Porous Fe3O4–NCs-in-Carbon Nanofoils as High-Rate and High-Capacity Anode Materials for Lithium-Ion Batteries from Na–Citrate-Mediated Growth of Super-Thin Fe–Ethylene Glycolate Nanosheets

Porous Fe3O4/C composite nanofoils, characterized by a thickness of ∼20 nm and with ∼8 nm open pores and ∼5 nm Fe3O4 nanoparticles embedded in the carbon matrix, were prepared for the first time using Na–citrate to mediate the growth of hexagonal Fe–ethylene glycolate nanosheets and subsequently annealing them at 350 °C in N2. It has been found that the Fe–ethylene glycolate nanosheets can be effectively slimmed by increasing the concentration of Na–citrate, and the microstructures of Fe3O4/C nanocomposites may be tailored by the annealing temperature. When tested as the anode materials in LIBs, the Fe3O4/C nanofoils obtained after annealing at 350 °C were found to exhibit superior electrochemical performance due to its optimal microstructure, featured by a reversible capacity of 1314.4 mAh g–1 at 0.4 A g–1 over 100 cycles, 1034.2 mAh g–1 at 1 A g–1, and 686.4 mAh g–1 at 5 A g–1 after 500 cycles, whereas the annealing treatments at 450 and 550 °C render the Fe3O4/C nanocomposites with the inferior electro...