Structural Reconstruction via Carbon Nanotube Spatially Confined Metal Catalysis: A Morphology-Controlled Approach to Convert Polycyclic Aromatic Hydrocarbon into Carbon Nanofibers for Highly Active Anodes in Li-Ion Batteries

Abstract

By a carbon nanotube (CNT) spatially confined metal-catalyzed structural reconstruction, carbon nanofibers (CNFs) with a hollow, hollow-solid, solid graphite core, and CNT shell are prepared using nitrogen heterocycle (NHC) and polycyclic aromatic hydrocarbon (PAH) as carbon sources. The formation mechanism of CNFs with oriented graphene layers and enlarged intergraphene spacing is studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction analysis. It revealed that this one-dimensional nanoconfined metal-catalyzed carbon rearrangement is totally different from the reported spatially localized metal-catalyzed graphitization of electrospun polymer and nanocasted carbohydrate nanofibers, as the graphene orientation, cavity volume, and interlayer distance of CNFs can be controlled by the carbon concentration-related competitive metal-catalyzed tip growth of latitudinal and longitudinal graphene layers from NHC and PAH. The unique CNF structure renders good electronic/ionic conductivity, abundant Li⁺ storage interlayer gaps, and robust mechanical durability, resulting in outstanding electrochemical properties as anodes in lithium-ion batteries. The optimum CNF anode delivers a stable discharge capacity of 475 mA h g^–1 at 0.1 C, an extraordinary rate capability of 303 mA h g^–1 at 5 C, and a remarkable long-term cycling stability of 378 mA h g^-1 after 600 cycles at 1 C. This 1D nanoconfined metal catalysis synthesis could be useful for the development of efficient CNF anodes in many electrochemical reactions with a potential for industrial applications.