Bio-assisted engineering of hierarchical porous carbon nanofiber host in-situ embedded with iron carbide nanocatalysts toward high-performance Li–S batteries

Developing high-energy-density lithium-sulfur batteries (LSBs) heavily depends on the rational design of cathodes in order to address the key challenge on suppressing the notorious polysulfide shuttling, particular in high-sulfur-loading electrodes. Herein, a unique hierarchical porous N-doped carbon nanofiber architecture with in-situ generated iron carbide nanocatalysts (Fe 3 C@PCNFs) is delicately designed by using natural collagen fibers as the precursor matrix and the structure-directing agent, which can be applied as an advanced sulfur host in LSBs. Benefiting from the thermal-induced etching by ferric species combined with ZrO 2 hard-template management, such transformed Fe 3 C@PCNFs framework exhibits enhanced graphitization degree, impressive hierarchical porous architecture, and high specific surface area near 1300 m 2  g −1 . The in-situ embedded polar Fe 3 C nanoparticles are proved to possess excellent chemical adsorption and catalysis effect toward the immobilization-conversion of polysulfides and fast Li 2 S nucleation. Thus, a target cathode (S–Fe 3 C@PCNFs) with >76 wt% sulfur content can deliver outstanding rate capability (632 mAh g −1 at 5C) and superb cycling performance (∼0.067% capacity decay per cycle over 500 cycles). Impressively, when applied with high-areal-loading of 6.3 mg cm −2 , the S–Fe 3 C@PCNFs still exhibits a stable cycling life together with a significant high areal capacity of 5.0 mAh cm −2 , manifesting a promising application in practical LSBs.