Ultrafine FeSe nanoparticles embedded into 3D carbon nanofiber aerogels with FeSe/Carbon interface for efficient and long-life sodium storage

Abstract The key challenge for high-performance sodium-ion batteries is the exploitation of appropriate electrode materials with a long cycling stability and high rate capability. This study reports the synthesis of a composite of ultrafine FeSe nanoparticles (NPs) and carbon nanofiber aerogel (CNFA) as anode material for SIBs. The composite features ultra-small (∼5 nm) NPs of FeSe uniformly embedded in interconnect three dimensional (3D) carbon nanofiber with large surface area, highly conductive network, and robust structural stability. As expected, the FeSe-CNFA-700 sample delivers a capacity as high as ∼313 mA h g −1  at 2000 mA g −1 after 1000 cycles and ultrahigh rate capability up to 20000 mA g −1 . The significantly improved electrochemical performance could be attributed to the unique structure that combines a variety of advantages: easy access of electrolyte to the 3D network structure, pseudocapacitve charge storage and fast Na ion diffusion processes. The results confirm the intercalation of Na + into the 3D ultrafine FeSe nanoparticles/carbon nanofiber aerogel is enhanced through the strong interaction between FeSe nanocrystals and the carbon layer. The density functional theory calculations demonstrate that the unique FeSe/carbon layer interface in 3D network structure can enhance Na storage due to the small energy barrier and negative adsorption energy.