Shapeable carbon fiber networks with hierarchical porous structure for high-performance Zn-I2 batteries

Aqueous rechargeable zinc-iodine batteries (ZIBs) emerged as a promising energy storage alternative has attracted considerable attention. However, ZIBs still suffer from the severe shuttle effect of polyiodide and poor reversibility, leading to the poor cycling lifetime and potential safety issues. Herein, the assembly of Al-based metal-organic frameworks (Al-MOFs) in the presence of polyacrylonitrile (PAN) via electrospinning technique enables the formation of Al-MOF/PAN fibers. With the subsequent pyrolysis, the hierarchical porous carbon fibers with nitrogen doping (NPCNFs) are prepared for loading iodine. Benefiting from the confinement effect of the highly porous carbon network and the nitrogen doping, the self-supported carbon nanofiber electrode is capable of inhibiting the shuttle effect of polyiodide species. Especially, the in-situ Raman spectroscopy reveals the reversible two-step conversion reaction between iodine and polyiodide, which enables the best cycling stability for over 6,000 cycles with negligible capacity. This work demonstrates an efficient approach to regulating the porous structure and surface properties in the design of advanced iodine electrodes for high-performance ZIBs.