Hierarchical porous Fe/N doped carbon nanofibers as host materials for high sulfur loading Li–S batteries

Abstract

Improving the sulfur utilization and cycling stability especially under high sulfur loading (>2 mg cm⁻²) is challenging due to the poor conductivity of sulfur and high soluble nature of polysulfides. Herein, we develop novel self-supporting carbon nanofibers with hierarchical porous structures and Fe/N absorption/nucleation centers (Fe/N-HPCNF) as high performance sulfur hosts via a facile co-spinning method. The highly interior porous carbon fiber structure provides good electrolyte infiltration, stable conductive networks and sufficient surfaces for fast Li⁺/electron transport and sulfur redox while maintaining high sulfur area loading. In addition, the abundant Fe/N heteroatoms evenly dispersed in the fiber strongly restrain polysulfide diffusion through a chemisorption effect and meanwhile regulate homogeneous sulfur nucleation, enhancing the stability of cathodes. Consequently, S@Fe/N-HPCNF cathodes realize a high initial specific capacity of 1273 mA h g⁻¹ (areal capacity: 4.5 mA h cm⁻²) and long cycle life over 500 cycles with a high sulfur loading of 3.5 mg cm⁻². A stable capacity of 6.6 mA h cm⁻² is achieved even under 9 mg cm⁻² sulfur. What's more, a pouch cell prototype with an ultrahigh sulfur area density (54 mg cm⁻²) was assembled and successfully lighted 10 yellow light-emitting diodes (LED), demonstrating the convenient scale-up of our S@Fe/N-HPCNF cathodes.