Rational construction of 3D porous Fe3N@C frameworks for high-performance sodium-ion half/full batteries

Abstract

Metal nitrides have excellent electrical property and high theoretical capacities, which have great potential as anode materials for sodium-ion batteries. However, the inferior air stability and serious pulverization problems are urgent to be solved for their applications. Herein, the three-dimensional porous Fe3N@carbon frameworks (Fe3N@C/3DPCF) composed of Fe3N nanoparticles and hierarchical porous carbon network were synthesized by the sol-gel and post-annealing method at 500 °C with the polystyrene spheres as soft templates. The hierarchical porous carbon structure can protect Fe3N nanoparticles from the air oxidation, accommodate the volumetric expansion of Fe3N, and accelerate the diffusion of electrolytes and the transmission of electrons during Na+ insertion and extraction processes. Meanwhile, the interface coupling effect between Fe3N nanoparticles and porous carbon further improved the electrochemical performance and structural integrity of the electrode. The Fe3N@C/3DPCF electrode for sodium-ion battery exhibited a reversible capacity of 494.6 mA h g−1 at 0.1 A g−1, long cycle life over 1000 times, and high rate capacity of 310 mA h g−1 at 2 A g−1. Moreover, the full cell and flexile cell assembled with pre-sodiated Fe3N@C/3DPCF as anode and Na3V2(PO4)3@C as cathode respectively delivered the discharge specific capacities of 351.2 and 390.5 mA h g−1 at 0.1 A g−1. Therefore, this work will pave the way for the air unstable conversion materials for the applications as sodium-ion battery anode.