Skin-like quasi-solid-state electrolytes for spontaneous zinc-ion dehydration toward ultra-stable zinc–iodine batteries

Abstract

Rechargeable aqueous zinc–iodine (Zn–I₂) batteries are cost-effective alternative candidates for conventional metal-based batteries due to their sustainable fabrication and abundant resources. However, the issues of the shuttle effect of polyiodides and Zn anode side reactions need to be urgently addressed for their large-scale energy storage applications. Here, we propose a biologically inspired concept of a skin-like quasi-solid-state electrolyte (skin-QSSE), which features an asymmetric structure composed of covalent organic framework (COF) nanolayers and aramid fiber hydrogel layers. The electrostatic repulsion between the negatively charged nitrogen sites on the triazine COF skeleton and the polyiodide ensures efficient utilization of the iodine-activated material. Notably, DFT calculations revealed that ANF aramid fiber hydrogels induced a spontaneous dehydration process by lowering the desolvation energy barrier (−0.66 eV vs. 7.09 eV for the liquid electrolyte) of hydrated zinc ions (Zn(H₂O)₆²⁺), which alleviates corrosion and dendrite formation at the Zn anode interface. Ultimately, the Zn–I₂ batteries with the skin-QSSE demonstrated ultra-stable cycling reversibility with an extremely low capacity decay rate of only 0.0018‰ over 45 000 cycles at 10C. This work presents novel insights from the standpoint of asymmetric electrolytes for coping with the anode and cathode interface issues in aqueous Zn batteries.