Polyvinylpyrrolidone assisted synthesized ultra-small Na4Fe3(PO4)2(P2O7) particles embedded in 1D carbon nanoribbons with enhanced room and low temperature sodium storage performance

Na4Fe3(PO4)2P2O7 is considered to be a practical cathode material due to the wide source and low price of raw materials. However, the inherent isolation properties of the PO43− group result in low electronic conductivity and, subsequently, a low discharge capacity and poor cycling stability. Herein, polyvinylpyrrolidone assisted electrospinning method is used to synthesize Na4Fe3(PO4)2P2O7 nanoparticles embedded in carbon nanoribbons. The network structure of active materials wrapped in crosslinked carbon nanoribbons not only enables the ultra-fast transfer of electrons on the three-dimensional “highway” between the nanoparticles but also inhibits the aggregation of nanoparticles. These nanoribbons exhibit remarkable electrochemical performance, resulting from their exceptional electronic and ionic conductivity: high capacity of 128.6 mAh g−1 at 0.1C (1 C = 128.9 mAh g−1), extra-high rate capability (61.2 mAh g−1 at 50 C), and ultra-long cycle (72% capacity retention after 5000 cycles at 50 C). Meanwhile, Na4Fe3(PO4)2P2O7 nanoribbon also shows excellent low temperature properties. At −15 °C, the nanoribbon delivers 84.5 mAh g−1 of discharge capacity at 0.05C and displays long-term cycle performance (80.8% capacity retention after 700 cycles at 0.5C). Therefore, the Na4Fe3(PO4)2P2O7 nanoribbon with excellent electrochemical performance can be considered an attractive cathode electrode for the commercialization of sodium-ion battery.