Benefits of vanadium doping in Na3MnTi(PO4)3/C as a potential candidate for sodium-ion batteries

Na 3 MnTi(PO 4 ) 3 /C is a high-energy sodium-ion battery (SIBs) cathode material. However, the low rate performance and unfavorable cycle life limit its practical applications. Herein, Na 3 Mn 1-x V x Ti(PO 4 ) 3 /C (x = 0, 0.01, 0.05, 0.10) were synthesized by a facile sol-gel method and the performance has been researched via the difference of vanadium doping amount. X-ray diffraction (XRD) indicates that vanadium doping has no obvious effect on the crystal structure. X-ray photoelectron spectroscopy (XPS) and Energy dispersive X-ray spectroscopy (EDS) mapping images show that vanadium has been successfully doped into the material. Cyclic voltammogram (CV) displays obviously three pairs of redox couples, corresponding to the Ti 3+ /Ti 4+ , Mn 2+ /Mn 3+ and Mn 3+ /Mn 4+ redox couples, respectively, and is mainly controlled by diffusion and exhibits pseudo-capacitance behavior. The experimental results indicate that vanadium doping can improve the electrochemical performance of Na 3 MnTi(PO 4 ) 3 /C, the high specific capacity (116.5 mAh g −1 with a coulomb efficiency of 100% at 0.2C after 100 cycles, 91.8 mAh g −1 higher than that of undoped sample), outstanding cyclability (≈73.6% capacity retention after 500 cycles at 1C, 58.3% higher than that of undoped sample) for Na 3 Mn 0.95 V 0.05 Ti(PO 4 ) 3 make the vanadium doping become a promising modification method. • A promising NASICON-structured Na 3 MnTi(PO 4 ) 3 material is modified by vanadium doping. • Vanadium doping greatly improves the dynamics. • The optimal composites show outstanding electrochemical performance.