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The energy and power density of lithium-ion batteries (LIBs) can be effectively improved by designing flexible free-standing electrodes. Here, a flexible film composed of Fe3O4 nanoparticles (NPs) embedded in N-doped carbon nanofibers (Fe3O4/NCNFs) was prepared through electrospinning and subsequent annealing process. The Fe3O4/NCNFs film can be directly used as anode materials for LIBs without conductive additive, current collector, and binder. Electrochemical measurement results indicate that the Fe3O4/NCNFs electrode exhibits excellent cycling stability and retains the capacity of 522 mAh g−1 after 200 cycles at 0.1 A g−1. Furthermore, the Fe3O4/NCNFs electrode also shows good rate performance and still obtains a specific capacity of 407 mAh g−1 even at 5 A g−1. The superior electrochemical performance should be attributed to the flexible self-standing characteristic of the electrode and the synergistic effects between 3D conductive NCNFs and Fe3O4 NPs.

Kapok fibres were used as micro-tube biotemplate and bio-carbon source to synthesise Fe 3 O 4 /C composites, which were then utilised as anode materials. Fe 3 O 4 nanoparticles were grown uniformly onto the external surface and internal channel of kapok carbon fibres. The flexibility, high specific surface area and electronic conduction of kapok fibres can buffer the volume expansion as well as inhibit the aggregation of Fe 3 O 4 nanoparticles. Thus, the electrical integrity and structural of the Fe 3 O 4 /C composites electrode during lithiation/delithiation processes. The Fe 3 O 4 /C composites electrode delivers a high reversible capacity of 596 mA h g −1 after 100 cycles and an ultra-high coulombic efficiency approaching 100%. The high electrochemical performance of the Fe 3 O 4 /C composites can be caused by the synergistic effect of the Fe 3 O 4 nanoparticles and the structure of kapok carbon fibres.

High performance nitrogen-doped carbon (NC) materials decorated with MnO hybrid (MnO@NC) composites with a nanopeapod appearance were synthesized by with a simple hydrothermal method and insuit-polymeric route. As an anode material for lithium ion batteries (LIBs), the nanopeapod structure of MnO@NC composites with internal void spaces exhibits good rate capability, high conductivity and excellent cycling stability. After 200 cycles, the nanopeapod composites yield a specific capacity of 775.4 mAh g−1 at 100 mA g−1 and a high-rate capacity of 559.7 mAh g−1 at 1000 mA g−1. The proposed synthesis of nanopeapod structure composites with an internal room is an efficient design with excellent electrode materials for rechargeable LIBs.