The dispersion of iron nitride among porous carbon fibers to enhance redox conversion for high-performance zinc-iodine batteries

To address the insulating nature and the shuttle effect of iodide species that would deteriorate the battery performance, herein iron nitride is well-dispersed into porous carbon fibers with good flexibility via the facile electrospinning method and subsequent pyrolysis. The polyacrylonitrile precursor introduces the nitrogen doping under thermal treatment while the addition of iron acetylacetonate leads to the in-situ formation of iron nitride among the carbon matrix. The crucial pyrolysis procedure is adjustable to determine the hierarchical porous structure and final composition of the novel carbon fiber composites. As the self-supporting electrode for loading iodine, the zinc-iodine battery exhibits a large specific capacity of 214 mAh/g and good cycling stability over 1600 h. In the combination of in-situ/ex-situ experimental measurements with the theoretical analysis, the in-depth understanding of intrinsic interaction between composited support and iodine species elucidates the essential mechanism to promote the redox kinetics of iodine via the anchoring effect and electrocatalytic conversion, thus improving cycling life and rate performance. Such fundamental principles on the basic redox conversion of iodine species would evoke the rational design of advanced iodine-based electrodes for improving battery performance.