Facile Synthesis of High Electrochemical Performance Na2FePO4F@CNT&GN Cathode Material as Sodium Ion Batteries

Here, we report a novel material structure for sodium ion battery cathodes. The material has an enormously enhanced conductive framework of Na2FePO4F (NFPF), combining both 1D carbon nanotube (CNT) and 2D graphene nanosheets (GNs). Uniform Na2FePO4F nanorods were synthesized first via a one-step hydrothermal method. Then, the highly efficient conductive network of NFPF@CNT&GN was synthesized with a straightforward mechanical ball milling technique. The obtained NFPF@CNT&GN shows a reversible capacity of 67.5 mA h g(-1) at 10C rate, which exceeds all of the published results for NFPF to date. Remarkably, the degradation rate is only 0.02% per cycle even after 2500 cycles at the 5C rate. The electrochemical impedance spectroscopy kinetic study demonstrates that the superior electrochemical properties for NFPF@CNT&GN should be attributed to the great improvement of the electronic conductivity and sodium-ion diffusion ability.