Nitrogen-doped carbon coated Na3V2O2(PO4)2F as a cathode for high-performance sodium-ion batteries

Na₃V₂O₂(PO₄)₂F (NVOPF), a cathode known for the advantages of high voltage, exceptional energy density, and thermal stability, is seen as a promising candidate for sodium-ion battery cathodes. However, the NVOPF exhibits poor performance in sodium storage. Here, we report a NVOPF composite cathode with a nitrogen-doped carbon produced from dopamine hydrochloride at an elevated temperature. Firstly, neutron power diffraction (NPD) is employed to determine the structure of pure NVOPF at different temperatures, including oxygen coordination and the mobility of Na⁺. The nitrogen-doped carbon layer facilitates electron conduction, prevents NVOPF nanoparticle agglomeration, and thus promotes efficient electron and ion transfer during sodium ion insertion/extraction process, thereby improving the stability of the material structure. These results indicate that the N doped carbon@NVOPF cathode material exhibits outstanding electrochemical performance (111mAh/g at 0.1C and 85mAh/g at 1C), while maintaining a capacity retention of 91.06 % after 500 cycles. The enhanced electrochemical performance attributes to efficient charge transfer kinetics offer novel perspectives, and the method can be effectively adapted to other cathode materials.