Fe7Se8 nanoparticles anchored on N-doped carbon nanofibers as high-rate anode for sodium-ion batteries

On account of increasing demand for large-scale energy storage devices, sodium-ion batteries have shown great potential to replace lithium-ion batteries owing to the abundant reserve, low cost and environmental benignity of sodium resources. Here, we report a facile electrospinning method to fabricate a hybrid material of ultrasmall Fe7Se8 nanoparticles/N-doped carbon nanofibers (Fe7Se8/N-CNFs). As an anode material in sodium-ion batteries, the Fe7Se8/N-CNF hybrid exhibits superior rate property with a specific capacity of 286.3 mAh g(-1) at a current density of 20 A g(-1), outperforming other metal selenides. Such an excellent performance originates from the synergistic effects of ultrasmall Fe7Se8 nanoparticles as well as the unique and interconnected network of N-rich CNFs, which offer short Na+ diffusion distance, provide efficient electrolyte diffusion paths, supply numerous defects and active sites for Na+ adsorption, enhance surface pseudocapacitive behavior, improve the electronic conductivity, and thus facilitate the electron/ion transport and electrochemical reaction kinetics.