Melamine-assisted synthesis of Fe3N featuring highly reversible crystalline-phase transformation for ultrastable sodium ion storage

Metal nitride-based materials are deemed to be promising anodes for sodium ion batteries (SIBs) due to their attractive electrical conductivity and considerable theoretical capacity. However, the poor electrochemical stability of metal nitrides caused by amorphorization and pulverization during a long-term sodiation/desodiation process limits their practical applications. Herein, a combination of facile chemical binding engineering with a fast electronic/ionic transport construction strategy is firstly proposed to mitigate these problems. As a demonstration, core-shell Fe3N@C nanoparticles are chemically immobilized on three-dimensional N-doped carbon foam (3DNCF) via a straightforward and scalable adsorption-annealing route. Arising from the synergistic effects from strong chemical binding between Fe3N nanoparticles and 3DNCF, fast electronic/ionic transport pathways and a robust carbon coating layer, the flexible and self-supported Fe3N@C/3DNCF anode can maintain highly reversible crystalline-phase transformation without significant pulverization in the whole cycling process when evaluated as an anode for SIBs. As a result, Fe3N@C/3DNCF shows a remarkable capacity retention rate of 94.9% for 2000 cycles at 1.0 A g(-1) with a high capacity of 374.8 mA h g(-1). This work may provide an alternative strategy to design long-cycle-life conversion-type anodes for SIBs.