Syntheses, structure and properties of a new Fillowite-type compound Na 0.48 Mn 1.22 PO 4

Abstract Searching for excellent polyanionic cathode materials for Na-ion batteries attract considerable attention in recent years. Herein, a new polyanionic cathode candidate Na 0.48 Mn 1.22 PO 4 , crystallizing in the space group R-3 with the unit cell parameters of a  = 15.3672 (17) A, c  = 43.503 (5) A and V = 8896.91 (2) A 3 , belonging to the Fillowite-type structure, is reported for the first time. In the structure of Na 0.48 Mn 1.22 PO 4 , the Mn O connectivity exhibits three-dimensional Mn O Mn network. More interestingly, some Mn 5 O 6 clusters embed in the network. Electrochemical tests revealed that Na 0.48 Mn 1.22 PO 4 can be very effectively cycled against a Na metal electrode with an average voltage of 3.35 V. In addition, The XANES and magnetic tests were also employed for the characterization of the material.