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

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 Fe 3 N@carbon frameworks (Fe 3 N@C/3DPCF) composed of Fe 3 N 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 Fe 3 N nanoparticles from the air oxidation , accommodate the volumetric expansion of Fe 3 N, and accelerate the diffusion of electrolytes and the transmission of electrons during Na + insertion and extraction processes. Meanwhile, the interface coupling effect between Fe 3 N nanoparticles and porous carbon further improved the electrochemical performance and structural integrity of the electrode. The Fe 3 N@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 Fe 3 N@C/3DPCF as anode and Na 3 V 2 (PO 4 ) 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.