Encapsulating highly crystallized mesoporous Fe3O4 in hollow N-doped carbon nanospheres for high-capacity long-life sodium-ion batteries

摘要

High capacity transition metal oxides have attracted much attention as potential sodium-ion batteries (SIBs) anodes. However, the fast capacity fading greatly limits their practical applications. In this study, highly crystallized mesoporous Fe3O4 nanoparticles encapsulated in the hollow nitrogen-doped carbon nanospheres (denoted as HCM-Fe3O4@void@N-C) have been synthesized and then explored as anode materials for SIBs. The resultant HCM-Fe3O4@void@N-C nanospheres possess a uniform particle size of similar to 180 nm with highly crystallized mesoporous Fe3O4 cores (similar to 100 nm in diameter), a large surface area of similar to 250 m 2 g(-1) and a nitrogen-doped carbon shell (similar to 7.6 wt%). Notably, a high discharge capacity of 372 mA h g(-1) is obtained after the first five cycles at 160 mA g(-1), which can gradually increase and be maintained at an ultrahigh specific capacity of 522 mA h g(-1) even after 800 cycles. Besides, remarkable rate performance with a capacity of 196 mA h g at a current density of 1200 mA g(-1) and a high Coulombic efficiency (similar to 100%) are obtained. Such good performance can be attributed to the unique yolk-shell nanostructure with a high crystallized mesoporous Fe3O4 core, a high conducive N-doped carbon shell, and a suitable void space, paving a new way to design and synthesize high-performance anode materials for SIBs.