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

Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 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 PO 4 3− 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 Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 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, Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 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 Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 nanoribbon with excellent electrochemical performance can be considered an attractive cathode electrode for the commercialization of sodium-ion battery.