it gives a limited rate capability and poor capacity retention. However, the electrochemical performance of Fe-doped Na2Mn3-xFex(P2O7)(2) (0 <= x <= 2) can beimproved significantly where cycle performance and rate capability can be improved significantly than that of the pristine one. Sodium ion diffusion coefficient can be increased by about two orders of magnitude with the Fe doping content higher than x = 0.5.