High-capacity anode materials of transition-metal oxides (TMOs) usually undergo low conductivities and drastic volume variation derived from a multielectron-transfer conversion reaction mechanism, which seriously hinder the cycling stability and rate performance toward their commercialization. Herein, a free-standing Fe2O3/C shells/reduced graphene oxide (Fe2O3/C/RGO) film as an additive-free anode is fabricated by a facile two-step strategy accompanied by the physical cross-linking feature of chitosan. In this free-standing structure, the Fe2O3 nanoparticles (NPs) with diameters of 20–30 nm are encapsulated by chitosan pyrolytic C shells and further confined within a highly ordered RGO film. As a consequence, the ultrasmall Fe2O3 NPs can effectively reduce the Li+ diffusion pathway, while the C shell and RGO sheets act as a matrix to alleviate the huge volumetric change of Fe2O3 NPs during the charge/discharge process. Benefiting from the advantages of a free-standing film, the well-designed Fe2O3/C/RGO film effectively resolves long-standing challenges and achieves an admirable capacity of 609 mAh·g–1 at 1 A·g–1, a good rate performance (up to 4 A·g–1), and an outstanding cycling performance over 1000 cycles. These results provide a universal strategy to integrate TMOs with RGO to construct a flexible self-supported film for superior lithium-ion batteries.

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Developing green materials applied in lithium-ion batteries is of significant importance for the present-day society. Herein, a feasible strategy to construct Fe3O4 nanoparticles (NPs) embedded in three-dimensional (3D) honeycomb biochar derived from pleurotus eryngii was proposed. The obtained material consists of Fe3O4 NPs (35–85 nm) encapsulated in 3D honeycomb biochar possesses a high specific capacity of 723 mAh g−1 at 1.5 A g−1 after 1000 cycles. The effectively enhanced cycling life of Fe3O4@C nanocomposites can be ascribed to the small Fe3O4 NPs provide lower degree of cracking and high specific capacity, while the honeycomb biochar function like a cage to inhibit huge volume change of Fe3O4 NPs during the charge–discharge process.

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