The precise synthesis of twin-born Fe3O4/FeS/carbon nanosheets for high-rate lithium-ion batteries

Metal oxides/sulfides have been considered as promising anode candidates for use in next-generation lithium-ion batteries (LIBs), but the large volume changes and poor electron and ion conductivities limit their practical applications. Here, twin-born Fe3O4/FeS/carbon nanosheets (TB-FeOSC-NS) were precisely fabricated for the first time by using MIL-88b(Fe) as a self-sacrificing template. By adjusting the amount of citric acid and the annealing temperature, the structure and phase composition could be accurately controlled. Benefitting from its unique structure, TB-FeOSC-NS can provide an abundant contact interface with electrolytes and active sites for redox reactions, providing a short diffusion path for electrons and ions. Therefore, as an anode material for use in LIBs, the TB-FeOSC-NS electrode exhibits admirable electrochemical performance, including a high specific capacity, excellent cycling stability, and superior rate performance, with a high capacity of 400 mA h g(-1) at an ultrahigh current density of 20 A g(-1). More importantly, this work deepens our understanding of the precise synthesis of heterostructured materials for electrochemical energy storage and the synergistic modulation of morphologies, phase compositions, and interfaces.