NASICON-structure Na3+xMnVxTi1-x(PO4)3/C cathode for sodium-ion battery with excellent cycling performance and high specific capacity

The recently discovered Na 3 MnTi(PO 4 ) 3 cathode material has an extremely high theoretical capacity, but its poor cycling performance makes it challenging to apply. In this work, a series of NASICON-type Na 3+x MnV x Ti 1-x (PO 4 ) 3 /C (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1) cathode materials were prepared by sol-gel method for sodium-ion batteries. X-ray diffraction (XRD) indicates that vanadium doping has increased the cell spacing within the material and the cell volume. From the results of X-ray photoelectron spectroscopy (XPS) and Energy dispersive X-ray spectroscopy (EDS) mapping images, it is shown that vanadium has been successfully doped into the material. Among them, the Na 3·3 MnV 0·3 Ti 0·7 (PO 4 ) 3 /C delivers an outstanding specific capacity (121.7 mAh g −1 at 0.1C, C = 135 mA g −1 ) and Na 3·4 MnV 0·4 Ti 0·6 (PO 4 ) 3 /C shows an excellent capacity retention (80.88 % after 1500 cycles at 1C). Notably, the coulombic efficiency of both materials during cycling is close to 100 %, indicating that these materials have great practical application value.