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.