Fe single-atom-regulated carbon nanofibers for high-performance lithium/sodium ion battery anode

Carbon-based materials, commonly used as commercial anodes in lithium/sodium ion batteries, nevertheless suffer from sluggish kinetic properties. Constructing electrode materials with one-dimensional nanostructures that offer convenient ion/electron transport pathways can improve Li⁺/Na⁺ storage behavior. Recently, metal single-atom doping has also emerged as an effective strategy to enhance storage kinetics. However, it remains challenging to construct one-dimensional carbon materials doped with metal single atoms using simple methods to achieve outstanding Li⁺/Na⁺ storage performance. Herein, three-dimensional intertwined short carbon nanofibers (SCNFs) coupled with single atomic iron dopants were tailored through a hydrothermal strategy followed by high-temperature carbonization free from strong acids etching metals. In the SCNFs, only a trace amount of Fe (0.37 at.%) was introduced; the nitrogen-coordinated Fe single atoms and the nanofibers-intertwined structure promoted Li-ion adsorption, improved diffusion kinetics, and enhanced conductivity, thereby facilitating Li⁺/Na⁺ storage capacity. Acting as an anode in lithium/sodium batteries, SCNFs demonstrated an outstanding electrochemical performance. After assembling lithium ion batteries, the optimal Fe-N-C-2 exhibited a high reversible capacity of 903.4 mAh g^-1 at 50 mA g^-1 with retention of 518.7 mAh g^-1 at 1.0 A g^-1. For sodium-ion storage, Fe-N-C-2 preserved excellent high-rate cyclic stability, maintaining 152.6 mAh g^-1 after 500 cycles at 0.5 A g^-1. Moreover, the hydrothermal method is simple and convenient for large-scale preparation. Our strategy offers a heuristic perspective on the controllable design of nitrogen-coordinated atomic metals for energy storage applications.