Hierarchical dopamine-derived N-doped carbon-encapsulated iron oxide/sulfide hollow nanospheres for enhanced lithium-ion storage

Iron-based anode materials have aroused wide attention due to the multiple advantages of high capacity, abundant resources, eco-friendly and low-cost features, whereas the big volume changes upon cycling and low conductivity limit their practical applications. Herein, the dopamine N-doped carbon-encapsulated Fe3O4 and Fe7S8 hollow nanospheres (Fe3O4@NC and Fe7S8@NC) have been designed via a facile synthesis strategy. The hierarchical hollow structure of inner Fe3O4/Fe7S8 restrains the big volume fluctuation upon cycling. The outer tightly wrapped N-doped carbon shell effectively enhances the conductivity of overall electrode and meanwhile serves as the protective layer to inhibit the structure collapse. The strong chemical bonding effects between Fe3O4/Fe7S8 and N-doped carbon construct such stable structures. As expected, both two composites show excellent lithium storage performances owing to the cooperative effect of N-doped carbon shell and internal active material. The reversible capacity of Fe3O4@NC/Fe7S8@NC reaches as high as 830/690 mAh g(-1) over 1500/500 loops even at a high rate of 2 A g(-1). The excellent electrochemical performances of Fe3O4@NC/Fe7S8@NC demonstrate their potential merits as next-generation anodes for lithium-ion batteries.

Automated summary

Iron-based anode materials with dopamine N-doped carbon-encapsulated Fe3O4 and Fe7S8 hollow nanospheres have been successfully designed. The hierarchical hollow structure and tightly wrapped N-doped carbon shell address the volume fluctuation and low conductivity issues of iron-based anode materials. These composites exhibit excellent lithium storage performances, even at high rates.