Nitrogen-Doped Carbon Nanofibers as Free-Standing and Binder-Free Anode Materials for Lithium-Ion Batteries

Electrospun carbon nanofibers (CNFs) reinforced by metal–organic frameworks (MOFs) exhibit a wide range of applications in the energy storage field. In this study, a nitrogen-doped carbon nanofiber electrode material (CNMs@Co) modified with metal monomers was successfully synthesized without requiring additional binders, conductive agents, or current collectors. The CNMs@Co were fabricated via in situ growth of zeolite imidazolate framework-67 (ZIF-67) on polyimide (PI) fibers to obtain the precursor PI@ZIF-67, followed by carbonization. The composite integrates the advantages of stable CNFs and porous nitrogen-doped carbon, boasting excellent electrolyte wettability, high specific surface area, good electrical conductivity, and short ionic diffusion and electron transport distances, thereby demonstrating excellent electrochemical performance. The CNMs@Co electrodes display a specific capacity of 674.27 mAh g–1 at 0.05 A g–1. After 2000 cycles at a high current density of 1 A g–1, the specific capacity stays at 278.94 mAh g–1, with a rate of capacity retention of 79%, highlighting the excellent long-term stability. In addition, the doping of nitrogen atoms and modification of cobalt nanoparticles in the CNMs@Co boosts the active sites and improve the electrical conductivity, which facilitates fast electron transport. This unique self-supporting network structure not only effectively shortens the electron and ion transport pathways but also significantly reduces the extent to which the active material expands in volume. Considering these remarkable properties of CNMs@Co electrode materials, they show promising prospects for use in energy storage systems such as flexible lithium-ion batteries.