Hierarchical Fe3O4@C nanofoams derived from metal–organic frameworks for high-performance lithium storage

A facile method was employed to in situ prepare hierarchical mesoporous Fe3O4@C nanofoams through pyrolysis of a post-treated MIL-53(Fe) precursor. Well-defined carbon network-encapsulated ultrasmall and uniform Fe3O4 octahedrons can be obtained by controlling the pyrolysis temperature. This unique artificial shows the excellent lithium storage performance. A reversible discharge capacity of 861.9 mAh·g−1 is observed at 0.1 A·g−1 after 300 cycles. Even at a high current density of 1 A·g−1, the reversible discharge capacity can still reach 605.2 mAh·g−1 after 500 cycles. Good rate capability is also observed, as the specific discharge capacities are 833.6, 729.9, 666.8, 643.6 and 635.6 mAh·g−1 at current density of 0.2, 0.5, 0.8, 1.0 and 1.2 A·g−1, respectively. The attractive electrochemical performance of Fe3O4@C nanofoams should be attributed to the hierarchical foam-like structure, which can effectively relieve the volume change during the lithiation/delithiation process and facilitate fast lithium-ion and electron transport.