Fe7S8 Nanoparticles Embedded in Sulfur–Nitrogen Codoped Carbon Nanotubes: A High-Performance Anode Material for Lithium-Ion Batteries with Multilevel Confinement Structure

Fe₇S₈ nanoparticle-embedded sulfur–nitrogen codoped carbon nanotube composite (Fe₇S₈@CT-NS) has been successfully designed as a high-performance anode material for lithium-ion batteries through a multistage confinement strategy. Constructed with a nitrogen-doped carbon nanotube framework derived from melamine and a sulfurization process controlled via a polydopamine (PDA) intermediate layer, this composite features FeSC covalent bonding at the interface and a hierarchical porous structure. This multilevel confinement strategy integrates physical encapsulation within a nitrogen–sulfur codoped carbon framework and chemical stabilization via FeSC covalent bonding to synergistically enhance electrochemical performances. Electrochemical performance tests show that Fe₇S₈@CT-NS retains a capacity of 527.9 mAh g⁻¹ after 1000 cycles at a high current density of 5 A g⁻¹, demonstrating excellent reversibility and high-rate performance across a wide current density range. This material, with its unique structural confinement, chemical bonding, and functional synergy, provides new insights into the development of high-stability, high-power lithium-ion battery anode materials.