Dual-functional C-composited Na3.16Fe2.42(P2O7)2 cathode toward superior electrochemical performance for sodium-ion batteries

The development of a polyanion cathode for sodium-ion batteries is expected to accelerate the application of sodium-ion batteries in large-scale energy storage systems. However, the poor electrode conductivity is still a great challenge. In this paper, the novel carbon composite polyanion compound Na3.16Fe2.42(P2O7)(2)@C (NFP@C) is developed through high-energy ball milling followed by annealing. The porous NFP nanoparticles modified with dual-functional C-composited for amorphous carbon coating and carbon nanofibers interpenetrating deliver excellent capacity retention of 85.3% after 1000 cycles at 5 C, which is more outstanding than pure NFP. X-ray diffraction, in situ galvanostatic intermittent titration techniques, electrochemical impedance spectroscopy, and cyclic voltammetry were performed to investigate the stability and sodium diffusion of NFP@C. The results show that the systematic and comprehensive dual-functional conductive network modification enables NFP exhibit excellent electronic and ionic conductivities, thereby improving the rate capability and cycling stability. Furthermore, a soft package sodium-ion full battery assembled based on NFP@C reveals a high-capacity retention of 95.2% for 150 cycles at 0.5C. This carbon composite strategy is simple and efficient and could be easily and widely extended to other cathodes in grid-scale energy storage applications.