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Nitrogen-doped carbon-coated Fe3O4/reduced graphite oxide (NC@Fe3O4/rGO) nanocomposites with in situ polymerized melamine-formaldehyde resin (MFR) as the carbon sources were synthesized via the decomposition of MFR/Fe3O4/rGO nanocomposites. Fe3O4 NPs were embedded in the integrated carbon matrix composed of protective carbon layer and conductive rGO sheets offering excellent buffer effect. The NC@Fe3O4/rGO nanocomposites were tested as anode materials for lithium-ion batteries (LIBs) and displayed a large reversible specific capacity of above 900 mA h g−1 after 100 cycles at a current density of 50 mA g−1, high coulombic efficiency (~ 98%) with an initial coulombic efficiency of 86%. The high initial coulombic efficiency is critical for the practical application of the transition metal oxide–based anode materials. [ABSTRACT FROM AUTHOR]

Magnetite (Fe3O4) has drawn great attention in the field of lithium‐ion batteries (LIBs) due to its promising high theoretical capacity and abundance in nature. However, rapid capacity fading, low charge/discharge rate and low capacity exceedingly limit the application of bare Fe3O4 anode. Here, we report a facile and scalable method to construct multilayered reduced graphene oxide (rGO)/Fe3O4@polydopamine (PDA) hydrogel (rGO/Fe3O4@PDA hydrogel) for the anodes of LIBs. During the lithiation/delithiation processes, PDA and rGO can effectively inhibit the volume change and avoid structural pulverization. rGO backbone also provides sufficient electrical conductivity and a high specific surface area. The PDA layer suppresses the repetitive growth and thickening of solid‐electrolyte interphase (SEI), playing a role of artificial SEI. As a result, high capacity and superior cycle stability (1358 mAh g−1 after 300 cycle at 1 A g−1) as well as satisfying rate performance (around 600 mAh g−1 at 3 C), fast charge/discharge rate (712 mAh g−1 after 2000 cycles at 3 A g−1), high columbic efficiency and stable reverse reaction are achieved. Interestingly, capacity growth can be observed in the multilayered rGO/Fe3O4@PDA anode owing to the gradual activation of tight encapsulation by rGO sheets. This design concept and structural construction strategy are hopeful be extended to other systems for the next‐generation advanced LIBs. A multilayered hydrogel is fabricated by a facile and scalable method for the anodes of lithium‐ion batteries. A superior performance at a fast charge/discharge rate (712 mAh g−1 after 2000 cycles at 3 A g−1) and a capacity growth (1358 mAh g−1 after 300 cycles at 1 A g−1) can be observed in the multilayered rGO/Fe3O4@PDA anodes (rGO: reduced graphene oxide; PDA: polydopamine). [ABSTRACT FROM AUTHOR]