Controllable Synthesis of Carbon-Coated Fe3O4 Nanorings with High Li/Na Storage Performance

Abstract Fe3O4 with high capacity and low cost has been a promising anode for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, the intrinsic issues from the severe volume change of Fe3O4 during cycling and its inferior electronic conductivity result in the poor capacity retention. Herein, carbon-coated Fe3O4 nanorings (R-Fe3O4@C) were fabricated by a facile method. The hollow nanorings with a small size below 80 nm are designed to mitigate the severe volume expansion of Fe3O4 upon cycles, whereas the amorphous carbon layer with a thickness of 12 nm is created to induce the fast electronic transfer. Benefiting from the unique carbon-coated nanostructure, R-Fe3O4@C exhibits superior electrochemical behaviors in both LIBs and SIBs. As an anode of LIBs, it delivers a high capacity of 1003.4 mAh g-1 at 0.5 A g-1 over 100 cycles, and of 421.2 mAh g-1 at 5 A g-1 over 800 cycles. Being an anode for SIBs, it shows a considerable capacity of 365.1 mAh g-1 at 0.1 A g-1 after 200 cycles, and of 160.3 mAh g-1 at 2 A g-1 after 300 cycles. Our work achieves the remarkable electrochemical properties of R-Fe3O4@C via the facile fabrication in which relatively low-cost ingredients are used.