Flexible Free-Standing Fe₂O₃ Nanoparticle/Carbon Shells/Graphene Films for Advanced Lithium-Ion Batteries

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.